Dipeptidyl peptidase-4 inhibition with linagliptin prevents western diet-induced vascular abnormalities in female mice

Emerging role of α-Klotho in energy metabolism and cardiometabolic diseases

BACKGROUND AND AIM

Klotho was first identified as a gene associated with aging and longevity in 1997. α-Klotho is an anti-aging protein and its role in energy metabolism, various cardiovascular diseases (CVDs), and metabolic disorders is increasingly being recognized. In this review, we aimed to outline the potential protective role and therapeutic prospects of α-Klotho in energy metabolism and cardiometabolic diseases (CMDs).

METHODS

We comprehensively reviewed the relevant literature in PubMed using the keywords 'Klotho', 'metabolism', 'cardiovascular', 'diabetes', 'obesity', 'metabolic syndrome', and 'nonalcoholic fatty liver disease'.

RESULTS

α-Klotho can be divided into membrane-bound Klotho, secreted Klotho, and the most studied circulating soluble Klotho that can act as a hormone. Klotho gene polymorphisms have been implicated in energy metabolism and CMDs. α-Klotho can inhibit insulin/insulin growth factor-1 signaling and its overexpression can lead to a 'healthy insulin resistance' and may exert beneficial effects on the regulation of glycolipid metabolism and central energy homeostasis. α-Klotho, mainly serum Klotho, has been revealed to be protective against CVDs, diabetes and its complications, obesity, and nonalcoholic fatty liver disease. Human recombinant Klotho protein/Klotho gene delivery, multiple drugs, or natural products, and exercise can increase α-Klotho expression.

CONCLUSION

Overall, α-Klotho has demonstrated its potential as a promising target for modulating energy metabolism and CMDs, and further research is needed to explore its utilization in clinical practice in the future.

Differential Effects of High Fat Diets on Resilience to H2O2-Induced Cell Death in Mouse Cerebral Arteries: Role for Processed Carbohydrates

High fat, western-style diets increase vascular oxidative stress. We hypothesized that smooth muscle cells and endothelial cells adapt during the consumption of high fat diets to become more resilient to acute oxidative stress. Male C57Bl/6J mice were fed a western-style diet high in fat and processed carbohydrates (WD), a high fat diet that induces obesity (DIO), or their respective control (CD) and standard (SD) diets for 16 weeks. Posterior cerebral arteries (PCAs) were isolated and pressurized for study. During acute exposure to H₂O₂ (200 µM), smooth muscle cell and endothelial cell death were reduced in PCAs from WD, but not DIO mice. WD selectively attenuated mitochondrial membrane potential depolarization and vessel wall Ca²⁺ influx during H₂O₂ exposure. Selective inhibition of transient receptor potential (TRP) V4 or TRPC3 channels reduced smooth muscle cell and endothelial cell death in concert with the vessel wall [Ca²⁺]_i response to H₂O₂ for PCAs from CD mice and eliminated differences between CD and WD. Inhibiting Src kinases reduced smooth muscle cell death along with [Ca²⁺]_i response to H₂O₂ only in PCAs from CD mice and eliminated differences between diets. However, Src kinase inhibition did not alter endothelial cell death. These findings indicate that consuming a WD, but not high fat alone, leads to adaptations that limit Ca²⁺ influx and vascular cell death during exposure to acute oxidative stress.

Dipeptidyl peptidase 4 inhibition rescues PKA-eNOS signaling and suppresses aortic hypercontractility in male rats with heart failure

AIMS

Vascular dysfunction and elevated circulating dipeptidyl peptidase 4 (DPP4) activity are both reported to be involved in the progression of heart failure (HF). While the cardiac benefits of DPP4 inhibitors (DPP4i) have been extensively studied, little is known about the effects of DPP4i on vascular dysfunction in nondiabetic HF. This study tested the hypothesis that vildagliptin (DPP4i) mitigates aortic hyperreactivity in male HF rats.

MATERIALS AND METHODS

Male Wistar rats were subjected to left ventricle (LV) radiofrequency ablation to HF induction or sham operation (SO). Six weeks after surgery, radiofrequency-ablated rats who developed HF were treated with vildagliptin (120 mg⸱kg^-1⸱day^-1) or vehicle for 4 weeks. Thoracic aorta reactivity, dihydroethidium fluorescence, immunoblotting experiments, and enzyme-linked immunosorbent assays were performed.

KEY FINDINGS

DPP4i ameliorated the hypercontractility of HF aortas to the α-adrenoceptor agonist phenylephrine towards SO levels. In HF, the reduced endothelium and nitric oxide (NO) anticontractile effect on phenylephrine response was restored by DPP4i. At the molecular level, this vasoprotective effect of DPP4i was accompanied by (i) reduced oxidative stress and NADPH oxidase 2 (Nox2) expression, (ii) enhanced total endothelial nitric oxide synthase (eNOS) expression and phosphorylation at Ser1177, and (iii) increased PKA activation, which acts upstream of eNOS. Additionally, DPP4i restored the higher serum angiotensin II concentration towards SO.

SIGNIFICANCE

Our data demonstrate that DPP4i ameliorates aortic hypercontractility, most likely by enhancing NO bioavailability, showing that the DPP4i-induced cardioprotection in male HF may arise from effects not only in the heart but also in conductance arteries.

Klotho's impact on diabetic nephropathy and its emerging connection to diabetic retinopathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide and is a significant burden on healthcare systems. α-klotho (klotho) is a protein known for its anti-aging properties and has been shown to delay the onset of age-related diseases. Soluble klotho is produced by cleavage of the full-length transmembrane protein by a disintegrin and metalloproteases, and it exerts various physiological effects by circulating throughout the body. In type 2 diabetes and its complications DN, a significant decrease in klotho expression has been observed. This reduction in klotho levels may indicate the progression of DN and suggest that klotho may be involved in multiple pathological mechanisms that contribute to the onset and development of DN. This article examines the potential of soluble klotho as a therapeutic agent for DN, with a focus on its ability to impact multiple pathways. These pathways include anti-inflammatory and oxidative stress, anti-fibrotic, endothelial protection, prevention of vascular calcification, regulation of metabolism, maintenance of calcium and phosphate homeostasis, and regulation of cell fate through modulation of autophagy, apoptosis, and pyroptosis pathways. Diabetic retinopathy shares similar pathological mechanisms with DN, and targeting klotho may offer new insights into the prevention and treatment of both conditions. Finally, this review assesses the potential of various drugs used in clinical practice to modulate klotho levels through different mechanisms and their potential to improve DN by impacting klotho levels.

Pathobiology of the Klotho Antiaging Protein and Therapeutic Considerations

The α-Klotho protein (henceforth denoted Klotho) has antiaging properties, as first observed in mice homozygous for a hypomorphic Klotho gene (kl/kl). These mice have a shortened lifespan, stunted growth, renal disease, hyperphosphatemia, hypercalcemia, vascular calcification, cardiac hypertrophy, hypertension, pulmonary disease, cognitive impairment, multi-organ atrophy and fibrosis. Overexpression of Klotho has opposite effects, extending lifespan. In humans, Klotho levels decline with age, chronic kidney disease, diabetes, Alzheimer’s disease and other conditions. Low Klotho levels correlate with an increase in the death rate from all causes. Klotho acts either as an obligate coreceptor for fibroblast growth factor 23 (FGF23), or as a soluble pleiotropic endocrine hormone (s-Klotho). It is mainly produced in the kidneys, but also in the brain, pancreas and other tissues. On renal tubular-cell membranes, it associates with FGF receptors to bind FGF23. Produced in bones, FGF23 regulates renal excretion of phosphate (phosphaturic effect) and vitamin D metabolism. Lack of Klotho or FGF23 results in hyperphosphatemia and hypervitaminosis D. With age, human renal function often deteriorates, lowering Klotho levels. This appears to promote age-related pathology. Remarkably, Klotho inhibits four pathways that have been linked to aging in various ways: Transforming growth factor β (TGF-β), insulin-like growth factor 1 (IGF-1), Wnt and NF-κB. These can induce cellular senescence, apoptosis, inflammation, immune dysfunction, fibrosis and neoplasia. Furthermore, Klotho increases cell-protective antioxidant enzymes through Nrf2 and FoxO. In accord, preclinical Klotho therapy ameliorated renal, cardiovascular, diabetes-related and neurodegenerative diseases, as well as cancer. s-Klotho protein injection was effective, but requires further investigation. Several drugs enhance circulating Klotho levels, and some cross the blood-brain barrier to potentially act in the brain. In clinical trials, increased Klotho was noted with renin-angiotensin system inhibitors (losartan, valsartan), a statin (fluvastatin), mTOR inhibitors (rapamycin, everolimus), vitamin D and pentoxifylline. In preclinical work, antidiabetic drugs (metformin, GLP-1-based, GABA, PPAR-γ agonists) also enhanced Klotho. Several traditional medicines and/or nutraceuticals increased Klotho in rodents, including astaxanthin, curcumin, ginseng, ligustilide and resveratrol. Notably, exercise and sport activity increased Klotho. This review addresses molecular, physiological and therapeutic aspects of Klotho.

Effects of dipeptidyl peptidase-4 inhibition on portal hypertensive and cirrhotic rats

BACKGROUND

Portal hypertension is a pathophysiological abnormality with distinct vascular derangements associated with liver cirrhosis. Dipeptidyl peptidase-4 (DPP-4) inhibitors are antidiabetic agents which exert pleiotropic vascular effects, but their relevant impact on portal hypertension and liver cirrhosis remains unclear. This study aims to clarify this issue.

METHODS

Rats receiving partial portal vein ligation (PVL) and common bile duct ligation (BDL) served as experimental models for portal hypertension and cirrhosis, respectively. After linagliptin (a DPP-4 inhibitor) treatment, the survival rate, hemodynamics, biochemistry parameters and liver histopathology were evaluated. In addition, the collateral vascular responsiveness and severity of portal-systemic shunting were examined. mRNA and protein expression in the vasculature and liver were also examined.

RESULTS

Linagliptin significantly reduced portal pressure (control vs linagliptin: 12.9 ± 1.2 vs 9.1 ± 2.0 mmHg, p = 0.001) and upregulated nitric oxide synthase expression in the collateral vessel, superior mesentery artery, and liver of PVL rats. However, the portal hypotensive effect was insignificant in BDL rats. Glucose plasma levels, liver and renal biochemistry parameters were not significantly altered by linagliptin. The degree of portal-systemic shunting and collateral vascular responsiveness were also not significantly altered by linagliptin treatment. Linagliptin did not improve liver fibrosis and hepatic inflammation in BDL rats.

CONCLUSION

DPP-4 inhibition by linagliptin reduced portal pressure in portal hypertensive rats but not in cirrhotic rats. It may act by decreasing intrahepatic resistance via upregulation of hepatic nitric oxide synthase in portal hypertensive rats.

Omarigliptin Prevents TNF-α-Induced Cellular Senescence in Rat Aorta Vascular Smooth Muscle Cells

Cellular senescence is one of the most significant factors involved in aging and age-related diseases. Senescence of vascular smooth muscle cells (VSMCs) adversely affects the function of the cardiovascular system and contributes to the development of atherosclerosis, hypertension, and other cardiovascular diseases. Glucagon-like peptide-1 (GLP-1) is an important incretin hormone involved in insulin release and vascular tone. GLP-1 is quickly degraded by the enzyme dipeptidyl peptidase-4 (DPP-4). Omarigliptin is a new DPP-4 inhibitor that has demonstrated anti-inflammatory and antioxidative stress properties. In the present study, we investigated the effects of the selective DPP-4 inhibitor omarigliptin (OMG) on VSMCs exposed to insult from tumor necrosis factor-α (TNF-α), one of the main inflammatory signaling molecules involved in cellular senescence. We found that OMG could suppress TNF-α-induced expression of pro-inflammatory cytokines (interleukin-1β (IL-1β), IL-6, and IL-8) and inhibit oxidative stress by reducing the production of H2O2 and protein carbonyl. OMG ameliorated the increase in senescence-associated β-galactosidase (SA-β-gal) and telomerase activity induced by TNF-α. The plasminogen activator inhibitor-1 (PAI-1)/p53/p21 pathway is a key inducer of cellular senescence. OMG ameliorated the acetylation of p53 at lysine 382 (K382) and subsequent activation of p21 via inhibition of PAI-1. Importantly, our experiments revealed that blockage of silent information-regulator 1 (SIRT1) abolished the inhibitory effects of OMG on p53 acetylation, SA-β-gal activity, and telomerase activity in VSMCs. These results suggest that OMG may have the potential to delay or prevent the progression of age-related cardiovascular diseases by modulating the activity of SIRT1.

High-Fat Diets Modify the Proteolytic Activities of Dipeptidyl-Peptidase IV and the Regulatory Enzymes of the Renin-Angiotensin System in Cardiovascular Tissues of Adult Wistar Rats

(1) Background: The replacement of diets high in saturated fat (SAFA) with monounsaturated fatty acids (MUFA) is associated with better cardiovascular function and is related to the modulation of the activity of the local renin–angiotensin system (RAS) and the collagenase activity of dipeptidyl peptidase IV (DPP-IV). The objective of the work was to verify the capacity of different types of dietary fat on the regulatory activities of RAS and DPP-IV. (2) Methods: Male Wistar rats were fed for 24 weeks with three different diets: the standard diet (S), the standard diet supplemented with virgin olive oil (20%) (VOO), or with butter (20%) plus cholesterol (0.1%) (Bch). The proteolytic activities were determined by fluorometric methods in the soluble (sol) and membrane-bound (mb) fractions of the left ventricle and atrium, aorta, and plasma samples. (3) Results: With the VOO diet, angiotensinase values were significantly lower than with the Bch diet in the aorta (GluAP and ArgAP (mb)), ventricle (ArgAP (mb)) and atrium (CysAP (sol)). Significant decreases in DPP-IV (mb) activity occurred with the Bch diet in the atrium and aorta. The VOO diet significantly reduced the activity of the cardiac damage marker LeuAP (mb) in the ventricle and aorta, except for LeuAP (sol) in the ventricle, which was reduced with the Bch diet. (4) Conclusions: The introduction into the diet of a source rich in MUFA would have a beneficial cardiovascular effect on RAS homeostasis and cardiovascular functional stability.

Sacubitril/valsartan inhibits obesity-associated diastolic dysfunction through suppression of ventricular-vascular stiffness

OBJECTIVE

Cardiac diastolic dysfunction (DD) and arterial stiffness are early manifestations of obesity-associated prediabetes, and both serve as risk factors for the development of heart failure with preserved ejection fraction (HFpEF). Since the incidence of DD and arterial stiffness are increasing worldwide due to exponential growth in obesity, an effective treatment is urgently needed to blunt their development and progression. Here we investigated whether the combination of an inhibitor of neprilysin (sacubitril), a natriuretic peptide-degrading enzyme, and an angiotensin II type 1 receptor blocker (valsartan), suppresses DD and arterial stiffness in an animal model of prediabetes more effectively than valsartan monotherapy.

METHODS

Sixteen-week-old male Zucker Obese rats (ZO; n = 64) were assigned randomly to 4 different groups: Group 1: saline control (ZOC); Group 2: sacubitril/valsartan (sac/val; 68 mg•kg-1•day-1; ZOSV); Group 3: valsartan (31 mg•kg-1•day-1; ZOV) and Group 4: hydralazine, an anti-hypertensive drug (30 mg•kg-1•day-1; ZOH). Six Zucker Lean (ZL) rats that received saline only (Group 5) served as lean controls (ZLC). Drugs were administered daily for 10 weeks by oral gavage.

RESULTS

Sac/val improved echocardiographic parameters of impaired left ventricular (LV) stiffness in untreated ZO rats, without altering the amount of food consumed or body weight gained. In addition to improving DD, sac/val decreased aortic stiffness and reversed impairment in nitric oxide-induced vascular relaxation in ZO rats. However, sac/val had no impact on LV hypertrophy. Notably, sac/val was more effective than val in ameliorating DD. Although, hydralazine was as effective as sac/val in improving these parameters, it adversely affected LV mass index. Further, cytokine array revealed distinct effects of sac/val, including marked suppression of Notch-1 by both valsartan and sac/val, suggesting that cardiovascular protection afforded by both share some common mechanisms; however, sac/val, but not val, increased IL-4, which is increasingly recognized for its cardiovascular protection, possibly contributing, in part, to more favorable effects of sac/val over val alone in improving obesity-associated DD.

CONCLUSIONS

These studies suggest that sac/val is superior to val in reversing obesity-associated DD. It is an effective drug combination to blunt progression of asymptomatic DD and vascular stiffness to HFpEF development in a preclinical model of obesity-associated prediabetes.

Characterization of combined linagliptin and Y2R agonist treatment in diet-induced obese mice

Dipeptidyl peptidase IV (DPP-IV) inhibitors improve glycemic control by prolonging the action of glucagon-like peptide-1 (GLP-1). In contrast to GLP-1 analogues, DPP-IV inhibitors are weight-neutral. DPP-IV cleavage of PYY and NPY gives rise to PYY_3-36 and NPY_3-36 which exert potent anorectic action by stimulating Y2 receptor (Y2R) function. This invites the possibility that DPP-IV inhibitors could be weight-neutral by preventing conversion of PYY/NPY to Y2R-selective peptide agonists. We therefore investigated whether co-administration of an Y2R-selective agonist could unmask potential weight lowering effects of the DDP-IV inhibitor linagliptin. Male diet-induced obese (DIO) mice received once daily subcutaneous treatment with linagliptin (3 mg/kg), a Y2R-selective PYY_3-36 analogue (3 or 30 nmol/kg) or combination therapy for 14 days. While linagliptin promoted marginal weight loss without influencing food intake, the PYY_3-36 analogue induced significant weight loss and transient suppression of food intake. Both compounds significantly improved oral glucose tolerance. Because combination treatment did not further improve weight loss and glucose tolerance in DIO mice, this suggests that potential negative modulatory effects of DPP-IV inhibitors on endogenous Y2R peptide agonist activity is likely insufficient to influence weight homeostasis. Weight-neutrality of DPP-IV inhibitors may therefore not be explained by counter-regulatory effects on PYY/NPY responses.

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.

Coronary remodeling and biomechanics: Are we going with the flow in 2020?

Under normal conditions, coronary blood flow (CBF) provides critical blood supply to the myocardium so that it can appropriately meet the metabolic demands of the body. Dogmatically, there exist several known regulators and modulators of CBF that include local metabolites and neurohormonal factors that can influence the function of the coronary circulation. In disease states such as diabetes and myocardial ischemia, these regulators are impaired or shifted such that CBF is reduced. Although functional considerations have been and continued to be well studied, more recent evidence builds upon established studies that collectively suggest that the relative roles of coronary structure, biomechanics, and the influence of cardiac biomechanics via extravascular compression may also play a significant role in dictating CBF. In this mini review, we discuss these regulators of CBF under normal and pathophysiological conditions and their potential influence on the control of CBF.

Aortic adventitial thickness as a marker of aortic atherosclerosis, vascular stiffness, and vessel remodeling in systemic lupus erythematosus

INTRODUCTION

There is limited human imaging data on the association of adventitial thickness (AT) with arterial disease. Systemic lupus erythematosus (SLE) is a prototypical disease model for studying markers of premature arterial disease.

OBJECTIVE

To determine if increased aortic AT is associated with aortic atherosclerosis [increased intima media thickness (IMT) or plaques], stiffness [increased pressure-strain elastic modulus (PSEM)], and vessel remodeling.

METHODS

In total, 70 SLE patients and 26 age- and sex-matched controls underwent transesophageal echocardiography (TEE). Two-dimensional guided M-mode images were obtained to assess AT, IMT, and plaques, and PSEM at the proximal, mid, and distal thoracic aorta. Images were interpreted by 3 observers unaware of the subjects' clinical data and each other's measurements. Abnormal aortic AT, IMT, and PSEM were defined as > 2SD above the overall mean values in controls and corresponded to > 1 mm, > 1 mm, and > 10.6 Pascal units, respectively. Plaques were defined as focal-protruding IMT > 50% of the surrounding vessel wall.

RESULTS

Abnormal aortic AT, atherosclerosis, and abnormal stiffness were more frequent in SLE patients than in controls (all p ≤ 0.02). In SLE patients, abnormal AT combined with atherosclerosis was associated with larger aortic end-diastolic diameters than in controls (p ≤ 0.05). In SLE patients, aortic AT was greater in patients with atherosclerosis and in those with abnormal stiffness than in patients without these abnormalities (all p ≤ 0.02). In patients with abnormal AT, the degree of aortic stiffness was similar to those with atherosclerosis (p = 0.22).

CONCLUSION

In patients with SLE, increased aortic AT is associated with aortic atherosclerosis, abnormal stiffness, and eccentric vessel remodeling. Key Points • In patients with SLE, abnormal aortic adventitial thickness is associated with aortic atherosclerosis, abnormal stiffness, and eccentric vessel remodeling. • In patients with SLE, aortic adventitial thickening may contribute to the extent of aortic atherosclerosis, abnormal aortic stiffness, and vessel remodeling. • To our knowledge, this is the first human imaging study to characterize the aortic adventitial layer and delineate its association with aortic disease.

Gemigliptin Inhibits Interleukin-1β-Induced Endothelial-Mesenchymal Transition via Canonical-Bone Morphogenetic Protein Pathway

BACKGROUND

Endothelial-to-mesenchymal transition (EndMT) contributes to inflammatory conditions inducing conversion of endothelial cells (ECs) into activated fibroblasts, promoting fibrotic diseases. Pro-inflammatory cytokine is the most potent inducer of EndMT. We investigated inhibition of interleukin-1β (IL-1β)-induced EndMT by gemigliptin, a dipeptidyl peptidase-IV inhibitor.

METHODS

We exposed human umbilical vein endothelial cells (HUVECs) to 10 ng/mL IL-1β/20 μM gemigliptin and analyzed the expression of endothelial, smooth muscle, mesenchymal, and osteoblastic markers, bone morphogenetic protein (BMP), Smad, and non-Smad signaling pathway proteins.

RESULTS

Morphological changes showed gemigliptin blocked IL-1β-induced EndMT, upregulated EC markers, and downregulated smooth muscle and mesenchymal markers. IL-1β activation of HUVECs is initiated by the BMP/Smad and non-smad BMP signaling pathways. Gemigliptin inhibited IL-1β induction of BMP2 and 7, activin receptor type IA, BMP receptor type IA, and BMP receptor type II. Reversal of IL-1β-mediated inhibition of BMP-induced Smad1/5/8, Smad2, and Smad3 phosphorylation by gemigliptin suggests involvement of the Smad pathway in gemigliptin action. In the non-Smad BMP pathway, gemigliptin treatment significantly increased the deactivation of extracellular regulated protein kinase (ERK), p38, and JNK by IL-1β. Gemigliptin treatment suppressed BMP-2-induced expression of key osteoblastic markers including osterix, runt-related transcription factor 2, and hepcidin during IL-1β-induced EndMT.

CONCLUSION

We demonstrated a novel protective mechanism of gemigliptin against fibrosis by suppressing IL-1β-induced EndMT.

Diabetes and calcification: The potential role of anti-diabetic drugs on vascular calcification regression

Vascular calcification (VC) has been well-established as an independent and strong predictor of cardiovascular diseases (CVD) as well as major cardiac adverse events (MACE). VC is associated with increased mortality in patients with CVD. Pathologically, VC is now believed to be a multi-directional active process ultimately resulting in ectopic calcium deposition in vascular beds. On the other hand, prevalence of diabetes mellitus (DM) is gradually increasing thus making the current population more prone to future CVD. Although the mechanisms involved in development and progression of VC in DM patients are not fully understood, a series of evidences demonstrated positive association between DM and VC. It has been highlighted that different cellular pathways are involved in this process. These intermediates such as tumor necrosis factor alpha (TNF-α), various interleukins (ILs) and different cell-signaling pathways are over-expressed in DM patients leading to development of VC. Thus, considering the burden and significance of VC it is of great importance to find a therapeutic approach to prevent or minimize the development of VC in DM patients. Over the past few years various anti diabetic drugs (ADDs) have been introduced and many of them showed desired glucose control. But no study demonstrated the effects of these medications on regression of VC. In this review, we will briefly discuss the current understanding on DM and VC and how commonly used ADDs modulate the development or progression of VC.

Reduced stiffness and augmented traction force in type 2 diabetic coronary microvascular smooth muscle

Type 2 diabetic (T2DM) coronary resistance microvessels (CRMs) undergo inward hypertrophic remodeling associated with reduced stiffness and reduced coronary blood flow in both mice and pig models. Since reduced stiffness does not appear to be due to functional changes in the extracellular matrix, this study tested the hypothesis that decreased CRM stiffness in T2DM is due to reduced vascular smooth muscle cell (VSMC) stiffness, which impacts the traction force generated by VSMCs. Atomic force microscopy (AFM) and traction force microscopy (TFM) were conducted on primary low-passage CRM VSMCs from normal Db/db and T2DM db/db mice in addition to low-passage normal and T2DM deidentified human coronary VSMCs. Elastic modulus was reduced in T2DM mouse and human coronary VSMCs compared with normal (mouse: Db/db 6.84 ± 0.34 kPa vs. db/db 4.70 ± 0.19 kPa, P < 0.0001; human: normal 3.59 ± 0.38 kPa vs. T2DM 2.61 ± 0.35 kPa, P = 0.05). Both mouse and human T2DM coronary microvascular VSMCs were less adhesive to fibronectin compared with normal. T2DM db/db coronary VSMCs generated enhanced traction force by TFM (control 692 ± 67 Pa vs. db/db 1,507 ± 207 Pa; P < 0.01). Immunoblot analysis showed that T2DM human coronary VSMCs expressed reduced β₁-integrin and elevated β₃-integrin (control 1.00 ± 0.06 vs. T2DM 0.62 ± 0.14, P < 0.05 and control 1.00 ± 0.49 vs. T2DM 3.39 ± 1.05, P = 0.06, respectively). These data show that T2DM coronary VSMCs are less stiff and less adhesive to fibronectin but are able to generate enhanced force, corroborating previously published computational findings that decreasing cellular stiffness increases the cells' ability to generate higher traction force.NEW & NOTEWORTHY We show here that a potential causative factor for reduced diabetic coronary microvascular stiffness is the direct reduction in coronary vascular smooth muscle cell stiffness. These cells were also able to generate enhanced traction force, validating previously published computational models. Collectively, these data show that smooth muscle cell stiffness can be a contributor to overall tissue stiffness in the coronary microcirculation, and this may be a novel area of interest for therapeutic targets.

Female sex and Western-style diet protect mouse resistance arteries during acute oxidative stress

A Western-style diet (WD; high in fat and carbohydrates) increases vascular oxidative stress. We hypothesized that vascular cells adapt to a WD by developing resilience to oxidative stress. Male and female C57BL/6J mice (4 wk of age) were fed a control diet (CD) or a WD for 16-20 wk. Superior epigastric arteries (SEAs; diameter, ~125 µm) were isolated and pressurized for study. Basal reactive oxygen species production was greatest in SEAs from males fed the WD. During exposure to H₂O₂ (200 μM, 50 min), propidium iodide staining identified nuclei of disrupted endothelial cells (ECs) and smooth muscle cells (SMCs). For mice fed the CD, death of SMCs (21%) and ECs (6%) was greater (P < 0.05) in SEAs from males than females (9% and 2%, respectively). WD consumption attenuated cell death most effectively in SEAs from males. With no difference at rest, H₂O₂ increased intracellular Ca²⁺ concentration ([Ca²⁺]_i) to the greatest extent in SEAs from males, as shown by fura 2 fluorescence. Selective disruption of the endothelium (luminal air bubble) increased [Ca²⁺]_i and SMC death during H₂O₂ exposure irrespective of sex; the WD reduced both responses most effectively in males. Nonselective transient receptor potential (TRP) channel inhibition (ruthenium red, 5 μM) attenuated the rise of [Ca²⁺]_i, as did selective inhibition of TRP vanilloid type 4 (TRPV4) channels (HC-067047, 1 μM), which also attenuated cell death. In contrast, inhibition of voltage-gated Ca²⁺ channels (diltiazem, 50 μM) was without effect. Thus, for resistance arteries during acute oxidative stress: 1) ECs are more resilient than (and can protect) SMCs, 2) vessels from females are inherently more resilient than those from males, and 3) a WD increases vascular resilience by diminishing TRPV4 channel-dependent Ca²⁺ entry.

Effect of Linagliptin on the Ratio of Apoptosis Regulators in the Model of Non-Alcoholic Fatty Liver Disease in db/db Mice

We studied the effects of dipeptidyl peptidase 4 (DPP4) inhibitor linagliptin on the expression of apoptosis regulator proteins Bcl-2 and Bad in the liver of db/db mice with genetically determined obesity and type 2 diabetes mellitus. The mice received daily linagliptin or saline (placebo) by gavage from week 10 to week 18 of life. In the liver of non-treated mice, the area positively stained for Bad was greater than the area of Bcl-2 expression, which created the conditions for apoptosis activation in liver at this age. Administration of linagliptin decreased Bad stained area and increased Bcl-2 stained area in the liver cells. At the same time, Bad stained area remained larger in treated mice than the area of Bcl-2 expression area, which attested to partial normalization of pro- and antiapoptotic protein balance.

DPP-4 inhibition enhanced renal tubular and myocardial GLP-1 receptor expression decreased in CKD with myocardial infarction

Background

Chronic kidney disease (CKD) is strongly associated with cardiovascular disease and is a significant risk factor for increased morbidity and mortality. In contrast, GLP-1 receptor (GLP-1R) activation has been shown to confer both renal and cardiovascular protection, though its relationship with CKD and CKD with myocardial ischemia/reperfusion (MI/R) remains poorly understood. Here, we investigated changes in renal and myocardial GLP-1R expression in the CKD rat model with MI/R.

Methods

Male Sprague Dawley rats with 5/6 nephrectomy were used as a rat model of CKD and CKD with MI/R. For myocardial ischemia, the left coronary artery was ligated and released for 30 min 1 week after 5/6 nephrectomy. Dipeptidyl-peptidase 4 (DPP-4) inhibitors were administered orally with linagliptin once daily for 8 weeks. Renal cortical and myocardial GLP-1R expression were measured via immunohistochemistry and western blot analysis.

Results

DPP-4 activity was increased in CKD. Western blot density of GLP-1R in renal cortex extracts revealed increased abundance 2 weeks after 5/6 nephrectomy, followed by a decrease at 8 weeks. In contrast, CKD and CKD with MI/R rats showed decreases in renal and cardiac expression of GLP-1R; these effects were attenuated in rats treated with linagliptin.

Conclusions

In CKD with MI/R, linagliptin attenuated renal injury and increased renal and myocardial GLP-1R expression. These data suggest that activation of renal and myocardial GLP-1R expression may provide both cardio- and renoprotective effects.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1243-z) contains supplementary material, which is available to authorized users.

Effect of vildagliptin versus glibenclamide on endothelial function and arterial stiffness in patients with type 2 diabetes and hypertension: a randomized controlled trial

AIMS

Several trials have reported that dipeptidyl peptidase-4 (DPP-4) inhibitors, used to treat type 2 diabetes (T2DM), improve endothelial function. The current study investigated the effects of vildagliptin, a DPP-4 inhibitor, compared to glibenclamide on endothelial function, arterial stiffness, and blood pressure in patients with T2DM and hypertension.

METHODS

Patients aged over 35 years with T2DM and hypertension, but without cardiovascular disease, were randomly allocated to treatment with vildagliptin (n = 25) or glibenclamide (n = 25). Both groups took metformin. Endothelial function was evaluated by peripheral artery tonometry (Endo-PAT 2000) to calculate the reactive hyperemia index (RHI) and arterial stiffness. Primary outcome was change in the RHI after 12 weeks of treatment. Twenty-four-hour non-invasive ambulatory blood pressure monitoring was performed using a Mobil-O-Graph^® 24-h PWA monitor. Arterial stiffness was assessed using the augmentation index corrected for 75 bpm (AIx75), pulse wave velocity (PWV) and central systolic blood pressure (cSBP).

RESULTS

There were no changes in the RHI in the vildagliptin group (before 2.35 ± 0.59; after 2.24 ± 0.60; p value = NS) or in the glibenclamide group (before 2.36 ± 0.52; after 2.34 ± 0.50; p value = NS), with no differences between groups (p value = NS). There was also no difference between vildagliptin and glibenclamide treatment in respect to AIx75 (p value = NS), cSBP (p value = NS) or PWV (p value = NS).

CONCLUSIONS

Vildagliptin and glibenclamide similarly do not change the endothelial function and arterial stiffness after 12 weeks of treatment in diabetic and hypertensive patients without cardiovascular disease. Thus, vildagliptin has a neutral effect on vascular function.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02145611, registered on 11 Jun 2013.

Improvement in Mortality and End-Stage Renal Disease in Patients With Type 2 Diabetes After Acute Kidney Injury Who Are Prescribed Dipeptidyl Peptidase-4 Inhibitors

OBJECTIVE

To focus on the potential beneficial effects of the pleiotropic effects of dipeptidyl peptidase-4 inhibitors (DPP4is) on attenuating progression of diabetic kidney disease in reducing the long-term effect of the acute kidney injury (AKI) to chronic kidney disease (CKD) transition.

PATIENTS AND METHODS

Data from the National Health Insurance Research Database from January 1, 1999, to July 31, 2011, were analyzed, and patients with diabetes weaning from dialysis-requiring AKI were identified. Cox proportional hazards models and inverse-weighted estimates of the probability of treatment were used to adjust for treatment selection bias. The outcomes were incident end-stage renal disease (ESRD) and mortality, major adverse cardiovascular events, and hospitalized heart failure.

RESULTS

Of a total of 6165 patients with diabetes weaning from dialysis-requiring AKI identified, 5635 (91.4%) patients were DPP4i nonusers and 530 (8.6%) patients were DPP4i users. Compared with DPP4i nonusers, DPP4i users had a lower risk of ESRD (hazard ratio, 0.81; 95% CI, 0.70-0.94; P=.04) and all-cause mortality (hazard ratio, 0.28; 95% CI, 0.23-0.34; P<.001) after adjustments for CKD, advanced CKD, and angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker use. In contrast, the risk of major adverse cardiovascular events and hospitalized heart failure did not differ significantly between groups.

CONCLUSION

Dipeptidyl peptidase-4 inhibitor users had a lower risk of ESRD and mortality than did nonusers among patients with diabetes after weaning from dialysis-requiring AKI. Therefore, a prospective study of AKI to CKD transitions after episodes of AKI is needed to optimally target DPP4i interventions.

Vascular protection of DPP-4 inhibitors in retinal endothelial cells in in vitro culture

People with diabetes are at high risk of developing diabetes-related eye disease, termed as diabetic retinopathy, due damage being caused to the blood vessels in the retina. An efficient medical treatment to reduce diabetic retinopathy can improve the quality of life for diabetes patients. In our study, we show that linagliptin, a commercially available DPP-4 inhibitor, plays a protective role in retinal vascular endothelial cells. The presence of linagliptin protects retinal endothelial cells against TNF-α-induced cytotoxicity and enhances their viability. Linagliptin treatment suppresses TNF-α-induced production of reactive oxygen species and improves mitochondrial membrane potential. Moreover, linagliptin suppresses TNF-α-induced production of pro-inflammatory and pro-adhesive vascular cytokines including IL-6, IL-8, ICAM-1, and VCAM-1. The presence of linagliptin in cell media can reduce the number of THP-1 cells that adhere to retina endothelial cells. Mechanistically, linagliptin potently suppresses TNF-α-induced accumulation of NF-κB nuclear protein p65 and activation of NF-κB promoter. Our data indicate that linagliptin is an anti-inflammatory diabetic agent, with the potential to be applied as a treatment for diabetic retinopathy.

Glycemic control by the SGLT2 inhibitor empagliflozin decreases aortic stiffness, renal resistivity index and kidney injury

Background

Arterial stiffness is emerging as an independent risk factor for the development of chronic kidney disease. The sodium glucose co-transporter 2 (SGLT2) inhibitors, which lower serum glucose by inhibiting SGLT2-mediated glucose reabsorption in renal proximal tubules, have shown promise in reducing arterial stiffness and the risk of cardiovascular and kidney disease in individuals with type 2 diabetes mellitus. Since hyperglycemia contributes to arterial stiffness, we hypothesized that the SGLT2 inhibitor empagliflozin (EMPA) would improve endothelial function, reduce aortic stiffness, and attenuate kidney disease by lowering hyperglycemia in type 2 diabetic female mice (db/db).

Materials/methods

Ten-week-old female wild-type control (C57BLKS/J) and db/db (BKS.Cg-Dock7m+/+Leprdb/J) mice were divided into three groups: lean untreated controls (CkC, n = 17), untreated db/db (DbC, n = 19) and EMPA-treated db/db mice (DbE, n = 19). EMPA was mixed with normal mouse chow at a concentration to deliver 10 mg kg⁻¹ day⁻¹, and fed for 5 weeks, initiated at 11 weeks of age.

Results

Compared to CkC, DbC showed increased glucose levels, blood pressure, aortic and endothelial cell stiffness, and impaired endothelium-dependent vasorelaxation. Furthermore, DbC exhibited impaired activation of endothelial nitric oxide synthase, increased renal resistivity and pulsatility indexes, enhanced renal expression of advanced glycation end products, and periarterial and tubulointerstitial fibrosis. EMPA promoted glycosuria and blunted these vascular and renal impairments, without affecting increases in blood pressure. In addition, expression of “reversion inducing cysteine rich protein with Kazal motifs” (RECK), an anti-fibrotic mediator, was significantly suppressed in DbC kidneys and partially restored by EMPA. Confirming the in vivo data, EMPA reversed high glucose-induced RECK suppression in human proximal tubule cells.

Conclusions

Empagliflozin ameliorates kidney injury in type 2 diabetic female mice by promoting glycosuria, and possibly by reducing systemic and renal artery stiffness, and reversing RECK suppression.

New insights into arterial stiffening: does sex matter?

This review discusses sexual dimorphism in arterial stiffening, disease pathology interactions, and the influence of sex on mechanisms and pathways. Arterial stiffness predicts cardiovascular mortality independent of blood pressure. Patients with increased arterial stiffness have a 48% higher risk for developing cardiovascular disease. Like other cardiovascular pathologies, arterial stiffness is sexually dimorphic. Young women have lower stiffness than aged-matched men, but this sex difference reverses during normal aging. Estrogen therapy does not attenuate progressive stiffening in postmenopausal women, indicating that currently prescribed drugs do not confer protection. Although remodeling of large arteries is a protective adaptation to higher wall stress, arterial stiffening increases afterload to the left ventricle and transmits higher pulsatile pressure to smaller arteries and target organs. Moreover, an increase in aortic stiffness may precede or exacerbate hypertension, particularly during aging. Additional studies are needed to elucidate the mechanisms by which females are protected from arterial stiffness to provide insight into its mechanisms and, ultimately, therapeutic targets for treating this pathology.

Effects of linagliptin on endothelial function and postprandial lipids in coronary artery disease patients with early diabetes: a randomized, placebo-controlled, double-blind trial

Background

Early glucose lowering intervention in subjects with type 2 diabetes mellitus was demonstrated to be beneficial in terms of micro- and macrovascular risk reduction. However, most of currently ongoing cardiovascular outcome trials are performed in subjects with manifest atherosclerosis and long-standing diabetes. Therefore, the aim of this study is to investigate the effects of the dipeptidylpeptidase-4 inhibitor linagliptin in subjects with coronary artery disease (CAD) but early type 2 diabetes mellitus (T2DM) on a set of cardiovascular surrogate measurements.

Methods

In this randomized, placebo-controlled, double-blind, single-center study, we included subjects with early diabetes (postchallenge diabetes (2 h glucose > 200 mg/dl) or T2DM treated with diet only or on a stable dose of metformin monotherapy and an HbA1c < 75 mmol/mol) and established CAD. Participants were randomized to receive either linagliptin (5 mg) once daily orally or placebo for 12 weeks. The primary outcome was the change in flow mediated dilatation (FMD). The secondary objective was to investigate the effect of linagliptin treatment on arginine bioavailability ratios [Global arginine bioavailability ratio (GABR) and arginine to ornithine ratio (AOR)]. Arginine, ornithine and citrulline were measured in serum samples with a conventional usual amino acid analysis technique, involving separation of amino acids by ion exchange chromatography followed by postcolumn continuous reaction with ninhydrin. GABR was calculated by l-arginine divided by the sum of (l-ornithine plus l-citrulline). The AOR was calculated by dividing l-arginine by l-ornithine levels. Group comparisons were calculated by using a two-sample t-test with Satterthwaite adjustment for unequal variances.

Results

We investigated 43 patients (21% female) with a mean age of 63.3 ± 8.2 years. FMD at baseline was 3.5 ± 3.1% in the linagliptin group vs. 4.0 ± 2.9% in the placebo group. The change in mean FMD in the linagliptin group was not significantly different compared to the change in the placebo group (0.43 ± 4.84% vs. − 0.45 ± 3.01%; p = 0.486). No significant improvements were seen in the arginine bioavailability ratios (GABR; p = 0.608 and AOR; p = 0.549).

Conclusion

Linagliptin treatment in subjects with CAD and early T2DM did not improve endothelial function or the arginine bioavailability ratios.

Trial registration ClinicalTrials.gov, NCT02350478 (https://clinicaltrials.gov/ct2/show/NCT02350478)

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0716-x) contains supplementary material, which is available to authorized users.

The role of dipeptidylpeptidase-4 inhibitors in management of cardiovascular disease in diabetes; focus on linagliptin

Multiple population based analyses have demonstrated a high incidence of cardiovascular disease (CVD) and cardiovascular (CV) mortality in subjects with T2DM that reduces life expectancy by as much as 15 years. Importantly, the CV system is particularly sensitive to the metabolic and immune derangements present in obese pre-diabetic and diabetic individuals; consequently, CV dysfunction is often the initial CV derangement to occur and promotes the progression to end organ/tissue damage in T2DM. Specifically, diabetic CVD can manifest as microvascular complications, such as nephropathy, retinopathy, and neuropathy, as well as, macrovascular impairments, including ischemic heart disease, peripheral vascular disease, and cerebrovascular disease. Despite some progress in prevention and treatment of CVD, mainly via blood pressure and dyslipidemia control strategies, the impact of metabolic disease on CV outcomes is still a major challenge and persists in proportion to the epidemics of obesity and diabetes. There is abundant pre-clinical and clinical evidence implicating the DPP-4-incretin axis in CVD. In this regard, linagliptin is a unique DPP-4 inhibitor with both CV and renal safety profiles. Moreover, it exerts beneficial CV effects beyond glycemic control and beyond class effects. Linagliptin is protective for both macrovascular and microvascular complications of diabetes in preclinical models, as well as clinical models. Given the role of endothelial-immune cell interactions as one of the key events in the initiation and progression of CVD, linagliptin modulates these cell–cell interactions by affecting two important pathways involving stimulation of NO signaling and potent inhibition of a key immunoregulatory molecule.

The role of renal dipeptidyl peptidase-4 in kidney disease: renal effects of dipeptidyl peptidase-4 inhibitors with a focus on linagliptin

Emerging evidence suggests that dipeptidyl peptidase-4 (DPP-4) inhibitors used to treat type 2 diabetes may have nephroprotective effects beyond the reduced renal risk conferred by glycemic control. DPP-4 is a ubiquitous protein with exopeptidase activity that exists in cell membrane-bound and soluble forms. The kidneys contain the highest levels of DPP-4, which is increased in diabetic nephropathy. DPP-4 inhibitors are a chemically heterogeneous class of drugs with important pharmacological differences. Of the globally marketed DPP-4 inhibitors, linagliptin is of particular interest for diabetic nephropathy as it is the only compound that is not predominantly excreted in the urine. Linagliptin is also the most potent DPP-4 inhibitor, has the highest affinity for this protein, and has the largest volume of distribution; these properties allow linagliptin to penetrate kidney tissue and tightly bind resident DPP-4. In animal models of kidney disease, linagliptin elicited multiple renoprotective effects, including reducing albuminuria, glomerulosclerosis, and tubulointerstitial fibrosis, independent of changes in glucagon-like peptide-1 (GLP-1) and glucose levels. At the molecular level, linagliptin prevented the pro-fibrotic endothelial-to-mesenchymal transition by disrupting the interaction between membrane-bound DPP-4 and integrin β1 that enhances signaling by transforming growth factor-β1 and vascular endothelial growth factor receptor-1. Linagliptin also increased stromal cell derived factor-1 levels, ameliorated endothelial dysfunction, and displayed unique antioxidant effects. Although the nephroprotective effects of linagliptin are yet to be translated to the clinical setting, the ongoing Cardiovascular and Renal Microvascular Outcome Study with Linagliptin in Patients with Type 2 Diabetes Mellitus (CARMELINA®) study will definitively assess the renal effects of this DPP-4 inhibitor. CARMELINA® is the only clinical trial of a DPP-4 inhibitor powered to evaluate kidney outcomes.

Linagliptin and cardiovascular outcomes in type 2 diabetes after acute coronary syndrome or acute ischemic stroke

Background

The cardiovascular safety and efficacy of linagliptin, a dipeptidyl peptidase-4 inhibitor, in patients with type 2 diabetes mellitus (T2DM) after acute coronary syndrome (ACS) or acute ischemic stroke (AIS) are unclear. The aim of our real-world cohort study was to evaluate the cardiovascular outcomes of linagliptin in patients with T2DM after ACS or AIS.

Methods

An open observational noncrossover retrospective cohort study was conducted between June 1, 2012 and December 31, 2013 utilizing Taiwan National Health Insurance Research Database. A total of 1203 patients with T2DM after ACS or AIS were selected as the study cohort. Cardiovascular safety and efficacy of linagliptin were evaluated by comparing outcomes of 401 subjects receiving linagliptin after ACS or AIS to 802 matched control subjects not receiving any incretin-based therapy after ACS or AIS. The primary composite outcome included cardiovascular death, non-fatal myocardial infarction and non-fatal ischemic stroke.

Results

The primary composite outcome after 15-month follow-up was 7% (28 patients) in the linagliptin group compared with 6.1% (49 patients) in the control group [hazard ratio (HR) 1.06; 95% confidence interval (CI) .66–1.68]. The linagliptin group also had similar risks of all-cause mortality, hospitalization for heart failure, percutaneous coronary intervention and coronary artery bypass grafting compared to the control group in terms of the secondary outcomes.

Conclusions

In T2DM patients after ACS or AIS, treatment with linagliptin was not associated with increased risks of cardiovascular death, non-fatal myocardial infarction, or non-fatal ischemic stroke.

DPP-4 inhibition with linagliptin ameliorates the progression of premature aging in klotho-/- mice

BACKGROUND

The potential of anti-aging effect of DPP-4 inhibitors is unknown. This study was performed to determine whether linagliptin, a DPP-4 inhibitor, could protect against premature aging in klotho-/- mice.

METHODS

Klotho-/- mice exhibit multiple phenotypes resembling human premature aging, including extremely shortened life span, cognitive impairment, hippocampal neurodegeneration, hair loss, muscle atrophy, hypoglycemia, etc. To investigate the effect of linagliptin on these aging-related phenotypes, male klotho-/- mice were divided into two groups: (1) control group fed the standard diet, and (2) linagliptin group fed the standard diet containing linagliptin. Treatment with linagliptin was performed for 4 weeks. The effect of linagliptin on the above mentioned aging-related phenotypes was examined.

RESULTS

Body weight of klotho-/- mice was greater in linagliptin group than in control group (11.1 ± 0.3 vs 9.9 ± 0.3 g; P < 0.01), which was associated with greater gastrocnemius muscle weight (P < 0.01) and greater kidney weight (P < 0.05) in linagliptin group. Thus, linagliptin significantly prevented body weight loss in klotho-/- mice. Survival rate of klotho-/- mice was greater in linagliptin group (93%) compared to control group (67%), although the difference did not reach statistical significance (P = 0.08). None of linagliptin-treated klotho-/- mice had alopecia during the treatment (P < 0.05 vs control klotho-/- mice). Latency of klotho-/- mice in passive avoidance test was larger in linagliptin group than in control group (P < 0.05), indicating the amelioration of cognitive impairment by linagliptin. Cerebral blood flow of klotho-/- mice was larger in linagliptin group than in control group (P < 0.01), being associated with greater cerebral phospho-eNOS levels (P < 0.05) in linagliptin group. Neuronal cell number in hippocampal CA1 region was greater in linagliptin group than in control group (P < 0.05). Linagliptin group had greater cerebral phospho-Akt (P < 0.05) and phospho-CREB (P < 0.05) than control group. Thus, linagliptin ameliorated brain aging in klotho-/- mice. The degree of hypoglycemia in klotho-/- mice was less in linagliptin group than in control group, as estimated by the findings of OGTT.

CONCLUSIONS

Out work provided the evidence that DPP-4 inhibition with linagliptin slowed the progression of premature aging in klotho-/- mice, and provided a novel insight into the potential role of DPP-4 in the mechanism of premature aging.

AFM-based detection of glycocalyx degradation and endothelial stiffening in the db/db mouse model of diabetes

Degradation of the glycocalyx and stiffening of endothelium are important pathophysiological components of endothelial dysfunction. However, to our knowledge, these events have not been investigated in tandem in experimental diabetes. Here, the mechanical properties of the glycocalyx and endothelium in ex vivo mouse aorta were determined simultaneously in indentation experiments with an atomic force microscope (AFM) for diabetic db/db and control db/+ mice at ages of 11–19 weeks. To analyze highly heterogeneous aorta samples, we developed a tailored classification procedure of indentation data based on a bi-layer brush model supplemented with Hertz model for quantification of nanomechanics of endothelial regions with and without the glycocalyx surface. In db/db mice, marked endothelial stiffening and reduced glycocalyx coverage were present already in 11-week-old mice and persisted in older animals. In contrast, reduction of the effective glycocalyx length was progressive and was most pronounced in 19-week-old db/db mice. The reduction of the glycocalyx length correlated with an increasing level of glycated haemoglobin and decreased endothelial NO production. In conclusion, AFM nanoindentation analysis revealed that stiffening of endothelial cells and diminished glycocalyx coverage occurred in early diabetes and were followed by the reduction of the glycocalyx length that correlated with diabetes progression.

Vildagliptin ameliorates pulmonary fibrosis in lipopolysaccharide-induced lung injury by inhibiting endothelial-to-mesenchymal transition

BACKGROUND

Pulmonary fibrosis is a late manifestation of acute respiratory distress syndrome (ARDS). Sepsis is a major cause of ARDS, and its pathogenesis includes endotoxin-induced vascular injury. Recently, endothelial-to-mesenchymal transition (EndMT) was shown to play an important role in pulmonary fibrosis. On the other hand, dipeptidyl peptidase (DPP)-4 was reported to improve vascular dysfunction in an experimental sepsis model, although whether DPP-4 affects EndMT and fibrosis initiation during lipopolysaccharide (LPS)-induced lung injury is unclear. The aim of this study was to investigate the anti-EndMT effects of the DPP-4 inhibitor vildagliptin in pulmonary fibrosis after systemic endotoxemic injury.

METHODS

A septic lung injury model was established by intraperitoneal injection of lipopolysaccharide (LPS) in eight-week-old male mice (5 mg/kg for five consecutive days). The mice were then treated with vehicle or vildagliptin (intraperitoneally, 10 mg/kg, once daily for 14 consecutive days from 1 day before the first administration of LPS.). Flow cytometry, immunohistochemical staining, and quantitative polymerase chain reaction (qPCR) analysis was used to assess cell dynamics and EndMT function in lung samples from the mice.

RESULTS

Lung tissue samples from treated mice revealed obvious inflammatory reactions and typical interstitial fibrosis 2 days and 28 days after LPS challenge. Quantitative flow cytometric analysis showed that the number of pulmonary vascular endothelial cells (PVECs) expressing alpha-smooth muscle actin (α-SMA) or S100 calcium-binding protein A4 (S100A4) increased 28 days after LPS challenge. Similar increases in expression were also confirmed by qPCR of mRNA from isolated PVECs. EndMT cells had higher proliferative activity and migration activity than mesenchymal cells. All of these changes were alleviated by intraperitoneal injection of vildagliptin. Interestingly, vildagliptin and linagliptin significantly attenuated EndMT in the absence of immune cells or GLP-1.

CONCLUSIONS

Inhibiting DPP-4 signaling by vildagliptin could ameliorate pulmonary fibrosis by downregulating EndMT in systemic LPS-induced lung injury.

The effects of vildagliptin compared with metformin on vascular endothelial function and metabolic parameters: a randomized, controlled trial (Sapporo Athero-Incretin Study 3)

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) inhibitors may have protective effects in the early stage of atherosclerosis in patients with type 2 diabetes, although similar effects in advanced atherosclerosis were not shown in recent randomized placebo-controlled studies. Therefore, we investigated the efficacy of DPP-4 inhibitor on endothelial function and glycemic metabolism compared with high-dose metformin.

METHODS

In this multicenter, open-labeled, prospective, randomized, parallel-group comparison study, patients with type 2 diabetes treated with low-dose metformin (500-750 mg/day) were enrolled and randomly assigned to a vildagliptin, a DPP-4 inhibitor, add-on group (Vilda) or a double dose of metformin group (high Met) for 12 weeks. Flow-mediated dilation (FMD) and serum metabolic markers were assessed before and after treatment. In addition, glycemic control and metabolic parameters were also assessed.

RESULTS

Ninety-seven subjects (aged 58.7 ± 11.0 years; body mass index, 25.9 ± 4.4 kg/m2; HbA1c, 7.3 ± 0.5%; FMD, 5.8 ± 2.6%) were enrolled. Eight subjects dropped out by the end of the study. There were no significant differences between the two groups in baseline characteristics. After 12 weeks, HbA1c was significantly improved in the Vilda group compared with the high Met group (- 0.80 ± 0.38% vs. - 0.40 ± 0.47%, respectively; p < 0.01). However, there were no significant differences in FMD (- 0.51 [- 1.08-0.06]% vs. - 0.58 [- 1.20-0.04]%). Although the apolipoprotein B/apolipoprotein A1 ratio was significantly reduced in the Vilda group compared with baseline (0.66-0.62; p < 0.01), the change did not differ significantly between the two groups (- 0.04 vs. 0.00; p = 0.27). Adiponectin levels were significantly increased in the Vilda group compared with the high Met group (0.75 μg/mL vs. 0.01 μg/mL; p < 0.01).

CONCLUSIONS

Regardless of glycemic improvement, combination therapy of vildagliptin and metformin did not affect endothelial function but may exert favorable effects on adipokine levels and lipid profile in patients with type 2 diabetes without advanced atherosclerosis.

Effect of linagliptin on pulse wave velocity in early type 2 diabetes: A randomized, double-blind, controlled 26-week trial (RELEASE)

AIMS

To evaluate the effects of the dipeptidyl peptidase-4 (DPP-4) inhibitor linagliptin on aortic pulse wave velocity (PWV) as a surrogate marker of arterial stiffness and early atherosclerosis in people with early type 2 diabetes.

METHODS

A total of 45 people with type 2 diabetes (median [interquartile range] age 63 [54-66] years, 61% men, mean ± standard deviation glycated haemoglobin [HbA1c] 6.3% ± 0.4% [45 ± 4.6 mmol/mol]), without cardiovascular disease and naïve to antidiabetic treatment, were randomized (1:1) to treatment with linagliptin 5 mg once daily or placebo for 26 weeks in a double-blind fashion. PWV was assessed at baseline, 4 and 26 weeks of treatment, and again at 30, 4 weeks after treatment. The primary endpoint was between-group difference in PWV (corrected for systolic blood pressure [SBP]) at week 26. Secondary endpoints included differences in central SBP and augmentation index (AIx).

RESULTS

Compared with placebo, 26 weeks of linagliptin decreased PWV by an average of 0.91 m/s (95% confidence interval -1.76 to -0.06; P = .035). PWV returned to baseline after 4 weeks washout. Differences in central SBP and AIx were not different between linagliptin and placebo. Linagliptin decreased HbA1c (-0.4%; P < .001), fasting plasma glucose (-0.7 mmol/L; P = .002) and triglycerides (-0.49 mmol/L; P = .019) as compared with placebo. The changes in body weight, cholesterol and high-sensitivity C-reactive protein did not differ between groups.

CONCLUSIONS

Linagliptin decreased aortic PWV in people with early-stage type 2 diabetes as compared with placebo after 26 weeks of treatment. These results suggest that linagliptin has a favourable effect on arterial stiffness.

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.

The regulatory role of DPP4 in atherosclerotic disease

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

Dipeptidyl peptidase-4 (DPP-4) inhibition with linagliptin reduces western diet-induced myocardial TRAF3IP2 expression, inflammation and fibrosis in female mice

Background

Diastolic dysfunction (DD), a hallmark of obesity and primary defect in heart failure with preserved ejection fraction, is a predictor of future cardiovascular events. We previously reported that linagliptin, a dipeptidyl peptidase-4 inhibitor, improved DD in Zucker Obese rats, a genetic model of obesity and hypertension. Here we investigated the cardioprotective effects of linagliptin on development of DD in western diet (WD)-fed mice, a clinically relevant model of overnutrition and activation of the renin-angiotensin-aldosterone system.

Methods

Female C56Bl/6 J mice were fed an obesogenic WD high in fat and simple sugars, and supplemented or not with linagliptin for 16 weeks.

Results

WD induced oxidative stress, inflammation, upregulation of Angiotensin II type 1 receptor and mineralocorticoid receptor (MR) expression, interstitial fibrosis, ultrastructural abnormalities and DD. Linagliptin inhibited cardiac DPP-4 activity and prevented molecular impairments and associated functional and structural abnormalities. Further, WD upregulated the expression of TRAF3IP2, a cytoplasmic adapter molecule and a regulator of multiple inflammatory mediators. Linagliptin inhibited its expression, activation of its downstream signaling intermediates NF-κB, AP-1 and p38-MAPK, and induction of multiple inflammatory mediators and growth factors that are known to contribute to development and progression of hypertrophy, fibrosis and contractile dysfunction. Linagliptin also inhibited WD-induced collagens I and III expression. Supporting these in vivo observations, linagliptin inhibited aldosterone-mediated MR-dependent oxidative stress, upregulation of TRAF3IP2, proinflammatory cytokine, and growth factor expression, and collagen induction in cultured primary cardiac fibroblasts. More importantly, linagliptin inhibited aldosterone-induced fibroblast activation and migration.

Conclusions

Together, these in vivo and in vitro results suggest that inhibition of DPP-4 activity by linagliptin reverses WD-induced DD, possibly by targeting TRAF3IP2 expression and its downstream inflammatory signaling.