title: The acute effects of differential dietary fatty acids on human skeletal muscle pyruvate dehydrogenase activity.
abstract: Pyruvate dehydrogenase (PDH) is an important regulator of carbohydrate oxidation during exercise, and its activity can be downregulated 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 the PDH complex (PDHa activity) at rest and at the onset of moderate-intensity exercise. University-aged male subjects (n = 7) underwent two fat-loading trials spaced at least 2 wk apart. Subjects consumed approximately 300 g saturated (SFA) or n-6 polyunsaturated fatty acid (PUFA) fat over the course of 5 h. Following this, participants cycled at 65% of their maximum oxygen uptake for 15 min. Muscle biopsies were taken before 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 h with SFA and from 0.11 +/- 0.04 to 0.35 +/- 0.13 mM with n-6 PUFA and were significantly lower throughout the n-6 PUFA trial. PDHa activity was unchanged following fat loading but increased at the onset of exercise in the SFA trial, from 1.18 +/- 0.27 to 2.16 +/- 0.37 mmol x min(-1) x kg wet wt(-1). This effect was negated in the n-6 PUFA trial (1.04 +/- 0.20 to 1.28 +/- 0.36 mmol x min(-1) x kg wet wt(-1)). PDH kinase was unchanged in both trials, suggesting that the attenuation of PDHa activity with n-6 PUFA was a result of changes in the concentrations of intramitochondrial effectors, potentially intramitochondrial NADH or Ca(2+). Our findings suggest that attenuated PDHa activity contributes to the preferential oxidation of n-6 PUFA during moderate-intensity exercise.
authors.affiliation: Faculty of Applied Health Sciences, Brock Univ., St. Catharines, Ontario, Canada.
authors.forename: Nicolette S
authors.initials: NS
authors.lastname: Bradley
authors.forename: George J F
authors.initials: GJ
authors.lastname: Heigenhauser
authors.forename: Brian D
authors.initials: BD
authors.lastname: Roy
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Staples
authors.forename: J Greig
authors.initials: JG
authors.lastname: Inglis
authors.forename: Paul J
authors.initials: PJ
authors.lastname: LeBlanc
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Peters
mesh_terms: D000328:Adult; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism*; D004734:Energy Metabolism / Q000187:drug effects; D004789:Enzyme Activation; D015444:Exercise / Q000502:physiology*; D005227:Fatty Acids / Q000008:administration & dosage / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005231:Fatty Acids, Unsaturated / Q000008:administration & dosage / Q000378:metabolism*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011659:Pulmonary Gas Exchange; D030481:Pyruvate Dehydrogenase (Lipoamide) / Q000378:metabolism*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D013997:Time Factors
chemical_list: D004041:Dietary Fats; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D005231:Fatty Acids, Unsaturated; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex; D030481:Pyruvate Dehydrogenase (Lipoamide); C065640:pyruvate dehydrogenase E1alpha subunit; D017346:Protein Serine-Threonine Kinases