Thursday, November 03, 2011

Two Hints of the Possibility for a Healthy Long Life

The first hint comes from the Mayo Clinic's Darren Baker. Baker has developed a way of delaying symptoms of old age in mice, and has even been able to reverse some signs of aging in already aged mice. Here's more:
Baker has developed a way of killing all of a mouse’s senescent cells by feeding them with a specific drug. When he did that in middle age, he gave the mice many more healthy years. He delayed the arrival of cataracts in their eyes, put off the weakening of their muscles, and held back the loss of their body fat. He even managed to reverse some of these problems by removing senescent cells from mice that had already grown old. There is a lot of work to do before these results could be applied to humans, but for now, Baker has shown that senescent cells are important players in the ageing process.

Note that the mice in this study didn’t live any longer; they just spent more of their life being healthy.

Baker exploited the fact that many senescent cells rely on a protein called p16-Ink4a. He created a genetic circuit that reacts to the presence of p16-Ink4a by manufacturing an executioner: a protein called caspase-8 that kills its host cell. Caspase-8 is like a pair of scissors – it comes in two halves that only work when they unite. Baker could link the two halves together using a specific drug. By sneaking the drug into a mouse’s food, he activated the executioners, which only killed off the cells that have lots of p16-Ink4a. Only the senescent ones get the chop.

Baker tested out this system in a special strain of genetically engineered mice that age very quickly. It worked. The senescent cells disappeared, and that substantially delayed the onset of muscle loss, cataracts, and fat loss. Typically, around half of these mice show signs of muscle loss by five months of age. Without their senescent cells, only a quarter of them showed the same signs at ten months. Their muscle fibres were larger, and they ran further on treadmills. Even old mice, whose bodies had started to decline, showed improvements. _Discover
Another look at this research from the Economist:
Dr Baker genetically engineered a group of mice that were already quite unusual. They had a condition called progeria, meaning that they aged much more rapidly than normal mice. (A few unfortunate humans suffer from a similar condition.) The extra tweak he added to the DNA of these mice was a way of killing cells that produce P16INK4A. He did this by inserting into the animals’ DNA, near the gene for P16INK4A, a second gene that was, because of this proximity, controlled by the same genetic switch. This second gene, activated whenever the gene for P16INK4A was active, produced a protein that was harmless in itself, but which could be made deadly by the presence of a particular drug. Giving a mouse this drug, then, would kill cells which had reached their Hayflick limits while leaving other cells untouched. Dr Baker raised his mice, administered the drug, and watched.

The results were spectacular. Mice given the drug every three days from birth suffered far less age-related body-wasting than those which were not. They lost less fatty tissue. Their muscles remained plump (and effective, too, according to treadmill tests). And they did not suffer cataracts of the eye. They did, though, continue to experience age-related problems in tissues that do not produce P16INK4A as they get old. In particular, their hearts and blood vessels aged normally (or, rather, what passes for normally in mice with progeria). For that reason, since heart failure is the main cause of death in such mice, their lifespans were not extended.

The drug, Dr Baker found, produced some benefit even if it was administered to a mouse only later in life. Though it could not clear cataracts that had already formed, it partly reversed muscle-wasting and fatty-tissue loss. Such mice were thus healthier than their untreated confrères. _Economist
This research will require replication and a great deal of clarification, before it moves from mice to larger mammals such as humans. But it opens up a number of possible avenues of research.

The second hint of likely means to achieve healthier long lives, is research done in fruit flies at the Salk Institute, in southern California.
Although it is a well-documented fact that restricting calories during daily food intake is the easiest strategy to extend life spans for both humans and animals, little is known about biological mechanisms underlying this phenomenon.

..."Fruit flies and humans have a lot more in common than most people think," said Leanne Jones, an Associate Professor at Salk's Laboratory of Genetics and a lead scientist on the project, "There is a tremendous amount of similarity between a human small intestine and the fruit fly intestine."

The researchers found that boosting the activity of dPGC-1, the Fruit Fly version of the gene, resulted in greater numbers of mitochondria and more energy-production in flies; the same phenomenon is seen in organisms on calorie restricted diets.

When the activity of the gene was accelerated in stem and progenitor cells of the intestine, which serve to replenish intestinal tissues, these cellular changes correspond with better health and longer lifespan.

The flies lived between 20 and 50 percent longer, depending on the method and extent to which the activity of the gene was altered. _ibtimes
The fruit fly research suggests that not only healthier long lives are possible, but "longer long" lives are possible as well.

The approach taken by the SENS Foundation involves using multiple approaches to extending healthy lifespan. Destroying senescent cells -- such as Darren Baker is learning to do -- is one of the main approaches that SENS is following. Improving the function of mitochondria is another of the main tactics of SENS.

As humans in advanced societies are putting less and less energy into raising children, and putting more and more energy into raising themselves, thoughts of increased longevity and lifespan are coming more into the mainstream of respectability. The main limitation to further research into life extension is -- as always -- funding. But even with unlimited funding, moving the research from animal models into human therapeutics would take a matter of decades.

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