Synthetic and phytocompounds based dipeptidyl peptidase-IV (DPP-IV) inhibitors for therapeutics of diabetes

Exploring cutting-edge approaches in diabetes care: from nanotechnology to personalized therapeutics

Diabetes mellitus (DM) is a persistent condition characterized by high levels of glucose in the blood due to irregularities in the secretion of insulin, its action, or both. The disease was believed to be incurable until insulin was extracted, refined, and produced for sale. In DM, insulin delivery devices and insulin analogs have improved glycemic management even further. Sulfonylureas, biguanides, alpha-glucosidase inhibitors, and thiazolidinediones are examples of newer-generation medications having high efficacy in decreasing hyperglycemia as a result of scientific and technological advancements. Incretin mimetics, dual glucose-dependent insulinotropic polypeptide, GLP-1 agonists, PPARs, dipeptidyl peptidase-4 inhibitors, anti-CD3 mAbs, glucokinase activators, and glimins as targets have all performed well in recent clinical studies. Considerable focus was placed on free FA receptor 1 agonist, protein tyrosine phosphatase-1B inhibitors, and Sparc-related modular calcium-binding protein 1 which are still being studied. Theranostics, stem cell therapy, gene therapy, siRNA, and nanotechnology are some of the new therapeutic techniques. Traditional Chinese medicinal plants will also be discussed. This study seeks to present a comprehensive analysis of the latest research advancements, the emerging trends in medication therapy, and the utilization of delivery systems in treating DM. The objective is to provide valuable insights into the application of different pharmaceuticals in the field of diabetes mellitus treatment. Also, the therapeutic approach for diabetic patients infected with COVID-19 will be highlighted. Recent clinical and experimental studies evidence the Egyptian experience. Finally, as per the knowledge of the state of the art, our conclusion and future perspective will be declared.

Hallmarks of diabetes mellitus and insights into the therapeutic potential of synergy-based combinations of phytochemicals in reducing oxidative stress-induced diabetic complications

Diabetes mellitus (DM) is a serious health issue and is still one of the major causes of mortality around the globe. Natural products have progressively integrated into modern, advanced medical practices. Phytoconstituents from some medicinal plants have demonstrated therapeutic activity in treating different metabolic disorders and have been used to treat DM and its severe complications. The present review provides details of the major anti-diabetic targets identified in the literature and also provides comprehensive information regarding the therapeutic role of a synergy-based combination of phytoconstituents that functions by controlling specific molecular pathways synchronously by inhibiting certain key regulators involved in the development and progression of DM. The review also implicated the role of oxidative stress in diabetic complications and presented scientific validations of phytochemicals and their synergy-based combination using in vitro and or in vivo approaches.

Unveiling the Evidence for the Use of Pulses in Managing Type 2 Diabetes Mellitus: A Scoping Review

Management of type 2 diabetes mellitus (T2DM) is a pressing global healthcare challenge. Innovative strategies that integrate superior medical and nutritional practices are essential for holistic care. As such, pulse consumption is encouraged for its potential benefit in reducing hypercholesterolaemia, dyslipidaemia, and triglyceride levels, as well as enhancing glycaemic control. This scoping review aims to assess the depth of evidence supporting the recommendation for pulse consumption in T2DM management and to identify gaps in the existing literature. We conducted a comprehensive search across the databases MEDLINE, Global Health, EMBASE, CINAHL, Web of Science, and the Cochrane Library (up to July 2023). We included population-based studies of any design, and excluded review-style articles. Articles published in languages other than English were also excluded. From the 2449 studies initially identified, 28 met our inclusion criteria. Acute postprandial trials demonstrated improved glucose responses and enhanced insulin responses to pulse-based intervention. Meanwhile, long-term trials reported meaningful improvements in T2DM indicators such as haemoglobin A1C (HbA1c), fasting glucose, fasting insulin, C-peptide, and markers of insulin resistance like homeostatic model assessment (HOMA). Integrating more pulses into the diets of diabetic individuals might offer an efficient and cost-effective strategy in the global initiative to combat T2DM.

Heterocyclic Compounds as Dipeptidyl Peptidase-IV Inhibitors with Special Emphasis on Oxadiazoles as Potent Anti-Diabetic Agents

Dipeptidyl peptidase-IV (DPP-IV) inhibitors, often known as gliptins, have been used to treat type 2 diabetes mellitus (T2DM). They may be combined with other medications as an additional treatment or used alone as a monotherapy. In addition to insulin, sulfonylureas, thiazolidinediones, and metformin, these molecules appear as possible therapeutic options. Oxadiazole rings have been employed in numerous different ways during drug development efforts. It has been shown that including them in the pharmacophore increases the amount of ligand that may be bound. The exceptional hydrogen bond acceptor properties of oxadiazoles and the distinct hydrocarbon bonding potential of their regioisomers have been established. Beside their anti-diabetic effects, oxadiazoles display a wide range of pharmacological properties. In this study, we made the assumption that molecules containing oxadiazole rings may afford a different approach to the treatment of diabetes, not only for controlling glycemic levels but also for preventing atherosclerosis progression and other complications associated with diabetes. It was observed that oxadiazole fusion with benzothiazole, 5-(2,5,2-trifluoroethoxy) phenyl, β-homophenylalanine, 2-methyl-2-{5-(4-chlorophenyl), diamine-bridged bis-coumarinyl, 5-aryl-2-(6′-nitrobenzofuran-2′-yl), nitrobenzofuran, and/or oxindole leads to potential anti-diabetic activity.

DPP-4 inhibition mediated antidiabetic potential of phytoconstituents of an aqueous fruit extract of Withania coagulans (Stocks) Dunal: in-silico, in-vitro and in-vivo assessments

The DPP-4 inhibition is an interesting target for the development of antidiabetic agents which promotes the longevity of GPL-1(Glucagon-like peptide 1). The current study was intended to assess DPP-4(Dipeptidyl Peptidase-4) inhibition mediated antidiabetic effect of phytocompounds of an aqueous fruit extract of Withania coagulans (Stocks) Dunal by in-vitro, in-silico and in-vivo approaches. The phytoconstituents screening was executed by LCMS (Liquid Chromatography with tandem mass spectrometry). The in-vitro and in-vivo, DPP-4 assays were performed by using available kits. The in-vitro DPP-4 activity was inhibited up to 68.3% by the test extract. Accordingly, in-silico determinations of molecular docking, molecular dynamics and pharmacokinetics were performed between the target enzyme DPP-4 and leading phytocompounds. The molecular dynamics authenticated the molecular docking data by crucial parameters of cytosolic milieu by the potential energy, RSMD (Root Mean Square Deviation), RSMF (Root Mean Square Fluctuation), system density, NVT (Number of particles at fixed volume, ensemble) and NPT (Number of particles at fixed pressure, ensemble). Accordingly, ADMET predictions assessed the druggability profile. Subsequently, the course of the test extract and the sitagliptin (positive control), instigated significant (p ≤ 0.001) ameliorations in HOMA indices and the equal of antioxidants in nicotinamide-streptozotocin induced type 2 diabetic animal model. Compassionately, the histopathology represented increased pancreatic cellular mass which caused in restoration of histoarchitectures. It has been concluded that phytoconstituents in W. coagulans aqueous fruit extract can regulate DPP-4, resulting in improved glucose homeostasis and enhanced endocrinal pancreatic cellular mass.Communicated by Ramaswamy H. Sarma.

Structure-function relationship of fermented skate skin gelatin-derived bioactive peptides: a peptidomics approach

In this study, we investigated the multi-functionality of bioactive peptides derived from fermented skate (Raja kenojei) skin gelatin hydrolysates. The extracted gelatin was hydrolyzed using a combination of food grade subtilisin and actinidin. The hydrolysates were then fractionated via ultrafiltration, and the fractions with the highest dipeptidyl peptidase-IV (DPP-IV) inhibitory, angiotensin-converting enzyme (ACE) inhibitory, and antibacterial proprieties were further purified via ion exchange, solid phase extraction, and reverse phase high performance liquid chromatography. Analysis of the obtained extract revealed a direct relationship between hydrolysis time, degree of hydrolysis, and biological activities. The peptides GRPGNRGE (P1) and AKDYEVDAT (P2), with a molecular weight of 841.42 and 1010.46 Da, respectively, were identified through tandem mass spectrometry. P1 had a lower ACE and DPP-IV inhibitory activity, with a half maximal inhibitory concentration [IC₅₀] of 0.74 and 0.69 mg.mL^-1, respectively, than P2 (0.52 and 0.58 mg.mL^-1, respectively). Antibacterial analysis showed similar results, with a minimum inhibitory concentration of 0.52 and 0.46 mg.mL^-1 against Staphylococcus aureus (highest activity) and 1.75 and 1.44 mg.mL^-1 against Klebsiella pneumonia (lowest activity) for P1 and P2, respectively. Overall, this study revealed two fish gelatin-derived multifunctional peptides, exhibiting ACE inhibitory, DPP-IV inhibitory, and antibacterial activities, as natural nutraceuticals.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-00998-6.

Dipeptidyl Peptidase (DPP)-IV Inhibitors with Antioxidant Potential Isolated from Natural Sources: A Novel Approach for the Management of Diabetes

Type 2 diabetes mellitus (T2DM) is characterized by hyperglycemia that is predominantly caused by insulin resistance or impaired insulin secretion, along with disturbances in carbohydrate, fat and protein metabolism. Various therapeutic approaches have been used to treat diabetes, including improvement of insulin sensitivity, inhibition of gluconeogenesis, and decreasing glucose absorption from the intestines. Recently, a novel approach has emerged using dipeptidyl peptidase-IV (DPP-IV) inhibitors as a possible agent for the treatment of T2DM without producing any side effects, such as hypoglycemia and exhaustion of pancreatic β-cells. DPP-IV inhibitors improve hyperglycemic conditions by stabilizing the postprandial level of gut hormones such as glucagon-like peptide-1, and glucose-dependent insulinotropic polypeptides, which function as incretins to help upregulate insulin secretion and β-cell mass. In this review, we summarized DPP-IV inhibitors and their mechanism of inhibition, activities of those isolated from various natural sources, and their capacity to overcome oxidative stress in disease conditions.

Structure-function engineering of novel fish gelatin-derived multifunctional peptides using high-resolution peptidomics and bioinformatics

The multifunctional properties of fish gelatin hydrolysates have not been completely elucidated. Here, the biological characterization of these peptides was performed to engineer multifunctional peptides. Bioactive peptides were produced from mackerel byproducts via successive enzymatic hydrolysis reactions using subtilisin A and actinidin as microbial and herbal proteases. The antibacterial activity against both gram-negative and -positive food-borne pathogens, including Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae, as well as the inhibitory potential of angiotensin-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV), was accessed in vitro. The synthesized peptides demonstrated multifunctional properties, which were further confirmed by in silico protocols. The ACE and DPP-IV inhibitory (IC₅₀) values of P1, P2, and P3 were 0.92 and 0.87, 0.51 and 0.93, 0.78 and 1.16 mg mL⁻¹, respectively. Moreover, the binding energy was sufficient for all three peptides to inhibit both ACE and DPP-IV enzymes with excellent three-dimensional conformation (RMSD = 0.000) for all six docking mechanisms.

Quercetin and Coumarin Inhibit Dipeptidyl Peptidase-IV and Exhibits Antioxidant Properties: In Silico, In Vitro, Ex Vivo

Quercetin and coumarin, two naturally occurring phytochemicals of plant origin, are known to regulate hyperglycemia and oxidative stress. The present study was designed to evaluate the inhibitory activity of quercetin and coumarin on dipeptidyl peptidase-IV (DPP-IV) and their antioxidant potential. DPP-IV inhibition assays were performed, and evaluated IC₅₀ values of diprotin A, quercetin, coumarin, and sitagliptin were found to be 0.653, 4.02, 54.83, and 5.49 nmol/mL, respectively. Furthermore, in silico studies such as the drug-likeliness and docking efficiency of quercetin and coumarin to the DPP-IV protein were performed; the ex vivo antiperoxidative potential of quercetin and coumarin were also evaluated. The results of the present study showed that the DPP-IV inhibitory potential of quercetin was slightly higher than that of sitagliptin. Virtual docking revealed the tight binding of quercetin with DPP-IV protein. Quercetin and coumarin reduced oxidative stress in vitro and ex vivo systems. We report for the first time that both compounds inhibited the DPP-IV along with antioxidant activity and thus may be use as function food ingredients in the prevention of diabetes.

A dipyrrole derivative from Aloe vera inhibits an anti-diabetic drug target Dipeptidyl Peptidase (DPP)-IV in vitro

Aloe vera, a succulent herb, has a long history of use in traditional medicine, including diabetes. Earlier studies from our laboratory demonstrated that the Aloe vera extract has the ability to inhibit the diabetic drug target dipeptidyl peptidase (DPP) IV in vitro. This current study focuses on the isolation of small water soluble active molecule(s) involved in DPP-IV inhibition from Aloe vera extract, and further to characterize its structure and to elucidate the mode of inhibition of the DPP-IV enzyme. Aloe vera gel ethanolic extract was subjected to preparative reverse-phase high-pressure liquid chromatography (RP-HPLC), LH-20 Sephadex gel filtration chromatography, followed by analytical RP-HPLC, to isolate the active molecule involved in DPP-IV inhibition. Based on the spectroscopic studies, the structure of the isolated DPP-IV inhibitor was predicted to be 3, 6-dioxo-3, 3a, 6, 6 a-tetrahydropyrrolo [3, 4-c] pyrrole-1, 4-dicarboxamide with the chemical formula C8H6N4O4, having the molecular weight of 225.175 Da. This molecule inhibited the DPP-IV enzyme in a noncompetitive manner with an IC50 value of 8.59 ± 2.61 µM, with a Ki of 4.7 ± 0.038 µM. Thus, the mechanism of DPP-IV inhibition and the inhibitory constants were determined. The results of our studies suggested that the inhibition of the DPP-IV enzyme as one of the pathways by which the Aloe vera extract may restore the pancreatic islets cell mass in diabetic animal model.

The dipeptidyl peptidase-4 inhibitory effect of flavonoids is hindered in protein rich environments

Dipeptidyl peptidase-4 (DPP-4) inhibitors present a unique approach for the management of type 2 diabetes (T2D). In the present study, the inhibition of DPP-4 was evaluated for a large panel of flavonoids, important components of the human diet, using in vitro and ex vivo models. The activity of the isolated enzyme was assayed in vitro. Subsequently, the most active flavonoids were tested ex vivo in human whole blood and plasma. In this study, contrary to the in vitro fluorometric tests, flavonoids did not show inhibitory activity against DPP-4. Due to the discrepancy in the results between the in vitro and ex vivo approaches, plasma protein binding values were determined, presenting values from 43.9 to 100.0%. This work provides a new insight into the inhibitory activity for DPP-4, based on the flavonoid scaffold. Additionally, the obtained results showed that the inhibitory effect of flavonoids against DPP-4 was hindered in protein rich environments, like that occurring in blood, and indicated the need for experimental refinement in drug discovery for blood targets.

Dual Glycation-Inflammation Modulation, DPP-IV and Pancraetic Lipase Inhibitory Potentials and Antiproliferative Activity of Novel Fluoroquinolones

Paramount efforts by pharmaceutical industry to identify new targets for obesity-diabetes (Diabesity) pharmacological intervention have led to a number of agents developed and directed at DPP IV [dipeptidyl peptidase IV] enzyme inhibition thereby enhancing endogenous insulinotropic incretins. Besides antioxidative-antiinflammtory molecules that inhibit accumulation of advanced glycation end products (AGEs) can be good candidates for ameliorating diabetic complications. Fluoroquinolones (FQs) have been identified recently as potent inhibitors of pancreatic lipase (PL). The suggested association between obesity and colorectal cancer initiated the evaluation of antiproliferative activity of the new FQs and TFQs against a panel of obesity related colorectal cells (HT29, HCT116, SW620 CACO2 and SW480). The aim of the current study is to examine the potential of newly synthesized FQs and triazolofluoroquinolones (TFQs) derivatives as dual inhibitors for glycation and inflammation, DPP IV inhibitors, PL inhibitors for dual management of obesity and diabetes, as well as antiprolifertaive efficacy against colorectal cancer cell lines. Sulforodamine B (SRB) colorimetric assay revealed that some derivatives exhibited unselective cytotoxity against HT29, HCT116, SW620 CACO2 and SW480. The superior antiglycation activity of the reduced derivatives 4a and 4b over that of aminoguanidine with respective IC50 (μM) values of 3.05±0.33 and 8.51±3.21; none of the tested synthetic compounds could perform equally effectively to Diprotin A, a dose dependent inhibitor of DPP IV. Compounds 4a, 5a, 3b, 4b and 5b demonstrated anti-inflammatory IC50 values exceeding that of indomethacin. Compounds 3a and 4a showed IC50 lower than 10 μM as PL inhibitors. In conclusion, FQ and TFQ derivatives may unveil new antiobesity and anticancer agents in the future. Our research qualifies FQs and TFQs as promising candidates for the development of related α-dicarbonyl scavengers as therapeutic agents to protect cells against carbonyl stress.

First report of chromenyl derivatives from spineless marine cuttlefish Sepiella inermis: Prospective antihyperglycemic agents attenuate serine protease dipeptidyl peptidase-IV

Spineless marine cuttlefish Sepiella inermis has been considered as a popular dietary cephalopod species in Asian and Mediterranean coasts. Bioassay-directed purification of organic extract of S. inermis ensued in the characterization of two chromenyl derivatives. The studied compounds exhibited significantly greater antioxidant potencies (IC₅₀  ≤ 0.5 mg/ml) when compared with α-tocopherol. The substituted 1H-isochromenyloxy-11-hydroxyethyl pentanoate isoform (compound 1) efficiently inhibited the carbolytic enzymes along with key regulator of insulin secretion dipeptidyl peptidase-IV (IC₅₀ 0.16 mg/ml). The molecular docking simulations displayed optimum binding affinity of the compound 1 (-10.01 kcal/mol) with dipeptidyl peptidase-IV and lesser inhibition constant (K_i 46.41 nM), which along with its permissible hydrophobic-hydrophilic balance (log P_ow  ~ 2) appeared to play significant roles in its greater antihyperglycemic activity compared to other studied chromenyl isoform. The greater antioxidant and antidiabetic properties of compound 1 could be utilized as an important natural lead against hyperglycemic-related disorders. PRACTICAL APPLICATIONS: The edible spineless marine cuttlefish Sepiella inermis are ubiquitously available in Asian and Mediterranean coasts. The sequential chromatographic purification of the organic extract of S. inermis led to the identification of two pure chromenyl chemotypes. The metabolites with substituted 1H-isochromenyloxy-11-hydroxyethyl pentanoate isoform (compound 1) displayed potential antioxidative and antihyperglycemic activities compared to the chemotype (2) bearing 3H-isochromen-5-yl moiety. The attenuating potential of chromenyl chemotype 1 against carbohydrate hydrolyzing enzymes and insulin secretion regulator attributed towards its efficiency as an important natural lead against postprandial hyperglycemia and incretin hormone regulation to maintain glucose homeostasis in the biological system. The chromenyl metabolites isolated from S. inermis could be utilized as a functional food ingredient in the nutraceutical formulations against hyperglycemic-related disorders.

In Silico Analysis of Bioactive Peptides Released from Giant Grouper (Epinephelus lanceolatus) Roe Proteins Identified by Proteomics Approach

Major proteins contained in dried giant grouper roe (GR) such as vitellogenin (from Epinephelus coioides; NCBI accession number: AAW29031.1), apolipoprotein A-1 precursor (from Epinephelus coioides; NCBI accession number: ACI01807.1) and apolipoprotein E (from Epinephelus bruneus; NCBI accession number: AEB31283.1) were characterized through compiled proteomics techniques (SDS-PAGE, in-gel digestion, mass spectrometry and on-line Mascot database analysis). These proteins were subjected to in silico analysis using BLAST and BIOPEP-UWM database. Sequence similarity search by BLAST revealed that the aligned vitellogenin sequences from Epinephelus coioides and Epinephelus lanceolatus share 70% identity, which indicates that the sequence sample has significant similarity with proteins in sequence databases. Moreover, prediction of potential bioactivities through BIOPEP-UWM database resulted in high numbers of peptides predominantly with dipeptidyl peptidase-IV (DPP-IV) and angiotensin-I-converting enzyme (ACE-I) inhibitory activities. Pepsin (pH > 2) was predicted to be the most promising enzyme for the production of bioactive peptides from GR protein, which theoretically released 82 DPP-IV inhibitory peptides and 47 ACE-I inhibitory peptides. Overall, this work highlighted the potentiality of giant grouper roe as raw material for the generation of pharmaceutical products. Furthermore, the application of proteomics and in silico techniques provided rapid identification of proteins and useful prediction of its potential bioactivities.

Recent developments in solid lipid nanoparticle and surface-modified solid lipid nanoparticle delivery systems for oral delivery of phyto-bioactive compounds in various chronic diseases

Solid lipid nanoparticle (SLN) delivery systems have a wide applicability in the delivery of phyto-bioactive compounds to treat various chronic diseases, including diabetes, cancer, obesity and neurodegenerative diseases. The multiple benefits of SLN delivery include improved stability, smaller particle size, leaching prevention and enhanced lymphatic uptake of the bioactive compounds through oral delivery. However, the burst release makes the SLN delivery systems inadequate for the oral delivery of various phyto-bioactive compounds that can treat such chronic diseases. Recently, the surface-modified SLN (SMSLN) was observed to overcome this limitation for oral delivery of phyto-bioactive compounds, and there is growing evidence of an enhanced uptake of curcumin delivered orally via SMSLNs in the brain. This review focuses on different SLN and SMSLN systems that are useful for oral delivery of phyto-bioactive compounds to treat various chronic diseases.

Flaxseed: its bioactive components and their cardiovascular benefits

Cardiovascular disease remains the leading cause of mortality and morbidity worldwide. The inclusion of functional foods and natural health products in the diet are gaining increasing recognition as integral components of lifestyle changes in the fight against cardiovascular disease. Several preclinical and clinical studies have shown the beneficial cardiovascular effects of dietary supplementation with flaxseed. The cardiovascular effects of dietary flaxseed have included an antihypertensive action, antiatherogenic effects, a lowering of cholesterol, an anti-inflammatory action, and an inhibition of arrhythmias. Its enrichment in the ω-3 fatty acid α-linolenic acid and the antioxidant lignan secoisolariciresinol diglucoside as well as its high fiber content have been implicated primarily in these beneficial cardiovascular actions. Although not as well recognized, flaxseed is also composed of other potential bioactive compounds such as proteins, cyclolinopeptides, and cyanogenic glycosides, which may also produce biological actions. These compounds could also be responsible for the cardiovascular effects of flaxseed. This article will not only summarize the cardiovascular effects of dietary supplementation with flaxseed but also review its bioactive compounds in terms of their properties, biological effects, and proposed mechanisms of action. It will also discuss promising research directions for the future to identify additional health-related benefits of dietary flaxseed.