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

Exenatide improves endothelial function assessed by flow mediated dilation technique in subjects with type 2 diabetes: results from an observational research

The GLP-1 receptor agonist exenatide has been approved for adjunctive treatment of type 2 diabetes. Continuous GLP-1 infusion improves endothelial function in vivo; no evidence about a beneficial effect of exenatide on vascular function has been published. The aim of our observational study was to evaluate whether exenatide would improve brachial artery function evaluated by the flow mediated dilation (FMD) technique, compared with glimepiride, in subjects with type 2 diabetes. FMD time course was assessed by ultrasound, after 5 min forearm ischaemia, at baseline and after 16-week treatment. At the end of the study FMD was significantly higher in subjects who assumed exenatide compared with glimepiride (9.1 ± 3.6 vs. 5.6 ± 1.0, p = 0.01). Even if limited by the small number of studied subjects, who were not matched in the two treatment groups, this research study represents the first FMD evidence suggesting that chronic administration of exenatide improves arterial dilation.

Weight change with liraglutide and comparator therapies: an analysis of seven phase 3 trials from the liraglutide diabetes development programme

AIM

We investigated the relationship between weight change and related factors in subjects with type 2 diabetes mellitus (T2DM) treated with liraglutide versus comparator diabetes therapies.

METHODS

Twenty-six-week data from seven phase 3, randomized trials in the liraglutide T2DM development programme were analysed by trial and treatment group: liraglutide (1.2 and 1.8 mg), active comparator and placebo. Outcome measures included proportions of subjects in various weight change categories and their percentage weight change from baseline; impact of body mass index (BMI) and gastrointestinal (GI) adverse events (AEs) on weight change and correlation of weight change with change in glycosylated haemoglobin (HbA1c).

RESULTS

A number of subjects experienced >5% weight loss during the trials (24.4% liraglutide 1.8 mg and 17.7% liraglutide 1.2 mg; 17.7% exenatide, 10.0% sitagliptin, 3.6-7.0% sulphonylurea, 2.6% thiazolidinedione and 2.6% glargine; 9.9% placebo). More weight loss was seen with liraglutide 1.2 and 1.8 mg than with active comparators except exenatide. Across trials, higher initial BMI was associated with slightly greater weight loss with liraglutide. Mean weight loss increased slightly the longer GI AEs persisted. Although HbA1c reduction was slightly larger in higher weight loss categories across treatments (including placebo), sample sizes were small and no clear correlation could be determined. Liraglutide-treated subjects experienced additional HbA1c reduction beyond that which appeared weight induced; thus, not all HbA1c-lowering effect appears weight mediated.

CONCLUSIONS

The majority of liraglutide-treated T2DM subjects experienced weight loss in this analysis. Weight loss was greater and occurred more in glucagon-like peptide-1 receptor agonist-treated subjects than in active comparator-treated subjects.

Obesity-related hypertension: pathogenesis, cardiovascular risk, and treatment--a position paper of the The Obesity Society and The American Society of Hypertension

In light of the worldwide epidemic of obesity, and in recognition of hypertension as a major factor in the cardiovascular morbidity and mortality associated with obesity, The Obesity Society and The American Society of Hypertension agreed to jointly sponsor a position paper on obesity-related hypertension to be published jointly in the journals of each society. The purpose is to inform the members of both societies, as well as practicing clinicians, with a timely review of the association between obesity and high blood pressure, the risk that this association entails, and the options for rational, evidenced-based treatment. The position paper is divided into six sections plus a summary as follows: pathophysiology, epidemiology and cardiovascular risk, the metabolic syndrome, lifestyle management in prevention and treatment, pharmacologic treatment of hypertension in the obese, and the medical and surgical treatment of obesity in obese hypertensive patients.

Obesity-related hypertension: pathogenesis, cardiovascular risk, and treatment: a position paper of The Obesity Society and the American Society of Hypertension

In light of the worldwide epidemic of obesity, and in recognition of hypertension as a major factor in the cardiovascular morbidity and mortality associated with obesity, The Obesity Society and the American Society of Hypertension agreed to jointly sponsor a position paper on obesity-related hypertension to be published jointly in the journals of each society. The purpose is to inform the members of both societies, as well as practicing clinicians, with a timely review of the association between obesity and high blood pressure, the risk that this association entails, and the options for rational, evidenced-based treatment. The position paper is divided into six sections plus a summary as follows: pathophysiology, epidemiology and cardiovascular risk, the metabolic syndrome, lifestyle management in prevention and treatment, pharmacologic treatment of hypertension in the obese, and the medical and surgical treatment of obesity in obese hypertensive patients.

A comparison of currently available GLP-1 receptor agonists for the treatment of type 2 diabetes

INTRODUCTION

Glucagon-like peptide-1 (GLP-1) receptor agonists are a valuable addition to the type 2 diabetes armamentarium. They increase insulin secretion and reduce glucagon secretion in a glucose-dependent manner, posing a relatively low hypoglycemia risk. GLP-1 receptor agonists also offer weight-loss benefits. Because GLP-1 receptor agonists are relatively new agents, there is limited direction on their use.

AREAS COVERED

This article aims to provide guidance to physicians when considering GLP-1 receptor agonist use in individual patients. It examines the clinical profiles of the currently available GLP-1 receptor agonists: exenatide twice-daily (BID), liraglutide once daily and exenatide extended release (ER) once weekly. Phase III clinical trial data on efficacy, safety and patient satisfaction are compared, with a primary focus on head-to-head trials.

EXPERT OPINION

Liraglutide seems to be the most effective GLP-1 receptor agonist in terms of HbA(1c) reduction and weight loss. Exenatide BID may offer an advantage where postprandial glucose control is a primary concern. Exenatide ER generally outperforms exenatide BID and is a good option for patients who struggle to adhere to more frequent regimens. The future may hold interesting developments in terms of reduced dosing frequency, oral formulations and alternative therapeutic uses.

Treatment with exenatide once weekly or twice daily for 30 weeks is associated with changes in several cardiovascular risk markers

Background

Dyslipidemia and type 2 diabetes are two of the most significant risk factors for the development of cardiovascular disease. Measurement of lipoprotein subclasses provides important information about derangements in lipid metabolism and helps refine cardiovascular risk assessment. Exenatide, a glucagon-like peptide 1 receptor agonist, improved glycemic control, obesity, hypertension, and dyslipidemia in patients with type 2 diabetes in clinical trials.

Methods

In the DURATION-1 trial, patients with type 2 diabetes were treated with exenatide once weekly or twice daily for 30 weeks. This post hoc analysis evaluated the impact of exenatide on lipoprotein subclasses in 211 DURATION-1 patients using vertical auto profile methodology and the Statistical Package for the Social Sciences general linear model adjusted for glycosylated hemoglobin (HbA_1c) and weight.

Results

Baseline lipids and high sensitivity C-reactive protein were normal overall based on the standard lipid panel. Once-weekly exenatide reduced apolipoprotein B and the apolipoprotein B to apolipoprotein A1 ratio (P < 0.05), independent of glycemic improvement and weight loss. A significant shift in lipoprotein pattern away from small, dense low-density lipoprotein-4 cholesterol was also observed (P < 0.05). Exenatide once weekly increased high-density lipoprotein-2 cholesterol, even after adjustment for changes in HbA_1c and weight (P < 0.05). Triglycerides, very low-density lipoprotein cholesterol, and high sensitivity C-reactive protein were reduced with both the once-weekly and twice-daily exenatide regimens (P < 0.05).

Conclusion

In this post hoc analysis, exenatide significantly improved a number of cardiovascular risk markers. Continuous exenatide exposure with exenatide once weekly elicited a greater response than did immediate-release exenatide twice daily, generally independent of glycemic improvement and weight loss. Thus, in addition to improving glycemic control, exenatide induced favorable changes in lipid and lipoprotein metabolism and decreased systemic inflammation.

A review of exenatide: optimizing glycemic control and associated cardiovascular risk factors in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a well-recognized risk factor for the development of cardiovascular disease. With an increasing prevalence of obesity, this risk has increased further. Management of T2DM in obese patients is particularly challenging as treatment with the majority of glucose-lowering agents results in weight gain. Thus, the development of a therapeutic option which could improve glycemic control without weight gain or hypoglycemia, such as the glucagon-like peptide-1 (GLP-1) analog exenatide, is a welcome addition to the currently available therapies in the management of T2DM. With recognition and better understanding of the role of incretin hormones in T2DM, exenatide was developed and introduced into clinical practice in 2005. Both randomized controlled trials and retrospective observational studies have shown that treatment with exenatide not only improves glycemic control, with a low risk of hypoglycemia, but also results in concurrent weight loss and the additional benefit of improvement in cardiovascular risk factors. This article will provide an overview of both short- and long-acting exenatide in the management of T2DM and associated cardiovascular risk factors.

An update in incretin-based therapy: a focus on glucagon-like peptide-1 receptor agonists

The glucagon-like peptide-1 receptor agonists, exenatide and liraglutide, offer a unique mechanism in the treatment of type 2 diabetes mellitus (T2DM) as part of the incretin system. Their mechanism of action is to increase insulin secretion, decrease glucagon release, reduce food intake, and slow gastric emptying. They target postprandial blood glucose values and have some effect on fasting levels as well. In addition, they promote weight loss and may help to preserve β-cell function, both major problems in T2DM patients. Changes in hemoglobin A1c are similar to those produced by other T2DM agents, including thiazolidinediones, low-dose metformin, and sulfonylureas, and better than those caused by α-reductase inhibitors and dipeptidyl peptidase-4 inhibitors. These agents have been safely studied in combination with metformin, sulfonylureas, meglitinides, thiazolidinediones, and insulin therapy. Overall, data are limited for head-to-head comparisons, but it appears that liraglutide may have better efficacy and tolerability compared with exenatide; however, more studies are needed. They are overall well tolerated, with the main adverse events being similar to those with metformin (gastrointestinal intolerances that are transient and dose dependent). However, patients must be monitored for pancreatitis as a rare but possible side effect. For T2DM patients willing to use an injectable agent, exenatide and liraglutide offer another therapeutic option to control hyperglycemia with the potential for weight loss and may be combined with other agents safely.

The effect of sitagliptin versus glibenclamide on arterial stiffness, blood pressure, lipids, and inflammation in type 2 diabetes mellitus patients

AIM

This study evaluated the effect of sitagliptin versus glibenclamide on arterial stiffness, blood pressure, lipid profile, oxidative stress, and high-sensitivity C-reactive protein (hsCRP) in type 2 diabetes mellitus patients.

SUBJECTS AND METHODS

Forty diabetes patients, inadequately controlled on metformin, were randomly assigned to either sitagliptin (100 mg/day) or glibenclamide (5 mg/day) for 3 months. Following a 1-month washout period, a crossover switch from glibenclamide to sitagliptin and vice versa was performed for an additional 3 months. Arterial stiffness, 24-h ambulatory blood pressure monitoring, lipids, hsCRP, glycated hemoglobin, fasting glucose, STAT-8-isoprostane (a measure of oxidative stress), body mass index (BMI), and waist circumference were measured at baseline and at 3 months with each of the study drugs.

RESULTS

Thirty-four patients completed the study. Glibenclamide had a better glucose-lowering effect than sitagliptin, but this was associated with more hypoglycemic events. BMI increased following glibenclamide treatment, whereas sitagliptin proved weight-neutral. Mean BMI gain was +0.5±1.0 kg/m(2) for glibenclamide versus -0.01±0.9 kg/m(2) for sitagliptin (P<0.001). Triglyceride levels significantly dropped following sitagliptin, although they remained unaltered after glibenclamide treatment. Mean triglyceride decrease was -18.4±45 mg/mL after sitagliptin but -0.2±57 mg/dL following glibenclamide treatment (P=0.018). There was no change in low-density lipoprotein, high-density lipoprotein, arterial stiffness, blood pressure monitoring, hsCRP, or STAT-8-isoprostane with each of the study drugs.

CONCLUSIONS

Sitagliptin, but not glibenclamide, demonstrated a significant beneficial effect on BMI and triglyceride levels. However, arterial stiffness, blood pressure, oxidative stress, and inflammatory status were not significantly affected by adding sitagliptin or glibenclamide to metformin-treated type 2 diabetes patients.

Alterations in energy balance following exenatide administration

Exenatide is a medication similar in structure and effect to native glucagon-like peptide-1, an incretin hormone with glucose-lowering properties. The aim of the study was to measure the change in total energy expenditure (TEE) and body composition during exenatide administration and by deduction the relative contributions of energy expenditure and energy intake to exenatide-induced weight loss. Forty-five obese (body mass index, 30-40 kg·m⁻²) subjects were identified. After exclusion criteria application, 28 subjects entered into the study and 18 subjects (12 female, 6 male) completed the study, which consisted of 6 visits over 14 weeks and injection of exenatide for an average of 84 ± 5 days. Respiratory gas analysis and doubly labeled water measurements were performed before initiation of exenatide and after approximately 3 months of exenatide administration. The average weight loss from the beginning of injection period to the end of the study in completed subjects was 2.0 ± 2.8 kg (p = 0.01). Fat mass declined by 1.3 ± 1.8 kg (p = 0.01) while the fat-free mass trended downward but was not significant (0.8 ± 2.2 kg, p = 0.14). There was no change in weight-adjusted TEE (p = 0.20), resting metabolic rate (p = 0.51), or physical activity energy expenditure (p = 0.38) and no change in the unadjusted thermic effect of a meal (p = 0.37). The significant weight loss because of exenatide administration was thus the result of decreasing energy intake. In obese nondiabetic subjects, exenatide administration did not increase TEE and by deduction the significant weight loss and loss of fat mass was due to decreased energy intake.

Bone: incretin hormones perceiver or receiver?

Novel incretin-based drugs, such as glucagon-like peptide-1 receptor agonists (GLP-1 RA) and dipeptidyl peptidase-4 inhibitors (DPP-4i), have been last introduced in the pharmacological treatment of type 2 diabetes. In the last few years, the interest on the relationship of gut hormones with bone metabolism in diabetes has been increasing. The aim of present paper is to examine in vitro and in vivo evidence on the connections between incretin hormones and bone metabolism. We also discuss results of clinical trials and metaanalysis, explore the effects of incretin drugs in vitro on osteogenic cells and osteoclasts, and speculate on the possibility of different effects of GLP-1 RA and DPP-4i on the risk of bone fractures risk in humans. Although existing preliminary evidence suggests a protective effect on the bone, at least for DPP-4i, further controlled, long-term studies with measurement of bone markers, bone density, and clinical fractures rates are needed to substantiate and confirm those findings.

Harnessing the incretin system beyond glucose control: potential cardiovascular benefits of GLP-1 receptor agonists in type 2 diabetes

The management of type 2 diabetes continues to evolve as new data emerge. Although glycaemic control is still important, other risk factors--such as hypertension, dyslipidaemia and obesity--must also be addressed in order to reduce the long-term risks of cardiovascular complications and mortality. In this context, targeting the incretin system, and glucagon-like peptide-1 (GLP-1) in particular, has generated much interest. GLP-1 is released from the gut in response to food ingestion and plays a crucial role in glucose homeostasis. GLP-1 receptors are expressed in the heart and vasculature, prompting evaluation of their physiological role and pharmacological stimulation, both in healthy and disease states. These studies indicate that GLP-1 and GLP-1-based therapies appear to have direct, beneficial effects on the cardiovascular system, in addition to their glucose-lowering properties, such as modulation of blood pressure, endothelial function, and myocardial contractility. Intriguingly, some of these effects appear to be independent of GLP-1 receptor signalling. Data from clinical studies of the GLP-1 receptor agonists, exenatide and liraglutide on cardiovascular risk factors, in patients with type 2 diabetes are also promising and the results from prospective studies to assess cardiovascular outcomes are eagerly awaited.

Current treatments and strategies for type 2 diabetes: can we do better with GLP-1 receptor agonists?

Abstract Diet, lifestyle modification, and pharmacotherapy with metformin are appropriate initial treatments for many patients with type 2 diabetes (T2DM). However, most individuals do not maintain glycemic control with metformin alone. Addition of other oral antidiabetes drugs (OADs), including sulfonylurea, meglitinide, or thiazolidinedione, is often the next step. Newer options, including incretin-based glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) and dipeptidyl peptidase-4 (DPP-4) inhibitors, offer important benefits as monotherapies or in combination with OADs, with low risk for hypoglycemia. Reductions in glycated hemoglobin (A1C) have been reported among patients treated with GLP-1 RAs (exenatide, -0.8 to -1.1%; liraglutide, -0.8 to -1.6%), as has weight loss (exenatide, -1.6 to -3.1 kg; liraglutide, -1.6 to -3.2 kg). GLP-1 RAs also stimulate β-cell responses and have positive effects on cardiovascular risk factors often present in patients with T2DM. The most common adverse events associated with GLP-1 RAs are nausea, which diminishes over time, and hypoglycemia (when used in combination with a sulfonylurea). A large number of trials demonstrated benefits of GLP-1 RAs, suggesting they could provide suitable treatment options for patients with T2DM.

Non-insulin injectable treatments (glucagon-like peptide-1 and its analogs) and cardiovascular disease

Glucagon-like peptide-1 (GLP-1) [GLP-1 (7-36)-amide] plays a fundamental role in regulating postprandial nutrient metabolism. GLP-1 acts through a G-protein-coupled receptor present on the membranes of many tissues, including myocardium and endothelium. GLP-1 is cleaved by the dipeptidyl peptidase-4 enzyme to its metabolite GLP-1 (9-36)-amide within 1-2 min of its release into the circulation. Investigations have been done in humans and in animal models to determine whether GLP-1 has effects on the myocardium. Infusions of GLP-1 increase cardiac function in ischemic and non-ischemic cardiovascular disease. In humans and animal models, constant infusions of GLP-1 decrease the size of infarction and improve myocardial function in ischemic/reperfusion injury. In cardiomyopathy and heart failure, infusions of GLP-1 improve myocardial function. These beneficial effects of GLP-1 on cardiac function are mediated by both GLP-1 receptor activation and GLP-1 receptor independent actions. Infusions of the metabolite GLP-1 (9-36)-amide improve cardiac function in experimental animals with cardiovascular disease even though the metabolite does not bind to the GLP-1 receptor. The beneficial effects of GLP-1 on the heart occur in the presence of a GLP-1 receptor antagonist and in animals devoid of GLP-1 receptors. Preliminary data in animals with available GLP-1 receptor agonists and cardiac disease suggest that exenatide has beneficial effects in porcine models of ischemic heart disease. The animal data with liraglutide are inconclusive. Clinical trials with exenatide and liraglutide show significant improvements in weight, systolic blood pressure, lipid profiles, and other cardiovascular risk factors. Whether these will decrease cardiovascular events is currently under investigation.

Gastric stimulation for weight loss

The prevalence of obesity is growing to epidemic proportions, and there is clearly a need for minimally invasive therapies with few adverse effects that allow for sustained weight loss. Behavior and lifestyle therapy are safe treatments for obesity in the short term, but the durability of the weight loss is limited. Although promising obesity drugs are in development, the currently available drugs lack efficacy or have unacceptable side effects. Surgery leads to long-term weight loss, but it is associated with morbidity and mortality. Gastric electrical stimulation (GES) has received increasing attention as a potential tool for treating obesity and gastrointestinal dysmotility disorders. GES is a promising, minimally invasive, safe, and effective method for treating obesity. External gastric pacing is aimed at alteration of the motility of the gastrointestinal tract in a way that will alter absorption due to alteration of transit time. In addition, data from animal models and preliminary data from human trials suggest a role for the gut-brain axis in the mechanism of GES. This may involve alteration of secretion of hormones associated with hunger or satiety. Patient selection for gastric stimulation therapy seems to be an important determinant of the treatment’s outcome. Here, we review the current status, potential mechanisms of action, and possible future applications of gastric stimulation for obesity.

The effects of exenatide bid on metabolic control, medication use and hospitalization in patients with type 2 diabetes mellitus in clinical practice: a systematic review

The objective of this systematic review was to assess the published literature on the effectiveness of exenatide twice daily (exenatide) in clinical practice, specifically its effects on haemoglobin A1c (A1C), fasting glucose (FG), weight, systolic blood pressure (SBP), medication use, hospitalization and cardiovascular disease (CVD) outcomes. A systematic literature search using the MEDLINE database of English language literature published between January 2005 and May 2011 was performed. The review included retrospective or prospective observational studies that included 100 or more patients per treatment group. A total of 15 studies meeting the inclusion criteria were identified. The studies revealed significant reductions of -0.4 to -0.9% in A1C, -10 mg/dl in FG, -2 to -11 kg in body weight and -2 to -11 mmHg in SBP. Statistically significant reductions in the use or dosage of either oral glucose-lowering medications or insulin after initiating exenatide treatment were found in every observational study that assessed medication changes, including reductions in dosage of up to 75% in sulphonylureas dosages, 22% in metformin, 66% in thiazolidinediones (TZD) or TZD combination therapy and 75% in prandial insulin. Exenatide-treated patients experienced significantly lower rates of all-cause and CVD-related hospitalization and CVD events than patients treated with other therapies overall. In this review of observational studies, exenatide initiation was associated with significant reductions in clinically relevant outcomes. Improvements in A1C, FG, weight and SBP in the observational studies in this review were consistent with improvements observed in controlled clinical trials.

Cardiovascular biology of the incretin system

Glucagon-like peptide-1 (GLP-1) is an incretin hormone that enhances glucose-stimulated insulin secretion and exerts direct and indirect actions on the cardiovascular system. GLP-1 and its related incretin hormone, glucose-dependent insulinotropic polypeptide, are rapidly inactivated by the enzyme dipeptidyl peptidase 4 (DPP-4), a key determinant of incretin bioactivity. Two classes of medications that enhance incretin action, GLP-1 receptor (GLP-1R) agonists and DPP-4 inhibitors, are used for the treatment of type 2 diabetes mellitus. We review herein the cardiovascular biology of GLP-1R agonists and DPP-4 inhibitors, including direct and indirect effects on cardiomyocytes, blood vessels, adipocytes, the control of blood pressure, and postprandial lipoprotein secretion. Both GLP-1R activation and DPP-4 inhibition exert multiple cardioprotective actions in preclinical models of cardiovascular dysfunction, and short-term studies in human subjects appear to demonstrate modest yet beneficial actions on cardiac function in subjects with ischemic heart disease. Incretin-based agents control body weight, improve glycemic control with a low risk of hypoglycemia, decrease blood pressure, inhibit the secretion of intestinal chylomicrons, and reduce inflammation in preclinical studies. Nevertheless, there is limited information on the cardiovascular actions of these agents in patients with diabetes and established cardiovascular disease. Hence, a more complete understanding of the cardiovascular risk to benefit ratio of incretin-based therapies will require completion of long-term cardiovascular outcome studies currently underway in patients with type 2 diabetes mellitus.

Non-glycaemic effects mediated via GLP-1 receptor agonists and the potential for exploiting these for therapeutic benefit: focus on liraglutide

The glucagon-like peptide-1 receptor agonists (GLP-1 RAs) liraglutide and exenatide can improve glycaemic control by stimulating insulin release through pancreatic β-cells in a glucose-dependent manner. GLP-1 receptors are not restricted to the pancreas; therefore, GLP-1 RAs cause additional non-glycaemic effects. Preclinical and clinical trial data suggest a multitude of additional beneficial effects related to GLP-1 RA therapy, including improvements in β-cell function, systolic blood pressure and body weight. These effects are of a particular advantage to patients with type 2 diabetes, as most are affected by β-cell dysfunction, obesity and hypertension. Transient gastrointestinal adverse events, such as nausea and diarrhoea, are also common. To improve gastrointestinal tolerability, an incremental dosing approach is used with liraglutide and exenatide twice daily. A potential protective role for GLP-1 RAs in the cardiovascular and central nervous systems has been suggested from animal studies and short-term clinical trials. These effects and other safety aspects of GLP-1 therapy are currently being investigated in ongoing long-term clinical studies.

The design of the liraglutide clinical trial programme

Liraglutide is a once-daily human glucagon-like peptide-1 analogue used in the treatment of type 2 diabetes (T2D). It has been prospectively investigated in a series of multinational, randomised, controlled phase 3 trials (the Liraglutide Effect and Action in Diabetes programme), as well as in an additional direct head-to-head study with sitagliptin. These trials were designed to clarify the use and safety of liraglutide in clinical practice across the treatment continuum of T2D, and consequently involved a large number and diverse range of patients. These studies also included active comparisons against antidiabetic agents including metformin, rosiglitazone, glimepiride, insulin glargine, exenatide and sitagliptin, and therefore have helped to examine clinical differences and similarities between liraglutide and these commonly used agents.

Effects of exenatide in poorly controlled type 2 diabetes

AIM

The aim of this retrospective analysis was to assess the clinical effectiveness of exenatide in patients with type 2 diabetes in routine clinical practice.

METHODS

Patients with type 2 diabetes mellitus and inadequate glycemic control were commenced on exenatide in an out-patient setting. Effects on Hba1c, weight and BMI at 3- and 6-month intervals were recorded by a retrospective review of medical records.

RESULTS

We examined a cross-section of 61 patients. The mean weight at treatment initiation was 114 kg and baseline Hba1c was 9.8% (84 mmol/mol). Mean reduction in Hba1c at 3 months was 0.8% (10 mmol/mol, P < 0.01) and mean reduction at 6 months was 0.5% (6 mmol/mol, P < 0.05). Mean weight loss at 3 months was 4.2 kg (P < 0.0001) and at 6 months was 6.6 kg (P < 0.0001). Seventeen patients were prescribed exenatide in addition to insulin, against current guidelines. This cohort of patients showed a greater mean reduction in weight (7.4 vs 6.2 kg) as compared to the group on exenatide without insulin, but mean Hba1c increased at 6 months by 0.35% (4 mmol/mol).

CONCLUSION

Adjunctive exenatide treatment in patients with suboptimally controlled type 2 diabetes on oral hypoglycaemic medications, achieved reductions in Hba1c and weight, in line with published studies. However, in patients already on insulin, favourable results can be achieved by the addition of exenatide by careful patient selection and follow-up.

Comparison of liraglutide versus other incretin-related anti-hyperglycaemic agents

The two classes of incretin-related therapies, dipeptidyl peptidase-4 (DPP-4) inhibitors and glucagon-like peptide-1 receptor agonists (GLP-1 RAs), have become important treatment options for patients with type 2 diabetes. Sitagliptin, saxagliptin, vildagliptin and linagliptin, the available DPP-4 inhibitors, are oral medications, whereas the GLP-1 RAs-twice-daily exenatide, once-weekly exenatide and once-daily liraglutide-are administered subcutaneously. By influencing levels of GLP-1 receptor stimulation, these medications lower plasma glucose levels in a glucose-dependent manner with low risk of hypoglycaemia, affecting postprandial plasma glucose more than most other anti-hyperglycaemic medications. Use of GLP-1 RAs has been shown to result in greater glycaemic improvements than DPP-4 inhibitors, probably because of higher levels of GLP-1 receptor activation. GLP-1 RAs can also produce significant weight loss and may reduce blood pressure and have beneficial effects on other cardiovascular risk factors. Although both classes are well tolerated, DPP-4 inhibitors may be associated with infections and headaches, whereas GLP-1 RAs are often associated with gastrointestinal disorders, primarily nausea. Pancreatitis has been reported with both DPP-4 inhibitors and GLP-1 RAs, but a causal relationship between use of incretin-based therapies and pancreatitis has not been established. In clinical trials, liraglutide has shown efficacy and tolerability and resulted in certain significant benefits when compared with exenatide and sitagliptin.

Differentiating among incretin-based therapies in the management of patients with type 2 diabetes mellitus

The glucagon-like peptide-1 receptor (GLP-1R) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors have become important options for the management of patients with type 2 diabetes mellitus. While the GLP-1R agonists and DPP-4 inhibitors act on the incretin system to regulate glucose homeostasis, there are important clinical differences among the five agents currently available in the U.S. For example, the GLP-1R agonists require subcutaneous administration, produce pharmacological levels of GLP-1 activity, promote weight loss, have a more robust glucose-lowering effect, and have a higher incidence of adverse gastrointestinal effects. In contrast, the DPP-4 inhibitors are taken orally, increase the half-life of endogenous GLP-1, are weight neutral, and are more commonly associated with nasopharyngitis. Differences in efficacy, safety, tolerability, and cost among the incretin-based therapies are important to consider in the primary care management of patients with type 2 diabetes mellitus.

Safety and tolerability of glucagon-like peptide-1 receptor agonists in the treatment of type 2 diabetes

Conventional pharmacotherapies for type 2 diabetes effectively lower blood glucose levels but are associated with side effects that preclude their optimal use or raise safety concerns. Novel treatments based on the endogenous hormone glucagon-like peptide-1 (GLP-1) may overcome some of these obstacles. The GLP-1 receptor agonists, exenatide and liraglutide, have a lower risk of hypoglycaemia than some conventional agents and can provide significant weight loss. Although they can cause gastrointestinal symptoms, effects are transient and can be reduced by gradual dose escalation. No cardiac safety issues have been reported and animal studies suggest that they may confer cardiovascular benefits. Pancreatitis has occurred among patients receiving GLP-1 receptor agonists, but it is unclear whether this is drug-related or due to the increased risk of pancreatitis in type 2 diabetes. Despite findings in rodents that GLP-1 receptor activation of thyroid C-cells results in calcitonin release and C-cell pathology, such effects have not been seen with long-term exposure in humans. Immunogenicity does not appear to be a safety concern. In summary, currently available data indicate that GLP-1 receptor agonists provide an effective and generally well tolerated therapeutic option for the management of type 2 diabetes.

Dipeptidyl peptidase-4 (DPP-4) inhibitors are favourable to glucagon-like peptide-1 (GLP-1) agonists: no

Incretin-based therapies, which include the GLP-1 receptor agonists and DPP-4 inhibitors, use the antidiabetic properties of potentiating the GLP-1 receptor signalling via the regulation of insulin and glucagon secretion, inhibition of gastric emptying and suppression of appetite. Most physicians will start antidiabetic treatment with metformin, but adding a GLP-1 receptor agonist as the second drug seems to be optimal since more patients will reach an HbA1c below 7% than with a DPP-4 inhibitor or another oral antidiabetic agents and with minimal risk of hypoglycaemia. The GLP-1 receptor agonists are also more effective in weight and systolic blood pressure control than DPP-4 inhibitors. The side effects of the GLP-1 receptor agonists are primarily nausea and vomiting, which is less pronounced with the long acting agonists and often transient. A GLP-1 receptor agonist can be recommended before a DPP-4 inhibitor in obese type 2 diabetic patients, who want to lose weight. Furthermore, the GLP-1 receptor agonists cover the whole spectrum of treatment from time of diagnosis with lifestyle treatment to combination treatment with basal insulin.

Effects of incretins on blood pressure: a promising therapy for type 2 diabetes mellitus with hypertension

The prevalence of type 2 diabetes mellitus (T2DM) has increased markedly worldwide. A recent epidemiological study reported that approximately 63% of T2DM patients also have high blood pressure (>130/80 mmHg), which doubles their risk of cardiac events. Of the medications used to treat T2DM, the incretins are a group of peptides that not only regulate blood glucose effectively and moderately, but also protect patients against cardiovascular events and improve several cardiovascular parameters. Here were review data from preclinical and short- and long-term clinical studies investigating the antihypertensive effects of incretins. We also elucidate four possible mechanisms underlying the antihypertensive effects of incretins. We conclude that incretins can lower blood pressure of T2DM patients, independent of weight loss, and will surely improve the prognosis of these patients.

Additive feeding inhibitory and aversive effects of naltrexone and exendin-4 combinations

Objective

One developing strategy for obesity treatment has been to use combinations of differently acting pharmacotherapies to improve weight loss with fewer adverse effects. The purpose of this study was to determine whether the combination of naltrexone, an opioid antagonist acting on the reward system, and exendin-4, a glucagon-like peptide 1 (GLP-1) agonist, acting on satiety signaling, would produce larger reductions in food intake than either alone in rats. Because the anorectic potencies of both compounds have been associated with nausea and malaise, the influence of these drug combinations on the acquisition of a conditioned taste aversion (CTA) was also determined.

Methods

In Experiment 1, the acute anorectic effects of naltrexone (0.32–3.2 mg/kg; IP) and exendin-4 (1–10 µg/kg; IP) were assessed alone or in combination. Combinational doses were further investigated by the repeated daily administration of 1 mg/kg naltrexone + 3.2 µg/kg exendin-4 for 4 days. In Experiment 2, both compounds alone or in combination were used as unconditioned stimuli in a series of CTA tests.

Results

Naltrexone and exendin-4, alone or in combination, suppressed food intake in a dose dependent fashion, and the interaction on food intake between naltrexone and exendin-4 was additive. In the CTA paradigm, naltrexone (1 mg/Kg) alone did not support acquisition, whereas a CTA was evident with doses of Ex-4 (1 or 3.2 µg/Kg). Combinations of naltrexone and exendin-4 also resulted in a more rapid and robust acquisition of a CTA.

Conclusion

Given that the Nal and Ex-4 combination produces additive effects on not only food intake reduction but also food aversion learning, this specific drug combination does not have the benefit of minimizing the adverse effects associated with each individual drug. These data suggest that it is necessary to evaluate both the positive and adverse effects at early stages of combinational drug development.

Glucagon-like peptide 1 (GLP-1) can reverse AMP-activated protein kinase (AMPK) and S6 kinase (P70S6K) activities induced by fluctuations in glucose levels in hypothalamic areas involved in feeding behaviour

The anorexigenic peptide, glucagon-like peptide-1 (GLP-1), reduces glucose metabolism in the human hypothalamus and brain stem. The brain activity of metabolic sensors such as AMP-activated protein kinase (AMPK) responds to changes in glucose levels. The mammalian target of rapamycin (mTOR) and its downstream target, p70S6 kinase (p70S6K), integrate nutrient and hormonal signals. The hypothalamic mTOR/p70S6K pathway has been implicated in the control of feeding and the regulation of energy balances. Therefore, we investigated the coordinated effects of glucose and GLP-1 on the expression and activity of AMPK and p70S6K in the areas involved in the control of feeding. The effect of GLP-1 on the expression and activities of AMPK and p70S6K was studied in hypothalamic slice explants exposed to low- and high-glucose concentrations by quantitative real-time RT-PCR and by the quantification of active-phosphorylated protein levels by immunoblot. In vivo, the effects of exendin-4 on hypothalamic AMPK and p70S6K activation were analysed in male obese Zucker and lean controls 1 h after exendin-4 injection to rats fasted for 48 h or after re-feeding for 2-4 h. High-glucose levels decreased the expression of Ampk in the lateral hypothalamus and treatment with GLP-1 reversed this effect. GLP-1 treatment inhibited the activities of AMPK and p70S6K when the activation of these protein kinases was maximum in both the ventromedial and lateral hypothalamic areas. Furthermore, in vivo s.c. administration of exendin-4 modulated AMPK and p70S6K activities in those areas, in both fasted and re-fed obese Zucker and lean control rats.

GLP-1 neurons in the nucleus of the solitary tract project directly to the ventral tegmental area and nucleus accumbens to control for food intake

Central glucagon-like-peptide-1 (GLP-1) receptor activation reduces food intake; however, brain nuclei and mechanism(s) mediating this effect remain poorly understood. Although central nervous system GLP-1 is produced almost exclusively in the nucleus of the solitary tract in the hindbrain, GLP-1 receptors (GLP-1R) are expressed throughout the brain, including nuclei in the mesolimbic reward system (MRS), e.g. the ventral tegmental area (VTA) and the nucleus accumbens (NAc). Here, we examine the MRS as a potential site of action for GLP-1-mediated control of food intake and body weight. Double immunohistochemistry for Fluorogold (monosynaptic retrograde tracer) and GLP-1 neuron immunoreactivity indicated that GLP-1-producing nucleus tractus solitarius neurons project directly to the VTA, the NAc core, and the NAc shell. Pharmacological data showed that GLP-1R activation in the VTA, NAc core, and NAc shell decreased food intake, especially of highly-palatable foods, and body weight. Moreover, blockade of endogenous GLP-1R signaling in the VTA and NAc core resulted in a significant increase in food intake, establishing a physiological relevance for GLP-1 signaling in the MRS. Current data highlight these nuclei within the MRS as novel sites for GLP-1R-mediated control of food intake and body weight.

Anti-Obesity Drugs: A Review about Their Effects and Safety

The current recommendations for the treatment of obese people include increased physical activity and reduced calories intake. When the behavioral approach is not sufficient, a pharmacologic treatment is recommended. In past years, numerous drugs have been approved for the treatment of obesity; however, most of them have been withdrawn from the market because of their adverse effects. In fact, amphetamine, rimonabant and sibutramine licenses have been withdrawn due to an increased risk of psychiatric disorders and non-fatal myocardial infarction or stroke. Even if orlistat is not as effective as other drugs in reducing body weight, orlistat is presently the only available choice for the treatment of obesity because of its safety for cardiovascular events and positive effects on diabetic control. Hopefully, more effective and better tolerated anti-obesity drugs will be developed through an improved understanding of the multiple mechanisms and complex physiological systems targeting appetite.

Gastrointestinal regulatory peptides and central nervous system mechanisms of weight control

PURPOSE OF REVIEW

This review focuses on recent advances in understanding the multiple roles of gastrointestinal peptides in the control of food intake and body weight with specific emphasis on ghrelin, amylin and glucagon-like peptide 1.

RECENT FINDINGS

Recent studies support a role for ghrelin, amylin and glucagon-like peptide 1 in short-term and long-term effects on food intake and body weight. Apart from contributing to energy homeostasis, ghrelin's participation in reward and sensory processing has been the focus of much recent work. New findings on amylin's effects on food intake and energy balance provide further support for its role in meal-related food intake and suggest that it may also function as an adiposity signal. New investigations on the role of central and peripheral glucagon-like peptide 1 receptors in mediating the anorexic effects of glucagon-like peptide 1 have suggested that they differentially contribute to short-term and long term effects on food intake.

SUMMARY

Gastrointestinal peptides can influence food intake through mechanisms that involve short-term meal-related effects or through activation of central pathways involved in energy balance. An appreciation of the multiple actions of gastrointestinal peptides on food intake will aid in developing new strategies for weight management.

The pharmacologic basis for clinical differences among GLP-1 receptor agonists and DPP-4 inhibitors

The incretin system plays an important role in glucose homeostasis, largely through the actions of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Unlike GIP, the actions of GLP-1 are preserved in patients with type 2 diabetes mellitus, which has led to the development of injectable GLP-1 receptor (GLP-1R) agonists and oral dipeptidyl peptidase-4 (DPP-4) inhibitors. GLP-1R agonists-which can be dosed to pharmacologic levels-act directly upon the GLP-1R. In contrast, DPP-4 inhibitors work indirectly by inhibiting the enzymatic inactivation of native GLP-1, resulting in a modest increase in endogenous GLP-1 levels. GLP-1R agonists generally lower the fasting and postprandial glucose levels more than DPP-4 inhibitors, resulting in a greater mean reduction in glycated hemoglobin level with GLP-1R agonists (0.4%-1.7%) compared with DPP-4 inhibitors (0.4%-1.0%). GLP-1R agonists also promote satiety and reduce total caloric intake, generally resulting in a mean weight loss of 1 to 4 kg over several months in most patients, whereas DPP-4 inhbitors are weight-neutral overall. GLP-1R agonists and DPP-4 inhibitors are generally safe and well tolerated. The glucose-dependent manner of stimulation of insulin release and inhibition of glucagon secretion by both GLP-1R agonists and DPP-4 inhibitors contribute to the low incidence of hypoglycemia. Although transient nausea occurs in 26% to 28% of patients treated with GLP-1R agonists but not DPP-4 inhibitors, this can be reduced by using a dose-escalation strategy. Other adverse events (AEs) associated with GLP-1R agonists include diarrhea, headache, and dizziness. The main AEs associated with DPP-4 inhibitors include upper respiratory tract infection, nasopharyngitis, and headache. Overall, compared with other therapies for type 2 diabetes mellitus with similar efficacy, incretin-based agents have low risk of hypoglycemia and weight gain. However, GLP-1R agonists demonstrate greater comparative efficacy and weight benefit than DPP-4 inhibitors.

Hindbrain leptin and glucagon-like-peptide-1 receptor signaling interact to suppress food intake in an additive manner

Background

The physiological control of feeding behavior involves modulation of the intake inhibitory effects of gastrointestinal satiation signaling via endogenous hindbrain leptin receptor (LepR) and glucagon-like-peptide-1 receptor (GLP-1R) activation.

Design and Results

Using a variety of dose-combinations of hindbrain delivered (4^th icv) leptin and the GLP-1R agonist exendin-4, experiments demonstrate that hindbrain LepR and GLP-1R signaling interact to control food intake and body weight in an additive fashion. In addition, the maximum intake suppressive response that could be achieved by 4^th icv leptin alone in non-obese rats (~33%) was shown to be further suppressed when exendin-4 was co-administered. Importantly, it was determined that the interaction between hindbrain LepR signaling and GLP-1R signaling is relevant to endogenous food intake control, as hindbrain GLP-1R blockade by the selective antagonist exendin-(9–39) attenuated the intake inhibitory effects of hindbrain leptin delivery.

Conclusions

Collectively, the findings reported here show that hindbrain LepR and GLP-1R activation interact in at least an additive fashion to control food intake and body weight. As evidence is accumulating that combination pharmacotherapies offer greater sustained food intake and body weight suppression in obese individuals when compared to mono-drug therapies or lifestyle modifications alone, these findings highlight the need for further examination of combined CNS GLP-1R and LepR signaling as a potential drug target for obesity treatment.

Short-term exenatide treatment leads to significant weight loss in a subset of obese women without diabetes

OBJECTIVE

To investigate the effect of treatment with the glucagon-like peptide 1 receptor agonist exenatide on weight loss and metabolic parameters in obese nondiabetic women.

RESEARCH DESIGN AND METHODS

Forty-one obese women (aged 48 ± 11 years and BMI 33.1 ± 4.1 kg/m(2)) participated in a 35-week randomized, double-blind, placebo-controlled, crossover study, including two 16-week treatment periods separated by a 3-week washout period. There was no lifestyle intervention. The primary outcome was change in body weight.

RESULTS

Subjects treated with exenatide lost an average of 2.49 ± 0.66 kg compared with a 0.43 ± 0.63 kg weight gain during placebo treatment. Weight loss with exenatide treatment was noted at 2 weeks. The degree of weight loss could be stratified. A total of 30% of subjects were high responders who lost ≥5% body weight (-7.96 ± 0.52%), 39% were moderate responders who lost <5% body weight (-2.43 ± 0.45%), and 31% were nonresponders who gained weight (1.93 ± 0.53%). Waist circumference also decreased significantly with exenatide treatment. Subjects experienced more nausea during exenatide treatment compared with placebo, but the severity decreased over time and did not correlate with weight loss.

CONCLUSIONS

Short-term exenatide treatment was associated with modest weight loss and decreased waist circumference in a cohort of obese nondiabetic women. A subset of individuals demonstrated robust weight loss that was detected very early in the course of treatment.

Safety and tolerability of exenatide twice daily in patients with type 2 diabetes: integrated analysis of 5594 patients from 19 placebo-controlled and comparator-controlled clinical trials

BACKGROUND

Exenatide twice daily is a first-in-class glucagon-like peptide receptor agonist approved for the treatment of type 2 diabetes. The objective of this analysis was to evaluate the safety profile of exenatide twice daily and to compare its profile with that of a pooled comparator (placebo and insulin) in patients with type 2 diabetes.

METHODS

Data from 19 completed, randomized, controlled clinical trials of exenatide twice daily (5 μg and 10 μg) were pooled and analyzed; the pooled data included 5594 intent-to-treat patients who were followed for 12-52 weeks. Incidence rates, exposure-adjusted incidence rates, and 95% confidence intervals around risk differences between groups were calculated.

RESULTS

Baseline demographics and exposure time were comparable between groups (exenatide, N = 3261; pooled comparator, N = 2333; mean exposure time 166-171 days). Transient, mild- to-moderate nausea was the most frequent adverse event with exenatide (36.9% versus 8.3% in the pooled comparator). The incidence of hypoglycemia (minor or major) with concomitant sulfonylurea (exenatide 26.5%, pooled comparator 20.7%) was higher than that without sulfonylurea (exenatide 3.1%, pooled comparator 2.7%) in all groups. Serious adverse events, discontinuations due to serious adverse events, and deaths were reported with similar frequency in the exenatide and pooled comparator groups. Composite exposure-adjusted incidence rates were not statistically different between groups for pancreatitis, renal impairment, or major adverse cardiac events; there was a difference in incidence rates for benign thyroid neoplasm (0.3% versus 0%).

CONCLUSION

Overall, this analysis, representing over 1500 patient-years of exposure, demonstrated that exenatide twice daily was safe and generally well tolerated in patients with type 2 diabetes. The incidence of most adverse events, including serious adverse events, was similar in both exenatide-treated and comparator-treated patients. The most distinct differences between groups were in gastrointestinal-related adverse events, which is consistent with other therapies within the glucagon-like peptide class.

The role of nausea in food intake and body weight suppression by peripheral GLP-1 receptor agonists, exendin-4 and liraglutide

The FDA-approved glucagon-like-peptide-1 receptor (GLP-1R) agonists exendin-4 and liraglutide reduce food intake and body weight. Nausea is the most common adverse side effect reported with these GLP-1R agonists. Whether food intake suppression by exendin-4 and liraglutide occurs independently of nausea is unknown. Further, the neurophysiological mechanisms mediating the nausea associated with peripheral GLP-1R agonist use are poorly understood. Using two established rodent models of nausea [conditioned taste avoidance (CTA) and pica (ingestion of nonnutritive substances)], results show that all peripheral doses of exendin-4 that suppress food intake also produce CTA, whereas one dose of liraglutide suppresses intake without producing CTA. Chronic (12 days) daily peripheral administration of exendin-4 produces a progressive increase in pica coupled with stable, sustained food intake and body weight suppression, whereas the pica response and food intake reduction by daily liraglutide are more transient. Results demonstrate that the nausea response accompanying peripheral exendin-4 occurs via a vagal-independent pathway involving GLP-1R activation in the brain as the exendin-4-induced pica response is attenuated with CNS co-administration of the GLP-1R antagonist exendin-(9-39), but not by vagotomy. Direct administration of exendin-4 to the medial subnucleus of the nucleus tractus solitarius (mNTS), but not to the central nucleus of the amygdala, reduced food intake and produced a pica response, establishing the mNTS as a potential GLP-1R-expressing site mediating nausea responses associated with GLP-1R agonists.

Regulation of energy balance and body weight by the brain: a distributed system prone to disruption

Maintaining adequate energy supply via regulation of food intake and energy expenditure is crucial for survival and reproduction. The neural control of energy balance is highly complex, occurs across distributed central and peripheral areas, and incorporates multiple domains of control (including homeostatic and hedonic processes). The sheer number of active compounds (such as leptin and GLP-1) involved in the regulation of food intake speaks to the redundancy and complexity of the system. The balance between energy intake and expenditure is under CNS control. Constant bidirectional communication between the brain and the GI tract, as well as between the brain and other relevant tissues (ie, adipose tissue, pancreas, and liver), ensures that the brain constantly perceives and responds accordingly to the energy status/needs of the body. This elegant biological system is subject to disruption by a toxic obesogenic environment, leading to syndromes such as leptin and insulin resistance, and ultimately further exposing obese individuals to further weight gain and T2DM. Recent imaging studies in humans are beginning to examine the influence that higher-order/hedonic brain regions have on homeostatic areas, as well as their responsiveness to homeostatic peripheral signals. With greater understanding of these mechanisms, the field moves closer to understanding and eventually treating the causalities of obesity.

Glucagon-like peptide-1 receptor agonists suppress water intake independent of effects on food intake

Glucagon-like peptide-1 (GLP-1) is produced by and released from the small intestine following ingestion of nutrients. GLP-1 receptor (GLP-1R) agonists applied peripherally or centrally decrease food intake and increase glucose-stimulated insulin secretion. These effects make the GLP-1 system an attractive target for the treatment of type 2 diabetes mellitus and obesity. In addition to these more frequently studied effects of GLP-1R stimulation, previous reports indicate that GLP-1R agonists suppress water intake. The present experiments were designed to provide greater temporal resolution and site specificity for the effect of GLP-1 and the long-acting GLP-1R agonists, exendin-4 and liraglutide, on unstimulated water intake when food was and was not available. All three GLP-1R ligands suppressed water intake after peripheral intraperitoneal administration, both in the presence of and the absence of food; however, the magnitude and time frame of water intake suppression varied by drug. GLP-1 had an immediate, but transient, hypodipsic effect when administered peripherally, whereas the water intake suppression by IP exendin-4 and liraglutide was much more persistent. Additionally, intracerebroventricular administration of GLP-1R agonists suppressed water intake when food was absent, but the suppression of intake showed modest differences depending on whether the drug was administered to the lateral or fourth ventricle. To the best of our knowledge, this is the first demonstration of GLP-1 receptor agonists affecting unstimulated, overnight intake in the absence of food, the first test for antidipsogenic effects of hindbrain application of GLP-1 receptor agonists, and the first test of a central effect (forebrain or hindbrain) of liraglutide on water intake. Overall, these results show that GLP-1R agonists have a hypodipsic effect that is independent of GLP-1R-mediated effects on food intake, and this occurs, in part, through central nervous system GLP-1R activation.

Glucagon-like peptide analogues for type 2 diabetes mellitus

BACKGROUND

Glucagon-like peptide analogues are a new class of drugs used in the treatment of type 2 diabetes that mimic the endogenous hormone glucagon-like peptide 1 (GLP-1). GLP-1 is an incretin, a gastrointestinal hormone that is released into the circulation in response to ingested nutrients. GLP-1 regulates glucose levels by stimulating glucose-dependent insulin secretion and biosynthesis, and by suppressing glucagon secretion, delayed gastric emptying and promoting satiety.

OBJECTIVES

To assess the effects of glucagon-like peptide analogues in patients with type 2 diabetes mellitus.

SEARCH STRATEGY

Studies were obtained from electronic searches of The Cochrane Library (last search issue 1, 2011), MEDLINE (last search March 2011), EMBASE (last search March 2011), Web of Science (last search March 2011) and databases of ongoing trials.

SELECTION CRITERIA

Studies were included if they were randomised controlled trials of a minimum duration of eight weeks comparing a GLP-1 analogue with placebo, insulin, an oral anti-diabetic agent, or another GLP-1 analogue in people with type 2 diabetes.

DATA COLLECTION AND ANALYSIS

Data extraction and quality assessment of studies were done by one reviewer and checked by a second. Data were analysed by type of GLP-1 agonist and comparison treatment. Where appropriate, data were summarised in a meta-analysis (mean differences and risk ratios summarised using a random-effects model).

MAIN RESULTS

Seventeen randomised controlled trials including relevant analyses for 6899 participants were included in the analysis. Studies were mostly of short duration, usually 26 weeks.In comparison with placebo, all GLP-1 agonists reduced glycosylated haemoglobin A1c (HbA1c) levels by about 1%. Exenatide 2 mg once weekly and liraglutide 1.8 mg reduced it by 0.20% and 0.24% respectively more than insulin glargine. Exenatide 2 mg once weekly reduced HbA1c more than exenatide 10 μg twice daily, sitagliptin and pioglitazone. Liraglutide 1.8 mg reduced HbA1c by 0.33% more than exenatide 10 μg twice daily. Liraglutide led to similar improvements in HbA1c compared to sulphonylureas but reduced it more than sitagliptin and rosiglitazone.Both exenatide and liraglutide led to greater weight loss than most active comparators, including in participants not experiencing nausea. Hypoglycaemia occurred more frequently in participants taking concomitant sulphonylurea. GLP-1 agonists caused gastrointestinal adverse effects, mainly nausea. These adverse events were strongest at the beginning and then subsided. Beta-cell function was improved with GLP-1 agonists but the effect did not persist after cessation of treatment.None of the studies was long enough to assess long-term positive or negative effects.

AUTHORS' CONCLUSIONS

GLP-1 agonists are effective in improving glycaemic control.

Understanding the cardiovascular effects of incretin

Cardiovascular disease (CVD), a leading cause of death in patients with diabetes mellitus, has several pathogenic mechanisms that are well established. However, the traditional hypoglycemic agents do not have proven positive effects on macrovascular disease. Novel therapeutic agents target the incretin pathway including the glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) agonists and the dipeptidyl peptidase-4 inhibitors. The glucose-regulatory actions of these agents function by increasing insulin secretion and suppressing glucagon. They also act to increase weight loss not only by inhibiting gastric emptying, but also by reducing appetite. Although GLP-1 and GLP-1R agonists have demonstrated beneficial effects on myocardium and vascular endothelium including coronary and peripheral mouse vessels, they also have anti-inflammatory and anti-atherogenic actions. These agents also have positive effects on the lipid profile and blood pressure. Although these cardioprotective actions seem to be beyond the effects of glucose control and weight loss, they are mediated through GLP-1R- or GLP-1R-independent actions of cleaved GLP-1 (9-36). Larger randomized controlled trials are necessary to elucidate the clinical promise of these beneficial CVD effects.

[Anti-diabetic drugs. Weight reduction as a favourable side effect]

The increasing prevalence of type 2 diabetes mellitus in the last years is mainly attributable to an increase in life expectancy and the high incidence of obesity. Nearly 90% of all type 2 diabetic patients in Germany are overweight or obese. The attributable risk of obesity in the development of type 2 diabetes mellitus is approximately 70%. Oral anti-diabetic drugs like sulfonylurea, glinides, and glitazones as well as insulin increase body weight within years by up to 8 kg with damaging side effects on cardiovascular organs. Dipeptidylpeptidase 4 (DPP-4) inhibitors do not affect body weight and metformin as well as glucagon like peptid 1 (GLP-1) receptor agonists decrease it. A reduction in body weight by changes in life style is effective but only a few overweight patients achieve the therapeutic goals. By using anti-diabetic drugs as monotherapy or in combination with other anti-diabetic compounds body weight, glycemic control and other cardiovascular risk factors may be influenced favorably.

GLP-1 receptor agonists today

Type 2 diabetes mellitus (T2DM) is a complex, progressive disease affecting an estimated 257 million people worldwide. A number of unmet needs exist with traditional T2DM therapies, which can lead to insufficient glycaemic control and increased risk of diabetes-associated complications. An emerging class of diabetes therapeutics, the glucagon-like peptide-1 (GLP-1) receptor agonists, appear to address many of the unmet needs of patients with T2DM. This review summarises the recent findings and current clinical guidelines of the currently approved GLP-1 receptor agonists and explores the new GLP-1 receptor agonists in development. It also concentrates on the physiological basis for early use of GLP-1 receptor agonists, their use as an alternative to insulin therapy, the rationale for combining them with insulin and their cost-effectiveness.

Beyond glucose lowering: glucagon-like peptide-1 receptor agonists, body weight and the cardiovascular system

AIM

Glucagon-like peptide-1 (GLP-1) belongs to the incretin hormone family: in the presence of elevated blood glucose, it stimulates insulin secretion and inhibits glucagon production. In addition, GLP-1 slows gastric emptying. GLP-1 secretion has also been reported to potentially affect patients with type 2 diabetes (T2DM) compared with non-diabetics and, as enzymatic inactivation by dipeptidyl peptidase-4 (DPP-4) shortens the GLP-1 half-life to a few minutes, GLP-1 receptor agonists such as exenatide twice daily (BID) and liraglutide have been developed, and have become part of the management of patients with T2DM. This review focuses on the potential beneficial effects of these compounds beyond those associated with improvements in blood glucose control and weight loss, including changes in the cardiovascular and central nervous systems.

METHODS

This was a state-of-the-art review of the literature to evaluate the relationships between GLP-1, GLP-1 receptor agonists, weight and the cardiovascular system.

RESULTS

GLP-1 receptor agonists improve glucose control and do not significantly increase the risk of hypoglycaemia. Also, this new class of antidiabetic drugs was shown to favour weight loss. Mechanisms may involve central action, direct action by reduction of food intake and probably indirect action through slowing of gastric emptying. The relative importance of each activity remains unclear. Weight loss may improve cardiovascular outcomes in patients with T2DM, although GLP-1 receptor agonists may have other direct and indirect effects on the cardiovascular system. Reductions in myocardial infarct size and improvements in cardiac function have been seen in animal models. Beneficial changes in cardiac function were also demonstrated in patients with myocardial infarcts or heart failure. Indirect effects could involve a reduction in blood pressure and potential effects on oxidation. However, the mechanisms involved in the pleiotropic effects of GLP-1 receptor agonists have yet to be completely elucidated and require further study.

CONCLUSION

These compounds may play an important role in the treatment of patients with T2DM as their potential effects go beyond glucose-lowering (weight loss, potential improvement of cardiovascular risk factors). However, to better understand their place in the management of T2DM, further experimental and clinical prospective studies are required.

The common hepatic branch of the vagus is not required to mediate the glycemic and food intake suppressive effects of glucagon-like-peptide-1

The incretin and food intake suppressive effects of intraperitoneally administered glucagon-like peptide-1 (GLP-1) involve activation of GLP-1 receptors (GLP-1R) expressed on vagal afferent fiber terminals. Central nervous system processing of GLP-1R-driven vagal afferents results in satiation signaling and enhanced insulin secretion from pancreatic-projecting vagal efferents. As the vast majority of endogenous GLP-1 is released from intestinal l-cells following ingestion, it stands to reason that paracrine GLP-1 signaling, activating adjacent GLP-1R expressed on vagal afferent fibers of gastrointestinal origin, contributes to glycemic and food intake control. However, systemic GLP-1R-mediated control of glycemia is currently attributed to endocrine action involving GLP-1R expressed in the hepatoportal bed on terminals of the common hepatic branch of the vagus (CHB). Here, we examine the hypothesis that activation of GLP-1R expressed on the CHB is not required for GLP-1's glycemic and intake suppressive effects, but rather paracrine signaling on non-CHB vagal afferents is required to mediate GLP-1's effects. Selective CHB ablation (CHBX), complete subdiaphragmatic vagal deafferentation (SDA), and surgical control rats received an oral glucose tolerance test (2.0 g glucose/kg) 10 min after an intraperitoneal injection of the GLP-1R antagonist, exendin-(9-39) (Ex-9; 0.5 mg/kg) or vehicle. CHBX and control rats showed comparable increases in blood glucose following blockade of GLP-1R by Ex-9, whereas SDA rats failed to show a GLP-1R-mediated incretin response. Furthermore, GLP-1(7-36) (0.5 mg/kg ip) produced a comparable suppression of 1-h 25% glucose intake in both CHBX and control rats, whereas intake suppression in SDA rats was blunted. These findings support the hypothesis that systemic GLP-1R mediation of glycemic control and food intake suppression involves paracrine-like signaling on GLP-1R expressed on vagal afferent fibers of gastrointestinal origin but does not require the CHB.

Peripheral and central GLP-1 receptor populations mediate the anorectic effects of peripherally administered GLP-1 receptor agonists, liraglutide and exendin-4

The long-acting glucagon-like peptide-1 receptor (GLP-1R) agonists, exendin-4 and liraglutide, suppress food intake and body weight. The mediating site(s) of action for the anorectic effects produced by peripheral administration of these GLP-1R agonists are not known. Experiments addressed whether food intake suppression after i.p. delivery of exendin-4 and liraglutide is mediated exclusively by peripheral GLP-1R or also involves direct central nervous system (CNS) GLP-1R activation. Results showed that CNS delivery [third intracerebroventricular (3(rd) ICV)] of the GLP-1R antagonist exendin-(9-39) (100 μg), attenuated the intake suppression by i.p. liraglutide (10 μg) and exendin-4 (3 μg), particularly at 6 h and 24 h. Control experiments show that these findings appear to be based neither on the GLP-1R antagonist acting as a nonspecific competing orexigenic signal nor on blockade of peripheral GLP-1R via efflux of exendin-(9-39) to the periphery. To assess the contribution of GLP-1R expressed on subdiaphragmatic vagal afferents to the anorectic effects of liraglutide and exendin-4, food intake was compared in rats with complete subdiaphragmatic vagal deafferentation and surgical controls after i.p. delivery of the agonists. Both liraglutide and exendin-4 suppressed food intake at 3 h, 6 h, and 24 h for controls; for subdiaphragmatic vagal deafferentation rats higher doses of the GLP-1R agonists were needed for significant food intake suppression, which was observed at 6 h and 24 h after liraglutide and at 24 h after exendin-4.

CONCLUSION

Food intake suppression after peripheral administration of exendin-4 and liraglutide is mediated by activation of GLP-1R expressed on vagal afferents as well as direct CNS GLP-1R activation.

A review of weight control strategies and their effects on the regulation of hormonal balance

The estimated prevalence of obesity in the USA is 72.5 million adults with costs attributed to obesity more than 147 billion dollars per year. Though caloric restriction has been used extensively in weight control studies, short-term success has been difficult to achieve, with long-term success of weight control being even more elusive. Therefore, novel approaches are needed to control the rates of obesity that are occurring globally. The purpose of this paper is to provide a synopsis of how exercise, sleep, psychological stress, and meal frequency and composition affect levels of ghrelin, cortisol, insulin GLP-1, and leptin and weight control. We will provide information regarding how hormones respond to various lifestyle factors which may affect appetite control, hunger, satiety, and weight control.