Glucagon-like peptide-1 (GLP-1) analog liraglutide inhibits endothelial cell inflammation through a calcium and AMPK dependent mechanism

SGLT-2 inhibitors and GLP-1 receptor agonists for nephroprotection and cardioprotection in patients with diabetes mellitus and chronic kidney disease. A consensus statement by the EURECA-m and the DIABESITY working groups of the ERA-EDTA

Chronic kidney disease (CKD) in patients with diabetes mellitus (DM) is a major problem of public health. Currently, many of these patients experience progression of cardiovascular and renal disease, even when receiving optimal treatment. In previous years, several new drug classes for the treatment of type 2 DM have emerged, including inhibitors of renal sodium-glucose co-transporter-2 (SGLT-2) and glucagon-like peptide-1 (GLP-1) receptor agonists. Apart from reducing glycaemia, these classes were reported to have other beneficial effects for the cardiovascular and renal systems, such as weight loss and blood pressure reduction. Most importantly, in contrast to all previous studies with anti-diabetic agents, a series of recent randomized, placebo-controlled outcome trials showed that SGLT-2 inhibitors and GLP-1 receptor agonists are able to reduce cardiovascular events and all-cause mortality, as well as progression of renal disease, in patients with type 2 DM. This document presents in detail the available evidence on the cardioprotective and nephroprotective effects of SGLT-2 inhibitors and GLP-1 analogues, analyses the potential mechanisms involved in these actions and discusses their place in the treatment of patients with CKD and DM.

Liraglutide exerts an anti-inflammatory action in obese patients with type 2 diabetes

INTRODUCTION

Liraglutide (L) is the analogue of human glucagon-like peptide 1 which stimulates glucose-dependent insulin secretion and can modify the level of inflammatory biomarkers. L can influence NF-kB inflammatory cascade, but the mechanisms of anti-inflammatory activities of L remain to be determined. In animal models L influenced an activity of Sirtuin 1(SIRT1). Moreover, recent evidences strongly suggest that SIRT1 up-regulation may serve as a potent therapeutic approach against development and progression of diabetic complications. The aim of this study was to investigate L effects directed on the pro-inflammatory NF-kB pathway and expression of SIRT1 in obese patients with type 2 diabetes mellitus (DM).

MATERIALS AND METHODS

15 obese patients with type 2 diabetes were studied, all using metformin (1-2 g/day) and sulfonylurea (glimiperide). All patients received L 1.2 mg daily add-on to stable therapy for 6 weeks. Blood samples were collected before, 6 weeks after start of treatment and after an overnight fast 6 weeks after stopping L, mononuclear cells (MNC) were isolated. The mRNA expressions of TNF-α, TLR2, TLR4, NOD1, IL-2 and SIRT1 were measured in MNC by RT-PCR. Ceruloplasmin concentration was measured in plasma by photometric method.

RESULTS

In this add-on pilot clinical investigation we received new data that L can inhibit proinflammatory NF-kB pathway by increased SIRT1 expression in obese patients with type 2 DM improving metabolic profile. The mRNA expression in MNC of TNF-α, IkB, TLR2, TLR4, and plasma ceruloplasmin fell after 6 weeks of L. Expressions of IL-2 and NOD-1 were stable. There was a significant increase of SIRT1 mRNA expression. The mRNA expression in MNC of TNF-α, IkB, TLR2, TLR4, NOD1, SIRT1 and ceruloplasmin concentrations did not reverse to baseline levels after 6 weeks stopping of L treatment. IL-2 expression decreased in comparison with basic level.

CONCLUSIONS

L has a potent anti-inflammatory effect as do GLP-1 agonists due to inhibition of NF-kB pathways and up-regulate SIRT1 expression, down-regulating pro-inflammatory factors including cytokines (TNF-α), extra- and intracellular receptors (TLR2, TLR4), and inflammation markers such as ceruloplasmin. Long lasting effects of L can be mediated by epigenetic regulation of NF-kB pathway by SIRT-1.

Glucagon-like peptide-1 receptor agonists and the risk of cardiovascular events in diabetes patients surviving an acute myocardial infarction

AIMS

Trial evidence indicates that glucagon-like peptide-1 receptor agonists (GLP-1 RAs) may reduce the risk of cardiovascular (CV) events in patients with diabetes and myocardial infarction (MI). We aimed to expand this observation to routine care settings.

METHODS AND RESULTS

Prospective observational study including all patients with diabetes surviving an MI and registered in the nationwide SWEDEHEART registry during 2010-17. Multivariable Cox regression analyses were used to estimate the association between GLP-1 RAs use and the study outcome, which was a composite of stroke, heart failure, Re-infarction, or CV death. Covariates included demographics, comorbidities, presentation at admission, and use of secondary CV prevention therapies. In total, 17 868 patients with diabetes were discharged alive after a first event of MI. Their median age was 71 years, 36% were women and their median estimated glomerular filtration rate was 75 mL/min/1.73m2. Of those, 365 (2%) were using GLP-1 RAs. During median 3 years of follow-up, 7005 patients experienced the primary composite outcome. Compared with standard of diabetes care, use of GLP-1 RAs was associated with a lower event risk [adjusted hazard ratio (HR) 0.72; 95% confidence interval (CI): 0.56-0.92], mainly attributed to a lower rate of re-infarction and stroke. Results were similar after propensity score matching or when compared with users of sulfonylurea. There was no suggestion of heterogeneity across subgroups of age, sex, chronic kidney disease, and STEMI.

CONCLUSION

GLP-1 RAs use, compared with standard of diabetes care, was associated with lower risk for major CV events in healthcare-managed survivors of an MI.

Glucagon-Like Peptide-1 Receptor Agonist Liraglutide Ameliorates the Development of Periodontitis

Periodontitis is one of the diabetic complications due to its high morbidity and severity in patients with diabetes. The prevention of periodontitis is especially important in diabetic patients because the relationship between diabetes and periodontitis is bidirectional. Here, we evaluated the impacts of glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide on the amelioration of periodontitis. Five-wk-old Male Sprague-Dawley (SD) rats (n = 30) were divided into 3 groups: normal, periodontitis, and periodontitis with liraglutide treatment groups. Periodontitis was induced by ligature around the maxillary second molar in SD rats. Half of the rats were administered liraglutide for 2 weeks. Periodontitis was evaluated by histological staining, gene expressions of inflammatory cytokines in gingiva, and microcomputed tomography. Periodontitis increased inflammatory cell infiltration, macrophage accumulation, and gene expressions of tumor necrosis factor-α and inducible nitric oxide synthase in the gingiva, all of which were ameliorated by liraglutide. Liraglutide decreased M1 macrophages but did not affect M2 macrophages in periodontitis. Moreover, ligature-induced alveolar bone resorption was ameliorated by liraglutide. Liraglutide treatment also reduced osteoclasts on the alveolar bone surface. These results highlight the beyond glucose-lowering effects of liraglutide on the treatment of periodontitis.

Anti-inflammatory Property of AMP-activated Protein Kinase

BACKGROUND

One of the many debated topics in inflammation research is whether this scenario is really an accelerated form of human wound healing and immunityboosting or a push towards autoimmune diseases. The answer requires a better understanding of the normal inflammatory process, including the molecular pathology underlying the possible outcomes. Exciting recent investigations regarding severe human inflammatory disorders and autoimmune conditions have implicated molecular changes that are also linked to normal immunity, such as triggering factors, switching on and off, the influence of other diseases and faulty stem cell homeostasis, in disease progression and development.

METHODS

We gathered around and collected recent online researches on immunity, inflammation, inflammatory disorders and AMPK. We basically searched PubMed, Scopus and Google Scholar to assemble the studies which were published since 2010.

RESULTS

Our findings suggested that inflammation and related disorders are on the verge and interfere in the treatment of other diseases. AMPK serves as a key component that prevents various kinds of inflammatory signaling. In addition, our table and hypothetical figures may open a new door in inflammation research, which could be a greater therapeutic target for controlling diabetes, obesity, insulin resistance and preventing autoimmune diseases.

CONCLUSION

The relationship between immunity and inflammation becomes easily apparent. Yet, the essence of inflammation turns out to be so startling that the theory may not be instantly established and many possible arguments are raised for its clearance. However, this study might be able to reveal some possible approaches where AMPK can reduce or prevent inflammatory disorders.

Anti-inflammatory potentials of incretin-based therapies used in the management of diabetes

GLP-1 receptor agonists (GLP-1RA) and dipeptidyl peptidase 4 inhibitors (DPP-4i) are two classes of antidiabetic agents used in the management of diabetes based on incretin hormones. There is emerging evidence that they have anti-inflammatory effects. Since most long-term complications of diabetes have a background of chronic inflammation, these agents may be beneficial against diabetic complications not only due to their hypoglycemic potential but also via their anti-inflammatory effects. However, the exact molecular mechanisms by which GLP-1RAs and DPP-4i exert their anti-inflammatory effects are not clearly understood. In this review, we discuss the potential molecular pathways by which these incretin-based therapies exert their anti-inflammatory effects.

DPP-4 Inhibitor Linagliptin is Neuroprotective in Hyperglycemic Mice with Stroke via the AKT/mTOR Pathway and Anti-apoptotic Effects

Dipeptidyl peptidase 4 (DPP-4) inhibitors have been shown to have neuroprotective effects in diabetic patients suffering from stroke, but less research has focused on patients with mild hyperglycemia below the threshold for a diagnosis of diabetes. In this investigation, a hyperglycemic mouse model was generated by intraperitoneal injection of streptozotocin and then subjected to focal cerebral ischemia. We demonstrated that the DPP-4 inhibitor linagliptin significantly decreased the infarct volume, reduced neuronal cell death, decreased inflammation, and improved neurological deficit compared with control mice. Linagliptin up-regulated the expression of p-Akt and p-mTOR and regulated the apoptosis factors Bcl-2, Bax, and caspase 9. Taken together, these results suggest that linagliptin exerts a neuroprotective action likely through activation of the Akt/mTOR pathway along with anti-apoptotic and anti-inflammatory mechanisms. Therefore, linagliptin may be considered as a therapeutic treatment for stroke patients with mild hyperglycemia.

Endothelial GLP-1 (Glucagon-Like Peptide-1) Receptor Mediates Cardiovascular Protection by Liraglutide In Mice With Experimental Arterial Hypertension

Supplemental Digital Content is available in the text.

Cardiovascular outcome trials demonstrated that GLP-1 (glucagon-like peptide-1) analogs including liraglutide reduce the risk of cardiovascular events in type 2 diabetes mellitus. Whether GLP-1 analogs reduce the risk for atherosclerosis independent of glycemic control is challenging to elucidate as the GLP-1R (GLP-1 receptor) is expressed on different cell types, including endothelial and immune cells.

Vildagliptin, a DPP-4 Inhibitor, Attenuates Endothelial Dysfunction and Atherogenesis in Nondiabetic Apolipoprotein E-Deficient Mice

Dipeptidyl peptidase-4 (DPP-4) inhibitors are novel antidiabetic agents with possible vascular protection effects. Endothelial dysfunction is an initiation step in atherogenesis. The purpose of this study was to investigate whether vildagliptin (Vilda) attenuates the development of endothelial dysfunction and atherosclerotic lesions in nondiabetic apolipoprotein E-deficient (ApoE^-/-) mice. Eight-week-old nondiabetic ApoE^-/- mice fed a Western-type diet received Vilda (50 mg/kg/day) for 20 weeks or 8 weeks. After 20 weeks of treatment, Vilda administration reduced atherogenesis in the aortic arch as determined by en face Sudan IV staining compared with the vehicle group (P < 0.05). Vilda also reduced lipid accumulation (P < 0.05) and vascular cell adhesion molecule-1 (VCAM-1) expression (P < 0.05) and tended to decrease macrophage infiltration (P = 0.05) into atherosclerotic plaques compared with vehicle. After 8 weeks of treatment, endothelium-dependent vascular reactivity was examined. Vilda administration significantly attenuated the impairment of endothelial function in nondiabetic ApoE^-/- mice compared with the vehicle group (P < 0.05). Vilda treatment did not alter metabolic parameters, including blood glucose level, in both study protocols. To investigate the mechanism, aortic segments obtained from wild-type mice were incubated with exendin-4 (Ex-4), a glucagon-like peptide-1 (GLP-1) analog, in the presence or absence of lipopolysaccharide (LPS). Ex-4 attenuated the impairment of endothelium-dependent vasodilation induced by LPS (P < 0.01). Furthermore, Ex-4 promoted phosphorylation of eNOS at Ser1177 which was decreased by LPS in human umbilical endothelial cells (P < 0.05). Vilda inhibited the development of endothelial dysfunction and prevented atherogenesis in nondiabetic ApoE^-/- mice. Our results suggested that GLP-1-dependent amelioration of endothelial dysfunction is associated with the atheroprotective effects of Vilda.

Glucagon-like peptide-1 increased the vascular relaxation response via AMPK/Akt signaling in diabetic mice aortas

The incretin glucagon-like peptide-1 (GLP-1) elicits direct favorable effects on the cardiovascular system. This study aimed to evaluate the acute effects of GLP-1 on improving aortic endothelial dysfunction in diabetic mice. Additionally, we examined whether GLP-1 elucidated the underlying mechanisms. Using the diabetic mouse models induced by nicotinamide and streptozotocin, we investigated the functional changes in the aorta caused by GLP-1. Organ baths were performed for vascular reactivity in isolated aortic rings, and western blotting was used for protein analysis. The diabetic aortas showed enhanced GLP-1-induced relaxation response and nitric oxide (NO) production. However, the pretreatment of GLP-1 did not significantly change the endothelial-dependent relaxation response to acetylcholine and -independent relaxation response to sodium nitroprusside. On the other hand, the GLP-1-induced relaxation response and NO production were abolished by the endothelial NO synthase inhibitor, GLP-1 receptor antagonist, Akt inhibitor, and AMP-activated protein kinase (AMPK) inhibitor. Finally, in diabetic mice, considerable increases in phosphorylation of Akt and AMPK were found in aortas stimulated with GLP-1, both of which were decreased by pretreatment with the AMPK inhibitor. GLP-1 significantly enhanced endothelial-dependent relaxation in diabetic aortas. The effect may be mediated through activation of the AMPK/Akt pathway via a GLP-1 receptor-dependent mechanism.

Therapeutic Effects of Endogenous Incretin Hormones and Exogenous Incretin-Based Medications in Sepsis

BACKGROUND

Sepsis, a complex disorder characterized by a dysregulated immune response to an inciting infection, affects over one million Americans annually. Dysglycemia during sepsis hospitalization confers increased risk of organ dysfunction and death, and novel targets for the treatment of sepsis and maintenance of glucose homeostasis are needed. Incretin hormones are secreted by enteroendocrine cells in response to enteral nutrients and potentiate insulin release from pancreatic β cells in a glucose-dependent manner, thereby reducing the risk of insulin-induced hypoglycemia. Incretin hormones also reduce systemic inflammation in preclinical studies, but studies of incretins in the setting of sepsis are limited.

METHODS

In this bench-to-bedside mini-review, we detail the evidence to support incretin hormones as a therapeutic target in patients with sepsis. We performed a PubMed search using the medical subject headings "incretins," "glucagon-like peptide-1," "gastric inhibitory peptide," "inflammation," and "sepsis."

RESULTS

Incretin-based therapies decrease immune cell activation, inhibit proinflammatory cytokine release, and reduce organ dysfunction and mortality in preclinical models of sepsis. Several small clinical trials in critically ill patients have suggested potential benefit in glycemic control using exogenous incretin infusions, but these studies had limited power and were performed in mixed populations. Further clinical studies examining incretins specifically in septic populations are needed.

CONCLUSIONS

Targeting the incretin hormone axis in sepsis may provide a means of not only promoting euglycemia in sepsis but also attenuating the proinflammatory response and improving clinical outcomes.

Endothelial Toxicity of High Glucose and its by-Products in Diabetic Kidney Disease

Alterations of renal endothelial cells play a crucial role in the initiation and progression of diabetic kidney disease. High glucose per se, as well as glucose by-products, induce endothelial dysfunction in both large vessels and the microvasculature. Toxic glucose by-products include advanced glycation end products (AGEs), a group of modified proteins and/or lipids that become glycated after exposure to sugars, and glucose metabolites produced via the polyol pathway. These glucose-related endothelio-toxins notably induce an alteration of the glomerular filtration barrier by increasing the permeability of glomerular endothelial cells, altering endothelial glycocalyx, and finally, inducing endothelial cell apoptosis. The glomerular endothelial dysfunction results in albuminuria. In addition, high glucose and by-products impair the endothelial repair capacities by reducing the number and function of endothelial progenitor cells. In this review, we summarize the mechanisms of renal endothelial toxicity of high glucose/glucose by-products, which encompass changes in synthesis of growth factors like TGF-β and VEGF, induction of oxidative stress and inflammation, and reduction of NO bioavailability. We finally present potential therapies to reduce endothelial dysfunction in diabetic kidney disease.

Activation of pCREB/Nrf-2 signaling mediates re-positioning of liraglutide as hepato-protective for methotrexate -induced liver injury (MILI)

Methotrexate (MTX) is commonly used to treat several types of cancer and autoimmune diseases. However, there is increasing concern over its organs toxicities particularly liver toxicity. Liraglutide, a glucagon like peptide-1 agonist, possesses antioxidant and anti-inflammatory features. This study aimed to explore the potential protective effect of liraglutide pre-treatment in ameliorating MTX-induced hepatotoxicity and to further investigate the underlying mechanisms. Rats received 1.2 mg/kg liraglutide intraperitoneal twice daily for 7 days before MTX. Results revealed that liraglutide significantly decreased activities of liver enzymes and oxidative stress in hepatocytes. Furthermore, NF-kB expression and related inflammatory markers (TNF-α, COX-2 and IL-6) were reduced in the pre-treatment group of liraglutide. These data validate the advantageous effects of liraglutide in MTX hepatotoxic animals. In addition, liraglutide increased the expression of the antioxidant transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf-2), along with the transcription of downstream phosphorylated cAMP response element-binding protein (pCREB) which increases the activity of Nrf-2. Additionally, caspase-3 expression/activity and BAX/Bcl-2 ratio were decreased following liraglutide pre-treatment. In conclusion, it was confirmed that liraglutide enhanced the antioxidant activity of liver cells by activating the Nrf-2 and pCREB signaling, thereby, reducing liver cell inflammation and apoptosis induced by MTX.

Adenosine monophosphate-activated protein kinase-based classification of diabetes pharmacotherapy

The current classification of both diabetes and antidiabetes medication is complex, preventing a treating physician from choosing the most appropriate treatment for an individual patient, sometimes resulting in patient-drug mismatch. We propose a novel, simple systematic classification of drugs, based on their effect on adenosine monophosphate-activated protein kinase (AMPK). AMPK is the master regular of energy metabolism, an energy sensor, activated when cellular energy levels are low, resulting in activation of catabolic process, and inactivation of anabolic process, having a beneficial effect on glycemia in diabetes. This listing of drugs makes it easier for students and practitioners to analyze drug profiles and match them with patient requirements. It also facilitates choice of rational combinations, with complementary modes of action. Drugs are classified as stimulators, inhibitors, mixed action, possible action, and no action on AMPK activity. Metformin and glitazones are pure stimulators of AMPK. Incretin-based therapies have a mixed action on AMPK. Sulfonylureas either inhibit AMPK or have no effect on AMPK. Glycemic efficacy of alpha-glucosidase inhibitors, sodium glucose co-transporter-2 inhibitor, colesevelam, and bromocriptine may also involve AMPK activation, which warrants further evaluation. Berberine, salicylates, and resveratrol are newer promising agents in the management of diabetes, having well-documented evidence of AMPK stimulation medicated glycemic efficacy. Hence, AMPK-based classification of antidiabetes medications provides a holistic unifying understanding of pharmacotherapy in diabetes. This classification is flexible with a scope for inclusion of promising agents of future.

Molecular mechanisms by which GLP-1 RA and DPP-4i induce insulin sensitivity

Glucagon-like peptide-1 is a peptide of incretin family which is used in the management of diabetes as glucagon-like peptide-1 receptor agonist (GLP-1RA). Dipeptidyl peptidase-4 enzyme metabolizes glucagon-like peptide-1 and various dipeptidyl peptidase-4 enzyme inhibitors (DPP-4i) are also used in the management of diabetes. These antidiabetic agents provide anti-hyperglycemic effects via several molecular mechanisms including promoting insulin secretion, suppression of glucagon secretion and slowing the gastric emptying. There is some research suggesting that they can induce insulin sensitivity in peripheral tissues. In this study, we review the possible molecular mechanisms by which GLP-1RA and DPP-4i can improve insulin resistance and increase insulin sensitivity in insulin-dependent peripheral tissues.

Liraglutide improves insulin sensitivity in high fat diet induced diabetic mice through multiple pathways

Glucagon like peptide-1 (GLP-1) promotes postprandial insulin secretion. Liraglutide, a full agonist of the GLP-1 receptor, reduces body weight, improve insulin sensitivity, and alleviate Non Alcoholic Fatty Liver Disease (NAFLD). However, the underlying mechanisms remain unclear. This study aims to explore the underlying mechanisms and cell signaling pathways involved in the anti-obesity and anti-inflammatory effects of liraglutide. Mice were fed a high fat high sucrose diet to induce diabetes, diabetic mice were divided into two groups and injected with liraglutide or vehicle for 14 days. Liraglutide treatment improved insulin sensitivity, accompanied with reduced expression of the phosphorylated Acetyl-CoA carboxylase-2 (ACC2) and upregulation of long chain acyl CoA dehydrogenase (LCAD) in insulin sensitive tissues. Furthermore, liraglutide induced adenosine monophosphate-activated protein kinase-α (AMPK-α) and Sirtuin-1(Sirt-1) protein expression in liver and perigonadal fat. Liraglutide induced elevation of fatty acid oxidation in these tissues may be mediated through the AMPK-Sirt-1 cell signaling pathway. In addition, liraglutide induced brown adipocyte differentiation in skeletal muscle, including induction of uncoupling protein-1 (UCP-1) and PR-domain-containing-16 (PRDM-16) protein in association with induction of SIRT-1. Importantly, liraglutide displayed anti-inflammation effect. Specifically, liraglutide led to a significant reduction in circulating interleukin-1 β (IL-1 β) and interleukin-6 (IL-6) as well as hepatic IL-1 β and IL-6 content. The expression of inducible nitric oxide synthase (iNOS-1) and cyclooxygenase-2 (COX-2) in insulin sensitive tissues was also reduced following liraglutide treatment. In conclusion, liraglutide improves insulin sensitivity through multiple pathways resulting in reduction of inflammation, elevation of fatty acid oxidation, and induction of adaptive thermogenesis.

Liraglutide Increases VEGF Expression via CNPY2-PERK Pathway Induced by Hypoxia/Reoxygenation Injury

Liraglutide (Lir) is a glucagon-like peptide-1 receptor agonist that lowers blood sugar and reduces myocardial infarct size by improving endothelial cell function. However, its mechanism has not yet been clarified. Unfolded protein response (UPR) plays an important role in the pathogenesis of myocardial ischemia-reperfusion injury. It determines the survival of cells. Endoplasmic reticulum position protein homologue 2 (CNPY2) is a novel initiator of UPR that also participates in angiogenesis. To this extent, the current study further explored whether Lir regulates angiogenesis through CNPY2. In our article, a hypoxia/reoxygenation (H/R) injury model of human umbilical vein endothelial cells (HUVECs) was established and the effect of Lir on HUVECs was first evaluated by the Cell Counting Kit-8. Endothelial tube formation was used to analyze the ability of Lir to induce angiogenesis. Subsequently, the effect of Lir on the concentrations of hypoxia-inducible factor 1α (HIF1α), vascular endothelial growth factor (VEGF), and CNPY2 was detected by enzyme-linked immunosorbent assay. To assess whether Lir regulates angiogenesis through the CNPY2-initiated UPR pathway, the expression of UPR-related pathway proteins (CNPY2, GRP78, PERK, and ATF4) and angiogenic proteins (HIF1α and VEGF) was detected by reverse transcription-polymerase chain reaction and Western blot. The results confirmed that Lir significantly increased the expression of HIF1α and VEGF as well as the expression of CNPY2-PERK pathway proteins in HUVECs after H/R injury. To further validate the experimental results, we introduced the PERK inhibitor GSK2606414. GSK2606414 was able to significantly decrease both the mRNA and protein expression of ATF4, HIF1α, and VEGF in vascular endothelial cells after H/R injury. The effect of Lir was also inhibited using GSK2606414. Therefore, our study suggested that the CNPY2-PERK pathway was involved in the mechanism of VEGF expression after H/R injury in HUVECs. Lir increased the expression of VEGF through the CNPY2-PERK pathway, which may promote endothelial cell angiogenesis and protect HUVEC from H/R damage.

Liraglutide Inhibits Endothelial-to-Mesenchymal Transition and Attenuates Neointima Formation after Endovascular Injury in Streptozotocin-Induced Diabetic Mice

Hyperglycaemia causes endothelial dysfunction, which is the initial process in the development of diabetic vascular complications. Upon injury, endothelial cells undergo an endothelial-to-mesenchymal transition (EndMT), lose their specific marker, and gain mesenchymal phenotypes. This study investigated the effect of liraglutide, a glucagon-like peptide 1 (GLP-1) receptor agonist, on EndMT inhibition and neointima formation in diabetic mice induced by streptozotocin. The diabetic mice with a wire-induced vascular injury in the right carotid artery were treated with or without liraglutide for four weeks. The degree of neointima formation and re-endothelialisation was evaluated by histological assessments. Endothelial fate tracing revealed that endothelium-derived cells contribute to neointima formation through EndMT in vivo. In the diabetic mouse model, liraglutide attenuated wire injury-induced neointima formation and accelerated re-endothelialisation. In vitro, a high glucose condition (30 mmol/L) triggered morphological changes and mesenchymal marker expression in human umbilical vein endothelial cells (HUVECs), which were attenuated by liraglutide or Activin receptor-like 5 (ALK5) inhibitor SB431542. The inhibition of AMP-activated protein kinase (AMPK) signaling by Compound C diminished the liraglutide-mediated inhibitory effect on EndMT. Collectively, liraglutide was found to attenuate neointima formation in diabetic mice partially through EndMT inhibition, extending the potential therapeutic role of liraglutide.

Antiatherogenic effects of liraglutide in hyperglycemic apolipoprotein E-null mice via AMP-activated protein kinase-independent mechanisms

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) exert potent glucose-lowering effects without increasing risks for hypoglycemia and weight gain. Preclinical studies have demonstrated direct antiatherogenic effects of GLP-1RAs in normoglycemic animal models; however, the underlying mechanisms in hyperglycemic conditions have not been fully clarified. Here we aimed to elucidate the role of AMP-activated protein kinase (AMPK) in antiatherogenic effects of GLP-1RAs in hyperglycemic mice. Streptozotocin-induced hyperglycemic apolipoprotein E-null mice were treated with vehicle, low-dose liraglutide (17 nmol·kg^-1·day^-1), or high-dose liraglutide (107 nmol·kg^-1·day^-1) in experiment 1 and the AMPK inhibitor dorsomorphin, dorsomorphin + low-dose liraglutide, or dorsomorphin + high-dose liraglutide in experiment 2. Four weeks after treatment, aortas were collected to assess atherosclerosis. In experiment 1, metabolic parameters were similar among the groups. Assessment of atherosclerosis revealed that high-dose liraglutide treatments reduced lipid deposition on the aortic surface and plaque volume and intraplaque macrophage accumulation at the aortic sinus. In experiment 2, liraglutide-induced AMPK phosphorylation in the aorta was abolished by dorsomorphin; however, the antiatherogenic effects of high-dose liraglutide were preserved. In cultured human umbilical vein endothelial cells, liraglutide suppressed tumor necrosis factor-induced expression of proatherogenic molecules; these effects were maintained under small interfering RNA-mediated knockdown of AMPKα1 and in the presence of dorsomorphin. Conversely, in human monocytic U937 cells, the anti-inflammatory effects of liraglutide were abolished by dorsomorphin. In conclusion, liraglutide exerted AMPK-independent antiatherogenic effects in hyperlipidemic mice with streptozotocin-induced hyperglycemia, with the possible involvement of AMPK-independent suppression of proatherogenic molecules in vascular endothelial cells.

Role of adipose tissue GLP-1R expression in metabolic improvement after bariatric surgery in patients with type 2 diabetes

We aimed to explore the relationship between GLP-1 receptor (GLP-1R) expression in adipose tissue (AT) and incretin secretion, glucose homeostasis and weight loss, in patients with morbid obesity and type 2 diabetes undergoing bariatric surgery. RNA was extracted from subcutaneous (SAT) and visceral (VAT) AT biopsies from 40 patients randomized to metabolic gastric bypass, sleeve gastrectomy or greater curvature plication. Biochemical parameters, fasting plasma insulin, glucagon and area under the curve (AUC) of GLP-1 following a standard meal test were determined before and 1 year after bariatric surgery. GLP-1R expression was higher in VAT than in SAT. GLP-1R expression in VAT correlated with weight (r = −0.453, p = 0.008), waist circumference (r = −0.494, p = 0.004), plasma insulin (r = −0.466, p = 0.007), and systolic blood pressure (BP) (r = −0.410, p = 0.018). At 1 year, GLP-1R expression in VAT was negatively associated with diastolic BP (r = −0.361, p = 0.039) and, following metabolic gastric bypass, with the increase of GLP-1 AUC, (R² = 0.46, p = 0.038). Finally, GLP-1R in AT was similar independently of diabetes outcomes and was not associated with weight loss after surgery. Thus, GLP-1R expression in AT is of limited value to predict incretin response and does not play a role in metabolic outcomes after bariatric surgery.

Glucagon-like peptide-1 receptor activation alleviates lipopolysaccharide-induced acute lung injury in mice via maintenance of endothelial barrier function

Glucagon-like peptide-1 (GLP-1), which is well known for regulating glucose homeostasis, exhibits multiple actions in cardiovascular disorders and renal injury. However, little is known about the effect of GLP-1 receptor (GLP-1R) activation on acute lung injury (ALI). In this study, we investigated the effect of GLP-1R on ALI and the potential underlying mechanisms with the selective agonist liraglutide. Our results show that GLP-1 levels decreased in serum, though they increased in bronchoalveolar lavage fluid (BALF) and lung tissue in a mouse model of lipopolysaccharide (LPS)-induced ALI. Liraglutide prevented LPS-induced polymorphonuclear neutrophil (PMN) extravasation, lung injury, and alveolar-capillary barrier dysfunction. In cultured human pulmonary microvascular endothelial cells (HPMECs), liraglutide protected against LPS-induced endothelial barrier injury by restoring intercellular tight junctions and adherens junctions. Moreover, liraglutide prevented PMN-endothelial adhesion by inhibiting the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), and thereafter suppressed PMN transendothelial migration. Furthermore, liraglutide suppressed LPS-induced activation of Rho/NF-κB signaling in HPMECs. In conclusion, our results show that GLP-1R activation protects mice from LPS-induced ALI by maintaining functional endothelial barrier and inhibiting PMN extravasation. These results also suggest that GLP-1R may be a potential therapeutic target for the treatment of ALI.

AMPK is associated with the beneficial effects of antidiabetic agents on cardiovascular diseases

Diabetics have higher morbidity and mortality in cardiovascular disease (CVD). A variety of antidiabetic agents are available for clinical choice. Cardiovascular (CV) safety assessment of these agents is crucial in addition to hypoglycemic effect before clinical prescription. Adenosine 5'-monophosphate-activated protein kinase (AMPK) is an important cell energy sensor, which plays an important role in regulating myocardial energy metabolism, reducing ischemia and ischemia/reperfusion (I/R) injury, improving heart failure (HF) and ventricular remodeling, ameliorating vascular endothelial dysfunction, antichronic inflammation, anti-apoptosis, and regulating autophagy. In this review, we summarized the effects of antidiabetic agents to CVD according to basic and clinical research evidence and put emphasis on whether these agents can play roles in CV system through AMPK-dependent signaling pathways. Metformin has displayed definite CV benefits related to AMPK. Sodium-glucose cotransporter 2 inhibitors also demonstrate sufficient clinical evidence for CV protection, but the mechanisms need further exploration. Glucagon-likepeptide1 analogs, dipeptidyl peptidase-4 inhibitors, α-glucosidase inhibitors and thiazolidinediones also show some AMPK-dependent CV benefits. Sulfonylureas and meglitinides may be unfavorable to CV system. AMPK is becoming a promising target for the treatment of diabetes, metabolic syndrome and CVD. But there are still some questions to be answered.

The effect of DPP-4-protected GLP-1 (7-36) on coronary microvascular function in obese adults

Objective

Glucagon-like-peptide-1 (GLP-1) receptor analogues have been shown to reduce cardiovascular events in patients with type 2 diabetes. However, the mechanism behind is still unknown. The aim of the study was to investigate the effect of intact GLP-1 (7-36) on coronary microcirculation in overweight adults.

Design and methods

A double-blinded randomized cross-over study was performed, with 12 overweight participants. Effects of intact GLP-1 (7-36) infusion were compared with a saline infusion on separate days. A DPP-4 inhibitor was administered to block degradation of intact GLP-1 (7-36) to the GLP-1 metabolite (9-36). Coronary microcirculation was assessed by Doppler coronary flow velocity reserve (CFVR) before and after 2 h of infusion. Peripheral endothelial function was assessed by flow mediated dilation (FMD) before and after one hour of infusion.

Results

CFVR was 3.77 ± 1.25 during GLP-1 infusion and 3.85 ± 1.32 during saline infusion, endothelial function was 16.3 ± 15.5 % during GLP-1 infusion and 7.85 ± 7.76 % during saline infusion. When adjusting for baseline values no significant differences in CFVR (ΔCFVR 0.38 ± 0.92 vs. ΔCFVR 0.71 ± 1.03, p = 0.43) and no difference in peripheral endothelial function (ΔFMD 7.34 ± 11.5 % vs. ΔFMD -1.25 ± 9.23%, p = 0.14) was found.

Conclusions

We found no effect of intact GLP-1 (7-36), protected from DPP4 mediated degradation on coronary microcirculation in overweight adults.

A review of the anti-inflammatory properties of antidiabetic agents providing protective effects against vascular complications in diabetes

The global prevalence of Type 2 diabetes mellitus and its associated complications are growing rapidly. Although the role of hyperglycemia is well recognized in the pathophysiology of diabetic complications, its exact underlying mechanisms are not fully understood. In this regard, accumulating evidence suggests that the role of inflammation appears pivotal, with studies showing that most diabetic complications are associated with an inflammatory response. Several classes of antidiabetic agents have been introduced for controlling glycemia, with evidence that these pharmacological agents may have modulatory effects on inflammation beyond their glucose-lowering activity. Here we review the latest evidence on the anti-inflammatory effects of commonly used antidiabetic medications and discuss the relevance of these effects on preventing diabetic complications.

Multiple target tissue effects of GLP-1 analogues on non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH)

Accumulating experimental and clinical evidences over the last decade indicate that GLP-1 analogues have a series of central nervous system and peripheral target tissues actions which are able to significantly influence the liver metabolism. GLP-1 analogues pleiotropic effects proved to be efficacious in T2DM subjects not only reducing liver steatosis and ameliorating NAFLD and NASH, but also in lowering plasma glucose and liver inflammation, improving cardiac function and protecting from kidney dysfunction. While the experimental and clinical data are robust, the precise mechanisms of action potentially involved in these protective multi-target effects need further investigation. Here we present a systematic review of the most recent literature data on the multi-target effects of GLP-1 analogues on the liver, on adipose and muscular tissue and on the nervous system, all capable of influencing significant aspects of the fatty liver disease physiopathology. From this analysis, we can conclude that the multi-target beneficial action of the GLP-1 analogues could explain the positive effects observed in animal and human models on progression of NAFLD to NASH.

Liraglutide Treatment Reduces Endothelial Endoplasmic Reticulum Stress and Insulin Resistance in Patients With Diabetes Mellitus

Background Prior studies have shown that nutrient excess induces endoplasmic reticulum ( ER ) stress in nonvascular tissues from patients with diabetes mellitus ( DM ). ER stress and the subsequent unfolded protein response may be protective, but sustained activation may drive vascular injury. Whether ER stress contributes to endothelial dysfunction in patients with DM remains unknown. Methods and Results To characterize vascular ER stress, we isolated endothelial cells from 42 patients with DM and 37 subjects without DM. Endothelial cells from patients with DM displayed higher levels of ER stress markers compared with controls without DM. Both the early adaptive response, evidenced by higher phosphorylated protein kinase-like ER eukaryotic initiation factor-2a kinase and inositol-requiring ER-to-nucleus signaling protein 1 ( P=0.02, P=0.007, respectively), and the chronic ER stress response evidenced by higher C/ EBP α-homologous protein ( P=0.02), were activated in patients with DM . Higher inositol-requiring ER-to-nucleus signaling protein 1 activation was associated with lower flow-mediated dilation, consistent with endothelial dysfunction ( r=0.53, P=0.02). Acute treatment with liraglutide, a glucagon-like peptide 1 receptor agonist, reduced p-inositol-requiring ER-to-nucleus signaling protein 1 ( P=0.01), and the activation of its downstream target c-jun N-terminal kinase ( P=0.025) in endothelial cells from patients with DM . Furthermore, liraglutide restored insulin-stimulated endothelial nitric oxide synthase activation in patients with DM ( P=0.019). Conclusions In summary, our data suggest that ER stress contributes to vascular insulin resistance and endothelial dysfunction in patients with DM . Further, we have demonstrated that liraglutide ameliorates ER stress, decreases c-jun N-terminal kinase activation and restores insulin-mediated endothelial nitric oxide synthase activation in endothelial cells from patients with DM .

Hypothalamic AMPK and energy balance

AMP-activated protein kinase (AMPK) is the main cellular energy sensor. Activated following a depletion of cellular energy stores, AMPK will restore the energy homoeostasis by increasing energy production and limiting energy waste. At a central level, the AMPK pathway will integrate peripheral signals (mostly hormones and metabolites) through neuronal networks. Hypothalamic AMPK is directly implicated in feeding behaviour, brown adipose tissue (BAT) thermogenesis and browning of white adipose tissue (WAT). It also participates in other metabolic functions: glucose and muscle metabolisms, as well as hepatic function. Numerous anti-obesity and/or antidiabetic agents, such as nicotine, metformin and liraglutide, are known to induce their effects through a modulation of AMPK pathway, either at central or at peripheral levels. Moreover, the weight-gaining side effects of antipsychotic drugs, such as olanzapine, are also mediated by hypothalamic AMPK. Therefore, considering hypothalamic AMPK as a therapeutic target in metabolic diseases appears as an interesting strategy due to its implication in feeding and energy expenditure, the two sides of the energy balance equation.

Glycogen Metabolism and Rheumatoid Arthritis: The Role of Glycogen Synthase 1 in Regulation of Synovial Inflammation via Blocking AMP-Activated Protein Kinase Activation

Objective

To investigate the role of glycogen metabolism in regulating rheumatoid fibroblast-like synoviocyte (FLS)-mediated synovial inflammation and its underlying mechanism.

Methods

FLSs were separated from synovial tissues (STs) obtained from rheumatoid arthritis (RA) patients. Glycogen content was determined by periodic acid Schiff staining. Protein expression was analyzed by Western blot or immunohistochemistry. Gene expression of cytokines and matrix metalloproteinases (MMPs) was evaluated by quantitative real-time PCR. FLS proliferation was detected by EdU incorporation. Migration and invasion were measured by Boyden chamber assay.

Results

Glycogen levels and glycogen synthase 1 (GYS1) expression were significantly increased in the ST and FLSs of RA patients. TNF-α or hypoxia induced GYS1 expression and glycogen synthesis in RA FLSs. GYS1 knockdown by shRNA decreased the expression of IL-1β, IL-6, CCL-2, MMP-1, and MMP-9 and proliferation and migration by increasing AMP-activated protein kinase (AMPK) activity in RA FLS. AMPK inhibitor or knockdown AMPK could reverse the inhibitory effect of GYS1 knockdown on the inflammatory response in RA FLSs; however, an AMPK agonist blocked RA FLS activity. We further determined that hypoxia-inducible factor-1α mediates TNF-α- or hypoxia-induced GYS1 expression and glycogen levels. Local joint depletion of GYS1 or intraperitoneal administration with an AMPK agonist ameliorated the severity of arthritis in rats with collagen-induced arthritis.

Conclusion

Our data demonstrate that GYS1-mediated glycogen accumulation contributes to FLS-mediated synovial inflammation in RA by blocking AMPK activation. In our knowledge, this is a first study linking glycogen metabolism to chronic inflammation. Inhibition of GYS1 might be a novel therapeutic strategy for chronic inflammatory arthritis, including RA.

After the LEADER trial and SUSTAIN-6, how do we explain the cardiovascular benefits of some GLP-1 receptor agonists?

Recent cardiovascular outcome trials - the LEADER with liragutide and SUSTAIN-6 with semaglutide - have shown significant reductions of major cardiovascular (CV) events with these glucagon-like peptide (GLP)-1 receptor agonists. Progressive separation of the treatment and placebo curves, starting clearly between 12 and 18 months of the trial period, and significant reductions in the risk of myocardial infarction and stroke, indicate that the beneficial CV effects observed with GLP-1 receptor agonists could be due to an antiatherogenic effect. So far, the reasons for such an effect of GLP-1 receptor agonists have not been entirely clear, although several hypotheses may be proposed. As the reductions in glycated haemoglobin and systolic blood pressure (SBP) in these trials were modest, and both trials lasted only a short period of time, reductions in hyperglycaemia and SBP are unlikely to be involved in the beneficial CV effects of GLP-1 receptor agonists. On the other hand, their effect on lipids and, in particular, the dramatic decrease in postprandial hypertriglyceridaemia may explain their beneficial CV actions. Reduction of body weight, including a significant decrease in visceral fat in patients using GLP-1 receptor agonists, may also have beneficial CV effects by reducing chronic proatherogenic inflammation. In addition, there are in-vitro data showing a direct anti-inflammatory effect with these agents that could also be involved in their beneficial CV effects. Moreover, studies in humans have shown significant beneficial effects on ischaemic myocardium after a very short treatment period, suggesting a direct effect of GLP-1 receptor agonists on myocardium, although the precise mechanism remains unclear. Finally, as a reduction in insulin resistance has been associated with a decrease in CV risk, it cannot be ruled out that the lowering of insulin resistance induced by GLP-1 receptor agonists might also be involved in their beneficial CV actions.

Molecular Mechanisms Underlying the Cardiovascular Benefits of SGLT2i and GLP-1RA

PURPOSE OF REVIEW

In addition to their effects on glycemic control, two specific classes of relatively new anti-diabetic drugs, namely the sodium glucose co-transporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP-1RA) have demonstrated reduced rates of major adverse cardiovascular events (MACE) in subjects with type 2 diabetes (T2D) at high risk for cardiovascular disease (CVD). This review summarizes recent experimental results that inform putative molecular mechanisms underlying these benefits.

RECENT FINDINGS

SGLT2i and GLP-1RA exert cardiovascular effects by targeting in both common and distinctive ways (A) several mediators of macro- and microvascular pathophysiology: namely (A1) inflammation and atherogenesis, (A2) oxidative stress-induced endothelial dysfunction, (A3) vascular smooth muscle cell reactive oxygen species (ROS) production and proliferation, and (A4) thrombosis. These agents also exhibit (B) hemodynamic effects through modulation of (B1) natriuresis/diuresis and (B2) the renin-angiotensin-aldosterone system. This review highlights that while GLP-1RA exert direct effects on vascular (endothelial and smooth muscle) cells, the effects of SGLT2i appear to include the activation of signaling pathways that prevent adverse vascular remodeling. Both SGLT2i and GLP-1RA confer hemodynamic effects that counter adverse cardiac remodeling.

Molecular and clinical roles of incretin-based drugs in patients with heart failure

Glucagon-like peptide-1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors produce some beneficial and deleterious effects in diabetic patients not mediated by their glycemic lowering effects, and there is a need for better understanding of the molecular basis of these effects. They possess antioxidant and anti-inflammatory effects with some direct vasodilatory action (animal and human trial data) that may indirectly influence heart failure (HF). Unlike GLP-1R agonists, signaling for HF adverse effects was observed with two DPP-4 inhibitors, saxagliptin and alogliptin. Accordingly, these drugs should be used with caution in heart failure patients.

Liraglutide suppresses non-esterified free fatty acids and soluble vascular cell adhesion molecule-1 compared with metformin in patients with recent-onset type 2 diabetes

Background

It has been suggested that liraglutide could have an impact on glucose and lipid metabolism disorder and adhesion molecule activation, which may play important roles in the vascular damage of diabetes. In this study, we examined the effects of liraglutide versus metformin on non-esterified free fatty acids, beta-cell insulin secretion, and adhesion molecule levels in patients with recent-onset type 2 diabetes mellitus.

Methods

In this study, 60 patients newly diagnosed with type 2 diabetes mellitus (mean age 33.97 ± 5.67 years) were randomly assigned to receive once-daily subcutaneous liraglutide or oral metformin. Before the study and after the 8-week treatment period, a 75 g oral glucose tolerance test was performed. Plasma glucose, lipids and lipoprotein, plasma insulin, glycaemic and insulin responses, non-esterified free fatty acids (NEFA), and soluble vascular cell adhesion molecule-1 (sVCAM-1) levels were evaluated.

Results

After 8 weeks, 120 min of NEFA (155 ± 125 vs 99 ± 73 µmol/L, P = 0.026) and the levels of sVCAM-1 (465 ± 136 vs 382 ± 131 ng/ml, P = 0.013) significantly decreased, while the early phase insulin secretion index (24.94 [7.78, 38.89] vs. 31.13 [17.67, 59.09], P = 0.031), fasting plasma insulin (104 [51, 123] vs 113 [54, 171] mIU/L, P = 0.015), 60 min plasma insulin (326 [165, 441] vs 471 [334, 717] mIU/L, P = 0.005), 120 min plasma insulin (401 [193, 560] vs 500 [367, 960] mIU/L, P = 0.047), and insulin area under the curve (AUCins) (648 [321, 742] vs 738 [451, 1118] mIU/L, P = 0.005) remarkably increased for patients in the liraglutide treatment group. The levels of sVCAM-1 dramatically decreased after 8 weeks of liraglutide treatment (503 ± 182 vs 382 ± 131 ng/ml, P = 0.046) compared to that of the metformin treatment group. At the same time, the differences before and after liraglutide treatment in 120 min of NEFA (− 32 [− 96, − 5] vs 5 [− 35, 38] µmol/L, P = 0.033) and AUCins (738 [451, 1118] vs 594 [357, 1216] mIU/L, P = 0.014) were remarkably enhanced compared to that of the metformin therapy. Nevertheless, there were no significant differences in fasting NEFA after liraglutide or metformin treatment. The reduction of 120 min NEFA (ΔNEFA) was positively correlated with the decrease of sVCAM-1 (ΔsVCAM-1) after 8 weeks of liraglutide treatment (r = 0.523, P = 0.003).

Conclusions

Our results demonstrate that liraglutide administration is more effective than metformin in reducing 120 min NEFA and suppressing sVCAM-1 levels for recent-onset type 2 diabetes mellitus. We suggest that this outcome may be because liraglutide is associated with potentiating insulin secretion capacity, inhibiting vascular inflammatory cytokines, and antagonizing atherosclerosis.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0701-4) contains supplementary material, which is available to authorized users.

Modulation of GLP-1 Levels by a Genetic Variant That Regulates the Cardiovascular Effects of Intensive Glycemic Control in ACCORD

OBJECTIVE

A genome-wide association study in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial identified two markers (rs57922 and rs9299870) that were significantly associated with cardiovascular mortality during intensive glycemic control and could potentially be used, when combined into a genetic risk score (GRS), to identify patients with diabetes likely to derive benefit from intensive control rather than harm. The aim of this study was to gain insights into the pathways involved in the modulatory effect of these variants.

RESEARCH DESIGN AND METHODS

Fasting levels of 65 biomarkers were measured at baseline and at 12 months of follow-up in the ACCORD-Memory in Diabetes (ACCORD-MIND) MRI substudy (n = 562). Using linear regression models, we tested the association of the GRS with baseline and 12-month biomarker levels, and with their difference (Δ), among white subjects, with genotype data (n = 351) stratified by intervention arm.

RESULTS

A significant association was observed between GRS and ΔGLP-1 (glucagon-like peptide 1, active) in the intensive arm (P = 3 × 10-4). This effect was driven by rs57922 (P = 5 × 10-4). C/C homozygotes, who had been found to derive cardiovascular benefits from intensive treatment, showed a 22% increase in GLP-1 levels during follow-up. By contrast, T/T homozygotes, who had been found to experience increased cardiac mortality with intensive treatment, showed a 28% reduction in GLP-1 levels. No association between ΔGLP-1 and GRS or rs57922 was observed in the standard treatment arm.

CONCLUSIONS

Differences in GLP-1 axis activation may mediate the modulatory effect of variant rs57922 on the cardiovascular response to intensive glycemic control. These findings highlight the importance of GLP-1 as a cardioprotective factor.

Exenatide exhibits anti-inflammatory properties and modulates endothelial response to tumor necrosis factor α-mediated activation

INTRODUCTION

Cardiovascular disease is the main cause of mortality and morbidity in the industrialized world. Incretin-mimetic compounds such as exenatide are currently used in the treatment of type 2 diabetes.

AIMS

We investigated the effects of incretin drugs on apoptosis, adhesion molecule expression, and concentration of extracellular matrix (ECM) metalloproteinases under inflammatory conditions within the context of atherosclerotic plaque formation of both human coronary artery endothelial cells (hCAECs) and human aortic endothelial cells (hAoECs). TNF-α-stimulated hCAEC and hAoEC were treated with exenatide (1 and 10 nmol/L) and GLP-1 (10 and 100 nmol/L) then evaluated for caspase 3/7 activity and assayed for protein levels of adhesion molecules sICAM-1, sVCAM-1, and P-selectin. Concentrations of matrix metalloproteinases (MMPs) MMP-1, MMP-2, MMP-9, and their inhibitors-tissue inhibitor of metalloproteinases (TIMPs), TIMP-1, TIMP-2 were also measured to evaluate the effects on extracellular matrix turnover within an inflammatory environment. Intracellular signaling pathways were evaluated via transfection of endothelial cells with a GFP vector under the NF-κB promoter.

RESULTS

Our experimental data suggest that GLP-1 receptor (GLP-1R) agonists downregulate activation of NF-κB and adhesion molecules ICAM and VCAM, but not P-selectin, in both endothelial cell lines. Exendin-4 and GLP-1 modulate the expression of MMPs and TIMPs, with statistically significant effects observed at high concentrations of both incretins. Expressive modulation may be mediated by NF-κB as observed by activation of the vector when stimulated under inflammatory conditions.

CONCLUSION

These findings indicate that GLP-1 analogs have anti-inflammatory properties in endothelial cells that may play an important role in preventing atherosclerosis.

Effect of liraglutide on dietary lipid-induced insulin resistance in humans

AIMS

To test whether liraglutide suppresses postprandial elevations in lipids and thus protects against high saturated fatty acid (SFA) diet-induced insulin resistance.

METHODS

In a randomized placebo-controlled crossover study, 32 participants with normal or mildly impaired glucose tolerance received liraglutide and placebo for 3 weeks each. Insulin suppression tests (IST) were conducted at baseline and after a 24-hour SFA-enriched diet after each treatment. Plasma glucose, insulin, triglycerides and non-esterified fatty acids (NEFA) were measured over the initial 8 hours (breakfast and lunch) on the SFA diet. A subset of participants underwent ex vivo measurements of insulin-mediated vasodilation of adipose tissue arterioles and glucose metabolism regulatory proteins in skeletal muscle.

RESULTS

Liraglutide reduced plasma glucose, triglycerides and NEFA concentrations during the SFA diet (by 50%, 25% and 9%, respectively), and the SFA diet increased plasma glucose during the IST (by 36%; all P < .01 vs placebo). The SFA diet-induced impairment of vasodilation on placebo (-9.4% vs baseline; P < .01) was ameliorated by liraglutide (-4.8%; P = .1 vs baseline). In skeletal muscle, liraglutide abolished the SFA-induced increase in thioredoxin-interacting protein (TxNIP) expression (75% decrease; P < .01 vs placebo) and increased 5'AMP-activated protein kinase (AMPK) phosphorylation (50% vs -3%; P = .04 vs placebo).

CONCLUSIONS

Liraglutide blunted the SFA-enriched diet-induced peripheral insulin resistance. This effect may be related to improved microvascular function and modulation of TxNIP and AMPK pathways in skeletal muscle.

Liraglutide dictates macrophage phenotype in apolipoprotein E null mice during early atherosclerosis

BACKGROUND

Macrophages play a pivotal role in atherosclerotic plaque development. Recent evidence has suggested the glucagon-like peptide-1 receptor (GLP-1R) agonist, liraglutide, can attenuate pro-inflammatory responses in macrophages. We hypothesized that liraglutide could limit atherosclerosis progression in vivo via modulation of the inflammatory response.

METHODS

Human THP-1 macrophages and bone marrow-derived macrophages, from both wild-type C57BL/6 (WT) and apolipoprotein E null mice (ApoE-/-) were used to investigate the effect of liraglutide on the inflammatory response in vitro. In parallel, ApoE-/- mice were fed a high-fat (60% calories from fat) high-cholesterol (1%) diet for 8 weeks to induce atherosclerotic disease progression with/without daily 300 μg/kg liraglutide administration for the final 6 weeks. Macrophages were analysed for MΦ1 and MΦ2 macrophage markers by Western blotting, RT-qPCR, ELISA and flow cytometry. Atherosclerotic lesions in aortae from ApoE-/- mice were analysed by en face staining and monocyte and macrophage populations from bone marrow derived cells analysed by flow cytometry.

RESULTS

Liraglutide decreased atherosclerotic lesion formation in ApoE-/- mice coincident with a reduction in pro-inflammatory and increased anti-inflammatory monocyte/macrophage populations in vivo. Liraglutide decreased IL-1beta in MΦ0 THP-1 macrophages and bone marrow-derived macrophages from WT mice and induced a significant increase in the MΦ2 surface marker mannose receptor in both MΦ0 and MΦ2 macrophages. Significant reduction in total lesion development was found with once daily 300 μg/kg liraglutide treatment in ApoE-/- mice. Interestingly, liraglutide inhibited disease progression at the iliac bifurcation suggesting that it retards the initiation and development of disease. These results corresponded to attenuated MΦ1 markers (CCR7, IL-6 and TNF-alpha), augmented MΦ2 cell markers (Arg-1, IL-10 and CD163) and finally decreased MΦ1-like monocytes and macrophages from bone marrow-derived cells.

CONCLUSIONS

This data supports a therapeutic role for liraglutide as an atheroprotective agent via modulating macrophage cell fate towards MΦ2 pro-resolving macrophages.

Liraglutide mitigates TNF-α induced pro-atherogenic changes and microvesicle release in HUVEC from diabetic women

BACKGROUND

To evaluate whether exposure to GLP-1 receptor agonist Liraglutide could modulate pro-atherogenic alterations previously observed in endothelial cells obtained by women affected by gestational diabetes (GD), thus exposed in vivo to hyperglycemia, oxidative stress, and inflammation and to evaluate endothelial microvesicle (EMV) release, a new reliable biomarker of vascular stress/damage.

METHODS

We studied Liraglutide effects and its plausible molecular mechanisms on monocyte cell adhesion and adhesion molecule expression and membrane exposure in control (C-) human umbilical vein endothelial cells (HUVEC) as well as in HUVEC of women affected by GD exposed in vitro to TNF-α. In the same model, we also investigated Liraglutide effects on EMV release.

RESULTS

In response to TNF-α, endothelial monocyte adhesion and VCAM-1 and ICAM-1 expression and exposure on plasma membrane was greater in GD-HUVEC than C-HUVEC. This was the case also for EMV release. In GD-HUVEC, Liraglutide exposure significantly reduced TNF-α induced endothelial monocyte adhesion as well as VCAM-1 and ICAM-1 expression and exposure on plasma membrane. In the same cells, Liraglutide exposure also reduced MAPK/NF-kB activation, peroxynitrite levels, and EMV release.

CONCLUSIONS

TNF-α induced pro-atherogenic alterations are amplified in endothelial cells chronically exposed to hyperglycemia in vivo. Liraglutide mitigates TNF-α effects and reduces cell stress/damage indicators, such as endothelial microvesicle (EMV) release. These results foster the notion that Liraglutide could exert a protective effect against hyperglycemia and inflammation triggered endothelial dysfunction.

The GLP-1 analogue lixisenatide decreases atherosclerosis in insulin-resistant mice by modulating macrophage phenotype

AIMS/HYPOTHESIS

Recent clinical studies indicate that glucagon-like peptide-1 (GLP-1) analogues prevent acute cardiovascular events in type 2 diabetes mellitus but their mechanisms remain unknown. In the present study, the impact of GLP-1 analogues and their potential underlying molecular mechanisms in insulin resistance and atherosclerosis are investigated.

METHODS

Atherosclerosis development was evaluated in Apoe ^-/- Irs2 ^+/- mice, a mouse model of insulin resistance, the metabolic syndrome and atherosclerosis, treated with the GLP-1 analogues lixisenatide or liraglutide. In addition, studies in Apoe ^-/- Irs2 ^+/- mice and mouse-derived macrophages treated with lixisenatide were performed to investigate the potential inflammatory intracellular pathways.

RESULTS

Treatment of Apoe ^-/- Irs2 ^+/- mice with either lixisenatide or liraglutide improved glucose metabolism and blood pressure but this was independent of body weight loss. Both drugs significantly decreased atheroma plaque size. Compared with vehicle-treated control mice, lixisenatide treatment generated more stable atheromas, with fewer inflammatory infiltrates, reduced necrotic cores and thicker fibrous caps. Lixisenatide-treated mice also displayed diminished IL-6 levels, proinflammatory Ly6C^high monocytes and activated T cells. In vitro analysis showed that, in macrophages from Apoe ^-/- Irs2 ^+/- mice, lixisenatide reduced the secretion of the proinflammatory cytokine IL-6 accompanied by enhanced activation of signal transducer and activator of transcription (STAT) 3, which is a determinant for M2 macrophage differentiation. STAT1 activation, which is essential for M1 phenotype, was also diminished. Furthermore, atheromas from lixisenatide-treated mice showed higher arginase I content and decreased expression of inducible nitric oxide synthase, indicating the prevalence of the M2 phenotype within plaques.

CONCLUSIONS/INTERPRETATION

Lixisenatide decreases atheroma plaque size and instability in Apoe ^-/- Irs2 ^+/- mice by reprogramming macrophages towards an M2 phenotype, which leads to reduced inflammation. This study identifies a critical role for this drug in macrophage polarisation inside plaques and provides experimental evidence supporting a novel mechanism of action for GLP-1 analogues in the reduction of cardiovascular risk associated with insulin resistance.

Glucagon and glucagon-like peptide-1 as novel anti-inflammatory and immunomodulatory compounds

Glucagon and glucagon-like peptide-1 (GLP-1) are polypeptide hormones that are produced by pancreatic α-cells and the intestine, respectively, whose main function is to control glucose homeostasis. The glucagon and GLP-1 levels are imbalanced in diabetes. Furthermore, type 1 diabetic patients and animals present with a diminished inflammatory response, which is related to some morbidities of diabetes, such as a higher incidence of infectious diseases, including sepsis. The focus of this review is to briefly summarize the state of the art concerning the effects of glucagon and GLP-1 on the inflammatory response. Here, we propose that glucagon and GLP-1 have anti-inflammatory properties, making them possible prototypes for the design and synthesis of new compounds to treat inflammatory diseases. In addition, glucagon, GLP-1 or their analogues or new derivatives may not only be important for managing inflammatory diseases but may also have the therapeutic potential to prevent, cure or ameliorate diabetes in patients by counteracting the deleterious effects of pro-inflammatory cytokines on the function and viability of pancreatic β-cells. In addition, GLP-1, its analogues or drugs that inhibit GLP-1 metabolism may have a doubly beneficial effect in diabetic patients by inhibiting the inflammatory response and reducing glycaemia.

Molecular mechanisms of appetite and obesity: a role for brain AMPK

Feeding behaviour and energy storage are both crucial aspects of survival. Thus, it is of fundamental importance to understand the molecular mechanisms regulating these basic processes. The AMP-activated protein kinase (AMPK) has been revealed as one of the key molecules modulating energy homoeostasis. Indeed, AMPK appears to be essential for translating nutritional and energy requirements into generation of an adequate neuronal response, particularly in two areas of the brain, the hypothalamus and the hindbrain. Failure of this physiological response can lead to energy imbalance, ultimately with extreme consequences, such as leanness or obesity. Here, we will review the data that put brain AMPK in the spotlight as a regulator of appetite.

Glucagon-Like Peptide 1 Receptor: A Novel Pharmacological Target for Treating Human Bronchial Hyperresponsiveness

Asthma is associated with several comorbidities, such as type 2 diabetes mellitus, which may lead to bronchial hyperresponsiveness (BHR). Because glucagon-like peptide (GLP) 1 regulates glucose homeostasis, we pharmacologically investigated the influence of the GLP1 receptor (GLP1-R) agonist, exendin-4, on BHR induced in human isolated airways. The effect of exendin-4 was assessed in human isolated airways undergoing overnight passive sensitization and high-glucose stimulation, two conditions mimicking ex vivo the BHR typical of patients with asthma and diabetes, respectively. GLP1-R activation modulated the bronchial contractile tone induced by transmural stimulation (maximum effect -56.7 ± 3.6%; onset of action, 28.2 ± 4.4 min). Exendin-4 prevented BHR induced by both high-glucose stimulation and passive sensitization (-37.8 ± 7.5% and -74.9 ± 3.9%, P < 0.05 versus control, respectively) through selective activation of GLP1-R and in an epithelium-independent manner. The cAMP-dependent protein kinase A inhibitor, KT5720, reduced the protective role of exendin-4 (P > 0.05 versus passively sensitized tissues). The GLP1-R stimulation by overnight incubation with exendin-4 induced the overexpression of adenylyl cyclase isoform V (+48.4 ± 1.3%, P < 0.05 versus passively sensitized tissues) and restored the cAMP levels depleted by this procedure (+330.8 ± 63.3%, P < 0.05 versus passively sensitized tissues). In conclusion, GLP1-R may represent a novel target for treating BHR by activating the cAMP-dependent protein kinase A pathway in human airways, and GLP1-R agonists could be used as a "new" class to treat patients with asthma and patients with type 2 diabetes mellitus with BHR.

AMP-Activated Protein Kinase: An Ubiquitous Signaling Pathway With Key Roles in the Cardiovascular System

The AMP-activated protein kinase (AMPK) is a key regulator of cellular and whole-body energy homeostasis, which acts to restore energy homoeostasis whenever cellular energy charge is depleted. Over the last 2 decades, it has become apparent that AMPK regulates several other cellular functions and has specific roles in cardiovascular tissues, acting to regulate cardiac metabolism and contractile function, as well as promoting anticontractile, anti-inflammatory, and antiatherogenic actions in blood vessels. In this review, we discuss the role of AMPK in the cardiovascular system, including the molecular basis of mutations in AMPK that alter cardiac physiology and the proposed mechanisms by which AMPK regulates vascular function under physiological and pathophysiological conditions.

EJE PRIZE 2017: Hypothalamic AMPK: a golden target against obesity?

AMP-activated protein kinase (AMPK) is a cellular gauge that is activated under conditions, such as low energy, increasing energy production and reducing energy waste. Centrally, the AMPK pathway is a canonical route regulating energy homeostasis, by integrating peripheral signals, such as hormones and metabolites, with neuronal networks. Current evidence links hypothalamic AMPK with feeding, brown adipose tissue (BAT) thermogenesis and browning of white adipose tissue (WAT), as well as muscle metabolism, hepatic function and glucose homeostasis. The relevance of these data is interesting from a therapeutic point of view as several agents with potential anti-obesity and/or antidiabetic effects, some currently in clinical use, such as nicotine, metformin and liraglutide are known to act through AMPK, either peripherally or centrally. Furthermore, the orexigenic and weight-gaining effects of the worldwide use of antipsychotic drugs (APDs), such as olanzapine, are also mediated by hypothalamic AMPK. Overall, this evidence makes hypothalamic AMPK signaling an interesting target for the drug development, with its potential for controlling both sides of the energy balance equation, namely feeding and energy expenditure through defined metabolic pathways.

Targeting endothelial metaflammation to counteract diabesity cardiovascular risk: Current and perspective therapeutic options

The association of obesity and diabetes, termed "diabesity", defines a combination of primarily metabolic disorders with insulin resistance as the underlying common pathophysiology. Cardiovascular disorders associated with diabesity represent the leading cause of morbidity and mortality in the Western world. This makes diabesity, with its rising impacts on both health and economics, one of the most challenging biomedical and social threats of present century. The emerging comprehension of the genes whose alteration confers inter-individual differences on risk factors for diabetes or obesity, together with the potential role of genetically determined variants on mechanisms controlling responsiveness, effectiveness and safety of anti-diabetic therapy underlines the need of additional knowledge on molecular mechanisms involved in the pathophysiology of diabesity. Endothelial cell dysfunction, resulting from the unbalanced production of endothelial-derived vascular mediators, is known to be present at the earliest stages of insulin resistance and obesity, and may precede the clinical diagnosis of diabetes by several years. Once considered as a mere consequence of metabolic abnormalities, it is now clear that endothelial dysfunctional activity may play a pivotal role in the progression of diabesity. In the vicious circle where vascular defects and metabolic disturbances worsen and reinforce each other, a low-grade, chronic, and 'cold' inflammation (metaflammation) has been suggested to serve as the pathophysiological link that binds endothelial and metabolic dysfunctions. In this paradigm, it is important to consider how traditional antidiabetic treatments (specifically addressing metabolic dysregulation) may directly impact on inflammatory processes or cardiovascular function. Indeed, not all drugs currently available to treat diabetes possess the same anti-inflammatory potential, or target endothelial cell function equally. Perspective strategies pointing at reducing metaflammation or directly addressing endothelial dysfunction may disclose beneficial consequences on metabolic regulation. This review focuses on existing and potential new approaches ameliorating endothelial dysfunction and vascular inflammation in the context of diabesity.

Liraglutide, a GLP-1 receptor agonist, inhibits vascular smooth muscle cell proliferation by enhancing AMP-activated protein kinase and cell cycle regulation, and delays atherosclerosis in ApoE deficient mice

BACKGROUND AND AIMS

Several studies have demonstrated that both native glucagon-like peptide-1 (GLP-1) and GLP-1 receptor agonists suppress the progression of atherosclerosis in animal models.

METHODS

We investigated whether liraglutide, a GLP-1 analogue, could prevent the development of atherosclerosis in apolipoprotein E knockout mice (ApoE^-/-) on a high-fat diet. We also examined the influence of liraglutide on angiotensin II-induced proliferation of rat vascular smooth muscle cells (VSMCs) via enhancement of AMP-activated protein kinase (AMPK) signaling and regulation of cell cycle progression.

RESULTS

Treatment of ApoE^-/- mice with liraglutide (400 μg/day for 4 weeks) suppressed atherosclerotic lesions and increased AMPK phosphorylation in the aortic wall. Liraglutide also improved the endothelial function of thoracic aortas harvested from ApoE^-/- mice in an ex vivo study. Furthermore, liraglutide increased AMPK phosphorylation in rat VSMCs, while liraglutide-induced activation of AMPK was abolished by exendin 9-39, a GLP-1 antagonist. Moreover, angiotensin (Ang) II-induced proliferation of VSMCs was suppressed by liraglutide in a dose-dependent manner, and flow cytometry of Ang II-stimulated VSMCs showed that liraglutide reduced the percentage of cells in G2/M phase (by arrest in G0/G1 phase).

CONCLUSIONS

These findings suggest that liraglutide may inhibit Ang II-induced VSMC proliferation by activating AMPK signaling and inducing cell cycle arrest, thus delaying the progression of atherosclerosis independently of its glucose-lowering effect.

Estradiol effects on hypothalamic AMPK and BAT thermogenesis: A gateway for obesity treatment?

In addition to their prominent roles in the control of reproduction, estrogens are important modulators of energy balance, as evident in conditions of deficiency of estrogens, which are characterized by increased feeding and decreased energy expenditure, leading to obesity. AMP-activated protein kinase (AMPK) is a ubiquitous cellular energy gauge that is activated under conditions of low energy, increasing energy production and reducing energy wasting. Centrally, the AMPK pathway is a canonical route regulating energy homeostasis, by integrating peripheral signals, such as hormones and metabolites, with neuronal networks. As a result of those actions, hypothalamic AMPK modulates feeding, as well as brown adipose tissue (BAT) thermogenesis and browning of white adipose tissue (WAT). Here, we will review the central actions of estrogens on energy balance, with particular focus on hypothalamic AMPK. The relevance of this interaction is noteworthy, because some agents with known actions on metabolic homeostasis, such as nicotine, metformin, liraglutide, olanzapine and also natural molecules, such as resveratrol and flavonoids, exert their actions by modulating AMPK. This evidence highlights the possibility that hypothalamic AMPK might be a potential target for the treatment of obesity.