Partial purification and identification of three antioxidant peptides with hepatoprotective effects from blue mussel ( Mytilus edulis ) hydrolysate by peptic hydrolysis

Sturgeon (Acipenser schrenckii) spinal cord peptides: Antioxidative and acetylcholinesterase inhibitory efficacy and mechanisms

Providing antioxidants and targeting acetylcholinesterase (AChE) are key strategies in treating neurocognitive dysfunction. In this study, bioactive sturgeon (Acipenser schrenckii) spinal cord peptides (SSCPs) with antioxidant and AChE inhibitory potency were extracted and separated from sturgeon spinal cord by enzymatic hydrolysis and ultrafiltration, and targeted peptide PGGW was screened via computer simulated molecular docking. Further, the molecular dynamic interactions of the PGGW with superoxide dismutase (SOD) and AChE were analyzed, and the protective effect of PGGW on glutamate-induced PC12 cells in vitro was evaluated. The <3 kDa fraction of SSCPs displays the most potent antioxidative efficacy (1 mg/mL, DPPH•: 89.07%, ABTS+: 76.35%). Molecular dynamics simulation showed that PGGW was stable within AChE and tightly bound to residues SER203, PHE295, ILE294 and TRP236. When combined with SOD, the indole group of PGGW was stuck inside SOD, but the tail chain PGG fluctuated greatly outside. Surface plasmon resonance demonstrated that PGGW has a high binding affinity for AChE (KD = 1.4 mM) and 0.01 mg/mL PGGW provided good protection against glutamate-induced apoptosis. The findings suggest a promising strategy for drug research on neurodegenerative diseases.

Blue mussel (Mytilus edulis) water extract ameliorates intestinal immune response in high-fat diet-streptozotocin-induced diabetic mice

Diabetes mellitus is a metabolic disease characterized by high blood glucose levels or hyperglycemia. Diabetes causes a decrease in immune function in the human body. Mytilus edulis has been identified as having anti-inflammatory properties and the ability to improve inflammation. Thus, this study aimed to investigate the function of Matsu M. edulis water extract (MWE) in mediating the regulation of immune responses and dysregulating the intestinal immune system in hyperglycemia mouse models. The mice were treated with MWE for seven weeks. The results showed that treatment with MWE has the ability to decrease triglyceride and total cholesterol concentrations. MWE also increases the interleukin (IL)-10 concentration and natural killer cell activation. It also improves the phagocytic capacity of monocytes in the colon and the proliferative capacity of lymphocytes in the mesentery. Furthermore, MWE also regulates the IL-6 concentration and the ratio of T helper 17 cells to regulatory T cells. Collectively, this extract can improve dyslipidemia, inflammatory responses, and dysregulation of the intestinal immune system. Therefore, M. edulis water extract can be used as an alternative treatment to reduce diabetes complications.

Bioactive peptides as a novel strategy to prevent alcoholic liver injury

Alcohol intake has become one of the leading risks to human health and wellness, among which acute and/or chronic alcohol-induced liver injury is a leading threaten, with few therapeutic options other than abstinence. In recent years, studies suggested that certain bioactive peptides from food sources could represent natural and safe alternatives for the prevention of alcoholic liver injury. Hence, this chapter focus on the advanced research on bioactive peptides exerting hepatoprotective activity against alcoholic liver injury. The main sources of protein, strategies for the preparation of hepatoprotective hydrolysates and peptides, underlying mechanisms of peptides on hepatoprotection, and possible structure-activity relationship between peptides and hepatoprotective activity were summarized and discussed, aiming to give a systematic insight into the research progress of hepatoprotective peptides. However, more efforts would be needed to give a clearer insight into the underlying mechanisms and structure-activity relationship before using hepatoprotective peptides as functional food ingredients or dietary supplements.

Unlocking the Therapeutic Potential of a Manila Clam-Derived Antioxidant Peptide: Insights into Mechanisms of Action and Cytoprotective Effects against Oxidative Stress

Reactive oxygen species (ROS) are implicated in various pathological conditions due to their ability to induce oxidative damage to cellular components. In this study, we investigated the antioxidant properties of a peptide isolated from the hydrolysate of Manila clam (Ruditapes philippinarum) muscle. Purification steps yielded RPTE2-2-4, exhibiting potent scavenging activities against DPPH•, HO•, and O2•-, akin to Vitamin C. Structural analysis showed that the isolated peptide, LFKKNLLTL, exhibited characteristics associated with antioxidant activity, including a short peptide length and the presence of aromatic and hydrophobic amino acid residues. Moreover, our study demonstrated the cytoprotective effects of the peptide against H2O2-induced oxidative stress in HepG2 cells. Pretreatment with the peptide resulted in a dose-dependent reduction in intracellular ROS levels and elevation of glutathione (GSH) levels, indicating its ability to modulate cellular defense mechanisms against oxidative damage. Furthermore, the peptide stimulated the expression of the cytoprotective enzyme heme oxygenase-1 (HO-1), further reinforcing its antioxidant properties. Overall, our findings highlight the potential of the Manila clam-derived peptide as a natural antioxidant agent with therapeutic implications for oxidative stress-related diseases. Further investigation into its mechanisms of action and in vivo efficacy is warranted to validate its therapeutic potential.

Identification and molecular mechanism of novel bifunctional peptides from Duroc × (Landrace × Yorkshire) pig dry-cured ham: A peptidomics and in silico analysis

Duroc × (Landrace × Yorkshire) pigs are popular in the Chinese market because of their rapid growth, leanness, and economic value. Despite their widespread use in dry-cured ham processing, there is a lack of research on the bioactive peptides of Duroc × (Landrace × Yorkshire) pig ham (DLYH). This study aimed to investigate the presence of peptides with antioxidant and α-glucosidase inhibitory activities in DLYH using peptidomics and in silico analysis. A total of 453 peptides were identified from DLYH, originating mainly from myosin, actin, and the EF-hand domain-containing protein. Notably, two peptides, YDEAGPSIVH (YH10) and FAGDDAPRAVF (FF11), emerged as novel bioactive peptides with antioxidant and α-glucosidase inhibitory activities. Among these peptides, YH10 exhibited a high DPPH radical scavenging activity (IC50 = 1.93 mM), ABTS radical scavenging activity (IC50 = 0.10 mM), α-glucosidase inhibitory activity (IC50 = 2.13 mM), and good gastrointestinal tolerance. Molecular docking analysis showed that YH10 was bound to the ABTS and DPPH radicals and the active site of α-glucosidase (3A4A) primarily through hydrogen bonding and hydrophobic interactions. Furthermore, molecular dynamics (MD) simulation indicated that the YH10-3A4A complexes maintained stable and compact conformations. In conclusion, our findings indicated that peptide YH10 derived from DLYH possesses bifunctional properties of α-glucosidase inhibition and antioxidant activity, which could be beneficial for maintaining ham quality and promoting human health.

Protein Hydrolysates from Fishery Processing By-Products: Production, Characteristics, Food Applications, and Challenges

Fish processing by-products such as frames, trimmings, and viscera of commercial fish species are rich in proteins. Thus, they could potentially be an economical source of proteins that may be used to obtain bioactive peptides and functional protein hydrolysates for the food and nutraceutical industries. The structure, composition, and biological activities of peptides and hydrolysates depend on the freshness and the actual composition of the material. Peptides isolated from fishery by-products showed antioxidant activity. Changes in hydrolysis parameters changed the sequence and properties of the peptides and determined their physiological functions. The optimization of the value of such peptides and the production costs must be considered for each particular source of marine by-products and for their specific food applications. This review will discuss the functional properties of fishery by-products prepared using hydrolysis and their potential food applications. It also reviews the structure-activity relationships of the antioxidant activity of peptides as well as challenges to the use of fishery by-products for protein hydrolysate production.

The recent progress of peptide regulators for the Wnt/β-catenin signaling pathway

Wnt signaling plays an important role in many biological processes such as stem cell self-renewal, cell proliferation, migration, and differentiation. The β-catenin-dependent signaling pathway mainly regulates cell proliferation, differentiation, and migration. In the Wnt/β-catenin signaling pathway, the Wnt family ligands transduce signals through LRP5/6 and Frizzled receptors to the Wnt/β-catenin signaling cascades. Wnt-targeted therapy has garnered extensive attention. The most commonly used approach in targeted therapy is small-molecule regulators. However, it is difficult for small-molecule regulators to make great progress due to their inherent defects. Therapeutic peptide regulators targeting the Wnt signaling pathway have become an alternative therapy, promising to fill the gaps in the clinical application of small-molecule regulators. In this review, we describe recent advances in peptide regulators for Wnt/β-catenin signaling.

Silver Carp (Hypophthalmichthys molitrix) Scales Collagen Peptides (SCPs): Preparation, Whitening Activity Screening and Characterization

This study involves the preparation of scale collagen peptides (SCPs) with whitening activity from silver carp (Hypophthalmichthys molitrix) and their characterization and peptide sequence identification. In this article, scanning electron microscopy (SEM) was used to observe structure changes of sliver carp scales; enzymatic hydrolysis was optimized through protease screening and response surface optimization. The ultrafiltration was used to separate SCPs and the whitening activity was comprehensively evaluated using radical scavenging rate and tyrosinase-inhibiting activity, among others. An optimal component was characterized and identified using various modern spectral analysis techniques. The results showed that the surface of silver carp scales after decalcification was smooth and clear. The pepsin had the highest peptide yield and tyrosinase-inhibiting activity (90.01% and 82.25%, respectively). The optimal enzymatic hydrolysis conditions were an enzyme dosage of 16.1%, a solid–liquid ratio of 1:15.6 and a time of 4.9 h. The proportions of hydrophobic and basic amino acids in the peptide composition were 32.15% and 13.12%, respectively. Compared with SCPs2, SCPs1 (6096.68–9513.70 Da) showed better ·OH scavenging ability, tyrosinase-inhibiting activity and moisture absorption. SCPs1 was a macromolecular fragment of type I collagen with a triple helix structure, containing three peptide sequences with the potential for tyrosinase activity inhibition (AGPPGADGQTGQRGE, SGPAGIAGPAGPRGPAGPNGPPGKD and KRGSTGEQGSTGPLGMRGPRGAA). These results show that SCPs1 is a collagen peptide product with whitening potential.

Musculus senhousei as a promising source of bioactive peptides protecting against alcohol-induced liver injury

Alcohol-induced liver injury has become a leading risk for human health, however, effective strategies for the prevention or treatment are still lacking. Hence, the present study explored the potential of Musculus senhousei as a source of hepatoprotective peptides against alcoholic liver injury using in vitro, in vivo and in silico methods. Results indicated that Musculus senhousei peptides (MSP, extracted by simulated gastrointestinal digestion of cooked mussel) exhibited notable antioxidant (ABTS and DPPH assays) and alcohol dehydrogenase (ADH) stabilizing activity in vitro. The ingestion of MSP markedly alleviated alcohol-induced liver injury in mice, as indicated by the decrease of serum transaminases (AST and ALT). In line with in vitro assays, significantly increased hepatic ADH activity and activated antioxidative defense system (GSH, SOD, GSH-Px and CAT) were observed, whereas the oxidative stress (MDA) was decreased. Peptidomic analysis revealed over 6000 peptides with favorable amino acid compositions, and a total of 20 potentially novel peptides with bioactivity and bioavailability were excavated among 746 of the most influential peptides using an in silico strategy. Peptides (i.e. WLPMKL, WLWLPA, RLC and RCL) were further synthesized and validated in vitro to be bioactive. These findings suggest that Musculus senhousei can be an ideal source of bioactive peptides for the prevention of alcoholic liver injury.

Transepithelial transport and cellular mechanisms of food-derived antioxidant peptides

Considering the involvement of oxidative stress in the etiology of many non-communicable diseases, food-derived antioxidant peptides (FDAPs) are strong candidates for nutraceutical development for disease prevention and management. This paper reviews current evidence on the transepithelial transport and cellular mechanisms of antioxidant activities of FDAPs. Several FDAPs have multiple health benefits such as anti-inflammatory and anti-photoaging activities, in addition to antioxidant properties through which they protect cellular components from oxidative damage. Some FDAPs have been shown to permeate the intestinal epithelium, which could facilitate their bioavailability and physiological bioactivities. Molecular mechanisms of FDAPs include suppression of oxidative stress as evidenced by reduction in intracellular reactive oxygen species production, lipid peroxidation and apoptotic protein activation as well as increase in antioxidant defense mechanisms (enzymatic and non-enzymatic). Since many FDAPs have demonstrated promising antioxidant activity, future investigation should focus on further elucidation of molecular mechanisms and human studies to explore their practical application for the prevention and management of oxidative stress-related diseases.

Fish Gelatin: Current Nutritional, Medicinal, Tissue Repair Applications and Carrier of Drug Delivery

Gelatin is obtained via partial denaturation of collagen and is extensively used in various industries. The majority of gelatin utilized globally is derived from a mammalian source. Several health and religious concerns associated with porcine/bovine gelatin were reported. Therefore, gelatin from a marine source is widely being investigated for its efficiency and utilization in a variety of applications as a potential substitute for porcine/bovine gelatin. Although fish gelatin is less durable and possesses lower melting and gelling temperatures compared to mammal-derived gelatin, various modifications are being reported to promote its rheological and functional properties to be efficiently employed. The present review describes in detail the current innovative applications of fish gelatin involving the food industry, drug delivery and possible therapeutic applications. Gelatin bioactive molecules may be utilized as carriers for drug delivery. Due to its versatility, gelatin can be used in different carrier systems, such as microparticles, nanoparticles, fibers and hydrogels. The present review also provides a perspective on the other potential pharmaceutical applications of fish gelatin, such as tissue regeneration, antioxidant supplementation, antihypertensive and anticancer treatments.

Identification of a novel peptide that activates alcohol dehydrogenase from crucian carp swim bladder and how it protects against acute alcohol-induced liver injury in mice

Alcoholism is a severe threat to public health, and there are no adequate treatments for alcoholic liver disease. The aim of this study was to identify bioactive peptides derived from natural proteins that prevent acute alcohol-induced liver injury. We identified a peptide with the sequence Gly-Leu-hydroxyproline-Gly-Glu-Arg (GLpGER) from the hydrolysate of crucian carp swim bladder using size-exclusion chromatography and reversed-phase chromatography. The in vitro EC₅₀ value of GLpGER to activate alcohol dehydrogenase (ADH) was 137.9 ± 9 µM. Molecular docking experiments indicated that the mechanism by which GLpGER activates ADH may be related to the formation of stable complexes with ADH active pockets through hydrogen bonding, and electrostatic and hydrophobic interactions. Oral administration of GLpGER one hour before acute alcohol ingestion significantly increased alcohol metabolism, manifesting as reduced incidence of the loss of righting reflex, increased alcohol tolerance time, shortened sobering time, and decreased blood alcohol concentration level. GLpGER restored liver ADH activity, maintained the typical morphology of hepatocytes, and reduced serum levels of alanine aminotransferase and aspartate aminotransferase. These findings suggest that GLpGER might reduce acute alcohol-induced liver injury and may have the potential to be developed as an anti-inebriation ingredient.

Seventeen novel angiotensin converting enzyme (ACE) inhibitory peptides from protein hydrolysate of Mytilus edulis: Isolation, identification, molecular docking study, and protective function on HUVECs

In the study, seventeen angiotensin converting enzyme (ACE) inhibitory peptides were isolated from protein hydrolysate of blue mussel (Mytilus edulis) and identified as MFR, MFV, FV, KP, QP, QVK, IK,...

Biomaterials from the sea: Future building blocks for biomedical applications

Marine resources have tremendous potential for developing high-value biomaterials. The last decade has seen an increasing number of biomaterials that originate from marine organisms. This field is rapidly evolving. Marine biomaterials experience several periods of discovery and development ranging from coralline bone graft to polysaccharide-based biomaterials. The latter are represented by chitin and chitosan, marine-derived collagen, and composites of different organisms of marine origin. The diversity of marine natural products, their properties and applications are discussed thoroughly in the present review. These materials are easily available and possess excellent biocompatibility, biodegradability and potent bioactive characteristics. Important applications of marine biomaterials include medical applications, antimicrobial agents, drug delivery agents, anticoagulants, rehabilitation of diseases such as cardiovascular diseases, bone diseases and diabetes, as well as comestible, cosmetic and industrial applications.

Cytoprotective Peptides from Blue Mussel Protein Hydrolysates: Identification and Mechanism Investigation in Human Umbilical Vein Endothelial Cells Injury

Cardiovascular disease represents a leading cause of mortality and is often characterized by the emergence of endothelial dysfunction (ED), a physiologic condition that takes place in the early progress of atherosclerosis. In this study, two cytoprotective peptides derived from blue mussel chymotrypsin hydrolysates with the sequence of EPTF and FTVN were purified and identified. Molecular mechanisms underlying the cytoprotective effects against oxidative stress which lead to human umbilical vein endothelial cells (HUVEC) injury were investigated. The results showed that pretreatment of EPTF, FTVN and their combination (1:1) in 0.1 mg/mL significantly reduced HUVEC death due to H₂O₂ exposure. The cytoprotective mechanism of these peptides involves an improvement in the cellular antioxidant defense system, as indicated by the suppression of the intracellular ROS generation through upregulation of the cytoprotective enzyme heme oxygenase-1. In addition, H₂O₂ exposure triggers HUVEC damage through the apoptosis process, as evidenced by increased cytochrome C release, Bax protein expression, and the elevated amount of activated caspase-3, however in HUVEC pretreated with peptides and their combination, the presence of those apoptotic stimuli was significantly decreased. Each peptide showed similar cytoprotective effect but no synergistic effect. Taken together, these peptides may be especially important in protecting against oxidative stress-mediated ED.

Antioxidant Mechanisms of the Oligopeptides (FWKVV and FMPLH) from Muscle Hydrolysate of Miiuy Croaker against Oxidative Damage of HUVECs

In this work, the antioxidant mechanisms of bioactive oligopeptides (FWKVV and FMPLH) from protein hydrolysate of miiuy croaker muscle against H₂O₂-damaged human umbilical vein endothelial cells (HUVECs) were researched systemically. The finding demonstrated that the HUVEC viability treated with ten antioxidant peptides (M1 to M10) at 100.0 μM for 24 h was not significantly affected compared with that of the normal group (P < 0.05). Furthermore, FWKVV and FMPLH at 100.0 μM could very significantly enhance the viabilities (75.89 ± 1.79% and 70.03 ± 4.37%) of oxidative-damaged HUVECs by H₂O₂ compared with those of the model group (51.66 ± 2.48%) (P < 0.001). The results indicated that FWKVV and FMPLH played their protective functions through increasing the levels of antioxidant enzymes including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and decreasing the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and nitric oxide (NO) in oxidative-damaged HUVECs in a dose-dependent manner. In addition, the comet assay revealed that FWKVV and FMPLH could dose-dependently protect deoxyribonucleic acid (DNA) from oxidative damage in the HUVEC model. These results suggested that antioxidant pentapeptides (FWKVV and FMPLH) could serve as potential antioxidant additives applied in the food products, pharmaceuticals, and health supplements.

Hydrolysate from Mussel Mytilus galloprovincialis Meat: Enzymatic Hydrolysis, Optimization and Bioactive Properties

Mussel production generates losses and waste since their commercialisation must be aligned with target market criteria. Since mussels are rich in proteins, their meat can be explored as a source of bioactive hydrolysates. Thus, the main objective of this study was to establish the optimal production conditions through two Box–Behnken designs to produce, by enzymatic hydrolysis (using subtilisin and corolase), hydrolysates rich in proteins and with bioactive properties. The factorial design allowed for the evaluation of the effects of three factors (hydrolysis temperature, enzyme ratio, and hydrolysis time) on protein/peptides release as well as antioxidant and anti-hypertensive properties of the hydrolysates. The hydrolysates produced using the optimised conditions using the subtilisin protease showed 45.0 ± 0.38% of protein, antioxidant activity via ORAC method of 485.63 ± 60.65 µmol TE/g of hydrolysate, and an IC₅₀ for the inhibition of ACE of 1.0 ± 0.56 mg of protein/mL. The hydrolysates produced using corolase showed 46.35 ± 1.12% of protein, antioxidant activity of 389.48 ± 0.21 µmol TE/g of hydrolysate, and an IC₅₀ for the inhibition of ACE of 3.7 ± 0.33 mg of protein/mL. Mussel meat losses and waste can be used as a source of hydrolysates rich in peptides with relevant bioactive properties, and showing potential for use as ingredients in different industries, such as food and cosmetics, contributing to a circular economy and reducing world waste.

Antioxidant activities of peptides derived from mutton ham, Xuanwei ham and Jinhua ham

The aim of the study was to evaluate antioxidant activity of crude peptides with molecular weight less than 3 KDa extracted from Xuanwei ham, Jinhua ham and mutton ham. UPLC-Q-TOF-MS/MS was used for composition analysis of peptides and homologous protein matching. Further, crude peptide (<3 KDa) was purified using G-15 gel filtration chromatography, and the main antioxidant peptide identified. Analysis showed that mutton ham peptide (MHP) has the highest Fe²⁺ chelating ability, whereas Jinhua ham peptide (JHP) had the highest ABTS and DPPH free radical scavenging ability (P < 0.05). A total of 346, 203 and 296 peptides were identified in JHP, Xuanwei ham peptides (XHP) and MHP, respectively. Most of the peptides were derived from myosin, accounting for 21.97% in JHP, 18.72% in XHP, and 21.96% in MHP. Myosin, actin, myoglobin, troponin, tropomyosin and pyruvate kinase proteins were the main source of peptide differences in the three types of dry cured ham.

The three-spot seahorse-derived peptide PAGPRGPA attenuates ethanol-induced oxidative stress in LO2 cells through MAPKs, the Keap1/Nrf2 signalling pathway and amino acid metabolism

Alcoholic liver diseases (ALDs) impose a substantial health burden on many countries. Bioactive peptides isolated from people, marine organisms, animals and plants have shown hepatoprotective effects on animal and hepatocyte models. In this study, an LO2 cell model of ethanol-induced liver injury in vitro was constructed. We investigated the hepatoprotective effects of the three-spot seahorse bioactive peptide (SBP) PAGPRGPA (Pro-Ala-Gly-Pro-Arg-Gly-Pro-Ala; 721.39 Da) and characterised the underlying metabolic pathways and biomarkers through a nontargeted metabolomics approach. We found that ethanol-induced oxidative stress impaired the cellular antioxidant system, leading to an imbalance in cellular homeostasis. However, SBP with a certain antioxidant activity inhibited reactive oxygen species (ROS) production, excessive intracellular Ca2+ level and abnormal apoptosis. It also restored the superoxide dismutase (SOD) and glutathione (GSH) levels and attenuated ethanol-induced oxidative damage and inflammation. SBP suppressed the activation of mitogen-activated protein kinase (MAPK) in ethanol-stimulated LO2 cells. It also regulated the Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) signalling pathway to protect LO2 cells from oxidative damage by promoting the expression of antioxidant enzymes, such as heme oxygenase-1 (HO-1). Furthermore, the metabolomics approach demonstrated nine different biomarkers and six metabolic pathways. In summary, the hepatoprotective mechanisms of SBP in vitro, which can be attributed to the upregulation of antioxidant substances and amino acid metabolism, attenuate ethanol-induced oxidative stress.

Cytoprotective Role of Edible Seahorse (Hippocampus abdominalis)-Derived Peptides in H2O2-Induced Oxidative Stress in Human Umbilical Vein Endothelial Cells

Oxidative stress-induced endothelial dysfunction is strongly linked to the pathogenesis of cardiovascular diseases. A previous study revealed that seahorse hydrolysates ameliorated oxidative stress-mediated human umbilical vein endothelial cells (HUVECs) injury. However, the responsible compounds have not yet been identified. This study aimed to identify cytoprotective peptides and to investigate the molecular mechanism underlying the cytoprotective role in H₂O₂-induced HUVECs injury. After purification by gel filtration and HPLC, two peptides were sequenced by liquid chromatography-tandem mass spectrometry as HGSH (436.43 Da) and KGPSW (573.65 Da). The synthesized peptides and their combination (1:1 ratio) showed significant HUVECs protection effect at 100 μg/mL against H₂O₂-induced oxidative damage via significantly reducing intracellular reactive oxygen species (ROS). Two peptides and their combination treatment resulted in the increased heme oxygenase-1 (HO-1), a phase II detoxifying enzyme, through the activation of nuclear transcription factor-erythroid 2-related factor (Nrf2). Additionally, cell cycle and nuclear staining analysis revealed that two peptides and their combination significantly protected H₂O₂-induced cell death through antiapoptotic action. Two peptides and their combination treatment led to inhibit the expression of proapoptotic Bax, the release of cytochrome C into the cytosol, the activation of caspase 3 by H₂O₂ treatment in HUVECs, whereas antiapoptotic Bcl-2 expression was increased with concomitant downregulation of Bax/Bcl-2 ratio. Taken together, these results suggest that seahorse-derived peptides may be a promising agent for oxidative stress-related cardiovascular diseases.

Blue Mussel-Derived Peptides PIISVYWK and FSVVPSPK Trigger Wnt/β-Catenin Signaling-Mediated Osteogenesis in Human Bone Marrow Mesenchymal Stem Cells

Marine-derived bioactive peptides have shown potential bone health promoting effects. Although various marine-derived bioactive peptides have potential nutraceutical or pharmaceutical properties, only a few of them are commercially available. This study presented an osteogenic mechanism of blue mussel-derived peptides PIISVYWK and FSVVPSPK as potential bone health promoting agents in human bone marrow-derived mesenchymal stem cells (hBMMSCs). Alkaline phosphatase (ALP) activity and mineralization were stimulated using PIISVYWK and FSVVPSPK as early and late markers of osteogenesis in a concentration-dependent manner. Western blot and RT-qPCR results revealed that PIISVYWK and FSVVPSPK increased osteoblast differentiation of hBMMSCs by activating canonical Wnt/β-catenin signaling-related proteins and mRNAs. Immunofluorescence images confirmed nuclear translocation of β-catenin in osteogenic differentiation. Treatment with the pharmacological inhibitor DKK-1 blocked PIISVYWK- and FSVVPSPK-induced ALP activity and mineralization, as well as mRNA expression of the canonical Wnt/β-catenin signaling pathway in hBMMSC differentiation into osteoblasts. These findings suggested that PIISVYWK and FSVVPSPK promoted the canonical Wnt/β-catenin signaling pathway in osteogenesis of hBMMSCs. Blue mussel-derived PIISVYWK and FSVVPSPK might help develop peptide-based therapeutic agents for bone-related diseases.

Ark shell protein-derived bioactive peptides promote osteoblastic differentiation through upregulation of the canonical Wnt/β-catenin signaling in human bone marrow-derived mesenchymal stem cells

In this study, the stimulating effect of ark shell protein-derived peptides AWLNH and PHDL on osteoblast differentiation in human bone marrow-derived mesenchymal stem cells (hBMMSCs) and its molecular mechanism was investigated. The hBMMSCs were cultured with two peptides and osteogenic markers were analyzed. Results showed that enhanced ALP activity and calcification were detected in the presence of AWLNH and PHDL. Based on western blotting, RT-qPCR, and immunostaining analysis, AWLNH and PHDL are specific for osteoblast differentiation of hBMMSCs through activating the canonical Wnt/β-catenin signaling pathway followed by activating Runx2, osterix, and type I collagen. Loss-of-function assay with DKK-1, a Wnt antagonist, showed that the canonical Wnt/β-catenin signaling was essential for AWLNH and PHDL-induced osteogenesis in hBMMSCs. These findings suggested that AWLNH and PHDL can stimulate osteoblast differentiation of hBMMSCs via upregulating the canonical Wnt/β-catenin signaling and may be useful for a potential nutraceuticals or pharmaceuticals to treat osteoporosis. PRACTICAL APPLICATIONS: Ark shell is a popular foodstuff in Korea. However, biological effects of its protein and peptide have not been explored in many ways. This study demonstrated that ark shell protein-derived peptides promoted osteoblast differentiation in hBMMSCs through upregulating the canonical Wnt/β-catenin signaling. The results of this study could be a basis to promote its application as functional foods and/or nutraceuticals.

Anti-Osteoporotic Effects of Antioxidant Peptides PIISVYWK and FSVVPSPK from Mytilus edulis on Ovariectomized Mice

Numerous amounts of evidence suggest that bioactive peptides with diverse physiological activities can be nutraceuticals or potential drug candidates. In this study, blue mussel-derived antioxidant peptides PIISVYWK and FSVVPSPK were subjected to evaluate their osteogenic effect in mouse bone marrow mesenchymal stem cells (mBMMSCs) followed by an in vivo anti-osteoporotic effect. Treatment of PIISVYWK and FSVVPSPK on mBMMSCs stimulated alkaline phosphatase activity and calcification. Western blot results revealed that PIISVYWK and FSVVPSPK increased the expression of bone morphogenetic protein-2/4 (BMP-2/4) followed by upregulating p-Smad1/5, type I collagen, and transcription factors including Runx2 and osterix in mBMMSCs. Two peptides also activated the phosphorylation of MAPKs (p-p38, p-ERK, and p-JNK). Treatment of MAPK inhibitors significantly inhibited the BMP signaling pathway, indicating that PIISVYWK and FSVVPSPK stimulated osteoblast differentiation of mBMMSCs through the MAPK-dependent BMP signaling pathway. The anti-osteoporotic effect of PIISVYWK and FSVVPSPK in ovariectomized (OVX) mice was investigated. Treatment of PIISVYWK and FSVVPSPK for ten weeks showed a notable anti-osteoporotic effect in OVX mice via increasing bone mineral density and other bone parameters compared to OVX mice without peptides. Serum analysis also showed that treatment of PIISVYWK and FSVVPSPK completely reduced osteocalcin and ALP (alkAline phosphatase) activity. Taken together, these results suggest that PIISVYWK and FSVVPSPK could be health-promoting functional food ingredients against osteoporosis.

Extraction of antioxidant peptides from rice dreg protein hydrolysate via an angling method

Selective enrichment of the highly active antioxidant peptides is required as the lack of an efficient method leads to long screening processes, hampering the research of antioxidant peptides. A simple synthetic metal-organic framework MIL-53 (Cr) was initially applied to extract specific antioxidant peptides from rice dreg protein hydrolysate. The highest active fraction was further purified by reversed-phase high-performance liquid chromatography. The antioxidant peptides with the highest antioxidant activities were identified as Gly-Asp-Met-Asn-Pro and Leu-Leu-Leu-Arg-Trp by LC-MS. These two peptides were synthesized and also exhibited good scavenging activity on the DPPH free radical, superoxide anion free radical and hydroxyl radical, and good chelating ability on Fe²⁺. The results confirmed that the angling method was effective for antioxidant peptide enrichment from protein hydrolysates.

Low molecular weight blue mussel hydrolysates inhibit adipogenesis in mouse mesenchymal stem cells through upregulating HO-1/Nrf2 pathway

Blue mussel proteins are a good source of bioactive peptides. In this study, blue mussel hydrolysate (BMH) with anti-adipogenic effect in mouse mesenchymal stem cells (mMSC) was produced by peptic hydrolysis at 1:500 of pepsin/substrate ratio for 120 min. Additionally, BMH with below 1 kDa (BMH < 1 kDa) showed the highest anti-adipogenic effect in mMSC. BMH < 1 kDa increased lipolysis and down-regulated adipogenic transcription factors including peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), and sterol regulatory element-binding protein 1 (SREBP1). Generation of intracellular reactive oxygen species during adipogenesis was markedly decreased by BMH < 1 kDa treatment, which is attributed to the up-regulation of heme oxygenase-1 (HO-1) through Nrf2 translocation into the nucleus. Moreover, ZnPP, HO-1 inhibitor, treatment abolished BMH < 1 kDa-mediated HO-1 expression and anti-adipogenic effect in mMSCs through down-regulating adipogenic transcription factors. Taken together, BMH < 1 kDa may be a potential ingredient of nutraceuticals and/or functional foods in ameliorating obesity.

Antioxidant and anti-inflammatory peptide fraction from oyster soft tissue by enzymatic hydrolysis

Recent studies have confirmed that the peptide fractions derived from marine organisms exhibit good antioxidant and anti-inflammatory activity, and oyster is an excellent nutrient resource with high-protein content. In this study, the peptide fractions from oyster soft tissue were prepared after hydrolysis by pepsin (pH 2, 37°C), trypsin (pH 8, 37°C), and Maxipro PSP (pH 4.2, 50°C) with the optimized parameters (enzyme-to-substrate (E/S) ratio, 1:100 (w/w); hydrolysis time, 4 hr), respectively. Four fractions named as PEP-1, PEP-2, TRYP-2, and MIX-2 were obtained after separation with elution consisting of 20% or 40% ethanol. The MIX-2 exhibited the highest hydrophobicity correlated well with its hydrophobic amino acid content, and TRYP-2 exhibited much better antioxidant activity than other three elution samples. Furthermore, all of the bioactive peptide fractions were noncytotoxic and could selectively repress pro-inflammatory mediators, TNF-α, IL-1β, IL-6, and i-NOS, at transcription level in RAW264.7 macrophage cells after LPS stimulation. The result suggests that the peptide fraction TRYP-2 from oyster soft tissue hydrolysates might be a potential resource for natural anti-inflammatory components.

Antioxidant Peptides from the Protein Hydrolysate of Monkfish (Lophius litulon) Muscle: Purification, Identification, and Cytoprotective Function on HepG2 Cells Damage by H2O2

In the work, defatted muscle proteins of monkfish (Lophius litulon) were separately hydrolyzed by pepsin, trypsin, and in vitro gastrointestinal (GI) digestion methods, and antioxidant peptides were isolated from proteins hydrolysate of monkfish muscle using ultrafiltration and chromatography processes. The antioxidant activities of isolated peptides were evaluated using radical scavenging and lipid peroxidation assays and H2O2-induced model of HepG2 cells. In which, the cell viability, reactive oxygen species (ROS) content, and antioxidant enzymes and malondialdehyde (MDA) levels were measured for evaluating the protective extent on HepG2 cells damaged by H2O2. The results indicated that the hydrolysate (MPTH) prepared using in vitro GI digestion method showed the highest degree of hydrolysis (27.24 ± 1.57%) and scavenging activity on a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (44.54 ± 3.12%) and hydroxyl radical (41.32 ± 2.73%) at the concentration of 5 mg protein/mL among the three hydrolysates. Subsequently, thirteen antioxidant peptides (MMP-1 to MMP-13) were isolated from MPTH. According to their DPPH radical and hydroxyl radical scavenging activity, three peptides with the highest antioxidant activity were selected and identified as EDIVCW (MMP-4), MEPVW (MMP-7), and YWDAW (MMP-12) with molecular weights of 763.82, 660.75, and 739.75 Da, respectively. EDIVCW, MEPVW, and YWDAW showed high scavenging activities on DPPH radical (EC50 0.39, 0.62, and 0.51 mg/mL, respectively), hydroxyl radical (EC50 0.61, 0.38, and 0.32 mg/mL, respectively), and superoxide anion radical (EC50 0.76, 0.94, 0.48 mg/mL, respectively). EDIVCW and YWDAW showed equivalent inhibiting ability on lipid peroxidation with glutathione in the linoleic acid model system. Moreover, EDIVCW, MEPVW, and YWDAW had no cytotoxicity to HepG2 cells at the concentration of 100.0 µM and could concentration-dependently protect HepG2 cells from H2O2-induced oxidative damage through decreasing the levels of reactive oxygen species (ROS) and MDA and activating intracellular antioxidant enzymes of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). These present results indicated that the protein hydrolysate and isolated antioxidant peptides from monkfish muscle, especially YWDAW could serve as powerful antioxidants applied in the treatment of some liver diseases and healthcare products associated with oxidative stress.

Isolation and identification of antioxidant peptides from tartary buckwheat albumin (Fagopyrum tataricum Gaertn.) and their antioxidant activities

Tartary buckwheat (Fagopyrum tataricum Gaertn.) albumin was hydrolyzed by alkaline protease, and three new antioxidant peptides (P1, P2, and P3) were successfully separated from the hydrolysate (TBAH). The sequences of the three antioxidant peptides were Gly-Glu-Val-Pro-Trp (GEVPW), Tyr-Met-Glu-Asn-Phe (YMENF), and Ala-Phe-Tyr-Arg-Trp (AFYRW), and their molecular weights were 586.65, 702.79, and 741.85 Da, respectively. All three peptides have a good antioxidant capacity, and P3 (AFYRW) demonstrates the best antioxidant activity of the three. The IC₅₀ values of AFYRW for scavenging hydroxyl radicals (OH·) and (1,1-diphenyl-2-picrylhydrazyl) DPPH· free radicals were 0.65 and 0.64 mM, respectively. In addition, AFYRW exhibits the strongest lipid peroxidation inhibition ability and the highest reducing power. The results of this research indicate that the three isolated peptides can be used in the development of various antioxidant additives in the food and pharmaceutical industries.

Effects of collagen peptides from skate (Raja kenojei) skin on improvements of the insulin signaling pathway via attenuation of oxidative stress and inflammation

It has been well established that hepatic insulin signaling is significantly affected by the antioxidative status of the liver.

Housefly Pupae-Derived Antioxidant Peptides Exerting Neuroprotective Effects on Hydrogen Peroxide-Induced Oxidative Damage in PC12 Cells

In this study, two antioxidant peptides were identified and characterized from the alcalase-hydrolysate of housefly (Musca domestica L.) pupae guided by ABTS cation radical scavenging activity. Peptides sequences were identified as DFTPVCTTELGR (DR12, 1338.48 Da) and ARFEELCSDLFR (AR12, 1485.66 Da) using nano-liquid chromatography-tandem mass spectrometry (LC-MS/MS). Both DR12 and AR12 exert strong ABTS cation radical scavenging ability with EC₅₀ values of 0.39 and 0.35 mM, respectively. Moreover, AR12 can effectively protect PC12 cells from oxidative damage induced by hydrogen peroxide (H₂O₂) by decreasing intracellular reactive oxygen species (ROS) and malonaldehyde (MDA), recovering cellular mitochondrial membrane potential (MMP), and increasing the activity of intracellular superoxide dismutase (SOD). Stability tests suggest that AR12 is competent for the challenge of heating, acid, alkali or simulated gastrointestinal (GI) digestion and exhibits great activity to remove ABTS cation radical. DR12 shows a great stability against heating, but its antioxidative ability declines after being treated with acid, alkali or simulated GI digestion. In general, both DR12 and AR12 identified from housefly pupae hydrolysate stand a chance of being potential antioxidants or precursors to antioxidants and AR12 might be applied in the field of neuroprotection.

Antioxidant Characteristics and Identification of Peptides from Sorghum Kafirin Hydrolysates

Grain sorghum is gaining interest for various uses as a highly sustainable crop. Kafirin is the main storage protein in grain sorghum. However, the antioxidant activities of kafirin hydrolysates have not been systematically investigated. The objectives of this study were to characterize the antioxidative hydrolysates and their ultrafiltrated fractions from sorghum kafirin using chemical assays and model systems and to identify the representative peptides. Kafirin Neutrase hydrolysates displayed promising yield and antioxidant capacity among those prepared with several different proteases. The effects of critical variables including protein substrate content, enzyme-to-substrate ratio, and reaction time on antioxidant production were studied. Selected hydrolysates were further fractionated through ultrafiltration and gel filtration chromatography (GFC). Medium-sized fraction (3 to 10 kDa) revealed relatively higher total phenolic content and stronger antioxidative activities with regard to free radical scavenging activity, metal ion chelating activity, reducing power, and oxygen radical absorbance capacity. In an oil-in-water emulsion system, incorporation of selected fraction of hydrolysates inhibited the formation of primary and secondary oxidation products by 83.03% and 65.59%, respectively, by the end of a 14-day incubation period. Similar oxidation inhibition effect was also observed in a ground meat system. Peptide compositions of the most promising fraction from GFC and reversed-phase high-performance liquid chromatography were identified using matrix-assisted laser desorption ionization-time of flight/time of flight mass spectrometry. PRACTICAL APPLICATION: This study provided a feasible approach to produce peptide antioxidants from sorghum kafirin. The novel naturally derived antioxidants could be potentially used as alternatives or synergetic components to synthetic antioxidants in improving the oxidative stability of various food products.

Purification and Characterization of Antioxidant Peptides from Alcalase-Hydrolyzed Soybean ( Glycine max L.) Hydrolysate and Their Cytoprotective Effects in Human Intestinal Caco-2 Cells

This study aimed to purify and identify antioxidant peptides from the low-molecular-weight fraction (SPH-I, MW < 3 kDa) of Alcalase-hydrolyzed soybean ( Glycine max L.) hydrolysate and further evaluate the cytoprotective effects of synthesized peptides against oxidative stress in human intestinal Caco-2 cells. After purification by gel filtration chromatography and reversed-phase HPLC, four major peptides were sequenced by nano-LC-ESI-MS/MS as VVFVDRL (847 Da, SPH-IA), VIYVVDLR (976 Da, SPH-IB), IYVVDLR (877 Da, SPH-IC), and IYVFVR (795 Da, SPH-ID). The antioxidant peptides were synthesized and displayed desirable DPPH radical-scavenging activity (from 16.5 ± 0.5 to 20.3 ± 1.0 μM Trolox equivalent (TE)/μM), ABTS•+ radical-scavenging activity (from 3.42 ± 0.2 to 4.24 ± 0.4 mM TE/μM), ORAC (from 143 ± 2.1 to 171 ± 4.8 μM TE/μM), and FRAP (from 54.7 ± 1.2 to 79.0 ± 0.6 mM Fe2+/μM). Moreover, the synthesized peptides protected Caco-2 cells against H2O2-induced oxidative damage via significantly downregulating intracellular ROS generation and lipid peroxidation ( p < 0.05). Additionally, SPH-IC and SPH-ID statistically upregulated total reduced glutathione synthesis, enhanced activities of catalase and glutathione reductase, and suppressed ROS-mediated inflammatory responses via inhibiting interleukin-8 secretion ( p < 0.05).

Four Antioxidant Peptides from Protein Hydrolysate of Red Stingray (Dasyatis akajei) Cartilages: Isolation, Identification, and In Vitro Activity Evaluation

In the work, water-soluble proteins of red stingray (Dasyatis akajei) cartilages were extracted by guanidine hydrochloride and hydrolyzed using trypsin. Subsequently, four antioxidant peptides (RSHP-A, RSHP-B, RSHP-C, and RSHP-D) were isolated from the water-soluble protein hydrolysate while using ultrafiltration and chromatographic techniques, and the amino acid sequences of RSHP-A, RSHP-B, RSHP-C, and RSHP-D were identified as Val-Pro-Arg (VPR), Ile-Glu-Pro-His (IEPH), Leu-Glu-Glu--Glu-Glu (LEEEE), and Ile-Glu-Glu-Glu-Gln (IEEEQ), with molecular weights of 370.46 Da, 494.55 Da, 647.64 Da, and 646.66 Da, respectively. VPR, IEPH, LEEEE, and IEEEQ exhibited good scavenging activities on the DPPH radical (EC50 values of 4.61, 1.90, 3.69, and 4.01 mg/mL, respectively), hydroxyl radical (EC50 values of 0.77, 0.46, 0.70, and 1.30 mg/mL, respectively), superoxide anion radical (EC50 values of 0.08, 0.17, 0.15, and 0.16 mg/mL, respectively), and ABTS cation radical (EC50 values of 0.15, 0.11, 0.19, and 0.18 mg/mL, respectively). Among the four isolated antioxidant peptides, IEPH showed the strongest reducing power and lipid peroxidation inhibition activity, but LEEEE showed the highest Fe2+-chelating ability. The present results suggested that VPR, IEPH, LEEEE, and IEEEQ might have the possibility of being an antioxidant additive that is used in functional food and pharmaceuticals.