Glucagon-like peptide-1 (GLP-1) and protective effects in cardiovascular disease: a new therapeutic approach for myocardial protection

Effect of Milk Protein-Polyphenol Conjugate on the Regulation of GLP-1 Hormone

Modern functional foods are designed to provide health benefits beyond basic nutrition. They are enriched with bioactive ingredients like probiotics, vitamins, minerals, and antioxidants. These foods support overall health, enhance immune function, and help prevent chronic diseases. Milk proteins and tea are known to influence satiety and regulate body weight. Studies have shown that green tea polyphenols, namely, (-)-epigallocatechin gallate (EGCG), and whey proteins, predominantly lactoferrin (LF) from milk, play a role in regulating satiety. This study aims to investigate the effect of conjugating EGCG with apo-lactoferrin (Apo-LF) and assessing these effects on satiety through monitoring glucagon-like peptide-1 (GLP-1) regulation in a human colon (NCI-H716) cell line. Apo-LF-EGCG conjugates were synthesized and characterized in terms of structural and functional properties. The effect on GLP-1 regulation was assessed by real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) to monitor gene and protein expressions, respectively. The results revealed that the protein-polyphenol interaction occurs through the complex formation of hydrogen bonds at the O-H and carbonyl groups of EGCG. The conjugates also showed a significant up-regulation of gene and protein expression levels of GLP-1 while also preventing EGCG from degradation, thereby preserving its antioxidant properties. The Apo-LF-EGCG conjugates increase satiety via increasing GLP-1 secretion in human colon cells while simultaneously retaining the antioxidant properties of EGCG. Therefore, these conjugates show potential for use as dietary supplements to enhance satiety.

Sensory Nutrition and Bitterness and Astringency of Polyphenols

Recent studies have demonstrated that the interaction of dietary constituents with taste and olfactory receptors and nociceptors expressed in the oral cavity, nasal cavity and gastrointestinal tract regulate homeostasis through activation of the neuroendocrine system. Polyphenols, of which 8000 have been identified to date, represent the greatest diversity of secondary metabolites in plants, most of which are bitter and some of them astringent. Epidemiological studies have shown that polyphenol intake contributes to maintaining and improving cardiovascular, cognitive and sensory health. However, because polyphenols have very low bioavailability, the mechanisms of their beneficial effects are unknown. In this review, we focused on the taste of polyphenols from the perspective of sensory nutrition, summarized the results of previous studies on their relationship with bioregulation and discussed their future potential.

Glucagon-Like Peptide-1 (GLP-1) Rescue Diabetic Cardiac Dysfuntions in Human iPSC-Derived Cardiomyocytes

Glucagon-like peptide-1 (GLP-1) can improve cardiac function and cardiovascular outcomes in diabetic cardiomyopathy; however, the beneficial effect of GLP-1 on human diabetic cardiomyocytes (DCMs) and its mechanism have not been fully elucidated. Here, the DCMs model by human-induced pluripotent stem cells-derived cardiomyocytes is developed. Two subtypes of GLP-1, GLP-17-36 and GLP-19-36 , are evaluated for their efficacy on the DCMs model. Diabetogenic condition is sufficient to induce most characteristics of diabetic cardiomyopathy in vitro, such as cardiac hypertrophy, lipid accumulation, impaired calcium transients, and abnormal electrophysiological properties. GLP-17-36 and GLP-19-36 can restore cardiomyocyte hypertrophic phenotype, impaired calcium transient frequency, abnormal action potential amplitude, depolarization, and repolarization velocity. Interestingly, RNA-seq reveals different pathways altered by GLP-17-36 and GLP-19-36 , respectively. Differentially expressed gene analysis reveals that possible targets of GLP-17-36 involve the regulation of mitotic nuclear division and extracellular matrix-receptor interaction, while possible targets of GLP-19-36 involve kinetochore assembly, and the complement and coagulation cascades. This study demonstrates the therapeutic effects of GLP-1 on human DCMs and provides a novel platform to unveil the cellular mechanisms of diabetic cardiomyopathy, shedding light on discovering better targets for novel therapeutic interventions.

Novelties in the pharmacological approaches for chronic heart failure: new drugs and cardiovascular targets

Despite recent advances in chronic heart failure (HF) management, the prognosis of HF patients is poor. This highlights the need for researching new drugs targeting, beyond neurohumoral and hemodynamic modulation approach, such as cardiomyocyte metabolism, myocardial interstitium, intracellular regulation and NO-sGC pathway. In this review we report main novelties on new possible pharmacological targets for HF therapy, mainly on new drugs acting on cardiac metabolism, GCs-cGMP pathway, mitochondrial function and intracellular calcium dysregulation.

Hypoglycemic drug liraglutide alleviates low muscle mass by inhibiting the expression of MuRF1 and MAFbx in diabetic muscle atrophy

BACKGROUND

Low muscle mass, that is, muscular atrophy, is an independent risk factor for type 2 diabetes mellitus (T2DM). Few studies investigated whether hypoglycemic drugs can alleviate low muscle mass and related mechanisms.

METHODS

This study recruited 51 type 2 diabetes mellitus (T2DM) patients, who were divided into two groups based on skeletal muscle index (SMI) evaluated by Dual-energy X-ray absorptiometry (DXA): the experiment group (n = 25, SMI < 7 kg/m 2 ) and the control group (n = 26, SMI≥7 kg/m 2 ). GLP-1 levels were measured by ELISA. In vitro, 10 KK-A y mice (11- to 12-week-old) were assigned into two groups: liraglutide group (n = 5) and saline group (n = 5). Real-time PCR and Western blot were used to determine the expression levels of muscle specific ubiquitin protease E3, MuRF1, and MAFbx.

RESULTS

T2DM patients with a higher SMI had significantly higher GLP-1 levels (t = 3.77, p < 0.001). SMI were positively associated with GLP-1 levels (β = 0.435, p = 0.001) and inversely associated with age (β = 0.299, p = 0.015). The incidence of low muscle mass at below the second quartiles was 10.55 times that of above the second quartiles (odds ratio = 10.556, p < 0.001). Liraglutide-treatment mice showed significant decrease in food intake, final body weight, fasting blood glucose, and significant increase in skeletal muscle mass, which coincided with the significant decrease in the expression levels of ubiquitin protease E3 MuRF1 and MAFbx. In vitro studies showed that liraglutide promoted myogenic differentiation and attenuated dexamethasone (DEX)-induced myotube atrophy. Ectopic expression of MuRF1 and MAFbx antagonized the beneficial effects of liraglutide on DEX-induced myotube atrophy.

CONCLUSION

T2DM patients have muscular atrophy, and liraglutide alleviates muscular atrophy at least in part by inhibiting the expression of MuRF1 and MAFbx.

Symptomatic and Disease-Modifying Therapy Pipeline for Alzheimer's Disease: Towards a Personalized Polypharmacology Patient-Centered Approach

Since 1906, when Dr. Alois Alzheimer first described in a patient "a peculiar severe disease process of the cerebral cortex", people suffering from this pathology have been waiting for a breakthrough therapy. Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative brain disorder and the most common form of dementia in the elderly with a long presymptomatic phase. Worldwide, approximately 50 million people are living with dementia, with AD comprising 60-70% of cases. Pathologically, AD is characterized by the deposition of amyloid β-peptide (Aβ) in the neuropil (neuritic plaques) and blood vessels (amyloid angiopathy), and by the accumulation of hyperphosphorylated tau in neurons (neurofibrillary tangles) in the brain, with associated loss of synapses and neurons, together with glial activation, and neuroinflammation, resulting in cognitive deficits and eventually dementia. The current competitive landscape in AD consists of symptomatic treatments, of which there are currently six approved medications: three AChEIs (donepezil, rivastigmine, and galantamine), one NMDA-R antagonist (memantine), one combination therapy (memantine/donepezil), and GV-971 (sodium oligomannate, a mixture of oligosaccharides derived from algae) only approved in China. Improvements to the approved therapies, such as easier routes of administration and reduced dosing frequencies, along with the developments of new strategies and combined treatments are expected to occur within the next decade and will positively impact the way the disease is managed. Recently, Aducanumab, the first disease-modifying therapy (DMT) has been approved for AD, and several DMTs are in advanced stages of clinical development or regulatory review. Small molecules, mAbs, or multimodal strategies showing promise in animal studies have not confirmed that promise in the clinic (where small to moderate changes in clinical efficacy have been observed), and therefore, there is a significant unmet need for a better understanding of the AD pathogenesis and the exploration of alternative etiologies and therapeutic effective disease-modifying therapies strategies for AD. Therefore, a critical review of the disease-modifying therapy pipeline for Alzheimer's disease is needed.

Benefits of Adding Glucagon-Like Peptide 1 Receptor Agonists to Sodium-Glucose Co-Transporter 2 Inhibitors in Diabetic Patients With Atherosclerotic Disease and Heart Failure

Sodium-glucose co-transporter 2 inhibitors (SGLT2i) reduce the risk of cardiovascular events and heart failure hospitalization (HFH) in patients with heart failure with reduced ejection fraction (HFrEF), diabetes mellitus type 2 (DM2), and atherosclerotic cardiovascular disease (ASCVD). The role of glucagon-like peptide 1 agonists (GLP1a) in these patients is unclear. We designed this study to assess if the addition of GLP1a to SGLT2i therapy improves outcomes in patients with HFrEF, DM2, and ASCVD. This was a retrospective cohort study of patients with DM2, ASCVD, and HFrEF in the national Veterans Affairs database. Patients on SGLT2i were propensity matched to patients on both SGTL2i and GLP1a. The co-primary outcomes were HFH and the composite of all-cause death, myocardial infarction, and stroke. We assessed them through a Cox regression model including unbalanced baseline characteristics. From a cohort of 5,576 patients, 343 were propensity matched to each study arm. The addition of GLP1a was associated with a 67% reduction in the 1-year risk of a composite event compared with therapy with SGLT2i (confidence interval 0.138 to 0.714, p = 0.007). The risk of HFH was not significantly different between both arms (p = 0.199). Sensitivity analyses in the unmatched dataset confirmed these findings. In conclusion, the addition of GLP1a to SGLT2i may reduce the risk of adverse events in patients with HFrEF who have DM2 and ASCVD, but it does not affect the risk of HFH.

The Role of Glp-1 Receptor Agonists in Insulin Resistance with Concomitant Obesity Treatment in Polycystic Ovary Syndrome

Insulin resistance is documented in clamp studies in 75% of women with polycystic ovary syndrome (PCOS). Although it is not included in the diagnostic criteria of PCOS, there is a crucial role of this metabolic impairment, which along with hormonal abnormalities, increase each other in a vicious circle of PCOS pathogenesis. Insulin resistance in this group of patients results from defects at the molecular level, including impaired insulin receptor-related signaling pathways enhanced by obesity and its features: Excess visceral fat, chronic inflammation, and reactive oxygen species. While lifestyle intervention has a first-line role in the prevention and management of excess weight in PCOS, the role of anti-obesity pharmacological agents in achieving and maintaining weight loss is being increasingly recognized. Glucagon-like peptide-1 receptor agonists (GLP1-RAs) not only act by reducing body weight but also can affect the mechanisms involved in insulin resistance, like an increasing expression of glucose transporters in insulin-dependent tissues, decreasing inflammation, reducing oxidative stress, and modulating lipid metabolism. They also tend to improve fertility either by increasing LH surge in hypothalamus-pituitary inhibition due to estrogen excess connected with obesity or decreasing too high LH levels accompanying hyperinsulinemia. GLP1-RAs seem promising for effective treatment of obese PCOS patients, acting on one of the primary causes of PCOS at the molecular level.

Interplay Between Systemic Metabolic Cues and Autonomic Output: Connecting Cardiometabolic Function and Parasympathetic Circuits

There is consensus that the heart is innervated by both the parasympathetic and sympathetic nervous system. However, the role of the parasympathetic nervous system in controlling cardiac function has received significantly less attention than the sympathetic nervous system. New neuromodulatory strategies have renewed interest in the potential of parasympathetic (or vagal) motor output to treat cardiovascular disease and poor cardiac function. This renewed interest emphasizes a critical need to better understand how vagal motor output is generated and regulated. With clear clinical links between cardiovascular and metabolic diseases, addressing this gap in knowledge is undeniably critical to our understanding of the interaction between metabolic cues and vagal motor output, notwithstanding the classical role of the parasympathetic nervous system in regulating gastrointestinal function and energy homeostasis. For this reason, this review focuses on the central, vagal circuits involved in sensing metabolic state(s) and enacting vagal motor output to influence cardiac function. It will review our current understanding of brainstem vagal circuits and their unique position to integrate metabolic signaling into cardiac activity. This will include an overview of not only how metabolic cues alter vagal brainstem circuits, but also how vagal motor output might influence overall systemic concentrations of metabolic cues known to act on the cardiac tissue. Overall, this review proposes that the vagal brainstem circuits provide an integrative network capable of regulating and responding to metabolic cues to control cardiac function.

Cardiovascular outcomes trials with incretin-based medications: a critical review of data available on GLP-1 receptor agonists and DPP-4 inhibitors

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) and dipeptidyl peptidase-4 (DPP-4) inhibitors are so called "incretin-based therapies" (IBTs) that represent innovative therapeutic approaches and are commonly used in clinical practice for the treatment of type 2 diabetes mellitus (T2DM). The cardiovascular outcome trials (CVOTs) have provided useful information that has helped to shape changes in clinical practice guidelines for the management of T2DM. At the same time, the mechanisms that may explain the nonglycemic and cardiovascular (CV) benefits of these medications are still being explored. A summary of the main findings from CVOTs performed to-date with particular emphasis on various outcomes and inconsistencies observed in the trials is provided. Overall, available data is favourable to the early deployment of GLP-1RAs in clinical practice, fully in line with recommendations from international scientific guidelines, and based on their effects on glucose metabolism parameters, body weight reduction and CV outcomes. Evidence further suggest that the CV benefits of GLP-1RAs may not be a class effect, with GLP-1 analogues having a greater benefit rather than exendin-based agents.

Mechanisms Involved in Cardioprotection Induced by Physical Exercise

Significance: Regular exercise training can reduce myocardial damage caused by acute ischemia/reperfusion (I/R). Exercise can reproduce the phenomenon of ischemic preconditioning, due to the capacity of brief periods of ischemia to reduce myocardial damage caused by acute I/R. In addition, exercise may also activate the multiple kinase cascade responsible for cardioprotection even in the absence of ischemia. Recent Advances: Animal and human studies highlighted the fact that, besides to reduce risk factors related to cardiovascular disease, the beneficial effects of exercise are also due to its ability to induce conditioning of the heart. Exercise behaves as a physiological stress that triggers beneficial adaptive cellular responses, inducing a protective phenotype in the heart. The factors contributing to the exercise-induced heart preconditioning include stimulation of the anti-radical defense system and nitric oxide production, opioids, myokines, and adenosine-5'-triphosphate (ATP) dependent potassium channels. They appear to be also involved in the protective effect exerted by exercise against cardiotoxicity related to chemotherapy. Critical Issues and Future Directions: Although several experimental evidences on the protective effect of exercise have been obtained, the mechanisms underlying this phenomenon have not yet been fully clarified. Further studies are warranted to define precise exercise prescriptions in patients at risk of myocardial infarction or undergoing chemotherapy.

Targeting the DPP-4-GLP-1 pathway improves exercise tolerance in heart failure patients: a systematic review and meta-analysis

BACKGROUND

The most significant manifestation of heart failure is exercise intolerance. This systematic review and meta-analysis was performed to investigate whether dipeptidyl peptidase-4 (DPP-4) inhibitors or glucagon-like peptide 1 receptor agonists (GLP-1 RAs), widely used anti-diabetic drugs, could improve exercise tolerance in heart failure patients with or without type 2 diabetes mellitus.

METHODS

An electronic search of PubMed, EMBASE and the Cochrane Library was carried out through March 8th, 2019, for eligible trials. Only randomized controlled studies were included. The primary outcome was exercise tolerance [6-min walk test (6MWT) and peak O2 consumption], and the secondary outcomes included quality of life (QoL), adverse events (AEs) and all-cause death.

RESULT

After the literature was screened by two reviewers independently, four trials (659 patients) conducted with heart failure patients with or without type 2 diabetes met the eligibility criteria. The results suggested that targeting the DPP-4-GLP-1 pathway can improve exercise tolerance in heart failure patients [MD 24.88 (95% CI 5.45, 44.31), P = 0.01] without decreasing QoL [SMD -0.51 (95% CI -1.13, 0.10), P = 0.10]; additionally, targeting the DPP-4-GLP-1 pathway did not show signs of increasing the incidence of serious AEs or mortality.

CONCLUSION

Our results suggest that DPP-4 inhibitors or GLP-1 RAs improve exercise tolerance in heart failure patients. Although the use of these drugs for heart failure has not been approved by any organization, they may be a better choice for type 2 diabetes mellitus patients with heart failure. Furthermore, as this pathway contributes to the improvement of exercise tolerance, it may be worth further investigation in exercise-intolerant patients with other diseases.

A Prospective Randomized Controlled Trial of the Metabolic Effects of Sleeve Gastrectomy with Transit Bipartition

PURPOSE

To compare the effects of the sleeve gastrectomy with transit bipartition (SG + TB) procedure with standard medical therapy (SMT) in mildly obese patients with type II diabetes (T2D).

METHODS

This is a prospective, randomized, controlled trial. Twenty male adults, ≤ 65 years old, with T2D, body mass index (BMI) > 28 kg/m² and < 35 kg/m², and HbA1c level > 8% were randomized to SG + TB or to SMT. Outcomes were the remission in the metabolic and cardiovascular risk variables up to 24 months.

RESULTS

At 24 months, SG + TB group showed a significant decrease in HbaA1c values (9.3 ± 2.1 versus 5.5 ± 1.1%, P = < 0.05) whereas SMT group maintained similar levels from baseline (8.0 ± 1.5 versus 8.3 ± 1.1%, P = NS). BMI values were lower in the SG + TB group (25.3 ± 2.8 kg/m² versus 30.9 ± 2.5 kg/m²; P = < 0.001). At 24 months, none patient in SG + TB group needed medications for hyperlipidemia/hypertension. HDL-cholesterol levels increased in the SG + TB group (33 ± 8 to 45 ± 15 mg/dL, P < 0.001). After 24 months, the area under the curve (AUC) of GLP1 increased and in the SG + TB group and the AUC of the GIP concentrations was lower in the SG + TB group than in the SMT. At 3 months, SG + TB group showed a marked increase in FGF19 levels (74.1 ± 45.8 to 237.3 ± 234 pg/mL; P = 0.001).

CONCLUSIONS

SG + TB is superior to SMT and was associated with a better metabolic and cardiovascular profile.

Liraglutide protects high-glucose-stimulated fibroblasts by activating the CD36-JNK-AP1 pathway to downregulate P4HA1

BACKGROUND

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes mellitus. It's known that glucagon-like peptide-1 (GLP-1) and prolyl 4-hydroxylase subunit alpha-1 (P4HA1) have significant effect on cardiovascular function, but their interaction in cardiac fibroblasts (CFs) is still being unraveled.

METHODS AND RESULTS

The present study demonstrated that glucose promotes CFs proliferation and cardiac fibrosis. Using qRT-PCR, Western blot, CCK-8, EdU, flow cytometry, wound healing and Transwell assays to explore the functions of liraglutide and P4HA1 in high-glucose (HG)-induced CFs, we proved that liraglutide as well as silencing of P4HA1 inhibited cell proliferation, migration and invasion, and promoted cell cycle arrest and apoptosis in HG-induced CFs. In addition, liraglutide downregulated P4HA1 expression, upregulated CD36 and P-JNK expression levels, and enhanced the DNA binding activity of AP-1 on P4HA1. Inhibition of CD36 or p--JNK promoted P4HA1 expression.

CONCLUSIONS

Liraglutide may down-regulate P4HA1 expression at least partly though CD36-JNK-AP1 pathway, thereby reducing myocardial fibrosis. Therefore, our study provides novel insight into the molecular mechanism and function of liraglutide in HG-mediated CFs.

Effects of glucagon-like peptide 1 receptor agonists on comorbidities in older patients with diabetes mellitus

Elderly patients with diabetes are at high risk of polypharmacy because of multiple coexisting diseases and syndromes. Polypharmacy increases the risk of drug–drug and drug–disease interactions in these patients, who may already have age-related sensory and cognitive deficits; such deficits may delay timely communication of early symptoms of adverse drug events. Several glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have been approved for diabetes: liraglutide, exenatide, lixisenatide, dulagluatide, semaglutide, and albiglutide. Some are also approved for treatment of obesity. The current review of literature along with clinical case discussion provides evidence supporting GLP-1 RAs as diabetes medications for polypharmacy reduction in older diabetes patients because of their multiple pleiotropic effects on comorbidities (e.g. hyperlipidemia, hypertension, and fatty liver) and syndromes (e.g. osteoporosis and sleep apnea) that commonly co-occur with diabetes. Using one medication (in this case, GLP-1 RAs) to address multiple conditions may help reduce costs, medication burden, adverse drug events, and medication nonadherence.

Glucagon-like peptide-1 receptor antagonism impairs basal exercise capacity and vascular adaptation to aerobic exercise training in rats

Cardiorespiratory fitness (CRF) inversely predicts cardiovascular (CV) mortality and CRF is impaired in people with type 2 diabetes (T2D). Aerobic exercise training (ET) improves CRF and is associated with decreased risk of premature death in healthy and diseased populations. Understanding the mechanisms contributing to ET adaptation may identify targets for reducing CV mortality of relevance to people with T2D. The antihyperglycemic hormone glucagon-like peptide-1 (GLP-1) influences many of the same pathways as exercise and may contribute to CV adaptation to ET. We hypothesized that GLP-1 is necessary for adaptation to ET. Twelve-week-old male Wistar rats were randomized (n = 8-12/group) to receive PBS or GLP-1 receptor antagonist (exendin 9-39 (Ex(9-39)) via osmotic pump for 4 weeks ± ET. CRF was greater with ET (P < 0.01). Ex(9-39) treatment blunted CRF in both sedentary and ET rats (P < 0.001). Ex(9-39) attenuated acetylcholine-mediated vasodilation, while this response was maintained with Ex(9-39)+ET (P = 0.04). Aortic stiffness was greater with Ex(9-39) (P = 0.057) and was made worse when Ex(9-39) was combined with ET (P = 0.004). Ex vivo aortic vasoconstriction with potassium and phenylephrine was lower with Ex(9-39) (P < 0.0001). Carotid strain improved with PBS + ET but did not change in the Ex(9-39) rats with ET (P < 0.0001). Left ventricular mitochondrial respiration was elevated with Ex(9-39) (P < 0.02). GLP-1 receptor antagonism impairs CRF with and without ET, attenuates the vascular adaptation to ET, and elevates cardiac mitochondrial respiration. These data suggest that GLP-1 is integral to the adaptive vascular response to ET.

GLP-1 receptor agonists and heart failure in diabetes

The prevalence of heart failure (HF) is increasing in patients with type 2 diabetes (T2D), and glucose-lowering agents have distinctive effects on the risk of developing HF that requires hospitalization. Such an increased risk has been consistently reported with thiazolidinediones (glitazones) and perhaps also with the dipeptidyl peptidase (DPP)-4 inhibitor saxagliptin (at least in SAVOR - TIMI 53), whereas a markedly decreased risk was highlighted with the sodium - glucose cotransporter type 2 (SGLT2) inhibitor empagliflozin in EMPA-REG OUTCOME. Yet, the effects of glucagon-like peptide-1 receptor agonists (GLP-1RAs) on myocardial function remain controversial. Whereas some promising observations have been reported in various animal models, the effects of GLP-1RAs on myocardial function in humans are more heterogeneous, while the positive effect on left ventricular ejection fraction (LVEF), if any, appears to be inconsistent and rather modest in most patients with HF. However, no increased risk of hospitalization for HF has been reported with GLP-1RAs in meta-analyses of phase-II/III trials (exenatide, albiglutide, dulaglutide, liraglutide), demonstrating the safety of this pharmacological class, and such findings have been confirmed by three large prospective cardiovascular outcome trials (ELIXA with lixisenatide, LEADER with liraglutide and SUSTAIN-6 with semaglutide). In particular, LEADER reported a trend towards a reduction in HF hospitalization (-13%, P = 0.14), together with a significant reduction in cardiovascular and all-cause mortality in patients with T2D at risk of cardiovascular disease. These results are reassuring in the face of the somewhat negative results of the FIGHT trial, which evaluated the effects of liraglutide in patients with advanced HF and low LVEF, such that further studies and caution are now required when using this agent to treat such patients in clinical practice.

Cardioprotection by exenatide: A novel mechanism via improving mitochondrial function involving the GLP-1 receptor/cAMP/PKA pathway

Accumulating evidence suggests that glucagon-like peptide-1 (GLP-1) and its analogues exert cardioprotective effects via modulating cardiomyocyte metabolism. Mitochondria play a pivotal role in the regulation of cell metabolism. It was hypothesized that treatment with exenatide, a GLP-1 analogue, may exert cardioprotective effects by improving mitochondrial function in an in vitro model of hypoxia/reoxygenation (H/R). H9c2 cells were employed to establish an in vitro model of H/R. Exenatide was added to the cells for 30 min prior to exposure to hypoxia. The GLP-1 receptor antagonist exendin‑(9‑39), the cyclic adenosine monophosphate (cAMP) inhibitor Rp-cAMPS and the protein kinase A (PKA) inhibitor H-89 were added to the cells for 10 min prior to treatment with exenatide. The release of lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) and cardiomyocyte apoptosis were evaluated. The characteristics of mitochondrial morphology and functions, including ATP synthesis, membrane potential (ΔΨm), mitochondrial permeability transition pore (mPTP), mitochondrial ATPase activity and oxidative stress, were determined. the mitochondrial uncoupling protein-3 (UCP-3) and nuclear respiratory factor-1 (Nrf-1) were also investigated by western blot analysis. Exenatide pretreatment significantly decreased LDH and CK-MB release and cardiomyocyte apoptosis in H9c2 cells subjected to H/R. More importantly, to the best of our knowledge, this is the first report of exenatide pretreatment decreasing mitochondrial abnormalities and reducing oxidative stress, while enhancing ATP synthesis, mitochondrial ATPase activity and ΔΨm in H9c2 cells subjected to H/R. Exenatide pretreatment also decreased mitochondrial calcium overload and inhibited the opening of mPTP in H9c2 cells subjected to H/R. Furthermore, exenatide pretreatment upregulated UCP-3 and Nrf-1 expression in H9c2 cells subjected to H/R. However, the abovementioned observed effects of exenatide were all abolished when exenatide was co-administered with exendin‑(9‑39), Rp-cAMPS and̸or H-89. Therefore, the GLP-1 analogue exenatide was found to exert cardioprotective effects in an in vitro model of H/R, and this cardioprotection may be attributed to the improvement of mitochondrial function. These effects are most likely associated with the activation of the GLP-1 receptor/cAMP/PKA signaling pathway.

Glucagon-like peptide-1 protects against ischemic left ventricular dysfunction during hyperglycemia in patients with coronary artery disease and type 2 diabetes mellitus

Background

Enhancement of myocardial glucose uptake may reduce fatty acid oxidation and improve tolerance to ischemia. Hyperglycemia, in association with hyperinsulinemia, stimulates this metabolic change but may have deleterious effects on left ventricular (LV) function. The incretin hormone, glucagon-like peptide-1 (GLP-1), also has favorable cardiovascular effects, and has emerged as an alternative method of altering myocardial substrate utilization. In patients with coronary artery disease (CAD), we investigated: (1) the effect of a hyperinsulinemic hyperglycemic clamp (HHC) on myocardial performance during dobutamine stress echocardiography (DSE), and (2) whether an infusion of GLP-1(7-36) at the time of HHC protects against ischemic LV dysfunction during DSE in patients with type 2 diabetes mellitus (T2DM).

Methods

In study 1, twelve patients underwent two DSEs with tissue Doppler imaging (TDI)—one during the steady-state phase of a HHC. In study 2, ten patients with T2DM underwent two DSEs with TDI during the steady-state phase of a HHC. GLP-1(7-36) was infused intravenously at 1.2 pmol/kg/min during one of the scans. In both studies, global LV function was assessed by ejection fraction and mitral annular systolic velocity, and regional wall LV function was assessed using peak systolic velocity, strain and strain rate from 12 paired non-apical segments.

Results

In study 1, the HHC (compared with control) increased glucose (13.0 ± 1.9 versus 4.8 ± 0.5 mmol/l, p < 0.0001) and insulin (1,212 ± 514 versus 114 ± 47 pmol/l, p = 0.01) concentrations, and reduced FFA levels (249 ± 175 versus 1,001 ± 333 μmol/l, p < 0.0001), but had no net effect on either global or regional LV function. In study 2, GLP-1 enhanced both global (ejection fraction, 77.5 ± 5.0 versus 71.3 ± 4.3%, p = 0.004) and regional (peak systolic strain −18.1 ± 6.6 versus −15.5 ± 5.4%, p < 0.0001) myocardial performance at peak stress and at 30 min recovery. These effects were predominantly driven by a reduction in contractile dysfunction in regions subject to demand ischemia.

Conclusions

In patients with CAD, hyperinsulinemic hyperglycemia has a neutral effect on LV function during DSE. However, GLP-1 at the time of hyperglycemia improves myocardial tolerance to demand ischemia in patients with T2DM.

Trial Registration: http://www.isrctn.org. Unique identifier ISRCTN69686930

Histone deacetylase (HDAC) inhibition improves myocardial function and prevents cardiac remodeling in diabetic mice

BACKGROUND

Recent evidence indicates that inhibition of histone deacetylase (HDAC) protects the heart against myocardial injury and stimulates endogenous angiomyogenesis. However, it remains unknown whether HDAC inhibition produces the protective effect in the diabetic heart. We sought to determine whether HDAC inhibition preserves cardiac performance and suppresses cardiac remodeling in diabetic cardiomyopathy.

METHODS

Adult ICR mice received an intraperitoneal injection of either streptozotocin (STZ, 200 mg/kg) to establish the diabetic model or vehicle to serve as control. Once hyperglycemia was confirmed, diabetic mice received sodium butyrate (1%), a specific HDAC inhibitor, in drinking water on a daily basis to inhibit HDAC activity. Mice were randomly divided into following groups, which includes Control, Control + Sodium butyrate (NaBu), STZ and STZ + Sodium butyrate (NaBu), respectively. Myocardial function was serially assessed at 7, 14, 21 weeks following treatments.

RESULTS

Echocardiography demonstrated that cardiac function was depressed in diabetic mice, but HDAC inhibition resulted in a significant functional improvement in STZ-injected mice. Likewise, HDAC inhibition attenuates cardiac hypertrophy, as evidenced by a reduced heart/tibia ratio and areas of cardiomyocytes, which is associated with reduced interstitial fibrosis and decreases in active caspase-3 and apoptotic stainings, but also increased angiogenesis in diabetic myocardium. Notably, glucose transporters (GLUT) 1 and 4 were up-regulated following HDAC inhibition, which was accompanied with increases of GLUT1 acetylation and p38 phosphorylation. Furthermore, myocardial superoxide dismutase, an important antioxidant, was elevated following HDAC inhibition in the diabetic mice.

CONCLUSION

HDAC inhibition plays a critical role in improving cardiac function and suppressing myocardial remodeling in diabetic heart.

Effect of the glucagon-like peptide-1 analogue liraglutide on coronary microvascular function in patients with type 2 diabetes - a randomized, single-blinded, cross-over pilot study

Background

Impaired coronary microcirculation is associated with a poor prognosis in patients with type 2 diabetes. In the absence of stenosis of major coronary arteries, coronary flow reserve (CFR) reflects coronary microcirculation. Studies have shown beneficial effects of glucagon-like peptide-1 (GLP-1) on the cardiovascular system. The aim of the study was to explore the short-term effect of GLP-1 treatment on coronary microcirculation estimated by CFR in patients with type 2 diabetes.

Methods

Patients with type 2 diabetes and no history of coronary artery disease were treated with either the GLP-1 analogue liraglutide or received no treatment for 10 weeks, in a randomized, single-blinded, cross-over setup with a 2 weeks wash-out period. The effect of liraglutide on coronary microcirculation was evaluated using non-invasive trans-thoracic Doppler-flow echocardiography during dipyridamole induced stress. Peripheral microvascular endothelial function was assessed by Endo-PAT2000®. Interventions were compared by two-sample t-test after ensuring no carry over effect.

Results

A total of 24 patients were included. Twenty patients completed the study (15 male; mean age 57 ± 9; mean BMI 33.1 ± 4.4, mean baseline CFR 2.35 ± 0.45). There was a small increase in CFR following liraglutide treatment (change 0.18, CI95% [-0.01; 0.36], p = 0.06) but no difference in effect in comparison with no treatment (difference between treatment allocation 0.16, CI95% [-0.08; 0.40], p = 0.18). Liraglutide significantly reduced glycated haemoglobin (HbA1c) (-10.1 mmol/mol CI95% [-13.9; -6.4], p = 0.01), systolic blood pressure (-10 mmHg CI95% [-17; -3], p = 0.01) and weight (-1.9 kg CI95% [-3.6; -0.2], p = 0.03) compared to no treatment. There was no effect on peripheral microvascular endothelial function after either intervention.

Conclusions

In this short-term treatment study, 10 weeks of liraglutide treatment had no significant effect on neither coronary nor peripheral microvascular function in patients with type 2 diabetes. Further long-term studies, preferably in patients with more impaired microvascular function and using a higher dosage of GLP-1 analogues, are needed to confirm these findings.

Trial registration

ClinicalTrials.gov: NCT01931982.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-015-0206-3) contains supplementary material, which is available to authorized users.

PEGylated exendin-4, a modified GLP-1 analog exhibits more potent cardioprotection than its unmodified parent molecule on a dose to dose basis in a murine model of myocardial infarction

A Site-specifically PEGylated exendin-4 (denoted as PEG-Ex4) is an exendin-4 (denoted as Ex4) analog we developed by site-specific PEGylation of exendin-4 with a high molecular weight trimeric poly(ethylene glycol) (tPEG). It has been shown to possess prolonged half-life in vivo with similar receptor binding affinity compared to unmodified exendin-4 by our previous work. This study is sought to test whether PEG-Ex4 is suitable for treating myocardial infarction (MI). In the MI model, PEG-Ex4 was administered every 3 days while equivalent amount of Ex4 was administered every 3 days or twice daily. Animal survival rate, heart function, remodeling and neoangiogenesis were evaluated and compared. Tube formation was examined in endothelial cells. In addition, Western blotting and histology were performed to determine the markers of cardiac hypertrophy and angiogenesis and to explore the possible molecular mechanism involved. PEG-Ex4 and Ex4 showed comparable binding affinity to GLP-1 receptor. In MI mice, PEG-Ex4 given at 3 days interval achieved similar extent of protection as Ex4 given twice daily, while Ex4 given at 3 days interval failed to produce protection. PEG-Ex4 elevated endothelial tube formation in vitro and capillary density in the border area of MI. PEG-Ex4 increased Akt activity and VEGF production in a GLP-1R dependent manner in endothelial cells and antagonism of GLP-1R, Akt or VEGF abolished the protection of PEG-Ex4 in the MI model. PEG-Ex4 is a potent long-acting GLP-1 receptor agonist for the treatment of chronic heart disease. Its protection might be attributed to enhanced angiogenesis mediated by the activation of Akt and VEGF.

GLP-1: benefits beyond pancreas

INTRODUCTION

Glucagon-like peptide 1 (GLP-1) is an intestinal hormone secreted after the ingestion of various nutrients. The main role of GLP-1 is to stimulate insulin secretion in a glucose-dependent manner. However, the expression of GLP-1 receptor was found to be expressed in a variety of tissues beyond pancreas such as lung, stomach, intestine, kidney, heart and brain. Beyond pancreas, a beneficial effect of GLP-1 on body weight reduction has been shown, suggesting its role for the treatment of obesity. In addition, GLP-1 has been demonstrated to reduce cardiovascular risk factors and to have a direct cardioprotective effect, fostering heart recovery after ischemic injury. Further, data from both experimental animal models and human studies have shown beneficial effect of GLP-1 on bone metabolism, either directly or indirectly on bone cells.

MATERIALS AND METHODS

We review here the recent findings of the extra-pancreatic effects of GLP-1 focusing on both basic and clinical studies, thus opening future perspectives to the use of GLP-1 analogs for the treatment of disease beyond type 2 diabetes.

CONCLUSION

Finally, the GLP-1 has been demonstrated to have a beneficial effect on both vascular, degenerative diseases of central nervous system and psoriasis.

Cardiovascular effects of glucagon-like peptide 1 (GLP-1) receptor agonists

Patients with type 2 diabetes have a several-fold increased risk of developing cardiovascular disease when compared with nondiabetic controls. Myocardial infarction and stroke are responsible for 75% of all death in patients with diabetes, who present a 2-4× increased incidence of death from coronary artery disease. Patients with diabetes are considered for cardiovascular disease secondary prevention because their risk level is similar to that reported in patients without diabetes who have already suffered a myocardial infarction. More recently, with a better risk factors control, mainly in intensive LDL cholesterol targets with statins, a significant decrease in acute cardiovascular events was observed in population with diabetes. Together with other major risk factors, type 2 diabetes must be considered as an important cause of cardiovascular disease.Glucagon like peptide-1 receptor agonists represent a novel class of anti-hyperglycemic agents that have a cardiac-friendly profile, preserve neuronal cells and inhibit neuronal degeneration, an anti-inflammatory effect in liver protecting it against steatosis, increase insulin sensitivity, promote weight loss, and increase satiety or anorexia.This review is intended to rationally compile the multifactorial cardiovascular effects of glucagon-like peptide-1 receptor agonists available for the treatment of patients with type 2 diabetes.

Stimulation of glucagon-like peptide-1 receptor through exendin-4 preserves myocardial performance and prevents cardiac remodeling in infarcted myocardium

We have demonstrated that GLP-1 improved myocardial functional recovery in acute myocardial ischemic injury. However, whether stimulation of the GLP-1 receptor (GLP-1R) with exendin-4, a selective GLP-1R agonist, could initiate a protective effect in the heart remains to be determined. Mouse myocardial infarction (MI) was created by ligation of the left descending artery. After 48 h of MI, animals were divided into the following groups (n = 5-7/group): 1) sham (animals that underwent thoracotomy without ligation), 2) MI [animals that underwent MI and received a daily dose of intraperitoneal injection (ip) of saline]; and 3) MI + exendin-4 [infarcted mice that received injections of exendin-4 (0.1 mg/kg ip)]. Two weeks later, cardiac function was assessed by echocardiography and an isovolumetrically perfused heart. Compared with control MI hearts, stimulation of GLP-1R improved cardiac function, which was associated with attenuation of myocardial hypertrophy, the mitigation of interstitial fibrosis, and an increase in survival rate in post-MI hearts. Furthermore, H9c2 cardiomyoblasts were preconditioned with exendin-4 at a dose of 100 nmol/l and then subjected to hydrogen peroxide exposure at concentrations of 50 and 100 μmol/l. The exendin-4 treatment decreased lactate dehydrogenase leakage and increased cell survival. Notably, this event was also associated with the reduction of cleaved caspase-3 and caspase-9 and attenuation of reactive oxygen species production. Exendin-4 treatments improved mitochondrial respiration and suppressed the opening of mitochondrial permeability transition pore and protected mitochondria function. Our results indicate that GLP-1R serves as a novel approach to eliciting cardioprotection and mitigating oxidative stress-induced injury.

AMPK activation by glucagon-like peptide-1 prevents NADPH oxidase activation induced by hyperglycemia in adult cardiomyocytes

Exposure of cardiomyocytes to high glucose concentrations (HG) stimulates reactive oxygen species (ROS) production by NADPH oxidase (NOX2). NOX2 activation is triggered by enhanced glucose transport through a sodium-glucose cotransporter (SGLT) but not by a stimulation of glucose metabolism. The aim of this work was to identify potential therapeutic approaches to counteract this glucotoxicity. In cultured adult rat cardiomyocytes incubated with 21 mM glucose (HG), AMP-activated protein kinase (AMPK) activation by A769662 or phenformin nearly suppressed ROS production. Interestingly, glucagon-like peptide 1 (GLP-1), a new antidiabetic drug, concomitantly induced AMPK activation and prevented the HG-mediated ROS production (maximal effect at 100 nM). α2-AMPK, the major isoform expressed in cardiomyocytes (but not α1-AMPK), was activated in response to GLP-1. Anti-ROS properties of AMPK activators were not related to changes in glucose uptake or glycolysis. Using in situ proximity ligation assay, we demonstrated that AMPK activation prevented the HG-induced p47phox translocation to caveolae, whatever the AMPK activators used. NOX2 activation by either α-methyl-d-glucopyranoside, a glucose analog transported through SGLT, or angiotensin II was also counteracted by GLP-1. The crucial role of AMPK in limiting HG-mediated NOX2 activation was demonstrated by overexpressing a constitutively active form of α2-AMPK using adenoviral infection. This overexpression prevented NOX2 activation in response to HG, whereas GLP-1 lost its protective action in α2-AMPK-deficient mouse cardiomyocytes. Under HG, the GLP-1/AMPK pathway inhibited PKC-β2 phosphorylation, a key element mediating p47phox translocation. In conclusion, GLP-1 induces α2-AMPK activation and blocks HG-induced p47phox translocation to the plasma membrane, thereby preventing glucotoxicity.

Glucose Control and Cardiovascular Outcomes in Clinical Trials of Sodium Glucose Co-transporter 2 Inhibitor Treatments in Type 2 Diabetes

Currently available medications for the treatment of type 2 diabetes have limitations, and many patients do not achieve glycaemic control. Recently, a new approach has emerged using sodium glucose co-transporter 2 (SGLT2) inhibitors that decrease glucose reabsorption in the kidneys, increasing urinary glucose excretion. These agents offer the potential to improve glycaemic control independently of insulin pathways while avoiding hypoglycaemia. Two drugs of this class, canagliflozin and dapagliflozin, have been approved by the US Food and Drug Administration (FDA); another, empagliflozin, has been filed for regulatory approval and several others are in advanced development. These drugs have been shown to effectively reduce blood glucose, fasting plasma glucose and glycated haemoglobin (HbA_1C) levels in phase III clinical trials when used as monotherapy and as add-on therapy to other diabetes medications, including insulin. Another advantage of the SGLT2 inhibitors over existing treatments is the improvement in cardiovascular risk factors, particularly in terms of reductions in blood pressure and body weight. SGLT2 inhibitors have been generally well tolerated. While more long-term safety data are required to elucidate the benefit-risk profile of SGLT2 inhibitors, the rationale for their use in type 2 diabetes therapy is strong.

GLP-1-mediated gene therapy approaches for diabetes treatment

Glucagon-like peptide (GLP)-1 is an incretin hormone with several antidiabetic functions including stimulation of glucose-dependent insulin secretion, increase in insulin gene expression and beta-cell survival. Despite the initial technical difficulties and profound inefficiency of direct gene transfer into the pancreas that seriously restricted in vivo gene transfer experiments with GLP-1, recent exploitation of various routes of gene delivery and alternative means of gene transfer has permitted the detailed assessment of the therapeutic efficacy of GLP-1 in animal models of type 2 diabetes (T2DM). As a result, many clinical benefits of GLP-1 peptide/analogues observed in clinical trials involving induction of glucose tolerance, reduction of hyperglycaemia, suppression of appetite and food intake linked to weight loss have been replicated in animal models using gene therapy. Furthermore, GLP-1-centered gene therapy not only improved insulin sensitivity, but also reduced abdominal and/or hepatic fat associated with obesity-induced T2DM with drastic alterations in adipokine profiles in treated subjects. Thus, a comprehensive assessment of recent GLP-1-mediated gene therapy approaches with detailed analysis of current hurdles and resolutions, is discussed.

Changes in liraglutide-induced body composition are related to modifications in plasma cardiac natriuretic peptides levels in obese type 2 diabetic patients

Background and aims

Liraglutide treatment can improve glycemic control with a concomitant weight loss, but the underlying mechanism on weight loss is not completely understood. Cardiac natriuretic peptides (NPs) can resist body fat accumulation through increasing adipocytes lypolysis. In this study, we tested the hypothesis that liraglutide-induced weight loss was associated with increased plasma NPs concentrations.

Methods

Thirty-one outpatients with type 2 diabetes (T2D) treated with metformin and other oral antidiabetic drugs except for thiazolidinediones (TZDs) were subcutaneously administered with liraglutide for 12 weeks. Body composition, abdominal visceral adipose tissue areas (VAT) and subcutaneous adipose tissue areas (SAT) were assessed at pre- and post-treatment by dual-energy X-ray absorptiometry (DXA) scanning and abdominal computerized tomography (CT). Plasma atrial natriuretic peptides (ANP) and B-type ventricular natriuretic peptides (BNP) concentrations were tested by commercial ELISA Kit quantitatively.

Results

Following 12-week liraglutide treatment, body weight, waist circumference, total fat and lean mass, fat percentage, SAT and VAT areas were significantly reduced from baseline. Concurrently, plasma ANP and BNP levels were significantly increased following 12-week liraglutide treatment. There were significant correlations between the reductions in body compositions and the increases in both plasma ANP and BNP levels.

Conclusions

There were significant correlations between increases in both plasma ANP and BNP levels and changes in liraglutide-induced body composition. Our data implied that increases in plasma NPs may add a novel dimension to explain how liraglutide induces weight loss.

DPP4 deficiency preserved cardiac function in abdominal aortic banding rats

Dipeptidyl peptidase-4 (DPP4) enzyme inhibition has been reported to increase plasma glucagon-like peptide-1 (GLP-1) level for controlling postprandial glucose concentration. A prominent GLP-1 level in DPP4-deficient rats contributed to the resistance of endotoxemia and myocardial infarction. DPP4 deficiency also increased the capability against H₂O₂-induced stress in cardiomyocyte. However, long term effect of loss DPP4 activity on cardiac performance remained unclear. We used abdominal aortic banding (AAB) to induce pressure overload in wild-type and DPP4-deficient rats, and investigated the progression of heart failure. Cardiac histology and function were determined. Blood sample was collected for the plasma biochemical marker measurement. Heart weight to body weight ratio increased 1.2-fold after 6 weeks of AAB surgery. Cardiac function was compensated against pressure overload after 6 weeks of AAB surgery, but progressed to deterioration after 10 weeks of AAB surgery. AAB induced cardiac dysfunction was alleviated in DPP4-deficient rats. DPP4 activity increased significantly in wild-type rats after 10 weeks of AAB surgery, but remained unchanged in DPP4-deficient rats. In contrast, GLP-1 concentration was elevated by AAB after 6 weeks of surgery in DPP4-deficient rats, and remained high after 10 weeks of surgery. Ang II level markedly increased after 6 weeks of AAB surgery, but were less in DPP4-deficient rats. Massive collagen deposits in wild-type rat hearts appeared after 10 weeks of AAB surgery, which were alleviated in DPP4-deficient rats. Long term deficiency of DPP4 activity improved cardiac performance against pressure overload in rat, which may be attributed to a great quantity of GLP-1 accumulation during AAB.