Muscle Building

Science's STKE  20 Aug 2002:
Vol. 2002, Issue 146, pp. tw307
DOI: 10.1126/stke.2002.146.tw307

How can you acquire more slow-twitching muscles--the kind that are less prone to fatigue? Endurance training or electrical stimulation of nerves and muscles can increase type I skeletal muscle fiber mass. Lin et al. report that type I muscle expresses peroxisome-proliferator-activated receptor-γ coactivator (PGC-1α), and when that protein was specifically expressed in type II muscle of transgenic mice, a conversion to type I muscle was observed. This implicates the transcriptional co-activator in muscle fiber specification. The muscle conversion was accompanied by increased expression of mitochondrial genes involved in oxidative metabolism and of myofibrillar proteins characteristic of type I muscle. Isolated muscles showed fatigue resistance and sustained muscle activity in response to electrical stimulation. It remains unclear how PGC1-α expression is regulated and what genes are regulated that lead to type I muscle development. However, because calcium signaling through calcineurin is known to control type I muscle gene expression, the authors propose that PGC1-α could integrate calcium signaling with the modulation of certain transcription factors such as Mef2 in muscle development.

J. Lin, H. Wu, P. T. Tarr, C.-Y. Zhang, Z. Wu, O. Boss, L. F. Michael, P. Pulgserver, E. Isotani, E. N. Olson, B. B. Lowell, R. Bassel-Dubym, B. M. Speigelman, Transcriptional co-activator PGC-1α drives the formation of slow-twitch muscle fibres. Nature 418 797-801 (2002). [Online Journal]