Location: Boston, Massachusetts2013 Annual Report
1a. Objectives (from AD-416):
LAB: Nutrition & Neurocognition 1. Determine the role of nutritional factors, especially B-vitamins and choline, in preventing age-related cognitive impairment using human intervention and population studies. 2. Characterize mechanisms by which nutritionally induced hyperhomocysteinemia affects neuronal function and cognitive performance using other animal models of human cognitive decline. LAB: Neuroscience 1. Use cell models to develop mechanistic interpretations of the positive benefits of berry polyphenols and fatty acids by examining their direct effects on deficits in stress and protective signaling. 2. Establish the effects of dietary berry fruit extracts and/or fatty acids on behavioral and neuronal deficits in aging to assess the mechanisms involved and the most effective polyphenols/fatty acids in animal and human models.
1b. Approach (from AD-416):
LAB: Nutrition & Neurocognition With the population aging, the imperativeness to understand and prevent age-related cognitive decline and disability grows more important. We approach this problem with nutritional studies in human populations and in studies of animal models. Observational and cohort studies in humans examine the association of modifiable nutritional factors especially B vitamins, vitamin D, and polyunsaturated fatty acids with the trajectory of cognitive decline and measurable brain volumes with age. Intervention studies with B vitamins to lower homocysteine levels in blood and protect against neurological and vascular degeneration examine our ability to delay cognitive decline, dementia, and disability. Genotyping focusing on methylation pathways provide insight into how genetic variability may modify or modulate the neurological response to nutrition and dietary factors. Animal models of aging and dementia are employed to examine the mechanism of nutritional modification of neural and cerebrovascular degeneration with effects on behavior. Rodents are made deficient in B vitamins or polyunsaturated fatty acids or choline and effects on brain function (behavior), brain biochemistry, and brain histology provide insights into pathways by which nutritional perturbations influence aging brain chemistry and function. LAB: Neuroscience The focus of the current project is to elucidate the mechanisms involved in the beneficial effects of berry fruit and polyunsaturated fatty acids (PUFAs) from fish or nut oils on reducing neurodegeneration mediated by oxidative stress (OS) and inflammation (INF). Mixed neuron/ glial cultures obtained from rats of different ages will be employed to delineate the neuroprotective effects of berry fruit or PUFA against OS/INF and subsequent stress mediated by glial cells. Additionally, muscarinic receptor-transfected COS-7 cells will be used to assess OS/INF localization and the effects of membrane lipids on the cellular responses to OS/INF. Extensive motor and cognitive assessments will also be made of senescent animals fed diets containing berry fruit or PUFAs. Finally, we will translate the behavioral findings obtained in our animal studies to the human condition by examining the effects of berry fruit or walnut supplementation on human gait and motor ability. This project will contribute to fundamental new knowledge of the putative role of berry fruit and PUFAs on reducing OS/INF and behavioral deficits in aging. These studies will span basic cellular signaling, animal behavior and cognition, and human motor abilities, allowing for a comprehensive examination of the beneficial effects of berry fruit and nutritional PUFAs on the aging brain.
3. Progress Report:
NEUROSCIENCE: We have shown that supplementation with fruits, vegetables, and nuts can forestall and reverse the deleterious effects of aging on neuronal (brain cell) functioning and behavior in rodents. While polyphenolic compounds found in these foods may have direct effects on oxidative stress (OS) and inflammation in aging, they also may enhance protective cellular communication (signaling), neuronal housekeeping (autophagy), and neuronal growth. Discovery of these additional mechanisms might lead to important dietary information for an aging population. Additionally, determining which components might be responsible for the beneficial effects is important, although it might be that the combination of polyphenols or fatty acids present in berries or nuts may have synergistic effects, which provide increased protection from age-related declines relative to individual constituent compounds. This year we continued to study the mechanisms responsible for the beneficial effects of berry fruit and fatty acids and whether metabolites from these foods would also provide beneficial effects, using brain cells (in vitro), animal models, and human studies. We showed that serum from rats fed walnuts, açaí fruit, strawberries, or blueberries protected brain cells in culture against stresses by attenuating OS and inflammation. Furthermore, reductions in inflammatory markers were correlated with improved behavior in aged rats. We continued to test several fruits/vegetables high in polyphenols for their beneficial effects in reversing age-related deficits in behavioral and brain function when fed to old rats. We fed aged animals different species of acai fruit, tart cherries, or mushrooms at various doses and tested the rats on a battery of motor and cognitive tests. These foods were able to protect against age-induced deficits in behavior and we are correlating these results with brain antioxidant and/or anti-inflammatory levels, as well as measures of signaling and autophagy (a process by which toxic debris is recycled and cleared in neurons), to understand the mechanisms of action through which the polyphenols in these foods could be producing their effects. We showed that two aging models that elicit inflammation and OS (exposure to cosmic rays and high-fat diets) caused decrements in cognition, gene expression, and autophagy, which were prevented by pre-feeding the animals with blueberry and/or strawberry diets. We also began a clinical study to examine the effects of feeding one cup of blueberries/day to adults 60-75 years of age on measures of gait, balance, and cognition.
1. NEUROSCIENCE: Serum metabolites from walnut-fed aged rats attenuate stress-induced neurotoxicity in brain cells in culture. Walnuts are rich in polyphenols, polyunsaturated fatty acids (PUFAs) and other nutrients, and have been demonstrated to improve learning and memory in aging. ARS funded researchers at JMUSDA-HNRCA at Tufts University at Boston, Massachusetts found that feeding aged animals diets containing 0, 6 or 9% walnuts, equivalent to 0, 1, and 1.5oz/day for humans, improved learning and memory and protected brain cells by activating the brain’s natural housekeeping mechanisms. Serum collected from walnut-fed animals showed enhanced protection on stressed brain cells in culture, while serum from control-fed rats did not elicit similar rescuing effects. These results suggest that walnut serum metabolites can protect or enhance membrane-associated functions in brain cells.
2. NEUROSCIENCE: Berry diets are protective in aging models that produce inflammation and oxidative stress. Exposure to high energy and charge radiation (cosmic rays) or high-fat diets has been shown to cause memory, learning, and behavioral deficits in young animals. ARS funded researchers at JMUSDA-HNRCA at Tufts University at Boston, Massachusetts, in collaboration with researchers at University of Maryland-Baltimore County, found that cosmic rays cause biological damage to brain cells of young animals, similar to that seen in old animals, possibly due to increases in oxidative and inflammatory stresses and subsequent accumulation of damaged proteins in key regions of the brain. The radiation caused changes in gene expression as well as substantial accumulation of biological debris in the brain which is often toxic and a known cause of many diseases of the brain. Feeding animals with either a blueberry or strawberry diet prior to irradiation protected the brain by boosting defense mechanisms and enhancing the clearance of toxic debris. Additionally, supplementing a high-fat diet with blueberries prevented recognition memory deficits seen in mice consuming the high-fat diet alone. These studies extend evidence for the health-promoting properties of berries against oxidative and inflammatory stresses.
3. NEUROSCIENCE: Açai fruit improves motor and cognitive function in aged rats by reducing inflammation. Açai is a black-purple fruit known for its high polyphenolic levels and anti-inflammatory properties. ARS funded researchers at JMUSDA-HNRCA at Tufts University in Boston, Massachusetts, found that feeding old rats two species of acai fruit [Euterpe oleracea Mart. (EO) or Euterpe precatoria Mart. (EP)] improved behavioral and neurocognitive function. Specifically, both the EO and EP diet improved working memory, relative to controls; however, only the EO diet improved reference memory. Subsequently, cells in culture treated with serum from açai-fed rats showed reductions in two biomarkers of inflammation, and reductions in these markers correlated with improved behavior in the rats. These results lend further support that fruits high in phytochemicals have the potential to contribute to “health span” in aging, as they are able to combat some of the inflammatory mediators of aging at the cellular level.
4. NEUROSCIENCE: Cognition and mobility decline with advancing age. Functional changes in the brain and motor neurons during aging can alter learning and memory, gait, and balance - in some cases leading to early cognitive decline, disability, or injurious falls among older adults. ARS funded researchers at JMUSDA-HNRCA at Tufts University at Boston, Massachusetts recruited men and women between the ages of 21 and 75 years to investigate age-related alterations in cognition and mobility. Results show age-related declines in balance, gait, and cognition are measurable in adults as early as their 40’s-50’s. Specifically, increased age was associated with increased postural sway during quiet standing, declines in preferred walking speed, declines in spatial navigation ability, and declines in executive function. These findings are important because they confirm the types of age-related declines seen in older adults and provide an age-range during which these declines present, therefore affording an age-range for intervention studies.
5. NUTRITION AND NEUROCOGNITION LAB: Plasma homocysteine is associated with cognitive impairment and MRI indicators of cerebrovascular pathology in older adults. Elevated plasma homocysteine concentration has been implicated as a risk factor for cardiovascular disease, stroke, and dementia. ARS funded researchers at JMUSDA-HNRCA at Tufts University at Boston, Massachusetts evaluated the relationship between homocysteine, sub-types of cerebrovascular pathology on magnetic resonance imaging (MRI), and cognition in a subset of 340 community-dwelling elders from the Nutrition Aging and Memory (NAME) study through brain MRIs and neuropsychological tests. We observed that cerebrovascular pathology, particularly small vessel infarct and periventricular white matter hyperintensity (WMHI), was associated with elevated fasting Hcy independent of other risk factors. Hcy was associated with total brain atrophy in those participants with periventricular WMHI, and was inversely related to measures of executive function. The results of our study suggest cerebrovascular disease and associated cognitive impairment as a target for Hcy lowering treatment.
6. NUTRITION AND NEUROCOGNITION LAB: Hyperhomocysteinemia (Hcy) predicts small vessel MRI pathology and cognitive impairment with high amyloid-B-peptide degrading proteases in the NAME elderly cohort. ARS funded researchers at JMUSDA-HNRCA at Tufts University at Boston, Massachusetts studied 318 home bound multi-ethnic elderly- Nutrition Aging and Memory Study (NAME) with nutritional, cognitive, and magnetic resonance imaging (MRI) to assess the relationship of small vessel pathology (infarcts and white matter abnormalities) with high blood homocysteine and cognitive impairments while noticing the association of small vessel infarcts to elevated amyloid-beta-peptide degrading enzymes. Total cerebrovascular pathology, particularly small vessel infarcts and periventricular white matter hyperintensities was associated with elevated fasting Hcy which was inversely related to measures of executive cognitive function. Small vessel infarcts were related to elevated activities of amyloid-beta-peptide degrading enzyme activity. These observations of small vessel pathology in brain with high Hcy and cognitive impairment and now with beta-amyloid processing emphasize the importance of considering vascular elements of age-related dementia and even the relations of cerebrovascular and beta-amyloid pathogenesis in Alzheimer’s Dementia.
7. NUTRITION AND NEUROCOGNITION LAB: Homocysteine lowering with B-vitamin supplements and cognitive function in renal transplant recipients. There is a high prevalence of hyper-homocysteinemia in individuals with chronic kidney disease. Epidemiologic studies have shown that elevated plasma total homocysteine (tHcy) concentrations are associated with diminished cognitive function in the general population, and significantly increase the risk of cognitive impairment, cerebrovascular disease, stroke and dementia. In this study ARS-funded researchers at JMUSDA-HNRCA at Tufts University at Boston, Massachusetts assessed whether homocysteine-lowering B-vitamin therapy would prevent cognitive decline in kidney-transplant patients with hyper-homocysteinemia in both a North American and a Brazilian cohort. Almost none of the participants in either the high-dose-B-vitamin or control groups were B-vitamin deficient prior to intervention. Our results showed that while cognitive impairment was common, elevated tHcy was not associated with the degree of this impairment. Treatment with high-doses of Bvitamins was efficacious in lowering tHcy levels, but had modest and inconsistent effects on cognitive function, mostly in the executive function domain. While it’s possible that chronically high tHcy is a risk factor for cognitive impairment in this group, it may be that damage from long-term exposure cannot be reversed. It is also possible that individuals with poorer nutritional status would benefit more from B-vitamin supplementation.
8. NUTRITION AND NEUROCOGNITION LAB: Non-invasive assessment of age-related changes in cerebral tissue perfusion and vasoconstriction using Near Infrared Spectroscopy (NIRS) approach in animals. Age remains the strongest risk factor for developing cognitive decline and dementia. Since structural and functional disturbances in brain vasculature are prevalent in dementia, these vascular changes have been suggested to contribute to the development of and affect the severity of age-related neurodegeneration and cognitive decline. A Near Infrared Spectoscopy (NIRS) technique has been developed by ARS-funded researchers at JMUSDA-HNRCA at Tufts University at Boston, Massachusetts in order to measure non-invasively the amount cerebral blood volume. In order to assess the effect of age on cerebral tissue perfusion and vascular stiffness, we have measured cerebral blood volume and vasomotor reactivity on WKY rats during a year time frame, using NIRS instrumentation. By longitudinally following the rats from young to middle-age, we were able to record a significant age-related decrease in cerebral blood volume, suggesting a reduction in tissue perfusion. Vasomotor reactivity, on the other hand, did not appear to be significantly affected by age, as seen by the similar extent of vasodilatation following hypercapnic challenge at both age. A comprehensive understanding of the factors affecting brain vascular health together with the ability to detect the first signs of dysfunction will allow better and quicker treatments to age-related cognitive disorders.
9. NUTRITION AND NEUROCOGNITION LAB: Long-term hypertension affects cerebral vasomotor reactivity but does not aggravate age-related decrease in tissue perfusion in rats. Vascular dementia has been suggested to be a long-term complication of hypertension. The reported changes in vascular morphology due to hypertension share many common features with those seen in age-related neurodegenerative disorders such as Alzheimer’s disease. ARS-funded researchers at JMUSDA-HNRCA at Tufts University at Boston, Massachusetts therefore hypothesized that hypertension drives a general decrease in blood supply to brain tissue and a reduction in vascular elasticity. We therefore submitted Spontaneous Hypertensive rats (SHRs) to NIRS at a young age (4 months), and then followed-up a year later at middle-age (16 months). Decreased cerebral blood volume was recorded in middle-aged hypertensive rats, but the magnitude of decrease occurring between young to middle-age appeared similar to the one seen in WKY (normotensive) strain (study described above). Therefore hypertension itself did not appear to aggravate the impact of age on cerebral tissue perfusion. On the other hand, the vasodilatory capacity (represented through the response to a hypercapnic challenge) appeared greatly reduced in the hypertensive animals from a young age and was further reduced at middle-age. These results emphasize the detrimental effect of hypertension, already apparent at the early stages of the disease.
10. NUTRITION AND NEUROCOGNITION LAB: Long-term folate deficiency and homocysteine findings. Long-term dietary vitamin B-induced deficiency results in hyperhomocysteinemia and dysregulation of choline metabolism in double transgenic mouse model of Alzheimer’s disease. ARS-funded researchers at JMUSDA-HNRCA at Tufts University at Boston, Massachusetts evaluated the impact of B-vitamin deficiency on behavior, Alzheimer’s disease-related pathology and choline metabolism in the brain regions of double transgenic mice. It was found that long-term dietary vitamin B deficiency resulted in hyperhomocysteinemia, diminished levels of choline-containing lipids in the cortex but not in the hippocampus. The size of the plaques was also significantly larger in the cortex of vitamin B deficient mice as compared to those in the control group; and it was negatively correlated with the cortical choline-containing lipids. Study results also showed that vitamin B deficiency significantly affected behavior controlled by the cortex whereas behavior controlled by the hippocampus was not affected. These findings are important because they reveal that the effects of long-term vitamin B deficiency on Alzheimer’s disease-related pathology are brain region-specific and mediated through dysregulation of choline-containing lipid metabolism.
Carey, A.N., Fisher, D.R., Joseph, J.J., Shukitt Hale, B. 2013. The ability of walnut extract and fatty acids to protect against the deleterious effects of oxidative stress and inflammation in hippocampal cells. Nutritional Neuroscience. 16(1):13-20.