Prothrombotic effects of hyperhomocysteinemia and hypercholesterolemia in ApoE-deficient mice

Objective-We tested the hypothesis that hyperhomocysteinemia and hypercholesterolemia promote arterial thrombosis in mice. Methods and Results-Male apolipoprotein E (Apoe)-deficient mice were fed one of four diets: control, hyperhomocysteinemic (HH), high fat (HF), or high fat/hyperhomocysteinemic (HF/HH). Total cholesterol was elevated 2-fold with the HF or HF/HH diets compared with the control or HH diets (P < 0.001). Plasma total homocysteine (tHcy) was elevated (12 to 15 mu mol/L) with the HH or HF/HH diets compared with the control or HF diets (4 to 6 mu mol/L; P < 0.001). Aortic sinus lesion area correlated strongly with total cholesterol (P < 0.001) but was independent of tHcy. At 12 weeks of age, the time to thrombotic occlusion of the carotid artery after photochemical injury was > 50% shorter in mice fed the HF diets, with or without hyperhomocysteinemia, compared with the control diet (P < 0.05). At 24 weeks of age, carotid artery thrombosis was also accelerated in mice fed the HH diet (P < 0.05). Endothelium-dependent nitric oxide-mediated relaxation of carotid artery rings was impaired in mice fed the HF, HH, or HF/HH diets compared with the control diet (P < 0.05). Conclusions-Hyperhomocysteinemia and hypercholesterolemia, alone or in combination, produce endothelial dysfunction and increased susceptibility to thrombosis in Apoe-deficient mice.