Carrier Proteins/metabolism; Hypertension, Pulmonary/etiology; Hypoxia/complications; Intercellular Signaling Peptides and Proteins/metabolism; Pulmonary Artery/metabolism; Receptors, G-Protein-Coupled/metabolism; Signal Transduction; AMP-Activated Protein Kinases/metabolism; Adipokines; Adult; Animals; Apelin; Apelin Receptors; Carrier Proteins/genetics; Case-Control Studies; Cells, Cultured; Disease Models, Animal; Female; Humans; Hypertension, Pulmonary/diagnostic imaging; Hypertension, Pulmonary/genetics; Hypertension, Pulmonary/metabolism; Hypertension, Pulmonary/physiopathology; Hypoxia/genetics; Hypoxia/metabolism; Intercellular Signaling Peptides and Proteins/genetics; Kruppel-Like Transcription Factors/metabolism; Male; Mice; Mice, 129 Strain; Mice, Knockout; Middle Aged; Nitric Oxide/metabolism; Nitric Oxide Synthase Type III/metabolism; Phosphorylation; Pulmonary Artery/diagnostic imaging; Pulmonary Artery/physiopathology; Receptors, G-Protein-Coupled/blood; Severity of Illness Index; X-Ray Microtomography