Scientists discover chemical switch that determines muscle fiber type

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Might some day enable physicians to give weakened patients a drug to build up muscular endurance without exercise

Published in the Aug. 15, 2002 issue of the journal Nature, findings from a multi-institutional team describe the pivotal role of a molecule called PGC-1 in transforming “fast twitch” fibers (Type II) to “slow twitch” fibers (Type I). “Fast twitch” fibers create the bulkier, strong but quickly fatigued muscles of weightlifters or sprinters. Most muscles contain a combination of the two fibers. While researchers caution they’re not promising a new athletic stamina-enhancing drug, they say it’s certainly possible that this might benefit people who are deficient in muscle fibers because of medical conditions. “PGC-1 appears to be the switch, or a major component of it, that enables your body’s muscles to adjust to the demands being put on them,” explains Dana-Farber’s Bruce M. Spiegelman, a cell biologist and the study’s senior author who is also a professor of cell biology at Harvard Medical School. “Understanding how this system works could make it possible to develop a drug to manipulate this system.” The research team included investigators from Dana-Farber, Beth Israel Deaconess Medical Center, Boston, and the University of Texas Southwestern Medical Center, Dallas. The study was funded principally by the National Institutes of Health.