Sex-dependent transcriptional and imaging responses to metformin in young-adult mice with SuHx-induced pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive cardiopulmonary disease characterised by pulmonary vascular remodelling, right ventricular (RV) pressure overload, and ventricular metabolic reprogramming. Metformin has been proposed as a candidate therapy for PAH on the basis on encouraging preclinical results, most of which have been obtained in rat models and in single-sex cohorts. Its preventive effects in mice and its dependence on biological sex remain incompletely characterised. Based on the Sugen5416/hypoxia (SuHx) model, male and female mice were exposed to normoxia (Ctrl) or Sugen5416/Hypoxia (SuHx) conditions (PAH group) for 21 days, with two parallel groups, Ctrl + Met and PAH + Met, receiving metformin 0.25% w/v (effective dose 410–503 mg/kg/day) ad libitum in drinking water. The endpoints comprised cardiac cine and phase-contrast MRI, invasive RV systolic pressure (RVSP), Fulton index, [ 18 F]-FDG PET, glucose and fatty acid related RT-qPCRs, histology and weekly measured body weight. These experimental data suggested that SuHx reliably induced RV mass gain and elevated RVSP in both sexes. Also, metformin did not attenuate the primary structural or haemodynamic features of the model in either sex. In fact, metformin triggers sex- and ventricle-specific responses detectable at multiple levels: a opposite transcriptional changes in RV's Glut 4 between sexes, together with a coordinated downregulation of left ventricle (LV) fatty acid oxidation transcripts under both SuHx and metformin. Also, the histological analysis performed with WGA revealed that sex-specific cardiomyocyte hypertrophy phenotypes emerge only with metformin. Finally, the MRI determination of RV volumes and ejection fraction along with the pulmonary artery dilatation highlighted this sex-dysmorphism. Collectively, our data argue against a preventive benefit of metformin on the core SuHx-PAH phenotype in either male or female mice. Furthermore, they highlight cardiopulmonary and cellular markers that vary by sex and caution against the assumption that the beneficial effects of metformin in PAH models can be extrapolated without explicit confirmation stratified by sex.