Association between BsmI vitamin D receptor gene polymorphism and serum concentration of vitamin D with progression of rheumatoid arthritis

INTRODUCTION: Vitamin D is an important modulator of the autoimmune process exerting its effects through the nuclear vitamin D receptor (VDR) with transcription factor properties. Mutations in the VDR gene may be important for vitamin D action on immunocompetent cells. Studies on the influence of serum levels of vitamin D and of vitamin D supplementation on rheumatoid arthritis (RA) activity, progression, and prognosis are sparse, limited to a few parameters, and often conflicting. The aim of this study was (a) to assess the relationship between the presence of BsmI VDR gene polymorphism and RA susceptibility, activity, and progression; (b) to compare vitamin D serum concentration in RA patients and in the control group; (c) to correlate vitamin D concentration in serum, vitamin D substitution in patients, demographic data, disease duration, RA functional and radiologic grade, RA activity, and presence of some antibodies. MATERIAL AND METHODS: The study was performed in 102 RA patients treated at the Department of Rheumatology and Internal Diseases, Pomeranian Medical University in Szczecin (PAM), and at the Rheumatology Outpatient Clinic of the First Public Clinical Hospital. The control group consisted of 57 volunteers with no connective tissue disease. 100 persons formed a control group for genetic tests. The study protocol was approved by the Bioethics Committee of the PAM. RESULTS: Low concentrations of vitamin D were found in RA patients and in the control group. Significantly lower serum concentrations of vitamin D were found in elderly patients. Elevated serum levels of 25(OH)D were associated with high functional status radiologic grades and with high RF levels. No significant correlation was found between BsmI VDR gene polymorphism and RA susceptibility or activity. BsmI polymorphism correlated only with RA functional status. CONCLUSIONS: Vitamin D serum concentration and BsmI VDR gene polymorphism may show some correlation with RA activity and progression.