Oxidized protein repair agent and agent for suppressing oxidative stress through repair of oxidized protein

Abstract

[Problem] To provide an oxidized protein repair agent, an oxidized protein repair method, an agent for suppressing oxidative stress through the repair of an oxidized protein, and a method for suppressing oxidative stress. [Solution] Provided are: an oxidized protein repair agent and an agent for suppressing oxidative stress through the repair of an oxidized protein that contain a water-soluble nuclear protein, namely, a low-molecular-weight compound having a molecular weight of approximately 250 to 15,000 obtained by enzyme treatment of fish milt; a health food containing the repair agent or the agent for suppressing oxidative stress; a method for repairing oxidized proteins damaged by oxidative stress, the method involving orally ingesting the repair agent or the agent for suppressing oxidative stress; and a method for suppressing oxidative stress through the abovementioned repair.

Description

Oxidized protein repair agents and oxidative stress inhibitors via the repair of oxidized proteins

[0001] The present invention relates to an agent for repairing oxidized proteins and a method for repairing oxidized proteins by oral administration thereof, in particular to an agent for suppressing oxidative stress via the repair of oxidized proteins and a method for suppressing oxidative stress via the repair of oxidized proteins by oral administration thereof. The present invention also relates to an agent for increasing the oxidized methionine repair enzyme gene response and a method for increasing the oxidized methionine repair enzyme gene response by oral administration thereof.

[0002] In recent years, reflecting the growing public interest in health, health foods have been provided that use, as raw materials or active ingredients, deoxyribonucleic acid (DNA), ribonucleic acid (RNA), or salmon milt extract (also called water-soluble nucleoprotein), which is a complex of these nucleic acids and protein. For example, water-soluble nucleoprotein is known to have immunomodulatory, antioxidant, vasodilatory, and other effects. Furthermore, a cancer cell proliferation inhibitor containing a low-molecular-weight water-soluble nucleic acid or the water-soluble nucleic acid and an amino acid has been proposed (Patent Document 1).

[0003] JP 2014-152144 A

[0004] It has been reported that the ingestion of nucleic acids (DNA, RNA) and water-soluble nuclear proteins has various effects, including antioxidant properties. However, there have been no reports to date that their ingestion affects the repair of oxidized proteins.

[0005] An objective of the present invention is to provide an agent for repairing oxidized proteins and a method for repairing oxidized proteins, as well as an agent for suppressing oxidative stress and a method for suppressing oxidative stress via the repair of oxidized proteins.

[0006] The present invention relates to an agent for repairing oxidized proteins, specifically an agent for repairing oxidized proteins containing a water-soluble nucleoprotein, and in particular to an agent for repairing oxidized proteins containing a water-soluble nucleoprotein that has been degraded to a molecular weight of 250 to 15,000 and obtained by enzymatically treating fish milt. The present invention also relates to a health food for repairing oxidized proteins containing the agent for repairing oxidized proteins, such as a health food in the form of a tablet, drink, capsule, granule, pill, or jelly. The present invention also relates to a method for repairing oxidized proteins damaged by oxidative stress using the agent for repairing oxidized proteins.

[0007] In particular, the present invention relates to an oxidative stress inhibitor that inhibits oxidative stress via the repair of oxidized proteins, specifically an oxidative stress inhibitor containing a water-soluble nucleoprotein, particularly an oxidative stress inhibitor containing a water-soluble nucleoprotein that has been degraded to a molecular weight of 250 to 15,000 and obtained by enzymatically treating fish milt. The present invention also relates to a health food for inhibiting oxidative stress via the repair of oxidized proteins, containing the oxidative stress inhibitor, and the health food may be in the form of, for example, a tablet, drinkable agent, capsule, granule, pill, or jelly. Furthermore, the present invention also relates to a method for inhibiting oxidative stress via the repair of oxidized proteins damaged by oxidative stress, using the oxidative stress inhibitor.

[0008] The present invention also relates to an oxidized methionine repair enzyme gene response enhancer containing a water-soluble nucleoprotein, particularly an oxidized methionine repair enzyme gene response enhancer containing a water-soluble nucleoprotein that has been degraded to a molecular weight of 250 to 15,000 and is obtained by enzymatically treating fish milt. The present invention also relates to a health food for increasing oxidized methionine repair enzyme gene response, containing the oxidized methionine repair enzyme gene response enhancer, such as a health food in the form of a tablet, drinkable agent, capsule, granule, pill, or jelly. The present invention also relates to a method for increasing oxidized methionine repair enzyme gene response using the oxidized methionine repair enzyme gene response enhancer. Effects of the present invention

[0009] According to the present invention, by using a water-soluble nuclear protein containing low-molecular-weight DNA, for example by oral ingestion, methionine sulfoxide reductase (methionine oxide repair enzyme; MSR), an enzyme that reduces oxidized methionine, is increased, thereby achieving the effect of repairing oxidized proteins and also achieving the effect of suppressing oxidative stress.

[0010] FIG. 1 shows the results of gene expression analysis of methionine sulfoxide reductase A (MSRA), thioredoxin (TXN), and methionine sulfoxide reductase B2 (MSRB2) obtained from total RNA of blood samples from subjects before and after intake (week 0, week 8) in a test tablet group in which subjects took test tablets containing water-soluble nucleoprotein for 8 weeks, and in a placebo tablet group in which subjects took placebo tablets not containing water-soluble nucleoprotein for 8 weeks (Thermo Fisher Figure 2 shows the relative ratio of the results of methionine sulfoxide reductase A (MSRA) obtained by gene expression analysis of the blood of subjects before and after intake (week 0, week 8) by digital PCR in a test tablet group in which subjects took test tablets containing water-soluble nucleoprotein for 8 weeks and a placebo tablet group in which subjects took placebo tablets not containing water-soluble nucleoprotein for 8 weeks (measured by microarray manufactured by Scientific) ((A) MSRA, (B) TXN, (C) MSRB2 gene expression levels (rate of change from week 0 to week 8 (placebo tablet group set to 1)). Figure 3 shows the relative ratio of the results of methionine sulfoxide reductase A (MSRA) obtained by gene expression analysis of the blood of subjects before and after intake (week 0, week 8) by digital PCR in a test tablet group in which subjects took test tablets containing water-soluble nucleoprotein for 8 weeks and a placebo tablet group in which subjects took placebo tablets not containing water-soluble nucleoprotein for 8 weeks (rate of change in MSRA gene expression from week 0 to week 8 (placebo tablet group set to 1)). 1). Figure 3 shows the results of oxidative stress level d-ROMs tests and oxidative stress index (OSI) tests conducted on the blood of subjects before and after intake of test tablets containing water-soluble nucleoprotein for 8 weeks (a test tablet group) and placebo tablets not containing water-soluble nucleoprotein for 8 weeks ((A) oxidative stress level (d-ROMs), (B) oxidative stress index (OSI)). Figure 4 shows the survival rate of yeast after adding water-soluble nucleoprotein (and control) to yeast and then applying oxidative stress (hydrogen peroxide), as well as the results of microarray and real-time PCR methionine sulfoxide reductase 2 (MXR2) gene expression analysis (B) obtained from the analysis of yeast to which water-soluble nucleoprotein was added.

[0011] The oxidized protein repair agent and oxidative stress inhibitor of the present invention contain a water-soluble nuclear protein. The inventors have newly confirmed that this water-soluble nuclear protein has the function of increasing the oxidized methionine repair enzyme (methionine sulfoxide reductase; MSR), an enzyme that reductively repairs oxidized methionine, a particularly susceptible amino acid residue in proteins. The inventors have also discovered that oral administration of this water-soluble nuclear protein results in the repair of oxidized proteins and the suppression of oxidative stress through the repair of oxidized proteins. While conventional antioxidant mechanisms involve the decomposition and elimination of reactive oxygen species by antioxidant enzymes or antioxidant substances, the present invention achieves antioxidant effects by repairing proteins damaged by oxidative stress, thereby achieving antioxidant effects through a completely different mechanism from the conventional mechanisms. In relation to the above-mentioned methionine sulfoxide reductase (Msr), a cosmetic composition containing an oxidized peptide [oxidized methionine enkephalin (SEQ ID NO: 1: Y-G-G-F-M-O)] has been proposed, and there is a report that this oxidized peptide increased Msr gene expression (Japanese Patent Publication No. 2012-523436). In this report, the application of a synthesized oxidized peptide prevented skin damage caused by oxidative stress, such as UV radiation. On the other hand, the water-soluble nuclear protein of the oxidized protein repair agent and oxidative stress inhibitor of the present invention, when ingested as a food product derived from natural products, promotes the expression of genes related to oxidized protein reductase (methionine sulfoxide reductase) in the body, thereby reducing oxidative stress in the blood. Therefore, it is believed that the effects of the oxidized peptide in the above report and the water-soluble nuclear protein of the present invention are exerted through different mechanisms of action. The oxidized peptides in the above report are intended to be effective by applying them to the skin (transdermal absorption) as cosmetics, etc., whereas the present invention is intended to be effective by orally ingesting a water-soluble nucleoprotein, as described below.

[0012] The water-soluble nuclear protein of the present invention functions as a repair agent for oxidized proteins (oxidized proteins) and also as an inhibitor of oxidative stress via the repair of oxidized proteins. This specification discloses a method for repairing oxidized proteins using the water-soluble nuclear protein (repair agent), and a method for suppressing oxidative stress via the repair of oxidized proteins damaged by oxidative stress using the water-soluble nuclear protein (inhibitor). Furthermore, the present invention also relates to an agent for increasing the response of oxidized methionine repair enzyme genes. The present invention will be described in detail below.

[0013] The water-soluble nuclear protein used in the oxidized protein repair agent and oxidative stress inhibitor of the present invention can be a water-soluble nuclear protein obtained by extracting nucleic acids from biological cells and enzymatically treating them to reduce their molecular weight. In other words, the term "water-soluble nuclear protein" as used herein can be rephrased as an extract of fish milt that has been reduced in molecular weight. An example of such a water-soluble nuclear protein is a water-soluble nuclear protein obtained by reducing the molecular weight of fish milt through enzymatic treatment or the like. In this specification, "water-soluble" refers to the ability to dissolve in water at a concentration of 0.1% by mass or more.

[0014] Examples of the fish include salmon, trout, herring, etc. Among these, salmon milt is preferably used, which contains a large amount of nucleic acids but has not been effectively utilized as a resource and has been discarded in large amounts in the past.

[0015] Examples of enzymatic treatment of fish milt include crushing the milt, treating the resulting suspension with protease, and then treating it with nuclease. Typically, DNA extracted from milt has a molecular weight of 1,000,000 or more, and is then depolymerized by enzymatic treatment. Preferred water-soluble nucleoproteins include those containing nucleosides / nucleotides / oligonucleotides / polynucleotides (hereinafter also referred to as "depolymerized products") having a molecular weight of 250 to 100,000, e.g., 250 to 20,000, 250 to 15,000, 500 to 13,200, or 250 to 10,000, or 250 to 6,600, preferably at a concentration of 20% by mass or more, more preferably 30% by mass or more. More preferably, the water-soluble nuclear protein of the present invention can contain 2% by mass or more of low molecular weight substances having a molecular weight of 500 to 15,000 and 18% by mass or more of low molecular weight substances having a molecular weight of 250 to 6,600.

[0016] The proteases include not only serine proteases but also cysteine ​​proteases, metalloproteases, aspartic acid proteases, and the like. Because milt contains proteins other than protamine, proteases with low substrate specificity are particularly preferred. A good example of a protease is the protease manufactured by Novozymes Japan Co., Ltd. Hydrolysis using the protease can be carried out at a temperature of 30 to 60°C, e.g., 40 to 50°C, and a pH of 6 to 7, taking into account the activation and inactivation of the protease. The nuclease hydrolyzes the 3,5'-phosphodiester bond of deoxyribonucleic acid (DNA) to generate 5'-nucleotides for oligomerization. While there are no particular limitations on the properties of the nuclease, it is preferable for it to have a certain degree of thermostability. Such nucleases are commercially available from, for example, Amano Enzyme Inc. and Sigma. The hydrolysis treatment using the nuclease can be carried out, for example, at a temperature in the range of 60 to 75°C and a pH in the range of 5 to 6, taking into consideration the activation and inactivation of the nuclease. Specifically, the enzymatic treatment procedure involves first treating the salmon milt with a protease to hydrolyze proteins contained in the salmon milt. After hydrolysis, nucleic acids can be broken down into smaller molecules by nuclease treatment.

[0017] The present invention also relates to a health food for oxidized protein repair containing the oxidized protein repair agent, and a health food for oxidative stress suppression through oxidized protein repair containing an oxidative stress inhibitor. The health food of the present invention contains as an active ingredient the oxidized protein repair agent or oxidative stress inhibitor, i.e., a water-soluble nucleoprotein that is a low-molecular-weight product with a molecular weight of 250 to 15,000, or for example, 250 to 10,000, obtained by enzymatically treating, for example, fish milt, and also contains other ingredients depending on the various product forms described below. The content of the oxidized protein repair agent or oxidative stress inhibitor in the health food can be appropriately adjusted with reference to the clinical dosage described below.

[0018] The health food of the present invention can be mixed with various known ingredients such as sweeteners, acidulants, vitamins, etc. to produce a product that suits the user's taste. The product form can be provided in the form of tablets, capsules, granules, pills, syrups, liquids, emulsions, suspensions, etc., as well as in the form of drinks, jellies, dairy products such as yogurt, seasonings, processed foods, desserts, confectioneries, etc.

[0019] For example, the tablets, capsules, granules, pills and the like for oral administration can be formulated by conventional means, and these are prepared using excipients such as sucrose, lactose, glucose, starch, mannitol; binders such as hydroxypropyl cellulose, syrup, gum arabic, gelatin, sorbitol, tragacanth, methylcellulose, polyvinylpyrrolidone; disintegrants such as starch, carboxymethylcellulose or a calcium salt thereof, microcrystalline cellulose, polyethylene glycol; lubricants such as talc, magnesium or calcium stearate, silica; and lubricants such as sodium laurate, glycerol and the like. Furthermore, the syrups, solutions, emulsions, suspensions, etc. can also be formulated by conventional means, and are prepared using solvents for the oxidized protein repair agent or oxidative stress inhibitor (water-soluble nucleoprotein), which are the active ingredients, such as water, ethyl alcohol, isopropyl alcohol, propylene glycol, 1,3-butylene glycol, and polyethylene glycol; surfactants such as sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene ethers of hydrogenated castor oil, and lecithin; suspending agents such as carboxymethyl sodium salts, cellulose derivatives such as methylcellulose, and natural gums such as tragacanth and gum arabic; and preservatives such as esters of parahydroxybenzoic acid, benzalkonium chloride, and sorbates. Furthermore, the above-mentioned drinks and jellies, as well as dairy products, seasonings, processed foods, desserts, confectioneries, etc. may contain, in addition to their constituent ingredients, oligo-RNA, zinc, collagen, chondroitin, hyaluronic acid, vitamins (vitamins of the B group such as vitamin B1, vitamin B2, vitamin B6, vitamin B12, etc., vitamin C, etc.), glutathione (glutathione-containing yeast extract, reduced glutathione, oxidized glutathione, etc.).More specifically, for example, for drink applications, although not limited to this application, porcine collagen peptides, rare sugar-containing syrup, RNA-containing edible yeast extract, zinc-containing edible yeast, chondroitin-containing shark cartilage extract, hyaluronic acid-containing cockscomb extract / acidulant, vitamin C, arginine, magnesium carbonate, niacin, vitamin B6, vitamin B2, vitamin B1, folic acid, vitamin B12, anserine-containing fish meat extract, citrulline, salmon ovarian membrane extract, and porcine placenta extract may be added. Furthermore, for example, for tablet applications, although not limited to this application, brewer's yeast, ginkgo biloba extract, and S-allyl cysteine-containing garlic extract may be added. Furthermore, for example, for jelly applications, although not limited to this application, fish collagen peptides may be added.

[0020] Furthermore, the health food of the present invention may contain, in addition to the active ingredients, the agent for repairing oxidized proteins and the agent for suppressing oxidative stress, other compounds that are pharmaceutically or veterinarily active.

[0021] The present invention also relates to a method for repairing oxidized proteins using the oxidized protein repairing agent, and also to a method for suppressing oxidative stress using the oxidative stress inhibitor, which uses the oxidative stress inhibitor to repair oxidized proteins damaged by oxidative stress. The protein repairing method or oxidative stress suppressing method of the present invention uses the oxidized protein repairing agent or oxidative stress inhibitor, i.e., a water-soluble nucleoprotein that is a low-molecular-weight product having a molecular weight of, for example, 250 to 15,000, or for example, 250 to 10,000, obtained by enzymatically treating fish milt, thereby repairing oxidized proteins and suppressing oxidative stress through the repair of oxidized proteins.

[0022] The clinical dosage of the oxidized protein repair agent or oxidative stress inhibitor of the present invention varies depending on factors such as age, body weight, patient sensitivity, and the severity of symptoms. A typical effective dose of the water-soluble nucleoprotein for an adult is, for example, approximately 100 mg to 950 mg per day. However, amounts outside the above ranges can be used as needed. The above-mentioned effective dosage guidelines also apply to the oxidized protein repair agent or oxidative stress inhibitor of the present invention, as well as health foods containing them. In the case of health foods, the amount of the oxidized protein repair agent or oxidative stress inhibitor in the health food can be appropriately adjusted, for example, based on the daily intake of the health food itself, with reference to the above-mentioned daily dosage guidelines.

[0023] As mentioned above, the present invention also relates to an oxidized methionine repair enzyme gene response enhancer, a health food containing the enhancer for enhancing oxidized methionine repair enzyme gene response, and a method for enhancing oxidized methionine repair enzyme gene response using the enhancer. The oxidized methionine repair gene (methionine sulfoxide reductase: MSR) has two forms, called MSRA and MSRB (MSRB2), depending on the stereoisomerism of methionine sulfoxide. The oxidized methionine repair enzyme gene enhancer contains a water-soluble nucleoprotein, and the water-soluble nucleoproteins used in the aforementioned oxidized protein repair agents and oxidative stress inhibitors can be suitably used. The health food containing the oxidized methionine repair enzyme gene enhancer can preferably use the same aspects, ingredients, etc. as those listed for the health food containing the aforementioned oxidized protein repair agent and oxidative stress inhibitor. Furthermore, the method for enhancing oxidized methionine repair enzyme gene response can be suitably applied using the same methods, clinical dosages (recommended amounts), etc. as those used in the aforementioned methods for repairing oxidized proteins damaged by oxidative stress and methods for suppressing oxidative stress via such repair.

[0024] <Water-soluble nucleoprotein> The water-soluble nucleoprotein obtained from salmon milt using hydrolases such as proteases and nucleases contained 20 to 30% by mass of nucleic acids (water-soluble nucleic acids with molecular weights ranging from 250 to 15,000) and 50% by mass of amino acids (including 15% by mass of arginine).

[0025] <Preparation of Test Tablets> According to Table 1, test tablets (tablets A) containing the water-soluble nucleoprotein obtained in the above Preparation Example and placebo tablets (tablets B) not containing the water-soluble nucleoprotein were prepared.

[0026]

[0027] <Test Example 1: Human Subject Study> A double-blind, randomized, placebo-controlled study was conducted on 41 healthy subjects (male, no medication, no underlying diseases, etc.) aged 40 to 60 years who experienced daily fatigue. The subjects were divided into two groups: a test tablet group (tablet A, 20 subjects) and a placebo tablet group (tablet B, 21 subjects), and each test group took either tablet A or tablet B for 8 weeks. The test tablet group was administered with a quantity of tablet A adjusted to provide a daily intake of 360 mg of water-soluble nucleoprotein (6 tablets per day), and the placebo tablet group was administered with the same amount of tablet B (6 tablets per day) as tablet A. Blood samples were collected from the subjects before and after intake (week 0 and week 8). Total RNA was extracted from the collected blood, and the gene expression levels of methionine sulfoxide reductase A (MSRA), thioredoxin (TXN), and methionine sulfoxide reductase B2 (MSRB2) were measured using a Thermo Fisher Scientific microarray: Clariom S Assay, Human. Total RNA was extracted from the blood collected in the same manner, and the gene expression level of methionine sulfoxide reductase A (MSRA) was measured by digital PCR using a QIAcuity One 2plex (digital PCR device) (kit used: QIAcuity EG PCR KIT / Qiagen, plate used: QIAcuity Nanoplate 8.5K, 96-well) (Qiagen). The results are shown in Figure 1 [Thermo Fisher Scientific microarray: (A) MSRA, (B) TXN, (C) MSRB2 gene expression level measurement results (rate of change from week 0 to week 8 (placebo tablet group defined as 1))] and Figure 2 [Digital PCR: MSRA measurement results (rate of change in MSRA gene expression from week 0 to week 8 (placebo tablet group defined as 1))].

[0028] Furthermore, the collected blood was subjected to a d-ROMs (Reactive Oxygen Metabolites-derived Compounds) test (Wismer test kit) to comprehensively evaluate the oxidative stress level in the body by measuring hydroperoxides, which are metabolites of free radicals in the blood. The blood was also subjected to a BAP (Biologica Antioxidant Potential) test (Wismer test kit) to measure antioxidant potential. The oxidative stress index (OSI) was calculated from the BAP (antioxidative potential) results and the d-ROM (oxidative stress level) results. The results are shown in Figure 3 [(A) Oxidative stress level (d-ROMs), (B) Oxidative Stress Index (OSI)]. The oxidative stress level is evaluated based on the balance between the degree of oxidation and antioxidant capacity, and the ratio of the degree of oxidation to antioxidant capacity is often used as an indicator. The oxidative stress index (OSI) used in this example is a method reported by Fukuda et al. in 2016 (Biological Psychology 118(2016)88-93). It is an indicator of oxidation balance calculated by multiplying the ratio of the measured oxidative stress level (d-ROMs) to the antioxidant capacity (BAP) by a correction factor (8.85) calculated based on data obtained from healthy Japanese subjects (see the formula below). Oxidative stress index (OSI) = (d-ROMs / BAP) × correction factor (8.85). Note that an OSI value of 1 represents the average value for Japanese people, and an OSI value higher than 1 indicates a higher degree of oxidation than the average value for Japanese people. Furthermore, the OSI value typically increases with age.

[0029] As shown in Figure 1, the results of microarray analysis confirmed that the gene expression levels of methionine sulfoxide reductase A (MSRA), thioredoxin (TXN), and methionine sulfoxide reductase B2 (MSRB2) all tended to increase compared to the placebo tablet group. Thioredoxin is a type of oxidoreductase, and thioredoxin, MSRA, and MSRB2 cooperate to repair oxidized methionine (an amino acid residue that is particularly susceptible to oxidation among the amino acid residues that make up proteins). Furthermore, to verify the results of Figure 1, analysis was performed using digital PCR. As a result, as shown in Figure 2, the test tablet group that took tablet A containing a water-soluble nucleoprotein for 8 weeks showed a significant increase in methionine sulfoxide reductase A (MSRA) gene expression compared to the placebo tablet group (p value < 0.05). These results demonstrate that ingestion of water-soluble nucleoprotein increases the levels of methionine oxidative repair enzymes (MSRA, MSRB2) and thioredoxin (TXN), which act synergistically with these enzymes to repair oxidized methionine (an amino acid residue that is particularly susceptible to oxidation among the amino acid residues that make up proteins), thus confirming its potential for repair of oxidized proteins in humans. Furthermore, as shown in Figure 3, the test tablet group that took Tablet A containing water-soluble nucleoprotein for 8 weeks showed a significant decrease in d-ROMs (reduction of oxidative stress markers) compared to the placebo group (Figure 3(A)), and also showed a significant decrease in oxidative stress index (OSI) (Figure 3(B)). Thus, ingestion of water-soluble nucleoprotein promoted both oxidized protein repair and reduction of oxidative stress markers, confirming a positive correlation between oxidized protein repair and reduction of oxidative stress. The relationship between protein repair and the reduction of oxidative stress markers has been anticipated for some time, but this is the first time that the ingestion of the water-soluble nuclear protein targeted by this invention promotes gene expression of enzymes involved in protein repair, and actually reduces oxidative stress markers and the oxidative stress index.

[0030] Test Example 2: Yeast Test To allow budding yeast in liquid medium to ingest water-soluble nuclear protein, the water-soluble nuclear protein prepared in the above manufacturing example was added. After 24 hours, the water-soluble nuclear protein was removed to prepare a test sample. As a control, budding yeast without the addition of the water-soluble nuclear protein was prepared. This test sample or a control sample (without the addition of water-soluble nuclear protein) was added to a medium containing hydrogen peroxide as an oxidative stress agent and a medium without hydrogen peroxide, respectively, and the yeast was cultured for 72 hours. For each sample, the ratio of the number of yeast colonies in the medium without hydrogen peroxide to the number of yeast colonies in the medium without hydrogen peroxide was measured as the yeast viability (%). The results are shown in Figure 4(A). Total RNA was also extracted from the yeast with the addition of water-soluble nuclear protein, and the expression level of the methionine sulfoxide reductase 2 (MXR2) gene was measured using a QuantStudio 7 Flex Realtime PCR system. The results are shown in Figure 4(B) (relative gene expression levels when the control group is set to 1). As shown in Figure 4(A), the group to which the water-soluble nuclear protein was added to yeast had a higher yeast survival rate than the control group. Furthermore, as shown in Figure 4(B), MXR2 in the group to which the water-soluble nuclear protein was added to yeast was significantly increased (>1.5), while MXR2 in the control group remained unchanged. The test results using yeast shown in Figures 4(A) and (B) also confirmed that ingestion of the water-soluble nuclear protein of the present invention promotes both oxidative stress reduction (improvement of yeast survival rate) and an increase in oxidized methionine repair enzyme (MXR2), thereby promoting the repair of oxidized proteins, and that there is a positive correlation between the repair of oxidized proteins and the reduction of oxidative stress.

[0031] These results suggest that oxidatively damaged proteins can be repaired by ingesting water-soluble nuclear proteins, and that oxidative stress can be suppressed (reduced) through the repair of oxidized proteins.

Claims

1. An oxidized protein repair agent containing a water-soluble nucleoprotein.

2. The oxidized protein repair agent according to claim 1, wherein the water-soluble nucleoprotein is a water-soluble nucleoprotein having a molecular weight of 250 to 15,000 obtained by enzymatically treating fish milt.

3. A health food for repairing oxidized proteins, comprising the oxidized protein repair agent according to claim 1 or 2.

4. The health food according to claim 3, which is in the form of a tablet, drink, capsule, granule, pill, or jelly.

5. A method for repairing oxidized proteins damaged by oxidative stress, using the oxidized protein repairing agent according to claim 1 or 2.

6. An oxidative stress inhibitor containing a water-soluble nucleoprotein that mediates the repair of oxidized proteins.

7. The oxidative stress inhibitor according to claim 6, wherein the water-soluble nuclear protein is a water-soluble nuclear protein having a molecular weight of 250 to 15,000 obtained by enzymatically treating fish milt.

8. A health food for suppressing oxidative stress through the repair of oxidized proteins, comprising the oxidative stress inhibitor according to claim 6 or 7.

9. The health food according to claim 8, which is in the form of a tablet, drink, capsule, granule, pill, or jelly.

10. A method for suppressing oxidative stress using the oxidative stress suppressant according to claim 6 or 7, which method involves repairing oxidized proteins damaged by oxidative stress.

11. An agent for increasing the response of oxidized methionine repair enzyme genes, containing a water-soluble nuclear protein.

12. The agent for increasing the gene response of oxidized methionine repair enzyme genes according to claim 11, wherein the water-soluble nuclear protein is a water-soluble nuclear protein having a molecular weight of 250 to 15,000 obtained by enzymatically treating fish milt.

13. A health food for increasing oxidized methionine repair enzyme gene response, comprising the agent for increasing oxidized methionine repair enzyme gene response according to claim 11 or 12.

14. The health food according to claim 13, which is in the form of a tablet, drink, capsule, granule, pill, or jelly.

15. A method for increasing oxidized methionine repair enzyme gene response, using the agent for increasing oxidized methionine repair enzyme gene response according to claim 11 or 12.

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