Adipose-specific VDR deletion leads to Hepatic steatosis in female mice fed a low fat diet

Risk factors for non-alcoholic hepatic steatosis include obesity and vitamin D deficiency which commonly co-exist. Thus, the role of vitamin D signaling in the prevention of hepatic steatosis in the absence of obesity or a “western” high fat diet is unclear. These studies were performed to address the role of the adipocyte Vitamin D Receptor (VDR) in the prevention of hepatic steatosis in mice fed a chow diet containing 5% fat by weight. Female mice with adipocyte VDR ablation (Adipoq-Cre; VDR flox/flox) exhibited a mild increase in weight gain at 70 days of age, accompanied by an increase in visceral adipose tissue (VAT) weight. While they did not exhibit evidence of hepatic inflammation or fibrosis, an increase in hepatic lipid content was observed. This was accompanied by an increase in the hepatic expression of genes involved in fatty acid transport and synthesis, as well as fatty acid oxidation. Markers of hepatic inflammation and fibrosis were unaffected by adipocyte VDR ablation. Consistent with the increase in VAT weight in the Adipoq-Cre; VDR flox/flox mice, higher levels of transcripts encoding adiopogenesis related genes were observed in VAT. In contrast to other models of impaired vitamin D signaling studied in the setting of a high fat or “western” diet, the Adipoq-Cre; VDR flox/flox mice do not exhibit hepatic inflammation or fibrosis. These findings suggest that the adipocyte VDR regulates hepatic lipid accumulation, but in the absence of obesity or a high fat diet, is not required to prevent hepatic inflammation or fibrosis.

Role of Vitamin D in Cognitive Dysfunction: New Molecular Concepts and Discrepancies between Animal and Human Findings

Purpose of review: increasing evidence suggests that besides the several metabolic, endocrine, and immune functions of 1alpha,25-dihydroxyvitamin D (1,25(OH)2D), the neuronal effects of 1,25(OH)2D should also be considered an essential contributor to the development of cognition in the early years and its maintenance in aging. The developmental disabilities induced by vitamin D deficiency (VDD) include neurological disorders (e.g., attention deficit hyperactivity disorder, autism spectrum disorder, schizophrenia) characterized by cognitive dysfunction. On the other hand, VDD has frequently been associated with dementia of aging and neurodegenerative diseases (e.g., Alzheimer’s, Parkinson’s disease). Recent findings: various cells (i.e., neurons, astrocytes, and microglia) within the central nervous system (CNS) express vitamin D receptors (VDR). Moreover, some of them are capable of synthesizing and catabolizing 1,25(OH)2D via 25-hydroxyvitamin D 1alpha-hydroxylase (CYP27B1) and 25-hydroxyvitamin D 24-hydroxylase (CYP24A1) enzymes, respectively. Both 1,25(OH)2D and 25-hydroxyvitamin D were determined from different areas of the brain and their uneven distribution suggests that vitamin D signaling might have a paracrine or autocrine nature in the CNS. Although both cholecalciferol and 25-hydroxyvitamin D pass the blood–brain barrier, the influence of supplementation has not yet demonstrated to have a direct impact on neuronal functions. So, this review summarizes the existing evidence for the action of vitamin D on cognitive function in animal models and humans and discusses the possible pitfalls of therapeutic clinical translation.

Role of Vitamin D in Preeclampsia

Pathogenesis of preeclampsia involves immune dysfunction, placental implantation, abnormal angiogenesis, excessive inflammation, hypertension that may be affected by vitamin D. Human placenta expresses all the components for vitamin D signaling: Vitamin D receptor (VDR), retinoid X receptor (RXR), 1-alpha- hydroxylase (CYP27B1) and 24- hydroxylase (CYP24A1). Vitamin D binding protein plays a role in binding and transportation of 25 hydroxyvitamin D [25(OH)D] and 1,25(OH)2D3. Vitamin D is activated by 25-hydroxylase (CYP2R1) and 1-alpha -hydroxylase (CYP27B1) and is degraded by 24-hydroxylase (CYP24A1). Vitamin D supplementation is not recommended by WHO for pregnant women and allows recommended nutrient intake (RNI) of 200 IU (5 μg) per day. Further research requires serum 25(OH)D analysis and assessment of maternal and infant outcomes; pre-conceptional vitamin D status.

Normal T and B Cell Responses Against SARS-CoV-2 in a Family With a Non-Functional Vitamin D Receptor: A Case Report

The coronavirus disease 2019 (COVID-19) pandemic has severely impacted daily life all over the world. Any measures to slow down the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to decrease disease severity are highly requested. Recent studies have reported inverse correlations between plasma levels of vitamin D and susceptibility to SARS-CoV-2 infection and COVID-19 severity. Therefore, it has been proposed to supplement the general population with vitamin D to reduce the impact of COVID-19. However, by studying the course of COVID-19 and the immune response against SARS-CoV-2 in a family with a mutated, non-functional vitamin D receptor, we here demonstrate that vitamin D signaling was dispensable for mounting an efficient adaptive immune response against SARS-CoV-2 in this family. Although these observations might not directly be transferred to the general population, they question a central role of vitamin D in the generation of adaptive immunity against SARS-CoV-2.

A Newly Identified lncBCAS1-4_1 Associated With Vitamin D Signaling and EMT in Ovarian Cancer Cells

Long noncoding RNAs (lncRNAs) were identified rapidly due to their important role in many biological processes and human diseases including cancer. 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] and its analogues are widely applied as preventative and therapeutic anticancer agents. However, the expression profile of lncRNAs regulated by 1α,25(OH)2D3 in ovarian cancer remains to be clarified. In the present study, we found 606 lncRNAs and 102 mRNAs that showed differential expression (DE) based on microarray data. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that the DE genes were mainly enriched in TGF-β, MAPK, Ras, PI3K-Akt, and Hippo signaling pathways, as well as the vitamin D-related pathway. We further assessed the potential lncRNAs that linked vitamin D signaling with EMT, and lncBCAS1-4_1 was identified in the first time. Moreover, we found that the most upregulated lncBCAS1-4_1 showed 75% same transcripts with CYP24A1 (metabolic enzyme of 1α,25(OH)2D3). Finally, the lncBCAS1-4_1 gain-of-function cell model was established, which demonstrated that the knockdown of lncBCAS1-4_1 inhibited the proliferation and migration of ovarian cancer cells. Furthermore, lncBCAS1-4_1 could resist the antitumor effect of 1α,25(OH)2D3, which was associated with upregulated ZEB1. These data provide new evidences that lncRNAs served as a target for the antitumor effect of 1α,25(OH)2D3.

Vitamin D, infections and immunity

Vitamin D, best known for its role in skeletal health, has emerged as a key regulator of innate immune responses to microbial threat. In immune cells such as macrophages, expression of CYP27B1, the 25-hydroxyvitamin D 1α-hydroxylase, is induced by immune-specific inputs, leading to local production of hormonal 1,25-dihydroxyvitamin D (1,25D) at sites of infection, which in turn directly induces the expression of genes encoding antimicrobial peptides. Vitamin D signaling is active upstream and downstream of pattern recognition receptors, which promote front-line innate immune responses. Moreover, 1,25D stimulates autophagy, which has emerged as a mechanism critical for control of intracellular pathogens such as M. tuberculosis. Strong laboratory and epidemiological evidence links vitamin D deficiency to increased rates of conditions such as dental caries, as well as inflammatory bowel diseases arising from dysregulation of innate immune handling intestinal flora. 1,25D is also active in signaling cascades that promote antiviral innate immunity; 1,25D-induced expression of the antimicrobial peptide CAMP/LL37, originally characterized for its antibacterial properties, is a key component of antiviral responses. Poor vitamin D status is associated with greater susceptibility to viral infections, including those of the respiratory tract. Although the severity of the COVID-19 pandemic has been alleviated in some areas by the arrival of vaccines, it remains important to identify therapeutic interventions that reduce disease severity and mortality, and accelerate recovery. This review outlines of our current knowledge of the mechanisms of action of vitamin D signaling in the innate immune system. It also provides an assessment of the therapeutic potential of vitamin D supplementation in infectious diseases, including an up-to-date analysis of the putative benefits of vitamin D supplementation in the ongoing COVID-19 crisis.

Vitamin D deficiency enhances expression of autophagy-regulating miR-142-3p in mouse and 'involved' IBD patient intestinal tissues

Vitamin D deficiency is an environmental factor involved in the pathogenesis of inflammatory bowel disease (IBD), however, the mechanisms surrounding its role remain unclear. Previous studies conducted in an intestinal epithelial-specific vitamin D receptor (VDR) knockout model suggest that a lack of vitamin D signaling causes a reduction in intestinal autophagy. A potential link between vitamin D deficiency and dysregulated autophagy is microRNA (miR)-142-3p, which suppresses autophagy. In this study, we found that wildtype C57BL/6 mice fed a vitamin D deficient diet for 5 weeks had increased miR-142-3p expression in ileal tissues compared to mice fed a matched control diet. Interestingly, there was no difference in expression of key autophagy markers ATG16L1 and LC3II in the ileum whole tissue. However, Paneth cells of vitamin D deficient mice were morphologically abnormal and had an accumulation of the autophagy adaptor protein p62 which was not present in the total crypt epithelium. These findings suggest that Paneth cells exhibit early markers of autophagy dysregulation within the intestinal epithelium in response to vitamin D deficiency and enhanced miR-142-3p expression. Finally, we demonstrated that treatment-naïve IBD patients with low levels of vitamin D have an increase in miR-142-3p expression in colonic tissues procured from 'involved' areas of disease. Taken together, our findings demonstrate that insufficient vitamin D levels alter expression of autophagy-regulating miR-142-3p in intestinal tissues of mice and IBD patients, providing insight into the mechanisms by which vitamin D deficiency modulates IBD pathogenesis.

TaaI/Cdx-2 AA Variant of VDR Defines the Response to Phototherapy amongst Patients with Psoriasis

1,25-dihydroxyvitamin-D3 plays a central role in the immune system via binding to the vitamin D receptor. VDR polymorphisms have been associated with multiple autoimmune disorders, including psoriasis. Until now, five VDR polymorphisms, FokI, ApaI, BsmI, TaqI and TaaI/Cdx2, have been studied in psoriasis, with contradicting results. Therefore, this study aimed to evaluate the association of VDR polymorphisms with susceptibility to psoriasis, effectiveness of NB-UVB phototherapy and concentration of proinflammatory cytokines and vitamin D amongst the Polish population. VDR polymorphisms were analyzed by PCR-RFLP or real-time PCR. We found that the frequency of the TaaI/Cdx-2 GG genotype was significantly higher in psoriasis patients and was associated with regulation of IL-17 and IL-23 concentration. Moreover, TaaI/Cdx-2 AA might have a significant effect on the response to phototherapy amongst patients with psoriasis. Our results suggest that VDR is a susceptibility factor for psoriasis development. Moreover, TaaI/Cdx-2 variants have a significant effect on the response to phototherapy amongst patients with psoriasis and regulation of inflammatory response via decrease of IL-17 and IL-23 level after UVB phototherapy in the Polish population. Results of our study provide some evidence in support of the hypothesis that the vitamin D signaling pathway may be of relevance for pathogenesis and treatment of psoriasis.