Friday, March 31, 2006

The longevity genes

As we age, our bodies lose the ability to regenerate cells at the rate that they do when they are younger. Why that is and what processes guide the regeneration of cells are questions that biologists have been trying to discover for years, if not centuries. Answering this question may lead scientists to discover all sorts of treatments that could extend the human lifespan.

Yet we and other researchers have found that a family of genes involved in an organism's ability to withstand a stressful environment, such as excessive heat or scarcity of food or water, have the power to keep its natural defense and repair activities going strong regardless of age. By optimizing the body's functioning for survival, these genes maximize the individual's chances of getting through the crisis. And if they remain activated long enough, they can also dramatically enhance the organism's health and extend its life span. In essence, they represent the opposite of aging genes--longevity genes.

Scientists are now finding that individual cells divide for a period, but over time a "mother" cell, which is a cell that has divided many times, ends up having stray copies of DNA rings that have spun off the main DNA chain when it copies itself. Cells that build up stray rings become crippled and die.

But there is an enzyme in cells that controls how tightly DNA coils around host proteins, preventing them from releasing stray rings leading to the deterioration of the cell.

This sounds complicated, but the article explains it well. The authors are trying to find out and explain what produces or activates the enzymes, and they think that it is biological stressors. Things that stress our systems (not emotional or psychological stress) into fighting for survival. For instance, they discovered that reducing the caloric intake of certain simple organisms and animals, that they lived longer and were healthier.

Restricting an animal's calorie intake is the most famous intervention known to extend life span. Discovered more than 70 years ago, it is still the only one absolutely proven to work. The restricted regime typically involves reducing an individual's food consumption by 30 to 40 percent compared with what is considered normal for its species. Animals ranging from rats and mice to dogs and possibly primates that remain on this diet not only live longer but are far healthier during their prolonged lives. Most diseases, including cancer, diabetes and even neurodegenerative illnesses, are forestalled. The organism seems to be supercharged for survival.


The phenomenon was long attributed to a simple slowing down of metabolism--cells' production of energy from fuel molecules--and therefore reduction of its toxic by-products in response to less food.

But this view now appears to be incorrect. Calorie restriction does not slow metabolism in mammals, and in yeast and worms, metabolism is both sped up and altered by the diet. We believe, therefore, that calorie restriction is a biological stressor like natural food scarcity that induces a defensive response to boost the organism's chances of survival. In mammals, its effects include changes in cellular defenses, repair, energy production and activation of programmed cell death known as apoptosis.

They then spend much time talking about the enzyme SIRT1 and how it might be the key in how the body reacts to reduced caloric intake.

Over the course of a lifetime, cell loss from apoptosis may be an important factor in aging, particularly in nonrenewable tissues such as the heart and brain, and slowing cell death may be one way Sirtuins promote health and longevity.

So they haven’t really discovered why it is that caloric reduction causes sirtuin reaction to delay cellular decay. But it’s a really interesting article, and fascinating to think that scientists are on the verge of extending life another 20 or 30 years with the knowledge.

I’ve been finding it hard to reduce my diet lately. My lovely wife cooks way to well, and I really enjoy food. I have this tendency to dress down in cold weather, liking cold weather as I do, and I tried to convince her that perhaps I’m just stressing my body into some sort of survival mode that’s increasing my siruins, and so by wearing shorts on cold days it’s actually increasing my lifespan and improving my health. I don’t think she’s buying it.

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