About the benefits of vitamins and... free radicals
Niacin – the source of eternal youth?
LifeSciencesToday based on the materials of ETH Zurich: Niacin, the fountain of youthWho wouldn't want to live a long and healthy life?
A completely affordable dietary supplement can help with this. Scientists at the Federal Higher Technical School of Zurich (Eidgenossische Technische Hochschule Zurich) have demonstrated that vitamin B3, or niacin (nicotinic acid), and its metabolite nicotinamide increase the life expectancy of roundworms by about ten percent. Article by Schmeisser et al. The role of sirtuins in lifespan regulation is linked to methylation of nicotinamide published in the journal Nature Chemical Biology.
A specialist in the field of energy metabolism, Professor Michael Ristow and an international group of scientists led by him have experimentally proved that niacin and nicotinamide cause this effect, contributing to the formation of so-called free radicals.
"The life of roundworms is prolonged by reactive oxygen species," says Professor Ristov.
In his opinion, "there is no scientific evidence of the usefulness of antioxidants." Such a statement from the mouth of a scientist may seem surprising, since reactive oxygen species (ROS) are considered to be agents that destroy nuclear and mitochondrial DNA. The views of the Swiss researcher also contradict the academic ideas advocated by many of his colleagues. As is known, reactive oxygen species damage somatic cells, causing so-called oxidative (oxidative) stress. Antioxidants contained in vegetables, fruits and some vegetable oils are able to neutralize free radicals. Many scientists believe that antioxidants are good for health.
"The statement that taking antioxidants, especially in the form of tablets, has a positive effect on almost all aspects of human health, has no scientific basis," continues Professor Ristov.
The scientist does not dispute the fact that fruits and vegetables are useful. However, this may rather be due to other compounds contained in them, for example, polyphenols.
"Fruits and vegetables are healthy, despite the fact that they contain antioxidants," Ristov believes.
Based on the results of his latest work and many other earlier studies, he is convinced that small amounts of reactive oxygen species and the oxidative stress they cause have a positive effect on health.
"Cells cope well with oxidative stress and neutralize it."
In his earlier studies on humans, Professor Ristov showed that the health effect of power sports is mediated by increased formation of reactive oxygen species, and antioxidants neutralize this effect. Based on the results of this work, he concludes that from a metabolic point of view, niacin mimics the effect of strength sports.
"Niacin tricks the body into believing that it is exercising – even if it is not," explains the scientist.
The researchers conducted their experiments on the model organism Caenorhabditis elegans. The lifespan of this tiny worm is only about one month, it is easy to keep, which makes this animal an ideal model for studying the aging process.
According to the Swiss professor, the results of the study may also apply to the human body. After all, in roundworms and higher organisms, the metabolic pathways of niacin are very close. The question of whether niacin has a similar effect on the lifespan of mice is the subject of an ongoing study. However, earlier experiments have already confirmed the healing effect of niacin observed in people with elevated cholesterol levels in the blood.
The role of histone deacetylases of sirtuins in the regulation of life expectancy is hotly debated by the scientific community. In contrast to recent observations, Professor Ristov and his colleagues concluded that overexpression of sir-2.1, an orthologue of mammalian SirT1, does indeed increase the lifespan of Caenorhabditis elegans. Sirtuins convert NAD+ to nicotinamide (NAM). Nicotinamide and its metabolite, 1-methylnicotinamide (MNA), increase the lifespan of C. elegans even in the absence of sir-2.1. Scientists have identified in C. elegans a previously unknown nicotinamide-N-methyltransferase (NNMT) encoded by a gene, now called anmt-1, converting nicotinamide to 1-methylnicotinamide. Suppression and overexpression of anmt-1 have the opposite effect on life expectancy independently of sirtuins. The loss of anmt-1 completely inhibits sir-2.1-mediated increase in life expectancy. 1-methylnicotinamide serves as a substrate of the newly identified aldehyde oxidase, GAD-3, (in Figure AOx1), which forms hydrogen peroxide, acting as a signal contributing to an increase in the lifespan of C. elegans. In general, sirtuin-mediated increase in life expectancy depends on nicotinamide methylation, presenting an unexpected mechanistic role of sirtuins in addition to histone deacetylation. (Fig. Nature Chemical Biology)Nicotinic acid and nicotinamide have been used as food additives for decades.
In addition, niacin is naturally found in a number of foods, including meat, liver, fish, peanuts, mushrooms, rice and wheat bran. However, is the consumption of niacin in the quantities in which it is contained in food sufficient to improve health or even increase life expectancy? Ristov does not know the answer to this question yet.
The latest study of the effect of niacin and nicotinamide on life expectancy is directly related to a certain class of enzymes – NAD+-dependent histone deacetylases, known as sirtuins, which convert niacin into nicotinamide. In addition, they are involved in the regulation of genes, suppressing the activity of some of them.
This work suggests that the activity of sirtuins really prolongs the life of roundworms. However, this effect is determined not by the regulation of genes, as previously thought, but by the conversion of nicotinic acid into nicotinamide. Studying genetically modified roundworms deprived of the ability to convert nicotinamide into its metabolites, scientists have not observed an increase in life expectancy even with overexpression of sirtuins, which in other cases causes such an effect.
The scientific debate about whether sirtuins really have an impact on life expectancy is ongoing and, apparently, far from over.
Portal "Eternal youth" http://vechnayamolodost.ru04.10.2013