As part of my science module for my degree I recently wrote an essay about aging, I hope you dont mind if I share it here.
On Tuesday, February 19 th 2002, the Guardian newspaper contained an article entitled Rats give pointer to elixir of youth (Radford, 2002). The article goes on to report about research into the effects of two combined dietary supplements on the health and vitality of aging rats. The research, carried out at the University of California (Juvenon, 2002), indicates that the two supplements (acety-L-carintine and alpha-lipoic acid) had dramatic positive effects on the rats in that they had more energy and improved memory. According to Radford, this has opened up the prospect of rejuvenating aging humans.
The promise of immortality has long held a fascination for the human race. Thousands of years ago people preserved their bodies by mummification in an attempt to send something of themselves to future generations. Today, the more sophisticated technique of cryonics - freezing a body at death in the hope that it can be revived sometime in the future when a cure has been found, has replaced the old methods of mummification. This primal urge to resist the passing of our consciousness has until recently mainly been in the purview of the religious, through the promise of everlasting life after death. However, recent scientific research into the process of aging has generated interest in the possibility of extending the average life expectancy of humans through secular means.
There are many therapies and theories related to the understanding and delaying of aging. These include changes in lifestyle, genetics and cellular breakdown. It is clear that choices of lifestyle, such as not smoking, can have a positive effect on how long you live, and there is also an established link between our inherited genes and longevity; we are more likely to live to a ripe old age if our parents and grandparents did. However, in this piece, I wish to concentrate on the theories of aging related to research at a cellular level.
How and why do we age? These are extremely complex questions and scientists around the world are looking closely at the cells in our bodies to try and find the answers. Cells are the critical building blocks of our bodies. There are millions of cells in the human body, transforming energy to provide for its various processes or specialising into a myriad of different functions such as blood cells or brain cells. The fact that these cells eventually lose their ability to function and reproduce is thought by many to be at the heart of the aging process. What, then, are the theories of aging that relate to the cells? There are many areas of research related to aging; it is not possible even to list them all within the confines of this assignment. However, these are the two areas that I found to be of particular interest: oxidative damage, and Telomeres.
Oxidative Damage
Also known as the free radical theory of aging, this theory is concerned with the damage that is occurring in cells due to normal metabolic processes. Research into oxidative damage, according to Beckman and Ames (1998) is:
rapidly attracting the interest of the mainstream ofbiological research. From its origins in radiation biology, througha decade or so of dormancy and two decades of steady phenomenologicalresearch, it has attracted an increasing number of scientistsfrom an expanding circle of fields. During the past decade, severallines of evidence have convinced a number of scientists that oxidantsplay an important role in aging.
Throughout our lives, during the normal process of oxidation (turning oxygen into energy), our bodies produce toxic by-products called free radicals. These highly reactive oxidising substances can attack healthy cells and DNA. Normally these substances are eliminated from our systems by chemicals called antioxidants but this process is not 100% efficient. Therefore, over time, the damage to cells and DNA accumulates resulting in aging and age related illnesses. Scientists are researching the possible benefits of taking increased antioxidants in our food. Three of the most powerful of these are the vitamins E, and C and the mineral Selenium. In addition to the effect oxidisation has on an individuals life expectancy, the free radical theory has also sought to explain differences between species' life spans in terms of oxidants. That is, a species that has a higher metabolic rate will produce more oxidants and will therefore have a shorter life span. Beckman and Ames (1998), however, caution against jumping to this conclusion:
there is a danger that in the excitement of theoretical confirmation, certain nuances are lost. For instance, therevelation that oxygen radicals may be involved in neurodegenerationdoes not mean that oxidative stress determines life span. And advises that the scope of the free radical theory of aging shouldinclude aging-associated oxidative stress in general, rather thanlimiting itself to those oxidative events that may determine lifespan.
Is free radical theory more than just a theory? Can it be said that oxidants play a role in the aging process? It seems clear that it can. The main benefits of the combination of substances developed by the scientists in the rat trial mentioned above are an increase in cellular energy and reduction of oxidative damage. In their research paper on the free radical theory, Beckmann and Ames (1998) conclude: The answer to the question of whether or not the free radical theory has yet been confirmed depends on one's conception ofwhat the theory predicts. In its broader sense ("oxidants contributesignificantly to the process of degenerative senescence"), thetheory has clearly been validated. However, the effect on the life expectancy of a human who supplements their diet with anti-oxidants has not been clearly established.
Telomeres
Many scientists believe that such deleterious processes as oxidative damage and/or wear and tear mechanisms are responsible for cellular senescence. Others have opted for theories of "programmed"aging, in which a specific lifespan is believed to be encoded within an animals cells.
Before we consider the function and relationship to aging of telomeres it is necessary to understand the importance of cell division to the life of an organism. Many cells in our body degenerate quickly and must be replaced, for example skin cells and the cells which line our digestive tract. They replace themselves by undergoing cell division, or mitosis. Inside the nucleus of our cells are chromosomes (46 in all). At the tips of these chromosomes are repeating sequences of genetic material called Telomeres. These telomeres have an important function in the replication or duplication of chromosomes during cell division. It has been discovered that each time a cell divides the telomeres are slightly shortened. Eventually, they become so short that cell division can no longer occur and the cell becomes senescent and dies. This is the critical point: as our cells age so do we. This programmed number of times that a cell can divide is sometimes referred to as the Hayflick limit after Dr. Leonard Hayflick who first observed this phenomena over forty years ago. Some scientists are working on the possibility of being able to reset this biological clock and thus give cells a new lease of life. However, this may present dangers: cells that do not have a telomeres limiter already exist. Cancer cells divide limitlessly and out of control, and it is feared that an attempt to reset normal cells may turn them cancerous.
In doing the research for this assignment it occurred to me that the idea of extending human life could theoretically be as much a threat to religion as Darwins Origin of the species. How will some faiths view the idea of increasing the human lifespan beyond what is natural? Eventually, if it ever becomes possible to prevent aging (and therefore death) altogether, how will the proponents of life after death react to this? Will scientists be seen as interfering where they ought not, as in other areas of science (i.e. cloning) what are the ethics of playing God? Will the worldview offered by religions now appear obsolete? Scientists understanding of the aging process is increasing at an extremely rapid rate. It seems to me that antagonism between these two great forces will continue to be inevitable for the foreseeable future.
Dean Moorhouse
February 2002
References and Bibliography
(AFAR) American Federation for Aging Research. | Website: Accessed 27/2/02 www.infoaging.org/b-tel-home.html |
Beckman, K. & Ames , B. (1998) | Journal: Physiological Reviews Vol. 78 pp.547-581 No.2 April 1998. The Free Radical Theory of Aging Matures Published by American Physiological Society. |
Juvenon (2002) | Website Accessed 26/2/02 |
Mackean, D,G. (1988) | Human LifeJohn Murray Publishers, London. |
Radford, T (2002) | Website: Accessed 27/2/02Guardian NewspaperOnline article ref: www.guardian.co.uk/Archive/Article/0,4273,4358683,00.html |
Salehomoum, N & Shiow, L (2000) | Berkeley Scientific JournalNo. 00S02 Spring 2000. Current Theories On How And Why We Age |
Aging Research Centre | Website: Accessed 27/2/02www.arclab.org |
P.S.
The Juvenon website now sells a supplement that contains elements they claim helps to slow down aging related damage.