Berberine decreases insulin resistance in a PCOS rats by improving GLUT4: Dual regulation of the PI3K/AKT and MAPK pathways

Berberine has been found to exhibit an array of pharmacological activities relating to the lowering of blood glucose and the treatment of polycystic ovarian syndrome (PCOS). The mechanism underlying these activites, however, is poorly understood. In the present study, female Sprague-Dawley (SD) rats were given oral letrozole to establish a model of insulin-resistant PCOS, and animals were then randomized into untreated or berberine-treated groups (400, 200, or 100 mg/kg). After 28 days, we measured homeostasis model assessment of insulin resistance (HOMA-IR) and insulin sensitivity index (ISI) values in these animals. We further conducted H&E staining of ovarian tissues, assessed mRNA expression of glucose transporter 4 (GLUT4) via real time PCR, and used Western blotting to measure GLUT4 and PI3K/AKT and MAPK pathway protein levels. Berberine treatment was able to help restore HOMA-IR and ISI values to normal levels while simultaneously bolstering the expression of GLUT4. Normal ovarian morphology was also restored upon berberine treatment. We further found that 400 mg/kg berberine treatment was associated with activation of PI3K/AKT signaling and suppression of the MAPK pathway. In conclusion, berberine has the potential to reduce PCOS pathology and IR values in a rat model system through a mechanism linked to GLUT4 upregulation via PI3K/AKT activation and MAPK pathway suppression.