BACKGROUND The mechanisms underlying diabetes remission after duodenal-jejunal bypass(DJB) remain elusive. In DJB surgery, the duodenum is excluded. However, the duodenum has emerged as an important regulator of gluco...BACKGROUND The mechanisms underlying diabetes remission after duodenal-jejunal bypass(DJB) remain elusive. In DJB surgery, the duodenum is excluded. However, the duodenum has emerged as an important regulator of glucose homeostasis, and elevated duodenal SIRT1 leads to improved hepatic insulin sensitivity. After DJB, bile acids(BAs) in the duodenum are not mixed and diluted by the ingested food. And activation of BA receptors promotes SIRT1 expression in many tissues. We hypothesized that BA-mediated upregulation of SIRT1 may contribute to diabetic control after DJB.AIM To investigate the surgical effects of DJB on duodenal SIRT1 expression and uncover the potential crosslinks between BAs and SIRT1.METHODS Twenty diabetic rats were randomly allocated to the sham(n = 10) and DJB(n = 10) groups. Body weight, food intake, fasting blood glucose(FBG), serum and intraduodenal total BA(TBA) levels were measured accordingly. Oral glucose tolerance test(OGTT) and intraperitoneal pyruvate tolerance test(ip PTT) were performed to evaluate the effects of surgeries on systemic glucose disposal and hepatic gluconeogenesis. The key genes of BA signaling pathway in the duodenal mucosa, including farnesoid X receptor(FXR), small heterodimer partner(SHP), and Takeda G-protein-coupled receptor 5(TGR5) were evaluated by real-time quantitative polymerase chain reaction 8 wk postoperatively. The duodenal SIRT1, AMPK, and phosphorylated AMPK(p-AMPK) levels were evaluated by western blotting. Rat small intestine epithelial IEC-6 cells were treated with GW4064 and INT-777 to verify the effects of BAs on SIRT1 expression in enterocytes.RESULTS The DJB group exhibited body weight and food intake comparable to those of the sham group at all postoperative time points. The FBG level and area under the curve for the OGTT and ip PTT were significantly lower in the DJB group. The DJB group exhibited higher fasting and postprandial serum TBA levels than the sham group at both 2 and 8 wk postoperatively. At 8 wk after surgery, the DJB group showed higher intraluminal TBA concentration, upregulated m RNA expression of FXR and SHP, and elevated protein expression of SIRT1 and p-AMPK in the descending and horizontal segments of the duodenum. Activation of FXR and TGR5 receptors by GW4064 and INT-777 increased the m RNA and protein expression of SIRT1 and promoted the phosphorylation of AMPK in IEC-6 cells.CONCLUSION DJB elevates intraduodenal BA levels and activates the duodenal BA signaling pathway, which may upregulate duodenal SIRT1 and further contribute to improved glucose homeostasis after DJB.展开更多
基金Supported by the National Natural Science Foundation of China,No.81600617,81700708,81702647 and 82100853the Natural Science Foundation of Shandong Province,No.ZR2020MH246,ZR2021LZL003 and ZR2021QH028.
文摘BACKGROUND The mechanisms underlying diabetes remission after duodenal-jejunal bypass(DJB) remain elusive. In DJB surgery, the duodenum is excluded. However, the duodenum has emerged as an important regulator of glucose homeostasis, and elevated duodenal SIRT1 leads to improved hepatic insulin sensitivity. After DJB, bile acids(BAs) in the duodenum are not mixed and diluted by the ingested food. And activation of BA receptors promotes SIRT1 expression in many tissues. We hypothesized that BA-mediated upregulation of SIRT1 may contribute to diabetic control after DJB.AIM To investigate the surgical effects of DJB on duodenal SIRT1 expression and uncover the potential crosslinks between BAs and SIRT1.METHODS Twenty diabetic rats were randomly allocated to the sham(n = 10) and DJB(n = 10) groups. Body weight, food intake, fasting blood glucose(FBG), serum and intraduodenal total BA(TBA) levels were measured accordingly. Oral glucose tolerance test(OGTT) and intraperitoneal pyruvate tolerance test(ip PTT) were performed to evaluate the effects of surgeries on systemic glucose disposal and hepatic gluconeogenesis. The key genes of BA signaling pathway in the duodenal mucosa, including farnesoid X receptor(FXR), small heterodimer partner(SHP), and Takeda G-protein-coupled receptor 5(TGR5) were evaluated by real-time quantitative polymerase chain reaction 8 wk postoperatively. The duodenal SIRT1, AMPK, and phosphorylated AMPK(p-AMPK) levels were evaluated by western blotting. Rat small intestine epithelial IEC-6 cells were treated with GW4064 and INT-777 to verify the effects of BAs on SIRT1 expression in enterocytes.RESULTS The DJB group exhibited body weight and food intake comparable to those of the sham group at all postoperative time points. The FBG level and area under the curve for the OGTT and ip PTT were significantly lower in the DJB group. The DJB group exhibited higher fasting and postprandial serum TBA levels than the sham group at both 2 and 8 wk postoperatively. At 8 wk after surgery, the DJB group showed higher intraluminal TBA concentration, upregulated m RNA expression of FXR and SHP, and elevated protein expression of SIRT1 and p-AMPK in the descending and horizontal segments of the duodenum. Activation of FXR and TGR5 receptors by GW4064 and INT-777 increased the m RNA and protein expression of SIRT1 and promoted the phosphorylation of AMPK in IEC-6 cells.CONCLUSION DJB elevates intraduodenal BA levels and activates the duodenal BA signaling pathway, which may upregulate duodenal SIRT1 and further contribute to improved glucose homeostasis after DJB.
