Abstract:
A composition of matter comprising zinc and an extract of animal prostatic tissue provides a convenient source of both fatty acids and zinc for dietary and therapeutic purposes. The pharmaceutical composition is useful for the treatment of diabetes. 05411748821 00000000000000000465034000000000000000000000000000000000000000000000000000000098

Description:
ACKNOWLEDGEMENT OF GOVERNMENT SUPPORT 
     This invention was made with Government support, namely, the facilities, equipment, and materials of the Department of Veterans&#39; Affairs. The Government has certain rights in this invention. 
    
    
     This application is a continuation of application Ser. No. 07/964,879, filed Oct. 22, 1992, now abandoned. 
    
    
     BACKGROUND 
     This invention is directed to compositions and pharmaceutical preparations containing zinc chelated by essential fatty acids. 
     Diabetes, despite the availability of insulin treatment, remains an extremely serious disease, responsible for many deaths and substantial morbidity in the United States and other developed countries. Although insulin can regulate blood sugar levels in diabetics, the degree of control achieved with insulin is typically insufficient to prevent the occurrence of many sequelae from diabetes. These sequelae can include eye damage, often leading to blindness; circulatory problems; problems with wound healing; and other serious consequences. Therefore, improved treatments for diabetes are urgently required. 
     It is known that prostaglandins (PGs) bind zinc and regulate intestinal zinc transport (M. K. Song &amp; N. F. Adham, &#34;Role of Prostaglandin E 2  in Zinc Absorption in the Rat,&#34; Am. J. Physiol. 234:E99-E105 (1978)) and that zinc influences prostaglandin synthesis activity in the small intestine and the vascular system of rats (M. K. Song &amp; N. F. Adham, &#34;Relationship Between Zinc and Prostaglandin Metabolisms in Plasma in Small Intestine of Rats,&#34; Am. J. Clin. Nutr. 41:1201-1209 (1985)). A relationship between zinc and the inhibition of glucose absorption is known (S. Southon et al., &#34;Hexose Transport and Mucosal Morphology in the Small Intestine of the Zinc-Deficient Rat,&#34; Br. J. Nutr. 52:371-380 (1984)). Essential fatty acids include unsaturated fatty acids that are prostaglandin precursors, and administration of essential fatty acids is believed to be beneficial to diabetics (R. J. Illman et al., Atherosclerosis 59:313-321 (1986)). 
     However, because of the interaction between zinc metabolism and prostaglandin synthesis, administration of unsaturated fatty acids or essential fatty acids alone does not yield an optimum improvement in diabetes. Therefore, there is a need to provide an improved treatment of diabetes and other conditions in which zinc metabolism and fatty acid metabolism play roles by providing a convenient source of both zinc and essential fatty acids. 
     SUMMARY 
     A composition of matter comprising crystalline zinc chelated unsaturated fatty acids meets this need by providing a convenient source of both zinc and essential fatty acids for treatment of diabetes and other conditions. Preferably, the unsaturated fatty acids comprise essential fatty acids. The essential fatty acids can comprise fatty acids selected from the group consisting of prostaglandins and prostaglandin precursors. Typically, the essential fatty acids comprise at least one fatty acid selected from the group consisting of linoleic, linolenic, and arachidonic acids. 
     Another aspect of the present invention is a pharmaceutical composition comprising, in a form administrable to a mammal: 
     (1) the crystalline zinc chelated unsaturated fatty acids of the present invention; 
     (2) zinc chloride; 
     (3) a protein hydrolysate; and 
     (4) at least one pharmaceutically acceptable excipient. 
     Preferably, the essential fatty acids, the zinc chloride, and the protein hydrolysate are present in a ratio of about 10:1:5 in the pharmaceutical composition. The pharmaceutical composition can be in tablet form or capsule form; preferably, each tablet or capsule contains about 20 milligrams of zinc, with the essential fatty acids, the zinc chloride, and the protein hydrolysate being present in a ratio of about 10:1:5. 
     Another aspect of the present invention is a method of treating diabetes comprising administering a pharmaceutical composition according to the present invention to a diabetic mammal in a quantity sufficient to reduce blood glucose concentration in the mammal. 
     DESCRIPTION 
     I have discovered that a composition of matter comprising crystalline zinc chelated unsaturated fatty acids, and pharmaceutical compositions comprising the crystalline fatty acids, zinc chloride, and a protein hydrolysate provide both zinc and fatty acids and are useful for treatment of diabetes and other conditions affecting zinc and essential fatty acid metabolism. 
     I. CRYSTALLINE ZINC CHELATED UNSATURATED FATTY ACIDS 
     One aspect of the present invention is crystalline zinc chelated unsaturated fatty acids, i.e., crystals in which negatively charged fatty acids are bound by positively charged zinc ions. 
     Preferably, the unsaturated fatty acids comprise essential fatty acids. The essential fatty acids preferably are selected from the group consisting of prostaglandins and prostaglandin precursors. These fatty acids can be obtained from animal prostates, such as cow, sheep, or goat by resuspending the prostates in a buffered aqueous solution, extracting the saturated fatty acids with a highly non-polar organic solvent such as petroleum ether or hexane, extracting unsaturated fatty acids with a more polar organic solvent such as ethyl acetate or chloroform, and then adding zinc chloride in a quantity sufficient to chelate the fatty acids present. Further details of the extraction procedure are given in Example 1, below. 
     Typically, such essential fatty acids include at least one fatty acid selected from the group consisting of linoleic, linolenic, and arachidonic acid, which are unsaturated fatty acids that are precursors to prostaglandins. 
     II. PHARMACEUTICAL COMPOSITIONS 
     Another aspect of the present invention is pharmaceutical compositions. Pharmaceutical compositions according to the present invention contain: (1) essential fatty acids as disclosed above; (2) zinc chloride; (3) protein hydrolysate; and (4) at least one pharmaceutically acceptable excipient. 
     The protein hydrolysate may be in the form of amino acids or incompletely hydrolyzed protein such as proteoses, peptones, or other partially hydrolyzed proteins, such as casein or albumin. 
     Preferably, pharmaceutical compositions according to the present invention contain essential fatty acids, zinc chloride, and protein hydrolysate in a ratio of about 10:1:5 by weight. The pharmaceutical compositions can be packaged in tablet or capsule form by procedures well-known in the pharmaceutical art. Preferably, each tablet or capsule contains about 200 mg of essential fatty acids, about 20 mg of zinc, and about 100 mg of protein hydrolysate, in addition to the pharmaceutically acceptable excipient or excipients. Suitable pharmaceutically acceptable excipients for tablets and capsules include inert diluents, such as calcium carbonate, sodium carbonate or bicarbonate, lactose, or calcium phosphate; or binding agents, such as starch, gelatin, or acacia; or lubricating agents such as magnesium stearate, stearic acid, or talc. The coating of the capsules can be gelatin or a soluble polymer, as is well-understood in the art. The tablets or capsules are suitable for oral administration. 
     The pharmaceutical compositions are useful for the treatment of diabetes, hypertension, impotence, and other diseases in which zinc or prostaglandin metabolism is impaired. In particular, diabetes can be treated by administering a pharmaceutical composition according to the present invention to a diabetic mammal in a quantity sufficient to reduce blood glucose concentration in the mammal. Typical doses for patients with diabetes or hypertension, stated as the quantity of zinc, are from about 80 mg to about 300 mg of zinc. These doses can be adjusted by one of ordinary skill in the art according to such factors as the weight, age, sex, and state of health of the patient, as well as according to the response to a particular dosage. 
    
    
     EXAMPLES 
     EXAMPLE 1 
     Preparation of Crystalline Zinc Chelated Unsaturated Fatty Acids 
     Prostates from a cow or goat were obtained from a slaughterhouse, frozen at 70° C. and minced into small pieces. The sliced tissue was suspended in a 10-fold excess (w/v) of 5.0 mM Tris-HCl buffer, pH 8.0, homogenized with a homogenizer such as a Virtis-45 homogenizer (Virtis Co., Gardner, N.Y.), and centrifuged at 4° C. for 20 minutes at 3000 xg. The upper part of the fat was removed physically, and the supernatant was incubated at 37° C. for one hour. The saturated fatty acids were extracted with petroleum ether. The aqueous solution remaining, including the unsaturated fatty acids, was acidified to pH 3.0 with 0.2 N HCl, and the unsaturated fatty acid mixture including prostaglandins was extracted 2 to 3 times with one volume each time of ethyl acetate or chloroform. The ethyl acetate or chloroform extracts were combined. The unsaturated fatty acid solutions were freeze-dried to dryness or evaporated under vacuum. The product at this stage was unsaturated fatty acids in an oil. Then 200 mg of the extract was mixed with 40 mg zinc chloride and 100 mg protein hydrolysate to form a preparation of zinc chelated unsaturated fatty acids. 
     EXAMPLE 2 
     Effect of Dietary Zinc on the Survival Rate of Diabetic Rats 
     Fifty-one rats were divided into three groups of 17 rats each. All of the rats were made diabetic by injection of streptozotocin. One week later, the rats were fed diets with defined quantities of zinc. The first group of 17 rats was fed a zinc-deficient diet with 1 μg Zn/g, the second group of 17 rats was fed a zinc-adequate diet (37.5 μg Zn/g), and the third group of 17 rats a zinc-excess diet (1 mg Zn/g). Twenty-five days later, the number of surviving rats was counted. Only 8 out of 17 rats in the zinc-deficient group survived while 11 out of 17 rats in the zinc-adequate group and 15 out of 17 rats in the zinc-excess group survived. Glucose concentration in the tissues of these rats is shown in Table 1. This data clearly indicates that an increase in dietary zinc enhances survival in diabetic rats and reduces the level of glucose present in the tissues of such rats. Because many diabetes complications are believed due to the presence of excess glucose in tissues, these results emphasize that an adequate zinc supply is important in preventing sequelae of diabetes. 
     
                       TABLE I______________________________________GLUCOSE CONCENTRATIONSIN TISSUES OF DIABETIC RATS FEDDIETS WITH DIFFERENT CONCENTRATIONS OF ZINC   Glucose Concentration     Zinc-Deficient                 Zinc-Adequate                             Zinc-ExcessOrgan     (1 μg Zn/g)                 (37.5 μg Zn/g)                             (1 mg Zn/g)______________________________________Heart.sup.a     5.54        1.17        0.95Lung.sup.a     1.59        1.28        0.86Liver.sup.a     8.39        5.20        5.54Pancreas.sup.a     1.20        0.82        0.96Spleen.sup.a     1.01        0.72        0.62Kidney.sup.a     2.54        1.79        1.52Muscle.sup.a     6.52        2.37        2.20Small Intestine.sup.a     2.54        1.48        1.38Colon.sup.a     3.18        3.05        2.81Skin.sup.a     4.91        3.81        3.33Plasma.sup.b     158         156         162______________________________________ .sup.a mg glucose/mg protein .sup.b mg glucose/mg plasma 
    
     ADVANTAGES OF THE INVENTION 
     The present invention provides compositions that are a convenient source of both zinc and essential fatty acids as a dietary supplement or treatment for diabetes or other conditions. Because the metabolism of zinc and the metabolism of essential fatty acids, including prostaglandin precursors, are interlinked, the use of such compositions is more effective than is the use of either zinc or fatty acids alone in treating diabetes. 
     Although the present invention has been described in considerable detail, with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.