Leah Olson

What do fish brains, weight loss, and the maximum human lifespan have in common? Leah Olson, biology faculty member since 1987, explains.

Reprinted from the September 2007 issue of the Alumnae/i Community Update eNewsletter

You just finished the third year of the Summer Science Program at SLC, where students and faculty members work together on an ongoing research project. What are you studying?

I’m looking at the energy decisions of two species of blennies—small fish that live in holes in coral reefs. My project grew out of Ray Clarke’s study of the habitat choices of these fish. The species are very similar and eat much the same food, but one lives at the bottom of the reef and the other lives higher up. Through a series of experiments Ray found that both species would rather live in the top part of the reef, because there’s more food there. But one species is much more aggressive than the other and will fight for—and win—the more desirable spot. The aggressive species has a much higher metabolism, so it needs almost twice as much food as the other fish. It couldn’t survive if it lived on the bottom of the reef. Because it has a higher metabolism, it also has more energy for fighting.

You teach classes like Pschyoneuroimmunology and The Biology of Living and Dying—what does that have to do with fish habitats?

These blennies, like humans, have a hormone called leptin. When leptin was discovered in 1994, people called it the “fat hormone,” because it is produced in fat cells. It tells the brain how much fat you have, and controls whether you feel hungry or full.

Can altering your leptin levels make you lose weight?

That’s what people thought at first. They did experiments on mice that were genetically modified to be obese. The mice were so fat they could barely waddle to their food bowls, but when they received leptin injections their weight quickly returned to normal. Unfortunately, this doesn’t work in humans, except for the very few whose obesity is caused by a genetic abnormality that affects leptin production.

Sounds like a dead end.

Not at all—these experiments opened up our understanding of metabolism and regulation systems in the brain. Leptin, it turns out, controls not just whether you feel hungry, but your overall metabolism, telling it whether to speed up or slow down to deal with the amount of food you’re consuming.

…Which is related to reef ecology?

Yes. Leptin can influence what ecologists call “life history traits”— where to live, when to reproduce, how many offspring to bear, and how long to live. These are all energy decisions, and leptin is a major player in them. What’s going on between the two species of blennies is a difference in their energy decisions. My project is looking at the leptin system in the blennies to find a physiological explanation for their behavior.

How are the students involved in the research?

They’re directly involved with the process of discovery. To answer these huge questions about energy decisions and how they affect habitat choices on the reef, we are creating a detailed brain atlas of the two species. The students take slices of the fishes’ brains, stain them, and examine them under a microscope to see which parts of the brain respond to leptin. It’s an incredible lesson in neuroanatomy for them. And it’s a brand-new area of research—no one has looked at these fishes’ brains before.