Sardina pilchardus and Sardinella aurita protein hydrolysates reduce cholesterolemia and oxidative stress in rat fed high cholesterol diet

Objective: The present study was designed to determine in rats fed high cholesterol diet whether serum cholesterol concentration and its distribution in lipoprotein fractions could be improved by sardine (Sardina pilchardus) and sardinelle (Sardinella aurita) protein hydrolysates. In addition, lipid peroxidation in different lipoprotein fractions and in two target tissues of atherosclosis and their antioxidant enzymes activities were also evaluated. Materials and Methods: Eighteen adult male Wistar rats (350 ± 15 g) fed 20% casein with 1% cholesterol were divided into three groups. Group I and Group II were designated as ‘sardine’ and ‘sardinelle’ groups received 300 mg of the respective fish protein hydrolysates for 14 days by oral gavage while the third group received water in the same conditions and constituted the control group (CG). Results: Compared with CG, cholesterolemia was 1.7-fold lower in sardine and sardinelle groups. This was meanly due to their reduced low-density lipoproteinhigh-density lipoprotein (HDL1)-cholesterol contents while those of HDL3 were enhanced. Thiobarbituric acid reactive substances contents were found to be lowered in red blood cells (RBC), heart and aorta of sardine and sardinelle group rats compared to CG. In the same groups, paraoxonase activity was also higher than CG. RBC and heart superoxide dismutase activity was higher in sardinelle group versus CG. In aorta, glutathione peroxidase activity was higher in both sardine and sardinelle groups. Glutathione reductase activity in RBC and aortic tissue was also increased in sardine and sardinelle groups. Conclusion: Sardine and particularly sardinelle protein hydrolysates could be considered as two bioactive ingredients with a potent cholesterol-lowering effect accompanied by efficient decrease in lipid peroxidation in serum and target tissues, related with increased antioxidant enzymes activity in rats fed a high cholesterol diet.