Deletion of EHD2 Attenuated Adipocyte Hypertrophic Expansion and Ameliorated Diet-Induced Obesity and Insulin Resistance

Abstract

Abstract Objectives Obesity induces adipocyte hypertrophy, which promotes metabolic dysfunction. The EPS15-Homology Domain-Containing (EHD) 2 is an endocytic traffic-regulatory protein regulating caveolae stability, thereby participating cell size expansion. Although EHD2 is abundantly expressed in adipocytes, very little information is available on its role on adipose metabolism. This study aimed to define the role of EHD2 on governing adipocyte size, lipid metabolism and insulin sensitivity. Methods To prepare the EHD2-deficient adipocytes, primary ear mesenchymal stem cells were isolate from wildtype (WT) and EHD2 KO mice and induced differentiation into adipocytes. To induce obesity and insulin resistance, EHD2 KO and WT male mice were fed a high-fat diet (50% calorie from lard) for 8 weeks. The changes in body weight was monitored weekly. Fasting plasma glucose and insulin levels were determined by glucometer and ELISA respectively. Glucose tolerance test (GTT) was conducted after HF diet feeding. To investigate insulin signaling, human recombinant insulin (1 U/kg BW) was injected peritoneally and epididymal fat was collected immediately for measuring the phosphorylation levels of AKT (p-AKT), a downstream target for insulin. To determine the lipogenic gene and protein expression, qPCR and Western blot analysis were conducted. Results Deletion of EHD2 markedly upregulated EHD1 expression in primary adipocytes. Also, deletion of EHD2 significantly attenuated adipocyte differentiation and maintained smaller lipid droplets. Consistently, absence of EHD2 was linked with reduced lipogenic gene expression. In vivo study, EHD2 KO mice exhibited slightly lower total body weight, but fat mass was markedly reduced. After 8 weeks of HF diet, EHD2 KO mice had lower levels of plasma glucose and insulin levels compared with WT. EHD2 KO mice were more glucose tolerant during GTT. Insulin signaling study revealed that EHD2 KO mice showed higher levels of insulin-stimulated p-AKT compared to WT mice, indicating EHD2 deletion promotes insulin sensitivity. Conclusions This study suggests that EHD2 is required for maximal adipocyte differentiation and hypertrophic expansion. The absence of EHD2 was linked with improved insulin and glucose sensitivity, presumably due to reduced adiposity and adipocyte size. Funding Sources Nebraska EPSCoR (Food for Health 2017) Seed Grant.