Who remembers Road Runner gradually appearing on the front of the TV screen and letting off the popular ‘Beep! Beep!’ before it sped off and disappeared in the opposite direction in a cloud of dust? Road Runner was lean, fast and never seemed to tire. Much to Wile E. Coyote’s disgust. What is it that kept him going? EPO? Coyote? PPARδ?
PPARδ? What could that be? Peroxisome proliferator-activated receptor delta. A transcriptional factor that has an effect on the formation of skeletal muscle. But not any old skeletal muscle. Skeletal muscle sports two types of fibers: a lazy fiber that is fatigue-resistant and a more brisk fiber which is far more susceptible to fatigue. PPARδ drives the formation of the lazy fiber, far wealthier in myoglobin and mitochondria than its fellow fiber. And hence far more well-off in oxidative capacity and ATP.
Could Road Runner have been transgenic? No. But researchers did create a genetically-modified mouse whose PPARδ was grossly enhanced. And what did they observe? A mouse that could run twice as fast than its mates and what is more showed no signs of exhaustion whatsoever. And not only did this marathon mouse acquire speed and stamina but also a propensity to remain slim. No wonder, with all this running you are thinking. Well no. When this particular rodent was forced onto a high-fat diet and no exercise, the scales didn’t budge.
Could PPARδ be a dream therapy against obesity? Even an enhancer of athletic performance? It is far too early to say. But what is sure is that Road Runner didn’t know about it.