Autophagy-dependent hepatocyte secretion of DBI/ACBP induced by glucocorticoids determines the pathogenesis of Cushing syndrome.

DBI/ACBP is a phylogenetically ancient hormone that stimulates appetite and lipo-anabolism. In response to starvation, DBI/ACBP is secreted through a noncanonical, macroautophagy/autophagy-dependent pathway. The physiological hunger reflex involves starvation-induced secretion of DBI/ACBP from multiple cell types. DBI/ACBP concentrations subsequently increase in extracellular fluids to stimulate food intake. Recently, we observed that glucocorticoids, which are endogenous stress hormones as well as anti-inflammatory drugs, upregulate DBI/ACBP expression at the transcriptional level and stimulate autophagy in hepatocytes, thereby causing a surge in circulating DBI/ACBP levels. Prolonged increase in glucocorticoid concentrations causes an extreme form of metabolic syndrome, dubbed "Cushing syndrome", which is characterized by clinical features including hyperphagia, hyperdipsia, dyslipidemia, hyperinsulinemia, insulin resistance, lipodystrophy, visceral adiposity, steatosis, sarcopenia and osteoporosis. Mice and patients with Cushing syndrome exhibit supraphysiological DBI/ACBP plasma levels. Of note, neutralization of extracellular DBI/ACBP protein with antibodies or mutation of the DBI/ACBP receptor (i.e. the GABRG2 subunit of GABR [gamma-aminobutyric acid type A receptor]) renders mice resistant to the induction of Cushing syndrome. Similarly, knockout of