Tissue lipid peroxidation and serum lipoproteins in hamsters are affected by dietary protein composition

In the present study, the relationship between hyperlipidemia induced by ingestion of animal protein and tissue lipid peroxidation was examined. Male Golden Syrian hamsters were fed for 27 days cholesterol-enriched (0.088 wt%) semi-purified diets having either 15 wt% casein (CAS) or egg white (EGG) as the protein source. Hamsters fed the CAS diet showed higher concentrations of serum total cholesterol and triglycerides as compared with EGG-fed hamsters. The change in total serum cholesterol and triglyceride concentrations over the 27-day dietary period was significantly greater in the CAS-fed hamsters than in the EGG group. Lipid peroxidation as measured by lipid hydroperoxides (LPO) was increased in the serum and liver of CAS-fed relative to the EGG-fed hamsters. Liver concentrations of thiobarbituric acid reactive substances, another index of lipid peroxidation, were unaffected by dietary protein composition. When the two dietary treatments were grouped together, a positive correlation was observed between serum LPO and serum apolipoprotein B (r=0.52; P < 0.05) and a negative correlation was noted between serum LPO and the serum apolipoprotein A-I to apolipoprotein B ratio (r= −0.84; P < 0.005). This study supports the hypothesis that the amino acid composition of proteins can modulate tissue lipid peroxidation concentrations in the Syrian hamster and that an oxidative challenge induced by CAS-based diets could play a role in this dietary-induced hyperlipidemia.