September 16, 2015 | David F. Coppedge

How Exercise Benefits Bones and Muscles

Will it be possible in the future to reduce fat, build muscle, and strengthen bones with an injection of a hormone?

A hormone that seems to turn mice into mighty mouse is showing more promise (see 3/11/15 and 11/07/06) despite controversy over initial claims (Science article). A new paper in PNAS finds that the newly discovered hormone irisin helps mice build stronger bones. Is a cure for osteoporosis around the corner?

Although exercise is a well known and potent stimulus for new bone formation, and weightlessness or muscle loss characteristically cause bone loss, it has remained unclear how muscle talks to bone, despite their close proximity. Here, we show that a molecule irisin derived from skeletal muscle in response to exercise has profound effects in enhancing mass and improving the geometry and strength specifically of cortical bone, the key function of which is to resist bending and torsion. Trabecular bone, which is a reservoir for bodily calcium, is remarkably spared. Irisin may therefore not only be the molecule responsible for muscle–bone connectivity, but could also become a therapy for sarcopenia and osteoporosis, which occur in tandem in the elderly.

Science Magazine speculates on the connection this hormone makes between the two tissues: “They don’t yet know which receptors irisin interacts with, but they suggest it prompts the production of proteins that in turn increase the expression of key genes—those that drive immature cells to differentiate into osteoblasts, which synthesize new bone.” Science Mag reminded readers that irisin has also shown promise for building muscle and reducing fat:

Previous research found that exercise prompts muscles to secrete this protein fragment into the bloodstream, and that it may help burn fat by causing energy-storing white fat cells to act like energy-burning brown fat cells, although its activity in humans is still controversial.

Science Daily says that the new finding helps explain why exercise is good for the bones. “Implications of the study are far reaching,” the article states. “It is known that physical exercise, and the physical force it applies to bone, benefits metabolic and skeletal health.” Since muscle atrophy and bone weakness often occur together, “Understanding this molecular connection between muscle and bone gives us hope for treating age-related bone and muscle loss at the same time, with the same agent,” the lead author says.

Outdoor Vitality

Couch potatoes will love irisin pills some day. They can flop on the couch and watch football games, and afterward look like the players. Whether or not that day comes, there is still good reason to get outdoors. Medical Xpress says that our immune system may be the pathway between nature and good health.

Research has found evidence that spending time in nature provides protections against a startling range of diseases, including depression, diabetes, obesity, ADHD, cardiovascular disease, cancer, and many more. How this exposure to green space leads to better health has remained a mystery. After reviewing hundreds of studies examining nature’s effects on health, University of Illinois environment and behavior researcher Ming Kuo believes the answer lies in nature’s ability to enhance the functioning of the body’s immune system.

Not only that, nature can help prevent asthma. Science Magazine also reports that children raised around farm animals are exposed to bacteria in farm dust that stimulates an immune response in the lungs that later protects them from asthmatic disease. As a result, children raised on farms are much less likely to develop asthma and other respiratory maladies. A study published in Science “offers new support for the so-called hygiene hypothesis, a 26-year-old idea that posits that our modern zeal for cleanliness and widespread use of antibiotics have purged the environment of microorganisms that once taught a child’s developing immune system not to overreact to foreign substances.”

Hygiene freaks may need to reconsider their habits. Cleanliness is good, but our bodies need some exposure to bacteria to hone our immune systems. As for antibacterial soaps, don’t bother; they are no threat to germs, Medical Xpress says. Live Science adds that regular soaps work just as well as the antibacterial varieties. One needs to get a little bit dirty to enjoy natural scenes like this:

Barn in Grand Teton National Park, Wyoming

Our Creator always gives more than we give Him. When we take the time to explore His magnificent creation by getting outdoors, and glorifying Him with thanksgiving, He rewards us with better bones, stronger muscles, an enhanced immune system, and mental health. You can’t outgive God.

 

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