Efforts to find disease-modifying treatments for Alzheimer’s disease (AD) have met with limited success in part because they have focused on identifying a specific pathogenic mechanism targeted by a specific drug. AD is a complex disease mechanistically associated with multiple pathways of aging so the probability of effectively targeting all of them would be greatly increased by using drugs in combination, each targeting different pathways. Previous studies have shown that a novel cocktail of the anti-aging FDA approved drugs rapamycin, acarbose and phenylbutyrate prevents age-related cognitive decline in mice by targeting distinct pathways of aging. These findings provided the rationale to test this drug cocktail for ability to alleviate cognitive impairment in a mouse model of AD. Transgenic 5xFAD male and female mice, with multiple mutant amyloid precursor proteins and expression of pathogenic Aβ42 peptide, were fed diet containing all 3 drugs, while control mice were fed a non-medicated diet. After 8 months of treatment, preliminary observations suggest 5xFAD mice fed the cocktail diet performed better in a spatial navigation learning task compared to mice fed the control diet. Laboratory procedures to confirm these observations will include rtPCR and immunohistochemistry to identify differences in expression of specific protein biomarkers of aging pathways in the brains of treated versus control mice. More work would be needed but observations from this study might be helpful in designing potential investigations to alleviate early phases of AD in patients using drugs already approved for human use.

The SirT6 gene is protective against systemic aging by enhancing DNA repair, decreasing inflammation and epigenetic deacetylation, and maintaining efficient lipid and glucose metabolism. Studies have shown that SirT6 function gradually decreases with increasing age with a loss in protective mechanisms. The role of SirT6 in brain aging has not been well established, and would be of interest to determine possible therapeutic targeting for conditions of age-related neurological dysfunction including cognitive impairment and dementia associated with Alzheimer’s disease. A mouse line was obtained from the NIH National Mouse Repository with genetic inactivation of one allele of the SirT6 gene (SirT6-/+) resulting in a partial loss of function. Older aged mice were tested in a spatial navigation learning task for exploratory behavior and memory. SirT6-/+ mice were unable to find escape holes as quickly as unaltered littermates (SirT6+/+) with a P-value of 0.003 significance. This observation suggests that partial absence of SirT6 function is associated with cognitive impairment. Following cognitive testing, mice were humanely euthanized, and brains collected and formalin fixed for immunohistochemistry staining to identify specific biomarkers of aging pathways including gamma H2AX for DNA damage response, HDAC-2 for epigenetic alterations, MCP-1 for inflammation, nitrotyrosine for oxidative stress, and p21 for senescence. Stains will be digitally imaged and heat maps generated for quantitative analysis of specific areas of brains from SirT6-/+ and SirT6+/+ mice. Results are expected to provide new knowledge on the role of aging pathways in the downregulation of SirT6 and age-related decline of learning and memory, and insight into possible conditions for development of more severe neurodegenerative diseases associated with dementia such as Alzheimer’s disease.

Biological age generally occurs earlier or later than chronological age and can be used as a biomarker for aging intervention studies. The rate of wound healing is known to decrease with increasing age, such that a simple skin wound might demonstrate overall aging of all organs and tissues of the body. This concept was tested in a mouse model of wound healing consisting of a 2 mm through and through ear biopsy. Cohorts of male and female C57BL/6 mice at 5, 13, and 21 months of age were biopsied, and the area of closure measured over 3 weeks. Ear biopsy cores were used to obtain DNA methylation signatures to a database of age-related signatures to compare biological age. The 5-month-old mice showed a higher percentage of wound healing than the 21-month-old mice 2.5 weeks following the biopsy with a p-value of 0.04. DNA methylation results used to calculate expected wound healing percentage correlated with measured healing percentage with an R2 value of 0.82. Additional validation of biological age will use a computational paradigm to assess severity of age-related lesions on an inter and intra-organ basis. Preliminary observations from this study indicate that a simple skin biopsy procedure can be used to predict biological age, with important translational implications for the treatment and prevention of aging and age-related diseases.

Alzheimer’s disease (AD) is a complex neurodegenerative condition that commonly affects aged populations; therefore, increasing resilience to aging may increase resilience to age-related diseases including AD. To test this concept, a preclinical mouse study was designed to investigate the effects of anti-aging drugs rapamycin, acarbose, and phenylbutyrate in combination (cocktail) previously shown to delay aging phenotypes in mice. Cohorts of C57BL/6 mice, 22 months of age and of both sexes, were fed standard chow containing the drug cocktail or standard control chow for two months. Mice were then given an intravenous injection of a neuronal-specific adeno-associated virus (AAV) vector consisting of Aβ and phosphorylated (p) tau, the major pathogenic components of AD, or AAV sham, and followed for another three months. Mice were then tested for cognitive function using a spatial navigation learning task. Overall, AD mice treated with the drug cocktail showed faster learning times, specifically in trial 2 for females (p<0.05) and trial 3 for males (p<0.05), compared to AD mice not receiving the drug cocktail. Following humane euthanasia, brain tissues will be assessed for Aβ and ptau neuropathology and pathways of aging using a combination of special stains and digital imaging to determine the cellular and molecular effects of the drug cocktail. The preliminary observation that the drug cocktail can prevent cognitive impairment associated with the early stages of AD suggests that targeting resilience to aging has potential translational implications for the early diagnosis and treatment of AD in human patients. Future efforts will work to establish molecular evidence of these observations and validate results in additional models of AD.

Cognitive decline with increasing age is an aspect of growing old. Age-related cognitive impairment (ARCI) entails the early stages of decline and is extremely common, affecting millions of older people. However, little is known about why some people have ARCI and some are cognitively normal at older ages. A recently characterized mouse model of naturally occurring ARCI, showing a distribution of affected and non-affected animals similar to older humans, was used to interrogate brain samples for transcriptomic profiles generated by RNA sequencing (RNA-seq). Hippocampal brain samples were collected from 22-month-old male and female C57BL/6 mice with and without ARCI (as determined by a spatial navigation learning task). RNA-seq was done by the NovoGene UC Davis sequencing Center. Preliminary data show a stronger presence of pathways of neurodegeneration and oxidative phosphorylation in the hippocampus of mice with ARCI compared to mice without ARCI. Detailed computational analysis will be done to investigate gene-expression quantifications using sequencing pipelines aligning Differential Gene Expression, KEGG orthology pathways, and Star RNA-seq read mapper in order to more accurately identify unique transcriptomic profiles in the brains of mice with and without ARCI. These findings will help identify genetic pathways that could be therapeutically targeted to ameliorate and possibly reverse the effects of ARCI, and provide insight into internal brain factors responsible for an increased risk in developing more severe conditions of neurodegeneration and dementia such as Alzheimer’s disease.