Intraperitoneal insulin reduces plasma leptin concentration in diabetic patients on CAPD.

OBJECTIVE: To determine the effects of subcutaneous (SC) and intraperitoneal (IP) insulin on serum leptin concentration in type I diabetic patients with end-stage renal failure treated with continuous ambulatory peritoneal dialysis (CAPD). DESIGN: Prospective, open, before-after study. SETTING: Tertiary-care university hospital. PARTICIPANTS: Twelve type I diabetic patients with stabilized CAPD, age 43.9 +/- 2.8 years, and duration of diabetes 30.4 +/- 3.5 years. INTERVENTION: After stabilized CAPD therapy, all patients were treated first with SC insulin for a median of 3 months, and thereafter with IP insulin for another 3 months. MAIN OUTCOME MEASURES: Plasma leptin, insulin sensitivity with euglycemic clamp, and glycemic and uremic status after both treatment periods. RESULTS: During SC insulin therapy, plasma leptin concentration was significantly higher than during IP insulin (19.8 +/- 5.9 ng/mL and 12.8 +/- 6.2 ng/mL, respectively; p < 0.001). Leptin concentration was higher in CAPD patients and was related to body mass index in both genders. No correlation was detected between plasma leptin and fasting insulin, glycemic control, glucose disposal rate, or serum lipids. CONCLUSION: Plasma leptin concentration is lower during IP insulin therapy compared to SC insulin. Insulin has probably a direct effect on both peritoneal leptin clearance and adipose tissue leptin production. The significance of leptin in regulating appetite and anorexia in uremia remains unclear.