MicroRNA-375 promotes 3T3-L1 adipocyte differentiation through modulation of extracellular signal-regulated kinase signalling

P>1. Adipocyte hypertrophy and hyperplasia are important processes in the development of obesity. To understand obesity and its associated diseases, it is important to elucidate the molecular mechanisms governing adipogenesis. MicroRNA-375 has been shown to inhibit differentiation of neurites, and participate in the regulation of insulin secretion and blood homeostasis. However, it is unknown whether miR-375 plays a role in adipocyte differentiation. 2. To investigate the role of miR-375 in adipocyte differentiation, we compared the miR-375 expression level between 3T3-L1 pre-adipocytes and adipocytes using miRNA microarray and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) analysis. Furthermore, we evaluated the effects of overexpression or inhibition of miR-375 on 3T3-L1 adipocyte differentiation. 3. In the present study, we found that miR-375 expression was increased after induction of adipogenic differentiation. Overexpression of miR-375 enhanced 3T3-L1 adipocyte differentiation, as evidenced by its ability to increase mRNA levels of both CCAAT/enhancer binding protein-alpha (C/EBP alpha) and peroxisome proliferator-activated receptor-gamma (PPAR gamma 2), and induction of adipocyte fatty acid-binding protein (aP2) and triglyceride (TG) accumulation. Furthermore, we found overexpression of miR-375 suppressed phosphorylation levels of extracellular signal-regulated kinases 1/2 (ERK1/2). In contrast, anti-miR-375 increased ERK1/2 phosphorylation levels and inhibited mRNA expression of C/EBP alpha, PPAR gamma 2 and aP2 in 3T3-L1 adipocyte, accompanied by decreased adipocyte differentiation. 4. Taken together, these data suggest that miR-375 promotes 3T3-L1 adipocyte differentiation, possibly through modulating the ERK-PPAR gamma 2-aP2 pathway.