Coronary Artery Disease Correlates with Reduced Myelin Integrity in the Brain
Myelin is a protein that forms an insulating sheath around the axons that connect neurons, enabling the effective transmission of nerve impulses. It is essential for the normal function of the nervous system and brain, and thus demyelinating diseases such as multiple sclerosis that cause extensive loss of myelin are particularly debilitating. A lesser but still significant loss of myelin integrity occurs with aging, and thus forms of therapy that encourage myelin formation that are under development as potential treatments for multiple sclerosis may eventually find more widespread use in the aging population. Myelin is maintained by a population of specialized cells called oligodendrocytes, and all aspects of aging that degrade cell function in the brain and nervous system thus contribute to a progressive loss of myelin integrity. The example here for cardiovascular disease is likely connected to a number of mechanisms, from reduced blood flow to the brain to the inflammation and high burden of cell and tissue damage that contributes to both cardiovascular and nervous system degeneration.
A new study applied a novel multivariate approach to brain assessment using 12 separate metrics. The researchers compared test results and MRI scans of 43 patients with coronary artery disease (CAD) to those of 36 healthy individuals. All participants were over age 50. The multivariate approach of bundling individual white matter metrics into one overarching metric provides advantages over past studies. It allows the researchers to simplify complex aspects of brain health into a single metric that can be compared to the same metric in healthy controls.
The researchers found that individuals with CAD had widespread structural changes in their white matter compared to their healthy counterparts. The changes were particularly noticeable in the parts of the brain fed by the middle cerebral artery and anterior cerebral artery. Both regions are key for cognitive and motor functions.
The researchers found that the changes were mainly linked to reduced myelin content - the fatty coating that insulates nerve fibers and allows signals to travel quickly through the brain. Myelin loss can slow communication between brain cells and is often an early sign of cognitive aging. Interestingly, participants with higher measures of myelin integrity performed better on tests of processing speed, a key aspect of thinking and attention. However, no significant differences were observed between groups in overall cognitive scores, suggesting that brain changes may precede noticeable symptoms.