The older we get, the more our endurance decreases. This is partially due to blood vessels losing their capacity to deliver oxygen and nutrients to muscle tissue. But a new scientific study has shown it is "surprisingly easy" to reverse this age-related endurance loss and muscle aging in mice.
Researchers at the Massachusetts Institute of Technology (MIT) treated elderly mice with a compound that promotes new blood vessel growth to test just that. The study results, which were published this month in the academic journal Cell, found that mice that underwent the treatment increased their endurance by up to 80 percent in treadmill tests.
Although it remains to be seen whether the results can be replicated in humans, researchers believe this muscle mass restoring technique may be used to counter some of the effects of age-related frailty. This may mean elderly individuals could live longer, healthier and more active lives.
"We'll have to see if this plays out in people, but you may actually be able to rescue muscle mass in an aging population by this kind of intervention," Dr. Leonard Guarente, the Novartis Professor of Biology at MIT and one of the senior authors of the study, told MIT News. "There's a lot of cross-talk between muscle and bone, so losing muscle mass ultimately can lead to loss of bone, osteoporosis, and frailty, which is a major problem in aging."
For the research, scientists took a closer look at at the cells that make up the inner lining of blood vessels in mammals. They specifically examined surtuins, a family of protein molecules that have previously been dubbed "longevity proteins".
Scientists found that by deleting the genetic code in mice that allows them to generate one type of these proteins (surtuin one), they could significantly reduce the animal's network of blood-carrying capillaries. This greatly reduced their fitness despite their young age. After observing this effect, they wanted to see if the reverse was also true.
"In normal aging, the number of blood vessels goes down, so you lose the capacity to deliver nutrients and oxygen to tissues like muscle, and that contributes to decline," Guarente said, according to The Independent.
The enzyme nicotinamide adenine dinucleotide (NAD) activates surtuin one, but it starts to break down with age. To create more of this substance, the body requires another substance called nicotinamide mononucleotide (NMN). Scientists gave 18-month-old mice (an age roughly equivalent to mid-fifties in humans) NMN for two months and then studied the effects.
Remarkably, they saw their capillary networks restored to levels that are normal in young mice. Additionally, the old mice had much higher fitness levels. In treadmill tests, they were able to run significantly longer, increasing their endurance by of 56 to 80 percent.
"The approach stimulates blood vessel growth and boosts stamina and endurance in mice and sets the stage for therapies in humans to address the spectrum of diseases that arise from vascular aging," fellow senior investigator Dr. David Sinclair a professor in the Department of Genetics at Harvard Medical School, explained.
Sinclair went on to say that this treatment potentially could provide the same benefits as significant physical activity and exercise.
"Here we have the potential of having a pill give the benefits of basically running for 10 miles a day without having to do that," he said, according to TIME, pointing out that this is important for elderly individuals who are growing frail.
"It's not just about trying to replace exercise when you are middle-aged, but giving you the benefits of exercise when you are too old to be able to do it."
If the results do translate to humans, it could completely change the quality of life experienced by elderly individuals.
"What this paper would suggest is that you may actually be able to rescue muscle mass in an aging population by this kind of intervention with an NAD precursor," Guarente said.
Back in 2014, Guarente founded a company that sells a dietary supplement containing a different precursor of NAD – known as NR. The company, Elysium Health, has been met with praise and skepticism from the broader scientific community.