AMES, Iowa --
Research by an Iowa State University scientist suggests
that cholesterol-reducing drugs known as statins may lessen brain function.
Yeon-Kyun Shin, a biophysics professor in the department of
biochemistry, biophysics and molecular biology, says the results of his
study show that drugs that inhibit the liver from making cholesterol may
also keep the brain from making cholesterol, which is vital to efficient
brain function.
"If you deprive cholesterol from the brain, then you directly affect the
machinery that triggers the release of neurotransmitters," said Shin.
"Neurotransmitters affect the data-processing and memory functions. In
other words -- how smart you are and how well you remember things."
Shin's findings will be published in this month's edition of the journal
Proceedings of the National Academy of Sciences of the United States of
America.
Cholesterol is one of the building blocks of cells and is made in the
liver. Low-density lipoprotein (LDL) -- often referred to as bad
cholesterol -- is cholesterol in the bloodstream from the liver on the
way to cells in the body. High-density lipoprotein (HDL) -- so-called
good cholesterol -- is cholesterol being removed from cells. Too much
LDL going to cells and not enough being removed can lead to cholesterol
deposits and hardening of the cells.
"If you have too much cholesterol, your internal machinery is not going
to be able to take away enough cholesterol from the cells," said Shin.
"Then cells harden and you can get these deposits."
Cholesterol-reducing statin drugs are helpful because they keep the
liver from synthesizing cholesterol so less of the substance is carried
to the cells. This lowers LDL cholesterol.
It is the function of reducing the synthesis of cholesterol that Shin's
study shows may also harm brain function.
"If you try to lower the cholesterol by taking medicine that is
attacking the machinery of cholesterol synthesis in the liver, that
medicine goes to the brain too. And then it reduces the synthesis of
cholesterol which is necessary in the brain," said Shin.
In his experiments, Shin tested the activity of the
neurotransmitter-release machinery from brain cells without cholesterol
present and measured how well the machinery functioned. He then included
cholesterol in the system and again measured the protein function.
Cholesterol increased protein function by five times.
"Our study shows there is a direct link between cholesterol and the
neurotransmitter release," said Shin. "And we know exactly the molecular
mechanics of what happens in the cells. Cholesterol changes the shape of
the protein to stimulate thinking and memory."
While reducing the cholesterol in the brain may make you have less
memory and cognitive skills, more cholesterol in the blood does not make
people smarter. Because cholesterol in the blood cannot get across the
blood brain barrier, there is no connection to the amount of cholesterol
a person eats and brain function.
Shin says that for many people taking cholesterol-lower statins can be
very healthful and they should listen to their doctor when taking
medication.
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