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, hypothesizing that distinct biochemical parameters would be associated with different VDR genotypes. Methods: 12 hypercalciuric, 15 normocalciuric nephrolithiasis patients, and 150 healthy subjects were recruited. The individual genetic pattern for VDR was evaluated by DNA extraction followed by polymerase chain reaction amplification of the VDR gene and digestion with the restriction enzyme Bsml. Results: In the hypercalciuric group, Bb patients represented 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 patients and controls (Bb 72%; bb 16%; BE 72%). In the nonhypercalciuric group, the prevalence of the bb genotype (7/15; 47%) was th rice the percentage of control subjects, while the percentage of BE patients was similar to that of the control group (2/15; 13%). Patients with the bb haplotype exhibited a higher daily urinary calcium excretion. Among hypercalciuric patients, after a calcium-restricted diet, bb patients showed a 39% reduction in daily urinary calcium excretion in comparison with a non-significant 13% reduction observed in BE subjects (p=0.004). Conclusions: The effects of VDR gene polymorphism on calcium metabolism contribute to the understanding of the pathogenesis of urinary calculi.