Transgenic (tg) mice with amyloid precursor protein (APP) gene mutation show amyloid beta-protein (Aβ) deposition in brain and memory deficit, and serve as an animal model of Alzheimer’s disease (AD). Several reports have suggested neurotoxic effects of Aβ and role of oxidative stress in AD. Walnut is rich in substances such as melatonin, vitamin E, ellagic acid and flavonoids that have anti-oxidant properties. We studied the effect of dietary supplementation of walnuts on the memory, anxiety and learning skills in AD mouse model.
The mice with double Swedish APP mutation (APP/Tg2576sw) were purchased from Taconic Farm. The experimental groups of APP-transgenic mice from the age of 4 months were fed custom-mix diets (pellets) containing 6% walnuts or 9% walnuts. The control groups, i.e. tg mice and wild-type mice were fed diet without walnuts. The diets for the experimental and control mice were comparable as regards to total calories, and the contents of protein, carbohydrate and fat. These experimental and control mice were examined at the age of 13-14 months and 18-19 months by Morris water maze test (for spatial memory and learning ability), T maze test (for position discrimination learning ability), rota rod test (for psychomotor coordination) and elevated plus maze test (for anxiety-related behavior) to analyze the effect of diet rich in walnuts on learning skills, memory, anxiety, locomotors activity, and motor coordination.
Alzheimer’s transgenic mice at the age of 13-14 months and 18-19 months that were fed control diet without walnuts 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 mice on the same diet. Both the diets rich in 6% or 9% walnuts when fed to tg mice showed a significant improvement in memory, learning ability, anxiety and motor development compared to the AD tg mice on diet without walnuts. The effects of 6% and 9% walnuts diets were similar.
Our results suggest that dietary supplementation of walnuts may have beneficial effect in reducing the risk, delaying the onset or slowing the progression of Alzheimer’s disease.