Excess Protein O-GlcNAcylation Links Metabolic Derangements to Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

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.

Sex Differences in Right Ventricular Dysfunction: Insights From the Bench to Bedside

“…Future studies that continue to investigate the direct effects of sex hormones on the RV and dissect the mechanisms leading to the sex differences in RV function in PH and ARVC/D will hopefully identify novel therapeutic targets for these devastating diseases. In addition to sex hormones, there are additional compounds that exhibit RV-enhancing activity in preclinical studies (Prisco et al, 2020 ). Because of the important biological discrepancies in RV function based on sex, we will need to consider how biological sex may modulate drug efficacy when translating these molecules to humans.…”

“…Furthermore, aldosterone antagonists do not seem to directly enhance RV function in preclinical studies (Boehm et al, 2018 ). The inability to translate therapies for LV failure to the dysfunctional RV may be due to developmental, anatomical, and functional differences between the RV and LV, which are reviewed elsewhere (Prisco et al, 2020 ). Consequently, further research is needed to define novel pathways that can be exploited to combat RV dysfunction to improve outcomes in PH and ARVC/D patients.…”

Oxygen sensing, mitochondrial biology and experimental therapeutics for pulmonary hypertension and cancer

“…The elevated glucose flux required to support energy homeostasis in a state of uncoupled glycolysis is also pathologic. Increased glucose levels in the PAH RV contribute to RV dysfunction by a form of posttranslational modification of proteins called O-GlcNAcylation [156]. Increased O-GlcNAcylation of mitochondrial proteins in MCT RVs leads to mitochondrial dysfunction and RVF in MCT-PAH and this glucose-related dysfunction can be reversed by colchicine [156].…”

Proteomic analysis of pulmonary arterial hypertension

“…These authors further investigated quantitative mitochondrial proteomics in the lungs of AA-induced PH rats, detecting significant changes in 28 proteins with severe impairment in fatty acid pathways, the TCA cycle, the electron transport chain and amino acid metabolism. Using TMT-labeled quantitative proteomics analysis of MCT-induced rat models, Prisco et al 43 demonstrated that increased glucose flux through the hexosamine biosynthetic pathway (HBP) adversely affected the RV by promoting excess O-GlcNAcylation of mitochondrial proteins. Using an iTRAQ-based LC-MS approach, Hołda et al 44 investigated the RV myocardial proteomic profile of rats with MCT-induced PAH at different stages.…”