beta-cell failure in diabetes and preservation by clinical treatment

Interaction of herbal compounds with biological targets: a case study with berberine

Berberine is one of the main alkaloids found in the Chinese herb Huang lian (Rhizoma Coptidis), which has been reported to have multiple pharmacological activities. This study aimed to analyze the molecular targets of berberine based on literature data followed by a pathway analysis using the PANTHER program. PANTHER analysis of berberine targets showed that the most classes of molecular functions include receptor binding, kinase activity, protein binding, transcription activity, DNA binding, and kinase regulator activity. Based on the biological process classification of in vitro berberine targets, those targets related to signal transduction, intracellular signalling cascade, cell surface receptor-linked signal transduction, cell motion, cell cycle control, immunity system process, and protein metabolic process are most frequently involved. In addition, berberine was found to interact with a mixture of biological pathways, such as Alzheimer's disease-presenilin and -secretase pathways, angiogenesis, apoptosis signalling pathway, FAS signalling pathway, Hungtington disease, inflammation mediated by chemokine and cytokine signalling pathways, interleukin signalling pathway, and p53 pathways. We also explored the possible mechanism of action for the anti-diabetic effect of berberine. Further studies are warranted to elucidate the mechanisms of action of berberine using systems biology approach.

Grape seed procyanidin extract modulates proliferation and apoptosis of pancreatic beta-cells

Grape seed procyanidin extract (GSPE) modulates glucose homeostasis and insulinemia in several animal models. Under pathological conditions, insulin levels are dependent on pancreatic beta-cell functionality, as well as on the beta-cell mass expansion or apoptosis in the pancreas. In this study, we analysed the effects of GSPE on modulating apoptosis and proliferation in beta-cells. We tested the effects of GSPE in the INS-1E pancreatic beta-cell line, either under basal or altered conditions with high glucose, insulin or palmitate levels. GSPE enhanced the pro-apoptotic effect of high glucose and showed clear antiproliferative effects under high glucose, insulin and palmitate conditions. These antiproliferative effects are likely due to high molecular weight compounds contained in the extract. GSPE also modulated pro- and anti-apoptotic markers in the pancreas of rats fed a cafeteria diet, with the effect depending on the dose of GSPE and duration of treatment. Thus, GSPE is able to modulate apoptosis and proliferation of beta-cells under altered, but not basal, conditions.

Future detection and monitoring of diabetes may entail analysis of both β-cell function and volume: how markers of β-cell loss may assist

Disease heterogeneity is as major issue in Type II Diabetes Mellitus (T2DM), and this patient inter-variability might not be sufficiently reflected by measurements of glycated haemoglobin (HbA1c).Β-cell dysfunction and β-cell death are initiating factors in development of T2DM. In fact, β-cells are known vanish prior to the development of T2DM, and autopsy of overt T2DM patients have shown a 60% reduction in β-cell mass.As the decline in β-cell function and mass have been proven to be pathological traits in T2DM, methods for evaluating β-cell loss is becoming of more interest. However, evaluation of β-cell death or loss is currently invasive and unattainable for the vast majority of diabetes patients. Serological markers, reflecting β-cell loss would be advantageous to detect and monitor progression of T2DM. Biomarkers with such capacities could be neo-epitopes of proteins with high β-cell specificity containing post translational modifications. Such tools may segregate T2DM patients into more appropriate treatment groups, based on their β-cell status, which is currently not possible. Presently individuals presenting with adequately elevated levels of both insulin and glucose are classified as T2DM patients, while an important subdivision of those is pending, namely those patients with sufficient β-cell capacity and those without. This may warrant two very different treatment options and patient care paths.Serological biomarkers reflecting β-cell health status may also assist development of new drugs for T2DM and aid physicians in better characterization of individual patients and tailor individual treatments and patient care protocols.

Short-term intensified insulin treatment in type 2 diabetes: long-term effects on β-cell function

The natural history of type 2 diabetes (T2DM) is characterized by progressive deterioration of pancreatic β-cell function, leading to worsening glycemia over time. As current antidiabetic therapies have not yet been shown to profoundly alter this natural history, many patients ultimately will require exogenous insulin therapy to obtain adequate glycemic control. Interestingly, the temporary use of short-term intensive insulin therapy early in the course of T2DM has recently emerged as a therapeutic option that may offer favourable long-term effects on β-cell function. Indeed, after receiving this treatment, many patients will experience sustained euglycemia without requiring any antidiabetic therapy. This apparent 'remission' of diabetes is likely secondary to improved β-cell function and can last for more than a year, although it is not sustained and hyperglycemia eventually will return. Nevertheless, owing to its effects on β-cell function, short-term intensive insulin therapy holds promise as a means for modifying the natural history of T2DM and warrants further study in this context. In this report, we will review the rationale and evidence underlying this interesting therapeutic option, and its implications for both clinical research and the management of patients with T2DM.

Effects of a 6-Month Exenatide Therapy on HbA1c and Weight in Korean Patients with Type 2 Diabetes: A Retrospective Cohort Study

BACKGROUND

While many studies have shown the good efficacy and safety of exenatide in patients with diabetes, limited information is available about exenatide in clinical practice in Korean populations. Therefore, this retrospective cohort study was designed to analyze the effects of exenatide on blood glucose level and body weight in Korean patients with type 2 diabetes mellitus.

METHODS

We reviewed the records of the patients with diabetes who visited Seoul St. Mary's Hospital and for whom exenatide was prescribed from June 2009 to October 2011. After excluding subjects based on their race/ethnicity, medical history, whether or not they changed more than 2 kinds of oral hypoglycemic agents with exenatide treatment, loss to follow-up, or whether they stopped exenatide therapy within 6 months, a total of 52 subjects were included in the final analysis.

RESULTS

The mean glycated hemoglobin (HbA1c) level and weight remarkably decreased from 8.5±1.7% to 6.7±1.0% (P<0.001) and from 82.3±15.8 kg to 78.6±16.3 kg (P<0.001), respectively. The multiple regression analysis indicated that the reduction in HbA1c level was significantly associated with a shorter duration of diabetes, a higher baseline HbA1c level, and greater weight reduction, whereas weight loss had no significant correlation with other factors. No severe adverse events were observed.

CONCLUSION

These results suggest that a 6-month exenatide injection therapy significantly improved patients' HbA1c levels and body weights without causing serious adverse effects in Korean patients with type 2 diabetes.

DPP4 inhibitor vildagliptin preserves β-cell mass through amelioration of endoplasmic reticulum stress in C/EBPB transgenic mice

The development of type 2 diabetes is accompanied by a progressive decline in β-cell mass and function. Vildagliptin, a dipeptidyl peptidase 4 inhibitor, is representative of a new class of antidiabetic agents that act through increasing the expression of glucagon-like peptide-1. The protective effect of this agent on β cells was studied in diabetic mice. Diabetic pancreatic β cell-specific C/EBPB transgenic (TG) mice exhibit decreased β-cell mass associated with increased apoptosis, decreased proliferation, and aggravated endoplasmic reticulum (ER) stress. Vildagliptin was orally administered to the TG mice for a period of 24 weeks, and the protective effects of this agent on β cells were examined, along with the potential molecular mechanism of protection. Vildagliptin ameliorated hyperglycemia in TG mice by increasing the serum concentration of insulin and decreasing the serum concentration of glucagon. This agent also markedly increased β-cell mass, improved aggravated ER stress, and restored attenuated insulin/IGF1 signaling. A decrease in pancreatic and duodenal homeobox 1 expression was also observed in β cells isolated from our mouse model, but this was also restored by vildagliptin treatment. The expression of C/EBPB protein, but not mRNA, was unexpectedly downregulated in vildagliptin-treated TG mice and in exenatide-treated MIN6 cells. Activation of the GLP1 pathway induced proteasome-dependent C/EBPB degradation in β cells as the proteasome inhibitor MG132 restored the downregulation of C/EBPB protein by exenatide. Vildagliptin elicits protective effects on pancreatic β cells, possibly through C/EBPB degradation, and has potential for preventing the progression of type 2 diabetes.

High glucose predisposes gene expression and ERK phosphorylation to apoptosis and impaired glucose-stimulated insulin secretion via the cytoskeleton

Chronic high glucose (HG) inflicts glucotoxicity on vulnerable cell types such as pancreatic β cells and contributes to insulin resistance and impaired insulin secretion in diabetic patients. To identify HG-induced cellular aberrations that are candidate mediators of glucotoxicity in pancreatic β cells, we analyzed gene expression in ERoSHK6, a mouse insulin-secreting cell line after chronic HG exposure (six-day exposure to 33.3 mM glucose). Chronic HG exposure which reduced glucose-stimulated insulin secretion (GSIS) increased transcript levels of 185 genes that clustered primarily in 5 processes namely cellular growth and proliferation; cell death; cellular assembly and organization; cell morphology; and cell-to-cell signaling and interaction. The former two were validated by increased apoptosis of ERoSHK6 cells after chronic HG exposure and reaffirmed the vulnerability of β cells to glucotoxicity. The three remaining processes were partially substantiated by changes in cellular morphology and structure, and instigated an investigation of the cytoskeleton and cell-cell adhesion. These studies revealed a depolymerized actin cytoskeleton that lacked actin stress fibers anchored at vinculin-containing focal adhesion sites as well as loss of E-cadherin-mediated cell-cell adherence after exposure to chronic HG, and were concomitant with constitutive ERK1/2 phosphorylation that was refractory to serum and glucose deprivation. Although inhibition of ERK phosphorylation by PD98059 promoted actin polymerization, it increased apoptosis and GSIS impairment. These findings suggest that ERK phosphorylation is a proximate regulator of cellular processes targeted by chronic HG-induced gene expression and that dynamic actin polymerization and depolymerization is important in β cell survival and function. Therefore, chronic HG alters gene expression and signal transduction to predispose the cytoskeleton towards apoptosis and GSIS impairment.

In vivo screening for secreted proteins that modulate glucose handling identifies interleukin-6 family members as potent hypoglycemic agents

Diabetes is a disease of abnormal glucose homeostasis characterized by chronic hyperglycemia and a broad array of consequent organ damage. Because normal glucose homeostasis is maintained by a complex interaction between behavior (feeding and physical activity) and metabolic activity that is modulated by inter-organ signaling through secreted factors, disease modeling in vitro is necessarily limited. In contrast, in vivo studies allow complex metabolic phenotypes to be studied but present a barrier to high throughput studies. Here we present the development of a novel in vivo screening platform that addresses this primary limitation of in vivo experimentation. Our platform leverages the large secretory capacity of the liver and the hepatocyte transfection technique of hydrodynamic tail vein injection to achieve supraphysiologic blood levels of secreted proteins. To date, the utility of hydrodynamic transfection has been limited by the deleterious impact of the variable transfection efficiency inherent to this technique. We overcome this constraint by co-transfection of a secreted luciferase cDNA whose product can be easily monitored in the blood of a living animal and used as a surrogate marker for transfection efficiency and gene expression levels. To demonstrate the utility of our strategy, we screened 248 secreted proteins for the ability to enhance glucose tolerance. Surprisingly, interleukin-6 and several of its family members but not other well-recognized insulin sensitizing agents were identified as potent hypoglycemic factors. We propose this experimental system as a powerful and flexible in vivo screening platform for identifying genes that modulate complex behavioral and metabolic phenotypes.

Synthesis and structure-activity relationship of fused-pyrimidine derivatives as a series of novel GPR119 agonists

A series of fused-pyrimidine derivatives have been discovered as potent and orally active GPR119 agonists. A combination of the fused-pyrimidine structure and 4-chloro-2,5-difluorophenyl group provided the 5,7-dihydrothieno[3,4-d]pyrimidine 6,6-dioxide derivative 14a as a highly potent GPR119 agonist. Further optimization of the amino group at the 4-position in the pyrimidine ring led to the identification of 2-{1-[2-(4-chloro-2,5-difluorophenyl)-6,6-dioxido-5,7-dihydrothieno[3,4-d]pyrimidin-4-yl]piperidin-4-yl}acetamide (16b) as an advanced analog. Compound 16b was found to have extremely potent agonistic activity and improved glucose tolerance at 0.1 mg/kg po in mice. We consider compound 16b and its analogs to have clear utility in exploring the practicality of GPR119 agonists as potential therapeutic agents for the treatment of type 2 diabetes mellitus.

Increased 1,5-anhydroglucitol predicts glycemic remission in patients with newly diagnosed type 2 diabetes treated with short-term intensive insulin therapy

BACKGROUND

Short-term intensive insulin therapy has been shown to induce long-term glycemic remission in patients with newly diagnosed type 2 diabetes. However, predictors of remission are still uncertain. This study was conducted to evaluate whether changes of 1,5-anhydroglucitol (1,5AG) and fructosamine (FA) could be a predictor of remission.

SUBJECTS AND METHODS

Newly diagnosed drug-naive patients with type 2 diabetes (n = 64) were enrolled. After baseline assessments, continuous subcutaneous insulin infusion (CSII) was administered in all patients until euglycemia was achieved and maintained for another 2 weeks. Patients were subsequently followed monthly for 3 months. 1,5AG and FA were measured before and after therapy and at 1-month follow-up.

RESULTS

After CSII, A1C and FA decreased from baseline, whereas 1,5AG increased. 1,5AG was higher at 1-month follow-up (11.5 ± 4.1 vs. 6.7 ± 2.8 mg/L, P<0.001), whereas FA was lower (273.1 ± 56.1 vs. 316.2 ± 39.3 μmol/L, P = 0.021) in the remission group. Stepwise logistic regression analysis showed that 1,5AG at 1-month follow-up rather than FA was an independent predictor of remission after adjusting for other confounders (odds ratio 1.56, 95% confidence interval [CI] 1.15-2.12, P = 0.004). The area under the curve of the receiver operating characteristic curve analysis was 0.85 (95% CI 0.75-0.96, P<0.001). The optimal cutoff point for 1,5AG at 1-month follow-up was 8.9 mg/L (specificity, 83.3%; sensitivity, 78.6%).

CONCLUSIONS

Improvement of 1,5AG predicts maintenance of glycemic remission after intensive insulin therapy in patients with newly diagnosed type 2 diabetes.

Improvement in β-cell function after diet-induced weight loss is associated with decrease in pancreatic polypeptide in subjects with type 2 diabetes

OBJECTIVE

The aim of our study was to evaluate the effect of a lifestyle intervention program on β-cell function and to explore the role of gastrointestinal peptides in subjects with T2D.

METHODS

Subjects with T2D (n=74) received 24 weeks of intervention: 12 weeks of slimming diet (-500 kcal/day) and the subsequent 12 weeks of diet were combined with aerobic exercise. All subjects were examined at weeks 0, 12 and 24. β-cell function was assessed during standard meal tests. Insulin secretory rate (ISR) was calculated by C-peptide deconvolution, and β-cell function was quantified with a mathematical model. Plasma concentrations of gastrointestinal peptides were measured in a fasting state and during hyperinsulinemia induced by hyperinsulinemic isoglycemic clamp.

RESULTS

Mean weight loss was 5.03±4.38 kg (p<0.001) in weeks 0-12. Weight did not change significantly in weeks 12-24. Both insulin secretion at the reference level and glucose sensitivity increased in weeks 0-12 (by 33%±54% and by 26%±53%, respectively, p<0.001) and remained unchanged in weeks 12-24. Both fasting and hyperinsulinemic plasma concentrations of pancreatic polypeptide (PP) decreased in weeks 0-12 (p<0.05 for both) and did not change significantly in weeks 12-24. Changes in insulin secretion at the reference level correlated negatively with plasma concentrations of PP during hyperinsulinemia (r=-0.36; p<0.001). Changes in glucose sensitivity correlated negatively with changes in plasma concentrations of PP, both in fasting and during hyperinsulinemia (r=-0.2; p=0.01 for both). The correlations remained significant after adjustment for changes in body-mass-index.

CONCLUSIONS

After diet-induced weight loss, β-cell function improved in T2D subjects and remained unchanged after the addition of exercise. We demonstrate for the first time that these changes are associated with a decrease in PP secretion.

Peptide-based delivery to bone

Peptides are attractive as novel therapeutic reagents, since they are flexible in adopting and mimicking the local structural features of proteins. Versatile capabilities to perform organic synthetic manipulations are another unique feature of peptides compared to protein-based medicines, such as antibodies. On the other hand, a disadvantage of using a peptide for a therapeutic purpose is its low stability and/or high level of aggregation. During the past two decades, numerous peptides were developed for the treatment of bone diseases, and some peptides have already been used for local applications to repair bone defects in the clinic. However, very few peptides have the ability to form bone themselves. We herein summarize the effects of the therapeutic peptides on bone loss and/or local bone defects, including the results from basic studies. We also herein describe some possible methods for overcoming the obstacles associated with using therapeutic peptide candidates.

Effect of exposure to non-esterified fatty acid on progressive deterioration of insulin secretion in patients with Type 2 diabetes: a long-term follow-up study

AIM

The aim of the study was to determine whether fasting serum non-esterified fatty acid (NEFA) could be associated with long-term progressive deterioration of insulin secretion in patients with Type 2 diabetes.

METHODS

Seventy-seven Japanese patients with Type 2 diabetes (mean BMI 23.3 kg/m(2) ) were followed for 10 years. We measured fasting C-peptide level every 1-2 years. By using the slope of regression line between fasting C-peptide level and duration, we calculated its individual annual decline as an index of insulin secretion. During the follow-up periods of C-peptide, the patients were evaluated for fasting serum non-esterified fatty acid, LDL cholesterol, HDL cholesterol and HbA(1c) levels for the last 8 years. We excluded patients who had renal dysfunction or anti-insulin antibodies from among the insulin-treated patients. Association between the individual annual decline of fasting C-peptide level and related factors were evaluated.

RESULTS

The mean individual annual decline of fasting serum C-peptide level was -0.013 ± 0.027 nmol/l/year. Fasting serum non-esterified fatty acid level had no significant difference between the first and the last 2 years of the 8-year observation period of non-esterified fatty acid. Using multiple regression analysis, mean fasting serum non-esterified fatty acid level was associated with the individual annual decline of fasting serum C-peptide level (standardized regression coefficient -0.358, P=0.0056), although other related factors, including HbA(1c) level, were not associated.

CONCLUSIONS

Mean fasting serum non-esterified fatty acid level during an 8-year observation was independently associated with long-term progressive deterioration of insulin secretion in Japanese patients with Type 2 diabetes.

Bariatric surgery for type 2 diabetes

Bariatric surgery provides substantial, sustained weight loss and major improvements in glycaemic control in severely obese individuals with type 2 diabetes. However, uptake of surgery in eligible patients is poor, and the barriers are difficult to surmount. We examine the indications for and efficacy and safety of conventional bariatric surgical procedures and their effect on glycaemic control in type 2 diabetes. How surgical gastrointestinal interventions achieve these changes is of great research interest, and is evolving rapidly. Old classifications about restriction and malabsorption are inadequate, and we explore understanding of putative mechanisms. Some bariatric procedures improve glycaemic control in people with diabetes beyond that expected for weight loss, and understanding this additional effect could provide insights into the pathogenesis of type 2 diabetes and assist in the development of new procedures, devices, and drugs both for obese and non-obese patients.

Transaminase levels in the upper normal range are associated with oral hypoglycemic drug therapy failure in patients with type 2 diabetes

Incident diabetes and the worsening of diabetes have recently been linked to hepatic steatosis. Aim of our study was to determine whether oral hypoglycemic agent failure is associated with higher transaminase levels (valid measure of liver steatosis). We selected 200 patients, attenders (3 consecutive annual evaluations) in our clinic, with type 2 diabetes among which 100 with oral hypoglycemic agents failure and 100 who were still responsive to oral therapy. Failure to therapy was defined as glycated hemoglobin >7.5% despite maximal-dose oral therapy. We analyzed patient histories and laboratory data. Compared with oral-therapy-responsive patients, those with failure had a significantly higher level mostly of alanine aminotransferase at the time of therapy failure and 2 years before. They were more likely to have had symptoms of hyperglycemia at the time of diabetes diagnosis. Regression analysis indicated that each 5-unit increase in transaminase levels independently increased the risk for oral hypoglycemic agents failure by 1.70. Higher liver transaminase levels, especially in patients who had symptomatic hyperglycemia at diabetes diagnosis, associate with oral hypoglycemic agent failure. The possible pathogenetic link between transaminase and declining islet function might consist of insulin resistance and increased circulating fatty acid levels, in turn causing liver steatosis and beta-cell dysfunction.

β-cell preservation and regeneration for diabetes treatment: where are we now?

Over the last decade, our knowledge of β-cell biology has expanded with the use of new scientific techniques and strategies. Growth factors, hormones and small molecules have been shown to enhance β-cell proliferation and function. Stem cell technology and research into the developmental biology of the pancreas have yielded new methods for in vivo and in vitro regeneration of β cells from stem cells and endogenous progenitors as well as transdifferentiation of non-β cells. Novel pharmacological approaches have been developed to preserve and enhance β-cell function. Strategies to increase expression of insulin gene transcription factors in dysfunctional and immature β cells have ameliorated these impairments. Hence, we suggest that strategies to minimize β-cell loss and to increase their function and regeneration will ultimately lead to therapy for both Type 1 and 2 diabetes.

Obesity and type 2 diabetes: which patients are at risk?

An estimated 72.5 million American adults are obese, and the growing US obesity epidemic is responsible for substantial increase in morbidity and mortality, as well as increased health care costs. Obesity results from a combination of personal and societal factors, but is often viewed as a character flaw rather than a medical condition. This leads to stigma and discrimination towards obese individuals and decreases the likelihood of effective intervention. Conditions related to obesity are increasingly common, such as metabolic syndrome, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), all of which indicate high risk for type 2 diabetes (T2DM). This paper reviews the progression from obesity to diabetes, identifying physiological changes that occur along this path as well as opportunities for patient identification and disease prevention. Patients with prediabetes (defined as having IFG, IGT or both) and/or metabolic syndrome require interventions designed to preserve insulin sensitivity and β-cell function, both of which start to deteriorate prior to T2DM diagnosis. Lifestyle modification, including both healthy eating choices and increased physical activity, is essential for weight management and diabetes prevention. Although sustained weight loss is often considered by patients and physicians as being impossible to achieve, effective interventions do exist. Specifically, the Diabetes Prevention Program (DPP) and programs modelled along its parameters have shown repeated successes, even with long-term maintenance. Recent setbacks in the development of medications for weight loss further stress the importance of lifestyle management. By viewing obesity as a metabolic disorder rather than a personal weakness, we can work with patients to address this increasingly prevalent condition and improve long-term health outcomes.

Do obese children with diabetic ketoacidosis have type 1 or type 2 diabetes?

OBJECTIVE

Many obese children with unprovoked diabetic ketoacidosis (DKA) display clinical features of type 2 diabetes during follow up. We describe the clinical presentation, autoimmune markers and the long-term course of obese and lean children with DKA.

RESEARCH DESIGN AND METHODS

We reviewed the medical records on the initial acute hospitalization and outpatient follow-up care of 21 newly diagnosed obese and 20 lean children with unprovoked DKA at Emory University affiliated children's hospitals between 1/2003 and 12/2006.

RESULTS

Obese children with DKA were older and predominantly male, had acanthosis nigricans, and had lower prevalence of autoantibodies to islet cells and glutamic acid decarboxylase than lean children. Half of the obese, but none of the lean children with DKA achieve near-normoglycemia remission and discontinued insulin therapy during follow-up. Time to achieve remission was 2.2±2.3 months. There were no differences on clinical presentation between obese children who achieved near-normoglycemia remission versus those who did not. The addition of metformin to insulin therapy shortly after resolution of DKA resulted in lower hemoglobin A1c (HbA1c) levels, higher rates of near-normoglycemia remission, and lower frequency of DKA recurrence. Near-normoglycemia remission, however, was of short duration and the majority of obese patients required reinstitution of insulin treatment within 15 months of follow-up.

CONCLUSION

In contrast to lean children with DKA, many obese children with unprovoked DKA display clinical and immunologic features of type 2 diabetes during follow-up. The addition of metformin to insulin therapy shortly after resolution of DKA improves glycemic control, facilitates achieving near-normoglycemia remission and prevents DKA recurrence in obese children with DKA.

Some cannabinoid receptor ligands and their distomers are direct-acting openers of SUR1 K(ATP) channels

Here, we examined the chronic effects of two cannabinoid receptor-1 (CB1) inverse agonists, rimonabant and ibipinabant, in hyperinsulinemic Zucker rats to determine their chronic effects on insulinemia. Rimonabant and ibipinabant (10 mg·kg⁻¹·day⁻¹) elicited body weight-independent improvements in insulinemia and glycemia during 10 wk of chronic treatment. To elucidate the mechanism of insulin lowering, acute in vivo and in vitro studies were then performed. Surprisingly, chronic treatment was not required for insulin lowering. In acute in vivo and in vitro studies, the CB1 inverse agonists exhibited acute K channel opener (KCO; e.g., diazoxide and NN414)-like effects on glucose tolerance and glucose-stimulated insulin secretion (GSIS) with approximately fivefold better potency than diazoxide. Followup studies implied that these effects were inconsistent with a CB1-mediated mechanism. Thus effects of several CB1 agonists, inverse agonists, and distomers during GTTs or GSIS studies using perifused rat islets were unpredictable from their known CB1 activities. In vivo rimonabant and ibipinabant caused glucose intolerance in CB1 but not SUR1-KO mice. Electrophysiological studies indicated that, compared with diazoxide, 3 μM rimonabant and ibipinabant are partial agonists for K channel opening. Partial agonism was consistent with data from radioligand binding assays designed to detect SUR1 K(ATP) KCOs where rimonabant and ibipinabant allosterically regulated ³H-glibenclamide-specific binding in the presence of MgATP, as did diazoxide and NN414. Our findings indicate that some CB1 ligands may directly bind and allosterically regulate Kir6.2/SUR1 K(ATP) channels like other KCOs. This mechanism appears to be compatible with and may contribute to their acute and chronic effects on GSIS and insulinemia.

Effects of a combination of oral anti-diabetes drugs with basal insulin therapy on β-cell function and glycaemic control in patients with newly diagnosed type 2 diabetes

BACKGROUND

Oral anti-diabetes drugs plus basal insulin (OAD + insulin) therapy in patients with newly diagnosed type 2 diabetes might improve β-cell function and result in extended glycaemic remission. This randomised trial compared the effect on β-cell function and diabetes remission rate between oral drug alone or with addition of basal insulin.

METHODS

One hundred and twenty-nine patients, aged 35-50 years, were enrolled between June 2005 and June 2009. For initial correction of hyperglycaemia, patients with fasting plasma glucose ≥9.0 mmol/L and HbA(1c) ≥ 9.0%, were randomly assigned to therapy with oral drugs + insulin or oral drugs alone. Treatment was stopped after normoglycaemia was maintained for 3 months. Patients were then followed-up with diet and physical exercise. Blood glucose, HbA(1c) and insulin were measured prior to treatment and at 1-year follow-up.

RESULTS

More patients achieved target glycaemic control in the oral drugs + insulin group [98.3% (58 of 59)] in less time [(10.4 ± 2.5) days] than those in the oral drug group [95.7% (67 of 70) and (12.4 ± 3.4) days]. At 1-year follow-up, more patients maintained target glycaemia without any drugs in the oral drug + insulin group than in the oral drug group [37.9% (22 of 58) vs 20.9% (14 of 67)]. Both treatments improved homeostasis model assessment-β (HOMA-β) and homeostasis model assessment-insulin resistance (HOMA-IR) significantly. They had similar effects on insulin resistance [lg(HOMA-IR): (0.50 ± 0.09) vs (0.48 ± 0.09), p = 0.23]. However, oral drugs + insulin could recover β-cell function much more than OAD alone could [lg(HOMA-β): (2.17 ± 0.14) vs (2.11 ± 0.13), p = 0.03].

CONCLUSION

In newly diagnosed type 2 diabetes, therapy with oral drugs + insulin has had favourable outcomes on recovery and maintenance of β-cell function and protracted glycaemic remission compared with treatment with oral drugs alone.

Effects of Extract from Solid-State Fermented Cordyceps sinensis on Type 2 Diabetes Mellitus

Diabetes mellitus is the most common chronic disease in the world, and a wide range of drugs, including Chinese herbs, have been evaluated for the treatment of associated metabolic disorders. This study investigated the potential hypoglycemic and renoprotective effects of an extract from the solid-state fermented mycelium of Cordyceps sinensis (CS). We employed the KK/HIJ diabetic mouse model, in which the mice were provided with a high-fat diet for 8 weeks to induce hyperglycemia, followed by the administration of CS or rosiglitazone for 4 consecutive weeks. Several parameters were evaluated, including changes in body weight, plasma lipid profiles, oral glucose tolerance tests, insulin tolerance tests, and plasma insulin concentrations. Our results show that the CS extract significantly elevated HDL/LDL ratios at 4 weeks and decreased body weight gain at 8 weeks. Interestingly, CS treatment did not lead to obvious improvements in hyperglycemia or resistance to insulin, while in vitro MTT assays indicated that CS protects pancreatic beta cells against the toxic effects of STZ. CS also enhanced renal NKA activity and reduced the accumulation of mesangial matrix and collagen deposition. In conclusion, CS extract can potentially preserve β-cell function and offer renoprotection, which may afford a promising therapy for DM.

Early basal insulin therapy decreases new-onset diabetes after renal transplantation

No effective interventions to reduce risk for new-onset diabetes after transplantation (NODAT), a condition associated with postoperative hyperglycemia and reduced patient and graft survival, have been established. In this 1-year, proof-of-concept clinical trial, we randomly assigned 50 renal transplant recipients to immediate-postoperative isophane insulin for evening blood glucose ≥140 mg/dl (treatment group) or short-acting insulin and/or oral antidiabetic agents for blood glucose ≥180-250 mg/dl (standard-of-care control group). We included only patients without a history of diabetes who received tacrolimus. By the third postoperative evening, all patients in the treatment group had blood glucose ≥140 mg/dl and were subsequently treated with basal insulin; during the first 3 weeks after transplantation, the mean ± SD daily insulin dosage was 17±11 IU/d. Among controls, 23 (92%) of 25 had blood glucose ≥200 mg/dl and 18 (72%) of 25 received standard-of-care antihyperglycemic treatment. Asymptomatic hypoglycemia occurred five times in the treatment group and once in the control group. Throughout follow-up, the treatment group had 73% lower odds of NODAT (odds ratio, 0.27) than the control group, and hemoglobin A1c was on average 0.38% lower in the treatment group than the control group. Twelve months after transplantation, all patients in the treatment group were insulin-independent, whereas 7 (28%) of 25 controls required antidiabetic agents. The groups did not differ for insulin sensitivity, but the treatment group showed better β-cell function throughout the 1-year follow-up. In conclusion, this study suggests regimens that include basal insulin significantly reduce the odds for NODAT after renal transplantation, presumably via insulin-mediated protection of β cells.

Adenosine kinase inhibition selectively promotes rodent and porcine islet β-cell replication

Diabetes is a pathological condition characterized by relative insulin deficiency, persistent hyperglycemia, and, consequently, diffuse micro- and macrovascular disease. One therapeutic strategy is to amplify insulin-secretion capacity by increasing the number of the insulin-producing β cells without triggering a generalized proliferative response. Here, we present the development of a small-molecule screening platform for the identification of molecules that increase β-cell replication. Using this platform, we identify a class of compounds [adenosine kinase inhibitors (ADK-Is)] that promote replication of primary β cells in three species (mouse, rat, and pig). Furthermore, the replication effect of ADK-Is is cell type-selective: treatment of islet cell cultures with ADK-Is increases replication of β cells but not that of α cells, PP cells, or fibroblasts. Short-term in vivo treatment with an ADK-I also increases β-cell replication but not exocrine cell or hepatocyte replication. Therefore, we propose ADK inhibition as a strategy for the treatment of diabetes.

FGF21 analogs of sustained action enabled by orthogonal biosynthesis demonstrate enhanced antidiabetic pharmacology in rodents

Fibroblast growth factor 21 (FGF21) mitigates many of the pathogenic features of type 2 diabetes, despite a short circulating half-life. PEGylation is a proven approach to prolonging the duration of action while enhancing biophysical solubility and stability. However, in the absence of a specific protein PEGylation site, chemical conjugation is inherently heterogeneous and commonly leads to dramatic loss in bioactivity. This work illustrates a novel means of specific PEGylation, producing FGF21 analogs with high specific activity and salutary biological activities. Using homology modeling and structure-based design, specific sites were chosen in human FGF21 for site-specific PEGylation to ensure that receptor binding regions were preserved. The in vitro activity of the PEGylated FGF21 ana-logs corresponded with the site of PEG placement within the binding model. Site-specific PEGylated analogs demonstrated dramatically increased circulating half-life and enhanced efficacy in db/db mice. Twice-weekly dosing of an optimal FGF21 analog reduced blood glucose, plasma lipids, liver triglycerides, and plasma glucagon and enhanced pancreatic insulin content, islet number, and glucose-dependent insulin secretion. Restoration of insulin sensitivity was demonstrated by the enhanced ability of insulin to induce Akt/protein kinase B phosphorylation in liver, muscle, and adipose tissues. PEGylation of human FGF21 at a specific and preferred site confers superior metabolic pharmacology.

Early insulin therapy prevents beta cell loss in a mouse model for permanent neonatal diabetes (Munich Ins2(C95S))

AIMS

Heterozygous male Munich Ins2(C95S) mutant mice, a model for permanent neonatal diabetes mellitus, demonstrate a progressive diabetic phenotype with severe loss of functional beta cell mass. The aim of this study was to investigate the influence of early insulin treatment on glucose homeostasis and beta cell destruction in male Munich Ins2(C95S) mutants.

METHODS

One group of male Ins2(C95S) mutants was treated with subcutaneous insulin pellets, as soon as blood glucose levels began to rise; placebo-treated mutants and wild-type mice served as controls. An additional group of mutant mice received a sodium-dependent glucose transporter 2 (SGLT2) inhibitor (AVE2268) via rodent chow.

RESULTS

Insulin treatment normalised blood glucose concentrations, improved oral glucose tolerance, preserved insulin sensitivity and inhibited oxidative stress of Munich Ins2(C95S) mutant mice. Pancreatic C-peptide content, as well as total beta cell and isolated beta cell volumes, of insulin-treated mutant mice were higher than those of placebo-treated mutants. In addition, alpha cell dysfunction and hyperplasia of non-beta cells were completely normalised in insulin-treated mutant mice. Treatment with the SGLT2 inhibitor lowered blood glucose, improved glucose tolerance and normalised insulin sensitivity as well as oxidative stress of Ins2(C95S) mutants. The abundance of the endoplasmic reticulum (ER) stress markers binding Ig protein (BiP) and phosphorylated eukaryotic translation initiation factor 2 alpha (P-eIF2α) was significantly increased in the islets of mutants, before onset of hyperglycaemia, vs wild-type mice.

CONCLUSIONS

We conclude that early insulin treatment protects Munich Ins2(C95S) mutant mice from insulin resistance, alpha cell hyperfunction, beta cell loss and hyperplasia of non-beta cells, some well-known features of human diabetes mellitus. Therefore, insulin treatment may be considered early for human patients harbouring INS mutations.

Early improvement in glycemic control after bariatric surgery and its relationships with insulin, GLP-1, and glucagon secretion in type 2 diabetic patients

BACKGROUND

The surgical treatment of obesity ameliorates metabolic abnormalities in patients with type 2 diabetes. The objective of this study was to evaluate the early effects of Roux-en-Y gastric bypass (RYGB) on metabolic and hormonal parameters in patients with type 2 diabetes (T2DM).

METHODS

Ten patients with T2DM (BMI, 39.7 ± 1.9) were evaluated before and 7, 30, and 90 days after RYGB. A meal test was performed, and plasma insulin, glucose, glucagon, and glucagon-like-peptide 1 (GLP-1) levels were measured at fasting and postprandially.

RESULTS

Seven days after RYGB, a significant reduction was observed in HOMA-IR index from 7.8 ± 5.5 to 2.6 ± 1.7; p < 0.05 was associated with a nonsignificant reduction in body weight. The insulin and GLP-1 curves began to show a peak at 30 min after food ingestion, while there was a progressive decrease in glucagon and blood glucose levels throughout the meal test. Thirty and 90 days after RYGB, along with progressive weight loss, blood glucose and hormonal changes remained in the same direction and became more expressive with the post-meal insulin curve suggesting recovery of the first phase of insulin secretion and with the increase in insulinogenic index, denoting improvement in β-cell function. Furthermore, a positive correlation was found between changes in GLP-1 and insulin levels measured at 30 min after meal (r = 0.6; p = 0.000).

CONCLUSION

Our data suggest that the RYGB surgery, beyond weight loss, induces early beneficial hormonal changes which favor glycemic control in type 2 diabetes.

Noninferiority effects on glycemic control and β-cell function improvement in newly diagnosed type 2 diabetes patients: basal insulin monotherapy versus continuous subcutaneous insulin infusion treatment

AIMS

In newly diagnosed type 2 diabetes mellitus (T2DM) patients, short-term insulin therapy might improve β-cell function and glycemic control. This study aimed to compare the effects of basal insulin monotherapy with continuous subcutaneous insulin infusion (CSII) treatment.

METHODS

Fifty-nine cases of newly diagnosed T2DM patients with fasting plasma glucose of 9.0-16.7 mmol/L were recruited into this study. They were hospitalized and randomly assigned to a basal insulin monotherapy group (n=27) or a CSII group (n=32). Insulin dosage was titrated according to fasting capillary blood glucose levels, and treatment was stopped after 2 weeks. Intravenous glucose tolerance tests were performed, and blood glucose, insulin, C-peptide, and lipid profiles were measured before therapy and 2 days after therapy withdrawal.

RESULTS

Both treatments reduced fasting and postprandial blood glucose levels (after treatment vs. baseline, both P<0.05). Fasting glycemic control target was achieved in 52 cases (88.14%) with 2 weeks of insulin treatment, and there were no significant differences between the glargine and CSII groups (P=0.059). The time to achieve fasting glycemic target in the CSII group was shorter than that in the glargine group (P<0.01). Plasma lipid profiles such as triglycerides and total cholesterol also decreased significantly after the intervention. Overall β-cell function improved significantly after insulin intervention (P<0.01). Variation did not differ between two groups, nor did the effects on insulin and C-peptide secretion (P>0.05).

CONCLUSIONS

The effect of basal insulin monotherapy was similar to that of CSII, and thus basal insulin monotherapy might be a reasonable alternative to CSII for initial insulin therapy in newly diagnosed T2DM patients.

Beta-cell specific deletion of Dicer1 leads to defective insulin secretion and diabetes mellitus

Mature microRNAs (miRNAs), derived through cleavage of pre-miRNAs by the Dicer1 enzyme, regulate protein expression in many cell-types including cells in the pancreatic islets of Langerhans. To investigate the importance of miRNAs in mouse insulin secreting β-cells, we have generated mice with a β-cells specific disruption of the Dicer1 gene using the Cre-lox system controlled by the rat insulin promoter (RIP). In contrast to their normoglycaemic control littermates (RIP-Cre^+/− Dicer1^Δ/wt), RIP-Cre^+/−Dicer1^flox/flox mice (RIP-Cre Dicer1^Δ/Δ) developed progressive hyperglycaemia and full-blown diabetes mellitus in adulthood that recapitulated the natural history of the spontaneous disease in mice. Reduced insulin gene expression and concomitant reduced insulin secretion preceded the hyperglycaemic state and diabetes development. Immunohistochemical, flow cytometric and ultrastructural analyses revealed altered islet morphology, marked decreased β-cell mass, reduced numbers of granules within the β-cells and reduced granule docking in adult RIP-Cre Dicer1^Δ/Δ mice. β-cell specific Dicer1 deletion did not appear to disrupt fetal and neonatal β-cell development as 2-week old RIP-Cre Dicer1^Δ/Δ mice showed ultrastructurally normal β-cells and intact insulin secretion. In conclusion, we have demonstrated that a β-cell specific disruption of the miRNAs network, although allowing for apparently normal β-cell development, leads to progressive impairment of insulin secretion, glucose homeostasis and diabetes development.

Alogliptin as a third oral antidiabetic drug in patients with type 2 diabetes and inadequate glycaemic control on metformin and pioglitazone: a 52-week, randomized, double-blind, active-controlled, parallel-group study

AIM

To assess the efficacy and safety of adding alogliptin versus uptitrating pioglitazone in patients with type 2 diabetes and inadequate glycaemic control on metformin and pioglitazone.

METHODS

In this randomized, double-blind, active-controlled, parallel-group study, patients with type 2 diabetes and A1c ≥7.0 and ≤10.0% on metformin (≥1500 mg or maximum tolerated dose; Met) and pioglitazone 30 mg (Pio30) received alogliptin 25 mg (Alo25; n = 404) or pioglitazone 15 mg (n = 399) added to Met+Pio30 for 52 weeks. The primary endpoint was change from baseline (CFB) in A1c at weeks 26 and 52, with sequential testing for non-inferiority of Met+Pio30+Alo25 at weeks 26 and 52 and then for superiority at week 52.

RESULTS

Met+Pio30+Alo25 showed superior glycaemic control versus Met+Pio45 at week 52 [least squares (LS) mean CFB in A1c, -0.70 vs. -0.29%; p < 0.001]. At week 52, Met+Pio30+Alo25 resulted in greater CFB in A1c regardless of baseline A1c (p < 0.001); higher proportions of patients achieving A1c ≤7.0 (33.2 vs. 21.3%) and ≤6.5% (8.7 vs. 4.3%; p < 0.001); greater CFB in fasting plasma glucose (FPG; LS mean CFB, -0.8 vs. -0.2 mmol/L; p < 0.001); and greater improvements in measures of β-cell function (p < 0.001). Hypoglycaemia incidence was low (Met+Pio30+Alo25, 4.5%; Met+Pio45, 1.5%), mostly mild to moderate, but with two severe events in the Met+Pio30+Alo25 group. No meaningful differences in incidences of individual adverse events were observed between treatments.

CONCLUSIONS

Adding alogliptin to an existing metformin-pioglitazone regimen provided superior glycaemic control and potentially improved β-cell function versus uptitrating pioglitazone in patients with type 2 diabetes, with no clinically important differences in safety.

Development of a nongenetic mouse model of type 2 diabetes

Insulin resistance and loss of β-cell mass cause Type 2 diabetes (T2D). The objective of this study was to generate a nongenetic mouse model of T2D. Ninety-six 6-month-old C57BL/6N males were assigned to 1 of 12 groups including (1) low-fat diet (LFD; low-fat control; LFC), (2) LFD with 1 i.p. 40 mg/kg BW streptozotocin (STZ) injection, (3), (4), (5), (6) LFD with 2, 3, 4, or 5 STZ injections on consecutive days, respectively, (7) high-fat diet (HFD), (8) HFD with 1 STZ injection, (9), (10), (11), (12) HFD with 2, 3, 4, or 5 STZ injections on consecutive days, respectively. After 4 weeks, serum insulin levels were reduced in HFD mice administered at least 2 STZ injections as compared with HFC. Glucose tolerance was impaired in mice that consumed HFD and received 2, 3, or 4 injections of STZ. Insulin sensitivity in HFD mice was lower than that of LFD mice, regardless of STZ treatment. Islet mass was not affected by diet but was reduced by 50% in mice that received 3 STZ injections. The combination of HFD and three 40 mg/kg STZ injections induced a model with metabolic characteristics of T2D, including peripheral insulin resistance and reduced β-cell mass.

Novel GLP-1 receptor agonists for diabetes

INTRODUCTION

GLP-1 receptor agonists have been shown to be effective in the treatment of type 2 diabetes mellitus (T2DM). Although the first GLP-1 receptor agonist, exenatide, was approved in the mid-2000s, other agents with longer durations of action (that do not require twice-daily dosing) are now being developed. Indeed, liraglutide, a once-daily GLP-1 receptor agonist, was approved in 2010, and more recently, a once-weekly formulation of exenatide was approved in 2011. This review considers the mechanism of action of GLP-1 receptor agonists and considers the various agents in this class.

AREAS COVERED

The importance of GLP-1 itself in glycemic control and the use of GLP-1 receptor agonists in T2DM are discussed. An overview of the clinical development of the five GLP-1 receptor agonists (exenatide, liraglutide, lixisenatide, albiglutide and taspoglutide) since 2005 is provided and their mechanisms of action, efficacy in terms of glycemic control and weight loss, and tolerability are reviewed.

EXPERT OPINION

GLP-1 receptor agonists result in clinically meaningful weight loss in addition to their beneficial effects on glucose homeostasis. These agents provide substantial clinical benefits for patients compared with sulfonylureas or DPP-4 inhibitors and will, therefore, become one of the major therapeutic choices for patients with T2DM.

[Pharmacogenetics of insulin secretagogue antidiabetics]

Type 2 diabetes is making up to 90% of the all diabetic cases. In addition to insulin resistance, insufficient B-cell function also plays an important role in the pathogenesis of the disease. The insufficient production and secretion of insulin can be increased by secretagogue drugs, like sulfonylureas and incretin mimetics/enhancers. In recent years growing number of genetic failures of the B-cells has been detected. These genetic variants can influence the efficacy of secretagogue drugs. Some of these gene polymorphisms were identified in the genes encoding the KATP channel (KCNJ11 and ABCC8). These mutations are able either to reduce or increase the insulin secretion and can modify the insulin response to sulfonylurea treatment. Other polymorphisms were found on genes encoding enzymes or transcription factors. In recent years, the genetic variants of TCF7L2 and its clinical importance have been intensely studied. Authors give a summary of the above gene polymorphisms and their role in insulin secretion.

The role of incretin therapy at different stages of diabetes

The pathogenetic mechanisms causing type 2 diabetes are complex, and include a significant reduction of the incretin effect. In patients with type 2 diabetes, GLP-1 secretion may be impaired, while GIP secretion seems unaffected. In contrast, the insulinotropic activity of GIP is severely altered, whereas that of GLP-1 is maintained to a great extent. Better understanding of the role of incretin hormones in glucose homeostasis has led to the development of incretin-based therapies that complement and offer important advantages over previously used agents. Incretin-based agents have significant glucose-lowering effects, promote weight loss (or are weight-neutral), inhibit glucagon secretion while maintaining counter-regulatory mechanisms, exhibit cardiovascular benefits, and protect β-cells while possessing a low risk profile. At present, incretin-based therapies are most widely used as add on to metformin to provide sufficient glycemic control after metformin failure. However, they are also recommended as monotherapy early in the disease course, and later in triple combination. These agents may also be a promising therapeutic tool in prediabetic subjects. Therefore, a therapeutic algorithm is needed for their optimal application at different stages of diabetes, as suggested in this article.

Incretin therapy--present and future

Although newer treatments for type 2 diabetes (T2D) patients have produced continual improvements in outcome, a large and growing population with prediabetes remains under-treated. In the last few years, incretin-based therapies have become an important treatment option for patients with T2D. There are two classes of incretin agents: the dipeptidyl peptidase-4 (DPP-4) inhibitors and the glucagon like peptide 1 (GLP-1) receptor agonists. The ultimate goal of agents within both of these classes is to increase GLP-1 signaling, which results in augmented glucose-induced insulin secretion, inhibition of glucagon secretion, and decreased appetite. This should result in improved regulation of glucose homeostasis. GLP-1 receptor agonists enable patients to achieve significant weight loss. In contrast, DPP-4 inhibitors result in a less dramatic increase in GLP-1 levels; therefore, they are weight neutral. Incretin therapies are currently recommended for use early in the treatment algorithm for T2D patients whose disease is not manageable by diet and exercise alone, but the potential for these agents may be farther reaching. Current studies are evaluating the potential benefits of combining incretin therapies with basal insulin to provide continuous glucose control before and after meals. In addition, these agents may be promising for patients with prediabetes since they effectively reduce glycosylated hemoglobin levels and fasting plasma glucose levels, enable weight control, and have the potential to preserve β-cell function. Clearly, all of these properties are desirable for patients with prediabetes.

The physiology of incretins

The discovery of incretins − glucagon-like peptide (GLP)-1 and glucose-dependent insulinotrop peptide (GIP) −, clarification of their physiological properties as well as therapeutic application of incretin-based blood glucose lowering drugs opened new perspectives in the medical management of type 2 diabetes. New results of basic research investigations led to revaluation of the role of GIP in metabolic processes and a more established use of GLP-1 action. The article overviews the most relevant data of production and effects of incretins, as well as future possibilities of their therapeutic use. Orv. Hetil., 2011, 152, 1922–1930.

Otelixizumab in the treatment of Type 1 diabetes mellitus

Anti-CD3 antibodies have been demonstrated in both animal and human studies to be able to reverse autoimmune diseases; for example Type 1 diabetes. Not only does treatment with anti-CD3 antibodies result in the removal of pathogenic T cells but evidence suggests that a state of operational tolerance can be induced through the effects on regulatory T cells. The clinical use of anti-CD3 antibodies has been hampered by their safety profile. However, the introduction of humanized, nonmitogenic, aglycosylated anti-CD3 antibodies, such as otelixizumab, and promising results reported in newly-diagnosed patients with Type 1 diabetes, have renewed the interest for these antibodies in the treatment of autoimmune diseases.

Early and intensive therapy for management of hyperglycemia and cardiovascular risk factors in patients with type 2 diabetes

BACKGROUND

Type 2 diabetes mellitus (T2DM) results in significant morbidity and mortality. Results of recent randomized controlled trials demonstrated the ability of early and intensive therapy to reduce the risk of microvascular complications. However, controversy surrounds the ability of such therapy to reduce the risk for macrovascular complications.

OBJECTIVES

This article reviews results from recent clinical trials in patients with T2DM as well as extended follow-up of earlier trials to determine if early, intensive, and individualized therapy aimed at the underlying pathogenesis of the disease could decrease the risk for long-term complications, including cardiovascular disease (CVD).

METHODS

Information was obtained by a search of the PUBMED and EMBASE databases using the search terms type 2 diabetes mellitus, glycosylated hemoglobin, pathophysiology of type 2 diabetes, glycemic control, early intervention, multifactorial intervention, cardiovascular disease, β-cell function, and antidiabetes therapy for the period between 1995 and 2010. Articles dealing with outcomes trials, impact of therapy on microvascular and macrovascular complications, effects of therapeutic agents on the pathophysiology of T2DM, and the impact of agents on CV risk factors were then preferentially selected for in-depth review.

RESULTS

Large-scale clinical trials in patients with T2DM, although largely negative at 5 years for macrovascular end points, suggested benefit for patients with a shorter duration of T2DM (ie, <10 years) and still supported a treatment strategy of early, intensive, and individualized therapy to prevent long-term complications of the disease. In Steno-2, after 13 years of follow-up, early, intensive, multifactorial therapy was associated with a 56% lower risk of all-cause death (P = 0.02) and a 57% lower risk of death from CVD (P = 0.04). In the 10-year follow-up to the United Kingdom Prospective Diabetes Study, intensive therapy was associated with a significant 15% reduction in the risk of myocardial infarction (P = 0.01) and a significant 13% reduction in the risk of death from any cause (P = 0.007). Therapy should be aimed at correcting underlying pathophysiologic defects, including β-cell failure and insulin resistance, and should also correct underlying risk factors for CVD whenever possible.

CONCLUSIONS

Early and intensive antidiabetes treatment was recommended in patients with T2DM, particularly those with a shorter duration of disease and without a history of CVD. The goal was to safely lower glycosylated hemoglobin to <7%, therefore providing beneficial effects on the risk for complications. Hypoglycemia should be avoided. In addition, less aggressive treatment might be suitable for older patients with longstanding diabetes and a history of CVD events. Clinical trial results also provided support for a second important aspect of individualized treatment for patients with T2DM-multifactorial intervention aimed at controlling CVD risk factors.

Management of patients with type 2 diabetes

BACKGROUND

The number of treatment options in the diabetes arena has grown dramatically in a short period of time, with a corresponding increase in the breadth and depth of literature from which physicians and diabetes organizations make evidence-based decisions. Thus, the purpose of this article is to provide an up-to-date review of the literature describing current treatment options and guidelines available for the management of type 2 diabetes and prevention of its complications.

METHODS

Pubmed searches were conducted for recent literature pertaining to the prevention of complications in type 2 diabetes. Comprehensive search terms were devised to identify articles describing micro- and macrovascular complications including nephropathy, neuropathy, retinopathy, and cardiovascular disease associated with type 2 diabetes.

CONCLUSIONS

The current body of literature demonstrates that a significant reduction in the incidence of diabetic complications is achievable with early initiation and long-term maintenance of controlled blood glucose and cardiovascular risk factors. Screening for diabetic complications should be initiated early and continued at regular intervals to ensure early pharmacological intervention.

Clarifying the role of incretin-based therapies in the treatment of type 2 diabetes mellitus

BACKGROUND

Glucose homeostasis is the result of a complex interaction of a spectrum of hormones, including insulin, glucagon, amylin, and the incretins. Incretins are released by enteroendocrine cells in the intestine in response to a meal. Incretin dysfunction, along with a number of other defects, has been implicated in contributing to the pathogenesis of type 2 diabetes mellitus (T2DM). Therapies that restore incretin activity may reduce the pathophysiologic consequences of diabetes.

OBJECTIVES

The aim of this article was to review incretin physiology and studies of incretin therapy with glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors that were developed to specifically address the blunted incretin response in patients with T2DM.

METHODS

Relevant English-language publications between 1995 and 2010 were identified through a search of the MEDLINE and EMBASE databases using the search terms incretin, type 2 diabetes mellitus, GLP-1, glucose-dependent insulinotropic polypeptide, and DPP-4. Review articles and preclinical and clinical trials that described relevant details of the epidemiology of diabetes and incretin physiology in health and in T2DM were selected for review and inclusion. Clinical trials were used to describe the clinical efficacy and safety of the GLP-1 receptor agonists and DPP-4 inhibitors in patients with T2DM. An occasional systematic review article and/or meta-analysis summarizing numerous clinical trials of a particular agent was selected for summarizing key data.

RESULTS

Pharmacologic modulation of incretin pathophysiology by GLP-1 receptor agonists and DPP-4 inhibitors significantly improved glycemic control, benefited β-cell function, improved dyslipidemia, and lowered the risk of hypoglycemia compared with insulin and sulfonylureas. Unlike the DPP-4 inhibitors, GLP-1 receptor agonist therapy also produced weight loss, an important consideration given the close association among T2DM, overweight/obesity, and cardiovascular disease. The most common adverse events with GLP-1 receptor agonist therapy included nausea (28%-44%), vomiting (13%-17%), and diarrhea (11%-17%), which generally reduced in incidence and severity with continued therapy. The tolerability profile of the DPP-4 inhibitors was very good, with the incidence of adverse events similar to that of placebo. There was a suggestion of an increased incidence of nasopharyngitis versus placebo (5%-6% vs 3%-4%) with sitagliptin and urinary tract infection (6.8% vs 6.1% with placebo) and headache with saxagliptin (6.5% vs 5.9% with placebo).

CONCLUSION

The 2 incretin drug classes provided effective and consistent glycemic control with a good tolerability profile. These agents might also improve long-term β-cell function and either reduce body weight or be weight neutral. Their role in the therapeutic armamentarium of T2DM is evolving as their potential strengths and weaknesses become better defined.

Evaluating treatment algorithms for the management of patients with type 2 diabetes mellitus: a perspective on the definition of treatment success

BACKGROUND

Traditional treatment of type 2 diabetes mellitus (T2DM) has focused on correcting hyperglycemia. However, T2DM is often accompanied by other conditions and risk factors, including hypertension, overweight/obesity, and dyslipidemia, that affect morbidity and mortality. A broader view toward treating the array of physiologic derangements may provide significant long-term outcomes benefits.

OBJECTIVE

This perspective paper reviews recent data regarding the pathophysiology of T2DM, evaluates current treatment recommendations/algorithms, and discusses potential risks and benefits associated with the various therapeutic options and their combinations.

METHODS

Information was obtained by a search of the PubMed and Embase databases using the key words type 2 diabetes mellitus, glycosylated hemoglobin, pathophysiology of type 2 diabetes, glycemic control, antidiabetes therapy, multifactorial therapy, and treatment algorithms for the period of 1985 to 2010. A representative number of relevant articles dealing with these topics was then selected for review.

RESULTS

Three recently proposed treatment algorithms, the American Diabetes Association/European Association for the Study of Diabetes less well-validated algorithm, the American Association of Clinical Endocrinologists/American College of Endocrinology algorithm, and the DeFronzo algorithm, were compared and contrasted. Metformin is usually the first oral agent to be used when not contraindicated because of its ability to suppress hepatic glucose production. Some recommended agents, such as sulfonylureas, drive β-cell failure even as they improve glycosylated hemoglobin. Others, such as glucagon-like peptide-1 (GLP-1) receptor agonists and thiazolidinediones, support and enhance β-cell function. Also, some agents predispose to weight gain (eg, sulfonylureas and insulin), whereas others are weight neutral (eg, dipeptidyl-peptidase-4 inhibitors) or result in weight loss (eg, GLP-1 receptor agonists, pramlintide). Finally, the impact of these agents on associated cardiovascular risk factors is varied. Agents that improve glycemic control while favorably affecting blood lipid levels and/or systemic blood pressure may lead to improvements in morbidity and mortality. Attention to the mechanisms of action and associated consequences of the numerous pharmacologic treatment choices may provide clinicians a better selection of agents in treating patients with T2DM.

CONCLUSIONS

Physicians should evaluate the array of treatment options available for patients with T2DM. An aggressive regimen including metformin, a thiazolidinedione, and a GLP-1 receptor agonist may improve insulin sensitivity and enhance β-cell function. Addressing the pathophysiologic defects associated with T2DM, as well as the various associated cardiovascular risk factors, with combination therapy may slow the natural progression of the disease and development of its associated complications.

Medicinal Chemistry and Applications of Incretins and DPP-4 Inhibitors in the Treatment of Type 2 Diabetes Mellitus

Diabetes mellitus (DM) is a major metabolic disorder currently affecting over 200 million people worldwide. Approximately 90% of all diabetic patients suffer from Type 2 diabetes mellitus (T2DM). The world's economy coughs out billions of dollars annually to diagnose, treat and manage patients with diabetes. It has been shown that the naturally occurring gut hormones incretins, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) can preserve the morphology and function of pancreatic beta cell. In addition, GIP and GLP-1 act on insulin receptors to facilitate insulin-receptor binding, resulting in optimal glucose metabolism. This review examines the medicinal chemistry and roles of incretins, specifically, GLP-1 and drugs which can mimic its actions and prevent its enzymatic degradation. The review discussed GLP-1 agonists such as exenatide, liraglutide, taspoglutide and albiglutide. The paper also identified and reviewed a number of inhibitors, which can block dipeptidyl peptidase 4 (DPP-4), the enzyme responsible for the rapid degradation of GLP-1. These DPP-4 inhibitors include sitagliptin, saxagliptin, vildagliptin and many others which are still in the experimental phase.

Enhanced glycemic control with combination therapy for type 2 diabetes in primary care

Type 2 diabetes mellitus is an increasingly common medical problem for primary care clinicians to address. Treatment of diabetes has evolved from simple replacement of insulin (directly or through insulin secretagogs) through capture of mechanisms such as insulin sensitizers, alpha-glucosidase inhibitors, and incretins. Only very recently has recognition of the critical role of the gastrointestinal system as a major culprit in glucose dysregulation been established. Since glycated hemoglobin A(1c) reductions provide meaningful risk reduction as well as improved quality of life, it is worthwhile to explore evolving paths for more efficient use of the currently available pharmacotherapies. Because diabetes is a progressive disease, even transiently successful treatment will likely require augmentation as the disorder progresses. Pharmacotherapies with complementary mechanisms of action will be necessary to achieve glycemic goals. Hence, clinicians need to be well informed about the various noninsulin alternatives that have been shown to be successful in glycemic goal attainment. This article reviews the benefits of glucose control, the current status of diabetes control, pertinent pathophysiology, available pharmacological classes for combination, limitations of current therapies, and suggestions for appropriate combination therapies, including specific suggestions for thresholds at which different strategies might be most effectively utilized by primary care clinicians.

Effects of exenatide on measures of β-cell function after 3 years in metformin-treated patients with type 2 diabetes

OBJECTIVE

We previously showed that exenatide (EXE) enhanced insulin secretion after 1 year of treatment, relative to insulin glargine (GLAR), with a similar glucose-lowering action. These effects were not sustained after a 4-week off-drug period. This article reports the results after additional 2 years of exposure.

RESEARCH DESIGN AND METHODS

Sixty-nine metformin-treated patients with type 2 diabetes were randomized to EXE or GLAR. Forty-six patients entered the 2-year extension study in which they continued their allocated therapy. Thirty-six completed (EXE: n = 16; GLAR: n = 20) the 3-year exposure period. Insulin sensitivity (M value) and β-cell function were measured by euglycemic hyperinsulinemic clamp followed by hyperglycemic clamp with arginine stimulation at pretreatment (week 52) and 4 weeks after discontinuation of study medication (week 56 and week 172). First-phase glucose stimulated C-peptide secretion was adjusted for M value and calculated as the disposition index (DI).

RESULTS

At 3 years, EXE and GLAR resulted in similar levels of glycemic control: 6.6 ± 0.2% and 6.9 ± 0.2%, respectively (P = 0.186). EXE compared with GLAR significantly reduced body weight (-7.9 ± 1.8 kg; P < 0.001). After the 4-week off-drug period, EXE increased the M value by 39% (P = 0.006) while GLAR had no effect (P = 0.647). Following the 4-week off-drug period, the DI, compared with pretreatment, increased with EXE, but decreased with GLAR (1.43 ± 0.78 and -0.99 ± 0.65, respectively; P = 0.028).

CONCLUSIONS

EXE and GLAR sustained HbA(1c) over the 3-year treatment period, while EXE reduced body weight and GLAR increased body weight. Following the 3-year treatment with EXE, the DI was sustained after a 4-week off-drug period. These findings suggest a beneficial effect on β-cell health.

Involvement of P2X receptors in the regulation of insulin secretion, proliferation and survival in mouse pancreatic β-cells

In order to clarify the functional role of ionotropic purinergic (P2X) receptors in pancreatic β-cells, we examined the effect of several P2 receptor agonists and antagonists on insulin secretion by mouse pancreatic islets, mouse Beta-TC6 cell proliferation and survival of dispersed islet cells in culture. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed the expression of mRNAs of P2X(4) receptor in mouse islets and P2X(1), P2X(2), P2X(3), P2X(4), P2X(5) and P2X(7) receptors in Beta-TC6 cells. The presence of P2X(4) receptor proteins in islets and Beta-TC6 cells was confirmed by immunofluorescent staining and Western blot analysis. We have previously found that the functional P2Y(1) receptor but not P2Y(2) and P2Y(4) receptors was present in islets. In this study we found that a nonspecific P2 receptor agonist, ATP (1 μM) stimulated insulin secretion by islets in the presence of high glucose (20 mM) in culture. The effect of ATP was partially inhibited by a P2 receptor antagonist PPADS as well as a P2Y(1) receptor antagonist MRS2179. In addition, a P2X(4) receptor potentiator ivermectin per se augmented glucose-induced insulin secretion and slightly potentiated the effect of ATP. These results suggested the involvement of P2Y(1)and P2X receptors. We also found that ATP inhibited proliferation of Beta-TC6 cells in a concentration-dependent manner during 72 h culture. The inhibitory effect of ATP was completely reversed by PPADS and partially by treating cells with small interfering RNA targeted for P2X(4) receptor mRNA. Furthermore, we found that the phosphorylation of the extracellular signal-regulated kinase 1 and 2 (ERK1/2) was suppressed by treatment with ATP in Beta-TC6 cells. In addition, we found that ATP reduced the cell viability and DNA synthesis of islet cells in culture. The effect of ATP on the cell viability was blocked by PPADS or MRS2179. These results suggested that P2X receptors as well as the P2Y(1) receptor played a role in the modulation of insulin secretion, proliferation and cell viability in mouse pancreatic β-cells.

The human insulin mRNA is partly translated via a cap- and eIF4A-independent mechanism

The aim of this study was to investigate whether cap-independent insulin mRNA translation occurs in human pancreatic islets at basal conditions, during stimulation at a high glucose concentration and at conditions of nitrosative stress. We also aimed at correlating cap-independent insulin mRNA translation with binding of the IRES trans-acting factor polypyrimidine tract binding protein (PTB) to the 5'-UTR of insulin mRNA. For this purpose, human islets were incubated for 2h in the presence of low (1.67 mM) or high glucose (16.7 mM). Nitrosative stress was induced by addition of 1 mM DETA/NO and cap-dependent mRNA translation was inhibited with hippuristanol. Insulin biosynthesis rates were determined by radioactive labeling and immunoprecipitation. PTB affinity to insulin mRNA 5'-UTR was assessed by a magnetic micro bead pull-down procedure. We observed that in the presence of 1.67 mM glucose, approximately 70% of the insulin mRNA translation was inhibited by hippuristanol. Corresponding value from islets incubated at 16.7 mM glucose was 93%. DETA/NO treatment significantly decreased the translation of insulin by 85% in high glucose incubated islets, and by 50% at a low glucose concentration. The lowered insulin biosynthesis rates of DETA/NO-exposed islets were further suppressed by hippuristanol with 55% at 16.7 mM glucose but not at 1.67 mM glucose. Thus, hippuristanol-induced inhibition of insulin biosynthesis was less pronounced in DETA/NO-treated islets as compared to control islets. We observed also that PTB bound specifically to the insulin mRNA 5'-UTR in vitro, and that this binding corresponded well with rates of cap-independent insulin biosynthesis at the different conditions. In conclusion, our studies show that insulin biosynthesis is mainly cap-dependent at a high glucose concentration, but that the cap-independent biosynthesis of insulin can constitute as much as 40-100% of all insulin biosynthesis during conditions of nitrosative stress. These data suggest that the pancreatic β-cell is able to uphold basal insulin synthesis at conditions of starvation and stress via a cap- and eIF4A-independent mechanism, possibly mediated by the binding of PTB to the 5'-UTR of the human insulin mRNA.

Acute stimulation of glucagon secretion by linoleic acid results from GPR40 activation and [Ca2+]i increase in pancreatic islet {alpha}-cells

The role of free fatty acids (FFAs) in glucagon secretion has not been well established, and the involvement of FFA receptor GPR40 and its downstream signaling pathways in regulating glucagon secretion are rarely demonstrated. In this study, it was found that linoleic acid (LA) acutely stimulated glucagon secretion from primary cultured rat pancreatic islets. LA at 20 and 40 μmol/l dose-dependently increased glucagon secretion both at 3 mmol/l glucose and at 15 mmol/l glucose, although 15 mmol/l glucose reduced basal glucagon levels. LA induced an increase in cytoplasmic free calcium concentrations ([Ca(2)(+)](i)) in identified rat α-cells, which is reflected by increased Fluo-3 intensity under confocal microscopy recording. The increase in [Ca(2)(+)](i) was partly inhibited by removal of extracellular Ca(2)(+) and eliminated overall by further exhaustion of intracellular Ca(2)(+) stores using thapsigargin treatment, suggesting that both Ca(2)(+) release and Ca(2)(+) influx contributed to the LA-stimulated increase in [Ca(2)(+)](i) in α-cells. Double immunocytochemical stainings showed that GPR40 was expressed in glucagon-positive α-cells. LA-stimulated increase in [Ca(2)(+)](i) was blocked by inhibition of GPR40 expression in α-cells after GPR40-specific antisense treatment. The inhibition of phospholipase C activity by U73122 also blocked the increase in [Ca(2)(+)](i) by LA. It is concluded that LA activates GPR40 and phospholipase C (and downstream signaling pathways) to increase Ca(2)(+) release and associated Ca(2)(+) influx through Ca(2)(+) channels, resulting in increase in [Ca(2)(+)](i) and glucagon secretion.

Glucolipotoxicity and beta cells in type 2 diabetes mellitus: target for durable therapy?

Type 2 diabetes mellitus (T2DM) is characterised by beta-cell failure in the setting of obesity-related insulin resistance. Progressive beta-cell dysfunction determines the course of the disease, regardless of the treatment used. There is mounting evidence that chronically elevated circulating levels of glucose and fatty acids contribute to relentless beta-cell function decline, by endorsing processes commonly referred to as glucolipotoxicity. Mechanisms related to glucolipotoxicity include endoplasmic reticulum (ER) stress, oxidative stress, mitochondrial dysfunction and islet inflammation. The most commonly prescribed blood-glucose lowering agents, metformin and sul-fonylurea, may temporarily improve glycaemic control, however, these drugs do not alter the continuous decline in beta-cell function in T2DM patients. Evidence exists that novel classes of drugs, the thiazolidinediones (TZDs) and incretin-based therapies, may be able to preserve beta-cell function and functional beta-cell mass, amongst others by reducing glucolipotoxicity in the beta cell. The durability of the effects of TZDs and incretin-based therapies on beta-cell function, whether given as monotherapy or combined with other treatment, should be addressed in future, long-term clinical studies.

Efficacy of sitagliptin when added to ongoing therapy in korean subjects with type 2 diabetes mellitus

BACKGROUND

To evaluate the clinical efficacy of sitagliptin for reducing plasma glucose levels in Korean subjects with type 2 diabetes mellitus during a 14-week treatment period.

METHODS

Our study design involved the addition of 100 mg sitagliptin once-daily to three ongoing combination therapy regimens and changing from glimepiride and metformin to sitagliptin and metformin.

RESULTS

The addition of sitagliptin 100 mg/day produced a statistically significant reduction in mean HbA1c level (mean HbA1c reduction of 0.99±0.85%, P<0.01). In the group taking a combination of sitagliptin and metformin (n=143, initial mean HbA1c level=7.48%), the reductions in HbA1c, 2-hour postprandial glucose, and fasting glucose levels were 0.72±0.76% (P<0.01), 47±65 mg/dL (P<0.01), and 15±44 mg/dL (P<0.01), respectively. In the group taking a combination of sitagliptin, glimepiride, and metformin (n=125, initial mean HbA1c level=8.42%), the reductions in HbA1c, 2-hour postprandial glucose, and fasting glucose levels were 1.09±0.86% (P<0.01), 62±64 mg/dL (P<0.01), and 31±45 mg/dL (P<0.01), respectively. In the group taking a combination of sitagliptin, glimepiride, metformin, and α-glucosidase inhibitor (n=63, initial mean HbA1c level=9.19%), the reductions in HbA1c, 2-hour postprandial glucose, and fasting glucose levels were 1.27±0.70% (P<0.01), 72±65 mg/dL (P<0.01), and 35±51 mg/dL (P<0.01), respectively. In the group that had previous hypoglycemic events and that changed from glimepiride to sitagliptin, HbA1c level did not change but fasting glucose increased significantly (14±29 mg/dL, P<0.01).

CONCLUSION

Sitagliptin combination therapy for 14 weeks significantly improved glycemic control and was well-tolerated in Korean subjects with type 2 diabetes mellitus.

New type 2 diabetes risk genes provide new insights in insulin secretion mechanisms

Type 2 diabetes results from the inability of beta cells to increase insulin secretion sufficiently to compensate for insulin resistance. Insulin resistance is thought to result mainly from environmental factors, such as obesity. However, there is compelling evidence that the decline of both insulin sensitivity and insulin secretion have also a genetic component. Recent genome-wide association studies identified several novel risk genes for type 2 diabetes. The vast majority of these genes affect beta cell function by molecular mechanisms that remain unknown in detail. Nevertheless, we and others could show that a group of genes affect glucose-stimulated insulin secretion, a group incretin-stimulated insulin secretion (incretin sensitivity or secretion) and a group proinsulin-to-insulin conversion. The most important so far type 2 diabetes risk gene, TCF7L2, interferes with all three mechanisms. In addition to advancing knowledge in the pathophysiology of type 2 diabetes, the discovery of novel genetic determinants of diabetes susceptibility may help understanding of gene-environment, gene-therapy and gene-gene interactions. It was also hoped that it could make determination of the individual risk for type 2 diabetes feasible. However, the allelic relative risks of most genetic variants discovered so far are relatively low. Thus, at present, clinical criteria assess the risk for type 2 diabetes with greater sensitivity and specificity than the combination of all known genetic variants.