P431 Vitamin D binding protein in the limelight: IBD-related inflammation and circulating levels of vitamin D binding protein, total, free and bioavailable 25-hydroxyvitamin D

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Abstract Background Vitamin D deficiency occurs frequently in patients with Crohn’s disease (CD) and ulcerative colitis (UC). While recent cohort studies support an association of vitamin D with important clinical parameters and outcomes in IBD, the complex interplay of inflammation with vitamin D metabolism in IBD poses a viscious circle. We sought to further illucidate the relation between inflammation and different vitamin D parameters. To the best our knowledge, this was the first study to focus on the relationship between vitamin D binding protein (VDBP), circulating total, free, and bioavailable 25-hydroxyvitamin D (25(OH)D), and inflammation, in adult IBD patients. Methods This was a comparative, single-centred, cross-sectional study in patients with IBD aged 18–65 years. Full blood count, transferrin, albumin and hsCRP were determined by standard methods. The presence/absence of inflammation was assessed based on serum hsCRP levels (cutoff <5mg/l). VDBP levels were determined by ELISA, and 25(OH)D by LCMS. Free and bioavailable vitamin D levels were calculated using the validated formula. IBM SPSS version 25.0 was used for statistical analysis. Results In total, 129 subjects with IBD (70 male/59 female; 82 CD/47 UC; mean age 41.7 ± 12.6 years) were enrolled. Of these, 38/129 had inflammation (19 m/19 f; 26 CD/12 UC; 39.6 ± 12.9 years) while 91/129 had no inflammation (40 m/51 f; 56 CD/35 UC; 42.5 ± 12.5 years). Subjects with disease activity had significantly higher leukocyte, erythrocyte sedimentation rate (ESR) and hsCRP, but lower transferrin, transferrin saturation (TSAT) and albumin levels than those without inflammation (p < 0.05). Average serum levels of 25(OH)D (24.6[6.8–54.8] vs. 26.4[5.0–74.4]ng/ml), free 25(OH)D (5.9[1.3–13.3] vs. 1.0[1.0–21.4]ng/ml) and bioavailable 25(OH)D(2.3 [0.1–4.7] vs. 2.4[0.5–19.5]ng/ml) were similar in patients with vs. without inflammation (p > 0.05). However, VDBP levels were significantly higher in inflammatory conditions (359.6[252.2–530.6] mg/l vs. 327.4[183.5–560.3]mg/l; p < 0.05) and showed a positive correlation with CRP levels (0.293, p < 0.001). Ratio of free/total 25(OH)D correlated negatively with CRP levels (−0.282, p = 0.002). Conclusion High levels of circulating VDBP were associated with inflammatory activity. Moreover, free/total 25(OH)D ratio was inversely associated with inflammation. Other vitamin D parameters including total, free and bioavailable 25(OH)D showed no association with inflammation. These findings suggest that VDBP may play a bigger role than thought as a modulator of vitamin D and inflammation, and that simultaneous detection and investigation of plasma VDBP may provide additional insights into this complex interaction.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.