Cardiovascular Safety of Incretin-Based Therapies in Type 2 Diabetes: Systematic Review of Integrated Analyses and Randomized Controlled Trials

Introduction

Regulatory requirements mandate that new drugs for treatment of patients with type 2 diabetes mellitus (T2DM), such as dipeptidyl peptidase-4 (DPP-4) inhibitors and glucagon-like peptide-1 (GLP-1) receptor agonists, are evaluated to show that they do not increase cardiovascular (CV) risk.

Methods

A systematic review was undertaken to evaluate the association between DPP-4 inhibitor and GLP-1 receptor agonist use and major adverse cardiac events (MACE). The National Institutes of Health Medline database was searched for pooled analyses, meta-analyses, and randomized controlled trials (RCTs) of DPP-4 inhibitors and GLP-1 receptor agonists that included CV endpoints.

Results

Thirty-six articles met the inclusion criteria encompassing 11 pooled analyses, 17 meta-analyses, and eight RCTs (including secondary analyses). Over the short term (up to 4 years), patients with T2DM exposed to a DPP-4 inhibitor or GLP-1 receptor agonist were not at increased risk for MACE (or its component endpoints) compared with those who received comparator agents. Two meta-analyses showed a significant reduction in the incidence of MACE associated with DPP-4 inhibitor therapy as a drug class, but this beneficial effect was not observed in other meta-analyses that included large RCT CV outcome studies. In four RCTs that evaluated alogliptin, saxagliptin, sitagliptin, or lixisenatide, there was no overall increased risk for MACE relative to placebo in T2DM patients at high risk for CV events or with established CV disease, although there was an increased rate of hospitalization for heart failure associated with saxagliptin. A fifth RCT showed that liraglutide reduced MACE risk by 13% versus placebo.

Conclusion

Overall, incretin therapy does not appear to increase risk for MACE in the short term.

     

GLP-1受体激动剂与DPP-4抑制剂比较治疗2型糖尿病效果的系统评价

目的系统评价GLP-1受体激动剂与DPP-4抑制剂治疗2型糖尿病（T2DM）的有效性和安全性。方法计算机检索Pub Med、EMbase、h e Cochrane Library（2013年第4期）、Wan Fang Data、CBM和CNKI数据库,纳入GLP-1受体激动剂与DPP-4抑制剂比较治疗T2DM的随机对照试验（RCT）,检索时限截至2013年4月。由2位研究者按照纳入与排除标准筛选文献、提取资料和评价纳入研究的方法学质量后,采用Rev Man 5.2.5软件进行Meta分析。结果共纳入4个RCT。Meta分析结果显示：与DPP-4抑制剂相比,GLP-1受体激动剂能更有效地降低糖化血红蛋白[MD=–0.46,95%CI（–0.57,–0.35）,P〈0.000 01]、空腹血糖[MD=–1.13,95%CI（–1.39,–0.88）,P〈0.000 01]和体重[MD=–1.59,95%CI（–1.99,–1.19）,P〈0.000 01],其糖化血红蛋白〈7%和≤6.5%的达标率更高,但恶心[OR=4.31,95%CI（2.87,6.47）,P〈0.000 01]和腹泻[OR=2.11,95%CI（1.40,3.18）,P=0.000 4]的发生率明显高于DPP-4抑制剂。结论 GLP-1受体激动剂在控制T2DM患者的血糖和降低体重方面优于DPP-4抑制剂,但胃肠道不良反应更多。     

Saxagliptin: a new DPP-4 inhibitor for the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a global epidemic with increasing impact on individuals and healthcare providers. Available treatments (such as metformin, sulfonylureas, glitazones, and insulin) have proven unsatisfactory in producing a long-lasting impact on glycemic control. In addition, most of these treatments have undesirable side effects such as weight gain and hypoglycemia. As a result, exploring new treatment targets and new therapies is mandatory in order to treat this condition. The incretin pathway, in particular glucagon-like peptide (GLP-1), plays an important pathological role in the development of T2DM, and treatments targeting the incretin system have recently become available. These can mainly be divided into two broad categories; GLP-1 agonists/analogs (exenatide, liraglutide), and dipeptidyl peptidase-4 (DPP-4; the enzyme responsible for rapid inactivation of incretins) inhibitors (sitagliptin, vildagliptin). Saxagliptin is a novel DPP-4 inhibitor that has recently completed phase 3 studies. Saxagliptin is a potent and specific inhibitor of DPP-4 (in comparison with other dipeptidyl peptidase enzymes) that is given once daily. Current data suggest that saxagliptin as monotherapy or in combination with metformin, glyburide, or a glitazone results in significant reductions in fasting and postprandial plasma glucose and hemoglobin A_1c (HbA_1c). Saxagliptin is well tolerated and does not increase hypoglycemia compared with the placebo, and is probably weight neutral. Saxagliptin will be a new effective drug in the currently available variety of antidiabetic medications for patients with T2DM.     

Incretin-based therapies: Therapeutic rationale and pharmacological promise for type 2 diabetes

Purpose: To highlight the therapeutic promise of the incretin hormone glucagon-like peptide-1 (GLP-1), the consequent rationale for therapies acting through GLP-1-mediated pathways in type 2 diabetes mellitus (T2DM), and the emerging clinical role of the dipeptidyl peptidase-4 (DPP-4) inhibitors and GLP-1 receptor agonists.
Data sources: The PubMed database was searched (using terms including incretins, GLP-1, GIP, DPP-4), along with recent ADA and EASD abstracts.
Conclusions: Many traditional drugs used for T2DM fail to achieve and maintain glycemic control, and possess limitations such as risk for hypoglycemia and weight gain. GLP-1 is a gut-derived hormone that glucose-dependently stimulates insulin secretion while simultaneously reducing gastric emptying and appetite. Other physiological actions of GLP-1 may benefit the cardiovascular system and beta-cell function. Recently developed drug therapies that mimic or prolong the action of this hormone, therefore, have great promise in the treatment of T2DM.
Implications for practice: The GLP-1 receptor agonists and DPP-4 inhibitors are incretin-based therapies that are now becoming established as effective therapies for T2DM to be used either as monotherapy or added to other antidiabetes drugs. They enable improvements to be made in glycemic control without weight gain, with a low risk for hypoglycemia, and with potential additional clinical benefits.     

Unresolved bereavement

Abstract

Type 2 diabetes mellitus and comorbidities related to overweight/obesity are risk factors for the development of cardiovascular disease (CVD). In addition to insulin resistance and progressive β-cell failure as key factors in the pathogenesis of type 2 diabetes mellitus, defects in the incretin system are now known to contribute as well. Lifestyle modifications including diet and exercise are often insufficient for reducing glucose and weight, and most patients with type 2 diabetes will require pharmacotherapy to treat their hyperglycemia. Goals of therapy should be to reduce blood glucose to as low as possible, for as long as possible, without weight gain and hypoglycemia, and correcting cardiovascular risk factors. Numerous antidiabetes medications lower blood glucose; however, many are associated with weight gain and do not address risk factors present for CVD. Newer pharmacotherapies include the glucagon-like peptide-1 (GLP-1) receptor agonists, dipeptidyl peptidase-4 (DPP-4) inhibitors, and amylinomimetics. The GLP-1 receptor agonists and amylinomimetics reduce glucose while promoting weight loss and improving other cardiovascular risk factors with a low incidence of hypoglycemia. The DPP-4 inhibitors effectively lower glucose and are weight neutral.     

Focus on incretin-based therapies: targeting the core defects of type 2 diabetes

Glucose homeostasis is regulated by a complex interaction of hormones, principally including insulin, glucagon, amylin, and the incretins. Glucagon, cortisol, catecholamines, and growth hormone serve as the classic glucose counterregulatory hormones. The incretins are hormones released by enteroendocrine cells in the intestine in response to a meal. Classically, type 2 diabetes mellitus (T2DM) has been considered to be a triad of insulin resistance, increased hepatic gluconeogenesis, and progressive β-cell exhaustion/failure. However, disordered enteroendocrine physiology, specifically the reduced activity of glucagon-like peptide-1 (GLP-1), is also a principal pathophysiologic abnormality of the disease. Glucagon-like peptide-1 receptor agonists that have been studied include exenatide and liraglutide, which have been approved by the US Food and Drug Administration for use in patients with T2DM. Sitagliptin and saxagliptin, both approved for use in the United States, modulate incretin physiology by inhibiting degradation of GLP-1 by the enzyme dipeptidyl peptidase-4 (DPP-4). Modulators of incretin physiology have been shown to improve glycemic control with a low risk for hypoglycemia and beneficially affect β-cell function. Unlike the DPP-4 inhibitors, GLP-1 receptor agonist therapy also produces weight loss, an important consideration given the close association among T2DM, overweight/obesity, and cardiovascular disease. The GLP-1 receptor agonists have also demonstrated beneficial effects on cardiovascular risk factors other than hyperglycemia and excess body weight, such as lipid concentrations and blood pressure. This article describes incretin physiology and studies of pharmacologic therapy designed to address the blunted incretin response in patients with T2DM. Information was obtained by a search of the PubMed and MEDLINE databases for articles published from January 1, 1995 to June 1, 2009.     

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.     

Complementing Insulin Therapy to Achieve Glycemic Control

Introduction

Most patients with type 2 diabetes mellitus (T2DM) will need incrementally more complex therapeutic regimens to control hyperglycemia as the disease progresses. Insulin is very effective in reducing hyperglycemia and may improve β-cell function in patients with T2DM. However, insulin therapy is associated with weight gain and increased risk of hypoglycemia. Adding other antidiabetes medications to insulin can improve glycemic control and potentially lower the required insulin dose, resulting in less weight gain and lower risk for hypoglycemia. This article summarizes the advantages and disadvantages of different classes of commonly used antidiabetes agents, with emphasis on newer classes, for use as add-on therapy to insulin in patients with T2DM inadequately controlled on insulin therapy.

Methods

A PubMed search from July 1, 2003 to April 15, 2013 for peer-reviewed clinical and review articles relevant to insulin combination or add-on therapy in T2DM was conducted. Search terms included “insulin combination therapy,” “add-on therapy diabetes,” “dipeptidyl peptidase-4 (DPP-4) inhibitors,” “glucagon-like peptide-1 (GLP-1) receptor agonist,” “sodium-glucose cotransporter 2 (SGLT2) inhibitors”, “insulin metformin,” “insulin sulfonylurea,” and “insulin thiazolidinedione.” Bibliographies from retrieved articles were also searched for relevant articles. Study design, clinical relevance, and effect on insulin combination therapy were analyzed.

Results

Therapies used as add-on to insulin include agents associated with weight gain (thiazolidinediones and sulfonylureas) and/or hypoglycemia (sulfonylureas), which, therefore, may exacerbate risks already present with insulin. GLP-1 receptor agonists, DPP-4 inhibitors, and SGLT2 inhibitors improve glycemic control when added to insulin and have a low propensity for hypoglycemia and cause no change (DPP-4 inhibitors) or a reduction (GLP-1 receptor agonists, SGLT2 inhibitors) in body weight.

Conclusion

GLP-1 receptor agonists, DPP-4 inhibitors, and SGLT2 inhibitors improve glycemic control when combined with insulin. They also have low propensity for weight gain and hypoglycemia and so may be preferred treatment options for insulin combination when compared with traditional therapies.     

Glucagon-Like Peptide 1 Receptor Agonists and Chronic Lower Respiratory Disease Exacerbations Among Patients With Type 2 Diabetes

OBJECTIVEEmerging data from animal and human pilot studies suggest potential benefits of glucagon-like peptide 1 receptor agonists (GLP-1RA) on lung function. We aimed to assess the association of GLP-1RA and chronic lower respiratory disease (CLRD) exacerbation in a population with comorbid type 2 diabetes (T2D) and CLRD.RESEARCH DESIGN AND METHODSA new-user active-comparator analysis was conducted with use of a national claims database of beneficiaries with employer-sponsored health insurance spanning 2005–2017. We included adults with T2D and CLRD who initiated GLP-1RA or dipeptidyl peptidase 4 inhibitors (DPP-4I) as an add-on therapy to their antidiabetes regimen. The primary outcome was time to first hospital admission for CLRD. The secondary outcome was a count of any CLRD exacerbation associated with an inpatient or outpatient visit. We estimated incidence rates using inverse probability of treatment weighting for each study group and compared via risk ratios.RESULTSThe study sample consisted of 4,150 GLP-1RA and 12,540 DPP-4I new users with comorbid T2D and CLRD. The adjusted incidence rate of first CLRD admission during follow-up was 10.7 and 20.3 per 1,000 person-years for GLP-1RA and DPP-4I users, respectively, resulting in an adjusted hazard ratio of 0.52 (95% CI 0.32–0.85). For the secondary outcome, the adjusted incidence rate ratio was 0.70 (95% CI 0.57–0.87).CONCLUSIONSGLP-1RA users had fewer CLRD exacerbations in comparison with DPP-4I users. Considering both plausible mechanistic pathways and this real-world evidence, potential beneficial effects of GLP-1RA may be considered in selection of an antidiabetes treatment regimen. Randomized clinical trials are warranted to confirm our findings.     

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.     

Incretin related drugs

Incretin, GIP and GLP-1, are blood glucose lowering hormones secreted from K cells and L cells, and are rapidly degenerated by DPP-4 within a few minutes. Recently incretin related drugs, GLP-1 analogs and DPP-4 inhibitors are developed. GLP-1 analogs have amino acid substitutions, which make the GLP-1 peptide resistant to degeneration by DPP-4, while DPP-4 inhibitors prevent endogenous GLP-1 to be degenerated by DPP-4. Since they exert blood glucose lowering effect only when blood glucose levels are high, hypoglycemia rarely occurs when administrated without other anti-diabetic drugs. Incretin related drugs are expected to be a new strategy for treating type 2 diabetes.     

Novel therapeutics for type 2 diabetes: Incretin hormone mimetics (glucagon-like peptide-1 receptor agonists) and dipeptidyl peptidase-4 inhibitors

Known treatments of type 2 diabetes mellitus have limitations such as weight gain, and hypoglycaemias. A new perspective is the use of incretin hormones and incretin enhancers. Incretins are defined as being responsible for the higher insulin release after an oral glucose load compared to an intravenous glucose load. The delicate balance of glucose homeostasis, in which incretin hormones are involved, is disturbed in type 2 diabetes mellitus. The incretin GLP-1 helps to maintain glucose homeostasis through stimulation of insulin secretion and inhibition of glucagon release in a glucose-dependent manner. This is associated with reductions in body weight, and no risk of hypoglycaemias. When classical oral agents have failed to maintain adequate glycaemic control, incretin mimetics may be of particular value for obese patients and those who have little control over meal sizes. Exenatide was marketed as a GLP-1 analogue and longer acting incretin mimetics such as liraglutide, albiglutide and others have the same pharmacological profile.In addition to incretin mimetics incretin enhancers which inhibit/delay degradation of incretins were developed: so-called DPP-4 inhibitors such as sitagliptin and vildagliptin are approved in Europe. Their differences from incretin mimetics include: oral bioavailability, less side effects with overdose, no direct CNS effects (nausea and vomiting) and no effect on weight. In rodent models of diabetes, but not yet in humans, GLP-1 receptor agonists and DPP-4 inhibitors increase islet mass and preserve β-cell function.Incretin mimetics and enhancers expand type 2 diabetes treatment, are still not first line therapy and it is discussed if they are to be prophylactically used.     

Use of dipeptidyl peptidase-4 inhibitors for the treatment of patients with type 2 diabetes mellitus and chronic kidney disease

Choices of antidiabetic agents for patients with type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD) are limited. Available data suggest that the use of dipeptidyl peptidase-4 (DPP-4) inhibitors may be safe in patients at various stages of renal insufficiency. However, except for linagliptin, dosage adjustment is necessary. The efficacy of DPP-4 inhibitors in patients with renal insufficiency is generally similar to that of the general population with T2DM, with reductions in mean glycated hemoglobin (HbA1c) levels of 0.7% to 1.0% compared with baseline, and 0.4% to 0.7% compared with placebo. The frequency of moderate hypoglycemia is 21% to 80% higher with DPP-4 inhibitors compared with placebo, but the frequency of severe hypoglycemia is similar to that with placebo. The use of DPP-4 inhibitors in patients with renal insufficiency is associated with a slight weight loss of < 1 kg. Dipeptidyl peptidase-4 inhibitors may be used as monotherapy in patients with CKD and HbA1c levels < 8.5% as an alternative to insulin, glipizide, or pioglitazone. They can also be used as add-on therapy to glipizide and/or pioglitazone in patients with HbA1c levels < 9%, but studies are needed to evaluate these combinations in patients with renal insufficiency. Long-term and large-scale clinical trials are underway to better determine the safety and efficacy of DPP-4 inhibitors in patients with T2DM with and without CKD.     

Incorporating Incretin-Based Therapies into Clinical Practice for Patients with Type 2 Diabetes

Background

Effective, evidence-based management of type 2 diabetes (T2D) requires the integration of the best available evidence with clinical experience and patient preferences.

Methods

Studies published from 2000 to 2012 evaluating glucagon-like peptide-1 receptor agonists (GLP-1RAs) or dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors) were identified using PubMed. The author contextualized the study findings with his clinical experience.

Results

Incretin-based therapy targets multiple dysfunctional organs in T2D. Injectable GLP-1RAs provide substantial glycemic control and weight reduction; while oral DPP-4 inhibitors provide moderate glycemic control and weight neutrality. Both classes are effective, well tolerated, and associated with a low incidence of hypoglycemia when used alone or in combination with other antidiabetes agents. GLP-1RAs are associated with transient nausea and, like DPP-4 inhibitors, rare pancreatitis.

Conclusion

Data indicate and clinical experience confirms that incretins are well tolerated in appropriate patients and provide sustained glycemic control and weight loss or weight neutrality throughout T2D progression.     

Treatment of elderly patients with type 2 diabetes mellitus: a systematic review of the benefits and risks of dipeptidyl peptidase-4 inhibitors

Background: Achievement of glycemic control in elderly patients with type 2 diabetes mellitus (DM) is complicated by many factors.Objective: The aim of this article was to systematically review evidence on the effectiveness of dipeptidyl peptidase-4 (DPP-4) inhibitors (ie, lowering of glycosylated hemoglobin [HbA_1c]), the risk of hypoglycemia associated with these agents, and the effects of these agents on body weight in elderly patients with type 2 DM.Methods: The PubMed and Biosis databases were searched for reports of clinical trials and meeting presentations (eg, abstracts, posters) published in English between January 1, 2000, and October 25, 2009, that included elderly patients with type 2 DM who were treated with sitagliptin, saxagliptin, vildagliptin, alogliptin, BI-1356, DSP-7238, or PF-734200. Pharmacokinetic and pharmacodynamic studies were excluded from the review, as were studies that did not specifically provide quantitative clinical data on glycemic parameters or specifically list patients aged ≥65 years.Results: Eighty-five articles and 5 presentations were identified in the search; of those, 18 articles and 3 presentations were included in the review. These publications described studies of DPP-4 inhibitors administered as monotherapy or in combination with metformin, a thiazolidinedione, glimepiride, glibenclamide, or insulin. Quantitative data indicated that, in these elderly patients (generally defined as ≥65 years of age) with type 2 DM, DPP-4 inhibitors were associated with significant HbA_1c reductions that ranged from ~0.7% (baseline HbA_1c = 7.8%; P < 0.001) to 1.2% (baseline HbA_1c = 8.3%; P < 0.05). Additional studies that did not quantify the number of elderly patients (as would a subanalysis), but did specify that elderly patients were included and that patient age did not influence the results, were incorporated in this review to support the quantitative results. No significant differences were noted in the HbA_1c-lowering effects of these agents between elderly and younger patients. Less information about the incidence of hypoglycemia or weight gain in elderly patients was reported, but the available results suggested that the risk of hypoglycemia with DPP-4 inhibitors was not significantly different from that with placebo (sitagliptin 50 or 100 mg/d [0%] vs placebo [0%]; saxagliptin 5 mg/d [6.3%] vs placebo [8.0%]; vildagliptin 100 mg/d [2.32 events per patient-year] vs placebo [2.64 events per patient-year]; alogliptin 12.5 mg/d [8.0%] vs placebo [10.5%]) and that these agents were weight neutral (change, ≤0.9 kg).Conclusions: For elderly patients with type 2 DM, reductions in HbA_1c after treatment with a DPP-4 inhibitor were not significantly different from those in younger patients. Use of DPP-4 inhibitors in these studies was associated with a low risk of hypoglycemia, and these agents were weight neutral.     

Differentiating among incretin therapies: a multiple-target approach to type 2 diabetes

What is known and Objective: Incretin-based glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and dipeptidyl peptidase-4 (DPP-4) inhibitor therapies provide glycaemic control with reduced risks associated with weight gain or hypoglycaemia. Incretin therapies are compared with their mechanisms of action, effects on haemoglobin A(1C) (HbA(1C) ), fasting plasma glucose (FPG), post-prandial glucose (PPG), body weight, β-cell function, cardiovascular biomarkers and in their safety profiles to aid clinicians in the selection of individualized pharmacotherapy for patients with type 2 diabetes. Methods: Relevant articles for a systematic review were identified through PubMed. Randomized, head-to-head comparison studies among incretin therapies were identified and included in the review. Additionally, randomized, controlled monotherapy and combination therapy studies examining glycaemic and extraglycaemic effects of individual incretin therapies from 2007 to 2011 were reviewed. Results and Discussion: Glucagon-like peptide-1 receptor agonists are generally preferred over DPP-4 inhibitors because of their greater effectiveness in reducing HbA(1C) , FPG and PPG excursions, and greater weight loss potentiation. As a monotherapy option, longer-acting GLP-1 RAs, including liraglutide and exenatide once-weekly, may be preferred at higher HbA(1C) because of their more pronounced effects on FPG. At lower/near normal HbA(1C) , a short-acting GLP-1 RA, such as exenatide twice-daily, may be a better choice as its effects are more pronounced with PPG. Ideal patients or patient situations for DPP-4 inhibitors include patients who need minimal reduction in HbA(1C,) elderly patients, patients who are unwilling or unable to take an injectable agent, when GLP-1 RAs are contraindicated or when the patient will not benefit from weight loss. Treatment benefits common to all incretin-based therapies include minimal hypoglycaemia risk, potential preservation of β-cell function and effective targeting of multiple organs underlying type 2 diabetes and of comorbidities commonly associated with type 2 diabetes, such as obesity and hypertension. What is new and Conclusion: Key differences in mechanisms of action and in glycaemic and extra-glycaemic treatment outcomes exist among incretin therapies, both within the GLP-1 RA class, and between GLP-1 RAs and DPP-4 inhibitors. Clinical judgment acknowledging important differences among incretin therapies and treatment-related patient characteristics will aid in the selection of the appropriate incretin agent for individualized pharmacotherapy.     

Efficacy and Safety of Dipeptidyl Peptidase-4 Inhibitors in Combination with Metformin

Introduction

Use of dipeptidyl peptidase-4 (DPP-4) inhibitors is prevalent for the treatment of type 2 diabetes since they have fewer adverse effects compared with other non-insulin medications currently available; however, as monotherapy, the glycosylated hemoglobin (HbA1c)-lowering power of these agents is moderate. The aim of this article is to evaluate the current literature regarding the safety and efficacy of DPP-4 inhibitors in combination with metformin.

Methods

A literature search was conducted through MEDLINE (from 1950 to October 2012), PubMed (from 1966 to October 2012), EMBASE (from 1966 to October 2012), and International Pharmaceutical Abstracts (from 1970 to October 2012) using the search terms “sitagliptin,” “linagliptin,” “alogliptin,” “vildagliptin,” “saxagliptin,” and “metformin.” Studies that did not evaluate the DPP-4 inhibitors in combination with metformin and those that were not phase 3, were excluded.

Results

Many of the studies evaluated DPP-4 inhibitors in combination with metformin versus glucagon-like peptide-1 (GLP-1) agonists, placebo, DPP-4 inhibitors as monotherapy, thiazolidinediones, and sulfonylureas. The results of these noninferiority trials were that DPP-4 inhibitors as a whole are noninferior to either each other or other agents except for GLP-1 agonists. Also, in superiority studies, GLP-1 agonists proved to have greater HbA1c lowering.

Conclusion

In summary, DPP-4 inhibitors play a vital role in the treatment of diabetes. They have relatively limited adverse effects, especially regarding hypoglycemia. DPP-4 inhibitors in combination with metformin are generally well tolerated and are available as combination products to reduce pill burden and enhance compliance. The limitations to DPP-4 inhibitors are the lack of outcomes data and more limited HbA1c lowering than other medications currently approved for the treatment of type 2 diabetes. However, as previously stated, thiazolidinediones, glinides, sulfonylureas, pramlinitide, and GLP-1 agonists are all quite beneficial in HbA1c lowering but are not without major adverse effects. Therefore, DPP-4 inhibitors have a vital role as an oral add-on agent for the treatment of type 2 diabetes.     

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.     

Dipeptidyl Peptidase-4 Inhibitors in the Elderly: More Benefits or Risks?

Several studies have shown a high prevalence of type 2 diabetes mellitus (T2DM) in the elderly, characterized by a paucity of symptoms, which represents an obstacle for an early diagnosis. Frequently, T2DM in the elderly is diagnosed when a complication occurs, among which are cognitive disorders and/or affective disturbances. Moreover, hypoglycemia is a frequent side effect of therapeutic treatment with insulin, sulfonylureas or glinides, while other treatments (metformin, acarbose, thiazolidinediones, glucagon-like peptide-1 [GLP-1] receptor agonists, and dipeptidyl peptidase-4 [DPP4] inhibitors) are capable of reducing hyperglycemia without inducing hypoglycemia. Thus, considering that older persons are a very heterogeneous group of individuals, management of T2DM in the elderly is challenging but there are no available specific treatment goals or treatment algorithms for older diabetic patients. Metformin is the recommended first-line therapy in all T2DM patients. When metformin is not sufficient to achieve the desired therapeutic targets, a second drug can be added. Available options include sulfonylureas, meglitinides, alfa-glucosidase inhibitors, pioglitazone, insulin, GLP-1 receptor agonists, and DPP-4 inhibitors. The most intriguing therapy for older patients is the one based on the so-called incretins, i.e., gastrointestinal hormones that, mainly secreted in the postprandial phase, stimulate insulin secretion and inhibit glucagon secretion. The two most important human incretins are GLP-1 and glucose-dependent insulinotropic peptide (GIP). These hormones potentiate the acute effects of glucose on pancreatic alfa and beta cells, thus stimulating insulin secretion, and only GLP-1 inhibits glucagon secretion in a glucose-dependent manner (that is, only when glucose levels are increased); as a result, they reduce hyperglycemia with virtually no hypoglycemic risk. Due to their characteristics, DPP-4 inhibitors seem to be particularly interesting as potential agents for the treatment of older patients with T2DM.