Editorial: Vitamin D and IBD: Can We Get Over the "Causation" Hump?

Rising Incidence of Inflammatory Bowel Disease in South Asian Children in New Zealand-A Retrospective Population-Based Study

OBJECTIVES

High rates of inflammatory bowel disease (IBD) are reported in children of South Asian (SA) descent in some western countries. This population-based study describes the incidence and clinical course of IBD in SA children compared to non-South Asian (NSA) children in New Zealand (NZ).

METHODS

Children (≤15 years) with new-onset IBD presenting to a centralized tertiary referral center in Auckland, NZ from 2010 to 2020 were identified. Disease phenotype, clinical characteristics, response to exclusive enteral nutrition, clinical remission rates at 3 and 12 months, biologic use, corticosteroid exposure, and disease complications were compared by ethnicity; IBD incidence was calculated.

RESULTS

There were 127 (26 SA; 101 NSA) children with Crohn disease, 41 (10 SA; 31 NSA) with ulcerative colitis, and 10 (3 SA; 7 NSA) with IBD-unclassified. IBD incidence in SA and NSA children was 14.1 per 100,000 and 4.3 per 100,000 respectively ( P < 0.001). IBD incidence increased by 5.6% per year ( P = 0.022), due to a greater rise in incidence in SA (SA 16.8% per year, P = 0.015; NSA 4.5% per year, P = 0.317). At presentation, SA children had worse biochemical parameters, severe colitis, and vitamin D deficiency. SA children had lower rates of remission following exclusive enteral nutrition (28.5% vs 65.0%, P < 0.001) or biologic induction (35.7% vs 70.8%, P = 0.020), at 3-month (35.3% vs 69.8%, P < 0.001) and 12-month follow-up (29.4% vs 55.0%, P = 0.005). No significant differences were found in disease location or corticosteroid burden.

CONCLUSIONS

Increasing incidence of IBD was disproportionately represented by SA children with more severe disease and lower remission rates following exclusive enteral nutrition or biologic therapy.

Effects of Different Routes and Forms of Vitamin D Administration on Mesenteric Lymph Node CD4+ T Cell Polarization and Intestinal Injury in Obese Mice Complicated with Polymicrobial Sepsis

This study compared the efficacies of enteral cholecalciferol and/or intravenous (IV) calcitriol administration on mesenteric lymph node (MLN) cluster-of-differentiation-4-positive (CD4+) T cell distribution and intestinal barrier damage in obese mice complicated with sepsis. Mice were fed a high-fat diet for 16 weeks and then sepsis was induced by cecal ligation and puncture (CLP). Mice were divided into the following sepsis groups: without vitamin D (VD) (S); with oral cholecalciferol 1 day before CLP (G); with IV calcitriol 1 h after CLP (V); and with both cholecalciferol before and IV calcitriol after CLP (GV). All mice were sacrificed at 12 or 24 h after CLP. The findings show that the S group had a higher T helper (Th)17 percentage than the VD-treated groups at 12 h after CLP. The V group exhibited a higher Th1 percentage and Th1/Th2 ratio than the other groups at 24 h, whereas the V and GV groups had a lower Th17/regulatory T (Treg) ratio 12 h post-CLP in MLNs. In ileum tissues, the VD-treated groups had higher tight junction protein and cathelicidin levels, and higher mucin gene expression than the S group at 24 h post-CLP. Also, aryl hydrocarbon receptor (AhR) and its associated cytochrome P450 1A1 and interleukin 22 gene expressions were upregulated. In contrast, levels of lipid peroxides and inflammatory mediators in ileum tissues were lower in the groups with VD treatment after CLP. These results suggest that IV calcitriol seemed to have a more-pronounced effect on modulating the homeostasis of Th/Treg subsets in MLNs. Both oral cholecalciferol before and IV calcitriol after CLP promoted cathelicidin secretion, alleviated intestinal inflammation, and ameliorated the epithelial integrity in obese mice complicated with sepsis possibly via VD receptor and AhR signaling pathways.

Switching to a Healthy Diet Prevents the Detrimental Effects of Western Diet in a Colitis-Associated Colorectal Cancer Model

Inflammatory bowel disease increases the odds of developing colitis-associated cancer. We hypothesized that Western-style diet (WD) aggravates azoxymethane (AOM)/dextran sulfate sodium salt (DSS)-induced colitis-associated tumorigenesis and that switching to the standard AIN93G diet will ameliorate disease symptoms even after cancer initiation. Female BALB/c mice received either WD (WD group) or standard AIN93G diet (AIN group) for the whole experimental period. After five weeks, the mice received 12.5 mg/kg AOM intraperitoneally, followed by three DSS cycles. In one group of mice, the WD was switched to AIN93G the day before starting the first DSS cycle (WD/AIN group). Feeding the WD during the whole experimental period aggravated colitis symptoms, shortened the colon (p < 0.05), changed microbiota composition and increased tumor promotion. On molecular level, the WD reduced proliferation (p < 0.05) and increased expression of the vitamin D catabolizing enzyme Cyp24a1 (p < 0.001). The switch to the AIN93G diet ameliorated this effect, reflected by longer colons, fewer (p < 0.05) and smaller (p < 0.01) aberrant colonic crypt foci, comparable with the AIN group. Our results show that switching to a healthy diet, even after cancer initiation is able to revert the deleterious effect of the WD and could be an effective preventive strategy to reduce colitis symptoms and prevent tumorigenesis.

Vitamin D Inhibits Pro-Inflammatory T Cell Function in Patients With Inflammatory Bowel Disease

BACKGROUND AND AIMS

Dysregulated T cell responses contribute to the pathogenesis of inflammatory bowel disease [IBD]. Because vitamin D [vitD] deficiency is a risk factor for adverse disease outcomes, we aimed to characterize the impact of vitD on intestinal and peripheral T cell profiles.

METHODS

T cells were isolated from peripheral blood and intestinal biopsies of IBD patients, incubated with vitD and characterized by flow cytometry. To translate these in vitro findings to the clinic, serum vitD concentrations and clinical outcomes were correlated with T cell phenotype and function in a prospective patient cohort.

RESULTS

Incubation of peripheral and intestinal T cells with 1,25(OH)2-vitD resulted in strongly reduced frequencies of pro-inflammatory CD4+ and CD8+ T cells producing interferon γ [IFNγ], interleukin-17 [IL-17], IL-22, IL-9 and tumour necrosis factor [TNF]. Univariable analysis of 200 IBD patients revealed associations of vitD deficiency with non-compliant vitD intake, season of the year and anaemia in Crohn's disease [CD] as well as disease activity in ulcerative colitis [UC]. Ex vivo immunophenotyping revealed that CD4+ and CD8+ T cell subsets were not substantially altered in vitD-deficient vs vitD-sufficient patients while regulatory T cell frequencies were reduced in UC and non-smoking CD patients with vitD deficiency. However, normalization of serum vitD concentrations in previously deficient CD patients resulted in significantly reduced frequencies of CD4+ T cells producing IFNγ, IL-17 and IL-22.

CONCLUSION

vitD exerts profound anti-inflammatory effects on peripheral and intestinal CD4+ and CD8+ T cells of IBD patients in vitro and inhibits TH1 and TH17 cytokine production in CD patients in vivo.

Managing vitamin D deficiency in inflammatory bowel disease

Management of inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is generally cumbersome for patients and is a massive health-economic burden. In recent years, the immunomodulating effects of vitamin D have gained a huge interest in its possible pathogenic influence on the pathophysiology of IBD. Vitamin D deficiency is frequent among patients with IBD. Several clinical studies have pointed to a critical role for vitamin D in ameliorating disease outcomes. Although causation versus correlation unfortunately remains an overwhelming issue in the illusive chicken versus egg debate regarding vitamin D and IBD, here we summarise the latest knowledge of the immunological effects of vitamin D in IBD and recommend from available evidence that physicians regularly monitor serum 25(OH)D levels in patients with IBD. Moreover, we propose an algorithm for optimising vitamin D status in patients with IBD in clinical practice. Awaiting well-powered controlled clinical trials, we consider vitamin D supplementation to be an affordable and widely accessible therapeutic strategy to ameliorate IBD clinical outcomes.

The Role of Vitamin D in Inflammatory Bowel Disease: Mechanism to Management

Vitamin D has been linked to human health benefits that extend far beyond its established actions on calcium homeostasis and bone metabolism. One of the most well studied facets of extra-skeletal vitamin D is its activity as an immuno-modulator, in particular its potent anti-inflammatory effects. As a consequence, vitamin D deficiency has been associated with inflammatory diseases including inflammatory bowel disease (IBD). Low serum levels of the major circulating form of vitamin D, 25-hydroxyvitamin D (25-OH-D) are significantly more prevalent in patients with IBD, particularly in the winter and spring months when UV-induced synthesis of vitamin D is lower. Dietary malabsorption of vitamin D may also contribute to low serum 25(OH)D in IBD. The benefits of supplementation with vitamin D for IBD patients are still unclear, and improved vitamin D status may help to prevent the onset of IBD as well as ameliorating disease severity. Beneficial effects of vitamin D in IBD are supported by pre-clinical studies, notably with mouse models, where the active form of vitamin D, 1,25-dihydroxyvitamin D (1,25-(OH)2D) has been shown to regulate gastrointestinal microbiota function, and promote anti-inflammatory, tolerogenic immune responses. The current narrative review aims to summarise the different strands of data linking vitamin D and IBD, whilst also outlining the possible beneficial effects of vitamin D supplementation in managing IBD in humans.

The effects of two vitamin D regimens on ulcerative colitis activity index, quality of life and oxidant/anti-oxidant status

Background

The optimum dosage for vitamin D supplementation has not yet been elucidated in patients with Ulcerative colitis (UC). The aim of this study was to investigate the effects of two vitamin D regimens in UC patients with vitamin D deficiency.

Methods

In this double blind randomized clinical trial, 50 patients with mild to moderate UC, who met inclusion criteria, received either 1000 or 2000 IU/day of vitamin D (as low dose or high dose group, respectively) for 12 weeks. Serum 25-hydroxy vitamin D (25-OHD) level, total antioxidant capacity (TAC), and Total Oxidant Status (TOS), the inflammatory bowel disease questionnaire − 9 (IBDQ-9) score and the Simple Clinical Colitis Activity Index Questionnaire (SCCAI) score were assessed before and after intervention.

Results

At the end of study, serum 25-OHD levels significantly increased in the high dose group (P < 0.001) and the increase was significantly more than low dose group (6.7 ± 3.8 ng/mL in the high dose group versus 0.2 ± 0.5 ng/mL in the low dose group) (P < 0.001). Serum TOS concentration decreased significantly (− 0.37 ± 0.26) only in the high dose group (P value = 0.023). There was no statistically significant change in serum TAC between two groups during the study. IBDQ-9 mean score significantly increased in high dose group compared to the low dose group (P value = 0.001) and SCCAI score in both groups reduced (− 2.58 ± 2.16 and − 0.9 ± 0.3 in high dose and low dose respectively), while this reduction was significant only in the high dose group (P value ≥0.001).

Conclusion

Our results indicate that 2000 IU daily dose of vitamin D can increase serum 25-OHD concentration, and quality of life, while it reduces disease activity in UC patients with vitamin D deficiency. We recommend assessment of the vitamin D status in all patients with UC because they may benefit from vitamin D therapy.

Vitamin D: a brief overview of its importance and role in inflammatory bowel disease

Vitamin D has traditionally been known for its regulation of bone metabolism and homeostasis, but emerging evidence suggests that it also has a broad function in immune regulation, and inflammatory bowel disease (IBD). The etiology of IBD is thought to be multifactorial but stems in part due to the deregulation of the immune response to environmental factors in the setting of a pre-existing genetic disposition. Vitamin D, based on its mechanistic role at the cellular level in T-cell trafficking, had been postulated to have a direct effect on the immune system, This alludes to the fact that vitamin D may have the ability to not only potentiate the IBD phenotype, but also in doing so, its supplementation may serve a therapeutic role in amelioration of the diseased state. We review in this article the current literature as it pertains to the basic mechanism of Vitamin D, its role in the pathogenicity of IBD, how it regulates our immune system, interpretation and accuracy of obtaining levels, and the role there may be in supplementation in IBD.

Role of Vitamin D in the Natural History of Inflammatory Bowel Disease

Inflammatory bowel disease [IBD], including ulcerative colitis and Crohn's disease, is a chronic and unpredictable condition characterised by alternating periods of remission interspersed with relapses. In recent years, accumulating support for an immunomodulating effect of vitamin D on both the innate and the adaptive immune systems has been presented. Through the vitamin D receptor, the active form of vitamin D, 1,25[OH]2D, induces antimicrobial peptide secretion, decreases dendritic cell activity, and promotes Th2 and regulatory T cell development and activity. In addition, vitamin D promotes an increased ratio of anti-inflammatory cytokines to pro-inflammatory cytokines. Studies in IBD point to a role for vitamin D in ameliorating disease outcome. Suboptimal circulating levels of 25-hydroxyvitamin D are common in IBD and appear to be associated with an increased risk of flares, IBD-related hospitalisations and surgeries, an inadequate response to tumour necrosis factor [TNF] inhibitors, a deterioration in quality of life, and low bone mineral density. With only few available randomised double-blind, placebo-controlled studies investigating therapeutic effects of vitamin D related to IBD, further research is necessary to determine the true therapeutic potential of vitamin D, as well as to define its optimal range in serum to achieve and maintain quiescence of disease. This review aims to summarise the latest knowledge on the extraskeletal effects of vitamin D in IBD, and outlines the potential deleterious consequences of vitamin D deficiency in this patient cohort.