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Journal ArticleDOI

Vitamin D Receptor As an Intestinal Bile Acid Sensor

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TLDR
Activation of VDR by LCA or vitamin D induced expression in vivo of CYP3A, a cytochrome P450 enzyme that detoxifies LCA in the liver and intestine offers a mechanism that may explain the proposed protective effects of vitamin D and its receptor against colon cancer.
Abstract
The vitamin D receptor (VDR) mediates the effects of the calcemic hormone 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. We show that VDR also functions as a receptor for the secondary bile acid lithocholic acid (LCA), which is hepatotoxic and a potential enteric carcinogen. VDR is an order of magnitude more sensitive to LCA and its metabolites than are other nuclear receptors. Activation of VDR by LCA or vitamin D induced expression in vivo of CYP3A, a cytochrome P450 enzyme that detoxifies LCA in the liver and intestine. These studies offer a mechanism that may explain the proposed protective effects of vitamin D and its receptor against colon cancer.

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Citations
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Bile salt biotransformations by human intestinal bacteria.

TL;DR: The potential exists for altering the bile acid pool by targeting key enzymes in the 7α/β-dehydroxylation pathway through the development of pharmaceuticals or sequestering bile acids biologically in probiotic bacteria, which may result in their effective removal from the host after excretion.
Journal ArticleDOI

The Enzymes, Regulation, and Genetics of Bile Acid Synthesis

TL;DR: The synthesis and excretion of bile acids comprise the major pathway of cholesterol catabolism in mammals and causes a spectrum of human disease; this ranges from liver failure in early childhood to progressive neuropathy in adults.
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Role of Bile Acids and Bile Acid Receptors in Metabolic Regulation

TL;DR: Results suggest that modulation of FXR activity and BA metabolism may open new attractive pharmacological approaches for the treatment of the metabolic syndrome and type 2 diabetes.
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Bile acids: regulation of synthesis.

TL;DR: Bile acids are able to induce FGF 19 in human hepatocytes, and the FGF19 autocrine pathway may exist in the human livers, andThe mechanism by which FXR/FGF19/FGFR4 signaling inhibits CYP7A1 remains unknown.
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Targeting bile-acid signalling for metabolic diseases

TL;DR: How the signalling functions of bile acids can be exploited in the development of drugs for obesity, type 2 diabetes, hypertriglyceridaemia and atherosclerosis, as well as other associated chronic diseases such as non-alcoholic steatohepatitis are reviewed.
References
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Journal ArticleDOI

Identification of a Nuclear Receptor for Bile Acids

TL;DR: Results presented here show that bile acids are physiological ligands for the farnesoid X receptor (FXR), an orphan nuclear receptor, which demonstrates a mechanism by which bile acid transcriptionally regulate their biosynthesis and enterohepatic transport.
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Nuclear receptors and lipid physiology: opening the X-files.

TL;DR: Some general principles that govern the actions of this class of bioactive lipids and their nuclear receptors are considered here, and the scheme that emerges reveals a complex molecular script at work.
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An Orphan Nuclear Receptor Activated by Pregnanes Defines a Novel Steroid Signaling Pathway

TL;DR: The results provide evidence for the existence of a novel steroid hormone signaling pathway with potential implications in the regulation of steroid hormone and sterol homeostasis and the expression of the CYP3A family of steroid hydroxylases and modulates sterol and bile acid biosynthesis in vivo.
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Molecular basis for feedback regulation of bile acid synthesis by nuclear receptors.

TL;DR: An elaborate autoregulatory cascade mediated by nuclear receptors for the maintenance of hepatic cholesterol catabolism is revealed, showing that repression is coordinately regulated by a triumvirate of nuclear receptors, including the bile acid receptor, FXR, and the promoter-specific repressor, SHP.
Journal ArticleDOI

The nuclear vitamin D receptor: biological and molecular regulatory properties revealed.

TL;DR: The scope of this review will be limited to highlighting the actions of 1,25(OH)2D3 mediated by nuclear VDR and discussing new developments in the structure/function analysis of the receptor, including the phenotype of VDR knockout mice and the biochemical classification of patients with point mutations in the receptor.
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