Caloric restriction and Roux-en-Y Gastric Bypass promote white adipose tissue browning in mice

Caloric restriction (CR) and Roux-en-Y Gastric Bypass (RYGB) are considered effective means of body weight control, but the mechanism by which CR and RYGB protect against high-fat diet (HFD)-induced obesity remains elusive. The browning of white adipose tissue (WAT) is a potential approach to combat obesity. Here we assess whether browning of WAT is involved in CR- and RYGB-treatment. The average size of adipocytes was determined by histological analysis. Expression of thermogenic genes in both human subjects and mice were measured by quantitative real-time PCR and immunohistochemical staining. The average size of adipocytes was bigger, while the expression of thermogenic genes such as uncoupling protein 1 (UCP1), nuclear factor erythroid-2 like 1 (NRF1) and PPARγ coactivator-1 α (PGC1α) were lower in the WAT of obese subjects when compared to lean controls. Both CR and RYGB promoted weight and fat loss. Increment of the average adipocytes size and down-regulation of thermogenic genes were significantly reversed by both CR and RYGB in the WAT of obese mice. Our findings showed that CR and RYGB significantly improved high-fat diet-induced lipid accumulation by promoting the browning of WAT.