Trimethylamine N-Oxide: A Link among Diet, Gut Microbiota, Gene Regulation of Liver and Intestine Cholesterol Homeostasis and HDL Function

T329S Mutation in the FMO3 Gene Alleviates Lipid Metabolic Diseases in Chickens in the Late Laying Period

Simple Summary

The lipid deposition and health status of egg-laying hens is crucial to the development of the poultry industry. This study aimed to evaluate the effects of genetic variations in the flavin-containing monooxygenase 3 (FMO3) on the lipid metabolic diseases of laying hens during the late laying period. The results showed that the T329S mutation in FMO3 moderated the lipid parameters and decreased the atherosclerotic lesions and hepatic steatosis in laying hens with homozygous T329S mutation. In conclusion, the T329S mutation in FMO3 is closely associated with the improvement of lipid metabolic diseases in laying hens during the late laying period. The results of this study may contribute to overcoming the challenge of lipid metabolic diseases in laying hens during the late laying period.

Abstract

The T329S mutation in flavin-containing monooxygenase 3 (FMO3) impairs the trimethylamine (TMA) metabolism in laying hens. The TMA metabolic pathway is closely linked to lipid metabolic diseases, such as atherosclerosis and fatty liver disease. We aimed to evaluate the effects of the T329S mutation in FMO3 on lipid metabolism in chickens during the late laying period. We selected 18 FMO3 genotyped individuals (consisting of six AA, six AT, and six TT hens) with similar body weight and production performance. The lipid metabolism and deposition characteristics of the laying hens with different genotypes were compared. The T329S mutation moderated the serum-lipid parameters in TT hens compared to those in AA and AT hens from 49 to 62 weeks. Furthermore, it reduced the serum trimethylamine N-oxide concentrations and increased the serum total bile acid (p < 0.05) and related lipid transporter levels in TT hens. Moreover, it significantly (p < 0.01) decreased atherosclerotic lesions and hepatic steatosis in TT hens compared to those in the AA and AT hens. Our findings may help improve the health status in laying hens during the late laying period.

Gut Metabolite Trimethylamine N-Oxide Protects INS-1 β-Cell and Rat Islet Function under Diabetic Glucolipotoxic Conditions

Serum accumulation of the gut microbial metabolite trimethylamine N-oxide (TMAO) is associated with high caloric intake and type 2 diabetes (T2D). Impaired pancreatic β-cell function is a hallmark of diet-induced T2D, which is linked to hyperglycemia and hyperlipidemia. While TMAO production via the gut microbiome-liver axis is well defined, its molecular effects on metabolic tissues are unclear, since studies in various tissues show deleterious and beneficial TMAO effects. We investigated the molecular effects of TMAO on functional β-cell mass. We hypothesized that TMAO may damage functional β-cell mass by inhibiting β-cell viability, survival, proliferation, or function to promote T2D pathogenesis. We treated INS-1 832/13 β-cells and primary rat islets with physiological TMAO concentrations and compared functional β-cell mass under healthy standard cell culture (SCC) and T2D-like glucolipotoxic (GLT) conditions. GLT significantly impeded β-cell mass and function by inducing oxidative and endoplasmic reticulum (ER) stress. TMAO normalized GLT-mediated damage in β-cells and primary islet function. Acute 40µM TMAO recovered insulin production, insulin granule formation, and insulin secretion by upregulating the IRE1α unfolded protein response to GLT-induced ER and oxidative stress. These novel results demonstrate that TMAO protects β-cell function and suggest that TMAO may play a beneficial molecular role in diet-induced T2D conditions.

Predictive values of serum metabolites in early pregnancy and their possible pathways for gestational diabetes: A nested case-control study in Tianjin, China

AIMS

To investigate the associations and predictive values of serum metabolites in early pregnancy for later development of gestational diabetes mellitus (GDM), and further explore their metabolic pathways to GDM.

METHODS

We conducted a 1:1 nested case-control study including 486 pregnant women from Tianjin, China, and collected blood samples at their first registration (median at 10th gestational week). Liquid chromatography-tandem mass spectrometry was used to measure serum metabolites. Orthogonal partial least squares discriminant analysis was used to select specific metabolites associated with GDM, and pathway analysis was used to identify the metabolic pathways related to GDM.

RESULTS

A total of 64 serum metabolites were included in this analysis, 17 of which were identified as specific metabolites associated with GDM. Ten metabolites increased and seven metabolites decreased GDM risk. Inclusion of these specific metabolites to the model of traditional risk factors greatly increased the predictive value from 0.69 (95% confidence interval: 0.64-0.74) to 0.92 (0.90-0.95). In addition, we found that glycerophospholipid metabolism, sphingolipid metabolism and primary bile acid biosynthesis were main metabolic pathways related to GDM.

CONCLUSION

We identified a set of serum metabolites and their metabolic pathways in early pregnancy associated with GDM, which provided a theoretical basis for further research on the molecular pathways to GDM and early identification of GDM.

Serum lysophospholipidome of dietary origin as a suitable susceptibility/risk biomarker of human hypercholesterolemia: A cross-sectional study

BACKGROUND & AIMS

Whether bioactive lysophospholipids (lyso-PLs) and trimethylamine-N-oxide (TMAO) serve as non-invasive biomarkers in early human hypercholesterolemia (HC) is unknown. This study aimed to assess whether serum lyso-PLs and plasma TMAO may be suitable susceptibility/risk biomarkers of HC in humans. Secondarily, we aimed to evaluate the relationships between targeted metabolites, diet composition and circulating liver transaminases, and verify these results in hamsters.

METHODS

A targeted metabolomics and lipidomics approach determined plasma TMAO and serum lysophosphatidylcholines (lyso-PCs) and lysophosphatidylethanolamines (lyso-PEs) in low (L-LDL-c) and moderate to high (MH-LDL-c) LDL-cholesterol subjects. Additionally, the relationships between targeted metabolites, liver transaminases and diet, particularly fatty acid intake, were tested. In parallel, plasma and liver lyso-PL profiles were studied in 16 hamsters fed a moderate high-fat (HFD) or low-fat (LFD) diet for 30 days.

RESULTS

Predictive models identified lyso-PC15:0 and lyso-PE18:2 as the most discriminant lyso-PLs among groups. In MH-LDL-c (n = 48), LDL-cholesterol and saturated FAs were positively associated with lyso-PC15:0, whereas in L-LDL-c (n = 70), LDL-cholesterol and polyunsaturated fatty acids (PUFAs) were negatively and positively related to lyso-PE18:2, respectively. Interestingly, in MH-LDL-c, the lower lyso-PE 18:2 concentrations were indicative of higher LDL-cholesterol levels. Intrahepatic accumulation of lyso-PLs-containing essential n-6 PUFAs, including lyso-PE18:2, were higher in HFD-fed hamsters than LFD-fed hamsters.

CONCLUSIONS

Overall, results revealed a possible hepatic adaptive mechanism to counteract diet-induced steatosis in animal and hypercholesterolemia progression in humans. In particular, low serum lyso-PE18:2 suggests a suitable susceptibility/risk biomarker of HC in humans.

Are eggs good again? A precision nutrition perspective on the effects of eggs on cardiovascular risk, taking into account plasma lipid profiles and TMAO

Although eggs are a nutrient dense food delivering high quality protein and micronutrients, given that eggs are also rich in cholesterol and choline, whether egg intake is contraindicated for individuals at risk for cardiovascular disease (CVD) remains controversial. In this mini review, we provide a Precision Nutrition perspective, highlighting the importance of two factors: the effect of egg cholesterol on plasma cholesterol concentrations in most people and in cholesterol hyper-absorbers, and the effect of egg choline on plasma concentrations of trimethylamine-N-oxide (TMAO), a microbe-host co-metabolite independently associated with increased CVD risk. We discuss recent evidence from intervention studies showing that in most individuals egg intake does not have a deleterious effect on plasma lipid profiles, but also highlight that some individuals are cholesterol hyper-absorbers or individuals who are not able to maintain cholesterol homeostasis by suppressing endogenous cholesterol synthesis, and that for these individuals the intake of eggs and other dietary sources of cholesterol would be contraindicated. We also discuss the complex relationship between dietary sources of choline vs. phosphatidylcholine, the gut microbiome, and plasma TMAO concentrations, highlighting the high inter-individual variability in TMAO production and gut microbiome profiles among healthy individuals and those with metabolic conditions. Precision Nutrition approaches that allow the clinician to stratify risk and improve dietary recommendations for individual patients are desirable for improving patient compliance and health outcomes. More clinical studies are needed to determine how to identify individuals at risk for CVD for whom egg intake is contraindicated vs. those for whom egg intake is not associated with negative effects on plasma lipid profiles nor plasma TMAO concentrations.

Paediatric obesity: a systematic review and pathway mapping of metabolic alterations underlying early disease processes

BACKGROUND

The alarming trend of paediatric obesity deserves our greatest awareness to hinder the early onset of metabolic complications impacting growth and functionality. Presently, insight into molecular mechanisms of childhood obesity and associated metabolic comorbidities is limited. This systematic review aimed at scrutinising what has been reported on putative metabolites distinctive for metabolic abnormalities manifesting at young age by searching three literature databases (Web of Science, Pubmed and EMBASE) during the last 6 years (January 2015-January 2021). Global metabolomic profiling of paediatric obesity was performed (multiple biological matrices: blood, urine, saliva and adipose tissue) to enable overarching pathway analysis and network mapping. Among 2792 screened Q1 articles, 40 met the eligibility criteria and were included to build a database on metabolite markers involved in the spectrum of childhood obesity. Differential alterations in multiple pathways linked to lipid, carbohydrate and amino acid metabolisms were observed. High levels of lactate, pyruvate, alanine and acetate marked a pronounced shift towards hypoxic conditions in children with obesity, and, together with distinct alterations in lipid metabolism, pointed towards dysbiosis and immunometabolism occurring early in life. Additionally, aberrant levels of several amino acids, most notably belonging to tryptophan metabolism including the kynurenine pathway and its relation to histidine, phenylalanine and purine metabolism were displayed. Moreover, branched-chain amino acids were linked to lipid, carbohydrate, amino acid and microbial metabolism, inferring a key role in obesity-associated insulin resistance.

CONCLUSIONS

This systematic review revealed that the main metabolites at the crossroad of dysregulated metabolic pathways underlying childhood obesity could be tracked down to one central disturbance, i.e. impending insulin resistance for which reference values and standardised measures still are lacking. In essence, glycolytic metabolism was evinced as driving energy source, coupled to impaired Krebs cycle flux and ß-oxidation. Applying metabolomics enabled to retrieve distinct metabolite alterations in childhood obesity(-related insulin resistance) and associated pathways at early age and thus could provide a timely indication of risk by elucidating early-stage biomarkers as hallmarks of future metabolically unhealthy phenotypes.

Enterobacter aerogenes ZDY01 inhibits choline-induced atherosclerosis through CDCA-FXR-FGF15 axis

Atherosclerosis is the leading cause of cardiovascular diseases worldwide. Trimethylamine N-oxide (TMAO), a metabolite of intestinal flora from dietary quaternary amines, has been shown to be closely related to the development of atherosclerosis. Previous studies have shown that Enterobacter aerogenes ZDY01 significantly reduces the serum levels of TMAO and cecal trimethylamine (TMA) in Balb/c mice; however, its role in the inhibition of choline-induced atherosclerosis in ApoE^-/- mice remains unclear. Here, we demonstrated that E. aerogenes ZDY01 inhibited choline-induced atherosclerosis in ApoE^-/- mice fed with 1.3% choline by reducing cecal TMA and modulating CDCA-FXR/FGF15 axis. We observed that E. aerogenes ZDY01 decreased the cecal TMA and serum TMAO levels by utilizing cecal TMA as a nutrient, not by changing the expression of hepatic FMO3 and the composition of gut microbiota. Furthermore, E. aerogenes ZDY01 enhanced the expression of bile acid transporters and reduced the cecal CDCA levels, thereby attenuating the FXR/FGF15 pathway, upregulating the expression of Cyp7a1, promoting reverse cholesterol transport. Taken together, E. aerogenes ZDY01 attenuated choline-induced atherosclerosis in ApoE^-/- mice by decreasing cecal TMA and promoting reverse cholesterol transport, implying that E. aerogenes ZDY01 treatment might have therapeutic potential in atherosclerosis.

Liquid Chromatography-Mass Spectrometry for Clinical Metabolomics: An Overview

Metabolomics is a discipline that offers a comprehensive analysis of metabolites in biological samples. In the last decades, the notable evolution in liquid chromatography and mass spectrometry technologies has driven an exponential progress in LC-MS-based metabolomics. Targeted and untargeted metabolomics strategies are important tools in health and medical science, especially in the study of disease-related biomarkers, drug discovery and development, toxicology, diet, physical exercise, and precision medicine. Clinical and biological problems can now be understood in terms of metabolic phenotyping. This overview highlights the current approaches to LC-MS-based metabolomics analysis and its applications in the clinical research.

Effect of microbiota metabolites on the progression of chronic hepatitis B virus infection

Accumulating evidence shows that the intestinal microbiota is closely related to the pathophysiology and the disease progression of chronic hepatitis B virus (HBV) infection. The intestinal microbiota acts on the host through its metabolites. This review aimed to discuss the effects of gut microbiota metabolites on the disease progression of chronic HBV infection. A literature search on PubMed database and Wiley Online Library with pre-specified criteria yielded 96 unique results. After consensus by all authors, the contents from 86 original publications were extracted and included in this review. In liver disease with HBV infection, the intestinal microbiota changed in different stages and affected the production of bacterial metabolites. The abundance of bacteria producing short-chain fatty acids such as butyrate reduced, which was associated with bacterial translocation and the progression of liver disease. The intestinal microbiota-bile acid-host axis was destroyed, affecting the progression of the disease. Under the control of intestinal microbiota, tryptophan affected the gut-liver axis through three main metabolic pathways, among which the kynurenine pathway was closely related to the immune response of hepatitis B. The level of trimethylamine-N-oxide decreased in liver cancer with HBV infection and were used as a potential biomarker of liver cancer. Vitamin deficiencies, including those of vitamin D and vitamin A related to microbiota, were common and associated with survival. Hydrogen sulfide regulated by the intestinal microbiota was also closely related to the gut-liver axis. In liver disease with hepatitis B infection, the intestinal microbiota is imbalanced, and a variety of intestinal microbiota metabolites participate in the occurrence and development of the disease.

Dyslipidemia in Chronic Kidney Disease: Contemporary Concepts and Future Therapeutic Perspectives

BACKGROUND

Chronic kidney disease (CKD) is an increasingly prevalent disease state met with great morbidity and mortality primarily resulting from the high incidence of adverse cardiovascular outcomes. Therapeutic strategies in this patient population aim at controlling modifiable cardiovascular risk factors, including dyslipidemia.

SUMMARY

In this review article, we first provide the latest pathophysiologic evidence regarding the altered dyslipidemia pattern in CKD, followed by its contemporary management according to the latest guidelines. Moreover, we present the current progress regarding the emerging therapeutic strategies. Key Messages: The presence of renal impairment leads to alterations in cholesterol structure, metabolism, and reverse transport paired with increased oxidative stress. Statins remain the cornerstone of dyslipidemia management in patients with kidney dysfunction who are at risk for cardiovascular events. However, their efficacy is debatable in end-stage renal disease under renal replacement therapy. Therefore, novel treatment approaches aiming at hypertriglyceridemia, proprotein convertase subtilisin/kexin type 9, and lipoprotein(a) are under rigorous investigation while the research of gut microbiome might provide additional mechanistic and therapeutic insight.

The Capacity of APOB-Depleted Plasma in Inducing ATP-Binding Cassette A1/G1-Mediated Macrophage Cholesterol Efflux-But Not Gut Microbial-Derived Metabolites-Is Independently Associated with Mortality in Patients with ST-Segment Elevation Myocardial Infarction

Impaired HDL-mediated macrophage cholesterol efflux and higher circulating concentrations of trimethylamine N-oxide (TMAO) levels are independent risk factors for cardiovascular mortality. The TMAO precursors, γ-butyrobetaine (γBB) and Trimethyllysine (TML), have also been recently associated with cardiovascular death, but their interactions with HDL-mediated cholesterol efflux remain unclear. We aimed to determine the associations between APOB depleted plasma-mediated macrophage cholesterol efflux and plasma TMAO, γBB, and TML concentrations and explore their association with two-year follow-up mortality in patients with acute ST-elevation myocardial infarction (STEMI) and unstable angina (UA). Baseline and ATP-binding cassette transporter ABCA1 and ABCG1 (ABCA1/G1)-mediated macrophage cholesterol efflux to APOB-depleted plasma was decreased in patients with STEMI, and the latter was further impaired in those who died during follow-up. Moreover, the circulating concentrations of TMAO, γBB, and TML were higher in the deceased STEMI patients when compared with the STEMI survivors or UA patients. However, after statistical adjustment, only ABCA1/G1-mediated macrophage cholesterol efflux remained significantly associated with mortality. Furthermore, neither the TMAO, γBB, nor TML levels altered the HDL-mediated macrophage cholesterol efflux in vitro. We conclude that impaired ABCA1/G1-mediated macrophage cholesterol efflux is independently associated with mortality at follow-up in STEMI patients.

The Accumulation and Molecular Effects of Trimethylamine N-Oxide on Metabolic Tissues: It's Not All Bad

Since elevated serum levels of trimethylamine N-oxide (TMAO) were first associated with increased risk of cardiovascular disease (CVD), TMAO research among chronic diseases has grown exponentially. We now know that serum TMAO accumulation begins with dietary choline metabolism across the microbiome-liver-kidney axis, which is typically dysregulated during pathogenesis. While CVD research links TMAO to atherosclerotic mechanisms in vascular tissue, its molecular effects on metabolic tissues are unclear. Here we report the current standing of TMAO research in metabolic disease contexts across relevant tissues including the liver, kidney, brain, adipose, and muscle. Since poor blood glucose management is a hallmark of metabolic diseases, we also explore the variable TMAO effects on insulin resistance and insulin production. Among metabolic tissues, hepatic TMAO research is the most common, whereas its effects on other tissues including the insulin producing pancreatic β-cells are largely unexplored. Studies on diseases including obesity, diabetes, liver diseases, chronic kidney disease, and cognitive diseases reveal that TMAO effects are unique under pathologic conditions compared to healthy controls. We conclude that molecular TMAO effects are highly context-dependent and call for further research to clarify the deleterious and beneficial molecular effects observed in metabolic disease research.

Current progress in metabolomics of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is one of the most common metabolic disorders of pregnancy and can cause short- and long-term adverse effects in both pregnant women and their offspring. However, the etiology and pathogenesis of GDM are still unclear. As a metabolic disease, GDM is well suited to metabolomics study, which can monitor the changes in small molecular metabolites induced by maternal stimuli or perturbations in real time. The application of metabolomics in GDM can be used to discover diagnostic biomarkers, evaluate the prognosis of the disease, guide the application of diet or drugs, evaluate the curative effect, and explore the mechanism. This review provides comprehensive documentation of metabolomics research methods and techniques as well as the current progress in GDM research. We anticipate that the review will contribute to identifying gaps in the current knowledge or metabolomics technology, provide evidence-based information, and inform future research directions in GDM.

Intestinal Microbial Metabolites in Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease characterized by inflammation of axial joints and the pelvis. It is known that intestinal dysbiosis may exert direct pathogenic effects on gut homeostasis and may act as a triggering factor for the host innate immune system to activate and cause inflammation in extraintestinal sites in the so-called "gut-joint axis", contributing to AS pathogenesis. However, although the intestinal microbiota's influence on the clinical manifestation of AS is widely accepted, the mechanisms mediating the cross-talk between the intestinal lumen and the immune system are still not completely defined. Recent evidence suggests that the metabolism of microbial species may be a source of metabolites and small molecules participating in the complex network existing between bacteria and host cells. These findings may give inputs for further research of novel pharmacological targets and pave the way to applying dietary interventions to prevent the onset and ameliorate the clinical presentation of the disease. In this review, we discuss the role of some of the biological mediators of microbial origin, with a particular focus on short-chain fatty acids, tryptophan and vitamin B derivatives, and their role in barrier integrity and type 3 immunity in the context of AS.

The Role of Gut Microbiota on Cholesterol Metabolism in Atherosclerosis

Hypercholesterolemia plays a causal role in the development of atherosclerosis and is one of the main risk factors for cardiovascular disease (CVD), the leading cause of death worldwide especially in developed countries. Current data show that the role of microbiota extends beyond digestion by being implicated in several metabolic and inflammatory processes linked to several diseases including CVD. Studies have reported associations between bacterial metabolites and hypercholesterolemia. However, such associations remain poorly investigated and characterized. In this review, the mechanisms of microbial derived metabolites such as primary and secondary bile acids (BAs), trimethylamine N-oxide (TMAO), and short-chain fatty acids (SCFAs) will be explored in the context of cholesterol metabolism. These metabolites play critical roles in maintaining cardiovascular health and if dysregulated can potentially contribute to CVD. They can be modulated via nutritional and pharmacological interventions such as statins, prebiotics, and probiotics. However, the mechanisms behind these interactions also remain unclear, and mechanistic insights into their impact will be provided. Therefore, the objectives of this paper are to present current knowledge on potential mechanisms whereby microbial metabolites regulate cholesterol homeostasis and to discuss the feasibility of modulating intestinal microbes and metabolites as a novel therapeutic for hypercholesterolemia.

Diabetes Mellitus and Cardiovascular Diseases: Nutraceutical Interventions Related to Caloric Restriction

Type 2 diabetes (T2DM) and cardiovascular disease (CVD) are closely associated and represent a key public health problem worldwide. An excess of adipose tissue, NAFLD, and gut dysbiosis establish a vicious circle that leads to chronic inflammation and oxidative stress. Caloric restriction (CR) is the most promising nutritional approach capable of improving cardiometabolic health. However, adherence to CR represents a barrier to patients and is the primary cause of therapeutic failure. To overcome this problem, many different nutraceutical strategies have been designed. Based on several data that have shown that CR action is mediated by AMPK/SIRT1 activation, several nutraceutical compounds capable of activating AMPK/SIRT1 signaling have been identified. In this review, we summarize recent data on the possible role of berberine, resveratrol, quercetin, and L-carnitine as CR-related nutrients. Additionally, we discuss the limitations related to the use of these nutrients in the management of T2DM and CVD.

High-Density Lipoprotein Subfractions: Much Ado about Nothing or Clinically Important?

High-density lipoproteins (HDL) are a heterogenous group of plasma molecules with a large variety in composition. There is a wide specter in lipid content and the number of different proteins that has been associated with HDL is approaching 100. Given this heterogeneity and the fact that the total amount of HDL is inversely related to the risk of coronary heart disease (CHD), there has been increasing interest in the function of specific HDL subgroups and in what way measuring and quantifying these subgroups could be of clinical importance in determining individual CHD risk. If certain subgroups appear to be more protective than others, it may also in the future be possible to pharmacologically increase beneficial and decrease harmful subgroups in order to reduce CHD risk. In this review we give a short historical perspective, summarize some of the recent clinical findings regarding HDL subclassifications and discuss why such classification may or may not be of clinical relevance.

Therapeutic potential of human umbilical cord mesenchymal stem cells on aortic atherosclerotic plaque in a high-fat diet rabbit model

BACKGROUND

Atherosclerosis (AS) is a complex disease caused in part by dyslipidemia and chronic inflammation. AS is associated with serious cardiovascular disease and remains the leading cause of mortality worldwide. Mesenchymal stem cells (MSCs) have evolved as an attractive therapeutic agent in various diseases including AS. Human umbilical cord MSCs (UCSCs) have been used in cell therapy trials due to their ability to differentiate and proliferate. The present study aimed to investigate the effect of UCSCs treatment on atherosclerotic plaque formation and the progression of lesions in a high-fat diet rabbit model.

METHODS

Rabbits were fed a high-fat diet and then randomly divided into three groups: control, model, and treatment groups. Rabbits in the treatment group were injected with UCSCs (6 × 106 in 500 μL phosphate buffered saline) after 1 month of high-fat diet, once every 2 weeks, for 3 months. The model group was given PBS only. We analyzed serum biomarkers, used ultrasound and histopathology to detect arterial plaques and laser Doppler imaging to measure peripheral blood vessel blood filling, and analyzed the intestinal flora and metabolism.

RESULTS

Histological analysis showed that the aortic plaque area was significantly reduced in the treatment group. We also found a significant decrease in macrophage accumulation and apoptosis, an increase in expression of scavenger receptors CD36 and SRA1, a decrease in uptake of modified low-density protein (ox-LDL), and a decrease in levels of pro-inflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α following UCSCs treatment. We also found that anti-inflammatory cytokines IL-10 and transforming growth factor (TGF)-β expression increased in the aorta atherosclerotic plaque of the treatment group. UCSCs treatment improved the early peripheral blood filling, reduced the serum lipid level, and inhibited inflammation progression by regulating the intestinal flora dysbiosis caused by the high-fat diet. More specifically, levels of the microbiota-dependent metabolite trimethylamine-N-oxide (TMAO) were down-regulated in the treatment group.

CONCLUSIONS

UCSCs treatment alleviated atherosclerotic plaque burden by reducing inflammation, regulating the intestinal flora and TMAO levels, and repairing the damaged endothelium.

Chronic Intermittent Hypoxia Participates in the Pathogenesis of Atherosclerosis and Perturbs the Formation of Intestinal Microbiota

Chronic intermittent hypoxia (CIH) is the prominent signature of highly prevalent obstructive sleep apnea (OSA) pathophysiology, which leads to increased risk and aggravation of atherosclerotic cardiovascular diseases. However, whether intestinal microbiota is implicated in the mechanisms linking CIH to arteriosclerosis (AS) pathogenesis remains unclear. The association of CIH with the development of altered gut microbiota (GM) may provide the opportunity to develop preventive strategies for atherosclerotic cardiovascular risk reduction. Animal models of apolipoprotein E-deficient (apoE^-/-) mice treated with high-fat diet (HFD) and subjected to CIH conditions was applied to mimic the AS observed in patients with OSA. The physiological status and atherosclerotic lesion formation were confirmed by histological analysis. 16S rDNA sequencing of fecal samples was conducted to determine the changes in gut microbial composition. Morphometric analysis demonstrated that CIH caused aggravated atherosclerotic lesions and facilitated AS in apoE^-/- mice treated with HFD. The gut bacteria was significantly varied in AS and AS+CIH mice compared with that in the control mice. Significantly perturbed GM profiles were detected in AS mice with and without CIH, with altered microbial α- and β- diversity and shifts in bacterial compositions at phylum and genus levels. While the difference between AS and AS+CIH was observed at different bacteria taxa levels. Aggravation of reduced Sutterella and increased Halomonas, Halomonadaceae and Oceanospirillales was noted in CIH-treated AS mice. The correlation of intestinal bacterial parameters with pathological changes in artery indicated complicated interactions under CIH-induced GM dysbiosis. Furthermore, the gut microbial functions in the potential ability of replication recombination and repair proteins, glycan biosynthesis and metabolism, as well as metabolism of cofactors and vitamins were identified to be further suppressed by CIH. Our findings demonstrated a causal effect of CIH on GM alterations in AS mice and suggested that the disordered GM features in AS development were deteriorated by CIH, which may be associated with AS aggravation. Preventative strategies targeting gut microbiome are highly recommended for intervention of OSA-related AS.

Effect of D-allulose feeding on the hepatic metabolomics profile in male Wistar rats

The rare sugar d-allulose is a C-3 epimer of d-fructose and is known to have several health benefits such as anti-obesity and anti-diabetic effects through the alteration of enzymatic and genetic expressions in each organ. Most of the ingested d-allulose is absorbed in the small intestine and then rapidly excreted in the urine. As d-allulose was reported to be present in the liver before it is excreted, d-allulose may modulate some hepatic metabolites including glucose and lipid metabolism. Therefore, we investigated the hepatic metabolomics profile in rats after feeding d-allulose to study the overall alteration of hepatic metabolism. Wistar rats were fed an AIN-93G diet with/without 3% d-allulose for 4 weeks. Their liver samples were then collected and subjected to metabolomics analysis using CE-TOFMS and LC-TOFMS. The results showed that d-allulose induced significant increases in 42 metabolites and significant decreases in 21 metabolites. In particular, we found at the substance levels that d-allulose regulated metabolites involved in the metabolic pathways of fatty acid β-oxidation, cholesterol, and bile acid. In addition, this study newly showed the possibility that d-allulose alters glucuronic acid/xylulose pathways. In the future, we need more detailed research on the metabolomics profile of other organs related to these pathways for a comprehensive understanding of d-allulose functions.

Sex differences in the intestinal microbiome: interactions with risk factors for atherosclerosis and cardiovascular disease

Background

There are clearly sex differences in cardiovascular disease. On average, women experience cardiovascular events at an older age, and at any age, women, on average, have less atherosclerotic plaque than men. The role of the human intestinal microbiome in health and disease has garnered significant interest in recent years, and there have been indications of sex differences in the intestinal microbiome. The purpose of this narrative review was to evaluate evidence of sex differences in the interaction between the intestinal microbiome and risk factors for cardiovascular disease. Several studies have demonstrated changes in microbiota composition and metabolic profile as a function of diet, sex hormones, and host metabolism, among other factors. This dysbiosis has consequently been associated with several disease states, including atherosclerosis and cardiovascular disease. In this respect, there is a growing appreciation for the microbiota and its secreted metabolites, including trimethylamine N-oxide (TMAO), derived from intestinal bacterial metabolic pathways involving dietary choline and l-carnitine, as novel risk factors for atherosclerosis and cardiovascular outcomes. Although traditional risk factors for vascular disease have been studied broadly over the years, there exists little research to evaluate interactions of cardiovascular risk factors with a potentially sexually dimorphic intestinal microbiome. This review evaluates the role of sex differences in the composition of the intestinal microbiome, including effects of sex hormones on the microbiome, and the effects of these sex differences on cardiovascular risk factors. Diabetes and obesity exhibit sexual dimorphism, while the data concerning hypertension and dyslipidemia remain inconclusive based on the available literature. In addition, an increased proportion of gram-negative species capable of driving metabolic endotoxemia and a low-grade inflammatory response, as well as decreased numbers of butyrate-producing species, have been observed in relation to traditional vascular risk factors. In this context, circulating SCFAs and TMAO are recognized as key metabolites of the intestinal microbiome that can be readily measured in the blood for the evaluation of metabolic profile.

Conclusion

Novel strategies focused on resolving intestinal dysbiosis as a means to slow progression of atherosclerosis and reduce the risk of cardiovascular disease should be evaluated through a lens of sex differences.

Association of Urinary and Plasma Levels of Trimethylamine N-Oxide (TMAO) with Foods

Introduction: Trimethylamine N-oxide (TMAO) may play a key mediator role in the relationship between the diet, gut microbiota and cardiovascular diseases, particularly in people with kidney failure. The aim of this review is to evaluate which foods have a greater influence on blood or urinary trimethylamine N-oxide (TMAO) levels. Methods: 391 language articles were screened, and 27 were analysed and summarized for this review, using the keywords “TMAO” AND “egg” OR “meat” OR “fish” OR “dairy” OR “vegetables” OR “fruit” OR “food” in December 2020. Results: A strong correlation between TMAO and fish consumption, mainly saltwater fish and shellfish, but not freshwater fish, has been demonstrated. Associations of the consumption of eggs, dairy and meat with TMAO are less clear and may depend on other factors such as microbiota or cooking methods. Plant-based foods do not seem to influence TMAO but have been less investigated. Discussion: Consumption of saltwater fish, dark meat fish and shellfish seems to be associated with an increase in urine or plasma TMAO values. Further studies are needed to understand the relationship between increased risk of cardiovascular disease and plasma levels of TMAO due to fish consumption. Interventions coupled with long-term dietary patterns targeting the gut microbiota seem promising.

The Relationship of Large-Artery Atherothrombotic Stroke with Plasma Trimethylamine N-Oxide Level and Blood Lipid-Related Indices: A Cross-Sectional Comparative Study

Objective

The role of trimethylamine N-oxide (TMAO) in cardiovascular diseases has been highlighted. Nevertheless, the associations of large-artery atherosclerotic (LAA) stroke with TMAO and blood lipid-related indices are little investigated.

Methods

A cross-sectional comparative study was performed on 50 patients with LAA stroke and 50 healthy controls. Basic demographic data, common vascular risk factors, and blood lipid-related indices were collected. Plasma TMAO was detected through liquid chromatography tandem mass spectrometry. Multivariable unconditional logistic regression analyses were run to assess the associations of LAA stroke with plasma TMAO level and blood lipid-related indices. The area under the curve (AUC) of the receiver operating characteristic (ROC) was computed to assess the diagnostic performance of plasma TMAO level and blood lipid-related indices for LAA stroke.

Results

Compared with healthy controls, the elevated plasma TMAO level (odds ratio [OR], 7.03; 95% confidence interval [CI], 2.86, 17.25; p < 0.01) and Apo-B (OR, 1.74; 95% CI, 1.06, 2.85; p = 0.03) were observed in LAA stroke patients, while lower Apo-A1 (OR, 0.56; 95% CI, 0.34, 0.91; p = 0.02), Apo-A1 to Apo-B ratio (OR, 0.29; 95% CI, 0.15, 0.56; p < 0.01), and HDL-C (OR, 0.56; 95% CI, 0.35, 0.91; p = 0.02) were found in LAA stroke patients after adjusted for age and gender. Moreover, plasma TMAO (AUC, 0.89; 95% CI, 0.83, 0.95), Apo-A1 (AUC, 0.81; 95% CI, 0.72, 0.89), Apo-B (AUC, 0.81; 95% CI, 0.73, 0.90), Apo-A1 to Apo-B ratio (AUC, 0.85; 95% CI, 0.78, 0.93), and HDL-C (AUC, 0.81; 95% CI, 0.72, 0.89) showed good diagnostic values for LAA stroke in adjusted models.

Conclusions

The plasma TMAO level, Apo-A1, Apo-B, and HDL-C are important biomarkers for LAA stroke patients.

Dietary Strategies for Management of Metabolic Syndrome: Role of Gut Microbiota Metabolites

Metabolic syndrome (MetS) is a complex pathophysiological state with incidence similar to that of a global epidemic and represents a risk factor for the onset of chronic non-communicable degenerative diseases (NCDDs), including cardiovascular disease (CVD), type 2 diabetes mellitus, chronic kidney disease, and some types of cancer. A plethora of literature data suggest the potential role of gut microbiota in interfering with the host metabolism, thus influencing several MetS risk factors. Perturbation of the gut microbiota’s composition and activity, a condition known as dysbiosis, is involved in the etiopathogenesis of multiple chronic diseases. Recent studies have shown that some micro-organism-derived metabolites (including trimethylamine N-oxide (TMAO), lipopolysaccharide (LPS) of Gram-negative bacteria, indoxyl sulfate and p-cresol sulfate) induce subclinical inflammatory processes involved in MetS. Gut microbiota’s taxonomic species or abundance are modified by many factors, including diet, lifestyle and medications. The main purpose of this review is to highlight the correlation between different dietary strategies and changes in gut microbiota metabolites. We mainly focus on the validity/inadequacy of specific dietary patterns to reduce inflammatory processes, including leaky gut and subsequent endotoxemia. We also describe the chance of probiotic supplementation to interact with the immune system and limit negative consequences associated with MetS.

Berberine Regulated miR150-5p to Inhibit P2X7 Receptor, EMMPRIN and MMP-9 Expression in oxLDL Induced Macrophages

Elevated extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinase-9 (MMP-9) in oxidized low density lipoprotein (oxLDL)-induced macrophages leads to the progression of vulnerable plaques by degradation of the extracellular matrix. Our previous report showed that berberine regulates the expression of both EMMPRIN and MMP-9. In addition, P2X7 receptor (P2X7R) upregulation plays a crucial role in the development of atherosclerosis. However, it is unclear whether berberine regulated P2X7R level to inhibit both EMMPRIN and MMP-9 expession in macrophages. In the present study, we investigated the impact of berberine on P2X7R expression and the regulation of P2X7R in the expression of EMMPRIN and MMP-9 in oxLDL-induced macrophages. We found that P2X7R expression was increased, miR150-5p was reduced in oxLDL-induced macrophages, relatively. And A-438079 (a P2X7R inhibitor) or miR150-5p mimic treatment greatly reversed the upregulation of EMMPRIN and MMP-9 expression. Moreover, A-438079 significantly reduced oxLDL-induced AMP-activated protein kinase-α (AMPK-α) phosphorylation and reversed the activation of mitogen-activated protein kinase (MAPK), which in turn decreased the expression of EMMPRIN and MMP-9. These findings illustrate that P2X7R suppresses EMMPRIN and MMP-9 expression by inhibiting the AMPK-α/MAPK pathway in oxLDL-induced macrophages. Accordingly, exposure to berberine markedly upregulated miR150-5p, decreased P2X7R expression and downregulated MMP-9 and EMMPRIN levels in oxLDL-induced macrophages, resulting in AMPK-α/MAPK (JNK, p38, and ERK) inactivation. Overall, these results indicate that berberine increased miR150-5p level, subsequently inhibits P2X7R-mediated EMMPRIN and MMP-9 expression by suppressing AMPK-α and MAPK signaling in oxLDL-induced macrophages.

Neighborhood Environment Associates with Trimethylamine-N-Oxide (TMAO) as a Cardiovascular Risk Marker

BACKGROUND

Neighborhoods and the microbiome are linked to cardiovascular disease (CVD), yet investigations to identify microbiome-related factors at neighborhood levels have not been widely investigated. We sought to explore relationships between neighborhood deprivation index (NDI) and the microbial metabolite, trimethylamine-N-oxide. We hypothesized that inflammatory markers and dietary intake would be mediators of the relationship.

METHODS

African-American adults at risk for CVD living in the Washington, DC area were recruited to participate in a cross-sectional community-based study. US census-based neighborhood deprivation index (NDI) measures (at the census-tract level) were determined. Serum samples were analyzed for CVD risk factors, cytokines, and the microbial metabolite, trimethylamine-N-oxide (TMAO). Self-reported dietary intake based on food groups was collected.

RESULTS

Study participants (n = 60) were predominantly female (93.3%), with a mean (SD) age of 60.83 (+/-10.52) years. Mean (SD) NDI was -1.54 (2.94), and mean (SD) TMAO level was 4.99 (9.65) µmol/L. Adjusting for CVD risk factors and BMI, NDI was positively associated with TMAO (β = 0.31, p = 0.02). Using mediation analysis, the relationship between NDI and TMAO was significantly mediated by TNF-α (60.15%) and interleukin)-1 β (IL; 49.96%). When controlling for clustering within neighborhoods, the NDI-TMAO association was no longer significant (β = 5.11, p = 0.11). However, the association between NDI and IL-1 β (β = 0.04, p = 0.004) and TNF-α (β = 0.17, p = 0.003) remained. Neither NDI nor TMAO was significantly associated with daily dietary intake. Conclusion and Relevance: Among a small sample of African-American adults at risk for CVD, there was a significant positive relationship with NDI and TMAO mediated by inflammation. These hypothesis-generating results are initial and need to be confirmed in larger studies.

The microbiome’s relationship with congenital heart disease: more than a gut feeling

Patients with congenital heart disease (CHD) are at risk for developing intestinal dysbiosis and intestinal epithelial barrier dysfunction due to abnormal gut perfusion or hypoxemia in the context of low cardiac output or cyanosis. Intestinal dysbiosis may contribute to systemic inflammation thereby worsening clinical outcomes in this patient population. Despite significant advances in the management and survival of patients with CHD, morbidity remains significant and questions have arisen as to the role of the microbiome in the inflammatory process. Intestinal dysbiosis and barrier dysfunction experienced in this patient population are increasingly implicated in critical illness. This review highlights possible CHD-microbiome interactions, illustrates underlying signaling mechanisms, and discusses future directions and therapeutic translation of the basic research.

Contribution of Gut Microbiota-Derived Uremic Toxins to the Cardiovascular System Mineralization

Chronic kidney disease (CKD) affects more than 10% of the world population and leads to excess morbidity and mortality (with cardiovascular disease as a leading cause of death). Vascular calcification (VC) is a phenomenon of disseminated deposition of mineral content within the media layer of arteries preceded by phenotypic changes in vascular smooth muscle cells (VSMC) and/or accumulation of mineral content within the atherosclerotic lesions. Medial VC results in vascular stiffness and significantly contributes to increased cardio-vascular (CV) morbidity, whereas VC of plaques may rather increase their stability. Mineral and bone disorders of CKD (CKD-MBD) contribute to VC, which is further aggravated by accumulation of uremic toxins. Both CKD-MBD and uremic toxin accumulation affect not only patients with advanced CKD (glomerular filtration rate (GFR) less than 15 mL/min/1.72 m², end-stage kidney disease) but also those on earlier stages of a disease. The key uremic toxins that contribute to VC, i.e., p-cresyl sulphate (PCS), indoxyl sulphate (IS) and trimethylamine-N-oxide (TMAO) originate from bacterial metabolism of gut microbiota. All mentioned toxins promote VC by several mechanisms, including: Transdifferentiation and apoptosis of VSMC, dysfunction of endothelial cells, oxidative stress, interaction with local renin–angiotensin–aldosterone system or miRNA profile modification. Several attractive methods of gut microbiota manipulations have been proposed in order to modify their metabolism and to limit vascular damage (and VC) triggered by uremic toxins. Unfortunately, to date no such method was demonstrated to be effective at the level of “hard” patient-oriented or even clinically relevant surrogate endpoints.

Trimethylamine N-oxide (TMAO): a new attractive target to decrease cardiovascular risk

Cardiovascular disease (CVD) is one of the greatest disease burdens and takes the lives of many each year. There are many risk factors both modifiable and non-modifiable which contribute to the onset and progression of the disease. Trimethylamine N-oxide (TMAO) in recent years has been found to have a correlation with CVD onset. Those with increased levels of the metabolite have a markedly increased risk of future development of cardiometabolic disorders.This literature review aimed to critique past studies undertaken to find a consensus of the significance of the interrelationship between TMAO and cardiovascular risk. A definite link between TMAO levels and a CVD outcome was found. The majority of the literature stated the relationship with evidence; however, there is still some uncertainty as to why and how the correlation occurs. Further study needs to be done to further dissect and understand the relationship between TMAO and CVD risk.

1H NMR metabolomic and transcriptomic analyses reveal urinary metabolites as biomarker candidates in response to protein undernutrition in adult rats

Protein undernutrition contributes to the development of various diseases in broad generations. Urinary metabolites may serve as non-invasive biomarkers of protein undernutrition; however, this requires further investigation. We aimed to identify novel urinary metabolites as biomarker candidates responsive to protein undernutrition. Adult rats were fed control (CT; 14 % casein) or isoenergetic low-protein (LP; 5 % casein) diets for 4 weeks. 1H NMR metabolomics was applied to urine, plasma and liver samples to identify metabolites responsive to protein undernutrition. Liver samples were subjected to mRNA microarray and quantitative PCR analyses to elucidate the mechanisms causing fluctuations in identified metabolites. Urinary taurine levels were significantly lower in the LP group than in the CT group at week 1 and remained constant until week 4. Hepatic taurine level and gene expression level of cysteine dioxygenase type 1 were also significantly lower in the LP group than in the CT group. Urinary trimethylamine N-oxide (TMAO) levels were significantly higher in the LP group than in the CT group at week 2 and remained constant until week 4. Hepatic TMAO level and gene expression levels of flavin-containing mono-oxygenase 1 and 5 were also significantly higher in the LP group than in the CT group. In conclusion, urinary taurine and TMAO levels substantially responded to protein undernutrition. Furthermore, changes in hepatic levels of these metabolites and gene expressions associated with their metabolic pathways were also reflected in their fluctuating urinary levels. Thus, taurine and TMAO could act as non-invasive urinary biomarker candidates to detect protein undernutrition.

TMA/TMAO in Hypertension: Novel Horizons and Potential Therapies

Hypertension is the most prevalent chronic disease and a risk factor for various diseases. Although its mechanisms and therapies are constantly being updated and developed, they are still not fully clarified. In recent years, novel gut microbiota and its metabolites have attracted widespread attention. It is strongly linked with physiological and pathological systems, especially TMA and TMAO. TMA is formed by intestinal microbial metabolism of choline and L-carnitine and converted into TMAO by FMO3. This paper collected and collated the latest researches and mainly discussed the following four parts. It introduced gut microbiota; provided a focus on TMA, TMA-producing bacteria, and TMAO; summarized the alternations in hypertensive patients and animals; discussed the mechanisms of TMAO with two respects; and summarized the regulatory factors may be as new interventions and therapies of hypertension. And, more relevant studies are still prospected to be accomplished between hypertension and TMA/TMAO for further clinical services.

Epigenetic Regulation of Gut Microbial Dysbiosis

Microbiota inside the gut plays a vital role in maintaining human health. Microbial dysbiosis is associated with various complications leading to a range of diseases. Epigenetic changes enforced by various environmental and lifestyle factors lead to heritable modifications. These epigenetic modifications include DNA methylation, histone modifications, chromatin remodelling, and ribonucleic acid-based mechanisms. This review summarizes the impacts of environmental factors on the gut microbiome, epigenetic modifications, and their role in cardiovascular diseases.

Can diet modulate trimethylamine N-oxide (TMAO) production? What do we know so far?

BACKGROUND

Trimethylamine N-oxide (TMAO) is a metabolite that has attracted attention due to its positive association with several chronic non-communicable diseases such as insulin resistance, atherosclerotic plaque formation, diabetes, cancer, heart failure, hypertension, chronic kidney disease, liver steatosis, cardiac fibrosis, endothelial injury, neural degeneration and Alzheimer's disease. TMAO production results from the fermentation by the gut microbiota of dietary nutrients such as choline and carnitine, which are transformed to trimethylamine (TMA) and converted into TMAO in the liver by flavin-containing monooxygenase 1 and 3 (FMO1 and FMO3). Considering that TMAO is involved in the development of many chronic diseases, strategies have been found to enhance a healthy gut microbiota. In this context, some studies have shown that nutrients and bioactive compounds from food can modulate the gut microbiota and possibly reduce TMAO production.

OBJECTIVE

This review has as main objective to discuss the studies that demonstrated the effects of food on the reduction of this harmful metabolite.

METHODS

All relevant articles until November 2020 were included. The articles were searched in Medline through PubMed.

RESULTS

Both the food is eaten acutely and chronically, by altering the nature of the gut microbiota, influencing colonic TMA production. Furthermore, hepatic production of TMAO by the flavin monooxygenases in the liver may also be influenced by phenolic compounds present in foods.

CONCLUSION

The evidence presented in this review shows that TMAO levels can be reduced by some bioactive compounds. However, it is crucial to notice that there is significant variation among the studies. Further clinical studies should be conducted to evaluate these dietary components' effectiveness, dose, and intervention time on TMAO levels and its precursors.

Polycentric binding in complexes of trimethylamine-N-oxide with dihalogens

Dihalogens readily interact with trimethylamine-N-oxide under ambient conditions. Accordingly, herein, stable 1 : 1 adducts were obtained in the case of iodine chloride and iodine bromide. The crystal and molecular structure of the trimethylamine-N-oxide-iodine chloride adduct was solved. Furthermore, the geometry and electronic structure of the trimethylamine-N-oxide-dihalogen complexes were studied computationally. Only molecular ensembles were found in the global minimum for the 1 : 1 stoichiometry. The O⋯X-Y halogen bond is the main factor for the thermodynamic stability of these complexes. Arguments for electrostatic interactions as the driving force for this noncovalent interaction were discussed. Also, the equilibrium structures are additionally stabilised by weak C-H⋯X hydrogen bonds. Consequently, formally monodentate ligands are bound in a polycentric manner.

Association of Circulating Trimethylamine N-Oxide and Its Dietary Determinants with the Risk of Kidney Graft Failure: Results of the TransplantLines Cohort Study

Background. Due to the critical shortage of kidneys for transplantation, the identification of modifiable factors related to graft failure is highly desirable. The role of trimethylamine-N-oxide (TMAO) in graft failure remains undetermined. Here, we investigated the clinical utility of TMAO and its dietary determinants for graft failure prediction in renal transplant recipients (RTRs). Methods. We included 448 RTRs who participated in the TransplantLines Cohort Study. Cox proportional-hazards regression analyses were performed to study the association of plasma TMAO with graft failure. Net Benefit, which is a decision analysis method, was performed to evaluate the clinical utility of TMAO and dietary information in the prediction of graft failure. Results. Among RTRs (age 52.7 ± 13.1 years; 53% males), the baseline median TMAO was 5.6 (3.0–10.2) µmol/L. In multivariable regression analysis, the most important dietary determinants of TMAO were egg intake (Std. β = 0.09 [95%CI, 0.01; 0.18]; p = 0.03), fiber intake (Std. β = −0.14 [95%CI, −0.22, −0.05]; p = 0.002), and fish and seafood intake (Std. β = 0.12 [95%CI, 0.03,0.21]; p = 0.01). After a median follow-up of 5.3 (4.5–6.0) years, graft failure was observed in 58 subjects. TMAO was associated with an increased risk of graft failure, independent of age, sex, the body mass index (BMI), blood pressure, lipids, albuminuria, and the Estimated Glomerular Filtration Rate (eGFR) (Hazard Ratio per 1-SD increase of TMAO, 1.62 (95% confidence interval (CI): 1.22; 2.14, p < 0.001)). A TMAO and dietary enhanced prediction model offered approximately double the Net Benefit compared to a previously reported, validated prediction model for future graft failure, allowing the detection of 21 RTRs per 100 RTRs tested, with no false positives versus 10 RTRs, respectively. Conclusions. A predictive model for graft failure, enriched with TMAO and its dietary determinants, yielded a higher Net Benefit compared with an already validated model. This study suggests that TMAO and its dietary determinants are associated with an increased risk of graft failure and that it is clinically meaningful.

Ceramides and their interactive effects with trimethylamine-N-oxide metabolites on risk of gestational diabetes: A nested case-control study

AIMS

To explore associations between ceramides in early pregnancy and gestational diabetes mellitus (GDM); and interactions between ceramides and trimethylamine N-oxide (TMAO) metabolites for GDM.

METHODS

We organized a 1:1 nested case-control study (n = 486) from a prospective cohort of pregnant women. Conditional logistic regression and additive interaction were performed to examine relationships between ceramides and TMAO metabolites for GDM. We defined trimethylamine (TMA) conversion ratio (TMA_R) as TMA/its precursors and TMAO conversion ratio (TMAO_R) as TMAO/TMA. Copresence of high TMA_R and low TMAO_R indicated TMA accumulation status.

RESULTS

High ceramides 18:0 (per SD), 18:1 (per SD) and low ceramide 24:0 (≤ 3.60 nmol/mL) were associated with increased GDM risk (OR: 1.69, 1.72 & 3.59, respectively). High TMA enhanced the OR of low ceramide 24:0 for GDM from 1.53 (95%CI: 0.88-2.66) to 10.3 (2.83-37.5), high TMA_R enhanced it from 1.31 (0.67-2.56) to 24.3 (6.57-89.5) and TMA accumulation enhanced it from 1.42 (0.72-2.77) to 25.5 (6.80-95.7), with all additive interactions being significant. However, the interactions between high ceramide 18 and TMAO metabolites were not significant.

CONCLUSIONS

High ceramides 18:0, 18:1 and low ceramide 24:0 in early pregnancy were associated with increased GDM risk. Notably, TMA accumulation greatly amplified the risk-promoting effect of low ceramide 24:0 for GDM.

Metabolic networks of the human gut microbiota

The human gut microbiota controls factors that relate to human metabolism with a reach far greater than originally expected. Microbial communities and human (or animal) hosts entertain reciprocal exchanges between various inputs that are largely controlled by the host via its genetic make-up, nutrition and lifestyle. The composition of these microbial communities is fundamental to supply metabolic capabilities beyond those encoded in the host genome, and contributes to hormone and cellular signalling that support the dynamic adaptation to changes in food availability, environment and organismal development. Poor functional exchange between the microbial communities and their human host is associated with dysbiosis, metabolic dysfunction and disease. This review examines the biology of the dynamic relationship between the reciprocal metabolic state of the microbiota-host entity in balance with its environment (i.e. in healthy states), the enzymatic and metabolic changes associated with its imbalance in three well-studied diseases states such as obesity, diabetes and atherosclerosis, and the effects of bariatric surgery and exercise.

Cross-Talk between Diet-Associated Dysbiosis and Hand Osteoarthritis

Hand osteoarthritis (OA) is a degenerative joint disease which leads to pain and disability. Recent studies focus on the role of obesity and metabolic syndrome in inducing or worsening joint damage in hand OA patients, suggesting that chronic low-grade systemic inflammation may represent a possible linking factor. The gut microbiome has a crucial metabolic role which is fundamental for immune system development, among other important functions. Intestinal microbiota dysbiosis may favour metabolic syndrome and low-grade inflammation-two important components of hand OA onset and evolution. The aim of this narrative is to review the recent literature concerning the possible contribution of dysbiosis to hand OA onset and progression, and to discuss the importance of gut dysbiosis on general health and disease.

Association of FMO3 rs1736557 polymorphism with clopidogrel response in Chinese patients with coronary artery disease

PURPOSE

Dual antiplatelet therapy with aspirin and clopidogrel is commonly used for coronary artery disease (CAD) patients undergoing percutaneous coronary intervention to prevent stent thrombosis and ischemic events. However, some patients show high on-treatment platelet reactivity (HTPR) during clopidogrel therapy. Genetic factors such as loss-of-function variants of CYP2C19 are validated to increase the risk of HTPR. Flavin-containing monooxygenase 3 (FMO3) is reported to be associated with potency of platelet responsiveness and thrombosis. This study aimed to explore the association between FMO3 rs1736557 polymorphism and clopidogrel response.

METHODS

Five hundred twenty-two Chinese CAD patients treated with dual antiplatelet therapy were recruited from Xiangya Hospital. After oral administration of 300 mg loading dose (LD) clopidogrel for 12-24 h or 75 mg daily maintenance dose (MD) clopidogrel for at least 5 days, the platelet reaction index (PRI) was determined by vasodilator-stimulated phosphoprotein-phosphorylation assay. FMO3 rs1736557, CYP2C19*2, and CYP2C19*3 polymorphisms were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Mean PRI value was significantly higher in CYP2C19 poor metabolizers (PMs) and intermediate metabolizers (IMs) than the extensive metabolizers (EMs) (p < 0.001). In addition, FMO3 rs1736557 AA homozygotes showed significantly lower PRI as compared with carriers of the major rs1736557 G allele in the entire cohort and in the MD cohort (p = 0.011, p = 0.008, respectively). The risk of HTPR was decreased significantly in carriers of the rs1736557 A allele (AA vs GG: OR = 0.316, 95% CI: 0.137-0.726, p = 0.005; AA vs GA: OR = 0.249, 95% CI: 0.104-0.597, p = 0.001; AA vs GG+GA: OR = 0.294, 95% CI: 0.129-0.669, p = 0.002), and the association was observed mainly in patients carrying the CYP2C19 LOF allele and in those administered with MD.

CONCLUSION

The FMO3 rs1736557 AA genotype was related to an increased the antiplatelet potency of clopidogrel in Chinese CAD patients. Additional studies are required to verify this finding.

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.

A Novel Insight at Atherogenesis: The Role of Microbiome

There is an important task of current medicine to identify mechanisms and new markers of subclinical atherosclerosis in order to develop early targets for the diagnosis and treatment of this disease, since it causes such widespread diseases as myocardial infarction, stroke, sudden death, and other common reasons of disability and mortality in developed countries. In recent years, studies of the human microbiome in different fields of medicine have become increasingly popular; there is evidence from numerous studies of the significant contribution of microbiome in different steps of atherogenesis. This review attempted to determine the current status of the databases PubMed and Scopus (until May, 2020) to highlight current ideas on the potential role of microbiome and its metabolites in atherosclerosis development, its mechanisms of action in lipids metabolism, endothelial dysfunction, inflammatory pathways, and mitochondrial dysfunction. Results of clinical studies elucidating the relationship of microbiome with subclinical atherosclerosis and cardiovascular disease considered in this article demonstrate strong association of microbiome composition and its metabolites with atherosclerosis and cardiovascular disease. Data on microbiome impact in atherogenesis open a wide perspective to develop new diagnostic and therapeutic approaches, but further comprehensive studies are necessary.

Enzyme annotation in UniProtKB using Rhea

Motivation

To provide high quality computationally tractable enzyme annotation in UniProtKB using Rhea, a comprehensive expert-curated knowledgebase of biochemical reactions which describes reaction participants using the ChEBI (Chemical Entities of Biological Interest) ontology.

Results

We replaced existing textual descriptions of biochemical reactions in UniProtKB with their equivalents from Rhea, which is now the standard for annotation of enzymatic reactions in UniProtKB. We developed improved search and query facilities for the UniProt website, REST API and SPARQL endpoint that leverage the chemical structure data, nomenclature and classification that Rhea and ChEBI provide.

Availability and implementation

UniProtKB at https://www.uniprot.org; UniProt REST API at https://www.uniprot.org/help/api; UniProt SPARQL endpoint at https://sparql.uniprot.org/; Rhea at https://www.rhea-db.org.

Effects of gut microbial metabolite trimethylamine N-oxide (TMAO) on platelets and endothelial cells

Thrombotic events result from different pathologies and are the underlying causes of severe diseases like stroke or myocardial infarction. Recent basic research now revealed a link between food uptake, food conversion and gut metabolism. Gut microbial production of trimethylamine N-oxide (TMAO) from dietary nutrients like choline, lecithin and L-carnitine was associated with the development of cardiovascular diseases. Within this review we give a systematic overview about the influence of TMAO on blood components like platelets and endothelial cells which both are involved as key players in thrombotic processes. In summary, a mechanistic correlation between the gut microbiome, TMAO and cardiovascular diseases becomes obvious and emphasizes to the significance of the intestinal microbiome.

Role of gut microbiota in identification of novel TCM-derived active metabolites

Traditional Chinese Medicine (TCM) has been extensively used to ameliorate diseases in Asia for over thousands of years. However, owing to a lack of formal scientific validation, the absence of information regarding the mechanisms underlying TCMs restricts their application. After oral administration, TCM herbal ingredients frequently are not directly absorbed by the host, but rather enter the intestine to be transformed by gut microbiota. The gut microbiota is a microbial community living in animal intestines, and functions to maintain host homeostasis and health. Increasing evidences indicate that TCM herbs closely affect gut microbiota composition, which is associated with the conversion of herbal components into active metabolites. These may significantly affect the therapeutic activity of TCMs. Microbiota analyses, in conjunction with modern multiomics platforms, can together identify novel functional metabolites and form the basis of future TCM research.

Plasma trimethylamine n-oxide is associated with renal function in patients with heart failure with preserved ejection fraction

Background

Heart failure with preserved ejection fraction (HFpEF) is an emerging global health problem with less awareness. Renal dysfunction in HFpEF is associated with worse outcome. However, there is lack of rapid, noninvasive and accurate method for risk stratification in HFpEF and renal dysfunction. This study aimed to explore the utility of plasma trimethylamine n-oxide (TMAO) for evaluation of HFpEF and renal function.

Methods

Plasma TMAO levels were measured in total 324 subjects comprising 228 HFpEF patients and 96 healthy controls.

Results

TMAO levels were significantly elevated in patients with HFpEF compared with controls (12.65(9.32–18.66) μg/l vs 10.85(6.35–15.58) μg/l, p <  0.01). Subjects in higher TMAO tertile group had more incidences of HFpEF ((78.5%) in tertile 3 vs (73.39%) in tertile 2 vs (59.26%) in tertile 1, p <  0.01). TMAO concentrations were inversely correlated with estimated glomerular filtration rate (eGFR) and HFpEF patients with impaired renal function (eGFR < 60 ml/min/1.73 m²) had higher TMAO than those with normal eGFR (≥ 60 ml/min/1.73 m²) (14.18(10.4–23.06) μg/l vs 10.9(7.48–15.47) μg/l, p < 0.01). Increased TMAO levels were independently associated with higher risk of HFpEF (OR = 3.49, 95% CI: 1.23–9.86, p = 0.02) and renal dysfunction (OR = 9.57, 95% CI: 2.11–43.34, p < 0.01) after adjustment for multiple traditional risk factors. Furthermore, TMAO had good performance at distinguishing HFpEF from controls (AUC = 0.63, p < 0.01), and renal dysfunction from normal renal function in HFpEF (AUC = 0.67, p < 0.01).

Conclusion

In this cross-sectional study, HFpEF and renal function were closely related with plasma TMAO levels and TMAO may serve as a diagnostic biomarker for HFpEF and renal function.

Trimethylamine N-oxide levels are associated with NASH in obese subjects with type 2 diabetes

AIMS

Trimethylamine N-oxide (TMAO), choline and betaine serum levels have been associated with metabolic diseases including type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD). These associations could be mediated by insulin resistance. However, the relationships among these metabolites, insulin resistance and NAFLD have not been thoroughly investigated. Moreover, it has recently been suggested that TMAO could play a role in NAFLD by altering bile acid metabolism. We examined the association between circulating TMAO, choline and betaine levels and NAFLD in obese subjects.

METHODS

Serum TMAO, choline, betaine and bile acid levels were measured in 357 Mexican obese patients with different grades of NAFLD as determined by liver histology. Associations of NAFLD with TMAO, choline and betaine levels were tested. Moreover, association of TMAO levels with non-alcoholic steatohepatitis (NASH) was tested separately in patients with and without T2D.

RESULTS

TMAO and choline levels were significantly associated with NAFLD histologic features and NASH risk. While increased serum TMAO levels were significantly associated with NASH in patients with T2D, in non-T2D subjects this association lost significance after adjusting for sex, BMI and HOMA2-IR. Moreover, circulating secondary bile acids were associated both with increased TMAO levels and NASH.

CONCLUSIONS

In obese patients, circulating TMAO levels were associated with NASH mainly in the presence of T2D. Functional studies are required to evaluate the role of insulin resistance and T2D in this association, both highly prevalent in NASH patients.

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.