A terminal metabolite of niacin promotes vascular inflammation and contributes to cardiovascular disease risk.

Despite intensive preventive cardiovascular disease (CVD) efforts, substantial residual CVD risk remains even for individuals receiving all guideline-recommended interventions. Niacin is an essential micronutrient fortified in food staples, but its role in CVD is not well understood. In this study, untargeted metabolomics analysis of fasting plasma from stable cardiac patients in a prospective discovery cohort (n = 1,162 total, n = 422 females) suggested that niacin metabolism was associated with incident major adverse cardiovascular events (MACE). Serum levels of the terminal metabolites of excess niacin, N1-methyl-2-pyridone-5-carboxamide (2PY) and N1-methyl-4-pyridone-3-carboxamide (4PY), were associated with increased 3-year MACE risk in two validation cohorts (US n = 2,331 total, n = 774 females; European n = 832 total, n = 249 females) (adjusted hazard ratio (HR) (95% confidence interval) for 2PY: 1.64 (1.10-2.42) and 2.02 (1.29-3.18), respectively; for 4PY: 1.89 (1.26-2.84) and 1.99 (1.26-3.14), respectively). Phenome-wide association analysis of the genetic variant rs10496731, which was significantly associated with both 2PY and 4PY levels, revealed an association of this variant with levels of soluble vascular adhesion molecule 1 (sVCAM-1). Further meta-analysis confirmed association of rs10496731 with sVCAM-1 (n = 106,000 total, n = 53,075 females, P = 3.6 × 10-18). Moreover, sVCAM-1 levels were significantly correlated with both 2PY and 4PY in a validation cohort (n = 974 total, n = 333 females) (2PY: rho = 0.13, P = 7.7 × 10-5; 4PY: rho = 0.18, P = 1.1 × 10-8). Lastly, treatment with physiological levels of 4PY, but not its structural isomer 2PY, induced expression of VCAM-1 and leukocyte adherence to vascular endothelium in mice. Collectively, these results indicate that the terminal breakdown products of excess niacin, 2PY and 4PY, are both associated with residual CVD risk. They also suggest an inflammation-dependent mechanism underlying the clinical association between 4PY and MACE.

Assembling the anaerobic gamma-butyrobetaine to TMA metabolic pathway in Escherichia fergusonii and confirming its role in TMA production from dietary L-carnitine in murine models.

IMPORTANCE: The key atherosclerotic TMAO originates from the initial gut microbial conversion of L-carnitine and other dietary compounds into TMA. Developing therapeutic strategies to block gut microbial TMA production needs a detailed understanding of the different production mechanisms and their relative contributions. Recently, we identified a two-step anaerobic pathway for TMA production from L-carnitine through initial conversion by some microbes into the intermediate γBB which is then metabolized by other microbes into TMA. Investigational studies of this pathway, however, are limited by the lack of single microbes harboring the whole pathway. Here, we engineered E. fergusonii strain to harbor the whole two-step pathway and optimized the expression through cloning a specific chaperone from the original host. Inoculating germ-free mice with this recombinant E. fergusonii is enough to raise serum TMAO to pathophysiological levels upon L-carnitine feeding. This engineered microbe will facilitate future studies investigating the contribution of this pathway to cardiovascular disease.

Trimethylamine N-oxide is associated with long-term mortality risk: the multi-ethnic study of atherosclerosis.

AIMS: Little is known about associations of trimethylamine N-oxide (TMAO), a novel gut microbiota-generated metabolite of dietary phosphatidylcholine and carnitine, and its changes over time with all-cause and cause-specific mortality in the general population or in different race/ethnicity groups. The study aimed to investigate associations of serially measured plasma TMAO levels and changes in TMAO over time with all-cause and cause-specific mortality in a multi-ethnic community-based cohort. METHODS AND RESULTS: The study included 6,785 adults from the Multi-Ethnic Study of Atherosclerosis. TMAO was measured at baseline and year 5 using mass spectrometry. Primary outcomes were adjudicated all-cause mortality and cardiovascular disease (CVD) mortality. Secondary outcomes were deaths due to kidney failure, cancer, or dementia obtained from death certificates. Cox proportional hazards models with time-varying TMAO and covariates assessed the associations with adjustment for sociodemographics, lifestyles, diet, metabolic factors, and comorbidities. During a median follow-up of 16.9 years, 1704 participants died and 411 from CVD. Higher TMAO levels associated with higher risk of all-cause mortality [hazard ratio (HR): 1.12, 95% confidence interval (CI): 1.08-1.17], CVD mortality (HR: 1.09, 95% CI: 1.00-1.09), and death due to kidney failure (HR: 1.44, 95% CI: 1.25-1.66) per inter-quintile range, but not deaths due to cancer or dementia. Annualized changes in TMAO levels associated with higher risk of all-cause mortality (HR: 1.10, 95% CI: 1.05-1.14) and death due to kidney failure (HR: 1.54, 95% CI: 1.26-1.89) but not other deaths. CONCLUSION: Plasma TMAO levels were positively associated with mortality, especially deaths due to cardiovascular and renal disease, in a multi-ethnic US cohort.

Two distinct gut microbial pathways contribute to meta-organismal production of phenylacetylglutamine with links to cardiovascular disease.

Recent studies show gut microbiota-dependent metabolism of dietary phenylalanine into phenylacetic acid (PAA) is critical in phenylacetylglutamine (PAGln) production, a metabolite linked to atherosclerotic cardiovascular disease (ASCVD). Accordingly, microbial enzymes involved in this transformation are of interest. Using genetic manipulation in selected microbes and monocolonization experiments in gnotobiotic mice, we identify two distinct gut microbial pathways for PAA formation; one is catalyzed by phenylpyruvate:ferredoxin oxidoreductase (PPFOR) and the other by phenylpyruvate decarboxylase (PPDC). PPFOR and PPDC play key roles in gut bacterial PAA production via oxidative and non-oxidative phenylpyruvate decarboxylation, respectively. Metagenomic analyses revealed a significantly higher abundance of both pathways in gut microbiomes of ASCVD patients compared with controls. The present studies show a role for these two divergent microbial catalytic strategies in the meta-organismal production of PAGln. Given the numerous links between PAGln and ASCVD, these findings will assist future efforts to therapeutically target PAGln formation in vivo.

Gut Microbiota-Generated Phenylacetylglutamine and Heart Failure.

BACKGROUND: The gut microbiota-dependent metabolite phenylacetylgutamine (PAGln) is both associated with atherothrombotic heart disease in humans, and mechanistically linked to cardiovascular disease pathogenesis in animal models via modulation of adrenergic receptor signaling. METHODS: Here we examined both clinical and mechanistic relationships between PAGln and heart failure (HF). First, we examined associations among plasma levels of PAGln and HF, left ventricular ejection fraction, and N-terminal pro-B-type natriuretic peptide in 2 independent clinical cohorts of subjects undergoing coronary angiography in tertiary referral centers (an initial discovery US Cohort, n=3256; and a validation European Cohort, n=829). Then, the impact of PAGln on cardiovascular phenotypes relevant to HF in cultured cardiomyoblasts, and in vivo were also examined. RESULTS: Circulating PAGln levels were dose-dependently associated with HF presence and indices of severity (reduced ventricular ejection fraction, elevated N-terminal pro-B-type natriuretic peptide) independent of traditional risk factors and renal function in both cohorts. Beyond these clinical associations, mechanistic studies showed both PAGln and its murine counterpart, phenylacetylglycine, directly fostered HF-relevant phenotypes, including decreased cardiomyocyte sarcomere contraction, and B-type natriuretic peptide gene expression in both cultured cardiomyoblasts and murine atrial tissue. CONCLUSIONS: The present study reveals the gut microbial metabolite PAGln is clinically and mechanistically linked to HF presence and severity. Modulating the gut microbiome, in general, and PAGln production, in particular, may represent a potential therapeutic target for modulating HF. REGISTRATION: URL: https://clinicaltrials.gov/; Unique identifier: NCT00590200 and URL: https://drks.de/drks_web/; Unique identifier: DRKS00020915.

Dietary Meat, Trimethylamine N-Oxide-Related Metabolites, and Incident Cardiovascular Disease Among Older Adults: The Cardiovascular Health Study.

BACKGROUND: Effects of animal source foods (ASF) on atherosclerotic cardiovascular disease (ASCVD) and underlying mechanisms remain controversial. We investigated prospective associations of different ASF with incident ASCVD and potential mediation by gut microbiota-generated trimethylamine N-oxide, its L-carnitine-derived intermediates γ-butyrobetaine and crotonobetaine, and traditional ASCVD risk pathways. METHODS: Among 3931 participants from a community-based US cohort aged 65+ years, ASF intakes and trimethylamine N-oxide-related metabolites were measured serially over time. Incident ASCVD (myocardial infarction, fatal coronary heart disease, stroke, other atherosclerotic death) was adjudicated over 12.5 years median follow-up. Cox proportional hazards models with time-varying exposures and covariates examined ASF-ASCVD associations; and additive hazard models, mediation proportions by different risk pathways. RESULTS: After multivariable-adjustment, higher intakes of unprocessed red meat, total meat, and total ASF associated with higher ASCVD risk, with hazard ratios (95% CI) per interquintile range of 1.15 (1.01-1.30), 1.22 (1.07-1.39), and 1.18 (1.03-1.34), respectively. Trimethylamine N-oxide-related metabolites together significantly mediated these associations, with mediation proportions (95% CI) of 10.6% (1.0-114.5), 7.8% (1.0-32.7), and 9.2% (2.2-44.5), respectively. Processed meat intake associated with a nonsignificant trend toward higher ASCVD (1.11 [0.98-1.25]); intakes of fish, poultry, and eggs were not significantly associated. Among other risk pathways, blood glucose, insulin, and C-reactive protein, but not blood pressure or blood cholesterol, each significantly mediated the total meat-ASCVD association. CONCLUSIONS: In this large, community-based cohort, higher meat intake associated with incident ASCVD, partly mediated by microbiota-derived metabolites of L-carnitine, abundant in red meat. These novel findings support biochemical links between dietary meat, gut microbiome pathways, and ASCVD.

Association of Trimethylamine N-Oxide and Metabolites With Mortality in Older Adults.

Importance: Little is known about the association of trimethylamine N-oxide (TMAO), a novel plasma metabolite derived from L-carnitine and phosphatidylcholine, and related metabolites (ie, choline, betaine, carnitine, and butyrobetaine) with risk of death among older adults in the general population. Objective: To investigate the associations of serial measures of plasma TMAO and related metabolites with risk of total and cause-specific death (ie, deaths from cardiovascular diseases [CVDs] and non-CVDs) among older adults in the US. Design, Setting, and Participants: This prospective cohort study involved 5333 participants from the Cardiovascular Health Study-a community-based longitudinal cohort of adults aged 65 years or older-who were followed up from June 1, 1989, to December 31, 2015. Participants were from 4 communities in the US (Forsyth County, North Carolina; Sacramento County, California; Washington County, Maryland; and Allegheny County, Pennsylvania). Data were analyzed from March 17 to June 23, 2021. Exposures: Plasma TMAO, choline, betaine, carnitine, and butyrobetaine levels were measured using stored samples from baseline (June 1, 1989, to May 31, 1990, or November 1, 1992, to June 31, 1993) and follow-up examination (June 1, 1996, to May 31, 1997). Measurements were performed through stable-isotope dilution liquid chromatography with tandem mass spectrometry using high-performance liquid chromatography with online electrospray ionization tandem mass spectrometry. Main Outcomes and Measures: Deaths (total and cause specific) were adjudicated by a centralized Cardiovascular Health Study events committee based on information from medical records, laboratory and diagnostic reports, death certificates, and/or interviews with next of kin. The associations of each metabolite with mortality were assessed using Cox proportional hazards regression models. Results: Among 5333 participants in the analytic sample, the mean (SD) age was 73 (6) years; 2149 participants (40.3%) were male, 3184 (59.7%) were female, 848 (15.9%) were African American, 4450 (83.4%) were White, and 35 (0.01%) were of other races (12 were American Indian or Alaska Native, 4 were Asian or Pacific Islander, and 19 were of other races or ethnicities). During a median follow-up of 13.2 years (range, 0-26.9 years), 4791 deaths occurred. After adjustment for potential confounders, the hazard ratios for death from any cause (ie, total mortality) comparing extreme quintiles (fifth vs first) of plasma concentrations were 1.30 (95% CI, 1.17-1.44) for TMAO, 1.19 (95% CI, 1.08-1.32) for choline, 1.26 (95% CI, 1.15-1.40) for carnitine, and 1.26 (95% CI, 1.13-1.40) for butyrobetaine. Plasma betaine was not associated with risk of death. The extent of risk estimates was similar for CVD and non-CVD mortality. Conclusions and Relevance: In this cohort study, plasma concentrations of TMAO and related metabolites were positively associated with risk of death. These findings suggest that circulating TMAO is an important novel risk factor associated with death among older adults.

The pattern of apolipoprotein A-I lysine carbamylation reflects its lipidation state and the chemical environment within human atherosclerotic aorta.

Protein lysine carbamylation is an irreversible post-translational modification resulting in generation of homocitrulline (N-ε-carbamyllysine), which no longer possesses a charged ε-amino moiety. Two distinct pathways can promote protein carbamylation. One results from urea decomposition, forming an equilibrium mixture of cyanate (CNO-) and the reactive electrophile isocyanate. The second pathway involves myeloperoxidase (MPO)-catalyzed oxidation of thiocyanate (SCN-), yielding CNO- and isocyanate. Apolipoprotein A-I (apoA-I), the major protein constituent of high-density lipoprotein (HDL), is a known target for MPO-catalyzed modification in vivo, converting the cardioprotective lipoprotein into a proatherogenic and proapoptotic one. We hypothesized that monitoring site-specific carbamylation patterns of apoA-I recovered from human atherosclerotic aorta could provide insights into the chemical environment within the artery wall. To test this, we first mapped carbamyllysine obtained from in vitro carbamylation of apoA-I by both the urea-driven (nonenzymatic) and inflammatory-driven (enzymatic) pathways in lipid-poor and lipidated apoA-I (reconstituted HDL). Our results suggest that lysine residues within proximity of the known MPO-binding sites on HDL are preferentially targeted by the enzymatic (MPO) carbamylation pathway, whereas the nonenzymatic pathway leads to nearly uniform distribution of carbamylated lysine residues along the apoA-I polypeptide chain. Quantitative proteomic analyses of apoA-I from human aortic atheroma identified 16 of the 21 lysine residues as carbamylated and suggested that the majority of apoA-I carbamylation in vivo occurs on "lipid-poor" apoA-I forms via the nonenzymatic CNO- pathway. Monitoring patterns of apoA-I carbamylation recovered from arterial tissues can provide insights into both apoA-I structure and the chemical environment within human atheroma.

Vascular endothelial tissue factor contributes to trimethylamine N-oxide-enhanced arterial thrombosis.

AIMS: Gut microbiota and their generated metabolites impact the host vascular phenotype. The metaorganismal metabolite trimethylamine N-oxide (TMAO) is both associated with adverse clinical thromboembolic events, and enhances platelet responsiveness in subjects. The impact of TMAO on vascular Tissue Factor (TF) in vivo is unknown. Here, we explore whether TMAO-enhanced thrombosis potential extends beyond TMAO effects on platelets, and is linked to TF. We also further explore the links between gut microbiota and vascular endothelial TF expression in vivo. METHODS AND RESULTS: In initial exploratory clinical studies, we observed that among sequential stable subjects (n = 2989) on anti-platelet therapy undergoing elective diagnostic cardiovascular evaluation at a single-site referral centre, TMAO levels were associated with an increased incident (3 years) risk for major adverse cardiovascular events (MACE) (myocardial infarction, stroke, or death) [4th quartile (Q4) vs. Q1 adjusted hazard ratio (HR) 95% confidence interval (95% CI), 1.73 (1.25-2.38)]. Similar results were observed within subjects on aspirin mono-therapy during follow-up [adjusted HR (95% CI) 1.75 (1.25-2.44), n = 2793]. Leveraging access to a second higher risk cohort with previously reported TMAO data and monitoring of anti-platelet medication use, we also observed a strong association between TMAO and incident (1 year) MACE risk in the multi-site Swiss Acute Coronary Syndromes Cohort, focusing on the subset (n = 1469) on chronic dual anti-platelet therapy during follow-up [adjusted HR (95% CI) 1.70 (1.08-2.69)]. These collective clinical data suggest that the thrombosis-associated effects of TMAO may be mediated by cells/factors that are not inhibited by anti-platelet therapy. To test this, we first observed in human microvascular endothelial cells that TMAO dose-dependently induced expression of TF and vascular cell adhesion molecule (VCAM)1. In mouse studies, we observed that TMAO-enhanced aortic TF and VCAM1 mRNA and protein expression, which upon immunolocalization studies, was shown to co-localize with vascular endothelial cells. Finally, in arterial injury mouse models, TMAO-dependent enhancement of in vivo TF expression and thrombogenicity were abrogated by either a TF-inhibitory antibody or a mechanism-based microbial choline TMA-lyase inhibitor (fluoromethylcholine). CONCLUSION: Endothelial TF contributes to TMAO-related arterial thrombosis potential, and can be specifically blocked by targeted non-lethal inhibition of gut microbial choline TMA-lyase.

Ten-year changes in plasma L-carnitine levels and risk of coronary heart disease.

PURPOSE: L-Carnitine is abundant in animal source foods, particularly red meat, and circulating L-carnitine may be related to the incidence of coronary heart disease (CHD). We investigated whether long-term changes in plasma L-carnitine over 10 years were associated with the CHD incidence and also examined joint associations of carnitine-rich red meat consumption and L-carnitine changes on the subsequent risk of CHD. METHODS: This prospective nested case-control study included 772 healthy women at baseline (386 incident CHD cases and 386 healthy controls). Plasma L-carnitine levels were measured both at the first (1989-90) and second blood collections (2000-02). Incident cases of CHD were prospectively followed from the date of the second blood collection through 2016. RESULTS: Overall, a greater increase in L-carnitine from the first to the second time point was related to a higher risk of CHD, regardless of the initial L-carnitine levels (relative risk: 1.36 (95% CI 0.999, 1.84) per 1-SD increase). The 10-year changes in L-carnitine were positively associated with red meat consumption over time, and women with higher red meat intake (≥ 36 g/day) and with greater increases in L-carnitine had a 1.86 (95% CI 1.13, 3.09) times increased risk of CHD, as compared to those with lower red meat intake and lesser increases in L-carnitine. CONCLUSION: Long-term increases in L-carnitine levels were associated with the subsequent incidence of CHD, especially among women with higher intake of red meat. Our results suggest the importance of atherogenic L-carnitine changes and dietary intakes over time in the prevention of CHD.

The microbial gbu gene cluster links cardiovascular disease risk associated with red meat consumption to microbiota L-carnitine catabolism.

The heightened cardiovascular disease (CVD) risk observed among omnivores is thought to be linked, in part, to gut microbiota-dependent generation of trimethylamine-N-oxide (TMAO) from L-carnitine, a nutrient abundant in red meat. Gut microbial transformation of L-carnitine into trimethylamine (TMA), the precursor of TMAO, occurs via the intermediate γ-butyrobetaine (γBB). However, the interrelationship of γBB, red meat ingestion and CVD risks, as well as the gut microbial genes responsible for the transformation of γBB to TMA, are unclear. In the present study, we show that plasma γBB levels in individuals from a clinical cohort (n = 2,918) are strongly associated with incident CVD event risks. Culture of human faecal samples and microbial transplantation studies in gnotobiotic mice with defined synthetic communities showed that the introduction of Emergencia timonensis, a human gut microbe that can metabolize γBB into TMA, is sufficient to complete the carnitine → γBB → TMA transformation, elevate TMAO levels and enhance thrombosis potential in recipients after arterial injury. RNA-sequencing analyses of E. timonensis identified a six-gene cluster, herein named the γBB utilization (gbu) gene cluster, which is upregulated in response to γBB. Combinatorial cloning and functional studies identified four genes (gbuA, gbuB, gbuC and gbuE) that are necessary and sufficient to recapitulate the conversion of γBB to TMA when coexpressed in Escherichia coli. Finally, reanalysis of samples (n = 113) from a clinical, randomized diet, intervention study showed that the abundance of faecal gbuA correlates with plasma TMAO and a red meat-rich diet. Our findings reveal a microbial gene cluster that is critical to dietary carnitine → γBB → TMA → TMAO transformation in hosts and contributes to CVD risk.

The Nutritional Supplement L-Alpha Glycerylphosphorylcholine Promotes Atherosclerosis.

L-alpha glycerylphosphorylcholine (GPC), a nutritional supplement, has been demonstrated to improve neurological function. However, a new study suggests that GPC supplementation increases incident stroke risk thus its potential adverse effects warrant further investigation. Here we show that GPC promotes atherosclerosis in hyperlipidemic Apoe-/- mice. GPC can be metabolized to trimethylamine N-oxide, a pro-atherogenic agent, suggesting a potential molecular mechanism underlying the observed atherosclerosis progression. GPC supplementation shifted the gut microbial community structure, characterized by increased abundance of Parabacteroides, Ruminococcus, and Bacteroides and decreased abundance of Akkermansia, Lactobacillus, and Roseburia, as determined by 16S rRNA gene sequencing. These data are consistent with a reduction in fecal and cecal short chain fatty acids in GPC-fed mice. Additionally, we found that GPC supplementation led to an increased relative abundance of choline trimethylamine lyase (cutC)-encoding bacteria via qPCR. Interrogation of host inflammatory signaling showed that GPC supplementation increased expression of the proinflammatory effectors CXCL13 and TIMP-1 and activated NF-κB and MAPK signaling pathways in human coronary artery endothelial cells. Finally, targeted and untargeted metabolomic analysis of murine plasma revealed additional metabolites associated with GPC supplementation and atherosclerosis. In summary, our results show GPC promotes atherosclerosis through multiple mechanisms and that caution should be applied when using GPC as a nutritional supplement.

Changes in gut-microbiota-related metabolites and long-term improvements in lipoprotein subspecies in overweight and obese adults: the POUNDS lost trial.

BACKGROUND/OBJECTIVES: Alterations in gut microbiota have been linked to obesity and impaired lipid metabolism. Lipoproteins are heterogeneous, and lipoprotein subspecies containing apolipoprotein C-III (apoCIII) have adverse associations with obesity and related cardiometabolic abnormalities. We investigated associations of weight-loss diet-induced decreases in atherogenic gut-microbial metabolites, trimethylamine N-oxide (TMAO) and L-carnitine, with improvements in atherogenic lipoproteins containing apoCIII among patients with obesity. SUBJECTS/METHODS: This study included overweight and obese adults who participated in a 2-year weight-loss dietary intervention, the POUNDS Lost trial. Blood levels of TMAO and L-carnitine were measured at baseline and 6 months after the intervention; 6-month changes in the metabolites were calculated. We evaluated 2-year changes in lipid profiles (n = 395) and cholesterol [Chol] in lipoprotein (very-low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL)) subfractions defined by the presence or absence of apoCIII (n = 277). RESULTS: The initial (6-month) decrease in L-carnitine was significantly associated with long-term (2-year) reductions in non-HDL-Chol and LDL-Chol (p < 0.05). Also, the decrease in L-carnitine was significantly related to decreases in Chol in LDL with apoCIII (p = 0.034) and Chol in [LDL + VLDL] with apoCIII (p = 0.018). We found significant interactions between dietary fat and TMAO on changes in LDL-Chol (Pinteraction = 0.013) and Chol in [LDL + VLDL] with apoCIII (Pinteraction = 0.0048); a greater increase in TMAO was related to lesser improvements in the lipoprotein outcomes if participants consumed a high-fat compared to a low-fat diet. CONCLUSIONS: Changes in TMAO and L-carnitine induced by weight-loss diets were associated with long-term improvements in atherogenic lipoproteins containing apoCIII, implicating that these metabolic changes might be predictive of an individual's response to the dietary treatment to modify the unfavorable lipid profiles in obese patients. Dietary fat intake might modify associations of TMAO changes with long-term improvements of atherogenic cholesterol metabolism in overweight and obese adults. CLINICALTRIALS. GOV IDENTIFIER: NCT00072995.

Longitudinal Plasma Measures of Trimethylamine N-Oxide and Risk of Atherosclerotic Cardiovascular Disease Events in Community-Based Older Adults.

Background Trimethylamine N-oxide (TMAO) is a gut microbiota-dependent metabolite of dietary choline, L-carnitine, and phosphatidylcholine-rich foods. On the basis of experimental studies and patients with prevalent disease, elevated plasma TMAO may increase risk of atherosclerotic cardiovascular disease (ASCVD). TMAO is also renally cleared and may interact with and causally contribute to renal dysfunction. Yet, how serial TMAO levels relate to incident and recurrent ASCVD in community-based populations and the potential mediating or modifying role of renal function are not established. Methods and Results We investigated associations of serial measures of plasma TMAO, assessed at baseline and 7 years, with incident and recurrent ASCVD in a community-based cohort of 4131 (incident) and 1449 (recurrent) older US adults. TMAO was measured using stable isotope dilution liquid chromatography-tandem mass spectrometry (laboratory coefficient of variation, <6%). Incident ASCVD (myocardial infarction, fatal coronary heart disease, stroke, sudden cardiac death, or other atherosclerotic death) was centrally adjudicated using medical records. Risk was assessed by multivariable Cox proportional hazards regression, including time-varying demographics, lifestyle factors, medical history, laboratory measures, and dietary habits. Potential mediating effects and interaction by estimated glomerular filtration rate (eGFR) were assessed. During prospective follow-up, 1766 incident and 897 recurrent ASCVD events occurred. After multivariable adjustment, higher levels of TMAO were associated with a higher risk of incident ASCVD, with extreme quintile hazard ratio (HR) compared with the lowest quintile=1.21 (95% CI, 1.02-1.42; P-trend=0.029). This relationship appeared mediated or confounded by eGFR (eGFR-adjusted HR, 1.07; 95% CI, 0.90-1.27), as well as modified by eGFR (P-interaction <0.001). High levels of TMAO were associated with higher incidence of ASCVD in the presence of impaired renal function (eGFR <60 mL/min per 1.73 m2: HR, 1.56 [95% CI, 1.13-2.14]; P-trend=0.007), but not normal or mildly reduced renal function (eGFR ≥60 mL/min per 1.73 m2: HR, 1.03 [95% CI, 0.85-1.25]; P-trend=0.668). Among individuals with prior ASCVD, TMAO associated with higher risk of recurrent ASCVD (HR, 1.25 [95% CI, 1.01-1.56]; P-trend=0.009), without significant modification by eGFR. Conclusions In this large community-based cohort of older US adults, serial measures of TMAO were associated with higher risk of incident ASCVD, with apparent modification by presence of impaired renal function and with higher risk of recurrent ASCVD.

Gut microbes impact stroke severity via the trimethylamine N-oxide pathway.

Clinical studies have demonstrated associations between circulating levels of the gut-microbiota-derived metabolite trimethylamine-N-oxide (TMAO) and stroke incident risk. However, a causal role of gut microbes in stroke has not yet been demonstrated. Herein we show that gut microbes, through dietary choline and TMAO generation, directly impact cerebral infarct size and adverse outcomes following stroke. Fecal microbial transplantation from low- versus high-TMAO-producing human subjects into germ-free mice shows that both TMAO generation and stroke severity are transmissible traits. Furthermore, employing multiple murine stroke models and transplantation of defined microbial communities with genetically engineered human commensals into germ-free mice, we demonstrate that the microbial cutC gene (an enzymatic source of choline-to-TMA transformation) is sufficient to transmit TMA/TMAO production, heighten cerebral infarct size, and lead to functional impairment. We thus reveal that gut microbiota in general, specifically the metaorganismal TMAO pathway, directly contributes to stroke severity.

Abnormal levels of apolipoprotein A-I in chronic thromboembolic pulmonary hypertension.

Recent studies have shown low high-density lipoprotein cholesterol (HDL-C) and dysregulated lipid metabolism in chronic thromboembolic pulmonary hypertension (CTEPH). Apolipoprotein A-I (ApoA-I) is the major protein component of HDL-C and mediates most of its functions. We hypothesize that ApoA-1 and its oxidative state might be more sensitive biomarkers in CTEPH. Plasma levels of HDL-C, ApoA-I, paraoxonase-1 enzyme activity (PON1), and the oxidized dysfunctional ApoA-I (oxTrp72-ApoA-I) were measured in patients with CTEPH and compared to those in healthy controls. Association with markers of disease severity in CTEPH was assessed. We included a total of 61 patients with CTEPH (age: 61.2 ± 15 years; male 52.5%) and 28 control subjects (age: 60.1 ± 8 years; male 59.3%). When adjusting for age, sex, body mass index, and statin use, ApoA-I was lower in CTEPH compared to controls (CTEPH:125.2 ± 27 mg/dl; control:158.3 ± 29.4 mg/dl; p < 0.001), but HDL-C levels were not statistically different. There were no significant differences in PON and oxTrp72-ApoA-I/ApoA-I ratio. In exploratory analyses, ApoA-I was associated with mean right atrial pressure (rs = -0.32, p = 0.013) and N-terminal pro B-type natriuretic peptide (rs = -0.31, p = 0.038). There were no significant associations between HDL-C, PON1, or oxTrp72-ApoA-I/ApoA-I ratio and markers of disease severity. We conclude that ApoA-I is a more sensitive biomarker than HDL-C in CTEPH, and may be associated with right heart dysfunction.

Pulsed-electromagnetic-field induced osteoblast differentiation requires activation of genes downstream of adenosine receptors A2A and A3.

Pulsed-electromagnetic-field (PEMF) treatment was found to enhance cellular differentiation of the mouse preosteoblast, MC3T3-E1, to a more osteoblastic phenotype. Differentiation genes such as Alp, BSPI, cFos, Ibsp, Osteocalcin, Pthr1 and Runx2 showed increased expression in response to PEMF stimulation. Detailed molecular mechanisms linking PEMF to the activation of these genes are limited. Two adenosine receptors known to be modulated in response to PEMF, Adora2A and Adora3, were functionally impaired by CRISPR-Cas9-mediated gene disruption, and the consequences of which were studied in the context of PEMF-mediated osteoblastic differentiation. Disruption of Adora2A resulted in a delay of Alp mRNA expression, but not alkaline phosphatase protein expression, which was similar to that found in wild type cells. However, Adora3 disruption resulted in significantly reduced responses at both the alkaline phosphatase mRNA and protein levels throughout the PEMF stimulation period. Defects observed in response to PEMF were mirrored using a chemically defined growth and differentiation-inducing media (DM). Moreover, in cells with Adora2A disruption, gene expression profiles showed a blunted response in cFos and Pthr1 to PEMF treatment; whereas cells with Adora3 disruption had mostly blunted responses in AlpI, BSPI, Ibsp, Osteocalcin and Sp7 gene activation. To demonstrate specificity for Adora3 function, the Adora3 open reading frame was inserted into the ROSA26 locus in Adora3 disrupted cells culminating in rescued PEMF responsiveness and thereby eliminating the possibility of off-target effects. These results lead us to propose that there are complementary and parallel positive roles for adenosine receptor A2A and A3 in PEMF-mediated osteoblast differentiation.