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Insulin resistance and mitochondrial function in skeletal muscle. Int J Biochem Cell Biol 2012; 45:11-5. [PMID: 23036788 DOI: 10.1016/j.biocel.2012.09.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 09/14/2012] [Accepted: 09/25/2012] [Indexed: 12/28/2022]
Abstract
The mechanism(s) behind the decreased ability of insulin to facilitate glucose uptake in insulin sensitive tissues as seen in type 2 diabetes is not resolved. With the rapidly increasing prevalence of this disease world-wide, and the many complications that follow the disease, large resources are used in the attempt to resolve the mechanisms of insulin resistance. In this context, a dysfunction of mitochondria in the skeletal muscle has been suggested to play a pivotal role. It has been postulated that a decrease in the content of mitochondria in the skeletal muscle can explain the insulin resistance. Complementary to this also specific defects of components in the respiratory chain in the mitochondria have been suggested to play a role in insulin resistance. A key element in these mechanistic suggestions is inability to handle substrate fluxes and subsequently an accumulation of ectopic intramyocellular lipids, interfering with insulin signaling. In this review we will present the prevailing view-points and argue for the unlikelihood of this scenario being instrumental in human insulin resistance. This article is part of a Directed Issue entitled: Bioenergetic dysfunction.
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202
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Phielix E, Meex R, Ouwens DM, Sparks L, Hoeks J, Schaart G, Moonen-Kornips E, Hesselink MK, Schrauwen P. High oxidative capacity due to chronic exercise training attenuates lipid-induced insulin resistance. Diabetes 2012; 61:2472-8. [PMID: 22787138 PMCID: PMC3447923 DOI: 10.2337/db11-1832] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Fat accumulation in skeletal muscle combined with low mitochondrial oxidative capacity is associated with insulin resistance (IR). Endurance-trained athletes, characterized by a high oxidative capacity, have elevated intramyocellular lipids, yet are highly insulin sensitive. We tested the hypothesis that a high oxidative capacity could attenuate lipid-induced IR. Nine endurance-trained (age = 23.4 ± 0.9 years; BMI = 21.2 ± 0.6 kg/m(2)) and 10 untrained subjects (age = 21.9 ± 0.9 years; BMI = 22.8 ± 0.6 kg/m(2)) were included and underwent a clamp with either infusion of glycerol or intralipid. Muscle biopsies were taken to perform high-resolution respirometry and protein phosphorylation/expression. Trained subjects had ~32% higher mitochondrial capacity and ~22% higher insulin sensitivity (P < 0.05 for both). Lipid infusion reduced insulin-stimulated glucose uptake by 63% in untrained subjects (P < 0.05), whereas this effect was blunted in trained subjects (29%, P < 0.05). In untrained subjects, lipid infusion reduced oxidative and nonoxidative glucose disposal (NOGD), whereas trained subjects were completely protected against lipid-induced reduction in NOGD, supported by dephosphorylation of glycogen synthase. We conclude that chronic exercise training attenuates lipid-induced IR and specifically attenuates the lipid-induced reduction in NOGD. Signaling data support the notion that high glucose uptake in trained subjects is maintained by shuttling glucose toward storage as glycogen.
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Affiliation(s)
- Esther Phielix
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Ruth Meex
- Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands
| | - D. Margriet Ouwens
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Dusseldorf, Germany
| | - Lauren Sparks
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Joris Hoeks
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Gert Schaart
- Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Esther Moonen-Kornips
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands
- Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Matthijs K.C. Hesselink
- Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Patrick Schrauwen
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands
- Corresponding author: Patrick Schrauwen,
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203
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de Mol P, Fokkert MJ, de Vries ST, de Koning EJP, Dikkeschei BD, Gans ROB, Tack CJ, Bilo HJG. Metabolic effects of high altitude trekking in patients with type 2 diabetes. Diabetes Care 2012; 35:2018-20. [PMID: 22829523 PMCID: PMC3447827 DOI: 10.2337/dc12-0204] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Limited information is available regarding the metabolic effects of high altitude trekking in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS Thirteen individuals with type 2 diabetes took part in a 12-day expedition to the summit of Mount Toubkal (altitude, 4,167 m), Morocco, after 6 months of exercise training. Energy expenditure, body weight, blood glucose, fasting insulin, lipids, and HbA(1c) were assessed. RESULTS Training reduced fasting glucose (-0.7 ± 0.9 mmol/L, P = 0.026) and increased exercise capacity (+0.3 ± 0.3 W/kg, P = 0.005). High altitude trekking decreased fasting insulin concentrations (-3.8 ± 3.2 μU/L, P = 0.04), total cholesterol (-0.7 ± 0.8 mmol/L, P = 0.008), and LDL cholesterol (-0.5 ± 0.6 mmol/L, P = 0.007). CONCLUSIONS High altitude trekking preceded by exercise training is feasible for patients with type 2 diabetes. It improves blood glucose, lipids, and fasting insulin concentrations, while glucose control is maintained.
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Affiliation(s)
- Pieter de Mol
- Department of Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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204
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Hoeks J, Schrauwen P. Muscle mitochondria and insulin resistance: a human perspective. Trends Endocrinol Metab 2012; 23:444-50. [PMID: 22726362 DOI: 10.1016/j.tem.2012.05.007] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 05/16/2012] [Accepted: 05/21/2012] [Indexed: 01/07/2023]
Abstract
Reduced mitochondrial capacity in skeletal muscle has been suggested to underlie the development of insulin resistance and type 2 diabetes mellitus (T2DM). However, data obtained from human subjects concerning this putative relation indicate that the mitochondrial defect observed in diabetic muscle might be secondary to the insulin-resistant state instead of being a causal factor. Nonetheless, diminished mitochondrial function, even secondary to insulin resistance, may accelerate lipid deposition in non-adipose tissues and aggravate insulin resistance. Indeed, improving mitochondrial capacity via exercise training and calorie restriction is associated with positive metabolic health effects. Here we review muscle mitochondrial dysfunction in humans and propose that targeting muscle mitochondria to improve muscle oxidative capacity should be considered as a strategy for improving metabolic health.
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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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205
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van Tienen FHJ, Praet SFE, de Feyter HM, van den Broek NM, Lindsey PJ, Schoonderwoerd KGC, de Coo IFM, Nicolay K, Prompers JJ, Smeets HJM, van Loon LJC. Physical activity is the key determinant of skeletal muscle mitochondrial function in type 2 diabetes. J Clin Endocrinol Metab 2012; 97:3261-9. [PMID: 22802091 DOI: 10.1210/jc.2011-3454] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Conflicting data exist on mitochondrial function and physical activity in type 2 diabetes mellitus (T2DM) development. OBJECTIVE The aim was to assess mitochondrial function at different stages during T2DM development in combination with physical exercise in longstanding T2DM patients. DESIGN AND METHODS We performed cross-sectional analysis of skeletal muscle from 12 prediabetic 11 longstanding T2DM male subjects and 12 male controls matched by age and body mass index. INTERVENTION One-year intrasubject controlled supervised exercise training intervention was done in longstanding T2DM patients. MAIN OUTCOME MEASUREMENTS Extensive ex vivo analyses of mitochondrial quality, quantity, and function were collected and combined with global gene expression analysis and in vivo ATP production capacity after 1 yr of training. RESULTS Mitochondrial density, complex I activity, and the expression of Krebs cycle and oxidative phosphorylation system-related genes were lower in longstanding T2DM subjects but not in prediabetic subjects compared with controls. This indicated a reduced capacity to generate ATP in longstanding T2DM patients only. Gene expression analysis in prediabetic subjects suggested a switch from carbohydrate toward lipid as an energy source. One year of exercise training raised in vivo skeletal muscle ATP production capacity by 21 ± 2% with an increased trend in mitochondrial density and complex I activity. In addition, expression levels of β-oxidation, Krebs cycle, and oxidative phosphorylation system-related genes were higher after exercise training. CONCLUSIONS Mitochondrial dysfunction is apparent only in inactive longstanding T2DM patients, which suggests that mitochondrial function and insulin resistance do not depend on each other. Prolonged exercise training can, at least partly, reverse the mitochondrial impairments associated with the longstanding diabetic state.
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Affiliation(s)
- F H J van Tienen
- Department of Genetics and Cell Biology, Maastricht University Medical Centre, 6200 MD Maastricht, The Netherlands
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206
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Abstract
Magnetic resonance spectroscopy (MRS) methods offer a potentially valuable window into cellular metabolism. Measurement of flux between inorganic phosphate (Pi) and ATP using (31)P MRS magnetization transfer has been used in resting muscle to assess what is claimed to be mitochondrial ATP synthesis and has been particularly popular in the study of insulin effects and insulin resistance. However, the measured Pi→ATP flux in resting skeletal muscle is far higher than the true rate of oxidative ATP synthesis, being dominated by a glycolytically mediated Pi↔ATP exchange reaction that is unrelated to mitochondrial function. Furthermore, even if measured accurately, the ATP production rate in resting muscle has no simple relationship to mitochondrial capacity as measured either ex vivo or in vivo. We summarize the published measurements of Pi→ATP flux, concentrating on work relevant to diabetes and insulin, relate it to current understanding of the physiology of mitochondrial ATP synthesis and glycolytic Pi↔ATP exchange, and discuss some possible implications of recently reported correlations between Pi→ATP flux and other physiological measures.
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Affiliation(s)
- Graham J Kemp
- Department of Musculoskeletal Biology and Magnetic Resonance and Image Analysis Research Centre, University of Liverpool, Liverpool, UK.
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207
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Kolb H. Resistance to diabetes-promoting lifestyle factors -- what is the mechanism? Diabetes Res Clin Pract 2012; 97:172-4. [PMID: 22771053 DOI: 10.1016/j.diabres.2012.06.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 06/14/2012] [Indexed: 11/21/2022]
Abstract
Not all people exposed to diabetes-promoting lifestyle factors progress to overt type 2 diabetes. The emerging concept of hormesis provides an explanation for the resistance to metabolic stress. Hormesis requires limited stress or damage which elicits an adaptive repair and protective response which renders the organism resistant to further metabolic stress.
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Affiliation(s)
- Hubert Kolb
- Immunobiology Research Group, Institute of Molecular Medicine, University of Düsseldorf, D-4001 Düsseldorf, Germany.
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208
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Hutchison SK, Teede HJ, Rachoń D, Harrison CL, Strauss BJ, Stepto NK. Effect of exercise training on insulin sensitivity, mitochondria and computed tomography muscle attenuation in overweight women with and without polycystic ovary syndrome. Diabetologia 2012; 55:1424-34. [PMID: 22246378 DOI: 10.1007/s00125-011-2442-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Accepted: 12/09/2011] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS Polycystic ovary syndrome (PCOS) is an insulin resistant (IR) state. Increased skeletal muscle lipid content and impaired mitochondrial biogenesis have been implicated in the pathogenesis of IR. We investigated whether differences in these variables explain the IR of women affected by PCOS and whether improvements in IR with exercise are reflected by changes in these variables. METHODS Sixteen PCOS and 13 non-PCOS overweight women were assessed, and eight PCOS and seven non-PCOS women were reassessed after 12 weeks of moderate and vigorous exercise training. Outcomes included insulin sensitivity (glucose infusion rate [GIR]), skeletal muscle gene expression and protein abundance, enzyme activity of selected mitochondrial components, and computed tomography (CT) attenuation-estimated muscle lipid. RESULTS GIR was lower in women with PCOS versus those without (p = 0.01) and increased with exercise in both groups. Baseline CT muscle attenuation suggested a trend to less muscle lipid in PCOS, which increased with exercise training, with a difference in the change in muscle lipid (p = 0.01, age-corrected), compared with non-PCOS women. GIR correlated with PGC1A gene expression across the whole group; skeletal muscle expression of mitochondrial biogenesis markers was not different between groups at baseline, or after training. Neither lipid changes nor mitochondrial changes correlated with changes in GIR. CONCLUSIONS/INTERPRETATION Differences in IR in women with and without PCOS were not explained by differences in skeletal muscle lipid or mitochondrial parameters. Improvements in IR with exercise were dissociated from mitochondrial parameters. CT muscle attenuation suggested a differential capacity of PCOS muscle to store lipid compared with non-PCOS. TRIAL REGISTRATION Clinicaltrials.gov ISRCTN84763265. FUNDING National Health & Medical Research Council (Grant number 606553), Monash University and The Jean Hailes Foundation.
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Affiliation(s)
- S K Hutchison
- Jean Hailes Foundation Research, School of Public Health and Preventative Medicine, Monash University, Melbourne, VIC, Australia
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209
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Abstract
There is now evidence that a single bout of endurance (aerobic) or resistance exercise reduces 24 h post-exercise subcutaneous glucose profiles to the same extent in insulin-resistant humans with or without type 2 diabetes. However, it remains to be determined which group would benefit most from specific exercise protocols, particularly with regard to long-term glycaemic control. Acute aerobic exercise first accelerates translocation of myocellular glucose transporters via AMP-activated protein kinase, calcium release and mitogen-activated protein kinase, but also improves insulin-dependent glucose transport/phosphorylation via distal components of insulin signalling (phosphoinositide-dependent kinase 1, TBC1 domain family, members 1 and 4, Rac1, protein kinase C). Post-exercise effects involve peroxisome-proliferator activated receptor-γ coactivator 1α and lead to ATP synthesis, which may be modulated by variants in genes such as NDUFB6. While mechanisms of acute resistance-type exercise are less clear, chronic resistance training activates the mammalian target of rapamycin/serine kinase 6 pathway, ultimately increasing protein synthesis and muscle mass. Over the long term, adherence to rather than differences in metabolic variables between specific modes of regular exercise might ultimately determine their efficacy. Taken together, studies are now needed to address the variability of individual responses to long-term resistance and endurance training in real life.
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Affiliation(s)
- M Roden
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich-Heine University, 40225 Düsseldorf, Germany.
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210
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Hoeks J, Arany Z, Phielix E, Moonen-Kornips E, Hesselink MKC, Schrauwen P. Enhanced lipid-but not carbohydrate-supported mitochondrial respiration in skeletal muscle of PGC-1α overexpressing mice. J Cell Physiol 2012; 227:1026-33. [PMID: 21520076 DOI: 10.1002/jcp.22812] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Skeletal muscle mitochondrial dysfunction has been linked to several disease states as well as the process of aging. A possible factor involved is the peroxisome proliferator-activated receptor (PPAR) γ co-activator 1α (PGC-1α), a major player in the regulation of skeletal muscle mitochondrial metabolism. However, it is currently unknown whether PGC-1α, besides stimulating mitochondrial proliferation, also affects the functional capacity per mitochondrion. Therefore, we here tested whether PGC-1α overexpression, besides increasing mitochondrial content, also leads to intrinsic mitochondrial adaptations. Skeletal muscle mitochondria from 10 male, muscle-specific PGC-1α overexpressing mice (PGC-1αTg) and 8 wild-type (WT) mice were isolated. Equal mitochondrial quantities were then analyzed for their oxidative capacity by high-resolution respirometry, fuelled by a carbohydrate-derived (pyruvate) and a lipid (palmitoyl-CoA plus carnitine) substrate. Additionally, mitochondria were tested for reactive oxygen species (superoxide) production and fatty acid (FA)-induced uncoupling. PGC-1αTg mitochondria were characterized by an improved intrinsic mitochondrial fat oxidative capacity as evidenced by pronounced increase in ADP-stimulated respiration (P < 0.001) and maximal uncoupled respiration (P < 0.001) upon palmitoyl-CoA plus carnitine. Interestingly, intrinsic mitochondrial capacity on a carbohydrate-derived substrate tended to be reduced. Furthermore, the sensitivity to FA-induced uncoupling was diminished in PGC-1αTg mitochondria (P = 0.02) and this was accompanied by a blunted reduction in mitochondrial ROS production upon FAs in PGC-1αTg versus WT mitochondria (P = 0.04). Uncoupling protein 3 (UCP3) levels were markedly reduced in PGC-1αTg mitochondria (P < 0.001). Taken together, in addition to stimulating mitochondrial proliferation in skeletal muscle, we show here that overexpression of PGC-1α leads to intrinsic mitochondrial adaptations that seem restricted to fat metabolism.
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Affiliation(s)
- Joris Hoeks
- NUTRIM-School for Nutrition, Toxicology and Metabolism, Department of Human Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
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211
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Toth MJ, Miller MS, Ward KA, Ades PA. Skeletal muscle mitochondrial density, gene expression, and enzyme activities in human heart failure: minimal effects of the disease and resistance training. J Appl Physiol (1985) 2012; 112:1864-74. [PMID: 22461439 DOI: 10.1152/japplphysiol.01591.2011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Impaired skeletal muscle energetics could adversely affect physical and metabolic function in patients with heart failure (HF). The effect of HF on aspects of mitochondrial structure and function, independent of muscle disuse and other disease-related confounding factors, however, is unclear. Moreover, no study has evaluated whether resistance exercise training, a modality that increases functional capacity, might derive its benefits through modulation of mitochondrial structure and function. Thirteen HF patients and 14 age- and physical activity-matched controls were evaluated for skeletal muscle mitochondrial size/content, gene expression, and enzyme activity before and after an 18-wk resistance exercise-training program. At baseline, HF patients and controls had similar mitochondrial fractional areas, although HF patients had larger average mitochondrion size (P < 0.05) and a trend toward a reduced number of mitochondria (P ≤ 0.10). No differences in the expression of transcriptional regulators or cytochrome oxidase subunits or the activity of mitochondrial and cytosolic enzymes were noted. Relationships among transcriptional regulators suggested that networks controlling mitochondrial content and gene expression are intact. Resistance training increased (P < 0.01) mitochondrial transcription factor A expression in patients and controls, and this increase was related to improvements in muscle strength (P = 0.05). Training did not, however, alter mitochondrial size/content, enzyme activities, or expression of other transcriptional regulators. In conclusion, our results suggest that the HF syndrome has minimal effects on skeletal muscle mitochondrial biology when the confounding effects of muscle disuse and other disease-related factors are removed. Moreover, the beneficial effects of resistance training on physical function in HF patients and controls are likely not related to alterations in mitochondrial biology.
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Affiliation(s)
- Michael J Toth
- Department of Medicine, College of Medicine, University of Vermont, Burlington, VT, USA
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212
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Kacerovsky-Bielesz G, Kacerovsky M, Chmelik M, Farukuoye M, Ling C, Pokan R, Tschan H, Szendroedi J, Schmid AI, Gruber S, Herder C, Wolzt M, Moser E, Pacini G, Smekal G, Groop L, Roden M. A single nucleotide polymorphism associates with the response of muscle ATP synthesis to long-term exercise training in relatives of type 2 diabetic humans. Diabetes Care 2012; 35:350-7. [PMID: 22190678 PMCID: PMC3263890 DOI: 10.2337/dc11-1426] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Myocellular ATP synthesis (fATP) associates with insulin sensitivity in first-degree relatives of subjects with type 2 diabetes. Short-term endurance training can modify their fATP and insulin sensitivity. This study examines the effects of moderate long-term exercise using endurance or resistance training in this cohort. RESEARCH DESIGN AND METHODS A randomized, parallel-group trial tested 16 glucose-tolerant nonobese relatives (8 subjects in the endurance training group and 8 subjects in the resistance training group) before and after 26 weeks of endurance or resistance training. Exercise performance was assessed from power output and oxygen uptake (VO(2)) during incremental tests and from maximal torque of knee flexors (MaxT(flex)) and extensors (MaxT(ext)) using isokinetic dynamometry. fATP and ectopic lipids were measured with (1)H/(31)P magnetic resonance spectroscopy. RESULTS Endurance training increased power output and VO(2) by 44 and 30%, respectively (both P < 0.001), whereas resistance training increased MaxT(ext) and MaxT(flex) by 23 and 40%, respectively (both P < 0.001). Across all groups, insulin sensitivity (382 ± 90 vs. 389 ± 40 mL · min(-1) · m(-2)) and ectopic lipid contents were comparable after exercise training. However, 8 of 16 relatives had 26% greater fATP, increasing from 9.5 ± 2.3 to 11.9 ± 2.4 μmol · mL(-1) · m(-1) (P < 0.05). Six of eight responders were carriers of the G/G single nucleotide polymorphism rs540467 of the NDUFB6 gene (P = 0.019), which encodes a subunit of mitochondrial complex I. CONCLUSIONS Moderate exercise training for 6 months does not necessarily improve insulin sensitivity but may increase ATP synthase flux. Genetic predisposition can modify the individual response of the ATP synthase flux independently of insulin sensitivity.
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Affiliation(s)
- Gertrud Kacerovsky-Bielesz
- Karl-Landsteiner Institute for Endocrinology and Metabolism and 1st Medical Department, Hanusch Hospital, Vienna, Austria
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213
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Re-evaluating lipotoxic triggers in skeletal muscle: Relating intramyocellular lipid metabolism to insulin sensitivity. Prog Lipid Res 2012; 51:36-49. [DOI: 10.1016/j.plipres.2011.11.003] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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214
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Role of mitochondrial function in insulin resistance. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 942:215-34. [PMID: 22399424 DOI: 10.1007/978-94-007-2869-1_9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The obesity pandemic increases the prevalence of type 2 diabetes (DM2).DM2 develops when pancreatic β-cells fail and cannot compensate for the decrease in insulin sensitivity. How excessive caloric intake and weight gain cause insulin resistance has not completely been elucidated.Skeletal muscle is responsible for a major part of insulin stimulated whole-body glucose disposal and, hence, plays an important role in the pathogenesis of insulin resistance.It has been hypothesized that skeletal muscle mitochondrial dysfunction is involved in the accumulation of intramyocellular lipid metabolites leading to lipotoxicity and insulin resistance. However, findings on skeletal muscle mitochondrial function in relation to insulin resistance in human subjects are inconclusive. Differences in mitochondrial activity can be the result of several factors, including a reduced mitochondrial density, differences in insulin stimulated mitochondrial respiration, lower energy demand or reduced skeletal muscle perfusion, besides an intrinsic mitochondrial defect. The inconclusive results may be explained by the use of different techniques and study populations. Also, mitochondrial capacity is in far excess to meet energy requirements and therefore it may be questioned whether a reduced mitochondrial capacity limits mitochondrial fatty acid oxidation. Whether reduced mitochondrial function is causally related to insulin resistance or rather a consequence of the sedentary lifestyle remains to be elucidated.
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215
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Abstract
In vertebrates, adipose tissue is the main storage site for lipids within specialized lipid-laden mature adipocytes. While many species have evolved cells capable of lipid storage, the adipocyte represents a unique specialized cell involved in fuel storage, endocrine, nervous and immune function. However, the adipocytes are not the only cell type in mammals that can accumulate lipid droplets. The ectopic accumulation of lipid in non-adipose tissues including the liver, skeletal muscle, bone, pancreas, and heart in combination with its excessive accumulation in adipose tissue contributes to metabolic disease. Determining the lipid processing components that are necessary and sufficiently for lipid accumulation in adipose and non-adipose tissues, in addition to endocrine function, will lead to a clearer definition of an adipocyte.
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216
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Snel M, Jonker JT, Schoones J, Lamb H, de Roos A, Pijl H, Smit JWA, Meinders AE, Jazet IM. Ectopic fat and insulin resistance: pathophysiology and effect of diet and lifestyle interventions. Int J Endocrinol 2012; 2012:983814. [PMID: 22675355 PMCID: PMC3366269 DOI: 10.1155/2012/983814] [Citation(s) in RCA: 185] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 01/16/2012] [Accepted: 01/17/2012] [Indexed: 12/15/2022] Open
Abstract
The storage of triglyceride (TG) droplets in nonadipose tissues is called ectopic fat storage. Ectopic fat is associated with insulin resistance and type 2 diabetes mellitus (T2DM). Not the triglycerides per se but the accumulation of intermediates of lipid metabolism in organs, such as the liver, skeletal muscle, and heart seem to disrupt metabolic processes and impair organ function. We describe the mechanisms of ectopic fat depositions in the liver, skeletal muscle, and in and around the heart and the consequences for each organs function. In addition, we systematically reviewed the literature for the effects of diet-induced weight loss and exercise on ectopic fat depositions.
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Affiliation(s)
- M. Snel
- Departments of Endocrinology & Metabolism and General Internal Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - J. T. Jonker
- Departments of Endocrinology & Metabolism and General Internal Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - J. Schoones
- Walaeus Library, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - H. Lamb
- Department of Radiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - A. de Roos
- Department of Radiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - H. Pijl
- Departments of Endocrinology & Metabolism and General Internal Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - J. W. A. Smit
- Departments of Endocrinology & Metabolism and General Internal Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - A. E. Meinders
- Departments of Endocrinology & Metabolism and General Internal Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - I. M. Jazet
- Departments of Endocrinology & Metabolism and General Internal Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
- *I. M. Jazet:
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217
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Hesselink MKC, Schrauwen P. Diet or diet plus physical activity in patients with early type 2 diabetes. Lancet 2011; 378:2066-7; author reply 2067-8. [PMID: 22177505 DOI: 10.1016/s0140-6736(11)61892-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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218
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Lim EL, Hollingsworth KG, Smith FE, Thelwall PE, Taylor R. Effects of raising muscle glycogen synthesis rate on skeletal muscle ATP turnover rate in type 2 diabetes. Am J Physiol Endocrinol Metab 2011; 301:E1155-62. [PMID: 21917633 PMCID: PMC3233777 DOI: 10.1152/ajpendo.00278.2011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mitochondrial dysfunction has been implicated in the pathogenesis of type 2 diabetes. We hypothesized that any impairment in insulin-stimulated muscle ATP production could merely reflect the lower rates of muscle glucose uptake and glycogen synthesis, rather than cause it. If this is correct, muscle ATP turnover rates in type 2 diabetes could be increased if glycogen synthesis rates were normalized by the mass-action effect of hyperglycemia. Isoglycemic- and hyperglycemic-hyperinsulinemic clamps were performed on type 2 diabetic subjects and matched controls, with muscle ATP turnover and glycogen synthesis rates measured using (31)P- and (13)C-magnetic resonance spectroscopy, respectively. In diabetic subjects, hyperglycemia increased muscle glycogen synthesis rates to the level observed in controls at isoglycemia [from 19 ± 9 to 41 ± 12 μmol·l(-1)·min(-1) (P = 0.012) vs. 40 ± 7 μmol·l(-1)·min(-1) in controls]. This was accompanied by a modest increase in muscle ATP turnover rates (7.1 ± 0.5 vs. 8.6 ± 0.7 μmol·l(-1)·min(-1), P = 0.04). In controls, hyperglycemia brought about a 2.5-fold increase in glycogen synthesis rates (100 ± 24 vs. 40 ± 7 μmol·l(-1)·min(-1), P = 0.028) and a 23% increase in ATP turnover rates (8.1 ± 0.9 vs. 10.0 ± 0.9 μmol·l(-1)·min(-1), P = 0.025) from basal state. Muscle ATP turnover rates correlated positively with glycogen synthesis rates (r(s) = 0.46, P = 0.005). Changing the rate of muscle glucose metabolism in type 2 diabetic subjects alters demand for ATP synthesis at rest. In type 2 diabetes, skeletal muscle ATP turnover rates reflect the rate of glucose uptake and glycogen synthesis, rather than any primary mitochondrial defect.
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Affiliation(s)
- Ee L Lim
- Institute of Cellular Medicine, Newcastle Magnetic Resonance Centre, Newcastle University, Newcastle upon Tyne, United Kingdom
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219
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Timmers S, Konings E, Bilet L, Houtkooper RH, van de Weijer T, Goossens GH, Hoeks J, van der Krieken S, Ryu D, Kersten S, Moonen-Kornips E, Hesselink MKC, Kunz I, Schrauwen-Hinderling VB, Blaak E, Auwerx J, Schrauwen P. Calorie restriction-like effects of 30 days of resveratrol supplementation on energy metabolism and metabolic profile in obese humans. Cell Metab 2011; 14:612-22. [PMID: 22055504 PMCID: PMC3880862 DOI: 10.1016/j.cmet.2011.10.002] [Citation(s) in RCA: 938] [Impact Index Per Article: 72.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2011] [Revised: 09/20/2011] [Accepted: 10/11/2011] [Indexed: 12/13/2022]
Abstract
Resveratrol is a natural compound that affects energy metabolism and mitochondrial function and serves as a calorie restriction mimetic, at least in animal models of obesity. Here, we treated 11 healthy, obese men with placebo and 150 mg/day resveratrol (resVida) in a randomized double-blind crossover study for 30 days. Resveratrol significantly reduced sleeping and resting metabolic rate. In muscle, resveratrol activated AMPK, increased SIRT1 and PGC-1α protein levels, increased citrate synthase activity without change in mitochondrial content, and improved muscle mitochondrial respiration on a fatty acid-derived substrate. Furthermore, resveratrol elevated intramyocellular lipid levels and decreased intrahepatic lipid content, circulating glucose, triglycerides, alanine-aminotransferase, and inflammation markers. Systolic blood pressure dropped and HOMA index improved after resveratrol. In the postprandial state, adipose tissue lipolysis and plasma fatty acid and glycerol decreased. In conclusion, we demonstrate that 30 days of resveratrol supplementation induces metabolic changes in obese humans, mimicking the effects of calorie restriction.
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Affiliation(s)
- Silvie Timmers
- Top Institute Food and Nutrition (TIFN), 6700 Wageningen, The Netherlands.,Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Ellen Konings
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Lena Bilet
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Riekelt H Houtkooper
- Laboratory for Integrative and Systems Physiology, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Tineke van de Weijer
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Gijs H Goossens
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Joris Hoeks
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Sophie van der Krieken
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Dongryeol Ryu
- Laboratory for Integrative and Systems Physiology, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Sander Kersten
- Nutrition, Metabolism, and Genomics Group, Division of Human Nutrition, Wageningen University, 6700 Wageningen, The Netherlands
| | - Esther Moonen-Kornips
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Matthijs K C Hesselink
- Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Iris Kunz
- DSM Nutritional Products Ltd., 4303 Kaiseraugst, Switzerland
| | - Vera B Schrauwen-Hinderling
- Radiology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Ellen Blaak
- Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
| | - Johan Auwerx
- Laboratory for Integrative and Systems Physiology, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Patrick Schrauwen
- Top Institute Food and Nutrition (TIFN), 6700 Wageningen, The Netherlands.,Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, 6200 Maastricht, The Netherlands
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Abstract
Type 2 diabetes mellitus is characterized by subclinical systemic inflammation and impaired regulation of blood glucose levels. Interestingly, impairment of glycemic control occurs despite substantial insulin secretion early in the course of this disease. Dysfunction of several organs (including pancreatic islets, liver, skeletal muscle, adipose tissue, gut, hypothalamus and the immune system) has been implicated in the pathogenesis of type 2 diabetes mellitus. However, diabetes-promoting lifestyle factors do not inevitably cause disease in all persons exposed. Hence, defense mechanisms must exist that can keep the detrimental influence of these risk factors at bay. Hormesis describes the phenomenon that exposure to a mild stressor confers resistance to subsequent, otherwise harmful, conditions of increased stress. This Review discusses the emerging concept that the effectiveness of an adaptive (hormetic) response to detrimental lifestyle factors determines the extent of protection from progression to type 2 diabetes mellitus. Further analysis of these protective hormetic responses at the molecular level should help to identify novel targets for preventive or therapeutic intervention in patients at risk of developing type 2 diabetes mellitus or those with overt disease.
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Affiliation(s)
- Hubert Kolb
- Immunobiology Research Group, Institute of Molecular Medicine, University of Düsseldorf, D-40001 Düsseldorf, Germany.
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221
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Szendroedi J, Phielix E, Roden M. The role of mitochondria in insulin resistance and type 2 diabetes mellitus. Nat Rev Endocrinol 2011; 8:92-103. [PMID: 21912398 DOI: 10.1038/nrendo.2011.138] [Citation(s) in RCA: 415] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Type 2 diabetes mellitus (T2DM) has been related to alterations of oxidative metabolism in insulin-responsive tissues. Overt T2DM can present with acquired or inherited reductions of mitochondrial oxidative phosphorylation capacity, submaximal ADP-stimulated oxidative phosphorylation and plasticity of mitochondria and/or lower mitochondrial content in skeletal muscle cells and potentially also in hepatocytes. Acquired insulin resistance is associated with reduced insulin-stimulated mitochondrial activity as the result of blunted mitochondrial plasticity. Hereditary insulin resistance is frequently associated with reduced mitochondrial activity at rest, probably due to diminished mitochondrial content. Lifestyle and pharmacological interventions can enhance the capacity for oxidative phosphorylation and mitochondrial content and improve insulin resistance in some (pre)diabetic cases. Various mitochondrial features can be abnormal but are not necessarily responsible for all forms of insulin resistance. Nevertheless, mitochondrial abnormalities might accelerate progression of insulin resistance and subsequent organ dysfunction via increased production of reactive oxygen species. This Review discusses the association between mitochondrial function and insulin sensitivity in various tissues, such as skeletal muscle, liver and heart, with a main focus on studies in humans, and addresses the effects of therapeutic strategies that affect mitochondrial function and insulin sensitivity.
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Affiliation(s)
- Julia Szendroedi
- Institute for Clinical Diabetology, German Diabetes Center, D-40225 Düsseldorf, Germany
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222
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Eckardt K, Taube A, Eckel J. Obesity-associated insulin resistance in skeletal muscle: role of lipid accumulation and physical inactivity. Rev Endocr Metab Disord 2011; 12:163-72. [PMID: 21336841 DOI: 10.1007/s11154-011-9168-2] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
An alarming increase in the prevalence of obesity, type 2 diabetes mellitus, and associated diseases can be observed world-wide during the past 20 years. In obesity, profound alterations in the secretion profile of adipokines and inflammatory markers as well as increased lipolysis occur, leading besides other events to elevated levels of free fatty acids, which in turn are distributed to nonadipose tissue such as skeletal muscle. While the amount of intramyocellular lipids can be used as a marker of insulin resistance in physical inactive individuals, these neutral triglycerides themselves are not thought to be harmful. However, they provide a source for the generation of harmful lipid metabolites such as diacylglycerol and ceramide, which are implicated in insulin resistance by perturbing insulin signaling pathways. In this review, we will discuss the role of lipid metabolites in insulin resistance and potential mechanism involved in accumulation of intramyocellular lipids. Furthermore, we will highlight the key role of PGC-1α, which is a master regulator of mitochondrial biogenesis and coordinates the activation of genes involved in oxidative energy production as well as genes involved in fiber type transformation. Finally, the role of exercise in stimulating PGC-1α activity and expression as well as the release of contraction-induced myokines is discussed.
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Affiliation(s)
- Kristin Eckardt
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Duesseldorf, Germany.
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223
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Haus JM, Solomon TPJ, Lu L, Jesberger JA, Barkoukis H, Flask CA, Kirwan JP. Intramyocellular lipid content and insulin sensitivity are increased following a short-term low-glycemic index diet and exercise intervention. Am J Physiol Endocrinol Metab 2011; 301:E511-6. [PMID: 21712533 PMCID: PMC3174532 DOI: 10.1152/ajpendo.00221.2011] [Citation(s) in RCA: 30] [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: 05/04/2011] [Accepted: 06/27/2011] [Indexed: 12/31/2022]
Abstract
The relationship between intramyocellular (IMCL) and extramyocellular lipid (EMCL) accumulation and skeletal muscle insulin resistance is complex and dynamic. We examined the effect of a short-term (7-day) low-glycemic index (LGI) diet and aerobic exercise training intervention (EX) on IMCL and insulin sensitivity in older, insulin-resistant humans. Participants (66 ± 1 yr, BMI 33 ± 1 kg/m(2)) were randomly assigned to a parallel, controlled feeding trial [either an LGI (LGI/EX, n = 7) or high GI (HGI/EX, n = 8) eucaloric diet] combined with supervised exercise (60 min/day, 85% HR(max)). Insulin sensitivity was determined via 40 mU·m(-2)·min(-1) hyperinsulinemic euglycemic clamp and soleus IMCL and EMCL content was assessed by (1)H-MR spectroscopy with correction for fiber orientation. BMI decreased (kg/m(2) -0.6 ± 0.2, LGI/EX; -0.7 ± 0.2, HGI/EX P < 0.0004) after both interventions with no interaction effect of diet composition. Clamp-derived insulin sensitivity increased by 0.91 ± 0.21 (LGI/EX) and 0.17 ± 0.55 mg·kg(-1)·min(-1) (HGI/EX), P = 0.04 (effect of time). HOMA-IR was reduced by -1.1 ± 0.4 (LGI/EX) and -0.1 ± 0.2 (HGI/EX), P = 0.007 (effect of time), P = 0.02 (time × trial). Although both interventions increased IMCL content, (Δ: 2.3 ± 1.3, LGI/EX; 1.4 ± 0.9, HGI/EX, P = 0.03), diet composition did not significantly effect the increase. However, the LGI/EX group showed a robust increase in the [IMCL]/[EMCL] ratio compared with the HGI/EX group (Δ: 0.5 ± 0.2 LGI/EX vs. 0.07 ± 0.1, P = 0.03). The LGI/EX group also demonstrated greater reductions in [EMCL] than the HGI/EX group (Δ: -5.8 ± 3.4, LGI/EX; 2.3 ± 1.1, HGI/EX, P = 0.03). Changes in muscle lipids and insulin sensitivity were not correlated; however, the change in [IMCL]/[EMCL] was negatively associated with the change in FPI (r = -0.78, P = 0.002) and HOMA-IR (r = -0.61, P = 0.03). These data suggest that increases in the IMCL pool following a low glycemic diet and exercise intervention may represent lipid repartitioning from EMCL. The lower systemic glucose levels that prevail while eating a low glycemic diet may promote redistribution of lipid stores in the muscle.
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Affiliation(s)
- Jacob M Haus
- Dept. of Pathobiology, Lerner Research Institute, Cleveland Clinic, OH 44195, USA
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224
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Barquissau V, Morio B. Physiopathologie de l’insulinorésistance dans le muscle squelettique et implication des fonctions mitochondriales. NUTR CLIN METAB 2011. [DOI: 10.1016/j.nupar.2011.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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225
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Thackeray JT, Radziuk J, Harper ME, Suuronen EJ, Ascah KJ, Beanlands RS, Dasilva JN. Sympathetic nervous dysregulation in the absence of systolic left ventricular dysfunction in a rat model of insulin resistance with hyperglycemia. Cardiovasc Diabetol 2011; 10:75. [PMID: 21831292 PMCID: PMC3170183 DOI: 10.1186/1475-2840-10-75] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 08/10/2011] [Indexed: 12/19/2022] Open
Abstract
Background Diabetes mellitus is strongly associated with cardiovascular dysfunction, derived in part from impairment of sympathetic nervous system signaling. Glucose, insulin, and non-esterified fatty acids are potent stimulants of sympathetic activity and norepinephrine (NE) release. We hypothesized that sustained hyperglycemia in the high fat diet-fed streptozotocin (STZ) rat model of sustained hyperglycemia with insulin resistance would exhibit progressive sympathetic nervous dysfunction in parallel with deteriorating myocardial systolic and/or diastolic function. Methods Cardiac sympathetic nervous integrity was investigated in vivo via biodistribution of the positron emission tomography radiotracer and NE analogue [11C]meta-hydroxyephedrine ([11C]HED). Cardiac systolic and diastolic function was evaluated by echocardiography. Plasma and cardiac NE levels and NE reuptake transporter (NET) expression were evaluated as correlative measurements. Results The animal model displays insulin resistance, sustained hyperglycemia, and progressive hypoinsulinemia. After 8 weeks of persistent hyperglycemia, there was a significant 13-25% reduction in [11C]HED retention in myocardium of STZ-treated hyperglycemic but not euglycemic rats as compared to controls. There was a parallel 17% reduction in immunoblot density for NE reuptake transporter, a 1.2 fold and 2.5 fold elevation of cardiac and plasma NE respectively, and no change in sympathetic nerve density. No change in ejection fraction or fractional area change was detected by echocardiography. Reduced heart rate, prolonged mitral valve deceleration time, and elevated transmitral early to atrial flow velocity ratio measured by pulse-wave Doppler in hyperglycemic rats suggest diastolic impairment of the left ventricle. Conclusions Taken together, these data suggest that sustained hyperglycemia is associated with elevated myocardial NE content and dysregulation of sympathetic nervous system signaling in the absence of systolic impairment.
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Affiliation(s)
- James T Thackeray
- Molecular Function & Imaging Program, National Cardiac PET Centre, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, K1Y 4W7, Canada
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226
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Abstract
Over the last decades, substantial progress has been made in defining the molecular events and relevant tissues controlling insulin action and the potential defects that lead to insulin resistance and later on Type 2 diabetes mellitus (T2DM). Mitochondrial dysfunction has been postulated as a common mechanism implicated in the development of insulin resistance and T2DM aetiology. Since then there has been growing interest in this area of research and many studies have addressed whether mitochondrial function/dysfunction is implicated in the progression of T2DM or if it is just a consequence. Mitochondria are adjusted to the specific needs of the tissue and to the environmental interactions or pathophysiological state that it encounters. This review offers a current state of the subject in a tissue specific approach. We will focus our attention on skeletal muscle, liver, and white adipose tissue as the main insulin sensitive organs. Hypothalamic mitochondrial function will be also discussed.
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Affiliation(s)
- Pablo M Garcia-Roves
- Diabetes and Obesity Laboratory, Institute for Biomedical Research August Pi i Sunyer (IDIBAPS) and Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM), Barcelona, Spain.
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227
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Greenberg AS, Coleman RA, Kraemer FB, McManaman JL, Obin MS, Puri V, Yan QW, Miyoshi H, Mashek DG. The role of lipid droplets in metabolic disease in rodents and humans. J Clin Invest 2011; 121:2102-10. [PMID: 21633178 DOI: 10.1172/jci46069] [Citation(s) in RCA: 472] [Impact Index Per Article: 36.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Lipid droplets (LDs) are intracellular organelles that store neutral lipids within cells. Over the last two decades there has been a dramatic growth in our understanding of LD biology and, in parallel, our understanding of the role of LDs in health and disease. In its simplest form, the LD regulates the storage and hydrolysis of neutral lipids, including triacylglycerol and/or cholesterol esters. It is becoming increasingly evident that alterations in the regulation of LD physiology and metabolism influence the risk of developing metabolic diseases such as diabetes. In this review we provide an update on the role of LD-associated proteins and LDs in metabolic disease.
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Affiliation(s)
- Andrew S Greenberg
- Obesity and Metabolism Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts 02111, USA.
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228
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Duclos M, Virally ML, Dejager S. Exercise in the management of type 2 diabetes mellitus: what are the benefits and how does it work? PHYSICIAN SPORTSMED 2011; 39:98-106. [PMID: 21673489 DOI: 10.3810/psm.2011.05.1899] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In this article, we examine the results from meta-analyses of studies that have focused on the effects of supervised exercise in patients with established type 2 diabetes mellitus. Exercise has been clearly demonstrated to have benefits on blood glucose control (average reduction of glycated hemoglobin, 0.6%) and cardiovascular risk factors. These benefits are observed independently of any change in body mass index and fat mass, and are also seen in older populations. Multiple mechanisms are involved, and the improved insulin-sensitizing effect of exercise training is not restricted to muscle but extends to hepatic and adipose tissue. However, while the benefits of exercise in type 2 diabetes management are undisputable, it is not as easy to draw correlations between clinical benefit and the amount of physical activity included in daily life. Recent studies have shown encouraging results with moderate increases in physical activity, which are feasible for most patients and are sufficient to induce sustained positive changes for 2 years. Thus, the benefits of structured and supervised exercise in patients with type 2 diabetes have been consistently demonstrated. Currently, the primary challenge is to determine how long-term increased physical activity can be durably implemented in a patient's daily life.
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Affiliation(s)
- Martine Duclos
- Department of Sports Medicine and Functional Explorations, University-Hospital, Hopital Gabriel Montpied, Clermont-Ferrand, France
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229
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Gaesser GA, Angadi SS, Sawyer BJ. Exercise and diet, independent of weight loss, improve cardiometabolic risk profile in overweight and obese individuals. PHYSICIAN SPORTSMED 2011; 39:87-97. [PMID: 21673488 DOI: 10.3810/psm.2011.05.1898] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Diet and/or exercise are routinely advised as methods for weight loss in overweight/obese individuals, particularly those who are at high risk for cardiovascular disease and type 2 diabetes mellitus. However, physical activity and structured exercise programs rarely result in significant loss of body weight or body fat, and weight-loss diets have extraordinarily high recidivism rates. Despite only modest effects on body weight, exercise and ad libitum nutrient-dense diets for overweight/obese individuals have many health benefits, including skeletal muscle adaptations that improve fat and glucose metabolism, and insulin action; enhance endothelial function; have favorable changes in blood lipids, lipoproteins, and hemostatic factors; and reduce blood pressure, postprandial lipemia and glycemia, and proinflammatory markers. These lifestyle-induced adaptations occur independently of changes in body weight or body fat. Thus, overweight/obese men and women who are at increased risk for cardiovascular disease and type 2 diabetes as a result of sedentary lifestyle, poor diet, and excess body weight should be encouraged to engage in regular physical activity and improve their diet, regardless of whether the healthier lifestyle leads to weight loss.
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Affiliation(s)
- Glenn A Gaesser
- Healthy Lifestyles Research Center, Arizona State University, Mesa, AZ, USA.
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230
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Targeting thermogenesis and related pathways in anti-obesity drug discovery. Pharmacol Ther 2011; 131:295-308. [PMID: 21514319 DOI: 10.1016/j.pharmthera.2011.04.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2011] [Accepted: 03/29/2011] [Indexed: 01/12/2023]
Abstract
The health consequences of the obesity epidemic are a huge burden on patients and society. Yet it remains an unmet therapeutic need. Lifestyle or behaviour modification, although desirable, seems to benefit only a few and bariatric surgery is not an option for all and not without risks. Nevertheless, bariatric surgery is currently the gold standard in terms of weight loss therapy and any weight loss agent will be in combination with management of lifestyle modification. Sadly, there is a poor history for the pharmacological treatment of obesity and repeated safety concerns have attracted intense regulatory scrutiny. Indeed, recent market withdrawals leave us with just one agent approved for the long term treatment of obesity and that is only mildly efficacious in terms of weight loss, although it is beneficial in terms of metabolic health. There are two broad pharmacological approaches that can be applied in obesity drug discovery: reduce intake (or absorption) or increase expenditure (thermogenesis) of calories. In this review we will look at the latter approach. We will cover regulatory requirements and the rationale for this approach. We believe that post-obese subjects display abnormal metabolic responses to weight loss that almost inevitably leads to weight regain. We will then explore a number of approaches that potentially increase thermogenesis in humans. The challenge we have is in accumulating enough human data to validate this approach using drugs.
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231
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Tessari P, Cecchet D, Cosma A, Puricelli L, Millioni R, Vedovato M, Tiengo A. Insulin resistance of amino acid and protein metabolism in type 2 diabetes. Clin Nutr 2011; 30:267-72. [PMID: 21492974 DOI: 10.1016/j.clnu.2011.02.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 02/25/2011] [Accepted: 02/26/2011] [Indexed: 12/25/2022]
Abstract
Although insulin resistance in T2DM (type 2 diabetes mellitus) is usually referred to glucose and lipid metabolism, the question whether such a resistance affects also amino acid and protein metabolism is both relevant and not easy to be answered. Available data indicate a reduced response to insulin in the inhibition of proteolysis at low, near basal hormone levels, whereas such a response appears to be normal at high physiological doses. In most studies in T2DM subjects the stimulation of whole-body protein synthesis in the presence of hyperinsulinemia and euaminoacidemia appears to be normal, although one single study reported lower rates in male T2DM subjects with obesity. The response to insulin of plasma protein synthesis (albumin and fibrinogen) is also normal. However, some metabolic steps of amino acids related to vascular complications (methionine and arginine) exhibit a defective response to insulin in T2DM subjects with nephropathy. In summary, although gross alterations in the response of whole-body protein turnover are not evident in T2DM, specific investigations reveal subtle abnormalities in metabolic steps of selected amino acids. Furthermore, the effects of interaction between diabetes (with the associated insulin resistance) and older age in the pathogenesis of sarcopenia in the elderly deserve more specific studies.
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Affiliation(s)
- Paolo Tessari
- Dept. of Clinical and Experimental Medicine, Metabolism Division, University of Padova, Italy.
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232
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Timmers S, de Vogel-van den Bosch J, Hesselink MKC, van Beurden D, Schaart G, Ferraz MJ, Losen M, Martinez-Martinez P, De Baets MH, Aerts JMFG, Schrauwen P. Paradoxical increase in TAG and DAG content parallel the insulin sensitizing effect of unilateral DGAT1 overexpression in rat skeletal muscle. PLoS One 2011; 6:e14503. [PMID: 21264296 PMCID: PMC3021516 DOI: 10.1371/journal.pone.0014503] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 12/15/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The involvement of muscle triacylglycerol (TAG) storage in the onset of insulin resistance is questioned and the attention has shifted towards inhibition of insulin signalling by the lipid intermediate diacylglycerol (DAG). The enzyme 1,2-acylCoA:diacylglyceroltransferase-1 (DGAT1) esterifies a fatty acyl-CoA on DAG to form TAG. Therefore, the aim of the present study was to investigate if unilateral overexpression of DGAT1 in adult rat Tibialis anterior (TA) muscle will increase conversion of the lipid intermediate DAG into TAG, thereby improving muscle insulin sensitivity. METHODOLOGY/PRINCIPAL FINDINGS The DGAT1 gene construct was injected in the left TA muscle of male rats on chow or high-fat (45% kcal) diet for three weeks, followed by application of one 800 V/cm and four 80 V/cm pulses, using the contralateral leg as sham-electroporated control. Seven days after electroporation, muscle specific insulin sensitivity was assessed with a hyperinsulinemic euglycemic clamp using 2-deoxy-[3H]glucose. Here, we provide evidence that unilateral overexpression of DGAT1 in TA muscle of male rats is associated with an increased rather than decreased DAG content. Strikingly, this increase in DAG content was accompanied by improved muscle insulin sensitivity. Interestingly, markers of muscle lipolysis and mitochondrial function were also increased in DGAT1 overexpressing muscle. CONCLUSIONS/SIGNIFICANCE We conclude that unilateral DGAT1 overexpression can rescue insulin sensitivity, possibly by increasing DAG and TAG turnover in skeletal muscle. In case of a proper balance between the supply and oxidation of fatty acids in skeletal muscle, the lipid intermediate DAG may not exert harmful effects on insulin signalling.
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Affiliation(s)
- Silvie Timmers
- Top Institute Food and Nutrition (TIFN), Wageningen, The Netherlands
- Department of Human Biology, Maastricht University, Maastricht, The Netherlands
| | - Johan de Vogel-van den Bosch
- Top Institute Food and Nutrition (TIFN), Wageningen, The Netherlands
- Department of Human Biology, Maastricht University, Maastricht, The Netherlands
| | - Matthijs K. C. Hesselink
- Human Movement Sciences, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University, Maastricht, The Netherlands
| | - Denis van Beurden
- Department of Human Biology, Maastricht University, Maastricht, The Netherlands
| | - Gert Schaart
- Human Movement Sciences, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University, Maastricht, The Netherlands
| | - Maria Joao Ferraz
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Mario Losen
- Department of Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Pilar Martinez-Martinez
- Department of Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Marc H. De Baets
- Department of Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Johannes M. F. G. Aerts
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Patrick Schrauwen
- Top Institute Food and Nutrition (TIFN), Wageningen, The Netherlands
- Department of Human Biology, Maastricht University, Maastricht, The Netherlands
- * E-mail:
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233
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Abstract
Exercise, together with a low-energy diet, is the first-line treatment for type 2 diabetes type 2 diabetes . Exercise improves insulin sensitivity insulin sensitivity by increasing the number or function of muscle mitochondria mitochondria and the capacity for aerobic metabolism, all of which are low in many insulin-resistant subjects. Cannabinoid 1-receptor antagonists and β-adrenoceptor agonists improve insulin sensitivity in humans and promote fat oxidation in rodents independently of reduced food intake. Current drugs for the treatment of diabetes are not, however, noted for their ability to increase fat oxidation, although the thiazolidinediones increase the capacity for fat oxidation in skeletal muscle, whilst paradoxically increasing weight gain.There are a number of targets for anti-diabetic drugs that may improve insulin sensitivity insulin sensitivity by increasing the capacity for fat oxidation. Their mechanisms of action are linked, notably through AMP-activated protein kinase, adiponectin, and the sympathetic nervous system. If ligands for these targets have obvious acute thermogenic activity, it is often because they increase sympathetic activity. This promotes fuel mobilisation, as well as fuel oxidation. When thermogenesis thermogenesis is not obvious, researchers often argue that it has occurred by using the inappropriate device of treating animals for days or weeks until there is weight (mainly fat) loss and then expressing energy expenditure energy expenditure relative to body weight. In reality, thermogenesis may have occurred, but it is too small to detect, and this device distracts us from really appreciating why insulin sensitivity has improved. This is that by increasing fatty acid oxidation fatty acid oxidation more than fatty acid supply, drugs lower the concentrations of fatty acid metabolites that cause insulin resistance. Insulin sensitivity improves long before any anti-obesity effect can be detected.
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Affiliation(s)
- Jonathan R S Arch
- Clore Laboratory, University of Buckingham, Buckingham, MK18 1EG, UK
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234
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Yuzefovych L, Wilson G, Rachek L. Different effects of oleate vs. palmitate on mitochondrial function, apoptosis, and insulin signaling in L6 skeletal muscle cells: role of oxidative stress. Am J Physiol Endocrinol Metab 2010; 299:E1096-105. [PMID: 20876761 PMCID: PMC3006254 DOI: 10.1152/ajpendo.00238.2010] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 09/23/2010] [Indexed: 12/16/2022]
Abstract
The type of free fatty acids (FFAs), saturated or unsaturated, is critical in the development of insulin resistance (IR), since the degree of saturation correlates with IR. We compared the effects of the saturated FFA palmitate, the unsaturated FFA oleate, and a mixture of each on the production of mitochondrial reactive oxygen species (mtROS), mitochondrial DNA (mtDNA) damage, mitochondrial function, apoptosis, and insulin-signaling pathway in skeletal muscle cells. Only palmitate caused a significant increase of mtROS production, which correlated with concomitant mtDNA damage, mitochondrial dysfunction, induction of JNK, apoptosis, and inhibition of insulin signaling. Blocking de novo synthesis of ceramide abolished the effects of palmitate on mtROS production, viability, and insulin signaling. Oleate alone did not cause mtROS generation and mtDNA damage, and its addition to palmitate prevented palmitate-induced mtDNA damage, increased total ATP levels and cell viability, and prevented palmitate-induced apoptosis and inhibition of insulin-stimulated Akt (Ser(473)) phosphorylation. The peroxisome proliferator activator receptor-γ coactivator 1α (PGC-1α) protein level and promoter activity were decreased at concentrations of palmitate ≥0.5 mM, whereas addition of oleate increased both PGC-1α level and promoter activity. Expression of the mitochondrial transcription factor (TFAM) was significantly diminished after palmitate but not oleate treatment. Addition of the ROS scavenger, N-acetylcystein (NAC), to palmitate restored both the expression and promoter activity of PGC-1α as well as TFAM expression. We propose that 1) mtROS generation is the initial event in the induction of mitochondrial dysfunction and consequent apoptosis and the inhibition of insulin signaling and that 2) oleate ameliorates palmitate-induced mitochondrial dysfunction and thus may contribute to the prevention of palmitate-induced IR.
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Affiliation(s)
- Larysa Yuzefovych
- Dept. of Cell Biology and Neuroscience, Univ. of South Alabama, Mobile, AL 36688, USA
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235
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Han W, Chuang KH, Chang YT, Olivo M, Velan SS, Bhakoo K, Townsend D, Radda GK. Imaging metabolic syndrome. EMBO Mol Med 2010; 2:196-210. [PMID: 20533426 PMCID: PMC3377322 DOI: 10.1002/emmm.201000074] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Metabolic syndrome is a fast growing public health burden for almost all the developed countries and many developing nations. Despite intense efforts from both biomedical and clinical scientists, many fundamental questions regarding its aetiology and development remain unclear, partly due to the lack of suitable imaging technologies to visualize lipid composition and distribution, insulin secretion, β-cell mass and functions in vivo. Such technologies would not only impact on our understanding of the complexity of metabolic disorders such as obesity and diabetes, but also aid in their diagnosis, drug development and assessment of treatment efficacy. In this article we discuss and propose several strategies for visualization of physiological and pathological changes that affect pancreas and adipose tissue as a result of the development of metabolic diseases.
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Affiliation(s)
- Weiping Han
- Singapore Bioimaging Consortium, Agency for Science Technology and Research (A*STAR), Singapore, Singapore
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236
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Hey-Mogensen M, Højlund K, Vind BF, Wang L, Dela F, Beck-Nielsen H, Fernström M, Sahlin K. Effect of physical training on mitochondrial respiration and reactive oxygen species release in skeletal muscle in patients with obesity and type 2 diabetes. Diabetologia 2010; 53:1976-85. [PMID: 20526759 DOI: 10.1007/s00125-010-1813-x] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Accepted: 04/13/2010] [Indexed: 02/06/2023]
Abstract
AIM/HYPOTHESIS Studies have suggested a link between insulin resistance and mitochondrial dysfunction in skeletal muscles. Our primary aim was to investigate the effect of aerobic training on mitochondrial respiration and mitochondrial reactive oxygen species (ROS) release in skeletal muscle of obese participants with and without type 2 diabetes. METHODS Type 2 diabetic men (n = 13) and control (n = 14) participants matched for age, BMI and physical activity completed 10 weeks of aerobic training. Pre- and post-training muscle biopsies were obtained before a euglycaemic-hyperinsulinaemic clamp and used for measurement of respiratory function and ROS release in isolated mitochondria. RESULTS Training significantly increased insulin sensitivity, maximal oxygen consumption and muscle mitochondrial respiration with no difference between groups. When expressed in relation to a marker of mitochondrial density (intrinsic mitochondrial respiration), training resulted in increased mitochondrial ADP-stimulated respiration (with NADH-generating substrates) and decreased respiration without ADP. Intrinsic mitochondrial respiration was not different between groups despite lower insulin sensitivity in type 2 diabetic participants. Mitochondrial ROS release tended to be higher in participants with type 2 diabetes. CONCLUSIONS/INTERPRETATION Aerobic training improves muscle respiration and intrinsic mitochondrial respiration in untrained obese participants with and without type 2 diabetes. These adaptations demonstrate an increased metabolic fitness, but do not seem to be directly related to training-induced changes in insulin sensitivity.
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Affiliation(s)
- M Hey-Mogensen
- Center for Healthy Aging, Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3B, Copenhagen, Denmark.
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237
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Phielix E, Szendroedi J, Roden M. Mitochondrial function and insulin resistance during aging: a mini-review. Gerontology 2010; 57:387-96. [PMID: 20798481 DOI: 10.1159/000317691] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 06/22/2010] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Insulin resistance, i.e. impaired insulin sensitivity, and type 2 diabetes are more prevalent in elderly humans. Both conditions relate to lower aerobic performance and increased body fatness, which have been linked to reduced mitochondrial oxidative capacity. Thus, lower insulin sensitivity in the elderly could result from age-related diminished energy metabolism or from lifestyle-related abnormalities. OBJECTIVE This review addresses the question whether insulin sensitivity and mitochondrial oxidative capacity are independently affected during aging and type 2 diabetes. METHODS Only studies were analyzed which included elderly persons and employed state-of-the-art methodology to assess insulin sensitivity and oxidative capacity, e.g. electron microscopic imaging, in vivo magnetic resonance spectroscopy or ex vivo high-resolution respirometry. RESULTS Humans with or at risk of type 2 diabetes frequently exhibit insulin resistance along with structural and functional abnormalities of muscular mitochondria. Low mitochondrial oxidative capacity causes muscular fat accumulation, which impedes insulin signaling via lipid intermediates, in turn affecting oxidative capacity. However, insulin sensitivity is not generally reduced with age, when groups are carefully matched for physical activity and body fatness. Moreover, lifestyle intervention studies revealed discordant responses of mitochondrial oxidative capacity and insulin sensitivity. CONCLUSIONS In the elderly, low mitochondrial oxidative capacity likely results from age-related effects acquired during life span. Insulin resistance occurs independently of age mostly due to unhealthy lifestyle on top of genetic predisposition. Thus, insulin sensitivity and mitochondrial function may not be causally related, but mutually amplify each other during aging.
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Affiliation(s)
- Esther Phielix
- Institute for Clinical Diabetology, German Diabetes Center, Düsseldorf, Germany
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238
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Phielix E, Meex R, Moonen-Kornips E, Hesselink MKC, Schrauwen P. Exercise training increases mitochondrial content and ex vivo mitochondrial function similarly in patients with type 2 diabetes and in control individuals. Diabetologia 2010; 53:1714-21. [PMID: 20422397 PMCID: PMC2892060 DOI: 10.1007/s00125-010-1764-2] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Accepted: 03/11/2010] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS We previously showed that type 2 diabetic patients are characterised by compromised intrinsic mitochondrial function. Here, we examined if exercise training could increase intrinsic mitochondrial function in diabetic patients compared with control individuals. METHODS Fifteen male type 2 diabetic patients and 14 male control individuals matched for age, BMI and VO(2max) enrolled in a 12 week exercise intervention programme. Ex vivo mitochondrial function was assessed by high-resolution respirometry in permeabilised muscle fibres from vastus lateralis muscle. Before and after training, insulin-stimulated glucose disposal was examined during a hyperinsulinaemic-euglycaemic clamp. RESULTS Diabetic patients had intrinsically lower ADP-stimulated state 3 respiration and lower carbonyl cyanide 4-(trifluoro-methoxy)phenylhydrazone (FCCP)-induced maximal oxidative respiration, both on glutamate and on glutamate and succinate, and in the presence of palmitoyl-carnitine (p < 0.05). After training, diabetic patients and control individuals showed increased state 3 respiration on the previously mentioned substrates (p < 0.05); however, an increase in FCCP-induced maximal oxidative respiration was observed only in diabetic patients (p < 0.05). The increase in mitochondrial respiration was accompanied by a 30% increase in mitochondrial content upon training (p < 0.01). After adjustment for mitochondrial density, state 3 and FCCP-induced maximal oxidative respiration were similar between groups after training. Improvements in mitochondrial respiration were paralleled by improvements in insulin-stimulated glucose disposal in diabetic patients, with a tendency for this in control individuals. CONCLUSIONS/INTERPRETATION We confirmed lower intrinsic mitochondrial function in diabetic patients compared with control individuals. Diabetic patients increased their mitochondrial content to the same extent as control individuals and had similar intrinsic mitochondrial function, which occurred parallel with improved insulin sensitivity.
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Affiliation(s)
- E. Phielix
- NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Human Biology, Maastricht University Medical Centre, P.O. Box 616, NL6200 MD Maastricht, the Netherlands
| | - R. Meex
- NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Human Movement Sciences, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - E. Moonen-Kornips
- NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Human Movement Sciences, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - M. K. C. Hesselink
- NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Human Movement Sciences, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - P. Schrauwen
- NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Human Biology, Maastricht University Medical Centre, P.O. Box 616, NL6200 MD Maastricht, the Netherlands
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239
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Pazderska A, Wanic K, Nolan JJ. Skeletal muscle mitochondrial dysfunction in Type 2 diabetes. Expert Rev Endocrinol Metab 2010; 5:475-477. [PMID: 30780805 DOI: 10.1586/eem.10.21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Agnieszka Pazderska
- a Metabolic Research Unit, Department of Endocrinology, St James Hospital, Trinity College, Dublin 8, Ireland
| | - Krzysztof Wanic
- a Metabolic Research Unit, Department of Endocrinology, St James Hospital, Trinity College, Dublin 8, Ireland
| | - John J Nolan
- b Metabolic Research Unit, Department of Endocrinology, St James Hospital, Trinity College, Dublin 8, Ireland.
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240
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The use of statins potentiates the insulin-sensitizing effect of exercise training in obese males with and without Type 2 diabetes. Clin Sci (Lond) 2010; 119:293-301. [PMID: 20465545 DOI: 10.1042/cs20100153] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Exercise training is advocated in insulin resistance and statins are used to treat hyperlipidaemia, two cardiometabolic risk factors often presenting concurrently. Statin intake may blunt mitochondrial function and the adaptive response to exercise training. Thus combining exercise training with statin administration may have adverse effects. We examined whether improvements in cardiometabolic risk factors, insulin sensitivity and mitochondrial function mediated by progressive exercise training are affected by statin use. A group of 14 obese elderly males on statins (ST) and 22 matched control subjects (C) were examined. Results on in vivo mitochondrial function [MRS (magnetic resonance spectroscopy)], mitochondrial density (Western blotting), insulin sensitivity (clamp) and metabolic flexibility (indirect calorimetry) were compared before and after a 12-week combined progressive exercise training programme (3 x per week; 45 min per session). Except for LDL (low-density lipoprotein) cholesterol, all pre-training values were comparable between statin users and control subjects. In vivo mitochondrial function and mitochondrial density improved by training in both groups. Interestingly, blood-lipid profile, insulin sensitivity (+72%), non-oxidative and oxidative glucose disposal (+38% and +112%) and insulin-mediated suppression of fat oxidation (-62%) improved only in the ST group. We conclude that statin treatment did not impede exercise performance or tolerance, mitochondrial function or mass. In addition, training-induced improvements in glucose homoeostasis were preserved in the ST group. Strikingly, the insulin-sensitizing effect of training was more prominent in the ST group than in the C group. The combined prescription of statins along with exercise training is safe and should be considered for subjects prone to develop insulin resistance.
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