Vitamin D Levels and Associations With Disease Activity in Chinese Han Patients With Early Rheumatoid Arthritis

Vitamin D and Autoimmune Rheumatic Diseases

Vitamin D is a steroid hormone with potent immune-modulating properties. It has been shown to stimulate innate immunity and induce immune tolerance. Extensive research efforts have shown that vitamin D deficiency may be related to the development of autoimmune diseases. Vitamin D deficiency has been observed in patients with rheumatoid arthritis (RA) and has been shown to be inversely related to disease activity. Moreover, vitamin D deficiency may be implicated in the pathogenesis of the disease. Vitamin D deficiency has also been observed in patients with systemic lupus erythematosus (SLE). It has been found to be inversely related to disease activity and renal involvement. In addition, vitamin D receptor polymorphisms have been studied in SLE. Vitamin D levels have been studied in patients with Sjogren's syndrome, and vitamin D deficiency may be related to neuropathy and the development of lymphoma in the context of Sjogren's syndrome. Vitamin D deficiency has been observed in ankylosing spondylitis, psoriatic arthritis (PsA), and idiopathic inflammatory myopathies. Vitamin D deficiency has also been observed in systemic sclerosis. Vitamin D deficiency may be implicated in the pathogenesis of autoimmunity, and it may be administered to prevent autoimmune disease and reduce pain in the context of autoimmune rheumatic disorders.

Impact of vitamin D deficiency on clinical parameters in treatment-naïve rheumatoid arthritis patients

OBJECTIVE

To determine if patients with rheumatoid arthritis (RA) are at risk of vitamin D deficiency and whether the levels of vitamin D are correlated with clinical parameters in RA.

METHODS

A total of 280 treatment-naïve RA patients, and 140 age- and sex-matched healthy volunteers were enrolled. Serum levels of 1,25-dihydroxycholecalciferol (1,25(OH)₂D₃), the active form of vitamin D, were measured by enzyme-linked immunosorbent assay (ELISA). Concentrations of 1,25(OH)₂D₃ less than 25 ng/mL were defined as insufficient. Linear regression was performed to evaluate correlations as (modifying and) confounding factors were controlled.

RESULTS

The levels of serum 1,25(OH)₂D₃ in RA individuals (12.24 ± 6.68 ng/ml) were significantly lower than in healthy controls (21.08 ± 7.14 ng/ml; p < 0.05). An inverse association was found between the levels of 1,25(OH)₂D₃ and ESR in obese and overweight individuals with RA (β_obese = -0.385, β_overweight = -0.395, both p < 0.05), but not in normal and underweight subjects. A significant negative association between levels of 1,25(OH)₂D₃ and DAS28 score (β = -0.164, p = 0.018) was observed. The levels of 1,25(OH)₂D₃ were associated moderately and inversely with the absolute numbers of Th-17 (β = -0.158, p = 0.019) and positively with those of CD4⁺ regulatory T (Treg) cell (β = 0.146, p = 0.025). The levels of 1,25(OH)₂D₃ in anti-cyclic citrullinated peptide (anti-CCP)-positive patients with RA were lower than in the anti-CCP-negative RA patients (10.86 ng/ml versus 15.98 ng/ml; t = -3.08, p < 0.01).

CONCLUSIONS

A significant association was observed between levels of vitamin D and parameters of disease, including body mass index (BMI), DAS28, Th17 cell counts, Treg cell counts, and presence of anti-CCP antibody in RA patients.