Mice with no fat carriers are skinny

The two related fatty acid binding proteins (FABPs) called aP2 and mal1 did not seem destined for fame. “These are seemingly very dull molecules,” says Gökhan Hotamisligil (Harvard School of Public Health, Boston, MA). “They are like little clams attaching to fatty acids.” Yet somehow, he says, these “idle chaperone proteins,” which shuttle fatty acids around inside the cell, turn out to “determine lipid metabolism.” They may do so by bringing fatty acid species to regulatory proteins or enzymes.

Mice lacking one or the other FABP had been generated before by Hotamisligil and shown mild phenotypes. Now the Boston group, including Kazuhisa Maeda and Haiming Cao, characterizes mice lacking both proteins. The mice have less fat than normal, and after a high fat diet their body composition, blood glucose,...