Interim analysis of the effects of exenatide treatment on A1C, weight and cardiovascular risk factors over 82 weeks in 314 overweight patients with type 2 diabetes

Glycaemic control in type 2 diabetes: targets and new therapies

Type 2 diabetes mellitus (T2DM) is a worldwide public health challenge. Despite the availability of many antidiabetes agents and pharmacotherapies targeting cardiovascular risk factors, the morbidity, mortality and economic consequences of T2DM are still a great burden to patients, society, health care systems and the economy. The need for new therapies for glycaemic control is compounded by the fact that existing treatments have limitations either because of their side effects (particularly weight gain and hypoglycaemia) or contraindications that limit their use. Furthermore, none of the current therapies have a significant impact on disease progression. Incretin-based therapies offer a new therapeutic approach to the management of T2DM, and there are also several even newer therapies in development. There are two groups of incretin-based therapies currently available; dipeptidyl peptidase-4 (DPP-4) inhibitors and GLP-1 analogues/mimetics. The former are given orally while the latter subcutaneously. These drugs result in glucose-dependent insulin secretion and glucose-dependent glucagon suppression, with consequent low risk of hypoglycaemia when used as mono- or combination therapy (except when used with sulphonylureas). In addition, they are either weight neutral in the case of DPP-4 inhibitors or cause weight loss in the case of incretin mimetics/analogues. Furthermore, animal studies have shown that these agents prolong beta cell survival which offers the theoretical possibility of slowing the progression to T2DM. In this article we will review the currently available antidiabetes agents with particular emphasis on incretin-based and future therapies. In addition, we will review and discuss the evidence relating to glycaemic control and cardiovascular disease.

Pharmacotherapy of hyperglycemia

Type 2 diabetes mellitus (T2DM) is a chronic, progressive disorder that affects more than 230 million people worldwide and is expected to affect 366 million by 2030. Both the prevalence of T2DM and the cost of its long term complications has driven the focus and emphasis on treatments aimed at reducing hyperglycemia and controlling hypertension and dyslipidemia. In the last 5 years new glucose lowering drugs acting on novel pathways have been developed, licensed and launched. These drugs include the glucagon-like peptide (GLP-1) agonists, exenatide, and dipeptidyl peptidase (DPP-IV) inhibitors such as sitagliptin and saxagliptin. This review describes current approaches to T2DM treatment, focusing on newer agents which tend to be associated with less hypoglycemia and possible weight loss, and addresses the potential roles of novel oral pharmacologic agents in the late-stages of development that might provide new options for the management of this disease.

Type 2 diabetes: where we are today: an overview of disease burden, current treatments, and treatment strategies

OBJECTIVE

To provide an overview of the disease burden and current strategies in the treatment of patients with type 2 diabetes.

DATA SOURCES

Medline search of all relevant clinical and review articles.

STUDY SELECTION

By the author.

DATA EXTRACTION

By the author.

DATA SYNTHESIS

The prevalence of diabetes in the United States has reached epidemic proportions with the total diagnosed and undiagnosed cases among people aged 20 years or older estimated at 12.9%, and it continues to rise at an alarming rate. This upsurge has been paralleled by an increase in rates of obesity. Type 2 diabetes accounts for up to 95% of diabetes cases and is often comorbid with hypertension and dyslipidemia.

CONCLUSION

Tight glycemic control is necessary for the management of type 2 diabetes, but progressive deterioration of beta-cell function can lead to a loss of glycemic control. Oral antidiabetes drugs and insulin are effective but do not always correct the associated metabolic and glucoregulatory dysfunctions, and hypoglycemia and weight gain are common adverse effects of these agents. A clear need exists for aggressive therapeutic options-particularly incretin-based agents-that can be combined with existing agents to preserve beta-cell function and halt the progression of type 2 diabetes.

What are the risks and the benefits of current and emerging weight-loss medications?

Obesity is epidemic; new medications and therapeutic options are urgently needed to reduce the associated health care burden. The initial clinical strategy for weight loss is lifestyle modification involving a combination of diet, exercise, and behavior change. However, it is difficult for many to achieve and maintain weight loss solely through this approach. Only two drugs, orlistat and sibutramine, have been approved by the US Food and Drug Administration (FDA) to treat obesity long term, and both medications have undesirable side effects, leaving an enormous unmet need for efficacious and safe therapy for obesity. Other medications with weight-loss effects have been approved by the FDA for short-term treatment of obesity or for disorders other than obesity, but these also have potential adverse effects. This article discusses the perceived benefits and risks of these approved medications along with emerging drugs that have shown weight-loss effects.

A review of exenatide as adjunctive therapy in patients with type 2 diabetes

Background

Incretin glucagon-like peptide-1 (GLP-1) is a hormone released from cells in the gastrointestinal tract (GI), leading to glucose-dependent insulin release from the pancreas. It also suppresses postprandial hyperglycemia, glucagon secretion and slows gastric emptying. Exenatide (EXE), a functional analog of human GLP-1, was approved by the US FDA in April 2005.

Objective

This article reviews current primary literature on the clinical efficacy and safety of EXE in the treatment of type 2 diabetes mellitus (DM) and describes the pharmacokinetics, pharmacodynamics, dosing and administration of EXE.

Methods

English-language articles were identified through a search of MEDLINE (1966 to March 2009), International Pharmaceutical Abstracts (1970 to present), and Cochrane Database of Systemic Reviews (1995 to March 2009). Search terms included EXE, diabetes mellitus, postprandial hyperglycemia, gastric emptying, glucagon, pharmacokinetics and pharmacodynamics. Articles were selected for review if their designs were randomized, blinded and of controlled design that focused on clinical outcomes of patients with type 2 DM.

Results

EXE is administered subcutaneously in the thigh, abdomen or upper arm within the 60-minute period before the morning and evening meals. Its C_max is reached within 2.1 hours, and its T_1/2 in 2.4 hours. EXE’s metabolism is primarily through the kidneys. For the patients who received EXE 10 μg SC BID in three, 30-week, placebo-controlled studies with background sulfonylureas (SUs), metformin (MET), or SU + MET, there were significant reductions in HbA_1c (0.77 to 0.86%), fasting plasma glucose (0.6 mmol/L) and body weight (1.6 to 2.8 kg) (P ≤ 0.05 vs PCB) that were sustained in patients who completed two open-label phase trials with an additional 52 weeks of therapy. The use of thiazolidinediones was associated with a slight advantage over EXE in improving HbA_1c along with increased weight gain; those who received EXE lost weight, but experienced more GI adverse effects. Patients who received EXE lost significant body weight while patients who received insulin gained weight. Patients receiving insulin had lower fasting, prelunch and predinner glucose excursions while patients in the EXE groups had lower postprandial glucose levels. Nausea was most frequently (>20%) reported in patients receiving the highest dose of EXE (10 μg SC BID vs 5 μg SC BID).

Conclusions

EXE at the dose of 10 μg SC BID has been proven to decrease HbA_lc by 1.3% ± 0.1% and decrease body weight by up to 5.3 ± 0.8 kg at week 82. Nausea was the most frequently reported adverse event (>20%) especially in patients being treated with EXE 10 μg SC BID. EXE can be safely added to MET therapy, SU therapy or MET + SU combination to effectively target glycemic goals in patients with type 2 DM. Long-term, head-to-head studies assessing the effect of the EXE ± oral agents/insulins in patients with HbA_lc ≥ 10% are still needed to fully clarify the role of EXE in poorly controlled patients with type 2 DM.

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.

Impact of glycemic treatment choices on cardiovascular complications in type 2 diabetes

As the diabetic population has significant morbidity and mortality from cardiovascular disease (CVD), much of its medical care focuses on CVD prevention and treatment. Some medications used to treat hyperglycemia may have beneficial effects on CV outcomes, others may have negative effects, while still others seem to have no direct effect. Although past epidemiological studies have shown a relationship between glycated hemoglobin levels and CV events in patients with type 2 diabetes, recent large randomized clinical trials (ACCORD, ADVANCE, and VADT) lasting 3.5 to 5.6 years have found that intensive glycemic control either has no impact on CV outcomes or even worsens them. Results of the 10-year follow-up of the UKPDS suggest that tight glycemic control of younger, newly diagnosed patients with type 2 diabetes may have CV benefits many years later. Because the pathogenesis of atherosclerosis spans decades, it may be that beneficial effects of tight glycemic control on CV outcomes are mainly in younger patients without established macrovascular disease. There is an emerging notion that tight glycemic control may be beneficial in primary prevention of CVD in younger patients with diabetes, but may become deleterious in older patients with established or subclinical CVD. Thus, while tight control may lessen microvascular disease, it may increase the risk of hypoglycemia and possibly of adverse CV events. In each patient, the goals of glycemic control need to be individualized based on age, overall prognosis, presence of macrovascular disease, and risk of hypoglycemia.

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.

Recent results of exenatide use as adjunctive therapy in the treatment of patients with type 2 diabetes

Exenatide is a GLP-1 receptor agonist approved for use in type 2 diabetes mellitus. In clinical trials, significant reductions in serum glucose and weight were demonstrated for exenatide with primary glycemic effects of the twice daily formulation on prandial glucose control. In this paper, we review recent research with exenatide as adjunctive therapy in type 2 diabetes mellitus. In particular, studies demonstrate ongoing benefit on glycemic control and weight reduction with continued therapy up to 82 weeks duration and efficacy as adjunctive therapy for patients taking metformin, thiazolidinediones, and/or a sulfonylurea and as compared to sitagliptin and various insulin formulations. Compared to insulin, exenatide likely has greatest benefit for those patients who are overweight or who need improved prandial glucose control. The new long-acting release formulation of exenatide has demonstrated slightly improved efficacy compared to the twice daily formulation as well as a reduction in gastrointestinal side effects. Emerging research is further exploring novel benefits of exenatide as adjunctive DM therapy, effects on prandial glycemic control, markers of hepatic inflammation, alternative dosage forms including intra-nasal administration, and effects on beta cell function.

Endothelial dysfunction induced by triglycerides is not restored by exenatide in rat conduit arteries ex vivo

Exenatide (synthetic exendin-4) is a stable analogue of glucagon-like peptide 1 (GLP-1) and has recently been approved for clinical use against type 2 diabetes. Exenatide is believed to exert its effects via the GLP-1 receptor with almost the same potency as GLP-1 in terms of lowering blood glucose. Short term exenatide treatment normalizes the altered vascular tone in type 2 diabetic rats, probably due to the reduction in glycemia. The aim of this study was to investigate whether exenatide directly protects against triglyceride-induced endothelial dysfunction in rat femoral arterial rings ex vivo. Short term pre-incubation with Intralipid (0.5 and 2%) was found to dose-dependently induce endothelial dysfunction, in that it elicited a significant reduction in ACh-induced vasorelaxation by 29% and 35%, respectively. Paradoxically, this occurred with a concomitant increase in endothelial nitric oxide synthase (eNOS) activity. No such reduction in vasorelaxation by Intralipid was seen in response to the NO donor sodium nitroprusside (SNP), revealing an endothelium-dependent vascular dysfunction by Intralipid. However, exenatide did not protect against Intralipid-induced endothelial dysfunction. More surprisingly, the maximum vasorelaxation induced by exenatide (without Intralipid was only 3+/-2%, compared to the 23+/-4%, 38+/-4%, 79+/-3% and 97+/-4% relaxations induced by GLP-1, GLP-1 (9-36), ACh and SNP, respectively. This unexpected finding prompted us to ascertain that the exenatide preparation was biologically active, and both exenatide (10(-11) mol/l) and GLP-1 (10(-9) mol/l) significantly increased insulin secretion in pancreatic beta-cells from ob/ob mice in vitro. In conclusion, exenatide could neither confer any acute protective effects against triglyceride-induced endothelial dysfunction nor exert any significant vasorelaxant actions in this model of rat conduit arteries ex vivo.

Effect of antiobesity medications in patients with type 2 diabetes mellitus

Obesity is considered as a major health problem, as its prevalence continuously rises worldwide. One of the common health consequences of obesity is type 2 diabetes mellitus. Therefore, antiobesity management is a prerequisite in treating diabetic patients. Lifestyle modifications combined with pharmacological agents appear to be an effective approach. Sibutramine is a serotonin-noradrenaline reuptake inhibitor, which acts centrally by promoting the feeling of satiety and decreasing caloric intake, thus resulting in weight loss. A potential association with cardiovascular side effects has been noted. Orlistat, a gastric and pancreatic lipase inhibitor, also achieves significant weight loss and improves glycaemic status, but it has gastrointestinal side effects. Rimonabant, the first endocannabinoid CB1 antagonist, is associated with weight reduction and it improves diabetic parameters; nevertheless, it is associated with psychiatric disorders; indeed, a recently conducted safety review led to the temporal suspension of its commercialization. The above-mentioned medications seem to be currently useful agents for treating obesity in patients with type 2 diabetes mellitus. Other medications used for diabetes management, such as exenatide, liraglutide and pramlintide, have also shown body weight reduction. Ongoing research is needed to scrutinize the precise impact of these agents in the daily clinical practice of management of obesity in patients with type 2 diabetes mellitus.

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.

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.

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.

Improved glycemic control and reduction of cardiometabolic risk factors in subjects with type 2 diabetes and metabolic syndrome treated with exenatide in a clinical practice setting

BACKGROUND

Type 2 diabetes mellitus (T2DM) with the presence of metabolic syndrome (MetS) carries increased risk for cardiovascular disease. Adjunctive exenatide treatment in patients with T2DM is associated with improvements in glycemic control coupled with progressive weight reduction. We evaluated exenatide use on glycosylated hemoglobin A1c (HbA(1c)) and cardiometabolic risk factors in patients with T2DM and MetS in a single clinical practice setting.

METHODS

A retrospective analysis of clinical data extracted from the records of 176 adult patients with T2DM and MetS (106 women, 70 men) who received exenatide along with existing therapeutic regimes from 2005 to 2007 was performed. HbA(1c), lipid profiles, blood pressure, and anthropometric measures were evaluated at baseline and after 16 (+/-4) weeks of exenatide therapy.

RESULTS

Mean HbA(1c) was significantly reduced from baseline in 16 weeks (P < 0.001), with 68% of patients achieving HbA(1c) <7%. Total, high-density lipoprotein-, and low-density lipoprotein-cholesterol levels decreased significantly. This decline was not attributable to changes in lipid-lowering agents. Significant reductions were also noted in body mass index, mean body weight, and abdominal girth (AG) with the addition of exenatide. Additional analyses showed 76% of subjects lost weight. Lessening of AG was much more pronounced in female compared with male subjects with diabetes (P < 0.032). No consistent changes in blood pressure were observed.

CONCLUSIONS

We found that addition of exenatide to an existing treatment regimen in patients with T2DM and MetS resulted in significant reductions in HbA(1c) along with decline in lipids, AG, and body weight. This indicates improvement in these patients' metabolic profiles.

Manufacturing peptides as active pharmaceutical ingredients

Background: Today, there are more than 40 peptides on the pharmaceutical world market and more than 100 in several clinical phases. Although in the past the pharmaceutical industries had reduced their interest in peptides research, in recent decades, they have rekindled their interest in peptides as a result of contemporary novel technological accomplishments, strategic developments, advances in the areas of formulation and enhanced drug delivery technology of peptides. Thus, eight new peptide drugs that could previously have been characterized as difficult to prepare on the large scale required by industry, have entered the pharmaceutical market at the new millennium. Discussion: The manufacturing of most of these drugs has benefited from new technological advances. Traditional and most modern techniques have been applied to the manufacture of these new entries. Conclusion: Recent accomplishments, together with the traditional benefits of peptides (high biological activity, high specificity and low toxicity), have led pharmaceutical companies to refocus their attention on peptide-based agents. Therefore, several serious diseases can be treated using the potential next generation of peptide drugs.

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.

DPP-IV inhibition enhances the antilipolytic action of NPY in human adipose tissue

CONTEXT

Dipeptidyl peptidase IV (DPP-IV) inactivates the incretin hormone glucagon-like peptide. It can also affect the orexigenic hormone neuropeptide Y (NPY(1-36)) which is truncated by DPP-IV to NPY(3-36), as a consequence NPY's affinity changes from receptor Y1, which mediates the antilipolytic function of NPY, to other NPY receptors. Little is known whether DPP-IV inhibitors for the treatment of type 2 diabetic (T2DM) patients could influence these pathways.

AIMS

To investigate the in vitro effects of NPY with DPP-IV inhibition in isolated abdominal subcutaneous (AbdSc) adipocytes on fat metabolism, and assessment of NPY receptor and DPP-IV expression in adipose tissue (AT).

METHODS

Ex vivo human AT was taken from women undergoing elective surgery (body mass index: 27.5 (mean +/- s.d.) +/- 5 kg/m2, age: 43.7 +/- 10 years, n = 36). Isolated AbdSc adipocytes were treated with human recombinant (rh)NPY (1-100 nM) with and without DPP-IV inhibitor (1 M); glycerol release and tissue distribution of DPP-IV, Y1 and Y5 messenger RNA (mRNA) were measured and compared between lean and obese subjects.

RESULTS AND CONCLUSION

rhNPY reduced glycerol release, an effect that was further enhanced by co-incubation with a DPP-IV inhibitor [control: 224 (mean +/- s.e.) +/- 37 micromol/l; NPY, 100 nM: 161 +/- 27 micromol/l**; NPY 100 nM/DPP-IV inhibitor, 1 M: 127 +/- 14 micromol/l**; **p < 0.01, n = 14]. DPP-IV was expressed in AbdSc AT and omental AT with relative DPP-IV mRNA expression lower in AbdSc AT taken from obese [77 +/- 6 signal units (SU)] vs. lean subjects (186 +/- 29 SU*, n = 10). Y1 was predominantly expressed in fat and present in all fat depots but higher in obese subjects, particularly the AbdSc AT-depot (obese: 1944 +/- 111 SU vs. lean: 711 +/- 112 SU**, n = 10). NPY appears to be regulated by AT-derived DPP-IV. DPP-IV inhibitors augment the antilipolytic effect of NPY in AT. Further studies are required to show whether this explains the lack of weight loss in T2DM patients treated with DPP-IV inhibitors.

Intestinal microbiota during infancy and its implications for obesity

Obesity is a worldwide epidemic, threatening both industrialized and developing countries, and is accompanied by a dramatic increase in obesity-related disorders, including type 2 diabetes mellitus, hypertension, cardiovascular diseases, and nonalcoholic fatty liver disease. Recent studies have shown that the gut microbial community (microbiota) is an environmental factor that regulates obesity by increasing energy harvest from the diet and by regulating peripheral metabolism. However, there are no data on how obesogenic microbiotas are established and whether this process is determined during infancy. The sterile fetus is born into a microbial world and is immediately colonized by numerous species originating from the surrounding ecosystems, especially the maternal vaginal and fecal microflora. This initial microbiota develops into a complex ecosystem in a predictable fashion determined by internal (eg, oxygen depletion) and external (eg, mode of birth, impact of environment, diet, hospitalization, application of antibiotics) factors. We discuss how the gut microbiota regulates obesity and how environmental factors that affect the establishment of the gut microbiota during infancy may contribute to obesity later in life.

Preventing type 2 diabetes

The rapid and often relentless progression of type 2 diabetes suggests that high-risk patients should be provided with an equally aggressive strategy to protect their remaining beta-cell function and endogenous insulin secretion. Management of patients with prediabetes should incorporate both lifestyle and pharmacologic intervention. Although no specific recommendations are published for the management of prediabetes, one can assume that preservation of pancreatic beta-cell function, improvement in peripheral insulin resistance and pancreatic insulin secretion, reducing pancreatic alpha-cell secretion of glucagon, preventing long- and short-term diabetes-related complications, and assisting patients to loose weight are beneficial. Aggressive, timely, and physiologic management of prediabetes should be advocated.

Comparison of costs among patients with type 2 diabetes treated with exenatide or sitagliptin therapy

INTRODUCTION

Exenatide (Byetta, Amylin Pharmaceuticals Inc., CA, USA) and sitagliptin (Januvia, Merck & Co, NJ, USA) are two antidiabetic agents recently approved by the US Food and Drug Administration. The purpose of this analysis was to compare costs among patients with type 2 diabetes (T2D) treated with either of these agents.

METHODS

Data with dates of service from September 1, 2005 through August 31, 2007, were obtained from a large US retrospective claims database. Intent-to-treat cohorts of adults diagnosed with T2D who began taking either exenatide (n=1885) or sitagliptin (n=2482) and did not use the alternate medication in the 6-month follow-up period were created. Six-month total medical costs were estimated using stepwise multivariate regressions. Six-month total diabetes-related medical costs, a component of total medical costs, were also estimated using stepwise multivariate regressions. In addition, other cost components were examined using either stepwise multivariate regressions or a two-part model that controlled for the probability of using the medical service. Smearing estimates were used to transform estimated log costs into costs. The analysis controlled for the potential impact of patient demographics, general health, prior resource use, comorbidities, and timing of treatment initiation.

RESULTS

Exenatide was associated with lower total 6-month direct medical costs ($9340 vs. $9995; P<0.0001), despite some component costs being slightly higher with exenatide: diabetes-related drug costs ($1765 vs. $1743; P=0.0062), diabetes-related medical costs ($4142 vs. $4002; P<0.0001), and emergency room costs ($43 vs. $29; P=0.0388). Exenatide was associated with lower outpatient costs ($4498 vs. $5942; P<0.0001).

CONCLUSIONS

Compared with the use of sitagliptin, exenatide was associated with lower total medical costs (difference of $655) despite higher total diabetes-related costs (difference of $140). As a result, there appears to be overall cost savings associated with the use of exenatide relative to sitagliptin.

Effect of Diabetes Medications on Cardiovascular Risk and Surrogate Markers in Patients with Type 2 Diabetes

Objective:

To evaluate the effect of diabetes medications on the risk of cardiovascular disease and surrogate markers.

Data Sources:

Literature was accessed through MEDLINE (1950–July 2008) and PubMed using multiple terms for diabetes, cardiovascular risk, surrogate markers, and diabetes medications. In addition, reference citations from publications were reviewed.

Study Selection and Data Extraction:

English-language articles that met the above criteria, with clinical relevance, were evaluated.

Data Synthesis:

Evidence regarding the effect of diabetes medications on cardiovascular risk is sparse, with information on their effects on surrogate markers more widely available. Recent evidence demonstrates that glycemic control alone may not reduce the risk of macrovascular events. Multiple trials were reviewed to determine the effect of diabetes medications on this risk, as well as the effect on surrogate markers (eg, blood pressure, cholesterol, body weight). Metformin and acarbose demonstrated significant reductions in macrovascular events, including myocardial infarction. Data regarding sulfonylureas, thiazolidinediones, and insulin are conflicting. Pioglitazone may reduce cardiovascular events, except heart failure, whereas rosiglitazone may increase these events. Until direct evidence can be obtained, the full effect of diabetes medications on cardiovascular risk is unknown.

Conclusions:

Current literature provides little support that diabetes medications may lower the risk of cardiovascular events while some agents may increase this risk. Of the drugs available, metformin may be the least detrimental. Current literature regarding other diabetes medications provides conflicting results on their effect on cardiovascular outcomes. In the meantime, practitioners should treat all targets of cardiovascular risk in patients with diabetes.

ACPE Universal Program Numbers:

407-000-09-050-H01-P (Pharmacists); 407-000-09-050-H01-T (Technicians)

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.

Exenatide: incretin therapy for patients with Type 2 diabetes mellitus

Exenatide is the first in a novel class of drugs that mimics naturally occurring glucagon-like peptide 1. In patients with Type 2 diabetes mellitus (T2DM), control of both glycemia and bodyweight are important to minimize the risk of diabetes complications. Exenatide improves glycemic control through glucose-dependent insulin secretion, suppression of glucagon secretion, delaying gastric emptying and suppressing appetite. Exenatide therapy significantly reduced glycated hemoglobin (Hb_A1c) and fasting and postprandial plasma glucose when added to metformin and/or sulfonylureas, with an average weight loss of 2 kg. Furthermore, exenatide-treated patients sustained the reductions achieved in Hb_A1c at 12 weeks with a progressive reduction in bodyweight during 3-year follow-up. Exenatide is generally well tolerated; nausea is the most common side effect but significantly reduces over time and with gradual dose titration. Hypoglycemia at a rate greater than placebo only occurred in combination with sulfonylureas. Exenatide may enable patients with T2DM to improve glycemic control while reducing the risk of hypoglycemia and provoking weight loss.

GLP-1: physiological effects and potential therapeutic applications

Glucagon-like peptide 1 (GLP-1) is a gut-derived incretin hormone with the potential to change diabetes. The physiological effects of GLP-1 are multiple, and many seem to ameliorate the different conditions defining the diverse physiopathology seen in type 2 diabetes. In animal studies, GLP-1 stimulates beta-cell proliferation and neogenesis and inhibits beta-cell apoptosis. In humans, GLP-1 stimulates insulin secretion and inhibits glucagon and gastrointestinal secretions and motility. It enhances satiety and reduces food intake and has beneficial effects on cardiovascular function and endothelial dysfunction. Enhancing incretin action for therapeutic use includes GLP-1 receptor agonists resistant to degradation (incretin mimetics) and dipeptidyl peptidase (DPP)-4 inhibitors. In clinical trials with type 2 diabetic patients on various oral antidiabetic regimes, both treatment modalities efficaciously improve glycaemic control and beta-cell function. Whereas the incretin mimetics induce weight loss, the DPP-4 inhibitors are considered weight neutral. In type 1 diabetes, treatment with GLP-1 shows promising effects. However, several areas need clinical confirmation: the durability of the weight loss, the ability to preserve functional beta-cell mass and the applicability in other than type 2 diabetes. As such, long-term studies and studies with cardiovascular end-points are needed to confirm the true benefits of these new classes of antidiabetic drugs in the treatment of diabetes mellitus.

Metformin therapy and clinical uses

Metformin is now established as a first-line antidiabetic therapy for the management of type 2 diabetes. Its early use in treatment algorithms is supported by lack of weight gain, low risk of hypoglycaemia and its mode of action to counter insulin resistance. The drug's anti-atherosclerotic and cardioprotective effects have recently been confirmed in prospective and retrospective studies, and appear to reflect a collection of glucose-independent effects on the vascular endothelium, suppressant effects on glycation, oxidative stress and formation of adhesion molecules, stimulation of fibrinolysis and favourable effects on the lipid profile. Although avoidance of troublesome gastrointestinal tolerability issues requires careful dose titration, the risk of serious adverse events is considered low provided that contra-indications (especially with respect to renal function) are observed. As many of its actions go beyond glucose lowering, emerging evidence indicates potential benefits in other insulin-resistant states and possibly tumour suppression.

Evaluation of the cost effectiveness of exenatide versus insulin glargine in patients with sub-optimally controlled type 2 diabetes in the United Kingdom

OBJECTIVE

Exenatide belongs to a new therapeutic class in the treatment of diabetes (incretin mimetics), allowing glucose-dependent glycaemic control in type 2 diabetes. Randomised controlled trial data suggest that exenatide is as effective as insulin glargine at reducing HbA1c in combination therapy with metformin and sulphonylureas; with reduced weight but higher incidence of adverse gastrointestinal events. The objective of this study is to evaluate the cost effectiveness of exenatide versus insulin glargine using RCT data and a previously published model of type 2 diabetes disease progression that is based on the United Kingdom Prospective Diabetes Study; the perspective of the health-payer of the United Kingdom National Health Service.

METHODS

The study used a discrete event simulation model designed to forecast the costs and health outcome of a cohort of 1,000 subjects aged over 40 years with sub-optimally-controlled type 2 diabetes, following initiation of either exenatide, or insulin glargine, in addition to oral hypoglycaemic agents. Sensitivity analysis for a higher treatment discontinuation rate in exenatide patients was applied to the cohort in three different scenarios; (1) either ignored or (2) exenatide-failures excluded or (3) exenatide-failures switched to insulin glargine. Analyses were undertaken to evaluate the price sensitivity of exenatide in terms of relative cost effectiveness. Baseline cohort profiles and effectiveness data were taken from a published randomised controlled trial.

RESULTS

The relative cost-effectiveness of exenatide and insulin glargine was tested under a variety of conditions, in which insulin glargine was dominant in all cases. Using the most conservative of assumptions, the cost-effectiveness ratio of exenatide vs. insulin glargine at the current UK NHS price was -29,149 pounds/QALY (insulin glargine dominant) and thus exenatide is not cost-effective when compared with insulin glargine, at the current UK NHS price.

CONCLUSION

This study evaluated the relative cost effectiveness of insulin glargine versus exenatide in the management of type 2 diabetes using a published model. Given no significant difference in glycaemic control and applying the additional effectiveness of exenatide over insulin glargine, with respect to weight loss, and using the current UK NHS prices, insulin glargine was found to be dominant over exenatide in all modelled scenarios. With current clinical evidence, exenatide does not appear to represent a cost-effective treatment option for patients with type 2 diabetes when compared to insulin glargine.

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.

Initiating insulin therapy in type 2 diabetes: benefits of insulin analogs and insulin pens

Despite the development of alternative therapies in recent years, insulin injections remain essential treatment for type 2 diabetes once oral therapy alone becomes inadequate. However, neither patients nor physicians are proactive enough with regard to starting insulin, despite the well-known benefits of early insulin initiation and aggressive dose titration. Barriers to starting insulin therapy are being overcome by developments in insulin and delivery device technology and are the subject of this review. A literature search spanning the last 25 years was carried out to identify publications addressing issues of insulin initiation, how insulin analogs can help overcome barriers to initiation, and the advantages of pen-type insulin delivery systems. Seventy-five publications were identified. These references illustrate that the drawbacks associated with regular exogenous human insulins (soluble and NPH) are improved with modern insulin analogs. The more rapid absorption of prandial insulin analogs compared with human insulin eliminates the need for an injection-meal-interval, increasing convenience, while basal analogs have no discernible peak in activity. Modern insulin delivery devices also have advantages over the traditional vial and syringe. Currently available insulin pens are either durable (insulin cartridge is replaceable; e.g., HumaPen, Eli Lilly [Indianapolis, IN]; NovoPen series, Novo Nordisk [Bagsvaerd, Denmark]) or disposable (prefilled; e.g., FlexPen, Novo Nordisk; SoloSTAR, sanofi-aventis [Paris, France]), with features to aid ease-of-use. These include a large dose selector, dial-up and dial-down facility, and audible clicks when selecting the dose. The potential for dosing errors is thus reduced with pen-type devices, with other benefits including a discreet appearance, ease of learning, and greater user confidence. Collectively, these features contribute to overwhelming patient preference when compared with vials and syringes. Despite the greater cost of insulin pens relative to vials and syringes, improvements in treatment adherence with pens-and hence glycemic control-may offset these costs in the long term.

Pramlintide, the synthetic analogue of amylin: physiology, pathophysiology, and effects on glycemic control, body weight, and selected biomarkers of vascular risk

Pramlintide is a synthetic version of the naturally occurring pancreatic peptide called amylin. Amylin and pramlintide have similar effects on lowering postprandial glucose, lowering postprandial glucagon and delaying gastric emptying. Pramlintide use in type 1 and insulin requiring type 2 diabetes mellitus (DM) is associated with modest reductions in HbA1c often accompanied by weight loss. Limited data show a neutral effect on blood pressure. Small studies suggest small reductions in LDL-cholesterol in type 2 DM and modest reductions in triglycerides in type 1 DM. Markers of oxidation are also reduced in conjunction with reductions in postprandial glucose. Nausea is the most common side effect. These data indicate that pramlintide has a role in glycemic control of both type 1 and type 2 DM. Pramlintide use is associated with favorable effects on weight, lipids and other biomarkers for atherosclerotic disease.

Beyond insulin replacement: addressing the additional needs of the diabetes patient

The management of type 2 diabetes mellitus (T2DM) typically focuses on correcting dysglycaemia to reduce risk for microvascular and macrovascular complications, possibly by reducing glucose-mediated oxidative stress. However, other cardiometabolic risk factors, including abdominal obesity and dyslipidaemia are often overlooked in the quest for perfect glucose control. The currently used antidiabetic agents, including insulin, metformin, sulphonylureas and thiazolidinediones, have limited efficacy on these risk factors. A number of new therapeutic agents are undergoing clinical development, including glucagon-like peptide 1 mimetics (exenatide and liraglutide) and dipeptidyl peptidase 4 inhibitors (sitagliptin and vildagliptin), which target the incretin system, and the cannabinoid-1 receptor antagonists (rimonabant), which target the endocannabinoid system, may hold some promise for meeting these unmet needs. In this review, the clinical properties of these agents and potential treatment pathways to best use these agents are discussed for improving the management of T2DM and cardiovascular risk.

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.

Exploiting the antidiabetic properties of incretins to treat type 2 diabetes mellitus: glucagon-like peptide 1 receptor agonists or insulin for patients with inadequate glycemic control?

Type 2 diabetes mellitus is associated with progressive decreases in pancreatic beta-cell function. Most patients thus require increasingly intensive treatment, including oral combination therapies followed by insulin. Fear of hypoglycemia is a potential barrier to treatment adherence and glycemic control, while weight gain can exacerbate hyperglycemia or insulin resistance. Administration of insulin can roughly mimic physiologic insulin secretion but does not address underlying pathophysiology. Glucagon-like peptide 1 (GLP-1) is an incretin hormone released by the gut in response to meal intake that helps to maintain glucose homeostasis through coordinated effects on islet alpha- and beta-cells, inhibiting glucagon output, and stimulating insulin secretion in a glucose-dependent manner. Biological effects of GLP-1 include slowing gastric emptying and decreasing appetite. Incretin mimetics (GLP-1 receptor agonists with more suitable pharmacokinetic properties versus GLP-1) significantly lower hemoglobin A1c, body weight, and postprandial glucose excursions in humans and significantly improve beta-cell function in vivo (animal data). These novel incretin-based therapies offer the potential to reduce body weight or prevent weight gain, although the durability of these effects and their potential long-term benefits need to be studied further. This article reviews recent clinical trials comparing therapy with the incretin mimetic exenatide to insulin in patients with oral treatment failure, identifies factors consistent with the use of each treatment, and delineates areas for future research.

Exenatide as a treatment for diabetes and obesity: implications for cardiovascular risk reduction

Among the challenges in improving outcomes in patients with diabetes is effectively implementing existing pharmacotherapies. However, current therapies for diabetes are often limited by adverse effects such as edema, hypoglycemia, and weight gain. Understanding the role of the incretin effect on the pathophysiology of diabetes has led to the development of new therapeutic agents. Exenatide is the first in a new class of agents termed "incretin mimetics," which replicate several glucoregulatory effects of the endogenous incretin hormone, glucagon-like peptide-1. In clinical trials, patients with type 2 diabetes treated with exenatide demonstrate sustained improvements in glycemic control, with reductions in fasting and postprandial glucose levels and improvements in glycosylated hemoglobin levels. Improvements in glycemic control with exenatide are coupled with reductions in body weight. Lipid parameters, blood pressure, and C-reactive protein have been shown to improve favorably in patients treated with exenatide. The sustained glycemic improvements and progressive reduction in body weight with exenatide treatment support a shift toward a more favorable cardiovascular risk profile and may have a positive impact on decreasing the risk of associated long-term complications.

Role of metformin for weight management in patients without type 2 diabetes

OBJECTIVE

To evaluate the efficacy and safety of metformin for weight management in overweight and obese patients without type 2 diabetes.

DATA SOURCES

Literature was obtained through MEDLINE Ovid (1950-February week 3, 2008), EMBASE (all years), and a bibliographic review of relevant articles. Key words included metformin, obesity, overweight, and weight loss.

STUDY SELECTION/DATA EXTRACTION

All studies published in the English language that evaluated the effects of metformin on weight in obese or overweight individuals were critically analyzed. Relevant articles were selected for inclusion in this review.

DATA SYNTHESIS

Metformin is first-line pharmacotherapy in the treatment of overweight or obese patients with type 2 diabetes, with beneficial effects on weight in this population. Multiple trials have evaluated the effect of metformin on weight and other metabolic parameters in adults and adolescents without diabetes. Five of 12 trials in adults evaluated weight loss as a primary endpoint. Significant weight reduction was found in 4 of these studies; however, the trials were small and of weak design. Weight reduction was significant in 5 of the 6 adolescent trials; similarly, these studies were limited by weak study design and small patient population. Metabolic parameters (blood pressure, waist circumference, cholesterol parameters, insulin/glucose levels) often showed varying results. Metformin was well tolerated; gastrointestinal effects were the most frequently reported adverse effects.

CONCLUSIONS

The weight loss effects of metformin in overweight or obese adults and adolescents without diabetes appear promising; however, trials have been limited by small patient populations and weak design. Metformin may also have a positive effect on metabolic parameters such as waist circumference, fasting insulin and glucose levels, and triglycerides. Further research involving large-scale trials that evaluate weight loss as a primary outcome is necessary to firmly establish the role of metformin in this population.