Centuries ago, Ponce de Leon sought the Fountain of Youth in Florida. Today, his quest lives on in laboratories around the world.
The discoveries are coming thick and fast, too. Just last week Leonard Guarente and scientists at the Massachusetts Institute of Technology announced they have figured out how a gene found in yeast controls longevity.
The gene, Silent Information Regulator, or SIR2, is present in mice and humans, too. It apparently controls lifespan in yeast by deactivating whole sections of the yeast genome. This has the effect of slowing the yeast’s metabolic rate, and other studies have shown there’s a strong correlation between a slower metabolic rate and longevity: rats fed a nutritionally balanced but low-calorie diet live longer. Just like a car engine running at a lower rate of speed, an organism running at a lower metabolic rate suffers less wear and tear.
SIR2 apparently teams up with a co-enzyme called NAD, which is associated with the metabolic rate of cells. When an organism is starved for calories, the NAD level may go up, which in turn tells SIR2 to come in and turn off sections of the genome. In the study, yeast with an extra copy of the SIR2 gene lived almost one and a half times as long as yeast without that extra copy. If the gene works the same way in humans, we might be able to extend lifespan using gene therapy techniques to plant extra copies of the SIR2 genes in human cells.
But that’s just one possible way to extend human lifespans. There are many more.
For instance, we know that one of the culprits in the aging process is oxygen. When it’s broken down in the body, it produces harmful substances called free radicals, which can damage DNA and tissue. Scientists have now identified genes that produce enzymes that detoxify free radicals.
Researchers at the University of Guelph have increased the lifespan of a fruit fly by almost 50 percent by giving it a gene that works to detoxify free radicals in motor neurons, the nerve cells that control movement. This proved that modifying a single gene could have a significant impact on lifespan. Before that, scientists thought aging was too complex a process for any one gene to have that much of an effect
In similar work, researchers at the European Institute of Oncology were recently able to extend the lifespan of mice up to 35 percent by breeding them without a gene that produces a protein vulnerable to oxidation. That was the first time the lifespan of a mammal had been increased with genetic modification.
Another focus of research is an enzyme called telomerase. Telomerase is necessary to keep the tips of chromosomes, called telomeres, growing. In mature cells, telomerase is shut down. As a result, the telomeres get shorter each time a cell divides; eventually, the chromosomes get so short the cell doesn’t work anymore.
Last year, researchers in Texas and California announced that by introducing telomerase into normal human cells that didn’t contain the enzyme, they had created cells that lived for many more generations than they normally would. Even if this doesn’t lead to anti-aging therapies, it could help us treat a variety of problems, from skin damage caused by burns to artherosclerosis. As well, since telomerase is required by cancer cells to proliferate, drugs that inhibit its action might be able to stop cancer from growing.
Also last year, researchers at the University of Colorado in Boulder were able to extend the life of a type of earthworm by modifying a gene that helped the worms deal with environmental changes such as drought and fluctuations in temperature.
Don’t want to wait 10 or 20 years for anti-aging treatments? There are things you can do now. Earlier this month, researchers at the Mayo Clinic reported that a 30-year study has revealed that optimistic people live 19 percent longer than pessimists. (“I knew it!” said the optimists. “Just goes to show,” muttered the pessimists.)
Another recent study has revealed that elderly people who lead active social and community lives live an average of two and a half years longer than reclusive people. That’s as much of a benefit as regular exercise provides.
So whether science ever develops a true fountain of youth or not, there is at least scientific proof that “you’re only as old as you feel.”
And if you also happen to be yeast, a worm, a fruit fly or a mouse–hey, you’ve got it made!
