Do Sirtuins not increase life expectancy?
The genetic "source of eternal youth" turned out to be a myth
The effect of the sirtuin protein on life expectancy has been refuted. Previously, the healing properties of red wine and the usefulness of a low-calorie diet were explained by the action of this protein.
Kirill Stasevich, Compulenta
One of the most promising "sources of eternal youth" has dried up: scientists from University College London (UK) reported that the sirtuin protein gene does not affect life expectancy in any way. They conducted their research on nematodes and fruit flies, thus refuting the results of a number of works devoted to this "magic" gene.
For the first time, attention was drawn to the possible connection of sirtuin with life expectancy in 2001, when data were obtained that stimulation of the synthesis of this protein in the nematode Caenorhabditis elegans makes a long-lived worm. Later, similar results were demonstrated for fruit flies. And although sirtuin revealed many other remarkable properties associated with its participation in metabolism, all the attention of researchers was focused on how it slows down aging. It has been reported, for example, that the substance resveratrol contained in red dry wine increases the level of sirtuin, and this explains the beneficial properties of red wine.
Scheme of the resveratrol molecule – a component of red wine,
which increases the content of sirtuin protein in the body,
now the former "source of eternal youth"
(figure dr. Tim Evans).
In addition, the level of sirtuin allegedly increased with a low-calorie diet, which again summed up the scientific basis for the well-known belief that "thin people live longer."
In an article published in the journal Nature (Absence of effects of Sir2 overexpression on lifespan in C. elegans and Drosophila), an impressive team of authors states that it was not possible to confirm the connection of sirtuin with life expectancy. The researchers performed a simple genetic test. Nematodes Caenorhabditis elegans with a mutation in the sirtuin gene that stimulates its synthesis were crossed with ordinary, non-mutant worms. According to scientists, such a procedure is carried out when they want to establish an unambiguous link between a change in a gene and the detected effect. In other words, to make sure that in the process of interfering with genetics, we suddenly did not have unaccounted mutations that could distort the picture.
It turned out that the increased life expectancy in nematodes with the mutant sirtuin gene is not due to it, but to a change in another part of the genome responsible for the formation of sensory nerve cells. When it was possible to get rid of this mutation, the effect of longevity disappeared: nematodes with a high content of sirtuin lived as long as ordinary worms. The same result was obtained on fruit flies: these insects lived longer because together with the mutant sirtuin gene, a "service" piece of DNA – a nucleotide sequence that controlled the activity of a new sirtuin gene - got into their genome. Molecular genetics is full of mysteries; it was this additional sequence, without any sirtuin, that made long-lived flies.
Naturally, a storm has risen in the scientific community. Inflated expectations forced, for example, GlaxoSmithKline, one of the pharmaceutical giants, to spend $720 million on the development of "sirtuin longevity technologies". The discoverers of the remarkable effect themselves are trying to make a good face at a bad game: firstly, they reduced the increase in life expectancy from 15-50%, as stated in their first articles, to 10-14%; secondly, according to them, the role of sirtuin in the human body can be exactly what we want it to be, unlike low-organized nematodes and fruit flies.
On the other hand, the subversives hope that now there will be a turn towards studying other properties of this protein, whose effect on metabolism, including in mammals, has many intriguing features. But, of course, even in these studies, it is necessary to put at the forefront multiple and the strictest rechecks of the results obtained, in order to avoid the appearance of new molecular genetic myths.
Prepared based on the materials of Nature News: Longevity genes challenged.
Portal "Eternal youth" http://vechnayamolodost.ru23.09.2011