Basic And Clinical Research Of Treatment Of Roux-en-Y Gastric Bypass Surgery For Type-2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease characterized by the increased peripheral tissue resistance to insulin and progressive deterioration of islet cell functions. The apoptosis of B-cells may be a major contributing factor to the failure of these cells at the late stages of T2DM. Thus, any ideal treatment modality for diabetes should posses the capability to improve the functions ofβ-cells and increase their numbers. T2DM mainly manifest as abnormal metabolism of sugar, fat and proteins and may develop in to secondary vitamin, water, and electrolyte imbalance, as well as oxidative imbalance that have detrimental effect on the body. Even though the drug management has been mainstay of treatment for the T2DM, role of surgical management has also attracted great attention of the people, over the recent years.Roux-en-Y gastric bypass (RYGB) is a commonly used surgical treatment for patients with morbid obesity. It could not only significantly and lastingly reduce patients' body weight, but also could lower the serum levels of glucose and glycosylated hemoglobin in 80%-100% of T2DM patients. Furthermore, this treatment could also prevent impaired glucose intolerance from developing in to established diabetes, among these patients. Animal experiments have shown that RYGB treatment can improve the functions of pancreatic islets and the metabolism of glucose in both obese and non-obese diabetic rats. These results suggest that RYGB surgery is effective in the treatment of diabetes. Many efforts have been made to understand the mechanism of RYGB in ameliorating T2DM, however, the exact mechanism is still remain elusive. Clinical observations suggest that RYGB's ameliorating effect on T2DM may not be related to the weight loss or decreased food intake. Effect of the RYGB may be explained by it's effect on the gastro-intestinal hormones, which then influence the enteroinsular axis to regulate the endocrine function of the pancreas. Two of the most important intestinal hormones involved in this mechanism are glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP). It has been observed that RYGB surgery can increase GLP-1 levels in the sera of T2DM patients and in the experimental animals. This effect may last for 1 year and in some cases, even up to 20 years after RYGB surgeries. This may be one of the reasons why the diabetes is well controlled in both human beings and experimental rodents, post-surgically.It has been reported recently that after RYGB surgery, some patients developed nesidioblastosis, a serious life-threatening postprandial hyperinsulinism with hypoglycemia. These symptoms were alleviated, following the removal of part of the pancreas. Hypertrophy and hyperplasia of pancreatic islets are commonly seen in the resected specimens, and even multiple islet tumors detected in some specimens. Since the hyperplasia of islet cells are rarely found in the normal population, the above data suggest that RYGB is presumably associated with the regeneration and neogenesis of the pancreatic islets. Increased insulin secretion through the neogenesis and regeneration of islet cells could be another mechanism involved in ameliorating effect on the T2DM. However, this hypothesis hasn't been supported by any animal experiments.Pancreatic duodenal homeobox-1 (PDX-1) is known as the first and most important transcription factors during the embryonic development of the pancreas in experimental animals. All pancreatic cells are derived from the precursor cells with expression of PDX-1. The embryonic pancreas failed to develop in the Pdx-1 knockout mice. The expression level of PDX-1 in the pancreas gets to the peak in the first 10.5 days during the development of mouse embryos, and decline gradually afterwards. After birth and in adulthood, the expression of PDX-1 is very weak, which is only specifically found in 90% ofβcells and 10% ofδcells in the islets.PDX-1 is significantly re-expressed in proliferating cells in the ducts and islets during pancreas regeneration and may serve as a marker of cells that regain their pluripotency to differentiate into all pancreatic cell types. Furthermore, PDX-1 dramatically promoted cell proliferation, which was similar to the formation of the pancreas during embryonic development. Studies of animal models suggested that the down regulation of pdx1 expression in theβ-cells may underlie the pathogenesis ofβ-cell failure and T2DM. Therefore, the regeneration of isletβ-cells requires the activation and expression of Pdx-1. PDX-1 expression is the basis of regeneration of the pancreas.Goto-Kakizaki (GK) rat is a genetically non-overweight type 2 diabetes model rat, that posses similar characteristics of human T2DM and being used as the animal model for diabetic related laboratory studies. In this study also GK rats were used as the animal model and they were subjected to RYGB surgery and observed the effects of:①gastric bypass on carbohydrate and lipid metabolism in GK rats;②gastric bypass on expression of PDX-1 in pancreas and regeneration/neogenesis ofβ-cells;③the sources of regenerated/neogenesisedβ-cells;④Hence to provide laboratory evidence to support the idea of treating diabetes surgically and to provide evidence based explanation for the post surgical hypoglycemia in RYGB patients.This study was also intended to investigate the effects of gastric bypass on carbohydrate and lipid metabolism in non-obese patients with type 2 diabetes and gastric carcinoma, and the effects of surgery in T2DM. Chart I Roux- en-Y gastric bypass regulates the carbohydrate and lipid metabolism in diabetic ratsObjective:To observe the effects of Roux-en-Y gastric bypass on carbohydrate and lipid metabolism, as well as islet function in non-obese diabetic Goto-Kakizaki rats.Method:Eighteen male GK rats were randomly allocated into three groups: Roux-en-Y gastric bypass (RYGB) group (n=6), sham RYGB group (sham- RYGB) (n=6) and control group(n=6). (1) Each group was monitored for fasting glucose(FGlu), insulin(FIns), C-peptide(FC-p), body mass(BM), and food intake on 1st,2nd,4th,12th weeks, post operatively; (2) Each group was monitored for oral glucose tolerance test(OGTT), insulin and C-peptide, as well as plasma levels of glycosylated hemoglobin(HbAlc), total cholesterol(TC), triglycerides(TG), high density lipoprotein cholesterol(HDL-c), low density lipoprotein cholesterol(LDL-c) and free fatty acids (FFC) on 4th,12th weeks, post operatively.Results:(1) No significant differences were observed in food intake among all groups (P=0.322); (2) FGlu and HbAlc measured post operatively showed significant drop in RYGB group compared to two control groups (P=0.002); (3) FIns and FC-p measured post operatively showed significant elevation in RYGB group compared to two control groups (P<0.01); (4) On post operative 4th and 12th weeks, OGTT performed showed significant reduction of the area under the curve (AUC) of serum glucose (P<0.05) and significant increase was observed in AUC of serum insulin and C-peptide (p<0.01) in RYGB group; (5) The values of TC, TG, LDL-c and FFC in RYGB group were significantly lower than that of other two group on post operative 4th and 12th weeks (P<0.01).Conclusion:(1)Roux-en-Y gastric bypass is very effective in down-regulation of the carbohydrate metabolism, and has effective control on high sugar state; (2) Roux-en-Y gastric bypass surgery can improve glucose tolerance through the enhancement of serum insulin and C-peptide levels in non-obese diabetic GK rats, and improve the pancreatic islet function; (3) Roux-en-Y gastric bypass improves lipid metabolism in GK rats; (4)The effects on the carbohydrate and lipid metabolism are not resulted from weight loss or lower food intake in GK rats.Chart II Roux- en-Y gastric bypass promotes expression of PDX-1 and regeneration ofβ-cells in diabetic ratsObjective:To study the effect of Roux-en-Y gastric bypass (RYGB) on the expression of PDX-1 in pancreas, and pancreaticβ-cells regeneration/neogenesis, as well as to study their possible mechanisms in diabetics.Methods:Three groups of randomly selected non-obese diabetic Goto-Kakizaki (GK) rats were subjected to RYGB, sham-RYGB and sham-op surgery, respectively. The rats were euthanized at post-operative 1,2,4 and 12 weeks. Their pancreas were resected and analyzed by using reverse transcription polymerase chain reaction (RT-PCR) to detect the PDX-1mRNA. Western blotting and anti-PDX-1 immunohistochemistry (IHC) staining were used to detect the protein of PDX-1. Double IHC staining of anti-Brdu and -insulin was applied to detect regeneratedβ-cells. The index of double Brdu and insulin positive cells was calculated.The results were statistically analyzed.Results:(1) In comparison to sham-RYGB and control groups, a significant increase in the expressions of PDX-1 mRNA in RYGB group was observed, and there were significantly different in three group at all experimental time points. There were significantly different in RYGB group on all detected index. (2) PDX-1 protein in RYGB group had increased significantly, compared to both sham-RYGB and control groups at all experimental time points. There were significantly different in RYGB group on PDX-1 protein. (3) Immunohistochemistry showed that many PDX-1 positive cells could be found in the pancreatic islets of the rats in RYGB group at all time points, these cells mainly located in the islets. Few PDX-1 positive cells could be found in the pancreatic islets of the rats in other two groups at all time points. (5) Anti-Brdu and anti-insulin double stained cells could be found in the rat pancreas of RYGB group at each time points. The Brdu and insulin double positive cells were primarily seen in the islets and occasionally in the ducts. Single insulin positive cells found in the acini and there were many single Brdu positive cells in the acini of the pancreas. However, few Brdu and insulin double positive cells could be found in the rat pancreas in both sham-RYGB and control group at each time point after surgeries. The percentage of both Brdu and insulin positive cells showed a significant increase at 1,2,4 and 12 wk after surgeries being RYGB group highest at each time point.Conclusion:(1) RYGB could increase the expression of pancreatic PDX-1 mRNA in GK rats. (2) RYGB surgery can promote the expression of PDX-1 protein in diabetic GK rat pancreas. Many PDX-1 positive cells could be found in the pancreatic islets of the RYGB group. (3) RYGB surgery can promote pancreatic insulin-like cell regeneration and neogenesise in diabetic GK rats, regenerated insulin-like cells mainly in the islets, neogenesised insulin-like cells occasionally can be seen in acinar and duct. (4) RYGB could increase the regeneration ofβ-cells in GK rats. The associated regeneration of islet cells may be the mechanism that how RYGB could improve type 2 diabetes mellitus.ChartⅢRoux-en-Y gastric bypass improves carbohydrate and lipid metabolism in non-obese patients with type 2 diabetes and gastric carcinomaObjective:To observe the effects of Roux-en-Y Gastrointestinal reconstruction (RYGR) on carbohydrate and lipid metabolism in non-obese patients with type 2 diabetes and gastric carcinoma.Methods:Fifty seven cases of patients who underwent radical distal gastrectomy were studied and among them 35 patients had undergone Roux-en-Y gastrointestinal reconstruction (RYGR group) and 22 of them had undergone Billroth-Ⅰgastrointestinal reconstruction (B-ⅠGR group). Both groups were subjected to the measuring of pre-operative and post operative third, sixth months values of body mass index (BMI), glycosylated hemoglobin (GHbA1c), fasting glucose (FGlu), fasting insulin (FIns) and C-peptide (FC-p), as well as plasma levels of total cholesterol (TC), triglycerides(TG), high density lipoprotein (HDL-c) and low density lipoprotein (LDL-c). Plasma levels of 2 hour glucose (2hGlu),2 hour insulin(2hIns) and C-peptide(2hC-p) were also measured after oral glucose tolerance (OGTT). All findings were analyzed.Results:(1) No significant differences observed between two groups in pre-operative values (P＞0.05); (2) In RYGR group, serum levels measured in third and sixth post-operative months showed:FGlu, GHbA1c, TG, TC, LDL-c and 2hGlu significantly lower values compared to the pre-operative values (all P＜0.01); (3) In RYGR group, levels of FIns, FC-p, HDL-c,2hIns and 2hC-p were significantly higher than the pre-operative values (all P<0.01); (4)In B-I GR group, third and sixth post-operative months values of GHbA1c P=0.046) were lower than the pre-operative values; no significant differences were observed between pre and post operative values of other parameters. (5) No statistically significant difference was observed in BMI values measured post-operatively, between two groups (P>0.05); there were significant differences were observed between pre and post operative values of the other parameters, between two groups (P<0.05)Conclusion:(1) The RYGR surgery does not effect the BMI of non-obese patients with type 2 diabetes and gastric carcinoma; (2) The RYGR surgery can significantly improve the carbohydrate metabolism in non-obese patients with type 2 diabetes and gastric carcinoma, and the effect is not dependant upon the weight loss; (3) The RYGR surgery can significantly improve the lipid metabolism in non-obese patients with type 2 diabetes and gastric carcinoma, and the effect is dependant upon the weight loss; (4) The RYGR surgery can significantly improve the pancreatic function in non-obese patients with type 2 diabetes and gastric carcinoma.Conclusion of the overall studyThis study was intended to prove that the RYGB surgery improves fat and glucose metabolism and the pancreatic function in GK rats and the effect is not dependant upon either the weight loss or reduced food intake. Furthermore, RYGB could also increase the expression of pancreas specific gene PDX-1, which regulate pancreas development, and induces the regeneration of P-cells in GK rats. The associated regeneration of islet cells may be the possible mechanism of the RYGB's ameliorating effect on type 2 diabetes mellitus. Similarly, Roux-en-Y gastric bypass can significantly improve the metabolism of carbohydrates and lipids in non-obese patients with type 2 diabetes and gastric carcinoma, and the effects is not dependant upon the weight loss. Therefore, RYGB can be a treatment option for the carbohydrate and lipid metabolism disorders in patients with 2 type diabetes mellitus.