Highlights d Gut microbe formed phenylacetyl glutamine (PAGln) contributes to cardiac disease d Microbial porA and fldH impact host PAGln levels, platelet function, and thrombosis d PAGln transmits cellular responses via the a2A, a2B, and b2 adrenergic receptors d b blocker therapy attenuates PAGln-induced heightened thrombosis risk

Trimethylamine-N-oxide (TMAO), a microbiota-dependent metabolite derived from trimethylamine (TMA)-containing nutrients that are abundant in a Western diet, enhances both platelet responsiveness and in vivo thrombosis potential in animal models and predicts incident atherothrombotic event risks in clinical studies. Here, utilizing a mechanism-based inhibitor approach targeting a major microbial TMA-generating enzyme (CutC/D), we developed potent, time-dependent and irreversible inhibitors that do not affect commensal viability. In animal models, a single oral dose of a CutC/D inhibitor significantly reduced plasma TMAO levels for up to 3 days and rescued diet-induced enhanced platelet responsiveness and thrombus formation, without observable toxicity or increased bleeding risk. The inhibitor selectively accumulated within intestinal microbes to millimolar levels, a concentration over a million-fold higher than needed for a therapeutic effect. These studies reveal that mechanism-based inhibition of gut microbial TMA/TMAO production reduces thrombosis potential, a critical adverse complication in heart disease. They also offer a generalizable approach for the selective non-lethal targeting of gut microbial enzymes linked to host disease, while limiting systemic exposure of the inhibitor in the host.

Using an untargeted metabolomics approach in initial (N = 99 subjects) and replication cohorts (N = 1,162), we discovered and structurally identified a plasma metabolite associated with cardiovascular disease (CVD) risks, N6,N6,N6-trimethyl-L-lysine (trimethyllysine, TML). Stable-isotope-dilution tandem mass spectrometry analyses of an independent validation cohort (N = 2,140) confirmed TML levels are independently associated with incident (3-year) major adverse cardiovascular event risks (hazards ratio [HR], 2.4; 95% CI, 1.7-3.4) and incident (5-year) mortality risk (HR, 2.9; 95% CI, 2.0-4.2). Genome-wide association studies identified several suggestive loci for TML levels, but none reached genome-wide significance; and d9(trimethyl)-TML isotope tracer studies confirmed TML can serve as a nutrient precursor for gut microbiota-dependent generation of trimethylamine (TMA) and the atherogenic metabolite trimethylamine N-oxide (TMAO). Although TML was shown to be abundant in both plant- and animal-derived foods, mouse and human fecal cultures (omnivores and vegans) showed slow conversion of TML to TMA. Furthermore, unlike chronic dietary choline, TML supplementation in mice failed to elevate plasma TMAO or heighten thrombosis potential in vivo. Thus, TML is identified as a strong predictor of incident CVD risks in subjects and to serve as a dietary precursor for gut microbiota-dependent generation of TMAO; however, TML does not appear to be a major microbial source for TMAO generation in vivo.