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Hwang J, Thurmond DC. Exocytosis Proteins: Typical and Atypical Mechanisms of Action in Skeletal Muscle. Front Endocrinol (Lausanne) 2022; 13:915509. [PMID: 35774142 PMCID: PMC9238359 DOI: 10.3389/fendo.2022.915509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 05/11/2022] [Indexed: 11/18/2022] Open
Abstract
Insulin-stimulated glucose uptake in skeletal muscle is of fundamental importance to prevent postprandial hyperglycemia, and long-term deficits in insulin-stimulated glucose uptake underlie insulin resistance and type 2 diabetes. Skeletal muscle is responsible for ~80% of the peripheral glucose uptake from circulation via the insulin-responsive glucose transporter GLUT4. GLUT4 is mainly sequestered in intracellular GLUT4 storage vesicles in the basal state. In response to insulin, the GLUT4 storage vesicles rapidly translocate to the plasma membrane, where they undergo vesicle docking, priming, and fusion via the high-affinity interactions among the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) exocytosis proteins and their regulators. Numerous studies have elucidated that GLUT4 translocation is defective in insulin resistance and type 2 diabetes. Emerging evidence also links defects in several SNAREs and SNARE regulatory proteins to insulin resistance and type 2 diabetes in rodents and humans. Therefore, we highlight the latest research on the role of SNAREs and their regulatory proteins in insulin-stimulated GLUT4 translocation in skeletal muscle. Subsequently, we discuss the novel emerging role of SNARE proteins as interaction partners in pathways not typically thought to involve SNAREs and how these atypical functions reveal novel therapeutic targets for combating peripheral insulin resistance and diabetes.
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Affiliation(s)
| | - Debbie C. Thurmond
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes and Metabolism Research Institute, Beckman Research Institute at City of Hope, Duarte, CA, United States
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Abstract
Insulin receptors are highly expressed in the heart and vasculature. Insulin signaling regulates cardiac growth, survival, substrate uptake, utilization, and mitochondrial metabolism. Insulin signaling modulates the cardiac responses to physiological and pathological stressors. Altered insulin signaling in the heart may contribute to the pathophysiology of ventricular remodeling and heart failure progression. Myocardial insulin signaling adapts rapidly to changes in the systemic metabolic milieu. What may initially represent an adaptation to protect the heart from carbotoxicity may contribute to amplifying the risk of heart failure in obesity and diabetes. This review article presents the multiple roles of insulin signaling in cardiac physiology and pathology and discusses the potential therapeutic consequences of modulating myocardial insulin signaling.
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Affiliation(s)
- E Dale Abel
- Division of Endocrinology, Metabolism and Diabetes and Fraternal Order of Eagles Diabetes Research Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa
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3
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AKT2 regulates development and metabolic homeostasis via AMPK-depedent pathway in skeletal muscle. Clin Sci (Lond) 2021; 134:2381-2398. [PMID: 32880392 DOI: 10.1042/cs20191320] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 09/02/2020] [Accepted: 09/03/2020] [Indexed: 12/21/2022]
Abstract
Skeletal muscle is responsible for the majority of glucose disposal in the body. Insulin resistance in the skeletal muscle accounts for 85-90% of the impairment of total glucose disposal in patients with type 2 diabetes (T2D). However, the mechanism remains controversial. The present study aims to investigate whether AKT2 deficiency causes deficits in skeletal muscle development and metabolism, we analyzed the expression of molecules related to skeletal muscle development, glucose uptake and metabolism in mice of 3- and 8-months old. We found that AMP-activated protein kinase (AMPK) phosphorylation and myocyte enhancer factor 2 (MEF2) A (MEF2A) expression were down-regulated in AKT2 knockout (KO) mice, which can be inverted by AMPK activation. We also observed reduced mitochondrial DNA (mtDNA) abundance and reduced expression of genes involved in mitochondrial biogenesis in the skeletal muscle of AKT2 KO mice, which was prevented by AMPK activation. Moreover, AKT2 KO mice exhibited impaired AMPK signaling in response to insulin stimulation compared with WT mice. Our study establishes a new and important function of AKT2 in regulating skeletal muscle development and glucose metabolism via AMPK-dependent signaling.
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Bowman PRT, Smith GL, Gould GW. Cardiac SNARE Expression in Health and Disease. Front Endocrinol (Lausanne) 2019; 10:881. [PMID: 31920989 PMCID: PMC6930865 DOI: 10.3389/fendo.2019.00881] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 12/03/2019] [Indexed: 12/16/2022] Open
Abstract
SNARE proteins are integral to intracellular vesicular trafficking, which in turn is the process underlying the regulated expression of substrate transporters such as the glucose transporter GLUT4 at the cell surface of insulin target tissues. Impaired insulin stimulated GLUT4 trafficking is associated with reduced cardiac function in many disease states, most notably diabetes. Despite this, our understanding of the expression and regulation of SNARE proteins in cardiac tissue and how these may change in diabetes is limited. Here we characterize the array of SNARE proteins expressed in cardiac tissue, and quantify the levels of expression of VAMP2, SNAP23, and Syntaxin4-key proteins involved in insulin-stimulated GLUT4 translocation. We examined SNARE protein levels in cardiac tissue from two rodent models of insulin resistance, db/db mice and high-fat fed mice, and show alterations in patterns of expression are evident. Such changes may have implications for cardiac function.
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Affiliation(s)
- Peter R. T. Bowman
- Henry Wellcome Laboratory of Cell Biology, College of Medical, Veterinary and Life Sciences, Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Godfrey L. Smith
- College of Medical, Veterinary and Life Sciences, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Gwyn W. Gould
- Henry Wellcome Laboratory of Cell Biology, College of Medical, Veterinary and Life Sciences, Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
- *Correspondence: Gwyn W. Gould
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Hargreaves M, Spriet LL. Exercise Metabolism: Fuels for the Fire. Cold Spring Harb Perspect Med 2018; 8:cshperspect.a029744. [PMID: 28533314 DOI: 10.1101/cshperspect.a029744] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
During exercise, the supply of adenosine triphosphate (ATP) is essential for the energy-dependent processes that underpin ongoing contractile activity. These pathways involve both substrate-level phosphorylation, without any need for oxygen, and oxidative phosphorylation that is critically dependent on oxygen delivery to contracting skeletal muscle by the respiratory and cardiovascular systems and on the supply of reducing equivalents from the degradation of carbohydrate, fat, and, to a limited extent, protein fuel stores. The relative contribution of these pathways is primarily determined by exercise intensity, but also modulated by training status, preceding diet, age, gender, and environmental conditions. Optimal substrate availability and utilization before, during, and after exercise is critical for maintaining exercise performance. This review provides a brief overview of exercise metabolism, with expanded discussion of the regulation of muscle glucose uptake and fatty acid uptake and oxidation.
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Affiliation(s)
- Mark Hargreaves
- Department of Physiology, The University of Melbourne, Victoria 3010, Australia
| | - Lawrence L Spriet
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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Snook LA, Wright DC, Holloway GP. Postprandial control of fatty acid transport proteins' subcellular location is not dependent on insulin. FEBS Lett 2016; 590:2661-70. [PMID: 27311759 DOI: 10.1002/1873-3468.12260] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 04/28/2016] [Accepted: 06/14/2016] [Indexed: 01/09/2023]
Abstract
Fatty acid transport proteins rapidly translocate to the plasma membrane in response to various stimuli, including insulin, influencing lipid uptake into muscle. However, our understanding of the mechanisms regulating postprandial fatty acid transporter subcellular location remains limited. We demonstrate that the response of fatty acid transporters to insulin stimulation is extremely brief and not temporally matched in the postprandial state. We further show that high-fat diet-induced accumulation of fatty acid transporters on the plasma membrane can occur in the absence of insulin. Altogether, these data suggest that insulin is not the primary signal regulating fatty acid transporter relocation in vivo.
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Affiliation(s)
- Laelie A Snook
- Department of Human Health and Nutritional Sciences, University of Guelph, Canada
| | - David C Wright
- Department of Human Health and Nutritional Sciences, University of Guelph, Canada
| | - Graham P Holloway
- Department of Human Health and Nutritional Sciences, University of Guelph, Canada
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Jain SS, Luiken JJFP, Snook LA, Han XX, Holloway GP, Glatz JFC, Bonen A. Fatty acid transport and transporters in muscle are critically regulated by Akt2. FEBS Lett 2015; 589:2769-75. [PMID: 26296318 DOI: 10.1016/j.febslet.2015.08.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 08/07/2015] [Indexed: 10/23/2022]
Abstract
Muscle contains various fatty acid transporters (CD36, FABPpm, FATP1, FATP4). Physiological stimuli (insulin, contraction) induce the translocation of all four transporters to the sarcolemma to enhance fatty acid uptake similarly to glucose uptake stimulation via glucose transporter-4 (GLUT4) translocation. Akt2 mediates insulin-induced, but not contraction-induced, GLUT4 translocation, but its role in muscle fatty acid transporter translocation is unknown. In muscle from Akt2-knockout mice, we observed that Akt2 is critically involved in both insulin-induced and contraction-induced fatty acid transport and translocation of fatty acid translocase/CD36 (CD36) and FATP1, but not of translocation of fatty acid-binding protein (FABPpm) and FATP4. Instead, Akt2 mediates intracellular retention of both latter transporters. Collectively, our observations reveal novel complexities in signaling mechanisms regulating the translocation of fatty acid transporters in muscle.
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Affiliation(s)
- Swati S Jain
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Joost J F P Luiken
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, P.O. Box 616, Maastricht NL-6200 MD, The Netherlands.
| | - Laelie A Snook
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Xiao Xia Han
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Graham P Holloway
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Jan F C Glatz
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, P.O. Box 616, Maastricht NL-6200 MD, The Netherlands
| | - Arend Bonen
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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Paglialunga S, Ludzki A, Root-McCaig J, Holloway GP. In adipose tissue, increased mitochondrial emission of reactive oxygen species is important for short-term high-fat diet-induced insulin resistance in mice. Diabetologia 2015; 58:1071-80. [PMID: 25754553 DOI: 10.1007/s00125-015-3531-x] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Accepted: 01/28/2015] [Indexed: 12/20/2022]
Abstract
AIMS/HYPOTHESIS Consuming a high-fat diet (HFD) induces insulin resistance in white adipose tissue (WAT) within 1 week. However, little is known about the initiating events. One potential mechanism that has remained largely unexplored is excessive mitochondrial emission of reactive oxygen species (ROS). METHODS To determine the role of mitochondrial ROS emissions at the onset of insulin resistance, wild-type (WT) mice were placed on an HFD for 1 week. WAT insulin sensitivity and inflammation were assessed by western blot. In addition, we optimised/validated a method to determine ROS emissions in permeabilised WAT. RESULTS An HFD for 1 week resulted in impaired insulin signalling, increased c-Jun NH2-terminal kinase (JNK) phosphorylation and an increase in oxidative stress. These changes were associated with an increase in fatty-acid-mediated mitochondrial ROS emissions without any change in mitochondrial respiration/content. To determine that mitochondrial ROS causes insulin resistance, we used transgenic mice that express human catalase in mitochondria (MCAT) as a model of upregulated mitochondrial antioxidant enzyme capacity. MCAT mice displayed attenuated mitochondrial ROS emission, preserved insulin signalling and no inflammatory response following an HFD. CONCLUSIONS/INTERPRETATION Findings from this study suggest that elevated mitochondrial ROS emission contributes to HFD-induced WAT insulin resistance.
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Affiliation(s)
- Sabina Paglialunga
- Department of Human Health and Nutritional Sciences, University of Guelph, 50 Stone Rd, Guelph, ON, N1G 2W1, Canada
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Ramalingam L, Yoder SM, Oh E, Thurmond DC. Munc18c: a controversial regulator of peripheral insulin action. Trends Endocrinol Metab 2014; 25:601-8. [PMID: 25028245 PMCID: PMC4253632 DOI: 10.1016/j.tem.2014.06.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 06/12/2014] [Accepted: 06/20/2014] [Indexed: 12/19/2022]
Abstract
Insulin resistance, a hallmark of impaired glucose tolerance and type 2 diabetes (T2D), arises from dysfunction of insulin action and subsequent glucose uptake by peripheral tissues, predominantly skeletal muscle and fat. Exocytosis of glucose transporter (GLUT4)-containing vesicles facilitated by soluble NSF (N-ethylmaleimide-sensitive factor) attachment receptor (SNARE) protein isoforms, and Munc18c (mammalian homolog of Unc-18c) mediates this glucose uptake. Emerging evidences, including recent human clinical studies, point to pivotal roles for Munc18c in peripheral insulin action in adipose and skeletal muscle. Intriguing new advances are also initiating debates regarding the molecular mechanism(s) controlling Munc18c action. The objective of this review is therefore to present a balanced perspective of new continuities and controversies surrounding the regulation and requirement for Munc18c in the regulation of peripheral insulin action.
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Affiliation(s)
- Latha Ramalingam
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Stephanie M Yoder
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Eunjin Oh
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Debbie C Thurmond
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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Jordy AB, Serup AK, Karstoft K, Pilegaard H, Kiens B, Jeppesen J. Insulin sensitivity is independent of lipid binding protein trafficking at the plasma membrane in human skeletal muscle: effect of a 3-day, high-fat diet. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1136-45. [PMID: 25163924 DOI: 10.1152/ajpregu.00124.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of the present study was to investigate lipid-induced regulation of lipid binding proteins in human skeletal muscle and the impact hereof on insulin sensitivity. Eleven healthy male subjects underwent a 3-day hypercaloric and high-fat diet regime. Muscle biopsies were taken before and after the diet intervention, and giant sarcolemmal vesicles were prepared. The high-fat diet induced decreased insulin sensitivity, but this was not associated with a relocation of FAT/CD36 or FABPpm protein to the sarcolemma. However, FAT/CD36 and FABPpm mRNA, but not the proteins, were upregulated by increased fatty acid availability. This suggests a time dependency in the upregulation of FAT/CD36 and FABPpm protein during high availability of plasma fatty acids. Furthermore, we did not detect FATP1 and FATP4 protein in giant sarcolemmal vesicles obtained from human skeletal muscle. In conclusion, this study shows that a short-term lipid-load increases mRNA content of key lipid handling proteins in human muscle. However, decreased insulin sensitivity after a high-fat diet is not accompanied with relocation of FAT/CD36 or FABPpm protein to the sarcolemma. Finally, FATP1 and FATP4 protein was located intracellularly but not at the sarcolemma in humans.
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Affiliation(s)
- Andreas B Jordy
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Annette K Serup
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Kristian Karstoft
- The Centre of Inflammation and Metabolism and The Centre for Physical Activity Research, Department of Infectious Diseases, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and
| | - Henriette Pilegaard
- The Centre of Inflammation and Metabolism and The Centre for Physical Activity Research, Department of Infectious Diseases, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and CFAS, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Bente Kiens
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark;
| | - Jacob Jeppesen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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Matravadia S, Herbst EAF, Jain SS, Mutch DM, Holloway GP. Both linoleic and α-linolenic acid prevent insulin resistance but have divergent impacts on skeletal muscle mitochondrial bioenergetics in obese Zucker rats. Am J Physiol Endocrinol Metab 2014; 307:E102-14. [PMID: 24844257 DOI: 10.1152/ajpendo.00032.2014] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The therapeutic use of polyunsaturated fatty acids (PUFA) in preserving insulin sensitivity has gained interest in recent decades; however, the roles of linoleic acid (LA) and α-linolenic acid (ALA) remain poorly understood. We investigated the efficacy of diets enriched with either LA or ALA on attenuating the development of insulin resistance (IR) in obesity. Following a 12-wk intervention, LA and ALA both prevented the shift toward an IR phenotype and maintained muscle-specific insulin sensitivity otherwise lost in obese control animals. The beneficial effects of ALA were independent of changes in skeletal muscle mitochondrial content and oxidative capacity, as obese control and ALA-treated rats showed similar increases in these parameters. However, ALA increased the propensity for mitochondrial H2O2 emission and catalase content within whole muscle and reduced markers of oxidative stress (4-HNE and protein carbonylation). In contrast, LA prevented changes in markers of mitochondrial content, respiratory function, H2O2 emission, and oxidative stress in obese animals, thereby resembling levels seen in lean animals. Together, our data suggest that LA and ALA are efficacious in preventing IR but have divergent impacts on skeletal muscle mitochondrial content and function. Moreover, we propose that LA has value in preserving insulin sensitivity in the development of obesity, thereby challenging the classical view that n-6 PUFAs are detrimental.
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Affiliation(s)
- Sarthak Matravadia
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Eric A F Herbst
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Swati S Jain
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - David M Mutch
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Graham P Holloway
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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