Evidence for inhibition of leptin secretion by catecholamines in man.

The regulation of leptin secretion is complex and not entirely understood in humans. Insulin has been shown to stimulate leptin secretion in humans, whereas in vitro data suggest that catecholamines inhibit leptin secretion. The present studies were therefore undertaken to examine the leptin response to hyperinsulinemia in the presence and absence of elevated plasma levels of endogenous catecholamines in humans. Leptin concentrations were determined during both a euglycemic and hypoglycemic hyperinsulinemic clamp study in 10 normal and 10 type I diabetic subjects. Serum leptin increased during the hyperinsulinemic euglycemic clamp in normal (from 6.1 +/- 0.9 to 7.2 +/- 1.1 ng/dl, p = 0.003) and diabetic subjects (from 6.2 +/- 1.4 to 7.8 +/- 1.8 ng/dl, p = 0.001). During hyperinsulinemic hypoglycemia leptin concentrations increased significantly in type 1 diabetic patients (from 5.6 +/- 1.1 to 7.6 +/- 1.7 ng/dl, p = 0.003) but remained unaltered in normals (from 5.5 +/- 0.7 to 5.7 +/- 0.9 ng/dl, p = 0.7). During hypoglycemia in all subjects the increase in leptin was negatively correlated with the increase in epinephrine (r = 0.60, p = 0.005) and positively with the decrease in free fatty acids (r = 0.71, p = 0.003). In conclusion our results indicate that catecholamines play a suppressive role in the regulation of leptin secretion.