Positively charged peptides from casein hydrolysate show strong inhibitory effects on LDL oxidation and cellular lipid accumulation in Raw264.7 cells

Inhibiting low-density lipoprotein (LDL) oxidation and cellular lipid accumulation to reduce foam cell formation plays a key role in preventing atherosclerosis. Casein hydrolysate (66% < 1 kDa) was separated into four different charged fractions. The inhibitory effect of peptide fractions on LDL oxidation and cellular lipid accumulation was analysed using a CuSO4 cell-free system and a Cu2+-mediated and ox-LDL-induced Raw264.7 macrophage cell-based system. Casein peptide fractions not only significantly inhibited LDL oxidation but also prevented cellular lipid accumulation. Positively charged fractions exhibited stronger inhibitory effects than negatively charged fractions. Seven peptides with different charge properties were synthesised. With the increase in net positive charge, the ability of peptides to inhibit LDL oxidation was enhanced. Peptides containing lysine presented better inhibition than those that contained histidine. This study suggests that casein hydrolysate, especially positively charged peptide fractions, could be used as a natural antioxidant in functional foods to prevent atherosclerosis.