Composition for promoting muscle differentiation and composition for enhancing muscle strength

Abstract

To provide a novel application of procyanidin, a component of cacao.SOLUTION: Procyanidin is employed as an active constituent in a composition used to promote muscle differentiation (composition for promoting muscle differentiation), a composition used to enhance muscle strength (composition for enhancing muscle strength), a composition used to promote the expression of fast-twitch muscle fibers (composition for promoting expression of fast-twitch muscle fibers), and a composition used to promote the fast-twitching of muscle (composition for promoting fast-twitching of muscle).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a muscle-building composition that has a muscle differentiation promoting effect and is used to build muscle. The present invention also relates to a muscle-building composition that has an effect of promoting the expression of fast-twitch muscle fibers and is used to promote the formation of fast-twitch muscle fibers. [Background technology]

[0002] Skeletal muscle is a multifunctional tissue involved in various physiological processes. For example, skeletal muscle plays an important role in energy metabolism, the uptake of glucose, and other nutrients into the body, as well as in daily movements such as walking and maintaining posture, and in physical activities such as exercise. Skeletal muscle is formed as follows: satellite cells first differentiate into myoblasts through cell division, and then the myoblasts differentiate into myotubes. These myotubes then fuse to form muscle fibers. Connective cells fill the spaces between these cells to form muscle bundles, which then finally form skeletal muscle. Therefore, efficient differentiation of satellite cells and myoblasts is crucial for the formation of muscle fibers, the basic units of skeletal muscle.

[0003] Human skeletal muscle is composed of various types of muscle fibers. For example, based on their contractile and metabolic properties, muscle fiber types are classified as type I (slow-twitch, slow oxidative) and type II (fast-twitch), and type II is further subdivided into three types: type IIa (fast-twitch, fast oxidative), type IIx (fast-twitch, intermediate), and type IIb (fast-twitch, fast glycolytic). Slow-twitch fibers are characterized by slow contraction and low force, but are rich in mitochondria and myoglobin, allowing for prolonged contraction and high endurance (fatigue resistance). Therefore, they are important muscle fibers for aerobic endurance exercise. On the other hand, fast-twitch fibers are low in mitochondria and myoglobin and have poorer endurance (fatigue resistance), but are characterized by fast contraction and high power output. Therefore, they are important muscle fibers for exercise requiring explosive power.

[0004] Muscle fibers are dynamic structures whose phenotypes change variably from fast-twitch to slow-twitch or from slow-twitch to fast-twitch depending on various conditions, such as increases or decreases in neuromuscular activity, increases or decreases in mechanical load, changes in hormone secretion (especially thyroid hormone), and aging. As mentioned above, fast-twitch muscle fibers can exert powerful force instantaneously. Therefore, efficient formation and conversion of skeletal muscle fibers to fast-twitch muscle fibers is important not only for promoting physical health but also for improving athletic performance, particularly in sports requiring explosive power. Furthermore, muscle atrophy (thinning) due to aging results in a decrease in fast-twitch muscle fibers, which leads to a decline in the ability to exert powerful force instantaneously. One reason why elderly people are prone to falls is that they are unable to quickly react with the other foot when they stumble. Therefore, there is a great need to strengthen and increase muscles, especially fast-twitch muscle fibers, in order to prevent the decline in muscle capacity associated with aging and to live longer, healthier lives.

[0005] It has been known that green tea extract, which contains catechin as a main component, improves lipid metabolism and thereby enhances endurance (Non-Patent Document 1), and that high molecular weight polyphenols extracted from fermented tea have the effect of promoting slow-twitch muscle differentiation (Patent Document 1). However, these studies both increase slow-twitch muscle fibers, and there is no description of muscle strengthening by promoting differentiation into fast-twitch muscle fibers. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-37323 [Non-patent literature]

[0007] [Non-Patent Document 1] Murase T et al., Green tea extract improves endurance capacity and increase muscle lipid oxidation in mice. Am J Physiol Regul Integr Comp Physiol 2005; 288; R708-715 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide a composition used to promote muscle differentiation (muscle differentiation promoting composition), a composition used to build muscle (muscle building composition), a composition used to promote the expression of fast-twitch muscle fibers (fast-twitch muscle fiber expression promoting composition), and a composition for promoting the formation of fast-twitch muscle fibers (fast-twitch muscle formation promoting composition). [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above-mentioned problems, and as shown in the experimental examples described below, they have discovered that procyanidin C1 (PC1), a cacao-derived component, induces the expression of muscle differentiation marker genes (MyoD, Myogenin) via the intestinal epithelium. Based on this finding, they have discovered that oral ingestion of PC1 can promote muscle differentiation and, as a result, strengthen muscle (skeletal muscle). Furthermore, they have discovered that PC1 significantly induces the expression of the fast-twitch fiber gene (MyhcIIa) via the intestinal epithelium. Based on this finding, they have discovered that oral ingestion of PC1 can promote the expression of fast-twitch fiber, thereby promoting the development of fast-twitch muscle (strengthening fast-twitch muscle).

[0010] Based on these findings, the present inventors have confirmed that procyanidin is effective as an active ingredient in compositions for promoting muscle differentiation, compositions for building muscle, compositions for promoting the expression of fast-twitch muscle fibers, and compositions for promoting the formation of fast-twitch muscle fibers.

[0011] The present invention was completed based on these findings and includes the following embodiments. (1) A composition for promoting muscle differentiation, comprising procyanidin as an active ingredient. (2) A composition for muscle building containing procyanidin as an active ingredient. (3) A composition for promoting the expression of fast-twitch muscle fibers, comprising procyanidin as an active ingredient. (4) A composition for promoting fast muscle growth, comprising procyanidin as an active ingredient. (5) The composition according to any one of (1) to (4), which is an oral composition. (6) The composition according to any one of (1) to (5), wherein the procyanidin is procyanidin C1. [Effects of the Invention]

[0012] According to the present invention, a new use of procyanidins can be provided. Specifically, a new use of procyanidins can be provided as an active ingredient in a composition for promoting muscle differentiation, a composition for building muscle, a composition for promoting fast-twitch muscle fiber expression, and a composition for promoting fast-twitch muscle formation. In other words, a composition for promoting muscle differentiation, a composition for building muscle, a composition for promoting fast-twitch muscle fiber expression, and a composition for promoting fast-twitch muscle formation, each of which contains procyanidins as an active ingredient, can be provided.

[0013] According to the composition for promoting muscle differentiation or the composition for building muscle of the present invention, by orally administering (ingesting) it is possible to promote the differentiation of muscle satellite cells into myoblasts and the differentiation of myoblasts into myotubes, thereby promoting skeletal muscle formation (muscle building), based on the action of its active ingredient, procyanidin, via epithelial cells.

[0014] Furthermore, by orally administering (ingesting) the composition for promoting the expression of fast-twitch muscle fibers or the composition for promoting fast-twitch muscle formation of the present invention, it is possible to promote the expression of fast-twitch muscle fibers and promote the fast-twitch muscle formation (transition / conversion to fast-twitch muscle) of muscles based on the action of its active ingredient, procyanidins, via epithelial cells. As described above, fast-twitch muscle fibers are important for exerting explosive power, and therefore the composition for promoting the expression of fast-twitch muscle fibers or the composition for promoting fast-twitch muscle formation of the present invention can be effectively used to strengthen the muscles of sprint athletes or to compensate for the muscle loss that occurs with aging. [Brief explanation of the drawings]

[0015] [Figure 1] This figure shows the results of measuring the mRNA expression level of MyoD, a muscle differentiation regulatory factor (muscle differentiation marker) in an experimental example. In the figure, "P" indicates the results of the test group to which procyanidin C1 (PC1) was added, and "C" indicates the results of the control group to which DMSO was added instead of PC1. The same applies to Figures 2 to 4. [Figure 2] In the experimental example, the results of measuring the mRNA expression level of myogenin, a muscle differentiation control factor (muscle differentiation marker), are shown. [Figure 3] In an experimental example, the results of measuring the mRNA expression level of MyhcI, a muscle fiber marker, are shown. [Figure 4] In an experimental example, the results of measuring the mRNA expression level of MyhcIIa, a muscle fiber marker, are shown. DETAILED DESCRIPTION OF THE INVENTION

[0016] (1) Procyanidin Each of the compositions of the present invention contains procyanidin as an active ingredient. Procyanidins are oligomers formed by condensation of epicatechin or catechin, each consisting of a flavan-3-ol. Specifically, they are linear oligomers formed by linking flavan units consisting of flavan-3-ol only via C-C single bonds (bonds between the C4 and C8' positions). These oligomers include procyanidin B2, which corresponds to a dimer of epicatechin; procyanidin C1, which corresponds to a trimer; and cinnamtannin A2, which corresponds to a tetramer. Procyanidin C1 (hereinafter also referred to as "PC1") is preferred. That is, in the present invention, the term "procyanidin" is not limited as long as the effects of the present invention are achieved, but can be rephrased as "procyanidin C1" or PC1.

[0017] These procyanidins may be produced by chemical synthesis or may be isolated and prepared from natural sources. For example, procyanidins are known to be contained in cocoa beans, grapes, apples, etc. Therefore, they can be extracted and purified from natural products containing such procyanidins or processed products thereof. Furthermore, the present composition may contain a procyanidin-containing substance prepared by extraction (including crude extraction) or crude purification from such natural products or processed products thereof, as long as the effects of the present invention are achieved.

[0018] (2) Effects of procyanidins As shown in the experimental examples described below, procyanidins promote the expression of muscle differentiation control factors (muscle differentiation markers), MyoD and Myogenin, via intestinal epithelial cells (see Figures 1 and 2). This suggests that procyanidins promote the differentiation of muscle satellite cells into myoblasts and the differentiation of myoblasts into myotubes (including myoblast fusion) via intestinal epithelial cells, i.e., they have a muscle differentiation promoting effect. Oral ingestion of procyanidins therefore exerts this muscle differentiation promoting effect in vivo, making it possible to promote the formation and strengthening of muscle (skeletal muscle). In other words, procyanidins can be incorporated into oral compositions for the purpose of promoting muscle differentiation and / or the formation and strengthening of muscle (skeletal muscle).

[0019] Furthermore, as shown in the experimental examples described below, procyanidins exert the effect of promoting the expression of MyhcIIa, a fast-twitch muscle fiber marker, via intestinal epithelial cells (see Figures 3 and 4). This suggests that procyanidins, in addition to promoting muscle differentiation as described above, also promote the expression of fast-twitch muscle fibers and the transition or conversion of formed muscle fibers to fast-twitch muscle fibers, thereby promoting the conversion of muscle to fast-twitch muscle. Therefore, oral ingestion of procyanidins exerts these effects in vivo, making it possible to promote the strengthening of fast-twitch muscle. In other words, procyanidins can be incorporated into oral compositions for the purpose of promoting the expression of fast-twitch muscle fibers and / or the conversion of muscle (skeletal muscle) to fast-twitch muscle.

[0020] (3) Procyanidin-containing composition The present invention provides a composition containing procyanidins (hereinafter referred to as "the composition") that has the aforementioned effects. The composition is an oral composition.

[0021] The composition exerts the aforementioned effects via intestinal epithelial cells when orally administered, and so long as this is the case, the procyanidin content is not particularly limited. For example, the composition may be prepared and provided as one containing 0.1% by mass or more of procyanidin. The lower limit of the content is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more. There is no upper limit to the content, but examples include 99% by mass or less, 10% by mass or less, and 5% by mass or less.

[0022] This composition can be used as a composition for promoting muscle differentiation based on the muscle differentiation-promoting activity of its active ingredient, procyanidins, exerted via intestinal epithelial cells. Here, "muscle differentiation" specifically refers to the differentiation of muscle satellite cells into myoblasts and / or myoblasts into myotubes during the process of muscle fiber formation from muscle satellite cells. The muscle differentiation promoting activity of the composition of the present invention can be evaluated using the expression levels of the mRNA of the muscle differentiation markers MyoD and / or Myogenin as indicators. As described in detail in the Experimental Examples below, this can be carried out using an experimental system that mimics intestinal epithelial cells using commercially available cell culture insert products.

[0023] Furthermore, the present composition can be used as a muscle-building composition based on the muscle differentiation-promoting effect of its active ingredient, procyanidin, exerted via intestinal epithelial cells. Muscle-building compositions also include muscle-building promoting compositions used to promote muscle building. Here, "muscle building" includes increasing skeletal muscle (muscle) synthesis, inhibiting muscle breakdown, increasing / maintaining / inhibiting decline of muscle mass (weight and density), increasing / maintaining / inhibiting decline of muscle strength (power, especially fast-twitch muscle-based explosive power), and increasing / maintaining / inhibiting decline of athletic ability (especially athletic ability requiring fast-twitch muscle-based explosive power) based on muscle building. Muscles here are preferably exemplified by muscles primarily composed of fast-twitch muscle fibers (fast-twitch muscle).

[0024] The composition can be used as a composition for promoting the expression of fast muscle fibers based on the effect of its active ingredient, procyanidin, on promoting the expression of fast muscle fibers via intestinal epithelial cells. Based on this effect, the composition can also be used as a composition for promoting the formation of fast muscle fibers. The fast-twitch muscle fiber expression promoting effect of these compositions can be evaluated using the mRNA expression level of MyhcIIa, a fast-twitch muscle fiber marker, as an indicator. As described in detail in the experimental examples below, this can be performed using an experimental system that mimics intestinal epithelial cells using commercially available cell culture insert products.

[0025] (4) Use in food, beverages, medicines, quasi-drugs, feed, etc. The present composition has an oral administration (oral ingestion) form. As long as it has an oral administration form, the type of the composition (foods and beverages [including health functional foods and supplements such as foods for specified health uses, foods with functional claims, and nutritional functional foods], pharmaceuticals, and quasi-drugs) is not particularly limited. The present composition may also be applied to feed or pet food for animals other than humans (including livestock, poultry, and pets). Furthermore, the present composition may also be an additive added to foods and beverages, pharmaceuticals, quasi-drugs, feed, or pet food.

[0026] Oral dosage forms are not limited, and examples thereof include liquids (including extracts and syrups), jellies, powders, fine granules, or granules; capsules (hard capsules, soft capsules) in which liquids, powders, or granules are filled into capsules; or tablets obtained by further compressing powders or granules (solid formulations). Compositions having such dosage forms can be prepared by blending procyanidins with conventionally known edible carriers, excipients, etc. that are acceptable for pharmaceutical purposes or as food or feed, and molding the mixture into various dosage forms (oral dosage forms).

[0027] When the present composition is in the form of a liquid preparation, a wide variety of carriers conventionally known in the art can be used. Examples of suitable additives for preparing liquid preparations and syrups include water, ethanol, sucrose, invert sugar, glucose, maltose, and reduced starch syrup. When the present composition is in the form of a solid preparation, such as a tablet, a wide variety of carriers conventionally known in the art can be used. Examples of such carriers include excipients such as lactose, sucrose, sodium chloride, glucose, urea, starch, calcium carbonate, kaolin, and silicic acid; binders such as water, ethanol, propanol, simple syrup, glucose solution, starch solution, gelatin solution, carboxymethylcellulose, shellac, methylcellulose, potassium phosphate, polyvinylpyrrolidone, crystalline cellulose, hydroxypropylcellulose, hypromellose, and sodium alginate; and binders such as dry starch, powdered agar, powdered laminaran, sodium bicarbonate, and polyisoprene. Disintegrants such as ethylene sorbitan fatty acid esters, sodium lauryl sulfate, stearic acid monoglyceride, starch, crospovidone, povidone, and low-substituted hydroxypropyl cellulose can be used. Disintegration inhibitors such as stearin, cocoa butter, and hydrogenated oils can be used. Absorption promoters such as quaternary ammonium salts and sodium lauryl sulfate can be used. Wettable tablets can be coated with conventional coatings, such as sugar-coated tablets, gelatin-encapsulated tablets, enteric-coated tablets, and film-coated tablets, or can be double- or multi-layered tablets. Furthermore, capsules containing the active ingredient can be prepared by filling conventional capsules made from materials such as gelatin, pullulan, starch, gum arabic, and hydroxypropylmethylcellulose (HPMC).

[0028] In addition to the above, additives such as surfactants, absorption enhancers, adsorbents, fillers, preservatives, stabilizers, emulsifiers, solubilizers, etc. may be appropriately selected and used depending on the form of the preparation.

[0029] All of these forms can be prepared by conventional methods in the art, for example, tablets can be obtained by adding the above-mentioned active ingredient and other excipients necessary for obtaining tablets as appropriate, mixing and dispersing them well, and then compressing them into tablets, while powders can be obtained by adding the above-mentioned active ingredient and other excipients necessary for obtaining powders as appropriate, mixing them by a suitable method, and pulverizing them.

[0030] The present composition may be in the form of a formulation as described above, or may be in the form of a conventional food or beverage. Such food or beverage can be produced by adding the above-described procyanidins or additives containing procyanidins to various foods or beverages. The food or beverage may be in any form that can be orally ingested, such as a solution, suspension, emulsion, jelly (gel), sol, powder, or solid molding, and is not particularly limited. Specific examples include beverages such as soft drinks, fruit juice drinks, vegetable drinks, soy milk drinks, coffee drinks, cocoa drinks, tea drinks, powdered drinks, concentrated drinks, nutritional drinks, and alcoholic beverages; flour products such as bread, pasta, noodles, cake mix, fried chicken flour, and breadcrumbs; confectioneries such as candy, caramel, chewing gum, chocolate, cookies, biscuits, cakes, pies, snacks, crackers, Japanese sweets, and dessert sweets; and instant foods such as instant noodles, retort pouch foods, canned foods, microwaveable foods, instant soups and miso soups, and freeze-dried foods. Examples include: condiments such as sauces, processed tomato seasonings, flavor seasonings, cooking mixes, sauces, dressings, soups, and curry and stew bases; dairy products such as milk drinks, yogurts, cheese, fermented milk, lactic acid bacteria drinks, ice cream, and cream; processed egg products such as pudding and mayonnaise; processed seafood products such as fish ham and sausage, and fish paste products; processed livestock products such as meat ham and sausage; processed agricultural products such as canned agricultural products, jams and marmalades, pickles, boiled beans, and cereals; frozen foods, nutritional foods, etc.

[0031] Such foods and beverages (including foods in the form of formulations) may be labeled so that the effects of the composition are apparent to consumers, such as foods for specified health uses, foods with functional claims, etc. Examples of such labeling include, but are not limited to, "supports muscle-building power," "increases muscle strength," "increases explosive power," "suppresses muscle and strength decline," "maintains muscle mass and strength," "macho," "slim and muscular," "suppresses, maintains, improves, or enhances the decline of walking ability," and "prevents falls."

[0032] The composition may also be in the form of a conventional feed or pet food, which can also be produced by adding the above-described procyanidins to various feeds or pet foods.

[0033] The procyanidin content of the composition can be set as appropriate depending on the aforementioned form and type (food, beverage, pharmaceutical, quasi-drug, feed, pet food, etc.), with an upper limit of 100% by mass. The dosage (intake) of the composition can be varied as appropriate depending on the type of human or animal, the sex and age of the subject, and the condition and severity of symptoms (pathological condition) of the subject. For example, the daily dosage (intake) for a human adult (body weight 50 kg) can typically be about 5.0 to 100 mg, calculated as the amount of procyanidins contained in the composition, without limitation.

[0034] The subject of administration (ingestion) of the present composition may be any person who needs to strengthen their muscles, preferably those who need to strengthen fast-twitch muscles that exert explosive power. Examples of subjects include, but are not limited to, athletes and sports players (e.g., sprinters, baseball players, rugby players, soccer players, jumpers, karate players, etc.), sports enthusiasts, and people with weak legs and hips (e.g., the elderly).

[0035] (5) How to use procyanidins The present invention also provides methods of using procyanidins. One of the methods of use is the use of procyanidins to impart muscle differentiation promoting effects, muscle strengthening effects, fast-twitch muscle fiber expression promoting effects, and / or fast-twitch muscle formation promoting effects to oral compositions (including foods and beverages, pharmaceuticals, quasi-drugs, feed, pet food, etc.). This method can be carried out by incorporating an effective amount of procyanidin into the oral composition to exert the effects of promoting muscle differentiation, muscle strengthening, promoting the expression of fast-twitch muscle fibers, and / or promoting the formation of fast-twitch muscle fibers. The types of procyanidins to be incorporated, the methods for evaluating these effects, and the types of oral compositions to be incorporated are as described above, and the descriptions therein are incorporated by reference herein.

[0036] As described above, in this specification, the terms "comprise" and "contain" encompass the meanings of "consist of" and "consist essentially of." [Example]

[0037] The present invention will be explained below using experimental examples to aid in understanding the configuration and effects of the present invention. However, the present invention is not limited by these experimental examples. Unless otherwise specified, the following experiments were carried out at room temperature (25±5°C) and atmospheric pressure. Unless otherwise specified, "%" and "parts" in the following descriptions mean "% by mass" and "parts by mass," respectively.

[0038] The materials used in the following experiments and their sources are as follows: PC1: Procyanidin C1 (obtained from Cayman Chemical Company). C2C12 cells: mouse myoblasts (derived from mouse striated muscle) (obtained from ATCC). Caco2 cells: Human colon carcinoma-derived cells (obtained from ATCC). 12 well cell culture insert product: Corning. It consists of a container with an insert with 12 holes (recesses) and a plate container with 12 holes (recesses) that serve as a tray corresponding to the insert. The bottom of the insert is made of a filter with a pore size of 1.0 μm (cell culture surface treatment). FBS-NEAA-containing DMEM medium: DMEM (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) containing 1% NEAA (manufactured by the same company) (1% NEAA-DMEM) was prepared, and then FBS (manufactured by Corning) was mixed with this to give a ratio of FBS:1% NEAA-DMEM = 10:90. Prime Script RT reagent kit: manufactured by Takara Bio Inc. SsoAdvanced Universal SYBR Green Supermix: Manufactured by Bio-Rad Laboratories, Inc. Custom DNA primers: Invitrogen.

[0039] Experimental Method 1. Preparation of Reagents PC1 was prepared at 10 mM with 10% DMSO, stored at -12°C until use, and thawed immediately before use.

[0040] 2. Seeding and Culturing of C2C12 Cells 2 x 10 C2C12 cells 4 The cells were seeded into each well of a 12-well plate at a density of 100 cells / mL and pre-cultured in DMEM medium containing 10% FBS at 37°C for 24 hours.

[0041] 3. Seeding of Caco2 cells and addition of components Caco2 cells were cultured at 2 x 10 in DMEM medium containing 10% FBS-NEAA. 4 1 mL of Caco2 cells / mL was seeded into each well of a 12-well cell culture insert product, and 2.3 mL of DMEM medium containing 10% FBS-NEAA was added to the corresponding insert of the plate. The membrane resistance of the Caco2 cell monolayer was then measured to be 400 Ω cm. 2 The cells were cultured at 37°C until the temperature reached or exceeded this limit. This allows Caco2 cells to differentiate into intestinal epithelial-like cells. On the fifth day after seeding, the first medium change was performed with the same medium as above, and thereafter, the medium was changed every two days for approximately two weeks by adding 1 mL of medium to the insert and 2.3 mL to the plate. After culturing Caco2 cells, 1.5 mL of DMEM medium was added to the plate. Meanwhile, the insert (corresponding to the luminal side of the intestinal epithelium) was replaced with 10% FBS-DMEM medium containing 10 mM PC1, and the medium was changed three times every 24 hours (the control group received the same amount of DMSO alone). After adding PC1 (test group) or DMSO (control group) to the insert, the cells were cultured at 37°C. 72 hours after the first medium change, the medium in the plate corresponding to the insert (corresponding to the basement membrane side of the intestinal epithelium) was collected.

[0042] The C2C12 cells cultured and prepared in step 2 were mixed with 500 mL of the recovered medium and 500 mL of 1% FBS-DMEM medium. The medium was then replaced with a new medium and cultured at 37°C. The cells were harvested after 24, 48, and 72 hours. RNA was extracted from the harvested cells using the PrimeScript RT reagent kit according to the manufacturer's instructions, and cDNA was synthesized. Using the resulting cDNA as a template, quantitative real-time PCR was performed using primers (custom DNA primers) for MyoD, Myogenin, MyhcI, and MyhcIIa genes and SsoAdvanced Universal SYBR Green Supermix according to the manufacturer's instructions to measure the mRNA expression levels of MyoD, Myogenin, MyhcI, and MyhcIIa. Actb (actin β) primers were used as an endogenous control to measure the mRNA expression level of Actb.

[0043] MyoD and Myogenin are transcription factors that control muscle differentiation at each stage of differentiation. MyoD is a master gene of muscle cell differentiation that encodes a bHLH transcription factor that governs the differentiation of muscle cells, and is considered to be a gene necessary for satellite cells to differentiate into myoblasts. Therefore, the mRNA expression level of MyoD serves as an indicator of the differentiation of satellite cells into myoblasts. Myogenin is a downstream gene of MyoD and is a gene that functions when myoblasts differentiate into myotube cells. When Myogenin is induced, the fusion of mononuclear myoblasts (or myoblasts and muscle fibers) is promoted, and multinuclear myotube cells are formed. Therefore, the mRNA expression level of Myogenin serves as an indicator of the differentiation of myoblasts into myotube cells.

[0044] MyhcI and MyhcIIa are genes of myosin heavy chain (MyHC) molecular species that make up skeletal muscle. The molecular species mainly observed in human skeletal muscle are MyHCI, MyHCIIA, MyHCIIX / D, and MyHCIIB. There is a relationship of MyHCI < MyHCIIA < MyHCX / D < MyHCIIB in the maximum shortening velocity of a single muscle fiber containing these myosin heavy chain molecular species. From this, MyhcI, which is the gene of MyHCI, is useful as a marker gene for slow muscle fibers, and the mRNA expression level of MyhcI serves as an indicator of the slow muscle formation (induction or promotion) of muscle. On the other hand, MyhcIIa, which is the gene of MyHCIIA, is useful as a marker gene for fast muscle fibers, and the mRNA expression level of MyhcIIa serves as an indicator of the fast muscle formation (induction or promotion) of muscle.

[0045] Experimental results The results of measuring the mRNA expression levels of MyoD and Myogenin, which are muscle differentiation control factors (muscle differentiation markers), are shown in Figures 1 and 2, respectively. As shown in Figures 1 and 2, the mRNA expression levels of both MyoD and Myogenin were significantly increased in the test group (indicated by "P" in the figure) to which PC1 was added after 48 hours of culture. At 72 hours of culture, no significant difference was observed compared to the control group (indicated by "C" in the figure), which is thought to be due to the conversion of mRNA to protein over time. These results demonstrate that procyanidin (PC1) promotes the differentiation of muscle satellite cells into myoblasts and the differentiation of myoblasts into myotubes (including myoblast fusion) through intestinal epithelial cells.

[0046] The results of measuring the mRNA expression levels of MyhcI and MyhcIIa, which are muscle fiber markers, are shown in Figures 3 and 4, respectively. As shown in Figure 3, no significant difference was observed in the mRNA expression level of MyhcI, a slow-twitch muscle fiber marker, between the test group with PC1 added (indicated by "P" in the figure) and the control group (indicated by "C" in the figure) at any treatment time. In contrast, as shown in Figure 4, the mRNA expression level of MyhcIIa, a fast-twitch muscle fiber marker, was confirmed to be significantly increased in the test group with PC1 added after 24 hours of culture. These results demonstrate that procyanidin (PC1) not only promotes muscle differentiation, but also promotes the transition of formed muscle fibers to fast-twitch muscle fibers, thereby promoting the conversion of muscles to fast-twitch muscle fibers.

Claims

1. A composition for promoting muscle differentiation, comprising procyanidin as an active ingredient.

2. A composition for muscle building containing procyanidin as an active ingredient.

3. A composition for promoting the expression of fast-twitch muscle fibers, comprising procyanidin as an active ingredient.

4. A composition for promoting fast-twitch muscle growth, comprising procyanidin as an active ingredient.

5. The composition according to any one of claims 1 to 4, which is an oral composition.

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