Regional leptin kinetics in humans

Background: Leptin is known to be cleared by the kidney, a tissue with substantial leptin receptor mRNA expression; however, lung, liver, and muscle tissues also express leptin receptor messenger RNA and it is not known whether these tissues also clear leptin from the circulation. Objective: This study was conducted to determine whether net leptin clearance takes place in the pulmonary, splanchnic, and leg tissue beds to a similar extent as in the kidney. Design: Plasma leptin concentrations were measured in blood entering and exiting 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 leptin by the splanchnic or pulmonary vascular beds was detected; leg tissue was a net leptin producer. Net leptin release by leg tissue, relative to leg adipose tissue mass, was comparable with that reported previously for abdominal 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.