Effect of glucagon-like peptide-1 (7-37) on beta-cell function after islet transplantation in type 1 diabetes

Efficacy and safety of autologous bone marrow derived hematopoietic stem cell transplantation in patients with type 2 DM: A 15 months follow-up study

BACKGROUND

there are dearths of studies describing the effect of autologous bone marrow derived stem cell transplantation (ABMSCT) through targeted approach in Type 2 Diabetes Mellitus. This study reports the efficacy and safety of super-selective injection of ABMSCT in T2DM.

MATERIALS AND METHODS

Ten patients (8 men and 2 women) with T2DM, with duration of disease >5 years and with documented triple drug failure receiving insulin (0.7 U/Kg/day), metformin and pioglitazone underwent super-selective injection of stem cells into superior pancreaticoduodenal artery under fluoroscopic guidance. The primary outcome measure was decrease in insulin requirement by ≥50% (defined as responders), while secondary endpoints were improvement in glucagon stimulated C-peptide levels, changes in weight, HbA1c, lipid profile and quality of life (QOL) at the end of 15 months.

RESULTS

Six patients (60%) were 'responders' at 15 months of follow-up showing a reduction in mean insulin requirement by 74% as compared to baseline and one patient was off-insulin till the end of the study. Mean HbA1c reduction in 'responders' was 1.1% (8.1 ± 0.5% to 7.0 ± 0.6%, P = 0.03), accompanied with a significant improvement in glucagon stimulated C-peptide levels (P = 0.03), Homeostasis Model Assessment -β (P = 0.03) and QOL scores. However, 'non-responders' did not show any significant alterations in these parameters. No serious adverse events were noted.

CONCLUSION

Our observations indicate that ABMSCT is effective in management of T2DM and its efficacy is maintained over a period of 15 months without any adverse events. However, more number of patients and longer duration of follow-up are required to substantiate these observations.

Improved human islet preparations using glucocorticoid and exendin-4

OBJECTIVES

The effects of glucocorticoid during culture on human islet cells have been controversial. Exendin-4 (EX) enhances the insulin secretion and significantly improves clinical outcomes in islet cell transplantation. In this study, we examined the effects of glucocorticoids and EX on human islet cells during pretransplant culture.

METHODS

Methylprednisolone (MP) and/or EX were added to the standard culture medium for clinical islet cell transplantation. Islets were cultured for 24 hours with 3 different conditions (control, no additives; MP alone; and MP + EX). β-Cell fractional viability, cellular composition, multiple cytokine/chemokine production, multiple phosphorylation proteins, and glucose-induced insulin secretion were evaluated.

RESULTS

Viable β-cell survival in MP and MP + EX group was significantly higher than in the control group. Exendin-4 prevented MP-induced reduction of insulin secretion. Methylprednisolone supplementation to the culture medium decreased cytokine and chemokine production. Moreover, extracellular signal-regulated kinase 1/2 phosphorylation was significantly increased by MP and MP + EX.

CONCLUSIONS

Glucocorticoid supplementation into culture media significantly decreased the cytokine/chemokine production and increased the extracellular signal-regulated kinase 1/2 phosphorylation, resulting in the improvement of human β-cell survival. In addition, EX maintained the insulin secretion suppressed by MP. The supplementation of MP and EX together could be a useful strategy to create suitable human islets for transplantation.

Use of glucagon-like peptide-1 agonists to improve islet graft performance

Human islet transplantation is an effective and promising therapy for type I diabetes. However, long-term insulin independence is both difficult to achieve and inconsistent. De novo or early administration of incretin-based drugs is being explored for improving islet engraftment. In addition to its glucose-dependent insulinotropic effects, incretins also lower postprandial glucose excursion by inhibiting glucagon secretion, delaying gastric emptying, and can protect beta-cell function. Incretin therapy has so far proven clinically safe and tolerable with little hypoglycemic risk. The present review aims to highlight the new frontiers in research involving incretins from both in vitro and in vivo animal studies in the field of islet transplant. It also provides an overview of the current clinical status of incretin usage in islet transplantation in the management of type I diabetes.

Evolution of β-Cell Replacement Therapy in Diabetes Mellitus: Islet Cell Transplantation

Diabetes mellitus remains one of the leading causes of morbidity and mortality worldwide. According to the Centers for Disease Control and Prevention, approximately 23.6 million people in the United States are affected. Of these individuals, 5 to 10% have been diagnosed with Type 1 diabetes mellitus (T1DM), an autoimmune disease. Although it often appears in childhood, T1DM may manifest at any age, leading to significant morbidity and decreased quality of life. Since the 1960s, the surgical treatment for diabetes mellitus has evolved to become a viable alternative to insulin administration, beginning with pancreatic transplantation. While islet cell transplantation has emerged as another potential alternative, its role in the treatment of T1DM remains to be solidified as research continues to establish it as a truly viable alternative for achieving insulin independence. In this paper, the historical evolution, procurement, current status, benefits, risks, and ongoing research of islet cell transplantation are explored.

The evolution of the surgical treatment of chronic pancreatitis

OBJECTIVE

To establish the current status of surgical therapy for chronic pancreatitis, recent published reports are examined in the context of the historical advances in the field.

BACKGROUND

The basis for decompression (drainage), denervation, and resection strategies for the treatment of pain caused by chronic pancreatitis is reviewed. These divergent approaches have finally coalesced as the head of the pancreas has become apparent as the nidus of chronic inflammation.

METHODS

The recent developments in surgical methods to treat the complications of chronic pancreatitis and the results of recent prospective randomized trials of operative approaches were reviewed to establish the current best practices.

RESULTS

Local resection of the pancreatic head, with or without duct drainage, and duodenum-preserving pancreatic head resection offer outcomes as effective as pancreaticoduodenectomy, with lowered morbidity and mortality. Local resection or excavation of the pancreatic head offers the advantage of lowest cost and morbidity and early prevention of postoperative diabetes. The late incidences of recurrent pain, diabetes, and exocrine insufficiency are equivalent for all 3 surgical approaches.

CONCLUSIONS

Local resection of the pancreatic head appears to offer best outcomes and lowest risk for the management of the pain of chronic pancreatitis.

[Adjunctive therapies to glycaemic control of type 1 diabetes mellitus]

Since Diabetes Control and Complications Trial (DCCT), intensive therapy has been directed at achieving glucose and glycosylated hemoglobin (HbA1c) values as close to normal as possible regarding safety issues. However, hyperglycemia (especially postprandial hyperglycemia) and hypoglicemia continue to be problematic in the management of type 1 diabetes. The objective of associating other drugs to insulin therapy is to achieve better metabolic control lowering postprandial blood glucose levels. Adjunctive therapies can be divided in four categories based on their mechanism of action: enhancement of insulin action (e.g. the biguanides and thiazolidinediones), alteration of gastrointestinal nutrient delivery (e.g. acarbose and amylin) and other targets of action (e.g. pirenzepine, insulin-like growth factor I and glucagon-like peptide-1). Many of these agents have been found to be effective in short-term studies with decreases in HbA1c of 0.5-1%, lowering postprandial blood glucose levels and decreasing daily insulin doses.

Effect of glucagon-like peptide-1 on beta- and alpha-cell function in isolated islet and whole pancreas transplant recipients

CONTEXT

Glucose-dependent insulin secretion is often impaired after islet transplantation where reduced beta-cell secretory capacity indicates a low functional beta-cell mass.

OBJECTIVE

We sought to determine whether glucagon-like peptide-1 (GLP-1) enhanced glucose-dependent insulin secretion and glucagon suppression in islet recipients, and whether GLP-1 effects were dependent on functional beta-cell mass by simultaneously studying recipients of whole pancreas transplants.

SETTING

The study was performed in a clinical and translational research center.

PARTICIPANTS

Five intraportal islet and six portally drained pancreas transplant recipients participated in the study.

INTERVENTION

Subjects underwent glucose-potentiated arginine testing with GLP-1 (1.5 pmol . kg(-1) . min(-1)) or placebo infused on alternate randomized occasions, with 5 g arginine injected under basal and hyperglycemic clamp conditions.

RESULTS

Basal glucose was lower with increases in insulin and decreases in glucagon during GLP-1 vs. placebo in both groups. During the hyperglycemic clamp, a significantly greater glucose infusion rate was required with GLP-1 vs. placebo in both groups (P < 0.05), an effect more pronounced in the pancreas vs. islet group (P < 0.01). The increased glucose infusion rate was associated with significant increases in second-phase insulin secretion in both groups (P < 0.05) that also tended to be greater in the pancreas vs. islet group (P = 0.08), whereas glucagon was equivalently suppressed by the hyperglycemic clamp during GLP-1 and placebo infusions in both groups. The GLP-1-induced increase in second-phase insulin correlated with the beta-cell secretory capacity (P < 0.001). The proinsulin secretory ratio (PISR) during glucose-potentiated arginine was significantly greater with GLP-1 vs. placebo infusion in both groups (P < 0.05).

CONCLUSIONS

GLP-1 induced enhancement of glucose-dependent insulin secretion, but not glucagon suppression, in islet and pancreas transplant recipients, an effect dependent on the functional beta-cell mass that may be associated with depletion of mature beta-cell secretory granules.

Long-term insulin independence and improvement in insulin secretion after supplemental islet infusion under exenatide and etanercept

BACKGROUND

Progressive graft dysfunction (GDF) and loss of insulin independence (II) have been invariably observed in islet transplant recipients under the "Edmonton protocol." To reestablish II, we performed supplemental islet infusions (SI) in recipients of allogeneic islet transplant alone, displaying GDF. To improve the engraftment and long-term graft function of SI, exenatide (EXN) and etanercept treatment at islet infusion, and long-term EXN treatment were tested in a non-randomized pilot clinical trial.

METHODS

Patients with GDF received SI under Edmonton-like immunosuppression with daclizumab induction, either without interventions (SI-control; n=5) or with EXN and etanercept treatment (SI-EXN; n=4). Clinical and metabolic profiles were assessed during 18-month follow-up.

RESULTS

Long-term II (18 months) was observed in 100% of SI-EXN and in 20% of SI-control (P=0.04). SI-EXN subjects demonstrated restoration of function better than that seen after initial islet infusions. Comparison of SI-EXN and SI-control groups demonstrated better responses in SI-EXN subjects at 3 months post-SI. During the 18 months of follow-up, function was sustained in the SI-EXN subjects better than in SI-controls. Acute effects of EXN during mixed meal tolerance test and intravenous glucose tolerance test results in improved first and second phase insulin release in response to intravenous glucose tolerance test and suppressed postprandial hyperglucagonemia after mixed meal tolerance test.

CONCLUSION

These results suggest that the combination of EXN and etanercept improve engraftment and long-term islet survival and function in subjects undergoing SI. This data, however, must be interpreted with some caution because of small sample size, lack of randomization, and sequential comparison with historical controls.

Exendin-4 treatment expands graft beta-cell mass in diabetic mice transplanted with a marginal number of fresh islets

Exendin-4 stimulates insulin secretion, suppresses glucagons secretion, increases beta-cell replication and neogenesis, and reduces beta-cell apoptosis. However, it has been shown that posttransplant exendin-4 treatment did not improve glucose homeostasis in diabetic mice transplanted with a large number of freshly isolated islets. The aim of this study was to test if exendin-4 is beneficial for hyperglycemic recipients with a marginal number of fresh islets. We transplanted 150 C57BL/6 mouse islets under the kidney capsule of inbred streptozotocin-diabetic mice, and then treated the recipients with and without exendin-4 for 6 weeks. Before and after transplantation, recipients' blood glucose, body weight, and intraperitoneal glucose tolerance test were measured. At 6 weeks, the grafts were removed to determine beta-cell mass. Blood glucose levels in both groups decreased progressively after transplantation, and the exendin-4-treated group had had lower blood glucose than controls since day 3. By 6 weeks, euglycemia was achieved more in mice treated with exendin-4 than in controls (100% vs. 62.5%, p = 0.018). The time to obtain normoglycemia was shorter in the exendin-4-treated group than in controls (12 +/- 8 vs. 29 +/- 13 days, p < 0.001). Blood glucose at 6 weeks was 123 +/- 18 and 170 +/- 62 mg/dl in the exendin-4-treated group and controls, respectively (p = 0.008). Additionally, the exendin-4-treated group had better glucose tolerance than controls at 2 and 4 weeks (p <0.02). However, both groups exhibited increased body weight over time, and weight changes did not significantly differ between the two groups throughout the study period. At 6 weeks after transplantation, grafts in the exendin-4-treated group were more prominent and contained more insulin-stained cells than those of controls. They had 2.3-fold beta-cell mass of the graft compared with controls (0.30 +/- 0.11 vs. 0.13 +/- 0.03 mg, p = 0.012). These results indicate posttransplant exendin-4 treatment in the diabetic recipient with a marginal number of fresh islets expands graft beta-cell mass and improves transplantation outcome.

Liraglutide, a long-acting human glucagon-like peptide 1 analog, improves glucose homeostasis in marginal mass islet transplantation in mice

The current scarcity of high-quality deceased pancreas donors prevents widespread application of islet transplantation for treatment of labile type 1 diabetes mellitus. Opportunities for the improvement of current techniques include optimization of islet isolation and purification, use of culture with pharmacological insulinotropic agents, strategies to reduce graft rejection and inflammation, and the search for alternative insulin producing tissue. Here, we report our findings on the efficacy of the long-acting human glucagon-like peptide 1 analog, liraglutide, in a mouse model of marginal mass islet transplantation. Liraglutide was administered (200 microg/kg sc twice daily) after a marginal mass syngeneic islet transplant in streptozotocin-induced diabetic BALB/c mice. Time-to-normoglycemia was significantly shorter in liraglutide-treated animals (median 1 vs. 7 d; P = 0.0003), even in recipients receiving sirolimus (median 1 vs. 72.5 d; P < 0.0001). Liraglutide-treated animals also demonstrated improved glucose tolerance as assessed by an ip glucose tolerance test. Liraglutide discontinuation at postoperative d 90 resulted in diminished glucose tolerance during the ip glucose tolerance test, whereas a late-start liraglutide therapy 90 d after transplant resulted in no improvement. These findings suggest that liraglutide therapy mediates early and late insulinotropic effects. In accord with this hypothesis, insulin/terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick end labeling fluorescence microscopy showed reduced transplanted beta-cell apoptosis in liraglutide-treated recipients 48 h after transplant. In addition, liraglutide resulted in improved glucose-dependent insulin secretion. Overall, our data show that liraglutide has a beneficial impact on the engraftment and function of syngeneic islet transplants in mice, when administered continuously starting on the day of transplant.

The use of exenatide in islet transplant recipients with chronic allograft dysfunction: safety, efficacy, and metabolic effects

BACKGROUND

A current limitation of islet transplantation is reduced long-term graft function. The glucagon-like peptide-1 receptor agonist, exenatide (Byetta, Amylin Pharmaceuticals, CA) has properties that could improve existing islet function, prevent further loss of islet mass and possibly even stimulate islet regeneration.

METHODS

This prospective study evaluated the safety, efficacy, and metabolic effects of exenatide in subjects with type 1 diabetes mellitus and islet allograft dysfunction requiring exogenous insulin.

RESULTS

Sixteen subjects commenced exenatide, 12 continue (follow-up 214+/-57 days; range 108-287), four (25%) discontinued medication because of side effects. At 6 months, exogenous insulin was significantly reduced with stable glycemic control (0.15+/-0.02 vs. 0.11+/-0.025 U/kg per day; P<0.0001); three subjects discontinued insulin from 4, 5, and 9 U/day, respectively, two sustained insulin independence with A1c reduction below graft dysfunction criteria. Postprandial capillary blood glucose was significantly decreased (129.4+/-3.8 vs. 118.7+/-4.6 mg/dL; P<0.001), C-peptide and C-peptide-to-glucose ratio increased significantly by 5th and 6th months of treatment (ratio, 1.09+/-0.15 vs. 1.52+/-0.18; P<0.05). Weight loss more than 3 kg occurred in 8 of 12 (67%) subjects. Stimulation testing demonstrated improved glucose disposal and C-peptide secretion (glucose area under the curve 52,332+/-3,219 vs. 42,072+/-1,965; P=0.002 mg x min x dL, mixed meal stimulation index 0.50+/-0.06 vs. 0.66+/-0.09; P=0.03 pmol x mL), with marked suppression of glucagon secretion and progressive increase in amylin secretion. Side effects were more frequent and severe compared with published reports in type 2 diabetes, tolerated doses were lower.

CONCLUSIONS

Exenatide was tolerated in this patient population after appropriate dose titration and there appeared to be gradual but sustained positive effects on glycemic control and islet graft function.

Exendin-4 modulates diabetes onset in nonobese diabetic mice

Activation of the glucagon-like peptide-1 receptor (GLP-1R) is associated with expansion of beta-cell mass due to stimulation of cell proliferation and induction of antiapoptotic pathways coupled to beta-cell survival. Although the GLP-1R agonist Exenatide (exendin-4) is currently being evaluated in subjects with type 1 diabetes, there is little information available about the efficacy of GLP-1R activation for prevention of experimental type 1 diabetes. We examined the consequences of exendin-4 (Ex-4) administration (100 ng once daily and 2 microg twice daily) on diabetes onset in nonobese diabetic mice beginning at either 4 or 9 wk of age prior to the onset of diabetes. Ex-4 treatment for 26 wk (2 microg twice daily) initiated at 4 wk of age delayed the onset of diabetes (P = 0.007). Ex-4-treated mice also exhibited a significant reduction in insulitis scores, enhanced beta-cell mass, and improved glucose tolerance. Although GLP-1R mRNA transcripts were detected in spleen, thymus, and lymph nodes from nonobese diabetic mice, Ex-4 treatment was not associated with significant changes in the numbers of CD4+ or CD8+ T cells or B cells in the spleen. However, Ex-4 treatment resulted in an increase in the number of CD4+ and CD8+ T cells in the lymph nodes and a reduction in the numbers of CD4+CD25+Foxp3+ regulatory T cells in the thymus but not in lymph nodes. These findings demonstrate that sustained GLP-1R activation in the absence of concomitant immune intervention may be associated with modest but significant delay in diabetes onset in a murine model of type 1 diabetes.

Meal-stimulated glucagon release is associated with postprandial blood glucose level and does not interfere with glycemic control in children and adolescents with new-onset type 1 diabetes

CONTEXT

The role of glucagon in hyperglycemia in type 1 diabetes is unresolved, and in vitro studies suggest that increasing blood glucose might stimulate glucagon secretion.

OBJECTIVE

Our objective was to investigate the relationship between postprandial glucose and glucagon level during the first 12 months after diagnosis of childhood type 1 diabetes.

DESIGN

We conducted a prospective, noninterventional, 12-month follow-up study conducted in 22 centers in 18 countries.

PATIENTS

Patients included 257 children and adolescents less than 16 yr old with newly diagnosed type 1 diabetes; 204 completed the 12-month follow-up.

SETTING

The study was conducted at pediatric outpatient clinics.

MAIN OUTCOME MEASURES

We assessed residual beta-cell function (C-peptide), glycosylated hemoglobin (HbA(1c)), blood glucose, glucagon, and glucagon-like peptide-1 (GLP-1) release in response to a 90-min meal stimulation (Boost) at 1, 6, and 12 months after diagnosis.

RESULTS

Compound symmetric repeated-measurements models including all three visits showed that postprandial glucagon increased by 17% during follow-up (P = 0.001). Glucagon levels were highly associated with postprandial blood glucose levels because a 10 mmol/liter increase in blood glucose corresponded to a 20% increase in glucagon release (P = 0.0003). Glucagon levels were also associated with GLP-1 release because a 10% increase in GLP-1 corresponded to a 2% increase in glucagon release (P = 0.0003). Glucagon levels were not associated (coefficient -0.21, P = 0.07) with HbA(1c), adjusted for insulin dose. Immunohistochemical staining confirmed the presence of Kir6.2/SUR1 in human alpha-cells.

CONCLUSION

Our study supports the recent in vitro data showing a stimulation of glucagon secretion by high glucose levels. Postprandial glucagon levels were not associated with HbA(1c), adjusted for insulin dose, during the first year after onset of childhood type 1 diabetes.

An odyssey of islet transplantation for therapy of type 1 diabetes

Canadian surgical contributions to the field of islet transplantation have a rich heritage and a promising future. In this article, some seminal Canadian contributions to this field are reviewed, including contributions at the basic research laboratory and translational applications to bedside therapy of type 1 diabetes.

Incretins: Clinical Physiology and Bariatric Surgery –Correlating the Entero-endocrine System and a Potentially Anti-dysmetabolic Procedure

The digestive tract is well known for its endocrine functions. Recently, many studies have been reinforcing its role as a therapeutic target for both diabetes and obesity. Losing weight is clinically very difficult for most obese patients and the reason for this could be the effect of the physiological adipostatic system that triggers central nervous stimuli to compensate for variations in food intake and in physical activity. Gut hormones seem to have a key role in this complex, regulating body weight and satiety and contributing to glucose homeostasis. The enteroinsular axis appears to be impaired in both obese and diabetic patients. Recent data on bariatric surgery shows its striking effects on glucose control soon after the procedure, before a significant weight loss is achieved. The procedure appears to work beyond anti-obesity having a key metabolic impact possibly sharing a common mechanism with the new class of agents to treat type 2 diabetes mellitus: the incretin mimetics. This symposium discussed new data on the upcoming perspectives on both the pharmacological and the surgical approach to diabetes and obesity.

Effect of exenatide on beta cell function after islet transplantation in type 1 diabetes

BACKGROUND

Islet transplantation can reduce or eliminate the need for insulin in patients with type 1 diabetes. Exenatide is a long acting analogue of Glucagon-like peptide-1 (GLP-1) that augments glucose induced insulin secretion, and may increase beta cell mass. We evaluated the effect of exenatide on insulin secretion after islet transplantation.

METHODS

Eleven C-peptide positive islet cell recipients with elevated glucose levels were treated with exenatide for three months. Response was assessed by insulin requirements, meal tolerance tests, and hyperglycemic glucose clamps.

RESULTS

Ten patients responded to exenatide. Two patients who had not restarted insulin achieved good glycemic control and one patient who had received 5500 IE/kg in first islet infusion was able to stop insulin. Seven other patients decreased their insulin dose by 39% on exenatide. Hyperglycemic clamp studies showed a rise in second phase insulin release (before exenatide: 246+/-88 pM; during exenatide: 644+/-294 pM, P<0.01). Meal tolerance studies before and one month after stopping exenatide did not show a difference in glucose or C-peptide values. Nausea and vomiting were the major side effects.

CONCLUSIONS

Exenatide stimulates insulin secretion in islet transplant recipients. It reduces insulin dose in some patients and may delay the need to resume insulin in others. We did not find any evidence of a trophic effect on islets.