Adipose Tissue Depot-Specific Differences in Adipocyte ApoE Expression

Objective—Important differences in gene expression have been documented in adipocytes derived from specific adipose tissue depots. We have previously documented an important role for adipocyte apoE in modulating adipocyte and adipose tissue triglyceride and lipoprotein metabolism. Materials/Methods—We now evaluate the endogenous expression of apoE in adipocytes isolated from unique adipose tissue depots in four different species. Results—Adipocyte apoE expression is higher in subcutaneous fat compared to visceral fat in humans, mice, rats, and baboons. In baboons, evaluation of apoE expression in five adipose tissue depots (subcutaneous abdominal, subcutaneous gluteal, visceral, pericardial, epicardial) showed that compared to subcutaneous abdominal adipocytes, the level of apoE expression is similar in subcutaneous gluteal, lower in visceral and pericardial, and higher in epicardial adipocytes. Consistent with previously demonstrated suppression of adipocyte apoE by adipose tissue inflammation, adipose tissue depots with lower apoE expression demonstrated greater infiltration of macrophages and an increased expression of TNFα mRNA. Depot-specific differences in apoE expression were maintained after in vitro differentiation. Adipocytes isolated from depots with lower apoE expression manifested lower rates of triglyceride synthesis in the absence and presence of triglyceride-rich lipoproteins. Adenoviral-mediated increase of apoE expression in omental adipocytes increased triglyceride synthesis in these cells. © 2011 Elsevier Inc. All rights reserved. Correspondence to: Theodore Mazzone, MD, Section of Endocrinology, Diabetes and Metabolism (MC 797), University of Illinois at Chicago, 1819 W. Polk Street, Chicago, IL 60612, 312/996-7989 (ph), 312/413-0437 (fax), tmazzone@uic.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Disclosure Statement The authors have nothing to disclose. Author Contributions ZHH performed experiments, analyzed data, critically evaluated and approved the final manuscript; DJE performed experiments, analyzed data, critically evaluated and approved the final manuscript, AU recruited human subjects, obtained human adipose tissue, critically evaluated and approved the final manuscript; AH assisted with collection of human visceral and subcutaneous adipose tissue, critically reviewed and approved the final manuscript; JV assisted with collection of human visceral and subcutaneous adipose tissue, critically reviewed and approved the final manuscript; TM planned experiments, analyzed data, wrote final manuscript. NIH Public Access Author Manuscript Metabolism. Author manuscript; available in PMC 2012 December 1. Published in final edited form as: Metabolism. 2011 December ; 60(12): 1692–1701. doi:10.1016/j.metabol. 2011.04. 012. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript Conclusions—Our results demonstrate significant heterogeneity in adipocyte apoE expression across adipose tissue depots in several species. Because of its role in modulating adipocyte triglyceride and lipoprotein metabolism, depot-specific differences in endogenous adipocyte apoE could have important implications for modulating the accumulation of lipid in these depots.