Gut microbiota: a promising target against cardiometabolic diseases

When short-chain fatty acids meet type 2 diabetes mellitus: Revealing mechanisms, envisioning therapies

Evidence is accumulating that short-chain fatty acids (SCFAs) produced by the gut microbiota play pivotal roles in host metabolism. They contribute to the metabolic regulation and energy homeostasis of the host not only by preserving intestinal health and serving as energy substrates but also by entering the systemic circulation as signaling molecules, affecting the gut-brain axis and neuroendocrine-immune network. This review critically summarizes the current knowledge regarding the effects of SCFAs in the fine-tuning of the pathogenesis of type 2 diabetes mellitus (T2DM) and insulin resistance, with an emphasis on the complex relationships among diet, microbiota-derived metabolites, T2DM inflammation, glucose metabolism, and the underlying mechanisms involved. We hold an optimistic view that elucidating how diet can influence gut bacterial composition and activity, SCFA production, and metabolic functions in the host will advance our understanding of the mutual interactions of the intestinal microbiota with other metabolically active organs, and may pave the way for harnessing these pathways to develop novel personalized therapeutics for glucometabolic disorders.

Intestinal interstitial fluid isolation provides novel insight into the human host-microbiome interface

AIMS

The gastrointestinal (GI) tract is composed of distinct sub-regions, which exhibit segment-specific differences in microbial colonization and (patho)physiological characteristics. Gut microbes can be collectively considered as an active endocrine organ. Microbes produce metabolites, which can be taken up by the host and can actively communicate with the immune cells in the gut lamina propria with consequences for cardiovascular health. Variation in bacterial load and composition along the GI tract may influence the mucosal microenvironment and thus be reflected its interstitial fluid (IF). Characterization of the segment-specific microenvironment is challenging and largely unexplored because of lack of available tools.

METHODS AND RESULTS

Here, we developed methods, namely tissue centrifugation and elution, to collect IF from the mucosa of different intestinal segments. These methods were first validated in rats and mice, and the tissue elution method was subsequently translated for use in humans. These new methods allowed us to quantify microbiota-derived metabolites, mucosa-derived cytokines, and proteins at their site-of-action. Quantification of short-chain fatty acids showed enrichment in the colonic IF. Metabolite and cytokine analyses revealed differential abundances within segments, often significantly increased compared to plasma, and proteomics revealed that proteins annotated to the extracellular phase were site-specifically identifiable in IF. Lipopolysaccharide injections in rats showed significantly higher ileal IL-1β levels in IF compared to the systemic circulation, suggesting the potential of local as well as systemic effect.

CONCLUSION

Collection of IF from defined segments and the direct measurement of mediators at the site-of-action in rodents and humans bypasses the limitations of indirect analysis of faecal samples or serum, providing direct insight into this understudied compartment.

Association of serum 25-hydroxy vitamin D status with cardiometabolic risk factors and total and regional obesity in southern Iran: evidence from the PoCOsteo study

Cardiometabolic risk factors increase the chance of developing cardiovascular disease (CVD) and type 2 diabetes. Most CVD risk factors are influenced by total and regional obesity. A higher risk of developing CVD may be linked to vitamin D deficiency, which is more prevalent in the older population. With the goal of evaluating the association between vitamin D and cardiometabolic risk factors and total and regional obesity in older adults, this research included 25 (OH) vitamin D3 concentrations and biochemical markers associated with cardiometabolic diseases, as well as total and regional adiposity, which was measured by DXA. A total of 1991 older participants in the PoCOsteo study were included. Overall, 38.5% of participants had vitamin D deficiency. After adjusting for confounders, the results of multiple linear and logistic regression suggested an inverse association between vitamin D and body mass index (P = 0.04), waist circumference (P = 0.001), total fat (P = 0.02), android fat (P = 0.001), visceral fat (P < 0.001), subcutaneous fat (P = 0.01), trunk fat (P = 0.006), arm fat (P = 0.03), high systolic blood pressure (P = 0.004), high total cholesterol (P < 0.001), high LDL-cholesterol (P < 0.001), high serum triglycerides (P = 0.001), and high fasting glucose (P < 0.001). Additionally, higher vitamin D concentrations decreased the risk of dyslipidemia by 2%. Our results showed a significant association between serum vitamin D and a number of cardiometabolic risk factors, including total and regional obesity.

Novel Proteome Targets Marking Insulin Resistance in Metabolic Syndrome

CONTEXT/OBJECTIVE

In order to better understand which metabolic differences are related to insulin resistance in metabolic syndrome (MetSyn), we used hyperinsulinemic-euglycemic (HE) clamps in individuals with MetSyn and related peripheral insulin resistance to circulating biomarkers.

DESIGN/METHODS

In this cross-sectional study, HE-clamps were performed in treatment-naive men (n = 97) with MetSyn. Subjects were defined as insulin-resistant based on the rate of disappearance (Rd). Machine learning models and conventional statistics were used to identify biomarkers of insulin resistance. Findings were replicated in a cohort with n = 282 obese men and women with (n = 156) and without (n = 126) MetSyn. In addition to this, the relation between biomarkers and adipose tissue was assessed by nuclear magnetic resonance imaging.

RESULTS

Peripheral insulin resistance is marked by changes in proteins related to inflammatory processes such as IL-1 and TNF-receptor and superfamily members. These proteins can distinguish between insulin-resistant and insulin-sensitive individuals (AUC = 0.72 ± 0.10) with MetSyn. These proteins were also associated with IFG, liver fat (rho 0.36, p = 1.79 × 10-9) and visceral adipose tissue (rho = 0.35, p = 6.80 × 10-9). Interestingly, these proteins had the strongest association in the MetSyn subgroup compared to individuals without MetSyn.

CONCLUSIONS

MetSyn associated with insulin resistance is characterized by protein changes related to body fat content, insulin signaling and pro-inflammatory processes. These findings provide novel targets for intervention studies and should be the focus of future in vitro and in vivo studies.

Oral histidine affects gut microbiota and MAIT cells improving glycemic control in type 2 diabetes patients

Amino acids, metabolized by host cells as well as commensal gut bacteria, have signaling effects on host metabolism. Oral supplementation of the essential amino acid histidine has been shown to exert metabolic benefits. To investigate whether dietary histidine aids glycemic control, we performed a case-controlled parallel clinical intervention study in participants with type 2 diabetes (T2D) and healthy controls. Participants received oral histidine for seven weeks. After 2 weeks of histidine supplementation, the microbiome was depleted by antibiotics to determine the microbial contribution to histidine metabolism. We assessed glycemic control, immunophenotyping of peripheral blood mononucelar cells (PBMC), DNA methylation of PBMCs and fecal gut microbiota composition. Histidine improves several markers of glycemic control, including postprandial glucose levels with a concordant increase in the proportion of MAIT cells after two weeks of histidine supplementation. The increase in MAIT cells was associated with changes in gut microbial pathways such as riboflavin biosynthesis and epigenetic changes in the amino acid transporter SLC7A5. Associations between the microbiome and MAIT cells were replicated in the MetaCardis cohort. We propose a conceptual framework for how oral histidine may affect MAIT cells via altered gut microbiota composition and SLC7A5 expression in MAIT cells directly and thereby influencing glycemic control. Future studies should focus on the role of flavin biosynthesis intermediates and SLC7A5 modulation in MAIT cells to modulate glycemic control.

Obesity phenotypes and cardiovascular risk: From pathophysiology to clinical management

Obesity epidemic reached the dimensions of a real global health crisis with more than one billion people worldwide living with obesity. Multiple obesity-related mechanisms cause structural, functional, humoral, and hemodynamic alterations with cardiovascular (CV) deleterious effects. A correct assessment of the cardiovascular risk in people with obesity is critical for reducing mortality and preserving quality of life. The correct identification of the obesity status remains difficult as recent evidence suggest that different phenotypes of obesity exist, each one associated with different degrees of CV risk. Diagnosis of obesity cannot depend only on anthropometric parameters but should include a precise assessment of the metabolic status. Recently, the World Heart Federation and World Obesity Federation provided an action plan for management of obesity-related CV risk and mortality, stressing for the instauration of comprehensive structured programs encompassing multidisciplinary teams. In this review we aim at providing an updated summary regarding the different obesity phenotypes, their specific effects on CV risk and differences in clinical management.

Gut Microbiota Perturbation in Early Life Could Influence Pediatric Blood Pressure Regulation in a Sex-Dependent Manner in Juvenile Rats

The present study aimed to investigate whether gut dysbiosis induced by ceftriaxone in early life could influence pediatric blood pressure regulation in childhood with or without exposure to a high-fat diet (HFD). Sixty-three newborn pups of Sprague-Dawley rats were administered ceftriaxone sodium or saline solution until weaning at 3 weeks, and the rats were fed a HFD or regular diet from 3 to 6 weeks. Tail-cuff blood pressure, the expression levels of genes of the renin-angiotensin system (RAS), the concentrations of IL-1β, IL-6, and TNF-α in the colon and prefrontal cortex, and the composition of fecal microbiota were analyzed. Ceftriaxone treatment significantly increased the diastolic blood pressure of male rats at 3 weeks. At 6 weeks, systolic blood pressure (SBP) was significantly increased only in ceftriaxone treated male rats fed with HFD. The RAS showed increased activation in the kidney, heart, hypothalamus, and thoracic and abdominal aorta of male rats, but only in the kidney, heart, and hypothalamus of female rats. HFD-fed female rats showed a decreased level of IL-6 in the colon. α diversity of gut microbiota decreased and the Firmicutes to Bacteroidetes ratio increased in both male and female rats at 3 weeks; however, these parameters recovered to various degrees in female rats at 6 weeks. These results revealed that early-life gut dysbiosis induced by antibiotics combined with a HFD in childhood could be involved in pediatric blood pressure regulation and an increase in SBP in juvenile rats, and these effects occurred in a sex-dependent manner.

Cardiometabolic health, diet and the gut microbiome: a meta-omics perspective

Cardiometabolic diseases have become a leading cause of morbidity and mortality globally. They have been tightly linked to microbiome taxonomic and functional composition, with diet possibly mediating some of the associations described. Both the microbiome and diet are modifiable, which opens the way for novel therapeutic strategies. High-throughput omics techniques applied on microbiome samples (meta-omics) hold the unprecedented potential to shed light on the intricate links between diet, the microbiome, the metabolome and cardiometabolic health, with a top-down approach. However, effective integration of complementary meta-omic techniques is an open challenge and their application on large cohorts is still limited. Here we review meta-omics techniques and discuss their potential in this context, highlighting recent large-scale efforts and the novel insights they provided. Finally, we look to the next decade of meta-omics research and discuss various translational and clinical pathways to improving cardiometabolic health.

Association of the gut microbiota with coronary artery disease and myocardial infarction: A Mendelian randomization study

Background: Previous studies have indicated that the gut microbiota (GM) is associated with coronary artery disease (CAD), but the causality of these associations remains unestablished due to confounding factors and reverse causality. We conducted Mendelian randomization study (MR) to determine the causal effect of the specific bacterial taxa on CAD/myocardial infarction (MI) and identify the mediating factors involved. Methods: Two-sample MR, multivariable MR (MVMR) and mediation analysis were performed. Inverse-variance weighting (IVW) was the main method used to analyze causality, and sensitivity analysis was used to verify the reliability of the study. Causal estimates from CARDIoGRAMplusC4D and FinnGen databases were combined using the meta-analysis method, and repeated validation was conducted based on the UK Biobank (UKB) database. Confounders that may affect the causal estimates were corrected by MVMP and the potential mediation effects were investigated by using mediation analysis. Results: The study suggested that increased abundance of the RuminococcusUCG010 genus leads to a lower risk of CAD (OR, 0.88; 95% CI, 0.78, 1.00; p = 2.88 × 10^-2) and MI (OR, 0.88; 95% CI, 0.79, 0.97; p = 1.08 × 10^-2), with consistent results in both meta-analysis (CAD: OR, 0.86; 95% CI, 0.78, 0.96; p = 4.71 × 10^-3; MI: OR, 0.82; 95% CI, 0.73, 0.92; p = 8.25 × 10^-4) and repeated analysis of the UKB dataset (CAD: OR, 0.99; 95% CI, 0.99, 1.00, p = 2.53 × 10^-4; MI: OR, 0.99; 95% CI, 0.99, 1.00, p = 1.85 × 10-11). Based on multiple databases, T2DM was proved as a mediating factor in the causal effect of RuminococcusUCG010 and CAD/MI, with an average mediation effect proportion of 20% on CAD and 17% on MI, respectively. Conclusion: This MR study provided suggestive genetic evidence that the higher the RuminococcusUCG010 abundance is, the lower the risk of CAD and MI, with T2DM playing a mediating effect. This genus may become a novel target in strategies for treating and preventing CAD and MI.

Emerging computational paradigms to address the complex role of gut microbial metabolism in cardiovascular diseases

The human gut microbiota and its associated perturbations are implicated in a variety of cardiovascular diseases (CVDs). There is evidence that the structure and metabolic composition of the gut microbiome and some of its metabolites have mechanistic associations with several CVDs. Nevertheless, there is a need to unravel metabolic behavior and underlying mechanisms of microbiome-host interactions. This need is even more highlighted when considering that microbiome-secreted metabolites contributing to CVDs are the subject of intensive research to develop new prevention and therapeutic techniques. In addition to the application of high-throughput data used in microbiome-related studies, advanced computational tools enable us to integrate omics into different mathematical models, including constraint-based models, dynamic models, agent-based models, and machine learning tools, to build a holistic picture of metabolic pathological mechanisms. In this article, we aim to review and introduce state-of-the-art mathematical models and computational approaches addressing the link between the microbiome and CVDs.

Duodenal Anaerobutyricum soehngenii infusion stimulates GLP-1 production, ameliorates glycaemic control and beneficially shapes the duodenal transcriptome in metabolic syndrome subjects: a randomised double-blind placebo-controlled cross-over study

OBJECTIVE

Although gut dysbiosis is increasingly recognised as a pathophysiological component of metabolic syndrome (MetS), the role and mode of action of specific gut microbes in metabolic health remain elusive. Previously, we identified the commensal butyrogenic Anaerobutyricum soehngenii to be associated with improved insulin sensitivity in subjects with MetS. In this proof-of-concept study, we investigated the potential therapeutic effects of A. soehngenii L2-7 on systemic metabolic responses and duodenal transcriptome profiles in individuals with MetS.

DESIGN

In this randomised double-blind placebo-controlled cross-over study, 12 male subjects with MetS received duodenal infusions of A. soehngenii/ placebo and underwent duodenal biopsies, mixed meal tests (6 hours postinfusion) and 24-hour continuous glucose monitoring.

RESULTS

A. soehngenii treatment provoked a markedly increased postprandial excursion of the insulinotropic hormone glucagon-like peptide 1 (GLP-1) and an elevation of plasma secondary bile acids, which were positively associated with GLP-1 levels. Moreover, A. soehngenii treatment robustly shaped the duodenal expression of 73 genes, with the highest fold induction in the expression of regenerating islet-protein 1B (REG1B)-encoding gene. Strikingly, duodenal REG1B expression positively correlated with GLP-1 levels and negatively correlated with peripheral glucose variability, which was significantly diminished in the 24 hours following A. soehngenii intake. Mechanistically, Reg1B expression is induced upon sensing butyrate or bacterial peptidoglycan. Importantly, A. soehngenii duodenal administration was safe and well tolerated.

CONCLUSIONS

A single dose of A. soehngenii improves peripheral glycaemic control within 24 hours; it specifically stimulates intestinal GLP-1 production and REG1B expression. Further studies are needed to delineate the specific pathways involved in REG1B induction and function in insulin sensitivity.

TRIAL REGISTRATION NUMBER

NTR-NL6630.

Circulating Microbiota in Cardiometabolic Disease

The rapid expansion of microbiota research has significantly advanced our understanding of the complex interactions between gut microbiota and cardiovascular, metabolic, and renal system regulation. Low-grade chronic inflammation has long been implicated as one of the key mechanisms underlying cardiometabolic disease risk and progression, even before the insights provided by gut microbiota research in the past decade. Microbial translocation into the bloodstream can occur via different routes, including through the oral and/or intestinal mucosa, and may contribute to chronic inflammation in cardiometabolic disease. Among several gut-derived products identifiable in the systemic circulation, bacterial endotoxins and metabolites have been extensively studied, however recent advances in microbial DNA sequencing have further allowed us to identify highly diverse communities of microorganisms in the bloodstream from an -omics standpoint, which is termed "circulating microbiota." While detecting microorganisms in the bloodstream was historically considered as an indication of infection, evidence on the circulating microbiota is continually accumulating in various patient populations without clinical signs of infection and even in otherwise healthy individuals. Moreover, both quantitative and compositional alterations of the circulating microbiota have recently been implicated in the pathogenesis of chronic inflammatory conditions, potentially through their immunostimulatory, atherogenic, and cardiotoxic properties. In this mini review, we aim to provide recent evidence on the characteristics and roles of circulating microbiota in several cardiometabolic diseases, such as type 2 diabetes, cardiovascular disease, and chronic kidney disease, with highlights of our emerging findings on circulating microbiota in patients with end-stage kidney disease undergoing hemodialysis.

Knowledge Discovery-Based Analysis of Health Factors of Urinary Infections in Elderly Cardiology Inpatients

A set of semantic similarity calculation methods combining full-text text and domain knowledge topics is proposed for the current study of entity association relations such as disease-gene in medical texts combined with topics in knowledge discovery, which is insufficient to reveal the deep semantic association relations of medical domain knowledge at topic level. Taking urinary infections in elderly inpatients as the research subject, word embedding representation of word vectors and topic vectors is performed by the TWE model, and similarity calculation is performed by combining text and domain knowledge topics based on Siamese Network framework. The urinary microbiological culture results of both groups were dominated by Escherichia coli, accounting for 34.65% and 47.92%, respectively; the use of antimicrobial drugs in the symptomatic urinary infection group was 94.19% higher than that in the asymptomatic bacteriuria group, 77.27% (x 2  = 8.158, P=0.004).

Role of Butyrate, a Gut Microbiota Derived Metabolite, in Cardiovascular Diseases: A comprehensive narrative review

Cardiovascular diseases (CVD) are major causes of death worldwide. Recently, new roles for intestinal microbiota in pathology and treatment of CVD have been proposed. Butyrate, a bacterial metabolite, is synthesized in the gut and performs most of its functions in there. However, researchers have discovered that butyrate could enter to portal vein and interact with various organs. Butyrate exhibits a broad range of pharmacological activities, including microbiome modulator, anti-inflammatory, anti-obesity, metabolic pathways regulator, anti-angiogenesis, and antioxidant. In this article we review evidence supporting a potentially therapeutic role for butyrate in CVD and the mechanisms and pathways involved in the cardio-protective effects of butyrate from the gut and circulation to the nervous system. In summary, although butyrate exhibits a wide variety of biological activities in different pathways including energy homeostasis, glucose and lipid metabolism, inflammation, oxidative stress, neural signaling, and epigenetic modulation in experimental settings, it remains unclear whether these findings are clinically relevant and whether the molecular pathways are activated by butyrate in humans.

The Interaction between the Gut Microbiome and Bile Acids in Cardiometabolic Diseases

Cardio-metabolic diseases (CMD) are a spectrum of diseases (e.g., type 2 diabetes, atherosclerosis, non-alcohol fatty liver disease (NAFLD), and metabolic syndrome) that are among the leading causes of morbidity and mortality worldwide. It has long been known that bile acids (BA), which are endogenously produced signalling molecules from cholesterol, can affect CMD risk and progression and directly affect the gut microbiome (GM). Moreover, studies focusing on the GM and CMD risk have dramatically increased in the past decade. It has also become clear that the GM can function as a "new" endocrine organ. BA and GM have a complex and interdependent relationship with several CMD pathways. This review aims to provide a comprehensive overview of the interplay between BA metabolism, the GM, and CMD risk and progression.

The effect of Chinese herbal formulas combined with metformin on modulating the gut microbiota in the amelioration of type 2 diabetes mellitus: A systematic review and meta-analysis

To assess and analyse the effectiveness and safety of combined Chinese herbal formula (CHF) and metformin treatment in the modulation of the gut microbiota in the amelioration of type 2 diabetes mellitus(T2DM), all publications addressing the effect of this combination treatment on the quantitative alterations in the gut microbiota and glucose parameters were collected. Rob tool in the Cochrane handbook was performed to evaluate the methodological quality of all included studies. Relevant information and statistics were abstracted and synthesized in Review Manager 5.4 to evaluate the efficacy of combination treatment. Sensitivity analyses and subgroup analyses were used to analyse the sources of heterogeneity. Publication bias analyses were performed by Stata software to assess the robustness and quality of the outcomes. As a result, a total of 12 eligible RCTs with 1307 T2DM participants from 7 electronic databases were included. Combined CHF with metformin treatment showed better efficacies than metformin monotherapy in regulating the structure of the gut microbiota, characterized by increased Bifidobacterium, Lactobacillus and Bacteroidetes and decreased Enterobacteriaceae, Enterococcus, and Saccharomyces along with better decreases in glycated haemoglobin, fasting plasma glucose, 2-hour postprandial blood glucose, fasting insulin and homeostasis model assessment of insulin resistance. Subgroup analyses further analysed the effect of metformin doses and CHF classifications on controlling hyperglycaemia and altering the gut microbiota. In conclusion, our meta-analysis suggested that combined CHF with metformin treatment is promising for the modulation of the gut microbiota along with ameliorating hyperglycemia in T2DM patients. Importantly, more well-designed RCTs are needed to validate the outcomes and verify the treatment value for clinical purposes.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021291524, identifier CRD42021291524.

The Role of the Gut Microbiota on the Beneficial Effects of Ketogenic Diets

The ketogenic diet is a dietary regime focused on strongly reducing carbohydrate intake and increasing fat intake; leading to a state of ketosis. The ketogenic diet has gained much popularity over the years due to its effects on promoting weight loss, increasing insulin sensitivity and reducing dyslipidaemia. All these factors play a crucial role in the development of cardio-metabolic diseases; one of the greatest health challenges of the time. Moreover, the ketogenic diet has been known to reduce (epileptic) seizure activity. It is still poorly understood how following a ketogenic diet can lead to these beneficial metabolic effects. However, in recent years it has become clear that diet and the gut microbiota interact with one another and thus influence host health. The goal of this review is to summarize the current state of knowledge regarding the beneficial metabolic effects of the ketogenic diet and the role of gut microbiota in these effects.

Dissection of the Functional Mechanism of Human Gut Bacterial Strain AD16 by Secondary Metabolites' Identification, Network Pharmacology, and Experimental Validation

Gut microbiota plays important roles in several metabolic processes, such as appetite and food intake and absorption of nutrients from the gut. It is also of great importance in the maintenance of the health of the host. However, much remains unknown about the functional mechanisms of human gut microbiota itself. Here, we report the identification of one anticancer gut bacterial strain AD16, which exhibited potent suppressive effects on a broad range of solid and blood malignancies. The secondary metabolites of the strain were isolated and characterized by a bioactivity-guided isolation strategy. Five new compounds, streptonaphthalenes A and B (1-2), pestaloficins F and G (3-4), and eudesmanetetraiol A (5), together with nine previously known compounds, were isolated from the effective fractions of AD16. Structures of the new compounds were established by 1D and 2D NMR and MS analysis, and the absolute configurations were determined by the CD method. The analysis of network pharmacology suggested that 3, 2, and 13 could be the key components for the anti-NSCLC activity of AD16. In addition to the PI3K–Akt signaling pathway, the proteoglycans in cancer pathway could be involved in the anti-NSCLC action of AD16.

The Role of Gut Microbiota and Its Produced Metabolites in Obesity, Dyslipidemia, Adipocyte Dysfunction, and Its Interventions

Obesity is becoming an increasing problem worldwide and is often, but not invariably, associated with dyslipidemia. The gut microbiota is increasingly linked to cardiovascular disease, nonalcoholic fatty liver disease, and type 2 diabetes mellitus. However, relatively little focus has been attributed to the role of gut-microbiota-derived metabolites in the development of dyslipidemia and alterations in lipid metabolism. In this review, we discuss current data involved in these processes and point out the therapeutic potentials. We cover the ability of gut microbiota metabolites to alter lipoprotein lipase action, VLDL secretion, and plasma triglyceride levels, and its effects on reverse cholesterol transport, adipocyte dysfunction, and adipose tissue inflammation. Finally, the current intervention strategies for treatment of obesity and dyslipidemia is addressed with emphasis on the role of gut microbiota metabolites and its ability to predict treatment efficacies.

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

AIMS

Gut microbiota and their generated metabolites impact the host vascular phenotype. The metaorganismal metabolite trimethylamine N-oxide (TMAO) is both associated with adverse clinical thromboembolic events, and enhances platelet responsiveness in subjects. The impact of TMAO on vascular Tissue Factor (TF) in vivo is unknown. Here, we explore whether TMAO-enhanced thrombosis potential extends beyond TMAO effects on platelets, and is linked to TF. We also further explore the links between gut microbiota and vascular endothelial TF expression in vivo.

METHODS AND RESULTS

In initial exploratory clinical studies, we observed that among sequential stable subjects (n = 2989) on anti-platelet therapy undergoing elective diagnostic cardiovascular evaluation at a single-site referral centre, TMAO levels were associated with an increased incident (3 years) risk for major adverse cardiovascular events (MACE) (myocardial infarction, stroke, or death) [4th quartile (Q4) vs. Q1 adjusted hazard ratio (HR) 95% confidence interval (95% CI), 1.73 (1.25-2.38)]. Similar results were observed within subjects on aspirin mono-therapy during follow-up [adjusted HR (95% CI) 1.75 (1.25-2.44), n = 2793]. Leveraging access to a second higher risk cohort with previously reported TMAO data and monitoring of anti-platelet medication use, we also observed a strong association between TMAO and incident (1 year) MACE risk in the multi-site Swiss Acute Coronary Syndromes Cohort, focusing on the subset (n = 1469) on chronic dual anti-platelet therapy during follow-up [adjusted HR (95% CI) 1.70 (1.08-2.69)]. These collective clinical data suggest that the thrombosis-associated effects of TMAO may be mediated by cells/factors that are not inhibited by anti-platelet therapy. To test this, we first observed in human microvascular endothelial cells that TMAO dose-dependently induced expression of TF and vascular cell adhesion molecule (VCAM)1. In mouse studies, we observed that TMAO-enhanced aortic TF and VCAM1 mRNA and protein expression, which upon immunolocalization studies, was shown to co-localize with vascular endothelial cells. Finally, in arterial injury mouse models, TMAO-dependent enhancement of in vivo TF expression and thrombogenicity were abrogated by either a TF-inhibitory antibody or a mechanism-based microbial choline TMA-lyase inhibitor (fluoromethylcholine).

CONCLUSION

Endothelial TF contributes to TMAO-related arterial thrombosis potential, and can be specifically blocked by targeted non-lethal inhibition of gut microbial choline TMA-lyase.

Sodium acetate ameliorated systemic and renal oxidative stress in high-fructose insulin-resistant pregnant Wistar rats

Pregnancy is an insulin-resistant condition especially at near term predisposing maternal kidneys to hyperinsulinemia-induced oxidative stress. The impact of fructose on renal metabolic dysregulation and oxidative stress in pregnancy requires elucidation. Short-chain fatty acids (SCFAs) are known for protective roles in oxidative stress conditions. Therefore, the study aimed at investigating fructose-induced glucose dysregulation and renal oxidative stress in pregnant and non-pregnant rats and the possible preventive role of SCFA, acetate. Thirty female Wistar rats were grouped (n = 5/group). Three groups were made pregnant (P); the other three remained non-pregnant (NP). Both pregnant and non-pregnant rats received drinking water (control), 10% fructose (w/v) (NP+F or P+F), and 10% (w/v) fructose plus sodium acetate (200 mg/kg) (NP+F+A or P+F+A) for 3 weeks. Renal and plasma glutathione antioxidant index (GSH/GSSG), G6PDH, and adenosine were significantly lower in NP+F and P+F groups compared with control while renal and plasma adenosine deaminase (ADA), xanthine oxidase (XO), uric acid (UA), lactate dehydrogenase (LDH), and malonaldehyde (MDA) were significantly elevated in NP+F and P+F groups compared with controls. HOMA-IR showed marked impairment in both NP+F and P+F groups. The P+F group revealed greater suppression in plasma and renal G6PDH-dependent antioxidant index, adenosine, and aggravation of LDH, MDA compared with the NP+F group (p < 0.05). Sodium acetate reduces plasma and renal surrogate oxidative stress markers, improved G6PD-dependent antioxidant index, and HOMA-IR in NP+F and P+F groups. Pregnancy exacerbates fructose-induced insulin resistance and renal oxidative stress whereas acetate ameliorated fructose-induced redox and glucose dysregulation in pregnant and non-pregnant rats.

The Influence of Gut Microbiota on the Cardiovascular System Under Conditions of Obesity and Chronic Stress

PURPOSE OF REVIEW

Based on the available data, it can be assumed that microbiota is an integral part of the human body. The most heavily colonized area of the human body is the gut, with bacterial accumulation ranging from 101-103 cells/g in the upper intestine to 1011-1012 cells/g in the colon. However, colonization of the gut is not the same throughout, as it was shown that there are differences between the composition of the microbiota in the intestine lumen and in the proximity of the mucus layer.

RECENT FINDINGS

Gut microbiota gradient can be differentially regulated by factors such as obesity and chronic stress. In particular, a high fat diet influences the gut microbial composition. It was also found that chronic stress may cause the development of obesity and thus change the organization of the intestinal barrier. Recent research has shown the significant effect of intestinal microflora on cardiovascular function. Enhanced absorption of bacterial fragments, such as lipopolysaccharide (LPS), promotes the onset of "metabolic endotoxemia," which could activate toll-like receptors, which mediates an inflammatory response and in severe cases could cause cardiovascular diseases. It is presumed that the intestinal microbiota, and especially its metabolites (LPS and trimethylamine N-oxide (TMAO)), may play an important role in the pathogenesis of arterial hypertension, atherosclerosis, and heart failure. This review focuses on how gut microbiota can change the morphological and functional activity of the cardiovascular system in the course of obesity and in conditions of chronic stress.

Metabolite Profile of Treatment-Naive Metabolic Syndrome Subjects in Relation to Cardiovascular Disease Risk

Metabolic syndrome (MetSyn) is an important risk factor for type 2 diabetes and cardiovascular diseases (CVD). This study aimed to find distinct plasma metabolite profiles between insulin-resistant and non-insulin resistant subjects with MetSyn and evaluate if MetSyn metabolite profiles are related to CVD risk and lipid fluxes. In a cross-sectional study, untargeted metabolomics of treatment-naive males with MetSyn (n = 132) were analyzed together with clinical parameters. In a subset of MetSyn participants, CVD risk was calculated using the Framingham score (n = 111), and lipolysis (n = 39) was measured by a two-step hyperinsulinemic euglycemic clamp using [1,1,2,3,3-²H5] glycerol to calculate lipolysis suppression rates. Peripheral insulin resistance was related to fatty acid metabolism and glycerolphosphorylcholine. Interestingly, although insulin resistance is considered to be a risk factor for CVD, we observed that there was little correspondence between metabolites associated with insulin resistance and metabolites associated with CVD risk. The latter mainly belonged to the androgenic steroid, fatty acid, phosphatidylethanolamine, and phophatidylcholine pathways. These data provide new insights into metabolic changes in mild MetSyn pathophysiology and MetSyn CVD risk related to lipid metabolism. Prospective studies may focus on the pathophysiological role of the here-identified biomarkers.

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.

Impact drugs targeting cardiometabolic risk on the gut microbiota

PURPOSE OF REVIEW

Alterations in the gut microbiome composition or function are associated with risk factors for cardiometabolic diseases, including hypertension, hyperlipidemia and hyperglycemia. Based on recent evidence that also oral medications used to treat these conditions could alter the gut microbiome composition and function and, vice versa, that the gut microbiome could affect the efficacy of these treatments, we reviewed the literature on these observed interactions.

RECENT FINDINGS

While the interaction of metformin with the gut microbiome has been studied most, other drugs that target cardiometabolic risk are gaining attention and often showed associations with alterations in microbiome-related features, including alterations in specific microbial taxa or pathways, microbiome composition or microbiome-derived metabolites, while the gut microbiome was also involved in drug metabolism and drug efficacy. As for metformin, for some of them even a potential therapeutic effect via the gut microbiome is postulated. However, exact mechanisms remain to be elucidated.

SUMMARY

There is growing interest in clarifying the interactions between the gut microbiome and drugs to treat hypertension, hyperlipidemia and hyperglycemia as well as the first pass effect of microbiome on drug efficacy. While mostly analysed in animal models, also human studies are gaining more and more traction. Improving the understanding of the gut microbiome drug interaction can provide clinical directions for therapy by optimizing drug efficacy or providing new targets for drug development.

Effects of arsenic exposure on lipid metabolism: a systematic review and meta-analysis

Lipid metabolism dysfunction is a risk factor for cardiovascular diseases. Reportedly, arsenic exposure could affect lipid metabolism, but this finding remains controversial. Herein, we updated and reevaluated evidence regarding the relationship between arsenic exposure and lipid metabolism. Electronic and manual searches were performed to determine the effect of arsenic exposure on lipid metabolism from inception up to 30 November 2019. Overall, five studies were included in our meta-analysis. Two reviewers independently extracted information. Standardized mean difference (SMD) and 95% confidence intervals (CI) were used to analyze the combined effects of four indicators related to lipid metabolism (total cholesterol [TC], triglyceride [TG], high-density lipoprotein [HDL], low-density lipoprotein [LDL]). Afterwards, subgroup and sensitivity analyses were performed to explore the source of heterogeneity. Publication bias was tested using funnel plots and Begg's test. In this study, we observed that arsenic exposure can affect lipid metabolism by reducing serum HDL levels and increasing serum LDL levels. Following subgroup analysis, the arsenic concentration appeared to affect lipid metabolism. Funnel plot and Begg's test suggested no asymmetry. In conclusion, we recommend that potential influencing factors, including age, exposure time, and multiple concentration gradients, should be considered to further explore the relationship between arsenic exposure and lipid metabolism.

Metabolism and Metabolic Disorders and the Microbiome: The Intestinal Microbiota Associated With Obesity, Lipid Metabolism, and Metabolic Health-Pathophysiology and Therapeutic Strategies

Changes in the intestinal microbiome have been associated with obesity and type 2 diabetes, in epidemiological studies and studies of the effects of fecal transfer in germ-free mice. We review the mechanisms by which alterations in the intestinal microbiome contribute to development of metabolic diseases, and recent advances, such as the effects of the microbiome on lipid metabolism. Strategies have been developed to modify the intestinal microbiome and reverse metabolic alterations, which might be used as therapies. We discuss approaches that have shown effects in mouse models of obesity and metabolic disorders, and how these might be translated to humans to improve metabolic health.

Type 2 Diabetes Mellitus Associated with Obesity (Diabesity). The Central Role of Gut Microbiota and Its Translational Applications

Obesity is a condition of rising prevalence worldwide, with important socioeconomic implications, being considered as a growing public health concern. Frequently, obesity brings other complications in addition to itself—like Type 2 Diabetes Mellitus (T2DM)—sharing origin, risk factors and pathophysiological mechanisms. In this context, some authors have decided to include both conditions as a unique entity known as “diabesity”. In fact, understanding diabesity as a single disease is possible to maximise the benefits from therapies received in these patients. Gut microbiota plays a key role in individual’s health, and their alterations, either in its composition or derived products are related to a wide range of metabolic disorders like T2DM and obesity. The present work aims to collect the different changes reported in gut microbiota in patients with T2DM associated with obesity and their possible role in the onset, development, and establishment of the disease. Moreover, current research lines to modulate gut microbiota and the potential clinical translation derived from the knowledge of this system will also be reviewed, which may provide support for a better clinical management of such a complex condition.

Targeting the gut microbiota by Asian and Western dietary constituents: a new avenue for diabetes

Increasing numerous diabetes annually is a great concern in public health globally. Gut microbiota recently has been suggested to be an emerging organ acting as a critical regulator in diabetes. Notably, gut microbiota is closely affected through an individual's nutrient intake and dietary pattern. Moreover, the metabolites of diets through gut microbiota are closely associated with the development of diabetes. Increasing evidence has established the association of different dietary pattern with alterations of the gut microbiota profile, in particular, the Asian diet and Western diet are typically as essential components linked to the interactions between gut microbiota and induction of obesity which is a significant risk factor for diabetes. In addition, some bacteria-related therapeutic methods including probiotics, dietary short-chain fatty acids immunotherapy, and gut microbiome transfer would be applied in the clinical prevention and control diabetes. Taken together, based on current published observations, the gut microbiota may serve as regulator or targets by the Asian diet and Western diet, contributing to the prevention or induction of diabetes eventually. In general, in the upcoming future, one of the emerging strategies for the prevention and control of diabetes may modulate gut microbiota through precise dietary strategies.

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

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

Trimethylamine N-Oxide in Relation to Cardiometabolic Health-Cause or Effect?

Trimethylamine-N-oxide (TMAO) is generated in a microbial-mammalian co-metabolic pathway mainly from the digestion of meat-containing food and dietary quaternary amines such as phosphatidylcholine, choline, betaine, or L-carnitine. Fish intake provides a direct significant source of TMAO. Human observational studies previously reported a positive relationship between plasma TMAO concentrations and cardiometabolic diseases. Discrepancies and inconsistencies of recent investigations and previous studies questioned the role of TMAO in these diseases. Several animal studies reported neutral or even beneficial effects of TMAO or its precursors in cardiovascular disease model systems, supporting the clinically proven beneficial effects of its precursor, L-carnitine, or a sea-food rich diet (naturally containing TMAO) on cardiometabolic health. In this review, we summarize recent preclinical and epidemiological evidence on the effects of TMAO, in order to shed some light on the role of TMAO in cardiometabolic diseases, particularly as related to the microbiome.