title: Insulin Resistance Is Not Associated with an Impaired Mitochondrial Function in Contracting Gastrocnemius Muscle of Goto-Kakizaki Diabetic Rats In Vivo.
abstract: Insulin resistance, altered lipid metabolism and mitochondrial dysfunction in skeletal muscle would play a major role in type 2 diabetes mellitus (T2DM) development, but the causal relationships between these events remain conflicting. To clarify this issue, gastrocnemius muscle function and energetics were investigated throughout a multidisciplinary approach combining in vivo and in vitro measurements in Goto-Kakizaki (GK) rats, a non-obese T2DM model developing peripheral insulin resistant without abnormal level of plasma non-esterified fatty acids (NEFA). Wistar rats were used as controls. Mechanical performance and energy metabolism were assessed strictly non-invasively using magnetic resonance (MR) imaging and 31-phosphorus MR spectroscopy (31P-MRS). Compared with control group, plasma insulin and glucose were respectively lower and higher in GK rats, but plasma NEFA level was normal. In resting GK muscle, phosphocreatine content was reduced whereas glucose content and intracellular pH were both higher. However, there were not differences between both groups for basal oxidative ATP synthesis rate, citrate synthase activity, and intramyocellular contents for lipids, glycogen, ATP and ADP (an important in vivo mitochondrial regulator). During a standardized fatiguing protocol (6 min of maximal repeated isometric contractions electrically induced at a frequency of 1.7 Hz), mechanical performance and glycolytic ATP production rate were reduced in diabetic animals whereas oxidative ATP production rate, maximal mitochondrial capacity and ATP cost of contraction were not changed. These findings provide in vivo evidence that insulin resistance is not caused by an impairment of mitochondrial function in this diabetic model.
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, 13385, Marseille, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Macia
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, 13385, Marseille, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Pecchi
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, 13385, Marseille, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Vilmen
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, 13385, Marseille, France.
authors.forename: Martine
authors.initials: M
authors.lastname: Desrois
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, 13385, Marseille, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Lan
authors.affiliation: Universitx Paris-Diderot, Sorbonne Paris Cité, Laboratoire B2PE, Unité BFA, CNRS EAC 4413, Paris, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Portha
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, 13385, Marseille, France.
authors.forename: Monique
authors.initials: M
authors.lastname: Bernard
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, 13385, Marseille, France.
authors.forename: David
authors.initials: D
authors.lastname: Bendahan
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, 13385, Marseille, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Giannesini
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D004558:Electric Stimulation; D004734:Energy Metabolism; D006863:Hydrogen-Ion Concentration; D007333:Insulin Resistance; D008279:Magnetic Resonance Imaging; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D010725:Phosphocreatine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D010725:Phosphocreatine; D000255:Adenosine Triphosphate