<p>Increased Energy Expenditure and Energy Loss Through Feces Contribute to the Long-Term Outcome of Roux-en-Y Gastric Bypass in a Diet-Induced Obese Mouse Model</p>

Abstract

Background: Roux-en-Y gastric bypass (RYGB) has been proved to be more effective than other bariatric procedures in the long term on bodyweight loss and remission of diabetes. However, the mechanism remains poorly understood. Long-term changes in energy metabolism after RYGB have rarely been reported. Objective: To investigate the long-term effects of RYGB on energy metabolism on a dietinduced obesity (DIO) mouse model. Methods: DIO mice fed a high-fat diet were assigned to two groups: RYGB (n=8) and sham (n=7), followed by high-fat diet feeding until 12 weeks after surgery. Body weight and food intake were recorded weekly. Measurement of body composition and energy metabolism by metabolic chamber were conducted at weeks 4, 8, and 12 after surgery. Fecal energy measurement, intraperitoneal glucose-tolerance tests, and insulin-tolerance tests were conducted at postoperative week 12. Results: Food intake was reduced in the RYGB group within the first 3 weeks after surgery and increased to the same as the sham group from postoperative week 4. At 12 weeks after surgery, body weight had reduced by 36%±3.2% in the RYGB group compared to a 16%±2% bodyweight gain in the sham group, while fat mass had reduced significantly in the RYGB group compared to the sham group (9.2%±1.5% versus 30.1%±0.7%). Energy expenditure was significantly higher at postoperative week 8 in the RYGB group than the sham group. In comparison with the sham group, the respiratory exchange ratio was unchanged, decreased, and increased in the RYGB group at postoperative weeks 4, 8, and 12, respectively. Fecal energy measurement showed that feces from mice in the RYGB group contained higher energy levels than the sham group. Glucose metabolism had significantly improved in the RYGB group, in contrast to the sham group, demonstrated by intraperitoneal glucose tolerance tests (AUC 1,502±104 versus 2,277±198, respectively) and insulin tolerance tests (AUC 524±50 versus 838±63, respectively). Conclusion: Increased energy expenditure and energy loss through feces contribute to longterm bodyweight control after RYGB. Enhanced glucose utilization might play a role in long-term improvement in glucose metabolism.

Roux-en-Y gastric bypass potentially improved intestinal permeability by regulating gut innate immunity in diet-induced obese mice

“…2g). Furthermore, our previous study 28 indicated that the daily food intake of mice in the RYGB group was not different from that of mice in the sham group. Hence, the amount of food intake is not a confounding factor for the improved gut permeability in the RYGB model.…”