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Griffin JD, Zhu Y, Reeves A, Buhman KK, Greenberg AS. Intestinal Acyl-CoA synthetase 5 (ACSL5) deficiency potentiates postprandial GLP-1 & PYY secretion, reduces food intake, and protects against diet-induced obesity. Mol Metab 2024; 83:101918. [PMID: 38499083 PMCID: PMC10990902 DOI: 10.1016/j.molmet.2024.101918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 02/15/2024] [Accepted: 03/14/2024] [Indexed: 03/20/2024] Open
Abstract
OBJECTIVE In the small intestine, the products of digestion of dietary triacylglycerol (TAG), fatty acids (FA) and monoacylglycerol, are taken up by absorptive cells, enterocytes, for systemic energy delivery. These digestion products can also bind receptors on endocrine cells to stimulate the release of hormones capable of influencing systemic energy metabolism. The initial phase of intestinal FA absorption involves the acylation of FAs to acyl-CoA by the acyl-CoA long chain synthetase (ACSL) enzymes. ACSL5 is abundantly expressed in the small intestinal epithelium where it is the major ACSL isoform, contributing approximately 80% of total ACSL activity. In mice with whole body deficiency of ACSL5, the rate of dietary fat absorption is reduced and energy expenditure is increased. However, the mechanisms by which intestinal ACSL5 contributes to intestinal FA metabolism, enteroendocrine signaling, and regulation of energy expenditure remain undefined. Here, we test the hypothesis that intestinal ACSL5 regulates energy metabolism by influencing dietary fat absorption and enteroendocrine signaling. METHODS To explore the role of intestinal ACSL5 in energy balance and intestinal dietary fat absorption, a novel mouse model of intestine specific ACSL5 deficiency (ACSL5IKO) was generated by breeding ACSL5 floxed (ACSL5loxP/loxP) to mice harboring the tamoxifen inducible, villin-Cre recombinase. ACSL5IKO and control, ACSL5loxP/loxP mice were fed chow (low in fat) or a 60% high fat diet (HFD), and metabolic phenotyping was performed including, body weight, body composition, insulin and glucose tolerance tests, energy expenditure, physical activity, and food intake studies. Pair-feeding studies were performed to determine the role of food intake in regulating development of obesity. Studies of dietary fat absorption, fecal lipid excretion, intestinal mucosal FA content, and circulating levels of glucagon like peptide 1 (GLP-1) and peptide YY (PYY) in response to a TAG challenge were performed. Treatment with a GLP-1 receptor antagonist was performed to determine the contribution of GLP-1 to acute regulation of food intake. RESULTS We found that ACSL5IKO mice experienced rapid and sustained protection from body weight and fat mass accumulation during HFD feeding. While intestine specific deficiency of ACSL5 delayed gastric emptying and reduced dietary fat secretion, it did not result in increased excretion of dietary lipid in feces. Energy expenditure and physical activity were not increased in ACSL5IKO mice. Mice deficient in intestinal ACSL5 display significantly reduced energy intake during HFD, but not chow feeding. When HFD intake of control mice was matched to ACSL5IKO during pair-feeding studies, no differences in body weight or fat mass gain were observed between groups. Postprandial GLP-1 and PYY were significantly elevated in ACSL5IKO mice secondary to increased FA content in the distal small intestine. Blockade of GLP-1 signaling by administration of a long-acting GLP-1 receptor antagonist partially restored HFD intake of ACSL5IKO. CONCLUSIONS These data indicate that intestinal ACSL5 serves as a critical regulator of energy balance, protecting mice from diet-induced obesity exclusively by increasing satiety and reducing food intake during HFD feeding. The reduction in food intake observed in ACSL5IKO mice is driven, in part, by increased postprandial GLP-1 and PYY secretion. These effects are only observed during HFD feeding, suggesting that altered processing of dietary fat following intestinal ACSL5 ablation contributes to GLP-1 and PYY mediated increases in satiety.
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Affiliation(s)
- John D Griffin
- Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, USA
| | - Ying Zhu
- Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, USA
| | - Andrew Reeves
- Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, USA
| | | | - Andrew S Greenberg
- Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, USA; Tufts University School of Medicine, USA; Friedman School of Nutrition Science and Policy at Tufts University, USA.
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Kwon SJ, Khan MS, Kim SG. Intestinal Inflammation and Regeneration-Interdigitating Processes Controlled by Dietary Lipids in Inflammatory Bowel Disease. Int J Mol Sci 2024; 25:1311. [PMID: 38279309 PMCID: PMC10816399 DOI: 10.3390/ijms25021311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 01/15/2024] [Accepted: 01/18/2024] [Indexed: 01/28/2024] Open
Abstract
Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a disease of chronic inflammatory conditions of the intestinal tract due to disturbance of the inflammation and immune system. Symptoms of IBD include abdominal pain, diarrhea, bleeding, reduced weight, and fatigue. In IBD, the immune system attacks the intestinal tract's inner wall, causing chronic inflammation and tissue damage. In particular, interlukin-6 and interlukin-17 act on immune cells, including T cells and macrophages, to amplify the immune responses so that tissue damage and morphological changes occur. Of note, excessive calorie intake and obesity also affect the immune system due to inflammation caused by lipotoxicity and changes in lipids supply. Similarly, individuals with IBD have alterations in liver function after sustained high-fat diet feeding. In addition, excess dietary fat intake, along with alterations in primary and secondary bile acids in the colon, can affect the onset and progression of IBD because inflammatory cytokines contribute to insulin resistance; the factors include the release of inflammatory cytokines, oxidative stress, and changes in intestinal microflora, which may also contribute to disease progression. However, interfering with de novo fatty acid synthase by deleting the enzyme acetyl-CoA-carboxylase 1 in intestinal epithelial cells (IEC) leads to the deficiency of epithelial crypt structures and tissue regeneration, which seems to be due to Lgr5+ intestinal stem cell function. Thus, conflicting reports exist regarding high-fat diet effects on IBD animal models. This review will focus on the pathological basis of the link between dietary lipids intake and IBD and will cover the currently available pharmacological approaches.
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Affiliation(s)
| | | | - Sang Geon Kim
- Integrated Research Institute for Drug Development, College of Pharmacy, Dongguk University-Seoul, Goyang-si 10326, Gyeonggi-do, Republic of Korea; (S.J.K.); (M.S.K.)
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Agarwal AK, Tunison K, Vale G, McDonald JG, Li X, Horton JD, Garg A. Adipose-specific overexpression of human AGPAT2 in mice causes increased adiposity and mild hepatic dysfunction. iScience 2024; 27:108653. [PMID: 38274405 PMCID: PMC10809107 DOI: 10.1016/j.isci.2023.108653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 07/11/2023] [Accepted: 12/04/2023] [Indexed: 01/27/2024] Open
Abstract
AGPAT2, a critical enzyme involved in the biosynthesis of phospholipids and triacylglycerol (TAG), is highly expressed in adipose tissue (AT). Whether overexpression of AGPAT2 in AT will result in increased TAG synthesis (obesity) and its metabolic complications remains unknown. We overexpressed human AGPAT2 specifically in AT using the adiponectin promoter and report increased mass of subcutaneous, gonadal, and brown AT in wild-type mice. Unexpectedly, overexpression of hAGPAT2 did not change the pattern of phospholipid or TAG concentration of the AT depots. Although there is an increase in liver weight, plasma aspartate aminotransferase, and plasma insulin at various time points of the study, it did not result in significant liver dysfunction. Despite increased adiposity in the Tg-AT-hAGPAT2;mAgpat2+/+ mice, there was no significant increase in TAG concentration of AT. Therefore, this study suggests a role of AGPAT2 in the generation of AT, but not for adipocyte TAG synthesis.
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Affiliation(s)
- Anil K. Agarwal
- Section of Nutrition and Metabolic Diseases, Division of Endocrinology, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Katie Tunison
- Section of Nutrition and Metabolic Diseases, Division of Endocrinology, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Goncalo Vale
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Molecular Genetics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jeffrey G. McDonald
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Molecular Genetics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xilong Li
- Peter O’Donnell Jr. School of Public Health, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jay D. Horton
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Molecular Genetics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Abhimanyu Garg
- Section of Nutrition and Metabolic Diseases, Division of Endocrinology, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX 75390, USA
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Wang J, Jing J, Gong Z, Tang J, Wang L, Jia G, Liu G, Chen X, Tian G, Cai J, Kang B, Che L, Zhao H. Different Dietary Sources of Selenium Alleviate Hepatic Lipid Metabolism Disorder of Heat-Stressed Broilers by Relieving Endoplasmic Reticulum Stress. Int J Mol Sci 2023; 24:15443. [PMID: 37895123 PMCID: PMC10607182 DOI: 10.3390/ijms242015443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 10/18/2023] [Accepted: 10/20/2023] [Indexed: 10/29/2023] Open
Abstract
As global warming continues, the phenomenon of heat stress (HS) in broilers occurs frequently. The alleviating effect of different selenium (Se) sources on HS-induced hepatic lipid metabolism disorders in broilers remains unclear. This study compared the protective effects of four Se sources (sodium selenite; selenium yeast; selenomethionine; nano-Se) on HS-induced hepatic lipid metabolism disorder and the corresponding response of selenotranscriptome in the liver of broilers. The results showed that HS-induced liver injury and hepatic lipid metabolism disorder, which were reflected in the increased activity of serum alanine aminotransferase (ALT), the increased concentration of triacylglycerol (TG) and total cholesterol (TC), the increased activity of acetyl-CoA carboxylase (ACC), diacylglycerol O-acyltransferase (DGAT) and fatty acid synthase (FAS), and the decreased activity of hepatic lipase (HL) in the liver. The hepatic lipid metabolism disorder was accompanied by the increased mRNA expression of lipid synthesis related-genes, the decreased expression of lipidolysis-related genes, and the increased expression of endoplasmic reticulum (ER) stress biomarkers (PERK, IRE1, ATF6, GRP78). The dietary supplementation of four Se sources exhibited similar protective effects. Four Se sources increased liver Se concentration and promoted the expression of selenotranscriptome and several key selenoproteins, enhanced liver antioxidant capacity and alleviated HS-induced ER stress, and thus resisted the hepatic lipid metabolism disorders of broilers exposed to HS. In conclusion, dietary supplementation of four Se sources (0.3 mg/kg) exhibited similar protective effects on HS-induced hepatic lipid metabolism disorders of broilers, and the protective effect is connected to the relieving of ER stress.
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Affiliation(s)
- Jiayi Wang
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Jinzhong Jing
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Zhengyi Gong
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Jiayong Tang
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Longqiong Wang
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Gang Jia
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Guangmang Liu
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Xiaoling Chen
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Gang Tian
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Jingyi Cai
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Bo Kang
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China;
| | - Lianqiang Che
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
| | - Hua Zhao
- Key Laboratory for Animal Disease-Resistance Nutrition of Ministry of Education, of China Ministry of Agriculture and Rural Affairs, of Sichuan Province, Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; (J.W.); (J.J.); (Z.G.); (J.T.); (L.W.); (G.J.); (G.L.); (X.C.); (G.T.); (J.C.); (L.C.)
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Meng W, Brigance R, Mignone J, Negash L, Zhao G, Ahmad S, Wang W, Moore F, Ye XY, Sun JH, Mathur A, Li YX, Azzara A, Ma Z, Chu CH, Cullen MJ, Rooney S, Harvey S, Kopcho L, Abell L, O'Malley K, Keim W, Dierks EA, Chang S, Foster KA, Harden D, Dabros M, Goti V, De Oliveira C, Krishna G, Pelleymounter MA, Whaley J, Robl JA, Cheng D, Devasthale P. Discovery of 12 (BMS-986172) as a Highly Potent MGAT2 Inhibitor that Achieved Targeted Efficacious Exposures at a Low Human Dose for the Treatment of Metabolic Disorders. J Med Chem 2023; 66:13135-13147. [PMID: 37724542 DOI: 10.1021/acs.jmedchem.3c01147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/21/2023]
Abstract
A series of dihydropyridinone (DHP) compounds was prepared and evaluated for MGAT2 activity. The efforts led to the identification of novel tetrazolones with potent MGAT2 inhibitory activity and favorable in vitro profiles. Further tests of select analogues in mouse models revealed significant reduction in food intake and body weight. Subsequent studies in MGAT2 knockout mice with the lead candidate 12 (BMS-986172) showed on-target- and mechanism-based pharmacology. Moreover, its favorable pharmacokinetic (PK) profile and the lack of species variability in the glucuronidation potential resulted in a greater confidence level in the projection of a low dose for achieving targeted efficacious exposures in humans. Consistent with these projections, PK data from a phase 1 trial confirmed that targeted efficacious exposures could be achieved at a low dose in humans, which supported compound 12 as our second and potentially superior development candidate for the treatment of various metabolic disorders.
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Wang Y, Yan W, Lu Y, Du J, Tian X, Wu B, Peng S, Gu B, Cai W, Xiao Y. Intestinal Reg4 deficiency confers susceptibility to high-fat diet-induced liver steatosis by increasing intestinal fat absorption in mice. JHEP Rep 2023; 5:100700. [PMID: 37138677 PMCID: PMC10149362 DOI: 10.1016/j.jhepr.2023.100700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 01/31/2023] [Accepted: 01/31/2023] [Indexed: 05/05/2023] Open
Abstract
Background & Aims Regenerating gene family member 4 (REG4) is a novel marker for enteroendocrine cells and is selectively expressed in specialised enteroendocrine cells of the small intestine. However, the exact roles of REG4 are largely unknown. In this study we investigate the effects of REG4 on the development of dietary fat-dependent liver steatosis and the mechanisms involved. Methods Mice with intestinal-specific Reg4 deficiency (Reg4 ΔIEC ) and Reg4-floxed alleles (Reg4 fl/fl ) were generated to investigate the effects of Reg4 on diet-induced obesity and liver steatosis. Serum levels of REG4 were also measured in children with obesity using ELISA. Results Reg4 ΔIEC mice fed a high-fat diet demonstrated significantly increased intestinal fat absorption and were prone to obesity and hepatic steatosis. Importantly, Reg4 ΔIEC mice exhibit enhanced activation of adenosine monophosphate-activated protein kinase (AMPK) signalling and increased protein abundance of the intestinal fat transporters, as well as enzymes involved in triglyceride synthesis and packaging at the proximal small intestine. Moreover, REG4 administration reduced fat absorption, and decreased the expression of intestinal fat absorption-related proteins in cultured intestinal cells possibly via the CaMKK2-AMPK pathway. Serum REG4 levels were markedly lower in children with obesity with advanced liver steatosis (p <0.05). Serum REG4 levels were inversely correlated with levels of liver enzymes, homeostasis model assessment of insulin resistance, low-density lipoprotein cholesterol, and triglycerides. Conclusions Our findings directly link Reg4 deficiency with increased fat absorption and obesity-related liver steatosis, and suggest that REG4 may provide a potential target for prevention and treatment of liver steatosis in children. Impact and Implications Hepatic steatosis is a key histological feature of non-alcoholic fatty liver disease, which is the leading chronic liver disease in children leading to the development of metabolic diseases; however, little is known about mechanisms induced by dietary fat. Intestinal REG4 acts as a novel enteroendocrine hormone reducing high-fat-diet-induced liver steatosis with decreasing intestinal fat absorption. REG4 may be a novel target for treatment of paediatric liver steatosis from the perspective of crosstalk between intestine and liver.
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Affiliation(s)
- Ying Wang
- Division of Pediatric Gastroenterology and Nutrition, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Institute for Pediatric Research, Shanghai, China
- Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai, China
| | - Weihui Yan
- Division of Pediatric Gastroenterology and Nutrition, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Institute for Pediatric Research, Shanghai, China
- Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai, China
| | - Ying Lu
- Shanghai Institute for Pediatric Research, Shanghai, China
- Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai, China
| | - Jun Du
- Shanghai Institute for Pediatric Research, Shanghai, China
- Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai, China
| | - Xinbei Tian
- Division of Pediatric Gastroenterology and Nutrition, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Institute for Pediatric Research, Shanghai, China
- Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai, China
| | - Bo Wu
- Division of Pediatric Gastroenterology and Nutrition, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Department of Pediatric Surgery, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Shicheng Peng
- Shanghai Institute for Pediatric Research, Shanghai, China
- Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai, China
| | - Beilin Gu
- Shanghai Institute for Pediatric Research, Shanghai, China
- Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai, China
| | - Wei Cai
- Division of Pediatric Gastroenterology and Nutrition, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Institute for Pediatric Research, Shanghai, China
- Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai, China
- Department of Pediatric Surgery, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Corresponding authors. Addresses: Department of Pediatric Surgery, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University No. 1665, Kong Jiang Road, Shanghai 200092, China. Tel.: +86-21-25076441; Fax: +86-21-65791316.
| | - Yongtao Xiao
- Division of Pediatric Gastroenterology and Nutrition, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Institute for Pediatric Research, Shanghai, China
- Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai, China
- Department of Pediatric Surgery, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Division of Pediatric Gastroenterology and Nutrition, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, No. 1665, Kong Jiang Road, Shanghai 200092, China. Tel.: +86-21-25076445; Fax: +86-21-65791316.
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Li X, Liu Q, Pan Y, Chen S, Zhao Y, Hu Y. New insights into the role of dietary triglyceride absorption in obesity and metabolic diseases. Front Pharmacol 2023; 14:1097835. [PMID: 36817150 PMCID: PMC9932209 DOI: 10.3389/fphar.2023.1097835] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 01/20/2023] [Indexed: 02/05/2023] Open
Abstract
The incidence of obesity and associated metabolic diseases is increasing globally, adversely affecting human health. Dietary fats, especially triglycerides, are an important source of energy for the body, and the intestine absorbs lipids through a series of orderly and complex steps. A long-term high-fat diet leads to intestinal dysfunction, inducing obesity and metabolic disorders. Therefore, regulating dietary triglycerides absorption is a promising therapeutic strategy. In this review, we will discuss diverse aspects of the dietary triglycerides hydrolysis, fatty acid uptake, triglycerides resynthesis, chylomicron assembly, trafficking, and secretion processes in intestinal epithelial cells, as well as potential targets in this process that may influence dietary fat-induced obesity and metabolic diseases. We also mention the possible shortcomings and deficiencies in modulating dietary lipid absorption targets to provide a better understanding of their administrability as drugs in obesity and related metabolic disorders.
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Affiliation(s)
- Xiaojing Li
- Key Laboratory of Liver and Kidney Diseases (Ministry of Education), Institute of Liver Diseases, Shanghai Key Laboratory of Traditional Chinese Clinical Medicine, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Qiaohong Liu
- Institute of Clinical Pharmacology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yuqing Pan
- Key Laboratory of Liver and Kidney Diseases (Ministry of Education), Institute of Liver Diseases, Shanghai Key Laboratory of Traditional Chinese Clinical Medicine, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Si Chen
- Key Laboratory of Liver and Kidney Diseases (Ministry of Education), Institute of Liver Diseases, Shanghai Key Laboratory of Traditional Chinese Clinical Medicine, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yu Zhao
- Key Laboratory of Liver and Kidney Diseases (Ministry of Education), Institute of Liver Diseases, Shanghai Key Laboratory of Traditional Chinese Clinical Medicine, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China,*Correspondence: Yu Zhao, ; Yiyang Hu,
| | - Yiyang Hu
- Key Laboratory of Liver and Kidney Diseases (Ministry of Education), Institute of Liver Diseases, Shanghai Key Laboratory of Traditional Chinese Clinical Medicine, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China,Institute of Clinical Pharmacology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China,*Correspondence: Yu Zhao, ; Yiyang Hu,
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8
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Cook JR, Kohan AB, Haeusler RA. An Updated Perspective on the Dual-Track Model of Enterocyte Fat Metabolism. J Lipid Res 2022; 63:100278. [PMID: 36100090 PMCID: PMC9593242 DOI: 10.1016/j.jlr.2022.100278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 08/08/2022] [Accepted: 08/31/2022] [Indexed: 02/04/2023] Open
Abstract
The small intestinal epithelium has classically been envisioned as a conduit for nutrient absorption, but appreciation is growing for a larger and more dynamic role for enterocytes in lipid metabolism. Considerable gaps remain in our knowledge of this physiology, but it appears that the enterocyte's structural polarization dictates its behavior in fat partitioning, treating fat differently based on its absorption across the apical versus the basolateral membrane. In this review, we synthesize existing data and thought on this dual-track model of enterocyte fat metabolism through the lens of human integrative physiology. The apical track includes the canonical pathway of dietary lipid absorption across the apical brush-border membrane, leading to packaging and secretion of those lipids as chylomicrons. However, this track also reserves a portion of dietary lipid within cytoplasmic lipid droplets for later uses, including the "second-meal effect," which remains poorly understood. At the same time, the enterocyte takes up circulating fats across the basolateral membrane by mechanisms that may include receptor-mediated import of triglyceride-rich lipoproteins or their remnants, local hydrolysis and internalization of free fatty acids, or enterocyte de novo lipogenesis using basolaterally absorbed substrates. The ultimate destinations of basolateral-track fat may include fatty acid oxidation, structural lipid synthesis, storage in cytoplasmic lipid droplets, or ultimate resecretion, although the regulation and purposes of this basolateral track remain mysterious. We propose that the enterocyte integrates lipid flux along both of these tracks in order to calibrate its overall program of lipid metabolism.
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Affiliation(s)
- Joshua R. Cook
- Naomi Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, NY, USA,Division of Endocrinology, Diabetes & Metabolism, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - Alison B. Kohan
- Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Rebecca A. Haeusler
- Naomi Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, NY, USA,Department of Pathology and Cell Biology; Columbia University College of Physicians and Surgeons, New York, NY, USA,For correspondence: Rebecca A. Haeusler
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Ghanem M, Lewis GF, Xiao C. Recent advances in cytoplasmic lipid droplet metabolism in intestinal enterocyte. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159197. [PMID: 35820577 DOI: 10.1016/j.bbalip.2022.159197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 06/03/2022] [Accepted: 06/14/2022] [Indexed: 11/30/2022]
Abstract
Processing of dietary fats in the intestine is a highly regulated process that influences whole-body energy homeostasis and multiple physiological functions. Dysregulated lipid handling in the intestine leads to dyslipidemia and atherosclerotic cardiovascular disease. In intestinal enterocytes, lipids are incorporated into lipoproteins and cytoplasmic lipid droplets (CLDs). Lipoprotein synthesis and CLD metabolism are inter-connected pathways with multiple points of regulation. This review aims to highlight recent advances in the regulatory mechanisms of lipid processing in the enterocyte, with particular focus on CLDs. In-depth understanding of the regulation of lipid metabolism in the enterocyte may help identify therapeutic targets for the treatment and prevention of metabolic disorders.
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Affiliation(s)
- Murooj Ghanem
- Department of Anatomy, Physiology and Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Gary F Lewis
- Departments of Medicine and Physiology, University of Toronto, and University Health Network, Toronto, ON, Canada
| | - Changting Xiao
- Department of Anatomy, Physiology and Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
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10
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SCD1 is nutritionally and spatially regulated in the intestine and influences systemic postprandial lipid homeostasis and gut-liver crosstalk. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159195. [PMID: 35718096 DOI: 10.1016/j.bbalip.2022.159195] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 04/21/2022] [Accepted: 06/01/2022] [Indexed: 01/27/2023]
Abstract
Stearoyl-CoA desaturase-1 is an endoplasmic reticulum (ER)-membrane resident protein that inserts a double bond into saturated fatty acids, converting them into their monounsaturated counterparts. Previous studies have demonstrated an important role for SCD1 in modulating tissue and systemic health. Specifically, lack of hepatic or cutaneous SCD1 results in significant reductions in tissue esterified lipids. While the intestine is an important site of lipid esterification and assimilation into the body, the regulation of intestinal SCD1 or its impact on lipid composition in the intestine and other tissues has not been investigated. Here we report that unlike other lipogenic enzymes, SCD1 is enriched in the distal small intestine and in the colon of chow-fed mice and is robustly upregulated by acute refeeding of a high-sucrose diet. We generated a mouse model lacking SCD1 specifically in the intestine (iKO mice). These mice have significant reductions not only in intestinal lipids, but also in plasma triacylglycerols, diacylglycerols, cholesterol esters, and free cholesterol. Additionally, hepatic accumulation of diacylglycerols is significantly reduced in iKO mice. Comprehensive targeted lipidomic profiling revealed a consistent reduction in the myristoleic (14:1) to myristic (14:0) acid ratios in intestine, liver, and plasma of iKO mice. Consistent with the reduction of the monounsaturated fatty acid myristoleic acid in hepatic lipids of chow fed iKO mice, hepatic expression of Pgc-1α, Sirt1, and related fatty acid oxidation genes were reduced in chow-fed iKO mice. Further, lack of intestinal SCD1 reduced expression of de novo lipogenic genes in distal intestine of chow-fed mice and in the livers of mice fed a lipogenic high-sucrose diet. Taken together, these studies reveal a novel pattern of expression of SCD1 in the intestine. They also demonstrate that intestinal SCD1 modulates lipid content and composition of not only intestinal tissues, but also that of plasma and liver. Further, these data point to intestinal SCD1 as a modulator of gut-liver crosstalk, potentially through the production of novel signaling lipids such as myristoleic acid. These data have important implications to understanding how intestinal SCD1 may modulate risk for post-prandial lipemia, hepatic steatosis, and related pathologies.
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11
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The monoacylglycerol acyltransferase pathway contributes to triacylglycerol synthesis in HepG2 cells. Sci Rep 2022; 12:4943. [PMID: 35322811 PMCID: PMC8943211 DOI: 10.1038/s41598-022-08946-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 03/14/2022] [Indexed: 12/19/2022] Open
Abstract
The monoacylglycerol acyltransferase (MGAT) pathway has a well-established role in the small intestine where it facilitates the absorption of dietary fat. In enterocytes, MGAT participates in the resynthesis of triacylglycerol using substrates (monoacylglycerol and fatty acids) generated in the gut lumen from the breakdown of triacylglycerol consumed in the diet. MGAT activity is also present in the liver, but its role in triacylglycerol metabolism in this tissue remains unclear. The predominant MGAT isoforms present in human liver appear to be MGAT2 and MGAT3. The objective of this study was to use selective small molecule inhibitors of MGAT2 and MGAT3 to determine the contributions of these enzymes to triacylglycerol production in liver cells. We found that pharmacological inhibition of either enzyme had no effect on TG mass in HepG2 cells but did alter lipid droplet size and number. Inhibition of MGAT2 did result in decreased DG and TG synthesis and TG secretion. Interestingly, MGAT2 preferentially utilized 2-monoacylglycerol derived from free glycerol and not from exogenously added 2-monoacylglycerol. In contrast, inhibition of MGAT3 had very little effect on TG metabolism in HepG2 cells. Additionally, we demonstrated that the MGAT activity of DGAT1 only makes a minor contribution to TG synthesis in intact HepG2 cells. Our data demonstrated that the MGAT pathway has a role in hepatic lipid metabolism with MGAT2, more so than MGAT3, contributing to TG synthesis and secretion.
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12
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Stone SJ. Mechanisms of intestinal triacylglycerol synthesis. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159151. [PMID: 35296424 DOI: 10.1016/j.bbalip.2022.159151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 01/13/2022] [Accepted: 02/16/2022] [Indexed: 02/07/2023]
Abstract
Triacylglycerols are a major source of stored energy that are obtained either from the diet or can be synthesized to some extent by most tissues. Alterations in pathways of triacylglycerol metabolism can result in their excessive accumulation leading to obesity, insulin resistance, cardiovascular disease and nonalcoholic fatty liver disease. Most tissues in mammals synthesize triacylglycerols via the glycerol 3-phosphate pathway. However, in the small intestine the monoacylglycerol acyltransferase pathway is the predominant pathway for triacylglycerol biosynthesis where it participates in the absorption of dietary triacylglycerol. In this review, the enzymes that are part of both the glycerol 3-phosphate and monoacylglycerol acyltransferase pathways and their contributions to intestinal triacylglycerol metabolism are reviewed. The potential of some of the enzymes involved in triacylglycerol synthesis in the small intestine as possible therapeutic targets for treating metabolic disorders associated with elevated triacylglycerol is briefly discussed.
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Affiliation(s)
- Scot J Stone
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
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13
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Lebrun LJ, Moreira S, Tavernier A, Niot I. Postprandial consequences of lipid absorption in the onset of obesity: Role of intestinal CD36. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159154. [DOI: 10.1016/j.bbalip.2022.159154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 03/14/2022] [Accepted: 03/16/2022] [Indexed: 10/18/2022]
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14
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Zhu L, Fu J, Xiao X, Wang F, Jin M, Fang W, Wang Y, Zong X. Faecal microbiota transplantation-mediated jejunal microbiota changes halt high-fat diet-induced obesity in mice via retarding intestinal fat absorption. Microb Biotechnol 2021; 15:337-352. [PMID: 34704376 PMCID: PMC8719817 DOI: 10.1111/1751-7915.13951] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 09/13/2021] [Accepted: 10/06/2021] [Indexed: 01/21/2023] Open
Abstract
Faecal Microbiota Transplantation (FMT) is considered as a promising technology to fight against obesity. Wild boar has leanermuscle and less fat in comparison to the domestic pig, which were thought to be related with microbiota. To investigate the function and mechanism of the wild boar microbiota on obesity, we first analysed the wild boar microbiota composition via 16S rDNA sequencing, which showed that Firmicutes and Proteobacteria were the dominant bacteria. Then, we established a high‐fat diet (HFD)‐induced obesity model, and transfer low and high concentrations of wild boar faecal suspension in mice for 9 weeks. The results showed that FMT prevented HFD‐induced obesity and lipid metabolism disorders, and altered the jejunal microbiota composition especially increasing the abundance of the Lactobacillus and Romboutsia, which were negatively correlated with obesity‐related indicators. Moreover, we found that the anti‐obesity effect of wild boar faecal suspension was associated with jejunal N6‐methyladenosine (m6A) levels. Overall, these results suggest that FMT has a mitigating effect on HFD‐induced obesity, which may be due to the impressive effects of FMT on the microbial composition and structure of the jejunum. These changes further alter intestinal lipid metabolism and m6A levels to achieve resistance to obesity.
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Affiliation(s)
- Luoyi Zhu
- National Engineering Laboratory for Feed Safety and Pollution Prevention and Controlling, National Development and Reform Commission, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, Zhejiang, 310058, China
| | - Jie Fu
- National Engineering Laboratory for Feed Safety and Pollution Prevention and Controlling, National Development and Reform Commission, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, Zhejiang, 310058, China
| | - Xiao Xiao
- National Engineering Laboratory for Feed Safety and Pollution Prevention and Controlling, National Development and Reform Commission, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, Zhejiang, 310058, China
| | - Fengqin Wang
- National Engineering Laboratory for Feed Safety and Pollution Prevention and Controlling, National Development and Reform Commission, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, Zhejiang, 310058, China
| | - Mingliang Jin
- National Engineering Laboratory for Feed Safety and Pollution Prevention and Controlling, National Development and Reform Commission, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, Zhejiang, 310058, China
| | - Weihuan Fang
- Zhejiang University Institute of Preventive Veterinary Medicine, Hangzhou, Zhejiang, 310058, China.,Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, 310058, China
| | - Yizhen Wang
- National Engineering Laboratory for Feed Safety and Pollution Prevention and Controlling, National Development and Reform Commission, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, Zhejiang, 310058, China
| | - Xin Zong
- National Engineering Laboratory for Feed Safety and Pollution Prevention and Controlling, National Development and Reform Commission, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, Zhejiang, 310058, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, Zhejiang, 310058, China
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15
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Wang S, Liu J, Zhao W, Wang G, Gao S. Selection of candidate genes for differences in fat metabolism between cattle subcutaneous and perirenal adipose tissue based on RNA-seq. Anim Biotechnol 2021:1-12. [PMID: 34693889 DOI: 10.1080/10495398.2021.1991937] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The site of fat deposition plays an important role in meat quality and body health. Biologically, the perirenal visceral fat (PF) and back subcutaneous fat (BF) are distinct. Angus and Simmental cattle (Bos taurus) were used as models. HE staining, triglyceride assay kit and RNA-seq were used to analyze the differences in tissue morphology and lipid accumulation, co-genes, and differentially expressed genes (DEGs) between the two tissues. According to the findings, BF has a smaller cell area and greater lipid deposition ability than PF. RNA-seq generated approximately 10.99 Gb of data in each library, and 23,472 genes were identified. The genes FABP4, ADIRF, and SCD that are related to adipose deposition were highly expressed in four tissues. There were 1678 DEGs and 1955 DEGs between BF and PF in Angus and Simmental cattle respectively. Gene Ontology function analysis identified several DEGs involved in metabolism. KEGG pathway analysis showed that four pathways related to fat metabolism were enriched. In the BF, seven genes (COL1A1, COL1A2, COL3A1, COL2A1, RXRA, C1QTNF7, and MOGAT2) were up-regulated. Five genes (ADRB3, ABHD5, CPT1B, CD36, LPIN1) were down-regulated. This study identified candidate genes that led to differences in fat metabolism, which could be useful in cattle breeding.
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Affiliation(s)
- Siyuan Wang
- College of Animal Science and Technology, Inner Mongolia University for Nationalities, Tongliao, Inner Mongolia Autonomous Region, China
| | - Jie Liu
- Domestic Fowls Research Institute, Shandong Academy of Agricultural Sciences, Jinan, Shandong, China
| | - Weiming Zhao
- College of Animal Science and Technology, Inner Mongolia University for Nationalities, Tongliao, Inner Mongolia Autonomous Region, China
| | - Guofu Wang
- College of Animal Science and Technology, Inner Mongolia University for Nationalities, Tongliao, Inner Mongolia Autonomous Region, China
| | - Shuxin Gao
- College of Animal Science and Technology, Inner Mongolia University for Nationalities, Tongliao, Inner Mongolia Autonomous Region, China
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16
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Ochiai K, Hirooka R, Sakaino M, Takeuchi S, Hira T. 2-Arachidonoyl glycerol potently induces cholecystokinin secretion in murine enteroendocrine STC-1 cells via cannabinoid receptor CB1. Lipids 2021; 56:603-611. [PMID: 34533218 DOI: 10.1002/lipd.12323] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 08/09/2021] [Accepted: 09/01/2021] [Indexed: 11/05/2022]
Abstract
Cholecystokinin (CCK) is a peptide hormone secreted from enteroendocrine cells and regulates the exocrine pancreas, gastric motility, and appetite. Dietary triacylglycerols are hydrolyzed to fatty acids (FA) and 2-monoacylglycerols (2-MAG) in the small intestine. Although it is well known that FA stimulate CCK secretion, whether 2-MAG have the CCK-releasing activity remains unclear. We examined the CCK-releasing activity of four commercially available 2-MAG in a murine CCK-producing cell line, STC-1, and the molecular mechanism underlying 2-MAG-induced CCK secretion. CCK released from the cells was measured using ELISA. Among four 2-MAG (2-palmitoyl, 2-oleoyl, 2-linoleoyl, and 2-arachidonoyl monoacylglycerols) examined, 2-arachidonoyl glycerol (2-AG) potently stimulated CCK secretion in a dose-dependent manner. Structurally related compounds, such as 2-arachidonoyl glycerol ether and 1-arachidonoyl glycerol, did not stimulate CCK secretion. Both arachidonic acid and 2-AG stimulated CCK secretion at 100 μM, but only 2-AG did at 50 μM. 2-AG-induced CCK secretion but not arachidonic acid-induced CCK secretion was attenuated by treatment with a cannabinoid receptor 1 (CB1) antagonist. These results indicate that a specific 2-MAG, 2-AG, directly stimulates CCK secretion via CB1.
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Affiliation(s)
- Keita Ochiai
- Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
| | | | | | | | - Tohru Hira
- Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan
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17
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Tang J, Feng Y, Zhang B, Wu Y, Guo Z, Liang S, Zhou Z, Xie M, Hou S. Severe pantothenic acid deficiency induces alterations in the intestinal mucosal proteome of starter Pekin ducks. BMC Genomics 2021; 22:491. [PMID: 34193047 PMCID: PMC8246668 DOI: 10.1186/s12864-021-07820-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 06/18/2021] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Pantothenic acid deficiency (PAD) results in growth depression and intestinal hypofunction of animals. However, the underlying molecular mechanisms remain to be elucidated. Mucosal proteome might reflect dietary influences on physiological processes. RESULTS A total of 128 white Pekin ducks of one-day-old were randomly assigned to two groups, fed either a PAD or a pantothenic acid adequate (control, CON) diet. After a 16-day feeding period, two ducks from each replicate were sampled to measure plasma parameters, intestinal morphology, and mucosal proteome. Compared to the CON group, high mortality, growth retardation, fasting hypoglycemia, reduced plasma insulin, and oxidative stress were observed in the PAD group. Furthermore, PAD induced morphological alterations of the small intestine indicated by reduced villus height and villus surface area of duodenum, jejunum, and ileum. The duodenum mucosal proteome of ducks showed that 198 proteins were up-regulated and 223 proteins were down-regulated (> 1.5-fold change) in the PAD group compared to those in the CON group. Selected proteins were confirmed by Western blotting. Pathway analysis of these proteins exhibited the suppression of glycolysis and gluconeogenesis, fatty acid beta oxidation, tricarboxylic acid cycle, oxidative phosphorylation, oxidative stress, and intestinal absorption in the PAD group, indicating impaired energy generation and abnormal intestinal absorption. We also show that nine out of eleven proteins involved in regulation of actin cytoskeleton were up-regulated by PAD, probably indicates reduced intestinal integrity. CONCLUSION PAD leads to growth depression and intestinal hypofunction of ducks, which are associated with impaired energy generation, abnormal intestinal absorption, and regulation of actin cytoskeleton processes. These findings provide insights into the mechanisms of intestinal hypofunction induced by PAD.
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Affiliation(s)
- Jing Tang
- State Key Laboratory of Animal Nutrition, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Yulong Feng
- State Key Laboratory of Animal Nutrition, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.,Guizhou Animal Husbandry and Veterinary Research Institute, Guizhou Academy of Agricultural Sciences, Guiyang, 550000, Guizhou, China
| | - Bo Zhang
- State Key Laboratory of Animal Nutrition, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Yongbao Wu
- State Key Laboratory of Animal Nutrition, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Zhanbao Guo
- State Key Laboratory of Animal Nutrition, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Suyun Liang
- State Key Laboratory of Animal Nutrition, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Zhengkui Zhou
- State Key Laboratory of Animal Nutrition, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Ming Xie
- State Key Laboratory of Animal Nutrition, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Shuisheng Hou
- State Key Laboratory of Animal Nutrition, Key Laboratory of Animal (Poultry) Genetics Breeding and Reproduction, Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
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18
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Grevengoed TJ, Trammell SA, Svenningsen JS, Makarov MV, Nielsen TS, Jacobsen JCB, Treebak JT, Calder PC, Migaud ME, Cravatt BF, Gillum MP. An abundant biliary metabolite derived from dietary omega-3 polyunsaturated fatty acids regulates triglycerides. J Clin Invest 2021; 131:143861. [PMID: 33507883 DOI: 10.1172/jci143861] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 01/20/2021] [Indexed: 12/23/2022] Open
Abstract
Omega-3 fatty acids from fish oil reduce triglyceride levels in mammals, yet the mechanisms underlying this effect have not been fully clarified, despite the clinical use of omega-3 ethyl esters to treat severe hypertriglyceridemia and reduce cardiovascular disease risk in humans. Here, we identified in bile a class of hypotriglyceridemic omega-3 fatty acid-derived N-acyl taurines (NATs) that, after dietary omega-3 fatty acid supplementation, increased to concentrations similar to those of steroidal bile acids. The biliary docosahexaenoic acid-containing (DHA-containing) NAT C22:6 NAT was increased in human and mouse plasma after dietary omega-3 fatty acid supplementation and potently inhibited intestinal triacylglycerol hydrolysis and lipid absorption. Supporting this observation, genetic elevation of endogenous NAT levels in mice impaired lipid absorption, whereas selective augmentation of C22:6 NAT levels protected against hypertriglyceridemia and fatty liver. When administered pharmacologically, C22:6 NAT accumulated in bile and reduced high-fat diet-induced, but not sucrose-induced, hepatic lipid accumulation in mice, suggesting that C22:6 NAT is a negative feedback mediator that limits excess intestinal lipid absorption. Thus, biliary omega-3 NATs may contribute to the hypotriglyceridemic mechanism of action of fish oil and could influence the design of more potent omega-3 fatty acid-based therapeutics.
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Affiliation(s)
- Trisha J Grevengoed
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Samuel Aj Trammell
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens S Svenningsen
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Mikhail V Makarov
- Mitchell Cancer Institute, Department of Pharmacology, University of South Alabama, Mobile, Alabama, USA
| | - Thomas Svava Nielsen
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens Christian Brings Jacobsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jonas T Treebak
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Philip C Calder
- Faculty of Medicine, University of Southampton, Southampton, United Kingdom.,National Institute for Health Research (NIHR) Southampton Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust and University of Southampton, Southampton, United Kingdom
| | - Marie E Migaud
- Mitchell Cancer Institute, Department of Pharmacology, University of South Alabama, Mobile, Alabama, USA
| | - Benjamin F Cravatt
- Departments of Cell Biology and Chemistry, The Scripps Research Institute, La Jolla, California, USA
| | - Matthew P Gillum
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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19
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Levy E, Beaulieu JF, Spahis S. From Congenital Disorders of Fat Malabsorption to Understanding Intra-Enterocyte Mechanisms Behind Chylomicron Assembly and Secretion. Front Physiol 2021; 12:629222. [PMID: 33584351 PMCID: PMC7873531 DOI: 10.3389/fphys.2021.629222] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 01/06/2021] [Indexed: 11/13/2022] Open
Abstract
During the last two decades, a large body of information on the events responsible for intestinal fat digestion and absorption has been accumulated. In particular, many groups have extensively focused on the absorptive phase in order to highlight the critical "players" and the main mechanisms orchestrating the assembly and secretion of chylomicrons (CM) as essential vehicles of alimentary lipids. The major aim of this article is to review understanding derived from basic science and clinical conditions associated with impaired packaging and export of CM. We have particularly insisted on inborn metabolic pathways in humans as well as on genetically modified animal models (recapitulating pathological features). The ultimate goal of this approach is that "experiments of nature" and in vivo model strategy collectively allow gaining novel mechanistic insight and filling the gap between the underlying genetic defect and the apparent clinical phenotype. Thus, uncovering the cause of disease contributes not only to understanding normal physiologic pathway, but also to capturing disorder onset, progression, treatment and prognosis.
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Affiliation(s)
- Emile Levy
- Research Centre, CHU Ste-Justine, Université de Montréal, Montreal, QC, Canada
- Department of Nutrition, Université de Montréal, Montreal, QC, Canada
- Department of Pediatrics, Université de Montréal, Montreal, QC, Canada
| | - Jean François Beaulieu
- Laboratory of Intestinal Physiopathology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Schohraya Spahis
- Research Centre, CHU Ste-Justine, Université de Montréal, Montreal, QC, Canada
- Department of Nutrition, Université de Montréal, Montreal, QC, Canada
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20
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Singh Y, Datey A, Chakravortty D, Tumaney AW. Novel Cell-Based Assay to Investigate Monoacylglycerol Acyltransferase 2 Inhibitory Activity Using HIEC-6 Cell Line. ACS OMEGA 2021; 6:1732-1740. [PMID: 33490832 PMCID: PMC7818593 DOI: 10.1021/acsomega.0c05950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 12/23/2020] [Indexed: 06/12/2023]
Abstract
The dietary triacylglycerol (TAG) gets absorbed and accumulated in the body through the monoacylglycerol (MAG) pathway, which plays a major role in obesity and related disorders. The main enzyme of this pathway, monoacylglycerol acyltransferase 2 (MGAT2), is considered as a potential target for developing antiobesity compounds. Hence, there is a need for in vitro cell-based assays for screening the potential leads for MGAT2 inhibitors. Because of synthetic inhibitor's side effects, there is an increased interest in natural extracts as potential leads. Hence, we have optimized a 2-MAG-induced TAG accumulation inhibitory cell-based assay to screen natural extracts using the HIEC-6 cell line. A concentration-dependent TAG accumulation was observed when the HIEC-6 cells were fed with exogenous 2-MAG. The TAG accumulation was confirmed by in situ BODIPY staining and was quantified. However, no TAG accumulation was seen when the cells were fed with exogenous DAG or TAG, suggesting MGAT2-mediated MAG uptake and its conversion to TAG. We demonstrated the utility of this assay by screening five different plant-based aqueous extracts. These extracts showed various inhibition levels (25% to 30%) of 2-MAG-induced TAG accumulation in the HIEC-6. The MGAT2 inhibitory potential of these extracts was confirmed by an in vitro MGAT2 assay. This cell-based assay adds a new methodology for screening, developing, and evaluating MGAT2 inhibitors for addressing obesity and related disorders.
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Affiliation(s)
- Yeshvanthi Singh
- Academy
of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Department
of Lipid Science, Council of Scientific
and Industrial Research−Central Food Technological Research
Institute, Mysuru 570 020, India
| | - Akshay Datey
- Department
of Microbiology and Cell Biology, Indian
Institute of Science, Bangalore 560012, India
| | - Dipshikha Chakravortty
- Department
of Microbiology and Cell Biology, Indian
Institute of Science, Bangalore 560012, India
| | - Ajay W. Tumaney
- Academy
of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Department
of Lipid Science, Council of Scientific
and Industrial Research−Central Food Technological Research
Institute, Mysuru 570 020, India
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21
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Markovic MA, Srikrishnaraj A, Tsang D, Brubaker PL. Requirement for the intestinal epithelial insulin-like growth factor-1 receptor in the intestinal responses to glucagon-like peptide-2 and dietary fat. FASEB J 2020; 34:6628-6640. [PMID: 32212202 DOI: 10.1096/fj.202000169r] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/28/2020] [Accepted: 03/10/2020] [Indexed: 12/13/2022]
Abstract
The intestinal hormone, glucagon-like peptide-2 (GLP-2), enhances the enterocyte chylomicron production. However, GLP-2 is known to require the intestinal-epithelial insulin-like growth factor-1 receptor (IE-IGF-1R) for its other actions to increase intestinal growth and barrier function. The role of the IE-IGF-1R in enterocyte lipid handling was thus tested in the GLP-2 signaling pathway, as well as in response to a Western diet (WD). IE-IGF-1R knockout (KO) and control mice were treated for 11 days with h(GLY2 )GLP-2 or fed a WD for 18 weeks followed by a duodenal fat tolerance test with C14 -labeled triolein. Human Caco-2BBE cells were treated with an IGF-1R antagonist or signaling inhibitors to determine triglyceride-associated protein expression. The IE-IGF-1R was required for GLP-2-induced increases in CD36 and FATP-4 in chow-fed mice, and for expression in vitro; FATP-4 also required PI3K/Akt. Although WD-fed IE-IGF-1R KO mice demonstrated normal CD36 expression, the protein was incorrectly localized 2h post-duodenal fat administration. IE-IGF-1R KO also prevented the WD-induced increase in MTP and decrease in APOC3, increased jejunal mucosal C14 -fat accumulation, and elevated plasma triglyceride and C14 -fat levels. Collectively, these studies elucidate new roles for the IE-IGF-1R in enterocyte lipid handling, under basal conditions and in response to GLP-2 and WD-feeding.
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Affiliation(s)
| | | | - Derek Tsang
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Patricia L Brubaker
- Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Medicine, University of Toronto, Toronto, ON, Canada
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22
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Regulation of intestinal lipid metabolism: current concepts and relevance to disease. Nat Rev Gastroenterol Hepatol 2020; 17:169-183. [PMID: 32015520 DOI: 10.1038/s41575-019-0250-7] [Citation(s) in RCA: 208] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/02/2019] [Indexed: 12/21/2022]
Abstract
Lipids entering the gastrointestinal tract include dietary lipids (triacylglycerols, cholesteryl esters and phospholipids) and endogenous lipids from bile (phospholipids and cholesterol) and from shed intestinal epithelial cells (enterocytes). Here, we comprehensively review the digestion, uptake and intracellular re-synthesis of intestinal lipids as well as their packaging into pre-chylomicrons in the endoplasmic reticulum, their modification in the Golgi apparatus and the exocytosis of the chylomicrons into the lamina propria and subsequently to lymph. We also discuss other fates of intestinal lipids, including intestinal HDL and VLDL secretion, cytosolic lipid droplets and fatty acid oxidation. In addition, we highlight the applicability of these findings to human disease and the development of therapeutics targeting lipid metabolism. Finally, we explore the emerging role of the gut microbiota in modulating intestinal lipid metabolism and outline key questions for future research.
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23
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Lackey AI, Chen T, Zhou YX, Bottasso Arias NM, Doran JM, Zacharisen SM, Gajda AM, Jonsson WO, Córsico B, Anthony TG, Joseph LB, Storch J. Mechanisms underlying reduced weight gain in intestinal fatty acid-binding protein (IFABP) null mice. Am J Physiol Gastrointest Liver Physiol 2020; 318:G518-G530. [PMID: 31905021 PMCID: PMC7099495 DOI: 10.1152/ajpgi.00120.2019] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 12/13/2019] [Accepted: 12/13/2019] [Indexed: 02/06/2023]
Abstract
Intestinal-fatty acid binding protein (IFABP; FABP2) is a 15-kDa intracellular protein abundantly present in the cytosol of the small intestinal (SI) enterocyte. High-fat (HF) feeding of IFABP-/- mice resulted in reduced weight gain and fat mass relative to wild-type (WT) mice. Here, we examined intestinal properties that may underlie the observed lean phenotype of high fat-fed IFABP-/- mice. No alterations in fecal lipid content were found, suggesting that the IFABP-/- mice are not malabsorbing dietary fat. However, the total excreted fecal mass, normalized to food intake, was increased for the IFABP-/- mice relative to WT mice. Moreover, intestinal transit time was more rapid in the IFABP-/- mice. IFABP-/- mice displayed a shortened average villus length, a thinner muscularis layer, reduced goblet cell density, and reduced Paneth cell abundance. The number of proliferating cells in the crypts of IFABP-/- mice did not differ from that of WT mice, suggesting that the blunt villi phenotype is not due to alterations in proliferation. IFABP-/- mice were observed to have altered expression of genes and proteins related to intestinal structure, while immunohistochemical analyses revealed increased staining for markers of inflammation. Taken together, these studies indicate that the ablation of IFABP, coupled with high-fat feeding, leads to changes in gut motility and morphology, which likely contribute to the relatively leaner phenotype occurring at the whole-body level. Thus, IFABP is likely involved in dietary lipid sensing and signaling, influencing intestinal motility, intestinal structure, and nutrient absorption, thereby impacting systemic energy metabolism.NEW & NOTEWORTHY Intestinal fatty acid binding protein (IFABP) is thought to be essential for the efficient uptake and trafficking of dietary fatty acids. In this study, we demonstrate that high-fat-fed IFABP-/- mice have an increased fecal output and are likely malabsorbing other nutrients in addition to lipid. Furthermore, we observe that the ablation of IFABP leads to marked alterations in intestinal morphology and secretory cell abundance.
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Affiliation(s)
- Atreju I Lackey
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey
- Rutgers Center for Lipid Research, New Brunswick, New Jersey
| | - Tina Chen
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey
| | - Yin X Zhou
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey
| | - Natalia M Bottasso Arias
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Justine M Doran
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey
| | - Sophia M Zacharisen
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey
| | - Angela M Gajda
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey
- Rutgers Center for Lipid Research, New Brunswick, New Jersey
| | - William O Jonsson
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey
- Rutgers Center for Lipid Research, New Brunswick, New Jersey
| | - Betina Córsico
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Tracy G Anthony
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey
- Rutgers Center for Lipid Research, New Brunswick, New Jersey
| | - Laurie B Joseph
- Rutgers Center for Lipid Research, New Brunswick, New Jersey
- Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, New Brunswick, New Jersey
| | - Judith Storch
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey
- Rutgers Center for Lipid Research, New Brunswick, New Jersey
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24
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Liu H, Zhang H, Wang X, Yu X, Hu C, Zhang X. Alterations of DNA methylation profile in proximal jejunum potentially contribute to the beneficial effects of gastric bypass in a diabetic rat model. Surg Obes Relat Dis 2019; 15:1291-1298. [DOI: 10.1016/j.soard.2019.05.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Revised: 04/08/2019] [Accepted: 05/19/2019] [Indexed: 10/26/2022]
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25
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Yoshida K, Kita Y, Tokuoka SM, Hamano F, Yamazaki M, Sakimura K, Kano M, Shimizu T. Monoacylglycerol lipase deficiency affects diet-induced obesity, fat absorption, and feeding behavior in CB 1 cannabinoid receptor-deficient mice. FASEB J 2018; 33:2484-2497. [PMID: 30265576 DOI: 10.1096/fj.201801203r] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Excess energy intake causes obesity, which leads to insulin resistance and various other complications of metabolic syndrome, including diabetes, atherosclerosis, dyslipidemia, and nonalcoholic fatty liver disease. Although recent studies have depicted altered lipid metabolism as an underlying feature, the detailed mechanisms are still unclear. Here we describe a possible role in high-fat diet (HFD)-induced obesity for monoacylglycerol lipase (MGL), an enzyme that is also known to hydrolyze the endocannabinoid 2-arachidonoylglycerol in brain. MGL-deficient [MGL-knockout (KO)] mice fed a HFD gained less body weight than wild-type mice and were protected from insulin resistance and hepatic steatosis. Food intake and energy expenditure were not altered in MGL-KO mice, but blood triglyceride levels after oral olive oil gavage were suppressed, indicating a role for MGL in intestinal fat absorption. Experiments with cannabinoid receptor type 1 (CB1)/MGL double-KO mice revealed that these phenotypes may include mechanisms that are independent of CB1-receptor-mediated endocannabinoid functions. We also noted that MGL-KO mice had less preference for HFD over normal chow diet. Oral but not intraperitoneal lipid administration strongly suppressed the appetites of MGL-KO and CB1/MGL double-KO mice, but not of wild-type and CB1-KO mice. Appetite suppression was reversed by vagotomy, suggesting involvement of MGL in the gut-brain axis regulation of appetite. Our results provide mechanistic insights of MGL's role in diet-induced obesity, lipid metabolic disorder, and regulation of appetite.-Yoshida, K., Kita, Y., Tokuoka, S. M., Hamano, F., Yamazaki, M., Sakimura, K., Kano, M., Shimizu, T. Monoacylglycerol lipase deficiency affects diet-induced obesity, fat absorption, and feeding behavior in CB1 cannabinoid receptor-deficient mice.
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Affiliation(s)
- Kenji Yoshida
- Department of Lipidomics, The University of Tokyo, Tokyo, Japan
| | - Yoshihiro Kita
- Department of Lipidomics, The University of Tokyo, Tokyo, Japan.,Life Sciences Core Facility The University of Tokyo, Tokyo, Japan
| | | | - Fumie Hamano
- Department of Lipidomics, The University of Tokyo, Tokyo, Japan.,Life Sciences Core Facility The University of Tokyo, Tokyo, Japan.,Department of Lipid Signaling, National Center for Global Health and Medicine, Tokyo, Japan
| | - Maya Yamazaki
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan.,Department of Neurology, University of California, San Francisco, San Francisco, California, USA
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and.,International Research Center for Neurointelligence (WPI-IRCN), University of Tokyo Institutes for Advanced Study (UTIAS), The University of Tokyo, Tokyo, Japan
| | - Takao Shimizu
- Department of Lipidomics, The University of Tokyo, Tokyo, Japan.,Department of Lipid Signaling, National Center for Global Health and Medicine, Tokyo, Japan
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26
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Potts A, Uchida A, Deja S, Berglund ED, Kucejova B, Duarte JA, Fu X, Browning JD, Magnuson MA, Burgess SC. Cytosolic phosphoenolpyruvate carboxykinase as a cataplerotic pathway in the small intestine. Am J Physiol Gastrointest Liver Physiol 2018; 315:G249-G258. [PMID: 29631378 PMCID: PMC6139646 DOI: 10.1152/ajpgi.00039.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cytosolic phosphoenolpyruvate carboxykinase (PEPCK) is a gluconeogenic enzyme that is highly expressed in the liver and kidney but is also expressed at lower levels in a variety of other tissues where it may play adjunct roles in fatty acid esterification, amino acid metabolism, and/or TCA cycle function. PEPCK is expressed in the enterocytes of the small intestine, but it is unclear whether it supports a gluconeogenic rate sufficient to affect glucose homeostasis. To examine potential roles of intestinal PEPCK, we generated an intestinal PEPCK knockout mouse. Deletion of intestinal PEPCK ablated ex vivo gluconeogenesis but did not significantly affect glycemia in chow, high-fat diet, or streptozotocin-treated mice. In contrast, postprandial triglyceride secretion from the intestine was attenuated in vivo, consistent with a role in fatty acid esterification. Intestinal amino acid profiles and 13C tracer appearance into these pools were significantly altered, indicating abnormal amino acid trafficking through the enterocyte. The data suggest that the predominant role of PEPCK in the small intestine of mice is not gluconeogenesis but rather to support nutrient processing, particularly with regard to lipids and amino acids. NEW & NOTEWORTHY The small intestine expresses gluconeogenic enzymes for unknown reasons. In addition to glucose synthesis, the nascent steps of this pathway can be used to support amino acid and lipid metabolisms. When phosphoenolpyruvate carboxykinase, an essential gluconeogenic enzyme, is knocked out of the small intestine of mice, glycemia is unaffected, but mice inefficiently absorb dietary lipid, have abnormal amino acid profiles, and inefficiently catabolize glutamine. Therefore, the initial steps of intestinal gluconeogenesis are used for processing dietary triglycerides and metabolizing amino acids but are not essential for maintaining blood glucose levels.
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Affiliation(s)
- Austin Potts
- 1Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Aki Uchida
- 1Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Stanislaw Deja
- 2Center for Human Nutrition, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Eric D. Berglund
- 1Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Blanka Kucejova
- 2Center for Human Nutrition, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Joao A. Duarte
- 1Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Xiaorong Fu
- 2Center for Human Nutrition, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Jeffrey D. Browning
- 3Department of Clinical Nutrition, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Mark A. Magnuson
- 5Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Shawn C. Burgess
- 1Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas,4Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, Texas
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27
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Amos-Kroohs RM, Nelson DW, Hacker TA, Yen CLE, Smith SM. Does prenatal alcohol exposure cause a metabolic syndrome? (Non-)evidence from a mouse model of fetal alcohol spectrum disorder. PLoS One 2018; 13:e0199213. [PMID: 29953483 PMCID: PMC6023152 DOI: 10.1371/journal.pone.0199213] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 06/04/2018] [Indexed: 12/31/2022] Open
Abstract
Although prenatal alcohol exposure (PAE) reduces offspring growth, it may increase obesity risk at adolescence. Animal models of PAE display glucose intolerance and increased adiposity, suggesting that PAE causes metabolic reprogramming. We tested this hypothesis in a mouse model of binge PAE, wherein pregnant C57Bl/6J females received 3 g/kg alcohol (ETOH) daily from gestational day 12.5 to 17.5; maltodextrin (MD) and medium chain triglycerides (MCT) served as isocaloric nutritional controls, and sham (H2O) treatment controlled for gavage stress. Our comprehensive assessment quantified body composition, energy expenditure, glucose tolerance, and cardiovascular function in offspring at age 17 weeks. Although ETOH pups were initially lighter than all other groups, they did not have a unique obesogenic phenotype. Instead, a similar obesogenic phenotype emerged in all three caloric groups (MCT, MD, ETOH), such that caloric groups had greater post-weaning weight gain (both sexes), reduced gonadal fat weight (males), and reduced glucose clearance (males) compared against H2O offspring. PAE did not affect body composition, respiratory exchange ratio, metabolic adaption to high-fat or low-fat diet, eating behavior, and blood pressure, and ETOH values did not differ from those obtained from isocaloric controls. Exposure to a higher alcohol dose (4.5 g/kg) or a high-fat (60%) diet did not exacerbate differences in body composition or glucose tolerance. “PAE-specific” effects on postnatal growth, glucose tolerance, adiposity, or hypertension only emerged when PAE offspring were compared just against H2O controls, or against MD controls. We conclude that prior reports of obesity and glucose intolerance in adult PAE offspring reflect the contribution of added gestational calories, and not alcohol’s pharmacologic action. Results suggest that the increased adiposity risk in FASD is not caused by metabolic reprogramming, and instead originates from behavioral, medication, and/or dietary practices. This study highlights the importance of appropriate dietary controls in nutritional studies of PAE.
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Affiliation(s)
- Robyn M. Amos-Kroohs
- UNC Nutritional Research Institute and Department of Nutrition, University of North Carolina-Chapel Hill, Kannapolis, North Carolina, United States of America
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, United States of America
| | - David W. Nelson
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Timothy A. Hacker
- Cardiovascular Research Center, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
| | - Chi-Liang Eric Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Susan M. Smith
- UNC Nutritional Research Institute and Department of Nutrition, University of North Carolina-Chapel Hill, Kannapolis, North Carolina, United States of America
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, United States of America
- * E-mail:
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28
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AIDA Selectively Mediates Downregulation of Fat Synthesis Enzymes by ERAD to Retard Intestinal Fat Absorption and Prevent Obesity. Cell Metab 2018; 27:843-853.e6. [PMID: 29617643 DOI: 10.1016/j.cmet.2018.02.021] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 11/05/2017] [Accepted: 02/21/2018] [Indexed: 01/24/2023]
Abstract
The efficiency of intestinal absorption of dietary fat constitutes a primary determinant accounting for individual vulnerability to obesity. However, how fat absorption is controlled and contributes to obesity remains unclear. Here, we show that inhibition of endoplasmic-reticulum-associated degradation (ERAD) increases the abundance of triacylglycerol synthesis enzymes and fat absorption in small intestine. The C2-domain protein AIDA acts as an essential factor for the E3-ligase HRD1 of ERAD to downregulate rate-limiting acyltransferases GPAT3, MOGAT2, and DGAT2. Aida-/- mice, when grown in a thermal-neutral condition or fed high-fat diet, display increased intestinal fatty acid re-esterification, circulating and tissue triacylglycerol, accompanied with severely increased adiposity without enhancement of adipogenesis. Intestine-specific knockout of Aida largely phenocopies its whole-body knockout, strongly indicating that increased intestinal TAG synthesis is a primary impetus to obesity. The AIDA-mediated ERAD system may thus represent an anti-thrifty mechanism impinging on the enzymes for intestinal fat absorption and systemic fat storage.
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29
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Hansen HS, Vana V. Non-endocannabinoid N-acylethanolamines and 2-monoacylglycerols in the intestine. Br J Pharmacol 2018; 176:1443-1454. [PMID: 29473944 DOI: 10.1111/bph.14175] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 01/23/2018] [Accepted: 02/05/2018] [Indexed: 12/11/2022] Open
Abstract
This review focuses on recent findings of the physiological and pharmacological role of non-endocannabinoid N-acylethanolamines (NAEs) and 2-monoacylglycerols (2-MAGs) in the intestine and their involvement in the gut-brain signalling. Dietary fat suppresses food intake, and much research concerns the known gut peptides, for example, glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK). NAEs and 2-MAGs represent another class of local gut signals most probably involved in the regulation of food intake. We discuss the putative biosynthetic pathways and targets of NAEs in the intestine as well as their anorectic role and changes in intestinal levels depending on the dietary status. NAEs can activate the transcription factor PPARα, but studies to evaluate the role of endogenous NAEs are generally lacking. Finally, we review the role of diet-derived 2-MAGs in the secretion of anorectic gut peptides via activation of GPR119. Both PPARα and GPR119 have potential as pharmacological targets for the treatment of obesity and the former for treatment of intestinal inflammation. LINKED ARTICLES: This article is part of a themed section on 8th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc.
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Affiliation(s)
- Harald S Hansen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Vasiliki Vana
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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30
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Transcriptome Analysis Reveals Increases in Visceral Lipogenesis and Storage and Activation of the Antigen Processing and Presentation Pathway during the Mouth-Opening Stage in Zebrafish Larvae. Int J Mol Sci 2017; 18:ijms18081634. [PMID: 28758957 PMCID: PMC5578024 DOI: 10.3390/ijms18081634] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 07/20/2017] [Accepted: 07/21/2017] [Indexed: 12/11/2022] Open
Abstract
The larval phase of the fish life cycle has the highest mortality, particularly during the transition from endogenous to exogenous feeding. However, the transcriptional events underlying these processes have not been fully characterized. To understand the molecular mechanisms underlying mouth-opening acclimation, RNA-seq was used to investigate the transcriptional profiles of the endogenous feeding, mixed feeding and exogenous feeding stages of zebrafish larvae. Differential expression analysis showed 2172 up-regulated and 2313 down-regulated genes during this stage. Genes associated with the assimilation of exogenous nutrients such as the arachidonic acid metabolism, linoleic acid metabolism, fat digestion and absorption, and lipogenesis were activated significantly, whereas dissimilation including the cell cycle, homologous recombination, and fatty acid metabolism were inhibited, indicating a physiological switch for energy storage occurred during the mouth-opening stage. Moreover, the immune recognition involved in the antigen processing and presentation pathway was activated and nutritional supply seemed to be required in this event confirmed by qPCR. These results suggested the energy utilization during the mouth-opening stage is more tended to be reserved or used for some important demands, such as activity regulation, immune defense, and lipid deposition, instead of rapid growth. The findings of this study are important for understanding the physiological switches during the mouth-opening stage.
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31
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Ramachandran D, Clara R, Fedele S, Hu J, Lackzo E, Huang JY, Verdin E, Langhans W, Mansouri A. Intestinal SIRT3 overexpression in mice improves whole body glucose homeostasis independent of body weight. Mol Metab 2017; 6:1264-1273. [PMID: 29031725 PMCID: PMC5641632 DOI: 10.1016/j.molmet.2017.07.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 07/11/2017] [Accepted: 07/14/2017] [Indexed: 02/06/2023] Open
Abstract
OBJECTIVE Intestinal metabolism might play a greater role in regulating whole body metabolism than previously believed. We aimed to enhance enterocyte metabolism in mice and investigate if it plays a role in diet-induced obesity (DIO) and its comorbidities. METHODS Using the cre-loxP system, we overexpressed the mitochondrial NAD+ dependent protein deacetylase SIRT3 in enterocytes of mice (iSIRT3 mice). We chronically fed iSIRT3 mice and floxed-SIRT3 control (S3fl) mice a low-fat, control diet (CD) or a high-fat diet (HFD) and then phenotyped the mice. RESULTS There were no genotype differences in any of the parameters tested when the mice were fed CD. Also, iSIRT3 mice were equally susceptible to the development of DIO as S3fl mice when fed HFD. They were, however, better able than S3fl mice to regulate their blood glucose levels in response to exogenous insulin and glucose, indicating that they were protected from developing insulin resistance. This improved glucose homeostasis was accompanied by an increase in enterocyte metabolic activity and an upregulation of ketogenic gene expression in the small intestine. CONCLUSION Enhancing enterocyte oxidative metabolism can improve whole body glucose homeostasis.
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Affiliation(s)
| | - Rosmarie Clara
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland
| | - Shahana Fedele
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland
| | - Junmin Hu
- Functional Genomics Center Zurich (FGCZ), ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Endre Lackzo
- Functional Genomics Center Zurich (FGCZ), ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Jing-Yi Huang
- Gladstone Institute of Virology and Immunology, University of California, San Francisco, CA, USA
| | - Eric Verdin
- Gladstone Institute of Virology and Immunology, University of California, San Francisco, CA, USA
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland
| | - Abdelhak Mansouri
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland.
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32
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Ma Z, Onorato JM, Chen L, Nelson DW, Yen CLE, Cheng D. Synthesis of neutral ether lipid monoalkyl-diacylglycerol by lipid acyltransferases. J Lipid Res 2017; 58:1091-1099. [PMID: 28420705 DOI: 10.1194/jlr.m073445] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 04/14/2017] [Indexed: 12/29/2022] Open
Abstract
In mammals, ether lipids exert a wide spectrum of signaling and structural functions, such as stimulation of immune responses, anti-tumor activities, and enhancement of sperm functions. Abnormal accumulation of monoalkyl-diacylglycerol (MADAG) was found in Wolman's disease, a human genetic disorder defined by a deficiency in lysosomal acid lipase. In the current study, we found that among the nine recombinant human lipid acyltransferases examined, acyl-CoA:diacylglycerol acyltransferase (DGAT)1, DGAT2, acyl-CoA:monoacylglycerol acyltransferase (MGAT)2, MGAT3, acyl-CoA:wax-alcohol acyltransferase 2/MFAT, and DGAT candidate 3 were able to use 1-monoalkylglycerol (1-MAkG) as an acyl acceptor for the synthesis of monoalkyl-monoacylglycerol (MAMAG). These enzymes demonstrated different enzymatic turnover rates and relative efficiencies for the first and second acylation steps leading to the synthesis of MAMAG and MADAG, respectively. They also exhibited different degrees of substrate preference when presented with 1-monooleoylglycerol versus 1-MAkG. In CHO-K1 cells, treatment with DGAT1 selective inhibitor, XP-620, completely blocked the synthesis of MADAG, indicating that DGAT1 is the predominant enzyme responsible for the intracellular synthesis of MADAG in this model system. The levels of MADAG in the adrenal gland of DGAT1 KO mice were reduced as compared with those of the WT mice, suggesting that DGAT1 is a major enzyme for the synthesis of MADAG in this tissue. Our findings indicate that several of these lipid acyltransferases may be able to synthesize neutral ether lipids in mammals.
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Affiliation(s)
- Zhengping Ma
- Departments of Fibrosis Discovery Bristol-Myers Squibb Company, Princeton, NJ 08543-5400
| | - Joelle M Onorato
- Bioanalytical and Discovery Analytical Sciences, Research and Development, Bristol-Myers Squibb Company, Princeton, NJ 08543-5400
| | - Luping Chen
- Departments of Fibrosis Discovery Bristol-Myers Squibb Company, Princeton, NJ 08543-5400
| | - David W Nelson
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706
| | - Chi-Liang Eric Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706
| | - Dong Cheng
- Departments of Fibrosis Discovery Bristol-Myers Squibb Company, Princeton, NJ 08543-5400
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Zhang P, Reue K. Lipin proteins and glycerolipid metabolism: Roles at the ER membrane and beyond. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1583-1595. [PMID: 28411173 DOI: 10.1016/j.bbamem.2017.04.007] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 03/29/2017] [Accepted: 04/09/2017] [Indexed: 01/09/2023]
Abstract
The regulation of glycerolipid biosynthesis is critical for homeostasis of cellular lipid stores and membranes. Here we review the role of lipin phosphatidic acid phosphatase enzymes in glycerolipid synthesis. Lipin proteins are unique among glycerolipid biosynthetic enzymes in their ability to transit among cellular membranes, rather than remain membrane tethered. We focus on the mechanisms that underlie lipin protein interactions with membranes and the versatile roles of lipins in several organelles, including the endoplasmic reticulum, mitochondria, endolysosomes, lipid droplets, and nucleus. We also review the corresponding physiological roles of lipins, which have been uncovered by the study of genetic lipin deficiencies. We propose that the growing body of knowledge concerning the biochemical and cellular activities of lipin proteins will be valuable for understanding the physiological functions of lipin proteins in health and disease. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.
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Affiliation(s)
- Peixiang Zhang
- Human Genetics, David Geffen School of Medicine at UCLA, University of California, Los Angeles, United States
| | - Karen Reue
- Human Genetics, David Geffen School of Medicine at UCLA, University of California, Los Angeles, United States; Molecular Biology Institute, University of California, Los Angeles, United States.
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Structure-guided enzymology of the lipid A acyltransferase LpxM reveals a dual activity mechanism. Proc Natl Acad Sci U S A 2016; 113:E6064-E6071. [PMID: 27681620 DOI: 10.1073/pnas.1610746113] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Gram-negative bacteria possess a characteristic outer membrane, of which the lipid A constituent elicits a strong host immune response through the Toll-like receptor 4 complex, and acts as a component of the permeability barrier to prevent uptake of bactericidal compounds. Lipid A species comprise the bulk of the outer leaflet of the outer membrane and are produced through a multistep biosynthetic pathway conserved in most Gram-negative bacteria. The final steps in this pathway involve the secondary acylation of lipid A precursors. These are catalyzed by members of a superfamily of enzymes known as lysophospholipid acyltransferases (LPLATs), which are present in all domains of life and play important roles in diverse biological processes. To date, characterization of this clinically important class of enzymes has been limited by a lack of structural information and the availability of only low-throughput biochemical assays. In this work, we present the structure of the bacterial LPLAT protein LpxM, and we describe a high-throughput, label-free mass spectrometric assay to characterize acyltransferase enzymatic activity. Using our structure and assay, we identify an LPLAT thioesterase activity, and we provide experimental evidence to support an ordered-binding and "reset" mechanistic model for LpxM function. This work enables the interrogation of other bacterial acyltransferases' structure-mechanism relationships, and the assay described herein provides a foundation for quantitatively characterizing the enzymology of any number of clinically relevant LPLAT proteins.
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Qi J, Lang W, Connelly MA, Du F, Liang Y, Caldwell GW, Martin T, Hansen MK, Kuo GH, Gaul MD, Pocai A, Lee S. Metabolic tracing of monoacylglycerol acyltransferase-2 activity in vitro and in vivo. Anal Biochem 2016; 524:68-75. [PMID: 27665677 DOI: 10.1016/j.ab.2016.09.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 09/01/2016] [Accepted: 09/19/2016] [Indexed: 01/24/2023]
Abstract
Monoacylglycerol acyltransferase 2 (MGAT2) catalyzes the synthesis of diacylglycerol (DAG) from free fatty acids (FFA) and sn-monoacylglycerol (MG), the two major hydrolysis products of dietary fat. To demonstrate MGAT2-mediated cellular activity of triglyceride (TG) synthesis, we utilized 1-oleoyl-glycerol-d5 as a substrate to trace MGAT2-driven 1-oleoyl-glycerol-d5 incorporation into TG in HEK293 cells stably expressing human MGAT2. The oleoyl-glycerol-d5 incorporated major TG species were then quantified by liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS) in a 96-well format. Conventional MGAT2 target-engagement in vivo assays measure the elevation of total plasma TG by orally dosing a bolus of TG oil. We developed a novel LC/ESI/MS/MS-based fat absorption assay to assess the ability of MGAT2 inhibitors to inhibit fat absorption in CD1 mice by a meal tolerance test consisting of a mixture of liquid Boost plus® and 0.59 g/kg U13C-TG oil. The newly resynthesized plasma heavy TGs containing three 13C in the glycerol backbone and two U13C-acyl-chains, which represented the digested, absorbed and resynthesized TGs, were then quantitated by LC/ESI/MS/MS. With this assay, we identified a potent MGAT2 inhibitor that blocked MGAT2-mediated activity in vitro and in vivo. The use of 1-oleoyl-glycerol-d5 and U13C-TG oil followed by LC/ESI/MS/MS detection of stable-isotopic labeled DAG, TG, or glycerol provides a wide range of applications to study pathophysiological regulation of the monoacylglycerol pathway and MGAT2 activity.
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Affiliation(s)
- Jenson Qi
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA.
| | - Wensheng Lang
- Discovery Sciences, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Margery A Connelly
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Fuyong Du
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Yin Liang
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Gary W Caldwell
- Discovery Sciences, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Tonya Martin
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Michael K Hansen
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Gee-Hong Kuo
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Michael D Gaul
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Alessandro Pocai
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
| | - Seunghun Lee
- Cardiovascular and Metabolic Disease Research, Janssen Research & Development, LLC, 1400 McKean Road, Spring House, PA 19477-0776, USA
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Soayfane Z, Tercé F, Cantiello M, Robenek H, Nauze M, Bézirard V, Allart S, Payré B, Capilla F, Cartier C, Peres C, Al Saati T, Théodorou V, Nelson DW, Yen CLE, Collet X, Coméra C. Exposure to dietary lipid leads to rapid production of cytosolic lipid droplets near the brush border membrane. Nutr Metab (Lond) 2016; 13:48. [PMID: 27478484 PMCID: PMC4965885 DOI: 10.1186/s12986-016-0107-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 07/21/2016] [Indexed: 12/17/2022] Open
Abstract
Background Intestinal absorption of dietary lipids involves their hydrolysis in the lumen of proximal intestine as well as uptake, intracellular transport and re-assembly of hydrolyzed lipids in enterocytes, leading to the formation and secretion of the lipoproteins chylomicrons and HDL. In this study, we examined the potential involvement of cytosolic lipid droplets (CLD) whose function in the process of lipid absorption is poorly understood. Methods Intestinal lipid absorption was studied in mouse after gavage. Three populations of CLD were purified by density ultracentrifugations, as well as the brush border membranes, which were analyzed by western-blots. Immunofluorescent localization of membranes transporters or metabolic enzymes, as well as kinetics of CLD production, were also studied in intestine or Caco-2 cells. Results We isolated three populations of CLD (ranging from 15 to 1000 nm) which showed differential expression of the major lipid transporters scavenger receptor BI (SR-BI), cluster of differentiation 36 (CD-36), Niemann Pick C-like 1 (NPC1L1), and the ATP-binding cassette transporters ABCG5/G8 but also caveolin 2 and fatty acid binding proteins. The enzyme monoacylglycerol acyltransferase 2 (MGAT2) was identified in the brush border membrane (BBM) in addition to the endoplasmic reticulum, suggesting local synthesis of triglycerides and CLD at both places. Conclusions We show a very fast production of CLD by enterocytes associated with a transfer of apical constituents as lipid transporters. Our findings suggest that following their uptake by enterocytes, lipids can be partially metabolized at the BBM and packaged into CLD for their transportation to the ER. Electronic supplementary material The online version of this article (doi:10.1186/s12986-016-0107-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zeina Soayfane
- Institut des Maladies Métaboliques et Cardiovasculaires - I2MC, UMR 1048, Institut National de la Santé et de la Recherche Médicale, Université Toulouse III Paul Sabatier, Toulouse, F-31000 France
| | - François Tercé
- Institut des Maladies Métaboliques et Cardiovasculaires - I2MC, UMR 1048, Institut National de la Santé et de la Recherche Médicale, Université Toulouse III Paul Sabatier, Toulouse, F-31000 France
| | - Michela Cantiello
- Institut des Maladies Métaboliques et Cardiovasculaires - I2MC, UMR 1048, Institut National de la Santé et de la Recherche Médicale, Université Toulouse III Paul Sabatier, Toulouse, F-31000 France
| | - Horst Robenek
- Leibniz-Institut für Arterioskleroseforschung, Universität Münster, Münster, Germany
| | - Michel Nauze
- Institut des Maladies Métaboliques et Cardiovasculaires - I2MC, UMR 1048, Institut National de la Santé et de la Recherche Médicale, Université Toulouse III Paul Sabatier, Toulouse, F-31000 France
| | - Valérie Bézirard
- UMR 1331 Toxalim, INRA, Université de Toulouse, ENVT, INP-Purpan, 180 chemin de Tournefeuille, BP 93173, 31027 Toulouse, cedex 3, France
| | - Sophie Allart
- INSERM UMR 1043 (INSERM/UPS/CNRS/USC Inra), CHU Purpan, Toulouse, France
| | - Bruno Payré
- CMEAB, Faculté de Médecine Rangueil, Toulouse, France
| | - Florence Capilla
- INSERM/UPS - US006/CREFRE, Service d'Histopathologie, CHU Purpan, Toulouse, France
| | - Christel Cartier
- UMR 1331 Toxalim, INRA, Université de Toulouse, ENVT, INP-Purpan, 180 chemin de Tournefeuille, BP 93173, 31027 Toulouse, cedex 3, France
| | - Christine Peres
- Institut des Maladies Métaboliques et Cardiovasculaires - I2MC, UMR 1048, Institut National de la Santé et de la Recherche Médicale, Université Toulouse III Paul Sabatier, Toulouse, F-31000 France
| | - Talal Al Saati
- INSERM/UPS - US006/CREFRE, Service d'Histopathologie, CHU Purpan, Toulouse, France
| | - Vassilia Théodorou
- UMR 1331 Toxalim, INRA, Université de Toulouse, ENVT, INP-Purpan, 180 chemin de Tournefeuille, BP 93173, 31027 Toulouse, cedex 3, France
| | - David W Nelson
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI USA
| | - Chi-Liang Eric Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI USA
| | - Xavier Collet
- Institut des Maladies Métaboliques et Cardiovasculaires - I2MC, UMR 1048, Institut National de la Santé et de la Recherche Médicale, Université Toulouse III Paul Sabatier, Toulouse, F-31000 France
| | - Christine Coméra
- Institut des Maladies Métaboliques et Cardiovasculaires - I2MC, UMR 1048, Institut National de la Santé et de la Recherche Médicale, Université Toulouse III Paul Sabatier, Toulouse, F-31000 France.,UMR 1331 Toxalim, INRA, Université de Toulouse, ENVT, INP-Purpan, 180 chemin de Tournefeuille, BP 93173, 31027 Toulouse, cedex 3, France
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Costa DK, Huckestein BR, Edmunds LR, Petersen MC, Nasiri A, Butrico GM, Abulizi A, Harmon DB, Lu C, Mantell BS, Hartman DJ, Camporez JPG, O'Doherty RM, Cline GW, Shulman GI, Jurczak MJ. Reduced intestinal lipid absorption and body weight-independent improvements in insulin sensitivity in high-fat diet-fed Park2 knockout mice. Am J Physiol Endocrinol Metab 2016; 311:E105-16. [PMID: 27166280 PMCID: PMC4967148 DOI: 10.1152/ajpendo.00042.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 05/06/2016] [Indexed: 12/21/2022]
Abstract
Mitochondrial dysfunction is associated with many human diseases and results from mismatch of damage and repair over the life of the organelle. PARK2 is a ubiquitin E3 ligase that regulates mitophagy, a repair mechanism that selectively degrades damaged mitochondria. Deletion of PARK2 in multiple in vivo models results in susceptibility to stress-induced mitochondrial and cellular dysfunction. Surprisingly, Park2 knockout (KO) mice are protected from nutritional stress and do not develop obesity, hepatic steatosis or insulin resistance when fed a high-fat diet (HFD). However, these phenomena are casually related and the physiological basis for this phenotype is unknown. We therefore undertook a series of acute HFD studies to more completely understand the physiology of Park2 KO during nutritional stress. We find that intestinal lipid absorption is impaired in Park2 KO mice as evidenced by increased fecal lipids and reduced plasma triglycerides after intragastric fat challenge. Park2 KO mice developed hepatic steatosis in response to intravenous lipid infusion as well as during incubation of primary hepatocytes with fatty acids, suggesting that hepatic protection from nutritional stress was secondary to changes in energy balance due to altered intestinal triglyceride absorption. Park2 KO mice showed reduced adiposity after 1-wk HFD, as well as improved hepatic and peripheral insulin sensitivity. These studies suggest that changes in intestinal lipid absorption may play a primary role in protection from nutritional stress in Park2 KO mice by preventing HFD-induced weight gain and highlight the need for tissue-specific models to address the role of PARK2 during metabolic stress.
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Affiliation(s)
- Diana K Costa
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Brydie R Huckestein
- Department of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Lia R Edmunds
- Department of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Max C Petersen
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut
| | - Ali Nasiri
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Gina M Butrico
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Abudukadier Abulizi
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Daniel B Harmon
- Department of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Canying Lu
- Department of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Benjamin S Mantell
- Department of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Douglas J Hartman
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | | | - Robert M O'Doherty
- Department of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Center for Metabolic and Mitochondrial Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Gary W Cline
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Gerald I Shulman
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut; Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut; The Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut; and
| | - Michael J Jurczak
- Department of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Center for Metabolic and Mitochondrial Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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McFie PJ, Izzard S, Vu H, Jin Y, Beauchamp E, Berthiaume LG, Stone SJ. Membrane topology of human monoacylglycerol acyltransferase-2 and identification of regions important for its localization to the endoplasmic reticulum. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1192-1204. [PMID: 27373844 DOI: 10.1016/j.bbalip.2016.06.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 06/27/2016] [Accepted: 06/30/2016] [Indexed: 11/16/2022]
Abstract
Acyl CoA:2-monoacylglycerol acyltransferase (MGAT)-2 has an important role in dietary fat absorption in the intestine. MGAT2 resides in the endoplasmic reticulum and catalyzes the synthesis of diacylglycerol which is then utilized as a substrate for triacylglycerol synthesis. This triacylglycerol is then incorporated into chylomicrons which are released into the circulation. In this study, we determined the membrane topology of human MGAT2. Protease protection experiments showed that the C-terminus is exposed to the cytosol, while the N-terminus is partially buried in the ER membrane. MGAT2, like murine DGAT2, was found to have two transmembrane domains. We also identified a region of MGAT2 associated with the ER membrane that contains the histidine-proline-histidine-glycine sequence present in all DGAT2 family members that is thought to comprise the active site. Proteolysis experiments demonstrated that digestion of total cellular membranes from cells expressing MGAT2 with trypsin abolished MGAT activity, indicating that domains that are important for catalysis face the cytosol. We also explored the role that the five cysteines residues present in MGAT2 have in catalysis. MGAT activity was sensitive to two thiol modifiers, N-ethylmaleimide and 5,5'-dithiobis-(2-nitrobenzoic acid). Furthermore, mutation of four cysteines resulted in a reduction in MGAT activity. However, when the C-terminal cysteine (C334) was mutated, MGAT activity was actually higher than that of wild-type FL-MGAT2. Lastly, we determined that both transmembrane domains of MGAT2 are important for its ER localization, and that MGAT2 is present in mitochondrial-associated membranes.
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Affiliation(s)
- Pamela J McFie
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Sabrina Izzard
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Huyen Vu
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Youzhi Jin
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Erwan Beauchamp
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Luc G Berthiaume
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Scot J Stone
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
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Characterization of monoacylglycerol acyltransferase 2 inhibitors by a novel probe in binding assays. Anal Biochem 2016; 501:48-55. [PMID: 26925857 DOI: 10.1016/j.ab.2016.02.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/12/2016] [Accepted: 02/15/2016] [Indexed: 11/20/2022]
Abstract
Monoacylglycerol acyltransferase 2 (MGAT2) is a membrane-bound lipid acyltransferase that catalyzes the formation of diacylglycerol using monoacylglycerol and fatty acyl CoA as substrates. MGAT2 is important for intestinal lipid absorption and is an emerging target for the treatment of metabolic diseases. In the current study, we identified and characterized four classes of novel MGAT2 inhibitors. We established both steady state and kinetic binding assay protocols using a novel radioligand, [(3)H]compound A. Diverse chemotypes of MGAT2 inhibitors were found to compete binding of [(3)H]compound A to MGAT2, indicating the broad utility of [(3)H]compound A for testing various classes of MGAT2 inhibitors. In the dynamic binding assays, the kinetic values of MGAT2 inhibitors such as Kon, Koff, and T1/2 were systematically defined. Of particular value, the residence times of inhibitors on MGAT2 enzyme were derived. We believe that the identification of novel classes of MGAT2 inhibitors and the detailed kinetic characterization provide valuable information for the identification of superior candidates for in vivo animal and clinical studies. The current work using a chemical probe to define inhibitory kinetics can be broadly applied to other membrane-bound acyltransferases.
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Mansbach CM, Siddiqi S. Control of chylomicron export from the intestine. Am J Physiol Gastrointest Liver Physiol 2016; 310:G659-68. [PMID: 26950854 DOI: 10.1152/ajpgi.00228.2015] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 02/22/2016] [Indexed: 01/31/2023]
Abstract
The control of chylomicron output by the intestine is a complex process whose outlines have only recently come into focus. In this review we will cover aspects of chylomicron formation and prechylomicron vesicle generation that elucidate potential control points. Substrate (dietary fatty acids and monoacylglycerols) availability is directly related to the output rate of chylomicrons. These substrates must be converted to triacylglycerol before packaging in prechylomicrons by a series of endoplasmic reticulum (ER)-localized acylating enzymes that rapidly convert fatty acids and monoacylglycerols to triacylglycerol. The packaging of the prechylomicron with triacylglycerol is controlled by the microsomal triglyceride transport protein, another potential limiting step. The prechylomicrons, once loaded with triacylglycerol, are ready to be incorporated into the prechylomicron transport vesicle that transports the prechylomicron from the ER to the Golgi. Control of this exit step from the ER, the rate-limiting step in the transcellular movement of the triacylglycerol, is a multistep process involving the activation of PKCζ, the phosphorylation of Sar1b, releasing the liver fatty acid binding protein from a heteroquatromeric complex, which enables it to bind to the ER and organize the prechylomicron transport vesicle budding complex. We propose that control of PKCζ activation is the major physiological regulator of chylomicron output.
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Affiliation(s)
- Charles M Mansbach
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
| | - Shahzad Siddiqi
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
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D'Aquila T, Hung YH, Carreiro A, Buhman KK. Recent discoveries on absorption of dietary fat: Presence, synthesis, and metabolism of cytoplasmic lipid droplets within enterocytes. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:730-47. [PMID: 27108063 DOI: 10.1016/j.bbalip.2016.04.012] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 03/16/2016] [Accepted: 04/16/2016] [Indexed: 02/07/2023]
Abstract
Dietary fat provides essential nutrients, contributes to energy balance, and regulates blood lipid concentrations. These functions are important to health, but can also become dysregulated and contribute to diseases such as obesity, diabetes, cardiovascular disease, and cancer. Within enterocytes, the digestive products of dietary fat are re-synthesized into triacylglycerol, which is either secreted on chylomicrons or stored within cytoplasmic lipid droplets (CLDs). CLDs were originally thought to be inert stores of neutral lipids, but are now recognized as dynamic organelles that function in multiple cellular processes in addition to lipid metabolism. This review will highlight recent discoveries related to dietary fat absorption with an emphasis on the presence, synthesis, and metabolism of CLDs within this process.
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Affiliation(s)
- Theresa D'Aquila
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Yu-Han Hung
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Alicia Carreiro
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Kimberly K Buhman
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA.
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Pharmacological Inhibition of Monoacylglycerol O-Acyltransferase 2 Improves Hyperlipidemia, Obesity, and Diabetes by Change in Intestinal Fat Utilization. PLoS One 2016; 11:e0150976. [PMID: 26938273 PMCID: PMC4777574 DOI: 10.1371/journal.pone.0150976] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Accepted: 02/22/2016] [Indexed: 02/02/2023] Open
Abstract
Monoacylglycerol O-acyltransferase 2 (MGAT2) catalyzes the synthesis of diacylglycerol (DG), a triacylglycerol precursor and potential peripheral target for novel anti-obesity therapeutics. High-throughput screening identified lead compounds with MGAT2 inhibitory activity. Through structural modification, a potent, selective, and orally bioavailable MGAT2 inhibitor, compound A (compA), was discovered. CompA dose-dependently inhibited postprandial increases in plasma triglyceride (TG) levels. Metabolic flux analysis revealed that compA inhibited triglyceride/diacylglycerol resynthesis in the small intestine and increased free fatty acid and acyl-carnitine with shorter acyl chains than originally labelled fatty acid. CompA decreased high-fat diet (HFD) intake in C57BL/6J mice. MGAT2-null mice showed a similar phenotype as compA-treated mice and compA did not suppress a food intake in MGAT2 KO mice, indicating that the anorectic effects were dependent on MGAT2 inhibition. Chronic administration of compA significantly prevented body weight gain and fat accumulation in mice fed HFD. MGAT2 inhibition by CompA under severe diabetes ameliorated hyperglycemia and fatty liver in HFD-streptozotocin (STZ)-treated mice. Homeostatic model assessments (HOMA-IR) revealed that compA treatment significantly improved insulin sensitivity. The proximal half of the small intestine displayed weight gain following compA treatment. A similar phenomenon has been observed in Roux-en-Y gastric bypass-treated animals and some studies have reported that this intestinal remodeling is essential to the anti-diabetic effects of bariatric surgery. These results clearly demonstrated that MGAT2 inhibition improved dyslipidemia, obesity, and diabetes, suggesting that compA is an effective therapeutic for obesity-related metabolic disorders.
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Agarwal AK, Tunison K, Dalal JS, Yen CLE, Farese RV, Horton JD, Garg A. Mogat1 deletion does not ameliorate hepatic steatosis in lipodystrophic (Agpat2-/-) or obese (ob/ob) mice. J Lipid Res 2016; 57:616-30. [PMID: 26880786 DOI: 10.1194/jlr.m065896] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Indexed: 12/31/2022] Open
Abstract
Reducing triacylglycerol (TAG) in the liver continues to pose a challenge in states of nonalcoholic hepatic steatosis. MonoacylglycerolO-acyltransferase (MOGAT) enzymes convert monoacylglycerol (MAG) to diacylglycerol, a precursor for TAG synthesis, and are involved in a major pathway of TAG synthesis in selected tissues, such as small intestine. MOGAT1 possesses MGAT activity in in vitro assays, but its physiological function in TAG metabolism is unknown. Recent studies suggest a role for MOGAT1 in hepatic steatosis in lipodystrophic [1-acylglycerol-3-phosphateO-acyltransferase (Agpat)2(-/-)] and obese (ob/ob) mice. To test this, we deletedMogat1in theAgpat2(-/-)andob/obgenetic background to generateMogat1(-/-);Agpat2(-/-)andMogat1(-/-);ob/obdouble knockout (DKO) mice. Here we report that, despite the absence ofMogat1in either DKO mouse model, we did not find any decrease in liver TAG by 16 weeks of age. Additionally, there were no measureable changes in plasma glucose (diabetes) and insulin resistance. Our data indicate a minimal role, if any, of MOGAT1 in liver TAG synthesis, and that TAG synthesis in steatosis associated with lipodystrophy and obesity is independent of MOGAT1. Our findings suggest that MOGAT1 likely has an alternative function in vivo.
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Affiliation(s)
- Anil K Agarwal
- Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Katie Tunison
- Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Jasbir S Dalal
- Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Chi-Liang Eric Yen
- Gladstone Institute of Cardiovascular Disease San Francisco, San Francisco, CA 94158
| | - Robert V Farese
- Gladstone Institute of Cardiovascular Disease San Francisco, San Francisco, CA 94158
| | - Jay D Horton
- Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390 Division of Gastroenterology and Departments of Molecular Genetics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Abhimanyu Garg
- Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390
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Doler C, Schweiger M, Zimmermann R, Breinbauer R. Chemical Genetic Approaches for the Investigation of Neutral Lipid Metabolism. Chembiochem 2016; 17:358-77. [DOI: 10.1002/cbic.201500501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Indexed: 12/14/2022]
Affiliation(s)
- Carina Doler
- Institute of Organic Chemistry; Graz University of Technology; Stremayrgasse 9 8010 Graz Austria
| | - Martina Schweiger
- Institute of Molecular Biosciences; University of Graz; Heinrichstrasse 31/II 8010 Graz Austria
| | - Robert Zimmermann
- Institute of Molecular Biosciences; University of Graz; Heinrichstrasse 31/II 8010 Graz Austria
| | - Rolf Breinbauer
- Institute of Organic Chemistry; Graz University of Technology; Stremayrgasse 9 8010 Graz Austria
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Intrajejunal infusion of 2-monoacylglycerol reduced food intake without inducing diarrhea in rats. J Pharmacol Sci 2016; 130:136-8. [PMID: 26883454 DOI: 10.1016/j.jphs.2016.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 01/04/2016] [Accepted: 01/11/2016] [Indexed: 11/23/2022] Open
Abstract
Some nutrients, such as carbohydrate, fat and protein, are known to stimulate satiety. However, the effect of sn-2-monoacylglycerol (2-MG), one of the digestive products of triglycerides, on food intake is still unclear. In the present study, the effects of 2-MG on food intake and diarrhea were evaluated and compared with long-chain fatty acid (LCFA) in rats by intrajejunal infusion. Intrajejunal infusion of 2-MG reduced food intake. In addition, 2-MG did not induce diarrhea at the condition that it comparably reduced food intake as compared with LCFA. These results suggest that 2-MG stimulates satiety without inducing diarrhea, different from LCFA.
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Khatun I, Clark RW, Vera NB, Kou K, Erion DM, Coskran T, Bobrowski WF, Okerberg C, Goodwin B. Characterization of a Novel Intestinal Glycerol-3-phosphate Acyltransferase Pathway and Its Role in Lipid Homeostasis. J Biol Chem 2015; 291:2602-15. [PMID: 26644473 DOI: 10.1074/jbc.m115.683359] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Indexed: 01/01/2023] Open
Abstract
Dietary triglycerides (TG) are absorbed by the enterocytes of the small intestine after luminal hydrolysis into monacylglycerol and fatty acids. Before secretion on chylomicrons, these lipids are reesterified into TG, primarily through the monoacylglycerol pathway. However, targeted deletion of the primary murine monoacylglycerol acyltransferase does not quantitatively affect lipid absorption, suggesting the existence of alternative pathways. Therefore, we investigated the role of the glycerol 3-phosphate pathway in dietary lipid absorption. The expression of glycerol-3-phosphate acyltransferase (GPAT3) was examined throughout the small intestine. To evaluate the role for GPAT3 in lipid absorption, mice harboring a disrupted GPAT3 gene (Gpat3(-/-)) were subjected to an oral lipid challenge and fed a Western-type diet to characterize the role in lipid and cholesterol homeostasis. Additional mechanistic studies were performed in primary enterocytes. GPAT3 was abundantly expressed in the apical surface of enterocytes in the small intestine. After an oral lipid bolus, Gpat3(-/-) mice exhibited attenuated plasma TG excursion and accumulated lipid in the enterocytes. Electron microscopy studies revealed a lack of lipids in the lamina propria and intercellular space in Gpat3(-/-) mice. Gpat3(-/-) enterocytes displayed a compensatory increase in the synthesis of phospholipid and cholesteryl ester. When fed a Western-type diet, hepatic TG and cholesteryl ester accumulation was significantly higher in Gpat3(-/-) mice compared with the wild-type mice accompanied by elevated levels of alanine aminotransferase, a marker of liver injury. Dysregulation of bile acid metabolism was also evident in Gpat3-null mice. These studies identify GPAT3 as a novel enzyme involved in intestinal lipid metabolism.
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Affiliation(s)
- Irani Khatun
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Ronald W Clark
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Nicholas B Vera
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Kou Kou
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Derek M Erion
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Timothy Coskran
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Walter F Bobrowski
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Carlin Okerberg
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Bryan Goodwin
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
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da Silva RP, Kelly KB, Lewis ED, Leonard KA, Goruk S, Curtis JM, Vine DF, Proctor SD, Field CJ, Jacobs RL. Choline deficiency impairs intestinal lipid metabolism in the lactating rat. J Nutr Biochem 2015; 26:1077-83. [DOI: 10.1016/j.jnutbio.2015.04.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 04/28/2015] [Accepted: 04/30/2015] [Indexed: 10/23/2022]
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Yang M, Nickels JT. MOGAT2: A New Therapeutic Target for Metabolic Syndrome. Diseases 2015; 3:176-192. [PMID: 28943619 PMCID: PMC5548241 DOI: 10.3390/diseases3030176] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 08/13/2015] [Accepted: 08/17/2015] [Indexed: 12/26/2022] Open
Abstract
Metabolic syndrome is an ever-increasing health problem among the world’s population. It is a group of intertwined maladies that includes obesity, hypertriglyceridemia, hypertension, nonalcoholic fatty liver disease (NAFLD), and diabetes mellitus type II (T2D). There is a direct correlation between high triacylglycerol (triglyceride; TAG) level and severity of metabolic syndrome. Thus, controlling the synthesis of TAG will have a great impact on overall systemic lipid metabolism and thus metabolic syndrome progression. The Acyl-CoA: monoacylglycerolacyltransferase (MGAT) family has three members (MGAT1, -2, and -3) that catalyze the first step in TAG production, conversion of monoacylglycerol (MAG) to diacylglycerol (DAG). TAG is then directly synthesized from DAG by a Acyl-CoA: diacylglycerolacyltransferase (DGAT). The conversion of MAG → DAG → TAG is the major pathway for the production of TAG in the small intestine, and produces TAG to a lesser extent in the liver. Transgenic and pharmacological studies in mice have demonstrated the beneficial effects of MGAT inhibition as a therapy for treating several metabolic diseases, including obesity, insulin resistance, T2D, and NAFLD. In this review, the significance of several properties of MGAT physiology, including tissue expression pattern and its relationship to overall TAG metabolism, enzymatic biochemical properties and their effects on drug discovery, and finally what is the current knowledge about MGAT small molecule inhibitors and their efficacy will be discussed. Overall, this review highlights the therapeutic potential of inhibiting MGAT for lowering TAG synthesis and whether this avenue of drug discovery warrants further clinical investigation.
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Affiliation(s)
- Muhua Yang
- Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, NJ 08691, USA.
| | - Joseph T Nickels
- Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, NJ 08691, USA.
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JTP-103237, a monoacylglycerol acyltransferase inhibitor, prevents fatty liver and suppresses both triglyceride synthesis and de novo lipogenesis. J Pharmacol Sci 2015. [DOI: 10.1016/j.jphs.2015.06.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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50
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Yu M, Liu F, Zhu W, Sun M, Liu J, Li X. New features of triacylglycerol biosynthetic pathways of peanut seeds in early developmental stages. Funct Integr Genomics 2015; 15:707-16. [PMID: 26071211 DOI: 10.1007/s10142-015-0447-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 05/25/2015] [Accepted: 06/01/2015] [Indexed: 02/04/2023]
Abstract
The peanut (Arachis hypogaea L.) is one of the three most important oil crops in the world due to its high average oil content (50 %). To reveal the biosynthetic pathways of seed oil in the early developmental stages of peanut pods with the goal of improving the oil quality, we presented a method combining deep sequencing analysis of the peanut pod transcriptome and quantitative real-time PCR (RT-PCR) verification of seed oil-related genes. From the sequencing data, approximately 1500 lipid metabolism-associated Unigenes were identified. The RT-PCR results quantified the different expression patterns of these triacylglycerol (TAG) synthesis-related genes in the early developmental stages of peanut pods. Based on these results and analysis, we proposed a novel construct of the metabolic pathways involved in the biosynthesis of TAG, including the Kennedy pathway, acyl-CoA-independent pathway and proposed monoacylglycerol pathway. It showed that the biosynthetic pathways of TAG in the early developmental stages of peanut pods were much more complicated than a simple, unidirectional, linear pathway.
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Affiliation(s)
- Mingli Yu
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Daizong Road No.61, Tai'an, Shandong, 271000, China.
| | - Fengzhen Liu
- State Key Laboratory of Crop Biology, College of Agronomic Sciences, Shandong Agricultural University, Tai'an, Shandong, 271000, China.
| | - Weiwei Zhu
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Daizong Road No.61, Tai'an, Shandong, 271000, China.
| | - Meihong Sun
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Daizong Road No.61, Tai'an, Shandong, 271000, China.
| | - Jiang Liu
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Daizong Road No.61, Tai'an, Shandong, 271000, China.
| | - Xinzheng Li
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Daizong Road No.61, Tai'an, Shandong, 271000, China.
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