DPP-4 inhibitor and alpha-glucosidase inhibitor equally improve endothelial function in patients with type 2 diabetes: EDGE study

Postprandial glucose-lowering effects by sago (Metroxylon sagu Rottb.) resistant starch in spontaneously type 2 diabetes, Goto-Kakizaki rat

Introduction: The beneficial effects of resistant starch (RS) consumption on health in terms of reducing postprandial hyperglycaemia are evident. However, the potential of local Sarawak sago RS in regulating glucose has not been extensively studied. Objectives: This study aims to identify glucose-lowering effects of Sarawak sago RS, namely native (RS2) and chemically modified (RS4). Methodology: An oral glucose tolerance test (OGTT) was performed before and after 1 month treatment with sago RS2 and RS4 in spontaneously type 2 diabetes (T2D), Goto-Kakizaki (GK) rat. The mechanisms involved were further explored by screening the in vitro inhibitory activities of α-glucosidase and dipeptidyl peptidase (DPP)-IV. Histopathology examination for pancreas, kidney and liver tissues was done in response to sago RS intake using haematoxylin and eosin (H&E) staining. Results and discussion: The incremental area under the curve (iAUC) for blood glucose in RS-treated groups was decreased and significant in RS2-treated group (p < 0.05). Improved iAUC for insulin and higher glucagon-like peptide (GLP-1) levels were observed in all RS-treated groups (p < 0.05). Both sago RS may have potential roles in regulating glucose via α- glucosidase and DPP-IV inhibitory activities by reducing intestinal glucose absorption. For histopathology, although insignificant, sago RS2 and RS4 attenuated lesion scores of pancreatic tissue whereas the liver and kidney tissues significantly showed lesser lesion scores compared to the control diabetic group suggesting the potential of RS in reducing cell degeneration. Conclusion: Findings of this study indicates that RS2 showed greater glucose-lowering effect when compared to RS4, thus the therapeutic potential in the T2D management should be further explored.

The Roadmap of Plant Antimicrobial Peptides Under Environmental Stress: From Farm to Bedside

Antimicrobial peptides (AMPs) are the most favorable alternatives in overcoming multidrug resistance, alone or synergistically with conventional antibiotics. Plant-derived AMPs, as cysteine-rich peptides, widely compensate the pharmacokinetic drawbacks of peptide therapeutics. Compared to the putative genes encrypted in the genome, AMPs that are produced under stress are active forms with the ability to combat resistant microbial species. Within this study, plant-derived AMPs, namely, defensins, nodule-specific cysteine-rich peptides, snakins, lipid transfer proteins, hevein-like proteins, α-hairpinins, and aracins, expressed under biotic and abiotic stresses, are classified. We could observe that while α-hairpinins and snakins display a helix-turn-helix structure, conserved motif patterns such as β1αβ2β3 and β1β2β3 exist in plant defensins and hevein-like proteins, respectively. According to the co-expression data, several plant AMPs are expressed together to trigger synergistic effects with membrane disruption mechanisms such as toroidal pore, barrel-stave, and carpet models. The application of AMPs as an eco-friendly strategy in maintaining agricultural productivity through the development of transgenes and bio-pesticides is discussed. These AMPs can be consumed in packaging material, wound-dressing products, coating catheters, implants, and allergology. AMPs with cell-penetrating properties are verified for the clearance of intracellular pathogens. Finally, the dominant pharmacological activities of bioactive peptides derived from the gastrointestinal digestion of plant AMPs, namely, inhibitors of renin and angiotensin-converting enzymes, dipeptidyl peptidase IV and α-glucosidase inhibitors, antioxidants, anti-inflammatory, immunomodulating, and hypolipidemic peptides, are analyzed. Conclusively, as phytopathogens and human pathogens can be affected by plant-derived AMPs, they provide a bright perspective in agriculture, breeding, food, cosmetics, and pharmaceutical industries, translated as farm to bedside.

A Comprehensive Review of Clinical Studies Applying Flow-Mediated Dilation

Flow-mediated dilation (FMD) is a noninvasive method to evaluate vascular endothelial function, which manifests the vascular inflammatory response, cell proliferation, and autoregulation. Since FMD is noninvasive and assesses commonly in the brachial artery by ultrasound, compared to other invasive methods such as optical coherence tomography (OCT) and intravascular ultrasound (IVUS), it is widely used to evaluate endothelial function and allows serial assessment. In this review, we present the currently accepted mechanisms and methods of FMD measurement with the studies applied in the current clinical practice using FMD. After all, the association with cardiovascular diseases is of substance, and so we introduce clinical studies of FMD related to cardiovascular disease such as diabetes, hyperlipidemia, chronic kidney disease, coronary artery disease, and peripheral vascular disease. In addition, studies related to pregnancy and COVID-19 were also inspected. Yet, endothelial examination is not endorsed as a cardiovascular prevention measure, for the lack of a clear standardized value methodology. Still, many studies recommend practicable FMD and would be a better prognostic value in the cardiovascular prognosis in future clinical research.

Effect of DPP-4i inhibitors on renal function in patients with type 2 diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials

AIMS

About 20-40% patients with type 2 diabetes mellitus (T2DM) had an increased risk of developing diabetic nephropathy (DN). Dipeptidyl peptidase-4 inhibitors (DPP-4i) were recommended for treatment of T2DM, while the impact of DPP-4i on renal function remained unclear. This study aimed to explore the effect of DPP-4i on renal parameter of estimated glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR) in T2DM.

METHODS

A systematic search was performed across PubMed, Embase and Cochrane Library. A fixed or random-effects model was used for quantitative synthesis according to the heterogeneity, which was assessed with I2 index. Sensitivity analysis and publication bias were performed with standard methods, respectively.

RESULTS

A total of 17 randomized controlled trials were identified. Administration of DPP-4i produced no significant effect on eGFR (WMD, -0.92 mL/min/1.73m2, 95% CI, -2.04 to 0.19) in diabetic condition. DPP-4i produced a favorable effect on attenuating ACR (WMD, -2.76 mg/g, 95% CI, -5.23 to -0.29) in patients with T2DM. The pooled estimate was stable based on the sensitivity test. No publication bias was observed according to Begg's and Egger's tests.

CONCLUSIONS

Treatment with DPP-4i preserved the renal parameter of eGFR in diabetic condition. Available evidences suggested that administration of DPP-4i produced a favorable effect on attenuating ACR in patients with T2DM. INTERNATIONAL PROSPECTIVE REGISTER FOR SYSTEMATIC REVIEW (PROSPERO) NUMBER: CRD.42020144642.

The Impact of Modern Anti-Diabetic Treatment on Endothelial Progenitor Cells

Diabetes is one of the leading chronic diseases globally with a significant impact on mortality. This condition is associated with chronic microvascular and macrovascular complications caused by vascular damage. Recently, endothelial progenitor cells (EPCs) raised interest due to their regenerative properties. EPCs are mononuclear cells that are derived from different tissues. Circulating EPCs contribute to regenerating the vessel's intima and restoring vascular function. The ability of EPCs to repair vascular damage depends on their number and functionality. Diabetic patients have a decreased circulating EPC count and impaired EPC function. This may at least partially explain the increased risk of diabetic complications, including the increased cardiovascular risk in these patients. Recent studies have confirmed that many currently available drugs with proven cardiovascular benefits have beneficial effects on EPC count and function. Among these drugs are also medications used to treat different types of diabetes. This manuscript aims to critically review currently available evidence about the ways anti-diabetic treatment affects EPC biology and to provide a broader context considering cardiovascular complications. The therapies that will be discussed include lifestyle adjustments, metformin, sulphonylureas, gut glucosidase inhibitors, thiazolidinediones, dipeptidyl peptidase 4 inhibitors, glucagon-like peptide 1 receptor analogs, sodium-glucose transporter 2 inhibitors, and insulin.

Endothelial progenitor cells as biomarkers of diabetes-related cardiovascular complications

Diabetes mellitus (DM) constitutes a chronic metabolic disease characterized by elevated levels of blood glucose which can also lead to the so-called diabetic vascular complications (DVCs), responsible for most of the morbidity, hospitalizations and death registered in these patients. Currently, different approaches to prevent or reduce DM and its DVCs have focused on reducing blood sugar levels, cholesterol management or even changes in lifestyle habits. However, even the strictest glycaemic control strategies are not always sufficient to prevent the development of DVCs, which reflects the need to identify reliable biomarkers capable of predicting further vascular complications in diabetic patients. Endothelial progenitor cells (EPCs), widely known for their potential applications in cell therapy due to their regenerative properties, may be used as differential markers in DVCs, considering that the number and functionality of these cells are affected under the pathological environments related to DM. Besides, drugs commonly used with DM patients may influence the level or behaviour of EPCs as a pleiotropic effect that could finally be decisive in the prognosis of the disease. In the current review, we have analysed the relationship between diabetes and DVCs, focusing on the potential use of EPCs as biomarkers of diabetes progression towards the development of major vascular complications. Moreover, the effects of different drugs on the number and function of EPCs have been also addressed.

Edible Insects as a Novel Source of Bioactive Peptides: A Systematic Review

The production of food and feed to meet the needs of the growing world's population will soon become a serious challenge. In search for sustainable solutions, entomophagy is being proposed as an alternative source of proteins, with economic and environmental advantages when compared to meat. Edible insects are not only a valuable source of important nutrients, but their gastrointestinal digestion also originates small peptides with important bioactive properties. The present work intends to provide an exhaustive systematic review on research articles reporting bioactive peptides identified from edible insects, as demonstrated by in silico, in vitro, and/or in vivo assays. A total of 36 studies were identified following the PRISMA methodology, gathering 211 potentially bioactive peptides with antioxidant, antihypertensive, antidiabetic, antiobesity, anti-inflammatory, hypocholesterolemia, antimicrobial, anti-severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), antithrombotic, and immunomodulatory properties, originated from the hydrolysates of 12 different insect species. From these candidates, the bioactive properties of 62 peptides were characterized in vitro and 3 peptides were validated in vivo. Data establishing the scientific basis of the health benefits associated with the consumption of edible insects can be a valuable contribution to overcoming the cultural issues that hinder the introduction of insects in the Western diet.

Improving the Effects of Imeglimin on Endothelial Function: A Prospective, Single-Center, Observational Study

INTRODUCTION

Endothelial dysfunction is a risk factor for cardiovascular disease in patients with diabetes. We hypothesized that imeglimin, a novel oral hypoglycemic agent, would improve endothelial function.

METHODS

In this study, imeglimin was administered to patients with type 2 diabetes and HbA1c ≥ 6.5% who were not receiving insulin therapy. A meal tolerance test (592 kcal, glucose 75.0 g, fat 28.5 g) was performed before and 3 months after administration, and endothelial function, blood glucose, insulin, glucagon, and triglycerides were evaluated. Endothelial function was assessed by flow-mediated dilation (FMD).

RESULTS

Twelve patients (50% male) with a median age of 55.5 years old (interquartile range [IQR] 51.3-66.0) were enrolled. Fasting FMD did not differ before or 3 months after imeglimin administration (from 6.1 [3.9-8.5] to 6.6 [3.9-9.0], p = 0.092), but 2 h postprandial FMD was significantly improved 3 months after imeglimin administration (from 2.3 [1.9-3.4] to 2.9 [2.4-4.7], p = 0.013). In terms of the glucose profile, imeglimin administration significantly improved HbA1c (from 7.2 ± 0.6% to 6.9 ± 0.6%, p = 0.007), fasting glucose (from 138 ± 19 mg/dL to 128 ± 20 mg/dL, p = 0.020), and 2 h postprandial glucose (from 251 ± 47 mg/dL to 215 ± 68 mg/dL, p = 0.035). The change in 2 h postprandial FMD between before and 3 months after imeglimin administration (Δ2 h postprandial FMD) was negatively correlated with Δ2 h postprandial glucose (r = - 0.653, p = 0.021) in a univariate correlation coefficient analysis. Both patients with and without decreased postprandial glucose 3 months after imeglimin administration had improved postprandial FMD.

CONCLUSION

In this small study, imeglimin administration improved 2 h postprandial FMD. Both glycemic control-dependent and -independent mechanisms might contribute to improved endothelial function.

TRIAL REGISTRATION

This research was registered in the University Hospital Medical Information Network (UMIN, UMIN000046311).

2,5-Disubstituted furan derivatives containing imidazole, triazole or tetrazole moiety as potent α-glucosidase inhibitors

α-Glucosidase inhibitors (AGIs) are oral antidiabetic drugs, preferably used in treating type 2 diabetes mellitus, that delay the absorption of carbohydrates from the gastrointestinal system. In this work, 2,5-disubstituted furan derivatives containing imidazole, triazole or tetrazole moiety (III-01 ∼ III-45) were synthesized and characterized by elemental analysis, HRMS, ¹H NMR, ¹³C NMR and single crystal X-ray. Their inhibitory activity against α-glucosidase was screened. The most promising inhibitors were compound III-11 (IC₅₀ = 6.0 ± 1.1 μM), III-16 (IC₅₀ = 2.2 ± 0.2 μM) and III-39 (IC₅₀ = 4.6 ± 1.9 μM), respectively. Kinetic study revealed that compounds III-11 and III-39 were uncompetitive inhibitors against α-glucosidase. Meanwhile, III-16 (Ki = 5.1 ± 0.7 μM) was a competitive inhibitor. Furthermore, molecular docking studies indicated that the existence of the azole group played a critically important role in hydrogen bond interaction with α-glucosidase. Significantly, in vivo toxicity towards HEK293 cells, RAW264.7 cells and HepG2 cells suggested that compounds III-11 and III-39 possessed non-toxicity, that could be considered as potential candidates for further development of novel antidiabetic drugs.

Teneligliptin, a DPP-4 Inhibitor, Improves Vascular Endothelial Function via Divergent Actions Including Changes in Circulating Endothelial Progenitor Cells

PURPOSE

Dipeptidyl peptidase-4 (DPP-4) inhibitors increase endothelial progenitor cells (EPCs) in peripheral blood circulation. However, the underlying mechanisms and effects on vascular endothelial function remain unclear. We evaluated whether the DPP-4 inhibitor teneligliptin increases circulating EPCs by inhibiting stromal-derived factor-1α (SDF-1α) and improves flow-mediated vascular dilatation (FMD) in type 2 diabetes mellitus patients with acute coronary syndrome (ACS) or its risk factors.

PATIENTS AND METHODS

This single-center, open-label, prospective, randomized controlled trial evaluated 17 patients (hemoglobin A1c ≤7.5% and peak creatinine phosphokinase <2000 IU/mL) with ACS or a history of ACS or multiple cardiovascular risk factors. Metabolic variables of glucose and lipids, circulating EPCs, plasma DPP-4 activity, and SDF-1α levels, and FMD were evaluated at baseline and 28 ± 4 weeks after enrollment. Patients were randomly assigned to either the teneligliptin (n = 8) or control (n = 9) groups.

RESULTS

The DPP-4 activity (∆-509.5 ± 105.7 vs ∆32.8 ± 53.4 μU/mL) and SDF-1α levels (∆-695.6 ± 443.2 vs ∆11.1 ± 193.7 pg/mL) were significantly decreased after 28 weeks in the teneligliptin group than those in the control group. The number of EPCs showed an increasing trend in the teneligliptin treated group; albeit this did not reach statistical significance. Glucose and lipid levels were not significantly different between the groups before and after 28 weeks. However, FMD was significantly improved in the teneligliptin group when compared to the control group (∆3.8% ± 2.1% vs ∆-0.3% ± 2.9%, P=0.006).

CONCLUSION

Teneligliptin improved FMD through a mechanism other than increasing the number of circulating EPCs.

A cohort study of circulating progenitor cells after ST-segment elevation and non-ST segment elevation myocardial infarction in non-diabetic and diabetic patients

Background

Myocardial infarction induces elevation of progenitor cells in the circulation, a reparative response inhibited by type-2 diabetes.

Objectives

Determine if myocardial infarct severity and diabetes interactively influence the migratory activity of CD34+/CXCR4+ progenitor cells and if the migratory test predicts cardiac outcomes.

Materials and methods

A longitudinal study was conducted on patients with or without diabetes with a STEMI or NSTEMI. CD34+/CXCR4+ cells were measured in the peripheral blood using flow cytometry, and migratory activity was tested in vitro on cells isolated from samples collected on days 0 and 4 post-infarct. Cardiac function was assessed at three months using cardiac MRI.

Results

Of 1,149 patients screened, 71 (6.3%) were eligible and consented. Fifty had STEMI (16 with diabetes) and 21 NSTEMI (8 with diabetes). The proportion of CD34+/CXCR4+ cells within blood mononuclear cells was 1.96 times higher after STEMI compared with NSTEMI (GMR = 1.96, 95% CI 0.87, 4.37) and 1.55 times higher in patients with diabetes compared to patients without diabetes (GMR = 1.55, 95% CI 0.77, 3.13). In the latter, STEMI was associated with a 2.42-times higher proportion of migrated CD34 + /CXCR4 + cells compared with NSTEMI (GMR = 2.42, 95% CI 0.66, 8.81). In patients with diabetes, the association was the opposite, with a 55% reduction in the proportion of migrated CD34+/CXCR4+ cells. No statistically significant associations were observed between the frequency in peripheral blood or in vitro migration capacity of CD34+/CXCR4+ cells and MRI outcomes.

Conclusion

We document the interaction between infarct and diabetes on the migratory activity of CD34+/CXCR4+ cells. The test did not predict functional outcomes in the studied cohort.

Effects of sitagliptin on serum lipid levels in patients with type 2 diabetes: a systematic review and meta-analysis

AIM

Lipid abnormalities often occur in patients with diabetes mellitus and the coexistence of diabetes mellitus and dyslipidaemia will increase the risk of cardiovascular diseases. However, the specific effects of sitagliptin on lipid control remain elusive in diabetic patients. The aim of this meta-analysis is to investigate the effects of sitagliptin alone or with other antidiabetic agents on serum lipid control.

METHODS

PubMed, Cochrane Library, Embase and the ClinicalTrials.gov website were systematically searched from 2006 (the first year that sitagliptin entered market) to 16 January 2021. Eligible studies were randomized clinical trials (RCTs) of sitagliptin including outcomes of serum total cholesterol (TC), triglycerides, high-density lipoprotein cholesterol (HDL-C) or low-density lipoprotein cholesterol (LDL-C).

RESULTS

A total of 14 RCTs with 2654 patients were identified. Treatment with sitagliptin alone or in combination with other antidiabetic agents significantly reduced serum TC [mean difference (MD) = -5.52 95% confidence interval (95% CI), -7.88 to -3.15; P < 0.00001] and LDL-C (MD = -0.07; 95% CI, -0.14 to 0.00; P < 0.00001) in patients with type 2 diabetes. No statistical significances were found in serum triglycerides (MD = 1.53; 95% CI, -8.22 to 11.28; P = 0.76) or HDL-C (MD = 0.65; 95% CI, -1.59 to 0.29; P = 0.18). Subgroup analyses suggest that sitagliptin can significantly decrease serum LDL-C, TC and triglyceride levels compared with placebo alone, and no statistical significance was found in comparison with the serum HDLC levels.

CONCLUSION

Sitagliptin alone or in combination with other antidiabetic agents significantly reduces serum TC and LDL-C in patients with type 2 diabetes mellitus, while no significant difference was observed in serum triglycerides or HDL-C.

Effect of Anagliptin versus Sitagliptin on Renal Function: Subanalyzes from the REASON Trial

PURPOSE

The effects of two types of dipeptidyl peptidase-4 (DPP-4) inhibitors on renal function remain unclear. Thus, we investigated the effect of anagliptin (ANA) and sitagliptin (SITA) on renal function in patients with type 2 diabetes who participated in the randomized evaluation of ANA versus SITA on low-density lipoprotein-cholesterol (LDL-C) in diabetes (REASON) trial.

PATIENTS AND METHODS

We measured the estimated glomerular filtration rate (eGFR) and urinary albumin-creatinine ratio (UACR) before and after the REASON trial. ANA 200 mg/day was administered to 177 patients for 52 weeks, while SITA 50 mg/day was given to 176 patients. We investigated the relationship between differences in renal function and differences in hemoglobin A1c (HbA1c) levels, LDL-C levels, and blood pressure (BP).

RESULTS

No significant differences were found in baseline eGFR and UACR between the two groups. The eGFR levels were significantly decreased in both groups; however, the UACR level was unchanged in the ANA group but elevated in the SITA group, although the difference did not reach significance between the two groups. The difference in eGFR was affected by the differences in HbA1c level and BP, and the difference in the UACR was affected by the differences in LDL-C level and BP, which were reduced only in the ANA group.

CONCLUSION

These findings imply that the effects of DPP-4 inhibitors on renal function, especially on UACR, may be different between the types of DPP-4 inhibitors.

Comparison of the effects of empagliflozin and glimepiride on endothelial function in patients with type 2 diabetes: A randomized controlled study

Patients with type 2 diabetes who have cardiovascular disease and are receiving empagliflozin have a lower rate of primary composite cardiovascular outcomes. In contrast, glimepiride increases cardiovascular hospitalization when combined with metformin. Here, we assessed the effects of empagliflozin and glimepiride on endothelial function using flow-mediated dilation (FMD). In this prospective, open-label, randomized, parallel-group study, 63 patients with type 2 diabetes received metformin and insulin glargine U100 for 12 weeks. This was followed by additional treatment with empagliflozin or glimepiride for 12 weeks. The primary outcome was the change in the FMD measurement (ΔFMDs) at 24 weeks of additional treatment. Secondary outcomes comprised changes in metabolic markers and body composition. The empagliflozin group (n = 33) and glimepiride group (n = 30) showed no significant differences in ΔFMDs (empagliflozin, −0.11 [95%CI: -1.02, 0.80]%; glimepiride, −0.34 [95%CI: -1.28, 0.60]%; P = 0.73). Additionally, changes in glycated hemoglobin were similar between the two groups. However, a significant difference in body weight change was observed (empagliflozin, −0.58 [95%CI: -1.60, 0.43] kg; glimepiride, 1.20 [95%CI: 0.15, 2.26] kg; P = 0.02). Moreover, a body composition analysis revealed that body fluid volume significantly decreased after empagliflozin treatment (baseline, 35.8 ± 6.8 L; after 12 weeks, −0.33 ± 0.72 L; P = 0.03). Hence, although empagliflozin did not improve endothelial function compared with glimepiride for patients with type 2 diabetes, it did decrease body fluid volumes. Thus, the coronary-protective effect of empagliflozin is not derived from endothelial function protection, but rather from heart failure risk reduction.

Trial registration: This trial was registered on September 13, 2016; UMIN000024001.

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.

Diabetes pathogenesis and management: the endothelium comes of age

Endothelium, acting as a barrier, protects tissues against factors that provoke insulin resistance and type 2 diabetes and itself responds to the insult of insulin resistance inducers with altered function. Endothelial insulin resistance and vascular dysfunction occur early in the evolution of insulin resistance-related disease, can co-exist with and even contribute to the development of metabolic insulin resistance, and promote vascular complications in those affected. The impact of endothelial insulin resistance and vascular dysfunction varies depending on the blood vessel size and location, resulting in decreased arterial plasticity, increased atherosclerosis and vascular resistance, and decreased tissue perfusion. Women with insulin resistance and diabetes are disproportionately impacted by cardiovascular disease, likely related to differential sex-hormone endothelium effects. Thus, reducing endothelial insulin resistance and improving endothelial function in the conduit arteries may reduce atherosclerotic complications, in the resistance arteries lead to better blood pressure control, and in the microvasculature lead to less microvascular complications and more effective tissue perfusion. Multiple diabetes therapeutic modalities, including medications and exercise training, improve endothelial insulin action and vascular function. This action may delay the onset of type 2 diabetes and/or its complications, making the vascular endothelium an attractive therapeutic target for type 2 diabetes and potentially type 1 diabetes.

Targeting N-Terminal Human Maltase-Glucoamylase to Unravel Possible Inhibitors Using Molecular Docking, Molecular Dynamics Simulations, and Adaptive Steered Molecular Dynamics Simulations

There are multiple drugs for the treatment of type 2 diabetes, including traditional sulfonylureas biguanides, glinides, thiazolidinediones, α-glucosidase inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, dipeptidyl peptidase IV (DPP-4) inhibitors, and sodium-glucose cotransporter 2 (SGLT2) inhibitors. α-Glucosidase inhibitors have been used to control postprandial glucose levels caused by type 2 diabetes since 1990. α-Glucosidases are rather crucial in the human metabolic system and are principally found in families 13 and 31. Maltase-glucoamylase (MGAM) belongs to glycoside hydrolase family 31. The main function of MGAM is to digest terminal starch products left after the enzymatic action of α-amylase; hence, MGAM becomes an efficient drug target for insulin resistance. In order to explore the conformational changes in the active pocket and unbinding pathway for NtMGAM, molecular dynamics (MD) simulations and adaptive steered molecular dynamics (ASMD) simulations were performed for two NtMGAM-inhibitor [de-O-sulfonated kotalanol (DSK) and acarbose] complexes. MD simulations indicated that DSK bound to NtMGAM may influence two domains (inserted loop 1 and inserted loop 2) by interfering with the spiralization of residue 497–499. The flexibility of inserted loop 1 and inserted loop 2 can influence the volume of the active pocket of NtMGAM, which can affect the binding progress for DSK to NtMGAM. ASMD simulations showed that compared to acarbose, DSK escaped from NtMGAM easily with lower energy. Asp542 is an important residue on the bottleneck of the active pocket of NtMGAM and could generate hydrogen bonds with DSK continuously. Our theoretical results may provide some useful clues for designing new α-glucosidase inhibitors to treat type 2 diabetes.

Pathophysiological Association between Diabetes Mellitus and Endothelial Dysfunction

Endothelial dysfunction plays a critical role in atherosclerosis progression, leading to cardiovascular complications. There are significant associations between diabetes mellitus, oxidative stress, and endothelial dysfunction. Oxidative stress is increased by chronic hyperglycemia and acute glucose fluctuations induced by postprandial hyperglycemia in patients with diabetes mellitus. In addition, selective insulin resistance in the phosphoinositide 3-kinase/Akt/endothelial nitric oxide (NO) synthase pathway in endothelial cells is involved in decreased NO production and increased endothelin-1 production from the endothelium, resulting in endothelial dysfunction. In a clinical setting, selecting an appropriate therapeutic intervention that improves or augments endothelial function is important for preventing diabetic vascular complications. Hypoglycemic drugs that reduce glucose fluctuations by decreasing the postprandial rise in blood glucose levels, such as glinides, α-glucosidase inhibitors and dipeptidyl peptidase 4 inhibitors, and hypoglycemic drugs that ameliorate insulin sensitivity, such as thiazolidinediones and metformin, are expected to improve or augment endothelial function in patients with diabetes. Glucagon-like peptide 1 receptor agonists, metformin, and sodium-glucose cotransporter 2 inhibitors may improve endothelial function through multiple mechanisms, some of which are independent of glucose control or insulin signaling. Oral administration of antioxidants is not recommended in patients with diabetes due to the lack of evidence for the efficacy against diabetic complications.

Inconvenient relationship of haemoglobin A1c level with endothelial function in type 2 diabetes in a cross-sectional study

OBJECTIVE

The aim of this study was to determine the relationship of haemoglobin A1c (HbA1c) level with flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID) in patients with type 2 diabetes.

DESIGN

Cross-sectional study.

SETTING

22 university hospitals and affiliated clinics in Japan.

PARTICIPANTS

1215 patients with type 2 diabetes including 349 patients not taking antidiabetic drugs.

MEASURES

We evaluated FMD and HbA1c level. All patients were divided into four groups based on HbA1c level: <6.5%, 6.5%-6.9%, 7.0%-7.9% and ≥8.0%.

RESULTS

An inverted U-shaped pattern of association between HbA1c level and FMD was observed at the peak of HbA1c of about 7%. FMD was significantly smaller in the HbA1c <6.5% group than in the HbA1c 6.5%-6.9% group and HbA1c 7.0%-7.9% group (p<0.001 and p<0.001), and FMD values were similar in the HbA1c <6.5% group and HbA1c ≥8.0% group. There were no significant differences in NID values among the four groups. After adjustments for confounding factors, FMD was significantly smaller in the HbA1c <6.5% group than in the HbA1c 6.5%-6.9% and HbA1c 7.0%-7.9% group (p=0.002 and p=0.04). In patients not taking antidiabetic drugs, FMD was also significantly smaller in the HbA1c <6.5% group than in the HbA1c 6.5%-6.9% group and HbA1c 7.0%-7.9% group (p<0.001 and p=0.02), and there were no significant differences in NID values among the four groups.

CONCLUSIONS

These findings suggest that there is an inverted U-shaped pattern of association between FMD and HbA1c and that a low HbA1c level of <6.5% is associated with endothelial dysfunction.

TRIAL REGISTRATION NUMBER

UMIN000012950, UMIN000012951, UMIN000012952 and UMIN000003409.

Roles and Mechanisms of Dipeptidyl Peptidase 4 Inhibitors in Vascular Aging

Vascular aging is characterized by alterations in the constitutive properties and biological functions of the blood vessel wall. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are indispensability elements in the inner layer and the medial layer of the blood vessel wall, respectively. Dipeptidyl peptidase-4 (DPP4) inhibitors, as a hypoglycemic agent, play a protective role in reversing vascular aging regardless of their effects in meliorating glycemic control in humans and animal models of type 2 diabetes mellitus (T2DM) through complex cellular mechanisms, including improving EC dysfunction, promoting EC proliferation and migration, alleviating EC senescence, obstructing EC apoptosis, suppressing the proliferation and migration of VSMCs, increasing circulating endothelial progenitor cell (EPC) levels, and preventing the infiltration of mononuclear macrophages. All of these showed that DPP4 inhibitors may exert a positive effect against vascular aging, thereby preventing vascular aging-related diseases. In the current review, we will summarize the cellular mechanism of DPP4 inhibitors regulating vascular aging; moreover, we also intend to compile the roles and the promising therapeutic application of DPP4 inhibitors in vascular aging-related diseases.

Effect of Anagliptin versus Sitagliptin on Inflammatory Markers: Sub-Analysis from the REASON Trial

PURPOSE

Experimental evidence has suggested that dipeptidyl peptidase-4 (DPP-4) inhibitors have an anti-inflammatory effect as well as a glucose-lowering effect, but this has yet to be confirmed in diabetic patients. Therefore, we examined the anti-inflammatory effects of two kinds of DPP-4 inhibitors in patients who participated in the randomized evaluation of anagliptin (ANA) vs sitagliptin (SITA) on low-density lipoprotein cholesterol in diabetes (REASON) Trial, which compared low-density lipoprotein-cholesterol lowering effects between (ANA) and SITA in patients with type 2 diabetes, dyslipidemia, and atherosclerotic vascular lesions.

PATIENTS AND METHODS

The studied patients consisted of 177 patients who received ANA 200 mg per day and 176 patients who received SITA 50 mg per day for 52 weeks. We measured high-sensitivity C-reactive protein (hs-CRP), white blood cells (WBC), and interleukin-6 (IL-6) before and after treatment for 52 weeks, and the changes in inflammatory markers were measured as the differences between baseline and 52 weeks. Furthermore, we checked the relationship between the change in hs-CRP and several clinical factors such as the baseline hs-CRP level, use of a moderate-intensity statin, presence of coronary artery disease (CAD) and taking a previous DDP-4 inhibitor.

RESULTS

The levels of the inflammatory markers hs-CRP, WBC, and IL-6 were determined to have not significantly changed from baseline to the final follow-up in each arm; furthermore, the changes in these markers were not significantly different between the two groups. The change in hs-CRP level was not affected by the baseline hs-CRP level, use of a moderate-intensity statin, presence of coronary artery disease, and absence of prior DPP-4 inhibitor use.

CONCLUSION

In this sub-analysis from the REASON Trial, taking a DPP-4 inhibitor, either ANA or SITA, for 52 weeks did not affect the levels of inflammatory markers.

Anti-inflammatory properties of antidiabetic drugs: A "promised land" in the COVID-19 era?

Inflammation is implicated in the development and severity of the coronavirus disease 2019 (COVID-19), as well as in the pathophysiology of diabetes. Diabetes, especially when uncontrolled, is also recognized as an important risk factor for COVID-19 morbidity and mortality. Furthermore, certain inflammatory markers [i.e. C-reactive protein (CRP), interleukin-6 (IL-6) and ferritin] were reported as strong predictors of worse outcomes in COVID-19 positive patients. The same biomarkers have been associated with poor glycemic control. Therefore, achieving euglycemia in patients with diabetes is even more important in the era of the COVID-19 pandemic. Based on the above, it is clinically interesting to elucidate whether antidiabetic drugs may reduce inflammation, thus possibly minimizing the risk for COVID-19 development and severity. The present narrative review discusses the potential anti-inflammatory properties of certain antidiabetic drugs (i.e. metformin, pioglitazone, sitagliptin, linagliptin, vildagliptin, alogliptin, saxagliptin, liraglutide, dulaglutide, exenatide, lixisenatide, semaglutide, empagliflozin, dapagliflozin, canagliflozin), with a focus on CRP, IL-6 and ferritin.

Diabetes pharmacotherapy and circulating stem/progenitor cells. State of the art and evidence gaps

Diabetes is burdened with the development of several end-organ complications leading to excess mortality. Though the causes of such organ damage are far from being clarified, diabetes has been redefined as a disease of impaired damage control, wherein ongoing damage is not adequately compensated by activation of repair processes. Bone marrow-derived hematopoietic stem/progenitor cells (HSPCs) and their descendants endothelial progenitor cells (EPCs) have been extensively studied as major players in tissue homeostasis as well as biomarkers of diabetic complication risk. Thus, strategies to raise the levels of circulating HSPCs/EPCs have attracted interest for their potential to modify the future risk of complications. We herein discuss state-of-the-art of the effects exerted by diabetes pharmacotherapy on such cell populations. Further, we highlight which outstanding questions remain to be addressed for a more comprehensive understanding of this topic.

Clinical implications, diagnosis, and management of diabetes in patients with chronic liver diseases

Diabetes mellitus (DM) negatively affects the development and progression of chronic liver diseases (CLD) of various etiologies. Concurrent DM and CLD are also associated with worse clinical outcomes with respect to mortality, the occurrence of hepatic decompensation, and the development of hepatocellular carcinoma (HCC). Unfortunately, early diagnosis and optimal treatment of DM can be challenging, due to the lack of established clinical guidelines as well as the medical complexity of this patient population. We conducted an exploratory review of relevant literature to provide an up-to-date review for internists and hepatologists caring for this patient population. We reviewed the epidemiological and pathophysiological associations between DM and CLD, the impact of insulin resistance on the progression and manifestations of CLD, the pathogenesis of hepatogenic diabetes, as well as the practical challenges in diagnosis and monitoring of DM in this patient population. We also reviewed the latest clinical evidence on various pharmacological antihyperglycemic therapies with an emphasis on liver disease-related clinical outcomes. Finally, we proposed an algorithm for managing DM in patients with CLD and discussed the clinical and research questions that remain to be addressed.

The efficacy and safety of dipeptidyl peptidase-4 inhibitors compared to other oral glucose-lowering medications in the treatment of type 2 diabetes

INTRODUCTION

The dipeptidyl peptidase-4 inhibitors (DPP-4is), which belong to the class of incretin-based medications, are recommended as second or third-line therapies in guidelines for the management of type 2 diabetes mellitus. They have a favorable drug tolerability and safety profile compared to other glucose-lowering agents.

OBJECTIVE

This review discusses data concerning the use of DPP-4is and their cardiovascular profile, and gives an updated comparison with the other oral glucose-lowering medications with regards to safety and efficacy. Currently available original studies, abstracts, reviews articles, systematic reviews and meta-analyses were included in the review.

DISCUSSION

DPP4is are moderately efficient in decreasing the HbA1c by an average of 0.5% as monotherapy, and 1.0% in combination therapy with other drugs. They have a good tolerability and safety profile compared to other glucose-lowering drugs. However, there are possible risks pertaining to acute pancreatitis and pancreatic cancer.

CONCLUSION

Cardiovascular outcome trials thus far have proven the cardiovascular safety for ischemic events in patients treated with sitagliptin, saxagliptin, alogliptin, linagliptin and vildagliptin. Data showing increased rate of hospitalisation in the case of saxagliptin did not seem to be a class effect.

Endothelial Dysfunction in Diabetes

Diabetes is a worldwide health issue closely associated with cardiovascular events. Given the pandemic of obesity, the identification of the basic underpinnings of vascular disease is strongly needed. Emerging evidence has suggested that endothelial dysfunction is a critical step in the progression of atherosclerosis. However, how diabetes affects the endothelium is poorly understood. Experimental and clinical studies have illuminated the tight link between insulin resistance and endothelial dysfunction. In addition, macrophage polarization from M2 towards M1 contributes to the process of endothelial damage. The possibility that novel classes of anti-hyperglycemic agents exert beneficial effects on the endothelial function and macrophage polarization has been raised. In this review, we discuss the current status of knowledge regarding the pathological significance of insulin signaling in endothelium. Finally, we summarize recent therapeutic strategies against endothelial dysfunction with an emphasis on macrophage polarity.

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.

Acute Exenatide Therapy Attenuates Postprandial Vasodilation in Humans with Prediabetes: A Randomized Controlled Trial

Background: The state of prediabetes comprises atherosclerotic changes leading to decreased vascular function in humans. This study examined the effects on incretin mimetics on vascular physiology in the prediabetic postprandial state. Methods: Fifteen obese adults with prediabetes participated in a randomized, crossover, double-blinded trial comparing the postprandial effects of exenatide, saxagliptin, and placebo on peripheral vasodilation. All studies utilized a standardized high-fat meal. Resting and peak forearm blood flow (FBF) were measured via strain gauge venous occlusion plethysmography, and makers of vascular dysfunction were measured in plasma. Results: Exenatide attenuated resting FBF at 3 hr (P = 0.003) and 6 hr (P = 0.056) postmeal, compared to placebo. Nonsignificant reductions in resting FBF were observed between saxagliptin and placebo at the same time points. No group differences were observed for peak FBF, plasma nitrotyrosine, and plasma 8-iso-prostaglandin F2alpha. A transient increase in plasma triglyceride was abated in the exenatide group, when compared to saxagliptin and placebo groups. Only exenatide group showed no significant upsurge in plasma insulin. Plasma-free fatty acids significantly declined in all three groups, although less markedly for exenatide. Postmeal glucose increased at 2 hr with placebo and saxagliptin, but simultaneously decreased with exenatide. Conclusions: Acute treatment with exenatide blunted the postprandial vasodilatory effect of a high-fat meal in prediabetes. Exenatide's acute effects derived primarily from multiple endothelium-independent processes. Trial Registration Number: NCT02104739.

The protective role of DPP4 inhibitors in atherosclerosis

Diabetes is a chronic non-communicable disease whose incidence continues to grow rapidly, and it is one of the most serious and critical public health problems. Diabetes complications, especially atherosclerosis-related chronic vascular complications, are a serious threat to human life and health. Growing evidence suggests that dipeptidyl peptidase 4 (DPP4) inhibitors, beyond their role in improving glycemic control, are helpful in ameliorating endothelial dysfunction in humans and animal models of T2DM. In fact, DPP4 inhibitors have been shown by successive studies to play a protective effect against vascular complications. On one hand, in addition to their hypoglycemic effects, DPP4 inhibitors participate in the control of atherosclerotic risk factors by regulating blood lipids and lowering blood pressure. On the other hand, DPP4 inhibitors exert anti-atherosclerotic effects directly through multiple mechanisms, including improving endothelial cell dysfunction, increasing circulating endothelial progenitor cell (EPCs) levels, regulating mononuclear macrophages and smooth muscle cells, inhibiting inflammation and oxidative stress and improving plaque instability. Herein, we review the beneficial roles of DPP4 inhibitors in atherosclerosis as detailed.

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.

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.

Greater circulating DPP4 activity is associated with impaired flow-mediated dilatation in adults with type 2 diabetes mellitus

BACKGROUND AND AIM

Dipeptidyl peptidase 4 (DPP4) is a key enzyme involved in the regulation of the incretin system exerted by cleaving the glucagon-like peptide 1 (GLP-1); the blockage of DPP4, exerted by the antidiabetic agents DPP4-inhibitors (DPP4-I), results in greater GLP-1 concentration and improved glycaemic control. DPP4 acts also as a pro-inflammatory molecule and mediates vascular damage in experimental models. The relationship between DPP4 activity and endothelial function in diabetes has not been explored yet. Aim of this study was to investigate systemic plasma DPP4 activity in relation to endothelial function in patients with type 2 diabetes mellitus (T2DM).

METHODS AND RESULTS

Sixty-two T2DM individuals were recruited in our Diabetes outpatient clinics, Sapienza University, Rome, Italy. All participants underwent complete clinical work-up; endothelial function was evaluated by flow-mediated dilatation (FMD) test; plasma DPP4 activity was assessed by measuring the 7-amino-4-methylcoumarin (AMC) cleavage rate from the synthetic substrate H-glycyl-prolyl-AMC and compared with DPP4 activity measured in sixty-two age-, sex-, BMI-matched non-diabetic subjects. Patients with T2DM had significantly higher DPP4 activity than non-diabetic individuals (211,466 ± 87657 vs 158,087 ± 60267 nmol/min/ml, p < 0.001); in T2DM patients, greater DPP4 activity significantly correlated with lower FMD whereas was not associated with BMI and metabolic control. Greater systemic DPP4 activity was an independent predictor of reduced FMD after adjusting for age, gender and other confounders.

CONCLUSIONS

Circulating DPP4 activity is increased in individuals with T2DM and associated with signs of endothelial dysfunction such as impaired FMD. DPP4 may negatively affect endothelial function through mechanisms beyond glucose homeostasis and metabolic control.

Development of therapeutic options on type 2 diabetes in years: Glucagon-like peptide-1 receptor agonist’s role intreatment; from the past to future

Diabetes mellitus (DM) is a chronic metabolic disease characterized by hypergly-cemia. Type 2 diabetes (T2DM) accounting for 90% of cases globally. The worldwide prevalence of DM is rising dramatically over the last decades, from 30 million cases in 1985 to 382 million cases in 2013. It’s estimated that 451 million people had diabetes in 2017. As the pathophysiology was understood over the years, treatment options for diabetes increased. Incretin-based therapy is one of them. Glucagon-like peptide-1 receptor agonist (GLP-1 RA) not only significantly lower glucose level with minimal risk of hypoglycemia but also, they have an important advantage in themanagement of cardiovascular risk and obesity. Thus, we will review here GLP-1 RAsrole in the treatment of diabetes.

Head-to-Head Comparison of the Hypoglycemic Efficacy and Safety Between Dipeptidyl Peptidase-4 Inhibitors and α-Glucosidase Inhibitors in Patients With Type 2 Diabetes Mellitus: A Meta-Analysis of Randomized Controlled Trials

Background: The α-glucosidase inhibitors (AGIs) are commonly prescribed in Asian patients with type 2 diabetes mellitus (T2DM), but with a high incidence of gastrointestinal side effects. This study was aimed to compare the efficacy and safety of dipeptidyl peptidase-4 (DPP4) inhibitors and AGIs in T2DM patients in a meta-analysis.

Methods: Randomized controlled trials were identified via systematic search of PubMed, Embase, and Cochrane’s Library databases from inception to February, 2019. Meta-analyses were performed via a random or a fixed effect model according to the heterogeneity.

Results: Eighteen studies with a total of 4,051 patients with T2DM were included. The DPP4 inhibitors were associated with lower reduction of glycosylated hemoglobin (HbA1c) as compared with AGIs [weighed mean difference (WMD): −0.37%, p < 0.001]. Subgroup analyses indicated that the benefit of DPP4 inhibitors as compared with AGIs on HbA1c were independent of study design, scale, baseline HbA1c, with or without concurrent medications, or follow-up durations. Moreover, compared to AGIs, DPP4 inhibitors was associated with lower reductions of fasting blood glucose (WMD: −0.53 mmol/L, P < 0.001) and postprandial glucose at 2h (WMD: −0.60 mmol/L, P = 0.04), moderately increased body weight (WMD: 0.34 kg, P = 0.02), and decreased risk of gastrointestinal adverse events [risk ratio (RR): 0.48, P < 0.001], but unaffected risk of symptomatic hypoglycemia (RR: 0.96, P = 0.90).

Conclusions: The DPP4 inhibitors are superior to AGIs in T2DM patients for better glycemic control and lower risks of gastrointestinal side effects.

Effect of dipeptidyl-peptidase-4 inhibitors on C-reactive protein in patients with type 2 diabetes: a systematic review and meta-analysis

Background

Dipeptidyl peptidase-4 inhibitors (DPP-4i) are emerging glucose-lowering agents through interacting with DPP-4 substrate, impact of which on systemic inflammation in type 2 diabetes mellitus (T2DM) remains unknown. This study aimed to evaluate the effect of DPP-4i on modulating serum levels of C-reactive protein (CRP) in T2DM.

Methods

PubMed, Cochrane library and Embase databases were searched. Randomized controlled trials (RCTs) with comparators were selected. A random-effects model was used for quantitative data analysis. Heterogeneity was evaluated with I² index. Sensitivity analysis was performed using the one-study remove approach.

Results

Sixteen trials with 1607 patients with T2DM were included. Pooled analysis of DPP-4i demonstrated a significant decrease in serum CRP concentrations (− 0.86 mg/L, 95% CI, − 1.36 to − 0.36). No significant difference was found between DPP-4i and active comparators on serum CRP concentrations (0.64 mg/L, 95% CI, − 0.10 to 1.37). Pooled analysis proved to be stable and credible by sensitivity analysis. In subgroup analysis, changes in serum concentrations of CRP were significantly associated with short diabetes duration (− 0.23 mg/L, 95% CI, − 0.41 to − 0.05).

Conclusions

DDP-4i effectively reduced serum CRP levels and showed no stronger effect than traditional oral antidiabetic agents.

International Prospective Register for Systematic Review (PROSPERO) number: CRD42017076838.

Electronic supplementary material

The online version of this article (10.1186/s12944-019-1086-4) contains supplementary material, which is available to authorized users.

Effects of Dipeptidyl Peptidase-4 Inhibitors on Renal Outcomes in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis

BACKGROUND

To investigate the effects of dipeptidyl peptidase-4 (DPP-4) inhibitors on renal outcomes in patients with type 2 diabetes.

METHODS

MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials were searched to identify randomized controlled trials (RCTs) of DPP-4 inhibitors from inception to September 2017. We selected eligible RCTs comparing DPP-4 inhibitors with placebo or other antidiabetic agents and reporting at least one renal outcome. A meta-analysis was conducted to calculate standardized mean differences, weighted mean differences (WMDs), relative risks (RRs), and 95% confidence intervals (CIs) for each renal outcome.

RESULTS

We included 23 RCTs with 19 publications involving 41,359 patients. Overall changes in urine albumin-to-creatinine ratio were comparable between DPP-4 inhibitors and controls (P=0.150). However, DPP-4 inhibitors were associated with significantly lower risk of incident microalbuminuria (RR, 0.89; 95% CI, 0.80 to 0.98; P=0.022) and macroalbuminuria (RR, 0.77; 95% CI, 0.61 to 0.97; P=0.027), as well as higher rates of regression of albuminuria (RR, 1.22; 95% CI, 1.10 to 1.35; P<0.001) compared with controls. Although DPP-4 inhibitors were associated with small but significantly lower estimated glomerular filtration rate (WMD, -1.11 mL/min/1.73 m²; 95% CI, -1.78 to -0.44; P=0.001), there was no difference in the risk of end-stage renal disease between two groups (RR, 0.93; 95% CI, 0.76 to 1.14; P=0.475).

CONCLUSION

DPP-4 inhibitors had beneficial renal effects mainly by reducing the risk of development or progression of albuminuria compared with placebo or other antidiabetic agents.

Possible mechanisms of direct cardiovascular impact of GLP-1 agonists and DPP4 inhibitors

Diabetes mellitus is a leading cause of cardiovascular morbidity and mortality worldwide. Traditional antidiabetic therapies targeting hyperglycemia reduce diabetic microvascular complications but have minor effects on macrovascular complications, including cardiovascular disease. Instead, cardiovascular complications are improved by antidiabetic medications (metformin) and other therapies (statins, antihypertensive medications) ameliorating insulin resistance and other associated metabolic abnormalities. Novel classes of antidiabetic drugs have proven efficacious in improving glycemia, while at the same time exert beneficial effects on pathophysiologic mechanisms of diabetes-related cardiovascular disease. In the present review, we will present current evidence of the cardiovascular effects of two new classes of antidiabetic medications, glucagon-like peptide 1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP4) inhibitors, focusing from mechanistic preclinical and clinical investigation to late-phase clinical testing.

Therapeutic Options Targeting Oxidative Stress, Mitochondrial Dysfunction and Inflammation to Hinder the Progression of Vascular Complications of Diabetes

Type 2 diabetes mellitus is a leading cause of morbidity and mortality worldwide, given its serious associated complications. Despite constant efforts and intensive research, an effective, ubiquitous treatment still eludes the scientific community. As such, the identification of novel avenues of research is key to the potential discovery of this evasive "silver bullet." We focus on this review on the matter of diabetic injury to endothelial tissue and some of the pivotal underlying mechanisms, including hyperglycemia and hyperlipidemia evoked oxidative stress and inflammation. In this sense, we revisited the most promising therapeutic interventions (both non-pharmacological and antidiabetic drugs) targeting oxidative stress and inflammation to hinder progression of vascular complications of diabetes. This review article gives particular attention to the relevance of mitochondrial function, an often ignored and understudied organelle in the vascular endothelium. We highlight the importance of mitochondrial function and number homeostasis in diabetic conditions and discuss the work conducted to address the aforementioned issue by the use of various therapeutic strategies. We explore here the functional, biochemical and bioenergetic alterations provoked by hyperglycemia in the endothelium, from elevated oxidative stress to inflammation and cell death, as well as loss of tissue function. Furthermore, we synthetize the literature regarding the current and promising approaches into dealing with these alterations. We discuss how known agents and therapeutic behaviors (as, for example, metformin, dietary restriction or antioxidants) can restore normality to mitochondrial and endothelial function, preserving the tissue's function and averting the aforementioned complications.

Anti-atherosclerotic effect of incretin mimetics: a meta-analysis of randomized controlled trials

Background: Diabetes is a very common cause of cardiovascular disease, and metformin remains the first-line treatment of diabetes. Many trials were conducted to prove the efficacy and safety of other antidiabetic medication as the best add-on medication. Objectives: We aimed to evaluate the atherosclerotic effect of incretin mimetics in patients with diabetes.Methods: We searched in PubMed, clinicaltrials.gov and Cochrane Library for randomized controlled trials (RCTs) comparing incretin mimetic with conventional treatment. The primary outcome was the change in carotid intima-media thickness (CIMT) at the end of the trials.Results: Five RCTs (n = 1241), the mean age of patients included in the trials is 64.3 ± 11.4. The primary outcome was statistically significant for CIMT improvement in terms of long-term follow-up analysis between the incretin mimetic group and conventional group (mean difference [MD] -0.031; 95% Confidence interval [CI] -0.049 to 0.012; P = 0.001), whereas at short-term follow-up it wasn't (MD -0.004; 95% CI -0.024 to 0.016; P = 0.7) in the overall group of study participants. Additionally, the mean change in body mass index (BMI) (MD 0.064; 95% CI -0.54 to 0.67; P = 0.8), and mean change in systolic blood pressure (MD -0.42; 95% CI -3.2 to 2.3; P = 0.8) or diastolic blood pressure (MD 0.25; 95% CI -1.18 to 1.68; P = 0.7) were not significant.Conclusion: Long-term use of incretin mimetic medication results in significant improvement of atherosclerosis, which leads to fewer vascular events, with no apparent effect on blood pressure or BMI. Further dedicated trials are required to show the superiority of adding these medications to conventional treatment versus placebo.

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.

Vildagliptin improves high glucose-induced endothelial mitochondrial dysfunction via inhibiting mitochondrial fission

The dipeptidyl peptidase 4 inhibitor vildagliptin (VLD), a widely used anti-diabetic drug, exerts favourable effects on vascular endothelium in diabetes. We determined for the first time the improving effects of VLD on mitochondrial dysfunction in diabetic mice and human umbilical vein endothelial cells (HUVECs) cultured under hyperglycaemic conditions, and further explored the mechanism behind the anti-diabetic activity. Mitochondrial ROS (mtROS) production was detected by fluorescent microscope and flow cytometry. Mitochondrial DNA damage and ATP synthesis were analysed by real time PCR and ATPlite assay, respectively. Mitochondrial network stained with MitoTracker Red to identify mitochondrial fragmentation was visualized under confocal microscopy. The expression levels of dynamin-related proteins (Drp1 and Fis1) were determined by immunoblotting. We found that VLD significantly reduced mtROS production and mitochondrial DNA damage, but enhanced ATP synthesis in endothelium under diabetic conditions. Moreover, VLD reduced the expression of Drp1 and Fis1, blocked Drp1 translocation into mitochondria, and blunted mitochondrial fragmentation induced by hyperglycaemia. As a result, mitochondrial dysfunction was alleviated and mitochondrial morphology was restored by VLD. Additionally, VLD promoted the phosphorylation of AMPK and its target acetyl-CoA carboxylase in the setting of high glucose, and AMPK activation led to a decreased expression and activation of Drp1. In conclusion, VLD improves endothelial mitochondrial dysfunction in diabetes, possibly through inhibiting Drp1-mediated mitochondrial fission in an AMPK-dependent manner.

[Type 2 Diabetes and Vascular Endothelial Dysfunction]

Vascular endothelial function is important for maintaining the homeostasis of the living body. Especially, nitric oxide (NO) produced in vascular endothelial cells regulates blood vessel tone and has an antiatherosclerotic effect. Type 2 diabetes is a typical disease that causes impaired vascular endothelial function, resulting in various vascular complications and damage to organs. Cardiovascular disease associated with type 2 diabetes is a chronic inflammatory disease that starts with endothelial dysfunction (ED), and vascular ED is important as an initial change in arteriosclerotic lesions. Vascular ED in type 2 diabetes is thought to be caused by hyperglycemia, hyperinsulinemia associated with insulin resistance, and hypoglycemia, in which elevated oxidative stress accompanying postprandial hyperglycemia and blood glucose fluctuation are involved. Vascular ED is also caused by postprandial metabolic abnormalities, so correcting postprandial metabolic abnormalities is also important. Meanwhile, Glucagon-like peptide-1 (GLP-1) receptor agonist, thiazolidine, biguanide and Dipeptidyl peptidase-4 (DPP-4) inhibitor have an effect of protecting vascular endothelial function beyond glycemic control. In order to promote a healthy lifestyle for diabetes patients, it is important not only to lower HbA1c but also to avoid postprandial hyperglycemia, blood glucose fluctuation, and hypoglycemia. It is also important to conduct treatment with a view to suppressing vascular complications, such as the selection of antiarteriosclerosis medications.

Effect of Sitagliptin on Coronary Flow Reserve Assessed by Magnetic Resonance Imaging in Type 2 Diabetic Patients With Coronary Artery Disease

BACKGROUND

The present study was conducted to assess the cardiovascular effects of dipeptidyl peptidase-4 inhibitors (DPP4i) on coronary flow reserve (CFR), left ventricular (LV) function and endothelial function of the peripheral artery by comparison with those of α-glucosidase inhibitors (αGI) in patients with type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD).

METHODS AND RESULTS

We randomly assigned 30 patients with T2DM and CAD to receive either sitagliptin or voglibose, and 28 patients (age 69±9 years, 75% male, hemoglobin A1c [HbA1c] 6.62±0.48%) completed the study (14 in each group). CFR and LV function, assessed by cardiac magnetic resonance imaging, and endothelial function, assessed by reactive hyperemia peripheral arterial tonometry (RH-PAT), were measured at baseline and 24 weeks after treatment. Clinical and laboratory parameters, including HbA1c level, plasma active glucagon-like peptide-1 concentrations, and biomarkers of inflammation, were unchanged in both groups after 24 weeks of treatment. CFR were unchanged in both the αGI group (3.01±0.98 at baseline and 3.06±0.8 after treatment, P=NS) and the DPP4i group (4.29±2.04 at baseline and 3.63±1.31 after treatment, P=NS), with no interaction effect. LV functional parameters and the reactive hyperemia index also remained unchanged after the 24-week treatment.

CONCLUSIONS

DPP4i did not improve CFR, LV function or endothelial function of the peripheral artery in patients with relatively well-controlled T2DM and CAD.

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.