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Brown fat?

The weight many of us are trying to lose is white fat, tissue that stores energy. Scientists think more energy-burning brown fat - which exists in small deposits along the spine and neck - might help that effort.  

In a way, we’d all be a little better off if we had more fat, researchers are discovering.

Before you reach for the potato chips, know that they’re talking about a different kind of fat — brown fat, which is radically apart from the white fat that characterizes obesity. In a sense, they’re opposites. One burns energy; the other stores it.

Patrick Seale, associate professor of cell and development biology at the University of Pennsylvania’s Perelman School of Medicine, studies fats and their relationship to metabolic diseases such as diabetes.

Recently, the Endocrine Society, an international association focusing on hormone research, announced that he was one of 13 leading endocrinologists to get one of its annual Laureate Awards. Seale received the Richard E. Weitzman Outstanding Early Career Investigator Award for his study of brown fat.

Q: How different are brown and white fat? Are they really those colors?

A: They’re very different. Brown fat functions to burn energy, and it does this to make heat. The heat is really important, especially in small animals, for maintaining body temperature. For example, mice that have defective brown fat can’t survive in the cold.

White fat is the most prevalent fat tissue, especially in humans. Its main function is to store energy. It expands when people eat more than they burn off.

They actually are different colors. Brown fat looks brown, and the reason is it has a lot of mitochondria — what can be considered the energy powerhouses of the cell. They essentially make energy for cells, and brown fat has a lot of them.

The color of white fat is determined by the lipids that are stored there. It’s not really that white. In humans, it’s more of a yellow tinge. In mice, it’s white.

White fat is found in the subcutaneous region — right under your skin and it surrounds your internal organs. It forms in a lot of places. It’s far and away the largest type of fat that humans have.

Brown fat — there’s a lot less of it. And it’s in very specific places. The place it’s found in the largest quantities is right around the collar bone. There are also small amounts along the spinal column, and quite a bit in the neck. We don’t really know why.

It might be that the collar bone, spinal column, and neck are just a good place to be for warming the blood vessels. Brown fat probably did not form to keep us from becoming obese; it probably evolved to keep us warm. The heat that it makes can quickly get to the rest of the body.

Q: Tell us more about your research.

A: A lot of what we are trying to do is to figure out the genetic pathways for how both brown and white fat cells are made. We’re trying to understand the molecules and all the factors that go into this, with the thought that we’ll figure out how to make more of it or stimulate it in different ways for therapeutic effect.

The other thing we focus on is developing animal models so that we can understand what goes wrong in the setting of obesity and diabetes — how that affects fat tissue, both brown and white — and how we might be able to change the properties of that tissue to affect diabetes. When an animal or human gets obese, that has major effects on the fat tissues. So we’re trying to understand what is happening — what is good, what is potentially bad — so we can think about ways to intervene. If we understand the bad consequences, we might be able to block the effects. If we understand the good consequences, we might be able to promote them.

We now know a lot about how these different types of fat tissues work, and about the genetic factors that control them. What’s needed now is to try to find ways to manipulate it, to try to find therapies that target the fat tissue, for fighting obesity as well as diabetes. In particular, brown fat holds a lot of promise for fighting obesity. It’s a tough thing to crack, but that’s probably where the main thrust of the field is — how we can use our knowledge and develop ways to target brown fat to fight obesity. We have pretty good drugs for diabetes. Obesity is trickier. And obesity is often the thing that initiates these other problems.

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