Vitamin-D Receptor Genotype and Renal Disorder in Japanese Patients with Systemic Lupus erythematosus

Abstract

Background/Aims: It is known that allelic variants of the gene encoding the vitamin-D receptor (VDR) detected by Bsm I increase the risk of some advanced malignant tumors, suggesting that such variants may cause functional differences in 1,25(OH)₂ vitamin D₃. We examined the VDR genes of Japanese systemic lupus erythematosus (SLE) patients, to determine whether different genotypes are correlated with SLE or its criteria. Methods: VDR genotyping of 58 unrelated Japanese SLE patients was performed based on polymerase chain reaction-restriction fragment length polymorphism (RFLP). Following amplification, products were digested with Bsm I. The RFLPs were coded as Bb , where the uppercase letter signifies the absence of the digested site and the lowercase letter signifies the presence of the site. Results: The frequency of the VDR BB genotype was significantly higher in SLE patients (15.5%, n = 9/58, p < 0.0001) than in controls (5.7%, n = 5/87). Furthermore, a larger proportion of bb individuals was observed among patients with nephrotic syndrome (61.5%, n = 8/13) than among SLE patients without renal dysfunction (35.7%, n = 10/28). There was a significant tendency for the population of patients with the bb genotype to be correlated with that of patients with renal dysfunction (p = 0.0304). Conclusion: These findings suggest that the BB genotype might trigger the development of SLE, and that the bb genotype is associated with lupus nephritis.