The effect of continuous ambulatory peritoneal dialysis on change in serumleptin

Objective: Elevated serum leptin can contribute to anorexia and poor nutrit ion in patients with chronic renal failure, because leptin is elevated in c hronic renal failure patients with or without dialysis, especially in chron ic ambulatory peritoneal dialysis (CAPD) patients. The aim of this study wa s to find whether leptin can be removed by peritoneal dialysis (PD) and to analyze factors that can affect serum leptin after start of CAPD by observi ng the change in serum leptin shortly after start of CAPD and its correlati on with body mass index (BMI), with serum insulin, and with residual renal function. Design:Twenty patients who started CAPD during the observation period were studied. Serum leptin was measured by radioimmunoassay before start of CAPD , 3-5 days after start of CAPD, and 1 month and 3 months after start of CAP D. Simultaneously, body weight, serum insulin, and residual renal function were measured. To compensate for the circardian rhythm of leptin, removal o f leptin was assessed by measuring dialysate leptin divided by average seru m leptin before and after a peritoneal equilibration test (PET). Results: Leptin was eliminated by PD with a dialysate-to-serum ratio of 0.1 6 +/- 0.07, which was comparable to removal of beta(2)-microglobulin (0.14 +/- 0.06). The mean serum leptin concentrations did not decrease after 3-5 days of CAPD (8.4 +/- 13.1 ng/mL --> 11.0 +/- 18.0 ng/mL) despite its remov al by PD, and levels increased markedly to 189% of basal serum leptin 1 mon th after start of PD and to 260% of basal serum leptin 3 months after start of PD. Correlation coefficients (Spearman's rho) between change of serum l eptin and change of BMI, of serum insulin, of glomerular filtration rate (a verage of urine creatinine clearance and urine urea clearance) were 0.267 ( p > 0.05, n = 20), 0.441 (p > 0.05, n = 16), 0.706 (p > 0.05, n = 8) respec tively. Conclusion: Leptin is removed by peritoneal dialysis. Serum leptin did not decrease in 5 days after the start of PD despite its removal by PD, but inc reased markedly thereafter, within 3 months after start of PD. We could not find a significant correlation between the change in leptin and the change in BMI. Factors other than fat-mass gain can stimulate leptin increase sho rtly after start of PD.