Scientists explain why naked mole-rats' longevity contradicts accepted aging theory

FEBRUARY 10, 2020

by Missouri University of Science and Technology

Dr. Chen Hou and his research collaborators have found an answer to the decades-old question of why naked mole-rats with high oxidative damage live 10 times longer than mice of comparative weight.

"The long lifespan of the East African naked mole-rats raises one of the most serious paradoxes in the study of aging," says Hou, an associate professor of biological sciences at Missouri S&T. "And geriatric researchers are asking if the oxidative stress theory is dead."

The widely accepted theory of aging is based on a negative correlation between oxidative stress and animal lifespan. This theory posits that aging occurs because of accumulated cellular damage caused by the byproducts of oxidative metabolism—or the way we burn oxygen to produce energy. When a certain threshold of oxidative damage is reached, animals will die.

"We've observed the correlation between damage level and lifespan is the dynamic process of damage accumulation, which is largely determined by the animal's growth and metabolism," says Hou. "Besides offering a simple explanation to the 'naked mole-rats paradox' that has puzzled scientists for years, our results provide a starting point for new comparative aging studies."

To explain the contradiction, the researchers developed a data-based theoretical model that estimates oxidative damage accumulation with age. Their model highlights a tradeoff between the metabolic energy cost of growth versus damage repair. The tested hypothesis is if animals expend too much energy on growth, less will be available to repair their oxidative damage, which will accumulate. It also suggests that high metabolism leads to faster damage accumulation.

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Naked mole-rats just keep getting weirder and weirder

April 21, 2017


by John Hopton


Naked mole-rats are probably the weirdest and most wonderful animals in the world - and now it has been discovered they often behave more like plants than animals.

Why are naked mole-rats weird and wonderful? Take the name, for starters. All animals are naked (usually), but these actually look more naked than most. The next part of their name is two animals in one. But the way they look is far from being the most remarkable thing about them. They live like termites, in colonies of 300 where a queen produces worker offspring. They don't get cancer and they are immune to a lot of pain, including that caused by chilli peppers.

Whereas mice live for a maximum of three years, the world's oldest mole-rat, "Old Man", died aged 32.
Surviving in zero oxygen

One other incredible thing about naked mole-rats is that they can survive for up to 18 minutes without oxygen; this is compared to the 20 seconds of a mouse.

A new report in the journal Science explains that when mole-rats have to go without oxygen, they use fructose as their energy source. That's the sugar used by plants, in contrast to glucose which is used by humans and almost all other mammals.

Together with colleagues, Thomas Park, a University of Illinois at Chicago neurobiologist and co-author of the new study, put a mole rat into an oxygen chamber containing only five percent oxygen, and admitted the team were "tense". Humans could not survive on 5 percent.

However, “They didn’t even go to sleep,” Park told The Washington Post.

Down at zero percent oxygen, the animals' heart rate fell from 200 beats per minute to about 50, to account for their situation, but they made a quick recovery once oxygen was reintroduced.

“They were able to survive up to 18 minutes without any apparent neurological damage,” said Jane Reznick, a study co-author and molecular biologist at the Max Delbrück Center for Molecular Medicine in Berlin.
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What you didn't know about naked mole-rats

Date:October 22, 2015

Source:University of Virginia

The naked mole-rat is a particularly ugly or cute animal, depending on your definition. It is tubular in shape, like the tunnels it creates, hairless and wrinkled, for wiggling through those tunnels, and has long, chisel-like front teeth. It looks somewhat like a walrus in miniature. And these rodents can chew through concrete!

Do a Google search of the naked mole-rat, or read through a number of biology textbooks, and you will find numerous references to this African mammal as being "inbred" and "eusocial," meaning -- similar to some insects -- it has a fertile "queen" at the head of the colony, helpers who tend to her and may mate with her, and female "workers" who are sterile, expending their energy building tunnels and finding food.

This social system is rare among animals, and almost unheard-of among mammals, so evolutionary biologists have long taken particular interest in the unusual eusocial mating system of the naked mole-rat and its essentially homogeneous genetics. Why would this rodent have evolved to socialize and mate so differently from other mammals? From a natural selection standpoint -- where advantageous traits are passed down to succeeding generations -- what is gained by limiting genetic diversity by limiting the breeding pool?

Evolutionary biologists have puzzled over and debated this for decades. For this reason, the naked mole-rat has been an interesting oddball study model.

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Naked Mole-Rats May Hold Clues to Pain Relief

ScienceDaily (Sep. 21, 2012) — Naked mole-rats evolved to thrive in an acidic environment that other mammals, including humans, would find intolerable. Researchers at the University of Illinois at Chicago report new findings as to how these rodents have adapted to this environment.

The study was published online this week on PLOS ONE.

In the tightly crowded burrows of the African naked mole-rats' world, carbon dioxide builds up to levels that would be toxic for other mammals, and the air becomes highly acidic. These animals freely tolerate these unpleasant conditions, says Thomas Park, professor of biological sciences at UIC and principal investigator of the study -- which may offer clues to relieving pain in other animals and humans.

Much of the lingering pain of an injury, for example, is caused by acidification of the injured tissue, Park said.

Continued:   http://www.sciencedaily.com/releases/2012/09/120921180752.htm