Roux-en-Y gastric bypass promotes expression of PDX-1 and regeneration of β-cells in Goto-Kakizaki rats

Fufang-zhenzhu-tiaozhi formula protects islet against injury and promotes β cell regeneration in diabetic mice

ETHNOPHARMACOLOGICAL RELEVANCE

Fufang-zhenzhu-tiaozhi formula (FTZ) is a patented preparation of traditional Chinese medicine that has been used to treat hyperglycemia and hyperlipidemia in the clinic for almost 10 years. Our previous study had demonstrated that FTZ can protect islet β cell injury in vitro. However, the efficacy of FTZ on β cell regeneration in vivo and the involved anti-diabetic mechanism remains unknown.

AIM OF THE STUDY

We aim to investigate the effects of FTZ as a good remedy for islet protection and β cell regeneration, and to reveal the underlying mechanism.

MATERIALS AND METHODS

C57BL/6 mice were fed with high-fat diet for 3 weeks and then intraperitoneally injected with streptozotocin (90 mg/kg/d × 1 d) to establish type 2 diabetes (T2D) models. Mice in each group were divided into three batches that sacrificed after 3, 7 and 28 days of FTZ administration. Body weight, blood glucose, and oral glucose tolerance test were measured at indicated time points. Fasting insulin was determined by enzyme-linked immunosorbent assay (ELISA) kit. Neonatal β cell was assessed by insulin & PCNA double immunofluorescence staining, and the underlying mechanisms related to β cell regeneration were further performed by hematoxylin-eosin staining, insulin & glucagon double immunofluorescence staining and Western blot.

RESULTS

FTZ and metformin can significantly help with the symptoms of DM, such as alleviating weight loss, reducing blood glucose, improving the level of insulin in vivo, and relieving insulin resistance, suggesting FTZ and metformin treatment maintained the normal morphological function of islet. Notably, β cell regeneration, which is indicated by insulin and PCNA double-positive cells, was promoted by FTZ, whereas few neonatal β cells were observed in metformin group. Hematoxylin-eosin staining, and its quantification results showed that FTZ effectively prevented the invasion of inflammatory cells into the islets in diabetic mice. Most β cells in the islets of diabetic model mice were devoid, and the islets were almost all α cells, while the diabetic mice administered FTZ could still maintain about half of the β cells in the islet. Furthermore, FTZ upregulated the expression of critical transcription factors during β cell development and maturation (such as PDX-1, MAFA and NGN3) in diabetic mice.

CONCLUSIONS

FTZ can alleviate diabetes symptoms and promote β cell regeneration in diabetic mice. Moreover, FTZ promotes β cell regeneration by preserving islet (resisting inflammatory cells invading islets), maintaining the number of β cells in islets, and increasing the expression of PDX-1, MAFA and NGN3.

Bariatric Surgery: Targeting pancreatic β cells to treat type II diabetes

Pancreatic β-cell function impairment and insulin resistance are central to the development of obesity-related type 2 diabetes mellitus (T2DM). Bariatric surgery (BS) is a practical treatment approach to treat morbid obesity and achieve lasting T2DM remission. Traditionally, sustained postoperative glycemic control was considered a direct result of decreased nutrient intake and weight loss. However, mounting evidence in recent years implicated a weight-independent mechanism that involves pancreatic islet reconstruction and improved β-cell function. In this article, we summarize the role of β-cell in the pathogenesis of T2DM, review recent research progress focusing on the impact of Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) on pancreatic β-cell pathophysiology, and finally discuss therapeutics that have the potential to assist in the treatment effect of surgery and prevent T2D relapse.

"Dysfunctions" induced by Roux-en-Y gastric bypass surgery are concomitant with metabolic improvement independent of weight loss

Metabolic surgery has been increasingly recommended for obese diabetic patients, but questions remain as to its molecular mechanism that leads to improved metabolic parameters independently of weight loss from a network viewpoint. We evaluated the role of the Roux limb (RL) in Roux-en-Y gastric bypass (RYGB) surgery in nonobese diabetic rat models. Improvements in metabolic parameters were greater in the long-RL RYGB group. Transcriptome profiles reveal that amelioration of diabetes state following RYGB differs remarkably from both normal and diabetic states. According to functional analysis, RYGB surgery significantly affected a major gene group, i.e., the newly changed group, which represented diabetes-irrelevant genes abnormally expressed after RYGB. We hypothesize that novel "dysfunctions" carried by this newly changed gene group induced by RYGB rebalance diabetic states and contribute to amelioration of metabolic parameters. An unusual increase in cholesterol (CHOL) biosynthesis in RL enriched by the newly changed group was concomitant with ameliorated metabolic parameters, as demonstrated by measurements of physiological parameters and biodistribution analysis using [14C]-labeled glucose. Our findings demonstrate RYGB-induced "dysfunctions" in the newly changed group as a compensatory role contributes to amelioration of diabetes. Rather than attempting to normalize "abnormal" molecules, we suggest a new disease treatment strategy of turning "normal" molecules "abnormal" in order to achieve a new "normal" physiological balance. It further implies a novel strategy for drug discovery, i.e. targeting also on "normal" molecules, which are traditionally ignored in pharmaceutical development.

Pancreatic islet regeneration through PDX-1/Notch-1/Ngn3 signaling after gastric bypass surgery in db/db mice

In view of the compelling anti-diabetic effects of gastric bypass surgery (GBS) in the treatment of morbid obesity, it is important to clarify its enhancing effect on pancreatic islets, which is closely linked with diabetes remission in obese patients, as well as the underlying mechanisms. The present study evaluated the effects of GBS on glycemic control and other pancreatic changes in db/db mice. The db/db mice were divided into Control, Sham and GBS group. A significant improvement in fasting plasma glucose levels and glucose intolerance were observed post-surgery. At 4 weeks after surgery, further noteworthy changes were observed in the GBS group, including improved islet structure (revealed by immunohistochemical analysis), enhanced insulin secretion, pancreatic hyperplasia and a marked increase in the ratio of β-cells to non-β endocrine cells. Furthermore, notable changes in the levels of Notch-1, pancreatic and duodenal homeobox 1 (PDX-1) and neurogenin 3 (Ngn3) were observed in the GBS group, indicating a potential role of Notch signaling in pancreatic islet regeneration after surgery. In addition, results obtained in PDX-1 knockout (KO), Notch-1 KO and Ngn3 KO mouse models with GBS suggested that elevated PDX-1 resulted in the inhibition of Notch-1, further facilitated Ngn3 and thus promoted pancreatic β-cell regeneration after GBS. The present findings demonstrated that GBS in db/db mice resulted in pancreatic islet regeneration through the PDX-1/Notch-1/Ngn3 signaling pathway, which also reflected the important role of the gastrointestinal system in metabolism control.

Heterogeneity of proliferative markers in pancreatic β-cells of patients with severe hypoglycemia following Roux-en-Y gastric bypass

AIMS

Severe postprandial hypoglycemia with neuroglycopenia is an increasingly recognized, debilitating complication of Roux-en-Y gastric bypass (RYGB) surgery. Increased secretion of insulin and incretin hormones is implicated in its pathogenesis. Histopathologic examination of pancreas has demonstrated increased islet size and/or nuclear diameter in post-RYGB patients who underwent pancreatectomy for severe refractory hypoglycemia with neuroglycopenia (RYGB + NG). We aimed to determine whether β-cell proliferation or apoptosis is altered in RYGB + NG.

METHODS

We performed an observational study to analyze markers of proliferation, apoptosis, cell cycle, and transcription factor expression in pancreatic tissue from affected RYGB + NG patients (n = 12), normoglycemic patients undergoing pancreatic surgery for benign lesions (controls, n = 6), and individuals with hypoglycemia due to insulinoma (n = 52).

RESULTS

Proliferative cell nuclear antigen (PCNA) expression was increased in insulin-positive cells in RYGB + NG patients (4.5-fold increase, p < 0.001 vs. controls) and correlated with β-cell mass. Ki-67 immunoreactivity was low in both RYGB + NG and controls, but did not differ between groups. Phospho-histone H3 levels did not differ between RYGB + NG and controls. PCNA and Ki-67 were both significantly lower in both controls and RYGB + NG than insulinomas. Markers of apoptosis and cell cycle (M30, p27, and p21) did not differ between groups. PDX1 and menin exhibited similar expression patterns, while FOXO1 appeared to be more cytosolic in RYGB + NG.

CONCLUSIONS

Markers of proliferation are heterogeneous in patients with severe post-RYGB hypoglycemia. Increased β-cell proliferation in some individuals may contribute to increased β-cell mass observed in severely affected patients.

Risk Factors for Spontaneously Self-Reported Postprandial Hypoglycemia After Bariatric Surgery

CONTEXT

Postprandial hypoglycemia (PPHG) is a recognized complication of Roux-en-Y gastric bypass (RYGB) surgery. Data on PPHG after laparoscopic sleeve gastrectomy (LSG) are scant.

OBJECTIVE

The objective of the study was to identify preoperative predictors of PPHG in subjects spontaneously self-reporting PPHG after RYGB or LSG. Patients, Setting, and Intervention: Nondiabetic patients spontaneously self-reporting symptoms/signs of PPHG (PPHG group, 21 RYGB and 11 LSG) were compared in a case-control design with subjects who never experienced spontaneous or oral glucose tolerance test (OGTT)-induced hypoglycemia over 24 months after surgery (No-PPHG group, 13 RYGB and 40 LSG). Paired pre- and postoperative 3-hour OGTTs were analyzed in all participants.

MAIN OUTCOME MEASURES

Insulin sensitivity was assessed by the oral glucose insulin sensitivity index and β-cell function by mathematical modeling of the C-peptide response to glucose.

RESULTS

Before surgery, the body mass index was lower in PPHG than No-PPHG patients in the RYGB (P = .002) and trended similarly in the LSG group (P = .08). Fasting glycemia and the glucose-OGTT nadir were lower in the PPHG than the No-PPHG subjects in both surgery groups. Before surgery, insulin sensitivity was higher in PPHG than No-PPHG in the RYGB (393 ± 55 vs 325 ± 44 mL/min^-1 · m^-2, P = .001) and LSG groups (380 ± 48 vs 339 ± 60 mL/min^-1 · m^-2, P = .05) and improved to a similar extent in all groups after surgery. Before surgery, β-cell glucose sensitivity was higher in PPHG than No-PPHG in both RYGB (118 ± 67 vs 65 ± 24 pmol/min^-1 · m² · mM^-1) and LSG patients (114 ± 32 vs 86 ± 33) (both P = .02) and improved in all subjects after surgery.

CONCLUSIONS

In subjects self-reporting PPHG after surgery, lower presurgery plasma glucose concentrations, higher insulin sensitivity, and better β-cell glucose sensitivity are significant predictors of PPHG after both RYGB and LSG.

Effects of gastric bypass on FoxO1 expression in the liver and pancreas of diabetic rats

AIM

To explore the mechanism by which gastric bypass surgery (GBS) ameliorates type 2 diabetes mellitus (T2DM) by investigating whether FoxO1 (a transcription factor that plays a crucial role in the regulation of glycolipid metabolism) expression is altered in the liver and pancreatic islet cells in a rat model of GBS-treated T2DM.

METHODS

Sprague-Dawley rats were randomly divided into four groups (n = 10 rats each): diabetic rats treated by GBS (DM + GBS), diabetic rats subjected to sham operation (DM + sham), normal control rats (control), and diabetic rats without surgery (DM). Fasting levels of blood glucose (BG), insulin, and glucagon-like peptide-1 (GLP-1) were measured in all groups before and 4, 8, 16, and 24 weeks after operation. Rats were killed 24 weeks after surgery. Liver and pancreas expressions of FoxO1 were investigated by immunohistochemistry and Western blotting analyses.

RESULTS

In the DM + GBS group, fasting BG before and 24 weeks after surgery decreased from 20.2 ± 2.1 to 7.7 ± 1.1 mmol/L, respectively; fasting insulin showed no change (2.9 ± 0.1 and 3.0 ± 0.1 mU/L, respectively); and fasting GLP-1 increased from 8.7 ± 0.9 to 23.5 ± 0.2 pmol/L, respectively. Fasting BG levels after surgery in the DM + GBS group were significantly lower than those in the DM + sham and DM groups. FoxO1 expression levels in the liver and pancreatic islets of the DM + GBS group were reduced compared to those in the DM + sham and DM groups. FoxO1 in the pancreatic β-cells was expressed mainly in the cytoplasm.

CONCLUSIONS

Gastric bypass may improve type 2 diabetes mellitus by changing FoxO1 expression in the liver and pancreatic islet cells.

The Improvement of Hyperglycemia after RYGB Surgery in Diabetic Rats Is Related to Elevated Hypothalamus GLP-1 Receptor Expression

Objectives. This study aimed to explore the expression of GLP-1 receptor in hypothalamus and gastrointestinal tissues after Roux-en-Y gastric bypass (RYGB) surgery in diabetic rats. Methods. Male 12-week-old Wistar rats (control) and Goto-Kakizaki rats (diabetic) were randomly divided into two groups, respectively: control sham surgery group (C), control RYGB group (C + R), diabetic sham surgery group (D), and diabetic RYGB group (D + R). Body weight and blood glucose were monitored before and after surgery every week. Eight weeks after surgery, all rats were sacrificed and the serum fasting GLP-1 concentrations were measured by ELISA. GLP-1R and DPP-4 expression in hypothalamus and ileum were measured by RT-PCR. Results. The body weight and fasting/random blood glucose in the D + R group decreased significantly compared with the D group (P < 0.05). Serum GLP-1 levels in diabetic rats treated with RYGB were higher than the corresponding sham surgery rats. The expression of GLP-1R of hypothalamus in RYGB-treated diabetic rats was significantly higher than those of the sham surgery diabetic rats and both control group rats (P < 0.05). We found a negative correlation between hypothalamus GLP-1R mRNA and blood glucose level. No significant difference was seen in ileum GLP-1R and DPP-4 expression among all groups. Conclusions. RYGB efficiently promoted serum GLP-1 levels and the expression of GLP-1 receptor in the hypothalamus in diabetic rats. These data suggest that the hypothalamus GLP-1R may play an important role in the GLP-1 system for improving glucose homeostasis after reconstruction of the gastrointestinal tract.

Modified billiopancreatic diversion surgery improves glucose levels in Goto-Kakizaki rats

AIM: To compare the effect of modified billiopancreatic diversion (MBPD) surgery versus duodenal-jejunal bypass (DJB) surgery in improving glucose levels in Goto-Kakizaki (GK) rats, and to explore the possible mechanisms.

METHODS: Thirty male GK rats were randomized into three groups to undergo sham operation, MBPD surgery and DJB surgery, respectively. Body mass, fasting plasma glucose and random plasma glucose were determined 1 week before and 1, 4, 8 wk after operation. Insulin, oral glucose tolerance test (OGTT), cholesterol, triglyceride and free fatty acid were determined 1 wk before and 4 wk after operation.

RESULTS: One week after the surgery, body mass of MBPD- and DJB-treated rats significantly decreased (304.990 g ± 12.156 g vs 320.568 g ± 10.607 g, P = 0.011; 308.540 g ± 9.637 g vs 320.568 g ± 10.607 g, P = 0.024). MBPD- and DJB-treated rats had better oral glucose tolerance (17.350 mmol/L ± 2.220 mmol/L vs 20.600 mmol/L ± 2.381 mmol/L, P = 0.009; 18.238 mmol/L ± 1.364 mmol/L vs 20.600 mmol/L ± 2.381 mmol/L, P = 0.024) compared with the sham operation group. Random plasma glucose (9.620 mmol/L ± 0.794 mmol/L vs 14.471 mmol/L ± 2.531 mmol/L, P < 0.001; 9.200 mmol/L ± 1.000 mmol/L vs 14.471 mmol/L ± 2.531 mmol/L, P < 0.001), insulin (0.476 ng/mL± 0.068 ng/mL vs 0.724 ng/mL ± 0.192 ng/mL, P < 0.05; 0.542 ng/mL ± 0.055 ng/mL vs 0.724 ng/mL ± 0.192 ng/mL, P < 0.05), cholesterol (2.550 mmol/L ± 0.691 mmol/L vs 3.125 mmol/L ± 0.267 mmol/L, P < 0.05; 2.450 mmol/L ± 0.424 mmol/L vs 3.125 mmol/L ± 0.267 mmol/L, P < 0.05) and free fatty acid (697.667 μEq/L ± 103.77 μEq/L vs 994.667 μEq/L ± 257.817 μEq/L, P < 0.05; 670.333 μEq/L ± 129.421 μEq/L vs 994.667 μEq/L ± 257.817 μEq/L, P < 0.05) of NBPD- and DJB-treated rats were lower than those in the sham operation group after operation, but triglycerides (1.329 mmol/L ± 0.716 mmol/L vs 0.754 mmol/L ± 0.236 mmol/L, P < 0.05; 1.569 mmol/L ± 0.612 mmol/L vs 0.754 mmol/L ± 0.236 mmol/L, P < 0.05) of NBPD- and DJB-treated rats were significantly higher.

CONCLUSION: Modified billiopancreatic diversion surgery is superior to bowel bypass in improving glucose levels in Goto-Kakizaki rats.

The emerging role of the intestine in metabolic diseases

The intestine is an important metabolic organ that has gained attention in recent years for the newly identified role that it plays in the pathophysiology of various metabolic diseases including obesity, insulin resistance and diabetes. Recent insights regarding the role of enteroendocrine hormones, such as GIP, GLP-1, and PYY in metabolic diseases, as well as the emerging role of the gut microbial community and gastric bypass bariatric surgeries in modulating metabolic function and dysfunction have sparked a wave of interest in understanding the mechanisms involved, in an effort to identify new therapeutics and novel regulators of metabolism. This review summarizes the current evidence that the gastrointestinal tract has a key role in the development of obesity, inflammation, insulin resistance and diabetes and discusses the possible players that can be targeted for therapeutic intervention.

Lessons learned from gastric bypass operations in rats

Numerous studies using gastric bypass rat models have been recently conducted to uncover underlying physiological mechanisms of Roux-en-Y gastric bypass. Reflecting on lessons learned from gastric bypass rat models may thus aid the development of gastric bypass models in mice and other species. This review aims to discuss technical and experimental details of published gastric bypass rat models to understand advantages and limitations of this experimental tool. The review is based on PubMed literature using the search terms 'animal model', 'rodent model', 'bariatric surgery', 'gastric bypass', and 'Roux-en-Y gastric bypass'. All studies published up until February 2011 were included. 32 studies describing 15 different rat gastric bypass models were included. Description of surgical technique differs in terms of pouch size, limb lengths, preservation of the vagal nerve, and mortality rate. Surgery was carried out exclusively in male rats of different strains and ages. Pre- and postoperative diets also varied significantly. Technical and experimental variations in published gastric bypass rat models complicate comparison and identification of potential physiological mechanisms involved in gastric bypass. In summary, there is no clear evidence that any of these models is superior, but there is an emerging need for standardization of the procedure to achieve consistent and comparable data.