Intestinal Microbial Metabolites Are Linked to Severity of Myocardial Infarction in Rats

TMAO: how gut microbiota contributes to heart failure

An increasing amount of evidence reveals that the gut microbiota is involved in the pathogenesis and progression of various cardiovascular diseases. In patients with heart failure (HF), splanchnic hypoperfusion causes ischemia and intestinal edema, allowing bacterial translocation and bacterial metabolites to enter the blood circulation via an impaired intestinal barrier. This results in local and systemic inflammatory responses. Gut microbe-derived metabolites are implicated in the pathology of multiple diseases, including HF. These landmark findings suggest that gut microbiota influences the host's metabolic health, either directly or indirectly by producing several metabolites. In this review, we mainly discuss a newly identified gut microbiota-dependent metabolite, trimethylamine N-oxide (TMAO), which appears to participate in the pathologic processes of HF and can serve as an early warning marker to identify individuals who are at the risk of disease progression. We also discuss the potential of the gut-TMAO-HF axis as a new target for HF treatment and highlight the current controversies and potentially new and exciting directions for future research.

Microbiota, a New Playground for the Omega-3 Polyunsaturated Fatty Acids in Cardiovascular Diseases

Several cardioprotective mechanisms attributed to Omega-3 polyunsaturated fatty acids (PUFAs) have been studied and widely documented. However, in recent years, studies have supported the concept that the intestinal microbiota can play a much larger role than we had anticipated. Microbiota could contribute to several pathologies, including cardiovascular diseases. Indeed, an imbalance in the microbiota has often been reported in patients with cardiovascular disease and produces low-level inflammation. This inflammation contributes to, more or less, long-term development of cardiovascular diseases. It can also worsen the symptoms and the consequences of these pathologies. According to some studies, omega-3 PUFAs in the diet could restore this imbalance and mitigate its harmful effects on cardiovascular diseases. Many mechanisms are involved and included: (1) a reduction of bacteria producing trimethylamine (TMA); (2) an increase in bacteria producing butyrate, which has anti-inflammatory properties; and (3) a decrease in the production of pro-inflammatory cytokines. Additionally, omega-3 PUFAs would help maintain better integrity in the intestinal barrier, thereby preventing the translocation of intestinal contents into circulation. This review will summarize the effects of omega-3 PUFAs on gut micro-biota and the potential impact on cardiac health.

Changes in the Serum Metabolome of Patients Treated With Broad-Spectrum Antibiotics

Background:

The gut microbiome (GMB) generates numerous small chemicals that can be absorbed by the host and variously biotransformed, incorporated, or excreted. The resulting metabolome can provide information about the state of the GMB, of the host, and of their relationship. Exploiting this information in the service of biomarker development is contingent on knowing the GMB-sensitivity of the individual chemicals comprising the metabolome. In this regard, human studies have lagged far behind animal studies. Accordingly, we tested the hypothesis that serum levels of chemicals unequivocally demonstrated to be GMB-sensitive in rodent models would also be affected in a clinical patient sample treated with broad spectrum antibiotics.

Methods:

We collected serum samples from 20 hospitalized patients before, during, and after treatment with broad-spectrum antibiotics. We also collected samples from 5 control patients admitted to the hospital but not prescribed antibiotics. We submitted the samples for a non-targeted metabolomic analysis and then focused on chemicals known to be affected both by germ-free status and by antibiotic treatment in the mouse and/or rat.

Results:

Putative identification was obtained for 499 chemicals in human serum. An aggregate analysis did not show any time x treatment interactions. However, our literature search identified 10 serum chemicals affected both by germ-free status and antibiotic treatment in the mouse or rat. Six of those chemicals were measured in our patient samples and additionally met criteria for inclusion in a focused analysis. Serum levels of 5 chemicals (p-cresol sulfate, phenol sulfate, hippurate, indole propionate, and indoxyl sulfate) declined significantly in our group of antibiotic-treated patients but did not change in our patient control group.

Conclusions:

Broad-spectrum antibiotic treatment in patients lowered serum levels of selected chemicals previously demonstrated to be GMB-sensitive in rodent models. Interestingly, all those chemicals are known to be uremic solutes that can be derived from aromatic amino acids (L-phenylalanine, L-tyrosine, or L-tryptophan) by anaerobic bacteria, particularly Clostridial species. We conclude that judiciously selected serum chemicals can reliably detect antibiotic-induced suppression of the GMB in man and thus facilitate further metabolome-based biomarker development.

Gut Microbial Metabolites of Aromatic Amino Acids as Signals in Host-Microbe Interplay

Gut microbial metabolism is intimately coupled with host health and disease. Aromatic amino acid (AAA) catabolism by the gut microbiome yields numerous metabolites that may regulate immune, metabolic, and neuronal responses at local and distant sites. Such a chemical dialog between host cells and the gut microbiome is shaped by environmental cues, and may become dysregulated in gastrointestinal and systems diseases. Increasing knowledge of the bacterial pathway and signaling basis may shed additional light on metabolic host-microbiome crosstalk that remains untapped for drug discovery. Here, we update our understanding of microbial AAA metabolism and its impacts on host physiology and disease. We also consider open questions related to therapeutically mining these signaling metabolites and how recent concepts and tools may drive this area forward.

Interactions Between Therapeutics for Metabolic Disease, Cardiovascular Risk Factors, and Gut Microbiota

With improved standards of living, the incidence of multiple metabolic disorders has increased year by year, especially major risk factors for cardiovascular disease such as hyperglycemia and hyperlipidemia, continues to increase. Emerging epidemiological data and clinical trials have shown the additional protective effects of some metabolic therapy drugs against cardiovascular diseases. A series of studies have found that these drugs may work by modulating the composition of gut microbiota. In this review, we provide a brief overview of the contribution of the gut microbiota to both metabolic disorders and cardiovascular diseases, as well as the response of gut microbiota to metabolic therapy drugs with cardiovascular benefits. In this manner, we link the recent advances in microbiome studies on metabolic treatment drugs with their cardiovascular protective effects, suggesting that intestinal microorganisms may play a potential role in reducing cardiovascular risk factors. We also discuss the potential of microorganism-targeted therapeutics as treatment strategies for preventing and/or treating cardiovascular disease and highlight the need to establish causal links between therapeutics for metabolic diseases, gut microbiota modulation, and cardiovascular protection.

The Role of the Gut Microbiota in Coronary Heart Disease

PURPOSE OF REVIEW

This review focuses on recent evidence examining the role gut microbiota play in coronary heart disease. It also provides a succinct overview of current and future therapies targeting the gut microbiota for coronary heart disease risk reduction.

RECENT FINDINGS

A consensus has been reached that differences exist in the gut microbiotas of patients with coronary heart disease. Studies have shown that the gut microbiota is associated with obesity, diabetes, dyslipidemia, and hypertension, which are risk factors for coronary heart disease. The gut microbiota is involved in mediating basic metabolic processes, such as cholesterol metabolism, uric acid metabolism, oxidative stress, and inflammatory reactions, through its metabolites, which can induce the development of atherosclerosis and coronary heart disease. Interfering with the composition of gut microbiota, supplementing probiotics, and fecal donation are active areas of research to potentially prevent and treat coronary heart disease. Gut microbiota are causally associated with coronary heart disease. We analyzed the gut microbiota's effects on risk factors for coronary heart disease and studied the effects of gut microbiota metabolites on coronary heart disease. Gut microbiota is a potential target for preventing and treating coronary heart disease.

Microbial Peer Pressure: The Role of the Gut Microbiota in Hypertension and Its Complications

There is increasing evidence of the influence of the gut microbiota on hypertension and its complications, such as chronic kidney disease, stroke, heart failure, and myocardial infarction. This is not surprising considering that the most common risk factors for hypertension, such as age, sex, medication, and diet, can also impact the gut microbiota. For example, sodium and fermentable fiber have been studied in relation to both hypertension and the gut microbiota. By combining second- and, now, third-generation sequencing with metabolomics approaches, metabolites, such as short-chain fatty acids and trimethylamine N-oxide, and their producers, have been identified and are now known to affect host physiology and the cardiovascular system. The receptors that bind these metabolites have also been explored with positive findings-examples include known short-chain fatty acid receptors, such as G-protein coupled receptors GPR41, GPR43, GPR109a, and OLF78 in mice. GPR41 and OLF78 have been shown to have inverse roles in blood pressure regulation, whereas GPR43 and GPR109A have to date been demonstrated to impact cardiac function. New treatment options in the form of prebiotics (eg, dietary fiber), probiotics (eg, Lactobacillus spp.), and postbiotics (eg, the short-chain fatty acids acetate, propionate, and butyrate) have all been demonstrated to be beneficial in lowering blood pressure in animal models, but the underlying mechanisms remain poorly understood and translation to hypertensive patients is still lacking. Here, we review the evidence for the role of the gut microbiota in hypertension, its risk factors, and cardiorenal complications and identify future directions for this exciting and fast-evolving field.

Gut microbes in cardiovascular diseases and their potential therapeutic applications

Microbial ecosystem comprises a complex community in which bacteria interact with each other. The potential roles of the intestinal microbiome play in human health have gained considerable attention. The imbalance of gut microbial community has been looked to multiple chronic diseases. Cardiovascular diseases (CVDs) are leading causes of morbidity worldwide and are influenced by genetic and environmental factors. Recent advances have provided scientific evidence that CVD may also be attributed to gut microbiome. In this review, we highlight the complex interplay between microbes, their metabolites, and the potential influence on the generation and development of CVDs. The therapeutic potential of using intestinal microbiomes to treat CVD is also discussed. It is quite possible that gut microbes may be used for clinical treatments of CVD in the near future.

Implications of gut microbiome on coronary artery disease

Despite the enormous progress achieved in diagnosis and medical therapy of coronary artery disease (CAD) in the last decades, CAD continues to represent the leading cause of morbidity and mortality worldwide, leading to a massive health-care cost and social burden. Due to the dynamic and complex nature of CAD, the mechanisms underlying the progression of atherosclerotic plaque were largely unknown. With the development of metagenomics and bioinformatics, humans are gradually understanding the important role of the gut microbiome on their hosts. Trillions of microbes colonize in the human gut, they digest and absorb nutrients, as well as participate in a series of human functions and regulate the pathogenesis of diseases, including the cardiovascular disease (CVD) that has received much attention. Meanwhile, metabolomics studies have revealed associations between gut microbiota-derived metabolic bioactive signaling modules, including trimethylamine-N-oxide (TMAO), short-chain fatty acids (SCFAs), and bile acids (BAs), with the progression of CAD. Disturbance of the gut microbiome and microbial metabolites are important factors leading to CAD, which has become a novel target for CAD prevention and treatment. This review provides a brief overview of gut microbiome composition in CAD patients according to the recently reported studies, summarizes the underlying mechanisms, and highlights the prognostic value of the gut microbiome in CAD.

Gut microbiota metabolites as integral mediators in cardiovascular diseases (Review)

Cardiovascular diseases (CVDs), such as atherosclerosis, hypertension, myocardial infarction and diabetic heart disease, are associated with high morbidity and mortality rates worldwide, and may also induce multiple organ failure in their later stages, greatly reducing the long-term survival of the patients. There are several causes of CVDs, but after nearly a decade of investigation, researchers have found that CVDs are usually accompanied by an imbalance of gut microbiota and a decreased abundance of flora. More importantly, the metabolites produced by intestinal flora, such as trimethylamine and trimethylamine N-oxide, bile acids, short-chain fatty acids and aromatic amino acids, exert different effects on the occurrence and development of CVDs, as observed in the relevant pathways in the cells, which may either promote or protect against CVD occurrence. It is known that changes in the intestinal flora following antibiotic administration, diet supplementation with probiotics, or exercise, can interfere with the composition of the intestinal flora and may represent an effective approach to preventing or treating CVDs. The focus of this review was the analysis of gut microbiota metabolites to elucidate their effects on CVDs and to identify the most cost-effective and beneficial methods for treating CVDs with minimal side effects.

Huoxin Pill Attenuates Cardiac Inflammation by Suppression of TLR4/NF-κB in Acute Myocardial Ischemia Injury Rats

Huoxin Pill (HXP), a traditional Chinese medicine, has been prescribed widely in the treatment of coronary heart disease, angina pectoris, and other diseases. However, the possible protective mechanisms of HXP on myocardial ischemia remain unclear. In the current study, we investigated the effects and potential mechanism of HXP on myocardial ischemia and cardiac inflammation and the activation of TLR4/NF-κB pathway. Determination of electrocardiogram, echocardiography, and heart weight index (HWI) indicated that HXP treatment obviously attenuated the elevation of ST-segment, end-diastolic volume, and HWI in the AMI rat model. Enzyme-linked immunosorbent assay (ELISA) demonstrated that Huoxin Pill treatment significantly decreased the levels of CTnT, CK-MB, MDA, IL-6, and TNF-α, while it increased SOD content in serum of the AMI rat model. Moreover, hematoxylin and eosin (HE) and immunohistochemistry (IHC) staining revealed that HXP treatment alleviated pathological change, infiltration of inflammatory cells, levels of IL-6 and TNF-α, and expression of TLR4 and p-NF-κB in cardiac tissues of the AMI rat model. In conclusion, HXP treatment significantly improves cardiac function and attenuates cardiac inflammation by suppressing the activation of TLR4/NF-κB pathway in the ISO-induced AMI rat model. This study provides insights into the potential of HXP on prevention and treatment of AMI.

Gut Microbiota and Heart, Vascular Injury

The gut microbiota plays an important role in maintaining human health. Accumulating evidence has indicated an intimate relationship between gut microbiota and cardiovascular diseases (CVD) which has become the leading cause of death worldwide. The alteration of gut microbial composition (gut dysbiosis) has been proven to contribute to atherosclerosis, the basic pathological process of CVD. In addition, the metabolites of gut microbiota have been found to be closely related to the development of CVD. For example, short-chain fatty acids are widely acclaimed beneficial effect against CVD, whereas trimethylamine-N-oxide is considered as a contributing factor in the development of CVD. In this chapter, we mainly discuss the gut microbial metabolite-involved mechanisms of CVD focusing on atherosclerosis, hypertension, diabetes, obesity, and heart failure. Targeting gut microbiota and related metabolites are novel and promising strategies for the treatment of CVD.

Targeting the human microbiome and its metabolite TMAO in cardiovascular prevention and therapy

The human gut microbiota is the most important active part of the intestinal micro-ecosystem. Lifestyle modification, drug intake and nutrition have an impact on the composition of the gut microbiota and its metabolites. This review focuses on the effects of changes in the gut microbiota as well as the important metabolite Trimethylamine-N-oxide (TMAO). Furthermore, relevant therapeutic options to target the human microbiome in patients with cardiovascular disease are presented.

The effect of probiotics supplementation on blood pressure: a systemic review and meta-analysis

Background

Fermented milk has over the last decade been intensively studied because of the putative antihypertensive effect. The aim of our study is to investigate the role of probiotics support therapy in blood pressure and, as a kind of convenient and economic drugs for prevention and auxiliary treatment of hypertension.

Materials and methods

We performed a systemic review and meta-analysis to examine the effect of probiotics consumption on blood pressure. Databases including MEDLINE, EMBASE, Clinical trials, CNKI and the Cochrane library were searched. Also, the grey literature and references were searched.

Results

Twenty-three randomized controlled trials (RCTs) involving 2037 participants met the inclusion criteria and were included. Probiotic consumption significantly changed systolic blood pressure (SBP) by − 3.05 mmHg (95%CI: − 4.67, − 1.44; P < 0.001) and diastolic blood pressure (DBP) by − 1.51 mmHg (95%CI: − 2.38, − 0.65; P = 0.001). Subgroup analysis indicated that the benefit effect of probiotics supplementation in SBP was only observed in hypertension [weight mean difference (WMD) = − 3.31 mmHg, 95%CI: − 5.71, − 0.92; P = 0.007] or type 2 diabetes (WMD = -4.85 mmHg, 95%CI: − 9.28, − 0.42; P = 0.032) patients, and the decreased DBP level by probiotics supplementation was only observed in hypertension patients (WMD = -2.02 mmHg, 95%CI: − 3.68, − 0.36; P = 0.017).This effect could only last for a short-term time of 8 or 10 weeks, but not for a long-term time.

Conclusion

This meta-analysis found a moderate and statistically significant reduction for either SBP or DBP with probiotics supplement compared with controls. Thus, probiotics is a potential for the dietary treatment of hypertension.

Bifidobacterium animalis subsp. lactis 420 for Metabolic Health: Review of the Research

The growing worldwide epidemic of obesity and associated metabolic health comorbidities has resulted in an urgent need for safe and efficient nutritional solutions. The research linking obesity with gut microbiota dysbiosis has led to a hypothesis that certain bacterial strains could serve as probiotics helping in weight management and metabolic health. In the search for such strains, the effect of Bifidobacterium animalis subsp. lactis 420 (B420) on gut microbiota and metabolic health, and the mechanisms of actions, has been investigated in a variety of in vitro, pre-clinical, and clinical studies. In this review, we aim to highlight the research on B420 related to obesity, metabolic health, and the microbiota. Current research supports the hypothesis that gut dysbiosis leads to an imbalance in the inflammatory processes and loss of epithelial integrity. Bacterial components, like endotoxins, that leak out of the gut can invoke low-grade, chronic, and systemic inflammation. This imbalanced state is often referred to as metabolic endotoxemia. Scientific evidence indicates that B420 can slow down many of these detrimental processes via multiple signaling pathways, as supported by mechanistic in vitro and in vivo studies. We discuss the connection of these mechanisms to clinical evidence on the effect of B420 in controlling weight gain in overweight and obese subjects. The research further indicates that B420 may improve the epithelial integrity by rebalancing a dysbiotic state induced by an obesogenic diet, for example by increasing the prevalence of lean phenotype microbes such as Akkermansia muciniphila. We further discuss, in the context of delivering the health benefits of B420: the safety and technological aspects of the strain including genomic characterization, antibiotic resistance profiling, stability in the product, and survival of the live probiotic in the intestine. In summary, we conclude that the clinical and preclinical studies on metabolic health suggest that B420 may be a potential candidate in combating obesity; however, further clinical studies are needed.

The intestinal microbiome potentially affects thrombin generation in human subjects

BACKGROUND

The intestinal microbiome plays a versatile role in the etiology of arterial thrombosis. In venous thrombosis, driven chiefly by plasma coagulation, no such role has yet been established. We hypothesized that the intestinal microbiome composition affects coagulation in humans.

METHODS

We used healthy donor fecal microbiota transplant (FMT) to experimentally change the microbiome composition in metabolic syndrome patients. Thirty-five subjects were randomized in a blinded fashion to healthy donor FMT or autologous FMT as a control in a 2:1 ratio. We measured thrombin generation at baseline and after 6 weeks using automated calibrated thrombinography, and we determined plasma abundance of 32 coagulation related proteins using a targeted mass spectrometry-based quantitative proteomics assay with heavy labeled internal standards.

RESULTS

Healthy donor FMT prolonged the thrombinography lag time (median delta 0.0 versus 0.25 minutes, P = .039). The other thrombinography parameters showed no significant difference. Unsupervised cluster analysis suggested overall downregulation of coagulation related plasma proteins in subject clusters containing predominantly subjects that had a metabolic response to healthy donor FMT. FMT treatment status itself showed no clear clustering pattern with up- or downregulation, however, and proteins did not cluster according to an apparent biological grouping.

DISCUSSION

A single healthy donor FMT tends to modestly suppress the onset thrombin generation in metabolic syndrome patients, representing initial proof-of-principle that the intestinal microbiota composition might affect the coagulation system in humans. The findings merit external validation as a role for intestinal microbiota in coagulation can have clinically important implications.

Gut microbial taxa as potential predictive biomarkers for acute coronary syndrome and post-STEMI cardiovascular events

Plasma trimethylamine N-oxide (TMAO) is associated with coronary atherosclerotic plaque and cardiovascular disease risk, but associations between gut microbes in acute coronary syndrome (ACS) and post-ST-segment elevation myocardial infarction (post-STEMI) events are unknown. We investigated associations between gut microbial taxa and systemic TMAO levels and the possible TMAO contribution to incident post-STEMI cardiovascular events.

PATIENTS AND METHODS

A total of 60 patients, including 30 with unstable angina pectoris (UAP), 30 post-STEMI and 30 healthy controls, were enrolled from June to November 2017. Metagenomic sequencing was performed and TMAO and IL-6 were detected.

RESULTS

Minimal discriminators of gut microbial taxa (top 40) distinguished ACS patients from controls. Serum TMAO levels were positively associated with increased abundance of Aerococcaceae, Ruminococcaceae_UCG.005, Ruminococcaceae_UCC.014 and X. Eubacterium_fissicatena, and decreased abundance of Lachnospiraceae_FCS020 (P < 0.05). Elevated serum TMAO levels correlated independently with ACS (P < 0.05). Risk stratification for incident major adverse cardiovascular events (MACE) improved at one year in patients with serum TMAO levels ≦2.19 µM. Serum interleukin-6 levels were not significantly increased in patients with ACS and post-STEMI MACE.

CONCLUSIONS

ACS and incident post-STEMI MACE may be associated with the gut bacteria choline metabolite TMAO. The specific gut microbial taxa identified in association with serum TMAO levels may be potential predictive biomarkers for accurate diagnosis of ACS onset.

The gut microbiome in coronary artery disease and heart failure: Current knowledge and future directions

Host-microbiota interactions involving inflammatory and metabolic pathways have been linked to the pathogenesis of multiple immune-mediated diseases and metabolic conditions like diabetes and obesity. Accumulating evidence suggests that alterations in the gut microbiome could play a role in cardiovascular disease. This review focuses on recent advances in our understanding of the interplay between diet, gut microbiota and cardiovascular disease, with emphasis on heart failure and coronary artery disease. Whereas much of the literature has focused on the circulating levels of the diet- and microbiota-dependent metabolite trimethylamine-N-oxide (TMAO), several recent sequencing-based studies have demonstrated compositional and functional alterations in the gut microbiomes in both diseases. Some microbiota characteristics are consistent across several study cohorts, such as a decreased abundance of microbes with capacity for producing butyrate. However, the published gut microbiota studies generally lack essential covariates like diet and clinical data, are too small to capture the substantial variation in the gut microbiome, and lack parallel plasma samples, limiting the ability to translate the functional capacity of the gut microbiomes to actual function reflected by circulating microbiota-related metabolites. This review attempts to give directions for future studies in order to demonstrate clinical utility of the gut-heart axis.

Describing the fecal metabolome in cryogenically collected samples from healthy participants

The chemical composition of feces plays an important role in human metabolism. Metabolomics and lipidomics are valuable tools for screening the metabolite composition in feces. Here we set out to describe fecal metabolite composition in healthy participants in frozen stools. Frozen stool samples were collected from 10 healthy volunteers and cryogenically drilled in four areas along the specimen. Polar metabolites were analyzed using derivatization followed by two-dimensional gas chromatography and time of flight mass spectrometry. Lipids were detected using ultra high-performance liquid chromatography coupled with quadruple time-of-flight mass spectrometry. 2326 metabolic features were detected. Out of a total of 298 metabolites that were annotated we report here 185 that showed a technical variation of x < 30%. These metabolites included amino acids, fatty acid derivatives, carboxylic acids and phenolic compounds. Lipids predominantly belonged to the groups of diacylglycerols, triacylglycerols and ceramides. Metabolites varied between sampling areas, some were broadly homogeneous, others varied 80%. A LASSO-computed network using metabolites present in all areas showed two main clusters describing the system, DAG lipids and phenyllactic acid. In feces from healthy participants, the main groups detected were phenolic compounds, ceramides, diacylglycerols and triacylglycerols.

Effects of tetracycline on myocardial infarct size in obese rats with chemically-induced colitis

Background

Recent evidence suggests that antibiotic-induced changes in the composition of intestinal microflora, as well as the systemic immunoendocrine effects that result from them, can modulate myocardial tolerance to ischemia-reperfusion injury. The aim of this study was to investigate the effects of tetracycline (TTC) on myocardial infarct size in the isolated hearts obtained from obese rats with chemically-induced colitis (CIC). The association between TTC-induced changes in infarct size and intestinal microbiome composition as well as plasma levels of cytokines and short-chain fatty acids (SCFAs) was also studied.

Methods

Obesity was induced in Wistar rats by feeding them a high-fat, high-carbohydrate diet for five weeks. A single rectal administration of 3% acetic acid (2 mL) to the rats resulted in CIC. Healthy rats as well as obese rats with CIC received TTC (15 mg daily for 3 days) via gavage. The rats were euthanized, after which isolated heart perfusion with simulated global ischemia and reperfusion was performed. Infarct size was determined histochemically. Lipopolysaccharide (LPS) and cytokine levels in plasma were measured by enzyme-linked immunosorbent assay, whereas SCFA levels in plasma were measured by gas chromatography/mass spectrometry. The intestinal microbiome was analyzed using reverse transcription polymerase chain reaction.

Results

The treatment with TTC resulted in significant infarct size limitation (50 ± 7 vs. 62 ± 4% for the control mice, p < 0.05) in the hearts from intact animals. However, infarct size was not different between the control rats and the obese rats with CIC. Furthermore, infarct size was significantly larger in TTC-treated obese rats with CIC than it was in the control animals (77 ± 5%, p < 0.05). The concentrations of proinflammatory cytokines and LPS in serum were elevated in the obese rats with CIC. Compared to the control rats, the rats with both obesity and CIC had lower counts of Lactobacillus and Bifidobacterium spp. but higher counts of Escherichia coli. The effects of TTC on infarct size were not associated with specific changes in SCFA levels.

Conclusions

TTC reduced infarct size in the healthy rats. However, this effect was reversed in the obese animals with CIC. Additionally, it was associated with specific changes in gut microbiota and significantly elevated levels of cytokines and LPS.

Involvement of Aromatic Metabolites in the Pathogenesis of Septic Shock

INTRODUCTION

We hypothesized that aromatic microbial metabolites (AMM), such as phenyllactic (PhLA), p-hydroxyphenylacetic (p-HPhAA), and p-hydroxyphenyllactic (p-HPhLA) acids, contribute to the pathogenesis of septic shock.

METHODS

Clinical and laboratory data of patients with community-acquired pneumonia were obtained on intensive care unit admission and the next day. Patients were divided into two groups based on septic shock presence or absence. The levels of AMM (PhLA, p-HPhAA, p-HPhLA, and their sum, ∑3AMM), catecholamine metabolites (3,4-dihydroxymandelic [DHMA], 3,4-dihydroxyphenylacetic [DOPAC], and homovanillic [HVA] acids), lactate, N-terminal pro-brain natriuretic peptide (NT-proBNP), inducible nitric oxide synthase (iNOS), and procalcitonin (PCT) were compared. Correlations between AMM and clinical and laboratory data were calculated.

RESULTS

There were 20 patients in the septic shock group and 21 in the nonseptic shock group. On admission, the septic shock patients demonstrated significantly higher levels of PhLA (2.3 vs. 0.8 μmol/L), p-HPhAA (4.6 vs. 1.4 μmol/L), p-HPhLA (7.4 vs. 2.6 μmol/L), HVA, lactate, and significantly lower levels of iNOS. The next day, the two groups also showed significant differences in the levels of PCT and NT-proBNP. The correlation between ∑3AMM and presence of shock, levels of lactate, HVA, and NT-proBNP on admission was 0.44, 0.67, 0.57, and 0.38, respectively, and the correlation on the next day was 0.59, 0.73, 0.76, and 0.6, respectively (P < 0.01). These findings can be explained by the ability of AMM to reduce tyrosine hydroxylase activity, thus limiting the synthesis of catecholamines.

CONCLUSIONS

AMM are involved in the pathogenesis of septic shock.

Gut microbiota regulates cardiac ischemic tolerance and aortic stiffness in obesity

The gut microbiota has emerged as an important regulator of host physiology, with recent data suggesting a role in modulating cardiovascular health. The present study determined if gut microbial signatures could transfer cardiovascular risk phenotypes between lean and obese mice using cecal microbiota transplantation (CMT). Pooled cecal contents collected from obese leptin-deficient (Ob) mice or C57Bl/6j control (Con) mice were transplanted by oral gavage into cohorts of recipient Ob and Con mice maintained on identical low-fat diets for 8 wk (n = 9-11/group). Cardiovascular pathology was assessed as the degree of arterial stiffness (aortic pulse wave velocity) and myocardial infarct size following a 45/120 min ex vivo global cardiac ischemia-reperfusion protocol. Gut microbiota was characterized by 16S rDNA sequencing, along with measures of intestinal barrier function and cecal short-chain fatty acid (SCFA) composition. Following CMT, the gut microbiota of recipient mice was altered to resemble that of the donors. Ob CMT to Con mice increased arterial stiffness, left ventricular (LV) mass, and myocardial infarct size, which were associated with greater gut permeability and reduced cecal SCFA concentrations. Conversely, Con CMT to Ob mice increased cecal SCFA, reduced LV mass, and attenuated myocardial infarct size, with no effects on gut permeability or arterial stiffness. Collectively, these data demonstrate that obesity-related changes in the gut microbiota, independent of dietary manipulation, regulate hallmark measures of cardiovascular pathology in mice and highlight the potential of microbiota-targeted therapeutics for reducing cardiovascular pathology and risk in obesity.NEW & NOTEWORTHY These data are the first to demonstrate that cecal microbiota transplantation (CMT) can alter cardiovascular pathology in lean and obese mice independent from alterations in dietary intake. Myocardial infarct size was reduced in obese mice receiving lean CMT and worsened in lean mice receiving obese CMT. Lean mice receiving obese CMT also displayed increased aortic stiffness. These changes were accompanied by alterations in short-chain fatty acids and gut permeability.

Current understanding of gut microbiota alterations and related therapeutic intervention strategies in heart failure

OBJECTIVE

The purpose of this review is to stress the complicated interactions between the microbiota and the development of heart failure. Moreover, the feasibility of modulating intestinal microbes and metabolites as novel therapeutic strategies is discussed.

DATA SOURCES

This study was based on data obtained from PubMed up to March 31, 2019. Articles were selected using the following search terms: "gut microbiota," "heart failure," "trimethylamine N-oxide (TMAO)," "short-chain fatty acid (SCFA)," "bile acid," "uremic toxin," "treatment," "diet," "probiotic," "prebiotic," "antibiotic," and "fecal microbiota transplantation."

RESULTS

Accumulated evidence has revealed that the composition of the gut microbiota varies obviously in people with heart failure compared to those with healthy status. Altered gut microbial communities contribute to heart failure through bacterial translocation or affecting multiple metabolic pathways, including the trimethylamine/TMAO, SCFA, bile acid, and uremic toxin pathways. Meanwhile, modulation of the gut microbiota through diet, pre/probiotics, fecal transplantation, and microbial enzyme inhibitors has become a potential therapeutic approach for many metabolic disorders. Specifically, a few studies have focused on the cardioprotective effects of probiotics on heart failure.

CONCLUSIONS

The composition of the gut microbiota in people with heart failure is different from those with healthy status. A reduction in SCFA-producing bacteria in patients with heart failure might be a notable characteristic for patients with heart failure. Moreover, an increase in the microbial potential to produce TMAO and lipopolysaccharides is prominent. More researches focused on the mechanisms of microbial metabolites and the clinical application of multiple therapeutic interventions is necessarily required.

Cecal Gut Microbiota and Metabolites Might Contribute to the Severity of Acute Myocardial Ischemia by Impacting the Intestinal Permeability, Oxidative Stress, and Energy Metabolism

Emerging evidence highlights the role of gut microbiota in regulating the pathogenesis of coronary heart disease. Here, we performed 16S rRNA gene sequencing and UPLC-Q-TOF/MS-based metabolomics to investigate the gut microbiome and metabolomes of cecal contents in the isoproterenol (ISO)-induced acute myocardial ischemia (AMI) rats. As expected, considerable gut microbiota alterations were observed in the AMI rats compared with the control rats, paralleling with intestinal inflammation and apoptosis. At phylum level, the abundance of Firmicutes was significantly decreased, whereas the abundance of Bacteroidetes and Spirochaetae was strikingly enriched in the AMI group. At genus level, the significant alteration of genera Treponema 2, Rikenellaceae RC9 gut group, Prevotellaceae UCG-003, and Bacteroides may contribute to the pathogenesis of AMI. These altered microbiota might influence the intestinal permeability and subsequently impair intestinal barrier and stimulate gut inflammation. Consistently, significantly metabolic differences of cecal contents between the AMI and control groups were revealed, and threonic acid, L-urobilin and L-urobilinogen were considered the most associated cecal metabolites with AMI. These strikingly altered metabolites were mainly related to energy metabolism and oxidative stress which could lead to apoptosis and further affect gut barrier. Ultimately, we revealed the potential link of these altered gut microbiota/metabolomes and intestinal inflammatory factors and apoptotic proteins and further confirmed their intimate connections with intestinal inflammation and gut barrier. Our findings depict uncovered potential relationship among the gut microbiome, cecal metabolomes and AMI.

The Role of the Microbiota in the Diabetic Peripheral Artery Disease

Vascular complications of diabetes mellitus represent a major public health problem. Although many steps forward have been made to define the causes and to find the best possible therapies, the problem remains crucial. In recent years, more and more evidences have defined a link between microbiota and the initiation, promotion, and evolution of atherosclerotic disease, even in the diabetic scenario. There is an urgency to develop the knowledge of modern medicine about the link between gut microbiota and its host's metabolic pathways, and it would be useful to understand and justify the interindividual diversity of clinical disease presentation of diabetic vascular complication even if an optimization of pharmacological treatment has been made or in the case of young patients where hypertension, dyslipidemia, and diabetes are not able to justify a very quick progress of atherosclerotic process. The aim of the present review is to gather all the best available evidence in this regard and to define a new role of the microbiota in this field, from biomarker to possible therapeutic target.

Effect of Antiobiotic-Induced Disbiosis and Its Correction with Probiotics on Myocardial Tolerance to Ischemia-Reperfusion Injury in SPF Rats

Changes in morphofunctional parameters of the isolated heart subjected to global ischemia-reperfusion were studied in SPF Wistar rats with antibiotic-induced dysbiosis (AID) treated with lyophilized yeast Saccharomyces boulardii and inactivated probiotic bacteria Lactobacillus reuteri KR2017. In contrast to S. boulardii, correction of dysbiosis with L. reuteri KR2017 against the background of gastric hypersecretion and standard antimicrobial therapy led to an increase in fat content and a decrease in free and bound water in tissues and to a significant reduction in myocardial infarct size caused by ischemia/ reperfusion injury.

Endocrine organs of cardiovascular diseases: Gut microbiota

Gut microbiota (GM) is a collection of bacteria, fungi, archaea, viruses and protozoa, etc. They inhabit human intestines and play an essential role in human health and disease. Close information exchange between the intestinal microbes and the host performs a vital role in digestion, immune defence, nervous system regulation, especially metabolism, maintaining a delicate balance between itself and the human host. Studies have shown that the composition of GM and its metabolites are firmly related to the occurrence of various diseases. More and more researchers have demonstrated that the intestinal microbiota is a virtual 'organ' with endocrine function and the bioactive metabolites produced by it can affect the physiological role of the host. With deepening researches in recent years, clinical data indicated that the GM has a significant effect on the occurrence and development of cardiovascular diseases (CVD). This article systematically elaborated the relationship between metabolites of GM and its effects, the relationship between intestinal dysbacteriosis and cardiovascular risk factors, coronary heart disease, myocardial infarction, heart failure and hypertension and the possible pathogenic mechanisms. Regulating the GM is supposed to be a potential new therapeutic target for CVD.

Hypoxia evokes increased PDI and PDIA6 expression in the infarcted myocardium of ex-germ-free and conventionally raised mice

The prototypic protein disulfide isomerase (PDI), encoded by the P4HB gene, has been described as a survival factor in ischemic cardiomyopathy. However, the role of protein disulfide isomerase associated 6 (PDIA6) under hypoxic conditions in the myocardium remains enigmatic, and it is unknown whether the gut microbiota influences the expression of PDI and PDIA6 under conditions of acute myocardial infarction. Here, we revealed that, in addition to the prototypic PDI, the PDI family member PDIA6, a regulator of the unfolded protein response, is upregulated in the mouse cardiomyocyte cell line HL-1 when cultured under hypoxia. In vivo, in the left anterior descending artery (LAD) ligation mouse model of acute myocardial infarction, similar to PDI, PDIA6 protein expression was enhanced in the infarcted area (LAD+) relative to uninfarcted sham tissue or the neighbouring area at risk (LAD–) of C57BL/6J mice. Interestingly, we found that ex-germ-free (ex-GF) mice subjected to the LAD ligation model for 24 h had a reduced ejection fraction compared with their conventionally raised (CONV-R) SPF controls. Furthermore, the LAD+ area in the infarcted heart of ex-GF mice showed reduced PDIA6 expression relative to CONV-R controls, suggesting that the presence of a gut microbiota enhanced LAD ligation-triggered PDIA6 expression. Collectively, our results demonstrate that PDIA6 is upregulated in cardiomyocytes as a consequence of hypoxia. In the LAD mouse model, PDIA6 was also increased in the infarcted area under in vivo conditions, but this increase was suppressed in ex-GF mice relative to CONV-R controls.

This article has an associated First Person interview with the first author of the paper.

Summary: We identified PDIA6 as a hypoxia-induced element of the unfolded protein response in cardiomyocytes and infarcted mouse hearts. PDIA6 expression and ejection fractions were reduced in infarcted ex-germ-free mouse hearts.

Gut microbiota in common elderly diseases affecting activities of daily living

Gut microbiota are involved in the development or prevention of various diseases such as type 2 diabetes, fatty liver, and malignancy such as colorectal cancer, breast cancer and hepatocellular carcinoma. Alzheimer’s disease, osteoporosis, sarcopenia, atherosclerotic stroke and cardiovascular disease are major diseases associated with decreased activities of daily living (ADL), especially in elderly people. Recent analyses have revealed the importance of gut microbiota in the control of these diseases. The composition or diversity of these microbiota is different between patients with these conditions and healthy controls, and administration of probiotics or prebiotics has been shown effective in the treatment of these diseases. Gut microbiota may affect distant organs through mechanisms that include regulating the absorption of nutrients and/or the production of microbial metabolites, regulating and interacting with the systemic immune system, and translocating bacteria/bacterial products through disrupted mucosal barriers. Thus, the gut microbiota may be important regulators in the development of diseases that affect ADL. Although adequate exercise and proper diet are important for preventing these diseases, their combination with interventions that manipulate the composition and/or diversity of gut microbiota could be a promising strategy for maintaining health condition and preserving ADL. This review thus summarizes current understanding of the role of gut microbiota in the development or prevention of diseases closely associated with the maintenance of ADL.

Interaction between gut microbiome and cardiovascular disease

Traditional cardiovascular risk factors do not underlie all incidence of cardiovascular disease. In recent years, accumulating evidence has demonstrated that gut microbiota and its metabolites also play a pivotal role in the onset and development of cardiovascular disease, including atherosclerosis, hypertension, heart failure, atrial fibrillation and myocardial fibrosis. Trillions of bacteria indwell the gastrointestinal tract and metabolize nutrients into trimethylamine-N-oxide, short-chain fatty acids and so on. Targeting these microorganisms and relevant metabolic pathways has beneficial effects in cardiovascular disease. This review will summarize the role of gut microbiota and its metabolites, mainly trimethylamine-N-oxide, in the pathogenesis of cardiovascular diseases, and discuss the possible mechanisms that drive cardiovascular diseases and highlight potential therapies in this field.

Gut Microbiome in Critical Illness (Review)

Radical changes in the composition, diversity and metabolic activity of gut microbiome in critically ill patients most probably affect adversely the outcome of treatment. Microbiota dysfunction may be a predictor and presumably the main cause of infectious complications and sepsis. Clinicists use objective scales for evaluation of patient condition severity including specific parameters of disorders of organs and systems; however, microbiota function is not considered specific and, hence, not evaluated. Technical capabilities of the recent decade have allowed characterizing the intestinal microbiota and that helped understanding the ongoing processes. The authors have analyzed data about the role of intestinal microbiota as a metabolic 'reactor' during critical states, possible complications related to misbalance of 'harmful' and 'beneficial' bacteria, and examined potential of a targeted therapy aimed directly at correction of intestinal microbiota. Search for papers was carried out using Scopus and Web of Science databases 2001 to 2018 years: (Gut Microbiota) AND (Critically ill OR Intensive care unit), key words taken for the search were: intestinal microbiota, metabolism, sepsis, antibiotics, critically ill patients, multiple organ failure. A number of questions in understanding of the interaction between gut microbiome and host remain open. It is necessary to take into account interference of microbial metabolism while assessing metabolome of patients with sepsis. Among low-molecular compounds found in blood of sepsis patients, special attention should be paid to molecules that can be classified as ‘common metabolites’ of humans and bacteria, for example, degradation products of aromatic compounds, which many-fold rise in blood of septic patients. It is necessary to take into consideration and experimentally model changes in the human internal environment, which occur during radical transformation of microbiome in critically ill patients. Such approach brings in new prospects for objective monitoring of diseases by evaluating metabolic profile at a particular moment of time based on integral indices reflecting the status of microbiome/metabolome system, which will supply new targets for therapeutic intervention in future.

Single and multiple cardiovascular biomarkers in subjects without a previous cardiovascular event

Aims To assess the incremental value of biomarkers, including N-terminal prohormone of brain natriuretic peptide (NT-proBNP), high-sensitivity troponin T (hs-TnT), high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), growth differentiation factor 15 (GDF-15), and procollagen type 1 N-terminal propeptide (P1NP), in predicting incident cardiovascular events and mortality among asymptomatic individuals from the general population, beyond traditional risk factors, including fasting glucose and renal function (cystatin C), medication use, and echocardiographic measures. Methods and results Prospective population-based cohort study of 1324 subjects without a previous cardiovascular event, who underwent baseline echocardiography and biomarker assessment between 2002 and 2006. The clinical endpoint was the composite of myocardial infarction, invasively treated stable/unstable ischemic heart disease, heart failure, stroke, or all-cause mortality. Predictive capabilities were evaluated using Cox proportional-hazards regression, Harrell's concordance index (C-index), and net reclassification improvement. Median age was 66 (interquartile range: 60-70) years, and 413 (31%) were female. During median 8.6 (interquartile range: 8.1-9.2) follow-up years, 368 (28%) composite events occurred. NT-proBNP, hs-TnT, GDF-15, and IL-6 were significantly associated with outcome, independently of traditional risk factors, medications, and echocardiography ( p < 0.05 for all). Separate addition of NT-proBNP and GDF-15 to traditional risk factors, medications, and echocardiographic measurements provided significant improvements in discriminative ability (NT-proBNP: C-index 0.714 vs. 0.703, p = 0.03; GDF-15: C-index 0.721 vs. 0.703, p = 0.02). Both biomarkers remained significant predictors of outcome upon inclusion in the same model ( p < 0.05 for both). Conclusions NT-proBNP and GDF-15 each enhance prognostication beyond traditional risk factors, glucose levels, renal function, and echocardiography in individuals without known cardiovascular disease.

Gut Microbiota in Cardiovascular Health and Disease

Significant interest in recent years has focused on gut microbiota-host interaction because accumulating evidence has revealed that intestinal microbiota play an important role in human health and disease, including cardiovascular diseases. Changes in the composition of gut microbiota associated with disease, referred to as dysbiosis, have been linked to pathologies such as atherosclerosis, hypertension, heart failure, chronic kidney disease, obesity, and type 2 diabetes mellitus. In addition to alterations in gut microbiota composition, the metabolic potential of gut microbiota has been identified as a contributing factor in the development of diseases. Recent studies revealed that gut microbiota can elicit a variety of effects on the host. Indeed, the gut microbiome functions like an endocrine organ, generating bioactive metabolites, that can impact host physiology. Microbiota interact with the host through many pathways, including the trimethylamine/trimethylamine N-oxide pathway, short-chain fatty acids pathway, and primary and secondary bile acids pathways. In addition to these metabolism-dependent pathways, metabolism-independent processes are suggested to also potentially contribute to cardiovascular disease pathogenesis. For example, heart failure-associated splanchnic circulation congestion, bowel wall edema, and impaired intestinal barrier function are thought to result in bacterial translocation, the presence of bacterial products in the systemic circulation and heightened inflammatory state. These are thought to also contribute to further progression of heart failure and atherosclerosis. The purpose of the current review is to highlight the complex interplay between microbiota, their metabolites, and the development and progression of cardiovascular diseases. We will also discuss the roles of gut microbiota in normal physiology and the potential of modulating intestinal microbial inhabitants as novel therapeutic targets.

Bile acids at the cross-roads of gut microbiome-host cardiometabolic interactions

While basic and clinical research over the last several decades has recognized a number of modifiable risk factors associated with cardiometabolic disease progression, additional and alternative biological perspectives may offer novel targets for prevention and treatment of this disease set. There is mounting preclinical and emerging clinical evidence indicating that the mass of metabolically diverse microorganisms which inhabit the human gastrointestinal tract may be implicated in initiation and modulation of cardiovascular and metabolic disease outcomes. The following review will discuss this gut microbiome-host metabolism axis and address newly proposed bile-mediated signaling pathways through which dysregulation of this homeostatic axis may influence host cardiovascular risk. With a central focus on the major nuclear and membrane-bound bile acid receptor ligands, we aim to review the putative impact of microbial bile acid modification on several major phenotypes of metabolic syndrome, from obesity to heart failure. Finally, attempting to synthesize several separate but complementary hypotheses, we will review current directions in preclinical and clinical investigation in this evolving field.

Gut Bacteria and Hydrogen Sulfide: The New Old Players in Circulatory System Homeostasis

Accumulating evidence suggests that gut bacteria play a role in homeostasis of the circulatory system in mammals. First, gut bacteria may affect the nervous control of the circulatory system via the sensory fibres of the enteric nervous system. Second, gut bacteria-derived metabolites may cross the gut-blood barrier and target blood vessels, the heart and other organs involved in the regulation of the circulatory system. A number of studies have shown that hydrogen sulfide (H₂S) is an important biological mediator in the circulatory system. Thus far, research has focused on the effects of H₂S enzymatically produced by cardiovascular tissues. However, some recent evidence indicates that H₂S released in the colon may also contribute to the control of arterial blood pressure. Incidentally, sulfate-reducing bacteria are ubiquitous in mammalian colon, and H₂S is just one among a number of molecules produced by the gut flora. Other gut bacteria-derived compounds that may affect the circulatory system include methane, nitric oxide, carbon monoxide, trimethylamine or indole. In this paper, we review studies that imply a role of gut microbiota and their metabolites, such as H₂S, in circulatory system homeostasis.