Rather than contributing to disease, fat cells, or adipocytes (pronounced ah-dip-poe-sights), normally function as part of the immune system and help control lipid accumulation, so they actually may benefit human health, said Michael Spurlock, animal sciences professor.

"Adipocytes can be functional and beneficial without creating obesity," Spurlock said. "The key is that we want plenty of adipocytes to meet whatever immunological and endocrinological needs they fulfill, but we don't want them to overaccumulate lipid."

In the January issue of The American Journal of Physiology, Spurlock and Kolapo Ajuwon, both of the Department of Animal Sciences and the Comparative Medicine Program, report that pig fat cells respond to infections by producing hormone-like proteins that regulate certain aspects of the body's immune response.

"This is additional evidence that fat cells behave in many ways as immune cells," Spurlock said. "It also is the first evidence that adipocyte cells respond directly to bacterial toxins like classical immune cells."

To produce this infection-fighting response, Ajuwon, a doctoral student, performed experiments exposing fat cells to interferon-gamma, a small protein produced by infection-fighting T-cells. This caused the adipocytes to produce hormone-like proteins, called cytokines.

"Our research documents a pathway by which the adipocytes participate in the immune response," Spurlock said. "We have very clearly shown that interferon-gamma is increasing expression of cytokines in pig fat cells."

In another part of the study, the researchers found that a molecule, or ligand, binds to molecules on the outside of pig fat cells incubated in a laboratory dish. In this case the ligand is an i
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Contact: Susan A. Steeves
ssteeves@purdue.edu
765-496-7481
Purdue University
20-Jan-2004