THE EFFECT OF EXERCISE ON LEPTIN CONCENTRATION IN HEALTHY-MEN AND IN TYPE-1 DIABETIC-PATIENTS

Purpose: Leptin is a recently discovered hormone that appears as a reg ulator of energy balance. It is important to know whether Ieptin conce ntrations are changed under conditions of altered energy homeostasis. Consequently, we examined the effects of exercise with fasting and exe rcise with feeding on circulating Ieptin concentrations in healthy men and in type 1 diabetic patients with normal body weight and well cont rolled diabetes. Methods: Leptin concentrations were determined with r adioimmunoassay. Results: During a 3-h cycle ergometer exercise with f asting, Ieptin decreased by 42% (P < 0.01) in nine healthy men and by 23% (P = 0.05) in eight male type I diabetic patients. Leptin fell equ ally by 12% (P < 0.03) both in nine healthy men and in eight male type 1 diabetic patients who were studied as it resting control group. The absolute fall in leptin in healthy men was similar in the exercise an d resting control groups (0.8 +/- 0.1 mu g.L-1 vs 0.8 +/- 0.2 mu g.L-1 ). However, due to lower leptin concentration before the exercise, the relative decrease (42%) was greater than during the resting control s tudy (12%, P < 0.005). This difference was not seen in the diabetic pa tients. Fasting leptin concentration correlated positively with BMI (r = 0.75, P < 0.001) and fasting insulin (r = 0.71, P < 0.01) in health y men as well as with insulin level (r = 0.54, p<0.05) in type 1 diabe tic patients. When exercise was performed with feeding, and this was a ssociated with a significant rise in serum cortisol level (marathon ru n, 14 healthy men and 7 type I diabetic patients), Ieptin concentratio n did not change significantly. Conclusions: I) During morning hours, Ieptin decreases both in healthy men and in type I diabetic patients, reflecting a diurnal variation of Ieptin concentration and the effect of fasting on leptin concentration. 2) The fall in leptin during morni ng hours is augmented by physical exercise in healthy men. 3) If exerc ise is performed with feeding and associated with a rise in serum cort isol level, Ieptin concentration remains unchanged. These data suggest that although exercise may reduce circulating leptin levels, the effe ct is small and can be counterbalanced by feeding or a rise in serum c ortisol concentration.