beta-cell failure in diabetes and preservation by clinical treatment

From theory to clinical practice in the use of GLP-1 receptor agonists and DPP-4 inhibitors therapy

Promoting long-term adherence to lifestyle modification and choice of antidiabetic agent with low hypoglycemia risk profile and positive weight profile could be the most effective strategy in achieving sustained glycemic control and in reducing comorbidities. From this perspective, vast interest has been generated by glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 inhibitors (DPP-4i). In this review our ten-year clinical and laboratory experience by in vitro and in vivo studies is reported. Herein, we reviewed available data on the efficacy and safety profile of GLP-1 receptor agonists and DPP-4i. The introduction of incretin hormone-based therapies represents a novel therapeutic strategy, because these drugs not only improve glycemia with minimal risk of hypoglycemia but also have other extraglycemic beneficial effects. In clinical studies, both GLP-1 receptor agonists and DPP-4i, improve β cell function indexes. All these agents showed trophic effects on beta-cell mass in animal studies. The use of these drugs is associated with positive or neucral effect on body weight and improvements in blood pressure, diabetic dyslipidemia, hepatic steazosis markets, and myocardial function. These effects have the potential to reduce the burden of cardiovascular disease, which is a major cause of mortality in patients with diabetes.

In vivo conditional Pax4 overexpression in mature islet β-cells prevents stress-induced hyperglycemia in mice

OBJECTIVE

To establish the role of the transcription factor Pax4 in pancreatic islet expansion and survival in response to physiological stress and its impact on glucose metabolism, we generated transgenic mice conditionally and selectively overexpressing Pax4 or a diabetes-linked mutant variant (Pax4R129W) in β-cells.

RESEARCH DESIGN AND METHODS

Glucose homeostasis and β-cell death and proliferation were assessed in Pax4- or Pax4R129W-overexpressing transgenic animals challenged with or without streptozotocin. Isolated transgenic islets were also exposed to cytokines, and apoptosis was evaluated by DNA fragmentation or cytochrome C release. The expression profiles of proliferation and apoptotic genes and β-cell markers were studied by immunohistochemistry and quantitative RT-PCR.

RESULTS

Pax4 but not Pax4R129W protected animals against streptozotocin-induced hyperglycemia and isolated islets from cytokine-mediated β-cell apoptosis. Cytochrome C release was abrogated in Pax4 islets treated with cytokines. Interleukin-1β transcript levels were suppressed in Pax4 islets, whereas they were increased along with NOS2 in Pax4R129W islets. Bcl-2, Cdk4, and c-myc expression levels were increased in Pax4 islets while MafA, insulin, and GLUT2 transcript levels were suppressed in both animal models. Long-term Pax4 expression promoted proliferation of a Pdx1-positive cell subpopulation while impeding insulin secretion. Suppression of Pax4 rescued this defect with a concomitant increase in pancreatic insulin content.

CONCLUSIONS

Pax4 protects adult islets from stress-induced apoptosis by suppressing selective nuclear factor-κB target genes while increasing Bcl-2 levels. Furthermore, it promotes dedifferentiation and proliferation of β-cells through MafA repression, with a concomitant increase in Cdk4 and c-myc expression.

Effectiveness of adding vildagliptin to the treatment of diabetic patients nonresponsive to the combination of metformin and a sulphonylurea

OBJECTIVE: To evaluate the effectiveness of adding vildagliptin to the treatment of patients with inadequately controlled type 2 diabetes mellitus (T2DM) treated with a combination of metformin and a sulphonylurea. SUBJECTS AND METHODS: 37 T2DM patients with HbA1c ranging from 7.7% to 12.4% (mean of 9.30 ± 1.38), despite the use of metformin in combination with a sulphonylurea, were additionally treated with vildagliptin (100 mg/day) for at least 6 months. RESULTS: During triple oral therapy (TOT) HbA1c levels < 7% were achieved in 11 patients (29.7%), whereas levels of fasting plasma glucose (FPG) < 120 mg/dL were observed in 12 patients (32.4%). Both findings were observed in 10 patients (27.0%). Compared to nonresponsive subjects, lower mean baseline HbA1c and FPG levels were seen in responsive patients, but the difference was only statistically significant for fasting plasma glucose (FPG). Moreover, there was considerable overlap between the two groups. CONLUSION: Our preliminary results suggest that TOT with metformin, a sulphonylurea and vildagliptin may be useful for some T2DM patients nonresponsive to combination therapy with metformin and sulphonylurea.

Rosiglitazone as an option for patients with acromegaly: a case series

INTRODUCTION

In the patient with acromegaly, pituitary surgery is the therapeutic standard. Despite undergoing surgery, a significant number of patients with acromegaly continue to have uncontrolled growth hormone secretion. These patients require other treatments such as external irradiation and/or drug therapy.

CASE PRESENTATION

We present the clinical and laboratory responses to six months of treatment with rosiglitazone in four cases. In all four cases, the patients had persistent growth hormone overproduction despite previous surgical treatment and other conventional therapy. Case 1 is a 57-year-old Caucasian woman, case 2 is a 51-year-old Hispanic man, case 3 is a 32-year-old Hispanic woman, and case 4 is a 36-year-old Hispanic man. In three of these patients, basal and nadir growth hormone and insulin-like growth factor 1 levels were significantly decreased (P < 0.05 and P < 0.01, respectively).

CONCLUSION

Rosiglitazone could be a treatment option in select patients with acromegaly.

Preservation of beta-cell function in type 2 diabetes

OBJECTIVE

To review available data on preservation and potential improvement of beta-cell function in patients with type 2 diabetes mellitus (T2DM) with use of currently available strategies and agents.

METHODS

Using key words, we performed a MEDLINE search of the relevant literature published through 2009 regarding the effects of available agents on beta-cell function in humans with T2DM.

RESULTS

On the basis of current clinical data, no uniformly effective treatment for beta-cell preservation has been found. Lifestyle intervention and early intensive insulin therapy appear to have some preservative properties on beta-cell function. Glucagonlike peptide-1 agonists, dipeptidyl- peptidase-4 inhibitors, and thiazolidinediones result in maintenance and often improvement of beta-cell function during their active use; however, data on their ability to preserve beta-cell function when patients are not receiving active treatment are limited.

CONCLUSION

The continuous loss of beta-cell mass and beta-cell function is a critical mechanism underlying the progressive deterioration of glycemic control in T2DM. In light of the projected increase in individuals at risk for developing T2DM, strategies and agents aimed at delaying or preventing the progression and inducing a remission of the disease are needed. Future research on this topic should include comparative efficacy trials with washout periods incorporating currently available and novel medications and strategies for preservation of beta cells.

Hydrogen sulphide protects mouse pancreatic β-cells from cell death induced by oxidative stress, but not by endoplasmic reticulum stress

BACKGROUND AND PURPOSE

Hydrogen sulphide (H₂S), a potentially toxic gas, is also involved in the neuroprotection, neuromodulation, cardioprotection, vasodilatation and the regulation of inflammatory response and insulin secretion. We have recently reported that H₂S suppresses pancreatic β-cell apoptosis induced by long-term exposure to high glucose. Here we examined the protective effects of sodium hydrosulphide (NaHS), an H₂S donor, on various types of β-cell damage.

EXPERIMENTAL APPROACH

Isolated islets from mice or the mouse insulinoma MIN6 cells were cultured with palmitate, cytokines (a mixture of tumour necrosis factor-α, interferon-γ and interleukin-1β), hydrogen peroxide, thapsigargin or tunicamycin with or without NaHS. We examined DNA fragmentation, caspase-3 and -7 activities and reactive oxygen species (ROS) production in the treated cells thereafter. Apoptotic cell death in isolated islets was also assessed by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) method.

KEY RESULTS

NaHS suppressed DNA fragmentation and the activities of caspase-3 and -7 induced by palmitate, the cytokines or hydrogen peroxide. In contrast, NaHS failed to protect islets and MIN6 cells from apoptosis induced by thapsigargin and tunicamycin, both of which cause endoplasmic reticulum stress. NaHS suppressed ROS production induced by cytokines or hydrogen peroxide but it had no effect on ROS production in thapsigargin-treated cells. NaHS increased Akt phosphorylation in MIN6 cells treated with cytokines but not in cells treated with thapsigargin. Treatment with NaHS decreased TUNEL-positive cells in cytokine-exposed islets.

CONCLUSIONS AND IMPLICATIONS

H₂S may prevent pancreatic β-cells from cell apoptosis via an anti-oxidative mechanism and the activation of Akt signalling.

Recognition, pathogenesis, and treatment of different stages of nephropathy in patients with type 2 diabetes mellitus

Nephropathy is a common microvascular complication among patients with type 2 diabetes mellitus and a major cause of kidney failure. It is characterized by albuminuria (≥ 300 mg/d) and a reduced glomerular filtration rate and is often present at the time of diabetes diagnosis after the kidney has been exposed to chronic hyperglycemia during the prediabetic phase. A low glomerular filtration rate (<60 mL/min/1.73 m(2)) is also an independent risk factor for cardiovascular events and death. Detection of diabetic nephropathy during its initial stages provides the opportunity for early therapeutic interventions to prevent or delay the onset of complications and improve outcomes. An intensive and multifactorial management approach is needed that targets all risk determinants simultaneously. The strategy should comprise lifestyle modifications (smoking cessation, weight loss, increased physical activity, and dietary changes) coupled with therapeutic achievement of blood glucose, blood pressure, and lipid goals that are evidence-based. Prescribing decisions should take into account demographic factors, level of kidney impairment, adverse effects, risk of hypoglycemia, tolerability, and effects on other risk factors and comorbidities. Regular and comprehensive follow-up assessments with appropriate adjustment of the therapeutic regimen to maintain risk factor control is a vital component of care, including referral to specialists, when required.

Therapy in the early stage: incretins

The complex pathological mechanisms responsible for development of type 2 diabetes are not fully addressed by conventional drugs, which are also associated with inconvenient side effects such as weight gain or hypoglycemia. Two types of incretin-based therapies are now in use: incretin mimetics (glucagon-like peptide-1 [GLP-1] receptor agonists that bind specific receptors and mimic the action of natural GLP-1) and incretin enhancers (inhibitors of the enzyme that degrade the incretin hormones and thus prolong their activity). Both offer important advantages over previous agents. In addition to the proven glucose-lowering efficacy, they promote weight loss (or are weight neutral) by slowing gastric emptying and inducing satiety, inhibit glucagon secretion with maintenance of counterregulatory mechanisms, and exhibit cardiovascular benefits, while having a low risk profile. Importantly, short-term studies have shown that incretins/incretin-based therapies protect β-cells (by enhancing cell proliferation and differentiation and inhibiting apoptosis) and stimulate their function (by recruiting β-cells to the secretory process and increasing insulin biosynthesis/secretion). These therapies have the opportunity to interfere with the disease progression if used as an early intervention, when enough β-cell mass/function can still be preserved or restored.

Incretin-based therapy: a powerful and promising weapon in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a progressive multisystemic disease that increases significantly cardiovascular morbidity and mortality. It is associated with obesity, insulin resistance, beta-cell dysfunction, and hyperglucagonemia, the combination of which typically leads to hyperglycemia. Incretin-based treatment modalities, and in particular glucagon-like peptide 1 (GLP-1) receptor agonists, are able to successfully counteract several of the underlying pathophysiological abnormalities of T2DM. The pancreatic effects of GLP-1 receptor agonists include glucose-lowering effects by stimulating insulin secretion and inhibiting glucagon release in a strictly glucose-dependent manner, increased beta-cell proliferation, and decreased beta-cell apoptosis. GLP-1 receptors are widely expressed throughout human body; thus, GLP-1-based therapies exert pleiotropic and multisystemic effects that extend far beyond pancreatic islets. A large body of experimental and clinical data have suggested a considerable protective role of GLP-1 analogs in the cardiovascular system (decreased blood pressure, improved endothelial and myocardial function, functional recovery of failing and ischemic heart, arterial vasodilatation), kidneys (increased diuresis and natriuresis), gastrointestinal tract (delayed gastric emptying, reduced gastric acid secretion), and central nervous system (appetite suppression, neuroprotective properties). The pharmacologic use of GLP-1 receptor agonists has been shown to reduce bodyweight and systolic blood pressure, and significantly improve glycemic control and lipid profile. Interestingly, weight reduction induced by GLP-1 analogs reflects mainly loss of abdominal visceral fat. The critical issue of whether the emerging positive cardiometabolic effects of GLP-1 analogs can be translated into better clinical outcomes for diabetic patients in terms of long-term hard endpoints, such as cardiovascular morbidity and mortality, remains to be elucidated with prospective, large-scale clinical trials.

Significance of hydrogen sulfide production in the pancreatic β-cell

Hydrogen sulfide (H(2)S) is an important signaling molecule in various mammalian cells and tissues. H(2)S is synthesized from L-cysteine and regulates several cellular and physiological phenomena (vasorelaxation, hormone secretion, and apoptosis) and multicellular events (neuromodulation and inflammatory responses). H(2)S can be produced in pancreatic β-cells by cystathionine β-synthase (CBS) or cystathionine γ-lyase (CSE). H(2)S inhibits insulin release and regulates β-cell survival. We found that glucose stimulation increased CSE expression at transcript and protein levels in mouse pancreatic islets. We also found that H(2)S protects β-cells that were chronically exposed to high glucose from apoptotic cell death. Loss of β-cell mass and failures of β-cell function are important in the pathogenesis and/or progression of diabetes mellitus; therefore, molecular analyses of the mechanisms of H(2)S production and its protective effects on β-cells may lead to new insights into diabetes mellitus.

Effects of chronic administration of alogliptin on the development of diabetes and β-cell function in high fat diet/streptozotocin diabetic mice

AIM

Alogliptin is a potent and highly selective dipeptidyl peptidase-4 (DPP-4) inhibitor. The aim of this study was to determine its effects on glucose control and pancreas islet function and to identify the underlying molecular mechanisms after chronic administration, in a non-genetic mouse model of type 2 diabetes.

METHODS

Alogliptin (5, 15 and 45 mg/kg) was orally administered to high fat diet/streptozotocin (HFD/STZ) diabetic mice daily for 10 weeks. Postprandial and 6-h fasting blood glucose levels, blood A1C level, oral glucose tolerance and pancreas insulin content were measured during or after the treatment period. Alogliptin plasma concentration was determined by an LC/MS/MS method. Islet morphology and architectural changes were evaluated with immunohistochemical analysis. Islet endocrine secretion ability was assessed by measuring insulin release from isolated islets which were challenged with 16 mM glucose and 30 mM potassium chloride, respectively. Gene expression profiles of the pancreas were analysed using the mouse diabetes RT(2) Profiler PCR array which contains 84 genes related to the onset, development and progression of diabetes.

RESULTS

Alogliptin showed dose-dependent reduction of postprandial and fasting blood glucose levels and blood A1C levels. Glucose clearance ability and pancreas insulin content were both increased. Alogliptin significantly restored the β-cell mass and islet morphology, thus preserving islet function of insulin secretion. Expression of 10 genes including Ins1 was significantly changed in the pancreas of diabetic mice. Chronic alogliptin treatment completely or partially reversed the abnormalities in gene expression.

CONCLUSIONS

Chronic treatment of alogliptin improved glucose control and facilitated restoration of islet architecture and function in HFD/STZ diabetic mice. The gene expression profiles suggest that the underlying molecular mechanisms of β-cell protection by alogliptin may involve alleviating endoplasmic reticulum burden and mitochondria oxidative stress, increasing β-cell differentiation and proliferation, enhancing islet architecture remodelling and preserving islet function.

Influence of hepatic impairment on pharmacokinetics of the human GLP-1 analogue, liraglutide

AIMS

To compare the pharmacokinetics (PK) of a single-dose of liraglutide in subjects with hepatic impairment.

METHODS

This parallel group, open label trial involved four groups of six subjects with healthy, mild, moderate and severe hepatic impairment, respectively. Each subject received 0.75 mg of liraglutide (s.c., thigh), and blood samples were taken over 72 h for PK assessment. Standard laboratory and safety data were collected. The primary endpoint was area under the plasma liraglutide concentration–time curve from time zero to infinity (AUC(0,∞)).

RESULTS

Exposure to liraglutide was not increased by hepatic impairment. On the contrary, mean AUC(0,∞) was highest for healthy subjects and lowest for subjects with severe hepatic impairment (severe/healthy: 0.56, with 90% CI 0.39, 0.81) and equivalence in this parameter across groups was not demonstrated. C_max also tended to decrease with hepatic impairment (severe/healthy: 0.71, with 90% CI 0.52, 0.97), but t_max was similar across groups (11.3–13.2 h). There were no serious adverse events, hypoglycaemic episodes or clinically significant changes in laboratory parameters and liraglutide was considered well tolerated.

CONCLUSIONS

This study indicated no safety concerns regarding use of liraglutide in patients with hepatic impairment. Exposure to liraglutide was not increased by impaired liver function; rather, the results suggest a decreased exposure with increasing degree of hepatic impairment. However, data are not conclusive to suggest a dose increase of liraglutide. Thus, the results indicate that patients with type 2 diabetes mellitus and hepatic impairment can use standard treatment regimens of liraglutide. There is, however, currently limited clinical experience with liraglutide in patients with hepatic impairment.

Liraglutide - overview of the preclinical and clinical data and its role in the treatment of type 2 diabetes

Type 2 diabetes is characterized by a progressive decline in glycaemic control. Many standard diabetes treatments, however, fail to achieve or maintain glycaemic control, and are often associated with an increased risk of hypoglycaemia and weight gain. Recently developed incretin-based therapies are a promising addition to the current armamentarium of diabetes treatments. Two types of incretin-based therapies are currently available: glucagon-like peptide (GLP)-1 receptor agonists (liraglutide and exenatide) and dipeptidyl peptidase-4 inhibitors (sitaglipin, vildagliptin and saxagliptin). This review aims to summarize the key efficacy and safety data of liraglutide, a once-daily human GLP-1 analogue. Extensive phase III clinical trials have shown liraglutide to improve glycaemic control with additional benefits on body weight, blood pressure and β-cell function. Liraglutide is also generally well tolerated with a low risk of hypoglycaemia. Liraglutide has recently been approved for marketing in Europe, Japan and the USA.

Design, synthesis, and biological activity of potent and orally available G protein-coupled receptor 40 agonists

G protein-coupled receptor 40 (GPR40) is being recently considered to be a new potential drug target for the treatment of type 2 diabetes because of its role in the enhancement of free fatty acid-regulated glucose-stimulated insulin secretion in pancreatic β-cells. We initially identified benzyloxyphenylpropanoic acid (1b) (EC(50) = 510 nM), which was designed based on the structure of free fatty acids, as a promising lead compound with GPR40 agonist activity. Chemical modification of compound 1b led to the discovery of 3-{4-[(2',6'-dimethylbiphenyl-3-yl)methoxy]-2-fluorophenyl}propanoic acid (4p) as a potent GPR40 agonist (EC(50) = 5.7 nM). Compound 4p exhibited acceptable pharmacokinetic profiles and significant glucose-lowering effects during an oral glucose tolerance test in diabetic rats. Moreover, no hypoglycemic event was observed even after administration of a high dose of compound 4p to normal fasted rats. These pharmacological results suggest that GPR40 agonists might be novel glucose-dependent insulin secretagogues with little or no risk of hypoglycemia.

Inflammation of the hypothalamus leads to defective pancreatic islet function

Type 2 diabetes mellitus results from the complex association of insulin resistance and pancreatic β-cell failure. Obesity is the main risk factor for type 2 diabetes mellitus, and recent studies have shown that, in diet-induced obesity, the hypothalamus becomes inflamed and dysfunctional, resulting in the loss of the perfect coupling between caloric intake and energy expenditure. Because pancreatic β-cell function is, in part, under the control of the autonomic nervous system, we evaluated the role of hypothalamic inflammation in pancreatic islet function. In diet-induced obesity, the earliest markers of hypothalamic inflammation are present at 8 weeks after the beginning of the high fat diet; similarly, the loss of the first phase of insulin secretion is detected at the same time point and is restored following sympathectomy. Intracerebroventricular injection of a low dose of tumor necrosis factor α leads to a dysfunctional increase in insulin secretion and activates the expression of a number of markers of apoptosis in pancreatic islets. In addition, the injection of stearic acid intracerebroventricularly, which leads to hypothalamic inflammation through the activation of tau-like receptor-4 and endoplasmic reticulum stress, produces an impairment of insulin secretion, accompanied by increased expression of markers of apoptosis. The defective insulin secretion, in this case, is partially dependent on sympathetic signal-induced peroxisome proliferator receptor-γ coactivator Δα and uncoupling protein-2 expression and is restored after sympathectomy or following PGC1α expression inhibition by an antisense oligonucleotide. Thus, the autonomic signals generated in concert with hypothalamic inflammation can impair pancreatic islet function, a phenomenon that may explain the early link between obesity and defective insulin secretion.

Alogliptin: a review of its use in the management of type 2 diabetes mellitus

Alogliptin (Nesina®) is a dipeptidyl peptidase-4 inhibitor that is approved in Japan for the treatment of adult patients with type 2 diabetes mellitus that is inadequately controlled by diet and exercise alone or by diet plus treatment with an α-glucosidase inhibitor. Alogliptin plus diet and exercise is also approved in Japan for use in combination with a thiazolidinedione in patients with type 2 diabetes. In several large (n >250), double-blind, multinational trials of up to 26 weeks' duration, oral alogliptin as monotherapy or in combination with other oral antihyperglycaemic agents (metformin, glibenclamide or pioglitazone) or insulin therapy improved glycaemic control and was generally well tolerated in adult patients with inadequately controlled type 2 diabetes, including elderly patients. Significant improvements in glycaemic control were evident from as early as 1 week in terms of improvements in mean fasting plasma glucose levels and from 4 weeks onwards for improvements in mean glycosylated haemoglobin levels. In general, the incidence of hypoglycaemia was similar to that seen in placebo groups and alogliptin treatment had neutral effects on bodyweight and lipid parameters. The long-term safety of alogliptin therapy remains to be established in clinical studies and with clinical experience. A planned clinical trial evaluating long-term clinical outcomes in patients with acute coronary syndrome and other planned or ongoing short-term trials will help to more definitively determine the position of alogliptin therapy in relation to other available antihyperglycaemic therapies. In the meantime, alogliptin is a promising new option for the treatment of patients with type 2 diabetes, including elderly patients.

Ranolazine increases β-cell survival and improves glucose homeostasis in low-dose streptozotocin-induced diabetes in mice

In addition to its anti-ischemic and antianginal effects, ranolazine has been shown to lower hemoglobin A(1c) (HbA(1c)) in patients with coronary artery disease and diabetes. The present study was undertaken to test the hypothesis that ranolazine lowers HbA(1c) because of improved glucose homeostasis in an animal model. Diabetes in mice was induced by giving multiple low doses of streptozotocin. Ranolazine was given twice daily via an oral gavage (20 mg/kg) for 8 weeks. Fasting plasma glucose levels were significantly lower in the ranolazine-treated group (187 ± 19 mg/dl) compared with the vehicle group (273 ± 23 mg/dl) at 8 weeks. HbA(1c) was 5.8 ± 0.4% in the vehicle group and 4.5 ± 0.2% in the ranolazine-treated group (p < 0.05). Glucose disposal during the oral glucose tolerance test (OGTT) and insulin tolerance test were not different between the two groups; however, during OGTT, peak insulin levels were significantly (p < 0.05) higher in ranolazine-treated mice. Mice treated with ranolazine had healthier islet morphology and significantly (p < 0.01) higher β-cell mass (69 ± 2% per islet) than the vehicle group (50 ± 5% per islet) as determined from hematoxylin and eosin staining. The number of apoptotic cells was significantly (p < 0.05) less in the pancreas of the ranolazine-treated group (14 ± 2% per islet) compared with the vehicle group (24 ± 4% per islet). In addition, ranolazine increased glucose-stimulated insulin secretion in rat and human islets in a glucose-dependent manner. These data suggest that ranolazine may be a novel antidiabetic agent that causes β-cell preservation and enhances insulin secretion in a glucose-dependent manner in diabetic mice.

Liraglutide provides similar glycaemic control as glimepiride (both in combination with metformin) and reduces body weight and systolic blood pressure in Asian population with type 2 diabetes from China, South Korea and India: a 16-week, randomized, double-blind, active control trial(*)

AIM

To assess and compare the efficacy and safety of liraglutide with those of glimepiride, both in combination with metformin for the treatment of type 2 diabetes in Asian population from China, South Korea and India.

METHODS

A 16-week, randomized, double-blind, double-dummy, four-arm, active control trial was carried out. In total, 929 subjects with type 2 diabetes with a mean (±s.d.) age of 53.3 ± 9.5 years, HbA₁(c) of 8.6 ± 1.0% and body weight of 68.1 ± 11.7 kg were randomized (liraglutide 0.6, 1.2 or 1.8 mg once daily or glimepiride 4 mg once daily all in combination with metformin: 1 : 1 : 1 : 1). One subject withdrew immediately after randomization and before exposure.

RESULTS

HbA₁(c) was significantly reduced in all groups compared with baseline. Treatment with liraglutide 1.2 and 1.8 mg was non-inferior to glimepiride (mean HbA₁(c) reduction: 1.36% points, 1.45% points and 1.39% points, respectively). No significant difference was shown in the percentage of subjects reaching American Diabetes Association HbA₁(c) target <7% or American Association of Clinical Endocrinologists target ≤6.5% between liraglutide 1.2 and 1.8 mg and glimepiride. Liraglutide was associated with a 1.8-2.4 kg mean weight reduction, compared with a 0.1 kg mean weight gain with glimepiride. Liraglutide led to a significantly greater reduction in systolic blood pressure (SBP) compared with glimepiride. Two subjects in the glimepiride group reported major hypoglycaemia while none in the liraglutide groups. Liraglutide was associated with about 10-fold lower incidence of minor hypoglycaemia than glimepiride. Gastrointestinal disorders were the most common adverse events (AEs) for liraglutide, but were transient and resulted in few withdrawals.

CONCLUSIONS

In Asian subjects with type 2 diabetes, once-daily liraglutide led to improvement in glycaemic control similar to that with glimepiride but with less frequent major and minor hypoglycaemia. Liraglutide also induced a significant weight loss and reduced SBP and was generally well tolerated. The most frequently reported AE was transient nausea. The effect of liraglutide in this Asian population is comparable to the effects seen in Caucasian, African American and Hispanic populations in global liraglutide phase 3 trials.

Rosiglitazone improves glucose metabolism in obese adolescents with impaired glucose tolerance: a pilot study

Impaired glucose tolerance (IGT) is a prediabetic state fueling the rising prevalence of type 2 diabetes mellitus (T2DM) in adolescents with marked obesity. Given the importance of insulin resistance, the poor β-cell compensation and the altered fat partitioning as underlying defects associated with this condition, it is crucial to determine the extent to which these underlying abnormalities can be reversed in obese adolescents. We tested, in a pilot study, whether rosiglitazone (ROSI) restores normal glucose tolerance (NGT) in obese adolescents with IGT by improving insulin sensitivity and β-cell function. In a small randomized, double-blind, placebo (PLA)-controlled study, lasting 4 months, 21 obese adolescents with IGT received either ROSI (8 mg daily) (n = 12, 5M/7F, BMI z-score 2.44 ± 0.11) or PLA (n = 9, 4M/5F, BMI z-score 2.41 ± 0.09). Before and after treatment, all subjects underwent oral glucose tolerance test (OGTT), hyperinsulinemic-euglycemic clamp, magnetic resonance imaging, and (1)H NMR assessment. After ROSI treatment, 58% of the subjects converted to NGT compared to 44% in the PLA group (P = 0.528). Restoration of NGT was associated with a significant increase in insulin sensitivity (P < 0.04) and a doubling in the disposition index (DI) (P < 0.04), whereas in the PLA group, these changes were not significant. The short-term use of ROSI appears to be safe in obese adolescents with IGT. ROSI restores NGT by increasing peripheral insulin sensitivity and β-cell function, two principal pathophysiological abnormalities of IGT.

Buccal spray insulin in subjects with impaired glucose tolerance: the prevoral study

AIM

Postprandial hyperglycaemia is a consequence of reduced first phase insulin response and is associated with increased cardiovascular risk and mortality. The aim of this proof-of-concept study was to investigate the safety and efficacy of treatment with buccal spray insulin (Oral-lyn™, Generex Biotechnology Corporation, Toronto, Ontario, Canada) on postprandial plasma glucose and insulin levels in subjects with impaired glucose tolerance (IGT).

METHODS

A total of 19 female and 12 male Caucasian subjects, 52.2 ± 13.5 (SD) years old, having a body mass index of 33.1 ± 6 (SD) kg/m² with confirmed IGT were included in the study. Subjects were randomized to take 4, 6 or 12 Oral-lyn puffs (1 puff = 1 s.c. rapid insulin UI) split into two equal doses each, one before and the second 30 min after a standard 75 g oral glucose tolerance test (OGTT). Glucose and insulin levels were measured at baseline and 30, 60, 90, 120 and 180 min afterwards.

RESULTS

Glucose fluctuations during OGTT were not modified by 4 or 6 Oral-lyn puffs. Treatment with 12 puffs was followed by 29.6% decrease in plasma glucose at 2 h and 26.8% decrease at 3 h, altogether p = 0.01. Considering all time points of the OGTT, there was a mean reduction of 15.8% in glucose levels. With 6 of the total 12 puffs used in group C there was a significant increase in the insulin levels during OGTT at 30 min (p < 0.04) but not at 2 or 3 h. No hypoglycaemic episodes were observed at any time points of the OGTT.

CONCLUSIONS

This proof-of-concept study demonstrates that treatment with buccal spray insulin is a simple and valuable therapy for reducing postprandial hyperglycaemia in obese subjects with IGT. Importantly, this treatment is safe and none of the study subjects experienced hypoglycaemia.

Effect of alogliptin, pioglitazone and glargine on pancreatic β-cells in diabetic db/db mice

OBJECTIVE

Progressive β-cell dysfunction and loss of β-cell mass are fundamental pathogenic features of type 2 diabetes. To examine if anti-diabetic reagents, such as insulin, pioglitazone (pio), and alogliptin (alo), have protective effects on β-cell mass and function in vivo, we treated obese diabetic db/db mice with these reagents.

METHODS

Male db/db mice were treated with a chow including pio, alo, or both of them from 8 to 16 weeks of age. Insulin glargine (gla) was daily injected subcutaneously during the same period.

RESULTS

At 16 weeks of age, untreated db/db mice revealed marked increase of HbA1c level, whereas those treated with pio, pio+alo, or insulin revealed the almost same HbA1c levels as non-diabetic db/m mice. Islet mass evaluated by direct counting in the whole pancreas and insulin content in isolated islets were preserved in pio, pio+alo and gla groups compared with untreated or alo groups, and there was no difference among pio, pio+alo and gla groups. To precisely evaluate islet β-cell functions, islet perifusion analysis was performed. In pio, pio+alo and gla groups, biphasic insulin secretion was preserved compared with untreated or alo groups. In particular, pio+alo as well as gla therapy preserved almost normal insulin secretion, although pio therapy improved partially. To examine the mechanism how these reagents exerted beneficial effects on β-cells, we evaluated expression levels of various factors which are potentially important for β-cell functions by real-time RT-PCR and immunohistochemistry. The results showed that expression levels of MafA and GLP-1 receptor were markedly decreased in untreated and alo groups, but not in pio, pio+alo and gla groups.

CONCLUSION

Combination therapy with pio and alo almost completely normalized β-cell functions in vivo, which was comparable with gla treatment.

Does exercise have a role in the management of gestational diabetes mellitus?

Gestational diabetes mellitus (GDM) is associated with a marked increase in the long-term risk of type 2 diabetes and adverse pregnancy outcomes. Engaging in vigorous recreational physical activity prior to and during pregnancy significantly reduces the risk of developing GDM. In contrast, evidence of a therapeutic effect from participation in a structured exercise training regimen, although promising, is limited and requires further more substantial investigation. This paper briefly reviews the pathophysiology of GDM, the evidence related to physical activity participation and exercise regimen intervention on GDM, and the clinical considerations required for prescribing exercise.

Depletion of intranuclear rodlets in mouse models of diabetes

Intranuclear rodlets (INRs) are structures present within the nuclei of human insulin-secreting beta cells of the endocrine pancreas. Their physiological significance, and whether they are altered in disease, is unknown. In the present study, the proportion of pancreatic beta cells containing INRs was examined in mouse models of type II diabetes and in a model with improved beta cell function. To gain insights into the molecular regulators of INR formation, mice with a conditional adult beta cell-specific knockout of the serine/threonine protein kinase Lkb1 (Lkb1 adult beta cell knockout (LABKO) mice) were studied. To investigate INR changes in a pathophysiological context, beta cell INRs were examined in two models of human metabolic syndrome: (1) mice maintained on a high-fat diet and (2) leptin-deficient ob/ob mice. The proportion of beta cells containing INRs was significantly reduced in LABKO mice. This reduction was not mediated by two key downstream effectors of Lkb1, mTor and Mark2. High-fat diet regimen reduced beta cell INR frequency by more than 40%, and leptin-deficient ob/ob mice exhibited a dramatically (19-fold) reduced INR frequency relative to wild-type mice. Taken together, our results support the view that INR formation in pancreatic beta cells is a dynamic and regulated process. The substantial depletion of beta cell INRs in LABKO and diabetic mice suggests their relationship to beta cell function and potential involvement in diabetes pathogenesis.

Defining and achieving treatment success in patients with type 2 diabetes mellitus

Traditionally, successful treatment of patients with type 2 diabetes mellitus (DM) has been defined strictly by achievement of targeted glycemic control, primarily using a stepped-care approach that begins with changes in lifestyle combined with oral therapy that is slowly intensified as disease progression advances and β-cell function declines. However, stepped care is often adjusted without regard to the mechanism of hyperglycemia or without long-term objectives. A more comprehensive definition of treatment success in patients with type 2 DM should include slowing or stopping disease progression and optimizing the reduction of all risk factors associated with microvascular and macrovascular disease complications. To achieve these broader goals, it is important to diagnose diabetes earlier in the disease course and to consider use of more aggressive combination therapy much earlier with agents that have the potential to slow or halt the progressive β-cell dysfunction and loss characteristic of type 2 DM. A new paradigm for managing patients with type 2 DM should address the concomitant risk factors and morbidities of obesity, hypertension, and dyslipidemia with equal or occasionally even greater aggressiveness than for hyperglycemia. The use of antidiabetes agents that may favorably address cardiovascular risk factors should be considered more strongly in treatment algorithms, although no pharmacological therapy is likely to be ultimately successful without concomitant synergistic lifestyle changes. Newer incretin-based therapies, such as glucagon-like peptide 1 receptor agonists and dipeptidyl peptidase 4 inhibitors, which appear to have a favorable cardiovascular safety profile as well as the mechanistic possibility for a favorable cardiovascular risk impact, are suitable for earlier inclusion as part of combination regimens aimed at achieving comprehensive treatment success in patients with type 2 DM.

A novel treatment strategy for type 2 diabetes: Targeting glucose variability and β-cell failure

Blood glucose control has been a main focus for the treatment of type 2 diabetes. However, poor control and side-effect still are urgent problems to be solved. According to common blood glucose variability and its extremely deleterious diabetic-related complications in clinical practice, it should be considered as a potential key target. And β-cell failure has been approved that it can be reversible for early type 2 diabetes, which suggests another promising target. In this hypothesis, we propose a novel treatment strategy against on the two targets. An intelligent double-target drug delivery system is presented and characterized by dual-responsive functional gates for glucose sensitivity used controlled-release hypoglycemic agents and a sustained-release osmotic pump loaded drugs to repair impaired β-cell into the repository, respectively. The proposition may provide a new early therapeutic strategy for type 2 diabetes in order to better hold blood glucose homeostasis.

Oral insulin

Oral insulin is an exciting area of research and development in the field of diabetology. This brief review covers the various approaches used in the development of oral insulin, and highlights some of the recent data related to novel oral insulin preparation.

Comparison of metformin, gliclazide MR and rosiglitazone in monotherapy and in combination for type 2 diabetes

OBJECTIVE

To compare the efficacy and tolerability of metformin, rosiglitazone and gliclazide MR as monotherapy and in combination in the treatment of type 2 diabetes.

SUBJECTS AND METHODS

250 patients treated with oral antidiabetic agents for at least 24 weeks in monotherapy or in combination therapy were included in this retrospective study.

RESULTS

As monotherapy the reduction of fasting plasma glucose (FPG), postprandial glycemia (PPG) and HbA1c was similar with the three drugs after 24 weeks. Among patients on combination therapy, the reduction in HbA1c, FPG and PPG was significantly lower with rosiglitazone plus metformin, as compared to metformin plus gliclazide MR or gliclazide MR plus rosiglitazone. Patients treated with rosiglitazone achieved less favorable changes in lipid profile.

CONCLUSION

In monotherapy all drugs were equally effective in improving glycemic control, whereas the combination of metformin plus gliclazide MR provided the best results concerning the improvement of both, glycemic control and lipid profile.

DPP-4 inhibitors: what may be the clinical differentiators?

Attenuation of the prandial incretin effect, mediated by glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP), contributes to hyperglycemia in type 2 diabetes mellitus (T2DM). Since the launch of sitagliptin in 2006, a compelling body of evidence has accumulated showing that dipeptidyl peptidase-4 (DPP-4) inhibitors, which augment endogenous GLP-1 and GIP levels, represent an important advance in the management of T2DM. Currently, three DPP-4 inhibitors - sitagliptin, vildagliptin and saxagliptin - have been approved in various countries worldwide. Several other DPP-4 inhibitors, including linagliptin and alogliptin, are currently in clinical development. As understanding of, and experience with, the growing number of DPP-4 inhibitors broadens, increasing evidence suggests that the class may offer advantages over other antidiabetic drugs in particular patient populations. The expanding evidence base also suggests that certain differences between DPP-4 inhibitors may prove to be clinically significant. This therapeutic diversity should help clinicians tailor treatment to the individual patient, thereby increasing the proportion that safely attain target HbA(1c) levels, and reducing morbidity and mortality. This review offers an overview of DPP-4 inhibitors in T2DM and suggests some characteristics that may provide clinically relevant differentiators within this class.

Therapeutic Strategies to Increase Human β-Cell Growth and Proliferation by Regulating mTOR and GSK-3/β-Catenin Pathways

This perspective delineates approaches to develop therapeutic strategies to stimulate the proliferative potential of adult human β-cells in vitro. Previous findings demonstrated that nutrients, through regulation of mTOR signaling, promote regenerative processes including DNA synthesis, cell cycle progression and β-cell proliferation in rodent islets but rarely in human islets. Recently, we discovered that regulation of the Wnt/GSK-3/β-catenin pathway by directly inhibiting GSK-3 with pharmacologic agents, in combination with nutrient activation of mTOR, was required to increase growth and proliferation in human islets. Studies also revealed that nuclear translocation of β-catenin in response to GSK-3 inhibition regulated these processes and was rapamycin sensitive, indicating a role for mTOR. Human islets displayed a high level of insulin resistance consistent with the inability of exogenous insulin to activate Akt and engage the Wnt pathway by GSK-3 inhibition. This insulin resistance in human islets is not present in rodent islets and may explain the differential requirement in human islets to inhibit GSK-3 to enhance these regenerative processes. Human islets exhibited normal insulin secretion but a loss of insulin content, which was independent of all treatment conditions. The loss of insulin content may be related to insulin resistance, the isolation process or culture conditions. In this perspective, we provide strategies to enhance the proliferative capacity of adult human β-cells and highlight important differences between human and rodent islets: the lack of a nutrient response, requirement for direct GSK-3 inhibition, insulin resistance and loss of insulin content that emphasize the physiological significance of conducting studies in human islets.

The future use of liraglutide: implications of the LEAD-2 study for treatment guidelines in type 2 diabetes

The effective identification and management of type 2 diabetes (T2D) in primary care is a healthcare priority. New antidiabetic agents, including glucagon-like peptide (GLP)-1 receptor agonists, may help overcome drawbacks with current treatments. These new agents have been reviewed in the updated National Institute for Health and Clinical Excellence (NICE) guidelines for the treatment of T2D. Liraglutide, a GLP-1 receptor agonist, was licensed for use in patients with T2D after the development of the NICE guidelines. Data from Phase III trials evaluating liraglutide are presented here in the context of the role of GLP-1 receptor agonists in NICE guidelines.

FoxM1 is up-regulated by obesity and stimulates beta-cell proliferation

beta-Cell mass expansion is one mechanism by which obese animals compensate for insulin resistance and prevent diabetes. FoxM1 is a transcription factor that can regulate the expression of multiple cell cycle genes and is necessary for the maintenance of adult beta-cell mass, beta-cell proliferation, and glucose homeostasis. We hypothesized that FoxM1 is up-regulated by nondiabetic obesity and initiates a transcriptional program leading to beta-cell proliferation. We performed gene expression analysis on islets from the nondiabetic C57BL/6 Leptin(ob/ob) mouse, the diabetic BTBR Leptin(ob/ob) mouse, and an F2 Leptin(ob/ob) population derived from these strains. We identified obesity-driven coordinated up-regulation of islet Foxm1 and its target genes in the nondiabetic strain, correlating with beta-cell mass expansion and proliferation. This up-regulation was absent in the diabetic strain. In the F2 Leptin(ob/ob) population, increased expression of Foxm1 and its target genes segregated with higher insulin and lower glucose levels. We next studied the effects of FOXM1b overexpression on isolated mouse and human islets. We found that FoxM1 stimulated mouse and human beta-cell proliferation by activating many cell cycle phases. We asked whether FOXM1 expression is also responsive to obesity in human islets by collecting RNA from human islet donors (body mass index range: 24-51). We found that the expression of FOXM1 and its target genes is positively correlated with body mass index. Our data suggest that beta-cell proliferation occurs in adult obese humans in an attempt to expand beta-cell mass to compensate for insulin resistance, and that the FoxM1 transcriptional program plays a key role in this process.

The effect of early insulin therapy on pancreatic β-cell function and long-term glycemic control in newly diagnosed type 2 diabetic patients

BACKGROUND/AIMS

Based on the results of well designed clinical studies, intensive insulin therapy has been established to improve glycemic control in newly diagnosed diabetes. However, discrepancies exist between the findings of clinical trials and experiences in general practice. Furthermore, the efficacy of an early insulin therapy (EIT) - commonly used in general practice - on long-term glycemic control has not been established. Therefore, we evaluated the effects of EIT on pancreatic β-cell function and glycemic control using insulin-based methods widely employed in general practice.

METHODS

We performed a retrospective cohort study that initially involved reviewing patients' medical records. Following a thorough review, 61 patients who received either biphasic or prandial EIT at the time of diagnosis were enrolled. We then evaluated changes in β-cell function and glycemic control during a 48-month follow-up period.

RESULTS

Mean HbA1c decreased significantly as a result of EIT from 10.7 ± 1.8% to 6.2 ± 1.1% (p < 0.001). On average, 2.6 months was required to achieve an HbA1c value < 7%. EIT significantly improved the insulinogenic index. Glycemic control was well maintained for 48 months. More than 70% of patients were able to maintain glycemic control following lifestyle modifications or treatment with oral antidiabetic drugs. No significant differences were identified between patients receiving biphasic EIT and prandial EIT in terms of glycemic control or pancreatic β-cell function.

CONCLUSIONS

Our results suggest that regardless of the method of delivery, EIT significantly improves β-cell function and facilitates long-term glycemic control in patients with newly diagnosed type 2 diabetes mellitus.

Targeting beta-cell function early in the course of therapy for type 2 diabetes mellitus

OBJECTIVE

This report examines current perspectives regarding likely mechanisms of beta-cell failure in type 2 diabetes and their clinical implications for protecting or sparing beta-cells early in the disease progression. In addition, it considers translation strategies to incorporate relevant scientific findings into educational initiatives targeting clinical practice behavior.

PARTICIPANTS

On January 10, 2009, a working group of basic researchers, clinical endocrinologists, and primary care physicians met to consider whether current knowledge regarding pancreatic beta-cell defects justifies retargeting and retiming treatment for clinical practice. Based on this meeting, a writing group comprised of four meeting participants subsequently prepared this consensus statement. The conference was convened by The Endocrine Society and funded by an unrestricted educational grant from Novo Nordisk.

EVIDENCE

Participants reviewed and discussed published literature, plus their own unpublished data.

CONSENSUS PROCESS

The summary and recommendations were supported unanimously by the writing group as representing the consensus opinions of the working group.

CONCLUSIONS

Workshop participants strongly advocated developing new systems to address common barriers to glycemic control and recommended several initial steps toward this goal. These recommendations included further studies to establish the clinical value of pharmacological therapies, continuing basic research to elucidate the nature and mechanisms of beta-cell failure in type 2 diabetes mellitus, and exploring new educational approaches to promote pathophysiology-based clinical practices. The Endocrine Society has launched a new website to continue the discussion between endocrinologists and primary care physicians on beta-cell pathophysiology in type 2 diabetes and its clinical implications. Join the conversation at http://www.betacellsindiabetes.org

Exendin-4 stimulates proliferation of human coronary artery endothelial cells through eNOS-, PKA- and PI3K/Akt-dependent pathways and requires GLP-1 receptor

Endothelial cells have a robust capacity to proliferate and participate in angiogenesis, which underlies the maintenance of intimal layer integrity. We previously showed the presence of the GLP-1 receptor in human coronary artery endothelial cells (HCAECs) and the ameliorative actions of GLP-1 on endothelial dysfunction in type 2 diabetic patients. Here, we have studied the effect of exendin-4 on cell proliferation and its underlying mechanisms in HCAECs. Incubation of HCAECs with exendin-4 resulted in a dose-dependent increase in DNA synthesis and an increased cell number, associated with an enhanced eNOS and Akt activation, which were inhibited by PKA, PI3K, Akt or eNOS inhibitors and abolished by a GLP-1 receptor antagonist. Similar effects were obtained by applying GLP-1 (7-36) or GLP-1 (9-36). Co-incubation of exendin-4 and GLP-1 did not show additive effects. Our results suggest that exendin-4 stimulates proliferation of HCAECs through PKA-PI3K/Akt-eNOS activation pathways via a GLP-1 receptor-dependent mechanism.

A dose range finding study of novel oral insulin (IN-105) under fed conditions in type 2 diabetes mellitus subjects

AIM

The objective of the study was to establish the dose response of IN-105 tablets and explore a possible therapeutic window in type 2 diabetes subjects poorly controlled on metformin.

METHODS

The primary objective was to examine the effect of sequential single ascending doses of IN-105 on the plasma glucose concentration under fed conditions. All subjects received, sequentially, matching placebo, 10, 15, 20 and 30 mg IN-105 tablets in five consecutive periods. Tablets were administered 20 min prior to meal in all the periods. Plasma levels of immunoreactive insulin, C-peptide and glucose were measured up to 180 min from the time of dosing. The changes in postprandial glucose levels at 120 min in response to IN-105 administration were also compared against those of placebo.

RESULTS

Changes in glucose from baseline (mean +/- s.d.) at 140 min (2 h postprandial) were 94.84 +/- 22.3, 79.45 +/- 43.00, 70.68 +/- 35.71, 63.47 +/- 42.75 and 53.06 +/- 47.27 mg/dL, respectively, and exhibited linear dose-response. The insulin C(max) values were found to be 50.8 +/- 26.0 mU/L for placebo, 100.3 +/- 66.7 with 10 mg IN-105, 177.69 +/- 150.3 with 15 mg IN-105, 246.2 +/- 245.2 with 20 mg IN-105 and 352.5 +/- 279.3 mU/L with 30 mg of IN-105.

CONCLUSIONS

IN-105 absorption is proportional to the dose administered. The 2-h postprandial glucose excursion was reduced in a dose proportional manner. Circulating C-peptide levels were found to be suppressed in proportion to the IN-105 exposure. IN-105 reduces glucose excursion despite lower endogenous insulin secretion. IN-105 seems to have a wide therapeutic window as no clinical hypoglycaemia was observed at any of the doses studied.

Efficacy and safety of vildagliptin and voglibose in Japanese patients with type 2 diabetes: a 12-week, randomized, double-blind, active-controlled study

AIM

To confirm the efficacy of vildagliptin in patients with type 2 diabetes (T2D) by testing the hypothesis that glycosylated haemoglobin (HbA1c) reduction with vildagliptin is superior to that with voglibose after 12 weeks of treatment.

METHODS

In this 12-week, randomized, double-blind, active-controlled, parallel-group study, the efficacy and safety of vildagliptin (50 mg bid, n = 188) was compared with that of voglibose (0.2 mg tid, n = 192) in patients with T2D who were inadequately controlled with diet and exercise.

RESULTS

The characteristics of two groups were well matched at baseline. The mean age, body mass index (BMI) and HbA1c were 59.1 years, 24.9 kg/m(2) and 7.6%, respectively. At baseline, fasting plasma glucose (FPG) and 2-h postprandial glucose (PPG) were 9.01 mmol/l (162.2 mg/dl) and 13.57 mmol/l (244.3 mg/dl), respectively. The adjusted mean change in HbA1c from baseline to endpoint was -0.95 +/- 0.04% in the vildagliptin-treated patients and -0.38 +/- 0.04% in those receiving voglibose (between-group change = 0.57 +/- 0.06%, 95% confidence interval (CI) (-0.68 to -0.46%), p < 0.001), showing that vildagliptin was superior to voglibose. Endpoint HbA1c < or = 6.5% was achieved in 51% vildagliptin-treated patients compared with 24% patients who were on voglibose (p < 0.001). Vildagliptin also exhibited significantly (p < 0.001) greater reduction compared with voglibose in both FPG [1.34 vs. 0.43 mmol/l (24.1 vs. 7.8 mg/dl)] and 2-h PPG [2.86 vs. 1.1 mmol/l (51.5 vs. 19.8 mg/dl)]. Overall adverse events (AEs) were lower in the vildagliptin-treated patients compared with that in the voglibose-treated patients (61.2 vs. 71.4%), with no incidence of hypoglycaemia and serious adverse events with vildagliptin. Gastrointestinal AEs were significantly lower with vildagliptin compared with that of the voglibose (18.6 vs. 32.8%; p = 0.002).

CONCLUSIONS

Vildagliptin (50 mg bid) showed superior efficacy and better tolerability compared with voglibose in Japanese patients with T2D.

Sitagliptin: a review of its use in the management of type 2 diabetes mellitus

Sitagliptin (Januvia, Glactiv(R), Tesavel(R)) is a dipeptidyl peptidase-4 inhibitor indicated for the treatment of type 2 diabetes mellitus. Oral sitagliptin as monotherapy or combination therapy was generally well tolerated and improved glycaemic control in well designed clinical trials in patients with type 2 diabetes. Glycosylated haemoglobin (HbA(1c)) levels were significantly reduced with sitagliptin monotherapy relative to voglibose monotherapy or placebo, and with sitagliptin as initial combination therapy with metformin or pioglitazone relative to monotherapy with these agents or placebo. Moreover, sitagliptin monotherapy was noninferior to metformin monotherapy in terms of the reduction in HbA(1c) levels. Significant reductions in HbA(1c) levels, relative to background therapy, were also observed with sitagliptin add-on therapy to ongoing treatment with thiazolidinediones, sulfonylureas or insulin with or without metformin, or metformin alone. In terms of the reduction in HbA(1c) levels as add-on treatment to metformin, sitagliptin was noninferior to glipizide and generally did not differ from rosiglitazone, and as add-on treatment to pioglitazone, it did not differ significantly from metformin. Sitagliptin had a low risk of hypoglycaemia (except when used in combination with agents that may be associated with hypoglycaemia, such as sulfonylureas or insulin) and was generally weight-neutral. Although additional comparative data and longer-term studies with glycaemic and clinical outcomes are required to definitively position sitagliptin relative to other antihyperglycaemic agents, current evidence suggests that it is a useful treatment option for patients with type 2 diabetes, with potential advantages including oral administration, a generally weight-neutral effect and a low risk of hypoglycaemia.

Loss of AMP-activated protein kinase alpha2 subunit in mouse beta-cells impairs glucose-stimulated insulin secretion and inhibits their sensitivity to hypoglycaemia

AMPK (AMP-activated protein kinase) signalling plays a key role in whole-body energy homoeostasis, although its precise role in pancreatic beta-cell function remains unclear. In the present study, we therefore investigated whether AMPK plays a critical function in beta-cell glucose sensing and is required for the maintenance of normal glucose homoeostasis. Mice lacking AMPK alpha2 in beta-cells and a population of hypothalamic neurons (RIPCre alpha2KO mice) and RIPCre alpha2KO mice lacking AMPK alpha1 (alpha1KORIPCre alpha2KO) globally were assessed for whole-body glucose homoeostasis and insulin secretion. Isolated pancreatic islets from these mice were assessed for glucose-stimulated insulin secretion and gene expression changes. Cultured beta-cells were examined electrophysiologically for their electrical responsiveness to hypoglycaemia. RIPCre alpha2KO mice exhibited glucose intolerance and impaired GSIS (glucose-stimulated insulin secretion) and this was exacerbated in alpha1KORIPCre alpha2KO mice. Reduced glucose concentrations failed to completely suppress insulin secretion in islets from RIPCre alpha2KO and alpha1KORIPCre alpha2KO mice, and conversely GSIS was impaired. Beta-cells lacking AMPK alpha2 or expressing a kinase-dead AMPK alpha2 failed to hyperpolarize in response to low glucose, although KATP (ATP-sensitive potassium) channel function was intact. We could detect no alteration of GLUT2 (glucose transporter 2), glucose uptake or glucokinase that could explain this glucose insensitivity. UCP2 (uncoupling protein 2) expression was reduced in RIPCre alpha2KO islets and the UCP2 inhibitor genipin suppressed low-glucose-mediated wild-type mouse beta-cell hyperpolarization, mimicking the effect of AMPK alpha2 loss. These results show that AMPK alpha2 activity is necessary to maintain normal pancreatic beta-cell glucose sensing, possibly by maintaining high beta-cell levels of UCP2.

Type 2 diabetes mellitus and the cardiometabolic syndrome: impact of incretin-based therapies

The rates of type 2 diabetes mellitus, obesity, and cardiovascular disease (CVD) continue to increase at epidemic proportions. It has become clear that these disease states are not independent but are frequently interrelated. By addressing conditions such as obesity, insulin resistance, stress hyperglycemia, impaired glucose tolerance, and diabetes mellitus, with its micro- and macrovascular complications, a specific treatment strategy can be developed. These conditions can be addressed by early identification of patients at high risk for type 2 diabetes, prompt and aggressive treatment of their hyperglycemia, recognition of the pleiotropic and synergistic benefits of certain antidiabetes agents on CVD, and thus, avoiding potential complications including hypoglycemia and weight gain. Incretin-based therapies, which include glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-IV (DPP-IV) inhibitors, have the potential to alter the course of type 2 diabetes and associated CVD complications. Advantages of these therapies include glucose-dependent enhancement of insulin secretion, infrequent instances of hypoglycemia, weight loss with GLP-1 receptor agonists, weight maintenance with DPP-IV inhibitors, decreased blood pressure, improvements in dyslipidemia, and potential beneficial effects on CV function.

Pancreatic steatosis in humans: cause or marker of lipotoxicity?

PURPOSE OF REVIEW

Type 2 diabetes mellitus (T2DM) is characterized by impaired insulin secretion. Chronically increased levels of plasma nonesterified fatty acids (NEFA) and triglyceride-rich lipoproteins impair beta-cell function, a process referred to as lipotoxicity. Furthermore, when NEFA supply exceeds metabolic capacity, lipids accumulate in nonadipose tissues, such as pancreatic islets, inducing organ dysfunction. The purpose of this review is to describe the mechanisms underlying lipotoxicity in vitro, to discuss the evidence for lipotoxicity in vivo and to address whether pancreatic lipid accumulation interferes with insulin secretion in humans.

RECENT FINDINGS

Although numerous in-vitro studies have shown that chronically elevated NEFA levels induce beta-cell dysfunction and apoptosis, studies in humans are less conclusive. It has been acknowledged that concurrent hyperglycaemia amplifies the adverse effects of elevated plasma NEFA levels on beta-cell function; therefore glucolipotoxicity should be the preferred term. Lipid accumulation in pancreatic islets impaired beta-cell secretory capacity in leptin-deficient rodents. In humans, recent studies employing noninvasive magnetic resonance-technology and computed tomography-technology, lipid accumulation in the pancreas was increased in individuals with impaired glucose metabolism and T2DM. However, there was no clear association with beta-cell dysfunction.

SUMMARY

To date, it is difficult to provide evidence that intraislet lipid accumulation truly exists in humans and that it is indeed causal to beta-cell dysfunction. Additional research is warranted to further detail the nature and role of pancreatic lipid content in humans, its consequence for the postulated processes pertinent to glucolipotoxicity and its contribution to the progressive nature of beta-cell dysfunction in prediabetes.

Is the ADA/EASD algorithm for the management of type 2 diabetes (January 2009) based on evidence or opinion? A critical analysis

The ADA and the EASD recently published a consensus statement for the medical management of hyperglycaemia in patients with type 2 diabetes. The authors advocate initial treatment with metformin monotherapy and lifestyle modification, followed by addition of basal insulin or a sulfonylurea if glycaemic goals are not met (tier 1 recommendations). All other glucose-lowering therapies are relegated to a secondary (tier 2) status and only recommended for selected clinical settings. In our view, this algorithm does not offer physicians and patients the appropriate selection of options to individualise and optimise care with a view to sustained control of blood glucose and reduction both of diabetes complications and cardiovascular risk. This paper critically assesses the basis of the ADA/EASD algorithm and the resulting tiers of treatment options.

Avoiding hypoglycaemia while achieving good glycaemic control in type 2 diabetes through optimal use of oral agent therapy

BACKGROUND

Patients with type 2 diabetes appear to be at relatively low risk of severe hypoglycaemia and hypoglycaemia unawareness in the early stages of disease. However, declining endogenous insulin secretory capacity due to beta-cell dysfunction/failure eventually produces vulnerability similar to type 1 diabetes. Severe hypoglycaemia itself is associated with serious morbidity and sometimes mortality, and represents an important barrier to achieving glycaemic goals and thus may reduce the protection from diabetes-related morbidity provided by good glycaemic control. Achieving an optimal balance of good glycaemic control and low risk of hypoglycaemia is key to providing optimum care in individuals with type 2 diabetes. This article discusses the issues related specifically to hypoglycaemia associated with oral agent therapy and how these agents may be best employed to provide an optimal balance between hypoglycaemia and good glycaemic control.

METHODS

Embase and Medline searches from 1998 to 2009 using the search terms DPP-4 inhibitors, metformin, oral agents, sulphonylureas, thiazolidinediones AND hypoglycaemia were conducted to identify relevant articles. The limitations inherent in this retrospective, narrative review of previously published publications chosen at the author's discretion are acknowledged.

FINDINGS

Failure to address even mild hypoglycaemia and glycaemic control early in the course of the disease may compromise the success of treatment in the longer term. Metformin, thiazolidinediones and DPP-4 inhibitors, either as monotherapy or in combination with each other, have a well-characterised low propensity to cause hypoglycaemia compared with other therapies.

CONCLUSIONS

Metformin, thiazolidinediones and DPP-4 inhibitors appear to be the most appropriate oral options for minimising the risk of hypoglycaemia. Early and ongoing attention to hypoglycaemia should form an integral part of any long-term glucose control strategy.

Lessons from models of pancreatic beta cells for engineering glucose-sensing cells

Mathematical models of pancreatic beta cells suggest design principles that can be applied to engineering cells to sense glucose and secrete insulin. Engineering cells can potentially both contribute to future diabetes therapies and generate new insights into beta-cell function. The focus is on ion channels, Ca(2+)handling, and elements of metabolism that combine to produce the varied oscillatory patterns exhibited by beta cells.