Opioid peptide preparation

Abstract

The purpose of the present invention is to provide an opioid peptide preparation that is effective for securing stable sleep and suppressing anxiety, and especially can suppress or prevent circadian rhythm disorder including time difference blur.　This opioid peptide preparation contains, as an active ingredient, a casomorphin that is a peptide composed of 5 to 20 amino acid residues in total. The casomorphin is preferably a peptide that is composed of 10-17 amino acid residues in total and has at least an amino acid sequence having a structure such that tyrosine, proline, phenylalanine, proline, glycine, proline, isoleucine, proline, asparagine and serine are linked in this order from one end.

Description

Opioid peptide formulations

[0001] The present invention relates to an opioid peptide formulation, and in particular to a sleep stabilizer and an anxiolytic agent containing the opioid peptide formulation.

[0002] In modern society, various forms of sleep disorders have become a social problem. Examples of sleep disorders include jet lag caused by high-speed travel on aircraft, such as when traveling abroad or to space, and circadian rhythm disorders caused by irregular lifestyles such as shift work. These are known to cause insomnia and other physical and mental disorders in many cases. In addition, there are many cases of circadian rhythm disruption and insomnia caused by alterations in endogenous hormone secretion in the elderly, making ensuring stable sleep an important issue.

[0003] Sleeping pills and anti-anxiety drugs are considered as a means to improve the quality of sleep. In particular, the administration of endogenous hormones such as melatonin has been actively attempted in recent years. In addition, sleep improvers and sleep stabilizers using raw materials of foods and beverages and the natural ingredients contained therein have also been developed (e.g., Patent Documents 1 to 3, etc.).

[0004] JP 2023-133435 A JP 2017-079746 A JP 2015-110564 A

[0005] However, the use of sleeping pills or inappropriate anti-anxiety drugs may cause side effects, as described in, for example, Patent Document 1, and therefore requires a doctor's diagnosis before use. The administration of endogenous hormones such as melatonin may also affect various physiological phenomena other than circadian rhythms (see, for example, Patent Document 2). While the use of food and beverage ingredients is considered relatively safe, their mechanism of action has not been fully elucidated, and there is variation in the sleep-improving effects (see, for example, Patent Document 3).

[0006] The present invention has been made in view of the above circumstances, and aims to provide an opioid peptide preparation that can ensure stable sleep and suppress anxiety, and in particular can suppress or prevent circadian rhythm disorders such as jet lag.

[0007] As a result of intensive research and studies to solve the above problems, the inventors have discovered that casomorphins, which are peptides consisting of a total of 5 to 20 amino acid residues, are effective in ensuring stable sleep and suppressing anxiety, and in particular in suppressing or preventing circadian rhythm disorders.

[0008] That is, the present invention provides the following: (1) An opioid peptide formulation comprising, as an active ingredient, a casomorphin, which is a peptide consisting of a total of 5 to 20 amino acid residues. (2) The opioid peptide formulation of (1), wherein the casomorphin has at least an amino acid sequence in which, from one end, tyrosine, proline, phenylalanine, proline, and glycine are bound in this order. (3) The opioid peptide formulation of (1) or (2), wherein the casomorphin has at least an amino acid sequence in which, from one end, tyrosine, proline, phenylalanine, proline, glycine, proline, isoleucine, proline, asparagine, and serine are bound in this order. (4) The opioid peptide formulation of any one of (1) to (3), wherein the casomorphin has at least an amino acid sequence in which, from one end, tyrosine, proline, phenylalanine, proline, glycine, proline, isoleucine, proline, asparagine, serine, leucine, and proline are bound in this order. (5) A sleep stabilizer comprising the opioid peptide formulation of any one of (1) to (4). (6) An anxiolytic agent comprising the opioid peptide formulation of any one of (1) to (4).

[0009] According to the present invention, an opioid peptide formulation is provided that is effective in ensuring stable sleep, suppressing anxiety, and particularly suppressing or preventing circadian rhythm disorders such as jet lag. Furthermore, since the active ingredient, casomorphin, of the opioid peptide formulation of the present invention can be produced from food raw materials, it is highly safe and can be used as a food additive.

[0010] 1 is a graph showing the results of behavioral tests on mice in Example 1 and Comparative Example 1. 2 is a graph comparing opioid activity in Example 5. 3 is a graph showing the results of behavioral tests on mice in Example 6 and Comparative Example 3.

[0011] The present invention will be described in detail below based on embodiments.

[0012] <Opioid Peptide Preparations> The opioid peptide preparations of the present invention contain, as an active ingredient, a casomorphin, which is a peptide consisting of a total of 5 to 20 amino acid residues. Casomorphins themselves encompass compounds with various structures, and the opioid peptide preparations of the present invention can also contain other ingredients as desired, thus encompassing a variety of embodiments. Below, the main ingredients in the opioid peptide preparations of the present invention are described in further detail using representative embodiments as examples, but the present invention is not limited to these embodiments.

[0013] <Casomorphin> Casomorphin, the active ingredient in this embodiment, is a type of peptide with a molecular structure in which multiple amino acids are linked by peptide bonds. Casomorphins are also so-called opioid peptides that can bind to opioid receptors present in central and peripheral nerves. Delta receptors, kappa receptors, and μ receptors have been reported as human opioid receptors, and the casomorphin of this embodiment can bind to any of these receptors. While the present invention is not limited by any particular theory, it is thought that the opioid activity of casomorphins may bring about the sleep-stabilizing effect and anti-anxiety effect.

[0014] Casomorphins can be prepared by various known methods. For example, they can be obtained by hydrolyzing the milk protein casein with an enzyme derived from koji mold or the like, followed by separation and purification as desired. Casomorphins can also be synthesized by peptide bonding of desired amino acids.

[0015] (Casomorphin Structure) In this embodiment, the casomorphin may be any peptide with a total of 5 to 20 amino acid residues. Such peptides generally exhibit opioid activity of 50 U / mL or more and are likely to exhibit sleep-stabilizing and anxiolytic effects. Multiple types of casomorphins may also be included. In addition to a casomorphin with a total of 5 to 20 amino acid residues, other peptides, such as a casomorphin with a total of less than 5 amino acid residues and / or a casomorphin with a total of more than 20 amino acid residues, may also be included.

[0016] (Total Number of Amino Acid Residues) The casomorphin used as an active ingredient in this embodiment may be a peptide consisting of 5 to 20 total amino acid residues. From the viewpoint of further enhancing the sleep-stabilizing effect and anxiolytic effect, the total number of amino acid residues is preferably 7 or more, 9 or more, 10 or more, 11 or more, or even 12 or more, or 17 or less, particularly 15 or less. Casomorphins with such a total number of amino acid residues generally tend to exhibit opioid activity of 60 U / mL or more, particularly 70 U / mL or more. In particular, by including a casomorphin with a total number of amino acid residues of preferably 10 to 15, more preferably 12 to 14, even more excellent sleep-stabilizing effect and anxiolytic effect can be exhibited. Note that a casomorphin with a total number of amino acid residues of X, for example 10, may be referred to below as "CM-X," e.g., "CM-10."

[0017] (Amino Acid Sequence) A preferred casomorphin in this embodiment has at least an amino acid sequence in which, from one end, tyrosine, proline, phenylalanine, proline, and glycine are bound in this order. Casomorphins having such an amino acid sequence, particularly those with a total of 7 to 17 amino acid residues, are more likely to exhibit sleep-stabilizing effects, including the suppression or prevention of circadian rhythm disorders.

[0018] A more preferred casomorphin in this embodiment has at least an amino acid sequence in which, from one end, tyrosine, proline, phenylalanine, proline, glycine, proline, isoleucine, proline, asparagine, and serine are bound in this order. Casomorphins having such an amino acid sequence, particularly casomorphins with a total of 10 to 15 amino acid residues, such as CM-10, can exhibit even more excellent sleep-stabilizing effects and anti-anxiety effects, and also have the advantage of being easily prepared.

[0019] A more preferred casomorphin in this embodiment has at least an amino acid sequence in which, from one end, tyrosine, proline, phenylalanine, proline, glycine, proline, isoleucine, proline, asparagine, serine, leucine, and proline are bound in this order. Casomorphins having such an amino acid sequence, particularly casomorphins with a total of 12 to 14 amino acid residues, such as CM-12, can exhibit particularly excellent sleep-stabilizing effects and anti-anxiety effects, and also have the advantage of being easy to prepare.

[0020] The 20 amino acids that constitute peptides and proteins are each given a three-letter or one-letter abbreviation. For example, CM-12 having the above amino acid sequence can be expressed as Tyr-Pro-Phe-Pro-Gly-Pro-Ile-Pro-Asn-Ser-Leu-Pro or YPFPGPIPNSLP.

[0021] <Preparation of Casomorphin> As described above, the casomorphin contained in the opioid peptide formulation of the present embodiment can be prepared by various known methods, for example, peptide synthesis methods, etc. Below, a typical preparation method using casein degradation will be described, but the preparation method of casomorphin is not limited to this.

[0022] Casomorphins can be prepared, for example, by decomposing casein, a type of milk protein, with an enzyme such as a protease derived from Aspergillus oryzae. The product prepared after enzymatic decomposition may be separated and purified as desired.

[0023] (Casein) Casein is a protein found in cow's milk, goat's milk, and dairy products. Depending on the molecular species, it can be divided into α ｓ１ -Casein, α ｓ２ Casein is broadly classified into four types: β-casein, β-casein, and κ-casein. In this embodiment, any type of casein may be used as the raw material. Multiple types of casein may also be used in combination.

[0024] (Koji mold) The koji mold that decomposes casein is not particularly limited, and examples thereof include black koji mold, white koji mold, yellow koji mold, and red koji mold. Preferred koji molds include Aspergillus awamori (black koji mold), Aspergillus saitoi (black koji mold), Aspergillus nakazawai (black koji mold), Aspergillus usamii (black koji mold), Aspergillus luchensis (black koji mold), Aspergillus niger (black koji mold), and Aspergillus kawachi (black koji mold). kawachii (white koji mold), and Aspergillus oryzae (yellow koji mold), with Aspergillus oryzae being particularly preferred.

[0025] (Protease) Proteases derived from koji mold can be prepared by known methods. For example, koji mold containing a high concentration of protease is collected by solid culture, and the enzyme is suspended and extracted in distilled water or a buffer solution. The extracted enzyme may be subjected to precipitation by adding ethanol, precipitation by salting out, concentration using a membrane, concentration using an ion exchange column, or the like. Alternatively, commercially available proteases, such as Protease M "Amano" SD and Protease A "Amano" SD, can also be used.

[0026] (Casein Decomposition) Casein decomposition with the koji mold-derived protease may be carried out, for example, in water for about 12 to 30 hours at a temperature of about 30 to 60° C. The reaction buffer is not particularly limited.

[0027] (Separation and Purification) A digest (decomposition product) obtained by digesting casein with a protease derived from Aspergillus oryzae may be used as a crude peptide mixture as is in the opioid peptide formulation of this embodiment. Alternatively, the crude peptide mixture may be purified to obtain a concentrated mixture of peptides (casomorphins). Here, the sleep-stabilizing effect and anxiolytic effect can be further enhanced by separating casomorphins based on the total number of amino acid residues and / or amino acid sequence, and selecting and using desired peptides. For example, it is possible to prepare an opioid peptide formulation that exhibits particularly excellent effects by using casomorphins containing CM-10 or CM-12 as the main component.

[0028] The separation and purification method is not particularly limited, and any method known in the field of peptide or protein purification can be used. For example, purification can be performed by techniques such as reverse phase chromatography, hydrophobic interaction chromatography, gel filtration, ion exchange chromatography, and affinity chromatography. In particular, fast protein liquid chromatography (FPLC) is preferred, and high performance liquid chromatography (HPLC) can also be used for small lot production.

[0029] <Preparation> The opioid peptide preparation of this embodiment contains, as an active ingredient, a casomorphin, which is a peptide consisting of a total of 5 to 20 amino acid residues as described above. In this embodiment, the crude peptide mixture or the purified mixture described above may be directly formulated into, for example, a liquid preparation, or may be formulated into a liquid or solid composition containing other additives.

[0030] (Additives) The additives other than casomorphin contained in the opioid peptide formulation of this embodiment are not particularly limited. Examples include, but are not limited to, excipients, binders, disintegrants, emulsifiers, lubricants, flow enhancers, diluents, preservatives, colorants, flavorings, flavoring agents, stabilizers, humectants, antiseptics, antioxidants, suspending agents, emulsifiers, etc. In addition to these, water-soluble solvents such as physiological saline or Ringer's solution, water-insoluble solvents such as vegetable oils or fatty acid esters, isotonic agents such as glucose or sodium chloride, solubilizers, stabilizers, preservatives, etc. are also useful, particularly when the opioid peptide formulation is a parenteral preparation.

[0031] (Oral Administration Preparation) The opioid peptide preparation of this embodiment may be in any dosage form or by any administration method, as described above. For example, it can be made into an injection, but it is preferably made into an enteral administration preparation, particularly an oral administration preparation. As shown in the Reference Examples described below, an anxiolytic test in mice showed that oral administration of casomorphin was effective, and it is thought that the opioid peptide preparation of this embodiment may also exhibit better effects when made into an oral administration preparation.

[0032] (Dosage Form) The opioid peptide formulation of this embodiment, particularly the oral administration formulation, may be a solid or powdered formulation such as fine granules, granules, tablets, capsules, and pills, or a liquid or gel form such as a suspension, emulsion, syrup, and extract.

[0033] The oral administration formulation of this embodiment, particularly when it is solid, may contain, for example, gelatin, sodium alginate, starch, corn starch, sucrose, lactose, glucose, mannitol, carboxymethylcellulose, dextrin, polyvinylpyrrolidone, crystalline cellulose, soybean lecithin, sucrose, fatty acid esters, talc, magnesium stearate, polyethylene glycol, magnesium silicate, silicic anhydride, synthetic aluminum silicate, etc. These additives are useful as excipients, binders, etc., and many are edible, so they are suitable as additives for oral administration formulations.

[0034] (Composition Ratio) The opioid peptide formulation of this embodiment may contain various additives in addition to the active ingredient casomorphin as described above, but the composition ratio is not particularly limited. From the viewpoint of enhancing the sleep-stabilizing effect and anxiolytic effect, it is preferable to contain a peptide consisting of 5 to 20 amino acid residues in an amount of 1 to 99% by mass, 5 to 95% by mass, 10 to 90% by mass, 20 to 80% by mass, and particularly 30 to 70% by mass of the opioid peptide formulation (total 100% by mass). For example, an orally administered formulation may contain 20 to 80% by mass, particularly 30 to 70% by mass, of the active ingredient casomorphin, and 80 to 20% by mass, particularly 70 to 30% by mass, of other additives such as starch or sucrose.

[0035] <Administration of Opioid Peptide Preparation> There are no particular limitations on the dosage or intake of the opioid peptide preparation of this embodiment. The administration method, dosage, administration period, administration interval, and the like are preferably determined through controlled clinical trials, but can be adjusted appropriately depending on the dosage form, as well as the age, sex, body weight, and severity of disease symptoms of the user. For example, the dosage, calculated as the amount of casomorphin added as the active ingredient, can be preferably about 0.01 to 1000 mg / kg body weight / day, more preferably about 0.1 to 750 mg / kg body weight / day, even more preferably about 0.2 to 500 mg / kg body weight / day, 0.3 to 400 mg / kg body weight / day, 0.5 to 300 mg / kg body weight / day, 0.7 to 200 mg / kg body weight / day, and particularly preferably about 1 to 150 mg / kg body weight / day.

[0036] The method of administration of the opioid peptide formulation of this embodiment is preferably enteral administration, particularly oral administration, as described above, but is not particularly limited thereto. For example, it may be administered in the form of a food or beverage containing the active ingredient casomorphin. Specifically, it can be administered by mixing with freshly prepared foods such as salads, cooked foods, stir-fried foods, processed vegetable foods, noodles, fish paste products, dairy products, seasonings, soy foods such as tofu, konjac, confectioneries, or supplements. It can also be mixed into liquid foods or beverages.

[0037] The opioid peptide formulation of this embodiment can exhibit excellent sleep-stabilizing effects and anxiolytic effects as described above. Therefore, it is useful as a sleep stabilizer or anxiolytic. The present invention also encompasses a sleep stabilizer containing the above opioid peptide formulation and an anxiolytic containing the above opioid peptide formulation.

[0038] The opioid peptide preparation of this embodiment is primarily intended to suppress or prevent circadian rhythm disorders or suppress anxiety in humans, but may also exhibit effects as an analgesic, antidepressant, antistress agent, etc., in addition to acting as a sleep stabilizer or an anxiolytic. The subject of administration may also be animals other than humans, and the preparation may be administered to pets such as dogs, cats, rabbits, hamsters, guinea pigs, and squirrels; livestock such as cows and pigs; laboratory animals such as mice and rats; and animals kept in zoos, for example, after long-distance travel to stabilize sleep.

[0039] The present invention will be described in more detail below with reference to examples.

[0040] In this example, casein was decomposed with a protease to prepare casomorphin, which was then purified and administered to mice to evaluate its effect on suppressing circadian rhythm disorders (Example 1). The evaluation was performed by comparing the activity rate of the mice when the day-night cycle of their surrounding environment was reversed by 12 hours with that of mice not administered casomorphin (Comparative Example 1).

[0041] (Preparation of Casomorphin) 0.3 g of casein was dissolved in 30 mL of phosphate-buffered saline (20 mM, 137 mM NaCl, pH 6.8: PBS), 0.03 mg of protease was added, and the mixture was reacted at 45°C for 24 hours. After the reaction, the mixture was inactivated at 80°C for 20 minutes, and the supernatant was collected. The collected material was separated by reverse-phase HPLC (C-18 column, water / acetonitrile) and lyophilized to obtain a peptide (CM-10 yield: 32%). Analysis of the obtained peptide by TOF-MS revealed that it was a casomorphin (total number of amino acid residues: 10: CM-10) having an amino acid sequence consisting of tyrosine, proline, phenylalanine, proline, glycine, proline, isoleucine, proline, asparagine, and serine bound in this order. Furthermore, when CM-10 with the same structure was separately synthesized and subjected to HPLC analysis under the same conditions, it showed the same retention time as the purified peptide, confirming that the TOF-MS analysis results were correct.

[0042] (Evaluation of Activity Rate) Mice were placed in a test box equipped with lighting and a video monitor, and the lighting was turned on and off. The mouse's movements were observed on the monitor. The time (minutes) during which the mouse moved was measured every hour, and this was divided by 60 to obtain the activity rate (unit: %). The test was conducted for two full days. On the first day, the mice were given water, and the lights were turned on between 8:00 AM and 8:00 PM, and turned off between 8:00 PM and 8:00 AM the following day. On the second day, the mice were given water containing CM-10 (dosage: 0.1 mg / kg body weight / day), and the lights were turned off between 8:00 AM and 8:00 PM, and turned on between 8:00 PM and 8:00 AM the following day, creating a day-night reversed environment (Example 1). The activity rates of four female mice in this environment were measured, and the average was used to obtain the hourly activity rate. For comparison, a similar test was conducted on four other female mice on the second day, but only water was given (no CM-10 administration) (Comparative Example 1).

[0043] The results of the activity rate test are shown in Figure 1. In Figure 1, the activity rate for each time period is plotted at the midpoint of that time period. Because mice are nocturnal, their activity rate typically decreases between 8 PM on the second day and 8 AM the next day, for example, between 9 PM and 4 AM (9 PM to 4 AM). However, mice given only water (Comparative Example 1) were active at 30% or more between 10 PM and 2 AM on the second day, and sometimes at 40% or more, as was the case on the first day. This indicates that they were unable to adapt to the reversed day-night environment and were carrying over the sleep cycle from the previous day. On the other hand, mice administered CM-10 (Example 1) had activity rates of just under 30%, or even 20%, during the same time period on the second day, indicating that they had adapted to a certain extent to the reversed day-night environment. It has been revealed that CM-10, a type of casomorphin, exhibits an inhibitory effect on circadian rhythm disorders.

[0044] Example 2 In this example, the anxiolytic effect of the casomorphin prepared in Example 1 was investigated. An elevated plus-maze test was performed on mice administered CM-10 in Example 1, confirming the anxiolytic effect of CM-10. A similar test was performed on mice intravenously injected with the same amount of CM-10, but no clear anxiolytic effect was observed. It is believed that the anxiolytic effect of CM-10 is more likely to be expressed by ingestion via the intestine. It is suggested that an opioid peptide formulation containing casomorphin as an active ingredient is more effective when administered orally.

[0045] [Example 3, Comparative Example 2] In this example, HEK293 cells co-expressing the genes for the delta opioid receptor (DOR) and GloSensor cAMP biosensor were used to evaluate the comprehensive gene expression in the cells by adding CM-10.

[0046] HEK293 cells were cultured in DMEM + 10% FBS + 1% PS medium in the dark at 23°C, and then CM-10 was added and cultured for an additional hour (Example 3). Global gene expression in the cells was then evaluated by RNA sequencing. For comparison, a similar test was performed without the addition of CM-10 (Comparative Example 2).

[0047] In Example 3, in which CM-10 was added, the expression of 34 genes was significantly increased, and the expression of 560 genes was significantly decreased. Furthermore, in Example 3, unlike Comparative Example 2 in which CM-10 was not added, the expression levels of clock genes that control circadian rhythms were reduced. It is presumed that when the expression of clock genes is suppressed, the circadian rhythm before, for example, an airplane trip is not maintained and is more likely to be reset, resulting in less likelihood of circadian rhythm disorders such as jet lag. This example demonstrated that CM-10 is a component that can affect circadian rhythms, and therefore can exert a sleep stabilizing effect.

[0048] Example 4 In this example, the magnitude of opioid activity related to circadian rhythm was compared for various casomorphins differing in the total number of amino acid residues. Various casomorphins were prepared as in Example 1, and their amino acid sequences were determined. Opioid activity was evaluated by reacting the μ-opioid receptor (MOR) with each casomorphin for 1 hour under the same conditions as in Example 3, and measuring the decrease in luminescence associated with the decrease in cAMP due to binding between the two. The amino acid sequence and opioid activity of each casomorphin are shown in Table 1. The amino acid sequences of CM-5 to CM-17 are also shown in the attached sequence listing.

[0049]

[0050] While CM-3, which has a total of three amino acid residues, had an opioid activity of less than 40 U / mL, CM-5 to CM-17, which have a total of 5 to 17 amino acid residues, all exhibited high opioid activity of over 70 U / mL. These results suggest that casomorphins, which are peptides with a total of five or more amino acid residues, may also be effective in suppressing or preventing circadian rhythm disorders.

[0051] Example 5 In this example, we investigated whether the opioid activity of CM-12 differed depending on the preparation method. HEK cells expressing the μ-opioid receptor and cAMP / hygro were administered 7.5 μM of CM-12 (synthetic product) synthesized by the same method as in Example 1, or an A2 milk casein hydrolysate (hydrolysate product) containing an equivalent amount of CM-12, and the change in luminescence intensity after 60 minutes of incubation at 23°C was measured. The amino acid sequences of the synthetic and hydrolysate CM-12 products were analyzed in the same manner as in Example 1, and both were found to have the amino acid sequence YPFPGPIPNSLP.

[0052] The results of the evaluation of opioid activity are shown in Figure 2. As shown in Figure 2, casein hydrolysates containing CM-12 (hydrolysates) were confirmed to have activity comparable to that of the same amount of CM-12 synthetic peptide (synthetic product), suggesting that CM-12 is the major opioid peptide in casein hydrolysates. As such, casomorphins, the active ingredients of the present invention, can be produced from food raw materials and are therefore considered to be highly safe.

[0053] [Example 6, Comparative Example 3] In this example, the anxiolytic effect of CM-12 administration was investigated. Twelve 10-week-old female BALB / c mice were divided into two groups (six mice per group) and housed in a temperature-controlled room at 26°C. Synthetic CM-12 was added to the drinking water of test group mice (n=6), and CM-12 was orally administered at a dose of 5 mg / kg (Example 6: CM-12 administration). 200 μL of 0.1 M PBS was orally administered to control group mice (n=6) (Comparative Example 3: control). After oral administration, the mice were confined to a small space and subjected to stress for 15 minutes. Then, the mice were placed on the central platform of an elevated plus maze, and the time it took to enter the open arms was measured. The results are shown in Figure 3.

[0054] As shown in Figure 3, in the control group (Comparative Example 3), many individuals spent most of the time in the enclosed closed arms, whereas in the CM-12-administered group (Example 6), they spent an average of approximately 6 minutes in the open arms over the 10-minute period, showing a significant difference between the two groups. It is believed that administration of CM-12 increased stress tolerance and made the animals more active than the control group. This suggests that opioid peptide formulations containing CM-12 exert an anxiolytic effect.

[0055] As described above, the opioid peptide formulations of the present invention containing casomorphins as active ingredients are effective in suppressing or preventing circadian rhythm disorders. In particular, when the casomorphin is a peptide consisting of 5 to 20 amino acid residues in total, or when the opioid peptide formulation is an orally administered formulation, the suppressive or preventive effect on circadian rhythm disorders or the anxiolytic effect is thought to be enhanced.

Claims

1. An opioid peptide preparation containing, as an active ingredient, casomorphin, a peptide consisting of a total of 5 to 20 amino acid residues.

2. The opioid peptide formulation according to claim 1, wherein the casomorphin has at least an amino acid sequence in which tyrosine, proline, phenylalanine, proline and glycine are bound in this order from one end.

3. The opioid peptide formulation according to claim 1, wherein the casomorphin has at least an amino acid sequence in which, from one end, tyrosine, proline, phenylalanine, proline, glycine, proline, isoleucine, proline, asparagine and serine are bound in this order.

4. The opioid peptide formulation of claim 1, wherein the casomorphin has at least an amino acid sequence in which, from one end, tyrosine, proline, phenylalanine, proline, glycine, proline, isoleucine, proline, asparagine, serine, leucine and proline are bound in this order.

5. A sleep stabilizer comprising the opioid peptide formulation according to any one of claims 1 to 4.

6. An anti-anxiety agent comprising the opioid peptide formulation according to any one of claims 1 to 4.

Images