Can Exercise Keep You Young?

From the NY Times online…

March 2, 2011, 12:02 am

Can Exercise Keep You Young?

By GRETCHEN REYNOLDS

We all know that physical activity is beneficial in countless ways, but even so, Dr. Mark Tarnopolsky, a professor of pediatrics at McMaster University in Hamilton, Ontario, was startled to discover that exercise kept a strain of mice from becoming gray prematurely.

But shiny fur was the least of its benefits. Indeed, in heartening new research published last week in The Proceedings of the National Academy of Sciences, exercise reduced or eliminated almost every detrimental effect of aging in mice that had been genetically programmed to grow old at an accelerated pace.

In the experiment, Dr. Tarnopolsky and his colleagues used lab rodents that carry a genetic mutation affecting how well their bodies repair malfunctioning mitochondria, which are tiny organelles within cells. Mitochondria combine oxygen and nutrients to create fuel for the cells — they are microscopic power generators.

Mitochrondria have their own DNA, distinct from the cell’s own genetic material, and they multiply on their own. But in the process, mitochondria can accumulate small genetic mutations, which under normal circumstances are corrected by specialized repair systems within the cell. Over time, as we age, the number of mutations begins to outstrip the system’s ability to make repairs, and mitochondria start malfunctioning and dying.

Many scientists consider the loss of healthy mitochondria to be an important underlying cause of aging in mammals. As resident mitochondria falter, the cells they fuel wither or die. Muscles shrink, brain volume drops, hair falls out or loses its pigmentation, and soon enough we are, in appearance and beneath the surface, old.

The mice that Dr. Tarnopolsky and his colleagues used lacked the primary mitochondrial repair mechanism, so they developed malfunctioning mitochondria early in their lives, as early as 3 months of age, the human equivalent of age 20. By the time they reached 8 months, or their early 60s in human terms, the animals were extremely frail and decrepit, with spindly muscles, shrunken brains, enlarged hearts, shriveled gonads and patchy, graying fur. Listless, they barely moved around their cages. All were dead before reaching a year of age.

Except the mice that exercised.

Read on here.