Sitagliptin reduces plaque macrophage content and stabilises arteriosclerotic lesions in Apoe (-/-) mice

Combination therapy and drug co-delivery systems for atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of plaque within the arteries. Despite advances in therapeutic strategies including anti-inflammatory, antioxidant, and lipid metabolism modulation treatments over the past two decades, the treatment of atherosclerosis remains challenging, as arterial damage is the result of interconnected pathological factors. Therefore, current monotherapies often fail to address the complex nature of this disease, leading to insufficient therapeutic outcomes. This review addressed this paucity of effective treatment options by comprehensively exploring the potential for combination therapies and advanced drug co-delivery systems for the treatment of atherosclerosis. We investigated the pathological features of and risk factors for atherosclerosis, underscoring the importance of drug combination therapies for the treatment of atherosclerotic diseases. We discuss herein mathematical models for quantifying the efficacy of the combination therapies and provide a systematic summary of drug combinations for the treatment of atherosclerosis. We also provide a detailed review of the latest advances in nanoparticle-based drug co-delivery systems for the treatment of atherosclerosis, focusing on the design of carriers with high biocompatibility and efficacy. By exploring the possibilities and challenges inherent to this approach, we aim to highlight cutting-edge technologies that can foster the development of innovative strategies, optimize drug co-administration, improve treatment outcomes, and reduce the burden of atherosclerosis-related morbidity and mortality on the healthcare system.

Incretin-based therapy: a new horizon in diabetes management

Diabetes mellitus, a metabolic syndrome characterized by hyperglycemia and insulin dysfunction, often leads to serious complications such as neuropathy, nephropathy, retinopathy, and cardiovascular disease. Incretins, gut peptide hormones released post-nutrient intake, have shown promising therapeutic effects on these complications due to their wide-ranging biological impacts on various body systems. This review focuses on the role of incretin-based therapies, particularly Glucagon-like peptide-1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors, in managing diabetes and its complications. We also discuss the potential of novel agents like semaglutide, a recently approved oral compound, and dual/triple agonists targeting GLP-1/GIP, GLP-1/glucagon, and GLP-1/GIP/glucagon receptors, which are currently under investigation. The review aims to provide a comprehensive understanding of the beneficial impacts of natural incretins and the therapeutic potential of incretin-based therapies in diabetes management.

Pharmacological therapy targeting the immune response in atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease characterized by the formation of atherosclerotic plaques that consist of numerous cells including smooth muscle cells, endothelial cells, immune cells, and foam cells. The most abundant innate and adaptive immune cells, including neutrophils, monocytes, macrophages, B cells, and T cells, play a pivotal role in the inflammatory response, lipoprotein metabolism, and foam cell formation to accelerate atherosclerotic plaque formation. In this review, we have discussed the underlying mechanisms of activated immune cells in promoting AS and reviewed published clinical trials for the treatment of AS by suppressing immune cell activation. We have also presented some crucial shortcomings of current clinical trials. Lastly, we have discussed the therapeutic potential of novel compounds, including herbal medicine and dietary food, in alleviating AS in animals. Despite these limitations, further clinical trials and experimental studies will enhance our understanding of the mechanisms modulated by immune cells and promote widespread drug use to treat AS by suppressing immune system-induced inflammation.

Characteristics of metabolic inflammatory syndrome among inpatients with type 2 diabetes: A cross-sectional study in China

BACKGROUND

As meta-inflammation is a common feature for obesity, type 2 diabetes (T2D), nonalcoholic fatty liver disease and atherosclerosis, we have proposed a new concept, metabolic inflammatory syndrome (MIS), to cluster such diseases. We aimed to characterize MIS and explore its association with coronary heart disease (CHD) among T2D inpatients in China.

METHODS

A total number of 8344 T2D participants were enrolled. Each component of MIS and metabolic syndrome (MS) was analyzed. Their association with the risk of CHD was assessed using a binary logistic analysis.

RESULTS

Among the T2D inpatients, the detection rate of MIS was much higher than that of MS (93.6 % vs. 53.2 %). Among all the components of MIS and MS, carotid atherosclerosis (71.9 %) was most commonly detected, which increased with aging in subgroups. Surprisingly, the most common combination of MIS was with all 4 components in T2D patients, with a constituent ratio of 30.9 %. According to the odds ratios (ORs), MIS was a better predictor of CHD than MS, especially after adjustment for age, sex, smoking, and alcohol consumption (adjusted OR for MIS: 3.083; for MS: 1.515). The presence of more components of MIS was associated with a higher detection rate of CHD (P < 0.001). Among all the components of MIS and MS, carotid atherosclerosis best predicted the risk of CHD (adjusted OR: 1.787).

CONCLUSIONS

MIS is an independent risk factor for CHD, with a bigger OR value than MS. Carotid atherosclerosis, with the highest detection rate, was the best individual predictor of CHD and thus a critical component of MIS. The concept of MIS represents the understanding of metabolic diseases from the perspective of holistic integrative medicine.

The antiatherosclerotic action of 1G244 - An inhibitor of dipeptidyl peptidases 8/9 - is mediated by the induction of macrophage death

BACKGROUND

Targeting cell death to induce favorable functional and morphological changes within atherosclerotic plaques has long been postulated as a promising anti-atherosclerotic strategy. In this regard, inhibition of dipeptidyl peptidases 8/9 has received special attention in the context of chronic inflammatory diseases due to its regulatory role in macrophage death in vivo.

METHODS

The present study investigates the influence of prolonged treatment with 1G244 - an inhibitor of dipeptidyl peptidases 8/9 - on the development of the advanced atherosclerosis plaque in apoE-knockout mice, using morphometric and molecular methods.

RESULTS

1G244 administration has led to a reduction in atherosclerotic plaque size in an apoE-knockout mice model. Moreover, it reduced the content of in-plaque macrophages, attributed by immunohistochemical phenotyping to the pro-inflammatory M1-like activation state of these cells. Inhibition of dipeptidyl peptidases 8/9 augmented the lytic form of death response of activated macrophages in-vitro.

CONCLUSIONS

In summary, inhibition of DPP 8/9 elicited an anti-atherosclerotic effect in apoE^-/- mice, which can be attributed to the lytic form of death induction in activated macrophages, as assessed by the in vitro BMDM model. This, in turn, results in a reduction of the plaque area without its transformation towards a rupture-prone morphology.

Dipeptidyl Peptidase-4 Inhibitor Sitagliptin Phosphate Accelerates Cellular Cholesterol Efflux in THP-1 Cells

Cholesterol efflux is a major atheroprotective function of high-density lipoproteins (HDLs) which removes cholesterol from the foam cells of lipid-rich plaques in Type 2 diabetes. The dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin phosphate increases plasma glucagon-like peptide-1 (GLP-1) concentrations and is used to treat Type 2 diabetes. GLP-1 plays an important role in regulating insulin secretion and expression via the GLP-1 receptor (GLP-1R), which is expressed in pancreatic islets as well as freshly isolated human monocytes and THP-1 cells. Here, we identified a direct role of GLP-1 and DPP-4 inhibition in HDL function. Cholesterol efflux was measured in cultivated phorbol 12-myristate 13-acetate-treated THP-1 cells radiolabeled with 3H-cholesterol and stimulated with liver X receptor/retinoid X receptor agonists. Contrary to vildagliptin, sitagliptin phosphate together with GLP-1 significantly (p < 0.01) elevated apolipoprotein (apo)A1-mediated cholesterol efflux in a dose-dependent manner. The sitagliptin-induced increase in cholesterol efflux did not occur in the absence of GLP-1. In contrast, adenosine triphosphate-binding cassette transporter A1 (ABCA1) mRNA and protein expressions in the whole cell fraction were not changed by sitagliptin in the presence of GLP-1, although sitagliptin treatment significantly increased ABCA1 protein expression in the membrane fraction. Furthermore, the sitagliptin-induced, elevated efflux in the presence of GLP-1 was significantly decreased by a GLP-1R antagonist, an effect that was not observed with a protein kinase A inhibitor. To our knowledge, the present study reports for the first time that sitagliptin elevates cholesterol efflux in cultivated macrophages and may exert anti-atherosclerotic actions that are independent of improvements in glucose metabolism. Our results suggest that sitagliptin enhances HDL function by inducing a de novo HDL synthesis via cholesterol efflux.

The Anti-Inflammatory Effect of Novel Antidiabetic Agents

The incidence of type 2 diabetes (T2DM) has been increasing worldwide and remains one of the leading causes of atherosclerotic disease. Several antidiabetic agents have been introduced in trying to regulate glucose control levels with different mechanisms of action. These agents, and sodium-glucose cotransporter-2 inhibitors in particular, have been endorsed by contemporary guidelines in patients with or without T2DM. Their widespread usage during the last three decades has raised awareness in the scientific community concerning their pleiotropic mechanisms of action, including their putative anti-inflammatory effect. In this review, we delve into the anti-inflammatory role and mechanism of the existing antidiabetic agents in the cardiovascular system and their potential use in other chronic sterile inflammatory conditions.

Review of pharmaceutical and therapeutic approaches for type 2 diabetes and related disorders

One of the essential diseases that are increasing in the world is type 2 diabetes (T2D), which many people around the world live with this disease. Various studies have revealed that insulin resistance, lessened insulin production has been associated with T2D, and they also show that this disease can have a genetic origin and is associated with different genes such as KCNQ1, PPAR-γ, calpain-10, ADIPOR2, TCF7L2 that can be utilized as a therapeutic target. Different therapeutic approaches and strategies such as exercise and diet, pharmacological approaches, and utilization of nanoparticles in drug delivery and gene therapy can be effective in the treatment and control of T2D. Glucagon-like peptide 1 (GLP-1) and sodium glucose cotransporter-2 (SGLT2) have both been considered as drug classes in the treatment of T2D and T2D-related diseases such as cardiovascular disease and renal disease, and have considerable influences such as diminished cardiovascular mortality in individuals with T2D, ameliorate postprandial glycaemia, ameliorate fasting glycaemia, and diminish body weight on disease treatment and improvement process. In the present review article, we have made an attempt to explore the risk factors, Genes, and diseases associated with T2D, therapeutic approaches in T2D, the influences of drugs such as Dapagliflozin, Metformin, Acarbose, Januvia (Sitagliptin), and Ertugliflozin on T2D in clinical trials and animal model studies. Research in clinical trials has promising results that support the role of these drug approaches in T2D prophylaxis and ameliorate safety even though additional clinical research is still obligatory.

Cardiovascular protective effects of GLP-1:A focus on the MAPK signaling pathway

Cardiovascular and related metabolic diseases are significant global health challenges. Glucagon-like peptide 1 (GLP-1) is a brain-gut peptide secreted by ileal endocrine that is now an established drug target in type 2 diabetes (T2DM). GLP-1 targeting agents have been shown not only to treat T2DM, but also to exert cardiovascular protective effects through regulating multiple signaling pathways. The mitogen-activated protein kinase (MAPK) pathway, a common signal transduction pathway for transmitting extracellular signals to downstream effector molecules, is involved in regulating diverse cell physiological processes, including cell proliferation, differentiation, stress, inflammation, functional synchronization, transformation and apoptosis. The purpose of this review is to highlight the relationship between GLP-1 and cardiovascular disease (CVD), and discuss how GLP-1 exerts cardiovascular protective effects through MAPK signaling pathway. This review also discusses the future challenges in fully characterizing and evaluating the CVD protective effects of GLP-1 receptor agonists (GLP-1RA) at the cellular and molecular level. A better understanding of MAPK signaling pathway that are disregulated in CVD may aid in the design and development of promising GLP-1RA.

Antidiabetic drugs and oxidized low-density lipoprotein: A review of anti-atherosclerotic mechanisms

Cardiovascular disease is one of the leading causes of mortality globally. Atherosclerosis is an important step towards different types of cardiovascular disease. The role of oxidized low-density lipoprotein (oxLDL) in the initiation and progression of atherosclerosis has been thoroughly investigated in recent years. Moreover, clinical trials have established that diabetic patients are at a greater risk of developing atherosclerotic plaques. Hence, we aimed to review the clinical and experimental impacts of various classes of antidiabetic drugs on the circulating levels of oxLDL. Metformin, pioglitazone, and dipeptidyl peptidase-4 inhibitors were clinically associated with a suppressive effect on oxLDL in patients with impaired glucose tolerance. However, there is an insufficient number of studies that have clinically evaluated the relationship between oxLDL and newer agents such as agonists of glucagon-like peptide 1 receptor or inhibitors of sodium-glucose transport protein 2. Next, we attempted to explore the multitude of mechanisms that antidiabetic agents exert to counter the undesirable effects of oxLDL in macrophages, endothelial cells, and vascular smooth muscle cells. In general, antidiabetic drugs decrease the uptake of oxLDL by vascular cells and reduce subsequent inflammatory signaling, which prevents macrophage adhesion and infiltration. Moreover, these agents suppress the oxLDL-induced transformation of macrophages into foam cells by either inhibiting oxLDL entrance, or by facilitating its efflux. Thus, the anti-inflammatory, anti-oxidant, and anti-apoptotic properties of antidiabetic agents abrogate changes induced by oxLDL, which can be extremely beneficial in controlling atherosclerosis in diabetic patients.

Metabolic Hormones Modulate Macrophage Inflammatory Responses

Simple Summary

Macrophages are a type of immune cell which play an important role in the development of cancer. Obesity increases the risk of cancer and obesity also causes disruption to the normal levels of hormones that are produced to coordinate metabolism. Recent research now shows that these metabolic hormones also play important roles in macrophage immune responses and so through macrophages, disrupted metabolic hormone levels may promote cancer. This review article aims to highlight and summarise these recent findings so that the scientific community may better understand how important this new area of research is, and how these findings can be capitalised on for future scientific studies.

Abstract

Macrophages are phagocytotic leukocytes that play an important role in the innate immune response and have established roles in metabolic diseases and cancer progression. Increased adiposity in obese individuals leads to dysregulation of many hormones including those whose functions are to coordinate metabolism. Recent evidence suggests additional roles of these metabolic hormones in modulating macrophage inflammatory responses. In this review, we highlight key metabolic hormones and summarise their influence on the inflammatory response of macrophages and consider how, in turn, these hormones may influence the development of different cancer types through the modulation of macrophage functions.

Dipeptidyl peptidase-4 (DPP4) inhibitor sitagliptin alleviates liver inflammation of diabetic mice by acting as a ROS scavenger and inhibiting the NFκB pathway

As a common chronic metabolic disease, the development of diabetes mellitus (DM) may also be accompanied by liver damage and inflammatory disorders. Sitagliptin is an inhibitor of dipeptidyl peptidase-4 (DPP4, also known as CD26), which is clinically used for DM treatment. However, the mechanism of sitagliptin’s efficiency in liver diseases is largely unknown. In this study, mice suffering from streptozotocin (STZ) exhibit elevated liver DPP4 expression and activity, as well as inflammatory and chronic liver injury phenotype, whereas specifically inhibiting the activity of DPP4 in mouse liver tissues and hepatocytes by sitagliptin contributes to decreased cytokines, oxidative stress, cell apoptosis, and inflammation in STZ-induced diabetic mice. Moreover, sitagliptin reduced TNFα or LPS-induced cellular reactive oxygen species (ROS) level, cell apoptosis, and protein expression in the NFκB signaling pathway in HepG2 cells or primary mouse hepatocytes. Altogether, our study confirms that sitagliptin may protect liver tissue by alleviating ROS production and NFκB signaling activation, providing a putative mechanism for preventing the development of diabetic liver disease.

The role of incretins and incretin-based drugs in autoimmune diseases

Incretin hormones, including glucagon-like peptide (GLP)-1, GLP-2 and glucose-dependent insulinotropic polypeptide (GIP), are gastrointestinal peptides secreted from enteroendocrine cells. These hormones play significant roles in many physiological processes via binding to G-protein coupled receptors (GPCRs) on different organs and tissues; one of them is the immunomodulatory effect on the immune system and its molecular components such as cytokines and chemokines. Anti-inflammatory effects of incretins and dependent molecules involving long-acting analogs and DPP4 inhibitors through regulation of T and B cell activation may attenuate autoimmune diseases caused by immune system disorders in mistakenly recognizing self as the foreign agent. In this review, we investigate incretin effects on the immune system response and the potential benefits of incretin-based therapy for treating autoimmune diseases.

Dipeptidyl peptidase 4 inhibitors: Applications in innate immunity?

Dipeptidyl peptidase (DPP)-4 inhibitors are a class of orally available, small molecule inhibitors that prolong the insulinotropic activity of the incretin hormone glucagon-like peptide-1 (GLP-1) and are highly effective for the treatment of Type-2 diabetes. DPP4 can also cleave several immunoregulatory peptides including chemokines. Emerging evidence continues to implicate DPP4 inhibitors as immunomodulators, with recent findings suggesting DPP4 inhibitors modify specific aspects of innate immunity. This review summarises recent insights into how DPP4 inhibitors could be implicated in endothelial, neutrophil and monocyte/macrophage mediated immunity. Additionally, this review highlights additional avenues of research with DPP4 inhibitors in the context of the COVID-19 pandemic.

Sitagliptin, a dipeptidyl peptidase-4 inhibitor, attenuates apoptosis of vascular smooth muscle cells and reduces atherosclerosis in diabetic apolipoprotein E-deficient mice

Sitagliptin, a dipeptidyl peptidase-4(DPP-4) Inhibitor, has been found to have an anti-atherosclerotic effect. Since apoptosis of vascular smooth muscle cells (VSMCs) contributes to the occurrence of diabetic atherosclerosis. This study aimed to examine whether sitagliptin suppresses the atherosclerosis progression to hyperglycemia in a low-dose streptozotocin (STZ)-induced diabetic mouse model, and then investigated the effect of sitagliptin on VSMCs apoptosis and its underlying mechanism. In vivo studies, eight-week-old low-dose STZ-induced diabetic apolipoprotein E (apoE)-deficient (apoE-/-) mice fed a high-fat diet were administered a DPP-4 inhibitor, sitagliptin, 200 mg/kg/day, or Lantus insulin by daily subcutaneous injection of 1 unit/mouse over a period of 12 weeks. Aortic atherosclerosis and apoptosis in the plaque were determined using dUTP-biotin nick end labeling (TUNEL) staining and immunohistochemistry. In vitro studies utilized the VSMCs for determination of glucagon-like peptide 1 receptor (GLP-1R) and DPP-4 expression and flow cytometry and Western blotting were used to determine apoptosis and protein expression, respectively. Sitagliptin significantly reduced atherosclerotic lesion area (7.00 ± 0.13 vs. 12.80 ± 2.7%, p = 0.003) and suppressed vascular smooth muscle cell apoptosis (2.30 ± 1.34 vs. 4.8 ± 1.93%, p = 0.003) compared with vehicle treatment. In addition, sitagliptin significantly increased the expression of β-catenin in the aortic tissue(0.56 ± 0.13 vs.0.17 ± 0.02, p = 0.008)compared with vehicle treatment. In cultured mouse VSMCs, sitagliptin enhanced GLP-1 activity significantly retarded oxidative stress (H₂O₂)-induced apoptosis compared with GLP-1 or sitagliptin alone. Sitagliptin increased GLP-1-induced cytosolic levels of β-catenin compared with GLP-1 alone, resulted in increasing the expression of survivin, and suppressed proinflammatory cytokines, i.e., interleukin-6(IL-6) and tumor necrosis factor-alpha(TNF-α), production in response to H₂O₂. In conclusion, these results indicated that the anti-atherosclerotic effect of sitagliptin is mediated, at least in part, by its inhibition of VSMCs apoptosis.

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.

Insights into incretin-based therapies for treatment of diabetic dyslipidemia

Derangements in triglyceride and cholesterol metabolism (dyslipidemia) are major risk factors for the development of cardiovascular diseases in obese and type-2 diabetic (T2D) patients. An emerging class of glucagon-like peptide-1 (GLP-1) analogues and next generation peptide dual-agonists such as GLP-1/glucagon or GLP-1/GIP could provide effective therapeutic options for T2D patients. In addition to their role in glucose and energy homeostasis, GLP-1, GIP and glucagon serve as regulators of lipid metabolism. This review summarizes the current knowledge in GLP-1, glucagon and GIP effects on lipid and lipoprotein metabolism and frames the emerging therapeutic benefits of GLP-1 analogs and GLP-1-based multiagonists as add-on treatment options for diabetes associated dyslipidemia.

Sitagliptin on Carotid Intima-Media Thickness in Type 2 Diabetes Mellitus Patients and Anemia: A Subgroup Analysis of the PROLOGUE Study

Introduction

Randomized clinical trials have not shown an additional clinical benefit of sitagliptin treatment over conventional treatment alone. However, studies of sitagliptin treatment have not examined the relationship between anemia and treatment group outcomes.

Methods

The PROLOGUE study is a prospective clinical trial of 442 participants with type 2 diabetes mellitus (T2DM) randomized to sitagliptin treatment or conventional treatment which showed no treatment differences [Estimated mean (± standard error) common carotid intima-media thickness (CIMT) was 0.827 ± 0.007 mm and 0.837 ± 0.007 mm, respectively, with a mean difference of -0.009 mm (97.2% CI −0.028 to 0.011, p = 0.309) at 24 mo of follow-up]. This is a post hoc subanalysis using data obtained from the PROLOGUE study; the study population was divided into anemic groups (n = 94) and nonanemic group (n = 343) based on hemoglobin level. And we analyzed for the changes in each CIMT parameter from baseline to 24 months in subgroups.

Results

The treatment group difference in baseline-adjusted mean common carotid artery- (CCA-) IMT at 24 months was −0.003 mm (95% CI −0.022 to 0.015, p = 0.718) in the nonanemic subgroup and −0.007 mm (95% CI −0.043 to 0.030, p = 0.724) in the anemic subgroup. Although there were no significant differences in the other CIMT parameters between the treatment groups in the anemic subgroup, the changes in mean and max ICA-IMT at 24 months in the nonanemic subgroup were significantly lower in the sitagliptin group than the conventional group [−0.104 mm (95% CI −0.182 to −0.026), p = 0.009 and −0.142 mm (−0.252 to −0.033), p = 0.011, respectively].

Conclusion

These data suggest that nonanemia may indicate a potentially large subgroup of those with T2DM patients that sitagliptin therapy has a better antiatherosclerotic effect than conventional therapy. Further research is needed to confirm these preliminary observations.

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.

AMPK is associated with the beneficial effects of antidiabetic agents on cardiovascular diseases

Diabetics have higher morbidity and mortality in cardiovascular disease (CVD). A variety of antidiabetic agents are available for clinical choice. Cardiovascular (CV) safety assessment of these agents is crucial in addition to hypoglycemic effect before clinical prescription. Adenosine 5'-monophosphate-activated protein kinase (AMPK) is an important cell energy sensor, which plays an important role in regulating myocardial energy metabolism, reducing ischemia and ischemia/reperfusion (I/R) injury, improving heart failure (HF) and ventricular remodeling, ameliorating vascular endothelial dysfunction, antichronic inflammation, anti-apoptosis, and regulating autophagy. In this review, we summarized the effects of antidiabetic agents to CVD according to basic and clinical research evidence and put emphasis on whether these agents can play roles in CV system through AMPK-dependent signaling pathways. Metformin has displayed definite CV benefits related to AMPK. Sodium-glucose cotransporter 2 inhibitors also demonstrate sufficient clinical evidence for CV protection, but the mechanisms need further exploration. Glucagon-likepeptide1 analogs, dipeptidyl peptidase-4 inhibitors, α-glucosidase inhibitors and thiazolidinediones also show some AMPK-dependent CV benefits. Sulfonylureas and meglitinides may be unfavorable to CV system. AMPK is becoming a promising target for the treatment of diabetes, metabolic syndrome and CVD. But there are still some questions to be answered.

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.

Differential effect of concomitant antidiabetic agents on carotid atherosclerosis: a subgroup analysis of the PROLOGUE study

Accumulated evidence shows that some antidiabetic agents attenuate the progression of carotid atherosclerosis assessed as intima-media thickness (IMT). Although some studies have demonstrated an inhibitory effect of dipeptidyl peptidase-4 inhibitors on carotid IMT progression, in the PROLOGUE study sitagliptin failed to slow progression relative to conventional therapy for 24 months. We hypothesized that differences in the concomitant antidiabetic agents between the groups have influenced the progression of carotid IMT. We performed a post hoc analysis of the PROLOGUE study using subgroups stratified by concomitant antidiabetic agents. Although no subgroup with any combination of agents in the overall patients showed a significant difference between sitagliptin group and conventional therapy group in the changes from baseline in mean common carotid artery (CCA)-IMT at 24 months, a significant attenuation of mean CCA-IMT progression was observed in the sitagliptin group relative to conventional therapy group only in three combination subgroups aged < 70 years, namely no thiazolidinedione; no thiazolidinedione or biguanide; and no thiazolidinedione, biguanide or α-glucosidase inhibitor, even after adjustment for multiple confounding factors. In the three subgroups, no significant difference between sitagliptin group and conventional therapy group in the changes from baseline in HbA1c at 24 months was detected. Our data suggest that some concomitant agents, whose prescription frequencies were increased in the conventional therapy group, may have masked the inhibitory effect of sitagliptin on carotid IMT progression in the PROLOGUE study.

The incretin hormone GIP is upregulated in patients with atherosclerosis and stabilizes plaques in ApoE-/- mice by blocking monocyte/macrophage activation

OBJECTIVE

The incretin hormones GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic peptide) are secreted by the gut after food intake leading to pancreatic insulin secretion and glucose lowering. Beyond its role in glucose control, GLP-1 was found in mice and men to beneficially modulate the process of atherosclerosis, which has been linked to improved cardiovascular outcome of patients with diabetes at high cardiovascular risk treated with GLP-1 receptor agonists. However, little is known on the role of the other main incretin in the cardiovascular system. The aim of this study was to characterize GIP in atherosclerotic cardiovascular disease.

METHODS AND RESULTS

Serum concentrations of GIP were assessed in 731 patients who presented for elective coronary angiography at the University Hospital Aachen. While GIP concentrations were not associated with coronary artery disease (CAD), we found 97 patients with PAD (peripheral artery disease) vs. 634 without PAD to have higher circulating GIP levels (413.0 ± 315.3 vs. 332.7 ± 292.5 pg/mL, p = 0.0165). GIP levels were independently related to PAD after multivariable adjustment for CAD, age, sex, BMI, hypertension, diabetes, CRP, WBC, and smoking. To investigate the functional relevance of elevated GIP levels in human atherosclerotic disease, we overexpressed GIP (1-42) in ApoE^-/- mice fed a Western diet for 12 weeks using an adeno-associated viral vector system. GIP overexpression led to reduced atherosclerotic plaque macrophage infiltration and increased collagen content compared to control (LacZ) with no change in overall lesion size, suggesting improved plaque stability. Mechanistically, we found GIP treatment to reduce MCP-1-induced monocyte migration under In vitro conditions. Additionally, GIP prevented proinflammatory macrophage activation leading to reduced LPS-induced IL-6 secretion and inhibition of MMP-9 activity, which was attributable to GIP dependent inhibition of NfκB, JNK-, ERK, and p38 in endotoxin activated macrophages.

CONCLUSION

Elevated concentrations of the incretin hormone GIP are found in patients with atherosclerotic cardiovascular disease, while GIP treatment attenuates atherosclerotic plaque inflammation in mice and abrogates inflammatory macrophage activation in vitro. These observations identified GIP as a counterregulatory vasoprotective peptide, which might open new therapeutic avenues for the treatment of patients with high cardiovascular risk.

Comparison of the effects of linagliptin and voglibose on endothelial function in patients with type 2 diabetes and coronary artery disease: a prospective, randomized, pilot study (EFFORT)

Endothelial dysfunction contributes to poor cardiovascular prognosis in patients with type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD). The effect of dipeptidyl peptidase-4 inhibitors on endothelial function remains controversial. We sought to compare the effects of linagliptin and voglibose on endothelial function, as assessed by reactive hyperemia-peripheral arterial tonometry (RH-PAT). Sixteen patients with newly diagnosed T2DM and CAD were randomized 1:1 to linagliptin (5 mg, once-daily) or voglibose (0.9 mg, thrice-daily). The RH-PAT and laboratory parameters, including 75 g oral glucose tolerance test, were measured at baseline and 3 months. Linagliptin increased serum levels of active glucagon-like peptide-1 and high-molecular-weight adiponectin. Age-, sex-, and baseline-adjusted changes in logarithmic RH-PAT index (LnRHI) after 3 months were significant between groups (linagliptin, 0.135 ± 0.097; voglibose, - 0.124 ± 0.091; P = 0.047). In the linagliptin group, change in LnRHI was positively correlated with change in high-density lipoprotein cholesterol and negatively correlated with changes in both urine albumin-to-creatinine ratio and high-sensitivity C-reactive protein. Furthermore, linagliptin treatment for 3 months reduced serum levels of both glucose and insulin at 2 h, relative to voglibose, in the age-, sex-, and baseline-adjusted model. Linagliptin improved endothelial function relative to voglibose, accompanied by amelioration of glycemic, renal, and cardiometabolic parameters, in patients with newly diagnosed T2DM and CAD.Trial registration Unique Trial Number, UMIN 000029169 ( https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000012442 ).

Effect of sitagliptin on tissue characteristics of the carotid wall in patients with type 2 diabetes: a post hoc sub-analysis of the sitagliptin preventive study of intima-media thickness evaluation (SPIKE)

BACKGROUND

Ultrasonic gray-scale median (GSM) of the carotid wall reflects its composition and low-GSM carotid plaque is considered to be vulnerable. This study aimed to evaluate the effect of sitagliptin, a dipeptidyl peptidase-4 inhibitor, on the longitudinal change in GSM, an index of the tissue characteristics of the carotid wall, in patients with type 2 diabetes mellitus (T2DM).

METHODS

This is a post hoc sub-analysis using data obtained from the SPIKE trial, a randomized controlled trial that demonstrated the beneficial effect of sitagliptin on the progression of carotid intima-media thickness in patients with T2DM. A total of 274 T2DM patients with no past history of apparent cardiovascular disease (137 in the sitagliptin treatment group and 137 in the conventional treatment group) were enrolled. The primary outcome was the change from baseline in mean GSM-CCA during the 104-week treatment period.

RESULTS

The mean GSM-CCA significantly increased in the sitagliptin treatment group (adjusted ΔGSM = 2.40 ± 1.19 [mean ± SE], p = 0.044) but not in the conventional treatment group (adjusted ΔGSM = 1.32 ± 1.19, p = 0.27). However, there was no significant difference in changes in mean GSM-CCA between the treatment groups.

CONCLUSIONS

A post hoc sub-analysis suggests that the tissue characteristics of the carotid arterial wall were improved in the sitagliptin treatment group during the 104-week treatment period, but not in the conventional treatment group. However, there was no between-group difference in the changes of GSM values between the two treatment groups. Prespecified studies with large sample sizes would be necessary to confirm our findings. Trial registration UMIN000028664, Registered 15 August 2017 ("retrospectively registered").

Synergistic cytotoxicity of the dipeptidyl peptidase-IV inhibitor gemigliptin with metformin in thyroid carcinoma cells

PURPOSE

The influence of the dipeptidyl peptidase-IV inhibitor, gemigliptin alone or in combination with metformin on survival, proliferation, and migration of thyroid carcinoma cells was investigated.

METHODS

SW1736 and TPC-1 human thyroid carcinoma cells were used.

RESULTS

Gemigliptin and metformin caused cell death in a dose-dependent manner. In cells treated with both gemigliptin and metformin, compared with metformin alone, all of the combination index values were lower than 1.0, suggesting synergistic cytotoxicity of two agents. Cell viability, the percentage of viable cells, ATP levels, and mitochondrial membrane potential decreased; however, cytotoxic activity, and the protein levels of cleaved PARP, phospho-Akt and phospho-AMP-activated protein kinase (AMPK) increased. Administration of wortmannin, but not compound C, further decreased cell viability, and further increased cytotoxic activity. Moreover, compared with control, cell proliferation and migration as well as the protein levels of p53, p21, vascular cell adhesion molecule-1 (VCAM-1), and phospho-extracellular signal-regulated kinase (ERK) 1/2 decreased. The decrement of matrix metalloproteinase-2 and matrix metalloproteinase-9 protein levels was cell specific.

CONCLUSIONS

Our results demonstrate that gemigliptin induces cytotoxic activity, and has a synergistic activity with metformin in inducing cytotoxicity via regulation of Akt and AMPK in thyroid carcinoma cells. Furthermore, gemigliptin augments the inhibitory effect of metformin on proliferation and migration through involvement of matrix metalloproteinase-2, matrix metalloproteinase-9, p53, p21, VCAM-1, and ERK in thyroid carcinoma cells.

Evaluation of the Effect of Alogliptin on Tissue Characteristics of the Carotid Wall: Subanalysis of the SPEAD-A Trial

INTRODUCTION

Ultrasonic tissue characterization of the carotid wall using gray-scale median (GSM) reflects its composition and low-GSM plaque is considered to be unstable. The present study evaluated the effect of alogliptin, a dipeptidyl peptidase-4 inhibitor, on the longitudinal change in GSM, an index of the tissue characteristics of the carotid wall, in patients with type 2 diabetes (T2DM).

METHODS

This is a post hoc subanalysis using data obtained from the SPEAD-A trial, a randomized controlled trial that demonstrated the beneficial effect of alogliptin treatment on the progression of carotid intima-media thickness in patients with T2DM with no past history of apparent cardiovascular disease. A total of 322 subjects (161 in the alogliptin treatment group and 161 in the conventional treatment group) were enrolled. The primary outcome was the change from baseline in mean GSM-CCA (common carotid artery) during the 104-week observation period.

RESULTS

Both alogliptin treatment and conventional treatment significantly increased the mean GSM-CCA (from 60.7 ± 12.3 to 65.9 ± 10.1, p < 0.001 and 58.8 ± 14.4-65.2 ± 12.2, p < 0.001, respectively) and there was no significant difference in changes in mean GSM-CCA between the treatment groups (p = 0.95). Additionally, there were no differences in the changes in the left and right GSM-CCA between the groups.

CONCLUSIONS

A post hoc subanalysis revealed an improvement of tissue characteristics in the carotid arterial wall in both the alogliptin treatment group and the conventional treatment group during the 104-week treatment period and that there was no significant difference between the treatment groups.

CLINICAL TRIAL REGISTRATION

UMIN000019951.

Sitagliptin reduces inflammation, fibrosis and preserves diastolic function in a rat model of heart failure with preserved ejection fraction

BACKGROUND AND PURPOSE

Heart failure with preserved ejection fraction (HFpEF) is a systemic syndrome driven by co-morbidities, and its pathophysiology is poorly understood. Several studies suggesting that dipeptidyl peptidase 4 (DPP4) might be involved in the pathophysiology of heart failure have prompted experimental and clinical investigations of DPP4 inhibitors in the cardiovascular system. Here we have investigated whether the DPP4 inhibitor sitagliptin affected the progression of HFpEF independently of its effects on glycaemia.

EXPERIMENTAL APPROACH

Seven-week-old Dahl salt-sensitive rats were fed a high-salt diet for 5 weeks to induce hypertension. Then the rats continued with the high-salt diet and were treated with either sitagliptin (10 mg·kg-1 ) or vehicle for the following 8 weeks. Blood pressure and cardiac function were measured in vivo. Histochemical and molecular biology analyses of myocardium were used to assay cytokines, fibrotic markers, DPP4 and glucagon-like peptide-1 (GLP-1)/GLP-1 receptor.

KEY RESULTS

Treatment with sitagliptin attenuated diastolic dysfunction, reduced mortality and reduced cardiac DPP4 activity, along with increased circulating GLP-1 and myocardial expression of GLP-1 receptors. Myocardial levels of pro-inflammatory cytokines (TNF-α, IL-6 and CCL2) were reduced. Sitagliptin treatment decreased the levels of endothelial NOS monomer, responsible for generation of ROS, while the amount of NO-producing dimeric form increased. Markers of oxidative and nitrosative stress were decreased. Moreover, increased collagen deposition and activation of pro-fibrotic signalling, inducing elevated myocardial stiffness, were attenuated by sitagliptin treatment.

CONCLUSIONS AND IMPLICATIONS

Sitagliptin positively modulated active relaxation and passive diastolic compliance by decreasing inflammation-related endothelial dysfunction and fibrosis, associated with HFpEF.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

Sitagliptin attenuates high glucose-induced alterations in migration, proliferation, calcification and apoptosis of vascular smooth muscle cells through ERK1/2 signal pathway

Background/Aims

This study investigated the effects of sitagliptin on migration, proliferation, calcification and apoptosis of vascular smooth muscle cells (VSMCs) under high glucose (HG) conditions.

Methods

VSMCs were isolated from the thoracic aorta of Sprague Dawley rats. The cultured VSMCs were subjected to control medium, mannitol medium, HG medium (25 mM), pretreatment with 200 nM sitagliptin in control or HG medium, or the ERK1/2 inhibitor PD98059 in HG medium. Cell proliferation, migration, apoptosis and calcification were determined.

Results

HG conditions promoted the proliferation, migration, calcification and impairment of apoptosis in VSMCs compared with controls (P<0.05). Pretreatment with sitagliptin effectively attenuated proliferation, migration, calcification of cells and increased apoptosis of HG-cultured VSMCs as compared with the HG group (P<0.05). Culture with HG resulted in the up-regulation of p-ERK1/2 in VSMCs, whereas sitagliptin pretreatment could inhibit HG-induced p-ERK1/2 expression. In addition, the ERK1/2 inhibitor PD98059, inhibited proliferation, migration, calcification and promoted the apoptosis of HG-cultured VSMCs compared with the HG group (P<0.05).

Conclusion

The effects of sitagliptin on VSMC under high glucose condition were achieved through ERK1/2 signaling pathways.

Dipeptidyl peptidase-4 inhibitor gemigliptin protects against vascular calcification in an experimental chronic kidney disease and vascular smooth muscle cells

Although dipeptidyl peptidase-4 inhibitors, a class of antidiabetic drugs, have various pleiotropic effects, it remains undetermined whether gemigliptin has a beneficial effect on vascular calcification. Therefore, this study was performed to evaluate the effect of gemigliptin on vascular calcification in a rat model of adenine-induced chronic kidney disease and in cultured vascular smooth muscle cells. Gemigliptin attenuated calcification of abdominal aorta and expression of RUNX2 in adenine-induced chronic kidney disease rats. In cultured vascular smooth muscle cells, phosphate-induced increase in calcium content was reduced by gemigliptin. Gemigliptin reduced phosphate-induced PiT-1 mRNA expression, reactive oxygen species generation, and NADPH oxidase mRNA expression (p22phox and NOX4). The reduction of oxidative stress by gemigliptin was associated with the downregulation of phospho-PI3K/AKT expression. High phosphate increased the expression of frizzled-3 (FDZ3) and decreased the expression of dickkopf-related protein-1 (DKK-1) in the Wnt pathway. These changes were attenuated by gemigliptin treatment. Gemigliptin restored the decreased expression of vascular smooth muscle cells markers (α-SMA and SM22α) and increased expression of osteogenic makers (CBFA1, OSX, E11, and SOST) induced by phosphate. In conclusion, gemigliptin attenuated vascular calcification and osteogenic trans-differentiation in vascular smooth muscle cells via multiple steps including downregulation of PiT-1 expression and suppression of reactive oxygen species generation, phospho-PI3K/AKT, and the Wnt signaling pathway.

A Double-Blinded Randomized Study Investigating a Possible Anti-Inflammatory Effect of Saxagliptin versus Placebo as Add-On Therapy in Patients with Both Type 2 Diabetes And Stable Coronary Artery Disease

Background

Promising results regarding potential anti-inflammatory and antiatherosclerotic effects of gliptins have been reported. Our aim was to investigate whether saxagliptin treatment modifies expression of inflammatory markers, primarily in peripheral blood mononuclear cells (PBMCs) and in circulating leukocytes in patients with stable coronary artery disease (CAD) and T2DM.

Methods

Patients (n = 12) were randomized to saxagliptin 5 mg daily or placebo for 3 months. Samples were taken at baseline and end of study in fasting state prior to intake of medications. PBMCs were isolated and cryopreserved at −150°C until ex vivo exposed to 1 ng/mL of lipopolysaccharide (LPS) for 4 hours. Gene expression was performed with custom-designed TaqMan® Arrays and relative quantification by real-time PCR (RT-qPCR).

Results

HbA1c was reduced in the saxagliptin-treated group compared to that in the change with placebo (p = 0.042). In unstimulated PBMCs and in circulating leukocytes, we observed a significant increase in IL-10 expression in the saxagliptin group (p = 0.043, both), significantly different from that in the placebo (p = 0.009 and p = 0.032, resp.). No between group differences in changes were observed in any of the selected proinflammatory markers.

Conclusion

In our small cohort of patients with combined T2DM and CAD, a possible anti-inflammatory effect of saxagliptin, observed in the present study by upregulation of IL-10 in leukocytes, needs to be confirmed in larger studies.

Efficacy and Safety of the Dipeptidyl Peptidase-4 Inhibitor Sitagliptin on Atherosclerosis, β-Cell Function, and Glycemic Control in Japanese Patients with Type 2 Diabetes Mellitus Who are Treatment Naïve or Poorly Responsive to Antidiabetes Agents: A Multicenter, Prospective Observational, Uncontrolled Study

BACKGROUND

Sitagliptin, a dipeptidyl peptidase-4 inhibitor, is widely used in patients with type 2 diabetes. However, the pleiotropic effects of sitagliptin is not well understood.

OBJECTIVE

To assess the clinical efficacy and safety of sitagliptin on atherosclerosis, β-cell function, and glycemic control in Japanese patients with type 2 diabetes.

METHODS

A prospective observational study of 270 patients with type 2 diabetes mellitus was carried out. Patients (aged 64.3 [12.4] years, body mas index 25.2 [4.3]) with glycated hemoglobin >6.9% (52 mmol/mol) or fasting plasma glucose >130 mg/dL were treated with sitagliptin for 12 months. The primary end point was glycated hemoglobin level changes from baseline to 3 months. The secondary end points included changes in several biomarkers related to inflammation and β-cell function from baseline to 3 months, as well as changes in glycated hemoglobin level from baseline to 12 months.

RESULTS

Glycated hemoglobin levels were significantly lower in patients treated with sitagliptin for 3 months than at baseline (8.1% [1.4%]-7.3% [1.2%]) (65 [16.9]-56 [13.1] mmol/mol]) (P < 0.0001), which continued after 12 months (7.4% [1.3%]) (56 [15.2] mmol/mol) (P < 0.0001). In addition, a marker of vascular-specific inflammation, pentraxin-3, and a marker of β-cell function (proinsulin/insulin ratio), respectively, were lower after treatment with sitagliptin for 3 months than at baseline (1.88 [0.78]-1.65 [0.63] ng/mL [P = 0.0038] and 0.20 [0.14]-0.17 [0.11] [P = 0.01], respectively). On the other hand, a biomarker reflecting whole body inflammation; that is, high-sensitivity C-reactive protein level, was unchanged. Adverse events occurred in 14 patients (5.18%).

CONCLUSIONS

Sitagliptin may have beneficial effects on vascular inflammation and β-cell function in Japanese patients with type 2 diabetes. Pentraxin-3 may be an early predictive marker for detecting the antiatherosclerotic effects of dipeptidyl peptidase-4.

Dipeptidyl Peptidase-4 Inhibitors, Peripheral Arterial Disease, and Lower Extremity Amputation Risk in Diabetic Patients

BACKGROUND

Recent studies have elucidated the vascular protective effects of dipeptidyl peptidase-4 (DPP-4) inhibitors. However, to date, no large-scale studies have been carried out to determine the impact of DPP-4 inhibitors on the occurrence of peripheral arterial disease, and lower extremity amputation risk in patients with type 2 diabetes mellitus.

METHODS

We conducted a retrospective registry analysis using Taiwan's National Health Insurance Research Database to investigate the correlation between the use of DPP-4 inhibitors and risk of peripheral arterial disease in patients with type 2 diabetes mellitus. A total of 82,169 propensity score-matched pairs of DPP-4 inhibitor users and nonusers with type 2 diabetes mellitus were examined for the period 2009 to 2011.

RESULTS

The mean age of the study subjects was 58.9 ± 12.0 years, and 54% of subjects were male. During the mean follow-up of 3.0 years (maximum, 4.8 years), a total of 3369 DPP-4 inhibitor users and 3880 DPP-4 inhibitor nonusers were diagnosed with peripheral arterial disease. Compared with nonusers, DPP-4 inhibitor users were associated with a lower risk of peripheral arterial disease (hazard ratio 0.84; 95% confidence interval, 0.80-0.88). Additionally, DPP-4 inhibitor users had a decreased risk of lower-extremity amputation than nonusers (hazard ratio 0.65; 95% confidence interval, 0.54-0.79). The association between use of DPP-4 inhibitors and risk of peripheral arterial disease was also consistent in subgroup analysis.

CONCLUSIONS

This large-scale nationwide population-based cohort study is the first to demonstrate that treatment with DPP-4 inhibitors is associated with lower risk of peripheral arterial disease occurrence and limb amputation in patients with type 2 diabetes mellitus.

Cardiovascular Benefits of Native GLP-1 and its Metabolites: An Indicator for GLP-1-Therapy Strategies

Cardiovascular disease is a common co-morbidity and leading cause of death in patients with type 2 diabetes mellitus (T2DM). Glucagon-like peptide 1 (GLP-1) is a peptide hormone produced by intestinal L cells in response to feeding. Native GLP-1 (7-36) amide is rapidly degraded by diaminopeptidyl peptidase-4 (DPP4) to GLP-1 (9-36) amide, making 9-36a the major circulating form. While it is 7-36a, and not its metabolites, which exerts trophic effects on islet β-cells, recent studies suggest that both 7-36a and its metabolites have direct cardiovascular effects, including preserving cardiomyocyte viability, ameliorating cardiac function, and vasodilation. In particular, the difference in cardiovascular effects between 7-36a and 9-36a is attracting attention. Growing evidence has strengthened the presumption that their cardiovascular effects are overlapping, but distinct and complementary to each other; 7-36a exerts cardiovascular effects in a GLP-1 receptor (GLP-1R) dependent pathway, whereas 9-36a does so in a GLP-1R independent pathway. GLP-1 therapies have been developed using two main strategies: DPP4-resistant GLP-1 analogs/GLP-1R agonists and DPP4 inhibitors, which both aim to prolong the life-time of circulating 7-36a. One prominent concern that should be addressed is that the cardiovascular benefits of 9-36a are lacking in these strategies. This review attempts to differentiate the cardiovascular effects between 7-36a and 9-36a in order to provide new insights into GLP-1 physiology, and facilitate our efforts to develop a superior GLP-1-therapy strategy for T2DM and cardiovascular diseases.

Combination Therapy with a Sodium-Glucose Cotransporter 2 Inhibitor and a Dipeptidyl Peptidase-4 Inhibitor Additively Suppresses Macrophage Foam Cell Formation and Atherosclerosis in Diabetic Mice

Dipeptidyl peptidase-4 inhibitors (DPP-4is), in addition to their antihyperglycemic roles, have antiatherosclerotic effects. We reported that sodium-glucose cotransporter 2 inhibitors (SGLT2is) suppress atherosclerosis in a glucose-dependent manner in diabetic mice. Here, we investigated the effects of combination therapy with SGLT2i and DPP-4i on atherosclerosis in diabetic mice. SGLT2i (ipragliflozin, 1.0 mg/kg/day) and DPP-4i (alogliptin, 8.0 mg/kg/day), either alone or in combination, were administered to db/db mice or streptozotocin-induced diabetic apolipoprotein E-null (Apoe^-/- ) mice. Ipragliflozin and alogliptin monotherapies improved glucose intolerance; however, combination therapy did not show further improvement. The foam cell formation of peritoneal macrophages was suppressed by both the ipragliflozin and alogliptin monotherapies and was further enhanced by combination therapy. Although foam cell formation was closely associated with HbA1c levels in all groups, DPP-4i alone or the combination group showed further suppression of foam cell formation compared with the control or SGLT2i group at corresponding HbA1c levels. Both ipragliflozin and alogliptin monotherapies decreased scavenger receptors and increased cholesterol efflux regulatory genes in peritoneal macrophages, and combination therapy showed additive changes. In diabetic Apoe^-/- mice, combination therapy showed the greatest suppression of plaque volume in the aortic root. In conclusion, combination therapy with SGLT2i and DPP4i synergistically suppresses macrophage foam cell formation and atherosclerosis in diabetic mice.

Isoliquiritigenin Attenuates Atherogenesis in Apolipoprotein E-Deficient Mice

Isoliquiritigenin (ISL) exhibits antioxidation and anti-inflammation activity. We sought to investigate the effects and mechanism of ISL on the development of atherosclerotic lesions in apolipoprotein E-deficient (apoE^−/−) mice. Firstly, we determined that ISL reduced the mRNA levels of inflammatory factors interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), and monocyte chemotactic protein-1 (MCP-1), while it increased the expression of several lipoprotein-related genes in peritoneal macrophages treated with lipopolysaccharide (LPS). ISL also enhanced peroxisome proliferator-activated receptor gamma (PPARγ) protein levels and reversed the changes of ATP-binding cassette transporter A (ABCA1) and cluster of differentiation 36 (CD36) in macrophages treated with oxidative low-density lipoprotein (ox-LDL). Then, in an in vivo study, female apoE^−/− mice were fed a Western diet with ISL (0, 20, 100 mg/kg/day) added for 12 weeks. We found that ISL decreased the plasma cholesterol levels of very low-density lipoprotein (VLDL)/LDL, promoted plasma superoxide dismutase (SOD) and paraoxonase-1 (PON1) activities, and decreased plasma IL-6, TNF-α, and MCP-1 levels. Moreover, ISL significantly reduced the atherosclerotic lesions and hepatic steatosis in apoE^−/− mice. In the liver, ISL altered the expression of several key genes (such as SRBI, ABCA1, ABCG8, PPARγ, and FASN) involving cholesterol-selective uptake and excretion into bile, triglyceride (TG) biosynthesis, and inflammation. These results suggest that the atheroprotective effects of ISL are due to the improvement of lipid metabolism, antioxidation, and anti-inflammation, which involve PPARγ-dependent signaling.

DPP-4 Inhibition by Linagliptin Attenuates Obesity-Related Inflammation and Insulin Resistance by Regulating M1/M2 Macrophage Polarization

Dipeptidyl peptidase 4 (DPP-4) cleaves a large number of chemokine and peptide hormones involved in the regulation of the immune system. Additionally, DPP-4 may also be involved in macrophage-mediated inflammation and insulin resistance. Thus, the current study investigated the effect of linagliptin, an inhibitor of DPP-4, on macrophage migration and polarization in white adipose tissue (WAT) and liver of high-fat diet-induced obese (DIO) mice. DPP-4(+) macrophages in lean and obese mice were quantified by fluorescence-activated cell sorting (FACS) analysis. DPP-4 was predominantly expressed in F4/80(+) macrophages in crown-like structures compared with adipocytes in WAT of DIO mice. FACS analysis also revealed that, compared with chow-fed mice, DIO mice exhibited a significant increase in DPP-4(+) expression in cells within adipose tissue macrophages (ATMs), particularly M1 ATMs. Linagliptin showed a greater DPP-4 inhibition and antioxidative capacity than sitagliptin and reduced M1-polarized macrophage migration while inducing an M2-dominant shift of macrophages within WAT and liver, thereby attenuating obesity-induced inflammation and insulin resistance. Loss of macrophage inflammatory protein-1α, a chemokine and DPP-4 substrate, in DIO mice abrogated M2 macrophage-polarizing and insulin-sensitizing effects of linagliptin. Therefore, the inhibition of DPP-4 by linagliptin reduced obesity-related insulin resistance and inflammation by regulating M1/M2 macrophage status.

DPP-4 inhibitors in diabetic complications: role of DPP-4 beyond glucose control

Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) are an emerging class of antidiabetic drugs that constitutes approximately fifty percent of the market share of the oral hypoglycemic drugs. Its mechanism of action for lowering blood glucose is essentially via inhibition of the rapid degradation of incretin hormones, such as glucagon-like peptide (GLP)-1 and gastric inhibitory polypeptide (GIP), thus the plasma concentration of GLP-1 increases, which promotes insulin secretion from the pancreatic β cells and suppresses glucagon secretion from the α cells. In addition to the direct actions on the pancreas, GLP-1 exhibits diverse actions on different tissues through its action on GLP-1 receptor, which is expressed ubiquitously. Moreover, DPP-4 has multiple substrates besides GLP-1 and GIP, including cytokines, chemokines, neuropeptides, and growth factors, which are involved in many pathophysiological conditions. Recently, it was suggested that DPP-4 is a new adipokine secreted from the adipose tissue, which plays an important role in the regulation of the endocrine function in obesity-associated type 2 diabetes. Consequently, DPP-4 inhibitors have been reported to exhibit cytoprotective functions against various diabetic complications affecting the liver, heart, kidneys, retina, and neurons. This review outlines the current understanding of the effect of DPP-4 inhibitors on the complications associated with type 2 diabetes, such as liver steatosis and inflammation, dysfunction of the adipose tissue and pancreas, cardiovascular diseases, nephropathy, and neuropathy in preclinical and clinical studies.

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

Interaction between advanced glycation endproducts (AGEs) and receptor for AGEs (RAGE) as well as downstream pathways leads to vascular endothelial dysfunction in diabetes. Glucagon-like peptide-1 (GLP-1) has been reported to attenuate endothelial dysfunction in the models of atherosclerosis. However, whether GLP-1 exerts protective effects on aortic endothelium in diabetic animal model and the underlying mechanisms are still not well defined. Experimental diabetes was induced through administration with combination of high-fat diet and intraperitoneal injection of streptozotocin. Rats were randomly divided into four groups, including controls, diabetes, diabetes + sitagliptin (30 mg/kg/day), diabetes + exenatide (3 μg/kg/12 h). Eventually, endothelial damage, markers of inflammation and oxidative stress, were measured. After 12 weeks administration, diabetic rats received sitagliptin and exenatide showed significant elevation of serum NO level and reduction of ET-1 as well as inflammatory cytokines levels. Moreover, sitagliptin and exenatide significantly inhibited aortic oxidative stress level and improved aortic endothelial function in diabetic rats. Importantly, these drugs inhibited the protein expression level in AGE/RAGE-induced RhoA/ROCK/NF-κB/IκBα signaling pathways and activated AMPK in diabetic aorta. Finally, the target proteins of p-eNOS, iNOS, and ET-1, which reflect endothelial function, were also changed by these drugs. Our present study indicates that sitagliptin and exenatide administrations can improve endothelial function in diabetic aorta. Of note, RAGE/RhoA/ROCK and AMPK mediated NF-κB signaling pathways may be the intervention targets of these drugs to protect aortic endothelium.

The Effect of Sitagliptin on Carotid Artery Atherosclerosis in Type 2 Diabetes: The PROLOGUE Randomized Controlled Trial

BACKGROUND

Experimental studies have suggested that dipeptidyl peptidase-4 (DPP-4) inhibitors provide cardiovascular protective effects. We performed a randomized study to evaluate the effects of sitagliptin added on to the conventional therapy compared with conventional therapy alone (diet, exercise, and/or drugs, except for incretin-related agents) on the intima-media thickness (IMT) of the carotid artery, a surrogate marker for the evaluation of atherosclerotic cardiovascular disease, in people with type 2 diabetes mellitus (T2DM).

METHODS AND FINDINGS

We used a multicenter PROBE (prospective, randomized, open label, blinded endpoint) design. Individuals aged ≥30 y with T2DM (6.2% ≤ HbA1c < 9.4%) were randomly allocated to receive either sitagliptin (25 to 100 mg/d) or conventional therapy. Carotid ultrasound was performed at participating medical centers, and all parameters were measured in a core laboratory. Of the 463 enrolled participants with T2DM, 442 were included in the primary analysis (sitagliptin group, 222; conventional therapy group, 220). Estimated mean (± standard error) common carotid artery IMT at 24 mo of follow-up in the sitagliptin and conventional therapy groups was 0.827 ± 0.007 mm and 0.837 ± 0.007 mm, respectively, with a mean difference of -0.009 mm (97.2% CI -0.028 to 0.011, p = 0.309). HbA1c level at 24 mo was significantly lower with sitagliptin than with conventional therapy (6.56% ± 0.05% versus 6.72% ± 0.05%, p = 0.008; group mean difference -0.159, 95% CI -0.278 to -0.041). Episodes of serious hypoglycemia were recorded only in the conventional therapy group, and the rate of other adverse events was not different between the two groups. As it was not a placebo-controlled trial and carotid IMT was measured as a surrogate marker of atherosclerosis, there were some limitations of interpretation.

CONCLUSIONS

In the PROLOGUE study, there was no evidence that treatment with sitagliptin had an additional effect on the progression of carotid IMT in participants with T2DM beyond that achieved with conventional treatment.

TRIAL REGISTRATION

University Hospital Medical Information Network Clinical Trials Registry UMIN000004490.

Sitagliptin inhibits endothelin-1 expression in the aortic endothelium of rats with streptozotocin-induced diabetes by suppressing the nuclear factor-κB/IκBα system through the activation of AMP-activated protein kinase

Emerging evidence suggests that dipeptidyl peptidase-4 (DPP-4) inhibitors, including sitagliptin, exert favourable effects on the vascular endothelium. DPP-4 inhibitors suppress the degradation of glucagon-like peptide-1 (GLP‑1), which has been reported to enhance nitric oxide (NO) production. However, the effects of DPP-4 inhibitors on endothelin-1 (ET-1) expression in the aorta, as well as the underlying mechanisms responsible for these effects, have yet to be investigated in animal models of diabetes mellitus (DM). In the present study, the rats were randomly divided into the following four groups: i) control; ii) DM; iii) DM + low‑dose sitagliptin (10 mg/kg); and iv) DM + high‑dose sitagliptin (30 mg/kg). Apart from the control group, all the rats received a high-fat diet for 8 weeks prior to the induction of diabetes with an intraperitoneal injection of streptozotocin. The treatments were then administered for 12 weeks. The serum levels of ET-1, NO, GLP-1 and insulin were measured as well as endothelial function. The expression of ET-1, AMP-activated protein kinase (AMPK) and nuclear factor (NF)-κB/IκBα were determined. After 12 weeks of treatment, the diabetic rats receiving sitagliptin showed significantly elevated serum levels of GLP-1 and NO, and reduced levels of ET-1. Moreover, sitagliptin significantly attenuated endothelial dysfunction as well as the remodeling of the aortic wall. Notably, sitagliptin inhibited ET-1 expression at the transcriptional and translational level in the aorta, which may have been mediated by the suppression of the NF-κB/IκBα system induced by AMPK activation. The majority of the above-mentioned effects were dose dependent. Taken together, the findings of the present study indicate that sitagliptin inhibits ET-1 expression in the aortic endothelium by suppressing the NF-κB/IκBα system through the activation of the AMPK pathway in diabetic rats. These findings further demonstrate some of the vasoprotective properties of DPP-4 inhibitors in vivo.

Anti-atherogenic and anti-inflammatory properties of glucagon-like peptide-1, glucose-dependent insulinotropic polypepide, and dipeptidyl peptidase-4 inhibitors in experimental animals

We reported that native incretins, liraglutide and dipeptidyl peptidase‐4 inhibitors (DPP‐4i) all confer an anti‐atherosclerotic effect in apolipoprotein E‐null (Apoe^−/−) mice. We confirmed the anti‐atherogenic property of incretin‐related agents in the mouse wire injury model, in which the neointimal formation in the femoral artery is remarkably suppressed. Furthermore, we showed that DPP‐4i substantially suppresses plaque formation in coronary arteries with a marked reduction in the accumulation of macrophages in cholesterol‐fed rabbits. DPP‐4i showed an anti‐atherosclerotic effect in Apoe^−/− mice mainly through the actions of glucagon‐like peptide‐1 and glucose‐dependent insulinotropic polypepide. However, the dual incretin receptor antagonists partially attenuated the suppressive effect of DPP‐4i on atherosclerosis in diabetic Apoe^−/− mice, suggesting an incretin‐independent mechanism. Exendin‐4 and glucose‐dependent insulinotropic polypepide elicited cyclic adenosine monophosphate generation, and suppressed the lipopolysaccharide‐induced gene expression of inflammatory molecules, such as interleukin‐1β, interleukin‐6 and tumor necrosis factor‐α, in U937 human monocytes. This suppressive effect, however, was attenuated by an inhibitor of adenylate cyclase and mimicked by 8‐bromo‐cyclic adenosine monophosphate or forskolin. DPP‐4i substantially suppressed the lipopolysaccharide‐induced expression of inflammatory cytokines without affecting cyclic adenosine monophosphate generation or cell proliferation. DPP‐4i more strongly suppressed the lipopolysaccharide‐induced gene expression of inflammatory molecules than incretins, most likely through inactivation of CD26. Glucagon‐like peptide‐1 and glucose‐dependent insulinotropic polypepide suppressed oxidized low‐density lipoprotein‐induced macrophage foam cell formation in a receptor‐dependent manner, which was associated with the downregulation of acyl‐coenzyme A cholesterol acyltransferase‐1 and CD36, as well as the up‐regulation of adenosine triphosphate‐binding cassette transporter A1. Our studies strongly suggest that incretin‐related agents have favorable effects on macrophage‐driven atherosclerosis in experimental animals.

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.

Differential effects of GLP-1 receptor agonist on foam cell formation in monocytes between non-obese and obese subjects

OBJECTIVE

Monocytes/macrophages (Mϕ) transform into foam cells in the presence of oxidized-LDL (ox-LDL), releasing inflammatory mediators. The antiatherogenic role of a dipeptidyl peptidase-4 inhibitor is mediated, in part, through improving the unbalance of inflammatory (M1)/anti-inflammatory (M2) phenotypes in monocytes. In this study, we examined differential regulation of glucagon-like peptide-1 receptor (GLP-1R) signaling for antiatherogenesis in monocytes/Mϕ from normal-weight control subjects and obese patients.

METHODS

We evaluated the effects of exendin-4 (Ex-4), a GLP-1R agonist, on ox-LDL-stimulated foam cell formation, M1/M2 cytokine production, and organelle change in primary monocytes from control subjects and obese patients and human monocytic THP-1-derived Mϕ as well.

RESULTS

Here we report that Ex-4 suppressed foam cell formation and M1 cytokine expression and, interestingly, induced indicators of autophagy in ox-LDL-stimulated monocytes from control subjects. The suppressing effects on foam cell formation by Ex-4 were reversed by a cAMP inhibitor. In contrast to control subjects, Ex-4 did not induce indicators of autophagy, but did induce foam cell formation and M1 cytokine expression in monocytes from obese patients. GLP-1R expression level was comparable between control subjects and obese patients. The effects of Ex-4 on inducing indicators of autophagy and suppressing foam cell formation were observed in THP-1 Mϕ.

CONCLUSIONS

These data suggest that GLP-1R signaling induces autophagy, thereby suppressing foam cell formation in non-obese subjects. In obese patients, GLP-1R stimulation increased foam cell formation and IL-6, TNF-α, and IL-1β production. Such altered signaling in monocytes of obese patients may be involved in the development of atherosclerosis.

Effect of Dipeptidyl Peptidase-4 Inhibitor on All-Cause Mortality and Coronary Revascularization in Diabetic Patients

BACKGROUND

Anti-atherosclerotic effect of dipeptidyl peptidase-4 (DPP-4) inhibitors has been suggested from previous studies, and yet, its association with cardiovascular outcome has not been demonstrated. We aimed to evaluate the effect of DPP-4 inhibitors in reducing mortality and coronary revascularization, in association with baseline coronary computed tomography (CT).

METHODS

The current study was performed as a multi-center, retrospective observational cohort study. All subjects with diabetes mellitus who had diagnostic CT during 2007-2011 were included, and 1866 DPP-4 inhibitor users and 5179 non-users were compared for outcome. The primary outcome was all-cause mortality and secondary outcome included any coronary revascularization therapy after 90 days of CT in addition to all-cause mortality.

RESULTS

DPP-4 inhibitors users had significantly less adverse events [0.8% vs. 4.4% in users vs. non-users, adjusted hazard ratios (HR) 0.220, 95% confidence interval (CI) 0.102-0.474, p = 0.0001 for primary outcome, 4.1% vs. 7.6% in users vs. non-users, HR 0.517, 95% CI 0.363-0.735, p = 0.0002 for secondary outcome, adjusted variables were age, sex, presence of hypertension, high sensitivity C-reactive protein, glycated hemoglobin, statin use, coronary artery calcium score and degree of stenosis]. Interestingly, DPP-4 inhibitor seemed to be beneficial only in subjects without significant stenosis (adjusted HR 0.148, p = 0.0013 and adjusted HR 0.525, p = 0.0081 for primary and secondary outcome).

CONCLUSION

DPP-4 inhibitor is associated with reduced all-cause mortality and coronary revascularization in diabetic patients. Such beneficial effect was significant only in those without significant coronary stenosis, which implies that DPP-4 inhibitor may have beneficial effect in earlier stage of atherosclerosis.

Gliptins and their target dipeptidyl peptidase 4: implications for the treatment of vascular disease

Gliptins are accepted as a standard therapy for diabetes mellitus today. By inhibition of the enzyme dipeptidyl peptidase 4 (DPP4), gliptins prolong the GLP1-dependent insulin secretion in the pancreatic β-cells and thus support physiological blood glucose control. Various studies have now raised hope for an additional protective effect of pharmacological DPP4 inhibition in vascular diseases. Besides GLP1, especially, the inhibition of SDF1 cleavage has been shown to depict a relevant mechanism to enhance endothelial regeneration and reduce atherosclerosis progression via the SDF1-CXCR4 axis. Furthermore, several clinical trials have now shown an excellent safety profile of gliptin therapy in cardiovascular risk patients. In this review, we give a comprehensive overview on DPP4-dependent vascular functions and pathophysiological mechanisms with a detailed discussion of the underlying molecular mechanisms. We further analyse the role of pharmacological DPP4 inhibitors and their potential therapeutic impact on endothelial function and regeneration besides their effect during atherosclerosis development. Finally, we discuss presently available data from in vitro and in vivo studies with respect to the results of the recent clinical trials in diabetic and non-diabetic patients.