FOXO1 and pulmonary arterial hypertension: In the well-established Sugen 5416/hypoxia rat model of PAH (SU/Hx-PH), a clinically relevant rodent model, we found a decreased endurance in association with increased skeletal muscle FoxO1 levels, an increased proportion of fast glycolytic (Type II) fibers to slow oxidative (Type I) fibers, and the formation of sarcomeric aggregates in some muscles.