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Effects of dynamic exercise intensity on the activation of hormone‐sensitive lipase in human skeletal muscle
Author(s) -
Watt Matthew J.,
Heigenhauser George J. F.,
Spriet Lawrence L.
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2003.00301.x
Subject(s) - hormone sensitive lipase , endocrinology , medicine , skeletal muscle , phosphocreatine , chemistry , vo2 max , lipase , physical exercise , intramuscular fat , fatty acid , biochemistry , biology , enzyme , heart rate , energy metabolism , blood pressure
It has been proposed that hormone‐sensitive lipase (HSL) regulates intramuscular triacylglycerol hydrolysis in skeletal muscle. The primary purpose of this study was to examine the early activation of HSL and the changes in the putative intramuscular and hormonal regulators of HSL activity at various aerobic exercise intensities. Eight male subjects cycled for 10 min at power outputs corresponding to 30, 60 and 90 % peak oxygen uptake ( V̇ O2,peak ). Muscle samples were obtained at rest and following 1 and 10 min of exercise. Intramuscular triacylglycerol (mean ± s.e.m .: 24.3 ± 2.3 mmol (kg dry mass (DM)) ‐1 ), long‐chain fatty acyl CoA (13.9 ± 1.4 µmol (kg DM) ‐1 ) and HSL activity (1.87 ± 0.07 mmol min ‐1 (kg DM) ‐1 )) were not different between trials at rest. HSL activity increased at 1 min of exercise at 30 and 60 % V̇ O2,peak , and to a greater extent at 90 % V̇ O2,peak . HSL activity remained elevated after 10 min of exercise at 30 and 60 % V̇ O2,peak , and decreased at 90 % V̇ O2,peak from the rates observed at 1 min (1 min: 3.41 ± 0.3 mmol min ‐1 (kg DM) ‐1 ; 10 min: 2.92 ± 0.26 mmol min ‐1 (kg DM) ‐1 ), P < 0.05 ). There were no effects of exercise power output or time on long‐chain fatty acyl CoA content. At 90 % V̇ O2,peak , skeletal muscle contents of ATP and phosphocreatine were decreased ( P < 0.05 ), and free ADP and free AMP were increased ( P < 0.05 ) during exercise. No changes in these metabolites occurred at 30 % V̇ O2,peak and only modest changes were observed at 60 % V̇ O2,peak . Plasma adrenaline increased ( P < 0.05 ) during exercise at 90 % V̇ O2,peak only. These data suggest that a factor related to the onset of exercise (e.g. Ca 2+ ) activates HSL early in exercise. Given the activation of HSL early in exercise, at a time when intramuscular triacylglycerol hydrolysis and fat oxidation are considered to be negligible, we propose that the control of intramuscular triacylglycerol hydrolysis is not solely related to the level of HSL activation, but must also be regulated by postactivational factors.