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Gao R, Yang K, Le S, Chen H, Sun X, Dong Z, Gao P, Wang X, Shi J, Qu Y, Wei X, Hu K, Wang J, Jin L, Li Y, Ge J, Sun A. Aldehyde dehydrogenase 2 serves as a key cardiometabolic adaptation regulator in response to plateau hypoxia in mice. Transl Res 2024; 267:25-38. [PMID: 38181846 DOI: 10.1016/j.trsl.2023.12.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 12/08/2023] [Accepted: 12/22/2023] [Indexed: 01/07/2024]
Abstract
High-altitude heart disease (HAHD) is a complex pathophysiological condition related to systemic hypobaric hypoxia in response to transitioning to high altitude. Hypoxia can cause myocardial metabolic dysregulation, leading to an increased risk of heart failure and sudden cardiac death. Aldehyde dehydrogenase 2 (ALDH2) could regulate myocardial energy metabolism and plays a protective role in various cardiovascular diseases. This study aims to determine the effects of plateau hypoxia (PH) on cardiac metabolism and function, investigate the associated role of ALDH2, and explore potential therapeutic targets. We discovered that PH significantly reduced survival rate and cardiac function. These effects were exacerbated by ALDH2 deficiency. PH also caused a shift in the myocardial fuel source from fatty acids to glucose; ALDH2 deficiency impaired this adaptive metabolic shift. Untargeted/targeted metabolomics and transmission electron microscopy revealed that ALDH2 deficiency promoted myocardial fatty-acid deposition, leading to enhanced fatty-acid transport, lipotoxicity and mitochondrial dysfunction. Furthermore, results showed that ALDH2 attenuated PH-induced impairment of adaptive metabolic programs through 4-HNE/CPT1 signaling, and the CPT1 inhibitor etomoxir significantly ameliorated ALDH2 deficiency-induced cardiac impairment and improved survival in PH mice. Together, our data reveal ALDH2 acts as a key cardiometabolic adaptation regulator in response to PH. CPT1 inhibitor, etomoxir, may attenuate ALDH2 deficiency-induced effects and improved cardiac function in response to PH.
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Affiliation(s)
- Rifeng Gao
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China; Department of Cardiac Surgery, The Second Affiliated Hospital, Zhejiang University, Hangzhou, China; Department of Cardiology, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Kun Yang
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Shiguan Le
- Ministry of Education Key Laboratory of Contemporary Anthropology, School of Life Sciences, and Human Phenome Institute, Fudan University, Shanghai, China
| | - Hanchuan Chen
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Xiaolei Sun
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Zhen Dong
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Pingjin Gao
- Department of Cardiovascular Medicine, State Key Laboratory of Medical Genomics, Shanghai Key Laboratory of Hypertension, Shanghai Institute of Hypertension, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, China
| | - Xilu Wang
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Jiaran Shi
- Department of Cardiology, The First Affiliated Hospital, Zhejiang University, Hangzhou, China
| | - Yanan Qu
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Xiang Wei
- Department of Cardiology, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Kai Hu
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China; Key Laboratory of Viral Heart Diseases, National Health Commission, Shanghai, China; Key Laboratory of Viral Heart Diseases, Chinese Academy of Medical Sciences, Shanghai, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Jiucun Wang
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for Genetics and Development, School of Life Sciences, and Human Phenome Institute, Fudan University, Shanghai, China
| | - Li Jin
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for Genetics and Development, School of Life Sciences, and Human Phenome Institute, Fudan University, Shanghai, China
| | - Yi Li
- Ministry of Education Key Laboratory of Contemporary Anthropology, School of Life Sciences, and Human Phenome Institute, Fudan University, Shanghai, China.
| | - Junbo Ge
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China; Key Laboratory of Viral Heart Diseases, National Health Commission, Shanghai, China; Key Laboratory of Viral Heart Diseases, Chinese Academy of Medical Sciences, Shanghai, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Aijun Sun
- Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai, China; Key Laboratory of Viral Heart Diseases, National Health Commission, Shanghai, China; Key Laboratory of Viral Heart Diseases, Chinese Academy of Medical Sciences, Shanghai, China; Department of Cardiovascular Medicine, State Key Laboratory of Medical Genomics, Shanghai Key Laboratory of Hypertension, Shanghai Institute of Hypertension, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, China.
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Mendez Garcia MF, Matsuzaki S, Batushansky A, Newhardt R, Kinter C, Jin Y, Mann SN, Stout MB, Gu H, Chiao YA, Kinter M, Humphries KM. Increased cardiac PFK-2 protects against high-fat diet-induced cardiomyopathy and mediates beneficial systemic metabolic effects. iScience 2023; 26:107131. [PMID: 37534142 PMCID: PMC10391959 DOI: 10.1016/j.isci.2023.107131] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 04/27/2023] [Accepted: 06/10/2023] [Indexed: 08/04/2023] Open
Abstract
A healthy heart adapts to changes in nutrient availability and energy demands. In metabolic diseases like type 2 diabetes (T2D), increased reliance on fatty acids for energy production contributes to mitochondrial dysfunction and cardiomyopathy. A principal regulator of cardiac metabolism is 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2), which is a central driver of glycolysis. We hypothesized that increasing PFK-2 activity could mitigate cardiac dysfunction induced by high-fat diet (HFD). Wild type (WT) and cardiac-specific transgenic mice expressing PFK-2 (GlycoHi) were fed a low fat or HFD for 16 weeks to induce metabolic dysfunction. Metabolic phenotypes were determined by measuring mitochondrial bioenergetics and performing targeted quantitative proteomic and metabolomic analysis. Increasing cardiac PFK-2 had beneficial effects on cardiac and mitochondrial function. Unexpectedly, GlycoHi mice also exhibited sex-dependent systemic protection from HFD, including increased glucose homeostasis. These findings support improving glycolysis via PFK-2 activity can mitigate mitochondrial and functional changes that occur with metabolic syndrome.
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Affiliation(s)
- Maria F. Mendez Garcia
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Satoshi Matsuzaki
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Albert Batushansky
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
- Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Ryan Newhardt
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Caroline Kinter
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Yan Jin
- Center for Translational Science, Florida International University, Port St. Lucie, FL, USA
| | - Shivani N. Mann
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Michael B. Stout
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Haiwei Gu
- Center for Translational Science, Florida International University, Port St. Lucie, FL, USA
| | - Ying Ann Chiao
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Michael Kinter
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Kenneth M. Humphries
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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Huang M, Coral D, Ardalani H, Spegel P, Saadat A, Claussnitzer M, Mulder H, Franks PW, Kalamajski S. Identification of a weight loss-associated causal eQTL in MTIF3 and the effects of MTIF3 deficiency on human adipocyte function. eLife 2023; 12:84168. [PMID: 36876906 PMCID: PMC10023155 DOI: 10.7554/elife.84168] [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: 10/12/2022] [Accepted: 03/05/2023] [Indexed: 03/07/2023] Open
Abstract
Genetic variation at the MTIF3 (Mitochondrial Translational Initiation Factor 3) locus has been robustly associated with obesity in humans, but the functional basis behind this association is not known. Here, we applied luciferase reporter assay to map potential functional variants in the haplotype block tagged by rs1885988 and used CRISPR-Cas9 to edit the potential functional variants to confirm the regulatory effects on MTIF3 expression. We further conducted functional studies on MTIF3-deficient differentiated human white adipocyte cell line (hWAs-iCas9), generated through inducible expression of CRISPR-Cas9 combined with delivery of synthetic MTIF3-targeting guide RNA. We demonstrate that rs67785913-centered DNA fragment (in LD with rs1885988, r2 > 0.8) enhances transcription in a luciferase reporter assay, and CRISPR-Cas9-edited rs67785913 CTCT cells show significantly higher MTIF3 expression than rs67785913 CT cells. Perturbed MTIF3 expression led to reduced mitochondrial respiration and endogenous fatty acid oxidation, as well as altered expression of mitochondrial DNA-encoded genes and proteins, and disturbed mitochondrial OXPHOS complex assembly. Furthermore, after glucose restriction, the MTIF3 knockout cells retained more triglycerides than control cells. This study demonstrates an adipocyte function-specific role of MTIF3, which originates in the maintenance of mitochondrial function, providing potential explanations for why MTIF3 genetic variation at rs67785913 is associated with body corpulence and response to weight loss interventions.
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Affiliation(s)
- Mi Huang
- Genetic and Molecular Epidemiology Unit, Department of Clinical Sciences, Clinical Research Centre, Lund UniversityMalmöSweden
| | - Daniel Coral
- Genetic and Molecular Epidemiology Unit, Department of Clinical Sciences, Clinical Research Centre, Lund UniversityMalmöSweden
| | - Hamidreza Ardalani
- Department of Chemistry, Centre for Analysis and Synthesis, Lund UniversityLundSweden
| | - Peter Spegel
- Department of Chemistry, Centre for Analysis and Synthesis, Lund UniversityLundSweden
| | - Alham Saadat
- Metabolism Program, Broad Institute of MIT and HarvardCambridgeUnited States
| | - Melina Claussnitzer
- Metabolism Program, Broad Institute of MIT and HarvardCambridgeUnited States
| | - Hindrik Mulder
- Unit of Molecular Metabolism, Department of Clinical Sciences, Clinical Research Centre, Lund UniversityMalmöSweden
| | - Paul W Franks
- Genetic and Molecular Epidemiology Unit, Department of Clinical Sciences, Clinical Research Centre, Lund UniversityMalmöSweden
- Department of Nutrition, Harvard T.H. Chan School of Public HealthBostonUnited States
| | - Sebastian Kalamajski
- Genetic and Molecular Epidemiology Unit, Department of Clinical Sciences, Clinical Research Centre, Lund UniversityMalmöSweden
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Liu Z, Zhang L, Qian C, Zhou Y, Yu Q, Yuan J, Lv Y, Zhang L, Chang X, Li Y, Liu Y. Recurrent hypoglycemia increases hepatic gluconeogenesis without affecting glycogen metabolism or systemic lipolysis in rat. Metabolism 2022; 136:155310. [PMID: 36063868 DOI: 10.1016/j.metabol.2022.155310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 08/29/2022] [Accepted: 08/31/2022] [Indexed: 11/26/2022]
Abstract
INTRODUCTION Recurrent hypoglycemia (RH) impairs secretion of counterregulatory hormones. Whether and how RH affects responses within metabolically important peripheral organs to counterregulatory hormones are poorly understood. OBJECTIVE To study the effects of RH on metabolic pathways associated with glucose counterregulation within liver, white adipose tissue and skeletal muscle. METHODS Using a widely adopted rodent model of 3-day recurrent hypoglycemia, we first checked expression of counterregulatory hormone G-protein coupled receptors (GPCRs), their inhibitory regulators and downstream enzymes catalyzing glycogen metabolism, gluconeogenesis and lipolysis by qPCR and western blot. Then, we examined epinephrine-induced phosphorylation of PKA substrates to validate adrenergic sensitivity in each organ. Next, we measured hepatic and skeletal glycogen content, degree of breakdown by epinephrine and abundance of phosphorylated glycogen phosphorylase under hypoglycemia and that of phosphorylated glycogen synthase during recovery to evaluate glycogen turnover. Further, we performed pyruvate and lactate tolerance tests to assess gluconeogenesis. Additionally, we measured circulating FFA and glycerol to check lipolysis. The abovementioned studies were repeated in streptozotocin-induced diabetic rat model. Finally, we conducted epinephrine tolerance test to investigate systemic glycemic excursions to counterregulatory hormones. Saline-injected rats served as controls. RESULTS RH increased counterregulatory hormone GPCR signaling in liver and epidydimal white adipose tissue (eWAT), but not in skeletal muscle. For glycogen metabolism, RH did not affect total content or epinephrine-stimulated breakdown in liver and skeletal muscle. Although RH decreased expression of phosphorylated glycogen synthase 2, it did not affect hepatic glycogen biosynthesis during recovery from hypoglycemia or after fasting-refeeding. For gluconeogenesis, RH upregulated fructose 1,6-bisphosphatase 1 and monocarboxylic acid transporter 1 that imports lactate as precursor, resulting in a lower blood lactate profile during hypoglycemia. In agreement, RH elevated fasting blood glucose and caused higher glycemic excursions during pyruvate tolerance test. For lipolysis, RH did not affect circulating levels of FFA and glycerol after overnight fasting or upon epinephrine stimulation. Interestingly, RH upregulated the trophic fatty acid transporter FATP1 and glucose transporter GLUT4 to increase lipogenesis in eWAT. These aforementioned changes of gluconeogenesis, lipolysis and lipogenesis were validated in streptozotocin-diabetic rats. Finally, RH increased insulin sensitivity to accelerate glucose disposal, which was attributable to upregulated visceral adipose GLUT4. CONCLUSIONS RH caused metabolic adaptations related to counterregulation within peripheral organs. Specifically, adrenergic signaling was enhanced in liver and visceral fat, but not in skeletal muscle. Glycogen metabolism remained unchanged. Hepatic gluconeogenesis was augmented. Systemic lipolysis was unaffected, but visceral lipogenesis was enhanced. Insulin sensitivity was increased. These findings provided insights into mechanisms underlying clinical problems associated with intensive insulin therapy, such as high gluconeogenic flux and body weight gain.
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Affiliation(s)
- Zejian Liu
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Lingyu Zhang
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, Jiangsu 211100, China
| | - Chen Qian
- Department of Endocrinology, Zhangjiagang Hospital Affiliated to Soochow University, Zhangjiagang, Suzhou, Jiangsu 215699, China
| | - Ying Zhou
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, Jiangsu 211100, China
| | - Qiuyu Yu
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Jiaqi Yuan
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Yunfan Lv
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Leheng Zhang
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Xiaoai Chang
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Yangyang Li
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, Jiangsu 211100, China.
| | - Yu Liu
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, Jiangsu 211100, China.
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Manzano M, Giron MD, Salto R, Vilchez JD, Reche-Perez FJ, Cabrera E, Linares-Pérez A, Plaza-Díaz J, Ruiz-Ojeda FJ, Gil A, Rueda R, López-Pedrosa JM. Quality More Than Quantity: The Use of Carbohydrates in High-Fat Diets to Tackle Obesity in Growing Rats. Front Nutr 2022; 9:809865. [PMID: 35425792 PMCID: PMC9002105 DOI: 10.3389/fnut.2022.809865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 03/03/2022] [Indexed: 11/23/2022] Open
Abstract
Childhood obesity prevention is important to avoid obesity and its comorbidities into adulthood. Although the energy density of food has been considered a main obesogenic factor, a focus on food quality rather that the quantity of the different macronutrients is needed. Therefore, this study investigates the effects of changing the quality of carbohydrates from rapidly to slowly digestible carbohydrates on metabolic abnormalities and its impact on obesity in growing rats fed a high-fat diet (HFD). Growing rats were fed on HFD containing carbohydrates with different digestion rates: a HFD containing rapid-digesting carbohydrates (OBE group) or slow-digesting carbohydrates (ISR group), for 4 weeks and the effect on the metabolism and signaling pathways were analyzed in different tissues. Animals from OBE group presented an overweight/obese phenotype with a higher body weight gain and greater accumulation of fat in adipose tissue and liver. This state was associated with an increase of HOMA index, serum diacylglycerols and triacylglycerides, insulin, leptin, and pro-inflammatory cytokines. In contrast, the change of carbohydrate profile in the diet to one based on slow digestible prevented the obesity-related adverse effects. In adipose tissue, GLUT4 was increased and UCPs and PPARγ were decreased in ISR group respect to OBE group. In liver, GLUT2, FAS, and SRBP1 were lower in ISR group than OBE group. In muscle, an increase of glycogen, GLUT4, AMPK, and Akt were observed in comparison to OBE group. In conclusion, this study demonstrates that the replacement of rapidly digestible carbohydrates for slowly digestible carbohydrates within a high-fat diet promoted a protective effect against the development of obesity and its associated comorbidities.
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Affiliation(s)
| | - Maria D. Giron
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
| | - Rafael Salto
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
- *Correspondence: Rafael Salto,
| | - Jose D. Vilchez
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
| | - Francisco J. Reche-Perez
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
| | - Elena Cabrera
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
| | - Azahara Linares-Pérez
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
| | - Julio Plaza-Díaz
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
- Instituto de Investigación Biosanitaria de Granada (ibs.GRANADA), Complejo Hospitalario Universitario de Granada, Granada, Spain
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
| | - Francisco Javier Ruiz-Ojeda
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
- Instituto de Investigación Biosanitaria de Granada (ibs.GRANADA), Complejo Hospitalario Universitario de Granada, Granada, Spain
- Biomedical Research Center, Institute of Nutrition and Food Technology “José Mataix,” University of Granada, Granada, Spain
| | - Angel Gil
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
- Biomedical Research Center, Institute of Nutrition and Food Technology “José Mataix,” University of Granada, Granada, Spain
- CIBEROBN Physiopathology of Obesity and Nutrition, Institute of Health Carlos III, Madrid, Spain
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Welch RD, Billon C, Losby M, Bedia-Diaz G, Fang Y, Avdagic A, Elgendy B, Burris TP, Griffett K. Emerging Role of Nuclear Receptors for the Treatment of NAFLD and NASH. Metabolites 2022; 12:metabo12030238. [PMID: 35323681 PMCID: PMC8953348 DOI: 10.3390/metabo12030238] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 03/08/2022] [Accepted: 03/09/2022] [Indexed: 02/04/2023] Open
Abstract
Non-alcoholic fatty liver (NAFLD) over the past years has become a metabolic pandemic linked to a collection of metabolic diseases. The nuclear receptors ERRs, REV-ERBs, RORs, FXR, PPARs, and LXR are master regulators of metabolism and liver physiology. The characterization of these nuclear receptors and their biology has promoted the development of synthetic ligands. The possibility of targeting these receptors to treat NAFLD is promising, as several compounds including Cilofexor, thiazolidinediones, and Saroglitazar are currently undergoing clinical trials. This review focuses on the latest development of the pharmacology of these metabolic nuclear receptors and how they may be utilized to treat NAFLD and subsequent comorbidities.
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Affiliation(s)
- Ryan D. Welch
- Biology and Chemistry Department, Blackburn College, Carlinville, IL 62626, USA;
| | - Cyrielle Billon
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy and Washington University in St. Louis, St. Louis, MO 63110, USA; (C.B.); (G.B.-D.); (Y.F.); (A.A.); (B.E.)
| | - McKenna Losby
- Biochemistry, Biophysics and Structural Biology, School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA;
| | - Gonzalo Bedia-Diaz
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy and Washington University in St. Louis, St. Louis, MO 63110, USA; (C.B.); (G.B.-D.); (Y.F.); (A.A.); (B.E.)
| | - Yuanying Fang
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy and Washington University in St. Louis, St. Louis, MO 63110, USA; (C.B.); (G.B.-D.); (Y.F.); (A.A.); (B.E.)
| | - Amer Avdagic
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy and Washington University in St. Louis, St. Louis, MO 63110, USA; (C.B.); (G.B.-D.); (Y.F.); (A.A.); (B.E.)
| | - Bahaa Elgendy
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy and Washington University in St. Louis, St. Louis, MO 63110, USA; (C.B.); (G.B.-D.); (Y.F.); (A.A.); (B.E.)
- Department of Anesthesiology, School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Thomas P. Burris
- UF Genetics Institute, University of Florida, Gainesville, FL 32611, USA;
| | - Kristine Griffett
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
- Correspondence: ; Tel.: +1-344-844-5416
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Dietary Complex and Slow Digestive Carbohydrates Prevent Fat Deposits During Catch-Up Growth in Rats. Nutrients 2020; 12:nu12092568. [PMID: 32854204 PMCID: PMC7551611 DOI: 10.3390/nu12092568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 08/21/2020] [Accepted: 08/22/2020] [Indexed: 01/10/2023] Open
Abstract
A nutritional growth retardation study, which closely resembles the nutritional observations in children who consumed insufficient total energy to maintain normal growth, was conducted. In this study, a nutritional stress in weanling rats placed on restricted balanced diet for 4 weeks is produced, followed by a food recovery period of 4 weeks using two enriched diets that differ mainly in the slow (SDC) or fast (RDC) digestibility and complexity of their carbohydrates. After re-feeding with the RDC diet, animals showed the negative effects of an early caloric restriction: an increase in adiposity combined with poorer muscle performance, insulin resistance and, metabolic inflexibility. These effects were avoided by the SDC diet, as was evidenced by a lower adiposity associated with a decrease in fatty acid synthase expression in adipose tissue. The improved muscle performance of the SDC group was based on an increase in myocyte enhancer factor 2D (MEF2D) and creatine kinase as markers of muscle differentiation as well as better insulin sensitivity, enhanced glucose uptake, and increased metabolic flexibility. In the liver, the SDC diet promoted glycogen storage and decreased fatty acid synthesis. Therefore, the SDC diet prevents the catch-up fat phenotype through synergistic metabolic adaptations in adipose tissue, muscle, and liver. These coordinated adaptations lead to better muscle performance and a decrease in the fat/lean ratio in animals, which could prevent long-term negative metabolic alterations such as obesity, insulin resistance, dyslipidemia, and liver fat deposits later in life.
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8
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Jackson RM, Griesel BA, Gurley JM, Szweda LI, Olson AL. Glucose availability controls adipogenesis in mouse 3T3-L1 adipocytes via up-regulation of nicotinamide metabolism. J Biol Chem 2017; 292:18556-18564. [PMID: 28916720 DOI: 10.1074/jbc.m117.791970] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 09/13/2017] [Indexed: 12/21/2022] Open
Abstract
Expansion of adipose tissue in response to a positive energy balance underlies obesity and occurs through both hypertrophy of existing cells and increased differentiation of adipocyte precursors (hyperplasia). To better understand the nutrient signals that promote adipocyte differentiation, we investigated the role of glucose availability in regulating adipocyte differentiation and maturation. 3T3-L1 preadipocytes were grown and differentiated in medium containing a standard differentiation hormone mixture and either 4 or 25 mm glucose. Adipocyte maturation at day 9 post-differentiation was determined by key adipocyte markers, including glucose transporter 4 (GLUT4) and adiponectin expression and Oil Red O staining of neutral lipids. We found that adipocyte differentiation and maturation required a pulse of 25 mm glucose only during the first 3 days of differentiation. Importantly, fatty acids were unable to substitute for the 25 mm glucose pulse during this period. The 25 mm glucose pulse increased adiponectin and GLUT4 expression and accumulation of neutral lipids via distinct mechanisms. Adiponectin expression and other early markers of differentiation required an increase in the intracellular pool of total NAD/P. In contrast, GLUT4 protein expression was only partially restored by increased NAD/P levels. Furthermore, GLUT4 mRNA expression was mediated by glucose-dependent activation of GLUT4 gene transcription through the cis-acting GLUT4-liver X receptor element (LXRE) promoter element. In summary, this study supports the conclusion that high glucose promotes adipocyte differentiation via distinct metabolic pathways and independently of fatty acids. This may partly explain the mechanism underlying adipocyte hyperplasia that occurs much later than adipocyte hypertrophy in the development of obesity.
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Affiliation(s)
- Robert M Jackson
- From the Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104 and
| | - Beth A Griesel
- From the Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104 and
| | - Jami M Gurley
- From the Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104 and
| | - Luke I Szweda
- From the Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104 and.,the Program in Aging and Metabolism, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Ann Louise Olson
- the Program in Aging and Metabolism, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
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Ji Q, Zhao Y, Yuan A, Pu J, He B. Deficiency of liver-X-receptor-α reduces glucose uptake and worsens post-myocardial infarction remodeling. Biochem Biophys Res Commun 2017; 488:489-495. [PMID: 28511797 DOI: 10.1016/j.bbrc.2017.05.072] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 05/12/2017] [Indexed: 12/15/2022]
Abstract
Liver X receptor α (LXRα) is an endogenous protective receptor against ischemic heart diseases. However, whether LXRα regulated glucose metabolism in ischemic heart diseases has not been investigated. In this study we investigated the involvement of LXRα on glucose metabolism in cardiac remodeling after myocardial infarction (MI). MI was induced in mice by permanent ligation of the left anterior descending coronary artery (LCA). Genetic LXRα deletion significantly worsened cardiac remodeling and impaired cardiac function at 4 weeks after MI. Cardiac 18F-fluorodeoxyglucose (FDG) uptake by positron emission tomography (PET) demonstrated that the FDG standardized uptake value (SUV) was significantly lower in LXRα-/- mice as compared to WT mice. Mechanistically, GLUT1/4 and AMPK phosphorylation were significantly downregulated while CD36 expression was markedly upregulated in LXRα-/- mice. This study demonstrated that deficiency of LXRα decreased glucose uptake after MI, resulting in a metabolic shift that suppressed glucose metabolism, which was in association with adverse cardiac remodeling.
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Affiliation(s)
- Qingqi Ji
- Department of Cardiology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 160 PuJian Road, Shanghai 200127, China
| | - Yichao Zhao
- Department of Cardiology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 160 PuJian Road, Shanghai 200127, China
| | - Ancai Yuan
- Department of Cardiology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 160 PuJian Road, Shanghai 200127, China
| | - Jun Pu
- Department of Cardiology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 160 PuJian Road, Shanghai 200127, China.
| | - Ben He
- Department of Cardiology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 160 PuJian Road, Shanghai 200127, China.
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10
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Torchon E, Ray R, Hulver MW, McMillan RP, Voy BH. Fasting rapidly increases fatty acid oxidation in white adipose tissue of young broiler chickens. Adipocyte 2017; 6:33-39. [PMID: 28452587 DOI: 10.1080/21623945.2016.1263777] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Upregulating the fatty acid oxidation capacity of white adipose tissue in mice protects against diet-induced obesity, inflammation and insulin resistance. Part of this capacity results from induction of brown-like adipocytes within classical white depots, making it difficult to determine the oxidative contribution of the more abundant white adipocytes. Avian genomes lack a gene for uncoupling protein 1 and are devoid of brown adipose cells, making them a useful model in which to study white adipocyte metabolism in vivo. We recently reported that a brief (5 hour) period of fasting significantly upregulated many genes involved in mitochondrial and peroxisomal fatty acid oxidation pathways in white adipose tissue of young broiler chickens. The objective of this study was to determine if the effects on gene expression manifested in increased rates of fatty acid oxidation. Abdominal adipose tissue was collected from 21 day-old broiler chicks that were fasted for 3, 5 or 7 hours or fed ad libitum (controls). Fatty acid oxidation was determined by measuring and summing 14CO2 production and 14C-labeled acid-soluble metabolites from the oxidation of [1-14C] palmitic acid. Fasting induced a progressive increase in complete fatty acid oxidation and citrate synthase activity relative to controls. These results confirm that fatty acid oxidation in white adipose tissue is dynamically controlled by nutritional status. Identifying the underlying mechanism may provide new therapeutic targets through which to increase fatty acid oxidation in situ and protect against the detrimental effects of excess free fatty acids on adipocyte insulin sensitivity.
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Affiliation(s)
- Emmanuelle Torchon
- Department of Animal Science, University of Tennessee, Knoxville, TN, USA
| | - Rodney Ray
- Department of Animal Science, University of Tennessee, Knoxville, TN, USA
| | - Matthew W. Hulver
- Department of Human Nutrition, Foods and Exercise, Virginia Tech, Blacksburg, VA, USA
- The Metabolic Phenotyping Core at Virginia Tech, Virginia Tech, Blacksburg, VA, USA
| | - Ryan P. McMillan
- Department of Human Nutrition, Foods and Exercise, Virginia Tech, Blacksburg, VA, USA
- The Metabolic Phenotyping Core at Virginia Tech, Virginia Tech, Blacksburg, VA, USA
| | - Brynn H. Voy
- Department of Animal Science, University of Tennessee, Knoxville, TN, USA
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11
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Gurley JM, Ilkayeva O, Jackson RM, Griesel BA, White P, Matsuzaki S, Qaisar R, Van Remmen H, Humphries KM, Newgard CB, Olson AL. Enhanced GLUT4-Dependent Glucose Transport Relieves Nutrient Stress in Obese Mice Through Changes in Lipid and Amino Acid Metabolism. Diabetes 2016; 65:3585-3597. [PMID: 27679559 PMCID: PMC5127250 DOI: 10.2337/db16-0709] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Accepted: 09/20/2016] [Indexed: 12/17/2022]
Abstract
Impaired GLUT4-dependent glucose uptake is a contributing factor in the development of whole-body insulin resistance in obese patients and obese animal models. Previously, we demonstrated that transgenic mice engineered to express the human GLUT4 gene under the control of the human GLUT4 promoter (i.e., transgenic [TG] mice) are resistant to obesity-induced insulin resistance. A likely mechanism underlying increased insulin sensitivity is increased glucose uptake in skeletal muscle. The purpose of this study was to investigate the broader metabolic consequences of enhanced glucose uptake into muscle. We observed that the expression of several nuclear and mitochondrially encoded mitochondrial enzymes was decreased in TG mice but that mitochondrial number, size, and fatty acid respiration rates were unchanged. Interestingly, both pyruvate and glutamate respiration rates were decreased in TG mice. Metabolomics analyses of skeletal muscle samples revealed that increased GLUT4 transgene expression was associated with decreased levels of some tricarboxylic acid intermediates and amino acids, whereas the levels of several glucogenic amino acids were elevated. Furthermore, fasting acyl carnitines in obese TG mice were decreased, indicating that increased GLUT4-dependent glucose flux decreases nutrient stress by altering lipid and amino acid metabolism in skeletal muscle.
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Affiliation(s)
- Jami M Gurley
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Olga Ilkayeva
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Departments of Pharmacology and Cancer Biology and Medicine, Duke University, Durham, NC
| | - Robert M Jackson
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Beth A Griesel
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Phillip White
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Departments of Pharmacology and Cancer Biology and Medicine, Duke University, Durham, NC
| | - Satochi Matsuzaki
- Oklahoma Medical Research Foundation, Metabolism and Aging Program, Oklahoma City, OK
| | - Rizwan Qaisar
- Oklahoma Medical Research Foundation, Metabolism and Aging Program, Oklahoma City, OK
| | - Holly Van Remmen
- Oklahoma Medical Research Foundation, Metabolism and Aging Program, Oklahoma City, OK
| | - Kenneth M Humphries
- Oklahoma Medical Research Foundation, Metabolism and Aging Program, Oklahoma City, OK
| | - Christopher B Newgard
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Departments of Pharmacology and Cancer Biology and Medicine, Duke University, Durham, NC
| | - Ann Louise Olson
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
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12
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Gurley JM, Griesel BA, Olson AL. Increased Skeletal Muscle GLUT4 Expression in Obese Mice After Voluntary Wheel Running Exercise Is Posttranscriptional. Diabetes 2016; 65:2911-9. [PMID: 27411383 PMCID: PMC5033261 DOI: 10.2337/db16-0305] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 07/06/2016] [Indexed: 12/11/2022]
Abstract
Exercise promotes glucose clearance by increasing skeletal muscle GLUT4-mediated glucose uptake. Importantly, exercise upregulates muscle GLUT4 expression in an insulin-independent manner under conditions of insulin resistance, such as with type 2 diabetes. However, the insulin-independent mechanism responsible for rescued muscle GLUT4 expression is poorly understood. We used voluntary wheel running (VWR) in mice to test the prevailing hypothesis that insulin-independent upregulation of skeletal muscle GLUT4 protein expression with exercise is through increased Glut4 transcription. We demonstrate that 4 weeks of VWR exercise in obese mice rescued high-fat diet-induced decreased muscle GLUT4 protein and improved both fasting plasma insulin and hepatic triacylglyceride levels, but did not rescue muscle Glut4 mRNA. Persistent reduction in Glut4 mRNA suggests that a posttranscriptional mechanism regulated insulin-independent muscle GLUT4 protein expression in response to exercise in lean and obese mice. Reduction of GLUT4 protein in sedentary animals upon treatment with rapamycin revealed mTORC1-dependent GLUT4 regulation. However, no difference in GLUT4 protein expression was observed in VWR-exercised mice treated with either rapamycin or Torin 1, indicating that exercise-dependent regulation on GLUT4 was mTOR independent. The findings provide new insight into the mechanisms responsible for exercise-dependent regulation of GLUT4 in muscle.
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Affiliation(s)
- Jami M Gurley
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Beth A Griesel
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Ann Louise Olson
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
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13
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Tol MJ, Ottenhoff R, van Eijk M, Zelcer N, Aten J, Houten SM, Geerts D, van Roomen C, Bierlaagh MC, Scheij S, Hoeksema MA, Aerts JM, Bogan JS, Dorn GW, Argmann CA, Verhoeven AJ. A PPARγ-Bnip3 Axis Couples Adipose Mitochondrial Fusion-Fission Balance to Systemic Insulin Sensitivity. Diabetes 2016; 65:2591-605. [PMID: 27325287 PMCID: PMC5001173 DOI: 10.2337/db16-0243] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 06/09/2016] [Indexed: 12/19/2022]
Abstract
Aberrant mitochondrial fission plays a pivotal role in the pathogenesis of skeletal muscle insulin resistance. However, fusion-fission dynamics are physiologically regulated by inherent tissue-specific and nutrient-sensitive processes that may have distinct or even opposing effects with respect to insulin sensitivity. Based on a combination of mouse population genetics and functional in vitro assays, we describe here a regulatory circuit in which peroxisome proliferator-activated receptor γ (PPARγ), the adipocyte master regulator and receptor for the thiazolidinedione class of antidiabetic drugs, controls mitochondrial network fragmentation through transcriptional induction of Bnip3. Short hairpin RNA-mediated knockdown of Bnip3 in cultured adipocytes shifts the balance toward mitochondrial elongation, leading to compromised respiratory capacity, heightened fatty acid β-oxidation-associated mitochondrial reactive oxygen species generation, insulin resistance, and reduced triacylglycerol storage. Notably, the selective fission/Drp1 inhibitor Mdivi-1 mimics the effects of Bnip3 knockdown on adipose mitochondrial bioenergetics and glucose disposal. We further show that Bnip3 is reciprocally regulated in white and brown fat depots of diet-induced obesity and leptin-deficient ob/ob mouse models. Finally, Bnip3(-/-) mice trade reduced adiposity for increased liver steatosis and develop aggravated systemic insulin resistance in response to high-fat feeding. Together, our data outline Bnip3 as a key effector of PPARγ-mediated adipose mitochondrial network fragmentation, improving insulin sensitivity and limiting oxidative stress.
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Affiliation(s)
- Marc J Tol
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
| | - Roelof Ottenhoff
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
| | - Marco van Eijk
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands Leiden Institute of Chemistry, Leiden University, Leiden, the Netherlands
| | - Noam Zelcer
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
| | - Jan Aten
- Department of Pathology, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
| | - Sander M Houten
- Department of Genetic Metabolic Diseases, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands Department of Genetics and Genomic Sciences, Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Dirk Geerts
- Department of Human Genetics, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
| | - Cindy van Roomen
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
| | - Marlou C Bierlaagh
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
| | - Saskia Scheij
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
| | - Marten A Hoeksema
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
| | - Johannes M Aerts
- Leiden Institute of Chemistry, Leiden University, Leiden, the Netherlands
| | - Jonathan S Bogan
- Section of Endocrinology and Metabolism, Departments of Internal Medicine & Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Gerald W Dorn
- Centre for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO
| | - Carmen A Argmann
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands Department of Genetics and Genomic Sciences, Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Arthur J Verhoeven
- Department of Medical Biochemistry, University of Amsterdam, Academic Medical Centre, Amsterdam, the Netherlands
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14
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Cannon MV, Silljé HHW, Sijbesma JWA, Vreeswijk-Baudoin I, Ciapaite J, van der Sluis B, van Deursen J, Silva GJJ, de Windt LJ, Gustafsson JÅ, van der Harst P, van Gilst WH, de Boer RA. Cardiac LXRα protects against pathological cardiac hypertrophy and dysfunction by enhancing glucose uptake and utilization. EMBO Mol Med 2016; 7:1229-43. [PMID: 26160456 PMCID: PMC4568954 DOI: 10.15252/emmm.201404669] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Pathological cardiac hypertrophy is characterized by a shift in metabolic substrate utilization from fatty acids to glucose, but the molecular events underlying the metabolic remodeling remain poorly understood. Here, we investigated the role of liver X receptors (LXRs), which are key regulators of glucose and lipid metabolism, in cardiac hypertrophic pathogenesis. Using a transgenic approach in mice, we show that overexpression of LXRα acts to protect the heart against hypertrophy, fibrosis, and dysfunction. Gene expression profiling studies revealed that genes regulating metabolic pathways were differentially expressed in hearts with elevated LXRα. Functionally, LXRα overexpression in isolated cardiomyocytes and murine hearts markedly enhanced the capacity for myocardial glucose uptake following hypertrophic stress. Conversely, this adaptive response was diminished in LXRα-deficient mice. Transcriptional changes induced by LXRα overexpression promoted energy-independent utilization of glucose via the hexosamine biosynthesis pathway, resulting in O-GlcNAc modification of GATA4 and Mef2c and the induction of cytoprotective natriuretic peptide expression. Our results identify LXRα as a key cardiac transcriptional regulator that helps orchestrate an adaptive metabolic response to chronic cardiac stress, and suggest that modulating LXRα may provide a unique opportunity for intervening in myocyte metabolism.
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Affiliation(s)
- Megan V Cannon
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Herman H W Silljé
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Jürgen W A Sijbesma
- Department of Nuclear Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Inge Vreeswijk-Baudoin
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Jolita Ciapaite
- Department Pediatrics, Center for Liver, Digestive and Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Bart van der Sluis
- Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Jan van Deursen
- Department of Biochemistry & Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Gustavo J J Silva
- Department of Cardiology, CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands
| | - Leon J de Windt
- Department of Cardiology, CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands
| | - Jan-Åke Gustafsson
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA Department of Biosciences and Nutrition, Novum, Karolinska Institutet, Huddinge, Sweden
| | - Pim van der Harst
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Wiek H van Gilst
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Rudolf A de Boer
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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15
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Cannon MV, Silljé HHW, Sijbesma JWA, Khan MAF, Steffensen KR, van Gilst WH, de Boer RA. LXRα improves myocardial glucose tolerance and reduces cardiac hypertrophy in a mouse model of obesity-induced type 2 diabetes. Diabetologia 2016; 59:634-43. [PMID: 26684450 PMCID: PMC4742491 DOI: 10.1007/s00125-015-3827-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 11/05/2015] [Indexed: 12/11/2022]
Abstract
AIMS/HYPOTHESIS Diabetic cardiomyopathy is a myocardial disease triggered by impaired insulin signalling, increased fatty acid uptake and diminished glucose utilisation. Liver X receptors (LXRs) are key transcriptional regulators of metabolic homeostasis. However, their effect in the diabetic heart is largely unknown. METHODS We cloned murine Lxrα (also known as Nr1h3) behind the α-myosin heavy chain (αMhc; also known as Myh6) promoter to create transgenic (Lxrα-Tg) mice and transgene-negative littermates (wild-type [WT]). A mouse model of type 2 diabetes was induced by a high-fat diet (HFD, 60% energy from fat) over 16 weeks and compared with a low-fat diet (10% energy from fat). A mouse model of type 1 diabetes was induced via streptozotocin injection over 12 weeks. RESULTS HFD manifested comparable increases in body weight, plasma triacylglycerol and insulin resistance per OGTT in Lxrα-Tg and WT mice. HFD significantly increased left ventricular weight by 21% in WT hearts, but only by 5% in Lxrα-Tg. To elucidate metabolic effects in the heart, microPET (positron emission tomography) imaging revealed that cardiac glucose uptake was increased by 1.4-fold in WT mice on an HFD, but further augmented by 1.7-fold in Lxrα-Tg hearts, in part through 5' adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and restoration of glucose transporter 4 (GLUT4). By contrast, streptozotocin-induced ablation of insulin signalling diminished cardiac glucose uptake levels and caused cardiac dysfunction, indicating that insulin may be important in LXRα-mediated glucose uptake. Chromatin immunoprecipitation assays identified natriuretic peptides, atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP), as potential direct targets of cardiac LXRα overexpression. CONCLUSIONS/INTERPRETATION Cardiac-specific LXRα overexpression ameliorates the progression of HFD-induced left ventricular hypertrophy in association with increased glucose reliance and natriuretic peptide signalling during the early phase of diabetic cardiomyopathy. These findings implicate a potential protective role for LXR in targeting metabolic disturbances underlying diabetes.
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Affiliation(s)
- Megan V Cannon
- University of Groningen, University Medical Center Groningen, Department of Cardiology, Hanzeplein 1, 9713 GZ, Groningen, the Netherlands
| | - Herman H W Silljé
- University of Groningen, University Medical Center Groningen, Department of Cardiology, Hanzeplein 1, 9713 GZ, Groningen, the Netherlands
| | - Jürgen W A Sijbesma
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine, Hanzeplein 1, 9713 GZ, Groningen, the Netherlands
| | - Mohsin A F Khan
- University of Groningen, University Medical Center Groningen, Department of Cardiology, Hanzeplein 1, 9713 GZ, Groningen, the Netherlands
| | - Knut R Steffensen
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Wiek H van Gilst
- University of Groningen, University Medical Center Groningen, Department of Cardiology, Hanzeplein 1, 9713 GZ, Groningen, the Netherlands
| | - Rudolf A de Boer
- University of Groningen, University Medical Center Groningen, Department of Cardiology, Hanzeplein 1, 9713 GZ, Groningen, the Netherlands.
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16
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Yan H, Ajuwon KM. Mechanism of Butyrate Stimulation of Triglyceride Storage and Adipokine Expression during Adipogenic Differentiation of Porcine Stromovascular Cells. PLoS One 2015; 10:e0145940. [PMID: 26713737 PMCID: PMC4694642 DOI: 10.1371/journal.pone.0145940] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 12/10/2015] [Indexed: 12/18/2022] Open
Abstract
Short chain fatty acids (SCFA), products of microbial fermentation of dietary fiber, exert multiple metabolic effects in cells. Previously, we had demonstrated that soluble fiber influenced fat mass accumulation, gut microbial community structure and SCFA production in pigs. The current study was designed to identify effects of SCFA treatment during adipogenic differentiation of porcine stromovascular cells on lipid metabolism and adipokine expression. Differentiating cells were treated with varying concentrations of butyrate. Results show that butyrate treatment enhanced adipogenesis and lipid accumulation, perhaps through upregulation of glucose uptake and de novo lipogenesis and other mechanisms that include induction of SREBP-1c, C/EBPα/β, GLUT4, LPL, PPARγ, GPAT4, DGAT1 and DGAT2 expression. In addition, butyrate induced adiponectin expression, resulting in activation of downstream target genes, such as AMPK and AKT. Activation of AMPK by butyrate led to phosphorylation of ACC. Although increased ACO gene expression was seen with butyrate treatment, experiments with the peroxisomal fatty acid inhibitor, thioridazine, suggest that butyrate may have an inhibitory effect on peroxisomal fatty acid oxidation. Our studies also provide evidence that butyrate may inhibit lipolysis, perhaps in an FFAR3-dependent manner. Therefore, this study presents a novel paradigm for butyrate action in adipocytes and shows that adipocytes are capable of utilizing butyrate, leading to increased expression of adiponectin for enhanced glucose uptake and improved insulin sensitivity.
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Affiliation(s)
- Hui Yan
- Department of Animal Sciences, Purdue University, West Lafayette, Indiana, 47907–2054, United States of America
| | - Kolapo M. Ajuwon
- Department of Animal Sciences, Purdue University, West Lafayette, Indiana, 47907–2054, United States of America
- * E-mail:
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17
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Chu M, Sampath H, Cahana DY, Kahl CA, Somwar R, Cornea A, Roberts CT, Varlamov O. Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes. Mol Biol Cell 2014; 25:4096-105. [PMID: 25298400 PMCID: PMC4263452 DOI: 10.1091/mbc.e14-06-1085] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Real-time fluorescence microscopy is used to investigate the trafficking of metabolizable fluorescent fatty acid in unilocular adipocytes from adipose tissue of nonhuman primates. The study reveals novel cell biological features that may contribute to the mechanism of adipocyte hypertrophy. The spatiotemporal dynamics of triglyceride (TG) storage in unilocular adipocytes are not well understood. Here we applied ex vivo technology to study trafficking and metabolism of fluorescent fatty acids in adipose tissue explants. Live imaging revealed multiple cytoplasmic nodules surrounding the large central lipid droplet (cLD) of unilocular adipocytes. Each cytoplasmic nodule harbors a series of closely associated cellular organelles, including micro–lipid droplets (mLDs), mitochondria, and the endoplasmic reticulum. Exogenously added free fatty acids are rapidly adsorbed by mLDs and concurrently get esterified to TG. This process is greatly accelerated by insulin. mLDs transfer their content to the cLD, serving as intermediates that mediate packaging of newly synthesized TG in the large interior of a unilocular adipocyte. This study reveals novel cell biological features that may contribute to the mechanism of adipocyte hypertrophy.
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Affiliation(s)
- Michael Chu
- Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239
| | - Harini Sampath
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, Portland, OR 97239
| | - David Y. Cahana
- Divisions of Diabetes, Obesity, and Metabolism and Developmental and Reproductive Science, Beaverton, OR 97006
| | | | - Romel Somwar
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065
| | - Anda Cornea
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR 97006
| | - Charles T. Roberts
- Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239
- Divisions of Diabetes, Obesity, and Metabolism and Developmental and Reproductive Science, Beaverton, OR 97006
| | - Oleg Varlamov
- Divisions of Diabetes, Obesity, and Metabolism and Developmental and Reproductive Science, Beaverton, OR 97006
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18
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Zheng F, Zhang S, Lu W, Wu F, Yin X, Yu D, Pan Q, Li H. Regulation of insulin resistance and adiponectin signaling in adipose tissue by liver X receptor activation highlights a cross-talk with PPARγ. PLoS One 2014; 9:e101269. [PMID: 24972069 PMCID: PMC4074121 DOI: 10.1371/journal.pone.0101269] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 06/05/2014] [Indexed: 01/15/2023] Open
Abstract
Liver X receptors (LXRs) have been recognized as a promising therapeutic target for atherosclerosis; however, their role in insulin sensitivity is controversial. Adiponectin plays a unique role in maintaining insulin sensitivity. Currently, no systematic experiments elucidating the role of LXR activation in insulin function based on adiponectin signaling have been reported. Here, we investigated the role of LXR activation in insulin resistance based on adiponectin signaling, and possible mechanisms. C57BL/6 mice maintained on a regular chow received the LXR agonist, T0901317 (30 mg/kg.d) for 3 weeks by intraperitoneal injection, and differentiated 3T3-L1 adipocytes were treated with T0901317 or GW3965. T0901317 treatment induced significant insulin resistance in C57BL/6 mice. It decreased adiponectin gene transcription in epididymal fat, as well as serum adiponectin levels. Activity of AMPK, a key mediator of adiponectin signaling, was also decreased, resulting in decreased Glut-4 membrane translocation in epididymal fat. In contrast, adiponectin activity was not changed in the liver of T0901317 treated mice. In vitro, both T0901317 and GW3965 decreased adiponectin expression in adipocytes in a dose-dependent manner, an effect which was diminished by LXRα silencing. ChIP-qPCR studies demonstrated that T0901317 decreased the binding of PPARγ to the PPAR-responsive element (PPRE) of the adiponectin promoter in a dose-dependent manner. Furthermore, T0901317 exerted an antagonistic effect on the expression of adiponectin in adipocytes co-treated with 3 µM Pioglitazone. In luciferase reporter gene assays, T0901317 dose-dependently inhibited PPRE-Luc activity in HEK293 cells co-transfected with LXRα and PPARγ. These results suggest that LXR activation induces insulin resistance with decreased adiponectin signaling in epididymal fat, probably due to negative regulation of PPARγ signaling. These findings indicate that the potential of LXR activation as a therapeutic target for atherosclerosis may be limited by the possibility of exacerbating insulin resistance-related disease.
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Affiliation(s)
- Fenping Zheng
- Department of Endocrinology, Sir Run Run Shaw Hospital Affiliated with School of Zhejiang University, Hangzhou, Zhejiang, P. R. China
| | - Saifei Zhang
- Department of Endocrinology, Sir Run Run Shaw Hospital Affiliated with School of Zhejiang University, Hangzhou, Zhejiang, P. R. China
| | - Weina Lu
- Department of Endocrinology, Sir Run Run Shaw Hospital Affiliated with School of Zhejiang University, Hangzhou, Zhejiang, P. R. China
| | - Fang Wu
- Department of Endocrinology, Sir Run Run Shaw Hospital Affiliated with School of Zhejiang University, Hangzhou, Zhejiang, P. R. China
| | - Xueyao Yin
- Department of Endocrinology, Sir Run Run Shaw Hospital Affiliated with School of Zhejiang University, Hangzhou, Zhejiang, P. R. China
| | - Dan Yu
- Department of Endocrinology, Sir Run Run Shaw Hospital Affiliated with School of Zhejiang University, Hangzhou, Zhejiang, P. R. China
| | - Qianqian Pan
- Biomedical Research Center and Key Laboratory of Biotherapy of Zhejiang Province, Sir Run Run Shaw Hospital Affiliated with School of Zhejiang University, Hangzhou, Zhejiang, P.R. China
| | - Hong Li
- Department of Endocrinology, Sir Run Run Shaw Hospital Affiliated with School of Zhejiang University, Hangzhou, Zhejiang, P. R. China
- * E-mail:
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Klingerman CM, Stipanovic ME, Bader M, Lynch CJ. Second-generation antipsychotics cause a rapid switch to fat oxidation that is required for survival in C57BL/6J mice. Schizophr Bull 2014; 40:327-40. [PMID: 23328157 PMCID: PMC3932077 DOI: 10.1093/schbul/sbs196] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Some second-generation antipsychotics (SGAs) increase insulin resistance and fat oxidation, but counter intuitively they do not activate lipolysis. This seems unsustainable for meeting energy demands. Here, we measured dose-dependent effects of SGAs on rates of oxygen consumption (VO2), respiratory exchange ratio (RER), and physical activity in C57BL/6J mice. The role of H1-histamine receptors and consequences of blocking fat oxidation were also examined. Olanzapine, risperidone, and clozapine (2.5-10mg/kg) elicited rapid drops in dark-cycle RER (~0.7) within minutes, whereas aripiprazole exerted only modest changes. Higher doses of olanzapine decreased VO2, and this was associated with accumulation of glucose in plasma. Clozapine and risperidone also lowered VO2, in contrast to aripiprazole, whereas all decreased physical activity. Astemizole and terfenadine had no significant effects on RER, VO2, or physical activity. The VO2 and RER effects appear independent of sedation/physical activity or H1-receptors. CPT-1 inhibitors can enhance muscle glucose utilization and prevent fat oxidation. However, after etomoxir (2 × 30 mg/kg), a low dose of olanzapine that did not significantly affect VO2 by itself caused precipitous drops in VO2 and body temperature, leading to death within hours or a moribund state requiring euthanasia. One 30 mg/kg dose of either etomoxir or 2-tetradecylglycidate followed by olanzapine, risperidone, or clozapine, but not aripiprazole, dramatically lowered VO2 and body temperature. Thus, mice treated with some SGAs shift their fuel utilization to mostly fat but are unable to either switch back to glucose or meet their energy demands when either higher doses are used or when fat oxidation is blocked.
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Affiliation(s)
| | | | | | - Christopher J. Lynch
- *To whom correspondence should be addressed; Department of Cellular & Molecular Physiology, Penn State College of Medicine, 500 University Drive, MC-H166, Hershey, PA 17033, US; tel: 717-531-5170, fax: 717-531-7667, e-mail:
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Dib L, Bugge A, Collins S. LXRα fuels fatty acid-stimulated oxygen consumption in white adipocytes. J Lipid Res 2014; 55:247-57. [PMID: 24259533 PMCID: PMC3886663 DOI: 10.1194/jlr.m043422] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 10/28/2013] [Indexed: 02/06/2023] Open
Abstract
Liver X receptors (LXRs) are transcription factors known for their role in hepatic cholesterol and lipid metabolism. Though highly expressed in fat, the role of LXR in this tissue is not well characterized. We generated adipose tissue LXRα knockout (ATaKO) mice and showed that these mice gain more weight and fat mass on a high-fat diet compared with wild-type controls. White adipose tissue (WAT) accretion in ATaKO mice results from both a decrease in WAT lipolytic and oxidative capacities. This was demonstrated by decreased expression of the β2- and β3-adrenergic receptors, reduced level of phosphorylated hormone-sensitive lipase, and lower oxygen consumption rates (OCRs) in WAT of ATaKO mice. Furthermore, LXR activation in vivo and in vitro led to decreased adipocyte size in WAT and increased glycerol release from primary adipocytes, respectively, with a concomitant increase in OCR in both models. Our findings show that absence of LXRα in adipose tissue results in elevated adiposity through a decrease in WAT oxidation, secondary to attenuated FA availability.
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Affiliation(s)
- Lea Dib
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL
| | - Anne Bugge
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL
| | - Sheila Collins
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL
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Pettersson AML, Stenson BM, Lorente-Cebrián S, Andersson DP, Mejhert N, Krätzel J, Aström G, Dahlman I, Chibalin AV, Arner P, Laurencikiene J. LXR is a negative regulator of glucose uptake in human adipocytes. Diabetologia 2013; 56:2044-54. [PMID: 23765184 DOI: 10.1007/s00125-013-2954-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 05/16/2013] [Indexed: 01/14/2023]
Abstract
AIMS/HYPOTHESIS Obesity increases the risk of developing type 2 diabetes mellitus, characterised by impaired insulin-mediated glucose uptake in peripheral tissues. Liver X receptor (LXR) is a positive regulator of adipocyte glucose transport in murine models and a possible target for diabetes treatment. However, the levels of LXRα are increased in obese adipose tissue in humans. We aimed to investigate the transcriptome of LXR and the role of LXR in the regulation of glucose uptake in primary human adipocytes. METHODS The insulin responsiveness of human adipocytes differentiated in vitro was characterised, adipocytes were treated with the LXR agonist GW3965 and global transcriptome profiling was determined by microarray, followed by quantitative RT-PCR (qRT-PCR), western blot and ELISA. Basal and insulin-stimulated glucose uptake was measured and the effect on plasma membrane translocation of glucose transporter 4 (GLUT4) was assayed. RESULTS LXR activation resulted in transcriptional suppression of several insulin signalling genes, such as AKT2, SORBS1 and CAV1, but caused only minor changes (<15%) in microRNA expression. Activation of LXR impaired the plasma membrane translocation of GLUT4, but not the expression of its gene, SLC2A4. LXR activation also diminished insulin-stimulated glucose transport and lipogenesis in adipocytes obtained from overweight individuals. Furthermore, AKT2 expression was reduced in obese adipose tissue, and AKT2 and SORBS1 expression was inversely correlated with BMI and HOMA index. CONCLUSIONS/INTERPRETATION In contrast to murine models, LXR downregulates insulin-stimulated glucose uptake in human adipocytes from overweight individuals. This could be due to suppression of Akt2, c-Cbl-associated protein and caveolin-1. These findings challenge the idea of LXR as a drug target in the treatment of diabetes.
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Affiliation(s)
- A M L Pettersson
- Department of Medicine Huddinge, Karolinska Institutet, Hälsovägen 7, Novum, 14186 Stockholm, Sweden.
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Viscarra JA, Ortiz RM. Cellular mechanisms regulating fuel metabolism in mammals: role of adipose tissue and lipids during prolonged food deprivation. Metabolism 2013; 62:889-97. [PMID: 23357530 PMCID: PMC3640658 DOI: 10.1016/j.metabol.2012.12.014] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 12/06/2012] [Accepted: 12/25/2012] [Indexed: 01/11/2023]
Abstract
Food deprivation in mammals results in profound changes in fuel metabolism and substrate regulation. Among these changes are decreased reliance on the counter-regulatory dynamics by insulin-glucagon due to reduced glucose utilization, and increased concentrations of lipid substrates in plasma to meet the energetic demands of peripheral tissues. As the primary storage site of lipid substrates, adipose tissue must then be a primary contributor to the regulation of metabolism in food deprived states. Through its regulation of lipolysis, adipose tissue influences the availability of carbohydrate, lipid, and protein substrates. Additionally, lipid substrates can act as ligands to various nuclear receptors (retinoid x receptor (RXR), liver x receptor (LXR), and peroxisome proliferator-activated receptor (PPAR)) and exhibit prominent regulatory capabilities over the expression of genes involved in substrate metabolism within various tissues. Therefore, through its control of lipolysis, adipose tissue also indirectly regulates the utilization of metabolic substrates within peripheral tissues. In this review, these processes are described in greater detail and the extent to which adipose tissue and lipid substrates regulate metabolism in food deprived mammals is explored with comments on future directions to better assess the contribution of adipose tissue to metabolism.
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Affiliation(s)
- Jose Abraham Viscarra
- Department of Molecular and Cellular Biology, University of California, Merced, 5200 N Lake Rd., Merced, CA 95343, USA.
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Weems JC, Griesel BA, Olson AL. Class II histone deacetylases downregulate GLUT4 transcription in response to increased cAMP signaling in cultured adipocytes and fasting mice. Diabetes 2012; 61:1404-14. [PMID: 22403301 PMCID: PMC3357296 DOI: 10.2337/db11-0737] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insulin-mediated glucose uptake is highly sensitive to the levels of the facilitative glucose transporter protein, GLUT4. Repression of GLUT4 expression is correlated with insulin resistance in adipose tissue. We have shown that differentiation-dependent GLUT4 transcription was under control of class II histone deacetylases (HDACs). We hypothesized that HDACs may regulate gene expression in adipocytes as a result of adrenergic activation. To test this hypothesis, we activated cAMP signaling in 3T3-L1 adipocytes and in mice after an overnight fast. Chromatin immunoprecipitation experiments showed the association of HDAC4/5 with the GLUT4 promoter in vivo and in vitro in response to elevated cAMP. Knockdown of HDACs by small interfering RNA in cultured adipocytes prevented the cAMP-dependent decrease in GLUT4 transcription. HDAC4/5 recruitment to the GLUT4 promoter was dependent on the GLUT4 liver X receptor (LXR) binding site. Treatment of cells with an LXR agonist prevented the cAMP-dependent decrease in GLUT4 transcription. A loss of function mutation in the LXR response element was required for cAMP-dependent downregulation of GLUT4 expression in vitro, in fasted mice, and in mice subjected to diet-induced obesity. This suggests that activation of LXR signaling can prevent loss of GLUT4 expression in diabetes and obesity.
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Kuramoto K, Okamura T, Yamaguchi T, Nakamura TY, Wakabayashi S, Morinaga H, Nomura M, Yanase T, Otsu K, Usuda N, Matsumura S, Inoue K, Fushiki T, Kojima Y, Hashimoto T, Sakai F, Hirose F, Osumi T. Perilipin 5, a lipid droplet-binding protein, protects heart from oxidative burden by sequestering fatty acid from excessive oxidation. J Biol Chem 2012; 287:23852-63. [PMID: 22532565 DOI: 10.1074/jbc.m111.328708] [Citation(s) in RCA: 171] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Lipid droplets (LDs) are ubiquitous organelles storing neutral lipids, including triacylglycerol (TAG) and cholesterol ester. The properties of LDs vary greatly among tissues, and LD-binding proteins, the perilipin family in particular, play critical roles in determining such diversity. Overaccumulation of TAG in LDs of non-adipose tissues may cause lipotoxicity, leading to diseases such as diabetes and cardiomyopathy. However, the physiological significance of non-adipose LDs in a normal state is poorly understood. To address this issue, we generated and characterized mice deficient in perilipin 5 (Plin5), a member of the perilipin family particularly abundant in the heart. The mutant mice lacked detectable LDs, containing significantly less TAG in the heart. Particulate structures containing another LD-binding protein, Plin2, but negative for lipid staining, remained in mutant mice hearts. LDs were recovered by perfusing the heart with an inhibitor of lipase. Cultured cardiomyocytes from Plin5-null mice more actively oxidized fatty acid than those of wild-type mice. Production of reactive oxygen species was increased in the mutant mice hearts, leading to a greater decline in heart function with age. This was, however, reduced by the administration of N-acetylcysteine, a precursor of an antioxidant, glutathione. Thus, we conclude that Plin5 is essential for maintaining LDs at detectable sizes in the heart, by antagonizing lipase(s). LDs in turn prevent excess reactive oxygen species production by sequestering fatty acid from oxidation and hence suppress oxidative burden to the heart.
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Affiliation(s)
- Kenta Kuramoto
- Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
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Liang Y, Sheng S, Fang P, Ma Y, Li J, Shi Q, Sui Y, Shi M. Exercise-induced galanin release facilitated GLUT4 translocation in adipocytes of type 2 diabetic rats. Pharmacol Biochem Behav 2012; 100:554-9. [DOI: 10.1016/j.pbb.2011.10.026] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2011] [Revised: 10/24/2011] [Accepted: 10/31/2011] [Indexed: 12/23/2022]
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Jung JG, Choi SE, Hwang YJ, Lee SA, Kim EK, Lee MS, Han SJ, Kim HJ, Kim DJ, Kang Y, Lee KW. Supplementation of pyruvate prevents palmitate-induced impairment of glucose uptake in C2 myotubes. Mol Cell Endocrinol 2011; 345:79-87. [PMID: 21802492 DOI: 10.1016/j.mce.2011.07.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 07/08/2011] [Accepted: 07/08/2011] [Indexed: 12/22/2022]
Abstract
Elevated fatty acid levels have been thought to contribute to insulin resistance. Repression of the glucose transporter 4 (GLUT4) gene as well as impaired GLUT4 translocation may be a mediator for fatty acid-induced insulin resistance. This study was initiated to determine whether palmitate treatment repressed GLUT4 expression, whether glucose/fatty acid metabolism influenced palmitate-induced GLUT4 gene repression (PIGR), and whether attempts to prevent PIGR restored palmitate-induced impairment of glucose uptake (PIIGU) in C2 myotubes. Not only stimulators of fatty acid oxidation, such as bezafibrate, AICAR, and TOFA, but also TCA cycle substrates, such as pyruvate, leucine/glutamine, and α-ketoisocaproate/monomethyl succinate, significantly prevented PIGR. In particular, supplementing with pyruvate through methyl pyruvate resulted in nearly complete prevention of PIIGU, whereas palmitate treatment reduced the intracellular pyruvate level. These results suggest that pyruvate depletion plays a critical role in PIGR and PIIGU; thus, pyruvate supplementation may help prevent obesity-induced insulin resistance in muscle cells.
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Affiliation(s)
- Jong Gab Jung
- Department of Endocrinology and Metabolism, Ajou University School of Medicine, Suwon, Kyunggi-do, Republic of Korea
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Viscarra JA, Champagne CD, Crocker DE, Ortiz RM. 5'AMP-activated protein kinase activity is increased in adipose tissue of northern elephant seal pups during prolonged fasting-induced insulin resistance. J Endocrinol 2011; 209:317-25. [PMID: 21429964 PMCID: PMC3250370 DOI: 10.1530/joe-11-0017] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Northern elephant seals endure a 2- to 3-month fast characterized by sustained hyperglycemia, hypoinsulinemia, and increased plasma cortisol and free fatty acids, conditions often seen in insulin-resistant humans. We had previously shown that adipose Glut4 expression and 5'AMP-activated protein kinase (AMPK) activity increase and plasma glucose decreases in fasting seals suggesting that AMPK activity contributes to glucose regulation during insulin-resistant conditions. To address the hypothesis that AMPK activity increases during fasting-induced insulin resistance, we performed glucose tolerance tests (GTT) on early (n=5) and late (n=8)-fasted seal pups and compared adipose tissue expression of insulin signaling proteins, peroxisome proliferator-activated receptor γ (PPARγ), and AMPK, in addition to plasma adiponectin, leptin, cortisol, insulin, and non-esterified fatty acid (NEFA) levels. Fasting was associated with decreased glucose clearance, plasma insulin and adiponectin, and intracellular insulin signaling, as well as increased plasma cortisol and NEFAs, supporting the suggestion that seals develop insulin resistance late in the fast. The expression of Glut4 and VAMP2 increased (52 and 63% respectively) with fasting but did not change significantly during the GTT. PPARγ and phosphorylated AMPK did not change in the early fasted seals, but increased significantly (73 and 50% respectively) in the late-fasted seals during the GTT. Increased AMPK activity along with the reduction in the activity of insulin-signaling proteins supports our hypothesis that AMPK activity is increased following the onset of insulin resistance. The association between increased AMPK activity and Glut4 expression suggests that AMPK plays a greater role in regulating glucose metabolism in mammals adapted to prolonged fasting than in non-fasting mammals.
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Affiliation(s)
- Jose A Viscarra
- School of Natural Sciences, University of California, Merced, California 95348, USA.
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Weems J, Olson AL. Class II histone deacetylases limit GLUT4 gene expression during adipocyte differentiation. J Biol Chem 2010; 286:460-8. [PMID: 21047791 DOI: 10.1074/jbc.m110.157107] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Insulin-dependent glucose homeostasis is highly sensitive to the levels of insulin-responsive glucose transporter 4 (GLUT4) expression in adipocytes. The level of GLUT4 protein expression is highly dependent on the rate of GLUT4 gene transcription. GLUT4 gene transcription is decreased in a variety of physiologic states of insulin resistance including type 2 diabetes, obesity, and prolonged fasting. GLUT4 gene expression in adipocytes is differentiation-dependent, with full expression delayed until late in the differentiation program. In this paper, we have tested the hypothesis that differentiation-dependent GLUT4 gene expression in 3T3-L1 adipocytes is dependent on the nuclear concentration of a class II histone deacetylase (HDAC) protein, HDAC5. We have tested this hypothesis by reducing the levels of class II HDACs in the nuclear compartment of 3T3-L1 preadipocytes using two experimental approaches. First, preadipocytes were treated with phenylephrine, an α-adrenergic receptor agonist, to drive HDACS out of the nuclear compartment. Also, the class II HDAC concentrations were reduced using siRNA knockdown. In each case, reduction of nuclear class II HDAC concentration resulted in increased expression of endogenous GLUT4 mRNA in preadipocytes. Together, our data indicate that class II HDAC expression is the major regulatory mechanism for inhibiting GLUT4 expression in the predifferentiated state.
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Affiliation(s)
- Juston Weems
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190, USA
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