Dipeptidyl Peptidase IV Levels Research Articles

Antidiabetic activity of Commiphora mukul and Phyllanthus emblica and Computational analysis for the identification of active principles with dipeptidyl peptidase IV inhibitory activity.

The medicinal plants may serve as natural alternatives to synthetic antidiabetic medications such as dipeptidyl peptidase-IV (DPP-IV) inhibitors, which are commonly prescribed in clinical practise. The medicinal plants: Commiphora mukul and Phyllanthus emblica have considerable DPP-IV inhibitory efficacy, according to our findings. The present study is an extension of the previous study conducted in our laboratory and was designed to confirm the antidiabetic effects of C. mukul and P. emblica in the streptozotocin diabetes model and elucidate the active principles responsible for DPP-IV inhibition. C. mukul (Guggul) and P. emblica (Amla) have the ability to inhibit DPP-IV and have anti-diabetic properties in a Type 2 diabetes mellitus experimental model. The binding sites and affinity of the active principles of C. mukul (Gluggusterone E, Gluggusterone Z) and P. emblica (Pzrogallol, beta-glucogallin, and gallic acid) responsible for DPP-IV enzyme inhibition were identified using in silico studies and compared to Vildagliptin, a synthetic DPP-IV inhibitor. The Vildagliptin and therapy groups had significantly lower glycated hemoglobin and DPP-IV levels. The anti-diabetic effect of C. mukul and P. emblica is due to their DPP-IV inhibitory action. The DPP-IV inhibitory action of Gluggusterone E, Gluggusterone Z, and beta-Glucogallin was found to be superior to Vildagliptin in docking tests.

Dipeptidyl peptidase-IV in chronic heart failure with reduced ejection fraction

BackgroundAn association between dipeptidyl peptidase-IV (DPP-IV) inhibitors with worse prognosis in HF has been suggested. We aimed to assess the serum DPP-IV levels in chronic stable HF patients and determine their association with prognosis. Methods and resultsChronic stable HF patients with optimized prognostic-modifying therapy were prospectively recruited. Exclusion criteria: 1) ejection fraction>50%, 2) hospitalizations or therapeutic adjustments in the previous 2months; 3) patients on renal replacement therapy, and 4) use of DPP-IV inhibitors. A fasting venous blood sample was collected and DPP-IV was measured. Patients were followed-up for 3years and the endpoint studied was all-cause death. Patients' characteristics were compared according to DPP-IV quartiles. A Cox regression analysis was performed and multivariate models were built. The 3rd DPP-IV quartile was the reference category. We studied 264 patients. Mean age: 69 (±13)years, 70.5% were male and 33.7% diabetic. Median (IQR) serum DPP-IV levels were 455.6 (350.0–625.5)ng/mL. DPP-IV had an inverse relationship with age. Patients in 3rd DPP-IV quartile were in lower NYHA classes and had the lowest 3years all-cause mortality. Patients in the 1st DPP-IV quartile had a multivariate adjusted HR of 3-year mortality of 2.62 (95%CI: 1.15–5.95) when compared with reference category and the HR for the 4th quartile was of 3.79 (95%CI: 1.68–8.54). ConclusionsThere is a U-shaped association of serum DPP-IV with mortality in chronic systolic HF patients. Patients in the 3rd DPP-IV quartile have the best multivariate adjusted 3-year survival. DPP-IV inhibition might be harmful in patients with low DPP-IV.

Abstract 5108: Glucagon like peptide 1 (GLP1) up-regulation in hypoxic and nutrient deprived microenvironment promotes neuroblastoma cell survival

Abstract Introduction: Glucagon-like peptide 1 (GLP1) an incretin has demonstrated to increase insulin secretion in a glucose-dependent manner and is shown to be neuroprotective. GLP1 also promotes angiogenesis. Hypoxia, a common feature in solid tumors including neuroblastoma, promotes tumor progression by upregulation of hypoxia responsive factors. Little is known about alterations of GLP1 expression in neuroblastoma under hypoxic condition. GLP1 is rapidly inactivated by dipeptidyl peptidase IV (DPPIV) mediated enzymatic cleavage. Previously we have shown that DPPIV suppresses neuroblastoma survival and angiogenesis. In this study, we examined whether GLP1, its receptor GLP1R, and DPPIV expressions are altered after exposing neuroblastoma cells to hypoxic conditions of oxygen and nutrient deprivation (OND). We then examined the direct effects of GLP1 on neuroblastoma proliferation and survival, and evaluated if DPPIV modulates GLP1 mediated functions. Methods: We used Neuro-2a, a mouse neuroblastoma cells as a model. In vitro experiments were performed exposing these cells to conditions mimicking tumor areas that display oxygen and nutrient deprivation, followed by re-oxygenation. Immunofluorescence staining was used to analyze the protein expression of GLP1, GLP-1R, and DPPIV. RT-PCR was used to measure mRNA levels. Effects of DPPIV on GLP1 mediated Neuro-2a cell proliferation and survival was evaluated by MTT and live/dead cell assay. Levels of PI3K/AKT were determined by western blot analysis. Results: Neuro-2a cells subjected to OND showed about 2 fold increase in the GLP1 protein and mRNA levels at four hours of re-oxygenation after 4 hours of OND. However, GLP1 protein levels decreased drastically after one day of re-oxygenation, while DPPIV levels were highly upregulated. GLP1R was also downregulated at one day of re-oxygenation. At this time point, cell viability was decreased by 30-40%. Pre-treatment with DPPIV inhibitor rescued the protective effects of GLP1. Furthermore, exogenous GLP1 stimulated cell proliferation and increased Neuro-2a cell viability by 2-3 fold. GLP1dependent action was mediated via increased levels of phosphorylated AKT, a pro-survival signaling molecule. The effects of GLP1 were suppressed in presence of DPPIV. Conclusion: The results indicate an inverse correlation between DPPIV and GLP1 levels in Neuro-2a cells. Together, these studies indicate that GLP1-DPPIV interaction may play an important role in promoting neuroblastoma cell proliferation and survival. Citation Format: Umadevi V. Wesley, Nausheen Singh, Robert J. Dempsey. Glucagon like peptide 1 (GLP1) up-regulation in hypoxic and nutrient deprived microenvironment promotes neuroblastoma cell survival. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5108.

Berberine regulates glycemia via local inhibition of intestinal dipeptidyl peptidase-Ⅳ

Objective: To investigate the effect of berberine on glycemia regulation in rats with diabetes and the related mechanisms. Methods: Diabetic-like rat model was successfully induced by intraperitoneal injection of streptozotocin in 50 out of 60 male SD rats, which were then randomly divided into 5 groups with 10 rats in each:control group (received vehicle only), positive drug control group (sitagliptin 10 mg·kg-1·d-1), low-dose berberine group (30 mg·kg-1·d-1), moderate-dose berberine group (60 mg·kg-1·d-1), and high-dose berberine group (120 mg·kg-1·d-1). All animals were fed for 3 d, and fasting blood sampling was performed on day 3 of administration. Rats were given glucose (2 g/kg) by gavage 30 min after the last dose. Blood and intestinal samples were obtained 2 h after glucose loading. Fasting blood glucose (FBG) and 2-h postprandial plasma glucose (2h-PPG) were detected by using biochemical analyzer, and insulin, glucagon-like peptide-1 (GLP-1) and dipeptidyl peptidase-Ⅳ(DPP-Ⅳ) were measured by using ELISA kit. Results: No significant difference in FBG and serum DPP-Ⅳ level were found between berberine groups and control group (all P>0.05). Compared with control group, serum levels of GLP-1 and insulin were increased in high-and moderate-dose berberine groups, while 2h-PPG was decreased (all P<0.05); GLP-1 levels in the intestinal samples were increased, while DPP-Ⅳ levels were decreased in all berberine groups (all P<0.05). Conclusions: Short-term berberine administration can decrease 2h-PPG level in streptozotocin-induced diabetic rat model through local inhibition of intestinal DPP-Ⅳ. The efficacy of DPP-Ⅳ inhibitor may be associated with its intestinal pharmacokinetics.

Dipeptidyl peptidase IV as a potential target for selective prodrug activation and chemotherapeutic action in cancers.

The efficacy of chemotherapeutic drugs is often offset by severe side effects attributable to poor selectivity and toxicity to normal cells. Recently, the enzyme dipeptidyl peptidase IV (DPPIV) was considered as a potential target for the delivery of chemotherapeutic drugs. The purpose of this study was to investigate the feasibility of targeting chemotherapeutic drugs to DPPIV as a strategy to enhance their specificity. The expression profile of DPPIV was obtained for seven cancer cell lines using DNA microarray data from the DTP database, and was validated by RT-PCR. A prodrug was then synthesized by linking the cytotoxic drug melphalan to a proline-glycine dipeptide moiety, followed by hydrolysis studies in the seven cell lines with a standard substrate, as well as the glycyl-prolyl-melphalan (GP-Mel). Lastly, cell proliferation studies were carried out to demonstrate enzyme-dependent activation of the candidate prodrug. The relative RT-PCR expression levels of DPPIV in the cancer cell lines exhibited linear correlation with U95Av2 Affymetrix data (r2 = 0.94), and with specific activity of a standard substrate, glycine-proline-p-nitroanilide (r2 = 0.96). The significantly higher antiproliferative activity of GP-Mel in Caco-2 cells (GI50 = 261 μM) compared to that in SK-MEL-5 cells (GI50 = 807 μM) was consistent with the 9-fold higher specific activity of the prodrug in Caco-2 cells (5.14 pmol/min/μg protein) compared to SK-MEL-5 cells (0.68 pmol/min/μg protein) and with DPPIV expression levels in these cells. Our results demonstrate the great potential to exploit DPPIV as a prodrug activating enzyme for efficient chemotherapeutic drug targeting.

Comparison of Dipeptidyl‐Peptidase IV Levels in Plasma and Saliva (LB754)

Dipeptidyl‐Peptidase IV (DPP‐IV) is an enzyme present in the blood, acting as a regulator for incretin hormones, such as glucagon‐like peptide(GLP‐1) and glucose‐dependent insulinotropic polypeptide (GIP). As a result of this regulatory action, DPP‐IV has become an enzyme of interest in the pathology of Type 2 Diabetes. Currently, values are measured primarily in the plasma. It has been suggested that values can be measured in saliva; however, the relationship between DPP‐IV levels in plasma and saliva is not well researched. Plasma and saliva samples were collected from 5 healthy college aged students. Blood was collected using standard venipuncture from prominent antecubital vein. Plasma was separated by centrifugation for 10 minutes at 1,000g and 4°C. Saliva was collected by subjects spitting into a cup, then stored in 0.5mL aliquots at ‐80°C until analysis. DPP‐IV activity was determined using a fluorometric assay which measures the release of 4‐methoxy‐2‐naphthylamine. Enzymatic activity is defined as the amount of DPP‐IV that cleaves 1µmol of glycyl‐L‐proline‐4‐methoxy‐2‐nephthylamine per minute. From the activity, a linear regression analysis was performed to compare the data. Plasma samples had a mean DPP‐IV level of 36.69U/L ± 7.32, falling within normal reference values presented by Durinx et al. (2001). DPP‐IV levels were elevated in saliva samples with a mean of 43.71U/L ± 10.01. No association was found between the DPP‐IV levels in saliva and plasma (P‐value= 0.53, with significance set at 0.05). The use of saliva in the measurement of DPP‐IV does not yield results comparable to plasma.

Sitagliptin prevents inflammation and apoptotic cell death in the kidney of type 2 diabetic animals.

This study aimed to evaluate the efficacy of sitagliptin, a dipeptidyl peptidase IV (DPP-IV) inhibitor, in preventing the deleterious effects of diabetes on the kidney in an animal model of type 2 diabetes mellitus; the Zucker diabetic fatty (ZDF) rat: 20-week-old rats were treated with sitagliptin (10 mg/kg bw/day) during 6 weeks. Glycaemia and blood HbA1c levels were monitored, as well as kidney function and lesions. Kidney mRNA and/or protein content/distribution of DPP-IV, GLP-1, GLP-1R, TNF-α, IL-1β, BAX, Bcl-2, and Bid were evaluated by RT-PCR and/or western blotting/immunohistochemistry. Sitagliptin treatment improved glycaemic control, as reflected by the significantly reduced levels of glycaemia and HbA1c (by about 22.5% and 1.2%, resp.) and ameliorated tubulointerstitial and glomerular lesions. Sitagliptin prevented the diabetes-induced increase in DPP-IV levels and the decrease in GLP-1 levels in kidney. Sitagliptin increased colocalization of GLP-1 and GLP-1R in the diabetic kidney. Sitagliptin also decreased IL-1β and TNF-α levels, as well as, prevented the increase of BAX/Bcl-2 ratio, Bid protein levels, and TUNEL-positive cells which indicates protective effects against inflammation and proapoptotic state in the kidney of diabetic rats, respectively. In conclusion, sitagliptin might have a major role in preventing diabetic nephropathy evolution due to anti-inflammatory and antiapoptotic properties.

Identification of altered dipeptidyl-peptidase activities as potential biomarkers for unipolar depression

BackgroundChanges in circulatory aminopeptidases [dipeptidyl-peptidase-IV (DPP-IV), Prolyl-oligopeptidase (POP) and Leucine aminopeptidase (LAP)] activities have been found to be associated with psychiatric illnesses and inflammatory diseases. MethodsThe discriminatory indices of aminopeptidases activities were assessed by enzymatic assays in plasma samples from 240 unipolar depression (UD) patients and 264 matched controls. In addition the relationship between soluble and cellular DPP-IV activity was determined in plasma and blood cells from healthy subjects. ResultsGreater than 95% of the plasma DPP-IV activity could be blocked by inhibitors, demonstrating the specificity of the assay. Also, DPP-IV protein and activity levels were strongly correlated. In contrast, only 50% of the membrane-bound activity in blood cells was inhibited, which suggested that other similar peptidases may be present in these cells. UD patients had decreased plasma levels of DPP-IV and POP activities compared to healthy controls with a concomitant increase in LAP activity. Finally, testing of the LAP/DPP-IV ratio resulted in good discrimination of UD patients from controls with an area under the curve—receiver operating characteristic of 0.70. LimitationsFurther biological validation studies using different cohorts are warranted. ConclusionsThe finding that plasma DPP-IV activity was decreased and LAP activity was increased in UD patients suggests the potential value for testing the levels of these enzymes for improved classification of patients. In addition, the changes in these enzymes, suggests that the proteolytic maturation of their proneuropeptide and prohormone subtrates may also be affected in UD, resulting in altered production of the associated bioactive peptides.

POLYMORPHISMS IN DIPEPTIDYL PEPTIDASE IV GENE ARE ASSOCIATED WITH THE RISK OF MYOCARDIAL INFARCTION IN PATIENTS WITH ATHEROSCLEROSIS

0143-4179/$ see front matter 2012 Elsevier Ltd. A http://dx.doi.org/10.1016/j.npep.2012.10.001 ⇑ Corresponding author. Tel.: +1 617 636 5000. E-mail address: naghili@tuftsmedicalcenter.org (N Background: Dipeptidyl peptidase IV (DPP-IV) is not only important in pancreatic b-cell regulation but also has proinflammatory actions that can contribute to atherosclerosis progression. Previously, we showed that DPP-IV is co-localized with CD31 (an endothelial cell marker) in the neovessels within the human atherosclerotic plaques. These characteristics of DPP-IV may predispose patients with coronary artery disease (CAD) to plaque rupture and thus to myocardial infarction. The goal of this investigation was to determine whether genetic alterations in DPP-IV predispose to plaque vulnerability and myocardial infarction (MI). Methods: Between Aug 2004, and March 2007, blood samples of patients (age <60) with angiographically documented CAD were collected. Demographic, clinical, risk factor, and angiographic data were recorded. Eight hundred and seventy five patients of European ancestry with angiographic CAD were divided into those with MI (n = 421) and those without (n = 454). Methods: A genome-wide association study was performed using the Affymetrix 6.0 chip to identify loci that predispose to MI. In the current study we only focused on DPP4 gene to assess the association of single nucleotide polymorphisms (SNPs) in the DPP-IV gene and risk of MI in patients with CAD. For genotyped SNPs, association was tested by logistic regression with significance level of 0.05. Plasma DPP-IV level was measured using a commercial ELISA kit. Results: Average patients’ age at diagnosis of CAD was 46.8 years for MI group and 50.8 in the non MI group. There was no difference in distribution of traditional risk factors between the two groups. We identified one SNP (rs3788979) that was significantly related to angiographic CAD with MI, vs. without MI (OR: 1.36, p = 0.03). The association of the identified SNP to MI risk was not attenuated after adjustment for traditional risk factors. The SNP was associated with lower levels of plasma DPP-IV (p = 0.005). Moreover, CAD patients with the major alleles (GG) and no MI had highest plasma DPP-IV levels. (481.6, p = 0.002). Conclusions: A polymorphism in the DPP-IV gene in patients with known CADmay increase the risk of MI. This SNP is associated with decreased plasma DPP4 level in patients with MI. 2012 Elsevier Ltd. All rights reserved.

Abstract 4352: Systemic levels of neuropeptide Y are elevated in Ewing's sarcoma patients

Abstract Neuropeptide Y (NPY) is a neurotransmitter, which is released from normal sympathetic neurons, as well as tumors of sympathetic origin, such as neuroblastoma and pheochromocytoma. In neuroblastoma patients, the elevated systemic levels of NPY are associated with poor clinical outcome. We have found that, despite their different origin, Ewing's sarcoma cells (ES) also express and release NPY, which can stimulate angiogenesis via its endothelial Y2 receptor (Y2R) and induce apoptosis in ES cells via Y1 and Y5R. These seemingly opposing functions beg the question: Which of these NPY-mediated actions is clinically relevant? Thus, we sought to determine whether release of NPY from ES tumors will result in elevated systemic levels of the peptide and establish the potential correlation of NPY levels with clinical features of this devastating disease. Analysis of ES cell lines revealed NPY expression at the mRNA level in all investigated cell lines. NPY release (measured by ELISA) into culture media of ES cell lines bearing EWS/FLI type I translocations was not detectable. Interestingly, those bearing type II and III were found at levels comparable to that of sympathetic neuroblastoma. Analysis of serum NPY levels of 248 ES patients with localized disease (collected by Children's Oncology Group under the protocol # AEWS0031) revealed a similar trend in NPY release from tumor tissue. In particular, overall NPY levels were elevated in ES patients versus healthy controls and osteosarcoma patients (p=0.0069), with two distinct groups – ES patients that release NPY similarly to healthy controls and those at significantly higher levels. Furthermore, increased levels of NPY were associated with pelvic tumors (p&amp;lt;0.001), which carry a worse prognosis. The angiogenic properties of NPY are favored with a processing enzyme found to be expressed in ESFT, dipeptidyl peptidase IV (DPPIV), which converts NPY to a Y2R agonist. Thus, we also looked at the DPPIV activity in sera of ES patients and found it to be significantly lower than that of osteosarcoma patients (p=0.0254), but only slightly decreased relative to healthy controls. This suggests that the activity measured in the sera was not derived from tumor-associated DPPIV, but rather the enzyme was shed from other sources, such as immune or endothelial cells. Surprisingly, increased levels of DPPIV activity were found to have a strong predictive value of event free survival. Since DPPIV is known to be involved in immune function, this result may reflect an impaired immune response in ES patients with worse survival. In summary, this is the first report of elevated NPY levels and the first study on DPPIV activity in ES patients. We have found that NPY release was elevated in pelvic ES tumors, while higher DPPIV activity was associated with better prognosis. However, further study and analysis, such as levels of NPY and DPPIV in ES patients with metastatic disease, is needed to fully clarify the role of NPY in ES patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4352. doi:10.1158/1538-7445.AM2011-4352

Abstract 187: Dipeptidyl peptidases abolish growth inhibitory effect of neuropeptide Y in Ewing's sarcoma family of tumors

Abstract Ewing's sarcoma family of tumors (ESFT) is a group of aggressive pediatric malignancies which exhibit a variable degree of neuronal differentiation. Previously, we have shown that ESFT cells express a sympathetic neurotransmitter, neuropeptide Y (NPY), and its Y1 and Y5 receptors. We have shown that both endogenous and exogenous NPY can stimulate Y1/Y5R-mediated apoptosis in ESFT cells, which can lead to inhibition of ESFT tumor growth in vivo. However, our further studies suggested that the growth-inhibitory effect of NPY in ESFT cells can be abolished by dipeptidyl peptidase IV (DPPIV) – a membrane protease which cleaves the peptide to its shorter form, NPY3-36, that is inactive at Y1Rs. DPPIV, as well as its homologs with similar activities – membrane-bound fibroblast activation protein (FAP) and cytoplasmic DPP8 and DPP9, have been identified as therapeutic targets in a variety of other tumors. Moreover, numerous broad-spectrum and selective DPP inhibitors have been developed and tested in clinical trials for diabetes and cancer. Thus, the goal of this study was to elucidate the role of particular DPPs in the regulation of ESFT growth and their potential use as therapeutic targets. We have found that aside from expressing NPY and its receptors, all ESFT cells expressed variable levels of DPPIV and its homologs. Both exogenous and endogenous NPY significantly inhibited growth of ESFT cells with low DPP activities. This effect was blocked by Y1/Y5R antagonists and abolished by transfection with DPPIV mRNA. In contrast, cells with high DPP activities did not respond to exogenous NPY and the endogenous peptide had no effect on their growth, as shown by experiments with NPY siRNA. In these DPP-rich cells, the response to both exogenous and endogenous peptide was restored by DPP siRNAs or their selective inhibitors. Surprisingly, similar levels of growth reduction were achieved by blocking DPPIV, as with inhibiting cytoplasmic DPP8 and DPP9. Both effects were mediated by AIF, suggesting caspase-independent cell death, and blocked by Y1/Y5R antagonists, confirming that this was indeed NPY-mediated. In contrast, FAP did not affect the growth-inhibitory actions of NPY in ESFT cells, which is consistent with its low activity, while cleaving substrates with Tyrosine in the first position, such as NPY. In summary, DPPs are important regulators of the growth-inhibitory effect of NPY in ESFT cells, indicating their potential value as therapeutic targets in the treatment of these tumors. However, given the multiple functions of both DPPs and NPY itself, more studies are required to determine their effects on other functions of ESFT cells, such as migration and invasiveness. Moreover, the role of particular DPPs differ in vivo, since FAP and DPPIV are known to be highly expressed in tumor-associated fibroblasts and endothelial cells, and have been shown to modify interactions between tumor and stromal cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 187. doi:10.1158/1538-7445.AM2011-187

Fasting and Post Prandial Monitoring of Dipeptidyl Peptidase-IV (DPP-IV) - A Biomarker to Assess Incretin Response in Type-2 Diabetes

Dipeptidyl peptidase-IV (DPP-IV) could serve as a potential biomarker in monitoring the disease progression and improvement on treatment. To investigate fasting &amp; post prandial response of DPP-IV enzyme as indirect marker of incretin response failure after chronic treatment with metformin in type 2 diabetes. The study included twelve nondiabetic subjects, ten patients with glycosylated hemoglobin values (6-8%) and fifteen patients with glycosylated hemoglobin greater than 8 % of type-2 diabetes patients of either sex with metformin treatment above 3 years were recruited. Fasting and post prandial DPP-IV levels were calculated. HbA1c was used to assess diabetes status. DPP-IV activity (fasting) in type 2 diabetic subjects with HbA1c &gt; 8 % was significantly higher DPP-IV (44.67 ± 2.19 U/l) than in non diabetic subjects (24.39 ± 3.97 U/l). A significant correlation between DPP-IV (fasting / post prandial) and HbA1c (r = 0.821 &amp; r = 0.732, P&lt; 0.01) was observed in both diabetic (HbA1c 6-8, HbA1c &lt; 8) patients. Hyperglycemia induces significant increase in serum DPP-IV activity in fasting condition and might contribute to the reduction in active glucagon like peptide-1(GLP-1) in type 2 diabetic subjects. In normal subjects during post prandial condition, there is sudden increase followed by decrease of GLP-1 due to cleavage of GLP-1 to as substrate of DPP-IV is seen as upsurge of DPP-IV. This response was lacking in diabetic patients with high HbA1c indicates indirectly metformin failure to secrete GLP-1. High fasting level and decreased post prandial of DPP-IV may indicate drug failure in type-2 diabetes mellitus. Key words: Type 2 diabetes; metformin; DPP-IV; HbA1c; GLP-1.DOI: 10.3329/sjps.v2i2.1698Stamford Journal of Pharmaceutical Sciences Vol.2(2) 2009: 81-85

Relationship between GLP‐1 levels and dipeptidyl peptidase‐4 activity in different glucose tolerance conditions

The reduced levels of glucagon-like peptide 1 (GLP-1) after an oral glucose load in Type 2 diabetic patients could be dependent either on a reduced synthesis or an increased degradation; but GLP-1 and dipeptidyl peptidase IV (DPP-IV) levels during an oral glucose tolerance test (OGTT) have not been studied together. The aim of the present study was to investigate GLP-1 and DPP-IV levels during an OGTT in patients with different degrees of glucose tolerance. Fifty six subjects (34 female, 22 male) matched for sex, age, body mass index (BMI) and waist circumference underwent a 75 g oral glucose tolerance test. Twenty-eight had normal glucose tolerance, 15 had impaired glucose tolerance and 13 had Type 2 diabetes mellitus. GLP-1 assay was performed with an ELISA kit, and DPP-IV assay using a colorimetric method. At 30 min GLP-1 levels were significantly lower in subjects with impaired glucose tolerance and type 2 diabetes mellitus compared to those with normal glucose tolerance. The area under the GLP-1 curve was significantly different among the three groups; there was a significant decrease between subjects with normal and impaired glucose tolerance(P = 0.004) and between those with normal glucose tolerance and type 2 diabetes mellitus. (P < 0.001), while the area under the curve for DPP-IV showed no significant difference between the groups. These results suggest that an increase of GLP-1 degradation does not play a role in the early stages of diabetes mellitus.

Effect of intraperitoneal and intravenous administration of cholecystokinin-8 and apolipoprotein AIV on intestinal lymphatic CCK-8 and apo AIV concentration

CCK and apolipoprotein AIV (apo AIV) are gastrointestinal satiety signals whose synthesis and secretion by the gut are stimulated by fat absorption. Intraperitoneally administered CCK-8 is more potent in suppressing food intake than a similar dose administered intravenously, but the reason for this disparity is unclear. In contrast, both intravenous and intraperitoneally administered apo AIV are equally as potent in inhibiting food intake. When we compared the lymphatic concentration of CCK-8 and apo AIV, we found that neither intraperitoneally nor intravenously administered CCK-8 or apo AIV altered lymphatic flow rate. Interestingly, intraperitoneal administration of CCK-8 produced a significantly higher lymphatic concentration at 15 min than did intravenous administration. Intraperitoneal injection of apo AIV also yielded a higher lymphatic concentration at 30 min than did intravenous administration. Intraperitoneal administration of CCK-8 and apo AIV also resulted in a much longer period of elevated CCK-8 and apo AIV peptide concentration in lymph than intravenous administration. Furthermore, enzymatic activity of dipeptidyl peptidase IV (DPPIV) and aminopeptidase was higher in plasma than in lymph during fasting, and so, satiation peptides, such as CCK-8 and apo AIV in the lymph, are protected from degradation by the significantly lower DPPIV and aminopeptidase activity levels in lymph than in plasma. Therefore, the higher potency of intraperitoneally administered CCK-8 compared with intravenously administered CCK-8 in inhibiting food intake may be explained by both its higher concentration in lymph and the prolonged duration of its presence in the lamina propria.

Seprase, Dipeptidyl Peptidase IV and Urokinase-Type Plasminogen Activator Expression in Dysplasia and Invasive Squamous Cell Carcinoma of the Esophagus

Objective: Seprase, dipeptidyl peptidase IV (DPPIV) and urokinase-type plasminogen activator (uPA) play a crucial role in the degradation of the extracellular matrix and in the progression of various human tumors. However, their pathophysiologic significance in esophageal carcinoma has not yet been fully elucidated. Methods: The expression of seprase, DPPIV and uPA in esophageal dysplasia, squamous cell carcinoma (SCC) and normal epithelium was examined by immunohistochemistry. Results: Seprase, DPPIV and uPA immunoreactivity was found in dysplastic and cancer cells as well as in stromal cells adjacent to dysplasia and cancer sites, but not in normal epithelium. We found a significant association between uPA expression and sex, tumor size and histological classification in carcinomas. High expression of DPPIV in cancer cells correlated with longer survival of the patients. No significant associations between seprase and clinicopathological features either in dysplasia or in carcinomas were found. Finally, we demonstrated higher levels of seprase, DPPIV and uPA in SCC cell lines than in normal esophageal epithelial cell lines. Conclusions: Our results showed that seprase, DPPIV and uPA are expressed in both premalignant and malignant forms of SCC, but are lacking in normal esophageal epithelia, suggesting that they are involved in SCC neoplastic progression.

Lymphatic-specific expression of dipeptidyl peptidase IV and its dual role in lymphatic endothelial function

Lymphatic vessels play an important role in the maintenance of tissue fluid homeostasis and in the transport of immune cells to lymph nodes, but they also serve as the major conduit for cancer metastasis to regional lymph nodes. However, the molecular mechanisms regulating these functions are poorly understood. Based on transcriptional profiling studies of cultured human dermal lymphatic (LEC) versus blood vascular endothelial cells (BEC), we found that dipeptidyl peptidase IV (DPPIV) mRNA and protein are much more strongly expressed by cultured lymphatic endothelium than by blood vascular endothelium that only expressed low levels of DPPIV in culture. The enzymatic cleavage activity of DPPIV was significantly higher in cultured LEC than in BEC. Differential immunofluorescence analyses of human organ tissue microarrays for DPPIV and several vascular lineage-specific markers revealed that DPPIV is also specifically expressed in situ by lymphatic vessels of the skin, esophagus, small intestine, breast and ovary. Moreover, siRNA-mediated DPPIV knockdown inhibited LEC adhesion to collagen type I and to fibronectin, and also reduced cell migration and formation of tube-like structures. These results identify DPPIV as a novel lymphatic marker and mediator of lymphatic endothelial cell functions.

Inhibition of Dipeptidyl Peptidase IV With Sitagliptin (MK0431) Prolongs Islet Graft Survival in Streptozotocin-Induced Diabetic Mice

Dipeptidyl peptidase-IV (DPP-IV) inhibitors have been introduced as therapeutics for type 2 diabetes. They partially act by blocking degradation of the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), thus increasing circulating levels of active hormones. In addition to their insulinotropic actions, GLP-1 and GIP also promote beta-cell proliferation and survival, and DPP-IV inhibitors exert similar effects in rodent type 2 diabetes models. The study objective was to establish whether DPP-IV inhibitor treatment prolonged survival of transplanted islets and to determine whether positron emission tomography (PET) was appropriate for quantifying the effect of inhibition on islet mass. Effects of the DPP-IV inhibitor MK0431 (sitagliptin) on glycemic control and functional islet mass in a streptozotocin (STZ)-induced type 1 diabetes mouse model were determined with metabolic studies and microPET imaging. The type 1 diabetes mouse model exhibited elevated plasma DPP-IV levels that were substantially inhibited in mice on an MK0431 diet. Residual beta-cell mass was extremely low in STZ-induced diabetic mice, and although active GLP-1 levels were increased by the MK0431 diet, there were no significant effects on glycemic control. After islet transplantation, mice fed normal diet rapidly lost their ability to regulate blood glucose, reflecting the suboptimal islet transplant. By contrast, the MK0431 group fully regulated blood glucose throughout the study, and PET imaging demonstrated a profound protective effect of MK0431 on islet graft size. Treatment with a DPP-IV inhibitor can prolong islet graft retention in an animal model of type 1 diabetes.

Dipeptidyl peptidase IV (DPPIV), a candidate tumor suppressor gene in melanomas is silenced by promoter methylation

Dipeptidyl peptidase IV (DPPIV), a serine protease is expressed by normal melanocytes but not by melanomas, the malignant counterpart. DPPIV is encoded by a gene that contains a 5 CpG island spanning a transcriptional regulatory region. Previously we have demonstrated that DPPIV abrogates growth factor independence and functions as a tumor suppressor gene in melanomas. In this study we show that loss of DPPIV occurs at RNA level and demethylating agent, 5-aza-2'-deoxycytidine (5-AZA-Cdr) treatment of DPPIV negative melanoma cell lines results in increase of DPPIV mRNA, protein, and enzyme activities. By using sodium bisulfite genomic DNA modifications, PCR, and sequencing we confirmed that DPPIV gene promoter is methylated in eight out of ten melanoma cell lines tested. Further more, 5-AZA-Cdr induced increases in DPPIV levels correlated with growth inhibition and apoptosis in melanoma cells. All together these findings suggest that frequent downregulation of DPPIV expression in melanoma can be attributed, in large part, to aberrant promoter hypermethylation and this loss of DPPIV may be a critical event contributing to melanoma development.

Possible involvement of SDF-1α/CXCR4-DPPIV axis in TGF-β1-induced enhancement of migratory potential in human peritoneal mesothelial cells

We have previously reported that human peritoneal mesothelial cells (HPMCs) express a large amount of dipeptidyl peptidase IV (DPPIV) and that its expression is regulated by a variety of bioactive substances in malignant ascites from ovarian cancer patients. The aim of this study has been to examine the expression and role of the SDF-1alpha/CXCR4-DPPIV axis in HPMCs. We have demonstrated that the expression levels of DPPIV and E-cadherin in HPMCs decrease, following TGF-beta1-induced morphological change, in a time- and concentration-dependent manner. Additionally, we show that both SDF-1alpha (a chemokine and substrate for DPPIV) and its receptor, CXCR4, are expressed on HPMCs, and that their expression levels are upregulated by TGF-beta1 treatment, resulting in an increased migratory potential of HPMCs. Furthermore, the migratory potential of HPMCs is significantly enhanced in the presence of SDF-1alpha or DPPIV-specific inhibitor in the wound-healing assay. These results suggest that DPPIV and SDF-1alpha/CXCR4 play crucial roles in regulating the migratory potential of HPMCs, which may be involved in the re-epithelialization of denuded basement membrane at the site of peritoneal injury.

Peptide YY(1-36) and Peptide YY(3-36): Part II. Changes after Gastrointestinal Surgery and Bariatric Surgery: Part I. Distribution, Release and Actions appeared in the last issue (May 2006)

Peptide YY (PYY) is secreted as a 36 amino acid, straight chain polypeptide, and is found in greatest concentrations in the terminal ileum, colon and rectum. After secretion, dipeptidyl peptidase IV (DPP-IV) cleaves the N-terminal Tyrosine-Proline residues from PYY(1-36), producing PYY(3-36). PYY(1-36) acts at all four human Y receptors, Y1, Y2, Y4 and Y5, while PYY(336) is a specific Y2 receptor agonist. PYY participates in the regulation of appetite and weight balance through hypothalamic-based mechanisms. PYY(1-36) stimulates appetite and weight gain through Y1 and Y5 receptors. PYY(3-36) suppresses appetite and stimulates weight loss through Y2 receptors. GI diseases that cause malabsorption increase both basal and meal-stimulated PYY levels. In contrast, obesity decreases both basal and meal-stimulated PYY levels. Mutations in the human PYY and Y2 receptor genes may contribute to the development of obesity. Small bowel resection elevates PYY levels in humans. Colon resections increase PYY levels in animal models but not in man. PYY changes following bariatric operations are incompletely studied. Vertical banded gastroplasty, open Roux-en-Y gastric bypass and jejunoileal bypass significantly elevate basal and meal-stimulated PYY levels. In dogs with Pavlov pouches, Roux-en-Y duodenojejunostomy (duodenal switch) increases PYY levels compared to Roux-en-Y gastrojejunostomy. DPP-IV activity is increased in obese individuals and remains increased after biliopancreatic diversion. Thus, diseases or operations which cause malabsorption, elevate basal and meal-stimulated PYY levels. Bariatric operations also increase basal and meal-stimulated PYY levels. This suggests that the combination of increased PYY levels and elevated levels of DPP-IV observed after bariatric operations may generate increased circulating levels of PYY(3-36), leading to hypothalamic-mediated suppression of appetite and promotion of weight loss through Y2 receptor mediated mechanisms.