Metabolic Program Execution and Switching
Many, if not most, of the rate-limiting enzymes involved in executing metabolic programs are regulated at the transcriptional levels. A small number of transcription factors and cofactors connect upstream hormonal and metabolic signals to the downstream metabolic enzymes. Chief among these are the nuclear receptors, PGC-1α cofactors, and FoxO transcription factors. These function as downstream targets of hormonal signals and as sensors and effectors of cellular nutrient and energy status signals. These will be discussed in this chapter along with another member of this elite group, the NAD+/NADH-sensitive sirtuins. A fifth group of important factors, the SREBPs, will be explored in the next chapter where the focus will be on the management of cholesterol.
Nuclear Receptors Are Ligand-Activated Transcription Factors
Nuclear receptors are intracellular transcription factors (TFs) that regulate gene expression in a ligand-dependent way. There are two main groups of nuclear receptor...