A single bout of exercise induces beta-adrenergic desensitization in humanadipose tissue

This study was designed to assess whether physiological activation of the s ympathetic nervous system induced by exercise changes adipose tissue respon siveness to catecholamines in humans. Lipid mobilization in abdominal subcu taneous adipose tissue was studied with the use of a microdialysis method i n 11 nontrained men (age: 22.3 +/- 1.5 yr; body mass index: 23.0 +/- 1.6). Adipose tissue adrenergic sensitivity was explored with norepinephrine, dob utamine (beta (1)-agonist), or terbutaline (beta (2)-agonist) perfused duri ng 30 min through probes before and after 60-min exercise (50% of the maxim al aerobic power). The increase in extracellular glycerol concentration dur ing infusion was significantly lower after the exercise when compared with the increase observed before the exercise (P < 0.05, P < 0.02, and P < 0.01 , respectively, for norepinephrine, dobutamine, and terbutaline). In a cont rol experiment realized without exercise, no difference in norepinephrine-i nduced glycerol increase between the two infusions was observed. To assess the involvement of catecholamines in the blunted <beta>-adrenergic-induced lipolytic response after exercise, adipose tissue adrenergic sensitivity wa s explored with two 60-min infusions of norepinephrine or epinephrine separ ated by a 60-min interval. With both catecholamines, the increase in glycer ol was significantly lower during the second infusion (P, 0.05). The findin gs suggest that aerobic exercise, which increased adrenergic activity, indu ces a desensitization in beta (1)- and beta (2)-adrenergic lipolytic pathwa ys in human subcutaneous adipose tissue.