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

Comparative effects of the long-acting GLP-1 receptor ligands, liraglutide and exendin-4, on food intake and body weight suppression in rats

The glucagon-like-peptide-1 receptor (GLP-1R) agonists, liraglutide (Victoza) and the synthetic product of exendin-4 (Byetta), are approved for type II diabetes mellitus (T2DM) treatment and may be efficacious in obesity treatment as well, in part, due to the drugs' resistance to enzymatic degradation and prolonged half-life relative to endogenous GLP-1. To address the need to directly compare the food intake- and body weight-suppressive effects of these two GLP-1R ligands, acute and chronic dosing experiments were performed. Once-daily (q.d.) exendin-4 (0, 0.33, 1.5, and 3.0 µg/kg) and liraglutide (0, 50, 100, and 300 µg/kg, q.d.) both reduced the chow intake in nonobese rats in a dose-dependent fashion following either intraperitoneal (IP) or subcutaneous (SC) administration, whereas only liraglutide reduced 24 and 48 h body weight in nonobese, chow-maintained rats. Chow intake and body weight suppression by liraglutide were of greater magnitude and shorter latency following IP compared to SC delivery, whereas for exendin-4, the magnitude of intake-suppression was similar for IP and SC administration. The effects of chronic delivery (7 consecutive days; IP) of liraglutide (25 and 50 µg/kg; q.d.) and exendin-4 (3 µg/kg; q.d. and twice-daily (b.i.d.)) on food intake and body weight were also examined in diet-induced obese (DIO) rats. Liraglutide (50 µg/kg q.d.) and exendin-4 (3 µg/kg b.i.d.) were comparable in suppressing overall high fat/sucrose diet (HFS; 60% kcal from fat) intake. Both drugs regimens yielded marked weight loss over the 7-day period. The weight loss effect of liraglutide was achieved in the first 2 days and remained stable for the duration of the experiment; weight loss with exendin-4 appeared more linear over the 7-day period. In conclusion, administration of the GLP-1R ligands, exendin-4 (b.i.d.) and liraglutide (q.d.), lead to comparable and pronounced suppression of food intake and body weight in DIO rats, suggesting a potential role for these drugs as a clinical tool for obesity treatment.

A review of diabetes treatment adherence and the association with clinical and economic outcomes

BACKGROUND

The benefits of drug therapy to diabetic patients in terms of glycemic control, microvascular complications, cardiovascular event risk, mortality, and quality of life have been well established by clinical trial data. However, it has been a challenge to quantify the relationship between adherence and outcomes such as glycemic control, disease-related events, hospitalizations, cost, and quality of life.

OBJECTIVE

This article provides a comprehensive summary of empirical studies that examine the associations between adherence and glycemic control, health care utilization, quality of life, and mortality in patients with diabetes. It is intended to provide a framework for researchers interested in conducting studies to improve their understanding of the value of medication adherence for patients with diabetes.

METHODS

Relevant published articles were identified through searches of the National Center for Biotechnology PubMed database. Medical subject heading (MESH) terms diabetes mellitus, hypoglycemic agents, and insulin, were each combined with the MESH term medication adherence and with the subheadings economics, prevention and control, psychology, statistics and numerical data, therapy, adverse effects, therapeutic use, and administration and dosage, where available. Studies were included if they met the following criteria: (1) analyzed empirical data on some measure of patient adherence to diabetes pharmacotherapy; (2) described methods for measuring patient adherence; (3) evaluated economic, clinical, or humanistic outcomes related to diabetes; and (4) had as a goal of the research to evaluate the link between patient adherence and outcomes (as a primary or secondary objective). The data from the articles meeting these criteria were then abstracted, including mention of the specific interventions being compared, specific methods for measuring adherence, outcomes compared between adherent and nonadherent patients and how these outcomes were measured, and information on variables that were adjusted for in predictive and causal multivariable models.

RESULTS

A total of 37 articles that met all 4 criteria in this review underwent data extraction. Of these studies, 22 (59%) used objective measures to assess adherence, with 1 study using pill counts to assess adherence and 21 using either pharmacy claims or similar refill records to assess refill behavior. The remaining 15 (41%) studies used a wide variety of subjective patient-reported adherence assessments. The majority (13/23 [57%]) of the glycemic control studies reported that improved adherence was associated with better glycemic control. The ability to draw a distinction between adherence and glycemic control tended to occur more frequently [7/9 (78%)] among studies that characterized adherence in terms of prescription refills compared with studies that used various constructs for patient-reported adherence measures.

CONCLUSIONS

Based on the literature, better adherence was found to be associated with improved glycemic control and decreased health care resource utilization. There was no consistent association between improved adherence and decreased health care costs. Little data were available on the association between adherence and quality of life.

Advances in the treatment of type 2 diabetes mellitus

There is a rising worldwide prevalence of diabetes, especially type 2 diabetes mellitus (T2DM), which is one of the most challenging health problems in the 21st century. The associated complications of diabetes, such as cardiovascular disease, peripheral vascular disease, stroke, diabetic neuropathy, amputations, renal failure, and blindness result in increasing disability, reduced life expectancy, and enormous health costs. T2DM is a polygenic disease characterized by multiple defects in insulin action in tissues and defects in pancreatic insulin secretion, which eventually leads to loss of pancreatic insulin-secreting cells. The treatment goals for T2DM patients are effective control of blood glucose, blood pressure, and lipids (if elevated) and, ultimately, to avert the serious complications associated with sustained tissue exposure to excessively high glucose concentrations. Prevention and control of diabetes with diet, weight control, and physical activity has been difficult. Treatment of T2DM has centered on increasing insulin levels, either by direct insulin administration or oral agents that promote insulin secretion, improving sensitivity to insulin in tissues, or reducing the rate of carbohydrate absorption from the gastrointestinal tract. This review presents comprehensive and up-to-date information on the mechanism(s) of action, efficacy, pharmacokinetics, pleiotropic effects, drug interactions, and adverse effects of the newer antidiabetic drugs, including (1) peroxisome proliferator-activated-receptor-γ agonists (thiazolidinediones, pioglitazone, and rosiglitazone); (2) the incretin, glucagon-like peptide-) receptor agonists (incretin-mimetics, exenatide. and liraglutide), (3) inhibitors of dipeptidyl-peptidase-4 (incretin enhancers, sitagliptin, and vildagliptin), (4) short-acting, nonsulfonylurea secretagogue, meglitinides (repaglinide and nateglinide), (5) amylin anlog-pramlintide, (6) α-glucosidase inhibitors (miglitol and voglibose), and (7) colesevelam (a bile acid sequestrant). In addition, information is presented on drug candidates in clinical trials, experimental compounds, and some plants used in the traditional treatment of diabetes based on experimental evidence. In the opinion of this reviewer, therapy based on orally active incretins and incretin mimetics with long duration of action that will be efficacious, preserve the β-cell number/function, and block the progression of diabetes will be highly desirable. However, major changes in lifestyle factors such as diet and, especially, exercise will also be needed if the growing burden of diabetes is to be contained.

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

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

Anti-inflammatory properties of exenatide in human pancreatic islets

Exenatide is an analog of the incretin hormone glucagon-like peptide (GLP-1) that is used for the treatment of T2D for their metabolic effects. In addition to its insulinotropic effects, exenatide increases functional islet mass and improves their survival. Improved outcomes have been reported in recent clinical islet transplantation trials for the treatment of type 1 diabetes. The purpose of this study was to investigate whether exenatide has anti-inflammatory properties in human islets. Exenatide treatment improved islet function, significantly reduced content of inflammation-related molecules (tissue factor, IFN-γ, IL-17, IL-1β, and IL-2) and caspase 3 activation, whereas increased phosphorylation of ERK1/2, STAT3, and Akt in vitro. Immunostaining showed expression of GLP-1R in β-cells but not in α-cells. IL-1β colocalized with GLP-1R in β-cells. Induction of serine proteinase inhibitor 9 (PI-9) was detected after exposure of human islets to exenatide in vitro and after transplantation into immunodeficient mice. GLP-1 induced PI-9 expression in vitro but to a lower extent than exenatide. This effect was partially blocked by the antagonist exendin-9 in vitro. As assessed by immunostaining PI-9 is mostly expressed in β-cells but not in α-cells. In conclusion, we describe anti-inflammatory and cytoprotective properties of exenatide in human islets. Exenatide-mediated PI-9 expression, the only known granzyme B inhibitor, unveils potential immunoregulatory properties.

Improved glycemic control and reduced bodyweight with exenatide: A double-blind, randomized, phase 3 study in Japanese patients with suboptimally controlled type 2 diabetes over 24 weeks

Aims/Introduction:  To evaluate the efficacy and safety of the glucagon-like peptide-1 receptor agonist, exenatide, in Japanese patients with type 2 diabetes mellitus suboptimally controlled despite therapeutic doses of a sulfonylurea alone or combined with a biguanide or thiazolidinedione.

MATERIALS AND METHODS

  Patients were randomized to a placebo or exenatide, either 5 or 10 μg, given subcutaneously b.i.d. in addition to oral therapy. Patients randomized to 10 μg exenatide received 5 μg b.i.d. for the first 4 weeks, followed by 10 μg b.i.d. for the last 20 weeks.

RESULTS

  A total of 179 patients received the study drug and composed the full analysis set (n = 35, placebo; n = 72, exenatide 5 μg; n = 72, exenatide 10 μg; 68% male; 58 ± 10 years; body mass index 25.5 ± 4.1 kg/m(2); HbA1c 8.2 ± 0.9%; means ± standard deviations). Baseline to end-point (least-squares means ± standard errors) HbA1c changes (%) were -0.28 ± 0.15 (placebo), -1.34 ± 0.11 (exenatide 5 μg) and -1.62 ± 0.11 (exenatide 10 μg) (both P < 0.001, exenatide vs placebo). Baseline to end-point bodyweight changes (kg) were -0.47 ± 0.39 (placebo), -0.39 ± 0.28 (exenatide 5 μg) and -1.54 ± 0.27 (exenatide 10 μg; P = 0.026, exenatide 10 μg vs placebo). Nausea, generally mild to moderate, was reported in 8.6% (placebo), 25.0% (exenatide 5 μg) and 36.1% (exenatide 10 μg) of patients. Mild to moderate hypoglycemia was reported in 22.9% (placebo), 51.4% (exenatide 5 μg) and 58.3% (exenatide 10 μg) of patients.

CONCLUSIONS

  Over 24 weeks, exenatide vs the placebo improved glycemic control, reduced bodyweight (10 μg) and was well tolerated in Japanese patients with type 2 diabetes mellitus suboptimally controlled, despite oral therapy including a sulfonylurea. This trial was registered with ClinicalTrials.gov (no. NCT00577824). (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00084.x, 2011).

Exenatide treatment did not affect bone mineral density despite body weight reduction in patients with type 2 diabetes

Preclinical studies suggest that incretin-based therapies may be beneficial for the bone; however, clinical data are largely lacking. We assessed whether the differential effects of these therapies on body weight differed with respect to their effect on bone mineral density (BMD) and markers of calcium homeostasis in patients with type 2 diabetes (T2D). Sixty-nine metformin-treated patients with T2D were randomized to exenatide twice daily (n = 36) or insulin glargine once daily (n = 33). Total body BMD, measured by dual-energy X-ray absorptiometry, and serum markers of calcium homeostasis were assessed before and after 44-week treatment. Exenatide or insulin glargine treatment decreased body weight by 6%. Endpoint BMD was similar in both groups after 44-week therapy (LSmean ± s.e.m. between-group difference -0.002 ± 0.007 g/cm(2) ; p = 0.782). Fasting serum alkaline phosphatase, calcium and phosphate remained unaffected. Forty-four-week treatment with exenatide or insulin glargine had no adverse effects on bone density in patients with T2D, despite differential effects on body weight.

Glucagon-like peptide-1-based therapies and cardiovascular disease: looking beyond glycaemic control

Type 2 diabetes mellitus is a well-established risk factor for cardiovascular disease (CVD). New therapeutic approaches have been developed recently based on the incretin phenomenon, such as the degradation-resistant incretin mimetic exenatide and the glucagon-like peptide-1 (GLP-1) analogue liraglutide, as well as the dipeptidyl dipeptidase (DPP)-4 inhibitors, such as sitagliptin, vildagliptin, saxagliptin, which increase the circulating bioactive GLP-1. GLP-1 exerts its glucose-regulatory action via stimulation of insulin secretion and glucagon suppression by a glucose-dependent way, as well as by weight loss via inhibition of gastric emptying and reduction of appetite and food intake. These actions are mediated through GLP-1 receptors (GLP-1Rs), although GLP-1R-independent pathways have been reported. Except for the pancreatic islets, GLP-1Rs are also present in several other tissues including central and peripheral nervous systems, gastrointestinal tract, heart and vasculature, suggesting a pleiotropic activity of GLP-1. Indeed, accumulating data from both animal and human studies suggest a beneficial effect of GLP-1 and its metabolites on myocardium, endothelium and vasculature, as well as potential anti-inflammatory and antiatherogenic actions. Growing lines of evidence have also confirmed these actions for exenatide and to a lesser extent for liraglutide and DPP-4 inhibitors compared with placebo or standard diabetes therapies. This suggests a potential cardioprotective effect beyond glucose control and weight loss. Whether these agents actually decrease CVD outcomes remains to be confirmed by large randomized placebo-controlled trials. This review discusses the role of GLP-1 on the cardiovascular system and addresses the impact of GLP-1-based therapies on CVD outcomes.

Incretin physiology beyond glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide: cholecystokinin and gastrin peptides

Gastrin and cholecystokinin (CCK) are homologous hormone systems known to regulate gastric acid secretion, gallbladder emptying, and cell growth in the pancreas and stomach. They are, however, also involved in the development and secretory functions of pancreatic islet cells. For instance, foetal and neonatal islets express significant amounts of gastrin, and human as well as porcine islet cells express the gastrin/CCK-B receptor abundantly. Therefore, exogenous gastrin and CCK peptides stimulate insulin and glucagon secretion in man. Accordingly, endogenous hypergastrinaemia is accompanied by islet cell hyperplasia and increased insulin secretion. Conventionally, the effect of gastrointestinal hormones on insulin secretion (the incretin effect) has been defined and quantified in relation to oral versus intravenous glucose loadings. Under these unphysiological conditions, the release of gastrin and CCK and, hence, their effect on insulin secretion are modest in comparison with the effects of glucose-dependent insulinotropic polypeptide and glucagon-like peptide 1 (GLP-1). Consequently, the interest of CCK and gastrin in incretin research has for decades been limited. A few years ago, however, it was suggested that gastrin together with epidermal growth factor or later GLP-1 might stimulate beta cell growth and secretion. Recent studies have shown that the combination of gastrin and GLP-1 actually restores normoglycaemia in diabetic mice. Therefore, a short review of the incretin system in a broader functional context that includes gastrin and CCK peptides may be timely.

Cardiovascular safety of exenatide BID: an integrated analysis from controlled clinical trials in participants with type 2 diabetes

It is important for patients that treatments for diabetes not increase cardiovascular (CV) risk. The objective of this analysis was to examine retrospectively the CV safety of exenatide BID, a GLP-1 receptor agonist approved for treating hyperglycemia in patients with type 2 diabetes not adequately controlled with diet and exercise. Individual participant data was pooled to assess the relative risk (RR) of CV events with exenatide BID versus a pooled comparator (PC) group treated with either placebo or insulin from 12 controlled, randomized, clinical trials ranging from 12-52 weeks. Mean baseline values for HbA_1c (8.33-8.38%), BMI (31.3-31.5 kg/m²), and duration of diabetes (8 y) were similar between groups. Trials included patients with histories of microvascular and/or macrovascular disease. Customized primary major adverse CV events (MACE) included stroke, myocardial infarction, cardiac mortality, acute coronary syndrome, and revascularization procedures. The Primary MACE RR (0.7; 95% CI 0.38, 1.31), calculated by the Mantel-Haenszel method (stratified by study), suggested that exenatide use (vs. PC) did not increase CV risk; this result was consistent across multiple analytic methods. Because the trials were not designed to assess CV outcomes, events were identified retrospectively from a list of preferred terms by physicians blinded to treatment. Other limitations included the low number of CV events, the short duration of trials (≤1 y), and a single active comparator (insulin). The results of these analyses are consistent with those of a recent retrospective analysis of a large insurance database that found that patients treated with exenatide twice daily were less likely to have a CV event than were patients treated with other glucose-lowering therapies.

Keywords: GLP-1 receptor agonist, diabetes, cardiovascular safety

Present and future: pharmacologic treatment of obesity

Obesity now presents one of the biggest health problems of our times. Diet and exercise are best for both prevention and treatment; unfortunately, both require much discipline and are difficult to maintain. Medications offer a possible adjunct, but their effect is modest, they are limited by side effects, and the weight loss lasts only as long as the drug is being taken, since as soon as treatment is stopped, the weight is regained. Sibutramine, a sympathomimetic medication which was available for long-term treatment, is the most recent of the drugs to be withdrawn from the market due to side effects; in this case it was an increased risk of cardiovascular events. This paper reviews those medications which are available for treatment of obesity, including many of those recently taken off the market. It also discusses some of the newer treatments that are currently being investigated.

The evidence for medical nutrition therapy for type 1 and type 2 diabetes in adults

This article reviews the evidence and nutrition practice recommendations from the American Dietetic Association's nutrition practice guidelines for type 1 and type 2 diabetes in adults. The research literature was reviewed to answer nutrition practice questions and resulted in 29 recommendations. Here, we present the recommendations and provide a comprehensive and systematic review of the evidence associated with their development. Major nutrition therapy factors reviewed are carbohydrate (intake, sucrose, non-nutritive sweeteners, glycemic index, and fiber), protein intake, cardiovascular disease, and weight management. Contributing factors to nutrition therapy reviewed are physical activity and glucose monitoring. Based on individualized nutrition therapy client/patient goals and lifestyle changes the client/patient is willing and able to make, registered dietitians can select appropriate interventions based on key recommendations that include consistency in day-to-day carbohydrate intake, adjusting insulin doses to match carbohydrate intake, substitution of sucrose-containing foods, usual protein intake, cardioprotective nutrition interventions, weight management strategies, regular physical activity, and use of self-monitored blood glucose data. The evidence is strong that medical nutrition therapy provided by registered dietitians is an effective and essential therapy in the management of diabetes.

Cardiovascular comorbidities of type 2 diabetes mellitus: defining the potential of glucagonlike peptide-1-based therapies

The global epidemic of diabetes mellitus (~95% type 2 diabetes) has been fueled by a parallel increase in obesity and overweight. Together, these metabolic disease epidemics have contributed to the increasing incidence and prevalence of cardiovascular disease. The accumulation of metabolic and cardiovascular risk factors in patients with type 2 diabetes--risk factors that may exacerbate one another--complicates treatment. Inadequate treatment, treatment that fails to achieve goals, increases the risk for cardiovascular morbidity and mortality. From a clinical perspective, type 2 diabetes is a cardiovascular disease, an observation that is supported by a range of epidemiologic, postmortem, and cardiovascular imaging studies. Vascular wall dysfunction, and particularly endothelial dysfunction, has been posited as a "common soil" linking dysglycemic and cardiovascular diseases. Vascular wall dysfunction promoted by environmental triggers (e.g., sedentary lifestyle) and metabolic triggers (chronic hyperglycemia, obesity) has been associated with the upregulation of reactive oxygen species and chronic inflammatory and hypercoagulable states, and as such with the pathogenesis of type 2 diabetes, atherosclerosis, and cardiovascular disease. Glucagon-like peptide-1 (GLP)-1, an incretin hormone, and synthetic GLP-1 receptor agonists represent promising new areas of research and therapeutics in the struggle not only against type 2 diabetes but also against the cardiovascular morbidity and mortality associated with type 2 diabetes. In a number of small trials in humans, as well as in preclinical and in vitro studies, both native GLP-1 and GLP-1 receptor agonists have demonstrated positive effects on a range of cardiovascular disease pathologies and clinical targets, including such markers of vascular inflammation as high-sensitivity C-reactive protein, plasminogen activator inhibitor-1, and brain natriuretic peptide. Reductions in markers of dyslipidemia such as elevated levels of triglycerides and free fatty acids have also been observed, as have cardioprotective functions. Larger trials of longer duration will be required to confirm preliminary findings. In large human trials, GLP-1 receptor agonists have been associated with significant reductions in both blood pressure and weight.

GLP-1 playing the role of a gut regulatory compound

Gastric emptying is the first step in the metabolic endocrine cascade that takes place after food intake. The incretin hormones originating in the gut, particularly GLP-1, exert multiple antihyperglycaemic actions such as enhancement of glucose-dependent insulin secretion, suppression of glucagon secretion, slowing of gastric emptying with an ensuing decrease in food intake and weight loss. From extensive studies in experimental animals and humans we have found that GLP-1 also exerts a motility-inhibiting and antispasmodic effect in the gut that was verified in healthy volunteers and patients with irritable bowel syndrome (IBS). In order to further investigate the effect of GLP-1 in humans, we used the dipeptidyl peptidase-IV resistant GLP-1 analogue ROSE-010, thereby extending its biological activity. A randomized, double-blinded, prospective clinical trial was carried out in order to investigate the effect of two doses of ROSE-010 in 166 patients suffering from pain attacks of IBS. We found that injections of ROSE-010 were twice as effective as placebo in terms of total pain relief response in those affected by pain attacks due to IBS. Our results show that basal physiological research studies can be translated into clinical use. The current pharmaceutical incentive with incretin mimetics, such as GLP-1 analogues and exenatide, is an interesting development that apart from its obvious use in diabetes type 2, may also be useful in terms of gut motility-regulating effects with effects on appetite, food intake and motility disorders that may provide an opportunity to bring about new improvements in medical care.

Healthcare resource utilization and costs assessment of type 2 diabetes patients initiating exenatide BID or glargine: a retrospective database analysis

OBJECTIVE

To examine resource utilization and healthcare costs associated with the use of exenatide versus glargine in type 2 diabetes (T2D) patients.

METHODS

A retrospective analysis comprised of patients with T2D initiating exenatide (n = 7,255) or glargine (n = 2,819) between 04/01/2005 and 06/30/2007. Propensity score matching was used (2,506 matched pairs) to control for baseline demographic, clinical, resource use, and cost variables to balance treatment groups. Mean medical costs and other cost components were estimated using nonparametric bootstrapping.

RESULTS

Exenatide-treated patients had 19% lower likelihood of all-cause hospitalizations (odds ratio [OR]: 0.81, p = 0.009) compared to glargine-treated patients. Exenatide-treated patients had significantly lower total medical costs of $2,597 (p = 0.008). Exenatide-treated patients had significantly lower inpatient costs of $1,968 (p = 0.004) and outpatient costs of $1,324 (p = 0.011), but higher prescription costs of $706 (p < 0.001). Exenatide-treated patients further incurred lower hospitalization costs of $1,910 (p = 0.005) and physician office visit costs of $608 (p = 0.008).

KEY LIMITATIONS

Lack of availability of clinical measures including duration of diabetes, severity of T2D and lack of control for unmeasured confounding.

CONCLUSIONS

Patients initiating exenatide treatment had significantly lower healthcare resource utilization and total medical costs. Cost offsets were observed in inpatient and outpatient costs despite higher prescription costs.

Pharmacotherapies for obesity: past, current, and future therapies

Past therapies for the treatment of obesity have typically involved pharmacological agents usually in combination with a calorie-controlled diet. This paper reviews the efficacy and safety of pharmacotherapies for obesity focusing on drugs approved for long-term therapy (orlistat), drugs approved for short-term use (amfepramone [diethylpropion], phentermine), recently withdrawn therapies (rimonabant, sibutamine) and drugs evaluated in Phase III studies (taranabant, pramlintide, lorcaserin and tesofensine and combination therapies of topiramate plus phentermine, bupropion plus naltrexone, and bupropion plus zonisamide). No current pharmacotherapy possesses the efficacy needed to produce substantial weight loss in morbidly obese patients. Meta-analyses support a significant though modest loss in bodyweight with a mean weight difference of 4.7 kg (95% CI 4.1 to 5.3 kg) for rimonabant, 4.2 kg (95% CI 3.6 to 4.8 kg) for sibutramine and 2.9 kg (95% CI 2.5 to 3.2 kg) for orlistat compared to placebo at ≥12 months. Of the Phase III pharmacotherapies, lorcaserin, taranabant, topiramate and bupropion with naltrexone have demonstrated significant weight loss compared to placebo at ≥12 months. Some pharmacotherapies have also demonstrated clinical benefits. Further studies are required in some populations such as younger and older people whilst the long term safety continues to be a major consideration and has led to the withdrawal of several drugs.

Add-on therapies to metformin for type 2 diabetes

IMPORTANCE OF THE FIELD

As of 2010, approximately 285 million people worldwide have diabetes; that number is estimated to increase to 439 million by 2030. The majority of these individuals (> 90%) have type 2 diabetes, a chronic and progressive disease.

AREAS COVERED IN THIS REVIEW

Metformin monotherapy is a safe and effective option. However, its effects on glycemia are typically of limited durability. Progressive loss of β-cell function and failure of metformin monotherapy to control glucose adequately prompt the addition of other oral antidiabetic drugs, such as sulfonylureas and thiazolidinediones, which have their own limitations. Evidence suggests that incretin-based agents can successfully achieve glycemic control while potentially providing cardiovascular and β-cell-function benefits.

WHAT THE READER WILL GAIN

Knowledge of the available clinical evidence on the incretin-based therapies and other pharmacotherapeutic options for patients with type 2 diabetes who fail first-line therapy with metformin, through an analysis of improved glycemic parameters and overall risk:benefit profiles.

TAKE HOME MESSAGE

Traditional oral antidiabetic agents, recommended as first- and second-line therapies in patients with type 2 diabetes inadequately controlled with diet/exercise or monotherapy, have limited durability of effect and are associated with an increased risk of adverse events. Glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors provide glycemic control and are promising additions to the pharmacotherapeutic armamentarium.

A placebo-controlled trial of exenatide twice-daily added to thiazolidinediones alone or in combination with metformin

AIM

To test the hypothesis that glycaemic control with exenatide added to thiazolidinediones (TZDs) with or without metformin was superior to placebo.

METHODS

A 26-week, multi-country (Canada, Mexico, Romania, South Africa and the USA), randomized, double-blind, placebo-controlled study compared exenatide twice-daily vs. placebo in 165 subjects suboptimally controlled with TZDs with or without metformin [HbA(1c) 8.2% (s.d. 0.9), fasting serum glucose 9.1 (2.6) mmol/l, body weight 93.9 (17.8) kg, diabetes duration 6.4 (4.3) years]. After a 2-week, single-blind, lead-in period, subjects were randomly assigned (2 : 1) to add exenatide or placebo to current regimens. The primary endpoint was HbA(1c) change at endpoint (Week 26 or last-observation-carried-forward).

RESULTS

Only 8 subjects were treated with concomitant TZD alone. Exenatide reduced HbA(1c) significantly more than placebo [-0.84% (s.e. 0.20) vs. -0.10% (0.23), treatment difference -0.74% (0.16), p < 0.001)]. Mean reductions in body weight were similar in both treatments at endpoint [exenatide, -1.4 (s.e. 0.6) kg vs. placebo, -0.8 (0.7) kg, p = 0.176)]. Nearly 71% of subjects had both a reduction in HbA(1c) and body weight with exenatide compared with 54% with placebo. The most common adverse events (exenatide vs. placebo) were nausea (12% vs. 2%, p = 0.037), vomiting (8% vs. 0%, p = 0.031) and headache (4% vs. 4%). Confirmed (blood glucose <3.0 mmol/l) minor hypoglycaemia was experienced by 4 and 2% of subjects treated with exenatide and placebo, respectively. Incidence of hypoglycaemia was not significantly different between groups.

CONCLUSIONS

Exenatide added to TZDs alone or in combination with metformin significantly improved glycaemic control as determined by significant improvement in HbA(1c) without associated hypoglycaemia.

Glucagon-like peptide 1--a cardiologic dimension

Recent experimental data suggest glucagon-like peptide 1 (GLP-1) and its analogs to have direct effects on the cardiovascular system, in addition to their classic glucoregulatory actions. These direct effects may be cardioprotective, contractility augmenting, and vasorelaxant. A few preliminary clinical trials appear to support a mechanical function improvement after GLP-1 administration to patients with a weakened left ventricle. Based on animal studies, diminished lethal injury to the postischemic reperfused myocardium appears to be a particularly promising prospect, awaiting to be tested in clinical settings.

Glucagon-like peptide-1 and the exenatide analogue AC3174 improve cardiac function, cardiac remodeling, and survival in rats with chronic heart failure

BACKGROUND

Accumulating evidence suggests glucagon-like peptide-1 (GLP-1) exerts cardioprotective effects in animal models of myocardial infarction (MI). We hypothesized that chronic treatment with GLP-1 or the exenatide analog AC3174 would improve cardiac function, cardiac remodeling, insulin sensitivity, and exercise capacity (EC) in rats with MI-induced chronic heart failure (CHF) caused by coronary artery ligation.

METHODS

Two weeks post-MI, male Sprague-Dawley rats were treated with GLP-1 (2.5 or 25 pmol/kg/min), AC3174 (1.7 or 5 pmol/kg/min) or vehicle via subcutaneous infusion for 11 weeks. Cardiac function and morphology were assessed by echocardiography during treatment. Metabolic, hemodynamic, exercise-capacity, and body composition measurements were made at study end.

RESULTS

Compared with vehicle-treated rats with CHF, GLP-1 or AC3174 significantly improved cardiac function, including left ventricular (LV) ejection fraction, and end diastolic pressure. Cardiac dimensions also improved as evidenced by reduced LV end diastolic and systolic volumes and reduced left atrial volume. Vehicle-treated CHF rats exhibited fasting hyperglycemia and hyperinsulinemia. In contrast, GLP-1 or AC3174 normalized fasting plasma insulin and glucose levels. GLP-1 or AC3174 also significantly reduced body fat and fluid mass and improved exercise capacity and respiratory efficiency. Four of 16 vehicle control CHF rats died during the study compared with 1 of 44 rats treated with GLP-1 or AC3174. The cellular mechanism by which GLP-1 or AC3174 exert cardioprotective effects appears unrelated to changes in GLUT1 or GLUT4 translocation or expression.

CONCLUSIONS

Chronic treatment with either GLP-1 or AC3174 showed promising cardioprotective effects in a rat model of CHF. Hence, GLP-1 receptor agonists may represent a novel approach for the treatment of patients with CHF or cardiovascular disease associated with type 2 diabetes.

In support of an early polypharmacy approach to the treatment of type 2 diabetes

Type 2 diabetes (T2DM) is a multifaceted disease, characterized by hyperglycaemia, resulting from a combination of insulin resistance, impaired incretin action and β-cell dysfunction leading to relative insulin deficiency. Although traditional anti-diabetes agents improve hyperglycaemia, they do so at a cost, which may entail hypoglycemia and increased body weight; exacerbating dyslipidemia, hypertension and components of insulin resistance and metabolic syndrome associated with T2DM-potentially increasing cardiovascular risk. At diagnosis, many patients with T2DM are treated with medical nutritional therapy (MNT) and exercise, then single or multiple oral anti-diabetes agents until treatment failure, when insulin is used. This strategy has been challenged by recommendations for polypharmacy approaches to the treatment of T2DM, as current strategies are unable to improve multiple aspects of the disease, nor are they likely to address underlying pathophysiology. Although the 2009 American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD) treatment algorithm recommends a stepwise approach with MNT and metformin, later adding oral agents, incretin-based therapies or insulin, some experts have recommended a more aggressive approach. In his 2008 ADA Banting Lecture, Dr. Ralph DeFronzo recommended early treatment with metformin, TZD and exenatide at initiation of therapy. The authors' of this article recommend an aggressive early polypharmacy approach addressing underlying pathophysiology, including the incretin defect-with MNT and exercise, metformin and an incretin-based therapy and/or basal insulin if glycemic goal is not achieved within 3 months. This approach attempts to modify the disease, aiming for tight glycemic control, weight loss, reduced hypoglycemia, improvements to hypertension, dyslipidemia and insulin resistance-and improved cardiovascular outcomes.

Incretin-based therapies for type 2 diabetes mellitus: current status and future prospects

Incretin-based therapies encompass two new classes of antidiabetic drugs: glucagon-like peptide-1 (GLP-1) receptor agonists (e.g., liraglutide, exenatide, and exenatide long-acting release), which are structurally related to GLP-1, and the dipeptidyl peptidase-4 (DPP-4) inhibitors (e.g., sitagliptin and saxagliptin), which limit the breakdown of endogenous GLP-1. To evaluate the safety and effectiveness of incretin-based therapies for the treatment of type 2 diabetes mellitus and the role of these therapies in clinical practice, a MEDLINE search (January 1985-November 2009) was conducted. Relevant references from the publications identified were also reviewed. Of 28 studies identified, 22 were randomized controlled trials. Data show that these therapies affect insulin secretion in a glucose-dependent manner, achieving clinically meaningful reductions in hemoglobin A(1c) levels, with very low rates of hypoglycemia. In addition, reductions in body weight have been observed with GLP-1 receptor agonists, which also exert a pronounced effect on systolic blood pressure. Various human and animal studies show that GLP-1 improves beta-cell function and increases beta-cell proliferation in vitro, which may slow disease progression. Thus, incretin-based therapies represent a promising addition to the available treatments for type 2 diabetes.

[Panorama of currently available treatments for patients with type 2 diabetes. The ADA/EASD treatment algorithm. Safety and tolerability]

Type 2 diabetes is defined by chronic hyperglycemia due to at least two pathogenic alterations: resistance to the action of peripheral insulin and insufficient pancreatic insulin secretion. The pharmacological treatment of hyperglycemia in type 2 diabetes should be individualized. The choice of specific oral drug (or combination of drugs) is based on the drug's physiological mechanism, the general recommendations of the clinical practice guidelines, systematic reviews and analysis of data from clinical trials and observational studies. In general terms, clinical practice guidelines recommend starting with lifestyle modifications together with metformin, either from the outset or at 3 months; the combination should be individualized depending on the patient's profile. Therapy may be intensified every 3-6 months until targets (HbA1c 6.5-7.5%) have been reached. To chose the second drug, both its efficacy (mechanism of action) and side effects (hypoglycemic episodes, effect on weight, intestinal effects, edema/cardiac insufficiency and renal or liver insufficiency) should be considered. The controversy on the safety of oral drugs and insulin is constantly reviewed. The cardiovascular safety of intensive hyperglycemia treatment in patients with type 2 diabetes, particularly with certain agents, is an open debate. Finally, the association between insulin and cancer has aroused huge interest but the clinical significance of this association remains uncertain and further analyses are required to clarify this issue.

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

OBJECTIVE

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

PARTICIPANTS

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

EVIDENCE

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

CONSENSUS PROCESS

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

CONCLUSIONS

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

The exenatide analogue AC3174 attenuates hypertension, insulin resistance, and renal dysfunction in Dahl salt-sensitive rats

Background

Activation of glucagon-like peptide-1 (GLP-1) receptors improves insulin sensitivity and induces vasodilatation and diuresis. AC3174 is a peptide analogue with pharmacologic properties similar to the GLP-1 receptor agonist, exenatide. Hypothetically, chronic AC3174 treatment could attenuate salt-induced hypertension, cardiac morbidity, insulin resistance, and renal dysfunction in Dahl salt-sensitive (DSS) rats.

Methods

DSS rats were fed low salt (LS, 0.3% NaCl) or high salt (HS, 8% NaCl) diets. HS rats were treated with vehicle, AC3174 (1.7 pmol/kg/min), or GLP-1 (25 pmol/kg/min) for 4 weeks via subcutaneous infusion. Other HS rats received captopril (150 mg/kg/day) or AC3174 plus captopril.

Results

HS rat survival was improved by all treatments except GLP-1. Systolic blood pressure (SBP) was lower in LS rats and in GLP-1, AC3174, captopril, or AC3174 plus captopril HS rats than in vehicle HS rats (p < 0.05). AC3174 plus captopril attenuated the deleterious effects of high salt on posterior wall thickness, LV mass, and the ratio of LV mass to body weight (P ≤ 0.05). In contrast, GLP-1 had no effect on these cardiovascular parameters. All treatments reduced LV wall stress. GLP-1, AC3174, captopril, or AC3174 plus captopril normalized fasting insulin and HOMA-IR (P ≤ 0.05). AC3174, captopril, or AC3174 plus captopril improved renal function (P ≤ 0.05). Renal morphology in HS rats was associated with extensive sclerosis. Monotherapy with AC3174, captopril, or GLP-1 attenuated renal damage. However, AC3174 plus captopril produced the most effective improvement.

Conclusions

Thus, AC3174 had antihypertensive, cardioprotective, insulin-sensitizing, and renoprotective effects in the DSS hypertensive rat model. Furthermore, AC3174 improved animal survival, an effect not observed with GLP-1.

Effectiveness of exenatide in Asian Indians in a clinical care setting

BACKGROUND

This study reports on the effectiveness of exenatide compared to insulin glargine or NPH insulin in patients with type 2 diabetes mellitus, unable to achieve glycemic control with oral glucose-lowering therapies in a clinical care setting.

PATIENTS AND METHODS

Patients with type 2 diabetes mellitus (n = 47) whose glycemia was not controlled adequately with oral hypoglycemic agents at maximum recommended therapeutic doses were initiated on exenatide therapy. Age-, sex-, and body mass index-matched patients receiving insulin glargine (n = 54) or NPH insulin (n = 23) served as controls. Data analysis included glycated hemoglobin, fasting and postprandial plasma glucose, lipid profile, body weight, and the occurrence of hypoglycemia.

RESULTS

A statistically significant reduction in glycated hemoglobin value was noted after initiating exenatide (pre-exenatide 9.7 +/- 1.4% vs. post-exenatide 8.7 +/- 1.5%; P < 0.05), which was comparable to values after insulin glargine (9.8 +/- 1.1% vs. 9.0 +/- 1.5%, respectively; P < 0.05) and NPH insulin (9.6 +/- 1.4% vs. 8.9 +/- 1.3%, respectively; P < 0.05). Exenatide therapy was associated with net weight loss (mean, 1.6 kg), but therapy with insulin glargine and NPH insulin was associated with weight gain (1.8 and 2.3 kg, respectively).

CONCLUSIONS

In a group of select Asian Indian type 2 diabetes patients with secondary failure to oral hypoglycemic agents seen at a diabetes center, exenatide treatment in combination with oral drug regimens resulted in significant lowering of glycated hemoglobin similar to insulin glargine or NPH insulin but with the additional benefit of weight loss, albeit a small amount.

Weight loss, glycemic control, and changes in cardiovascular biomarkers in patients with type 2 diabetes receiving incretin therapies or insulin in a large cohort database

OBJECTIVE

Weight loss in patients with type 2 diabetes can improve glycemic control, lower blood pressure, and improve dyslipidemia. Glucagon-like peptide (GLP-1) receptor agonists are associated with weight loss and have potentially beneficial effects on cardiovascular risk biomarkers; however, there is limited information to indicate whether these effects remain outside of clinical trials.

RESEARCH DESIGN AND METHODS

Medical records from the General Electric Centricity research database were analyzed retrospectively to evaluate the relationship between weight loss and glycemic control and changes in blood pressure and lipids in patients with type 2 diabetes initiating therapy with exenatide, sitagliptin, or insulin. Baseline and follow-up (90-365 days after the index date) for weight, A1C, fasting blood glucose (FBG), blood pressure, triglycerides, and LDL, HDL, and total cholesterol were assessed.

RESULTS

A total of 6,280, 5,861, and 32,398 patients receiving exenatide, sitagliptin, or insulin, respectively, were included in the analysis. Exenatide-treated patients lost a mean +/- SD of 3.0 +/- 7.33 kg, sitagliptin-treated patients lost 1.1 +/- 5.39 kg, and insulin-treated patients gained 0.6 +/- 9.49 kg. There was a significant association between weight loss and a reduction in A1C and FBG with exenatide only and a reduction in blood pressure for all therapies. Weight loss was associated with some improvements in lipids, primarily in the GLP-1 receptor agonist group, with little association in the insulin group.

CONCLUSIONS

Weight reduction with GLP-1 receptor agonists was associated with a shift toward a more favorable cardiovascular risk profile. Outcome trials are needed to determine whether improvement in biomarkers translates into a reduction in cardiovascular events in patients with type 2 diabetes.

Role of the glucagon-like-peptide-1 receptor in the control of energy balance

The peripheral and central glucagon-like-peptide-1 (GLP-1) systems play an essential role in glycemic and energy balance regulation. Thus, pharmacological targeting of peripheral and/or central GLP-1 receptors (GLP-1R) may represent a potential long-term treatment option for both obesity and type-II diabetes mellitus (T2DM). Uncovering and understanding the neural pathways, physiological mechanisms, specific GLP-1R populations, and intracellular signaling cascades that mediate the food intake inhibitory and incretin effects produced by GLP-1R activation are vital to the development of these potential successful therapeutics. Particular focus will be given to the essential role of the nucleus tractus solitarius (NTS) in the caudal brainstem, as well as the gut-to-brain communication by vagal afferent fibers in mediating the physiological and behavioral responses following GLP-1R activation. The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009.

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

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

Type 2 diabetes: an expanded view of pathophysiology and therapy

Type 2 diabetes mellitus is a complicated metabolic disease affecting millions of individuals worldwide. The medications used to manage the disease are based on different pharmacologic approaches, including decreasing hepatic gluconeogenesis, stimulating pancreatic insulin production, slowing polysaccharide digestion, and increasing insulin sensitivity in muscle, liver, and fat to lower blood glucose. Incretin-based therapies, including glucagon-like peptide-1 (GLP-1) receptor agonists, mimic the effects of native GLP-1, while dipeptidyl peptidase-4 inhibitors increase circulating concentrations of endogenous GLP-1. This review focuses on means by which primary care physicians might evaluate the utility of pharmacologic agents based on their relation to the pathogenesis of type 2 diabetes. In general, patients with type 2 diabetes should be treated to their lowest targeted glycemic goals as soon as they are diagnosed, for as long as possible, as safely as possible, and as rationally as possible.

[Incretins: do they exert cardiovascular effects?]

The physiological effects of the incretin hormone glucagon-like peptide-(GLP-)1 have contributed to the important role that incretin-based therapies with GLP-1 analogs or dipeptidyl peptidase-(DPP-)4 inhibitors already play in type 2 diabetes treatment. This development is not only due to the glucose-dependent insulinotropic effect of GLP-1 as well as the positive effects on beta cell function and, probably, beta cell mass, but also to the beneficial effects on body weight.Lately, the data on positive cardiovascular effects of GLP-1 have been growing. In animal models, GLP-1 improves left ventricular function and diminishes myocardial defects in ischemia models. In clinical studies with GLP-1 analogs, a normalization of blood pressure was observed and some of the data from animal studies after myocardial infarction or after invasive cardiologic or cardiosurgical interventions were also found under clinical conditions in humans. Additionally, an improvement of cardiovascular surrogate parameters was observed with incretin-based therapies. This review gives an overview on the cardiovascular effects of GLP-1 and incretin-based therapies.

The nucleus tractus solitarius: a portal for visceral afferent signal processing, energy status assessment and integration of their combined effects on food intake

For humans and animal models alike there is general agreement that the central nervous system processing of gastrointestinal (GI) signals arising from ingested food provides the principal determinant of the size of meals and their frequency. Despite this, relatively few studies are aimed at delineating the brain circuits, neurochemical pathways and intracellular signals that mediate GI-stimulation-induced intake inhibition. Two additional motivations to pursue these circuits and signals have recently arisen. First, the success of gastric-bypass surgery in obesity treatment is highlighting roles for GI signals such as glucagon-like peptide-1 (GLP-1) in intake and energy balance control. Second, accumulating data suggest that the intake-reducing effects of leptin may be mediated through an amplification of the intake-inhibitory effects of GI signals. Experiments reviewed show that: (1) the intake-suppressive effects of a peripherally administered GLP-1 receptor agonist is mediated by caudal brainstem neurons and that forebrain-hypothalamic neural processing is not necessary for this effect; (2) a population of medial nucleus tractus solitarius (NTS) neurons that are responsive to gastric distention is also driven by leptin; (3) caudal brainstem-targeted leptin amplifies the food-intake-inhibitory effects of gastric distention and intestinal nutrient stimulation; (4) adenosine monophosphate-activated protein kinase (AMPK) activity in NTS-enriched brain lysates is elevated by food deprivation and reduced by refeeding and (5) the intake-suppressive effect of hindbrain-directed leptin is reversed by elevating hindbrain AMPK activity. Overall, data support the view that the NTS and circuits within the hindbrain mediate the intake inhibition of GI signals, and that the effects of leptin on food intake result from the amplification of GI signal processing.

Diabetes and obesity: therapeutic targeting and risk reduction - a complex interplay

Obesity is a major risk factor for the development of diabetes and predisposes individuals to hypertension and dyslipidaemia. Together these pathologies increase the risk for cardiovascular disease (CVD), the major cause of morbidity and mortality in type 2 diabetes mellitus (T2DM). Worsening trends in obesity and T2DM raise a serious conundrum, namely, how to control blood glucose, blood pressure, and lipids when many antidiabetic agents cause weight gain and thereby exacerbate other cardiovascular risk factors associated with T2DM. Further, evidence suggests that some established antihypertensive agents may worsen glucose intolerance. Many patients who are obese, hypertensive, and/or hyperlipidaemic fail to achieve blood pressure, lipid and glycaemic goals, and this failure may in part be explained by physician reluctance to utilize complex combination regimens for fear of off-target effects. Thus, a clear need exists for clinicians to understand the risks and benefits of different pharmacologic, and indeed non-pharmacologic, options in order to maximize treatment outcomes. While intensive lifestyle modification remains an elusive gold standard, newer diabetes targets, including the incretin axis, may offer greater cardiovascular risk reduction than other antidiabetes therapies, although definitive clinical trial data are needed. The glucagon-like peptide-1 (GLP-1) receptor agonists exenatide and liraglutide and the dipeptidyl peptidase-4 (DPP-4) inhibitors sitagliptin and vildagliptin effectively lower HbA1c; exenatide and liraglutide reduce weight and blood pressure and improve lipid profiles. Sitagliptin and vildagliptin are weight neutral but also appear to improve lipid profiles. Integration of incretin therapies into the therapeutic armamentarium is a promising approach to improving outcomes in T2DM, and perhaps even in reducing complications of T2DM, such as co-morbid hypertension and dyslipidaemia. Additional long-term studies, including CVD end-point studies, will be necessary to determine the appropriate places for incretin-based therapies in treatment algorithms.

Clinical experience with exenatide in a routine secondary care diabetes clinic

Exenatide use in type 2 diabetes is limited in routine clinical practice. We examined a cross-section of 90 patients. Mean weight and HBA(1c) were 114.9+/-20.6 kg, 10.3+/-2.1% at initiation; 108.0+/-15.3 kg (p<0.0001), 9.0+/-2.1% (p<0.001) at 3 months; 109.2+/-18.2 kg (p<0.0001), 9.5+/-2.3% (p=0.08) at 6 months. Exenatide appears effective in reducing HBA(1c) and weight.

Incretin-based therapies: review of current clinical trial data

Incretin hormones are secreted in response to food ingestion and help manage glycemic control by regulating insulin and glucagon release, slowing gastric emptying, and reducing caloric intake. Glucagonlike peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide, secreted from the L-cells of the lower gut and K-cells of the intestines, respectively, are responsible for these incretin effects, which are reduced in patients with type 2 diabetes mellitus. Initially, the rapid degradation of either incretin by dipeptidyl peptidase-4 (DPP-4) complicated the development of viable therapeutics based on either hormone. However, the US Food and Drug Administration (FDA) has approved 2 incretin-based therapies in which their mechanisms of action augment or amplify the effects of naturally occurring GLP-1. Exenatide, a first-in-class GLP-1 receptor agonist, exhibits the same mechanisms of action as native GLP-1. Sitagliptin inhibits the DPP-4 enzyme, thus increasing the half-life of endogenous GLP-1. This review examines data from recent GLP-1 receptor agonist and DPP-4 inhibitor studies in patients with type 2 diabetes, as well as data on other incretin-based therapies in clinical development.

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.

[Gastrointestinal hormones in food intake control]

The discovery of gut hormones regulating the energy balance has aroused great interest in the scientific community. Some of these hormones modulate appetite and satiety, acting on the hypothalamus or the solitary tract nucleus in the brainstem. In general, the endocrine signals generated in the gut have direct or indirect (through the autonomous nervous system) anorexigenic effects. Only ghrelin, a gastric hormone, has been consistently associated with the initiation of food intake and is regarded as the main orexigenic signal both in animal models and humans. In this review, we provide a brief description of the major gastrointestinal hormones implicated in the regulation of food intake. Given the increased importance of food intake disturbances, especially obesity, a better understanding of the underlying mechanisms of action of the gastrointestinal hormones might contribute to the development of new molecules that could increase the therapeutic arsenal for treating obesity and its associated comorbidities.

Glucagon-like peptide-1 gastrointestinal regulatory role in metabolism and motility

Gastrointestinal (GI) motility, primarily gastric emptying, balances the hormonal output that takes place after food intake in order to maintain stable blood sugar. The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP), work together to reduce postprandial hyperglycemia by glucose-dependent insulin secretion and inhibition of glucagon release, as well as inhibition of GI motility and gastric emptying. GLP-1 is considered the more effective of the two incretins due to its additional inhibitory effects on GI motility. It is observed that patients on treatment with GLP-1 analogues or exenatide achieve a considerable weight loss during treatment. This is of benefit to improve insulin resistance in type 2 diabetes. Furthermore, weight loss per se is of considerable benefit in an even longer health perspective. The weight loss is considered to be due to the inhibition of GI motility. This effect has been studied in animal experimentation, and from there taken to involve studies on GI motility in healthy volunteers and patients with irritable bowel syndrome (IBS). Evolving to a phase II study in IBS, the GLP-1 analogue (ROSE-010) was recently shown to be effective for treatment of acute pain attacks in IBS. Taken together, data speak in favor of GI motility as a central component not only in metabolic disorders but also in IBS, be it due to a direct relaxing effect on GI smooth muscle or a slow emptying of gastric contents resulting in a less outspoken nutritional demand on hormonal regulatory functions in the GI tract.

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.

Does glucagon-like peptide-1 receptor agonist therapy add value in the treatment of type 2 diabetes? Focus on exenatide

Type 2 diabetes (T2DM) is a heterogeneous syndrome, characterized by beta-cell failure in the setting of obesity-related insulin resistance. T2DM has a progressive course and is associated with a high cardiovascular disease (CVD) risk, regardless of the treatment used. The incretin hormones glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP) are secreted in the gut upon meal ingestion and lower blood glucose by glucose-dependent stimulation of insulin secretion and production. Exogenously administered GLP-1 lowers postprandial glucose excursions by inhibiting glucagon secretion and delaying gastric emptying, improves beta-cell function, and promotes satiety and weight loss. Native GLP-1 is degraded rapidly by the ubiquitous enzyme dipeptidyl-peptidase (DPP)-4. Thus, injectable DPP-4-resistant GLP-1 receptor agonists (GLP-1RA) and oral DPP-4 inhibitors have been developed. Exenatide is the first GLP-1RA that became available for the treatment of T2DM patients. Exenatide has unique characteristics, as to date it is the only agent that addresses the multiple defects of the T2DM phenotype, including hyperglycaemia, islet-cell dysfunction, alimentary obesity, insulin resistance, hypertension and dyslipidaemia. In animals, exenatide also increased beta-cell mass. Long-term prospective studies in high-risk populations should address the potentially disease modifying effect of exenatide and its effect on CVD risk, in addition to its safety and tolerability.

Treating type 2 diabetes: incretin mimetics and enhancers

As a consequence of excess abdominal adiposity and genetic predisposition, type 2 diabetes is a progressive disease, often diagnosed after metabolic dysfunction has taken hold of multiple organ systems. Insulin deficiency, insulin resistance and impaired glucose homeostasis resulting from beta-cell dysfunction characterize the disease. Current treatment goals are often unmet due to insufficient treatment modalities. Even when combined, these treatment modalities are frequently limited by safety, tolerability, weight gain, edema and gastrointestinal intolerance. Recently, new therapeutic classes have become available for treatment. This review will examine the new therapeutic classes of incretin mimetics and enhancers in the treatment of type 2 diabetes.