Amyloid beta-protein (Aβ) is the major protein of amyloid deposits in the brain of patients with Alzheimer’s disease (AD). Extensive evidence suggests neurotoxic effects of soluble oligomers of Aβ, and the role of oxidative stress and inflammation in AD. Walnuts are rich in components that have antioxidant and anti-inflammatory properties. Previous <i>in vitro</i> studies have shown that walnut extract inhibits Aβ fibrillization, solubilizes its fibrils, and has protective effects against Aβ-induced oxidative stress and cell death. In the Tg2576 transgenic mouse model of AD (AD-tg), we have reported the beneficial effects of dietary supplementation of 6% (T6) or 9% walnuts (T9) [equivalent to 1 or 1.5 oz of walnuts per day in human] on the memory, anxiety and learning skills. The diets for the experimental and control mice were comparable as regards to total calories and the contents of protein, carbohydrate and fat. AD-tg mice on control diet without walnuts (T0) showed memory deficit, anxiety-related behavior, and severe impairment in spatial learning ability, position discrimination learning ability and motor coordination compared to the wild-type (Wt) mice on the same diet. AD-tg mice on diet with walnuts (T6, T9) showed a significant improvement in memory, learning skills, anxiety and motor development compared to AD-tg mice on diet without walnuts (T0). Recently, we have also analyzed Aβ levels in the brain and blood samples of these mice at the ages of 4 months (before starting diet with walnuts), 14.5 and 19 months. At the age of 4 months, Aβ levels (brain and blood) were similar in T0 and Wt mice. At the age of 14.5 and 19 months, T0 mice had significantly higher Aβ levels than Wt mice. In the brain, T6 and T9 mice had significantly lower levels of soluble Aβ oligomers compared to T0 mice. In the blood samples, the levels of Aβ 1- 40 and 1- 42 were increased in T6 and T9 mice compared to T0 mice, suggesting that walnuts in the diet can increase the clearance of Aβ from brain to the blood. These findings suggest that dietary supplementation with walnuts may have a beneficial effect in reducing the risk, delaying the onset, or slowing the progression of AD because it can (a) inhibit Aβ fibrillization, Aβ-induced oxidative stress and Aβ-mediated cytotoxicity, and (b) reduce the levels of soluble Aβ oligomers in the brain and increase Aβ clearance.

Potential beneficial effects of a diet with walnuts in Alzheimer's disease

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.