Memory performance of hypercholesterolemic mice in response to treatment with soy isoflavones.

The aim of this study is to investigate the memory performance of hypercholesterolemic mice in response to soy isoflavones (SI) treatment and the mechanism involved. In this study, 64 mice were randomly divided into four groups: control, high lipid diet without SI, high lipid diet with a low SI level (50 mg/kg bw) and high lipid diet with a high SI level (100 mg/kg bw). The experimental period was 30 days. The results indicated that the mice given the different treatments showed the different percentages of good, medium and poor memory performance. chi(2) analysis revealed significant difference in memory performance (P<0.05) between the high lipid diet without SI group and the high lipid diet with a low SI level group or high lipid diet with a high SI level group. Moreover, SI treatment resulted in a decrease in blood cholesterol (TC) level (high lipid diet without SI group versus high lipid diet with a low SI level group or high lipid diet with a high SI level group, P<0.05) and triglyceride (TG) level (high lipid diet without SI group versus high lipid diet with a low SI level group or high lipid diet with a high SI level group, P<0.05). In addition, SI treatment resulted in a significant decrease in acetylcholinesterase (AChE) activity and significant increases in glutamic acid and aspartic acid contents in the frontal cerebral cortex and hippocampus. The results suggest that SI improve the memory performance of hypercholesterolemic mice, and the mechanism underlying the improvement might closely correlate with its roles in decreasing high blood lipid levels and modulating the metabolism of neurotransmitters such as acetylcholine and amino acids in brain areas of hypercholesterolemic mice.