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Reduced metabolic rate during beta-adrenergic blockade in humans
S Welle1, R G Schwartz, M Statt
1Department of Medicine (Endocrine and Cardiology Units), University of Rochester School of Medicine and Dentistry, NY.
Metabolism: Clinical and Experimental
|June 1, 1991
Summary
Beta-adrenergic blockade significantly reduces resting metabolic rate (RMR) in healthy men. Nadolol, a beta-blocker, lowered RMR by 7% without affecting thyroid hormones, indicating beta-adrenergic activity
Area of Science:
- Endocrinology
- Metabolic Physiology
- Pharmacology
Background:
- Previous studies indicated propranolol reduces resting metabolic rate (RMR).
- The mechanism for propranolol's effect on RMR was unclear, with potential involvement of reduced serum triiodothyronine (T3).
Purpose of the Study:
- To investigate the role of beta-adrenergic blockade in RMR regulation.
- To differentiate the effects of beta-adrenergic blockade from changes in thyroid hormone levels on RMR.
Main Methods:
- A study involving five healthy men treated with nadolol (a nonselective beta-adrenergic antagonist that does not affect T3 production) at 240 mg/d for 6 to 10 days.
- Measurement of postabsorptive and postprandial resting metabolic rate (RMR) and serum thyroid hormone (T3 and T4) concentrations before and after nadolol treatment.
- Comparison with a hospitalized control group and previously published data for propranolol.
Main Results:
- Nadolol treatment resulted in a 7% decline in mean postabsorptive RMR (P < .01) without significant changes in serum T3 or T4.
- The reduction in RMR with nadolol was comparable to that observed with propranolol.
- Nadolol slightly reduced the thermic response to a meal (12%), but mean postprandial RMR was significantly lower (8%, P < .01) primarily due to the reduced postabsorptive RMR.
Conclusions:
- Beta-adrenergic activity contributes significantly to resting energy expenditure in humans.
- The reduction in RMR by beta-blockers like propranolol is primarily mediated by beta-adrenergic blockade, not by alterations in thyroid hormone levels.