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Regulation of PDH in human arm and leg muscles at rest and during intense exercise

¹Copenhagen Muscle Research Centre, ²Centre of Inflammation and Metabolism, and ³Department of Molecular Biology, August Krogh Building, University of Copenhagen; ⁴Rigshospitalet, Copenhagen; and ⁵Section of Human Physiology, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark

Submitted 6 June 2007 ; accepted in final form 8 October 2007

To test the hypothesis that pyruvate dehydrogenase (PDH) is differentially regulated in specific human muscles, regulation of PDH was examined in triceps, deltoid, and vastus lateralis at rest and during intense exercise. To elicit considerable glycogen use, subjects performed 30 min of exhaustive arm cycling on two occasions and leg cycling exercise on a third day. Muscle biopsies were obtained from deltoid or triceps on the arm exercise days and from vastus lateralis on the leg cycling day. Resting PDH protein content and phosphorylation on PDH-E1 sites 1 and 2 were higher (P 0.05) in vastus lateralis than in triceps and deltoid as was the activity of oxidative enzymes. Net muscle glycogen utilization was similar in vastus lateralis and triceps (50%) but less in deltoid (likely reflecting less recruitment of deltoid), while muscle lactate accumulation was 55% higher (P 0.05) in triceps than vastus lateralis. Exercise induced (P 0.05) dephosphorylation of both PDH-E1 site 1 and site 2 in all three muscles, but it was more pronounced at PDH-E1 site 1 in triceps than in vastus lateralis (P 0.05). The increase in activity of the active form of PDH (PDH_a) after 10 min of exercise was more marked in vastus lateralis (246%) than in triceps (160%), but when it was related to total PDH-E1 protein content, no difference was evident. In conclusion, PDH protein content seems to be related to metabolic enzyme profile, rather than myosin heavy chain composition, and less PDH capacity in triceps is a likely contributing factor to higher lactate accumulation in triceps than in vastus lateralis.

pyruvate dehydrogenase; pyruvate dehydrogenase activity; pyruvate dehydrogenase phosphorylation; muscle type

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