Friday, October 19, 2012

100 Years

By Adrienne M. Roehrich, Chemistry Editor
Photo of the author with her 100 year old grandmother 10-1-2012


100 is such a nice round number. 

Should I start with a disclaimer? I'm a chemist, not a biologist. Perhaps I should leave a post on centenarians to the biologists, but I have a vested interest in the topic. On October 1 of this year, my grandmother turned 100, so I've been a little obsessed with living until 100. In the United States, an estimated 1 in 4400 people reach the age of 100 and the highest number worldwide. The next highest number of centenarians reside in Japan, with a rate of 1 in 3500 people. 

The question is, why do these people live so long? This is a highly studied question. When one delves into the literature, as with most questions, there is no simple answer and often studies conflict with each other. There are different modes of study: some scientists study those who have become centenarians to try to determine what they have done to reach this rare milestone while other scientists work in theories, then animal models to study what pathways lead to longevity.

Studies have found that healthy centenarians in some areas have high levels of vitamin A and vitamin E1 and higher red blood cell glutathione reductase and catalase activities.2,3 But the presence of higher levels of these vitamins and glutathione reductase is not present in all centenarians, and the mere presence of these high levels does not necessarily indicate longevity.

 
Molecules that may or may not help longevity


You may have heard exclamations about antioxidants or calorie restriction. While antioxidants (the aforementioned vitamin A and vitamin E) are known to protect the body from the harmful effects of free-radicals, which occur in the normal processes of the body, evidence does not support that simply adding more antioxidants to the diet will slow aging. There are studies also showing that calorie restriction may have beneficial effects in terms of markers of aging in some animals, but many animals that are commonly used as human models do not extend longevity under calorie restriction, and such a course of action may have deleterious effects. The safety and benefits of long-term calorie restriction is currently unknown. Scientists are working towards answering these questions. 

Genetics plays an important role. The best predictor of a person reaching 100 is having a sibling live past 100. Variations in genes abound, but other than children of long-lived parents living longer, specifics are elusive. Oddly, being born in the Fall (September through November) is linked with a higher likelihood of becoming a centenarian.4 And functional independence for a longer period of time (past the age of 90) was found to be strongly correlated to centenarians. 90% of the participants in the New England Centenarian study were found to have been so.

Hormones are integral to our body function and have been studied for their potential pathways in longevity. Testosterone has been focused on, and lately a study of Korean eunuchs gave a higher rate of centenarians, 3 in 81 individuals. Due to the wide variability of the amount of testosterone produced by individuals, whether more or less testosterone exposure is beneficial or deleterious is unknown. 

What causes aging? This question is so important the National Institutes of Health (NIH) has devoted National Institute on Aging, the leading research institute on aging. A summary in more detail than I have gone into here is given on the NIH NIA’s site about preventing aging

If we look at the cellular level, scientists discovered that complete copying of DNA is dictated by telomeres and the enzyme telomerase, which earned 3 scientists the Nobel Prize in Physiology and Medicine in 2009. The unique DNA sequence in the telomeres protects chromosomes from degradation. When telomeres are shortened, cells age. Eventually, the telomeres will shorten, and cells will age and die. Unfortunately, extending telomeres or increasing the activity of telomerase enzyme does not help anti-aging, it contributes towards the growth of cancerous cells. 

A conversation with Dr. Mark D Johnson on twitter gave me these neat facts: Complete natural Homo sapiens LifeSpan = 120 years! All mammals except humans, bonobos, and chimpanzees, live six times their growth cycle. We grow within 20 years. That means natural mammal lifespan of 120. 

Overall, the contributing factors towards ageing and longevity are deemed to be complicated and there is no short-order anti-aging remedy.

Turning more towards my own field of expertise, the Maillard Reaction, a chemical reaction that makes cooked food tasty, also turns 100. Obviously, the actual chemical reaction goes back longer than 100 years - to when amino acids began to react with sugars at elevated temperatures. However, the French chemist Louis-Camille Maillard first reported the nature of these reactions in 1912.5 Maillard chemistry not only describes the molecules in baked bread, grilled veggies, and brewing of beer, but also other molecules as products, so many that chemists did not study Maillard chemistry in detail until World War II. Nearly 60 years ago, African American chemist John E. Hodge reported a mechanism for the Maillard reaction6

Hodge’s Flowchart of the Maillard Reaction

Products of the Maillard reaction range from molecules that are both welcome and abhorrent. The usually enjoyed flavor and aroma of roasted coffee is a product of the Maillard reaction, as is the char on the surface of grilled food which is considered to be carcinogenic. 

Roasted Coffee Beans, photo by Adrienne Roehrich
Grilled Yams, photo by Adrienne Roehrich


Do you know someone or something that has reached the anniversary of 100 years on this earth? 


References:
(1) Mecocci, P.; Polidori, M. C.; Troiano, L.; Cherubini, A.; Cecchetti, R.; Pini, G.; Straatman, M.; Monti, D.; Stahl, W.; Sies, H.; Franceschi, C.; Senin, U. Free Radical Biology and Medicine 2000, 28, 1243.
(2) Klapcinska, B.; Derejczyk, J.; Wieczorowska-Tobis, K.; Sobczak, A.; Sadowska-Krepa, E.; Danch, A. Acta Biochimica Ponoica 2000, 47, 281.
(3) Andersen, H. R.; Jeune, B.; Nybo, H.; Neilsen, J. B.; Andersen-Randberg, K.; Grandjean, P. Age and Ageing 1998, 27, 643.
(4) Journal of Aging Research 2011, 2011.
(5) Maillard, L.-C. Comp. Rend. 1912, 66.
(6) Hodge, J. E. Journal of Agricultural and Food Chemistry 1953, 1, 928.


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