Alexander N. Orekhov
Institute of Experimental Cardiology, Moscow Russia
The effect of garlic powder tablets. Kwai, on atherogenic potential of blood serum of coronary artery disease patients was investigated in a placebo-controlled double-blind study. Two and four hours after a single dose of Kwai (1 tablet containing 300 mg garlic powder) the atherogenicity of patients' sera was markedly decreased: the sera induced much lesser cholesterol accumulation in cultured human aortic smooth muscle cells compared with the sera obtained prior to the drug administration. After 4 weeks of long-term Kwai therapy (300 mg, 3 times daily) blood serum atherogenicity was significantly lower compared with the initial level. At the same time, the atherogenicity of sera obtained from patients on placebo remained virtually unchanged throughout the observation period. Low density lipoprotein (LDL) is the major component responsible for the serum atherogenicity. Long-term therapy lowered the atherogenicity of LDL isolated from patients' plasma. However, the atherogenicity of LDL isolated from the blood of patients 2 hours after a single dose of garlic powder did not change and it remained unchanged during 7 days of the therapy. The ability of LDL to induce intracellular cholesterol accumulation was significantly decreased by 38% on the 28th day of therapy. This indicates that reduction of lipoprotein atherogenicity is an indirect and relatively long process. The ability of LDL to stimulate proliferation of cultured cells (another parameter of LDL atherogenicity) was also decreased as a result of a long-term therapy with garlic powder tablets. To elucidate the mechanism of LDL atherogenicity reduction, LDL susceptibility to oxidation in vitro in the presence of Cu2+ was examined. Susceptibility to oxidation was decreased significantly in 2 hours after a single dose, it was decreased to a greater degree during 28-day therapy, while it remained unchanged in patients on placebo. Atherogenic LDL isolated from patients' blood has a lower content of sialic acid compared with native LDL of healthy subjects. Sialic acid content was measured in LDL isolated from the blood of patients treated with garlic powder. Sialic acid content of LDL did not change after a single-dose administration and after 7 days of the therapy. However, at the end of the 28-day therapy the sialic acid content of LDL was significantly higher than at the beginning of the therapy and was comparable to the sialic acid content of native LDL of healthy subjects. This suggests that the decrease in LDL atherogenicity caused by long-term therapy with garlic powder tablets is due to increased sialic acid content rather than to decreased susceptibility of LDL to oxidation.
The mechanism of garlic powder anti-atherosclerosis related effects has been studied using cell culture. An aqueous extract from garlic powder (GPE) was added to smooth muscle cells cultured from atherosclerotic plaques of the human aorta. During a 24 hour incubation, GPE significantly inhibited cell proliferative activity. In addition, GPE inhibited cell proliferation stimulated by atherogenic blood serum. Thus garlic powder manifests direct anti-atherosclerotic and anti- atherogenic effects in vitro. The addition of GPE abolished atherogenic blood serum-induced accumulation of free cholesterol, triglycerides, and cholesteryl esters in smooth muscle cells derived from uninvolved (normal) intima. In cells isolated from atherosclerotic plaque, GPE lowered these lipids. GPE inhibited lipid synthesis both in normal and atherosclerotic cells. It inhibited acyl- coA:cholesterol acyltransferase activity that participates in the cholesteryl ester formation and stimulated cholesteryl ester hydrolase that degrades cholesteryl esters. This may explain the lipid reduction caused by GPE in atherosclerotic cells. GPE inhibited uptake of modified LDL and degradation of lipoprotein-derived cholesteryl esters, thus considerably reducing the intracellular accumulation of cholesteryl esters. This suggests the mechanism responsible for the prevention of lipid accumulation in aortic cells caused by atherogenic blood serum.
Garlic powder extract has been fractionated using thin layer chromatography. Fifteen separate fractions were isolated. Nine fractions of garlic powder had anti-atherosclerotic and anti-atherogenic effect on human aortic intimal cells. Two fractions had significant anti-atherosclerotic effect, but possessed no anti-atherogenic activity. Three fractions were proatherogenic, i.e. they potentiate serum atherogenic effect. One fraction possessed neither anti-atherogenic nor anti-atherosclerotic effects, i.e. it was indifferent. An individual substance, ajoene, has been detected in one active fraction. Ajoene isolated and purified from garlic possessed an anti-atherosclerotic effect in vitro. Investigation and identification of other garlic fractions are in progress.