Adrenergic regulation of lipolysis in human fat cells during exercise

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Abstract
The adrenergic regulation of lipolysis was studied, before and after 30 min of submaximal exercise, in isolated adipocytes removed from the abdominal and gluteal regions of healthy non‐obese men and women. Noradrenaline‐induced lipolysis was significantly enhanced in gluteal adipocytes from men but not in women after exercise. However, the pure beta‐adrenergic responsiveness was equally increased in gluteal adipocytes of both sexes after exercise, as judged by the effect of isoprenaline. Furthermore, the alpha2‐adrenergic anti‐lipolytic responsiveness was more apparent after exercise in females than in males thereby counter‐balancing the increase in the beta‐adrenergic effect in the gluteal region in the former. The increased beta‐adrenergic responsiveness induced by exercise in gluteal adipocytes of males could be mimicked by agents acting at the levels of adenylate cyclase, coupling proteins, phosphodiesterase, and protein kinase and seems to be due to an adaptive enhancement at the hormone‐sensitive‐lipase level. There was no change in the stoichiometric properties of beta‐adrenoceptors of gluteal adipocytes after exercise. Abdominal adipocytes of both sexes were four to five times more responsive to noradrenaline than gluteal ones. However, exercise induced no further enhancement of the catecholamine‐stimulated lipolysis rate in fat cells from this site. Thus, the influence of exercise on catecholamine‐stimulated lipolysis is regional and sex dependent. Men, but not women, have a greater ability to adapt lipolysis to increasing energy demands during exercise that are due to an acute increase in the effectiveness of the hormone‐sensitive lipase complex. This effect was observed only in the gluteal region, whereas lipolysis in the abdominal region did not adapt to exercise. Women, in general, were more responsive than males to catecholamines in the abdominal region.