Hyperhomocysteinemia induced by methionine supplementation does not independently cause atherosclerosis in C57BL/6J mice

Abstract

A causal relationship between diet-induced hyperhomocysteinemia (HHcy) and accelerated atherosclerosis has been established in apolipoprotein E-deficient (apoE −/− ) mice. However, it is not known whether the proatherogenic effect of HHcy in apoE −/− mice is independent of hyperlipidemia and/or deficiency of apoE. In this study, a comprehensive dietary approach using C57BL/6J mice was used to investigate whether HHcy is an independent risk factor for accelerated atherosclerosis or dependent on additional dietary factors that increase plasma lipids and/or inflammation. C57BL/ 6J mice at 4 wk of age were divided into 6 dietary groups: chow diet (C), chow diet + methionine (C+M), western-type diet (W), western-type diet + methionine (W+M), atherogenic diet (A), or atherogenic diet + methionine (A+M). After 2, 10, 20, or 40 wk on the diets, mice were sacrificed, and the levels of total plasma homocysteine, cysteine, and glutathione, as well as total plasma cholesterol and triglycerides were analyzed. Aortic root sections were examined for atherosclerotic lesions. HHcy was induced in all groups supplemented with methionine, compared to diet-matched control groups. Plasma total cholesterol was significantly increased in mice fed the W or A diet. However, the W diet increased LDL/IDL and HDL levels, while the A diet significantly elevated plasma VLDL and LDL/IDL levels without increasing HDL. No differences in plasma total cholesterol levels or lipid profiles were observed between methionine-supplemented groups and the diet-matched control groups. Early atherosclerotic lesions containing macrophage foam cells were only observed in mice fed the A or A + M diet. Furthermore, lesion size was significantly larger in the A + M group compared to the A group at 10 and 20 wk; however, mature lesions were never observed even after 40 wk on these diets. The presence of lymphocytes, increased hyaluronan staining, and the expression of endoplasmic reticulum (ER) stress markers were also increased in atherosclerotic lesions from the A + M group. Taken together, these results suggest that HHcy does not independently cause atherosclerosis in C57BL/6J mice even in the presence of increased total Clinical and epidemiological studies have established that elevated plasma total homocysteine (tHcy) is an independent risk factor for cardiovascular disease and stroke (1,2). Furthermore, accelerated atherosclerosis has been demonstrated in apolipoprotein E-deficient (apoE −/− ) mice with dietary hyperhomocysteinemia (HHcy) (3-5) and in cystathionine β-synthase (CBS)/apoE −/− double-knockout mice (6). These findings suggest that HHcy accelerates atherogenesis in a hyperlipidemic mouse model that develops spontaneous atherosclerosis. However, a causal relationship between atherogenesis and HHcy has not been established in other species, including rats, rabbits, pigs, and primates (7-10).Patients with inborn errors of methionine metabolism due to deficiencies in CBS or 5,10-methylenetetrahydrofolate reductase (MTHFR) present with severe...

Decreased Endogenous Production of Hydrogen Sulfide Accelerates Atherosclerosis

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Prolonged High-Fat Feeding Enhances Aortic 18F-FDG and 99mTc-Annexin A5 Uptake in Apolipoprotein E-Deficient and Wild-Type C57BL/6J Mice

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Murine Models of Hyperhomocysteinemia and Their Vascular Phenotypes

“…However, hyperhomocysteinemia has been observed to potentiate the development of atherosclerosis in susceptible strains of mice, such as hyperlipidemic Apoe Ϫ/Ϫ mice 37 or C57BL/6 mice fed an atherogenic diet containing cholate. 84 Hofmann et al reported that Apoe Ϫ/Ϫ mice fed a hyperhomocysteinemic diet developed atherosclerotic lesions in the aortic sinus that were of greater size and complexity than those seen in Apoe Ϫ/Ϫ mice fed normal chow. 37 Several other investigators, using a variety of dietary and genetic approaches to induce hyperhomocysteinemia in Apoe Ϫ/Ϫ mice, have confirmed and extended the observations of Hofmann.…”