Muscle mass maintenance in the elderly has become the subject of a lot of discussion in the medical community, and that’s definitely good news. Unless dealing with pathologies like muscular dystrophy (a genetic disorder) or even amyotrophic lateral sclerosis—ALS—(now wide-known thanks to the ice bucket challenge), the topic of muscle health, muscle-building, and muscle maintenance was really only brought up among bodybuilders, athletes, and fitness enthusiasts.
And herein lies the danger. Muscle mass isn’t just about physical appearance and top performance. The main function of our muscles is movement, as only muscular tissue can contract and, as a result, move our body. The second but equally important role that muscles carry out in the body is maintaining posture. In light of these two functions, which are vital for healthy and comfortable operation, it’s pretty clear why taking care of your muscles should never leave your radar, especially as you get old.
We achieve our peak muscle mass somewhere in our late 30s or early 40s. Then, we gradually begin losing some of our muscle, which can manifest itself as age-related weakness and fatigue, or it can be more serious, leading to increased risk of falls (and resulting injuries) or limited functionality. Slowing down the decline in muscle mass is the objective of researchers from Sanford-Burnham Prebys Medical Discovery Institute, who have uncovered the mechanism that stops muscle cell regeneration as people get older. And, like many recent discoveries in the area of aging, it has to do with stem cells.
Hope for muscle regeneration in the future?
For the most part, muscle stem cells remain in a resting state and do not express MyoD—an important protein for muscle differentiation—because they want to keep their “stemness” or initial state of undifferentiation, with the potential for specializing into a particular cell type if need be. To start creating new muscle fibers (in other words, regenerating muscle tissue), these muscle stem cells need to activate. Once they are “awoken,” they specialize in a specific type of muscle and unleash the expression of the MyoD protein.
That’s how it works in a young body. But what happens when we get older? Muscle stem cells age as well—they become senescent, which is characterized by a state of permanent inactivity from which they cannot be woken up.
The research team, led by Dr. Lorenzo Puri, studied mouse models and human fibroblasts—cells that produce collagen and other fibers. The scientists discovered that aged muscle stem cells can trigger a spontaneous DNA damage response (DDR), which is a cascade of cellular pathways that assess and repair lesions in our genetic code. In a normal DDR, the signaling ends once the DNA in question has been fixed, but in the case of old muscle stem cells, the signaling continues because there’s nothing to be repaired.
Why is this a problem? Age-related DDR blocks the activity of the protein MyoD and, as a result, prevents the differentiation of muscle stem cells.
The researchers came up with a few strategies aimed at making these senescent muscle stem cells generate muscle tissue, but it is not as simple and safe as it sounds, running the risk of genetic abnormalities or a muscle that is not completely functional.
The discovery may not hold the key to eternal youth and muscle loss reversal, but it paves way for possible treatments to slow down muscle deterioration and preserve healthy function into old age.
While the future may seem bright, you can also do a lot to keep your muscles strong and supple. Yes, we’re back to recommending diet and exercise. Ample protein intake and an active lifestyle should be a part of every adult’s healthy and fulfilling life.
Related: How aging affects muscles, joints, and bone health