THSR Mediated MiR374b Targeting C/EBP β/FOXO1 to Accelerate Thyroid Stimulating Hormone-Induced Hepatic Steatosis.

Purpose: Thyroid-stimulating hormone (TSH) has been identified as an independent risk factor for non-alcoholic fatty liver disease (NAFLD), TSH binds to the TSH receptor (TSHR) to exert its function. However, the underlying mechanisms by which TSHR influences NAFLD development remain unclear. This study investigates the role of miR374b in NAFLD progression.

Methods: Firstly, a rat model of non-alcoholic fatty liver was constructed and divided into a normal group and a model group. The liver tissue pathology and fat accumulation were detected by Oil Red O staining and hematoxylin-eosin staining. Western blot and Real time PCR were used to detect for the impact of TSHR/miR-374b/C/EBP β/ FoxO1 pathway in the NAFLD model, and the expression of relevant inflammatory factors in each group was detected by ELISA assay. A NAFLD cell model was constructed using HepG2 cells, TSHR overexpression and interference, combined with miR-374b inhibitor and mimics, were transfected simultaneously to demonstrate TSHR/miR-374b/C/EBP β/ The mechanism of FoxO1 adipogenesis in vitro.

Results: TSHR stimulates miR374b secretion in human liver cancer cells (HepG2) and promotes lipid accumulation in the liver. Deficiency of miR374b in HepG2 cells attenuated NAFLD progression. Mechanistically, TSH increases miR374b expression, which then suppresses the transcription of its target genes, CCAAT/enhancer binding protein-b (C/EBP β) and Forkhead Box Protein O1 (FOXO1). This suppression influences the expression of downstream lipid metabolism proteins, including PPARγ, SREBP2, and SREBP1c. Additionally, miR374b directly targets the 3'UTR of C/EBP β and FOXO1, establishing a negative feedback loop in lipid metabolism.

Conclusion: These findings suggest that TSHR-induced upregulation of miR374b accelerates NAFLD progression by modulating lipid metabolism pathways through C/EBP β and FOXO1.