DALLAS Jan. 29, 2009 Mice whose fat cells were allowed to grow larger than fat cells in normal mice developed "healthy" obesity when fed a high-fat diet, researchers at UT Southwestern Medical Center found in a new study.
The fat but healthy mice lacked a protein called collagen VI, which normally surrounds fat cells and limits how large they can grow, like a cage around a water balloon. The findings appear online and in a future edition of Molecular and Cellular Biology.
"The mice lacking collagen VI fared much better metabolically than their counterparts that retained this particular collagen," said Dr. Philipp Scherer, director of the Touchstone Center for Diabetes Research at UT Southwestern and the study's senior author. "The mice without collagen VI don't develop inflammation or insulin resistance. They still get obese, but it's a 'healthy' obesity."
When people take in more calories than needed, excess calories are stored in adipose or fatty tissue. The fat cells are embedded in and secrete substances into an extracellular matrix, a type of connective tissue that provides support to fat tissue, like scaffolding. Collagen VI is one component of the extracellular matrix. Too much of this connective tissue prevents individual cells from expanding and can lead to fibrosis and eventually inflammation.
Inflammation is thought to be an underlying cause of metabolic disorders in humans, said Dr. Scherer. Large fat cells are often considered a bad omen, he said, because they typically lead to increased cell death and systemic insulin resistance. Under normal circumstances, fat cells continue to grow until they reach a point where the extracellular matrix they've built around themselves is so strong that it's no longer flexible.
"In this particular case, however, the large fat cells are not as inflamed as they would normally be," Dr. Scherer said. "Fat cells that lack collagen VI can grow to a huge size wi
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| Contact: Kristen Holland Shear kristen.hollandshear@utsouthwestern.edu 214-648-3404 UT Southwestern Medical Center Source:Eurekalert |