VITAMIN D LEVEL IN PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS AND ITS ASSOCIATION WITH BONE TURNOVER MARKERS

PV028 / #749 Poster Topic: AS04 - Biomarkers Background/Purpose According to scientific sources, vitamin D insufficiency has been detected in two-thirds of patients with systemic lupus erythematosus (SLE), while the deficiency is observed in 1 of 5 individuals. Hypovitaminosis D in SLE patients can be caused by kidney damage, chronic administration of glucocorticoids and, possibly, hydroxychloroquine, use of sunscreens, formation of antibodies to vitamin D, etc. It is also known that SLE patients demonstrate a tendency to rapid bone loss caused by impaired differentiation and decreased activity of osteoblasts, increased maturation and activity of osteoclasts, and accelerated apoptosis of osteocytes in chronic inflammations. Here, serum bone turnover markers may play a role in assessing synthesis and resorption progress. At the same time, the information about vitamin D influencing bone metabolism requires further study. The study is intended to determine vitamin D levels in SLE patients and assess their relationship with bone turnover markers. Methods We examined 65 SLE patients (mean age 48.95±1.46 years) and 30 the control group subjects of the corresponding age and sex. The main group consisted of 54 (83.08%) women and 11 (16.92%) men. The average duration of the disease was 12.05±1.09 years. We used ELISA to determine vitamin D concentration and characterized it as optimal (30–50 ng/ ml), insufficient (20–30 ng/ml) and deficient one (<20 ng/ml). The blood serum osteocalcin, procollagen type I C-terminal propeptide and C-terminal telopeptide of type I collagen were determined using ELISA. Results Blood serum vitamin D concentration in SLE patients was 18.58±0.97 ng/ml, while the one in the control group subjects was 27.44±1.28 ng/ml. Vitamin D deficiency and insufficiency was diagnosed in 43 (66.15%) and 16 (24.62%) patients, respectively, while only 6 (9.23%) subjects had the optimal vitamin D level. The control group presented normal 25(OH)D concentration, vitamin D insufficiency, and deficiency in 11 (36.67%), 11 (36.67%), and 8 (26.66%) subjects, respectively. Vitamin D levels were associated with the metabolic state of bone tissue, as indicated by a proportional change in the concentration of synthesis markers, such as osteocalcin (OC), procollagen type I C-terminal propeptide (PICP) and a resorption marker, C-terminal telopeptide of type I collagen (CTX). For example, patients with vitamin D deficiency had average OC and PICP 21.45% and 25.72% lower, accordingly, than had the patients of the group with optimal vitamin D concentration (p < 0.05). The average CTX in patients with vitamin D deficiency was 38.71% higher than the one in the group of patients that presented no hypovitaminosis D (p < 0.01). The results of the correlation analysis confirmed the close relationship between the vitamin D concentration and OC (r = 0.32; p = 0.01), and CTX (r = -0.25; p < 0.05). A reliable direct correlation was also established between CTX and the total dose of glucocorticoids (r = 0.48; p < 0.001). Conclusions Our study has demonstrated a significant prevalence of vitamin D deficiency and insufficiency in the Ukrainian population of SLE patients, as well as close association of hypovitaminosis D with changes in bone turnover markers (OC, PICP, CTX).