Background The etiology of rheumatoid arthritis (R.A.), an autoimmune, polygenic, inflammatory disease, has not yet been clarified despite the intense research1. In addition to its more commonly known metabolic effects such as those associated with calcium homeostasis, vitamin D has, in general, suppressive effects on the immune system, especially on T helper cell function. T cells are critical in the development of autoimmune reactions and autoimmune diseases. Low vitamin D levels have been associated with the risk of development of R.A., an autoimmune disease2. Vitamin D functions are mainly accomplished through vitamin D receptor (VDR). Several VDR gene polymorphisms have been described, and they may affect the function of vitamin D3.
Objectives The aim of this study is to detect whether the frequence of 4 VDR gene polymorphisms (ApaI, BsmI, FokI ve TaqI) differ in R.A. patients with respect to healthy controls. Whether these polymorphisms cause a difference in several clinical activation parameters (ESR, CRP, RF, DAS28 and Sharp score) of the patients was also determined.
Methods Study groups consisted of a R.A. group of 100 patients and 100 healthy controls. ApaI, BsmI, FokI and TaqI gene polymorphisms were studied by using polymerase chain reaction.
Results Statistically significant difference was only detected in only one of the 4 VDR gene polymorphisms, the BsmI gene, in the study. BB genotype of BsmI gene was more common in the R.A. group with respect to controls (p<0.05, odds ratio: 3.6, confidence interval: 1,4-9,7, chi2:1,03). There was no significant difference in the other 3 VDR genes. Within the clinical features studied, only CRP showed statistically significant difference in patients with any VDR gene polymorphism. High CRP was determined to be significantly more common in the R.A. patients with TaqI polymorphism with respect to the other patients (p=0.025).
Conclusions In this study, no significant correlation was found between VDR gene polymorphisms and
RA activity. Statistically significant difference was only detected in only one of the 4 VDR gene polymorphisms, the BsmI gene. BB genotype of BsmI gene was more common in the R.A. group. BsmI polymorphism may be a preventing feature of R.A development.
Seldin MF, Amos CI, Ward R, Gregersen PK. The genetics revolution and the assault on rheumatoid arthritis. Arthritis Rheum. Jun 1999;42(6):1071-1079.
Cantorna MT, Mahon BD. Mounting evidence for vitamin D as an environmental factor affecting autoimmune disease prevalence. Exp Biol Med (Maywood). Dec 2004;229(11):1136-1142.
Guo SW, Magnuson VL, Schiller JJ, Wang X, Wu Y, Ghosh S. Meta-analysis of vitamin D receptor polymorphisms and type 1 diabetes: a HuGE review of genetic association studies. Am J Epidemiol. Oct 15 2006;164(8):711-724.
Disclosure of Interest None Declared