Phosphatidylcholine Causes Lipolysis and Apoptosis in Adipocytes through the Tumor Necrosis Factor Alpha-Dependent Pathway

A phosphatidylcholine (PPC) formulation has been used to treat cellulite; however, its underlying mechanism of action remains unclear. In this study, we demonstrated that PPC induces lipolysis and apoptosis in adipocytes, and evaluated a possible tumor necrosis factor alpha (TNFα)-dependent pathway, whereby PPC exerts these effects. For in vitro study, fully differentiated 3T3-L1 cells, mouse adipocytes were treated with various concentrations of PPC and cell apoptosis and lipolysis were assayed. For in vivo experiments, mice fed on a high-fat diet for 8 weeks were injected twice to abdominal subcutaneous fat tissues of either vehicle or PPC. We found that PPC induced lipolysis and apoptosis dose-dependently in fully differentiated 3T3-L1 cells. In addition, PPC augmented both expression and release of TNFα in a dose-dependent fashion. Induction of TNFα by PPC was associated with the stimulation of nuclear factor kappa B (NFκB)-mediated transcriptional activity. Small interfering RNA (siRNA)-mediated suppression of NFκB abrogated the effect of PPC on TNFα secretion. Suppression of TNFα with specific siRNA abrogated the effects of PPC on lipolysis and apoptosis. Through in vivo experiments, we demonstrated that PPC injection not only stimulated the local lipolysis and apoptosis, resulting in weight loss, but also induced TNFα mRNA expression and neutrophil infiltration. Furthermore, PPC injection prevented lipogenesis and suppressed the mRNA -expression of adipokines (such as adiponectin and leptin), due to the down-sizing of adipocytes. In conclusion, we suggest that PPC induces lipolysis and apoptosis in adipocytes through TNFα-dependent pathways.