Dipeptidyl-peptidase-4 inhibitor, alogliptin, attenuates arterial inflammation and neointimal formation after injury in low-density lipoprotein (LDL) receptor-deficient mice

Therapeutic effects of anti-diabetic drugs on traumatic brain injury

AIMS

In this narrative review, we have analyzed and synthesized current studies relating to the effects of anti-diabetic drugs on traumatic brain injury (TBI) complications.

METHODS

Eligible studies were collected from Scopus, Google Scholar, PubMed, and Cochrane Library for clinical, in-vivo, and in-vitro studies published on the impact of anti-diabetic drugs on TBI.

RESULTS

Traumatic brain injury (TBI) is a serious brain disease that is caused by any type of trauma. The pathophysiology of TBI is not yet fully understood, though physical injury and inflammatory events have been implicated in TBI progression. Several signaling pathways are known to play pivotal roles in TBI injuries, including Nuclear factor erythroid 2-related factor 2 (Nrf2), High mobility group box 1 protein/Nuclear factor kappa B (HMGB1/NF-κB), Adiponectin, Mammalian Target of Rapamycin (mTOR), Toll-Like Receptor (TLR), Wnt/β-catenin, Janus Kinase/Signal Transducers and Activators of Transcription (JAK/STAT), Nod-like receptor protein3 (NLRP3) inflammasome, Phosphoglycerate kinase 1/Kelch-like ECH-associated protein 1 (PGK1/KEAP1)/Nrf2, and Mitogen-activated protein kinase (MAPK) . Recent studies suggest that oral anti-diabetic drugs such as biguanides, thiazolidinediones (TZDs), sulfonylureas (SUs), sodium-glucose cotransporter-2 inhibitors (SGLT2is), dipeptidyl peptidase-4 inhibitors (DPPIs), meglitinides, and alpha-glucosidase inhibitors (AGIs) could have beneficial effects in the management of TBI complications. These drugs may downregulate the inflammatory pathways and induce antioxidant signaling pathways, thus alleviating complications of TBI.

CONCLUSION

Based on this comprehensive literature review, antidiabetic medications might be considered in the TBI treatment protocol. However, evidence from clinical trials in patients with TBI is still warranted.

Effect of Anagliptin on Vascular Injury in the Femoral Artery of Type 2 Diabetic Rats

Patients with diabetes mellitus (DM) often experience complications such as peripheral arterial disease (PAD), which is thought to be caused by vascular damage resulting from increased oxidative stress. Dipeptidyl peptidase-4 inhibitors have been reported to reduce oxidative stress, although the exact mechanism remains unclear. This study aimed to investigate the impact of long-term (6 weeks) anagliptin treatment at a dose of 200 mg/kg/d against oxidative stress in the femoral artery of Otsuka Long-Evans Tokushima Fatty (OLETF) rats using a well-established animal model for type 2 DM. Serum toxic advanced glycation end-products concentrations and blood glucose levels after glucose loading were significantly elevated in OLETF rats compared to Long-Evans Tokushima Otsuka (LETO) rats but were significantly suppressed by anagliptin administration. Plasma glucagon-like peptide-1 concentrations after glucose loading were significantly increased in anagliptin-treated rats. Superoxide production and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in femoral arteries were significantly increased in OLETF rats compared to LETO rats but were significantly decreased by anagliptin administration. The expressions of NADPH oxidase components (p22phox in the intima region and p22phox and gp91phox in the media region) in the femoral artery were significantly increased in OLETF rats compared to LETO rats but were significantly suppressed by anagliptin administration. Furthermore, the femoral artery showed increased wall thickness in OLETF rats compared to LETO rats, but anagliptin administration reduced the thickening. This study suggests that long-term anagliptin administration can reduce oxidative stress in femoral arteries and improve vascular injury.

DPP4 as a Potential Candidate in Cardiovascular Disease

The rising prevalence of cardiovascular disease has become a global health concern. The occurrence of cardiovascular disease is the result of long-term interaction of many risk factors, one of which is diabetes. As a novel anti-diabetic drug, DPP4 inhibitor has been proven to be cardiovascular safe in five recently completed cardiovascular outcome trials. Accumulating studies suggest that DPP4 inhibitor has potential benefits in a variety of cardiovascular diseases, including hypertension, calcified aortic valve disease, coronary atherosclerosis, and heart failure. On the one hand, in addition to improving blood glucose control, DPP4 inhibitor is involved in controlling cardiovascular risk factors. On the other hand, DPP4 inhibitor directly regulates the occurrence and progression of cardiovascular diseases through a variety of mechanisms. In this review, we summarize the recent advances of DPP4 in cardiovascular disease, aiming to discuss DPP4 inhibitor as a potential option for cardiovascular therapy.

Protective effect of alogliptin against cyclophosphamide-induced lung toxicity in rats: Impact on PI3K/Akt/FoxO1 pathway and downstream inflammatory cascades

Cyclophosphamide (CP)-induced lung toxicity is a remaining obstacle against the beneficial use of this chemotherapeutic agent. More considerations were given to the role of Alogliptin (ALO) in ameliorating CP-induced toxicities in many tissues. We designed this study to clarify the protective potential of ALO against CP-induced lung toxicity in rats. ALO was administered for 7 days. Single-dose CP was injected on the 2nd day (200 mg/kg: i.p.) to induce lung toxicity. Rats were divided into four groups: control, ALO-treated, CP-treated and ALO + CP-treated group. Leucocytic count, total proteins, LDH activity, TNF-α, and IL-6 were estimated in the bronchoalveolar lavage fluid (BALF). The oxidative/antioxidants (MDA, Nrf2, TAO and GSH), inflammatory (NFκB), fibrotic (TGF-β1) and apoptotic (PI3K/Akt/FoxO1) markers in pulmonary homogenates were biochemically evaluated. Rat lung sections were examined histologically (light and electron microscopic examination) and immunohistochemically (for iNOS and CD68 positive alveolar macrophages). CP significantly increased oxidative stress, inflammation, fibrosis, and apoptosis markers as well as deteriorated the histopathological pulmonary architecture. These hazardous effects were significantly ameliorated by ALO treatment. ALO protected against CP-induced lung toxicity by mitigating the oxidative, inflammatory and fibrotic impacts making it a promising pharmacological therapy for mitigating CP-induced lung toxicity.

Dipeptidyl peptidase-4 inhibitors reduced long-term cardiovascular risk in diabetic patients after percutaneous coronary intervention via insulin-like growth factor-1 axis

Dipeptidyl-peptidase-4 inhibitors (DPP4i) have been the most used antidiabetic medications worldwide due to their good safety profiles and tolerability with a low risk of hypoglycemia, however, large cardiovascular outcome trials (CVOTs) have not shown any significant the prognostic superiority. On the contrary, since observational studies have suggested the effects of DPP4i are enhanced some populations, such as Asians and those who without overweight, their prognostic benefit is still under debate. The aim of this study was thus to assess the prognostic impact of DPP4i in patients with both diabetes and coronary artery disease (CAD) who underwent percutaneous coronary intervention (PCI) through the insulin-like growth factor-1 (IGF-1) axis, a substrate of DPP4. This single-center analysis involved consecutive Japanese diabetic patients who underwent PCI for the first time between 2008 and 2018 (n = 885). Primary and secondary endpoints were set as cardiovascular (CV) death and the composite of CV death, non-fatal myocardial infarction and ischemic stroke (3P-MACE). Serum levels of IGF-1 and its main binding protein (insulin-like growth factor binding protein-3: IGFBP-3) were measured. In consequences, unadjusted Kaplan–Meier analyses revealed reduced incidences of CV-death and 3P-MACE by DPP4i, which was particularly enhanced in patients who were not overweight (BMI ≤ 25). Multivariate Cox hazard analyses consistently indicated reduced risks of CV death by DPP4i at PCI (hazard ratio (HR) 0.39, 95% confidence interval (CI) 0.16–0.82, p = 0.01) and 3P-MACE (HR 0.47, 95% CI 0.25–0.84, p = 0.01), respectively. Moreover, elevated IGF-1 activity indicated by the IGF-1/IGFBP-3 ratio was associated with decreased risks of both endpoints and it was significantly higher in patients with DPP4i (p < 0.0001). In conclusion, the findings of the present study indicate beneficial effects of DPP4i to improve outcomes in Japanese diabetic patients following PCI, which might be mediated by DPP4–IGF-1 axis.

Hypertension in diabetes care: emerging roles of recent hypoglycemic agents

Patients with type 2 diabetes (T2D) frequently have multiple cardiovascular, metabolic, and renal comorbidities, such as hypertension, dyslipidemia, hyperuricemia, chronic kidney disease, and heart failure. Accordingly, this patient population often requires polypharmacy, which is associated with an increased risk of drug-drug interactions, poor adherence, and even adverse outcomes. Accumulating evidence on newer hypoglycemic agents, such as glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors, has highlighted the marked improvements in cardiovascular and renal outcomes associated with the off-target benefits for relevant comorbidities, including hypertension. These classes of hypoglycemic agents are unique, as they achieve consistently modest but significant reductions in systolic and diastolic blood pressure (BP), an effect that has not been targeted and observed with conventional hypoglycemic agents. In addition to this BP-lowering effect, these agents also have multifaceted beneficial impacts on other cardiometabolic and renal parameters, which appear to be helpful for providing an important comprehensive therapeutic approach to improve the prognosis in patients with T2D. The clinical advantages of these agents may reduce the dose and number of concomitant medications used to treat T2D and related comorbidities. These positive spillover effects may also enhance the clinical use of agents to achieve better diabetes care. As a consequence, the clinical significance of these hypoglycemic agents now extends beyond their hypoglycemic effects, thereby providing a new-normal strategy to use in an evidence-based, patient-centric approach to diabetes care.

DPP4 Activity, Hyperinsulinemia, and Atherosclerosis

CONTEXT

Obesity and type 2 diabetes are associated with chronic hyperinsulinemia, elevated plasma levels of dipeptidyl peptidase-4 (DPP4), and a pro-atherosclerotic milieu.

EVIDENCE ACQUISITION

PubMed search of the term "insulin and atherosclerosis," "hyperinsulinemia," "atherosclerosis," or "cardiovascular outcomes" cross-referenced with "DPP4." Relevant research and review articles were reviewed.

EVIDENCE SYNTHESIS

Hyperinsulinemia in the setting of insulin resistance promotes vascular inflammation, vascular smooth muscle cell growth, pathological cholesterol profile, hypertension, and recruitment of immune cells to the endothelium, all contributing to atherosclerosis. DPP4 has pleiotropic functions and its activity is elevated in obese humans. DPP4 mirrors hyperinsulinemia's atherogenic actions in the insulin resistant state, and genetic deletion of DPP4 protects rodents from developing insulin resistance and improves cardiovascular outcomes. DPP4 inhibition in pro-atherosclerotic preclinical models results in reduced inflammation and oxidative stress, improved endothelial function, and decreased atherosclerosis. Increased incretin levels may have contributed to but do not completely account for these benefits. Small clinical studies with DPP4 inhibitors demonstrate reduced carotid intimal thickening, improved endothelial function, and reduced arterial stiffness. To date, this has not been translated to cardiovascular risk reduction for individuals with type 2 diabetes with prior or exaggerated risk of cardiovascular disease.

CONCLUSION

DPP4 may represent a key link between central obesity, insulin resistance, and atherosclerosis. The gaps in knowledge in DPP4 function and discrepancy in cardiovascular outcomes observed in preclinical and large-scale randomized controlled studies with DPP4 inhibitors warrant additional research.

Alogliptin Attenuates Lipopolysaccharide-Induced Neuroinflammation in Mice Through Modulation of TLR4/MYD88/NF-κB and miRNA-155/SOCS-1 Signaling Pathways

BACKGROUND

Endotoxin-induced neuroinflammation plays a crucial role in the pathogenesis and progression of various neurodegenerative diseases. A growing body of evidence supports that incretin-acting drugs possess various neuroprotective effects that can improve learning and memory impairments in Alzheimer's disease models. Thus, the present study aimed to investigate whether alogliptin, a dipeptidyl peptidase-4 inhibitor, has neuroprotective effects against lipopolysaccharide (LPS)-induced neuroinflammation and cognitive impairment in mice as well as the potential mechanisms underlying these effects.

METHODS

Mice were treated with alogliptin (20 mg/kg/d; p.o.) for 14 days, starting 1 day prior to intracerebroventricular LPS injection (8 μg/μL in 3 μL).

RESULTS

Alogliptin treatment alleviated LPS-induced cognitive impairment as assessed by Morris water maze and novel object recognition tests. Moreover, alogliptin reversed LPS-induced increases in toll-like receptor 4 and myeloid differentiation primary response 88 protein expression, nuclear factor-κB p65 content, and microRNA-155 gene expression. It also rescued LPS-induced decreases in suppressor of cytokine signaling gene expression, cyclic adenosine monophosphate (cAMP) content, and phosphorylated cAMP response element binding protein expression in the brain.

CONCLUSION

The present study sheds light on the potential neuroprotective effects of alogliptin against intracerebroventricular LPS-induced neuroinflammation and its associated memory impairment via inhibition of toll-like receptor 4/ myeloid differentiation primary response 88/ nuclear factor-κB signaling, modulation of microRNA-155/suppressor of cytokine signaling-1 expression, and enhancement of cAMP/phosphorylated cAMP response element binding protein signaling.

Cardiovascular surrogate markers and cardiometabolic therapeutics: a viewpoint learned from clinical trials on dipeptidyl peptidase-4 inhibitors

Clinical trials are often performed to investigate the effects of various types of cardiometabolic therapies on cardiovascular surrogate markers, including vascular function and biomarkers. This study platform has the potential to provide information on the suspected actions of drugs and mechanistic insights into their prognostic impact. However, despite using the same class of drugs and similar study designs we are often faced with inconsistent and even conflicting results, possibly leading to some confusion in the clinical setting. When interpreting these results, it is important to investigate what caused the differences and carefully assess the information, taking into account the research situation and the patient population investigated. Using this approach, assessment of the impact on cardiovascular surrogate markers observed in clinical studies from multiple perspectives should help to better understand the potential cardiovascular effects. In this commentary we discuss how we should interpret the effects of cardiometabolic therapeutics on vascular surrogate markers, based on viewpoints learned from the results of clinical trials on dipeptidyl peptidase-4 inhibitors. This learning strategy could also be helpful for appropriate selection of drugs for evidence-based, patient-centric, tailored medication.

Plasma levels of DPP4 activity and sDPP4 are dissociated from inflammation in mice and humans

Dipeptidyl peptidase-4 (DPP4) modulates inflammation by enzymatic cleavage of immunoregulatory peptides and through its soluble form (sDPP4) that directly engages immune cells. Here we examine whether reduction of DPP4 activity alters inflammation. Prolonged DPP4 inhibition increases plasma levels of sDPP4, and induces sDPP4 expression in lymphocyte-enriched organs in mice. Bone marrow transplantation experiments identify hematopoietic cells as the predominant source of plasma sDPP4 following catalytic DPP4 inhibition. Surprisingly, systemic DPP4 inhibition increases plasma levels of inflammatory markers in regular chow-fed but not in high fat-fed mice. Plasma levels of sDPP4 and biomarkers of inflammation are lower in metformin-treated subjects with type 2 diabetes (T2D) and cardiovascular disease, yet exhibit considerable inter-individual variation. Sitagliptin therapy for 12 months reduces DPP4 activity yet does not increase markers of inflammation or levels of sDPP4. Collectively our findings dissociate levels of DPP4 enzyme activity, sDPP4 and biomarkers of inflammation in mice and humans.

Alogliptin inhibits IL-1β-induced inflammatory response in fibroblast-like synoviocytes

Excessive production of pro-inflammatory cytokines such as interleukin (IL)-1β plays an important role in the chronic inflammation in fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA). Alogliptin, an important selective dipeptidyl peptidase-4 (DPP-4) inhibitor licensed for the treatment of type 2 diabetes, has displayed a wide range of pharmacological capacities. In the present study, we aimed to investigate whether alogliptin possessed a protective effect against IL-1β-induced insult in FLS. Our results indicate that alogliptin treatment ameliorated IL-1β-induced production of reactive oxygen species, the expression of matrix metalloproteinase-3 (MMP-3) and MMP-13, secretions of tumor necrosis factor-α (TNF-α), IL-6, and IL-8. Additionally, we found that alogliptin inhibited c-Jun N-terminal kinase (JNK)/activator protein 1 (AP-1) signaling by reducing IL-1β-induced phosphorylation of JNK, the expression of c-Jun and c-Fos, and the luciferase activity of AP-1. Importantly, alogliptin suppressed IL-1β-induced activation of IκBα/NF-κB signaling by preventing the phosphorylation and degradation of IκBα, nuclear translocation of NF-κB p65, as well as the luciferase activity of AP-1. These findings suggest that alogliptin might have therapeutic potential for the treatment of chronic inflammation in RA.

Dipeptidyl peptidase-4 is increased in the abdominal aortic aneurysm vessel wall and is associated with aneurysm disease processes

BACKGROUND

Abdominal aortic aneurysm (AAA) is a potentially life-threatening disease, and until today there is no other treatment available than surgical intervention. Dipeptidyl peptidase-4 (DPP4)-inhibitors, used clinically to treat type 2 diabetes, have in murine models been shown to attenuate aneurysm formation and decrease aortic wall matrix degradation, inflammation and apoptosis. Our aim was to investigate if DPP4 is present, active and differentially expressed in human AAA.

METHODS AND RESULTS

DPP4 gene expression was elevated in both media and adventitia of AAA tissue compared with control tissue, as measured by microarrays and qPCR, with consistent findings in external data. The plasma activity of DPP4 was however lower in male patients with AAA compared with age- and gender-matched controls, independently of comorbidity or medication. Immunohistochemical double staining revealed co-localization of DPP4 with cells positive for CD68, CD4 and -8, CD20, and SMA. Gene set enrichment analysis demonstrated that expression of DPP4 in AAA tissue correlated with expression of biological processes related to B- and T-cells, extracellular matrix turnover, peptidase activity, oxidative stress and angiogenesis whereas it correlated negatively with muscle-/actin-related processes.

CONCLUSION

DPP4 is upregulated in both media and adventitia of human AAA and correlates with aneurysm pathophysiological processes. These results support previous murine mechanistic studies and implicate DPP4 as a target in AAA disease.

Nanofibrous vildagliptin-eluting stents enhance re-endothelialization and reduce neointimal formation in diabetes: in vitro and in vivo

BACKGROUND

The high lifetime risk of vascular disease is one of the important issues that plague patients with diabetes mellitus. Systemic oral vildagliptin administration favors endothelial recovery and inhibits smooth muscle cell (SMC) proliferation. However, the localized release of vildagliptin in the diabetic vessel damage has seldom been investigated.

RESEARCH DESIGN AND METHODS

In this work, nanofiber-eluting stents that loaded with vildagliptin, a dipeptidyl peptidase-4 enzyme (DPP-4) inhibitor, was fabricated to treat diabetic vascular disease. To prepare nanofibers, the poly (D,L)-lactide-co-glycolide (PLGA) and vildagliptin were mixed using hexafluoroisopropanol and electrospinning process. In vitro and in vivo release rates of the vildagliptin were characterized using high-performance liquid chromatography.

RESULTS

Effective vildagliptin concentrations were delivered for more than 28 days from the nanofibrous membranes coating on the surface of the stents in vitro and in vivo. The vildagliptin-eluting PLGA membranes greatly accelerated the recovery of diabetic endothelia and reduced SMC hyperplasia. The type I collagen content of the diabetic vascular intimal area that was treated by vildagliptin-eluting stents was lower than that of the non-vildagliptin-eluting group.

CONCLUSION

The experimental results revealed that stenting with vildagliptin-eluting PLGA membranes could potentially promote healing for diabetic arterial diseases.

miR-29b Mediates the Chronic Inflammatory Response in Radiotherapy-Induced Vascular Disease

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Radiotherapy is a powerful treatment strategy in patients with oncological diseases.

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Radiation-induced vasculopathy can dose dependently increase the risk of ischemic cardiovascular diseases (e.g., myocardial infarction, heart failure, stroke).

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The microRNA miR-29b is repressed in radiation-induced vasculopathy (human irradiated vs. nonirradiated tissue specimen, as well as in murine and cell culture models of irradiation).

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Pentraxin-3 and dipeptidyl-peptidase 4 are the main downstream effectors of miR-29b in radiation-induced vasculopathy.

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miR-29b mimics were able to limit pentraxin-3 and dipeptidyl-peptidase 4 levels in the irradiated vasculature (murine model) and to constrain the burden of vascular inflammation.

As a consequence of the success of present-day cancer treatment, radiotherapy-induced vascular disease is emerging. This disease is caused by chronic inflammatory activation and is likely orchestrated in part by microRNAs. In irradiated versus nonirradiated conduit arteries from patients receiving microvascular free tissue transfer reconstructions, irradiation resulted in down-regulation of miR-29b and up-regulation of miR-146b. miR-29b affected inflammation and adverse wound healing through its targets pentraxin-3 and dipeptidyl-peptidase 4. In vitro and in vivo, we showed that miR-29b overexpression therapy, through inhibition of pentraxin-3 and dipeptidyl-peptidase 4, could dampen the vascular inflammatory response.

A closer look at heart failure in patients with concurrent diabetes mellitus using glucose lowering drugs

INTRODUCTION

Type 2 diabetes (T2D) is an independent risk factor for heart failure (HF). With concomitant T2D and HF, recent data suggests an incremental risk of cardiovascular death and hospitalization for HF, as compared to patients with HF without T2D. Areas covered: Management of these two diseases has been a challenge for physicians. The treatment goals for HF patients in T2D are very important. They serve as the endpoint in using a specific treatment for management and treatment of T2D patients hence, decreasing mortality rates. In this review, we examine the effects of oral antidiabetic drugs on HF patients, discussing current evidence-based up-to-date management strategies and guidelines in the general population with HF and T2D. Expert commentary: Future in the management of T2D in HF patients looks bright. Augmenting data on potential cardiovascular side effects of antidiabetic drugs is valuable since millions of people are treated over many years. Newer novel drugs targeting specific signaling pathways are approaching the stages of clinical investigation. They have been a highly attractive concept for the future in the management of these patients. However, while advances in technology elucidated many aspects of these diseases, many mysteries still remain.

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

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

Effects of Linagliptin on Vessel Wall Healing in the Rat Model of Arterial Injury Under Normal and Diabetic Conditions

Diabetic patients suffer an increased risk of restenosis and late stent thrombosis after angioplasty, complications which are related to a defective reendothelialization. Dipeptidyl peptidase-4 inhibitors have been suggested to exert a direct effect on endothelial and smooth muscle cells (SMCs). Therefore, the objective was to study if the dipeptidyl peptidase-4 inhibitor linagliptin could influence vascular repair and accelerate reendothelialization after arterial injury in healthy and diabetic animals. Diabetic Goto-Kakizaki and healthy Wistar rats were subjected to arterial injury and treated with linagliptin or vehicle. Vessel wall healing was monitored noninvasively using ultrasound, and on sacrifice, with Evans blue staining and immunohistochemistry. The effect of linagliptin on SMCs was also studied in vitro. We found that linagliptin reduced the proliferation and dedifferentiation of SMCs in vitro, and modulated the inflammatory response in the SMCs after arterial injury in vivo. However, these effects of linagliptin did not affect the neointima formation or the reendothelialization under normal and diabetic conditions. Although linagliptin did not influence vessel wall healing, it seems to possess a desirable antiproliferative influence on SMCs in vitro and an antiinflammatory effect in vivo. These pharmacological properties might carry a potential significance for favorable outcome after vascular interventions in diabetic patients.

The effect of anagliptin on intimal hyperplasia of rat carotid artery after balloon injury

The present study evaluated the effect of anagliptin on intimal hyperplasia following carotid artery injury in Sprague-Dawley rats. Sprague-Dawley rats weighing 280–300 g were injured using a 2F Fogarty balloon embolectomy catheter. The rats were divided into injury-(saline) and anagliptin-(10 mg/kg/day) treated groups. vascular injuries were induced in the left carotid artery, followed by evaluation of neointima formation at 28 days. The right and left carotid arteries were harvested and evaluated with histological evaluation, and the plasma activity of glucagon-like peptide 1 receptor (GLP-1), stromal cell-derived factor (SDF)-1α, interleukin (IL)-6, IL-1β and tumor necrosis factor (TNF)-α were detected by ELISA analysis. Treatment with anagliptin decreased balloon injury-induced neointima formation, compared with the injury group (P<0.01). Body weight and food consumption did not alter following treatment with anagliptin. Anagliptin caused an increase in the serum active GLP-1 concentration, compared with the injury group. In addition, serum SDF-1α was significantly decreased by treatment with anagliptin (P<0.001). Anagliptin altered the serum activity of IL-6, IL-1β and TNF-α (P<0.01). The results of the present study demonstrated that anagliptin appeared to attenuate neointimal formation by inhibiting inflammatory cytokines and chemokines following balloon injury, and that treatment with a dipeptidyl peptidase 4 inhibitor may be useful for future preclinical studies and potentially for the inhibition of thrombosis formation following percutaneous coronary intervention.

New Antihyperglycemic Drugs and Heart Failure: Synopsis of Basic and Clinical Data

The assessment of the cardiovascular safety profile of any newly developed antihyperglycemic drug is mandatory before registration, as a meta-analysis raised alarm describing a significant increase in myocardial infarction with the thiazolidinedione rosiglitazone. The first results from completed cardiovascular outcome trials are already available: TECOS, SAVOR-TIMI, and EXAMINE investigated dipeptidyl peptidase 4 (DPP-4) inhibitors, ELIXA, LEADER, and SUSTAIN-6 investigated glucagon-like peptide 1 (GLP-1) receptor agonists, and EMPA-REG OUTCOME and CANVAS investigated sodium-dependent glucose transporter 2 (SGLT-2) inhibitors. LEADER, SUSTAIN-6, EMPA-REG OUTCOME, and CANVAS showed potential beneficial results, while the SAVOR-TIMI trial had an increased rate of hospitalization for heart failure. Meanwhile, the same drugs are investigated in preclinical experiments mainly using various animal models, which aim to find interactions and elucidate the underlying downstream mechanisms between the antihyperglycemic drugs and the cardiovascular system. Yet the direct link for observed effects, especially for DPP-4 and SGLT-2 inhibitors, is still unknown. Further inquiry into these mechanisms is crucial for the interpretation of the clinical trials' outcome and, vice versa, the clinical trials provide hints for an involvement of the cardiovascular system. The synopsis of preclinical and clinical data is essential for a detailed understanding of benefits and risks of new antihyperglycemic drugs.

The regulatory role of DPP4 in atherosclerotic disease

The increasing prevalence of atherosclerosis has become a worldwide health concern. Although significant progress has been made in the understanding of atherosclerosis pathogenesis, the underlying mechanisms are not fully understood. Recent studies suggest dipeptidyl peptidase-4 (DPP4), a regulator of inflammation and metabolism, may be involved in the development of atherosclerotic diseases. There has been increasing clinical and pre-clinical evidence showing DPP4-incretin axis is involved in cardiovascular disease. Although the cardiovascular outcome of DPP4 inhibition or incretin analogues has been or being evaluated by several large scale clinical trials, the exact role of DPP4 in atherosclerotic diseases is not completely understood. In the current review, we will summarize the recent advances in direct and indirect regulatory role of DPP4 in atherosclerosis.

Dipeptidyl peptidase- IV inhibitor alogliptin improves stress-induced insulin resistance and prothrombotic state in a murine model

BACKGROUND

Stress evokes lipolytic release of free fatty acid (FFA) and low-grade inflammation in visceral adipose tissue, mediated by increased adipokine secretion, and contributes to glucose metabolism disorder and prothrombotic state. We tested the hypothesis that alogliptin, a dipeptidyl peptidase-4 inhibitor, can ameliorate the biological effects of chronic stress in mice.

METHOD AND RESULTS

C57BL/6J mice were subjected to 2-week intermittent restraint stress and orally treated with vehicle or alogliptin (dose: 15 or 45mg/kg/day). Plasma levels of lipids, proinflammatory cytokines (monocyte chemoattractant protein-1, tumor necrosis factor-α, and interleukin-6), and 8-hydroxydeoxyguanosine were measured with enzyme-linked immunosorbent assay. Monocyte/macrophage accumulation in inguinal white adipose tissue (WAT) was examined by CD11b-positive cell count and mRNA expression of CD68 and F4/80 was examined by immunohistochemistry and RT-PCR, respectively. The mRNA levels of the above-mentioned proinflammatory cytokines, NADPH oxidase 4, adiponectin, and coagulation factors (plasminogen activation inhibitor-1 and tissue factor) in WAT were also assessed with RT-PCR. Glucose metabolism was assessed by glucose and insulin tolerance tests, plasma levels of DPP-4 activity, glucagon-like peptide-1, expression of DPP-4, insulin receptor substrate-1 and glucose transporter 4 in WAT and skeletal muscle. Alogliptin administration suppressed stress-induced FFA release, oxidative stress, adipose tissue inflammation, DPP-4 activation, and prothrombotic state in a dose-dependent manner, and improved insulin sensitivity in stressed mice.

CONCLUSIONS

The results indicate that alogliptin improves stress-induced prothrombotic state and insulin resistance; suggesting that alogliptin could have beneficial therapeutic effects against cardiovascular complications in diabetic patients under stress.

Increased Plasma Dipeptidyl Peptidase-4 Activities in Patients with Coronary Artery Disease

Dipeptidyl peptidase-4 (DPP4) is one of the most potent mammalian serine proteases participated in the pathogenesis of subclinical atherosclerosis. Here we investigated whether the plasma soluble form of DPP4 is associated with the prevalence of coronary artery disease (CAD) with and without diabetes mellitus (DM). A cross-sectional study was conducted of 496 aged 26–81 years with (n = 362) and without (n = 134) CAD. Plasma DPP4 activity, high sensitive C-reactive protein (hs-CRP), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein levels were measured. The coronary atherosclerotic plaques were evaluated by coronary angiography. The CAD patients with (n = 84) and without (n = 278) DM had significantly higher DPP4 levels (11.8 ± 3.1 vs. 6.9 ± 3.5 ng/mL, P<0.01) than the nonCAD subjects. The acute coronary syndrome patients (n = 299) had elevated DPP4 levels than those with stable angina patients (n = 83). CAD patients even without DM had increased plasma DPP4 activities as compared with nonCAD subjects (10.9 ± 4.9 vs. 6.4 ± 3.1, ng/L, P< 0.01). A linear regression analysis revealed that overall, the DPP4 levels were positively associated with LCL-C and hs-CRP levels as well as syntax scores. A multiple logistic regression analysis demonstrated that plasma DPP4 activity was independent predictor of CAD (odds ratio, 1.56; 95% CI, 1.19–1.73; P<0.01). Our study shows that increased DPP4 activity levels are associated with the presence of CAD and that the plasma DPP4 level serves as a novel biomarker for CAD even without DM.

DPP-4 inhibitors and cardiovascular disease in type 2 diabetes mellitus. Expectations, observations and perspectives

AIMS

Cardiovascular disease (CVD) is the greatest burden of type 2 diabetes mellitus (T2DM) in terms of morbility, mortality and costs for individuals and societies. Therefore, its prevention is a major goal in diabetes care. Optimal treatment of hyperglycemia is certainly instrumental to CVD prevention. Optimal treatment means both establishing the most appropriate glycemic target for the given individual and selecting the medication(s) with the most favourable benefit/safety ratio. CVD safety, if not a clear CVD benefit, is certainly required for all antidiabetic agents. Dipeptidyl-peptidase-4 (DPP-4) inhibitors are among the classes of antidiabetic agents most recently made available for diabetes care. A major question to be addressed is the effect of these compounds on CVD. Expectations were high for their mechanism of action, which targets also post-prandial glucose and minimize hypoglycemia risk, thereby providing a sort of global glucose control, and for some potentially beneficial extra-glycemic effects. This article reviews the existing literature on this issue.

DATA SYNTHESIS

Data published so far document that DPP-4 inhibitors have a wide spectrum of glycemic and extra-glycemic effects potentially reducing the risk of CVD as well as favourable effects on intermediate or surrogate CVD endpoints. These data heralded a better CVD outcome. Accordingly, pooling CVD safety data from phase 3 and 4 studies conducted with DPP-4 inhibitors suggested that their use might translate into a better CVD outcome. Data from three CVD outcome RCTs with alogliptin, saxagliptin and sitagliptin documented no harm but did not show any benefit on major CVD events. A modest but significant increased risk of hospitalization for heart failure was observed with saxagliptin and with alogliptin (only in subjects with no history of heart failure before randomization) but not with sitagliptin. A study currently in progress with linagliptin will provide further insights in the issue of CVD safety and benefit.

CONCLUSIONS

It should be considered that most alternative oral antidiabetic agents generally do not possess a better CVD risk profile than DPP-4 inhibitors and that some of them, indeed, should be used with caution because of potentially adverse effects on heart and vasculature. Overall, the selection of antidiabetic agent(s) with the most favourable CVD profile is mandatory but still challenging in diabetes care.

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

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

Soluble DPP-4 up-regulates toll-like receptors and augments inflammatory reactions, which are ameliorated by vildagliptin or mannose-6-phosphate

OBJECTIVE

Studies have shown that dipeptidyl peptidase-4 (DPP-4) inhibitors have anti-inflammatory effects. Soluble DPP-4 (sDPP-4) has been considered as an adipokine of which actions need to be further characterized.

METHODS

We investigated the pro-inflammatory actions of sDPP-4 and the anti-inflammatory effects of DPP-4 inhibition, using vildagliptin, as an enzymatic inhibitor, and mannose-6-phosphate (M6P) as a competitive binding inhibitor.

RESULTS

In lipopolysaccharide (LPS)-stimulated RAW264.7 cells, vildagliptin suppressed the increased expression of inducible nitric oxide synthase (iNOS) and phosphorylated JNK (pJNK), activation of the NF-κB pathway, and the resultant NO and proinflammatory cytokine production. Although sDPP-4 alone did not affect the protein level of iNOS or pJNK or the production of NO in RAW264.7 cells, it did amplify iNOS expression, NO responses, and proinflammatory cytokine production in LPS-stimulated RAW264 cells. As a probable mechanism, we found that sDPP-4 caused dose-dependent increases in the expression levels of toll-like receptor 4 (TLR4) and TLR2 in RAW264.7 cells, and that these alterations were inhibited by vildagliptin, M6P, or bisindolylmaleimide II, a protein kinase C inhibitor. Either vildagliptin or M6P suppressed iNOS expression and NO and cytokine production in LPS+DPP-4-co-stimulated macrophages, while combined treatment of the co-stimulated cells with both agents had increased anti-inflammatory effects compared with either treatment alone. Intravenous injection of sDPP-4 to C57BL/6J mice increased the expression of both TLRs in kidney and white adipose tissues.

CONCLUSION

Our findings suggest that sDPP-4 enhances inflammatory actions via TLR pathway, while DPP-4 inhibition with either an enzymatic or binding inhibitor has anti-inflammatory effects.

Antidiabetic treatment with gliptins: focus on cardiovascular effects and outcomes

The traditional oral pharmacological therapy for type 2 diabetes mellitus (T2DM) has been based on the prescription of metformin, a biguanide, as first line antihyperglycemic agent world over. It has been demonstrated that after 3 years of treatment, approximately 50 % of diabetic patients could achieve acceptable glucose levels with monotherapy; but by 9 years this had declined to only 25 %. Therefore, the implementation of a combined pharmacological therapy acting via different pathways becomes necessary, and its combination with a compound of the sulfonylurea group was along decades the most frequently employed prescription in routine clinical practice. Meglitinides, glitazones and alpha-glucosidase inhibitors were subsequently developed, but the five mentioned groups of oral antihyperglycemic agents are associated with variable degrees of undesirable or even severe cardiovascular events. The gliptins—also called dipeptidyl peptidase 4 (DPP4) inhibitors—are an additional group of antidiabetic compounds with increasing clinical use. We review the status of the gliptins with emphasis on their capabilities to positively or negatively affect the cardiovascular system, and their potential involvement in major adverse cardiovascular events (MACE). Alogliptin, anagliptin, linagliptin, saxagliptin, sitagliptin, teneligliptin and vildagliptin are the compounds currently in clinical use. Regardless differences in chemical structure and metabolic pathways, gliptins as a group exert favorable changes in experimental models. These changes, as an almost general rule, include improved endothelial function, reduction of inflammatory markers, oxidative stress ischemia/reperfusion injury and atherogenesis. In addition, increased adiponectin levels and modest decreases in lipidemia and blood pressure were reported. In clinical settings, several trials—notably the longer one, employing sitagliptin, with a mean follow-up period of 3 years—did not show an increased risk for ischemic events. Anyway, it should be emphasized that the encouraging results from basic science were not yet translated into clinical evidence, probably due the multiple and pleiotropic enzymatic effects of DPP4 inhibition. Moreover, when employing saxagliptin, while the drug was not associated with an augmented risk for ischemic events, it should be pinpointed that the rate of hospitalization for heart failure was significantly increased. Gliptins as a group constitute a widely accepted therapy for the management of T2DM, usually as a second-line medication. Nonetheless, for the time being, a definite relationship between gliptins treatment and improved cardiovascular outcomes remains uncertain and needs yet to be proven.

The Dipeptidyl Peptidase Family, Prolyl Oligopeptidase, and Prolyl Carboxypeptidase in the Immune System and Inflammatory Disease, Including Atherosclerosis

Research from over the past 20 years has implicated dipeptidyl peptidase (DPP) IV and its family members in many processes and different pathologies of the immune system. Most research has been focused on either DPPIV or just a few of its family members. It is, however, essential to consider the entire DPP family when discussing any one of its members. There is a substantial overlap between family members in their substrate specificity, inhibitors, and functions. In this review, we provide a comprehensive discussion on the role of prolyl-specific peptidases DPPIV, FAP, DPP8, DPP9, dipeptidyl peptidase II, prolyl carboxypeptidase, and prolyl oligopeptidase in the immune system and its diseases. We highlight possible therapeutic targets for the prevention and treatment of atherosclerosis, a condition that lies at the frontier between inflammation and cardiovascular disease.