Association of low GLP-1 with oxidative stress is related to cardiac disease and outcome in patients with type 2 diabetes mellitus: A pilot study

Oxidative stress (OS) contributes to cardiovascular damage in type 2 diabetes mellitus (T2DM). The peptide glucagon-like peptide-1 (GLP-1) inhibits OS and exerts cardiovascular protective actions. Our aim was to investigate whether cardiac remodeling (CR) and cardiovascular events (CVE) are associated with circulating GLP-1 and biomarkers of OS in T2DM patients. We also studied GLP-1 antioxidant effects in a model of cardiomyocyte lipotoxicity. We examined 72 T2DM patients with no coronary or valve heart disease and 14 nondiabetic subjects. A median of 6 years follow-up information was obtained in 60 patients. Circulating GLP-1, dipeptidyl peptidase-4 activity, and biomarkers of OS were quantified. In T2DM patients, circulating GLP-1 decreased and OS biomarkers increased, compared with nondiabetics. Plasma GLP-1 was inversely correlated with serum 3-nitrotyrosine in T2DM patients. Patients showing high circulating 3-nitrotyrosine and low GLP-1 levels exhibited CR and higher risk for CVE, compared to the remaining patients. In palmitate-stimulated HL-1 cardiomyocytes, GLP-1 reduced cytosolic and mitochondrial oxidative stress, increased mitochondrial ATP synthase expression, partially restored mitochondrial membrane permeability and cytochrome c oxidase activity, blunted leakage of creatine to the extracellular medium, and inhibited oxidative damage in total and mitochondrial DNA. These results suggest that T2DM patients with reduced circulating GLP-1 and exacerbated OS may exhibit CR and be at higher risk for CVE. In addition, GLP-1 exerts antioxidant effects in HL-1 palmitate-overloaded cardiomyocytes. It is proposed that therapies aimed to increase GLP-1 may counteract OS, protect from CR, and prevent CVE in patients with T2DM.     

取代环丁烷结构的非肽类胰高血糖素样肽-1受体激动剂

应用胰高血糖素样肽-1（glucagon-like peptide-1,GLP-1）及其类似物治疗2型糖尿病是代谢性疾病研究领域近年来的热点,尤其是胰高血糖素样肽-1独特的作用机制倍受业界的关注。它能同时作用于2型糖尿病的多个发病环节,在有效降低血糖的同时,避免低血糖的发生并能减轻体重。但这类药物因其多肽性质而存在诸多的使用限制（如需反复注射）。简要介绍一类取代环丁烷结构的新型非肽类胰高血糖素样肽-1受体小分子激动剂的发现过程、基本药理学特征和体内抗糖尿病和抗肥胖症效应。     

胰高血糖素样多肽-1拮抗2型糖尿病胰岛细胞凋亡损伤

胰高血糖素样多肽-1（glucogen like peptide 1, GLP-1）在胰岛素分泌过程中扮演重要角色,并在改善β细胞功能方面有着令人瞩目的效应,但有关其作用机制尚需更深入研究。本研究探讨GLP-1对2型糖尿病（type 2 diabetes mellitus, T2DM）大鼠模型胰岛细胞损伤的影响,观察GLP-1在T2DM大鼠胰岛细胞凋亡损伤机制中所发挥的作用。HE染色结果发现,糖尿病大鼠胰岛损伤。ELISA结果表明,糖尿病患者和糖尿病大鼠血清中GLP-1表达水平上调。放射免疫结果表明,GLP-1和谷氧还蛋白1（Grx1）促进HIT-T 15细胞分泌胰岛素,Cd抑制胰岛素的分泌。免疫组化结果表明,糖尿病大鼠GLP-1加药处理后,各组与糖尿病组相比,药物提高了Grx1和胰岛素表达水平,降低了胰高血糖素表达水平,同时降低了活性胱天蛋白酶3（caspase-3）的表达。本研究结果提示,GLP-1在肥胖T2DM大鼠胰岛细胞凋亡中起保护作用,同时可调节胰岛素和胰高血糖素水平,其机制可能与Grx1相关     

新型降糖药物Exenatide研究进展及前景展望

Exenatide是胰高血糖素样肽-1（GLP-1）受体的一种激动剂,可模拟人体自身激素GLP-1的功能,具有促进胰腺p-细胞增殖、改善其功能,以及促进胰岛素分泌,增加机体对胰岛素的敏感性和延缓胃排空等作用,因而有着传统治疗糖尿病药物不可比拟的优点,近年来已经成为糖尿病治疗领域的研究热点,应用前景非常广阔。简要介绍了Exenatide的生物活性、作用机理和临床应用现状,并对Exenatide长效降糖方面的研究进行了展望。     

GLP-1RAs in type 2 diabetes: mechanisms that underlie cardiovascular effects and overview of cardiovascular outcome data

Patients with type 2 diabetes (T2DM) have a substantial risk of developing cardiovascular disease. The strong connection between the severity of hyperglycaemia, metabolic changes secondary to T2DM and vascular damage increases the risk of macrovascular complications. There is a challenging demand for the development of drugs that control hyperglycaemia and influence other metabolic risk factors to improve cardiovascular outcomes such as cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, hospitalization for unstable angina and heart failure (major adverse cardiovascular events). In recent years, introduction of the new drug class of glucagon-like peptide-1 receptor agonists (GLP-1RAs) has changed the treatment landscape as GLP-1RAs have become well-established therapies in T2DM. The benefits of GLP-1RAs are derived from their pleiotropic effects, which include appetite control, glucose-dependent secretion of insulin and inhibition of glucagon secretion. Importantly, their beneficial effects extend to the cardiovascular system. Large clinical trials have evaluated the cardiovascular effects of GLP-1RAs in patients with T2DM and elevated risk of cardiovascular disease and the results are very promising. However, important aspects still require elucidation, such as the specific mechanisms involved in the cardioprotective effects of these drugs. Careful interpretation is necessary because of the heterogeneity across the trials concerning the definition of cardiovascular risk or cardiovascular disease, baseline characteristics, routine care and event rates. The aim of this review is to describe the main clinical aspects of the GLP-1RAs, compare them using data from both the mechanistic and randomized controlled trials and discuss potential reasons for improved cardiovascular outcomes observed in these trials. This review may help clinicians to decide which treatment is most appropriate in reducing cardiovascular risk in patients with T2DM.     

GLP-1 receptor agonists (GLP-1RAs): cardiovascular actions and therapeutic potential

Type 2 diabetes mellitus (T2DM) is closely associated with cardiovascular diseases (CVD), including atherosclerosis, hypertension and heart failure. Some anti-diabetic medications are linked with an increased risk of weight gain or hypoglycemia which may reduce the efficacy of the intended anti-hyperglycemic effects of these therapies. The recently developed receptor agonists for glucagon-like peptide-1 (GLP-1RAs), stimulate insulin secretion and reduce glycated hemoglobin levels without having side effects such as weight gain and hypoglycemia. In addition, GLP1-RAs demonstrate numerous cardiovascular protective effects in subjects with or without diabetes. There have been several cardiovascular outcomes trials (CVOTs) involving GLP-1RAs, which have supported the overall cardiovascular benefits of these drugs. GLP1-RAs lower plasma lipid levels and lower blood pressure (BP), both of which contribute to a reduction of atherosclerosis and reduced CVD. GLP-1R is expressed in multiple cardiovascular cell types such as monocyte/macrophages, smooth muscle cells, endothelial cells, and cardiomyocytes. Recent studies have indicated that the protective properties against endothelial dysfunction, anti-inflammatory effects on macrophages and the anti-proliferative action on smooth muscle cells may contribute to atheroprotection through GLP-1R signaling. In the present review, we describe the cardiovascular effects and underlying molecular mechanisms of action of GLP-1RAs in CVOTs, animal models and cultured cells, and address how these findings have transformed our understanding of the pharmacotherapy of T2DM and the prevention of CVD.     

用抗糖尿病药物GLP-1及其类似物治疗阿尔茨海默病

流行病学和基础研究表明阿尔茨海默病（Alzheimert＇s disease,AD）与2型糖尿病（type 2 diabetes mellitus,T2DM）存在密切关联：T2DM是AD的危险因素之一;而AD脑内也出现胰岛素信号异常、胰岛素抵抗状态,因而被称为“第3类型的糖尿病”。近年来治疗T2DM的新药——胰高血糖素样肽-1（glucagon-1ike peptide-1,GLP-1）及其类似物,已被证实具有神经保护作用,且能改善AD模型的记忆和认知功能,为AD治疗药物的研究提供了新的策略。     

胰升血糖素样肽-1及其受体与 2 型糖尿病的治疗

胰岛素对治疗 2 型糖尿病有一定效果,但长期使用会引起低血糖反应;双胍类药物降糖疗效显著,但会引起消化道不良反应 . 因此,寻找一种安全有效的药物是 2 型糖尿病治疗的当务之急 . 胰升血糖素样肽-1 作为一种胰岛素分泌促进剂和胰岛素增敏剂越来越受人们的关注,将它用于治疗糖尿病不会产生低血糖,对 1 型和 2 型糖尿病都有疗效 . 讨论胰升血糖素样肽-1及其受体的最新研究状况 .     

Adenoviral vector-mediated glucagon-like peptide 1 gene therapy improves glucose homeostasis in Zucker diabetic fatty rats

BACKGROUND: Glucagon-like peptide-1 (GLP-1) is a gut-derived incretin hormone that plays an important role in glucose homeostasis. Its functions include glucose-stimulated insulin secretion, suppression of glucagon secretion, deceleration of gastric emptying, and reduction in appetite and food intake. Despite the numerous antidiabetic properties of GLP-1, its therapeutic potential is limited by its short biological half-life due to rapid enzymatic degradation by dipeptidyl peptidase IV. The present study aimed to demonstrate the therapeutic effects of constitutively expressed GLP-1 in an overt type 2 diabetic animal model using an adenoviral vector system. METHODS: A novel plasmid (pAAV-ILGLP-1) and recombinant adenoviral vector (Ad-ILGLP-1) were constructed with the cytomegalovirus promoter and insulin leader sequence followed by GLP-1(7-37) cDNA. RESULTS: The results of an enzyme-linked immunosorbent assay showed significantly elevated levels of GLP-1(7-37) secreted by human embryonic kidney cells transfected with the construct containing the leader sequence. A single intravenous administration of Ad-ILGLP-1 into 12-week-old Zucker diabetic fatty (ZDF) rats, which have overt type 2 diabetes mellitus (T2DM), achieved near normoglycemia for 3 weeks and improved utilization of blood glucose in glucose tolerance tests. Circulating plasma levels of GLP-1 increased in GLP-1-treated ZDF rats, but diminished 21 days after treatment. When compared with controls, Ad-ILGLP-1-treated ZDF rats had a lower homeostasis model assessment for insulin resistance score indicating amelioration in insulin resistance. Immunohistochemical staining showed that cells expressing GLP-1 were found in the livers of GLP-1-treated ZDF rats. CONCLUSIONS: These data suggest that GLP-1 gene therapy can improve glucose homeostasis in fully developed diabetic animal models and may be a promising treatment modality for T2DM in humans.     

Exenatide promotes cognitive enhancement and positive brain metabolic changes in PS1-KI mice but has no effects in 3xTg-AD animals

Recent studies have shown that type 2 diabetes mellitus (T2DM) is a risk factor for cognitive dysfunction or dementia. Insulin resistance is often associated with T2DM and can induce defective insulin signaling in the central nervous system as well as increase the risk of cognitive impairment in the elderly. Glucagone like peptide-1 (GLP-1) is an incretin hormone and, like GLP-1 analogs, stimulates insulin secretion and has been employed in the treatment of T2DM. GLP-1 and GLP-1 analogs also enhance synaptic plasticity and counteract cognitive deficits in mouse models of neuronal dysfunction and/or degeneration. In this study, we investigated the potential neuroprotective effects of long-term treatment with exenatide, a GLP-1 analog, in two animal models of neuronal dysfunction: the PS1-KI and 3xTg-AD mice. We found that exenatide promoted beneficial effects on short- and long-term memory performances in PS1-KI but not in 3xTg-AD animals. In PS1-KI mice, the drug increased brain lactate dehydrogenase activity leading to a net increase in lactate levels, while no effects were observed on mitochondrial respiration. On the contrary, exenatide had no effects on brain metabolism of 3xTg-AD mice. In summary, our data indicate that exenatide improves cognition in PS1-KI mice, an effect likely driven by increasing the brain anaerobic glycolysis rate.     

¿Es eficiente el tratamiento con liraglutida?

In the current context of limited economic and health resources, efficiency of drug treatments is of paramount importance, and their clinical effects and related direct costs should therefore be analyzed. Liraglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist approved for the treatment of type 2 diabetes mellitus (T2DM) which, in addition to its normoglycemic effects, induces a significant improvement in body weight and several cardiovascular risk factors. The aim of this narrative review is to summarize the available evidence about the effects of liraglutide upon cardiovascular risk factors and how these improve its cost-effectiveness profile. Despite the relatively higher cost of liraglutide as compared to other alternative therapies, liraglutide has been shown to be cost-effective when clinical indicators and total costs associated to T2DM management are analyzed.     

2型糖尿病患者早期使用胰高血糖素样受体激动剂

糖尿病目前已成为继心血管疾病和肿瘤之后的第三位主要非传染性疾病,其中90%为2型糖尿病患者。胰高血糖素样肽-1类似物(GLP-I类似物)作为一种新型的降糖药物,具有降低体重、降低收缩压、改善胰岛细胞功能,已成为2型糖尿病治疗的新热点。艾塞那肽和利拉鲁肽作为肠促胰素激素,与人体内天然GLP-1保持了高度同源性(97%)。近几年来受到人们广泛关注。本综述针对2型糖尿病患者早期使用胰岛素样受体激动剂艾塞那肽和利拉鲁肽的安全性和有效性进行评估。     

Recent progress and future options in the development of GLP-1 receptor agonists for the treatment of diabesity

The dramatic rise of the twin epidemics, type 2 diabetes and obesity is associated with increased mortality and morbidity worldwide. Based on this global development there is clinical need for anti-diabetic therapies with accompanied weight reduction. From the approved therapies, the injectable glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are the only class of agents which are associated with a modest weight reduction. Physiological effects of the gastro-intestinal hormone GLP-1 are improvement of glycemic control as well as a reduction in appetite and food intake. Different approaches are currently under clinical evaluation to optimize the therapeutic potential of GLP-1 RAs directed to once-weekly up to once-monthly administration. The next generation of peptidic co-agonists comprises the activity of GLP-1 plus additional gastro-intestinal hormones with the potential for increased therapeutic benefits compared to GLP-1 RAs.     

Multifactorial effects of hyperglycaemia,hyperinsulinemia and inflammation on bone remodelling in type 2 diabetes mellitus

Bones undergo continuous cycles of bone remodelling that rely on the balance between bone formation and resorption. This balance allows the bone to adapt to changes in mechanical loads and repair microdamages. However, this balance is susceptible to upset in various conditions, leading to impaired bone remodelling and abnormal bones. This is usually indicated by abnormal bone mineral density (BMD), an indicator of bone strength. Despite this, patients with type 2 diabetes mellitus (T2DM) exhibit normal to high BMD, yet still suffer from an increased risk of fractures. The activity of the bone cells is also altered as indicated by the reduced levels of bone turnover markers in T2DM observed in the circulation. The underlying mechanisms behind these skeletal outcomes in patients with T2DM remain unclear. This review summarises recent findings regarding inflammatory cytokine factors associated with T2DM to understand the mechanisms involved and considers potential therapeutic interventions.     

GLP-1 C-terminal structures affect its blood glucose lowering-function.

Glucagon-like peptide-1 (GLP-1), which is an endogenous insulinotropic peptide that can stimulate islet cells to secret insulin, is a promising new drug candidate for the treatment of type 2 diabetes. However, due to the very short half-life of this peptide, the clinical value of GLP-1 is restricted. A GLP-1 peptide analog that had been altered by deletion of five amino acids from the C-terminus (sGLP-1) was selected and investigated in vivo for the therapeutic effect on GK rats with type II DM (T2DM). The results revealed that sGLP-1 exhibited decreased blood glucose-lowering ability compared to GLP-1 in the first week, as measured after once-daily administration. However, after drug administration for 2 weeks, the blood glucose-lowering effect of sGLP-1 became superior to that of GLP-1. sGLP-1 reduced apoptosis of the old islets, enhanced insulin production, and promoted new islets replication. sGLP-1 is a shorter but more efficient GLP-1 analog for type 2 diabetes management. Because sGLP-1 prolonged the proliferation and recovery of islet cells, the ability to maintain blood glucose (BG) within a normal range was still present 2 weeks after drug withdrawal. These results confirmed the importance of the C-terminus of GLP-1 molecule, and further demonstrated that GLP-1 (7-37) can be truncated till the 32nd amino acid to have a better long-term BG lowing function. This result may imply for the presence of glucagon family clearance receptors in vivo and demonstrates that the C-terminus participates in GLP-1 clearance.     

GLP-1 for type 2 diabetes

Glucagon-like peptide-1 (GLP-1)-based therapy of type 2 diabetes is executed either by GLP-1 receptor agonists, which stimulate the GLP-1 receptors, or by dipeptidyl peptidase-4 (DPP-4) inhibitors, which prevent the inactivation of endogenous GLP-1 thereby increasing the concentration of endogenous active GLP-1. GLP-1 activates pancreatic receptors resulting in improved glycemia through glucose-dependent stimulation of insulin secretion and inhibition of glucagon secretion. There is also a potential beta cell preservation effect, as judged from rodent studies. GLP-1 receptors are additionally expressed in extrapancreatic tissue, having potential for the treatment to reduce body weight and to potentially have beneficial cardio- and endothelioprotective effects. Clinical trials in subjects with type 2 diabetes have shown that in periods of 12 weeks or more, these treatments reduce HbA_1c by ≈ 0.8–1.1% from baseline levels of 7.7–8.5%, and they are efficient both as monotherapy and in combination therapy with metformin, sulfonylureas, thiazolidinediones or insulin. Furthermore, GLP-1 receptor agonists reduce body weight, whereas DPP-4 inhibitors are body weight neutral. The treatment is safe with very low risk for adverse events, including hypoglycaemia. GLP-1 based therapy is thus a novel and now well established therapy of type 2 diabetes, with a particular value in combination with metformin in patients who are inadequately controlled by metformin alone.     

Add-on therapy with anagliptin in Japanese patients with type-2 diabetes mellitus treated with metformin and miglitol can maintain higher concentrations of biologically active GLP-1/total GIP and a lower concentration of leptin

Metformin, α-glucosidase inhibitors (α-GIs), and dipeptidyl peptidase 4 inhibitors (DPP-4Is) reduce hyperglycemia without excessive insulin secretion, and enhance postprandial plasma concentration of glucagon-like peptide-1 (GLP-1) in type-2 diabetes mellitus (T2DM) patients. We assessed add-on therapeutic effects of DPP-4I anagliptin in Japanese T2DM patients treated with metformin, an α-GI miglitol, or both drugs on postprandial responses of GLP-1 and glucose-dependent insulinotropic polypeptide (GIP), and on plasma concentration of the appetite-suppressing hormone leptin. Forty-two Japanese T2DM patients with inadequately controlled disease (HbA1c: 6.5%–8.0%) treated with metformin (n = 14), miglitol (n = 14) or a combination of the two drugs (n = 14) received additional treatment with anagliptin (100 mg, p.o., b.i.d.) for 52 weeks. We assessed glycemic control, postprandial responses of GLP-1 and glucose-dependent insulinotropic polypeptide (GIP), and on plasma concentration of leptin in those patients. Add-on therapy with anagliptin for 52 weeks improved glycemic control and increased the area under the curve of biologically active GLP-1 concentration without altering obesity indicators. Total GIP concentration at 52 weeks was reduced by add-on therapy in groups treated with miglitol compared with those treated with metformin. Add-on therapy reduced leptin concentrations. Add-on therapy with anagliptin in Japanese T2DM patients treated with metformin and miglitol for 52 weeks improved glycemic control and enhanced postprandial concentrations of active GLP-1/total GIP, and reduce the leptin concentration.     

Management of Type 2 Diabetes Mellitus in the Very Elderly: One Practice’s Experience

ObjectiveType 2 diabetes mellitus (T2DM) affects 25% of adults over age 65. Nevertheless, few clinical trials include patients over age 75.MethodsThis case series reports retrospective data on a cohort of 85 patients aged 80 and over (mean 88.1, range 80-104) with T2DM, managed by a single endocrinologist. The practice’s computerized data base was searched for all patients 80 years of age and older with a diagnosis of T2DM.ResultsThe major observations were the significant decrease in the use of agents associated with hypoglycemia (sulfonylureas and insulin), and the beneficial and well-tolerated use of glucagon like peptide-1 receptor analogues (GLP-1 RA). The mean A1c in the entire cohort dropped from 7.6% to 6.6% over a mean of 9 months. Nearly one-half of the cohort were treated with GLP1-RA, reflecting studies demonstrating the safety and efficacy of this class of drugs in less elderly patients. At presentation, 75% were on sulfonylurea and/or insulin; this number was reduced to 27%. Furthermore, none of the patients required short-acting (bolus) insulin to achieve the individualized A1c target.ConclusionPatients with T2DM aged 80 and over respond well to GLP1-RA drugs, drastically reducing the need for agents associated with hypoglycemia. The important question, which will require larger and prospective studies, is whether the lowering of A1c, as shown in this paper, and the use of GLP-1 RA specifically, are associated with improved morbidity and mortality in the very elderly.     

在实验动物水平通过恢复和改善胰岛β细胞功能的糖尿病治疗新进展

糖尿病是一个世界性问题,在中国就有超过1.3亿人患有糖尿病.糖尿病主要分为1型糖尿病和2型糖尿病.遗憾的是,糖尿病至今尚未达成有效的预防和治愈手段.但是,近年来的一系列突破性的研究成果,让我们看到了治愈糖尿病的希望.在这里我们回顾了目前关于1型糖尿病和2型糖尿病可能的治愈途径的研究进展.这些途径包括胰岛移植和1型糖尿病...     

A novel GLP-1 analog,a dimer of GLP-1 via covalent linkage by a lysine,prolongs the action of GLP-1 in the treatment of type 2 diabetes

GLP-1 is an incretin hormone that can effectively lower blood glucose, however, the short time of biological activity and the side effect limit its therapeutic application. Many methods have been tried to optimize GLP-1 to extend its in vivo half-time, reduce its side effect and enhance its activity. Here we have chosen the idea to dimerize GLP-1 with a C-terminal lysine to form a new GLP-1 analog, DLG3312. We have explored the structure and the biological property of DLG3312, and the results indicated that DLG3312 not only remained the ability to activate the GLP-1R, but also strongly stimulated Min6 cell to secrete insulin. The in vivo bioactivities have been tested on two kinds of animal models, the STZ induced T2DM mice and the db/db mice, respectively. DLG3312 showed potent anti-diabetic ability in glucose tolerance assay and single-dose administration of DLG3312 could lower blood glucose for at least 10 hours. Long-term treatment with DLG3312 can reduce fasted blood glucose, decrease water consumption and food intake and significantly reduce the HbA1c level by 1.80% and 2.37% on STZ induced T2DM mice and the db/db mice, respectively. We also compared DLG3312 with liraglutide to investigate its integrated control of the type 2 diabetes. The results indicated that DLG3312 almost has the same effect as liraglutide but with a much simpler preparation process. In conclusion, we, by using C-terminal lysine as a linker, have synthesized a novel GLP-1 analog, DLG3312. With simplified preparation and improved physiological characterizations, DLG3312 could be considered as a promising candidate for the type 2 diabetes therapy.