Aim: To investigate the relationship of vitamin D receptor (VDR) gene Fok I polymorphism with systemic lupus erythematosus (SLE) and to observe VDR mRNA levels in Chinese Han SLE patients.
Methods: Genomic DNAs from 271 Chinese SLE patients and 130 healthy controls were determined for Fok I polymorphism by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP), and VDR mRNA levels from 48 Chinese SLE patients and 38 healthy controls were detected by real-time polymerase chain reaction (RT-PCR).
Results: Gene frequencies of allelic F and f were significantly different between the SLE patients and the controls (P=0.001).The relative risk of SLE in the presence of allelic gene F was 1.630 (95%CI=1.210-2.196, P=0.001). The frequency of homozygote FF in the SLE patients was higher than that in the controls (42.8% vs 25.4%, x(2);=11.417, P=0.001). Serositis, anti-dsDNA antibody, anti-Sm antibody and anti-histone antibody in the SLE patients carrying homozygote FF and heterozygote Ff were higher than those in the SLE patients carrying homozygote ff (P=0.001, P=0.001, P=0.047, P=0.001, respectively). The VDR mRNA was decreased in the SLE patients, with a delta;Ct value of 9.26 ± 2.37 (P=0.026), as compared with a delta;Ct value of 7.82 ± 3.05 in the controls (the bigger of the delta;Ct value, the lower of VDR mRNA expression). The delta;Ct value of VDR mRNA in the SLE patients carrying FF and Ff was bigger than that in the SLE patients carrying ff (10.54 ± 1.88 vs 7.15 ± 3.78, P=0.019).
Conclusion: VDR gene Fok I polymorphism is associated with SLE in the Han population of southern China. The SLE patients carrying F allel ± are more likely to have serositis and produce anti-dsDNA antibody, anti-Sm antibody and anti-Histone antibody, presumably as a result of down-regulation of VDR mRNA.