RF10 | PMON249 MicroRNA-21 Ablation Exacerbates Androgen-Mediated White Adipose Tissue Dysfunction and Impaired Insulin Signaling in a Mouse Model of Polycystic Ovary Syndrome

Abstract

Abstract Background Polycystic ovary syndrome (PCOS) is characterized by oligo- or anovulation, polycystic ovaries, and hyperandrogenism. PCOS is associated with white adipose tissue (WAT) expansion and dysfunction, which has been linked to impaired insulin signaling in a number of metabolic diseases. MicroRNAs dysregulation in WAT is involved in the development of obesity and its associated complications. MicroRNA-21 (miR-21), the most abundant circulatory microRNA in women with PCOS, regulates androgen receptor (AR) expression in prostate cancer however, its role in WAT dysfunction in PCOS, and the associated systemic insulin resistance, is unknown. Using a well-established PCOS model of hyperandrogenemia we aim to test the hypothesis that miR-21 regulates AR expression to modulate androgen-mediated WAT dysfunction and the associated local and systemic insulin resistance. Methods Three-week-old miR-21 knockout (miR-21KO) or wild type (WT) female mice were treated with dihydrotestosterone (DHT, 8 mg/Silastic tube) or vehicle for 90 days (n=6/group). Body composition (EchoMRI) and oral glucose tolerance test (OGTT) were assessed. HOMA-IR index was calculated from fasting serum glucose and insulin levels. Retroperitoneal fat (RPF), a WAT depot that is linked to poor plasma glycemic indices and systemic inflammation, was collected to assess adipocyte size and perform molecular determinations. RPF miR-21 levels, as well as gene and protein expression of AR, and insulin signaling markers (IRS-1/2, insulin receptor-β, PI3K, AKT, Glut4, GSK-α, PTEN) were quantified by RT-qPCR and Western blot. Results In WT mice, DHT increased body weight (25.07 ± 0.52 vs 21.79 ± 0.47 g, p<0.05), fat mass (4.60 ± 0.46 vs 1.98 ± 0.12 g, p<0.05), RPF mass (29.68 ± 3.39 vs. 172.64 ± 32.75 g, p<0.05), RPF miR-21 (2.5-fold) and AR expression (2.1-fold). Adipocyte size analysis revealed a hypertrophic response to DHT, which was associated with impaired OGTT (186.10 ± 5.99 vs 250.70 ± 14.76 mg. min/dL, p<0.05) and downregulation of IRS-1/2, insulin receptor-β, and AKT, indicating impaired insulin signaling. MiR-21 ablation had no effect on DHT-mediated total fat or RPF mass increases, but it exacerbated DHT-mediated AR upregulation, RPF hypertrophy, and insulin resistance as measured by the HOMA-IR index. DHT-mediated reduction in GSK-α, which mediates obesity-induced inflammation, was abolished in miR-21KO mice. Glut4 protein was only downregulated in miR-21KO DHT-treated mice, despite DHT downregulating Glut4 mRNA in both strains. Furthermore, DHT only upregulated PTEN, a negative insulin signaling regulator and known target of miR-21 in miR-21KO mice. Conclusion and significance: These findings imply that WAT miR-21 plays a protective role in PCOS by alleviating androgen-mediated adipose tissue structural and molecular derangements, as well as the associated local and systemic insulin resistance via downregulating AR. Modulation of miR-21 levels in adipose tissue could be a novel therapeutic approach for the treatment of PCOS-related metabolic derangements. Presentation: Saturday, June 11, 2022 1:00 p.m. - 1:05 p.m., Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.