Plasma Immunoreactive Leptin and Neuropeptide Y Levels in Kidney Transplant Patients

Abstract

Leptin and neuropeptide Y (NPY) seem to play an important role in food intake and energy expenditure. Leptin is secreted by adipose tissue in proportion fo fat stores and is presumed to be an important anorectic hormone. NPY is produced by the hypothalamus, and in contrast to leptin, is one of the most potent appetite stimulants yet demonstrated. On the other hand, in most patients increased appetite is present after successful kidney transplantation. Finally, a stimulatory effect of glucocorticoids on leptin secretion was reported. The present study aimed to assess the relationship between plasma leptin and NPY levels and body mass index (BMI) in haemodialyzed patients (HDP) with chronic renal failure and in kidney transplant patients (KTP). In both groups, BMI was of the same magnitude as in healthy controls. Despite the presence of a normal BMI, leptin levels in KTP (25.2 ± 3.6 ng/ml) and in HDP with chronic renal failure (25.3 ± 4.2 ng/ml) were higher than in controls (11.7 ± 1.8 ng/ml). The mean plasma NPY level in KTP (168.0 ± 10.3 pg/ml) was significantly higher (p < 0.01) than in controls (70.7 ± 5.9 pg/ml) and in HDP (77.0 ± 5.7 pg/ml). In all examined groups, a significant positive correlation was found between leptinaemia and BMI. Conclusions: (1) KTP are characterized by significantly elevated leptinaemia in spite of a normal BMI. In KTP this increased leptinaemia does not seem to be dependent only upon the fat mass and the kind and dosis of immunosuppressive therapy. (2) Similarly to healthy subjects, female KTP and HDP show markedly higher leptinaemia than males. (3) In contrast to healthy subjects and HDP, KTP are characterized by significantly elevated plasma NPY levels.