Antioxidant and anti-inflammatory peptide fraction from salmon byproduct protein hydrolysates by peptic hydrolysis

Atlantic salmon (Salmo salar) waste as a unique source of biofunctional protein hydrolysates: Emerging productions, promising applications, and challenges mitigation

The Atlantic salmon is an extremely popular fish for its nutritional value and unique taste among several fish species. Researchers are focusing on the utilization of Atlantic salmon waste for generating protein hydrolysates rich in peptides and amino acids and investigating their health benefits. Several technological approaches, including enzymatic, chemical, and the recently developed subcritical water hydrolysis, are currently used for the production of Atlantic salmon waste protein hydrolysates. Hydrolyzing various wastes, e.g., heads, bones, skin, viscera, and trimmings, possessing antioxidant, blood pressure regulatory, antidiabetic, and anti-inflammatory properties, resulting in applications in human foods and nutraceuticals, animal farming, pharmaceuticals, cell culture, and cosmetics industries. Furthermore, future applications, constraints several challenges associated with industrial hydrolysate production, including sensory, safety, and economic constraints, which could be overcome by suggested techno processing measures. Further studies are recommended for developing large-scale, commercially viable production methods, focusing on eradicating sensory constraints and facilitating large-scale application.

Protein and Polysaccharide Recovery from Shrimp Wastes by Natural Deep Eutectic Solvent Mediated Subcritical Water Hydrolysis for Biodegradable Film

Environmental pollution is a significant problem due to the improper disposal of plastics and shrimp shells outdoors. Therefore, the synthesis of biodegradable film from waste materials is highly important. The novelty of this research lies in the extraction of protein hydrolysates and chitosan from shrimp shells, as well as the fabrication of biodegradable film from these materials. In this study, the composite films were produced using the solution casting method. Moreover, the combined effect of ultrasound pretreatments (UPT) and natural deep eutectic solvents (NADES) was investigated as extraction media, to determine their potential impact on shrimp waste subcritical water hydrolysis (SWH). Shrimp shells were submitted to UPT in NADES solution, followed by SWH at different temperatures ranging from 150 to 230 °C under 3 MPa for 20 min. Then, the physiochemical properties and bioactivities of the hydrolysates were assessed to determine their suitability for use in biodegradable packaging films. Additionally, the physiochemical properties and bioactivities of the resulting hydrolysates were also analyzed. The highest amount of protein (391.96 ± 0.48 mg BSA/g) was obtained at 190 °C/UPT/NADES, and the average molecular size of the protein molecules was less than 1000 Da with different kinds of peptide. Overall, combined UPT and SWH treatments yielded higher antioxidant activity levels than individual treatments. Finally, the application of composite films was evaluated by wrapping fish samples and assessing their lipid oxidation. The use of higher concentrations of protein hydrolysates significantly delayed changes in the samples, thereby demonstrating the film's applicability.

Evaluation of Prebiotic and Health-Promoting Functions of Honeybee Brood Biopeptides and Their Maillard Reaction Conjugates

This study addresses the growing interest in natural functional ingredients by evaluating the prebiotic and health-promoting functions of honeybee brood biopeptides (HBb-Bps) and their conjugates. The purpose was to investigate their antioxidant activities, enzyme inhibition properties, and effects on probiotic growth and short-chain fatty acid (SCFA) production. The HBb-Bps were conjugated with honey, glucose, and fructose via the Maillard reaction. Antioxidant activities were assessed using DPPH and ABTS assays. The inhibitory effects on amylase, pancreatic lipase, and the angiotensin-converting enzyme (ACE) were measured. Probiotic growth and SCFA production were evaluated using L. plantarum TISTR846, and L. lactis TISTR1464. The HBb-Bps and their conjugates exhibited enhanced antioxidant activities post-Maillard reaction. They showed moderate enzyme inhibition, which decreased after conjugation. However, ACE inhibition increased with conjugation. The HBb-Bps significantly promoted probiotic growth and SCFA production, with further enhancement by the Maillard reaction. Overall, the HBb-Bps and their conjugates demonstrate significant prebiotic and health-promoting functions, suggesting their potential as natural ingredients in functional foods and nutraceuticals. Further research should focus on the in vivo effects and, given their solubility and stability these biopeptides could be incorporated into functional food formulations, such as health beverages, protein bars, and other fortified foods designed to deliver specific health benefits.

Antioxidant peptides, the guardian of life from oxidative stress

Reactive oxygen species (ROS) are produced during oxidative metabolism in aerobic organisms. Under normal conditions, ROS production and elimination are in a relatively balanced state. However, under internal or external environmental stress, such as high glucose levels or UV radiation, ROS production can increase significantly, leading to oxidative stress. Excess ROS production not only damages biomolecules but is also closely associated with the pathogenesis of many diseases, such as skin photoaging, diabetes, and cancer. Antioxidant peptides (AOPs) are naturally occurring or artificially designed peptides that can reduce the levels of ROS and other pro-oxidants, thus showing great potential in the treatment of oxidative stress-related diseases. In this review, we discussed ROS production and its role in inducing oxidative stress-related diseases in humans. Additionally, we discussed the sources, mechanism of action, and evaluation methods of AOPs and provided directions for future studies on AOPs.

Physicochemical characteristics and antioxidant stability of spray-dried soy peptide fractions

The direct addition of health-promoting peptides to food products is limited due to their physicochemical instability and bitter taste as well as their bio-functionality may be influenced by M_W. In this study, SPI hydrolysate (SPIH) was Alcalase-prepared, size-fractionated (<10, 10-30, and 30-100 kD), and the amino acid composition of peptide fractions determined. The physicochemical properties, morphology, and antioxidant stability of the fractions were also investigated after spray-drying encapsulation in maltodextrin-WPC carrier. The two low M_W peptide fractions (especially, PF < 10) were more active than intact SPI, SPIH, and high M_W peptide fraction in scavenging free radicals and chelating transition metal ions. As compared to the particles containing SPIH, those containing the smallest peptide fraction (PF < 10) had higher solubility and hygroscopicity, lower production yield and wettability, and more wrinkles, indentations and surface roughness. The highest antioxidant stability during spray-drying was observed for the two low M_W peptide fractions, which examined by scavenging of free radicals of DPPH (88%), ABTS (97%), OH (93%) and NO (80%), chelating of iron (88%) and copper (87-90%) ions, reducing power (93%), and total antioxidant activity (90%). This finding reflects more structural and biological stability of the low M_W fractions to shear stress and dehydration during spray-drying, as compared with SPIH. The spray-drying encapsulated soy peptide fractions may be used as nutraceuticals for the development of functional foods.

Eighteen Novel Bioactive Peptides from Monkfish (Lophius litulon) Swim Bladders: Production, Identification, Antioxidant Activity, and Stability

In the study, papain was chosen from five proteases to hydrolyze proteins of monkfish swim bladders for effectively utilizing monkfish (Lophius litulon) processing byproducts, and the hydrolysis conditions of papain were optimized as hydrolysis temperature of 65 °C, pH 7.5, enzyme dose 2.5% and time 5 h using single-factor and orthogonal experiments. Eighteen peptides were purified from the swim bladder hydrolysate of monkfish by ultrafiltration and gel permeation chromatography methods and identified as YDYD, QDYD, AGPAS, GPGPHGPSGP, GPK, HRE, GRW, ARW, GPTE, DDGGK, IGPAS, AKPAT, YPAGP, DPT, FPGPT, GPGPT, GPT and DPAGP, respectively. Among eighteen peptides, GRW and ARW showed significant DPPH· scavenging activities with EC₅₀ values of 1.053 ± 0.003 and 0.773 ± 0.003 mg/mL, respectively; YDYD, QDYD, GRW, ARW and YPAGP revealed significantly HO· scavenging activities with EC₅₀ values of 0.150 ± 0.060, 0.177 ± 0.035, 0.201 ± 0.013, 0.183 ± 0.0016 and 0.190 ± 0.010 mg/mL, respectively; YDYD, QDYD, ARW, DDGGK and YPAGP have significantly O2-· scavenging capability with EC₅₀ values of 0.126 ± 0.0005, 0.112 ± 0.0028, 0.127 ± 0.0002, 0.128 ± 0.0018 and 0.107 ± 0.0002 mg/mL, respectively; and YDYD, QDYD and YPAGP showed strong ABTS⁺· scavenging ability with EC₅₀ values of 3.197 ± 0.036, 2.337 ± 0.016 and 3.839 ± 0.102 mg/mL, respectively. YDYD, ARW and DDGGK displayed the remarkable ability of lipid peroxidation inhibition and Ferric-reducing antioxidant properties. Moreover, YDYD and ARW can protect Plasmid DNA and HepG2 cells against H₂O₂-induced oxidative stress. Furthermore, eighteen isolated peptides had high stability under temperatures ranging from 25-100 °C; YDYD, QDYD, GRW and ARW were more sensitive to alkali treatment, but DDGGK and YPAGP were more sensitive to acid treatment; and YDYD showed strong stability treated with simulated GI digestion. Therefore, the prepared antioxidant peptides, especially YDYD, QDYD, GRW, ARW, DDGGK and YPAGP from monkfish swim bladders could serve as functional components applied in health-promoting products because of their high-antioxidant functions.

The Bioaccessibility of Yak Bone Collagen Hydrolysates: Focus on Analyzing the Variation Regular of Peptides and Free Amino Acids

The lack of a bioaccessibility test for yak bone collagen hydrolysates (YBCH) limits their development as functional foods. In this study, simulated gastrointestinal digestion (SD) and absorption (SA) models were utilized to evaluate the bioaccessibility of YBCH for the first time. The variation in peptides and free amino acids was primarily characterized. There was no significant alteration in the concentration of peptides during the SD. The transport rate of peptides through the Caco-2 cell monolayers was 22.14 ± 1.58%. Finally, a total of 440 peptides were identified, more than 75% of them with lengths ranging from 7 to 15. The peptide identification indicated that about 77% of the peptides in the beginning sample still existed after the SD, and about 76% of the peptides in the digested YBCH could be observed after the SA. These results suggested that most peptides in the YBCH resist gastrointestinal digestion and absorption. After the in silico prediction, seven typical bioavailable bioactive peptides were screened out and they exhibited multi-type bioactivities in vitro. This is the first study to characterize the changes in peptides and amino acids in the YBCH during gastrointestinal digestion and absorption, and provides a foundation for analyzing the mechanism of YBCH's bioactivities.

Yeast Expressed Hybrid Peptide CLP Abridged Pro-Inflammatory Cytokine Levels by Endotoxin Neutralization

The aim of this study was to apply a strategy to express a recombinant CLP peptide and explore its application as a product derived from natural compounds. The amphiphilic CLP peptide was hybridized from three parent peptides (CM4, LL37, and TP5) and was considered to have potent endotoxin-neutralizing activity with minimal cytotoxic and hemolytic activity. To achieve high secretion expression, an expression vector of pPICZαA-HSA-CLP was constructed by the golden gate cloning strategy before being transformed into Pichia pastoris and integrated into the genome. The recombinant CLP was purified through the Ni-NTA affinity chromatography and analyzed by SDS-PAGE and mass spectrometry. The Limulus amebocyte lysate (LAL) test exhibited that the hybrid peptide CLP inhibited lipopolysaccharides (LPS) in a dose-dependent manner and was significantly (p < 0.05) more efficient compared to the parent peptides. In addition, it essentially diminished (p < 0.05) the levels of nitric oxide and pro-inflammatory cytokines (including TNF-α, IL6, and IL-1β) in LPS-induced mouse RAW264.7 macrophages. As an attendant to the control and the parental peptide LL37, the number of LPS-induced apoptotic cells was diminished compared to the control parental peptide LL37 (p < 0.05) with the treatment of CLP. Consequently, we concluded that the hybrid peptide CLP might be used as a therapeutic agent.

Anti-inflammatory effects of extracellular vesicles from Morchella on LPS-stimulated RAW264.7 cells via the ROS-mediated p38 MAPK signaling pathway

Morchella is a kind of important edible and medicinal fungi, which is rich in polysaccharides, enzymes, fatty acids, amino acids and other active components. Extracellular vesicles (EVs) have a typical membrane structure, and the vesicles contain some specific lipids, miRNAs and proteins, and their can deliver the contents to different cells to change their functions. The present study investigated whether Morchella produce extracellular vesicles and its anti-inflammatory effect on lipopolysaccharide (LPS)-induced RAW246.7 macrophages. The experimental results showed that Morchella produced extracellular vesicles and significantly reduced the production of nitric oxide (NO) and reactive oxygen species (ROS) in a model of LPS-induced inflammation. In addition, the expression of inflammatory factor-related genes such as inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and cyclooxygenase-2 (COX-2) showed dose-dependent inhibition. Morchella extracellular vesicles also can inhibit the inflammatory response induced by LPS by inhibiting the production of ROS and reducing the phosphorylation levels of the p38 MAPK signaling pathway. These results indicate that the Morchella extracellular vesicles can be used as a potential anti-inflammatory substance in the treatment of inflammatory diseases.

Protein Characteristics and Bioactivity of Fish Protein Hydrolysates from Tra Catfish (Pangasius hypophthalmus) Side Stream Isolates

Enzymatic hydrolysis is a novel method to recover highly potent bioactive fish protein hydrolysates (FPHs) from fish processing side-streams. The common way of producing FPHs directly from fish side-streams may be inappropriate due to the excess of lipids and pro-oxidants, especially in lipid-rich streams, as obtained from Tra catfish. This study aimed to optimise the hydrolysis conditions for a commercial enzyme (Alcalase® 2.4 L) (enzyme concentrate, temperature, and time) in FPH production from the fish protein isolate obtained from Tra catfish dark muscle (DM-FPI) using the pH-shift method. The degree of hydrolysis (DH), protein recovery (PR), and antioxidant properties, including DPPH radical scavenging activity (DPPH-RSA) and total reducing power capacity (TRPC), were measured to evaluate the effects of the hydrolysis conditions on the FPHs. Optimal hydrolysis was obtained at an enzyme/substrate protein ratio of 3% (v/w) and a hydrolysis temperature of 50 °C for 3 h. The FPHs obtained from different substrates, including DM-FPI, abdominal cut-off (ACO) FPI, and head and backbone blend (HBB) FPI, had similar DHs under these optimum conditions, ranging from 22.5% to 24.0%. However, the FPH obtained from abdominal cut-off isolate (ACO-FPH) showed the highest PR of 81.5 ± 4.3% and the highest antioxidant properties, with a DPPH-RSA of 86.1 ± 1.6% and a TRPC of 6.4 ± 0.4 equivalent mg vitamin C/g protein. The resulting FPHs present a natural source of antioxidants with great potential for food applications, especially the ACO-FPH. In addition, all FPHs had excellent amino acid profiles, indicating strong potential for their use as supplements. Tra catfish protein-rich side-streams can thus be processed into high-value bioactive FPHs using Alcalase for human consumption.

Anti-inflammatory action of ark shell (Scapharca subcrenata) protein hydrolysate in LPS-stimulated RAW264.7 murine macrophages

Potential anti-inflammatory effects of ark shell (Scapharca subcrenata) protein hydrolysates were investigated. Ark shell protein hydrolysates were prepared using Alcalase® and pepsin and were designated ASAH and ASPH, respectively. The nitric oxide (NO) inhibitory activity of ASAH and ASPH was determined in lipopolysaccharides (LPS)-stimulated RAW264.7 murine macrophages, and the results showed that ASAH inhibited better NO inhibitory activity than ASPH. ASAH suppressed inflammatory mediator, a prostaglandin E2, secretion of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), and production of reactive oxygen species (ROS) dose dependently. It inhibited the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and simulated heme oxygenase-1 (HO-1) protein expression. However, the pharmacological approach revealed that pretreatment with zinc protoporphyrin ІX (ZnPP), an inhibitor of HO-1, reversed the anti-inflammatory effect of ASAH. Moreover, ASAH upregulated phosphorylation of mitogen-activated protein kinases (MAPKs) including ERK1/2, JNK1/2, and p38 MAPK. To find out the role of MAPKs phosphorylation, MAPKs inhibitors were used, and the results showed that ASAH-mediated HO-1 protein expression and Nrf2 nuclear translocation were abolished. Taken all together, this study revealed that ASAH has a potential anti-inflammatory activity through regulation of the MAPK-dependent HO-1/Nrf2 pathway. PRACTICAL APPLICATIONS: Food-derived marine bioactive peptides, due to their pivotal role in biological activities, are gaining much attention recently. However, the anti-inflammatory activities of ark shell protein hydrolysates still remain to be investigated. This study investigated that ASAH shows potential anti-inflammatory activities through regulation of the MAPK-dependent HO-1/Nrf2 pathway in RAW264.7 murine macrophages. These findings indicated that ASAH may be used as a dietary supplement, functional food, and medicinal drug for the management of inflammation and inflammation-associated diseases.

In Vitro Biological Activity and In Vivo Human Study of Porcine-Placenta-Extract-Loaded Nanovesicle Formulations for Skin and Hair Rejuvenation

Porcine placenta extract (PPE) contains many water-soluble macromolecular compounds, such as proteins and growth factors, which have limited transportation through the skin. This study aimed to assess the effect of porcine-placenta-extract (PPE)-loaded nano-transdermal systems for skin repair and hair growth promotion. The potentials of the nanoformulation for cytotoxicity, cell proliferation, intracellular reactive oxygen species (ROS) reduction, lipoxygenase inhibition, intracellular inflammatory cytokine reduction, and cell aggregation were evaluated. PPE-entrapped niosome nanovesicles were produced by thin-film hydration and probe-sonication methods, followed by incorporation in a skin serum formulation. The physicochemical properties of the formulation were examined, and the efficacy of the serum formulation was elucidated in humans. The results showed that PPE had no toxicity and was able to induce cell growth and cell aggregation. In addition, PPE significantly decreased intracellular ROS, inhibited lipoxygenase activity, and reduced the production of intracellular tumor necrosis factor-α. In the in vivo human study, the PPE nanovesicles-loaded serum could improve skin properties by increasing skin hydration. Moreover, it was capable of promoting hair growth by increasing hair elongation and melanin index after application for one month. Consequently, the PPE nanovesicles-loaded serum was effective for skin anti-aging and hair rejuvenation.

Separation and identification of collagen peptides derived from enzymatic hydrolysate of Salmo salar skin and their anti-inflammatory activity in lipopolysaccharide (LPS)-induced RAW264.7 inflammatory model

Inflammation is considered as a major risk for the pathogenesis of chronic diseases. Due to the adverse events caused by the long-term use of anti-inflammatory drugs, it is necessary to develop alternative and safe dietary supplements from natural products against inflammation. In this study, flavourzyme hydrolysate (for 0.5 hr) presented the strongest anti-inflammatory activity, which was further separated by ultrafiltration and column chromatography, followed by LC-MS/MS identification. Peptide APD, QA, KA, and WG were identified as anti-inflammatory peptides, which significantly reduced secretion of NO, IL-6, IL-1β, and TNF-α in inflammatory macrophages. Among them, peptide QA showed the best overall anti-inflammatory effect, with the IC₅₀ value against NO production of 849.3 μM. Most of the identified anti-inflammatory peptides were stably against digestion, and they had abundant frequencies in the α (I/II) chain of Salmo salar collagen. Our findings indicated the potential of S. salar skin hydrolysates as functional food to prevent inflammation. PRACTICAL APPLICATIONS: Long-term use of anti-inflammatory drugs causes adverse events like gastrorrhagia, and it is necessary to develop alternative and safe dietary supplements from natural products against inflammation. Salmo salar skin, as a major byproduct of total fish, has not been effectively utilized during processing. In this study, novel anti-inflammatory oligopeptides with high activities were separated and identified from S. salar skin gelatin hydrolysate, which were stably against digestion, and presented a high bioavailability and abundant frequencies in collagen. Our study highlighted the added value of aquatic by-products and suggested that S. salar skin collagen hydrolysate could be used as a promising dietary supplement against inflammatory diseases.

Purification, characterization and molecular docking study of angiotensin-I converting enzyme (ACE) inhibitory peptide from shortfin scad (Decapterus macrosoma) protein hydrolysate

Hypertension is a threatening chronic disease, which become a global killer among the adult population. The mortality rate increasing day by day even several Angiotensin I-converting enzyme (ACE) inhibitor drugs were introduced. Bioactive peptides derived from aquatic resources exhibits potential ACE inhibitory activity. The objective of this work is to report the purification and molecular docking studies of angiotensin-I converting enzyme (ACE) inhibitory peptide isolated from shortfin scad (Decapterus macrosoma) waste protein hydrolysate (SWH), enzymatically prepared by using alcalase. The purification process included ultrafiltration, gel filtration and reverse phase high performance liquid chromatography (RP-HPLC). Results showed that ultra-filtered peptide fraction (< 3 kDa) possessed the highest ACE inhibitory activity, followed by the fraction 14 by gel filtration. Fraction P obtained by RP-HPLC, with the amino acid sequence of RGVGPVPAA (IC₅₀ = 0.20 mg/ml) was identified. In terms of ACE inhibition, the Lineweaver-Burk plot showed that the SWH peptide obtained acted as a competitive ACE inhibitor. The molecular docking studies showed that the SWH peptide exhibit hydrogen bonds and Pi-interactions with ACE by Z-dock scores. These results showed that the purified peptide isolated from shortfin scad waste hydrolysate has potential antihypertensive properties which could potentially be used as functional food ingredients.

A Review of Bioactive Peptides: Chemical Modification, Structural Characterization and Therapeutic Applications

In recent years, the development and applications of protein drugs have attracted extensive attention from researchers. However, the shortcomings of protein drugs also limit their further development. Therefore, bioactive peptides isolated or simulated from protein polymers have broad application prospects in food, medicine, biotechnology, and other industries. Such peptides have a molecular weight distribution between 180 and 1000 Da. As a small molecule substance, bioactive peptide is usually degraded by various enzymes in the organism and have a short half-life. At the same time, such substances have poor stability and are difficult to produce and store. Therefore, these active peptides may be modified through phosphorylation, glycosylation, and acylation. Compared with other protein drugs, the modified active peptides are more easily absorbed by the body, have longer half-life, stronger targeting, and fewer side effects in addition to higher bioavailability. In the light of their functions, bioactive peptide can be divided into antimicrobial, anti-tumour, anti-angiogenic, antioxidant, anti-fatigue, and anti-hypertensive peptides. This article mainly focuses on the introduction of several promising biologically active peptides functioning as antimicrobial, anti-tumour, antiangiogenic, and antioxidant peptides from the three aspects modification, structural characteristics and mechanism of action.

Intracellular ROS scavenging and antioxidant regulation of WL15 from cysteine and glycine-rich protein 2 demonstrated in zebrafish in vivo model

Antioxidant peptides are naturally present in food, especially in fishes, and are considered to contain rich source of various bioactive compounds that are structurally heterogeneous. This study aims to identify and characterize the antioxidant property of the WL15 peptide, derived from Cysteine and glycine-rich protein 2 (CSRP2) identified from the transcriptome of a freshwater food fish, Channa striatus. C. striatus is already studied to contain high levels of amino acids and fatty acids, besides traditionally known for its pharmacological benefits in the Southeast Asian region. In our study, in vitro analysis of WL15 peptide exhibited strong free radical scavenging activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), superoxide anion radical and hydrogen peroxide (H2O2) scavenging assay. Further, to evaluate the cytotoxicity and dose-response, the Human dermal fibroblast (HDF) cells were used. Results showed that the treatment of HDF cells with varying concentrations (10, 20, 30, 40 and 50 μM) of WL15 peptide was not cytotoxic. However, the treatment concentrations showed enhanced antioxidant properties by significantly inhibiting the levels of free radicals. For in vivo assessment, we have used zebrafish larvae for evaluating the developmental toxicity and for determining the antioxidant property of the WL15 peptide. Zebrafish embryos were treated with the WL15 peptide from 4 h of post-fertilization (hpf) to 96 hpf covering the embryo-larval developmental period. At the end of the exposure period, the larvae were exposed to H2O2 (1 mM) for inducing generic oxidative stress. The exposure of WL15 peptide during the embryo-larval period showed no developmental toxicity even in higher concentrations of the peptide. Besides, the WL15 peptide considerably decreased the intracellular reactive oxygen species (ROS) levels induced by H2O2 exposure. WL15 peptide also inhibited the H2O2-induced caspase 3-dependent apoptotic response in zebrafish larvae was observed using the whole-mount immunofluorescence staining. Overall results from our study showed that the pre-treatment of WL15 (50 μM) in the H2O2-exposed zebrafish larvae, attenuated the expression of activated caspase 3 expressions, reduced Malondialdehyde (MDA) levels, and enhanced antioxidant enzymes, including superoxide dismutase (SOD) and catalase (CAT). The gene expression of antioxidant enzymes such as glutathione S-transferase (GST), glutathione peroxide (GPx) and γ-glutamyl cysteine synthetase (GCS) was found to be upregulated. In conclusion, it can be conceived that pre-treatment with WL15 could mitigate H2O2-induced oxidative injury by elevating the activity and expression of antioxidant enzymes, thereby decreasing MDA levels and cellular apoptosis by enhancing the antioxidant response, demonstrated by the in vitro and in vivo experiments.

Fractionation of Flaxseed-Derived Bioactive Peptides and Their Influence on Nanoliposomal Carriers

This study addressed the extraction, enzymatic hydrolysis, and production of peptide fractions (PF) from defatted flaxseed meal and their loading into nanoliposomes. Enzymatic hydrolysis significantly increased the free hydrophobic (from 19 to 134 mg/g) and antioxidant (from 8 to 46 mg/g) amino acids. The PF with lower molecular weights (MW < 10 kDa) had the highest scavenging capacity of DPPH^- free radicals (61.82%), ABTS⁺ (86.37%), Trolox equivalent antioxidant capacity, TEAC (2.34 mM), hydroxyl (61.91%), reducing power (0.94 Abs₇₀₀), total antioxidant activity (1.76 Abs₆₉₅), nitric oxide (49.9%), iron (69.34%), and copper (24.58%) chelating activities compared with other fractions. The physical properties (such as particle size and polydispersity index), stability, and encapsulation efficiency of nanoliposomes were affected by temperature, stress type (freeze and thaw tension), MW, and in vitro conditions (release of PF in simulated biological fluids at different times). Besides, the Fourier-transform infrared spectroscopy (FTIR) results showed the placement of peptides inside the polar regions and the bilayer membrane. The scanning electron microscopy (SEM) images of nanocarriers indicated agglomerated and relatively spherical structures. Our findings revealed the efficiency of nanoliposomes as appropriate carriers for the delivery of peptide fractions with the highest antioxidant activity.

Herring Milt and Herring Milt Protein Hydrolysate Are Equally Effective in Improving Insulin Sensitivity and Pancreatic Beta-Cell Function in Diet-Induced Obese- and Insulin-Resistant Mice

Although genetic predisposition influences the onset and progression of insulin resistance and diabetes, dietary nutrients are critical. In general, protein is beneficial relative to carbohydrate and fat but dependent on protein source. Our recent study demonstrated that 70% replacement of dietary casein protein with the equivalent quantity of protein derived from herring milt protein hydrolysate (HMPH; herring milt with proteins being enzymatically hydrolyzed) significantly improved insulin resistance and glucose homeostasis in high-fat diet-induced obese mice. As production of protein hydrolysate increases the cost of the product, it is important to determine whether a simply dried and ground herring milt product possesses similar benefits. Therefore, the current study was conducted to investigate the effect of herring milt dry powder (HMDP) on glucose control and the associated metabolic phenotypes and further to compare its efficacy with HMPH. Male C57BL/6J mice on a high-fat diet for 7 weeks were randomized based on body weight and blood glucose into three groups. One group continued on the high-fat diet and was used as the insulin-resistant/diabetic control and the other two groups were given the high-fat diet modified to have 70% of casein protein being replaced with the same amount of protein from HMDP or HMPH. A group of mice on a low-fat diet all the time was used as the normal control. The results demonstrated that mice on the high-fat diet increased weight gain and showed higher blood concentrations of glucose, insulin, and leptin, as well as impaired glucose tolerance and pancreatic β-cell function relative to those on the normal control diet. In comparison with the high-fat diet, the replacement of 70% dietary casein protein with the same amount of HMDP or HMPH protein decreased weight gain and significantly improved the aforementioned biomarkers, insulin sensitivity or resistance, and β-cell function. The HMDP and HMPH showed similar effects on every parameter except blood lipids where HMDP decreased total cholesterol and non-HDL-cholesterol levels while the effect of HMPH was not significant. The results demonstrate that substituting 70% of dietary casein protein with the equivalent amount of HMDP or HMPH protein protects against obesity and diabetes, and HMDP is also beneficial to cholesterol homeostasis.

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.

Optimization of Oyster (Crassostrea talienwhanensis) Protein Hydrolysates Using Response Surface Methodology

Oyster (Crassostrea talienwhanensis) protein was hydrolyzed by trypsin to produce peptides with different response values, and response surface methodology (RSM) was applied to optimize the hydrolysis conditions. The highest degree of hydrolysis (DH) of the oyster peptide (OP) was obtained at an enzyme concentration of 1593.2 U/g, a pH of 8.2, a hydrolysis temperature of 40.1 °C, a hydrolysis time of 6.0 h, and a water/material ratio of 8.2. The greatest hydroxyl-radical-scavenging activity of OP was obtained at an enzyme concentration of 1546.3 U/g, a pH of 9.0, a hydrolysis temperature of 50.2 °C, a hydrolysis time of 5.1 h, and a water/material ratio of 5.6. The largest branched-chain amino acid (BCAA) content of OP was obtained at an enzyme concentration of 1323.8 U/g, a pH of 8.3, a hydrolysis temperature of 41.7 °C, a hydrolysis time of 6.7 h, and a water/material ratio of 4.8. The three experimental values were significantly in agreement with the predicted values within the 95% confidence interval. Furthermore, ultrafiltration and chromatographic methods were used to purify the OP, and 13 peptides that were rich in Lys, Arg, His, and Thr were identified by LC-MS/MS. The results of this study offer different optimum hydrolysis conditions to produce target peptides from oyster protein by using RSM, and this study provide a theoretical basis for the high-value utilization of oyster protein.

In vitro Impact of Yeast Expressed Hybrid Peptide CATH-2TP5 as a Prophylactic Measure Toward Sepsis and Inflammation

CATH-2TP5 is a linear cationic hybrid peptide, consequent from naturally occurring antimicrobial peptide (AMPs) Cathelicidin-2 (CATH-2) and Immunomodulatory peptide Thymopentin (TP5) having dynamic and potent anti-inflammatory activities without hemolytic effect. The biocompatible mechanism of CATH-2TP5 is favored to explore new methodologies in the direction of biomedical applications. In this retrospectively study, an antiendotoxin and anti-inflammatory hybrid peptide CATH-2TP5 was emulated into pPICZα-A and successfully expressed in Pichia pastoris (P. pastoris). The recombinant CATH-2TP5 was purified through the Ni-affinity column and reversed-phase HPLC. The purified CATH-2TP5 peptide exhibited robust anti-endotoxin activity and significantly (p < 0.05) neutralized the effect of lipopolysaccharide (LPS). Furthermore, the down-regulated effect of CATH-2TP was more pronounced (p < 0.05) on LPS-induced cytotoxic effects, nitric oxide secretion and pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) in murine RAW264.7 macrophages. As associated to control and parental peptide the number of apoptotic cells was also contracted with the treatment of CATH-2TP5. Thus, we concluded that CATH-2TP5 peptide may be used in various biomedical applications as a therapeutic drug.

A Hybrid Peptide DEFB-TP5 Expressed in Methylotrophic Yeast Neutralizes LPS With Potent Anti-inflammatory Activities

DEFB-TP5 is a novel auspicious health-beneficial peptide derivative from two naturally occurring peptides, β-Defensin (DEFB) and thymopentin (TP5), and shows strong anti-inflammatory activity and binds to LPS without cytotoxicity and hemolytic effect. Furthermore, the application of DEFB-TP5 peptide is inadequate by its high cost. In the current study, we developed a biocompatible mechanism for expression of the DEFB-TP5 peptide in Pichia pastoris. The transgenic strain of hybrid DEFB-TP5 peptide with a molecular weight of 6.7kDa as predictable was obtained. The recombinant DEFB-TP5 peptide was purified by Ni-NTA chromatography, estimated 30.41 mg/L was obtained from the cell culture medium with 98.2% purity. Additionally, The purified DEFB-TP5 peptide significantly (p< 0.05) diminished the release of nitric oxide (NO), TNF-α, IL-6, IL-1β in LPS-stimulated RAW264.7 macrophages in a dose-dependent manner. This study will not only help to understand the molecular mechanism of expression that can potentially be used to develop an anti-endotoxin peptide but also to serve as the basis for the development of antimicrobial and anti-inflammatory agents as well, which also provides a potential source for the production of recombinant bioactive DEFB-TP5 at the industrial level.

Anti-Hyperglycemic Effects of Green Crab Hydrolysates Derived by Commercially Available Enzymes

The predation and burrowing activity of invasive green crabs have had detrimental effects on important marine resources and habitats. Our objective is to develop bioactive hydrolysates by enzymatic proteolysis of underutilized green crab. Mechanically separated mince was hydrolyzed with Alcalase, Protamex, Flavourzyme, and Papain (1%) for 60 min. Subsequently, the hydrolysates were introduced to a simulated gastrointestinal digestion model. Selected samples were fractionated by ultrafiltration, and their anti-hyperglycemic effects including α-glucosidase, α-amylase, and dipeptidyl peptidase-IV (DPP-IV) inhibitory activities and glucagon-like 1 (GLP-1) secretory activity were evaluated. The Protamex treatment showed the highest α-glucosidase inhibitory activity (IC₅₀ 1.38 ± 0.19 mg/mL) compared to other enzyme treatments and the crab mince control, and its α-amylase inhibitory activity (IC₅₀ 11.02 ± 0.69 mg/mL) was lower than its α-glucosidase inhibitory activity. Its GLP-1 secretory activity was approximately four times higher than the positive control (10 mM glutamine). The <3 kD fraction contributed significantly to the anti-hyperglycemic activity of Protamex-derived hydrolysates, and this activity was stable after simulated digestion. Our results suggest that green crab hydrolysates obtained by Protamex treatment have the potential for type 2 diabetes management and could be incorporated in food products as a health-promoting ingredient.

Protein Hydrolysates from Anchovy (Engraulis encrasicolus) Waste: In Vitro and In Vivo Biological Activities

Fish waste utilization to obtain protein hydrolysates has been demonstrated to be a useful strategy to face both environmental and economic impacts while obtaining high-value products with remarkable biological and nutritional properties. In the present study, protein hydrolysates obtained from anchovy Engraulis encrasicolus (APH) by-products were assessed for their potential biological activities in both in vitro and in vivo models. The treatment with APH exerted a significant protection against LPS-induced inflammation in RAW 264.7 cells, decreasing the protein expression of pro-inflammatory mediators (i.e., COX-2) and inhibiting the nuclear translocation of NF-κB through IκB-α. Moreover, APH modulated the expression of iNOS, MnSOD and HO-1, thus decreasing the severity of oxidative stress. The supplementation of APH in the diet of ApoE knockout mice down-regulated the proinflammatory cytokines (i.e., TNF-α, IL-1α, IL-1β, IL-6) in both aorta and heart tissues, and modulated the expression of oxidative stress-related genes (Cu/ZnSod, MnSod, Cat, Gpx and Ho), indicating that APH can exert a beneficial role, having anti-inflammatory and antioxidant activities. The nutritional properties of APH, together with their biological activities herein reported, highlight the possibility of obtaining bioactive molecules from fish waste and encourage their use as potential nutraceuticals in food and pharmaceutical industries in the next future.

Identification and characterization of multifunctional cationic peptides from enzymatic hydrolysates of soybean proteins

In this study, we used the commercial soybean protein hydrolysate Hinute-DC6 as a novel starting material from which to purify and identify multifunctional cationic peptides. After fractionation, Hinute-DC6 was separated into 20 fractions with varying isoelectric points (pI) by ampholyte-free isoelectric focusing (autofocusing). Subsequently, we purified and identified the cationic peptides from fractions 19 and 20, which had pI values greater than 12, using reversed-phase high-performance liquid chromatography and matrix-assisted laser/desorption ionization-time-of-flight mass spectrometry. Of the 83 cationic peptides identified, 14 had high pI values and net charges greater than +2, and were chemically synthesized and assayed for various bioactivities, including hemolytic, antimicrobial, lipopolysaccharide (LPS)-neutralizing, and angiogenic activities. None of the 14 cationic peptides tested exhibited hemolytic activity toward mammalian red blood cells at concentrations up to 1000 μM. Five of the cationic peptides exhibited antimicrobial activities against at least one of four human-pathogenic microorganisms tested. In addition, in chromogenic LPS-neutralizing assays using Limulus amebocyte lysates, the 50% effective concentrations of these 14 peptides were between 0.069 and 5.2 μM. Tube-formation assays in human umbilical vein endothelial cells showed that each of the 14 cationic peptides exhibited significant angiogenic activities at 10 μM, with values similar to those of the positive control LL-37. Our results demonstrate that the 14 identified cationic peptides have multiple functions with negligible hemolytic activity. These data indicate that the cationic peptides isolated from Hinute-DC6 and fractions containing these cationic peptides have the potential to be used as multifunctional ingredients for healthcare applications.

Evaluation of the protein and bioactive compound bioaccessibility/bioavailability and cytotoxicity of the extracts obtained from aquaculture and fisheries by-products

Bioavailability, bioaccessibility, bioactivity and cytotoxicity define if a bioactive compound obtained from aquaculture and associated by-products can be assimilated and used for the body in a safe and efficient way. Four models are used to evaluate the bioavailability: in vitro (simulated gastrointestinal digestion using intestinal epithelial Caco-2 cell cultures); ex vivo (gastrointestinal organs or organoids in laboratory conditions); in situ (intestinal perfusion in animals) and in vivo (animal studies and human studies). In vitro models are very effective, predicting in vivo actions since they evaluate multiple conditions regardless physiological effects. However, in vivo systems are essential for the validation of the results. The use of a combined model between human digestion and cell culture-based models would solve these difficulties, allowing valid conclusions. These studies must be completed with the evaluation of cytotoxicity and oxidative stress markers, providing most accurate results regarding the adverse effect on the body. These methods would test the effect of food structure, food composition, dietary factors and the effect of food processing on bioavailability. Further studies should be carried out to establish a standardized method and achieve a balance between the use of in vivo and in vitro systems.

Investigation on activation in RAW264.7 macrophage cells and protection in cyclophosphamide-treated mice of Pseudostellaria heterophylla protein hydrolysate

Our previous study has demonstrated that Pseudostellaria heterophylla protein hydrolysate (PPH) has immunomodulatory activity on murine spleen lymphocytes. The aim of this study was to investigate the excitation of PPH in RAW264.7 macrophage cells and the protective effect in cyclophosphamide (CTX)-treated mice. The results showed PPH of 50 μg/mL could stimulate macrophages resulting in significant promotions of nitric oxide (NO) production, endocytosis and reactive oxygen species formation. Meanwhile, enzyme-linked immunosorbent assay (ELISA) revealed that the levels of tumor necrosis factor-α and interleukin-10 were significantly upregulated by PPH. Furthermore, 50 mg/kg per day PPH restored the T lymphocyte proliferation and natural killer cell activity, and increased NO production and pinocytosis of peritoneal macrophages in CTX-treated mice. These findings indicate PPH plays a crucial role in RAW264.7 macrophage cells activation and in the protection against immunosuppression in CTX-treated mice and could be used as a potential immunostimulant agent.

Immunomodulatory Activity of Low Molecular-Weight Peptides from Nibea japonica in RAW264.7 Cells via NF-κB Pathway

In this study, a low molecular-weight (Mw) peptide named NJP (<1 kDa), was purified from a protein hydrolysate of Nibea japonica by ultrafiltration, and its immunomodulatory effect on RAW264.7 cells was evaluated. The lactate dehydrogenase (LDH) and MTT assays were performed to explore the cytotoxicity of NJP. The results showed that NJP promoted cell proliferation and had no significant toxic effects on RAW264.7 cells. Moreover, the cells formed multiple pseudopodia indicating that they were in activated state. Further tests showed that NJP significantly promoted phagocytic capacity, and the secretion of proinflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β). It also increased the synthesis of nitric oxide (NO) by upregulating inducible nitric oxide synthase (iNOS) protein level. Flow cytometry revealed that NJP promoted cell cycle progression and increased the percentage of cells in G0/G1 phase. NJP promoted IκBα degradation, p65 and nuclear factor (NF)-κB activation and translocation by up-regulating IKKα/β protein expression. In conclusion, these results indicated that NJP exerts immunomodulatory effects on RAW264.7 cells through the NF-κB signaling pathway. Therefore, NJP can be incorporated in the production of functional foods or nutraceuticals.

Expression and Purification of Hybrid LL-37Tα1 Peptide in Pichia pastoris and Evaluation of Its Immunomodulatory and Anti-inflammatory Activities by LPS Neutralization

This study pertains to the new approach for the development of hybrid peptide LL-37Tα1 and its biomedical applications. A linear cationic hybrid peptide, LL-37Tα1 was derived from two parental peptides (LL-37 and Tα1) recognized as potent anti-endotoxin without any hemolytic or cytotoxic activity. We successfully cloned the gene of hybrid peptide LL-37Tα1 in PpICZαA vector and expressed in the Pichia pastoris. The recombinant peptide was purified by Ni-affinity column and reverse-phase high performance liquid chromatography (RP-HPLC) with an estimated molecular mass of 3.9 kDa as determined by SDS-PAGE and mass spectrometry. We analyzed the LPS neutralization by limulus amebocyte lysate (LAL) activity and the results indicate that the hybrid peptide LL-37Tα1 directly binds endotoxin and significantly (p < 0.05) neutralizes the effect of LPS in a dose-dependent manner. Lactate dehydrogenase (LDH) assay revealed that LL-37Tα1 successfully reduces the LPS-induced cytotoxicity in mouse RAW264.7 macrophages. Moreover, it significantly (p < 0.05) decreased the levels of nitric oxide, proinflammatory cytokines including TNF-α, IL-6, IL-1β, and diminished the number of apoptotic cells in LPS-stimulated mouse RAW264.7 macrophages. Our results suggest that the P. pastoris expression system is cost-effective for commercial production of the immunomodulatory and anti-inflammatory hybrid peptide (IAHP) LL-37Tα1 and the peptide may serve as effective anti-endotoxin/anti-inflammatory agent with minimal cytotoxicity.

Antimicrobial and Immunomodulatory Properties and Applications of Marine-Derived Proteins and Peptides

Marine organisms provide an abundant source of potential medicines. Many of the marine-derived biomaterials have been shown to act as different mechanisms in immune responses, and in each case they can significantly control the immune system to produce effective reactions. Marine-derived proteins, peptides, and protein hydrolysates exhibit various physiologic functions, such as antimicrobial, anticancer, antioxidant, antihypertensive, and anti-inflammatory activities. Recently, the immunomodulatory properties of several antimicrobial peptides have been demonstrated. Some of these peptides directly kill bacteria and exhibit a variety of immunomodulatory activities that improve the host innate immune response and effectively eliminate infection. The properties of immunomodulatory proteins and peptides correlate with their amino acid composition, sequence, and length. Proteins and peptides with immunomodulatory properties have been tested in vitro and in vivo, and some of them have undergone different clinical and preclinical trials. This review provides a comprehensive overview of marine immunomodulatory proteins, peptides, and protein hydrolysates as well as their production, mechanisms of action, and applications in human therapy.

Chia Seed (Salvia hispanica L.) Pepsin Hydrolysates Inhibit Angiotensin-Converting Enzyme by Interacting with its Catalytic Site

High blood pressure can lead to cardiovascular diseases. The objective of this work was to obtain protein hydrolysates with antihypertensive potential from chia oil industry meal byproduct. Chia seed protein isolates (CPIs) were obtained from chia seed meal byproduct. CPI was hydrolyzed using different proteases (alcalase, pepsin, trypsin, and α-chymotrypsin) and their biological potential was evaluated using in vitro and in silico approaches. Chia seed pepsin protein hydrolysate showed the highest angiotensin-converting enzyme inhibition potential IC₅₀ of 0.128 mg/mL (P < 0.05) compared to the rest of hydrolysates. Peptide sequence LIVSPLAGRL presented the lowest predicted binding energy and highest inhibition potential (-9.5 kcal/mol) compared to other sequenced peptides and positive controls (captopril and lisinopril). Chia peptides showed potential to block angiotensin-converting enzyme by interacting with its catalytic site. Chia seed oil industry meal byproduct could be used as an inexpensive source of protein and bioactive peptides with antihypertensive potential. PRACTICAL APPLICATION: This research shows an upcycling alternative for chia oil industry byproduct. Chia meal is a rich source of protein and can be used to generate bioactive peptides with antihypertensive potential. Chia protein isolate was obtained from chia meal and hydrolyzed using different enzymes, pepsin showed the highest antihypertensive potential. Chia meal waste could be a low-cost source of protein and protein hydrolysates that could be used as a food ingredient with antihypertensive potential.

Anti-Oxidative and Anti-Aging Activities of Porcine By-Product Collagen Hydrolysates Produced by Commercial Proteases: Effect of Hydrolysis and Ultrafiltration

To investigate methods for improving the processing of porcine waste, porcine skin was hydrolyzed using different commercially available proteases (Alcalase, Flavorzyme, Neutrase, Bromeline, Protamex, and Papain) under several optimal conditions. Following enzymatic hydrolysis, the collagen hydrolysates (CHs) were fractionated by molecular weight (3 kDa) via membrane ultrafiltration. The CHs were analyzed for physical properties (pH, protein recovery, free amino group content, molecular weight distribution, and amino composition) as well as for functional properties (antioxidant activities and anti-aging activities). Among the CHs, CHs hydrolyzed by Alcalase (CH-Alcalase) exhibited the highest degree of hydrolysis compared to other CHs. Both “CH-Alcalase” and “CH-Alcalase < 3 kDa” fractions showed a considerably high antioxidant activity and collagenase inhibition activity. Therefore, resulting bioactives have potential for development as antioxidants and anti-aging ingredients in the food, cosmetics, and pharmaceuticals, from animal by-products.

Influence of spray drying encapsulation on the retention of antioxidant properties and microstructure of flaxseed protein hydrolysates

In this research, bioactive peptides produced from flaxseed protein by alcalase, pancreatin, trypsin and pepsin, were encapsulated by spray drying. After analysis of amino acid composition and antioxidant properties of hydrolysates, the effect of spray-drying encapsulation via different maltodextrin (MD) to hydrolysate ratios (1:1, 2:1 and 3:1 w/w) on the production yield, physicochemical properties, functional activities, chemical structure, and morphology of final powder particles were evaluated. Among the hydrolysates, peptides produced with alcalase had the highest hydrolysis degree (38.2%), hydrophobic amino acids (255 mg/g) and antioxidants (126 mg/g). Among spray-dried samples, the powders obtained by 3:1 w/w ratio (MD: peptide) showed the highest radical scavenging activity for DPPH^- (68.93%), ABTS⁺ (85.62%), hydroxyl (94.97%), nitric oxide (64.03%), reducing power (95.49%), total antioxidant activity (96.68%), and iron (95.31%) and copper (95.49%) chelating activity. Evaluation of chemical structure (FTIR) indicated that hydrolysates were coated and dispersed within maltodextrin matrix. SEM images showed the effect of different carrier ratios on the production of irregular and shrunk particles with different sizes and matrix-type structures.

The protective effects of Nile tilapia (Oreochromis niloticus) scale collagen hydrolysate against oxidative stress induced by tributyltin in HepG2 cells

Oxidative stress is regarded as one of the most important factors associated with many diseases, such as atherosclerosis, cancer, and diabetes. Various chemicals are released into the environment, causing environmental pollution. Importantly, many of them may cause damage to organisms through oxidative stress. In this work, we investigated the possible protective effects of Nile tilapia (Oreochromis niloticus) scale collagen hydrolysate (TSCH) (molecular weight approximately 4 kDa) against tributyltin (TBT)-induced oxidative stress in vitro. The results showed that pretreatment with TSCH protected against decreases in cell viability and changes in cell morphology in HepG2 cells exposed to TBT. Treatment with TSCH reduced the TBT-induced elevation in malondialdehyde (MDA) levels in HepG2 cells in a dose-dependent manner. Pretreatment with TSCH increased glutathione reductase (GR) and superoxide dismutase (SOD) activity. Moreover, TSCH decreased the expression of the proapoptotic protein Bax, reducing apoptosis. These results suggest that the protective mechanism of TSCH may be associated with its ability to scavenge MDA, increase antioxidant enzyme activity and downregulate the expression of Bax.

Cationic peptides from enzymatic hydrolysates of soybean proteins exhibit LPS-neutralizing and angiogenic activities

In this study, we prepared fractions containing multifunctional cationic peptides by separating the commercial soybean protein hydrolysate Hinute-AM into 20 fractions. These fractions contained peptides with various isoelectric points (pI), as indicated by ampholyte-free isoelectric focusing (autofocusing). Thus, we purified and identified the cationic peptides from fractions 19 and 20, which had pH values greater than 10, using reversed-phase high-performance liquid chromatography and matrix-assisted laser/desorption ionization-time-of-flight mass spectroscopy. Among 19 identified cationic peptides, NKNAKPPSPR, PGKKNAIV, KSGPGMSPR, NVSKPPRVV, RKVGAGGRKPLG, and LPCVIGGVPKRV had high pI values and were included as chemically synthesized peptides in assays of various functions, including lipopolysaccharide (LPS)-neutralizing and angiogenic activities. Chromogenic LPS-neutralizing assays using Limulus amebocyte lysates showed that 50% effective concentrations of these six peptides were between 1.63 and 2.65 μM, and were higher than that (0.12 μM) of polymyxin B. Moreover, in tube-formation assays in human umbilical vein endothelial cells, all of the six cationic peptides except LPCVIGGVPKRV exhibited angiogenic activities similar to those of the positive control LL-37. In addition, the six identified cationic peptides had no hemolytic activity at concentrations up to 500 μM in mammalian red blood cells. Our results demonstrate that five of the identified cationic peptides, excluding LPCVIGGVPKRV, have multiple functions and little or no hemolytic activity. These data indicate that fractions containing cationic peptides from Hinute-AM have the potential to be used as dietary supplements and functional ingredients in food products.