Fat findings may help regulate major disease
a vital part of the body's immune system, report researchers, who
have found the first evidence that the cells respond directly to
toxins just like immune cells.
The research also suggests that altering the balance of fatty acids can distort the function of these fat cells, helping to explain the link between obesity and insulin resistance.
The scientists from Purdue University in the US are hoping to further investigate fatty acids, which could help them manipulate the immune response. Dutch company Loders Croklaan Lipid Nutrition last year presented research that demonstrated the immune boosting function of its conjugated linoleic acid Safflorin.
The new study, published in January's issue of The American Journal of Physiology, shows that pig fat cells respond to infections by producing hormone-like proteins that regulate certain aspects of the body's immune response - further evidence that fat cells behave as immune cells.
"Adipocytes can be functional and beneficial without creating obesity," said author Michael Spurlock. "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 experiments, fat cells exposed to interferon-gamma, a small protein produced by infection-fighting T-cells, produced hormone-like proteins called cytokines.
This establishes the pathway by which the adipocytes participate in the immune response, said Spurlock. "We have very clearly shown that interferon-gamma is increasing expression of cytokines in pig fat cells."
Later the researchers found that a molecule, or ligand, binds to molecules on the outside of pig fat cells. This binding with the receptor molecule on the pig fat cell signals fat cells to produce more of another hormone-like cytokine.
The study shows that the ligand and interferon-gamma regulate production of cytokines that impact both energy metabolism and immune function - significant in studying human diseases, including cancer and diabetes.
This means that the amount of lipid, also known as fatty acid or tricylglycerol, in the fat tissue is also important. As adipocytes accumulate excess lipid, their normal function is distorted and they produce too much of some biochemicals and not enough of others. These abnormalities can culminate in disease.
"For a long time, we have looked for the link between the immune system, obesity and insulin resistance," Spurlock said. "The fact that fat cells actually promote or secrete factors, such as the cytokine interleukin-6, may be fundamentally linked to insulin resistance in diabetes. This makes adipocytes very important cells."
Adipocytes normally produce factors that promote insulin regulation of glucose levels, but these factors do not function properly when obesity is involved, note the researchers.
The team now wants to determine other factors, such as certain classes of fatty acids, that will activate or suppress an inflammatory receptor.
"If we can discover these regulators, then we might be able to find a way to manipulate the receptors and immune pathways to regulate the body's energy metabolism and apply that to diabetes and cancer."
