SUN-477 The Gut Microbe Rothia Mucilaginosa Induces a Polycystic Ovarian Syndrome-Like Phenotype in a Rat Model

Abstract G. Parodi: None. R. de Souza Santos: None. G. Leite: None. F. Medeiros: None. G.M. Barlow: None. W. Morales: None. S.R. Weitsman: None. M. Sanchez: None. I. Rivera: None. M. Villanueva-Millan: None. F. Faria: None. D. Flor: None. L. Choi: None. M. Pimentel: None. R. Mathur: None. Polycystic ovary syndrome (PCOS) is an endocrine disorder affecting ∼12% of reproductive-age women. Its clinical signatures include hyperandrogenism, ovarian dysfunction, infertility, and insulin resistance. We hypothesize that bacterial testosterone (T) biosynthesis is a source of excess T in PCOS. The small bowel, an active site of steroid hormone metabolism, harbors specific microbes with T production machinery. Of these, we have shown that Rothia mucilaginosa can produce testosterone in vitro, and that gavaging female rats with this microbe results in PCOS-like phenotypes, including higher insulin levels, significant disruption of estrous cycles, and longer exposure to peak T levels. Here, we further investigate the effects of R. mucilaginosa on the development of ovarian and metabolic PCOS-like features in this rat model. Methods: Reproductive-age female rats were gavaged with 108 CFU/mL R. mucilaginosa or PBS (controls) daily for 4 weeks. Serum T was measured by LC-MS/MS, and fasting insulin and glucose by ELISA. Ovaries were harvested for whole transcriptomics, histology, and androgen receptor immunohistochemistry. Results: We previously showed that Rothia-gavaged rats spend ∼75% of their estrous cycles in the luteal phase (metestrus/diestrus) vs. 50% in controls, with increased overall T exposure and higher ovarian weights. Here, detailed analyses reveal that Rothia-gavaged rats have altered ovarian histology vs. controls, with higher numbers of atretic follicles (10.9±4.0 vs. 6.7±4.8, P=0.04) and reduced minimal thickness of the granulosa cell layer in the largest antral follicle (77.5±12.6mm vs. 97.9±17.5mm, P=0.04) in the follicular phase (proestrus/estrus), as well as greater maximal thickness of the theca interna cell layer in the largest antral follicle (37.9±8.8μm vs. 28.2±9.8μm) and higher size of the largest atretic follicle (793.0±197.9mm vs. 596.2±179.3mm, P=0.04) in the luteal phase. Ovarian androgen receptor levels are lower in Rothia-gavaged rats (P=0.05), and negatively correlate with R. mucilaginosa levels in stool (Spearman R=-0.576, P=0.001). Transcriptomic analyses reveal several steroid metabolism-associated pathways are altered in the ovaries of Rothia-gavaged rats vs. controls, including synthesis of steroids (P=5.38E-4) and secretion of steroids (P=5.90E-5). Lastly, in addition to higher fasting insulin, Rothia-gavaged rats have higher fasting glucose levels (129.0±3.3 mg/mL vs. 119.2±2.8 mg/mL, P=0.014), and HOMA-IR index (5.0±0.5 vs. 3.1±0.4, P=0.002) vs. controls. Conclusion: Here we provide further evidence that Rothia mucilaginosa, a testosterone-producing microbe, induces a PCOS-like phenotype in rats, now including significantly altered ovarian histology, changes in ovarian pathways related to steroid metabolism, and insulin resistance. Sunday, June 2, 2024