Regulation of glucose kinetics during intense exercise in humans: Effects of α- and β-adrenergic blockade

Kirsten F. Howlett, Matthew J. Watt, Mark Hargreaves, Mark A. Febbraio

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This study examined the effect of combined α- and β-adrenergic blockade on glucose kinetics during intense exercise. Six endurance-trained men exercised for 20 minutes at approximately 78% of their peak oxygen consumption (Vo2) following ingestion of a placebo (CON) or combined α- (prazosin hydrochloride) and β- (timolol maleate) adrenoceptor antagonists (BLK). Plasma glucose increased during exercise in CON (0 minutes: 5.5 ± 0.1; 20 minutes: 6.5 ± 0.3 mmol.L-1, P < .05). In BLK, the exercise-induced increase in plasma glucose was abolished (0 minutes: 5.7 ± 0.3; 20 minutes: 5.7 ± 0.1 mmol.L-1). Glucose kinetics were measured using a primed, continuous infusion of [6,6-2H] glucose. Glucose production was not different between trials; on average these values were 25.3 ± 3.9 and 30.9 ± 4.4 μ in CON and BLK, respectively. Glucose uptake during exercise was greater (P < .05) in BLK (30.6 ± 4.6 μ compared with CON (18.4 ± 2.5 μ In BLK, plasma insulin and catecholamines were higher (P < .05), while plasma glucagon was unchanged from CON. Free fatty acids (FFA) and glycerol were lower (P < .05) in BLK. These findings demonstrate that adrenergic blockade during intense exercise results in a blunted plasma glucose response that is due to enhanced glucose uptake, with no significant change in glucose production.

Original languageEnglish
Pages (from-to)1615-1620
Number of pages6
JournalMetabolism: Clinical and Experimental
Issue number12
Publication statusPublished - 1 Jan 2003
Externally publishedYes

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