Discovery of Food-Derived Dipeptidyl Peptidase IV Inhibitory Peptides: A Review

Artificial intelligence in antidiabetic drug discovery: The advances in QSAR and the prediction of α-glucosidase inhibitors

Artificial Intelligence is transforming drug discovery, particularly in the hit identification phase of therapeutic compounds. One tool that has been instrumental in this transformation is Quantitative Structure-Activity Relationship (QSAR) analysis. This computer-aided drug design tool uses machine learning to predict the biological activity of new compounds based on the numerical representation of chemical structures against various biological targets. With diabetes mellitus becoming a significant health challenge in recent times, there is intense research interest in modulating antidiabetic drug targets. α-Glucosidase is an antidiabetic target that has gained attention due to its ability to suppress postprandial hyperglycaemia, a key contributor to diabetic complications. This review explored a detailed approach to developing QSAR models, focusing on strategies for generating input variables (molecular descriptors) and computational approaches ranging from classical machine learning algorithms to modern deep learning algorithms. We also highlighted studies that have used these approaches to develop predictive models for α-glucosidase inhibitors to modulate this critical antidiabetic drug target.

Multiple roles of food-derived bioactive peptides in the management of T2DM and commercial solutions: A review

Type 2 diabetes mellitus (T2DM), a disease that threatens public health worldwide and can cause a series of irreversible complications, has been a major concern. Although the treatment based on hypoglycemic drugs is effective, its side effects should not be ignored, which has led to an urgent need for developing new hypoglycemic drugs. Bioactive peptides with antidiabetic effects obtained from food proteins have become a research hotspot as they are safer and with higher specificity than traditional hypoglycemic drugs. Here, we reviewed antidiabetic peptides that have the ability to inhibit key enzymes (α-glucosidase, α-amylase, and DPP-IV) in T2DM, the hypoglycemic mechanisms and structure-activity relationships were summarized, some antidiabetic peptides that improve insulin resistance and reverse gut microbiota and their metabolites were overviewed, the bitterness of antidiabetic peptides was predicted in silico, proposed solutions to the current challenges encountered in the development of antidiabetic peptide drugs, and provided an outlook on the future focus of commercial production. It provides a reference for the application of food-derived antidiabetic peptides.

Solid-state fermentation of green lentils by Lactiplantibacillus plantarum leads to formation of distinct peptides that are absorbable and enhances DPP-IV inhibitory activity in an intestinal Caco-2 cell model

Food-derived bioactive compounds mimicking the effects of incretin therapies offer promising opportunities for combination therapies with functional foods, where food matrix interactions, gastrointestinal enzyme activity, and in situ bioactivity should be key considerations. In this study, green lentils were solid-state fermented with Lactiplantibacillus plantarum ATCC8014, in vitro digested and exposed to brush border enzymes of a Caco-2 cell monolayer. Intestinal absorption of peptides and DPP-IV inhibitory activity were then investigated. LC-MS/MS profiles showed that peptides mainly originated from parental proteins of the vicilin, convicilin and legumin families. Fermentation led to the formation of more hydrophobic peptides when compared to the unfermented flour and up to 33.6% of them were transported to the basolateral side of a Caco-2 cell monolayer. Peptides with more than 22 amino acids and with a mass greater than 2000 Da were minimally transported. 73 peptides were uniquely identified in the basolateral fraction suggesting that they resulted from the activity of the brush border enzymes. The DPP-IV activity of Caco-2 cells grown as a polarized monolayer was decreased by 37.3% when exposed to in vitro digested 72 h-fermented lentil flour and 10% when exposed to the unfermented one. Inhibition of DPP-IV in the basolateral fluids was improved in a dose-dependent manner and reached 7.9% when 500 mg mL-1 of in vitro digested 72 h fermented lentil flour was used. Glucose absorption and uptake were minimally affected, suggesting that the previously observed hypoglycemic properties of lentils are likely due to activity on DPP-IV rather than on the inhibition of glucose absorption.

Tracking bioactive peptides and their origin proteins during the in vitro digestion of meat and meat products

Existing reviews address bioactive peptides of meat proteins; however, comprehensive reviews summarizing the released sequences and their corresponding parent meat proteins in the digesta are limited. This review explores the bioactive peptides released during the in vitro gastrointestinal (GI) digestion of meat, connecting with parent proteins. The primary bioactivities of meat-derived peptides include angiotensin-converting enzyme (ACE) and dipeptidyl peptidase (DPP)-IV inhibition and antioxidant effects. Myofibrillar, sarcoplasmic, and stromal proteins play a significant role in peptide release during digestion. The release of bioactive peptides varies according to the parent protein and cryptides had short chains, non-toxicity, and great bioavailability and GI absorption scores. Moreover, the structural stability and bioactivities of peptides can be influenced by the digestive properties and amino acid composition of parent proteins. Investigating the properties and origins of bioactive peptides provides insights for enhancing the nutritional quality of meat and understanding its potential health benefits.

Consumption of a Sourdough-Leavened Croissant Enriched with a Blend of Fibers Influences Fasting Blood Glucose in a Randomized Controlled Trial in Healthy Subjects

BACKGROUND

An incorrect lifestyle, including diet, is responsible for the worldwide dramatic increase in obesity and type 2 diabetes. Increasing dietary fiber consumption may lead to health benefits, and reformulation of bakery products may be a strategy to globally improve the diet.

OBJECTIVES

This study aimed to assess the impact of a 2-wk breakfast consumption with a sourdough-leavened croissant containing a blend of dietary fiber from 10 sources (4.8 g/100 g, croissant enriched with dietary fibers [FIBCRO]), compared with a control croissant (dietary fibers 1.3 g/100 g, CONCRO) on daily energy intake, appetite, metabolic variables, and the gut microbiome.

METHODS

Thirty-two healthy participants were randomly allocated to 2 groups consuming FIBCRO or CONCRO. Participants self-recorded their diet and appetite through 7-d weighted food diaries and visual analog scales every day over the 2 wk. At baseline and after the intervention, fasting blood and urine samples, and fecal samples were collected beside blood pressure, anthropometry, and body composition. Serum glucose, lipids, C-reactive protein, and insulin according to the official methods and serum dipeptidyl peptidase-4 (DPPIV) activity by photometric method were measured. Polyphenols and urolithins in urines were analyzed by Liquid chromatography-tandem mass spectrometry (LC/MS/MS), whereas gut microbiome in feces by shotgun metagenomics.

RESULTS

FIBCRO consumption improved fasting blood glucose compared with CONCRO (mean changes from baseline -2.0 mg/dL in FIBCRO compared with +3.1 mg/dL in CONCRO, P = 0.022), also reducing serum DPPIV activity by 1.7 IU/L (P = 0.01) and increasing urinary excretion of urolithin A-sulfate by 6.9 ng/mg creatinine (P = 0.04) compared with baseline. No further changes in any of the monitored variables or in the gut microbiome were detected.

CONCLUSIONS

Results suggested that a 2-wk consumption of a sourdough croissant claimed as "source of dietary fiber" improved fasting glycemia compared with a conventional sourdough croissant in healthy subjects. The reduced serum DPPIV activity and increased bioavailability of urolithin likely contributed to determine that effect independently from gut microbiome changes. This trial was registered at clinicaltrials.gov as NCT04999280.

Peptide array screening with anti-GLP-1 monoclonal antibody: Discovery of cysteine-containing DPP-IV inhibitory peptides

Inhibition of dipeptidyl peptidase IV (DPP-IV) is an effective pharmacotherapy for the management of type 2 diabetes. Recent findings have suggested that various dietary proteins can serve as precursors to peptides that inhibit DPP-IV. Although several DPP-IV inhibitory peptides derived from food materials have been reported, more effective inhibitory peptides remain to be discovered. This study aimed to identify potent DPP-IV inhibitory peptides that earlier approaches had overlooked by employing a screening method that combined peptide arrays and neutralizing antibodies. Octa-peptides covering the complete amino acid sequences of four casein proteins and two whey proteins were synthesized on arrays via a solid-phase method. These peptides were then reacted with a monoclonal antibody specifically engineered to recognize glucagon-like peptide 1 (GLP-1), a substrate of DPP-IV. The variable region of the anti-GLP-1 monoclonal antibody is utilized to mimic the substrate-binding region of DPP-IV, enabling the antibody to bind to peptides that interact with DPP-IV. Based on this feature, 26 peptides were selected as DPP-IV inhibitory peptide candidates, 11 of which showed strong DPP-IV inhibitory activity. Five of these peptides consistently contained cysteines positioned two to four residues from the N-terminus. Treatment with disulfide formation decreased the DPP-IV inhibitory activity of these cysteine-containing peptides, while the inhibitory activity of α-lactalbumin hydrolysates increased with reducing treatment. These results revealed that the thiol group is important for DPP-IV inhibitory activity. This study provides a useful screen for DPP-IV inhibitory peptides and indicates the importance of reductive cysteine residues within DPP-IV inhibitory peptides.

In Silico Screening of Therapeutic Targets as a Tool to Optimize the Development of Drugs and Nutraceuticals in the Treatment of Diabetes mellitus: A Systematic Review

The Target-Based Virtual Screening approach is widely employed in drug development, with docking or molecular dynamics techniques commonly utilized for this purpose. This systematic review (SR) aimed to identify in silico therapeutic targets for treating Diabetes mellitus (DM) and answer the question: What therapeutic targets have been used in in silico analyses for the treatment of DM? The SR was developed following the guidelines of the Preferred Reporting Items Checklist for Systematic Review and Meta-Analysis, in accordance with the protocol registered in PROSPERO (CRD42022353808). Studies that met the PECo strategy (Problem, Exposure, Context) were included using the following databases: Medline (PubMed), Web of Science, Scopus, Embase, ScienceDirect, and Virtual Health Library. A total of 20 articles were included, which not only identified therapeutic targets in silico but also conducted in vivo analyses to validate the obtained results. The therapeutic targets most frequently indicated in in silico studies were GLUT4, DPP-IV, and PPARγ. In conclusion, a diversity of targets for the treatment of DM was verified through both in silico and in vivo reassessment. This contributes to the discovery of potential new allies for the treatment of DM.

Antihypertensive and Antidiabetic Drug Candidates from Milkfish (Chanos chanos)-Identification and Characterization through an Integrated Bioinformatic Approach

Integrated bioinformatics tools have created more efficient and robust methods to overcome in vitro challenges and have been widely utilized for the investigation of food proteins and the generation of peptide sequences. This study aimed to analyze the physicochemical properties and bioactivities of novel peptides derived from hydrolyzed milkfish (Chanos chanos) protein sequences and to discover their potential angiotensin-converting enzyme (ACE)- and dipeptidyl peptidase-4 (DPPIV)-inhibitory activities using machine learning-based tools, including BIOPEP-UWM, PeptideRanker, and the molecular docking software HADDOCK 2.4. Nine and three peptides were predicted to have ACE- and DPPIV-inhibitory activities, respectively. The DPPIV-inhibitory peptides were predicted to inhibit the compound with no known specific mode. Meanwhile, two tetrapeptides (MVWH and PPPS) were predicted to possess a competitive mode of ACE inhibition by directly binding to the tetra-coordinated Zn ion. Among all nine discovered ACE-inhibitory peptides, only the PPPS peptide satisfied the drug-likeness analysis requirements with no violations of the Lipinski rule of five and should be further investigated in vitro.

Exploring the dipeptidyl peptidase IV inhibitory potential of probiotic-fermented milk: An in vitro and in silico comprehensive investigation into peptides from milk of different farm animals

Bioactive peptides produced via enzymatic hydrolysis have been widely investigated for their dipeptidyl peptidase-IV (DPP-IV) inhibitory properties. However, deficit of studies on fermentation as a mean to produce DPP-IV inhibitory peptides prompted us to draw a comparative study on DPP-IV inhibitory peptides generated from cow, camel, goat, and sheep milk using probiotic fermentation. Further, peptide identification, in silico molecular interactions with DPP-IV, and ensemble docking were performed. Results obtained suggested that goat milk consistently exhibited higher hydrolysis than other milk types. Further, Pediococcus pentosaceus (PP-957) emerged as a potent probiotic, with significantly lower DPP-IV-IC50 values 0.17, 0.12, and 0.25 µg/mL protein equivalent in fermented cow, camel, and goat milk, respectively. Overall, peptides (RPPPPVAM, CHNLDELKDTR, and VLSLSQPK) exhibited strong binding affinity with binding energies of -9.31, -9.18 and -8.9 Kcal·mol-1, respectively, suggesting their potential role as DPP-IV inhibitors. Overall, this study, offers valuable information toward antidiabetic benefits of fermented milk products via inhibition of DPP-IV.

Characterization of peptides released from frozen-then-aged beef after digestion in an in vitro infant gastrointestinal model

This study investigated whether the freezing-then-aging treatment of beef affects protein digestibility and release of potentially bioactive peptides using an in vitro infant digestion model. After 28 days of storage, aged-only (AO) and frozen-then-aged (FA) beef exhibited higher α-amino group contents in the 10% trichloroacetic acid-soluble fraction compared to day 0 (P < 0.05). Following in vitro digestion in the infant model, FA showed higher contents of α-amino groups and smaller proteins (<3 and 1 kDa) than day 0 and AO (P < 0.05). Relative contributions of myofibrillar, sarcoplasmic, and stromal proteins to the bioactive peptides released from AO and FA differed from those of day 0. In addition, FA exhibited a higher proportion of potential bioactive peptide sequences. Overall, freezing-then-aging treatment can enhance the potential health benefits of beef to be used as a protein source for complementary foods.

Exploration of nutritional and bioactive peptide properties in goat meat from various primal cuts during in vitro gastrointestinal digestion and absorption

OBJECTIVE

This research aims to explore the nutritional and bioactive peptide properties of goat meat taken from various primal cuts, including the breast, shoulder, rib, loin, and leg, to produce these bioactive peptides during in vitro gastrointestinal (GI) digestion and absorption.

METHODS

The goat meat from various primal cuts was obtained from Boer goats with an average carcass weight of 30±2 kg. The meat was collected within 3 h after slaughter and was stored at -80°C until analysis. A comprehensive assessment encompassed various aspects, including the chemical composition, cooking properties, in vitro GI digestion, bioactive characteristics, and the bioavailability of the resulting peptides.

RESULTS

The findings indicate that the loin muscles contain the highest protein and essential amino acid composition. When the meats were cooked at 70°C for 30 min, they exhibited distinct protein compositions and quantities in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile, suggesting they served as different protein substrates during GI digestion. Subsequent in vitro simulated GI digestion revealed that the cooked shoulder and loin underwent the most significant hydrolysis during the intestinal phase, resulting in the strongest angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) inhibition. Following in vitro GI peptide absorption using a Caco-2 cell monolayer, the GI peptide derived from the cooked loin demonstrated greater bioavailability and a higher degree of ACE and DPP-IV inhibition than the shoulder peptide.

CONCLUSION

This study highlights the potential of goat meat, particularly cooked loin, as a functional meat source for protein, essential amino acids, and bioactive peptides during GI digestion and absorption. These peptides promise to play a role in preventing and treating metabolic diseases due to their dual inhibitory effects on ACE and DPP-IV.

Computational Screening for the Dipeptidyl Peptidase-IV Inhibitory Peptides from Putative Hemp Seed Hydrolyzed Peptidome as a Potential Antidiabetic Agent

Dipeptidyl peptidase-IV (DPPIV) inhibitory peptides are a class of antihyperglycemic drugs used in the treatment of type 2 diabetes mellitus, a metabolic disorder resulting from reduced levels of the incretin hormone GLP-1. Given that DPPIV degrades incretin, a key regulator of blood sugar levels, various antidiabetic medications that inhibit DPPIV, such as vildagliptin, sitagliptin, and linagliptin, are employed. However, the potential side effects of these drugs remain a matter of debate. Therefore, we aimed to investigate food-derived peptides from Cannabis sativa (hemp) seeds. Our developed bioinformatics pipeline was used to identify the putative hydrolyzed peptidome of three highly abundant proteins: albumin, edestin, and vicilin. These proteins were subjected to in silico digestion by different proteases (trypsin, chymotrypsin, and pepsin) and then screened for DPPIV inhibitory peptides using IDPPIV-SCM. To assess potential adverse effects, several prediction tools, namely, TOXINpred, AllerCatPro, and HemoPred, were employed to evaluate toxicity, allergenicity, and hemolytic effects, respectively. COPID was used to determine the amino acid composition. Molecular docking was performed using GalaxyPepDock and HPEPDOCK, 3D visualizations were conducted using the UCSF Chimera program, and MD simulations were carried out with AMBER20 MD software. Based on the predictive outcomes, FNVDTE from edestin and EAQPST from vicilin emerged as promising candidates for DPPIV inhibitors. We anticipate that our findings may pave the way for the development of alternative DPPIV inhibitors.

Hempseed protein-derived short- and medium-chain peptides and their multifunctional properties

Nowadays, the growing knowledge about the high nutritional value and potential functionality of hempseeds, the edible fruits of the Cannabis sativa L. plant, has sparked a surge in interest in exploring the worthwhile attributes of hempseed proteins and peptides. This trend aligns with the increasing popularity of hemp-based food, assuming a vital role in the global food chain. This chapter targets the nutritional and chemical composition of hempseed in terms of short- and medium-chain bioactive peptides. The analytical approaches for their characterization and multifunctional properties are summarized in detail. Moreover, the processing, functionality, and application of various hempseed protein products are discussed. In the final part of the chapter-for evaluating their propensity to be transported by intestinal cells-the transepithelial transport of peptides within hempseed protein hydrolysate is highlighted.

Computational Modeling of the Interactions between DPP IV and Hemorphins

Type 2 diabetes is a chronic metabolic disorder characterized by high blood glucose levels due to either insufficient insulin production or ineffective utilization of insulin by the body. The enzyme dipeptidyl peptidase IV (DPP IV) plays a crucial role in degrading incretins that stimulate insulin secretion. Therefore, the inhibition of DPP IV is an established approach for the treatment of diabetes. Hemorphins are a class of short endogenous bioactive peptides produced by the enzymatic degradation of hemoglobin chains. Numerous in vitro and in vivo physiological effects of hemorphins, including DPP IV inhibiting activity, have been documented in different systems and tissues. However, the underlying molecular binding behavior of these peptides with DPP IV remains unknown. Here, computational approaches such as protein-peptide molecular docking and extensive molecular dynamics (MD) simulations were employed to identify the binding pose and stability of peptides in the active site of DPP IV. Findings indicate that hemorphins lacking the hydrophobic residues LVV and VV at the N terminal region strongly bind to the conserved residues in the active site of DPP IV. Furthermore, interactions with these critical residues were sustained throughout the duration of multiple 500 ns MD simulations. Notably, hemorphin 7 showed higher binding affinity and sustained interactions by binding to S1 and S2 pockets of DPP IV.

Screening of novel DPP-IV inhibitory peptides derived from bovine milk proteins using a peptide array platform

Dipeptidyl peptidase IV (DPP-IV) has become an important target in the prevention and treatment of diabetes. Although many DPP-IV inhibitory peptides have been identified by a general approach involving the repeated fractionation of food protein hydrolysates, the obtained results have been dependent on the content of each peptide and fractionation conditions. In the present study, a peptide array that provides comprehensive assays of peptide sequences was used to identify novel DPP-IV inhibitory peptides derived from bovine milk proteins; these peptides were then compared with those identified using the general approach. While the general approach identified only known peptides that were abundant in the hydrolysate, the peptide array-based approach identified 10 novel DPP-IV inhibitory peptides, all of which had proline at the second residue from the N-terminus. The proper or combined use of these two approaches, which have different advantages, will enable the efficient development of novel bioactive foods and drugs.

Identification, characterization, and insights into the mechanism of novel dipeptidyl peptidase-IV inhibitory peptides from yak hemoglobin by in silico exploration, molecular docking, and in vitro assessment

Dipeptidyl peptidase IV (DPP-IV) inhibitory peptides were screened and identified from yak hemoglobin for the first time by in silico analysis, molecular docking, and in vitro evaluation. Results showed that yak hemoglobin had a high potential to produce DPP-IV inhibitory peptides based on the sequence alignment and bioactive potential evaluation. Furthermore, "pancreatic elastase + stem bromelain" was the optimal combined-enzymatic strategy by simulated proteolysis. Additionally, 25 novel peptides were found from its simulated hydrolysate, among which 10 peptides had high binding affinities with DPP-IV by molecular docking. Most of these peptides were also in silico characterized with favorable physicochemical properties and biological potentials, including relatively low molecular weight, high hydrophobicity, several net charges, good water solubility, nontoxicity, acceptable sensory quality, and good human intestinal absorption. Finally, six novel DPP-IV inhibitory peptides were identified via in vitro assessment, among which EEKA (IC50 = 235.26 μM), DEV (IC50 = 339.45 μM), and HCDKL (IC50 = 632.93 μM) showed the strongest capacities. The hydrogen bonds and electrostatic attractions formed with core residues within the S2 pocket of DPP-IV could be mainly responsible for their inhibition performances. This work provided a time-saving method and broadened application for yak by-products development as sources of functional foods.

Formation of dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides from Jack Bean (Canavalia ensiformis (L.) DC.) sprout in simulated digestion

Bean sprouts are potential plant proteins that produce DPP-IV inhibitory peptides. These peptides must be stable and active in the brush border membrane of the small intestine to inhibit DPP-IV. The purpose of this research is to evaluate the DPP-IV inhibitory activity of jack bean sprouts using pepsin-pancreatin during simulated digestion, as well as the absorption of these peptides through the everted gut sac method. The results showed that after 180 min of digestion simulation, the Mw < 1 kDa peptide fraction of jack bean hydrolysate, which germinated for 60 h (HG60), had the highest inhibitory activity. The duodenum absorbs most of the peptides with inhibitory activity of 61.77%, which is slightly lower than activity after digestion (62.19%). These outcomes suggest that the DPP-IV inhibitory activity of HG60 can be maintained after digestion and absorption. Two novel peptides KAVGDPI and QGVVLRP identified after absorption contain crucial amino acids confirming as DPP-IV inhibitor.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01343-9.

Enzymatic Preparation and Processing Properties of DPP-IV Inhibitory Peptides Derived from Wheat Gluten: Effects of Pretreatment Methods and Protease Types

The choice of appropriate proteases and pretreatment methods significantly influences the preparation of bioactive peptides. This study aimed to investigate the effects of different pretreatment methods on the hydrolytic performance of diverse proteases during the production of dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides derived from wheat and their foaming and emulsion properties. Dry heating, aqueous heating, and ultrasound treatment were employed as pretreatments for the protein prior to the enzymatic hydrolysis of wheat gluten. FTIR analysis results indicated that all pretreatment methods altered the secondary structure of the protein; however, the effects of dry heating treatment on the secondary structure content were opposite to those of aqueous heating and ultrasound treatment. Nevertheless, all three methods enhanced the protein solubility and surface hydrophobicity. By using pretreated proteins as substrates, five different types of proteases were employed for DPP-IV inhibitory peptide production. The analysis of the DPP-IV inhibitory activity, degree of hydrolysis, and TCA-soluble peptide content revealed that the specific pretreatments had a promoting or inhibiting effect on DPP-IV inhibitory peptide production depending on the protease used. Furthermore, the pretreatment method and the selected type of protease collectively influenced the foaming and emulsifying properties of the prepared peptides.

GC-MS, alpha-amylase, and alpha-glucosidase inhibition and molecular docking analysis of selected phytoconstituents of small wild date palm fruit (Phoenix pusilla)

Phoenix pusilla (Arecaceae), commonly known as "small wild date palm", is regarded as one of the underutilized fruit crops in South India. Methanol extract of P. pusilla ripened fruits (PPRF) was analyzed for in vitro porcine pancreatic alpha-amylase (PPAA) and rat small intestine alpha-glucosidase (RIAG) inhibition activities, and through gas chromatography-mass spectrometry (GC-MS) analysis. The GC-MS analysis showed the presence of 25 phytoconstituents from PPRF which was further assessed on the docking behavior of five targeted enzymes diabetes mellitus (DM) namely (i) human aldose reductase, (ii) protein tyrosine phosphatase 1B, (iii) pancreatic alpha-amylase, (iv) peroxisome proliferator-activated receptor gamma, and (v) dipeptidyl peptidase IV by using the AutoDock Vina method. In addition to this physicochemical, bioactivity score, absorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis was performed using the Molinspiration and pkCSM free online servers. Methanolic extract of PPRF showed 50% inhibition concentration (IC50) at 69.86 and 72.60 μg/mL levels against PPAA and RIAG enzymes activities, respectively. Interestingly in the present study, GC-MS analysis showed the presence of 25 phytoconstituents from PPRF. Physicochemical analysis of PPRF has exhibited that 13 ligands have complied well with Lipinski's Rule of Five (RoF). With regard to ADMET analysis, one ligand (9,12-octadecadienoic acid [Z,Z]) has predicated to possess both the hepatotoxicity (HT) and skin sensitization (SS) effect. The docking studies showed that 1-formyl-2,5-dimethoxy-6,9,10-trimethyl-anthracene exhibited the maximum atomic contact energy (ACE) for all the five target enzymes of DM. Thus, the current study suggested that the methanolic extract of PPRF and its phytoconstituents could be considered as potent antidiabetic agents.

Exploring antidiabetic potential of a polyherbal formulation Madhurakshak Activ: An in vitro and in silico study

Madhurakshak Activ (MA), a commercial polyherbal antidiabetic preparation is known to manage diabetes mellitus (DM) by reducing blood glucose levels. However, lacks systematic mechanistic evaluation for their molecular and cellular mode of actions. In the present study, hydro-alcoholic and aqueous extract of MA were evaluated for their effects on glucose adsorption, diffusion, amylolysis kinetics and transport across the yeast cells using in vitro techniques. Bioactive compounds identified from MA by LC-MS/MS were assessed for their binding potential against DPP-IV and PPARγ via an in silico approach. Our results revealed that the adsorption of glucose increased dose dependently (5 mM -100 mM). Both extracts exhibited linear glucose uptake into the yeast cells (5 mM - 25 mM), whereas glucose diffusion was directly proportional to time (30-180 min). Pharmacokinetic analysis revealed drug-like properties and low toxicity levels for all the selected compounds. Among the tested compounds, 6-hydroxyluteolin (-8.9 against DPP-IV and PPARγ) and glycyrrhetaldehyde (DPP-IV -9.7 and PPARγ -8.5) have exhibited higher binding affinity compared to the positive control. Therefore, the above compounds were further considered for molecular dynamics simulation which showed stability of the docked complexes. Hence, studied mode of actions might produce a concerted role of MA in increasing the rate of glucose absorption and uptake followed by the in silico studies which suggest that the compounds identified from MA may inhibit DPP-IV and PPARγ phosphorylation.

Chemical and biological characterization of the DPP-IV inhibitory activity exerted by lupin (Lupinus angustifolius) peptides: From the bench to the bedside investigation

Dipeptidyl peptidase IV (DPP-IV) is considered a key target for the diabetes treatment, since it is involved in glucose metabolism. Although lupin protein consumption shown hypoglycemic activity, there is no evidence of its effect on DPP-IV activity. This study demonstrates that a lupin protein hydrolysate (LPH), obtained by hydrolysis with Alcalase, exerts anti-diabetic activity by modulating DPP-IV activity. In fact, LPH decreased DPP-IV activity in a cell-free and cell-based system. Contextually, Caco-2 cells were employed to identify LPH peptides that can be intestinally trans-epithelial transported. Notably, 141 different intestinally transported LPH sequences were identified using nano- and ultra-chromatography coupled to mass spectrometry. Hence, it was demonstrated that LPH modulated the glycemic response and the glucose concentration in mice, by inhibiting the DPP-IV. Finally, a beverage containing 1 g of LPH decreased DPP-IV activity and glucose levels in humans.

Evaluation of the multifunctional dipeptidyl-peptidase IV and angiotensin converting enzyme inhibitory properties of a casein hydrolysate using cell-free and cell-based assays

The objective of the study was the evaluation of the potential pleiotropic effect of a commercial casein hydrolysate (CH). After an analysis of the composition, the BIOPEP-UWM database suggested that these peptides contained numerous sequences with potential inhibitory activities on angiotensin converting enzyme (ACE) and dipeptidyl-peptidase IV (DPP-IV). The anti-diabetic and anti-hypertensive effects of these peptides were thus assessed using either cell-free or cell-based assays. In the cell-free system, CH displayed inhibitory properties against DPP-IV (IC₅₀ value equal to 0.38 ± 0.01 mg/mL) and ACE (IC₅₀ value equal to 0.39 ± 0.01 mg/mL). Further, CH reduced the DPP-IV and ACE activities expressed by human intestinal Caco-2 cells by 61.10 ± 1.70% and 76.90 ± 4.47%, respectively, versus untreated cells, after 6 h of treatment at the concentration of 5 mg/mL. This first demonstration of the multifunctional behavior of this material suggests that it may become an anti-diabetic and/or anti-hypertensive ingredient to be included in the formulation of different functional food or nutraceutics.

Purification and characterization of the dipeptidyl peptidase-IV inhibitory peptides from eel (Anguilla rostrata) scraps enzymatic hydrolysate for the treatment of type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a serious threat to human health. Owing to the action of dipeptidyl peptidase-IV (DPP-IV), the half-life of entero-insulin hormone after secretion is extremely short, causing insufficient insulin secretion in diabetic patients. Dipeptidyl peptidase-IV inhibitors can be used as a new treatment for T2DM. In this study, the proteins of eel (Anguilla rostrata) scraps hydrolyzed using Protamex protease (EPHs) were found to have strong DPP-IV inhibitory activity. The study also provided research ideas for the development and utilization of A. rostrata scraps.

RESULTS

The median inhibition concentration (IC₅₀ ) value of EPHs was 5.455 ± 0.24 mg mL^-1 . The peptide fractions with the highest DPP-IV inhibitory activity were sequentially separated by ultrafiltration, gel filtration chromatography (GFC), and reversed-phase high performance liquid chromatography (RP-HPLC) in a continuous hierarchical manner and analyzed using matrix-assisted laser desorption/ionization time-of-flight/ time-of-flight mass spectrometry/mass spectrometry (MALDI-TOF/TOF MS/MS). Three peptides that revealed significant inhibitory activity were screened among the identified sequences, with sequences of Phe-Pro-Arg (IC₅₀  = 62.14 ± 1.47 μM), Tyr-Pro-Pro-Ser-Phe-Ser (IC₅₀  = 102.65 ± 4.57 μM), and Tyr-Pro-Tyr-Pro-Ala-Ser (IC₅₀  = 68.30 ± 3.85 μM). Molecular docking simulations revealed that their inhibitory effect was mainly due to the formation of hydrogen bonds with amino acid residues in the active sites of DPP-IV. Analysis of the inhibition patterns of the synthetic peptides displayed that Phe-Pro-Arg and Tyr-Pro-Pro-Ser-Phe-Ser displayed competitive inhibition, whereas Tyr-Pro-Tyr-Pro-Ala-Ser showed mixed competitive/non-competitive inhibition.

CONCLUSIONS

The protein hydrolysates isolated from eel scraps are potential functional food ingredients for the treatment of T2DM. © 2023 Society of Chemical Industry.

In silico structure-based design of peptides or proteins as therapeutic tools for obesity or diabetes mellitus: A protocol for systematic review and meta analysis

BACKGROUND

In silico studies using dynamic simulation or molecular docking have boosted the screening and identification of molecules and/or targets in studies aimed at treating diseases such as obesity and diabetes mellitus, optimizing the development of new drugs. This study aims to describe a systematic review protocol on peptides and proteins evaluated in silico as potential therapeutic agents for obesity or diabetes mellitus.

METHODS

This protocol followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses Protocols and was registered in the International Prospective Register of Systematic Reviews database (number: CRD42022355540). The databases to be searched will be PubMed, ScienceDirect, Scopus, Web of Science, virtual health library, and EMBASE. It will be included in silico studies that evaluate the simulation by dynamics or molecular docking of proteins or peptides involved in treating obesity or diabetes mellitus. Two independent reviewers will select studies, extract data, and assess methodological quality using the adapted Strengthening the reporting of empirical simulation studies. A narrative synthesis of the included studies will be performed for the systematic reviews.

RESULTS

This protocol contemplates the production of 2 systematic reviews to be developed focusing on obesity or diabetes mellitus.

CONCLUSION

The reviews will enable knowledge of peptides and proteins involved in research treating these diseases and will emphasize the importance of in silico studies in this context and for the development of future studies.

Identification of Novel Peptides with Alcohol Dehydrogenase (ADH) Activating Ability in Chickpea Protein Hydrolysates

Alcohol dehydrogenase (ADH) is one of the main rate-limiting enzymes in alcohol metabolism. Food protein-derived peptides are thought to have ADH activating ability. We verified for the first time that chickpea protein hydrolysates (CPHs) had the ability to activate ADH and identified novel peptides from them. CPHs obtained by hydrolysis with Alcalase for 30 min (CPHs-Pro-30) showed the highest ADH activating ability, and the ADH activation rate could still maintain more than 80% after in vitro simulated gastrointestinal digestion. We have verified four peptides with activation ability to ADH: ILPHF, MFPHLPSF, LMLPHF and FDLPALRF (concentration for 50% of maximal effect (EC₅₀): 1.56 ± 0.07 µM, 1.62 ± 0.23 µM, 1.76 ± 0.03 µM and 9.11 ± 0.11 µM, respectively). Molecular docking showed that the mechanism for activating ADH was due to the formation of a stable complex between the peptide and the active center of ADH through hydrogen bonding. The findings suggest that CPHs and peptides with ADH activating ability may be developed as natural anti-alcoholic ingredients to prevent alcoholic liver disease (ALD).

In Vitro Assessment Methods for Antidiabetic Peptides from Legumes: A Review

Almost 65% of the human protein supply in the world originates from plants, with legumes being one of the highest contributors, comprising between 20 and 40% of the protein supply. Bioactive peptides from various food sources including legumes have been reported to show efficacy in modulating starch digestion and glucose absorption. This paper will provide a comprehensive review on recent in vitro studies that have been performed on leguminous antidiabetic peptides, focusing on the α-amylase inhibitor, α-glucosidase inhibitor, and dipeptidyl peptidase-IV (DPP-IV) inhibitor. Variations in legume cultivars and methods affect the release of peptides. Different methods have been used, such as in sample preparation, including fermentation (t, T), germination (t), and pre-cooking; in protein extraction, alkaline extraction, isoelectric precipitation, phosphate buffer extraction, and water extraction; in protein hydrolysis enzyme types and combination, enzyme substrate ratio, pH, and time; and in enzyme inhibitory assays, positive control type and concentration, inhibitor or peptide concentration, and the unit of inhibitory activity. The categorization of the relative scale of inhibitory activities among legume samples becomes difficult because of these method differences. Peptide sequences in samples were identified by means of HPLC/MS. Software and online tools were used in bioactivity prediction and computational modelling. The identification of the types and locations of chemical interactions between the inhibitor peptides and enzymes and the type of enzyme inhibition were achieved through computational modelling and enzyme kinetic studies.

The many facets of CD26/dipeptidyl peptidase 4 and its inhibitors in disorders of the CNS - a critical overview

Dipeptidyl peptidase 4 is a serine protease that cleaves X-proline or X-alanine in the penultimate position. Natural substrates of the enzyme are glucagon-like peptide-1, glucagon inhibiting peptide, glucagon, neuropeptide Y, secretin, substance P, pituitary adenylate cyclase-activating polypeptide, endorphins, endomorphins, brain natriuretic peptide, beta-melanocyte stimulating hormone and amyloid peptides as well as some cytokines and chemokines. The enzyme is involved in the maintenance of blood glucose homeostasis and regulation of the immune system. It is expressed in many organs including the brain. DPP4 activity may be effectively depressed by DPP4 inhibitors. Apart from enzyme activity, DPP4 acts as a cell surface (co)receptor, associates with adeosine deaminase, interacts with extracellular matrix, and controls cell migration and differentiation. This review aims at revealing the impact of DPP4 and DPP4 inhibitors for several brain diseases (virus infections affecting the brain, tumours of the CNS, neurological and psychiatric disorders). Special emphasis is given to a possible involvement of DPP4 expressed in the brain.While prominent contributions of extracerebral DPP4 are evident for a majority of diseases discussed herein; a possible role of "brain" DPP4 is restricted to brain cancers and Alzheimer disease. For a number of diseases (Covid-19 infection, type 2 diabetes, Alzheimer disease, vascular dementia, Parkinson disease, Huntington disease, multiple sclerosis, stroke, and epilepsy), use of DPP4 inhibitors has been shown to have a disease-mitigating effect. However, these beneficial effects should mostly be attributed to the depression of "peripheral" DPP4, since currently used DPP4 inhibitors are not able to pass through the intact blood-brain barrier.

Bioactive and Sensory Di- and Tripeptides Generated during Dry-Curing of Pork Meat

Dry-cured pork products, such as dry-cured ham, undergo an extensive proteolysis during manufacturing process which determines the organoleptic properties of the final product. As a result of endogenous pork muscle endo- and exopeptidases, many medium- and short-chain peptides are released from muscle proteins. Many of them have been isolated, identified, and characterized, and some peptides have been reported to exert relevant bioactivity with potential benefit for human health. However, little attention has been given to di- and tripeptides, which are far less known, although they have received increasing attention in recent years due to their high potential relevance in terms of bioactivity and role in taste development. This review gathers the current knowledge about di- and tripeptides, regarding their bioactivity and sensory properties and focusing on their generation during long-term processing such as dry-cured pork meats.

Identification, Screening, and Comprehensive Evaluation of Novel DPP-IV Inhibitory Peptides from the Tilapia Skin Gelatin Hydrolysate Produced Using Ginger Protease

PURPOSE

Inhibition of dipeptidyl peptidase-IV (DPP-IV) is an effective therapy for treating type II diabetes (T2D) that has been widely applied in clinical practice. We aimed to evaluate the DPP-IV inhibitory properties of ginger protease hydrolysate (GPH) and propose a comprehensive approach to screen and evaluate DPP-IV inhibitors.

METHODS

We evaluated the in vitro inhibitory properties of fish skin gelatin hydrolysates produced by five proteases, namely, neutral protease, alkaline protease, bromelain, papain, and ginger protease, toward DPP-IV. We screened the most potent DPP-IV inhibitory peptide (DIP) using liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with in silico analysis. Next, surface plasmon resonance (SPR) technology was innovatively introduced to explore the interactions between DPP-IV and DIP, as well as the IC₅₀. Furthermore, we performed oral administration of DIP in rats to study its in vivo absorption.

RESULTS

GPH displayed the highest degree of hydrolysis (20.37%) and DPP-IV inhibitory activity (65.18%). A total of 292 peptides from the GPH were identified using LC-MS/MS combined with de novo sequencing. Gly-Pro-Hyp-Gly-Pro-Pro-Gly-Pro-Gly-Pro (GPXGPPGPGP) was identified as the most potent DPP-IV inhibitory peptide after in silico screening (Peptide Ranker and molecular docking). Then, the in vitro study revealed that GPXGPPGPGP had a high inhibitory effect on DPP-IV (IC₅₀: 1012.3 ± 23.3 μM) and exhibited fast kinetics with rapid binding and dissociation with DPP-IV. In vivo analysis indicated that GPXGPPGPGP was not absorbed intact but partially, in the form of dipeptides and tripeptides.

CONCLUSION

Overall, the results suggested that GPH would be a natural functional food for treating T2D and provided new ideas for searching and evaluating potential antidiabetic compounds. The obtained GPXGPPGPGP can be structurally optimized for in-depth evaluation in animal and cellular experiments.

Integrated Evaluation of Dual-Functional DPP-IV and ACE Inhibitory Effects of Peptides Derived from Sericin Hydrolysis and Their Stabilities during In Vitro-Simulated Gastrointestinal and Plasmin Digestions

Sericin, a byproduct of the silk industry, is an underutilized protein derived from the yellow silk cocoon. This research aimed to produce and characterize the bioactive peptides from sericin using various enzymatic hydrolysis methods. Alcalase, papain, neutrase, and protease were tested under their respective digestion conditions. Among the enzymes tested, neutrase-catalyzed sericin into specific peptides with the strongest dipeptidyl peptidase IV (DPP-IV) and angiotensin-converting enzyme (ACE) inhibitory properties. The peptides were subjected to a simulated in vitro gastrointestinal (GI) digestion in order to determine their stability. The GI peptides that were produced by neutrase hydrolysis continued to have the highest DPP-IV and ACE inhibitory activities. The neutrase -digested peptides were then fractionated via ultrafiltration; the peptide fraction with a molecular weight <3 kDa (UF3) inhibited DPP-IV and ACE activities. After being subjected to in vitro blood plasma hydrolysis, the UF3 was slightly degraded but retained its bioactivity. As a result of these findings, sericin peptides can be utilized as novel dietary ingredients that may alleviate some metabolic syndromes via the dual inhibitory properties of DPP-IV and ACE.

Multi-Bioactivity of Protein Digests and Peptides from Oat (Avena sativa L.) Kernels in the Prevention of the Cardiometabolic Syndrome

The aim of this study was to characterize the digests and peptides derived from oat kernel proteins in terms of their major enzyme inhibitory activities related to the prevention of cardiometabolic syndrome. It also entailed the characteristics of antioxidant bioactivity of the analyzed material. The study was carried out using coupled in silico and in vitro methods. The additional goal was to investigate whether identified peptides can pervade Caco-2 cells. Based on the results of bioinformatic analysis, it was found that the selected oat proteins may be a potential source of 107 peptides with DPP-IV and/or ACE inhibitory and/or antioxidant activity. The duodenal digest of oat kernels revealed multiple activities. It inhibited the activities of the following enzymes: DPP-IV (IC₅₀ = 0.51 vs. 10.82 mg/mL of the intact protein), α-glucosidase (IC₅₀ = 1.55 vs. 25.20 mg/mL), and ACE (IC₅₀ = 0.82 vs. 34.52 mg/mL). The DPPH^• scavenging activity was 35.7% vs. 7.93% that of the intact protein. After in silico digestion of oat proteins, 24 peptides were selected for identification using LC-Q-TOF-MS/MS. Among them, 13 sequences were successfully identified. One of them, i.e., VW peptide, exhibited triple activities, i.e., DPP-IV and ACE inhibitory and DPPH^• scavenging activity. The multifunctional peptides: PW, TF, VF, and VW, were identified in the basolateral samples after transport experiments. Both in silico and in vitro analyses demonstrated that oat kernel proteins were the abundant sources of bioactive digests and peptides to be used in a diet for patients suffering from cardiometabolic syndrome.

Tenebrio molitor Proteins-Derived DPP-4 Inhibitory Peptides: Preparation, Identification, and Molecular Binding Mechanism

Inhibition of dipeptidyl peptidase-4 (DPP-4) is an effective way to control blood glucose in diabetic patients. Tenebrio (T.) molitor is an edible insect containing abundant protein. T. molitor protein-derived peptides can suppress the DPP-4 activity. However, the amino acid sequence and binding mechanism of these DPP-4 inhibitory peptides remain unclear. This study used the flavourzyme for T. molitor protein hydrolysis, identified the released peptides with DPP-4 inhibitory effect, and investigated the binding interactions of these peptides with DPP-4. The results showed that flavourzyme efficiently hydrolyzed the T. molitor protein, as demonstrated by the high degree of hydrolysis, disappearance of protein bands in SDS-PAGE, and changes to protein structure. The 4-h flavourzyme hydrolysates showed a good inhibitory effect on DPP-4 (IC₅₀ value of 1.64 mg/mL). The fragment of 1000-3000 Da accounted for 10.39% of the total peptides, but showed the strongest inhibitory effect on DPP-4. The peptides LPDQWDWR and APPDGGFWEWGD were identified from this fraction, and their IC₅₀ values against DPP-4 were 0.15 and 1.03 mg/mL, respectively. Molecular docking showed that these two peptides interacted with the DPP-4 active site via hydrogen bonding, hydrophobic interactions, salt bridge formation, π-cation interactions, and π-π stacking. Our findings indicated that T. molitor protein-derived peptides could be used as natural DPP-4 inhibitors.

Critical Review for the Production of Antidiabetic Peptides by a Bibliometric Approach

The current bibliometric review evaluated recent papers that researched dietary protein sources to generate antidiabetic bioactive peptides/hydrolysates for the management of diabetes. Scopus and PubMed databases were searched to extract bibliometric data and, after a systematic four-step process was performed to select the articles, 75 papers were included in this review. The countries of origin of the authors who published the most were China (67%); Ireland (59%); and Spain (37%). The journals that published most articles on the subject were Food Chemistry (n = 12); Food & Function (n = 8); and Food Research International (n = 6). The most used keywords were ‘bioactive peptides’ (occurrence 28) and ‘antidiabetic’ (occurrence 10). The most used enzymes were Alcalase^® (17%), Trypsin (17%), Pepsin, and Flavourzyme^® (15% each). It was found that different sources of protein have been used to generate dipeptidyl peptidase IV (DPP-IV), α-amylase, and α-glucosidase inhibitory peptides. In addition to antidiabetic properties, some articles (n = 30) carried out studies on multifunctional bioactive peptides, and the most cited were reported to have antioxidant and antihypertensive activities (n = 19 and 17, respectively). The present review intended to offer bibliometric data on the most recent research on the production of antidiabetic peptides from dietary proteins to those interested in their obtention to act as hypoglycemic functional ingredients. The studies available in this period, compiled, are not yet enough to point out the best strategies for the production of antidiabetic peptides from food proteins and a more systematic effort in this direction is necessary to allow a future scale-up for the production of these possible functional ingredients.

Food-derived dipeptidyl peptidase IV inhibitory peptides: Production, identification, structure-activity relationship, and their potential role in glycemic regulation

Dipeptidyl Peptidase IV (DPP-IV) inhibitory peptides are attracting increasing attention, owing to their potential role in glycemic regulation by preventing the inactivation of incretins. However, few reviews have summarized the current understanding of DPP-IV inhibitory peptides and their knowledge gaps. This paper reviews the production, identification and structure-activity relationships (SAR) of DPP-IV inhibitory peptides. Importantly, their bioavailability and hypoglycemic effects are critically discussed. Unlike the traditional method to identifying peptides after separation step by step, the bioinformatics approach identifies peptides via virtual screening that is more convenient and efficient. In addition, the bioinformatics approach was also used to investigate the SAR of peptides. Peptides with proline (Pro) or alanine (Ala) residue at the second position of N-terminal are exhibit strong DPP-IV inhibitory activity. Besides, the bioavailability of DPP-IV inhibitory peptides is related to their gastrointestinal stability and cellular permeability, and in vivo studies showed that the glucose homeostasis has been improved by these peptides. Especially, the intestinal transport of DPP-IV inhibitory peptides and cell biological assays used to evaluate their potential role in glycemic regulation are innovatively summarized. For further successful development of DPP-IV inhibitory peptides in glycemic regulation, future study should elucidate their SAR and in vivo hypoglycemic effects .

Rapid Screening of Novel Dipeptidyl Peptidase-4 Inhibitory Peptides from Pea (Pisum sativum L.) Protein Using Peptidomics and Molecular Docking

Pea protein hydrolysates (PPHs) possess good hypoglycemic effects; however, their dipeptidyl peptidase-4 (DPP-4) inhibitory activity is poorly understood, and none of the DPP-4 inhibitory peptides have been identified from PPHs. This paper aims to rapidly screen these peptides from PPHs by combining peptidomics and molecular docking. In this study, 543 peptides were identified by peptidomics, and four peptides (IPYWTY, IPYWT, LPNYN, and LAFPGSS) with DPP-4 half-maximal inhibitory concentration (IC50) values <100 μM were screened for the first time. Significantly, peptide IPYWTY exhibited the most potent DPP-4 inhibitory activity (IC50 = 11.04 μM) mainly because it formed hydrophobic interactions with the S1 pocket in DPP-4. These results indicated that combining peptidomics and molecular docking is an effective strategy for rapidly screening DPP-4 inhibitory peptides.

Food proteins in the regulation of blood glucose control

Food proteins, depending on their origin, possess unique characteristics that regulate blood glucose via multiple physiological mechanisms, including the insulinotropic effects of amino acids, the activation of incretins, and slowing gastric emptying rate. The strategies aimed at curbing high blood glucose are important in preventing impaired blood glucose control, including insulin resistance, prediabetes and diabetes. The effect of proteins on blood glucose control can be achieved with high-protein foods short-term, and high-protein diets long-term using foods that are naturally high in protein, such as dairy, meat, soy and pulses, or by formulating high-protein functional food products using protein concentrates and isolates, or blended mixtures of proteins from different sources. Commercial sources of protein powders are represented by proteins and hydrolysates of caseins, whey proteins and their fractions, egg whites, soy, yellow pea and hemp which will be reviewed in this chapter. The effective doses of food protein that are capable of reducing postprandial glycemia start from 7 to 10g and higher per serving; however, the origin of protein, and macronutrient composition of a meal will determine the magnitude and duration of their effect on glycemia. The theoretical and methodological framework to evaluate the effect of foods, including food proteins, on postprandial glycemia for substantiation of health claims on food has been proposed in Canada and is discussed in the context of global efforts to harmonize the international food regulation and labeling.

In Vivo and In Vitro Comparison of the DPP-IV Inhibitory Potential of Food Proteins from Different Origins after Gastrointestinal Digestion

Dipeptidyl-peptidase IV (DPP-IV) plays an essential role in glucose metabolism by inactivating incretins. In this context, food-protein-derived DPP-IV inhibitors are promising glycemic regulators which may act by preventing the onset of type 2 diabetes in personalized nutrition. In this study, the DPP-IV-inhibitory potential of seven proteins from diverse origins was compared for the first time in vitro and in vivo in rat plasma after the intestinal barrier (IB) passage of the indigested proteins. The DPP-IV-inhibitory potentials of bovine hemoglobin, caseins, chicken ovalbumin, fish gelatin, and pea proteins were determined in rat plasma thirty minutes after oral administration. In parallel, these proteins, together with bovine whey and gluten proteins, were digested using the harmonized INFOGEST protocol adapted for proteins. The DPP-IV half-maximal inhibitory concentration (IC50) was determined in situ using Caco-2 cells. The DPP-IV-inhibitory activity was also measured after IB passage using a Caco2/HT29-MTX mixed-cell model. The peptide profiles were analyzed using reversed-phase high-performance liquid chromatography tandem mass spectrometry (RP-HPLC-MS/MS) with MS data bioinformatics management, and the IC50 of the identified peptides was predicted in silico. The in vitro and in vivo DPP-IV-inhibitory activity of the proteins differed according to their origin. Vegetable proteins and hemoglobin yielded the highest DPP-IV-inhibitory activity in vivo. However, no correlation was found between the in vivo and in vitro results. This may be partially explained by the differences between the peptidome analysis and the in silico predictions, as well as the study complexity.

Understanding enemy's weapons to an effective prevention: common virulence effects across microbial phytopathogens kingdoms

Plant-pathogens interaction is an ongoing confrontation leading to the emergence of new diseases. The majority of the invading microorganisms inject effector proteins into the host cell, to bypass the sophisticated defense system of the host. However, the effectors could also have other specialized functions, which can disrupt various biological pathways of the host cell. Pathogens can enrich their effectors arsenal to increase infection success or expand their host range. This usually is accomplished by the horizontal gene transfer. Nowadays, the development of specialized software that can predict proteins structure, has changed the experimental designing in effectors' function research. Different effectors of distinct plant pathogens tend to fold alike and have the same function and focussed structural studies on microbial effectors can help to uncover their catalytic/functional activities, while the structural similarity can enable cataloguing the great number of pathogens' effectors. In this review, we collectively present phytopathogens' effectors with known enzymatic functions and proteins structure, originated from all the kingdoms of microbial plant pathogens. Presentation of their common domains and motifs is also included. We believe that the in-depth understanding of the enemy's weapons will help the development of new strategies to prevent newly emerging or re-emerging plant pathogens.

Whole grain rice: Updated understanding of starch digestibility and the regulation of glucose and lipid metabolism

Nowadays, resulting from disordered glucose and lipid metabolism, metabolic diseases (e.g., hyperglycemia, type 2 diabetes, and obesity) are among the most serious health issues facing humans worldwide. Increasing evidence has confirmed that dietary intervention (with healthy foods) is effective at regulating the metabolic syndrome. Whole grain rice (WGR) rich in dietary fiber and many bioactive compounds (e.g., γ-amino butyric acid, γ-oryzanol, and polyphenols) can not only inhibit starch digestion and prevent rapid increase in the blood glucose level, but also reduce oxidative stress and damage to the liver, thereby regulating glucose and lipid metabolism. The rate of starch digestion is directly related to the blood glucose level in the organism after WGR intake. Therefore, the effects of different factors (e.g., additives, cooking, germination, and physical treatments) on WGR starch digestibility are examined in this review. In addition, the mechanisms from human and animal experiments regarding the correlation between the intake of WGR or its products and the lowered blood glucose and lipid levels and the reduced incidence of diabetes and obesity are discussed. Moreover, information on developing WGR products with the health benefits is provided.

Metabolic Profiling for Evaluating the Dipeptidyl Peptidase-IV Inhibitory Potency of Diverse Green Tea Cultivars and Determining Bioactivity-Related Ingredients and Combinations

There are numerous cultivars of tea (Camellia sinensis L.), but the differences in their anti-hyperglycemic-related effects are largely unknown. The inhibition of the dipeptidyl peptidase (DPP)-IV enzyme plays an essential role in controlling hyperglycemia in diabetes by blocking the degradation of incretin hormones, which is necessary for insulin secretion. In this study, we examined the DPP-IV inhibitory activity of leaf extracts from diverse Japanese green tea cultivars. The inhibitory rates differed among tea extracts. Metabolic profiling (MP), using liquid chromatography-mass spectrometry, of all cultivars revealed compositional differences among cultivars according to their DPP-IV inhibitory capacity. Epigallocatechin-3-O-(3-O-methyl)gallate, kaempferol-3-O-rutinoside, myricetin-3-O-glucoside/galactoside, and theogallin were newly identified as DPP-IV inhibitors. The bioactivity of a tea extract was potentiated by adding these ingredients in combination. Our results show that MP is a useful approach for evaluating the DPP-IV inhibitory potency of green tea and for determining bioactivity-related ingredients and combinations.

A comprehensive review on the glucoregulatory properties of food-derived bioactive peptides

Diabetes mellitus, a group of metabolic disorders characterized by persistent hyperglycemia, affects millions of people worldwide and is on the rise. Dietary proteins, from a wide range of food sources, are rich in bioactive peptides with antidiabetic properties. Notable examples include AGFAGDDAPR, a black tea-derived peptide, VRIRLLQRFNKRS, a β-conglycinin-derived peptide, and milk-derived peptide VPP, which have shown antidiabetic effects in diabetic rodent models through variety of pathways including improving beta-cells function, suppression of alpha-cells proliferation, inhibiting food intake, increasing portal cholecystokinin concentration, enhancing insulin signaling and glucose uptake, and ameliorating adipose tissue inflammation. Despite the immense research on glucoregulatory properties of bioactive peptides, incorporation of these bioactive peptides in functional foods or nutraceuticals is widely limited due to the existence of several challenges in the field of peptide research and commercialization. Ongoing research in this field, however, is fundamental to pave the road for this purpose.

Extraction, Chemical Characterization, In Vitro Antioxidant, and Antidiabetic Activity of Canola (Brassica napus L.) Meal

Canola (Brassica napus L.) meal is a by-product after oil extraction from canola seed and is of relatively low value. This meal may have additional value in the biotechnology, food, and pharmaceutical industries if health-promoting useful bioactive compounds can be identified. Hence, seven canola meal extracts (CMEs) were generated using different organic solvents for two genotypes. HPLC and LCMS analyses were employed for the determination of the phenolic and antioxidant activity of meal extracts, including recovery of major biological compounds. When comparing genotype-1 with genotype-2, the latter had higher antioxidant activity in acetone extract (AE). This study also indicated seven major glucosinolates in CMEs in which water (WE) appeared to be the best solvent for the recovery of glucosinolates. Higher quantities of phenolic, glucosinolate, and antioxidant were present in genotype-2 compared with genotype-1. Using HPLC-DAD and LC-MS analysis 47 compounds were detected. We could identify 32 compounds in canola meal extracts: nine glucosinolates and twenty-three phenolic derivatives. Phenolic compounds in canola meal were conjugates and derivatives of hydroxycinnamic acid (sinapic, ferulic, and caffeic acids). Among phenolics, kaempherol as conjugate with sinapic acid was found; sinapine and trans-sinapic acid were the most abundant, as well as major contributors to the antioxidant and free radical scavenging activities of canola meal extracts. Some samples exhibited mild to moderate in-vitro antidiabetic activity in a Dipeptidyl Peptidase-IV inhibition assay.