title: Effect of high-fat and high-carbohydrate diets on pulmonary O2 uptake kinetics during the transition to moderate-intensity exercise.
abstract: Mitochondrial pyruvate dehydrogenase (PDH) regulates the delivery of carbohydrate-derived substrate to the mitochondrial tricarboxylic acid cycle and electron transport chain. PDH activity at rest and its activation during exercise is attenuated following high-fat (HFAT) compared with high-carbohydrate (HCHO) diets. Given the reliance on carbohydrate-derived substrate early in transitions to exercise, this study examined the effects of HFAT and HCHO on phase II pulmonary O2 uptake (V̇o2 p) kinetics during transitions into the moderate-intensity (MOD) exercise domain. Eight active adult men underwent dietary manipulations consisting of 6 days of HFAT (73% fat, 22% protein, 5% carbohydrate) followed immediately by 6 days of HCHO (10% fat, 10% protein, 80% carbohydrate); each dietary phase was preceded by a glycogen depletion protocol. Participants performed three MOD transitions from a 20 W cycling baseline to work rate equivalent to 80% of estimated lactate threshold on days 5 and 6 of each diet. Steady-state V̇o2 p was greater (P < 0.05), and respiratory exchange ratio and carbohydrate oxidation rates were lower (P < 0.05) during HFAT. The phase II V̇o2 p time constant (τV̇o2 p) [HFAT 40 ± 16, HCHO 32 ± 19 s (mean ± SD)] and V̇o2 p gain (HFAT 10.3 ± 0.8, HCHO 9.4 ± 0.7 ml·min(-1·)W(-1)) were greater (P < 0.05) in HFAT. The overall adjustment (effective time constant) of muscle deoxygenation (Δ[HHb]) was not different between diets (HFAT 24 ± 4 s, HCHO 23 ± 4 s), which coupled with a slower τV̇o2 p, indicates a slowed microvascular blood flow response. These results suggest that the slower V̇o2 p kinetics associated with HFAT are consistent with inhibition and slower activation of PDH, a lower rate of pyruvate production, and/or attenuated microvascular blood flow and O2 delivery.
authors.affiliation: Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada;
authors.forename: J A
authors.initials: JA
authors.lastname: Raper
authors.affiliation: Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada; Department of Kinesiology, Centre for Bone and Muscle Health, Brock University, St. Catharines, Ontario, Canada.
authors.forename: L K
authors.initials: LK
authors.lastname: Love
authors.affiliation: Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada;
authors.forename: D H
authors.initials: DH
authors.lastname: Paterson
authors.affiliation: Department of Kinesiology, Centre for Bone and Muscle Health, Brock University, St. Catharines, Ontario, Canada.
authors.forename: S J
authors.initials: SJ
authors.lastname: Peters
authors.affiliation: Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and.
authors.forename: G J F
authors.initials: GJ
authors.lastname: Heigenhauser
authors.affiliation: Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada; Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada; jkowalch@uwo.ca.
authors.forename: J M
authors.initials: JM
authors.lastname: Kowalchuk
mesh_terms: D000328:Adult; D050260:Carbohydrate Metabolism; D059305:Diet, High-Fat; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage* / Q000378:metabolism; D015444:Exercise; D064368:Healthy Volunteers; D006339:Heart Rate; D006801:Humans; D050356:Lipid Metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000201:enzymology; D009132:Muscles / Q000098:blood supply / Q000378:metabolism; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D055815:Young Adult
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D011768:Pyruvate Dehydrogenase Complex
keywords: O2 uptake kinetics; high-carbohydrate diet; high-fat diet; muscle deoxygenation; near-infrared spectroscopy; substrate oxidation