Novel peptides derived from egg white protein inhibiting alpha-glucosidase

Insetos comestíveis como potenciais fontes de proteínas para obtenção de peptídeos bioativos

Resumo O consumo de insetos como uma fonte alternativa de proteínas é considerado uma tendência futura e uma estratégia viável, com potencial notório para garantia do fornecimento de alimentos em nível global. Os insetos são uma fonte não convencional de proteínas, seja para consumo humano direto ou indiretamente, como ingredientes em alimentos formulados. Além disso, estudos científicos têm demonstrado que a hidrólise enzimática destas proteínas resulta na produção de peptídeos com atividades biológicas de grande interesse, como atividade antioxidante, antidiabética, anti-hipertensiva e antimicrobiana. O uso desses peptídeos com fim nutracêutico pode substituir ou reduzir o uso de drogas sintéticas, as quais estão associadas a efeitos colaterais indesejáveis. O presente trabalho teve como objetivo abordar o uso de insetos na alimentação humana, destacando sua aplicação como substrato proteico na hidrólise enzimática para produção de peptídeos bioativos. As principais propriedades bioativas dos peptídeos foram relatadas.

Identification and characterization of novel α-amylase and α-glucosidase inhibitory peptides from camel whey proteins

This study explores the inhibitory properties of camel whey protein hydrolysates (CWPH) toward α-amylase (AAM) and α-glucosidase (AG). A general full factorial design (3 × 3) was applied to study the effect of temperature (30, 37, and 45°C), time (120, 240, and 360 min), and enzyme (pepsin) concentration (E%; 0.5, 1, and 2%). The results showed that maximum degree of hydrolysis was obtained when hydrolysis was carried out at higher temperature (45°C; P < 0.05), compared with lower temperatures of 30 and 37°C. Electrophoretic pattern displays degradation of all protein bands upon hydrolysis by pepsin at various hydrolysis conditions applied. All the 27 CWPH generated showed significant AAM and AG inhibitory potential as indicated by their lower IC₅₀ values (mg/mL) compared with intact whey proteins. In total 196 peptides were identified from selected hydrolysates and 15 potential peptides (PepSite score > 0.8; http://pepsite2.russelllab.org/) were explored via in silico approach. Novel peptides PAGNFLMNGLMHR, PAVACCLPPLPCHM, MLPLMLPFTMGY, and PAGNFLPPVAAAPVM were identified as potential inhibitors for both AAM and AG due to their high number of binding sites and highest binding probability toward the target enzymes. CCGM and MFE, as well as FCCLGPVPP were identified as AG and AAM inhibitory peptides, respectively. This is the first study that reports novel AG and AAM inhibitory peptides from camel whey proteins. The future direction for this research involves synthesis of these potential AG and AAM inhibitory peptides in a pure form and investigate their antidiabetic properties in the in vitro, as well as in vivo models. Thus, CWPH can be considered for potential applications in glycaemic regulation.

An insight on egg white: From most common functional food to biomaterial application

Natural egg white tis widely used as an ingredient in nutritional foods and for food processing. Due to its characteristic foaming, emulsification, adhesion, and gelation, and its heat setting, biocompatibility, and low cost, research into the application and development of egg white in biomaterials, especially medical biomaterials, have been receiving attention. The composition and characteristics of egg white protein, and the physical mixing and chemically cross-linking of egg white with other materials used to make degradable packaging films, bioceramics, bioplastics, biomimetic films, hydrogels, 3D scaffolds, bone regeneration, biopatterning, biosensors, and so forth, are reviewed in detail in this report. The novel egg white-based biomaterials in various forms and applications could be constructed mostly through physical treatments such as ultrasonic wave, ultraviolet, laser and other radiation or high-temperature calcination. Furthermore, the application and prospects for the use of egg white in biomaterials is also discussed.

Role of Bioactive Peptide Sequences in the Potential Impact of Dairy Protein Intake on Metabolic Health

For years, there has been an increasing move towards elucidating the complexities of how food can interplay with the signalling networks underlying energy homeostasis and glycaemic control. Dairy foods can be regarded as the greatest source of proteins and peptides with various health benefits and are a well-recognized source of bioactive compounds. A number of dairy protein-derived peptide sequences with the ability to modulate functions related to the control of food intake, body weight gain and glucose homeostasis have been isolated and characterized. Their being active in vivo may be questionable mainly due to expected low bioavailability after ingestion, and hence their real contribution to the metabolic impact of dairy protein intake needs to be discussed. Some reports suggest that the differential effects of dairy proteins-in particular whey proteins-on mechanisms underlying energy balance and glucose-homeostasis may be attributed to their unique amino acid composition and hence the release of free amino acid mixtures enriched in essential amino acids (i.e., branched-chain-amino acids) upon digestion. Actually, the research reports reviewed in this article suggest that, among a number of dairy protein-derived peptides isolated and characterized as bioactive compounds in vitro, some peptides can be active in vivo post-oral administration through a local action in the gut, or, alternatively, a systemic action on specific molecular targets after entering the systemic circulation. Moreover, these studies highlight the importance of the enteroendocrine system in the cross talk between food proteins and the neuroendocrine network regulating energy balance.

Use of Alcalase in the production of bioactive peptides: A review

This review aims to cover the uses of the commercially available protease Alcalase in the production of biologically active peptides since 2010. Immobilization of Alcalase has also been reviewed, as immobilization of the enzyme may improve the final reaction design enabling the use of more drastic conditions and the reuse of the biocatalyst. That way, this review presents the production, via Alcalase hydrolysis of different proteins, of peptides with antioxidant, angiotensin I-converting enzyme inhibitory, metal binding, antidiabetic, anti-inflammatory and antimicrobial activities (among other bioactivities) and peptides that improve the functional, sensory and nutritional properties of foods. Alcalase has proved to be among the most efficient proteases for this goal, using different protein sources, being especially interesting the use of the protein residues from food industry as feedstock, as this also solves nature pollution problems. Very interestingly, the bioactivities of the protein hydrolysates further improved when Alcalase is used in a combined way with other proteases both in a sequential way or in a simultaneous hydrolysis (something that could be related to the concept of combi-enzymes), as the combination of proteases with different selectivities and specificities enable the production of a larger amount of peptides and of a smaller size.

Synthesis of new curcumin derivatives as influential antidiabetic α-glucosidase and α-amylase inhibitors with anti-oxidant activity

In this study, a new class of curcumin derivatives was synthesized using a multicomponent reaction containing curcumin, aldehydes, and malononitrile. This new protocol afforded a novel class of 4H-pyran heterocycles incorporating curcumin moiety. The products were obtained in the presence of p-toluenesulfonic acid (PTSA) as a catalyst in ethanol solvent in good to excellent yields. The synthetic compounds indicated a notable inhibitory activity against α-glucosidase (α-Gls) and revealed a weak inhibitory property against α-amylase (α-Amy). Also, these synthetic compounds indicated significant antioxidant activity. The new curcumin derivatives were also discovered to display no significant effect against the growth of two bacterial microflora in the human intestine. A molecular docking study was done to realize the binding interaction of the synthetic curcumin derivatives with the α-Gls enzyme. The results of our study introduced new synthetic curcumin derivatives as potential antidiabetic drugs.

Current genetic engineering strategies for the production of antihypertensive ACEI peptides

Hypertension is a major and highly prevalent risk factor for various diseases. Among the most frequently prescribed antihypertensive first-line drugs are synthetic angiotensin I-converting enzyme inhibitors (ACEI). However, since  their use in hypertension therapy has been linked to various side effects, interest in the application of food-derived ACEI peptides (ACEIp) as antihypertensive agents is rapidly growing. Although promising, the industrial production of ACEIp through conventional methods such as chemical synthesis or enzymatic hydrolysis of food proteins has been proven troublesome. We here provide an overview of current antihypertensive therapeutics, focusing on ACEI, and illustrate how biotechnology and bioengineering can overcome the limitations of ACEIp large-scale production. Latest advances in ACEIp research and current genetic engineering-based strategies for heterologous production of ACEIp (and precursors) are also presented. Cloning approaches include tandem repeats of single ACEIp, ACEIp fusion to proteins/polypeptides, joining multivariate ACEIp into bioactive polypeptides, and producing ACEIp-containing modified plant storage proteins. Although bacteria have been privileged ACEIp heterologous hosts, particularly when testing for new genetic engineering strategies, plants and microalgae-based platforms are now emerging. Besides being generally safer, cost-effective and scalable, these "pharming" platforms can perform therelevant posttranslational modifications and produce (and eventually deliver) biologically active protein/peptide-based antihypertensive medicines.

Evaluation of antidiabetic activity of Pleurotus pulmonarius against streptozotocin-nicotinamide induced diabetic wistar albino rats

The current research aims to evaluate the antidiabetic properties of Pleurotus pulmonarius, an edible basidiomycetes mushroom fungi in diabetic induced wistar albino rats. Mycelial Hot Water Extracts (HWE) and Acetone Extracts (AE) of Pleurotus pulmonarius was orally administrated to STZ-NA induced (55 mg/kilogram body weight) diabetic wistar albino rats at a concentration of 200 and 400 mg/kg for 4 weeks. The outcomes revealed that the HWE of Pleurotus pulmonarius resulted in a significant (p < 0.001) reduction in blood glucose level. A noteworthy (p < 0.001) reduction in serum lipid profile and elevation in High-Density Lipoprotein Cholesterol (HDL-C) after administration with HWE, also demonstrating the protective effects of HWE in diabetes-related complications. Besides all antidiabetic parameters, pathological morphology of the pancreas, liver and kidney are regularised. This observation indicated that HWE of Pleurotus pulmonarius possessed higher antidiabetic activity than AE. Besides, HWE also promoted a significant control of alpha amylase enzyme in a concentration-dependent manner with a maximum activity of 99.23% inhibition at 1000 µg/ml. The outcomes of the present study indicated that the HWE possesses a potential antidiabetic activity both in vitro and in vivo. Thus, it can be used as a nontoxic complementary drug in the controlling of diabetes and related complications, thus providing scientific authentication of its use as an antidiabetic agent.

A multi-approach peptidomic analysis of hen egg white reveals novel putative bioactive molecules

Chicken egg white is a raw material broadly used as additive for the preparation of food and cosmetoceutical products. To describe its molecular properties, various proteomic investigations were performed in the last decade characterizing highly abundant components. No peptidomic counterparts were accomplished so far; scientific literature only reports on the characterization of specific bioactive peptides or preparations from egg white and its hydrolysates, which was performed through dedicated functional assays. In this study, a broad description of the egg white peptidome at 24, 336 and 672 h after laying was achieved using three peptide extraction procedures, which were combined with MALDI-TOF-TOF-MS and nanoLC-ESI-Q-Orbitrap-MS/MS analyses. In the whole, 506 peptides were characterized; they mostly resulted from the physiological degradation of intact proteins following the activity of endoprotease ArgC-, trypsin- and plasmin-like enzymes. Eventual detection of peptide post-translational modifications also provided structural information on parental proteins. When analyzed by bioinformatics and/or compared with literature data, identified peptides allowed recognizing a number of protein fragments associated with different hypothetical biological activities. These results confirmed previous observations regarding functional characteristics of egg white unfractionated preparations or purified molecules, emphasizing the useful application of this raw material in human nutrition and cosmetics. Finally, a comparative label-free peptidomic evaluation of samples stored for different times under refrigeration identified 31 peptides showing significant quantitative changes during storage. BIOLOGICAL SIGNIFICANCE: This study provided the largest inventory of peptides described in chicken egg while so far. In addition, it identified a number of protein fragments associated with hypothetical antihypertensive, antioxidant, antiinflammatory, antimicrobial, anticancer, antiviral, antibiofilm, calcium-binding, antidiabetic, antithrombotic, adipogenic differentiating, stimulating/immunostimulating, hormonal, lipid-binding and cell adhesion-affecting activities. These results confirmed previous observations regarding functional characteristics of egg white unfractionated preparations or purified molecules, emphasizing the useful application of this raw material in human nutrition and cosmetics.

N-Acetyl-l-cysteine/l-Cysteine-Functionalized Chitosan-β-Lactoglobulin Self-Assembly Nanoparticles: A Promising Way for Oral Delivery of Hydrophilic and Hydrophobic Bioactive Compounds

Self-assembled and cross-linked hybrid hydrogels for entrapment and delivery of hydrophilic and hydrophobic bioactive compounds were developed based on N-acetyl-l-cysteine (NAC)- or l-cysteine (CYS)-functionalized chitosan-β-lactoglobulin nanoparticles (NPs). In both the systems, amphiphilic protein β-lactoglobulin (β-lg) was self-assembled by using glutaraldehyde for affinity binding with egg white-derived peptides (EWDP) and curcumin and then coated with NAC- or CYS-functionalized chitosan (CS) by electrostatic interaction. The resulting NPs were characterized in terms of size, polydispersity, and surface charge by dynamic light scattering. Results corroborated pH-sensitive properties of NAC-CS-β-lg NPs and CYS-CS-β-lg NPs with the particle size as small as 118 and 48 nm, respectively. The two kinds of NPs also showed excellent entrapment of EWDP and curcumin with the entrapment efficiency (EE) of EWDP and curcumin ranging from 51 to 89% and 42 to 57% in NAC-CS-β-lg NPs, as well as 50-81% and 41-57% in CYS-CS-β-lg NPs under different pH values. Fourier transform infrared and molecular docking studies provided support for the interaction mechanism of NAC/CYS-CS with β-lg as well as the NPs with EWDP and curcumin. Strikingly, the in vitro release kinetics of EWDP and curcumin exhibited the controlled and sustained release properties up to 58 and 70 h from the NPs, respectively. Note that the permeability of QIGLF (pentapeptide, isolated from EWDP) and curcumin passing through Caco-2 cell monolayers were all improved after the entrapment in the NPs. This work offers promising methods for effective entrapment and oral delivery of both hydrophilic and hydrophobic bioactive compounds.

Dietary Whole Egg Reduces Body Weight Gain in a Dose-Dependent Manner in Zucker Diabetic Fatty Rats

BACKGROUND

We previously reported that a whole-egg-based diet attenuated weight gain in rats with type 2 diabetes (T2D) and more effectively maintained vitamin D status than an equivalent amount of supplemental cholecalciferol.

OBJECTIVES

The objective of this study was to determine the lowest dose of whole egg effective at maintaining vitamin D homeostasis and attenuating the obese phenotype in T2D rats.

METHODS

Zucker diabetic fatty (ZDF) rats (n = 40; age 6 wk; prediabetic) and their lean controls (n = 40; age 6 wk) were randomly assigned to a diet containing 20% casein (CAS) or 20%, 10%, 5%, or 2.5% protein from whole egg (20% EGG, 10% EGG, 5% EGG, and 2.5% EGG, respectively). All diets contained 20% total protein (wt:wt). All rats received their respective diets for 8 wk, at a stage of growth and development that translates to adolescence in humans, until 14 wk of age, a point at which ZDF rats exhibit overt T2D. Weight gain was measured 5 d/wk, and circulating 25-hydroxyvitamin D [25(OH)D] was measured by ELISA. Mean values were compared by 2-factor ANOVA.

RESULTS

The 20% EGG diet maintained serum 25(OH)D at 30 nmol/L in ZDF rats, whereas the 10%, 5%, and 2.5% EGG diets did not prevent insufficiency, resulting in mean serum 25(OH)D concentrations of 24 nmol/L in ZDF rats. Body weight gain was reduced by 29% (P < 0.001) and 31% (P < 0.001) in ZDF rats consuming 20% and 10% EGG diets, respectively, and by 16% (P = 0.004) and 12% (P = 0.030) in ZDF rats consuming 5% and 2.5% EGG diets, respectively, compared with CAS.

CONCLUSIONS

Whole-egg-based diets exerted a dose-dependent response with respect to attenuating weight gain. These data could support dietary recommendations aimed at body weight management in individuals predisposed to obesity and T2D.

LUTI: a double-function inhibitor isolated from naked flax seeds

Acute glucose fluctuation during the postprandial period causes a risk for type 2 diabetes mellitus (T2DM). α-Glucosidase inhibitors have been approved as therapeutic agents for diabetes. In the present study, a protein with α-glucosidase inhibitory activity from Flax (Linum usitatissimum) seeds was isolated using a one-step purification with Q-Sepharose4B column, followed by Sephacryl S-200 size-exclusion chromatography. It was identified as a trypsin inhibitor, named L. usitatissimum trypsin inhibitor (LUTI). The half maximal inhibitory concentration (IC50) of LUTI was 113.92 μM for α-glucosidase and 6.17 μM for trypsin. Lineweaver-Burk kinetic experiment showed that the protein exhibited two distinct inhibitory modes, a competitive inhibitor type for α-glucosidase and a non-competitive type for trypsin. The interaction between LUTI and α-glucosidase was detected through gel filtration chromatography and dynamic light scattering. Increased glucose consumption and lactic acid production were also observed following LUTI treatment in Caco-2 and HepG2 cells. LUTI inhibits not only the activity of trypsin but also the activity of α-glucosidase. It is expected that LUTI will become an oral hypoglycemic polypeptide drug for T2DM.

Preparation of bioactive peptides with antidiabetic, antihypertensive, and antioxidant activities and identification of α-glucosidase inhibitory peptides from soy protein

In this study, the peptides of soy protein obtained by enzymatic digestion with proteases were analyzed for their antidiabetic, antihypertensive, and antioxidant activities. Peptides prepared with alkaline proteinase (AP) exhibited the highest α-glucosidase inhibitory activity compared with those from papain and trypsin digestion. AP hydrolysates also exhibited dipeptidyl peptidase IV (DPP-IV) inhibitory, angiotensin-converting enzyme (ACE) inhibitory, and antioxidant activities. Gastrointestinal digestion of peptides enhanced α-glucosidase, DPP-IV, and ACE inhibitory activities compared with AP hydrolysates. AP peptides showing highest α-glucosidase inhibitory activity were purified by anion-exchange and size-exclusion chromatography， and identified using tandem MS. We found three novel α-glucosidase inhibitory peptides with sequences LLPLPVLK, SWLRL, and WLRL with IC50 of 237.43 ± 0.52, 182.05 ± 0.74, and 162.29 ± 0.74 μmol/L, respectively. Therefore, peptides hydrolyzed from soy protein are promising natural ingredients for nutraceutical applications assisting in the management of diabetes.

Elucidation of an α-glucosidase inhibitor from the peel of Allium cepa by principal component analysis

We conducted liquid chromatography-mass spectrometry measurements on hot-water extracts of peel from different varieties of Allium cepa. Some quercetin glycosides were identified as potential α-glucosidase inhibitors by principal component analysis of the liquid chromatography-mass spectrometry data. α-Glucosidase inhibitory activity assays identified quercetin-4ʹ-O-glucoside as an α-glucosidase inhibitor.

Antihyperglycemic and hypoglycemic activity of naturally occurring peptides and protein hydrolysates from easy-to-cook and hard-to-cook beans (Phaseolus vulgaris L.)

The present study was undertaken to examine the antidiabetic potential of naturally occurring peptides and hydrolysate fractions from easy-to-cook (ETC) and hard-to-cook (HTC) beans. All fractions were tested regarding their in vitro inhibitory activities against α-amylase and α-glucosidase as well as in vivo anti-hyperglycemic and hypoglycemic effects. Results evidenced that the peptide fractions with the lowest molecular weight (<3 kDa) have the highest inhibitory activities, and a 16.9%-89.1% inhibition of α-amylase and 34.4%-89.2% inhibition of α-glucosidase were observed. Regarding the antihyperglycemic activity, the fraction ETCNO3-10 showed a better performance than the positive control (acarbose). In addition, results from hypoglycemic activity evidenced that the tested peptide fractions were able to decrease the glucose levels at the same extension of glibenclamide, maintaining a constant basal glucose level without a postprandial hyperglycemia peak. Finally, it is possible to suggest that the naturally occurring peptides and hydrolysate fractions obtained from ETC and HTC common beans could be used in functional food production or pharmaceutical formulations to prevent diabetes.

Mechanism and Potential of Egg Consumption and Egg Bioactive Components on Type-2 Diabetes

Type-2 diabetes (T2D) is one of the major global health challenges and a substantial economic burden. Egg and egg-derived components have been indicated to possess antioxidant, anti-inflammatory, anti-hypertensive, immunomodulatory, and anti-cancer activities. However, the scientific evidence about the benefits of egg on T2D is debatable. The relationship between egg consumption and the risk of T2D from observational epidemiological studies is not consistent. Interventional clinical studies, however, provide promising evidence that egg consumption ameliorates the risk of T2D. Current research progress also indicates that some egg components and egg-derived peptides might be beneficial in the context of T2D, in terms of insulin secretion and sensitivity, oxidative stress, and inflammation, suggesting possible application on T2D management. The current review summarizes recent clinical investigations related to the influence of egg consumption on T2D risk and in vivo and in vitro studies on the effect and mechanism of egg components and egg-derived peptides on T2D.

Recently isolated antidiabetic hydrolysates and peptides from multiple food sources: a review

Diabetes, a metabolic syndrome of global importance has been on a progressive rise in recent years. Several pharmacological approaches have been made, which have proved effective, but with underlying side effects. Bioactive hydrolysates (BHs) and peptides (BPs) from food sources, however, have shown the relative advantage of imparting less adverse effects. Furthermore, BHs and BPs from food have been discovered to impart their antidiabetic potentials through one or more mechanisms such as inhibition of digestive enzymes, inhibition of the antigenic enzyme - Dipeptyl peptidase IV (DPP-IV), decrease in blood glucose levels and increase in insulin uptake. Several plants and animal sources have been used as protein sources for the isolation of antidiabetic hydrolysates and peptides through different mechanisms and analytical techniques. This review integrates recent research information about several popular and unconventional food sources of BHs and BPs, their isolation techniques, antidiabetic effects and protein profiles. In addition, the fractionation technique(s) employed in each study and inhibition potentials of BHs and BPs are reviewed. This article is intended to supplement accessible scholarly literature and intellectual awareness on the subject of food-oriented approach for the management of diabetes.

The kinetics and mechanism of α-glucosidase inhibition by F5-SP, a novel compound derived from sericin peptides

The inhibition of α-glucosidase decreases postprandial blood glucose and therefore plays an important role in the treatment of type 2 diabetes mellitus. The present study investigated and characterized a peptide fraction of sericin hydrolysate, the kinetics of peptide-induced inhibition of α-glucosidase, and the interaction mechanism between the peptides and α-glucosidase. The fraction that eluted with 0.4 M NaCl (F5-SPs) on a DEAE-cellulose column exhibited significant inhibitory activity with an IC₅₀ of 41 ± 1.94 μg mL^-1. A kinetics analysis revealed that the F5-SP-induced inhibition was a reversible and parabolic mixed-type inhibition with a K_i value of 86.63 ± 0.014 μg mL^-1. F5-SPs can bind to α-glucosidase at multiple sites to alter the conformation of α-glucosidase. F5-SPs were found to be rich in Gly, Ser, Glu, Tyr, Arg, and Pro, and had a sericin-conserved sequence SEDSSEVDIDLGNLG, as analyzed by Nano LC-MS/MS. Fluorescence spectra analysis showed that F5-SPs quenched the intrinsic fluorescence of α-glucosidase by a static quenching mechanism, and circular dichroism analysis suggested that the binding of F5-SPs to α-glucosidase resulted in the alteration of the secondary structure of an enzyme. The results of this study support the dietary recommendation of F5-SPs for the treatment of type 2 diabetes.

Rational in silico design of novel α-glucosidase inhibitory peptides and in vitro evaluation of promising candidates

Treatment of type 2 diabetes is achieved through the inhibition of carbohydrate hydrolyzing enzymes such as α-glucosidase and α-amylase. The present study was conducted to identify novel α-glucosidase inhibitory peptides and to validate the α-glucosidase and α-amylase inhibitory activities of two promising candidates. A total of 4210 potential α-glucosidase inhibitory peptides with 3-5 amino acid residues were designed and individually subjected to in silico simulated gastrointestinal (GIT) digestion using the BIOPEP database. Subsequently, 844 GIT resistant peptides were then subjected to molecular docking using Autodock Vina to determine their binding free energy against human α-glucosidase (PDB ID: 3L4Y). Among all the peptides, SVPA and SEPA were found to have the lowest binding free energies of -8.7 and -8.6 kcal/mol, respectively. Docking of SVPA and SEPA on human α-amylase (PDB ID, 4GQR) identified that both peptides also bind to α-amylase with binding energies of -6.5 and -6.9 kcal/mol, respectively. Hydrogen bond interactions were critical for the binding of both peptides to the α-glucosidase and α-amylase. In vitro, SVPA and SEPA inhibited α-glucosidase and α-amylase activities with IC₅₀ values several fold lower than acarbose except for SVPA that had a significantly higher (p <  0.05) IC₅₀ value than acarbose against α-glucosidase. Lineweaver-Burk analyses revealed that SVPA was an uncompetitive inhibitor of the two enzymes, while SEPA inhibited α-glucosidase and α-amylase non-competitively and uncompetitively, respectively. This study has identified two novel and active α-glucosidase inhibitory peptides that could resist GIT digestion and therefore, have the potential to retard postprandial hyperglycemia in diabetic patients.

Anti-Alzheimers activity and molecular mechanism of albumin-derived peptides against AChE and BChE

Alzheimer's disease (AD) is a global health issue affecting millions of elderly people worldwide. The aim of the present study was to identify novel anti-AD peptides isolated from albumin. Anti-AD activities of the peptides were evaluated via inhibitory activities on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Furthermore, the potential molecular mechanisms of the KLPGF/AChE were investigated by CDOCKER of Discovery studio 2017. The results revealed that peptide KLPGF could effectively inhibit AChE with an inhibition rate of 61.23% at a concentration of 50 μg mL^-1. In addition, the peptide KLPGF came in contact with acylation sites and peripheral anion sites of AChE. The present study demonstrates that the peptide KLPGF could become a potential functional food intervention in AD.

Identification of Bioactive Peptides with α-Amylase Inhibitory Potential from Enzymatic Protein Hydrolysates of Red Seaweed (Porphyra spp)

Inhibition of α-amylase enzyme is one therapeutic approach in lowering glucose level in the blood to manage diabetes mellitus. In this study α-amylase inhibitory peptides were identified from proteolytic enzymes hydrolysates of red seaweed laver ( Porphyra species) using consecutive chromatographic techniques. In the resultant fractions from RP-HPLC (D₁-₁₀), D₂ inhibited α-amylase activity (88.67 ± 1.05%) significantly ( p ≤ 0.5) at 1 mg/mL protein concentration. A mass spectrometry (ESI-Q-TOF- MS) analysis was used to identify peptides from this fraction. Two novel peptides were identified as Gly-Gly-Ser-Lys and Glu-Leu-Ser. To validate their α-amylase inhibitory activity, these peptides were synthesized chemically. The peptides were demonstrated inhibitory activity at IC₅₀ value: 2.58 ± 0.08 mM (Gly-Gly-Ser-Lys) and 2.62 ± 0.05 mM (Glu-Leu-Ser). The inhibitory kinetics revealed that these peptides exhibited noncompetitive binding mode. Thus, laver can be a potential source of novel ingredients in food and pharmaceuticals in diabetes mellitus management.

Egg and Soy-Derived Peptides and Hydrolysates: A Review of Their Physiological Actions against Diabetes and Obesity

Type 2 diabetes and obesity are two chronic conditions associated with the metabolic syndrome and their prevalences are increasing worldwide. The investigation of food protein-derived bioactive peptides that can improve the pathophysiology of diabetes or obesity while causing minimal side effects is desired. Egg and soy proteins generate bioactive peptides with multiple biological effects, exerting nutritional and physiological benefits. This review focuses on the anti-diabetic and anti-obesity effects of egg- and soy-derived peptides and hydrolysates in vivo and in vitro relevant to these conditions. Studies using the intact protein were considered only when comparing the results with the hydrolysate or peptides. In vivo evidence suggests that bioactive peptides from egg and soy can potentially be used to manage elements of glucose homeostasis in metabolic syndrome; however, the mechanisms of action on glucose and insulin metabolism, and the interaction between peptides and their molecular targets remain unclear. Optimizing the production of egg- and soy-derived peptides and standardizing the physiological models to study their effects on diabetes and obesity could help to clarify the effects of these bioactive peptides in metabolic syndrome-related conditions.

Fabrication of reusable electrochemical biosensor and its application for the assay of α-glucosidase activity

A reusable biosensor has been fabricated in this work for the assay of α-glucosidase activity and the inhibitor screening. In this design, the aptamer of ATP is split as split aptamer 1 (Apt 1) and split aptamer 2 (Apt 2), and Apt 2 can link gold nanoparticles (AuNPs) modified with Apt 1 and 4-aminophenyl-α-d-glucopyranoside (pAPG). Consequently, the functional AuNPs can be immobilized onto the surface of gold electrode, allowing for salt-induced regeneration. In the presence of α-glucosidase, the glycosyl of pAPG is cut off, and the electroactive phenolic hydroxyls appear to give a strong current signal. Furthermore, the biosensor can be recovered very easily by incubating it in water to dissociate the AuNPs modified with Apt 1 and pAPG. So, a new biosensor for α-glucosidase activity detection and inhibitor screening is developed based on enzyme-activated signal generation and recovery. The biosensor may also exhibit good sensitivity for α-glucosidase determination with the detection limit 0.005 U/mL and can be reused by water-washing regeneration with good repeatability. Meanwhile this biosensor can also be utilized for inhibitor screening, which may have potential for clinical applications.

Egg White Hydrolysate Can Be a Low-Allergenic Food Material to Suppress Ectopic Fat Accumulation in Rats Fed an Equicaloric Diet

Egg white (EW) is known as a nutritional protein but can induce allergic reactions in humans. We investigated the dietary effects of EW and its hydrolysate (EWH), which contains less allergen, on body fat accumulation in Wistar rats fed an equicaloric high-fat and high-sucrose diet for 8 wk (Exp A). The pair-feeding of EW and equicaloric-feeding of EWH increased fecal fat excretion and suppressed lipid accumulation in the liver and muscles but not in the abdominal adipose tissues, carcass, or total body. Dietary EWH also suppressed the serum glucose level and alkaline phosphatase activity. Further, we showed a higher dispersibility of EW and EWH in physicochemical assay (Exp B). Next, we investigated the suppressive effects of a single administration of EW and EWH on lipid-induced hypertriglyceridemia and small intestinal meal transit in ddY mice (Exp C). However, a single administration of EW or EWH did not suppress the lipid-induced hypertriglyceridemia nor did it delay the rate of small intestinal transit. These findings indicated that dietary EW and EWH reduce hepatic and muscular (ectopic) fat accumulation mainly by suppressing fat absorption and supplying fat to the liver and muscles. Therefore, the low-allergenic EWH can be effective for the prevention of high-fat-diet-induced obesity.

Egg Protein-Derived Bioactive Peptides: Preparation, Efficacy, and Absorption

The hen's egg is an important protein source of human diet. On average one large egg contains ~6g protein, which contributes to ~11% of daily protein intake. As a high-quality protein, egg proteins are well recognized as excellent sources of bioactive peptides. The objectives of this chapter are to introduce generation, bioactivities, and absorption of egg protein-derived bioactive peptides. Research on egg protein-derived bioactive peptides has been progressed during the past decades. Enzymatic hydrolysis is the major technique to prepare bioactive peptides from egg protein. Quantitative structure-activity relationships-aided in silico prediction is increasingly applied as a promising tool for efficient prediction of novel bioactive peptides. A number of bioactive peptides from egg proteins have been characterized for antioxidant, immunomodulatory, antihypertensive, antidiabetic, anticancer, and antimicrobial activities. Egg protein-derived peptides that can improve bone health have been reported as well. However, molecular mechanisms of many peptides are not fully understood. The stability and absorption routes, bioavailability, safety, and production of bioactive peptides await further investigation.

Peptides Derived from Foods as Supportive Diet Components in the Prevention of Metabolic Syndrome

Metabolic syndrome (MSyn) includes physiological, biochemical, clinical, and metabolic abnormalities, leading to an increase in health problems like obesity, dyslipidemia, cardiovascular diseases, and diabetes, which contribute to an increase in mortality rate. One of the main factors having a key impact on our health is the food we consume. Thus, scientists work towards the discovery of novel bioactive compounds with therapeutic potential to address MSyn. According to scientific reports, peptides derived from food proteins exhibit bioactivities important for the prevention of MSyn diseases; that is, they regulate blood pressure and glycemia; reduce cholesterol level and body mass; and scavenge free radicals. The aim of this review is to study the potential role of peptides in the prevention of MSyn. Particularly peptides which exhibit the following activities: antihypertensive [angiotensin-converting enzyme (ACE) inhibition (EC 3.4.15.1)], antidiabetic [dipeptidyl peptidase IV (DPP-IV) (EC 3.4.14.5)/α-glucosidase (EC 3.2.1.20)/α-amylase (EC 3.2.1.1) inhibition)], cholesterol level reduction, antioxidative, and obesity prevention, were studied. If possible, special attention is paid in the review to the bioactivities of peptides that were measured in vivo. Some examples of peptides showing dual or multiple action against MSyn targets are presented. Moreover, using the database of bioactive peptide sequences (BIOPEP) we made a list of peptides serving simultaneous functions in counteracting MSyn dysfunctions. Such an approach may simplify the discovery of MSyn preventive peptides, as well as highlight some of them as potent bioactive ingredients that may be incorporated into foods. Moreover, the research strategy involving the in silico and in vitro/in vivo methodologies may be useful in the production of food protein hydrolysates supporting the treatment of MSyn dysfunctions.

Structural properties of bioactive peptides with α-glucosidase inhibitory activity

Bioactive peptides are emerging as promising class of drugs that could serve as α-glucosidase inhibitors for the treatment of type 2 diabetes. This article identifies structural and physicochemical requirements for the design of therapeutically relevant α-glucosidase inhibitory peptides. So far, a total of 43 fully sequenced α-glucosidase inhibitory peptides have been reported and 13 of them had IC₅₀ values several folds lower than acarbose. Analysis of the peptides indicates that the most potent peptides are tri- to hexapeptides with amino acids containing a hydroxyl or basic side chain at the N-terminal. The presence of proline within the chain and alanine or methionine at the C-terminal appears to be relevant for high activity. Hydrophobicity and isoelectric points are less important variables for α-glucosidase inhibition whilst a net charge of 0 or +1 was predicted for the highly active peptides. In silico simulated gastrointestinal digestion revealed that the high and moderately active peptides, including the most potent peptide (STYV), were gastrointestinally unstable, except SQSPA. Molecular docking of SQSPA, STYV, and STY (digestion fragment of STYV) with α-glucosidase suggested that their hydrogen bonding interactions and binding energies were comparable with acarbose. The identified criteria will facilitate the design of new peptide-derived α-glucosidase inhibitors.

Bioactive peptides derived from egg proteins: A review

Egg proteins have various functional and biological activities which make them potential precursor proteins for bioactive peptide production. Simulated in vitro gastrointestinal digestion and enzymatic hydrolysis using non-gastrointestinal proteases have been used as tools to produce these peptides. Bioactive peptides derived from egg proteins are reported to display various biological activities, including angiotensin I-converting enzyme (ACE) inhibitory (antihypertensive), antioxidant, antimicrobial, anti-inflammatory, antidiabetic and iron-/calcium-binding activities. More importantly, simulated in vitro gastrointestinal digestion has indicated that consumption of egg proteins has physiological benefits due to the release of such multifunctional peptides. This review encompasses studies reported to date on the bioactive peptide production from egg proteins.

Biosynthesis of α-Glucosidase Inhibitors by a Newly Isolated Bacterium, Paenibacillus sp. TKU042 and Its Effect on Reducing Plasma Glucose in a Mouse Model

Paenibacillus sp. TKU042, a bacterium isolated from Taiwanese soil, produced α-glucosidase inhibitors (aGIs) in the culture supernatant when commercial nutrient broth (NB) was used as the medium for fermentation. The supernatant of fermented NB (FNB) showed stronger inhibitory activities than acarbose, a commercial anti-diabetic drug. The IC50 and maximum α-glucosidase inhibitory activities (aGIA) of FNB and acarbose against α-glucosidase were 81 μg/mL, 92% and 1395 μg/mL, 63%, respectively. FNB was found to be strongly thermostable, retaining 95% of its relative activity, even after heating at 100 °C for 30 min. FNB was also stable at various pH values. Furthermore, FNB demonstrated antioxidant activity (IC50 = 2.23 mg/mL). In animal tests, FNB showed remarkable reductions in the plasma glucose of ICR (Institute of Cancer Research) mice at a concentration of 200 mg/kg. Combining FNB and acarbose enhanced the effect even more, with an added advantage of eliminating diarrhea. According to HPLC (High-performance liquid chromatography) fingerprinting, the Paenibacillus sp. TKU042 aGIs were not acarbose. All of the results suggest that Paenibacillus sp. TKU042 FNB could have potential use as a health food or to treat type 2 diabetes.

Protein Hydrolysates and Biopeptides: Production, Biological Activities, and Applications in Foods and Health Benefits. A Review

In recent years, a great deal of interest has been expressed regarding the production, characterization, and applications of protein hydrolysates and food-derived biopeptides due to their numerous beneficial health effects. In this regard, research is mainly focused on investigating the therapeutic potential of these natural compounds. Based on their amino acids composition, sequences, hydrophobicity, and length, peptides released from food proteins, beyond their nutritional properties, can exhibit various biological activities including antihypertensive, antioxidative, antithrombotic, hypoglycemic, hypocholesterolemic, and antibacterial activities among others. Protein hydrolysates are essentially produced by enzymatic hydrolysis of whole protein sources by appropriate proteolytic enzymes under controlled conditions, followed by posthydrolysis processing to isolate desired and potent bioactive peptides from a complex mixture of active and inactive peptides. Therefore, because of their human health potential and safety profiles, protein hydrolysates and biopeptides may be used as ingredients in functional foods and pharmaceuticals to improve human health and prevent diseases. In this review, we have focused on the major variables influencing the enzymatic process of protein hydrolysates production. The biological properties of protein hydrolysates will be described as well as their applications in foods and health benefits.