Leptin in peritoneal dialysate from continuous ambulatory peritoneal dialysis patients

The adipocyte derived hormone leptin is the 16-kd product of the ob gene th at regulates food intake and body weight. Plasma leptin level is elevated i n patients with chronic renal failure, partly because of impaired clearance through the kidney. In this study, we examined whether leptin is cleared i nto peritoneal dialysate in patients with end-stage renal disease treated b y continuous ambulatory peritoneal dialysis (CAPD). The subjects were 46 CA PD patients and 67 age- and gender-matched healthy subjects. Leptin concent ration in peritoneal dialysate from CAPD patients was measurable by a sensi tive enzyme-linked immunosorbent assay (ELISA), and the daily loss of lepti n by the peritoneal route was estimated to correspond to the amount contain ed in approximately 2 L plasma. Dialysate leptin concentration correlated p ositively with plasma leptin level and with percent body fat measured by du al-energy X-ray absorptiometry. The dialysate-to-plasma (DIP) ratio of lept in concentration was twice higher than expected from its molecular weight. DIP ratios of beta 2-microglobulin, albumin, and transferrin showed strong correlations with each other (r = 0.768 to 0.801), whereas the correlation between DIP ratios of leptin and beta 2-microglobulin was less impressive ( r = 0.378), This was also the case with the relationship between apparent p eritoneal clearances of these macromolecules, suggesting that dialysate lep tin had some origins other than passive transport of plasma leptin, To test the hypothesis that abdominal visceral fat may contribute to the unexpecte dly raised peritoneal dialysate leptin concentration, multiple regression a nalysis was performed. Leptin concentration in peritoneal dialysate showed significant association with plasma leptin level and DIP ratio of beta 2-mi croglobulin, and it also showed an independent association with abdominal v isceral fat but not with subcutaneous fat assessed by ultrasonography, Thes e results showed that peritoneal dialysate from CAPD patients contained a s ignificant amount of leptin, which derived presumably from both plasma and local visceral fat tissue. (C) 1999 by the National Kidney Foundation, Inc.