Ghrelin acylation by ingestion of medium-chain fatty acids.

We found in a primary study that ingestion of medium-chain fatty acids (MCFAs) or medium-chain triacylglycerols (MCTs) increased the stomach contents of acyl ghrelin, and we further showed that the carbon-chain length of the acyl groups that modified the nascent ghrelin peptides corresponded to that of the ingested MCFAs or MCTs. These findings clearly demonstrated that the ingested MCFAs are directly used for the acyl-modification of ghrelin. Before the discovery of ghrelin-O-acyltransferase (GOAT), our in vivo study suggested that the putative GOAT preferred MCTs (composed of C6:0 to C10:0 FFAs) to either short- or long-chain triglycerides. In another study, we suggested that MCFAs or MCTs might represent a potential therapeutic modality for the clinical manipulation of energy metabolism through the modulation of ghrelin activity. After the discovery of GOAT, many studies have been done on the acylation of ghrelin using MCFAs, MCTs, or their derivatives; however, results and interpretations have been inconsistent, largely due to the differences in experimental conditions. This chapter describes detailed methods for the analysis of ghrelin acylation in vivo to facilitate future research in this field.