Cholesterol linked to brain changes that cause Alzheimer's disease

Cholesterol linked to brain changes that cause Alzheimer's disease

High levels of unhealthy cholesterol may contribute towards one of the key signs of Alzheimer’s disease developing in the brain. Researchers have found patients with high levels of “bad” cholesterol in their blood tended to have more harmful tangles of protein inside their brain cells.


These tangles, known as beta amyloid plaques, are one of the main physical signs of Alzheimer’s disease and are thought to interfere with the way brain cells work. The findings add to the growing evidence that suggests poor diet and cholesterol may play a role in the development of Alzheimer’s disease.


The exact causes are still to be understood, but the latest study showed that high levels of low density lipoprotein, or bad cholesterol – which is typically found in red meat – led to more tangles in the brain.


However, the higher levels of “good” cholesterol – high density lipoprotein which can be obtained from foods such as nuts and olive oil – were found to have a potential protective effect that lowered beta amyloid plaques. Doctors already recommend people to reduce the amount of bad cholesterol and increase the good cholesterol they consume due to the effects these have on heart disease.


Professor Bruce Reed, a neurologist at the University of California who led the study, said: "Unhealthy patterns of cholesterol could be directly causing the higher levels of amyloid known to contribute to Alzheimer's, in the same way that such patterns promote heart disease. "Our study shows that both higher levels of good cholesterol and lower levels of bad cholesterol in the blood stream are associated with lower levels of amyloid plaque deposits in the brain.”


Excessive levels of bad cholesterol in the blood are already known to increase the risk of heart disease by causing blood vessels to narrow and harden. Good cholesterol, however, seems to protect against heart disease and are thought to help to clear these fatty deposits in blood vessels.


Previous studies have also linked high levels of cholesterol to Alzheimer’s disease, and earlier this year scientist proposed this may be due to the cholesterol causing cells to divide incorrectly. This may lead to a build-up of the harmful amyloid protein in brain cells that form tangles and so impair the way they work.


The latest study looked at 74 men and women who were more than 70 years old and examined their blood cholesterol levels. Their brains were also scanned using tracer chemicals that bind to amyloid plaques to examine.


Three of those taking part suffered from mild dementia, 38 had mild cognitive impairment and 33 had no memory problems at all. The researchers found that high levels of LDL and low levels of HDL were both associated with more amyloid in the brain while high levels of HDL seemed to be linked to lower number of plaques.


The findings are published in the journal JAMA Neurology. Professor Reed said the findings could lead to new ways of helping to reduce the development of Alzheimer’s in people who are at risk.


He said: "It also suggests a method of lowering amyloid levels in people who are middle aged, when such build-up is just starting.“If modifying cholesterol levels in the brain early in life turns out to reduce amyloid deposits late in life, we could potentially make a significant difference in reducing the prevalence of Alzheimer's, a goal of an enormous amount of research and drug development effort."


The researchers said that anyone with an LDL level above 100 milligrams per decilitre of blood and an HDL of less than 40 mg/dL appeared to be at greatest risk. Recent research has suggested that statins, the drugs taken by millions of patients to lower their cholesterol, could also help to reduce the risk of dementia by a third.


Dr Laura Phipps, from the British charity Alzheimer's Research UK, warned, however, that there was still insufficient evidence to recommend that cholesterol lowering drugs such as statins should be used to treat Alzheimer’s.


She said: "This study found an association between high cholesterol and levels of amyloid in the brain, which can be an early indicator of Alzheimer's. "While this study did not investigate the mechanism behind the link, the findings add to existing evidence that cholesterol could play a role in the Alzheimer's disease process.

“Despite this, clinical trials carried out to date have not provided evidence to recommend cholesterol-lowering statin treatment as a way to treat or prevent Alzheimer's. "Current evidence suggests the best way to keep our brain healthy is to eat a balanced diet, maintain a healthy weight, not smoke, exercise regularly and keep blood pressure and cholesterol in check.”

By Richard Gray

The Telegraph, 31st December, 2013 

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