Association between vitamin D receptor gene polymorphism and nephrolithiasis

Aims: To study the distribution of vitamin D receptor (VDR) gene alleles in hypercalciuric and nonhypercalciuric nephrolithiasis patients, hypothesizi ng that distinct biochemical parameters would be associated with different VDR genotypes. Methods: 12 hypercalciuric, 15 normocalciuric nephrolithiasi s patients, and 150 healthy subjects were recruited. The individual genetic pattern for VDR was evaluated by DNA extraction followed by polymerase cha in reaction amplification of the VDR gene and digestion with the restrictio n enzyme Bsml. Results: In the hypercalciuric group, Bb patients represente d 50% (6/12); bb patients 33% (4/12), and BE cases were 16% (2/12), The VDR frequency distribution was not statistically different in hypercalciuric p atients and controls (Bb 72%; bb 16%; BE 72%). In the nonhypercalciuric gro up, the prevalence of the bb genotype (7/15; 47%) was th rice the percentag e of control subjects, while the percentage of BE patients was similar to t hat of the control group (2/15; 13%). Patients with the bb haplotype exhibi ted a higher daily urinary calcium excretion. Among hypercalciuric patients , after a calcium-restricted diet, bb patients showed a 39% reduction in da ily urinary calcium excretion in comparison with a non-significant 13% redu ction observed in BE subjects (p=0.004). Conclusions: The effects of VDR ge ne polymorphism on calcium metabolism contribute to the understanding of th e pathogenesis of urinary calculi.