Differential effects of nutritional folic acid deficiency and moderate hyperhomocysteinemia on aortic plaque formation and genome-wide DNA methylation in vascular tissue from ApoE -/- mice

Low folate intake is associated with vascular disease. Causality has been attributed to hyperhomocysteinemia. However, human intervention trials have failed to show the benefit of homocysteine-lowering therapies. Alternatively, low folate may promote vascular disease by deregulating DNA methylation. We investigated whether folate could alter DNA methylation and atherosclerosis in ApoE null mice. Mice were fed one of six diets (n¿=¿20 per group) for 16 weeks. Basal diets were either control (C; 4% lard) or high fat (HF; 21% lard and cholesterol, 0.15%) with different B-vitamin compositions: (1) folic acid and B-vitamin replete, (2) folic acid deficient (-F), (3) folic acid, B6 and B12 deficient (-F-B). -F diets decreased plasma (up to 85%; P¿<¿0.05), whole blood (up to 70%; P¿<¿0.05), and liver folate (up to 65%; P¿<¿0.05) and hepatic SAM/SAH (up to 80%; P¿<¿0.05). -F-B diets reduced plasma (up to 76%; P¿<¿0.05), whole blood (up to 72%; P¿<¿0.05), and liver B12 (up to 39%; P¿<¿0.05) and hepatic SAM/SAH (up to 90%; P¿<¿0.05). -F increased homocysteine 2-fold, while -F-B increased homocysteine 3.6- and 6.8-fold in the C and HF groups (P¿<¿0.05). Plaque formation was increased 2-fold (P¿<¿0.0001) in mice fed a HF diet. Feeding a HF–F diet increased lesion formation by 17% (P¿<¿0.05). There was no change in 5-methyldeoxycytidine in liver or vascular tissue (aorta, periadventitial tissue and heart). These data suggest that atherogenesis is not associated with genome-wide epigenetic changes in this animal model.