A single bout of exercise induces β-adrenergic desensitization in human adipose tissue

Abstract

This study was designed to assess whether physiological activation of the sympathetic nervous system induced by exercise changes adipose tissue responsiveness to catecholamines in humans. Lipid mobilization in abdominal subcutaneous adipose tissue was studied with the use of a microdialysis method in 11 nontrained men (age: 22. 3 +/- 1.5 yr; body mass index: 23.0 +/- 1.6). Adipose tissue adrenergic sensitivity was explored with norepinephrine, dobutamine (beta(1)-agonist), or terbutaline (beta(2)-agonist) perfused during 30 min through probes before and after 60-min exercise (50% of the maximal aerobic power). The increase in extracellular glycerol concentration during 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 control experiment realized without exercise, no difference in norepinephrine-induced 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 was explored with two 60-min infusions of norepinephrine or epinephrine separated by a 60-min interval. With both catecholamines, the increase in glycerol was significantly lower during the second infusion (P < 0.05). The findings suggest that aerobic exercise, which increased adrenergic activity, induces a desensitization in beta(1)- and beta(2)-adrenergic lipolytic pathways in human subcutaneous adipose tissue.

Major differences in noradrenaline action on lipolysis and blood flow rates in skeletal muscle and adipose tissue in vivo

“…However, during the second half of the infusion the glycerol levels continuously decreased towards basal levels. In agreement with previous findings [26,27], this phenomenon is best explained by catecholamine tachyphylaxia, i.e. desensitisation of the beta-adrenergic receptors in response to sustained [26] or repeated [27] catecholamine stimulation.…”

“…*p<0.05 for differences between noradrenaline concentrations line-induced increase in adipose tissue lipolysis rates was influenced by waning delivery of the catecholamine via the circulation, rather than being a reflection of adipocyte betaadrenoceptor desensitisation. However, the fact that repeated administration of noradrenaline to adipose tissue in situ resulted in a blunted lipolytic response but with no appreciable effect on blood flow rates [27], renders this possibility less likely. Further insight into this issue might be given by monitoring the interstitial concentrations of noradrenaline.…”

Human Skeletal Muscle Lipolysis Is More Responsive to Epinephrine Than to Norepinephrine Stimulationin Vivo

“…In adipose tissue, epinephrine mediated a concentrationdependent rise in glycerol levels, and the maximum response was significantly higher with epinephrine than norepinephrine; the latter being consistent with earlier reports (28,30). However, the lowest concentration of the two catecholamines causing a significant increase in adipose tissue glycerol was the same with norepinephrine as with epinephrine, which may suggest similar lipolytic sensitivity to either catecholamine in adipose tissue.…”

Activation of α2-adrenergic receptors blunts epinephrine-induced lipolysis in subcutaneous adipose tissue during a hyperinsulinemic euglycemic clamp in men

“…Then, the perfusion flow rate was set at 2.5 l/min for the remaining experimental period. This simplified but relevant and less time-consuming method was selected in this long-lasting study (24,30). The estimated extracellular glycerol concentration (EGC) was calculated by plotting (after log transformation) the concentration of glycerol in the dialysate measured at 0.5 and 2.5 l/min against the perfusion rates.…”