PYY and Insulin resistance: Butyrate has additional systemic effects and the effects of SCFAs are mainly mediated by specific action on protein-coupled receptors (GPRs) (especially 41 and 43) expressed on the pancreas, liver, adipocytes, brain, enteroendocrine L-cells, and immune cells, which explain the effects on appetite (via stimulation of peptide YY (PYY), leptin, and glucagon-like peptide-1 (GLP-1), and attenuation of insulin resistance), energy harvest, and hepatic lipid metabolism [39,77].