Certain vitamin D receptor (VDR) variants are associated with systemic lupus erythematosus (SLE) and contribute to the development of lupus nephritis, according to data from an eastern Indian cohort study.
The findings may identify subjects who would benefit from vitamin D supplementation in order to alleviate renal morbidity.
The study, “Association between vitamin D receptor polymorphisms and systemic lupus erythematosus in an Indian cohort,” was published in the International Journal of Rheumatic Diseases.
Several studies have established a link between vitamin D levels and disease manifestations in lupus, and vitamin D administration in a lupus mouse model resulted in increased survival rates.
The effect of vitamin D is exerted through the VDR, which transports vitamin D and plays an important role in the expression of vitamin D-responsive genes. Several single nucleotide polymorphisms — variants where only one letter differs from the original gene — of the gene coding for VDR have been reported, and four (FokI, TaqI, BsmI, and ApaI) have been extensively investigated. Although there have been studies regarding the link between VDR polymorphisms and lupus, the results do not show consistency.
Therefore, researchers at the Central University of Jharkhand, in India, aimed to investigate the association between VDR variants and lupus.
The study was conducted in the outpatient department at the Clinical Immunology and Rheumatology Unit, Department of Medicine, SCB Medical College Cuttack, Odisha India, and involved 331 women with lupus and 282 healthy women. Polymorphisms of VDR were assessed in the patients and controls.
The frequency of the FokI polymorphisms was significantly higher in lupus patients compared to controls. So were the frequencies of TaqI polymorphisms. No significant difference in frequency was observed between lupus patients and controls with respect to the other VDR polymorphisms.
Patients with SLE and those with lupus nephritis had significantly lower levels of 25-OH vitamin D compared to healthy controls and those without lupus nephritis. This suggests that vitamin D plays a role in lupus susceptibility and clinical severity.
There was no significant difference in any of the VDR polymorphisms between lupus nephritis patients and those without nephritis. Lupus nephritis and lower plasma levels of 25-OH vitamin D were, however, significantly associated with FokI and TaqI variants.
“Vitamin D and VDR polymorphism may have a combined and contributory role in the pre-disposition to SLE and in the development of lupus nephritis,” the researchers concluded. “Further studies assessing both VDR polymorphisms and levels of vitamin D in different populations and in larger cohorts may provide more definitive answers. Therapeutically, vitamin D supplementations in SLE patients with low vitamin D levels and susceptibility to associated VDR polymorphisms may alleviate renal morbidity.”