Antiphotoaging effect and purification of an antioxidant peptide from tilapia (Oreochromis niloticus) gelatin peptides

Separation, enrichment and cytoprotection of antioxidant peptides from Xuanwei ham using aqueous two-phase extraction

An ethanol/(NH4)2SO4 biphasic (aqueous two-phase) system was designed to effectively separate antioxidant peptides from Xuanwei ham, and its potential to prevent ultraviolet A-induced damage to skin cells was explored. Optimization via single factor experiments and response surface methodology revealed that under 20 % ethanol aqueous solution (w/w), 25.5 % (NH4)2SO4 aqueous solution (w/w), and pH 8.80 conditions, the optimal extraction ratio was 59.0 ± 1.73 %. In vitro antioxidant activity and cellular assays showed that the peptide purified in the upper phase exhibited strong antioxidant activity, increasing the viability of HaCat cells damaged by UVA irradiation from 56.14 ± 1.05 % to 66.3 ± 1.76 %. We used an in silico peptide screening strategy and identified 10 with potential antioxidant activity, emphasizing the important role of amino acids Pro, Gly, and Ala in antioxidant activity.

Marine Bioactive Peptides: Anti-Photoaging Mechanisms and Potential Skin Protective Effects

Skin photoaging, resulting from prolonged exposure to ultraviolet radiation, is a form of exogenous aging that not only impacts the aesthetic aspect of the skin but also exhibits a strong correlation with the onset of skin cancer. Nonetheless, the safety profile of non-natural anti-photoaging medications and the underlying physiological alterations during the process of photoaging remain inadequately elucidated. Consequently, there exists a pressing necessity to devise more secure interventions involving anti-photoaging drugs. Multiple studies have demonstrated the noteworthy significance of marine biomolecules in addressing safety concerns related to anti-photoaging and safeguarding the skin. Notably, bioactive peptides have gained considerable attention in anti-photoaging research due to their capacity to mitigate the physiological alterations associated with photoaging, including oxidative stress; inflammatory response; the abnormal expression of matrix metalloproteinase, hyaluronidase, and elastase; and excessive melanin synthesis. This review provides a systematic description of the research progress on the anti-photoaging and skin protection mechanism of marine bioactive peptides. The focus is on the utilization of marine bioactive peptides as anti-photoaging agents, aiming to offer theoretical references for the development of novel anti-photoaging drugs and methodologies. Additionally, the future prospects of anti-aging drugs are discussed, providing an initial reference for further research in this field.

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.

Study of the Antioxidant, Antimicrobial, and Wound Healing Properties of Raw Hydrolyzed Extract from Nile Tilapia Skin (Oreochromis niloticus)

Oreochromis niloticus (Nile tilapia) skin is a by-product of Brazilian fish farming, rich in collagen. The present study aims to evaluate the wound healing, antioxidant, and antimicrobial potential of the raw hydrolyzed extract of Nile tilapia skin, as well as the identification of the main compounds. The in vitro activity was performed using antioxidant, antimicrobial and scratch wound healing assays. An in vivo experiment was performed to evaluate the wound healing potential. On days 1, 7, 14 and 21, the lesions were photographed to assess wound retraction and on the 7th , 14th and 21st  days the skins were removed for histological evaluation and the blood of the animals was collected for glutamic oxaloacetic transaminase and glutamic pyruvic transaminase determination. The chemical study was carried out through liquid chromatography-tandem mass spectrometry and de novo sequencing of peptides. The in vitro assays showed a reduction of the gap area in 24 h, dose-dependent antimicrobial activity for both bacteria, and antioxidant activity. The chemical analysis highlighted the presence of active biopeptides. The histological evaluation showed that the raw hydrolyzed extract of Nile tilapia skin has a healing potential, and does not present toxicological effects; therefore, is promising for the treatment of wounds.

Analysis of Phenolic Acids and Flavonoids in Rabbiteye Blueberry Leaves by UPLC-MS/MS and Preparation of Nanoemulsions and Extracts for Improving Antiaging Effects in Mice

Rabbiteye blueberry leaves, a waste produced after harvest of blueberry, are rich in polyphenols. This study aims to analyze phenolic acids and flavonoids in blueberry leaves by UPLC-MS/MS and prepare nanoemulsions for determining anti-aging activity in mice. Overall, 30% ethanol was the most suitable extraction solvent for total phenolic acids and total flavonoids. A total of four phenolic acids and four flavonoids were separated within seven minutes for further identification and quantitation by UPLC-MS/MS in selective reaction monitoring (SRM) mode, with 3-O-caffeoylquinic acid being present in the highest amount (6474.2 μg/g), followed by quercetin-3-O-galactoside (1943.9 μg/g), quercetin-3-O-rutinoside (1036.6 μg/g), quercetin-3-O-glucoside (867.2 μg/g), 5-O-caffeoylquinic acid (815.8 μg/g), kaempferol-3-O-glucoside (309.7 μg/g), 3,5-dicaffeoylquinic acid (195.3 μg/g), and 4,5-dicaffeoylquinic acid (60.8 μg/g). The blueberry nanoemulsion was prepared by using an appropriate ratio of soybean oil, Tween 80, glycerol, ethanol, and water at 1.2%, 8%, 2%, 2%, and 86.8%, respectively, and mixing with dried blueberry extract, with the mean particle size and zeta potential being 16 nm and -54 mV, respectively. A high stability was observed during storage of nanoemulsion for 90 days at 4 °C and heated at 100 °C for 2 h. An animal study revealed that this nanoemulsion could elevate dopamine content in mice brain as well as superoxide dismutase, glutathione peroxidase, and catalase activities in mice liver while reducing the contents of malondialdehyde and protein carbonyl in mice brains. Collectively, the high-dose nanoemulsion possessed the highest efficiency in improving mice aging with a promising potential for development into a health food.

Purification and Identification of Novel Antioxidant Peptides from Hydrolysates of Peanuts (Arachis hypogaea) and Their Neuroprotective Activities

Peanut (Arachis hypogaea) peptides have various functional activities and a high utilization value. This study aims to isolate and characterize antioxidant peptides from peanut protein hydrolysates and further evaluate their neuroprotection against oxidative damage to PC12 cells induced by 6-hydroxydopamine (6-OHDA). After the peanut protein was hydrolyzed with pepsin and purified using ultrafiltration and gel chromatography, six peptides were identified and sequenced by high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Out of these six peptides, Pro-Gly-Cys-Pro-Ser-Thr (PGCPST) exhibited a desirable antioxidant capacity, as determined using the 1,1-diphenyl-2-picrylhydrazyl, 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, and hydroxyl radical scavenging assays. Moreover, our results indicated that the peptide PGCPST effectively increased the cell viability and reduced the cell apoptosis in 6-OHDA-induced PC12. RNA sequencing further showed that the neuroprotective effect of the peptide PGCPST was mediated via sphingolipid metabolism-related pathways. With further research efforts, the peptide PGCPST was expected to develop into a new neuroprotective agent.

Effect and mechanism of fish scale extract natural hydrogel on skin protection and cell damage repair after UV irradiation

Skin lesions caused by ultraviolet radiation exposure seriously reduce people's life quality, safe natural products development to prevent and repair ultraviolet damage is an effective strategy. We investigated the protective and reparative effects of the natural composite gel (SE-gel) derived from fish scales on UV-irradiated skin by inhibiting reactive oxygen species (ROS) -mediated oxidative stress and inflammatory responses. Our results showed that SE-gel rich in glycine and proline had good ultraviolet absorption, water absorption, moisturizing and free radical scavenging abilities. In vitro, SE-gel could improve UV-irradiated L929 cell viability by 1.24 times via inhibiting 50% ROS production and malondialdehyde, and improving superoxide dismutase activity to reduce oxidative stress caused by UV irradiation. In UV-irradiated mouse skin damage model, SE-gel prevent UV-induced skin erythema, epidermal thickening, collagen fiber degradation and disruption, and reduced UV-induced inflammatory response via NF-κB signaling pathway, showing potential application in UV-irradiated skin damage prevention and repair.

An Analysis of the Plant- and Animal-Based Hydrocolloids as Byproducts of the Food Industry

Hydrocolloids are naturally occurring polysaccharides or proteins, which are used to gelatinize, modify texture, and thicken food products, and are also utilized in edible films and drug capsule production. Moreover, several hydrocolloids are known to have a positive impact on human health, including prebiotics rich in bioactive compounds. In this paper, plant-derived hydrocolloids from arrowroot (Maranta arundinacea), kuzu (Pueraria montana var lobata), Sassafras tree (Sassafras albidum) leaves, sugarcane, acorn, and animal-derived gelatin have been reviewed. Hydrocolloid processing, utilization, physicochemical activities, composition, and health benefits have been described. The food industry generates waste such as plant parts, fibers, residue, scales, bones, fins, feathers, or skin, which are often discarded back into the environment, polluting it or into landfills, where they provide no use and generate transport and storage costs. Food industry waste frequently contains useful compounds, which can yield additional income if acquired, thus decreasing the environmental pollution. Despite conventional manufacturing, the aforementioned hydrocolloids can be recycled as byproducts, which not only minimizes waste, lowers transportation and storage expenses, and boosts revenue, but also enables the production of novel, functional, and healthy food additives for the food industry worldwide.

Bioactive Peptides from Skipjack Tuna Cardiac Arterial Bulbs: Preparation, Identification, Antioxidant Activity, and Stability against Thermal, pH, and Simulated Gastrointestinal Digestion Treatments

Cardiac arterial bulbs of Skipjack tuna (Katsuwonus pelamis) are rich in elastin, and its hydrolysates are high quality raw materials for daily cosmetics. In order to effectively utilizing Skipjack tuna processing byproducts-cardiac arterial bulbs and to prepare peptides with high antioxidant activity, pepsin was selected from six proteases for hydrolyzing proteins, and the best hydrolysis conditions of pepsin were optimized. Using ultrafiltration and chromatographic methods, eleven antioxidant peptides were purified from protein hydrolysate of tuna cardiac arterial bulbs. Four tripeptides (QGD, PKK, GPQ and GLN) were identified as well as seven pentapeptides (GEQSN, GEEGD, YEGGD, GEGER, GEGQR, GPGLM and GDRGD). Three out of them, namely the tripeptide PKK and the pentapeptides YEGGD and GPGLM exhibited the highest radical scavenging activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and superoxide anion assays. They also showed to protect plasmid DNA and HepG2 cells against H₂O₂-induced oxidative stress. Furthermore, they exhibited high stability under temperature ranged from 20-100 °C, pH values ranged from 3-11, and they simulated gastrointestinal digestion for 240 min. These results suggest that the prepared eleven antioxidant peptides from cardiac arterial bulbs, especially the three peptides PKK, YEGGD, and GPGLM, could serve as promising candidates in health-promoting products due to their high antioxidant activity and their stability.

Antioxidant Activity, Functional Properties, and Cytoprotective Effects on HepG2 Cells of Tree Peony (Paeonia suffruticosa Andr.) Seed Protein Hydrolysate as Influenced by Molecular Weights Fractionation

In recent years, plant protein hydrolysates have gained increased attention due to their superior antioxidant activity and potential to prevent several chronic diseases associated with oxidative stress. This study aimed to investigate the antioxidant activity, functional properties, and cytoprotective effects of the tree peony seed protein hydrolysate (TPSPH) with different molecular weights (MWs). The antioxidant activities were evaluated by DPPH, hydroxyl radicals scavenging, Fe2+ chelating, and inhibition of the β-carotene oxidation abilities. The protective effects and mechanism against oxidative stress were determined using H2O2-stressed HepG2 cells. MW > 30 kDa of TPSPH showed the highest radical scavenging (DPPH IC50 = 0.04, hydroxyl IC50 = 0.89 mg/mL) and inhibition of β-carotene oxidation (80.07% at 2.0 mg/mL) activity. Moreover, MW > 30 kDa possessed high hydrophobicity, emulsifying capacity, and abundant antioxidant amino acids (28.22% of hydrophobic amino acids and 8.3% of aromatic amino acids). MW 5−10 kDa exhibited more effective protection against H2O2-induced HepG2 cells, by reducing reactive oxygen species (ROS), malonaldehyde (MDA), lactate dehydrogenase (LDH), and activating antioxidant enzymes (superoxide dismutase and catalase). These results indicated the potential application of TPSPH as an antioxidant in food and functional foods.

Identification of Antioxidant Peptides Derived from Tilapia (Oreochromis niloticus) Skin and Their Mechanism of Action by Molecular Docking

Antioxidants, which can activate the body’s antioxidant defence system and reduce oxidative stress damage, are important for maintaining free radical homeostasis between oxidative damage and antioxidant defence. Six antioxidant peptides (P1–P6) were isolated and identified from the enzymatic hydrolysate of tilapia skin by ultrafiltration, reversed-phase high-performance liquid chromatography (RP-HPLC) and liquid chromatography–tandem mass spectrometry (LC–MS/MS). Moreover, the scavenging mechanism of the identified peptides against DPPH (2,2-Diphenyl-1-picrylhydrazyl) and ABTS (2-azido-bis (3-ethylbenzothiazoline-6-sulfonic acid) was studied by molecular docking. It was found that Pro, Ala and Tyr were the characteristic amino acids for scavenging free radicals, and hydrogen bonding and hydrophobic interactions were the main interactions between the free radicals and antioxidant peptides. Among them, the peptide KAPDPGPGPM exhibited the highest DPPH free radical scavenging activity (IC₅₀ = 2.56 ± 0.15 mg/mL), in which the hydrogen bond between the free radical DDPH and Thr-6 was identified as the main interaction, and the hydrophobic interactions between the free radical DDPH and Ala, Gly and Pro were also identified. The peptide GGYDEY presented the highest scavenging activity against ABTS (IC₅₀ = 9.14 ± 0.08 mg/mL). The key structures for the interaction of this peptide with the free radical ABTS were identified as Gly-1 and Glu-5 (hydrogen bond sites), and the amino acids Tyr and Asp provided hydrophobic interactions. Furthermore, it was determined that the screened peptides are suitable for applications as antioxidants in the food industry, exhibit good water solubility and stability, are likely nonallergenic and are nontoxic. In summary, the results of this study provide a theoretical structural basis for examining the mechanism of action of antioxidant peptides and the application of enzymatic hydrolysates from tilapia skin.

Novel Antioxidant Collagen Peptides of Siberian Sturgeon (Acipenser baerii) Cartilages: The Preparation, Characterization, and Cytoprotection of H2O2-Damaged Human Umbilical Vein Endothelial Cells (HUVECs)

For making full use of aquatic by-products to produce high value-added products, Siberian sturgeon (Acipenser baerii) cartilages were degreased, mineralized, and separately hydrolyzed by five kinds of proteases. The collagen hydrolysate (SCH) generated by Alcalase showed the strongest 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) and hydroxide radical (HO·) scavenging activity. Subsequently, thirteen antioxidant peptides (SCP1-SCP3) were isolated from SCH, and they were identified as GPTGED, GEPGEQ, GPEGPAG, VPPQD, GLEDHA, GDRGAEG, PRGFRGPV, GEYGFE, GFIGFNG, PSVSLT, IELFPGLP, LRGEAGL, and RGEPGL with molecular weights of 574.55, 615.60, 583.60, 554.60, 640.64, 660.64, 885.04, 700.70, 710.79, 602.67, 942.12, 714.82, and 627.70 Da, respectively. GEYGFE, PSVSLT, and IELFPGLP showed the highest scavenging activity on DPPH· (EC₅₀: 1.27, 1.05, and 1.38 mg/mL, respectively) and HO· (EC₅₀: 1.16, 0.97, and 1.63 mg/mL, respectively), inhibiting capability of lipid peroxidation, and protective functions on H₂O₂-damaged plasmid DNA. More importantly, GEYGFE, PSVSLT, and IELFPGLP displayed significant cytoprotection on HUVECs against H₂O₂ injury by regulating the endogenous antioxidant enzymes of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to decrease the contents of reactive oxygen species (ROS) and malondialdehyde (MDA). Therefore, the research provided better technical assistance for a higher-value utilization of Siberian sturgeon cartilages and the thirteen isolated peptides—especially GEYGFE, PSVSLT, and IELFPGLP—which may serve as antioxidant additives for generating health-prone products to treat chronic diseases caused by oxidative stress.

Theragra chalcogramma Hydrolysates, Rich in Gly-Leu-Pro-Ser-Tyr-Thr, Exerts Anti-Photoaging Potential via Targeting MAPK and NF-κB Pathways in SD Rats

Previous studies have revealed that excessive exposure to UV irradiation is the main cause of skin photoaging and the signaling pathways of MAPK and NF-κB are involved in this progression. The present study aims to investigate the anti-photoaging effects of low molecular weight hydrolysates from Theragra chalcogramma (TCH) and to clarify the underlying mechanism. The degradation of mechanical barrier functions in photoaged skin was substantially ameliorated after TCH administration; meanwhile, TCH significantly elevated the antioxidant capacity and suppressed the over-production of inflammatory cytokine IL-1β. Moreover, the histopathological deteriorations such as epidermal hyperplasia and dermal loss were significantly alleviated, along with the increase in procollagen type I content and decrease in MMP-1 activity (p < 0.05). Furthermore, TCH effectively blocked the MAPK and NF-κB signaling pathways through inhibition of the phosphorylation of p38, JNK, ERK, iκB, and p65 proteins. Collectively, these data indicate that TCH has potential as a novel ingredient for the development of anti-photoaging foods.

Oral supplementation of sea cucumber and its hydrolysate mitigates ultraviolet A-induced photoaging in hairless mice

BACKGROUND

Chronic exposure to ultraviolet (UV) radiation promotes skin photoaging, which is clinically characterized by dryness, laxity, and wrinkling. Sea cucumber (Stichopus japonicus) (SC) is a marine organism with culinary and medicinal applications, especially in Asian countries. It is also a potential nutraceutical as it exhibits bioactive effects, such as antioxidant, antitumor, and anticancer activity. This study examined the effects of SC and its hydrolysate (SCH) on ultraviolet A (UVA) induced skin barrier function and wrinkle formation using hairless mice.

RESULTS

Ultraviolet A significantly induced transepidermal water loss and wrinkle formation, which were significantly mitigated upon oral administration of SC and SCH. Sea cucumber also mitigated the UVA-induced downregulation of epidermal natural moisturizing factors and the upregulation of Aqp3, Mmp13, Tnfa, and Il6 mRNA levels in the mouse skin.

CONCLUSION

Taken together, these results suggest that dietary SC and SCH exert anti-photoaging effects by modulating filaggrin synthesis and desquamation in the epidermis and regulating the NF-κB pathway in the skin. Our research indicates that SC and SCH have potential applications in nutricosmetics for photoaging. © 2021 Society of Chemical Industry.

Purification and Characterization of a Novel Calcium-Binding Heptapeptide from the Hydrolysate of Tilapia Bone with Its Osteogenic Activity

In this study, a calcium-binding peptide was obtained by hydrolyzing tilapia bone and its osteogenic activity was evaluated. Animal protease was selected from nine enzymes, and its hydrolysate was purified through preparative and semi-preparative reverse phase high-performance liquid chromatography. The purified peptide was identified as DGPSGPK (656.32 Da) and its calcium-binding capacity reached 111.98 µg/mg. The peptide calcium chelate (DGPSGPK-Ca) was obtained, and its structure was characterized through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and mass spectrometry (MS). The results of XRD and SEM showed that DGPSGPK-Ca was formed as a new compound. The carboxyl and amino groups of Lys and Asp residues may be the chelating sites of DGPSGPK according to the FTIR and MS results. The molecular simulation showed the carbonyl groups of Asp, Pro, Ser, and Lys residues involved in the binding of calcium. The interaction of DGPSGPK and different integrins was evaluated by molecular docking simulation, and the main forces involved were electrostatic interaction forces, hydrogen bonding and hydrophobic interactions. Furthermore, DGPSGPK could inhibit the differentiation of osteoclast and promote the proliferation, differentiation and mineralization of osteoblasts.

Tilapia skin peptides restore cyclophosphamide-induced premature ovarian failure via inhibiting oxidative stress and apoptosis in mice

Tilapia (Oreochromis mossambicus) skin high value-added compounds have not been fully utilized in tilapia processing. Here, the protective effects of tilapia skin peptides (TSP) on primary ovarian failure (POF) and their underlying mechanisms in mice were investigated. Cyclophosphamide (CP) was injected intraperitoneally (ip) for 14 days (10 mg kg^-1 d^-1) to establish a mouse model of POF. At the same time, the mice were given intragastrically (ig) TSP for 30 days (250 mg kg^-1 d^-1, 500 mg kg^-1 d^-1, and 1000 mg kg^-1 d^-1, respectively). The ovarian index, estrous cycle, hormone level, changes in the number of follicles at various levels, and biochemical tests were carried out at the end of the experiment. The body weight and ovarian index of mice in the POF group were markedly lower than that of the control group. Treatment with TSP reversed these changes significantly. TSP administration significantly restored the estrous cycle disorder of the mice versus that of the POF group. The level changes of progesterone (P), estradiol (E2), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) induced by CP were significantly reversed by TSP treatment. TSP inhibited oxidative stress in CP-induced mice by enhancing the total superoxide dismutase (T-SOD) activity and reducing malondialdehyde (MDA) levels in the ovaries. TSP improved the apoptosis of ovarian granulosa cells in CP-induced mice compared with the POF group. Furthermore, TSP regulated the Bcl-2/Bax/caspase-3 apoptosis pathway and enhanced the Nrf2/HO-1 signaling pathway. In conclusion, TSP could improve CP-induced POF via alleviating ovarian oxidative stress and granulosa cell apoptosis.

The pH dependence of emulsifying properties for glutathione disulfide at oil-water interfaces

Although peptides were widely used in many fields, their interface behaviors as surfactants have not been explored. The results of the surface tension experiments by an automatic surface tension meter indicate that the stability and emulsifying ability of glutathione disulfide (GSSG) under alkaline conditions were stronger than those under acidic conditions. With encoding the different oxygen and nitrogen atoms in GSSG, as well as the different hydrogen atoms bonded with oxygen and nitrogen atoms. The pH Dependence of the number of hydrogen bonds, affected by the protonation and deprotonation of the functional groups in GSSG, is calculated by LAMMPS software. The results demonstrate that GSSG forms twice as many hydrogen bonds under alkaline conditions as under acidic conditions, resulting in a better surface-interface activity in alkaline conditions. The interface properties of the GSSG surfactant can be regulated by pH. Therefore, GSSG is a potential pH-responsive surfactant.

Attenuation of UV-induced skin photoaging in rats by walnut protein hydrolysates is linked to the modulation of MAPK/AP-1 and TGF-β/Smad signaling pathways

There is growing evidence that prevention of skin photoaging by oral administration of food-derived proteins hydrolysates is intricately linked to its alleviation against oxidative stress through modulation of the signaling pathway. Previously, walnut protein hydrolysates (WPHs) were prepared by enzymatic hydrolysis by our group and exhibited excellent anti-photoaging effect through regulation of extracellular matrix metabolism and the NF-κB signaling pathway. However, its response to oxidative stress and cascade mechanism remain unknown. In the present study, Sprague-Dawley rats were exposed periodically to UV irradiation and orally administered with WPHs to further examine the effects of WPHs on the redox state, MAPK/AP-1 and TGF-β/Smad signaling pathways, type I procollagen synthesis, and histopathological impairments in photoaging skin. Intervention with WPHs for 18 weeks significantly alleviated the photoaging morphology, enhanced the antioxidant components, and downregulated the phosphorylation levels of extracellular signal-regulated kinase (ERK) and C-Jun N-terminal kinase (JNK and p38 proteins) in photoaging tissues, while significant alterations on the gene expression levels of ERK, JNK and p38 were not observed. Meanwhile, WPHs significantly activated the TGF-β/Smad signaling pathway and type I procollagen production. Furthermore, histopathological analysis illustrated that WPHs predominately attenuated epidermal hyperplasia, reduced inflammatory filtration, and promoted the deposition of collagen fibers in photoaging skin. Altogether, the underlying mechanism of WPHs attenuating skin photoaging might lie in the synergistic modulation by increasing the antioxidant capacity, modulating the MAPK/AP-1/MMP-1 and TGF-β/Smad signaling pathways, stimulating the synthesis of type I procollagen, and restoring the impaired architecture structure. Our findings suggest that WPHs are promising agents for preventing skin photoaging.

Protective effect of antioxidant peptides from grass carp scale gelatin on the H2O2-mediated oxidative injured HepG2 cells

The protective effect of antioxidant peptides from grass carp scale gelatin on hydrogen peroxide (H₂O₂)-mediated oxidative injured HepG2 cells was investigated, and the protective mechanism as well as peptide structure were studied. Pretreated with grass carp scale gelatin hydrolysates (GSGH) for 24 h significantly increased the survival rates and decreased the apoptosis rates of H₂O₂-mediated oxidative injured HepG2 cells. The increase in SOD, CAT and GPX activities, reduce in ROS level and MDA content, and weaken in damage on cell membrane and DNA could be responsible for the protective effect of GSGH on H₂O₂-mediated oxidative injured HepG2 cells. Peptide sequences of GSGH were analyzed by LC-ESI-Q-Orbitrap-MS/MS, and results showed that most of them were low molecular weight peptide at 358-986 Da. Synergistic effect existed among antioxidant peptides and contributed to the strong antioxidant activities of GSGH.

Purification, Identification, Activity Evaluation, and Stability of Antioxidant Peptides from Alcalase Hydrolysate of Antarctic Krill (Euphausia superba) Proteins

For utilizing the largest source of marine proteins, Antarctic krill (Euphausia superba) proteins were defatted and hydrolyzed separately using pepsin, alcalase, papain, trypsin, and netrase, and alcalase hydrolysate (EPAH) showed the highest DPPH radical (DPPH·) and hydroxyl radical (HO·) scavenging activity among five hydrolysates. Using ultrafiltration and chromatography methods, fifteen antioxidant peptides were purified from EPAH and identified as Asn-Gln-Met (NQM), Trp-Phe-Pro-Met (WFPM), Gln-Asn-Pro-Thr (QNPT), Tyr-Met-Asn-Phe (YMNF), Ser-Gly-Pro-Ala (SGPA), Ser-Leu-Pro-Tyr (SLPY), Gln-Tyr-Pro-Pro-Met-Gln-Tyr (QYPPMQY), Glu-Tyr-Glu-Ala (EYEA), Asn-Trp-Asp-Asp-Met-Arg-Ile-Val-Ala-Val (NWDDMRIVAV), Trp-Asp-Asp-Met-Glu-Arg-Leu-Val-Met-Ile (WDDMERLVMI), Asn-Trp-Asp-Asp-Met-Glu-Pro-Ser-Phe (NWD-DMEPSF), Asn-Gly-Pro-Asp-Pro-Arg-Pro-Ser-Gln-Gln (NGPDPRPSQQ), Ala-Phe-Leu-Trp-Asn (AFLWA), Asn-Val-Pro-Asp-Met (NVPDM), and Thr-Phe-Pro-Ile-Tyr-Asp-Tyr-Pro-Gln (TFPIYDPQ), respectively, using a protein sequencer and ESI/MS. Among fifteen antioxidant peptides, SLPY, QYPPMQY and EYEA showed the highest scavenging activities on DPPH· (EC₅₀ values of 1.18 ± 0.036, 1.547 ± 0.150, and 1.372 ± 0.274 mg/mL, respectively), HO· (EC₅₀ values of 0.826 ± 0.027, 1.022 ± 0.058, and 0.946 ± 0.011 mg/mL, respectively), and superoxide anion radical (EC₅₀ values of 0.789 ± 0.079, 0.913 ± 0.007, and 0.793 ± 0.056 mg/mL, respectively). Moreover, SLPY, QYPPMQY and EYEA showed strong reducing power, protective capability against H₂O₂-damaged plasmid DNA, and lipid peroxidation inhibition ability. Furthermore, SLPY, QYPPMQY, and EYEA had high stability under temperatures lower than 80 °C, pH values ranged from 6-8, and simulated GI digestion for 180 min. The results showed that fifteen antioxidant peptides from alcalase hydrolysate of Antarctic krill proteins, especially SLPY, QYPPMQY and EYEA, might serve as effective antioxidant agents applied in food and health products.

Ingestion of collagen hydrolysates alleviates skin chronological aging in an aged mouse model by increasing collagen synthesis

Although the use of collagen hydrolysates (CHs) as nutraceutical agents to protect skin against photoaging has been widely investigated, little is known about their effects on skin chronological aging and the underlying mechanism. Nutritional supplementation, such as collagen and related hydrolysates, might have beneficial effects on chronologically aged skin just as on photoaged skin. Hence, 13-month-old female Kunming mice ingested CHs for eight weeks to evaluate the effects of CHs on ameliorating skin chronological aging. CHs were enzymatically prepared using alcalase or collagenase, named ACH and CCH, respectively. The results showed that CHs or proline intake had no obvious effects on skin moisture and hyaluronic acid contents. However, ACHs significantly decreased skin laxity, increased collagen I content, normalized the ratio of collagen I/III and repaired dermal collagen fibers in a dose-dependent manner. At an identical dose, ACH showed an advantage over CCH or proline in significantly increasing collagen I content. Further study indicated that CHs mainly improved skin condition by activating the transforming growth factor β (TGF-β)/Smad signaling pathway to promote the synthesis of collagen I rather than inhibiting collagen I degradation by deregulating activator protein-1 (AP-1). The results indicated that CHs could benefit skin in both extrinsic and intrinsic aging as active dietary supplements.

Icariin enhances youth-like features by attenuating the declined gut microbiota in the aged mice

We previously reported the neuroprotective effects of icariin in rat cortical neurons. Here, we present a study on icariin's anti-aging effect in 24-month aged mice by treating them with a single daily dose of 100 mg/kg of icariin for 15 consecutive days. Icariin treatment improved motor coordination and learning skills while lowered oxidative stress biomarkers in the serum, brain, kidney, and liver of the aged mice. In addition, icariin improved the intestinal integrity of the aged mice by upregulating tight junction adhesion molecules and the Paneth and goblet cells, along with the reduction of iNOS and pro-inflammatory cytokines (IL-1β, TNF-α, IL-2 and IL-6, and IL-12). Icariin treatments also significantly upregulated aging-related signaling molecules, Sirt 1, 3 & 6, Pot1α, BUB1b, FOXO1, Ep300, ANXA3, Calb1, SNAP25, and BDNF in old mice. Through gut microbiota (GM) analysis, we observed icariin-associated improvements in GM composition of aged mice by reinstating bacteria found in the young mice, while suppressing some bacteria found in the untreated old mice. To clarify whether icariin's anti-aging effect is rooted in the GM, we performed fecal microbiota transfer (FMT) from icariin-treated old mice to the old mice. FMT-recipients exhibited similar improvements in the rotarod score and age-related biomarkers as observed in the icariin-treated old mice. Equal or better improvement on the youth-like features was noticed when aged mice were FMT with feces from young mice. Our study shows that both direct treatments with icariin and fecal transplant from the icariin-treated aged mice produce similar anti-aging phenotypes in the aged mice. We prove that GM plays a pivotal role in the healing abilities of icariin. Icariin has the potentials to be developed as a medicine for the wellness of the aged adults.

Cosmetic, Biomedical and Pharmaceutical Applications of Fish Gelatin/Hydrolysates

There are several reviews that separately cover different aspects of fish gelatin including its preparation, characteristics, modifications, and applications. Its packaging application in food industry is extensively covered but other applications are not covered or covered alongside with those of collagen. This review is comprehensive, specific to fish gelatin/hydrolysate and cites recent research. It covers cosmetic applications, intrinsic activities, and biomedical applications in wound dressing and wound healing, gene therapy, tissue engineering, implants, and bone substitutes. It also covers its pharmaceutical applications including manufacturing of capsules, coating of microparticles/oils, coating of tablets, stabilization of emulsions and drug delivery (microspheres, nanospheres, scaffolds, microneedles, and hydrogels). The main outcomes are that fish gelatin is immunologically safe, protects from the possibility of transmission of bovine spongiform encephalopathy and foot and mouth diseases, has an economic and environmental benefits, and may be suitable for those that practice religious-based food restrictions, i.e., people of Muslim, Jewish and Hindu faiths. It has unique rheological properties, making it more suitable for certain applications than mammalian gelatins. It can be easily modified to enhance its mechanical properties. However, extensive research is still needed to characterize gelatin hydrolysates, elucidate the Structure Activity Relationship (SAR), and formulate them into dosage forms. Additionally, expansion into cosmetic applications and drug delivery is needed.

Fish Waste: From Problem to Valuable Resource

Following the growth of the global population and the subsequent rapid increase in urbanization and industrialization, the fisheries and aquaculture production has seen a massive increase driven mainly by the development of fishing technologies. Accordingly, a remarkable increase in the amount of fish waste has been produced around the world; it has been estimated that about two-thirds of the total amount of fish is discarded as waste, creating huge economic and environmental concerns. For this reason, the disposal and recycling of these wastes has become a key issue to be resolved. With the growing attention of the circular economy, the exploitation of underused or discarded marine material can represent a sustainable strategy for the realization of a circular bioeconomy, with the production of materials with high added value. In this study, we underline the enormous role that fish waste can have in the socio-economic sector. This review presents the different compounds with high commercial value obtained by fish byproducts, including collagen, enzymes, and bioactive peptides, and lists their possible applications in different fields.

Polygoni Multiflori Radix Preparat Delays Skin Aging by Inducing Mitophagy

Background

As the skin is the largest organ of the human body, it is aging inevitably and produces cosmetic and psychological problems, and even disease. Therefore, the molecular mechanisms related to the prevention of skin aging need to be further explored.

Methods

Aging models were constructed by D-galactose. Mice were administrated with polygoni multiflori radix preparat (PMRP), PMRP and 3-methyladenine, or PMRP and rapamycin intragastrically. The apparent and viscera index of aged rats was measured. Then, the physicochemical property, antioxidant ability, histological structure, mitochondrial membrane potential, ATP and ROS levels, and mitophagy of aged skins were determined. Finally, the expression of PINK1, Parkin, P62, and LC3II/I; apoptosis-related proteins; and the percentage of apoptotic cells were measured.

Results

PMRP relieved skin aging with reducing of thymus index, improvement of pathological damage and histological structure, increase of the expression area of fibrous tissue, the ratio of type I to type III collagen, and antioxidant ability of aged skins. Importantly, PMRP also improved mitochondrial dysfunction with an increase in the content of mitochondrial membrane potential and ATP and a decrease of ROS levels. Moreover, mitophagy was enhanced with the treatment of PMRP when observed using electron microscopy, and the expression of PINK1, Parkin, and LC3I/II was increased with PMRP treatment but P62 expression was decreased. Meanwhile, PMRP alleviated apoptosis with a decrease of apoptotic cell and the expression of Cleaved-cas3, Bax, Cyt-c, AIF, and Smac as well as an increase of Bcl-2 expression.

Conclusion

The results demonstrated that the polygoni multiflori radix preparata may delay skin aging by inducing mitophagy.

Recent Advances in Molecular Docking for the Research and Discovery of Potential Marine Drugs

Marine drugs have long been used and exhibit unique advantages in clinical practices. Among the marine drugs that have been approved by the Food and Drug Administration (FDA), the protein–ligand interactions, such as cytarabine–DNA polymerase, vidarabine–adenylyl cyclase, and eribulin–tubulin complexes, are the important mechanisms of action for their efficacy. However, the complex and multi-targeted components in marine medicinal resources, their bio-active chemical basis, and mechanisms of action have posed huge challenges in the discovery and development of marine drugs so far, which need to be systematically investigated in-depth. Molecular docking could effectively predict the binding mode and binding energy of the protein–ligand complexes and has become a major method of computer-aided drug design (CADD), hence this powerful tool has been widely used in many aspects of the research on marine drugs. This review introduces the basic principles and software of the molecular docking and further summarizes the applications of this method in marine drug discovery and design, including the early virtual screening in the drug discovery stage, drug target discovery, potential mechanisms of action, and the prediction of drug metabolism. In addition, this review would also discuss and prospect the problems of molecular docking, in order to provide more theoretical basis for clinical practices and new marine drug research and development.

Protein Recovery from Underutilised Marine Bioresources for Product Development with Nutraceutical and Pharmaceutical Bioactivities

The global demand for dietary proteins and protein-derived products are projected to dramatically increase which cannot be met using traditional protein sources. Seafood processing by-products (SPBs) and microalgae are promising resources that can fill the demand gap for proteins and protein derivatives. Globally, 32 million tonnes of SPBs are estimated to be produced annually which represents an inexpensive resource for protein recovery while technical advantages in microalgal biomass production would yield secure protein supplies with minimal competition for arable land and freshwater resources. Moreover, these biomaterials are a rich source of proteins with high nutritional quality while protein hydrolysates and biopeptides derived from these marine proteins possess several useful bioactivities for commercial applications in multiple industries. Efficient utilisation of these marine biomaterials for protein recovery would not only supplement global demand and save natural bioresources but would also successfully address the financial and environmental burdens of biowaste, paving the way for greener production and a circular economy. This comprehensive review analyses the potential of using SPBs and microalgae for protein recovery and production critically assessing the feasibility of current and emerging technologies used for the process development. Nutritional quality, functionalities, and bioactivities of the extracted proteins and derived products together with their potential applications for commercial product development are also systematically summarised and discussed.

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.

Comparison of an angiotensin-I-converting enzyme inhibitory peptide from tilapia (Oreochromis niloticus) with captopril: inhibition kinetics, in vivo effect, simulated gastrointestinal digestion and a molecular docking study

BACKGROUND

In order to utilize tilapia skin gelatin hydrolysate protein, which is normally discarded as industrial waste in the process of fish manufacture, we study the in vivo and in vitro angiotensin-I-converting enzyme (ACE) inhibitory activity of the peptide Leu-Ser-Gly-Tyr-Gly-Pro (LSGYGP). The aim was to provide a pharmacological basis of the development of minimal side effects of ACE inhibitors by comparative analysis with captopril in molecular docking.

RESULTS

This peptide from protein-rich wastes showed excellent ACE inhibitory activity (IC₅₀  = 2.577 μmol L^-1 ) and exhibited a mixed noncompetitive inhibitory pattern with Lineweaver-Burk plots. Furthermore, LSGYGP and captopril groups both showed significant decreases in blood pressure after 6 h and maintained good digestive stability over 4 h. Molecular bond interactions differentiate competitive captopril upon hydrogen bond interactions and Zn(II) interaction. The C-terminal Pro generates three interactions (hydrogen bonds, hydrophilic interactions and Van der Waals interactions) in the peptide and effectively interacts with the S1 and S2 pockets of ACE.

CONCLUSION

LSGYGP, with an IC₅₀ value of 2.577 μmol L^-1 , has an antihypertensive effect in spontaneously hypertensive rats. Through comparison with captopril, this study revealed that LSGYGP may be a potential food-derived ACE inhibitory peptide and could act as a functional food ingredient to prevent hypertension. © 2019 Society of Chemical Industry.

Low molecular polypeptide from oyster hydrolysate recovers photoaging in SKH-1 hairless mice

When the human skin is chronically exposed to external stimuli such as ultraviolet (UV) radiation, the skin tissue suffers damage and the structure of the extracellular matrix (ECM) in the skin is disrupted. This eventually causes symptoms such as wrinkles loss of elasticity, skin sagging, and skin cancer. We previously found that hydrolysate extracted from pacific oyster (Crassostrea gigas) is effective in improving wrinkle formation. In this study, we selected a pentapeptide that was expected to have the most wrinkle reduction effect among the various peptides in oyster hydrolysate through preliminary in vitro screening and examined whether the pentapeptide derived from oyster hydrolysate (OHP) is effective in reducing wrinkles in vivo. We investigated the wrinkle-reducing effect of the OHP through 18-week SKH-1 hairless mice model. Our results showed that the OHP reduces wrinkles lengths, depths, and epidermal thickness which were increased by UVB radiation, and restores the amount of collagen. The OHP recovered the activity of antioxidant enzymes and regulated the expression of proinflammatory cytokines. We also found that OHP increases the expression of type I collagen through stimulating the TGFβ/Smad signaling pathway and inhibits the MMPs expression by regulating the MAPK/AP-1 signaling pathway. This study has shown that the OHP plays crucial roles in collagen production and wrinkle reduction in hairless mice and we proved the possibility of the OHP as a component for inhibiting wrinkle formation which was induced by photoaging.

Gelatin and Antioxidant Peptides from Gelatin Hydrolysate of Skipjack Tuna (Katsuwonus pelamis) Scales: Preparation, Identification and Activity Evaluation

For full use of fish by-products, scale gelatin (TG) and antioxidant peptides (APs) of skipjack tuna (Katsuwonus pelamis) were prepared, and their properties were characterized using an amino acid analyzer, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared spectroscopy (FTIR), electrospray ionization mass spectrometers (ESI-MS), and radical scavenging assays. The results indicate that TG with a yield of 3.46 ± 0.27% contained Gly (327.9 ± 5.2 residues/1000 residues) as the major amino acid and its imino acid content was 196.1 residues/1000 residues. The structure of TG was more unstable than that of type I collagen from scales of skipjack tuna (TC) and TG was more suitable for preparation of hydrolysate by protease than mammalian gelatins. Therefore, TG was separately hydrolyzed under five proteases (pepsin, papain, trypsin, neutrase, and alcalase) and ten APs (TGP1–TGP10) were isolated from the alcalase-hydrolysate. Among them, TGP5, TGP7, and TGP9 with high antioxidant activity were identified as His-Gly-Pro-Hyp-Gly-Glu (TGP5), Asp-Gly-Pro-Lys-Gly-His (TGP7) and Met-Leu-Gly-Pro-Phe-Gly-Pro-Ser (TGP9), respectively. Furthermore, TGP5, TGP7, and TGP9 exhibited a high radical scavenging capability on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (EC₅₀ values of 1.34, 0.54, and 0.67 mg/mL, respectively), hydroxyl radical (EC₅₀ values of 1.03, 0.41, and 0.74 mg/mL, respectively), and superoxide anion radical (EC₅₀ values of 1.19, 0.71, and 1.59 mg/mL, respectively). These results suggest that three APs (TGP5, TGP7, and TGP9), especially TGP7, have a strong antioxidant activity and could act as potential antioxidant ingredients applied in functional products.

Identification and Active Evaluation of Antioxidant Peptides from Protein Hydrolysates of Skipjack Tuna (Katsuwonus pelamis) Head

For the full use of fish by-products to produce antioxidant peptides, skipjack tuna (Katsuwonus pelamis) heads generated during can processing were defatted and hydrolyzed using the in vitro gastrointestinal (GI) digestion (pepsin–trypsin system) method and six antioxidant peptides (P1 to P6) were purified from the head hydrolysate (KPH) using ultrafiltration and serial chromatography methods. Six isolated peptides (P1 to P6) were identified as Val-Glu-Glu (VEE, P1), Trp-Met-Phe-Asp-Trp (WMFDW, P2), Asp-Ala-Gly-Pro-Tyr-Gly-Pro-Ile (DAGPYGPI, P3), Trp-Met-Gly-Pro-Tyr (WMGPY, P4), Glu-Arg-Gly-Pro-Leu-Gly-Pro-His (ERGPLGPH, P5), and Glu-Met- Gly-Pro-Ala (EMGPA, P6), respectively, using a protein sequencer and electrospray ionization-mass spectrometer. Among skipjack tuna head hydrolysates, fractions, and six isolated peptides (P1 to P6), WMFDW (P2), WMGPY (P4), and EMGPA (P6) showed the highest radical scavenging activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH) (EC₅₀ values of 0.31, 0.33, and 0.46 mg/mL for WMFDW, WMGPY, and EMGPA, respectively), hydroxyl (EC₅₀ values of 0.30, 0.43, and 0.52 mg/mL for WMFDW, WMGPY, and EMGPA, respectively), and superoxide anion (EC₅₀ values of 0.56, 0.38, and 0.71 mg/mL for WMFDW, WMGPY, and EMGPA, respectively). Moreover, WMFDW, WMGPY, and EMGPA showed strong capability in reducing power and lipd peroxidation inhibition in the linoleic acid system. In addition, WMFDW, WMGPY, and EMGPA can retain strong antioxidant activity at temperatures lower than 60 °C and pH values ranged from 5 to 9. The results showed that six isolated peptides (P1 to P6) from skipjack tuna heads, especially WMFDW, WMGPY, and EMGPA, might be applied in health care products acting as powerful antioxidant agents.

A Peptide YGDEY from Tilapia Gelatin Hydrolysates Inhibits UVB-mediated Skin Photoaging by Regulating MMP-1 and MMP-9 Expression in HaCaT Cells

In this study, we investigated the protective effects of a peptide (YGDEY, Tyr-Gly-Asp-Glu-Tyr) isolated from tilapia skin gelatin hydrolysates (TGHs), against UVB-induced photoaging in human keratinocytes (HaCaT) cells. Results showed that YGDEY significantly decreased levels of intracellular reactive oxygen species (ROS), increased antioxidant factors (Superoxide Dismutase, SOD and Glutathione, GSH) expression and maintained balance between GSH and GSSG in HaCaT cells. Comet assay shows that YGDEY can protect DNA from oxidative damage. Furthermore, it significantly inhibited MMP-1 (collagenase) and MMP-9 (gelatinase) expression and increased Type I procollagen production. In addition, the molecular docking study showed that YGDEY may form active sites with MMP-1 and MMP-9. Moreover, Western blot analysis was utilized to measure the protein levels of UVB-induced mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways. Therefore, these results suggested that YGDEY has a therapeutic effectiveness in prevention of UVB-induced cellular damage, and it is a candidate worthy of being developed as a potential natural antioxidant and food additive.

Oral administration of oyster (Crassostrea gigas) hydrolysates protects against wrinkle formation by regulating the MAPK pathway in UVB-irradiated hairless mice

Chronic ultraviolet (UV) irradiation induces wrinkle formation. UV exposure increases reactive oxygen species (ROS) and upregulates the expression of matrix metalloproteinases (MMPs), which results in skin photoaging. Oyster (Crassostrea gigas), which is an abundant food resource in Asia and Europe, contains various sources of biological compounds and has several effects. Also, oyster hydrolysate (OH) has many biological activities. We investigated the inhibitory effects of OH on wrinkle formation in UVB-irradiated hairless mice. We induced UVB irradiation in hairless mice for 18 weeks and administered OH orally from the 9th week to the 18th week. We performed skin replicas and histological analyses in UVB-irradiated hairless mice dorsal skins. To determine the inhibitory mechanism of OH on wrinkle formation, we measured gene and protein expressions in dorsal skin using RT-qPCR and western blot analyses respectively. In our study, OH decreases wrinkle formation, epidermal thickness and collagen degradation in UVB-irradiated hairless mice. The gene expressions of MMPs were decreased and the gene expressions of collagen type I and TIMP-1 were increased in OH administered groups. Like gene expression tendencies, the protein expressions of MMPs were reduced and that of collagen type I was increased. Furthermore, the phosphorylation levels of ERK, JNK, and p38 were reduced in OH administered groups. We found that OH inhibits wrinkle formation, skin thickening, and collagen degradation by downregulating the MMP expression via the regulation of phosphorylation of MAPK. The results showed that OH significantly prevents UVB-induced photoaging in dorsal skin. Consistent with in vivo data, OH has potential as an anti-wrinkle agent.

In Vitro Vascular-Protective Effects of a Tilapia By-Product Oligopeptide on Angiotensin II-Induced Hypertensive Endothelial Injury in HUVEC by Nrf2/NF-κB Pathways

Angiotensin II (Ang II) is closely involved in endothelial injury during the development of hypertension. In this study, the protective effects of the tilapia by-product oligopeptide Leu-Ser-Gly-Tyr-Gly-Pro (LSGYGP) on oxidative stress and endothelial injury in Angiotensin II (Ang II)-stimulated human umbilical vein endothelial cells (HUVEC) were evaluated. LSGYGP dose-dependently suppressed the fluorescence intensities of nitric oxide (NO) and reactive oxygen species (ROS), inhibited the nuclear factor-kappa B (NF-κB) pathway, and reduced inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and endothelin-1 (ET-1) expression, as shown by western blot. In addition, it attenuated the expression of gamma-glutamyltransferase (GGT) and heme oxygenase 1 (HO-1), as well as increasing superoxide dismutase (SOD) and glutathione (GSH) expression through the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. Other experiments revealed that LSGYGP increased the apoptotic inhibition ratio between cleaved-caspase-3/procaspase-3, reduced expressions of pro-apoptotic ratio between Bcl-2/Bax, inhibited phosphorylation of mitogen-activated protein kinases (MAPK), and increased phosphorylation of the serine/threonine kinase (Akt) pathway. Furthermore, LSGYGP significantly decreased Ang II-induced DNA damage in a comet assay, and molecular docking results showed that the steady interaction between LSGYGP with NF-κB may be attributed to hydrogen bonds. These results suggest that this oligopeptide is effective in protecting against Ang II-induced HUVEC injury through the reduction of oxidative stress and alleviating endothelial damage. Thus, it has the potential for the therapeutic treatment of hypertension-associated diseases.

Protective effects of collagen polypeptide from tilapia skin against injuries to the liver and kidneys of mice induced by d-galactose

We wished to investigate the role of a tilapia skin collagen polypeptide (TSCP; molecular weight <3 kDa) in alleviating liver and kidney injuries in aging mice induced by d-galactose (d-gal) and its underlying mechanism of action. First, we characterized TSCP. TSCP was passed through a 3-kDa ultrafiltration membrane, desalted in water by a solid-phase extraction column, purified further by reverse phase-high performance liquid chromatography, and analyzed by electrospray ionization mass spectrometry and tandem mass spectrometry. TSCP contained 17 types of amino acids (AAs) and 41 peptide chains of length 7 AAs to 22 AAs. The content of free AAs and total AAs of TSCP was 13.5% and 93.79%, respectively. Next, we undertook animal experiments. Mice were injected once-daily with D-gal (300 mg/kg body weight, s.c.) for 8 weeks, and TSCP was administered simultaneously once-daily by intragastric gavage. TSCP could visibly improve the decreased body weight, depressed appetite, and mental deterioration of mice triggered by d-gal. TSCP could also alleviate d-gal-induced damage to the liver and kidneys according to histopathology (especially high-dose TSCP). Consistent with these macroscopic and pathologic changes, TSCP could also prevent d-gal-induced increases in serum levels of alanine aminotransferase, aspartate transaminase, alkaline phosphatase, lipid peroxidation, creatinine and uric acid, as well as decreases in serum levels of immunoglobulin (Ig)G and IgM. Moreover, TSCP improved the activities of superoxide dismutase, catalase, and glutathione peroxidase, but also inhibited the increases in the levels of malondialdehyde and inducible nitric oxide synthase expression in the liver and kidneys of d-gal-treated mice. These results suggest that TSCP can alleviate the injuries to the liver and kidneys in aging mice induced by d-gal, and that its mechanism of action might be, at least partially, associated with attenuation of oxidative stress and enhancement of immune function.

Effects of rambutan (Nephelium lappaceum) peel phenolics and Leu-Ser-Gly-Tyr-Gly-Pro on hairless mice skin photoaging induced by ultraviolet irradiation

Rambutan peel phenolics (RPP) have high antioxidant and anti-inflammatory activities. Leu-Ser-Gly-Tyr-Gly-Pro (LSGYGP) possesses good radical scavenging activity and matrix metalloproteinase (MMPs) inhibitory ability. These underlying mechanisms indicated that RPP and LSGYGP may be used for antiphotoaging. Few data on the effects of RPP and LSGYGP on in vivo photoaging are available. We evaluated the effects of RPP and/or LSGYGP on ultraviolet (UV)-induced hairless mice skin photoaging. In particular, we analyzed the additive effect of RPP and LSGYGP. The biochemical indices of mice skin, including composition (collagen and hyaluronic acid [HA] contents), oxidant stress (antioxidant enzyme activities and glutathione and malondialdehyde contents), MMPs (MMP-1, MMP-3, and MMP-9 levels), inflammatory cytokines (interleukin (IL)-1α, tumor nuclear factor-α, and IL-6 levels) and the phosphorylation of the mitogen-activated protein kinase pathway, were determined. Results showed a protective effect of RPP and/or LSGYGP on photoaging skin. LSGYGP showed considerable effects on skin collagen and HA contents. RPP showed improved effects on the regulation of the oxidant stress and inflammatory cytokine levels. RPP and LSGYGP exerted an additive effect on the amelioration of the biochemical indices of UV-induced photoaging skin. The histological changes showed that RPP and LSGYGP recovered the changes in skin tissue and endogenous collagen.

Preparation and Characterization of Gelatin and Antioxidant Peptides from Gelatin Hydrolysate of Skipjack Tuna (Katsuwonus pelamis) Bone Stimulated by in vitro Gastrointestinal Digestion

In China, a large amount of fish bones are produced during the processing of tuna cans production. For full use of those by-products, gelatin (STB-G) with a yield of 6.37 ± 0.64% was extracted from skipjack tuna (Katsuwonus pelamis) bone using water at 60 °C for 8 h. Amino acid analysis showed that STB-G contained Gly (340.3 residues/1000 residues) as the major amino acid and its imino acid content was 177.3 residues/1000 residues. Amino acid composition, SDS-PAGE, and Fourier transform infrared (FTIR) spectrum investigations confirmed that the physicochemical properties of STB-G were similar to those of type I collagen from skipjack tuna bone (STB-C), but partial high molecular weight components of STB-G were degraded during the extraction process, which induced that the gelatin was easier to be hydrolyzed by protease than mammalian gelatins and was suitable for preparation of hydrolysate. Therefore, STB-G was hydrolyzed under in vitro gastrointestinal digestion (pepsin-trypsin system) and five antioxidant peptides were purified from the resulted hydrolysate (STB-GH) and identified as GPDGR, GADIVA, GAPGPQMV, AGPK, and GAEGFIF, respectively. Among the gelatin hydrolysate, fractions, and isolated peptides, GADIVA and GAEGFIF exhibited the strongest scavenging activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (EC50 0.57 and 0.30 mg/mL), hydroxyl radical (EC50 0.25 and 0.32 mg/mL), superoxide anion radical (EC50 0.52 and 0.48 mg/mL), and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical (EC50 0.41 and 0.21 mg/mL). Moreover, GADIVA and GAEGFIF showed a high inhibiting ability on lipid peroxidation in a linoleic acid model system. The strong activities of five isolated peptides profited by their small molecular sizes and the antioxidant amino acid residues in their sequences. These results suggested that five isolated peptides (STP1⁻STP5), especially GADIVA and GAEGFIF, might serve as potential antioxidants applied in health food industries.