Overweight and body fat are predictors of hypovitaminosis D in renal transplant patients

BACKGROUND: Hypovitaminosis D has been frequently reported after renal transplantation, but the impact of obesity and other factors in the reduction of vitamin D levels is not well established. We aimed to evaluate risk factors contributing to hypovitaminosis D among nondiabetic renal transplant recipients (RTR) with serum creatinine <2.0 mg/dL, at least 6 months after transplantation. METHODS: One hundred RTR were subjected to anthropometric evaluation and body composition assessment through bioelectrical impedance analysis; blood samples were drawn for biochemical and hormonal determinations and clinical data were retrieved from the medical records. RESULTS: Hypovitaminosis D was observed in 65% and overweight (body mass index, BMI >25 kg/m(2)) in 59% of cases with a significant median weight gain after transplantation of 5.1 kg. An inadequate distribution of body fat was evidenced in 50% of males and in 58% of females. Patients with either vitamin D deficiency or insufficiency presented significantly higher median values of body fat and weight gain since transplantation, as well as lower lean mass compared with patients with normal vitamin D levels (P < 0.001). Moreover, median values of waist circumference, BMI, serum leptin and parathyroid hormone levels were significantly higher in the group with vitamin D deficiency. A multivariate linear regression analysis then revealed that body fat and leptin levels, but not skin color, gender, age, glucocorticoid use, renal function, microalbuminuria and other confounding factors, were independently associated with low levels of 25 hydroxyvitamin D3 even after adjustments for seasonal variations. CONCLUSION: In conclusion, the present study showed body fat and serum leptin levels to be the only independent risk factors for hypovitaminosis D among RTR.