Effects of glucagon-like peptide-1 on advanced glycation endproduct-induced aortic endothelial dysfunction in streptozotocin-induced diabetic rats: possible roles of Rho kinase- and AMP kinase-mediated nuclear factor κB signaling pathways

Targeting Diabetic Atherosclerosis: The Role of GLP-1 Receptor Agonists, SGLT2 Inhibitors, and Nonsteroidal Mineralocorticoid Receptor Antagonists in Vascular Protection and Disease Modulation

Atherosclerosis is a closely related complication of diabetes mellitus (DM), driven by endothelial dysfunction, inflammation, and oxidative stress. The progression of atherosclerosis is accelerated by hyperglycemia, insulin resistance, and hyperlipidemia. Novel antidiabetic agents, SGLT2 inhibitors, and GLP-1 agonists improve glycemic control and offer cardiovascular protection, reducing the risk of major adverse cardiovascular events (MACEs) and heart failure hospitalization. These agents, along with nonsteroidal mineralocorticoid receptor antagonists (nsMRAs), promise to mitigate metabolic disorders and their impact on endothelial function, oxidative stress, and inflammation. This review explores the potential molecular mechanisms through which these drugs may prevent the development of atherosclerosis and cardiovascular disease (CVD), supported by a summary of preclinical and clinical evidence.

Therapeutic Potential of GLP-1 Receptor Agonists in Diabetes and Cardiovascular Disease: Mechanisms and Clinical Implications

BACKGROUND

Glucagon-like peptide-1 (GLP-1) is a crucial incretin hormone secreted by intestinal endocrine L cells. Given its pivotal physiological role, researchers have developed GLP-1 receptor agonists (GLP-1 RAs) through structural modifications. These analogues display pharmacological effects similar to those of GLP-1 but with augmented stability and are regarded as an effective means of regulating blood glucose levels in clinical practice.

OBJECTIVE

This review aims to comprehensively summarize the role of GLP-1 RAs in the management of diabetes mellitus (DM) and cardiovascular disease (CVD), with a particular emphasis on the underlying signal transduction pathways and their therapeutic potential.

METHODS

A comprehensive review was carried out through literature research.

RESULTS AND DISCUSSION

In pancreatic β-cells, GLP-1 RAs regulate the secretion of insulin and glucagon in a glucosedependent manner by influencing signaling pathways such as cAMP, PI3K, and MAPK. They also contribute to the regulation of blood glucose levels by promoting the proliferation of β-cells and inhibiting apoptosis in these cells. Recent comprehensive studies have also demonstrated the favorable impact of GLP-1 RAs on cardiovascular wellbeing. In addition to the cardiovascular protection afforded by glucose metabolism regulation, a large body of evidence from animal and cellular studies has corroborated the beneficial effects of GLP-1 RAs on conditions such as heart failure (HF), hypertension, and ischemic cardiomyopathy. These benefits are mainly attributed to the alleviation of inflammatory responses, reduction of oxidative stress, and prevention of cell apoptosis. Clinical data shows that GLP-1 RAs can reduce the risk of major adverse cardiovascular events (MACE) in diabetic patients.

CONCLUSION

GLP-1 RAs play an important role in the management of both diabetes and cardiovascular diseases. They show potential therapeutic value through the modulation of multiple signal transduction pathways. However, there may still be some issues in practical applications that require further research and resolution.

Glucagon-like Peptide-1 analogues and delipidation of coronary atheroma in statin-treated type 2 diabetic patients with coronary artery disease: The prespecified sub-analysis of the OPTIMAL randomized clinical trial

Background and aims

Randomized clinical trials have demonstrated the ability of glucagon-like peptide-1 analogues (GLP-1RAs) to reduce atherosclerotic cardiovascular disease events in patients with type 2 diabetes (T2D). How GLP-1RAs modulate diabetic atherosclerosis remains to be determined yet.

Methods

The OPTIMAL study was a prospective randomized controlled study to compare the efficacy of 48-week continuous glucose monitoring- and HbA1c-guided glycemic control on near infrared spectroscopty (NIRS)/intravascular ultrasound (IVUS)-derived plaque measures in 94 statin-treated patients with T2D (jRCT1052180152, UMIN000036721). Of these, 78 patients with evaluable serial NIRS/IVUS images were analyzed to compare plaque measures between those treated with (n = 16) and without GLP-1RAs (n = 72).

Results

All patients received a statin, and on-treatment LDL-C levels were similar between the groups (66.9 ± 11.6 vs. 68.1 ± 23.2 mg/dL, p = 0.84). Patients receiving GLP-1RAs demonstrated a greater reduction of HbA1c [-1.0 (-1.4 to -0.5) vs. -0.4 (-0.6 to -0.2)%, p = 0.02] and were less likely to demonstrate a glucose level >180 mg/dL [-7.5 (-14.9 to -0.1) vs. 1.1 (-2.0 - 4.2)%, p = 0.04], accompanied by a significant decrease in remnant cholesterol levels [-3.8 (-6.3 to -1.3) vs. -0.1 (-0.8 - 1.1)mg/dL, p = 0.008]. On NIRS/IVUS imaging analysis, the change in percent atheroma volume did not differ between the groups (-0.9 ± 0.25 vs. -0.2 ± 0.2%, p = 0.23). However, GLP-1RA treated patients demonstrated a greater frequency of maxLCBI4mm regression (85.6 ± 0.1 vs. 42.0 ± 0.6%, p = 0.01). Multivariate analysis demonstrated that the GLP-1RA use was independently associated with maxLCBI4mm regression (odds ratio = 4.41, 95%CI = 1.19-16.30, p = 0.02).

Conclusions

In statin-treated patients with T2D and CAD, GLP-1RAs produced favourable changes in lipidic plaque materials, consistent with its stabilization.

Inhalation of particulate matter containing environmentally persistent free radicals induces endothelial dysfunction mediated via AhR activation at the air-blood interface

Particulate matter (PM) containing environmentally persistent free radicals (EPFR) is formed by the incomplete combustion of organic wastes, resulting in the chemisorption of pollutants to the surface of PM containing redox-active transition metals. In prior studies in mice, EPFR inhalation impaired endothelium-dependent vasodilation. These findings were associated with aryl hydrocarbon receptor (AhR) activation in the alveolar type-II (AT-II) cells that form the air-blood interface in the lung. We thus hypothesized that AhR activation in AT-II cells promotes the systemic release of mediators that promote endothelium dysfunction peripheral to the lung. To test our hypothesis, we knocked down AhR in AT-II cells of male and female mice and exposed them to 280 µg/m3 EPFR lo (2.7e + 16 radicals/g) or EPFR (5.5e + 17 radicals/g) compared with filtered air for 4 h/day for 1 day or 5 days. AT-II-AhR activation-induced EPFR-mediated endothelial dysfunction, reducing endothelium-dependent vasorelaxation by 59%, and eNOS expression by 50%. It also increased endothelin-1 mRNA levels in the lungs and peptide levels in the plasma in a paracrine fashion, along with soluble vascular cell adhesion molecule-1 and iNOS mRNA expression, possibly via NF-kB activation. Finally, AhR-dependent increases in antioxidant response signaling, coupled to increased levels of 3-nitrotyrosine in the lungs of EPFR-exposed littermate control but not AT-II AhR KO mice suggested that ATII-specific AhR activation promotes oxidative and nitrative stress. Thus, AhR activation at the air-blood interface mediates endothelial dysfunction observed peripheral to the lung, potentially via release of systemic mediators.

GLP-1 receptor agonists and atherosclerosis protection: the vascular endothelium takes center stage

Atherosclerotic cardiovascular disease is a chronic condition that often copresents with type 2 diabetes and obesity. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are incretin mimetics endorsed by major professional societies for improving glycemic status and reducing atherosclerotic risk in people living with type 2 diabetes. Although the cardioprotective efficacy of GLP-1RAs and their relationship with traditional risk factors are well established, there is a paucity of publications that have summarized the potentially direct mechanisms through which GLP-1RAs mitigate atherosclerosis. This review aims to narrow this gap by providing comprehensive and in-depth mechanistic insight into the antiatherosclerotic properties of GLP-1RAs demonstrated across large outcome trials. Herein, we describe the landmark cardiovascular outcome trials that triggered widespread excitement around GLP-1RAs as a modern class of cardioprotective agents, followed by a summary of the origins of GLP-1RAs and their mechanisms of action. The effects of GLP-1RAs at each major pathophysiological milestone of atherosclerosis, as observed across clinical trials, animal models, and cell culture studies, are described in detail. Specifically, this review provides recent preclinical and clinical evidence that suggest GLP-1RAs preserve vessel health in part by preventing endothelial dysfunction, achieved primarily through the promotion of angiogenesis and inhibition of oxidative stress. These protective effects are in addition to the broad range of atherosclerotic processes GLP-1RAs target downstream of endothelial dysfunction, which include systemic inflammation, monocyte recruitment, proinflammatory macrophage and foam cell formation, vascular smooth muscle cell proliferation, and plaque development.

Cardiovascular benefits of SGLT2 inhibitors and GLP-1 receptor agonists through effects on mitochondrial function and oxidative stress

Overloaded glucose levels in several metabolic diseases such as type 2 diabetes (T2D) can lead to mitochondrial dysfunction and enhanced production of reactive oxygen species (ROS). Oxidative stress and altered mitochondrial homeostasis, particularly in the cardiovascular system, contribute to the development of chronic comorbidities of diabetes. Diabetes-associated hyperglycemia and dyslipidemia can directly damage vascular vessels and lead to coronary artery disease or stroke, and indirectly damage other organs and lead to kidney dysfunction, known as diabetic nephropathy. The new diabetes treatments include Na+-glucose cotransporter 2 inhibitors (iSGLT2) and glucagon-like 1 peptide receptor agonists (GLP-1RA), among others. The iSGLT2 are oral anti-diabetic drugs, whereas GLP-1RA are preferably administered through subcutaneous injection, even though GLP-1RA oral formulations have recently become available. Both therapies are known to improve both carbohydrate and lipid metabolism, as well as to improve cardiovascular and cardiorenal outcomes in diabetic patients. In this review, we present an overview of current knowledge on the relationship between oxidative stress, mitochondrial dysfunction, and cardiovascular therapeutic benefits of iSGLT2 and GLP-1RA. We explore the benefits, limits and common features of the treatments and remark how both are an interesting target in the prevention of obesity, T2D and cardiovascular diseases, and emphasize the lack of a complete understanding of the underlying mechanism of action.

Anti-inflammatory role of glucagon-like peptide 1 receptor agonists and its clinical implications

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) have emerged as promising therapeutic agents with potent anti-inflammatory properties and diverse clinical implications. This in-depth review article explores the mechanisms behind the anti-inflammatory actions of GLP-1RAs and assesses their prospective applicability in a wide range of disease scenarios. The current review establishes the significance of comprehending the anti-inflammatory role of GLP-1RAs and identifies pertinent research gaps. A concise overview of inflammation and its clinical consequences underscores the critical need for effective anti-inflammatory interventions. Subsequently, the article elucidates the intricate mechanisms through which GLP-1RAs modulate immune cell signaling and regulate the nuclear factor-kappa B (NF-κB) pathway. Detailed discussions encompass their impact on inflammatory responses, cytokine production, and attenuation of oxidative stress. The exposition is substantiated by a collection of pertinent examples and an extensive array of references from both preclinical and clinical investigations. The historical trajectory of GLP-1RA drugs, including exenatide, lixisenatide, liraglutide, and semaglutide, is traced to delineate their development as therapeutic agents. Moreover, the review emphasizes the therapeutic potential of GLP-1RAs in specific disease contexts like type 2 diabetes, a neurodegenerative disorder, and inflammatory bowel disease (IBD), shedding light on their anti-inflammatory effects through rigorous examination of preclinical and clinical studies. The article also provides an outlook on future perspectives for GLP-1RAs, encompassing the domains of diabetes, neurodegenerative diseases, and IBD. In conclusion, GLP-1RAs exhibit substantial anti-inflammatory effects, rendering them promising therapeutic agents with broad clinical implications. They are very useful in a wide variety of diseases because they regulate immunological responses, block NF-κB activation, and decrease production of pro-inflammatory cytokines. Ongoing research endeavors aim to optimize their therapeutic use, delineate patient-specific treatment paradigms, and explore novel therapeutic applications. GLP-1RAs represent a significant breakthrough in anti-inflammatory therapy, offering novel treatment options, and improved patient outcomes.

GLP-1 Receptor Agonists for the Reduction of Atherosclerotic Cardiovascular Risk in Patients With Type 2 Diabetes

Patients with type 2 diabetes are at high risk for development of cardiovascular disease, including myocardial infarction, stroke, heart failure, and cardiovascular death. Multiple large cardiovascular outcome trials with novel glucose-lowering agents, namely SGLT2i (SGLT2 inhibitors) and GLP-1 RA (GLP-1 receptor agonists), have demonstrated robust and significant reductions of major adverse cardiovascular events and additional cardiovascular outcomes, such as hospitalizations for heart failure. This evidence has changed the landscape for treatment of patients with type 2 diabetes. Both diabetes and cardiology guidelines and professional societies have responded to this paradigm shift by including strong recommendations to use SGLT2i and/or GLP-1 RA, with evidence-based benefits to reduce cardiovascular risk in high-risk individuals with type 2 diabetes, independent of the need for additional glucose control. GLP-1 RA were initially developed as glucose-lowering drugs because activation of the GLP-1 receptor by these agents leads to a reduction in blood glucose and an improvement in postprandial glucose metabolism. By stimulating GLP-1R in hypothalamic neurons, GLP-1 RA additionally induce satiety and lead to weight loss. Data from cardiovascular outcome trials demonstrated a robust and consistent reduction in atherothrombotic events, particularly in patients with established atherosclerotic cardiovascular disease. Despite the consistent evidence of atherosclerotic cardiovascular disease benefit from these trials, the number of patients receiving these drugs remains low. This overview summarizes the experimental and clinical evidence of cardiovascular risk reduction offered by GLP-1 RA, and provides practical information on how these drugs should be implemented in the treatment of type 2 diabetes in the cardiology community.

Protective Effect of High-Intensity Interval Training (HIIT) and Moderate-Intensity Continuous Training (MICT) against Vascular Dysfunction in Hyperglycemic Rats

Background

Hyperglycemia is a major risk factor for endothelial dysfunction. Endothelial dysfunction is associated with the inability of endothelial cells to maintain homeostasis of the cardiovascular system. Regular exercise may be considered as an effective and low-cost nonpharmacological tool for improving vascular function, though there is no agreement on the best type of exercise.

Objectives

To determine how high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) may prevent endothelial dysfunction under hyperglycemic conditions, and to compare these two interventions.

Method

Twenty-four eight-week-old male Wistar rats were randomly assigned into four groups: healthy nonexercising control (C), hyperglycemic control (HG-C), hyperglycemic + HIIT (HG-IT), and hyperglycemic + MICT (HG-CT). Hyperglycemia was induced by a single injection of streptozotocin. Hyperglycemic animals were subjected to HIIT or MICT protocols six days a week for six weeks. Decapitation was performed the day after the exercise protocols were completed. The ascending aorta (until the abdominal artery) was examined. An enzyme-linked immunosorbent assay (ELISA) was used to measure the glucagon-likepeptide-1 (GLP-1), endothelial nitric oxide synthase (eNOS), and tumor necrosis factor-alpha (TNFα) levels. A colorimetric assay was used to measure superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels. Quantitative real-time polymerase chain reaction (PCR) was used to measure the expression of the receptor for advanced glycation end-products (RAGE) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Hematoxylin and eosin (H&E) staining was used to histologically analyze the aortas.

Results

There was a significantly higher level of GLP-1 and lower expression of RAGE, NF-κB, and TNFα in the HG-IT and HG-CT group compared to the HG-C group. Microscopic examination of aortic tissue showed a better tissue arrangement in both treatment groups than in the HG-C group. Except for the MDA level, there were no significant differences in any of the measured parameters between the HG-IT and HG-CT groups.

Conclusion

Under hyperglycemic conditions, both HIIT and MICT have a protective role against endothelial dysfunction.

Possible effects of dietary advanced glycation end products on maternal and fetal health: a review

Excessive accumulation of advanced glycation end products (AGEs) in the body has been associated with many adverse health conditions. The common point of the pathologies associated at this point is oxidative stress and inflammation. Pregnancy is an important period in which many physiological, psychological, and biological changes are experienced. Along with the physiological changes that occur during this period, the mother maintaining an AGE-rich diet may cause an increase in the body's AGE pool and may increase oxidative stress and inflammation, as seen in healthy individuals. Studies have reported the negative effects of maternal AGE levels on maternal and fetal health during pregnancy. Although gestational diabetes, preeclampsia, endothelial dysfunction, and pelvic diseases constitute maternal complications, a number of pathological conditions such as intrauterine growth retardation, premature birth, neural tube defect, neurobehavioral developmental disorders, fetal death, and neonatal asphyxia constitute fetal complications. It is thought that the mechanisms of these complications have not been confirmed yet and more clinical studies are needed on this subject. The possible effects of dietary AGE levels during pregnancy on maternal and fetal health are examined in this review.

Endogenous Vasoactive Peptides and Vascular Aging-Related Diseases

Vascular aging is a specific type of organic aging that plays a central role in the morbidity and mortality of cardiovascular and cerebrovascular diseases among the elderly. It is essential to develop novel interventions to prevent/delay age-related vascular pathologies by targeting fundamental cellular and molecular aging processes. Endogenous vasoactive peptides are compounds formed by a group of amino acids connected by peptide chains that exert regulatory roles in intercellular interactions involved in a variety of biological and pathological processes. Emerging evidence suggests that a variety of vasoactive peptides play important roles in the occurrence and development of vascular aging and related diseases such as atherosclerosis, hypertension, vascular calcification, abdominal aortic aneurysms, and stroke. This review will summarize the cumulative roles and mechanisms of several important endogenous vasoactive peptides in vascular aging and vascular aging-related diseases. In addition, we also aim to explore the promising diagnostic function as biomarkers and the potential therapeutic application of endogenous vasoactive peptides in vascular aging-related diseases.

Nonalcoholic Steatohepatitis (NASH) and Atherosclerosis: Explaining Their Pathophysiology, Association and the Role of Incretin-Based Drugs

Nonalcoholic steatohepatitis (NASH) is the most severe manifestation of nonalcoholic fatty liver disease (NAFLD), a common complication of type 2 diabetes, and may lead to cirrhosis and hepatocellular carcinoma. Oxidative stress and liver cell damage are the major triggers of the severe hepatic inflammation that characterizes NASH, which is highly correlated with atherosclerosis and coronary artery disease. Regarding drug therapy, research on the role of GLP-1 analogues and DPP4 inhibitors, novel classes of antidiabetic drugs, is growing. In this review, we outline the association between NASH and atherosclerosis, the underlying molecular mechanisms, and the effects of incretin-based drugs, especially GLP-1 RAs, for the therapeutic management of these conditions.

Anti-inflammatory potential of liraglutide, a glucagon-like peptide-1 receptor agonist, in rats with peripheral acute inflammation

The present study aimed to explore the possible anti-inflammatory actions of liraglutide (LRG), a glucagon-like peptide-1 (GLP-1) receptor agonist, and to compare with tramadol (TR) or LRG, and TR combination treatment by investigating the inflammatory signs such as pain hypersensitivity, edema, and fever in carrageenan (CG)-induced acute peripheral inflammation model in rats. The levels of several biomarkers for inflammatory status, angiogenesis, and oxidative stress were also measured in inflamed tissues. CG induced inflammation in the paws of rats identified by hypersensitivities, redness, edema and fever. LRG, significantly improved the hypersensitivity to mechanical (from 4 to 35.5 g) or cold (from 5 to 44.2 s) stimuli, reduced the edema (paw mass, from 2.54 to 1.85 g), and fever (paw temperature, from 33.6 to 27.3 °C). LRG dramatically suppressed the inflammatory signs when compared to those of TR. In addition, co-administration of TR and LRG resulted in further reduction of sensitivity to mechanical and cold stimuli. Anti-inflammatory potential of LRG altered depending on their inhibitory effects in the biomarkers of inflamed paws. Consequently, the suppressive actions of LRG in the inflammation induced hypersensitivities, edema, and fever, indicating that these drugs have significant anti-inflammatory potential with anti-hypersensitivities, anti-edema, and anti-pyretic effects. LRG with anti-inflammatory actions may be a highly promising therapeutic option for the management of inflammatory conditions or inflammatory-related various diseases.

Liraglutide, a glucagon-like peptide-1 receptor agonist, induces ADAM10-dependent ectodomain shedding of RAGE via AMPK activation in human aortic endothelial cells

AIMS

Glucagon-like peptide-1 alleviates the deleterious effects of advanced glycation end products (AGEs), but the underlying mechanisms are not fully understood. In this study, we investigated the protective mechanism using liraglutide, a glucagon-like peptide-1 receptor agonist, in cultured human aortic endothelial cells (HAECs).

MAIN METHODS

Following liraglutide treatment in HAECs, the receptor for AGEs (RAGE) was measured in both cell lysate and culture supernatant, the cytosolic free Ca²⁺ level was monitored using Fluo-4 AM, the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) was analyzed, and immunofluorescence staining was used to visualize a disintegrin and metalloprotease 10 (ADAM10) on the cell surface.

KEY FINDINGS

Liraglutide (100 nM) induced ectodomain shedding of RAGE within 30 min and inhibited the expression of intercellular adhesion molecule-1 (ICAM-1) induced by AGEs of bovine serum albumin (AGE-BSA). Further experiments revealed that liraglutide rapidly increased extracellular Ca²⁺ influx through L-type calcium channels and activated AMPK, resulting in translocation of ADAM10 to the cell surface, whereas siRNA-mediated ADAM10 depletion prevented liraglutide-induced ectodomain shedding of RAGE and eliminated liraglutide's inhibitory effect on AGE-BSA-induced ICAM-1 expression. Moreover, compound C-mediated AMPK inhibition and siRNA-mediated AMPK depletion both prevented ADAM10 translocation to the cell surface and ADAM10-mediated ectodomain shedding of RAGE.

SIGNIFICANCE

Liraglutide reduces the number of intact RAGE on the cell surface by inducing ADAM10-mediated ectodomain shedding, which decreases the inflammatory effects of AGEs. AMPK activated by extracellular Ca²⁺ influx is critically involved in the translocation of ADAM10 to the cell surface, where it cleaves RAGE.

Insight Into Rho Kinase Isoforms in Obesity and Energy Homeostasis

Obesity and associated complications increasingly jeopardize global health and contribute to the rapidly rising prevalence of type 2 diabetes mellitus and obesity-related diseases. Developing novel methods for the prevention and treatment of excess body adipose tissue expansion can make a significant contribution to public health. Rho kinase is a Rho-associated coiled-coil-containing protein kinase (Rho kinase or ROCK). The ROCK family including ROCK1 and ROCK2 has recently emerged as a potential therapeutic target for the treatment of metabolic disorders. Up-regulated ROCK activity has been involved in the pathogenesis of all aspects of metabolic syndrome including obesity, insulin resistance, dyslipidemia and hypertension. The RhoA/ROCK-mediated actin cytoskeleton dynamics have been implicated in both white and beige adipogenesis. Studies using ROCK pan-inhibitors in animal models of obesity, diabetes, and associated complications have demonstrated beneficial outcomes. Studies via genetically modified animal models further established isoform-specific roles of ROCK in the pathogenesis of metabolic disorders including obesity. However, most reported studies have been focused on ROCK1 activity during the past decade. Due to the progress in developing ROCK2-selective inhibitors in recent years, a growing body of evidence indicates more attention should be devoted towards understanding ROCK2 isoform function in metabolism. Hence, studying individual ROCK isoforms to reveal their specific roles and principal mechanisms in white and beige adipogenesis, insulin sensitivity, energy balancing regulation, and obesity development will facilitate significant breakthroughs for systemic treatment with isoform-selective inhibitors. In this review, we give an overview of ROCK functions in the pathogenesis of obesity and insulin resistance with a particular focus on the current understanding of ROCK isoform signaling in white and beige adipogenesis, obesity and thermogenesis in adipose tissue and other major metabolic organs involved in energy homeostasis regulation.

The Role of Gasotransmitters in Gut Peptide Actions

Although gasotransmitters nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) receive a bad connotation; in low concentrations these play a major governing role in local and systemic blood flow, stomach acid release, smooth muscles relaxations, anti-inflammatory behavior, protective effect and more. Many of these physiological processes are upstream regulated by gut peptides, for instance gastrin, cholecystokinin, secretin, motilin, ghrelin, glucagon-like peptide 1 and 2. The relationship between gasotransmitters and gut hormones is poorly understood. In this review, we discuss the role of NO, CO and H2S on gut peptide release and functioning, and whether manipulation by gasotransmitter substrates or specific blockers leads to physiological alterations.

Comparative effects of incretin-based therapy on early-onset diabetic nephropathy in rats: Role of TNF-α, TGF-β and c-caspase-3

AIMS

Diabetic nephropathy, a major threat to diabetic patients, is considered as the main reason for end-stage renal disease. Fortunately, incretin-based therapy has been aroused as considerable source to attenuate diabetic renal damage. This study aimed to investigate whether superior protective effects on the progression of diabetic kidney are exerted by glucagon-like peptide-1 analog, exenatide, or dipeptidyl peptidase-4 inhibitor, sitagliptin.

MATERIALS AND METHODS

Male Wistar rats were fed high-fat diet for 2 weeks followed by injection of low dose streptozotocin to induce type 2 diabetes mellitus. Four weeks after induction of diabetes, diabetic rats were administered vehicle, exenatide (5 μg/kg/day, SC) or sitagliptin (10 mg/kg/day, orally) for 4 weeks.

KEY FINDINGS

Different incretin mimetic agents improved renal function as evident by significant decreases in serum creatinine and urea levels with decline in urinary microalbuminuria and marked improvement in histological alterations. Both treated diabetic rats also exhibited a significant improvement in metabolic intolerance with more pronounced effect of exenatide on glucose regulation. Ameliorated renal oxidative stress alongside significant downregulation in transforming growth factor-beta, tumor necrosis factor-alpha and cleaved-caspase-3 protein expressions in renal tissues were recorded in treated diabetic rats.

SIGNIFICANCE

Administration of either exenatide or sitagliptin showed ameliorative effects on early diabetic nephropathy without notable differences between their renal protective effects. However, further clinical studies are still required to ensure their comparative promising effects on the management of renal complication of diabetes.

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

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

AGEs/RAGE blockade downregulates Endothenin-1 (ET-1), mitigating Human Umbilical Vein Endothelial Cells (HUVEC) injury in deep vein thrombosis (DVT)

This study is aimed at identifying the roles of AGE/RAGE and ET-1 in deep vein thrombosis (DVT). Advanced glycation end products (AGEs) in glycated human serum albumin (M-HSA) were detected by ELISA. The viability of HUVECs was examined by CCK-8 assay. Flow cytometry was performed to detect cell apoptosis, followed by ELISA for the detection of inflammatory cytokine level and oxidative stress level in HUVECs. Immunofluorescence was performed to detect ET-1 and eNOS expression. The expression of specific proteins was assayed by western blot. As a result, decreased HUVEC viability was observed after stimulation with M-HSA, whereas RAGE inhibitor improved it. Cell apoptosis showed the opposite trend. Additionally, M-HSA-induced inflammatory cytokine release and oxidative stress of HUVECs were both alleviated by RAGE inhibitor. RAGE inhibitor also increased the levels of NO and eNOS while decreasing the level of ET-1 in M-HSA-stimulated HUVECs. Furthermore, decreased protein expression of Bax, cleaved-caspase3, RAGE, p65, ET-1 and iNOS was observed after treatment with RAGE inhibitor, in addition to increased protein expression of Bcl-2 and eNOS. In conclusion, blocking AGE/RAGE pathway downregulates ET-1, thereby mitigating HUVEC damage in DVT.

Active Components and Pharmacological Effects of Cornus officinalis: Literature Review

Cornus officinalis Sieb. et Zucc. (Shanzhuyu), a herb and food plant in east Asia, has the properties of tonifying the liver and kidney, and nourishing the essence according to the theory of traditional Chinese medicine. C. officinalis has been commonly used to treat asthenia diseases, liver, and kidney diseases, and reproductive system diseases since ancient times. The objectives of this article were to review the pharmacological effects and phytochemistry of C. officinalis. We conducted a literature review of the pharmacological effects of C. officinalis by different systems and compared the effects with the traditional usages, discussed the research status and potential blanks to be filled. The experimental studies showed that C. officinalis extract and its active components had various pharmacological effects such as anti-oxidation, anti-apoptosis, anti-inflammation, anti-diabetes, anti-osteoporosis, immunoregulation, neuroprotection, and cardiovascular protection, but clinical studies are still needed to assess whether the reported pharmacological activities have confirmed efficacy.

GLP-1 receptor agonists in the treatment of type 2 diabetes - state-of-the-art

BACKGROUND

GLP-1 receptor agonists (GLP-1 RAs) with exenatide b.i.d. first approved to treat type 2 diabetes in 2005 have been further developed to yield effective compounds/preparations that have overcome the original problem of rapid elimination (short half-life), initially necessitating short intervals between injections (twice daily for exenatide b.i.d.).

SCOPE OF REVIEW

To summarize current knowledge about GLP-1 receptor agonist.

MAJOR CONCLUSIONS

At present, GLP-1 RAs are injected twice daily (exenatide b.i.d.), once daily (lixisenatide and liraglutide), or once weekly (exenatide once weekly, dulaglutide, albiglutide, and semaglutide). A daily oral preparation of semaglutide, which has demonstrated clinical effectiveness close to the once-weekly subcutaneous preparation, was recently approved. All GLP-1 RAs share common mechanisms of action: augmentation of hyperglycemia-induced insulin secretion, suppression of glucagon secretion at hyper- or euglycemia, deceleration of gastric emptying preventing large post-meal glycemic increments, and a reduction in calorie intake and body weight. Short-acting agents (exenatide b.i.d., lixisenatide) have reduced effectiveness on overnight and fasting plasma glucose, but maintain their effect on gastric emptying during long-term treatment. Long-acting GLP-1 RAs (liraglutide, once-weekly exenatide, dulaglutide, albiglutide, and semaglutide) have more profound effects on overnight and fasting plasma glucose and HbA1c, both on a background of oral glucose-lowering agents and in combination with basal insulin. Effects on gastric emptying decrease over time (tachyphylaxis). Given a similar, if not superior, effectiveness for HbA1c reduction with additional weight reduction and no intrinsic risk of hypoglycemic episodes, GLP-1RAs are recommended as the preferred first injectable glucose-lowering therapy for type 2 diabetes, even before insulin treatment. However, GLP-1 RAs can be combined with (basal) insulin in either free- or fixed-dose preparations. More recently developed agents, in particular semaglutide, are characterized by greater efficacy with respect to lowering plasma glucose as well as body weight. Since 2016, several cardiovascular (CV) outcome studies have shown that GLP-1 RAs can effectively prevent CV events such as acute myocardial infarction or stroke and associated mortality. Therefore, guidelines particularly recommend treatment with GLP-1 RAs in patients with pre-existing atherosclerotic vascular disease (for example, previous CV events). The evidence of similar effects in lower-risk subjects is not quite as strong. Since sodium/glucose cotransporter-2 (SGLT-2) inhibitor treatment reduces CV events as well (with the effect mainly driven by a reduction in heart failure complications), the individual risk of ischemic or heart failure complications should guide the choice of treatment. GLP-1 RAs may also help prevent renal complications of type 2 diabetes. Other active research areas in the field of GLP-1 RAs are the definition of subgroups within the type 2 diabetes population who particularly benefit from treatment with GLP-1 RAs. These include pharmacogenomic approaches and the characterization of non-responders. Novel indications for GLP-1 RAs outside type 2 diabetes, such as type 1 diabetes, neurodegenerative diseases, and psoriasis, are being explored. Thus, within 15 years of their initial introduction, GLP-1 RAs have become a well-established class of glucose-lowering agents that has the potential for further development and growing impact for treating type 2 diabetes and potentially other diseases.

Salidroside and isorhamnetin attenuate urotensin II-induced inflammatory response in vivo and in vitro: Involvement in regulating the RhoA/ROCK II pathway

Urotensin II (UII), a vital vasoconstrictor peptide, causes an inflammatory response in the pathogenesis of atherosclerosis. Previous studies have reported that the Ras homolog gene family, member A (RhoA)/Rho kinases (ROCK) pathway modulates the inflammatory response of the atherosclerotic process. However, to the best of our knowledge, whether the RhoA/ROCK pathway mediates the inflammatory effect of UII has not been previously elucidated. Salidroside and isorhamnetin are two early developed antioxidant Tibetan drugs, both displaying cardioprotective effects against atherosclerosis. Therefore, the aim of the present study was to investigate the protective effects of salidroside, isorhamnetin or combination of these two drugs on the UII-induced inflammatory response in vivo (rats) or in vitro [primary vascular smooth muscle cells (VSMCs)], as well as to examine the role of the RhoA/ROCK pathway in these processes. The levels of inflammatory markers were measured via ELISA. The mRNA and protein expression levels of RhoA and ROCK II were detected using reverse transcription-quantitative PCR assay and western blot analysis. It was demonstrated that salidroside, isorhamnetin and both in combination decreased the levels of the serum pro-inflammatory cytokines TNF-α and IL-1β, as well as increased the levels of the anti-inflammatory cytokine IL-10 and macrophage migration inhibitory factor in rats with subacute infusion of UII and in the culture supernatant from primary VSMCs-exposed to UII. Moreover, salidroside, isorhamnetin and both in combination attenuated the mRNA and protein expression levels of RhoA and ROCK II in vivo and in vitro, at concentrations corresponding to human therapeutic blood plasma concentrations. Thus, these drugs could inhibit the RhoA/ROCK II pathway under UII conditions. The combination of salidroside and isorhamnetin did not display a stronger inhibitory effect on the inflammatory response and the RhoA/ROCK II pathway compared with salidroside and isorhamnetin in isolation. Collectively, the results indicated that salidroside, isorhamnetin and both in combination inhibited the RhoA/ROCK II pathway, which then attenuated the inflammatory response under UII-induced conditions, resulting in cardioprotection in atherosclerosis.

Effect of combined therapy of mesenchymal stem cells with GLP-1 receptor agonist, exenatide, on early-onset nephropathy induced in diabetic rats

Diabetic nephropathy is the principal cause of end-stage renal failure and current interventions for its recession remains unsatisfactory. Mesenchymal stem cells (MSCs) hold an attractive source for renovating injured tissues. Unfortunately, limited self-renewal and migration capacity of MSCs after transplantation hinder their clinical applicability which demands a new policy for enhancing their biological functions. This study aimed to investigate whether the renoprotective potential of adipose-derived MSCs (ADMSCs) in diabetic rats could be promoted by exenatide, a glucagon-like peptide-1 (GLP-1) analogue. These effects were studied in type 2 diabetes mellitus rats which were administrated ADMSCs, exenatide or their combination four weeks post-induction. Four weeks later, renal function parameters were evaluated. To address the possible underlying mechanisms, parameters indicating glycolipid metabolism tolerance and oxidative stress biomarkers were assessed in renal tissues alongside evaluation of protein expression of tumor necrosis factor-alpha, transforming growth factor-beta1 and cleaved caspase-3. The results showed that the combined therapy had superior renoprotective effect as evident by significant improvement in kidney function and renal architecture changes through rebalancing of inflammatory, fibrotic and apoptotic markers. Based on these outcomes, ADMSCs with exenatide were supposed to effectively ameliorate diabetic renal dysfunction compared to ADMSCs solely, presenting a promise therapy for diabetic nephropathy with further clinical studies warranted to validate this effect.

Cardiovascular Safety and Benefits of Semaglutide in Patients With Type 2 Diabetes: Findings From SUSTAIN 6 and PIONEER 6

To exclude an excess risk of cardiovascular (CV) events, CV outcomes trials (CVOTs) have assessed the effects of new glucose-lowering therapies, including glucagon-like peptide-1 receptor agonists (GLP-1RAs), in patients with type 2 diabetes and established CV disease or CV risk factors. The CV safety of semaglutide vs. placebo, when added to standard care, was evaluated in the SUSTAIN 6 trial for the formulation administered once-weekly subcutaneously and in PIONEER 6 for the new once-daily oral formulation. In SUSTAIN 6 and PIONEER 6, both powered to demonstrate noninferiority (upper 95% confidence interval [CI] of the hazard ratio [HR] <1.8), there were fewer first major adverse CV events with semaglutide vs. placebo, with HRs of 0.74 (95% CI 0.58-0.95) and 0.79 (0.57-1.11), respectively. In SUSTAIN 6, the results were significant for noninferiority and superiority, although the latter was not prespecified. Surprisingly, CV and all-cause mortality were significantly reduced by oral semaglutide in PIONEER 6. The ongoing SOUL CVOT will further inform about CV outcomes with oral semaglutide vs. placebo (NCT03914326). Findings from SUSTAIN 6 and PIONEER 6 fall within the spectrum reported with other GLP-1RA CVOTs: noninferiority vs. placebo for major CV events was seen with lixisenatide and exenatide extended-release, while superiority was demonstrated with liraglutide, albiglutide, and dulaglutide. Beneficial outcomes have been recognized in international guidelines, which recommend subcutaneous liraglutide, semaglutide, and dulaglutide to reduce the risk of CV events in high-risk patients. Both indirect mechanisms via risk factor modification and direct effects via GLP-1 receptors in the CV system have been proposed to be responsible for CV event reductions. The exact mechanism(s) remains to be characterized, but appears to be mainly linked to anti-atherosclerotic effects. Further research is needed to elucidate the relevant mechanisms for CV benefits of GLP-1RAs.

Protective role of mitoquinone against impaired mitochondrial homeostasis in metabolic syndrome

Mitochondria control various processes in cellular metabolic homeostasis, such as adenosine triphosphate production, generation and clearance of reactive oxygen species, control of intracellular Ca²⁺ and apoptosis, and are thus a critical therapeutic target for metabolic syndrome (MetS). The mitochondrial targeted antioxidant mitoquinone (MitoQ) reduces mitochondrial oxidative stress, prevents impaired mitochondrial dynamics, and increases mitochondrial turnover by promoting autophagy (mitophagy) and mitochondrial biogenesis, which ultimately contribute to the attenuation of MetS conditions, including obesity, insulin resistance, hypertension and cardiovascular disease. The regulatory effect of MitoQ on mitochondrial homeostasis is mediated through AMPK and its downstream signaling pathways, including MTOR, SIRT1, Nrf2 and NF-κB. However, there are few reviews focusing on the critical role of MitoQ as a therapeutic agent in the treatment of MetS. The purpose of this review is to summarize the mitochondrial role in the pathogenesis of MetS, especially in obesity and type 2 diabetes, and discuss the effect and underlying mechanism of MitoQ on mitochondrial homeostasis in MetS.

Advanced Glycation End Products: Potential Mechanism and Therapeutic Target in Cardiovascular Complications under Diabetes

The occurrence and development of cardiovascular complications are predominantly responsible for the increased morbidity and mortality observed in patients with diabetes. Oxidative stress under hyperglycemia is currently considered the initial link to diabetic cardiovascular complications and a key node for the prevention and treatment of diabetes-related fatal cardiovascular events. Numerous studies have indicated that the common upstream pathway in the context of oxidative stress in the cardiovascular system under diabetic conditions is the interaction of advanced glycation end products (AGEs) with their receptors (RAGEs). Therefore, a further understanding of the relationship between oxidative stress and AGEs is of great significance for the prevention and treatment of cardiovascular complications in patients with diabetes. In this review, we will briefly summarize the recent research advances in diabetes with an emphasis on oxidative stress and its association with AGEs in diabetic cardiovascular complications.

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.

Exendin-4 promotes actin cytoskeleton rearrangement and protects cells from Nogo-A-Δ20 mediated spreading inhibition and growth cone collapse by down-regulating RhoA expression and activation via the PI3K pathway

Exendin-4 is a protein of the GLP-1 family currently used to treat diabetes. Recently, a greater number of biological properties have been associated with the GLP-1 family. Our data shows that exendin-4 treatment significantly increases the cytoskeleton rearrangement, which leads to an increasingly differentiated phenotype and reduced cell migration. We also found that exendin-4 could prevent SH-SY5Y and PC12 cells from Nogo-A-Δ20 mediated spreading inhibition and neurite collapse. Western blot analysis indicated that exendin-4 treatment both reduced the expression and activation of RhoA via the PI3K signaling pathway. These data suggest that exendin-4 may protect nerve regeneration by preventing the inhibition of Nogo-A via down-regulating RhoA expression and activation.

Lipopolysaccharide inhibits hepatic gluconeogenesis in rats: The role of immune cells

AIMS/INTRODUCTION

Bacterial septicemia has diverse clinical symptoms including severe hypoglycemia. However, sepsis-induced hypoglycemia has not yet been examined in detail. The aim of the present study was to investigate the mechanisms underlying hypoglycemia in sepsis.

MATERIALS AND METHODS

We induced endotoxin shock in rats using lipopolysaccharide (LPS). After an intraperitoneal injection of LPS, we measured gluconeogenesis using the pyruvate tolerance test. The effects of LPS on glucose metabolism were investigated in perfused livers and isolated hepatocytes. Furthermore, its effects on the production of inflammatory cytokines were examined in isolated splenocytes. The interaction between splenocytes and hepatocytes in response to LPS was investigated in vitro using a co-culture of splenocytes and hepatocytes.

RESULTS

In the pyruvate tolerance test, the pretreatment with LPS decreased gluconeogenesis. The in vivo pretreatment of rats with LPS did not inhibit glucose production in perfused livers. The in vitro treatment of isolated hepatocytes with LPS did not decrease hepatic gluconeogenesis. Although LPS increased the production of inflammatory cytokines (tumor necrosis factor-α, interferon-γ, interleukin-1β, interleukin-6 and interleukin-10) and nitric oxide in isolated splenocytes, only nitric oxide significantly inhibited gluconeogenesis in isolated hepatocytes. When splenocytes and hepatocytes were co-cultured in medium containing LPS, the messenger ribonucleic acid expression of glucose-6-phosphatase in hepatocytes was suppressed.

CONCLUSIONS

LPS reduced hepatic gluconeogenesis, at least in part, by stimulating the production of nitric oxide in splenocytes. This effect could contribute to the mechanisms responsible for septicemia-induced hypoglycemia.

Suppression of Rho-kinase 1 is responsible for insulin regulation of the AMPK/SREBP-1c pathway in skeletal muscle cells exposed to palmitate

AIMS

Clinical and experimental data suggest that early insulin therapy could reduce lipotoxicity in subjects and animal models with type 2 diabetes mellitus. However, the underlying mechanisms need to be clarified. Sterol regulatory element-binding protein 1c (SREBP-1c), which is negatively regulated by AMP-activated protein kinase (AMPK), plays a critical role in lipotoxicity and insulin resistance in skeletal muscle cells. Here, we investigated the effect and molecular mechanism of insulin intervention on the AMPK/SREBP-1c pathway in skeletal muscle cells with chronic exposure to palmitic acid (PA).

METHODS

Male C57BL/6 mice were fed with a high-fat diet for 12 weeks and were then treated with insulin, AMPK inhibitor, or metformin. L6 myotubes incubated with palmitic acid (PA) were treated with insulin or metformin. Dominant-negative AMPKα2 (DN-AMPKα2) lentivirus, AMPKα2 siRNA, or Rho-kinase 1 (ROCK1) siRNA were transfected into PA-treated L6 myotubes.

RESULTS

We found that the ability of PA to stimulate SREBP-1c and inhibit AMPK was reversed by insulin in L6 cells. Moreover, DN-AMPKα2 lentivirus and AMPKα2 siRNA were transfected into PA-treated L6 myotubes, and the decrease in SREBP-1c expression caused by insulin was blocked by AMPK inhibition independent of the phosphatidylinositol-4,5-biphosphate-3-kinase (PI3K)/AKT pathway. The serine/threonine kinase Rho-kinase (ROCK) 1, a downstream effector of the small G protein RhoA, was activated by PA. Interestingly, knockdown of ROCK1 by siRNA blocked the downregulation of AMPK phosphorylation under PA-treated L6 myotubes, which indicated that ROCK1 mediated the effect of insulin action on AMPK.

CONCLUSIONS

Our study indicated that insulin reduced lipotoxicity via ROCK1 and then improved AMPK/SREBP-1c signaling in skeletal muscle under PA-induced insulin resistance.

Incretin-Based Therapies for Diabetic Complications: Basic Mechanisms and Clinical Evidence

An increase in the rates of morbidity and mortality associated with diabetic complications is a global concern. Glycemic control is important to prevent the development and progression of diabetic complications. Various classes of anti-diabetic agents are currently available, and their pleiotropic effects on diabetic complications have been investigated. Incretin-based therapies such as dipeptidyl peptidase (DPP)-4 inhibitors and glucagon-like peptide-1 receptor agonists (GLP-1RA) are now widely used in the treatment of patients with type 2 diabetes. A series of experimental studies showed that incretin-based therapies have beneficial effects on diabetic complications, independent of their glucose-lowering abilities, which are mediated by anti-inflammatory and anti-oxidative stress properties. Based on these findings, clinical studies to assess the effects of DPP-4 inhibitors and GLP-1RA on diabetic microvascular and macrovascular complications have been performed. Several but not all studies have provided evidence to support the beneficial effects of incretin-based therapies on diabetic complications in patients with type 2 diabetes. We herein discuss the experimental and clinical evidence of incretin-based therapy for diabetic complications.

Exenatide and metformin express their anti-inflammatory effects on human monocytes/macrophages by the attenuation of MAPKs and NFκB signaling

Metformin and exenatide are effective antidiabetic drugs, and they seem to have pleiotropic properties improving cardiovascular outcomes. Macrophages' phenotype is essential in the development of atherosclerosis, and it can be modified during antidiabetic therapy, resulting in attenuated atherogenesis. The mechanism orchestrating this phenomenon is not fully clear. We examined the impact of exenatide and metformin on the level of TNF alpha, MCP-1, reactive oxygen species (ROS), and the activation of mitogen-activated protein kinases (MAPK), nuclear factor kappa B (NFκB), and CCAAT/enhancer-binding protein beta (C/EBP beta) in human monocytes/macrophages. We found that both drugs reduced levels of TNF alpha, ROS, and NFκB binding activity to a similar extent. Compared to metformin, exenatide was more effective in reducing MCP-1 levels. We noted that Compound C (AMPK inhibitor) reduced the impact of exenatide on cytokines, ROS, and NFκB in cultures. Both drugs elevated the C/EBP beta phosphorylation level. Experiments on MAPKs showed effective inhibitory potential of exenatide toward p38, JNK, and ERK, whereas metformin inhibited JNK and ERK only. Exenatide was more effective in the inhibition of JNK than metformin. Interestingly, an in vitro setting additive effect of drugs was absent. In conclusion, here, we report that metformin and exenatide inhibit the proinflammatory phenotype of human monocytes/macrophages via influence on MAPK, C/EBP beta, and NFκB. Exenatide was more effective than metformin in reducing MCP-1 expression and JNK activity. We also showed that some effects of exenatide relied on AMPK activation. This shed light on the possible mechanisms responsible for pleiotropic effects of metformin and exenatide.

Anti-Inflammatory Effects of GLP-1-Based Therapies beyond Glucose Control

Glucagon-like peptide-1 (GLP-1) is an incretin hormone mainly secreted from intestinal L cells in response to nutrient ingestion. GLP-1 has beneficial effects for glucose homeostasis by stimulating insulin secretion from pancreatic beta-cells, delaying gastric emptying, decreasing plasma glucagon, reducing food intake, and stimulating glucose disposal. Therefore, GLP-1-based therapies such as GLP-1 receptor agonists and inhibitors of dipeptidyl peptidase-4, which is a GLP-1 inactivating enzyme, have been developed for treatment of type 2 diabetes. In addition to glucose-lowering effects, emerging data suggests that GLP-1-based therapies also show anti-inflammatory effects in chronic inflammatory diseases including type 1 and 2 diabetes, atherosclerosis, neurodegenerative disorders, nonalcoholic steatohepatitis, diabetic nephropathy, asthma, and psoriasis. This review outlines the anti-inflammatory actions of GLP-1-based therapies on diseases associated with chronic inflammation in vivo and in vitro, and their molecular mechanisms of anti-inflammatory action.