INTER-ORGAN LEPTIN EXCHANGE IN HUMANS

To assess the individual role of splanchnic organs, kidney, and periph eral tissues on leptin metabolism, leptin exchange across the splanchn ic bed, kidney, and leg has been evaluated by the arterio-venous techn ique in postabsorptive non-obese subjects. Leptin levels in the hepati c and renal veins were significantly lower (p < 0.001), while femoral vein levels were consistently greater (p < 0.05) than in the artery. T he fractional extraction of leptin, namely the percentage of arterial leptin extracted, was greater in splanchnic organs (16%) than in the k idney (9.5%). Urinary excretion of leptin was undetectable in most sub jects, indicating that leptin is degraded within the kidney. There was no correlation between fractional extraction of leptin and glomerular filtration rate, whereas leptin fractional extraction was directly re lated to renal plasma flow (p = 0.017),Renal leptin clearance was abou t 50% of the glomerular filtration rate. Our data demonstrate that bot h splanchnic organs and the kidney cooperate in the disposal of leptin , while peripheral tissues add significant amounts of leptin to the ci rculation. In non-obese subjects the contribution of the kidney to who le body clearance is no more than 50%. The removal of leptin by the ki dney depends on renal plasma flow but not on glomerular filtration rat e or filtered leptin. (C) 1998 Academic Press.