Gut microbiota from coronary artery disease patients contributes to vascular dysfunction in mice by regulating bile acid metabolism and immune activation

Gut microbes metabolize strawberry phytochemicals and mediate their beneficial effects on vascular inflammation

Evidence suggests that a healthy gut microbiome is essential for metabolizing dietary phytochemicals. However, the microbiome's role in metabolite production and the influence of gut dysbiosis on this process remain unclear. Further, studies on the relationship among gut microbes, metabolites, and biological activities of phytochemicals are limited. We addressed this knowledge gap using strawberry phytochemicals as a model. C57BL/6J mice were fed a standard diet [C]; strawberry-supplemented diet (~2 human servings) [CS]; strawberry-supplemented diet and treated with antibiotics (to deplete gut microbes) [CSA]; high-fat diet (HFD) [HF]; strawberry-supplemented HFD [HS]; and strawberry-supplemented HFD and treated with antibiotics [HSA] for 12 weeks. First, antibiotic treatment suppressed the production of selected metabolites (CSA vs. CS), and p-coumaric acid was identified as a strawberry-derived microbial metabolite. Second, HFD-induced dysbiosis negatively affected metabolite production (HS vs. HF), and hippuric acid was identified as a microbial metabolite in HFD conditions. Third, dietary strawberries improved HFD-induced vascular inflammation (HS vs. HF). However, antibiotic treatment reduced metabolite production and abolished the vascular effects of strawberries (HSA vs. HS), indicating the importance of gut microbes in mediating the vascular benefits of strawberries via metabolites. Fourth, strawberry supplementation decreased Coprobacillus that was positively associated with vascular inflammation, whereas it increased Lachnospiraceae that was negatively associated with vascular inflammation and positively associated with hippuric acid. Fifth, hippuric acid was negatively associated with vascular inflammation. Our study fills in some pieces of the giant puzzle regarding the influence of gut microbes on the biological activities of phytochemicals. HFD-induced gut dysbiosis negatively impacts metabolite production and a strong association exists among gut microbes, strawberry-derived microbial metabolites, and the vascular benefits of dietary strawberries. Further, our study provides significant proof of concept to warrant future research on the use of strawberries as a nutritional strategy to prevent vascular complications.

The identification of metabolites from gut microbiota in coronary heart disease via network pharmacology

Although the gut microbial metabolites exhibit potential effects on coronary heart disease (CHD), the underlying mechanism remains unclear. In this study, the active gut microbial metabolites acting on CHD and their potential mechanisms of action were explored through a network pharmacological approach. We collected a total of 208 metabolites from the gutMgene database and 726 overlapping targets from the similarity ensemble approach (SEA) and SwissTargetPrediction (STP) database, and ultimately identified 610 targets relevant to CHD. In conjunction with the gutMGene database, we identified 12 key targets. The targets of exogenous substances were removed, and 10 core targets involved in CHD were eventually retained. The microbiota-metabolites-targets-signalling pathways network analysis revealed that C-type lectin receptor signalling pathway, Lachnospiraceae, Escherichia, mitogen-activated protein kinase 1, prostaglandin-endoperoxidase synthase 2, phenylacetylglutamine and alcoholic acid are notable components of CHD and play important roles in the development of CHD. The results of molecular docking experiments demonstrated that AKT1-glycocholic acid and PTGS2-phenylacetylglutamine complexes may act on C-type lectin receptor signalling pathways. In this study, the key substances and potential mechanisms of gut microbial metabolites were analysed via network pharmacological methods, and a scientific basis and comprehensive idea were provided for the effects of gut microbial metabolites on CHD.

Erythrocyte Very Long-Chain Saturated Fatty Acids, Gut Microbiota-Bile Acid Axis, and Incident Coronary Artery Disease in Adults: A Prospective Cohort Study

BACKGROUND

Prior research has highlighted inverse associations between concentrations of circulating very long-chain saturated fatty acids (VLCSFAs) and coronary artery disease (CAD). However, the intricate links involving VLCSFAs, gut microbiota, and bile acids remain underexplored.

OBJECTIVES

This study examined the association of erythrocyte VLCSFAs with CHD incidence, focusing on the mediating role of gut microbiota and fecal bile acids.

METHODS

This 10-y prospective study included 2383 participants without CHD at baseline. Erythrocyte VLCSFAs [arachidic acid (C20:0), behenic acid (C22:0), and lignoceric acid (C24:0)] were measured using gas chromatography at baseline, and 274 CHD incidents were documented in triennial follow-ups. Gut microbiota in 1744 participants and fecal bile acid metabolites in 945 participants were analyzed using 16S ribosomal ribonucleic acid sequencing and ultra-performance liquid chromatography-tandem mass spectrometry at middle-term.

RESULTS

The multivariable-adjusted hazard ratios (95% confidence interval) for CHD incidence in highest compared with lowest quartiles were 0.87 (0.61, 1.25) for C20:0, 0.63 (0.42, 0.96) for C22:0, 0.59 (0.41, 0.85) for C24:0, and 0.57 (0.39, 0.83) for total VLCSFAs. Participants with higher total VLCSFA concentrations exhibited increased abundances of Holdemanella, Coriobacteriales Incertae Sedis spp., Ruminococcaceae UCG-005 and UCG-010, and Lachnospiraceae ND3007 group. These 5 genera generated overlapping differential microbial scores (ODMSs) that accounted for 11.52% of the total VLCSFAs-CHD association (Pmediation = 0.018). Bile acids tauro_α_ and tauro_β_muricholic acid were inversely associated with ODMS and positively associated with incident CHD. Opposite associations were found for glycolithocholic acid and glycodeoxycholic acid. Mediation analyses indicated that glycolithocholic acid, glycodeoxycholic acid, and tauro_α_ and tauro_β_muricholic acid explained 56.40%, 35.19%, and 26.17% of the ODMS-CHD association, respectively (Pmediation = 0.002, 0.008, and 0.020).

CONCLUSIONS

Elevated erythrocyte VLCSFAs are inversely associated with CHD risk in the Chinese population, with gut microbiota and fecal bile acid profiles potentially mediating this association. The identified microbiota and bile acid metabolites may serve as potential intervention targets in future studies. This trial was registered at www.

CLINICALTRIALS

gov as NCT03179657.

The therapeutic effect and possible mechanisms of alginate oligosaccharide on metabolic syndrome by regulating gut microbiota

Metabolic syndrome (MetS) is a disease condition incorporating the abnormal accumulation of various metabolic components, including overweight or abdominal obesity, insulin resistance and abnormal glucose tolerance, hypertension, atherosclerosis, or dyslipidemia. It has been proved that the gut microbiota and microbial-derived products play an important role in regulating lipid metabolism and thus the onset and development of MetS. Previous studies have demonstrated that oligosaccharides with prebiotic effects, such as chitosan oligosaccharides, can regulate the structure of the microbial community and its derived products to control weight and reduce MetS associated with obesity. Alginate oligosaccharides (AOS), natural products extracted from degraded alginate salts with high solubility and extensive biological activity, have also been found to modulate gut microbiota. This review aims to summarize experimental evidence on the positive effects of AOS on different types of MetS while providing insights into mechanisms through which AOS regulates gut microbiota for preventing and treating MetS.

BCAA-producing Clostridium symbiosum promotes colorectal tumorigenesis through the modulation of host cholesterol metabolism

Identification of potential bacterial players in colorectal tumorigenesis has been a focus of intense research. Herein, we find that Clostridium symbiosum (C. symbiosum) is selectively enriched in tumor tissues of patients with colorectal cancer (CRC) and associated with higher colorectal adenoma recurrence after endoscopic polypectomy. The tumorigenic effect of C. symbiosum is observed in multiple murine models. Single-cell transcriptome profiling along with functional assays demonstrates that C. symbiosum promotes the proliferation of colonic stem cells and enhances cancer stemness. Mechanistically, C. symbiosum intensifies cellular cholesterol synthesis by producing branched-chain amino acids (BCAAs), which sequentially activates Sonic hedgehog signaling. Low dietary BCAA intake or blockade of cholesterol synthesis by statins could partially abrogate the C. symbiosum-induced cell proliferation in vivo and in vitro. Collectively, we reveal C. symbiosum as a bacterial driver of colorectal tumorigenesis, thus identifying a potential target in CRC prediction, prevention, and treatment.

Intestinal permeability in human cardiovascular diseases: a systematic review and meta-analysis

Background

There is a link between cardiovascular diseases and intestinal permeability, but it is not clear. This review aimed to elucidate intestinal permeability in cardiovascular diseases by meta-analysis.

Methods

Multidisciplinary electronic databases were searched from the database creation to April 2023. All included studies were assessed for risk of bias according to the Joanna Briggs Institute Critical Appraisal Checklist. The heterogeneity of each study was estimated using the I2 statistic, and the data were analyzed using Review Manager 5.3 and Stata 16.0.

Results

In total, studies in 13 pieces of literature were included in the quantitative meta-analysis. These studies were conducted among 1,321 subjects mostly older than 48. Patients had higher levels of intestinal permeability markers (lipopolysaccharide, d-lactate, zonulin, serum diamine oxidase, lipopolysaccharide-binding protein, intestinal fatty acid binding protein, and melibiose/rhamnose) than controls (standard mean difference SMD = 1.50; 95% CI = 1.31-1.88; p < 0.00001). Similarly, lipopolysaccharide levels were higher in patients than in controls (SMD = 1.61; 95% CI = 1.02-2.21; p < 0.00001); d-lactate levels were higher in patients than in controls (SMD = 1.16; 95% CI = 0.23-2.08; p = 0.01); zonulin levels were higher in patients than in controls (SMD = 1.74; 95% CI = 1.45-2.03; p < 0.00001); serum diamine oxidase levels were higher in patients than in controls (SMD = 2.51; 95% CI = 0.29-4.73; p = 0.03).

Conclusion

The results of the meta-analysis verified that the intestinal barrier was damaged and intestinal permeability was increased in patients with cardiovascular diseases. These markers may become a means of the diagnosis and treatment of cardiovascular diseases.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=414296, identifier CRD42023414296.

Insights from metagenomics into gut microbiome associated with acute coronary syndrome therapy

Acute coronary syndrome (ACS) is a predominant cause of mortality, and the prompt and precise identification of this condition is crucial to minimize its impact. Recent research indicates that gut microbiota is associated with the onset, progression, and treatment of ACS. To investigate its role, we sequenced the gut microbiota of 38 ACS patients before and after percutaneous coronary intervention and statin therapy at three time points, examining differential species and metabolic pathways. We observed a decrease in the abundance of Parabacteroides, Escherichia, and Blautia in patients after treatment and an increase in the abundance of Gemalla, Klebsiella variicola, Klebsiella pneumoniae, and others. Two pathways related to sugar degradation were more abundant in patients before treatment, possibly correlated with disorders of sugar metabolism and risk factors, such as hyperglycemia, insulin resistance, and insufficient insulin secretion. Additionally, seven pathways related to the biosynthesis of vitamin K2 and its homolog were reduced after treatment, suggesting that ACS patients may gradually recover after therapy. The gut microbiota of patients treated with different statins exhibited notable differences after treatment. Rosuvastatin appeared to promote the growth of anti-inflammatory bacteria while reducing pro-inflammatory bacteria, whereas atorvastatin may have mixed effects on pro-inflammatory and anti-inflammatory bacteria while increasing the abundance of Bacteroides. Our research will provide valuable insights and enhance comprehension of ACS, leading to better patient diagnosis and therapy.

Modulation of Gut Microbial Biomarkers and Metabolites in Cancer Management by Tea Compounds

Cancers are causing millions of deaths and leaving a huge clinical and economic burden. High costs of cancer drugs are limiting their access to the growing number of cancer cases. The development of more affordable alternative therapy could reach more patients. As gut microbiota plays a significant role in the development and treatment of cancer, microbiome-targeted therapy has gained more attention in recent years. Dietary and natural compounds can modulate gut microbiota composition while providing broader and more accessible access to medicine. Tea compounds have been shown to have anti-cancer properties as well as modulate the gut microbiota and their related metabolites. However, there is no comprehensive review that focuses on the gut modulatory effects of tea compounds and their impact on reshaping the metabolic profiles, particularly in cancer models. In this review, the effects of different tea compounds on gut microbiota in cancer settings are discussed. Furthermore, the relationship between these modulated bacteria and their related metabolites, along with the mechanisms of how these changes led to cancer intervention are summarized.

Gut microbial metabolism is linked to variations in circulating non-high density lipoprotein cholesterol

BACKGROUND

Non-high-density lipoprotein cholesterol (non-HDL-c) was a strong risk factor for incident cardiovascular diseases and proved to be a better target of lipid-lowering therapies. Recently, gut microbiota has been implicated in the regulation of host metabolism. However, its causal role in the variation of non-HDL-c remains unclear.

METHODS

Microbial species and metabolic capacities were assessed with fecal metagenomics, and their associations with non-HDL-c were evaluated by Spearman correlation, followed by LASSO and linear regression adjusted for established cardiovascular risk factors. Moreover, integrative analysis with plasma metabolomics were performed to determine the key molecules linking microbial metabolism and variation of non-HDL-c. Furthermore, bi-directional mendelian randomization analysis was performed to determine the potential causal associations of selected species and metabolites with non-HDL-c.

FINDINGS

Decreased Eubacterium rectale but increased Clostridium sp CAG_299 were causally linked to a higher level of non-HDL-c. A total of 16 microbial capacities were found to be independently associated with non-HDL-c after correcting for age, sex, demographics, lifestyles and comorbidities, with the strongest association observed for tricarboxylic acid (TCA) cycle. Furthermore, decreased 3-indolepropionic acid and N-methyltryptamine, resulting from suppressed capacities for microbial reductive TCA cycle, functioned as major microbial effectors to the elevation of circulating non-HDL-c.

INTERPRETATION

Overall, our findings provided insight into the causal effects of gut microbes on non-HDL-c and uncovered a novel link between non-HDL-c and microbial metabolism, highlighting the possibility of regulating non-HDL-c by microbiota-modifying interventions.

FUNDING

A full list of funding bodies can be found in the Sources of funding section.

Oral-gut microbial transmission promotes diabetic coronary heart disease

BACKGROUND

Diabetes is a predominant driver of coronary artery disease worldwide. This study aims to unravel the distinct characteristics of oral and gut microbiota in diabetic coronary heart disease (DCHD). Simultaneously, we aim to establish a causal link between the diabetes-driven oral-gut microbiota axis and increased susceptibility to diabetic myocardial ischemia-reperfusion injury (MIRI).

METHODS

We comprehensively investigated the microbial landscape in the oral and gut microbiota in DCHD using a discovery cohort (n = 183) and a validation chohort (n = 68). Systematically obtained oral (tongue-coating) and fecal specimens were subjected to metagenomic sequencing and qPCR analysis, respectively, to holistically characterize the microbial consortia. Next, we induced diabetic MIRI by administering streptozotocin to C57BL/6 mice and subsequently investigated the potential mechanisms of the oral-gut microbiota axis through antibiotic pre-treatment followed by gavage with specific bacterial strains (Fusobacterium nucleatum or fecal microbiota from DCHD patients) to C57BL/6 mice.

RESULTS

Specific microbial signatures such as oral Fusobacterium nucleatum and gut Lactobacillus, Eubacterium, and Roseburia faecis, were identified as potential microbial biomarkers in DCHD. We further validated that oral Fusobacterium nucleatum and gut Lactobacillus are increased in DCHD patients, with a positive correlation between the two. Experimental evidence revealed that in hyperglycemic mice, augmented Fusobacterium nucleatum levels in the oral cavity were accompanied by an imbalance in the oral-gut axis, characterized by an increased coexistence of Fusobacterium nucleatum and Lactobacillus, along with elevated cardiac miRNA-21 and a greater extent of myocardial damage indicated by TTC, HE, TUNEL staining, all of which contributed to exacerbated MIRI.

CONCLUSION

Our findings not only uncover dysregulation of the oral-gut microbiota axis in diabetes patients but also highlight the pivotal intermediary role of the increased abundance of oral F. nucleatum and gut Lactobacillus in exacerbating MIRI. Targeting the oral-gut microbiota axis emerges as a potent strategy for preventing and treating DCHD. Oral-gut microbial transmission constitutes an intermediate mechanism by which diabetes influences myocardial injury, offering new insights into preventing acute events in diabetic patients with coronary heart disease.

The gut microbiome as a modulator of arterial function and age-related arterial dysfunction

The arterial system is integral to the proper function of all other organs and tissues. Arterial function is impaired with aging, and arterial dysfunction contributes to the development of numerous age-related diseases, including cardiovascular diseases. The gut microbiome has emerged as an important regulator of both normal host physiological function and impairments in function with aging. The purpose of this review is to summarize more recently published literature demonstrating the role of the gut microbiome in supporting normal arterial development and function and in modulating arterial dysfunction with aging in the absence of overt disease. The gut microbiome can be altered due to a variety of exposures, including physiological aging processes. We explore mechanisms by which the gut microbiome may contribute to age-related arterial dysfunction, with a focus on changes in various gut microbiome-related compounds in circulation. In addition, we discuss how modulating circulating levels of these compounds may be a viable therapeutic approach for improving artery function with aging. Finally, we identify and discuss various experimental considerations and research gaps/areas of future research.

A toolbox for genetic manipulation in intestinal Clostridium symbiosum

Gut microbes are closely related with human health, but remain much to learn. Clostridium symbiosum is a conditionally pathogenic human gut bacterium and regarded as a potential biomarker for early diagnosis of intestinal tumors. However, the absence of an efficient toolbox that allows diverse genetic manipulations of this bacterium limits its in-depth studies. Here, we obtained the complete genome sequence of C. symbiosum ATCC 14940, a representative strain of C. symbiosum. On this basis, we further developed a series of genetic manipulation methods for this bacterium. Firstly, following the identification of a functional replicon pBP1 in C. symbiosum ATCC 14940, a highly efficient conjugative DNA transfer method was established, enabling the rapid introduction of exogenous plasmids into cells. Next, we constructed a dual-plasmid CRISPR/Cas12a system for genome editing in this bacterium, reaching over 60 % repression for most of the chosen genes as well as efficient deletion (>90 %) of three target genes. Finally, this toolbox was used for the identification of crucial functional genes, involving growth, synthesis of important metabolites, and virulence of C. symbiosum ATCC 14940. Our work has effectively established and optimized genome editing methods in intestinal C. symbiosum, thereby providing strong support for further basic and application research in this bacterium.

Chinese Herbal Medicines for Coronary Heart Disease: Clinical Evidence, Pharmacological Mechanisms, and the Interaction with Gut Microbiota

Coronary heart disease (CHD) is a common type of cardiovascular disease (CVD) that has been on the rise in terms of both incidence and mortality worldwide, presenting a significant threat to human health. An increasing body of studies has shown that traditional Chinese medicine (TCM), particularly Chinese herbal medicines (CHMs), can serve as an effective adjunctive therapy to enhance the efficacy of Western drugs in treating CHD due to their multiple targets and multiple pathways. In this article, we critically review data available on the potential therapeutic strategies of CHMs in the intervention of CHD from three perspectives: clinical evidence, pharmacological mechanisms, and the interaction with gut microbiota. We identified 20 CHMs used in clinical practice and it has been found that the total clinical effective rate of CHD patients improved on average by 17.78% with the intervention of these CHMs. Subsequently, six signaling pathways commonly used in treating CHD have been identified through an overview of potential pharmacological mechanisms of these 20 CHMs and the eight representative individual herbs selected from them. CHMs could also act on gut microbiota to intervene in CHD by modulating the composition of gut microbiota, reducing trimethylamine-N-oxide (TMAO) levels, increasing short-chain fatty acids (SCFAs), and maintaining appropriate bile acids (BAs). Thus, the therapeutic potential of CHMs for CHD is worthy of further study in view of the outcomes found in existing studies.

Gut microbiota dysbiosis -associated obesity and its involvement in cardiovascular diseases and type 2 diabetes. A systematic review

INTRODUCTION

Obesity is a complex, multifactorial disease caused by various factors. Recently, the role of the gut microbiota in the development of obesity and its complications has attracted increasing interest.

PURPOSE

This article focuses on the mechanisms by which gut microbiota dysbiosis induces insulin resistance, type 2 diabetes, and cardiovascular diseases linked to obesity, highlighting the mechanisms explaining the role of gut microbiota dysbiosis-associated inflammation in the onset of these pathologies.

METHODS

A systematic study was carried out to understand and summarize the published results on this topic. More than 150 articles were included in this search, including different types of studies, consulted by an online search in English using various electronic search databases and predefined keywords related to the objectives of our study.

RESULTS

We have summarized the data from the articles consulted in this search, and we have found a major gut microbiota alteration in obesity, characterized by a specific decrease in butyrate-producing bacteria and the production of metabolites and components that lead to metabolic impairments and affect the progression of various diseases associated with obesity through distinct signaling pathways, including insulin resistance, type 2 diabetes, and cardiovascular diseases (CVD). We have also focused on the major role of inflammation as a link between gut microbiota dysbiosis and obesity-associated metabolic complications by explaining the mechanisms involved.

CONCLUSION

Gut microbiota dysbiosis plays a crucial role in the development of various obesity-related metabolic abnormalities, among them type 2 diabetes and CVD, and represents a major challenge for chronic disease prevention and health. Indeed, the intestinal microbiota appears to be a promising target for the nutritional or therapeutic management of these diseases.

Effect of gut flora mediated-bile acid metabolism on intestinal immune microenvironment

According to reports, gut microbiota and metabolites regulate the intestinal immune microenvironment. In recent years, an increasing number of studies reported that bile acids (BAs) of intestinal flora origin affect T helper cells and regulatory T cells (Treg cells). Th17 cells play a pro-inflammatory role and Treg cells usually act in an immunosuppressive role. In this review, we emphatically summarised the influence and corresponding mechanism of different configurations of lithocholic acid (LCA) and deoxycholic acid (DCA) on intestinal Th17 cells, Treg cells and intestinal immune microenvironment. The regulation of BAs receptors G protein-coupled bile acid receptor 1 (GPBAR1/TGR5) and farnesoid X receptor (FXR) on immune cells and intestinal environment are elaborated. Furthermore, the potential clinical applications above were also concluded in three aspects. The above will help researchers better understand the effects of gut flora on the intestinal immune microenvironment via BAs and contribute to the development of new targeted drugs.

The molecular insights of bile acid homeostasis in host diseases

Bile acids (BAs) function as detergents promoting nutrient absorption and as hormones regulating nutrient metabolism. Most BAs are key regulatory factors of physiological activities, which are involved in the regulation of glucose, lipid, and drug metabolisms. Hepatic and intestinal diseases have close connections with the systemic cycling disorders of BAs. The abnormal in BA absorption came up with overmuch BAs could be involved in the pathophysiology of liver and bowel and metabolic disorders such as fatty liver diseases and inflammatory bowel diseases. The primary BAs (PBAs), which are synthesized in the liver, can be transformed into the secondary BAs (SBAs) by gut microbiota. The transformation processes are tightly associated with the gut microbiome and the host endogenous metabolism. The BA biosynthesis gene cluster bile-acid-inducible operon is essential for modulating BA pool, gut microbiome composition, and the onset of intestinal inflammation. This forms a bidirectional interaction between the host and its gut symbiotic ecosystem. The subtle changes in the composition and abundance of BAs perturb the host physiological and metabolic activity. Therefore, maintaining the homeostasis of BAs pool contributes to the balance of the body's physiological and metabolic system. Our review aims to dissect the molecular mechanisms underlying the BAs homeostasis, assess the key factors sustaining the homeostasis and the role of BA acting on host diseases. By linking the BAs metabolic disorders and their associated diseases, we illustrate the effects of BAs homeostasis on health and potential clinical interventions can be taken under the latest research findings.

Dingxin recipe Ⅲ ameliorates hyperlipidemia injury in SD rats by improving the gut barrier, particularly the SCFAs/GPR43 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Dingxin Recipe Ⅲ (DXR Ⅲ) is a traditional Chinese medicine compound used for hyperlipidemia treatment in clinical practice. However, its curative effects and pharmacological mechanisms in hyperlipidemia have not been clarified to date.

AIM OF THE STUDY

Studies have demonstrated that gut barrier was strongly implicated in lipid deposition. Based on gut barrier and lipid metabolism, this study examined the effects and molecular mechanisms of DXR Ⅲ in hyperlipidemia.

MATERIALS AND METHODS

The bioactive compounds of DXR Ⅲ were detected by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry, and its effects were evaluated in high-fat diet-fed rats. Specifically, the serum levels of lipids and hepatic enzymes were measured using the appropriate kits; colon and liver sections were obtained for histological analyses; gut microbiota and metabolites were analyzed by 16S rDNA sequencing and liquid chromatography-MS/MS; and the expression of genes and proteins was determined by real-time quantitative polymerase chain reaction and western blotting and immunohistochemistry, respectively. The pharmacological mechanisms of DXR Ⅲ were further explored by fecal microbiota transplantation and short-chain fatty acid (SCFAs)-based interventions.

RESULTS

DXR Ⅲ treatment significantly downregulated serum lipid levels, mitigated hepatocyte steatosis and improved lipid metabolism. Moreover, DXR Ⅲ improved the gut barrier, specifically by improving the physical barrier in the colon, causing part composition changes in the gut microbiota, and increasing the serum SCFAs level. DXR Ⅲ also upregulated the expression of colon GPR43/GPR109A. Fecal microbiota transplantation from rats treated with DXR Ⅲ downregulated part hyperlipidemia-related phenotypes, while the SCFAs intervention significantly improved most of the hyperlipidemia-related phenotypes and upregulated the expression of GPR43. Moreover, both DXR Ⅲ and SCFAs upregulated the expression of colon ABCA1.

CONCLUSION

DXR Ⅲ protects against hyperlipidemia by improving the gut barrier, particularly the SCFAs/GPR43 pathway.

Gut Microbiota Composition and Cardiovascular Disease: A Potential New Therapeutic Target?

A great deal of evidence has revealed an important link between gut microbiota and the heart. In particular, the gut microbiota plays a key role in the onset of cardiovascular (CV) disease, including heart failure (HF). In HF, splanchnic hypoperfusion causes intestinal ischemia resulting in the translocation of bacteria and their metabolites into the blood circulation. Among these metabolites, the most important is Trimethylamine N-Oxide (TMAO), which is responsible, through various mechanisms, for pathological processes in different organs and tissues. In this review, we summarise the complex interaction between gut microbiota and CV disease, particularly with respect to HF, and the possible strategies for influencing its composition and function. Finally, we highlight the potential role of TMAO as a novel prognostic marker and a new therapeutic target for HF.

Characterization of gut microbiota in adults with coronary atherosclerosis

Background

Cardiovascular disease, which is mainly caused by coronary atherosclerosis, is one of the leading causes of death and disability worldwide. Gut microbiota likely play an important role in coronary atherosclerosis. This study aims to investigate the microbiota profile of adults with coronary atherosclerosis to provide a theoretical basis for future research.

Methods

Fecal samples were collected from 35 adult patients diagnosed with coronary atherosclerosis and 32 healthy adults in Nanjing, China, and the V3-V4 region of 16S rDNA genes was sequenced using high-throughput sequencing. Differences in alpha diversity, beta diversity, and gut microbiota composition between the two groups were then compared.

Results

A beta diversity analysis revealed significant differences between adults with coronary atherosclerosis and controls, but there was no statistical difference in alpha diversity between the two groups. There were also differences in the composition of the gut microbiota between the two groups. The genera, Megamonas, Streptococcus, Veillonella, Ruminococcus_torques_group, Prevotella_2, Tyzzerella_4, were identified as potential biomarkers for coronary atherosclerosis.

Conclusion

There are some differences in the gut microbiota of adults with coronary atherosclerosis compared to healthy adults. The insights from this study could be used to explore microbiome-based mechanisms for coronary atherosclerosis.

T helper 17 (Th17) cell responses to the gut microbiota in human diseases

The gut microbiota colonizing the gastrointestinal tract, is an indispensable "invisible organ" that affects multiple aspects of human health. The gut microbial community has been assumed to be an important stimulus to the immune homeostasis and development, and increasing data support the role of the gut microbiota-immunity axis in autoimmune diseases. Host's immune system requires recognition tools to communicate with the gut microbial evolutionary partners. Among these microbial perceptions, T cells enable the widest spectrum of gut microbial recognition resolution. Specific gut microbiota direct the induction and differentiation of Th17 cells in intestine. However, the detailed links between the gut microbiota and Th17 cells have not been well established. In this review, we describe the generation and characterization of Th17 cells. Notably, we discuss the induction and differentiation of Th17 cells by the gut microbiota and their metabolites, as well as recent advances in our understanding of interactions between Th17 cells and the gut microbiota in human diseases. In addition, we provide the emerging evidences in support of interventions targeting the gut microbes/Th17 cells in human diseases.

Emerging Roles of Gut Microbial Modulation of Bile Acid Composition in the Etiology of Cardiovascular Diseases

Despite advances in preventive measures and treatment options, cardiovascular disease (CVD) remains the number one cause of death globally. Recent research has challenged the traditional risk factor profile and highlights the potential contribution of non-traditional factors in CVD, such as the gut microbiota and its metabolites. Disturbances in the gut microbiota have been repeatedly associated with CVD, including atherosclerosis and hypertension. Mechanistic studies support a causal role of microbiota-derived metabolites in disease development, such as short-chain fatty acids, trimethylamine-N-oxide, and bile acids, with the latter being elaborately discussed in this review. Bile acids represent a class of cholesterol derivatives that is essential for intestinal absorption of lipids and fat-soluble vitamins, plays an important role in cholesterol turnover and, as more recently discovered, acts as a group of signaling molecules that exerts hormonal functions throughout the body. Studies have shown mediating roles of bile acids in the control of lipid metabolism, immunity, and heart function. Consequently, a picture has emerged of bile acids acting as integrators and modulators of cardiometabolic pathways, highlighting their potential as therapeutic targets in CVD. In this review, we provide an overview of alterations in the gut microbiota and bile acid metabolism found in CVD patients, describe the molecular mechanisms through which bile acids may modulate CVD risk, and discuss potential bile-acid-based treatment strategies in relation to CVD.

Gut Microbial Metabolites on Host Immune Responses in Health and Disease

Intestinal microorganisms interact with various immune cells and are involved in gut homeostasis and immune regulation. Although many studies have discussed the roles of the microorganisms themselves, interest in the effector function of their metabolites is increasing. The metabolic processes of these molecules provide important clues to the existence and function of gut microbes. The interrelationship between metabolites and T lymphocytes in particular plays a significant role in adaptive immune functions. Our current review focuses on 3 groups of metabolites: short-chain fatty acids, bile acids metabolites, and polyamines. We collated the findings of several studies on the transformation and production of these metabolites by gut microbes and explained their immunological roles. Specifically, we summarized the reports on changes in mucosal immune homeostasis represented by the Tregs and Th17 cells balance. The relationship between specific metabolites and diseases was also analyzed through latest studies. Thus, this review highlights microbial metabolites as the hidden treasure having potential diagnostic markers and therapeutic targets through a comprehensive understanding of the gut-immune interaction.

Mechanisms, therapeutic implications, and methodological challenges of gut microbiota and cardiovascular diseases: a position paper by the ESC Working Group on Coronary Pathophysiology and Microcirculation

The human gut microbiota is the microbial ecosystem in the small and large intestines of humans. It has been naturally preserved and evolved to play an important role in the function of the gastrointestinal tract and the physiology of its host, protecting from pathogen colonization, and participating in vitamin synthesis, the functions of the immune system, as well as glucose homeostasis and lipid metabolism, among others. Mounting evidence from animal and human studies indicates that the composition and metabolic profiles of the gut microbiota are linked to the pathogenesis of cardiovascular disease, particularly arterial hypertension, atherosclerosis, and heart failure. In this review article, we provide an overview of the function of the human gut microbiota, summarize, and critically address the evidence linking compositional and functional alterations of the gut microbiota with atherosclerosis and coronary artery disease and discuss the potential of strategies for therapeutically targeting the gut microbiota through various interventions.

Oyster (Crassostrea gigas) Polysaccharide Ameliorates High-Fat-Diet-Induced Oxidative Stress and Inflammation in the Liver via the Bile Acid-FXR-AMPKα Pathway

Oyster polysaccharides (OPS) have a variety of biological activities. In this study, we aimed to investigate the potential mechanisms of OPS to ameliorate hepatic oxidative stress and inflammation in mice induced by a high-fat diet (HFD). The results showed that OPS reduced the HFD-induced increases in serum transaminase levels and alleviated hepatic oxidative stress and inflammation. Moreover, OPS regulated bile acid metabolism and increased bile acid content in the liver, serum, and feces. Serum bile acid profile results indicated that OPS reduced levels of chenodeoxycholic acid, deoxycholic acid, and lithocholic acid associated with high-affinity agonists of Farnesol X receptor (FXR). Western blot analysis showed that OPS accelerated bile acid metabolism by downregulating hepatic FXR expression and promoting its downstream CYP7A1, CYP27A1, and CYP8B1 protein expression. Meanwhile, OPS ameliorated oxidative stress and inflammation in the liver by modulating FXR-AMPKα-Nrf2/NF-κB signaling to reduce p-IκBα/IκBα, p-NF-κB p65/NF-κB p65, IL-1β, and TNF-α expression and increase p-Nrf2/Nrf2, HO-1, and NQO-1 expression. This study was the first to explore the possible mechanism of OPS in improving liver oxidative stress and inflammation from the perspective of bile acid metabolism, providing a theoretical basis for OPS as a new source of functional food.

The Gut Microbiota and Vascular Aging: A State-of-the-Art and Systematic Review of the Literature

The gut microbiota is a critical regulator of human physiology, deleterious changes to its composition and function (dysbiosis) have been linked to the development and progression of cardiovascular diseases. Vascular ageing (VA) is a process of progressive stiffening of the arterial tree associated with arterial wall remodeling, which can precede hypertension and organ damage, and is associated with cardiovascular risk. Arterial stiffness has become the preferred marker of VA. In our systematic review, we found an association between gut microbiota composition and arterial stiffness, with two patterns, in most animal and human studies: a direct correlation between arterial stiffness and abundances of bacteria associated with altered gut permeability and inflammation; an inverse relationship between arterial stiffness, microbiota diversity, and abundances of bacteria associated with most fit microbiota composition. Interventional studies were able to show a stable link between microbiota modification and arterial stiffness only in animals. None of the human interventional trials was able to demonstrate this relationship, and very few adjusted the analyses for determinants of arterial stiffness. We observed a lack of large randomized interventional trials in humans that test the role of gut microbiota modifications on arterial stiffness, and take into account BP and hemodynamic alterations.

Multi-Omics Analysis Reveals Aberrant Gut-Metabolome-Immune Network in Schizophrenia

Schizophrenia (SCZ) is associated with several immune dysfunctions, including elevated levels of pro-inflammatory cytokines. Microorganisms and their metabolites have been found to regulate the immune system, and that intestinal microbiota is significantly disturbed in schizophrenic patients. To systematically investigate aberrant gut-metabolome-immune network in schizophrenia, we performed an integrative analysis of intestinal microbiota, serum metabolome, and serum inflammatory cytokines in 63 SCZ patients and 57 healthy controls using a multi-omics strategy. Eighteen differentially abundant metabolite clusters were altered in patients displayed higher cytokine levels, with a significant increase in pro-inflammatory metabolites and a significant decrease in anti-inflammatory metabolites (such as oleic acid and linolenic acid). The bacterial co-abundance groups in the gut displayed more numerous and stronger correlations with circulating metabolites than with cytokines. By integrating these data, we identified that certain bacteria might affect inflammatory cytokines by modulating host metabolites, such as amino acids and fatty acids. A random forest model was constructed based on omics data, and seven serum metabolites significantly associated with cytokines and α-diversity of intestinal microbiota were able to accurately distinguish the cases from the controls with an area under the receiver operating characteristic curve of 0.99. Our results indicated aberrant gut-metabolome-immune network in SCZ and gut microbiota may influence immune responses by regulating host metabolic processes. These findings suggest a mechanism by which microbial-derived metabolites regulated inflammatory cytokines and insights into the diagnosis and treatment of mental disorders from the microbial-immune system in the future.

An integrative understanding of the large metabolic shifts induced by antibiotics in critical illness

Antibiotics are commonly used in the Intensive Care Unit (ICU); however, several studies showed that the impact of antibiotics to prevent infection, multi-organ failure, and death in the ICU is less clear than their benefit on course of infection in the absence of organ dysfunction. We characterized here the compositional and metabolic changes of the gut microbiome induced by critical illness and antibiotics in a cohort of 75 individuals in conjunction with 2,180 gut microbiome samples representing 16 different diseases. We revealed an "infection-vulnerable" gut microbiome environment present only in critically ill treated with antibiotics (ICU⁺). Feeding of Caenorhabditis elegans with Bifidobacterium animalis and Lactobacillus crispatus, species that expanded in ICU⁺ patients, revealed a significant negative impact of these microbes on host viability and developmental homeostasis. These results suggest that antibiotic administration can dramatically impact essential functional activities in the gut related to immune responses more than critical illness itself, which might explain in part untoward effects of antibiotics in the critically ill.

Inflammation in Coronary Microvascular Dysfunction

Chronic low-grade inflammation is involved in coronary atherosclerosis, presenting multiple clinical manifestations ranging from asymptomatic to stable angina, acute coronary syndrome, heart failure and sudden cardiac death. Coronary microvasculature consists of vessels with a diameter less than 500 μm, whose potential structural and functional abnormalities can lead to inappropriate dilatation and an inability to meet the required myocardium oxygen demands. This review focuses on the pathogenesis of coronary microvascular dysfunction and the capability of non-invasive screening methods to detect the phenomenon. Anti-inflammatory agents, such as statins and immunomodulators, including anakinra, tocilizumab, and tumor necrosis factor-alpha inhibitors, have been assessed recently and may constitute additional or alternative treatment approaches to reduce cardiovascular events in atherosclerotic heart disease characterized by coronary microvascular dysfunction.

Evaluating Causal Relationship Between Metabolites and Six Cardiovascular Diseases Based on GWAS Summary Statistics

Cardiovascular diseases (CVDs) remain the main cause of morbidity and mortality worldwide. The pathological mechanism and underlying biological processes of these diseases with metabolites remain unclear. In this study, we conducted a two-sample Mendelian randomization (MR) analysis to evaluate the causal effect of metabolites on these diseases by making full use of the latest GWAS summary statistics for 486 metabolites and six major CVDs. Extensive sensitivity analyses were implemented to validate our MR results. We also conducted linkage disequilibrium score regression (LDSC) and colocalization analysis to investigate whether MR findings were driven by genetic similarity or hybridization between LD and disease-associated gene loci. We identified a total of 310 suggestive associations across all metabolites and CVDs, and finally obtained four significant associations, including bradykinin, des-arg(9) (odds ratio [OR] = 1.160, 95% confidence intervals [CIs]: 1.080-1.246, false discovery rate [FDR] = 0.022) on ischemic stroke, N-acetylglycine (OR = 0.946, 95%CIs: 0.920-0.973, FDR = 0.023), X-09026 (OR = 0.845, 95%CIs: 0.779-0.916, FDR = 0.021) and X-14473 (OR = 0.938, 95%CIs = 0.907-0.971, FDR = 0.040) on hypertension. Sensitivity analyses showed that these causal associations were robust, the LDSC and colocalization analyses demonstrated that the identified associations were unlikely confused by LD. Moreover, we identified 15 important metabolic pathways might be involved in the pathogenesis of CVDs. Overall, our work identifies several metabolites that have a causal relationship with CVDs, and improves our understanding of the pathogenesis and treatment strategies for these diseases.

Effects of Tartary Buckwheat Protein on Gut Microbiome and Plasma Metabolite in Rats with High-Fat Diet

The prevalence of lipid metabolism diseases, mainly obesity, fatty liver, and hyperlipidemia, is increasing in the world. Tartary buckwheat is a kind of medicinal and edible crop, and clinical experiments have also confirmed that dietary Tartary buckwheat can effectively regulate lipid metabolism disorders. Tartary buckwheat protein (TBP), as the main active ingredient of Tartary buckwheat, has an effect of blood lipid reduction that has been widely reported. In this paper, we investigated the constituents of TBP and then evaluated the hypolipidemic effect of TBP in hyperlipidemia rats. Male Sprague–Dawley rats were fed a high-fat diet for six weeks to induce hyperlipidemia and then given TBP orally for five weeks. The effects of TBP on body weight, serum lipids, liver lipids, liver oxidative stress, pathological organization, gut microbiota, and plasma metabolites were analyzed. At the serum level, TBP supplement significantly decrease the level of LDL-C and increase the level of HDL-C. At the liver level, it can reduce the levels of TC, TG, and LDL-C. The potential mechanism of action is, on the one hand, to increase the abundance of the Lachnospiraceae and the Ruminococcaceae by modulating the gut microbiota, facilitating the productivity of short-chain fatty acids, and increasing fecal bile acid excretion and, on the other hand, may be related to the improvement of bile acid metabolism.

The gut-cardiovascular connection: new era for cardiovascular therapy

Our gut microbiome is constituted by trillions of microorganisms including bacteria, archaea and eukaryotic microbes. Nowadays, gut microbiome has been gradually recognized as a new organ system that systemically and biochemically interact with the host. Accumulating evidence suggests that the imbalanced gut microbiome contributes to the dysregulation of immune system and the disruption of cardiovascular homeostasis. Specific microbiome profiles and altered intestinal permeability are often observed in the pathophysiology of cardiovascular diseases. Gut-derived metabolites, toxins, peptides and immune cell-derived cytokines play pivotal roles in the induction of inflammation and the pathogenesis of dysfunction of heart and vasculature. Impaired crosstalk between gut microbiome and multiple organ systems, such as gut-vascular, heart-gut, gut-liver and brain-gut axes, are associated with higher cardiovascular risks. Medications and strategies that restore healthy gut microbiome might therefore represent novel therapeutic options to lower the incidence of cardiovascular and metabolic disorders.

Distinguishing feature of gut microbiota in Tibetan highland coronary artery disease patients and its link with diet

The prevalence of coronary artery disease (CAD) in Tibetan Highlanders is lower than that in plain-living individuals, but the mechanism still unclear. Gut microbiota (GM) disorder is considered one of the potential factors involved in the pathogenesis of CAD, but the GM characteristics of Tibetan Highlanders suffering from CAD are unknown. We sequenced the V3-V4 region of the 16S ribosomal RNA of gut bacteria from fecal samples from Tibetan and Han CAD patients and healthy individuals inhabiting the Qinghai-Tibet Plateau, as well as from Han CAD patients and healthy individuals living at sea level, and we analyzed the GM characteristics of these subjects by bioinformatics analysis. The results showed that Tibetan Highlanders suffering from CAD had higher GM α-diversity, with differently distributed cluster compared with healthy Tibetan Highlanders and Han CAD patients living at high and low altitudes. Genera Catenibacterium, Clostridium_sensu_stricto, Holdemanella, and Ruminococcus 2 were enriched in Tibetan Highlanders suffering from CAD compared with healthy Tibetan Highlanders and Han CAD patients living at high- and low-altitudes. Prevotella was enriched in Tibetan Highlanders suffering from CAD compared with Han CAD patients living at high- and low-altitudes. Moreover, Catenibacterium was positively correlated with Prevotella. Additionally, Catenibacterium, Holdemanella, and Prevotella were positively correlated with fermented dairy product, carbohydrate and fiber intake by the subjects, while Clostridium_sensu_stricto was negatively correlated with protein intake by the subjects. In conclusion, our study indicated that Tibetan Highlanders suffering from CAD showed distinct GM, which was linked to their unique dietary characteristics and might associated with CAD.

Novel ι-Carrageenan Tetrasaccharide Alleviates Liver Lipid Accumulation via the Bile Acid-FXR-SHP/PXR Pathway to Regulate Cholesterol Conversion and Fatty Acid Metabolism in Insulin-Resistant Mice

ι-Carrageenan tetrasaccharide (ιCTs), a novel oligosaccharide, was hydrolyzed from ι-carrageenan with targeting marine tool-enzyme Cgi82A. Previously, we have found ιCTs exhibited a hypoglycemic effect, whether it could regulate lipid metabolism remains unknown. In this study, the insulin-resistant mice induced by high-fat-high-sucrose diet were orally administrated with ιCTs (30 mg/kg·bw) for 20 weeks. The results showed that the contents of triglyceride and cholesterol in both serum and liver were reduced by ιCTs, and their excretion in feces were promoted, suggesting lipid accumulation was inhibited. Intriguingly, the overall levels of bile acid in serum, liver, and feces were all raised by ιCTs. Given that bile acids are the essential signal factors for regulating lipid metabolism via the farnesoid-X-receptor (FXR), we conducted serum bile acid profile analysis and found that the levels of high-affinity agonists deoxycholic acid and lithocholic acid were decreased in the ιCTs group, showing that ιCTs failed to activate FXR. Western blot analysis showed that ιCTs downregulated hepatic FXR and small heterodimer partner (SHP) expression and increased downstream CYP7A1 expression via regulating the FXR-SHP signal to accelerate liver cholesterol conversion. Meanwhile, ιCTs decreased the expression of PXR and SREBP1c and elevated the expression of PPARα and CPT1α via regulating the FXR-PXR-SREBP1c/PPARα signal to inhibit fatty acid synthesis and promote fatty acid β-oxidation. To the best of our knowledge, this study for the first time reported that ιCTs alleviated liver lipid accumulation via the bile acid-FXR-SHP/PXR signal to regulate cholesterol conversion and fatty acid metabolism, which highlighted a new idea for ameliorating insulin resistance.

Microbiota-Associated Metabolites and Related Immunoregulation in Colorectal Cancer

A growing body of research has found close links between the human gut microbiota and colorectal cancer (CRC), associated with the direct actions of specific bacteria and the activities of microbiota-derived metabolites, which are implicated in complex immune responses, thus influencing carcinogenesis. Diet has a significant impact on the structure of the microbiota and also undergoes microbial metabolism. Some metabolites, such as short-chain fatty acids (SCFAs) and indole derivatives, act as protectors against cancer by regulating immune responses, while others may promote cancer. However, the specific influence of these metabolites on the host is conditional. We reviewed the recent insights on the relationships among diet, microbiota-derived metabolites, and CRC, focusing on their intricate immunomodulatory responses, which might influence the progression of colorectal cancer.

Gut microbiota dysbiosis in stable coronary artery disease combined with type 2 diabetes mellitus influences cardiovascular prognosis

BACKGROUND AND AIMS

Host-microbiota interactions involving metabolic pathways have been linked to the pathogenesis of atherosclerotic disease and type 2 diabetes. As stable coronary artery disease (SCAD) patients combined with type 2 diabetes have significantly increased risk for cardiac event, we focused on elucidating the role of microbiota affecting cardiometabolic disease development.

METHODS AND RESULTS

We used multi-omics analyses (metagenomics and metabolomics) of fecal and serum samples from a prospective cohort including stable coronary artery disease combined with diabetes mellitus (SCAD + T2DM, n = 38), SCAD (n = 71), and healthy control (HC, n = 55). We linked microbiome features to disease severity in a three-pronged association analysis and identified prognostic bacterial biomarkers. We identified that bacterial and metabolic signatures varied significantly between SCAD and SCAD + T2DM groups. SCAD + T2DM individuals were characterized by increased levels of aromatic amino acids and carbohydrates, which correlate with a gut microbiome with enriched biosynthetic potential. Our study also addressed how metformin may confound gut dysbiosis and increase the potential for nitrogen metabolism. In addition, we found that specific bacterial taxa Ruminococcus torques [HR: 2.363 (08-4.56), P = 0.03] was predictive of cardiac survival outcomes.

CONCLUSION

Overall, our study identified relationships between features of the gut microbiota (GM) and circulating metabolites, providing a new direction for future studies aiming to understand the host-GM interplay in atherosclerotic cardiovascular pathogenesis.

Gut microbiome and bile acids in obesity-related diseases

Dysbiosis has been implemented in the etiologies of obesity-related chronic diseases such as type 2 diabetes, NAFLD and cardiovascular diseases. Bile acids, a class of amphipathic steroids produced in the liver and extensively modified by the microbiome, are increasingly recognized as actors in onset and progression of these diseases. Indeed, human obesity is associated with altered bile acid metabolism. Bile acids facilitate intestinal fat absorption but also exert hormone-like functions through activation of nuclear and membrane-bound receptors and thereby modulate glucose, lipid and energy metabolism, intestinal integrity and immunity. Bile acid-signaling pathways have thus been identified as potential pharmacological targets for obesity-related diseases. Interfering with microbiome composition may also be considered, as liver- and microbiome-derived bile acid species have different signaling functions. This review summarizes recent developments in this rapidly expanding field of research and addresses potential clinical prospects of interference with bile acid signaling pathways in human diseases.

Investigating causality with fecal microbiota transplantation in rodents: applications, recommendations and pitfalls

In recent years, studies investigating the role of the gut microbiota in health and diseases have increased enormously - making it essential to deepen and question the research methodology employed. Fecal microbiota transplantation (FMT) in rodent studies (either from human or animal donors) allows us to better understand the causal role of the intestinal microbiota across multiple fields. However, this technique lacks standardization and requires careful experimental design in order to obtain optimal results. By comparing several studies in which rodents are the final recipients of FMT, we summarize the common practices employed. In this review, we document the limitations of this method and highlight different parameters to be considered while designing FMT Studies. Standardizing this method is challenging, as it differs according to the research topic, but avoiding common pitfalls is feasible. Several methodological questions remain unanswered to this day and we offer a discussion on issues to be explored in future studies.

Hormone Replacement Therapy Reverses Gut Microbiome and Serum Metabolome Alterations in Premature Ovarian Insufficiency

OBJECTIVE

We explored the gut microbiome and serum metabolome alterations in patients with premature ovarian insufficiency (POI) and the effects of hormone replacement therapy (HRT) with the aim to unravel the pathological mechanism underlying POI.

METHODS

Fecal and serum samples obtained from healthy females (HC, n = 10) and patients with POI treated with (n = 10) or without (n = 10) HRT were analyzed using 16S rRNA gene sequencing and untargeted metabolomics analysis, respectively. Peripheral blood samples were collected to detect serum hormone and cytokine levels. Spearman's rank correlation was used to evaluate correlations between sex hormones and cytokines and between the gut microbiota and serum metabolites. To further confirm the correlation between Eggerthella and ovarian fibrosis, the mice were inoculated with Eggerthella lenta (E. lenta) through oral gavage.

RESULTS

The abundance of genus Eggerthella significantly increased in the fecal samples of patients with POI compared to that observed in the samples of HCs. This increase was reversed in patients with POI treated with HRT. Patients with POI showed significantly altered serum metabolic signatures and increased serum TGF-β1 levels; this increase was reversed by HRT. The abundance of Eggerthella was positively correlated with altered metabolic signatures, which were, in turn, positively correlated with serum TGF-β1 levels in all subjects. Estrogen ameliorated ovarian fibrosis induced by E. lenta in mice.

CONCLUSIONS

The interactions between the gut microbiota, serum metabolites, and serum TGF-β1 in patients with POI may play a critical role in the development of POI. HRT not only closely mimicked normal ovarian hormone production in patients with POI but also attenuated gut microbiota dysbiosis and imbalance in the levels of serum metabolites and TGF-β1, which are reportedly associated with fibrosis. The findings of this study may pave the way for the development of preventive and curative therapies for patients with POI.