INS and metabolic syndrome: Butyrate is a volatile fatty acid (VFA) produced by the gut microbiota; in humans, it has been reported that butyrate helps in controlling metabolic syndrome through the improvement of glucose uptake in adipose tissue, enhancing insulin signaling in liver and increasing the secretion of glucagon like peptide 1 (GLP-1) [55]; in farm animals, it has been reported that butyrate promotes body weight and composition [56].