Decreased Serum Levels of the Insulin Resistance-Related microRNA miR-320a in Patients with Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is often associated with metabolic abnormalities in the affected patients such as obesity or a dysregulated glucose metabolism/insulin resistance (IR). IR affects the serum levels of several circulating microRNAs; however, studies on the association between IR-related microRNAs and PCOS are scarce. Therefore, we quantified the serum levels of the IR-associated microRNAs miR-93, miR-148a, miR-216a, miR-224 and miR-320a via qPCR in a cohort of 358 infertility patients, of whom 136 were diagnosed with PCOS. In bivariate correlation analyses, the serum levels of miR-93 and miR-216a were inversely associated with dipeptidyl peptidase 4 serum concentrations, and the miR-320a serum levels were significantly downregulated in PCOS patients (p = 0.02, Mann-Whitney U test). Interestingly, in all patients who achieved pregnancy after Assisted Reproductive Technology (ART) cycles, the serum levels of the five IR-associated microRNAs were significantly elevated compared to those of non-pregnant patients. In cell culture experiments, we detected a significant upregulation of miR-320a expression following testosterone stimulation over 24 and 48 h in KGN and COV434 granulosa carcinoma cells. In conclusion, we demonstrated a significantly reduced serum level of the IR-associated miR-320a in our patient cohort. This result once again demonstrates the close relationship between metabolic disorders and the dysregulation of microRNA expression patterns in PCOS.