Good HDL cholesterol may keep Alzheimer's away: study

Having good cholesterol or high-density lipoprotein (HDL) in the body is essential to health as it may protect the brain and keep Alzheimer’s disease at bay, according to a recent study.

Researchers from University of Southern California’s (USC) Keck School of Medicine have discovered that a higher number of tiny HDL particles in spine fluid samples was linked to two critical markers that the particles may protect against Alzheimer’s disease.

Alzheimer’s, a debilitating condition that primarily affects older adults, who become forgetful and 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.

“This study represents the first time that small HDL particles in the brain have been counted,” said study co-author Dr. Hussein Yassine, an associate professor of medicine and neurology at the Keck School of Medicine in Los Angeles.

Researchers analysed concentrations of HDL, referred to as “good cholesterol”, in the cerebrospinal fluid of 180 healthy volunteers with an average age of nearly 77.

The study linked a higher number of small HDL particles in cerebrospinal fluid with two key indicators that they might protect against Alzheimer’s.

One indicator is better performance on tests of memory and thinking (or “cognitive”) skills.

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Of the 141 participants who completed a series of these cognitive tests, those with higher levels of small HDL particles in their cerebrospinal fluid had better scores.

The result was independent of age, sex, education or whether they carried the APOE4 gene, which boosts Alzheimer’s risk, the researchers said.

The link was even stronger among those who had no cognitive impairment, the findings showed.

The other indicator of a protective effect is that people with higher levels of small HDL particles also had higher levels of a peptide called amyloid beta 42 in their cerebrospinal fluid.

Even though the peptide contributes to Alzheimer’s disease when it mis-folds and clumps onto neurons, a higher level of it circulating around the brain and spine has been linked to a lower risk for the disease, according to the report published online recently in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

The result suggests that small HDL particles may point the way to treatment for early Alzheimer’s, long before mental decline occurs.

“They may be involved with the clearance and excretion of the peptides that form the amyloid plaques we see in Alzheimer’s disease, so we speculate that there could be a role for these small HDL particles in prevention,” Yassine said in a university news release.

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“Before the onset of mental impairment, these small HDL particles are lubricating the system and keeping it healthy”, he explained.

“You’ve got a time to intervene with exercise, drugs or whatever else to keep brain cells healthy,” Yassine said.

“We still need to understand the mechanisms that promote the production of these particles, in order to make drugs that increase small HDL in the brain.”