The effect of selective beta adrenergic blockade on glucose-induced thermogenesis in man.
We have previously shown that the increase in energy expenditure following glucose/insulin infusion is, in large part, mediated by the sympathetic nervous system and that this sympathetic component can be blocked by the nonselective beta-1, beta-2 antagonist propranolol. To examine which beta adrenergic receptor mediates this thermogenic response, we performed euglycemic insulin clamp studies in eight healthy control subjects with and without metoprolol at a dose known to block only the beta-1 adrenergic receptor. Basal glucose oxidation and energy expenditure were similar in the control and metoprolol groups. During the last hour of the insulin clamp study, glucose oxidation (3.06 +/- 0.25 v 2.92 +/- 0.21 mg/kg X min), total body glucose uptake (8.17 +/- 0.70 v 7.13 +/- 0.49 mg/kg X min), and nonoxidative glucose uptake (5.11 +/- 0.60 v 4.21 +/- 0.44 mg/kg X min) were not different in the control compared to the metoprolol group. However, the increment in energy expenditure was inhibited by 64% during metoprolol infusion (0.04 +/- 0.01 v 0.11 +/- 0.02 kcal/min, P less than 0.01). Glucose/insulin-induced thermogenesis was similarly reduced by metoprolol (2.56 +/- 0.81 v 5.04 +/- 0.74%, P less than 0.01). These results are quantitatively quite similar to those observed with propranolol. We conclude that the beta adrenergic nervous system and, specifically, the beta-1 receptor mediates the thermogenic response to glucose/insulin infusion.
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001831:Body Temperature / Q000187:drug effects*; D004734:Energy Metabolism / Q000187:drug effects*; D005947:Glucose / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000097:blood / Q000494:pharmacology; D008297:Male; D008790:Metoprolol / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects
D001786:Blood Glucose; D007328:Insulin; D008790:Metoprolol; D005947:Glucose