Measurement of serum leptin in patients with chronic renal failure on hemodialysis

Background: Leptin, the product of the obese gene, is produced exclusively in fat cells. Subjects, materials and methods: To evaluate the clinical significance of measuring serum leptin in 56 patients with chronic renal failure on hemodialysis (HD), we measured leptin levels using radioimmunoassay in 34 normal volunteers and in 56 patients on HD. Results: Normal serum leptin averaged 5.7 +/- 0.7 (mean +/- SEM) ng/ml, which correlated significantly (p < 0.001) with the body fat percentage as measured by bioelectrical impedance analysis. Serum leptin in HD patients ranged from 1.3 to 142 ng/ml. The mean serum leptin analyzed after the logarithmic conversion was 5.6 ng/ml, which was not significantly different from the normal control value, although the body fat percentage was significantly lower than normal volunteers. There was a significant (p < 0.01) positive correlation between body fat percentage and serum leptin in both normal controls and I-ID patients. The slope of the regression curve was steeper in HD patients than in normal controls. Conclusion: (1) serum leptin levels to body fat mass are significantly higher in HD patients than controls, (2) the variability is much wider in HD patients; and (3) a significant relation exists between percent body fat and log serum leptin, the relation being steeper in HD patients than in controls.