Rapid down-regulation of mitochondrial fat metabolism in human muscle after training cessation is dissociated from changes in insulin sensitivity.

The association between impairment in mitochondrial muscle fat oxidative capacity (OX(FA)) and occurrence of insulin resistance was examined in 14 healthy trained men (age, 24+/-4 yr) submitted to 4 weeks of training cessation. Training stop induced a significant decrease in mRNA levels of proteins involved in muscle fat metabolism, particularly PPARalpha (-58%, P<0.01) and PGC-1alpha (-30%, P<0.

Muscle fat oxidative capacity is not impaired by age but by physical inactivity: association with insulin sensitivity.

The study aimed at determining whether aging and/or sedentariness impairs muscle fat oxidative capacity (OXFA) and whether this was associated with increased risk to develop insulin resistance. We first examined muscle mitochondrial functions, OXFA 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.