Tuesday, June 1, 2010

Telomeres, Aging and Cancer

This year’s Nobel Prize for Physiology and Medicine was awarded to three American Scientists who made an important discovery related to both aging and cancer: “how chromosomes can be copied in a complete way during cell divisions and how they are protected against degradation.”

The new word out there in the field of aging and possibly cancer prevention is “telomere.” Telomeres are protective DNA-protein complexes positioned at the ends or tips of chromosomes. They have been compared with the tips of plastic at the end of shoelaces, which are protective and maintain the integrity of the laces.

Telomeres are important because of the functions they serve during cellular division. When cells divide, the exact sequence of DNA must be transcribed from the chromosomes of the parent cell to create chromosomes for the new cell. A piece of the telomere is clipped off and donated to the DNA sequence at the end of the chromosome so that the copying is complete and accurate. Most cells (e.g, those that line the intestinal tract) normally divide about 50-70 times, their telomeres getting progressively shorter until the cells lose their ability to divide, sustain genetic damage (which can cause cancer), or die.

Can anything counteract or slow down telomere shortening? Less frequent cell division is one possibility. Things that slow down cell division include calorie restricted diets, and avoidance of inflammation and injury. In addition, there is an enzyme called “telomerase” which can add chemical components to the ends of telomeres, which slows their erosion. However, telomerase is a two-edged sword.

If telomerase is too available all of the time, there is no slowing down of cell division, and there is an increased risk for cancer due to inaccuracies (mutations) in the gene copying process. While scientists have been examining telomerase as a possible “fountain of youth” substance, they also realize its potential for causing or increasing cancer risk in some individuals.

Scientists have found that telomere length does appear to be related to aging. One study has found that individuals with longer telomeres tended to live five years more than individuals with shorter telomeres. However, research is also showing that there are other factors that more strongly affect the number of years that humans live. These include chronological age, gender, and exposure to something called “oxidative stress.” Oxidative stress is damage to DNA, body proteins and fats caused by highly reactive substances that contain oxygen (oxidants and free radicals). These substances are produced normally when we breathe, but they are also increased by eating certain types of fats (polyunsaturated oils, trans fats, saturated fats); infections, smoking and overconsumption of alcohol also increases oxidants and free radicals. Consuming antioxidants contained in brightly colored fruits and vegetables can help counteract this effect, and slow the aging process down.

So, while telomeres are interesting and important, they are not the only factor involved in aging long and well! This is a complicated topic, so be sure to go to the following references to learn more:

http://learn.genetics.utah.edu/content/begin/traits/telomeres/
http://www.telomere.net/
http://www.scientificamerican.com/article.cfm?id=telomeres-telomerase-and
http://mcb.berkeley.edu/courses/mcb135k/telomeres.html

McCloy
Constance McCloy, PT, EdD
Associate Professor

2 Comments:

Ron Kustek said...

I suppose that a diet with less calories, and avoiding getting hurt is something that we all can take from this blog post! It is definately interesting to learn about the telomeres and how they are important. Thank you for this great post.

GERO 584 said...

Thanks for your reply and interest Ron. RE: diet, it is that old "fruits and veggies" thing, and I also heard a speaker on PBS last night who quoted some studies that state that lower intake of animal products (especially red meat) was associated with longer healthier years of life. The researcher quoted was looking at diets of people in China (high veggie, low meat) and people who were vegetarian (associated with being 7th Day Adventists). Enjoy the summer fruits and veggies!