The beneficial effects of fruit polyphenols on brain aging

Abstract

Brain aging is characterized by the continual concession to battle against insults accumulated over the years. One of the major insults is oxidative stress, which is the inability to balance and to defend against the cellular generation of reactive oxygen species (ROS). These ROS cause oxidative damage to nucleic acid, carbohydrate, protein, and lipids. Oxidative damage is particularly detrimental to the brain, where the neuronal cells are largely post-mitotic. Therefore, damaged neurons cannot be replaced readily via mitosis. During normal aging, the brain undergoes morphological and functional modifications resulting in the observed behavioral declines such as decrements in motor and cognitive performance. These declines are augmented by neurodegenerative diseases including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and Parkinson's disease (PD). Research from our laboratory has shown that nutritional antioxidants, such as the polyphenols found in blueberries, can reverse age-related declines in neuronal signal transduction as well as cognitive and motor deficits. Furthermore, we have shown that short-term blueberry (BB) supplementation increases hippocampal plasticity. These findings are briefly reviewed in this paper.

Introduction

Normal aging is accompanied by declines in motor and cognitive performance [43]. These declines are amplified in age-related neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and Parkinson's disease (PD). As the elderly population increases, so will the prevalence of these age-related disorders [19], [20], [62]. In order to improve the quality of life for the elderly and to alleviate the social and economic burdens imposed by the prolongation of life expectancy, it is crucial to devise strategies to impede or reverse age-related neuronal declines. There is substantial evidence that oxidative stress plays an important role in the aging process [33], [34], [35]. According to Dr. Denham Harman's free radical theory, aging is the accumulation of oxidative damage to cells and tissues over time. It has been suggested that the behavioral and neuronal deficits seen in the elderly population are the result of an increasing vulnerability to damage by free radicals [22], [54]. This theory has fostered the field of nutraceutical research, which investigates the effects of dietary antioxidants as a means to reverse or slow the aging process [5], [30], [40], [41], [42], [45], [88]. Our research has shown that supplementation with fruits and vegetables are beneficial in both forestalling and reversing the deleterious effects of aging on neuronal communication and behavior (reviewed in [43]). The observed protection may be the result of the antioxidant and anti-inflammatory properties of the polyphenolic compounds found in these fruits and vegetables [66].