Exenatide effects on diabetes, obesity, cardiovascular risk factors and hepatic biomarkers in patients with type 2 diabetes treated for at least 3 years

Current issues in the treatment of type 2 diabetes. Overview of newer agents: where treatment is going

Impaired insulin secretion (beta-cell), increased hepatic glucose production (liver), and decreased peripheral (muscle) glucose utilization constitute the traditional primary defects responsible for the development and progression of type 2 diabetes mellitus. beta-Cell failure, ultimately leading to decreased insulin secretion, is now known to occur much earlier in the natural history of type 2 diabetes than originally believed. Additionally, a better understanding of the pathophysiology of type 2 diabetes reveals other etiologic mechanisms beyond the classic triad, now referred to as the ominous octet. In addition to the beta-cell, liver, and muscle, other pathogenic mechanisms include adipocyte insulin resistance (increased lipolysis), reduced incretin secretion/sensitivity (gastrointestinal), increased glucagon secretion (alpha-cell), enhanced glucose reabsorption (kidney), and central nervous system insulin resistance resulting from neurotransmitter dysfunction (brain). Currently, the management of type 2 diabetes focuses on glucose control via lowering of blood glucose (fasting and postprandial) and hemoglobin A(1c). However, the goal of therapy should be to delay disease progression and eventual treatment failure. Treatment should target the known pathogenic disturbances of the disease (i.e., reducing the deterioration of beta-cell function and improving insulin sensitivity). In recent years, treatment strategies have focused on the development of novel therapeutic options that affect many of the defects contributing to type 2 diabetes and that provide durable glucose control through a blunting of disease progression. Optimal management of type 2 diabetes should include early initiation of therapy using multiple drugs, with different mechanisms of action, in combination.

Regulation of lipid metabolism by energy availability: a role for the central nervous system

The central nervous system (CNS) is crucial in the regulation of energy homeostasis. Many neuroanatomical studies have shown that the white adipose tissue (WAT) is innervated by the sympathetic nervous system, which plays a critical role in adipocyte lipid metabolism. Therefore, there are currently numerous reports indicating that signals from the CNS control the amount of fat by modulating the storage or oxidation of fatty acids. Importantly, some CNS pathways regulate adipocyte metabolism independently of food intake, suggesting that some signals possess alternative mechanisms to regulate energy homeostasis. In this review, we mainly focus on how neuronal circuits within the hypothalamus, such as leptin- ghrelin-and resistin-responsive neurons, as well as melanocortins, neuropeptide Y, and the cannabinoid system exert their actions on lipid metabolism in peripheral tissues such as WAT, liver or muscle. Dissecting the complicated interactions between peripheral signals and neuronal circuits regulating lipid metabolism might open new avenues for the development of new therapies preventing and treating obesity and its associated cardiometabolic sequelae.

Benefit-risk assessment of exenatide in the therapy of type 2 diabetes mellitus

Exenatide is the first incretin mimetic, introduced into type 2 diabetes mellitus therapy in 2005, with first approval in the US. It is a glucagon-like peptide-1 (GLP-1) receptor agonist that can be used for treatment by twice-daily injection. A long-acting release formulation for once-weekly injection is in clinical development. Clinical studies and postmarketing experience with exenatide have shown a significant and sustained reduction in glycosylated haemoglobin (HbA(1c)) by approximately 1% together with other gylcaemic parameters without an intrinsic risk for hypoglycaemias, and a reduction in bodyweight by 5.3 kg in 82 weeks. Blood pressure and lipids are also favourably affected, but hard cardiovascular endpoints are not yet available. Animal studies show an improvement of beta-cell function and an increase in beta-cell mass after exenatide treatment. The most frequent adverse events associated with exenatide therapy are nausea and antibody formation (both approximately 40%). Nausea, mostly mild and transient, was responsible for a 6% dropout rate in clinical studies. A recent review on the association of acute pancreatitis with exenatide treatment showed no increased risk (relative risk 1.0; 95% CI 0.6, 1.7). This review gives a benefit-risk assessment of exenatide.

Impact of data from recent clinical trials on strategies for treating patients with type 2 diabetes mellitus

Type 2 diabetes is associated with increased risk for the development of cardiovascular disease (CVD) secondary to hyperglycemia’s toxicity to blood vessels. The escalating incidence of CVD among patients with type 2 diabetes has prompted research into how lowering glycated hemoglobin (HbA_1c) may improve CVD-related morbidity and mortality. Data from recent studies have shown that some patients with type 2 diabetes actually have increased mortality after achieving the lowest possible HbA_1c using intensive antidiabetes treatment. Multiple factors, such as baseline HbA_1c, duration of diabetes, pancreatic β-cell decline, presence of overweight/obesity, and the pharmacologic durability of antidiabetes medications influence diabetes treatment plans and therapeutic results. Hypertension and dyslipidemia are common comorbidities in patients with type 2 diabetes, which impact the risk of CVD independently of glycemic control. Consideration of all of these risk factors provides the best option for reducing morbidity and mortality in patients with type 2 diabetes. Based on the results of recent trials, the appropriate use of current antidiabetes therapies can optimize glycemic control, but use of intensive glucose-lowering therapy will need to be tailored to individual patient needs and risks.

Effect of exenatide on heart rate and blood pressure in subjects with type 2 diabetes mellitus: a double-blind, placebo-controlled, randomized pilot study

Background

Cardiovascular effects of glucose-lowering agents are of increasing interest. Our aim was to assess the effects of the glucagon-like peptide-1 receptor agonist exenatide on heart rate (HR) and blood pressure (BP) in subjects with type 2 diabetes mellitus (T2DM).

Methods

In this double-blind, placebo-controlled trial, subjects with T2DM on metformin and/or a thiazolidinedione were randomized to receive exenatide (5 μg for 4 weeks followed by 10 μg) or placebo BID for 12 weeks. Heart rate and BP were assessed with 24-hour ambulatory BP monitoring. The primary measure was change from baseline in mean 24-hour HR.

Results

Fifty-four subjects (28 exenatide, 26 placebo) were randomized and comprised the intent-to-treat population. Baseline values (exenatide and placebo) were (mean ± SE) 74.4 ± 2.1 and 74.5 ± 1.9 beats/minute for HR, 126.4 ± 3.2 and 119.9 ± 2.8 mm Hg for systolic BP (SBP), and 75.2 ± 2.1 and 70.5 ± 2.0 mm Hg for diastolic BP (DBP). At 12 weeks, no significant change from baseline in 24-hour HR was observed with exenatide or placebo (LS mean ± SE, 2.1 ± 1.4 versus -0.7 ± 1.4 beats/minute, respectively; between treatments, p = 0.16). Exenatide therapy was associated with trends toward lower 24-hour, daytime, and nighttime SBP; changes in DBP were similar between groups. No changes in daytime or nighttime rate pressure product were observed. With exenatide, body weight decreased from baseline by -1.8 ± 0.4 kg (p < 0.0001; treatment difference -1.5 ± 0.6 kg, p < 0.05). The most frequently reported adverse event with exenatide was mild to moderate nausea.

Conclusions

Exenatide demonstrated no clinically meaningful effects on HR over 12 weeks of treatment in subjects with T2DM. The observed trends toward lower SBP with exenatide warrant future investigation.

Trial registration

NCT00516074

Emerging cardiovascular actions of the incretin hormone glucagon-like peptide-1: potential therapeutic benefits beyond glycaemic control?

Glucagon-like peptide-1 (GLP-1) is an incretin hormone secreted by the small intestine in response to nutrient ingestion. It has wide-ranging effects on glucose metabolism, including stimulation of insulin release, inhibition of glucagon secretion, reduction of gastric emptying and augmentation of satiety. Importantly, the insulinotropic actions of GLP-1 are uniquely dependent on ambient glucose concentrations, and it is this particular characteristic which has led to its recent emergence as a treatment for type 2 diabetes. Although the major physiological function of GLP-1 appears to be in relation to glycaemic control, there is growing evidence to suggest that it may also play an important role in the cardiovascular system. GLP-1 receptors (GLP-1Rs) are expressed in the heart and vasculature of both rodents and humans, and recent studies have demonstrated that GLP-1R agonists have wide-ranging cardiovascular actions, such as modulation of heart rate, blood pressure, vascular tone and myocardial contractility. Importantly, it appears that these agents may also have beneficial effects in the setting of cardiovascular disease (CVD). For example, GLP-1 has been found to exert cardioprotective actions in experimental models of dilated cardiomyopathy, hypertensive heart failure and myocardial infarction (MI). Preliminary clinical studies also indicate that GLP-1 infusion may improve cardiac contractile function in chronic heart failure patients with and without diabetes, and in MI patients after successful angioplasty. This review will discuss the current understanding of GLP-1 biology, examine its emerging cardiovascular actions in both health and disease and explore the potential use of GLP-1 as a novel treatment for CVD.

Clinical approaches to preserve beta-cell function in diabetes

In type 2 diabetes (DM2) there is progressive deterioration in beta-cell function and mass. It was found that islet function was about 50% of normal at the time of diagnosis and reduction in beta-cell mass of about 60% at necropsy (accelerated apoptosis). Among the interventions to preserve the beta-cells, those to lead to short-term improvement of beta-cell secretion are weight loss, metformin, sulfonylureas, and insulin. The long-term improvement was demonstrated with short-term intensive insulin therapy of newly diagnosed DM2, the use of antiapoptotic drugs such as glitazones, and the use of glucagon-like peptide-1 receptor agonists (GLP-1 mimetics), not inactivated by the enzyme dipeptidyl peptidase 4 and/or to inhibit that enzyme (GLP-1 enhancers). The incretin hormones are released from the gastrointestinal tract in response to nutrient ingestion to enhance glucose-dependent insulin secretion from the pancreas and overall maintenance of glucose homeostasis. From the two major incretins, GLP-1 and GIP (glucose-dependent insulinotropic polypeptide), only the first one or its mimetics or enhancers can be used for treatment. The GLP-1 mimetics exenatide and liraglutide as well as the DPP 4 inhibitors (sitagliptin and vildagliptin) were approved for treatment of DM2.

Preclinical and Clinical Data on Extraglycemic Effects of GLP-1 Receptor Agonists

The diverse actions of the incretin hormone glucagon-like peptide (GLP)-1 include insulinotropic, beta-cell preservative, cardioprotective and vasodilatory effects. This spectrum makes GLP-1 an appealing therapeutic option for patients with type 2 diabetes. However, its rapid metabolism by the enzyme dipeptidyl peptidase (DPP)-4 renders it impractical. Incretin-based analogues have been developed to extend endogenous GLP-1 action (GLP-1 receptor agonists) and to hamper its degradation (DPP-4 inhibitors). Evidence suggests that GLP-1 receptor agonists and DPP-4 inhibitors have different pharmacodynamic and pharmacokinetic effects. For example, GLP-1 receptor agonists deliver supraphysiologic levels of GLP-1 analogues designed to resist inactivation by DPP-4, whereas DPP-4 inhibition conserves native GLP-1 resulting in concentrations within the physiologic range. Furthermore, GLP-1 receptor agonists induce glucose-dependent insulin secretion, beta-cell protection, and other extraglycemic benefits such as weight loss and improvement in markers of cardiovascular risk. In contrast, DPP-4 inhibitors are weight neutral and have modest effects on glucose control. DPP-4 inhibition is dependent on the availability of endogenous GLP-1, which appears to be adversely affected by type 2 diabetes and its progression. Therefore, DPP-4 inhibitors may be better suited for patients with mild hyperglycemia without comorbidities. This review examines the present understanding of the pancreatic effects of endogenous GLP-1, and the extrapancreatic actions it exerts on human bodily systems. Also, it analyzes available preclinical and clinical data on incretin therapies with respect to glycemia, lipids, blood pressure, and weight.

Six-month outcomes on A1C and cardiovascular risk factors in patients with type 2 diabetes treated with exenatide in an ambulatory care setting

AIM

This study evaluated changes in clinical effectiveness measures of patients with type 2 diabetes initiating exenatide therapy in a real-world setting.

METHODS

Eligible patients identified in the General Electric (GE) electronic medical record (EMR) research database from 1 January 2000 through 31 December 2007 were > or =18 years old with type 2 diabetes. Patients had prescription orders in the previous 395 days for metformin, a sulfonylurea, or a thiazolidinedione as monotherapy or in combination, and had at least 6 months of follow-up activity. Baseline clinical measures were documented from 45 days prior up to 15 days after exenatide initiation and follow-up measures documented at 6 months +/- 45 days.

RESULTS

A total of 1709 patients were identified for study inclusion. The overall mean A1C reduction (s.e.m.) at 6 months was -0.8% (0.05) (p<0.001), weight loss was -3.2 kg (0.14) (p<0.001), blood pressure (BP) lowering was -1.9 mmHg (0.46) systolic blood pressure (SBP) (p<0.001) and -0.5 mmHg (0.27) diastolic blood pressure (DBP) (p = 0.078). Changes in low-density lipoprotein (LDL), triglycerides and HDL were -7.4 mg/dl (1.7) (p<0.001), -23.2 mg/dl (6.7) (p = 0.001) and -0.8 mg/dl (0.33) (p = 0.012) respectively. In a quartile analysis by weight loss, mean A1C reduction ranged from -1.1 to -0.65% in the highest to lowest weight loss quartiles respectively.

CONCLUSIONS

In a real-world setting, exenatide initiation is associated with significant improvements in the measures of clinical effectiveness for type 2 diabetes. These reductions were comparable to those reported in randomized, controlled registration trials after 6 months of therapy.

Weight loss with liraglutide, a once-daily human glucagon-like peptide-1 analogue for type 2 diabetes treatment as monotherapy or added to metformin, is primarily as a result of a reduction in fat tissue

AIM

The effect on body composition of liraglutide, a once-daily human glucagon-like peptide-1 analogue, as monotherapy or added to metformin was examined in patients with type 2 diabetes (T2D).

METHODS

These were randomized, double-blind, parallel-group trials of 26 [Liraglutide Effect and Action in Diabetes-2 (LEAD-2)] and 52 weeks (LEAD-3). Patients with T2D, aged 18-80 years, body mass index (BMI) < or =40 kg/m(2) (LEAD-2), < or =45 kg/m(2) (LEAD-3) and HbA1c 7.0-11.0% were included. Patients were randomized to liraglutide 1.8, 1.2 or 0.6 mg/day, placebo or glimepiride 4 mg/day, all combined with metformin 1.5-2 g/day in LEAD-2 and to liraglutide 1.8, 1.2 or glimepiride 8 mg/day in LEAD-3. LEAD-2/3: total lean body tissue, fat tissue and fat percentage were measured. LEAD-2: adipose tissue area and hepatic steatosis were assessed.

RESULTS

LEAD-2: fat percentage with liraglutide 1.2 and 1.8 mg/metformin was significantly reduced vs. glimepiride/metformin (p < 0.05) but not vs. placebo. Visceral and subcutaneous adipose tissue areas were reduced from baseline in all liraglutide/metformin arms. Except with liraglutide 0.6 mg/metformin, reductions were significantly different vs. changes seen with glimepiride (p < 0.05) but not with placebo. Liver-to-spleen attenuation ratio increased with liraglutide 1.8 mg/metformin possibly indicating reduced hepatic steatosis. LEAD-3: reductions in fat mass and fat percentage with liraglutide monotherapy were significantly different vs. increases with glimepiride (p < 0.01).

CONCLUSION

Liraglutide (monotherapy or added to metformin) significantly reduced fat mass and fat percentage vs. glimepiride in patients with T2D.

Safety, tolerability, pharmacokinetics and pharmacodynamics of albiglutide, a long-acting GLP-1-receptor agonist, in Japanese subjects with type 2 diabetes mellitus

OBJECTIVE

To investigate safety, pharmacokinetics and pharmacodynamics of albiglutide in Japanese subjects with type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

This randomized, single-blind, placebo-controlled study examined four doses/dose schedules of subcutaneously (sc) administered albiglutide: 15 mg weekly, 30 mg weekly, 50 mg biweekly, and 100 mg monthly (cohorts A-D, respectively) in 40 subjects (mean age 54.5 years, mean range of glycosylated hemoglobin [HbA(1c)] 7.1-8.3%), over a 4-week treatment period.

MAIN OUTCOME MEASURES

Safety parameters, including adverse events, clinical laboratory tests, vital signs, and 12-lead electrocardiogram; plasma concentrations of albiglutide; and pharmacodynamic parameters, including change from baseline and weighted mean AUC(0-4) in plasma glucose, glucagon, insulin, and C-peptide levels.

CLINICAL TRIAL REGISTRATION

NCT00530309.

RESULTS

At day 29, mean changes from baseline (vs. placebo) in fasting plasma glucose (FPG) were: cohort A, -1.92 mmol/L; B, -1.98 mmol/L; C, -1.74 mmol/L; D, -0.73 mmol/L; changes in weighted mean glucose AUC(0-4) were: cohort A, -2.86 mmol/L; B, -3.58 mmol/L; C, -2.51 mmol/L; D, -1.44 mmol/L (for FPG and AUC(0-4), all p < or = 0.002 except 100 mg sc monthly, p = NS); changes from baseline HbA(1c) were: cohort A, -0.58%; B, -0.57%; C, -0.63%; and D, -0.51% (all p < 0.03). Albiglutide sc had a median half-life of 5.3 days, plasma apparent systemic clearance of 68.7 mL/h, and apparent volume of distribution of 12.6 L. Incidence of adverse events was low and comparable to sc placebo in all albiglutide treatment arms except 100 mg sc monthly, where gastrointestinal (GI) adverse events were most common. Limitations of this study include the small sample size, short treatment duration, and enrollment of predominantly male subjects.

CONCLUSIONS

Weekly and biweekly albiglutide improved glycemic control and were well-tolerated in Japanese subjects with type 2 diabetes mellitus.

Optimizing outcomes with incretin-based therapies: practical information for nurse practitioners to share with patients

PURPOSE

To introduce the role of incretin therapies and suggest strategies for nurse practitioners to implement them in practice.

DATA SOURCES

PubMed, Medline, summary of product characteristics/package inserts.

CONCLUSIONS

Incretin-based therapies offer a new alternative to currently available agents. They provide adequate levels of glycemic control and are associated with low incidence of hypoglycemia and weight gain. Dipeptidyl peptidase-4 inhibitors, for example sitagliptin, have a modest effect on A1c levels (-0.7%) as monotherapy; however, they reduce A1c to a greater extent when combined with metformin ( approximately 2.0%). Typical starting dose of sitagliptin is 100 mg; dose adjustments are required in subjects with renal complications. Glucagon-like peptide-1 receptor agonists, exenatide and liraglutide, reduce A1c levels (often in excess of 1.5%) and body weight. Exenatide has a starting dose of 5 mug and is not recommended for patients with hepatic impairment or severe/end-stage renal disease. Liraglutide has been found to benefit from a stepwise dose escalation (i.e., 0.6 mg weekly increments) until a 1.8-mg dose is reached. Unlike exenatide, dose adjustments in patients with renal and hepatic complications are not required.

IMPLICATIONS FOR PRACTICE

Incretin-based therapies may help to overcome some of the drawbacks of current therapies used to treat type 2 diabetes.

The impact of weight gain on motivation, compliance, and metabolic control in patients with type 2 diabetes mellitus

Patients with type 2 diabetes, approximately 85% of whom are overweight or obese, often have an increased incidence of cardiovascular disease (CVD) risk factors such as hypertension and dyslipidemia. Both type 2 diabetes and obesity are independent risk factors for CVD. Unfortunately, many therapies aimed at maintaining and improving glucose control are associated with weight gain. Among the older antidiabetes agents, most, including the insulin secretagogues and sensitizers, can lead to weight gain, except for metformin, which is weight-neutral. Among the newer agents, the dipeptidyl peptidase-4 inhibitors generally are weight-neutral in addition to lowering glucose, while the glucagon-like peptide-1 receptor agonists lead to weight reduction. Patients with type 2 diabetes are at an increased risk for both diabetes- and CV-related outcomes, and weight reduction is an important component of diabetes management. Weight gain in patients with type 2 diabetes can contribute to patient frustration and may negatively impact their compliance to therapeutic regimens. The selection of antidiabetes agents that not only improve glucose control but reduce or have a neutral effect on weight with beneficial effects on lipids are ideal options for managing patients with type 2 diabetes.

Evaluation of exenatide vs. insulin glargine in type 2 diabetes: cost-effectiveness analysis in the German setting

OBJECTIVES

The objective of this analysis was to determine the cost-effectiveness of exenatide vs. insulin glargine in patients with type 2 diabetes failing to achieve glycaemic control with oral antidiabetic agents, in the German setting, from a third-party payer perspective.

METHODS

Data from a published randomized controlled trial were used in combination with a published, validated computer simulation model of type 2 diabetes to project clinical and cost outcomes over a time horizon of 10 years. Cost data were obtained from published literature and expert opinion. Clinical and cost outcomes were discounted at 5% per annum. Sensitivity analyses were performed to establish key drivers and parameters.

RESULTS

Treatment with exenatide compared with insulin glargine was projected to be associated with improvements in life expectancy of 0.016 years and quality-adjusted life expectancy of 0.280 quality-adjusted life years (QALYs), increased lifetime direct medical costs of euro 3854 (euro 22 095 vs. euro 18 242) and an incremental cost-effectiveness ratio (ICER) of euro 13 746 per QALY. If quality of life was not taken into account, exenatide was associated with an ICER of euro 238 201 per life year gained vs. insulin glargine. Sensitivity analyses revealed that outcomes were most sensitive to changes in assumptions for (dis)utility values relating to weight change and the rate of self-monitored blood glucose testing.

CONCLUSIONS

Exenatide was projected to be associated with similar clinical outcomes and increased costs compared with insulin glargine. Analysis of cost-effectiveness from a third-party perspective suggests that exenatide is likely to represent good value for money in the German setting.

Insulin sensitizers in nonalcoholic fatty liver disease and steatohepatitis: Current status

Nonalcoholic fatty liver disease (NAFLD), first described in 1980, is now recognized as one of the most common causes of elevated liver enzymes and chronic liver disease in Western countries. The incidence of NAFLD in both adults and children is rising, in conjunction with the burgeoning epidemics of obesity and type 2 diabetes mellitus. NAFLD often coexists with other sequelae of the metabolic syndrome: central obesity, type 2 diabetes, hypertension, and hyperlipidemia. NAFLD encompasses a spectrum of pathologic liver diseases ranging from simple hepatic steatosis to a predominant lobular necro-inflammation, with or without centrilobular fibrosis (called nonalcoholic steatohepatitis or NASH). NASH can progress to cirrhosis, decompensated liver disease, and hepatocellular carcinoma. Though the natural history of NASH is still not clearly defined, it has been observed to progress to cirrhosis in 15%-220% of those affected. Insulin resistance is nearly universal in NASH and is thought to play an important role in its pathogenesis leading to dysregulated lipid metabolism. The prevalence of insulin resistance is reported in the general population to be approaching 45%, suggesting that NAFLD and NASH will contin nue to be an important public health concern. To date, NASH has proven to be a difficult disease to treat. Front-line therapy with lifestyle modifications resulting in weight loss through decreased caloric intake and moderate exercise is generally believed to be beneficial in patients with NASH, but is often difficult to maintain long term. Given that insulin resistance plays a dominant role in the pathogenesis, many studies have examined the use of insulin sensitizers: the biguanides (metformin), thiazolidinediones (pioglitazone, troglitazone, and rosiglitazone), glucagon-like peptide-1-receptor agonists, or incretins (exenatide)in NASH. This review will provide an overview of insulin resistance in NAFLD and provide a detailed summary on the clinical data regarding the use of insulin sensitizers in NASH.

Exenatide efficacy and safety: a systematic review

OBJECTIVE

To examine the efficacy, effectiveness and side effects of exenatide when compared with oral glucose-lowering agents or insulin therapy.

RESEARCH DESIGN AND METHODS

Relevant citations were identified from searches of multiple bibliographic databases supplemented with searches of the US Food and Drug Administration website and other sources. A qualitative synthesis was performed, with a random effects meta-analysis when appropriate.

RESULTS

We identified 17 studies. In placebo-controlled trials of subjects with poorly controlled diabetes (with both groups receiving various oral glucose-lowering agents), exenatide 10 microg twice daily improved glycated haemoglobin (HbA(1c)) by approximately 1.0% over 30 weeks [pooled estimate -0.97%, 95% confidence interval (CI), -1.16 to -0.79%, P < 0.0001] and exenatide treatment over 16-30 weeks was associated with weight loss of 1.0-2.5 kg. Exenatide appeared to confer a similar benefit to various insulin regimes for glycaemic control at follow-up between 16 and 52 weeks (pooled estimate HbA(1c)-0.04%, 95% CI, -0.14 to 0.06%, P = 0.41), but was advantageous over insulin with respect to weight loss (3-6 kg loss at up to 52 weeks of follow-up). Nausea was the most common adverse event in placebo- and active-controlled trials. Rates of hypoglycaemia were similar in exenatide and insulin groups, but were higher with exenatide 10 microg twice daily compared with placebo and hypoglycaemia was most frequent when a sulphonylurea was administered.

CONCLUSIONS

In subjects with poorly controlled diabetes, exenatide was associated with a reduction in HbA(1c) that was similar to introducing another oral agent or insulin. Weight loss may be an advantage with exenatide. Long-term studies in diverse and unselected populations are needed to clarify the benefit vs. harm profile of this drug.

Present and Prospective Pharmacotherapy for the Management of Patients with Type 2 Diabetes

Diabetes Mellitus is a chronic condition prevalent worldwide. Type 2 diabetes is the most common form of diabetes, comprising 90% to 95% of all cases. Over the last few decades, the importance of glycemic control and its impact on prevention of diabetes-related complications has been documented in multiple clinical trials. As most patients with type 2 diabetes will require pharmacologic intervention to achieve and maintain appropriate glycemic control, new medications targeting different aspects of the pathophysiology of type 2 diabetes have been a significant focus of research and development. During the last decade, multiple new medications for diabetes management have become available: these medications have novel mechanisms of action, differences in effectiveness, and varying side effect profiles which will be reviewed in this article. Some of these newer medications, such as the GLP-1 analogues and DPP-4 inhibitors, have become widely accepted as therapeutic options for the management of type 2 diabetes.Additional classes of glucose-lowering medications are expected to become available in the near future. This manuscript will summarize available data regarding these newer and prospective medications for the management of type 2 diabetes.

Exenatide and liraglutide: different approaches to develop GLP-1 receptor agonists (incretin mimetics)--preclinical and clinical results

The GLP-1 analogues exenatide and liraglutide stimulate insulin secretion and inhibit glucagon output in a glucose-dependent manner, slow gastric emptying and decrease appetite. The injectable glucagon-like peptide-1 (GLP-1) receptor agonist exenatide significantly improves glycaemic control, with average reductions in HbA1c of about 1.0% point, fasting plasma glucose of about 1.4 mmol l(-1), and causes a weight loss of approximately 2-3 kg after 30 weeks of treatment. The adverse effects are transient nausea and vomiting. The long-acting once-daily human GLP-1 receptor agonist liraglutide reduces HbA1c by about 1.0-2.0% point, weight by 1-3 kg and seems to have fewer gastrointestinal side effects than exenatide. The final place of the GLP-1 receptor agonists in the diabetes treatment algorithm will be clarified when we have long-term trials with cardiovascular end-points and data illustrating the effects on the progression of type 2 diabetes.

Treatment of type 2 diabetes with glucagon-like peptide-1 receptor agonists

The incretin system is an area of great interest for the development of new therapies for the management of type 2 diabetes. Existing antidiabetic drugs are often insufficient at getting patients to glycaemic goals. Furthermore, current treatment modalities are not able to prevent the continued ongoing decline in pancreatic beta-cell function and, lastly, they have a number of side effects including hypoglycaemia and weight gain. Glucagon-like peptide-1 (GLP-1) receptor agonists are a new class of pharmacological agents, which improve glucose homeostasis in a multifaceted way. Their effects include potentiation of glucose-stimulated insulin secretion, glucose-dependent inhibition of glucagon secretion and reduction in gastric emptying, appetite, food intake and body weight. Additionally, preclinical data suggest that they may preserve beta-cell mass and function. The incidence of hypoglycaemia with GLP-1 receptor agonists is low, the compounds have clinically relevant effects on body weight, and data are suggesting beneficial effects on cardiovascular risk factors. Exenatide was released in 2005 for the treatment of type 2 diabetes and liraglutide is expected to be approved by the Food and Drug Administration in US and the European Medical Agency in Europe for use in 2009. In this review, the available data on the two drugs are presented and discussed.

Improved treatment satisfaction and weight-related quality of life with exenatide once weekly or twice daily

AIMS

To assess treatment satisfaction and weight-related quality of life (QOL) in subjects with Type 2 diabetes treated with exenatide once weekly (QW) or twice daily (BID).

METHODS

In this 52-week randomized, multi-centre, open-label study, 295 subjects managed with diet and exercise and/or oral glucose-lowering medications received either exenatide QW or BID during weeks 1-30; thereafter, subjects receiving exenatide BID were switched to exenatide QW, with 258 total subjects receiving exenatide QW during weeks 30-52. Diabetes Treatment Satisfaction Questionnaire-status (DTSQ-s) and Impact of Weight on Quality of Life-Lite (IWQOL-Lite) were assessed at baseline and weeks 30 and 52. Mean group changes from baseline to week 30 were estimated by ancova; changes from week 30 to week 52 were assessed by Student's t-test.

RESULTS

Statistically significant improvements from baseline to week 30 were observed in both treatment groups for DTSQ-s and IWQOL-Lite measures, with significantly greater reduction in perceived frequency of hyperglycaemia and greater satisfaction with continuing treatment in the QW group compared with the BID group. Effect sizes for change in DTSQ-s total scores were 0.84 QW, 0.64 BID; for IWQOL-Lite: 0.96 QW, 0.82 BID. Treatment satisfaction and QOL improved significantly between weeks 30 and 52 for those switching from BID to QW. Occurrence of adverse events did not affect patients' improvements in treatment satisfaction and QOL.

CONCLUSIONS

Patients treated with exenatide QW or BID experienced significant and clinically meaningful improvements in treatment satisfaction and QOL. Patients who switched from exenatide BID to exenatide QW administration reported further significant improvements.

Exenatide: a review from pharmacology to clinical practice

BACKGROUND

Exenatide is an incretin mimetic that activates glucagon-like-peptide-1 receptors. It blunts the postprandial rise of plasma glucose by increasing glucose-dependent insulin secretion, suppressing inappropriately high glucagon secretion and delaying gastric emptying.

METHODS

In seven clinical trials performed in 2845 adult patients with type 2 diabetes mellitus who were inadequately controlled by a sulphonylurea and/or metformin (glycosylated haemoglobin, HbA1c <or=11%), or by thiazolidinediones (with or without metformin) and treated for periods from 16 weeks to 3 years, exenatide (5 microg b.i.d. s.c. for the first 4 weeks of treatment and 10 microg b.i.d. s.c. thereafter) reduced HbA1c, fasting and postprandial glucose, and body weight dose dependently, and was similar to insulin glargine and biphasic insulin aspart in reducing HbA1c. Body weight diminished with exenatide, whereas it increased with both insulin preparations. Positive effects on the lipid profile and a reduction in C-reactive protein were also recorded with exenatide. Treatment extensions up to 3 years showed that benefits were maintained in the long term. Adverse events were usually mild to moderate in intensity, and generally the frequency decreased with continued therapy. The most common was nausea (whose incidence may be reduced by gradual dose escalation from 5 microg b.i.d. to 10 microg b.i.d.), vomiting, diarrhoea, headache and hypoglycaemia (almost exclusively in patients treated with a sulphonylurea).

RESULTS AND CONCLUSIONS

Exenatide is a new, promising therapeutic option for type 2 diabetic patients inadequately controlled by oral agents, before insulin therapy, offering the added benefits of body weight reduction and tight postprandial glucose control.

Clinical application of incretin-based therapy: therapeutic potential, patient selection and clinical use

Incretin-based therapies address the progressive nature of type 2 diabetes mellitus, not only by addressing glucose control but also with weight-neutral (i.e., dipeptidyl peptidase-4 inhibitors sitagliptin and vildagliptin) and weight-reducing effects (i.e., glucagonlike peptide-1 [GLP-1] receptor agonists exenatide and liraglutide). Preclinical data suggest that incretin-based therapies may also preserve beta-cell function, holding promise of a truly disease-modifying therapy. This article examines clinical trial data and accepted algorithms with a view toward elucidating the application of these agents in routine clinical practice. We propose a systematic approach to treatment, addressing (1) patient selection, (2) optimal treatment combinations, and (3) timing and guidance for both initiation and intensification of therapy. The GLP-1 receptor agonists, for example, could be particularly beneficial in patients whose weight significantly increases cardiovascular risk. Early use of these agents may be effective in preventing diabetes in those at risk, or in halting or retarding disease progression in patients with frank diabetes. Additional clinical investigation will be required to test such hypotheses. Given the ever-increasing incidence of diabetes worldwide, the link between obesity and the development of type 2 diabetes, and the need for more effective, weight-focused, convenient and sustainable treatments, the data from such studies will be invaluable to further clarify the role of the incretins in the management of patients with type 2 diabetes.

Incretin therapies: effects beyond glycemic control

Impaired insulin secretion plays a major role in the pathogenesis of type 2 diabetes mellitus, and progressive loss of beta-cell function is a pathophysiologic hallmark of type 2 diabetes. Recent science has elaborated on the role of the incretin hormones on beta-cell function and insulin secretion, as well as the role that incretin-based pharmacotherapies may have on glycemic control and beta-cell function, possibly altering the progressive loss of beta-cell function and possibly reversing/halting disease progression. However, incretin-based therapies may also have benefits extending beyond glycemic control and insulin secretion. In this review we examine some of those "beyond-glycemic" benefits, including presentation of data on weight reduction, blood pressure lowering, beneficial changes in the lipid profile, and improvements in myocardial and endothelial function. We investigate how those effects may help ameliorate the cardiovascular burden in patients with diabetes.

Incretin-based therapies: new treatments for type 2 diabetes in the new millennium

The advent of 'incretin-based therapies' - GLP-1 agonists and dipeptidyl-peptidase-4 inhibitors - which result in improvements in glycemic control comparable to those with existing oral hypoglycemic agents, and potentially improve cardiovascular and pancreatic beta-cell function, represents a major therapeutic advance in the management of type 2 diabetes. Gastrointestinal adverse effects occur commonly with GLP-1 agonists, and rarely with DPP-4 inhibitors, but are dose-dependent and usually transient. The low risk of hypoglycemia, and beneficial or neutral effects on body weight, render GLP-1 agonists and DPP-4 inhibitors suitable alternatives to insulin secretagogues and insulin in overweight and elderly patients. Incretin-based therapies also improve quality of life in patients with type 2 diabetes, and may be cost-effective in the long term.

Minireview: Gut peptides: targets for antiobesity drug development?

Gut peptides play multiple roles in the controls of gastrointestinal function and in the initiation and termination of meals. Plasma levels of these peptides are differentially affected by the presence of nutrients in the digestive tract, and the patterns of peptide release are consistent with both their feeding stimulatory and inhibitory actions. A number of these peptide systems have been investigated as potential targets for antiobesity drug development. Progress has been made in developing long-acting peptide analogs and, in some cases, nonpeptide agonists and antagonists. Whether any individual approach will have significant long-term efficacy remains to be demonstrated. Approaches that target multiple systems may hold the most promise.

GLP-1 agonist-based therapies: an emerging new class of antidiabetic drug with potential cardioprotective effects

Cardiovascular disease is a leading cause of death in the United States and across the world, and better therapies are constantly being sought to improve patient outcomes. Recent studies have brought our attention to the mechanisms of glucagon-like peptide 1 (GLP-1). Not only does it demonstrate beneficial effects in regard to cardiovascular risk factors (i.e., diabetes, lipid management, and weight control), but it also has been shown in animal studies to have positive cardiac effects irrespective of its effects on glucose control and weight loss. This review discusses the biology of GLP-1 and its effects on cardiovascular risk factors, and it also elaborates on the positive direct cardiovascular outcomes of GLP-1 in animal studies.

Islet G protein-coupled receptors as potential targets for treatment of type 2 diabetes

Islet dysfunction - characterized by a combination of defective insulin secretion, inappropriately high glucagon secretion and reduced beta-cell mass - has a central role in the pathophysiology of type 2 diabetes. Several G protein-coupled receptors (GPCRs) expressed in islet beta-cells are known to be involved in the regulation of islet function, and therefore are potential therapeutic targets. This is evident from the recent success of glucagon-like peptide 1 (GLP1) mimetics and dipeptidyl peptidase 4 (DPP4) inhibitors, which promote activation of the GLP1 receptor to stimulate insulin secretion and inhibit glucagon secretion, and also have the potential to increase beta-cell mass. Other islet beta-cell GPCRs that are involved in the regulation of islet function include the glucose-dependent insulinotropic peptide (GIP) receptor, lipid GPCRs, pleiotropic peptide GPCRs and islet biogenic amine GPCRs. This Review summarizes islet GPCR expression, signalling and function, and highlights their potential as targets for the treatment of type 2 diabetes.

The role of incretins in cardiovascular control

Glucagon-like peptide-1 (GLP-1) is an incretin secreted in response to nutrient ingestion. Understanding the incretin effect on diabetes pathophysiology has led to development of a new class of agents termed incretin mimetics. Exenatide is the first GLP-1 agonist approved to treat type 2 diabetes mellitus (T2DM). Clinical studies have demonstrated exenatide's efficacy in improving glycemic control, often coupled with weight loss. Studies are investigating the potential cardiovascular benefits of GLP-1 agonists. Blood pressure, cholesterol levels, C-reactive protein, and insulin resistance may improve in patients treated with exenatide. The direct effect of GLP-1 on cardiac myocytes and vascular smooth muscle has been an active area of investigation. Infusions of GLP-1 in animal models and human subjects with heart failure have demonstrated significantly improved cardia parameters. In patients with T2DM, GLP-1 infusion has been shown to improve endothelial function, irrespective of changes in insulin sensitivity. These pilot studies provide a foundation for developing therapies aimed at modulating incretin physiology for the additional benefit on the cardiovascular system in patients with T2DM and heart disease.

Potential of liraglutide in the treatment of patients with type 2 diabetes

Liraglutide is a long-acting analog of GLP-1, being developed by Novo Nordisk and currently undergoing regulatory review for the treatment of type 2 diabetes. Upon injection, liraglutide binds non-covalently to albumin, giving it a pharmacokinetic profile suitable for once-daily administration. In clinical trials of up to 1 year duration, liraglutide has been demonstrated to have beneficial effects on islet cell function, leading to improvements in glycemic control. Both fasting and postprandial glucose concentrations are lowered, and are associated with lasting reductions in HbA1c levels. Liraglutide is effective as monotherapy and in combination therapy with oral antidiabetic drugs, and reduces HbA1c by up to approximately 1.5% from baseline (8.2%-8.4%). Because of the glucose-dependency of its action, there is a low incidence of hypoglycemia. Liraglutide is associated with body weight loss, and reductions in systolic blood pressure have been observed throughout the clinical trials. The most common adverse events reported with liraglutide are gastrointestinal (nausea, vomiting and diarrhea). These tend to be most pronounced during the initial period of therapy and decline with time. Further clinical experience with liraglutide will reveal its long-term durability, safety and efficacy.

New treatments in type 2 diabetes: a focus on the incretin-based therapies

The demonstration that the incretin hormone glucagon-like peptide 1 can improve glycaemic control in patients with type 2 diabetes has led to the rapid development during the last decade of promising new classes of agent for the management of type 2 diabetes. These agents possess a range of physiological effects that are associated with improved glycaemic control in diabetes including stimulation of glucose-dependent insulin secretion, suppression of glucagon secretion, slowing of gastric emptying, and reduction of food intake. In addition, preclinical studies suggest that incretin-based therapies may improve beta-cell function via enhancement of beta-cell mass and induction of genes important for differentiated beta-cell function. Exenatide, and the dipeptidyl peptidase-4 inhibitors, sitagliptin and vildagliptin are already approved, and liraglutide is currently completing Phase 3 trials. As these agents and standard oral therapies for type 2 diabetes lower glucose levels through different, but potentially complementary mechanisms, their use in combination should provide effective, potentially additive, glycaemic control. The incretin-based therapies also offer other advantages such as weight loss with exenatide and liraglutide, a reduced risk of hypoglycaemia, and as suggested by preclinical studies, a potential beta-cell preserving effect. Long-term outcome and safety data are not available for these agents, but they appear generally well-tolerated in comparison with existing therapies for type 2 diabetes. The multiple underlying glucose-lowering actions of the incretin-based therapies, as well as a lack of weight gain or even weight loss, make these important new additions to available antidiabetic agents expanding the treatment options available for patients.

The effect of antidiabetic drugs on genes regulating lipid metabolism

PURPOSE OF REVIEW

Hyperglycaemia and dyslipidaemia are closely linked, yet, there has been difficulty in demonstrating that lowering blood sugar reduces cardiovascular events. The pathways linking abnormalities in fatty acid metabolism, insulin resistance and diabetes with abnormalities in cholesterol metabolism are being rapidly unravelled with new understandings of the effect of antidiabetic drugs on lipoprotein metabolism. The purpose of this review is to explore the recent literature.

RECENT FINDINGS

Postprandial lipoproteins are now firmly established as a postprandial risk factor. Both insulin resistance and diabetes are associated with abnormalities in chylomicron production, and clearance and regulatory genes have been identified. Metformin, the most commonly used drug in type 2 diabetes, has multiple actions affecting numerous genes. The peroxisome proliferator-activated receptor-gamma regulation of insulin sensitivity and the important effects on lipoproteins are described. The entero-insulin axis and glucagon-like peptide-1 agonists, together with inhibitors of dipeptidyl peptidase 4 may have lipoprotein implications, but the evidence at present is sparse even though glucagon-like peptide-1 is found in high concentrations in the lymph.

SUMMARY

Although antidiabetic drugs affect lipid metabolism, there is little evidence to suggest that these drugs can prevent atherosclerosis in diabetes and some may promote atherosclerosis through their adverse effect on lipoproteins.

Targeting the pathophysiology of type 2 diabetes: rationale for combination therapy with pioglitazone and exenatide

OBJECTIVE

The objectives of this article are to review the pathophysiology of type 2 diabetes mellitus (T2DM), present the rationale for a pathophysiologically based treatment approach for patients with T2DM and discuss the role of the therapeutic combination of pioglitazone and exenatide in the management of T2DM.

METHODS

References were identified from searches of the PubMed database that were conducted in May 2007, October 2007 and March 2008 and updates to product labeling that occurred between May 2007 and December 2007. Information was selected for inclusion on the basis of its relevance to the pathophysiology of T2DM or the clinical use of thiazolidinediones or exenatide. Discussion of other anti-diabetic treatment strategies is not included.

RESULTS

T2DM results from a combination of insulin resistance and beta-cell dysfunction. The combination of a thiazolidinedione and an incretin mimetic offers a combination of characteristics (e.g., glycemic control, reduced insulin resistance, decreased weight, potential cardiovascular benefits, beta-cell preservation) that addresses many of the pathophysiologic underpinnings of T2DM. A recent small placebo-controlled study assessed the effects of exenatide used with a thiazolidinedione (TZD; pioglitazone or rosiglitazone) with or without metformin. Exenatide demonstrated a greater incidence of glycosylated hemoglobin (HbA(1c)) < 7%; greater reductions in fasting blood glucose, postprandial plasma glucose and body weight; and improved beta-cell function versus the TZD/placebo group. However, exenatide was associated with a high dropout rate, and the 16-week duration of treatment in this study precluded evaluation of the long-term effects of the exenatide/pioglitazone combination. Furthermore, exenatide/pioglitazone has not been compared with any other anti-diabetic combination in a head-to-head clinical study.

CONCLUSIONS

Dual effects on insulin sensitivity (TZD) and insulin secretion (exenatide) make the TZD/exenatide combination a rational treatment option for patients who do not attain glycemic control with a single agent. Studies undertaken to evaluate the effects on cardiovascular outcomes and the potential for prevention of T2DM with impaired glucose tolerance may reveal additional advantages of this combination approach.

Treatment of patients with diabetes with GLP-1 analogues or DPP-4- inhibitors: a hot topic for cardiologists?

Novel drugs for the treatment of patients with diabetes are of interest for cardiologists if they reduce the risk of cardiovascular events. However, as documented by the current discussion about the potential benefits of glitazones, high hopes can fail. Initial beneficial cardiovascular effects shown in proof-of-concept studies were muted by the apparent higher mortality in the metaanalysis of studies with rosiglitazone. Having this in mind, how should one judge about new, emerging antidiabetic therapies, in particular those influencing the incretin axis? The rapidly increasing use of GLP-1 analogues and DPP-4 inhibitors for the treatment of type 2 diabetes mellitus may be of major interest for the cardiologist. Potential beneficial actions on the cardiovascular system so far shown in animal experiments and small proof of concept studies may provide the rationale for using these drugs specifically in diabetic patients with secondary complications such as macrovascular disease or diabetic cardiomyopathy. Theoretically, these new therapies could also proof beneficial in patients with heart failure, independently of concomittend diabetes mellitus. However, many unanswered questions need to be addressed in the near future to extend the experimental findings to potential benefits of real life patients. In summary a new class of antidiabetic drugs, which could possibly directly influence cardiovascular effects of diabetes mellitus and thus possibly treat or even prevent life threatening complications has become available. Further studies both assessing surrogate parameters as well as hard endpoint studies are needed to support the hypothesis generated from the summarized experimental studies.

Effects of exenatide versus sitagliptin on postprandial glucose, insulin and glucagon secretion, gastric emptying, and caloric intake: a randomized, cross-over study

BACKGROUND

This study evaluated the effects of exenatide, a GLP-1 receptor agonist, and sitagliptin, a DPP-4 inhibitor, on 2-h postprandial glucose (PPG), insulin and glucagon secretion, gastric emptying, and caloric intake in T2D patients.

METHODS

This double-blind, randomized cross-over, multi-center study was conducted in metformin-treated T2D patients: 54% female; BMI: 33 +/- 5 kg/m(2); HbA(1c): 8.5 +/- 1.2%; 2-h PPG: 245 +/- 65 mg/dL. Patients received exenatide (5 microg BID for 1 week, then 10 microg BID for 1 week) or sitagliptin (100 mg QAM) for 2 weeks. After 2 weeks, patients crossed-over to the alternate therapy. Postprandial glycemic measures were assessed via standard meal test; caloric intake assessed by ad libitum dinner (subset of patients). Gastric emptying was assessed by acetaminophen absorption (Clinicaltrials.gov Registry Number: NCT00477581).

RESULTS

After 2 weeks of therapy, 2-h PPG was lower with exenatide versus sitagliptin: 133 +/- 6 mg/dL versus 208 +/- 6 mg/dL, p < 0.0001 (evaluable, N = 61). Switching from exenatide to sitagliptin increased 2-h PPG by +73 +/- 11 mg/dL, while switching from sitagliptin to exenatide further reduced 2-h PPG by -76 +/- 10 mg/dL. Postprandial glucose parameters (AUC, C(ave), C(max)) were lower with exenatide than sitagliptin (p < 0.0001). Reduction in fasting glucose was similar with exenatide and sitagliptin (-15 +/- 4 mg/dL vs. -19 +/- 4 mg/dL, p = 0.3234). Compared to sitagliptin, exenatide improved the insulinogenic index of insulin secretion (ratio exenatide to sitagliptin: 1.50 +/- 0.26, p = 0.0239), reduced postprandial glucagon (AUC ratio exenatide to sitagliptin: 0.88 +/- 0.03, p = 0.0011), reduced postprandial triglycerides (AUC ratio exenatide to sitagliptin: 0.90 +/- 0.04, p = 0.0118), and slowed gastric emptying (acetaminophen AUC ratio exenatide to sitagliptin: 0.56 +/- 0.05, p < 0.0001). Exenatide reduced total caloric intake compared to sitagliptin (-134 +/- 97 kcal vs. +130 +/- 97 kcal, p = 0.0227, N = 25). Common adverse events with both treatments were mild to moderate in intensity and gastrointestinal in nature.

CONCLUSIONS

Although this study was limited by a 2-week duration of exposure, these data demonstrate that, exenatide had: (i) a greater effect than sitagliptin to lower postprandial glucose and (ii) a more potent effect to increase insulin secretion and reduce postprandial glucagon secretion in T2D patients. In contrast to sitagliptin, exenatide slowed gastric emptying and reduced caloric intake. These key findings differentiate the therapeutic actions of the two incretin-based approaches, and may have meaningful clinical implications.

Incretin-based therapies in type 2 diabetes mellitus

CONTEXT

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide are incretins secreted from enteroendocrine cells postprandially in part to regulate glucose homeostasis. Dysregulation of these hormones is evident in type 2 diabetes mellitus (T2DM). Two new drugs, exenatide (GLP-1 mimetic) and sitagliptin [dipeptidyl peptidase (DPP) 4 inhibitor], have been approved by regulatory agencies for treating T2DM. Liraglutide (GLP-1 mimetic) and vildagliptin (DPP 4 inhibitor) are expected to arrive on the market soon.

EVIDENCE ACQUISITION

The background of incretin-based therapy and selected clinical trials of these four drugs are reviewed. A MEDLINE search was conducted for published articles using the key words incretin, glucose-dependent insulinotropic polypeptide, GLP-1, exendin-4, exenatide, DPP 4, liraglutide, sitagliptin, and vildagliptin.

EVIDENCE SYNTHESIS

Exenatide and liraglutide are injection based. Three-year follow-up data on exenatide showed a sustained weight loss and glycosylated hemoglobin (HbA(1c)) reduction of 1%. Nausea and vomiting are common. Results from phase 3 studies are pending on liraglutide. Sitagliptin and vildagliptin are orally active. In 24-wk studies, sitagliptin reduces HbA(1c) by 0.6-0.8% as monotherapy, 1.8% as initial combination therapy with metformin, and 0.7% as add-on therapy to metformin. Vildagliptin monotherapy lowered HbA(1c) by 1.0-1.4% after 24 wk. Their major side effects are urinary tract and nasopharyngeal infections and headaches. Exenatide and liraglutide cause weight loss, whereas sitagliptin and vildagliptin do not.

CONCLUSIONS

The availability of GLP-1 mimetics and DPP 4 inhibitors has increased our armamentarium for treating T2DM. Unresolved issues such as the effects of GLP-1 mimetics and DPP 4 inhibitors on beta-cell mass, the mechanism by which GLP-1 mimetics lowers glucagon levels, and exactly how DPP 4 inhibitors lead to a decline in plasma glucose levels without an increase in insulin secretion, need further research.

Efficacy and safety of exenatide administered before the two largest daily meals of Latin American patients with type 2 diabetes

OBJECTIVE

To evaluate whether exenatide administered before breakfast and dinner (BD) or before lunch and dinner (LD) provided similar glycemic control in Latin American patients with type 2 diabetes mellitus (T2DM) who consume a small breakfast.

METHODS

In this open-label, 2-arm study, patients taking metformin, sulfonylureas, and/or thiazolidinediones were randomized to exenatide before BD or before LD (5-mug exenatide for 4 weeks, then 10-microg exenatide for 8 weeks). Treatment assignment was determined by a computer-generated random sequence using an interactive response system. Patients were eligible for study inclusion if they consumed <15% of their total caloric intake at breakfast. The primary endpoint was HbA(1c) change from baseline to endpoint. Secondary endpoints included fasting serum glucose (FSG) level, 7-point SMBG profile, and safety. Clinicaltrials.gov Identifier: NCT00359879.

RESULTS

377 participants (55% female, age 54 +/- 10 years, weight 82 +/- 15 kg, BMI 31 +/- 4 kg/m(2), HbA(1c) 8.4 +/- 0.9%; mean +/- SD) from Brazil and Mexico were randomized to study treatment. HbA(1c) reduction with exenatide administration before BD was non-inferior to administration before LD (mean difference between (LD-BD) treatments: 0.14%; 95% CI -0.04 to 0.32%, p=0.120). Both treatments resulted in statistically significant HbA(1c) reductions at endpoint (BD -1.2% and LD -1.1%, respectively, p<0.001). In Brazil, the non-inferiority criteria were met for HbA(1c) reduction between treatment arms (-0.12%; CI -0.37 to 0.13%, p=0.344), whereas in Mexico, there was a difference favoring exenatide administration before BD (0.41%; CI 0.16 to 0.66%, p=0.002). At endpoint, there were no statistical significant differences between the BD and LD arms in mean change in FSG (0.50 mmol/L; CI -0.02 to 1.02 mmol/L, p=0.058) and daily mean change in SMBG (0.19 mmol/L; CI -0.17 to 0.54 mmol/L, p=0.295). The rates of symptomatic hypoglycemia (5.2 events/patient-year vs. 6.1 events/patient-year) and nausea (23% vs. 25%), were similar between the BD and LD arms, respectively. A limitation of the study design was that caloric intake of patients and meal times were not monitored.

CONCLUSIONS

In T2DM patients who consume a small breakfast, exenatide administration before breakfast or lunch resulted in significant improvement in glycemic control.

Drugs in the pipeline for the obesity market

Obesity is a major public health problem. For many obese patients, diet and exercise are an inadequate treatment and bariatric surgery may be too extreme of a treatment. As with many other chronic diseases, pharmacologic treatment may be an attractive option for selected obese patients. Antiobesity drugs may potentially work through one of three mechanisms: (1) appetite suppression, (2) interference with absorption of nutrients, and (3) increased metabolism of nutrients. The three most widely prescribed drugs approved to treat obesity are phentermine, sibutramine, and orlistat. Drugs approved for treating obesity usually result in an additional weight loss of approximately 2-5 kg in addition to placebo. For pharmacologic therapy in obesity to be widely utilized, greater effectiveness and safety will be needed. Four types of single-agent drugs are in late stage development, including (1) selective central cannabinoid-1 receptor blockers, (2) selective central 5-hydroxytryptamine 2C serotonin receptor agonists, (3) an intestinal lipase blocker, and (4) central-acting incretin mimetic drugs. Four combination agent compounds in late stage development include (1) Contrave, which combines long-acting versions of naltrexone and bupropion; (2) Empatic, which combines long-acting bupropion and long-acting zonisamide; (3) Qnexa, which combines phentermine with controlled release topiramate; and (4) an injectable combination of leptin and pramlintide. Peptide YY and melanin-concentrating hormone receptor-1 antagonists are centrally acting agents in early stage development. It is expected that several new drug products for obesity will become available over the next few years. Their role in managing this disease remains to be determined.

Targeting Incretins in Type 2 Diabetes: Role of GLP-1 Receptor Agonists and DPP-4 Inhibitors

Until recently, the pathogenesis of type 2 diabetes mellitus (T2DM) has been conceptualized in terms of the predominant defects in insulin secretion and insulin action. It is now recognized that abnormalities in other hormones also contribute to the development of hyperglycemia. For example, the incretin effect, mediated by glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP), is attenuated in T2DM. Intravenous administration of GLP-1 ameliorates hyperglycemia in patients with T2DM, but an extremely short half-life limits its utility as a therapeutic agent. Strategies to leverage the beneficial effects of GLP-1 include GLP-1 receptor agonists or analogs or dipeptidyl peptidase-4 (DPP-4) inhibitors-agents that act by slowing the inactivation of endogenous GLP-1 and GIP. The GLP-1 agonist exenatide has been shown to improve HbA1c and decrease body weight. However, exenatide is limited by its relatively short pharmacologic half-life, various gastrointestinal (GI) side effects, and the development of antibodies. Studies of a long-acting exenatide formulation suggest that it has improved efficacy and also promotes weight loss. Another prospect is liraglutide, a once-daily human GLP-1 analog. In phase 2 studies, liraglutide lowered HbA1c by up to 1.7% and weight by approximately 3 kg, with apparently fewer GI side effects than exenatide. DPP-4 inhibitors such as sitagliptin and vildagliptin result in clinically significant reductions in HbA1c, and are weight neutral with few GI side effects. This review will provide an overview of current and emerging agents that augment the incretin system with a focus on the role of GLP-1 receptor agonists and DPP-4 inhibitors.

Incretin mimetics and dipeptidyl peptidase-4 inhibitors: innovative treatment therapies for type 2 diabetes

The prevalence of diabetes and impaired glucose tolerance is predicted to dramatically increase over the next two decades. Clinical therapies for type 2 diabetes mellitus (T2DM) have traditionally included lifestyle modification, oral anti-diabetic agents, and ultimately insulin initiation. In this report, we review the clinical trial results of two innovative T2DM treatment therapies that are based on the glucoregulatory effects of incretin hormones. Incretin mimetics are peptide drugs that mimic several of the actions of glucagon-like peptide-1 (GLP-1) and have been shown to lower glycated hemoglobin (A1C) levels in patients with T2DM. Additionally, incretin mimetics lower postprandial and fasting glucose, suppress elevated glucagon release, and are associated with progressive weight reduction. Dipeptidyl peptidase-4 (DPP-4) inhibitors increase endogenous GLP-1 levels by inhibiting the enzymatic degradation of GLP-1. Clinical studies in patients with T2DM have shown that DPP-4 inhibitors reduce elevated A1C, lower postprandial and fasting glucose, suppress glucagon release, and are weight neutral. Collectively, these new drugs, given in combination with other antidiabetic agents, such as metformin, sulfonylureas, and/or thiazolidinediones, can help restore glucose homeostasis in poorly controlled patients with T2DM.

Glucagon-like peptide receptor agonists and dipeptidyl peptidase-4 inhibitors in the treatment of diabetes: a review of clinical trials

PURPOSE OF REVIEW

To discuss the virtues and shortcomings of the glucagon-like peptide-1 receptor agonists and the dipeptidyl peptidase-4 inhibitors in the treatment of type 2 diabetes.

RECENT FINDINGS

The injectable glucagon-like peptide-1 receptor agonists exenatide significantly improves glycaemic control, with average reductions in haemoglobin A1c of about 1.0%, fasting plasma glucose of about 1.4 mmol/l, and causes a weight loss of approximately 2-3 kg after 30 weeks of treatment in patients with type 2 diabetes. The adverse effects are transient nausea and vomiting. The long-acting glucagon-like peptide-1 receptor agonists liraglutide and exenatide long-acting release reduce haemoglobin A1c by about 1.0-2.0% and have fewer gastrointestinal side-effects. The orally available dipeptidyl peptidase-4 inhibitors, that is sitagliptin and vildagliptin reduce haemoglobin A1c by 0.5-1.0%, are weight neutral and without gastrointestinal side-effects.

SUMMARY

The benefits and position of the glucagon-like peptide-1 analogues and the dipeptidyl peptidase-4 inhibitors in the diabetes treatment algorithm will be clarified when we have long-term trials with hard cardiovascular endpoints and data illustrating the effects on the progression of type 2 diabetes.

Effects of exenatide on diabetes, obesity, cardiovascular risk factors, and hepatic biomarkers in patients with type 2 diabetes

Obesity increases the risk of diabetes up to 90-fold and worsens hyperglycemia, hyperinsulinemia, insulin resistance, dyslipidemia, and nonalcoholic fatty liver disease. For patients with type 2 diabetes, weight loss can trigger improvements in all these conditions and decrease the need for glucose-lowering agents. The incretin mimetic exenatide shares many glucoregulatory properties with native glucagon-like peptide-1, including enhancement of glucose-dependent insulin secretion, glucose-dependent suppression of inappropriately high glucagon secretion, slowing of gastric emptying, and reduction of food intake in patients with type 2 diabetes. Exenatide treatment was associated with progressive weight loss in the majority of patients in clinical trials. In addition, patients with elevated markers of liver injury at baseline showed improvements. Therefore, exenatide represents a unique option for adjunctive therapy for patients with type 2 diabetes not achieving adequate glycemic control on oral antidiabetic agents, especially in patients for whom weight gain would be an additional contraindication.