The secret of eternal youth
What are the causes of aging and death of a person
Maxim Skulachev, Forbes, 02.02.2018
We are aging for a reason, but as a result of a special biological program. But there is an African naked digger in the world, an animal that looks like a mouse and is unable to grow old. Scientists have found out why people age, but diggers do not.
This article is the fourth in a small biological series about youth, aging, death and genetic programs.
Death for the sake of life
In case you are too lazy to read the three previous articles (1, 2 and 3) or in the constant turmoil of our life you have forgotten what was discussed there, here is a "summary of the previous series".
I am of the opinion that the life of an individual, a single individual of some biological species, is a very valuable thing, but there are more important things. Namely, the view itself. That is, in fact, a complete set of genes (this is called a gene), which is contained in each individual of this species and, in fact, determines what it is. In our opinion, it is more correct to consider any living beings simply as a temporary receptacle for the genes that they received from their parents and will pass on to their children. For the first time, such an idea was formulated explicitly, probably, by Richard Dawkins in his famous book "The Selfish Gene".
As a rule, the interests of the genome and its temporary carrier (a living being) coincide. But sometimes not. And then it instantly turns out who is the boss in the house: of course, the genome. If the genome of a species is in danger or the species just needs to develop, then the carrier can be safely sacrificed – the next generations will "give birth to new ones".
As a result, I am sure that the genomes of most (if not all) living creatures contain special harmful programs. From which nothing good happens to the creatures themselves, but which are necessary for the development of the species. First of all, death programs that ensure the change of generations and, accordingly, evolution. And sometimes they are arranged in a "fast" way – for example, in annual plants that die, killed by their own seeds after their maturation, and sometimes – "slow". And the most disgusting program of slow suicide is the aging program. Which causes many species, including you and me, to "deteriorate" with age and eventually die.
Wrong mouse
The fact that we are aging for a reason, but as a result of the activities of a special biological program, is not an obvious thing and requires proof. I tried to build it "from the opposite", showing you an example of an animal that turned off the aging program for itself. Because he no longer needs to accelerate his own evolution so much – he's already good! This, like you and me, is a mammal, a fairly close relative of an ordinary mouse – the African rodent naked digger! If a mouse lives for 2-3 years, manages to grow old completely during this time and dies of old age, then the digger lives for more than 30 years and, if he sometimes shows some signs of aging, they are usually not fatal. Most biologists agree that a naked digger is an ageless animal (or, to put it more scientifically, an animal with negligible aging).
And now in our series it's time to answer the main "question about diggers": how did he do it? How did he turn off his aging??!
Even a couple of years ago I would have had nothing to say on this topic. But in 2017, in one of the most prestigious scientific journals in the world, "Physiological reviews", we managed to publish a theoretical paper explaining the phenomenon of non-aging of a naked digger. At the end of 2017, its version was released in Russian.
It all started, as always, with mitochondria. These are such small power plants that are in every cell and with which we breathe. I hope that there will be a separate episode of our series about them. The study of mitochondria is the main specialty of Academician Vladimir Petrovich Skulachev. Actually, in his laboratory at the end of the 60s, it was found out how they work. For the last 20 years, the academician, in addition to mitochondria, has been interested in the problems of aging and, of course, has made titanic efforts to conduct an experiment with the mitochondria of a naked digger. I should note that mitochondria are very strongly associated with aging, but more on this in the next series.
Studies of the mitochondria of the naked digger were crowned with success. At the institute at the Berlin Zoo, experiments were carried out on diggers, Vladimir Skulachev's employee, the famous biologist Mikhail Vysokykh, who specially arrived from Moscow for this purpose, managed to obtain a sample of the digger's tissue and measure various parameters of the mitochondria in this tissue. There was nothing particularly interesting in them, except for a slightly strange curve showing the rate of oxygen uptake by mitochondria (they also breathe) under certain conditions.
Back in Moscow, Mikhail showed this curve to the manager, to whom it also reminded something, but they could not remember what exactly. So biologists were racking their brains until they showed the graph to another colleague, Boris Chernyak, head of the laboratory of cell bioenergetics, who is known for never forgetting anything (well, at least if it is related to mitochondria, respiration and living cells). He looked and immediately said: exactly the same curve can be obtained by registering the respiration of the mitochondria of newborn baby rats!
And here Vladimir Petrovich had an idea. Captured him so much that he packed up and went to Berlin to personally look at the naked digger (photo above – "Academician and digger"). What did he discover? That he (the digger) is naked. And do you know who he looks like because of this?
Look: the photo above shows naked diggers. And nearby – not at all diggers. These are newborn baby rats. See how similar they are? In a few days, the baby rats will grow up, dress up with fur and turn into normal rats. But the diggers don't. They will remain like newborns for the rest of their lives.
Further investigation showed that the diggers have more than 40 signs of such "newbornness", or "childishness", compared with rats. Here are some of them:
- Small weight compared to other species of the family.
- Lack of hair (rodents always have it).
- Absence of auricles.
- Limited capacity to maintain a constant body temperature (as in newborn mammals).
- High cognitive abilities (curiosity).
- Low susceptibility to pain.
- The ability of neurons to regenerate and increase the lifespan of neurons.
- No decrease in the level of insulin-like growth factor 2 (IGF2) with age.
- No decrease in the levels of superoxide dismutases 1 and 2, as well as catalase with age.
- As well as several dozen more external, physiological and biochemical signs.
That is, it turns out that the digger stopped the program of his individual development at the stage of a newborn rodent. A similar phenomenon has been described before for, for example, amphibians, and it is called neotenia.
In fairness, I must say that Vladimir Skulachev was not the first to draw attention to the fact that the digger is a neotenic animal. Before him, this was noticed by Richard Alexander in 1991 and some other scientists. But they did not associate this phenomenon with longevity at all (Alexander simply did not know about the life expectancy of these animals).
Getting stuck in childhood
Academician Skulachev formulated a very simple idea: if the digger stopped at the cub stage, then his individual development program simply does not reach the place when it's time to start aging. Children don't get old! Thus, we get the most important proof: aging is part of the program of development and life of the body. The same as birth, growth, maturation. And if this whole program is stopped, then so is aging!
That's what happened to the diggers. If this had happened to an ordinary species, it would have disappeared very soon, because in the absence of aging, its evolution would have greatly slowed down. And the digger was saved by his eusociality. Life in the "anthill mode" turned out to be so much more stable that he could afford to turn off aging as an evolutionary tool.
And, it seems, in the evolution of the most interesting species of biological beings for us – Homo sapiens – exactly the same story began that happened with the naked digger. Have you ever noticed that people are most like... baby monkeys? But more on that in the next episode. Which will be dedicated to the human aging program!
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