Leptin and Exercise

It is established that plasma leptin is associated with satiety and that leptin stimulates lipid metabolism,and increases energy expenditure.These effects implicate leptin as a major regulator of energy homeostasis,which may serve to limit excess energy storage.As plasma leptin concentrations are tightly coupled with fat mass in humans,decreases in adipose mass with weight loss coincide with decreased concentrations of circulating leptin.However,many findings raise speculation that exercise-associated reductions in leptin may be due to alterations in nutrient availability or nutrient flux at the level of the adipocytes,the primary site of leptin production and secretion.Thus,one purpose of this review is to discuss the effects of exercise on circulating leptin concentrations with special emphasis on studies that have examined single exercise bouts that are associated with high levels of energy expenditure and energy deficit.In addition,a 'nutrient sensing pathway'(the hexosamine biosynthetic pathway),wich regulates leptin gene expression,will be discussed as a possible mechanism by wich exercise-induced energy deficit may modulate serum leptin concentrations.