Ghadi Antoun1, Fiona McMurray1, A Brianne Thrush1, David A Patten2, Alyssa C Peixoto1, Ruth S Slack2, Ruth McPherson3, Robert Dent4, Mary-Ellen Harper5. 1. Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON, Canada, K1H 8M5. 2. Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada. 3. Atherogenomics Laboratory, University of Ottawa Heart Institute, Ottawa, ON, Canada. 4. Ottawa Hospital Weight Management Clinic, The Ottawa Hospital, Ottawa, ON, Canada. 5. Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON, Canada, K1H 8M5. mharper@uottawa.ca.
Abstract
AIMS/HYPOTHESIS: Skeletal muscle mitochondrial dysfunction has been documented in patients with type 2 diabetes mellitus; however, specific respiratory defects and their mechanisms are poorly understood. The aim of the current study was to examine oxidative phosphorylation and electron transport chain (ETC) supercomplex assembly in rectus abdominis muscles of 10 obese diabetic and 10 obese non-diabetic individuals. METHODS: Twenty obese women undergoing Roux-en-Y gastric bypass surgery were recruited for this study. Muscle samples were obtained intraoperatively and subdivided for multiple analyses, including high-resolution respirometry and assessment of supercomplex assembly. Clinical data obtained from referring physicians were correlated with laboratory findings. RESULTS: Participants in both groups were of a similar age, weight and BMI. Mitochondrial respiration rates were markedly reduced in diabetic vs non-diabetic patients. This defect was observed during maximal ADP-stimulated respiration in the presence of complex I-linked substrates and complex I- and II-linked substrates, and during maximal uncoupled respiration. There were no differences in fatty acid (octanoyl carnitine) supported respiration, leak respiration or isolated activity of cytochrome c oxidase. Intriguingly, significant correlations were found between glycated haemoglobin (HbA1c) levels and maximal respiration or respiration supported by complex I, complex I and II or fatty acid. In the muscle of diabetic patients, blue native gel electrophoresis revealed a striking decrease in complex I, III and IV containing ETC supercomplexes. CONCLUSIONS/ INTERPRETATION: These findings support the hypothesis that ETC supercomplex assembly may be an important underlying mechanism of muscle mitochondrial dysfunction in type 2 diabetes mellitus.
AIMS/HYPOTHESIS: Skeletal muscle mitochondrial dysfunction has been documented in patients with type 2 diabetes mellitus; however, specific respiratory defects and their mechanisms are poorly understood. The aim of the current study was to examine oxidative phosphorylation and electron transport chain (ETC) supercomplex assembly in rectus abdominis muscles of 10 obese diabetic and 10 obese non-diabetic individuals. METHODS: Twenty obesewomen undergoing Roux-en-Y gastric bypass surgery were recruited for this study. Muscle samples were obtained intraoperatively and subdivided for multiple analyses, including high-resolution respirometry and assessment of supercomplex assembly. Clinical data obtained from referring physicians were correlated with laboratory findings. RESULTS:Participants in both groups were of a similar age, weight and BMI. Mitochondrial respiration rates were markedly reduced in diabetic vs non-diabeticpatients. This defect was observed during maximal ADP-stimulated respiration in the presence of complex I-linked substrates and complex I- and II-linked substrates, and during maximal uncoupled respiration. There were no differences in fatty acid (octanoyl carnitine) supported respiration, leak respiration or isolated activity of cytochrome c oxidase. Intriguingly, significant correlations were found between glycated haemoglobin (HbA1c) levels and maximal respiration or respiration supported by complex I, complex I and II or fatty acid. In the muscle of diabeticpatients, blue native gel electrophoresis revealed a striking decrease in complex I, III and IV containing ETC supercomplexes. CONCLUSIONS/ INTERPRETATION: These findings support the hypothesis that ETC supercomplex assembly may be an important underlying mechanism of muscle mitochondrial dysfunction in type 2 diabetes mellitus.
Entities:
Keywords:
Bioenergetics; Electron transport chain; Mitochondria; Obesity; Skeletal muscle; Type 2 diabetes mellitus
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