Beneficial effect of black rice (Oryza sativa L. var. japonica) extract on amyloid beta-induced cognitive dysfunction in a mouse model

Abstract

Alzheimer's disease (AD) is an age-dependent progressive neurodegenerative disease, resulting in memory loss and cognitive dysfunction. The accumulation of amyloid beta (A beta) has been identified as the most important risk factor for AD. Black rice (BR; Oryza sativa L. var. japonica), which is widely consumed in Asia, is a good source of bioactive compounds including anthocyanins. Therefore, the aim of the present study was to evaluate the protective effect of BR extracts against A beta(25-35)-induced memory impairment in an in vivo AD mouse model. After intracerebroventricular injection of A beta(25-35), mice were treated with BR extract supplementation for 14 days. Memory and cognition function were evaluated over this period in both treated and untreated animals using T-maze, novel object recognition and Morris water maze tests. After behavioral tests, malondialdehyde (MDA) and nitric oxide (NO) concentrations in brain, liver and kidney tissues were analyzed. Mice treated with A beta(25-35) had impaired memory and cognitive function; however, mice administered BR extract (100 mg/kg/day) demonstrated an improvement in cognition and memory function compared with the A beta(25-35)-injected control group. Furthermore, injection of A beta(25-35) significantly increased MDA and NO generation in the brain, liver and kidney of mice. However, the group administered with BR extract had significantly inhibited lipid peroxidation and NO generation in the brain, liver and kidney. In addition, the protective effect of BR on lipid peroxidation and NO production by A beta(25-35) was stronger in the brain compared with other tissues. Collectively, these findings suggested that BR supplementation may prevent memory and cognition deficits caused by A beta(25-35)-induced oxidative stress.