Manipulating mitochondria: playing in the fountain of youth

Nutrition Action Healthletter, Dec, 2008 by David Schardt

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"How are your mitochondria?"

Some day, that question may be as common as asking about a person's blood pressure or cholesterol.

Scientists are learning that the state of your mitochondria--tiny furnaces within most of the body's cells that burn food for fuel--can have a profound impact on your health.

Can you increase and strengthen your mitochondria? Can you recapture the mitochondria of your youth? Researchers have uncovered some intriguing clues.

MIGHTY MITOCHONDRIA

"Mitochondria are the power plants of our cells," says Simon Melov, director of the Genomics Core at the Buck Institute for Age Research in Novato, California. "They convert food into energy, which the body uses to live."

Most cells in the human body contain somewhere between 500 to 2,000 mitochondria (pronounced MY-toe-CON-dree-ah). In fact, mitochondria account for as much as 60 percent of the volume of muscle cells and 40 percent of the volume of heart cells.

"Mitochondria are linked to almost every essential process in cells," says Rafael de Cabo, a researcher at the National Institute on Aging in Baltimore. "That explains why you can trace almost any condition that has to do with energy balance--like diabetes or sarcopenia, which is muscle wasting with age--at least in part, to problems with mitochondria."

Mitochondria are unusual among the structures within cells because they have their own genes--their own DNA. (All other DNA is found inside the cell's nucleus.) And mitochondrial DNA is more likely to get damaged in the course of everyday living.

That's no surprise. Mitochondria sit at ground zero, the place within the cell where carbohydrate, fat, and protein are burned, or oxidized, for energy. Unfortunately, the process generates free radicals--rogue molecules that can damage the mitochondria's DNA and membranes.

Some researchers speculate that, over a lifetime, damage to the mitochondria may be the ultimate cause of aging.

"The belief is that as we age, these mitochondrial mutations accumulate and the mitochondria slow down in all our tissues, says Gerald Shulman, professor of medicine and cellular & molecular physiology at Yale University.

"Mitochondria have been called the Achilles' heel of the cell in aging, adds lifespan researcher Tory Hagen of the Linus Pauling Institute in Corvallis, Oregon.

Damaged mitochondria can also lead to disease.

It's possible that weakened mitochondria leave people more susceptible to Parkinson's disease or accelerate the progression of Alzheimer's disease," notes Mark Mattson, chief of the Cellular and Molecular Neurosciences Section of the National Institute on Aging.

Can you protect--or restore--your mitochondria? Here's what the latest research shows.

EXERCISE

"Aerobic exercise can increase the number of mitochondria in your muscle cells by 40 to 50 percent in six weeks," says David Hood, Canada Research Chair in Cell Physiology at York University in Toronto. Researchers have known that--from studies in animals and humans--for more than 30 years. (1)

To get the benefit, though, you need to run, cycle, swim, walk briskly, or do other exercises to at least half of your maximum capacity for at least 15 to 20 minutes a day, three to four times a week.

"You'll notice less fatigue, lower perceived exertion, and more endurance," says Hood. That's because mitochondria are efficiently burning more fat, rather than carbohydrate, for energy.

In 2006, Elizabeth Menshikova and her colleagues at the University of Pittsburgh School of Medicine got eight overweight and sedentary men and women in their late 60s to walk outdoors or use treadmills or stationary bicycles four to six days a week for 30 to 40 minutes each time. (2)

After 12 weeks, the mitochondria in their quadriceps (thigh muscles) increased by about 50 percent.

"To maintain the new level of mitochondria," notes Hood, "you need to keep exercising at least two or three times a week."

Strength-training exercise, like lifting weights, doesn't seem to increase mitochondria in young people, says Hood. Older people may be another story.

In a 2007 study, the genes in the quadriceps muscles of 14 healthy older men and women (average age: 70) were much less active than the genes in the quadriceps of 16 younger adults (average age: 26). (3) That was no surprise.

But after twice weekly strength-training sessions for six months, "there was a remarkable reversal of the older people's genetic profile to more-youthful levels," says the Buck Institute's Simon Melov. In other words, their quadriceps genes--many of which contain the instructions for making mitochondria--had become more active.

"Any exercise, including aerobic and strength training, will improve mitochondrial content and the endurance of older, less-active individuals," notes Hood.

And that may lead to "younger" muscles. "Physical exercise has been proven to be one of the best ways of delaying aging in the muscles, because it fine-tunes energy metabolism in their mitochondria," says the National Institute on Aging's Rafael de Cabo.