High Mobility Group Box 1 Mediates TMAO-Induced Endothelial Dysfunction

Trimethylamine N-Oxide in Aquatic Foods

Trimethylamine N-oxide (TMAO), a characteristic nonprotein nitrogen compound, is widely present in seafood, which exhibits osmoregulatory effects for marine organisms in vivo and plays an important role in aquaculture and aquatic product preservation. However, much attention has been focused on the negative effect of TMAO since it has recently emerged as a putative promoter of chronic diseases. To get full knowledge and maximize our ability to balance the positive and negative aspects of TMAO, in this review, we comprehensively discuss the TMAO in aquatic products from the aspects of physiological functions for marine organisms, flavor, quality, the conversion of precursors, the influences on human health, and the seafood ingredients interaction consideration. Though the circulating TMAO level is inevitably enhanced after seafood consumption, dietary seafood still exhibits beneficial health effects and may provide nutraceuticals to balance the possible adverse effects of TMAO.

Molecular Insights into the Relationship Between Platelet Activation and Endothelial Dysfunction: Molecular Approaches and Clinical Practice

Platelets are one of the coagulation cells. When platelet activation occurs, many mediators are released and affect endothelial cells (ECs) and lead to endothelial dysfunction (ED). ED plays an important role in the pathogenesis of many diseases, including cardiovascular disease (CVD). Platelet are of important factors in ED. The release of mediators by platelets causes the stimulation of inflammatory pathways, oxidative stress, and apoptosis, which ultimately result in ED.On the other hand, platelet activation in CVD patients can be associated with a bad prognosis. Platelet activation can increase the level of markers such as p-selectin in the serum. Also, in this study, we have discussed the role of platelet as a diagnostic factor, as well as its use as a treatment option. In addition, we discussed some of the molecular pathways that are used to target platelet activation.

The Role of Gut Microbiota in the Etiopathogenesis of Multiple Chronic Diseases

Chronic diseases (CD) may result from a combination of genetic factors, lifestyle and social behaviours, healthcare system influences, community factors, and environmental determinants of health. These risk factors frequently coexist and interact with one another. Ongoing research and a focus on personalized interventions are pivotal strategies for preventing and managing chronic disease outcomes. A wealth of literature suggests the potential involvement of gut microbiota in influencing host metabolism, thereby impacting various risk factors associated with chronic diseases. Dysbiosis, the perturbation of the composition and activity of the gut microbiota, is crucial in the etiopathogenesis of multiple CD. Recent studies indicate that specific microorganism-derived metabolites, including trimethylamine N-oxide, lipopolysaccharide and uremic toxins, contribute to subclinical inflammatory processes implicated in CD. Various factors, including diet, lifestyle, and medications, can alter the taxonomic species or abundance of gut microbiota. Researchers are currently dedicating efforts to understanding how the natural progression of microbiome development in humans affects health outcomes. Simultaneously, there is a focus on enhancing the understanding of microbiome-host molecular interactions. These endeavours ultimately aim to devise practical approaches for rehabilitating dysregulated human microbial ecosystems, intending to restore health and prevent diseases. This review investigates how the gut microbiome contributes to CD and explains ways to modulate it for managing or preventing chronic conditions.

Stroke and Vascular Cognitive Impairment: The Role of Intestinal Microbiota Metabolite TMAO

The gut microbiome interacts with the brain bidirectionally through the microbiome-gutbrain axis, which plays a key role in regulating various nervous system pathophysiological processes. Trimethylamine N-oxide (TMAO) is produced by choline metabolism through intestinal microorganisms, which can cross the blood-brain barrier to act on the central nervous system. Previous studies have shown that elevated plasma TMAO concentrations increase the risk of major adverse cardiovascular events, but there are few studies on TMAO in cerebrovascular disease and vascular cognitive impairment. This review summarized a decade of research on the impact of TMAO on stroke and related cognitive impairment, with particular attention to the effects on vascular cognitive disorders. We demonstrated that TMAO has a marked impact on the occurrence, development, and prognosis of stroke by regulating cholesterol metabolism, foam cell formation, platelet hyperresponsiveness and thrombosis, and promoting inflammation and oxidative stress. TMAO can also influence the cognitive impairment caused by Alzheimer's disease and Parkinson's disease via inducing abnormal aggregation of key proteins, affecting inflammation and thrombosis. However, although clinical studies have confirmed the association between the microbiome-gut-brain axis and vascular cognitive impairment (cerebral small vessel disease and post-stroke cognitive impairment), the molecular mechanism of TMAO has not been clarified, and TMAO precursors seem to play the opposite role in the process of poststroke cognitive impairment. In addition, several studies have also reported the possible neuroprotective effects of TMAO. Existing therapies for these diseases targeted to regulate intestinal flora and its metabolites have shown good efficacy. TMAO is probably a new target for early prediction and treatment of stroke and vascular cognitive impairment.

Contribution of membrane raft redox signalling to visfatin-induced inflammasome activation and podocyte injury

Recently we have shown that adipokine visfatin-induced NLRP3 inflammasome activation contributes to podocyte injury. However, the molecular mechanisms of how visfatin-induces the Nlrp3 inflammasome activation and podocyte damage is still unknown. The present study tested whether membrane raft (MR) redox signalling pathway plays a central role in visfatin-induced NLRP3 inflammasomes formation and activation in podocytes. Upon visfatin stimulation an aggregation of NADPH oxidase subunits, gp91phox and p47phox was observed in the membrane raft (MR) clusters, forming a MR redox signalling platform in podocytes. The formation of this signalling platform was blocked by prior treatment with MR disruptor MCD or NADPH oxidase inhibitor DPI. In addition, visfatin stimulation significantly increased the colocalization of Nlrp3 with Asc or Nlrp3 with caspase-1, IL-β production, cell permeability in podocytes compared to control cells. Pretreatment with MCD, DPI, WEHD significantly abolished the visfatin-induced colocalization of NLRP3 with Asc or NLRP3 with caspase-1, IL-1β production and cell permeability in podocytes. Furthermore, Immunofluorescence analysis demonstrated that visfatin treatment significantly decreased the podocin and nephrin expression (podocyte damage) and prior treatments with DPI, WEHD, MCD attenuated this visfatin-induced podocin and nephrin reduction. In conclusion, our results suggest that visfatin stimulates membrane raft clustering in the membrane of podocytes to form redox signaling platforms by aggregation and activation of NADPH oxidase subunits enhancing O2·- production and leading to NLRP3 inflammasome activation in podocytes and ultimate podocyte injury.

Emerging Evidence Linking the Liver to the Cardiovascular System: Liver-derived Secretory Factors

Cardiovascular diseases (CVDs) remain the leading cause of morbidity and mortality worldwide. Recently, accumulating evidence has revealed hepatic mediators, termed as liver-derived secretory factors (LDSFs), play an important role in regulating CVDs such as atherosclerosis, coronary artery disease, thrombosis, myocardial infarction, heart failure, metabolic cardiomyopathy, arterial hypertension, and pulmonary hypertension. LDSFs presented here consisted of microbial metabolite, extracellular vesicles, proteins, and microRNA, they are primarily or exclusively synthesized and released by the liver, and have been shown to exert pleiotropic actions on cardiovascular system. LDSFs mainly target vascular endothelial cell, vascular smooth muscle cells, cardiomyocytes, fibroblasts, macrophages and platelets, and further modulate endothelial nitric oxide synthase/nitric oxide, endothelial function, energy metabolism, inflammation, oxidative stress, and dystrophic calcification. Although some LDSFs are known to be detrimental/beneficial, controversial findings were also reported for many. Therefore, more studies are required to further explore the causal relationships between LDSFs and CVDs and uncover the exact mechanisms, which is expected to extend our understanding of the crosstalk between the liver and cardiovascular system and identify potential therapeutic targets. Furthermore, in the case of patients with liver disease, awareness should be given to the implications of these abnormalities in the cardiovascular system. These studies also underline the importance of early recognition and intervention of liver abnormalities in the practice of cardiovascular care, and a multidisciplinary approach combining hepatologists and cardiologists would be more preferable for such patients.

A study of the correlation between stroke and gut microbiota over the last 20years: a bibliometric analysis

Purpose

This study intends to uncover a more thorough knowledge structure, research hotspots, and future trends in the field by presenting an overview of the relationship between stroke and gut microbiota in the past two decades.

Method

Studies on stroke and gut microbiota correlations published between 1st January 2002 and 31st December 2021 were retrieved from the Web of Science Core Collection and then visualized and scientometrically analyzed using CiteSpace V.

Results

A total of 660 papers were included in the study, among which the United States, the United Kingdom, and Germany were the leading research centers. Cleveland Clinic, Southern Medical University, and Chinese Academy of Science were the top three institutions. The NATURE was the most frequently co-cited journal. STANLEY L HAZEN was the most published author, and Tang WHW was the most cited one. The co-occurrence analysis revealed eight clusters (i.e., brain-gut microbiota axis, fecal microbiome transplantation, gut microbiota, hypertension, TMAO, ischemic stroke, neuroinflammation, atopobiosis). "gut microbiota," "Escherichia coli," "cardiovascular disease," "risk," "disease," "ischemic stroke," "stroke," "metabolism," "inflammation," and "phosphatidylcholine" were the most recent keyword explosions.

Conclusion

Findings suggest that in the next 10 years, the number of publications produced annually may increase significantly. Future research trends tend to concentrate on the mechanisms of stroke and gut microbiota, with the inflammation and immunological mechanisms, TMAO, and fecal transplantation as hotspots. And the relationship between these mechanisms and a particular cardiovascular illness may also be a future research trend.

Gut-Derived Metabolite, Trimethylamine-N-oxide (TMAO) in Cardio-Metabolic Diseases: Detection, Mechanism, and Potential Therapeutics

Trimethylamine N-oxide (TMAO) is a biologically active gut microbiome-derived dietary metabolite. Recent studies have shown that high circulating plasma TMAO levels are closely associated with diseases such as atherosclerosis and hypertension, and metabolic disorders such as diabetes and hyperlipidemia, contributing to endothelial dysfunction. There is a growing interest to understand the mechanisms underlying TMAO-induced endothelial dysfunction in cardio-metabolic diseases. Endothelial dysfunction mediated by TMAO is mainly driven by inflammation and oxidative stress, which includes: (1) activation of foam cells; (2) upregulation of cytokines and adhesion molecules; (3) increased production of reactive oxygen species (ROS); (4) platelet hyperreactivity; and (5) reduced vascular tone. In this review, we summarize the potential roles of TMAO in inducing endothelial dysfunction and the mechanisms leading to the pathogenesis and progression of associated disease conditions. We also discuss the potential therapeutic strategies for the treatment of TMAO-induced endothelial dysfunction in cardio-metabolic diseases.

Gut Molecules in Cardiometabolic Diseases: The Mechanisms behind the Story

Atherosclerotic cardiovascular disease is the most common cause of morbidity and mortality worldwide. Diabetes mellitus increases cardiovascular risk. Heart failure and atrial fibrillation are associated comorbidities that share the main cardiovascular risk factors. The use of incretin-based therapies promoted the idea that activation of alternative signaling pathways is effective in reducing the risk of atherosclerosis and heart failure. Gut-derived molecules, gut hormones, and gut microbiota metabolites showed both positive and detrimental effects in cardiometabolic disorders. Although inflammation plays a key role in cardiometabolic disorders, additional intracellular signaling pathways are involved and could explain the observed effects. Revealing the involved molecular mechanisms could provide novel therapeutic strategies and a better understanding of the relationship between the gut, metabolic syndrome, and cardiovascular diseases.

Lessons from Cardiac and Vascular Biopsies from Patients with and without Inflammatory Rheumatic Diseases

Feiring Heart Biopsy Study enables searching for potential pathogenetic mechanisms, therapeutic targets, and biomarkers through the assessment of clinical data and multiple blood and tissue samples from patients with and without inflammatory rheumatic diseases (IRDs), undergoing coronary artery bypass grafting. Some of our findings, for example, more inflammation (including the presence of immune cells and expression of proinflammatory cytokines) in vessels and the heart, and the presence of certain bacteria and autoantigens in vessels, could contribute to the increased risk of ischemia, aneurysms, and/or cardiac dysfunction in IRDs. Furthermore, some of the detected factors could be involved in the pathomechanisms of these conditions in general.

Gut Microbiota-Derived TMAO: A Causal Factor Promoting Atherosclerotic Cardiovascular Disease?

Trimethylamine-N-oxide (TMAO) is the main diet-induced metabolite produced by the gut microbiota, and it is mainly eliminated through renal excretion. TMAO has been correlated with an increased risk of atherosclerotic cardiovascular disease (ASCVD) and related complications, such as cardiovascular mortality or major adverse cardiovascular events (MACE). Meta-analyses have postulated that high circulating TMAO levels are associated with an increased risk of cardiovascular events and all-cause mortality, but the link between TMAO and CVD remains not fully consistent. The results of prospective studies vary depending on the target population and the outcome studied, and the adjustment for renal function tends to decrease or reverse the significant association between TMAO and the outcome studied, strongly suggesting that the association is substantially mediated by renal function. Importantly, one Mendelian randomization study did not find a significant association between genetically predicted higher TMAO levels and cardiometabolic disease, but another found a positive causal relationship between TMAO levels and systolic blood pressure, which-at least in part-could explain the link with renal function. The mechanisms by which TMAO can increase this risk are not clearly elucidated, but current evidence indicates that TMAO induces cholesterol metabolism alterations, inflammation, endothelial dysfunction, and platelet activation. Overall, there is no fully conclusive evidence that TMAO is a causal factor of ASCVD, and, especially, whether TMAO induces or just is a marker of hypertension and renal dysfunction requires further study.

Aorta- and liver-generated TMAO enhances trained immunity for increased inflammation via ER stress/mitochondrial ROS/glycolysis pathways

We determined whether gut microbiota-produced trimethylamine (TMA) is oxidized into trimethylamine N-oxide (TMAO) in nonliver tissues and whether TMAO promotes inflammation via trained immunity (TI). We found that endoplasmic reticulum (ER) stress genes were coupregulated with MitoCarta genes in chronic kidney diseases (CKD); TMAO upregulated 190 genes in human aortic endothelial cells (HAECs); TMAO synthesis enzyme flavin-containing monooxygenase 3 (FMO3) was expressed in human and mouse aortas; TMAO transdifferentiated HAECs into innate immune cells; TMAO phosphorylated 12 kinases in cytosol via its receptor PERK and CREB, and integrated with PERK pathways; and PERK inhibitors suppressed TMAO-induced ICAM-1. TMAO upregulated 3 mitochondrial genes, downregulated inflammation inhibitor DARS2, and induced mitoROS, and mitoTEMPO inhibited TMAO-induced ICAM-1. β-Glucan priming, followed by TMAO restimulation, upregulated TNF-α by inducing metabolic reprogramming, and glycolysis inhibitor suppressed TMAO-induced ICAM-1. Our results have provided potentially novel insights regarding TMAO roles in inducing EC activation and innate immune transdifferentiation and inducing metabolic reprogramming and TI for enhanced vascular inflammation, and they have provided new therapeutic targets for treating cardiovascular diseases (CVD), CKD-promoted CVD, inflammation, transplantation, aging, and cancer.

The gut microbial metabolite trimethylamine N-oxide and cardiovascular diseases

Morbidity and mortality of cardiovascular diseases (CVDs) are exceedingly high worldwide. Researchers have found that the occurrence and development of CVDs are closely related to intestinal microecology. Imbalances in intestinal microecology caused by changes in the composition of the intestinal microbiota will eventually alter intestinal metabolites, thus transforming the host physiological state from healthy mode to pathological mode. Trimethylamine N-oxide (TMAO) is produced from the metabolism of dietary choline and L-carnitine by intestinal microbiota, and many studies have shown that this important product inhibits cholesterol metabolism, induces platelet aggregation and thrombosis, and promotes atherosclerosis. TMAO is directly or indirectly involved in the pathogenesis of CVDs and is an important risk factor affecting the occurrence and even prognosis of CVDs. This review presents the biological and chemical characteristics of TMAO, and the process of TMAO produced by gut microbiota. In particular, the review focuses on summarizing how the increase of gut microbial metabolite TMAO affects CVDs including atherosclerosis, heart failure, hypertension, arrhythmia, coronary artery disease, and other CVD-related diseases. Understanding the mechanism of how increases in TMAO promotes CVDs will potentially facilitate the identification and development of targeted therapy for CVDs.

Advances in the Bioactivities of Phytochemical Saponins in the Prevention and Treatment of Atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease characterized by hardening and narrowing of arteries. AS leads to a number of arteriosclerotic vascular diseases including cardiovascular diseases, cerebrovascular disease and peripheral artery disease, which pose a big threat to human health. Phytochemicals are a variety of intermediate or terminal low molecular weight secondary metabolites produced during plant energy metabolism. Phytochemicals from plant foods (vegetables, fruits, whole grains) and traditional herb plants have been shown to exhibit multiple bioactivities which are beneficial for prevention and treatment against AS. Many types of phytochemicals including polyphenols, saponins, carotenoids, terpenoids, organic sulfur compounds, phytoestrogens, phytic acids and plant sterols have already been identified, among which saponins are a family of glycosidic compounds consisting of a hydrophobic aglycone (sapogenin) linked to hydrophilic sugar moieties. In recent years, studies have shown that saponins exhibit a number of biological activities such as anti-inflammation, anti-oxidation, cholesterol-lowering, immunomodulation, anti-platelet aggregation, etc., which are helpful in the prevention and treatment of AS. This review aims to summarize the recent advances in the anti-atherosclerotic bioactivities of saponins such as ginsenoside, soyasaponin, astra-galoside, glycyrrhizin, gypenoside, dioscin, saikosaponin, etc.

Positive Association of Plasma Trimethylamine-N-Oxide and Atherosclerosis in Patient with Acute Coronary Syndrome

Aim. Atherosclerosis is the major cause of acute coronary syndrome (ACS) which is a significant contributor to both morbidity and mortality in the world. The microbiome-derived metabolite trimethylamine-N-oxide (TMAO) has aroused great interest and controversy as a risk factor of atherosclerosis. Therefore, in this study, we aimed at investigating whether plasma TMAO can be a risk factor of atherosclerosis in coronary artery of patients with ACS and how this relates to lipids and proinflammatory cytokines in plasma. Methods. We enrolled consecutive patients with ACS who underwent percutaneous coronary intervention (PCI). Gensini scoring was used to evaluate angiographic atherosclerosis in the coronary artery of the patients. 13 patients were divided into low ( $\text{Gensini}\text{score}<25$ ), 33 into intermediate (Gensini score 25-50), and 81 into severe atherosclerosis (Gensini score ≥50). Plasma TMAO, vasculitis factors, and cardiovascular biomarkers were measured by clinical biochemistry, intima-media thickness (IMT) of carotid artery was determined by the Color Doppler ultrasound, and the atherosclerotic lesion in coronary artery was assessed in PCI. Results. Plasma TMAO concentrations were positively associated with Gensini score ( $\text{OR}=0.629$ , $p<0.001$ ) and Gensini subgroup ( $\text{R}=0.604$ , $p<0.0$ 01). Plasma TMAO concentrations in patients with severe coronary atherosclerosis were higher than those of patients with moderate coronary atherosclerosis, and the plasma TMAO concentrations of patients with moderate coronary atherosclerosis were higher than those of patients with mild coronary atherosclerosis, the difference was statistically significant [4.73 (3.13, 4.62) versus 1.13 (0.63, 3.34) versus 0.79 (0.20, 1.29), $p<0.001$ ], respectively. Furthermore, ROC analysis showed that plasma TMAO could identify the severity of atherosclerosis ( $p<0.001$ ). The AUC of TMAO for severe atherosclerosis was 0.852 ( $95\%\text{CI}=0.779-0.925$ ). The sensitivity and specificity of TMAO for identifying severe atherosclerosis are 96.3% and 63.0% when the cut-off value of TMAO was set at 1.2715 pg/ml. Furthermore, logistic regression analysis showed plasma TMAO concentrations were positively associated with severity of atherosclerosis in coronary artery ( $\text{OR}=1.934$ , $95\%\text{CI}=1.522-2.459$ , $p<0.001$ ). For all that, negatively association was observed between TMAO and age ( $\text{OR}=-0.224$ , $p<0.05$ ), B-type natriuretic peptide (BNP) ( $\text{OR}=-0.175$ , $p<0.05$ ), and interleukin-8 (IL-8) ( $\text{OR}=-0.324$ , $p<0.001$ ), while positive association was observed between TMAO and nitric oxide (NO) ( $\text{OR}=0.234$ , $p<0.01$ ). However, there is no obvious association was observed between Gensini score and cardiovascular biomarkers, vasculitis factors, and carotid IMT, respectively. Conclusion. Our cross-sectional observation suggested that plasma TMAO concentrations positively associated with coronary atherosclerosis in ACS patients and serve as a risk factor for severe atherosclerosis. Plasma TMAO also correlated with age, BNP, IL-8, and NO. However, no obvious association was found between atherosclerosis with vasculitis factors and cardiovascular biomarkers in this study, and there was no conclusive evidence showing TMAO enhance atherosclerosis via regulation of inflammation or lipid.

Trimethylamine oxide induces pyroptosis of vascular endothelial cells through ALDH2/ROS/NLRP3/GSDMD pathway

OBJECTIVES

Trimethylamine oxide (TMAO) is a metabolite of intestinal flora and is known to promote the progression of atherosclerotic plaques. However, how TMAO works, including its effect on vascular endothelial cells, is not fully understood. This study aims to explore the biological role of TMAO in human umbilical vein endothelial cells (HUVECs) and the underlying mechanism.

METHODS

Cell pyroptosis and the loss of plasma membrane integrity were induced under TMAO stimulation in HUVECs. The plasma membrane integrity of the cells was measured by Hoechst 33342/propidium iodide (PI) staining and lactate dehydrogenase leakage assay, and the changes in cell morphology were observed by atomic force microscope. The expression of proteins related to pyroptosis was determined by Western blotting or immunofluorescence. Mitochondrial acetaldehyde dehydrogenase 2 (ALDH2) activity in HUVECs was measured by the ALDH2 activity assay kit, and the level of reactive oxygen species (ROS) was detected by fluorescent probe DCFH-DA.

RESULTS

TMAO induced pyroptotic cell death, manifesting by the presence of propidium iodide-positive cells, the leakage of lactate dehydrogenase, the production of N-terminal gasdermin D (GSDMD-N), and the formation of plasma membrane pores. Moreover, TMAO induced elevated expression of inflammasome components, nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC), and caspase-1 in cells. TMAO significantly inhibited ALDH2 activity and increased intracellular ROS production. However, the activation of ALDH2 by pharmacological manipulation attenuated TMAO-induced inflammasome activation and GSDMD-N production.

CONCLUSIONS

TMAO induces pyroptosis of vascular endothelial cells through the ALDH2/ROS/NLRP3/GSDMD signaling pathway, which may be a potential therapeutic target for improving the treatment of atherosclerosis.

Trimethylamine-N-oxide (TMAO) promotes balloon injury-induced neointimal hyperplasia via upregulating Beclin1 and impairing autophagic flux

BACKGROUND AND AIMS

TMAO is a microbiota-dependent metabolite associated with increased risk of various cardiovascular diseases. However, the relationship between TMAO and vascular injury-related neointimal hyperplasia is unclear. This study aimed to explore whether TMAO promotes neointimal hyperplasia after balloon injury and elucidate the underlying mechanism.

METHODS AND RESULTS

Through hematoxylin and eosin staining and immunohistochemistry staining, we found that supplementary TMAO promoted balloon injury-induced neointimal hyperplasia, while reducing TMAO by antibiotic administration produced the opposite result. TMAO showed limited effect on rat aortic vascular smooth muscle cells (RAOSMCs) proliferation and migration. However, TMAO notably induced dysfunction of rat aortic vascular endothelial cells (RAOECs) in vitro and attenuated reendothelialization of carotid arteries after balloon injury in vivo. Autophagic flux was measured by fluorescent mRFP-GFP-LC3, transmission electron microscopy, and western blot. TMAO impaired autophagic flux, as evidenced by the accumulation of p62 and LC3II and high autophagosome to autolysosome ratios. Furthermore, we confirmed that Beclin1 level increased in TMAO-treated RAOECs and carotid arteries. Knocking down Beclin1 alleviated TMAO-induced autophagic flux impairment and neointimal hyperplasia.

CONCLUSIONS

TMAO promoted neointimal hyperplasia through Beclin1-induced autophagic flux blockage, suggesting that TMAO is a potential target for improvement of vascular remodeling after injury.

The Role of Gut and Airway Microbiota in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe clinical condition that is characterized pathologically by perivascular inflammation and pulmonary vascular remodeling that ultimately leads to right heart failure. However, current treatments focus on controlling vasoconstriction and have little effect on pulmonary vascular remodeling. Better therapies of PAH require a better understanding of its pathogenesis. With advances in sequencing technology, researchers have begun to focus on the role of the human microbiota in disease. Recent studies have shown that the gut and airway microbiota and their metabolites play an important role in the pathogenesis of PAH. In this review, we summarize the current literature on the relationship between the gut and airway microbiota and PAH. We further discuss the key crosstalk between the gut microbiota and the lung associated with PAH, and the potential link between the gut and airway microbiota in the pathogenesis of PAH. In addition, we discuss the potential of using the microbiota as a new target for PAH therapy.

Effects of acute administration of trimethylamine N-oxide on endothelial function: a translational study

Elevated circulating levels of nutrient-derived trimethylamine N-oxide (TMAO) have been associated with the onset and progression of cardiovascular disease by promoting athero-thrombosis. However, in conditions like bariatric surgery (Roux-en-Y gastric bypass, RYGB), stable increases of plasma TMAO are associated with improved endothelial function and reduced cardiovascular morbidity and mortality, thus questioning whether a mechanistic relationship between TMAO and endothelial dysfunction exists. Herein, we translationally assessed the effects of acute TMAO exposure on endothelial dysfunction, thrombosis and stroke. After RYGB, fasting circulating levels of TMAO increased in patients and obese rats, in parallel with an improved gluco-lipid profile and higher circulating bile acids. The latter enhanced FXR-dependent signalling in rat livers, which may lead to higher TMAO synthesis post RYGB. In lean rats, acute TMAO injection (7 mg kg^-1) 1.5-h before sacrifice and ex-vivo 30-min incubation of thoracic aortas with 10^-6 M TMAO did not impair vasodilation in response to acetylcholine (Ach), glucagon-like peptide 1, or insulin. Similarly, in lean WT mice (n = 5-6), TMAO injection prior to subjecting mice to ischemic stroke or arterial thrombosis did not increase its severity compared to vehicle treated mice. Endothelial nitric oxide synthase (eNOS) activity and intracellular stress-activated pathways remained unaltered in aorta of TMAO-injected rats, as assessed by Western Blot. Pre-incubation of human aortic endothelial cells with TMAO (10^-6 M) did not alter NO release in response to Ach. Our results indicate that increased plasmatic TMAO in the near-physiological range seems to be a neutral bystander to vascular function as translationally seen in patients after bariatric surgery or in healthy lean rodent models and in endothelial cells exposed acutely to TMAO.

A Novel Trimethylamine Oxide-Induced Model Implicates Gut Microbiota-Related Mechanisms in Frailty

Frailty is a complicated syndrome that occurs at various ages, with highest incidence in aged populations, suggesting associations between the pathogenesis of frailty and age-related changes. Gut microbiota (GM) diversity and abundance change with age, accompanied by increased levels of trimethylamine oxide (TMAO), a systemic inflammation-inducing GM metabolite. Thus, we hypothesized that TMAO may be involved in the development of frailty. We successfully established and verified a novel model of frailty in adult mice based on a 4-week intraperitoneal injection regime of TMAO followed by LPS challenge. The frailty index significantly increased in TMAO-treated mice after LPS challenge. TMAO also decreased claudin-1 immunofluorescent staining intensity in the jejunum, ileum, and colon, indicating that the destruction of intestinal wall integrity may increase vulnerability to exogenous pathogens and invoke frailty. 16S sequencing showed that TMAO significantly reduced the GM Firmicutes/Bacteroidetes (F/B) ratio, but not α-diversity. Interestingly, after LPS challenge, more genera of bacterial taxa were differently altered in the control mice than in the TMAO-treated mice. We infer that a variety of GM participate in the maintenance of homeostasis, whereas TMAO could blunt the GM and impair the ability to recover from pathogens, which may explain the continuous increase in the frailty index in TMAO-treated mice after LPS challenge. TMAO also significantly increased serum imidazole metabolites, and led to different patterns of change in serum peptide and phenylpropanoid metabolites after LPS stimulation. These changes indicate that glucose metabolism may be one mechanism by which GM inactivation causes frailty. In conclusion, TMAO leads to frailty by destroying intestinal barrier integrity and blunting the GM response.

TMAO-Activated Hepatocyte-Derived Exosomes Impair Angiogenesis via Repressing CXCR4

Objective: Trimethylamine-N-oxide (TMAO) was found to play crucial roles in vascular endothelial function. However, the exact molecular mechanisms are not yet entirely clear. Recently, we found that exosomes (Exos) isolated from TMAO-treated hepatocytes (TMAO-Exos) contained a distinctive profile of miRNAs compared to those from the TMAO-free group (Control-Exos). Furthermore, TMAO-Exos could notably promote inflammation, damage vascular endothelial cells (VECs), and impair endothelium-dependent vasodilation. This study aimed to further evaluate the effects of TMAO-Exos on VECs and explore the underlying mechanisms.

Methods: Exos were isolated from the hepatocyte culture supernatant with or without TMAO, using differential centrifugation. Then, VECs were treated with these Exos for 48 h and subjected to RNA-sequencing for detecting the changes of alternative polyadenylation (APA) and mRNA. After validation by qPCR and western blotting, the recombinant viruses were used to mediate the overexpression of C-X-C motif chemokine receptor 4 (CXCR4). The in vitro VEC function was evaluated by cell migration and tube formation, and in vivo angiogenesis was investigated in hindlimb ischemia models.

Results: Exos released from hepatocytes were differentially regulated by TMAO; both could be taken up by VECs; and furthermore, TMAO-Exos significantly reduced cell migration and tube formation in vitro and impaired perfusion recovery and angiogenesis after hindlimb ischemia, by down-regulating the CXCR4 expression. However, TMAO-Exos failed to regulate the splicing events, at least in this experimental setting, which suggested that TMAO-Exos may affect CXCR4 expression via an APA-independent manner.

Conclusions: Our findings revealed a novel indirect mechanism by which TMAO impaired endothelial function through stimulating hepatocytes to produce Exos that possessed distinctive activity. The crosstalk between the liver and vascular endothelial mediated by these Exos may offer a new target for restraining the harmful effects induced by TMAO.

Diet-Induced High Serum Levels of Trimethylamine-N-oxide Enhance the Cellular Inflammatory Response without Exacerbating Acute Intracerebral Hemorrhage Injury in Mice

Trimethylamine-N-oxide (TMAO), an intestinal flora metabolite of choline, may aggravate atherosclerosis by inducing a chronic inflammatory response and thereby promoting the occurrence of cerebrovascular diseases. Knowledge about the influence of TMAO-related inflammatory response on the pathological process of acute stroke is limited. This study was designed to explore the effects of TMAO on neuroinflammation, brain injury severity, and long-term neurologic function in mice with acute intracerebral hemorrhage (ICH). We fed mice with either a regular chow diet or a chow diet supplemented with 1.2% choline pre- and post-ICH. In this study, we measured serum levels of TMAO with ultrahigh-performance liquid chromatography-tandem mass spectrometry at 24 h and 72 h post-ICH. The expression level of P38-mitogen-protein kinase (P38-MAPK), myeloid differentiation factor 88 (MyD88), high-mobility group box1 protein (HMGB1), and interleukin-1β (IL-1β) around hematoma was examined by western blotting at 24 h. Microglial and astrocyte activation and neutrophil infiltration were examined at 72 h. The lesion was examined on days 3 and 28. Neurologic deficits were examined for 28 days. A long-term choline diet significantly increased serum levels of TMAO compared with a regular diet at 24 h and 72 h after sham operation or ICH. Choline diet-induced high serum levels of TMAO did not enhance the expression of P38-MAPK, MyD88, HMGB1, or IL-1β at 24 h. However, it did increase the number of activated microglia and astrocytes around the hematoma at 72 h. Contrary to our expectations, it did not aggravate acute or long-term histologic damage or neurologic deficits after ICH. In summary, choline diet-induced high serum levels of TMAO increased the cellular inflammatory response probably by activating microglia and astrocytes. However, it did not aggravate brain injury or worsen long-term neurologic deficits. Although TMAO might be a potential risk factor for cerebrovascular diseases, this exploratory study did not support that TMAO is a promising target for ICH therapy.

Trimethylamine-N-oxide-stimulated hepatocyte-derived exosomes promote inflammation and endothelial dysfunction through nuclear factor-kappa B signaling

Background

Trimethylamine-N-oxide (TMAO) has been proven to be a new proatherogenic compound for promoting inflammation and endothelial dysfunction. Hepatocyte-derived exosomes (Exos), including those derived from hepatocytes, play a pivotal role in the regulation of inflammation and endothelial function. As TMAO is produced in the liver, hepatocytes may be the potential target of TMAO. However, it is not yet clear whether TMAO can directly stimulate hepatocytes to produce Exos to mediate the detrimental effects of TMAO on vascular endothelial cells (VECs).

Methods

Hepatocytes treated with TMAO and Exos (TMAO-Exos) were isolated from the supernatant, and added to human aortic endothelial cells (HAECs). The expressions of interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor-α (TNF-α) were detected by quantitative polymerase chain reaction (qPCR). Cell apoptosis was evaluated using Hoechst 33342 staining and flow cytometry assay, and cell migration was assessed by scratch and transwell assay. C57BL/6 mice were treated with Exos for 24 h and the thoracic aortas were isolated, then the in vitro aortic ring bioassay was conducted to determine the changes of vasodilation. The expressions of cluster of differentiation 81, tumor susceptibility gene 101, nuclear factor-kappa B (NF-κB) p65, and Phospho-NF-κB p65 were detected by western blotting. The micro ribonucleic acid (miRNA) profiles of the Exos were then identified using RNA-sequencing and validated by qPCR. The miRNA-messenger RNA networks were constructed, and the biological functions of the target genes were annotated using bioinformatics methods.

Results

TMAO was found to stimulate hepatocytes to release Exos that could be taken up by HAECs, thus inducing inflammation and cell apoptosis, impairing cell migration, and inhibiting endothelium-dependent vasodilation. Additionally, the miRNAs such as miR-302d-3p carried by the TMAO-Exos were quite different to those in the TMAO-free group. A further analysis showed that the potential target genes for these miRNAs, such as mitogen-activated protein kinase 8, caspase 9 and BCL2-like 11, appeared to be involved with inflammation and endothelial function. Finally, we found that NF-κB signaling could be activated by TMAO-Exos.

Conclusions

These novel findings provide evidence that TMAO can indirectly talk to VECs by promoting hepatocytes to produce Exos that carry important genetic information.

Trimethylamine N-oxide promotes atherosclerosis via regulating the enriched abundant transcript 1/miR-370-3p/signal transducer and activator of transcription 3/flavin-containing monooxygenase-3 axis

Atherosclerosis (AS) is one of the main causes of cardiovascular diseases (CVDs). Trimethylamine N-oxide (TMAO) exacerbates the development of AS. This study aimed to investigate the roles of TMAO in AS. In this study, mice were fed with high fat food (HF) and/or injected with TMAO. Oil red O staining was applied for histological analysis. ELISA, qRT-PCR, and Western blot were conducted to determine the TMAO, serum, mRNA, and protein levels. CCK-8, colony formation assay, and flow cytometry assays were performed to detect the functions of human aortic endothelial cells (HUVECs). The results showed that TMAO induced thick internal and external walls and intimal plaques in vivo, and HUVEC dysfunction in vitro. TMAO and lncRNA enriched abundant transcript 1 (NEAT1) were increased in AS clinical samples and TMAO-HUVECs. Downregulated NEAT1 inhibited proliferation and promoted the apoptosis of HUVECs. NEAT1 regulated the expression of signal transducer and activator of transcription 3 (STAT3) via sponging miR-370-3p. Overexpression of miR-370-3p facilitated the effects of NEAT1 on the cellular functions of HUVECs, while STAT3 exerted opposing effects. The activation of STAT3 promoted the expression of flavin-containing monooxygenase-3 (FMO3). Taken together, our results show that TMAO-NEAT1/miR-370-3p/STAT3/FMO3 forms a positive feedback loop to exacerbate the development of AS. This novel feedback loop may be a promising therapeutic target for AS.

Toll-Like Receptor 4: A Macrophage Cell Surface Receptor Is Activated By Trimethylamine-N-Oxide

OBJECTIVE

Trimethylamine-N-Oxide (TMAO) is considered as a risk factor for atherosclerosis which further leads to inflammation during atherosclerosis. The exact mechanism(s) by which TMAO induces the inflammatory reactions remains to be determined. TMAO can cause the endoplasmic reticulum (ER) stress that triggers activation of Toll-Like Receptors (TLRs). In macrophages, this process stimulates the production of proinflammatory cytokines. This study designed to evaluate the expression level of TLR4 in TMAO-treated macrophages.

MATERIALS AND METHODS

In this experimental study, different concentrations of TMAO (37.5, 75, 150, and 300 μM) were exposed to murine macrophage (J774A.1 cell line) for 8, 18, 24, and 48 hours. The cells were also treated with 2.5 mM of 4-phenyl butyric acid as well as 2μg/ml of tunicamycin respectively as negative and positive controls for inducing ER-stress. We measured the viability of treated cells by the MTT test. Besides, the expression levels of TLR4 gene and protein were evaluated using western blotting and reverse transcription- quantitative polymerase chain reaction (RT-qPCR) analysis. One-Way ANOVA was used for statistical analysis.

RESULTS

No cell death was observed in treated cells. The cells treated with 150 and 300 μM doses of TMAO for 24 hours showed a significant elevation in the protein and/or mRNA levels of TLR4 when compared to normal control or tunicamycin-treated cells.

CONCLUSION

Our results may in part elucidate the mechanism by which TMAO induces the macrophage inflammatory reactions in response to the induction of ER stress, similar to what happens during atherosclerosis. It also provides documentation to support the direct contribution of TLR4 in TMAO-induced inflammation.

High mobility group box 1 and homocysteine as preprocedural predictors for contrast-induced acute kidney injury after percutaneous coronary artery intervention

PURPOSE

High mobility group box 1 (HMGB1) and homocysteine (Hcy) play important roles in contrast-induced acute kidney injury (CI-AKI). We compared HMGB1 to Hcy as preprocedural predictors for CI-AKI in coronary artery disease (CAD) patients after percutaneous coronary artery intervention (PCI).

METHODS

We included 257 eligible patients who were categorized into CI-AKI ( +) and CI-AKI ( -) group. The differences in clinical characteristics and biochemical indexes between two groups were analyzed.

RESULTS

We observed that thirty-eight (14.8%) of 257 eligible CAD patients developed CI-AKI. HMGB1 (14.65 [11.13-24.89] vs 10.88 [7.94-13.23], p < 0.001) and Hcy (14.07 [12.07-17.31] vs 12.09 [10.71-13.47], p < 0.001) increased significantly in CI-AKI ( +) group. Both age (r = 0.210, p = 0.001), serum creatinine (r = 0.509, p < 0.001), eGFR (r =  - 0.459, p < 0.001) and Hcy (r = 0.531, p < 0.001) were significantly correlated with HMGB1. Among all patients, HMGB1 (OR 1.181, 95% CI 1.081-1.290, p < 0.001) and Hcy (OR 1.260, 95% CI 1.066-1.489, p = 0.007) were independent predictors for the development of CI-AKI. We built the propensity score matching (PSM) using 38 pairs of patients. After adjustment, HMGB1 (OR 1.169, 95% CI 1.035-1.322, p = 0.012) and Hcy (OR 1.457, 95% CI 1.064-1.997, p = 0.019) were also independent predictors for the development of CI-AKI. Both HMGB1 (AUC: 0.704, 95% CI: 0.588-0.819, p = 0.002) and Hcy (AUC: 0.708, 95% CI: 0.593-0.823, p = 0.002) had predictive values for CI-AKI.

CONCLUSION

There is a significant positive association between HMGB1 and Hcy in CAD patients. Both HMGB1 and Hcy are potential preprocedural predictors of CI-AKI after PCI.

Myeloid cell-specific Irf5 deficiency stabilizes atherosclerotic plaques in Apoe-/- mice

OBJECTIVE

Interferon regulatory factor (IRF) 5 is a transcription factor known for promoting M1 type macrophage polarization in vitro. Given the central role of inflammatory macrophages in promoting atherosclerotic plaque progression, we hypothesize that myeloid cell-specific deletion of IRF5 is protective against atherosclerosis.

METHODS

Female Apoe-/-LysmCre/+Irf5fl/fl and Apoe-/-Irf5fl/fl mice were fed a high-cholesterol diet for three months. Atherosclerotic plaque size and compositions as well as inflammatory gene expression were analyzed. Mechanistically, IRF5-dependent bone marrow-derived macrophage cytokine profiles were tested under M1 and M2 polarizing conditions. Mixed bone marrow chimeras were generated to determine intrinsic IRF5-dependent effects on macrophage accumulation in atherosclerotic plaques.

RESULTS

Myeloid cell-specific Irf5 deficiency blunted LPS/IFNγ-induced inflammatory gene expression in vitro and in the atherosclerotic aorta in vivo. While atherosclerotic lesion size was not reduced in myeloid cell-specific Irf5-deficient Apoe-/- mice, plaque composition was favorably altered, resembling a stable plaque phenotype with reduced macrophage and lipid contents, reduced inflammatory gene expression and increased collagen deposition alongside elevated Mertk and Tgfβ expression. Irf5-deficient macrophages, when directly competing with wild type macrophages in the same mouse, were less prone to accumulate in atherosclerotic lesion, independent of monocyte recruitment. Irf5-deficient monocytes, when exposed to oxidized low density lipoprotein, were less likely to differentiate into macrophage foam cells, and Irf5-deficient macrophages proliferated less in the plaque.

CONCLUSION

Our study provides genetic evidence that selectively altering macrophage polarization induces a stable plaque phenotype in mice.

High-Mobility Group Box-1 and Its Potential Role in Perioperative Neurocognitive Disorders

Aseptic surgical trauma provokes the release of HMGB1, which engages the innate immune response after binding to pattern-recognition receptors on circulating bone marrow-derived monocytes (BM-DM). The initial systemic inflammation, together with HMGB1, disrupts the blood-brain barrier allowing penetration of CCR2-expressing BM-DMs into the hippocampus, attracted by the chemokine MCP-1 that is upregulated by HMGB1. Within the brain parenchyma quiescent microglia are activated and, together with the translocated BM-DMs, release proinflammatory cytokines that disrupt synaptic plasticity and hence memory formation and retention, resulting in postoperative cognitive decline (PCD). Neutralizing antibodies to HMGB1 prevents the inflammatory response to trauma and PCD.

High-Mobility Group Box-1 Is Critical in the Pathogenesis of Mouse Experimental Necrotizing Enterocolitis

Although high-mobility group box-1 (HMGB1) is related to the persistent intestinal inflammation in the development of necrotizing enterocolitis (NEC), the role of HMGB1 in the regulation of the intestinal microcirculation in NEC is not well understood. Therefore, we investigated the mechanism(s) by which HMGB1 regulates the generation of the following vasodilatory signals during the development of NEC: endothelial nitric oxide synthase (eNOS) and nitric oxide (NO). Experimental NEC was induced in full-term C57BL/6 mouse pups through the formula gavage and hypoxia technique. The blockade of HMGB1 was achieved with a subcutaneous injection of anti-HMGB1 antibody. Intestinal tissues and blood samples were collected at predetermined time points for the assessment of intestinal microcirculation, lipid peroxidation levels, and evaluation of eNOS activation. We found elevations in HMGB1 expression as early as 12 h after induction of NEC stress, which preceded intestinal injury. Treatment of mouse pups with HMGB1 neutralizing antibody attenuated the intestinal microvascular features and symptoms of NEC, but this improvement was not found in the eNOS knockout mice, suggesting that HMGB1 inhibition increased intestinal microcirculatory perfusion in an eNOS-dependent manner. Moreover, HMGB1 inhibition rescued NO production and eliminated O₂^•- production in experimental NEC mice through eNOS activation. These data indicate that excessive HMGB1 signaling is associated with the pathogenesis of NEC, suggesting that HMGB1 inhibition might be a promising strategy for NEC treatment.

JTE-013 Alleviates Inflammatory Injury and Endothelial Dysfunction Induced by Sepsis In Vivo and In Vitro

BACKGROUND

Nowadays, there is no approved targeted agent for lung injury induced by sepsis. S1PR2 is confirmed to be a promising diagnosis and treatment target. JTE-013 as S1PR2 antagonists may be an agent of great potential. In this research, we sought to determine the functional role of JTE-013 in lung injury induced by sepsis.

MATERIALS AND METHODS

Seventy-two rats were assigned into normal group, sepsis model group and JTE-013 group. The animal model of lung injury induced by sepsis was constructed by cecal ligation and puncture. The human pulmonary microvascular endothelial cells (HPMECs) were divided into control, LPS and LPS + JTE-013 group. HPMECs induced by LPS served as the cell model of lung injury induced by sepsis. HE staining assay was performed for assessment of the pathological condition and Evans blue was applied for assessment of pulmonary tissue permeability. Wet/dry ratio was measured as indicators of pulmonary edema degree and neutrophil count was measured as indicators of infection status. The levels of inflammatory factors were detected by corresponding kits, cell survival by CCK-8 assay and protein expression level by western blot.

RESULTS

S1PR2 was highly expressed in vivo model of lung injury induced by sepsis. It was observed that JTE-013 as antagonist of S1PR2 alleviated the lung tissue injury, endothelial dysfunction and pulmonary edema induced by sepsis. In addition, JTE-013 reduced neutrophil count and levels of inflammatory factors. Moreover, results confirmed that JTE-013 enhanced cell viability and mitigated inflammatory response in cell model of sepsis.

CONCLUSIONS

Overall, JTE-013 as an antagonist of S1PR2 could relieve inflammatory injury and endothelial dysfunction induced by sepsis in vivo and vitro, resulting in attenuation of lung injury. These findings elucidated that JTE-013 may be a promising targeted agent for lung injury induced by sepsis.

Association between Dietary Choline Intake and Diabetic Retinopathy: National Health and Nutrition Examination Survey 2005-2008

PURPOSE

To explore whether there is an association between dietary choline intake and odds of diabetic retinopathy (DR) in the US diabetic population.

METHODS

A cross-sectional study was conducted using the combined data of the National Health and Nutrition Examination Survey (NHANES) 2005-2008 of a complex, multistage, and probability-sampling design. Energy-adjusted choline intake was calculated separately for men and women using the residual method. Binary logistic regression adjusting for covariates was used to identify the variables associated with DR.

RESULTS

We included 644 male and 628 female diabetic subjects, which were equivalent to a weighted survey sample of 9,339,124 for males and 10,109,553 for females respectively. Female DR patients consumed more choline than non-DR patients (268.6 mg/d vs 250.9 mg/d; p = .046). The estimated prevalence of DR was 17.4%, 21.9%, and 29.7% across three levels of dietary choline intake in females, respectively. In multivariable logistic-regression models, the odds ratio (OR) of DR for female patients in the highest choline intake group was 2.14 (95% confidence interval [CI], 1.38-3.31; p = .001) compared with those in the lowest intake group. This association was positive but not statistically significant in males.

CONCLUSION

Higher intake of dietary choline is associated with increased odds of DR in females, but not in males. Further studies are warranted to investigate the direct role of choline in DR development and determine the recommended daily intake of choline for diabetic patients weighing the pros and cons of dietary choline consumption.

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.

Trimethylamine/Trimethylamine-N-Oxide as a Key Between Diet and Cardiovascular Diseases

Trimethylamine (TMA) is a gut microbiota-derived metabolite which comes from diets rich of choline, betaine or L-carnitine and could be further converted to Trimethylamine-N-oxide (TMAO) in the liver. As the function of gut microbiota and its metabolites being explored so far, studies suggest that TMAO may be a potential risk factor of cardiovascular diseases independent of other traditional risk factors. However, the precise role of TMAO is controversial as some converse results were discovered. In recent studies, it is hypothesized that TMA may also participate in the progression of cardiovascular diseases and some cytotoxic effect of TMA has been discovered. Thus, exploring the relationship between TMA, TMAO and CVD may bring a novel insight into the diagnosis and therapy of cardiovascular diseases. In this review, we discussed the factors which influence the TMA/TMAO's process of metabolism in the human body. We have also summarized the pathogenic effect of TMA/TMAO in cardiovascular diseases, as well as the limitation of some controversial discoveries.

Inflammatory Mechanisms Contributing to Endothelial Dysfunction

Maintenance of endothelial cell integrity is an important component of human health and disease since the endothelium can perform various functions including regulation of vascular tone, control of hemostasis and thrombosis, cellular adhesion, smooth muscle cell proliferation, and vascular inflammation. Endothelial dysfunction is encompassed by complex pathophysiology that is based on endothelial nitric oxide synthase uncoupling and endothelial activation following stimulation from various inflammatory mediators (molecular patterns, oxidized lipoproteins, cytokines). The downstream signaling via nuclear factor-κB leads to overexpression of adhesion molecules, selectins, and chemokines that facilitate leukocyte adhesion, rolling, and transmigration to the subendothelial space. Moreover, oscillatory shear stress leads to pro-inflammatory endothelial activation with increased monocyte adhesion and endothelial cell apoptosis, an effect that is dependent on multiple pathways and flow-sensitive microRNA regulation. Moreover, the role of neutrophil extracellular traps and NLRP3 inflammasome as inflammatory mechanisms contributing to endothelial dysfunction has recently been unveiled and is under further investigation. Consequently, and following their activation, injured endothelial cells release inflammatory mediators and enter a pro-thrombotic state through activation of coagulation pathways, downregulation of thrombomodulin, and an increase in platelet adhesion and aggregation owing to the action of von-Willebrand factor, ultimately promoting atherosclerosis progression.

Ethanol: striking the cardiovascular system by harming the gut microbiota

Ethanol consumption represents a significant public health problem, and excessive ethanol intake is a risk factor for cardiovascular disease (CVD), one of the leading causes of death and disability worldwide. The mechanisms underlying the effects of ethanol on the cardiovascular system are complex and not fully comprehended. The gut microbiota and their metabolites are indispensable symbionts essential for health and homeostasis and therefore, have emerged as potential contributors to ethanol-induced cardiovascular system dysfunction. By mechanisms that are not completely understood, the gut microbiota modulates the immune system and activates several signaling pathways that stimulate inflammatory responses, which in turn, contribute to the development and progression of CVD. This review summarizes preclinical and clinical evidence on the effects of ethanol in the gut microbiota and discusses the mechanisms by which ethanol-induced gut dysbiosis leads to the activation of the immune system and cardiovascular dysfunction. The cross talk between ethanol consumption and the gut microbiota and its implications are detailed. In summary, an imbalance in the symbiotic relationship between the host and the commensal microbiota in a holobiont, as seen with ethanol consumption, may contribute to CVD. Therefore, manipulating the gut microbiota, by using antibiotics, probiotics, prebiotics, and fecal microbiota transplantation might prove a valuable opportunity to prevent/mitigate the deleterious effects of ethanol and improve cardiovascular health and risk prevention.

Roles of Gut Microbial Metabolites in Diabetic Kidney Disease

Diabetes is a highly prevalent metabolic disease that has emerged as a global challenge due to its increasing prevalence and lack of sustainable treatment. Diabetic kidney disease (DKD), which is one of the most frequent and severe microvascular complications of diabetes, is difficult to treat with contemporary glucose-lowering medications. The gut microbiota plays an important role in human health and disease, and its metabolites have both beneficial and harmful effects on vital physiological processes. In this review, we summarize the current findings regarding the role of gut microbial metabolites in the development and progression of DKD, which will help us better understand the possible mechanisms of DKD and explore potential therapeutic approaches for DKD.

Association of Trimethylamine N-Oxide and Its Precursor With Cerebral Small Vessel Imaging Markers

Background: High plasma levels of trimethylamine N-oxide (TMAO) and its precursor choline have been linked to stroke; however, their association with cerebral small vessel disease remains unclear. Here we evaluated the association of plasma levels of TMAO and choline with imaging markers of cerebral small vessel disease, including white matter hyperintensities, lacunes, and cerebral microbleeds.

Methods: We performed a baseline cross-sectional analysis of a multicenter hospital-based cohort study from 2015 to 2018. The data were collected from 30 hospitals in China and included 1,098 patients with ischemic stroke/transient ischemic attack aged ≥18 years. White matter hyperintensities, lacunes, and cerebral microbleeds were evaluated with the patients' demographic, clinical, and laboratory information removed. White matter hyperintensities were rated using the Fazekas visual grading scale, while the degree of severity of the lacunes and cerebral microbleeds was defined by the number of lesions.

Results: Increased TMAO levels were associated with severe white matter hyperintensities [adjusted odds ratio (aOR) for the highest vs. lowest quartile, 1.5; 95% confidence interval (CI), 1.0–2.1, p = 0.04]. High TMAO levels were more strongly associated with severe periventricular white matter hyperintensities (aOR for the highest vs. lowest quartile, 1.6; 95% CI, 1.1–2.3, p = 0.009) than deep white matter hyperintensities (aOR for the highest vs. lowest quartile, 1.3; 95% CI, 0.9–1.9, p = 0.16). No significant association was observed between TMAO and lacunes or cerebral microbleeds. Choline showed trends similar to that of TMAO in the association with cerebral small vessel disease.

Conclusions: In patients with ischemic stroke or transient ischemic attack, TMAO and choline appear to be associated with white matter hyperintensities, but not with lacunes or cerebral microbleeds; TMAO and choline were associated with increased risk of a greater periventricular, rather than deep, white matter hyperintensities burden.

Elevated plasma trimethylamine-N-oxide levels are associated with diabetic retinopathy

AIMS

To determine the relationship between plasma levels of trimethylamine-N-oxide (TMAO) and odds of diabetic retinopathy (DR).

METHODS

A cross-sectional study was conducted. Blood samples were obtained from 122 type 2 diabetes mellitus (T2DM) patients with or without DR. Multivariable logistic regression analyses were performed to identify the association between plasma TMAO and DR. The diagnostic value of plasma TMAO was assessed by the area under the receiver operating characteristic curve (AUROC) and integrated discrimination improvement (IDI).

RESULTS

In the T2DM patients, plasma levels of TMAO were significantly higher in patients with DR compared with those without DR (P = 0.001). As logarithmic (ln) transformation of TMAO increased per standard deviation (SD), there was higher probability to have DR [odds ratio (OR) = 2.31; P = 0.005]. As ln-transformed TMAO increased per SD, the severity of DR was more likely to get worse (OR = 2.05; P = 0.004). In the diagnostic model, the addition of TMAO contributed to the improvement in AUROC from 0.646 to 0.734 (P = 0.043), and the IDI was 10.7% (P < 0.001).

CONCLUSION

Elevated levels of plasma TMAO were associated with higher odds and worse severity of DR in T2DM patients, and further investigation is required for the causality of this association.

Non-alcoholic fatty liver disease: a metabolic burden promoting atherosclerosis

Non-alcoholic fatty liver disease (NAFLD) has become the fastest growing chronic liver disease, with a prevalence of up to 25% worldwide. Individuals with NAFLD have a high risk of disease progression to cirrhosis, hepatocellular carcinoma (HCC), and liver failure. With the exception of intrahepatic burden, cardiovascular disease (CVD) and especially atherosclerosis (AS) are common complications of NAFLD. Furthermore, CVD is a major cause of death in NAFLD patients. Additionally, AS is a metabolic disorder highly associated with NAFLD, and individual NAFLD pathologies can greatly increase the risk of AS. It is increasingly clear that AS-associated endothelial cell damage, inflammatory cell activation, and smooth muscle cell proliferation are extensively impacted by NAFLD-induced systematic dyslipidemia, inflammation, oxidative stress, the production of hepatokines, and coagulations. In clinical trials, drug candidates for NAFLD management have displayed promising effects for the treatment of AS. In this review, we summarize the key molecular events and cellular factors contributing to the metabolic burden induced by NAFLD on AS, and discuss therapeutic strategies for the improvement of AS in individuals with NAFLD.

Vascular reactivity stimulated by TMA and TMAO: Are perivascular adipose tissue and endothelium involved?

Trimethylamine (TMA), formed by intestinal microbiota, and its Flavin-Monooxygenase 3 (FMO3) product Trimethylamine-N-Oxide (TMAO), are potential modulators of host cardiometabolic phenotypes. High circulating levels of TMAO are associated with increased risk for cardiovascular diseases. We hypothesized that TMA/TMAO could directly change the vascular tone. Perivascular adipose tissue (PVAT) helps to regulate vascular homeostasis and may also possess FMO3. Thoracic aorta with(+) or without(-) PVAT, also + or - the endothelium (E), of male Sprague Dawley rats were isolated for measurement of isometric tone in response to TMA/TMAO (1nM-0.5 M). Immunohistochemistry (IHC) studies were done to identify the presence of FMO3. TMA and TMAO elicited concentration-dependent arterial contraction. However, at a maximally achievable concentration (0.2 M), contraction stimulated by TMA was of a greater magnitude (141.5 ± 16% of maximum phenylephrine contraction) than that elicited by TMAO (19.1 ± 4.03%) with PVAT and endothelium intact. When PVAT was preserved, TMAO-induced contraction was extensively reduced the presence (19.1 ± 4.03%) versus absence of E (147.2 ± 20.5%), indicating that the endothelium plays a protective role against TMAO-induced contraction. FMO3 enzyme was present in aortic PVAT, but the FMO3 inhibitor methimazole did not affect contraction stimulated by TMA in aorta + PVAT. However, the l-type calcium channel blocker nifedipine reduced TMA-induced contraction by ∼50% compared to the vehicle. Though a high concentration of these compounds was needed to achieve contraction, the findings that TMA-induced contraction was independent of PVAT and E and mediated by nifedipine-sensitive calcium channels suggest metabolite-induced contraction may be physiologically important.

Involvement of Gut Microbiota, Microbial Metabolites and Interaction with Polyphenol in Host Immunometabolism

Immunological and metabolic processes are inextricably linked and important for maintaining tissue and organismal health. Manipulation of cellular metabolism could be beneficial to immunity and prevent metabolic and degenerative diseases including obesity, diabetes, and cancer. Maintenance of a normal metabolism depends on symbiotic consortium of gut microbes. Gut microbiota contributes to certain xenobiotic metabolisms and bioactive metabolites production. Gut microbiota-derived metabolites have been shown to be involved in inflammatory activation of macrophages and contribute to metabolic diseases. Recent studies have focused on how nutrients affect immunometabolism. Polyphenols, the secondary metabolites of plants, are presented in many foods and beverages. Several studies have demonstrated the antioxidant and anti-inflammatory properties of polyphenols. Many clinical trials and epidemiological studies have also shown that long-term consumption of polyphenol-rich diet protects against chronic metabolic diseases. It is known that polyphenols can modulate the composition of core gut microbiota and interact with the immunometabolism. In the present article, we review the mechanisms of gut microbiota and its metabolites on immunometabolism, summarize recent findings on how the interaction between microbiota and polyphenol modulates host immunometabolism, and discuss future research directions.

Trimethylamine-N-oxide Specifically Impairs Endothelium-Derived Hyperpolarizing Factor-Type Relaxation in Rat Femoral Artery

Although substantial evidence suggests that an increase in the level of trimethylamine-N-oxide (TMAO) is associated with the risk of cardiovascular diseases, including atherosclerosis, chronic kidney diseases, and hypertension, the direct effect of TMAO on vascular endothelial function remains unclear. Therefore, we investigated the acute effects of TMAO on endothelium-dependent relaxation induced by acetylcholine (ACh) in the superior mesenteric arteries and femoral arteries of rat. In endothelium-intact preparations, it was observed that TMAO (300 µmol/L for 60 min) did not affect ACh-induced relaxation in either of the two arteries. In endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation under nitric oxide synthase (NOS) and cyclooxygenase (COX) inhibitions by N^ω-nitro-L-arginine (L-NNA) and indomethacin, respectively, TMAO specifically impairs the relaxation in femoral arteries but not in the superior mesenteric arteries. Under the inhibitory actions of NOS and as well as blockade of intermediate-conductance calcium-activated potassium channel (IK_Ca) (by TRAM-34) and small-conductance calcium-activated potassium channel (SK_Ca) (by apamin), which are putative sources of EDHF, ACh-induced relaxation was low, and there were no differences between the control and TMAO-treated groups with respect to both arteries. In femoral arteries, TMAO slightly reduces ACh-induced relaxation in the presence of indomethacin (preserved NO and EDHF signals) but does not affect ACh-induced NO-mediated relaxation under the combined presence of indomethacin, TRAM-34, and apamin. These results suggest that acute treatment with TMAO specifically impairs EDHF-mediated relaxation in the femoral arteries but not in the superior mesenteric arteries. These novel observations show that TMAO is a causative factor in the development of peripheral arterial disease.

P53 in the impaired lungs

Our laboratory is focused on investigating the supportive role of P53 towards the maintenance of lung homeostasis. Acute lung injury, acute respiratory distress syndrome, chronic obstructive pulmonary disease, pulmonary fibrosis, bronchial asthma, pulmonary arterial hypertension, pneumonia and tuberculosis are respiratory pathologies, associated with dysfunctions of this endothelium defender (P53). Herein we review the evolving role of P53 towards the aforementioned inflammatory disorders, to potentially reveal new therapeutic possibilities in pulmonary disease.

The Relationship between Choline Bioavailability from Diet, Intestinal Microbiota Composition, and Its Modulation of Human Diseases

Choline is a water-soluble nutrient essential for human life. Gut microbial metabolism of choline results in the production of trimethylamine (TMA), which, upon absorption by the host is converted into trimethylamine-N-oxide (TMAO) in the liver. A high accumulation of both components is related to cardiovascular disease, inflammatory bowel disease, non-alcoholic fatty liver disease, and chronic kidney disease. However, the relationship between the microbiota production of these components and its impact on these diseases still remains unknown. In this review, we will address which microbes contribute to TMA production in the human gut, the extent to which host factors (e.g., the genotype) and diet affect TMA production, and the colonization of these microbes and the reversal of dysbiosis as a therapy for these diseases.

Dietary bioactive ingredients to modulate the gut microbiota-derived metabolite TMAO. New opportunities for functional food development

There is a growing body of clinical evidence that supports a strong association between elevated circulating trimethylamine N-oxide (TMAO) levels with increased risk of developing adverse cardiovascular outcomes such as atherosclerosis and thrombosis. TMAO is synthesized through a meta-organismal stepwise process that involves (i) the microbial production of TMA in the gut from dietary precursors and (ii) its subsequent oxidation to TMAO by flavin-containing monooxygenases in the liver. Choline, l-carnitine, betaine, and other TMA-containing compounds are the major dietary precursors of TMA. TMAO can also be absorbed directly from the gastrointestinal tract after the intake of TMAO-rich foods such as fish and shellfish. Thus, diet is an important factor as it provides the nutritional precursors to eventually produce TMAO. A number of studies have attempted to associate circulating TMAO levels with the consumption of diets rich in these foods. On the other hand, there is growing interest for the development of novel food ingredients that reduce either the TMAO-induced damage or the endogenous TMAO levels through the interference with microbiota and host metabolic processes involved in TMAO pathway. Such novel functional food ingredients would offer great opportunities to control circulating TMAO levels or its effects, and potentially contribute to decrease cardiovascular risk. In this review we summarize and discuss current data regarding the effects of TMA precursors-enriched foods or diets on circulating TMAO levels, and recent findings regarding the circulating TMAO-lowering effects of specific foods, food constituents and phytochemicals found in herbs, individually or in extracts, and their potential beneficial effect for cardiovascular health.

Endothelial Damage, Inflammation and Immunity in Chronic Kidney Disease

Chronic kidney disease (CKD) patients have an accelerated atherosclerosis, increased risk of thrombotic-ischemic complications, and excessive mortality rates when compared with the general population. There is also evidence of an endothelial damage in which the proinflammatory state, the enhanced oxidative stress, or the accumulation of toxins due to their reduced renal clearance in uremia play a role. Further, there is evidence that uremic endothelial cells are both involved in and victims of the activation of the innate immunity. Uremic endothelial cells produce danger associated molecular patterns (DAMPS), which by binding to specific pattern recognition receptors expressed in multiple cells, including endothelial cells, induce the expression of adhesion molecules, the production of proinflammatory cytokines and an enhanced production of reactive oxygen species in endothelial cells, which constitute a link between immunity and inflammation. The connection between endothelial damage, inflammation and defective immunity in uremia will be reviewed here.

The gut microbiota and its interactions with cardiovascular disease

The intestine is colonized by a considerable community of microorganisms that cohabits within the host and plays a critical role in maintaining host homeostasis. Recently, accumulating evidence has revealed that the gut microbial ecology plays a pivotal role in the occurrence and development of cardiovascular disease (CVD). Moreover, the effects of imbalances in microbe-host interactions on homeostasis can lead to the progression of CVD. Alterations in the composition of gut flora and disruptions in gut microbial metabolism are implicated in the pathogenesis of CVD. Furthermore, the gut microbiota functions like an endocrine organ that produces bioactive metabolites, including trimethylamine/trimethylamine N-oxide, short-chain fatty acids and bile acids, which are also involved in host health and disease via numerous pathways. Thus, the gut microbiota and its metabolic pathways have attracted growing attention as a therapeutic target for CVD treatment. The fundamental purpose of this review was to summarize recent studies that have illustrated the complex interactions between the gut microbiota, their metabolites and the development of common CVD, as well as the effects of gut dysbiosis on CVD risk factors. Moreover, we systematically discuss the normal physiology of gut microbiota and potential therapeutic strategies targeting gut microbiota to prevent and treat CVD.

Trimethylamine-N-oxide acutely increases cardiac muscle contractility

Cardiovascular disease is a major cause of morbidity and mortality among patients with chronic kidney disease (CKD). Trimethylamine-N-oxide (TMAO), a uremic metabolite that is elevated in the setting of CKD, has been implicated as a nontraditional risk factor for cardiovascular disease. While association studies have linked elevated plasma levels of TMAO to adverse cardiovascular outcomes, its direct effect on cardiac and smooth muscle function remains to be fully elucidated. We hypothesized that pathological concentrations of TMAO would acutely increase cardiac and smooth muscle contractility. These effects may ultimately contribute to cardiac dysfunction during CKD. High levels of TMAO significantly increased paced, ex vivo human cardiac muscle biopsy contractility (P < 0.05). Similarly, TMAO augmented contractility in isolated mouse hearts (P < 0.05). Reverse perfusion of TMAO through the coronary arteries via a Langendorff apparatus also enhanced cardiac contractility (P < 0.05). In contrast, the precursor molecule, trimethylamine (TMA), did not alter contractility (P > 0.05). Multiphoton microscopy, used to capture changes in intracellular calcium in paced, adult mouse hearts ex vivo, showed that TMAO significantly increased intracellular calcium fluorescence (P < 0.05). Interestingly, acute administration of TMAO did not have a statistically significant influence on isolated aortic ring contractility (P > 0.05). We conclude that TMAO directly increases the force of cardiac contractility, which corresponds with TMAO-induced increases in intracellular calcium but does not acutely affect vascular smooth muscle or endothelial function of the aorta. It remains to be determined if this acute inotropic action on cardiac muscle is ultimately beneficial or harmful in the setting of CKD.NEW & NOTEWORTHY We demonstrate for the first time that elevated concentrations of TMAO acutely augment myocardial contractile force ex vivo in both murine and human cardiac tissue. To gain mechanistic insight into the processes that led to this potentiation in cardiac contraction, we used two-photon microscopy to evaluate intracellular calcium in ex vivo whole hearts loaded with the calcium indicator dye Fluo-4. Acute treatment with TMAO resulted in increased Fluo-4 fluorescence, indicating that augmented cytosolic calcium plays a role in the effects of TMAO on force production. Lastly, TMAO did not show an effect on aortic smooth muscle contraction or relaxation properties. Our results demonstrate novel, acute, and direct actions of TMAO on cardiac function and help lay the groundwork for future translational studies investigating the complex multiorgan interplay involved in cardiovascular pathogenesis during CKD.

Trimethylamine N-oxide promotes apoE-/- mice atherosclerosis by inducing vascular endothelial cell pyroptosis via the SDHB/ROS pathway

Trimethylamine N-oxide (TMAO) is produced from the phosphatidylcholine metabolism of gut flora and acts as a risk factor of cardiovascular disease. However, the underlying mechanisms for its proatherogenic action remain unclear. This study aimed to observe the effect of TMAO on endothelial cell pyroptosis and explore the underlying mechanisms. Our results showed that TMAO promoted the progression of atherosclerotic lesions in apolipoprotein E-deficient (apoE^-/- ) mice fed a high-fat diet. Pyroptosis and succinate dehydrogenase complex subunit B (SDHB) upregulation were detected in the vascular endothelial cells of apoE^-/- mice and in cultured human umbilical vein endothelial cells (HUVECs) treated with TMAO. Overexpression of SDHB in HUVECs enhanced pyroptosis and impaired mitochondria and high reactive oxygen species (ROS) level. Pyroptosis in the SDHB overexpression of endothelial cells was inhibited by the ROS scavenger NAC. In summary, TMAO promotes vascular endothelial cell pyroptosis via ROS induced through SDHB upregulation, thereby contributing to the progression of atherosclerotic lesions.