Recovery, viscoelastic and functional properties of Barbel skin gelatine: investigation of anti-DPP-IV and anti-prolyl endopeptidase activities of generated gelatine polypeptides

Fish waste biorefinery: A novel approach to promote industrial sustainability

In pursuit of sustainability and resource efficiency, concept of the circular economy has emerged as a promising framework for industries worldwide. The global fish processing industry generates a significant amount of waste, posing environmental challenges and economic inefficiencies. The substantial volume of fish waste generated globally along with its environmental impact highlights the urgent need to adopt sustainable practices. However, there is significant transformative potential in leveraging fish processing waste to generate industrial value. There are numerous applications of fish processing waste such as extraction of enzymes, protein hydrolysates, collagen, and gelatin. Moreover, the capacity of fish waste to generate chitin, fish oil, and biofuels foresees a future for sustainable resource management. However, it is also necessary to emphasize the need for innovation, and cross-sector collaboration to unlock this potential. While challenges lie ahead, this review explores transformative power of circular economy in reshaping the fisheries industry towards more sustainable future.

Bioactive Properties of Enzymatic Gelatin Hydrolysates Based on In Silico, In Vitro, and In Vivo Studies

This current study aims to analyze the potential bioactivities possessed by the enzymatic hydrolysates of commercial bovine, porcine, and tilapia gelatins using bioinformatics in combination with in vitro and in vivo studies. The hydrolysate with superior inhibition of angiotensin converting enzyme (ACE) activity was used to treat the D-galactose (DG)-induced amnesic mice. In silico digestion of the gelatins led to the identification of peptide sequences with potential antioxidant, ACE-inhibitory, and anti-amnestic properties. The results of in vitro digestion revealed that the <1 kDa peptide fraction of porcine gelatin hydrolysate obtained after 1 h digestion with papain (PP) (PP1, <1 kDa) potently inhibited ACE, acetylcholinesterase, and prolyl endopeptidase activities at 87.42%, 21.24%, and 48.07%, respectively. Administering the PP1 to DG-induced amnesic mice ameliorated the spatial cognitive impairment and Morris water maze learning abilities. The dentate area morphology in the PP1-treated mice was relatively similar to the control group. In addition, PP1 enhanced the antioxidant capacity in the DG-induced amnesic mice. This study suggests that PP1 could serve as a potential treatment tool against oxidative stress, hypertension, and neurodegenerative diseases.

A Review on Fish Skin-Derived Gelatin: Elucidating the Gelatin Peptides-Preparation, Bioactivity, Mechanistic Insights, and Strategies for Stability Improvement

Fish skin-derived gelatin has garnered significant attention recently due to its abundant availability and promising bioactive properties. This comprehensive review elucidates various intricacies concerning fish skin-derived gelatin peptides, including their preparation techniques, bioactive profiles, underlying mechanisms, and methods for stability enhancement. The review investigates diverse extraction methods and processing approaches for acquiring gelatin peptides from fish skin, emphasizing their impact on the peptide composition and functional characteristics. Furthermore, the review examines the manifold bioactivities demonstrated by fish skin-derived gelatin peptides, encompassing antioxidant, antimicrobial, anti-inflammatory, and anticancer properties, elucidating their potential roles in functional food products, pharmaceuticals, and nutraceuticals. Further, mechanistic insights into the functioning of gelatin peptides are explored, shedding light on their interactions with biological targets and pathways. Additionally, strategies aimed at improving the stability of gelatin peptides, such as encapsulation, modification, and integration into delivery systems, are discussed to extend the shelf life and preserve the bioactivity. Overall, this comprehensive review offers valuable insights into using fish skin-derived gelatin peptides as functional ingredients, providing perspectives for future research endeavors and industrial applications within food science, health, and biotechnology.

Effect of thermal pretreatment and gastrointestinal digestion on the bioactivity of dry-cured ham bone enzymatic hydrolyzates

This study reports the effect of thermal pretreatment and the use of different commercial proteolytic enzymes (Protamex, Flavourzyme, Protana prime, and Alcalase) on the free amino acid content (FAA), peptide profile, and antioxidant, antidiabetic, antihypertensive, and anti-inflammatory potential (DPPH, FRAP, and ABTS assay, DPP-IV, ACE-I, and NEP inhibitory activities) of dry-cured ham bone hydrolyzates. The effect of in vitro digestion was also determined. Thermal pretreatment significantly increased the degree of hydrolysis, the FAA, and the DPP-IV and ACE-I inhibitory activities. The type of peptidase used was the most significant factor influencing antioxidant activity and neprilysin inhibitory activity. Protana prime hydrolyzates failed to inhibit DPP-IV and neprilysin enzymes and had low values of ACE-I inhibitory activity. After in vitro digestion, bioactivities kept constant in most cases or even increased in ACE-I inhibitory activity. Therefore, hydrolyzates from dry-cured ham bones could serve as a potential source of functional food ingredients for health benefits.

Identification of Polyphenols in Sea Fennel (Crithmum maritimum) and Seaside Arrowgrass (Triglochin maritima) Extracts with Antioxidant, ACE-I, DPP-IV and PEP-Inhibitory Capacity

Sea fennel and seaside arrowgrass are two abundant but underutilized halophytes along the Atlantic and Mediterranean coasts. This study investigated the antioxidant capacity and the potential antihypertensive (Angiotensin Converting Enzyme I, ACE-I inhibition), hypoglycaemic (Dipeptidyl Peptidase IV, DPP-IV inhibition), and nootropic (Prolyl Endopeptidase, PEP inhibition) activity of their polyphenol extracts. They had a high phenol content (21-24 mEq GA/g), antioxidant capacity evaluated using the ABTS (17-2 mg ascorbic acid/g) and FRAP (170-270 mM Mohr's salt/g) assays, and effective ACE-inhibiting properties (80-90% inhibiting activity at final concentration of 0.5 mg/mL). Additionally, the sea fennel extract displayed high DPP-IV inhibitory capacity (73% at 1 mg/mL), while the seaside arrowgrass extract exhibited potent Prolyl endopeptidase inhibitory capacity (75% at 1 mg/mL). Fractionation by HPLC concentrated the bioactive molecules in two fractions, for which the composition was analyzed by LC-MS/MS. Different chlorogenic acids seemed to play an important role in the bioactivity of sea fennel extract, and different flavonoids, mainly apigenin, luteolin and chrysoeriol, in the bioactivity of the seaside arrowgrass extract. Given their potential health benefits, these extracts could serve as valuable bioactive ingredients and could potentially encourage the cultivation of these species in regions where traditional crops face challenges in growth.

Techno-functional characterization of gelatin extracted from the smooth-hound shark skins: Impact of pretreatments and drying methods

Gelatin derived from marine by-products could be an interesting alternative to classic mammalian gelatin. The pretreatment and extraction conditions could influence the size of the resulting peptide chains and therefore their techno-functional properties. Thus, it is important to optimize the production process to get a gelatin for the appropriate applications. Skin pretreatment was done by microwaves or oven-drying and the extracted gelatin was dried by spray- or freeze-drying. Freeze-dried gelatin extracted from untreated skin (FGUS) had the highest gelatin yield (10.40%). Gelatin proximate composition showed that proteins were the major component (87.12-89.95%), while lipids showed the lowest contents (0.65-2.26%). Glycine showed the highest level (299-316/1000 residues) in the extracted gelatins. Proline and hydroxyproline residues of gelatins from untreated skin were significantly higher than those from pretreated skin-gelatin. FTIR spectra were characterized by peaks of the amide A (3430-3284 cm-1), B (3000-2931 cm-1), I (1636-1672 cm-1), II (1539-1586 cm-1) and III (1000-1107 cm-1). Spray-drying decreased the gelling properties of gelatins, since it reduced gelling and melting temperatures compared to freeze-drying. Skin pretreatment significantly reduced the gel strength of gelatin by about 50-100 g depending on the gelatin drying method. The FGUS showed better surface properties compared to other gelatins. The highest emulsion activity index (39.42 ± 1.02 m2/g) and foaming expansion (172.33 ± 2.35%) were measured at 3% FGUS. Therefore, the promising properties of freeze-dried gelatin derived from untreated skin, gave it the opportunity to be successfully used as a techno-functional ingredient in many formulations.

The biological role of prolyl oligopeptidase and the procognitive potential of its peptidic inhibitors from food proteins

Prolyl oligopeptidase (POP) is a conserved serine protease belonging to proline-specific peptidases. It has both enzymatic and non-enzymatic activity and is involved in numerous biological processes in the human body, playing a role in e.g., cellular growth and differentiation, inflammation, as well as the development of some neurodegenerative and neuropsychiatric disorders. This article describes the physiological and pathological aspects of POP activity and the state-of-art of its peptidic inhibitors originating from food proteins, with a particular focus on their potential as cognition-enhancing agents. Although some milk, meat, fish, and plant protein-derived peptides have the potential to be applied as natural, procognitive nutraceuticals, their effectiveness requires further evaluation, especially in clinical trials. We demonstrated that the important features of the most promising POP-inhibiting peptides are very short sequence, high content of hydrophobic amino acids, and usually the presence of proline residue.

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.

Antioxidant, Antihypertensive, Hypoglycaemic and Nootropic Activity of a Polyphenolic Extract from the Halophyte Ice Plant (Mesembryanthemum crystallinum)

This study aims to determine the potential antioxidant, antihypertensive, hypoglycaemic and nootropic activity of a purified polyphenolic extract from the halophyte ice plant (Mesembryanthemum crystallinum). The ice plant extract showed good antioxidant activity measured by DPPH, ORAC, TEAC, FRAP and ferrous ion chelating activity. Moreover, the extract showed potent ACE, DPP-IV and PEP-inhibitory activity (90.5%, 98.6% and 73.1%, respectively, at a final concentration of 1 mg/mL). The extract was fractionated and the fraction with the highest content of total phenolic compounds showed the highest bioactivity, suggesting that polyphenols could be mainly responsible for the abovementioned activities. The tentative polyphenol identification by HPLC-ESI-QTOF-MS in this fraction revealed that flavones (>65%) are the major group, with apigenin (38%) predominating, followed by diosmin (17.7%) and luteolin (11.9%). They could presumably be the main elements responsible for the enzymatic inhibition activity. Additionally, 4-hydroxybenzoic acid, p-coumaric acid and a hydroxycinnamic acid derivative (2-O-(p-cumaroyl)-l-malic acid) were found in the extract. To our knowledge, this is the first time that some of these activities have been reported for halophyte extracts.

Bioactive peptides identified from enzymatic hydrolysates of sturgeon skin

BACKGROUND

Recent studies demonstrate that fish byproducts can be used as sources of bioactive peptides for functional foods. Sturgeon skin contains abundant proteins but it has commonly been discarded during sturgeon processing. The objective of the present work was to identify and characterize the bioactive peptides from protein hydrolysates of sturgeon skin.

RESULTS

Sturgeon skin protein extract (SKPE) hydrolyzed by flavourzyme for 60 min exhibited high antioxidant activity, dipeptidyl peptidase IV (DPP-IV) and angiotensin converting enzyme (ACE) inhibitory activity. The sequences of peptides from flavourzyme hydrolysates were identified using high-performance liquid chromatography-tandem mass spectrometry. Gly-Asp-Arg-Gly-Glu-Ser-Gly-Pro-Ala (P1) showed the highest DPPH radical scavenging activity (DPPH IC₅₀  = 1.93 mmol L^-1 ). Gly-Pro-Ala-Gly-Glu-Arg-Gly-Glu-Gly-Gly-Pro-Arg (P11) (DPP-IV IC₅₀  = 2.14 mmol L^-1 ) and Ser-Pro-Gly-Pro-Asp-Gly-Lys-Thr-Gly-Pro-Arg (P12) (DPP-IV IC₅₀  = 2.61 mmol L^-1 ) exhibited the strongest DPP-IV inhibitory activity. Gly-Pro-Pro-Gly-Ala-Asp-Gly-Gln-Ala-Gly-Ala-Lys (P6) displayed the highest ACE inhibitory activity (ACE IC₅₀  = 3.77 mmol L^-1 ). The molecular docking analysis revealed that DPP-IV inhibition of P11 and P12 are mainly attributed to hydrogen bonds and hydrophobic interactions, whereas ACE inhibition of P6 is mainly attributed to strong hydrogen bonds.

CONCLUSIONS

These results indicate that SKPE hydrolysates generated by flavourzyme are potential sources of bioactive peptides that could be used in the health food industry. © 2021 Society of Chemical Industry.

Beneficial effects of fish and fish peptides on main metabolic syndrome associated risk factors: Diabetes, obesity and lipemia

The definition of metabolic syndrome (MetS) fairly varies from one to another guideline and health organization. Per description of world health organization, occurrence of hyperinsulinemia or hyperglycemia in addition to two or more factors of dyslipidemia, hypoalphalipoproteinemia, hypertension and or large waist circumference factors would be defined as MetS. Conventional therapies and drugs, commonly with adverse effects, are used to treat these conditions and diseases. Nonetheless, in the recent decades scientific community has focused on the discovery of natural compounds to diminish the side effects of these medications. Among many available bioactives, biologically active peptides have notable beneficial effects on the management of diabetes, obesity, hypercholesterolemia, and hypertension. Marine inclusive of fish peptides have exerted significant bioactivities in different experimental in-vitro, in-vivo and clinical settings. This review exclusively focuses on studies from the recent decade investigating hypoglycemic, hypolipidemic, hypercholesterolemic and anti-obesogenic fish and fish peptides. Related extraction, isolation, and purification methodologies of anti-MetS fish biopeptides are reviewed herein for comparison purposes only. Moreover, performance of biopeptides in simulated gastrointestinal environment and structure-activity relationship along with absorption, distribution, metabolism, and excretion properties of selected oligopeptides have been discussed, in brief, to broaden the knowledge of readers on the design and discovery trends of anti-MetS compounds.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2022.2052261 .

Protein Hydrolysis and Glycosylation as Strategies to Produce Bioactive Ingredients from Unmarketable Prawns

The present work shows a procedure to valorize non-commercial boiled shrimp to produce functional ingredients, using a combined treatment based on enzymatic hydrolysis and subsequent glycation under mild conditions. Antioxidant and prolyl endopeptidase-inhibiting activities were determined as a function of hydrolysis and glycation times (0-120 min and 0-180 min, respectively). The reaction products were characterized by determining the degree of hydrolysis, browning, fluorescent compounds, free amino acids, phenol content, Fourier transform infrared spectroscopy (FTIR), and molecular weight of the different fractions obtained. Enzymatic hydrolysis generated hydrolysates with significant antioxidant and prolyl endopeptidase-inhibiting activities. Glycation under mild conditions was used as a strategy to improve the antioxidant and potential nootropic properties of the hydrolysates. During glycation, the free amino acid content decreased, total phenols and fluorescent compounds increased significantly, and low molecular weight melanoidins were formed. The presence of peptide-glucose conjugates was also confirmed by FTIR. Glycation increased the antioxidant activities of the hydrolysates; however, their prolyl-endopeptidase-inhibiting activity was lost. Results showed that compounds with promising antioxidant (hydrolysis and glycation) and potential nootropic (hydrolysis) activities and applications in food systems were obtained from the biotechnological strategy used.

Study on the Mechanism of the Blood-Glucose-Lowering Effect of Collagen Peptides from Sturgeon By-Products

In a previous study, we found that the collagen peptides prepared from the by-products of Bester sturgeon had an inhibitory effect on elevated blood glucose levels in a glucose tolerance test with ICR mice. In the present study, we examine the mechanism of the effect of sturgeon collagen peptides (SCPs) in detail. When glucose was orally administered to mice along with the SCPs, it was found that the glucose remained in the stomach for a longer time. In the above tests, the amount of glucose excreted in the feces of mice also increased. On the contrary, it was revealed that the SCPs have a dipeptidyl-peptidase-IV (DPP-IV) inhibitory ability in an in vitro test. In subsequent oral and intravenous glucose administration tests, glucagon-like peptide-1 (GLP-1) and insulin levels in the blood of mice were maintained at high levels. These results suggested the following three mechanisms: SCPs slow the rate of transportation of glucose from the stomach into the small intestine, resulting in delayed glucose absorption; SCPs suppress the absorption of glucose in the small intestine and excrete it from the body; SCPs inhibit DPP-IV in the blood and maintain a high GLP-1 level in blood, which in turn stimulates insulin secretion.

Fish protein hydrolysates as a health-promoting ingredient-recent update

Dietary habits and lifestyle-related diseases indicate that food has a direct impact on individual health. Hence, a diet containing essential nutrients is important for healthy living. Fish and fish products are important in diets worldwide because of their nutritional value, especially their easily digestible proteins with essential amino acids. Similarly, fish protein hydrolysate (FPH) obtained from fish muscle and by-products has been reported to exhibit various biological activities and to have functional properties, which make FPH a suitable nutraceutical candidate. This review focuses on the health-promoting ability of FPH in terms of skin health, bone and cartilage health, blood lipid profile, and body-weight management studied in rats and human model systems. The absorption and bioavailability of FPH in humans is discussed, and challenges and obstacles of FPH as a functional food ingredient are outlined.

A Narrative Review of the Anti-Hyperglycemic and Satiating Effects of Fish Protein Hydrolysates and Their Bioactive Peptides

Prevalence of type 2 diabetes and overweight/obesity are increasing globally. Food supplementation as a preventative option has become an attractive option in comparison to increased pharmacotherapy dependency. Hydrolysates of fish processing waste and by-products have become particularly interesting in a climate of increased food wastage awareness and are rapidly gaining traction in food research. This review summarizes the available research so far on the potential effect of these hydrolysates on diabetes and appetite suppression. Scopus and Web of Science are searched using eight keywords (fish, hydrolysate, peptides, satiating, insulinotropic, incretin, anti-obesity, DPP-4 [dipeptidylpeptidase-4/IV]) returning a total of 2549 results. Following exclusion criteria (repeated appearances, non-fish marine sources [e.g., macroalgae], and irrelevant bioactivities [e.g., immunomodulatory, anti-thrombotic]), 44 relevant publications are included in this review. Stimulation of hormone secretion, regulation of glucose uptake, anorexigenic potential, identified mechanisms of action, and research conducted on the most potent bioactive peptides identified within these hydrolysates are all specifically addressed. Results of this review conclude that despite wide methodological variation between studies, there is significant potential for the application of fish protein hydrolysates in the management of bodyweight and hyperglycemia.

Production and identification of dipeptidyl peptidase IV (DPP-IV) inhibitory peptides from discarded Sardine pilchardus protein

Production of bioactive peptides via enzymatic hydrolysis is a sustainable way to take advantage of proteinaceous by-products from food industry, such as fish discards. Sardine pilchardus protein was subjected to different enzymatic treatments using two endopeptidases of different selectivity and one exopeptidase in order to produce hydrolysates with antidiabetic activity. The highest dipeptidyl peptidase IV inhibitory activity was obtained by the combination of three enzymes (subtilisin, trypsin and flavourzyme) employed sequentially. This hydrolysate was subsequently purified by size exclusion chromatography to obtain fractions sorted by size (hydrodynamic volume). Peptides below 1400 Dalton had the highest activity, and these pools were analysed by mass spectrometry in order to identify the peptides responsible for that activity. Numerous peptides with adequate molecular features, it is, owning an alanine (A) as their penultimate N-terminal residue (e.g. NAPNPR, YACSVR) were identified and are proposed to be antidiabetic peptides from Sardine pilchardus muscle.

Effect of heat extraction on water-soluble taste substances in processing products of chilled large yellow croaker (Pseudosciaena crocea)

In this paper, we analyzed the umami amino acids composition and content in minced meat (MM), fish head meat (HM), and fish roe (R). According to different ratios of material to liquid, we extracted water-soluble taste substances from the three materials and then compared composition and content of the umami amino acids and taste nucleotides in the different water-soluble taste substances. Finally, we analyzed Taste Activity Value (TAV) and the Equivalent Umami Concentration (EUC) between umami amino acids and taste nucleotides. The results showed that umami amino acids total content in MM, HM, and R samples were, respectively, 50.63 mg/100 g, 41.95 mg/100 g, and 67.06 mg/100 g. When the water-soluble taste substances extracted from the above samples were in the "D" state (MM), the "C" state (HM), and the "C" state (R), respectively, the umami amino acid content could be comparable to the original sample. And the highest EUCs were respectively 1.37 g MSG/100 g, 0.87 g MSG/100 g, and 0.49 g MSG/100 g (MSG: Sodium Glutamate). To some extent, the results of this study indicated that the water-soluble taste substances could be equivalent to the original sample and could be further applied as a taste regulator in some respects.

The perceptions of natural compounds against dipeptidyl peptidase 4 in diabetes: from in silico to in vivo

Dipeptidyl peptidase IV (DPP-4), an incretin glucagon-like peptide-1 (GLP-1) degrading enzyme, contains two forms and it can exert various physiological functions particular in controlling blood glucose through the action of GLP-1. In diabetic use, the DPP-4 inhibitor can block the DDP-4 to attenuate GLP-1 degradation and prolong GLP-1 its action and sensitize insulin activity for the purpose of lowering blood glucose. Nonetheless the adverse effects of DPP-4 inhibitors severely hinder their clinical applications, and notably there is a clinical demand for novel DPP-4 inhibitors from various sources including chemical synthesis, herbs, and plants with fewer side effects. In this review, we highlight various strategies, namely computational biology (in silico), in vitro enzymatic and cell assays, and in vivo animal tests, for seeking natural DPP-4 inhibitors from botanic sources including herbs and plants. The pros and cons of all approaches for new inhibitor candidates or hits will be under discussion.

Viscoelastic and Functional Properties of Cod-Bone Gelatin in the Presence of Xylitol and Stevioside

The physical, rheological, structural and functional properties of cod bone gelatin (CBG) with various concentrations (0, 2, 4, 6, 10, and 15%) of low-calorie sweeteners [xylitol (X) and stevioside (S)] to form gels were investigated. The gel strength of CBGX increased with increased xylitol due presumably to hydrogen bonds between xylitol and gelatin, but with CBGS the highest gel strength occurred when S concentration was 4%. Viscosity of CBGS samples were higher than CBGX due to S's high molecular mass. The viscoelasticity (G′ and G′′), foaming capacity and fat binding capacity of CBGX were higher while foam stability was lower. The emulsion activity and emulsion stability of CBGX were a little lower than CBGS at the same concentration. The structure of X is linear making it easier to form a dense three-dimensional network structure, while the complex cyclic structure of S had more difficulty forming a network structure with cod bone gelatin. Therefore, X may be a better choice for sweetening gelatin gels.

Tryptophan-Containing Dual Neuroprotective Peptides: Prolyl Endopeptidase Inhibition and Caenorhabditis elegans Protection from β-Amyloid Peptide Toxicity

Neuroprotective peptides represent an attractive pharmacological strategy for the prevention or treatment of age-related diseases, for which there are currently few effective therapies. Lactoferrin (LF)-derived peptides (PKHs) and a set of six rationally-designed tryptophan (W)-containing heptapeptides (PACEIs) were characterized as prolyl endopeptidase (PEP) inhibitors, and their effect on β-amyloid peptide (Aβ) toxicity in a Caenorhabditis elegans model of Alzheimer's disease (AD) was evaluated. Two LF-derived sequences, PKH8 and PKH11, sharing a W at the C-terminal end, and the six PACEI heptapeptides (PACEI48L to PACEI53L) exhibited significant in vitro PEP inhibition. The inhibitory peptides PKH11 and PACEI50L also alleviated Aβ-induced paralysis in the in vivo C. elegans model of AD. Partial or total loss of the inhibitory effect on PEP was achieved by the substitution of W residues in PKH11 and PACEI50L and correlated with the loss of protection against Aβ toxicity, pointing out the relevance of W on the neuroprotective activity. Further experiments suggest that C. elegans protection might not be mediated by an antioxidant mechanism but rather by inhibition of Aβ oligomerization and thus, amyloid deposition. In conclusion, novel natural and rationally-designed W-containing peptides are suitable starting leads to design effective neuroprotective agents.

Generation of dipeptidyl peptidase IV (DPP-IV) inhibitory peptides during the enzymatic hydrolysis of tropical banded cricket (Gryllodes sigillatus) proteins

Cricket (Gryllodes sigillatus) protein hydrolysates inhibit dipeptidyl peptidase IV (DPP-IV) in vitro.

Protein digestomic analysis reveals the bioactivity of deer antler velvet in simulated gastrointestinal digestion

Proteins are the most prominent bioactive component in deer antler velvet. The aim of the present study was to track the fate of protein of antler velvet by protein digestomics. The peptide profile identified by LC-MS/MS and the in vitro bioactivity of antler velvet aqueous extract (AAE) were investigated in simulated gastrointestinal digestion. A total of 23, 387 and 417 peptides in AAE, gastric and pancreatic digests were identified using LC-MS/MS, respectively. Collagens, the predominant proteins, released 34 peptides in gastric digests and 146 peptides in pancreatic digests. The gastric and pancreatic digests presented dipeptidyl peptidase IV (DPP-IV) and prolyl endopeptidase (PEP) inhibition activities. Four peptides from digests were proved to be DPP-IV and PEP inhibitory peptides. The results showed that the peptides released from antler velvet protein contributed to the bioactivity of antler velvet during digestion.

Response surface methodology applied to the generation of casein hydrolysates with antioxidant and dipeptidyl peptidase IV inhibitory properties

BACKGROUND

Hydrolysis parameters affecting the release of dipeptidyl peptidase IV (DPP-IV) inhibitory and antioxidant peptides from milk proteins have not been extensively studied. Therefore, a multifactorial (i.e. pH, temperature and hydrolysis time) composite design was used to optimise the release of bioactive peptides (BAPs) with DPP-IV inhibitory and antioxidant [oxygen radical absorbance capacity (ORAC)] properties from sodium caseinate.

RESULTS

Fifteen sodium caseinate hydrolysates (H1-H15) were generated with Protamex^TM , a bacillus proteinase activity. Hydrolysis time (1 to 5 h) had the highest influence on both DPP-IV inhibitory properties and ORAC activity (P < 0.05). Alteration of incubation temperature (40 to 60 °C) and pH (6.5 to 8.0) had an effect on the DPP-IV inhibitory properties but not the ORAC activity of the Protamex sodium caseinate hydrolysates. A multi-functional hydrolysate, H12, was identified having DPP-IV inhibitory (actual: 0.82 ± 0.24 vs. predicted optimum: 0.68 mg mL^-1 ) and ORAC (actual: 639 ± 66 vs. predicted optimum: 639 µmol TE g^-1 ) activity of the same order (P > 0.05) as the response surface methodology (RSM) predicted optimum bioactivities.

CONCLUSION

Generation of milk protein hydrolysates through multifactorial design approaches may aid in the optimal enzymatic release of BAPs with serum glucose lowering and antioxidant properties. © 2016 Society of Chemical Industry.

Transport of a Prolyl Endopeptidase Inhibitory Peptide across the Blood-Brain Barrier Demonstrated Using the hCMEC/D3 Cell Line Transcytosis Assay

The blood-brain barrier (BBB) remains a significant hurdle for treatment of central nervous system (CNS) and mental health disorders. A prolyl endopeptidase (PEP) inhibitory peptide with the amino acid sequence proline-proline-leucine (PPL) was chemically synthesized labeled with 5-FAM and assessed using a transcytosis assay for its ability to cross the BBB. Transport of this peptide across the BBB was determined using an in vitro model of the human BBB, which utilizes the human cerebral microvascular endothelial cell line (hCMEC/D3). Uptake and transport of 5-FAM-PPL across the hCMEC/D3 cell model was determined using confocal microscopy and mass spectrometry. This is an important parameter in determining whether peptides may reach the target organ (i.e., the brain and central nervous system).This work assessed, for the first time, the ability of a food-derived PEP inhibitory peptide to cross the BBB without the use of animal models.

Helix aspersa gelatin as an emulsifier and emulsion stabilizer: functional properties and effects on pancreatic lipolysis

Emulsions are widely used in food and pharmaceutical applications for the encapsulation, solubilization, entrapment, and controlled delivery of active ingredients.

Enhancement of ACE and prolyl oligopeptidase inhibitory potency of protein hydrolysates from sardine and tuna by-products by simulated gastrointestinal digestion

This work was focused on the study of the bioactive potential of three fish protein hydrolysates, prepared from industrial sardine and tuna by-products.