Good' cholesterol may decrease risk of Alzheimer's

• Good cholesterol or high-density lipoprotein (HDL) is essential to health. Still, the impact of HDL on the brain is not fully understood.
• Alzheimer’s disease is a disorder that impacts people’s ability to think and function in everyday life. Researchers are still working on developing treatments and understanding the condition.
• A recent study suggests that higher levels of small high-density lipoproteins might decrease the risk for Alzheimer’s disease.

Alzheimer’s disease is a debilitating condition that primarily affects older adults. People who have it can become forgetful and become unable to carry out tasks of daily living. Currently, the disorder has no cure. Researchers are still trying to understand how the disease develops, how to prevent it, and how to best treat it.

A recent study published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association offers new insight. Researchers studied the connection between small HDLs or “good” cholesterol in the cerebrospinal fluid and the risk for Alzheimer’s disease. The results suggest that higher levels of small HDL were associated with a lower risk of developing Alzheimer’s disease.

What is “good” cholesterol?

Cholesterol is a substance that your body needs. For example, the body uses cholesterol to make certain hormones, properly digest food, and make new cells. The body makes cholesterol, but people can also get it from food sources.

As noted by the American Heart Association, cholesterol exists in the body in two primary forms: low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDLs can build up in the bloodstream and increase the risk of strokes and heart attacks, so it is essential for your LDL count not to be too high.

The body’s HDL or “good” cholesterol helps to carry cholesterol back to the liver so that the liver can break it down. But HDLs can impact other areas of health in ways researchers do not fully understand. For example, researchers are still trying to understand how HDL levels affect the brain. The study authors note that the HDL in the brain is slightly different from the HDL in the rest of the body.

What is Alzheimer’s disease?

Alzheimer’s disease is a disorder that impacts the brain, and it typically occurs in adults over the age of sixty. It impacts the brain’s nerves and is related to the buildup of specific proteins in the brain. Ultimately, the neurons in the brain die and lose their ability to communicate with other brain cells.

This damage causes people with Alzheimer’s disease to have memory, language, and decision-making problems. It can be debilitating, and those with Alzheimer’s disease often slowly lose their ability to function independently.

Research is ongoing about what causes Alzheimer’s disease and how we can best develop treatments.

Good cholesterol and Alzheimer’s disease

The study in question included 180 participants aged 60 or older. Participants engaged in the study through the University of Southern California (USC) Alzheimer Disease Research Center (ADRC) and the Huntington Memorial Research Institute (HMRI) Aging Program.

Researchers looked at participants’ cognitive functions through a variety of cognitive tests. They took cerebrospinal fluid (CSF), the fluid surrounding the brain and the spinal cord, and plasma samples from participants and isolated the DNA. Researchers tested for the APOE ε4 gene from the DNA, a potential risk factor for Alzheimer’s disease.

Researchers then examined the levels of small HDL particles in the CSF. They found that higher levels of the small HDL particles were associated with better cognitive function among participants. They found this result to be the same even after accounting for the APOE ε4 gene, age, sex, and amount of education.

Results of the study may lead to the development of new treatments for Alzheimer’s disease. Study author Hussein Yassine noted the following to Medical News Today:

The discovery of lipid particles (LDL, HDL) in [the] blood led to several advances in drug discovery for cardiovascular disease treatment and prevention. Here for the first time, we measure HDL particles in cerebrospinal fluid as a surrogate of brain HDL and find that greater levels of small HDL correlate with better performance on cognitive measures.

Now that we have this biomarker, our next step is to figure out what promotes the formation of these small HDL particles in the brain. Such new discoveries could then lead to a new list of medications in our fight against Alzheimer’s.

Study limitations and continued research

The study authors noted that their study had several limitations. First, it is difficult to identify which of these particles has the protective properties because there are many subtypes of the small HDLs. They acknowledge that more research is needed to understand the interactions and differences between the HDLs in the brain and those in general circulation.

Researchers further acknowledge that the study’s findings cannot be generalized, and the study does not show cause. Further research can look at whether HDL levels can predict the development of cognitive problems and if increasing HDL levels could help prevent Alzheimer’s disease. Researchers note that future studies could include more participants and have more long-term follow-ups.

The Alzheimer’s Association was optimistic about the study’s results. Percy Griffin, Ph.D., the Director of Scientific Engagement for the Alzheimer’s Association, noted the following to MNT:

This work is interesting and adds to the growing body of research examining different species in the cerebrospinal fluid. These findings on small high-density lipoprotein particles are intriguing and may inform the development of biomarkers that can help predict how quickly people will progress through Alzheimer’s disease. However, the sample size is pretty small and more research is needed.

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