Ectopic overexpression of MCPIP1 impairs adipogenesis by modulating microRNAs.

Adipogenesis, process of fat tissue formation, requires activity of transcription factors, growth factors and others molecules, including miRNAs. Monocyte chemoattractant protein-1-induced protein 1 (MCPIP1) has been shown to be an important regulator of adipocyte differentiation and its forced expression impairs adipogenesis. MCPIP1 exerts its anti-adipogenic role by a direct degradation of the C/EBPβ transcript. Moreover, MCPIP1 has been identified as a broad suppressor of the miRNA biogenesis. We expect that besides C/EBPβ, miRNAs essential for adipogenesis are under the direct control of MCPIP1. Using Next-Generation Sequencing we compared miRNA expression profile in 3T3-L1 adipocytes overexpressing MCPIP1 and control cells. We identified 58 differentially expressed miRNAs, of which 30 were down- and 28 up-regulated in MCPIP1-overexpressing adipocytes. To define the adipogenic-related miRNAs which expression is dependent on MCPIP1, we examined 24 miRNAs with significantly decreased expression level (P-value <0.01) at least 1.5-times. By Q-RT-PCR we confirmed a decreased expression of 3 miRNAs (mir-152-3p, mir-26b and mir-30e) which function in adipogenesis was known and 2 miRNAs (mir-9-3p and mir-32) which expression has never been linked with adipocyte biology before. Furthermore, for the functional annotation we performed target predictions analysis of co-expressed miRNAs. We identified MAPK signaling pathway as the most significantly modulated by investigated down-regulated miRNAs. Moreover, for selected miRNAs we evaluated their target genes by demonstrating increase of their expression on the mRNA level in Q-RT-PCR analysis. Our data indicate an impact of adipocyte-related miRNAs in adipocyte biology and may help to explain the negative role of MCPIP1 in adipocyte differentiation.