As any angler will tell you, fish are amazing creatures. They may have a brain the size of a pea, but they astound us constantly with their ability to do things.
Salmon fry will memorize the odour of the water in the Yukon River, for example, then spend up to six years wandering the Pacific Ocean using the Earth’s magnetic field to navigate, before they return to the river mouth, swim as many as two thousand miles upstream and spawn on the very same rocks and pebbles where they were born.
But it’s the way fish appear to control the size of their hearts that has Canadian researchers scratching their heads in amazement. In fact, they think it may well hold the secret to better managing heart disease in humans.
Bet you didn’t know this, but structurally speaking, the heart of a rainbow trout is not that much different from yours or mine. What is poles apart, however, is that humans are warm blooded while fish are cold blooded.
What this means is that our internal body temperature is always the same, regardless of the temperature of the water or air around us. As a result, when we feel cold, we turn up the heat or put on a sweater. When we’re hot, we don t-shirts and shorts and turn on the air conditioner.
But a fish is always the temperature of the water in which it swims. Every species also has a preferred or optimal temperature range, and swims to deeper or shallower parts of a lake, river, reservoir, pit or pond in order to regulate and find the most favourable conditions.
That is all well and good in the summer, when the water temperature will vary over a huge range, but what do fish do in the winter when ice locks up a lake and the water temperature remains generally close to freezing?
Researchers at the University of Guelph, my old alma mater, have discovered that fish—rainbow trout in particular—change the size of their hearts. That’s right, according to integrative biology professor Todd Gillis, by expanding and contracting the size of their hearts, fish can cope with otherwise extremely stressful conditions. They do it by adding collagen to their heart cells in the winter, and then removing it in the summer. Gillis and his team have also isolated the specific protein, TGF-Beta1, by which they do it.
What it means for humans is obvious. If researchers can figure out the specific way the trout control the size of their hearts, especially how they remove the collagen in the summer months, it means we may be able adapt the process to humans, so that heart attack victims can repair what, up to now, has been irreparable damage.