2011 Annual Report
1a.Objectives (from AD-416)
We hypothesize that walnuts will reverse age-related disturbances in behavior, neuronal functioning, and microglial activation and will test this hypothesis with the following aims:.
1)Determine the effects of dietary supplementation with walnuts or walnut components on motor and cognitive function..
2)Determine the efficacy of walnuts or walnut components on reversing the age-associated increase in neuronal vulnerability..
3)Investigate the anti-inflammatory actions of walnuts and walnut components on microglial activation. These studies will serve to characterize the effects of dietary walnut supplementation in aging, focusing on cognitive, behavioral, neuronal, and microglial effects of walnuts. In addition, these studies will examine the neuroprotective effects of individual walnut components in order to determine the efficacy of the whole food versus individual components of walnuts.
1b.Approach (from AD-416)
1) Determine the effects of dietary supplementation with walnuts or walnut components on motor and cognitive function. Walnuts will be supplemented in the diet at 6%, walnut components will be given as a portion of the 6% concentration that they comprise in the whole food. The effects of these diets on age-sensitive motor (probes sensitive to balance, strength, and coordination) and cognitive behaviors (short- and long-term memory) will then be examined in Fischer 344 (F344) rats after 8 weeks of supplementation.
2) Determine the efficacy of walnuts or walnut components on reversing the age-associated increase in neuronal vulnerability. The effects of dietary supplementation with walnuts and walnut components on hippocampal neurogenesis (proliferation and survival of newly born neurons) will be assessed in subjects utilized for Aim 1. Additionally, the effects of walnuts on neuronal stress and protective signaling will be accomplished through the use of a hippocampal cell line. Hippocampal cells will be used to determine if walnuts and walnut components alter neuronal stress and protective signaling pathways which have been reported to be altered in the aging brain.
3) Investigate the anti-inflammatory actions of walnuts and walnut components on microglial activation. Prolonged microglial activation is a hallmark of neurodegenerative disorders as well as normal brain aging. The effects of dietary walnut supplementation on age-associated microglial activation will be quantified in tissues harvested from subjects in Aim 1. Further studies on the molecular mechanisms of the anti-inflammatory properties of walnut oil and walnut components will be undertaken in the BV2 microglial cell line.
We had shown previously under this agreement that exposure of BV-2 microglia to walnut extract contributes to the “clean-up” of damaged cells in the brain and suppresses inflammation and oxidative stress, thereby protecting neurons. We also previously determined that walnut extract enhanced cellular calcium function in hippocampal neurons. Additionally, we found that two of the major components of walnuts, the omega-6 fatty acid linoleic acid (LA) and the omega-3 fatty acid, alpha-linolenic acid (ALA), may mediate some of these beneficial effects. This year we investigated further the effects of polyunsaturated fatty acids (PUFA) metabolites found in walnuts on brain cell function. In the brain, ALA is metabolized into docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), while LA is metabolized into arachidonic acid (AA). We assessed the effects of the metabolites of walnut PUFAs on hippocampal cells and microglia cells. We found that ALA and its metabolite DHA were effective in preventing oxidative stress-induced hippocampal cell death and calcium dysregulation, but LA was not. Currently we are assessing the effects of the metabolites on inflammation in microglial cells, specifically examining DHA, EPA, AA, and oleic acid, another component of walnuts. The effects of walnut extract and walnut PUFAs on BV-2 microglial cells are novel and demonstrate that fruits and nuts can induce dramatic alterations in the stress responses of cells involved in age-related cognitive decline. It is important to determine the active components in walnuts responsible for their beneficial effects and also to determine the type of protection offered by walnuts and metabolites in different brain cell types.