Sensing Nutrition

Abstract

This chapter will describe distinct mechanisms of sensing the abundance of fatty acids, amino acids and glucose via membrane receptors, metabolic enzymes, regulatory kinases and transcription factors. The latter, in particular members of the nuclear receptor superfamily, play a key role in nutrient-sensing pathways. Many nuclear receptors bind macro- and micronutrients or their metabolites, such as fatty acids to PPARs, oxysterols to LXRs (liver X receptors) and vitamin D metabolites to VDR (vitamin D receptor), i.e., nuclear receptors are able to translate nutrient fluctuations into responses of the genome. In metabolic organs nuclear receptors respond to nutrient changes and specifically activate hundreds of their target genes. Moreover, also the immune system is triggered in its inflammatory and antigen response by nuclear receptors and their ligands. In addition, nuclear receptors belong to those transcription factors that play a central role in managing the circadian clock both in the CNS as well as in peripheral organs. Basically all tissues and cell types of our body display a functional molecular clock, the coordination of which is essential for optimal physiology including metabolism.