Dipeptidyl Peptidase-4 Inhibitory Activity Research Articles

Anti-diabetic and anti-inflammatory activities of commonly available cephalopods

ABSTRACTAnti-diabetic and anti-inflammatory activities of ethyl acetate-methanol extracts of cephalopods namely, Amphioctopus marginatus, Urothethis duvauceli, Sepia pharaonis, Sepiella inermis, and Cistopus indicus were evaluated. The ethyl acetate-methanol extracts of C. indicus exhibited significantly greater (p < 0.05) cyclooxygenase inhibition activities (IC90 ~ 1 mg/mL, respectively) compared to other cephalopod species. Likewise, C. indicus displayed greater 5-lipoxygenase inhibitory activity (IC90 1.69 mg/mL) compared to the other cephalopod species (IC90 > 2 mg/mL) considered in the present study. The solvent extracts derived from the members of the order Octopoda demonstrated fairly good α-amylase inhibitory activity (IC90 ≤ 2.5 mg/mL). Dipeptidyl peptidase-4 inhibitory activity of the ethyl acetate-methanol extract of C. indicus was found to be significantly greater (IC50 2.51 mg/mL) than other species of cephalopods (IC50 3.4–5.4 mg/mL; p < 0.05). The labeling of protons associated with different magnetic environments of the functional groups exhibited in the ethyl acetate-methanol extracts were analyzed by proton nuclear magnetic resonance spectroscopy that supported the in vitro anti-diabetic and anti-inflammatory results. The ethyl acetate-methanol extract of C. indicus and S. inermis displayed greater proton integrals (ΣH) of highly electronegative moieties appeared in the low-field region in the proton nuclear magnetic resonance spectroscopy spectra (C. indicus ΣHδ3.5–4.5 5.34, ΣHδ4.5–6.5 6.41; S. inermis ΣHδ3.5–4.5 6.52, and ΣHδ4.5–6.5 15.39) than other cephalopod species. A significant co-linearity was found between the electronegative groups present in the downfield position of nuclear magnetic resonance spectroscopy spectra vis-à-vis anti-diabetic and anti-inflammatory activities.

Navigating the chemical space of dipeptidyl peptidase-4 inhibitors.

This study represents the first large-scale study on the chemical space of inhibitors of dipeptidyl peptidase-4 (DPP4), which is a potential therapeutic protein target for the treatment of diabetes mellitus. Herein, a large set of 2,937 compounds evaluated for their ability to inhibit DPP4 was compiled from the literature. Molecular descriptors were generated from the geometrically optimized low-energy conformers of these compounds at the semiempirical AM1 level. The origins of DPP4 inhibitory activity were elucidated from computed molecular descriptors that accounted for the unique physicochemical properties inherently present in the active and inactive sets of compounds as defined by their respective half maximal inhibitory concentration values of less than 1 μM and greater than 10 μM, respectively. Decision tree analysis revealed the importance of molecular weight, total energy of a molecule, topological polar surface area, lowest unoccupied molecular orbital, and number of hydrogen-bond donors, which correspond to molecular size, energy, surface polarity, electron acceptors, and hydrogen bond donors, respectively. The prediction model was subjected to rigorous independent testing via three external sets. Scaffold and chemical fragment analysis was also performed on these active and inactive sets of compounds to shed light on the distinguishing features of the functional moieties. Docking of representative active DPP4 inhibitors was also performed to unravel key interacting residues. The results of this study are anticipated to be useful in guiding the rational design of novel and robust DPP4 inhibitors for the treatment of diabetes.

Lactobacilli possess inhibitory activity against dipeptidyl peptidase-4 (DPP-4)

Dipeptidyl peptidase-4 (DPP-4) plays an important role in the enzymatic inactivation of incretin hormones. In this context, drugs that inhibit DPP-4 have been developed and clinically approved as therapies for type 2 diabetes. As the primary substrates of DPP-4 are produced in the intestinal lining, we investigated whether lactobacilli colonizing the gut could inhibit this enzyme. Fifteen Lactobacillus strains (Lb 1–15) from human infant faecal samples were isolated, identified, extracted and screened for inhibitory activity against DPP-4. Activity was compared against Lactobacillus reference strains (Ref 1–7), a Gram-positive control (Ctrl 1) and two Gram-negative controls (Ctrl 2–3). A range of DPP-4 inhibitory activity was observed (10–32 %; p < 0.05–0.001). Strains of L. plantarum (12–25 %) and L. fermentum (14 %) had significant inhibitory activity. However, we noted that Escherichia coli (Ctrl 2) and Salmonella Typhimurium (Ctrl 3) had the greatest inhibitory activity (30–32 %). Contrastingly, some isolates (Lb 12–15) and reference cultures (Ref 1–4), instead of inhibiting DPP-4, actually enhanced it, perhaps indicating the presence of X-prolyl-dipeptidyl-amino-peptidase (PepX). This provides a future rationale for using probiotic bacteria or their components for management of type 2 diabetes via DPP-4 inhibition.

Design, Synthesis, and Pharmacological Evaluation of Fused β-Homophenylalanine Derivatives as Potent DPP-4 Inhibitors.

Dipeptidyl peptidase-4 (DPP-4) inhibitors are accepted as a favorable class of agents for the treatment of type 2 diabetes. Herein, a series of fused β-homophenylalanine derivatives as novel DPP-4 inhibitors were designed, synthesized, and evaluated for their inhibitory activities against DPP-4. Most of them displayed excellent DPP-4 inhibitory activities and good selectivity. Among them, 9aa, 18a, and 18m also showed good efficacy in an oral glucose tolerance test (OGTT) in ICR mice. Moreover, when dosed 8 h prior to glucose challenge, 18m showed significantly greater potency than sitagliptin. It thus provides potential candidates for the further development into potent drugs targeting DPP-4.

Plants Fagonia cretica L. and Hedera nepalensis K. Koch contain natural compounds with potent dipeptidyl peptidase-4 (DPP-4) inhibitory activity

Ethnopharmacological relevanceThe two plants investigated here (Fagonia cretica L. and Hedera nepalensis K. Koch) have been previously reported as natural folk medicines for the treatment of diabetes but until now no scientific investigation of potential anti-diabetic effects has been reported. Materials and methodsIn vitro inhibitory effect of the two tested plants and their five isolated compounds on the dipeptidyl peptidase 4 (DPP-4) was studied for the assessment of anti-diabetic activity. ResultsA crude extract of Fagonia cretica possessed good inhibitory activity (IC50 value: 38.1μg/ml) which was also present in its n-hexane (FCN), ethyl acetate (FCE) or aqueous (FCA) fractions. A crude extract of Hedera nepalensis (HNC) possessed even higher inhibitory activity (IC50 value: 17.2μg/ml) and this activity was largely retained when further fractionated in either ethyl acetate (HNE; IC50: 34.4μg/ml) or n-hexane (HNN; 34.2μg/ml). Bioactivity guided isolation led to the identification of four known compounds (isolated for the first time) from Fagonia cretica: quinovic acid (1), quinovic acid-3β-O-β-d-glycopyranoside (2), quinovic acid-3β-O-β-d-glucopyranosyl-(28→1)-β-d-glucopyranosyl ester (3), and stigmasterol (4) all of which inhibited DPP-4 activity (IC50: 30.7, 57.9, 23.5 and >100µM, respectively). The fifth DPP-4 inhibitor, the triterpenoid lupeol (5) was identified in Hedera nepalensis (IC50: 31.6μM). ConclusionThe experimental study revealed that Fagonia cretica and Hedera nepalensis contain compounds with significant DPP-4 inhibitory activity which should be further investigated for their anti-diabetic potential.

Synthesis and biological evaluation of pyrrolidine-2-carbonitrile and 4-fluoropyrrolidine-2-carbonitrile derivatives as dipeptidyl peptidase-4 inhibitors for the treatment of type 2 diabetes

A novel series of pyrrolidine-2-carbonitrile and 4-fluoropyrrolidine-2-carbonitrile derivatives was designed, synthesized, and found to act as dipeptidyl peptidase-4 (DPP-4) inhibitors. From this series of compounds, compound 17a was identified as an efficacious, safe, and selective inhibitor of DPP-4. In vivo studies in ICR and KKAy mice showed that administration of this compound resulted in decreased blood glucose in these mice after an oral glucose challenge. Compound 17a showed high DPP-4 inhibitory activity (IC50=0.017μM), moderate selectivity against DPP-4 (selective ratio: DPP-8/DPP-4=1324; DPP-9/DPP-4=1164), and good efficacy in oral glucose tolerance tests in ICR and KKAy mice. These in vivo anti-diabetic properties and its desirable pharmacokinetic profile in Sprague–Dawley rats demonstrate that compound 17a is a promising candidate for development as an anti-diabetic agent.

Design, Synthesis, Biological Evaluation, and Docking Studies of (S)‐Phenylalanine Derivatives with a 2‐Cyanopyrrolidine Moiety as Potent Dipeptidyl Peptidase 4 Inhibitors

A novel series of (S)-phenylalanine derivatives with a 2-cyanopyrrolidine moiety were designed and synthesized through a rational drug design strategy. Biological evaluation revealed that most tested compounds were potent dipeptidyl peptidase 4 (DPP-4) inhibitors; among them, the cyclopropyl-substituted phenylalanine derivative 11h displayed the most potent DPP-4 inhibitory activity with an IC50 value of 0.247μm. In addition, molecular docking analysis of the representative compounds 11h, 11k, and 15a were performed, which not only revealed the impact of binding modes on DPP-4 inhibitory activity but also provided additional methodological values for design and optimization.

A Time‐Resolved Fluorescence Probe for Dipeptidyl Peptidase 4 and Its Application in Inhibitor Screening

The prevalence of type 2 diabetes is increasing dramatically throughout the world. Recently, dipeptidyl peptidase 4 (DPP4) was identified as a potential antidiabetes target. Many DPP4 inhibitors, such as sitagliptin and vildagliptin, have been developed and marketed, but superior therapeutic agents are still required. Therefore, we have developed new methodology for screening of DPP4 inhibitors. Absorption-based measurements with para-nitroaniline or fluorescence-based measurements with the coumarin derivative 7-amino-4-methylcoumarin are often used for the screening of protease inhibitors, including DPP4 inhibitors, but these strategies are not sufficiently sensitive because of interfering background absorption and fluorescence, thus giving rise to many false-positive and false-negative results. Therefore, we have designed and synthesised a novel DPP4 probe (Gly-Pro-BCD-Tb; Gly=glycine, Pro=proline, andBCD defines the backbone of the probe comprising an aniline derivative as on/off switch, a 7-amino-4-methyl-2(1H)-quinolinone (cs-124) as antenna moiety, and a diethylenetriamine-N,N,N',N'',N''-pentaacetic acid (DTPA) as chelator moiety, Tb=terbium) for time-resolved fluorescence (TRF) measurements. TRF measurements with Gly-Pro-BCD-Tb showed high sensitivity and reliability in the inhibitory assay relative to Gly-Pro-MCA (MCA=4-methylcoumarin-7-amide), a conventional fluorescence probe for DPP4. Further, we employed our probe for high-throughput DPP4 inhibitor screening with 3841 randomly selected compounds and found that epibestatin, an epimer of bestatin (a well-known anticancer drug and general aminopeptidase inhibitor), showed dose-dependent DPP4 inhibitory activity. Interestingly, bestatin did not exhibit DPP4 inhibitory activity. We believe that this screening system will be useful for the discovery of DPP4 inhibitors with novel structural scaffolds.

Anti-diabetic Properties of Serviceberry(Amelanchier alnifolia)

Diabetes mellitus afflicts an estimated 18.2 million Americans and costs about $132 billion annually. Several plant-based remedies offer cost-effective management of diabetes, but few plant species adapted to North America have been validated for their antidiabetic properties. One such species is serviceberry (Amelanchier alnifolia), found in Browning, MT which has been traditionally used by the American Indians for managing Type 2 diabetes. The objective of this study was to validate and identify potential antidiabetic mechanisms of serviceberry using cell culture techniques. Serviceberry plant samples consisting of leaves, twigs, and leaves with berries were extracted and fractionated. The ethyl acetate and water fractions were tested for activation of 2-deoxyglucose uptake, dipeptidyl peptidase-4 (DPP-4) inhibitory activity, and alpha-glucosidase inhibition. In L6GLUT4myc skeletal muscle cells, insulin (100 nM) induced a 1.5–2.0 fold activation of 2-deoxyglucose uptake. Two of the water fractions demonstrated modest activation of 2-deoxyglucose uptake. The ethyl acetate and water fractions were devoid of DPP-4 inhibitory activity. Water fractions from leaves and twigs demonstrated inhibition of alpha-glucosidase activity, similar to that of the positive control, acarbose. The activity was enhanced 2–7 fold, after chromatographic purification. Water fractions also demonstrated a dose-dependent suppression of dexamethasone-induced gluconeogenic gene expression in H4IIE rat hepatoma cells. These findings suggest that the alpha-glucosidase inhibitory activity, which slows down the digestion of complex carbohydrates, and the suppression of hepatic gluconeogenesis, may be potential mechanisms that can lead to lowering of blood glucose levels and conferring an anti-diabetic effect of serviceberry. Acknowledgements: Funding from the USDA/CSREES Tribal Colleges Research Grants Program is gratefully acknowledged.

Synthesis and structure–activity relationship of N-acyl-Gly-, N-acyl-Sar- and N-blocked-boroPro inhibitors of FAP, DPP4, and POP

The structure–activity relationship of various N-acyl-Gly-, N-acyl-Sar-, and N-blocked-boroPro derivatives against three prolyl peptidases was explored. Several N-acyl-Gly- and N-blocked-boroPro compounds showed low nanomolar inhibitory activity against fibroblast activation protein (FAP) and prolyl oligopeptidase (POP) and selectivity against dipeptidyl peptidase-4 (DPP4). N-Acyl-Sar-boroPro analogs retained selectivity against DPP4 and potent POP inhibitory activity but displayed decreased FAP inhibitory activity.