Maximal-intensity exercise does not fully restore muscle pyruvate dehydrogenase complex activation after 3 days of high-fat dietary intake

Abstract

Exercise activates muscle pyruvate dehydrogenase complex (PDC), but moderate intensity exercise fails to fully activate muscle PDC after high-fat diet [1]. We investigated whether maximal intensity exercise overcomes this inhibition. Quadriceps femoris muscle biopsy samples were obtained from healthy males at rest, and after 46 and 92 electrically-evoked maximal intermittent isometric contractions, which were preceded by 3 days of either low- (18%) or high- (69%) isocaloric dietary fat intake (LFD and HFD, respectively). The ratio of PDCa (active form) to total PDCt (fully activated) at rest was 50% less after HFD (0.32±0.01 vs 0.15±0.01; P<0.05). This ratio increased to 0.77±0.06 after 46 contractions (P<0.001) and to 0.98±0.07 after 92 contractions (P<0.001) in LFD. The corresponding values after HFD were less (0.54±0.06; P<0.01 and 0.70±0.07; P<0.01, respectively). Resting muscle acetyl-CoA and acetylcarnitine content was greater after HFD than LFD (both P<0.05), but their rate of accumulation in the former was reduced during contraction. Muscle lactate content after 92 contractions was 30% greater after HFD (P<0.05). Muscle force generation during contraction was no different between interventions, but HFD lengthened muscle relaxation time (P<0.05). Daily urinary total carnitine excretion after HFD was 2.5-fold greater than after LFD (P<0.01). A bout of maximal intense exercise did not overcome dietary fat-mediated inhibition of muscle pyruvate dehydrogenase complex activation, and was associated with greater muscle lactate accumulation, as a result of lower PDC flux, and increased muscle relaxation time.