Knorst, Marli Maria

Introduction: Pulmonary arterial hypertension (PAH) is a fatal disease and vasodilators are the mainstay for its therapy. However, they offer restricted advancement opportunities for the control and treatment of PAH. Thus, the PAH field needs a paradigm-shifting strategy for its successful management and control. Objective: To test the hypothesis that gut microbial dysbiosis and its increased permeability are associated with PAH. Methods: Healthy control subjects and patients with PAH were recruited from two hospitals in the Americas to ascertain the wider applicability of our hypothesis. Fecal samples of PAH patients (n=19) and control, reference subjects (n=16) were obtained at the Hospital de Clinicas de Porto Alegre, Brazil, for microbiota analysis. Plasma/serum samples were collected from PAH patients (n=22) and control, reference subjects (n=19) at the Mayo Clinic, Jacksonville, Florida, USA, for analysis of gut leakiness and inflammatory biomarkers. Results: In PAH patients, a significant decrease in abundance, diversity and evenness of gut microbial population was observed as measured by 16S ribosomal DNA analyses of fecal samples. Analysis of fecal bacteria populations also demonstrated significant increases in gram-positive, facultative-anaerobic genera, such as Actinomyces, Bifidobacterium Slackia, and Streptococcus in PAH patients. Further, plasma zonulin and iFABP, the biomarkers for gut leakiness increased by 40.3% (p=0.0018) and 81% (p=0.0012), respectively in PAH patients. High plasma LPS, HMGB1, and TIMP1 levels are involved in increased gut inflammation and gut mucosal injury. We also observed LPS, HMGB1, and TIMP1 levels were increased by 363% (p=0.0096), 20.5% (p=0.0027), and 213% (p<0.0001), respectively in PAH patients. Conclusions: PAH patients demonstrate profound gut microbial dysbiosis and increased permeability and inflammation. Further characterization of PAH specific microbial species holds novel management potential with the use of pre- and probiotics, designer antibiotics, appropriate fecal/bacterial transplantation, on top of background proven therapies.

Objectives: Pulmonary arterial hypertension (PAH) is a deadly disease without any effective cure. Identification of the PAH-associated gut microbiome may shift conceptual paradigms of the disease that could lead to new therapeutic advancement. We tested the hypothesis that PAH patients have distinct gut microbiome composition contributing to PAH that predicts the disease. Methods: A total of 71 participants were recruited. Fecal microbiomes of 18 type 1 PAH patients (mean pulmonary arterial pressure [mPAP] 57.4±16.7 mmHg) and 13 reference subjects were compared by shotgun metagenomics methods. Plasma from 22 PAH patients (mPAP 48.3± 18.4 mmHg) and 18 reference subjects was used in untargeted metabolomic analysis. Results: Significant taxonomic and functional changes in the microbiome of the PAH cohort were observed. PAH patients had increased gut barrier dysfunction and inflammation as evidenced by plasma markers and metagenomics. A random forest model predicted PAH from gut microbiome composition with 82.6% accuracy. Changes in the gut microbiome were associated with purine metabolism, arginine biosynthesis, trimethylamine production and tryptophan biosynthesis, all previously associated with PAH. Area under the curve of the multi-variate receiver operating characteristics (ROC) plot for metabolites of these pathways had a predictive accuracy of 0.965. Conclusions: The gut microbiome/metabolites of PAH patients predict disease in random forest models and ROC analyses. The unique PAH gut microbiome influences carnitine, arginine and purine metabolisms contributing to pathophysiology. These highlight previously unknown roles of gut bacteria and their metabolites in PAH that could lead to new therapeutic or management paradigms.