Sitagliptin ameliorates lipid profile changes and endothelium dysfunction induced by atherogenic diet in rabbits

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

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

Sitagliptin Reduces Endothelial Dysfunction and Apoptosis Induced by High-Fat Diet and Palmitate in Thoracic Aortas and Endothelial Cells via ROS-ER Stress-CHOP Pathway

Macrovascular disease is tightly associated with obesity-induced metabolic syndrome. Sitagliptin (SIT), an orally stable selective inhibitor of Dipeptidyl peptidase-4 (DPP-4), has protective effects on endothelium. However, the mechanisms enabling SIT to exhibit resistance to diet-induced obesity (DIO) related with reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress in the aorta and endothelial cells have not been reported yet. Therefore, the present study was conducted to determine if SIT exerts protective role in the thoracic aortas isolated from the high-fat diet (HFD)-treated rats and palmitate (PA)-treated endothelial cells by alleviating ROS and ER stress. Male Sprague Dawley rats were randomly divided into standard chow diet (SCD), HFD and HFD plus sitagliptin administration (HFD + SIT) groups. The rats of latter two groups were given HFD fodder for 12 weeks, then the HFD + SIT rats were treated with SIT (10 mg/kg/d) by intragastric administration for another 8 weeks. The body mass, vascular tension, serum oxidative stress indices and inflammatory parameters, pathological changes, protein expression of endothelial nitric oxide synthase (eNOS), the genes associated with ER stress and apoptosis in the thoracic aorta were measured. Furthermore, cell proliferation, ROS and the protein expression associated with ER stress (especially CHOP) and apoptosis were assessed in human umbilical vein endothelial cells (HUVECs) incubated with SIT and PA. Compared to the SCD rats, the HFD rats had higher serum lipid levels, decreased vascular tension, increased inflammation, oxidative and ER stress, and apoptosis of endothelial cells. PA promoted ROS generation, ER stress and apoptosis, inhibited cell proliferation in HUVECs. SIT treatment obviously ameliorated apoptosis via alleviating ROS and ER stress in the thoracic aortas isolated from HFD-fed rats and PA-treated HUVECs. The results suggest that SIT improved endothelial function via promoting cell proliferation and alleviating ROS-ER stress-CHOP pathway both in vivo and in vitro.

Sitagliptin Accelerates Endothelial Regeneration after Vascular Injury Independent from GLP1 Receptor Signaling

INTRODUCTION

DPP4 inhibitors (gliptins) are commonly used antidiabetic drugs for the treatment of type 2 diabetes. Gliptins also act in a glucose-independent manner and show vasoregenerative effects. We have shown that gliptins can remarkably accelerate vascular healing after vascular injury. However, the underlying mechanisms remain unclear. Here, we examined potential signaling pathways linking gliptins to enhanced endothelial regeneration.

METHODS AND RESULTS

We used wild-type and GLP1 receptor knockout (Glp1r-/-) mice to investigate the underlying mechanisms of gliptin-induced reendothelialization. The prototype DPP4 inhibitor sitagliptin accelerated endothelial healing in both animal models. Improved endothelial growth was associated with gliptin-mediated progenitor cell recruitment into the diseased vascular wall via the SDF1-CXCR4 axis independent of GLP1R-dependent signaling pathways. Furthermore, SDF1 showed direct proproliferative effects on endothelial cells. Excessive neointimal formation was not observed in gliptin- or placebo-treated Glp1r-/- mice.

CONCLUSION

We identified the SDF1-CXCR4 axis as a crucial signaling pathway for endothelial regeneration after acute vascular injury. Furthermore, SDF1 can directly increase endothelial cell proliferation. Gliptin-mediated potentiation of endothelial regeneration was preserved in Glp1r-/- animals. Thus, gliptin-mediated endothelial regeneration proceeds through SDF-1/CXCR4 in a GLP1R-independent manner after acute vascular injury.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL TRIAL REGISTRATION

UMIN000019951.

Sitagliptin Attenuates Endothelial Dysfunction of Zucker Diabetic Fatty Rats: Implication of the Antiperoxynitrite and Autophagy

Although the contributions of sitagliptin to endothelial function in diabetes mellitus were previously reported, the potential mechanisms still remain undefined. Our research was intended to explore the underlying mechanisms of protective effects of sitagliptin treatment on endothelial dysfunction in Zucker diabetic fatty (ZDF) rats. Male lean nondiabetic Zucker rats were used as control and male obese ZDF rats were randomly divided into ZDF and ZDF + sitagliptin groups. The significant decrease in endothelium-dependent relaxation induced by acetylcholine was observed in mesenteric arteries and thoracic aorta rings of ZDF rats. The administration of sitagliptin restored the vascular function effectively. The morphology study showed severe endothelial injuries in thoracic aortas of ZDF rats, and sitagliptin treatment attenuated these changes. The increased malondialdehyde levels and decreased superoxide dismutase activities in serum of ZDF rats were reversed by sitagliptin treatment. Sitagliptin also increased the expression of endothelial nitric oxide synthase and microtubule-associated protein 1 light chain 3 (LC3) and decreased the expression of inducible nitric oxide synthase, 3-nitrotyrosine, and p62 in ZDF rats. After giving Fe (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride porphyrin pentachloride (FeTMPyP, a peroxynitrite [ONOO^-] scavenger) or sitagliptin to high-glucose (30 mmol/L, 48 hours) cultured human umbilical vein endothelial cells (HUVECs), the increased levels of Beclin-1 and lysosome-associated membrane protein type 2 were detected. Both FeTMPyP and sitagliptin also significantly increased the number of mRFP-GFP-LC3 dots per cell, suggesting that autophagic flux was increased in HUVECs. Our study indicated that sitagliptin treatment can improve the endothelium-dependent relaxation and attenuate the endothelial impairment of ZDF rats. The protective effects of sitagliptin are possibly related to antiperoxynitrite and promoting autophagy.

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

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

Effect of Metformin and Sitagliptin on Doxorubicin-Induced Cardiotoxicity in Rats: Impact of Oxidative Stress, Inflammation, and Apoptosis

Doxorubicin (DOX) is a widely used antineoplastic drug whose efficacy is limited by its cardiotoxicity. The aim of this study was to investigate the possible protective role of the antidiabetic drugs metformin (250 mg/kg dissolved in DW p.o. for seven days) and sitagliptin (10 mg/kg dissolved in DW p.o. for seven days) in a model of DOX-induced (single dose 15 mg/kg i.p. at the fifth day) cardiotoxicity in rats. Results of our study revealed that pretreatment with metformin or sitagliptin produced significant (P < 0.05) cardiac protection manifested by a significant decrease in serum levels of LDH and CK-MB enzymes and cardiac MDA and total nitrites and nitrates levels, a significant increase in cardiac SOD activity, and remarkable improvement in the histopathological features as well as a significant reduction in the immunohistochemical expression of COX-2, iNOS, and caspase-3 enzymes as compared to DOX group. These results may suggest using metformin and/or sitagliptin as preferable drugs for diabetic patients suffering from cancer and receiving DOX in their chemotherapy regimen.

Inhibition of airway inflammation and remodeling by sitagliptin in murine chronic asthma

In this study the role of sitagliptin, dipeptidyl peptidase inhibitor, DPP-4, and dexamethasone in ameliorating inflammation and remodeling of chronic asthma in a mouse model were investigated. Mice sensitized to ovalbumin were chronically challenged with aerosolized antigen for 3days a week continued for 8weeks. During this period animals were treated with sitagliptin or dexamethasone daily. Assessment of inflammatory cell, oxidative markers, total nitrate/nitrite (NOx), interleukin (IL)-13, transforming growth factor-beta1 (TGF-β1) in bronchoalveolar lavage (BAL) and/or lung tissue were done. Also histopathological and immuno-histochemical analysis for lung was carried out. Compared with vehicle alone, treatment with sitagliptin or dexamethasone significantly reduced accumulation of eosinophils and chronic inflammatory cells, subepithelial collagenization, and thickening of the airway epithelium. Also both drug reduced goblet cell hyperplasia, oxidative stress, TGF-β1, IL-13 and epithelial cytoplasmic immunoreactivity for nuclear factor κ-B (NFκ-B). These data indicate that sitagliptin like dexamethasone may play a beneficial role reducing airway inflammation and remodeling in chronic murine model of asthma.