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Muscle fat oxidative capacity is not impaired by age but by physical inactivity: association with insulin sensitivity
Author(s) -
Rimbert Virginie,
Boirie Yves,
Bedu Mario,
Hocquette JeanFrançois,
Ritz Patrick,
Morio Béatrice
Publication year - 2004
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.03-1104fje
Subject(s) - medicine , endocrinology , insulin resistance , insulin sensitivity , insulin , sedentary lifestyle , diabetes mellitus , ageing , stepwise regression , obesity
The study aimed at determining whether aging and/or sedentariness impairs muscle fat oxidative capacity (OX FA ) and whether this was associated with increased risk to develop insulin resistance. We first examined muscle mitochondrial functions, OX FA and insulin sensitivity (ISI; evaluated during an oral glucose tolerance test) in a cross‐sectional study with 32 sedentary (S) and endurance‐trained (T), young (Y) and elderly (E) men (24.2±2.6 vs. 66.6±3.2 yr). As for mitochondrial functions, OX FA was higher in T than in S but similar between age groups (SY 41.8±11.3, TY 68.0±17.7, SE 40.1±14.1, TE 73.1±20.1 palmitate.min –1 .g wet tissue –1 ; activity P <0.0001, age P =NS, activity × age P =NS). Similar results were obtained with ISI (SY 6.2±2.2, TY 11.4±4.4, SE 5.9±1.5, TE 11.0±3.5, activity P <0.001, age P =NS, activity × age P =NS). Stepwise regression showed that, among body composition, VO 2max and muscle biochemical characteristics, OX FA was the main predictor of ISI ( r =0.60, P <0.001). We subsequently showed in eight sedentary elderly subjects (63.5±3.3 yr) that OX FA and insulin sensitivity (measured using insulin clamp) improved in parallel after 8 weeks of endurance training ( r =0.79, P <0.01). We concluded that mitochondrial functions, OX FA and ISI, are not impaired by age but by physical inactivity and are closely correlated.