A new mouse expressing a particular energy-metabolizing protein has shown significant increases in "slow-twitch" muscle fibers-the kind that gives distance runners their muscular stamina.

With partial support from National Institute of Arthritis and Musculoskeletal and Skin Diseases, a team of scientists from Boston and Dallas created a transgenic mouse that expressed the protein PGC-1α in muscles. The presence of this protein, which had been shown to activate genes controlling cell metabolism, resulted in the formation of more slow-twitch (Type I) muscle fibers, with fewer of the fast-twitch (Type II) fibers coveted by sprint runners. Tests of individual PGC-1α-laden muscles showed that they have roughly twice the stamina of normal mouse muscles.

The finding has caused some to speculate that further work in this area could benefit research efforts against muscle-wasting diseases like the muscular dystrophies.

The study was carried out at Harvard Medical School and the University of Texas Southwestern Medical Center, with additional funding from the National Institute of Diabetes, Digestive and Kidney Diseases, the National Heart, Lung, and Blood Institute, and the American Heart Association.

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Lin J, Wu H, Tarr P, Zhang C-Y, Wu Z, Boss O, Michael L, Puigserver P, Isotani E, Olson E, Lowell B, Bassel-Duby R, Spiegelman B. Transcriptional co-activator PGC-1α drives the formation of slow-twitch muscle fibres. Nature 2002;418:797-801.