Project description:Vitamin D is an important calcium-regulating hormone with diverse functions in numerous tissues including the brain. Increasing evidence suggests that vitamin D may play a role in maintaining cognitive function and that vitamin D deficiency may accelerate age-related cognitive decline. Using aging rodents, we attempted to model the range of human serum vitamin D levels, from deficient to sufficient, to test whether vitamin D could preserve or improve cognitive function with aging. For 5-6 months, middle-aged F344 rats were fed diets containing low, medium (typical amount) or high vitamin D3 (100, 1000 or 10,000 IU/kg diet, respectively) and then hippocampal-dependent learning and memory were tested in the Morris water maze. Rats on high vitamin D achieved the highest blood levels (in the sufficient range) and significantly outperformed low and medium groups on maze reversal, a particularly challenging task that detects more subtle changes in memory. In addition to calcium-related processes, hippocampal gene expression microarrays identified pathways pertaining to synaptic transmission, cell communication and G-protein function as being up-regulated with high vitamin D. Basal synaptic transmission also was enhanced corroborating observed effects on gene expression and learning and memory. Our studies demonstrate a causal relationship between vitamin D status and cognitive function and suggest that vitamin D-mediated changes in hippocampal gene expression may improve the likelihood of successful brain aging.
Project description:Vitamin D is an important calcium-regulating hormone with diverse functions in numerous tissues including the brain. Increasing evidence suggests that vitamin D may play a role in maintaining cognitive function and that vitamin D deficiency may accelerate age-related cognitive decline. Using aging rodents, we attempted to model the range of human serum vitamin D levels, from deficient to sufficient, to test whether vitamin D could preserve or improve cognitive function with aging. For 5-6 months, middle-aged F344 rats were fed diets containing low, medium (typical amount) or high vitamin D3 (100, 1000 or 10,000 IU/kg diet, respectively) and then hippocampal-dependent learning and memory were tested in the Morris water maze. Rats on high vitamin D achieved the highest blood levels (in the sufficient range) and significantly outperformed low and medium groups on maze reversal, a particularly challenging task that detects more subtle changes in memory. In addition to calcium-related processes, hippocampal gene expression microarrays identified pathways pertaining to synaptic transmission, cell communication and G-protein function as being up-regulated with high vitamin D. Basal synaptic transmission also was enhanced corroborating observed effects on gene expression and learning and memory. Our studies demonstrate a causal relationship between vitamin D status and cognitive function and suggest that vitamin D-mediated changes in hippocampal gene expression may improve the likelihood of successful brain aging. Sixty, middle-aged male F344 rats were divided into three groups, each receiving for 5-6 months a different dietary amount of cholecalciferol (vitamin D3; VitD3). Purified AIN-93G (Harlan-Teklad) diet was modified to contain low, medium or high VitD3 (IU/kg diet): High = 10,000, Standard (Control) = 1000; Low = 100. Animal weight and amount of food consumed was recorded 2-3 times/week. Serum levels of 25-hydroxy vitamin D were determined using liquid chromatography/tandem mass spectrometry (ZRT Laboratory). Hippocampal RNA was isolated, quantified and checked for RNA integrity. One low VitD3 sample failed RNA quality control. Remaining RNA samples were applied to Affymetrix Rat Gene 1.0 ST arrays (one array/subject). Pre-statistical filtering removed poorly annotated probe sets, low intensity signals, and outlier values (>2SD of the group mean). Filtered data were analyzed by 1-way ANOVA to identify significant differences and the False Discovery Rate (FDR) procedure was used to estimate the error of multiple testing. FDR was compared at 0.31 and 0.17. Significant genes were assigned to one of four idealized expression patterns using Pearson’s test and separated by the sign of their correlation; relative gene expression values are provided on the log-2 scale. Functional categorization for significant genes was determined using DAVID bioinformatic tools. Please note that 'Marked' and 'Unmarked' (in the sample titles) refers to whether the rat had a mark on its tail. The rats were pair-housed and this is how two rats in one cage were distinguished.
Project description:The aim of this study was to identify alterations in hippocampal synaptic mRNA expression with aging and cognitive decline. Transcriptional profiling and subsequent bioinformatic analysis was performed to identify the most highly regulated pathways of genes. Interestingly, the antigen processing and presentation pathway was identified as the most highly regulated pathway with aging. Adult (12 month) and aged (28 month) Fischer 344 x Brown Norway (F1) hybrid rats were assessed for cognitive performance using the Morris water maze task and were divided into Adult (n=5), Aged Cognitively Intact (n=8), and Aged Cognitively Impaired (n=7) groups. One week following testing, all animals were sacrificed, the hippocampi were dissected, and synaptosomes were isolated for subsequent transcriptomic profiling. Only 5 cognitively intact animals were processed on the arrays.
Project description:Age-related cognitive decline is a serious health concern in our aging society. Decreased cognitive function observed during healthy brain aging is most likely caused by changes in brain connectivity and synaptic dysfunction in particular brain regions. Here we show that aged C57BL/6J wildtype mice have hippocampus-dependent spatial memory impairments. To identify the molecular mechanisms that are relevant to these memory deficits we investigated the temporal profile of mouse hippocampal synaptic proteome changes at 20, 40, 50, 60, 70, 80, 90 and 100 weeks of age. Extracellular matrix proteins were the only group of proteins that showed a robust and progressive upregulation over time. This was confirmed by immunoblotting and histochemical analysis, indicating that the increased levels of hippocampal extracellular matrix may limit synaptic plasticity as a potential cause of age-related cognitive decline. In addition, we observed that stochasticity in synaptic protein expression increased with age, in particular for proteins that were previously linked with various neurodegenerative diseases, whereas low variance in expression was observed for proteins that play a basal role in neuronal function and synaptic neurotransmission. Together, our findings show that both specific changes and increased variance in synaptic protein expression are associated with aging and may underlie reduced synaptic plasticity and impaired cognitive performance at old age.
Project description:Aging is associated with low-grade chronic systemic inflammation. Elevated peripheral serum cytokines and chemokines contribute to age-related diseases and correlate with cognitive decline. This study compared the effects of repeated lipopolysaccharide (LPS) treatment in young rats to age-related changes in hippocampal-dependent cognition, synaptic transmission, and transcription. Young (5-7 months) Fischer 344 X Brown Norway hybrid rats were injected intraperitoneally once a week for 6-7 weeks with either LPS (1 mg/kg) or vehicle. Older (14-16 months) rats received a similar injection schedule of vehicle. Older-vehicle animals and young-LPS rats exhibited impaired retention of spatial memory. Examination of the transcriptome of the CA1 and the dentate gyrus indicated that older-vehicle and young-LPS animals exhibited an increase in immune response genes. In contrast to aging, young-LPS animals exhibited an increased expression of genes related to the synapse. Even though young-LPS animals increased the expression of synaptic genes, LPS treatment reduced hippocampal CA3-CA1 total synaptic response and N-methyl-D-aspartate receptor (NMDAR)-mediated component of the synaptic response. Interestingly, the decrease in NMDAR function was not redox-sensitive. This study demonstrates that repeated exposure to LPS has long-term effects on hippocampal synaptic transmission and memory; however, young animals exhibited transcriptional recovery after LPS treatment. Recovery likely results from the acute nature of repeated LPS injections, relative to chronic systemic inflammation observed during aging.
Project description:The aim of this study was to identify alterations in hippocampal synaptic mRNA expression with aging and cognitive decline. Transcriptional profiling and subsequent bioinformatic analysis was performed to identify the most highly regulated pathways of genes. Interestingly, the antigen processing and presentation pathway was identified as the most highly regulated pathway with aging.
Project description:The current study employed next-generation RNA sequencing to examine gene expression related to brain aging and cognitive decline. Young and aged rats were trained on a spatial episodic memory task. Hippocampal regions CA1, CA3 and the dentate gyrus (DG) were isolated. Poly-A mRNA was examined using two different platforms, Illumina and Ion Proton. The Illumina platform was used to generate lists of genes that were differentially expressed across regions, ages, and in association with cognitive function. The gene lists were then retested using the Ion Proton platform. The results describe regional differences in gene expression and point to regional differences in vulnerability to aging. Aging was associated with increased expression of immune response related genes, particularly in the dentate gyrus. Finally, for the memory task used, impaired performance of aged animals was linked to the regulation of Ca2+ and synaptic function in region CA1.
Project description:Young blood or plasma and young bone marrow improves cognitive function in aged animals, though the cell type responsible for these regenerative effects remains unknown. This study evaluated the potential of induced pluripotent stem cell-derived mononuclear phagocytes (iMPs) as a therapeutic for age-associated cognitive and neural decline. Aging mice receiving intravenous delivery of iMPs for 3 weeks showed significant improvements in hippocampus dependent cognitive tasks and neural health markers, including increased levels of the synaptic transporter VGLUT1 and decreases in both astrogliosis and activated microglia. Proteomics on plasma and single nuclei RNA sequencing of the hippocampus identified several key aging specific pathways. iMP treatment of aging mice was able to reverse the increases in complement and amyloid pathway proteins, restore a lost subpopulation of hippocampal mossycells, and nearly eliminate a population of activated microglia. These findings suggest that iMPs provide a novel individualized therapeutic strategy to target age-related neural decline.
Project description:Repeated excessive alcohol consumption increases the risk of developing cognitive decline and dementia. Hazardous drinking among older adults further increases such vulnerabilities. In order to understand the molecular mechanisms underlying alcohol-induced cognitive deficits in older adults, we performed a chronic intermittent ethanol exposure paradigm (ethanol or water gavage every other day 10 times) in 8-week-old young adult and 70-week-old aged rats. While spatial memory retrieval ascertained by probe trials in the Morris water maze was not significantly different between ethanol-treated and water-treated rats in both age groups after the fifth and tenth gavages, behavioral flexibility was impaired in ethanol-treated rats than water-treated rats in the aged group but not in the young adult group. Further proteomic and phosphoproteomic analyses on their hippocampal tissues by tandem mass tag mass spectrometry revealed ethanol-treatment-associated proteomic and phosphoproteomic differences distinct to the aged rats, including the upregulations of Prkcd protein level, several of its phosphosites, and its kinase activity and the same aspects in Camk2a but downregulated, and were enriched in pathways involved in neurotransmission regulation, synaptic plasticity, neuronal apoptosis, and insulin receptor signaling. In conclusion, our behavioral and proteomic results added several candidate proteins and pathways potentially associated with alcohol-induced cognitive decline in aged adults.