Physiologist Tejvir Khurana of the University of Pennsylvania and his colleagues believe they have linked the absence of Gene IL-15Ra to athletic endurance. Although previous studies had suggested a link between IL-15Ra and muscle strength, it had never been studied in a living animal. In order to test the connection, Khurana genetically engineered mice to lack the IL-15Ra gene and observed their activity.
The scientists found that every night the modified mice ran six times farther on the exercise wheels than normal mice. In order to ensure their findings, the researchers then dissected muscles from the longer running mice and found increased numbers of energy-generating mitochondria and extra muscle fibers. The researchers also stimulated the muscles with electricity and found that they contracted longer than normal, which meant they took longer to use up their energy stores.
To study the effect of IL-15Ra on human endurance, Khurana collaborated with Australian researchers who keep genetic samples from Olympic and world-class athletes. By comparing genetic samples Khurana found that certain variants of the IL-15Ra gene were more common in endurance athletes than sprinters, suggesting that successful endurance athletes possibly have a variant that gives them an edge on other opponents.
Some researchers wonder whether a drug blocking Gene IL-15Ra might one day enhance endurance, though with the side effects still unknown, caution athletes to stick to their regular routines for now.