How Excess Fat Causes Inflammation
Researchers are delving deeper into the mechanisms that link fat tissue with chronic inflammation, a source of damage to the body that raises the risk of age-related disease: "Researchers have new evidence to explain how saturated fatty acids, which soar in those who are obese, can lead the immune system to respond in ways that add up to chronic, low-grade inflammation. The new results could lead to treatments designed to curb that inflammatory state, and the insulin resistance and type 2 diabetes that come with it. One key [is] an immune receptor (called Toll-like receptor 4 or Tlr4) at the surface of blood cells, including a particularly 'angry' class of macrophages known to pump out toxic molecules and spur inflammation. It now appears that fatty acids may in essence 'hijack' those immune cells via Tlr4. ... Tlr4 is out there to sense bacterial products, but one of those looks a lot like fatty acids. They don't know it's not bacteria. ... Scientists had suspected that Tlrs might be the 'sensors' linking obesity to inflammation. Indeed, earlier studies had supported that notion. In the new study, the researchers show that this interaction is particularly important in the bloodstream. Mice lacking Tlr4 only in blood cells grew obese when they were fed a high-fat diet, but they were largely spared the metabolic consequences of their obesity. The mice were fat, but metabolically they continued to 'look pretty normal.'"
Link: http://www.eurekalert.org/pub_releases/2009-11/cp-hsf102809.php