title: De novo synthesis of steroids and oxysterols in adipocytes.
abstract: Local production and action of cholesterol metabolites such as steroids or oxysterols within endocrine tissues are currently recognized as an important principle in the cell type- and tissue-specific regulation of hormone effects. In adipocytes, one of the most abundant endocrine cells in the human body, the de novo production of steroids or oxysterols from cholesterol has not been examined. Here, we demonstrate that essential components of cholesterol transport and metabolism machinery in the initial steps of steroid and/or oxysterol biosynthesis pathways are present and active in adipocytes. The ability of adipocyte CYP11A1 in producing pregnenolone is demonstrated for the first time, rendering adipocyte a steroidogenic cell. The oxysterol 27-hydroxycholesterol (27HC), synthesized by the mitochondrial enzyme CYP27A1, was identified as one of the major de novo adipocyte products from cholesterol and its precursor mevalonate. Inhibition of CYP27A1 activity or knockdown and deletion of the Cyp27a1 gene induced adipocyte differentiation, suggesting a paracrine or autocrine biological significance for the adipocyte-derived 27HC. These findings suggest that the presence of the 27HC biosynthesis pathway in adipocytes may represent a defense mechanism to prevent the formation of new fat cells upon overfeeding with dietary cholesterol.
authors.affiliation: From the Research Institute, McGill University Health Centre, and.
authors.forename: Jiehan
authors.initials: J
authors.lastname: Li
authors.forename: Edward
authors.initials: E
authors.lastname: Daly
authors.forename: Enrico
authors.initials: E
authors.lastname: Campioli
authors.forename: Martin
authors.initials: M
authors.lastname: Wabitsch
authors.forename: Vassilios
authors.initials: V
authors.lastname: Papadopoulos
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism; D000818:Animals; D053898:Biosynthetic Pathways / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D053493:Cholestanetriol 26-Monooxygenase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D056945:Hep G2 Cells; D006801:Humans; D006888:Hydroxycholesterols / Q000378:metabolism*; D015151:Immunoblotting; D008297:Male; D008798:Mevalonic Acid / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000201:enzymology; D011284:Pregnenolone / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D013256:Steroids / Q000096:biosynthesis*
chemical_list: D006888:Hydroxycholesterols; D013256:Steroids; C076996:27-hydroxycholesterol; D011284:Pregnenolone; D053493:Cholestanetriol 26-Monooxygenase; C506832:Cyp27a1 protein, mouse; D008798:Mevalonic Acid
keywords: Adipocyte; CYP11A1; CYP27A1; Cholesterol; Differentiation; Human; Mouse; Oxysterol; Rat; Steroidogenesis