Modulatory impact of <i>Bifidobacterium longum</i> subsp. <i>longum</i> BL21 on the gut–brain–ovary axis in polycystic ovary syndrome: insights into metabolic regulation, inflammation mitigation, and neuroprotection

This study evaluates the efficacy of <i>Bifidobacterium longum</i> subsp. <i>longum</i> BL21 in mitigating symptoms of polycystic ovarian syndrome (PCOS) in DHT-induced PCOS model mice. It focuses on BL21's role in modulating metabolic dysregulation, inflammation, and neuroprotection via the gut-brain-ovary axis. Employing an 8-week treatment regimen, this research assessed the effects of BL21 on prenatal androgen-induced PCOS in ICR mice. Evaluations included body weight, glucose tolerance tests, serum analyses of BDNF, inflammatory markers, sex hormone levels, and 16S rRNA gene sequencing for gut microbiota diversity and composition. Twenty-four ICR mice with induced PCOS served as subjects to examine the probiotic's impact. Mice were administered a daily oral dose of 1 × 10⁹ CFU of BL21 continuously for a total of 8 weeks. BL21 significantly enhanced sex hormone levels (<i>P</i> < 0.05), particularly those of follicle-stimulating hormone (FSH) and estradiol (E2), indicating improved ovarian function and offering a novel PCOS treatment approach. The intervention notably curbed weight gain and improved glucose tolerance in PCOS mice (<i>P</i> < 0.05). BL21 reduced inflammatory markers such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and lipopolysaccharides (LPS), while increasing IL-10, BDNF, FSH, and E2 levels (<i>P</i> < 0.05 for all). It also enriched gut microbiota diversity, enhancing populations of <i>Bifidobacterium</i> and <i>Lactobacillus</i>. Correlation analyses underscored the positive shifts in microbiota linked to beneficial hormonal and inflammatory profiles. BL21 shows promise in alleviating PCOS symptoms through metabolic regulation, inflammation reduction, and neuroprotection, validating its potential in integrated therapeutic strategies.IMPORTANCEPolycystic ovarian syndrome (PCOS) is a prevalent endocrine disorder affecting women of reproductive age, characterized by metabolic irregularities, hormonal imbalances, and chronic inflammation. Existing treatments are often inadequate, addressing symptoms without targeting the underlying etiological factors. The investigation of <i>Bifidobacterium longum</i> subsp. <i>longum</i> BL21 as a probiotic intervention offers a novel approach by potentially regulating the gut-brain-ovary axis. This could lead to innovative therapeutic strategies that not only manage but also potentially reverse the multifaceted symptoms of PCOS, enhancing quality of life and reproductive health.