Two Triacylglycerol Pathway Genes, CTDNEP1 and LPIN1, are Down-Regulated by hsa-miR-122-5p in Hepatocytes.

BACKGROUND Expression of miR-122 is highly specific to hepatocytes of the liver.  This miRNA is involved in lipid hemostasis of the tissue; however, there is no comprehensive understanding of its function in lipid hemostasis. MATERIALS AND METHODS Since hepatocytes are responsible for part of Triacylglycerol (TAG) synthesis in the body, we hypothesized that miR-122, as the most abundant miRNA in the tissue, might regulate TAG metabolism by targeting key enzymes that are involved in its production pathway. A systematic computational analysis of putative targets of miR-122 identified CTDNEP1 and LPIN1 genes in the TAG pathway. We used dual-luciferase reporter assay, quantitative RT-PCR as well as western blot to confirm the repressive effect of miR-122 on CTDNEP1 and LPIN1 in TAG pathway. RESULTS Real time PCR on liver needle biopsies with hepatosteatosis showed that miR-122 is up-regulated in hepatosteatosis. Surprisingly, the protein and RNA level of identified targets of miR-122 are also up-regulated in clinical samples, probably as a disproportionate feedback response to the high level of miR-122. CONCLUSION Our findings suggest that up-regulation of miR-122 can trigger the compensatory response of LPIN1 and CTDNEP1 in hepatosteatosis.