Sitagliptin protects rat kidneys from acute ischemia-reperfusion injury via upregulation of GLP-1 and GLP-1 receptors

Synergic effect of combined xenogeneic mesenchymal stem cells and ceftriaxone on acute septic arthritis

BACKGROUND

This study tested the hypothesis that combined ceftriaxone (Cef) and human umbilical cord-derived mesenchymal stem cells (HUCDMSCs) was better than either therapy for alleviating acute septic arthritis (ASA).

METHODS AND RESULTS

Adult-male C57BL/6 mice were categorized into control group (Clt), group A (ASA only), group B [ASA + Cef (5 mg/kg, IM per day, at days 2 to 16 after ASA induction)], group C [ASA + HUCDMSCs (5 × 105 per mice at days 2, 3, 4 after ASA induction)], and group D (ASA + Cef + HUCDMSCs). Animals were euthanized by day 28. The result demonstrated that the body weight was significantly lower, whereas the ratio of kidney or spleen weight to WB, circulatory WBC count, bacterial colony-formation-unit from circulatory/kidney extraction were significantly higher in group A than in other groups (all P < .001). The proinflammatory cytokines (IL-6/TNF-α) of knee joint fluid were lowest in Clt and significantly and progressively reduced from groups A to D, whereas the circulatory levels of these 2 parameters at the time points of days 3/7/28 exhibited an identical pattern as knee joint fluid among the groups (all P-value < .0001). The scores of vertebral-bone destructions/inflamed synovium were lowest in Clt, highest in group A, significantly higher in group C than in groups B/D, and significantly higher in group C than in group D (all P < .0001).

CONCLUSION

Combined antibiotics and Cef and HUCDMSCs was superior to just one therapy for suppressing circulatory and tissue levels of inflammation and knee joint destruction in ASA.

Sitagliptin alleviates renal steatosis and endoplasmic reticulum stress in high fat diet-induced obese rats by targeting SREBP-1/CD36 signaling pathway

High fat diet (HFD) consumption can cause dysregulation of glucose and lipid metabolism, coupled with increased ectopic lipid deposition in renal tissue leading to steatosis and dysfunction. Sitagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor clinically used for type II diabetes therapy; however its effect on renal steatosis in obese state is still uncertain. Herein, obesity was induced by feeding male Wistar rats HFD for 18 weeks, thereafter received either drug vehicle, or sitagliptin (10 mg/kg, PO) along with HFD for further 6 weeks and compared with age-matched rats receiving normal chow diet (NCD). After 24 weeks, serum and kidneys were collected for histological and biochemical assessments. Compared to NCD-fed group, HFD-fed rats displayed marked weight gain, increased fat mass, insulin resistance, dyslipidemia, impaired kidney functions and renal histological alterations. Sitagliptin effectively ameliorated obesity and related metabolic perturbations and improved kidney architecture and function. There were increased levels of triglycerides and cluster of differentiation 36 (CD36) in kidneys of obese rats, that were lowered by sitagliptin therapy. Sitagliptin significantly repressed the expression of lipogenesis genes, while up-regulated genes involved in mitochondrial biogenesis and fatty acid oxidation in kidneys of HFD-fed rats. Sitagliptin was found to induce down-regulation of endoplasmic reticulum (ER) stress and apoptotic markers in kidneys of obese rats. These findings together may emphasize a novel concept that sitagliptin can be an effective therapeutic approach for halting obesity-related renal steatosis and CKD.

The benefits of oral glucose-lowering agents: GLP-1 receptor agonists, DPP-4 and SGLT-2 inhibitors on myocardial ischaemia/reperfusion injury

Myocardial infarction (MI) is a life-threatening cardiovascular disease that, on average, results in 8.5 million deaths worldwide each year. Timely revascularization of occluded vessels is a critical method of myocardial salvage. However, reperfusion paradoxically leads to the worsening of myocardial damage known as myocardial ischaemia/reperfusion injury (MI/RI). Therefore, reducing the size of myocardial infarction after reperfusion is critical and remains an important therapeutic goal. The susceptibility of the myocardium to MI/RI may be increased by diabetes. Currently, some traditional antidiabetic agents such as metformin reduce MI/RI by decreasing inflammation, inhibiting oxidative stress, and improving vascular endothelial function. This appears to be a new direction for the treatment of MI/RI. Recent cardiovascular outcome trials have shown that several oral antidiabetic agents, including glucagon-like peptide-1 receptor agonists (GLP-1RAs), dipeptidyl peptidase-4 inhibitors (DPP-4is), and sodium-glucose-linked transporter-2 inhibitors (SGLT-2is), not only have good antidiabetic effects but also have a protective effect on myocardial protection. This article aims to discuss the mechanisms and effects of oral antidiabetic agents, including GLP-1RAs, DPP-4is, and SGLT-2is, on MI/RI to facilitate their clinical application.

Adverse cardiac events of hypercholesterolemia are enhanced by sitagliptin in sprague dawley rats

BACKGROUND

Cardiovascular disease (CVD) affects millions worldwide and is the leading cause of death among non-communicable diseases. Western diets typically comprise of meat and dairy products, both of which are rich in cholesterol (Cho) and methionine (Met), two well-known compounds with atherogenic capabilities. Despite their individual effects, literature on a dietary combination of the two in the context of CVD are limited. Therefore, studies on the combined effects of Cho and Met were carried out using male Sprague Dawley rats. An additional interest was to investigate the cardioprotective potential of sitagliptin, an anti-type 2 diabetic drug. We hypothesized that feeding a dietary combination of Cho and Met would result in adverse cardiac effects and would be attenuated upon administration of sitagliptin.

METHODS

Adult male Sprague-Dawley rats were fed either a control (Con), high Met (1.5%), high Cho (2.0%), or high Met (1.5%) + high Cho (2.0%) diet for 35 days. They were orally gavaged with an aqueous preparation of sitagliptin (100 mg/kg/d) or vehicle (water) from day 10 through 35. On day 36, rats were euthanized, and tissues were collected for analysis.

RESULTS

Histopathological evaluation revealed a reduction in myocardial striations and increased collagen deposition in hypercholesterolemia (HChol), responses that became exacerbated upon sitagliptin administration. Cardiac pro-inflammatory and pro-fibrotic responses were adversely impacted in similar fashion. The addition of Met to Cho (MC) attenuated all adverse structural and biochemical responses, with or without sitagliptin.

CONCLUSIONS

Adverse cardiac outcomes in HChol were enhanced by the administration of sitagliptin, and such effects were alleviated by Met. Our findings could be significant for understanding or revisiting the risk-benefit evaluation of sitagliptin in type 2 diabetics, and especially those who are known to consume atherogenic diets.

Cyclosporine-induced kidney damage was halted by sitagliptin and hesperidin via increasing Nrf2 and suppressing TNF-α, NF-κB, and Bax

Cyclosporine A (CsA) is employed for organ transplantation and autoimmune disorders. Nephrotoxicity is a serious side effect that hampers the therapeutic use of CsA. Hesperidin and sitagliptin were investigated for their antioxidant, anti-inflammatory, and tissue-protective properties. We aimed to investigate and compare the possible nephroprotective effects of hesperidin and sitagliptin. Male Wistar rats were utilized for induction of CsA nephrotoxicity (20 mg/kg/day, intraperitoneally for 7 days). Animals were treated with sitagliptin (10 mg/kg/day, orally for 14 days) or hesperidin (200 mg/kg/day, orally for 14 days). Blood urea, serum creatinine, albumin, cystatin-C (CYS-C), myeloperoxidase (MPO), and glucose were measured. The renal malondialdehyde (MDA), glutathione (GSH), catalase, and SOD were estimated. Renal TNF-α protein expression was evaluated. Histopathological examination and immunostaining study of Bax, Nrf-2, and NF-κB were performed. Sitagliptin or hesperidin attenuated CsA-mediated elevations of blood urea, serum creatinine, CYS-C, glucose, renal MDA, and MPO, and preserved the serum albumin, renal catalase, SOD, and GSH. They reduced the expressions of TNF-α, Bax, NF-κB, and pathological kidney damage. Nrf2 expression in the kidney was raised. Hesperidin or sitagliptin could protect the kidney against CsA through the mitigation of oxidative stress, apoptosis, and inflammation. Sitagliptin proved to be more beneficial than hesperidin.

Adverse Cardiac Events of Hypercholesterolemia Are Enhanced by Sitagliptin Administration in Sprague Dawley Rats

Background

Cardiovascular disease (CVD) affects millions worldwide and is the leading cause of death among non-communicable diseases. Western diets typically comprise of meat and dairy products, both of which are rich in cholesterol (Cho) and methionine (Met), two well-known compounds with atherogenic capabilities. Despite their individual effects, literature on a dietary combination of the two in the context of CVD are limited. An additional interest was to investigate the cardioprotective potential of sitagliptin, an anti-type 2 diabetic drug. Thus, we hypothesized that atherogenic feeding would result in adverse cardiac effects and would attenuate upon sitagliptin administration.

Methods

Six-week-old adult male Sprague-Dawley rats were fed either a control (Con), high Met (1.5%), high Cho (2.0%), or high Met (1.5%) + high Cho (2.0%) diet for 35 days. They were orally gavaged with vehicle (water) or sitagliptin (100 mg/kg/d) from day 10 through 35. On day 36, rats were euthanized, and tissues were collected for analysis.

Results

Histopathological evaluation revealed a reduction in myocardial striations and increased collagen deposition in hypercholesterolemia (HChol), responses that became exacerbated upon sitagliptin administration. Cardiac pro-inflammatory and pro-fibrotic responses were adversely impacted in similar fashion. The addition of Met to Cho (MC) attenuated all adverse structural and biochemical responses, with or without sitagliptin.

Conclusion

Adverse cardiac outcomes in HChol were enhanced with sitagliptin administration and such effects were alleviated by Met. Our findings could be significant for understanding the risk-benefit of sitagliptin in type 2 diabetics who are known to consume atherogenic diets.

Dipeptidyl peptidase 4 inhibitor reduces tumor-associated macrophages and enhances anti-PD-L1-mediated tumor suppression in non-small cell lung cancer

PURPOSE

The efficacy of immune checkpoint inhibitors such as programmed cell death ligand 1 (PD-L1) antibodies in non-small cell lung cancer (NSCLC) is limited, and combined use with other therapies is recommended. Dipeptidyl peptidase 4 (DPP4) inhibitors, a class of small molecule inhibitors, are highly effective for treating type 2 diabetes. Emerging evidence implicates DPP4 inhibitors as immunomodulators that modify aspects of innate and adaptive immunity. We evaluated the combination of a DPP4 inhibitor (anagliptin) and PD-L1 blockade in an NSCLC mouse model.

METHODS

The effect of the combination of anti-PD-L1 and anagliptin was evaluated in subcutaneous mouse models of NSCLC. Tumor-infiltrating immune cells were analyzed by flow cytometry. Bone marrow-derived monocytes of C57BL/6 mice were isolated in vitro to examine the underlying mechanism of anagliptin on the differentiation and polarization of macrophage.

RESULTS

Anagliptin dramatically improved the efficacy of PD-L1 antibody monotherapy by inhibiting macrophage formation and M2 polarization in the tumor microenvironment. Mechanistically, anagliptin suppressed the production of reactive oxygen species in bone marrow monocytes by inhibiting NOX1 and NOX2 expression induced by macrophage colony-stimulating factor, reduced late ERK signaling pathway activation, and inhibited monocyte-macrophage differentiation. However, the inhibitory effect was reactivated by lipopolysaccharide and interferon-gamma interacting with corresponding receptors during M1 macrophage polarization, but not M2.

CONCLUSIONS

Anagliptin can enhance PD-L1 blockade efficacy in NSCLC by inhibiting macrophage differentiation and M2 macrophage polarization, and combination therapy may be a promising strategy for treating PD-L1 blockade therapy-resistant patients with NSCLC.

Enteroendocrine cells and gut hormones as potential targets in the crossroad of the gut-kidney axis communication

Recent studies suggest that disruptions in intestinal homeostasis, such as changes in gut microbiota composition, infection, and inflammatory-related gut diseases, can be associated with kidney diseases. For instance, genomic investigations highlight how susceptibility genes linked to IgA nephropathy are also correlated with the risk of inflammatory bowel disease. Conversely, investigations demonstrate that the use of short-chain fatty acids, produced through fermentation by intestinal bacteria, protects kidney function in models of acute and chronic kidney diseases. Thus, the dialogue between the gut and kidney seems to be crucial in maintaining their proper function, although the factors governing this crosstalk are still emerging as the field evolves. In recent years, a series of studies have highlighted the significance of enteroendocrine cells (EECs) which are part of the secretory lineage of the gut epithelial cells, as important components in gut-kidney crosstalk. EECs are distributed throughout the epithelial layer and release more than 20 hormones in response to microenvironment stimuli. Interestingly, some of these hormones and/or their pathways such as Glucagon-Like Peptide 1 (GLP-1), GLP-2, gastrin, and somatostatin have been shown to exert renoprotective effects. Therefore, the present review explores the role of EECs and their hormones as regulators of gut-kidney crosstalk and their potential impact on kidney diseases. This comprehensive exploration underscores the substantial contribution of EEC hormones in mediating gut-kidney communication and their promising potential for the treatment of kidney diseases.

SOD1 is a novel prognostic biomarker of acute kidney injury following cardiothoracic surgery

BACKGROUND

Acute kidney injury (AKI) is a major burden among hospitalized and critical care patients. Among hospitalized patients that progress to severe AKI there is increased risk for morbidity, mortality, and the need for renal replacement therapy (RRT). As there are no specific treatments for AKI, the discovery of novel biomarkers that predict the progression of AKI may aid in timely implementation of supportive care to improve outcomes.

METHODS

We collected urine from 204 patients that developed Stage 1 AKI by AKIN criteria within 72 h following cardiothoracic surgery. Urine samples were collected at the time of the initial diagnosis of AKI and stored at -80° C. Among the 204 patients, 25 progressed to a composite primary outcome of Stage 3 AKI, requirement of RRT, or 30-day mortality. The remaining 179 patients did not progress beyond Stage 2 AKI and were considered controls. Urinary concentrations of SOD1 and SOD1 activity were measured following collection of all samples. Samples were thawed and urinary superoxide dismutase 1 (SOD1) concentrations were measured by sandwich ELISA and urinary SOD1 activity was measured through a commercially available colorimetric assay.

RESULTS

Urinary concentrations of SOD1 were significantly elevated (67.0 ± 10.1 VS 880.3 ± 228.8 ng/ml, p < 0.0001) in patients that progressed to severe AKI and were able to predict the progression to severe AKI (AUC - 0.85, p < 0.0001). Furthermore, total SOD activity also increased in the urine of patients that required RRT (77.6% VS 49.81% median inhibition, p < 0.01) and was able to predict the need for RRT (AUC: 0.83, p < 0.01).

CONCLUSION

These findings show that urinary SOD1 concentrations and SOD activity are novel prognostic biomarkers for severe AKI following cardiothoracic surgery.

Influence of ursodeoxycholic acid on blood glucose, insulin and GLP-1 in rats with liver fibrosis induced by bile duct ligation

BACKGROUND

The prevalence of impaired glucose tolerance and diabetes is much higher in people with cirrhosis than that in the general population. However, there are inadequate concrete guidelines for the management of diabetes in these patients, particularly in the early stage. Bile aids (BAs) have been found to exert hormone-like functions in the control of lipid and glucose metabolism. We studied the effect of ursodeoxycholic acid (UDCA) on glucose levels in rats with cirrhosis induced by bile duct ligation (BDL).

METHODS

SD rats were divided into three groups: sham operation (Group A); BDL (Group B), and UDCA plus BDL (Group C). After 4 weeks, oral glucose tolerance tests were performed. Serum biochemical parameters and the levels of glucose, insulin, and glucagon-like peptide 1 (GLP-1) were measured. Histopathology of the liver and islet was observed. The gene expression of cholesterol 7α-hydroylase (CYP7A1), microsomal oxysterol 7a-hydroxylase (CYP7B1) in the liver, and Takeda G-protein-coupled receptor-5 (TGR5) in the intestine was determined by real-time PCR.

RESULTS

Compared with Group A, fasting glucose and 1-h and 2-h postprandial glucose levels increased slightly (all P > 0.05), 2-h postprandial insulin levels increased significantly (P < 0.05), 15 min postprandial GLP-1 levels decreased (P < 0.05) in Group B. Compared with Group B, fasting glucose and 1-h postprandial glucose levels decreased (all P < 0.05), 2-h postprandial insulin levels decreased (P < 0.01), and 15 min postprandial GLP-1 levels increased (P < 0.05) in Group C. After UDCA intervention, liver fibrosis induced by BDL was alleviated, and the islet areas were increased (P < 0.05). Compared with Group A, the mRNA expression of CYP7A1 and CYP7B1 in the liver increased, and the mRNA expression of TGR5 in the intestine decreased in Group B (all P < 0.05). Compared with Group B, the mRNA expression of CYP7A1 and CYP7B1 in the liver decreased, and TGR5 in the intestine increased in Group C (P < 0.05).

CONCLUSIONS

After 4 weeks of BDL, the rats developed liver fibrosis and abnormal glucose metabolism. UDCA administration improved liver fibrosis, increased islet area, decreased glucose levels, inhibited genes in BA synthesis, enhanced TGR5 gene expression in the intestine, and further improved islet function.

The potential value of exosomes as adjuvants for novel biologic local anesthetics

The side effects of anesthetic drugs are a key preoperative concern for anesthesiologists. Anesthetic drugs used for general anesthesia and regional blocks are associated with a potential risk of systemic toxicity. This prompted the use of anesthetic adjuvants to ameliorate these side effects and improve clinical outcomes. However, the adverse effects of anesthetic adjuvants, such as neurotoxicity and gastrointestinal reactions, have raised concerns about their clinical use. Therefore, the development of relatively safe anesthetic adjuvants with fewer side effects is an important area for future anesthetic drug research. Exosomes, which contain multiple vesicles with genetic information, can be released by living cells with regenerative and specific effects. Exosomes released by specific cell types have been found to have similar effects as many local anesthetic adjuvants. Due to their biological activity, carrier efficacy, and ability to repair damaged tissues, exosomes may have a better efficacy and safety profile than the currently used anesthetic adjuvants. In this article, we summarize the contemporary literature about local anesthetic adjuvants and highlight their potential side effects, while discussing the potential of exosomes as novel local anesthetic adjuvant drugs.

Sitagliptin ameliorates diabetic nephropathy by upregulating renal nephrin and podocin expression through modulation of adipokines levels

Diabetic nephropathy is the leading cause of end-stage renal failure, but the effectiveness of currently available strategies for preventing diabetic nephropathy remains unsatisfactory. This study was designed to evaluate the changes in adipokines levels caused by dipeptidyl peptidase-4 inhibitor sitagliptin therapy as one of the possible mechanisms of sitagliptin's amelioration of diabetic nephropathy. Twenty-four male Wistar rats weighing 180-200 g were taken and divided into three groups, that is, control, diseased, and treatment group. High-fat diet and streptozotocin-induced Type 2 diabetic rats were divided into diseased and treatment groups. The treatment group was given sitagliptin orally, 10 mg/kg per day for 6 weeks. Serum glucose, serum insulin, serum blood urea nitrogen, serum creatinine, and 24-h urinary protein levels were measured in serum and urine samples. mRNA expression levels of podocin, nephrin, and adipokines in renal tissues were determined. Results showed that sitagliptin treatment effectively reduced serum glucose, serum creatinine, serum blood urea nitrogen, and 24-h proteinuria, along with partial prevention of insulinopenia, in the treatment group as compared to the diseased group. The renal mRNA expression levels of podocin, nephrin, and adiponectin were significantly upregulated, while those of leptin and resistin were significantly downregulated in the diabetic rats receiving sitagliptin therapy compared to the non-treated diabetic rats. Based on these findings, it is suggested that sitagliptin, via mediating the modulation of adipokines levels, upregulates renal nephrin and podocin expression, which leads to the amelioration of diabetic nephropathy.

Dipeptidyl peptidase-4 inhibitor: Sitagliptin down-regulated toll-like receptor 4 signaling pathway to reduce uterine injury in rats

OBJECTIVES

Uterine ischemia is a common problem with ongoing controversy about its pathogenesis and prevention. The present study aimed to investigate the protective role of sitagliptin against uterine ischemia-reperfusion injury (IRI).

MATERIALS AND METHODS

Rats were allocated into 4 groups: control, sitagliptin (SIT) (5 mg/kg), IR; ischemia was induced followed by reperfusion, and IR+SIT; SIT was administered 1 hr before IRI. Uteri were removed for histopathological and biochemical observations. Malondialdehyde (MDA), total nitrites (NOx), reduced glutathione (GSH), superoxide dismutase (SOD) activity, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and toll-like receptor 4 (TLR4) were all measured. Hematoxylin and eosin (H&E) stain, Periodic acid-Schiff stain (PAS), and caspase-3 immunostaining were applied.

RESULTS

In the IR+SIT group; NOx, GSH, and SOD activities increased significantly. Meanwhile, the levels of MDA, TNF-α, IL-6, TLR4, and caspase-3 immunoexpression showed a significant reduction, as compared with the IR group. In the IR+SIT group, an improvement in the histopathological picture was noticed.

CONCLUSION

The results showed that sitagliptin confers protection against uterine IRI through anti-oxidant, anti-inflammatory, and anti-apoptotic effects with a possible role for TLR4.

Protective effect of saxagliptin against renal ischaemia reperfusion injury in rats

Saxagliptin is an effective and selective dipeptidyl peptidase-4 (DPP-4) inhibitor. This study was designed to determine possible protective effects of saxagliptin against damage caused by renal ischaemia/reperfusion (I/R) in rats. In this study, 40 rats were divided into 4 groups (n = 10 for each). Group 1 (Control), Group 2 (I/R) in both kidneys ischaemia of 45 min was performed, and then reperfusion was applied for 24 h. Saxagliptin (Group 3: 2 mg/kg and Group 4: 10 mg/kg) was administered by oral gavage to the animals in treatment groups, before the I/R. Saxagliptin decreased the markers (BUN, Cre, NGAL, KIM-1 and IL-18) of acute renal damage in blood and kidney tissue. Saxagliptin provided increase in antioxidant enzyme levels and decrease in MDA and apoptosis. Histological results showed that the administration of saxagliptin exhibited a protective effect against renal damage caused by I/R. These results indicates that saxagliptin provide protection against kidney injury caused by I/R.

Obeticholic Acid Reduces Kidney Matrix Metalloproteinase Activation following Partial Hepatic Ischemia/Reperfusion Injury in Rats

We have previously demonstrated that the farnesoid X receptor (FXR) agonist obeticholic acid (OCA) protects the liver via downregulation of hepatic matrix metalloproteinases (MMPs) after ischemia/reperfusion (I/R), which can lead to multiorgan dysfunction. The present study investigated the capacity of OCA to modulate MMPs in distant organs such as the kidney. Male Wistar rats were dosed orally with 10 mg/kg/day of OCA (5 days) and were subjected to 60-min partial hepatic ischemia. After 120-min reperfusion, kidney biopsies (cortex and medulla) and blood samples were collected. Serum creatinine, kidney MMP-2, and MMP-9-dimer, tissue inhibitors of MMPs (TIMP-1, TIMP-2), RECK, TNF-alpha, and IL-6 were monitored. MMP-9-dimer activity in the kidney cortex and medulla increased after hepatic I/R and a reduction was detected in OCA-treated I/R rats. Although not significantly, MMP-2 activity decreased in the cortex of OCA-treated I/R rats. TIMPs and RECK levels showed no significant differences among all groups considered. Serum creatinine increased after I/R and a reduction was detected in OCA-treated I/R rats. The same trend occurred for tissue TNF-alpha and IL-6. Although the underlying mechanisms need further investigation, this is the first study showing, in the kidney, beneficial effects of OCA by reducing TNF-alpha-mediated expression of MMPs after liver I/R.

Modulation of Prostanoids Profile and Counter-Regulation of SDF-1α/CXCR4 and VIP/VPAC2 Expression by Sitagliptin in Non-Diabetic Rat Model of Hepatic Ischemia-Reperfusion Injury

Molecular mechanisms underlying the beneficial effect of sitagliptin repurposed for hepatic ischemia-reperfusion injury (IRI) are poorly understood. We aimed to evaluate the impact of IRI and sitagliptin on the hepatic profile of eicosanoids (LC-MS/MS) and expression/concentration (RTqPCR/ELISA) of GLP-1/GLP-1R, SDF-1α/CXCR4 and VIP/VPAC1, VPAC2, and PAC1 in 36 rats. Animals were divided into four groups and subjected to ischemia (60 min) and reperfusion (24 h) with or without pretreatment with sitagliptin (5 mg/kg) (IR and SIR) or sham-operated with or without sitagliptin pretreatment (controls and sitagliptin). PGI₂, PGE₂, and 13,14-dihydro-PGE₁ were significantly upregulated in IR but not SIR, while sitagliptin upregulated PGD₂ and 15-deoxy-12,14-PGJ₂. IR and sitagliptin non-significantly upregulated GLP-1 while Glp1r expression was borderline detectable. VIP concentration and Vpac2 expression were downregulated in IR but not SIR, while Vpac1 was significantly downregulated solely in SIR. IRI upregulated both CXCR4 expression and concentration, and sitagliptin pretreatment abrogated receptor overexpression and downregulated Sdf1. In conclusion, hepatic IRI is accompanied by an elevation in proinflammatory prostanoids and overexpression of CXCR4, combined with downregulation of VIP/VPAC2. Beneficial effects of sitagliptin during hepatic IRI might be mediated by drug-induced normalization of proinflammatory prostanoids and upregulation of PGD₂ and by concomitant downregulation of SDF-1α/CXCR4 and reinstating VIP/VCAP2 signaling.

Sitagliptin Modulates Oxidative, Nitrative and Halogenative Stress and Inflammatory Response in Rat Model of Hepatic Ischemia-Reperfusion

A possibility of repurposing sitagliptin, a well-established antidiabetic drug, for alleviating injury caused by ischemia-reperfusion (IR) is being researched. The aim of this study was to shed some light on the molecular background of the protective activity of sitagliptin during hepatic IR. The expression and/or concentration of inflammation and oxidative stress-involved factors have been determined in rat liver homogenates using quantitative RT-PCR and Luminex^® xMAP^® technology and markers of nitrative and halogenative stress were quantified using targeted metabolomics (LC-MS/MS). Animals (n = 36) divided into four groups were treated with sitagliptin (5 mg/kg) (S and SIR) or saline solution (C and IR), and the livers from IR and SIR were subjected to ischemia (60 min) and reperfusion (24 h). The midkine expression (by 2.2-fold) and the free 3-nitrotyrosine (by 2.5-fold) and IL-10 (by 2-fold) concentration were significantly higher and the Nox4 expression was lower (by 9.4-fold) in the IR than the C animals. As compared to IR, the SIR animals had a lower expression of interleukin-6 (by 4.2-fold) and midkine (by 2-fold), a lower concentration of 3-nitrotyrosine (by 2.5-fold) and a higher Nox4 (by 2.9-fold) and 3-bromotyrosine (by 1.4-fold). In conclusion, IR disturbs the oxidative, nitrative and halogenative balance and aggravates the inflammatory response in the liver, which can be attenuated by low doses of sitagliptin.

MMP-9-mediated regulation of hypoxia-reperfusion injury-related neutrophil inflammation in an in vitro proximal tubular cell model

Background

Hypoxia-reperfusion (HR) and inflammation are causes of renal allograft injury. Pathological evidence has indicated that ischemia followed by reperfusion leads to the proteolysis and destruction of the extracellular matrix (ECM) in renal tubular epithelial cells. Matrix metalloproteinases (MMPs), such as MMP-2 and MMP-9, play roles in cleaving and reshaping the ECM. Acute accumulation of MMP-9 secreted from neutrophils promotes the incidence of inflammation and exacerbates graft trauma. Our goal was to investigate the activities of MMP-9/MMP-2 and their correlation with HR injury and neutrophil-related inflammation in renal proximal tubular cells.

Methods

This model was established by placing HK-2 cells under hypoxic conditions (5% CO₂, 1% O₂) for 6 h and then exposing them to reperfusion (5% CO₂, 21% O₂) for 12 h in a tri-gas incubator. The cell culture medium was collected for culturing polymorphonuclear leukocytes (PMNs). BB-94 (MMP-9 inhibitor) was added to the culture medium in the inhibitor group.

Results

Flow cytometry showed a significant increase in reactive oxygen species (ROS) levels in HK-2 cells from the HR injury group. MMP-9 expression was significantly increased and MMP-2 expression was significantly decreased in HK-2 cells from the HR group. MMP-9 and MPO expression were significantly increased in the HR group, while MPO expression was significantly decreased in the PMN inhibitor group.

Conclusions

The outcomes indicated that MMP-9 and MMP-2 are important components of an underlying pathophysiological mechanism of injury following HR. MMP-9 inhibition may be a potential approach to mitigateHR injury.

CD161a-positive natural killer (NK) cells and α-smooth muscle actin-positive myofibroblasts were upregulated by extrarenal DPP4 in a rat model of acute renal rejection

AIMS

Systemic inhibition of dipeptidyl peptidase 4 (DPP4) showed a protective effect in several transplant models. Here we assessed the specific role of extrarenal DPP4 in renal transplant rejection.

METHODS

Kidneys from wildtype (wt) F344 rats were either transplanted in wt Dark Agouti or congenic rats not expressing DPP4. The remaining, not transplanted donor kidney served as healthy controls. To investigate early inflammatory events rats were sacrificed 3 days after transplantation and kidneys were evaluated for inflammatory cells, capillary rarefaction, proliferation, apoptosis and myofibroblasts by immunohistochemistry.

RESULTS

Capillary ERG-1-positive endothelial cells were significantly more abundant in renal cortex when transplanted into DPP4 deficient compared to wt recipients. In contrast, TGF-ß and myofibroblasts were reduced by more than 25% in kidneys transplanted into DPP4 deficient compared to wt recipients. Numbers of CD161a-positive NK-cells were significantly lower in allografts in DPP4 deficient compared to wt recipients. Numbers of all other investigated immune cells were not affected by the lack of extrarenal DPP4.

CONCLUSION

In early transplant rejection extrarenal DPP4 is involved in the recruitment of NK-cells and early fibrosis. Beneficial effects were less pronounced than reported for systemic DPP4 inhibition, indicating that renal DPP4 is an important player in transplantation-mediated injury.

Anti-inflammatory and protective effects of combined treatment with sitagliptin and melatonin in cardiac ischemia reperfusion injury in obese rats: Involvement of TLR-4/NF-κB pathway

Background: Obesity is associated with an augmented risk of myocardial ischemia/reperfusion (I/R) injury. Reduction of I/R injury by effective cardioprotective strategies needs to be investigated in obese subjects. This study aimed to evaluate the combined effects of sitagliptin and melatonin on inflammatory response and TLR4/IκBα/NF-κB signaling following cardiac I/R damage in obese rats. Methods: Sixty-six male Wistar rats (180–200 g) were fed a low fat diet (10% Kcal from lipids) or high fat (45% Kcal from lipids) diets for 12 weeks. High fat-fed (obese) rats experienced 30 min left anterior descending occlusion followed by 24 h reperfusion. Obese rats received sitagliptin (20 mg/kg/day) for 1 month before I/R surgery. Melatonin (10 mg/kg) was injected at early reperfusion. Myocardial infarct size (IS), cTn-I release, pro-inflammatory cytokines, myeloperoxidase (MPO), COX-2 and iNOS, and the protein expressions of TLR4, p-NF-κB/p65, and p-IκBα were evaluated. Results: Monotherapies with sitagliptin-preconditioning or melatonin-postconditioning had no cardioprotective effects in obese rats. However, combined therapy with sitagliptin and melatonin significantly reduced IS, and the release of cTn-I, in comparison to untreated obese rats ( p < .01) Moreover, this combination decreased the production of pro-inflammatory cytokines, MPO, COX-2 and iNOS, and the expression of TLR4 and p-NF-κB/p65, while reduced the expression of p-IκBα, in comparison with untreated or monotherapies-received obese rats ( p < .01 for all). Conclusion: Combination therapy with sitagliptin and melatonin was a good cardioprotective strategy to modulate the inflammatory responses and TLR4/NF-κB signaling pathway in obese patients with cardiac I/R injury.

Renoprotective effect of vildagliptin following hepatic ischemia/reperfusion injury

Remote renal injury is a drastic consequence of hepatic ischemia/reperfusion (IR) injury. Vildagliptin (V) is a dipeptidyl peptidase-4 inhibitor that has a hepatorenal protective effect against models of liver and renal IR. This research was done to explore the protective role of vildagliptin against renal injury following hepatic IR injury as well as the possible involvement of transforming growth factor-beta (TGF-β)/Smad/alpha-smooth muscle actin (α-SMA) expressions in the pathophysiological mechanism of the remote renal injury. Three groups of male Wistar rats were organized into: sham group, IR group, and V + IR group in which 10 mg/kg/day of vildagliptin was pretreated for 10 days intraperitoneally. Blood in addition to renal and hepatic tissue samples was used for biochemical and histopathological studies. Hepatic IR induced a marked increase in serum creatinine, blood urea nitrogen, liver enzymes, renal nitric oxide, malondialdehyde, tumor necrosis factor-alpha levels with a marked upregulation of renal mRNA expressions of TGF-β, Smad2, Smad3, and α-SMA in addition to a marked decline in renal catalase content comparing to the sham group. Abnormal histopathological findings of hepatic and renal injury were detected in the IR group. Vildagliptin significantly improved these biochemical markers as well as the histopathological changes. The upregulation of renal TGF-β/Smad/α-SMA mRNA expressions was involved for the first time in the pathogenesis of the renal injury following hepatic IR and vildagliptin ameliorated this renal injury through blocking these expressions.

Dipeptidyl Peptidase-4 deficiency effectively protects the brain and neurological function in rodent after acute Hemorrhagic Stroke

This study tested the hypothesis that abrogated dipeptidyl peptidase-4 (DPP4) activity played a crucial role on reducing stroke volume and preserving neurological function in rodent after acute hemorrhagic stroke (AHS). Animals (n=6/each group) were categorized into group 1 (sham-control of F344 rat), group 2 (sham-control of DPP4-deficiency rat), group 3 [AHS by right cerebral injection of autologous blood (100 µL) in F344 rat], group 4 (AHS + sitagliptin/600 mg/kg 3 h prior to and at 3 h then once per day after AHS) and group 5 (AHS in DPP4-deficiency rat). The results of corner test showed the neurological function was significantly improved from days 3, 7, and 14 in groups 4 and 5 than in group 3 (all p<0.001). By days 1 and 14 after AHS procedure, the circulating levels of SDF-1α and GLP-1 were significantly increased from groups 1/2 to group 5 (all p<0.001), whereas circulating DPP4 activity was significantly increased in group 3 than other groups (all p<0.001). The brain ischemic area (BIA) was highest in group 3, lowest in groups 1/2 and significantly lower in group 5 than in group 4 (all p<0.0001). The protein expressions of oxidative-stress/inflammatory/apoptotic/cell-proliferation signaling, and the cellular expressions of inflammatory/DNA-damaged biomarkers exhibited a similar pattern to BIA among the groups (all p<0.01). In conclusion, deprivation of DPP4 activity protected the brain from AHS damage and preserved neurological function.

Alogliptin attenuates cyclophosphamide-induced nephrotoxicity: a novel therapeutic approach through modulating MAP3K/JNK/SMAD3 signaling cascade

Cyclophosphamide (CP) is widely used as a chemotherapy against various types of cancers. However, CP is accompanied with multiple organ toxicity due to production of reactive oxygen species (ROS), induction of inflammation and consequently apoptosis. Alogliptin (Alo) is a dipeptidyl peptidase 4 (DPP-IV) inhibitor, which is booming as an antidiabetic agent. Interestingly, gliptins are currently studied for their counter-regulatory effects against oxidative stress and inflammation via multiple pathways, among which is the mitogen-activated protein kinase (MAPK)/c-Jun N-terminal kinase (JNK) pathway. This cascade can reduce inflammation via mitigating the activity of mothers against decapentaplegic homolog 3 (SMAD3) and c-Jun. However, Alo effect against CP-induced kidney injury has not been previously elucidated. This tempted us to investigate the possible beneficial effect of Alo against CP-induced kidney injury via modulating the MAP3K/JNK/SMAD3 signaling cascade. Thirty-two male Wistar rats were randomly allocated into four groups. CP-treated group received a single dose of CP (200 mg/kg; i.p.). Alo-treated group received Alo (20 mg/kg/day; p.o.) for 7 days with single CP injection on day 2. Marked decrease in renal injury was observed upon Alo treatment, as evidenced through declined serum kidney function markers, oxidative stress and apoptosis markers, MAP3K expression, phospho (p)-SMAD3, p-JNK, and p-c-Jun levels. These cellular effects were reflected in reduced transforming growth factor beta (TGF-β) and tumor necrosis factor alpha (TNF-α) fibrotic and inflammatory mediators, coinciding with improved histopathological portrait. In conclusion, the current study provides novel application of Alo as a therapeutic modality against CP-induced nephrotoxicity.

Sitagliptin improves functional recovery via GLP-1R-induced anti-apoptosis and facilitation of axonal regeneration after spinal cord injury

Axon growth and neuronal apoptosis are considered to be crucial therapeutic targets against spinal cord injury (SCI). Growing evidences have reported stimulation of glucagon‐like peptide‐1 (GLP‐1)/GLP‐1 receptor (GLP‐1R) signalling axis provides neuroprotection in experimental models of neurodegeneration disease. Endogenous GLP‐1 is rapidly degraded by dipeptidyl peptidase‐IV (DPP4), resulting in blocking of GLP‐1/GLP1R signalling process. Sitagliptin, a highly selective inhibitor of DPP4, has approved to have beneficial effects on diseases in which neurons damaged. However, the roles and the underlying mechanisms of sitagliptin in SCI repairing remain unclear. In this study, we used a rat model of SCI and PC12 cells/primary cortical neurons to explore the mechanism of sitagliptin underlying SCI recovery. We discovered the expression of GLP‐1R decreased in the SCI model. Administration of sitagliptin significantly increased GLP‐1R protein level, alleviated neuronal apoptosis, enhanced axon regeneration and improved functional recovery following SCI. Nevertheless, treatment with exendin9‐39, a GLP‐1R inhibitor, remarkably reversed the protective effect of sitagliptin. Additionally, we detected the AMPK/PGC‐1α signalling pathway was activated by sitagliptin stimulating GLP‐1R. Taken together, sitagliptin may be a potential agent for axon regrowth and locomotor functional repair via GLP‐1R‐induced AMPK/ PGC‐1α signalling pathway after SCI.

Exendin-4, a GLP-1 receptor agonist regulates retinal capillary tone and restores microvascular patency after ischaemia-reperfusion injury

Background and Purpose

The aim of this study is to investigate the vasorelaxant effect of exendin‐4, a GLP‐1 receptor agonist on retinal capillaries under normal and ischaemia–reperfusion (I/R) conditions.

Experimental Approach

Capillary diameters in the whole‐mounted retina were directly observed using infrared differential interference contrast microscopy. A model of retinal I/R was established inraats,using high perfusion pressure in an anterior chamber. To assess the effects of exendin‐4, it was administered through subcutaneous injection, intravitreal injection, or eye drops. The underlying mechanism was explored by immunofluorescence, qPCR, and capillary western blots.

Key Results

Immunofluorescence staining showed that GLP‐1 receptors were expressed in endothelial cells of retinal capillaries. Exendin‐4 relaxed the capillaries precontracted by noradrenaline, an effect abolished by denuding endothelium with CHAPS and inhibited by GLP‐1 receptor antagonist exendin‐9‐39, endothelial NOS (eNOS) inhibitor l‐NAME, and the guanylate cyclase blocker ODQ but not by a COX inhibitor, indomethacin. Retinal capillaries were constricted in I/R injury, an effect reversed by perfusion of exendin‐4. Expression of PI3K and Akt, phosphorylation level of eNOS and NO production after I/R were lower than that in the normal control group. Administration of exendin‐4 improved the changes.

Conclusion and Implications

Exendin‐4 can restore injured microvascular patency in I/R. Exendin‐4 may regulate retinal capillaries through the GLP‐1 receptor‐PI3K/Akt‐eNOS/NO‐cGMP pathway. Therefore, exendin‐4 may be an effective treatment for improving tissue perfusion in I/R‐related conditions.

Renoprotective Effect of a Dipeptidyl Peptidase-4 Inhibitor on Aging Mice

Dipeptidyl peptidase 4 (DPP-4) inhibitors exert pleiotropic effects beyond glycemic control. We investigated the renoprotective effects of DPP-4 inhibitors on aging mice mediated by the renin-angiotensin system (RAS). C57BL/6 mice were divided into three groups: the two-month-old mice (YM group), the eighteen-month-old mice (AM group) and the eighteen-month-old, linagliptin-treated mice (AM + LIN group). Renal function was improved, based on serum creatinine and cystatin-C levels (p < 0.05 compared with the AM group for both parameters). Fibrotic areas and the levels of proteins related to fibrosis improved in the AM + LIN group (p < 0.001 compared with the AM group for all parameters). In the AM + LIN group, the DPP-4-positive area and activity and expressions of DPP-4 were decreased (p < 0.05 compared with the AM group for all parameters). The levels of proteins related to the RAS, including prorenin receptor, angiotensin-converting enzyme, angiotensin II and angiotensin 1 receptor, were decreased in the AM + LIN group (p < 0.05, p < 0.01, p < 0.05, and p < 0.01 compared with the AM group, respectively). NADPH oxidase 2 and NADPH oxidase 4 levels decreased in the AM + LIN group (p < 0.001 compared with the AM group for both proteins), whereas the levels of endothelial nitric oxide synthase (eNOS) phosphorylated at serine¹¹⁷⁷ and superoxide dismutase 1 were increased (p < 0.01 compared with the AM group for both proteins). DPP-4 inhibitors may exert renoprotective effects via prorenin receptor/angiotensin-converting enzyme/angiotensin II/angiotensin 1 receptor axis.

The hepatoprotective effect of sitagliptin against hepatic ischemia reperfusion-induced injury in rats involves Nrf-2/HO-1 pathway

BACKGROUND

Oxidative stress and inflammation play a key role in the development of hepatic ischemia reperfusion (HIR)-induced injury. Nuclear factor-erythroid 2-related factor-2 (Nrf-2) is a main regulator of numerous genes, encoding cytoprotective molecules including heme oxygenase-1 (HO-1). Sitagliptin (Sit) is an incretin enhancer acting via inhibition of dipeptidyl peptidase-4 (DPP-4) enzyme. This study was undertaken to investigate the ability of Sit to prevent the hepatic pathological changes of HIR induced injury and to modify Nrf-2 and its target HO-1.

METHODS

Pringle's maneuver was used to induce total HIR in adult male rats that were randomly assigned into 4 groups. Group1 (sham-operated control), Group 2 (sham-operated + Sit-control group), Group 3 (HIR non-treated), and Group 4 (HIR + Sit). Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities together with hepatic contents of malondialdhyde (MDA), nitric oxide (NO) and reduced glutathione (GSH) and superoxide dismutase (SOD) activity were evaluated. Hepatic tissue mRNA of Nrf-2 and protein content of HO-1 along with histopathological examination and scoring of hepatic injury were performed.

RESULTS

Sit caused a significant reduction in ALT and AST activities together with attenuation of HIR-induced histopathological liver injury. Effect of Sit was associated with decreased hepatic level of MDA and NO with increased GSH level and SOD activity. Non-treated rats with HIR showed an increase in Nrf-2 mRNA expression and HO-1 content in hepatic tissue which was further increased by Sit treatment.

CONCLUSIONS

These results indicate that hepatoprotective activity of Sit against HIR is attributed at least in part to modulation of Nrf-2/ HO-1 signaling pathway.

Protective effect of dipeptidyl peptidase-4 inhibitors in testicular torsion/detorsion in rats: a possible role of HIF-1α and nitric oxide

Spermatic cord torsion is a serious and common urologic emergency. It requires early diagnosis for prevention of subfertility and testicular necrosis. Vildagliptin and sitagliptin are anti-diabetic drugs of the dipeptidyl peptidase-4 (DPP-4) inhibitors that have a protective role against cerebral ischemic stroke and cardiac ischemia reperfusion. This study aimed to investigate the role and mechanism of action of vildagliptin and sitagliptin in a model of testicular ischemia/reperfusion injury by testicular torsion/detorsion (T/D). Testicular T/D was done and vildagliptin and sitagliptin were administered either alone or in combination with nitric oxide synthase (NOS) inhibitor. Serum total cholesterol and testosterone were measured, while in testicular tissue testosterone, malondialdehyde (MDA) level, total antioxidant capacity (TAC), nitric oxide level, caspase-3, superoxide dismutase (SOD), hypoxia-inducible factor-1α (HIF-1α), tumor necrosis factor-α (TNF-α) and endothelial NOS (eNOS), and inducible NOS (iNOS) and neuronal NOS (nNOS) were measured. Histopathology of testicular tissue was done. Vildagliptin and sitagliptin increased serum testosterone, expression, and activity of SOD and testicular TAC. It also reduced total serum cholesterol, testicular MDA, caspase-3, HIF-1α, TNF-α, and expression of eNOS, iNOS, and nNOS. Vildagliptin and sitagliptin also improved histopathological picture of testicular tissue. NOS inhibitor produced similar result to DDP-4 inhibitors; however, its co-administration augmented the effect of vildagliptin and sitagliptin on these parameters. DPP-4 inhibitors, vildagliptin, and sitagliptin were protective against testicular T/D-induced injury mostly by anti-oxidative stress, and anti-apoptotic and anti-inflammatory actions that was augmented by NOS inhibition with a possible role for HIF-1α expression.

Sitagliptin protects male albino rats with testicular ischaemia/reperfusion damage: Modulation of VCAM-1 and VEGF-A

Twisting of the spermatic cord is considered a popular problem in the urological field, which may lead to testicular necrosis and male infertility. Sitagliptin, a glucose-lowering agent, proved to have a vindicatory function in myocardial and renal ischaemia/reperfusion (I/R), but its role in testicular I/R has not yet been studied. The current work investigates its capability to recover the testicular I/R injury with shedding more light on the mechanism of its action. Four groups were used: sham, sham pretreated with sitagliptin, I/R and sitagliptin/I/R-pretreated groups. The outcomes proved that I/R significantly decreased the serum testosterone, with a major increase in oxidative, inflammatory and nitrosative stress, along with a reduction in testicular vascular endothelial growth factor-A level with marked germinal cell apoptosis. However, pretreatment with sitagliptin significantly reversed the profound testicular I/R damaging effects, on the basis of its antioxidant, anti-inflammatory and anti-apoptotic activities with the ability of recuperation of the testicular vascularity.

Novel repair mechanisms in a renal ischaemia/reperfusion model: Subsequent saxagliptin treatment modulates the pro-angiogenic GLP-1/cAMP/VEGF, ANP/eNOS/NO, SDF-1α/CXCR4, and Kim-1/STAT3/HIF-1α/VEGF/eNOS pathways

The reno-protective effects of antidiabetic dipeptidyl peptidase (DPP)-4 inhibitors have been studied regarding their antioxidant and anti-inflammatory properties. However, the potential ability of saxagliptin to ameliorate renal injury by enhancing neovascularization has not been elucidated. To address this issue, saxagliptin (10 and 30 mg/kg) was administered to Wistar rats after the induction of renal ischaemia/reperfusion (I/R). Our results showed that saxagliptin operated through different axes to ameliorate I/R injury. By inhibiting DPP-4, saxagliptin maintained stromal cell-derived factor-1α expression and upregulated its chemokine receptor CXCR4 to trigger vasculogenesis through the enhanced migration of endothelial progenitor cells (EPCs). Additionally, this compound rescued the levels of glucagon-like peptide-1 and its downstream mediator cAMP to increase vascular endothelial growth factor (VEGF) and CXCR4 levels. Moreover, saxagliptin stimulated atrial natriuretic peptide/endothelial nitric oxide synthase to increase nitric oxide levels and provoke angiogenesis and renal vasodilation. In addition to inhibiting DPP-4, saxagliptin increased the renal kidney injury molecule-1/pY705-STAT3/hypoxia-inducible factor-1α/VEGF pathway to enhance angiogenesis. Similar to other gliptins, saxagliptin exerted its anti-inflammatory and antioxidant effects by suppressing the renal contents of p (S536)-nuclear factor-κB p65, tumour necrosis factor-α, monocyte chemoattractant protein-1, myeloperoxidase, and malondialdehyde while boosting the glutathione content. These events improved the histological structure and function of the kidney, as evidenced by decreased serum creatinine, blood urea nitrogen, and cystatin C and increased serum albumin. Accordingly, in addition to its anti-inflammatory and antioxidant activities, saxagliptin dose-dependently ameliorated I/R-induced renal damage by enhancing neovascularization through improved tissue perfusion and homing of bone marrow-derived EPCs to mediate repair processes.

Sitagliptin and shock wave-supported peripheral blood derived endothelial progenitor cell therapy effectively preserves residual renal function in chronic kidney disease in rat-role of dipeptidyl peptidase 4 inhibition

This study tested whether sitagliptin and shock wave (SW)-assisted circulatory-derived autologous endothelial progenitor cell (EPC) therapy would effectively preserve residual renal function in chronic kidney disease (CKD) induced by 5/6 left-nephrectomy/remove right kidney plus daily feeding high-protein diet (H^PD) in rat. Adult-male SD rats (n = 40) were categorized into group 1 (sham-operated control with H^PD), group 2 (H^PD-CKD), group 3 [H^PD-CKD + EPC (1.2 × 10⁶ cell)/intra-vessel administration by day 14 after CKD-induction], group 4 [H^PD-CKD + SW (0.12 mJ/mm²/180 shorts) at days 14/21/28 after CKD-induction by ultrasound-guided application] and group 5 [H^PD-CKD + SW + EPC + sitagliptin (Sita; 600 mg/kg/day since day 14 after CKD induction)]. All animals were euthanized by day 60. By day 60, renal blood flow (RBF) was highest in group 1 and progressively increased from groups 2 to 5, whereas the levels of creatinine/BUN/proteinuria exhibited an opposite pattern of RBF among the five groups (all p < 0.001). The circulating levels of GLP-1/SDF-1α and protein levels of angiogenesis (VEGF/SDF-1α/CXCR4) and GLP-1R in kidney were progressively increased from groups 1 to 5, whereas circulating DPP4 activity exhibited an opposite pattern of SDF-1α among the groups (all p < 0.0001). The protein expressions of oxidative-stress (NOX-1/NOX-2/oxidized protein), apoptosis (Bax/caspase-3/PARP), fibrosis (Smad3/TGF-ß) and inflammation (TNF-α/NF-κB/MMP-2) and kidney injury score displayed an opposite pattern, whereas the protein expressions of TMP2, endothelial-cell markers (CD31/eNOS) and podocyte integrity biomarkers (podocin/ZO-1/synaptopodin) exhibited an identical pattern of RBF among the groups (all p < 0.001). In conclusion Sita associated SW-assisted EPC effectively protected residual renal function in CKD.

Neuroprotective influence of sitagliptin against cisplatin-induced neurotoxicity, biochemical and behavioral alterations in Wistar rats

Cisplatin has been extensively used as a chemotherapeutic agent since around 40 years, though its usage is limited due to severe adverse effects like neurotoxicity that might be because of oxidative stress. Hence, the present study was planned to investigate the possible protective role of sitagliptin against cisplatin-associated neurotoxic, biochemical, and behavioral alterations in male Wistar rats. Sitagliptin is a dipeptidyl peptidase-4 inhibitor that shows dual effects by improving the control on metabolism as well as decreasing the debility in cognitive function that is associated with increased insulin sensitivity and antioxidant property. For the in vitro assay, cultured rat pheochromocytoma (PC12) cells were exposed to different concentrations (10, 20, and 50 mM) of sitagliptin for 24 h. Cisplatin at 5 mM concentrations was added and cell viability was assessed using MTT assay. For in vivo study, animals were divided into four groups. Group I (Vehicle control): animals were administered 0.9% (w/v) of normal saline (1 mL/100 g; p.o.). Group II (Cisplatin): animals were treated with cisplatin (2 mg/kg; i.p.). Group III (Cisplatin + sitagliptin): animals were administered cisplatin along with sitagliptin. Group IV (Sitagliptin): animals were given sitagliptin (10 mg/kg; p.o.). All the treatments were administered for 8 weeks. On last day of treatment, behavioral evaluations including locomotor and rotarod studies were performed. In addition, several antioxidant enzymes were also estimated from cerebellum tissues; such as levels of thiobarbituric acid reactive substance (TBARS) were determined as a marker of lipid peroxidation, reduced glutathione (GSH) and catalase (CAT) were also estimated. Histological study of cerebellum tissue was also performed after performing the behavioral study. Exposure to cisplatin decreased cell viability in PC12 cells which were significantly increased by co-treatment with sitagliptin. In in vivo study, cisplatin significantly elevated the level of TBARS and reduced the level of antioxidant enzymes such as GSH and CAT which were significantly restored in sitagliptin + cisplatin group of rats. In addition, cisplatin impaired performance on the locomotor and rotarod activities, whereas sitagliptin significantly improved the performance of both activities. These results suggested the neuroprotective influence of sitagliptin by protecting cerebellum part of brain against cisplatin-induced toxicity.

Vildagliptin Attenuates Hepatic Ischemia/Reperfusion Injury via the TLR4/NF-κB Signaling Pathway

The Toll-like receptor-4 (TLR4)/nuclear factor kappa B (NF-κB) signaling pathway is vital in the pathogenesis of hepatic ischemia/reperfusion (HIR) injury. Dipeptidyl peptidase-4 (DPP4) inhibitors exert protective effects on IR injury of the kidney, heart, and lung; however, their effect on the liver is still unknown. Thus, the purpose of this study was to examine whether pretreatment with vildagliptin (Vilda), a DPP4 inhibitor, produces hepatic protection against IR injury and to investigate its influence on TLR4/NF-κB signaling in a rat model. Thirty male Wistar rats were divided into 3 groups: the sham group: subjected to a sham operation and received normal saline; the HIR group: subjected to HIR and received normal saline; and the Vilda + HIR group: subjected to HIR with pretreatment of 10 mg/kg/day Vilda for 10 days intraperitoneally. Hepatic ischemia lasted for 45 minutes followed by 3-hour reperfusion; then blood and liver samples were collected for biochemical and histopathological examination. The HIR group produced a significant increase in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), hepatic malondialdehyde (MDA), nitric oxide (NO), and tumor necrosis factor alpha (TNF-α) levels and a significant reduction in the hepatic catalase level in comparison to the sham group. Moreover, a significant upregulation of gene and protein expressions of TLR4, NF-κB, and high-mobility group box-1 (HMGB1) along with caspase-3 protein expression was observed in the HIR group when compared with the sham group. Histopathological examination of the liver from the HIR group showed necrosis, sinusoidal congestion, hemorrhage, and hepatocyte degeneration. Administration of Vilda ameliorated the biochemical and histopathological changes caused by HIR. Vildagliptin showed for the first time a hepatoprotective effect in HIR injury through downregulation of TLR4/NF-κB/HMGB1 and caspase-3 hepatic expressions.

Sitagliptin attenuates intestinal ischemia/reperfusion injury via cAMP/PKA, PI3K/Akt pathway in a glucagon-like peptide 1 receptor-dependent manner

AIMS

This study investigated the effect of sitagliptin prophylactic treatment on intestinal I/R rat model and explored the possible underlying mechanism.

MAIN METHODS

Forty-five male Sprague-Dawley rats were randomly assigned to 3 groups: Sham group (operation without clamping), I/R group (operation with clamping) and sitagliptin pretreated group (300 mg/kg/day; p.o.) for 2 weeks before I/R insult. Intestinal I/R was performed by clamping the superior mesenteric artery for 30 min, followed by 60 min reperfusion after removal of clamping. At the end of the experimental period, all rats were sacrificed for histopathological, biochemical, PCR and western blot assessment.

KEY FINDINGS

Pretreatment with sitagliptin remarkably alleviated the pathological changes induced by I/R in the jejunum, suppressed upregulated NF-κB, TNF-α, IL-1βand MPO caused by I/R. Moreover, sitagliptin decreased the Bax/Bcl-2 ratio and accordingly suppressed apoptotic tissue damage as reflected by a caspase-3 level reduction in rat intestine subjected to I/R injury. Interestingly, sitagliptin could obviously increase the active GLP-1 level and GLP-1 receptor mRNA expression in the jejunum of I/R rats. This was associated with the augmentation of the cAMP level and enhancement of PKA activity. Simultaneously, sitagliptin treatment was able to increase the protein expression levels of phosphorylated PI3K and Akt.

SIGNIFICANCE

Sitagliptin has shown protective effects against intestinal I/R injury in rats through reduction of intestinal inflammation and apoptosis. The molecular mechanisms may be partially correlated with activation of cAMP/PKA and PI3K/Akt signaling pathway by the GLP-1/GLP-1 receptor.

Anti-CD47 monoclonal antibody therapy reduces ischemia-reperfusion injury of renal allografts in a porcine model of donation after cardiac death

We investigated whether blockade of the CD47 signaling pathway could reduce ischemia-reperfusion injury (IRI) of renal allografts donated after cardiac death (DCD) in a porcine animal model of transplantation. Renal allografts were subjected to 30 minutes of warm ischemia, 3.5 hours of cold ischemia, and then perfused with a humanized anti-CD47 monoclonal antibody (CD47mAb) in the treatment group or HTK solution in the control group (n = 4/group). The animals were euthanized five days after transplantation. At the time of reperfusion, indocyanine green-based in vivo imaging showed that CD47mAb-treated organs had greater and more uniform reperfusion. On post-transplant days 3-5, the treatment group had lower values compared to the control for creatinine and blood urea nitrogen. Histological examination of allograft tissues showed a significant decrease of acute tubular injury in the CD47mAb-treated group compared to control. Compared to the control group, CD47mAb treatment significantly decreased genes expression related to oxidative stress (sod-1, gpx-1, and txn), the inflammatory response (il-2, il-6, inf-g, and tgf-b), as well as reduced protein levels of BAX, Caspase-3, MMP2, and MMP9. These data demonstrate that CD47mAb blockade decreases IRI and subsequent tissue injury in DCD renal allografts in a large animal transplant model.

Sitagliptin ameliorates diabetic nephropathy by blocking TGF-β1/Smad signaling pathway

Diabetic nephropathy (DN) is the leading cause of end-stage failure of the kidney, but the efficacy of current strategies available for the prevention of DN remains unsatisfactory. The purpose of this study was to assess whether sitagliptin (SIT) has therapeutic potential for prevention of DN and to investigate its possible mechanism. The effects of SIT on DN were investigated in rats with type 2 diabetes mellitus (T2DM) and rat mesangial cells (MCs) induced by high glucose. T2DM rats were administered at a dose of 10 mg/kg SIT. The kidney index, 24 h urinary protein, blood urea nitrogen (BUN), serum creatinine (Cr), accumulation of glycogen and collagens were investigated by different methods. MCs were administered with SIT at doses of 0.1, 1 and 10 µmol/ml. The possible mechanism of SIT on protection of diabetic kidney injury was examined by expression of transforming growth factor-β1 (TGF-β1)/Smad pathway. The results showed that the SIT-treated diabetic rats significantly reduced diabetic kidney injury by inhibiting the kidney index and attenuating 24 h urinary protein, reducing BUN and serum creatinine, inhibiting progressive renal fibrosis and increassing extracellular matrix including collagen IV and fibronectin. Further studies showed that inhibition of renal fibrosis in SIT-treated diabetic rats and MCs were associated with rebalancing of TGF-β1/Smad pathway. Sitagliptin may be a potent agent for preventing the progression of DN through inhabiting TGF-β1/Smad-mediated renal fibrosis.

Protective Effects of Gemigliptin, a Dipeptidyl Peptidase-4 Inhibitor, against Cisplatin-Induced Nephrotoxicity in Mice

Dipeptidyl peptidase-4 (DPP-4) inhibitors are widely used antihyperglycemic agents for the treatment of type 2 diabetes mellitus. Recently, the pleiotropic actions of DPP-4 inhibitors have drawn much attention. In the present study, we aimed to examine whether gemigliptin, a recently developed DPP-4 inhibitor, could protect against cisplatin-induced nephrotoxicity. We showed that pretreatment with gemigliptin attenuated cisplatin-induced renal dysfunction, as shown by analysis of plasma creatinine levels and blood urea nitrogen and histological damage. Elevated plasma levels of active glucagon-like peptide-1 were observed in gemigliptin-pretreated mice after cisplatin treatment, compared to that in cisplatin alone-treated mice. Gemigliptin attenuated cisplatin-induced apoptotic cell death, as assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and Western blot analysis in the kidneys. Gemigliptin also decreased the plasma levels of tumor necrosis factor-α and monocyte chemoattractant protein-1 and attenuated nuclear staining of nuclear factor kappa-B p65 in the kidneys. In addition, gemigliptin increased the protein expression of heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO1) in the kidneys of cisplatin-treated mice. Taken together, these results suggest that pretreatment with gemigliptin protects against cisplatin-induced nephrotoxicity in mice, possibly via inhibition of apoptotic cell death and inflammatory responses through induction of HO-1 and NQO1 expression.

Renal outcomes with dipeptidyl peptidase-4 inhibitors

Dipeptidyl peptidase-4 inhibitors (DPP-4is) are increasingly being used in the management of type 2 diabetes (T2D). The present review summarizes the current knowledge of the effects of DPP-4is on renal outcomes by analyzing the experimental preclinical data, the effects of DPP-4is on urinary albumin-creatinine ratios (UACRs) and estimated glomerular filtration rates (eGFRs) from observational studies and clinical trials, and renal events (including kidney failure requiring renal replacement therapy) in recent large prospective cardiovascular outcome trials. Renal protection has been demonstrated in various animal models that have implicated different underlying mechanisms independent of glucose control, whereas prevention of new onset microalbuminuria and/or progression of albuminuria has been reported in some clinical studies, but with no significant effects on eGFR in most of them. The long-term clinical effects of DPP-4is on renal outcomes and the development of end-stage renal disease remain largely unknown and, thus, demand further investigations in prospective trials and long-term observational studies. In conclusion, despite promising results in animal models, data on surrogate biological markers of renal function and clinical renal outcomes remain rather scanty in patients with T2D, and mostly demonstrate the safety rather than true efficacy of DPP-4is.

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

BACKGROUND AND PURPOSE

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

EXPERIMENTAL APPROACH

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

KEY RESULTS

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

CONCLUSIONS AND IMPLICATIONS

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

LINKED ARTICLES

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

GLP-1 and the kidney: from physiology to pharmacology and outcomes in diabetes

The gastrointestinal tract - the largest endocrine network in human physiology - orchestrates signals from the external environment to maintain neural and hormonal control of homeostasis. Advances in understanding entero-endocrine cell biology in health and disease have important translational relevance. The gut-derived incretin hormone glucagon-like peptide 1 (GLP-1) is secreted upon meal ingestion and controls glucose metabolism by modulating pancreatic islet cell function, food intake and gastrointestinal motility, amongst other effects. The observation that the insulinotropic actions of GLP-1 are reduced in type 2 diabetes mellitus (T2DM) led to the development of incretin-based therapies - GLP-1 receptor agonists and dipeptidyl peptidase 4 (DPP-4) inhibitors - for the treatment of hyperglycaemia in these patients. Considerable interest exists in identifying effects of these drugs beyond glucose-lowering, possibly resulting in improved macrovascular and microvascular outcomes, including in diabetic kidney disease. As GLP-1 has been implicated as a mediator in the putative gut-renal axis (a rapid-acting feed-forward loop that regulates postprandial fluid and electrolyte homeostasis), direct actions on the kidney have been proposed. Here, we review the role of GLP-1 and the actions of associated therapies on glucose metabolism, the gut-renal axis, classical renal risk factors, and renal end points in randomized controlled trials of GLP-1 receptor agonists and DPP-4 inhibitors in patients with T2DM.

Sitagliptin ameliorates high glucose-induced cell proliferation and expression of the extracellular matrix in glomerular mesangial cells

Diabetic nephropathy (DN) is one of the most important causes that leads to end-stage renal disease and the efficacy of strategies currently available for the prevention of DN remains unsatisfactory. Sitagliptin (SIT), which is a dipeptidyl peptidase-4 inhibitor, exhibited a modest beneficial effect on glycated hemoglobin levels and is capable of ameliorating renal ischemia reperfusion injury. By determining the expression of transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF), collagen type IV (ColIV) and fibronectin (FN) levels in high glucose-cultured glomerular mesangial cells (MCs), the present study aimed to assess the anti-proliferative and anti-fibrotic effects of SIT on the therapeutic potential for the prevention of DN and its mechanism. Specifically, cell proliferation was determined via cell counting kit-8 assay, and the expression levels of TGF-β1 and CTGF mRNA were detected by reverse transcription polymerase chain reaction analysis. Furthermore, the secretion of TGF-β1, CTGF, ColIV and FN proteins was measured via enzyme-linked immunosorbent assays. The results demonstrated that high glucose induced the proliferation of MCs and enhanced the expression of TGF-β1, CTGF, ColIV and FN. Furthermore, treatment with SIT inhibited cell proliferation and the expression of TGF-β1, CTGF, ColIV and FN induced by high glucose. In conclusion, SIT inhibits cell proliferation and the expression of the major extracellular matrix proteins induced by high glucose, indicating its value for treating or relieving DN.

Exendin-4-assisted adipose derived mesenchymal stem cell therapy protects renal function against co-existing acute kidney ischemia-reperfusion injury and severe sepsis syndrome in rat

This study tested the hypothesis that combined therapy with exendin-4 (Ex4) and autologous adipose-derived mesenchymal stem cells (ADMSCs) was superior to either alone for protecting renal function against acute kidney ischemia-reperfusion (IR; 40-min ischemia/27-h reperfusion) injury when complicated by sepsis syndrome (SS; by cecal-ligation-puncture). Adult-male Sprague-Dawley rats (n=40) were equally divided into group 1 (sham-control), group 2 (IR-SS), group 3 (IR-SS + Ex4, 10 μg/kg subcutaneously 30 min after reperfusion and daily for 3 days), group 4 [IR-SS + ADMSC (1.2 × 10⁶)], and group 5 (IR-SS + Ex4 + ADMSC). The circulating levels of BUN and creatinine and the ratio of urine protein to creatinine were highest in group 2, lowest in group 1, significantly higher in groups 3 and 4 than group 5, and significantly higher in group 3 than in group 4 (all P<0.0001). Microscopic findings of kidney injury score, inflammatory cells (CD14+, F4/80+), and expressions of glomerular-damage indicators (FSP-1+/WT-1+) and renal tubular-damage indicators (KIM-1+/snail+) showed an identical pattern, whereas expressions of indices of glomerular-integrity (ZO-1+/p-cadherin+/podocin+/synaptopodin+) and angiogenesis (CD31+/vWF+/number of small vessels) biomarkers demonstrated an opposite pattern, to that of creatinine level (all P<0.001). Protein expressions of inflammatory (MMP-9/IL-1ß/TNF-α/TLR-2/TLR-4), apoptotic (cleaved caspase-3/PARP/mitochondrial Bax), and oxidative-stress (NOX-1/NOX-2/oxidized protein) biomarkers exhibited an identical pattern, whereas anti-inflammatory (IL-10/IL-4) biomarkers displayed an opposite pattern, to that of creatinine level (all P<0.001). In conclusion, combined Ex4 and ADMSC therapy significantly protected kidney from acute IR-SS injury.

Head-to-head comparison of structurally unrelated dipeptidyl peptidase 4 inhibitors in the setting of renal ischemia reperfusion injury

Background and Purpose

Results regarding protective effects of dipeptidyl peptidase 4 (DPP4) inhibitors in renal ischaemia–reperfusion injury (IRI) are conflicting. Here we have compared structurally unrelated DPP4 inhibitors in a model of renal IRI.

Experimental Approach

IRI was induced in uninephrectomized male rats by renal artery clamping for 30 min. The sham group was uninephrectomized but not subjected to IRI. DPP4 inhibitors or vehicle were given p.o. once daily on three consecutive days prior to IRI: linagliptin (1.5 mg·kg⁻¹·day⁻¹), vildagliptin (8 mg·kg⁻¹·day⁻¹) and sitagliptin (30 mg·kg⁻¹·day⁻¹). An additional group received sitagliptin until study end (before IRI: 30 mg·kg⁻¹·day⁻¹; after IRI: 15 mg·kg⁻¹·day⁻¹).

Key Results

Plasma‐active glucagon‐like peptide type 1 (GLP‐1) increased threefold to fourfold in all DPP4 inhibitor groups 24 h after IRI. Plasma cystatin C, a marker of GFR, peaked 48 h after IRI. Compared with the placebo group, DPP4 inhibition did not reduce increased plasma cystatin C levels. DPP4 inhibitors ameliorated histopathologically assessed tubular damage with varying degrees of drug‐specific efficacies. Renal osteopontin expression was uniformly reduced by all DPP4 inhibitors. IRI‐related increased renal cytokine expression was not decreased by DPP4 inhibition. Renal DPP4 activity at study end was significantly inhibited in the linagliptin group, but only numerically reduced in the prolonged/dose‐adjusted sitagliptin group. Active GLP‐1 plasma levels at study end were increased only in the prolonged/dose‐adjusted sitagliptin treatment group.

Conclusions and Implications

In rats with renal IRI, DPP4 inhibition did not alter plasma cystatin C, a marker of glomerular function, but may protect against tubular damage.

Matrix Metalloproteinases in Kidney Disease: Role in Pathogenesis and Potential as a Therapeutic Target

Matrix metalloproteinases (MMPs) are large family of proteinases. In addition to a fundamental role in the remodeling of the extracellular matrix, they also cleave a number of cell surface proteins and are involved in multiple cellular processes. MMP activity is regulated via numerous mechanisms, including inhibition by endogenous tissue inhibitors of metalloproteinases (TIMPs). Similar to MMPs, a role for TIMPs has been established in multiple cell signaling pathways. Aberrant expression of MMPs and TIMPS in renal pathophysiology has long been recognized, and with the generation of specific knockout mice, the mechanistic role of several MMPs and TIMPs is becoming more understood and has revealed both pathogenic and protective roles. This chapter will focus on the expression and localization of MMPs and TIMPs in the kidney, as well as summarizing the current information linking these proteins to acute kidney injury and chronic kidney disease. In addition, we will summarize studies suggesting that MMPs and TIMPs may be biomarkers of renal dysfunction and represent novel therapeutic targets to attenuate kidney disease.