Oyster Peptides Research Articles

Novel Insights into Ethanol-Soluble Oyster Peptide-Zinc-Chelating Agents: Structural Characterization, Chelation Mechanism, and Potential Protection on MEHP-Induced Leydig Cells.

Numerous studies have reported that mono-(2-ethylhexyl) phthalate (MEHP) (bioactive metabolite of Di(2-ethylhexyl) phthalate) has inhibitory effects on Leydig cells. This study aims to prepare an oyster peptide-zinc complex (PEP-Zn) to alleviate MEHP-induced damage in Leydig cells. Zinc-binding peptides were obtained through the following processes: zinc-immobilized affinity chromatography (IMAC-Zn2+), liquid chromatography-mass spectrometry technology (LC-MS/MS) analysis, molecular docking, molecular dynamic simulation, and structural characterization. Then, the Zn-binding peptide (PEP) named Glu-His-Ala-Pro-Asn-His-Asp-Asn-Pro-Gly-Asp-Leu (EHAPNHDNPGDL) was identified. EHAPNHDNPGDL showed the highest zinc-chelating ability of 49.74 ± 1.44%, which was higher than that of the ethanol-soluble oyster peptides (27.50 ± 0.41%). In the EHAPNHDNPGDL-Zn complex, Asn-5, Asp-7, Asn-8, His-2, and Asp-11 played an important role in binding to the zinc ion. Additionally, EHAPNHDNPGDL-Zn was found to increase the cell viability, significantly increase the relative activity of antioxidant enzymes and testosterone content, and decrease malondialdehyde (MDA) content in MEHP-induced TM3 cells. The results also indicated that EHAPNHDNPGDL-Zn could alleviate MEHP-induced apoptosis by reducing the protein level of p53, p21, and Bax, and increasing the protein level of Bcl-2. These results indicate that the zinc-chelating peptides derived from oyster peptides could be used as a potential dietary zinc supplement.

The Discovery and Characterization of a Potent DPP-IV Inhibitory Peptide from Oysters for the Treatment of Type 2 Diabetes Based on Computational and Experimental Studies.

The inhibition of dipeptidyl peptidase-IV (DPP-IV) is a promising approach for regulating the blood glucose levels in patients with type 2 diabetes (T2D). Oysters, rich in functional peptides, contain peptides capable of inhibiting DPP-IV activity. This study aims to identify the hypoglycemic peptides from oysters and investigate their potential anti-T2D targets and mechanisms. This research utilized virtual screening for the peptide selection, followed by in vitro DPP-IV activity assays to validate the chosen peptide. Network pharmacology was employed to identify the potential targets, GO terms, and KEGG pathways. Molecular docking and molecular dynamics simulations were used to provide virtual confirmation. The virtual screening identified LRGFGNPPT as the most promising peptide among the screened oyster peptides. The in vitro studies confirmed its inhibitory effect on DPP-IV activity. Network pharmacology revealed that LRGFGNPPT exerts an anti-T2D effect through multiple targets and signaling pathways. The key hub targets are AKT1, ACE, and REN. Additionally, the molecular docking results showed that LRGFGNPPT exhibited a strong binding affinity with targets like AKT1, ACE, and REN, which was further confirmed by the molecular dynamics simulations showcasing a stable peptide-target interaction. This study highlights the potential of LRGFGNPPT as a natural anti-T2D peptide, providing valuable insights for potential future pharmaceutical or dietary interventions in T2D management.

The Preventive Effect of Low-Molecular Weight Oyster Peptides on Lipopolysaccharide-Induced Acute Colitis in Mice by Modulating Intestinal Microbiota Communities.

Colitis causes inflammation, diarrhoea, fever, and other serious illnesses, posing a serious threat to human health and safety. Current medications for the treatment of colitis have serious side effects. Therefore, the new strategy of creating a defence barrier for immune function by adding anti-inflammatory foods to the daily diet is worth advocating for. Low-molecular weight oyster peptides (LOPs) are a natural food with anti-inflammatory activity extracted from oysters, so intervention with LOPs is likely to be an effective preventive solution. The aim of this study was to investigate the preventive effect of LOPs on lipopolysaccharide (LPS)-induced acute colitis inflammation in mice and its underlying mechanism. The results showed that LOPs not only inhibited the colonic histopathy in mice induced by LPS-induced inflammation but also reduced the inflammatory response in the blood. In addition, LOPs significantly increased the number of beneficial bacteria (Alistipes, Mucispirillum, and Oscillospira), decreased the number of harmful bacteria (Coprobacillus, Acinetobater) in the intestinal microbiota, and further affected the absorption and utilisation of short-chain fatty acids (SCFAs) in the intestinal tract. In conclusion, dietary supplementation with LOPs is a promising health-promoting dietary supplement and nutraceutical for the prevention of acute colitis by reducing the inflammatory response and modulating the intestinal microbial communities.

Natural zinc-rich oyster peptides ameliorate DSS-induced colitis via antioxidation, anti-inflammation, intestinal barrier repair, microbiota modulation, and SCFA accumulation

Natural oyster zinc-rich peptide (OZP) was extracted and purified. The higher zinc concentration in natural OZP may be closely related to the high zinc affinity of amino acids containing Lys, His, Cys, Val, Arg and Ser residues. FTIR analysis indicated that amino, amide, carboxyl and carbonyl groups may contribute to the binding sites for zinc and peptides. Administration of OZP ameliorated the symptoms of DSS-induced ulcerative colitis (UC) in mice, including weight loss, colonic damage, mucosal edema, goblet cell exhaustion and crypt disappearance. Natural OZP suppressed oxidative stress by significantly reducing the level of NO, MDA and MPO as well as increasing SOD activity. The anti-inflammatory effects of OZP were associated with the inhibition of TLR4/NF-κB pathways by diminishing NF-κB, TLR4, COX-2, iNOS, TNF-α, IL-6 and IFN-γ and elevating IL-10. By promoting mucus secretion, repairing goblet cells and enhancing the expression of tight junction proteins including occludin, claudin-1 and ZO-1, natural OZP maintained the intestinal barrier function. Furthermore, natural OZP regulated the microbial composition by remarkedly enhancing the beneficial microbial abundance like Faecalibaculum, Odoribacter and Anaerostipes, which in turn led to a significant increase in SCFA production. Collectively, natural OZP exerted the synergistic capacity to protect against DSS-induced UC by improving antioxidation and anti-inflammation, repairing intestinal barrier and modulating intestinal microbiota and SCFA.

Oyster Peptides Ameliorate Dextran Sulfate Sodium-Induced Ulcerative Colitis via Modulating the Gut Microbiota and Inhibiting the TLR4/NF-κB Pathway.

Ulcerative colitis (UC) is an inflammatory bowel disease with an increasing prevalence year over year, and the medications used to treat patients with UC clinically have severe side effects. Oyster peptides (OPs) have anti-inflammatory and antioxidant properties as functional foods that can alleviate a wide range of inflammatory conditions. However, the application of oyster peptides in ulcerative colitis is not well studied. In this work, an animal model of acute colitis was established using 3% dextran sulfate sodium (DSS), and the impact of OP therapy on colitis in mice was examined. Supplementing with OPs prevented DSS-induced colitis from worsening, reduced the expression of oxidative stress and inflammatory markers, and restored the intestinal barrier damage caused by DSS-induced colitis in mice. The 16S rDNA results showed that the OP treatment improved the gut microbiota structure of the UC mice, including increasing microbial diversity, increasing beneficial bacteria, and decreasing harmful bacteria. In the UC mice, the OP therapy decreased the relative abundance of Family_XIII_AD3011_group and Prevotella_9 and increased the relative abundance of Alistipes. In conclusion, OP treatment can inhibit the TLR4/NF-κB pathway and improve the intestinal microbiota in UC mice, which in turn alleviates DSS-induced colitis, providing a reference for the treatment of clinical UC patients.

Preparation of oyster peptide and Pfaffia glomerata pressed candy and its ameliorative effect on sexual dysfunction in male mice.

Oyster peptide (OP) and Pfaffia glomerata extract (PGE) were used as raw materials. The optimal formulation of the pressed candy (PC) was optimized by one-way experiment and D-optimal mixture experiment design, and animal experiment was used to evaluate the effect of PC on male sexual dysfunction. The results showed that PC intervention significantly improved the sexual behavior of male mice with sexual dysfunction, including a significant shortening of the mount latency (ML) and intromission latency, and a significant increase in the mount frequency (MF) and intromission frequency (IF). At the same time, the concentrations of serum testosterone (T) and luteinizing hormone (LH) in mice were restored, and the erectile parameters and pathological changes of penile tissue were improved. Further studies found that PC intervention increased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and reduced the content of malondialdehyde (MDA) in testicular tissue. In addition, PC intervention improved testicular tissue morphology. In conclusion, the obtained PC has good taste quality, and the relevant quality indicators are qualified. It has a good ameliorative effect on male sexual dysfunction and may be a potential dietary supplement.

Carboxymethyl cellulose and carboxymethyl chitosan-based composite nanogel as a stable delivery vehicle for oyster peptides: Characterization, absorption and transport mechanism

An oyster peptide (OPs)-loaded composite nanogel based on carboxymethyl cellulose and carboxymethyl chitosan (CMC@CMCS@OPs) was prepared, and the characterization, absorption and transport mechanism were further investigated. CMC@CMCS@OPs, a dense spherical microstructure with a diameter of ∼64 nm, which enhanced the thermal and digestive stabilities of individual OPs and improved its retention rate of hypoglycemic activity in vitro. The swelling response and in-vitro release profiles showed that CMC@CMCS@OPs could help OPs achieve targeted and controlled release in the intestine. In addition, CMC@CMCS@OPs had no cytotoxicity on Caco-2 cells, and its apparent permeability coefficients increased 4.70–7.45 times compared with OPs, with the absorption rate increased by 129.38 %. Moreover, the transcytosis of CMC@CMCS@OPs nanogel occurred primarily through the macropinocytosis pathway, endocytosis pathway and intestinal efflux transporter-mediated efflux. Altogether, these results suggested that CMC@CMCS@OPs nanogel could be as an effective OPs delivery device for enhancing its stability and absorption.

Oyster (Ostrea Plicatula Gmelin) Peptides Improve Exercise Endurance Capacity via Activating AMPK and HO-1

Objective Previous studies have shown that oyster peptides (OPs) have antioxidant and anti-fatigue activities. This study aimed to investigate the effects of OPs on swimming endurance in mice and the underlying mechanisms. Methods The mice were subjected to gavage with OPs and subjected to exercise training. After 14 days, various biochemical indicators in the blood and gastrocnemius muscle of mice were assessed, and real-time PCR was utilized to detect the level of signal pathway regulation by OPs in the gastrocnemius muscle. Molecular docking technology was employed to observe the potential active components in OPs that regulate signal pathways. Results In this study, OPs supplementation combined with and without exercise significantly extended swimming time compared to the sedentary group. OPs supplementation with exercise also increased glycogen levels and decreased blood urea nitrogen, lactate dehydrogenase, and lactic acid levels. Additionally, mice in the exercise with OPs group exhibited higher activities of antioxidant enzymes. OPs can upregulate metabolic regulatory factors such as AMP-activated protein kinase, peroxisome proliferator-activated receptor gamma coactivator-1 alpha, peroxisome proliferator-activated receptor delta, and glucose transporter 4, thereby increasing energy supply during exercise. Additionally, OPs enhances the expression of heme oxygenase 1 and superoxide dismutase 2, thereby reducing oxidative stress during physical activity. Molecular docking analyses revealed that peptides found in OPs formed hydrogen bonds with AMPK and HO-1, indicating that they can exert bioactivity by activating target proteins such as AMPK and HO-1. Conclusions OPs supplementation improved energy reserves, modulated energy metabolism pathways, and coordinated antioxidative stress responses, ultimately enhancing swimming endurance. These findings suggest that OPs have the potential to improve exercise levels by promoting metabolism and improving energy utilization efficiency.

Modulation of lipid metabolism by oyster peptides in mice with high-fat diet-induced obesity

Oysters (Crassostrea gigas) are rich in proteins and a source of valuable peptides. Previous studies have revealed that oral administration of oyster peptides (OP) obtained by simulating gastrointestinal digestion reduced the weight of mice. However, the underlying regulatory mechanisms are unclear. We speculate that OP may be able to reduce fatty acid absorption by inhibiting pancreatic lipase activity. Therefore, we investigated the regulatory effects of OP on lipid metabolism in mice with high-fat diet-induced obesity. The body weight (BW), fat weight, lipid parameters, lipid metabolism-related gene expression, and serum lipid profiles were determined by MS-based lipidomics. Daily supplementation with 500 mg of OP/kg BW in obese mice reduced their BW gain and organ weights, improved dyslipidemia, and downregulated the genes expression of encoding proteins involved in fatty acid uptake, including acetyl coenzyme A carboxylase 1 (Acc1), fatty acid synthase (Fas), and sterol regulatory element binding protein 1c (Srebp-1c). Moreover, administration of OP resulted in significant changes in the lipid profile of mice. We screened 129 differential metabolites to identify biomarkers for OP intervention and analyzed the effects of OP on the metabolism of sphingolipids, glycerophospholipids, linoleic acid, and α-linolenic acid. In summary, OP can improve obesity-induced lipid metabolism dysfunctions by inhibiting enzyme activity and regulating fatty acid uptake.

Identification and detection of protein-derived adulterants in oyster peptide powder through an untargeted and targeted proteomics workflow

Oyster peptides are one of the main deep-processing commercial products of oysters, which are generally circulated in the form of peptide powder to preserve and extend the shelf life. The purpose of this study was to qualitatively and quantitatively detect protein-derived adulterants in oyster peptide powder through a combination of untargeted and targeted proteomics strategies. Various peptides derived from non-oyster proteins, mainly collagens of fish, porcine, chicken, and bovine, were detected in the adulterated samples through untargeted proteomics technology. Three signature peptides of gelatin-derived adulterants, namely GPPGKPGP, SGPAGPR, and GPPGPAGPA, were identified and confirmed. On this basis, an MRM-based quantitative method was established using the three signature peptides, which showed good linear relationships with correlation coefficients greater than 0.99 and recovery ranging from 98% to 127%. The established method could quantify the adulteration detection of protein-derived adulterants in oyster peptide powder products, contributing to the quality control of food-derived peptides.

Electrospun starch-based nanofiber mats for odor adsorption of oyster peptides: Recyclability and structural characterization

The off-odor of seafood, which negatively affected its flavor and quality, was removed mainly by non-recyclable liquid-phase deodorization methods at present. In this work, octenylsuccinylated starch (OSS)-pullulan (PUL) nanofiber mats were regenerated after physical adsorption and thermal desorption of off-odor compounds in oyster peptides. The mat structure was characterized and the adsorption process was investigated. The regenerated nanofiber mats maintained a favorable appearance and microscopic morphology even after 25 adsorption-desorption cycles, with a reduction in average fiber diameter and average pore area, an increase in hydrophobicity and alterations in surface groups. Their adsorption rate first decreased and then stabilized as the number of cycles increased and was as high as 81.76% after 25 cycles. Correlation analysis revealed that the adsorption efficiency of regenerated nanofiber mats was related to their microstructure, surface groups and hydrophobicity. These findings could provide a theoretical basis for odor removal by electrospun nanofiber mats and their recycling.

Selective adsorption of volatile compounds of oyster peptides by V-type starch for effective deodorization

Oyster peptides extracted from oysters have strong off-odors, which hinders consumer acceptance. The “empty” V-type starches (V6a, V6h, V7a, V7h, V8a, and V8h) prepared from high amylose maize starch were used as adsorbents to improve the flavor of oyster peptides. The total adsorption rates measured through headspace gas chromatography mass spectrometry (HS-GC-MS) follow the order of V6a > V7a > V6h > V7h > V8a > V8h. Moreover, the V-type starches with different structures exhibit adsorption selectivity. The V6- and V7-type starches with a smaller cavity size show selective adsorption capacity for alcohols, acids, ketones and other similar classes of volatile compounds, while the V8-type starches with a larger cavity selectively adsorb amines. In addition, successful preparation of “empty” V-type starches were confirmed through X-ray diffraction (XRD), and the inclusion complexes (ICs) between V-type starches and volatile compounds of oyster peptides were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and differential scanning calorimetry (DSC). It was found that the O/C ratio of V6a-ICs, V6h-ICs, and V7a-ICs increased, while that of V7h-ICs, V8a-ICs, and V8h-ICs decreased after the deodorization. Pearson's correlations indicated that the adsorption rates of aldehydes, alcohols, ketones, and alkanes have a significant negative correlation with temperature range (ΔT) and enthalpy change (ΔH). While a significant positive correlation was observed between the ratio of peak intensity at 1047/1022 cm−1 and the amine adsorption rate. These results suggested that V-type starch can improve the flavor of aquatic products effectively.

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Analyzing the mechanism by which oyster peptides target IL-2 in melanoma cell apoptosis based on RNA-seq and m6A-seq.

Melanoma is a kind of skin cancer with high malignancy and strong proliferation and invasion abilities. Chemotherapy drugs in the clinic have the disadvantages of high price and high toxicity. Peptides are natural active ingredients that have many functions and are safe and effective. Previous studies have shown that oysters are rich in protein and have antitumor effects. In this study, a high-throughput strategy combined with MALDI TOF/TOF-MS and molecular docking was developed to screen peptides with antitumor functions from oyster hydrolysate. Three dominant peptides were predicted to have similar functions to IL-2 via molecular docking. Then, the activity of the peptides was confirmed in B16 cells, and we found that the three peptides increased the apoptosis of B16 cells. Furthermore, via RNA-seq and m6A-seq of B16 cells treated with the peptides, we found that ILADSAPR downregulates the expression of Pcna, Tlr4, and Ncbp2 and upregulates the expression of Bax, Bad, Pak4, Rasa2, Cct6, and Gbp2. ILADSAPR inhibited B16 cell proliferation and promoted cell apoptosis by regulating the expression of these genes. In addition, the result of metabolic pathway analysis also proved this point. This study provides a preliminary reference for antitumor research on oyster peptides.

Effect of ultrasonic power on the stability of low-molecular-weight oyster peptides functional-nutrition W1/O/W2 double emulsion

Ultrasonic-assisted treatment is an eco-friendly and cost-effective emulsification method, and the acoustic cavitation effect produced by ultrasonic equipment is conducive to the formation of stable emulsion. However, its effect on the underlying stability of low-molecular-weight oyster peptides (LOPs) functional-nutrition W1/O/W2 double emulsion has not been reported. The effects of different ultrasonic power (50, 75, 100, 125, and 150W) on the stability of double emulsions and the ability to mask the fishy odor of LOPs were investigated. Low ultrasonic power (50W and 75W) treatment failed to form a well-stabilized double emulsion, and excessive ultrasound treatment (150W) destroyed its structure. At an ultrasonic power of 125W, smaller particle-sized double emulsion was formed with more uniform distribution, more whiteness, and a lower viscosity coefficient. Meanwhile, the cavitation effect generated by 125W ultrasonic power improved storage, and oxidative stabilities, emulsifying properties of double emulsion by reducing the droplet size and improved sensorial acceptability by masking the undesirable flavor of LOPs. The structure of the double emulsion was further confirmed by optical microscopy and confocal laser scanning microscopy. The ultrasonic-assisted treatment is of potential value for the industrial application of double emulsion in functional-nutrition foods.

Electrospun octenylsuccinylated starch-pullulan nanofiber mats: Adsorption for the odor of oyster peptides and structural characterization

Oyster peptides usually have strong off-flavors, which seriously affect the acceptability and application of products. Electrospinning of three commercial octenylsuccinylated (OS) starches (Purity Gum Ultra (PGU), Hi-Cap 100 (HC100) and Purity Gum 2000 (PG2000)) and pullulan (PUL) may be a potential method of adsorbing the odor of oyster peptides, which is simple, green and sustainable. All the electrospun PUL-OS starch fiber mats had an excellent white appearance with smooth, continuous, bead-free and randomly oriented nanofibers (70–240 nm). The adsorption rates of PUL-PGU, PUL-HC100 and PUL-PG2000 nanofiber mats for the volatile compounds of oyster peptides were 50.58%, 34.36% and 20.88%, respectively, attributing to physical adsorption evidenced by X-ray diffraction and Fourier transform infrared spectroscopy. A significant positive correlation was observed between the pore areas of nanofiber mats and the adsorption rates of acids and alkanes, which may be related to the formation of π-complexes on the nanofiber surface. For the first time, we demonstrated that the starch-based nanofiber mats prepared using a green process can improve the flavors of marine products.

Effects of Aerobic Exercise Combined with Oyster Peptide Supplement on the Formation of CTX-induced Late-Onset Hypogonadism in Male Rats.

The purpose of this study is to investigate the effect of aerobic exercise (AE) training and/or oyster peptide (OP) supplementation on the formation of late-onset hypogonadism (LOH). AE training and/or OP supplement was performed during Cytoxan (CTX)-induced LOH formation in male SD rats for 6 consecutive weeks. Low dose of CTX could decrease mating times, the levels of luteinizing hormone (LH), total testosterone (TT), free testosterone (FT) in serum and TT, androgen receptor (AR), androgen binding protein (ABP), and glutathione peroxidase (GSH-Px) in testicle, but increase capture latency, mating latency, and malondialdehyde, and downregulate the mRNA expression of steroidogenic acute regulatory (StAR), P450 cholesterol side chain cleavage enzyme (P450scc), and StAR-related lipid transfer domain 7 (StARD7) in testicle. Every change was altered by AE training combined with OP supplement significantly, except for serum LH. Moreover, the effect of AE training combined with OP supplement was better than that of AE training on serum TT, FSH, testicular TT, mating latency, capture times, and mating times. AE training combined with OP supplement during CTX-induced LOH formation can prevent the LOH development by enhancing pituitary-gonads axis's function and reducing testicular oxidative stress to promote testosterone synthesis and spermatogenesis.

Low-molecular-weight oyster peptides ameliorate cyclophosphamide-chemotherapy side-effects in Lewis lung cancer mice by mitigating gut microbiota dysbiosis and immunosuppression

• Low-molecular-weight oyster peptides enhanced immune cell differentiation and immunoglobulin expression. • Low-molecular-weight oyster peptides increased the beneficial bacteria in the intestine. • Hydrophobic amino acids and glutamic acid may be main components effects of low-molecular-weight oyster peptides. Low-molecular-weight oyster peptides (LOPs) are typical bioactive peptides with ameliorated immunomodulatory properties. However, the mechanism underlying its effect on immune functions and intestinal flora after chemotherapy has not been reported. In this study, Lewis lung cancer mice were used along with cytotoxic chemotherapy to establish model to investigate the ameliorative effects of LOPs on immunomodulatory function and intestinal flora structure. Our results showed that administration of LOPs alleviated weight loss, reduced spleen tissue damage, increased splenic T -lymphocytes, and markedly increased secretion of serum immunoglobulins and decreased inflammatory factors. Additionally, LOPs significantly increased the abundance of beneficial bacteria ( Lactobacillus and Coriobacteriaceae_UCG ) and decreased pathogenic bacteria ( Clostridium ) present in intestine. Hydrophobic amino acids and glutamate may be the underlying components to mitigate negative effects of chemotherapy. This study provides a theoretical basis for the use of LOPs as a nutritional base for the development of formula foods for cancer patients undergoing chemotherapy.

Hepatoprotective Effect of Oyster Peptide on Alcohol-Induced Liver Disease in Mice.

Alcohol-induced liver disease (ALD) has become one of the major global health problems, and the aim of this study was to investigate the characterization of the structure as well as the hepatoprotective effect and mechanism of oyster peptide (OP, MW < 3500 Da) on ALD in a mouse model. The results demonstrate that ethanol administration could increase the activities of aspartate aminotransferase (AST), alanine transaminase (ALT), γ-Glutamyl transferase (GGT), reactive oxygen species (ROS), malondialdehyde (MDA), and triglycerides (TG), as well as increase the interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor (TNF-α) levels (p < 0.01), and reduce the activity of superoxide dismutase (SOD) and the concentration of glutathione (GSH). Those changes were significantly reversed by the application of different doses of OP. Furthermore, the mRNA expressions of nuclear factor elythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and quinone oxidoreductase1 (NQO1) were significantly up-regulated in OP groups, and the mRNA expressions of nuclear factor kappa-light chain enhancer of B cells (NF-κB), TNF-α, and IL-6 were markedly reduced in OP groups compared to that of the model group. Thus, OP had a significant protective effect on ALD through the enhancement of the in vivo antioxidant ability and the inhibition of the inflammatory response as possible mechanisms of action, which therefore suggests that OP might be useful as a natural source to protect the liver from alcohol damage.

Protective Effect of Oyster Peptides Derived From Crassostrea gigas on Intestinal Oxidative Damage Induced by Cyclophosphamide in Mice Mediated Through Nrf2-Keap1 Signaling Pathway.

Oyster peptide (OP) has exhibited useful biological activities and can be used in multi-functional foods. OP has been reported to play a significant role in intestinal protection, but its specific mechanism is still not completely understood. The aim of this study was to analyze the potential effect of OP on oxidative damage of mice intestine induced by cyclophosphamide (Cy). The experimental results revealed that intragastric administration of OP significantly increased average bodyweight, improved ileum tissue morphology and villus structure, as well as increased the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in oxidized mice serum and liver. The content of malondialdehyde (MDA) in the mice serum and liver homogenate was found to be markedly decreased. Moreover, OP significantly increased the relative mRNA expression levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), quinone oxidoreductase (NQO1) and heme oxidase-1 (HO-1) in ileum. Western-blot results indicated that prior administration of OP significantly up-regulated the Nrf2 production in ileum, and substantially decreased then Keap1 gene expression. In conclusion, intake of OP was found to markedly improve intestinal oxidative stress in vivo, and this effect was primarily mediated through the simulation of antioxidant Nrf2-Keap1 signaling pathway. This study is beneficial to the application of peptide nutrients in the prevention or mitigation of intestinal oxidative damage.