WO1995010292A1

WO1995010292A1 - Diabetes treatment and prophylaxis

Info

Publication number: WO1995010292A1
Application number: PCT/US1994/010657
Authority: WO
Inventors: Arun K. Chaterji
Original assignee: Biomedica California, Inc.
Priority date: 1993-10-14
Filing date: 1994-09-20
Publication date: 1995-04-20

Abstract

Glucose metabolism in a human patient is regulated by dosage forms that contain a naturally occuring, plant derived carbohydrate in combination with a non-metabolizable polysaccharide. Preferred are extracts from the leaves of Gymnema sylvestre in combination with exudates of Sterculia urens, i.e., karaya gum.

Description

DIABETES TREATMENT AND PROPHYLAXIS

Field of the Invention

This invention relates to the regulation of glucose metabolism in a human patient with naturally occurring, plant-derived carbohydrates. Background of the Invention

The concentration of glucose in the human bloodstream must be controlled within a relatively tight range (60-120 milligrams per deciliter of blood) to maintain normal health. If blood glucose drops too low, a condition known as hypoglycemia results, with symptoms such as faintness, weakness, headache, confusion and personality changes. Severe hypoglycemia can progress to convulsions, coma and death. Excessive blood glucose, or hyperglycemia, causes excess urine production, thirst, weight loss, fatigue, and in the most severe cases, dehydration, coma and death. Chronic hyperglycemia causes tissue damage due to the chemical reactions between the excess glucose and proteins in cells, tissues and organs. This damage is thought to cause the diabetic complications of blindness, kidney failure, impotence, atherosclerosis, and increased vulnerability to infection. The pancreas makes hormones that cause the removal or addition of glucose to the blood. Insulin lowers blood glucose levels; when glucose level rises after a meal, the pancreas secretes insulin which causes muscle and other tissues to take up glucose from the blood stream. Glucagon raises blood glucose levels; when blood glucose levels fall, the pancreas secretes glucagon to signal the liver to make stored glucose available.

A third glucose-regulating hormone, amylin, was discovered in 1987. Physiologists now generally consider that all three hormones play a role in the complex aspects of glucose metabolism. The chemical structure of a ylin and its metabolic action on muscle and pancreas tissue has recently been elucidated. Amylin is said to work with insulin to moderate the glucose-lowering effects of insulin under certain circumstances, to help replenish liver glycogen after a meal, and to encourage the synthesis of fat from excess glucose. As a result, amylin, like glucagon, can raise blood glucose level.

Diabetes mellitus is associated with continuous and pathologically elevated blood glucose; it is the third leading cause of death in the United States and is responsible for about 5% of all mortality. Diabetes is divided into two major sub-classes: Type I, also known as juvenile diabetes of Insulin-Dependent Diabetes Mellitus (IDDM) , and Type II, also known as adult onset diabetes of Non-Insulin-Dependent Diabetes Mellitus (NIDDM) . According to the American Diabetes

Association, there are over 1 million juvenile diabetics in the United States. This disease is of autoimmune origin. Autoantibodies produced by the patients completely or partially destroy the insulin producing cells of the pancreas. Juvenile diabetics must therefore receive exogenous insulin during their lifetime. Without treatment, excessive acidosis, dehydration, kidney damage and death may result. Even with treatment, complications such as blindness, atherosclerosis, and impotence can occur.

There are more than 5 million Type II (adult onset) diabetics diagnosed in the United States. Type II disease usually begins during middle age; the exact cause is unknown. In Type II diabetics, rising blood glucose levels after meals do not properly stimulate insulin production by the pancreas, additionally, peripheral tissues are resistant to the effects of insulin. The resulting high blood glucose levels (hyperglycemia) can cause extensive tissue damage. Type II diabetics are often referred to as insulin resistant. They often have higher than normal plasma insulin levels (hyperinsulinomia) as the body attempts to overcome its insulin resistance. Some researchers now believe that hyperinsulinomia may be a causative factor in the development of high blood pressure, high levels of circulating low density lipo-proteins (LDLs) , and lower than normal levels of the beneficial high density lipo- proteins (HDLs) . While moderate insulin resistance can be compensated for in the early stages of Type II diabetes by increased insulin secretion, in advanced disease states insulin secretion is also impaired. Successful treatment of Type II diabetes must address both insulin resistance and faulty insulin secretion. Insulin resistance and hyperinsulinomia have also been linked with two other metabolic disorders that pose considerable health risks: impaired glucose tolerance and metabolic obesity. Impaired glucose tolerance is characterized by normal glucose levels before eating but a tendency toward elevated levels (hyperglycemia) following a meal. According to the

World Health organization, approximately 11% of the U.S. population between the ages of 20 and 74 are estimated to have impaired glucose tolerance. These individuals are considered to be at higher risk for diabetes and coronary artery disease.

Obesity may also be associated with insulin resistance. A causal linkage among obesity, impaired glucose tolerance, and Type II diabetes has been proposed, but a physiological basis has not been established as yet. Some researchers believe that impaired glucose tolerance and diabetes are clinically observed and diagnosed only later in the^'disease process after one has developed insulin resistance and hyperinsulinomia. Insulin resistance is frequently associated with hypertension, coronary artery disease (arteriosclerosis) , and lactic acidosis, as well as related disease states. The fundamental relationship between these disease states, and a method of treatment, has not been established.

Insulin and sulfonylureas (oral hypoglycemia agents) are the two major diabetes medicines prescribed today in the United States. Insulin is prescribed for both Type I and Type II diabetes, while sulfonylurea is usually prescribed for Type II diabetics only.

Sulfonylurea stimulates natural insulin secretion and reduces insulin resistance; these compounds do not replace the function of insulin in metabolism. Approximately one-third of patients who receive sulfonylurea become resistant to it; some Type II diabetics do not respond to this class of drug. Of patients who do respond to initial treatment with sulfonylureas, 5-10% are likely to experience a loss of sulfonylurea effectiveness after ten years. Insulin itself has a relatively narrow therapeutic window. Relatively high insulin doses can produce hypoglycemic shock as the blood glucose drops too low. Low or infrequent doses may result in hyperglycemia. In Europe, two other classes of oral hypoglycemic agents are available — biguanides and alpha-glucosidase inhibitors. Biguanides work by reducing glucose production in the liver and limiting glucose absorption. Although biguanides are also used in Canada, they are banned in the U.S. due to increased incidence of mortality. Alpha-glucoεidase inhibitors are sold in certain European countries but have not obtained FDA approval for use in the U.S. These drugs reduce high blood glucose levels by slowing the uptake of ingested foods. Side effects include flatulence, diarrhea and abdominal pain.

U.S. Patent No. 4,761,286 to Hiji discloses that an aqueous extract derived from the leaves of Gv nema sylvestre can be utilized in combination with a foodstuff which is absorbed as glucose by the intestinal tract so as to inhibit glucose absorption.

It has now been found, however, that glucose metabolism in a human patient can be effectively modulated by oral administration of an extract derived from the leaves of G. sylvestre in combination with a bio-inert, i.e., non-metabolizable by the patient, polysaccharide. Summary of the Invention

The present invention contemplates, in one aspect thereof, oral dosage forms comprising an aqueous and water-miscible polar solvent extract, preferably an aqueous and ethanolic extract, of Gymnema sylvestre and a non-metabolizable polysaccharide, preferably a Sterculia urens exudate, in a respective weight ratio in the range of about 1:2 to about 2:1. Preferably the aforementioned extract is lyophilized.

Another aspect of the present invention contemplates a method for modulating glucose metabolism in a human patient by administering orally to the patient an effective amount of the aforesaid combination of ingredients which is sufficient to at least stabilize, and preferably reduce, the blood glucose level of the patient.

The present invention is useful as a dietary supplement, to delay the onset of diabetes, as an adjunct therapy with insulin for Type I diabetic patients to assist in blood sugar level control, and to reduce the likelihood of the onset of gestation-induced diabetes in expectant mothers who are genetically predisposed to become diabetic during pregnancy. Description of Preferred Embodiments

Gymnema sylvestre is a plant that belongs to the family Asclepiadaceae. The plant grows in Central and Western India, in tropical Africa and in Australia. Aqueous extracts from the leaves of G. sylvestre have been described as inhibiting temporarily the taste of sweet substances. It has also been reported that the raw leaves of G. sylvestre have been used in India as a folk medicine for various afflictions including diabetes mellitus. Some fourteen or fifteen different compounds are reported to have been isolated from the leaves of G. sylvestre by various techniques. Stocklin, J. Agr. Food Che . 17.(4) :704-708 (1969); Sinsheimer, J. Pharm. Sci. 5_9(5) :622-628 (1970) . However, applicant is not aware of scientific information as to whether any of the noted chemicals, individually or collectively, contribute to the hypoglycemic properties. It has now been found, however, that the present aqueous and water-miscible polar solvent extract contains at least four fractions that are insulinotropic. Two of these fractions exhibit substantially equal and relatively strong insulinotropic activity.

The active principles are extracted from fresh leaves of G. sylvestre utilizing water and a water- miscible polar solvent such as a monohydric C-_ to C₄ alcohol (e.g., ethanol, isopropanol, or the like), a C₂ to C₄ ketone (e.g., acetone, methyl ethyl ketone, or the like) .

The presently contemplated preferred aqueous and ethanolic extract is prepared by soaking fresh leaves of G. sylvestre for at least about 24 hours at ambient temperature in an ethanol-water solution containing at least about 40 volume percent of ethanol. The resulting liquid extract is filtered to remove extraneous solids and distilled to drive off ethanol and produce an aqueous bottoms solution which is then treated with sulfuric acid to lower the pH thereof to a value of no more than about 2 and to precipitate out water-insoluble salts that had been produced. The precipitates are removed by filtration and the filtrate neutralized with sodium hydroxide to produce a solution of the active factors suitable for practicing the present invention.

This aqueous and ethanolic extract is then lyophilized and combined with a patient non- metabolizable polysaccharide such as Sterculia urens exudate or hydroxypropylmethylcellulose (HPMC) to produce the oral dosage forms embodying the present invention. Also suitable for the present purposes as a patient non-metabolizable polysaccharide are the partially esterified oligosaccharides and polysaccharides disclosed in U.S. Patent No. 4,959,466 to White. Illustrative are polysaccharides such as xanthan gum, guar gum, gum arabic, the alginates, hydroxypropyl cellulose, cellulose hydrolysis products, starch hydrolysis products, casein, karaya gum, and pectin transesterified with fatty acid methyl esters, and the like.

Preferred for the present purposes is the dried exudate of the tree S. urens. found in India, and readily available commercially.

The lyophilized aqueous and ethanolic extract can be combined with the S. urens exudate in a weight ratio in the range of about 2:1 to about 1:2, respectively. A preferred weight ratio of the extract to the exudate is about 1:1.5. The resulting combination can then be filled into hard"gelatin capsules for oral administration.

The dosage to be administered to a human patient for modulating glucose metabolism of the patient will vary depending upon, inter alia, the age, weight and condition of the patient. The usual daily dosage is in the range of about 200 milligrams to about 900 milligrams of the lyophilized extract per day, preferably in conjunction with about 300 milligrams to about 1350 milligrams of S. urens exudate.

A preferred schedule of administration using capsules containing 100 milligrams of the lyophilized product and 150 milligrams S. urens exudate is as follows: patient w/hyperinsulinemia 1-2 capsules b.i.d. diagnosed Type I! diabetic (moderate) 2 capsules b.i.d. diagnosed Type II diabetic (high) 2-3 capsules t.i.d. diagnosed Type I diabetic (moderate)¹ 1 capsule b.i.d. diagnosed Type I diabetic (high)¹ 2 capsules t.i.d.

The present oral dosage forms are eminently well suited as prophylactics for patients pre-disposed toward gestation induced diabetes. To that end, expectant mothers identified as likely to be so pre-disposed on the basis of family history, can take oral doses of the aforedescribed lyophilized aqueous and ethanolic extract throughout the full terms of their respective pregnancies. The likelihood of elevated blood sugar levels for the mothers and their newborn babies is greatly minimized in this manner. For expectant mothers, the preferred oral dosage is 200 milligrams of the lyophilized G. sylvestre extract together with 300 milligrams of S. urens exudate twice

with insulin as adjunct therapy. daily, i.e., a 500 milligram capsule, b.i.d. containing the lyophilized G. sylvestre extract and'the S. urens exudate in a respective weight ratio of about 2:3.

The present invention is further illustrated by the following examples.

EXAMPLE 1: Aσueous Preparation of Lyophilized Product

Fresh leaves of Gymnema sylvestre were purchased and identified by a botanist. The fresh leaves were soaked for about 18 hours in tap water (1 kg leaves/4 L tap water) at ambient temperature. 90 volume percent ethyl alcohol was added thereto in sufficient quantity to bring the net alcohol percent level to 40 vol.-%, and the entire batch was distributed with stirring to ten erlenmeyer flasks. Flasks were placed on a shaker table and shaken for four hours.

The flask contents were strained and the recovered liquid extract was distilled in several batches to remove ethyl alcohol. The obtained aqueous bottoms solutions were combined, and dilute sulfuric acid (about 1 to 2 molar) was added thereto to reach a final pH of about 2. A sludge composed of insoluble salts was formed and was removed by filtration. Soluble salts of sodium and potassium, inherent from the leaves, remained in the filtrate. The filtrate was neutralized with dilute sodium hydroxide and deionized by passing through an ion exchange column. The resulting solution (eluate) was concentrated to a semi-solid light-brown mass (a "syrupy" mass the consistency of molasses) using a rotary flask equipped with a vacuum, with the rotary flask rotated at a 45° angle on a water bath heated to about 55-70°C. The resulting semi-solid was lyophilized and the lyophilized product stored in a refrigerator until use. EXAMPLE 2: Animal Studies in Rats

The first set of twelve albino^*rats of both sexes, weighing 100-150 gms, were made diabetic by intraperitoneal injection (i.p. route) of streptozotocin (Sz) at a single dose of 60 mg/kg in presence of citrate buffer (pH 4.3-4.5) or by alloxan [2,4,5,6 (1H,3H) - pyrimidinetetrone; 100 mg/kg] in normal saline by i.p. route. The control group received an equal volume of the vehicle only. Five rats were used in each experimental group and in the control group.

Blood sugar (BS) was determined by the glucose oxidase method. All animal experiments were carried out under fasting conditions for 18 hours. The lyophilized product produced in Example 1 was dispersed into a buffered solution (physiological pH) , and was given orally.

No hypoglycemic effect was observed either in normal fasting rats or in glucose-fed (1.75 g/kg) normal fasting rats. The lyophilized product did affect blood sugar levels in rats rendered diabetic by Sz, however. A single dose of the lyophilized product of Example 1 (500 mg/kg) was given to six rats 48 hours after Sz was given. The blood sugar level observed 2 hours after administration of the lyophilized product was reduced by 126 ± 28 mg % (mean ± SD) . These results indicate that the lyophilized product was efficacious in reducing blood glucose levels in diabetic rats and was readily bio-available when administered orally. The time- dependent protective activity of the lyophilized product against Sz-diabetic rats was characterized from the trend of blood sugar at different intervals.

Neither hypoglycemia nor any sign of toxicity was observed with high dose therapy utilizing the lyophilized product. On the other hand, a gain in weight was noted along the remission stage. The other set of twelve rats were pretreated with half of the dosage (250 mg/kg) of the lyophilized product before inducing diabetes. Alloxan, used to induce experimental diabetes in animals in dosage of 100 mg/kg, failed to induce a diabetic state in any of the rats in presence of the lyophilized product; but when alloxan was repeated on three of these rats after the withdrawal of the lyophilized product, all three became severely diabetic and died. The oral LD-50 of the lyophilized product was observed to be about 2.78 g/kg in white mice and 4.5 g/kg in rats. Chronic toxicity in rats at a dose level of 200 mg/kg daily (100 times the minimal maintenance dose for a diabetic patient) for four months did not show any signs of toxicity.

The foregoing discussion and the examples are intended as illustrative of the present invention and are not to be taken as limiting. Still other variations within the spirit and scope of the present invention are possible and will readily present themselves to those skilled in the art.

Claims

I CLAIM:

1. A method for modulating glucose metabolism in a human patient which comprises administering to said patient orally an aqueous and water-miscible polar solvent extract from Gymnema sylvestre leaves together with Sterculia urens exudate in a respective weight ratio in the range of about 2:1 to about 1:2 and in an amount and at a frequency sufficient to maintain said patient's blood glucose level at a predetermined value.

2. The method in accordance with claim 1 wherein the extract is an aqueous and ethanolic extract.

3. The method in accordance with claim 2 wherein the weight ratio of said aqueous and ethanolic extract to the exudate is about 1:1.5.

4. The method in accordance with claim 1 wherein said aqueous and ethanolic extract is administered in lyophilized form.

5. An oral composition suitable for regulating blood glucose level in a human patient which consists essentially of a water and water-miscible polar solvent extract from Gymnema sylvestre leaves and of Sterculia urens exudate in a respective weight ratio in the range of about 2:1 to about 1:2.

6. The composition in accordance with claim

5 wherein the weight ratio of said extract to the exudate is about 1:1:5.

7. The composition in accordance with claim 5 in capsule form.

8. The composition in accordance with claim

5 wherein said extract is an extract by water and a monohydric alcohol wherein the alcohol contains 1 to 4 carbon atoms, inclusive.

9. The composition in accordance with claim 5 wherein the extract is an aqueous and ethanolic extract.

10. A method for treating a human patient genetically predisposed toward Type II diabetes which comprises orally administering to said patient an aqueous and ethanolic extract from leaves of Gymnema sylvestre together with Sterculia urens exudate in an amount sufficient to prevent an abnormal elevation of blood glucose level in said patient.

11. A method for treating a patient suffering from Type I diabetes and receiving insulin therapy which comprises orally administering to said patient, as an adjunct to insulin therapy, an aqueous and ethanolic extract from the leaves of Gymnema sylvestre and

Sterculia urens exudate in a weight ratio of about 2:1 to about 1:2, respectively; the daily dose of said aqueous and ethanolic extract being in the range of about 100 milligrams to about 600 milligrams.