Mechanisms of action of vitamin D in colon cancer

Genomic and epigenomic active vitamin D responses in human colonic organoids

Active vitamin D, 1α,25(OH)₂D₃, is a nuclear hormone with roles in colonic homeostasis and carcinogenesis; yet, mechanisms underlying these effects are incompletely understood. Human organoids are an ideal system to study genomic and epigenomic host-environment interactions. Here, we use human colonic organoids to measure 1α,25(OH)₂D₃ responses on genome-wide gene expression and chromatin accessibility over time. Human colonic organoids were cultured and treated in triplicate with 100 nM 1α,25(OH)₂D₃ or vehicle control for 4 h and 18 h for chromatin accessibility, and 6 h and 24 h for gene expression. ATAC- and RNA-sequencing were performed. Differentially accessible peaks were analyzed using DiffBind and edgeR; differentially expressed genes were analyzed using DESeq2. Motif enrichment was determined using HOMER. At 6 h and 24 h, 2,870 and 2,721 differentially expressed genes, respectively (false discovery rate, FDR < 5%), were identified with overall stronger responses with 1α,25(OH)₂D₃. Similarly, 1α,25(OH)₂D₃ treatment led to stronger chromatin accessibility especially at 4 h. The vitamin D receptor (VDR) motif was strongly enriched among accessible chromatin peaks with 1α,25(OH)₂D₃ treatment accounting for 30.5% and 11% of target sequences at 4 h and 18 h, respectively (FDR < 1%). A number of genes such as CYP24A1, FGF19, MYC, FOS, and TGFBR2 showed significant transcriptional and chromatin accessibility responses to 1α,25(OH)₂D₃ treatment with accessible chromatin located distant from promoters for some gene regions. Assessment of chromatin accessibility and transcriptional responses to 1α,25(OH)₂D₃ yielded new observations about vitamin D genome-wide effects in the colon facilitated by application of human colonic organoids. This framework can be applied to study host-environment interactions between individuals and populations in the future.

The Role of Gut Barrier Dysfunction and Microbiome Dysbiosis in Colorectal Cancer Development

Accumulating evidence indicates that breakdown of the+ protective mucosal barrier of the gut plays a role in colorectal cancer (CRC) development. Inflammation and oxidative stress in the colonic epithelium are thought to be involved in colorectal carcinogenesis and the breakdown of the integrity of the colonic barrier may increase the exposure of colonocytes to toxins from the colonic milieu, enhancing inflammatory processes and release of Reactive Oxygen Species (ROS). The aetiological importance of the gut microbiome and its composition - influenced by consumption of processed meats, red meats and alcoholic drinks, smoking, physical inactivity, obesity - in CRC development is also increasingly being recognized. The gut microbiome has diverse roles, such as in nutrient metabolism and immune modulation. However, microbial encroachment towards the colonic epithelium may promote inflammation and oxidative stress and even translocation of species across the colonic lumen. Recent research suggests that factors that modify the above mechanisms, e.g., obesity and Western diet, also alter gut microbiota, degrade the integrity of the gut protective barrier, and expose colonocytes to toxins. However, it remains unclear how obesity, lifestyle and metabolic factors contribute to gut-barrier integrity, leading to metabolic disturbance, colonocyte damage, and potentially to CRC development. This review will discuss the interactive roles of gut-barrier dysfunction, microbiome dysbiosis, and exposure to endogenous toxins as another mechanism in CRC development, and how biomarkers of colonic mucosal barrier function may provide avenues for disease, prevention and detection.

Associations of vitamin D status with colorectal cancer risk and survival

Biological evidence suggests that vitamin D has numerous anticancer functions, but the associations between vitamin D status and colorectal cancer (CRC) risk and survival remain inconclusive. Based on UK Biobank, we prospectively evaluated the associations of season-standardized 25-hydroxyvitamin D (25(OH)D) concentrations with CRC risk among 360 061 participants, and with survival among 2509 CRC cases. We observed an inverse linear relationship between 25(OH)D concentrations and CRC risk (P for linearity = .01; HR per 1-SD increment, 0.95; 95% CI, 0.91-0.99). Compared to the lowest quartile of 25(OH)D, the highest quartile was associated with a 13% (HR, 0.87; 95% CI, 0.77-0.98) lower risk of CRC. For CRC survival, compared to those in the lowest quartile of 25(OH)D, cases in the highest quartile had a 20% (HR, 0.80; 95% CI, 0.65-0.99) lower risk for overall death. Our findings indicate that higher concentrations of serum 25(OH)D are associated with lower incidence and improved survival of CRC, suggesting a role of vitamin D in the pathogenesis of CRC.

Quantitative Proteomics Analysis of Berberine-Treated Colon Cancer Cells Reveals Potential Therapy Targets

Simple Summary

Colon cancer is one of the most common malignant tumors and beberine has been found to exert potential anti-colon cancer activity in vitro and in vivo. In this study, by using proteomics and bioinformatics approaches, we report that berberine may inhibit the proliferation of colon cancer cells by regulating mitochondrial translation and ribosome biogenesis, as well as by promoting calcium mobilization and metabolism of fat-soluble vitamins. Moreover, GTPase ERAL1 and mitochondrial ribosomal proteins MRPL11, 15, 30, 37, 40, and 52 have great potential to serve as potential therapeutic targets for colon cancer treatment.

Abstract

Colon cancer is one of the most lethal malignancies worldwide. Berberine has been found to exert potential anti-colon cancer activity in vitro and in vivo, although the detailed regulatory mechanism is still unclear. This study aims to identify the underlying crucial proteins and regulatory networks associated with berberine treatment of colon cancer by using proteomics as well as publicly available transcriptomics and tissue array data. Proteome profiling of berberine-treated colon cancer cells demonstrated that among 5130 identified proteins, the expression of 865 and 675 proteins were changed in berberine-treated HCT116 and DLD1 cells, respectively. Moreover, 54 differently expressed proteins that overlapped in both cell lines were mainly involved in mitochondrial protein synthesis, calcium mobilization, and metabolism of fat-soluble vitamins. Finally, GTPase ERAL1 and mitochondrial ribosomal proteins including MRPL11, 15, 30, 37, 40, and 52 were identified as hub proteins of berberine-treated colon cancer cells. These proteins have higher transcriptional and translational levels in colon tumor samples than that of colon normal samples, and were significantly down-regulated in berberine-treated colon cancer cells. Genetic dependency analysis showed that silencing the gene expression of seven hub proteins could inhibit the proliferation of colon cancer cells. This study sheds a light for elucidating the berberine-related regulatory signaling pathways in colon cancer, and suggests that ERAL1 and several mitochondrial ribosomal proteins might be promising therapeutic targets for colon cancer.

Vitamin D regulation of energy metabolism in cancer

Vitamin D exerts anti-cancer effects in recent clinical trials and preclinical models. The actions of vitamin D are primarily mediated through its hormonal form, 1,25-dihydroxyvitamin D (1,25(OH)₂ D). Previous literature describing in vitro studies has predominantly focused on the anti-tumourigenic effects of the hormone, such as proliferation and apoptosis. However, recent evidence has identified 1,25(OH)₂ D as a regulator of energy metabolism in cancer cells, where requirements for specific energy sources at different stages of progression are dramatically altered. The literature suggests that 1,25(OH)₂ D regulates energy metabolism, including glucose, glutamine and lipid metabolism during cancer progression, as well as oxidative stress protection, as it is closely associated with energy metabolism. Mechanisms involved in energy metabolism regulation are an emerging area in which vitamin D may inhibit multiple stages of cancer progression.

Intestine-specific FXR agonists as potential therapeutic agents for colorectal cancer

Colorectal cancer (CRC) is one of the most malignant cancers in the world. A major cause of death in CRC patients is the limited therapeutic options in its advanced stages. The Farnesoid X receptor (FXR) is a member of the nuclear superfamily, which is effective in slowing the progression of colorectal cancer in addition to its extraordinary role in regulating metabolic disorders. Due to the systemic side-effects caused by non-selective agonists, the intestine-restricted FXR agonists can induce a whole-body benefit without activating the hepatic FXR, suggesting intestinal FXR activation as a potentially safer therapy in the treatment of CRC. This review highlights the effects of FXR on the disturbed bile acid circulation and the carcinogenesis of CRC and with a specific emphasis on listing the functions of several intestinal-restricted FXR agonists.

Sufficient 25-Hydroxyvitamin D Levels 2 Years after Colorectal Cancer Diagnosis are Associated with a Lower Risk of All-cause Mortality

BACKGROUND

Whether changes in 25 hydroxy vitamin D₃ (25(OH)D₃) levels after colorectal cancer diagnosis influence clinical outcomes is unclear. We investigated the association of trajectories of 25(OH)D₃ levels with recurrence and all-cause mortality.

METHODS

In total, 679 patients were included in our data analyses. Trajectories of 25(OH)D₃ levels were defined on the basis of vitamin D status at diagnosis, at 6 months, and 2 years after diagnosis. Observed trajectories of 25(OH)D₃ levels were consistent deficient levels (20%), consistent sufficient levels (39%), increasing levels (20%), and a temporary drop in levels (13%). Associations of trajectories of 25(OH)D₃ with recurrence and all-cause mortality were assessed using multivariable Cox proportional hazards regression models.

RESULTS

During a follow-up time of 2.2 years for recurrence and 3.5 years for all-cause mortality, 31 and 65 events occurred, respectively. No statistically significant associations were observed for vitamin D trajectories and the risk of recurrence. Patients who were consistently sufficient compared with patients who were consistently deficient had a lower risk of all-cause mortality [HR 0.39; 95% confidence interval (CI), 0.21-0.73]. The risk of all-cause mortality seems lower in patients with increasing levels or a temporary drop in levels (HR 0.54; 95% CI, 0.27-1.10 and HR 0.40 95% CI, 0.17-0.93) relative to patients with consistent deficient levels.

CONCLUSIONS

Patients with colorectal cancer following a trajectory characterized by sufficient levels of 25(OH)D₃ 2 years after diagnosis all appeared to have a lower risk of all-cause mortality compared with patients having consistent deficient levels.

IMPACT

Further studies should investigate how trajectories of 25(OH)D₃ levels are associated with colorectal cancer recurrence.

Promoter hypermethylation regulates vitamin D receptor (VDR) expression in colorectal cancer-A study from Kashmir valley

BACKGROUND

Colorectal carcinogenesis (CRC) is a multistep process, involving both genetic and epigenetic modifications of genes involved in diverse pathways ranging from tumor suppression to DNA mismatch repair.

PURPOSE

This study was undertaken to assess the role of promoter methylation of vitamin D receptor (VDR) gene, a transcription factor with myriad biological functions, in relation to its expression and clinicopathological parameters.

METHODS

Tissue specimens were taken from a total of 75 colorectal cancer cases paired with their normal surrounding epithelium and analyzed by Real-time RT-PCR for assessing the expression profile and MS-PCR for analyzing the promoter methylation status of the VDR gene. Blood sample from the same patients was drawn for vitamin D estimation.

RESULTS

The frequency of promoter methylation in cancerous tissue was 37.33% against 9.33% in normal tissues (p<0.001). The hypermethylated status of VDR promoter showed significantly inverse association with its expression (p=0.008). Furthermore, when compared with the clinical parameters, methylation status of VDR promoter was significantly associated with tumor staging (p=0.008), grading (p<0.001), depth of invasion (p=0.002) and lymph node metastases (p<0.001). Univariate and multivariate analysis indicated patients with increased VDR expression (p<0.001) and decreased methylation status (p=0.012) exhibited longer overall survival. Additionally, serum 25(OH)D₃ levels were not significantly associated with any of the patient characteristics.

CONCLUSION

Our study, first of its kind from Kashmir, indicated that VDR shows aberrant methylation pattern in CRC with consequent loss in its expression.

Functional effects of vitamin D: From nutrient to immunomodulator

Vitamin D can be obtained from the endogenous synthesis in the epidermis by exposure to UVB light, and from foods and supplements in the form of ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃). The main metabolite used to measure vitamin D serum status is calcidiol [25(OH)D]. However, its active metabolite calcitriol [1α,25(OH)₂D] performs pleiotropic effects in the cardiovascular, neurological, and adipose tissue as well as immune cells. Calcitriol exerts its effects through genomic mechanisms modulated by the nuclear vitamin D receptor (VDR)/retinoid X receptor (RXR) complex, to bind to vitamin D response elements (VDRE) in target genes of several cells such as activated T and B lymphocytes, neutrophils, macrophages, and dendritic cells; besides of its genomic mechanisms, VDR performs novel non-genomic mechanisms that involve its membrane expression and soluble form; highlighting that vitamin D could be an immunomodulatory nutrient that plays a key role during physiological and pathological events. Therefore, the aim of this comprehensive literature review was to describe the most relevant findings of vitamin D dietary sources, absorption, synthesis, metabolism, and factors that influence its serum status, signaling pathways, and biological effects of this immunonutrient in the health and disease.

Angiogenesis-Related Functions of Wnt Signaling in Colorectal Carcinogenesis

Simple Summary

Angiogenesis belongs to the most clinical characteristics of colorectal cancer (CRC) and is strongly linked to the activation of Wnt/β-catenin signaling. The most prominent factors stimulating constitutive activation of this pathway, and in consequence angiogenesis, are genetic alterations (mainly mutations) concerning APC and the β-catenin encoding gene (CTNNB1), detected in a large majority of CRC patients. Wnt/β-catenin signaling is involved in the basic types of vascularization (sprouting and nonsprouting angiogenesis), vasculogenic mimicry as well as the formation of mosaic vessels. The number of known Wnt/β-catenin signaling components and other pathways interacting with Wnt signaling, regulating angiogenesis, and enabling CRC progression continuously increases. This review summarizes the current knowledge about the role of the Wnt/Fzd/β-catenin signaling pathway in the process of CRC angiogenesis, aiming to improve the understanding of the mechanisms of metastasis as well as improvements in the management of this cancer.

Abstract

Aberrant activation of the Wnt/Fzd/β-catenin signaling pathway is one of the major molecular mechanisms of colorectal cancer (CRC) development and progression. On the other hand, one of the most common clinical CRC characteristics include high levels of angiogenesis, which is a key event in cancer cell dissemination and distant metastasis. The canonical Wnt/β-catenin downstream signaling regulates the most important pro-angiogenic molecules including vascular endothelial growth factor (VEGF) family members, matrix metalloproteinases (MMPs), and chemokines. Furthermore, mutations of the β-catenin gene associated with nuclear localization of the protein have been mainly detected in microsatellite unstable CRC. Elevated nuclear β-catenin increases the expression of many genes involved in tumor angiogenesis. Factors regulating angiogenesis with the participation of Wnt/β-catenin signaling include different groups of biologically active molecules including Wnt pathway components (e.g., Wnt2, DKK, BCL9 proteins), and non-Wnt pathway factors (e.g., chemoattractant cytokines, enzymatic proteins, and bioactive compounds of plants). Several lines of evidence argue for the use of angiogenesis inhibition in the treatment of CRC. In the context of this paper, components of the Wnt pathway are among the most promising targets for CRC therapy. This review summarizes the current knowledge about the role of the Wnt/Fzd/β-catenin signaling pathway in the process of CRC angiogenesis, aiming to improve the understanding of the mechanisms of metastasis as well as improvements in the management of this cancer.

circRNA_100859 functions as an oncogene in colon cancer by sponging the miR-217-HIF-1α pathway

Circular RNAs (circRNAs) play an important role in cancer development and progression by regulating gene expression. The present study aimed to investigate the function of circRNA_100859 in colon cancer. circRNA expression profiles from a human circRNAs chip were analyzed. The effects of circRNA_100859 on cell proliferation and apoptosis were assessed in vitro and interactions between circRNA_100859 and its micro (mi)RNA and target genes were analyzed. The diagnostic and prognostic significance of circRNA_100859 was also investigated. It was identified that circRNA_100859 was overexpressed in colon cancer tissues and promoted cell proliferation and inhibited cell apoptosis. Additionally, bioinformatics and a dual-luciferase reporter assay confirmed that circRNA_100859 acted as a miR-217 sponge, and miR-217 directly targeted hypoxia-inducible factor (HIF)-1α. Rescue assays demonstrated that HIF-1α protein and mRNA expression levels and cell proliferation were regulated by the circRNA_100859/miR-217 axis (P<0.05). Furthermore, statistical analysis showed that the circRNA_100859-miR-217-HIF-1α axis was associated with Tumor-Node-Metastasis (TNM) stage, histological grade, and KRAS mutations, and also showed high diagnostic and prognostic value for patients with colon cancer (P<0.05). Therefore, it was concluded that circRNA_100859 functions as an oncogene in colon cancer by sponging the miR-217-HIF-1α pathway. In addition, the circRNA_100859-miR-217-HIF-1α axis may serve as a novel diagnostic and prognostic biomarker for patients with colon cancer.

Vitamin D deficiency as a potential risk factor for accelerated aging, impaired hippocampal neurogenesis and cognitive decline: a role for Wnt/β-catenin signaling

Vitamin D is an essential fat-soluble vitamin that participates in several homeostatic functions in mammalian organisms. Lower levels of vitamin D are produced in the older population, vitamin D deficiency being an accelerating factor for the progression of the aging process. In this review, we focus on the effect that vitamin D exerts in the aged brain paying special attention to the neurogenic process. Neurogenesis occurs in the adult brain in neurogenic regions, such as the dentate gyrus of the hippocampus (DG). This region generates new neurons that participate in cognitive tasks. The neurogenic rate in the DG is reduced in the aged brain because of a reduction in the number of neural stem cells (NSC). Homeostatic mechanisms controlled by the Wnt signaling pathway protect this pool of NSC from being depleted. We discuss in here the crosstalk between Wnt signaling and vitamin D, and hypothesize that hypovitaminosis might cause failure in the control of the neurogenic homeostatic mechanisms in the old brain leading to cognitive impairment. Understanding the relationship between vitamin D, neurogenesis and cognitive performance in the aged brain may facilitate prevention of cognitive decline and it can open a door into new therapeutic fields by perspectives in the elderly.

Bi-Directional interactions between microbiota and ionizing radiation in head and neck and pelvic radiotherapy - clinical relevance

Purpose: Rapid developments in high throughput screening technology for the detection and identification of the human microbiota have helped in understanding its influence on human health and disease. In the recent past, several seminal studies have demonstrated the influence of microbiota on outcomes of therapy-associated radiation exposure. In this review, we highlight the concepts related to the mechanisms by which radiation alters the microbiota composition linked with radiation-associated toxicity in head and neck and pelvic regions. We further discuss specific microbial changes that can be employed as a biomarker for radiation and tumor response.Conclusion: Knowledge of the influence of microbiota in radiation response and advances in microbiota manipulation techniques would help to design personalized treatment augmenting the efficacy of radiotherapy.

Vitamin D, magnesium, calcium, and their interaction in relation to colorectal cancer recurrence and all-cause mortality

BACKGROUND

Higher concentrations of 25-hydroxyvitamin D3 [25(OH)D3] at diagnosis are associated with a lower mortality risk in colorectal cancer (CRC) patients. However, magnesium and calcium are important in vitamin D metabolism.

OBJECTIVES

We aimed to investigate 25(OH)D3, magnesium, or calcium and their interaction among patients with CRC in relation to recurrence and all-cause mortality.

METHODS

The study population included 1169 newly diagnosed stage I-III CRC patients from 2 prospective cohorts. Associations between 25(OH)D3 concentrations, magnesium or calcium intake through diet and/or supplements at diagnosis, and recurrence and all-cause mortality were evaluated using multivariable Cox proportional hazard models. The interaction between 25(OH)D3 and magnesium or calcium was assessed by investigating 1) joint compared with separate effects, using a single reference category; and 2) the effect estimates of 1 factor across strata of another.

RESULTS

Serum 25(OH)D3, calcium, and magnesium, alone and their interactions, were not associated with recurrence. Serum 25(OH)D3 concentrations seemed to be associated with all-cause mortality. An inverse association between magnesium intake (HRQ3 vs. Q1: 0.55; 95% CI: 0.32, 0.95 and HRQ4 vs. Q1: 0.65; 95% CI: 0.35, 1.21), but not calcium intake, and all-cause mortality was observed. When investigating the interaction between 25(OH)D3 and magnesium, we observed the lowest risk of all-cause mortality in patients with sufficient vitamin D concentrations (≥50 nmol/L) and a high magnesium intake (median split) (HR: 0.53; 95% CI: 0.31, 0.89) compared with patients who were vitamin D deficient (<50 nmol/L) and had a low magnesium intake. No interactions between calcium and vitamin D in relation to all-cause mortality were observed.

CONCLUSIONS

Our findings suggest that the presence of an adequate status of 25(OH)D3 in combination with an adequate magnesium intake is essential in lowering the risk of mortality in CRC patients, yet the underlying mechanism should be studied. In addition, diet and lifestyle intervention studies are needed to confirm our findings. The COLON study was registered at clinicaltrials.gov as NCT03191110. The EnCoRe study was registered at trialregister.nl as NTR7099.

Hospital-Based Preliminary Observations of Dietary Intake and Physical Activity in Saudi Patients with Colorectal Polyps: A Call for Nutrition Care Integration after Polypectomy Procedure

Aim: In Saudi Arabia, the incidence of colorectal cancer (CRC) is increasing. Lifestyle modification, including diet and physical activity, is as important as the standard procedure of colonoscopy screening in reducing CRC development. I explored the dietary intake, physical activity, and selected nutritional biomarkers in Saudi patients with colorectal polyps, a precursor of CRC. Methods: Thirty polypectomy patients (aged 35–84 years) were recruited from an endoscopy unit at King Abdulaziz University Hospital. Demographic, anthropometric, physical activity, and food frequency data were collected. Plasma C-reactive protein, serum 25-hydroxy vitamin D, and folate levels were measured. Results: The median body mass index (BMI) of the patients was within the overweight cut-off range. The median consumption of carbohydrate and protein was within the recommended dietary allowance (RDA). Median fat consumption was above the RDA, while median fiber intake was below the RDA. Patients met the recommended servings/day of fruits, vegetables, dairy products, and protein but exceeded the recommended intake of fats and sweets. Most patients were non-active, with an inadequate level of serum vitamin D. Conclusion: We observed several risk factors previously associated with CRC, including low levels of physical activity, serum vitamin D, and fiber intake, and high BMI and fat intake among polypectomy patients.

The effects of mitotane and 1α,25-dihydroxyvitamin D3 on Wnt/beta-catenin signaling in human adrenocortical carcinoma cells

PURPOSE

Mitotane is the only chemotherapeutic agent available for the treatment of adrenocortical carcinoma (ACC), however, the anti-neoplastic efficacy is limited due to several side-effects in vivo. There is, therefore, a need of exploring for new anti-tumoral agents which can be used either alone or in combination with mitotane. The active vitamin D metabolite 1α,25-dihydroxyvitamin D₃ (1α,25(OH)₂D₃) acts as an anti-proliferative agent in human cancer by inhibiting the Wnt/beta-catenin pathway through the vitamin D receptor (VDR). The aim of this study was to study the effects of mitotane and 1α,25(OH)₂D₃, individually or in combination, in an in vitro model with H295R ACC cells, and to elucidate the molecular events behind their effects involving the Wnt/beta-catenin signaling.

METHODS AND RESULTS

Multiple concentrations of mitotane and 1α,25(OH)₂D₃, individually or in combination, were tested on H295R cells for 24-96 h, and the effects analysed by MTT. A reduction in cell growth was observed in a dose/time-dependent manner for both mitotane and 1α,25(OH)₂D₃. In addition, a combination of clinically sub-therapeutic concentrations of mitotane with 1α,25(OH)₂D₃, had an additive anti-proliferative effect (Combination Index = 1.02). In a wound healing assay, individual treatments of both mitotane and 1α,25(OH)₂D₃ reduced the migration ability of H295R cells, with the effect further enhanced on combining both the agents. Western blotting and qRT-PCR analysis showed a modulation of the Wnt/beta-catenin and VDR signaling pathways.

CONCLUSION

Our results show an additive effect of mitotane and 1α,25(OH)₂D₃ on the inhibition of H295R ACC cell growth and viability, and suggest that molecular mechanisms of their effects involve a functional link between VDR and Wnt/beta-catenin pathways.

Consensus statement from 2nd International Conference on Controversies in Vitamin D

The 2nd International Conference on Controversies in Vitamin D was held in Monteriggioni (Siena), Italy, September 11-14, 2018. The aim of this meeting was to address ongoing controversies and timely topics in vitamin D research, to review available data related to these topics and controversies, to promote discussion to help resolve lingering issues and ultimately to suggest a research agenda to clarify areas of uncertainty. Several issues from the first conference, held in 2017, were revisited, such as assays used to determine serum 25-hydroxyvitamin D [25(OH)D] concentration, which remains a critical and controversial issue for defining vitamin D status. Definitions of vitamin D nutritional status (i.e. sufficiency, insufficiency and deficiency) were also revisited. New areas were reviewed, including vitamin D threshold values and how they should be defined in the context of specific diseases, sources of vitamin D and risk factors associated with vitamin D deficiency. Non-skeletal aspects related to vitamin D were also discussed, including the reproductive system, neurology, chronic kidney disease and falls. The therapeutic role of vitamin D and findings from recent clinical trials were also addressed. The topics were considered by 3 focus groups and divided into three main areas: 1) "Laboratory": assays and threshold values to define vitamin D status; 2) "Clinical": sources of vitamin D and risk factors and role of vitamin D in non-skeletal disease and 3) "Therapeutics": controversial issues on observational studies and recent randomized controlled trials. In this report, we present a summary of our findings.

Vitamin D, gut microbiota, and radiation-related resistance: a love-hate triangle

Radiation resistance is a serious issue in radiotherapy. Increasing evidence indicates that the human gut microbiome plays a role in the development of radiation resistance. Vitamin D is an important supplement for cancer patients treated with radiotherapy. Against this background, this paper reviewed research regarding the associations among vitamin D, microbiota dysbiosis, and radiation resistance. A hypothesis is developed to describe the relationships among vitamin D, the gut microbiota, and radiotherapy outcomes. Radiotherapy changes the composition of the gut microbiota, which in turn influence the serum level of vitamin D, and its distribution and metabolism in the body. Alteration of vitamin D level influences the patient response to radiotherapy, where the underlying mechanisms may be associated with the intestinal microenvironment, immune molecules in the intestines, gut microbiome metabolites, and signaling pathways associated with vitamin D receptors. Our understanding of the contribution of vitamin D and the gut microbiota to radiotherapy outcomes has been increasing gradually. A better understanding of the relationships among vitamin D, the gut microbiota, and radiotherapy outcomes will shed more light on radiation resistance, and also promote the development of new strategies for overcoming it, thus addressing an important challenge associated with the currently available radiotherapy modalities for cancer patients.

Vitamin D alleviates acute graft-versus-host disease through promoting the generation of Foxp3+ T cells

Background

Acute graft-versus-host disease (aGVHD) is a medical complication which may result in significant morbidity and mortality after transplantation. The aim of this study investigated the therapeutic effect and underlying mechanism of 1,25-dihydroxyvitamin D3 (1α,25(OH)₂D₃) in the treatment of aGVHD.

Method

An aGVHD model was built by transferring splenocytes of B6 mice into B6D2F1 mice. 1α,25(OH)₂D₃ was added to evaluate the protective function to aGVHD; the phenotype and cytokine expression profile of spleen cells from the aGVHD model were determined using flow cytometry 2 weeks after the model is established.

Result

Administration of 1α,25(OH)₂D₃ significantly slowed aGVHD progression and improved survival of B6D2F1 recipients of grafted B6 splenocytes. 1α,25(OH)₂D₃ treatment also resulted in an increased number of CD4⁺Foxp3⁺ regulatory T cells (Tregs) but decreased the number of CD4⁺IL-4⁺ cells. In vitro analysis demonstrated that 1α,25(OH)₂D₃ directly increased forkhead box P3 (Foxp3) and IL-10 expression and enhanced the function of induced Tregs (iTregs).

Conclusions

This analysis indicated that the effect of 1α,25(OH)₂D₃ is mediated in part by improving the number of Tregs. 1α,25(OH)₂D₃ administration thus represents a viable approach for treating aGVHD.

Current evidence for vitamin D in intestinal function and disease

Vitamin D activity is associated with the modulation of a wide variety of biological systems, in addition to its roles in calcium homeostatic mechanisms. While vitamin D is well known to promote gastrointestinal calcium absorption, vitamin D also plays a role in attenuating and/or preventing the progression of several gastrointestinal diseases including Crohn’s disease, ulcerative colitis, and colorectal cancer, and may also play a role in chemotherapy-induced intestinal mucositis. The pro-differentiation, immunomodulatory, and anti-inflammatory effects of vitamin D, which has been reported in numerous circumstances, are key potential mechanisms of action in the prevention of gastrointestinal disorders. While the debate of the effectiveness of vitamin D to treat bone pathologies continues, the clinical importance of vitamin D therapy to prevent gastrointestinal disorders should be investigated given current evidence, using both nutritional and pharmaceutical intervention approaches.

Impact statement

The non-skeletal functions of vitamin D play an important role in health and disease. The anti-inflammatory properties and maintenance of intestinal function fulfilled by vitamin D impact other systems in the body though downstream processing. This review provides insight into the mechanisms underpinning the potential benefits of vitamin D in both maintaining intestinal homeostasis and associated diseased states.

Vitamin D differentially regulates colon stem cells in patient-derived normal and tumor organoids

Intestine is a major target of vitamin D and several studies indicate an association between vitamin D deficiency and inflammatory bowel diseases (IBD), but also increased colorectal cancer (CRC) risk and mortality. However, the putative effects of 1α,25‐dihydroxyvitamin D₃ (calcitriol), the active vitamin D metabolite, on human colonic stem cells are unknown. Here we show by immunohistochemistry and RNAscope in situ hybridization that vitamin D receptor (VDR) is unexpectedly expressed in LGR5⁺ colon stem cells in human tissue and in normal and tumor organoid cultures generated from patient biopsies. Interestingly, normal and tumor organoids respond differentially to calcitriol with profound and contrasting changes in their transcriptomic profiles. In normal organoids, calcitriol upregulates stemness‐related genes, such as LGR5,SMOC2,LRIG1,MSI1,PTK7, and MEX3A, and inhibits cell proliferation. In contrast, in tumor organoids calcitriol has little effect on stemness‐related genes while it induces a differentiated phenotype, and variably reduces cell proliferation. Concordantly, electron microscopy showed that calcitriol does not affect the blastic undifferentiated cell phenotype in normal organoids but it induces a series of differentiated features in tumor organoids. Our results constitute the first demonstration of a regulatory role of vitamin D on human colon stem cells, indicating a homeostatic effect on colon epithelium with relevant implications in IBD and CRC.

Potential Role of Vitamin D for the Management of Depression and Anxiety

Vitamin D, a fat-soluble vitamin, plays a role not only in calcium and phosphate homeostasis but also in several other functions, including cell growth and neuromuscular and immune function. The deficiency of vitamin D is highly prevalent throughout the world and has been suggested to be associated with an enhanced risk of major depressive disorder (MDD) and anxiety disorders. Therefore, vitamin D supplementation has been investigated for the prevention and treatment of these disorders. This review presents preclinical and clinical evidence of the effects of vitamin D supplementation in these disorders. Although preclinical studies provide limited evidence on the possible mechanisms underlying the beneficial effects of vitamin D for the management of these disorders, most of the clinical studies have indicated that vitamin D supplementation is associated with the reduction of symptoms of depression and anxiety, particularly when the supplementation was carried out in individuals with an MDD diagnosis (of the 13 studies in which MDD diagnosis was established, 12 had positive results with vitamin supplementation). However, some heterogeneity in the outcomes was observed and might be associated with an absence of overt psychiatric symptoms in several studies, genetic polymorphisms that alter vitamin D metabolism and bioavailability, differences in the supplementation regimen (monotherapy, adjunctive therapy, or large bolus dosing), and levels of 25-hydroxyvitamin D₃ (25(OH)D) at baseline (individuals with low vitamin D status may respond better) and attained after supplementation. Additionally, factors such as sex, age, and symptom severity also need to be further explored in relation to the effects of vitamin D. Therefore, although vitamin D may hold significant potential for mental health, further preclinical and clinical studies are clearly necessary to better understand its role on mood/affect modulation.

Vitamin D and Wnt3A have additive and partially overlapping modulatory effects on gene expression and phenotype in human colon fibroblasts

The Wnt/β-catenin signalling pathway is essential for intestinal epithelium homeostasis, but its aberrant activation is a hallmark of colorectal cancer (CRC). Several studies indicate that the bioactive vitamin D metabolite 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) inhibits proliferation and promotes epithelial differentiation of colon carcinoma cells in part through antagonism of the Wnt/β-catenin pathway. It is now accepted that stromal fibroblasts are crucial in healthy and pathologic intestine: pericryptal myofibroblasts are constituents of the stem cell niche and cancer-associated fibroblasts (CAFs) contribute to CRC progression. However, studies on the combined action of 1,25(OH)₂D₃ and Wnt factors in colon fibroblasts are lacking. Here we show by global transcriptomic studies that 1,25(OH)₂D₃ and Wnt3A have profound, additive, partially overlapping effects on the gene expression profile of CCD-18Co human colon myofibroblasts. Moreover, 1,25(OH)₂D₃ and Wnt3A inhibit CCD-18Co cell proliferation and migration, while 1,25(OH)₂D₃ reduces, but Wnt3A increases, their capacity to contract collagen gels (a marker of fibroblast activation). These data were largely confirmed in patient-derived primary colon normal fibroblasts and CAFs, and in fibroblasts from other origins. Our results indicate that 1,25(OH)₂D₃ and Wnt3A are strong regulators of colon fibroblast biology and contribute to a better knowledge of intestinal homeostasis and stromal fibroblast action in CRC.

Losartan and Vitamin D Inhibit Colonic Tumor Development in a Conditional Apc-Deleted Mouse Model of Sporadic Colon Cancer

Colorectal cancer is a leading cause of cancer deaths. The renin-angiotensin system (RAS) is upregulated in colorectal cancer, and epidemiologic studies suggest RAS inhibitors reduce cancer risk. Because vitamin D (VD) receptor negatively regulates renin, we examined anticancer efficacy of VD and losartan (L), an angiotensin receptor blocker. Control Apc^+/LoxP mice and tumor-forming Apc^+/LoxP Cdx2P-Cre mice were randomized to unsupplemented Western diet (UN), or diets supplemented with VD, L, or VD+L, the latter to assess additive or synergistic effects. At 6 months, mice were killed. Plasma Ca²⁺, 25(OH)D3, 1α, 25(OH)2D3, renin, and angiotensin II (Ang II) were quantified. Colonic transcripts were assessed by qPCR and proteins by immunostaining and blotting. Cancer incidence and tumor burden were significantly lower in Cre+ VD and Cre+ L, but not in the Cre+ VD+L group. In Apc^+/LoxP mice, VD increased plasma 1,25(OH)2D3 and colonic VDR. In Apc^+/LoxP-Cdx2P-Cre mice, plasma renin and Ang II, and colonic tumor AT1, AT2, and Cyp27B1 were increased and VDR downregulated. L increased, whereas VD decreased plasma renin and Ang II in Cre+ mice. VD or L inhibited tumor development, while exerting differential effects on plasma VD metabolites and RAS components. We speculate that AT1 is critical for tumor development, whereas RAS suppression plays a key role in VD chemoprevention. When combined with L, VD no longer increases active VD and colonic VDR in Cre- mice nor suppresses renin and Ang II in Cre+ mice, likely contributing to lack of chemopreventive efficacy of the combination.