Visual Abstract

The hexosamine biosynthetic pathway (HBP) converts glucose to uridine-diphosphate-N-acetylglucosamine, which, when added to serines or threonines, modulates protein function through protein O-GlcNAcylation. Glutamine-fructose-6-phosphate amidotransferase (GFAT) regulates HBP flux, and AMP-kinase phosphorylation of GFAT blunts GFAT activity and O-GlcNAcylation. While numerous studies demonstrate increased right ventricle (RV) glucose uptake in pulmonary arterial hypertension (PAH), the relationship between O-GlcNAcylation and RV function in PAH is unexplored. Therefore, we examined how colchicine-mediated AMP-kinase activation altered HBP intermediates, O-GlcNAcylation, mitochondrial function, and RV function in pulmonary artery-banded (PAB) and monocrotaline (MCT) rats. AMPK activation induced GFAT phosphorylation and reduced HBP intermediates and O-GlcNAcylation in MCT but not PAB rats. Reduced O-GlcNAcylation partially restored the RV metabolic signature and improved RV function in MCT rats. Proteomics revealed elevated expression of O-GlcNAcylated mitochondrial proteins in MCT RVs, which fractionation studies corroborated. Seahorse micropolarimetry analysis of H9c2 cardiomyocytes demonstrated colchicine improved mitochondrial function and reduced O-GlcNAcylation. Presence of diabetes in PAH, a condition of excess O-GlcNAcylation, reduced RV contractility when compared to nondiabetics. Furthermore, there was an inverse relationship between RV contractility and HgbA1C. Finally, RV biopsy specimens from PAH patients displayed increased O-GlcNAcylation. Thus, excess O-GlcNAcylation may contribute to metabolic derangements and RV dysfunction in PAH.

Background Intermittent fasting (IF) confers pleiotropic cardiovascular benefits including restructuring of the gut microbiome and augmentation of cellular metabolism. Pulmonary arterial hypertension (PAH) is a rare and lethal disease characterized by right ventricular (RV) mitochondrial dysfunction and resultant lipotoxicity and microbiome dysbiosis. However, the effects of IF on RV function in PAH are unexplored. Therefore, we investigated how IF altered gut microbiota composition, RV function, and survival in the monocrotaline model of PAH. Methods and Results Male Sprague Dawley rats were randomly allocated into 3 groups: control, monocrotaline‐ad libitum feeding, and monocrotaline‐IF (every other day feeding). Echocardiography and invasive hemodynamics showed IF improved RV systolic and diastolic function despite no significant change in PAH severity. IF prevented premature mortality (30% mortality rate in monocrotaline‐ad libitum versus 0% in monocrotaline‐IF rats, P =0.04). IF decreased RV cardiomyocyte hypertrophy and reduced RV fibrosis. IF prevented RV lipid accrual on Oil Red O staining and ceramide accumulation as determined by metabolomics. IF mitigated the reduction in jejunum villi length and goblet cell abundance when compared with monocrotaline‐ad libitum. The 16S ribosomal RNA gene sequencing demonstrated IF changed the gut microbiome. In particular, there was increased abundance of Lactobacillus in monocrotaline‐IF rats. Metabolomics profiling revealed IF decreased RV levels of microbiome metabolites including bile acids, aromatic amino acid metabolites, and gamma‐glutamylated amino acids. Conclusions IF directly enhanced RV function and restructured the gut microbiome. These results suggest IF may be a non‐pharmacological approach to combat RV dysfunction, a currently untreatable and lethal consequence of PAH.