Title: Suppression of 2,3-Oxidosqualene Cyclase by High Fat Diet Contributes to Liver X Receptor--mediated Improvement of
Abstract:The liver X receptors (LXRs) sense oxysterols and regulategenesinvolvedincholesterolmetabolism.SyntheticagonistsofLXRs are potent stimulators of fatty acid synthesis, which ismediated largely by stero...The liver X receptors (LXRs) sense oxysterols and regulategenesinvolvedincholesterolmetabolism.SyntheticagonistsofLXRs are potent stimulators of fatty acid synthesis, which ismediated largely by sterol regulatory element-binding pro-tein-1c (SREBP-1c). Paradoxically, an improved hepatic lipidprofilebyLXRwasobservedinmicefedaWesternhighfat(HF)diet. To explore the underlying mechanism, we administeredmicenormalchoworanHFdietandoverexpressedLXR intheliver.TheHFdietwithtail-veininjectionofadenovirusofLXRincreasedtheexpressionofLXR-targetedgenesinvolvedincho-lesterol reverse transport but not those involved in fatty acidsynthesis.Asimilareffectwasalsoobservedwiththeuseof22R-hydroxycholesterol, an LXR ligand, in cultured hepatocytes.Consequently, SREBP-1c maturation was inhibited by the HFdiet,whichresultedfromtheinductionofInsig-2a.Importantly,increasedcholesterollevelsuppressedtheexpressionof2,3-ox-idosqualene cyclase (OSC), which led to an increase in endoge-nousLXRligand(s).Furthermore,siRNA-mediatedknockdownof OSC expression enhanced LXR activity and selectively up-regulated LXR-targeted genes involved in cholesterol reversetransport. Thus, down-regulation of OSC may account for anovel mechanism underlying the LXR-mediated lipid metabo-lism in the liver of mice fed an HF diet.Read More
Publication Year: 2009
Publication Date: 2009-01-01
Language: en
Type: article
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