miR-3666 inhibits development of hepatic steatosis by negatively regulating PPARγ

PPARγ is a crucial transcription factor involved in development of hepatic steatosis, an early stage of NAFLD. PPARγ is tightly regulated through various positive and negative regulators including miRNAs. In this study, we report for the first time miR-3666 as a negative regulator of PPARγ and its involvement in development of hepatic steatosis.

Binding of miR-3666 to regulate PPARγ was checked by luciferase assay and was confirmed by mutating PPARγ 3'UTR. Regulation of PPARγ was determined by overexpression of miR-3666 in HepG2 cells. Hepatic steatotic state in HepG2 cells was developed by exposure to excess palmitic acid and expression of PPARγ, miR-3666 and some PPARγ target and non-target genes was checked. Involvement of mir-3666 by regulating PPARγ in hepatic steatosis was also examined in liver of HFD fed mice.

On overexpression of miR-3666, PPARγ expression decreased significantly in a dose-dependent manner in HepG2 cells. Binding of miR-3666 to PPARγ was confirmed as the luciferase activity using pMIR-REPORT with PPARγ 3'UTR decreased in PA treated HepG2 cells overexpressing miR-3666 and remained unchanged when PPARγ 3'UTR was mutated. In PA treated HepG2 cells during development of hepatic steatosis PPARγ was significantly up-regulated concomitant with down-regulation of miR-3666. Overexpression of miR-3666 in these cells decreased the extent of hepatic steatosis. Significant up-regulation of PPARγ and down-regulation of miR-3666 was also observed in liver of HFD fed mice indicating that miR-3666 regulates PPARγ in vivo.

miR-3666 negatively regulates PPARγ by binding to its 3'UTR during development of hepatic steatosis.