An international team of scientists has found that naked mole rats have the ability to transform into plants in the process of survival in such conditions that are fatal to most other animals. Scientists have tried to determine how these strange mammals, more like insects, change their metabolism and survive in an environment devoid of oxygen.
Naked mole rats are animals that live in Africa, to a certain extent resemble insects than mammals. Just like ants and bees, they are characterized by the creation of eusocial colonies in which there are sterile workers and a fertile female. These almost blind and cold-blooded rodents dig tunnels underground, which in total reach several kilometers in length. With the help of these passages, living quarters, latrines and storerooms are connected. These animals communicate with each other using sound signals, and their "language" is much richer than that of other rodent species.
Many people know that naked mole rats do not get cancer. But in reality this is not so: they form cancerous tumors, but this happens very rarely. For the first time, American scientists discovered cancer in these rodents last year - they reported several cases of the disease, which were recorded in Washington at the National Zoo, as well as in Illinois at the Brookfield Zoo. Thanks to this, scientists received information that these animals are not one hundred percent protected from carcinogenesis, although there is an opinion that it was precisely because the rodents were kept in captivity that they developed dangerous neoplasms.
Some researchers say that in naked mole rats, cancer resistance is due to their lifestyle. These rodents live in an environment in which the oxygen content is relatively low (only 2-9 percent), while a person breathes air, for oxygen in which it reaches 21 percent. Such an environment should somehow activate anti-cancer protection, although this hypothesis has not yet been confirmed.
At the same time, the hypoxia in which these rodents live is related to another unusual property of naked mole rats. Their skin is insensitive to capsaicin (a burning substance found in pepper) and acid. Scientists tried to explain why such adaptation is needed for rodents, which spend almost their entire life underground, practically not getting to the surface. Carbon dioxide accumulates in underground tunnels. When it dissolves in water, carbonic acid is formed, which can cause rodents to burn on moist mucous membranes. In order to feel comfortable enough in such conditions, in naked mole rats, pain sensitivity is to a certain extent lost.
Rodents are able to withstand high concentrations of carbon dioxide for a long time. They do not react in any way if the level of carbon dioxide inside the hole rises to 7-10 percent: they do not make any attempts to go to places where there is more oxygen. Moreover, they show no signs of tissue acidosis or hyperventilation. Even if the concentration of carbon dioxide reaches 80 percent, they are able to exist in such conditions for five hours.
Experts wondered how these animals survive in underground burrows, where there is so little oxygen. As it turned out, naked mole rats look like not only insects, but also plants. In an environment where O2 is deficient, rodents change their metabolism and begin to break down fructose anaerobically. Through this process, enough energy is released, which is necessary for the brain cells and which prevents the death of these cells.
As part of the experiment, scientists put the rodents in atmospheric chambers, recreating the conditions of hypoxia. The oxygen content was only five percent. Naked mole rats did well for five hours, while normal mice died after about 15 minutes. However, the researchers did not stop there. They removed all the oxygen from the chambers, killing the mice in less than a minute. The diggers lost consciousness in half a minute, but did not give up their attempts to breathe for several minutes. Eventually, breathing ceased, however, as soon as they were transferred to room conditions, the rodents revived and did not show any signs that their brain was damaged. Thus, naked mole rats survived even after 18 minutes in an environment completely devoid of oxygen.
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Scientists have found that under conditions of prolonged hypoxia, a fairly large amount of sucrose and fructose enters the blood of these animals. Molecular pumps, previously found exclusively in the intestines of mammals, transport carbohydrates to brain cells. Metabolization of fructose is carried out through glycolysis, which proceeds with the participation of glucose under normal conditions.
At the same time, it is impossible to use glucose due to the fact that one of the stages of glycolysis requires an active enzyme called phosphofructokinase-1. The activity of this enzyme is highly dependent on the energy state of the cell, which deteriorates sharply without oxygen. Ultimately, the glycolysis process stops, and the cell can no longer produce the energy that is needed to carry out life. Fructose can bypass this barrier by producing lactate or lactic acid, which renews energy production, albeit in small amounts.
As the researchers note, this ability to change their metabolism to survive in extreme conditions is typical for plants, but not for mammals.
The researchers hope that their discovery will provide an opportunity to develop new methods to prevent damage to heart tissue during hypoxia, which is associated with coronary heart disease.