Nicotinamide mononucleotide (NMN) improves ovarian inflammation via lactate-mediated NLRP3 modifications in premature ovarian insufficiency

Premature ovarian insufficiency (POI) significantly impacts female fertility, yet its mechanisms and treatment strategies remain unclear. This study aimed to elucidate POI pathogenesis and identify potential therapies. NMN is an orally bioavailable NAD+ precursor naturally present in various foods, was investigated as a therapeutic agent. A rat model of POI revealed upregulation of inflammatory cytokines, including NLRP3, IL-1β, and IL-18. Treatment with NMN and estradiol (E2) improved ovarian reserve function, with NMN notably increasing lactate production in ovaries and granulosa cells (GCs). Western blotting showed altered protein acetylation and lactylation levels in the rat ovarian tissues, modulated by lactate, which was found to bind to lysine residues on NLRP3. Adding sodium lactate decreased NLRP3 acetylation while increasing lactylation. All seven mammalian SIRT isoforms (SIRT1–7) were initially screened, revealing that SIRT3 inhibits NLRP3 acetylation, SIRT2 is a main de-lactylase, and PCAF is a common writer for NLRP3 acetylation and lactylation. Additionally, the acetylation and lactylation modification sites of the NLRP3 protein were identified as K570 and K599, respectively. Lastly, lactate inhibited NLRP3 and downstream inflammatory cytokines in the human granulosa-like tumor cell line KGN. These findings suggest that lactate regulates NLRP3 modifications, providing new therapeutic targets for POI treatment.