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ลำดับตอนที่ #64 : 'Good' cholesterol not always good, study suggests
http://www.bbc.com/news/health-35775318
Some
people with high levels of supposedly "good" cholesterol are at much
greater risk of heart disease, a study suggests.
A
bloodstream tussle
takes place between "bad" cholesterol dumping fatty material in the
arteries and good cholesterol taking it away.
But a Cambridge University study in the journal Science showed more good
cholesterol was not always better.
It
is thought the findings may help find new ways to protect the heart.
Eating
olive oil, fish and nuts raises levels of high-density lipoprotein (HDL) - which is more commonly
known as good cholesterol.
It
is one of the things doctors test for when predicting your risk of a heart
attack.
However, repeated trials that raise HDL with drugs have flopped, leading doctors to think something
else is going on.
Rare mutation
Some
insight has come
from studying rare mutations that leave people with high levels of good
cholesterol.
Trials
showed people with a mutation in a gene called SCARB1, which affects
one-in-1,700 people, had very high levels of good cholesterol.
But
they also had an 80% increased risk of heart disease - that is roughly the same
increased risk as for smoking.
Further
experiments showed the mutation was preventing HDL from dumping the fat it had
collected in the liver for processing.
Prof
Adam Butterworth, one of the researchers from the University of Cambridge, told
the BBC News website: "This is significant because we had always believed
that good cholesterol is associated with a lower risk of heart disease.
"This
is one of the first studies to show that some people that have high levels of
'good' cholesterol actually have a higher risk of heart disease so it
challenges our conventional wisdom about whether 'good' cholesterol is
protecting people from heart disease or not."
There
have been huge efforts put into drugs to raise HDL in the hope they have the
same impact as statins,
which lower the bad cholesterol.
Prof
Butterworth warned that drugs aimed simply at "trying to raise HDL may not
be that useful".
He
said the size of different HDL particles or how good they are at transporting
may be more important than the overall levels.
And
that may be a more productive avenue of research.
While
the researchers have questioned the importance of boosting levels of HDL
cholesterol, they insist it still remains a valuable tool for predicting the
risk of a heart attack.
Although fellow researcher Dr Daniel Rader, from the University
of Pennsylvania, added: "Eventually we may want to perform genetic testing
in persons with high HDL to make sure they don't have mutations, like this one,
that raise HDL but don't protect against, or may even increase, risk for heart
disease."
Dr Tim Chico, a consultant cardiologist based at the University
of Sheffield, said: "This important study adds to other results showing it
isn't as simple as good and bad.
"It is worth noting that exercise both increases HDL and
reduces the risk of heart disease.
"These results suggest that the beneficial effect of
exercise is probably not caused by higher HDL levels, although more research is
needed to fully understand the complex relationship between HDL and risk of
heart disease."
Prof Peter Weissberg, the medical director at the British Heart
Foundation, said: "This is an important study that sheds light on one of the major puzzles
relating to cholesterol and heart disease.
"These new findings suggest that the way in which HDL is
handled by the body is more important in determining risk of a heart attack than the levels
of HDL in the blood.
"Only by understanding the underlying biology that links
HDL-C with heart attacks can we develop new treatments to prevent them."
tussle (v.)
to have difficult disagreements or strong arguments
(FIGHT)to fight with another person using your arms and body:
density (n.)
the number of people or things in a placewhen compared with the size of the place:
the relationship between the mass of a substance and its size:
flop
(v.)
If
a book, play, film, etc. flops, it is not successful:
(n.)
a failure:
insight (n.)
(the ability to have) a clear, deep, and sometimes suddenunderstanding of a complicated problem or situation:
Statins (n.)
a drug that reduces the level of cholesterol (= a substancecontaining fat in your blood that can cause heart disease)
avenue (n.)
a method or way of doing something:
sheds (v.)
(often used in newspapers) to get rid of something you do not need or want:
to lose a covering, such as leaves, hair, or skin, because it falls off naturally,
or to drop something in a natural way or by accident:
(PRODUCE) shed
tears, blood, light, etc.
to produce tears, light, blood, etc.:
(n.)
a small building, usually made of wood, used for storingthings:
a large, simple building used for a particular purpose:
determine
(v.)
to control or influence something directly, or to decide what will happen:
to discover the facts or truth about
something:
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