Serum leptin concentration in peritoneal dialysis patients: determinants, longitudinal evolution and circadian rhythm

The serum concentration of leptin, an hormone secreted by adipocytes, is increased in obese and chronic renal failure patients. To determine the influence of peritoneal dialysis (PD) therapy on serum leptin levels, we analyzed its concentration in 23 patients on PD for an average of 26.8 +/- 7.1 months and compared it to that of 18 patients with chronic renal failure (creatinine clearance: 49.1 +/- 8.8 ml/min) and of 35 healthy control subjects. Leptin level was also reevaluated in 11 PD patients 9.3 +/- 1 months after the initial analysis. Finally, circadian leptin production was determined in 4 patients on automated PD (APD). Serum leptin was significantly higher in PD (31.9 +/- 7.8 ng/ml) than in chronic renal failure patients (15.2 +/- 5.9 ng/ml) and in healthy control subjects (9.6 +/- 1.1 ng/ml). Serum leptin level was significantly correlated with BMI in all three groups (except in PD males) and with the percentage of fat mass in both male and female PD patients. It did not correlate in PD patients with serum albumin concentration, free fat mass, residual diuresis, time on PD and characteristics of peritoneal permeability. At the second determination, serum leptin level had significantly increased in the PD patients although their respective BMI and serum creatinine concentration had remained virtually unchanged. Finally, in APD patients, the highest leptin level was observed at 08.00 a.m. These results demonstrate that serum leptin level is increased in PD patients and that it progressively rises under PD therapy. The circadian leptin production is delayed in APD patients probably suggesting a negative effect of the nocturnal glucose load on the regulation of its secretion.