Effect of gut microbiota modulation with probiotics on inflammatory markers in the letrozole-induced polycystic ovary syndrome rat model

Objective: Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with chronic low-grade inflammation. This study aimed to evaluate whether probiotic supplementation (Lactobacillus and Bifidobacterium) could restore serum interleukin‑10 (IL‑10) and tumour necrosis factor‑alpha (TNF‑α) levels in a letrozole‑induced PCOS rat model, compared with metformin. Methods: Twenty‑eight female albino Wistar rats were randomly divided into four groups (n=7 each): control (normal diet), PCOS model (letrozole 1 mg/kg plus high‑fat diet for 21 days), metformin (300 mg/kg/day for 28 days after induction), and probiotic (1×10⁹ CFU/day of Lactobacillus and Bifidobacterium for 28 days after induction). Serum IL‑10 was measured by ELISA, and TNF‑α by CLIA. Data were analysed using one‑way ANOVA with Bonferroni post‑hoc test. Results: PCOS induction significantly decreased IL‑10 by 32.98% (p<0.001) and increased TNF‑α by 46.33% (p<0.001) compared with controls. Probiotic treatment significantly raised IL‑10 by 27.51% (p<0.001) relative to the model group, but IL‑10 remained 14.54% lower than in controls (p=0.003). Probiotics reduced TNF‑α by only 4.69% (p=1.000), which was not statistically significant. Metformin increased IL‑10 by 36.88% (p<0.001) and reduced TNF‑α by 7.71% (p=1.000) compared with the model group. Conclusion: Probiotic supplementation partially improves the anti‑inflammatory IL‑10 but does not significantly reduce TNF‑α in this PCOS model. Probiotics alone are insufficient to reverse the inflammatory profile of PCOS fully.