Clues to Why Drinking Can Protect Heart
Alcohol ‘Preconditions’ Laboratory Guinea Pigs
By Charles Petit, Chronicle Science Writer
SF Chronicle Copywrite
San Francisco scientists are reporting today the first solid clues —
gleaned from feeding alcohol to guinea pigs — to why moderate drinking
reduces the risk of heart attacks.
For years, doctors have reported evidence that people who have one or
two drinks a day reduce their chance of heart attacks by as much as a
third, and significantly reduce the severity of heart attacks that do
occur.
Heavier drinking leads to increased risk of heart disease as well as
liver problems.
“It’s a U-shaped risk distribution,” said Dr. Vincent Figueredo, a
cardiologist at San Francisco General Hospital and assistant professor of
medicine at the University of California at San Francisco. “Alcoholics,
and people who don’t drink at all, are worse off than people who
regularly drink a little.”
Figueredo is the lead author of a study published today in the journal
Proceedings of the National Academy of Sciences. It reports experiments
that he, post-doctoral fellow Masami Mayamae, and three other colleagues
performed on the hearts of laboratory guinea pigs to try to find out what
alcohol does to allay heart attacks.
Alcohol, the scientists concluded, serves to “precondition” the
animals’ heart muscle to withstand a heart attack.
Its effect is identical to that of established laboratory methods used
to toughen the hearts of lab animals against severe loss of oxygen. Such
preconditioning is done by subjecting the animals’ hearts to brief, but
harmless episodes of low oxygen. Then, when the equivalent of a full
heart attack is caused in such preconditioned animals, their survival
goes up dramatically.
The new study of the hearts of guinea pigs revealed that alcohol
increases levels of a natural substance called adenosine in the fluids
surrounding the heart muscle cells. Adenosine is critically important to
a cell’s use of energy it gets from nutrients in the blood. Muscle cells
also release large quantities of adenosine when they are cut off from
oxygen, as in a heart attack.
Now, it looks as though alcohol causes heart muscles to prepare for an
emergency in somewhat the same way as does a sudden drop in oxygen
levels. So, if a heart attack occurs, with its prolonged lack of oxygen
to parts of the heart, muscle cells there have already begun to get ready
for hard times. “Maybe there is something about adenosine that causes the
heart muscle to start hoarding energy,” Figueredo said.
The next step toward helping hearts to protect themselves is to look
for medications that might cause the same effect on adenosine levels and
on the substances in the cells that react to adenosine — but without the
side effects of alcohol. In addition, further research is needed to learn
exactly what changes occur inside a cell in response to higher levels of
adenosine.
“The bottom line is that if you consume alcohol on a regular basis in
moderation, you are more likely to survive a heart attack,” Figueredo
said. “What this paper is doing is to suggest a mechanism.” Turning that
mechanism into a useful medical procedure — other than to recommend
light drinking for people at risk of heart disease and with no history of
alcoholism — may take several years.
