Cell 134, 933–944 (2008)

A little fat might be good for you — if it's the fatty acid palmitoleate, now discovered to be a fat-cell-derived hormone that regulates metabolism throughout the body.

Gökhan Hotamisligil at Harvard School of Public Health in Boston, Massachusetts, and his colleagues studied knockout mice lacking two proteins that normally chaperone lipids out of the bloodstream into adipose tissue. These mice are more resistant than normal mice to the bad effects of a high-fat diet. The team found increased synthesis of palmitoleate and other unsaturated fatty acids in fat cells in these mice and a consequent rise in palmitoleate levels in the blood.

They showed that palmitoleate regulates the lipid-generating program of gene expression in the liver of the mice and also stimulates muscle cells to take up glucose — and that mice infused with palmitoleate use glucose more efficiently than untreated mice.