Background: Trimethylamine‐N‐oxide ( TMAO ), a diet‐derived, gut microbial–host cometabolite, has been associated with adverse cardiovascular outcomes in patient populations; however, evidence is lacking from prospective studies conducted in general populations and non‐Western populations. Methods and Results: We evaluated urinary levels of TMAO and its precursor metabolites (ie, choline, betaine, and carnitine) in relation to risk of coronary heart disease ( CHD ) among Chinese adults in a nested case–control study, including 275 participants with incident CHD and 275 individually matched controls. We found that urinary TMAO , but not its precursors, was associated with risk of CHD . The odds ratio for the highest versus lowest quartiles of TMAO was 1.91 (95% CI, 1.08–3.35; P _trend =0.008) after adjusting for CHD risk factors including obesity, diet, lifestyle, and metabolic diseases and 1.75 (95% CI, 0.96–3.18; P _trend =0.03) after further adjusting for potential confounders or mediators including central obesity, dyslipidemia, inflammation, and intake of seafood and deep‐fried meat or fish, which were associated with TMAO level in this study. The odds ratio per standard deviation increase in log‐ TMAO was 1.30 (95% CI, 1.03–1.63) in the fully adjusted model. A history of diabetes mellitus modified the TMAO – CHD association. A high TMAO level (greater than or equal to versus lower than the median) was associated with odds ratios of 6.21 (95% CI, 1.64–23.6) and 1.56 (95% CI, 1.00–2.43), respectively, among diabetic and nondiabetic participants ( P _interaction =0.02). Diabetes mellitus status also modified the associations of choline, betaine, and carnitine with risk of CHD ; significant positive associations were found among diabetic participants, but null associations were noted among total and nondiabetic participants. Conclusions: Our study suggests that TMAO may accelerate the development of CHD , highlighting the importance of diet–gut microbiota–host interplay in cardiometabolic health.

Acinetobacter baumannii is a leading cause of ventilator-associated pneumonia and a critical threat due to multidrug resistance. The A. baumannii outer membrane is an asymmetric lipid bilayer composed of inner leaflet glycerophospholipids and outer leaflet lipooligosaccharides. Deleting mlaF of the maintenance of lipid asymmetry (Mla) system causes A. baumannii to become more susceptible to pulmonary surfactants and antibiotics and decreases bacterial survival in the lungs of mice. Spontaneous suppressor mutants isolated from infected mice contain an ISAba11 insertion upstream of the ispB initiation codon, an essential isoprenoid biosynthesis gene. The insertion restores antimicrobial resistance and virulence to ΔmlaF. The suppressor strain increases lipooligosaccharides, suggesting that the mechanism involves balancing the glycerophospholipids/lipooligosaccharides ratio on the bacterial surface. An identical insertion exists in an extensively drug-resistant A. baumannii isolate, demonstrating its clinical relevance. These data show that the stresses bacteria encounter during infection select for genomic rearrangements that increase resistance to antimicrobials.

The reverse transsulfuration pathway is the major route for the metabolism of sulfur-containing amino acids. The role of this metabolic pathway in macrophage response and function is unknown. We show that the enzyme cystathionine γ-lyase (CTH) is induced in macrophages infected with pathogenic bacteria through signaling involving phosphatidylinositol 3-kinase (PI3K)/MTOR and the transcription factor SP1. This results in the synthesis of cystathionine, which facilitates the survival of pathogens within myeloid cells. Our data demonstrate that the expression of CTH leads to defective macrophage activation by (i) dysregulation of polyamine metabolism by depletion of S-adenosylmethionine, resulting in immunosuppressive putrescine accumulation and inhibition of spermidine and spermine synthesis, and (ii) increased histone H3K9, H3K27, and H3K36 di/trimethylation, which is associated with gene expression silencing. Thus, CTH is a pivotal enzyme of the innate immune response that disrupts host defense. The induction of the reverse transsulfuration pathway by bacterial pathogens can be considered an unrecognized mechanism for immune escape. IMPORTANCE Macrophages are professional immune cells that ingest and kill microbes. In this study, we show that different pathogenic bacteria induce the expression of cystathionine γ-lyase (CTH) in macrophages. This enzyme is involved in a metabolic pathway called the reverse transsulfuration pathway, which leads to the production of numerous metabolites, including cystathionine. Phagocytized bacteria use cystathionine to better survive in macrophages. In addition, the induction of CTH results in dysregulation of the metabolism of polyamines, which in turn dampens the proinflammatory response of macrophages. In conclusion, pathogenic bacteria can evade the host immune response by inducing CTH in macrophages.