The Research Of Vitamin D Levels With Inflammatory Bowel Disease And Its Mechanism

Inflammatory bowel disease (IBD) is a group of diseases characterized by chronically recurrent episodes of intestinal inflammation, and includes ulcerative colitis (UC) and Crohn’s disease (CD). The etiology of IBD is complex, and includes genetic susceptibility, environmental factors, and abnormal mucosal immune responses to antigenic material in the gut, such as the symbiotic bacteria.It has been shown that vitamin D (VitD) has anti-inflammatory, anti-cancer and immune regulatory effects, in addition to its traditional role regulating calcium and phosphorus metabolism. Vit D can modulate the immune system development and function, its active form can directly or indirectly inhibit the function of the IBD pathogenic T cells, induce regulatory T cells which can suppress the development of IBD, then have an impact on the incidence of IBD. IBD patients prone to have bone loss/osteoporosis, resulting in significantly higher risk of fracture, seriously affect the life quality of IBD patients. Vit D plays the role of regulatory on bone metabolism. The relationship between Vit D and IBD is becoming increasingly concerned. Therefore, we aim to:1. Explore serum25(OH) D3levels, bone metabolism status and the relationship with IBD disease activity in Chinese IBD patients, analyze the risk factors; asses the intervention treatment effects of supplying VitD on25(OH) D3levels, bone metabolism status and IBD severity.2. Explore the regulation effects of different doses vitamin D on T cell immunity regulation in rats with experimental colitis induced by trinitrobenzene sulfonic acid (TNBS) model.Part1. Vitamin D Levels and Bone Metabolism in Chinese Adult Patients with Inflammatory Bowel Disease.Objective:Explore serum25(OH) D3levels, bone metabolism status and the relationship with IBD disease activity in Chinese IBD patients, analyze the risk factors; asses the intervention treatment effects of supplying VitD on25(OH) D3levels, bone metabolism status and IBD severity.Methods:1. The clinical data of107ulcerative colitis (UC) patients,105Crohn’s disease (CD) patients and160normal controls, were collected. The serum25(OH) D3levels, the bone mineral density of IBD patients were measured.2.212IBD patients with initially osteopenia/osteoporosis were randomized into the calcium supplement or calcium and vitamin D supplemental group. IBD patients with normal BMD were randomized into placebo, calcium supplement, or calcium and vitamin D supplemental groups. Calcium supplement group paitents take calcium600mg per day, vitamin D supplemental group patients take VitD350000IU per3months. All patients were followed on3months,6months and12months for Mayo index/simplify CDAI score, serum25(OH) D3levels, and BMD at12months intervals.Results:1. Serum25(OH) D3levels of UC patients were significant decreased than nrmal control group (10.55±4.27VS12.89±5.32, P<0.001), also the serum25(OH) D3levels of CD patients were significant decreased than nrmal control group (11.53±4.84VS12.89±5.32, P=0.040). Within the UC group, serum25(OH) D3levels was negatively correlated with the IBD severity (r=-0.337, P<0.001). Within the UC group,25(OH) D3levels were negatively and significantly correlated with disease severity (r=-0.387, P<0.001). Similar results were also observed within the CD group (r=-0.285, p=0.030). The prevalence of osteopenia and osteoporosis were high in IBD patients (45.8%and2.8%, respectively, in UC; and38.1%and5.7%, respectively, in CD). Cumulative quantities of glucocorticoid use was significantly associated with osteopenia/osteoporosis in both UC (OR=1.219,95%CI1.054-1.410, p=0.008) and CD (OR=1.288,95%CI1.033-1.606, p=0.025) patients.2. The elevated25(OH) D3levels of VitD supplement group in UC and CD patients were obviously higher than the no VitD supplement group after1year (P<0.001); the mean improvement levels of femoral neck, femur and lumbar1-4bone mineral density were higher in VitD supplement group, but did not reach statistical significance (P>0.05); the Mayo score/simplify CDAI score decreased degree was no significant difference between2groups (P>0.05).Conclusions:IBD patients were found to have25(OH) D3deficiencies that correlate with the IBD severity; IBD patients prone to have osteopenia/osteoporosis, the cumulative amount of glucocorticoid was a risk factor; supplemental VitD can significantly increase serum25(OH) D3levels, but did not find a significant improvement in BMD and IBD severity. Part2. Effects of vitamin D on trinitrobenzene sulfonic acid induced colitis in rats.Objective:Explore the effects of different doses vitamin D in rats with experimental colitis induced by trinitrobenzene sulfonic acid (TNBS).Methods:1. Establishment of TNBS experimental colitis model and drug intervention grouping:54SD rats were randomly divided into9groups (n=6), in addition to the normal control group, experimental colitis of remaining8groups were induced by enema administration of TNBS. After24hours, drug intervention was done by gavage.5-ASA group [daily0.40g/(kg·d)], conventional dose of VitD3group(lst day1800UVitD3), single high dose of VitD3group(lst day7500U VitD3) and continuous high dose of VitD3group (daily7500UVitD3), and conventional dose of VitD3+5-ASA group, single high doses of VitD3+5-ASA group, continuous high dose of VitD3+5-ASA group.2. Evaluation of therapeutic effect:Assess disease activity index (DAI) score after establishment of TNBS experimental colitis model, all rats were sacrificed the10th day and assessed disease activity index (DAI), macroscopic lesion, histological damage score, the activity of myeloperoxidase (MPO) was measured.3. Immune Mechanism:Detected interleukin (IL)-2, IL-17and IFN-y of colonic tissue homogenates by ELISA, colon T-bet and GATA-3level by reverse transcription polymerase chain reaction (RT-PCR).Results:1. DAI score, anatomical lesion score, histopathology score, MPO activity of TNBS group were significantly higher than the normal control group (P<0.001). Compared with TNBS group, macroscopic injury score and histological score in single high dose and continuous high dose VitD3combined with5-ASA groups were significantly decreased (P<0.05); MPO activity in all drugs intervention groups was decreased significantly (P<0.001). Rats in continuous high dose VitD3group and combined with5-ASA group had hypercalcemia, and serum level of creatinine in continuous high dose VitD3group was significantly increased than all the other groups (P<0.05).2. The levels of IL-2and IFN-y in each group had no significant difference (P>0.05). IL-17levels in conventional dose of VitD3group was significantly lower than the TNBS group,5-ASA group (P<0.05). No T-bet expression in normal control group, weak expression in TNBS group,5-ASA group, single high dose of VitD3group, continuous high dose of VitD3group and combined with5-ASA group decreased to missing. GATA-3mRNA expression in5-ASA group, continuous high dose VitD3group was significantly increased compared to TNBS group (P=0.037and0.035, respectively).Conclusions:VitD3can alleviate TNBS induced experimental colitis by regulating T cell immunity.