Enhanced pyruvate dehydrogenase activity does not affect muscle O2uptake at onset of intense exercise in humans
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abstract
It has been proposed that the activation state of pyruvate dehydrogenase (PDH) may influence the rate of skeletal muscle O2uptake during the initial phase of exercise; however, this has not been directly tested in humans. To remedy this, we used dichloroacetate (DCA) infusion to increase the active form of PDH (PDHa) and, subsequently, measured leg O2uptake and markers of anaerobic ATP provision during conditions of intense dynamic exercise, when the rate of muscle O2uptake would be very high. Six subjects performed brief bouts of one-legged knee-extensor exercise at ∼110% of thigh peak O2uptake (65.3 ± 3.7 W) on several occasions: under noninfused control (Con) and DCA-supplemented conditions. Needle biopsy samples from the vastus lateralis muscle were obtained at rest and after 5 s, 15 s, and 3 min of exercise during both experimental conditions. In addition, thigh blood flow and femoral arteriovenous differences for O2and lactate were measured repeatedly during the 3-min work bouts (Con and DCA) to calculate thigh O2uptake and lactate release. After DCA administration, PDHawas four- to eightfold higher ( P < 0.05) than Con at rest, and PDHaremained ∼130% and 100% higher ( P< 0.05) after 5 and 15 s of exercise, respectively. There was no difference between trials after 3 min. Despite the marked difference in PDHabetween trials at rest and during the initial phase of exercise, thigh O2uptake was the same. In addition, muscle phosphocreatine utilization and lactate production were similar after 5 s, 15 s, and 3 min of exercise in DCA and Con. The present findings demonstrate that increasing PDHadoes not alter muscle O2uptake and anaerobic ATP provision during the initial phase of intense dynamic knee-extensor exercise in humans.
