Microbial conversion of daidzein to S-equol enhances protection against menopause-associated metabolic dysfunction by suppressing pancreatic inflammation, inhibiting DPP-4/PTP1B, activating AMPK/Akt, and enhancing energy catabolism.

Menopause-induced estrogen deficiency is associated with metabolic dysregulation, pancreatic inflammation, and oxidative stress. This study investigated the protective effects of microbial conversion of daidzein (Dzn) to S-equol (Eq), in ovariectomized (OVX) rats. The microbial biotransformation of Dzn into Eq by Slackia isoflavoniconvertens was confirmed using UV-Visible spectroscopy, HPLC, and FTIR analyses. OVX markedly reduced plasma 17β-estradiol (-84%), increased pancreatic myeloperoxidase (MPO) and elastase (ELA) activities, and elevated oxidative stress markers including hydrogen peroxide (H₂O₂), thiobarbituric acid reactive substances (TBARS), and total oxidant status, while decreasing total antioxidant status. In parallel, OVX impaired insulin signaling through increased dipeptidyl peptidase-4 (DPP-4) and protein tyrosine phosphatase 1B (PTP1B) activities and reduced AMP-activated protein kinase (AMPK) and Akt/PKB activation, leading to hyperglycemia, dyslipidemia, and increased body weight. Oral administration of Eq or Dzn (150 mg/kg) significantly restored estradiol levels (+315% and +185%, respectively) and improved pancreatic structure by reducing neutrophil infiltration and inflammatory enzyme activities. Both treatments attenuated oxidative stress by lowering H₂O₂, TBARS, and total oxidant status, while enhancing antioxidant defenses, with Eq showing greater efficacy. Moreover, Eq and Dzn improved insulin signaling by inhibiting DPP-4 and PTP1B and activating AMPK and Akt/PKB pathways, and stimulated carbohydrate and lipid catabolism via increased activities of Krebs cycle enzymes (IDH, SDH, and MDH). Collectively, these findings showed that microbial Eq as a potent phytoestrogen that mitigates menopausal metabolic and pancreatic alterations.