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floating around in space sounds amazing
like there's a reason people pay
thousands of dollars to go on zero g
flights but when it comes to being a
weightless astronaut there's a catch if
astronauts don't exercise for two hours
a day or more they risk debilitating
muscle loss in microgravity muscles in
the neck back and legs just don't need
to work as hard to support a person so
without regular full body exercises
those muscles can waste away on even a
one or two week stay in space except
here's the thing there are some animals
on earth that can go an entire winter
with limited movement and then wake up
in the spring fit healthy and ready to
go i'm talking of course about
hibernation and it turns out that
studying one hibernating animal in
particular could help us humans fight
muscle atrophy on long space flights
ground squirrels now you might think
bears are an obvious model for this kind
of long chill slumber they're large
omnivorous mammals like we are and we
have learned some things by studying
them for instance scientists believe
that hormones like testosterone and
estrogen which help regulate metabolism
also help bears preserve muscle mass
they also think that genes governing
protein synthesis in the muscles are
involved based on this scientists have
tried manipulating similar genes in lab
mice which don't hibernate to see if
that would also preserve their muscle
mass in space in this 2020 experiment
mice sent to the international space
station were injected with a drug that
blocked a gene involved in regulating
muscle growth it was like the
researchers shut down an off switch in
the mice so by blocking this gene they
actually stimulated muscle growth as a
result the treated mice showed less
atrophy than untreated animals after
their stay on the iss unfortunately just
injecting some hormones or toying with
genes in a human astronaut isn't a very
practical solution to our muscle loss
problem hormones and genes can affect so
much that modifying them just to prevent
muscle loss could have long-term
consequences we don't fully understand
also we still have a lot to learn about
what exactly is happening in bears when
they take that long winter break so
although some scientists are still
working on bear research others are also
looking at different mammals to get an
idea of how they maintain muscle mass
over their hibernation period and that's
where squirrels come in 13 lined ground
squirrels specifically these striped and
spotted squirrels live in the central
united states and canada and they
typically hibernate for a full five or
six months over the winter they wake up
in spring just in time for mating season
where they need their physical fitness
how do they do it turns out these
squirrels have got the guts for it
literally the microbes in their guts
help them maintain elevated levels of
protein synthesis that keeps muscles
from wasting away the key thing is how
those microbes handle urea urea is a
waste product that's rich in nitrogen
and it normally accumulates in urine and
is released from the body but these gut
microbes metabolize urea they turn that
nitrogen back into a form that both the
microbes and the squirrel can use to
build proteins this helps prevent the
urea from building up in an animal that
isn't going to the bathroom all winter
and it gets both parties an important
resource this process happens all year
but the microbiome ramps up this
activity during the hibernation period
when the squirrel is fasting and not
actively eating a normal diet and it was
pretty simple for scientists to figure
this out too in one experiment published
in 2022 they treated squirrels with
antibiotics to wipe out their standard
gut bacteria and when they did they saw
less protein synthesis happen in the
squirrel's muscles this nitrogen
recycling may also happen in other
animals including bears but scientists
will need more data to know for sure and
either way the great news is that
there's a hint that this strategy could
actually be a practical approach for
humans scientists have been
investigating nitrogen salvage in humans
for at least half a century and they
found some encouraging data for instance
a 1992 study showed that people on a low
protein diet increased their gut
nitrogen salvage in a similar way to
those fasting squirrels that said there
are a lot of unanswered questions like
we don't know if nitrogen salvage in
humans could be enough to stave off
muscle loss or how to get this change
without a restrictive low protein diet
we also don't know which bacterial
strains are the best candidates for the
job understanding how the process works
in other animals brings us one step
closer to creating a supplement that
could promote this kind of gut
microbiome in humans that would be great
for helping people who are bedridden or
malnourished here on earth to preserve
healthy muscle mass or it could just be
an aid for the demands of growing
children or pregnant people and maybe in
the future if you board that long
distance shuttle to mars a special diet
or a little probiotic pill could help
you stay healthy and fit on your trip to
deep space
without having to do so much exercise
but before we leave it behind we've got
to make sure our planet is healthy too
that's why this episode is sponsored by
ren a website where you calculate your
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you can answer a few questions about
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reduce it no one can reduce their carbon
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you