Upregulated Monocyte Expression of Plin2 Depends Upon Proteasome Impairment and is Associated with Early Atherosclerosis in Obese Children

Background: Perilipin (Plin) 2 regulates intracellular lipid metabolism in macrophages, thus playing a role in atherosclerosis. Aim of the study was to evaluate whether dysregulation of Plin2 is involved in the onset of the early atherosclerosis seen in children with obesity and to rule out mechanisms of dysregulation.Methods: We enrolled 63 children with overweight/obesity and 21 age- and sex-matched normal-weight controls; we evaluated carotid intima media thickness (cIMT). We determined mRNA expression of Plin2 and proteasome subunits (PSMD3, PSMC4) by RealTime PCR and protein expression of Plin2, LAMP2A and Hsc70 by western blot analysis. We performed transient LAMP2A downregulation by siRNA. We quantified intracellular lipids in monocytes by Nile Red staining and flow cytometry analysis.Results: Levels of Plin2 protein were significantly higher in obese children than in normal-weight controls and correlated with cIMT in children with obesity after adjusting for confounders. Accordingly, monocytes of children with obesity showed a higher intracellular amount of lipids compared to normal weight children. mRNA expression of the regulatory subunits PSMC4 and PSMD3 and proteasome activity were lower in children with obesity than in controls while expression of LAMP2A and Hsc70 proteins, belonging to chaperone mediated autophagy (CMA) pathway, was not different indicating that Plin2 dysregulation in monocytes was not CMA-mediated but likely due to an impairment of proteasome efficiency.Conclusion: Plin2 was overexpressed in monocytes of children with obesity likely owing to reduced protein degradation by the proteasome. Overexpression of Plin2 could contribute to the early onset of atherosclerosis in these children.