PRKAA1 and pulmonary arterial hypertension: However, in PAH, AMPK activity and expression can be either inhibited or promoted depending on cell type and branch pulmonary artery diameter (Ibe et al., 2013; Omura et al., 2016; Zhang et al., 2018), which is discussed in section “Clinical Trials of Pulmonary Hypertension Treatment Using Metformin.”