OR14-04 Knockout of TLR4 Restores Fertility and Glucose Tolerance in a PCOS Mouse Model

Abstract Disclosure: K.D. Wiggins: None. Z. Del Mundo: None. J.A. Ayala Angulo: None. A. Saba: None. N. Naidu: None. D. Nicholas: None. Polycystic Ovary Syndrome (PCOS), a complex endocrine disorder affecting millions of women globally, presents intricate reproductive and metabolic challenges linked to chronic inflammation. Recent evidence suggests a significant correlation between gut health and dysfunction in PCOS, with elevated serum lipopolysaccharide (LPS) levels playing a crucial role in driving inflammation. We hypothesized that Toll-like receptor 4 (TLR4) orchestrates these disturbances by affecting gut barrier permeability and modulating the inflammatory response. To test this hypothesis, we conducted a five-week study using the aromatase inhibitor Letrozole (LET) to induce PCOS in prepubertal C57BL6J (wild type) and TLR4 knockout (TLR4-/-) female mice. LET-treated wild type mice exhibited prolonged diestrus, mirroring the irregular menstruation seen in women with PCOS. In contrast, LET-treated TLR4-/- mice maintained normal estrous cycles and demonstrated reduced luteinizing hormone (LH) levels. Remarkably, 60% of LET-treated TLR4-/- mice successfully produced offspring, a stark contrast to their non-reproductive LET-treated wild type counterparts. Furthermore, TLR4 deletion resulted in significant metabolic improvements, even in the presence of LET treatment. Specifically, TLR4-/- mice exhibited decreased body weight over the course of the five-week study period. After 4 weeks of LET treatment, TLR4-/- mice demonstrated enhanced glucose tolerance, clearing a bolus of glucose to return to baseline blood glucose levels over 120 minutes at a significantly faster rate than their wild type counterparts. While serum insulin levels in TLR4-/- mice did not fully return to those of placebo-treated animals, they were notably reduced compared to LET-treated wild type mice. The persistent reproductive and metabolic disturbances in LET-treated wild type mice were associated with increased gut permeability, a dominant Th17 inflammatory cytokine signature in fecal and serum samples, and elevated IgA production. Strikingly, these pathological changes were absent in LET-treated TLR4-/- mice. Our findings establish TLR4 as a critical mediator in the complex interplay between gut health, inflammation, and PCOS-related dysfunctions, representing a paradigm shift in our understanding of this syndrome. By elucidating the role of TLR4 in both reproductive and metabolic aspects of PCOS, we open new avenues for targeted therapies that address the syndrome's multifaceted nature. Presentation: Sunday, July 13, 2025