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.
Background: Mesenteric adipose tissue (MAT) plays a critical role in the intestinal physiological ecosystems. Small and large intestines have evidently intrinsic and distinct characteristics. However, whether there exist any mesenteric differences adjacent to the small and large intestines (SMAT and LMAT) has not been properly characterized. We studied the important facets of these differences, such as morphology, gene expression, cell components and immune regulation of MATs, to characterize the mesenteric differences. Methods: The SMAT and LMAT of mice were utilized for comparison of tissue morphology. Paired mesenteric samples were analyzed by RNA-seq to clarify gene expression profiles. MAT partial excision models were constructed to illustrate the immune regulation roles of MATs, and 16S-seq was applied to detect the subsequent effect on microbiota. Results: Our data show that different segments of mesenteries have different morphological structures. SMAT not only has smaller adipocytes but also contains more fat-associated lymphoid clusters than LMAT. The gene expression profile is also discrepant between these two MATs in mice. B-cell markers were abundantly expressed in SMAT, while development-related genes were highly expressed in LMAT. Adipose-derived stem cells of LMAT exhibited higher adipogenic potential and lower proliferation rates than those of SMAT. In addition, SMAT and LMAT play different roles in immune regulation and subsequently affect microbiota components. Finally, our data clarified the described differences between SMAT and LMAT in humans. Conclusions: There were significant differences in cell morphology, gene expression profiles, cell components, biological characteristics, and immune and microbiota regulation roles between regional MATs.
Background Roux-en-Y gastric bypass (RYGB) has been proved to be more effective than other bariatric procedures in long-term on body weight loss and remission of diabetes. However, the mechanism remains poorly understood. Long-term change of energy metabolism after RYGB has rarely been reported. Objectives To investigate the long-term outcome of RYGB on mouse model and its mechanism from the perspective of energy metabolism. Methods High-fat diet induced obesity (DIO) mice were assigned to two groups receiving RYGB(n=8) and sham operation(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 on week 4, 8 and 12 after surgery. Fecal energy measurement, Intraperitoneal Glucose Tolerance Test (IPGTT) and Insulin Tolerance Test (ITT) were conducted on week 12 after surgery.Results Food intake was reduced in RYGB group within the first 3 weeks after surgery and increased to be the same withSham group from postoperative week 4. At 12 weeks after surgery, body weight reduced by 36±3.2% in RYGB group comparing to 16±2% body weight gain in Sham group, while fat mass was significantly reduced in RYGB group than in Sham group (9.2±1.5% versus 30.1±0.7%). Energy expenditure was significantly higher on postoperative week 8 in RYGB group than in Sham group. In comparison with Sham group, respiratory exchange ratio (RER) was unchanged, decreased and increased in RYGB group at postoperative week 4, 8 and 12, respectively. Fecal energy measurementshowed that feces from mice in RYGB group contained higher energy level than Sham group. Glucose metabolism was significantly improved in RYGB group in contrast to Sham group, demonstrated by the result of Intraperitoneal Glucose Tolerance Test (IPGTT) (AUC: 1502± 104 versus 2277±198, respectively) and the Insulin Tolerance Test (ITT) (AUC: 524 ±50 versus 838±63, respectively). Conclusions Increased energy expenditure and energy loss through feces contribute to the long-term body weight control after RYGB. Enhanced glucose utilization might play a role in the long-term improvement of glucose metabolism.
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