Use of Magnesium-Pyridoxal-5'-Phosphate-Glutaminate for the Prevention of Diseases Which Result From Vascular Lesions

The invention concerns the use of magnesium-pyridoxal-5'-phosphate-glutaminate to prevent diseases which are caused by LDL-bound peroxides and which result in vascular lesions.

In the last four decades, a rapid increase could be observed in the Western industrial countries in metabolic disturbances, especially in disturbances of the fat metabolism. The main reason for this is excessive nutrition and/or too fatty foods with simultaneous lack of movement. Under these conditions, increased cholesterol and lipid values may form in the blood, which increase the risk arteriosclerotic, cardiac and peripheral vascular diseases. It is known that increased blood cholesterol levels are co-responsible for the emergence of arterial vascular sclerosis. Hypercholesteraemia is a metabolic disturbance which always accompanies hyperlipidaemia. The pathogenetically different but symptomatically similar clinical pictures of hyperlipidaemia (turbidity of the serum by chylomicrons) and of hypercholesteraemia (increase of the cholesterol content in the blood plasma to more than 200 mg %) are summarized under the collective concepts hyperlipoproteinaemia or hyperlipidaemia.

For the treatment of hypercholesteraemia, predominantly aryloxyacetic acid derivates, especially alpha-(p-chlorophenoxy)-isobutyric acid-ethylesters, as well as nicotinic acid derivatives are used.

In addition, DE-PS 24 61 742 of the applicant describes the use of pyridoxin-5'-phosphoric acid ester-glutaminates and -asparaginates for the treatment and prophylaxis of hypercholesteraemia.

Without it being necessary for the clinical picture of hypercholesteraemia or hyperlipidaemia to be present, in the case of an endangered group of persons, namely smokers, diabetics, ageing persons and those with high blood pressure or persons who are exposed to great stress, vascular lesions may occur. This is traced back to the presence of an increased concentration of peroxides in the blood, which are bonded by LDL (low density lipoprotein). These LDL-bonded peroxides cause and accelerate the formation of atheromae and arteriosclerotic plaques in the vessels and can be regarded as the cause of diabetic angiopathy. The presence of increased concentrations of peroxidizing products and their correlation with vascular lesions is described by J. M. C. Gutteridge et al. in Trends in Biochemical Sciences, April 1990, pages 129 to 135 and by D. W. Morel et al. in Journal of Lipid Research, Vol. 30, 1989, pages 1827 to 1834.

It is known that the arteriosclerotic changes in the vessels are a result of endothelial lesions, and the pathogenesis proceeds as follows: endolethelial lesion-platelet adhesion-proliferation of smooth muscle cells-lipid deposit.

The first step, the endolethial lesion, may have a plurality of causes, namely mechanical damage due to shearing forces in the case of hypertonia, chemical damage due to cholesterol in hypercholesteraemia and in particular toxic damage due to contaminants in the blood. It is assumed that the further course is almost identical with all three types of damage.

The consequence of an endothelial lesion as well as of the subsequent fat deposit between and in the cells of the arterial intima is an increased aggregation of thrombocytes, accompanied by a proliferation of smooth muscle cells, caused by the further increased inflow of lipoproteins in the connective tissue basic substance, where complex formation with glucose aminoglycans of the connective tissue and metabolic defects result on the cellular level. Then the formation of calcium in the damaged zones forms the conclusion of all the changes, which, in the final analysis, lead to a constriction of the vessels.

Tests were carried out on hypercholesteremic rabbits and rats by W. Schneider in his dissertation concluded in 1987 at the Johannes Gutenberg University of Mainz, which showed that when administering relatively high concentrations of magnesium-pyridoxal-5'-phosphate-glutaminate (MPPG), the liver and aorta lipid concentrations are reduced. But this work does not provide any indications with reference to the mechanism which initiates the vessel atheroma formation in the endangered groups of persons, so that on the basis of the results of W. Schneider, it cannot be concluded that an atheroma formation can be prevented by the elimination of the initiating contaminants in the blood.

For some time past it has been suspected that peroxides in the blood may function as the initiators of metabolic disturbances. U. P. Steinbrecher et al. describe in J. Biol. Chem., Vol. 264, No. 26, pages 15216 to 15223 (1989) the presence of oxidizingly modified LDL as well as a receptor for it. The applicant has now proven in purposeful tests that this concerns LDL-bonded peroxides. By tests made in vitro one of the mechanisms underlying toxic endothelial lesion could be clarified and it was shown that it is possible to intercept these peroxides and to render them harmless.

FIG. 1 shows the spectrum of linolenic acid (0.88 mM). The main peak is at 211 nm, whereas at about 232 a smaller peak is found, which points to the presence of a small percentage of oxidized linolenic acid.

FIG. 2 reflects the spectrum of MPPG (concentration 0.125 nM) which shows peaks at 222, 327 and 387.

FIG. 3 shows the spectrum of a solution of linolenic acid and MPPG. This spectrum has peaks at 211, 243 and 289 nm. The peak previously obtained in FIG. 1 at 232 is no longer present in FIG. 3. Instead, FIG. 3 shows two new peaks at 243 and 289 nm.

FIGS. 4a and 4b show the stimulation of ACC dissociation by MPPG or PP depending on the CumOOH concentration.

The object of the invention is to provide of a pharmaceutical for the reduction of LDL-bonded peroxides in order thereby to avoid and/or to delay vascular lesions, especially the formation of atheromae or of arteriosclerotic plaques in the arterial vessels, as well as angiopathic diseases in the case of diabetics. It is especially the object of the present invention to provide a pharmaceutical also for those of the above cases where there is no diagnosis of hyperlipidaemia or hypercholesteraemia.

The object above is achieved according to the invention by the use of magnesium-pyridoxal-5'-phosphate-glutaminate to prepare a pharmaceutical which is suitable for the prophylaxis of diseases caused by vascular lesions. In particular, according to the invention, atheromatosis as well as angiophatic diseases are to be prevented for an endangered group of persons, consisting of diabetics, smokers, ageing people, hypertonic persons and those under stress.

Magnesium-pyridoxal-5'-phosphate (MPPG) is a substance which previously was used to reduce increased blood fats. The substance (MPPG) is known under the tradename of Sedalipid.RTM. and is distributed by the firm Steigerwald Arzneimittelwerk, Darmstadt. Until now it was not known that magnesium-pyridoxal-5'-phosphate-glutaminate acts as a radical interceptor in the blood and therefore is capable of preventing a chain reaction caused by lipid peroxide. On the basis of this effect as a radical interceptor, the use of MPPG is suitable for prophylaxis of vascular lesions especially in the absence of hyperlipidaemia and/or hypercholesteraemia.

MPPG is a derivate of pyridoxin and has the following formula: ##STR1##

In the sense of the invention, the endangered groups of persons are particularly smokers, diabetics, those with high blood pressure as well as all persons under stress, such as top sportsmen, and ageing people.

According to the invention the above compound MPPC is administered to those endangered persons who have a high concentration of LDL-bound peroxides, however, do not suffer from the symptoms of hyperlipidaemia and/or hypercholesteraemia. These symptoms are usually determined on the basis of cholesterol levels as well as cholesterol and triglyceride levels. There exist in Europe as well as in the USA recommendations as to what may be considered normal and increased cholesterol and triglyceride levels. As to this, reference is made to the recommendations of the US National Cholesterol Education Programme (NCEP) and the guidelines provided by The European Atherosclerosis Society Study Group. In the following Tables 1 and 2 values are summarized as to what may be considered normal cholesterol and triglyceride levels, and when treatment has to be initiated:

Similarly there exist published recommendations from the British Cardiac Society Working Group on Coronary Prevention, the British Hyperlipidaemia Association and the Canadian Consensus Conference on Cholesterol.

From the data shown in the above tables it is obvious that values differ slightly as to when the cholesterol content is to be considered harmful. Nevertheless, it is especially useful to realize that even below these borderlines or especially in a grey zone between still normal and increased levels, the administration of MPPG according to the invention is beneficial for those persons who belong to endangered groups having high LDL-bound peroxides.

Though no definite borderline can be given as to when a diagnosed cholesterol level is to be interpreted as a hyperlipidaemia, it is assumed that as a general guideline one may assume that approximately 240 mg/dl (according to US recommendations) or 250 mg/dl (according to EG recommendations) may be interpreted as the beginning of hyperlipidaemia. Thus, administration of MPPG according to the invention is especially considered below the above given cholesterol levels.

The inventors have carried out a number of tests to show clearly that in the endangered group of persons these high levels of LDL-bound peroxides do exist. It was also possible to show that upon addition of MPPG the detection signals indicating LDL-bound peroxides vanished. Thus, it was concluded that the application of MPPG to patients belonging to an endangered group is justified and useful.

For the increased initiation of atheroma formation, particularly in the above-named group of persons, the following mechanism is assumed, which will be documented by the tests in vitro described below:

LDL is oxidized by the reactive oxygen species (superoxide radical O.sub.2.sup.-, hydroxylradical OH.degree.), especially peroxide, which are present in the blood, to form LDL peroxide. This LDL peroxide is substantially not absorbed by the macrophages, but binds on a scavenger receptor, which is located on the endothelial cells (see the literature named above by Steinbrecher et al.). In this way LDL deposits are formed on the endothelial cells which then attract further lipid deposits.

Further damage to the vessel endothelial cells is caused by the oxidation of glutathione by peroxide and/or LDL-bonded peroxide. This oxidation may lead to the death of cells, because the cell can no longer maintain its redox potential (K. Kuzuya et al. in Biochem. Biophys. Res. Comm., Vol. 163, No. 3, 1989, pages 1466 to 1472).

The following statements provide a more detailed explanation of the mechanism for the influence of MPPG on LDL-bonded peroxide. The subsequent tests show on the basis of fatty acid bonded peroxides that the latter are decomposed in the presence of MPPG and can be made harmless thereby.

The following outline reflects the assumed reaction mechanism during oxidation of a fatty acid, as is described e.g. by J. M. C Gutteridge et al. in Trends in Biochemical Sciences, April 1990, p. 130: ##STR2##

Initially there is an attack on the bridging-CH.sub.2 group by a H.degree. radical. This causes a transposition, so that conjugated double bonds are formed from the isolated double bonds. The result is the formation of a fatty acid radical, which forms in the presence of oxygen a peroxide radical. In the presence of a further fatty acid molecule, fatty acid hydroperoxide as well as a fatty acid radical are formed, whereby a chain reaction is commenced.

The reaction outline shown above can be followed at 234 nm by proof of the diene reaction.

From FIGS. 1 to 3 it can be inferred that the peak for oxidized linolenic acid disappears at 232 nm (FIG. 1) by the addition of MPPG in a concentration of 0.125 mM (FIG. 3), whereby the chain reaction triggered above is interrupted and therefore the progress of the disease as well.

For the decomposition of the hydroperoxide in the presence of the substance MPPG used in accordance with the invention, the following mechanism catalyzed by manganese salt is assumed: ##STR3##

It is now possible to prove this decomposition reaction by means of the indicator substance, aminocyclopropane carboxylic acid (ACC). ACC is a basic substance occurring in nature for the formation of ethylene. The ethylene released can be quantitatively determined.

The decomposition of the hydroperoxide can e.g. be followed with cumen hydroperoxide. ACC functions as an indicator. It is assumed that the reaction progresses via the amine in the pyridoxal phosphate, which causes the formation of a radical. This radical initiates decomposition of ACC into CH.sub.2 H.sub.4, CO.sub.2 and cyanide.

The following tests show the stimulation of ACC dissociation with MPPG in the presence of cumen hydroperoxide, depending on the cumen hydroperoxide (CumOOH) concentration. At the same time comparative tests were carried out with corresponding molar amounts of pyridoxal phosphate (PP).

Test example:

The following solutions were prepared in phosphate buffer (0.1M) pH 7.4, with different concentrations of cumen hydroperoxide.

In the ACC dissociation with pyridoxal phosphate, a measurable release of ethylene was observed, in contrast to MPPG, in the lower concentration range which was used for cumenhydroperoxide (0.006 mM). At 0.12 nM CumOOH, in the presence of MPPG, a stimulation of the ACC dissociation of 70% was found. With CumOOH concentrations of 0.6 mM and 1.2 mM, clearly higher stimulation effects were measured in the presence of MPPG, by comparison with PP.