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United States Department of Agriculture

Agricultural Research Service

Research Project: THE ROLE OF STRAWBERRIES ON COGNITION, MOTOR BEHAVIOR, NEURONAL FUNCTION AND MICROGLIAL ACTIVITY IN AGING: REDUCTIONS IN STRESS MEDIATORS

Location: Human Nutrition Research Center on Aging

2011 Annual Report


1a.Objectives (from AD-416)
1: Determine the effects of SB supplementation on behavioral aging using paradigms sensitive to cognitive (short and long-term memories) behaviors.

2: Determine the effects of SB supplementation on calcium dependent and neuronal signaling (2) and neurogenesis (2b) correlate these with alterations in behavioral parameters determined in SA 1.

3: Determine whether the efficacies of these supplementations in the behavioral assays are associated with enhanced resistance to oxidative stress or inflammation.

4: Establish the effects of nutritional modulation (e.g., berry fruit) on behavioral (e.g., cognition, gait, force and balance) and neuronal deficits in aging to assess the mechanisms involved and the most effective dietary supplements in animal and human models.


1b.Approach (from AD-416)
Aim 1. The effects of SB dietary supplementation (2% SB extract in the diet for 8 weeks. After 8 weeks performance will be examined in the rats using age-sensitive cognitive behaviors that are selective for reference and working memories. The latter behaviors will be assessed using the Morris water maze and the radial arm water maze, as well as novelty tests. All of these tests have been validated as being age sensitive (e.g. demonstrated a significant decline as a function of age). Aim 2. The effects of SB dietary supplementation on neurogenesis and differentiation will be examined using immunocytochemistry, bromodeoxyuridine (BrDU) incorporation in hippocampus and olfactory bulb obtained from the supplemented behaviorally-assessed animals Calcium signaling will be assessed by examining Ca45 clearance in tissues (as above) taken from the brain. Aim 3. For the basal assessments we will use immunohistochemistry to assess various markers of oxidative stress (e.g., HO-1) and inflammation (e.g., cytokines) as well as immunoblotting to detect HO-1 and bcl 2 expression. The responses of the tissue (muscarinic receptor sensitivity, HSP-70 activation) to oxidant (hydrogen peroxide, 10 uM) or inflammatory (LPS) stressors will be assessed by exposing cross-cut slices of the various brain regions obtained from the supplemented animals.

Conduct studies using a specialized Noraxon treadmill in order to measure parameters of gait including balance, stepping up and down, and walking patterns in humans. The recently developed hardware by Noraxon will allow us to focus on more subtle variations in gait that include stride to stride fluctuations (e.g., symmetry) and associated alterations in electromyography (EMG). The Noraxon measurement system allows an objective kinematic analysis of the human gait by means of analyzing the tracks of body surface markers. Additionally, cognition will be measured with a battery of tests that measure memory and vigilance.


3.Progress Report

Previously, we have shown that whole, crude berry extracts are able to reverse several parameters of brain aging, as well as age-related motor and cognitive deficits when fed to rats from 19-21 months of age. These effects may be the result of direct effects on brain signaling or indirect effects through antioxidant and anti-inflammatory properties of the polyphenols. However, it is not known where in the brain these berries are working to produce these effects. Previous studies in our lab have shown that the polyphenols in strawberries might be acting primarily on one area of the brain, the hippocampus, while those in blueberries might be acting primarily in the striatum. This year we attempted to further test this hypothesis by using a version of the radial arm water maze, a spatial test of learning and memory, which would track both reference and working memory errors. Reference memory errors (visiting an arm which never had the platform) and working memory errors (revisits to a baited arm) are thought to be mediated by the striatum and hippocampus, respectively. We showed that, compared to young rats, aged control-diet fed rats displayed impaired cognitive performance in the radial arm water maze that was indicative of impaired function of different memory areas of the brain. However, perhaps due to the difficulty of the task which may have obscured any behavioral enhancements, the aged, strawberry- and blueberry-supplemented rats were not improved compared to control rats. Analyses are currently underway to measure levels of inflammatory cytokines in different brain areas to associate with behavioral performance. If the different polyphenolic compounds in these berry fruits are acting in different brain regions to produce their beneficial effects, then it becomes important to eat a variety of fruits and vegetables to maintain cognitive function in old age. Additionally, these results suggest that multiple mechanisms may be involved in the beneficial effects of high-antioxidant fruits on aging.


Last Modified: 8/21/2014
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