Oxytocin modulates glucose metabolism to protect against cardiac remodeling via the STAT3/eNOS Axis

Oxytocin (OT), an endogenous cardiovascular homeostatic hormone, is currently attracting considerable attention because it can improve energy metabolism and cardiac function. This study investigated whether OT mitigates cardiac remodeling in association with alterations in glucose metabolism. In vivo, cardiac hypertrophy and fibrosis were induced in C57BL/6 J mice via angiotensin II (Ang II), while in vitro H9c2 cardiomyoblasts and neonatal rat cardiac fibroblasts (NRCFs) were treated with Ang II or TGF-β1, respectively, with or without OT. We found that OT suppressed cardiac hypertrophy and fibrosis, increased ATP and glucose levels, reduced lactate accumulation, suppressed glycolysis, and enhanced glucose oxidation in cardiomyocytes. Mechanistically, OT upregulated its receptor and inhibited Pyruvate Kinase M2 (PKM2) in TGF-β1-stimulated NRCFs. In hypertrophic cardiomyocytes induced by Ang II, transcription factor STAT3 was activated and eNOS was downregulated, while OT suppressed STAT3 activation and nuclear translocation of p-STAT3, and enhanced the expression of eNOS. Either STAT3 overexpression or Nos3 downregulation attenuated OT's beneficial and metabolic effects. Additionally, we demonstrated that the transcription factor STAT3 is enriched at and interacts with the Nos3 promoter region. Overexpression of eNOS partially restored OT-associated protective effects that were attenuated by STAT3 overexpression. Collectively, these findings suggest that OT attenuates cardiac remodeling, at least in part, in association with modulation of glucose metabolism and the STAT3/eNOS pathway, providing mechanistic insight into its cardioprotective effects.