The role of microRNAs in the regulation of adipogenesis

Aims: MicroRNAs (miRNAs) are a family of short, endogenously expressed, non-coding RNAs which regulate gene expression, particularly in developmental processes. Recent studies indicate a critical role in adipocyte differentiation.

Objective: In this study we investigated the effect of inhibition of miRNA processing on adipocyte differentiation. Furthermore, we searched for miRNAs that are differentially regulated during human adipocyte differentiation and their putative target genes.

Methods: In vitro experiments were performed in human Simpson-Golabi-Behmel syndrome (SGBS) cells, a cell model for adipogenesis. MiRNA processing was inhibited by knock down of Drosha and Dicer, key enzymes of the processing machinery. Effects on adipogenesis were measured by Oilred staining, counting of differentiated cells and expression analysis of PPARg. Regulated microRNAs were identified using Illumina technology based miRNA sequencing and results were validated by real time PCR. Putative miRNA target genes were selected using the Pictar database.

Results: Knock down of Drosha and/or Dicer significantly reduced fat accumulation to 42 ± 6.8% and PPARg expression by trend to 58 ± 26%. Sequencing experiments identified 7 miRNAs at least 2.5 fold induced and 12 miRNAs at least 0.4 fold repressed during adipogenesis. MiR378 was the most pronouncedly upregulated (44 fold) miRNA at d12 of differentiation. Progranulin is inversely regulated compared to miR107 during SGBS adipogenesis. Ectopic expression of miR107 in preadipocytes mediated a reduction of Progranulin and inhibits adipogenesis.

Conclusion: An inhibition of miRNA processing reduced human adipocyte differentiation capacity. This supports a regulatory function of miRNA during adipogenesis. We identified 19 miRNAs differential regulated during human adipogenesis and showed that Progranulin is a target of the upregulated miR107.