Brown Fat Transplants May Spur Weight Loss
Dec. 10, 2012 -- Mice given brown fat transplants lose weight and avoid the kinds of metabolic changes that lead to type 2 diabetes, even on high-fat diets, a new study shows.
Scientists hope the same approach may one day lead to treatments for obesity and diabetes in people.
Unlike white fat, which stores calories, brown fat burns calories like a furnace. Its main job seems to be to keep the body warm.
People have deposits of brown fat between the shoulder blades and along the spine, around the heart, on the side of the neck, and near the collarbones. But those stores are tiny compared to the pounds of white fat most people carry. Researchers have wondered if adding more brown fat might jump-start a body’s sluggish metabolism.
To test that theory, researchers took a tenth of a gram of brown fat from the backs of male mice and injected it into other mice that were the same sex and age.
Scientists have tried brown fat transplants before but they haven’t worked very well, says researcher Laurie J. Goodyear, PhD, head of the Section on Integrative Physiology and Metabolism at Harvard’s Joslin Diabetes Center in Boston.
Goodyear thinks that was partly because of where the brown fat was placed in the body and how long researchers waited to see results.
This time, Goodyear and her team placed the brown fat in the gut, a place it’s not normally found. Studies have shown that fat in the abdomen, especially fat around the liver, influences insulin resistance and also the release of blood fats called triglycerides.
After eight weeks, mice that got injections of brown fat processed blood sugar more normally, had less insulin resistance, and were leaner than mice given placebo procedures.
“These effects were really very pronounced and very dramatic,” Goodyear says.
Encouraged by their results, the team next gave brown fat transplants to mice on high-fat diets. In both people and mice, high-fat diets reliably lead to weight gain and drive up blood sugar, setting the stage for type 2 diabetes.