<i>In vivo</i> oxidative capacity of <i>tibialis anterior</i> (TA) muscle, assessed by ³¹P MRS.

<p>Representative examples of ³¹P MR spectra obtained during rest with 32 averages (A) and at the end of the electrical-stimulation protocol with 4 averages (B). (C) Representative examples of relative PCr concentrations during rest, muscle stimulation and recovery (time resolution = 20 s) for a water-treated diabetic rat (open symbols) and a diabetic rat treated with metformin at 300 mg/kg body weight/day (filled symbols). PCr concentrations are expressed as a percentage of the resting PCr concentration. Mono-exponential functions (dark lines) were fit to the recovery data and the PCr recovery rate constants were 0.63 and 0.21 min^-1 for the water-treated and metformin-treated animal, respectively. (D) Rate constants of PCr recovery, <i>k</i>_PCr, after electrical stimulation in TA muscle of lean and diabetic rats treated with water or 30, 100 or 300 mg/kg body weight/day metformin (MET30, MET100 and MET300 respectively). Data is represented as mean ± SD (n = 6 per group). <i>k</i>_PCr was significantly lower in diabetic rats compared with lean rats, independent of treatment regimen (ANOVA: P<0.001). In addition, treatment had a significant effect on <i>k</i>_PCr, independent of genotype, and a pairwise analysis of differences is provided by Bonferroni-corrected post-hoc tests: ^* P<0.001 when compared with water-treated animals, ^† P<0.001 when compared with MET30-treated animals, ^‡ P<0.001 when compared with MET100-treated animals.