The purpose of this experiment was to determine whether β3-adrenergic receptor blockade attenuates fat metabolism during exercise. Twenty-eight male Sprague-Dawley rats were randomly assigned to one of four groups: control (C; n=8), exercise (E; n=8), control + β3 blockade (Cβ3; n=6), or exercise + β3 blockade (Eβ3; n=6). Exercise consisted of a 55-min-long treadmill run, while the control animals were placed in cages (for the same time) in the room with the treadmill. Thirty minutes prior to the exercise and control conditions a highly specific β3 receptor blocking compound, SR 59230A, or vehicle were tube fed to the animals. SR 59230A was given at a dose of 20 mg/kg and was kindly provided by Dr. L. Manara (Research Center Sanofi Midy, Milan, Italy). SR 59230A had no effect on serum FFA in the resting state but resulted in higher (p < 0.05) FFA levels during exercise (i.e., 0.727 ± 0.034 mmol for Eβ3 vs. 0.501 ± 0.004 mmol for E). Serum leptin levels were unaffected by the SR 59230A compound at rest or during exercise; however, there was a significant main effect of exercise to increase (p < 0.05) serum leptin levels, independent of the SR 59230A compound (i.e., 5.0 ± 0.6 ng/ml for E vs. 3.1 ± 0.2 ng/ml for C). These data suggest that instead of preventing a rise in serum FFA during exercise, β3-adrenergic receptor blockade increased FFA availability. It is possible that β3 receptor blockade increased the sensitivity of β1 and β2 receptors to circulating catecholamines thereby enhancing lipolysis. Secondly, while in humans acute exercise has no influence on serum leptin levels, the effect in male Sprague-Dawley rats is to increase serum leptin.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Molecular Biology