LEPTIN IS PRESENT IN HUMAN CORD-BLOOD

It has recently been reported that the ob gene receptor was expressed on human and murine hematopoietic stem cells and that the ob gene prod uct leptin stimulated hemato- and lymphopoiesis at the stem cell level . These findings suggest a role for leptin in hemato- and lymphopoiesi s during fetal development. There is at present no evidence, however, that leptin is synthesized and released by the fetus. To investigate t his possibility, we have measured plasma leptin concentrations in the cord blood of 78 newborn infants. We found that leptin was present in all 78 infants in concentrations comparable with those found in adults (0.6-55.7 ng/ml). Overall, plasma leptin concentrations in the cord b lood of infants correlated with birth weight (r = 0.74, P < 0.001). Th ese observations show that leptin is synthesized and released by fetal fat cells. In addition, they are compatible with the concept that lep tin may play a role in human fetal hematopoiesis.