Animals that defy the rules of aging help scientists study longevity

Neil Bromhall/Shutterstock

• Some long-living animals seem to defy the
  rules of aging, so scientists are studying them.
• Two animals of interest to researchers are the naked
  mole rat, which lives decades longer than its rodent relatives,
  and turtles, which can live up to 200 years. 
• Researchers have found noticeable differences in the
  ways these animals’
  metabolisms and
  mitochondria function. 

Being a freak of nature isn’t always a bad thing, especially if
you defy the conventions of
aging. 

Naked
mole rats and
turtles are outliers when it comes to the rules of nature.
The mole rat lives up to 31 years, decades longer than its other
rodent relatives. Turtles are one of the longest-living creatures
on Earth. 

Comparing the biology of these
animals to others that age poorly provides valuable insights to
scientists about which biological pathways are most important for
longevity. That information could ultimately help
them find ways to increase human lifespans. 

A cornucopia of factors are at play as a younger organism gets
older: proteins get damaged, they build up and disrupt cell
functions, mutations occur, and once-harmless cells turn
into cancer. But the
important question when it comes to aging is not how it happens,
according to Richard Miller, director of the Glenn Center of Aging
Research at the University of Michigan.

“The real question is what has
been done across species or within a species to slow
it,” Miller told Business Insider.

Long live the naked mole rat

A popular theory in the field
of aging is that an organism puts most of its resources —
such as nutrients, energy, time and effort — either into maintaining
their body or reproducing, but not both. In people, for
example, women’s average lifespan decreases if they
have children. Scientists believe this happens
because human reproduction can cause damage to cells and
deplete resources in the body that would otherwise have been used
for cellular repair.

But paradoxically, breeding seems
to extend the life of the naked mole rat. 

Scientists Martin Bens and Alessandro Ori at the The Leibniz
Institute on Aging in Germany are working to
understand this anomaly. 

Each colony of mole rats designates a
queen, the same way ants do, and only she breeds and bears
young. There is also only one breeding male per colony. But
non-breeders can transition to become a breeder, so Bens
and Ori studied that transition process. 

Their results suggested that the signal pathways involved
in mole rats’ transition to breeding are also involved in their
aging process.

In males, some of these
overlapping pathways are related to their metabolism, the process
of converting food to usable units of energy in the body.
Scientists found that breeding male mole rats produced
greater-than-normal amounts of energy in their testes cells, and
lower-than-normal amounts in their skin cells. Diverting energy
in this way could play a role in delaying the aging
process. 

Brandon
Vick, University of Rochester

Ori and Bens also observed
differences in the composition of the mole
rats’ mitochondria:
the small organelles in cells that power metabolic processes.
They observed that the naked mole
rats had a reduced mitochondria respiration rate compared to
guinea pigs, which meant that the mole rats were making less
energy and using less fuel and oxygen.

The researchers also found that
all the naked mole rats preferred to use lipids or fats as an
energy source, rather than the carbohydrates or sugars that
shorter-lived rodents mostly use. 

Another factor that allows naked
mole rats to live so long is their abnormally low body
temperature. Lower
basal body temperatures in animals are usually correlated
with prolonged healthspan, and naked mole rats are mammals but
aren’t warm-blooded, which makes them an anomaly in the rodent
family.

Finally, Ori and Bens examined
naked mole rats’ livers. Livers generally detoxify the body and
eliminate chemicals that can damage cells and accelerate aging.
In mole rats, these detox pathways were more active
than the same systems in guinea pigs, suggesting that mole
rats keep their cells healthy and undamaged from toxins more
efficiently. That could also explain why they out-live their
rodent cousins.

The tortoise and the human

Tortoises and turtles are masters
of aging. Jonathan, a Seychelles giant tortoise, is the oldest
known terrestrial animal at 186 years of age, and is going
strong.

Rozalyn Anderson, an associate
professor at the University of Wisconsin School of Medicine and
Public Health, told Business Insider that it’s hard to
ignore how big a role metabolism and energy balance play in
aging. Anderson studies
caloric restriction in
 monkeys, and said evidence is starting
to show that age-related diseases show up with increased
prevalence in people who have metabolic issues and
obesity.

“I think it’s all about energy:
energy use, energy storage, and the type of pathways that are
being engaged to derive energy,” Anderson said.