Sensing of nutrients and microbes in the gut.

Abstract

Sensing of nutrients and microbes in the gut are fundamental processes necessary for life. This review aims to provide an overview of the basic background and new data on cellular nutrient, energy, and microbe sensors. The nutrient sensors 5' adenosine monophosphate-activated protein kinase, activating transcription factor 4 and mechanistic target of rapamycin (mTOR) are critical in control of the cell cycle. Recent data demonstrate their role in metabolic syndrome, in cell growth, and as therapeutic targets. Regulation of mTOR by the amino acids is the subject of intense investigation. Recent studies have further elucidated the exact mechanism of amino acid-dependent mTOR regulation. Pathogen recognition receptors (PRRs) are receptors that recognize conserved microbial molecules. New data demonstrate how lymphocyte-specific PRRs are necessary to maintain homeostasis. Moreover, new studies explore the role of PRRs in controlling the gut bacterial and fungal microbiome. Nutrient sensing molecules are central to cell growth and metabolism and are implicated in cancer and the metabolic syndrome. Regulation of nutrient sensors is complex, and may be amenable to therapeutic targeting. Microbial sensors play critical roles in homeostasis and maintenance of the gut fungal and bacterial microbiome.