Abstract 13116: Profiling the Role of Gut Microbiota-Derived Trimethylamine- N -Oxide in Cardiac Fibrosis — Evidence From a Primary Human in vitro Model

Introduction: The gut derived trimethylamine- N -oxide (TMAO) is correlated with increased atrial inflammation and fibrosis and associated with atrial fibrillation, heart failure, and stroke. However, the mechanisms mediating these links remain unresolved. Hypothesis: TMAO and its precursor metabolite L-carnitine (LCART) induce the transformation of atrial fibroblasts into pro-fibrotic phenotypes. Aim: To characterise the association between TMAO and cardiac fibrosis. Methods: Primary human cardiac (atrial) fibroblasts (hCFs) were sourced from healthy donors. hCFs were starved for 24 h and treated with PBS (control), 20 ng/mL transforming growth factor beta 1 (TGFβ1), 10 mM TMAO, or 1.0 mM LCART for 72 h (n=6 in each), then analysed by flow cytometry for α-smooth muscle actin (αSMA) expression. Unbiased proteomics was performed using LC-MS/MS to determine protein expression profile. Results: Analysis of αSMA expression revealed 3 hCF states: quiescent (Fbs), quiescent-to-myofibroblast (intermediate [Fbs-myoFbs]), and fully activated myofibroblast (myoFbs), (Fig-A). Compared to controls, there was no difference in the intermediate state after TGFβ1, TMAO, or LCART treatment (p=0.30). TMAO and LCART resulted in a significant induction of myofibroblast states compared to controls and TGFβ1 group. Unbiased proteomics identified 92, 65, and 43 proteins to be overexpressed and 84, 46, and 78 proteins downregulated following TGFβ1, TMAO, and LCART treatments (Fig-B). Both TGFβ1 and TMAO demonstrated shared enrichment for oxidative stress-regulated ferroptosis pathway (fold enrichment [FE] 31.8 and 22.2, p <.01 and 0.03); LCART showed enrichment for cell motility (FE 3.8, p=0.03). Conclusions: TMAO and its precursor L-carnitine are associated with activation of pro-fibrotic states, which may be due to oxidative stress and abnormal cell migration related mechanisms.