Location: Jean Mayer Human Nutrition Research Center On Aging
2024 Annual Report
Objectives
Objective 1: Determine the effects of genetic, molecular and environmental influences on the aging brain, and the modifying impact of specific phytonutrients on neural cell function and behavior, including cognition.
Sub-Objective 1a: Characterize genetic and molecular signatures, especially pro-inflammatory markers, of normal adult brain stem/progenitor and differentiated cells, including neurons and microglia, in vitro and following the introduction of whole berry fruits and a combination phytonutrient: polymolecular botanical compound (PBC).
Sub-Objective 1b: Characterize genetic and molecular signatures of normal neural stem/progenitor and differentiated cells from Sub-Objective 1a in vivo following their grafting to the forebrains of immunocompromised mice, and subsequent feeding of the phytonutrients assayed in the in vitro model of Sub-Objective 1a.
Sub-Objective 1c: Characterize the genetic and molecular signatures, especially those associated with chronic inflammatory pathways, and the cognitive behavioral profile in aging models in rodents following feeding of phytonutrient compounds studied in Sub-Objectives 1a and b.
Sub-Objective 1d: Analyze biomarkers, especially those related to chronic inflammation and the cognitive behavioral profile, from liquid biopsies (e.g., serum) collected in human studies following phytonutrient supplementation with the candidate fruit and plant compounds studied in Sub-Objectives 1a-c.
Objective 2: Characterize in vitro and in vivo models that manifest aspects of human age-related neurological diseases, such as Parkinson’s and Alzheimer’s disease, for screening combinations of phytonutrient that can prevent or delay chronic inflammation and other deleterious micro-environmental conditions that contribute to cell degeneration in the neurodegenerative disorders.
Sub-Objective 2a: Characterize, in vitro, the genetic and molecular signatures, especially those associated with chronic inflammatory pathways, of stem/progenitor and differentiated neural and microglial cells (and exosomes isolated from them) isolated from patients with Parkinson’s Disease, following phytonutrient treatments studied in Objective 1.
Sub-Objective 2b: Characterize, in vivo, the genetic and molecular signatures (including mutant LRRK2-associated inflammation, stem cell and cell death/protection gene pathways) of cells, and exosomes derived from them, following xenotransplantation to the forebrain of immunocompromised mice and feeding of the phytonutrients studied in Objective 1.
Sub-Objective 2c: Characterize the genetic and molecular signatures of neural cells at-risk for abnormal functioning and cell death in transgenic mouse models of Parkinson’s disease, including behavioral studies, following feeding of candidate phytonutrient compounds studied in Objective 1.
Approach
As Americans are living longer, the incidence of age-related neurological disorders is a growing burden for older adults and the healthcare system. Our lab studies how plant-derived phytonutrients benefit the aging brain, especially in maintaining mobility and cognitive function and slowing the progression of neurological disease. Specifically, we look at the ways phytonutrients can counteract the changes in the aging brain that make it more susceptible to neurological disorders. We focus on the persistent activation of inflammatory pathways that reduce brain plasticity and, over time, contribute to destructive cellular changes which affect the nervous system’s functioning and ability to adapt to new experiences. We will analyze the anti-inflammatory properties of phytonutrient combinations and berries that contain numerous beneficial bioactives that target aging processes involving cellular communication and the propagation of disease. In vitro and in vivo bioassays utilizing human stem/progenitor cells and the brain’s innate immune cells, microglia, will be used to test combinations of phytonutrient components in normal aging and neuropathological models (i.e. Parkinson’s disease in the proposed studies here). Exosome microvesicles isolated from these assays are used as sensitive biomarkers for gene and protein expression patterns in interactive anti-inflammatory, neurogenic, and cell survival networks. Phytonutrient screening along with molecular and behavioral findings from cell culture, in vivo xenotransplantation, and human studies will establish phytonutrient effects that help counter neurodegeneration.
Progress Report
A. We established various in vitro cells assays and in vivo animal and human models to investigate how nutritional interventions alleviate age-related impairments in cognition through alterations in neuroinflammation, neurogenesis, and neuronal connectivity. Nutrient supplements such as polyphenol-rich berries, combination of Epigallocatechin-3-gallate (EGCG), curcumin, and sulforaphane-containing broccoli sprouts, myo-inositol, DHA, vitamin K, walnut oil, and green leafy vegetables all demonstrated protective effects on our models. These outcomes enhance our knowledge of certain nutritional interventions that may provide long-term benefits for the aging brain. Understanding the underlying mechanisms for preventing or mitigating cognitive decline in aging will lead to more precise and evidence-based recommendations on nutrient intakes among the aging population.
B. As part of Objective 1, we evaluated the beneficial effects of bioactive compounds in rodent models. In collaboration with researchers at North Carolina State, we assessed the association of blueberry metabolites with motor and cognitive alterations following continuous or intermittent wild blueberry supplementation in old rats. We used targeted metabolomics to analyze the bioavailability of polyphenolics and their metabolites in four different brain regions of aged rats fed one of three blueberry diets (continuous control, a continuous BB, or intermittent BB). We found that 50% of the metabolites we measured were found in the striatum, and these levels were higher in the intermittent-fed group compared to the control group.
C. In another study, we investigated the effect of vitamin K intake on cognition and potential biological pathways related to this effect in mice. We found that animals on the low dietary vitamin K (LVK) diet had impaired cognitive function. This impairment was associated with reduced hippocampal neurogenesis, and a loss of hippocampal synapses, especially among males. Further mechanistical investigation performed during this reporting period indicated that LVK intake may elevate neuroinflammation, which is closely associated with aging and neurodegeneration, and negatively impact hippocampal neurogenesis and synapses. Specifically, we compared the complexity of hippocampal microglia in mice fed control diet or LVK diet. Our data indicated that the total number of branches and endpoints of branches, as well as the length of primary processes (branches that originate from the cell body) were all significantly lower in microglia from LVK diet-fed mice. Decreased complexity and length are characteristic of activated microglia, suggesting increased neuroinflammation in LVK mice. This increased neuroinflammation may contribute to the LVK-induced cognitive decline.
D. We completed a multi-center, double-blind, placebo-controlled, crossover study in older (55–70-year-old), overweight/obese (BMI 27-35) adults to study the effects of acute raspberry intake on the relationship between enhanced metabolic control and cognitive and psychomotor function. This project is in collaboration with Illinois Institute of Technology (ITT) in Chicago. We found that red raspberries improve cognition by restoring meal-induced metabolic/inflammatory balance via supplementation with red raspberries. For this reporting period, we showed that microglia treated with serum from participants who consumed raspberry demonstrated reduced LPS-induced neuroinflammation on expression of inflammatory markers, compared to cells treated with serum from participants who consumed a placebo, at both 2 and 6 hours. These changes in protection aligned with the biphasic increase in plasma concentrations of phenolic acid metabolites, with some peaking at 1–2 hours and others at 6 hours. We have finished data analyses and are currently writing these results for publication.
E. As part of Objective 2, we evaluated beneficial effects of bioactive compounds using established in vitro assays of adult human neuronal progenitor cells (AHNPs) derived from hippocampus, rodent/human primary neurons, and microglial cell lines. Our data indicated that treatments of myo-Inositol and omega-3 fatty acid docosahexaenoic acid (DHA), as well as menaquinone-4 (the main vitamin K metabolite in the brain), have protective effects on the survival and proliferation of the human hippocampal AHNPs and rodent microglial cells, especially under stressed conditions. Myo-inositol in combination with DHA also improved synapse maturation of human neurons. Potential underlying mechanisms of these effects are under investigation. Our data suggest that the protective effects of these bioactive compounds may be related to their anti-inflammatory and antioxidant properties as they are able to decrease the expression levels of certain oxidative stress and inflammation markers induced by cellular stress. Similar outcomes were also identified with AHNPs derived from midbrain or substantia nigra of Parkinson’s disease patients. Additionally, with the established rodent microglia models, we studied the mechanisms behind the protective effects of kale and elderberry, and their main flavonoid components, by assessing their ability to reduce inflammatory stress signaling. We found that the whole foods were more beneficial than the single nutrients, suggesting that different compounds may work synergistically to produce their beneficial effects. Investigating additional mechanisms will be a focus in our future studies.
Accomplishments
Review Publications
Cahoon, D., Rabin, B., Fisher, D.R., Shukitt Hale, B. 2023. Effects of HZE particle exposure location and energy on brain inflammation and oxidative stress in rats. Radiation Research. 200(5):431-443. https://doi.org/10.1667/RADE-22-00041.1.
Cahoon, D., Fisher, D.R., Rabin, B.M., Lamon-Fava, S., Wu, D., Zheng, T., Shukitt Hale, B. 2024. Galactic cosmic ray particle exposure does not increase inflammation or oxidative stress in rat microglial cells in vitro. International Journal of Molecular Sciences. 25(11):5923. https://doi.org/10.3390/ijms25115923.