Different effects of low- and high-density lipoproteins in egg yolk on lipid metabolism of mouse: Role of phospholipids-to-cholesterol intake ratio.

Recent evidence increasingly indicates that moderate egg consumption (up to one egg per day) poses no significant risk of cardiovascular diseases in healthy individuals, leading researchers to speculate whether other lipids in eggs affect lipid metabolism. In this research, C57BL/6J mice were given chow diets containing egg yolk low-density lipoprotein (LDL) and high-density lipoprotein (HDL), two natural components with different proportions of phospholipids and cholesterol, to explore the effects of the phospholipids-to-cholesterol intake ratio on lipid metabolism. Increases in liver weight and liver index were observed following LDL intake, while body weight and epididymal fat decreased after HDL intake in a dose-dependent manner. The food efficiency of chow diets decreased with increasing phospholipids content. Lipid biomarkers indicated that LDL intake significantly increased plasma LDL cholesterol and liver cholesterol levels. At equivalent cholesterol doses, the cholesterol-raising effects of HDL were weaker than those of LDL. Higher protein expression of cytochrome P450 family 7 subfamily A member 1 in the HDL groups suggested increased bile acid excretion at higher phospholipids-to-cholesterol intake ratios. Fecal metabolite analysis revealed significant changes in lipid composition, primarily involving glycerophospholipids, sphingolipids, and sterol lipids, consistent with the lipid profiles of LDL and HDL. The upregulation of cholic acid and deoxycholic acid in feces further confirmed increased bile acid excretion. This study highlights the differences in lipid metabolism in mice under varying phospholipids-to-cholesterol intake ratios, which may be associated with changes in dietary energy supply and bile excretion following phospholipids involvement.