Dietary methionine restriction ameliorates atherosclerosis by remodeling the gut microbiota in apolipoprotein E-knockout mice

Dietary methionine restriction (MR) has been shown to reduce the risk of atherosclerosis, but the specific regulatory effects and mechanisms remain unclear. This research intends to investigate the effects of MR on atherosclerosis in apolipoprotein E-knockout (ApoE^-/-) mice fed a high-fat, high-cholesterol, high-choline diet and their mechanisms. ApoE^-/- mice were fed a normal diet (0.86% methionine + 4.5% fat + 0% cholesterol + 0.2% choline), a high-fat, high-cholesterol, high-choline diet (0.86% methionine + 20% fat + 1% cholesterol + 1% choline), or a high-fat, high-cholesterol, high-choline + MR diet (0.17% methionine + 20% fat + 1% cholesterol + 1% choline) for 8 consecutive weeks. The results show that MR reduced body weight, fat mass, fat deposition in the liver and adipocytes, and plasma lipid levels; improved the morphological structure of the aorta; and reduced the aortic lesion area and lipid levels. In addition, MR downregulated aortic pro-inflammatory cytokine levels, upregulated aortic anti-inflammatory cytokine levels, and improved aortic oxidative stress. Moreover, metagenomic sequencing results suggested that MR improved the gut microbiota composition, particularly through increased relative abundance of short-chain fatty acid (SCFA)-producing bacteria, and changed the relative abundance of inflammation-, lipid metabolism-, and bile acid metabolism-related bacteria at the species level. Furthermore, MR promoted SCFA production and bile acid metabolism, and reduced cell adhesion molecules and foam cell formation in the aorta. Thus, our findings indicated that MR improved the gut microbiota composition, especially increased SCFA production, and ameliorated oxidative stress and inflammation in the aorta, thereby preventing atherosclerosis.