Background: Leptin is a 16 kDa hormone synthesized by adipocytes and involved in body weight regulation.
Objectives: To determine serum leptin concentrations in heart, liver and kidney transplant recipients.
Methods: We investigated 57 patients: 18 male heart transplant recipients (age 25-69 years) at 1-66 months after transplantation, 6 female and 8 male liver transplant recipients (age 33-70) at 11-73 months after transplantation, and 10 female and 15 male kidney transplant recipients (age 20-61) at 3-138 months after transplantation. All recipients were receiving immunosuppressive therapy, including prednisone 0-20 mg/day, azathioprine 75-125 mg/day, cyclosporin 100-250 mg/day or tacrolimus 2-10 mg/day. The results were compared to those of 10 female and 10 male healthy controls. Morning serum concentrations of leptin were measured with a commercial radioimmunoassay (Linco Research Inc., USA), and serum insulin and cortisol levels were measured by radioimmunoassay.
Results: Patients (both men and women) after heart, liver and kidney transplantation exhibited significantly higher serum concentrations of leptin and leptin/body mass index ratios than controls. Serum leptin concentrations were significantly higher in women than in men and correlated very significantly with BMI in all cases. The multivariate stepwise analyses showed that among parameters including BMI, gender, age, time after transplantation, prednisone dose, hematocrit, serum concentrations of glucose, albumin, creatinine, cortisol and insulin, only BMI, gender, cortisol and insulin were significant independent determinants of serum leptin levels in these patients.
Conclusions: This is the first report showing that, in addition to body mass index and gender, basal cortisol and insulin levels affect the hyperleptinemia in transplant patients. The clinical relevance of hyperleptinemia in these patients will require further investigation.