Human epicardial adipocytes have distinct functional and structural properties as compared to subcutaneous and perirenal adipocytes

Abstract

Growing evidence suggests that adipose tissue is an important endocrine organ, and that adipocytes (Ads) from different fat depots have distinct functional properties. Epicardial (EC) fat has been shown to produce inflammatory mediators, but the functional properties of isolated EC Ads have not been determined. For our studies, we compared isolated human EC Ads with subcutaneous (SQ) and perirenal (PR) Ads from the same donors (n = 3). EC fat was more highly vascularized and had a greater density of extracellular matrix than did SQ fat. Upon differentiation, both SQ and PR Ads exhibited significant accumulation of large lipid droplets, whereas EC Ads exhibited slower lipid accumulation and smaller lipid droplets. Microarray analysis showed that EC Ads expressed higher levels of pro‐inflammatory genes, including MMP1, MMP9, IL6, IL8, MCP1, and COX2. Conversely, EC Ads expressed lower levels of leptin and of the anti‐inflammatory, cardioprotective adipokine adiponectin. EC Ads also released less adiponectin as measured by ELISA. These results suggest that EC Ads exhibit structural and functional differences as compared to SQ and PR Ads. Furthermore, the increased adiponectin expression and release by SQ Ads suggests a potential basis for the observed cardioprotective effect of gluteofemoral fat. Funding for these studies was provided by the NIH (NHLBI) and the University of Iowa Department of Emergency Medicine.