GLP-1: physiological effects and potential therapeutic applications

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

初发2型糖尿病患者GLP-1水平变化对胰高血糖素及早相胰岛素分泌的影响

目的探讨初发2型糖尿病（T2DM）患者血胰高血糖素样肽-1（GLP-1）对胰高血糖素及早相胰岛素分泌的影响。方法以新发T2DM患者（T2DM组）、健康体检者（对照组）为研究对象,采用标准馒头餐试验,观察空腹、进餐后30 min、120 min静脉血浆GLP-1动态变化及对血浆葡萄糖、胰高血糖素、胰岛素分泌的影响。结果初发T2DM组患者馒头餐各时点GLP-1水平均分别较对照组显著降低,差异有统计学意义（P〈0.05）,馒头餐后30 min、120 min胰岛素水平显著降低（P〈0.05）,但空腹胰岛素无明显差异（P〉0.05）;而胰高血糖素则较对照组各时点显著升高,差异有统计学意义（P〈0.05）。初发T2DM组早相胰岛素分泌指数（ΔFINS30/ΔG30）显著低于对照组,差异有统计学意义（P〈0.05）。结论初发T2DM患者存在GLP-1分泌减少,GLP-1缺乏可能是T2DM患者胰岛β细胞分泌缺乏及胰高血糖素分泌过多的重要因素。     

Effects of glucagon-like peptide-1 receptor agonists on non-alcoholic fatty liver disease and inflammation

Glucagon-like peptide1 (GLP-1) is secreted from Langerhans cells in response to oral nutrient intake. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are a new class of incretin-based anti-diabetic drugs. They function to stimulate insulin secretion while suppressing glucagon secretion. GLP-1-based therapies are now well established in the management of type 2 diabetes mellitus (T2DM), and recent literature has suggested potential applications of these drugs in the treatment of obesity and for protection against cardiovascular and neurological diseases. As we know, along with change in lifestyles, the prevalence of non-alcoholic fatty liver disease (NAFLD) in China is rising more than that of viral hepatitis and alcoholic fatty liver disease, and NAFLD has become the most common chronic liver disease in recent years. Recent studies further suggest that GLP-1RAs can reduce transaminase levels to improve NAFLD by improving blood lipid levels, cutting down the fat content to promote fat redistribution, directly decreasing fatty degeneration of the liver, reducing the degree of liver fibrosis and improving inflammation. This review shows the NAFLD-associated effects of GLP-1RAs in animal models and in patients with T2DM or obesity who are participants in clinical trials.     

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

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

艾塞那肽临床研究新进展

肠促胰素是肠道在进餐后分泌的激素,能促进胰岛素的分泌.胰高糖素样肽1(GLP-1)是主要的肠促胰素,通过葡萄糖依赖的方式促进胰岛素分泌、抑制胰高糖素分泌以及延缓胃排空、增加饱腹感等作用维持体内血糖的稳定.另外,在2型糖尿病患者中,它还可改善β细胞功能.但是天然的GLP-1半寿期很短,无法用于临床治疗.艾塞那肽是从希拉巨蜥唾液中分离得到的一种多肽,它可与GLP-1受体结合,产生与GLP-1相似的生理效应,但它的半寿期远比GLP-1长,因此每天两次皮下注射即可产生满意的疗效.临床研究显示艾塞那肽可显著降低2型糖尿病患者HbA_(1C)、空腹血糖及餐后血糖,并降低体重.动物研究表明艾塞那肽还可改善β细胞功能、增加β细胞量.由于GLP-1受体激动剂的独特疗效,新近的糖尿病治疗指南已将其列入2型糖尿病的治疗药物.     

GLP-1类似物在1型糖尿病和胰岛移植中的研究进展

1型糖尿病是在遗传和环境因素共同作用下,机体产生针对胰岛β细胞的自身免疫反应,随疾病进展大量β细胞被破坏而导致胰岛素分泌不足而致病.对1型糖尿病的理想冶疗模式是一方面阻断对β细胞的免疫损伤,另一方面促进β细胞再生,增加β细胞数量.体内和体外的研究表明胰升糖素样肽(GLP)-1类似物有促进胰岛素的合成与分泌,促进母细胞增殖并减少B细胞凋亡的作用,因此对于1型糖尿病有潜在的治疗作用.本文就近期发表的研究回顾了GLP-1类似物在1型糖尿病和胰岛移植中的研究进展,同时展望了未来的研究方向.     

Glucagon-like peptide-1 (GLP-1) receptor agonists,obesity and psoriasis: diabetes meets dermatology

Type 2 diabetes mellitus is characterised by beta cell failure, which frequently develops in the setting of insulin resistance. Inflammation contributes to the pathophysiology of type 2 diabetes by impairing insulin action in peripheral tissues and via reduction of beta cell function. Inflammation may also play an important role in the development of complications that arise in patients with type 2 diabetes. Hence, the anti-inflammatory actions of commonly used glucose-lowering drugs may contribute, indirectly, to their mechanisms of action and therapeutic benefit. Herein we highlight the anti-inflammatory actions of glucagon-like peptide-1 (GLP-1), which exerts direct and indirect actions on immune function. The observations that GLP-1 receptor agonists exert anti-inflammatory actions in preclinical studies, taken together with case reports linking improvements in psoriasis with GLP-1 receptor agonist therapy, illustrates the emerging clinical implications of non-classical anti-inflammatory actions of incretin-based therapeutics.     

The incretin system and its role in type 2 diabetes mellitus

The incretin hormones are released during meals from gut endocrine cells. They potentiate glucose-induced insulin secretion and may be responsible for up to 70% of postprandial insulin secretion. The incretin hormones include glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), both of which may also promote proliferation/neogenesis of beta cells and prevent their decay (apoptosis). Both hormones contribute to insulin secretion from the beginning of a meal and their effects are progressively amplified as plasma glucose concentrations rise. The current interest in the incretin hormones is due to the fact that the incretin effect is severely reduced or absent in patients with type 2 diabetes mellitus (T2DM). In addition, there is hyperglucagonaemia, which is not suppressible by glucose. In such patients, the secretion of GIP is near normal, but its effect on insulin secretion, particularly the late phase, is severely impaired. The loss of GIP action is probably a consequence of diabetes, since it is also observed in patients with diabetes secondary to chronic pancreatitis, in whom the incretin effect is also lost. GLP-1 secretion, on the other hand, is also impaired, but its insulinotropic and glucagon-suppressive actions are preserved, although the potency of GLP-1 in this respect is decreased compared to healthy subjects. However, in supraphysiological doses, GLP-1 administration may completely normalize beta as well as alpha cell sensitivity to glucose. The impaired action of GLP-1 and GIP in T2DM may be at least partly restored by improved glycaemic control, as shown in studies involving 4 weeks of intensive insulin therapy. The reduced incretin effect is believed to contribute to impaired regulation of insulin and glucagon secretion in T2DM, and, in support of this, exogenous GLP-1 administration may restore blood glucose regulation to near normal levels. Thus, the pathogenesis of T2DM seems to involve a dysfunction of both incretins. Enhancement of incretin action may therefore represent a therapeutic solution. Clinical strategies therefore include the development of metabolically stable activators of the GLP-1 receptor; and inhibition of DPP-4, the enzyme that destroys native GLP-1 almost immediately. Orally active DPP-4 inhibitors and the metabolically stable activators, exenatide (Byetta), are now on the market, and numerous clinical studies have shown that both principles are associated with durable antidiabetic activity.     

The effects of glucagon-like peptide-1 on the beta cell

Type 2 diabetes is a progressive disease characterized by insulin resistance and impaired beta-cell function. Treatments that prevent further beta-cell decline are therefore essential for the management of type 2 diabetes. Glucagon-like peptide-1 (GLP-1) is an incretin hormone that is known to stimulate glucose-dependent insulin secretion. Furthermore, GLP-1 appears to have multiple positive effects on beta cells. However, GLP-1 is rapidly degraded by dipeptidyl peptidase-4 (DPP-4), which limits the clinical relevance of GLP-1 for the treatment of type 2 diabetes. Two main classes of GLP-1-based therapies have now been developed: DPP-4 inhibitors and GLP-1 receptor agonists. Liraglutide and exenatide are examples of GLP-1 receptor agonists that have been developed to mimic the insulinotropic characteristics of endogenous GLP-1. Both have demonstrated improved beta-cell function in patients with type 2 diabetes, as assessed by homoeostasis model assessment-B analysis and proinsulin : insulin ratio. Additionally, liraglutide and exenatide are able to enhance first- and second-phase insulin secretion and are able to restore beta-cell sensitivity to glucose. Preclinical studies have shown that both liraglutide and exenatide treatment can increase beta-cell mass, stimulate beta-cell proliferation, increase beta-cell neogenesis and inhibit beta-cell apoptosis. Clinical studies are needed to confirm these findings in humans. Replication of these data in humans could have important clinical implications for the treatment of type 2 diabetes.     

Current evidence for a role of GLP-1 in Roux-en-Y gastric bypass-induced remission of type 2 diabetes

Weight-reducing surgical procedures such as Roux-en-Y gastric bypass (RYGB) have proven efficient as means of decreasing excess body weight. Furthermore, some studies report that up to 80% of patients with type 2 diabetes mellitus (T2DM) undergoing RYGB experience complete remission of their T2DM. Interestingly, the majority of remissions occur almost immediately following the operation and long before significant weight loss has taken place. Following RYGB, dramatic increases in postprandial plasma concentrations of the incretin hormone glucagon-like peptide-1 (GLP-1) have been recorded, and the known antidiabetic effects of GLP-1 are thought to be key mediators in RYGB-induced remission of T2DM. However, the published studies on the impact of RYGB on GLP-1 secretion are few, small and often not controlled properly. Furthermore, mechanistic studies delineating the role of endogenous GLP-1 secretion in RYGB-induced remission of T2DM are lacking. This article critically evaluates the current evidence for a role of GLP-1 in RYGB-induced remission of T2DM.     

Rationale Use of GLP-1 Receptor Agonists in Patients with Type 1 Diabetes

Clinicians and patients are rapidly adapting GLP-1 receptor agonists as efficacious and safe therapeutic options for managing type 2 diabetes (T2DM). GLP-1 receptor agonists stimulate insulin production and secretion from the pancreatic β cells in a glucose-dependent manner, improve gastric emptying, favor weight reduction, and reduce postabsorptive glucagon secretion from pancreatic α cells. GLP-1 receptor activity is impaired in patients with T2DM. GLP-1 secretion and subsequent physiologic actions in patients with type 1 diabetes (T1DM) is ill-defined. Some researchers have suggested that the use of GLP-1 receptor agonists in T1DM may reduce excessive postprandial glucagon secretion allowing patients to reduce their total daily dose of exogenous insulin. Hypoglycemia risk may also be minimized in T1DM as glucagon counter-regulation can be preserved to some degree via the glucose-dependent action of the GLP-1 receptor agonists. This paper will consider the physiologic and pharmacologic benefits of adding GLP-1 receptor agonists to therapeutic regimens of patients with T1DM.     

胰高血糖素样肽-1受体激动剂类药物的临床应用

对肠促胰素在维持葡萄糖稳定作用的认识,促进了对2型糖尿病患者以肠促胰素活性缺乏为靶向的药物研发。胰高血糖素样肽-1(GLP-1)是在营养物质的刺激下由小肠L细胞分泌的一种肽类激素。由于天然GLP-1循环半衰期短,需要开发新型GLP-1受体激动剂以便于临床应用。GLP-1受体激动剂以葡萄糖浓度依赖性刺激胰岛素分泌,还具有抑制胰高血糖素分泌和减慢胃排空,抑制食欲等作用。GLP-1受体激动剂作为治疗糖尿病的新型药物得到广泛应用。新的临床证据表明,GLP-1受体激动剂除了良好的血糖控制作用外还具有较好的安全性和心血管益处。文章综述GLP-1受体激动剂的临床疗效和安全性,剖析此类药物在2型糖尿病治疗中的地位。     

Cardiometabolic Effects of Glucagon-Like Peptide-1 Agonists

Cardiovascular disease is the leading cause of death among adults in the USA. Both type 1 (T1DM) and type 2 diabetes mellitus (T2DM) are known risk factors for cardiovascular disease. Despite the development of numerous effective anti-glycemic therapies, we have been unable to completely mitigate cardiovascular risk with glucose lowering alone, and prevention of cardiovascular disease in patients with diabetes is primarily achieved with the use of medications that address other risk factors such as anti-hypertensives or statins. Glucagon-like peptide-1 (GLP-1) is a key hormone in the pathophysiology of diabetes. GLP-1 agonists have been recently approved for the treatment of T2DM as well as for chronic weight management. In this review, we aim to explore the effects of GLP-1 agonists on cardiovascular health with a focus on cardiometabolic variables and cardiac function.     

Impact of Glucagon-like peptide 1 receptor agonists on peripheral arterial disease in people with diabetes mellitus: A narrative review

Peripheral arterial disease (PAD) is a common macrovascular complication of diabetes mellitus (DM). Glucagon-like peptide 1 (GLP-1) receptor agonists (GLP-1RAs) are among the latest class of antidiabetic medications that stimulate insulin synthesis and secretion and have been used for the management of type 2 DM. Apart from the effect on glycaemic control, GLP-1RAs also have a robust impact on weight reduction and have shown favorable effects on cardiovascular morbidity and mortality in cardiovascular outcome trials (CVOTs). The aim of this review was to examine the impact of GLP1-RAs on PAD among people with DM based on CVOTs, randomized controlled trials, observational studies as well as systematic reviews and meta-analyses. Data from retrospective studies and meta-analyses have shown superiority of these agents in comparison with other antidiabetic medications such as sodium-glucose cotransporter type 2 inhibitors and dipeptidyl peptidase-4 inhibitors in terms of PAD-related events. Nevertheless, data from CVOTs regarding the impact of GLP-1RAs on PAD are scarce and hence, safe conclusions regarding their effects cannot be drawn. Further prospective studies are needed to examine the impact of GLP-1RAs on PAD-related incidents including major adverse limb events, lower limb amputations and revascularization procedures.     

Therapy of type 2 diabetes mellitus based on the actions of glucagon-like peptide-1

GLP-1 is a peptide hormone from the intestinal mucosa. It is secreted in response to meal ingestion and normally functions in the so-called ileal brake, that is, inhibition of upper gastrointestinal motility and secretion when nutrients are present in the distal small intestine. It also induces satiety and promotes tissue deposition of ingested glucose by stimulating insulin secretion. Thus, it is an essential incretin hormone. In addition, the hormone has been demonstrated to promote insulin biosynthesis and insulin gene expression and to have trophic effects on the beta cells. The trophic effects include proliferation of existing beta cells, maturation of new cells from duct progenitor cells and inhibition of apoptosis. Furthermore, glucagon secretion is inhibited. Because of these effects, the hormone effectively improves metabolism in patients with type 2 diabetes mellitus. Thus, continuous subcutaneous administration of the peptide for six weeks in patients with rather advanced disease greatly improved glucose profiles and lowered body weight, haemoglobin A(1C), and free fatty acids (FFA). In addition, insulin sensitivity doubled and insulin responses to glucose were greatly improved. There were no side effects. Continuous administration is necessary because of rapid degradation by the enzyme dipeptidyl peptidase-IV. Alternative approaches include the use of analogues that are resistant to the actions of the enzyme, as well as inhibitors of the enzyme. Both approaches have shown remarkable efficacy in both experimental and clinical studies. The GLP-1-based therapy of type 2 diabetes, therefore, represents a new and attractive alternative.     

Differential effects of GLP-1 receptor agonists on components of dysglycaemia in individuals with type 2 diabetes mellitus

Metabolic consequences of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are the result of enhanced glucose-stimulated insulin secretion, inhibition of glucagon release, delayed gastric emptying and increased satiety. These attributes make GLP-1 agonists a treatment option in type 2 diabetes mellitus (T2DM). To optimise treatment choice, a detailed understanding of the effects of GLP-1 RAs on glucose homeostasis in individuals with T2DM is necessary. Although the various GLP-1 RAs share the same basic mechanisms of action, differences in pharmacokinetic/pharmacodynamic characteristics translate into differential effects on parameters of glycaemia. Head-to-head comparisons between long-acting non-prandial (liraglutide once daily and exenatide once weekly) and shorter-acting prandial (exenatide twice daily and lixisenatide once daily prandial) GLP-1 RAs confirm their differential effects on fasting plasma glucose (FPG) and post-prandial glucose (PPG). Liraglutide once daily and exenatide once weekly demonstrate greater reductions in FPG but lesser impacts on PPG excursions plasma than exenatide twice daily. Prandial GLP-1 RAs have a profound effect on post-prandial glycaemia, mediated by delaying gastric emptying, which is not subject to the tachyphylaxis occurring due to the sustained elevated plasma GLP-1 concentrations after treatment with long-acting GLP-1 RAs. Lixisenatide once-daily prandial, in contrast to liraglutide, strongly suppresses post-prandial glucagon secretion, further contributing to the more pronounced PPG-lowering effect found with lixisenatide. Evidence suggests that the GLP-1 RAs that predominantly target the prandial glucose excursions, such as exenatide twice daily and lixisenatide once-daily prandial, are therefore best used as combination therapy with basal insulin and will form an important new treatment option for individuals with T2DM.     

Double-strand adeno-associated virus-mediated exendin-4 expression in salivary glands is efficient in a diabetic rat model

Aim

Exendin-4 (Ex-4) is an agonist of the glucagon-like peptide 1 (GLP-1) receptor, approved for the treatment of type 2 diabetes (T2DM). Several strategies have been tried to develop stable and efficacious Ex-4 expression systems. The purpose of the current study was to determine whether double-stranded adeno-associated virus (dsAAV)-mediated in vivo expression of exendin-4 in salivary glands (SG), improves pathology in the Sprague–Dawley (SD) rat model of diabetes mellitus (DM).

Methods

The effects of Ex-4 expression by recombinant dsAAV-NT4-Ex-4 were evaluated in vitro compared with a single-strand (ss) AAV. The dsAAV was delivered into SGs and the blood glucose and insulin levels were assessed in a rat model of DM.

Results

DsAAV-NT4-Ex-4 virus induces significant exendin-4 expression in vitro. Furthermore, Ex-4 expressed from dsAAV virus in SGs enhances insulins secretion in vivo and significantly controls the onset of hyperglycemia in rat model of DM.

Conclusions

Results suggest that sustained secretion of Ex-4 following dsAAV-mediated gene therapy is feasible. SGs appear to be promising targets with potential clinical applicability for the treatment of DM. This represents the example of a successful use of Ex-4 for diabetes therapy, providing support for direct AAV-mediated in vivo as an easy, safe and efficient therapeutic strategy.     

Harnessing the Therapeutic Potential of Glucagon-Like Peptide-1

Glucagon-like peptide-1 (GLP-1) is synthesized from proglucagon in enteroendocrine cells and regulates glucose homeostasis via multiple complementary actions on appetite, gastrointestinal motility and islet hormone secretion. GLP-1 is secreted from the distal gut in response to food ingestion, and levels of circulating GLP-1 may be diminished in patients with type 2 diabetes mellitus. GLP-1 administration stimulates glucose-dependent insulin secretion, inhibits glucagon secretion, and lowers blood glucose in normal and diabetic rodents and in humans. GLP-1 exerts additional glucose-lowering actions in patients with diabetes mellitus already treated with metformin or sulfonylurea therapy. GLP-1 inhibits gastric emptying in healthy individuals and those with diabetes mellitus, and excess GLP-1 administration may cause nausea or vomiting in susceptible individuals. Chronic GLP-1 treatment of normal or diabetic rodents is associated with bodyweight loss and GLP-1 agonists transiently inhibit food intake and may prevent bodyweight gain in humans. The potential for GLP-1 therapy to prevent deterioration of beta-cell function is exemplified by studies demonstrating that GLP-1 analogs stimulate proliferation and neogenesis of beta-cells, leading to expansion of beta-cell mass in diabetic rodents. The rapid N-terminal inactivation of bioactive GLP-1 by dipeptidyl peptidase-IV (DPP-IV) limits the utility of the native peptide for the treatment of patients with diabetes mellitus, and has fostered the development of more potent and stable protease-resistant GLP-1 analogs which exhibit longer durations of action. The importance of DPP-IV for glucose control is illustrated by the phenotype of rodents with genetic inactivation of DPP-IV which exhibit reduced glycemic excursion and increased levels of circulating GLP-1 in vivo. Inhibitors of DPP-IV potentiate incretin action by preventing degradation of GLP-1 and glucose-dependent insulinotropic peptide, and lower blood glucose in normal rodents and in experimental models of diabetes mellitus. Hence, orally available DPP-IV inhibitors also represent a new class of therapeutic agents that enhance incretin action for the treatment of patients with type 2 diabetes mellitus.     

Alpha cell function in health and disease: influence of glucagon-like peptide-1

Although there is abundant evidence that hyperglucagonaemia plays a key role in the development of hyperglycaemia in type 2 diabetes, efforts to understand and correct this abnormality have been overshadowed by the emphasis on insulin secretion and action. However, recognition that the incretin hormone glucagon-like peptide-1 (GLP-1) exerts opposing effects on glucagon and insulin secretion has revived interest in glucagon, the neglected partner of insulin, in the bihormonal hypothesis. In healthy subjects, glucagon secretion is regulated by a variety of nutrient, neural and hormonal factors, the most important of which is glucose. The defect in alpha cell function that occurs in type 2 diabetes reflects impaired glucose sensing. GLP-1 inhibits glucagon secretion in vitro and in vivo in experimental animals, and suppresses glucagon release in a glucose-dependent manner in healthy subjects. This effect is also evident in diabetic patients, but GLP-1 does not inhibit glucagon release in response to hypoglycaemia, and may even enhance it. Early clinical studies with agents acting through GLP-1 signalling mechanisms (e.g. exenatide, liraglutide and vildagliptin) suggest that GLP-1 can improve alpha cell glucose sensing in patients with type 2 diabetes. Therapeutic approaches based around GLP-1 have the potential to improve both alpha cell and beta cell function, and could be of benefit in patients with a broad range of metabolic disorders.