The Significance of Bile in the Biliopancreatic Limb on Metabolic Improvement After Duodenal-Jejunal Bypass.

INTRODUCTION: Duodenal-jejunal bypass (DJB) is an experimental procedure in metabolic surgery that does not have a restrictive component. Changes in bile acid (BA) dynamics and intestinal microbiota are possibly related to metabolic improvement after DJB. Our previous studies involving obese diabetic rats showed the crucial role of the biliopancreatic limb (BPL) in metabolic improvement after DJB caused by BA reabsorption. We established a new DJB procedure to prevent bile from flowing into the BPL and aimed to elucidate the importance of bile in the BPL after DJB. METHODS: Otsuka Long-Evans Tokushima Fatty rats with diabetes were divided into three groups: two DJB groups and a sham group (n = 11). Duodenal-jejunal anastomosis was performed proximal to the papilla of Vater in the DJB group (n = 11). However, the DJB-D group (n = 11) underwent a new procedure with duodenal-jejunal anastomosis distal to the papilla of Vater for preventing bile flow into the BPL. RESULTS: Glucose metabolism improved and weight gain was suppressed in the DJB group, but not in the DJB-D and sham groups. Serum BA level and conjugated BA concentration were elevated in the DJB group. The gut microbiota was altered only in the DJB group; the abundance of Firmicutes and Bacteroidetes decreased and that of Actinobacteria increased. However, the DJB-D group exhibited no apparent change in the gut microbiota, similar to the sham group. CONCLUSION: BAs are essential in the BPL for metabolic improvement after DJB; they can improve the gut microbiota in these processes.

Impact of Prevascularization on Immunological Environment and Early Engraftment in Subcutaneous Islet Transplantation.

BACKGROUND: The utilization of islet-like cells derived from pluripotent stem cells may resolve the scarcity of islet transplantation donors. The subcutaneous space is a promising transplantation site because of its capacity for graft observation and removal, thereby ensuring safety. To guarantee subcutaneous islet transplantation, physicians should ensure ample blood supply. Numerous methodologies, including prevascularization, have been investigated to augment blood flow, but the optimal approach remains undetermined. METHODS: From C57BL/6 mice, 500 syngeneic islets were transplanted into the prevascularized subcutaneous site of recipient mice by implanting agarose rods with basic fibroblast growth factor at 1 and 2 wk. Before transplantation, the blood glucose levels, cell infiltration, and cytokine levels at the transplant site were evaluated. Furthermore, we examined the impact of the extracellular matrix capsule on graft function and the inflammatory response. RESULTS: Compared with the 1-wk group, the 2-wk group exhibited improved glycemic control, indicating that longer prevascularization enhanced transplant success. Flow cytometry analysis detected immune cells, such as neutrophils and macrophages, in the extracellular matrix capsules, whereas cytometric bead array analysis indicated the release of inflammatory and proinflammatory cytokines. Treatment with antitumor necrosis factor and anti-interleukin-6R antibodies in the 1-wk group improved graft survival, similar to the 2-wk group. CONCLUSIONS: In early prevascularization before subcutaneous transplantation, neutrophil and macrophage accumulation prevented early engraftment owing to inflammatory cytokine production.

Impact of Bariatric Surgery on Subtilisin/Kexin Type 9 (PCSK9) Gene Expression and Inflammation in the Adipose Tissue of Obese Diabetic Rats.

Bariatric surgery improves dyslipidaemia and reduces body weight, but it remains unclear how bariatric surgery modulates gene expression in fat cells to influence the proprotein convertase subtilisin/kexin type 9 (PCSK-9) and low-density lipoprotein receptor (LDLR) gene expression. The expression of the PCSK9/LDLR/tumor necrosis factor-alpha (TNFα) gene in adipose tissue was measured in two groups of Zucker Diabetic Sprague Dawley (ZDSD) rats after Roux-en-Y gastric bypass (RYGB) surgery or 'SHAM' operation. There was lower PCSK9 (p = 0.02) and higher LDLR gene expression (p = 0.02) in adipose tissue in rats after RYGB. Weight change did not correlate with PCSK9 gene expression (r = -0.5, p = 0.08) or TNFα gene expression (r = -0.4, p = 0.1). TNFα gene expression was positively correlated with PCSK9 gene expression (r = 0.7, p = 0.001) but not correlated with LDLR expression (r = -0.3, p = 0.3). Circulating triglyceride levels were lower in RYGB compared to the SHAM group (1.1 (0.8-1.4) vs. 1.5 (1.0-4.2), p = 0.038) mmol/L with no difference in cholesterol levels. LDLR gene expression was increased post-bariatric surgery with the potential to reduce the number of circulating LDL particles. PCSK9 gene expression and TNFα gene expression were positively correlated after RYGB in ZDSD rats, suggesting that the modulation of pro-inflammatory pathways in adipose tissue after RYGB may partly relate to PCSK9 and LDLR gene expression.

Enhanced glucose homeostasis via Clostridium symbiosum-mediated glucagon-like peptide 1 inhibition of hepatic gluconeogenesis in mid-intestinal bypass surgery.

BACKGROUND: The small intestine is known to play a crucial role in the development and remission of diabetes mellitus (DM). However, the exact mechanism by which mid-small intestinal bypass improves glucose metabolism in diabetic rats is not fully understood. AIM: To elucidate the mechanisms by which mid-small intestinal bypass improves glucose metabolism. METHODS: Streptozotocin (STZ) was used to induce DM in Sprague-Dawley (SD) rats at a dose of 60 mg/kg. The rats were then randomly divided into two groups: The mid-small intestine bypass (MSIB) group and the sham group (underwent switch laparotomy). Following a 6-wk recovery period post-surgery, the rats underwent various assessments, including metabolic parameter testing, analysis of liver glycogen levels, measurement of key gluconeogenic enzyme activity, characterization of the gut microbiota composition, evaluation of hormone levels, determination of bile acid concentrations, and assessment of the expression of the intestinal receptors Takeda G protein-coupled receptor 5 and farnesoid X receptor. RESULTS: The MSIB group of rats demonstrated improved glucose metabolism and lipid metabolism, along with increased hepatic glycogen content. Furthermore, there was a decrease in the expression of the key gluconeogenic enzymes phosphoenolpyruvate carboxykinase 1 and glucose-6-phosphatase. Importantly, the MSIB group exhibited a substantial increase in the abundances of intestinal Lactobacillus, Clostridium symbiosum, Ruminococcus gnavus, and Bilophila. Moreover, higher levels of secondary bile acids, such as intestinal lithocholic acid, were observed in this group. Remarkably, the changes in the gut microbiota showed a significant correlation with the expression of key gluconeogenic enzymes and glucagon-like peptide 1 (GLP-1) at 6 wk postoperatively, highlighting their potential role in glucose regulation. These findings highlight the beneficial effects of mid-small intestine bypass on glucose metabolism and the associated modulation of the gut microbiota. CONCLUSION: The findings of this study demonstrate that the introduction of postoperative intestinal Clostridium symbiosum in the mid-small intestine contributes to the enhancement of glucose metabolism in nonobese diabetic rats. This improvement is attributed to the increased inhibition of hepatic gluconeogenesis mediated by GLP-1, resulting in a favorable modulation of glucose homeostasis.

Regulation of Pancreatic TXNIP-Insulin Expression Levels after Bariatric Surgery Using Diabetic Rodent Model.

Purpose: The purpose of this study was to investigate the effect of bariatric surgery on pancreatic thioredoxin-interacting protein (TXNIP) and insulin expression levels. The research question is does bariatric surgery induce changes in the pancreatic TXNIP level, given that TXNIP has been proposed as a key glucose control factor? Methods: Using nondiabetic and diabetic rats, we investigated whether our streptozotocin-induced diabetic rat models exhibited changes in pancreatic TXNIP regulation. Following this confirmation, we randomly divided the diabetic rats into the following three groups: the gastric bypass group (n = 16), pair-fed group (n = 10), and sham group (n = 10). Preoperatively and 3 weeks postoperatively, all the rats underwent an oral glucose tolerance test, insulin tolerance test, and blood sampling procedures for hormonal analysis. Results: The TXNIP messenger ribonucleic acid (mRNA) and protein expression levels were significantly lower in the gastric bypass group than in the other groups. Regarding the gastric bypass group, the pancreatic mRNA expression levels of microRNA-204 (miR-204) and MafA were significantly lower and higher, respectively, than in the other groups. Furthermore, the levels of pancreatic insulin expression at the mRNA and protein levels were also significantly higher in the gastric bypass group than in the other groups. Conclusion: Bariatric surgery significantly improved glucose control and regulated the pancreatic insulin production pathways of TXNIP, miR-204, and MafA. The regulation of TXNIP, miR-204, and MafA might play an important role in the mechanism of diabetes remission following bariatric surgery.

Duodenal-jejunal bypass increases intraduodenal bile acids and upregulates duodenal SIRT1 expression in high-fat diet and streptozotocin-induced diabetic rats.

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 (ipPTT) 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 ipPTT 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 mRNA 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 mRNA 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.

Pancreas Preservation in Modified Histidine-lactobionate Solution Is Superior to That in University of Wisconsin Solution for Porcine Islet Isolation.

BACKGROUND: We previously reported that modified extracellular-type trehalose-containing Kyoto (MK) solution, which contains a trypsin inhibitor (ulinastatin), significantly improved the islet yield compared with University of Wisconsin (UW) preservation, which is the gold standard for organ preservation for islet isolation. In this study, we evaluated the efficiency of a modified histidine-lactobionate (MHL) solution in addition to UW or MK solution. The MHL solution has a high sodium-low potassium composition with low viscosity compared with the UW solution. Moreover, similar to MK solution, MHL solution also contains ulinastatin. METHODS: Porcine pancreata were preserved in UW, MK, or MHL solution, followed by islet isolation. An optimized number (1500 IE) of isolated islets from each group were then transplanted into streptozotocin-induced diabetic mice. RESULTS: The islet yield before and after purification was significantly higher in the MHL group than in the UW group. On the contrary, the islet yield before and after purification was not significantly different between the MHL and MK groups. Preserving the porcine pancreata in MHL solution improved the outcome of islet transplantation in streptozotocin-induced diabetic mice compared with that in UW solution. CONCLUSIONS: Pancreas preservation with MHL solution preserves islet function better than UW solution. The effect of MHL solution is similar to that of MK solution, suggesting that MHL solution can be used as an alternative to MK solution for pancreatic islet transplantation.

The Effect of Adipose Derived Stromal Vascular Fraction on Flap Viability in Experimental Diabetes Mellitus and Chronic Renal Disease.

BACKGROUND: The presence of chronic renal disease(CRD) concurrently with diabetes mellitus(DM) increases the flap failure. Adipose derived stromal vascular fraction (SVF) is known to enhance skin flap viability in both healthy and diabetic individuals. The aim of this experimental study was to investigate the effect of SVF on skin flap viability in rats with DM and CRD. METHODS: 48 Sprague-Dawley rats were separated into four groups as follows: group I (control), group II (diabetes mellitus), group III (chronic renal disease), and group IV (diabetes with chronic renal disease).Two dorsal flaps were elevated. Flaps on left side of all groups received 0.5 cc of SVF, while same amount of plasma-buffered saline (PBS) was injected into right side. On postoperative day 7, flaps were harvested for macroscopic, histopathologic and biochemical assessments. Areas of flap survival were measured macroscopically. Blood level of vascular endothelial growth factor (VEGF) was measured after injection of SVF. RESULTS: Macroscopically, SVF has significantly improved flap viability (p < 0.05). Flap viability percentage was lower in DM and CRD groups when compared with healthy control group. In respect of new capillary formation, there was a statistically significant difference between SVF injected flaps and PBS injected sides (p < 0.05). Similarly, VEGF levels were higher in all study groups and there was a significant difference in comparison to control group (p < 0.05). CONCLUSIONS: The study showed that injection of SVF increased flap viability via endothelial differentiation and neovascularization. In vivo function of stem cells might be impaired due to uremia and diabetes-related microenviromental changes.

Explore the Link between the Improvement of Metabolic Indicators in Diabetic Rats with Sleeve Gastrectomy and Changes in the Composition of Intestinal Flora.

Diabetes mellitus (DM) has become a major medical and health problem in my country and even the world. Doctors and patients have gradually realized that a new type of metabolic surgery is a way to treat diabetes. The operation is relatively simple, and the effect of the operation is no less than that of the gastric shunt. The initial hypothesis could not fully explain the blood pressure and blood sugar reduction mechanism in waist and abdominal surgery. According to requirements, they were divided into the sleeve gastrectomy group (SG group, n = 10) and sham operation group (SS group, n = 10), and corresponding measures were taken. Observe their weight changes; perform an oral glucose tolerance test (GB) before surgery and at 2, 8, and 16 weeks after surgery to evaluate the effect of surgery on improving the glucose metabolism. The postoperative GLP-1 specificity curve was detected in the two groups of patients; the immunohistochemical method was used to detect the postoperative changes of the digestive tract l cells in the two groups; RT-PCR was used to detect the mRNA transcription level of the digestive tract GLP-1 receptor. The bodyweight was significantly different 4 weeks after the operation. Food intake and bodyweight were not significantly different between the SG and SS groups. FBG: one week after operation, the SG group was significantly smaller than the SS group. The SS group was significantly lower than the SG group at 12 weeks after operation, and the SS group was significantly lower than the SG group at 14 weeks after operation. The transcription levels of c-kit mRNA and SCF mRNA in jejunum and ileum tissues are significantly different: the transcription levels of c-kit mRNA and SCF mRNA in the SG group are higher than those in the SS group, jejunum and ileum in the SG group. The number of cell 1 was significantly greater than that of the SS group. Sleeve gastrectomy can improve the regulation of the glucose metabolism in diabetic rats. The increase in small bowel motility may be related to the increase in ICC cells, intestinal cells, and GLP after gastric sleeve resection. The increase is in -1R and faster insoluble CHM in bowel motility. It has better contact with cell 1 and GLP-1R and stimulates cell 1 to secrete GLP-1.

Bypassing Different Parts of the Small Intestine Determines Different Metabolic Effects in Streptozotocin-Induced Diabetic Rats.

PURPOSE: Side-to-side jejunoileal bypass with proximal loop ligation (SSJIBL) has significant glucose-lowering and weight-control effects; however, no study has elucidated which segment is most effective in SSJIBL. This study investigated the effect of proximal small intestinal bypass (PSIB), middle small intestinal bypass (MSIB), and distal small intestinal bypass (DSIB) on metabolic improvement in streptozotocin (STZ)-induced diabetic rats. MATERIALS AND METHODS: STZ-induced diabetic rats were divided into four groups: PSIB, MSIB, DSIB, and sham-operated. The primary outcome measures were body weight, food intake, fasting blood glucose (FBG) levels, oral glucose tolerance (OGTT), insulin tolerance (ITT), serum insulin, gut hormones, serum lipid profile, and liver function levels. RESULTS: Global body weight in the DSIB group was lower than that in the PSIB group. The global food intake in the PSIB group was lower than that in the MSIB group. The PSIB group had a slightly better glucose-lowering effect than the MSIB and DSIB groups. The PSIB, MSIB, and DSIB groups all had improvement in insulin sensitivity at postoperative week 6. The MSIB group exhibited the best improvement in lipid homeostasis. Serum insulin and leptin levels were higher, and serum ghrelin levels were lower in the operated groups than in the sham group. CONCLUSIONS: This study provides experimental evidence that PSIB surgery induces a better glucose-lowering effect than DSIB surgery, and MSIB induced the best improvement in lipid homeostasis, whereas DSIB was even more advantageous in terms of weight control in the STZ-induced diabetic rat model.

Hypoxia preconditioning increases the ability of healthy but not diabetic rat-derived adipose stromal/stem cells (ASC) to improve histological lesions of streptozotocin-induced diabetic nephropathy.

BACKGROUND: Mesenchymal stromal cells (MSC) have demonstrated ability to improve diabetic nephropathy (DN) in experimental models, as well as by improving kidney endogenous progenitor cells proliferation and differentiation. Many studies have demonstrated the effect of hypoxia on MSC improving their functionality but the potential enhancement of the nephroprotective properties of MSC cultured under low oxygen concentration has been explored in few studies, none of them in the context of DN. On the other hand, diabetes is associated with abnormalities in MSCs functionality. These findings related to the hypoxia preconditioning ability to enhance adipose-tissue derived-MSC (ASC) performance have led us to wonder if hypoxia could increase the known beneficial effect of normal ASC in DN and if it could correct the expected inability of diabetic rat-derived ASC to exert this effect in vivo. To answer these questions, in the present study we have used ASC from healthy and diabetic-induced rats, cultured under standard conditions or hypoxia preconditioned, in a DN rat model induced by streptozotocin (STZ). METHODS: Diabetes was induced in Wistar-rats by 60 mg/kg streptozotocin (STZ) intraperitoneal injection. Fifteen days thereafter, five diabetic-induced rats and five healthy, previously injected with saline, were sacrificed and used as ASC donors . Both healthy and diabetic rat-derived ASC (cASC and dASC, respectively) were cultured under standard conditions (21%O2)(N) or were subjected to a 48 h conditioning period in hypoxia (3%O2)(H). Thus, four types of cells were generated depending on their origin (healthy or diabetic-induced rats) and the culture conditions(N or H):cASC-N, cASC-H, dASC-N and dASC-H. DN experimental study were carried out fifteen days after STZ induction of diabetes in fifty-two healthy rats. DN-induced-animals were randomly assigned to be injected with 200 µL saline as placebo or with 3 × 106 cASC-N, cASC-H, dASC-N or dASC-H, according to the study group. Serum glucose, urea and creatinine, and urine albumin levels were measured at 2-weeks intervals until day+ 45 after ND-induction.Animals were sacrificed and kidneys extracted for histopathological and transmission electron microcopy analysis RESULTS: None of the four study groups that received cell treatment showed significant changes in serum glucose, urea and creatinine levels, urine albumin concentration and body weight compared to placebo ND-induced group. Interestingly, only the group that received cASC-H showed a reduction in glucose and creatinine levels although it did not reach statistical significance.All DN-induced groups treated with ASC reduced significantly renal lesions such as mesangial expansion, mesangiolysis, microaneurysms and acute tubular necrosis compared to ND-induced placebo group (p ≤ 0.05). Renal injuries such as clear tubular cell changes, thickening of tubular basement membrane, tubular cysts and interstitial fibrosis significantly showed reduction in ND-induced rats treated with cASC-H regarding to their received cASCN (p ≤ 0.05). Non statistical differences were observed in the improvement capacity of cASC and dASC culture under standard condition.However, hypoxia preconditioning reduces the presence of tubular cysts (p ≤ 0.01). CONCLUSIONS: Hypoxia preconditioning enhances the ability of healthy rat-derived ASC to improve kidney injury in a rat model of DN. Moreover, diabetic-derived ASC exhibits a similar ability to healthy ASC which is clearly more than expected, but it is not significantly modified by hypoxia preconditioning.

Role of Proximal Intestinal Glucose Sensing and Metabolism in the Blood Glucose Control in Type 2 Diabetic Rats After Duodenal Jejunal Bypass Surgery.

BACKGROUND: Although gastric surgery can significantly improve blood glucose homeostasis in type 2 diabetes mellitus (T2DM), its mechanism remains unclear. This study evaluated the role of intestinal glucose sensing, glucose transport, and metabolism in the alimentary limb (A limb) of T2DM rats after duodenal jejunal bypass (DJB) surgery. METHODS: A T2DM rat model was induced via a high-glucose high-fat diet and low-dose streptozotocin injection. The diabetic rats were divided into two groups: the DJB surgery (T2DM-DJB) group and the sham surgery (T2DM-Sham) group. Wistar rats were used as wild-type control (Control). Small animal PET was used to assess the change in glucose metabolic status in the intestine. The intestinal villi height and the number of EECs after DJB were evaluated. The expressions of sweet taste receptors (T1R2/T1R3), glucose transporters (SGLT1/GLUT2), and key enzymes involved in glucose metabolism (HK2, PFK2, PKM2, G6Pase, and PCK1) in the A limb after DJB was detected by Western blot and qRT-PCR. RESULTS: Small animal PET analysis showed the intestinal glucose metabolism increased significantly 6 weeks after DJB surgery. The intestinal villi height and the number of EECs in the A limb 6 weeks after surgery increased significantly in T2DM-DJB rats comparing to T2DM-Sham rats. The mRNA and protein expression of T1R1/T1R3 and SGLT1/GLUT2 were downregulated in DJB-T2DM rats, while enzymes involved in glucose metabolism was upregulated in the A limb in T2DM-DJB rats. CONCLUSION: Proximal intestinal glucose sensing and metabolism play an important role in blood glucose homeostasis by DJB.

Three-dimensional Vascularized ß-cell Spheroid Tissue Derived From Human Induced Pluripotent Stem Cells for Subcutaneous Islet Transplantation in a Mouse Model of Type 1 Diabetes.

BACKGROUND: Islet transplantation is an effective replacement therapy for type 1 diabetes (T1D) patients. However, shortage of donor organ for allograft is obstacle for further development of the treatment. Subcutaneous transplantation with stem cell-derived ß-cells might overcome this, but poor vascularity in the site is burden for success in the transplantation. We investigated the effect of subcutaneous transplantation of vascularized ß-cell spheroid tissue constructed 3-dimensionally using a layer-by-layer (LbL) cell-coating technique in a T1D model mouse. METHODS: We used MIN6 cells to determine optimal conditions for the coculture of ß-cell spheroids, normal human dermal fibroblasts, and human umbilical vein endothelial cells, and then, under those conditions, we constructed vascularized spheroid tissue using human induced pluripotent stem cell-derived ß-cells (hiPS ß cells). The function of insulin secretion of the vascularized hiPS ß-cell spheroid tissue was evaluated in vitro. Furthermore, the function was investigated in T1D model NOD/SCID mice subcutaneously transplanted with the tissue. RESULTS: In vitro, the vascularized hiPS ß-cell spheroid tissue exhibited enhanced insulin secretion. The vascularized hiPS ß-cell spheroid tissue also significantly decreased blood glucose levels in diabetic immunodeficient mice when transplanted subcutaneously. Furthermore, host mouse vessels were observed in the explanted vascularized hiPS ß-cell spheroid tissue. CONCLUSIONS: Vascularized hiPS ß-cell spheroid tissue decreased blood glucose levels in the diabetic mice. This therapeutic effect was suggested due to host angiogenesis in the graft. This method could lead to a promising regenerative treatment for T1D patients.

Exosomes Secreted by Umbilical Cord Blood-Derived Mesenchymal Stem Cell Attenuate Diabetes in Mice.

Mesenchymal stem cell (MSC) therapy is an innovative approach in diabetes due to its capacity to modulate tissue microenvironment and regeneration of glucose-responsive insulin-producing cells. In this study, we investigated the role of MSC-derived exosomes in pancreatic regeneration and insulin secretion in mice with streptozotocin-induced diabetes. Mesenchymal stem cells (MSCs) were isolated and characterized from umbilical cord blood (UCB). Exosomes were isolated and characterized from these MSCs. Diabetes was induced in male C57Bl/6 mice by streptozotocin (STZ; 40 mg/kg body weight, i.p.) for five consecutive days. The diabetic mice were administered (i.v.) with MSC (1 × 105 umbilical cord blood MSC cells/mice/day), their derived exosomes (the MSC-Exo group that received exosomes derived from 1 × 105 MSC cells/mice/day), or the same volume of PBS. Before administration, the potency of MSCs and their exosomes was evaluated in vitro by T cell activation experiments. After day 7 of the treatments, blood samples and pancreatic tissues were collected. Histochemistry was performed to check cellular architecture and ß cell regeneration. In body weight, blood glucose level, and insulin level, cell proliferation assay was done to confirm regeneration of cells after MSC and MSC-Exo treatments. Hyperglycemia was also attenuated in these mice with a concomitant increase in insulin production and an improved histological structure compared to mice in the PBS-treated group. We found increased expression of genes associated with tissue regeneration pathways, including Reg2, Reg3, and Amy2b in the pancreatic tissue of mice treated with MSC or MSC-Exo relative to PBS-treated mice. MicroRNA profiling of MSC-derived exosomes showed the presence of miRs that may facilitate pancreatic regeneration by regulating the Extl3-Reg-cyclinD1 pathway. These results demonstrate a potential therapeutic role of umbilical cord blood MSC-derived exosomes in attenuating insulin deficiency by activating pancreatic islets' regenerative abilities.

The effect of sleeve ablation of gastric mucosa on body weight and glucose homeostasis in Sprague-Dawley rat model.

BACKGROUND: The gastric mucosa is an important endocrine organ, most of which is resected in sleeve gastrectomy (SG). The effect of removing most of the gastric mucosa has not been studied. OBJECTIVE: To assess the effect of ablating the gastric mucosa (an area proportional to that in SG), on obesity and diabetes in a rat model. SETTING: The Affiliated Hospital of Xuzhou Medical University in Xuzhou Jiangsu, P. R. China. METHODS: Among 34 fatty Sprague-Dawley rats, 26 randomly received low-dose streptozotocin (STZ) to induce diabetes and then were randomly assigned to gastric mucosa ablation (GMA, n = 10), sleeve gastrectomy (SG, n = 8), and sham (n = 8) groups. The remaining normal fatty rats were assigned to the non-diabetic gastric mucosa ablation (nGMA, n = 8) group. In the GMA groups, the gastric mucosa was thermally ablated using electrocautery. Rats were followed for 8 weeks postoperatively. Preoperative oral glucose tolerance test (OGTT), insulin tolerance test (ITT), and mixed meal tolerance test (MMTT) were repeated at designated time points postoperatively. Changes in body weight, food intake, and fasting blood glucose were also recorded. RESULTS: Fasting ghrelin concentration and area under curve (AUC) decreased significantly (P < .05) in the GMA groups and the SG group after surgery. Gastrin concentration remained unchanged in SG but decreased significantly in the GMA groups after surgery. Significantly increased GLP-1 AUC was found in the GMA groups and the SG group postoperatively. The decrease in fasting blood glucose did not differ significantly between the diabetic GMA and SG groups after surgery. Glucose AUC during OGTT in both SG and diabetic GMA groups was decreased significantly from the preoperative level, but the decreased glucose AUC in the SG group was significantly greater (P < .05). The decrease in body weight and food intake in the SG group was significantly greater than in the GMA groups. CONCLUSION: Ablation of most of the gastric mucosa along the greater curvature is effective in weight loss and glycemic control in a rodent model.

Biliopancreatic Limb Length of Small Intestinal Bypass in Non-obese Goto-Kakizaki (GK) Rats Correlates with Gastrointestinal Hormones, Adipokines, and Improvement in Type 2 Diabetes.

BACKGROUND: The purpose of this study was to explore the effects on type 2 diabetes, gastrointestinal hormones, and adipokines after the small intestinal bypass of different biliopancreatic limb (BPL) lengths in non-obese type 2 diabetic rats. METHOD: Small intestinal bypass with the BPL length at 10cm, 20cm, 30cm, and 40cm, respectively, and sham surgery were performed in non-obese GK rats. Fasting serum was collected at 2 days preoperatively and 1, 3, 6, and 9 weeks postoperatively. Body weight and fasting blood glucose (FBG) were measured during the experiment. Glycated hemoglobin (GHb), fasting insulin (FINS), C-peptide, ghrelin, leptin, adiponectin, and somatostatin were measured postoperatively. RESULT: Rats with a bypassed length of 40cm died within 5-9 weeks. No statistically significant was observed in body weight between the sham group and the bypass groups at the 9th week postoperatively. FBG, GHb, FINS, C-peptide, and HOMA-IR in the bypass groups were lower than those in the sham group postoperatively and were negatively correlated with BPL length. Ghrelin and leptin declined compared with preoperative but were not associated with BPL length. Adiponectin of the bypass groups increased after operation and was positively correlated with BPL length. Somatostatin remained stable among groups during the experiment. CONCLUSION: Ghrelin and leptin of non-obese GK rats decreased postoperatively without a linear relationship with the BPL length, while adiponectin increased with positively correlation with the BPL length. In addition, somatostatin remained steady after small intestinal bypass. Further studies are expected to confirm the effect of the BPL length of small intestinal bypass on gastrointestinal hormones and adipokines.

Exosome loaded immunomodulatory biomaterials alleviate local immune response in immunocompetent diabetic mice post islet xenotransplantation.

Foreign body response (FBR) to biomaterials compromises the function of implants and leads to medical complications. Here, we report a hybrid alginate microcapsule (AlgXO) that attenuated the immune response after implantation, through releasing exosomes derived from human Umbilical Cord Mesenchymal Stem Cells (XOs). Upon release, XOs suppress the local immune microenvironment, where xenotransplantation of rat islets encapsulated in AlgXO led to >170 days euglycemia in immunocompetent mouse model of Type 1 Diabetes. In vitro analyses revealed that XOs suppressed the proliferation of CD3/CD28 activated splenocytes and CD3+ T cells. Comparing suppressive potency of XOs in purified CD3+ T cells versus splenocytes, we found XOs more profoundly suppressed T cells in the splenocytes co-culture, where a heterogenous cell population is present. XOs also suppressed CD3/CD28 activated human peripheral blood mononuclear cells (PBMCs) and reduced their cytokine secretion including IL-2, IL-6, IL-12p70, IL-22, and TNFα. We further demonstrate that XOs mechanism of action is likely mediated via myeloid cells and XOs suppress both murine and human macrophages partly by interfering with NFκB pathway. We propose that through controlled release of XOs, AlgXO provide a promising new platform that could alleviate the local immune response to implantable biomaterials.

Effects of three types of bariatric interventions on myocardial infarct size and vascular function in rats with type 2 diabetes mellitus.

AIMS: The effects of three types of bariatric interventions on myocardial infarct size were tested in the rat model of type 2 diabetes mellitus (T2DM). We also evaluated the effects of bariatric surgery on no-reflow phenomenon and vascular dysfunction caused by T2DM. MAIN METHODS: Rats with T2DM were assigned into groups: without surgery, sham-operated, ileal transposition, Roux-en-Y gastric bypass, and sleeve gastrectomy. Oral glucose tolerance, glucagon-like peptide-1, and insulin levels were measured. Six weeks after surgery, the animals were subjected to myocardial ischemia-reperfusion followed by histochemical determination of infarct size (IS), no-reflow zone, and blood stasis area size. Vascular dysfunction was characterized using wire myography. KEY FINDINGS: All bariatric surgery types caused significant reductions in animal body weight and resulted in T2DM compensation. All bariatric interventions partially normalized glucagon-like peptide-1 responses attenuated by T2DM. IS was significantly smaller in animals with T2DM. Bariatric surgery provided no additional IS limitation compared with T2DM alone. Bariatric surgeries reversed T2DM-induced enhanced contractile responses of the mesenteric artery to 5-hydroxytryptamine. Sleeve gastrectomy normalized decreased nitric oxide synthase contribution to the endothelium-dependent vasodilatation in T2DM. SIGNIFICANCE: T2DM resulted in a reduction of infarct size and no-reflow zone size. Bariatric surgery provided no additional infarct-limiting effect, but it normalized T2DM-induced augmented vascular contractility and reversed decreased contribution of nitric oxide to endothelium-dependent vasodilatation typical of T2DM. All taken together, we suggest that this type of surgery may have a beneficial effect on T2DM-induced cardiovascular diseases.

All-in-One Silk Fibroin Sponge as the Vitrification Cryodevice of Rat Pancreatic Islets and the VEGF-Embedded Scaffold for Subrenal Transplantation.

Islet transplantation is a promising option for the clinical treatment of insulin-dependent diabetes, but a reliable islet cryopreservation/transplantation protocol should be established to overcome the donor shortage. The current study reports that a silk fibroin (SF) sponge disk can be used as a cryodevice for vitrification of large quantity pancreatic islets and the scaffold for subsequent subrenal transplantation in a rat model. The marginal islet mass (550 islet equivalents [IEQs]) on an SF sponge disk was vitrified-warmed and transplanted beneath the kidney capsule of a streptozotocin-induced diabetic rat with or without vascular endothelial growth factor (VEGF). Subrenal transplantation (no scaffold) of 550 IEQ fresh islets and post-warm islets vitrified on a nylon mesh device resulted in achieving euglycemia of recipient rats at 60% and 0%, respectively. Transplantation of 550 IEQ islets vitrified-warmed on an SF sponge disk failed to achieve euglycemia of recipient rats (0%), but the VEGF inclusion in the SF sponge disk contributed to acquiring the euglycemic recipients (33%). All cured recipient rats regained hyperglycemia after nephrectomy, and the histopathologic analysis exhibited a well-developing blood vessel network into the islet engrafts. Thus, an SF sponge disc was successively available as the cryodevice for islet vitrification, the transporter of the angiogenic VEGF, and the scaffold for subrenal transplantation in the rat model.

Roux-en-Y gastric bypass restores islet function and morphology independent of body weight in ZDF rats.

Reductions in ß-cell number and function contribute to the onset type 2 diabetes (T2D). Roux-en-Y gastric bypass (RYGB) surgery can resolve T2D within days of operation, indicating a weight-independent mechanism of glycemic control. We hypothesized that RYGB normalizes glucose homeostasis by restoring ß-cell structure and function. Male Zucker Diabetic Fatty (fa/fa; ZDF) rats were randomized to sham surgery (n = 16), RYGB surgery (n = 16), or pair feeding (n = 16). Age-matched lean (fa/+) rats (n = 8) were included as a secondary control. Postprandial metabolism was assessed by oral glucose tolerance testing before and 27 days after surgery. Fasting and postprandial plasma GLP-1 was determined by mixed meal tolerance testing. Fasting plasma glucagon was also measured. ß-cell function was determined in isolated islets by a glucose-stimulated insulin secretion assay. Insulin and glucagon positive areas were evaluated in pancreatic sections by immunohistochemistry. RYGB reduced body weight (P < 0.05) and improved glucose tolerance (P < 0.05) compared with sham surgery. RYGB reduced fasting glucose compared with both sham (P < 0.01) and pair-fed controls (P < 0.01). Postprandial GLP-1 (P < 0.05) was elevated after RYGB compared with sham surgery. RYGB islets stimulated with 20 mM glucose had higher insulin secretion than both sham and pair-fed controls (P < 0.01) and did not differ from lean controls. Insulin content was greater after RYGB compared with the sham (P < 0.05) and pair-fed (P < 0.05) controls. RYGB improves insulin secretion and pancreatic islet function, which may contribute to the remission of type 2 diabetes following bariatric surgery.NEW & NOTEWORTHY The onset and progression of type 2 diabetes (T2D) results from failure to secrete sufficient amounts of insulin to overcome peripheral insulin resistance. Here, we demonstrate that Roux-en-Y gastric bypass (RYGB) restores islet function and morphology compared to sham and pair-fed controls in ZDF rats. The improvements in islet function were largely attributable to enhanced insulin content and secretory function in response to glucose stimulation.