Naked mole rats, found primarily on the Horn of Africa, are a quirky bunch. The animals rarely contract cancer, and their 31-year lifespan is practically an eternity among rodents. Scientists can now add another oddity to the naked mole rats’ repertoire: they can go for hours without much oxygen.
Naked mole rats can survive for six hours in extremely low oxygen environments, according to new research from labs in Chicago and Berlin, and for 18 minutes with no oxygen at all. The mole rat’s secret:sugar.
Your cells, like those of all mammals, typically use oxygen and glucose — a type of sugar — for fuel. Take away the oxygen, and most mammalian cells start to die.
The mole rat’s body, however, has a shortcut. Gary Lewin, a neurobiologist at the Max Delbrück Center for Molecular Medicine in Berlin and coauthor of the study published in Science, said he and his team found when a mole rat’s brain and heart are deprived of oxygen, its cells switch to digesting a different sugar called fructose, a process akin to what yeast sometimes does when fermenting alcohol.
By metabolizing fructose, Lewin said, the mole rats are effectively entering a form of “suspended animation” that keeps their vital organs safe. Oxygen deprivation causes damage to vital organs and features in fatal human conditions like carbon dioxide (CO2) poisoning and strokes.
“In a low oxygen environment, you have to keep your heart going, because that’s typically the first thing that goes,” Lewin said. “When conditions improve and you encounter oxygen again, you have to start breathing. [This] breathing is started by the brain.”
Unfortunately for the rodent, one of the byproducts of using fructose is lactic acid, which could result in cellular breakdown if access to oxygen isn’t restored. In the lab, the naked mole rats attempted occasionally to take a breath while lying dormant in a zero-oxygen environment, as if continuously checking for the “all-clear” signal. Add back oxygen, and the rodents awoke in seconds.
This evolutionary adaptation might allow the mole rats to survive when oxygen levels drop in their tunnel system habitats — which, the researchers argue, happens quite often. Since the mole rats are breathing in a closed environment, the oxygen supply can rapidly run out; carbon dioxide levels can be thousands of times higher in mole rat tunnels than on the surface of the Earth.
“This seems to be sort of a rescue mechanism for the mole rat’s heart and neural cells, because they can continue to use fructose even though the products of this metalysis would wind up toxic to them,” Lewin said. “But it’s more important to produce energy right away and have that risk as opposed to die and stop producing energy anyway.”
People who live in and work in pressure extremes, such as mountain climbers and deep-sea divers, tend to have a heightened metabolisms, Lewin told NewsHour. Because of this tendency, the researchers believe that the mole rat’s suffocation-fighting ability may exist in other mammals, humans included. Lewin argued that doctors might be able to use this stasis effect to fight brain damage in stroke patients, but he isn’t the first to claim such a thing.
“Just for context, there’s a 1960s paper that talks about woodchucks and their ability to breathe in low oxygen,” said Mark Roth, a cell biologist at the Fred Hutchinson Cancer Research Center who wasn’t involved in the study. “I think people need to realize that similar findings have been published before.”
For further research, Lewin wants to test his high-altitude human hypothesis, but first, scientists have to figure out where this fructose originated inside the bodies of the rodents, because mole rat cells do not typically make it on their own.
“It’s not common in their diet,” Lewin said.