The Role of Fruit Polyphenolics in Brain Aging
James A. Joseph1, Gemma Casadesus1, Rachel L. Galli2 and Barbara Shukitt-Hale2
1United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111; 2Department of Psychology, Simmons College, Boston, MA 02115
Dietary supplementation (S) with fruit or vegetable extracts high in
antioxidants (e.g., blueberry, BB, spinach) can decrease the enhanced
vulnerability to oxidative stress (OS) that occurs in aging and these
reductions are expressed as improvements in neuronal signaling and
behavioral. In addition, recent examinations using striatal or
hippocampal tissue isolated from BB supplemented aged animals, have
shown that striatal slices show reductions in H2O2 -induced decrements
in muscarinic receptor sensitivity decrements, while the hippocampal
slices show decreases in baseline levels of HSP-70 and increases in
HSP-70 responsiveness to lipopolysaccharide (LPS) exposure. Moreover,
there are also indications that BB supplementation can also reduce the
sensitivity to neurotoxic agents (kainic acid) that induce oxidative
stress and inflammation. Additional experiments suggest that BB
effects also may include enhancement of neuronal signaling, and that
these increases can offset the putative deleterious consequences of
amyloid beta deposition in APP/PS-1 mice. Therefore, it appears that
polyphenolic compounds such as those found in BB may exert their
beneficial effects by enhancing the endogenous anti-inflammatory,
antioxidant and neuronal signaling capabilities of the organism. In
addition, recent work from our laboratory has indicated that one of the
most striking effects of BB supplementation may involve increases in
neurogenesis. It is known that factors such as head injury,
depression and stress that lead to decreases in neurogenesis are all
associated with greater rates of cognitive decline. Conversely,
exercise and environmental enrichment can improve both neurogenesis and
cognitive function in aging. The results of our recent work has
indicated that aged BB-supplemented rats, tested in the radial arm
water maze (RAWM) and given injections of BrdU showed that the number
of proliferating cells in the dentate gyrus were significantly higher
(p <0.05) in the BB-fed rats. Moreover, these findings were correlated
with improvements in the RAWM performance such that as the number of
proliferated cells increased, the number of memory errors decreased
(reference memory errors: r = - 0.654, p< .05, working memory errors: r
= -0.646, p< .05, total memory errors: r = -0.587, p=.08). Subsequent
research has indicated anthocyanins from BB supplementation can
localize in various brain regions and that the number of the
anthocyanins that localize in regions such as the cortex are negatively
correlated with the amount of errors made in the Morris water maze on
the probe trials. Taken together, these findings suggest that
antioxidant-rich fruits such as BBs may improve cognitive performance
by increasing proliferation of neural precursor cells in the
hippocampus (i.e., RAM Kempermann, 2002) and enhancing signaling in
areas such as cortex, hippocampus, and striatum which may offset
deficits in in aging or via genetic modifications.
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