Integration of Deep Learning and Sequential Metabolism to Rapidly Screen Dipeptidyl Peptidase (DPP)-IV Inhibitors from Gardenia jasminoides Ellis.

Traditional Chinese medicine (TCM) possesses unique advantages in the management of blood glucose and lipids. However, there is still a significant gap in the exploration of its pharmacologically active components. Integrated strategies encompassing deep-learning prediction models and active validation based on absorbable ingredients can greatly improve the identification rate and screening efficiency in TCM. In this study, the affinity prediction of 11,549 compounds from the traditional Chinese medicine system's pharmacology database (TCMSP) with dipeptidyl peptidase-IV (DPP-IV) based on a deep-learning model was firstly conducted. With the results, Gardenia jasminoides Ellis (GJE), a food medicine with homologous properties, was selected as a model drug. The absorbed components of GJE were subsequently identified through in vivo intestinal perfusion and oral administration. As a result, a total of 38 prototypical absorbed components of GJE were identified. These components were analyzed to determine their absorption patterns after intestinal, hepatic, and systemic metabolism. Virtual docking and DPP-IV enzyme activity experiments were further conducted to validate the inhibitory effects and potential binding sites of the common constituents of deep learning and sequential metabolism. The results showed a significant DPP-IV inhibitory activity (IC50 53 ± 0.63 µg/mL) of the iridoid glycosides' potent fractions, which is a novel finding. Genipin 1-gentiobioside was screened as a promising new DPP-IV inhibitor in GJE. These findings highlight the potential of this innovative approach for the rapid screening of active ingredients in TCM and provide insights into the molecular mechanisms underlying the anti-diabetic activity of GJE.

Omega-3 Fatty Acids Interact with DPP10 Region Genotype in Association with Childhood Atopy.

Associations of omega-3 fatty acids (n-3) with allergic diseases are inconsistent, perhaps in part due to genetic variation. We sought to identify and validate genetic variants that modify associations of n-3 with childhood asthma or atopy in participants in the Vitamin D Antenatal Asthma Reduction Trial (VDAART) and the Copenhagen Prospective Studies on Asthma in Childhood 2010 (COPSAC). Dietary n-3 was derived from food frequency questionnaires and plasma n-3 was measured via untargeted mass spectrometry in early childhood and children aged 6 years old. Interactions of genotype with n-3 in association with asthma or atopy at age 6 years were sought for six candidate genes/gene regions and genome-wide. Two SNPs in the region of DPP10 (rs958457 and rs1516311) interacted with plasma n-3 at age 3 years in VDAART (p = 0.007 and 0.003, respectively) and with plasma n-3 at age 18 months in COPSAC (p = 0.01 and 0.02, respectively) in associationwith atopy. Another DPP10 region SNP, rs1367180, interacted with dietary n-3 at age 6 years in VDAART (p = 0.009) and with plasma n-3 at age 6 years in COPSAC (p = 0.004) in association with atopy. No replicated interactions were identified for asthma. The effect of n-3 on reducing childhood allergic disease may differ by individual factors, including genetic variation in the DPP10 region.

Harnessing affinity-based protein profiling to reveal a novel target of nintedanib.

Nintedanib (BIBF1120), a triple angiokinase inhibitor, was first approved for idiopathic pulmonary fibrosis (IPF) therapy and is also efficacious for lung carcinoma, and interstitial lung diseases, far beyond its inhibition of VEGFR/PDGFR/FGFR. We identified tripeptidyl-peptidase 1 (TPP1) as one of the direct targets of nintedanib employing the affinity-based protein profiling (AfBPP) technique. This may be a new mechanism for nintedanib's role different from tyrosine kinase inhibition.

Dipeptidyl peptidase like 6 promoter methylation is a potential prognostic biomarker for pancreatic ductal adenocarcinoma.

BACKGROUND: Hypermethylation of gene promoters plays an important role in tumorigenesis. The present study aimed to identify and validate promoter methylation-driven genes (PMDGs) for pancreatic ductal adenocarcinoma (PDAC). METHODS: Based on GSE49149 and the PDAC cohort of The Cancer Genome Atlas (TCGA), differential analyses of promoter methylation, correlation analysis, and Cox regression analysis were performed to identify PMDGs. The promoter methylation level was assessed by bisulfite sequencing polymerase chain reaction (BSP) in paired tumor and normal tissues of 72 PDAC patients. Kaplan-Meier survival analyses were performed to evaluate the clinical value of PMDGs. RESULTS: In GSE49149, the ß-value of the dipeptidyl peptidase like 6 (DPP6) promoter was significantly higher in tumor compared with normal samples (0.50 vs. 0.24, P<0.001). In the PDAC cohort of TCGA, the methylation level of the DPP6 promoter was negatively correlated with mRNA expression (r = -0.54, P<0.001). In a multivariate Cox regression analysis, hypermethylation of the DPP6 promoter was an independent risk factor for PDAC (hazard ratio (HR) = 543.91, P=0.002). The results of BSP revealed that the number of methylated CG sites in the DPP6 promoter was greater in tumor samples than in normal samples (7.43 vs. 2.78, P<0.001). The methylation level of the DPP6 promoter was moderately effective at distinguishing tumor from normal samples (area under ROC curve (AUC) = 0.74, P<0.001). Hypermethylation of the DPP6 promoter was associated with poor overall (HR = 3.61, P<0.001) and disease-free (HR = 2.01, P=0.016) survivals for PDAC patients. CONCLUSION: These results indicate that DPP6 promoter methylation is a potential prognostic biomarker for PDAC.

Pharmacological evaluation of Rhazya stricta root extract / Evaluación farmacológica del extracto de raíz de Rhazya stricta

The present study aimed to screen the Rhazya stricta Decne root for its antihyperglycemic and antioxidants potential through invitro assays along with phytochemical and elemental analyses. The crude extract was prepared through maceration and fractionated using solvent-solvent extraction technique. The spectroscopic studies indicated the presence of various phytochemical classes in the extract and its fractions. The antioxidant assays showed notable results along with a good concentration of phenolic and flavonoid contents. Enzyme inhibition assays demonstrated glucose-lowering effects by inhibiting the enzyme activity which could reduce post-prandial blood glucose level. The Dipeptidyl peptidase-IV (DPP-IV) inhibition assay results showed the novel DPP-IV inhibition activity of the plant extract and all fractions showed noteworthy enzyme inhibition and antihyperglycemic activity. Conclusively, the Rhazya stricta root extract displayed its antioxidant and antihyperglycemic potential due to the presence of various classes of phytochemicals and micro-nutrients.

El presente estudio tuvo como objetivo examinar la raíz de Rhazya stricta Decne por su potencial antihiperglicémico y antioxidante a través de ensayos in vitro junto con análisis fitoquímicos y elementales. El extracto crudo se preparó por maceración y se fraccionó usando una técnica de extracción solvente-solvente. Los estudios espectroscópicos indicaron la presencia de varias clases fitoquímicas en el extracto y sus fracciones. Los ensayos antioxidantes mostraron resultados notables junto con una importante concentración de contenido fenólico y flavonoide. Los ensayos de inhibición enzimática demostraron efectos reductores de la glucosa al inhibir la actividad enzimática que podría reducir el nivel de glucosa posprandial en sangre. Los resultados del ensayo de inhibición de Dipeptidyl peptidase-IV (DPP-IV) mostraron la nueva actividad de inhibición de DPP-IV del extracto de la planta y todas las fracciones mostraron una notable inhibición enzimática y actividad antihiperglicémica. En conclusión, el extracto de raíz de Rhazya stricta Decne mostró su potencial antioxidante y antihiperglicémico debido a la presencia de varias clases de fitoquímicos y micronutrientes.

Evaluation of Dipeptidyl Peptidase-4 Inhibitors versus Thiazolidinediones or Insulin in Patients with Type 2 Diabetes Uncontrolled with Metformin and a Sulfonylurea in a Real-World Setting.

BACKGROUND: Guidelines do not make clear recommendations for third add-on agents to metformin plus a sulfonylurea. This study compared the effectiveness and safety of dipeptidyl peptidase-4 inhibitors (DPP4is) to thiazolidinedione (TZD) or insulin as a third add-on agent to metformin plus a sulfonylurea in an integrated health care setting. METHODS: This retrospective database cohort study included adults with type 2 diabetes not at goal hemoglobin A1C (HbA1C) who initiated DPP4i, TZD, or insulin as a third add-on agent to metformin plus a sulfonylurea from January 2006 to June 2016. Primary outcomes were the proportion of patients who achieved goal HbA1C after starting the third add-on agent and change in HbA1C. Subgroup analysis was performed for patients with baseline HbA1C greater than 9%. RESULTS: In this study, 2080 patients started on a DPP4i were matched to 8320 patients started on TZD and to 8320 patients taking insulin. A significantly higher percentage of patients taking TZD reached goal HbA1C (31.0% versus 23.6%; p < 0.05) and had a significantly larger HbA1C reduction (-0.94% ± 1.34% versus -0.79% ± 1.23%; p < 0.01) compared to patients taking a DPP4i. No difference in the percentage of patients meeting goal HbA1C nor in change in HbA1C was demonstrated between insulin versus DPP4i regimens. For patients with baseline HbA1C greater than 9%, insulin or TZD resulted in a significantly higher proportion of patients achieving goal HbA1C compared to DPP4i (17.3% and 19.0% versus 12.4%, respectively; p < 0.01). CONCLUSION: TZD was more effective than DPP4i but DPP4i was as effective as insulin as a third add-on agent in the overall study population. Insulin was more effective than DPP4i only in the subgroup analysis of patients with baseline HbA1C greater than 9%.

Identification of Plasmodium dipeptidyl aminopeptidase allosteric inhibitors by high throughput screening.

Dipeptidyl aminopeptidases (DPAPs) are cysteine proteases that cleave dipeptides from the N-terminus of protein substrates and have been shown to play important roles in many pathologies including parasitic diseases such as malaria, toxoplasmosis and Chagas's disease. Inhibitors of the mammalian homologue cathepsin C have been used in clinical trials as potential drugs to treat chronic inflammatory disorders, thus proving that these enzymes are druggable. In Plasmodium species, DPAPs play important functions at different stages of parasite development, thus making them potential antimalarial targets. Most DPAP inhibitors developed to date are peptide-based or peptidomimetic competitive inhibitors. Here, we used a high throughput screening approach to identify novel inhibitor scaffolds that block the activity of Plasmodium falciparum DPAP1. Most of the hits identified in this screen also inhibit Plasmodium falciparum DPAP3, cathepsin C, and to a lesser extent other malarial clan CA proteases, indicating that these might be general DPAP inhibitors. Interestingly, our mechanism of inhibition studies indicate that most hits are allosteric inhibitors, which opens a completely new strategy to inhibit these enzymes, study their biological function, and potentially develop new inhibitors as starting points for drug development.

Fragment-based discovery of the first nonpeptidyl inhibitor of an S46 family peptidase.

Antimicrobial resistance is a global public threat and raises the need for development of new antibiotics with a novel mode of action. The dipeptidyl peptidase 11 from Porphyromonas gingivalis (PgDPP11) belongs to a new class of serine peptidases, family S46. Because S46 peptidases are not found in mammals, these enzymes are attractive targets for novel antibiotics. However, potent and selective inhibitors of these peptidases have not been developed to date. In this study, a high-resolution crystal structure analysis of PgDPP11 using a space-grown crystal enabled us to identify the binding of citrate ion, which could be regarded as a lead fragment mimicking the binding of a substrate peptide with acidic amino acids, in the S1 subsite. The citrate-based pharmacophore was utilized for in silico inhibitor screening. The screening resulted in an active compound SH-5, the first nonpeptidyl inhibitor of S46 peptidases. SH-5 and a lipophilic analog of SH-5 showed a dose-dependent inhibitory effect against the growth of P. gingivalis. The binding mode of SH-5 was confirmed by crystal structure analysis. Thus, these compounds could be lead structures for the development of selective inhibitors of PgDPP11.

Genome-wide analyses as part of the international FTLD-TDP whole-genome sequencing consortium reveals novel disease risk factors and increases support for immune dysfunction in FTLD.

Frontotemporal lobar degeneration with neuronal inclusions of the TAR DNA-binding protein 43 (FTLD-TDP) represents the most common pathological subtype of FTLD. We established the international FTLD-TDP whole-genome sequencing consortium to thoroughly characterize the known genetic causes of FTLD-TDP and identify novel genetic risk factors. Through the study of 1131 unrelated Caucasian patients, we estimated that C9orf72 repeat expansions and GRN loss-of-function mutations account for 25.5% and 13.9% of FTLD-TDP patients, respectively. Mutations in TBK1 (1.5%) and other known FTLD genes (1.4%) were rare, and the disease in 57.7% of FTLD-TDP patients was unexplained by the known FTLD genes. To unravel the contribution of common genetic factors to the FTLD-TDP etiology in these patients, we conducted a two-stage association study comprising the analysis of whole-genome sequencing data from 517 FTLD-TDP patients and 838 controls, followed by targeted genotyping of the most associated genomic loci in 119 additional FTLD-TDP patients and 1653 controls. We identified three genome-wide significant FTLD-TDP risk loci: one new locus at chromosome 7q36 within the DPP6 gene led by rs118113626 (p value = 4.82e - 08, OR = 2.12), and two known loci: UNC13A, led by rs1297319 (p value = 1.27e - 08, OR = 1.50) and HLA-DQA2 led by rs17219281 (p value = 3.22e - 08, OR = 1.98). While HLA represents a locus previously implicated in clinical FTLD and related neurodegenerative disorders, the association signal in our study is independent from previously reported associations. Through inspection of our whole-genome sequence data for genes with an excess of rare loss-of-function variants in FTLD-TDP patients (n ≥ 3) as compared to controls (n = 0), we further discovered a possible role for genes functioning within the TBK1-related immune pathway (e.g., DHX58, TRIM21, IRF7) in the genetic etiology of FTLD-TDP. Together, our study based on the largest cohort of unrelated FTLD-TDP patients assembled to date provides a comprehensive view of the genetic landscape of FTLD-TDP, nominates novel FTLD-TDP risk loci, and strongly implicates the immune pathway in FTLD-TDP pathogenesis.

Identification of novel therapeutic target genes and pathway in pancreatic cancer by integrative analysis.

BACKGROUND: Gene alterations are crucial to the molecular pathogenesis of pancreatic cancer. The present study was designed to identify the potential candidate genes in the pancreatic carcinogenesis. METHODS: Gene Expression Omnibus database (GEO) datasets of pancreatic cancer tissue were retrieval and the differentially expressed genes (DEGs) from individual microarray data were merged. Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, protein-protein interaction (PPI) networks, and gene coexpression analysis were performed. RESULTS: Three GEO datasets, including 74 pancreatic cancer samples and 55 controls samples were selected. A total of 2325 DEGs were identified, including 1383 upregulated and 942 downregulated genes. The GO terms for molecular functions, biological processes, and cellular component were protein binding, small molecule metabolic process, and integral to membrane, respectively. The most significant pathway in KEGG analysis was metabolic pathways. PPI network analysis indicated that the significant hub genes including cytochrome P450, family 2, subfamily E, polypeptide 1 (CYP2E1), mitogen-activated protein kinase 3 (MAPK3), and phospholipase C, gamma 1 (PLCG1). Gene coexpression network analysis identified 4 major modules, and the potassium channel tetramerization domain containing 10 (KCTD10), kin of IRRE like (KIRREL), dipeptidyl-peptidase 10 (DPP10), and unc-80 homolog (UNC80) were the hub gene of each modules, respectively. CONCLUSION: Our integrative analysis provides a comprehensive view of gene expression patterns associated with the pancreatic carcinogenesis.

Dipeptidyl peptidase-IV inhibitory activity of dimeric dihydrochalcone glycosides from flowers of Helichrysum arenarium.

A methanol extract of everlasting flowers of Helichrysum arenarium L. Moench (Asteraceae) was found to inhibit the increase in blood glucose elevation in sucrose-loaded mice at 500 mg/kg p.o. The methanol extract also inhibited the enzymatic activity against dipeptidyl peptidase-IV (DPP-IV, IC50 = 41.2 µg/ml), but did not show intestinal α-glucosidase inhibitory activities. From the extract, three new dimeric dihydrochalcone glycosides, arenariumosides V-VII (2-4), were isolated, and the stereostructures were elucidated based on their spectroscopic properties and chemical evidence. Of the constituents, several flavonoid constituents, including 2-4, were isolated, and these isolated constituents were investigated for their DPP-IV inhibitory effects. Among them, chalconaringenin 2'-O-ß-D-glucopyranoside (16, IC50 = 23.1 µM) and aureusidin 6-O-ß-D-glucopyranoside (35, 24.3 µM) showed relatively strong inhibitory activities.

Nonclinical evaluation of CNS-administered TPP1 enzyme replacement in canine CLN2 neuronal ceroid lipofuscinosis.

The CLN2 form of neuronal ceroid lipofuscinosis, a type of Batten disease, is a lysosomal storage disorder caused by a deficiency of the enzyme tripeptidyl peptidase-1 (TPP1). Patients exhibit progressive neurodegeneration and loss of motor, cognitive, and visual functions, leading to death by the early teenage years. TPP1-null Dachshunds recapitulate human CLN2 disease. To characterize the safety and pharmacology of recombinant human (rh) TPP1 administration to the cerebrospinal fluid (CSF) as a potential enzyme replacement therapy (ERT) for CLN2 disease, TPP1-null and wild-type (WT) Dachshunds were given repeated intracerebroventricular (ICV) infusions and the pharmacokinetic (PK) profile, central nervous system (CNS) distribution, and safety were evaluated. TPP1-null animals and WT controls received 4 or 16mg of rhTPP1 or artificial cerebrospinal fluid (aCSF) vehicle every other week. Elevated CSF TPP1 concentrations were observed for 2-3 days after the first ICV infusion and were approximately 1000-fold higher than plasma levels at the same time points. Anti-rhTPP1 antibodies were detected in CSF and plasma after repeat rhTPP1 administration, with titers generally higher in TPP1-null than in WT animals. Widespread brain distribution of rhTPP1 was observed after chronic administration. Expected histological changes were present due to the CNS delivery catheters and were similar in rhTPP1 and vehicle-treated animals, regardless of genotype. Neuropathological evaluation demonstrated the clearance of lysosomal storage, preservation of neuronal morphology, and reduction in brain inflammation with treatment. This study demonstrates the favorable safety and pharmacology profile of rhTPP1 ERT administered directly to the CNS and supports clinical evaluation in patients with CLN2 disease.

Vascular origin of vildagliptin-induced skin effects in Cynomolgus monkeys: pathomechanistic role of peripheral sympathetic system and neuropeptide Y.

The purpose of this article is to characterize skin lesions in cynomolgus monkeys following vildagliptin (dipeptidyl peptidase-4 inhibitor) treatment. Oral vildagliptin administration caused dose-dependent and reversible blister formation, peeling and flaking skin, erosions, ulcerations, scabs, and sores involving the extremities at ≥5 mg/kg/day and necrosis of the tail and the pinnae at ≥80 mg/kg/day after 3 weeks of treatment. At the affected sites, the media and the endothelium of dermal arterioles showed hypertrophy/hyperplasia. Skin lesion formation was prevented by elevating ambient temperature. Vildagliptin treatment also produced an increase in blood pressure and heart rate likely via increased sympathetic tone. Following treatment with vildagliptin at 80 mg/kg/day, the recovery time after lowering the temperature in the feet of monkeys and inducing cold stress was prolonged. Ex vivo investigations showed that small digital arteries from skin biopsies of vildagliptin-treated monkeys exhibited an increase in neuropeptide Y-induced vasoconstriction. This finding correlated with a specific increase in NPY and in NPY1 receptors observed in the skin of vildagliptin-treated monkeys. Present data provide evidence that skin effects in monkeys are of vascular origin and that the effects on the NPY system in combination with increased peripheral sympathetic tone play an important pathomechanistic role in the pathogenesis of cutaneous toxicity.

[Effects of anti-diabetic therapy on overweight/obesity and dyslipidemia: traditional hypoglycemic agents (metformin, sulfonylureas, thiazolidinediones) versus glucagon-like peptide-1 analogs and dipeptidyl peptidase-4 inhibitors]. / Effetti della terapia del diabete su sovrappeso/obesità e dislipidemia: terapie tradizionali (metformina, sulfaniluree, tiazolidinedioni) versus analoghi del glucagon-like peptide-1 e inibitori della dipeptidil peptidasi-4.

Obesity and dyslipidemia often coexist in patients with type 2 diabetes and contribute to increase the risk of cardiovascular events. Pharmacological treatments of diabetes often result in weight gain, an undesirable event associated with a worse cardiovascular risk profile and decreased adherence to therapy. Dipeptidyl peptidase-4 (DPP-4) inhibitors and glucagon-like peptide-1 (GLP-1) analogs have been shown to improve glycemic control without promoting weight gain and to exert beneficial effects on lipid profile by reducing total and LDL cholesterol, triglycerides, and free fatty acid levels. DPP-4 inhibitors have demonstrated to be weight neutral whereas treatment with GLP-1 analogs is associated with a significant weight loss. DPP-4 and GLP-1 analogs represent a new therapeutic option for type 2 diabetes, which offers the advantage of combining glycemic control with beneficial effects on body weight and lipid profile, thus providing greater cardiovascular protection.

Animal models for lysosomal storage disorders.

The lysosomal storage disorders (LSD) represent a heterogeneous group of inherited diseases characterized by the accumulation of non-metabolized macromolecules (by-products of cellular turnover) in different tissues and organs. LSDs primarily develop as a consequence of a deficiency in a lysosomal hydrolase or its co-factor. The majority of these enzymes are glycosidases and sulfatases, which in normal conditions participate in degradation of glycoconjugates: glycoproteins, glycosaminoproteoglycans, and glycolipids. Significant insights have been gained from studies of animal models, both in understanding mechanisms of disease and in establishing proof of therapeutic concept. These studies have led to the introduction of therapy for certain LSD subtypes, primarily by enzyme replacement or substrate reduction therapy. Animal models have been useful in elucidating molecular changes, particularly prior to onset of symptoms. On the other hand, it should be noted certain animal (mouse) models may have the underlying biochemical defect, but not show the course of disease observed in human patients. There is interest in examining therapeutic options in the larger spontaneous animal models that may more closely mimic the brain size and pathology of humans. This review will highlight lessons learned from studies of animal models of disease, drawing primarily from publications in 2011-2012.

Aqueous seed extract of Syzygium cuminiinhibits the dipeptidyl peptidase IV and adenosine deaminase activities, but it does not change the CD26 expression in lymphocytes in vitro

Syzygium cumini (Sc) have been intensively studied in the last years due its beneficial effects including anti-diabetic and anti-inflammatory potential. Thus, the aim of this study was to evaluate the effect of aqueous seed extract of Sc (ASc) in the activity of enzymes involved in lymphocyte functions. To perform this study, we isolated lymphocytes from healthy donors. Lymphocytes were exposed to 10, 30, and 100 mg/mL of ASc during 4 and 6 h and adenosine deaminase (ADA), dipeptidyl peptidase IV (DPP-IV), and acetylcholinesterase (AChE) activities as well as CD26 expression and cellular viability were evaluated. ASc inhibited the ADA and DPP-IV activities without alteration in the CD26 expression (DPP-IV protein). No alterations were observed in the AChE activity or in the cell viability. These results indicate that the inhibition of the DPP-IV and ADA activities was dependent on the time of exposition to ASc. We suggest that ASc exhibits immunomodulatory properties probably via the pathway of DPP-IV–ADA complex, contributing to the understanding of these proceedings in the purinergic signaling (AU)

Inhibition of intracellular dipeptidyl peptidases 8 and 9 enhances parthenolide's anti-leukemic activity.

Parthenolide is selectively toxic to leukemia cells; however, it also activates cell protective responses that may limit its clinical application. Therefore, we sought to identify agents that synergistically enhance parthenolide's cytotoxicity. Using a high-throughput combination drug screen, we identified the anti-hyperglycemic, vildagliptin, which synergized with parthenolide to induce death of the leukemia stem cell line, TEX (combination index (CI)=0.36 and 0.16, at effective concentration (EC) 50 and 80, respectively; where CI <1 denotes statistical synergy). The combination of parthenolide and vildagliptin reduced the viability and clonogenic growth of cells from acute myeloid leukemia patients and had limited effects on the viability of normal human peripheral blood stem cells. The basis for synergy was independent of vildagliptin's primary action as an inhibitor of dipeptidyl peptidase (DPP) IV. Rather, using chemical and genetic approaches we demonstrated that the synergy was due to inhibition of the related enzymes DPP8 and DPP9. In summary, these results highlight DPP8 and DPP9 inhibition as a novel chemosensitizing strategy in leukemia cells. Moreover, these results suggest that the combination of vildagliptin and parthenolide could be useful for the treatment of leukemia.

A novel N-terminal motif of dipeptidyl peptidase-like proteins produces rapid inactivation of KV4.2 channels by a pore-blocking mechanism.

The somatodendritic subthreshold A-type K(+) current in neurons (I(SA)) depends on its kinetic and voltage-dependent properties to regulate membrane excitability, action potential repetitive firing, and signal integration. Key functional properties of the K(V)4 channel complex underlying I(SA) are determined by dipeptidyl peptidase-like proteins known as dipeptidyl peptidase 6 (DPP6) and dipeptidyl peptidase 10 (DPP10). Among the multiple known DPP10 isoforms with alternative N-terminal sequences, DPP10a confers exceptionally fast inactivation to K(V)4.2 channels. To elucidate the molecular basis of this fast inactivation, we investigated the structure-function relationship of the DPP10a N-terminal region and its interaction with the K(V)4.2 channel. Here, we show that DPP10a shares a conserved N-terminal sequence (MNQTA) with DPP6a (aka DPP6-E), which also induces fast inactivation. Deletion of the NQTA sequence in DPP10a eliminates this dramatic fast inactivation, and perfusion of MNQTA peptide to the cytoplasmic face of inside-out patches inhibits the K(V)4.2 current. DPP10a-induced fast inactivation exhibits competitive interactions with internally applied tetraethylammonium (TEA), and elevating the external K(+) concentration accelerates recovery from DPP10a-mediated fast inactivation. These results suggest that fast inactivation induced by DPP10a or DPP6a is mediated by a common N-terminal inactivation motif via a pore-blocking mechanism. This mechanism may offer an attractive target for novel pharmacological interventions directed at impairing I(SA) inactivation and reducing neuronal excitability.

Dipeptidyl peptidase inhibitors, an emerging drug class for inflammatory disease?

Dipeptidyl peptidase (DPP)-4 is a member of the S9b serine protease family, which also includes DPP8 and DPP9. DPP4 cleaves a number of regulatory factors, including chemokines and growth factors. DPP4 inhibitors have recently emerged as an effective treatment option for type 2 diabetes. Early in vitro studies demonstrated that DPP4 inhibitors inhibit T-cell proliferation and cytokine production, leading to their investigation in numerous pre-clinical models of inflammatory diseases, including arthritis, multiple sclerosis and inflammatory bowel disease. Recent data suggest that the early DPP4-specific inhibitors might also bind DPP8 and DPP9, thus exerting their effects through non-specific binding. This review highlights recent insights into the applicability of DPP inhibitors as novel pharmacological agents for inflammatory disease.

Participation of the secreted dipeptidyl and tripeptidyl aminopeptidases in asaccharolytic growth of Porphyromonas gingivalis.

BACKGROUND AND OBJECTIVE: Porphyromonas gingivalis secretes gingipains, endopeptidases essential for the asaccharolytic growth of this bacterium. P. gingivalis also secretes dipeptidyl aminopeptidases (DPPIV and DPP-7) and a tripeptidyl aminopeptidase (PTP-A), although their role in asaccharolytic growth is unclear. The present study was carried out to elucidate the role of these dipeptidyl/tripeptidyl aminopeptidases on the asaccharolytic growth of P. gingivalis. MATERIAL AND METHODS: Knockout mutants for the DPPIV (dpp), dpp7 and/or PTP-A genes were constructed. Brain-heart infusion medium supplemented with sterile hemin and menadione (BHIHM) was used as a complex medium, and the minimal medium used was GA, in which the sole energy source was a mixture of immunoglobulin G and bovine serum albumin. Growth of P. gingivalis was monitored by measuring the optical density of the culture. RESULTS: All knockout mutants for DPPIV, dpp7 and PTP-A grew as well as strain W83 in BHIHM. In GA, growth of single-knockout and double-knockout mutants was similar to that of W83, whereas growth of a triple-knockout mutant (83-47A) was reduced. We purified recombinant DPPIV and recombinant PTP-A from recombinant Escherichia coli overproducers, and purified DPP-7 from the triple-knockout mutant 83-4A. GA supplemented with the three purified dipeptidyl/tripeptidyl aminopeptidases supported the growth of 83-47A. CONCLUSION: DPPIV, DPP-7 and PTP-A contribute to the normal growth of P. gingivalis by cleaving substrate peptides into short-chain polypeptides that are efficient energy sources for P. gingivalis.