Muscle mitochondrial oxidative phosphorylation activity, but not content, is altered with abdominal obesity in sedentary men: synergism with changes in insulin sensitivity.
BACKGROUND
Abdominal obesity is a major risk factor for muscle insulin resistance. Mitochondria may play a key role in this etiology.


OBJECTIVE
Changes in muscle mitochondrial content and function were examined according to abdominal obesity and insulin sensitivity in men.


METHODS
The descriptive MitHyCal study was conducted on the general population of Clermont-Ferrand, France.


METHODS
Forty-two healthy sedentary men (41.7 +/- 4.3 yr) were divided into four groups according to waist circumference: 87 cm or less (group 1, n = 10); 88-93 cm (group 2, n = 12); 94-101 cm (group 3, n = 10); and 102 cm or greater (group 4, n = 10).


METHODS
Plasma metabolic check-up was performed, and insulin sensitivity index was calculated from glucose and insulin responses to a 3-h oral glucose tolerance test. Muscle biopsies were obtained to assess mitochondrial content, oxidative phosphorylation activity, and superoxide anion (reactive oxygen species) production.


METHODS
Assessment of muscle mitochondrial content and function was planned before data collection began.


RESULTS
Abdominal obesity was negatively correlated to insulin sensitivity index (r = -0.39; P < 0.01), and only group 4 was insulin-resistant (P < 0.05). There were no between-group differences in muscle mitochondrial content and maximal activity of key oxidative enzymes. In contrast, muscle mitochondrial ADP-stimulated respiration rate was 24% higher in groups 2 and 3 compared to groups 1 and 4 (P < 0.05). Mitochondrial ATP and reactive oxygen species production rates were 27 and 48% lower in group 4 than in group 1 (P < 0.05).


CONCLUSIONS
Abdominal obesity is associated with alterations in intrinsic muscle mitochondrial function but not content. These adaptations mainly result in reduced mitochondrial ATP production rate in response to insulin resistance.
Chanseaume
Emilie
E
Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1019, Centre de Recherche en Nutrition Humaine Auvergne, F-63000 Clermont-Ferrand, France.
Barquissau
Valentin
V
Salles
Jérôme
J
Aucouturier
Julien
J
Patrac
Véronique
V
Giraudet
Christophe
C
Gryson
Céline
C
Duché
Pascale
P
Boirie
Yves
Y
Chardigny
Jean-Michel
JM
Morio
Béatrice
B
D050153:Abdominal Fat / Q000502:physiology*; D015502:Absorptiometry, Photon; D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D001706:Biopsy; D001823:Body Composition / Q000502:physiology; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D017931:DNA Primers / Q000235:genetics; D004032:Diet; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism*; D009043:Motor Activity / Q000502:physiology*; D009765:Obesity / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption / Q000502:physiology; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055105:Waist Circumference
D017931:DNA Primers; D012313:RNA; D004247:DNA