Long-term dipeptidyl-peptidase 4 inhibition reduces atherosclerosis and inflammation via effects on monocyte recruitment and chemotaxis

Dipeptidyl peptidase 4 deficiency improves survival after focal cerebral ischemia in mice and ameliorates microglia activation and specific inflammatory markers

Dipeptidyl peptidase 4 (DPP4; CD26) is involved in the regulation of various metabolic, immunological, and neurobiological processes in healthy individuals. Observations based on epidemiological data indicate that DPP4 inhibition by gliptins, typically used in patients with diabetes, may reduce the risk for cerebral ischemia and may also improve related outcomes. However, as DPP4 inhibitor application is neither complete nor specific for suppression of DPP4 enzymatic activity and DPP4 has non-enzymatic functions as well, the variety of consequences is a matter of debate. Therefore, we here used DPP4 knock-out (KO) mice to analyze the specific contribution of DPP4 to cellular, immunological, and functional consequences of experimental focal cerebral ischemia. We observed a significantly higher survival rate of DPP4 KO mice after ischemia, which was accompanied by a lower abundance of the pro-inflammatory chemokine CCL2 and reduced activation of Iba1-positive microglia cells in brain tissue of DPP4 KO mice. In addition, after ischemia for 24 h to 72 h, decreased concentrations of CCL5 and CCL12 in plasma and of CCL17 in brain tissue of DPP4 KO mice were observed when compared to wild type mice. Other aspects analyzed, such as the functional Menzies score, astrocyte activation and chemokine levels in plasma and brain tissue were affected by ischemia but appeared to be unaffected by the DPP4 KO genotype. Taken together, experimental ablation of DPP4 functions in mice improves survival and ameliorates aspects of cellular and molecular inflammation after focal cerebral ischemia.

New Insights into the Pleiotropic Actions of Dipeptidyl Peptidase-4 Inhibitors Beyond Glycaemic Control

Dipeptidyl peptidase-4 (DPP-4) is a multifunctional serine ectopeptidase that cleaves and modifies a plethora of substrates, including regulatory peptides, cytokines and chemokines. DPP-4 is implicated in the regulation of immune response, viral entry, cellular adhesion, metastasis and chemotaxis. Regarding its numerous substrates and extensive expression inside the body, multitasking DPP-4 has been assumed to participate in different pathophysiological mechanisms. DPP-4 inhibitors or gliptins are increasingly used for the treatment of type 2 diabetes mellitus. Several reports from experimental and clinical studies have clarified that DPP-4 inhibitors exert many beneficial pleiotropic effects beyond glycaemic control, which are mediated by anti-inflammatory, anti-oxidant, anti-fibrotic and anti-apoptotic actions. The present review will highlight the most recent findings in the literature about these pleiotropic effects and the potential mechanisms underlying these benefits, with a specific focus on the potential effectiveness of DPP-4 inhibitors in coronavirus disease-19 and diabetic kidney disease.

Comparative outcomes of systemic diseases in people with type 2 diabetes, or obesity alone treated with and without GLP-1 receptor agonists: a retrospective cohort study from the Global Collaborative Network : Author list

BACKGROUND

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are increasingly used to manage type 2 diabetes (T2D) and obesity. Despite their recognized benefits in glycemic control and weight management, their impact on broader systemic has been less explored.

OBJECTIVE

This study aimed to evaluate the impact of GLP-1RAs on a variety of systemic diseases in people with T2D or obesity.

METHODS

We conducted a retrospective cohort study using data from the Global Collaborative Network, accessed through the TriNetX analytics platform. The study comprised two primary groups: individuals with T2D and those with obesity. Each group was further divided into subgroups based on whether they received GLP-1RA treatment or not. Data were analyzed over more than a 5-year follow-up period, comparing incidences of systemic diseases; systemic lupus erythematosus (SLE), systemic sclerosis (SS), rheumatoid arthritis (RA), ulcerative colitis (UC), crohn's disease (CD), alzheimer's disease (AD), parkinson's disease (PD), dementia, bronchial asthma (BA), osteoporosis, and several cancers.

RESULTS

In the T2D cohorts, GLP-1RA treatment was associated with significantly lower incidences of several systemic and metabolic conditions as compared to those without GLP-1RA, specifically, dementia (Risk Difference (RD): -0.010, p < 0.001), AD (RD: -0.003, p < 0.001), PD (RD: -0.002, p < 0.001), and pancreatic cancer (RD: -0.003, p < 0.001). SLE and SS also saw statistically significant reductions, though the differences were minor in magnitude (RD: -0.001 and - 0.000 respectively, p < 0.001 for both). Conversely, BA a showed a slight increase in risk (RD: 0.002, p < 0.001).

CONCLUSIONS

GLP-1RAs demonstrate potential benefits in reducing the risk of several systemic conditions in people with T2D or obesity. Further prospective studies are needed to confirm these effects fully and understand the mechanisms.

Potential neuroprotective and autophagy-enhancing effects of alogliptin on lithium/pilocarpine-induced seizures in rats: Targeting the AMPK/SIRT1/Nrf2 axis

BACKGROUND

Status epilepticus (SE) as a severe neurodegenerative disease, greatly negatively affects people's health, and there is an urgent need for innovative treatments. The valuable neuroprotective effects of glucagon-like peptide-1 (GLP-1) in several neurodegenerative diseases have raised motivation to investigate the dipeptidyl peptidase-4 (DPP-4) inhibitor; alogliptin (ALO), an oral antidiabetic drug as a potential treatment for SE. ALO has shown promising neuroprotective effects in Alzheimer's and Parkinson's diseases, but its impact on SE has not yet been studied.

AIM

The present study aimed to explore the repurposing potential for ALO in a lithium/pilocarpine (Li/Pil)-induced SE model in rats.

MAIN METHODS

ALO (30 mg/kg/day) was administered via gavage for 14 days, and SE was subsequently induced in the rats using a single dose of Li/Pil (127/60 mg/kg), while levetiracetam was used as a standard antiepileptic drug.

KEY FINDINGS

The results showed that ALO reduced seizure severity and associated hippocampal neurodegeneration. ALO also increased γ-aminobutyric acid (GABA) levels, diminished glutamate spikes, and corrected glial fibrillary acidic protein (GFAP) changes. At the molecular level, ALO increased GLP-1 levels and activated its downstream signaling pathway, AMP-activated protein kinase (AMPK)/sirtuin-1 (SIRT1). ALO also dampened the brain's pro-oxidant response, curbed neuroinflammation, and counteracted hippocampal apoptosis affording neuroprotection. In addition, it activated autophagy as indicated by Beclin1 elevation.

SIGNIFICANCE

This study suggested that the neuroprotective properties and autophagy-enhancing effects of ALO make it a promising treatment for SE and can potentially be used as a management approach for this condition.

Dipeptidyl Peptidase (DPP)-4 Inhibitors and Pituitary Adenylate Cyclase-Activating Polypeptide, a DPP-4 Substrate, Extend Neurite Outgrowth of Mouse Dorsal Root Ganglia Neurons: A Promising Approach in Diabetic Polyneuropathy Treatment

Individuals suffering from diabetic polyneuropathy (DPN) experience debilitating symptoms such as pain, paranesthesia, and sensory disturbances, prompting a quest for effective treatments. Dipeptidyl-peptidase (DPP)-4 inhibitors, recognized for their potential in ameliorating DPN, have sparked interest, yet the precise mechanism underlying their neurotrophic impact on the peripheral nerve system (PNS) remains elusive. Our study delves into the neurotrophic effects of DPP-4 inhibitors, including Diprotin A, linagliptin, and sitagliptin, alongside pituitary adenylate cyclase-activating polypeptide (PACAP), Neuropeptide Y (NPY), and Stromal cell-derived factor (SDF)-1a-known DPP-4 substrates with neurotrophic properties. Utilizing primary culture dorsal root ganglia (DRG) neurons, we meticulously evaluated neurite outgrowth in response to these agents. Remarkably, all DPP-4 inhibitors and PACAP demonstrated a significant elongation of neurite length in DRG neurons (PACAP 0.1 μM: 2221 ± 466 μm, control: 1379 ± 420, p < 0.0001), underscoring their potential in nerve regeneration. Conversely, NPY and SDF-1a failed to induce neurite elongation, accentuating the unique neurotrophic properties of DPP-4 inhibition and PACAP. Our findings suggest that the upregulation of PACAP, facilitated by DPP-4 inhibition, plays a pivotal role in promoting neurite elongation within the PNS, presenting a promising avenue for the development of novel DPN therapies with enhanced neurodegenerative capabilities.

The Regulation of Metabolic Homeostasis by Incretins and the Metabolic Hormones Produced by Pancreatic Islets

In healthy humans, the complex biochemical interplay between organs maintains metabolic homeostasis and pathological alterations in this process result in impaired metabolic homeostasis, causing metabolic diseases such as diabetes and obesity, which are major global healthcare burdens. The great advancements made during the last century in understanding both metabolic disease phenotypes and the regulation of metabolic homeostasis in healthy individuals have yielded new therapeutic options for diseases like type 2 diabetes (T2D). However, it is unlikely that highly desirable more efficacious treatments will be developed for metabolic disorders until the complex systemic regulation of metabolic homeostasis becomes more intricately understood. Hormones produced by pancreatic islet beta-cells (insulin) and alpha-cells (glucagon) are pivotal for maintaining metabolic homeostasis; the activity of insulin and glucagon are reciprocally correlated to achieve strict control of glucose levels (normoglycaemia). Metabolic hormones produced by other pancreatic islet cells and incretins produced by the gut are also crucial for maintaining metabolic homeostasis. Recent studies highlighted the incomplete understanding of metabolic hormonal synergism and, therefore, further elucidation of this will likely lead to more efficacious treatments for diseases such as T2D. The objective of this review is to summarise the systemic actions of the incretins and the metabolic hormones produced by the pancreatic islets and their interactions with their respective receptors.

Activation of CD14+ Monocytes via the IFN-γ Signaling Pathway Is Associated with Immune-Related Adverse Events in Hepatocellular Carcinoma Patients Receiving PD-1 Inhibition Combination Therapy

(1) Background: Immune-related adverse events (irAEs) are a series of unique organ-specific inflammatory toxicities observed in patients with hepatocellular carcinoma (HCC) undergoing PD-1 inhibition combination therapy. The specific underlying mechanisms remain unclear. (2) Methods: We recruited 71 patients with HCC undergoing PD-1 inhibition combination therapy. These patients were then divided into two groups based on irAE occurrence: 34 had irAEs and 37 did not. Using Olink proteomics, we analyzed the aberrant inflammation-related proteins (IRPs) in these patient groups. For single-cell RNA sequencing (scRNA-seq) analysis, we collected peripheral blood mononuclear cells (PBMCs) from two representative patients at the pretreatment, irAE occurrence, and resolution stages. (3) Results: Our study revealed distinct plasma protein signatures in HCC patients experiencing irAEs after PD-1 inhibition combination therapy. We clarified the relationship between monocyte activation and irAEs, identified a strongly associated CD14-MC-CCL3 monocyte subset, and explored the role of the IFN-γ signaling pathway in monocyte activation during irAEs. (4) Conclusions: The activation of monocytes induced by the IFN-γ signaling pathway is an important mechanism underlying the occurrence of irAEs in HCC patients receiving PD-1 inhibition combination therapy.

The role and therapeutic potential of macrophages in the pathogenesis of diabetic cardiomyopathy

This review provides a comprehensive analysis of the critical role played by macrophages and their underlying mechanisms in the progression of diabetic cardiomyopathy (DCM). It begins by discussing the origins and diverse subtypes of macrophages, elucidating their spatial distribution and modes of intercellular communication, thereby emphasizing their significance in the pathogenesis of DCM. The review then delves into the intricate relationship between macrophages and the onset of DCM, particularly focusing on the epigenetic regulatory mechanisms employed by macrophages in the context of DCM condition. Additionally, the review discusses various therapeutic strategies aimed at targeting macrophages to manage DCM. It specifically highlights the potential of natural food components in alleviating diabetic microvascular complications and examines the modulatory effects of existing hypoglycemic drugs on macrophage activity. These findings, summarized in this review, not only provide fresh insights into the role of macrophages in diabetic microvascular complications but also offer valuable guidance for future therapeutic research and interventions in this field.

Understanding the intricacies of cellular senescence in atherosclerosis: Mechanisms and therapeutic implications

Cardiovascular disease is currently the largest cause of mortality and disability globally, surpassing communicable diseases, and atherosclerosis is the main contributor to this epidemic. Aging is intimately linked to atherosclerosis development and progression, however, the mechanism of aging in atherosclerosis is not well known. To emphasize the significant research on the involvement of senescent cells in atherosclerosis, we begin by outlining compelling evidence that indicates various types of senescent cells and SASP factors linked to atherosclerotic phenotypes. We subsequently provide a comprehensive summary of the existing knowledge, shedding light on the intricate mechanisms through which cellular senescence contributes to the pathogenesis of atherosclerosis. Further, we cover that senescence can be identified by both structural changes and several senescence-associated biomarkers. Finally, we discuss that preventing accelerated cellular senescence represents an important therapeutic potential, as permanent changes may occur in advanced atherosclerosis. Together, the review summarizes the relationship between cellular senescence and atherosclerosis, and inspects the molecular knowledge, and potential clinical significance of senescent cells in developing senescent-based therapy, thus providing crucial insights into their biology and potential therapeutic exploration.

Functional Roles of CD26/DPP4 in Bleomycin-Induced Pulmonary Hypertension Associated with Interstitial Lung Disease

Pulmonary hypertension (PH) with interstitial lung diseases (ILDs) often causes intractable conditions. CD26/Dipeptidyl peptidase-4 (DPP4) is expressed in lung constituent cells and may be related to the pathogenesis of various respiratory diseases. We aimed to clarify the functional roles of CD26/DPP4 in PH-ILD, paying particular attention to vascular smooth muscle cells (SMCs). Dpp4 knockout (Dpp4KO) and wild type (WT) mice were administered bleomycin (BLM) intraperitoneally to establish a PH-ILD model. The BLM-induced increase in the right ventricular systolic pressure and the right ventricular hypertrophy observed in WT mice were attenuated in Dpp4KO mice. The BLM-induced vascular muscularization in small pulmonary vessels in Dpp4KO mice was milder than that in WT mice. The viability of TGFβ-stimulated human pulmonary artery SMCs (hPASMCs) was lowered due to the DPP4 knockdown with small interfering RNA. According to the results of the transcriptome analysis, upregulated genes in hPASMCs with TGFβ treatment were related to pulmonary vascular SMC proliferation via the Notch, PI3K-Akt, and NFκB signaling pathways. Additionally, DPP4 knockdown in hPASMCs inhibited the pathways upregulated by TGFβ treatment. These results suggest that genetic deficiency of Dpp4 protects against BLM-induced PH-ILD by alleviating vascular remodeling, potentially through the exertion of an antiproliferative effect via inhibition of the TGFβ-related pathways in PASMCs.

Immunomodulatory activity of dipeptidyl peptidase-4 inhibitors in immune-related diseases

Dipeptidyl peptidase-4 (DPP-4), also known as CD26, is a 110-kDa cell surface glycoprotein with enzymatic and signal transducing activity. DPP-4/CD26 is expressed by various cells, including CD4+ and CD8+ T cells, B cells, dendritic cells, macrophages, and NK cells. DPP-4 inhibitors (DPP-4i) were introduced to clinics in 2006 as new oral antihyperglycemic drugs approved for type 2 diabetes mellitus treatment. In addition to glucose-lowering effects, emerging data, from clinical studies and their animal models, suggest that DPP-4i could display anti-inflammatory and immunomodulatory effects as well, but the molecular and immunological mechanisms of these actions are insufficiently investigated. This review focuses on the modulatory activity of DPP-4i in the immune system and the possible application of DPP-4i in other immune-related diseases in patients with or without diabetes.

Targeting the NOD-Like Receptor Pyrin Domain Containing 3 Inflammasome to Improve Healing of Diabetic Wounds

Significance: Chronic skin wounds are a significant health problem around the world, often leading to amputation and even death. Although persistent inflammation is a hallmark of these poorly healing wounds, few available therapies have been designed to target inflammation. In this review, we summarize available evidence of the role of the NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome in impaired wound healing and describe strategies to inhibit the inflammasome to improve wound healing. Recent Advances: The NLRP3 inflammasome plays an important physiological role in skin wound healing, during which transient inflammasome activity contributes to both epidermal and dermal healing. In contrast, sustained activity of the NLRP3 inflammasome leads to impaired epidermal and dermal healing associated with diabetes. Of importance, preclinical studies have demonstrated that inhibiting the NLRP3 inflammasome-induced resolution of inflammation, increased granulation tissue formation and collagen deposition, and accelerated reepithelialization and wound closure. Critical Issues: NLRP3 inflammasome inhibitors have appealing potential for translation into therapies for chronic wounds. Although preclinical studies have shown promising results, there is a need for human/clinical studies to evaluate dosing formulations, potential therapeutic effects, dose-response relationships, and possible side effects. Future Directions: Among strategies to inhibit the NLRP3 inflammasome, glyburide, metformin, peroxisome proliferator-activated receptor agonists, and the dipeptidyl peptidase 4 inhibitor saxagliptin appear to be closest to clinical translation, as these drugs are already Food and Drug Administration approved for other indications. Future clinical studies are needed to develop topical formulations of these drugs, and to assess the safety and efficacy of these inhibitors, to improve healing of chronic wounds.

Long-term efficacy and safety of early alogliptin initiation in subjects with type 2 diabetes: an extension of the SPEAD-A study

We previously reported in the study of preventive effects of alogliptin on diabetic atherosclerosis (SPEAD-A) that alogliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, attenuated the progression of carotid atherosclerosis in subjects with type 2 diabetes and no history of cardiovascular disease. This extension study of the SPEAD-A trial investigated whether early alogliptin initiation improved long-term cardiovascular outcomes. The SPEAD-A trial randomized 341 subjects with type 2 diabetes to either alogliptin or conventional treatment to investigate the effects of alogliptin on atherosclerosis. All subjects who completed that trial were eligible for this prospective, observational cohort study. The primary endpoint was the first occurrence of a major cardiovascular event, defined as death due to any cause, acute myocardial infarction, or stroke. During the 520-week follow-up period, composite primary outcome events occurred in only a few subjects in each group [8 (5.4%) in the alogliptin group and 9 in the conventional treatment group (5.9%)]. There were no significant differences in the incidence rate of the primary outcome between the two groups. Post hoc Poisson regression analysis showed no significant difference between the two groups in the incidence rate of composite recurrence events for the same outcomes as the primary endpoint. On the other hand, this incidence rate was significantly lower in subjects who received DPP-4 inhibitors before an initial cardiovascular event than in those who did not (5.8 vs. 13.3 per 1000 person-years, respectively, p = 0.04). Early initiation of alogliptin was not associated with a reduced risk of composite cardiovascular disease, which could be attributed to fewer events and/or the addition of DPP-4 inhibitors during the follow-up period.

Incretins-Based Therapies and Their Cardiovascular Effects: New Game-Changers for the Management of Patients with Diabetes and Cardiovascular Disease

Atherosclerosis is the leading cause of death worldwide, especially in patients with type 2 diabetes mellitus (T2D). GLP-1 receptor agonists and DPP-4 inhibitors were demonstrated to play a markedly protective role for the cardiovascular system beyond their glycemic control. Several cardiovascular outcome trials (CVOT) reported the association between using these agents and a significant reduction in cardiovascular events in patients with T2D and a high cardiovascular risk profile. Moreover, recent evidence highlights a favorable benefit/risk profile in myocardial infarction and percutaneous coronary revascularization settings. These clinical effects result from their actions on multiple molecular mechanisms involving the immune system, platelets, and endothelial and vascular smooth muscle cells. This comprehensive review specifically concentrates on these cellular and molecular processes mediating the cardiovascular effects of incretins-like molecules, aiming to improve clinicians' knowledge and stimulate a more extensive use of these drugs in clinical practice as helpful cardiovascular preventive strategies.

DPP-4 inhibitors for treating T2DM - hype or hope? an analysis based on the current literature

DPP-4 inhibition is an interesting line of therapy for treating Type 2 Diabetes Mellitus (T2DM) and is based on promoting the incretin effect. Here, the authors have presented a brief appraisal of DPP-4 inhibitors, their modes of action, and the clinical efficiency of currently available drugs based on DPP-4 inhibitors. The safety profiles as well as future directions including their potential application in improving COVID-19 patient outcomes have also been discussed in detail. This review also highlights the existing queries and evidence gaps in DPP-4 inhibitor research. Authors have concluded that the excitement surrounding DPP-4 inhibitors is justified because in addition to controlling blood glucose level, they are good at managing risk factors associated with diabetes.

Alogliptin: a DPP-4 inhibitor modulating adipose tissue insulin resistance and atherogenic lipid

AIMS

The purpose of this study is to investigate the regulation of adipose tissue insulin resistance with DPP-4 inhibitors in treatment-naive subjects with T2DM and to examine its relation to other diabetic parameters.

SUBJECTS AND METHODS

A total of 147 subjects were treated with alogliptin 12.5-25 mg/day (n = 55), sitagliptin 25-50 mg/day (n = 49), or teneligliptin 10-20 mg/day (n = 43) monotherapy for 3 months. Changes in adipo-IR, a mathematical model used to evaluate adipose tissue insulin resistance, and various diabetic parameters were analyzed in this prospective, non-randomized observational study.

RESULTS

Among these three drugs, only alogliptin significantly reduced adipo-IR (-25.9%, p < 0.004) and some lipid parameters, such as LDL-C, T-C/HDL-C, log(TG)/HDL-C, non-HDL-C/HDL-C, and LDL-C/HDL-C. Subjects in the alogliptin group were divided into two groups with distinct changes in adipo-IR. Group A had a significant decrease in adipo-IR (-56.5%, p < 0.00001, n = 28), whereas group B had an insignificant increase (19.1%, p = 0.055, n = 27). Significant reductions in FBG or HbA1c were observed in groups A and B, respectively. Group A also showed significant reductions in HOMA-R, T-C/HDL-C, TG, log(TG)/HDL-C, non-HDL-C/HDL-C, LDL-C/HDL-C, and FFA, as well as increases in QUICKI or HDL-C. In contrast, group B showed significant reductions in QUICKI or LDL-C, and increases in HOMA-R, insulin, HOMA-B, C-peptide, or CPR-index.

CONCLUSIONS

In contrast to other tested DPP-4 inhibitors, alogliptin demonstrated the ability to down-regulate insulin resistance in adipose tissue, as well as certain atherogenic lipids. This study provides the initial evidence of a DPP-4 inhibitor's potential to regulate adipose tissue insulin resistance. Furthermore, adipo-IR is associated with non-LDL-C lipid parameters instead of glycemic control in those receiving alogliptin.

An Overview of the Cardioprotective Effects of Novel Antidiabetic Classes: Focus on Inflammation, Oxidative Stress, and Fibrosis

Metabolic diseases, particularly diabetes mellitus (DM), are significant global public health concerns. Despite the widespread use of standard-of-care therapies, cardiovascular disease (CVD) remains the leading cause of death among diabetic patients. Early and evidence-based interventions to reduce CVD are urgently needed. Large clinical trials have recently shown that sodium-glucose cotransporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP-1RA) ameliorate adverse cardiorenal outcomes in patients with type 2 DM. These quite unexpected positive results represent a paradigm shift in type 2 DM management, from the sole importance of glycemic control to the simultaneous improvement of cardiovascular outcomes. Moreover, SGLT2i is also found to be cardio- and nephroprotective in non-diabetic patients. Several mechanisms, which may be potentially independent or at least separate from the reduction in blood glucose levels, have already been identified behind the beneficial effect of these drugs. However, there is still much to be understood regarding the exact pathomechanisms. This review provides an overview of the current literature and sheds light on the modes of action of novel antidiabetic drugs, focusing on inflammation, oxidative stress, and fibrosis.

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.

Depletion of polyfunctional CD26highCD8+ T cells repertoire in chronic lymphocytic leukemia

BACKGROUND

CD8⁺ T cells play an essential role against tumors but the role of human CD8⁺CD26⁺ T cell subset against tumors, in particular, haematological cancers such as chronic lymphocytic leukemia (CLL) remains unknown. Although CD4⁺CD26^high T cells are considered for adoptive cancer immunotherapy, the role of CD8⁺CD26⁺ T cells is ill-defined. Therefore, further studies are required to better determine the role of CD8⁺CD26⁺ T cells in solid tumors and haematological cancers.

METHODS

We studied 55 CLL and 44 age-sex-matched healthy controls (HCs). The expression of CD26 on different T cell subsets (e.g. naïve, memory, effector, and etc.) was analyzed. Also, functional properties of CD8⁺CD26⁺ and CD8⁺CD26^- T cells were evaluated. Finally, the plasma cytokine/chemokine and Galectin-9 (Gal-9) levels were examined.

RESULTS

CD26 expression identifies three CD8⁺ T cell subsets with distinct immunological properties. While CD26^negCD8⁺ T cells are mainly transitional, effector memory and effectors, CD26^lowCD8⁺ T cells are mainly naïve, stem cell, and central memory but CD26^high T cells are differentiated to transitional and effector memory. CD26⁺CD8⁺ T cells are significantly reduced in CLL patients versus HCs. CD26^high cells are enriched with Mucosal Associated Invariant T (MAIT) cells co-expressing CD161TVα7.2 and IL-18Rα. Also, CD26^high cells have a rich chemokine receptor profile (e.g. CCR5 and CCR6), profound cytokine (TNF-α, IFN-γ, and IL-2), and cytolytic molecules (Granzyme B, K, and perforin) expression upon stimulation. CD26^high and CD26^low T cells exhibit significantly lower frequencies of CD160, 2B4, TIGIT, ICOS, CD39, and PD-1 but higher levels of CD27, CD28, and CD73 versus CD26^neg cells. To understand the mechanism linked to CD26^high depletion, we found that malignant B cells by shedding Galectin-9 (Gal-9) contribute to the elevation of plasma Gal-9 in CLL patients. In turn, Gal-9 and the inflammatory milieu (IL-18, IL-12, and IL-15) in CLL patients contribute to increased apoptosis of CD26^high T cells.

CONCLUSIONS

Our results demonstrate that CD26⁺ T cells possess a natural polyfunctionality to traffic and exhibit effector functions and resist exhaustion. Therefore, they can be proposed for adoptive cancer immunotherapy. Finally, neutralizing and/or inhibiting Gal-9 may preserve CD26^highCD8⁺ T cells in CLL.

GLP-1 receptor agonist as a modulator of innate immunity

Glucagon-like peptide-1 (GLP-1) is a 30-amino acid hormone secreted by L cells in the distal ileum, colon, and pancreatic α cells, which participates in blood sugar regulation by promoting insulin release, reducing glucagon levels, delaying gastric emptying, increasing satiety, and reducing appetite. GLP-1 specifically binds to the glucagon-like peptide-1 receptor (GLP-1R) in the body, directly stimulating the secretion of insulin by pancreatic β-cells, promoting proliferation and differentiation, and inhibiting cell apoptosis, thereby exerting a glycemic lowering effect. The glycemic regulating effect of GLP-1 and its analogues has been well studied in human and murine models in the circumstance of many diseases. Recent studies found that GLP-1 is able to modulate innate immune response in a number of inflammatory diseases. In the present review, we summarize the research progression of GLP-1 and its analogues in immunomodulation and related signal pathways.

Effects of vildagliptin on wound healing and markers of inflammation in patients with type 2 diabetic foot ulcer: a prospective, randomized, double-blind, placebo-controlled, single-center study

INTRODUCTION

Diabetic foot ulcers (DFU) are one of the leading long-term complications experienced by patients with diabetes. Dipeptidyl Peptidase 4 inhibitors (DPP4is) are a class of antihyperglycemic medications prescribed to patients with diabetes to manage glycaemic control. DPP4is may also have a beneficial effect on DFU healing. This study aimed to determine vildagliptin's effect on inflammatory markers and wound healing.

TRIAL DESIGN

Prospective, randomized, double-blind, placebo-controlled, single-center study.

METHODS

Equal number of participants were randomized into the treatment and placebo groups. The treatment was for 12 weeks, during which the participants had regular visits to the podiatrist, who monitored their DFU sizes using 3D camera, and blood samples were taken at baseline, six weeks, and 12 weeks during the study for measurement of inflammatory markers. In addition, demographic characteristics, co-morbidities, DFU risk factors, and DFU wound parameters were recorded.

RESULTS

50 participants were recruited for the study, with 25 assigned to placebo and 25 to treatment group. Vildagliptin treatment resulted in a statistically significant reduction of HBA1c (p < 0.02) and hematocrit (p < 0.04), total cholesterol (p < 0.02), LDL cholesterol (p < 0.04), and total/HDL cholesterol ratio (P < 0.03) compared to the placebo group. Also, vildagliptin had a protective effect on DFU wound healing, evidenced by the odds ratio (OR) favoring the intervention of 11.2 (95% CI 1.1-113.5; p < 0.04) and the average treatment effect on the treated (ATET) for vildagliptin treatment group showed increased healing by 35% (95%CI; 10-60, p = 0.01) compared to placebo with the model adjusted for microvascular complications, smoking, amputation, dyslipidemia, peripheral vascular disease (PVD) and duration of diabetes.

CONCLUSIONS

Vildagliptin treatment was effective in healing DFU in addition to controlling the diabetes. Our findings support the use of DPP4is as a preferred option for treating ulcers in patients with diabetes. Further studies on a larger population are warranted to confirm our findings and understand how DPP4is could affect inflammation and DFU healing.

Targeting Immune Senescence in Atherosclerosis

Atherosclerosis is one of the main underlying causes of cardiovascular diseases (CVD). It is associated with chronic inflammation and intimal thickening as well as the involvement of multiple cell types including immune cells. The engagement of innate or adaptive immune response has either athero-protective or atherogenic properties in exacerbating or alleviating atherosclerosis. In atherosclerosis, the mechanism of action of immune cells, particularly monocytes, macrophages, dendritic cells, and B- and T-lymphocytes have been discussed. Immuno-senescence is associated with aging, viral infections, genetic predispositions, and hyperlipidemia, which contribute to atherosclerosis. Immune senescent cells secrete SASP that delays or accelerates atherosclerosis plaque growth and associated pathologies such as aneurysms and coronary artery disease. Senescent cells undergo cell cycle arrest, morphological changes, and phenotypic changes in terms of their abundances and secretome profile including cytokines, chemokines, matrix metalloproteases (MMPs) and Toll-like receptors (TLRs) expressions. The senescence markers are used in therapeutics and currently, senolytics represent one of the emerging treatments where specific targets and clearance of senescent cells are being considered as therapy targets for the prevention or treatment of atherosclerosis.

Role of CD40(L)-TRAF signaling in inflammation and resolution-a double-edged sword

Cardiovascular diseases (CVD) and cardiovascular risk factors are the leading cause of death in the world today. According to the Global Burden of Disease Study, hypertension together with ischemic heart and cerebrovascular diseases is responsible for approximately 40% of all deaths worldwide. The major pathomechanism underlying almost all CVD is atherosclerosis, an inflammatory disorder of the vascular system. Recent large-scale clinical trials demonstrated that inflammation itself is an independent cardiovascular risk factor. Specific anti-inflammatory therapy could decrease cardiovascular mortality in patients with atherosclerosis (increased markers of inflammation). Inflammation, however, can also be beneficial by conferring so-called resolution, a process that contributes to clearing damaged tissue from cell debris upon cell death and thereby represents an essential step for recovery from, e.g., ischemia/reperfusion damage. Based on these considerations, the present review highlights features of the detrimental inflammatory reactions as well as of the beneficial process of immune cell-triggered resolution. In this context, we discuss the polarization of macrophages to either M1 or M2 phenotype and critically assess the role of the CD40L-CD40-TRAF signaling cascade in atherosclerosis and its potential link to resolution. As CD40L can bind to different cellular receptors, it can initiate a broad range of inflammatory processes that may be detrimental or beneficial. Likewise, the signaling of CD40L downstream of CD40 is mainly determined by activation of TRAF1-6 pathways that again can be detrimental or beneficial. Accordingly, CD40(L)-based therapies may be Janus-faced and require sophisticated fine-tuning in order to promote cardioprotection.

DPP-4 inhibitors and GLP-1RAs: cardiovascular safety and benefits

Glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors are commonly used treatments for patients with type 2 diabetes mellitus (T2DM). Both anti-diabetic treatments function by playing key modulatory roles in the incretin system. Though these drugs have been deemed effective in treating T2DM, the Food and Drug Administration (FDA) and some members of the scientific community have questioned the safety of these therapeutics relative to important cardiovascular endpoints. As a result, since 2008, the FDA has required all new drugs for glycemic control in T2DM patients to demonstrate cardiovascular safety. The present review article strives to assess the safety and benefits of incretin-based therapy, a new class of antidiabetic drug, on the health of patient cardiovascular systems. In the process, this review will also provide a physiological overview of the incretin system and how key components function in T2DM.

A Glimpse of Inflammation and Anti-Inflammation Therapy in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a common complication of diabetes mellitus and a major cause of end-stage kidney disease (ESKD). The pathogenesis of DKD is very complex and not completely understood. Recently, accumulated evidence from in vitro and in vivo studies has demonstrated that inflammation plays an important role in the pathogenesis and the development of DKD. It has been well known that a variety of pro-inflammatory cytokines and related signaling pathways are involved in the procession of DKD. Additionally, some anti-hyperglycemic agents and mineralocorticoid receptor antagonists (MRAs) that are effective in alleviating the progression of DKD have anti-inflammatory properties, which might have beneficial effects on delaying the progression of DKD. However, there is currently a lack of systematic overviews. In this review, we focus on the novel pro-inflammatory signaling pathways in the development of DKD, including the nuclear factor kappa B (NF-κB) signaling pathway, toll-like receptors (TLRs) and myeloid differentiation primary response 88 (TLRs/MyD88) signaling pathway, adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling pathways, inflammasome activation, mitochondrial DNA (mtDNA) release as well as hypoxia-inducible factor-1(HIF-1) signaling pathway. We also discuss the related anti-inflammation mechanisms of metformin, finerenone, sodium-dependent glucose transporters 2 (SGLT2) inhibitors, Dipeptidyl peptidase-4 (DPP-4) inhibitors, Glucagon-like peptide-1 (GLP-1) receptor agonist and traditional Chinese medicines (TCM).

Epicardial Adipose Tissue and Cardiac Arrhythmias: Focus on Atrial Fibrillation

Atrial Fibrillation (AF) is the most frequent cardiac arrhythmia and its prevalence increases with age. AF is strongly associated with an increased risk of stroke, heart failure and cardiovascular mortality. Among the risk factors associated with AF onset and severity, obesity and inflammation play a prominent role. Numerous recent evidence suggested a role of epicardial adipose tissue (EAT), the visceral fat depot of the heart, in the development of AF. Several potential arrhythmogenic mechanisms have been attributed to EAT, including myocardial inflammation, fibrosis, oxidative stress, and fat infiltration. EAT is a local source of inflammatory mediators which potentially contribute to atrial collagen deposition and fibrosis, the anatomical substrate for AF. Moreover, the close proximity between EAT and myocardium allows the EAT to penetrate and generate atrial myocardium fat infiltrates that can alter atrial electrophysiological properties. These observations support the hypothesis of a strong implication of EAT in structural and electrical atrial remodeling, which underlies AF onset and burden. The measure of EAT, through different imaging methods, such as echocardiography, computed tomography and cardiac magnetic resonance, has been proposed as a useful prognostic tool to predict the presence, severity and recurrence of AF. Furthermore, EAT is increasingly emerging as a promising potential therapeutic target. This review aims to summarize the recent evidence exploring the potential role of EAT in the pathogenesis of AF, the main mechanisms by which EAT can promote structural and electrical atrial remodeling and the potential therapeutic strategies targeting the cardiac visceral fat.

Plasma-Soluble Dipeptidyl Peptidase 4 and Risk of Major Cardiovascular Events After Ischemic Stroke: Secondary Analysis of China Antihypertensive Trial in Acute Ischemic Stroke (CATIS)

BACKGROUND AND OBJECTIVES

Recent studies have suggested that plasma soluble dipeptidyl peptidase-4 (sDPP4) have important physiological effects, which may influence the prognosis of ischemic stroke. Our study aimed to examine the relationship between plasma sDDP4 levels and long-term clinical outcomes among acute ischemic stroke patients.

METHODS

Secondary analysis was conducted among 3,564 participants (2,270 men and 1,294 women) from the China Antihypertensive Trial in Acute Ischemic Stroke with baseline measurement of plasma sDPP4 levels. We evaluated the associations between plasma sDPP4 levels and 2-year clinical outcomes using logistic regression and Cox regression models. We further investigated the predictive utility of sDPP4 by calculating net reclassification index (NRI) and integrated discrimination improvement (IDI).

RESULTS

The highest plasma sDPP4 quartile was associated with lower risk of cardiovascular events (HR 0.62, 95% CI 0.45-0.87), recurrent stroke (HR 0.70, 95% CI 0.49-0.99), all-cause mortality (HR 0.62, 95% CI 0.44-0.87), stroke-specific mortality (HR 0.65, 95% CI 0.44-0.94) and poor functional outcomes (OR 0.66, 95% CI 0.53-0.82) at 2 years compared with the lowest sDPP4 category in multivariable models. The addition of plasma sDPP4 to conventional risk factors model significantly improved risk prediction of all outcomes.

DISCUSSION

In this study, we found that higher plasma sDPP4 levels in acute ischemic stroke patients were associated with decreased risks of cardiovascular events, recurrent stroke, all-cause mortality, and poor functional outcomes after ischemic stroke. These findings suggest that plasma sDPP4 may be a potential prognostic marker for initial risk stratification in patients with acute ischemic stroke.

The Dipeptidyl Peptidase-4 Inhibitor Linagliptin Ameliorates Endothelial Inflammation and Microvascular Thrombosis in a Sepsis Mouse Model

The pathophysiology of sepsis involves inflammation and hypercoagulability, which lead to microvascular thrombosis and compromised organ perfusion. Dipeptidyl peptidase (DPP)-4 inhibitors, e.g., linagliptin, are commonly used anti-diabetic drugs known to exert anti-inflammatory effects. However, whether these drugs confer an anti-thrombotic effect that preserves organ perfusion in sepsis remains to be investigated. In the present study, human umbilical vein endothelial cells (HUVECs) were treated with linagliptin to examine its anti-inflammatory and anti-thrombotic effects under tumor necrosis factor (TNF)-α treatment. To validate findings from in vitro experiments and provide in vivo evidence for the identified mechanism, a mouse model of lipopolysaccharide (LPS)-induced systemic inflammatory response syndrome was used, and pulmonary microcirculatory thrombosis was measured. In TNF-α-treated HUVECs and LPS-injected mice, linagliptin suppressed expressions of interleukin-1β (IL-1β) and intercellular adhesion molecule 1 (ICAM-1) via a nuclear factor-κB (NF-κB)–dependent pathway. Linagliptin attenuated tissue factor expression via the Akt/endothelial nitric oxide synthase pathway. In LPS-injected mice, linagliptin pretreatment significantly reduced thrombosis in the pulmonary microcirculation. These anti-inflammatory and anti-thrombotic effects were independent of blood glucose level. Together the present results suggest that linagliptin exerts protective effects against endothelial inflammation and microvascular thrombosis in a mouse model of sepsis.

Emerging Role of Dipeptidyl Peptidase-4 in Autoimmune Disease

Dipeptidyl-peptidase IV (DPP4), originally identified as an aminopeptidase in 1960s, is an ubiquitously expressed protease presented as either a membrane-bound or soluble form. DPP4 cleaves dipeptide off from the N-terminal of its substrates, altering the bioactivity of its substrates. Subsequent studies reveal that DPP4 is also involved in various cellular processes by directly binding to a number of ligands, including adenosine deaminase, CD45, fibronectin, plasminogen, and caveolin-1. In recent years, many novel functions of DPP4, such as promoting fibrosis and mediating virus entry, have been discovered. Due to its implication in fibrotic response and immunoregulation, increasing studies are focusing on the potential role of DPP4 in inflammatory disorders. As a moonlighting protein, DPP4 possesses multiple functions in different types of cells, including both enzymatic and non-enzymatic functions. However, most of the review articles on the role of DPP4 in autoimmune disease were focused on the association between DPP4 enzymatic inhibitors and the risk of autoimmune disease. An updated comprehensive summary of DPP4’s immunoregulatory actions including both enzymatic dependent and independent functions is needed. In this article, we will review the recent advances of DPP4 in immune regulation and autoimmune rheumatic disease.

Role of Epicardial Adipose Tissue in Cardiovascular Diseases: A Review

Cardiovascular diseases (CVDs) are the leading causes of death worldwide. Epicardial adipose tissue (EAT) is defined as a fat depot localized between the myocardial surface and the visceral layer of the pericardium and is a type of visceral fat. EAT is one of the most important risk factors for atherosclerosis and cardiovascular events and a promising new therapeutic target in CVDs. In health conditions, EAT has a protective function, including protection against hypothermia or mechanical stress, providing myocardial energy supply from free fatty acid and release of adiponectin. In patients with obesity, metabolic syndrome, or diabetes mellitus, EAT becomes a deleterious tissue promoting the development of CVDs. Previously, we showed an adverse modulation of gene expression in pericoronary adipose tissue in patients with coronary artery disease (CAD). Here, we summarize the currently available evidence regarding the role of EAT in the development of CVDs, including CAD, heart failure, and atrial fibrillation. Due to the rapid development of the COVID-19 pandemic, we also discuss data regarding the association between EAT and the course of COVID-19. Finally, we present the potential therapeutic possibilities aiming at modifying EAT's function. The development of novel therapies specifically targeting EAT could revolutionize the prognosis in CVDs.

Gastrointestinal Incretins-Glucose-Dependent Insulinotropic Polypeptide (GIP) and Glucagon-like Peptide-1 (GLP-1) beyond Pleiotropic Physiological Effects Are Involved in Pathophysiology of Atherosclerosis and Coronary Artery Disease-State of the Art

Simple Summary

The presented manuscript contains the most current and extensive summary of the role of the most predominant gastrointestinal hormones—GIP and GLP-1 in the pathophysiology of atherosclerosis and coronary artery disease both in animals and humans. We have described GIP and GLP-1 as (1) expressed in many human tissues, (2) emphasized relationship between GIP and GLP-1 and inflammation, (3) highlighted importance of GIP and GLP-1-dependent pathways in atherosclerosis and coronary artery disease and (4) proved that GIP and GLP-1 could be used as markers of incidence, clinical course and recurrence of coronary artery disease, and related to extent and severity of atherosclerosis and myocardial ischemia. Our initial review may state a cornerstone for the future, however, there are still many unknowns and understatements on this topic. Due to the widespread growing interest for the potential use of incretins in cardiovascular diseases, we think that further research in this direction is desirable. For the future, we would like to recognize GIP and GLP-1 as widely implemented into clinical practice as new biomarkers of atherosclerosis and coronary artery disease.

Abstract

Coronary artery disease (CAD), which is the manifestation of atherosclerosis in coronary arteries, is the most common single cause of death and is responsible for disabilities of millions of people worldwide. Despite numerous dedicated clinical studies and an enormous effort to develop diagnostic and therapeutic methods, coronary atherosclerosis remains one of the most serious medical problems of the modern world. Hence, new markers are still being sought to identify and manage CAD optimally. Trying to face this problem, we have raised the question of the most predominant gastrointestinal hormones; glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), mainly involved in carbohydrates disorders, could be also used as new markers of incidence, clinical course, and recurrence of CAD and are related to extent and severity of atherosclerosis and myocardial ischemia. We describe GIP and GLP-1 as expressed in many animal and human tissues, known to be connected to inflammation and related to enormous noncardiac and cardiovascular (CV) diseases. In animals, GIP and GLP-1 improve endothelial function and lead to reduced atherosclerotic plaque macrophage infiltration and stabilize atherosclerotic lesions by directly blocking monocyte migration. Moreover, in humans, GIPR activation induces the pro-atherosclerotic factors ET-1 (endothelin-1) and OPN (osteopontin) but also has anti-atherosclerotic effects through secretion of NO (nitric oxide). Furthermore, four large clinical trials showed a significant reduction in composite of CV death, MI, and stroke in long-term follow-up using GLP-1 analogs for DM 2 patients: liraglutide in LEADER, semaglutide in SUSTAIN-6, dulaglutide in REWIND and albiglutide in HARMONY. However, very little is known about GIP metabolism in the acute phase of myocardial ischemia or for stable patients with CAD, which constitutes a direction for future research. This review aims to comprehensively discuss the impact of GIP and GLP-1 on atherosclerosis and CAD and its potential therapeutic implications.

The Multiple Biological Functions of Dipeptidyl Peptidase-4 in Bone Metabolism

Dipeptidyl peptidase-4 (DPP4) is a ubiquitously occurring protease involved in various physiological and pathological processes ranging from glucose homeostasis, immunoregulation, inflammation to tumorigenesis. Recently, the benefits of DPP4 inhibitors as novel hypoglycemic agents on bone metabolism have attracted extensive attraction in many studies, indicating that DPP4 inhibitors may regulate bone homeostasis. The effects of DPP4 on bone metabolism are still unclear. This paper thoroughly reviews the potential mechanisms of DPP4 for interaction with adipokines, bone cells, bone immune cells, and cytokines in skeleton system. This literature review shows that the increased DPP4 activity may indirectly promote bone resorption and inhibit bone formation, increasing the risk of osteoporosis. Thus, bone metabolic balance can be improved by decreasing DPP4 activities. The substantial evidence collected and analyzed in this review supports this implication.

Targeting Epicardial Fat in Obesity and Diabetes Pharmacotherapy

Epicardial adipose tissue surrounds and infiltrates the heart. Epicardial fat displays unique anatomic, genetic, and biomolecular properties. People with obesity and in particular, those with abdominal obesity and associated type 2 diabetes mellitus, have an increased amount of epicardial adipose tissue (EAT). Epicardial fat works well as therapeutic target due to its fast-responding metabolism, organ fat specificity, and easy measurability. Epicardial fat responds to thiazolidinediones (TZD), glucagon-like peptide 1-receptor agonists (GLP1A), sodium-glucose cotransporter 2 inhibitors (SGLT2i), dipeptidyl peptidase-4 inhibitors (DPP4i), and statins. Modulating epicardial fat morphology and genetic profile with targeted pharmacological agents suggests novel strategies in the pharmacotherapy of diabetes and obesity.

Epicardial Fat Expansion in Diabetic and Obese Patients With Heart Failure and Preserved Ejection Fraction-A Specific HFpEF Phenotype

Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous syndrome with diverse etiologies and pathophysiological factors. Obesity and type 2 diabetes mellitus (T2DM), conditions that coexist frequently, induce a cluster of metabolic and non-metabolic signaling derangements which are in favor to induce inflammation, fibrosis, myocyte stiffness, all hallmarks of HFpEF. In contrast to other HFpEF risk factors, obesity and T2DM are often associated with the generation of enlarged epicardial adipose tissue (EAT). EAT acts as an endocrine tissue that may exacerbate myocardial inflammation and fibrosis via various paracrine and vasocrine signals. In addition, an abnormally large EAT poses mechanical stress on the heart via pericardial restrain. HFpEF patients with enlarged EAT may belong to a unique phenotype that can benefit from specific EAT-targeted interventions, including life-style modifications and pharmacologically via statins and fat modifying anti-diabetics drugs; like metformin, sodium-glucose cotransporter 2 inhibitors, or glucagon-like peptide-1 receptor agonists, respectively.

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.

Mechanisms and Therapeutic Prospects of Diabetic Cardiomyopathy Through the Inflammatory Response

The incidence of heart failure (HF) continues to increase rapidly in patients with diabetes. It is marked by myocardial remodeling, including fibrosis, hypertrophy, and cell death, leading to diastolic dysfunction with or without systolic dysfunction. Diabetic cardiomyopathy (DCM) is a distinct myocardial disease in the absence of coronary artery disease. DCM is partially induced by chronic systemic inflammation, underpinned by a hostile environment due to hyperglycemia, hyperlipidemia, hyperinsulinemia, and insulin resistance. The detrimental role of leukocytes, cytokines, and chemokines is evident in the diabetic heart, yet the precise role of inflammation as a cause or consequence of DCM remains incompletely understood. Here, we provide a concise review of the inflammatory signaling mechanisms contributing to the clinical complications of diabetes-associated HF. Overall, the impact of inflammation on the onset and development of DCM suggests the potential benefits of targeting inflammatory cascades to prevent DCM. This review is tailored to outline the known effects of the current anti-diabetic drugs, anti-inflammatory therapies, and natural compounds on inflammation, which mitigate HF progression in diabetic populations.

Effects of Incretin-Related Diabetes Drugs on Bone Formation and Bone Resorption

Patients with type 2 diabetes have an increased risk of fracture compared to the general population. Glucose absorption is accelerated by incretin hormones, which induce insulin secretion from the pancreas. The level of the incretin hormone, glucagon-like peptide-1 (GLP-1), shows an immediate postprandial increase, and the circulating level of intact GLP-1 is reduced rapidly by dipeptidyl peptidase-4 (DPP-4)-mediated inactivation. Therefore, GLP-1 receptor agonists and DPP-4 inhibitors are effective in the treatment of type 2 diabetes. However, these incretin-related diabetic agents have been reported to affect bone metabolism, including bone formation and resorption. These agents enhance the expression of bone markers, and have been applied to improve bone quality and bone density. In addition, they have been reported to suppress chronic inflammation and reduce the levels of inflammatory cytokine expression. Previously, we reported that these incretin-related agents inhibited both the expression of inflammatory cytokines and inflammation-induced bone resorption. This review presents an overview of current knowledge regarding the effects of incretin-related diabetes drugs on osteoblast differentiation and bone formation as well as osteoclast differentiation and bone resorption. The mechanisms by which incretin-related diabetes drugs regulate bone formation and bone resorption are also discussed.

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.

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.

Effects of sitagliptin on ß-adrenoceptor mediated relaxation in streptozotocin-diabetic rat aorta

Background/aim

Dipeptidyl peptidase-4 (DPP4) inhibitors, a class of oral antidiabetic drugs, have been shown to be protective on the vascular system because of their antiinflammatory, antiatherosclerotic, and vasodilatory effects. ß2-adrenoceptors (ß2-ARs) mediate the vasorelaxation in the aorta. However, ß3-adrenoceptor-mediated relaxation has not been studied in diabetic aorta yet. Thus, we aimed to study the effect of sitagliptin treatment on ß2- and ß3-adrenoceptor-mediated relaxations in the diabetic rat aorta.

Materials and methods

Eight-week old Sprague Dawley rats were divided into three groups: control, diabetic, sitagliptin treated diabetic. Diabetes was induced by injection of streptozotocin (35 or 40 mg/kg, intraperitoneally). After 10 weeks of diabetes, some of the diabetic rats were treated with sitagliptin (orally, 10mg/kg/day). ß2- and ß3-AR-mediated relaxation responses were evaluated by using isoprenaline and CL 316,243, respectively. ß3-AR-mediated relaxation experiments were repeated in presence of L-NAME. Western blotting and immunohistochemistry were performed to determine the abundance of ß3-adrenoceptor and endothelial nitric oxide synthase (eNOS).

Results

The isoprenaline-mediated relaxation response was impaired in the diabetic group and sitagliptin treatment did not improve it. There was no significant change in CL316,243 mediated-relaxation or protein expression of ß3-ARs among the groups. However, the ratio of phosphorylated eNOS/NOS protein was increased markedly in the sitagliptin treated group, which points the stimulating effect of this drug towards the eNOS pathway.

Conclusion

Our results indicate that sitagliptin treatment does not alter ß-AR-mediated relaxation in streptozotocin-diabetic rat aorta; however, it significantly stimulates the eNOS pathway. Future studies are needed to clarify the relationship between the eNOS pathway and DPP-4 inhibition.

Development of an In Vitro-In Vivo Correlation for Sitagliptin and Metformin Prolonged-release Tablet Formulations

Objectives

The objective of this study was to establish and validate an in vitro-in vivo correlation (IVIVC). To investigate the safety of a fixed-dose combination (FDC) versus the reference formulations (Januvia^® 100 mg Filmtabletten co-administered with Glucophage^® SR 1000 mg prolonged-release tablets), a bioequivalence study was conducted in the fasted and fed states, and the data generated were used to establish the correlation.

Materials and Methods

The formulations used in the bioequivalence study were a FDC (sitagliptin hydrochloride equivalent to 100 mg of sitagliptin and metformin hydrochloride 1000 mg prolonged release) and Januvia^® 100 mg co-administered with Glucophage^® SR 1000 mg. The plasma profiles from the bioequivalence study and respective dissolution data were then utilized to establish "level A" IVIVC. The procedure comprises pharmacokinetic modeling to derive the empirical constants for further use in deconvolution and convolution procedures. Levy plots were constructed to understand the relationship between in vitro and in vivo properties. The internal and external predictabilities were evaluated by comparing the predicted pharmacokinetics with the observed values from the bioequivalence study.

Results

The formulations showed approximately 91%-95% and 89%-91% dissolution, respectively in fasted and fed-state dissolution media for sitagliptin. The dissolution of metformin was 96%-98% and 89%-95%, respectively, in fasted and fed-state media. The regression coefficients of all the Levy plots were more than 0.900, indicating a linear correlation between in vitro release and in vivo parameters. The prediction error value of internal and external predictabilities was below 10 and met the US Food and Drug Administration criteria. Therefore, it can be stated that the correlation models are validated and can be used for predictions and to setting the dissolution specifications. The safety and tolerability of the FDC was found to be superior to those of the reference formulations, as fewer adverse events occurred following administration of the FDC.

Conclusion

Correlation models can be useful for the prediction of FDCs during the management life cycle of the product. The models can also serve as a surrogate for in vivo studies. The FDC was tolerable, and the adverse events were mild and similar to those observed with the reference products. Therefore, the FDC is safe for use in human subjects.

Fluorescence Determination of Peptidase Activity Based on the Quenching of a Fluorophore-Labelled Peptide by Graphene Oxide

In this study, a fluorescence detection strategy is reported for the peptidase activity assay, which is based on fluorescence resonance energy transfer (FRET) from a fluorophore-labelled peptide to graphene oxide (GO). By the hydrolysis of the peptide, the fluorophore-labelled peptide releases the fluorophore 5-carboxyfluorescein, which can avoid quenching from GO. Thus, the increased intensity of the obtained fluorescence signal in the assay is directly dependent on the peptidase activity. As a model case of the developed strategy, the activity determination of pancreatic elastase (PE) is performed. Under the optimal experimental conditions at an excitation wavelength of 494 nm, the activity of PE can be determined in the range from 0.003 to 0.10 U/mL, with a detection limit of 0.001 U/mL at the emission wavelength of 518 nm. This is ultra-sensitive for the determination of PE. The specificity of the method is demonstrated by the analysis of PE under complex conditions using fetal bovine serum as the substrate. Hence, the developed method might provide an intrinsically convenient, sensitive platform for the PE activity assay and related biochemical studies due to its homogeneous, and fluorescence-based detection strategy.

Towards Better Drug Repositioning: Targeted Immunoinflammatory Therapy for Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common and important microvascular complications of diabetes mellitus (DM). The main clinical features of DN are proteinuria and a progressive decline in renal function, which are associated with structural and functional changes in the kidney. The pathogenesis of DN is multifactorial, including genetic, metabolic, and haemodynamic factors, which can trigger a sequence of events. Controlling metabolic risks such as hyperglycaemia, hypertension, and dyslipidaemia is not enough to slow the progression of DN. Recent studies emphasized immunoinflammation as a critical pathogenic factor in the progression of DN. Therefore, targeting inflammation is considered a potential and novel treatment strategy for DN. In this review, we will briefly introduce the inflammatory process of DN and discuss the anti-inflammatory effects of antidiabetic drugs when treating DN.

Influence of cardiometabolic comorbidities on myocardial function, infarction, and cardioprotection: Role of cardiac redox signaling

The morbidity and mortality from cardiovascular diseases (CVD) remain high. Metabolic diseases such as obesity, hyperlipidemia, diabetes mellitus (DM), non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) as well as hypertension are the most common comorbidities in patients with CVD. These comorbidities result in increased myocardial oxidative stress, mainly from increased activity of nicotinamide adenine dinucleotide phosphate oxidases, uncoupled endothelial nitric oxide synthase, mitochondria as well as downregulation of antioxidant defense systems. Oxidative and nitrosative stress play an important role in ischemia/reperfusion injury and may account for increased susceptibility of the myocardium to infarction and myocardial dysfunction in the presence of the comorbidities. Thus, while early reperfusion represents the most favorable therapeutic strategy to prevent ischemia/reperfusion injury, redox therapeutic strategies may provide additive benefits, especially in patients with heart failure. While oxidative and nitrosative stress are harmful, controlled release of reactive oxygen species is however important for cardioprotective signaling. In this review we summarize the current data on the effect of hypertension and major cardiometabolic comorbidities such as obesity, hyperlipidemia, DM, NAFLD/NASH on cardiac redox homeostasis as well as on ischemia/reperfusion injury and cardioprotection. We also review and discuss the therapeutic interventions that may restore the redox imbalance in the diseased myocardium in the presence of these comorbidities.

Comparative Renal Effects of Dipeptidyl Peptidase-4 Inhibitors and Sodium-Glucose Cotransporter 2 Inhibitors on Individual Outcomes in Patients with Type 2 Diabetes: A Systematic Review and Network Meta-Analysis

BACKGROUND

To compare the renal effects of dipeptidyl peptidase-4 (DPP-4) inhibitors and sodium-glucose cotransporter 2 (SGLT2) inhibitors on individual outcomes in patients with type 2 diabetes.

METHODS

We searched electronic databases (MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials) from inception to June 2019 to identity eligible randomized controlled trials of DPP-4 inhibitors or SGLT2 inhibitors that reported at least one kidney outcome in patients with type 2 diabetes. Outcomes of interest were microalbuminuria, macroalbuminuria, worsening nephropathy, and end-stage kidney disease (ESKD). We performed an arm-based network meta-analysis using Bayesian methods and calculated absolute risks and rank probabilities of each treatment for the outcomes.

RESULTS

Seventeen studies with 87,263 patients were included. SGLT2 inhibitors significantly lowered the risks of individual kidney outcomes, including microalbuminuria (odds ratio [OR], 0.64; 95% credible interval [CrI], 0.41 to 0.93), macroalbuminuria (OR, 0.48; 95% CrI, 0.24 to 0.72), worsening nephropathy (OR, 0.65; 95% CrI, 0.44 to 0.91), and ESKD (OR, 0.65; 95% CrI, 0.46 to 0.98) as compared with placebo. However, DPP-4 inhibitors did not lower the risks. SGLT2 inhibitors were considerably associated with higher absolute risk reductions in all kidney outcomes than DPP-4 inhibitors, although the benefits were statistically insignificant. The rank probabilities showed that SGLT2 inhibitors were better treatments for lowering the risk of albuminuria and ESKD than placebo or DPP-4 inhibitors.

CONCLUSION

SGLT2 inhibitors were superior to DPP-4 inhibitors in reducing the risk of albuminuria and ESKD in patients with type 2 diabetes.

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

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

Discovery of new therapeutic redox targets for cardioprotection against ischemia/reperfusion injury and heart failure

Global epidemiological studies reported a shift from maternal/infectious communicable diseases to chronic non-communicable diseases and a major part is attributable to atherosclerosis and metabolic disorders. Accordingly, ischemic heart disease was identified as a leading risk factor for global mortality and morbidity with a prevalence of 128 million people. Almost 9 million premature deaths can be attributed to ischemic heart disease and subsequent acute myocardial infarction and heart failure, also representing a substantial socioeconomic burden. As evidenced by typical oxidative stress markers such as lipid peroxidation products or oxidized DNA/RNA bases, the formation of reactive oxygen species by various sources (NADPH oxidases, xanthine oxidase and mitochondrial resperatory chain) plays a central role for the severity of ischemia/reperfusion damage. The underlying mechanisms comprise direct oxidative damage but also adverse redox-regulation of kinase and calcium signaling, inflammation and cardiac remodeling among others. These processes and the role of reactive oxygen species are discussed in the present review. We also present and discuss potential targets for redox-based therapies that are either already established in the clinics (e.g. guanylyl cyclase activators and stimulators) or at least successfully tested in preclinical models of myocardial infarction and heart failure (mitochondria-targeted antioxidants). However, reactive oxygen species have not only detrimental effects but are also involved in essential cellular signaling and may even act protective as seen by ischemic pre- and post-conditioning or eustress - which makes redox therapy quite challenging.