CORRELATIONS BETWEEN LEPTIN, BODY COMPOSITION, BONE MINERAL DENSITY AND BONE METABOLISM IN KIDNEY TRANSPLANT RECIPIENTS AND DIALYZED PATIENTS

Abstract

P301 Aims: In kidney transplant recipients leptin levels are often elevated and BMD decreased, however, so far data about correlations between leptin and BMD in this population is lacking. It has been suggested that leptin is a predictor of BMD in postmenopausal women. Moreover, leptin acts a a marker of fat stores. We examined the relationships between leptinemia, some markers of nutritional status, BMD and bone metabolism in kidney transplant recipients as well as in dialyzed patients (hemodialyzed -HD, peritoneally dialyzed -CAPD). We also assessed whether leptin is significant and independent predictor of BMD in this population. Methods: Methods: BMD and fat content (global, percentage, trunk) was measured using dual energy X-ray absorptiometry (DEXA) in 27 kidney allograft recipients, 25 HD and 23 CAPD patients,. Intact PTH and osteocalcin were studied by radioimmunoassay using commercially available kits from Cis, France. Vitamin 1,25 (OH)2D3 and IGF-1 concentrations were measured RIA using commercially available kits from Biosource, Europe S.A., Belgium. Levels of IGF-BP-1 and 3 were assayed by IRMA (Diagnostic Systems Laboratories, Inc, USA). Levels of PICP (procollagen type I carboxy-terminal extension peptide) and ICTP (procollagen type I cross-linked carboxy-terminal telopeptide) were estimated by radioimmunoassays (Orion Diagnostica, Finland). Bone-specifc alkaline phosphatase-bALP was estimated using ELISA kit from Metra Biosystem, USA. Serum beta2microglobulin was estimated using kits from AlphaDialab, Vienna, Austria. Beta Ctx (degradation products of C-terminal telopeptides of type I collagen), were assayed by ELISA (Osteometer, Denmark). Serum tartrate-resistant acid phosphatase-TRAP was estimated using kit from Suomen Bioanalytiikka Oy, Finland. DPD (deoxypirydynoline) in urine was assayed by immunochemiluminescence (ACS 180 Bayer) and expressed as DPD/creatinine ratios. Serum leptin was assessed by RIA using kits from Linco Research, USA. Results: Leptin correlated with percentage of body fat, trunk fat, lean body mass, serum creatinine and urea. Insulin growth factor binding protein 1 was negatively related to waist-hip ratio, global and trunk fat., whereas BMD of the lumbar spine was related to the dose of prednisone, azathioprine, level of cyclosporine, serum calcium as well as osteoprotegerin level in kidney transplant recipients. In femoral neck BMD was significantly higher in CAPD patients, without significant differences in BMD in lumbar spine. There was a negative correlation between BMD at the femoral neck and time on hemodialysis (r=-0.45, p<0.05). In CAPD patients BMD at the lumbar spine correlated negatively with vitamin D3 (r=-0.54, p<0.05), osteocalcin (r=-0.54, p<0.05), and positively with BMI (r=0.63, p<0.01). BMD at the femoral neck correlated positively with BMI (r=0.59, p<0.01), and negatively with osteocalcin (r=-0.63, p<0.05) and time on CAPD (r=-0.52, p<0.05). Leptin correlate only with cholesterol (r=0.25, p<0.05), TSH (r=0.35, p<0.01), beta2microglobulin (r=0.32, p<0.001) and BMD at the femoral neck (r=-0.23, p<0.05) in all dialyzed (HD and CAPD) patients. Conclusions: Leptin levels are associated with renal function and body fat in kidney allograft recipients. Leptin is not related to nutritional status, BMD and bone metabolism BMD in kidney allograft recipients, but depends on currents dosage of immunosuppressants and serum calcium. Leptin is not a predictor of BMD in dialyzed patients.