In type 2 diabetic mice, altered gut microbiota composition, e.g., higher abundance of Firmicutes, Proteobacteria, and Fibrobacteres phyla, regulates expression of apelin/APJ in adipose tissue through low-grade inflammatory tone and eCB system (121), indicating definite relationships between the gut microbiota and the apelin system. The gene discussed is APLN; the disease is type 2 diabetes mellitus.