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Saturday, March 12, 2011

The Lobster Life: Couldn't Feel Better at 90



Maybe I was the only one on the planet who didn't know that the sole way to gauge the exact age of a lobster would be by its shell; however, since lobsters shed their shells so often, it is impossible to determine their actual age?

If it doesn't meet the fate of the lemon wedge and parsley, a lobster can grow very, very old. Knowledge of body size at age makes scientists believe that lobsters can attain a maximum age of 100 years. The normal life span is about 15 years, and lobsters can grow to be 3 feet long in overall body length. But, the biggest lobster ever seen tipped the scales at 40-plus pounds. Lobsters are basically eating, molting, growing machines .

Animal facts - enough already? Wait just a minute because the lobster may just have the key to something humans desire. How would you like to live a sharp, lively, active life in your 80s or even into your 90s? If you were a 90 year-old lobster, all of your fellow geezer nonagenarians would be kicking up their heels.

It seems lobsters age so gracefully they show no measurable signs of aging: no loss of appetite, no change in metabolism, no loss of reproductive urge or ability, or no decline in strength or health.

If a lobster dies, it seems the demise is due to external causes. They get fished by humans, eaten by seals, wasted by parasites, but they don't seem to die from within. Of course, no one really knows how the average lobster dies. There are no definitive studies.(Robert Krulwich, "Long Live the Lobster: Forever Young?" www.npr.org/templates, National Public Radio, June 26 2007)

Theoretically, if a lobster has no insults to its system that would shutdown its basic metabolism, it would  continue to live and get bigger and bigger.And, guess what? Lobsters have hearts and circulatory systems. Scientists have yet to meet a lobster dead from a heart attack. And, ladies, did you know that old female lobsters have more babies than the younger gals? Talk about flowing productive juices.

If the lobster avoids the cage by living in the proper geographic location, its life is just -- eat, molt, and expand over and over. Don't get the picture wrong. Lobsters face life-threatening problems like pollution, acid rain, and hungry seals. But, left alone, they continually eat, molt, and expand. (Robert Krulwich, "The Long and Happy Lives of Lobsters, National Public Radio, November 16 2007)



Where Do You Fit Into the Lobster Story?

Harvard Dana-Farber Cancer Institute announced in 2010 that they had succeeded in reversing age-related decline in mice, using genetic engineering techniques. The scientists created transgenic mice with a gene for telomerase expression that could be switched on and off with a chemical signal.

Bennett Foddy wrote, "Telomerase is an enzyme which renews telomeres, repetitive regions of DNA that are attached to the ends of our chromosomes. Telomeres allow cellular replication to take place without loss of information; but after a certain number of cell divisions, the telomeres become depleted and no further replication can take place." ("Our Future As Human Lobsters," Practical Ethics, University of Oxford, November 29 2010)

In mammals, telomerase is expressed by a gene which is only active in  gametes, stem cells, very young somatic cells, and T-cells. For example, T-cells distribute telomerase in younger humans, but stop doing so when we are around 45 years old.

So, the absence of telomerase in your older body prevents new telomeres from being formed, which means that your stem cells are ultimately unable to continue to renew their own telomeres. Your stem cells begin to die as their telomeres are depleted, and you lose your capacity to regenerate tissue.

Of course, aging relates to loss of brain cells and cognitive function, loss of bone density, muscle wastage, wounds that heal more slowly, and so forth. Age-related illnesses such as Alzheimer's disease, artherosclerosis, macular degeneration, and liver cirrhosis are often devastating.

Human beings with abnormally low levels of telomerase suffer from premature aging. But lobsters, by contrast, express high levels of telomerase in their bodies throughout their lives, and their bodies remain characteristically youthful until they die.

Could you age more like lobsters if someone could simply increase the amount of telomerase in your body, leading to longer telomeres and longer cellular lifespan? Well, one problem with such an application is that telomerase-based interventions would increase the rate of cancer. Cancerous cells switch on the telomerase gene in your DNA, allowing themselves to rapidly replicate and spread throughout your body.

Still, it is thought that the loss of telomeres is a major contributing factor to the formation of new cancers. Until now, researcher have no indication of whether increasing telomerase would be beneficial or burdensome.

Back to the Harvard research. The discovery by the Ronald DePinho's team at Harvard lends promise. The team deactivated the telomerase gene in their transgenic mice, causing them to undergo premature aging in the form of cognitive decline and loss of fertility. Then, they switched the gene back on, and the symptoms of age were reversed—their brains grew new tissue, their cognitive skills improved and their testicles began to grow and function normally.

Foddy reported that the treated mice lived longer than the mice whose telomerase gene remained inactive. Crucially, the mice did not show any significant increase in the rates of cancer. ("Our Future As Human Lobsters," Practical Ethics, University of Oxford, November 29 2010)

Now, please understand, the mice did not live longer than normal, un-modified strains. And, there are major differences in mechanisms of senescence and cancer-resistance between mice and humans, so the beneficial effects may be smaller or absent in humans. Telomere-shortening is only one component of age-related decline; scientists still need to address other mechanisms which cause you to decline and die as you age, such as genetic diseases, cancers, glycation, and oxidation.

In a final caution, Foddy said before doctors could implement a telomerase therapy in humans that could be used in a widespread way, they would need to find a way to do it that did not involve germline genetic enhancements such as those used in the experiments.

In short, a pill which will help you live longer by a decade is a long way off. Yet, the Harvard discovery shows that one of the major obstacles to telomerase-baded treatments -- cancer -- may not be an obstacle at all.


Challenges


1. If doctors can treat the process of aging, does this blur the line between health, disease and disability? 

2. If there are treatments that can reverse the effects of aging, will we need to change how we  decide who deserves disability payments, what counts as discrimination, and how to deal with retirement?

3. Should we use the technologies at all to extend life span? In other words, is it right to either choose to save life by extending it or choose to let people die once they have reached an "appropriate" age?

If only lobsters could talk, maybe they could tell us how they have solved the questions. One thing is sure, we would want to consult with the oldest lobster to find answers because it would definitely still be very well minded.

Why doesn’t the lobster like to share with his friends?
Because he’s shellfish!
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