Alzheimer’s and heart disease are two of the leading causes of death and affect hundreds of thousands of … [+]
Alzheimer’s and heart disease are two of the leading causes of death, affecting hundreds of thousands of individuals all over the world. Now, a growing variety of studies are finding that there could also be more connection between brain and heart health than first thought. At the interface between brain cells and blood vessels, the blood-brain barrier suffers damage with age that appears to contribute to a decline in cognitive function. In the newest episode of this series on Alzheimer’s disease, we discussed the role that insulin receptors within the blood-brain barrier may play in the event of Alzheimer’s. Here, we’ll dive deeper into the functions of the blood-brain barrier and have a look at how we may find a way to lengthen normal cognitive function in Alzheimer’s patients.
As we age, tiny lesions develop on the blood-brain barrier, increasing its permeability and impairing its function. Recent studies have found that increased blood-brain barrier dysfunction appears to occur early within the disease course, possibly before neurodegeneration, brain atrophy, and even cognitive symptoms. How this dysfunction contributes to Alzheimer’s disease was not well understood. A team from the Medical College of Georgia and collaborating institutions found that tiny lesions within the brain’s razor-thin microvascular vessels are related to changes in white matter that ultimately contribute to deterioration in cognitive functions and memory deficits.
What is white matter? Unlike gray matter, which is made up of nerve cell bodies, white matter is myelinated or encased axon fibers that allow for the rapid transmission of nerve impulses. White matter is important to brain health and the performance of on a regular basis functions similar to memory, problem solving, and coordination. Not surprisingly, clinical observations have shown that changes within the brain’s white matter during Alzheimer’s disease correlate with memory deficits and impaired cognition.
In an earlier report, the team found a link between white matter deficits and blood-brain barrier dysfunction. It appears that the presence of tiny lesions within the blood-brain barrier microvessels generates oxidative stress and inflammation. Subsequent MRI scans showed that the increased inflammation may contribute to changes within the brain’s white matter.
To understand how disruption of the blood-brain barrier causes white matter changes in Alzheimer’s, Bagi et al. studied the brains of 28 people over the age of 65. This cohort included each men and girls diagnosed with Alzheimer’s, with or without obvious microvascular damage, in addition to healthy controls. They took samples of white matter and cerebral vessels from the prefrontal cortex, an area of the brain that is especially vulnerable to degeneration in Alzheimer’s.
When first examined, researchers found that the cerebral blood vessels within the patients diagnosed with Alzheimer’s were significantly impaired. These blood vessels didn’t appear to dilate properly, even when exposed to strong dilating aspects. The ability of blood vessels to dilate is critical for controlling blood flow across the blood-brain barrier. Impaired dilation can’t only result in more inflammation and oxidative stress, but additionally puts blood vessels in danger for further lesions.
Bagi et al. also found that greater microvascular damage was related to greater white matter changes. To their surprise, this was accompanied by increased numbers of specific brain cells called astrocytes. As a key component of the blood-brain barrier, these supportive cells regulate the exchange of nutrients and waste products between the brain and blood. Researchers suspect that as microvascular dysfunction progresses in Alzheimer’s disease, astrocytes change, making them more reactive and inflammatory. The additional damage these cells inflict on the brain-brain barrier and neighboring cells makes the brain more vulnerable to cognitive changes.
Overall, this study provides further evidence that inflammation throughout the blood-brain barrier causes structural changes within the brain. Fortunately, unlike neurodegeneration, vascular inflammation will be influenced by weight-reduction plan and exercise. Dr. Zsolt Bagi, lead writer and a biologist on the Medical College of Georgia, wrote, “We hypothesize that by preventing the development of the microvascular component, Alzheimer’s patients can be given at least several years of normal functioning.” Understanding the connection between heart and brain health may sooner or later enable early detection of Alzheimer’s and other types of dementia through routine blood tests.
