Inhibition of preadipocyte differentiation and adipogenesis by zinc‐α2‐glycoprotein treatment in 3T3‐L1 cells

AIMS/INTRODUCTION Zinc-α2-glycoprotein (ZAG) is associated with the loss of adipose tissue in cancer cachexia, and has recently been proposed to be a candidate factor in the regulation of bodyweight. The aim of the study was to investigate the effects of ZAG on the proliferation and differentiation of 3T3-L1 preadipocytes. MATERIALS AND METHODS 3-(4,5-Dimethylthiazol-2-yl) 2,5-diphenyl tetrazolium bromide (MTT) spectrophotometry, Oil Red O staining, intracellular triglyceride assays, real-time quantitative reverse transcription polymerase chain reaction and transient transfection methods were used to explore the action of ZAG. RESULTS Ectopic ZAG expression significantly stimulates 3T3-L1 cells proliferation in a dose- and time-dependent manner. The maximum influence of ZAG on proliferation was 1.43-fold higher than what was observed in control cells. This effect was observed 144 h after transfection with 0.16 μg of murine ZAG (mZAG) plasmid (P < 0.001). The intracellular lipids content in mZAG over-expressing cells were decreased as much as 37% when compared with the control cells after differentiation (P < 0.05, P < 0.01). The messenger ribonucleic acid levels of peroxisome proliferators-activated receptor-γ (PPARγ), CCAAT enhancer-binding protein-α (C/EBPα) and the critical lipogenic gene, fatty acid synthase (FAS), are also downregulated by up to 50% in fully differentiated ZAG-treated adipocytes. ZAG suppresses FAS messenger ribonucleic acid expression by reducing FAS promoter activity. CONCLUSIONS Zinc-α2-glycoprotein stimulates the proliferation and inhibits the differentiation of 3T3-L1 murine preadipocytes. The inhibitory action of ZAG on cell differentiation might be a result of the attenuation of the expression of PPARγ, C/EBPα and the lipogenic-specific enzyme FAS by reducing FAS promoter activity.