Loss of HNF1? Function Contributes to Hepatocyte Proliferation and Abnormal Cholesterol Metabolism via Downregulating miR-122: A Novel Mechanism of MODY3.
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ABSTRACT: Purpose:Mutations in hepatocyte nuclear factor 1? (HNF1?) are the cause of maturity-onset diabetes of the young type 3 (MODY3) and involved in the development of hepatocellular adenoma and abnormal lipid metabolism. Previously, we have found that the serum microRNA (miR)-122 levels in MODY3 patients were lower than those in type 2 diabetes mellitus and healthy controls. This study aimed to investigate the mechanism of decreased miR-122 levels in patients with MODY3 and whether low levels of miR-122 mediate tumorigenesis and abnormal lipid metabolism associated with HNF1? deficiency in human hepatocytes. Methods:The expression of miR-122 was examined by real-time PCR. Dual-luciferase reporter assay was performed to confirm the transcriptional regulation of miR-122 by HNF1?. HepG2 cells were transfected with siRNA or miRNA mimic to downregulate or upregulate the expression of HNF1? or miR-122, respectively. CCK-8 and colony formation assay were used to determine cell proliferation. Lipid accumulation was examined by Oil Red O staining and intracellular triglyceride and cholesterol quantification assays. Results:HNF1? regulated the expression of miR-122 by directly binding to its promoter. Knockdown of HNF1? in HepG2 cells reduced the expression of miR-122, increased proliferation and promoted intracellular cholesterol accumulation. Overexpression of miR-122 partially rescued the phenotypes associated with HNF1? deficiency in human hepatocytes. Mechanistically, HNF1? modulated cholesterol homeostasis via miR-122-dependent activation of sterol regulatory element-binding protein-2 (SREBP-2) and regulation of proprotein convertase subtilisin/kexin type 9 (PCSK9). Moreover, circulating miR-122 levels were associated with serum cholesterol levels. Conclusion:Loss of HNF1? function led to hepatocyte proliferation and abnormal cholesterol metabolism by downregulating miR-122. Our findings revealed a novel mechanism that low levels of miR-122 mediate tumorigenesis and abnormal lipid metabolism associated with MODY3. MiR-122 may be a potential therapeutic target for the treatment of MODY3.
SUBMITTER: Hu M
PROVIDER: S-EPMC7060037 | biostudies-literature | 2020
REPOSITORIES: biostudies-literature
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