Journal of Applied Physiology, Vol 67, Issue 1 221-225, Copyright © 1989 by American Physiological Society

ARTICLES

Beta-adrenergic blockade alters whole-body leucine metabolism in humans

L. S. Lamont, D. G. Patel and S. C. Kalhan
Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44109.

This study examined the effects of a nonselective beta-blocking agent on whole-body leucine metabolism in humans. Five normal, healthy subjects (4 male, 1 female) underwent a 6-h primed, constant-rate infusion of L-[1-13C]leucine after 5 days of twice daily oral use of 80 mg propranolol and a placebo. Leucine turnover was determined by tracer dilution and leucine oxidation by 13C enrichment of the expired CO2. Propranolol decreased the total daily energy expenditure from 1,945 +/- 177.5 to 1,619 +/- 92.5 kcal/day (P less than 0.05). A fasting associated decrease in blood glucose and an attenuated rise in free fatty acids and ketones were observed during beta-blockade. Propranolol also increased plasma leucine concentrations (73.1 +/- 8.7 to 103.4 +/- 7.3 mumol/l; P less than 0.05) and leucine oxidation (13.2 +/- 1.2 to 17.1 +/- 1.3 mumol.kg-1.h-1; P less than 0.05), although leucine turnover was not significantly altered (100.5 +/- 7.3 vs. 126.0 +/- 12.3 mumol.kg-1.h-1). In addition, the urinary urea nitrogen-to-creatinine ratio was greater during propranolol administration (0.24 +/- 0.04 vs. 0.34 +/- 0.02 mol/g; P less than 0.05). These data suggest that the beta-adrenergic system plays a role in the modulation of whole-body leucine metabolism in humans. Whether these changes are the result of a direct effect on skeletal muscle or an indirect effect mediated by altering the fuel supply to skeletal muscle cannot be discriminated by the present study.

This article has been cited by other articles:

				N. R. Stob, D. R. Seals, J. Jensen, M. A. van Baak, A. J. Steig, R. C. Lindstrom, B. T. Bikman, and C. Bell Autonomic Neuroscience: Increased thermogenic responsiveness to intravenous {beta}-adrenergic stimulation in habitually exercising humans is not related to skeletal muscle {beta}2-adrenergic receptor density Exp Physiol, September 1, 2007; 92(5): 823 - 830. [Abstract] [Full Text] [PDF]

				C. Bell, N. R. Stob, and D. R. Seals Thermogenic responsiveness to nonspecific beta-adrenergic stimulation is not related to genetic variation in codon 16 of the beta2-adrenergic receptor Am J Physiol Endocrinol Metab, April 1, 2006; 290(4): E703 - E707. [Abstract] [Full Text] [PDF]

				C. Bell, N. R. Stob, and D. R. Seals Thermogenic responsiveness to {beta}-adrenergic stimulation is augmented in exercising versus sedentary adults: role of oxidative stress J. Physiol., February 1, 2006; 570(3): 629 - 635. [Abstract] [Full Text] [PDF]

				M. J. Hamadeh, M. C. Devries, and M. A. Tarnopolsky Estrogen Supplementation Reduces Whole Body Leucine and Carbohydrate Oxidation and Increases Lipid Oxidation in Men during Endurance Exercise J. Clin. Endocrinol. Metab., June 1, 2005; 90(6): 3592 - 3599. [Abstract] [Full Text] [PDF]

				L. S. Lamont, A. J. McCullough, and S. C. Kalhan Gender differences in the regulation of amino acid metabolism J Appl Physiol, September 1, 2003; 95(3): 1259 - 1265. [Abstract] [Full Text] [PDF]

				C. Bell, D. R. Seals, M. B. Monroe, D. S. Day, L. F. Shapiro, D. G. Johnson, and P. P. Jones Tonic Sympathetic Support of Metabolic Rate Is Attenuated with Age, Sedentary Lifestyle, and Female Sex in Healthy Adults J. Clin. Endocrinol. Metab., September 1, 2001; 86(9): 4440 - 4444. [Abstract] [Full Text] [PDF]

				M. B. Monroe, D. R. Seals, L. F. Shapiro, C. Bell, D. Johnson, and P. P. Jones Direct evidence for tonic sympathetic support of resting metabolic rate in healthy adult humans Am J Physiol Endocrinol Metab, May 1, 2001; 280(5): E740 - E744. [Abstract] [Full Text] [PDF]

				L. S. Lamont, A. J. McCullough, and S. C. Kalhan Comparison of leucine kinetics in endurance-trained and sedentary humans J Appl Physiol, January 1, 1999; 86(1): 320 - 325. [Abstract] [Full Text] [PDF]