Researchers explain how naked mole rats survive 18 minutes with no oxygen
Naked mole rats may not be the most attractive creatures to look at. But they're very interesting for researchers to study.
They're the only cold-blooded mammal, explains Thomas Park — a professor in the department of biological sciences at the University of Illinois at Chicago. He says naked mole rat colonies also have a "queen," similar to ants or bees.
Now, a new study by Park and a team of researchers describes how naked mole rats can survive without any oxygen for nearly 20 minutes. The research was published this month in the journal Science. Here's part of Park's interview with As it Happens host Carol Off about his study.
CAROL OFF: Professor Park, when did you first suspect that naked mole rats could survive without oxygen for quite long periods of time?
THOMAS PARK: We started to suspect several years ago. There were some really good clues that they might be super tolerant to oxygen deprivation. The first is that it's known that their burrows have the lowest amount of oxygen of any subterranean mammal. That's because they live in such large numbers. Their colony size can be two to three hundred individuals.
The second clue [is that] it has been known for some time that the hemoglobin in their blood is very sticky for oxygen. So even in a very low oxygen environment, their blood can pull oxygen molecules out of the air.
TP: We began by kind of arbitrarily just choosing a low oxygen concentration to try. We picked five per cent because we knew that humans and laboratory mice cannot survive in five percent. That was a very tense experiment. We were ready to pull the guy out if he looked like he was having trouble. And we were amazed because after an hour there was no sign of trouble. After five hours, the researchers started to get pretty tired, but the mole rat looked fine. So, we were surprised and we decided to just say five hours is the limit that we're going to go today.
CO: And then you went further. You put them in a zero per cent oxygen environment.
Under zero per cent oxygen, they rapidly slow their heart rate and respiration rate, they stop moving around, and they go into a state of suspended animation.- Thomas Park
TP: That's right. We wanted to really push the envelope and see what they are capable of. I think in nature they would sometimes get close to zero per cent oxygen. But, I think, we were really pushing the envelope.
We were shocked to see what happened. Under zero per cent oxygen, they rapidly slow their heart rate and respiration rate, they stop moving around, and they go into a state of suspended animation. And at the same time, they release a large amount of fructose — the simple sugar fructose — into their blood. Fructose is carried to the brain cells … We then discovered that the brain cells are covered with fructose transporters to move the fructose inside the cells. And inside the cells, they've got a huge amount of the enzyme that can convert fructose directly into energy. The significance is that this pathway, that we're calling the fructose pathway, can operate without oxygen — whereas what we normally use is glucose, the other simple sugar, and it requires oxygen. So, that was a pretty cool discovery.
CO: Okay, so if I understand, other mammals — like us — we use glucose in our metabolic system. And we need oxygen to burn the glucose. [With] fructose, you don't need oxygen to burn.
TP: Correct. And, so, because we're in an oxygen rich environment, it's a better choice for us to choose glucose because glucose is actually more efficient than fructose. But for the naked mole rat, in an oxygen poor environment, they've decided to go strong with the fructose pathway.
CO: Tell us a bit more about naked mole rats. They're pretty wonderful and strange creatures.
TP: You know, I really like them. I think that they're evolved to be very friendly and nice because they have to live in such large numbers and such close quarters. You can pick up a wild naked mole rat, no problem. They're very friendly. If you pick up a wild mouse or a wild laboratory rat, they'd probably bite you.
CO: What about how they organize themselves?
TP: They organize themselves much like an ant colony or a bee colony. There's only one breeding female. We call her the queen. She is in charge of all of the other hundreds of non-breeding animals. So, she goes around everyday — goes through the colony — and makes sure that each colony member knows that she's in charge.
CO: You love these animals and they're fascinating. But, you're hoping that this might lead you to some discoveries — something that can help humans, I guess. What do you hope comes out of this research?
TP: So, what I'm hoping is that somebody smarter than me, perhaps with a background in neuro-engineering or bio-engineering, would tackle the problem of how do we upregulate the fructose pathway in humans … 99.99 per cent of the time, we're fine, we have plenty of air. But when there's a tragedy like a heart attack, and we can't get oxygen to the brain, it would be great if give a drug or a treatment that would upregulate the fructose pathway and allow the patient to survive longer.
This interview has been edited for length and clarity. To hear more of our conversation with Thomas Park, listen to the full interview above.