Prolonging life: hydrogen sulfide instead of starvation

Hydrogen sulfide prolongs life

Alexandra Bruter, <url>

For some time now, it has been a commonplace in science that a not too fanatical restriction in food contributes to an increase in life expectancy. This effect is observed in a variety of species from yeast to humans. The mechanism of this, however, is unknown. Speaking of a person, one can imagine that reducing the diet reduces weight, and reduced weight reduces the risk of cardiovascular diseases and diabetes. Probably, this mechanism really contributes to the causal relationship between food restrictions and an increase in life expectancy. But yeast has no heart, no blood vessels, no hormonally active adipose tissue, and there is an effect. And drosophila does, and mice, and in general, almost all the studied animal species.

What is the matter here, and how to achieve the same effect, without limiting themselves in anything, was probably figured out by an American-Austrian group of scientists whose article was published in the journal Cell (Hine et al., Endogenous Hydrogen Sulfide Production Is Essential for Dietary Restriction Benefits). The article shows that it is not the restriction in food as such that leads to an increase in life expectancy, but a decrease in the use of two sulfur-containing amino acids. The direct effect causes an increased release of hydrogen sulfide.

Fig.: Christopher Hine et al./Cell

The authors suggest that their results are due to the effect of hormesis. The concept of hormesis (Greek. hormaein "forward movement, motivation, aspiration") is that stress (poison, radiation) in small doses strengthens the body. Anything that doesn't kill makes us stronger. From the point of view of modern biology, this effect is explained by the fact that light harmful effects do not cause tangible harm to the body, but activate processes designed to minimize this harm. Because of this, resistance to external influences increases, regeneration accelerates, one's own immunity, including antitumor, increases, and as a result, life expectancy increases.

The effect of hormesis was first noticed back in the XIX century, when the German pharmacist Hugo Schultz noticed that small concentrations of some poisons accelerate the growth of yeast.  Similar experiments on animals were conducted by Rudolf Arndt, who, however, served this scientific concept badly. The fact is that Arndt spoke out a lot in support of homeopathy, it still didn't help homeopathy, but they began to be skeptical of all the other ideas of the scientist. Again, the idea was introduced into the scientific community in the middle of the XX century.

At first, the concept concerned only toxic substances coming from the outside world. But over time, when the knowledge about the molecular events of intracellular life expanded sufficiently, it became clear that some substances formed during normal metabolism are toxic. First of all – free radicals formed in mitochondria during the extraction of energy by redox reactions. Free radicals are highly active and therefore toxic. It would seem that they should harm the body, accelerate aging and shorten life. And taking antioxidants, on the contrary, improves well–being, slows down aging and prolongs life. None of this happens in practice, it's the opposite. This is evidenced by experimental data, and epidemiological data for humans. This effect is called mitohormesis (mitochondria + hormesis).

Free radicals are not the only toxic metabolites. The composition of proteins includes two sulfur-containing amino acids: methionine and cysteine. Methionine is an essential amino acid, it cannot be completely removed from the diet, because the body cannot synthesize methionine itself. Cysteine is a replaceable amino acid, you can not eat it, the body will cope on its own. To synthesize cysteine, the body borrows sulfur from methionine. It is during the transfer of sulfur atoms from the molecule to the molecule that hydrogen sulfide is formed. In high concentrations, it is toxic, but in the body it is sometimes used as a signaling molecule: for example, it can transmit a signal that leads to a decrease in pressure.

So, in the course of experiments, it turned out that the withdrawal of cysteine from the diet and the restriction of methionine leads to an intensification of sulfur transfer processes. At the same time, hydrogen sulfide concentrations are increasing.

Then it was necessary to prove the existence of a causal relationship between the concentration of hydrogen sulfide and changes in diet on the one hand and positive changes on the other hand. An increase in the rate of recovery after ischemia and subsequent liver reperfusion was considered as positive changes. Ischemia followed by reperfusion occurs in a variety of conditions (heart attacks, strokes on the one hand, surgical interventions and organ transplants on the other). The bottom line is that at first, due to ischemia, there is a shortage of oxygen and nutrients in the tissue, and when the blood flow is restored (reperfusion), inflammation also develops.

It turned out that if animals on a reduced diet were given standard doses of methionine and cysteine separately, then the effect of rapid recovery would not be observed. On the other hand, it turned out (great news) that the introduction of appropriate doses of hydrogen sulfide without any restrictions in the diet allowed to achieve the effect.

Portal "Eternal youth" http://vechnayamolodost.ru29.12.2014