Conclusions
Maintenance of plasma APOA4 via exogenous APOA4 protein parallels elevation of BAT and IWAT thermogenesis, hepatic fatty acid β oxidation, and overall energy expenditure, with subsequent prevention of additional weight gain in HFD-fed obese mice.
Methods
BAT and inguinal white adipose tissue (IWAT) thermogenesis, body composition, energy intake and expenditure, and locomotor activity were measured using an infrared camera, immunoblots, quantitative magnetic resonance imaging, and a comprehensive lab animal monitoring system. An intraperitoneal glucose tolerance test and hepatic lipid accumulation and steatosis were assayed.
Objective
Apolipoprotein A4 (APOA4) is synthesized by the small intestine in response to dietary lipids. Chronic exposure to a high-fat diet (HFD) desensitizes lipid-induced APOA4 production and attenuates brown adipose tissue (BAT) thermogenesis. We hypothesized that exogenous APOA4 could increase BAT thermogenesis and energy expenditure in HFD-fed mice, resulting in decreased obesity and improved glucose tolerance.
Results
Mice receiving continuous infusion of APOA4 for the last 4 weeks of 10 weeks of HFD feeding gained no additional body weight and had reduced fat mass but enhanced BAT and IWAT thermogenesis and energy expenditure, despite unaltered food intake and locomotor activity. Additionally, APOA4 infusion elevated fatty acid β oxidation; decreased lipogenesis, lipid accumulation, and steatosis in liver; and improved glucose tolerance. Conclusions: Maintenance of plasma APOA4 via exogenous APOA4 protein parallels elevation of BAT and IWAT thermogenesis, hepatic fatty acid β oxidation, and overall energy expenditure, with subsequent prevention of additional weight gain in HFD-fed obese mice.