Impact of vitamin D status and obesity on C-reactive protein in kidney-transplant patients

Objective: We examined whether vitamin D status and obesity are associated with low-grade systemic inflammation, as assessed by serum concentrations of C-reactive protein (CRP) in an adult population of kidney-transplant patients. Design: This was a single-center, cross-sectional study. Setting and Patients: Data were collected between December 2005 and April 2006 from 161 adult (aged >18 years) kidney-transplant patients (mean age, 53.1 years; SD, 11.5 years; females/males, 78/83), with a median kidney-graft age of 7.0 years and serum CRP levels :<= 10 mg/L. Methods: Vitamin D status was assessed by serum concentrations of 25-hydroxyvitamin D (25-OHD) and 1,25-dihydroxyvitamin D (1,25(OH)(2)D). The presence of low-grade systemic inflammation was assessed by serum CRP. Selected lifestyle factors and anthropometric variables were determined in a subgroup of patients (n = 90). Bivariate correlation and multiple regression analyses were performed. Results: Hypovitaminosis D (ie, S-25-OHD <= 75 nmol/L) was present in 73% of females, and 89% of males. The median level of serum CRP was 1.7 mg/L. Vitamin D status was not significantly associated with serum CRP. In the patient subgroup, indices of obesity (body mass index, body weight, and fat mass) correlated positively, and lean body mass correlated negatively, with serum CRP. Only fat mass remained significantly associated with serum CRP in multiple regression analysis. Conclusions: No impact of vitamin D status on low-grade systemic inflammation was found. Fat mass correlated positively with CRP, suggesting that obesity may increase the risk of cardiovascular disease and chronic allograft rejection in kidney-transplant patients. (C) 2008 by the National Kidney Foundation, Inc.