Nervonic acid triggered ovarian inflammation by inducing mitochondrial oxidative stress to activate NLRP3/ IL-1β pathway.

Introduction: Metabolic syndrome is a serious public health concern across the globe. However, the typical metabolites and mechanisms underlying the decreased fertility related to metabolic syndrome is still elusive.

Objectives: The aim of the present study was to explore the typical metabolites and mechanisms underlying the decreased fertility related with metabolic syndrome.

Methods: Utilizing metabolomics, a comparative analysis was conducted on fatty acid compositions in various tissues of sows with high and low reproductive performance. Additionally, serum fatty acid compositions in a metabolic syndrome model (obese mice) induced by a high-fat diet (HFD) were investigated to elucidate the lipid metabolites associated with metabolic syndrome. Furthermore, the impact of nervonic acid (NA) on ovarian function was examined using rodent animal models (rats and mice). Through biological techniques such as transcriptomics, CUT&Tag, and analysis of post-translational protein modifications, the molecular mechanisms underlying NA mediated ovarian inflammation were further elucidated based on models utilizing ovarian granulosa cells from pigs, humans, and mice. Finally, validation was performed on ovaries from patients diagnosed with polycystic ovary syndrome.

Results: In vitro, targeted serum lipidomic analysis revealed that sows with low embryo survival rates exhibited abnormal lipid metabolism characterized by abnormal accumulation of NA in the liver, ovary, and adipose tissue. Additionally, elevated NA levels trigger ovarian inflammation to cause ovarian dysfunction in both sows and rats. Mechanistically, NA induce mitochondrial oxidative stress through inhibiting respiratory chain proteins CYTB and NDFUB8 to activate NLRP3 inflammasome, which triggers procaspase-1 into active caspase-1, and convert the cytokine precursors pro-IL-1β into biologically active IL-1β in ovarian granulosa cells. Notably, we evidenced that NA promotes IL-1β activities by increasing H3K9ac modification level of IL-1β promoter regions and regulating the expression of the transcription factor AP-1. Finally, we found that the decreased expression of CerS2 in ovaries and the increased level of chemokine CXCL14 may be the cause of abnormal NA accumulation. Surprisingly, individuals with polycystic ovary syndrome, obesity, non-alcoholic fatty liver or gestational diabetes mellitus exhibit a high level of serum NA.

Conclusion: Collectively, our current study suggests that NA is a typical metabolite of metabolic syndrome, which strongly influences the ovarian function and embryo survival and also provides that interfering with mitochondrial ROS production is a potential strong strategy for target solving abnormal NA accumulation.