In primary cultures of adult rat hepatocytes the level of cholesterol 7-alpha-hydroxylase steady-state mRNA markedly decreased by 72 h. However, the addition of L-thyroxine (T4) and dexamethasone synergistically returned cholesterol…
Cholesterol 7alpha-hydroxylase, the rate-determining enzyme in the bile acid biosynthesis pathway, is regulated in a negative feedback manner by hydrophobic bile salts returning to the liver via the portal circulation. The role of cholesterol in the…
Growth hormone (GH) is a key metabolic regulator mediating glucose and lipid metabolism. Ataxia telangiectasia mutated (ATM) is a member of the phosphatidylinositol 3-kinase superfamily and regulates cell cycle progression. The orphan nuclear…
Activation of farnesoid X receptor (Fxr, Nr1h4) is a major mechanism in suppressing bile-acid synthesis by reducing the expression levels of genes encoding key bile-acid synthetic enzymes (e.g., cytochrome P450 [CYP]7A1/Cyp7a1 and CYP8B1/Cyp8b1).…
Orphan nuclear receptor small heterodimer partner (SHP) plays a key role in transcriptional repression of gluconeogenic enzyme gene expression. Here, we show that SHP inhibited protein kinase A-mediated transcriptional activity of cAMP-response…
The regulation of the rabbit apical sodium-dependent bile acid transporter ( ASBT) was studied both in vivo and in vitro. New Zealand White rabbits were fed 0.5% deoxycholic acid (DCA) or SC-435, a competitive ASBT inhibitor, for 1 wk. In DCA-fed…
Curcumin (diferuloylmethane), a major active component of turmeric (Curcuma longa), is a natural polyphenolic compound. Herein the effect of curcumin on endoplasmic reticulum (ER) stress responsive gene expression was investigated. We report that…
Purified cholesterol 7 alpha-hydroxylases (C7 alpha H) from human and rat liver microsomes, and from transformed Escherichia coli expression systems, were incubated with 0.3 mmol/L [gamma-P-32] adenosine triphosphate (ATP) in the presence and absence…
Bile acids activate a nuclear receptor, farnesoid X receptor (FXR), that induces bile salt export pump (BSEP) but inhibits cholesterol 7alpha-hydroxylase (CYP7A1) gene transcription in the liver. Guggulsterone, a plant sterol that lowers serum…
Background/Aims: The decrease in cholesterol 7 alpha-hydroxylase induced by intraduodenal infusion of taurocholate in bile fistula vats may be indirect, i.e., mediated through release or absorption of an intestinal factor in response to the presence…
In primary cultures of rat hepatocytes, transcription of the cholesterol 7 alpha-hydroxylase gene is induced synergistically by glucocorticoid and thyroid hormones. The objective of the present study was to evaluate the role of glucocorticoid and…
Cholesterol 7-alpha-hydroxylase catalyzes the rate-limiting step in the bile acid biosynthetic pathway. Regulation of this pathway is thought to occur solely as a result of a negative feedback control mechanism that is dependent upon the flux and…
