Evaluation of the relationship between bioactive vitamind level and DVBP polymorphisms with disease activity and bone mineral density in pediatric patients with juvenile idiopathic arthritis

Since juvenile idiopathic arthritis (JIA) is a chronic disease with multifactorial, environmental and genetic effects, which is the most common among childhood rheumatic diseases, it may cause various problems such as bone health deterioration, anemia, and malnutrition in the long term. It is known that there are various measures such as exercise, good nutrition and vitamin D supplements in order to protect these patients from the effects of the disease. Especially in recent years, the importance of vitamin D and its metabolites in chronic diseases such as JIA has begun to be understood more. In our study, it was aimed to determine the levels of 25 (OH) vitamin D, free vitamin D and bioactive vitamin D, DVBP polymorphisms and to evaluate their relationship with disease activity and bone mineral density in children with a diagnosis of JIA. Eighty-nine children with a diagnosis of JIA for at least 6 months and forty healthy children were included in the study, then levels of total vitamin D, free vitamin D and bioactive vitamin D, calcium, phosphorus, alkene phosphatase, albumin, vitamin D binding protein (DVBP) were determined from serum samples taken by appropriate methods. DNAs were obtained by PCR method in order to examine the DVBP genetic polymorphism and were genotyped for two common nucleotide changes (rs4588 and rs7041) in the coding region and evaluated for the GC variant. In the patient group, bone mineral density was evaluated using the linear absorption method, and disease activity was evaluated with the Juvenile Arthritis Disease Activity Score (JADAS). Of the 89 children in the study group, 50 patients were girls (56.2%), the mean age was 11.76 ± 3.51 (5-18) years, the follow-up period was 45 ± 29 months, the JADAS score was 8 (0-40). There was no difference in age and gender distribution between the patient and control groups. Bioactive vitamin D 91 level [mean 23.89 nmol / L (7.76-40.31), 16.48 nmol / L (4.26-58.49), respectively] and free vitamin D level [mean 60.17 pmol / L (18.28-100.94) 40.61 pmol / L (9.59-156), respectively] was found to be significantly higher in the control group compared to children with a diagnosis of JIA (p <0.001). It has been shown that the difference between the two groups in vitamin D and its metabolites may be related to DVBP level. Age, gender, follow-up time, JIA subgroup, JADAS score, total vitamin D, free vitamin D and bioactive vitamin D levels of 33 patients with low bone mineral density (lumbar or femoral z score <-2) were compared and there was no significant difference between them (all p> 0.05). However, the mean 25 (OH) D level was found to be 23.6 (ng / ml) in the group with low bone mineral density, while the mean 25 (OH) D level was found to be 21.8 (ng / ml) in the group with good bone mineral density. In addition, although bioactive D and free vitamin D were not statistically significant, on the contrary, it was found lower in the group with low bone mineral density. In patients with low bone mineral density, the free / total vitamin D ratio was found to be significantly lower (p = 0.003) and the DVBP level was found to be significantly higher (p = 0.003). There was no significant relationship between DVBP genetic polymorphisms (GC1F, GC1S, GC2) and bone mineral density (all p> 0.05). Bone mineral density was significantly better in the group that received vitamin D supplements than the group that did not receive vitamin D supplements (p = 0.003). In our study group, the highest rate was 28.7% homozygous GC1S / S (GG: CC) polymorphism and the lowest 0.7% homozygous GC1F / F (TT: CC) polymorphism. The results of the study suggested that studying different vitamin D forms and DVBP levels in children with a diagnosis of JIA may provide an additional advantage in evaluating bone health. It has been shown that studying DVBP polymorphism has no significant effect on disease activity and bone health. Also, the superiority of vitamin D forms to 25(OH) vitamin D in showing disease activation was not demonstrated. Keywords: Bioactive Vitamin D, DBP, JIA