Adipose-specific phospholipase as regulator of adiposity.

A white adipose-tissue-specific intracellular phospholipase, which releases arachidonic acid from position sn-2 of phospholipids, was recently discovered and named AdPLA. When AdPLA was induced by feeding or by insulin treatment, the arachidonic acid released from phospholipids acted as a precursor for the formation of prostaglandin E(2) (PGE(2)). Subsequent activation of the prostaglandin receptor EP3 caused decreased levels of cAMP that led to decreased lipolysis and increased adiposity. Ablation of AdPLA in knockout mice resulted in the reverse sequence of events, with a decline in arachidonic acid release and prostaglandin synthesis and an increase in levels of cAMP, leading to increased lipolysis and a decline in adiposity, even though food intake was not affected. The newly discovered AdPLA enzyme in white adipose tissue functions as a regulator of lipolysis by acting as an antilipolytic agent mediated by increased PGE(2) formation and decreased intracellular cAMP.