Chemistry and Biofunctional Significance of Bioactive Peptide Interactions with Food and Gut Components

Preparation and identification of antioxidant peptides from Quasipaa spinosa skin through two-step enzymatic hydrolysis and molecular simulation

Frog skin, a by-product of Quasipaa Spinosa farming, is rich in protein and potentially a valuable raw material for obtaining antioxidant peptides. This study used papain combined with acid protease to digest frog skin in a two-step enzymatic hydrolysis method. Based on a single factor and response surface experiments, experimental conditions were optimized, and the degree of hydrolysis was 30 %. A frog skin hydrolysate (QSPH-Ⅰ-3) was obtained following ultrafiltration and gel filtration chromatography. IC50 for DPPH, ABTS, and hydroxyl radical scavenging capacities were 1.68 ± 0.05, 1.20 ± 0.14 and 1.55 ± 0.11 mg/mL, respectively. Peptide sequences (17) were analyzed and, through molecular docking, peptides with low binding energies for KEAP1 were identified, which might affect the NRF2-KEAP1 pathway. These findings suggest protein hydrolysates and antioxidant peptide derivatives might be used in functional foods.

Identification of the Bioavailable Peptidome of Chia Protein Hydrolysate and the In Silico Evaluation of Its Antioxidant and ACE Inhibitory Potential

The incorporation of novel, functional, and sustainable foods in human diets is increasing because of their beneficial effects and environmental-friendly nature. Chia (Salvia hispanica L.) has proved to be a suitable source of bioactive peptides via enzymatic hydrolysis. These peptides could be responsible for modulating several physiological processes if able to reach the target organ. The bioavailable peptides contained in a hydrolysate obtained with Alcalase, as functional foods, were identified using a transwell system with Caco-2 cell culture as the absorption model. Furthermore, 20 unique peptides with a molecular weight lower than 1000 Da and the higher statistical significance of the peptide-precursor spectrum match (-10 log P) were assessed by in silico tools to suggest which peptides could be those exerting the demonstrated bioactivity. From the characterized peptides, considering the molecular features and the results obtained, the peptides AGDAHWTY, VDAHPIKAM, PNYHPNPR, and ALPPGAVHW are anticipated to be contributing to the antioxidant and/or ACE inhibitor activity of the chia protein hydrolysates.

Untargeted and Targeted Metabolomics Reveal the Active Peptide of Eupolyphaga sinensis Walker against Hyperlipidemia by Modulating Imbalance in Amino Acid Metabolism

The active peptide (APE) of Eupolyphaga sinensis Walker, which is prepared by bioenzymatic digestion, has significant antihyperlipidemic effects in vivo, but its mechanism of action on hyperlipidemia is not clear. Recent studies on amino acid metabolism suggested a possible link between it and hyperlipidemia. In this study, we first characterized the composition of APE using various methods. Then, the therapeutic effects of APE on hyperlipidemic rats were evaluated, including lipid levels, the inflammatory response, and oxidative stress. Finally, the metabolism-regulating mechanisms of APE on hyperlipidemic rats were analyzed using untargeted and targeted metabolomic approaches. The results showed that APE significantly reduced the accumulation of fat, oxidative stress levels, and serum pro-inflammatory cytokine levels. Untargeted metabolomic analysis showed that the mechanism of the hypolipidemic effect of APE was mainly related to tryptophan metabolism, phenylalanine metabolism, arginine biosynthesis, and purine metabolism. Amino-acid-targeted metabolomic analysis showed that significant differences in the levels of eight amino acids occurred after APE treatment. Among them, the expression of tryptophan, alanine, glutamate, threonine, valine, and phenylalanine was upregulated, and that of arginine and proline was downregulated in APE-treated rats. In addition, APE significantly downregulated the mRNA expression of SREBP-1, SREBP-2, and HMGCR. Taking these points together, we hypothesize that APE ameliorates hyperlipidemia by modulating amino acid metabolism in the metabolome of the serum and feces, mediating the SREBP/HMGCR signaling pathway, and reducing oxidative stress and inflammation levels.

Shifting archetype to nature's hidden gems: from sources, purification to uncover the nutritional potential of bioactive peptides

Contemporary scientific findings revealed that our daily food stuffs are enriched by encrypted bioactive peptides (BPs), evolved by peptide linkage of amino acids or encrypted from the native protein structures. Remarkable to these BPs lies in their potential health benefiting biological activities to serve as nutraceuticals or a lead addition to the development of functional foods. The biological activities of BPs vary depending on the sequence as well as amino acid composition. Existing database records approximately 3000 peptide sequences which possess potential biological activities such as antioxidants, antihypertensive, antithrombotic, anti-adipogenics, anti-microbials, anti-inflammatory, and anti-cancerous. The growing evidences suggest that BPs have very low toxicity, higher accuracy, less tissue accretion, and are easily degraded in the disposed environment. BPs are nowadays evolved as biologically active molecules with potential scope to reduce microbial contamination as well as ward off oxidation of foods, amend diverse range of human diseases to enhance the overall quality of human life. Against the clinical and health perspectives of BPs, this review aimed to elaborate current evolution of nutritional potential of BPs, studies pertaining to overcome limitations with respect to special focus on emerging extraction, protection and delivery tools of BPs. In addition, the nano-delivery mechanism of BP and its clinical significance is detailed. The aim of current review is to augment the research in the field of BPs production, identification, characterisation and to speed up the investigation of the incredible potentials of BPs as potential nutritional and functional food ingredient.

Food-derived bioactive peptides as momentous food components: Can functional peptides passed through the PI3K/Akt/mTOR pathway and NF-κB pathway to repair and protect the skeletal muscle injury?

Muscle injury is defined as an overuse injury or traumatic distraction of a muscle, which is latent in any sport event, from amateur to large events. Based on previous numbers of muscle injuries and time spent to the athletes' recovery, the use of dietary functional factors intervention strategies is essential to enhance the recovery process and health. In recent years, there has been increasing evidence that biologically active peptides played an important role in sports nutrition and muscle injure recovery. Food-derived bioactive peptides were physiologically active peptides mostly derived from proteins following hydrolysis, which could be resorbed in intact form to reduce muscle damage following exercise and induce beneficial adaptions within the connective tissue. However, the complexity of the histoarchitectural considerations for skeletal muscle injuries and the repair mechanism of damaged skeletal muscle were not well known. In the following overview, the potential mechanisms and possible limitations regarding the damaged skeletal muscle metabolism were summarized, which aimed to present an overview of the nutritional strategies and recommendations after a muscular sports injury, emphasizing the use of main bioactive peptides. In addition, this review will provide implications for the studies of dietary bioactive peptides in the future.

Cardamonin targets KEAP1/NRF2 signaling for protection against atherosclerosis

Atherosclerosis (AS)-induced cardiovascular disease is a leading cause of death worldwide. To date, there is still a lack of effective approaches for AS intervention. Cardamonin (CAD) is a bioactive food component, but its effect on AS is unknown. In this work, CAD was investigated for its effect on AS using low-density lipoprotein receptor knockout mice and tumor necrosis factor-alpha (TNF-α)-stimulated endothelial cells (ECs). After a 12-week intervention, CAD was found to significantly prevent AS formation in the aortic root and aortic tree, reduce the necrotic core area, and inhibit aortic inflammation and oxidative stress. Moreover, CAD quenched TNF-α-provoked inflammation and oxidative stress in ECs. RNA-sequencing identified nuclear factor erythroid-2 related factor 2 (NFE2L2, NRF2)/heme oxidase 1 (HO1) signaling to be drastically activated by CAD. CAD is a known activator of the aryl hydrocarbon receptor (AHR) which is a transcription factor of the NFE2L2 gene. Surprisingly, AHR was not required for CAD's action on the activation of NRF2/HO1 signaling since AHR gene silencing did not reverse this effect. Furthermore, a molecular docking assay showed a strong binding potential of CAD to the Kelch domain of the Kelch-like ECH-associated protein 1 (KEAP1) which sequesters NRF2 in the cytoplasm. Both CAD and the Kelch domain inhibitor Ki696 promoted NRF2 nuclear translocation, whereas the combination of CAD and Ki696 did not yield a greater effect compared with either CAD or Ki696, confirming the interaction of CAD with the Kelch domain. This work provides an experimental basis for CAD as a novel and effective bioactive food component in future AS interventions.

Bioactive food-derived peptides for functional nutrition: Effect of fortification, processing and storage on peptide stability and bioactivity within food matrices

New challenges in food production and processing are appearing due to increasing global population and the purpose of achieving a sustainable food system. Bioactive peptides obtained from food proteins can be employed to prevent or pre-treat several diseases such as diabetes, cardiovascular diseases, inflammation, thrombosis, cancer, etc. Research on the bioactivity of protein hydrolysates is very extensive, especially in vitro tests, although there are also tests in animal models and in humans studies designed to verify their efficacy. However, there is very little published literature on the functionality of these protein hydrolysates as an ingredient in food matrices, as well as the effect that thermal or non-thermal processing, and storage may have on the bioactivity of these bioactive peptides. This review aims to summarize the published literature on protein hydrolysates as a functional ingredient including processing, storage and simulated gastrointestinal digestion regarding the bioactivity of these peptides inside food matrices.

Potential of Food Protein-Derived Bioactive Peptides against Sarcopenia: A Comprehensive Review

Sarcopenia is an age-related progressive muscle disorder characterized by accelerated loss of muscle mass, strength, and function, which are important causes of physiological dysfunctions in the elderly. At present, the main alleviating method includes protein supplements to stimulate synthesis of muscle proteins. Food protein-derived peptides containing abundant branched-chain amino acids have a remarkable effect on the improvement of sarcopenia. Understanding the underlying molecular mechanism and clarifying the structure-activity relationship is essential for the mitigation of sarcopenia. This present review recaps the epidemiology, pathogenesis, diagnosis, and treatment of sarcopenia, which facilitates a comprehensive understanding of sarcopenia. Moreover, the latest research progress on food-derived antisarcopenic peptides is reviewed, including their antisarcopenic activity, molecular mechanism as well as structural characteristics. Food-derived bioactive peptides can indeed alleviate/mitigate sarcopenia. These antisarcopenic peptides play a pivotal role mainly by activating the PI3K/Akt/mTOR and MAPK pathways and inhibiting the ubiquitin-proteasome system and AMPK pathway, thus promoting the synthesis of muscle proteins and inhibiting their degradation. Antisarcopenic peptides alleviate sarcopenia via specific peptides, which may be absorbed into the circulation and exhibit their bioactivity in intact forms. The present review provides a theoretical reference for mitigation and prevention of sarcopenia by food protein-derived bioactive peptides.

Biological functions of peptides from legumes in gastrointestinal health. A review legume peptides with gastrointestinal protection

Extensively consumed worldwide, legumes such as beans, soybeans, chickpeas, and peas represent a great source of protein. Legume-derived proteins provide bioactive peptides, small sequences of amino acids produced by enzymatic hydrolysis, gastrointestinal digestion, fermentation, or germination. Recent studies showed diverse biological effects of these peptides as antioxidants, antihypertensives, anti-inflammatory, antimicrobial, antithrombotic, antidiabetic, hypocholesterolemic, and even immunomodulators. These beneficial effects aid in preventing and treating chronic illnesses, particularly inflammatory disorders, obesity, and cardiovascular diseases. Thus, this work discusses these biological functions in gastrointestinal digestion health of bioactive peptides obtained from common beans, soybeans, chickpeas, peas, and other legumes. PRACTICAL APPLICATIONS: Knowledge of the nutraceutical properties of legumes can encourage the use of these seeds as ingredients in the development and design of functional foods.

Food-derived bioactive oligopeptide iron complexes ameliorate iron deficiency anemia and offspring development in pregnant rats

This study aimed to investigate anemia treatment and other potential effects of two food-derived bioactive oligopeptide iron complexes on pregnant rats with iron deficiency anemia (IDA) and their offspring. Rats with IDA were established with a low iron diet and then mated. There were one control group and seven randomly assigned groups of pregnant rats with IDA: Control group [Control, 40 ppm ferrous sulfate (FeSO₄)]; IDA model group (ID, 4 ppm FeSO₄), three high-iron groups (H-FeSO₄, 400 ppm FeSO₄; MCOP-Fe, 400 ppm marine fish oligopeptide iron complex; WCOP-Fe, 400 ppm whey protein oligopeptide iron complex) and three low-iron groups (L-FeSO₄, 40 ppm FeSO₄; MOP-Fe, 40 ppm marine fish oligopeptide iron complex; WOP-Fe, 40 ppm whey protein oligopeptide iron complex). Rats in each group were fed the corresponding special diet during pregnancy until the day of delivery. After different doses of iron supplement, serum hemoglobin, iron, and ferritin levels in rats with IDA were significantly increased to normal levels (P < 0.05). Serum iron levels were significantly lower in two food-derived bioactive oligopeptide low-iron complex groups than in the low FeSO₄ group (P<0.05). Liver malondialdehyde levels were significantly increased in the three high-iron groups compared with the other five groups (P < 0.05), and hemosiderin deposition was observed in liver tissue, indicating that the iron dose was overloaded and aggravated the peroxidative damage in pregnant rats. Liver inflammation was reduced in the three low-iron groups. Tumor necrosis factor α secretion was significantly decreased in all groups with supplemented oligopeptide (P < 0.05), with the concentration of tumor necrosis factor α declining to normal levels in the two whey protein oligopeptide iron complex groups. In the marine fish oligopeptide iron complex groups, body length, tail length, and weight of offspring were significantly increased (P < 0.05) and reached normal levels. Therefore, food-derived bioactive oligopeptide (derived from marine fish skin and milk) iron complexes may be an effective type of iron supplement for pregnancy to improve anemia, as well as reduce the side effects of iron overload, and improve the growth and nutritional status of offspring.

C-Terminal Modification on the Immunomodulatory Activity, Antioxidant Activity, and Structure–Activity Relationship of Pulsed Electric Field (PEF)-Treated Pine Nut Peptide

In this study, a novel peptide VNAVL was synthesized by removing the C-terminal histidine on the basis of a bioactive peptide VNAVLH obtained from pine nut (Pinus koraiensis Sieb. et Zucc) protein. The effects of removing histidine on antioxidant activity, immunomodulatory activity, and secondary structure of the PEF-treated peptide were discussed. Compared with VNAVLH, VNAVL only exhibited lower antioxidant activity, but no immunomodulatory activity to release TNF-α, IL-6, and NO by activating RAW 264.7 cells. In addition, both antioxidant and immune activities of VNAVLH were significantly more sensitive to treatment with 40 kV/cm than other field intensities, whereas VNAVL was not sensitive to field strength changes. CD spectra and DSSP analysis verified that both peptides consisted of a β structure and random coil, but the ability of VNAVL to transform the random coil via PEF treatment is weaker than that of VNAVLH. Therefore, PEF treatment might expose the key active site located on the C-terminal histidine by altering the secondary structure of the peptide.

Recent findings on the cellular and molecular mechanisms of action of novel food-derived antihypertensive peptides

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Hypertension has remained a silent-killer.

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Novel peptides recently isolated from food proteins.

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Molecular mechanism of blood pressure-lowering: renin and ACE-inhibition, and beyond.

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Proposed molecular mechanisms for future research.

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Novel peptides are excellent candidates for nutraceutical development.

Hypertension impacts negatively on the quality of life of sufferers, and complications associated with uncontrolled hypertension are life-threatening. Hence, many research efforts are exploring the antihypertensive properties of bioactive peptides derived from food proteins using in vitro ACE-inhibitory assay, experimentally-induced and spontaneous hypertensive rats, normotensive and hypertensive human models. In this study, the cellular and molecular mechanisms of blood pressure-lowering properties of novel peptides reported in recent studies (2015-July 30, 2021) were discussed. In addition to common mechanisms such as the inhibition of angiotensin I-converting enzyme (ACE) and renin activities, recently recognized mechanisms through which bioactive peptides exert their antihypertensive properties including the induction of vasodilation via upregulation of cyclo-oxygenase (COX) and prostaglandin receptor and endothelial nitric oxide synthase expression and L-type Ca²⁺ channel blockade were presented. Similarly, emerging mechanisms of blood pressure-lowering by bioactive peptides such as modulation of inflammation (TNF-α, and other cytokines signaling), oxidative stress (Keap-1/Nrf2/ARE/HO-1 and related signaling pathways), PPAR-γ/caspase3/MAPK signaling pathways and inhibition of lipid accumulation were discussed. The review also highlighted factors that influence the antihypertensive properties of peptides such as method of hydrolysis (type and number of enzymes, and chemical used for hydrolysis, and microbial fermentation), and amino acid sequence and chain length of peptides.

Encapsulation of bioactive peptides: a strategy to improve the stability, protect the nutraceutical bioactivity and support their food applications

In recent decades, bioactive peptides have become an emerging field of interest in the scientific community as well as the food, pharmaceutical, and cosmetics industries. A growing body of research indicates that consumption of bioactive peptides may play a vital role in health through their broad spectrum of bioactivity such as antioxidant, antihypertensive, antimicrobial, anti-inflammatory, immunomodulatory, and anti-proliferative activities. In addition, bioactive peptides can be used as food preservatives due to their antimicrobial and antioxidant activities. However, some factors limit their nutraceutical and commercial applications, including easy chemical degradation (e.g., pH, enzymatic), food matrix interaction, low water-solubility, hygroscopicity, and potential bitter taste. Bearing that in mind, the encapsulation of bioactive peptides in different materials can help overcome these challenges. Studies have demonstrated that encapsulation of bioactive peptides increases their bioactivity, improves their stability, sensory properties, increases solubility, and decreases hygroscopicity. However, there is limited scientific evidence about the bioavailability and food matrix interactions of encapsulated peptides. Besides, the diverse colloidal systems used to encapsulate bioactive peptides have shown stability and good encapsulation efficiency. This review provides an overview of current advances in the encapsulation of bioactive peptides, considering the technology, developments, and innovations in the last lustrum.

LC-MS-Based Metabolomics Discriminates Premium from Standard Chilean cv. Cabernet Sauvignon Wines from Different Valleys

Cabernet Sauvignon grapes in Chile, mainly grown between the 30° S and 36° S, account for more than 30% of Chilean wine production, and yield wines with different characteristics which influence their quality. The aim of this study was to apply a liquid chromatography – mass spectrometry (LC–MS)-based metabolomic protocol to investigate the quality differentiation in a sample set of monovarietal wines from eight valleys covering 679 km of the north-south extension. All samples were produced using a standardized red winemaking process and classified according to a company categorization in two major groups: premium and standard, and each group in two subcategories. The results pointed out that N-containing metabolites (mainly small peptides) are promising biomarkers for quality differentiation. Moreover, the premium wines were characterized by higher amounts of anthocyanins and other glycosylated and acetylated flavonoids, as well as phenolic acids; standard quality wines, on the other hand, presented stilbenoids and sulfonated catabolites of tryptophan and flavanols.

Pepsin Diffusivity and In Vitro Gastric Digestion of Soymilk as Affected by Binding of Tea Polyphenols to Soy Proteins

This study aimed to investigate the effect of tea polyphenol extract (TPE) on the in vitro gastric digestion of soymilk. Fluorescence recovery after photobleaching was applied to measure pepsin diffusivity in soymilk. The characteristics of soymilk digesta were evaluated by gel electrophoresis, degree of hydrolysis (DH), molecular weight distribution, free amino acid analysis, particle size, antioxidant capacity, and trypsin/chymotrypsin inhibitor activity (TIA/CIA). The binding between soy proteins and tea polyphenols could significantly impair in vitro gastric digestion of soymilk by decreasing pepsin diffusivity from 91.3 to 70.3 μm²/s and DH from 17.13 to 13.93% with 1.2 mg/g TPE addition. Soymilk with 0.6 mg/g TPE addition exhibited low TIA/CIA and a strong antioxidant capacity in gastric digesta, which might be good for the following intestinal digestion. A better understanding of the effect of polyphenol on the digestion of protein-based food may be beneficial to innovation in food manufacturing.

Antioxidant properties of Klunzinger's mullet (Liza klunzingeri) protein hydrolysates prepared with enzymatic hydrolysis using a commercial protease and microbial hydrolysis with Bacillus licheniformis

Antioxidant activity of Klunzinger's mullet (Liza klunzingeri) muscle hydrolysates obtained using Bacillus licheniformis fermentation and enzymatic hydrolysis was determined. Hydrolysates obtained after 6 days of fermentation with B. licheniformis showed the highest free radical scavenging activity, metal chelating ability and ferric reducing antioxidant power (FRAP) (P ≤ 0.05). Microbial fermentation led to a higher percentage of small peptides and higher solubility compared with Alcalase hydrolysis (P ≤ 0.05). Hydrolysates showing the highest antioxidant properties attenuated serum, liver, and kidney oxidative stress biomarkers in male Wister rats stressed by carbon tetrachloride (P ≤ 0.05). At 300 mg/kg oral administration, hydrolysates increased serum, renal, and hepatic total antioxidant capacity (TAC) (P ≤ 0.05) and reduced their elevated levels of malondialdehyde (MDA), nitric oxide (NO^•), and serum liver enzymes (AST, ALP, and ALT) (P ≤ 0.05). The hydrolysates were able to ameliorate hepatic damage by reducing necrosis, fatty changes, and inflammation. Results showed the antioxidant and hepato-toxic protective activities of Klunzinger's mullet muscle hydrolysates obtained using microbial fermentation, which may, therefore, potentially be considered as a functional food ingredient.

Peptide-Mineral Complexes: Understanding Their Chemical Interactions, Bioavailability, and Potential Application in Mitigating Micronutrient Deficiency

Iron, zinc, and calcium are essential micronutrients that play vital biological roles to maintain human health. Thus, their deficiencies are a public health concern worldwide. Mitigation of these deficiencies involves micronutrient fortification of staple foods, a strategy that can alter the physical and sensory properties of foods. Peptide-mineral complexes have been identified as promising alternatives for mineral-fortified functional foods or mineral supplements. This review outlines some of the methods used in the determination of the mineral chelating activities of food protein-derived peptides and the approaches for the preparation, purification and identification of mineral-binding peptides. The structure-activity relationship of mineral-binding peptides and the potential use of peptide-mineral complexes as functional food ingredients to mitigate micronutrient deficiency are discussed in relation to their chemical interactions, solubility, gastrointestinal digestion, absorption, and bioavailability. Finally, insights on the current challenges and future research directions in this area are provided.

In Vitro Pepsin Digestion Characteristics of Silver Carp (Hypophthalmichthys molitrix) Surimi Gels with Different Degrees of Cross-Linking Induced by Setting Time and Microbial Transglutaminase

Surimi gels are favored for their abundant proteins and unique taste. In this study, the pepsin digestion behaviors of surimi gels with different degrees of cross-linking induced by microbial transglutaminase (MTGase) and different setting times were investigated. For gels without (CK group) and with (TG group) MTGase, the slowest digestion rate (t_M/2 = 20.13 and 79.19 min for CK and TG group, respectively), the least amino acid concentration (5.32 and 3.73 μmol/mL for CK and TG group, respectively), and the peptide amounts (1355 and 1788 for CK and TG group, respectively) were obtained at a moderate setting time (1-4 h) with the finest microstructure. However, the excessive setting time (8-12 h) formed an inhomogenous network, which accelerated the hydrolysis of gel proteins (t_M/2 = 9.40 and 52.33 min for CK and TG group, respectively) and produced more amino acids (6.63 and 5.15 μmol/mL for CK and TG group, respectively) and peptide amounts (1644 and 2143 for CK and TG group, respectively). The above results also demonstrated that the presence of MTGase strengthened the compactness of gels as well as slowed down the digestion process with the release of less amino acids but more peptides. A large proportion of unique peptides were from the tail domain of myosin heavy chain. The discrepancy in bioactive peptides between different gels might be reduced in the subsequent intestinal digestion according to the in silico methods, demonstrating the diminished difference in the gastrointestinal digestion process in the aspect of releasing functional peptides. This study provides the theoretical basis and guideline in the field of gelation food digestion and surimi food industry to produce healthier surimi-based food.