The beneficial effects of exercise on obesity--and associated conditions such as diabetes--are widely thought to depend on increased metabolic expenditure and are thus expected to correlate with how strenuous and long-lasting a particular physical activity is. Noting that daily exposure to brief periods of high-frequency, low-intensity mechanical signals is anabolic for bone and muscle and that adipocytes, osteoblasts, and myocytes all derive from a common progenitor (the mesenchymal stem cell), Rubin et al. investigated the effects of low-magnitude mechanical signals (LMMS) on adipogenesis. After several months’ exposure to a high-frequency mechanical stimulus of lower magnitude than would be incurred by walking (15 minutes 5 days a week of whole-body vibration on an oscillating platform), the fat volume of the torsos of LMMS mice was reduced about 27% relative to that of control mice. This difference, which could not be attributed to changes in food intake, was accompanied by a decrease in liver nonesterified free fatty acid and triglyceride content (both risk factors for type II diabetes). Flow cytometry analysis of mice that had received transplants of green fluorescent protein (GFP)-labeled bone marrow cells indicated that a smaller fraction of marrow-derived mesenchymal stem cells had differentiated into adipocytes in mice subjected for 6 weeks to LMMS. Thus, the authors conclude that brief exposure to high-frequency LMMS can decrease adiposity, at least in part by influencing the generation of adipocytes from mesenchymal stem cells, and speculate that these findings may lead to nonpharmacologic interventions against obesity that do not require prolonged and strenuous physical activity.
C. T. Rubin, E. Capilla, Y. K. Luu, B. Busa, H. Crawford, D. J. Nolan, V. Mittal, C. J. Rosen, J. E. Pessin, S. Judex, Adipogenesis is inhibited by brief, daily exposure to high-frequency, extremely low-magnitude mechanical signals. Proc. Natl. Acad. Sci. U.S.A. 104, 17879-17884 (2007). [Abstract] [Full Text]