Vitamin D status in systemic lupus erythematosus patients and its association with selected clinical and laboratory parameters

Objectives: To identify relationships between vitamin D serum levels and the presence of autoantibodies directed against vitamin D and levels of interleukin(IL)-17 and IL-23 in patients with systemic lupus erythematosus (SLE). Methods: The study included 49 patients with SLE. Serum concentrations of 25(OH)D3 were measured with electrochemiluminescence immunoassay (ECLIA). Enzyme-linked immunosorbent assays (ELISA) were used to determine antibodies directed against 1,25(OH)2D3 and levels of IL-17 and IL-23 in serum of SLE patients. In evaluation of vitamin D status, the control group consisted of 49 age and gender matched healthy individuals, whereas in assessment of anti-vitamin D antibodies the control group comprised 30 sera from blood donors. Results: Serum concentration of 25(OH)D3 in SLE patients during the warm season was 18.47 ± 9.14 ng/ml, which was significantly decreased as compared with that of the control group – 31.27 ± 12.65 ng/ml (p = 0.0005). During the cold season a trend toward lower concentration of 25(OH)D3 in SLE patients was revealed; however, it did not reach statistical significance (11.71 ± 7.21 ng/ml vs. 16.01 ± 8.46 ng/ml; p = 0.054). Results within the recommended range for vitamin D (30–80 ng/ml; 70–200 nmol/l) were observed only in three patients. The 25(OH)D3 concentration was decreased in SLE patients with renal disease or leucopenia as compared with the levels in patients who did not have either problem (p = 0.006 and p = 0.047, respectively). The cold season was found to be a risk factor for vitamin D deficiency (<20 ng/ml) (odds ratio = 9.25; p = 0.005). Autoantibodies directed against 1,25(OH)2D3 were detected in three SLE patients. No significant difference in 25(OH)D3 serum concentrations was found between SLE patients with and without these autoantibodies. No link was shown between the existence of autoantibodies against 1,25(OH)2D3 and clinical or laboratory findings, including IL-17 and IL-23 levels. However, serum concentrations of IL-23 were lower in patients with vitamin D deficiency (p = 0.037). Conclusions: SLE patients, especially those with leucopenia or renal involvement, are at high risk of vitamin D deficiency and require vitamin D supplementation. Some SLE patient sera contained 1,25(OH)2D3 antibodies, but these antibodies do not appear to affect vitamin D levels.

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