Effect of acute hypoxia on plasma leptin concentrations in men

Rationale: Leptin, a hormone secreted by the adipose tissue, is tightly involved in the endocrine control of energy expenditure and body weight regulation. Previous studies emphasize a relationship between hypoxia and leptin, but are contradicting. The aim of this study was to investigate the effects of brief hypoxia on leptin concentrations in healthy men. Methods: In a double-blind within-subject crossover design, we examined 14 healthy young men with age between 20 and 25 years and body mass index of < 25 kg/m². Hypoxic versus normoxic conditions were induced by decreasing oxygen saturation to 75% (vs. 96% in the control condition) under the condition of an euglycaemic clamp. Plasma leptin concentrations were determined at baseline, after 3 h of euglycaemic clamp, during hypoxia and the following 2.5 h thereafter. Results: T-test comparisons revealed no significant differences between the conditions at baseline (p=0.446). Also, at the euglycaemic equilibrium after 3h, plasma leptin concentrations were comparable (p>0.137). During hypoxia (p>0.195) as well as 2.5 h after hypoxia (p=0.476) plasma leptin concentrations remained equal in both conditions. There were no statistical differences between hypoxic and normoxic conditions in ANOVA (p=0.269). AUC comparison remained non-significant (p=0.180). Overall, leptin increases significantly in hypoxia (p<0.001) and normoxia (p=0.001) during the course of 6 h. Conclusions: Our results show an increase of plasma leptin concentrations after 6 h of clamping most likely reflecting the known diurnal variation of the hormone. We found no significant changes in leptin concentrations during and after brief hypoxia under euglycaemic clamp conditions. Leptin levels, therefore, seem to be unaffected by short hypoxic episodes of moderate degree.