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United States Department of Agriculture

Agricultural Research Service

Research Project: The Effects of Walnuts on Neuronal Communication and Stress Signaling in Aging
2012 Annual Report


1a.Objectives (from AD-416):
A major focus of this proposal is concerned with the possible beneficial effects of dietary supplementation of antioxidants and anti-inflammatories in reducing the deleterious effects of reactive oxygen species and inflammation when their levels overwhelm the organism’s defense capacities and damage to cellular macromolecules such as lipids, proteins, and DNA occurs. There have been numerous studies in which antioxidants have been examined with respect to reducing the deleterious effects of brain aging, with mixed results. However, our research suggests that the combinations of antioxidant/anti-inflammatory polyphenolics found in fruits and vegetables may show efficacy in aging. Therefore, in the present study we will determine the effects of these supplementations on stress signaling, microglial activation and neurogenesis and correlate these with alterations in behavioral parameters. The effects of these supplementations on neurogenesis and differentiation will be examined using immunocytochemistry, bromodeoxyuridine (BrDU) incorporation in hippocampus obtained from the supplemented behaviorally-assessed animals.


1b.Approach (from AD-416):
We will utilize several techniques (e.g., Western blot analyses and immunocytochemistry) to assess the changes in several markers of phosphorylation that are important in cell communication (e.g., calcium-dependent protein kinase C, PKC; extracellular signal regulated kinases, ERK) and other markers of stress signaling (e.g., p38 MAPK) in vitro in BV-2 cells and in primary hippocampal neurons.


3.Progress Report:

Age-associated declines in the brain’s defense mechanisms are often associated with an inability to thwart oxidative stress and inflammation. Among the many approaches to boost brain cell communication and internal defense is supplementing diets with antioxidant and omega fatty acid-rich walnuts. In this study we explored whether supplementing old rats with 3-9% walnut diets for 12 weeks would yield the desired neurochemical changes. We published these findings in the Journal of Nutritional Biochemistry this year, where we reported that supplementing old rats with 6 or 9% walnut diets, which is equivalent to 1-1.5oz/day for human consumption, yields desirable inter-neuronal communication by enhancing clearance of toxic protein accumulations. The study also found that walnut diet supplementation enhanced protective neuronal signaling proteins, which are critical in protecting brain cells against oxidative damage. The mechanistic assessments of these results were done using rodent brain cells grown in culture, such as BV2 microglia and HT22 hippocampal neurons. The serum collected from walnut-fed animals, when applied to brain cells grown in culture, rescued the cells from chemically-induced toxicity. The results further confirm that the rescuing effects of walnuts are also mediated via enhancing protective stress signaling. The results are being analyzed for the preparation of a second manuscript.


Last Modified: 11/20/2014
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