Investigators in this featured study contribute findings to the growing body of research on the capacity of fruit and vegetable consumption to reduce the risk of numerous age-related chronic diseases. Specifically, their research focuses on the possible role fruit and vegetable consumption may have on the reduction of chronic diseases due to neurodegeneration. While epidemiological evidence is available suggesting antioxidant supplementation may protect against several neurodegenerative disorders such as Alzheimer's disease, less is known about specific dietary agents and their mechanisms of neuroprotection. Duffy et al note several studies suggesting increased amounts of polyphenolic rich dietary compounds may account for the reported neuroprotection reported in the literature. Blueberries (BB), which are high in polyphenolic flavonoids, have been observed to reduce neuronal damage in rodents with brain trauma as well as improve performance in mice with Alzheimer-like impairments.
In their rodent study, Duffy et al, tested a hypothesis that "dietary pretreatment with BB would protect against neurotoxicity caused by central injections of kainic acid (KA) in rats and that plasma collected from BB-fed rats would protect cells from H2O2 mediated stress." Their approach refers to another hypothesis for Alzheimer's disease, the "excitotoxicity hypothesis," that excessive stimulation of glutamate receptors may result in neurodegeneration by oxidative stress. This featured study involved two very similar experiments in which rats were each given a diet supplemented with 2% BB extract for a minimum of eight weeks before surgery and behavioral testing. The control diet included was 2% dried corn (CN). After eight weeks, rats began to receive bilateral hippocampal injections of KA, or a control of saline. A week later, behavioral testing commenced utilizing a 14-unit T-maze.
The collective results of rodent performance in the maze clearly indicate that BB group rats subjected to KA had significantly enhanced performance when compared to the CN group who also underwent KA injection surgery. Moreover, following stereological analysis it was determined that as compared to the CN group, the BB-enriched diet reduced neuronal loss consequent to excitotoxic effects of KA. Finally, the in vitro analysis confirmed that the BB diet protected against oxidative damage, as FaO cells reared in serum from BB rats were better protected against H202 induced death than FaO cells in control serum. While the authors of this study note the mechanisms accounting for the above results remain to be determined, they also assert that these findings "suggest that a diet enriched in BB might attenuate degenerative processes due to oxidative or inflammatory stressors similar to effectiveness of pharmacological strategies related to this hypothesis of AD."
Study:Duffy, K.B., et al, Neurobiology of Aging, 29: 1680- 1689 (2008)