6 Exercise Induced Growth Factor Increases Directly and Indirectly Reduce Systemic Vascular Risk Parameters: Translational Project Amongst Midlife Human and Animal Models of Preclinical Alzheimer’s disease and Vascular Dementia

Abstract

Objective:

Using a humanized APOE3/4 (Alzheimer’s disease genetic risk allele) mouse model we investigated the potential modulating effects of exercise on systemic risk factors and the ability of this mouse model to translate to active or sedentary, midlife, human participants. We present preliminary results of an ongoing, translational pilot study.

Participants and Methods:

26 Midlife individuals, ages 40-65, were recruited from the community and dichotomized into active or sedentary groups following health screening and cognitive assessment. Blood samples were drawn from human participants for lipid assessment and other general health measures as well as peripheral growth factors concentrations (VEGF, BDNF and FGF21). Traditional, transgenic mouse models have helped the scientific community to understand biological mechanisms of Alzheimer’s disease (AD), but they do not develop significant neuronal loss, a hallmark of AD pathology. The MODEL-AD consortium has created a new “humanized” APOE4 model that has the human APOE4 allelic sequence in place of the mouse APOE gene; the model has shown known human phenotypes including deficits in cholesterol trafficking, amyloid clearance and BBB integrity. Of upmost importance, this model does not develop a full AD phenotype indicating that additional genetics and/or environmental factors are required as would be seen in human populations. We used males and females of this model to complete identical sedentary and active measures of each APOE genotype.

Results:

Lipid and general health marker assessment between mouse and human were similar and reproduced published literature. In both humans and mice we saw increased total cholesterol and HDL in active females and decreased total cholesterol and HDL in active males. We also saw similar relationships between APOE genotype, sex, and activity with regards to triglycerides. Although total cholesterol, HDL and LDL measures are the primary lipids needed to confirm or deny translation, other lipid measurements were not equivalent between the two models. Growth factor assessment in both species are also similar and reproduce published literature with regards to VEGF and BDNF as we see trending elevated levels in the active group. Less published on is the finding seen between active females and these elevated growth factors levels; our results indicates that although elevated as a result of exercise, this increase may be more prominent in females.

Conclusions:

Based on the results found here we conclude that The Jackson Laboratory’s humanized APOE3/4 mouse model is a translatable model of vascular dysfunction, dementia and Alzheimer’s disease. We also conclude that exercise modulates these aspects by growth factor activation and increases resulting in downstream effects that reduce peripheral vascular risk factors and therefore reduce the risk of Alzheimer’s disease as a result of neuroinflammation. Complete, APOE genotype results from human participants are still ongoing. Descriptive analysis is limited by human samples size.