Cell-autonomous, paracrine and neuroendocrine feedback regulation of autophagy by DBI/ACBP (diazepam binding inhibitor, acyl-CoA binding protein): the obesity factor

Abstract

DBI/ACBP (diazepam binding protein, acyl-CoA binding protein) participates in the regulation of fatty acid metabolism when it is localized within cells, whereas outside of cells it acts as a diazepam-binding protein. Recent results indicate that many different mammalian cell types release DBI/ACBP upon in vitro or in vivo starvation in a macroautophagy/autophagy-dependent fashion. The autophagy-associated release of DBI/ACBP elicits feedback inhibition of autophagy through 3 independent mechanisms. First, the depletion of DBI/ACBP from cells limits autophagy in a cell-autonomous fashion. Second, extracellular DBI/ACBP acts in a paracrine fashion to inhibit autophagy. Third, DBI/ACBP increasing in the systemic circulation acts as an activator of lipo-anabolism and feeding behavior, thus removing the cause of autophagy induction (starvation) and suppressing the phenomenon. DBI/ACBP expression is upregulated at the mRNA and protein levels in obese mice and humans, and its extracellular neutralization by antibodies controls food intake and increases lipo-catabolism. Current data support the contention that DBI/ACBP is an important pro-obesity factor. Abbreviations: DBI: diazepam binding protein, acyl-CoA binding protein; GABR: gamma-aminobutyric acid type A receptor; TSPO: translocator protein.