Increased plasma leptin/fat ratio in patients with chronic renal failure: a cause of malnutrition?

into dialysis fluids, and particularly reduced food Methods. Plasma leptin was measured by radio- intake due to anorexia, nausea, and vomiting. immunoassay in 93 individuals in groups of undialysed, The obesity gene protein, now known as leptin, with peritoneal dialysed, and haemodialysed patients and a molecular weight of 16 kDa, was first cloned in 1994 controls. Body composition was determined by DEXA. [5]. Recent studies have shown that leptin has an Results. Protein-energy malnutrition was evident in endocrine function for lowering food intake and regunon-dialysed and dialysed patients from low lean or lating body composition [6‐8 ] and is produced exclusfat tissues, plasma albumin and transferrin. A third of ively in fat cells from animals and humans. In humans, the dialysis patients were eating less than prescribed leptin correlates with percentage body fat but obese intakes. Leptin relative to total fat mass (ng/ml/kg) persons are insensitive to this endogenous leptin prowas significantly greater for patients than for controls, duction [9 ]. Leptin resistence in obesity is probably particularly the dialysed patients. Leptin was highly due to a reduced eYciency of brain leptin delivery correlated with total, arm, leg, and all other fat meas- [10,11]. urements, e.g. r for leptin vs% total fat was: undialysed A recent study in this unit investigated total and 0.88, PD 0.81, HD 0.93, and controls 0.83 (P<0.0001 regional body composition in undialysed and dialysed for all ). Dialysis patients with the highest leptin/fat patients with CRF and controls [12 ]. The patients had mass ratio had low protein intakes and significantly significant lean tissue depletion together with lower lower lean tissue mass. Leptin/fat ratio correlated percentage of body fat than controls. The aim of this inversely with dietary intake e.g. with protein intake study was to measure plasma leptin in these subjects in g/day and marginally in g/kg of ideal weight/day. to establish whether leptin concentrations, or their Leptin concentration was unrelated to plasma creatin- relationship with body composition and dietary intake, ine or residual renal function or to the protein ‘nutri- could account for any loss of appetite or the incidence tional indices’, albumin and transferrin. of malnutrition. Conclusions. Our data suggests that leptin is markedly increased in some patients with chronic renal failure. The association of increased leptin with low protein Subjects and methods intake and loss of lean tissue is consistent with leptin contributing to malnutrition but a definitive role Ninety-three individuals were investigated: 11 female and 12 cannot be substantiated by this study.