Lack of protein linked to ‘healthy’ obesity in mice

January 30th, 2009 - 7:48 pm ICT by IANS  

Washington, Jan 30 (IANS) Mice whose fat cells were engineered to grow bigger than normal fat cells in their counterparts developed “healthy” obesity when fed with a high-fat diet.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 mice lacking collagen VI fared much better metabolically than their counterparts that retained this particular collagen,” said Philipp Scherer, director Touchstone Centre for Diabetes Research, University of Texas (UT) Southwestern and 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,” he said.

When people eat 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 extra-cellular 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 Scherer. Large fat cells typically lead to increased cell death and systemic insulin resistance, said an UT release.

“In this particular case, however, the large fat cells are not as inflamed as they would normally be,” Scherer said. “Fat cells that lack collagen VI can grow to a huge size without becoming inflamed, suggesting that collagen VI directly affects the ability of fat cells to expand.”

The findings appear online in Molecular and Cellular Biology.

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