Naked Mole-rats "Turn Into Plants" When Oxygen Is Low

Deprived of oxygen, naked mole-rats can
survive by metabolizing fructose just as plants
do, researchers report this week in the journal
Science.

Understanding how the animals do this could
lead to treatments for patients suffering crises of
oxygen deprivation, as in heart attacks and
strokes.

"This is just the latest remarkable discovery
about the naked mole-rat -- a cold-blooded
mammal that lives decades longer than other
rodents, rarely gets cancer, and doesn't feel
many types of pain," says Thomas Park,
professor of biological sciences at the University
of Illinois at Chicago, who led an international
team of researchers from UIC, the Max Delbrück
Institute in Berlin and the University of Pretoria
in South Africa on the study.

In humans, laboratory mice, and all other known
mammals, when brain cells are starved of
oxygen they run out of energy and begin to die.

But naked mole-rats have a backup: their brain
cells start burning fructose, which produces
energy anaerobically through a metabolic
pathway that is only used by plants -- or so
scientists thought.

In the new study, the researchers exposed naked
mole-rats to low oxygen conditions in the
laboratory and found that they released large
amounts of fructose into the bloodstream. The
fructose, the scientists found, was transported
into brain cells by molecular fructose pumps
that in all other mammals are found only on
cells of the intestine.

"The naked mole-rat has simply rearranged
some basic building-blocks of metabolism to
make it super-tolerant to low oxygen
conditions," said Park, who has studied the
strange species for 18 years.

At oxygen levels low enough to kill a human
within minutes, naked mole-rats can survive for
at least five hours, Park said. They go into a
state of suspended animation, reducing their
movement and dramatically slowing their pulse
and breathing rate to conserve energy. And they
begin using fructose until oxygen is available
again.

The naked mole-rat is the only known mammal
to use suspended animation to survive oxygen
deprivation.

The scientists also showed that naked mole-rats
are protected from another deadly aspect of low
oxygen -- a buildup of fluid in the lungs called
pulmonary edema that afflicts mountain
climbers at high altitude.

The scientists think that the naked mole-rats'
unusual metabolism is an adaptation for living
in their oxygen-poor burrows. Unlike other
subterranean mammals, naked mole-rats live in
hyper-crowded conditions, packed in with
hundreds of colony mates. With so many
animals living together in unventilated tunnels,
oxygen supplies are quickly depleted.

Source: Sciencedaily