Add Years to Your Life?
According to the results of two new
studies done on yeast cells, reducing calories activates the silenced
information regulator (Sir2) gene, which prolongs cell life.
It's still not quite clear, however,
exactly how Sir2 is activated.
In one study, published in the
Jan. 1 issue of Genes and Development, researchers found
a coenzyme of nicotinamide adenine dinucleotide (NAD), called
NADH, causes the activation of Sir2.
"We are interested in how diet
influences health and longevity," says lead author Leonard Guarente,
a professor of biology at the Massachusetts Institute of Technology.
"Particularly in how lowering calories extends life and health."
The finding that limiting calories
extends life and health is not a new finding, Guarente adds. But
how this occurs remains a question.
In previous studies, Guarente's
team had identified Sir2 as a key gene to extending cell life.
In their current paper, the team studied what was happening in
cells as calorie intake was reduced to activate this gene.
The researchers found levels of
NADH, a molecule inside of cells, changed in response to a low-calorie
diet. "When the levels of this molecule decrease, the activity
of Sir2 goes up, making cells live longer," Guarente says.
The researchers found that by activating
Sir2, cells extended their life span by 30 percent. "In human
terms, that would be decades," Guarente says.
"Our hopes are to extend these
studies beyond yeast to mammals," he adds.
This finding may lead to the creation
of drugs that can offer the same benefit of a low-calorie diet
without having to live on only 1,000 calories a day, Guarente
says. "Right now, people can't expect to eat so little that this
mechanism would be triggered. What they should do is eat a sensible
In the second study, Dr. David
Sinclair, an assistant professor of pathology at the Harvard Medical
School, and his associates -- also working with yeast -- found
it is not NADH that activates Sir2, but another gene called pyrazinamidase/nicotinamidase
Their study appears in the Dec.
19 issue of Science.
"We both agree that Sir2 is key
to understanding life span and the effect of calorie restriction
on extending life," Sinclair says. "In reality, it may be a combination
of NADH and PNC1."
"Our goal is to find drugs that
use these molecules to fight the diseases of aging such as cancer,
diabetes and heart disease, not to extend normal life," Sinclair
Dr. Ronen Marmorstein, a researcher
from the Wistar Institute at the University of Pennsylvania, says
both papers are very interesting. However, since the methods used
in each study are different, it is hard to compare them, he adds.
Marmorstein agrees that both NADH
and PNC1 may affect Sir2 function.
It is not clear what the ultimate
clinical implication might be in humans, Marmorstein notes. "No
one has showed that Sir2 functions to extend life in human cells.
Whether or not any of the current experiments is relevant to human
cells is an open question."
To learn more about aging, visit
National Institute on Aging or the
National Aging Association.
Reference Source 101