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P088 Evaluation of Free Vitamin D levels in IBD pediatric patients: the role of inflammation

Strisciuglio C.*1, Cenni S.2, Giugliano F.P.2, Miele E.2, Cirillo G.1, Martinelli M.2, Vitale A.1, Staiano A.2, Miraglia del Giudice E.1, Perrone L.1

1Second University of Naples, Department of Woman, Child and General and Specialistic Surgery, Naples, Italy 2University Federico II of Naples, Department of Translational Medical Science, Section of Pediatrics, Naples, Italy

Background

Vitamin D is an important regulator factor of the immune system and induces the development of self-tolerance. An association between vitamin D deficiency and inflammatory bowel diseases (IBD) has been described. Studies examining vitamin D levels in IBD usually do not consider the effect of inflammation on vitamin D and do not calculate the unbound, free vitamin D, which is the active form. The aim of our study was to investigate the levels of total 25-hydroxyvitamin-D (T-25OH-D) and free 25-hydroxyvitamin-D (F-25OH-D) in a cohort of IBD pediatric patients and to correlate these values with the disease activity and the markers of inflammation.

Methods

Between January 2015 and May 2016 we enrolled all consecutive children with a new diagnosis of IBD (group A), a group of IBD patients at follow-up in clinical remission (group B) and a group of age- and sex- matched healthy controls (group C). In each subject T-25OH-D and F-25OH-D levels were measured with an enzyme-linked immunosorbent assay (ELISA). Comparison between groups were made using non-parametric Mann-Whitney test. The disease activity was measured with Pediatric Crohn Disease Activity Index and Pediatric Ulcerative Colitis Activity Index for CD and UC, respectively. Moreover, as markers of inflammation, C reactive protein and and fecal calprotectin were measured and they were correlated to T-25OH-D and F-25OH-D levels by a linear regression test.

Results

Sixthy-four consecutive children were enrolled (group=n): group A=37, group B=27 and group C=18. Levels of T-25OH-D were higher in group A than in group B (19.9±1.7 ng/ml vs 14.2±1.3ng/ml; p=0.01) but were lower in both groups A and B when compared to group C (19.9±1.7 ng/ml vs 28.2±2.8 ng/ml; p=0.008 and 14.2±1.3ng/ml vs 28.2±2.8 ng/ml; p<0.001, respectively). Levels of F-25OH-D were higher in group A compared to both group C (5.3±0.3 pg/ml vs 3.2±0.3 pg/ml; p=0.001) and B (5.3±0.3 pg/ml vs 3.6±0.3 pg/ml; p=0.001). A significant direct correlation was found between F-25OH-D and activity index of disease (r2: 0.18; p≤0.001). A direct correlation, not reaching statistical significance, was also found between F-25OH-D and both C-reactive protein and fecal calprotectin.

Conclusion

IBD children, both at diagnosis and at follow up, have lower levels of T-25OH-D compared to healthy controls. However, among IBD patients, those at diagnosis showed higher levels of T-25OH-D and F-25OH-D than those with longer disease duration. Higher levels of both forms of Vitamin D are present in acute inflammation, suggesting that chronic inflammation is associated with a more severe deficiency of Vitamin D.