Dipeptidyl Peptidase-4 Activity Research Articles

Glucagon-like Peptide-1 Secretion Is Inhibited by Lysophosphatidic Acid.

Glucagon-like peptide-1 (GLP-1) potentiates glucose-stimulated insulin secretion (GSIS). While dozens of compounds stimulate GLP-1 secretion, few inhibit. Reduced GLP-1 secretion and impaired GSIS occur in chronic inflammation. Lysophosphatidic acids (LPAs) are bioactive phospholipids elevated in inflammation. The aim of this study was to test whether LPA inhibits GLP-1 secretion in vitro and in vivo. GLUTag L-cells were treated with various LPA species, with or without LPA receptor (LPAR) antagonists, and media GLP-1 levels, cellular cyclic AMP and calcium ion concentrations, and DPP4 activity levels were analyzed. Mice were injected with LPA, with or without LPAR antagonists, and serum GLP-1 and DPP4 activity were measured. GLUTag GLP-1 secretion was decreased ~70–90% by various LPAs. GLUTag expression of Lpar1, 2, and 3 was orders of magnitude higher than Lpar4, 5, and 6, implicating the former group in this effect. In agreement, inhibition of GLP-1 secretion was reversed by the LPAR1/3 antagonist Ki16425, the LPAR1 antagonists AM095 and AM966, or the LPAR2 antagonist LPA2-antagonist 1. We hypothesized involvement of Gαi-mediated LPAR activity, and found that intracellular cyclic AMP and calcium ion concentrations were decreased by LPA, but restored by Ki16425. Mouse LPA injection caused an ~50% fall in circulating GLP-1, although only LPAR1 or LPAR1/3 antagonists, but not LPAR2 antagonism, prevented this. GLUTag L-cell and mouse serum DPP4 activity was unchanged by LPA or LPAR antagonists. LPA therefore impairs GLP-1 secretion in vitro and in vivo through Gαi-coupled LPAR1/3 signaling, providing a new mechanism linking inflammation with impaired GSIS.

ZD-2, a novel DPP4 inhibitor, protects islet β-cell and improves glycemic control in high-fat-diet-induced obese mice

AimsDipeptidyl peptidase-4 (DPP-4) inhibitors have been extensively used for the treatment of type 2 diabetes mellitus. Nevertheless, side effects like sore throat and diarrhea also occur in DPP-4 inhibitors treatment. The study aims to identify and develop novel DPP-4 inhibitors with better therapeutic profiles. Materials and methodsHere we synthesized a series of vildagliptin analogs, and among which, ZD-2 showed the moderate inhibition of DPP-4 activity compared with vildagliptin. High-fat-diet (HFD) mice were treated with ZD-2 (4.5 and 7.5 mg/kg) or vildagliptin (6 mg/kg) for 7 weeks following the examinations of metabolic index and pancreatic β-cell function. Mouse pancreatic cell line MIN6 was used to evaluate β-cell function, and intestinal enteroendocrine cell line STC-1 was used to evaluate the expression of gut hormones. Key findingsThe IC50 of ZD-2 was over 30-fold higher than vildagliptin. However, both ZD-2 and vildagliptin treatment showed comparable effects on improving glucose tolerance and reducing the steatosis of liver and fat mass in HFD mice. Moreover, ZD-2 exerted β-cell-protective actions by preserving islet β-cell mass and increasing the expression of functional β-cell-related genes. Additionally, ZD-2 also stimulated the expression of gut hormones in STC-1 cells. SignificanceZD-2 showed comparable anti-diabetic activities in HFD-fed mice although its lower potency on inhibition of DPP-4 compared with vildagliptin. Protection of β-cell function might contribute to its anti-diabetic effects.

GLP1 Exerts Paracrine Activity in the Intestinal Lumen of Human Colon.

GLP1 produced in the upper part of the gut is released after food intake and acts by activating insulin secretion, but the role of GLP1 in the colon, where it is predominantly produced, remains unknown. Here we characterized the apical versus basolateral secretion of GLP1 and PYY and the paracrine mechanisms of action of these enterohormones in the human colon. We stimulated human colon tissue in different ex vivo models with meat peptone and we used immunofluorescence to study the presence of canonical and non-canonical receptors of GLP1. We found that PYY and GLP1 are secreted mainly at the gut lumen in unstimulated and stimulated conditions. We detected DPP4 activity and found that GLP1R and GCGR are widely expressed in the human colon epithelium. Unlike GLP1R, GCGR is not expressed in the lamina propria, but it is located in the crypts of Lieberkühn. We detected GLP1R expression in human colon cell culture models. We show that the apical secretion of PYY and GLP1 occurs in humans, and we provide evidence that GLP1 has a potential direct paracrine function through the expression of its receptors in the colon epithelium, opening new therapeutic perspectives in the use of enterohormones analogues in metabolic pathologies.

Proline-specific peptidase activities (DPP4, PRCP, FAP and PREP) in plasma of hospitalized COVID-19 patients

BackgroundCOVID-19 patients experience several features of dysregulated immune system observed in sepsis. We previously showed a dysregulation of several proline-selective peptidases such as dipeptidyl peptidase 4 (DPP4), fibroblast activation protein alpha (FAP), prolyl oligopeptidase (PREP) and prolylcarboxypeptidase (PRCP) in sepsis. In this study, we investigated whether these peptidases are similarly dysregulated in hospitalized COVID-19 patients. MethodsFifty-six hospitalized COVID-19 patients and 32 healthy controls were included. Enzymatic activities of DPP4, FAP, PREP and PRCP were measured in samples collected shortly after hospital admission and in longitudinal follow-up samples. ResultsCompared to healthy controls, both DPP4 and FAP activities were significantly lower in COVID-19 patients at hospital admission and FAP activity further decreased significantly in the first week of hospitalization. While PRCP activity remained unchanged, PREP activity was significantly increased in COVID-19 patients at hospitalization and further increased during hospital stay and stayed elevated until the day of discharge. ConclusionThe changes in activities of proline-selective peptidases in plasma are very similar in COVID-19 and septic shock patients. The pronounced decrease in FAP activity deserves further investigation, both from a pathophysiological viewpoint and as its utility as a part of a biomarker panel.

Development, validation and application of aliquid chromatography-tandem mass spectrometry method for the activity and inhibition of DPP-4.

Background: Inhibition of the enzyme dipeptidyl peptidase 4 (DPP-4) is a pharmaceutical treatment for type 2 diabetes. To demonstrate bioequivalence of enzyme inhibition of a new dosage form of the inhibitor vildagliptin, a method for enzyme activity was developed, validated and applied using liquid chromatography and tandem mass spectrometry (LC-MS/MS). Results: The method was validated fit for purpose, including accuracy, precision as well as thestability of the activity and the inhibition of DPP-4in human plasma. Conclusion: A method for the determination of the activity and inhibition of DPP-4 was developed using LC-MS/MS readout; the characteristics and performance of the method met predefined acceptance criteria and were fit for the purpose of a bioequivalence clinical trial.

Decreased circulating dipeptidyl peptidase-4 enzyme activity is prognostic for severe outcomes in COVID-19 inpatients.

Aim:To investigate the serum circulating DPP4 activity in patients with COVID-19 disease.Materials & methods:Serum samples from 102 hospitalized COVID-19 patients and 43 post-COVID-19 plasma donors and 39 SARS-CoV-2 naive controls and their medical data were used. Circulating DPP4 activities according to different COVID-19 disease peak severity (WHO) groups at sampling and at peak were assessed.Results:A significant decrease (p < 0.0001) in serum DPP4 activity was found in study groups of higher disease severity. When the circulating DPP4 activity was assessed as a prognostic marker, the logistic regression (p = 0.0023) indicated that the enzyme activity is a predictor of mortality (median 9.5 days before death) with receiver operating characteristic area under the curves of 73.33% (p[area = 0.5] < 0.0001) as single predictor and 83.45% (p[area = 0.5] < 0.0001) in combination with age among hospitalized patients with COVID-19.Conclusion:Decreased circulating DPP4 activity is associated with severe COVID-19 disease and is a strong prognostic biomarker of mortality.

Dipeptidyl peptidase-4 is associated with myogenesis in patients with adolescent idiopathic scoliosis possibly via mediation of insulin sensitivity

BackgroundAbnormal metabolic features have been previously described in adolescent idiopathic scoliosis (AIS) patients. As an important regulator involved in energy metabolism, DPP-4 activity was reported to be remarkably decreased in osteoblasts of AIS patients. To date, there was still a lack of knowledge concerning the role of DPP-4 in the myogenesis of AIS.MethodsCirculation DPP-4 level was assessed in the serum of 80 AIS girls and 50 healthy controls by ELISA. Myoblasts were purified from muscle specimens of AIS patients and LDH controls, and then treated with metabolic effectors including glucose and insulin. CCK-8 assay was used to assess the cell viability and myotube fusion index was calculated to evaluate myogenesis ability. Gene expressions of downstream signals of DPP-4 were evaluated by RT-qPCR and Western blot respectively.ResultsAIS girls had remarkably down-expressed DPP-4 in both serum level (0.76 fold) and tissue (0.68 fold) level. Treatment with metabolic effectors led to significantly increased DPP-4 expression in the control cells, while there was no increase of DPP-4 in AIS cells. CCK-8 assay showed that the proliferation rate of control cells was significantly increased after being treated. Remarkably higher fusion index was also observed in the treated control cells. By contrast, the fusion index and cell proliferation rate were comparable between the treated and the untreated AIS cells.ConclusionsOur study suggested a potential role of DPP-4 in abnormal metabolic condition of AIS patients. Compared with control cells, AIS myoblasts presented obviously impaired sensitivity to the treatment of glucose and insulin. Aberrant DPP-4 expression could lead to impaired insulin sensitivity in myoblasts and further influence the cell viability during myogenesis. The molecular mechanism connecting DPP-4 and insulin-related signaling in AIS is worthy of further investigation.

An Observational Study showing Dipeptidyl Peptidase-4 (DPP-4) Activity and Gene Expression Variation in Chronic Liver Disease (CLD) Patients from a Tertiary Care Hospital of Eastern India.

Introduction:The studies in animal models of cirrhosis suggest that dipeptidyl peptidase type 4 (DPP-4) enzymes play a crucial role in disease pathogenesis. In this clinical observational study, activity of DPP-4 and related gene expression were analysed in chronic liver disease patients.Objectives:To understand the DPP-4 enzyme activity variation in the common types of chronic liver disease by assessing plasma and peripheral blood mononuclear cell (PBMC) DPP-4 activity and comparing with healthy controls and to explore DPP-4 gene expression in PBMC.Methods:We recruited 130 study subjects in four cohorts—46 nonalcoholic fatty liver disease (NAFLD), 23 non-alcoholic cirrhosis (NAC) excluding viral aetiology, 21 alcoholic liver disease (ALC), and 40 control subjects. Blood samples were analysed for relevant biochemical parameters and plasma DPP-4 activity. PBMC fraction was used for the DPP-4 activity assay and gene expression analysis.Results:We found that lower plasma DPP-4 activity among patient cohorts but this was not statistically significant. The PBMC DPP-4 activity was significantly lower in NAFLD cohort. In the same cohort, DPP-4 gene expression in PBMC fraction was significantly increased (P < 0.05). There was significant correlation between plasma DPP-4 activity and liver injury marker alanine aminotransferase (ALT) among NAFLD (rho = 0.459, P < 0.01), NAC (rho = 0.475, P < 0.05), and ALC (rho = –0.572, P < 0.01) patients. Plasma DPP-4 activity modestly predicted ALT plasma level (beta coefficient = 0.489, P < 0.01).Conclusions:The PBMC DPP-4 activity and DPP-4 gene expression gets significantly altered in NAFLD patients. Plasma DPP-4 activity also shows correlation with ALT levels in CLD patients. The role of DPP-4 in disease pathology in NAFLD and other forms of CLD needs to be explored.

A haplotype in the dipeptidyl peptidase 4 gene impacts glycemic-related traits of Brazilian older adults.

Dipeptidyl peptidase 4 (DPP4) regulates various physiological pathways and has a pivotal role in glucose homeostasis. The objective of this study was to verify the association of a haplotype constituted by two single nucleotide polymorphisms (rs2268894 and rs6741949) in the DPP4 gene with type 2 diabetes mellitus (T2DM) and fasting glycemia-related variables in a sample of Brazilian older adults, taking serum levels and enzymatic activity of DPP4 into account. Clinical, biochemical, and anthropometric characteristics as well as DPP4 serum levels and enzymatic activity were determined in 800 elderly (≥60 years old) individuals. Assessment of polymorphic sites was performed by real-time PCR whereas haplotypes were inferred from genotypic frequencies. Statistical analyses compared measures and proportions according to T2DM diagnosis and DPP4 haplotypic groups. The most common haplotype consisted of the T-rs2268894/G-rs6741949 string, which was 20% more frequent among non-diabetics. Considering non-diabetic patients alone, carriers of the T/G haplotype had significantly lower levels of blood glucose, insulin, HOMA-IR index, and DPP4 activity. Among diabetic patients, the T/G haplotype was associated with lower DPP4 levels whereas glycemic scores were not affected by allelic variants. Our results suggested that the genetic architecture of DPP4 affects the glycemic profile and DPP4 serum levels and activity among elderly individuals according to the presence or absence of T2DM, with a possible implication of the T/G haplotype to the risk of T2DM onset.

Serum dipeptidyl peptidase-4 activity and progranulin level in polycystic ovary syndrome patients.

Background:Evidence showed that abnormal alteration of adipokines level may perform a key role in polycystic ovary syndrome (PCOS) pathogenesis. Dipeptidyl peptidase-4 (DPP4) and progranulin (PGRN) are two novel adipokines related to insulin resistance (IR). Thus, we aimed to determine the serum DPP4 activity and PGRN level in PCOS patients with and without IR, and non-PCOS women.Methods:Ninety women were recruited in the present study including 60 PCOS patients (divided into two groups of 30 IR and 30 non-IR) and 30 non-PCOS women. Serum levels of insulin, fasting blood glucose, PGRN, and DPP4 activity were measured, and IR indices were calculated.Results:DPP4 activity was significantly higher in PCOS-IR and PCOS-NIR patients than non-PCOS women (p<0.001, P=0.011, respectively), whereas no significant variation was detected between two groups of PCOS subjects. There was no significant difference in the level of PGRN in the three groups of the present study.Conclusion:The present study suggests that increasing DPP4 activity may be associated with PCOS.

Neuroprotective effects of linagliptin in a rotenone-induced rat model of Parkinson's disease.

The present study investigates the antiParkinsonian activity of dipeptidyl peptidase-4 (DPP-IV) inhibitor, linagliptin. The experimental Parkinson's disease (PD) was induced by administration of rotenone at a dose of 1.5 mg/kg at alternate day subcutaneously for 21 days. Standard drug (levodopa-200 mg/kg and carbidopa-50 mg/kg) and treatment drug (linagliptin-5 mg/kg, 10 mg/kg, and 20mg/kg) were administered orally daily 1 h before rotenone administration. In a rat rotenone model, linagliptin improved muscle coordination, motor performance, and corrected akinesia. Pretreatment with linagliptin showed significant higher levels of superoxide dismutase, catalase, and glutathione in brain homogenate of animals. Linagliptin significantly elevated the levels of striatal DA and active glucagon-like peptide 1 in brain homogenate of animals. Furthermore, linagliptin amended alterations induced by rotenone in the thiobarbituric acid reactive substances and inflammatory marker such as tumor necrosis factor-α level. The results of the present study indicate the neuroprotective potential of linagliptin for the management of PD might be due to remarkable improvement in motor functions, antioxidant, anti-inflammatory, anti-apoptotic, and neuroprotective mechanisms.

Virtual screening and in vitro assays of novel hits as promising DPP-4 inhibitors

Diabetes is a metabolic disorder that presents hyperglycemia and vascular complications due to the non-production of insulin or its inappropriate use by the body. One of the strategies to treat diabetes is the inhibition of dipeptidyl peptidase-4 (DPP-4) and it is interesting to conduct virtual screening studies to search for new inhibitors of the DPP-4 enzyme. This study involves a virtual screening using the crystallographic structure of DPP-4 and a compound subset from the ZINC database. To filter this compound subset, we used some physicochemical properties, positioning at the three DPP-4 binding sites, molecular interactions, and ADME-Tox properties. The conformations of ligands obtained from AutoDock Vina were analyzed using a consensus with other algorithms (AutoDock and GOLD). The compounds selected from virtual screening were submitted to biological assays using the “DPPIV-Glo™ protease assay”. Cytotoxicity tests were also performed. One promising compound (ZINC1572309) established interactions with important residues at the binding site. The results of the ADME-Tox prediction for ZINC1572309 were compared with a reference drug (sitagliptin). The cytotoxicity of sitagliptin and ZINC1572309 were evaluated using the XTT short-term cytotoxic assay, including normal and tumor cell lines to observe the cellular response to inhibitor treatment at different genetic bases. Both compounds (ZINC1572309 and the reference drug – sitagliptin) also inhibited DPP-4 activity, suggesting interesting biological effects of the selected compound at non-cytotoxic concentrations. Therefore, from in silico and in vitro studies, a potential hit as DPP-4 inhibitor was discovered and it can be structurally optimized to achieve suitable activity and pharmacokinetic profiles.

Distal mutation V486M disrupts the catalytic activity of DPP4 by affecting the flap of the propeller domain.

Dipeptidyl peptidase-4 (DPP4) plays a crucial role in regulating the bioactivity of glucagon-like peptide-1 (GLP-1) that enhances insulin secretion and pancreatic β-cell proliferation, making it a therapeutic target for type 2 diabetes. Although the crystal structure of DPP4 has been determined, its structure-function mechanism is largely unknown. Here, we examined the biochemical properties of sporadic human DPP4 mutations distal from its catalytic site, among which V486M ablates DPP4 dimerization and causes loss of enzymatic activity. Unbiased molecular dynamics simulations revealed that the distal V486M mutation induces a local conformational collapse in a β-propeller loop (residues 234–260, defined as the flap) and disrupts the dimerization of DPP4. The “open/closed” conformational transitions of the flap whereby capping the active site, are involved in the enzymatic activity of DPP4. Further site-directed mutagenesis guided by theoretical predictions verified the importance of the conformational dynamics of the flap for the enzymatic activity of DPP4. Therefore, the current studies that combined theoretical modeling and experimental identification, provide important insights into the biological function of DPP4 and allow for the evaluation of directed DPP4 genetic mutations before initiating clinical applications and drug development.

Inhibition of Podocytes DPP4 Activity Is a Potential Mechanism of Lobeliae Chinensis Herba in Treating Diabetic Kidney Disease.

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease and has become a serious public health problem worldwide. Dipeptidyl peptidase-4 (DPP4) inhibitors, an emerging drug for the treatment of diabetes, have been found to have renoprotective effects in addition to glucose-lowering effects and therefore have the potential to be a treatment modality for DKD. Lobeliae Chinensis Herba (LCH), a traditional Chinese herb widely used in the treatment of diabetes, has recently been found to have a hypoglycaemic mechanism related to the inhibition of DPP4. Firstly, analysis of single-cell sequencing data from mouse kidneys in the National Center for Biotechnology Information (NCBI) database revealed that DPP4 was specifically upregulated in DKD podocytes and was associated with podocyte proliferation. Subsequently, the network pharmacology approach was applied to the screening of compounds. Twelve LCH active ingredients targeting DPP4 were extracted from the Traditional Chinese Medicine System Pharmacology (TCMSP) database. In addition, these 12 compounds and DPP4 were molecularly docked to predict the probability of them affecting DPP4 activity. In vitro, Quercetin, Methyl rosmarinate, Kaempferol, Diosmetin and Acacetin were demonstrated to retard podocyte proliferation by inhibiting DPP4 activity and were the top five compounds predicted by molecular docking to be the most likely to affect DPP4 activity. The half maximal inhibitory concentration (IC50) of the five compounds for DPP4 activity were as follows. Acacetin Log IC50 = −8.349, 95%CI (−9.266, −7.265), Diosmtrin Log IC50 = −8.419, 95%CI (−8.889, −7.950), Log IC50 = −8.349, 95%CI (−9.266, −7.265), Methyl rosmarinate Log IC50 = −8.415, 95%CI (−8.751, −8.085), Kaempferol Log IC50 = −8.297, 95%CI (−9.001, −7.615), Quercetin Log IC50 = −8.864, 95%CI (−9.107, −8.615). Finally, Quercetin, Methyl rosmarinate, Kaempferol, Diosmetin and Acacetin qualified for pharmacokinetic and drug similarity screening and have the potential to be the most promising oral agents for the treatment of DKD.

Influence of Dipeptidyl Peptidase-4 (DPP4) on Mesenchymal Stem-Cell (MSC) Biology: Implications for Regenerative Medicine - Review.

Dipeptidyl peptidase IV (DPP4) is a ubiquitous protease that can be found in membrane-anchored or soluble form. Incretins are one of the main DPP4 substrates. These hormones regulate glucose levels, by stimulating insulin secretion and decreasing glucagon production. Because DPP4 levels are high in diabetes, DPP4 inhibitor (DPP4i) drugs derived from gliptin are widespread used as hypoglycemic agents for its treatment. However, as DPP4 recognizes other substrates such as chemokines, growth factors and neuropeptides, pleiotropic effects have been observed in patients treated with DPP4i. Several of these substrates are part of the stem-cell niche. Thus, they may affect different physiological aspects of mesenchymal stem-cells (MSC). They include viability, differentiation, mobilization and immune response. MSC are involved in tissue homeostasis and regeneration under both physiological and pathological conditions. Therefore, such cells and their secretomes have a high clinical potential in regenerative medicine. In this context, DPP4 activity may modulate different aspects of MSC regenerative capacity. Therefore, the aim of this review is to analyze the effect of different DPP4 substrates on MSC. Likewise, how the regulation of DPP4 activity by DPP4i can be applied in regenerative medicine. That includes treatment of cardiovascular and bone pathologies, cutaneous ulcers, organ transplantation and pancreatic beta-cell regeneration, among others. Thus, DPP4i has an important clinical potential as a complement to therapeutic strategies in regenerative medicine. They involve enhancing the differentiation, immunomodulation and mobilization capacity of MSC for regenerative purposes.

First-in-Human, Single-Ascending Dose and Food Effect Studies to Assess the Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of Cetagliptin, a Dipeptidyl Peptidase-4 Inhibitor for the Treatment of Type 2 Diabetes Mellitus.

Cetagliptin is a highly selective dipeptidyl peptidase-4 inhibitor under development to treat type 2 diabetes mellitus. This first-in-human study was conducted to characterise the pharmacokinetics, pharmacodynamics and tolerability of single-ascending oral doses of cetagliptin in healthy subjects. In addition, the effect of food on pharmacokinetics was evaluated. Study 1 enrolled 66 healthy subjects in a double-blind, randomised, placebo-controlled, single-dose escalation study; sitagliptin was employed as a positive open-label control. Forty-four subjects were assigned to seven cohorts (cetagliptin 12.5, 25, 50, 100, 200, 300 or 400 mg); 12 subjects were assigned to the placebo group. The remaining ten subjects received sitagliptin 100 mg as the positive control. Blood, urine and faeces were collected for the pharmacokinetic analysis and determination of plasma dipeptidyl peptidase-4 inhibition, active glucagon-like peptide-1, glucose and insulin levels. In Study 2, 14 healthy subjects were assigned to a randomised, open-label, two-period crossover study, and received a single oral dose of cetagliptin 100 mg in the fasted state or after a high-fat meal, with a 14-day washout period between treatments. Blood samples were collected to evaluate the effects of food on the pharmacokinetics of cetagliptin. Following administration of a single oral dose, cetagliptin was rapidly absorbed, presenting a median time to maximum concentration of 1.0-3.25 h. The terminal half-life ranged between 25.8 and 41.3 h, which was considerably longer than that of sitagliptin. The area under the plasma concentration-time curve was approximately dose proportional between 25 mg and 400 mg, and the increase in maximum concentration was greater than dose proportional. The unchanged drug was mainly excreted in the urine (27.2-46.2% of dose) and minimally via the faeces (1.4% of dose). Dipeptidyl peptidase-4 inhibition, an increase in active glucagon-like peptide-1 and a slight decrease in blood glucose were observed, whereas insulin was not significantly altered when compared with placebo. The weighted average dipeptidyl peptidase-4 inhibition by cetagliptin 100 mg was higher than that mediated by sitagliptin 100 mg. Cetagliptin was well tolerated up to a single oral dose of 400 mg. No food effects were noted. Cetagliptin inhibited plasma dipeptidyl peptidase-4 activity, increased levels of active glucagon-like peptide-1 and was well tolerated at single doses up to 400 mg, eliciting no dose-limiting toxicity in healthy volunteers. Food did not affect the pharmacokinetics of cetagliptin. The studies were registered at http://www.chinadrugtrials.org.cn (Nos. CTR20180167 and CTR20181331).

Evaluation of the efficacy of dipeptidyl peptidase-4 enzyme and selenium element in people with kidney failure in Kirkuk governorate

The samples were collected between the period 12/2020–3/2021, and the number of patient samples was 75 blood samples, which were divided into 30 blood samples from patients before and after the hemodialysis process, and 15 blood samples from patients taking treatment they did not undergo hemodialysis, their ages ranged between 20 and 55 years. Twenty-five 25 blood samples were collected from apparently healthy people, ranging in age from 20 to 55 years, and specialized doctors diagnosed the disease cases. The results showed a significant increase in the activity of the enzyme Dipeptidyl Peptidase-4 (DPP-4) in the total patients 59.161 ± 4.070 UI/L with a probability level of P ≤ 0.01 compared with the healthy controls 35.380 ± 10.278UI/L, where the rate of the activity of enzyme Dipeptidyl Peptidase-4 in the serum of patients with renal failure before hemodialysis 86.053 ± 12.008 UI/L as well as increased in the blood of patients with renal failure who are receiving treatment was 57,855 ± 9.415 UI/L. While the concentration of enzyme decreased in the serum of patients with renal failure after hemodialysis 51.579 ± 8.788 UI/L compared to the group of patients before hemodialysis and during treatment, and fall at the probability level of P ≤ 0.01 in the class and concentration of selenium at the total level of patients as well as before and after the hemodialysis process. In contrast, its level increased among the patients taking the treatment and at the level of the probability P ≤ 0.01 compared to its level in all patients and before and after the dialysis process bloody. The effect of age on the status of the enzyme Dipeptidyl Peptidase-4 and selenium was also studied in according groups of patients, it found a significant impact of age on the level of the enzyme and the selenium element, as substantial differences were found that indicated the high level of the enzyme and the selenium element in elderly patients aged 36–55 years, while it decreased slightly in young patients whose ages ranged from 20 to 35 years old.

Sitagliptin attenuates arterial calcification by downregulating oxidative stress-induced receptor for advanced glycation end products in LDLR knockout mice

Diabetes is a complex disease characterized by hyperglycemia, dyslipidemia, and insulin resistance. Plasma advanced glycation end products (AGEs) activated the receptor for advanced glycation end products (RAGE) and the activation of RAGE is implicated to be the pathogenesis of type 2 diabetic mellitus (T2DM) patient vascular complications. Sitagliptin, a dipeptidyl peptidase-4 (DPP4) inhibitor, is a new oral hypoglycemic agent for the treatment of T2DM. However, the beneficial effects on vascular calcification remain unclear. In this study, we used a high-fat diet (HFD)-fed low-density lipoprotein receptor deficiency (LDLR−/−) mice model to investigate the potential effects of sitagliptin on HFD-induced arterial calcification. Mice were randomly divided into 3 groups: (1) normal diet group, (2) HFD group and (3) HFD + sitagliptin group. After 24 weeks treatment, we collected the blood for chemistry parameters and DPP4 activity measurement, and harvested the aorta to evaluate calcification using immunohistochemistry and calcium content. To determine the effects of sitagliptin, tumor necrosis factor (TNF)-α combined with S100A12 was used to induce oxidative stress, activation of nicotinamide adenine dinucleotide phosphate (NADPH), up-regulation of bone markers and RAGE expression, and cell calcium deposition on human aortic smooth muscle cells (HASMCs). We found that sitagliptin effectively blunted the HFD-induced artery calcification and significantly lowered the levels of fasting serum glucose, triglyceride (TG), nitrotyrosine and TNF-α, decreased the calcium deposits, and reduced arterial calcification. In an in-vitro study, both S100A12 and TNF-α stimulated RAGE expression and cellular calcium deposits in HASMCs. The potency of S100A12 on HASMCs was amplified by the presence of TNF-α. Sitagliptin and Apocynin (APO), an NADPH oxidase inhibitor, inhibited the TNF-α + S100A12-induced NADPH oxidase and nuclear factor (NF)-κB activation, cellular oxidative stress, RAGE expression, osteo transcription factors expression and calcium deposition. In addition, treatment with sitagliptin, knockdown of RAGE or TNF-α receptor blunted the TNF-α + S100A12-induced RAGE expression. Our findings suggest that sitagliptin may suppress the initiation and progression of arterial calcification by inhibiting the activation of NADPH oxidase and NF-κB, followed by decreasing the expression of RAGE.

Dipeptidyl peptidase-4 (DPP4) inhibitor sitagliptin alleviates liver inflammation of diabetic mice by acting as a ROS scavenger and inhibiting the NF\u03baB pathway

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

Transient Dexamethasone Loading Induces Prolonged Hyperglycemia in Male Mice With Histone Acetylation in Dpp-4 Promoter.

Glucocorticoid causes hyperglycemia, which is common in patients with or without diabetes. Prolonged hyperglycemia can be experienced even after the discontinuation of glucocorticoid use. In the present study, we examined the time course of blood glucose level in hospital patients who received transient glucocorticoid treatment. In addition, the mechanism of prolonged hyperglycemia was investigated by using dexamethasone (Dexa)-treated mice and cultured cells. The blood glucose level in glucose tolerance tests, level of insulin and glucagon-like peptide 1 (GLP-1), and the activity of dipeptidyl peptidase 4 (DPP-4) were examined during and after Dexa loading in mice, with histone acetylation level of the promoter region. Mice showed prolonged hyperglycemia during and after transient Dexa loading accompanied by persistently lower blood GLP-1 level and higher activity of DPP-4. The expression level of Dpp-4 was increased in the mononuclear cells and the promoter region of Dpp-4 was hyperacetylated during and after the transient Dexa treatment. In vitro experiments also indicated development of histone hyperacetylation in the Dpp-4 promoter region during and after Dexa treatment. The upregulation of Dpp-4 in cultured cells was significantly inhibited by a histone acetyltransferase inhibitor. Moreover, the histone hyperacetylation induced by Dexa was reversible by treatment with a sirtuin histone deacetylase activator, nicotinamide mononucleotide. We identified persistent reduction in blood GLP-1 level with hyperglycemia during and after Dexa treatment in mice, associated with histone hyperacetylation of promoter region of Dpp-4. The results unveil a novel mechanism of glucocorticoid-induced hyperglycemia, and suggest therapeutic intervention through epigenetic modification of Dpp-4.