Upregulation of Aβ42 in the Brain and Bodily Fluids of Rhesus Monkeys with Aging

The cerebral accumulation of amyloid beta (A beta) is one of the key pathological hallmarks of Alzheimer's disease (AD). A beta is also found in bodily fluids such as the cerebrospinal fluid (CSF) and plasma. However, the significance of A beta accumulation in the brain and different bodily pools, as well as its correlation with aging and cerebral amyloid pathology, is not completely understood. To better understand this question, we selected the rhesus monkey, which is phylogenetically and physiologically highly similar to the human, as a model to study. We quantified the levels of the two main A beta isoforms (A beta 42 and A beta 40) in different sections of the brain (frontal cortex, temporal cortex, and hippocampus) and bodily fluids (CSF and plasma) of rhesus monkeys at different developmental phases (young, 5-9 years of age; mature, 10-19 years of age; and old, 21-24 years of age). We found that the levels of neuronal and insoluble A beta 42 increased significantly in the brain with aging, suggesting that this specific isoform might be directly involved in aging and AD-like pathophysiology. There was no significant change in the A beta 40 level in the brain with aging. In addition, the A beta 42 level, but not the A beta 40 level, in both the CSF and plasma increased with aging. We also identified a positive correlation between A beta 42 in the CSF and plasma and A beta 42 in the brain. Taken collectively, our results indicate that there is an association between A beta accumulation and age. These results support the increased incidence of AD with aging.