IRS1 and polycystic ovary syndrome: Melatonin significantly upregulated the expression of insulin receptor substrate 1 (IRS-1) and glucose transporter protein 4 (GLUT4), improved glucose uptake in PCOS patients, increased p-PI3K and p-Akt levels, and reduced IR in human ovarian granulosa cells (GCs) and palmitic acid (PA)-induced cells through the PI3K/Akt signaling pathway (55).