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Substantial working muscle glycerol turnover during two-legged cycle ergometry

Substantial working muscle glycerol turnover during two-legged cycle ergometry We combined tracer and arteriovenous (a-v) balance techniques to evaluate the effects of exercise and endurance training on leg triacylglyceride turnover as assessed by glycerol exchange. Measurements on an exercising leg were taken to be a surrogate for working skeletal muscle. Eight men completed 9 wk of endurance training 5 days/wk, 1 h/day, 75% peak oxygen consumption ( O 2peak ), with leg glycerol turnover determined during two pretraining trials 45 and 65% O 2peak (45% Pre and 65% Pre, respectively) and two posttraining trials 65% of pretraining O 2peak (ABT) and 65% of posttraining O 2peak (RLT) using 2 H 5 glycerol infusion, femoral a-v sampling, and measurement of leg blood flow. Endurance training increased O 2peak by 15% (45.2 ± 1.2 to 52.0 ± 1.8 ml·kg –1 ·min –1 , P < 0.05). At rest, there was tracer-measured leg glycerol uptake (41 ± 8 and 52 ± 15 µmol/min for pre- and posttraining, respectively) even in the presence of small, but significant, net leg glycerol release (–68 ± 19 and –50 ± 13 µmol/min, respectively; P < 0.05 vs. zero). Furthermore, while there was no significant net leg glycerol exchange during any of the exercise bouts, there was substantial tracer-measured leg glycerol turnover during exercise (i.e., simultaneous leg muscle uptake and leg release) (uptake, release: 45% Pre, 194 ± 41, 214 ± 33; 65% Pre, 217 ± 79, 201 ± 84; ABT, 275 ± 76, 312 ± 87; RLT, 282 ± 83, 424 ± 75 µmol/min; all P < 0.05 vs. corresponding rest). Leg glycerol turnover was unaffected by exercise intensity or endurance training. In summary, simultaneous leg glycerol uptake and release (indicative of leg triacylglyceride turnover) occurs despite small or negligible net leg glycerol exchange, and furthermore, leg glycerol turnover can be substantially augmented during exercise. exercise; crossover concept; stable isotopes; lipid metabolism Address for reprint requests and other correspondence: G. A. Brooks, Dept. of Integrative Biology, 3060 Valley Life Science Bldg., Univ. of California-Berkeley, Berkeley, CA 94720-3140 (e-mail: gbrooks@berkeley.edu ) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Endocrinology and Metabolism The American Physiological Society

Substantial working muscle glycerol turnover during two-legged cycle ergometry

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References (34)

Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0193-1849
eISSN
1522-1555
DOI
10.1152/ajpendo.00099.2007
pmid
17623753
Publisher site
See Article on Publisher Site

Abstract

We combined tracer and arteriovenous (a-v) balance techniques to evaluate the effects of exercise and endurance training on leg triacylglyceride turnover as assessed by glycerol exchange. Measurements on an exercising leg were taken to be a surrogate for working skeletal muscle. Eight men completed 9 wk of endurance training 5 days/wk, 1 h/day, 75% peak oxygen consumption ( O 2peak ), with leg glycerol turnover determined during two pretraining trials 45 and 65% O 2peak (45% Pre and 65% Pre, respectively) and two posttraining trials 65% of pretraining O 2peak (ABT) and 65% of posttraining O 2peak (RLT) using 2 H 5 glycerol infusion, femoral a-v sampling, and measurement of leg blood flow. Endurance training increased O 2peak by 15% (45.2 ± 1.2 to 52.0 ± 1.8 ml·kg –1 ·min –1 , P < 0.05). At rest, there was tracer-measured leg glycerol uptake (41 ± 8 and 52 ± 15 µmol/min for pre- and posttraining, respectively) even in the presence of small, but significant, net leg glycerol release (–68 ± 19 and –50 ± 13 µmol/min, respectively; P < 0.05 vs. zero). Furthermore, while there was no significant net leg glycerol exchange during any of the exercise bouts, there was substantial tracer-measured leg glycerol turnover during exercise (i.e., simultaneous leg muscle uptake and leg release) (uptake, release: 45% Pre, 194 ± 41, 214 ± 33; 65% Pre, 217 ± 79, 201 ± 84; ABT, 275 ± 76, 312 ± 87; RLT, 282 ± 83, 424 ± 75 µmol/min; all P < 0.05 vs. corresponding rest). Leg glycerol turnover was unaffected by exercise intensity or endurance training. In summary, simultaneous leg glycerol uptake and release (indicative of leg triacylglyceride turnover) occurs despite small or negligible net leg glycerol exchange, and furthermore, leg glycerol turnover can be substantially augmented during exercise. exercise; crossover concept; stable isotopes; lipid metabolism Address for reprint requests and other correspondence: G. A. Brooks, Dept. of Integrative Biology, 3060 Valley Life Science Bldg., Univ. of California-Berkeley, Berkeley, CA 94720-3140 (e-mail: gbrooks@berkeley.edu )

Journal

AJP - Endocrinology and Metabolism – The American Physiological Society

Published: Oct 1, 2007

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