Be Fit For Life

with Ellen Cohen-Kaplan

Getting to the marrow of the matter

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The research for the benefits of exercise continues to pile up . You’ve heard the studies regarding the effect of exercise on brain health, muscle strength, mood regulation, control of triglycerides and fat metabolism, and bone health.  A new study has found another mechanism by which exercise mediates one of the most active aspects of bone, the marrow. “Marrow, in particular, is a hub of activity, coordinating the formation of bone and cartilage while simultaneously churning out blood cells, immune cells, and cancerous cells.” Marrow also produces fat, and those special fat stores were previously thought to not be used to fuel exercise, unlike fat reserves in other parts of the body. There’s been intense interest in fat in marrow because there’s a strong association between high levels of marrow fat and low bone density.  This new study examined how this fat was influenced by exercise. For the full article, see https://www.sciencedaily.com/releases/2017/05/170518140220.htm

The researchers, lead by Maya Styner, a physician and assistant professor of endocrinology and metabolism at the University of North Carolina at Chapel Hill, used two groups of mice. One month after birth, one group was fed a high fat diet, resulting in obesity, while the other was fed a normal diet, resulting in the creation of a lean group.  At four months old, half of each group they were given an exercise wheel, and since mice like to run, both groups spent a lot of time running on the wheel. After 6 weeks, the exercising groups of both the obese mice and the lean mice showed significant drops in overall size and the amount of  fat cells in the marrow, reaching nearly identical levels.

“More surprising was the dramatic difference in the number of fat cells present in the marrow, which showed no change in lean mice but dropped by more than half in obese mice that exercised compared to obese mice that were sedentary. The tests also revealed that exercise improved the thickness of bone, and that this effect was particularly pronounced in obese mice.” The research leads us to believe that exercise can burn off fat cells in the marrow, and this in turn builds stronger, thicker bones. This has many implications for people with various conditions that cause osteopenia and osteoporosis, like post-menopausal women and those who have used steroids for extended periods. Other conditions include but are not limited to people with anorexia, diabetes, or arthritis.

There are caveats to this study, as there are in all research that compare mice to humans. Although the kind of the stem cells that produce bone and fat in humans are the same kind that produce them in mice, results are not directly translatable. Another major issue is that because marrow is encased in bone, it is difficult to study.  Previously, toxic tracers used with CT machines was the only way to examine marrow fat.  This study used a sophisticated MRI machine at UNC, eliminating the need for tracers, which can measure activity in living organisms. This will greatly expand opportunities to examine bone marrow activity in human subjects in the future.

What’s the take-away?

  • Exercise has a substantial, significant effect on bone health in everyone, but especially in obese populations.
  • Positive effects were seen after only 6 weeks of exercise
  • Although the exact amount of exercise wasn’t measured, we know that cardio exercise that involves impact (running, walking, weight training) improves bone density

If you haven’t been convinced yet about the importance of exercise, here’s another study to confirm its importance to continued vitality through bone health. So get out there, hit the road,  mountain,  forest, or whatever environment in which you can walk or run that makes your heart sing!

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