beta-cell failure in diabetes and preservation by clinical treatment

Determinants of reversibility of β-cell dysfunction in response to short-term intensive insulin therapy in patients with early type 2 diabetes

Short-term intensive insulin therapy (IIT) can improve pancreatic β-cell function when administered early in the course of type 2 diabetes mellitus (T2DM). However, the degree of improvement in response to this therapy varies between patients. Thus, we sought to characterize the determinants of improvement in β-cell function in response to short-term IIT in early T2DM. Sixty-three patients with mean 3.0 ± 2.1 yr duration of T2DM and Hb A1c of 6.8 ± 0.8% underwent 4 wk of IIT consisting of basal insulin detemir and premeal insulin aspart, with oral glucose tolerance test administered at baseline and 1 day post-IIT. β-Cell function before and after IIT was assessed by Insulin Secretion Sensitivity Index-2 (ISSI-2). Reversibility of β-cell dysfunction was defined as percentage change in ISSI-2 of ≥25%. Overall, the study population experienced an increase in ISSI-2 from baseline to post-IIT (P = 0.01), with one-third of participants achieving ≥25% improvement in ISSI-2. Compared with their peers, those with increases in ISSI-2 of ≥25% had greater decrements in fasting glucose (P < 0.0001), Hb A1c (P = 0.001), ALT (P = 0.04), AST (P = 0.02), and HOMA-IR (P < 0.0001). On logistical regression analysis, baseline Hb A1c (OR = 2.83, 95% CI 1.16-6.88, P = 0.02) and change in HOMA-IR (OR = 0.008, 95%CI 0.0004-0.16, P = 0.001) emerged as independent predictors of reversibility of β-cell dysfunction. Indeed, reversibility of β-cell dysfunction was achieved in only those participants in whom IIT yielded an improvement in HOMA-IR. In conclusion, decline in HOMA-IR may be a key determinant of improvement of β-cell function in response to short-term IIT, suggesting a fundamental contribution of insulin resistance to the reversible component of β-cell dysfunction in early T2DM.

Impact of three oral antidiabetic drugs on markers of β-cell function in patients with type 2 diabetes: a meta-analysis

Background

The effect of metformin, pioglitazone and sitagliptin on β-cell function in the treatment of type 2 diabetes is controversial. Therefore, we performed a systematic review and meta-analysis to obtain a better understanding in the β-cell effects of metformin, pioglitazone and sitagliptin.

Methods

We searched Pubmed and the Cochrane Center Register of Controlled Trials to identify relevant studies. Trials investigating effects of sitagliptin, metformin or pioglitazone on β-cell function were identified. The primary outcomes were homeostasis model assessment of β-cells (HOMA-β) and proinsulin/insulin ratio (PI/IR). Secondary outcome was hemoglobin A1c level. We used version 2 of the Comprehensive Meta Analysis software for all statistical analyses.

Results

Metformin monotherapy was more effective than sitagliptin in improving HOMA-β (18.01% (95% CI 11.09% to 24.94%) vs. 11.29% (95% CI 9.21% to 13.37%), P = 0.040) and more effective (−0.137 (95% CI −0.082 to −0.192)) than both sitagliptin (−0.064 (95% CI −0.036 to −0.092), P = 0.019) and pioglitazone (−0.068 (95% CI −0.044 to −0.093), P = 0.015) in decreasing PI/IR. Metformin and sitagliptin combined (40.23% (95%CI 32.30% to 48.16%)) were more effective than sitagliptin and pioglitazone (11.82% (95% CI 6.61% to 17.04%), P = 0.000) and pioglitazone and metformin(9.81% (95% CI 1.67% to 17.95%), P = 0.022) in improving HOMA-β and decreasing PI/IR (−0.177 (95% CI −0.118 to −0.237); −0.080 (95% CI −0.045 to −0.114), P = 0.007; −0.038 (95% CI, −0.005 to 0.071), P = 0.023).

Limitations

The included RCTs were of short duration (12–54 weeks). We could not determine long term effects on β-cells.

Conclusions

Metformin improves β-cell function more effectively than pioglitazone or sitagliptin in type 2 diabetes patients. Metformin and sitagliptin improved HOMA-β and PI/IR more than other combinations.

Effects of short-term intensive glycemic control on insulin, glucagon, and glucagon-like peptide-1 secretion in patients with Type 2 diabetes

BACKGROUND

Short-term intensive insulin therapy (IIT) in patients with Type 2 diabetes mellitus (T2DM) has beneficial effects on insulin secretion. However, IIT effect on glucagon and glucagon-like peptide-1 (GLP-1) secretion is unknown.

AIM

We evaluated short-term intensive glycemic control effects on insulin, glucagon, and GLP-1 secretory dynamics in T2DM.

MATERIALS AND METHODS

Twenty-six patients with T2DM were hospitalized and treated with IIT for 10-14 days. A meal tolerance test was performed before and after IIT and the differences in serum immunoreactive insulin (IRI) and C-peptide immunoreactivity (CPR) as well as plasma glucagon and active GLP-1 levels were evaluated.

RESULTS

Glycoalbumin levels decreased significantly from 23.0% before to 19.6% after IIT (p<0.001). However, pre- and post-IIT, IRI and CPR levels were not significantly different; post-IIT glucose levels were significantly decreased. The post-IIT glucagon levels at 0 and 60 min were lower than pre-IIT levels. Moreover, post- IIT area under the curve (AUC) of glucagon significantly reduced from 6755 ± 996 pg/dl · 60 min to 5796 ± 1074 pg/dl · 60 min (p<0.001). Furthermore, post-IIT GLP-1 levels and AUC were significantly higher than pre-IIT values.

CONCLUSIONS

Our results suggest that patients with T2DM who received shortterm IIT demonstrated decreased postprandial glucagon levels and increased GLP-1 levels following a meal tolerance test.

Influence of islet function on typing and prognosis of new-onset diabetes after intensive insulin therapy

Background

It is difficult in clinical practice to differentiate patients with newly diagnosed diabetes and ketosis. The aim of this study was to investigate the effect of intensive insulin therapy on islet function in patients with new-onset diabetes and concomitant ketosis, and to determine the value of alternation in islet function in the typing of diabetes.

Material/Methods

A total of 206 inpatients with new-onset diabetes and ketosis were recruited after intensive insulin therapy and followed for 36 months. Patients were divided into type 1 diabetes group (Group A) and type 2 diabetes group (Group B). Islet function was compared between the 2 groups before and after intensive insulin therapy, and the influence of islet function on the typing of diabetes and the selection of therapeutic strategies is discussed.

Results

In group A, the AUC_I, AUC_C, HOMA-β cell and HOMA-IR were significantly lower than those in Group B before and after intensive insulin therapy. The sensitivity and accuracy of antibody test were at a low level in Group A. An insulin release test was done after intensive insulin therapy. Results showed that the peaks of insulin and C peptide appeared at 0.5–1 h after glucose administration in Group A, which was earlier than that before therapy, but the maximal levels were no more than 2 times those of baseline levels. In Group B, the peaks appeared at 2 h, and the maximal levels were about 10 times those of baseline levels.

Conclusions

Poor islet function, incomplete recovery of islet function after intensive insulin therapy, and a short “honeymoon” period are characteristics of type 1 diabetes. Detection of diabetes-related antibodies is not reliable.

Evidence-based clinical use of insulin premixtures

Brazil is expected to have 19.6 million patients with diabetes by the year 2030. A key concept in the treatment of type 2 diabetes mellitus (T2DM) is establishing individualized glycemic goals based on each patient's clinical characteristics, which impact the choice of antihyperglycemic therapy. Targets for glycemic control, including fasting blood glucose, postprandial blood glucose, and glycated hemoglobin (A1C), are often not reached solely with antihyperglycemic therapy, and insulin therapy is often required. Basal insulin is considered an initial strategy; however, premixed insulins are convenient and are equally or more effective, especially for patients who require both basal and prandial control but desire a more simplified strategy involving fewer daily injections than a basal-bolus regimen. Most physicians are reluctant to transition patients to insulin treatment due to inappropriate assumptions and insufficient information. We conducted a nonsystematic review in PubMed and identified the most relevant and recently published articles that compared the use of premixed insulin versus basal insulin analogues used alone or in combination with rapid-acting insulin analogues before meals in patients with T2DM. These studies suggest that premixed insulin analogues are equally or more effective in reducing A1C compared to basal insulin analogues alone in spite of the small increase in the risk of nonsevere hypoglycemic events and nonclinically significant weight gain. Premixed insulin analogues can be used in insulin-naïve patients, in patients already on basal insulin therapy, and those using basal-bolus therapy who are noncompliant with blood glucose self-monitoring and titration of multiple insulin doses. We additionally provide practical aspects related to titration for the specific premixed insulin analogue formulations commercially available in Brazil.

Predictive factors of durability to sitagliptin: Slower reduction of glycated hemoglobin, older age and higher baseline glycated hemoglobin

Aims/Introduction

The goal of the present study was to evaluate predictive factors for good efficacy and durability to sitagliptin with ongoing metformin or metformin plus glimepiride therapy in a real practice situation. The present observational study was carried out over a 60‐week period and involved Korean patients with type 2 diabetes mellitus.

Materials and Methods

A total of 100 mg of sitagliptin were added once daily to the two most popular therapy regimens (group 1: metformin, group 2: metformin plus glimepiride). Before adding sitagliptin, mean initial glycated hemoglobin (HbA1c) levels were 7.8% (62 mmol/mol) and mean diabetes duration was 8.3 years.

Results

After 60 weeks, the mean change in HbA1c from baseline was −0.9% (−10 mmol/mol) in group 1 and −1.0% (−11 mmol/mol) in group 2. Decreased HbA1c levels were significantly associated with higher initial HbA1c and lower log‐transformed C‐peptide levels in a multivariate regression analysis. Logistic regression analysis showed that a sustained reduction in HbA1c levels after 12 weeks was significantly associated with older age (≥60 years), higher baseline HbA1c (group 1 ≥ 7.0% [53 mmol/mol], group 2 ≥ 7.5% [58 mmol/mol]) and slower reduction of HbA1c (ΔHbA1c <1.0% [11 mmol/mol]) in group 1 and group 2. In group 2, a higher ratio of reduction of postprandial glucose/reduction of fasting plasma glucose (ΔPPG/ΔFPG) during 12 weeks was also associated with a sustained reduction in HbA1c levels after 12 weeks.

Conclusions

The effects of sitagliptin lasted more than 12 weeks in older patients with a higher baseline HbA1c, and slower reduction of HbA1c during 12 weeks.

MicroRNA-24/MODY gene regulatory pathway mediates pancreatic β-cell dysfunction

Overnutrition and genetics both contribute separately to pancreatic β-cell dysfunction, but how these factors interact is unclear. This study was aimed at determining whether microRNAs (miRNAs) provide a link between these factors. In this study, miRNA-24 (miR-24) was highly expressed in pancreatic β-cells and further upregulated in islets from genetic fatty (db/db) or mice fed a high-fat diet, and islets subject to oxidative stress. Overexpression of miR-24 inhibited insulin secretion and β-cell proliferation, potentially involving 351 downregulated genes. By using bioinformatic analysis combined with luciferase-based promoter activity assays and quantitative real-time PCR assays, we identified two maturity-onset diabetes of the young (MODY) genes as direct targets of miR-24. Silencing either of these MODY genes (Hnf1a and Neurod1) mimicked the cellular phenotype caused by miR-24 overexpression, whereas restoring their expression rescued β-cell function. Our findings functionally link the miR-24/MODY gene regulatory pathway to the onset of type 2 diabetes and create a novel network between nutrient overload and genetic diabetes via miR-24.

Improvement of β-cell function after achievement of optimal glycaemic control via long-term continuous subcutaneous insulin infusion therapy in non-newly diagnosed type 2 diabetic patients with suboptimal glycaemic control

BACKGROUND

Achieving euglycaemia by continuous subcutaneous insulin infusion (CSII) therapy alone has been shown to restore β-cell function in patients with newly diagnosed type 2 diabetes. However, the efficacy has not been evaluated in patients with non-newly diagnosed type 2 diabetes and suboptimal glycaemic control.

METHODS

Of the 1220 patients with type 2 diabetes who began CSII therapy from March 2000 to March 2007, we retrospectively selected patients using the following inclusion criteria: glycosylated haemoglobin (HbA1c ) ≥ 7.0%, diabetes duration ≥ 1 year before CSII therapy, and duration of CSII therapy ≥ 6 months. We evaluated sequential changes in HbA1c and serum C-peptide levels measured at a 6- to 12-month intervals during CSII therapy.

RESULTS

In the 521 subjects included in this study [median diabetes duration 10 years; interquartile range (IQR) 6.0-17.0; CSII therapy ≤ 30 months], median HbA1c decreased from 8.7% (IQR 7.7-10.0) at baseline to 6.3% (IQR 5.9-6.9) after 6 months of CSII therapy (p < 0.0001). During the subsequent 24 months, median HbA1c levels were maintained between 6.3% and 6.5% (p < 0.0001 for all time points vs baseline). At 12 months after CSII therapy, median C-peptide levels began to increase compared with baseline (fasting level 23% increase, p < 0.0001; 2-h postprandial level 26% increase, p = 0.022), and the increase was maintained at 30 months (fasting level 39%; 2-h postprandial level 53%; p < 0.0001 for all vs baseline).

CONCLUSIONS

β-Cell function was significantly improved in patients with non-newly diagnosed and suboptimally controlled type 2 diabetes after achieving and maintaining optimal glycaemic control with long-term CSII therapy alone.

Current role of short-term intensive insulin strategies in newly diagnosed type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a progressive disease characterized by worsening insulin resistance and a decline in β-cell function. Achieving good glycemic control becomes more challenging as β-cell function continues to deteriorate throughout the disease process. The traditional management paradigm emphasizes a stepwise approach, and insulin has generally been reserved as a final armament. However, mounting evidence indicates that short-term intensive insulin therapy used in the early stages of type 2 diabetes could improve β-cell function, resulting in better glucose control and more extended glycemic remission than oral antidiabetic agents. Improvements in insulin sensitivity and lipid profile were also seen after the early initiation of short-term intensive insulin therapy. Thus, administering short-term intensive insulin therapy to patients with newly diagnosed T2DM has the potential to delay the natural process of this disease, and should be considered when clinicians initiate treatment. Although the early use of insulin is advocated by some guidelines, the optimal time to initiate insulin therapy is not clearly defined or easily recognized, and a pragmatic approach is lacking. Herein we summarize the current understanding of early intensive insulin therapy in patients with newly diagnosed T2DM, focusing on its clinical benefit and problems, as well as possible biological mechanisms of action, and discuss our perspective.

Short-term intensive insulin therapy in type 2 diabetes mellitus: a systematic review and meta-analysis

BACKGROUND

Studies have shown that, when implemented early in the course of type 2 diabetes mellitus, treatment with intensive insulin therapy for 2-3 weeks can induce a glycaemic remission, wherein patients are able to maintain normoglycaemia without any anti-diabetic medication. We thus did a systematic review and meta-analysis of interventional studies to assess the effect of short-term intensive insulin therapy on the pathophysiological defects underlying type 2 diabetes mellitus (pancreatic β-cell dysfunction and insulin resistance) and identify clinical predictors of remission.

METHODS

We identified studies published between 1950 and Nov 19, 2012, which assessed the effect of intensive insulin therapy on β-cell function or insulin resistance, or both, or assessed long-term drug-free glycaemic remission in adults aged 18 years or older with newly diagnosed type 2 diabetes mellitus. We calculated pooled estimates by random-effects model. This study is registered with International Prospective Register of Systematic Reviews, number CRD42012002829.

FINDINGS

We identified 1645 studies of which seven fulfilled inclusion criteria (n=839 participants). Five studies were non-randomised. A pooled analysis of the seven studies showed a post-intensive insulin therapy increase in Homeostasis Model Assessment of β-cell function as compared with baseline (1·13, 95% CI 1·02 to 1·25) and a decrease in Homeostasis Model Assessment of Insulin Resistance (-0·57, -0·84 to -0·29). In the four studies that assessed glycaemic remission (n=559 participants), the proportion of participants in drug-free remission was about 66·2% (292 of 441 patients) after 3 months of follow-up, about 58·9% (222 of 377 patients) after 6 months, about 46·3% (229 of 495 patients) after 12 months, and about 42·1% (53 of 126 patients) after 24 months. Patients who achieved remission had higher body-mass index than those who did not achieve remission (1·06 kg/m(2), 95% CI 0·55 to 1·58) and lower fasting plasma glucose (-0·59 mmol/L, 95% CI -1·11 to -0·07) at baseline.

INTERPRETATION

Short-term intensive insulin therapy can improve the underlying pathophysiology in early type 2 diabetes mellitus, and thus might provide a treatment strategy for modifying the natural history of diabetes.

FUNDING

None.

Overview of food products and dietary constituents with antidiabetic properties and their putative mechanisms of action: a natural approach to complement pharmacotherapy in the management of diabetes

Diabetes is one of the fastest growing chronic, noncommunicable diseases worldwide. Currently, 11 major classes of pharmacotherapy are available for the management of this metabolic disorder. However, the usage of these drugs is often associated with undesirable side effects, including weight gain and hypoglycemia. There is thus a need for new, safe and effective treatment strategies. Diet is known to play a major role in the prevention and management of diabetes. Numerous studies have reported the putative association of the consumption of specific food products, or their constituents, with the incidence of diabetes, and mounting evidence now suggests that some dietary factors can improve glycemic regulation. Foods and dietary constituents, similar to synthetic drugs, have been shown to modulate hormones, enzymes, and organ systems involved in carbohydrate metabolism. The present article reviews the major classes and modes of action of antidiabetic drugs, and examines the evidence on food products and dietary factors with antidiabetic properties as well as their plausible mechanisms of action. The findings suggest potential use of dietary constituents as a complementary approach to pharmacotherapy in the prevention and/or management of diabetes, but further research is necessary to identify the active components and evaluate their efficacy and safety.

In vivo activating transcription factor 3 silencing ameliorates the AMPK compensatory effects for ER stress-mediated β-cell dysfunction during the progression of type-2 diabetes

In obese Zucker diabetic fatty (ZDF) rats, ER stress is associated with insulin resistance and pancreatic β-cell dysfunction; however the exact mechanisms by which ER stress drives type-2 diabetes remain uncertain. Here, we investigated the role of ATF3 on the preventive regulation of AMPK against ER stress-mediated β-cell dysfunction during the end-stage progression of hyperglycemia in ZDF rats. The impaired glucose metabolism and β-cell dysfunction were significantly increased in late-diabetic phase 19-week-old ZDF rats. Although AMPK phosphorylation reduced in 6- and 12-week-old ZDF rats was remarkably increased at 19weeks, the increases of lipogenice genes, ATF3, and ER stress or ROS-mediated β-cell dysfunction were still remained, which were attenuated by in vivo-injection of chemical chaperon tauroursodeoxycholate (TUDCA), chronic AICAR, or antioxidants. ATF3 did not directly affect AMPK phosphorylation, but counteracts the preventive effects of AMPK for high glucose-induced β-cell dysfunction. Moreover, knockdown of ATF3 by delivery of in vivo-jetPEI ATF3 siRNA attenuated ER stress-mediated β-cell dysfunction and enhanced the beneficial effect of AICAR. Our data suggest that ATF3 may play as a counteracting regulator of AMPK and thus promote β-cell dysfunction and the development of type-2 diabetes and could be a potential therapeutic target in treating type-2 diabetes.

Effects of insulin glargine versus metformin on glycemic variability, microvascular and beta-cell function in early type 2 diabetes

We investigated whether basal insulin as first-line treatment in recently diagnosed type 2 diabetes (T2D) can improve glucose control, microvascular function and preserve insulin secretion in comparison with metformin (MET). In this open-label, randomized, prospective 36-week study, 75 patients (44 m, 31 f, mean age 60.7 ± 9.2 year) were allocated to treatment with either MET 1,000 mg b.i.d. (n = 36) or insulin glargine (GLA) at bedtime (n = 39). At baseline and study end, we performed a continuous glucose monitoring for assessment of interstitial glucose (IG) and measured microvascular function using Laser-Doppler fluxmetry. GLA versus MET treatment resulted in a more pronounced reduction in FPG (Δ: 3.1 ± 2.5 vs. 1.4 ± 1.5 mmol/l; p < 0.001) and overall IG (Δ AUC. 671 ± 507 vs. 416 ± 537 mmol/l min; p = 0.04). Postprandial PG and IG differences after a standardized test meal did not reach significance. Proinsulin/C-peptide and HOMA B as marker of endogenous insulin secretion were significantly more improved by GLA. Microvascular blood flow improved only in MET-treated patients. Early basal insulin treatment with GLA in T2D patients provided a better control of FPG, overall IG load and biomarker of beta-cell function compared to the standard treatment with MET. MET treatment resulted in an improvement of microvascular function. Studies of longer duration are needed to evaluate the durability of glucose control and β cell protection with early GLA treatment.

Long-term liraglutide treatment is associated with increased insulin content and secretion in β-cells, and a loss of α-cells in ZDF rats

The ultimate treatment goal of diabetes is to preserve and restore islet cell function. Treatment of certain diabetic animal models with incretins has been reported to preserve and possibly enhance islet function and promote islet cell growth. The studies reported here detail islet cell anatomy in animals chronically treated with the incretin analog, liraglutide. Our aim was to quantitatively and qualitatively analyze islet cells from diabetic animals treated with vehicle (control) or liraglutide to determine whether normal islet cell anatomy is maintained or enhanced with pharmaceutical treatment. We harvested pancreata from liraglutide and vehicle-treated Zucker Diabetic Fatty (ZDF) rats to examine islet structure and function and obtain isolated islets. Twelve-week-old male rats were assigned to 3 groups: (1) liraglutide-treated diabetic, (2) vehicle-treated diabetic, and (3) lean non-diabetic. Liraglutide was given SC twice daily for 9 weeks. As expected, liraglutide treatment reduced body weight by 15% compared to the vehicle-treated animals, eventually to levels that were not different from lean controls. At the termination of the study, blood glucose was significantly less in the liraglutide-treated rats compared to vehicle treated controls (485.8±22.5 and 547.2±33.1mg/dl, respectively). Insulin content/islet (measured by immunohistochemistry) was 34.2±0.7 pixel units in vehicle-treated rats, and 54.9±0.6 in the liraglutide-treated animals. Glucose-stimulated insulin secretion from isolated islets (measured as the stimulation index) was maintained in the liraglutide-treated rats, but not in the vehicle-treated. However, liraglutide did not preserve normal islet architecture. There was a decrease in the glucagon-positive area/islet and in the α-cell numbers/area with liraglutide treatment (6.5 cells/field), compared to vehicle (17.9 cells/field). There was an increase in β-cell numbers, the β- to α-cell ratio that was statistically higher in the liraglutide-treated rats (24.3±4.4) compared to vehicle (9.1±2.8). Disrupted mitochondria were more commonly observed in the α-cells (51.9±10.3% of cells) than in the β-cells (27.2±4.4%) in the liraglutide-treated group. While liraglutide enhanced or maintained growth and function of certain islet cells, the overall ratio of α- to β-cells was decreased and there was an absolute reduction in islet α-cell content. There was selective disruption of intracellular α-cell organelles, representing an uncoupling of the bihormonal islet signaling that is required for normal metabolic regulation. The relevance of the findings to long-term liraglutide treatment in people with diabetes is unknown and should be investigated in appropriately designed clinical studies.

Quantification of β-cell insulin secretory function using a graded glucose infusion with C-peptide deconvolution in dysmetabolic, and diabetic cynomolgus monkeys

BACKGROUND

Quantitation of β-cell function is critical in better understanding of the dynamic interactions of insulin secretion, clearance and action at different phases in the progression of diabetes. The present study aimed to quantify β-cell secretory function independently of insulin sensitivity in the context of differential metabolic clearance rates of insulin (MCRI) in nonhuman primates (NHPs).

METHODS

Insulin secretion rate (ISR) was derived from deconvolution of serial C-peptide concentrations measured during a 5 stage graded glucose infusion (GGI) in 12 nondiabetic (N), 8 prediabetic or dysmetabolic (DYS) and 4 overtly diabetic (DM) cynomolgus monkeys. The characterization of the monkeys was based on the fasting glucose and insulin concentrations, glucose clearance rate measured by intravenous glucose tolerance test, and insulin resistance indices measured in separate experiments. The molar ratio of C-peptide/insulin (C/I) was used as a surrogate index of hepatic MCRI.

RESULTS

Compared to the N monkeys, the DYS with normal glycemia and hyperinsulinemia had significantly higher basal and GGI-induced elevation of insulin and C-peptide concentrations and lower C/I, however, each unit of glucose-stimulated ISR increment was not significantly different from that in the N monkeys. In contrast, the DM monkeys with β-cell failure and hyperglycemia had a depressed GGI-stimulated ISR response and elevated C/I.

CONCLUSIONS

The present data demonstrated that in addition to β-cell hypersecretion of insulin, reduced hepatic MCRI may also contribute to the development of hyperinsulinemia in the DYS monkeys. On the other hand, hyperinsulinemia may cause the saturation of hepatic insulin extraction capacity, which in turn reduced MCRI in the DYS monkeys. The differential contribution of ISR and MCRI in causing hyperinsulinemia provides a new insight into the trajectory of β-cell dysfunction in the development of diabetes. The present study was the first to use the GGI and C-peptide deconvolution method to quantify the β-cell function in NHPs.

Correlation of serum homocysteine and previous history of gestational diabetes mellitus

Background

Gestational diabetes mellitus (GDM) is a common pregnancy condition. In this study, the risk of having a history of previous GDM (pGDM) on serum homocysteine level was assessed

Methods

Biomedical parameters, serum homocysteine, Insulin, homeostatic model assessment (HOMA) in women with (n = 52) and without pGDM (n = 51) were assessed. According to their current status of Oral Glucose Tolerance Test (GTT), the participants in each group were divided into two subgroups of normal or impaired GTT.

Results

Mean serum homocysteine in normal women was 8.56 ± 3.19 vs 11.44 ± 7.34 μmol/L (p < 0.01) in women with pGDM. Two groups had significant differences in respect to serum insulin levels (8.35 ± 5.12 vs 12.48 ± 5.44, p < 0.002), and HOMA-IR (1.90 ± 1.30 vs 2.91 ± 1.30, p < 0.002). In women without pGDM, serum homocysteine in normal and impaired GTT were 7.60 ± 1.69 and 10.52 ± 3.65 μmol/L (p = 0.03), respectively, while in women with pGDM, the figures were 8.38 ± 2.52 and 14.00 ± 10.17 (p < 0.01), respectively. In multi regression analysis an association between history of GDM and homocysteine levels was presented (OR: 7.71, 95% CI: 1.67-35.42, p < 0.001).

Conclusion

A trend of elevation of homocysteine is presented in women with pGDM, that is more prominent in women with impaired GTT, and shows a significant correlation with history of GDM. Further studies with larger sample size are suggested.

The higher diabetogenic risk of tacrolimus depends on pre-existing insulin resistance. A study in obese and lean Zucker rats

Insulin resistance may interact with calcineurin inhibitors, enhancing the diabetogenic effect of tacrolimus compared with cyclosporine-A. We studied both drugs in insulin-resistant animals: obese Zucker rats (n = 45), and insulin-sensitive animals: lean Zucker rats (n = 21). During 11 days, animals received saline-buffer, cyclosporine-A (2.5 mg/kg/day) or tacrolimus (0.3 mg/kg/day). At Days 0 and 12 animals underwent intraperitoneal glucose tolerance test (0-30-60-120 min). Islet morphometry, beta-cell proliferation, apoptosis and Ins2 gene expression were analyzed. By Day 12, no lean animal had developed diabetes, while all obese animals on tacrolimus and 40% on cyclosporine-A had. In obese animals, tacrolimus reduced beta-cell proliferation and Ins2 gene expression compared with cyclosporine-A. Five days after treatment discontinuation, partial recovery was observed, with only 10% and 60% of the animals on cyclosporine and tacrolimus remaining diabetic respectively. Beta-cell proliferation increased in animals on tacrolimus while Ins2 gene expression remained unaltered. In conclusion, insulin resistance exacerbated the diabetogenic effect of tacrolimus compared with cyclosporine-A. This may be explained by greater inhibition of Ins2 gene and beta-cell proliferation by tacrolimus in the insulin resistant state. Discontinuation of the drugs may allow the recovery of the metabolic alterations.

Insulin secretion enhancing activity of roselle calyx extract in normal and streptozotocin-induced diabetic rats

Background and Objective:

Our recent study revealed the antihyperglycemic activity of an ethanolic extract of roselle calyxes (Hibiscus sabdariffa) in diabetic rats. The present study had, therefore, an objective to investigate the mechanism underlying this activity.

Materials and Methods:

Male Sprague Dawley rats were induced to be diabetes by intraperitoneal injection of 45 mg/kg streptozotocin (STZ). Normal rats as well as diabetic rats were administered with the ethanolic extract of H. sabdariffa calyxes (HS-EE) at 0.1 and 1.0 g/kg/day, respectively, for 6 weeks. Then, blood glucose and insulin levels, at basal and glucose-stimulated secretions, were measured. The pancreas was dissected to examine histologically.

Results:

HS-EE 1.0 g/kg/day significantly decreased the blood glucose level by 38 ± 12% in diabetic rats but not in normal rats. In normal rats, treatment with 1.0 g/kg HS-EE increased the basal insulin level significantly as compared with control normal rats (1.28 ± 0.25 and 0.55 ± 0.05 ng/ml, respectively). Interestingly, diabetic rats treated with 1.0 g/kg HS-EE also showed a significant increase in basal insulin level as compared with the control diabetic rats (0.30 ± 0.05 and 0.15 ± 0.01 ng/ml, respectively). Concerning microscopic histological examination, HS-EE 1.0 g/kg significantly increased the number of islets of Langerhans in both normal rats (1.2 ± 0.1 and 2.0 ± 0.1 islet number/10 low-power fields (LPF) for control and HS-EE treated group, respectively) and diabetic rats (1.0 ± 0.3 and 3.9 ± 0.6 islet number/10 LPF for control and HS-EE treated group, respectively).

Conclusion:

The antidiabetic activity of HS-EE may be partially mediated via the stimulating effect on insulin secretion.

Vildagliptin and pioglitazone in patients with impaired glucose tolerance after kidney transplantation: a randomized, placebo-controlled clinical trial

BACKGROUND

New-onset diabetes after transplantation (NODAT) is a serious complication after kidney transplantation affecting graft and patient survival. Currently, no guidelines exist for the management of renal transplant patients with impaired glucose tolerance (IGT), a risk factor for the development of NODAT and an independent predictor of death.

METHODS

In a population of 48 stable renal transplant recipients at least 6 months from time of transplantation with newly diagnosed IGT, we tested the dipeptidylpeptidase-4 inhibitor vildagliptin, the thiazolidinedione pioglitazone, or placebo for 3 months in addition to lifestyle counseling. Outcome measures were difference in change in oral glucose tolerance test between the groups and between baseline and end of study as well as change in HbA1c, serum lipids, and renal and hepatic function.

RESULTS

In both treatment groups, 2-hr plasma glucose at 3 months was significantly reduced compared with baseline (vildagliptin: -20±24 mg/dL; P=0.002 and pioglitazone: -23±29 mg/dL; P=0.004), and pioglitazone also significantly improved fasting plasma glucose (-11±14 mg/dL; P=0.003), although the primary outcome (difference in change in 2-hr plasma glucose among the three groups) did not reach statistical significance. Furthermore, HbA1c was decreased in both treatment arms (vildagliptin: -0.1%±0.3%; P=0.046 and pioglitazone: -0.2%±0.3%; P=0.029). In the placebo group, no significant changes in these parameters were observed. Only mild adverse events occurred and at a similar rate in all three groups.

CONCLUSIONS

These data demonstrate that both vildagliptin and pioglitazone are of potential benefit in patients with IGT after renal transplantation in addition to lifestyle modification.

Insulin degludec compared with insulin glargine in insulin-naïve patients with type 2 diabetes: A 26-week, randomized, controlled, Pan-Asian, treat-to-target trial

Introduction

Insulin degludec (IDeg) is an ultra‐long‐acting basal insulin with a consistent action profile of >42 h. This trial compared the efficacy and safety of IDeg with insulin glargine (IGlar) in insulin‐naïve Asian patients with type 2 diabetes.

Materials and Methods

In this multinational, 26‐week, open‐label, treat‐to‐target trial, 435 participants (202 females, 233 males; mean age 58.6 years; mean body mass index 25 kg/m²; mean glycated hemoglobin [HbA_1c] 8.5%) were randomized (2:1) to IDeg or IGlar, each administered once daily with ≥1 oral antidiabetic drug(s) (OAD).

Results

After 26 weeks, HbA_1c had decreased by 1.24 and 1.35% in the IDeg and IGlar groups, respectively (treatment difference [IDeg – IGlar] 0.11%, 95% confidence interval [CI] −0.03 to 0.24), confirming non‐inferiority. Rates of overall confirmed hypoglycemia were similar for IDeg and IGlar during the full trial period (3.0 vs 3.7 episodes/patient‐year of exposure [PYE]; rate ratio [RR] 0.82, 95% CI 0.60 to 1.11, P = 0.20), but significantly lower (by 37%) for IDeg during the maintenance period (from week 16 onward; RR 0.63, 95% CI 0.42 to 0.94, P = 0.02). No significant difference in the rate of nocturnal confirmed hypoglycemia was found between IDeg and IGlar in the full trial period (0.8 vs 1.2 episodes/PYE; RR 0.62, 95% CI 0.38 to 1.04, P = 0.07) or maintenance period (RR 0.52, 95% CI 0.27 to 1.00, P = 0.05). Adverse event rates were similar between treatments.

Conclusions

Initiating insulin therapy with IDeg in Asian patients with type 2 diabetes, inadequately controlled with OADs, provides similar improvements in long‐term glycemic control to IGlar, but at a significantly lower rate of overall confirmed hypoglycemia once stable glycemic control and insulin dosing are achieved. This trial was registered with www.clinicaltrials.gov (no. NCT01059799).

Insulin therapy for type 2 diabetes

Insulin therapy provides effective glycemic control in patients with diabetes who have deficient beta-cell function and insulin secretion. Subjects with type 2 diabetes not adequately controlled on oral agents or incretin therapies can initiate basal insulin replacement to correct fasting hyperglycemia. While all basal insulin preparations have similar efficacy in lowering fasting plasma glucose and improving A1C, the newer basal insulin analogs are associated with a lower risk of hypoglycemia than NPH insulin. Patients whose A1C levels remain above goal despite adequate basal insulin replacement need to evaluate and correct post-prandial hyperglycemia. With progressive beta-cell deficiency, rapid-acting insulin preparations can be introduced before one or more meals and titrated to achieve post-prandial glycemic control. For many patients requiring full basal/bolus insulin replacement, a strategy of fixed prandial insulin doses can yield acceptable glycemic control when compared to a more sophisticated approach utilizing carbohydrate counting and matching to insulin. Concentrated insulin preparations such as U-500 have also been of value in patients with resistant type 2 diabetes. Regardless of the type of insulin replacement used, the blood glucose lowering effects of insulin need to be carefully balanced with the increasing risk of hypoglycemia, and the weight gain associated with insulin intensification.

Comparative efficacy of exenatide versus insulin glargine on glycemic control in type 2 diabetes mellitus patients inadequately treated with metformin monotherapy

PURPOSE

Comparative efficacy of exenatide versus insulin glargine primarily on glucemic control, and secondarily on body mass index (BMI), lipid profile and blood pressure, in type 2 diabetes mellitus (T2DM) patients suboptimally treated with metformin monotherapy.

MATERIAL/METHODS

Forty-seven inadequately treated T2DM patients on metformin assigned to exenatide (n=18) or insulin glargine (n=29) for 26 weeks. Glycosylated hemoglobin (HbA1c), serum lipids, BMI, systolic and diastolic blood pressure, and adverse events, including episodes of hypoglycemia and gastrointestinal symptoms, were recorded.

RESULTS

Either treatment had a similar favorable mean reduction in HbA1c. However, more patients in exenatide group achieved HbA1c ≤ 7% at the 26th week compared with insulin glargine group (p=0.036). Insulin glargine group had significantly more episodes of hypoglycemia compared with exenatide group (p=0.039). Gastrointestinal adverse events were non-significantly higher in the exenatide group. A significantly greater BMI reduction was observed in exenatide group, whereas ΒΜΙ was not altered in insulin glargine group. Total and LDL cholesterol (p=0.012), and triglycerides (p=0.016) significantly decreased, whereas HDL cholesterol increased (p=0.021) in the exenatide group, whereas only total cholesterol decreased in insulin glargine group. Changes in systolic and diastolic blood pressure were insignificant in both groups.

CONCLUSIONS

Exenatide provided similar reduction in HbA1c, but fewer episodes of hypoglycemia, compared with insulin glargine. Exenatide had also a favorable effect on weight loss, although more gastrointestinal adverse events. Exenatide may provide a justified alternative in second line treatment of T2DM, but more trials are required to elucidate its long-term safety and cost-effectiveness.

Increase in Insulin Secretion Induced by Panax ginseng Berry Extracts Contributes to the Amelioration of Hyperglycemia in Streptozotocininduced Diabetic Mice

Panax ginseng has long been used as a traditional herbal medicine. More recently, it has received attention for its anti-diabetic and anti-obesity effects in humans and in animal models of type 2 diabetes. In the present study, we tested the hypoglycemic effects of ginseng berry extract in beta-cell-deficient mice and investigated the mechanisms involved. Red (ripe) and green (unripe) berry extracts were prepared and administered orally (100 or 200 mg/kg body weight) to streptozotocin-induced diabetic mice daily for 10 wk. The body weight was measured daily, and the nonfasting blood glucose levels were measured after 5 and 10 wk after administration. Glucose tolerance tests were performed, and the serum insulin levels were measured. The proliferation of betacells was measured in vitro. The administration of red or green ginseng berry extract significantly reduced the blood glucose levels and improved the glucose tolerance in beta-cell deficient mice, with the higher doses resulting in better effects. Glucose-stimulated insulin secretion was significantly increased in berry extract-treated mice compared with streptozotocin-induced diabetic control mice. Treatment with ginseng berry extract increased beta-cell proliferation in vitro. Both red berry and green berry extracts improved glycemic control in streptozotocin-induced diabetic mice and increased insulin secretion, possibly due to increased beta-cell proliferation. These results suggest that ginseng berry extracts might have beneficial effects on beta-cell regeneration.

Efficacy and safety of teneligliptin in combination with pioglitazone in Japanese patients with type 2 diabetes mellitus

AIM

To confirm the efficacy and safety of teneligliptin in combination with pioglitazone in Japanese patients with type 2 diabetes mellitus inadequately controlled with pioglitazone monotherapy.

MATERIALS AND METHODS

In an initial 12-week, double-blind, placebo controlled, parallel-group study, patients (n = 204) were randomized to teneligliptin 20 mg or placebo once daily added to their stable pioglitazone therapy. This was followed by a 40-week, open-label period during which all patients received teneligliptin once daily. The primary end-point was the change in hemoglobin A1c (HbA1c) from baseline to week 12.

RESULTS

Patients in the teneligliptin group showed significantly greater reductions in HbA1c compared with the placebo group at week 12 (P < 0.001). The changes in HbA1c from baseline to week 12 were -0.9 ± 0.0% (least-squares mean ± standard error) in the teneligliptin group and -0.2 ± 0.0% in the placebo group. The change in fasting plasma glucose from baseline to week 12 was greater in the teneligliptin group than in the placebo group (P < 0.001). The blood glucose lowering effects of teneligliptin were sustained throughout the 40-week open-label period. Adverse events and adverse drug reactions occurred slightly more frequently in the teneligliptin group than in the placebo group, although the incidence of hypoglycemia was low. Bodyweight was unchanged in the double-blind period, but was slightly increased in the open-label period.

CONCLUSIONS

Add-on therapy with teneligliptin was effective and generally well tolerated throughout the study period in Japanese patients with type 2 diabetes mellitus inadequately controlled with pioglitazone monotherapy. This trial was registered with ClinicalTrials.gov (no. NCT01026194).

Imaging beta-cell mass and function in situ and in vivo

Glucose-stimulated insulin secretion (GSIS) from pancreatic beta-cells is critical to the maintenance of blood glucose homeostasis in animals. Both decrease in pancreatic beta-cell mass and defects in beta-cell function contribute to the onset of diabetes, although the underlying mechanisms remain largely unknown. Molecular imaging techniques can help beta-cell study in a number of ways. High-resolution fluorescence imaging techniques provide novel insights into the fundamental mechanisms underlying GSIS in isolated beta-cells or in situ in pancreatic islets, and dynamic changes of beta-cell mass and function can be noninvasively monitored in vivo by imaging techniques such as positron emission tomography and single-photon emission computed tomography. All these techniques will contribute to the better understanding of the progression of diabetes and the search for the optimized therapeutic measures that reverse deficits in beta-cell mass and function.

Stimulation of insulin secretion by large-dose oral arginine administration in healthy adults

The effects of large-dose oral arginine administration on the secretion of insulin by islet β-cells in healthy adults were determined. Eight non-obese healthy volunteers with normal glucose tolerance participated randomly in tests with four stages (with an interval of at least 3 days): the 300 ml purified water stage (PWS), the 75 g glucose stage (GSS), the 30 g arginine stage (ARS) and the 75 g glucose with 30 g arginine stage (GAS). Venous blood samples were collected to detect the concentrations of glucose and insulin at baseline (0) and at 15, 30, 45, 60 and 120 min after drug administration. The glucose and insulin levels were steady in the PWS. The remaining three stages had similarly shaped insulin concentration-time curves, which differed from that of the PWS. The peak concentration of blood insulin and the net incremental area under the curve of blood insulin in the GSS, ARS and GAS were significantly higher compared with those in the PWS (P<0.05). In the ARS, the glucose levels remained stable; however, the net incremental area under the curve for blood insulin in the ARS was much lower compared with that in the GSS or GAS (P<0.05). Large-dose oral arginine administration may slightly stimulate insulin secretion by islet β-cells in healthy adults with normal glucose tolerance in a manner that is independent of glucose concentration.

Novel insulin sensitizer modulates nutrient sensing pathways and maintains β-cell phenotype in human islets

Major bottlenecks in the expansion of human β-cell mass are limited proliferation, loss of β-cell phenotype, and increased apoptosis. In our previous studies, activation of Wnt and mTOR signaling significantly enhanced human β-cell proliferation. However, isolated human islets displayed insulin signaling pathway resistance, due in part to chronic activation of mTOR/S6K1 signaling that results in negative feedback of the insulin signaling pathway and a loss of Akt phosphorylation and insulin content. We evaluated the effects of a new generation insulin sensitizer, MSDC-0160, on restoring insulin/IGF-1 sensitivity and insulin content in human β-cells. This novel TZD has low affinity for binding and activation of PPARγ and has insulin-sensitizing effects in mouse models of diabetes and ability to lower glucose in Phase 2 clinical trials. MSDC-0160 treatment of human islets increased AMPK activity and reduced mTOR activity. This was associated with the restoration of IGF-1-induced phosphorylation of Akt, GSK-3, and increased protein expression of Pdx1. Furthermore, MSDC-0160 in combination with IGF-1 and 8 mM glucose increased β-cell specific gene expression of insulin, pdx1, nkx6.1, and nkx2.2, and maintained insulin content without altering glucose-stimulated insulin secretion. Human islets were unable to simultaneously promote DNA synthesis and maintain the β-cell phenotype. Lithium-induced GSK-3 inhibition that promotes DNA synthesis blocked the ability of MSDC-0160 to maintain the β-cell phenotype. Conversely, MSDC-0160 prevented an increase in DNA synthesis by blocking β-catenin nuclear translocation. Due to the counteracting pathways involved in these processes, we employed a sequential ex vivo strategy to first induce human islet DNA synthesis, followed by MSDC-0160 to promote the β-cell phenotype and insulin content. This new generation PPARγ sparing insulin sensitizer may provide an initial tool for relieving inherent human islet insulin signaling pathway resistance that is necessary to preserve the β-cell phenotype during β-cell expansion for the treatment of diabetes.

Glucagon-like peptide-1 triggers protective pathways in pancreatic beta-cells exposed to glycated serum

Advanced glycation end products (AGEs) might play a pathophysiological role in the development of diabetes and its complications. AGEs negatively affect pancreatic beta-cell function and the expression of transcriptional factors regulating insulin gene. Glucagon-like peptide-1 (GLP-1), an incretin hormone that regulates glucose homeostasis, might counteract the harmful effects of AGEs on the beta cells in culture. The aim of this study was to identify the intracellular mechanisms underlying GLP-1-mediated protection from AGE-induced detrimental activities in pancreatic beta cells. HIT-T15 cells were cultured for 5 days with glycated serum (GS, consisting in a pool of AGEs), in the presence or absence of 10 nmol/L GLP-1. After evaluation of oxidative stress, we determined the expression and subcellular localization of proteins involved in maintaining redox balance and insulin gene expression, such as nuclear factor erythroid-derived 2 (Nrf2), glutathione reductase, PDX-1, and MafA. Then, we investigated proinsulin production. The results showed that GS increased oxidative stress, reduced protein expression of all investigated factors through proteasome activation, and decreased proinsulin content. Furthermore, GS reduced ability of PDX-1 and MafA to bind DNA. Coincubation with GLP-1 reversed these GS-mediated detrimental effects. In conclusion, GLP-1, protecting cells against oxidants, triggers protective intercellular pathways in HIT-T15 cells exposed to GS.

Effect of early weight loss on type 2 diabetes mellitus after 2 years of gastric banding

OBJECTIVE

Laparoscopic adjustable gastric banding (LAGB) is an established bariatric surgical procedure that produces meaningful weight loss and improvements in patients with type 2 diabetes mellitus (T2DM) and a body mass index (BMI) ≥ 30 kg/m2. This study examined the effect of LAGB on T2DM status in severely obese patients with T2DM.

METHODS

This was a 2-year interim analysis of patients with T2DM who required daily hypoglycemic medication at baseline (N = 89) in the 5-year, open-label, prospective, observational LAP-BAND AP® EXperience (APEX) trial. Type 2 diabetes mellitus status was classified as "remission," "improved," "stable," or "worse" based on physician- and patient-reported changes in T2DM control and changes in hypoglycemic medication use.

RESULTS

At baseline, 89 (22.5%) of 395 patients required daily hypoglycemic medication; 66 patients had data available after 2 years. Remission of T2DM occurred in 32 (48.5%) patients, improvement occurred in 31 (47.0%) patients, and no change occurred in 3 (4.5%) patients. Overall, 95.5% of patients experienced remission or improvement in T2DM status. Duration of T2DM in patients with remission or improvement after 2 years was 4.0 and 6.7 years, respectively (P = 0.082 between groups), and was associated with change in T2DM status (logistic regression, P = 0.069). Baseline BMI, change in BMI, and percent weight loss were not significantly different between the T2DM response groups. Percent excess weight loss was numerically, but not statistically significantly, greater in remitted (-56.1%) compared with the improved response (-42.9%) group (P = 0.134), and was correlated with change in T2DM status (logistic regression, P = 0.052). After 2 years, patients experienced remission or improvement of other obesity comorbidities. The rate of revisional surgery or explantation was 3.4%, and it was not significantly different between patients with and without T2DM (P = 0.687).

CONCLUSION

Shorter duration of T2DM and greater percent excess weight loss were associated with an increased likelihood of remission or improvement in T2DM status through LAGB after 2 years. Laparoscopic adjustable gastric banding is a potential adjunctive treatment for obese patients with T2DM.

Generating β-cells in vitro: progress towards a Holy Grail

PURPOSE OF REVIEW

Diabetes is a debilitating disease characterized by a chronic inability to normalize blood glucose levels. Transplanting cadaveric pancreata or isolated pancreatic islets can restore glucose homeostasis, but organ demand outstrips supply. Consequently, there is significant interest in alternative tissue sources. This review summarizes state-of-the-art efforts to generate scalable, functional β-cells to treat diabetes.

RECENT FINDINGS

Applying knowledge gleaned from developmental biology, human pluripotent stem cells can be treated stepwise with combinations of small molecules, developmentally relevant growth factors, and morphogens to generate pancreatic progenitor cells (PPCs) in vitro. Transplanted PPCs can then further mature in vivo into functional islet-like tissues containing all of the endocrine hormone cells present in adult islets and can reverse hyperglycemia in a diabetic animal model. Recent publications demonstrate that skin, liver, and other cell lineages may also be reprogrammed to functional β-like cells.

SUMMARY

Although generation of fully functional β-cells in vitro has not yet been achieved, possible intermediate approaches to treat diabetes include using PPCs or reprogramming adult cells to β-like cells. A cell therapy with either approach will require isolation from the host immune response. Ongoing efforts are addressing this need through the use of immune-isolation devices to avoid immunosuppressive drugs.

Microarray analysis of isolated human islet transcriptome in type 2 diabetes and the role of the ubiquitin-proteasome system in pancreatic beta cell dysfunction

To shed light on islet cell molecular phenotype in human type 2 diabetes (T2D), we studied the transcriptome of non-diabetic (ND) and T2D islets to then focus on the ubiquitin-proteasome system (UPS), the major protein degradation pathway. We assessed gene expression, amount of ubiquitinated proteins, proteasome activity, and the effects of proteasome inhibition and prolonged exposure to palmitate. Microarray analysis identified more than one thousand genes differently expressed in T2D islets, involved in many structures and functions, with consistent alterations of the UPS. Quantitative RT-PCR demonstrated downregulation of selected UPS genes in T2D islets and beta cell fractions, with greater ubiquitin accumulation and reduced proteasome activity. Chemically induced reduction of proteasome activity was associated with lower glucose-stimulated insulin secretion, which was partly reproduced by palmitate exposure. These results show the presence of many changes in islet transcriptome in T2D islets and underline the importance of the association between UPS alterations and beta cell dysfunction in human T2D.

Insulin treatment of type 2 diabetes: considerations when converting from human insulin to insulin analogs

Type 2 diabetes mellitus is a highly prevalent disease characterized by insulin resistance, hyperglycemia, and diminished pancreatic β-cell function. Conventional insulin products used to manage this disease include regular human insulin and intermediate-acting human insulin. However, due to several limitations imposed by human insulins, such as onset and duration of action that do not coincide with physiologic needs and increased risk of hypoglycemia, insulin analogs were developed. Because they more closely mimic the physiologic action of endogenous insulin, insulin analogs are associated with more effective glucose control, a lower risk of hypoglycemia, greater convenience, and, in some instances, less weight gain. Switching from human insulin to insulin analogs is easily accomplished. Several studies have demonstrated a high rate of success with patient-initiated, self-adjusted dosing algorithms compared to investigator/clinician-initiated dose adjustments. These studies and several other published guidelines on insulin analogs provide patients and clinicians with information pertaining to better treatment options and can help increase overall patient satisfaction.

Reduction of connexin36 content by ICER-1 contributes to insulin-secreting cells apoptosis induced by oxidized LDL particles

Connexin36 (Cx36), a trans-membrane protein that forms gap junctions between insulin-secreting beta-cells in the Langerhans islets, contributes to the proper control of insulin secretion and beta-cell survival. Hypercholesterolemia and pro-atherogenic low density lipoproteins (LDL) contribute to beta-cell dysfunction and apoptosis in the context of Type 2 diabetes. We investigated the impact of LDL-cholesterol on Cx36 levels in beta-cells. As compared to WT mice, the Cx36 content was reduced in islets from hypercholesterolemic ApoE-/- mice. Prolonged exposure to human native (nLDL) or oxidized LDL (oxLDL) particles decreased the expression of Cx36 in insulin secreting cell-lines and isolated rodent islets. Cx36 down-regulation was associated with overexpression of the inducible cAMP early repressor (ICER-1) and the selective disruption of ICER-1 prevented the effects of oxLDL on Cx36 expression. Oil red O staining and Plin1 expression levels suggested that oxLDL were less stored as neutral lipid droplets than nLDL in INS-1E cells. The lipid beta-oxidation inhibitor etomoxir enhanced oxLDL-induced apoptosis whereas the ceramide synthesis inhibitor myriocin partially protected INS-1E cells, suggesting that oxLDL toxicity was due to impaired metabolism of the lipids. ICER-1 and Cx36 expressions were closely correlated with oxLDL toxicity. Cx36 knock-down in INS-1E cells or knock-out in primary islets sensitized beta-cells to oxLDL-induced apoptosis. In contrast, overexpression of Cx36 partially protected INS-1E cells against apoptosis. These data demonstrate that the reduction of Cx36 content in beta-cells by oxLDL particles is mediated by ICER-1 and contributes to oxLDL-induced beta-cell apoptosis.

Stimulating β-cell regeneration by combining a GPR119 agonist with a DPP-IV inhibitor

Background

Activating G-protein coupled receptor 119 (GPR119) by its agonists can stimulate glucagon like peptide-1 (GLP-1) release. GLP-1 is rapidly degraded and inactivated by dipeptidylpeptidase-IV (DPP-IV). We studied the efficiency of combining PSN632408, a GPR119 agonist, with sitagliptin, a DPP-IV inhibitor, on β-cell regeneration in diabetic mice.

Materials & Methods

Diabetes in C57BL/6 mice was induced by streptozotocin. PSN632408 and sitagliptin alone or in combination were administered to diabetic mice for 7 weeks along with BrdU daily. Nonfasting blood glucose levels were monitored. After treatment, oral glucose tolerance test (OGTT), plasma active GLP-1 levels, β-cell mass along with α- and β-cell replication, and β-cell neogenesis were evaluated.

Results

Normoglycemia was not achieved in vehicle-treated mice. By contrast, 32% (6 of 19) of PSN632408-treated diabetic mice, 36% (5 of 14) sitagliptin-treated diabetic mice, and 59% (13 of 22) diabetic mice treated with PSN632408 and sitagliptin combination achieved normoglycemia after 7 weeks treatment. Combination therapy significantly increased plasma active GLP-1 levels, improved glucose clearance, stimulated both α- and β-cell replication, and augmented β-cell mass. Furthermore, treatment with combination therapy induced β-cell neogenesis from pancreatic duct-derived cells.

Conclusion

Our results demonstrate that combining a GPR119 agonist with a DPP-IV inhibitor may offer a novel therapeutic strategy for stimulating β-cell regeneration and reversing diabetes.

[Impact of anti-diabetic therapy based on glucagon-like peptide-1 receptor agonists on the cardiovascular risk of patients with type 2 diabetes mellitus]

Anti-diabetic drugs have, in addition to their well-known glucose lowering-effect, different effects in the rest of cardiovascular factors that are associated with diabetes mellitus. Glucagon-like peptide-1 (GLP-1) receptor agonists have recently been incorporated to the therapeutic arsenal of type 2 diabetes mellitus. The objective of this review is to summarize the available evidence on the effect of the GLP-1 receptor agonists on different cardiovascular risk factors, mediated by the effect of GLP-1 receptor agonists on the control of hyperglycaemia and the GLP-1 receptor agonists effect on other cardiovascular risk factors (weight control, blood pressure control, lipid profile and all other cardiovascular risk biomarkers). In addition, we present the emerging evidence with regards to the impact that GLP-1 receptor agonists therapy could have in the reduction of cardiovascular events and the currently ongoing studies addressing this issue.

Clinical proof-of-concept study with MSDC-0160, a prototype mTOT-modulating insulin sensitizer

It may be possible to achieve insulin sensitivity through the recently identified mitochondrial target of thiazolidinediones (mTOT), thereby avoiding peroxisome proliferator–activated receptor-γ (PPAR-γ)-dependent side effects. In this phase IIb clinical trial, 258 patients with type 2 diabetes completed a 12-week protocol with 50, 100, or 150 mg of MSDC-0160 (an mTOT modulator), 45 mg pioglitazone HCl (a PPAR-γ agonist), or a placebo. The two active treatments lowered fasting glucose levels to the same extent. The decreases in glycated hemoglobin (HbA_1c) observed with the two higher doses of MSDC-0160 were not different from those associated with pioglitazone. By contrast, fluid retention as evidenced by reduction in hematocrit, red blood cells, and total hemoglobin was 50% less in the MSDC-0160–treated groups. There was also a smaller increase in high-molecular-weight (HMW) adiponectin with MSDC-0160 than with pioglitazone (P < 0.0001), suggesting that MSDC-0160 produces less expansion of white adipose tissue. Thus, mTOT modulators may have glucose-lowering effects similar to those of pioglitazone but without the adverse effects associated with PPAR-γ agonists.

Novel views on new-onset diabetes after transplantation: development, prevention and treatment

New-onset diabetes after transplantation (NODAT) is associated with increased risk of allograft failure, cardiovascular disease and mortality, and therefore, jeopardizes the success of renal transplantation. Increased awareness of NODAT and the prediabetic states (impaired fasting glucose and impaired glucose tolerance, IGT) has fostered previous and present recommendations, based on the management of type 2 diabetes mellitus (T2DM). Unfortunately, the idea that NODAT merely resembles T2DM is potentially misleading, because the opportunity to initiate adequate anti-hyperglycaemic treatment early after transplantation might be given away for 'tailored' immunosuppression in patients who have developed NODAT or carry personal risk factors. Risk factor-independent mechanisms, however, seem to render postoperative hyperglycaemia with subsequent development of overt or 'full-blown' NODAT, the unavoidable consequence of the transplant and immunosuppressive process itself, at least in many cases. A proof of the concept that timely preventive intervention with exogenous insulin against post-transplant hyperglycaemia may decrease NODAT was recently provided by a small clinical trial, which is awaiting confirmation from a multicentre study. However, because early insulin therapy aimed at beta-cell protection seems to contrast the currently recommended, stepwise approach of 'watchful waiting' prior to pancreatic decompensation, we here aim at reviewing recent concepts regarding the development, prevention and treatment of NODAT, some of which seem to challenge the traditional view on T2DM and NODAT. In summary, we suggest a novel, risk factor-independent management approach to NODAT, which includes glycaemic monitoring and anti-hyperglycaemic treatment in virtually everybody after transplantation. This approach has widespread implications for future research and is intended to tackle NODAT and also ultimately cardiovascular disease.

Oral salmon calcitonin attenuates hyperglycaemia and preserves pancreatic beta-cell area and function in Zucker diabetic fatty rats

BACKGROUND AND PURPOSE

Oral salmon calcitonin (sCT), a dual-action amylin and calcitonin receptor agonist, improved glucose homeostasis in diet-induced obese rats. Here, we have evaluated the anti-diabetic efficacy of oral sCT using parameters of glycaemic control and beta-cell morphology in male Zucker diabetic fatty (ZDF) rats, a model of type 2 diabetes.

EXPERIMENTAL APPROACH

Male ZDF rats were treated with oral sCT (0.5, 1.0 or 2 mg·kg(-1) ) or oral vehicle twice daily from age 8 to 18 weeks. Zucker lean rats served as control group. Fasting and non-fasted blood glucose, glycosylated haemoglobin (HbA1c) and levels of pancreas and incretin hormones were determined. Oral glucose tolerance test and i.p. glucose tolerance test were compared, and beta-cell area and function were evaluated.

KEY RESULTS

Oral sCT treatment dose-dependently attenuated fasting and non-fasted hyperglycaemia during the intervention period. At the end of the study period, oral sCT treatment by dose decreased diabetic hyperglycaemia by ∼9 mM and reduced HbA1c levels by 1.7%. Furthermore, a pronounced reduction in glucose excursions was dose-dependently observed for oral sCT treatment during oral glucose tolerance test. In addition, oral sCT treatment sustained hyperinsulinaemia and attenuated hyperglucagonaemia and hypersecretion of total glucagon-like peptide-1 predominantly in the basal state. Lastly, oral sCT treatment dose-dependently improved pancreatic beta-cell function and beta-cell area at study end.

CONCLUSIONS AND IMPLICATIONS

Oral sCT attenuated diabetic hyperglycaemia in male ZDF rats by improving postprandial glycaemic control, exerting an insulinotropic and glucagonostatic action in the basal state and by preserving pancreatic beta-cell function and beta-cell area.

Saxagliptin and Metformin in Fixed Combination for the Treatment of Type 2 Diabetes in Adults

Type 2 diabetes affects millions of people worldwide and significantly contributes to morbidity and mortality of those affected by it. Current guidelines recommend individualized treatment regimens following first line metformin therapy. Saxagliptin, a dipeptidyl-peptidase 4 inhibitor, provides a secondary mechanism of action to decrease hyperglycemia when used in combination with metformin. The combination of metformin and saxagliptin has shown improvements in hemoglobin A_1c and fasting plasma glucose in greater efficacy than when either agent is used alone. Adverse effects of combination therapy are similar to when these agents are used individually, and are rated as tolerable by patient satisfaction scores. Overall, the combination use of saxagliptin in addition to metformin is an attractive option for clinicians to use in the treatment of type 2 diabetes.

Evaluating insulin secretagogues in a humanized mouse model with functional human islets

OBJECTIVE

To develop a rapid, easy and clinically relevant in vivo model to evaluate novel insulin secretagogues on human islets, we investigated the effect of insulin secretagogues on functional human islets in a humanized mouse model.

MATERIALS/METHODS

Human islets were transplanted under the kidney capsule of streptozotocin (STZ)-induced diabetic mice with immunodeficiency. Human islet graft function was monitored by measuring non-fasting blood glucose levels. After diabetes was reversed, human islet transplanted mice were characterized physiologically by oral glucose tolerance and pharmacologically with clinically proven insulin secretagogues, glucagon-like peptide-1 (GLP-1), exenatide, glyburide, nateglinide and sitagliptin. Additionally, G protein-coupled receptor 40 (GPR40) agonists were evaluated in this model.

RESULTS

Long-term human islet graft survival could be achieved in immunodeficient mice. Oral glucose challenge in human islet transplanted mice resulted in an immediate incremental increase of plasma human C-peptide, while the plasma mouse C-peptide was undetectable. Treatments with GLP-1, exenatide, glyburide, nateglinide and sitagliptin effectively increased plasma human C-peptide levels and improved postprandial glucose concentrations. GPR40 agonists also stimulated human C-peptide secretion and significantly improved postprandial glucose in the human islet transplanted mice.

CONCLUSIONS

Our studies indicate that a humanized mouse model with human islet grafts could mimic the in vivo characteristics of human islets and could be a powerful tool for the evaluation of novel insulin secretagogues or other therapeutic agents that directly and/or indirectly target human β cells.

Short duration of diabetes and disuse of sulfonylurea have any association with insulin cessation of the patients with type 2 diabetes in a clinical setting in Japan (JDDM 30)

Insulin therapy is often required to achieve good glycemic control for the patients with type 2 diabetes mellitus (T2DM), while protraction of glycemic control without insulin therapy may be preferable for patients. To determine the characteristics of and therapeutic regimen in outpatients with T2DM who were able to stop insulin therapy with satisfactory glycemic control in a real clinical practice setting in Japan by a case-control study. The present study was performed on 928 patients with T2DM who started insulin therapy in 2007. Data regarding age, sex, body mass index, duration of diabetes, HbA1c, postprandial plasma glucose, plasma fasting C-peptide immunoreactivity and treatment modality were compared between patients who were able to stop insulin therapy and those who continued with insulin. Of the 928 patients, 37 had stopped insulin therapy within 1 year. In the patients who stopped insulin therapy, the duration of diabetes was significantly shorter and the daily insulin dosage at initiation and the prevalence of sulfonylurea pretreatment significantly lower compared with patients who continued on insulin. In conclusion, almost 4% of T2DM patients were able to stop insulin therapy with satisfactory glycemic control in a real clinical practice setting in Japan. Shorter duration of diabetes and disuse of sulfonylureas prior to insulin may associate with stopping insulin therapy as a near-normoglycemic remission in outpatients with T2DM in Japan.

Comparison of a multiple daily insulin injection regimen (glargine or detemir once daily plus prandial insulin aspart) and continuous subcutaneous insulin infusion (aspart) in short-term intensive insulin therapy for poorly controlled type 2 diabetes patients

Aims. To examine the potential differences between multiple daily injection (MDI) regimens based on new long-acting insulin analogues (glargine or detemir) plus prandial insulin aspart and continuous subcutaneous insulin aspart infusion (CSII) in patients with poorly controlled type 2 diabetes. Methods. Patients (n = 119) with poorly controlled type 2 diabetes of a duration exceeding five years were randomly assigned into three groups: Group A treated with CSII using insulin aspart; Group B treated with glargine-based MDI and Group C treated with detemir-based MDI. Results. Good glycemic control was achieved by patients in Group A in a significantly shorter duration than patients in Groups B and C. Total daily insulin, basal insulin dose and dose per kg body weight in Group A were significantly less than those in Groups B and C. Daily blood glucose fluctuation in Group A was significantly less than that in Groups B and C. There were no differences between Groups B and C. Conclusions. Aspart-based CSII may achieve good blood glucose control with less insulin doses over a shorter period compared with glargine or detemir-based MDI. No differences between glargine- and detemir-based MDI were detected in poorly controlled subjects with type 2 diabetes.

Incretin-based Therapies for Type 2 Diabetes

There is a growing interest in developing therapeutic strategies for type 2 diabetes based on the actions of the hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). These hormones are the major incretins released from the intestine in response to nutrient ingestion, and they stimulate insulin secretion in a glucosedependent manner. Both peptides are degraded by the enzyme dipeptidyl peptidase-4 (DPP-4), thus terminating their actions. Studies in animal models of diabetes have shown that the incretins also exert a number of additional actions that improve glucose disposal. GLP-1 reduces food intake and gastric emptying, as well as inhibiting glucagon secretion. Injectable formulations of DPP-4-resistant GLP-1-related peptides (incretin mimetics) that are now in clinical use (exenatide) or undergoing trials (e.g. liraglutide) have been shown to reduce fasting and postprandial glucose and glycosylated hemoglobin (A1C) levels and induce weight loss. Oral administration of DPP-4 inhibitors potentiates the actions of incretins released during a meal. Clinical trials have demonstrated that DPP-4 inhibitors are weight-neutral drugs that also effectively reduce plasma glucose and A1C levels. One inhibitor, sitagliptin, is now available in Canada and the United States, and another, vildagliptin, has recently been approved by the European Union. Other inhibitors are under development. Preclinical studies indicate that treatment with incretin mimetics or DPP-4 inhibitors also preserves beta cell mass by exerting mitogenetic and prosurvival effects. It is not known whether similar effects occur in humans.

Effect of anti-IL-1β antibody (canakinumab) on insulin secretion rates in impaired glucose tolerance or type 2 diabetes: results of a randomized, placebo-controlled trial

AIMS

Evaluate anti-interleukin-1β (IL-1β) antibody, canakinumab, in patients with type 2 diabetes and impaired glucose tolerance (IGT) in whom hyperglycaemia may trigger IL-1β-associated inflammation leading to suppressed insulin secretion and β-cell dysfunction.

METHODS

This 4-week, parallel-group study randomized 190 patients with type 2 diabetes 2 : 1, canakinumab versus placebo, into the following treatment arms: metformin monotherapy, metformin + sulfonylurea, metformin + sulfonylurea + thiazolidinedione or insulin ± metformin. IGT population (n = 54) was randomized 1 : 1, canakinumab versus placebo. Primary efficacy assessment was change from baseline in insulin secretion rate (ISR) relative to glucose 0-2 h.

RESULTS

Mean changes from baseline to week 4 in ISR relative to glucose at 0-2 h or other time points were not statistically significant for canakinumab versus placebo across groups. ISR (relative to glucose) at 0-0.5 h (first-phase insulin secretion) numerically favoured canakinumab versus placebo in insulin-treated patients {difference in mean change from baseline [point estimate (PE)] 3.81 pmol/min/m(2)/mmol/l; p = 0.0525} and in the IGT group (PE 3.92 pmol/min/m(2)/mmol/l; p = 0.1729). Mean change from baseline in fasting plasma glucose favoured canakinumab in the type 2 diabetes/metformin group and the IGT group; however, differences were not statistically significant. Mean change from baseline in peak insulin level and insulin AUC 0-4 h were statistically significantly higher in the canakinumab group in IGT patients. Canakinumab was well tolerated and consistent with known safety experience.

CONCLUSIONS

The trend towards improving ISR relative to glucose 0-0.5 h in patients treated with insulin supports the hypothesis that insulin secretion can be improved by blocking IL-1β.

Leptin therapy, insulin sensitivity, and glucose homeostasis

Glucose homeostasis is closely regulated not only by insulin, but also by leptin. Both hormones act centrally, regulating food intake and adiposity in humans. Leptin has several effects on the glucose-insulin homeostasis, some of which are independent of body weight and adiposity. Those effects of leptin are determined centrally in the hypothalamus and peripherally in the pancreas, muscles and liver. Leptin has beneficial effects on the glucose-insulin metabolism, by decreasing glycemia, insulinemia and insulin resistance. The understanding of the effects of leptin on the glucose-insulin homeostasis will lead to the development of leptin-based therapies against diabetes and other insulin resistance syndromes. In these review, we summarize the interactions between leptin and insulin, and their effects on the glucose metabolism.

The molecular mechanisms of pancreatic β-cell glucotoxicity: recent findings and future research directions

It is well established that regular physiological stimulation by glucose plays a crucial role in the maintenance of the β-cell differentiated phenotype. In contrast, prolonged or repeated exposure to elevated glucose concentrations both in vitro and in vivo exerts deleterious or toxic effects on the β-cell phenotype, a concept termed as glucotoxicity. Evidence indicates that the latter may greatly contribute to the pathogenesis of type 2 diabetes. Through the activation of several mechanisms and signaling pathways, high glucose levels exert deleterious effects on β-cell function and survival and thereby, lead to the worsening of the disease over time. While the role of high glucose-induced β-cell overstimulation, oxidative stress, excessive Unfolded Protein Response (UPR) activation, and loss of differentiation in the alteration of the β-cell phenotype is well ascertained, at least in vitro and in animal models of type 2 diabetes, the role of other mechanisms such as inflammation, O-GlcNacylation, PKC activation, and amyloidogenesis requires further confirmation. On the other hand, protein glycation is an emerging mechanism that may play an important role in the glucotoxic deterioration of the β-cell phenotype. Finally, our recent evidence suggests that hypoxia may also be a new mechanism of β-cell glucotoxicity. Deciphering these molecular mechanisms of β-cell glucotoxicity is a mandatory first step toward the development of therapeutic strategies to protect β-cells and improve the functional β-cell mass in type 2 diabetes.