Monitoring the partitioning of hepatic fatty acids in vivo: keeping track of control.

Noninvasive labelling of hepatic fatty acids in conscious, unrestrained rats shows how liver lipid metabolism responds acutely to physiological perturbations, such as the starved-to-refed transition. The speed with which the liver switches from fatty acid oxidation to esterification varies widely according to the requirement of the animal for continued synthesis of glucose 6-phosphate from three-carbon precursors. Ingestion of a meal also provides a strong signal for the diversion of fatty acids away from triacylglycerol synthesis and secretion, but insulin may only play an indirect role in this effect.