Roles for miRNA-378/378* in adipocyte gene expression and lipogenesis.
In this study, we explored the roles of microRNAs in adipocyte differentiation and metabolism. We first knocked down Argonaute2 (Ago2), a key enzyme in the processing of micro-RNAs (miRNAs), to investigate a potential role for miRNAs in adipocyte differentiation and/or metabolism. Although we did not observe dramatic differences in adipogenesis between Ago2 knock-down and control 3T3-L1 cells, incorporation of [(14)C]glucose or acetate into triacylglycerol, and steady-state levels of triacyglycerol were all reduced, suggesting a role for miRNAs in adipocyte metabolism. To study roles of specific miRNAs in adipocyte biology, we screened for miRNAs that are differentially expressed between preadipocytes and adipocytes for the 3T3-L1 and ST2 cell lines. Distinct subsets of miRNAs decline or increase during adipocyte conversion, whereas most miRNAs are not regulated. One locus encoding two miRNAs, 378/378*, contained within the intron of PGC-1beta is highly induced during adipogenesis. When overexpressed in ST2 mesenchymal precursor cells, miRNA378/378* increases the size of lipid droplets and incorporation of [(14)C]acetate into triacylglycerol. Although protein and mRNA expression levels of C/EBPalpha, C/EBPbeta, C/EBPdelta, and PPARgamma1 are unchanged, microarray and quantitative RT-PCR analyses indicate that a set of lipogenic genes are upregulated, perhaps due to increased expression of PPARgamma2. Knock-down of miRNA378 and/or miRNA378* decreases accumulation of triacylglycerol. Interestingly, we made the unexpected finding that miRNA378/378* specifically increases transcriptional activity of C/EBPalpha and C/EBPbeta on adipocyte gene promoters.
Gerin
Isabelle
I
Department of Molecular and Integrative Physiology, University of Michigan, 1301 E. Catherine St., Ann Arbor, MI 48109-5622, USA.
Bommer
Guido T
GT
McCoin
Colin S
CS
Sousa
Kyle M
KM
Krishnan
Venkatesh
V
MacDougald
Ormond A
OA
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D015870:Gene Expression / Q000235:genetics / Q000502:physiology*; D008055:Lipids / Q000096:biosynthesis; D050155:Lipogenesis / Q000235:genetics / Q000502:physiology*; D008156:Luciferases / Q000235:genetics; D051379:Mice; D035683:MicroRNAs / Q000235:genetics* / Q000302:isolation & purification; D046228:Microarray Analysis; D047495:PPAR gamma / Q000096:biosynthesis / Q000235:genetics; D010957:Plasmids; D012190:Retroviridae / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000502:physiology; D014162:Transfection; D014280:Triglycerides / Q000378:metabolism
D022763:CCAAT-Enhancer-Binding Protein-alpha; D008055:Lipids; D035683:MicroRNAs; D047495:PPAR gamma; D014280:Triglycerides; D008156:Luciferases