The acute effects of differential dietary fatty acids on PDHa activity in human skeletal muscle at the onset of exercise
Abstract
Pyruvate dehydrogenase (PDH) is an important regulator of carbohydrate
oxidation during exercise and its activity can be down-regulated by an increase in dietary
fat. The purpose of this study was to determine the acute metabolic effects of differential
dietary fatty acids on the activation of PDH in its active form (PDHa) at rest and at the
onset of moderate-intensity exercise. University-aged male subjects (n=7) underwent 2
fat loading trials spaced at least 2 weeks apart. Subjects consumed saturated (SFA) or
polyunsaturated (PUFA) fat over the course of 5 hours. Following this, participants
cycled at 65% VO2 max for 15 min. Muscle biopsies were taken prior to and following
fat loading and at 1 min exercise. Plasma free fatty acids increased from 0.15 ± 0.07 to
0.54 ± 0.19 mM over 5 hours with SFA and from 0.1 1 ± 0.04 to 0.35 ±0.13 mM with
PUFA. PDHa activity was unchanged following fat loading, but increased at the onset of
exercise in the SFA trial, from 1 .4 ± 0.4 to 2.2 ± 0.4 /xmol/min/kg wet wt. This effect
was negated in the PUFA trial (1 .2 ± 0.3 to 1 .3 ± 0.3 pimol/min/kg wet wt.). PDH kinase
(PDK) was unchanged in both trials, suggesting that the attenuation of PDHa activity
with PUFA was a result of changes in the concentrations of intramitochondrial effectors,
more specifically intramitochondrial NADH or Ca^*. Our findings suggest that attenuated
PDHa activity participates in the preferential oxidation of PUFA during moderateintensity
exercise.