The role and mechanism of quercetin in improving late-onset hypogonadism through network analysis and experimental validation.

The rising incidence of late-onset hypogonadism (LOH) profoundly diminishes the quality of life in men due to declining testosterone levels. Quercetin is an important active metabolite in various traditional botanical drugs that enhance male fertility, yet its mechanisms of action remain unclear. This study delves into the therapeutic potential and underlying mechanisms of quercetin in LOH management, proposing novel treatment strategies. An aging murine model was created and treated with quercetin starting at 12 weeks of age. Sperm parameters were evaluated, and serum and testicular testosterone and inflammatory cytokines were quantified via ELISA. Histological analyses of testicular tissue were performed. Network analysis and molecular docking studies predicted quercetin's therapeutic pathways in LOH. Key proteins involved in testosterone synthesis and testicular aging were verified using western blotting and immunofluorescence. Aged TM3 cells were treated with quercetin to corroborate the effects on testicular Leydig cells. In the murine model, the quercetin treatment group showed an increase in sperm average path velocity (VAP) by 1.21 ± 0.087-fold (p < 0.01), an increase in straight-line velocity (VCL) by 1.12 ± 0.18-fold (p < 0.01), a rise in serum testosterone levels by 0.27 ± 0.48-fold (p < 0.05), and an increase in testosterone levels in testicular tissue by 0.30 ± 0.20-fold (p < 0.05), while IL-1β levels decreased to 0.61 ± 0.13-fold (p < 0.01) compared to the aging group. Network analysis suggested quercetin's efficacy in LOH may be mediated through the AR and PI3K/AKT pathways. In quercetin-treated aged mice, a reduction in γH2AX and an increase in Ki67 expression were observed in testicular tissue, alongside upregulated expression of key testosterone synthesis proteins-steroidogenic acute regulatory (STAR) and scavenger receptor class B type 1 (SRB1), accompanied with enhanced AR expression and AKT1 phosphorylation. Similar results were confirmed in testicular Leydig cells. Compared to the group treated with bleomycin alone, the bleomycin plus quercetin treatment group showed a reduced positive area in β-gal staining, downregulation of the senescence-associated marker γH2AX, increased expression of the key testosterone synthesis protein SRB1, and elevated levels of expression of quercetin's potential target AR as well as phosphorylation of AKT1. Quercetin ameliorates the aging of testicular Leydig cells and promotes testosterone synthesis through modulation of the AR/PI3K/AKT signaling pathway, presenting a promising therapeutic approach for LOH.