Vitamin D deficiency inhibits microRNA-196b-5p which regulates ovarian granulosa cell hormone synthesis, proliferation, and apoptosis by targeting RDX and LRRC17

BACKGROUND: In polycystic ovary syndrome (PCOS), ovarian physiology is tightly linked to the metabolic disturbances observed in this disease. Vitamin D (VD) plays an important role in the regulation of ovulatory dysfunction and can influence genes involved in steroidogenesis in granulosa cells (GCs). However, its role in the proliferation and apoptosis of ovarian GCs is unclear. The present study aimed to investigate the role of microRNA-196-5p (miR-196b-5p) in the hormone synthesis, proliferation, and apoptosis of ovarian GCs. METHODS: The abnormal expression of miRNAs in ovarian tissues of VD-deficient mice was analyzed using transcriptome sequencing. The direct target of miR-196b-5p was predict and confirmed by bioinformatics analysis and the dual-luciferase reporter assay. Reverse transcription-quantitative PCR (RT-qPCR) was used to detect the levels of miR-196b-5p, cell proliferation was detected via the CCK8 assay, and cell apoptosis and reactive oxygen species (ROS) were measured via flow cytometry. The levels of radixin (RDX), leucine rich repeat containing 17 (LRRC17), aromatase (CYP19A1), and glucose transporter 4 (GLUT4) were detected by performing RT-qPCR or western blot. RESULTS: We found that miR-196b-5p was significantly downregulated among the 672 miRNAs that were differentially expressed (DE) in VD-deficient mice. In addition, the results demonstrated that downregulated expression of miR-196b-5p significantly increased the level of RDX and LRRC17, and reduced expression of miR-196b-5p significantly promoted ovarian GC apoptosis and inhibited cell proliferation. Downregulated expression of miR-196b-5p promoted cellular ROS production and inhibited sex hormone production and glucose uptake. Transfection with miR-196b-5p mimics significantly increased the expression of CYP19A1 and GLUT4 and decreased the RDX and LRRC17 levels in ovarian GCs. CONCLUSIONS: This study shows that miR-196b-5p can regulate the oxidative stress (OS), glucose uptake, and steroid production pathway of GCs, thus promoting follicular development and maturation. This is a step towards a feasible treatment for PCOS.