Loss of HNF1α Function Contributes to Hepatocyte Proliferation and Abnormal Cholesterol Metabolism via Downregulating miR-122: A Novel Mechanism of MODY3

Abstract

Purpose

Mutations in hepatocyte nuclear factor 1α (HNF1α) 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 HNF1α 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 HNF1α. HepG2 cells were transfected with siRNA or miRNA mimic to downregulate or upregulate the expression of HNF1α 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

HNF1α regulated the expression of miR-122 by directly binding to its promoter. Knockdown of HNF1α 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 HNF1α deficiency in human hepatocytes. Mechanistically, HNF1α 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 HNF1α 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.

Keywords:

• MODY3
• HNF1α
• miR-122
• cholesterol metabolism
• hepatocellular adenoma

Acknowledgments

This study was funded by National Key Research and Development Program (2016YFC1304901), Beijing Science and Technology Committee Funding (Z141100007414002 and D131100005313008), and the National High-Technology Research and Development Program of China (863 Program 2012AA02A509).

Disclosure

The authors report no conflicts of interest in this work.