Abstract
BackgroundMicroRNAs (miRNAs) emerge as new important regulators of lipid homeostasis by regulating corresponding genes. MiR-613 is a newly discovered microRNA, of which the biological function is unknown. A recent report has shown that miR-613 downregulates liver X receptor α (LXRα), a ligand-activated nuclear receptor playing an important role in the regulation of lipid metabolism. The purpose of this study is to explore the effect and the molecular basis of miR-613 on lipogenesis in HepG2 cells.MethodsHepG2 cells were transiently transfected with miR-613 mimic or control microRNA. Real time PCR, Western blot, Luciferase reporter assay and Oil Red O staining were employed to examine the expression of LXRα and its target genes involved in lipogenesis, binding site for miR-613 in 3′-untranslated region (3′-UTR) of LXRα mRNA and lipid droplet accumulation in the cells.ResultsMiR-613 dramatically suppressed the expression of LXRα and its target genes including sterol-regulatory element binding protein 1c (SREBP-1c), fatty acid synthase (FAS), carbohydrate responsive element-binding protein (ChREBP) and acetyl-CoA carboxylase (ACC). Reporter assay showed that miR-613 directly bound to 3′-UTR of LXRα mRNA. Moreover, miR-613 significantly repressed LXRα-induced lipid droplet accumulation in HepG2 cells. Ectopic expression of LXRα without 3′-UTR markedly attenuated the miR-613-mediated downregulation of LXRα’s target genes and LXRα-induced lipid droplet accumulation.ConclusionsMiR-613 suppresses lipogenesis by directly targeting LXRα in HepG2 cells, suggesting that miR-613 may serve as a novel target for regulating lipid homeostasis.
Highlights
MicroRNAs are a class of 22 nucleotide non-coding RNAs that regulate genes by binding to the 30-untranslated region (30-UTR) of target mRNAs
To examine whether these results are obtainable under our experimental conditions, HepG2 cells were transfected with miR-613 mimic or negative control (NC)
Western blot and real-time PCR analysis showed that endogenous liver X receptor α (LXRα) expression was repressed by miR-613 at both protein and mRNA levels (Figure 1A), while LXRβ expression was not affected, which suggested that miR-613 effect was specific for LXRα
Summary
MicroRNAs (miRNAs) are a class of 22 nucleotide non-coding RNAs that regulate genes by binding to the 30-untranslated region (30-UTR) of target mRNAs. Recent studies have shown that miRNAs play an important role in lipid metabolism and several miRNAs have been identified, such as miR-33, miR-122, miR-27, miR-370 [4,5]. MiR-613 is a newly discovered miRNA, whose function and molecular basis in the biological process and diseases is incompletely understood. It is reported that miR-613 plays inhibitory role in repressing the Wnt pathway, but its effect on the Wnt-dependent biological processes is unclear. MicroRNAs (miRNAs) emerge as new important regulators of lipid homeostasis by regulating corresponding genes. MiR-613 is a newly discovered microRNA, of which the biological function is unknown. A recent report has shown that miR-613 downregulates liver X receptor α (LXRα), a ligand-activated nuclear receptor playing an important role in the regulation of lipid metabolism. The purpose of this study is to explore the effect and the molecular basis of miR-613 on lipogenesis in HepG2 cells
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