From New Scientist
Chemical drink breathes life into damaged hearts
- 22:00 09 February 2009
by
After
drinking a chemical dissolved in water, mice with damaged hearts turn
from couch potatoes into treadmill tearaways, researchers say. The
finding raises hopes that the same substance can invigorate patients
weakened from heart attacks by increasing the supply of oxygen to
damaged cardiac muscle.
Designed to make haemoglobin release more of its oxygen than normal, the drug, myo-inositol
trispyrophosphate (ITPP) boosted exercise levels in the ailing mice by
35% when given dissolved in water. When given by injection into the
abdomen, exercise levels rose a massive 60%.
"ITPP doesn't deliver oxygen itself, but makes haemoglobin able to release a larger amount of oxygen to tissues," explains Jean-Marie Lehn of the University of Strasbourg in France.
Normally,
he says, haemoglobin releases only 25% of its oxygen cargo during one
circuit of the body. But when ITPP binds to haemoglobin, it releases
35% more than usual, boosting supplies of oxygen to tissues without
people having to inhale any extra air.
Sports warning
Further
evidence of increased oxygen supply came from blood samples taken from
the mice showing a fivefold reduction within just three days of
hypoxia-inducible factor, a chemical distress signal produced by
oxygen-starved tissue. The results also suggested that the effects from
a single dose could last almost a week, so patients wouldn't need to
take ITPP every day.
Unlike artificial blood substitutes, which have run into practical and ethical problems during clinical trials, ITPP simply boosts the efficiency with which
native blood supplies tissues with oxygen. It is also very similar to a
naturally occurring chemical made in the body, myo-inositol.
As
a result, Lehn hopes to begin clinical trials "as soon as possible".
For athletes tempted to use the substance to enhance performance, he
warns: "It could be very easily detected."
'Novel approach'
Lehn
says that studies are under way to find out exactly how ITPP interferes
with haemoglobin to make it give up more oxygen. He says that the
substance is not natural, but is related to myo-inositol, a substance found in rice and cereals.
Peter Weissberg, medical director of the British Heart Foundation,
says that inadequate oxygen delivery to tissue causes many symptoms of
heart failure. "Around 700,000 people in the UK alone are living with
heart failure, and inadequate tissue oxygen delivery is the cause of
many of the symptoms - particularly fatigue and poor exercise
tolerance," he says.
Such
a novel approach is welcome, says Weissberg, given the limited success
of existing treatments based on increasing heart output or improving
blood circulation.
"They've
found a molecule that can boost the amount of oxygen transferred from
blood to the muscles," he says. "If a similar effect can be achieved in
[humans], it will raise the possibility of a new treatment to improve
debilitating heart failure symptoms."
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0812381106)