NNMT and pulmonary arterial hypertension: NNMT activity in the liver increased progressively over the progression of MCT-induced PAH (48.10 ± 4.095 and 56.48 ± 2.183 vs 40.26 ± 2.212 μmol MNA/min/mg of wet liver tissue at 2 weeks and 4 weeks for post-MCT and Control groups, respectively; Fig. 3c).