Soybean Protein Hydrolysate Improves Plasma and Liver Lipid Profiles in Rats Fed High-Cholesterol Diet

Objective: This investigation attempted to clarify the hypolipidemic effects of non-dialyzed soybean protein hydrolysate (NSPH), which is hydrolyzed by pepsin from soybean acid-precipitated protein (APP), in rats fed a cholesterol-rich diet. Methods: Forty Sprague-Dawley rats were divided into four groups as the control group (19.7% casein), the APP group (14.7% casein + 5% APP), the NSPH group (14.7% casein + 5% NSPH), and the ISO group (19.7% casein + 0.0013% soy isoflavone). Results: After 12-week experimental period, the APP and NSPH groups had a significant lower plasma total cholesterol, triglycerides, and LDL-cholesterol concentrations compared with the control group. Additionally, the atherosclerosis index in APP and NSPH group had also markedly decreased. Liver cholesterol and triglyceride contents of the APP and NSPH group were significantly lower than those of the control group. There were no different in plasma LDL-C, liver cholesterol and triglycerides between the ISO group and control group. Fecal excretion of neutral steroids and nitrogen compounds was significantly higher in the APP and NSPH groups than that in the control group. An in vitro study also showed that NSPH, compared with casein, obviously decreased cholesterol micellar solubility. Conclusion: These results suggested that NSPH may decrease lipid accumulation in the liver and have a hypolipidemic effect by enhancing excretion and inhibiting absorption of lipids.