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Can we live forever? This is a centuries old question, Holy Grail of scientific research and ultimate goal of alchemists and magician of all sorts and kinds. Is it really achievable? Is aging completely inescapable? Can we stop the process of becoming old or at least slow it down? Why some people live much longer and look much younger than others? These and hundreds of other similar questions have never been answered by either science or philosophy. But it looks like the time to get answers has arrived.
Our understanding of the human body’s functioning has undergone a remarkable transformation in recent decades. Now we know much more about the way our body works and the way our biological clock ticks. Our understanding of aging has transformed from rather vague philosophical and religious concepts to clear and detailed biological mechanisms based on the functions of certain genes and proteins.
Why we become old?
It turned out that aging is, indeed, inescapable. It is programmed in our genes. No, we don’t have specific genes that instruct our body to become older. But we have genetic programs that simply stop working effectively when we enter the post-reproductive age. The ends of our chromosomes become shorter after each cell division, and eventually they become so short that any further cell division can damage the genetic material encoded in chromosomes and make cells non-functional. It doesn't matter how good and efficient everything else is in the body. Chromosomal ends shortening is the natural mechanism preventing us from living forever.
The existence of mechanism for chromosomal shortening was predicted in the 1960s, at the very beginning of modern molecular biology. At the same time it was hypothesized that there should be another mechanism in nature that counteracts chromosomal shortening and thus allows to preserve genetic information and pass it from one generation to the next. The mechanism turned out to rely on the function of specific and unusual ancient enzyme called telomerase that restores the chromosomal ends. Telomerase is inactivated in adults but works during human embryo development. It also becomes activated in cancers making cancer cells immortal and allowing them to divide and multiply forever.
Telomerase activation prevents the cellular senescence, but would it be equally helpful to prevent the aging of the whole body? Taking into account how telomerase works in cancer, it seems unlikely. Regulation of aging process is simply more complex and relies on many processes, not just on turning the telomerase on and off. Genetic program of aging involves many genes that work together.
Can aging be turned off?
Intriguingly, there are tantalizing evidences in nature that aging program can indeed be turned off. Some animals simply don’t age. Greenland whale is one of such unusual organisms. These mammal inhabiting cold arctic waters is not getting old. It grows all its life and usually dies as a result of various accidents. Greenland whale can live for up to 200 years and grow to 20 meters in length but even the biggest and oldest animals don’t show any signs of aging. It was recently found that even the century-old whale females remain fertile. Giant turtles and giant clams are other animals that live very long lives and don’t age.
Many scientists argue that animals which live longer don’t really have any particular aging program that is turned off. Instead, they have genetic program for extended survival. One way or another, the closer look on the genetics of these creatures would certainly help to solve the mysteries of our own age-related decline.
Human centenaries often show remarkable strength and activity for their age. Also, they often look many years younger than they real age. On the other hand, there are genetic conditions that accelerate aging. Hutchinson-Gilford Progeria Syndrome is one of such diseases: the children affected become old ten times faster than normal person and rarely live beyond the age of 13. Most of them die from various complications of atherosclerosis such as heart attacks and strokes.
The natural variations in the rate of aging demonstrate that the aging program is not completely fixed and unchangeable. At least, it can be influenced on genetic level. Once we achieve enough knowledge to manipulate human genes, turning off the aging program may become a reality.