Barbara Shukitt-Hale

Reversals of Age-Related Declines in Neuronal Signal Transduction, Cognitive, and Motor Behavioral Deficits with Blueberry, Spinach, or Strawberry Dietary Supplementation

Ample research indicates that age-related neuronal–behavioral decrements are the result of oxidative stress that may be ameliorated by antioxidants. Our previous study had shown that rats given dietary supplements of fruit and vegetable extracts with high antioxidant activity for 8 months beginning at 6 months of age retarded age-related declines in neuronal and cognitive function. The present study showed that such supplements (strawberry, spinach, or blueberry at 14.8, 9.1, or 18.6 gm of dried aqueous extract per kilogram of diet, respectively) fed for 8 weeks to 19-month-old Fischer 344 rats were also effective in reversing age-related deficits in several neuronal and behavioral parameters including: oxotremorine enhancement of K+-evoked release of dopamine from striatal slices, carbachol-stimulated GTPase activity, striatal Ca45buffering in striatal synaptosomes, motor behavioral performance on the rod walking and accelerod tasks, and Morris water maze performance. These findings suggest that, in addition to their known beneficial effects on cancer and heart disease, phytochemicals present in antioxidant-rich foods may be beneficial in reversing the course of neuronal and behavioral aging.

Long-Term Dietary Strawberry, Spinach, or Vitamin E Supplementation Retards the Onset of Age-Related Neuronal Signal-Transduction and Cognitive Behavioral Deficits

Recent research has indicated that increased vulnerability to oxidative stress may be the major factor involved in CNS functional declines in aging and age-related neurodegenerative diseases, and that antioxidants, e.g., vitamin E, may ameliorate or prevent these declines. Present studies examined whether long-term feeding of Fischer 344 rats, beginning when the rats were 6 months of age and continuing for 8 months, with diets supplemented with a fruit or vegetable extract identified as being high in antioxidant activity, could prevent the age-related induction of receptor-mediated signal transduction deficits that might have a behavioral component. Thus, the following parameters were examined: (1) oxotremorine-enhanced striatal dopamine release (OX-K+-ERDA), (2) cerebellar β receptor augmentation of GABA responding, (3) striatal synaptosomal45Ca2+ clearance, (4) carbachol-stimulated GTPase activity, and (5) Morris water maze performance. The rats were given control diets or those supplemented with strawberry extracts (SE), 9.5 gm/kg dried aqueous extract (DAE), spinach (SPN 6.4 gm/kg DAE), or vitamin E (500 IU/kg). Results indicated that SPN-fed rats demonstrated the greatest retardation of age-effects on all parameters except GTPase activity, on which SE had the greatest effect, whereas SE and vitamin E showed significant but equal protection against these age-induced deficits on the other parameters. For example, OX-K+-ERDA enhancement was four times greater in the SPN group than in controls. Thus, phytochemicals present in antioxidant-rich foods such as spinach may be beneficial in retarding functional age-related CNS and cognitive behavioral deficits and, perhaps, may have some benefit in neurodegenerative disease.

Anthocyanins in aged blueberry-fed rats are found centrally and may enhance memory

Abstract Research has shown that fruits and vegetables containing high levels of polyphenolics (flavonoids) display high total antioxidant activity. Our laboratory found that various fruit and vegetable extracts, particularly blueberry (BB), were effective in reversing age-related deficits in neuronal signaling and behavioral parameters following 8 weeks of feeding, possibly due to their polyphenolic content. However, it was unclear if these phytonutrients were able to directly access the brain from dietary BB supplementation (BBS). The present study examined whether different classes of polyphenols could be found in brain areas associated with cognitive performance following BBS. Thus, 19 month old F344 rats were fed a control or 2% BB diet for 8–10 weeks and tested in the Morris water maze (MWM), a measure of spatial learning and memory. LC–MS analyses of anthocyanins in the diet and subsequently in different brain regions of BBS and control rats were carried out. Several anthocyanins (cyanidin-3- O -ß-galactoside, cyanidin-3- O -ß-glucoside, cyanidin-3- O -ß-arabinose, malvidin-3- O -ß-galactoside, malvidin-3- O -ß-glucoside, malvidin-3- O -ß-arabinose, peonidin-3- O -ß-arabinose and delphinidin-3- O -ß-galactoside) were found in the cerebellum, cortex, hippocampus or striatum of the BBS rats, but not the controls. These findings are the first to suggest that polyphenolic compounds are able to cross the blood brain barrier and localize in various brain regions important for learning and memory. Correlational analyses revealed a relationship between MWM performance in BBS rats and the total number of anthocyanin compounds found in the cortex. These findings suggest that these compounds may deliver their antioxidant and signaling modifying capabilities centrally.

Blueberry Supplementation Enhances Signaling and Prevents Behavioral Deficits in an Alzheimer Disease Model

Abstract Previously, we showed that blueberry (BB) supplementation reversed the deleterious effects of aging on motor behavior and neuronal signaling in senescent rodents. We now report that BB-fed (from 4 months of age) APP+PS1 transgenic mice showed no deficits in Y-maze performance (at 12 months of age) with no alterations in amyloid beta burden. It appeared that the protective mechanisms are derived from BB-induced enhancement of memory-associated neuronal signaling (e.g. extracellular signal-regulated kinase) and alterations in neutral sphingomyelin-specific phospholipase C activity. Thus, our data indicate for the first time that it may be possible to overcome genetic predispositions to Alzheimer disease through diet.

Blueberry Supplementation Improves Memory in Older Adults

The prevalence of dementia is increasing with expansion of the older adult population. In the absence of effective therapy, preventive approaches are essential to address this public health problem. Blueberries contain polyphenolic compounds, most prominently anthocyanins, which have antioxidant and anti-inflammatory effects. In addition, anthocyanins have been associated with increased neuronal signaling in brain centers, mediating memory function as well as improved glucose disposal, benefits that would be expected to mitigate neurodegeneration. This study investigated the effects of daily consumption of wild blueberry juice in a sample of nine older adults with early memory changes. At 12 weeks, improved paired associate learning (p = 0.009) and word list recall (p = 0.04) were observed. In addition, there were trends suggesting reduced depressive symptoms (p = 0.08) and lower glucose levels (p = 0.10). We also compared the memory performances of the blueberry subjects with a demographically matched sample who consumed a berry placebo beverage in a companion trial of identical design and observed comparable results for paired associate learning. The findings of this preliminary study suggest that moderate-term blueberry supplementation can confer neurocognitive benefit and establish a basis for more comprehensive human trials to study preventive potential and neuronal mechanisms.

Antioxidant-rich diets improve cerebellar physiology and motor learning in aged rats.

The free radical theory of aging predicts that reactive oxygen species are involved in the decline in function associated with aging. The present paper reports that diets supplemented with either spinach, strawberries or blueberries, nutritional sources of antioxidants, reverse age-induced declines in beta-adrenergic receptor function in cerebellar Purkinje neurons measured using electrophysiological techniques. In addition the spinach diet improved learning on a runway motor task, previously shown to be modulated by cerebellar norepinephrine. Motor learning is important for adaptation to changes in the environment and is thus critical for rehabilitation following stroke, spinal cord injury, and the onset of some neurodegenerative diseases. These data are the first to indicate that age-related deficits in motor learning and memory can be reversed with nutritional interventions.

Blueberry polyphenols increase lifespan and thermotolerance in Caenorhabditis elegans

The beneficial effects of polyphenol compounds in fruits and vegetables are mainly extrapolated from in vitro studies or short‐term dietary supplementation studies. Due to cost and duration, relatively little is known about whether dietary polyphenols are beneficial in whole animals, particularly with respect to aging. To address this question, we examined the effects of blueberry polyphenols on lifespan and aging of the nematode, Caenorhabditis elegans, a useful organism for such a study. We report that a complex mixture of blueberry polyphenols increased lifespan and slowed aging‐related declines in C. elegans. We also found that these benefits did not just reflect antioxidant activity in these compounds. For instance, blueberry treatment increased survival during acute heat stress, but was not protective against acute oxidative stress. The blueberry extract consists of three major fractions that all contain antioxidant activity. However, only one fraction, enriched in proanthocyanidin compounds, increased C. elegans lifespan and thermotolerance. To further determine how polyphenols prolonged C. elegans lifespan, we analyzed the genetic requirements for these effects. Prolonged lifespan from this treatment required the presence of a CaMKII pathway that mediates osmotic stress resistance, though not other pathways that affect stress resistance and longevity. In conclusion, polyphenolic compounds in blueberries had robust and reproducible benefits during aging that were separable from antioxidant effects.

Modulation of Hippocampal Plasticity and Cognitive Behavior by Short-term Blueberry Supplementation in Aged Rats

Abstract During aging, reductions in hippocampal neurogenesis are associated with memory decline indicating a causal relationship. Indeed, insulin-like growth factor-1 (IGF-1), a major activator of the extracellular receptor kinase pathway that is central in learning and memory processes, is also a key modulator of hippocampal neurogenesis. Previously, we showed that age-related declines in spatial memory tasks can be improved by antioxidant-rich diets containing blueberries. In this study, to begin to understand the mechanisms responsible for the beneficial effects of blueberries, we assessed changes in hippocampal plasticity parameters such as hippocampal neurogenesis, extracellular receptor kinase activation, and IGF-1 and IGF-1R levels in blueberry-supplemented aged animals. Our results show that all these parameters of hippocampal neuronal plasticity are increased in supplemented animals and aspects such as proliferation, extracellular receptor kinase activation and IGF-1 and IGF-1R levels correlate with improvements in spatial memory. Therefore, cognitive improvements afforded by polyphenolic-rich fruits such as blueberries appear, in part, to be mediated by their effects on hippocampal plasticity.

Neurobehavioral aspects of antioxidants in aging.

Both aging and age‐associated neurodegenerative diseases are associated with various degrees of behavioral impairments, and among the prime candidates responsible for producing the neuronal changes mediating these behavioral deficits appear to be free radicals and the oxidative stress they generate. Therefore, there have been a number of studies which have examined the putative positive benefits of antioxidants in altering, reversing, or forestalling these neuronal/behavioral decrements, with varying degrees of success. Additional experiments have examined the effects of diets rich in fruits and vegetables or herbal extracts in reducing certain types of cancer and cardiovascular diseases, and evidence emerging from such experiments suggests that these kinds of dietary modifications may be beneficial in altering neuronal/behavioral deficits in aging, as well. These kinds of diets are particularly rich in antioxidants such as vitamins A, C, E, and bioflavonoids (such as flavones, tannins, and anthocyanins), and thus, there may be synergistic effects among them. The present paper will review studies concerning the influence of dietary and synthetic antioxidants on normal, pathological age‐related, and reactive oxygen species‐induced behavioral changes in human and animal subjects. The antioxidants reviewed are vitamin E, α‐lipoic acid, and the phytochemicals contained in herbals, fruits and vegetables.

Concord grape juice supplementation improves memory function in older adults with mild cognitive impairment

Concord grape juice contains polyphenol compounds, which have antioxidant and anti-inflammatory properties and influence neuronal signalling. Concord grape juice supplementation has been shown to reduce inflammation, blood pressure and vascular pathology in individuals with CVD, and consumption of such flavonoid-containing foods is associated with a reduced risk for dementia. In addition, preliminary animal data have indicated improvement in memory and motor function with grape juice supplementation, suggesting potential for cognitive benefit in ageing humans. In this initial investigation of neurocognitive effects, we enrolled twelve older adults with memory decline but not dementia in a randomised, placebo-controlled, double-blind trial with Concord grape juice supplementation for 12 weeks. We observed significant improvement in a measure of verbal learning and non-significant enhancement of verbal and spatial recall. There was no appreciable effect of the intervention on depressive symptoms and no effect on weight or waist circumference. A small increase in fasting insulin was observed for those consuming grape juice. These preliminary findings suggest that supplementation with Concord grape juice may enhance cognitive function for older adults with early memory decline and establish a basis for more comprehensive investigations to evaluate potential benefit and assess mechanisms of action.