Mild heat treatment ameliorates PCOS by activating PI3K/Akt signaling and inhibiting granulosa cell apoptosis

Polycystic ovary syndrome (PCOS) is commonly accompanied by insulin resistance (IR), ovarian dysfunction, and granulosa-cell injury. We investigated whether mild heat treatment (MHT) alleviates PCOS-like reproductive and metabolic abnormalities and explored the potential involvement of PI3K/Akt signaling. A dihydrotestosterone (DHT)-challenged KGN cell model and a dehydroepiandrosterone (DHEA)-induced rat model were used. In vitro, KGN cells were exposed to MHT at 40 °C for 1 h, with or without the PI3K inhibitor LY294002. Cell viability, mitochondrial membrane potential, apoptosis, and proliferation were assessed. In vivo, estrous cyclicity, ovarian morphology, androgen levels, fasting insulin, HOMA-IR, glucose tolerance, and insulin tolerance were evaluated. Ovarian IRS-1, GLUT4, PI3K/Akt/mTOR signaling, RNA-seq profiles, and inflammatory cytokines were also examined. In DHT-challenged KGN cells, MHT improved cell viability, preserved mitochondrial membrane potential, reduced apoptosis, and promoted proliferation; these effects were attenuated by LY294002, suggesting partial dependence on PI3K/Akt signaling in vitro. In DHEA-induced PCOS rats, MHT improved estrous cyclicity, reduced cystic and atretic ovarian changes, and lowered hyperandrogenemia. MHT also improved glucose homeostasis, as shown by reduced fasting insulin and HOMA-IR and improved glucose and insulin tolerance. At the ovarian level, MHT increased IRS-1 and GLUT4 expression and enhanced PI3K/Akt/mTOR phosphorylation, suggesting improved insulin-related signaling activity. RNA-seq indicated partial remodeling of insulin secretion, glycolysis/gluconeogenesis, AMPK, and PI3K/Akt-related transcriptional programs. MHT also reduced serum and ovarian IL-6, IL-1β, and TNF-α levels. MHT improved PCOS-like metabolic and ovarian phenotypes, reduced granulosa-cell apoptosis, and restored PI3K/Akt/mTOR signaling. In vitro PI3K inhibition further indicated that the protective effects of MHT in KGN cells were partly dependent on PI3K/Akt signaling. These findings suggest that MHT may represent a potential non-pharmacological strategy for improving insulin resistance and ovarian dysfunction in PCOS models.