How quickly you escape a predator or whether you catch the next meal is one of the key factors that decides whether you contribute to the greatest experiment on earth: evolution. Athletic performance varies enormously from individual to individual, and muscle performance is probably the main determinant of whether you’re a Usain Boult or one of the stragglers. Frank Seebacher and Isabel Walter from the University of Sydney, Australia, reasoned that the biochemical machinery that regulates how hard and fast muscle contracts determines whether zebrafish are elite athletes or laggards. The duo decided to investigate the muscle biochemistry of zebrafish to identify key components that determine a fish’s athleticism (p. 663).
Setting the fish a swimming challenge, the duo compared the animals’ endurance and sprint performance, expecting to find that the best sprinters had the poorest endurance. However, they found no correlation, so the fish had not traded off one performance against another.
Next, they looked to see if increasing the fish’s levels of a calcium handling protein – parvalbumin, which is involved in the regulation of muscular contraction – affected the fish’s endurance and sprint performance; and it did, improving their performance measurably. ‘This is the first demonstration that parvalbumin plays a role in determining whole-animal performance’, say Seebacher and Walter.
Finally, the duo investigated the fish’s metabolic machinery and found that the high performance fish – the fast sprinters and the fish with the greatest endurance – had higher expression of the muscle biochemistry regulators PPARδ and PGC-1α. They also found that the fastest sprinters were able to release energy faster because they had higher levels of the ATP-release enzyme creatine kinase, as well as having higher expression levels of dihydropyridine receptor and sarcoplasmic reticulum calcium ATPase (SERCA) 2, both of which regulate the release of calcium. And when they looked at the muscles of the high endurance swimmers, they found that those fish had higher levels of ryanodine receptor and SERCA 1, which are also involved in calcium regulation in the muscle.
Seebacher and Walter say, ‘We have identified a number of molecular traits that can explain differences in sprint and sustained locomotor performance in individuals’. They add, ‘Understanding how these traits function and what regulates their expression will provide new insights into locomotion, its evolution and into associated diseases’.