Obesity increases the risk of metabolic conditions such as insulin resistance by triggering inflammation. Lan Wu and Luc Van Kaer at Vanderbilt University in Nashville, Tennessee, and their colleagues have established that a subset of immune cells called invariant natural killer T (iNKT) cells links fat build-up with inflammation.

The authors fed mice a high-fat diet, which activated their iNKT cells, triggering the release of inflammatory proteins. When the animals' iNKT cells were stimulated with an injected molecule for eight weeks, the mice developed insulin resistance and fatty livers. By contrast, mice that were engineered to lack iNKT cells did not develop excess inflammation or metabolic conditions on a high-fat diet, despite becoming obese.

Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1200498109 (2012)