Nav: Home

Mitochondria may metabolize ADP differently in aging muscle, despite exercise resistance

March 13, 2018

Most adults reach their peak levels of muscle mass in their late 30s or early 40s. Even for those who exercise regularly, strength and function start to decline after that point. For those who don't exercise, the drops can be dramatic. Now, a study of twenty men published March 13 in the journal Cell Reports provides new clues about the cellular mechanisms of aging muscles, showing a key role for how mitochondria, the powerhouses of the cell, process ADP, which provides energy to cells.

ADP, or adenosine diphosphate, plays a role in how our cells release and store energy. But previous lab models that have looked at the mechanisms of aging in human cells have not included ADP. When ADP is metabolized in the mitochondria, it stimulates cellular respiration and decreases reactive oxidative species (ROS; also known as free radicals). Higher ROS levels are linked to damage in different components of the cell, a process also called oxidative stress.

In the study, the investigators developed an in vitro system employing individual muscle fibers taken from muscle biopsies. The fibers were put into a system in which mitochondrial function and respiration could be measured across a range of ADP concentrations that are relevant to those found in the human body. "The way people normally measure ROS is in a system that has ADP removed," says senior author Graham Holloway, an associate professor at the University of Guelph in Ontario. "But biologically, we always have ADP in the system. We started to think that maybe how we get ADP into the mitochondria is important for aging."

In the first part of the paper, the researchers compared muscle from ten healthy men in their 20s with muscle from ten healthy men in their early 70s. They found that there was an 8- to 10-fold decrease in ADP sensitivity, and therefore, when ADP was added to the system, there was a 2- to 3-fold higher rate of ROS emission in the muscle taken from the older men. ROS levels were determined by measuring emissions of hydrogen peroxide, a byproduct of activity in the cell.

The findings suggested that mitochondrial ADP sensitivity was somehow impaired in the muscles of the older men and that increased levels of ROS were contributing to sarcopenia, or the degenerative loss of muscle mass. "The magnitude of change was quite striking to us," Holloway explains. "For humans, it's remarkable to have such a big difference."

In the second part, the older men undertook a program of supervised resistance training, which included leg presses and upper-body exercises. But, after 12 weeks, there were no changes in the levels of hydrogen peroxide emitted, suggesting no improvements in age-associated cellular stress.

"This doesn't mean there's no hope for building strength in aging muscle," Holloway says. "I actually think that endurance training would be potentially beneficial, because we know with that kind of training you get increases in mitochondrial content." Endurance training includes aerobic exercise like cycling and swimming. "Moving forward, we plan to look at other types of exercise, to see if it can improve the dynamic response of mitochondria to ADP," he adds.

Other future work will use rodent models to delve into the cause-and-effect relationships of the molecular mechanisms of ADP metabolism. The investigators also plan to extend their studies to looking at different types of exercise in aging women. Early research in healthy young people has indicated that there are differences in sensitivity to ADP between men and women.
-end-
This study was funded by the Natural Sciences and Engineering Research Council of Canada and TI Food and Nutrition, a public-private partnership on precompetitive research in food and nutrition.

Cell Reports, Holloway et al. "Age-associated impairments in mitochondrial ADP sensitivity contribute to redox stress in senescent human skeletal muscle." http://www.cell.com/cell-reports/fulltext/S2211-1247(18)30264-X

Cell Reports (@CellReports), published by Cell Press, is a weekly open-access journal that publishes high-quality papers across the entire life sciences spectrum. The journal features reports, articles, and resources that provide new biological insights, are thought-provoking, and/or are examples of cutting-edge research. Visit: http://www.cell.com/cell-reports. To receive Cell Press media alerts, contact press@cell.com.

Cell Press

Related Aging Articles:

Brain development and aging
The brain is a complex organ -- a network of nerve cells, or neurons, producing thought, memory, action, and feeling.
Aging gracefully in the rainforest
In an article that appears in the current issue of Evolutionary Anthropology, researchers synthesize over 15 years of theoretical and empirical findings from long-term study of the Tsimane forager-farmers.
Reversing aging now possible!
DGIST's research team identified the mechanism of reversible recovery of aging cells by inducing lysosomal activation.
Brain-aging gene discovered
Researchers at Columbia University Medical Center have discovered a common genetic variant that greatly affects normal brain aging in older adults.
Aging can be good for you (if you're a yeast)
It's a cheering thought for anyone heading towards their golden years.
How eating less can slow the aging process
New research shows why calorie restriction made mice live longer and healthier lives.
Turning back the aging clock
By boosting genes that destroy defective mitochondrial DNA, researchers can slow down and potentially reverse an important part of the aging process.
Insilico Medicine launches a deep learned biomarker of aging, Aging.AI 2.0 for testing
Insilico Medicine, Inc., a company applying latest advances in deep learning to biomarker development, drug discovery and aging research, launched Aging.AI 2.0.
Substance with the potential to postpone aging
The coenzyme NAD+ plays a main role in aging processes.
What does a healthy aging cat look like?
Just as improved diet and medical care have resulted in increased life expectancy in humans, advances in nutrition and veterinary care have increased the life span of pet cats.

Related Aging Reading:

Aging Well: Surprising Guideposts to a Happier Life from the Landmark Harvard Study of Adult Development
by George E. Vaillant (Author)

Aging: An Apprenticeship
by Nan Narboe (Editor)

Aging as a Spiritual Practice: A Contemplative Guide to Growing Older and Wiser
by Lewis Richmond (Author)

The Gift of Years: Growing Older Gracefully
by Joan Chittister (Author)

Mindful Aging: Embracing Your Life After 50 to Find Fulfillment, Purpose, and Joy
by Andrea Brandt (Author)

Aging: Concepts and Controversies
by Harry R. Moody (Author), Jennifer R. Sasser (Author)

Dynamic Aging: Simple Exercises for Whole-Body Mobility
by Katy Bowman (Author), Joan Virginia Allen (Author)

The Grace in Aging: Awaken as You Grow Older
by Kathleen Dowling Singh (Author)

Choosing the StrongPath: Reversing the Downward Spiral of Aging
by Fred Bartlit (Author), Steven Droullard (Author), Marni Boppart ScD (Author)

From Age-Ing to Sage-Ing: A Revolutionary Approach to Growing Older
by Zalman Schachter-Shalomi (Author), Ronald S. Miller (Author)

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Dying Well
Is there a way to talk about death candidly, without fear ... and even with humor? How can we best prepare for it with those we love? This hour, TED speakers explore the beauty of life ... and death. Guests include lawyer Jason Rosenthal, humorist Emily Levine, banker and travel blogger Michelle Knox, mortician Caitlin Doughty, and entrepreneur Lux Narayan.
Now Playing: Science for the People

#491 Frankenstein LIVES
Two hundred years ago, Mary Shelley gave us a legendary monster, shaping science fiction for good. Thanks to her, the name of Frankenstein is now famous world-wide. But who was the real monster here? The creation? Or the scientist that put him together? Tune in to a live show from Dragon Con 2018 in Atlanta, as we breakdown the science of Frankenstein, complete with grave robbing and rivers of maggots. Featuring Tina Saey, Lucas Hernandez, Travor Valle, and Nancy Miorelli. Moderated by our own Bethany Brookshire. Related links: Scientists successfully transplant lab-grown lungs into pigs, by Maria Temming on Science...