Impact of DPP-4 inhibition on acute and chronic endothelial function in humans with type 2 diabetes on background metformin therapy

Treatment of type 2 diabetes patients with heart conditions

INTRODUCTION

While type 2 diabetes mellitus (T2DM) increases the risk of cardiac complications, diabetes treatment choices may increase or decrease the rates of cardiac events. In the present review, we comprehensively discussed the treatment options of diabetic subjects with cardiac conditions.

AREAS COVERED

Current evidence related to diabetes treatment in cardiac situations has been reviewed. Clinical trials and meta-analyses on cardiac safety of anti-diabetic medicines are discussed. Treatment choices with proven benefits and those at least without associated increased cardiac risk were drawn from clinical trials; meta-analyses and cardiac safety studies in the recent medical literature were the basis of the suggestions in the present review.

EXPERT OPINION

We can suggest that hypoglycemia and extreme hyperglycemia should be avoided in acute ischemic heart conditions. Certain diabetic treatment options, especially sodium-glucose cotransporter-2 (SGLT2) inhibitors, can reduce overall cardiovascular mortality and hospitalization due to heart failure. Therefore, we suggest that physicians should choose SGLT2 inhibitors as the first-line treatment option in diabetic patients with heart failure or those who have a high risk of heart failure development. T2DM increases the risk of atrial fibrillation (AF), and metformin and pioglitazone seem to reduce the risk of AF in diabetic population.

Glucose-dependent insulinotropic polypeptide and tissue inflammation: Implications for atherogenic cardiovascular disease

Glucose-dependent insulinotropic polypeptide (GIP) has pleiotropic actions on pancreatic endocrine function, adipose tissue lipid metabolism, and skeletal calcium metabolism. Recent data indicate a potential new role for GIP in the pathogenesis of cardiovascular disease. This review focuses on the emerging literature that highlights GIP’s role in inflammation—an established process in the initiation and progression of atherosclerosis. In vasculature tissue, GIP may reduce concentrations of circulating inflammatory cytokines, attenuate vascular endothelial inflammation, and directly limit atherosclerotic vascular damage. Important to recognize is that evidence exists to support both pro- and anti-inflammatory effects of GIP even within the same tissue/cell type. Therefore, future study designs must account for factors such as model heterogeneity, physiological relevance of doses/exposures, potential indirect effects on inflammatory pathways, and the glucose-dependent insulinotropic polypeptide receptor (GIPR) agonist form. Elucidating the specific effects of enhanced GIP signaling in vascular inflammation and atherosclerosis is crucial given the existing widespread use of DPP4 inhibitors and the emergence of dual-incretin receptor agonists for type 2 diabetes treatment.

Effects of Antidiabetic Drugs on Endothelial Function in Patients With Type 2 Diabetes Mellitus: A Bayesian Network Meta-Analysis

BACKGROUND

The changes of endothelial function in type 2 diabetes mellitus (T2DM) patients are closely associated with the development of cardiovascular disease (CVD). However, it is still unclear whether commonly used antidiabetic drugs can improve endothelial function. Flow-mediated dilation (FMD) is a noninvasive tool for evaluating endothelial function, which typically examines changes in the brachial artery diameter in response to ischemia using ultrasound. We performed a network meta-analysis (NMA) to explore the associations between changes in endothelial function and antidiabetic drugs by evaluating FMD in T2DM patients.

METHODS

We systematically searched several electronic databases for randomized controlled trials (RCTs) published from inception until January 25, 2022 with no language restriction. The primary outcome was FMD change in all studies, and we performed subgroup analysis in T2DM patients without CVD. NMA was performed to calculate the mean differences (MDs) with 95% confidence intervals (CIs).

RESULTS

From the 1,987 candidate articles identified in the initial search, 30 RCTs were eventually included in the analysis. In all studies, glucagon-like peptide-1 receptor (GLP-1R) agonists [MD = 3.70 (1.39-5.97)], TZD [MD = 1.96 (0.006-3.89)] produced improvement of FMD change compared to lifestyle intervention. GLP-1R agonists [MD = 3.33 (1.36-5.34) and MD = 3.30 (1.21-5.43)] showed significantly greater improvements in FMD change in pairwise comparisons with sulfonylureas and placebo. SGLT-2i also showed efficacy compared to sulfonylureas (MD = 1.89, 95% CI, 0.10, 3.75). In studies of T2DM patients without CVD, GLP-1R agonists [MD = 3.53 (1.24-5.76)], and TZD [MD = 2.30 (0.27-3.24)] produced improvements in FMD change compared to lifestyle treatment. GLP-1R agonists [MD = 3.25 (1.13-5.40), and MD = 3.85 (1.68-6.13)] showed significantly greater improvements in pairwise comparisons with sulfonylureas, and placebo.

CONCLUSION

In T2DM patients, both GLP-1R agonists, SGLT-2i and TZD have favorable effects to improve endothelial function in T2DM patients. In T2DM patients without CVD, GLP-1R agonists had a greater effect to improve endothelial function than sulfonylureas. These suggested that GLP-1R agonists are associated with significantly improved endothelial function in T2DM patients.

Retracted: Effect of dipeptidyl peptidase-4 inhibitors on the progression of atherosclerosis in patients with type 2 diabetes mellitus: A meta-analysis of randomised controlled trials

Yang, T, Li, W, Kan, Z, Liu, Y, Peng, M, Shi, H, Effect of dipeptidyl peptidase-4 inhibitors on the progression of atherosclerosis in patients with type 2 diabetes mellitus: A meta-analysis of randomised controlled trials. Int J Clin Pract. 2021; 00:e14213. https://onlinelibrary.wiley.com/doi/10.1111/ijcp.14213. The above article from the International Journal of Clinical Practice, published online on 5 April 2021 in Wiley Online Library (wileyonlinelibrary.com), has been retracted at the request of the authors, and by agreement of the journal Editor in Chief, Charles Young, and John Wiley and Sons Ltd. The retraction has been agreed following an author review of the research which led to the removal of some studies which did not meet the inclusion criteria. Following the removal of these studies the overall sample size was too small and the studies still included too heterogenuous for the results and conclusions to be reliable.

The Effects of Glucagon-Like Peptide-1 Receptor Agonists and Dipeptydilpeptidase-4 Inhibitors on Blood Pressure and Cardiovascular Complications in Diabetes

Glucagon-like peptide-1 receptor (GLP-1R) agonists are a class of newly introduced antidiabetic medications that potentially lower blood glucose by several molecular pathways. DPP-4 inhibitors are the other type of novel antidiabetic medications which act by preventing GLP-1 inactivation and thereby increasing the activity levels of GLP-1, leading to more glucose-induced insulin release from islet β-cells and suppression of glucagon release. Most patients with diabetes have concurrent hypertension and cardiovascular disorder. If antihyperglycemic agents can attenuate the risk of hypertension and cardiovascular disease, they will amplify their overall beneficial effects. There is conflicting evidence on the cardiovascular benefits of GLP-1R induction in laboratory studies and clinical trials. In this study, we have reviewed the main molecular mechanisms by which GLP-1R induction may modulate the cardiovascular function and the results of cardiovascular outcome clinical trials.

Diabetes Management in Patients with Heart Failure

Diabetes and heart failure (HF) are common diseases, each affecting large segments of the world population. Moreover, prevalence rates for both are expected to rise dramatically over coming decades. The high prevalence rates of both diseases and wellrecognized association of diabetes as a risk factor for HF make it inevitable that both diseases co-exist in a large number of patients, complicating their management and increasing the risk of a poor outcome. Management of diabetes has been shown to impact clinical events in patients with HF and there is emerging evidence that agents used to treat diabetes can reduce HF events, even in non-diabetic patients. In this review we summarize the clinical course and treatment of patients with type 2 diabetes mellitus (T2DM) and HF and review the efficacy and safety of pharmacological agents in patients with T2DM at risk for HF and those with established disease.

Dipeptidyl peptidase-4 inhibitor treatment and the risk of bullous pemphigoid and skin-related adverse events: A systematic review and meta-analysis of randomized controlled trials

AIMS

This meta-analysis aimed to evaluate the risk of developing bullous pemphigoid (BP) and other skin-related adverse events (AEs) in patients with type 2 diabetes (T2DM) undergoing dipeptidyl peptidase-4 inhibitor (DPP-4i) treatment in randomized controlled trials (RCTs).

METHODS

In this meta-analysis, the MEDLINE, Embase, and Cochrane Central Register of Controlled Trials databases were searched for RCTs, which involve patients with T2DM reporting skin-related AEs. RCTs that comparatively evaluated the effects of DPP-4i treatment and placebo on patients with T2DM and reported skin-related AEs were included in the analysis. The odds ratio (OR) and 95% confidence interval (CI) were calculated using the Peto's methods. The GRADE approach was used to rate the quality of evidence.

RESULTS

A total of 46 randomized placebo-controlled trials, including 3 trials with reports of BP (n = 38 011), that reported skin-related AEs were included (n = 59 332). Compared to the placebo group, the risk of developing BP was significantly higher in the DPP-4i treatment group (OR = 7.38, 95% CI 2.00-27.25, I² = 0%, P = .003; quality rating: very low). Additionally, DPP-4i treatment was associated with an increased overall risk of developing skin-related AEs (OR = 1.22, 95% CI 1.02-1.46, I² = 32%, P = .03; quality rating: moderate).

CONCLUSIONS

This meta-analysis suggested that treatment with DPP-4is, including sitagliptin, saxagliptin, and linagliptin, was associated with an increased risk of developing BP. Additionally, the risk of developing skin-related AEs increased when all DPP-4is were combined. Skin lesion, especially BP, should be monitored in patients with diabetes undergoing DPP-4i treatment. Future studies should evaluate the susceptible population and develop strategies for early detection of skin-related AEs.

Lactobacillus plantarum 299v probiotic supplementation in men with stable coronary artery disease suppresses systemic inflammation

Recent trials demonstrate that systemic anti-inflammatory therapy reduces cardiovascular events in coronary artery disease (CAD) patients. We recently demonstrated Lactobacillus plantarum 299v (Lp299v) supplementation improved vascular endothelial function in men with stable CAD. Whether this favorable effect is in part due to anti-inflammatory action remains unknown. Testing this hypothesis, we exposed plasma obtained before and after Lp299v supplementation from these subjects to a healthy donor's PBMCs and measured differences in the PBMC transciptome, performed gene ontological analyses, and compared Lp299v-induced transcriptome changes with changes in vascular function. Daily alcohol users (DAUs) (n = 4) had a significantly different response to Lp299v and were separated from the main analyses. Non-DAUs- (n = 15) showed improved brachial flow-mediated dilation (FMD) and reduced circulating IL-8, IL-12, and leptin. 997 genes were significantly changed. I.I.com decreased (1.01 ± 0.74 vs. 0.22 ± 0.51; P < 0.0001), indicating strong anti-inflammatory effects. Pathway analyses revealed downregulation of IL-1β, interferon-stimulated pathways, and toll-like receptor signaling, and an increase in regulator T-cell (Treg) activity. Reductions in GBP1, JAK2, and TRAIL expression correlated with improved FMD. In non-DAU men with stable CAD, post-Lp299v supplementation plasma induced anti-inflammatory transcriptome changes in human PBMCs that could benefit CAD patients. Future studies should delineate changes in circulating metabolites responsible for these effects.

Diabetes and Its Complications: Therapies Available, Anticipated and Aspired

Worldwide, diabetes ranks among the ten leading causes of mortality. Prevalence of diabetes is growing rapidly in low and middle income countries. It is a progressive disease leading to serious co-morbidities, which results in increased cost of treatment and over-all health system of the country. Pathophysiological alterations in Type 2 Diabetes (T2D) progressed from a simple disturbance in the functioning of the pancreas to triumvirate to ominous octet to egregious eleven to dirty dozen model. Due to complex interplay of multiple hormones in T2D, there may be multifaceted approach in its management. The 'long-term secondary complications' in uncontrolled diabetes may affect almost every organ of the body, and finally may lead to multi-organ dysfunction. Available therapies are inconsistent in maintaining long term glycemic control and their long term use may be associated with adverse effects. There is need for newer drugs, not only for glycemic control but also for prevention or mitigation of secondary microvascular and macrovascular complications. Increased knowledge of the pathophysiology of diabetes has contributed to the development of novel treatments. Several new agents like Glucagon Like Peptide - 1 (GLP-1) agonists, Dipeptidyl Peptidase IV (DPP-4) inhibitors, amylin analogues, Sodium-Glucose transport -2 (SGLT- 2) inhibitors and dual Peroxisome Proliferator-Activated Receptor (PPAR) agonists are available or will be available soon, thus extending the range of therapy for T2D, thereby preventing its long term complications. The article discusses the pathophysiology of diabetes along with its comorbidities, with a focus on existing and novel upcoming antidiabetic drugs which are under investigation. It also dives deep to deliberate upon the novel therapies that are in various stages of development. Adding new options with new mechanisms of action to the treatment armamentarium of diabetes may eventually help improve outcomes and reduce its economic burden.

When Good Guys Turn Bad: Bone Marrow's and Hematopoietic Stem Cells' Role in the Pathobiology of Diabetic Complications

Diabetes strongly contributes to the development of cardiovascular disease, the leading cause of mortality and morbidity in these patients. It is widely accepted that hyperglycemia impairs hematopoietic stem/progenitor cell (HSPC) mobilization from the bone marrow (BM) by inducing stem cell niche dysfunction. Moreover, a recent study demonstrated that type 2 diabetic patients are characterized by significant depletion of circulating provascular progenitor cells and increased frequency of inflammatory cells. This unbalance, potentially responsible for the reduction of intrinsic vascular homeostatic capacity and for the establishment of a low-grade inflammatory status, suggests that bone BM-derived HSPCs are not only victims but also active perpetrators in diabetic complications. In this review, we will discuss the most recent literature on the molecular mechanisms underpinning hyperglycemia-mediated BM dysfunction and differentiation abnormality of HSPCs. Moreover, a section will be dedicated to the new glucose-lowering therapies that by specifically targeting the culprits may prevent or treat diabetic complications.

Potential Benefits and Harms of Novel Antidiabetic Drugs During COVID-19 Crisis

Patients with diabetes have been reported to have enhanced susceptibility to severe or fatal COVID-19 infections, including a high risk of being admitted to intensive care units with respiratory failure and septic complications. Given the global prevalence of diabetes, affecting over 450 million people worldwide and still on the rise, the emerging COVID-19 crisis poses a serious threat to an extremely large vulnerable population. However, the broad heterogeneity and complexity of this dysmetabolic condition, with reference to etiologic mechanisms, degree of glycemic derangement and comorbid associations, along with the extensive sexual dimorphism in immune responses, can hamper any patient generalization. Even more relevant, and irrespective of glucose-lowering activities, DPP4 inhibitors and GLP1 receptor agonists may have a favorable impact on the modulation of viral entry and overproduction of inflammatory cytokines during COVID-19 infection, although current evidence is limited and not univocal. Conversely, SGLT2 inhibitors may increase the likelihood of COVID-19-related ketoacidosis decompensation among patients with severe insulin deficiency. Mindful of their widespread popularity in the management of diabetes, addressing potential benefits and harms of novel antidiabetic drugs to clinical prognosis at the time of a COVID-19 pandemic deserves careful consideration.

Endothelium as a Therapeutic Target in Diabetes Mellitus: From Basic Mechanisms to Clinical Practice

Endothelium plays an essential role in human homeostasis by regulating arterial blood pressure, distributing nutrients and hormones as well as providing a smooth surface that modulates coagulation, fibrinolysis and inflammation. Endothelial dysfunction is present in Diabetes Mellitus (DM) and contributes to the development and progression of macrovascular disease, while it is also associated with most of the microvascular complications such as diabetic retinopathy, nephropathy and neuropathy. Hyperglycemia, insulin resistance, hyperinsulinemia and dyslipidemia are the main factors involved in the pathogenesis of endothelial dysfunction. Regarding antidiabetic medication, metformin, gliclazide, pioglitazone, exenatide and dapagliflozin exert a beneficial effect on Endothelial Function (EF); glimepiride and glibenclamide, dipeptidyl peptidase-4 inhibitors and liraglutide have a neutral effect, while studies examining the effect of insulin analogues, empagliflozin and canagliflozin on EF are limited. In terms of lipid-lowering medication, statins improve EF in subjects with DM, while data from short-term trials suggest that fenofibrate improves EF; ezetimibe also improves EF but further studies are required in people with DM. The effect of acetylsalicylic acid on EF is dose-dependent and lower doses improve EF while higher ones do not. Clopidogrel improves EF, but more studies in subjects with DM are required. Furthermore, angiotensin- converting-enzyme inhibitors /angiotensin II receptor blockers improve EF. Phosphodiesterase type 5 inhibitors improve EF locally in the corpus cavernosum. Finally, cilostazol exerts favorable effect on EF, nevertheless, more data in people with DM are required.

The Effect of DPP-4i on Endothelial Function and Arterial Stiffness in Patients with Type 2 Diabetes: A Systematic Review of Randomized Placebo-controlled Trials

We systematically reviewed the literature regarding the impact of dipeptidyl peptidase-4 inhibitors (DPP-4i) on vascular function, including endothelial function and arterial stiffness, as predictors of atherosclerosis progression and cardiovascular disease in patients with type 2 diabetes mellitus (T2DM). We searched PubMed in order to identify clinical trials that investigated the effect of DPP-4i on vascular function in patients with T2DM when compared with placebo. Although 168 articles were initially found, only 6 studies (total 324 patients) investigated the effect of DPP-4i in comparison with placebo, specifically linagliptin and sitagliptin, and satisfied the inclusion criteria. There are scarce data to indicate that linagliptin may enhance endothelial function and exert a slight beneficial effect on arterial wall properties. Sitagliptin seems to have a neutral effect on these variables. Further trials are needed to elucidate the topic. The standards of reporting were in accordance with the PRISMA guidelines.

Circulating levels of mitochondrial uncoupling protein 2, but not prohibitin, are lower in humans with type 2 diabetes and correlate with brachial artery flow-mediated dilation

BACKGROUND

Excessive reactive oxygen species from endothelial mitochondria in type 2 diabetes individuals (T2DM) may occur through multiple related mechanisms, including production of mitochondrial reactive oxygen species (mtROS), inner mitochondrial membrane (Δψ_m) hyperpolarization, changes in mitochondrial mass and membrane composition, and fission of the mitochondrial networks. Inner mitochondrial membrane proteins uncoupling protein-2 (UCP2) and prohibitin (PHB) can favorably impact mtROS and mitochondrial membrane potential (Δψ_m). Circulating levels of UCP2 and PHB could potentially serve as biomarker surrogates for vascular health in patients with and without T2DM.

METHODS

Plasma samples and data from a total of 107 individuals with (N = 52) and without T2DM (N = 55) were included in this study. Brachial artery flow mediated dilation (FMD) was measured by ultrasound. ELISA was performed to measure serum concentrations of PHB1 and UCP2. Mitochondrial membrane potential was measured from isolated leukocytes using JC-1 dye.

RESULTS

Serum UCP2 levels were significantly lower in T2DM subjects compared to control subjects (3.01 ± 0.34 vs. 4.11 ± 0.41 ng/mL, P = 0.04). There were no significant differences in levels of serum PHB. UCP2 levels significantly and positively correlated with FMDmm (r = 0.30, P = 0.03) in T2DM subjects only and remained significant after multivariable adjustment. Within T2DM subjects, serum PHB levels were significantly and negatively correlated with UCP2 levels (ρ = - 0.35, P = 0.03).

CONCLUSION

Circulating UCP2 levels are lower in T2DM patients and correlate with endothelium-dependent vasodilation in conduit vessels. UCP2 could be biomarker surrogate for overall vascular health in patients with T2DM and merits additional investigation.

Understanding Bile Acid Signaling in Diabetes: From Pathophysiology to Therapeutic Targets

Diabetes and obesity have reached an epidemic status worldwide. Diabetes increases the risk for cardiovascular disease and non-alcoholic fatty liver disease. Primary bile acids are synthesized in hepatocytes and are transformed to secondary bile acids in the intestine by gut bacteria. Bile acids are nutrient sensors and metabolic integrators that regulate lipid, glucose, and energy homeostasis by activating nuclear farnesoid X receptor and membrane Takeda G protein-coupled receptor 5. Bile acids control gut bacteria overgrowth, species population, and protect the integrity of the intestinal barrier. Gut bacteria, in turn, control circulating bile acid composition and pool size. Dysregulation of bile acid homeostasis and dysbiosis causes diabetes and obesity. Targeting bile acid signaling and the gut microbiome have therapeutic potential for treating diabetes, obesity, and non-alcoholic fatty liver disease.

Bile Acids as Metabolic Regulators and Nutrient Sensors

Bile acids facilitate nutrient absorption and are endogenous ligands for nuclear receptors that regulate lipid and energy metabolism. The brain-gut-liver axis plays an essential role in maintaining overall glucose, bile acid, and immune homeostasis. Fasting and feeding transitions alter nutrient content in the gut, which influences bile acid composition and pool size. In turn, bile acid signaling controls lipid and glucose use and protection against inflammation. Altered bile acid metabolism resulting from gene mutations, high-fat diets, alcohol, or circadian disruption can contribute to cholestatic and inflammatory diseases, diabetes, and obesity. Bile acids and their derivatives are valuable therapeutic agents for treating these inflammatory metabolic diseases.

Pharmacology of dipeptidyl peptidase-4 inhibitors and its use in the management of metabolic syndrome: a comprehensive review on drug repositioning

OBJECTIVES

Despite advances in our understanding of metabolic syndrome (MetS) and the treatment of each of its components separately, currently there is no single therapy approved to manage it as a single condition. Since multi-drug treatment increases drug interactions, decreases patient compliance and increases health costs, it is important to introduce single therapies that improve all of the MetS components.

EVIDENCE ACQUISITION

We conducted a PubMed, Scopus, Google Scholar, Web of Science, US FDA, utdo.ir and clinicaltrial.gov search, gathered the most relevant preclinical and clinical studies that have been published since 2010, and discussed the beneficial effects of dipeptidyl peptidase (DPP)-4 inhibitors to prevent and treat different constituent of the MetS as a single therapy. Furthermore, the pharmacology of DPP-4 inhibitors, focusing on pharmacodynamics, pharmacokinetics, drug interactions and their side effects are also reviewed.

RESULTS

DPP-4 inhibitors or gliptins are a new class of oral anti-diabetic drugs that seem safe drugs with no severe side effects, commonly GI disturbance, infection and inflammatory bowel disease. They increase mass and function of pancreatic β-cells, and insulin sensitivity in liver, muscle and adipose tissue. It has been noted that gliptin therapy decreases dyslipidemia. DPP-4 inhibitors increase fatty oxidation, and cholesterol efflux, and decrease hepatic triglyceride synthase and de novo lipogenesis. They delay gastric emptying time and lead to satiety. Besides, gliptin therapy has anti-inflammatory and anti-atherogenic impacts, and improves endothelial function and reduces vascular stiffness.

CONCLUSION

The gathered data prove the efficacy of DPP-4 inhibitors in managing MetS in some levels beyond anti-diabetic effects. This review could be a lead for designing new DPP-4 inhibitors with greatest effects on MetS in future. Introducing drugs with polypharmacologic effects could increase the patient's compliance and decrease the health cost that there is not in multi-drug therapy. Graphical abstract ᅟ.

Influence of type-4 dipeptidyl peptidase inhibition on endothelium-dependent relaxation of aortae from a db/db mouse model of type 2 diabetes: a comparison with the effect of glimepiride

PURPOSE

The aim of this study was to investigate the effects of the type-4 dipeptidyl peptidase (DPP-4) inhibitors linagliptin and vildagliptin as well as the sulfonylurea glimepiride on endothelium-dependent relaxation of aortae from female db/db mice with established hyperglycemia to determine whether these treatments were able to attenuate diabetes-induced endothelial dysfunction.

MATERIALS AND METHODS

The mice were treated with glimepiride (2 mg/kg po per day, weeks 1-6, n=12), glimepiride plus vildagliptin (glimepiride 2 mg/kg po per day, weeks 1-6; vildagliptin 3 mg/kg po per day, weeks 4-6, n=11), glimepiride plus linagliptin (glimepiride 2 mg/kg po per day, weeks 1-6; linagliptin 3 mg/kg po per day, weeks 4-6, n=11) or linagliptin (3 mg/kg po per day, weeks 1-6, n=12). Endothelium-dependent relaxation using acetylcholine was assessed in the absence and presence of pharmacological tools (TRAM-34 1 μM; apamin 1 μM; N-nitro-L-arginine [L-NNA] 100 μM; 1H-[1,2,4]oxadiazolo [4,3-a]quinoxalin-1-one [ODQ] 10 μM) to distinguish relaxation mediated by nitric oxide (NO).

RESULTS

Linagliptin was associated with a significant improvement in endothelium-dependent relaxation (ACh Rmax; db/db 41±1%, linagliptin 73±6%, p<0.05). The enhanced response was maintained in the presence of TRAM-34+ apamin (ACh Rmax; db/db 23±6%, linagliptin 60±6%, p<0.01), ie, when the endothelium-dependent relaxation was mediated by NO. There was no evidence for a contribution from K_Ca channel opening to responses under any conditions. Glimepiride had no effect on endothelium-dependent relaxation when given alone (ACh Rmax 38±3%). The addition of linagliptin or vildagliptin to glimepiride did not significantly improve endothelium-dependent relaxation. All treatments caused some decrease in aortic superoxide production but the effect of linagliptin was significantly greater than glimepiride (linagliptin 534±60 relative luminescence unit [RLU], glimepiride 1471±265 RLU, p<0.05).

CONCLUSION

Linagliptin is superior to glimepiride in regard to the preservation of endothelium-dependent relaxation in the presence of hyperglycemia and the improvement in endothelial function in response to linagliptin treatment is associated with greater antioxidant activity compared to glimepiride.

Impact of dipeptidyl-peptidase 4 inhibitors on cardiovascular diseases

Dipeptidyl peptidase 4 (DPP-4) inhibitor is a novel group of medicine employed in type 2 diabetes mellitus (T2DM),which improves meal stimulated insulin secretion by protecting glucagon-like peptide-1 (GLP-1) and glucose dependent insulinotropic polypeptide (GIP) from enzymatic degradation. Cardiovascular diseases are serious complications and leading causes of mortality among individuals with diabetes mellitus. Glycemic control per se seems to fail in preventing the progression of diabetic cardiovascular complications. DPP-4 has the capability to inactivate not only incretins, but also a series of cytokines, chemokines, and neuropeptides involved in inflammation, immunity, and vascular function. Pre-clinical studies suggested that DPP-4 inhibitors may have potential cardiovascular protective effects in addition to their antidiabetic actions. In recent years, a number of clinical trials have been conducted to evaluate the effect of different DPP-4 inhibitors on the cardiovascular system. We herein review the available clinical studies in cardiovascular effects played by each DPP-4 inhibitor and discuss the prospective application of DPP-4 inhibitors on cardiovascular diseases.

Exogenous SERP1 attenuates restenosis by restoring GLP-1 receptor activity in diabetic rats following vascular injury

The activity of glucagon-like peptide 1 (GLP-1R) is essential for preventing restenosis following vascular injury; however, the mechanism of dysfunctional GLP-1R glycosylation and ways to enhance the activity of GLP-1R on vascular surfaces in diabetic patients are poorly understood. In the present study, we investigated the N-glycosylation level and role of stress-associated endoplasmic reticulum protein 1 (SERP1) in preventing restenosis following carotid injury in diabetic rats. Our results showed that N-glycosylation levels in both rat aortic endothelial cells (RAOECs) and rat vascular smooth muscle cells (VSMCs) decreased gradually following glucose treatment in a concentration dependant manner. Furthermore, co-immunoprecipitation (Co-IP) analyses indicated that SERP1 could interact with GLP-1R in RAOECs and VSMCs. Moreover, SERP1 enhanced GLP-1R N-glycosylation and increased the production of phosphorylated endothelial nitric oxide synthase (eNOS) as well as proliferation of RAOECs. SERP1 also increased phosphorylated adenosine monophosphate activated protein kinase (AMPK) and decreased the migration of VSMCs. Importantly, intima media thickness (IMT) and neointimal hyperplasia were alleviated in the carotid artery of diabetic rats injected with SERP1 following balloon injury. We also found an increase in re-endothelialization and a decrease in VSMC proliferation in the carotid artery of diabetic rats injected with SERP1. In summary, the remarkable effects of SERP1 on reducing restenosis following vascular injury may contribute to future advancements in the treatment of diabetic vascular complications.

Effects of Newer Antidiabetic Drugs on Endothelial Function and Arterial Stiffness: A Systematic Review and Meta-Analysis

BACKGROUND

Newer antidiabetic drugs, i.e., dipeptidyl peptidase-4 (DPP-4) inhibitors, sodium-glucose cotransporter-2 (SGLT-2) inhibitors, and glucagon-like peptide-1 receptor agonists (GLP-1 RAs) may exert distinct cardiovascular effects. We sought to explore their impact on vascular function.

METHODS

Published literature was systematically searched up to January 2018 for clinical studies assessing the effects of DPP-4 inhibitors, GLP-1 RAs, and SGLT-2 inhibitors on endothelial function and arterial stiffness, assessed by flow-mediated dilation (FMD) of the brachial artery and pulse wave velocity (PWV), respectively. For each eligible study, we used the mean difference (MD) with 95% confidence intervals (CIs) for FMD and PWV. The pooled MD for FMD and PWV were calculated by using a random-effect model. The presence of heterogeneity among studies was evaluated by the I ² statistic.

RESULTS

A total of 26 eligible studies (n = 668 patients) were included in the present meta-analysis. Among newer antidiabetic drugs, only SGLT-2 inhibitors significantly improved FMD (pooled MD 1.14%, 95% CI: 0.18 to 1.73, p = 0.016), but not DPP-4 inhibitors (pooled MD = 0.86%, 95% CI: -0.15 to 1.86, p = 0.095) or GLP-1 RA (pooled MD = 2.37%, 95% CI: -0.51 to 5.25, p = 0.107). Both GLP-1 RA (pooled MD = -1.97, 95% CI: -2.65 to -1.30, p < 0.001) and, to a lesser extent, DPP-4 inhibitors (pooled MD = -0.18, 95% CI: -0.30 to -0.07, p = 0.002) significantly decreased PWV.

CONCLUSIONS

Newer antidiabetic drugs differentially affect endothelial function and arterial stiffness, as assessed by FMD and PWV, respectively. These findings could explain the distinct effects of these drugs on cardiovascular risk of patients with type 2 diabetes.