Part 6: The 9 causes of ageing - Nutrient detection
The sixth cause of ageing that we discuss is related to the malfunctioning over time of the nutrient sensing chain. But what causes this mechanism to malfunction?
Nutrient detection pathways
In cells, nutrient sensing pathways adapt the behaviour of our cells and the activity of their metabolism to the amount of nutrients available to our cells.
Roughly speaking, at the level of the organism, if there is not enough to eat, the body tends to reduce the sexual appetite of the animal and to put the body in survival mode in order to live longer and reproduce in better times. A similar phenomenon occurs at the level of the cell.
Caloric restriction is the only scientifically validated method of increasing healthy life expectancy in all mammals tested. This increase can lead to a 30% increase in life expectancy, for example in some primates.
Nutrient sensing involves, not surprisingly, the signalling pathways related to insulin and glucose sensing at the cell surface. It also involves the sort of central switches AMPK, which detects nutrient scarcity, and the mTOR complex, which detects amino acid abundance. Sirtuins are also central switches that detect low energy states by detecting the concentration of NAD+, which is also the fuel for proteins that repair DNA...
Theoretically, it is now assumed that as we age, cellular stress and cell damage increase. The levels of free radicals in the body increase in parallel with this phenomenon, in order to preserve the organism.
Beyond a certain point, these levels would cease to maintain cellular balance and could aggravate the problems associated with age. So the role of free radicals is not yet clear to scientists; it is a matter of real debate.
In summary, this link between nutrient sensing and longevity explains why some diabetes drugs, such as metformin, appear to extend lifespan via AMPK activation in worms and mice. In fact, there are encouraging studies on its effect in humans. More comprehensive studies are underway.
SOURCES:
Guilhem Velvé Casquillas on http://www.longlonglife.org/