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Qiu YY, Zhang J, Zeng FY, Zhu YZ. Roles of the peroxisome proliferator-activated receptors (PPARs) in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Pharmacol Res 2023; 192:106786. [PMID: 37146924 DOI: 10.1016/j.phrs.2023.106786] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 04/28/2023] [Accepted: 05/02/2023] [Indexed: 05/07/2023]
Abstract
Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of disease phenotypes which start with simple steatosis and lipid accumulation in the hepatocytes - a typical histological lesions characteristic. It may progress to non-alcoholic steatohepatitis (NASH) that is characterized by hepatic inflammation and/or fibrosis and subsequent onset of NAFLD-related cirrhosis and hepatocellular carcinoma (HCC). Due to the central role of the liver in metabolism, NAFLD is regarded as a result of and contribution to the metabolic abnormalities seen in the metabolic syndrome. Peroxisome proliferator-activated receptors (PPARs) has three subtypes, which govern the expression of genes responsible for energy metabolism, cellular development, inflammation, and differentiation. The agonists of PPARα, such as fenofibrate and clofibrate, have been used as lipid-lowering drugs in clinical practice. Thiazolidinediones (TZDs) - ligands of PPARγ, such as rosiglitazone and pioglitazone, are also used in the treatment of type 2 diabetes (T2D) with insulin resistance (IR). Increasing evidence suggests that PPARβ/δ agonists have potential therapeutic effects in improving insulin sensitivity and lipid metabolism disorders. In addition, PPARs ligands have been considered as potential therapeutic drugs for hypertension, atherosclerosis (AS) or diabetic nephropathy. Their crucial biological roles dictate the significance of PPARs-targeting in medical research and drug discovery. Here, it reviews the biological activities, ligand selectivity and biological functions of the PPARs family, and discusses the relationship between PPARs and the pathogenesis of NAFLD and metabolic syndrome. This will open new possibilities for PPARs application in medicine, and provide a new idea for the treatment of fatty liver and related diseases.
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Affiliation(s)
- Yuan-Ye Qiu
- State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Avenida Wai Long, Taipa, 999078, Macau, China; Faculty of Chinese Medicine, Macau University of Science and Technology, Avenida Wai Long, Taipa, 999078, Macau, China.
| | - Jing Zhang
- University International College, Macau University of Science and Technology, Avenida Wai Long, Taipa, 999078, Macau, China.
| | - Fan-Yi Zeng
- State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Avenida Wai Long, Taipa, 999078, Macau, China; School of Pharmacy, Macau University of Science and Technology, Avenida Wai Long, Taipa, 999078, Macau, China; Shanghai Institute of Medical Genetics, Shanghai Children's Hospital, Shanghai Jiao Tong University, 24/1400 West Beijing Road, Shanghai, 200040, China.
| | - Yi Zhun Zhu
- State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Avenida Wai Long, Taipa, 999078, Macau, China; Faculty of Chinese Medicine, Macau University of Science and Technology, Avenida Wai Long, Taipa, 999078, Macau, China; School of Pharmacy, Macau University of Science and Technology, Avenida Wai Long, Taipa, 999078, Macau, China.
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Wang J, Zeng J, Yin G, Deng Z, Wang L, Liu J, Yao K, Long Z, Jiang X, Tan J. Long non-coding RNA FABP5P3/miR-22 axis improves TGFβ1-induced fatty acid oxidation deregulation and fibrotic changes in proximal tubular epithelial cells of renal fibrosis. Cell Cycle 2023; 22:433-449. [PMID: 36196456 PMCID: PMC9879175 DOI: 10.1080/15384101.2022.2122286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Severe hydronephrosis increases the risk of urinary tract infection and irretrievable renal fibrosis. While TGFβ1-mediated fibrotic changes in proximal tubular epithelial cells and fatty acid oxidation (FAO) deregulation contribute to renal fibrosis and hydronephrosis. Firstly, a few elements were analyzed in this paper, including differentially-expressed long non-coding RNAs (lncRNAs), and miRNAs correlated to CPT1A, RXRA, and NCOA1. This paper investigated TGFβ1 effects on lncRNA FABP5P3, CPT1A, RXRA, and NCOA1 expression and fibrotic changes in HK-2 cells and FABP5P3 overexpression effects on TGFβ1-induced changes. Moreover, this paper predicted and proved that miR-22 binding to lncRNA FABP5P3, 3'UTR of CPT1A, RXRA, and NCOA1 was validated. The dynamic effects of the FABP5P3/miR-22 axis on TGFβ1-induced changes were investigated. A Renal fibrosis model was established in unilateral ureteral obstruction (UUO) mice, and FABP5P3 effects were investigated. Eventually, this paper concluded that TGFβ1 inhibited lncRNA FABP5P3, CPT1A, RXRA, and NCOA1 expression, induced fibrotic changes in HK-2 cells, and induced metabolic reprogramming within HK-2 cells, especially lower FAO. FABP5P3 overexpression partially reversed TGFβ1-induced changes. miR-22 targeted lncRNA FABP5P3, CPT1A, RXRA, and NCOA1. LncRNA FABP5P3 counteracted miR-22 inhibition of CPT1A, NCOA1, and RXRA through competitive binding. TGFβ1 stimulation induced the activation of TGFβ/SMAD and JAG/Notch signaling pathways; Nocth2 knockdown reversed TGFβ1 suppression on lncRNA FABP5P3. FABP5P3 overexpression attenuated renal fibrosis in unilateral ureteral obstruction mice. The LncRNA FABP5P3/miR-22 axis might be a potent target for improving the FAO deregulation and fibrotic changes in proximal TECs under TGFβ1 stimulation.
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Affiliation(s)
- Jingrong Wang
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Jia Zeng
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Guangmin Yin
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Zhijun Deng
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Long Wang
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Jianye Liu
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Kun Yao
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Zhi Long
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Xianzhen Jiang
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Jing Tan
- Department of Urology, The Third Xiangya Hospital of Central South University, Changsha, China
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Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity. Cells 2020; 9:cells9071708. [PMID: 32708786 PMCID: PMC7407644 DOI: 10.3390/cells9071708] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 07/14/2020] [Accepted: 07/14/2020] [Indexed: 02/06/2023] Open
Abstract
Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes.
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Martin GG, Landrock D, McIntosh AL, Milligan S, Landrock KK, Kier AB, Mackie J, Schroeder F. High Glucose and Liver Fatty Acid Binding Protein Gene Ablation Differentially Impact Whole Body and Liver Phenotype in High-Fat Pair-Fed Mice. Lipids 2020; 55:309-327. [PMID: 32314395 DOI: 10.1002/lipd.12238] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 03/12/2020] [Accepted: 03/30/2020] [Indexed: 12/14/2022]
Abstract
Ad libitum-fed diets high in fat and carbohydrate (especially fructose) induce weight gain, obesity, and nonalcoholic fatty liver disease (NAFLD) in humans and animal models. However, interpretation is complicated since ad libitum feeding of such diets induces hyperphagia and upregulates expression of liver fatty acid binding protein (L-FABP)-a protein intimately involved in fatty acid and glucose regulation of lipid metabolism. Wild-type (WT) and L-fabp gene ablated (LKO) mice were pair-fed either high-fat diet (HFD) or high-fat/high-glucose diet (HFGD) wherein total carbohydrate was maintained constant but the proportion of glucose was increased at the expense of fructose. In LKO mice, the pair-fed HFD increased body weight and lean tissue mass (LTM) but had no effect on fat tissue mass (FTM) or hepatic fatty vacuolation as compared to pair-fed WT counterparts. These LKO mice exhibited upregulation of hepatic proteins in fatty acid uptake and cytosolic transport (caveolin and sterol carrier protein-2), but lower hepatic fatty acid oxidation (decreased serum β-hydroxybutyrate). LKO mice pair-fed HFGD also exhibited increased body weight; however, these mice had increased FTM, not LTM, and increased hepatic fatty vacuolation as compared to pair-fed WT counterparts. These LKO mice also exhibited upregulation of hepatic proteins in fatty acid uptake and cytosolic transport (caveolin and acyl-CoA binding protein, but not sterol carrier protein-2), but there was no change in hepatic fatty acid oxidation (serum β-hydroxybutyrate) as compared to pair-fed WT counterparts.
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Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Sherrelle Milligan
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Kerstin K Landrock
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - John Mackie
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
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Ghosh S, O'Connell JF, Carlson OD, González‐Mariscal I, Kim Y, Moaddel R, Ghosh P, Egan JM. Linoleic acid in diets of mice increases total endocannabinoid levels in bowel and liver: modification by dietary glucose. Obes Sci Pract 2019; 5:383-394. [PMID: 31452923 PMCID: PMC6700518 DOI: 10.1002/osp4.344] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 04/17/2019] [Accepted: 04/28/2019] [Indexed: 12/15/2022] Open
Abstract
AIM Linoleic acid (LA) is an essential fatty acid involved in the biosynthesis of arachidonic acid and prostaglandins. LA is known to induce obesity and insulin resistance. In this study, two concentrations of LA with or without added glucose (G) were fed to mice to investigate their effects on endocannabinoid (EC) biology. MATERIALS AND METHODS Four groups of C57BL/6 mice were provided with diets containing 1% or 8% LA with or without added G (LAG) for 8 weeks. Body weights, food intake, circulating glucose and insulin levels were measured throughout the study. Following euthanasia, plasma, bowel and hepatic ECs, monoacylglycerol lipase and fatty acid amide hydroxylase protein levels (enzymes responsible for EC degradation) and transcriptional activity of PPARα in liver were quantified. Liver was probed for evidence of insulin receptor activity perturbation. RESULTS Increasing dietary LA from 1% to 8% significantly increased circulating, small bowel and hepatic ECs. 1%LAG fed mice had lowest feed efficiency, and only liver levels of both ECs were reduced by addition of G. Addition of G to 1% LA diets resulted in elevated monoacylglycerol lipase and fatty acid amide hydroxylase protein levels (p < 0.001 and p < 0.001, respectively) in liver due to increased transcriptional activity of PPARα (p < 0.05). The reduced EC levels with addition of G also correlated with a measure of enhanced insulin action. CONCLUSION In conclusion, body weight of mice is influenced by the source of calorie intake. Furthermore, tissue EC/g are dependent on tissue-specific synthesis and degradation that are modulated by dietary LA and G which also influence food efficiency, and down-stream insulin signalling pathways. The findings could potentially be useful information for weight management efforts in humans.
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Affiliation(s)
- S. Ghosh
- National Institute on Aging, Laboratory of Clinical InvestigationNational Institutes of HealthBaltimoreMarylandUSA
- PharmacologyUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - J. F. O'Connell
- National Institute on Aging, Laboratory of Clinical InvestigationNational Institutes of HealthBaltimoreMarylandUSA
| | - O. D. Carlson
- National Institute on Aging, Laboratory of Clinical InvestigationNational Institutes of HealthBaltimoreMarylandUSA
| | - I. González‐Mariscal
- National Institute on Aging, Laboratory of Clinical InvestigationNational Institutes of HealthBaltimoreMarylandUSA
| | - Y. Kim
- National Institute on Aging, Laboratory of Clinical InvestigationNational Institutes of HealthBaltimoreMarylandUSA
| | - R. Moaddel
- National Institute on Aging, Laboratory of Clinical InvestigationNational Institutes of HealthBaltimoreMarylandUSA
| | - P. Ghosh
- National Institute on Aging, Laboratory of Clinical InvestigationNational Institutes of HealthBaltimoreMarylandUSA
| | - J. M. Egan
- National Institute on Aging, Laboratory of Clinical InvestigationNational Institutes of HealthBaltimoreMarylandUSA
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McIntosh AL, Atshaves BP, Martin GG, Landrock D, Milligan S, Landrock KK, Huang H, Storey SM, Mackie J, Schroeder F, Kier AB. Effect of liver fatty acid binding protein (L-FABP) gene ablation on lipid metabolism in high glucose diet (HGD) pair-fed mice. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:985-1004. [PMID: 30910689 DOI: 10.1016/j.bbalip.2019.03.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 03/02/2019] [Accepted: 03/21/2019] [Indexed: 01/06/2023]
Abstract
Liver fatty acid binding protein (L-FABP) is the major fatty acid binding/"chaperone" protein in hepatic cytosol. Although fatty acids can be derived from the breakdown of dietary fat and glucose, relatively little is known regarding the impact of L-FABP on phenotype in the context of high dietary glucose. Potential impact was examined in wild-type (WT) and Lfabp gene ablated (LKO) female mice fed either a control or pair-fed high glucose diet (HGD). WT mice fed HGD alone exhibited decreased whole body weight gain and weight gain/kcal food consumed-both as reduced lean tissue mass (LTM) and fat tissue mass (FTM). Conversely, LKO alone increased weight gain, lean tissue mass, and fat tissue mass while decreasing serum β-hydroxybutyrate (indicative of hepatic fatty acid oxidation)-regardless of diet. Both LKO alone and HGD alone significantly altered the serum lipoprotein profile and increased triacylglycerol (TG), but in HGD mice the LKO did not further exacerbate serum TG content. HGD had little effect on hepatic lipid composition in WT mice, but prevented the LKO-induced selective increase in hepatic phospholipid, free-cholesterol and cholesteryl-ester. Taken together, these findings suggest that high glucose diet diminished the effects of LKO on the whole body and lipid phenotype of these mice.
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Affiliation(s)
- Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Barbara P Atshaves
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, United States of America
| | - Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Sherrelle Milligan
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Kerstin K Landrock
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Stephen M Storey
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - John Mackie
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, United States of America
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843, United States of America.
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Huang H, McIntosh AL, Martin GG, Dangott LJ, Kier AB, Schroeder F. Structural and Functional Interaction of Δ 9-Tetrahydrocannabinol with Liver Fatty Acid Binding Protein (FABP1). Biochemistry 2018; 57:6027-6042. [PMID: 30232874 DOI: 10.1021/acs.biochem.8b00744] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Although serum Δ9-tetrahydrocannabinol (Δ9-THC) undergoes rapid hepatic clearance and metabolism, almost nothing is known regarding the mechanism(s) whereby this highly lipophilic phytocannabinoid is transported for metabolism/excretion. A novel NBD-arachidonoylethanolamide (NBD-AEA) fluorescence displacement assay showed that liver fatty acid binding protein (FABP1), the major hepatic endocannabinoid (EC) binding protein, binds the first major metabolite of Δ9-THC (Δ9-THC-OH) as well as Δ9-THC itself. Circular dichroism (CD) confirmed that not only Δ9-THC and Δ9-THC-OH but also downstream metabolites Δ9-THC-COOH and Δ9-THC-CO-glucuronide directly interact with FABP1. Δ9-THC and metabolite interaction differentially altered the FABP1 secondary structure, increasing total α-helix (all), decreasing total β-sheet (Δ9-THC-COOH, Δ9-THC-CO-glucuronide), increasing turns (Δ9-THC-OH, Δ9-THC-COOH, Δ9-THC-CO-glucuronide), and decreasing unordered structure (Δ9-THC, Δ9-THC-OH). Cultured primary hepatocytes from wild-type (WT) mice took up and converted Δ9-THC to the above metabolites. Fabp1 gene ablation (LKO) dramatically increased hepatocyte accumulation of Δ9-THC and even more so its primary metabolites Δ9-THC-OH and Δ9-THC-COOH. Concomitantly, rtPCR and Western blotting indicated that LKO significantly increased Δ9-THC's ability to regulate downstream nuclear receptor transcription of genes important in both EC ( Napepld > Daglb > Dagla, Naaa, Cnr1) and lipid ( Cpt1A > Fasn, FATP4) metabolism. Taken together, the data indicated that FABP1 may play important roles in Δ9-THC uptake and elimination as well as Δ9-THC induction of genes regulating hepatic EC levels and downstream targets in lipid metabolism.
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Affiliation(s)
- Huan Huang
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| | - Avery L McIntosh
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| | - Gregory G Martin
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| | - Lawrence J Dangott
- Protein Chemistry Laboratory , Texas A&M University , College Station , Texas 77843-2128 , United States
| | - Ann B Kier
- Department of Pathobiology , Texas A&M University , College Station , Texas 77843-4467 , United States
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
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Bougarne N, Weyers B, Desmet SJ, Deckers J, Ray DW, Staels B, De Bosscher K. Molecular Actions of PPARα in Lipid Metabolism and Inflammation. Endocr Rev 2018; 39:760-802. [PMID: 30020428 DOI: 10.1210/er.2018-00064] [Citation(s) in RCA: 378] [Impact Index Per Article: 63.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Accepted: 07/10/2018] [Indexed: 12/13/2022]
Abstract
Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor of clinical interest as a drug target in various metabolic disorders. PPARα also exhibits marked anti-inflammatory capacities. The first-generation PPARα agonists, the fibrates, have however been hampered by drug-drug interaction issues, statin drop-in, and ill-designed cardiovascular intervention trials. Notwithstanding, understanding the molecular mechanisms by which PPARα works will enable control of its activities as a drug target for metabolic diseases with an underlying inflammatory component. Given its role in reshaping the immune system, the full potential of this nuclear receptor subtype as a versatile drug target with high plasticity becomes increasingly clear, and a novel generation of agonists may pave the way for novel fields of applications.
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Affiliation(s)
- Nadia Bougarne
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
- Receptor Research Laboratories, Nuclear Receptor Laboratory, VIB Center for Medical Biotechnology, Ghent, Belgium
| | - Basiel Weyers
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
- Receptor Research Laboratories, Nuclear Receptor Laboratory, VIB Center for Medical Biotechnology, Ghent, Belgium
| | - Sofie J Desmet
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
- Receptor Research Laboratories, Nuclear Receptor Laboratory, VIB Center for Medical Biotechnology, Ghent, Belgium
| | - Julie Deckers
- Department of Internal Medicine, Ghent University, Ghent, Belgium
- Laboratory of Immunoregulation, VIB Center for Inflammation Research, Ghent (Zwijnaarde), Belgium
| | - David W Ray
- Division of Metabolism and Endocrinology, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester, United Kingdom
| | - Bart Staels
- Université de Lille, U1011-European Genomic Institute for Diabetes, Lille, France
- INSERM, U1011, Lille, France
- Centre Hospitalier Universitaire de Lille, Lille, France
- Institut Pasteur de Lille, Lille, France
| | - Karolien De Bosscher
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
- Receptor Research Laboratories, Nuclear Receptor Laboratory, VIB Center for Medical Biotechnology, Ghent, Belgium
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Landrock D, Milligan S, Martin GG, McIntosh AL, Landrock KK, Schroeder F, Kier AB. Effect of Fabp1/Scp-2/Scp-x Ablation on Whole Body and Hepatic Phenotype of Phytol-Fed Male Mice. Lipids 2017; 52:385-397. [PMID: 28382456 PMCID: PMC5500168 DOI: 10.1007/s11745-017-4249-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 03/28/2017] [Indexed: 11/29/2022]
Abstract
Liver fatty acid binding protein (Fabp1) and sterol carrier protein-2/sterol carrier protein-x (SCP-2/SCP-x) genes encode proteins that enhance hepatic uptake, cytosolic transport, and peroxisomal oxidation of toxic branched-chain fatty acids derived from dietary phytol. Since male wild-type (WT) mice express markedly higher levels of these proteins than females, the impact of ablating both genes (TKO) was examined in phytol-fed males. In WT males, high phytol diet alone had little impact on whole body weight and did not alter the proportion of lean tissue mass (LTM) versus fat tissue mass (FTM). TKO conferred on dietary phytol the ability to induce weight loss as well as reduce liver weight, FTM, and even more so LTM. Concomitantly TKO induced hepatic lipid accumulation, preferentially threefold increased phospholipid (PL) at the expense of decreased triacylglycerol (TG) and total cholesterol. Increased PL was associated with upregulation of membrane fatty acid transport/translocase proteins (FATP 2,4), cytosolic fatty acid/fatty acyl-CoA binding proteins (FABP2, ACBP), and the rate limiting enzyme in PL synthesis (Gpam). Decreased TG and cholesterol levels were not attributable to altered levels in respective synthetic enzymes or nuclear receptors. These data suggest that the higher level of Fabp1 and Scp2/Scpx gene products in WT males was protective against deleterious effects of dietary phytol, but TKO significantly exacerbated phytol effects in males.
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Affiliation(s)
- Danilo Landrock
- Department of Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, TVMC, College Station, TX, 77843-4467, USA
| | - Sherrelle Milligan
- Department of Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, TVMC, College Station, TX, 77843-4467, USA
| | - Gregory G Martin
- Department of Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Kerstin K Landrock
- Department of Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, TVMC, College Station, TX, 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Ann B Kier
- Department of Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, TVMC, College Station, TX, 77843-4467, USA.
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10
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Bedi S, Hines GV, Lozada-Fernandez VV, de Jesus Piva C, Kaliappan A, Rider SD, Hostetler HA. Fatty acid binding profile of the liver X receptor α. J Lipid Res 2016; 58:393-402. [PMID: 28011707 PMCID: PMC5282955 DOI: 10.1194/jlr.m072447] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 12/16/2016] [Indexed: 12/12/2022] Open
Abstract
Liver X receptor (LXR)α is a nuclear receptor that responds to oxysterols and cholesterol overload by stimulating cholesterol efflux, transport, conversion to bile acids, and excretion. LXRα binds to and is regulated by synthetic (T-0901317, GW3695) and endogenous (oxysterols) ligands. LXRα activity is also modulated by FAs, but the ligand binding specificity of FA and acyl-CoA derivatives for LXRα remains unknown. We investigated whether LXRα binds FA or FA acyl-CoA with affinities that mimic in vivo concentrations, examined the effect of FA chain length and the degree of unsaturation on binding, and investigated whether FAs regulate LXRα activation. Saturated medium-chain FA (MCFA) displayed binding affinities in the low nanomolar concentration range, while long-chain fatty acyl-CoA did not bind or bound weakly to LXRα. Circular dichroic spectra and computational docking experiments confirmed that MCFA bound to the LXRα ligand binding pocket similar to the known synthetic agonist of LXRα (T0901317), but with limited change to the conformation of the receptor. Transactivation assays showed that MCFA activated LXRα, whereas long-chain FA caused no effect. Our results suggest that LXRα functions as a receptor for saturated FA or acyl-CoA of C10 and C12 in length.
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Affiliation(s)
- Shimpi Bedi
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435
| | - Genesis Victoria Hines
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435
| | - Valery V Lozada-Fernandez
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435
| | - Camila de Jesus Piva
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435
| | - Alagammai Kaliappan
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435
| | - S Dean Rider
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435
| | - Heather A Hostetler
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435
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11
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Zheng J, Gao C, Wang M, Tran P, Mai N, Finley JW, Heymsfield SB, Greenway FL, Li Z, Heber D, Burton JH, Johnson WD, Laine RA. Lower Doses of Fructose Extend Lifespan in Caenorhabditis elegans. J Diet Suppl 2016; 14:264-277. [PMID: 27680107 DOI: 10.1080/19390211.2016.1212959] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Epidemiological studies indicate that the increased consumption of sugars including sucrose and fructose in beverages correlate with the prevalence of obesity, type-2 diabetes, insulin resistance, hyperinsulinemia, hypertriglyceridemia, and hypertension in humans. A few reports suggest that fructose extends lifespan in Saccharomyces cerevisiae. In Anopheles gambiae, fructose, glucose, or glucose plus fructose also extended lifespan. New results presented here suggest that fructose extends lifespan in Caenorhabditis elegans (C. elegans) wild type (N2). C. elegans were fed standard laboratory food source (E. coli OP50), maintained in liquid culture. Experimental groups received additional glucose (111 mM), fructose (55 mM, 111 mM, or 555 mM), sucrose (55 mM, 111 mM, or 555 mM), glucose (167 mM) plus fructose (167 mM) (G&F), or high fructose corn syrup (HFCS, 333 mM). In four replicate experiments, fructose dose-dependently increased mean lifespan at 55 mM or 111 m Min N2, but decreased lifespan at 555 mM (P < 0.001). Sucrose did not affect the lifespan. Glucose reduced lifespan (P < 0.001). Equal amount of G&F or HFCS reduced lifespan (P < 0.0001). Intestinal fat deposition (IFD) was increased at a higher dose of fructose (555 mM), glucose (111 mM), and sucrose (55 mM, 111 mM, and 555 mM). Here we report a biphasic effect of fructose increasing lifespan at lower doses and shortening lifespan at higher doses with an inverse effect on IFD. In view of reports that fructose increases lifespan in yeast, mosquitoes and now nematodes, while decreasing fat deposition (in nematodes) at lower concentrations, further research into the relationship of fructose to lifespan and fat accumulation in vertebrates and mammals is indicated.
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Affiliation(s)
- Jolene Zheng
- a Pennington Biomedical Research Center , Louisiana State University and A & M College , Baton Rouge , LA , USA
| | - Chenfei Gao
- b School of Nutrition and Food Sciences , Louisiana State University Agriculture Center , Baton Rouge , LA , USA
| | - Mingming Wang
- b School of Nutrition and Food Sciences , Louisiana State University Agriculture Center , Baton Rouge , LA , USA
| | - Phuongmai Tran
- c Department of Biological Sciences, and Department of Chemistry , Louisiana State University and A & M College , Baton Rouge , LA , USA
| | - Nancy Mai
- c Department of Biological Sciences, and Department of Chemistry , Louisiana State University and A & M College , Baton Rouge , LA , USA
| | - John W Finley
- b School of Nutrition and Food Sciences , Louisiana State University Agriculture Center , Baton Rouge , LA , USA
| | - Steven B Heymsfield
- a Pennington Biomedical Research Center , Louisiana State University and A & M College , Baton Rouge , LA , USA
| | - Frank L Greenway
- a Pennington Biomedical Research Center , Louisiana State University and A & M College , Baton Rouge , LA , USA
| | - Zhaoping Li
- d Department of Nutrition , University of California , Los Angeles , CA , USA
| | - David Heber
- d Department of Nutrition , University of California , Los Angeles , CA , USA
| | - Jeffrey H Burton
- a Pennington Biomedical Research Center , Louisiana State University and A & M College , Baton Rouge , LA , USA
| | - William D Johnson
- a Pennington Biomedical Research Center , Louisiana State University and A & M College , Baton Rouge , LA , USA
| | - Roger A Laine
- c Department of Biological Sciences, and Department of Chemistry , Louisiana State University and A & M College , Baton Rouge , LA , USA
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12
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Gao C, King ML, Fitzpatrick ZL, Wei W, King JF, Wang M, Greenway FL, Finley JW, Burton JH, Johnson WD, Keenan MJ, Enright FM, Martin RJ, Zheng J. Prowashonupana barley dietary fibre reduces body fat and increases insulin sensitivity in Caenorhabditis elegans model. J Funct Foods 2015; 18:564-574. [PMID: 27721901 PMCID: PMC5052015 DOI: 10.1016/j.jff.2015.08.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Prowashonupana barley (PWB) is high in β-glucan with moderate content of resistant starch. PWB reduced intestinal fat deposition (IFD) in wild type Caenorhabditis elegans (C. elegans, N2), and in sir-2.1 or daf-16 null mutants, and sustained a surrogate marker of lifespan, pharyngeal pumping rate (PPR), in N2, sir-2.1, daf-16, or daf-16/daf-2 mutants. Hyperglycaemia (2% glucose) reversed or reduced the PWB effect on IFD in N2 or daf-16/daf-2 mutants with a sustained PPR. mRNA expression of cpt-1, cpt-2, ckr-1, and gcy-8 were dose-dependently reduced in N2 or daf-16 mutants, elevated in daf-16/daf-2 mutants with reduction in cpt-1, and unchanged in sir-2.1 mutants. mRNA expressions were increased by hyperglycaemia in N2 or daf-16/daf-2 mutants, while reduced in sir-2.1 or daf-16 mutants. The effects of PWB in the C. elegans model appeared to be primarily mediated via sir-2.1, daf-16, and daf-16/daf-2. These data suggest that PWB and β-glucans may benefit hyperglycaemia-impaired lipid metabolism.
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Affiliation(s)
- Chenfei Gao
- School of Nutrition and Food Sciences, College of
Agriculture
| | | | | | - Wenqian Wei
- School of Life Sciences, Fudan University, Shanghai,
China
| | - Jason F. King
- School of Nutrition and Food Sciences, College of
Agriculture
| | - Mingming Wang
- School of Nutrition and Food Sciences, College of
Agriculture
| | - Frank L. Greenway
- Pennington Biomedical Research Center; Louisiana State
University, Baton Rouge, Louisiana 70803, 70808
| | - John W. Finley
- School of Nutrition and Food Sciences, College of
Agriculture
| | - Jeffrey H. Burton
- Pennington Biomedical Research Center; Louisiana State
University, Baton Rouge, Louisiana 70803, 70808
| | - William D. Johnson
- Pennington Biomedical Research Center; Louisiana State
University, Baton Rouge, Louisiana 70803, 70808
| | - Michael J. Keenan
- School of Nutrition and Food Sciences, College of
Agriculture
- Pennington Biomedical Research Center; Louisiana State
University, Baton Rouge, Louisiana 70803, 70808
| | | | | | - Jolene Zheng
- Pennington Biomedical Research Center; Louisiana State
University, Baton Rouge, Louisiana 70803, 70808
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13
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Gao C, Gao Z, Greenway FL, Burton JH, Johnson WD, Keenan MJ, Enright FM, Martin RJ, Chu Y, Zheng J. Oat consumption reduced intestinal fat deposition and improved health span in Caenorhabditis elegans model. Nutr Res 2015; 35:834-43. [PMID: 26253816 PMCID: PMC4561582 DOI: 10.1016/j.nutres.2015.06.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 06/08/2015] [Accepted: 06/26/2015] [Indexed: 12/15/2022]
Abstract
In addition to their fermentable dietary fiber and the soluble β-glucan fiber, oats have unique avenanthramides that have anti-inflammatory and antioxidant properties that reduce coronary heart disease in human clinical trials. We hypothesized that oat consumption will increase insulin sensitivity, reduce body fat, and improve health span in Caenorhabditis elegans through a mechanism involving the daf-2 gene, which codes for the insulin/insulin-like growth factor-1–like receptor, and that hyperglycemia will attenuate these changes. Caenorhabditis elegans wild type (N2) and the null strains sir-2.1, daf-16, and daf-16/daf-2 were fed Escherichia coli (OP50) and oat flakes (0.5%, 1.0%, or 3%) with and without 2% glucose. Oat feeding decreased intestinal fat deposition in N2, daf-16, or daf-16/daf-2 strains (P < .05); and glucose did not affect intestinal fat deposition response. The N2, daf-16, or sir-2.1 mutant increased the pharyngeal pumping rate (P < .05), a surrogate marker of life span, following oat consumption. Oat consumption increased ckr-1, gcy-8, cpt-1, and cpt-2 mRNA expression in both the N2 and the sir-2.1 mutant, with significantly higher expression in sir-2.1 than in N2 (P < .01). Additional glucose further increased expression 1.5-fold of the 4 genes in N2 (P < .01), decreased the expression of all except cpt-1 in the daf-16 mutant, and reduced mRNA expression of the 4 genes in the daf-16/daf-2 mutant (P < .01). These data suggest that oat consumption reduced fat storage and increased ckr-1, gcy-8, cpt-1, or cpt-2 through the sir-2.1 genetic pathway. Oat consumption may be a beneficial dietary intervention for reducing fat accumulation, augmenting health span, and improving hyperglycemia-impaired lipid metabolism.
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Affiliation(s)
- Chenfei Gao
- School of Nutrition and Food Sciences, Louisiana State University, Agricultural Center, Baton Rouge, LA, 70803
| | - Zhanguo Gao
- Antioxidant and Gene Regulation Laboratory, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA, 70808
| | - Frank L Greenway
- Outpatient unit, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA, 70808
| | - Jeffrey H Burton
- Department of Biostatistics, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA, 70808
| | - William D Johnson
- Department of Biostatistics, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA, 70808
| | - Michael J Keenan
- School of Nutrition and Food Sciences, Louisiana State University, Agricultural Center, Baton Rouge, LA, 70803
| | - Frederick M Enright
- School of Animal Sciences, Louisiana State University, Agricultural Center, Baton Rouge, LA, 70803
| | | | - YiFang Chu
- Quaker Oats Center of Excellence, PepsiCo Global R&D Nutrition, Barrington, IL, 60010
| | - Jolene Zheng
- Bioactive Screening Lab, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA, 70808.
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14
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Fang L, Cho HJ, Chan C, Feig M. Binding site multiplicity with fatty acid ligands: implications for the regulation of PKR kinase autophosphorylation with palmitate. Proteins 2014; 82:2429-42. [PMID: 24862841 DOI: 10.1002/prot.24607] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 04/17/2014] [Accepted: 05/09/2014] [Indexed: 01/09/2023]
Abstract
Saturated long chain-free fatty acids (FFAs), especially palmitate, have been implicated in apoptosis by inhibiting the activity of PKR (double-stranded RNA-dependent protein kinase). We recently found evidence that palmitate interacts directly with the kinase domain of PKR, subsequently inhibiting the autophosphorylation of PKR. To investigate the interactions of palmitate with PKR and its effects on PKR autophosphorylation, we performed extensive unbiased MD simulations combined with biochemical and biophysical experiments. The simulations predict multiple putative binding sites of palmitate on both the phosphorylated and unphosphorylated PKR with similar binding affinities. Ligand-protein interactions involving a large variety of different binding modes challenge the conventional view of highly specific, single binding sites. Key interactions of palmitate involve the αC-helix of PKR, especially near residue R307. Experimental mutation of R307 was found to affect palmitate binding and reduce its inhibitory effect. Based on this study a new allosteric mechanism is proposed where palmitate binding to the αC-helix prevents the inactive-to-active transition of PKR and subsequently reduces its ability to autophosphorylate.
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Affiliation(s)
- Liang Fang
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, 48824
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15
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Oswal DP, Alter GM, Rider SD, Hostetler HA. A single amino acid change humanizes long-chain fatty acid binding and activation of mouse peroxisome proliferator-activated receptor α. J Mol Graph Model 2014; 51:27-36. [PMID: 24858253 DOI: 10.1016/j.jmgm.2014.04.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 04/09/2014] [Accepted: 04/16/2014] [Indexed: 10/25/2022]
Abstract
Peroxisome proliferator-activated receptor α (PPARα) is an important regulator of hepatic lipid metabolism which functions through ligand binding. Despite high amino acid sequence identity (>90%), marked differences in PPARα ligand binding, activation and gene regulation have been noted across species. Similar to previous observations with synthetic agonists, we have recently reported differences in ligand affinities and extent of activation between human PPARα (hPPARα) and mouse PPARα (mPPARα) in response to long chain fatty acids (LCFA). The present study was aimed to determine if structural alterations could account for these differences. The binding of PPARα to LCFA was examined through in silico molecular modeling and docking simulations. Modeling suggested that variances at amino acid position 272 are likely to be responsible for differences in saturated LCFA binding to hPPARα and mPPARα. To confirm these results experimentally, LCFA binding, circular dichroism, and transactivation studies were performed using a F272I mutant form of mPPARα. Experimental data correlated with in silico docking simulations, further confirming the importance of amino acid 272 in LCFA binding. Although the driving force for evolution of species differences at this position are yet unidentified, this study enhances our understanding of ligand-induced regulation by PPARα and demonstrates the efficacy of molecular modeling and docking simulations.
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Affiliation(s)
- Dhawal P Oswal
- Department of Biochemistry & Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, United States
| | - Gerald M Alter
- Department of Biochemistry & Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, United States
| | - S Dean Rider
- Department of Biochemistry & Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, United States
| | - Heather A Hostetler
- Department of Biochemistry & Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, United States.
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16
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Balanarasimha M, Davis AM, Soman FL, Rider SD, Hostetler HA. Ligand-regulated heterodimerization of peroxisome proliferator-activated receptor α with liver X receptor α. Biochemistry 2014; 53:2632-43. [PMID: 24713062 PMCID: PMC4007980 DOI: 10.1021/bi401679y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Peroxisome proliferator-activated receptor α (PPARα) and liver X receptor α (LXRα) are members of the nuclear receptor superfamily that function to regulate lipid metabolism. Complex interactions between the LXRα and PPARα pathways exist, including competition for the same heterodimeric partner, retinoid X receptor α (RXRα). Although data have suggested that PPARα and LXRα may interact directly, the role of endogenous ligands in such interactions has not been investigated. Using in vitro protein-protein binding assays, circular dichroism, and co-immunoprecipitation of endogenous proteins, we established that full-length human PPARα and LXRα interact with high affinity, resulting in altered protein conformations. We demonstrated for the first time that the affinity of this interaction and the resulting conformational changes could be altered by endogenous PPARα ligands, namely long chain fatty acids (LCFA) or their coenzyme A thioesters. This heterodimer pair was capable of binding to PPARα and LXRα response elements (PPRE and LXRE, respectively), albeit with an affinity lower than that of the respective heterodimers formed with RXRα. LCFA had little effect on binding to the PPRE but suppressed binding to the LXRE. Ectopic expression of PPARα and LXRα in mammalian cells yielded an increased level of PPRE transactivation compared to overexpression of PPARα alone and was largely unaffected by LCFA. Overexpression of both receptors also resulted in transactivation from an LXRE, with decreased levels compared to that of LXRα overexpression alone, and LCFA suppressed transactivation from the LXRE. These data are consistent with the hypothesis that ligand binding regulates heterodimer choice and downstream gene regulation by these nuclear receptors.
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Affiliation(s)
- Madhumitha Balanarasimha
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University , Dayton, Ohio 45435, United States
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17
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Oswal DP, Balanarasimha M, Loyer JK, Bedi S, Soman FL, Rider SD, Hostetler HA. Divergence between human and murine peroxisome proliferator-activated receptor alpha ligand specificities. J Lipid Res 2013; 54:2354-65. [PMID: 23797899 DOI: 10.1194/jlr.m035436] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Peroxisome proliferator-activated receptor α (PPARα) belongs to the family of ligand-dependent nuclear transcription factors that regulate energy metabolism. Although there exists remarkable overlap in the activities of PPARα across species, studies utilizing exogenous PPARα ligands suggest species differences in binding, activation, and physiological effects. While unsaturated long-chain fatty acids (LCFA) and their thioesters (long-chain fatty acyl-CoA; LCFA-CoA) function as ligands for recombinant mouse PPARα (mPPARα), no such studies have been conducted with full-length human PPARα (hPPARα). The objective of the current study was to determine whether LCFA and LCFA-CoA constitute high-affinity endogenous ligands for hPPARα or whether there exist species differences for ligand specificity and affinity. Both hPPARα and mPPARα bound with high affinity to LCFA-CoA; however, differences were noted in LCFA affinities. A fluorescent LCFA analog was bound strongly only by mPPARα, and naturally occurring saturated LCFA was bound more strongly by hPPARα than mPPARα. Similarly, unsaturated LCFA induced transactivation of both hPPARα and mPPARα, whereas saturated LCFA induced transactivation only in hPPARα-expressing cells. These data identified LCFA and LCFA-CoA as endogenous ligands of hPPARα, demonstrated species differences in binding specificity and activity, and may help delineate the role of PPARα as a nutrient sensor in metabolic regulation.
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Affiliation(s)
- Dhawal P Oswal
- Department of Biochemistry & Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, USA
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18
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High glucose potentiates L-FABP mediated fibrate induction of PPARα in mouse hepatocytes. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:1412-25. [PMID: 23747828 DOI: 10.1016/j.bbalip.2013.05.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 05/17/2013] [Accepted: 05/30/2013] [Indexed: 01/22/2023]
Abstract
Although liver fatty acid binding protein (L-FABP) binds fibrates and PPARα in vitro and enhances fibrate induction of PPARα in transformed cells, the functional significance of these findings is unclear, especially in normal hepatocytes. Studies with cultured primary mouse hepatocytes show that: 1) At physiological (6mM) glucose, fibrates (bezafibrate, fenofibrate) only weakly activated PPARα transcription of genes in LCFA β-oxidation; 2) High (11-20mM) glucose, but not maltose (osmotic control), significantly potentiated fibrate-induction of mRNA of these and other PPARα target genes to increase LCFA β-oxidation. These effects were associated with fibrate-mediated redistribution of L-FABP into nuclei-an effect prolonged by high glucose-but not with increased de novo fatty acid synthesis from glucose; 3) Potentiation of bezafibrate action by high glucose required an intact L-FABP/PPARα signaling pathway as shown with L-FABP null, PPARα null, PPARα inhibitor-treated WT, or PPARα-specific fenofibrate-treated WT hepatocytes. High glucose alone in the absence of fibrate was ineffective. Thus, high glucose potentiation of PPARα occurred through FABP/PPARα rather than indirectly through other PPARs or glucose induced signaling pathways. These data indicated L-FABP's importance in fibrate-induction of hepatic PPARα LCFA β-oxidative genes, especially in the context of high glucose levels.
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19
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Bionaz M, Chen S, Khan MJ, Loor JJ. Functional Role of PPARs in Ruminants: Potential Targets for Fine-Tuning Metabolism during Growth and Lactation. PPAR Res 2013; 2013:684159. [PMID: 23737762 PMCID: PMC3657398 DOI: 10.1155/2013/684159] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2012] [Revised: 03/01/2013] [Accepted: 03/01/2013] [Indexed: 12/31/2022] Open
Abstract
Characterization and biological roles of the peroxisome proliferator-activated receptor (PPAR) isotypes are well known in monogastrics, but not in ruminants. However, a wealth of information has accumulated in little more than a decade on ruminant PPARs including isotype tissue distribution, response to synthetic and natural agonists, gene targets, and factors affecting their expression. Functional characterization demonstrated that, as in monogastrics, the PPAR isotypes control expression of genes involved in lipid metabolism, anti-inflammatory response, development, and growth. Contrary to mouse, however, the PPARγ gene network appears to controls milk fat synthesis in lactating ruminants. As in monogastrics, PPAR isotypes in ruminants are activated by long-chain fatty acids, therefore, making them ideal candidates for fine-tuning metabolism in this species via nutrients. In this regard, using information accumulated in ruminants and monogastrics, we propose a model of PPAR isotype-driven biological functions encompassing key tissues during the peripartal period in dairy cattle.
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Affiliation(s)
- Massimo Bionaz
- Animal and Rangeland Sciences, Oregon State University, Corvallis, OR 97330, USA
| | - Shuowen Chen
- Animal and Nutritional Sciences, University of Illinois, Urbana, IL 61801, USA
| | - Muhammad J. Khan
- Animal and Nutritional Sciences, University of Illinois, Urbana, IL 61801, USA
| | - Juan J. Loor
- Animal and Nutritional Sciences, University of Illinois, Urbana, IL 61801, USA
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20
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Inhibitors of Fatty Acid Synthesis Induce PPAR α -Regulated Fatty Acid β -Oxidative Genes: Synergistic Roles of L-FABP and Glucose. PPAR Res 2013; 2013:865604. [PMID: 23533380 PMCID: PMC3600304 DOI: 10.1155/2013/865604] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 12/21/2012] [Indexed: 12/21/2022] Open
Abstract
While TOFA (acetyl CoA carboxylase inhibitor) and C75 (fatty acid synthase inhibitor) prevent lipid accumulation by inhibiting fatty acid synthesis, the mechanism of action is not simply accounted for by inhibition of the enzymes alone.
Liver fatty acid binding protein (L-FABP), a mediator of long chain fatty acid signaling to peroxisome
proliferator-activated receptor-α (PPARα) in the nucleus, was found to bind
TOFA and its activated CoA thioester, TOFyl-CoA, with high affinity while binding C75 and C75-CoA
with lower affinity. Binding of TOFA and C75-CoA significantly altered L-FABP secondary structure. High (20 mM) but not physiological
(6 mM) glucose conferred on both TOFA and C75 the ability to induce PPARα transcription of the fatty
acid β-oxidative enzymes CPT1A, CPT2, and ACOX1 in cultured primary hepatocytes from wild-type (WT) mice.
However, L-FABP gene ablation abolished the effects of TOFA and C75 in the context of high glucose. These effects were not associated
with an increased cellular level of unesterified fatty acids but rather by increased intracellular glucose. These findings suggested that L-FABP may function as an intracellular fatty acid synthesis inhibitor binding protein
facilitating TOFA and C75-mediated induction of PPARα in the context of high glucose at levels similar to those in uncontrolled diabetes.
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21
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Petrescu AD, Huang H, Martin GG, McIntosh AL, Storey SM, Landrock D, Kier AB, Schroeder F. Impact of L-FABP and glucose on polyunsaturated fatty acid induction of PPARα-regulated β-oxidative enzymes. Am J Physiol Gastrointest Liver Physiol 2013; 304:G241-56. [PMID: 23238934 PMCID: PMC3566512 DOI: 10.1152/ajpgi.00334.2012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Liver fatty acid binding protein (L-FABP) is the major soluble protein that binds very-long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs) in hepatocytes. However, nothing is known about L-FABP's role in n-3 PUFA-mediated peroxisome proliferator activated receptor-α (PPARα) transcription of proteins involved in long-chain fatty acid (LCFA) β-oxidation. This issue was addressed in cultured primary hepatocytes from wild-type, L-FABP-null, and PPARα-null mice with these major findings: 1) PUFA-mediated increase in the expression of PPARα-regulated LCFA β-oxidative enzymes, LCFA/LCFA-CoA binding proteins (L-FABP, ACBP), and PPARα itself was L-FABP dependent; 2) PPARα transcription, robustly potentiated by high glucose but not maltose, a sugar not taken up, correlated with higher protein levels of these LCFA β-oxidative enzymes and with increased LCFA β-oxidation; and 3) high glucose altered the potency of n-3 relative to n-6 PUFA. This was not due to a direct effect of glucose on PPARα transcriptional activity nor indirectly through de novo fatty acid synthesis from glucose. Synergism was also not due to glucose impacting other signaling pathways, since it was observed only in hepatocytes expressing both L-FABP and PPARα. Ablation of L-FABP or PPARα as well as treatment with MK886 (PPARα inhibitor) abolished/reduced PUFA-mediated PPARα transcription of these genes, especially at high glucose. Finally, the PUFA-enhanced L-FABP distribution into nuclei with high glucose augmentation of the L-FABP/PPARα interaction reveals not only the importance of L-FABP for PUFA induction of PPARα target genes in fatty acid β-oxidation but also the significance of a high glucose enhancement effect in diabetes.
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Affiliation(s)
- Anca D. Petrescu
- 1Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, Texas; and
| | - Huan Huang
- 1Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, Texas; and
| | - Gregory G. Martin
- 1Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, Texas; and
| | - Avery L. McIntosh
- 1Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, Texas; and
| | - Stephen M. Storey
- 1Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, Texas; and
| | - Danilo Landrock
- 1Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, Texas; and
| | - Ann B. Kier
- 2Department of Pathobiology, Texas A&M University, TVMC, College Station, Texas
| | - Friedhelm Schroeder
- 1Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, Texas; and
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22
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Novel method to differentiate 3T3 L1 cells in vitro to produce highly sensitive adipocytes for a GLUT4 mediated glucose uptake using fluorescent glucose analog. J Cell Commun Signal 2013; 7:129-40. [PMID: 23292944 DOI: 10.1007/s12079-012-0188-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Accepted: 12/20/2012] [Indexed: 10/27/2022] Open
Abstract
Adipocytes play a vital role in glucose metabolism. 3T3 L1 pre adipocytes after differentiation to adipocytes serve as excellent in vitro models and are useful tools in understanding the glucose metabolism. The traditional approaches adopted in pre adipocyte differentiation are lengthy exercises involving the usage of IBMX and Dexamethasone. Any effort to shorten the time of differentiation and quality expression of functional differentiation in 3T3 L1 cells in terms of enhanced Insulin sensitivity has an advantage in the drug discovery process. Thus, there is a need to develop a new effective method of differentiating the pre adipocytes to adipocytes and to use such methods for developing efficacious therapeutic molecules. We observed that a combination of Dexamethasone and Troglitazone generated differentiated adipocytes over fewer days as compared to the combination of IBMX and Dexamethasone which constitutes the standard protocol followed in our laboratory. The experiments conducted to compare the quality of differentiation yielded by various differentiating agents indicated that the lipid droplet accumulation increased by 112 % and the GLUT4 mediated glucose uptake by 137 % in cells differentiated with Troglitazone and Dexamethasone than in cells differentiated traditionally. The comparative studies conducted for evaluating efficient measurable glucose uptake by GOPOD assay, radioactive (3)H-2-deoxy-D-glucose assay and by non-radioactive 6-NBDG (fluorescent analog of glucose) indicated that the non-radioactive method using 6-NBDG showed a higher signal to noise ratio than the conventional indirect glucose uptake method (GOPOD assay) and the radioactive (3)H-2-deoxy-D-glucose uptake method. Differentiated 3T3 L1 cells when triggered with 2.5 ng/mL of Insulin showed 3.3 fold more glucose uptake in non-radioactive method over the radioactive (3)H-2-deoxy-D-glucose uptake method. The results of this study have suggested that a combination of Dexamethasone and Troglitazone for 3T3 L1 cell differentiation helps in better quality differentiation over a short period of time with increased sensitivity to Insulin. The application of these findings for developing new methods of screening novel Insulin mimetics and for evaluating the immunological responses has been discussed.
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Wang C, Pan Y, Zhang QY, Wang FM, Kong LD. Quercetin and allopurinol ameliorate kidney injury in STZ-treated rats with regulation of renal NLRP3 inflammasome activation and lipid accumulation. PLoS One 2012; 7:e38285. [PMID: 22701621 PMCID: PMC3372527 DOI: 10.1371/journal.pone.0038285] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 05/03/2012] [Indexed: 12/22/2022] Open
Abstract
Hyperuricemia, hyperlipidemia and inflammation are associated with diabetic nephropathy. The NLRP3 inflammasome-mediated inflammation is recently recognized in the development of kidney injury. Urate and lipid are considered as danger signals in the NLRP3 inflammasome activation. Although dietary flavonoid quercetin and allopurinol alleviate hyperuricemia, dyslipidmia and inflammation, their nephroprotective effects are currently unknown. In this study, we used streptozotocin (STZ)-induced diabetic nephropathy model with hyperuricemia and dyslipidemia in rats, and found over-expression of renal inflammasome components NLRP3, apoptosis-associated speck-like protein and Caspase-1, resulting in elevation of IL-1β and IL-18, with subsequently deteriorated renal injury. These findings demonstrated the possible association between renal NLRP3 inflammasome activation and lipid accumulation to superimpose causes of nephrotoxicity in STZ-treated rats. The treatment of quercetin and allopurinol regulated renal urate transport-related proteins to reduce hyperuricemia, and lipid metabolism-related genes to alleviate kidney lipid accumulation in STZ-treated rats. Furthermore, quercetin and allopurinol were found to suppress renal NLRP3 inflammasome activation, at least partly, via their anti-hyperuricemic and anti-dyslipidemic effects, resulting in the amelioration of STZ-induced the superimposed nephrotoxicity in rats. These results may provide a basis for the prevention of diabetes-associated nephrotoxicity with urate-lowering agents such as quercetin and allopurinol.
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Affiliation(s)
- Chuang Wang
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, People's Republic of China
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24
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Abstract
Tight control of storage and synthesis of glucose during nutritional transitions is essential to maintain blood glucose levels, a process in which the liver has a central role. PPARα is the master regulator of lipid metabolism during fasting, but evidence is emerging for a role of PPARα in balancing glucose homeostasis as well. By using PPARα ligands and PPARα(-/-) mice, several crucial genes were shown to be regulated by PPARα in a direct or indirect way. We here review recent evidence that PPARα contributes to the adaptation of hepatic carbohydrate metabolism during the fed-to-fasted or fasted-to-fed transition in rodents.
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Hostetler HA, Balanarasimha M, Huang H, Kelzer MS, Kaliappan A, Kier AB, Schroeder F. Glucose regulates fatty acid binding protein interaction with lipids and peroxisome proliferator-activated receptor α. J Lipid Res 2010; 51:3103-16. [PMID: 20628144 DOI: 10.1194/jlr.m005041] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Although the pathophysiology of diabetes is characterized by elevated levels of glucose and long-chain fatty acids (LCFA), nuclear mechanisms linking glucose and LCFA metabolism are poorly understood. As the liver fatty acid binding protein (L-FABP) shuttles LCFA to the nucleus, where L-FABP directly interacts with peroxisome proliferator-activated receptor-α (PPARα), the effect of glucose on these processes was examined. In vitro studies showed that L-FABP strongly bound glucose and glucose-1-phosphate (K(d) = 103 ± 19 nM and K(d) = 20 ± 3 nM, respectively), resulting in altered L-FABP conformation, increased affinity for lipid ligands, and enhanced interaction with PPARα. In living cells, glucose stimulated cellular uptake and nuclear localization of a nonmetabolizable fluorescent fatty acid analog (BODIPY C-16), particularly in the presence of L-FABP. These data suggest for the first time a direct role of glucose in facilitating L-FABP-mediated uptake and distribution of lipidic ligands to the nucleus for regulation of PPARα transcriptional activity.
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Affiliation(s)
- Heather A Hostetler
- Departments of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, USA
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26
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Zhu JL, Zhang H, Zhang SH, Yao HT, Zhang JB, Zhu LL. Dynamic expression of L-FABP and PPAR-α mRNAs in nonalcoholic fatty liver disease in rats. Shijie Huaren Xiaohua Zazhi 2010; 18:1525-1530. [DOI: 10.11569/wcjd.v18.i15.1525] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To establish a rat model of nonalcoholic fatty liver disease (NAFLD) to detect the changes in the expression of liver fatty acid-binding protein (L-FABP) and peroxisome proliferator-activated receptor-α (PPAR-α) mRNAs in NAFLD and to explore the mechanism underlying the pathogenesis of the disease.
METHODS: Eighty-four male Wistar rats were randomly and equally divided into two groups: control group (fed a normal diet for 18 weeks) and model group (fed a high-fat diet for 12 wk and a normal diet for another 6 wk). Each group was further divided into 7 subgroups for testing at weeks 0, 2, 4, 8, 12, 16 and 18. Rats in the two groups were sacrificed at each time point. Blood samples were taken to measure serum ALT, TG, CHOL, HDL-C and LDL-C. Liver samples were taken for HE staining and for detection of the expression of L-FABP and PPAR-α mRNAs by real-time fluorescence quantitative RT-PCR.
RESULTS: The expression of L-FABP and PPAR-α mRNAs in control rats showed no obvious changes. No steatosis was observed at week 2 in rats fed a high-fat diet. The expression of L-FABP mRNA increased obviously in rats fed a high-fat diet at week 4 (0.59 ± 0.06 vs 0.52 ± 0.03, P < 0.05), reaching the peak at weeks 8 and 12 (0.91 ± 0.07 and 0.92 ± 0.08 vs 0.52 ± 0.03, respectively; both P < 0.01). At week 18, the expression level of L-FABP mRNA declined significantly (0.59 ± 0.04 vs 0.92 ± 0.08, P < 0.01) but was still higher than that in the control group (P < 0.05). The expression of PPAR-α mRNA decreased obviously in rats fed a high-fat diet at week 4 (1.05 ± 0.09 vs 1.13 ± 0.07, P < 0.05), reaching the lowest level at weeks 8 and 12 (0.89 ± 0.04 and 0.85 ± 0.07 vs 1.13 ± 0.07, respectively; both P < 0.01). At week 18, the expression level of PPAR-α mRNA was elevated obviously (1.04 ± 0.07 vs 0.85 ± 0.07, P < 0.01) but was still lower than that in the control group. Steatosis become worst at week 12 but was improved greatly at week 18.
CONCLUSION: In the progression of rat NAFLD, PPAR-α mRNA expression decreases and L-FABP mRNA expression increases as steatosis becomes worse. Steatosis can be improved through diet.
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Pyper SR, Viswakarma N, Yu S, Reddy JK. PPARalpha: energy combustion, hypolipidemia, inflammation and cancer. NUCLEAR RECEPTOR SIGNALING 2010; 8:e002. [PMID: 20414453 PMCID: PMC2858266 DOI: 10.1621/nrs.08002] [Citation(s) in RCA: 283] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 03/04/2010] [Indexed: 12/11/2022]
Abstract
The peroxisome proliferator-activated receptor alpha (PPARalpha, or NR1C1) is a nuclear hormone receptor activated by a structurally diverse array of synthetic chemicals known as peroxisome proliferators. Endogenous activation of PPARalpha in liver has also been observed in certain gene knockout mouse models of lipid metabolism, implying the existence of enzymes that either generate (synthesize) or degrade endogenous PPARalpha agonists. For example, substrates involved in fatty acid oxidation can function as PPARalpha ligands. PPARalpha serves as a xenobiotic and lipid sensor to regulate energy combustion, hepatic steatosis, lipoprotein synthesis, inflammation and liver cancer. Mainly, PPARalpha modulates the activities of all three fatty acid oxidation systems, namely mitochondrial and peroxisomal beta-oxidation and microsomal omega-oxidation, and thus plays a key role in energy expenditure. Sustained activation of PPARalpha by either exogenous or endogenous agonists leads to the development of hepatocellular carcinoma resulting from sustained oxidative and possibly endoplasmic reticulum stress and liver cell proliferation. PPARalpha requires transcription coactivator PPAR-binding protein (PBP)/mediator subunit 1(MED1) for its transcriptional activity.
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Affiliation(s)
| | | | | | - Janardan K. Reddy
- Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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28
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Nohara A, Kobayashi J, Mabuchi H. Retinoid X receptor heterodimer variants and cardiovascular risk factors. J Atheroscler Thromb 2009; 16:303-18. [PMID: 19672026 DOI: 10.5551/jat.no786] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Nuclear receptors are transcription factors that can be activated by specific ligands. Recent progress has shown that retinoid X receptor (RXR) and its heterodimerization partners, including peroxisome proliferator-activated receptors, regulate many important genes involved in energy homeostasis and atherosclerosis, and should be promising therapeutic targets of metabolic syndrome. RXR heterodimers regulate a number of complex cellular processes, and genetic studies of RXR heterodimers have provided important clinical information in addition to knowledge gained from basic research. Genetic variants of RXR heterodimers were screened and investigated, and some variants were shown to have a considerable impact on metabolic disorders, including phenotypic components of familial combined hyperlipidemia. The combined efforts of basic and clinical science regarding nuclear receptors have achieved significant progress in unraveling the inextricably linked control system of energy expenditure, lipid and glucose homeostasis, inflammation, and atherosclerosis.This review summarizes the current understanding regarding RXR heterodimers based on their human genetic variants, which will provide new clues to uncover the background of multifactorial disease, such as metabolic syndrome or familial combined hyperlipidemia.
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Affiliation(s)
- Atsushi Nohara
- Departments of Lipidology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan.
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Hostetler HA, McIntosh AL, Atshaves BP, Storey SM, Payne HR, Kier AB, Schroeder F. L-FABP directly interacts with PPARalpha in cultured primary hepatocytes. J Lipid Res 2009; 50:1663-75. [PMID: 19289416 DOI: 10.1194/jlr.m900058-jlr200] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although studies with liver type fatty acid binding protein (L-FABP) gene ablated mice demonstrate a physiological role for L-FABP in hepatic fatty acid metabolism, little is known about the mechanisms whereby L-FABP elicits these effects. Studies indicate that L-FABP may function to shuttle lipids to the nucleus, thereby increasing the availability of ligands of nuclear receptors, such as peroxisome proliferator-activated receptor-alpha (PPARalpha). The data herein suggest that such mechanisms involve direct interaction of L-FABP with PPARalpha. L-FABP was shown to directly interact with PPARalpha in vitro through co-immunoprecipitation (co-IP) of pure proteins, altered circular dichroic (CD) spectra, and altered fluorescence spectra. In vitro fluorescence resonance energy transfer (FRET) between Cy3-labeled PPARalpha and Cy5-labeled L-FABP proteins showed that these proteins bound with high affinity (Kd approximately 156 nM) and in close proximity (intermolecular distance of 52A). This interaction was further substantiated by co-IP of both proteins from liver homogenates of wild-type mice. Moreover, double immunogold electron microscopy and FRET confocal microscopy of cultured primary hepatocytes showed that L-FABP was in close proximity to PPARalpha (intermolecular distance 40-49A) in vivo. Taken together, these studies were consistent with L-FABP regulating PPARalpha transcriptional activity in hepatocytes through direct interaction with PPARalpha. Our in vitro and imaging experiments demonstrate high affinity, structural molecular interaction of L-FABP with PPARalpha and suggest a functional role for L-FABP interaction with PPARalpha in long chain fatty acid (LCFA) metabolism.
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Affiliation(s)
- Heather A Hostetler
- Department of Physiology and Pharmacology, Texas A&M University, College of Veterinary Medicine and Biomedical Sciences, College Station, TX 77843, USA
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30
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McIntosh AL, Atshaves BP, Hostetler HA, Huang H, Davis J, Lyuksyutova OI, Landrock D, Kier AB, Schroeder F. Liver type fatty acid binding protein (L-FABP) gene ablation reduces nuclear ligand distribution and peroxisome proliferator-activated receptor-alpha activity in cultured primary hepatocytes. Arch Biochem Biophys 2009; 485:160-73. [PMID: 19285478 DOI: 10.1016/j.abb.2009.03.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Revised: 03/03/2009] [Accepted: 03/05/2009] [Indexed: 11/29/2022]
Abstract
The effect of liver type fatty acid binding protein (L-FABP) gene ablation on the uptake and distribution of long chain fatty acids (LCFA) to the nucleus by real-time laser scanning confocal imaging and peroxisome proliferator-activated receptor-alpha (PPARalpha) activity was examined in cultured primary hepatocytes from livers wild-type L-FABP+/+ and gene ablated L-FABP-/- mice. Cultured primary hepatocytes from livers of L-FABP-/- mice exhibited: (i) reduced oxidation of palmitic acid, a common dietary long chain fatty acid (LCFA); (ii) reduced expression of fatty acid oxidative enzymes-proteins transcriptionally regulated by PPARalpha; (iii) reduced palmitic acid-induced PPARalpha co-immunoprecipitation with coactivator SRC-1 concomitant with increased PPARalpha co-immunoprecipitation with coinhibitor N-CoR; (iv) reduced palmitic acid-induced PPARalpha. Diminished PPARalpha activation in L-FABP null hepatocytes was associated with lower uptake of common dietary LCFA (palmitic acid as well as its fluorescent derivative BODIPY FL C(16)), reduced level of total unesterified LCFA, and real-time redistribution of BODIPY FL C(16) from the central nucleoplasm to the nuclear envelope. Taken together, these studies support the hypothesis that L-FABP may facilitate ligand (LCFA)-activated PPARalpha transcriptional activity at least in part by increasing total LCFA ligand available to PPARalpha for inducing PPARalpha-mediated transcription of proteins involved in LCFA metabolism.
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Affiliation(s)
- Avery L McIntosh
- Department of Physiology and Pharmacology, TVMC College Station, TX 77843-4466, USA
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Hostetler HA, Syler LR, Hall LN, Zhu G, Schroeder F, Kier AB. A novel high-throughput screening assay for putative antidiabetic agents through PPARalpha interactions. ACTA ACUST UNITED AC 2008; 13:855-61. [PMID: 18812576 DOI: 10.1177/1087057108323127] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
As natural peroxisome proliferator-activated receptor-alpha (PPARalpha) ligands, high levels of fatty acids and glucose could lead to hyperactivation of PPARalpha, like that seen in diabetes. Important diabetes research goals are to uncover new metabolic or signaling pathways involved in hyperglycemic cellular injury and to develop therapeutics for preventing or reversing this injury. Consequently, 1040 putative antidiabetic agents were screened for their ability to 1) affect PPARalpha lipid binding, 2) directly bind PPARalpha, and 3) alter PPARalpha transactivation in the presence of high glucose. A high-throughput fluorescent binding assay was developed to examine each compound's ability to restore fatty acyl-CoA binding to PPARalpha in the presence of high glucose concentrations. Approximately 1% of the compounds restored acyl-CoA binding by 60% or more. These compounds directly interacted with PPARalpha with high affinity (nM K(d)s), validating the primary screen. Furthermore, these compounds altered PPARalpha transactivation, and 1 strongly reversed the hyperactivation of PPARalpha found in the presence of clofibrate and high glucose levels.
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Affiliation(s)
- Heather A Hostetler
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, Texas 77843-4467, USA
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