Garlic extract attenuates hyperhomocysteinemia caused by folic acid deficiency in the rat

This study investigated the homocysteine lowering potential of garlic in rats rendered folic acid (FA) deficient. Rats fed AIN-93G diet devoid of FA exhibited mild folate deficiency and had a plasma level of total homocysteine higher than that for those fed AIN-93G diet containing FA (9 vs 5 μmol/L). Supplementation with aged garlic extract (AGE, 4%) to either diet did not alter plasma homocysteine levels. Subsequently, rats were made severely deficient in folate by feeding a folate-deficient l-amino acid diet containing succinyl sulfathiazole. Although folate concentrations in plasma, erythrocytes, liver, and kidneys were markedly depressed, plasma total homocysteine was increased to 32 μmol/L by the severe deficiency. Supplementation of AGE to the deficient diet reduced plasma protein-bound, free, and total homocysteine by 28% to 33%. The supplementation did not change plasma cysteine, cysteinylglycine, or glutathione concentrations. Liver concentration of S-adenosylmethionine was elevated by 26%, and S-adenosylhomocysteine was lowered by 15% in the AGE-supplemented group. It is speculated that the reduction of plasma homocysteine level by AGE stems, in part, from stimulation of transsulfuration via cystathionine β-synthase and inhibition of remethylation of homocysteine resulting from inactivated N5,N10-methylenehydrofolate reductase.