Vitamin D Receptor regulation of hepatic energy metabolism in zebrafish
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ABSTRACT: Vitamin D deficiency and mutations in Vitamin D Receptor (VDR) are associated with liver disease and obesity, but the functions of vitamin D signaling in metabolism are poorly understood. Though vitamin D signaling is best known for its functions in mineral homeostasis and skeleton calcification in terrestrial vertebrates, this is unlikely to be the evolutionary function of vitamin D signaling. We utilize tissue-specific genetic modulation of Vdr signaling to investigate the function of the vitamin D endocrine system in zebrafish. We find that hepatocyte Vdr regulates organismal response to nutritional cues and coordinates hepatic and organismal energy metabolism by balancing energy storage and tissue growth.
Project description:1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) plays an integral role in calcium homeostasis in higher organisms through its actions in the intestine, kidney and skeleton. Interestingly, while several intestinal genes are known to play a contributory role in calcium homeostasis, the entire caste of key components remains to be identified. To examine the vitamin D receptor (VDR) cistrome in this issue, we conducted a ChIP-seq analysis of binding sites for the VDR across the proximal intestine in vitamin D-sufficient normal mice treated with vehicle or 1,25(OH)2D3. The residual VDR cistrome was comprised of 4617 sites which was increased almost 4-fold following hormone treatment. Interestingly, the majority of the genes regulated by 1,25(OH)2D3 in each diet group as well as those found in common in both groups contained frequent VDR sites that likely regulated their expression. This study revealed a global VDR cistrome regulating a network of genes in the intestine that both represent direct targets of vitamin D action in mice and are involved in calcium absorption.
Project description:1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) plays an integral role in calcium homeostasis in higher organisms through its actions in the intestine, kidney and skeleton. Interestingly, while several intestinal genes are known to play a contributory role in calcium homeostasis, the entire caste of key components remains to be identified. To examine the vitamin D receptor (VDR) cistrome in this issue, we conducted a ChIP-seq analysis of binding sites for the VDR across the proximal intestine in vitamin D-sufficient normal mice treated with vehicle or 1,25(OH)2D3. The residual VDR cistrome was comprised of 4617 sites which was increased almost 4-fold following hormone treatment. Interestingly, the majority of the genes regulated by 1,25(OH)2D3 in each diet group as well as those found in common in both groups contained frequent VDR sites that likely regulated their expression. This study revealed a global VDR cistrome regulating a network of genes in the intestine that both represent direct targets of vitamin D action in mice and are involved in calcium absorption. Wildtype mice were fed a standard rodent chow diet (Harlan Teklad, #5008). At 8 weeks of age, 3 mice were treated with 1,25(OH)2D3 (10 ng/g bw) or vehicle control and the proximal half of the small intestine (duodenum and jejunum) was collected 1 h later.
Project description:Complex autoimmune diseases have proven difficult to dissect down to their causative genetic mechanisms. As a result, epidemiological data from different human association studies are often merged to arrive at a working hypothesis. In one of such examples, lack of sun exposure and consequent lower serum vitamin D3 levels has been proposed to increase risk of autoimmunity, attributing vitamin D3 an immune regulatory role. However, conclusive evidence demonstrating its efficacy in treating autoimmune diseases is missing. In this study, we have used a forward genetics approach to positionally identify polymorphic nucleotides controlling T cell-dependent inflammatory diseases using congenic mouse strains. Here, we identify the vitamin D3 receptor (Vdr) as a driver of inflammation. Congenic mice carrying a polymorphic Vdr allele overexpressed the receptor selectively in activated T cells, thereby escaping systemic calcaemic side effects that often constitute a confounding factor in the study of immunomodulation by vitamin D3. Mice overexpressing Vdr in T cells developed more severe collagen-induced arthritis (CIA) and exhibited an enhanced antigen-specific CD4+ T cell response. Deficiency of vitamin D3 completely protected mice from CIA by limiting the activation of antigen-specific T cell responses, and arthritis susceptibility was restored by re-administration of vitamin D3. We demonstrate that vitamin D3 signalling specifically through Vdr predominantly acts to enhance T cell proliferation, thereby contributing to inflammation. In conclusion, our results demonstrate that genetically determined expression of VDR codetermines the pro-inflammatory behaviour of activated T cells. Furthermore, our data suggest that the anti-inflammatory properties of vitamin D3 might be limited by high expression of VDR at the site of inflammation.
Project description:Mutations of the lamin A/C gene (LMNA) cause a variety of diseases including dilated cardiomyopathy (DCM). LMNA-related DCM often leads to severe heart failure, but the underlying pathophysiology is unknown. Here we show that vitamin D receptor (VDR) signaling is critically involved in LMNA-related DCM. We established iPS cells from DCM patients with an LMNA mutation and found that the iPS cell-derived cardiomyocytes (iPSCMs) showed remarkable DNA damage and reduced contractility compared with the isogenic control. Screening of a chemical library revealed that vitamin D2 reduced DNA damage of the mutant iPSCMs. RNA sequencing analysis showed that expression levels of putative downstream genes of VDR including DNA repair factors were downregulated in the mutant iPSCMs, which were upregulated by vitamin D2. Protein-protein interaction screening revealed that the binding of VDR to mutant LMNA was more robust than to wild-type LMNA, resulting in attenuated VDR signaling in the mutant iPSCMs. Vitamin D2 administration reduced DNA damage and improved cardiac function in pressure overload-induced heart failure mice. These results indicate that impaired DNA repair caused by reduced transcriptional activity of VDR induces cardiac dysfunction of LMNA-related DCM and suggest that VDR signaling is a potential therapeutic target for patients with DCM and heart failure.
Project description:Vitamin D3 metabolites are capable of controlling gene expression in mammalian cells through two independent pathways: vitamin D receptor (VDR) and sterol regulatory element-binding protein (SREBP) pathways. In the present study, we dissect the complex biological activity of vitamin D by designing synthetic vitamin D3 analogs specific for VDR or SREBP pathway, i.e., a VDR activator that lacks SREBP inhibitory activity, or an SREBP inhibitor devoid of VDR activity.
Project description:VDR deficiency in microglia markedly aggravated infarct volumes, neurological deficits, and neuroinflammation after cerebral ischemia. To investigate the role of VDR in microglia-regulated neuroinflammation, we performed RNA-seq analysis on microglia isolated from poststroke microglia-conditional VDR knockout (Vdr-cKO) mice and littermate controls. VDR elimination dramatically alters the gene expression profiles of postischemic microglia, implying that vitamin D signaling play a crucial role in microglia-modulated stroke pathogenesis.
Project description:BACKGROUND. Although 25-hydroxyvitamin D (25(OH)D) concentrations ≥30ng/mL are known to reduce injury risk and boost strength, the influence on anterior cruciate ligament reconstruction (ACLR) outcomes remains unexamined. This study aimed to define the vitamin D signaling response to ACLR, assess the relationship between vitamin D status and muscle fiber cross-sectional area (CSA) and bone density outcomes, and discover vitamin D receptor (VDR) targets post-ACLR. METHODS. 21 young, healthy, physically active participants with recent ACL tears were enrolled (62% female; 17.8 ± 3.2 yr, BMI: 26.0 ± 3.5 kg/m2). Data were collected through blood samples, vastus lateralis biopsies, DXA bone density measurements, and isokinetic dynamometer measures at baseline, 1 week, 4 months, and 6 months post-ACLR. The biopsies facilitated CSA, western blot, RNA-seq, and VDR ChIP-seq analyses. RESULTS. ACLR surgery led to decreased circulating bioactive vitamin D and increased VDR and activating enzyme expression in skeletal muscle one week post-operation. Participants with <30 ng/mL 25(OH)D levels (n=13) displayed more significant quadriceps fiber CSA loss one week and 4 months post-ACLR than those with ≥30 ng/mL (n=8; p<0.01 for post-hoc comparisons; p=0.041 for time x vitamin D status interaction). RNA-seq and ChIP-seq data integration revealed genes associated with energy metabolism and skeletal muscle recovery, potentially mediating the impact of vitamin D status on ACLR recovery. No difference in bone mineral density (BMD) losses between groups was observed.
Project description:As a highly heterogeneous tumor, pancreatic ductal adenocarcinoma (PDAC) exhibits non-uniform responses to therapies across subtypes. Overcoming therapeutic resistance due to tumor heterogeneity in PDAC remains a challenge. Here, we report that Vitamin D-resistant PDAC cells hijacked Vitamin D signaling to promote tumor progression, whereas epigenetic priming with glyceryl triacetate (GTA) and 5-Aza-2′-deoxycytidine (5-Aza) overcame Vitamin D resistance and shifted the transcriptomic phenotype of PDAC toward a Vitamin D-susceptible state. Increasing overall H3K27 acetylation with GTA and reducing overall DNA methylation with 5-Aza not only elevated the Vitamin D receptor (VDR) expression but also reprogrammed the Vitamin D-responsive genes. Consequently, Vitamin D inhibited cell viability and migration in the epigenetically primed PDAC cells by activating genes involved in apoptosis as well as genes involved in negative regulation of cell proliferation and migration, while the opposite effect of Vitamin D was observed in unprimed cells. Studies in genetically engineered mouse PDAC cells further validated the effects of epigenetic priming for enhancing the anti-tumor activity of Vitamin D. Using gain- and loss-of-function experiments, we further demonstrated that VDR was necessary for augmenting original Vitamin D responses, but was insufficient for shifting transcriptomic phenotype of PDAC toward a therapeutic response to Vitamin D, highlighting that both the VDR and Vitamin D-responsive genes were prerequisites for Vitamin D response. These data reveal a previously undefined mechanism in which epigenetic state orchestrates the expression of both VDR and Vitamin D-responsive genes, and determines the response to Vitamin D in PDAC.
Project description:Vitamin D (VitD) deficiency is estimated to affect ~40% of the world’s population. Notably, VitD deficiency has been associated with impaired muscle maintenance and insulin resistance. VitD exerts its actions through the ubiquitous Vitamin D-receptor (VDR), the expression of which was recently confirmed in fully-differentiated muscle. To seek a possible autonomous role of the VDR in skeletal muscle, we first generated stable VDR-knockdown cells, which exhibited impaired myogenesis (i.e. cell-cycling, differentiation and myotube formation). In vivo VDR-knockdown in rat hind-limbs elicited myofibre atrophy and triggered autophagy pathways. In contrast, in vivo VDR-overexpression yielded myofibre hypertrophy; enhancing translational efficiency (e.g. mTOR-signaling), ribosomal biogenesis and satellite cell content. Neither VDR-knockdown nor overexpression impacted muscle glucose uptake. Crucially, induction of VDR mRNA correlated with muscle hypertrophy in humans following long-term resistance exercise training, but not aspects of insulin sensitivity. The VDR autonomously regulates muscle mass, acting reciprocally to limit atrophy and promote hypertrophy.
Project description:The general objective of the study was to determine modulation of gene expression by environmental factors, with a special emphasis on bone formation. For this reason, the specific period of treatment was chosen between 5-6 days post-fertilization (dpf), when bone formation and calcification are taking place. We show that treatment with Vitamin D3 (VitD3) causes a clear increase of bone formation, as illustrated by cranial skeleton staining of the bone matrix by Alizarin Red, by morphometric analysis of the resulting images and by gene expression studies of selected genes. Thus, a whole genome micro-array experiment was conducted to identify genes that may be involved in the observed effect on bone formation.