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Masson SWC, Madsen S, Cooke KC, Potter M, Vegas AD, Carroll L, Thillainadesan S, Cutler HB, Walder KR, Cooney GJ, Morahan G, Stöckli J, James DE. Leveraging genetic diversity to identify small molecules that reverse mouse skeletal muscle insulin resistance. eLife 2023; 12:RP86961. [PMID: 37494090 PMCID: PMC10371229 DOI: 10.7554/elife.86961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023] Open
Abstract
Systems genetics has begun to tackle the complexity of insulin resistance by capitalising on computational advances to study high-diversity populations. 'Diversity Outbred in Australia (DOz)' is a population of genetically unique mice with profound metabolic heterogeneity. We leveraged this variance to explore skeletal muscle's contribution to whole-body insulin action through metabolic phenotyping and skeletal muscle proteomics of 215 DOz mice. Linear modelling identified 553 proteins that associated with whole-body insulin sensitivity (Matsuda Index) including regulators of endocytosis and muscle proteostasis. To enrich for causality, we refined this network by focusing on negatively associated, genetically regulated proteins, resulting in a 76-protein fingerprint of insulin resistance. We sought to perturb this network and restore insulin action with small molecules by integrating the Broad Institute Connectivity Map platform and in vitro assays of insulin action using the Prestwick chemical library. These complementary approaches identified the antibiotic thiostrepton as an insulin resistance reversal agent. Subsequent validation in ex vivo insulin-resistant mouse muscle and palmitate-induced insulin-resistant myotubes demonstrated potent insulin action restoration, potentially via upregulation of glycolysis. This work demonstrates the value of a drug-centric framework to validate systems-level analysis by identifying potential therapeutics for insulin resistance.
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Affiliation(s)
- Stewart W C Masson
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Søren Madsen
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Kristen C Cooke
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Meg Potter
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Alexis Diaz Vegas
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Luke Carroll
- Australian Proteome Analysis Facility, Macquarie University, Macquarie Park, Australia
| | - Senthil Thillainadesan
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Harry B Cutler
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Ken R Walder
- School of Medicine, Deakin University, Geelong, Australia
| | - Gregory J Cooney
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Grant Morahan
- Centre for Diabetes Research, Harry Perkins Institute of Medical Research, Murdoch, Australia
| | - Jacqueline Stöckli
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - David E James
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
- School of Medical Sciences University of Sydney, Sydney, Australia
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2
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Daily JW, Park S. Sarcopenia Is a Cause and Consequence of Metabolic Dysregulation in Aging Humans: Effects of Gut Dysbiosis, Glucose Dysregulation, Diet and Lifestyle. Cells 2022; 11:cells11030338. [PMID: 35159148 PMCID: PMC8834403 DOI: 10.3390/cells11030338] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/17/2022] [Accepted: 01/17/2022] [Indexed: 02/04/2023] Open
Abstract
Skeletal muscle mass plays a critical role in a healthy lifespan by helping to regulate glucose homeostasis. As seen in sarcopenia, decreased skeletal muscle mass impairs glucose homeostasis, but it may also be caused by glucose dysregulation. Gut microbiota modulates lipopolysaccharide (LPS) production, short-chain fatty acids (SCFA), and various metabolites that affect the host metabolism, including skeletal muscle tissues, and may have a role in the sarcopenia etiology. Here, we aimed to review the relationship between skeletal muscle mass, glucose homeostasis, and gut microbiota, and the effect of consuming probiotics and prebiotics on the development and pathological consequences of sarcopenia in the aging human population. This review includes discussions about the effects of glucose metabolism and gut microbiota on skeletal muscle mass and sarcopenia and the interaction of dietary intake, physical activity, and gut microbiome to influence sarcopenia through modulating the gut–muscle axis. Emerging evidence suggests that the microbiome can regulate both skeletal muscle mass and function, in part through modulating the metabolisms of short-chain fatty acids and branch-chain amino acids that might act directly on muscle in humans or indirectly through the brain and liver. Dietary factors such as fats, proteins, and indigestible carbohydrates and lifestyle interventions such as exercise, smoking, and alcohol intake can both help and hinder the putative gut–muscle axis. The evidence presented in this review suggests that loss of muscle mass and function are not an inevitable consequence of the aging process, and that dietary and lifestyle interventions may prevent or delay sarcopenia.
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Affiliation(s)
- James W. Daily
- Department of R & D, Daily Manufacturing Inc., Rockwell, 28138 NC, USA;
| | - Sunmin Park
- Department of Food & Nutrition, Obesity/Diabetes Center, Hoseo University, Asan 31499, Korea
- Correspondence: ; Tel.: +82-41-540-5345; Fax: +82-41-548-0670
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3
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Šimják P, Anderlová K, Cinkajzlová A, Pařízek A, Kršek M, Haluzík M. The possible role of endocrine dysfunction of adipose tissue in gestational diabetes mellitus. MINERVA ENDOCRINOL 2021; 45:228-242. [PMID: 33000620 DOI: 10.23736/s0391-1977.20.03192-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Gestational diabetes mellitus (GDM) is diabetes that is first diagnosed in the second or third trimester of pregnancy in patients who did not have a history of diabetes before pregnancy. Consequences of GDM include increased risk of macrosomia and birth complications in the infant and an increased risk of maternal type 2 diabetes mellitus (T2DM) after pregnancy. There is also a longer-term risk of obesity, T2DM, and cardiovascular diseases in the child. GDM is the result of impaired glucose tolerance due to pancreatic β-cell dysfunction on a background of insulin resistance that physiologically increases during pregnancy. The strongest clinical predictors of GDM are overweight and obesity. The fact that women with GDM are more likely to be overweight or obese suggests that adipose tissue dysfunction may be involved in the pathogenesis of GDM, similarly to T2DM. Adipose tissue is not only involved in energy storage but also functions as an active endocrine organ secreting adipokines (specific hormones and cytokines) with the ability to alter insulin sensitivity. Recent evidence points to a crucial role of numerous adipokines produced by fat in the development of GDM. The following text summarizes the current knowledge about a possible role of selected adipokines in the development of GDM.
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Affiliation(s)
- Patrik Šimják
- Department of Gynecology and Obstetrics, First Faculty of Medicine, Charles University and General University Hospital, Prague, Czech Republic
| | - Kateřina Anderlová
- Department of Gynecology and Obstetrics, First Faculty of Medicine, Charles University and General University Hospital, Prague, Czech Republic.,Third Department of Medicine, First Faculty of Medicine, Charles University and General University Hospital, Prague, Czech Republic
| | - Anna Cinkajzlová
- Center for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
| | - Antonín Pařízek
- Department of Gynecology and Obstetrics, First Faculty of Medicine, Charles University and General University Hospital, Prague, Czech Republic
| | - Michal Kršek
- Third Department of Medicine, First Faculty of Medicine, Charles University and General University Hospital, Prague, Czech Republic
| | - Martin Haluzík
- Diabetes Center, Institute for Clinical and Experimental Medicine, Prague, Czech Republic -
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N-acetyltaurine and Acetylcarnitine Production for the Mitochondrial Acetyl-CoA Regulation in Skeletal Muscles during Endurance Exercises. Metabolites 2021; 11:metabo11080522. [PMID: 34436463 PMCID: PMC8401229 DOI: 10.3390/metabo11080522] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 08/02/2021] [Accepted: 08/02/2021] [Indexed: 11/19/2022] Open
Abstract
During endurance exercises, a large amount of mitochondrial acetyl-CoA is produced in skeletal muscles from lipids, and the excess acetyl-CoA suppresses the metabolic flux from glycolysis to the TCA cycle. This study evaluated the hypothesis that taurine and carnitine act as a buffer of the acetyl moiety of mitochondrial acetyl-CoA derived from the short- and long-chain fatty acids of skeletal muscles during endurance exercises. In human subjects, the serum concentrations of acetylated forms of taurine (NAT) and carnitine (ACT), which are the metabolites of acetyl-CoA buffering, significantly increased after a full marathon. In the culture medium of primary human skeletal muscle cells, NAT and ACT concentrations significantly increased when they were cultured with taurine and acetate or with carnitine and palmitic acid, respectively. The increase in the mitochondrial acetyl-CoA/free CoA ratio induced by acetate and palmitic acid was suppressed by taurine and carnitine, respectively. Elevations of NAT and ACT in the blood of humans during endurance exercises might serve the buffering of the acetyl-moiety in mitochondria by taurine and carnitine, respectively. The results suggest that blood levels of NAT and ACT indicate energy production status from fatty acids in the skeletal muscles of humans undergoing endurance exercise.
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Labeit S, Hirner S, Bogomolovas J, Cruz A, Myrzabekova M, Moriscot A, Bowen TS, Adams V. Regulation of Glucose Metabolism by MuRF1 and Treatment of Myopathy in Diabetic Mice with Small Molecules Targeting MuRF1. Int J Mol Sci 2021; 22:2225. [PMID: 33672385 PMCID: PMC7926706 DOI: 10.3390/ijms22042225] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 02/13/2021] [Accepted: 02/15/2021] [Indexed: 01/07/2023] Open
Abstract
The muscle-specific ubiquitin ligase MuRF1 regulates muscle catabolism during chronic wasting states, although its roles in general metabolism are less-studied. Here, we metabolically profiled MuRF1-deficient knockout mice. We also included knockout mice for MuRF2 as its closely related gene homolog. MuRF1 and MuRF2-KO (knockout) mice have elevated serum glucose, elevated triglycerides, and reduced glucose tolerance. In addition, MuRF2-KO mice have a reduced tolerance to a fat-rich diet. Western blot and enzymatic studies on MuRF1-KO skeletal muscle showed perturbed FoxO-Akt signaling, elevated Akt-Ser-473 activation, and downregulated oxidative mitochondrial metabolism, indicating potential mechanisms for MuRF1,2-dependent glucose and fat metabolism regulation. Consistent with this, the adenoviral re-expression of MuRF1 in KO mice normalized Akt-Ser-473, serum glucose, and triglycerides. Finally, we tested the MuRF1/2 inhibitors MyoMed-205 and MyoMed-946 in a mouse model for type 2 diabetes mellitus (T2DM). After 28 days of treatment, T2DM mice developed progressive muscle weakness detected by wire hang tests, but this was attenuated by the MyoMed-205 treatment. While MyoMed-205 and MyoMed-946 had no significant effects on serum glucose, they did normalize the lymphocyte-granulocyte counts in diabetic sera as indicators of the immune response. Thus, small molecules directed to MuRF1 may be useful in attenuating skeletal muscle strength loss in T2DM conditions.
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Affiliation(s)
- Siegfried Labeit
- Department of Anesthesiology, Medical Faculty Mannheim, University of Heidelberg, 68169 Mannheim, Germany;
- Myomedix GmbH, 69151 Neckargemünd, Germany
| | - Stephanie Hirner
- Department of Anesthesiology, Medical Faculty Mannheim, University of Heidelberg, 68169 Mannheim, Germany;
| | | | - André Cruz
- Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo, 05508-000 Sao Paulo, Brazil; (A.C.); (A.M.)
| | - Moldir Myrzabekova
- Scientific Research Institute of Biology and Biotechnology Problems, al-Farabi Kasakh National University, Almaty 050040, Kazakhstan;
| | - Anselmo Moriscot
- Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo, 05508-000 Sao Paulo, Brazil; (A.C.); (A.M.)
| | | | - Volker Adams
- Laboratory of Molecular and Experimental Cardiology, TU Dresden, Heart Center Dresden, 01307 Dresden, Germany;
- Dresden Cardiovascular Research Institute and Core Laboratories GmbH, 01307 Dresden, Germany
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6
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Bergman BC, Goodpaster BH. Exercise and Muscle Lipid Content, Composition, and Localization: Influence on Muscle Insulin Sensitivity. Diabetes 2020; 69:848-858. [PMID: 32312901 DOI: 10.2337/dbi18-0042] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 02/17/2020] [Indexed: 11/13/2022]
Abstract
Accumulation of lipid in skeletal muscle is thought to be related to the development of insulin resistance and type 2 diabetes. Initial work in this area focused on accumulation of intramuscular triglyceride; however, bioactive lipids such as diacylglycerols and sphingolipids are now thought to play an important role. Specific species of these lipids appear to be more negative toward insulin sensitivity than others. Adding another layer of complexity, localization of lipids within the cell appears to influence the relationship between these lipids and insulin sensitivity. This article summarizes how accumulation of total lipids, specific lipid species, and localization of lipids influence insulin sensitivity in humans. We then focus on how these aspects of muscle lipids are impacted by acute and chronic aerobic and resistance exercise training. By understanding how exercise alters specific species and localization of lipids, it may be possible to uncover specific lipids that most heavily impact insulin sensitivity.
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7
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Unacylated ghrelin stimulates fatty acid oxidation to protect skeletal muscle against palmitate-induced impairment of insulin action in lean but not high-fat fed rats. Metabol Open 2020; 5:100026. [PMID: 32812929 PMCID: PMC7424793 DOI: 10.1016/j.metop.2020.100026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 01/28/2020] [Accepted: 01/29/2020] [Indexed: 11/29/2022] Open
Abstract
Background Ghrelin is a gut hormone that spikes in circulation before mealtime. Recent findings suggest that both ghrelin isoforms stimulate skeletal muscle fatty acid oxidation, lending to the possibility that it may regulate skeletal muscle’s handling of meal-derived substrates. It was hypothesized in the current study that ghrelin may preserve muscle insulin response during conditions of elevated saturated fatty acid (palmitate) availability by promoting its oxidation. Methods and results Soleus muscle strips were isolated from male rats to determine the direct effects of ghrelin isoforms on fatty acid oxidation, glucose uptake and insulin signaling. We demonstrate that unacylated ghrelin (UnAG) is the more potent stimulator of skeletal muscle fatty acid oxidation. Both isoforms of ghrelin generally protected muscle from impaired insulin-mediated phosphorylation of AKT Ser473 and Thr308, as well as downstream phosphorylation of AS160 Ser588 during high palmitate exposure. However, only UnAG was able to preserve insulin-stimulated glucose uptake during exposure to high palmitate concentrations. The use of etomoxir, an irreversible inhibitor of carnitine palmitoyltransferase (CPT-1) abolished this protection, strongly suggesting that UnAG’s stimulation of fatty acid oxidation may be essential to this protection. To our knowledge, we are also the first to investigate the impact of a chronic high-fat diet on ghrelin’s actions in muscle. Following 6 wks of a high-fat diet, UnAG was unable to preserve insulin-stimulated signaling or glucose transport during an acute high palmitate exposure. UnAG was also unable to further stimulate 5′ AMP-activated protein kinase (AMPK) or fatty acid oxidation during high palmitate exposure. Corticotropin-releasing hormone receptor-2 (CRF-2R) content was significantly decreased in muscle from high-fat fed animals, which may partially account for the loss of UnAG’s effects. Conclusions UnAG is able to protect muscle from acute lipid exposure, likely due to its ability to stimulation fatty acid oxidation. This effect is lost in high-fat fed animals, implying a resistance to ghrelin at the level of the muscle. The underlying mechanisms accounting for ghrelin resistance in high fat-fed animals remain to be discovered. Saturated lipids acutely impair muscle insulin signaling and glucose transport. Ghrelin isoforms consistently protect insulin signaling from lipid detriment. Unacylated ghrelin more potently stimulates fat oxidation, preserving glucose transport. Muscle of chronic high fat-fed rats may be resistant to ghrelin’s metabolic effects.
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Krycer JR, Elkington SD, Diaz-Vegas A, Cooke KC, Burchfield JG, Fisher-Wellman KH, Cooney GJ, Fazakerley DJ, James DE. Mitochondrial oxidants, but not respiration, are sensitive to glucose in adipocytes. J Biol Chem 2020; 295:99-110. [PMID: 31744882 PMCID: PMC6952605 DOI: 10.1074/jbc.ra119.011695] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Indexed: 11/06/2022] Open
Abstract
Insulin action in adipose tissue is crucial for whole-body glucose homeostasis, with insulin resistance being a major risk factor for metabolic diseases such as type 2 diabetes. Recent studies have proposed mitochondrial oxidants as a unifying driver of adipose insulin resistance, serving as a signal of nutrient excess. However, neither the substrates for nor sites of oxidant production are known. Because insulin stimulates glucose utilization, we hypothesized that glucose oxidation would fuel respiration, in turn generating mitochondrial oxidants. This would impair insulin action, limiting further glucose uptake in a negative feedback loop of "glucose-dependent" insulin resistance. Using primary rat adipocytes and cultured 3T3-L1 adipocytes, we observed that insulin increased respiration, but notably this occurred independently of glucose supply. In contrast, glucose was required for insulin to increase mitochondrial oxidants. Despite rising to similar levels as when treated with other agents that cause insulin resistance, glucose-dependent mitochondrial oxidants failed to cause insulin resistance. Subsequent studies revealed a temporal relationship whereby mitochondrial oxidants needed to increase before the insulin stimulus to induce insulin resistance. Together, these data reveal that (a) adipocyte respiration is principally fueled from nonglucose sources; (b) there is a disconnect between respiration and oxidative stress, whereby mitochondrial oxidant levels do not rise with increased respiration unless glucose is present; and (c) mitochondrial oxidative stress must precede the insulin stimulus to cause insulin resistance, explaining why short-term, insulin-dependent glucose utilization does not promote insulin resistance. These data provide additional clues to mechanistically link nutrient excess to adipose insulin resistance.
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Affiliation(s)
- James R Krycer
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Sarah D Elkington
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Alexis Diaz-Vegas
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Kristen C Cooke
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - James G Burchfield
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Kelsey H Fisher-Wellman
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27834
| | - Gregory J Cooney
- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Daniel J Fazakerley
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia; Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, United Kingdom.
| | - David E James
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales 2006, Australia.
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Phielix E, Begovatz P, Gancheva S, Bierwagen A, Kornips E, Schaart G, Hesselink MKC, Schrauwen P, Roden M. Athletes feature greater rates of muscle glucose transport and glycogen synthesis during lipid infusion. JCI Insight 2019; 4:127928. [PMID: 31672941 DOI: 10.1172/jci.insight.127928] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 10/02/2019] [Indexed: 01/13/2023] Open
Abstract
BACKGROUNDInsulin resistance results from impaired skeletal muscle glucose transport/phosphorylation, linked to augmented lipid availability. Despite greater intramuscular lipids, athletes are highly insulin sensitive, which could result from higher rates of insulin-stimulated glycogen synthesis or glucose transport/phosphorylation and oxidation. Thus, we examined the time course of muscle glycogen and glucose-6-phosphate concentrations during low and high systemic lipid availability.METHODSEight endurance-trained and 9 sedentary humans (VO2 peak: 56 ± 2 vs. 33 ± 2 mL/kg/min, P < 0.05) underwent 6-hour hyperinsulinemic-isoglycemic clamp tests with infusions of triglycerides or saline in a randomized crossover design. Glycogen and glucose-6-phosphate concentrations were monitored in vastus lateralis muscles using 13C/31P magnetic resonance spectroscopy.RESULTSAthletes displayed a 25% greater (P < 0.05) insulin-stimulated glucose disposal rate (Rd) than sedentary participants. During Intralipid infusion, insulin sensitivity remained higher in the athletes (ΔRd: 25 ± 3 vs. 17 ± 3 μmol/kg/min, P < 0.05), supported by higher glucose transporter type 4 protein expression than in sedentary humans. Compared to saline infusion, AUC of glucose-6-phosphate remained unchanged during Intralipid infusion in athletes (1.6 ± 0.2 mmol/L vs. 1.4 ± 0.2 [mmol/L] × h, P = n.s.) but tended to decrease by 36% in sedentary humans (1.7 ± 0.4 vs. 1.1 ± 0.1 [mmol/L] × h, P < 0.059). This drop was accompanied by a 72% higher rate of net glycogen synthesis in the athletes upon Intralipid infusion (47 ± 9 vs. 13 ± 3 μmol/kg/min, P < 0.05).CONCLUSIONAthletes feature higher skeletal muscle glucose disposal and glycogen synthesis during increased lipid availability, which primarily results from maintained insulin-stimulated glucose transport with increased myocellular glucose-6-phosphate levels for subsequent glycogen synthesis.TRIAL REGISTRATIONClinicalTrials.gov NCT01229059.FUNDINGGerman Federal Ministry of Health (BMG).
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Affiliation(s)
- Esther Phielix
- Institute for Clinical Diabetology, German Diabetes Center, Düsseldorf, Germany.,German Center for Diabetes Research, München-Neuherberg, Germany.,Department of Nutrition and Movement Sciences, School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, Netherlands
| | - Paul Begovatz
- Institute for Clinical Diabetology, German Diabetes Center, Düsseldorf, Germany.,German Center for Diabetes Research, München-Neuherberg, Germany
| | - Sofiya Gancheva
- Institute for Clinical Diabetology, German Diabetes Center, Düsseldorf, Germany.,German Center for Diabetes Research, München-Neuherberg, Germany.,Division of Endocrinology and Diabetology, Medical Faculty, Heinrich-Heine University, Düsseldorf, Germany
| | - Alessandra Bierwagen
- Institute for Clinical Diabetology, German Diabetes Center, Düsseldorf, Germany.,German Center for Diabetes Research, München-Neuherberg, Germany
| | - Esther Kornips
- Department of Nutrition and Movement Sciences, School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, Netherlands
| | - Gert Schaart
- Department of Nutrition and Movement Sciences, School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, Netherlands
| | - Matthijs K C Hesselink
- Department of Nutrition and Movement Sciences, School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, Netherlands
| | - Patrick Schrauwen
- Department of Nutrition and Movement Sciences, School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, Netherlands
| | - Michael Roden
- Institute for Clinical Diabetology, German Diabetes Center, Düsseldorf, Germany.,German Center for Diabetes Research, München-Neuherberg, Germany.,Division of Endocrinology and Diabetology, Medical Faculty, Heinrich-Heine University, Düsseldorf, Germany
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Small L, Brandon AE, Parker BL, Deshpande V, Samsudeen AF, Kowalski GM, Reznick J, Wilks DL, Preston E, Bruce CR, James DE, Turner N, Cooney GJ. Reduced insulin action in muscle of high fat diet rats over the diurnal cycle is not associated with defective insulin signaling. Mol Metab 2019; 25:107-118. [PMID: 31029696 PMCID: PMC6600078 DOI: 10.1016/j.molmet.2019.04.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/04/2019] [Accepted: 04/08/2019] [Indexed: 12/02/2022] Open
Abstract
Objective Energy metabolism and insulin action follow a diurnal rhythm. It is therefore important that investigations into dysregulation of these pathways are relevant to the physiology of this diurnal rhythm. Methods We examined glucose uptake, markers of insulin action, and the phosphorylation of insulin signaling intermediates in muscle of chow and high fat, high sucrose (HFHS) diet-fed rats over the normal diurnal cycle. Results HFHS animals displayed hyperinsulinemia but had reduced systemic glucose disposal and lower muscle glucose uptake during the feeding period. Analysis of gene expression, enzyme activity, protein abundance and phosphorylation revealed a clear diurnal regulation of substrate oxidation pathways with no difference in Akt signaling in muscle. Transfection of a constitutively active Akt2 into the muscle of HFHS rats did not rescue diet-induced reductions in insulin-stimulated glucose uptake. Conclusions These studies suggest that reduced glucose uptake in muscle during the diurnal cycle induced by short-term HFHS-feeding is not the result of reduced insulin signaling. Investigating metabolism in rodents over the diurnal cycle more accurately models normal animal physiology. Diurnal regulation of substrate oxidation is altered in muscle of HFHS-fed rats. There is a disconnect between glucose uptake and canonical insulin signaling in muscle. Activation of Akt2 does not rescue diet-induced reductions in insulin-stimulated glucose uptake in muscle.
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Affiliation(s)
- Lewin Small
- Diabetes and Metabolism Division, The Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Amanda E Brandon
- Diabetes and Metabolism Division, The Garvan Institute of Medical Research, Sydney, NSW, Australia; The University of Sydney, School of Medical Science, Charles Perkins Centre D17, Sydney, NSW, Australia
| | - Benjamin L Parker
- The University of Sydney, School of Life and Environmental Science, Charles Perkins Centre D17, Sydney, NSW, Australia
| | - Vinita Deshpande
- The University of Sydney, School of Life and Environmental Science, Charles Perkins Centre D17, Sydney, NSW, Australia
| | - Azrah F Samsudeen
- Department of Pharmacology, School of Medical Science, University of New South Wales, Sydney, NSW, Australia
| | - Greg M Kowalski
- Deakin University, School of Exercise and Nutrition Sciences, Faculty of Health, Institute for Physical Activity and Nutrition, Geelong, Australia
| | - Jane Reznick
- Diabetes and Metabolism Division, The Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Donna L Wilks
- Diabetes and Metabolism Division, The Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Elaine Preston
- Diabetes and Metabolism Division, The Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Clinton R Bruce
- Deakin University, School of Exercise and Nutrition Sciences, Faculty of Health, Institute for Physical Activity and Nutrition, Geelong, Australia
| | - David E James
- The University of Sydney, School of Life and Environmental Science, Charles Perkins Centre D17, Sydney, NSW, Australia
| | - Nigel Turner
- Department of Pharmacology, School of Medical Science, University of New South Wales, Sydney, NSW, Australia
| | - Gregory J Cooney
- Diabetes and Metabolism Division, The Garvan Institute of Medical Research, Sydney, NSW, Australia; The University of Sydney, School of Medical Science, Charles Perkins Centre D17, Sydney, NSW, Australia.
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Fritzen AM, Lundsgaard A, Jeppesen JF, Sjøberg KA, Høeg LD, Deleuran HH, Wojtaszewski JFP, Richter EA, Kiens B. Fatty acid type–specific regulation of SIRT1 does not affect insulin sensitivity in human skeletal muscle. FASEB J 2019; 33:5510-5519. [DOI: 10.1096/fj.201801950r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Andreas Mæchel Fritzen
- Section of Molecular PhysiologyDepartment of Nutrition, Exercise, and Sports, Faculty of ScienceUniversity of Copenhagen Copenhagen Denmark
| | - Anne‐Marie Lundsgaard
- Section of Molecular PhysiologyDepartment of Nutrition, Exercise, and Sports, Faculty of ScienceUniversity of Copenhagen Copenhagen Denmark
| | - Jacob Fuglsbjerg Jeppesen
- Section of Molecular PhysiologyDepartment of Nutrition, Exercise, and Sports, Faculty of ScienceUniversity of Copenhagen Copenhagen Denmark
| | - Kim Anker Sjøberg
- Section of Molecular PhysiologyDepartment of Nutrition, Exercise, and Sports, Faculty of ScienceUniversity of Copenhagen Copenhagen Denmark
| | - Louise Dalgas Høeg
- Section of Molecular PhysiologyDepartment of Nutrition, Exercise, and Sports, Faculty of ScienceUniversity of Copenhagen Copenhagen Denmark
| | - Henrik Hall Deleuran
- Section of Molecular PhysiologyDepartment of Nutrition, Exercise, and Sports, Faculty of ScienceUniversity of Copenhagen Copenhagen Denmark
| | - Jørgen F. P. Wojtaszewski
- Section of Molecular PhysiologyDepartment of Nutrition, Exercise, and Sports, Faculty of ScienceUniversity of Copenhagen Copenhagen Denmark
| | - Erik A. Richter
- Section of Molecular PhysiologyDepartment of Nutrition, Exercise, and Sports, Faculty of ScienceUniversity of Copenhagen Copenhagen Denmark
| | - Bente Kiens
- Section of Molecular PhysiologyDepartment of Nutrition, Exercise, and Sports, Faculty of ScienceUniversity of Copenhagen Copenhagen Denmark
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12
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Yaribeygi H, Atkin SL, Simental‐Mendía LE, Sahebkar A. Molecular mechanisms by which aerobic exercise induces insulin sensitivity. J Cell Physiol 2019; 234:12385-12392. [DOI: 10.1002/jcp.28066] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 12/18/2018] [Indexed: 12/14/2022]
Affiliation(s)
- Habib Yaribeygi
- Chronic Kidney Disease Research Center, Shahid Beheshti University of Medical Sciences Tehran Iran
| | | | | | - Amirhossein Sahebkar
- Neurogenic Inflammation Research Center, Mashhad University of Medical Sciences Mashhad Iran
- Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences Mashhad Iran
- School of Pharmacy, Mashhad University of Medical Sciences Mashhad Iran
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13
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Small L, Gong H, Yassmin C, Cooney GJ, Brandon AE. Thermoneutral housing does not influence fat mass or glucose homeostasis in C57BL/6 mice. J Endocrinol 2018; 239:313-324. [PMID: 30400016 DOI: 10.1530/joe-18-0279] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 09/05/2018] [Indexed: 12/15/2022]
Abstract
One major factor affecting physiology often overlooked when comparing data from animal models and humans is the effect of ambient temperature. The majority of rodent housing is maintained at ~22°C, the thermoneutral temperature for lightly clothed humans. However, mice have a much higher thermoneutral temperature of ~30°C, consequently data collected at 22°C in mice could be influenced by animals being exposed to a chronic cold stress. The aim of this study was to investigate the effect of housing temperature on glucose homeostasis and energy metabolism of mice fed normal chow or a high-fat, obesogenic diet (HFD). Male C57BL/6J(Arc) mice were housed at standard temperature (22°C) or at thermoneutrality (29°C) and fed either chow or a 60% HFD for 13 weeks. The HFD increased fat mass and produced glucose intolerance as expected but this was not exacerbated in mice housed at thermoneutrality. Changing the ambient temperature, however, did alter energy expenditure, food intake, lipid content and glucose metabolism in skeletal muscle, liver and brown adipose tissue. Collectively, these findings demonstrate that mice regulate energy balance at different housing temperatures to maintain whole-body glucose tolerance and adiposity irrespective of the diet. Despite this, metabolic differences in individual tissues were apparent. In conclusion, dietary intervention in mice has a greater impact on adiposity and glucose metabolism than housing temperature although temperature is still a significant factor in regulating metabolic parameters in individual tissues.
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Affiliation(s)
- Lewin Small
- Diabetes and Metabolism Division, Garvan Institute, Sydney, New South Wales, Australia
| | - Henry Gong
- The University of Sydney, School of Medical Sciences, Charles Perkins Centre, Sydney, New South Wales, Australia
| | - Christian Yassmin
- The University of Sydney, School of Medical Sciences, Charles Perkins Centre, Sydney, New South Wales, Australia
| | - Gregory J Cooney
- Diabetes and Metabolism Division, Garvan Institute, Sydney, New South Wales, Australia
- The University of Sydney, School of Medical Sciences, Charles Perkins Centre, Sydney, New South Wales, Australia
| | - Amanda E Brandon
- Diabetes and Metabolism Division, Garvan Institute, Sydney, New South Wales, Australia
- The University of Sydney, School of Medical Sciences, Charles Perkins Centre, Sydney, New South Wales, Australia
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14
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Plows JF, Stanley JL, Baker PN, Reynolds CM, Vickers MH. The Pathophysiology of Gestational Diabetes Mellitus. Int J Mol Sci 2018; 19:E3342. [PMID: 30373146 PMCID: PMC6274679 DOI: 10.3390/ijms19113342] [Citation(s) in RCA: 763] [Impact Index Per Article: 127.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 10/15/2018] [Accepted: 10/21/2018] [Indexed: 12/11/2022] Open
Abstract
Gestational diabetes mellitus (GDM) is a serious pregnancy complication, in which women without previously diagnosed diabetes develop chronic hyperglycemia during gestation. In most cases, this hyperglycemia is the result of impaired glucose tolerance due to pancreatic β-cell dysfunction on a background of chronic insulin resistance. Risk factors for GDM include overweight and obesity, advanced maternal age, and a family history or any form of diabetes. Consequences of GDM include increased risk of maternal cardiovascular disease and type 2 diabetes and macrosomia and birth complications in the infant. There is also a longer-term risk of obesity, type 2 diabetes, and cardiovascular disease in the child. GDM affects approximately 16.5% of pregnancies worldwide, and this number is set to increase with the escalating obesity epidemic. While several management strategies exist-including insulin and lifestyle interventions-there is not yet a cure or an efficacious prevention strategy. One reason for this is that the molecular mechanisms underlying GDM are poorly defined. This review discusses what is known about the pathophysiology of GDM, and where there are gaps in the literature that warrant further exploration.
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Affiliation(s)
- Jasmine F Plows
- Department of Preventive Medicine, University of Southern California, Los Angeles, CA 90033, USA.
| | - Joanna L Stanley
- Liggins Institute, University of Auckland, Auckland 1023, New Zealand.
| | - Philip N Baker
- University of Leicester, University Road, Leicester LE1 7RH, UK.
| | - Clare M Reynolds
- Liggins Institute, University of Auckland, Auckland 1023, New Zealand.
| | - Mark H Vickers
- Liggins Institute, University of Auckland, Auckland 1023, New Zealand.
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15
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Miyazaki T, Nakamura Y, Ebina K, Mizushima T, Ra SG, Ishikura K, Matsuzaki Y, Ohmori H, Honda A. Increased N-Acetyltaurine in the Skeletal Muscle After Endurance Exercise in Rat. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 975 Pt 1:403-411. [PMID: 28849471 DOI: 10.1007/978-94-024-1079-2_33] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Taurine is metabolized to a novel metabolite, N-acetyltaurine (NAT), through N-acetylation with acetate. Furthermore, NAT production increases when the endogenous production of acetate is elevated in some situations, such as alcohol catabolism and endurance exercise. We have previously reported that both the serum concentration and urinary excretion of NAT from humans were increased after endurance exercise, and that NAT was secreted by cultured skeletal muscle cells exposed to both acetate and taurine. The present study evaluated the hypothesis that NAT is synthesized in the skeletal muscle after endurance exercise. Normal rats were loaded to a transient treadmill running until exhaustion. Serum, skeletal muscle, and liver were collected immediately after the exercise. The NAT concentration in the plasma and in the soleus muscle from the exercised rats was significantly increased compared to that in the samples from the sedentary control rats. There was a significant positive correlation in the NAT concentration between the plasma and soleus muscle. The NAT concentration in the liver was unchanged after the endurance exercise. These results confirm that the significantly increased NAT in both the serum and urine after endurance exercise is derived from NAT synthesis in the skeletal muscle.
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Affiliation(s)
- Teruo Miyazaki
- Tokyo Medical University Ibaraki Medical Center, Ibaraki, Japan.
| | | | | | | | | | | | | | | | - Akira Honda
- Tokyo Medical University Ibaraki Medical Center, Ibaraki, Japan
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16
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Metcalfe LK, Smith GC, Turner N. Defining lipid mediators of insulin resistance - controversies and challenges. J Mol Endocrinol 2018; 62:JME-18-0023. [PMID: 30068522 DOI: 10.1530/jme-18-0023] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 07/04/2018] [Accepted: 07/31/2018] [Indexed: 12/31/2022]
Abstract
Essential elements of all cells, lipids play important roles in energy production, signalling and as structural components. Despite these critical functions, excessive availability and intracellular accumulation of lipid is now recognised as a major factor contributing to many human diseases, including obesity and diabetes. In the context of these metabolic disorders, ectopic deposition of lipid has been proposed to have deleterious effects of insulin action. While this relationship has been recognised for some time now, there is currently no unifying mechanism to explain how lipids precipitate the development of insulin resistance. This review summarises the evidence linking specific lipid molecules to the induction of insulin resistance, describing some of the current controversies and challenges for future studies in this field.
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Affiliation(s)
- Louise K Metcalfe
- L Metcalfe, Department of Pharmacology, School of Medical Sciences, UNSW Australia, Kensington, Australia
| | - Greg C Smith
- G Smith, Department of Pharmacology, School of Medical Sciences, UNSW Australia, Kensington, Australia
| | - Nigel Turner
- N Turner, Department of Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, Australia
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17
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Fazakerley DJ, Krycer JR, Kearney AL, Hocking SL, James DE. Muscle and adipose tissue insulin resistance: malady without mechanism? J Lipid Res 2018; 60:1720-1732. [PMID: 30054342 DOI: 10.1194/jlr.r087510] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 07/25/2018] [Indexed: 12/14/2022] Open
Abstract
Insulin resistance is a major risk factor for numerous diseases, including type 2 diabetes and cardiovascular disease. These disorders have dramatically increased in incidence with modern life, suggesting that excess nutrients and obesity are major causes of "common" insulin resistance. Despite considerable effort, the mechanisms that contribute to common insulin resistance are not resolved. There is universal agreement that extracellular perturbations, such as nutrient excess, hyperinsulinemia, glucocorticoids, or inflammation, trigger intracellular stress in key metabolic target tissues, such as muscle and adipose tissue, and this impairs the ability of insulin to initiate its normal metabolic actions in these cells. Here, we present evidence that the impairment in insulin action is independent of proximal elements of the insulin signaling pathway and is likely specific to the glucoregulatory branch of insulin signaling. We propose that many intracellular stress pathways act in concert to increase mitochondrial reactive oxygen species to trigger insulin resistance. We speculate that this may be a physiological pathway to conserve glucose during specific states, such as fasting, and that, in the presence of chronic nutrient excess, this pathway ultimately leads to disease. This review highlights key points in this pathway that require further research effort.
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Affiliation(s)
- Daniel J Fazakerley
- School of Life and Environmental Sciences, Central Clinical School, University of Sydney, Camperdown, New South Wales, Australia
| | - James R Krycer
- School of Life and Environmental Sciences, Central Clinical School, University of Sydney, Camperdown, New South Wales, Australia
| | - Alison L Kearney
- School of Life and Environmental Sciences, Central Clinical School, University of Sydney, Camperdown, New South Wales, Australia
| | - Samantha L Hocking
- Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales, Australia
| | - David E James
- School of Life and Environmental Sciences, Central Clinical School, University of Sydney, Camperdown, New South Wales, Australia .,Faculty of Medicine and Health, Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
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18
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The effects of canola and olive oils on insulin resistance, inflammation and oxidative stress in women with type 2 diabetes: a randomized and controlled trial. J Diabetes Metab Disord 2018; 17:85-91. [PMID: 30918840 DOI: 10.1007/s40200-018-0343-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 10/16/2017] [Indexed: 01/21/2023]
Abstract
Background A number of studies have shown that consumption of vegetable oils may improve diabetes complications including inflammatory response and oxidative stress, but no study has been done on the effects of canola oil (CO) and olive oil (OO) consumption in patients with type 2 diabetes. This clinical trial was done to compare the effects of CO and OO on insulin resistance, inflammation and oxidative stress in women with type 2 diabetes. Methods This randomized controlled clinical trial was done on 77 type 2 diabetic women. 4 weeks before the intervention, lipid-lowering drugs intakes were cut under the supervision of an endocrinologist. The participants were randomly divided into 2 intervention groups (Balanced diet +30 g/day CO or OO) and one control group (Balanced diet +30 g/day of sunflower oil (SFO)). Dietary intakes were assessed using three 24-h food records at baseline and at weeks 4 and 8 of the interventions. At baseline and after 8 weeks, height, weight, waist circumference, fasting blood sugar (FBS), serum insulin, C-reactive protein (CRP) and malondialdehyde (MDA) were measured. Results After the intervention in the inter-group analysis, CRP level was reduced significantly in CO and OO groups but no significant changes were observed in other factors. CRP reductions were also significant between all of the groups but not for other factors. Conclusions Replacing CO and OO with SFO as part of daily dietary fat in the diet of people with type 2 diabetes is recommended for reducing Inflammation and Oxidative Stress. Trial registration. This study is approved by the Ethics Committee of Shiraz University of Medical Sciences (IR.SUMS.REC.1394.27) and is recorded in the Iranian Registry of Clinical Trials (IRCT2015062722818N1).
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19
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Ambery AG, Tackett L, Penque BA, Brozinick JT, Elmendorf JS. Exercise training prevents skeletal muscle plasma membrane cholesterol accumulation, cortical actin filament loss, and insulin resistance in C57BL/6J mice fed a western-style high-fat diet. Physiol Rep 2018; 5:5/16/e13363. [PMID: 28811359 PMCID: PMC5582260 DOI: 10.14814/phy2.13363] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 06/20/2017] [Accepted: 06/27/2017] [Indexed: 12/21/2022] Open
Abstract
Insulin action and glucose disposal are enhanced by exercise, yet the mechanisms involved remain imperfectly understood. While the causes of skeletal muscle insulin resistance also remain poorly understood, new evidence suggest excess plasma membrane (PM) cholesterol may contribute by damaging the cortical filamentous actin (F-actin) structure essential for GLUT4 glucose transporter redistribution to the PM upon insulin stimulation. Here, we investigated whether PM cholesterol toxicity was mitigated by exercise. Male C57BL/6J mice were placed on low-fat (LF, 10% kCal) or high-fat (HF, 45% kCal) diets for a total of 8 weeks. During the last 3 weeks of this LF/HF diet intervention, all mice were familiarized with a treadmill for 1 week and then either sham-exercised (0 m/min, 10% grade, 50 min) or exercised (13.5 m/min, 10% grade, 50 min) daily for 2 weeks. HF-feeding induced a significant gain in body mass by 3 weeks. Sham or chronic exercise did not affect food consumption, water intake, or body mass gain. Prior to sham and chronic exercise, "pre-intervention" glucose tolerance tests were performed on all animals and demonstrated that HF-fed mice were glucose intolerant. While sham exercise did not affect glucose tolerance in the LF or HF mice, exercised mice showed an improvement in glucose tolerance. Muscle from sham-exercised HF-fed mice showed a significant increase in PM cholesterol, loss of cortical F-actin, and decrease in insulin-stimulated glucose transport compared to sham-exercised LF-fed mice. These HF-fed skeletal muscle membrane/cytoskeletal abnormalities and insulin resistance were improved in exercised mice. These data reveal a new therapeutic aspect of exercise being regulation of skeletal muscle PM cholesterol homeostasis. Further studies on this mechanism of insulin resistance and the benefits of exercise on its prevention are needed.
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Affiliation(s)
- Ashley G Ambery
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana.,Center for Diabetes Metabolic Disease Indiana University School of Medicine, Indianapolis, Indiana
| | - Lixuan Tackett
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana.,Center for Diabetes Metabolic Disease Indiana University School of Medicine, Indianapolis, Indiana
| | - Brent A Penque
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana.,Center for Diabetes Metabolic Disease Indiana University School of Medicine, Indianapolis, Indiana
| | - Joseph T Brozinick
- Department Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana.,Eli Lilly and Company, Indianapolis, Indiana
| | - Jeffrey S Elmendorf
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana .,Center for Diabetes Metabolic Disease Indiana University School of Medicine, Indianapolis, Indiana.,Department Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
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20
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Fazakerley DJ, Minard AY, Krycer JR, Thomas KC, Stöckli J, Harney DJ, Burchfield JG, Maghzal GJ, Caldwell ST, Hartley RC, Stocker R, Murphy MP, James DE. Mitochondrial oxidative stress causes insulin resistance without disrupting oxidative phosphorylation. J Biol Chem 2018; 293:7315-7328. [PMID: 29599292 PMCID: PMC5950018 DOI: 10.1074/jbc.ra117.001254] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 03/19/2018] [Indexed: 01/02/2023] Open
Abstract
Mitochondrial oxidative stress, mitochondrial dysfunction, or both have been implicated in insulin resistance. However, disentangling the individual roles of these processes in insulin resistance has been difficult because they often occur in tandem, and tools that selectively increase oxidant production without impairing mitochondrial respiration have been lacking. Using the dimer/monomer status of peroxiredoxin isoforms as an indicator of compartmental hydrogen peroxide burden, we provide evidence that oxidative stress is localized to mitochondria in insulin-resistant 3T3-L1 adipocytes and adipose tissue from mice. To dissociate oxidative stress from impaired oxidative phosphorylation and study whether mitochondrial oxidative stress per se can cause insulin resistance, we used mitochondria-targeted paraquat (MitoPQ) to generate superoxide within mitochondria without directly disrupting the respiratory chain. At ≤10 μm, MitoPQ specifically increased mitochondrial superoxide and hydrogen peroxide without altering mitochondrial respiration in intact cells. Under these conditions, MitoPQ impaired insulin-stimulated glucose uptake and glucose transporter 4 (GLUT4) translocation to the plasma membrane in both adipocytes and myotubes. MitoPQ recapitulated many features of insulin resistance found in other experimental models, including increased oxidants in mitochondria but not cytosol; a more profound effect on glucose transport than on other insulin-regulated processes, such as protein synthesis and lipolysis; an absence of overt defects in insulin signaling; and defective insulin- but not AMP-activated protein kinase (AMPK)-regulated GLUT4 translocation. We conclude that elevated mitochondrial oxidants rapidly impair insulin-regulated GLUT4 translocation and significantly contribute to insulin resistance and that MitoPQ is an ideal tool for studying the link between mitochondrial oxidative stress and regulated GLUT4 trafficking.
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Affiliation(s)
- Daniel J Fazakerley
- Charles Perkins Centre, School of Life and Environmental Sciences, Camperdown, New South Wales 2006, Australia
| | - Annabel Y Minard
- Charles Perkins Centre, School of Life and Environmental Sciences, Camperdown, New South Wales 2006, Australia
| | - James R Krycer
- Charles Perkins Centre, School of Life and Environmental Sciences, Camperdown, New South Wales 2006, Australia
| | - Kristen C Thomas
- Charles Perkins Centre, School of Life and Environmental Sciences, Camperdown, New South Wales 2006, Australia
| | - Jacqueline Stöckli
- Charles Perkins Centre, School of Life and Environmental Sciences, Camperdown, New South Wales 2006, Australia
| | - Dylan J Harney
- Charles Perkins Centre, School of Life and Environmental Sciences, Camperdown, New South Wales 2006, Australia
| | - James G Burchfield
- Charles Perkins Centre, School of Life and Environmental Sciences, Camperdown, New South Wales 2006, Australia
| | - Ghassan J Maghzal
- Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia; St. Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Stuart T Caldwell
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Richard C Hartley
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Roland Stocker
- Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia; St. Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Michael P Murphy
- MRC Mitochondrial Biology Unit, Hills Road, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - David E James
- Charles Perkins Centre, School of Life and Environmental Sciences, Camperdown, New South Wales 2006, Australia; Charles Perkins Centre, Sydney Medical School, University of Sydney, Camperdown, New South Wales 2006, Australia.
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21
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Perreault L, Newsom SA, Strauss A, Kerege A, Kahn DE, Harrison KA, Snell-Bergeon JK, Nemkov T, D'Alessandro A, Jackman MR, MacLean PS, Bergman BC. Intracellular localization of diacylglycerols and sphingolipids influences insulin sensitivity and mitochondrial function in human skeletal muscle. JCI Insight 2018; 3:96805. [PMID: 29415895 DOI: 10.1172/jci.insight.96805] [Citation(s) in RCA: 101] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 12/12/2017] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Accumulation of diacylglycerol (DAG) and sphingolipids is thought to promote skeletal muscle insulin resistance by altering cellular signaling specific to their location. However,the subcellular localization of bioactive lipids in human skeletal muscle is largely unknown. METHODS We evaluated subcellular localization of skeletal muscle DAGs and sphingolipids in lean individuals (n = 15), endurance-trained athletes (n = 16), and obese men and women with (n = 12) and without type 2 diabetes (n = 15). Muscle biopsies were fractionated into sarcolemmal, cytosolic, mitochondrial/ER, and nuclear compartments. Lipids were measured using liquid chromatography tandem mass spectrometry, and insulin sensitivity was measured using hyperinsulinemic-euglycemic clamp. RESULTS Sarcolemmal 1,2-DAGs were not significantly related to insulin sensitivity. Sarcolemmal ceramides were inversely related to insulin sensitivity, with a significant relationship found for the C18:0 species. Sarcolemmal sphingomyelins were also inversely related to insulin sensitivity, with the strongest relationships found for the C18:1, C18:0, and C18:2 species. In the mitochondrial/ER and nuclear fractions, 1,2-DAGs were positively related to, while ceramides were inversely related to, insulin sensitivity. Cytosolic lipids as well as 1,3-DAG, dihydroceramides, and glucosylceramides in any compartment were not related to insulin sensitivity. All sphingolipids but only specific DAGs administered to isolated mitochondria decreased mitochondrial state 3 respiration. CONCLUSION These data reveal previously unknown differences in subcellular localization of skeletal muscle DAGs and sphingolipids that relate to whole-body insulin sensitivity and mitochondrial function in humans. These data suggest that whole-cell concentrations of lipids obscure meaningful differences in compartmentalization and suggest that subcellular localization of lipids should be considered when developing therapeutic interventions to treat insulin resistance. FUNDING National Institutes of Health General Clinical Research Center (RR-00036), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (R01DK089170), NIDDK (T32 DK07658), and Colorado Nutrition Obesity Research Center (P30DK048520).
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Affiliation(s)
- Leigh Perreault
- Endocrinology, Diabetes, and Metabolism, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Sean A Newsom
- School of Biological and Population Health Sciences, Oregon State University, Corvallis, Oregon, USA
| | - Allison Strauss
- Endocrinology, Diabetes, and Metabolism, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Anna Kerege
- Endocrinology, Diabetes, and Metabolism, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Darcy E Kahn
- Endocrinology, Diabetes, and Metabolism, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Kathleen A Harrison
- Endocrinology, Diabetes, and Metabolism, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Janet K Snell-Bergeon
- Barbara Davis Center for Childhood Diabetes, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Travis Nemkov
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Matthew R Jackman
- Endocrinology, Diabetes, and Metabolism, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Paul S MacLean
- Endocrinology, Diabetes, and Metabolism, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
| | - Bryan C Bergman
- Endocrinology, Diabetes, and Metabolism, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA
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22
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Lackey DE, Lazaro RG, Li P, Johnson A, Hernandez-Carretero A, Weber N, Vorobyova I, Tsukomoto H, Osborn O. The role of dietary fat in obesity-induced insulin resistance. Am J Physiol Endocrinol Metab 2016; 311:E989-E997. [PMID: 27802965 PMCID: PMC5183884 DOI: 10.1152/ajpendo.00323.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/12/2016] [Accepted: 10/26/2016] [Indexed: 01/15/2023]
Abstract
Consumption of excess calories results in obesity and insulin resistance and has been intensively studied in mice and humans. The objective of this study was to determine the specific contribution of dietary fat rather than total caloric intake to the development of obesity-associated insulin resistance. We used an intragastric feeding method to overfeed excess calories from a low-fat diet (and an isocalorically matched high-fat diet) through a surgically implanted gastric feeding tube to generate obesity in wild-type mice followed by hyperinsulinemic-euglycemic clamp studies to assess the development of insulin resistance. We show that overfeeding a low-fat diet results in levels of obesity similar to high-fat diet feeding in mice. However, despite a similar body weight, obese high-fat diet-fed mice are more insulin resistant than mice fed an isocaloric low-fat diet. Therefore, increased proportion of calories from dietary fat further potentiates insulin resistance in the obese state. Furthermore, crossover diet studies revealed that reduction in dietary fat composition improves glucose tolerance in obesity. In the context of the current obesity and diabetes epidemic, it is particularly important to fully understand the role of dietary macronutrients in the potentiation and amelioration of disease.
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Affiliation(s)
- Denise E Lackey
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California
| | - Raul G Lazaro
- Southern California Research Center for ALPD and Cirrhosis and Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California; and
| | - Pingping Li
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California
| | - Andrew Johnson
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California
| | - Angelina Hernandez-Carretero
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California
| | - Natalie Weber
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California
| | - Ivetta Vorobyova
- Southern California Research Center for ALPD and Cirrhosis and Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California; and
| | - Hidekazu Tsukomoto
- Southern California Research Center for ALPD and Cirrhosis and Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California; and
- Department of Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
| | - Olivia Osborn
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California;
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23
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Miyamoto Y, Miyazaki T, Honda A, Shimohata H, Hirayama K, Kobayashi M. Retention of acetylcarnitine in chronic kidney disease causes insulin resistance in skeletal muscle. J Clin Biochem Nutr 2016; 59:199-206. [PMID: 27895387 PMCID: PMC5110933 DOI: 10.3164/jcbn.15-146] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 02/08/2016] [Indexed: 12/24/2022] Open
Abstract
Insulin resistance occurs frequently in patients with chronic kidney disease. However, the mechanisms of insulin resistance associated with chronic kidney disease are unclear. It is known that an increase in the mitochondrial acetyl-CoA (AcCoA)/CoA ratio causes insulin resistance in skeletal muscle, and this ratio is regulated by carnitine acetyltransferase that exchanges acetyl moiety between CoA and carnitine. Because excess acetyl moiety of AcCoA is excreted in urine as acetylcarnitine, we hypothesized that retention of acetylcarnitine might be a cause of insulin resistance in chronic kidney disease patients. Serum acetylcarnitine concentrations were measured in chronic kidney disease patients, and were significantly increased with reduction of renal function. The effects of excess extracellular acetylcarnitine on insulin resistance were studied in cultured skeletal muscle cells (C2C12 and human myotubes), and insulin-dependent glucose uptake was significantly and dose-dependently inhibited by addition of acetylcarnitine. The added acetylcarnitine was converted to carnitine via reverse carnitine acetyltransferase reaction, and thus the AcCoA concentration and AcCoA/CoA ratio in mitochondria were significantly elevated. The results suggest that increased serum acetylcarnitine in CKD patients causes AcCoA accumulation in mitochondria by stimulating reverse carnitine acetyltransferase reaction, which leads to insulin resistance in skeletal muscle.
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Affiliation(s)
- Yasunori Miyamoto
- Department of Internal Medicine, Division of Nephrology, Tokyo Medical University Ibaraki Medical Center, Ami, Inashiki, Ibaraki 300-0395, Japan
| | - Teruo Miyazaki
- Joint Research Center, Tokyo Medical University Ibaraki Medical Center, Ami, Inashiki, Ibaraki 300-0395, Japan
| | - Akira Honda
- Joint Research Center, Tokyo Medical University Ibaraki Medical Center, Ami, Inashiki, Ibaraki 300-0395, Japan; Department of Internal Medicine, Division of Gastroenterology and Hepatology, Tokyo Medical University Ibaraki Medical Center, Ami, Inashiki, Ibaraki 300-0395, Japan
| | - Homare Shimohata
- Department of Internal Medicine, Division of Nephrology, Tokyo Medical University Ibaraki Medical Center, Ami, Inashiki, Ibaraki 300-0395, Japan
| | - Kouichi Hirayama
- Department of Internal Medicine, Division of Nephrology, Tokyo Medical University Ibaraki Medical Center, Ami, Inashiki, Ibaraki 300-0395, Japan
| | - Masaki Kobayashi
- Department of Internal Medicine, Division of Nephrology, Tokyo Medical University Ibaraki Medical Center, Ami, Inashiki, Ibaraki 300-0395, Japan
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Metabolic adaptations to HFHS overfeeding: how whole body and tissues postprandial metabolic flexibility adapt in Yucatan mini-pigs. Eur J Nutr 2016; 57:119-135. [PMID: 27568059 DOI: 10.1007/s00394-016-1302-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 08/16/2016] [Indexed: 12/18/2022]
Abstract
PURPOSE In the present study, we aimed to metabolically characterize the postprandial adaptations of the major tissues involved in energy, lipids and amino acids metabolisms in mini-pigs. METHOD Mini-pigs were fed on high-fat-high-sucrose (HFHS) diet for 2 months and several tissues explored for metabolic analyses. Further, the urine metabolome was followed over the time to picture the metabolic adaptations occurring at the whole body level following overfeeding. RESULTS After 2 months of HFHS consumption, mini-pigs displayed an obese phenotype characterized by high circulating insulin, triglycerides and cholesterol levels. At the tissue level, a general (muscle, adipose tissue, intestine) reduction in the capacity to phosphorylate glucose was observed. This was also supported by the enhanced hepatic gluconeogenesis potential, despite the concomitant normoglycaemia, suggesting that the high circulating insulin levels would be enough to maintain glucose homoeostasis. The HFHS feeding also resulted in a reduced capacity of two other pathways: the de novo lipogenesis, and the branched-chain amino acids transamination. Finally, the follow-up of the urine metabolome over the time allowed determining breaking points in the metabolic trajectory of the animals. CONCLUSIONS Several features confirmed the pertinence of the animal model, including increased body weight, adiposity and porcine obesity index. At the metabolic level, we observed a perturbed glucose and amino acid metabolism, known to be related to the onset of the obesity. The urine metabolome analyses revealed several metabolic pathways potentially involved in the obesity onset, including TCA (citrate, pantothenic acid), amino acids catabolism (cysteine, threonine, leucine).
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Welsink-Karssies MM, Polderman JAW, Nieveen van Dijkum EJ, Preckel B, Schlack WS, Visser G, Hollak CE, Hermanides J. Very Long-Chain Acyl-Coenzyme A Dehydrogenase Deficiency and Perioperative Management in Adult Patients. JIMD Rep 2016; 34:49-54. [PMID: 27518779 DOI: 10.1007/8904_2016_6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 06/24/2016] [Accepted: 07/07/2016] [Indexed: 01/05/2023] Open
Abstract
Surgery and anesthesia pose a threat to patients with very long-chain acyl-CoA dehydrogenase deficiency (VLCADD), because prolonged fasting, stress, and pain are known risk factors for the induction of metabolic derangement. The optimal perioperative management in these patients is unknown and the use of volatile agents and agents dissolved in fatty acids has been related to postoperative metabolic complications. However, the occurrence of metabolic derangement is multifactorial and depends, amongst others, on the severity of the mutation and residual enzyme activity. Current guidelines suggest avoiding both volatile anesthetics as well as propofol, which seriously limits the options for providing safe anesthesia. Therefore, we reviewed the available literature on the perioperative management of patients with VLCADD. We concluded that the use of some medications, such as volatile anesthetics, in patients with VLCADD might be wrongfully avoided and could in fact prevent metabolic derangement by the adequate suppression of pain and stress during surgery. We will illustrate this with a case report of an adult VLCADD patient undergoing minor surgery. Besides the use of remifentanil, anesthesia was uneventfully maintained with the use of sevoflurane, a volatile agent, and continuous glucose infusion. The patient was monitored with a continuous glucose meter and creatinine kinase measurements.
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Affiliation(s)
- M M Welsink-Karssies
- Department of Anesthesiology, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
| | - J A W Polderman
- Department of Anesthesiology, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
| | | | - B Preckel
- Department of Anesthesiology, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
| | - W S Schlack
- Department of Anesthesiology, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
| | - G Visser
- Department of Metabolic Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands
| | - C E Hollak
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Academic Medical Centre, Amsterdam, The Netherlands
| | - J Hermanides
- Department of Anesthesiology, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
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Bergman BC, Brozinick JT, Strauss A, Bacon S, Kerege A, Bui HH, Sanders P, Siddall P, Wei T, Thomas MK, Kuo MS, Perreault L. Muscle sphingolipids during rest and exercise: a C18:0 signature for insulin resistance in humans. Diabetologia 2016; 59:785-98. [PMID: 26739815 DOI: 10.1007/s00125-015-3850-y] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 12/03/2015] [Indexed: 12/18/2022]
Abstract
AIMS/HYPOTHESES Ceramides and other sphingolipids comprise a family of lipid molecules that accumulate in skeletal muscle and promote insulin resistance. Chronic endurance exercise training decreases muscle ceramides and other sphingolipids, but less is known about the effects of a single bout of exercise. METHODS We measured basal relationships and the effect of acute exercise (1.5 h at 50% [Formula: see text]) and recovery on muscle sphingolipid content in obese volunteers, endurance trained athletes and individuals with type 2 diabetes. RESULTS Muscle C18:0 ceramide (p = 0.029), dihydroceramide (p = 0.06) and glucosylceramide (p = 0.03) species were inversely related to insulin sensitivity without differences in total ceramide, dihydroceramide, and glucosylceramide concentration. Muscle C18:0 dihydroceramide correlated with markers of muscle inflammation (p = 0.04). Transcription of genes encoding sphingolipid synthesis enzymes was higher in athletes, suggesting an increased capacity for sphingolipid synthesis. The total concentration of muscle ceramides and sphingolipids increased during exercise and then decreased after recovery, during which time ceramide levels reduced to significantly below basal levels. CONCLUSIONS/INTERPRETATION These data suggest ceramide and other sphingolipids containing stearate (18:0) are uniquely related to insulin resistance in skeletal muscle. Recovery from an exercise bout decreased muscle ceramide concentration; this may represent a mechanism promoting the insulin-sensitising effects of acute exercise.
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Affiliation(s)
- Bryan C Bergman
- Division of Endocrinology, Metabolism, and Diabetes, University of Colorado Anschutz Medical Campus, PO Box 6511, MS 8106, Aurora, CO, 80045, USA.
| | | | - Allison Strauss
- Division of Endocrinology, Metabolism, and Diabetes, University of Colorado Anschutz Medical Campus, PO Box 6511, MS 8106, Aurora, CO, 80045, USA
| | - Samantha Bacon
- Division of Endocrinology, Metabolism, and Diabetes, University of Colorado Anschutz Medical Campus, PO Box 6511, MS 8106, Aurora, CO, 80045, USA
| | - Anna Kerege
- Division of Endocrinology, Metabolism, and Diabetes, University of Colorado Anschutz Medical Campus, PO Box 6511, MS 8106, Aurora, CO, 80045, USA
| | | | | | | | - Tao Wei
- Eli Lilly and Company, Indianapolis, IN, USA
| | | | | | - Leigh Perreault
- Division of Endocrinology, Metabolism, and Diabetes, University of Colorado Anschutz Medical Campus, PO Box 6511, MS 8106, Aurora, CO, 80045, USA
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Brandon AE, Stuart E, Leslie SJ, Hoehn KL, James DE, Kraegen EW, Turner N, Cooney GJ. Minimal impact of age and housing temperature on the metabolic phenotype of Acc2-/- mice. J Endocrinol 2016; 228:127-34. [PMID: 26668208 PMCID: PMC4906541 DOI: 10.1530/joe-15-0444] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/14/2015] [Indexed: 12/13/2022]
Abstract
An important regulator of fatty acid oxidation (FAO) is the allosteric inhibition of CPT-1 by malonyl-CoA produced by the enzyme acetyl-CoA carboxylase 2 (ACC2). Initial studies suggested that deletion of Acc2 (Acacb) increased fat oxidation and reduced adipose tissue mass but in an independently generated strain of Acc2 knockout mice we observed increased whole-body and skeletal muscle FAO and a compensatory increase in muscle glycogen stores without changes in glucose tolerance, energy expenditure or fat mass in young mice (12-16 weeks). The aim of the present study was to determine whether there was any effect of age or housing at thermoneutrality (29 °C; which reduces total energy expenditure) on the phenotype of Acc2 knockout mice. At 42-54 weeks of age, male WT and Acc2(-/-) mice had similar body weight, fat mass, muscle triglyceride content and glucose tolerance. Consistent with younger Acc2(-/-) mice, aged Acc2(-/-) mice showed increased whole-body FAO (24 h average respiratory exchange ratio=0.95±0.02 and 0.92±0.02 for WT and Acc2(-/-) mice respectively, P<0.05) and skeletal muscle glycogen content (+60%, P<0.05) without any detectable change in whole-body energy expenditure. Hyperinsulinaemic-euglycaemic clamp studies revealed no difference in insulin action between groups with similar glucose infusion rates and tissue glucose uptake. Housing Acc2(-/-) mice at 29 °C did not alter body composition, glucose tolerance or the effects of fat feeding compared with WT mice. These results confirm that manipulation of Acc2 may alter FAO in mice, but this has little impact on body composition or insulin action.
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Affiliation(s)
- Amanda E Brandon
- Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Ella Stuart
- Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Simon J Leslie
- Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Kyle L Hoehn
- Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - David E James
- Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Edward W Kraegen
- Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Nigel Turner
- Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Gregory J Cooney
- Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia Diabetes and Metabolism DivisionGarvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, AustraliaSt Vincent's Clinical SchoolUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Medical SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Biotechnology and Biomolecular SciencesUniversity of New South Wales Australia, Sydney, New South Wales, AustraliaSchool of Molecular Bioscience and Sydney Medical SchoolCharles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
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28
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Trefely S, Khoo PS, Krycer JR, Chaudhuri R, Fazakerley DJ, Parker BL, Sultani G, Lee J, Stephan JP, Torres E, Jung K, Kuijl C, James DE, Junutula JR, Stöckli J. Kinome Screen Identifies PFKFB3 and Glucose Metabolism as Important Regulators of the Insulin/Insulin-like Growth Factor (IGF)-1 Signaling Pathway. J Biol Chem 2015; 290:25834-46. [PMID: 26342081 DOI: 10.1074/jbc.m115.658815] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Indexed: 01/02/2023] Open
Abstract
The insulin/insulin-like growth factor (IGF)-1 signaling pathway (ISP) plays a fundamental role in long term health in a range of organisms. Protein kinases including Akt and ERK are intimately involved in the ISP. To identify other kinases that may participate in this pathway or intersect with it in a regulatory manner, we performed a whole kinome (779 kinases) siRNA screen for positive or negative regulators of the ISP, using GLUT4 translocation to the cell surface as an output for pathway activity. We identified PFKFB3, a positive regulator of glycolysis that is highly expressed in cancer cells and adipocytes, as a positive ISP regulator. Pharmacological inhibition of PFKFB3 suppressed insulin-stimulated glucose uptake, GLUT4 translocation, and Akt signaling in 3T3-L1 adipocytes. In contrast, overexpression of PFKFB3 in HEK293 cells potentiated insulin-dependent phosphorylation of Akt and Akt substrates. Furthermore, pharmacological modulation of glycolysis in 3T3-L1 adipocytes affected Akt phosphorylation. These data add to an emerging body of evidence that metabolism plays a central role in regulating numerous biological processes including the ISP. Our findings have important implications for diseases such as type 2 diabetes and cancer that are characterized by marked disruption of both metabolism and growth factor signaling.
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Affiliation(s)
- Sophie Trefely
- From the Garvan Institute of Medical Research, Sydney 2010 NSW, Australia
| | - Poh-Sim Khoo
- From the Garvan Institute of Medical Research, Sydney 2010 NSW, Australia, Genentech Inc., South San Francisco, California 94080
| | - James R Krycer
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
| | - Rima Chaudhuri
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
| | - Daniel J Fazakerley
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
| | - Benjamin L Parker
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
| | - Ghazal Sultani
- From the Garvan Institute of Medical Research, Sydney 2010 NSW, Australia
| | - James Lee
- Genentech Inc., South San Francisco, California 94080
| | | | - Eric Torres
- Genentech Inc., South San Francisco, California 94080
| | - Kenneth Jung
- Genentech Inc., South San Francisco, California 94080
| | | | - David E James
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and the Sydney Medical School, University of Sydney, Sydney 2006 NSW, Australia
| | | | - Jacqueline Stöckli
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
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Ritter O, Jelenik T, Roden M. Lipid-mediated muscle insulin resistance: different fat, different pathways? J Mol Med (Berl) 2015; 93:831-43. [PMID: 26108617 DOI: 10.1007/s00109-015-1310-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 05/27/2015] [Accepted: 06/12/2015] [Indexed: 12/22/2022]
Abstract
Increased dietary fat intake and lipolysis result in excessive lipid availability, which relates to impaired insulin sensitivity. Over the last years, several mechanisms possibly underlying lipid-mediated insulin resistance evolved. Lipid intermediates such as diacylglycerols (DAG) associate with changes in insulin sensitivity in many models. DAG activate novel protein kinase C (PKC) isoforms followed by inhibitory serine phosphorylation of insulin receptor substrate 1 (IRS1). Activation of Toll-like receptor 4 (TLR4) raises another lipid class, ceramides (CER), which induce pro-inflammatory pathways and lead to inhibition of Akt phosphorylation. Inhibition of glucosylceramide and ganglioside synthesis results in improved insulin sensitivity and increased activatory tyrosine phosphorylation of IRS1 in the muscle. Incomplete fat oxidation can increase acylcarnitines (ACC), which in turn stimulate pro-inflammatory pathways. This review analyzed the effects of lipid metabolites on insulin action in skeletal muscle of humans and rodents. Despite the evidence for the association of both DAG and CER with insulin resistance, its causal relevance may differ depending on the subcellular localization and the tested cohorts, e.g., athletes. Nevertheless, recent data indicate that individual lipid species and their degree of fatty acid saturation, particularly membrane and cytosolic C18:2 DAG, specifically activate PKCθ and induce both acute lipid-induced and chronic insulin resistance in humans.
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Affiliation(s)
- Olesja Ritter
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225, Düsseldorf, Germany
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30
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Brandon AE, Tid-Ang J, Wright LE, Stuart E, Suryana E, Bentley N, Turner N, Cooney GJ, Ruderman NB, Kraegen EW. Overexpression of SIRT1 in rat skeletal muscle does not alter glucose induced insulin resistance. PLoS One 2015; 10:e0121959. [PMID: 25798922 PMCID: PMC4370576 DOI: 10.1371/journal.pone.0121959] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Accepted: 02/10/2015] [Indexed: 12/17/2022] Open
Abstract
SIRT1 is a NAD+-dependent deacetylase thought to regulate cellular metabolic pathways in response to alterations in nutrient flux. In the current study we investigated whether acute changes in SIRT1 expression affect markers of muscle mitochondrial content and also determined whether SIRT1 influenced muscle insulin resistance induced by acute glucose oversupply. In male Wistar rats either SIRT1 or a deacetylase inactive mutant form (H363Y) was electroprated into the tibialis cranialis (TC) muscle. The other leg was electroporated with an empty control vector. One week later, glucose was infused and hyperglycaemia was maintained at ~11mM. After 5 hours, 11mM glucose induced significant insulin resistance in skeletal muscle. Interestingly, overexpression of either SIRT1 or SIRT1 (H363Y) for 1 week did not change markers of mitochondrial content or function. SIRT1 or SIRT1 (H363Y) overexpression had no effect on the reduction in glucose uptake and glycogen synthesis in muscle in response to hyperglycemia. Therefore we conclude that acute increases in SIRT1 protein have little impact on mitochondrial content and that overexpressing SIRT1 does not prevent the development of insulin resistance during hyperglycaemia.
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Affiliation(s)
- Amanda E Brandon
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St., Darlinghurst, NSW, 2010, Australia
| | - Jennifer Tid-Ang
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St., Darlinghurst, NSW, 2010, Australia
| | - Lauren E Wright
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St., Darlinghurst, NSW, 2010, Australia
| | - Ella Stuart
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St., Darlinghurst, NSW, 2010, Australia
| | - Eurwin Suryana
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St., Darlinghurst, NSW, 2010, Australia
| | | | - Nigel Turner
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St., Darlinghurst, NSW, 2010, Australia; UNSW Medicine, University of New South Wales, Sydney, Australia
| | - Gregory J Cooney
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St., Darlinghurst, NSW, 2010, Australia; UNSW Medicine, University of New South Wales, Sydney, Australia
| | - Neil B Ruderman
- Boston University School of Medicine, Boston, Massachusetts, United States of America
| | - Edward W Kraegen
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St., Darlinghurst, NSW, 2010, Australia; UNSW Medicine, University of New South Wales, Sydney, Australia
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Connor T, Martin SD, Howlett KF, McGee SL. Metabolic remodelling in obesity and type 2 diabetes: pathological or protective mechanisms in response to nutrient excess? Clin Exp Pharmacol Physiol 2014; 42:109-15. [DOI: 10.1111/1440-1681.12315] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 09/17/2014] [Accepted: 09/19/2014] [Indexed: 12/31/2022]
Affiliation(s)
- Timothy Connor
- Metabolic Remodelling Laboratory; Metabolic Research Unit; School of Medicine; Deakin University; Geelong Vic. Australia
| | - Sheree D Martin
- Metabolic Remodelling Laboratory; Metabolic Research Unit; School of Medicine; Deakin University; Geelong Vic. Australia
| | - Kirsten F Howlett
- Centre for Physical Activity and Nutrition; School of Exercise and Nutrition Sciences; Deakin University; Geelong Vic. Australia
| | - Sean L McGee
- Metabolic Remodelling Laboratory; Metabolic Research Unit; School of Medicine; Deakin University; Geelong Vic. Australia
- Division of Cell Signalling and Metabolism; Baker IDI Heart and Diabetes Institute; Melbourne Vic. Australia
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Dubé JJ, Coen PM, DiStefano G, Chacon AC, Helbling NL, Desimone ME, Stafanovic-Racic M, Hames KC, Despines AA, Toledo FGS, Goodpaster BH. Effects of acute lipid overload on skeletal muscle insulin resistance, metabolic flexibility, and mitochondrial performance. Am J Physiol Endocrinol Metab 2014; 307:E1117-24. [PMID: 25352435 PMCID: PMC4269675 DOI: 10.1152/ajpendo.00257.2014] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We hypothesized that acute lipid-induced insulin resistance would be attenuated in high-oxidative muscle of lean trained (LT) endurance athletes due to their enhanced metabolic flexibility and mitochondrial capacity. Lean sedentary (LS), obese sedentary (OS), and LT participants completed two hyperinsulinemic euglycemic clamp studies with and without (glycerol control) the coinfusion of Intralipid. Metabolic flexibility was measured by indirect calorimetry as the oxidation of fatty acids and glucose during fasted and insulin-stimulated conditions, the latter with and without lipid oversupply. Muscle biopsies were obtained for mitochondrial and insulin-signaling studies. During hyperinsulinemia without lipid, glucose infusion rate (GIR) was lowest in OS due to lower rates of nonoxidative glucose disposal (NOGD), whereas state 4 respiration was increased in all groups. Lipid infusion reduced GIR similarly in all subjects and reduced state 4 respiration. However, in LT subjects, fat oxidation was higher with lipid oversupply, and although glucose oxidation was reduced, NOGD was better preserved compared with LS and OS subjects. Mitochondrial performance was positively associated with better NOGD and insulin sensitivity in both conditions. We conclude that enhanced mitochondrial performance with exercise is related to better metabolic flexibility and insulin sensitivity in response to lipid overload.
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Affiliation(s)
- John J Dubé
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania and
| | - Paul M Coen
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Sanford/Burnham Medical Research Institute, Orlando, Florida
| | - Giovanna DiStefano
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania and
| | - Alexander C Chacon
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania and
| | - Nicole L Helbling
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania and
| | - Marisa E Desimone
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania and
| | - Maja Stafanovic-Racic
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania and
| | - Kazanna C Hames
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania and
| | - Alex A Despines
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania and
| | - Frederico G S Toledo
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania and
| | - Bret H Goodpaster
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Sanford/Burnham Medical Research Institute, Orlando, Florida
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Hussey SE, Lum H, Alvarez A, Cipriani Y, Garduño-Garcia J, Anaya L, Dube J, Musi N. A sustained increase in plasma NEFA upregulates the Toll-like receptor network in human muscle. Diabetologia 2014; 57:582-91. [PMID: 24337154 PMCID: PMC3945433 DOI: 10.1007/s00125-013-3111-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 10/30/2013] [Indexed: 01/04/2023]
Abstract
AIMS/HYPOTHESIS Insulin-sensitive tissues (muscle, liver) of individuals with obesity and type 2 diabetes mellitus are in a state of low-grade inflammation, characterised by increased Toll-like receptor (TLR) expression and TLR-driven signalling. However, the cause of this mild inflammatory state is unclear. We tested the hypothesis that a prolonged mild increase in plasma NEFA will increase TLR expression and TLR-driven signalling (nuclear factor κB [NFκB] and mitogen-activated kinase [MAPK]) and impair insulin action in muscle of lean healthy individuals. METHODS Twelve lean, normal-glucose-tolerant participants were randomised to receive a 48 h infusion (30 ml/h) of saline or Intralipid followed by a euglycaemic-hyperinsulinaemic clamp. Vastus lateralis muscle biopsies were performed before and during the clamp. RESULTS Lipid infusion impaired insulin-stimulated IRS-1 tyrosine phosphorylation and reduced peripheral insulin sensitivity (p < 0.01). The elevation in circulating NEFA increased expression of TLR3, TLR4 and TLR5, and several MAPK (MAPK8, MAP4K4, MAP2K3) and inhibitor of κB kinase-NFκB (CHUK [IKKA], c-REL [REL] and p65 [RELA, NFKB3, p65]) signalling genes (p < 0.05). The lipid infusion also increased extracellular signal-regulated kinase (ERK) phosphorylation (p < 0.05) and tended to reduce the content of inhibitor of kappa Bα (p = 0.09). The muscle content of most diacylglycerol, ceramide and acylcarnitine species was unaffected. In summary, insulin resistance induced by prolonged low-dose lipid infusion occurs together with increased TLR-driven inflammatory signalling and impaired insulin-stimulated IRS-1 tyrosine phosphorylation. CONCLUSIONS/INTERPRETATION A sustained, mild elevation in plasma NEFA is sufficient to increase TLR expression and TLR-driven signalling (NFκB and MAPK) in lean individuals. The activation of this pathway by NEFA may be involved in the pathogenesis of insulin resistance in humans. TRIAL REGISTRATION ClinicalTrials.gov NCT01740817.
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Affiliation(s)
- Sophie E Hussey
- Department of Medicine-Diabetes Division, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
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Nellemann B, Vendelbo MH, Nielsen TS, Bak AM, Høgild M, Pedersen SB, Biensø RS, Pilegaard H, Møller N, Jessen N, Jørgensen JOL. Growth hormone-induced insulin resistance in human subjects involves reduced pyruvate dehydrogenase activity. Acta Physiol (Oxf) 2014; 210:392-402. [PMID: 24148194 DOI: 10.1111/apha.12183] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 09/09/2013] [Accepted: 10/17/2013] [Indexed: 12/15/2022]
Abstract
AIM Insulin resistance induced by growth hormone (GH) is linked to promotion of lipolysis by unknown mechanisms. We hypothesized that suppression of the activity of pyruvate dehydrogenase in the active form (PDHa) underlies GH-induced insulin resistance similar to what is observed during fasting. METHODS Eight healthy male subjects were studied four times in a randomized, single-blinded parallel design: Control, GH, Fasting (36 h) and GH + Fasting. GH (30 ng × kg(-1) × min(-1)) or saline was infused throughout the metabolic study day. Substrate metabolism and insulin sensitivity were assessed by indirect calorimetry and isotopically determined rates of glucose turnover before and after a hyperinsulinemic euglycemic clamp. PDHa activity, PDH-E1α phosphorylation, PDK4 expression and activation of insulin signalling proteins were assessed in skeletal muscle. RESULTS Both fasting and GH promoted lipolysis, which was associated with ≈50% reduction in insulin sensitivity compared with the control day. PDHa activity was significantly reduced by GH as well as fasting. This was associated with increased inhibitory PDH-E1α phosphorylation on site 1 (Ser(293)) and 2 (Ser(300)) and up-regulation of PDK4 mRNA, while canonical insulin signalling to glucose transport was unaffected. CONCLUSION Competition between intermediates of glucose and fatty acids seems to play a causal role in insulin resistance induced by GH in human subjects.
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Affiliation(s)
- B. Nellemann
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - M. H. Vendelbo
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - T. S. Nielsen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - A. M. Bak
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - M. Høgild
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - S. B. Pedersen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - R. S. Biensø
- Centre of Inflammation and Metabolism & August Krogh Centre; Department of Biology; University of Copenhagen; Copenhagen Denmark
| | - H. Pilegaard
- Centre of Inflammation and Metabolism & August Krogh Centre; Department of Biology; University of Copenhagen; Copenhagen Denmark
| | - N. Møller
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - N. Jessen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - J. O. L. Jørgensen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
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Turner N, Cooney GJ, Kraegen EW, Bruce CR. Fatty acid metabolism, energy expenditure and insulin resistance in muscle. J Endocrinol 2014; 220:T61-79. [PMID: 24323910 DOI: 10.1530/joe-13-0397] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Fatty acids (FAs) are essential elements of all cells and have significant roles as energy substrates, components of cellular structure and signalling molecules. The storage of excess energy intake as fat in adipose tissue is an evolutionary advantage aimed at protecting against starvation, but in much of today's world, humans are faced with an unlimited availability of food, and the excessive accumulation of fat is now a major risk for human health, especially the development of type 2 diabetes (T2D). Since the first recognition of the association between fat accumulation, reduced insulin action and increased risk of T2D, several mechanisms have been proposed to link excess FA availability to reduced insulin action, with some of them being competing or contradictory. This review summarises the evidence for these mechanisms in the context of excess dietary FAs generating insulin resistance in muscle, the major tissue involved in insulin-stimulated disposal of blood glucose. It also outlines potential problems with models and measurements that may hinder as well as help improve our understanding of the links between FAs and insulin action.
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Affiliation(s)
- Nigel Turner
- Department of Pharmacology School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia Diabetes and Obesity Division, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, Australia St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales, Australia Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
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Dyar KA, Ciciliot S, Wright LE, Biensø RS, Tagliazucchi GM, Patel VR, Forcato M, Paz MIP, Gudiksen A, Solagna F, Albiero M, Moretti I, Eckel-Mahan KL, Baldi P, Sassone-Corsi P, Rizzuto R, Bicciato S, Pilegaard H, Blaauw B, Schiaffino S. Muscle insulin sensitivity and glucose metabolism are controlled by the intrinsic muscle clock. Mol Metab 2013; 3:29-41. [PMID: 24567902 PMCID: PMC3929910 DOI: 10.1016/j.molmet.2013.10.005] [Citation(s) in RCA: 301] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 10/14/2013] [Accepted: 10/17/2013] [Indexed: 12/21/2022] Open
Abstract
Circadian rhythms control metabolism and energy homeostasis, but the role of the skeletal muscle clock has never been explored. We generated conditional and inducible mouse lines with muscle-specific ablation of the core clock gene Bmal1. Skeletal muscles from these mice showed impaired insulin-stimulated glucose uptake with reduced protein levels of GLUT4, the insulin-dependent glucose transporter, and TBC1D1, a Rab-GTPase involved in GLUT4 translocation. Pyruvate dehydrogenase (PDH) activity was also reduced due to altered expression of circadian genes Pdk4 and Pdp1, coding for PDH kinase and phosphatase, respectively. PDH inhibition leads to reduced glucose oxidation and diversion of glycolytic intermediates to alternative metabolic pathways, as revealed by metabolome analysis. The impaired glucose metabolism induced by muscle-specific Bmal1 knockout suggests that a major physiological role of the muscle clock is to prepare for the transition from the rest/fasting phase to the active/feeding phase, when glucose becomes the predominant fuel for skeletal muscle.
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Key Words
- 2-DG, 2-Deoxyglucose
- BSA, bovine serum albumin
- Bmal1
- Circadian rhythms
- GSEA, Gene Set Enrichment Analysis
- Glucose metabolism
- Glucose uptake
- HK2, hexokinase 2
- KHB, Krebs–Henseleit buffer
- Muscle insulin resistance
- PDH, pyruvate dehydrogenase
- PDK, PDH kinase
- PDP, PDH phosphatase
- SCN, suprachiasmatic nucleus
- Skeletal muscle
- ZT, Zeitgeber time
- imKO, inducible muscle-specific Bmal1 knockout
- mKO, muscle-specific Bmal1 knockout
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Affiliation(s)
- Kenneth A Dyar
- Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy
| | - Stefano Ciciliot
- Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy
| | - Lauren E Wright
- Department of Biomedical Sciences, University of Padova, Italy
| | - Rasmus S Biensø
- Department of Biology, Molecular Integrative Physiology, University of Copenhagen, Denmark
| | - Guidantonio M Tagliazucchi
- Center for Genome Research, Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Vishal R Patel
- Department of Computer Science, Institute for Genomics and Bioinformatics, UC Irvine, USA
| | - Mattia Forcato
- Center for Genome Research, Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Marcia I P Paz
- Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy
| | - Anders Gudiksen
- Department of Biology, Molecular Integrative Physiology, University of Copenhagen, Denmark
| | - Francesca Solagna
- Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy
| | - Mattia Albiero
- Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy
| | - Irene Moretti
- Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy ; CNR Institute of Neuroscience, Padova, Italy
| | | | - Pierre Baldi
- Department of Computer Science, Institute for Genomics and Bioinformatics, UC Irvine, USA
| | | | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Italy ; CNR Institute of Neuroscience, Padova, Italy
| | - Silvio Bicciato
- Center for Genome Research, Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Henriette Pilegaard
- Department of Biology, Molecular Integrative Physiology, University of Copenhagen, Denmark
| | - Bert Blaauw
- Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy ; Department of Biomedical Sciences, University of Padova, Italy
| | - Stefano Schiaffino
- Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy ; CNR Institute of Neuroscience, Padova, Italy
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Samjoo IA, Safdar A, Hamadeh MJ, Glover AW, Mocellin NJ, Santana J, Little JP, Steinberg GR, Raha S, Tarnopolsky MA. Markers of skeletal muscle mitochondrial function and lipid accumulation are moderately associated with the homeostasis model assessment index of insulin resistance in obese men. PLoS One 2013; 8:e66322. [PMID: 23776659 PMCID: PMC3680409 DOI: 10.1371/journal.pone.0066322] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 05/03/2013] [Indexed: 02/07/2023] Open
Abstract
Lower skeletal muscle mitochondrial oxidative phosphorylation capacity (OXPHOS) and intramyocellular lipid (IMCL) accumulation have been implicated in the etiology of insulin resistance (IR) in obesity. The purpose of this study was to examine the impact of endurance exercise on biochemical and morphological measures of IMCL and mitochondrial content, and their relationship to IR in obese individuals. We examined mitochondrial content (subunit protein abundance and maximal activity of electron transport chain enzymes), IMCL/mitochondrial morphology in both subsarcolemmal (SS) and intermyofibrillar (IMF) regions by transmission electron microscopy, and intracellular lipid metabolites (diacylglycerol and ceramide) in vastus lateralis biopsies, as well as, the homeostasis model assessment index of IR (HOMA-IR) prior to and following twelve weeks of an endurance exercise regimen in healthy age- and physical activity-matched lean and obese men. Obese men did not show evidence of mitochondrial OXPHOS dysfunction, disproportionate IMCL content in sub-cellular regions, or diacylglycerol/ceramide accretion despite marked IR vs. lean controls. Endurance exercise increased OXPHOS and mitochondrial size and density, but not number of individual mitochondrial fragments, with moderate improvements in HOMA-IR. Exercise reduced SS IMCL content (size, number and density), increased IMF IMCL content, while increasing IMCL/mitochondrial juxtaposition in both regions. HOMA-IR was inversely associated with SS (r = -0.34; P = 0.051) and IMF mitochondrial density (r = -0.29; P = 0.096), IMF IMCL/mitochondrial juxtaposition (r = -0.30; P = 0.086), and COXII (r = -0.32; P = 0.095) and COXIV protein abundance (r = -0.35; P = 0.052); while positively associated with SS IMCL size (r = 0.28; P = 0.119) and SS IMCL density (r = 0.25; P = 0.152). Our findings suggest that once physical activity and cardiorespiratory fitness have been controlled for, skeletal muscle mitochondrial and IMCL profile in obesity may only partially contribute to the development of IR.
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Affiliation(s)
- Imtiaz A. Samjoo
- Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Adeel Safdar
- Cardiovascular Institute, Beth Israel Deaconess Medical Centre, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Mazen J. Hamadeh
- Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, Ontario, Canada
| | - Alexander W. Glover
- Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Nicholas J. Mocellin
- Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Jose Santana
- Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Jonathan P. Little
- School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | | | - Sandeep Raha
- Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
| | - Mark A. Tarnopolsky
- Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
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Czech MP, Tencerova M, Pedersen DJ, Aouadi M. Insulin signalling mechanisms for triacylglycerol storage. Diabetologia 2013; 56:949-64. [PMID: 23443243 PMCID: PMC3652374 DOI: 10.1007/s00125-013-2869-1] [Citation(s) in RCA: 178] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 01/22/2013] [Indexed: 02/06/2023]
Abstract
Insulin signalling is uniquely required for storing energy as fat in humans. While de novo synthesis of fatty acids and triacylglycerol occurs mostly in liver, adipose tissue is the primary site for triacylglycerol storage. Insulin signalling mechanisms in adipose tissue that stimulate hydrolysis of circulating triacylglycerol, uptake of the released fatty acids and their conversion to triacylglycerol are poorly understood. New findings include (1) activation of DNA-dependent protein kinase to stimulate upstream stimulatory factor (USF)1/USF2 heterodimers, enhancing the lipogenic transcription factor sterol regulatory element binding protein 1c (SREBP1c); (2) stimulation of fatty acid synthase through AMP kinase modulation; (3) mobilisation of lipid droplet proteins to promote retention of triacylglycerol; and (4) upregulation of a novel carbohydrate response element binding protein β isoform that potently stimulates transcription of lipogenic enzymes. Additionally, insulin signalling through mammalian target of rapamycin to activate transcription and processing of SREBP1c described in liver may apply to adipose tissue. Paradoxically, insulin resistance in obesity and type 2 diabetes is associated with increased triacylglycerol synthesis in liver, while it is decreased in adipose tissue. This and other mysteries about insulin signalling and insulin resistance in adipose tissue make this topic especially fertile for future research.
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Affiliation(s)
- M P Czech
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA.
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Lee-Young RS, Bonner JS, Mayes WH, Iwueke I, Barrick BA, Hasenour CM, Kang L, Wasserman DH. AMP-activated protein kinase (AMPK)α2 plays a role in determining the cellular fate of glucose in insulin-resistant mouse skeletal muscle. Diabetologia 2013; 56:608-17. [PMID: 23224579 PMCID: PMC4075509 DOI: 10.1007/s00125-012-2787-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 11/01/2012] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS We determined whether: (1) an acute lipid infusion impairs skeletal muscle AMP-activated protein kinase (AMPK)α2 activity, increases inducible nitric oxide synthase (iNOS) and causes peripheral insulin resistance in conscious, unstressed, lean mice; and (2) restoration of AMPKα2 activity during the lipid infusion attenuates the increase in iNOS and reverses the defect in insulin sensitivity in vivo. METHODS Chow-fed, 18-week-old C57BL/6J male mice were surgically catheterised. After 5 days they received: (1) a 5 h infusion of 5 ml kg(-1) h(-1) Intralipid + 6 U/h heparin (Lipid treatment) or saline (Control); (2) Lipid treatment or Control, followed by a 2 h hyperinsulinaemic-euglycaemic clamp (insulin clamp; 4 mU kg(-1) min(-1)); and (3) infusion of the AMPK activator, 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR) (1 mg kg(-1) min(-1)), or saline during Lipid treatment, followed by a 2 h insulin clamp. In a separate protocol, mice producing a muscle-specific kinase-dead AMPKα2 subunit (α2-KD) underwent an insulin clamp to determine the role of AMPKα2 in insulin-mediated muscle glucose metabolism. RESULTS Lipid treatment decreased AMPKα2 activity, increased iNOS abundance/activation and reduced whole-body insulin sensitivity in vivo. AICAR increased AMPKα2 activity twofold; this did not suppress iNOS or improve whole-body or tissue-specific rates of glucose uptake during Lipid treatment. AICAR caused a marked increase in insulin-mediated glycogen synthesis in skeletal muscle. Consistent with this latter result, lean α2-KD mice exhibited impaired insulin-stimulated glycogen synthesis even though muscle glucose uptake was not affected. CONCLUSIONS/INTERPRETATION Acute induction of insulin resistance via lipid infusion in healthy mice impairs AMPKα2, increases iNOS and causes insulin resistance in vivo. However, these changes do not appear to be interrelated. Rather, a functionally active AMPKα2 subunit is required for insulin-stimulated muscle glycogen synthesis.
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Affiliation(s)
- R S Lee-Young
- Cellular and Molecular Metabolism Laboratory, Division of Metabolism and Obesity, Baker IDI Heart and Diabetes Institute, 75 Commercial Rd, Melbourne, VIC 3004, Australia.
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Gulli RA, Tishinsky JM, MacDonald T, Robinson LE, Wright DC, Dyck DJ. Exercise restores insulin, but not adiponectin, response in skeletal muscle of high-fat fed rodents. Am J Physiol Regul Integr Comp Physiol 2012; 303:R1062-70. [DOI: 10.1152/ajpregu.00176.2012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
High-fat (HF) diets impair skeletal muscle response to the insulin-sensitizing adipokine adiponectin (Ad) in rodents, preceding the development of insulin resistance. Skeletal muscle insulin response in HF-fed rats can be restored with chronic exercise; whether recovery of skeletal muscle Ad response is necessary for the exercise-induced recovery of insulin-stimulated glucose transport is not known. In the current study, insulin and Ad resistance were induced in rodents with 4 wk of HF feeding (HF4; low-fat fed animals used as control). Rats were then treadmill-exercised (HF5EX1, HF6EX2) or supplemented orally with the pharmacological agent β-guadinoproprionic acid (GPA; HF5GPA1, HF6GPA2) for 1 or 2 wk with continued HF feeding. Insulin and Ad responses (glucose transport and palmitate oxidation, respectively) were assessed 48 h after the last exercise bout ex vivo in isolated solei. Insulin response was impaired following 4 wk of HF feeding and improved with 1 and 2 wk of exercise and β-GPA supplementation (HF5EX1, HF6EX2, HF5GPA1, and HF6GPA2). The recovery of insulin response generally coincided with improved Akt Thr308 phosphorylation in HF5GPA1, HF6EX2, and HF6GPA2, although not in HF5EX1. Ad-stimulated palmitate oxidation was not restored with either treatment. Total protein contents of AdipoR1, AdipoR2, APPL1, and APPL2, as well as total and phosphorylated AMPK and ACC were unaltered by diet, exercise, and β-GPA at the assessed time points. We conclude that the exercise and pharmacologically (β-GPA)-induced recovery of skeletal muscle insulin response after HF feeding is not dependent on the restoration of Ad response, as assessed ex vivo.
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Affiliation(s)
- Roberto A. Gulli
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Justine M. Tishinsky
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Tara MacDonald
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Lindsay E. Robinson
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - David C. Wright
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - David J. Dyck
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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Patel SA, Hoehn KL, Lawrence RT, Sawbridge L, Talbot NA, Tomsig JL, Turner N, Cooney GJ, Whitehead JP, Kraegen EW, Cleasby ME. Overexpression of the adiponectin receptor AdipoR1 in rat skeletal muscle amplifies local insulin sensitivity. Endocrinology 2012; 153:5231-46. [PMID: 22989629 PMCID: PMC3498583 DOI: 10.1210/en.2012-1368] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Adiponectin is an adipokine whose plasma levels are inversely related to degrees of insulin resistance (IR) or obesity. It enhances glucose disposal and mitochondrial substrate oxidation in skeletal muscle and its actions are mediated through binding to receptors, especially adiponectin receptor 1 (AdipoR1). However, the in vivo significance of adiponectin sensitivity and the molecular mechanisms of muscle insulin sensitization by adiponectin have not been fully established. We used in vivo electrotransfer to overexpress AdipoR1 in single muscles of rats, some of which were fed for 6 wk with chow or high-fat diet (HFD) and then subjected to hyperinsulinemic-euglycemic clamp. After 1 wk, the effects on glucose disposal, signaling, and sphingolipid metabolism were investigated in test vs. contralateral control muscles. AdipoR1 overexpression (OE) increased glucose uptake and glycogen accumulation in the basal and insulin-treated rat muscle and also in the HFD-fed rats, locally ameliorating muscle IR. These effects were associated with increased phosphorylation of insulin receptor substrate-1, Akt, and glycogen synthase kinase-3β. AdipoR1 OE also caused increased phosphorylation of p70S6 kinase, AMP-activated protein kinase, and acetyl-coA carboxylase as well as increased protein levels of adaptor protein containing pleckstrin homology domain, phosphotyrosine binding domain, and leucine zipper motif-1 and adiponectin, peroxisome proliferator activated receptor-γ coactivator-1α, and uncoupling protein-3, indicative of increased mitochondrial biogenesis. Although neither HFD feeding nor AdipoR1 OE caused generalized changes in sphingolipids, AdipoR1 OE did reduce levels of sphingosine 1-phosphate, ceramide 18:1, ceramide 20:2, and dihydroceramide 20:0, plus mRNA levels of the ceramide synthetic enzymes serine palmitoyl transferase and sphingolipid Δ-4 desaturase, changes that are associated with increased insulin sensitivity. These data demonstrate that enhancement of local adiponectin sensitivity is sufficient to improve skeletal muscle IR.
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Affiliation(s)
- S A Patel
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, United Kingdom
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Pehmøller C, Brandt N, Birk JB, Høeg LD, Sjøberg KA, Goodyear LJ, Kiens B, Richter EA, Wojtaszewski JF. Exercise alleviates lipid-induced insulin resistance in human skeletal muscle-signaling interaction at the level of TBC1 domain family member 4. Diabetes 2012; 61:2743-52. [PMID: 22851577 PMCID: PMC3478539 DOI: 10.2337/db11-1572] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Excess lipid availability causes insulin resistance. We examined the effect of acute exercise on lipid-induced insulin resistance and TBC1 domain family member 1/4 (TBCD1/4)-related signaling in skeletal muscle. In eight healthy young male subjects, 1 h of one-legged knee-extensor exercise was followed by 7 h of saline or intralipid infusion. During the last 2 h, a hyperinsulinemic-euglycemic clamp was performed. Femoral catheterization and analysis of biopsy specimens enabled measurements of leg substrate balance and muscle signaling. Each subject underwent two experimental trials, differing only by saline or intralipid infusion. Glucose infusion rate and leg glucose uptake was decreased by intralipid. Insulin-stimulated glucose uptake was higher in the prior exercised leg in the saline and the lipid trials. In the lipid trial, prior exercise normalized insulin-stimulated glucose uptake to the level observed in the resting control leg in the saline trial. Insulin increased phosphorylation of TBC1D1/4. Whereas prior exercise enhanced TBC1D4 phosphorylation on all investigated sites compared with the rested leg, intralipid impaired TBC1D4 S341 phosphorylation compared with the control trial. Intralipid enhanced pyruvate dehydrogenase (PDH) phosphorylation and lactate release. Prior exercise led to higher PDH phosphorylation and activation of glycogen synthase compared with resting control. In conclusion, lipid-induced insulin resistance in skeletal muscle was associated with impaired TBC1D4 S341 and elevated PDH phosphorylation. The prophylactic effect of exercise on lipid-induced insulin resistance may involve augmented TBC1D4 signaling and glycogen synthase activation.
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Affiliation(s)
- Christian Pehmøller
- Department of Exercise and Sport Sciences, Molecular Physiology Group, University of Copenhagen, Copenhagen, Denmark
| | - Nina Brandt
- Department of Exercise and Sport Sciences, Molecular Physiology Group, University of Copenhagen, Copenhagen, Denmark
| | - Jesper B. Birk
- Department of Exercise and Sport Sciences, Molecular Physiology Group, University of Copenhagen, Copenhagen, Denmark
| | - Louise D. Høeg
- Department of Exercise and Sport Sciences, Molecular Physiology Group, University of Copenhagen, Copenhagen, Denmark
| | - Kim A. Sjøberg
- Department of Exercise and Sport Sciences, Molecular Physiology Group, University of Copenhagen, Copenhagen, Denmark
| | - Laurie J. Goodyear
- Joslin Diabetes Center, Section on Metabolism, Harvard Medical School, Boston, Massachusetts
| | - Bente Kiens
- Department of Exercise and Sport Sciences, Molecular Physiology Group, University of Copenhagen, Copenhagen, Denmark
| | - Erik A. Richter
- Department of Exercise and Sport Sciences, Molecular Physiology Group, University of Copenhagen, Copenhagen, Denmark
| | - Jørgen F.P. Wojtaszewski
- Department of Exercise and Sport Sciences, Molecular Physiology Group, University of Copenhagen, Copenhagen, Denmark
- Corresponding author: Jørgen F.P. Wojtaszewski,
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43
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Rinnankoski-Tuikka R, Silvennoinen M, Torvinen S, Hulmi JJ, Lehti M, Kivelä R, Reunanen H, Kainulainen H. Effects of high-fat diet and physical activity on pyruvate dehydrogenase kinase-4 in mouse skeletal muscle. Nutr Metab (Lond) 2012; 9:53. [PMID: 22682013 PMCID: PMC3407034 DOI: 10.1186/1743-7075-9-53] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 06/09/2012] [Indexed: 01/19/2023] Open
Abstract
Background The expression of PDK4 is elevated by diabetes, fasting and other conditions associated with the switch from the utilization of glucose to fatty acids as an energy source. It is previously shown that peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a master regulator of energy metabolism, coactivates in cell lines pyruvate dehydrogenase kinase-4 (PDK4) gene expression via the estrogen-related receptor α (ERRα). We investigated the effects of long-term high-fat diet and physical activity on the expression of PDK4, PGC-1α and ERRα and the amount and function of mitochondria in skeletal muscle. Methods Insulin resistance was induced by a high-fat (HF) diet for 19 weeks in C57BL/6 J mice, which were either sedentary or with access to running wheels. The skeletal muscle expression levels of PDK4, PGC-1α and ERRα were measured and the quality and quantity of mitochondrial function was assessed. Results The HF mice were more insulin-resistant than the low-fat (LF) -fed mice. Upregulation of PDK4 and ERRα mRNA and protein levels were seen after the HF diet, and when combined with running even more profound effects on the mRNA expression levels were observed. Chronic HF feeding and voluntary running did not have significant effects on PGC-1α mRNA or protein levels. No remarkable difference was found in the amount or function of mitochondria. Conclusions Our results support the view that insulin resistance is not mediated by the decreased qualitative or quantitative properties of mitochondria. Instead, the role of PDK4 should be contemplated as a possible contributor to high-fat diet-induced insulin resistance.
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Affiliation(s)
- Rita Rinnankoski-Tuikka
- Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
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Muoio DM, Noland RC, Kovalik JP, Seiler SE, Davies MN, DeBalsi KL, Ilkayeva OR, Stevens RD, Kheterpal I, Zhang J, Covington JD, Bajpeyi S, Ravussin E, Kraus W, Koves TR, Mynatt RL. Muscle-specific deletion of carnitine acetyltransferase compromises glucose tolerance and metabolic flexibility. Cell Metab 2012; 15:764-77. [PMID: 22560225 PMCID: PMC3348515 DOI: 10.1016/j.cmet.2012.04.005] [Citation(s) in RCA: 271] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 11/18/2011] [Accepted: 04/09/2012] [Indexed: 02/04/2023]
Abstract
The concept of "metabolic inflexibility" was first introduced to describe the failure of insulin-resistant human subjects to appropriately adjust mitochondrial fuel selection in response to nutritional cues. This phenomenon has since gained increasing recognition as a core component of the metabolic syndrome, but the underlying mechanisms have remained elusive. Here, we identify an essential role for the mitochondrial matrix enzyme, carnitine acetyltransferase (CrAT), in regulating substrate switching and glucose tolerance. By converting acetyl-CoA to its membrane permeant acetylcarnitine ester, CrAT regulates mitochondrial and intracellular carbon trafficking. Studies in muscle-specific Crat knockout mice, primary human skeletal myocytes, and human subjects undergoing L-carnitine supplementation support a model wherein CrAT combats nutrient stress, promotes metabolic flexibility, and enhances insulin action by permitting mitochondrial efflux of excess acetyl moieties that otherwise inhibit key regulatory enzymes such as pyruvate dehydrogenase. These findings offer therapeutically relevant insights into the molecular basis of metabolic inflexibility.
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Affiliation(s)
- Deborah M Muoio
- Sarah W. Stedman Nutrition and Metabolism Center, Department of Medicine, Duke University, Durham, NC 27704, USA.
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45
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Fisher-Wellman KH, Neufer PD. Linking mitochondrial bioenergetics to insulin resistance via redox biology. Trends Endocrinol Metab 2012; 23:142-53. [PMID: 22305519 PMCID: PMC3313496 DOI: 10.1016/j.tem.2011.12.008] [Citation(s) in RCA: 237] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Revised: 12/21/2011] [Accepted: 12/22/2011] [Indexed: 12/28/2022]
Abstract
Chronic overnutrition and physical inactivity are major risk factors for insulin resistance and type 2 diabetes. Recent research indicates that overnutrition generates an increase in hydrogen peroxide (H(2)O(2)) emission from mitochondria, serving as a release valve to relieve the reducing pressure created by fuel overload, as well as a primary signal that ultimately decreases insulin sensitivity. H(2)O(2) is a major input to cellular redox circuits that link to cysteine residues throughout the entire proteome to regulate cell function. Here we review the principles of mitochondrial bioenergetics and redox systems biology and offer new insight into how H(2)O(2) emission may be linked via redox biology to the etiology of insulin resistance.
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Affiliation(s)
- Kelsey H. Fisher-Wellman
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC 27834, USA
- Department of Kinesiology, East Carolina University, Greenville, NC 27834, USA
| | - P. Darrell Neufer
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC 27834, USA
- Department of Kinesiology, East Carolina University, Greenville, NC 27834, USA
- Department of Physiology, East Carolina University, Greenville, NC 27834, USA
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Hoeks J, Mensink M, Hesselink MKC, Ekroos K, Schrauwen P. Long- and medium-chain fatty acids induce insulin resistance to a similar extent in humans despite marked differences in muscle fat accumulation. J Clin Endocrinol Metab 2012; 97:208-16. [PMID: 22031508 DOI: 10.1210/jc.2011-1884] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Animal studies revealed that medium-chain fatty acids (MCFA), due to their metabolic characteristics, are not stored in skeletal muscle and may therefore not give rise to potentially hazardous lipid species impeding insulin signaling. OBJECTIVE We here hypothesized that infusion of medium-chain triacylglycerols (MCT) in healthy lean subjects does not lead to ectopic fat accumulation and hence does not result in lipid-induced insulin resistance. DESIGN AND METHODS Nine healthy lean male subjects underwent a 6-h hyperinsulinemic-euglycemic clamp with simultaneous infusion of 1) a 100% long-chain triacylglycerols (LCT) emulsion, 2) a 50/50% MCT/LCT emulsion, or 3) glycerol in a randomized crossover design. Muscle biopsies were taken before and after each clamp. RESULTS MCT/LCT infusion raised plasma free fatty acid levels to a similar level compared with LCT infusion alone. Despite elevated free fatty acid levels, intramyocellular triacylglycerol (IMTG) levels were not affected by the MCT/LCT emulsion, whereas LCT infusion resulted in an approximately 1.6-fold increase in IMTG. These differences in muscle fat accumulation did not result in significant differences in lipid-induced insulin resistance between LCT (-28%, P = 0.003) and MCT/LCT (-20%, P < 0.001). Total skeletal muscle ceramide content as well as lactosyl- and glucosylceramide levels were not affected by any of the interventions. In addition, the distribution pattern of all ceramide species remained unaltered. CONCLUSIONS Although we confirm that MCFA do not lead to ceramide and IMTG accumulation in skeletal muscle tissue in humans, they do induce insulin resistance. These results indicate that, in humans, MCFA may not be beneficial in preventing peripheral insulin resistance.
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Affiliation(s)
- Joris Hoeks
- NUTRIM School for Nutrition, Toxicology, and Metabolism, Department of Human Biology, Maastricht University Medical Center, 6200 MD Maastricht, The Netherlands.
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47
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Abstract
In modern societies, oversupply of calories leads to obesity and chronic metabolic stress, which may lead to development of disease. Oversupply of calories is often associated with elevated plasma lipid concentrations and accumulation of lipids in skeletal muscle leading to decreased insulin sensitivity. Consequently, enhanced fat oxidation might be beneficial in counteracting lipid accumulation. Exercise is the most effective way to increase fat oxidation, because it increases metabolic rate. Lipid metabolism can also be altered by dietary manipulations. Thus, a fat rich diet leads to increased potential for fat oxidation by increasing the content of several of the proteins in the fat oxidative pathway. The regulation of both exercise and diet induced lipid oxidation will be discussed in this review.
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Affiliation(s)
- B Kiens
- Molecular Physiology Group, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark.
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48
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Abstract
Type 2 diabetes is now a pandemic and shows no signs of abatement. In this Seminar we review the pathophysiology of this disorder, with particular attention to epidemiology, genetics, epigenetics, and molecular cell biology. Evidence is emerging that a substantial part of diabetes susceptibility is acquired early in life, probably owing to fetal or neonatal programming via epigenetic phenomena. Maternal and early childhood health might, therefore, be crucial to the development of effective prevention strategies. Diabetes develops because of inadequate islet β-cell and adipose-tissue responses to chronic fuel excess, which results in so-called nutrient spillover, insulin resistance, and metabolic stress. The latter damages multiple organs. Insulin resistance, while forcing β cells to work harder, might also have an important defensive role against nutrient-related toxic effects in tissues such as the heart. Reversal of overnutrition, healing of the β cells, and lessening of adipose tissue defects should be treatment priorities.
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Affiliation(s)
- Christopher J Nolan
- Department of Endocrinology, Canberra Hospital and Australian National University Medical School, Canberra, ACT, Australia.
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49
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Kovalik JP, Slentz D, Stevens RD, Kraus WE, Houmard JA, Nicoll JB, Lea-Currie YR, Everingham K, Kien CL, Buehrer BM, Muoio DM. Metabolic remodeling of human skeletal myocytes by cocultured adipocytes depends on the lipolytic state of the system. Diabetes 2011; 60:1882-93. [PMID: 21602515 PMCID: PMC3121442 DOI: 10.2337/db10-0427] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Adipocyte infiltration of the musculoskeletal system is well recognized as a hallmark of aging, obesity, and type 2 diabetes. Intermuscular adipocytes might serve as a benign storage site for surplus lipid or play a role in disrupting energy homeostasis as a result of dysregulated lipolysis or secretion of proinflammatory cytokines. This investigation sought to understand the net impact of local adipocytes on skeletal myocyte metabolism. RESEARCH DESIGN AND METHODS Interactions between these two tissues were modeled using a coculture system composed of primary human adipocytes and human skeletal myotubes derived from lean or obese donors. Metabolic analysis of myocytes was performed after coculture with lipolytically silent or activated adipocytes and included transcript and metabolite profiling along with assessment of substrate selection and insulin action. RESULTS Cocultured adipocytes increased myotube mRNA expression of genes involved in oxidative metabolism, regardless of the donor and degree of lipolytic activity. Adipocytes in the basal state sequestered free fatty acids, thereby forcing neighboring myotubes to rely more heavily on glucose fuel. Under this condition, insulin action was enhanced in myotubes from lean but not obese donors. In contrast, when exposed to lipolytically active adipocytes, cocultured myotubes shifted substrate use in favor of fatty acids, which was accompanied by intracellular accumulation of triacylglycerol and even-chain acylcarnitines, decreased glucose oxidation, and modest attenuation of insulin signaling. CONCLUSIONS The effects of cocultured adipocytes on myocyte substrate selection and insulin action depended on the metabolic state of the system. These findings are relevant to understanding the metabolic consequences of intermuscular adipogenesis.
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Affiliation(s)
- Jean-Paul Kovalik
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University, Durham, North Carolina
| | - Dorothy Slentz
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University, Durham, North Carolina
| | - Robert D. Stevens
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University, Durham, North Carolina
| | - William E. Kraus
- Department of Cardiology, Duke University, Durham, North Carolina
| | - Joseph A. Houmard
- Human Performance Laboratory, Department of Exercise and Sport Science, East Carolina University, Greenville, North Carolina
| | | | | | - Karen Everingham
- Department of Medicine, University of Vermont, Burlington, Vermont
| | - C. Lawrence Kien
- Department of Medicine, University of Vermont, Burlington, Vermont
- Department of Pediatrics, University of Vermont, Burlington, Vermont
| | | | - Deborah M. Muoio
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University, Durham, North Carolina
- Department of Medicine, Duke University, Durham, North Carolina
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina
- Corresponding author: Deborah M. Muoio,
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50
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Wright LE, Brandon AE, Hoy AJ, Forsberg GB, Lelliott CJ, Reznick J, Löfgren L, Oscarsson J, Strömstedt M, Cooney GJ, Turner N. Amelioration of lipid-induced insulin resistance in rat skeletal muscle by overexpression of Pgc-1β involves reductions in long-chain acyl-CoA levels and oxidative stress. Diabetologia 2011; 54:1417-26. [PMID: 21331471 DOI: 10.1007/s00125-011-2068-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Accepted: 01/06/2011] [Indexed: 02/08/2023]
Abstract
AIMS/HYPOTHESIS To determine if acute overexpression of peroxisome proliferator-activated receptor, gamma, coactivator 1 beta (Pgc-1β [also known as Ppargc1b]) in skeletal muscle improves insulin action in a rodent model of diet-induced insulin resistance. METHODS Rats were fed either a low-fat or high-fat diet (HFD) for 4 weeks. In vivo electroporation was used to overexpress Pgc-1β in the tibialis cranialis (TC) and extensor digitorum longus (EDL) muscles. Downstream effects of Pgc-1β on markers of mitochondrial oxidative capacity, oxidative stress and muscle lipid levels were characterised. Insulin action was examined ex vivo using intact muscle strips and in vivo via a hyperinsulinaemic-euglycaemic clamp. RESULTS Pgc-1β gene expression was increased >100% over basal levels. The levels of proteins involved in mitochondrial function, lipid metabolism and antioxidant defences, the activity of oxidative enzymes, and substrate oxidative capacity were all increased in muscles overexpressing Pgc-1β. In rats fed a HFD, increasing the levels of Pgc-1β partially ameliorated muscle insulin resistance, in association with decreased levels of long-chain acyl-CoAs (LCACoAs) and increased antioxidant defences. CONCLUSIONS Our data show that an increase in Pgc-1β expression in vivo activates a coordinated subset of genes that increase mitochondrial substrate oxidation, defend against oxidative stress and improve lipid-induced insulin resistance in skeletal muscle.
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Affiliation(s)
- L E Wright
- Diabetes & Obesity Research Program, Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, Sydney, NSW 2010, Australia
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