Association between vitamin D receptor gene polymorphism and nephrolithiasis

Area of Science:

• Genetics
• Nephrology
• Biochemistry

Background:

• Hypercalciuria is a significant risk factor for nephrolithiasis (kidney stones).
• The vitamin D receptor (VDR) gene plays a crucial role in calcium and phosphate homeostasis.
• VDR gene polymorphisms may influence individual susceptibility to calcium-related disorders like nephrolithiasis.

Purpose of the Study:

• To investigate the association between VDR gene alleles and nephrolithiasis, specifically in hypercalciuric and nonhypercalciuric patient groups.
• To determine if distinct biochemical parameters correlate with different VDR genotypes in kidney stone patients.

Main Methods:

• Genotyping of the VDR gene using DNA extraction, polymerase chain reaction amplification, and BsmI restriction enzyme digestion.
• Analysis of VDR allele frequencies in 12 hypercalciuric, 15 normocalciuric nephrolithiasis patients, and 150 healthy controls.
• Assessment of urinary calcium excretion in relation to VDR genotypes, particularly after dietary calcium restriction.

Main Results:

• The prevalence of the VDR bb genotype was significantly higher in nonhypercalciuric nephrolithiasis patients (47%) compared to controls (16%).
• Patients with the bb haplotype demonstrated increased daily urinary calcium excretion.
• In hypercalciuric patients, the bb genotype group showed a substantial 39% reduction in urinary calcium after a calcium-restricted diet, unlike the BB genotype group.

Conclusions:

• VDR gene polymorphism, specifically the bb genotype, is associated with altered calcium metabolism and may contribute to the pathogenesis of urinary calculi.
• Understanding VDR genotype-specific responses to dietary calcium can inform personalized management strategies for nephrolithiasis.