title: Endogenous ApoE expression modulates adipocyte triglyceride content and turnover.
abstract: Apolipoprotein E (apoE) is highly expressed in adipose tissue and adipocytes in which its expression is regulated by peroxisome proliferator-activated receptor (PPAR)-gamma agonists and tumor necrosis factor-alpha. There is, however, no information regarding a role for endogenous apoE in differentiated adipocyte function. In this report, we define a novel role for apoE in modulating adipocyte lipid metabolism. ApoE(-/-) mice have less body fat and smaller adipocytes compared with wild-type controls. Freshly isolated adipose tissue from apoE(-/-) mice contains lower levels of triglyceride and free fatty acid, and these differences are maintained in cultured adipocytes derived from preadipocytes. Adenoviral expression of apoE in apoE(-/-)-cultured adipocytes increases triglyceride and fatty acid content. During incubation with apoE-containing triglyceride-rich lipoproteins, apoE(-/-) adipose tissue accumulates less triglyceride than wild type. The absence of apoE expression in primary cultured adipocytes also leads to changes in the expression of genes involved in the metabolism/turnover of fatty acids and the triglyceride droplet. Markers of adipocyte differentiation were lower in freshly isolated and cultured apoE(-/-) adipocytes. Importantly, PPAR-gamma-mediated changes in lipid content and gene expression are markedly altered in cultured apoE(-/-) adipocytes. These results establish a novel role for endogenous apoE in adipocyte lipid metabolism and have implications for constructing an integrated model of adipocyte physiology in health and disease.
authors.affiliation: Section of Endocrinology, Diabetes and Metabolism (MC 797), University of Illinois, 1819 W. Polk St., Chicago, IL 60612, USA.
authors.forename: Zhi Hua
authors.initials: ZH
authors.lastname: Huang
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Reardon
authors.forename: Theodore
authors.initials: T
authors.lastname: Mazzone
mesh_terms: D017667:Adipocytes / Q000378:metabolism*; D000273:Adipose Tissue / Q000033:anatomy & histology / Q000502:physiology; D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D017931:DNA Primers; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005786:Gene Expression Regulation; D051379:Mice; D018345:Mice, Knockout; D009924:Organ Culture Techniques; D012333:RNA, Messenger / Q000235:genetics; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D001057:Apolipoproteins E; D017931:DNA Primers; D005230:Fatty Acids, Nonesterified; D012333:RNA, Messenger; D014280:Triglycerides