TLR4/NF-κB Signaling Contributes to the Inflammation in Ovary and Inguinal Fats of Polycystic Ovary Syndrome

Background Polycystic ovary syndrome (PCOS) is a complex reproductive endocrine disorder. It has highly heterogeneous clinical manifestations which are characterized by biochemical hyperandrogenemia, obesity, insulin resistance, dyslipidemia, anovulation, and polycystic ovaries. However, the etiologies of PCOS are still unclear. Recently, studies have found that the low-grade inflammation contributed to the occurrence of PCOS, and as a critical biomarker indicated the endocrine disruptions in PCOS. Objective This study is aimed to investigate the processes and mediators of inflammation in contributing to the development of PCOS. Methods Letrozole (LET) induced PCOS rat model was used in this study. Body weight, body temperature, inguinal fats weight, fasting glucose level, ovarian morphology, NF-κB signaling target genes in ovary, and protein expression levels of TLR4 and NF-κB in ovarian and inguinal fats were measured in rats with placebo and LET administrations for 6 and 12 weeks. Results PCOS rats, especially with LET intervention for 12 weeks, had higher body weight, inguinal fats weight and fasting glucose level compared to control group. The protein expression levels of TLR4 and NF-κB in cytoplasm of ovarian and inguinal fats were increased in LET-induced PCOS rats compared to control groups, while NF-κB in nucleus were reduced in PCOS rats. The expressions of ACTB, C3, CXCL3, NQO1 and SELP in ovarian were statistically different in PCOS rats induced by LET compared to control groups. Conclusion These findings indicated that stimulating TLR4/NF-κB pathway in inguinal fats and ovary tissues contributed to the increased inflammation in LET-induced PCOS rats, which, in turn, exacerbated the phenotype of PCOS including weight gain, adipose tissue accumulation, hyperglycemia and follicular dysplasia.