It is not necessary to starve
A substance from young blood created the effect of starvation in mice
Polina Loseva, N+1
French scientists have discovered that the substance GDF11 causes a condition in mice similar to the effect of a diet: animals lose weight without losing their appetite and remain healthy. This is an argument in favor of the fact that transfusion of young blood to elderly recipients can theoretically work, because GDF11 is one of the substances that are more in the blood of young animals and people than in the blood of old ones. The work was published in the journal Aging Cell (Katsimpardi et al., Systematic GDF11 stimulates the secretion of adiponectin and induces a calorie restriction‐like phenotype in aged mice).
The assumption that blood transfusion from a young animal to an old one can prolong the life of the latter still causes a lot of controversy. The results of animal experiments look rather optimistic, however, they mainly concern only the "rejuvenation" (that is, improvement of the work) of individual organs – for example, the brain or muscles – and not the prolongation of life as such.
In parallel, some scientists are trying to apply this technology to humans. However, it is unsafe to transfuse whole blood (especially regularly) – immune rejection may occur. Therefore, gerontologists are trying to find the main active ingredients in young blood in order to apply them separately.
One of the candidates for the role of such a "youth concentrate" is the GDF11 molecule. During the development of the embryo, GDF11 participates in the formation of the body structure plan, but its role in the adult body remains controversial. Despite the fact that not all studies reproduce her successes in the field of "rejuvenation", she continues to be closely studied. A few years ago, scientists introduced the GDF11 protein into the brains of elderly mice and, in addition to the expected increase in neurogenesis, found a sudden effect: the animals lost weight.
Therefore, Lida Catsimpardi and her colleagues from the Pasteur Institute suggested that the mechanisms of action of GDF11 may be somewhat similar to calorie restriction - another common method of prolonging the life of model organisms.
The researchers injected GDF11 into the abdominal cavity of elderly mice and compared their health status with a control group of old animals and with young mice. Injections were carried out during the week, every day at 7 pm – before the start of the active phase of the day in mice.
After a week-long course, the elderly mice lost about 4 grams. After that, their weight stabilized and remained at a level comparable to young mice for several weeks. Scientists have confirmed that weight loss was associated with a decrease in the thickness of the fat layer, and the condition of the muscles, judging by histological preparations, has not changed.
Then the researchers set up a similar experiment with calorie restriction: they also took two groups of elderly mice and put one of them on a strict diet. In starving mice, the concentration of GDF11 in the blood increased significantly – it exceeded by one and a half times not only the protein level in the blood of control old animals, but also in the blood of young ones.
Scientists have suggested that GDF11 may influence eating behavior in animals. However, they calculated that the elderly mice that were injected with GDF11 consumed as much food as the control animals. In the "open field" test, where researchers record the trajectory of mice moving through empty space, they found that both groups of old mice go the same way. Therefore, weight loss cannot be caused by hyperactivity.
Finally, they calculated the amount of absorbed water and excreted excrement, and also measured the concentrations of glucose, corticosterone (stress hormone) and leptin (appetite hormone) in the blood of animals. It was not possible to detect any significant differences in any of these parameters, which means that weight loss is not caused by loss of appetite.
But scientists noticed changes in metabolism: in animals that received GDF11 and were on a diet, the level of insulin in the blood decreased several times compared to both young and adult non-starving mice. In addition, there was less IGF-1 (insulin-like growth factor-1) in the blood of elderly mice who received GDF11.
Both of these substances – insulin and IGF-1 – are responsible for the absorption of glucose by cells and the launch of intracellular anabolic processes. It is believed that calorie restriction inhibits the excessive synthesis of substances in cells and thus inhibits their wear. In this sense, the effect of GDF11 turned out to be very similar to the effect of a diet. And this is another argument in the piggy bank of supporters of rejuvenation with the help of young blood or at least one of its components.
Despite the fact that the results of transfusion of young blood are extremely ambiguous, tests of this method on humans have been going on for several years. Ambrosia was one of the first companies: its founders reported that blood infusions have a positive effect on the health of recipients – however, the company recently closed its projects after a warning from the FDA (the American equivalent of the Ministry of Health). Another company, Alcahest, continues its research. Now its creators are trying to use young blood against Alzheimer's disease.
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