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Yang T, Duan H, Li Y, Xu N, Wang Z, Li Z, Chen Y, Du Y, Zhang M, Yan J, Sun C, Wang G, Li W, Li X, Ma F, Huang G. β-hydroxybutyrate and mitochondria mediate the association between medium-chain fatty acids, DHA and mild cognitive impairment: a nested case-control study. Nutr Neurosci 2024:1-10. [PMID: 39225171 DOI: 10.1080/1028415x.2024.2398364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
BACKGROUND Medium-chain fatty acids (MCFAs) and docosahexaenoic acid (DHA) could affect the occurrence of mild cognitive impairment (MCI). β-hydroxybutyrate (BHB), mitochondrial DNA copy number (mtDNAcn) and mitochondrial DNA (mtDNA) deletions might be their potential mechanisms. This study aimed to explore the relationship between MCFAs, DHA and MCI, and potential mechanisms. METHODS This study used data from Tianjin Elderly Nutrition and Cognition (TENC) cohort study, 120 individuals were identified with new onset MCI during follow-up, 120 individuals without MCI were selected by 1:1 matching sex, age, and education levels as the control group from TENC. Conditional logistic regression analysis and mediation effect analysis were used to explore their relationship. RESULTS Higher serum octanoic acid levels (OR: 0.633, 95% CI: 0.520, 0.769), higher serum DHA levels (OR: 0.962, 95% CI: 0.942, 0.981), and more mtDNAcn (OR: 0.436, 95% CI: 0.240, 0.794) were associated with lower MCI risk, while more mtDNA deletions was associated with higher MCI risk (OR: 8.833, 95% CI: 3.909, 19.960). Mediation analysis suggested that BHB and mtDNAcn, in series, have mediation roles in the association between octanoic acid and MCI risk, and mtDNA deletions have mediation roles in the association between DHA and MCI risk. CONCLUSION Higher serum octanoic acid and DHA levels were associated with lower MCI risk. Octanoic acid could affect the incidence of MCI through BHB, then mitochondria function, or through mitochondria function, or directly. Serum DHA level could affect the incidence of MCI through mitochondria function, or directly.
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Affiliation(s)
- Tong Yang
- Department of Epidemiology & Biostatistics, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
| | - Huilian Duan
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
- Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
| | - Yuan Li
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
- Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
| | - Ning Xu
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
- Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
| | - Zehao Wang
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
- Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
| | - Zhenshu Li
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
- Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
| | - Yongjie Chen
- Department of Epidemiology & Biostatistics, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
| | - Yue Du
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
- Department of Social Medicine and Health Management, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
| | - Meilin Zhang
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
- Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
| | - Jing Yan
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
- Department of Social Medicine and Health Management, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
| | - Changqing Sun
- Neurosurgical Department of Baodi Clinical College of Tianjin Medical University, Tianjin, People's Republic of China
| | - Guangshun Wang
- Department of Tumor, Baodi Clinical College of Tianjin Medical University, Tianjin, People's Republic of China
| | - Wen Li
- Department of Epidemiology & Biostatistics, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
| | - Xin Li
- Department of Neurology, The Second Hospital of Tianjin Medical University, Tianjin, People's Republic of China
| | - Fei Ma
- Department of Epidemiology & Biostatistics, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
| | - Guowei Huang
- Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, People's Republic of China
- Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, People's Republic of China
- The Province and Ministry Co-Sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin, People's Republic of China
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2
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Tang J, Li X, Li W, Cao C. The Protective Effect of Octanoic Acid on Sepsis: A Review. Nutr Rev 2024:nuae106. [PMID: 39101596 DOI: 10.1093/nutrit/nuae106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/06/2024] Open
Abstract
Sepsis, a systemic inflammation that occurs in response to a bacterial infection, is a significant medical challenge. Research conducted over the past decade has indicated strong associations among a patient's nutritional status, the composition of their gut microbiome, and the risk, severity, and prognosis of sepsis. Octanoic acid (OA) plays a vital role in combating sepsis and has a protective effect on both animal models and human patients. In this discussion, the potential protective mechanisms of OA in sepsis, focusing on its regulation of the inflammatory response, immune system, oxidative stress, gastrointestinal microbiome and barrier function, metabolic disorders and malnutrition, as well as organ dysfunction are explored. A comprehensive understanding of the mechanisms by which OA act may pave the way for new preventive and therapeutic approaches to sepsis.
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Affiliation(s)
- Jiabao Tang
- Department of General Surgery, Second Affiliated Hospital of Soochow University, Suzhou 215004, China
| | - Xiaohua Li
- Department of General Surgery, Second Affiliated Hospital of Soochow University, Suzhou 215004, China
- Department of Thyroid and Breast Surgery, Suzhou Wuzhong People's Hospital, Suzhou 215004, China
| | - Wei Li
- Department of General Surgery, Second Affiliated Hospital of Soochow University, Suzhou 215004, China
| | - Chun Cao
- Department of General Surgery, Second Affiliated Hospital of Soochow University, Suzhou 215004, China
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3
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Srour N, Caron A, Michael NJ. Do POMC neurons have a sweet tooth for leptin? Special issue: Role of nutrients in nervous control of energy balance. Biochimie 2024; 223:179-187. [PMID: 36122808 DOI: 10.1016/j.biochi.2022.09.006] [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] [Received: 05/21/2022] [Revised: 08/29/2022] [Accepted: 09/09/2022] [Indexed: 11/19/2022]
Abstract
Coordinated detection of changes in metabolic state by the nervous system is fundamental for survival. Hypothalamic pro-opiomelanocortin (POMC) neurons play a critical role in integrating metabolic signals, including leptin levels. They also coordinate adaptative responses and thus represent an important relay in the regulation of energy balance. Despite a plethora of work documenting the effects of individual hormones, nutrients, and neuropeptides on POMC neurons, the importance for crosstalk and additive effects between such signaling molecules is still underexplored. The ability of the metabolic state and the concentrations of nutrients, such as glucose, to influence leptin's effects on POMC neurons appears critical for understanding the function and complexity of this regulatory network. Here, we summarize the current knowledge on the effects of leptin on POMC neuron electrical excitability and discuss factors potentially contributing to variability in these effects, with a particular focus on the mouse models that have been developed and the importance of extracellular glucose levels. This review highlights the importance of the metabolic "environment" for determining hypothalamic neuronal responsiveness to metabolic cues and for determining the fundamental effects of leptin on the activity of hypothalamic POMC neurons.
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Affiliation(s)
- Nader Srour
- Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 chemin Sainte-Foy, Québec, QC, G1V 4G5, Canada; Faculté de Pharmacie, Université Laval, Québec, QC, Canada
| | - Alexandre Caron
- Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 chemin Sainte-Foy, Québec, QC, G1V 4G5, Canada; Faculté de Pharmacie, Université Laval, Québec, QC, Canada; Montreal Diabetes Research Center, QC, Canada.
| | - Natalie Jane Michael
- Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 chemin Sainte-Foy, Québec, QC, G1V 4G5, Canada; Faculté de Pharmacie, Université Laval, Québec, QC, Canada.
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Samsø Mathiasen S, Kanta JM, Frydenberg RP, Lundsgaard A, Guo Z, Fritzen AM, Kiens B, Wiking L, Kleinert M. Novel methodology to enrich medium- and short-chain fatty acids in milk fat to improve metabolic health. Food Funct 2024; 15:7951-7960. [PMID: 38980698 DOI: 10.1039/d4fo00267a] [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: 07/10/2024]
Abstract
Dietary short- and medium-chain fatty acids have been shown to elevate circulating ketone bodies and confer metabolic health benefits. Cow milk fat contains these lipids in a balanced mix but in relatively low concentrations. Enriching them could amplify health benefits of dairy products. Here, we used a volatility-based workflow to produce milk fat with a 2-fold enrichment of medium- and short-chain fatty acids (referred to as MSFAT). Our proof-of-concept studies in mice demonstrated that intake of MSFAT increased circulating ketone bodies, reduced blood glucose levels, and suppressed food intake. In humans, ingestion of MSFAT resulted in increased circulating ketone bodies, trended to attenuate (p = 0.07) postprandial glucose excursion, and acutely elevated energy expenditure. Our findings show that milk products enriched with MSFAT may hold significant metabolic advantages.
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Affiliation(s)
- Sally Samsø Mathiasen
- Department of Food Science, Aarhus University, Aarhus, Denmark.
- CiFood Multidisciplinary Center for Innovative Foods, Aarhus, Denmark
| | - Josephine M Kanta
- The August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
| | - Rikke P Frydenberg
- Department of Food Science, Aarhus University, Aarhus, Denmark.
- CiFood Multidisciplinary Center for Innovative Foods, Aarhus, Denmark
| | - Annemarie Lundsgaard
- The August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
| | - Zheng Guo
- CiFood Multidisciplinary Center for Innovative Foods, Aarhus, Denmark
- Department of Biological and Chemical Engineering, Aarhus University, Aarhus, Denmark
| | - Andreas M Fritzen
- The August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
- Department of Biomedical Sciences, Faculty of Medical and Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bente Kiens
- The August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
| | - Lars Wiking
- Department of Food Science, Aarhus University, Aarhus, Denmark.
- CiFood Multidisciplinary Center for Innovative Foods, Aarhus, Denmark
| | - Maximilian Kleinert
- The August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
- Department of Molecular Physiology of Exercise and Nutrition, German Institute of Human Nutrition (DIfE), Potsdam-Rehbruecke, Nuthetal, Germany.
- Institute of Nutritional Sciences, University of Potsdam, Nuthetal, Germany
- German Center for Diabetes Research (DZD), Munich, Germany
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5
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Cao C, Zhang H, He Z, Zhang K, Qian Z, Shen J, Zheng L, Xue M, Sun S, Li C, Zhao W, Jing J, Ma R, Ge X, Yao B. Octanoic acid mitigates busulfan-induced blood-testis barrier damage by alleviating oxidative stress and autophagy. Lipids Health Dis 2024; 23:180. [PMID: 38862993 PMCID: PMC11165768 DOI: 10.1186/s12944-024-02157-2] [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: 02/08/2024] [Accepted: 05/21/2024] [Indexed: 06/13/2024] Open
Abstract
BACKGROUND The management of male infertility continues to encounter an array of challenges and constraints, necessitating an in-depth exploration of novel therapeutic targets to enhance its efficacy. As an eight-carbon medium-chain fatty acid, octanoic acid (OCA) shows promise for improving health, yet its impact on spermatogenesis remains inadequately researched. METHODS Mass spectrometry was performed to determine the fatty acid content and screen for a pivotal lipid component in the serum of patients with severe spermatogenesis disorders. The sperm quality was examined, and histopathological analysis and biotin tracer tests were performed to assess spermatogenesis function and the integrity of the blood-testis barrier (BTB) in vivo. Cell-based in vitro experiments were carried out to investigate the effects of OCA administration on Sertoli cell dysfunction. This research aimed to elucidate the mechanism by which OCA may influence the function of Sertoli cells. RESULTS A pronounced reduction in OCA content was observed in the serum of patients with severe spermatogenesis disorders, indicating that OCA deficiency is related to spermatogenic disorders. The protective effect of OCA on reproduction was tested in a mouse model of spermatogenic disorder induced by busulfan at a dose 30 mg/kg body weight (BW). The mice in the study were separated into distinct groups and administered varying amounts of OCA, specifically at doses of 32, 64, 128, and 256 mg/kg BW. After evaluating sperm parameters, the most effective dose was determined to be 32 mg/kg BW. In vivo experiments showed that treatment with OCA significantly improved sperm quality, testicular histopathology and BTB integrity, which were damaged by busulfan. Moreover, OCA intervention reduced busulfan-induced oxidative stress and autophagy in mouse testes. In vitro, OCA pretreatment (100 µM) significantly ameliorated Sertoli cell dysfunction by alleviating busulfan (800 µM)-induced oxidative stress and autophagy. Moreover, rapamycin (5 µM)-induced autophagy led to Sertoli cell barrier dysfunction, while OCA administration exerted a protective effect by alleviating autophagy. CONCLUSIONS This study demonstrated that OCA administration suppressed oxidative stress and autophagy to alleviate busulfan-induced BTB damage. These findings provide a deeper understanding of the toxicology of busulfan and a promising avenue for the development of novel OCA-based therapies for male infertility.
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Affiliation(s)
- Chun Cao
- Department of Reproductive Medicine, Affiliated Jinling Hospital, The First School of Clinical Medicine, Southern Medical University, 305 Zhongshan East Road, Nanjing, 210002, China
| | - Hong Zhang
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China
| | - Zhaowanyue He
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China
| | - Kemei Zhang
- Reproductive Medical Center, Jinling Hospital Department, Nanjing Medical University, Nanjing, 210002, Jiangsu, China
| | - Zhang Qian
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China
| | - Jiaming Shen
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China
| | - Lu Zheng
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China
| | - Mengqi Xue
- Reproductive Medical Center, Jinling Hospital Department, Nanjing Medical University, Nanjing, 210002, Jiangsu, China
| | - Shanshan Sun
- College of Life Sciences, Nanjing Normal University, Nanjing, 210023, Jiangsu, China
| | - Chuwei Li
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China
| | - Wei Zhao
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China
| | - Jun Jing
- Reproductive Medical Center, Jinling Hospital Department, Nanjing Medical University, Nanjing, 210002, Jiangsu, China
| | - Rujun Ma
- Department of Reproductive Medicine, Affiliated Jinling Hospital, The First School of Clinical Medicine, Southern Medical University, 305 Zhongshan East Road, Nanjing, 210002, China
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China
| | - Xie Ge
- Department of Reproductive Medicine, Affiliated Jinling Hospital, The First School of Clinical Medicine, Southern Medical University, 305 Zhongshan East Road, Nanjing, 210002, China.
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China.
| | - Bing Yao
- Department of Reproductive Medicine, Affiliated Jinling Hospital, The First School of Clinical Medicine, Southern Medical University, 305 Zhongshan East Road, Nanjing, 210002, China.
- Center of Reproductive Medicine, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, 305 Zhongshan East Road, Nanjing, 210002, Jiangsu, China.
- Reproductive Medical Center, Jinling Hospital Department, Nanjing Medical University, Nanjing, 210002, Jiangsu, China.
- College of Life Sciences, Nanjing Normal University, Nanjing, 210023, Jiangsu, China.
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Dearden L, Furigo IC, Pantaleão LC, Wong LWP, Fernandez-Twinn DS, de Almeida-Faria J, Kentistou KA, Carreira MV, Bidault G, Vidal-Puig A, Ong KK, Perry JRB, Donato J, Ozanne SE. Maternal obesity increases hypothalamic miR-505-5p expression in mouse offspring leading to altered fatty acid sensing and increased intake of high-fat food. PLoS Biol 2024; 22:e3002641. [PMID: 38833481 PMCID: PMC11149872 DOI: 10.1371/journal.pbio.3002641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 04/25/2024] [Indexed: 06/06/2024] Open
Abstract
In utero exposure to maternal obesity programs increased obesity risk. Animal models show that programmed offspring obesity is preceded by hyperphagia, but the mechanisms that mediate these changes are unknown. Using a mouse model of maternal obesity, we observed increased intake of a high-fat diet (HFD) in offspring of obese mothers that precedes the development of obesity. Through small RNA sequencing, we identified programmed overexpression of hypothalamic miR-505-5p that is established in the fetus, lasts to adulthood and is maintained in hypothalamic neural progenitor cells cultured in vitro. Metabolic hormones and long-chain fatty acids associated with obesity increase miR-505-5p expression in hypothalamic neurons in vitro. We demonstrate that targets of miR-505-5p are enriched in fatty acid metabolism pathways and overexpression of miR-505-5p decreased neuronal fatty acid metabolism in vitro. miR-505-5p targets are associated with increased BMI in human genetic studies. Intra-cerebroventricular injection of miR-505-5p in wild-type mice increased HFD intake, mimicking the phenotype observed in offspring exposed to maternal obesity. Conversely, maternal exercise intervention in an obese mouse pregnancy rescued the programmed increase of hypothalamic miR-505-5p in offspring of obese dams and reduced HFD intake to control offspring levels. This study identifies a novel mechanism by which maternal obesity programs obesity in offspring via increased intake of high-fat foods.
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Affiliation(s)
- Laura Dearden
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
| | - Isadora C. Furigo
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
- Universidade de Sao Paulo, Instituto de Ciencias Biomedicas, Departamento de Fisiologia e Biofisica, Sao Paulo, Brazil
- Centre for Health and Life Sciences, Coventry University, Coventry, United Kingdom
| | - Lucas C. Pantaleão
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
| | - L W. P. Wong
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
| | - Denise S. Fernandez-Twinn
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
| | - Juliana de Almeida-Faria
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
- University of Campinas, Faculty of Medical Sciences, Department of Pharmacology, Campinas, Brazil
| | | | - Maria V. Carreira
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
| | - Guillaume Bidault
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
| | - Antonio Vidal-Puig
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
| | - Ken K. Ong
- MRC Epidemiology Unit, Institute of Metabolic Science, Cambridge, United Kingdom
| | - John R. B. Perry
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Epidemiology Unit, Institute of Metabolic Science, Cambridge, United Kingdom
| | - Jose Donato
- Universidade de Sao Paulo, Instituto de Ciencias Biomedicas, Departamento de Fisiologia e Biofisica, Sao Paulo, Brazil
| | - Susan E. Ozanne
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Cambridge, United Kingdom
- MRC Metabolic Diseases Unit, Institute of Metabolic Science, Cambridge, United Kingdom
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7
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Zhang Z, Li X, Cao C. Octanoic acid-rich enteral nutrition attenuated hypercatabolism through the acylated ghrelin-POMC pathway in endotoxemic rats. Nutrition 2024; 119:112329. [PMID: 38215672 DOI: 10.1016/j.nut.2023.112329] [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] [Received: 10/09/2023] [Revised: 12/02/2023] [Accepted: 12/12/2023] [Indexed: 01/14/2024]
Abstract
OBJECTIVES Metabolic disorders and no response to intravenous nutrition because of sepsis have been urgent problems for clinical nutrition support. Enteral nutrition (EN) has been an important clinical therapeutic measure in septic patients; however, simple EN has not demonstrated good performance. This study aimed to investigate the effects of different concentrations of octanoic acid (OA)-rich EN on hypercatabolism in endotoxemic rats and test whether OA-rich EN could attenuate hypercatabolism through the acylated ghrelin-proopiomelanocortin (POMC) pathway. METHODS Rats were randomly divided into six groups: sham, lipopolysaccharide (LPS), LPS + EN and LPS + EN + OA (0.25, 0.5, and 1 g/kg, respectively) groups to investigate the effects of different concentrations of OA-rich EN on hypercatabolism in endotoxemic rats. The rats were then randomly divided into four groups: sham, LPS, LPS + OA, and LPS + OA + Go-CoA-Tat, to test whether OA-rich EN attenuated hypercatabolism through the acylated ghrelin-POMC pathway. Rats received nutrition support via a gastric tube for 3 d (100 kcal/kg daily). Insulin resistance, muscle protein synthesis and atrophy, inflammatory cytokines, ghrelin in circulation and hypothalamus, ghrelin O-acyltransferase (GOAT), and the adenosine 5'-monophosphate-activated protein kinase (AMPK)-autophagy-POMC pathway were measured. RESULTS Compared with simple EN, OA-rich EN promoted the acylation of ghrelin in a dose-dependent manner and attenuated POMC-mediated hypercatabolism in endotoxemic rats. Inhibition of GOAT activity decreased the level of acylated ghrelin and aggravated POMC-mediated hypercatabolism conferred by OA-rich EN. CONCLUSIONS OA-rich EN could increase the level of acylated ghrelin and attenuate hypercatabolism through the acylated ghrelin-POMC pathway compared with simple EN in endotoxemic rats.
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Affiliation(s)
- Zihao Zhang
- Department of General Surgery, the Second Affiliated Hospital of Soochow University, Suzhou, China; Department of Anesthesiology, the Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Xiaohua Li
- Department of General Surgery, the Second Affiliated Hospital of Soochow University, Suzhou, China; Department of Thyroid and Breast Surgery, Suzhou Wuzhong People's Hospital, Suzhou, China
| | - Chun Cao
- Department of General Surgery, the Second Affiliated Hospital of Soochow University, Suzhou, China.
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8
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Baumanns S, Schmitt F, Spahn C, Ringelmann AE, Beis DM, Eckert GP, Wenzel U. Caprylic acid attenuates amyloid-β proteotoxicity by supplying energy via β-oxidation in an Alzheimer's disease model of the nematode Caenorhabditis elegans. Nutr Neurosci 2024; 27:252-261. [PMID: 36800228 DOI: 10.1080/1028415x.2023.2180870] [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: 02/18/2023]
Abstract
Computer-based analysis of motility was used as a measure of amyloid-β (Aβ) proteotoxicity in the transgenic strain GMC101, expressing human Aβ1-42 in body wall muscle cells. Aβ-aggregation was quantified to relate the effects of caprylic acid (CA) to the amount of the proteotoxic protein. Gene knockdowns were induced through RNA-interference (RNAi). Moreover, the estimation of adenosine triphosphate (ATP) levels, the mitochondrial membrane potential (MMP) and oxygen consumption served the evaluation of mitochondrial function. CA improved the motility of GMC101 nematodes and reduced Aβ aggregation. Whereas RNAi for orthologues encoding key enzymes for α-lipoic acid and ketone bodies synthesis did not affect motility stimulation by CA, knockdown of orthologues involved in β-oxidation of fatty acids diminished its effects. The efficient energy gain by application of CA was finally proven by the increase of ATP levels in association with increased oxygen consumption and MMP. In conclusion, CA attenuates Aβ proteotoxicity by supplying energy via FAO. Since especially glucose oxidation is disturbed in Alzheimer´s disease, CA could potentially serve as an alternative energy fuel.
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Affiliation(s)
- Stefan Baumanns
- Molecular Nutrition Research, Interdisciplinary Research Center, Justus-Liebig-University of Giessen, Giessen, Germany
| | - Fabian Schmitt
- Nutrition in Prevention and Therapy, Justus-Liebig-University of Giessen, Giessen, Germany
| | - Christopher Spahn
- Molecular Nutrition Research, Interdisciplinary Research Center, Justus-Liebig-University of Giessen, Giessen, Germany
| | - Anne E Ringelmann
- Molecular Nutrition Research, Interdisciplinary Research Center, Justus-Liebig-University of Giessen, Giessen, Germany
| | - Daniel M Beis
- Molecular Nutrition Research, Interdisciplinary Research Center, Justus-Liebig-University of Giessen, Giessen, Germany
| | - Gunter P Eckert
- Nutrition in Prevention and Therapy, Justus-Liebig-University of Giessen, Giessen, Germany
| | - Uwe Wenzel
- Molecular Nutrition Research, Interdisciplinary Research Center, Justus-Liebig-University of Giessen, Giessen, Germany
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9
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Tang J, Li X, Li W, Cao C. Effects of enteral nutrition supplemented with octanoic acid on lipopolysaccharide-induced intestinal injury: role of peroxisome proliferator-activated receptor γ/STAT-1/myeloid differentiation factor 88 pathway. Nutrition 2023; 116:112216. [PMID: 37776839 DOI: 10.1016/j.nut.2023.112216] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 08/26/2023] [Accepted: 09/01/2023] [Indexed: 10/02/2023]
Abstract
OBJECTIVE Enteral nutrition is the key therapy in septic patients. Different formulas of enteral nutrition have various effects on gastrointestinal sepsis. Therefore, we investigated the effects of enteral nutrition supplemented with octanoic acid on lipopolysaccharide-induced intestinal injury and explored the potential mechanism. METHODS First, to investigate the effects of enteral nutrition supplemented with octanoic acid on lipopolysaccharide-induced intestinal injury, rats were randomly divided into four groups: sham, lipopolysaccharide, lipopolysaccharide + enteral nutrition, and lipopolysaccharide + enteral nutrition + octanoic acid. Then, to explore whether enteral nutrition supplemented with octanoic acid can prevent lipopolysaccharide-induced intestinal injury via the peroxisome proliferator-activated receptor γ/STAT-1/myeloid differentiation factor 88 pathway, rats were randomly divided into five groups: sham, lipopolysaccharide, lipopolysaccharide + enteral nutrition + octanoic acid, lipopolysaccharide + enteral nutrition + octanoic acid + SR202, and lipopolysaccharide + pioglitazone. All rats received nutritional support for 3 d. We examined the serum levels of inflammatory factors, pathologic changes, goblet cell density, intestinal tight junction protein expression, and the peroxisome proliferator-activated receptor γ/STAT-1/myeloid differentiation factor 88 pathway in the ileum and colon. The effect of octanoic acid on intestinal epithelium injury was also explored in vitro. RESULTS Enteral nutrition supplemented with octanoic acid significantly decreased the serum levels of inflammatory factors and prevented intestinal barrier dysfunction compared with enteral nutrition alone (P < 0.05). Inhibiting the peroxisome proliferator-activated receptor γ/STAT-1/myeloid differentiation factor 88 pathway exacerbated effects of enteral nutrition supplemented with octanoic acid on intestinal injury (P < 0.05). Activation of the peroxisome proliferator-activated receptor γ/STAT-1/myeloid differentiation factor 88 pathway prevented intestinal injury (P < 0.05). Octanoic acid also exerted a similar effect on intestinal epithelium injury in vitro. CONCLUSIONS Enteral nutrition supplemented with octanoic acid prevents lipopolysaccharide-induced intestinal injury via the peroxisome proliferator-activated receptor γ/STAT-1/myeloid differentiation factor 88 pathway.
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Affiliation(s)
- Jiabao Tang
- Department of General Surgery, Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Xiaohua Li
- Department of Thyroid and Breast Surgery, Suzhou Wuzhong People's Hospital, Suzhou, China
| | - Wei Li
- Department of General Surgery, Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Chun Cao
- Department of General Surgery, Second Affiliated Hospital of Soochow University, Suzhou, China.
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10
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Zhao M, Zhang Z, Liu Y, Zhang W, Gong Y, Tang Y, Chen F, Zhang J, Liu G, Zhang H, Li Y, Mai K, Ai Q. Effects of supplemental octanoate on hepatic lipid metabolism, serum biochemical indexes, antioxidant capacity and inflammation-related genes expression of large yellow croaker (Larimichthys crocea) fed with high soybean oil diet. Front Immunol 2023; 14:1162633. [PMID: 37051230 PMCID: PMC10083288 DOI: 10.3389/fimmu.2023.1162633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 03/13/2023] [Indexed: 03/28/2023] Open
Abstract
Dietary high soybean oil (SO) levels might cause hepatic lipid deposition, induce oxidative stress and inflammatory response in aquatic animals, while octanoate (OCT) is beneficial to metabolism and health in mammals. However, the effect of OCT has been studied rarely in aquatic animals. In this study, a 10-week feeding trial was conducted to investigate the effect of supplemental OCT on hepatic lipid metabolism, serum biochemical indexes, antioxidant capacity and inflammatory response of large yellow croaker (Larimichthys crocea) fed with high SO levels diet. The negative control diet contained 7% fish oil (FO), while the positive control diet contained 7% SO. The other four experimental diets were supplemented with 0.7, 2.1, 6.3 and 18.9 g/kg sodium octanoate (OCT) based on the positive control diet. Results showed that OCT supplementation effectively reduced the hepatic crude lipid, triglyceride (TG), total cholesterol (TC) and non-esterified free fatty acids contents, and alleviated lipid accumulation caused by the SO diet. Meanwhile, OCT supplementation decreased the serum TG, TC, alanine transaminase, aspartate transaminase and low-density lipoprotein cholesterol levels, increased the serum high-density lipoprotein cholesterol level, improved the serum lipid profiles and alleviated hepatic injury. Furthermore, with the supplementation of OCT, the mRNA expression of genes related to lipogenesis (acc1, scd1, fas, srebp1, dgat1 and cebpα) and fatty acid (FA) transport (fabp3, fatp and cd36) were down-regulated, while the mRNA expression of genes related to lipolysis (atgl, hsl and lpl) and FA β-oxidation (cpt1 and mcad) were up-regulated. Besides that, dietary OCT increased the total antioxidant capacity, activities of peroxidase, catalase and superoxide dismutase and the content of reduced glutathione, decreased the content of 8-hydroxy-deoxyguanosine and malondialdehyde and relieved hepatic oxidative stress. Supplementation of 0.7 and 2.1 g/kg OCT down-regulated the mRNA expression of genes related to pro-inflammatory cytokines (tnfα, il1β and ifnγ), and suppressed hepatic inflammatory response. In conclusion, supplementation with 0.7-2.1 g/kg OCT could reduce hepatic lipid accumulation, relieve oxidative stress and regulate inflammatory response in large yellow croaker fed the diet with high SO levels, providing a new way to alleviate the hepatic fat deposition in aquatic animals.
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11
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Zhe L, Krogh U, Lauridsen C, Nielsen MO, Fang Z, Theil PK. Impact of dietary fat levels and fatty acid composition on milk fat synthesis in sows at peak lactation. J Anim Sci Biotechnol 2023; 14:42. [PMID: 36899401 PMCID: PMC9999577 DOI: 10.1186/s40104-022-00815-y] [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: 07/06/2022] [Accepted: 12/02/2022] [Indexed: 03/12/2023] Open
Abstract
BACKGROUND Dietary fat is important for energy provision and immune function of lactating sows and their progeny. However, knowledge on the impact of fat on mammary transcription of lipogenic genes, de novo fat synthesis, and milk fatty acid (FA) output is sparse in sows. This study aimed to evaluate impacts of dietary fat levels and FA composition on these traits in sows. Forty second-parity sows (Danish Landrace × Yorkshire) were assigned to 1 of 5 dietary treatments from d 108 of gestation until weaning (d 28 of lactation): low-fat control diet (3% added animal fat); or 1 of 4 high-fat diets with 8% added fat: coconut oil (CO), fish oil (FO), sunflower oil (SO), or 4% octanoic acid plus 4% FO (OFO). Three approaches were taken to estimate de novo milk fat synthesis from glucose and body fat. RESULTS Daily intake of FA was lowest in low-fat sows within fat levels (P < 0.01) and in OFO and FO sows within high-fat diets (P < 0.01). Daily milk outputs of fat, FA, energy, and FA-derived carbon reflected to a large extent the intake of those. On average, estimates for de novo fat synthesis were 82 or 194 g/d from glucose according to method 1 or 2 and 255 g de novo + mobilized FA/d according to method 3. The low-fat diet increased mammary FAS expression (P < 0.05) and de novo fat synthesis (method 1; P = 0.13) within fat levels. The OFO diet increased de novo fat synthesis (method 1; P < 0.05) and numerically upregulated mammary FAS expression compared to the other high-fat diets. Across diets, a daily intake of 440 g digestible FA minimized milk fat originating from glucose and mobilized body fat. CONCLUSIONS Sows fed diets with low-fat or octanoic acid, through upregulating FAS expression, increased mammary de novo fat synthesis whereas the milk FA output remained low in sows fed the low-fat diet or high-fat OFO or FO diets, indicating that dietary FA intake, dietary fat level, and body fat mobilization in concert determine de novo fat synthesis, amount and profiles of FA in milk.
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Affiliation(s)
- Li Zhe
- Key Laboratory for Animal Disease-Resistance Nutrition of China, Ministry of Education, Animal Nutrition Institute, Sichuan Agricultural University, 211 Huimin Road, Wenjiang District, Chengdu, 611130, China.,Department of Animal and Veterinary Sciences, Aarhus University, Foulum, Dk-8830, Tjele, Denmark
| | - Uffe Krogh
- Department of Animal and Veterinary Sciences, Aarhus University, Foulum, Dk-8830, Tjele, Denmark
| | - Charlotte Lauridsen
- Department of Animal and Veterinary Sciences, Aarhus University, Foulum, Dk-8830, Tjele, Denmark.
| | - Mette Olaf Nielsen
- Department of Animal and Veterinary Sciences, Aarhus University, Foulum, Dk-8830, Tjele, Denmark
| | - Zhengfeng Fang
- Key Laboratory for Animal Disease-Resistance Nutrition of China, Ministry of Education, Animal Nutrition Institute, Sichuan Agricultural University, 211 Huimin Road, Wenjiang District, Chengdu, 611130, China.
| | - Peter Kappel Theil
- Department of Animal and Veterinary Sciences, Aarhus University, Foulum, Dk-8830, Tjele, Denmark
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12
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Rahman MS, Lee Y, Park DS, Kim YS. Bifidobacterium bifidum DS0908 and Bifidobacterium longum DS0950 Culture-Supernatants Ameliorate Obesity-Related Characteristics in Mice with High-Fat Diet-Induced Obesity. J Microbiol Biotechnol 2023; 33:96-105. [PMID: 36457182 PMCID: PMC9899789 DOI: 10.4014/jmb.2210.10046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/11/2022] [Accepted: 11/14/2022] [Indexed: 12/05/2022]
Abstract
Probiotic supplements have promising therapeutic effects on chronic diseases. In this study, we demonstrated the anti-obesity effects of two potential probiotics, Bifidobacterium bifidum DS0908 (DS0908) and Bifidobacterium longum DS0950 (DS0950). Treatment with DS0908 and DS0950 postbiotics significantly induced the expression of the brown adipocyte-specific markers UCP1, PPARγ, PGC1α, PRDM16 and beige adipocyte-specific markers CD137, FGF21, P2RX5, and COX2 in C3H10T1/2 mesenchymal stem cells (MSCs). In mice with high-fat diet (HFD)-induced obesity, both potential probiotics and postbiotics noticeably reduced body weight and epididymal fat accumulation without affecting food intake. DS0908 and DS0950 also improved insulin sensitivity and glucose use in mice with HFD-induced obesity. In addition, DS0908 and DS0950 improved the plasma lipid profile, proved by reduced triglyceride, low-density lipoprotein, and cholesterol levels. Furthermore, DS0908 and DS0950 improved mitochondrial respiratory function, confirmed by the high expression of oxidative phosphorylation proteins, during thermogenesis induction in the visceral and epididymal fat in mice with HFD-induced obesity. Notably, the physiological and metabolic changes were more significant after treatment with potential probiotic culture-supernatants than those with the bacterial pellet. Finally, gene knockdown and co-treatment with inhibitor-mediated mechanistic analyses showed that both DS0908 and DS0950 exerted anti-obesity-related effects via the PKA/p38 MAPK signaling activation in C3H10T1/2 MSCs. Our observations suggest that DS0908 and DS0950 could potentially alleviate obesity as dietary supplements.
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Affiliation(s)
- M. Shamim Rahman
- Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan 31151, Republic of Korea,Department of Microbiology, College of Medicine, Soonchunhyang University, Cheonan 31151, Republic of Korea
| | - Youri Lee
- Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan 31151, Republic of Korea,Department of Microbiology, College of Medicine, Soonchunhyang University, Cheonan 31151, Republic of Korea
| | - Doo-Sang Park
- Biological Resource Center, Korea Research Institute of Bioscience and Biotechnology, Jeongeup 56212, Republic of Korea
| | - Yong-Sik Kim
- Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan 31151, Republic of Korea,Department of Microbiology, College of Medicine, Soonchunhyang University, Cheonan 31151, Republic of Korea,Corresponding author Phone: +82-41-570-2413 Fax: +82-41-575-2412 E-mail:
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13
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He W, Tran A, Chen CT, Loganathan N, Bazinet RP, Belsham DD. Oleate restores altered autophagic flux to rescue palmitate lipotoxicity in hypothalamic neurons. Mol Cell Endocrinol 2022; 557:111753. [PMID: 35981630 DOI: 10.1016/j.mce.2022.111753] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Revised: 07/29/2022] [Accepted: 08/10/2022] [Indexed: 01/18/2023]
Abstract
Accumulation of excess lipids in non-adipose tissues, such as the hypothalamus, is termed lipotoxicity and causative of free fatty acid-mediated pathology in metabolic disease. This study aimed to elucidate the molecular mechanisms behind oleate (OA)- and palmitate (PA)-mediated changes in hypothalamic neurons. Using the well-characterized hypothalamic neuronal cell model, mHypoE-46, we assessed gene changes through qRT-PCR, cell death with quantitative imaging, PA metabolism using stable isotope labeling, and cellular mechanisms using pharmacological modulation of lipid metabolism and autophagic flux. Palmitate (PA) disrupts gene expression, including Npy, Grp78, and Il-6 mRNA in mHypoE-46 hypothalamic neurons. Blocking PA metabolism using triacsin-C prevented the increase of these genes, implying that these changes depend on PA intracellular metabolism. Co-incubation with oleate (OA) is also potently protective and prevents cell death induced by increasing concentrations of PA. However, OA does not decrease U-13C-PA incorporation into diacylglycerol and phospholipids. Remarkably, OA can reverse PA toxicity even after significant PA metabolism and cellular impairment. OA can restore PA-mediated impairment of autophagy to prevent or reverse the accumulation of PA metabolites through lysosomal degradation, and not through other reported mechanisms. The autophagic flux inhibitor chloroquine (CQ) mimics PA toxicity by upregulating autophagy-related genes, Npy, Grp78, and Il-6, an effect partially reversed by OA. CQ also prevented the OA defense against PA toxicity, whereas the autophagy inducer rapamycin provided some protection. Thus, PA impairment of autophagic flux significantly contributes to its lipotoxicity, and OA-mediated protection requires functional autophagy. Overall, our results suggest that impairment of autophagy contributes to hypothalamic lipotoxicity.
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Affiliation(s)
- Wenyuan He
- Department of Physiology, University of Toronto, Ontario, Canada
| | - Andy Tran
- Department of Physiology, University of Toronto, Ontario, Canada
| | - Chuck T Chen
- Department of Nutritional Sciences, University of Toronto, Ontario, Canada
| | | | - Richard P Bazinet
- Department of Nutritional Sciences, University of Toronto, Ontario, Canada
| | - Denise D Belsham
- Department of Physiology, University of Toronto, Ontario, Canada; Department of Medicine, University of Toronto, Ontario, Canada; Department of Obstetrics and Gynaecology, University of Toronto, Ontario, Canada.
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14
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Shcherbakova K, Schwarz A, Apryatin S, Karpenko M, Trofimov A. Supplementation of Regular Diet With Medium-Chain Triglycerides for Procognitive Effects: A Narrative Review. Front Nutr 2022; 9:934497. [PMID: 35911092 PMCID: PMC9334743 DOI: 10.3389/fnut.2022.934497] [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: 05/02/2022] [Accepted: 06/15/2022] [Indexed: 01/09/2023] Open
Abstract
It is now widely accepted that ketosis (a physiological state characterized by elevated plasma ketone body levels) possesses a wide range of neuroprotective effects. There is a growing interest in the use of ketogenic supplements, including medium-chain triglycerides (MCT), to achieve intermittent ketosis without adhering to a strict ketogenic diet. MCT supplementation is an inexpensive and simple ketogenic intervention, proven to benefit both individuals with normal cognition and those suffering from mild cognitive impairment, Alzheimer's disease, and other cognitive disorders. The commonly accepted paradigm underlying MCT supplementation trials is that the benefits stem from ketogenesis and that MCT supplementation is safe. However, medium-chain fatty acids (MCFAs) may also exert effects in the brain directly. Moreover, MCFAs, long-chain fatty acids, and glucose participate in mutually intertwined metabolic pathways. Therefore, the metabolic effects must be considered if the desired procognitive effects require administering MCT in doses larger than 1 g/kg. This review summarizes currently available research on the procognitive effects of using MCTs as a supplement to regular feed/diet without concomitant reduction of carbohydrate intake and focuses on the revealed mechanisms linked to particular MCT metabolites (ketone bodies, MCFAs), highlighting open questions and potential considerations.
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Affiliation(s)
- Ksenia Shcherbakova
- I.P. Pavlov Department of Physiology, Institute of Experimental Medicine, Saint Petersburg, Russia,*Correspondence: Ksenia Shcherbakova
| | - Alexander Schwarz
- Laboratory of the Molecular Mechanisms of Neuronal Interactions, Institute of Evolutionary Physiology and Biochemistry (RAS), Saint Petersburg, Russia
| | - Sergey Apryatin
- I.P. Pavlov Department of Physiology, Institute of Experimental Medicine, Saint Petersburg, Russia
| | - Marina Karpenko
- I.P. Pavlov Department of Physiology, Institute of Experimental Medicine, Saint Petersburg, Russia
| | - Alexander Trofimov
- I.P. Pavlov Department of Physiology, Institute of Experimental Medicine, Saint Petersburg, Russia
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15
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Thomas AS, Sassi M, Angelini R, Morgan AH, Davies JS. Acylation, a Conductor of Ghrelin Function in Brain Health and Disease. Front Physiol 2022; 13:831641. [PMID: 35845996 PMCID: PMC9280358 DOI: 10.3389/fphys.2022.831641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/31/2022] [Indexed: 11/22/2022] Open
Abstract
Acyl-ghrelin (AG) is an orexigenic hormone that has a unique octanoyl modification on its third serine residue. It is often referred to as the “hunger hormone” due to its involvement in stimulating food intake and regulating energy homeostasis. The discovery of the enzyme ghrelin-O-acyltransferase (GOAT), which catalyses ghrelin acylation, provided further insights into the relevance of this lipidation process for the activation of the growth hormone secretagogue receptor (GHS-R) by acyl-ghrelin. Although acyl-ghrelin is predominantly linked with octanoic acid, a range of saturated fatty acids can also bind to ghrelin possibly leading to specific functions. Sources of ghrelin acylation include beta-oxidation of longer chain fatty acids, with contributions from fatty acid synthesis, the diet, and the microbiome. In addition, both acyl-ghrelin and unacyl-ghrelin (UAG) have feedback effects on lipid metabolism which in turn modulate their levels. Recently we showed that whilst acyl-ghrelin promotes adult hippocampal neurogenesis and enhances memory function, UAG inhibits these processes. As a result, we postulated that the circulating acyl-ghrelin:unacyl-ghrelin (AG:UAG) ratio might be an important regulator of neurogenesis and cognition. In this review, we discuss emerging evidence behind the relevance of ghrelin acylation in the context of brain physiology and pathology, as well as the current challenges of identifying the provenance of the acyl moiety.
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16
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Lin TY, Liu HW, Hung TM. The Ketogenic Effect of Medium-Chain Triacylglycerides. Front Nutr 2021; 8:747284. [PMID: 34888335 PMCID: PMC8650700 DOI: 10.3389/fnut.2021.747284] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 10/26/2021] [Indexed: 11/24/2022] Open
Abstract
Medium-chain triacylglycerides (MCTs) are dietary supplements that can induce ketosis without the need for a traditional ketogenic diet or prolonged fasting. They have the potential to marginally delay the progression of neurodegenerative diseases, such as Alzheimer's disease. However, there have been inconsistencies in reports of the MCT dose–response relationship, which may be due to differences in MCT composition, participant characteristics, and other factors that can influence ketone generation. To resolve these discrepancies, we reviewed studies that investigated the ketogenic effect of MCTs in healthy adults. Aside from the treatment dose, other factors that can influence the ketogenic response, such as accompanying meals, fasting duration, and caffeine intake, were assessed. Based on the available literature, four practical recommendations are made to optimize the ketogenic effect of MCTs and reduce unwanted side effects (primarily gastrointestinal discomfort and diarrhea). First, the starting dose should be either 5 g of octanoic acid [caprylic acid (C8); a component of MCTs] or 5 g of a combination of C8 and decanoic or capric acid (C10; another component of MCTs), and the dose should be progressively increased to 15–20 g of C8. Second, MCTs should be consumed after an overnight fast, without an accompanying meal if tolerable, or with a low-carbohydrate meal. Third, the addition of caffeine may slightly increase the ketogenic response. Fourth, emulsifying the MCTs might increase their ketogenic effect and alleviate side effects.
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Affiliation(s)
- Ting-Yu Lin
- Department of Physical Education and Sport Sciences, National Taiwan Normal University, Taipei City, Taiwan
| | - Hung-Wen Liu
- Department of Physical Education and Sport Sciences, National Taiwan Normal University, Taipei City, Taiwan
| | - Tsung-Min Hung
- Department of Physical Education and Sport Sciences, National Taiwan Normal University, Taipei City, Taiwan
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17
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Caron A, Jane Michael N. New Horizons: Is Obesity a Disorder of Neurotransmission? J Clin Endocrinol Metab 2021; 106:e4872-e4886. [PMID: 34117881 DOI: 10.1210/clinem/dgab421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Indexed: 11/19/2022]
Abstract
Obesity is a disease of the nervous system. While some will view this statement as provocative, others will take it as obvious. Whatever our side is, the pharmacology tells us that targeting the nervous system works for promoting weight loss. It works, but at what cost? Is the nervous system a safe target for sustainable treatment of obesity? What have we learned-and unlearned-about the central control of energy balance in the last few years? Herein we provide a thought-provoking exploration of obesity as a disorder of neurotransmission. We discuss the state of knowledge on the brain pathways regulating energy homeostasis that are commonly targeted in anti-obesity therapy and explore how medications affecting neurotransmission such as atypical antipsychotics, antidepressants, and antihistamines relate to body weight. Our goal is to provide the endocrine community with a conceptual framework that will help expending our understanding of the pathophysiology of obesity, a disease of the nervous system.
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Affiliation(s)
- Alexandre Caron
- Faculty of Pharmacy, Université Laval, Quebec City, QC, Canada
- Quebec Heart and Lung Institute, Quebec City, QC, Canada
- Montreal Diabetes Research Center, Montreal, QC, Canada
| | - Natalie Jane Michael
- Faculty of Pharmacy, Université Laval, Quebec City, QC, Canada
- Quebec Heart and Lung Institute, Quebec City, QC, Canada
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18
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Andersen JV, Westi EW, Jakobsen E, Urruticoechea N, Borges K, Aldana BI. Astrocyte metabolism of the medium-chain fatty acids octanoic acid and decanoic acid promotes GABA synthesis in neurons via elevated glutamine supply. Mol Brain 2021; 14:132. [PMID: 34479615 PMCID: PMC8414667 DOI: 10.1186/s13041-021-00842-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 08/22/2021] [Indexed: 11/23/2022] Open
Abstract
The medium-chain fatty acids octanoic acid (C8) and decanoic acid (C10) are gaining attention as beneficial brain fuels in several neurological disorders. The protective effects of C8 and C10 have been proposed to be driven by hepatic production of ketone bodies. However, plasma ketone levels correlates poorly with the cerebral effects of C8 and C10, suggesting that additional mechanism are in place. Here we investigated cellular C8 and C10 metabolism in the brain and explored how the protective effects of C8 and C10 may be linked to cellular metabolism. Using dynamic isotope labeling, with [U-13C]C8 and [U-13C]C10 as metabolic substrates, we show that both C8 and C10 are oxidatively metabolized in mouse brain slices. The 13C enrichment from metabolism of [U-13C]C8 and [U-13C]C10 was particularly prominent in glutamine, suggesting that C8 and C10 metabolism primarily occurs in astrocytes. This finding was corroborated in cultured astrocytes in which C8 increased the respiration linked to ATP production, whereas C10 elevated the mitochondrial proton leak. When C8 and C10 were provided together as metabolic substrates in brain slices, metabolism of C10 was predominant over that of C8. Furthermore, metabolism of both [U-13C]C8 and [U-13C]C10 was unaffected by etomoxir indicating that it is independent of carnitine palmitoyltransferase I (CPT-1). Finally, we show that inhibition of glutamine synthesis selectively reduced 13C accumulation in GABA from [U-13C]C8 and [U-13C]C10 metabolism in brain slices, demonstrating that the glutamine generated from astrocyte C8 and C10 metabolism is utilized for neuronal GABA synthesis. Collectively, the results show that cerebral C8 and C10 metabolism is linked to the metabolic coupling of neurons and astrocytes, which may serve as a protective metabolic mechanism of C8 and C10 supplementation in neurological disorders.
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Affiliation(s)
- Jens V Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen E, Denmark.
| | - Emil W Westi
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen E, Denmark
| | - Emil Jakobsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen E, Denmark
| | - Nerea Urruticoechea
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen E, Denmark
| | - Karin Borges
- Department of Pharmacology, School of Biomedical Sciences, The University of Queensland, St. Lucia, Australia
| | - Blanca I Aldana
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen E, Denmark.
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19
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Rahman MS, Kang I, Lee Y, Habib MA, Choi BJ, Kang JS, Park DS, Kim YS. Bifidobacterium longum subsp. infantis YB0411 Inhibits Adipogenesis in 3T3-L1 Pre-adipocytes and Reduces High-Fat-Diet-Induced Obesity in Mice. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:6032-6042. [PMID: 34008977 DOI: 10.1021/acs.jafc.1c01440] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Although the health benefits of probiotics have been widely known for decades, there has still been limited use of probiotic bacteria in anti-obesity therapy. Herein, we demonstrated the role of Bifidobacterium longum subsp. infantis YB0411 (YB, which was selected by an in vitro adipogenesis assay) in adipogenic differentiation in 3T3-L1 pre-adipocytes. We observed that YB-treatment effectively reduced triglyceride accumulation and the expression of CCAAT/enhancer-binding protein α, β, and δ (C/EBPα, C/EBPβ, and C/EBPδ), peroxisome proliferator-activated receptor γ (PPARγ), fatty acid-binding protein 4 (aP2), and acetyl-CoA carboxylase (ACC). YB-treatment also reduced the levels of core autophagic markers (p62 and LC3B) in 3T3-L1 pre-adipocytes. Small-interfering-RNA-mediated knockdown and competitive-chemical-inhibition assays showed that AMP-activated protein kinase (AMPK) commenced the anti-adipogenic effect of YB. In addition, YB supplement markedly reduced body weight and fat accretion in mice with high-fat-diet-induced obesity. Our findings suggest that YB may be used as a potential probiotic candidate to ameliorate obesity.
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Affiliation(s)
- Md Shamim Rahman
- Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
- Department of Microbiology, College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
| | - Inseok Kang
- College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
| | - Youri Lee
- Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
- Department of Microbiology, College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
| | - Md Ahasun Habib
- Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
- Department of Microbiology, College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
| | - Byeong Jo Choi
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanjiro, Cheongju 28116, Republic of Korea
| | - Jong Soon Kang
- Laboratory Animal Resource Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanjiro, Cheongju 28116, Republic of Korea
| | - Doo-Sang Park
- Biological Resource Center, Korea Research Institute of Bioscience and Biotechnology, Jeongeup 56212, Republic of Korea
| | - Yong-Sik Kim
- Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
- Department of Microbiology, College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
- College of Medicine, Soonchunhyang University, Cheonan, Chung-nam 31151, Republic of Korea
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20
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Salgado M, García-Robles MÁ, Sáez JC. Purinergic signaling in tanycytes and its contribution to nutritional sensing. Purinergic Signal 2021; 17:607-618. [PMID: 34018139 DOI: 10.1007/s11302-021-09791-w] [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: 03/07/2021] [Accepted: 04/19/2021] [Indexed: 10/21/2022] Open
Abstract
Tanycytes are hypothalamic radial glial-like cells with an important role in the regulation of neuroendocrine axes and energy homeostasis. These cells have been implicated in glucose, amino acids, and fatty acid sensing in the hypothalamus of rodents, where they are strategically positioned. While their cell bodies contact the cerebrospinal fluid, their extensive processes contact neurons of the arcuate and ventromedial nuclei, protagonists in the regulation of food intake. A growing body of evidence has shown that purinergic signaling plays a relevant role in this homeostatic role of tanycytes, likely regulating the release of gliotransmitters that will modify the activity of satiety-controlling hypothalamic neurons. Connexin hemichannels have proven to be particularly relevant in these mechanisms since they are responsible for the release of ATP from tanycytes in response to nutritional signals. On the other hand, either ionotropic or metabotropic ATP receptors are involved in the generation of intracellular Ca2+ waves in response to hypothalamic nutrients, which can spread between glial cells and towards neighboring neurons. This review will summarize recent evidence that supports a nutrient sensor role for tanycytes, highlighting the participation of purinergic signaling in this process.
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Affiliation(s)
- Magdiel Salgado
- Laboratorio de Biología Celular, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile.,Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - María Á García-Robles
- Laboratorio de Biología Celular, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile.
| | - Juan C Sáez
- Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.
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21
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Lundsgaard AM, Fritzen AM, Sjøberg KA, Kleinert M, Richter EA, Kiens B. Small Amounts of Dietary Medium-Chain Fatty Acids Protect Against Insulin Resistance During Caloric Excess in Humans. Diabetes 2021; 70:91-98. [PMID: 33122393 DOI: 10.2337/db20-0582] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 10/23/2020] [Indexed: 11/13/2022]
Abstract
Medium-chain fatty acids (MCFAs) have in rodents been shown to have protective effects on glucose homeostasis during high-fat overfeeding. In this study, we investigated whether dietary MCFAs protect against insulin resistance induced by a hypercaloric high-fat diet in humans. Healthy, lean men ingested a eucaloric control diet and a 3-day hypercaloric high-fat diet (increase of 75% in energy, 81-83% energy [E%] from fat) in randomized order. For one group (n = 8), the high-fat diet was enriched with saturated long-chain FAs (LCSFA-HFD), while the other group (n = 9) ingested a matched diet, but with ∼30 g (5E%) saturated MCFAs (MCSFA-HFD) in substitution for a corresponding fraction of the saturated long-chain fatty acids (LCFAs). A hyperinsulinemic-euglycemic clamp with femoral arteriovenous balance and glucose tracer was applied after the control and hypercaloric diets. In LCSFA-HFD, whole-body insulin sensitivity and peripheral insulin-stimulated glucose disposal were reduced. These impairments were prevented in MCSFA-HFD, accompanied by increased basal fatty acid oxidation, maintained glucose metabolic flexibility, increased nonoxidative glucose disposal related to lower starting glycogen content, and increased glycogen synthase activity, together with increased muscle lactate production. In conclusion, substitution of a small amount of dietary LCFAs with MCFAs rescues insulin action in conditions of lipid-induced energy excess.
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Affiliation(s)
- Anne-Marie Lundsgaard
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Andreas M Fritzen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Kim A Sjøberg
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Maximilian Kleinert
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center at Helmholtz Zentrum München - German Research Center for Environmental Health, Neuherberg, Germany
| | - Erik A Richter
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Bente Kiens
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
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Michael NJ, Watt MJ. Long Chain Fatty Acids Differentially Regulate Sub-populations of Arcuate POMC and NPY Neurons. Neuroscience 2020; 451:164-173. [PMID: 33002557 DOI: 10.1016/j.neuroscience.2020.09.045] [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: 04/28/2020] [Revised: 09/09/2020] [Accepted: 09/21/2020] [Indexed: 02/07/2023]
Abstract
Long chain fatty acids (LCFAs) have been suggested to influence the activity of hypothalamic neurons, however, limited studies have attempted to identify the neurochemical phenotype of these neurons. We aimed to determine if physiological levels of LCFAs alter the electrical excitability of pro-opiomelanocortin (POMC) and neuropeptide Y (NPY) neurons in the arcuate nucleus of the hypothalamus. We utilised whole-cell patch-clamp electrophysiology on brain slice preparations from genetic mouse models where green fluorescent protein was expressed in either POMC or NPY expressing cells. All animals had undergone an overnight fast to replicate conditions in which fatty acids would usually increase. Bath application of LCFAs were found to predominantly inhibit POMC neurons and predominantly excite NPY neurons. Differences between oleic and palmitic acid were not observed. These results suggest that LCFAs in the cerebrospinal fluid exert an underlying orexigenic tone to key hypothalamic neurons known to regulate energy homeostasis.
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Affiliation(s)
- Natalie J Michael
- Metabolic Disease, Obesity and Diabetes Program, Biomedicine Discovery Institute and the Department of Physiology, Monash University, Clayton 3800, VIC, Australia; Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec City G1V4G5, Québec, Canada.
| | - Matthew J Watt
- Department of Physiology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne 3010, VIC, Australia
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