Abstract: Purpose: To ascertain the combined effect of methionine restriction (MR) and collagen peptides on lipid metabolism and oxidative stress in high-fat-diet (HFD)-fed mice. Methods: Thirty-six male C57BL/6 mice were randomly and evenly divided into normal diet (ND), high-fat diet (HFD), high-fat with MR diet (MR), and MR diet supplemented with 1% collagen peptides (PMR) groups, respectively. Body weight was measured weekly. At the end of the 22-week feeding period, all mice were sacrificed. Plasma total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL) and free fatty acids (FFAs) were examined. The concentrations of TG and TC in liver were investigated. The levels of total antioxidant capacity (T-AOC), glutathion peroxidase (GSH-Px), and malondialdehyde (MDA) in liver and plasma were determined. The mRNA expression of fatty acid synthase (FAS), acetyl CoA-carboxylase 1 (ACC-1), sterol regulatory element-binding protein 1c (SREBP1c), cholesterol 7α-hydroxylase 1 (CYP7A1), carnitine palmityl transferase 1 (CPT1) and peroxisome proliferator activated receptor α (PPARα) in liver were assayed by quantitative real time polymerase chain reaction (qPCR). Results: Compared with the HFD group, MR significantly decreased body weight, TG and TC concentrations in liver (P < 0.01), MDA levels in plasma and liver and reactive oxygen species levels in blood and liver (P < 0.01), and down-regulated the expression of FAS (P < 0.01), SREBP1c (P < 0.01) and ACC-1 (P < 0.05) in liver. MR significantly increased GSH-Px and T-AOC activity in liver (P < 0.05) and plasma (P < 0.01), and up-regulated the expression of CYP7A1 (P < 0.01), PPARα (P < 0.01) and CPT1 (P < 0.05) in liver. Compared with the MR group, PMR significantly decreased body weight and TG concentration in liver (P < 0.01) as well as TG and TC concentrations in plasma (P < 0.05), down-regulated the expression of SREBP1c and ACC-1 in liver (P < 0.05), up-regulated the expression of PPARα and CPT1 (P < 0.05), and increased GSH-Px activity in liver (P < 0.05). Conclusion: Dietary methionine restriction can significantly decrease blood and liver lipid accumulation, enhance liver antioxidant capacity in HFD-fed mice and has a synergistic effect when combined with collagen peptides.

Key words: dietary methionine restriction, collagen peptides, combined effect, lipid metabolism, oxidative stress