Silymarin effect on amyloid- beta plaque accumulation and gene expression of APP in an Alzheimer's disease rat model

The deposition of amyloid peptides is associated with Alzheimer's disease (AD). These amyloid peptides are derived from the amyloid protein precursor (APP). Silymarin, a standardized extract of milk thistle, which is currently used in liver diseases, may be effective in the inhibition of amyloid formation. However, its effect has not been assessed on APP expression. In this study, first, the effect of silymarin was examined on the passive avoidance learning in a rat model of AD. This model was induced by the intracerebroventricular injection of A beta peptide in Wistar rats. Rats were treated with 70 and 140 mg/kg of the extract, once a day, for 4 weeks. Memory function that was evaluated in a shuttle-cage test, showed improvement upon administration of this extract. Brain amyloid plaques had also decreased upon administration of the extract. Furthermore, APP gene expression was compared in treated and untreated groups. The result showed that silymarin was able to suppress APP expression.