Beta-adrenergic blockade does not influence the thermogenic response to a mixed meal in man.

Abstract

The sympathetic nervous system has been implicated in the regulation of glucose-induced thermogenesis in man. The present study was undertaken to examine the influence of a pharmacological beta blockade on the thermogenic response after ingestion of a mixed meal. Ten healthy male volunteers were examined on two occasions, once during intravenous administration of beta-blocking agent (Series 1) and once without (Series 2). Five subjects received propranolol and the other five atenolol. Two subjects were also studied on a third occasion after 1 week of other propranolol medication (Series 3). Continuous respiratory gas exchange measurements were carried out for 1 h in the basal state and then for 3 h postprandially. The subjects ingested a standardized test meal in liquid form. After the meal oxygen uptake and energy expenditure both rose markedly during the first hour and then reached a relatively stable plateau. The average increase in oxygen uptake above basal during the whole study period was 27.0 +/- 1.4 vs. 26.7 +/- 1.4% (NS) in Series 1 and 2, respectively. The corresponding values for energy expenditure were 28.6 +/- 1.4 vs. 28.6 +/- 1.6%. Also in absolute terms, the increments above basal did not differ between the two series. Moreover, the basal measurements and the response to the meal were no different in the subjects in Series 1 receiving the selective beta-1 antagonist and the non-selective blocker, respectively. In conclusion, the present findings indicate that in healthy man, beta-adrenergically mediated sympathetic nervous system activity does not significantly influence the magnitude of the thermogenic response to a mixed meal.