Anagliptin, a dipeptidyl peptidase-4 inhibitor, decreases macrophage infiltration and suppresses atherosclerosis in aortic and coronary arteries in cholesterol-fed rabbits

Vasorelaxant mechanisms of the antidiabetic anagliptin in rabbit aorta: roles of Kv channels and SERCA pump

AIMS

The present study investigated the vasorelaxant mechanisms of an oral antidiabetic drug, anagliptin, using phenylephrine (Phe)-induced pre-contracted rabbit aortic rings.

METHODS

Arterial tone measurement was performed in rabbit thoracic aortic rings.

RESULTS

Anagliptin induced vasorelaxation in a dose-dependent manner. Pre-treatment with the classical voltagedependent K+ (Kv) channel inhibitors 4-aminopyridine and tetraethylammonium significantly decreased the vasorelaxant effect of anagliptin, whereas pre-treatment with the inwardly rectifying K+ (Kir) channel inhibitor Ba2+, the ATP-sensitive K+ (KATP) channel inhibitor glibenclamide, and the large-conductance Ca2+-activated K+ (BKCa) channel inhibitor paxilline did not attenuate the vasorelaxant effect. Furthermore, the vasorelaxant response of anagliptin was effectively inhibited by pre-treatment with the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump inhibitors thapsigargin and cyclopiazonic acid. Neither cAMP/protein kinase A (PKA)-related signaling pathway inhibitors (adenylyl cyclase inhibitor SQ 22536 and PKA inhibitor KT 5720) nor cGMP/protein kinase G (PKG)-related signaling pathway inhibitors (guanylyl cyclase inhibitor ODQ and PKG inhibitor KT 5823) reduced the vasorelaxant effect of anagliptin. Similarly, the anagliptin-induced vasorelaxation was independent of the endothelium.

CONCLUSIONS

Based on these results, we suggest that anagliptin-induced vasorelaxation in rabbit aortic smooth muscle occurs by activating Kv channels and the SERCA pump, independent of other vascular K+ channels, cAMP/PKA- or cGMP/PKG-related signaling pathways, and the endothelium.

Effective Therapeutic Verification of Crocin I, Geniposide, and Gardenia (Gardenia jasminoides Ellis) on Type 2 Diabetes Mellitus In Vivo and In Vitro

For many centuries, Gardenia (Gardenia jasminoides Ellis) was highly valued as a food homologous Chinese herbal medicine with various bioactive compounds, including crocin I and geniposide. However, the functional mechanism underlying the hypoglycemic effect of gardenia is absent in the literature. To evaluate the effect of gardenia and its different extracts on type 2 diabetes mellitus (T2DM) in in vivo and in vitro experiments, the dried gardenia powder was extracted using 60% ethanol and eluted at different ethanol concentrations to obtain the corresponding purified fragments. After that, the active chemical compositions of the different purified gardenia fragments were analyzed using HPLC. Then, the hypoglycemic effects of the different purified gardenia fragments were compared using in vitro and in vivo experiments. Finally, the different extracts were characterized using UPLC-ESI-QTOF-MS/MS and the mass spectrometric fragmentation pathway of the two main compounds, geniposide and crocin I, were identified. The experimental results indicated that the inhibitory effect of the 40% EGJ (crocin I) on the α-glucosidase was better than the 20% EGJ (geniposide) in vitro. However, the inhibitory effect of geniposide on T2DM was better than crocin I in the animal experiments. The different results in vivo and in vitro presumed potentially different mechanisms between crocin I and geniposide on T2DM. This research demonstrated that the mechanism of hypoglycemia in vivo from geniposide is not only one target of the α-glucosidase but provides the experimental background for crocin I and the geniposide deep processing and utilization.

Glycaemic Control in Patients Undergoing Percutaneous Coronary Intervention: What Is the Role for the Novel Antidiabetic Agents? A Comprehensive Review of Basic Science and Clinical Data

Coronary artery disease (CAD) remains one of the most important causes of morbidity and mortality worldwide, and revascularization through percutaneous coronary interventions (PCI) significantly improves survival. In this setting, poor glycaemic control, regardless of diabetes, has been associated with increased incidence of peri-procedural and long-term complications and worse prognosis. Novel antidiabetic agents have represented a paradigm shift in managing patients with diabetes and cardiovascular diseases. However, limited data are reported so far in patients undergoing coronary stenting. This review intends to provide an overview of the biological mechanisms underlying hyperglycaemia-induced vascular damage and the contrasting actions of new antidiabetic drugs. We summarize existing evidence on the effects of these drugs in the setting of PCI, addressing pre-clinical and clinical studies and drug-drug interactions with antiplatelet agents, thus highlighting new opportunities for optimal long-term management of these patients.

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.

Anagliptin prevented interleukin 1β (IL-1β)-induced cellular senescence in vascular smooth muscle cells through increasing the expression of sirtuin1 (SIRT1)

Vascular smooth muscle cell senescence plays a pivotal role in the pathogenesis of atherosclerosis. Anagliptin is a novel dipeptidyl peptidase-4 (DPP-4) inhibitor for the treatment of hyperglycemia. Recent progress indicates that DPP-4 inhibitors show a wide range of cardiovascular benefits. We hypothesize that Anagliptin plays a role in vascular smooth muscle cell senescence and this may imply its modulation of atherosclerosis. Here, the beneficial effect of Anagliptin against interleukin 1β (IL-1β)-induced cell senescence in vascular smooth muscle cells was studied to learn the promising therapeutic capacity of Anagliptin on atherosclerosis. Firstly, we found that Anagliptin treatment ameliorated the elevated secretions of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), and macrophage chemoattractant protein-1 (MCP-1). Secondly, our findings indicate that exposure to IL-1β reduced telomerase activity from 26.7 IU/L to 15.8 IU/L, which was increased to 20.3 and 24.6 IU/L by 2.5 and 5 μM Anagliptin, respectively. In contrast, IL-1β stimulation increased senescence- associated β-galactosidase (SA-β-gal) staining to 3.1- fold compared to the control group, it was then reduced to 2.3- and 1.6- fold by Anagliptin dose-dependently. Thirdly, Anagliptin dramatically reversed the upregulated p16, p21, and downregulated sirtuin1 (SIRT1) in IL-1β-treated vascular smooth muscle cells. Lastly, the protective effect of Anagliptin against cellular senescence in vascular smooth muscle cells was abolished by silencing of SIRT1. In conclusion, Anagliptin protects vascular smooth muscle cells from cytokine-induced senescence, and the action of Anagliptin in vascular smooth muscle cells requires SIRT1 expression.

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.

Therapies for the Treatment of Cardiovascular Disease Associated with Type 2 Diabetes and Dyslipidemia

Cardiovascular disease (CVD) is the leading cause of death worldwide and is the clinical manifestation of the atherosclerosis. Elevated LDL-cholesterol levels are the first line of therapy but the increasing prevalence in type 2 diabetes mellitus (T2DM) has positioned the cardiometabolic risk as the most relevant parameter for treatment. Therefore, the control of this risk, characterized by dyslipidemia, hypertension, obesity, and insulin resistance, has become a major goal in many experimental and clinical studies in the context of CVD. In the present review, we summarized experimental studies and clinical trials of recent anti-diabetic and lipid-lowering therapies targeted to reduce CVD. Specifically, incretin-based therapies, sodium-glucose co-transporter 2 inhibitors, and proprotein convertase subtilisin kexin 9 inactivating therapies are described. Moreover, the novel molecular mechanisms explaining the CVD protection of the drugs reviewed here indicate major effects on vascular cells, inflammatory cells, and cardiomyocytes, beyond their expected anti-diabetic and lipid-lowering control. The revealed key mechanism is a prevention of acute cardiovascular events by restraining atherosclerosis at early stages, with decreased leukocyte adhesion, recruitment, and foam cell formation, and increased plaque stability and diminished necrotic core in advanced plaques. These emergent cardiometabolic therapies have a promising future to reduce CVD burden.

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.

Dipeptidyl Peptidase-4 Inhibitor Reduces the Risk of Developing Hypertrophic Scars and Keloids following Median Sternotomy in Diabetic Patients: A Nationwide Retrospective Cohort Study Using the National Database of Health Insurance Claims of Japan

BACKGROUND

Hypertrophic scars and keloids, which are abnormalities of fibrosis, often occur in surgical wounds; however, their exact cause and preventive measures are unknown. The administration of dipeptidyl peptidase-4 inhibitors to humans is expected to suppress fibrosis in wounds and minimize hypertrophic scar and keloid formation.

METHODS

This study aimed to verify the suppressive effect of dipeptidyl peptidase-4 inhibitors on the formation of hypertrophic scars or keloids using real world data from the National Database of Health Insurance Claims and Specific Health Checkups of Japan. It is a retrospective cohort study, and data were extracted from the National Database between April of 2013 and March of 2015. Patients who underwent median sternotomy were included in the study based on their claimed surgical codes. Subjects who were prescribed dipeptidyl peptidase-4 inhibitors constituted the treatment group; subjects who were not prescribed or administered dipeptidyl peptidase-4 inhibitors during that period constituted the nontreatment group.

RESULTS

Subjects included 5430 patients throughout Japan (3509 men and 1921 women). Of the 446 subjects who were treated with dipeptidyl peptidase-4 inhibitors within 1 year before the procedure, fewer than 10 (<2 percent) developed either hypertrophic scars or keloids. Of the 4984 subjects who were not treated, 152 (3.05 percent) were at significantly lower risk for hypertrophic scars and keloids (p = 0.04). A logistic regression analysis was performed to adjust for confounding factors, with history of hypertrophic scar formation as the explained variable.

CONCLUSION

This study revealed that dipeptidyl peptidase-4 inhibitors suppress the onset of hypertrophic scars or keloids after surgery in humans.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Sitagliptin attenuates the progression of coronary atherosclerosis in patients with coronary disease and type 2 diabetes

BACKGROUND AND AIMS

Type 2 diabetes mellitus (T2DM) is a well-recognized independent risk factor for ASCVD, the aim of this study was to investigate the effects of a dipeptidyl peptidase-4 inhibitor, sitagliptin, on prevention of progression of coronary atherosclerosis assessed by three-dimensional quantitative coronary angiography (3D-QCA) in T2DM patients with coronary artery disease (CAD).

METHODS

This was a prospective, randomized, double-center, open-label, blinded end point, controlled 18-month study in patients with CAD and T2DM. A total of 149 patients, who had at least 1 atherosclerotic plaque with 20%-80% luminal narrowing in a coronary artery, and had not undergone intervention during a clinically indicated coronary angiography or percutaneous coronary intervention, were randomized to sitagliptin group (n = 74) or control group (n = 75). Atherosclerosis progression was measured by repeat 3D-QCA examination in 88 patients at study completion. The primary outcome was changes in percent atheroma volume (PAV) from baseline to study completion measured by 3D-QCA. Secondary outcomes included change in 3D-QCA-derived total atheroma volume (TAV) and late lumen loss (LLL).

RESULTS

The primary outcome of PAV increased of 1.69% (95%CL, -0.8%-4.2%) with sitagliptin and 5.12% (95%CL, 3.49%-6.74%) with the conventional treatment (p = 0.023). The secondary outcome of change in TAV in patients treated with sitagliptin increased of 6.45 mm³ (95%CL,-2.46 to 6.36 mm³) and 9.45 mm³ (95%CL,-4.52 to 10.14 mm³) with conventional treatment (p = 0.023), however, no significant difference between groups was observed (p = 0.175). Patients treated with sitagliptin had similar LLL as compared with conventional antidiabetics (-0.06, 95%CL, -0.22 to 0.03 vs. -0.08, -0.23 to -0.03 mm, p = 0.689).

CONCLUSIONS

In patients with type 2 diabetes and coronary artery disease, treatment with sitagliptin resulted in a significantly lower rate of progression of coronary atherosclerosis compared with conventional treatment.

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.

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

OBJECTIVES

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

EVIDENCE ACQUISITION

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

RESULTS

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

CONCLUSION

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

Dipeptidyl peptidase IV (DPP-4) inhibition alleviates pulmonary arterial remodeling in experimental pulmonary hypertension

Dipeptidyl peptidase IV (DPP-4) is well known for its role in glucose homeostasis, and DPP-4 inhibitor (DPP-4i) exhibits multiple actions in cardiovascular diseases. However, the effect of DPP-4i on pulmonary hypertension (PH) remains unclear. Therefore, this study aims to investigate the effect of DPP-4i on pulmonary arterial remodeling in rats with PH and the potential underlying mechanisms. Our results show that DPP-4 was expressed in epithelial cells, endothelial cells, smooth muscle cells, and inflammatory cells in lung. DPP-4i (Sitagliptin) attenuated right ventricular systolic pressure (RVSP), right ventricle remodeling, hypertrophy of pulmonary arterial medial layer, inflammatory cell infiltration, and endothelial-mesenchymal transition (EndMT) in monocrotaline (MCT)-induced PH rats. Similarly, DPP-4i also alleviated bleomycin- and chronic hypoxia-induced PH in rats. In cultured human pulmonary arterial smooth muscle cells (PASMCs), DPP-4i inhibited platelet derived growth factor (PDGF)-BB-induced proliferation and migration, which was abolished by phosphatase and tensin homolog deleted on chromosome ten (PTEN) knockout. These results demonstrate that DPP-4 inhibition alleviates pulmonary arterial remodeling in experimental PH by inhibiting proliferation and migration of PASMCs.

Dipeptidyl peptidase 4 inhibitor anagliptin ameliorates hypercholesterolemia in hypercholesterolemic mice through inhibition of intestinal cholesterol transport

Aims/Introduction

Recent data showed that dipeptidyl peptidase 4 (DPP‐4) inhibitors exert a lipid‐lowering effect in diabetes patients. However, the mechanism of action is not yet clearly understood. We investigated the effect of anagliptin on cholesterol metabolism and transport in the small intestine using non‐diabetic hyperlipidemic animals, to clarify the mechanisms underlying the cholesterol‐lowering action.

Materials and Methods

Male apolipoprotein E (ApoE)‐deficient mice were orally administered anagliptin in the normal chow. Serum cholesterol levels and lipoprotein profiles were measured, and cholesterol transport was assessed by measuring the radioactivity in the tissues after oral loading of ¹⁴C‐labeled cholesterol (¹⁴C‐Chol). In additional experiments, effects of exendin‐4 in mice and of anagliptin in DPP‐4‐deficient rats were assessed. Effects on target gene expressions in the intestine were analyzed by quantitative polymerase chain reaction in normal mice.

Results

The serum total and non‐high‐density lipoprotein cholesterol concentrations decreased after anagliptin treatment in the ApoE‐deficient mice. The cholesterol‐lowering effect was predominantly observed in the chylomicron fraction. The plasma ¹⁴C‐Chol radioactivity was significantly decreased by 26% at 2 h after cholesterol loading, and the fecal ¹⁴C‐Chol excretion was significantly increased by 38% at 72 h. The aforementioned effects on cholesterol transport were abrogated in rats lacking DPP‐4 activity, and exendin‐4 had no effect on the ¹⁴C‐Chol transport in ApoE‐deficient mice. Furthermore, significant decreases of the intestinal cholesterol transport‐related microsomal triglyceride transfer protein, acyl‐coenzyme A:cholesterol acyltransferase 2, ApoA2 and ApoC2 messenger ribonucleic acid expressions were observed in the mice treated with repeated doses of anagliptin.

Conclusions

These findings suggest that anagliptin might exert a cholesterol‐lowering action through DPP‐4‐dependent and glucagon‐like peptide 1‐independent suppression of intestinal cholesterol transport.

Practical strategies for improving outcomes in T2DM: The potential role of pioglitazone and DPP4 inhibitors

T2DM is a complex disease underlined by multiple pathogenic defects responsible for the development and progression of hyperglycaemia. Each of these factors can now be tackled in a more targeted manner thanks to glucose-lowering drugs that have been made available in the past 2 to 3 decades. Recognition of the multiplicity of the mechanisms underlying hyperglycaemia calls for treatments that address more than 1 of these mechanisms, with more emphasis placed on the earlier use of combination therapies. Although chronic hyperglycaemia contributes to and amplifies cardiovascular risk, several trials have failed to show a marked effect from intensive glycaemic control. During the past 10 years, the effect of specific glucose-lowering agents on cardiovascular risk has been explored with dedicated trials. Overall, the cardiovascular safety of the new glucose-lowering agents has been proven with some of the trials summarized in this review, showing significant reduction of cardiovascular risk. Against this background, pioglitazone, in addition to exerting a sustained glucose-lowering effect, also has ancillary metabolic actions of potential interest in addressing the cardiovascular risk of T2DM, such as preservation of beta-cell mass and function. As such, it seems a logical agent to combine with other oral anti-hyperglycaemic agents, including dipeptidyl peptidase-4 inhibitors (DPP4i). DPP4i, which may also have a potential to preserve beta-cell function, is available as a fixed-dose combination with pioglitazone, and could, potentially, attenuate some of the side effects of pioglitazone, particularly if a lower dose of the thiazolidinedione is used. This review critically discusses the potential for early combination of pioglitazone and DPP4i.

Therapeutic application of GPR119 ligands in metabolic disorders

GPR119 belongs to the G protein-coupled receptor family and exhibits dual modes of action upon ligand-dependent activation: pancreatic secretion of insulin in a glucose-dependent manner and intestinal secretion of incretins. Hence, GPR119 has emerged as a promising target for treating type 2 diabetes mellitus without causing hypoglycaemia. However, despite continuous efforts by many major pharmaceutical companies, no synthetic GPR119 ligand has been approved as a new class of anti-diabetic agents thus far, nor has any passed beyond phase II clinical studies. Herein, we summarize recent advances in research concerning the physiological/pharmacological effects of GPR119 and its synthetic ligands on the regulation of energy metabolism, and we speculate on future applications of GPR119 ligands for the treatment of metabolic diseases, focusing on non-alcoholic fatty liver disease.

A Dipeptidyl Peptidase-4 Inhibitor Suppresses Macrophage Foam Cell Formation in Diabetic db/db Mice and Type 2 Diabetes Patients

Dipeptidyl peptidase-4 (DPP-4) inhibitors could have antiatherosclerotic action, in addition to antihyperglycemic roles. Because macrophage foam cells are key components of atherosclerosis, we investigated the effect of the DPP-4 inhibitor teneligliptin on foam cell formation and its related gene expression levels in macrophages extracted from diabetic db/db (C57BLKS/J Iar -+Lepr^db/+Lepr^db ) mice and type 2 diabetes (T2D) patients ex vivo. We incubated mouse peritoneal macrophages and human monocyte-derived macrophages differentiated by 7-day culture with oxidized low-density lipoprotein in the presence/absence of teneligliptin (10 nmol/L) for 18 hours. We observed remarkable suppression of foam cell formation by teneligliptin treatment ex vivo in macrophages isolated from diabetic db/db mice (32%) and T2D patients (38%); this effect was accompanied by a reduction of CD36 (db/db mice, 43%; T2D patients, 46%) and acyl-coenzyme A: cholesterol acyltransferase-1 (ACAT-1) gene expression levels (db/db mice, 47%; T2D patients, 45%). Molecular mechanisms underlying this effect are associated with downregulation of CD36 and ACAT-1 by teneligliptin. The suppressive effect of a DPP-4 inhibitor on foam cell formation in T2D is conserved across species and is worth studying to elucidate its potential as an intervention for antiatherogenesis in T2D patients.

Caveolin-1, a binding protein of CD26, is essential for the anti-inflammatory effects of dipeptidyl peptidase-4 inhibitors on human and mouse macrophages

We previously reported that inhibition of dipeptidyl peptidase (DPP)-4, the catalytic site of CD26, prevents atherosclerosis in animal models through suppression of inflammation; however, the underlying molecular mechanisms have not been fully elucidated. Caveolin-1 (Cav-1), a major structural protein of caveolae located on the surface of the cellular membrane, has been reported to modulate inflammatory responses by binding to CD26 in T cells. In this study, we investigated the role of Cav-1 in the suppression of inflammation mediated by the DPP-4 inhibitor, teneligliptin, using mouse and human macrophages. Mouse peritoneal macrophages were isolated from Cav-1^+/+ and Cav-1^-/- mice after stimulation with 3% thioglycolate. Inflammation was induced by the toll-like receptor (TLR)4 agonist, lipopolysaccharide (LPS), isolated from Escherichia coli. The expression of pro-inflammatory cytokines was determined using reverse transcription-polymerase chain reaction. Co-expression of Cav-1 and CD26 was detected using immunohistochemistry in both mouse and human macrophages. Teneligliptin treatment (10 nmol/L) suppressed the LPS-induced expression of interleukin (IL)-6 (70%) and tumor necrosis factor-α (37%) in peritoneal macrophages isolated from Cav-1^+/+ mice. However, teneligliptin did not have any effect on the macrophages from Cav-1^-/- mice. In human monocyte/macrophage U937 cells, teneligliptin treatment suppressed LPS-induced expression of pro-inflammatory cytokines in a dose-dependent manner (1-10 nmol/L). These anti-inflammatory effects of teneligliptin were mimicked by gene knockdown of Cav-1 or CD26 using small interfering RNA transfection. Furthermore, neutralization of these molecules using an antibody against CD26 or Cav-1 also showed similar suppression. Teneligliptin treatment specifically inhibited TLR4 and TLR5 agonist-mediated inflammatory responses, and suppressed LPS-induced phosphorylation of IL-1 receptor-associated kinase 4, a downstream molecule of TLR4. Next, we determined whether teneligliptin could directly inhibit the physical interaction between Cav-1 and CD26 using the Biacore system. Binding of CD26 to Cav-1 protein was detected. Unexpectedly, teneligliptin also bound to Cav-1, but did not interfere with CD26-Cav-1 binding, suggesting that teneligliptin competes with CD26 for binding to Cav-1. In conclusion, we demonstrated that Cav-1 is a target molecule for DPP-4 inhibitors in the suppression of TLR4-mediated inflammation in mouse and human macrophages.

DPP4 Inhibition Ameliorates Cardiac Function by Blocking the Cleavage of HMGB1 in Diabetic Mice After Myocardial Infarction

High mobility group box 1 (HMGB1), a ubiquitous DNA-binding protein, promotes angiogenesis and tissue repair, resulting in restored cardiac function after myocardial infarction (MI). Although dipeptidyl peptidase 4 (DPP4) degrades certain peptides, it remains unclear as to whether HMGB1 is a substrate of DPP4 and whether DPP4 inhibition prevents the cleavage of HMGB1.In transgenic mice with cardiac-specific overexpression of HMGB1 (TG) and wild-type mice (WT), a diabetic state was induced by streptozotocin, and MI was created by ligation of the left anterior descending coronary artery. To inhibit DPP4 activity, a DPP4 inhibitor anagliptin was used. The plasma levels of HMGB1, infarct size, echocardiographic data, angiogenesis, and vascular endothelial growth factor (VEGF) expression in the peri-infarct area were compared among non-diabetic MI WT/TG, diabetic MI WT/TG, and anagliptin-treated diabetic MI WT/TG mice.DPP4 activity was increased in the diabetic state and blocked by anagliptin administration. The HMGB1 plasma levels were reduced in the diabetic TG compared with the non-diabetic TG mice, but DPP4 inhibition with anagliptin increased HMGB1 plasma levels in the diabetic TG mice. The infarct area was significantly larger in the diabetic TG than in the non-diabetic TG mice, and it was reduced by DPP4 inhibition. Cardiac function, angiogenesis, and VEGF expression were impaired in the diabetic TG mice, but they were ameliorated by the DPP4 inhibition to levels similar to those found in the non-diabetic TG mice.The DPP4 inhibitor ameliorated cardiac function by inhibiting the inactivation of HMGB1 in diabetic mice after MI.

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.

Macrophage functions in lean and obese adipose tissue

Interactions between macrophages and adipocytes influence both metabolism and inflammation. Obesity-induced changes to macrophages and adipocytes lead to chronic inflammation and insulin resistance. This paper reviews the various functions of macrophages in lean and obese adipose tissue and how obesity alters adipose tissue macrophage phenotypes. Metabolic disease and insulin resistance shift the balance between numerous pro- and anti-inflammatory regulators of macrophages and create a feed-forward loop of increasing inflammatory macrophage activation and worsening adipocyte dysfunction. This ultimately leads to adipose tissue fibrosis and diabetes. The molecular mechanisms underlying these processes have therapeutic implications for obesity, metabolic syndrome, and diabetes.

Dipeptidyl Peptidase-4 Inhibitor Anagliptin Prevents Intracranial Aneurysm Growth by Suppressing Macrophage Infiltration and Activation

Background

Chronic inflammation plays a key role in the pathogenesis of intracranial aneurysms (IAs). DPP‐4 (dipeptidyl peptidase‐4) inhibitors have anti‐inflammatory effects, including suppressing macrophage infiltration, in various inflammatory models. We examined whether a DPP‐4 inhibitor, anagliptin, could suppress the growth of IAs in a rodent aneurysm model.

Methods and Results

IAs were surgically induced in 7‐week‐old male Sprague Dawley rats, followed by oral administration of 300 mg/kg anagliptin. We measured the morphologic parameters of aneurysms over time and their local inflammatory responses. To investigate the molecular mechanisms, we used lipopolysaccharide‐treated RAW264.7 macrophages. In the anagliptin‐treated group, aneurysms were significantly smaller 2 to 4 weeks after IA induction. Anagliptin inhibited the accumulation of macrophages in IAs, reduced the expression of MCP‐1 (monocyte chemotactic protein 1), and suppressed the phosphorylation of p65. In lipopolysaccharide‐stimulated RAW264.7 cells, anagliptin treatment significantly reduced the production of tumor necrosis factor α, MCP‐1, and IL‐6 (interleukin 6) independent of GLP‐1 (glucagon‐like peptide 1), the key mediator in the antidiabetic effects of DPP‐4 inhibitors. Notably, anagliptin activated ERK5 (extracellular signal–regulated kinase 5), which mediates the anti‐inflammatory effects of statins, in RAW264.7 macrophages. Preadministration with an ERK5 inhibitor blocked the inhibitory effect of anagliptin on MCP‐1 and IL‐6 expression. Accordingly, the ERK5 inhibitor also counteracted the suppression of p65 phosphorylation in vitro.

Conclusions

A DPP‐4 inhibitor, anagliptin, prevents the growth of IAs via its anti‐inflammatory effects on macrophages.

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.

Lung ischemia reperfusion injury: the therapeutic role of dipeptidyl peptidase 4 inhibition

Dipeptidyl peptidase 4 (DPP4) is a cell surface protease that has been reported to play a role in glucose homeostasis, cancer, HIV, autoimmunity, immunology and inflammation. A role for DPP4 in ischemia-reperfusion injury (IRI) in the heart has been established. Dipeptidyl peptidase 4 inhibition (DPP4i) appeared to decrease infarct size, improves cardiac function and promotes myocardial regeneration. Lung ischemia reperfusion injury is caused by a complex mechanism in which macrophages and neutrophils play an important role. Generation of reactive oxygen species (ROS), uncoupling of nitric oxide synthase (NOS), activation of nuclear factor-κB (NF-κB), activation of nicotinamide adenine dinucleotide phosphate metabolism, and generation of pro-inflammatory cytokines lead to acute lung injury (ALI). In this review we present the current knowledge on DPP4 as a target to treat IRI in the lung. We also provide evidence of the roles of the DPP4 substrates glucagon-like peptide 1 (GLP-1), vasoactive intestinal peptide (VIP) and stromal cell-derived factor-1α (SDF-1α) in protection against oxidative stress through activation of the mitogen-activated protein kinase (MAPK) 1/2 and phosphatidylinositol 3'-kinase (PI3K)/Akt signal transduction pathways.

Dipeptidyl peptidase-4 inhibition: insights from the bench and recent clinical studies

PURPOSE OF REVIEW

Atherosclerosis is the leading cause of death globally. The pathophysiology of atherosclerosis is 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. Recent advances in the understanding of DPP4 function in atherosclerosis will be discussed in this review.

RECENT FINDINGS

Multiple preclinical and clinical studies suggest DPP4/glucagon-like peptide-1 axis is involved in the development of atherosclerotic disease. However, several recent trials assessing the cardiovascular effects of DPP4 inhibition indicate enzymatic inhibition of DPP4 lacks beneficial effects on cardiovascular disease.

SUMMARY

Catalytic inhibition of DPP4 with DPP4 inhibitors alters pathways that could favor cardioprotection. Glucagon-like peptide-1 receptor-independent aspects of DPP4 function may contribute to the overall neutral effects on cardiovascular outcome seen in the outcome trials.