An anti-hypertensive fish protein hydrolysate is provided, wherein the fish is of the genus Salmo or Oncorhynchus, and wherein the fish protein hydrolysate comprises at least 1 peptide selected from the group consisting of: Leu-Ala-Phe, Leu-Thr-Phe, Ile-Ile-Phe, Leu-Ala-Tyr, Ile-Ala-Tyr, Val-Phe-Tyr, Tyr-Ala-Tyr, Val-Leu-Trp, Ile-Ala-Trp, Tyr-Ala-Leu and Tyr-Asn-Arg. Methods of making and methods for using such fish protein hydrolysates are also provided.

FIELD OF THE INVENTION

The invention concerns an anti-hypertensive composition, a method of producing such composition and a dietary supplement made by way of such a method.

BACKGROUND OF THE INVENTION

Hypertension is a condition commonly associated with narrowing of the arteries. This causes blood to be pumped with excessive force against the artery walls. It is a sign that the heart and blood vessels are being overworked. If left untreated hypertension can cause serious cardiovascular disease. For example, the heart muscle can thicken (cardiac hypertrophy) and function abnormally, or dilate and contract less forcefully (dilated cardiomyopathy). High blood pressure can also cause injury to the brain, the eyes and/or the kidneys. Hypertensive patients are also at increased risk of having a stroke.

In vivo the renin/angiotensin system functions to regulate blood pressure. This system comprises the angiotensin I-converting enzyme (ACE) which catalyses the cleavage of inactive angiotensin I into the active vasoconstrictor, angiotensin II. ACE also catalyses the degradation of the vasodilator, bradykinin.

Various enzymatic hydrolysates and peptides derived from food protein have been reported to have ACE inhibitory activity.

In particular, Ono et al. (2003) report that a chum salmon hydrolysate, obtained using thermolysin, had ACE inhibitory activity. Thermolysin is a metalloendopeptidase with a specificity for peptide bonds on the N-terminal side of hydrophobic amino acids, and which is produced by Bacillus thermoproteolyticus).

Ohta et al. (1997) report that a hydrolysate obtained by hydrolysis of a chum salmon head with the commercial serine endopeptidase Biopurase SP10 (from Bacillus subtilis) had greater ACE inhibitory activity than hydrolysates prepared by digestion of the salmon head with any of the following commercial proteases: XP-415 (from Rhizopus delemar), Papain (from Carica papaya), DenazymeAP (from Aspergillus oryzae) or Denapsin2P (from Aspergillus niger).

However, neither Ono et al. nor Ohta et al. report the use of a bacillolysin in preparing anti-hypertensive fish protein hydrolysates.

SUMMARY OF THE INVENTION

Accordingly, in one aspect the invention provides an anti-hypertensive fish protein hydrolysate, wherein said fish is of the genus Salmo or Oncorhynchus, and wherein the fish protein hydrolysate comprises at least 1 peptide selected from the group consisting of:

Leu-Ala-Phe, Leu-Thr-Phe, Ile-Ile-Phe, Leu-Ala-Tyr, Ile-Ala-Tyr, Val-Phe-Tyr, Tyr-Ala-Tyr, Val-Leu-Trp, Ile-Ala-Trp, Tyr-Ala-Leu and Tyr-Asn-Arg.

Such hydrolysates may be prepared by hydrolyzing the fish protein with a bacillolysin.

In another aspect, the present invention provides an anti-hypertensive composition comprising an anti-hypertensive fish protein hydrolysate as described above.

In still another aspect, the present invention provides a dietary supplement, nutraceutical product, or functional food product comprising an anti-hypertensive fish protein hydrolysate as described above.

In yet another aspect, the present invention provides a method for treating or preventing hypertension in a patient comprising administering to a patient in need thereof an anti-hypertensive fish protein hydrolysate as described above.

The invention provides, in another aspect, a method for inhibiting angiotension I-converting enzyme (ACE) activity in a patient comprising administering to a patient in need thereof an anti-hypertensive fish protein hydrolysate as described above.

In still another aspect, the present invention provides a method for reducing mean blood pressure comprising administering to a patient in need thereof an anti-hypertensive fish protein hydrolysate.

In still yet another aspect, the present invention provides a method of producing an anti-hypertensive dietary supplement comprising hydrolyzing fish protein with a bacillolysin, wherein said fish is of the genus Salmo or Oncorhynchus.

In still a further aspect, the present invention provides an anti-hypertensive fish hydrolysate, obtained by or obtainable by the method described above.

DETAILED DESCRIPTION OF THE INVENTION

Fish Species

The fish species used in accordance with the present invention are of the salmonid type, which includes the genus Salmo or Oncorhynchus. Most preferably, the fish are selected from the group consisting of: atlantic salmon (Salmo salar) also know as kennebec salmon, sebago salmon, grilse or kelt; coho salmon (Oncorhynchus kisutch) also known as silver salmon, sea trout or blueback; chinook salmon (Oncorhynchus tshawytscha) also known as king salmon, tyee, spring salmon or quinnat; steelhead salmon (Oncorhynchus mykiss) also known as rainbow or silver trout; pink salmon (Oncorhynchus gorbuscha); and sockeye salmon (Oncorhynchus nerka)

The fish used in the invention may comprise the whole fish, a fillet, a rack, other fish parts, extracts or purified or partially purified fish proteins.

Hydrolysates

If the fish protein is initially provided in the form of, for example, a fish fillet, rack or whole fish, the fish material is preferably ground using a grinding machine known to those of skill in the art. The fish may also be de-boned using de-boning apparatus prior to grinding. Alternatively, the starting material may be pre-ground, or take the form of an extract or purified or partially purified fish protein product, in which case further grinding is not required.

The ground fish may be homogenized in water or other aqueous solution in, for example, a 1:1 ratio.

The water or aqueous solution may contain an anti-bacterial agent such as methyl and/or propyl parabens to minimize bacterial degradation. Typically, if both methyl- and propylparabens are added it may be in the ratio, 2 parts methylparabens and 1 part propylparabens. Optionally, a further preservative may be added.

The protein present in the homogenized mixture of water and ground fish may be preferably denatured using heat prior to hydrolysis. The denaturing temperature may be, for example, greater than 65.degree. C. and most preferably, about 70.degree. C.

Preferably, the denaturing step may be from, for example, 5 to 20 minutes in duration. More preferably, the denaturing step may be from 5 to 15 minutes in duration. Most preferably, the denaturing step may be about 10 minutes in duration.

The mixture may preferably be cooled, for example, to about 50.degree. C. and the pH of the mixture adjusted to, for example, between about pH 7 to pH 9 by the drop-wise addition of 1N sodium hydroxide. Preferably, the pH is adjusted to about 8.

Enzymatic hydrolysis is carried out using an enzyme of the metalloendopeptidase type selected from those in the Enzyme Commission class: EC 3.4.24.28, which are also known as bacillolysins. More particularly, the metalloendopeptidase may be selected from those that preferentially catalyse the hydrolysis of peptide bonds on the C-terminal side of, in descending order with the most preferred amino acid first, arginine, alanine, lysine, phenylalanine and leucine.

In one embodiment, the enzyme is a bacillolysin produced by fermentation of Bacillus stearothermophilus. A preferred type of bacillolysin is Protease S Amano. Protease S Amano is obtainable from Amano Enzyme USA Company Limited (Lombard, Ill.).

When Protease S Amano is used, it may be added at a ratio of from about 1.6% to 3.6% w/w Protease S Amano to fish protein substrate. For example, the ratio may be from about 2.0% to 3.0% w/w and most preferably about 2.6% w/w.

Hydrolysis of the fish protein may be performed at a temperature of, for example, from about 45.degree. C. to 75.degree. C. Preferably the hydrolysis is carried out at a temperature of from about 45.degree. C. to about 55.degree. C., most preferably at a temperature of about 50.degree. C.

Hydrolysis is preferably carried out until a degree of hydrolysis of about 10% to about 30% is achieved. A degree of about 17% hydrolysis is particularly preferred. Typically this takes from about 3 to about 8 hours to achieve. Preferably the hydrolysis reaction proceeds for about 5.5 to about 7.5 hours. Most preferably the hydrolysis reaction proceeds for about 6.5 to about 7 hours. Advantageously, it is not necessary to constantly maintain a steady pH value of the homogenized fish mixture during the hydrolysis reaction.

If desired, the protein content in the ground fish material may be determined by a method known to those skilled in the art, for example, by the Kjeldahl nitrogen method wherein the percentage protein is equal to the percentage nitrogen multiplied by 6.25. The degree of hydrolysis may be determined by the OPA reaction method.

The homogenized mixture may be heated to a temperature greater than 80.degree. C. for longer than 3 minutes to inactivate the metalloendopeptidase and thereby stop the hydrolysis reaction.

Bones and other, heavy, insoluble material may be removed from the mixture by, for example, filtration through a screen or two-phase centrifugation.

The, light, insoluble fraction and oil may be removed by, for example, three-phase centrifugation or vacuum filtration through a suitable filter or membrane, for example, diatomaceous earth.

The aqueous fraction is preferably dried such as by spray drying to obtain a powdered fish protein hydrolysate.

Alternatively, the aqueous fraction may be concentrated, for example, with a rotary evaporator, and then lyophilized, or spray-dried to yield a concentrated, powdered, protein hydrolysate.

Alternatively, the aqueous fraction may be further processed either before or after concentration and/or freeze-drying by for example, ethanol precipitation, ultrafiltration or reverse-phase chromatography to remove salt, high molecular weight peptides or protein fragments. The aqueous fraction may also be further processed by, for example, filtration, chromatography, dialysis and/or centrifugation, or any combination thereof, as are known in the art.

Advantageously, the fish protein hydrolysate of the present invention is not required to be processed further by, for example, ethanol precipitation, ultrafiltration or reverse-phase chromatography for it to be efficacious.

The fish protein hydrolysate comprises at least one peptide selected from the group consisting of Leu-Ala-Phe, Leu-Thr-Phe, Ile-Ile-Phe, Leu-Ala-Tyr, Ile-Ala-Tyr, Val-Phe-Tyr, Val-Leu-Trp, Ile-Ala-Trp, Tyr-Ala-Leu, and Tyr-Asn-Arg. Of this group Leu-Ala-Phe, Leu-Thr-Phe, Ile-Ile-Phe, Val-Phe-Tyr, Ile-Ala-Trp and Val-Leu-Trp are preferred, and the hydrolysate preferably comprises 1, 2, 3, 4, 5 or all of these peptides. Of this group, Leu-Ala-Phe, Ile-Ile-Phe, Val-Phe-Tyr, Val-Leu-Trp and Ile-Ala-Trp are more preferred, and the hydrolysate preferably comprises 1, 2, 3, 4 or 5 of these peptides. Most preferably, the hydrolysate comprises at least 1, 2, 3, 4, or 5 of the peptides Leu-Ala-Phe, Ile-Ile-Phe, Val-Phe-Tyr, Val-Leu-Trp and Ile-Ala-Trp.

The protein hydrolysate obtained by the methods of the present invention may be used in the production of a composition or compound comprising the above tri-peptides.

Uses

The fish protein hydrolysates of the present invention possess useful anti-hypertensive properties, having been demonstrated to be potent inhibitors of ACE and to reduce mean blood pressure in SHR. Accordingly, the hydrolysates of the invention are useful in the prevention and treatment of hypertension in a subject as well as in the treatment and prevention of the complications of hypertension, for example, cardiac hypertrophy, dilated cardiomyopathy, congestive heart failure, ischaemic heart disease, atherosclerosis, stroke, renal injury including aneurysm, arteriovenous fistula, arterial blockage or renal vein thrombosis; brain damage, loss of vision.

Obesity and diabetes mellitus are conditions in which blood pressure may be elevated. The hydrolysates of the present invention may be of use in the treatment of high blood pressure in these conditions.

The subject may be a mammal, such as a human, companion animal or other mammal of agricultural or commercial importance.

Compositions

Compounds and compositions according to the present invention may be used in a variety of products, for example, pharmaceutical or nutraceutical products, dietary supplements, nutritional supplements, food products, food ingredients and beverages. The fish protein hydrolysate may be microencapulated in order to improve palatability or processing characteristics of the food or beverage products. Alternatively, the fish protein hydrolysates may be used on their own.

Preferably, nutraceutical and pharmaceutical formulations of compositions and compounds in accordance with the present invention are intended for oral administration. The formulations comprise the composition of the present invention in combination with one or more physiologically acceptable ingredients, such as carriers, excipients or diluents. Compositions and formulations for oral administration are particularly preferred. Formulations may be prepared, for example, in unit dose forms, such as hard capsules, tablets, capsules, dragees, and ampoules or as a powder in a sachet for dissolving in a liquid. They may be prepared in a conventional manner, for example by means of conventional mixing, granulating, confectioning, dissolving or lyophilizing processes.

Typical physiologically acceptable ingredients include, for example: a) binding agents such as starch, polyvinylpyrrolidone, hydroxypropylmethyl cellulose and/or gelatine; b) fillers such as rice powder, sugars (for example, lactose, saccharose, mannitol, sorbitol) and amylopectin, cellulose preparations (for example, microcrystaline cellulose), calcium phosphates (for example, tricalcium phosphate, calcium hydrogen phosphate, lactose), magnesium stearate and/or titanium dioxide; c) lubricants such as steric acid, calcium stearate, magnesium stearate, talc, silica, silicic acid, polyethylene glycol and/or waxes; d) disintegrants such the above mentioned starches, carboxymethyl starch, cross-linked. polyvinylpyrrolidone, agar, alginic acid or a salt thereof (for example, sodium alginate) and/or sodium starch glycolate; e) wetting agents such as sodium lauryl sulphate; and/or f) stabilizers.

Soft gelatine capsules may be prepared with capsules containing a mixture of the fish protein hydrolysate composition together with paraffin oil, liquid polyethylene glycols, vegetable oil, fat and/or another suitable vehicle for soft gelatine capsules. Plasticizers such as glycerol or sorbitol may also be used. Hard gelatine capsules may contain granules of the composition. Hard gelatine capsules may also contain the composition in combination with solid powdered ingredients such as those listed above.

Liquid formulations for oral administration may be prepared in the form of solutions, syrups or suspensions. Liquid formulations typically comprise the fish protein hydrolysate composition with an excipient such as sugar or sugar alcohols, and a carrier such as ethanol, water, glycerol, propylene glycol, polyethylene glycol, almond oil, oily esters or mixtures thereof. If desired, such liquid formulations may also contain colouring agents, flavouring agents, saccharine, thickening agents (for example, carboxy methyl cellulose), suspending agents (for example, sorbitol syrup, methylcellulose, hydrogenated edible fats), emulsifying agents (for example, lecithin, acacia), and/or preservatives (for example, methyl p-hydroxy benzoates, propyl p-hydroxy benzoates, sorbic acid). Liquid formulations for oral administration may also be prepared in the form of a dry powder to be reconstituted with water or another suitable vehicle prior to use.

Formulations may contain one or more additional active ingredients particularly one or more further anti-hypertensive agents. The one or more further anti-hypertensive agents is preferably selected from the group consisting of alpha.sub.1-adrenergic antagonists, beta-adrenergic antagonists, combined alpha/beta-adrenergic antagonists, adrenergic neuron blocking agents, CNS-acting antihypertensives, angiotensin converting enzyme (ACE) inhibitors, angiotensin-II receptor antagonists, calcium channel blockers and diuretic agents.

An effective amount of the fish protein hydrolysate composition can be determined by the skilled person and may depend on various factors, such as the nature of the product, the condition to be prevented or treated, the method of administration, species of animal, age and/or individual condition. Typically, the dose may comprise between 1 to 5 grams of hydrolysate per day for a 70 Kg human. Preferably the dose comprises 1.5 grams of dry hydrolysate per day. Preferably, the hydrolysate may be taken between 2 to 4 times daily such that the dose does not have to be taken at once.

 

Claim 1 of 33 Claims

1. An anti-hypertensive fish protein hydrolysate, wherein said fish is of the Salmo spp. or Oncorhynchus spp. type, and wherein the fish protein hydrolysate comprises at least 2 peptides selected from the group consisting of: Leu-Ala-Phe, Leu-Thr-Phe, Ile-Ile-Phe, Val-Phe-Tyr, Ile-Ala-Trp and Val-Leu-Trp.

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