Regional leptin kinetics in humans

Background: Leptin is known to be cleared by the kidney, a tissue with subs tantial leptin receptor mRNA expression; however, lung, liver, and muscle t issues also express leptin receptor messenger RNA and it is not known wheth er these tissues also clear leptin from the circulation. Objective: This study was conducted to determine whether net leptin clearan ce takes place in the pulmonary, splanchnic, and leg tissue beds to a simil ar extent as in the kidney. Design: Plasma leptin concentrations were measured in blood entering and ex iting the renal bed, pulmonary bed, splanchnic bed, and leg in 4 groups of subjects. Regional plasma flow was measured in 3 of the 4 groups. Results: Renal leptin uptake was substantial, whereas no net uptake of lept in by the splanchnic or pulmonary vascular beds was detected; leg tissue wa s a net leptin producer. Net leptin release by leg tissue, relative to leg adipose tissue mass, was comparable with that reported previously for abdom inal subcutaneous adipose tissue. Conclusion: These results confirm that the kidney is a significant site of leptin clearance in humans, whereas pulmonary and splanchnic beds are not.