2016 — 2018 |
Velazquez, Ramon Oddo, Salvatore (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Elucidating the Molecular Mechanisms Linking Maternal Choline Supplementation to Healthy Cognitive Aging @ Arizona State University
Part 1: Non-technical Description This project is supported under the SBE Postdoctoral Research Fellowships (SPRF) program. Age-related cognitive decline, hereafter referred to as cognitive aging, is a fact of life. To this end, structural and functional brain changes invariably lead to decreased cognitive functions even in otherwise healthy individuals. Although there is a large body of work on ways to reduce cognitive deficits associated with disease states, little is known about the mechanisms underlying cognitive aging. This is concerning given that life expectancy is increasing and cognitive aging leads to a deterioration of general health for the aging population. One option to reduce cognitive aging is the supplementation of the maternal diet with choline (MCS), an essential nutrient grouped with the vitamin B complex. Preliminary work has demonstrated that MCS leads to amelioration of cognitive aging. The primary goal of this postdoctoral project is to elucidate the underlying neural and molecular mechanisms linked to MCS benefits. Additionally, the PI plans to examine genetic targets within brain structures associated with memory formation to isolate genes that are differentially altered by MCS and aging. This will likely reveal various gene targets that will be the focus of future cognitive aging studies. Because choline is a non-toxic nutrient found in food and can be easily supplemented orally, the research team believes that any modifications to the recommended daily intake amount to reduce cognitive aging will be expedited. To this end, the results of this application may help establish new guidelines on how a diet regimen of MCS should be implemented in expecting women to reduce cognitive aging in their offspring. Data will be shared with both the scientific and general community through presentations at conferences and public forums.
Part 2: Technical Description The loss of cognitive function is a pervasive and often debilitating feature of the aging process. To this end, structural and functional brain changes invariably lead to decreased cognitive functions even in otherwise healthy individuals. Recent work has shown that supplementation of choline, an essential nutrient grouped with the vitamin B complex, in the maternal diet (MCS) reduces cognitive aging. However, the molecular mechanisms linked to MCS benefits remains elusive. Elevated homocysteine levels correlate with cognitive aging, and aberrant gene expression mediated by reduced DNA methylation may contribute to cognitive aging. Choline is the major dietary source of methyl groups for the conversion of homocysteine to methionine, and for the production of S-Adenosyl methionine (SAM). SAM is a key substrate for epigenetic mechanisms, such as DNA methylation. Therefore, we hypothesize that MCS may reduce cognitive aging deficits by (1) reducing the buildup of homocysteine levels, and (2) by altering fetal epigenetic mechanisms during development leading to functional improvements in late life. Herein, we will breed 2-month-old C57Bl/6 mice. One-third of the breeding pairs will be kept on a CTL diet (choline normal diet, with standard choline content of 1.1 g/kg choline chloride), while the remaining mice will be kept on a maternal choline supplemented (MCS) diet (5 g/kg choline chloride), from conception through postnatal day 21. The offspring will be kept on the same choline diet as the parents until weaning at postnatal day 21. Notably, a group of dams from the MCS groups will be injected every other day with a betaine-homocysteine S-methyltransferase blocker S-(ä-carboxybutyl)-DL-homocysteine (CBHcy) that prevents the choline-mediated decrease in homocysteine levels. Thus, we will be able to determine whether the benefits of MCS are directly linked to homocysteine levels. Mice will be tested behaviorally using a longitudinal and a cross sectional strategy at 2, 8, 15 and 18 months of age to collect data at multiple time points and control for re-test effects. Tissue will be processed to (1) examine dendritic spine number and morphology within the hippocampus and (2) to examine alterations of DNA methylation in the promoter region of neuronal dendritic morphology-related genes (Dlg4, Rac1, RhoA, Doc2b). We will complement this work by using an unbiased approach to identify genes that are differentially methylated by MCS. These experiments will be done exclusively in hippocampal CA1 neurons isolated by laser-capture microdissection. If successful, our results would dissect the underlying molecular mechanisms whereby choline supplementation reduces cognitive aging. Understanding MCS benefits at the behavioral, neural and molecular level may lead to a modification in the recommended amounts of choline required for pregnant mothers for optimal cognitive functioning and prevention of cognitive aging.
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2019 — 2021 |
Velazquez, Ramon |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Identify Common Mechanisms of Neurodegeneration Between Alzheimer's Disease and Down Syndrome @ Arizona State University-Tempe Campus
Growing evidence indicates that Alzheimer's disease (AD) starts decades before its clinical manifestation and that early clinical interventions are needed to effectively mitigate the progression of AD. However, the initial triggers in the cascade of pathological events leading to AD remain elusive. Virtually 100% of people with Down syndrome (DS) will show brain accumulation of amyloid-? (A?) and tau in their fifth decade of life. Despite these striking data, little is known about the processes linking DS to AD. We postulate that dissecting the molecular mechanisms driving AD pathology in DS patients will lead to a better understanding of the etiology of AD. Published work and our preliminary data indicate that the mammalian target of rapamycin (mTOR) is hyperactive in human and animal models of DS and AD. Further, we and others have shown that hyperactive mTOR signaling facilitates the accumulation of A? and tau. Together, these novel and exciting findings may answer a fundamental unresolved question: which event triggers the development of AD neuropathology in DS. The answer to this question will unveil mechanistic changes linked to the etiology of AD. The overall hypothesis of this application is that Dysfunctional TSC2 complex increases mTOR activity in DS, which in turn contributes to the development of AD-like neurodegeneration by inducing necroptosis. To this end, we propose three Aims. Aim 1 will test the hypothesis that dysfunctional TSC2 activity contributes to mTOR hyperactivity in DS. Specifically, we will use three complementary approaches to systematically dissect the molecular pathways leading to dysfunctional TSC2/mTOR axis in DS. These experiments will elucidate the signaling pathways leading to mTOR hyperactivity in DS, which is a critical step towards understanding the link between DS and AD. Specific Aim 2 will test the hypothesis that hyperactive mTOR signaling contributes to the development of AD pathology in DS. Specifically, we will use three complementary approaches: (1) we will test the effects of reducing neuronal mTOR activity on the development of AD-like phenotype in Ts65Dn mice; (2) we will determine whether further increasing neuronal mTOR signaling in Ts65Dn mice, prior to the increase in A? levels, exacerbates AD-like pathology and cognitive deficits; (3) we will use state-of-the-art isobaric tags for relative and absolute quantitation (iTRAQ) technology to identify proteins that are differentially regulated by mTOR hyperactivity in DS. These experiments will lead to a better understanding of the mechanistic relationship among DS, mTOR, and AD. Specific Aim 3 will test whether hyperactive mTOR contributes to neuronal death by activating necroptosis. The mechanisms that govern neuronal death in DS and AD remain poorly understood. Our preliminary data show that necroptosis, a programmed form of necrosis, contributes to neurodegeneration in AD and DS mouse models. We will use complementary experiments to modulate necroptotic signaling and mTOR activity in animals and primary neurons. These experiments will lead to a better understanding of the mechanism leading to cell loss in DS and AD and will identify new therapeutic targets for these two disorders.
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2020 — 2021 |
Velazquez, Ramon |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
S6k1 as a Novel Link Between Aging and Alzheimer's Disease @ Arizona State University-Tempe Campus
Abstract Aging is the primary risk factor for Alzheimer's disease (AD) and related disorders. Nevertheless, the mechanisms by which aging contributes to the onset of the disease remain elusive. In this application, we will attempt to identify critical signaling pathways that might link aging to AD pathogenesis. We focus on the ribosomal protein S6 kinase 1 (S6K1), a ubiquitously expressed protein with an established link to aging. For example, genetic deletion of the S6K1 gene in mice increases lifespan and decreases the incident of age- dependent motor dysfunction, insulin sensitivity, and obesity. A large body of evidence also points to S6K1 as playing a pivotal role in regulating astrocyte function during physiological and pathological conditions. For instance, reduction of S6K1 signaling reduces secretion of pro-inflammatory cytokines in activated astrocytes. We and others have shown that S6K1 activity is increased in postmortem human AD brains. In addition, we show that genetic reduction of S6K1 ameliorates amyloid-? and tau pathology and improves synaptic function and cognition in 3xTg-AD mice, a widely used animal model of AD. Mechanistically, we identified the Retinoblastoma- Binding Protein 7 (Rbbp7), a chromatin remodeling factor, as a possible link between S6K1 and tau. These novel and exciting findings led us to the following hypothesis: S6K1 represents a link between aging and AD. Specific Aim 1 will identify the relative contribution of astrocytic and neuronal S6K1 hyperactivity in AD. These experiments will lead to a better understanding of how S6K1 modulates cognition and neurodegeneration in AD. Given the role of S6K1 in aging, this research is a critical step toward unveiling the mechanisms linking aging and AD. Specific Aim 2 will identify the mechanistic link between S6K1 and AD. These experiments will elucidate the signaling pathways linking S6K1 to AD pathogenesis. In addition, if successful, the results obtained here will corroborate Rbbp7 as a novel molecular target for AD and other tauopathies. Specific Aim 3 will identify the role of S6K1 in the gene expression dysregulation observed in AD. The results of this Aim will provide a detailed S6K1 gene regulatory network in the context of aging and AD and identify an S6K1-mediated gene expression signature that is unique between aging and AD. Impact: This application will define the mechanistic links between S6K1 and AD. Furthermore, given the role of S6K1 signaling in aging, our results may unveil new mechanisms by which aging contributes to the development of AD. Elucidating these mechanisms will likely identify several novel putative therapeutic targets for AD.
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