Group IIE secretory phospholipase A2 regulates lipolysis in adipocytes

Abstract

Objective To examine the function of group IIE secretory phospholipase A2 (sPLA2-IIE) in adipocytes and to explore the possible signaling mechanism involved. Methods The expression of sPLA2-IIE was demonstrated using real-time PCR and Western blot analysis. Lipid accumulation was evaluated via the measurement of cellular triglycerides (TG). Lipolysis was quantified by measuring the release of free glycerol. The expressions of M-type sPLA2 receptor (PLA2R1) and the genes encoding adipogenic proteins were measured using real-time PCR. The activities of the Janus kinase 2 (JAK2), extracellular regulated protein kinase (ERK), and hormone-sensitive lipase (HSL) were determined using Western blot. Results sPLA2-IIE-/- mice gained significantly more epididymal fat than wild-type (WT) mice. When treated with adipogenic stimuli ex vivo, stromal vascular cells isolated from the adipose tissue of sPLA2-IIE-/- mice accumulated significantly more TG than those from WT mice. Conversely, a significant reduction in lipid accumulation and an increase of free glycerol were observed in OP9 cells overexpressing sPLA2-IIE and in 3T3-L1 cells treated with sPLA2-IIE protein. Moreover, sPLA2-IIE significantly induced adipocyte glycerol release and HSL activity, which was inhibited by PD98059, an ERK inhibitor. Conclusions sPLA2-IIE regulates lipolysis in adipocytes, likely through the ERK/HSL signaling pathway.