The regulation of lipid metabolism and glucose utilization is critical for the maintenance of cellular energy homeostasis. Cells have developed several means to respond to internal and external stimuli that would signify an imbalance in metabolic processes and energy utilization. These means include rapid responses such as phosphorylation events as well as latent effects on gene transcription. Ultimately, the result of altered gene expression is the synthesis of new signaling molecules and enzymes that are able to meet the physiological needs of the cell and the organism. Thus, important components of the cell must be a sensor of fatty acids and their metabolites, and an effector of nuclear transcriptional regulation. These roles may be fulfilled by one type of protein.