A comparative study of the binding modes of recently launched dipeptidyl peptidase IV inhibitors in the active site

Inhibitory activity of xanthoangelol isolated from Ashitaba (Angelica keiskei Koidzumi) towards α-glucosidase and dipeptidyl peptidase-IV: in silico and in vitro studies

In Indonesia, the sap of Angelica keiskei Koidzumi has been utilized traditionally as a blood-sugar reducer, nonetheless, its molecular mechanism still needs to be studied. This study aimed to isolate xanthoangelol (XA) from the yellow sap of A. keiskei planted in Mount Rinjani, Indonesia, and to investigate its mechanism by in silico and in vitro methods towards α-glucosidase and dipeptidyl peptidase-IV (DPP-IV). The dried yellow sap was macerated using ethanol, subjected to liquid-liquid extraction using a different polarity of solvents, further gradient-eluted with column chromatography. The isolated compound, formed as yellow crystals, melting point 114–114.4 °C, λ_max 368 nm, m/z 393.20 [M + H]⁺, was confirmed as XA. Acarbose, an α-glucosidase inhibitor, and sitagliptin, a DPP-IV inhibitor, respectively, were employed as the reference drugs for both the in silico and in vitro studies. XA interacts with essential amino acid residues 232–237 in the N-terminal N-loop of α-glucosidase by forming a hydrogen bond with Ala234, a salt-bridge with Asp232, and 9 hydrophobic interactions (binding energy -7.81 kcal/mol; Ki = 1.99 μM). These binding modes resemble those of acarbose. Moreover, XA forms hydrogen bonds with Glu205 and Glu206 in the subsite S2 and π-π interaction with Phe357 in the extensive subsite S2 of DPP-IV (binding energy -8.34 kcal/mol; Ki = 0.873 μM), which are similar to those of sitagliptin. XA inhibits both α-glucosidase (IC₅₀ XA = 14.45 μM; IC₅₀ acarbose = 207 μM) and DPP-IV (IC₅₀ XA = 10.49 μM; IC₅₀ sitagliptin = 0.87 μM). Taken together, XA isolated from the yellow sap of A. keiskei Koidzumi might possess the potential to be further developed as an inhibitor of α-glucosidase and DPP-IV.

Validation of structural-based virtual screening protocols with the PDB Code 3G0B and prediction of the activity of Tinospora crispa compounds as inhibitors of dipeptidyl-peptidase-IV

Introduction: Brotowali (Tinospora crispa) has been traditionally used as an antidiabetic drug. DPP-IV inhibitor as an antidiabetic will increase insulin secretion. It indirectly escalates incretin hormones, such as Glucagon-Like peptide-1 (GLP-1) which depends on glucose. This study predicts potential compounds from the Brotowali plants, such as DPP-IV inhibitors, using the Molegro Virtual Docker (MVD).

Materials and methods: Before the molecular docking simulation, internal validation and external validation are necessary. Internal validation was carried out by re-docking the native ligands in the DPP-IV enzyme crystal structure (PDB codes 3G0B, 3W2T, and 3BJM). The external validation was carried out by simultaneous docking of 59 active compounds and 1918 inactive compounds (decoys) from the A Directory of Useful Decoys (DUD) database with PDB code 3G0B on 16 combinations, four search algorithms, and four functions scoring.

Results and discussion: The molecular docking simulation was carried out on 50 compounds from the Brotowali plant and alogliptin as standard compounds with PDB code 3G0B. The best results of the docking method validation yielded the RMSD values of 0.43 and EF1% of 20.34 and EF20% of 3.1 (the combination of search algorithm Moldock optimizer and scoring function Moldock score). The re-rank score of 5 compounds from the Brotowali plant (Rumphioside C, Borapetoside E, Borapetoside F, Rumphioside I, and 6’-O-Lactoyl Borapetoside B) were -107.7 kcal/mol; -105.4 kcal/mol; -104.2 kcal/mol, and -102.8 kcal/mol. Alogliptin (standard ligands) had a re-rank score of -101.6 kcal/mol. The combination of search algorithms MolDock optimizer and scoring function MolDock score is a valid protocol with a good result. The similarity of the binding sites of Borapetoside E and 6’-O-Lactoyl Borapetoside B is 75% when compared to the alogliptin binding sites (Glu 205, Glu 206, Tyr 547).

Conclusion: Based on the re-rank score and binding sites similarity, Borapetoside E and 6’-O-Lactoyl Borapetoside B have potential as an antidiabetic drug with a mechanism of action of DPP-IV inhibitors.

Repurposing of existing antibiotics for the treatment of diabetes mellitus

Proline specific serine protease enzyme, dipeptidyl peptidase IV (DPP-4) has become a promising target for diabetes, as it stops glucagon-like peptide 1 (GLP-1) from becoming inactive, resulting in higher levels of active GLP-1. This lowers glucose levels by increasing insulin secretion and decreasing glucagon secretion. DPP-4 is also linked to a higher BMI and a 0.7 to 1% reduction in HbA1c. Currently available DPP-4 inhibitor drugs showed less promising anti-diabetic activity as this class associated with many side effects due to non-selectivity and therefore searching on more potent DPP-4 inhibitors are still ongoing. In our present study, we investigate the inhibition of DPP-4 through a series of antibiotic compounds which were previously reported to be used in diabetic foot infections and compared with existing DPP-4 inhibitors. To obtain this objective, three-dimensional crystal structure of DPP-4 was retrieved from the protein data bank (PDB id: 1 × 70). A systematic computational method combining molecular docking, MM-GBSA binding energy calculation, MD simulations, MM-PBSA binding free energy calculations and ADME were used to find best DPP-4 inhibitor. Molecular docking results revealed that clindamycin has a higher affinity towards the catalytic sides of DPP-4 and built solid hydrophobic and polar interactions with the amino acids involved in the binding region of DPP-4, such as S1 subsite, S2 subsite and S2 extensive subsite. MD simulations results showed clindamycin as potent virtual hit and suggested that it binds with DPP-4 in competitive manner, which virtually indicate that besides antibiotic activity clindamycin has anti-diabetic activity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-021-00118-6.

Role and mechanism(s) of incretin-dependent therapies for treating diabetes mellitus

Diabetes mellitus (DM) is a worldwide ailment which leads to chronic complications like cardiac disorders, renal perturbations, limb amputation and blindness. Type one diabetes (T1DM), Type two diabetes (T2DM), Another types of diabetes, such as genetic errors in function of β-cell and action of insulin, cystic fibrosis, chemical-instigated diabetes or following tissue transplantation), and pregnancy DM (GDM). In response to nutritional ingestion, the gut may release a pancreatic stimulant that affects carbohydrate metabolism. The duodenum produces a 'chemical excitant' that stimulates pancreatic output, and researchers have sought to cure diabetes using gut extract injections, coining the word 'incretin' to describe the phenomena. Incretins include GIP and GLP-1. The 'enteroinsular axis' is the link between pancreas and intestine. Nutrient, neuronal and hormonal impulses from intestine to cells secreting insulin were thought to be part of this axis. In addition, the hormonal component, incretin, must meet two requirements: (1) it secreted by foods, mainly carbohydrates, and (2) it must induce an insulinotropic effect which is glucose-dependent. In this review, we clarify the ability of using incretin-dependent treatments for treating DM.

Design, Synthesis and Biological Evaluation of Neogliptin, a Novel 2-Azabicyclo[2.2.1]heptane-Based Inhibitor of Dipeptidyl Peptidase-4 (DPP-4)

Compounds that contain (R)-3-amino-4-(2,4,5-trifluorophenyl)butanoic acid substituted with bicyclic amino moiety (2-aza-bicyclo[2.2.1]heptane) were designed using molecular modelling methods, synthesised, and found to be potent DPP-4 (dipeptidyl peptidase-4) inhibitors. Compound 12a (IC50 = 16.8 ± 2.2 nM), named neogliptin, is a more potent DPP-4 inhibitor than vildagliptin and sitagliptin. Neogliptin interacts with key DPP-4 residues in the active site and has pharmacophore parameters similar to vildagliptin and sitagliptin. It was found to have a low cardiotoxic effect compared to sitagliptin, and it is superior to vildagliptin in terms of ADME properties. Moreover, compound 12a is stable in aqueous solutions due to its low intramolecular cyclisation potential. These findings suggest that compound 12a has unique properties and can act as a template for further type 2 diabetes mellitus drug development.

Analysis of the Structure and Activity of Dipeptidyl Peptidase IV (DPP-IV) Inhibitory Oligopeptides from Sorghum Kafirin

Potential dipeptidyl peptidase IV (DPP-IV) inhibitory oligopeptides from sorghum kafirin were developed using in silico and in vitro methodologies for the management of diabetes. Twenty-eight peptides with 5-10 residues were identified from the papain hydrolysates of sorghum kafirin. Sixteen nontoxic DPP-IV inhibitory peptides were screened with a computer method based on molecular docking. Molecular docking revealed that LPFYPQ (LP6), GPVTPPILG (GP9), and LPFYPQGV (LP8) effectively inactivated DPP-IV by binding to its active sites with a low interaction energy. An in silico analysis of these three inhibitory oligopeptides indicated that they were all bound to the S1 and S2 active pockets of DPP-IV through hydrogen bonds and hydrophobic interactions. The in vitro inhibitory activity was also verified. The DPP-IV inhibitory activities of LP6 and LP8 decreased after gastric digestion and remained stable after intestinal digestion, and the GP9 inhibitory activity remained stable after gastrointestinal digestion. Experimental results from Caco-2 cells showed further inhibitory effects of oligopeptides on DPP-IV. The results are relevant to the exploration of biofunctional DPP-IV inhibitory peptides from sorghum as a treatment for patients with diabetes or in medical research.

Generation, characterization and molecular binding mechanism of novel dipeptidyl peptidase-4 inhibitory peptides from sorghum bicolor seed protein

Food proteins and their constituent peptides impart huge health benefits besides their nutritional attributes. Sorghum bicolor protein hydrolysates (SPH) and derived bioactive peptides generated by simulated gastrointestinal digestion were studied for DPP-4 inhibitory properties using in vitro and in situ assays. Identified peptides, LSICGEESFGTGSDHIR (PEP1), SLGESLLQEDVEAHK (PEP2) and QLRDIVDK (PEP4) displayed potent DPP-4 inhibition with IC50 values of 73.5, 82.5 and 8.55 µM respectively. DPP-4 inhibition mechanism by the peptides was investigated by DPP4-peptide inhibition kinetics, molecular docking and microscale thermophoresis binding studies. The peptides bound to DPP-4 with micromolar affinities and PEP4 showed significantly increased affinity. The mixed type enzyme inhibition by peptides suggested that the peptides either block the active site of DPP-4 or changes the enzyme conformation via a secondary binding site. Overall, the results demonstrate that sorghum seeds are an adequate source of peptides with DPP-4 inhibitory properties that could be used in functional food formulations.

Discovery of tight-binding competitive inhibitors of dipeptidyl peptidase IV

Dipeptidyl peptidase IV (DPP-IV, EC 3.4.14.5) is an abundant serine aminopeptidase that preferentially cleaves N-terminal Xaa-Pro or Xaa-Ala dipeptides from oligopeptides. Inhibitors of DPP-IV activity are used for treating type 2 diabetes mellitus and other diseases. DPP-IV is also involved in tumor progression. We identified four new non-peptide tight-binding competitive inhibitors of porcine DPP-IV by virtual screening and enzymatic assays. Molecular docking simulations supported the competitive behavior, and the selectivity of one of the compounds in the DPP-IV family. Since three of these inhibitors are also aminopeptidase N (APN) inhibitors, we tested their impact on APN+/DPP-IV+ and DPP-IV+ human tumor cells' viability. Using kinetic assays, we determined that HL-60 tumor cells express both APN and DPP-IV activities and that MDA-MB-231 tumor cells express DPP-IV activity. The inhibitors had a slight inhibitory effect on human HEK-293 cell viability but reduced the viability of APN+/DPP-IV+ and DPP-IV+ human tumor cells more potently. Remarkably, the intraperitoneal injection of these compounds inhibited DPP-IV activity in rat brain, liver, and pancreas. In silico studies suggested inhibitors binding to serum albumin contribute to blood-brain barrier crossing. The spectrum of action of some of these compounds may be useful for niche applications.

DPP-IV Inhibitory Activity of the Ethanolic Extract of Red Gedi Leaves Abelmoschus manihot L. Medic

BACKGROUND: At present, there are many drugs used to manage diabetes including dipeptidyl peptidase-4 (DPP-IV) inhibitors which target insulin secretion. Abelmoschus manihot L. Medic, an endemic species of Minahasa, Indonesia, has been used as an antidiabetic herbal medicine. AIM: In this study, we studied its metabolites activities, in silico and in vitro, as inhibitor for DPP-IV, thus regulating insulin secretion. RESULTS: Of 38 identified metabolites, when docked into the catalytic site DPP-IV, 10 showed good binding energy within range of the standard gliptin drugs, that is, hibiscetin, gossypentin, gossypetin - 3-glucoside, myricetin, myricetin 3-glucoside, alpha spinasterol, quercetin, syringaresinol, stigmasterol, and isoquercetin. Three of those ten metabolites showed Ki within standard drugs values, that is, gossypetin, alpha spinasterol, and stigmasterol. The profile of molecular dynamic simulation, total energy and root mean square deviation of those metabolites were all similar with the standard gliptin drugs and predicted good stability of the complexes. The subsequent in vitro assay determining DPP-IV activity of the red Gedi leaves extract demonstrated that indeed the extract inhibited DPP-IV activity with IC50 860.67 μg/mL. Further studies are ongoing to prove the antidiabetic properties of the whole as well as isolated single compounds of the extract in particular gossypetin, alpha spinasterol, and stigmasterol as DPP-IV inhibitors. CONCLUSION: Our in silico studies showed that the compounds of ethanolic extract of red Gedi leaves potentially serve as DPP-IV inhibitors. Based on computed binding affinity, Ki, total energy, RMSD, and stability, the most potent compounds of the extract to inhibit DPP-IV activity are probably gossypetin, alpha spinasterol, and stigmasterol.

Differential Effects of DPP-4 Inhibitors, Anagliptin and Sitagliptin, on PCSK9 Levels in Patients with Type 2 Diabetes Mellitus who are Receiving Statin Therapy

Aim: Proprotein convertase subtilisin/kexin type 9 (PCSK9) degrades the low-density lipoprotein (LDL) receptor, leading to hypercholesterolemia and cardiovascular risk. Treatment with a statin leads to a compensatory increase in circulating PCSK9 level. Anagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, was shown to decrease LDL cholesterol (LDL-C) levels to a greater extent than that by sitagliptin, another DPP-4 inhibitor, in the Randomized Evaluation of Anagliptin versus Sitagliptin On low-density lipoproteiN cholesterol in diabetes (REASON) trial. We investigated PCSK9 concentration in type 2 diabetes mellitus (T2DM) and the impact of treatment with anagliptin or sitagliptin on PCSK9 level as a sub-analysis of the REASON trial.

Methods: PCSK9 concentration was measured at baseline and after 52 weeks of treatment with anagliptin ( n =122) or sitagliptin ( n =128) in patients with T2DM who were receiving statin therapy. All of the included patients had been treated with a DPP-4 inhibitor prior to randomization.

Results: Baseline PCSK9 level was positively, but not significantly, correlated with LDL-C and was independently associated with platelet count and level of triglycerides. Concomitant with reduction of LDL-C, but not hemoglobin A1c (HbA1c), by anagliptin, PCSK9 level was significantly increased by treatment with sitagliptin (218±98 vs. 242±115 ng/mL, P =0.01), but not anagliptin (233±97 vs. 250±106 ng/mL, P =0.07).

Conclusions: PCSK9 level is independently associated with platelet count and level of triglycerides, but not LDL-C, in patients with T2DM. Anagliptin reduces LDL-C level independent of HbA1c control in patients with T2DM who are on statin therapy possibly by suppressing excess statin-mediated PCSK9 induction and subsequent degradation of the LDL receptor.

Application of a Combined Peptidomics and In Silico Approach for the Identification of Novel Dipeptidyl Peptidase-IV-Inhibitory Peptides in In Vitro Digested Pinto Bean Protein Extract

The conventional approach in bioactive peptides discovery, which includes extensive bioassay-guided fractionation and purification processes, is tedious, time-consuming and not always successful. The recently developed bioinformatics-driven in silico approach is rapid and cost-effective; however, it lacks an actual physiological significance. In this study a new integrated peptidomics and in silico method, which combines the advantages of the conventional and in silico approaches by using the pool of peptides identified in a food hydrolysate as the starting point for subsequent application of selected bioinformatics tools, has been developed. Pinto bean protein extract was in vitro digested and peptides were identified by peptidomics. The pool of obtained peptides was screened by in silico analysis and structure–activity relationship modelling. Three peptides (SIPR, SAPI and FVPH) were selected as potential inhibitors of the dipeptidyl-peptidase-IV (DPP-IV) enzyme by this integrated approach. In vitro bioactivity assay showed that all three peptides were able to inhibit DPP-IV with the tetra-peptide SAPI showing the highest activity (IC50 = 57.7 μmol/L). Indeed, a new possible characteristic of peptides (i.e., the presence of an S residue at the N-terminus) able to inhibit DPP-IV was proposed.

Efficacy of omarigliptin, once-weekly dipeptidyl peptidase-4 inhibitor, in patients with type 2 diabetes

BACKGROUND

Omarigliptin is one of several once-weekly dipeptidyl peptidase-4 inhibitors (DPP-4is). Despite the high frequency of switching from various daily DPP-4is to omarigliptin in actual clinical practice, data regarding its efficacy in patients with type 2 diabetes (T2D) after switching are limited.

AIM

To analyze the efficacy of omarigliptin in Japanese patients with T2D who had previously received treatment with other glucose-lowering agents.

METHODS

Forty-nine T2D patients treated for the first time with omarigliptin were recruited retrospectively and divided into four groups defined as either add-on or switched from daily DPP-4is: switched from linagliptin, switched from sitagliptin, and switched from vildagliptin. During a 3-mo follow-up, the clinical parameters among these groups were assessed and compared, with the impact of the switch on glycemic variability as measured by continuous glucose monitoring also being evaluated in the switched groups.

RESULTS

Hemoglobin A1c levels saw a significant decrease of -0.32% ± 0.41% in the add-on group (P = 0.002). However, the other groups’ variables depended on the pre-switch daily DPP-4i: switched from linagliptin, -0.05% ± 0.22%; switched from sitagliptin, -0.17% ± 0.33%; and switched from vildagliptin, 0.45% ± 0.42%, which saw significant worsening (P = 0.0007). Multivariate logistic regression analysis revealed that switching from vildagliptin to omarigliptin was independently associated with worsening glycemic control (P = 0.0013). The mean and standard deviation of sensor glucose value, the mean amplitude of glycemic excursions, and the mean of daily difference significantly improved when switching the patient from either linagliptin or sitagliptin to omarigliptin. However, in patients switched from vildagliptin, not only did the glucose variability indices see no improvements, the mean of daily difference even underwent significant worsening.

CONCLUSION

Administering omarigliptin as add-on therapy or switching to it from sitagliptin and linagliptin, but not vildagliptin, improves glycemic control and thus should help in decision making when selecting DPP-4is for T2D patients.

StackDPPIV: A novel computational approach for accurate prediction of dipeptidyl peptidase IV (DPP-IV) inhibitory peptides

The development of efficient and effective bioinformatics tools and pipelines for identifying peptides with dipeptidyl peptidase IV (DPP-IV) inhibitory activities from large-scale protein datasets is of great importance for the discovery and development of potential and promising antidiabetic drugs. In this study, we present a novel stacking-based ensemble learning predictor (termed StackDPPIV) designed for identification of DPP-IV inhibitory peptides. Unlike the existing method, which is based on single-feature-based methods, we combined five popular machine learning algorithms in conjunction with ten different feature encodings from multiple perspectives to generate a pool of various baseline models. Subsequently, the probabilistic features derived from these baseline models were systematically integrated and deemed as new feature representations. Finally, in order to improve the predictive performance, the genetic algorithm based on the self-assessment-report was utilized to determine a set of informative probabilistic features and then used the optimal one for developing the final meta-predictor (StackDPPIV). Experiment results demonstrated that StackDPPIV could outperform its constituent baseline models on both the training and independent datasets. Furthermore, StackDPPIV achieved an accuracy of 0.891, MCC of 0.784 and AUC of 0.961, which were 9.4%, 19.0% and 11.4%, respectively, higher than that of the existing method on the independent test. Feature analysis demonstrated that our feature representations had more discriminative ability as compared to conventional feature descriptors, which highlights the combination of different features was essential for the performance improvement. In order to implement the proposed predictor, we had built a user-friendly online web server at http://pmlabstack.pythonanywhere.com/StackDPPIV.

Identification and structure-activity relationship exploration of uracil-based benzoic acid and ester derivatives as novel dipeptidyl Peptidase-4 inhibitors for the treatment of type 2 diabetes mellitus

Our previously reported carboxyl-containing DPP-4 inhibitors were highly potent but were poorly bioavailable. Esters of the carboxyl analogs exhibited a significant DPP-4 potency loss albeit with enhanced oral absorption. Herein, we described identification and structure-activity relationship (SAR) exploration of a novel series of benzoic acid and ester derivatives as low single-digit nanomolar DPP-4 inhibitors. Importantly, the esters displayed comparable activities to the acids counterparts. Molecular simulation revealed that ester adopts a similar binding mode to acid. Moreover, the selected esters and acids demonstrated high selectivity and low cytotoxicity, as well as good metabolic stability. And more importantly, the esters possessed excellent pharmacokinetic profiles for oral administration. The best compound ester 19b demonstrated long DPP-4 inhibition in vivo, and robustly improved the glucose tolerance in normal and db/db mice while ensuring glucose-lowering potency in chronic treatment. Our results supported that the compound 19b can be served as a potential candidate for the treatment of type 2 diabetes.

Efficacy and Safety of Switching to Teneligliptin in Patients with Type 2 Diabetes Inadequately Controlled with Dipeptidyl Peptidase-4 Inhibitors: 52-Week Results from a Prospective Observational Study

INTRODUCTION

The aim of this study was to assess the efficacy and safety of switching to teneligliptin from other dipeptidyl peptidase-4 (DPP-4) inhibitors in patients with type 2 diabetes mellitus (T2DM) inadequately controlled despite treatment with a stable dose of other DPP-4 inhibitors.

METHODS

Patients with glycosylated hemoglobin (HbA1c) ≥ 7% despite taking DPP-4 inhibitors other than teneligliptin, with or without other antidiabetic agents, for at least 3 months were enrolled in this study. Patients on DPP-4 inhibitors administered prior to participation in this study were switched to 20 mg teneligliptin once daily and the dose was maintained for the 52-week study period. The primary endpoint was the change in HbA1c at week 12. Fasting plasma glucose (FPG) and the blood lipid profile were also evaluated. Adverse events were monitored for safety assessment.

RESULTS

At weeks 12, 24, and 52, the HbA1c values significantly decreased by - 0.39, - 0.44, and - 0.52%, respectively, compared to the baseline value (p < 0.0001); in addition, 56.3, 60.3, and 62.3% of patients, respectively, achieved decreases in HbA1c of at least 0.3%, and 40.1, 46.5, and 52.4% of patients, respectively, achieved decreases in HbA1c of at least 0.5%. The proportion of the patient population achieving HbA1c < 7.0% increased throughout the study period, reaching 30.4, 35.4, and 36.9% at weeks 12, 24, and 52, respectively; at these same time points, the percentage of patients achieving HbA1c < 6.5% increased to 9.5, 11.9, and 13.2% of the total study population. FPG levels and lipid parameters were also significantly decreased after teneligliptin treatment. There were no significant safety concerns.

CONCLUSION

Our results suggest the significant glucose-lowering effect of teneligliptin after switching from other DPP-4 inhibitors in patients with T2DM. The improvement in glycemic control was maintained for up to 52 weeks without safety concerns.

Nitrile-containing pharmaceuticals: target, mechanism of action, and their SAR studies

The nitrile group is an important functional group widely found in both pharmaceutical agents and natural products. More than 30 nitrile-containing pharmaceuticals have been approved by the FDA for the management of a broad range of clinical conditions in the last few decades. Incorporation of a nitrile group into lead compounds has gradually become a promising strategy in rational drug design as it can bring additional benefits including enhanced binding affinity to the target, improved pharmacokinetic profile of parent drugs, and reduced drug resistance. This paper reviews the existing drugs with a nitrile moiety that have been approved or in clinical trials, involving their targets, molecular mechanism of pharmacology and SAR studies, and classifies them into different categories based on their clinical usages.

SARS-CoV-2 and diabetes: A potential therapeutic effect of dipeptidyl peptidase 4 inhibitors in diabetic patients diagnosed with COVID-19

COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 and has become an urgent economic and health challenge. Dipeptidyl peptidase 4 (DPP4), also mentioned as a cluster of differentiation 26 (CD26) is a serine exopeptidase found in two arrangements: a soluble form (sDPP-4) and a plasma membrane-bound form. Because other coronaviruses enter the cells by binding to DPP-4, it has been speculated that DPP-4 inhibitors may exert activity against COVID-19. Therefore, this review aimed to summarize the potential therapeutic effect of dipeptidyl peptidase 4 inhibitors in diabetic patients diagnosed with COVID-19. To include different studies, publications related to Dipeptidyl peptidase-4 inhibitor use and clinical outcomes from COVID-19 were searched from the databases such as Web of Science, PubMed, Medline, Elsevier, Google Scholar, and SCOPUS, via English key terms. A direct engrossment of DPP4 in COVID-19 needs to be elucidated, there is also evidence confirming that DPP4 inhibitors exert anti-fibrotic and modulate inflammation activity. Thus, the use of DPP-4 inhibitors could reduce mortality due to COVID-19 or improve the progression of COVID-19; this evidence may support the management of diabetic patients diagnosed with COVID-19; however more well-designed investigation is urgently required.

Dipeptidyl peptidase-IV inhibitory action of Calebin A: An in silico and in vitro analysis

BACKGROUND

Dipeptidyl peptidase-IV (DPP-IV) inhibitors, the enhancers of incretin are used for the treatment of diabetes. The non-glycaemic actions of these drugs (under developmental stage) also proved that repurposing of these molecules may be advantageous for other few complicated disorders like cardiovascular diseases, Parkinson's disease, Alzheimer's disease, etc. OBJECTIVE: The present study was aimed to investigate the DPP-IV inhibitory potential of Calebin-A, one of the constituents of Curcuma longa.

MATERIAL AND METHODS

The phytoconstituent was subjected for various in silico studies (using Schrödinger Suite) like, Docking analysis, molecular mechanics combined with generalized Born model and solvent accessibility method (MMGBSA) and Induced fit docking (IFD) after validating the protein using Ramachandran plot. Further, the protein-ligand complex was subjected to molecular dynamic simulation studies for 50 nanoseconds. And finally, the results were confirmed through enzyme inhibition study.

RESULTS

Insilico results revealed possible inhibitory binding interactions in the catalytic pocket (importantly Glu205, Glu206 and Tyr 662 etc.) and binding affinity in terms of glide g-score and MMGBSA dG bind values were found to be -6.2 kcal/mol and -98.721 kcal/mol. Further, the inhibitory action towards the enzyme was confirmed by an enzyme inhibition assay, in which it showed dose-dependent inhibition, with maximum % inhibition of 55.9 at 26.3 μM. From molecular dynamic studies (50 nanoseconds), it was understood that Calebin A was found to be stable for about 30 nanoseconds in maintaining inhibitory interactions.

CONCLUSION

From the in silico and in vitro analysis, the current research emphasizes the consideration of Calebin A to be as a promising or lead compound for the treatment of several ailments where DPP-IV action is culprit.

Docking-generated multiple ligand poses for bootstrapping bioactivity classifying Machine Learning: Repurposing covalent inhibitors for COVID-19-related TMPRSS2 as case study

In the present work we introduce the use of multiple docked poses for bootstrapping machine learning-based QSAR modelling. Ligand-receptor contact fingerprints are implemented as descriptor variables. We implemented this method for the discovery of potential inhibitors of the serine protease enzyme TMPRSS2 involved the infectivity of coronaviruses. Several machine learners were scanned, however, Xgboost, support vector machines (SVM) and random forests (RF) were the best with testing set accuracies reaching 90%. Three potential hits were identified upon using the method to scan known untested FDA approved drugs against TMPRSS2. Subsequent molecular dynamics simulation and covalent docking supported the results of the new computational approach.

Phenolic Extracts from Extra Virgin Olive Oils Inhibit Dipeptidyl Peptidase IV Activity: In Vitro, Cellular, and In Silico Molecular Modeling Investigations

Two extra virgin olive oil (EVOO) phenolic extracts (BUO and OMN) modulate DPP-IV activity. The in vitro DPP-IV activity assay was performed at the concentrations of 1, 10, 100, 500, and 1000 μg/mL, showing a dose-dependent inhibition by 6.8 ± 1.9, 17.4 ± 6.1, 37.9 ± 2.4, 57.8 ± 2.9, and 81 ± 1.4% for BUO and by 5.4 ± 1.7, 8.9 ± 0.4, 28.4 ± 7.2, 52 ± 1.3, and 77.5 ± 3.5% for OMN. Moreover, both BUO and OMN reduced the DPP-IV activity expressed by Caco-2 cells by 2.9 ± 0.7, 44.4 ± 0.7, 61.2 ± 1.8, and 85 ± 4.2% and by 3 ± 1.9, 35 ± 9.4, 60 ± 7.2, and 82 ± 2.8%, respectively, at the same doses. The concentration of the most abundant and representative secoiridoids within both extracts was analyzed by nuclear magnetic resonance (¹H-NMR). Oleuropein, oleacein, oleocanthal, hydroxytyrosol, and tyrosol, tested alone, reduced the DPP-IV activity, with IC₅₀ of 472.3 ± 21.7, 187 ± 11.4, 354.5 ± 12.7, 741.6 ± 35.7, and 1112 ± 55.6 µM, respectively. Finally, in silico molecular docking simulations permitted the study of the binding mode of these compounds.

Development of Bilayer Tablet Containing Saxagliptin Immediate Release and Metformin Sustained Release Using Quality by Design Approach

Objective:

Adequate glycemic control in diabetes patients requires oral combination therapy. Saxagliptin is a dipeptidyl peptidase-4 inhibitor having fewer adverse effects, and metformin is the first-line medicine for diabetes treatment. The aim of this research work is to develop a bilayer tablet of saxagliptin and metformin in fixed-dose combination (FDC) using quality by design (QbD) to acquire the immediate release of saxagliptin and sustained release of metformin from bilayer tablet to ultimately achieve superior patient compliance.

Methods:

The development of the bilayer tablet was done in four stages using QbD. In the first step, quality target product profile (QTPP) of bilayer tablet was defined, and critical quality attributes (CQAs) were identified by risk estimation matrix and taguchi design; an immediate release saxagliptin layer was optimized in the second step, optimization of sustained-release metformin layer was carried out in the third step, and in the final step, bilayer tablet was prepared and characterized. The effect of independent parameters, i.e., magnesium stearate level (X1), kneading time (X2) and lubrication time (X3) on Carr’s Index (Y1), percentage relative standard deviation of content uniformity (Y2) and drug release at 30 minutes (Y3), were estimated for optimization of immediate release saxagliptin layer using Box-Behnken design (BBD). The effect of independent parameters, i.e., hydroxypropyl methylcellulose level (X4), compritol level (X5) and magnesium stearate level (X6) on Carr’s Index (Y4), drug release at 2 h (Y5), drug release at 5 h (Y6) and drug release at 10 h (Y7) were estimated for optimization of sustained-release metformin layer using BBD.

Results:

The optimized composition of immediate release saxagliptin layer estimated using numerical optimization by Design expert was 0.88% (X1), 15 minutes (X2) and 3.85 minutes (X3) with predicted variables, i.e., 10.59% (Y1), 3.16% (Y2) and 85% (Y3). The optimized composition of sustained- release saxagliptin layer predicted through numerical optimization was 30% (X4), 3.36% (X5) and 0.9% (X6) having 10.89% (Y4), 43.44% (Y5), 60% (Y6) and 85.14% (Y7). In-vitro dissolution study of bilayer tablet showed immediate release of Saxagliptin (approximately 85% in 30 minutes) and sustained release of metformin illustrating 43.21±1.21, 60.86±2.96 and 86.26±1.38% drug release at 2, 5 and 10 h, respectively. The release exponent for the Korsmeyer-Peppas model for Saxagliptin and metformin was 0.237 (<0.45) and 1.536 (n>0.85), indicating Fickian and super case II transport drug release behavior, respectively.

Conclusion:

By QbD approach, bilayer tablet containing saxagliptin and metformin was successfully developed, and influence of various formulation parameters on CQAs of drug products was understood with fewer experiments. This leads to the conclusion that cost can be reduced using QbD in the development of FDC for improving patient compliance.

Structure-Activity Relationship Analysis of Cocrystallized Gliptin-like Pyrrolidine, Trifluorophenyl, and Pyrimidine-2,4-Dione Dipeptidyl Peptidase-4 Inhibitors

Approved and potent reported dipeptidyl peptidase-4 (DPP-4) inhibitors with gliptin-like structures are classified here according to their structures and mechanisms of the inhibition in three groups: (i) those with pyrrolidine or analogs as P1 fragment with α-aminoacyl linker, (ii) structures with trifluorophenyl moiety or analogs as P1 fragment with β-aminobutanoyl linker, and (iii) DPP-4 inhibitors with pyrimidine-2,4-dione or analogs as P1' fragment. The structure-activity relationship analysis was performed for those whose cocrystallized structures with the enzyme were published. While inhibitors with pyrrolidine and trifluorophenyl moiety or analogs as P1 fragment bind in a similar way in S1, S2 and S2 extensive domains of the enzyme, the binding mode of pyrimidine-2,4-dione derivatives/analogs differs with additional interactions in S1' and S2' pockets. Three general schemes of fragmented gliptins and gliptin-like structures with the enzyme and protein-ligand interaction fingerprints were made, which might be useful in the creation of DPP-4 inhibitor's design strategies.

Application of machine learning methods for the development of antidiabetic drugs

Diabetes is a chronic non-communicable disease caused by several different routes, which has attracted increasing attention. In order to speed up the development of new selective drugs, machine learning (ML) technology has been applied in the process of diabetes drug development, which opens up a new blueprint for drug design. This review provides a comprehensive portrayal of the application of ML in antidiabetic drug use.

Combination of vitamin D and dipeptidyl peptidase-4 inhibitors (VIDPP-4i) as an immunomodulation therapy for autoimmune diabetes

Type 1 diabetes (T1D) and latent autoimmune diabetes in adults (LADA) represent the most common types of autoimmune diabetes and are characterized by different age of onset, degrees of immune-mediated destruction of pancreatic beta cells and rates of disease progression towards insulin dependence. Several immunotherapies aimed to counteract autoimmune responses against beta cells and preserve beta-cell function are currently being investigated, particularly in T1D. Preliminary findings suggest a potential role of combination therapy with vitamin D and dipeptidyl peptidase-4 (DPP-4) inhibitors (VIDPP-4i) in preserving beta-cell function in autoimmune diabetes. This manuscript aims to provide a comprehensive overview of the immunomodulatory properties of vitamin D and DPP-4 inhibitors, as well as the rationale for investigation of their combined use as an immunomodulation therapy for autoimmune diabetes.

Design, synthesis and biological evaluation of glycolamide, glycinamide, and β-amino carbonyl 1,2,4-triazole derivatives as DPP-4 inhibitors

Through modification of the skeleton of Sitagliptin and Vildagliptin, we successfully synthesized and built-up four series of 1,2,4-triazole derivatives, containing N,O-disubstituted glycolamide, N,N'-disubstituted glycinamide, β-amino ester, and β-amino amide as linkers, for the development of new dipeptidyl peptidase 4 (DPP-4) inhibitors. The synthetic strategy for glycolamides or glycinamides involved convenient two-steps reaction: functionalized transformation of 2-chloro-N-(2,4,5-triflurophenyl)acetamide 9 (hydroxylation or amination) and esterification or amidation of 1,2,4-triazole-3-carboxylic acid. On the other hand, the one-pot synthesis procedure, including substitution and deprotection, was developed for the preparation of β-amino carbonyl 1,2,4-triazoles from (1H-1,2,4-triazol-3-yl)methanol 12 or (1H-1,2,4-triazol-3-yl)methanamine 13 and Boc-(R)-3-amino-4-(2,4,5-trifluoro-phenyl)-butyric acid 14. All of glycolamides, glycinamides, and β-amino carbonyl 1,2,4-triazoles were also evaluated against DPP-4 inhibitory activity. Based on the SAR study of DPP-4 inhibitory capacity, β-amino ester 5n and β-amino amide 1,2,4-triazoles 6d and 6p possessed the significant inhibition of DPP-4 (IC₅₀ < 51.0 nM), particularly for compound 6d (IC₅₀ = 34.4 nM). The selectivity evaluation indicated compound 5n and 6p had excellent selectivity over QPP, DPP-8, and DPP-9. In addition, the docking results revealed compounds 5n and 6p provided stronger π-π stacking interaction with residue Phe357 than 1,5-disubstituted 1,2,4-triazole 6d and Sitagliptin 1. In summary, compounds 5n and 6p could be promising lead compounds for further development of DPP-4 inhibitor.

Investigation of Chlorella pyrenoidosa Protein as a Source of Novel Angiotensin I-Converting Enzyme (ACE) and Dipeptidyl Peptidase-IV (DPP-IV) Inhibitory Peptides

Chlorella pyrenoidosa (C. pyrenoidosa) is a microalgae species with a remarkably high protein content that may potentially become a source of hypotensive and hypoglycemic peptides. In this study, C. pyrenoidosa proteins were extracted and hydrolyzed overnight with pepsin and trypsin with final degrees of hydrolysis of 18.7% and 35.5%, respectively. By LC-MS/MS, 47 valid peptides were identified in the peptic hydrolysate (CP) and 66 in the tryptic one (CT). At the concentration of 1.0 mg/mL, CP and CT hydrolysates inhibit in vitro the angiotensin-converting enzyme (ACE) activity by 84.2 ± 0.37% and 78.6 ± 1.7%, respectively, whereas, tested at cellular level at the concentration of 5.0 mg/mL, they reduce the ACE activity by 61.5 ± 7.7% and 69.9 ± 0.8%, respectively. At the concentration of 5.0 mg/mL, they decrease in vitro the DPP-IV activity by 63.7% and 69.6% and in Caco-2 cells by 38.4% and 42.5%, respectively. Short peptides (≤10 amino acids) were selected for investigating the potential interaction with ACE and DPP-IV by using molecular modeling approaches and four peptides were predicted to block both enzymes. Finally, the stability of these peptides was investigated against gastrointestinal digestion.

Covalent Small Molecule Immunomodulators Targeting the Protease Active Site

Cells of the immune system utilize multiple proteases to regulate cell functions and orchestrate innate and adaptive immune responses. Dysregulated protease activities are implicated in many immune-related disorders; thus, protease inhibitors have been actively investigated for pharmaceutical development. Although historically considered challenging with concerns about toxicity, compounds that covalently modify the protease active site represent an important class of agents, emerging not only as chemical probes but also as approved drugs. Here, we provide an overview of technologies useful for the study of proteases with the focus on recent advances in chemoproteomic methods and screening platforms. By highlighting covalent inhibitors that have been designed to target immunomodulatory proteases, we identify opportunities for the development of small molecule immunomodulators.

Efficacy and safety of teneligliptin added to metformin in Chinese patients with type 2 diabetes mellitus inadequately controlled with metformin: A phase 3, randomized, double-blind, placebo-controlled study

INTRODUCTION

We evaluated the efficacy and safety of teneligliptin compared with placebo when added to metformin therapy in Chinese patients with type 2 diabetes inadequately controlled with metformin monotherapy.

METHODS

This multicentre, randomized, double-blind, placebo-controlled, parallel-group study enrolled type 2 diabetes patients with glycosylated haemoglobin (HbA1c) 7.0%-<10.0% and fasting plasma glucose (FPG) <270 mg/dl, receiving a stable metformin dose ≥1000 mg/day. Teneligliptin 20 mg or placebo was administered orally once daily (qd) before breakfast for 24 weeks. The primary efficacy end-point was change in HbA1c from baseline to Week 24. Safety end-points included the incidence of adverse events (AEs).

RESULTS

The least square mean (LSM) change from baseline (standard error [SE]) was -0.72 (0.07) (95% confidence intervals [CI], -0.87, -0.58) for teneligliptin and -0.01 (0.07) (95% CI, -0.16, 0.13) for placebo. The differences (LSM ± SE) between the placebo and teneligliptin groups in HbA1c and FPG were -0.71% ± 0.11% (p < .0001) and -16.5 ± 4.7 mg/dl (p = .0005), respectively. Teneligliptin yielded significant changes in HbA1c (-0.81%; p < .0001) and FPG (-22.2 mg/dl; p < .0001) at Week 12. At Week 24, more patients achieved HbA1c <7.0% with teneligliptin (41.7%) compared with placebo (16.1%; p < .0001). Treatment-emergent AE incidence was similar with teneligliptin (58.9%) and placebo (68.3%); upper respiratory tract infection, hyperuricaemia and hyperlipidaemia were the most common AEs.

CONCLUSIONS

Teneligliptin 20 mg qd for 24 weeks added to ongoing metformin treatment significantly decreased HbA1c and FPG levels compared with placebo in Chinese type 2 diabetes patients. The combination was safe and tolerable.

Phase III, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of teneligliptin monotherapy in Chinese patients with type 2 diabetes mellitus inadequately controlled with diet and exercise

AIMS/INTRODUCTION

Although the efficacy of teneligliptin, a highly selective dipeptidyl peptidase-4 inhibitor, has been amply studied for the treatment of type 2 diabetes, no clinical trials of teneligliptin have been carried out in China. We evaluated the efficacy and safety of teneligliptin monotherapy compared with a placebo in Chinese patients with type 2 diabetes mellitus inadequately controlled with diet and exercise.

MATERIALS AND METHODS

This multicenter, randomized, double-blind, placebo-controlled, parallel-group study, carried out at 42 sites, enrolled type 2 diabetes patients with glycosylated hemoglobin 7.0 to <10.0% and fasting blood glucose <270 mg/dL. Patients were randomly assigned, in a 1:1 ratio, to treatment with 20 mg teneligliptin or a placebo (n = 127, each) administered orally once daily before breakfast for 24 weeks. Change in glycosylated hemoglobin from baseline to week 24 was the primary efficacy end-point. Safety was assessed by the incidence of adverse events and adverse drug reactions.

RESULTS

The least square mean (LSM) change in glycosylated hemoglobin from baseline to week 24 was -0.95% with teneligliptin versus -0.14% with a placebo, yielding an LSM difference (teneligliptin vs placebo) of -0.80% (P < 0.0001). For the secondary end-point, from baseline to week 24, the LSM change in fasting blood glucose was -21.9 mg/dL with teneligliptin versus -1.4 mg/dL with a placebo, yielding an LSM difference (teneligliptin vs placebo) of -20.5 mg/dL (P < 0.0001). The adverse event and adverse drug reaction incidence rates, including hypoglycemia, were similar in both groups.

CONCLUSIONS

At 24 weeks, teneligliptin was generally well tolerated and effective in Chinese patients with type 2 diabetes mellitus inadequately controlled with diet and exercise.

Simulated gastrointestinal digestion of camel and bovine casein hydrolysates: Identification and characterization of novel anti-diabetic bioactive peptides

Camel milk proteins are an important substrate for bioactive peptides generation. This study investigates in-vitro antidiabetic effect (via inhibition of α-amylase (AA), α-glucosidase (AG) and dipeptidyl peptidase IV (DPP-IV)) of bovine (BC) and camel casein (CC) hydrolysates. Further, effect of simulated gastrointestinal digestion (SGID) on inhibitory potential of generated hydrolysates was also explored. Both BC and CC hydrolysates displayed potent inhibitory properties against AA (IC₅₀ value- 0.58 & 0.59 mg/mL), AG (IC₅₀ value- 1.04 & 0.59 mg/mL) and DPP-IV (IC₅₀ value- 0.62 & 0.66 mg/mL), respectively. Among different peptides identified in BC and CC hydrolysates, it was observed that FLWPEYGAL was predicted to be most potent inhibitory peptide against AA. While LPTGWLM, MFE and GPAHCLL as most active inhibitor of AG and HLPGRG, QNVLPLH and PLMLP were predicted to be active against DPP-IV. Overall, BC and CC hydrolysates can be proposed to be used in different food formulations as functional antidiabetic agents.

Novel Potent and Selective DPP-4 Inhibitors: Design, Synthesis and Molecular Docking Study of Dihydropyrimidine Phthalimide Hybrids

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) inhibitors have emerged as anti-hyperglycemic agents that improve glycemic control in type 2 diabetic patients, either as monotherapy or in combination with other antidiabetic drugs.

METHODS

A novel series of dihydropyrimidine phthalimide hybrids was synthesized and evaluated for their in vitro and in vivo DPP-4 inhibition activity and selectivity using alogliptin as reference. Oral glucose tolerance test was assessed in type 2 diabetic rats after chronic treatment with the synthesized hybrids ± metformin. Cytotoxicity and antioxidant assays were performed. Additionally, molecular docking study with DPP-4 and structure activity relationship of the novel hybrids were also studied.

RESULTS

Among the synthesized hybrids, 10g, 10i, 10e, 10d and 10b had stronger in vitro DPP-4 inhibitory activity than alogliptin. Moreover, an in vivo DPP-4 inhibition assay revealed that 10g and 10i have the strongest and the most extended blood DPP-4 inhibitory activity compared to alogliptin. In type 2 diabetic rats, hybrids 10g, 10i and 10e exhibited better glycemic control than alogliptin, an effect that further supported by metformin combination. Finally, 10j, 10e, 10h and 10d had the highest radical scavenging activity in DPPH assay.

CONCLUSIONS

Hybrids 10g, 10i and 10e are potent DPP-4 inhibitors which may be beneficial for T2DM treatment.

DPP-4 Inhibitors Have Different Effects on Endothelial Low-Grade Inflammation and on the M1-M2 Macrophage Polarization Under Hyperglycemic Conditions

PURPOSE

We explored the anti-inflammatory role of the DPP-4 inhibitor teneligliptin, using sitagliptin as comparator, in different in vitro models of low-grade inflammation (LGI), evaluating the hyperglycemia-induced endothelial inflammation, the macrophage polarization, and the endothelium-macrophage interaction.

METHODS

The effects of DPP-4 and its inhibitors on macrophage polarization were evaluated in THP-1 cells by measuring mRNA expression of M1-M2 markers. HUVEC cells were used to analyze the effects of DPP-4 inhibitors on endothelial inflammation under normal and high glucose conditions. To evaluate the link between eNO and M1-M2 polarization, HUVECs were transfected with eNOS siRNA and co-cultured with THP-1 cells. The effects of DPP-4 inhibitors on macrophage polarization and eNO content were evaluated in a co-culture model of differentiated THP-1 cells + HUVECs under normal glucose (NG), high glucose (HG) and high metabolic memory (HM) conditions.

RESULTS

DPP-4 regulated M1/M2 macrophage polarization. Teneligliptin reduced M1 and enhanced M2 macrophage phenotype under DPP-4 stimulation, and attenuated hyperglycemia-induced endothelial inflammation. In THP-1 cells co-cultured with eNOS depleted HUVECs, M1 markers were enhanced, while M2 reduced, indicating an important role of eNO in polarization to M2 phenotype. In the co-culture model with HUVECs exposed to HG and HM, teneligliptin reduced M1 and enhanced M2 population, by increasing eNO levels. The anti-inflammatory effects of sitagliptin were not observed in these LGI models.

CONCLUSION

Teneligliptin, but not sitagliptin, has anti-inflammatory effects in the various LGI models, by promoting a switch from M1 toward M2 phenotype and by decreasing hyperglycaemia-induced endothelial inflammation, suggesting that effects for LGI are different among DPP-4 inhibitors.

High glucose-induced PRDX3 acetylation contributes to glucotoxicity in pancreatic β-cells: Prevention by Teneligliptin

Chronic hyperglycemia has deleterious effects on pancreatic β-cell function and survival in type 2 diabetes (T2D) due to the low expression level of endogenous antioxidants in the β-cells. Peroxiredoxin-3 (PRDX3) is a mitochondria specific H202 scavenger and protects the cell from mitochondrial damage. However, nothing is known about how glucotoxicity influences PRDX3 function in the pancreatic beta cells. Exposure of rat insulinoma INS-1 cells and human beta cells (1.1B4) to high glucose conditions (30mM) stimulated acetylation of PRDX3 which facilitates its hyper-oxidation causing mitochondrial dysfunction by SIRT1 degradation. SIRT1 deficiency induces beta cell apoptosis via NOX-JNK-p66Shc signalosome activation. Herein we investigated the direct effect of Teneligliptin, a newer DPP-4 inhibitor on beta-cell function and survival in response to high glucose conditions. Teneligliptin treatment enhances SIRT1 protein levels and activity by USP22, an ubiquitin specific peptidase. Activated SIRT1 prevents high glucose-induced PRDX3 acetylation by SIRT3 resulted in inhibition of PRDX3 hyper-oxidation thereby strengthening the mitochondrial antioxidant defense. Notably, we identify PRDX3 as a novel SIRT3 target and show their physical interaction. Intriguingly, inhibition of SIRT1 activity by EX-527 or SIRT1 siRNA knockdown exacerbated the SIRT3 mediated PRDX3 deacetylation which leads to peroxiredoxin-3 hyper-oxidation and beta-cell apoptosis by the activation of NOX-JNK-p66Shc signalosome. Collectively, our results unveil a novel and first direct effect of high glucose on PRDX3 acetylation on beta-cell dysfunction by impaired antioxidant defense and SIRT1 mediated SIRT3-PRDX3 activation by Teneligliptin suppresses high glucose-mediated mitochondrial dysfunction.

Molecular basis of the anti-diabetic properties of camel milk through profiling of its bioactive peptides on dipeptidyl peptidase IV (DPP-IV) and insulin receptor activity

The molecular basis of the anti-diabetic properties of camel milk reported in many studies and the exact active agent are still elusive. Recent studies have reported effects of camel whey proteins (CWP) and their hydrolysates (CWPH) on the activities of dipeptidyl peptidase IV (DPP-IV) and the human insulin receptor (hIR). In this study, CWPH were generated, screened for DPP-IV binding in silico and inhibitory activity in vitro, and processed for peptide identification. Furthermore, pharmacological action of intact CWP and their selected hydrolysates on hIR activity and signaling and on glucose uptake were investigated in cell lines. Results showed inhibition of DPP-IV by CWP and CWPH and their positive action on hIR activation and glucose uptake. Interestingly, the combination of CWP or CWPH with insulin revealed a positive allosteric modulation of hIR that was drastically reduced by the competitive hIR antagonist. Our data reveal for the first time the profiling and pharmacological actions of CWP and their derived peptides fractions on hIR and their pathways involved in glucose homeostasis. This sheds more light on the anti-diabetic properties of camel milk by providing the molecular basis for the potential use of camel milk in the management of diabetes.

Effect of Switching from Linagliptin to Teneligliptin Dipeptidyl Peptidase-4 Inhibitors in Older Patients with Type 2 Diabetes Mellitus

INTRODUCTION

Dipeptidyl peptidase-4 (DPP-4) inhibitors are widely prescribed for type 2 diabetes (T2D) and their glycemic control effects are well studied. However, information regarding the effects of switching DPP-4 inhibitors is limited, especially in older patients.

RESEARCH DESIGN AND METHODS

We investigated whether switching from linagliptin to teneligliptin decreases blood glucose in older (≥65 years) T2D patients. In total, 164 patients with T2D who switched from linagliptin to teneligliptin for >12 weeks were included and the primary outcome was glycemic changes.

RESULTS

Switching from linagliptin to teneligliptin ameliorated fasting blood glucose (148.1 ± 47.1 to 139.6 ± 43.4 mg/dL), glycated hemoglobin (HbA1c; 7.9 ± 1.3 to 7.5 ± 1.2%), and postprandial blood glucose (224.8 ± 77.4 to 205.8 ± 70.8 mg/dL) levels (all P < 0.05). Low-density lipoprotein cholesterol concentration was reduced while liver and kidney functions were maintained. Subgroup analysis showed that glucose control improved more in patients with uncontrolled hyperglycemia (HbA1c > 8.0%) and chronic kidney disease (estimated glomerular filtration rate <90 mL/min/1.73m2). Multiple logistic analysis indicated higher baseline HbA1c was the strongest predictor of teneligliptin switching response.

CONCLUSION

Switching from linagliptin to teneligliptin helps maintain kidney function and reduce blood glucose safely in older patients with T2D.

Dipeptidyl peptidase 4 inhibitors in the treatment of type 2 diabetes mellitus

Dipeptidyl peptidase 4 inhibitors (DPP4i) have been available for treating type 2 diabetes mellitus since 2006. Although they are a diverse group, DPP4i are all small, orally available molecules that interact with the catalytic site of DPP4 without disturbing any of its other known functions, including its effects on the immune system. DPP4i have no intrinsic glucose-lowering activity, so their efficacy as anti-diabetic agents is related directly to their ability to inhibit DPP4 activity and is mediated through the effects of the substrates they protect. Of these, the incretin hormone, glucagon-like peptide 1, is probably the most important. As the effects of glucagon-like peptide 1 are glucose-dependent, the risk of hypoglycaemia with DPP4i is low. Class effects, which are directly related to the mechanism of action, are common to all DPP4i; these include their overall good safety profile and tolerability, as well as their efficacy in improving glycaemic control, but also, potentially, a small increased risk of acute pancreatitis. Compound-specific effects are those related to their differing chemistries and/or pharmacokinetic profiles. These compound-specific effects could affect the way in which individual DPP4i are used therapeutically and potentially explain off-target adverse effects, such as hospitalization for heart failure, which is seen only with one DPP4i. Overall, DPP4i have a favourable therapeutic profile and are safe and effective in the majority of patients with type 2 diabetes mellitus.

A Single Second Shell Amino Acid Determines Affinity and Kinetics of Linagliptin Binding to Type 4 Dipeptidyl Peptidase and Fibroblast Activation Protein

Drugs targeting type 4 dipeptidyl peptidase (DPP‐4) are beneficial for glycemic control, whereas fibroblast activation protein alpha (FAP‐α) is a potential target for cancer therapies. Unlike other gliptins, linagliptin displays FAP inhibition. We compared biophysical and structural characteristics of linagliptin binding to DPP‐4 and FAP to better understand what differentiates linagliptin from other gliptins. Linagliptin exhibited high binding affinity (K_D) and a slow off‐rate (k_off) when dissociating from DPP‐4 (K_D 6.6 pM; k_off 5.1×10⁻⁵ s⁻¹), and weaker inhibitory potency to FAP (K_D 301 nM; k_off>1 s⁻¹). Co‐structures of linagliptin with DPP‐4 or FAP were similar except for one second shell amino acid difference: Asp663 (DPP‐4) and Ala657 (FAP). pH dependence of enzymatic activities and binding of linagliptin for DPP‐4 and FAP are dependent on this single amino acid difference. While linagliptin may not display any anticancer activity at therapeutic doses, our findings may guide future studies for the development of optimized inhibitors.

Teneligliptin Real-World Effectiveness Assessment in Patients with Type 2 Diabetes Mellitus in India: A Retrospective Analysis (TREAT-INDIA 2)

INTRODUCTION

Teneligliptin is an antidiabetic medication that has been approved for the management of type 2 diabetes mellitus (T2DM) in Japan, South Korea and India. It is one of the most commonly prescribed antihyperglycaemic agents. The aim of this study was to assess the effectiveness of teneligliptin in improving glycemic control amongst Indian patients with T2DM in a real-world setting.

METHODS

This was a retrospective observational study in which a predesigned structured proforma was used to collect information from hospital records of 18 medical centres across India. All participating centres were established primary care hospitals with adequate record keeping, a pre-determined condition in the study design. Data were collected during the period of January 2019 to June 2019. Data extracted from patient records, including glycaemic parameters, concomitant drugs, drug dosage and duration, were collated. The effectiveness of teneligliptin was assessed by analyzing the mean change in glycosylated haemoglobin (HbA1c), fasting plasma glucose (FPG) and post-prandial plasma glucose (PPG) at 12 weeks after initiation of teneligliptin.

RESULTS

Data from 10,623 patients were available for analysis. The mean age of the enrolled patients was 51.86 ± 11.76 years. At 12 weeks after initiation of teneligliptin as monotherapy or add-on to other medications (combination therapy), the patients showed a signficant decrease from baseline in mean HbA1c, FPG and PPG. Mean HbA1c dropped from 8.66 ± 1.15% at baseline to 7.67 ± 1.28% at 12 weeks (71 ± 12.6 to 60 ± 14 mmol/mol), with a difference of - 0.99% (95% confidence interval [CI] 0.96-1.02) or - 10.8 (95% CI 10.5-11.1) mmol/mol (p < 0.0001). The mean reductions in FPG and PPG were 43.12 mg/dL (2.39 mmol/L) and 87.73 mg/dL (4.87 mmol/L) (both p < 0.0001) respectively. HbA1c (%) reductions with teneligliptin when used as add-on to metformin, add-on to metformin + sulfonylurea combination and add-on to metformin + sulfonylurea + alpha glucosidase inhibitor combination were 0.76% (8.3 mmol/mol), 1.24% (13.6 mmol/mol) and 1.04% (11.4 mmol/mol), respectively. Teneligliptin also significantly reduced HbA1c (1.13% or 12.4 mmol/mol, p < 0.0001) in patients with impaired renal function, without worsening the estimated glomerular filtration rate. Teneligliptin consistently reduced HbA1c across all three age categories tested-by 1% (10.9 mmol/mol) in patients aged < 60 years, by 1.15% (12.6 mmol/mol) in patients aged 60-75 years and by 0.88% (9.6 mmol/mol) in patients aged > 75 years.

CONCLUSION

Teneligliptin significantly improved glycaemic parameters in Indian patients with T2DM when prescribed either as monotherapy or as an add-on to one or more other commonly prescribed antihyperglycaemic agents.

DPP-4 Inhibitors: Renoprotective Potential and Pharmacokinetics in Type 2 Diabetes Mellitus Patients with Renal Impairment

The continuously increasing incidence of diabetes worldwide has attracted the attention of the scientific community and driven the development of a novel class of antidiabetic drugs that can be safely and effectively used in diabetic patients. Of particular interest in this context are complications associated with diabetes, such as renal impairment, which is the main cause of high cardiovascular morbidity and mortality in diabetic patients. Intensive control of glucose levels and other risk factors associated with diabetes and metabolic syndrome provides the foundations for both preventing and treating diabetic nephropathy. Dipeptidyl peptidase-4 (DPP-4) inhibitors represent a highly promising novel class of oral agents used in the treatment of type 2 diabetes mellitus that may be successfully combined with currently available antidiabetic therapeutics in order to achieve blood glucose goals. Beyond glycemic control, emerging evidence suggests that DPP-4 inhibitors may have desirable off-target effects, including renoprotection. All type 2 diabetes mellitus patients with impaired renal function require dose adjustment of any DPP-4 inhibitor administered except for linagliptin, for which renal excretion is a minor elimination pathway. Thus, linagliptin is the drug most frequently chosen to treat type 2 diabetes mellitus patients with renal failure.

Efficacy and Safety of Novel Dipeptidyl-Peptidase-4 Inhibitor Evogliptin in the Management of Type 2 Diabetes Mellitus: A Meta-Analysis

AIMS

No meta-analysis is available which has summarized and holistically analyzed the efficacy and safety of evogliptin. We undertook this meta-analysis to address this gap in knowledge.

METHODS

Electronic databases were searched for RCTs involving diabetes patients receiving evogliptin in intervention arm and placebo/active comparator in control arm. Primary outcome was to evaluate changes in HbA1c. Secondary outcomes were to evaluate alterations in fasting glucose, postprandial glucose, lipids, insulin resistance, patients achieving glycemic targets of HbA1c <7% and <6.5%, and adverse events.

RESULTS

From initially screened 57 articles, data from six RCTs involving 887 patients was analyzed [three having sitagliptin/linagliptin as active comparator; three having placebo in control group]. Evogliptin was noninferior to sitagliptin/linagliptin regarding HbA1c reduction at 12 weeks [mean difference (MD) -0.06%; 95%CI: -0.23-0.11%; P = 0.48] and 24 weeks (MD 0.04%; 95%CI: -0.11-0.19%; P = 0.60) follow-up. Evogliptin was superior to placebo regarding HbA1c reduction at 12-weeks (MD -0.57%; 95%CI: -0.62- -0.52%; P < 0.001) and 24 weeks (MD -0.28%; 95%CI: -0.47 - -0.09%; P = 0.004). Evogliptin was noninferior to sitagliptin/linagliptin regarding patients achieving HbA1c <7% and <6.5% at 12 weeks and 24 weeks follow-up. Total adverse events [Risk ratio (RR) 0.98; 95% CI: 0.72-1.32; P = 0.89] and severe adverse events (RR 0.65; 95% CI: 0.25-1.67; P = 0.37) were not significantly different among groups. Patients receiving evogliptin did not have increased symptomatic (RR 0.46; 95% CI: 0.10-2.16; P = 0.32) and asymptomatic (RR 1.09; 95% CI: 0.61-1.97; P = 0.77) hypoglycaemia.

CONCLUSION

Evogliptin is well tolerated and has good glycemic efficacy over 6 months use for T2DM management.

Efficacy and safety of evogliptin treatment in patients with type 2 diabetes: A multicentre, active-controlled, randomized, double-blind study with open-label extension (the EVERGREEN study)

AIM

To investigate the efficacy and safety of evogliptin compared with linagliptin in patients with type 2 diabetes.

MATERIALS AND METHODS

In this 12-week, multicentre, randomized, double-blind, active-controlled, and 12-week open-label extension study, a total of 207 patients with type 2 diabetes who had HbA1c levels of 7.0%-10.0% were randomized 1:1 to receive evogliptin 5 mg (n = 102) or linagliptin 5 mg (n = 105) daily for 12 weeks. The primary efficacy endpoint was the change from baseline HbA1c at week 12. The secondary endpoint was the change in the mean amplitude of glycaemic excursion (MAGE) assessed by continuous glucose monitoring. In the extension study conducted during the following 12 weeks, evogliptin 5 mg daily was administered to both groups: evogliptin/evogliptin group (n = 95) and linagliptin/evogliptin group (n = 92).

RESULTS

After 12 weeks of treatment, the mean change in HbA1c in the evogliptin group and in the linagliptin group was -0.85% and -0.75%, respectively. The between-group difference was -0.10% (95% CI: -0.32 to 0.11), showing non-inferiority based on a non-inferiority margin of 0.4%. The change in MAGE was -24.6 mg/dL in the evogliptin group and -16.7 mg/dL in the linagliptin group. These values were significantly lower than the baseline values in both groups. However, they did not differ significantly between the two groups. In the evogliptin/evogliptin group at week 24, HbA1c decreased by -0.94%, with HbA1c values of <7.0% in 80.2% of the patients. The incidence and types of adverse events were comparable between the two groups for 24 weeks.

CONCLUSION

In this study, the glucose-lowering efficacy of evogliptin was non-inferior to linagliptin. It was maintained at week 24 with a 0.94% reduction in HbA1c. Evogliptin therapy improved glycaemic variability without causing any serious adverse events in patients with type 2 diabetes.

Combined Ligand-Based and Structure-Based Virtual Screening Approach for Identification of New Dipeptidyl Peptidase 4 Inhibitors

BACKGROUND

Dipeptidyl Peptidase 4 (DPP 4) enzyme cleaves an incretin-based glucoregulatory hormone Glucagon Like Peptide -1 from N-terminal where penultimate amino acid is either alanine or proline. Several DPP 4 inhibitors, "gliptins", are approved for the management of Type 2 Diabetes or are under clinical trial. In the present study, combined pharmacophore and docking-based virtual screening protocol were used for the identification of new hits from the Specs Database, which would inhibit DPP 4.

METHODS

The entire computational studies were performed using the Discovery Studio v. 4.1 software package, Pipeline Pilot v. 9.2 (Accelrys Inc.) and FRED v. 2.2.5 (OpenEye Scientific Software). Common feature pharmacophore model was generated from known DPP 4 inhibitors and validated by Receiver Operating curve analysis and GH-scoring method. Database search of Specs commercial database was performed using validated pharmacophore. Hits obtained from pharmacophore search were further docked into the binding site of DPP 4. Based on the analysis of docked poses of hits, 10 compounds were selected for in- vitro DPP 4 enzyme inhibition assay.

RESULTS

Based on docking studies, virtual hits were predicted to form interaction with essential amino acid residues of DPP 4 and have an almost similar binding orientation as that of the reference molecule. Three compounds having Specs database ID- AN-465/42837213, AP-064/42049348 and AN- 465/43369427 were found to inhibit DPP 4 enzyme moderately.

CONCLUSION

The present study demonstrates a successful utilization of in-silico tools in the identification of new DPP 4 inhibitor, which can serve as a starting point for the development of novel DPP 4 inhibitors.

The Dipeptidyl Peptidase-4 Inhibitor Linagliptin Directly Enhances the Contractile Recovery of Mouse Hearts at a Concentration Equivalent to that Achieved with Standard Dosing in Humans

Despite a similar mechanism of action underlying their glucose-lowering effects in type 2 diabetes, dipeptidyl peptidase-4 (DPP-4) inhibitors have diverse molecular structures, raising the prospect of agent-specific, glucose-independent actions. To explore the issue of possible DPP-4 inhibitor cardiac heterogeneity, we perfused different DPP-4 inhibitors to beating mouse hearts ex vivo, at concentrations equivalent to peak plasma levels achieved in humans with standard dosing. We studied male and female mice, young non-diabetic mice, and aged diabetic high fat diet-fed mice and observed that linagliptin enhanced recovery after ischemia-reperfusion, whereas sitagliptin, alogliptin, and saxagliptin did not. DPP-4 transcripts were not detected in adult mouse cardiomyocytes by RNA sequencing and the addition of linagliptin caused ≤0.2% of cardiomyocyte genes to be differentially expressed. In contrast, incubation of C166 endothelial cells with linagliptin induced cell signaling characterized by phosphorylation of Akt and endothelial nitric oxide synthase, whereas the nitric oxide (NO) donor, S-nitroso-N-acetylpenicillamine increased serine 16 phosphorylation of the calcium regulatory protein, phospholamban in cardiomyocytes. Furthermore, linagliptin increased cardiomyocyte cGMP when cells were co-cultured with C166 endothelial cells, but not when cardiomyocytes were cultured alone. Thus, at a concentration comparable to that achieved in patients, linagliptin has direct effects on mouse hearts. The effects of linagliptin on cardiomyocytes are likely to be either off-target or indirect, mediated through NO generation by the adjacent cardiac endothelium.