Research On The Mechanism Of RYGB Surgery In Treating T2DM By The Reduction Of LPS And Pancreatic Mast Cells

Part 1 Establishment of T2DM Rat Model with RYGB SurgeryObjective:To establish the T2DM rat model and confirming the definite hypoglycemic effect of RYGB surgery.To develop a proper animal model for studying the internal hypoglycemic mechanism of RYGB surgery.Methods:SD rats were fed with 40%high fat diet for 8 weeks and STZ(30mg/kg)was injected intraperitoneally to establish the T2DM rat model.Six T2DM rats were sham operated(Sham group),six T2DM rats were RYGB operated(RYGB group),and six healthy SD rats were fed with normal diets(Control group).The body weight,fasting blood glucose,fasting insulin level and HOMA-IR of three groups were compared four weeks after the operation.Results:The T2DM animal model was successfully established.Four weeks after the operation,the body weight,fasting blood glucose,fasting insulin level and HOMA-IR of the RYGB group were significantly lower than those of the Sham group.Conclusions:High fat diet combined with low dose STZ injection can successfully establish the T2DM rat model.RYGB operation has good weight-loss and hypoglycemic effect on this kind of T2DM rats,which is suitable for the mechanism research of RYGB treatment of diabetes.Part 2 Effects of RYGB Surgery on Inflammatory Status and Pancreatic Mast Cells in T2DM RatsObjective:To investigate the effects of RYGB surgery on the levels of LPS,TNF-?,IL-1?,IL-6 and IL-10 in the peripheral blood of T2DM rats,as well as on the number of pancreatic mast cells.The reason of the influence of operation on the level of LPS in the peripheral blood of T2DM rats was preliminarily discussed.Methods:The contents of LPS,TNF-?,IL-1?,IL-6 and IL-10 in the serum of rats in Part 1 were measured.The number of pancreatic mast cells was evaluated by detecting tryptase level in pancreatic tissue and immunohistochemistry.The intestinal propulsion rates of rats were measured,and the expression levels of the tight junction proteins including claudin-1,Claudin-3,claudin-4,Occludin and ZO-1 were detected.The tight junction structures of colons were observed by transmission electron microscope.Results:The levels of LPS,TNF-? and IL-1? in the RYGB group were significantly lower than those in the Sham group,and the number of mast cells in pancreatic tissue was decreased in rats undergoing surgery.The expression of Claudinl and Occludin in the colon of rats in the RYGB group was increased,and the repaired tight junction structure was observed in the rat of RYGB group by transmission electron microscope.Conclusions:RYGB surgery can significantly alleviate the systemic inflammatory state of T2DM rats and reduce the number of pancreatic mast cells.The decrease of LPS after RYGB is closely related to the repair of intestinal mucosal barrier.Part 3 LPS is a Key Factor for RYGB to Reduce Mast Cells of Pancreas in T2DM RatsObjective:To investigate whether LPS is a key factor for RYGB to reduce mast cells and improve glucose metabolism.Methods:Four groups of rats were fed:normal SD rats(Control group),SD rats injected with LPS for 8 weeks(Control+LPS group),T2DM rats operated with RYGB(RYGB group),and T2DM rats injected with LPS for 8 weeks after RYGB operation(RYGB+LPS group).The contents of LPS,TNF-?,IL-1?,IL-6 and IL-10 in peripheral blood were measured.The differences of pancreatic mast cells between groups were evaluated by detecting tryptase content in pancreatic tissue and immunohistochemistry.Results:The levels of LPS in the Control+LPS group and RYGB+LPS group were higher than those in the Control group and RYGB group.Compared with the Control group,the fasting insulin level,HOMA-IR index,TNF-?,IL-1? and the number of pancreatic mast cells of rats in the Control+LPS group was significantly increased.Compared with the RYGB group,the fasting blood glucose,fasting insulin level and HOMA-IR index of rats in the RYGB+LPS group were increased,and TNF-?,IL-1?,IL-10 and pancreatic mast cells were also increased significantly.Conclusions:LPS can increase the number of pancreatic mast cells,produce insulin resistance,and increase the fasting blood glucose of rats after RYGB.LPS is a key factor in RYGB surgery to reduce mast cells and improve glucose metabolism.