A Walnut-enriched Diet and Physical Activity Enhanced Cognitive and Motor Function in Aged Mice (P14-010-19)

Abstract

Objectives This study aims to investigate walnut's effect alone and in combination with an enriched environment on brain aging of aged NMRI mice by investigation of cognition and motor functions. Furthermore, it aims to identify the underlying mechanisms by evaluating the expression of relevant genes. Methods NMRI mice (12mo.) were fed with a 6% walnut-enriched diet (WED) or control diet respectively, for the duration of 6 months. Additionally, one WED group was exposed to an enriched environment. Cognition and motor functions were assessed to evaluate walnut's effect on spatial memory, general physical activity and motor coordination. Conducted tests included Y-Maze alternation, open field and rotarod. Expression levels of relevant genes including synaptophysin, NGF and BDNF were measured via qPCR in brain tissue. Mitochondrial function was investigated by testing for ATP levels and mitochondrial membrane potential in dissociated brain cells and oxygen consumption of the oxidative phosphorylation system of freshly isolated mitochondria. Results Intake of the walnut diet significantly increased the alternation rate in a Y-Maze experiment (P < 0.05). Physical activity did not further improve this effect on spatial memory of mice, but increased mice’ activity (P < 0.001) in general. Motor function in rotarod test was not improved by walnut intake alone, but significantly increased by added enrichment (P < 0.01). Gene expression of synaptophysin was significantly increased for walnuts alone (P < 0.05), while BDNF and NGF expression appeared to be unaffected. Additional enriched environment resulted in a trend for these genes to be increased as well. Results imply that mitochondrial function is not linked to these improvements. Conclusions Long term walnut diet significantly improved cognitive function in aged mice. Physical activity additionally improved motor functions. These benefits could possibly be explained by increased expression of genes involved in neuronal plasticity. Funding Sources Grant from California Walnut Commission.