Chronic inflammation, which is the long-term activation of the immune system is thought to be a risk factor for Alzheimer’s Disease (AD) and may even accelerate the disease progression. Scientists have long known that AD-related pathology develops long before clinical symptoms of AD appear, and inflammation is an underlying component of the disease.
Previous studies have shown that elevations in inflammatory markers may be present decades before any AD symptoms appear. However, what was unclear was whether peripheral inflammation (markers of inflammation in the blood) was related to brain inflammation (CNS inflammation). Researchers wanted to know whether markers of inflammation in blood (peripheral inflammation) reflected inflammation of the central nervous system. This association, if true, would be important as inflammation-associated brain abnormalities including but not limited to AD, could be predicted by looking at the inflammation markers in a blood sample.
An association between inflammation biomarkers in both blood plasma and cerebrospinal fluid (CSF) and markers of AD-associated pathology has been found by researchers at the University of Colorado Anschutz Medical Campus working with the University of Wisconsin Alzheimer’s Disease Research Center and the University of California San Francisco Memory and Aging Center. The new study* sheds light on the pathology of AD as well as on the communication between the brain and the rest of the body via the inflammation markers. The researchers tested blood and CSF samples from 173 middle-aged and older adults for various markers of inflammation. Participants were healthy adults in that they had no clinical symptoms of AD, although some had family histories of AD-associated dementia. The results suggested that although CSF markers of inflammation are strong predictors of brain abnormalities, in this case both plasma and CSF markers of inflammation independently relayed information about AD-related pathology and neuronal damage in head-to-head comparisons suggesting that there is close cross-talk between the brain and body. The presence of inflammation markers in the blood clearly indicated what was going on inside the brain suggesting the possibility of having a blood test to detect inflammation biomarkers years before symptoms of AD appear.
Although the presence of these markers alone does not indicate a diagnosis of AD nor does it mean that the subjects will develop AD in the future, the data add to a growing body of literature underscoring an important relationship between peripheral inflammation, central inflammation, and pathological outcomes of AD.
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*Bettcher, B.M., Johnson, S.C., Fitch, R., Casaletto, K.B., Heffernan, K.S., Asthana, S., Zetterberg, H., Blennow, K., Carlsson, C.M., Neuhaus, J., Bendlin, B.B., & Kramer, J.H. (2018). Cerebrospinal fluid and plasma levels of inflammation differentially relate to CNS markers of Alzheimer’s disease pathology and neuronal damage. Journal of Alzheimer’s Disease, 62(1). DOI 10.3233/JAD-170602