Trans-10,cis-12 CLA increases adipocyte lipolysis and alters lipid droplet-associated proteins: role of mTOR and ERK signaling

Lipiddroplet-associated proteins play an important role in adipocyte triglyceride (TG) metabolism. Here, weshow that trans-10,cis-12 conjugated linoleic acid (CLA), but notcis-9,trans-11 CLA, increased lipolysis and altered human adipocyte lipid dropletmorphology. Before this change in morphology, there was a rapid trans-10,cis-12CLA-induced increase in the accumulation of perilipin A in the cytosol, followed by the disappearance ofperilipin A protein. In contrast, protein levels of adipose differentiation-related protein (ADRP) wereincreased in cultures treated with trans-10,cis-12 CLA. Immunostaining revealed that ADRP localized to the surface of small lipid droplets, displacing perilipin. Intriguingly,trans-10,cis-12 CLA increased ADRP protein expression to a much greater extent thanADRP mRNA without affecting stability, suggesting translational control of ADRP. To this end, we foundthat trans-10,cis-12 CLA increased activation of the mammalian target ofrapamycin/p70 S6 ribosomal protein kinase/S6 ribosomal protein (mTOR/p70S6K/S6)pathway.Collectively, these data demonstrate that the trans-10,cis-12CLA-mediated reduction of human adipocyte TG content is associated with the differential localization andexpression of lipid droplet-associated proteins. This process involves both the translational control ofADRP through the activation of mTOR/p70S6K/S6 signaling and transcriptional control of perilipinA.