Flavin containing monooxygenase 3 exerts broad effects on glucose and lipid metabolism and atherosclerosis

PCSK9 and APOA4: The Dynamic Duo in TMAO-induced Cholesterol Metabolism and Cholelithiasis

Background and Aims

Cholesterol synthesis and gallstone formation are promoted by trimethylamine-N-oxide (TMAO), a derivative of trimethylamine, which is a metabolite of gut microbiota. However, the underlying mechanisms of TMAO-induced lithogenesis remain incompletely understood. This study aimed to explore the specific molecular mechanisms through which TMAO promotes gallstone formation.

Methods

Enzyme-linked immunosorbent assays were used to compare serum concentrations of TMAO, apolipoprotein A4 (APOA4), and proprotein convertase subtilisin/kexin type 9 (PCSK9) between patients with cholelithiasis and normal controls. A murine model of TMAO-induced cholelithiasis was employed, incorporating assays of gallstone weight and bile cholesterol content, along with RNA sequencing of murine hepatic tissue. A TMAO-induced AML12 hepatocyte line was constructed and transfected with targeted small interfering RNAs and overexpression plasmids. In vivo and in vitro experiments were performed to determine the expression and regulation of genes related to cholesterol metabolism.

Results

Serum TMAO and PCSK9 levels were elevated, whereas APOA4 levels were reduced in patients with cholelithiasis. Furthermore, our murine model demonstrated that TMAO upregulated hepatic expression of PCSK9, 3-hydroxy-3-methylglutaryl-CoA reductase, and ATP-binding cassette sub-family G member 5/8, while reducing APOA4 expression, thereby modulating cholesterol metabolism and promoting lithogenesis. PCSK9 and APOA4 were identified as key regulatory genes in the cholesterol metabolic pathway. PCSK9 knockdown increased APOA4 expression, while APOA4 overexpression led to reduced PCSK9 expression.

Conclusions

TMAO upregulated hepatic PCSK9 expression and reduced APOA4 expression, initiating a feedback loop that dysregulated cholesterol metabolism and promoted lithogenesis.

Trimethylamine-N-oxide, a New Risk Factor for Non-alcoholic Fatty Liver Disease Changes the Expression of miRNA-34a, and miRNA-122 in the Fatty Liver Cell Model

Non-alcoholic fatty liver disease is a multifactorial disorder with complicated pathophysiology ranging from simple steatosis to steatohepatitis and liver fibrosis. Trimethylamine-N-oxide (TMAO) production is believed to be correlated with choline deficiency. This study investigated the expression of miRNA-34a, miRNA-122, and miRNA-192 in the fatty liver cell model treated with different concentrations of TMAO. A fatty liver cell model was developed by exposing HepG2 cells to a mixture of palmitate and oleate in a ratio of 1:2 at a final concentration of 1200 μM for 24 h. The confirmed fatty liver cells were treated with 37.5, 75, 150, and 300 μM of TMAO for 24 h. RT-qPCR was used to quantify the expression of microRNAs in a cellular model. The cellular expression of all microRNAs was significantly higher in treated fatty liver cells compared to normal HepG2 cells (P < 0.05). Only 75 and 150 µM of TMAO significantly increased the expression of miRNA-34a and miRNA-122 compared to both fatty and normal control cells (P < 0.05). Our results provided an experimental documentation for the potential effect of TMAO to change the expression of miR-34a and miR-22 as a mechanism for contributing to the pathogenesis of non-alcoholic fatty liver disease.

Liver as a new target organ in Alzheimer's disease: insight from cholesterol metabolism and its role in amyloid-beta clearance

Alzheimer's disease, the primary cause of dementia, is characterized by neuropathologies, such as amyloid plaques, synaptic and neuronal degeneration, and neurofibrillary tangles. Although amyloid plaques are the primary characteristic of Alzheimer's disease in the central nervous system and peripheral organs, targeting amyloid-beta clearance in the central nervous system has shown limited clinical efficacy in Alzheimer's disease treatment. Metabolic abnormalities are commonly observed in patients with Alzheimer's disease. The liver is the primary peripheral organ involved in amyloid-beta metabolism, playing a crucial role in the pathophysiology of Alzheimer's disease. Notably, impaired cholesterol metabolism in the liver may exacerbate the development of Alzheimer's disease. In this review, we explore the underlying causes of Alzheimer's disease and elucidate the role of the liver in amyloid-beta clearance and cholesterol metabolism. Furthermore, we propose that restoring normal cholesterol metabolism in the liver could represent a promising therapeutic strategy for addressing Alzheimer's disease.

Trimethylamine Oxidation into the Proatherogenic Trimethylamine N-Oxide Is Higher in Coronary Heart Disease Men: From the CORDIOPREV Study

PURPOSE

Cardiovascular disease (CVD) is more prevalent in men than women, but the mechanisms responsible for this are not fully understood. We aimed to evaluate differences in trimethylamine (TMA), a microbial metabolite and its oxidized form, trimethylamine N-oxide (TMAO), which is thought to promote atherosclerosis, between men and women with coronary heart disease (CHD), using as a reference a non-CVD population.

MATERIALS AND METHODS

This study was carried out within the framework of the CORDIOPREV study (NCT00924937; June 19, 2009), a clinical trial which included 827 men and 175 women with CHD, with a non-CVD population of 375 individuals (270 men and 105 women) as a reference group. Plasma TMA and TMAO were measured by HPLC-MS/MS. The carotid study was ultrasonically assessed bilaterally by the quantification of intima-media thickness of both common carotid arteries (IMT-CC).

RESULTS

We found higher TMAO levels and TMAO/TMA ratio in CHD men than CHD women (p=0.034 and p=0.026, respectively). No TMA sex differences were found in CHD patients. The TMA and TMAO levels and TMAO/TMA ratio were lower, and no differences between sexes were found in the non-CVD population. TMAO levels in CHD patients were consistent with higher IMT-CC and more carotid plaques (p=0.032 and p=0.037, respectively) and lower cholesterol efflux in CHD men than CHD women (p<0.001).

CONCLUSIONS

Our results suggest that CHD men have augmented TMAO levels compared with CHD women, presumably as a consequence of higher rate of TMA to TMAO oxidation, which could be associated with CVD, as these sex differences are not observed in a non-CVD population.

Gut Microbe-Generated Metabolite Trimethylamine-N-Oxide and Ischemic Stroke

Trimethylamine-N-oxide (TMAO) is a gut microbiota-derived metabolite, the production of which in vivo is mainly regulated by dietary choices, gut microbiota, and the hepatic enzyme flavin monooxygenase (FMO), while its elimination occurs via the kidneys. The TMAO level is positively correlated with the risk of developing cardiovascular diseases. Recent studies have found that TMAO plays an important role in the development of ischemic stroke. In this review, we describe the relationship between TMAO and ischemic stroke risk factors (hypertension, diabetes, atrial fibrillation, atherosclerosis, thrombosis, etc.), disease risk, severity, prognostic outcomes, and recurrence and discuss the possible mechanisms by which they interact. Importantly, TMAO induces atherosclerosis and thrombosis through lipid metabolism, foam cell formation, endothelial dysfunction (via inflammation, oxidative stress, and pyroptosis), enhanced platelet hyper-reactivity, and the upregulation and activation of vascular endothelial tissue factors. Although the pathogenic mechanisms underlying TMAO's aggravation of disease severity and its effects on post-stroke neurological recovery and recurrence risk remain unclear, they may involve inflammation, astrocyte function, and pro-inflammatory monocytes. In addition, this paper provides a summary and evaluation of relevant preclinical and clinical studies on interventions regarding the gut-microbiota-dependent TMAO level to provide evidence for the prevention and treatment of ischemic stroke through the gut microbe-TMAO pathway.

Practical Aspects of Flavin-Containing Monooxygenase-Mediated Metabolism

Hepatic flavin-containing monooxygenase 3 (FMO3) is arguably the most important FMO in humans from the standpoint of drug metabolism. Recently, adult hepatic FMO3 has been linked to several conditions including cardiometabolic diseases, aging, obesity, and atherosclerosis in small animals. Despite the importance of FMO3 in drug and chemical metabolism, relative to cytochrome P-450 (CYP), fewer studies have been published describing drug and chemical metabolism. This may be due to the properties of human hepatic FMO3. For example, FMO3 is thermally labile, and often methods reported in the study of human hepatic FMO3 are not optimal. Herein, I describe some practical aspects for studying human hepatic FMO3 and other FMOs.

Intestinal microbiome as a diagnostic marker of coronary artery disease: a systematic review and meta-analysis

BACKGROUND

The intestinal microbiome has been recently linked to several metabolic and chronic disorders, one of which is coronary artery disease (CAD). Our study aimed to analyze the intestinal microbiome of CAD patients and assess the eligibility of dysbiosis as a diagnostic marker of CAD.

METHODS

PubMed, Scopus, Embase, and Web of Science were searched using terms, such as 'CAD' and 'microbiome'. Only observational controlled studies were included. R version 4.2.2 was used for the analysis.

RESULTS

A significant association was found between the CAD group and increased Simpson and Shannon Indices compared with the control group (MD=0.04, 95% CI=0.03-0.05, and MD=0.11, 95% CI=0.01-0.22, respectively). Our analysis yielded a statistically significant association between the CAD group and increased Prevotella genus (MD=13.27, 95% CI=4.12-22.42, P-value=0.004), Catenibacterium genus (MD=0.09, 95% CI=0.09-0.10), Pseudomonas genus (MD=0.54, 95% CI=0.29-0.78, P-value), and Subdoligranulum (MD=-0.06, 95% CI=-0.06 to -0.06) compared with the control group. Another significant association was detected between the CAD group and decreased Bacteroides vulgatus and Bacteroides dorei (MD=-10.31, 95% CI=-14.78 to -5.84, P-value <0.00001).

CONCLUSION

Dysbiosis is an acceptable diagnostic marker of CAD. Decreased B. dorei and B. vulgatus among CAD patients suggests a protective role of these bacteria. Future clinical trials are necessary to investigate the potential benefit of supplementation of these bacteria in treating or preventing CAD.

Trimethylamine-N-oxide and 5-year mortality: the role of gut microbiota-generated metabolite from the CORE-Thailand cohort

The gut microbiota metabolite trimethylamine-N-oxide (TMAO)-derived from dietary phosphatidylcholine-is mechanistically linked to cardiovascular disease (CVD) and increased cardiovascular risk. This study examined the relationship between fasting plasma TMAO levels and 5-year all-cause mortality in a cohort of patients at high risk of cardiovascular events (CORE-Thailand Registry). Of the 134 patients, 123 (92%) had established cardiovascular disease, and 11 (8%) had multiple risk factors. Fasting plasma TMAO levels were measured using nuclear magnetic resonance spectroscopy. Within this prospective cohort study, the median TMAO was 3.81 μM [interquartile range (IQR) 2.89-5.50 μM], with a mean age of 65 ± 11 years; 61% were men, and 39.6% had type II diabetes. Among 134 patients, 65 (49%) were identified as the high-TMAO group (≥ 3.8 μM), and 69 (51%) were identified as the low-TMAO group (< 3.8 μM). After a median follow-up of 58.8 months, the high-TMAO group was associated with a 2.88-fold increased mortality risk. Following adjustment for traditional risk factors, high-sensitivity cardiac troponin-T, estimated glomerular filtration rate, angiotensin-converting enzyme (ACEI), or angiotensin-receptor blocker (ARB) use, the high-TMAO group remained predictive of 5-year all-cause mortality risk (the high-TMAO vs. the low-TMAO group, adjusted hazard ratio 2.73, 95% CI 1.13-6.54; P = 0.025). Among Thai patients at high risk of cardiovascular events, increased plasma TMAO levels portended greater long-term mortality risk.

Antioxidant Role of Probiotics in Inflammation-Induced Colorectal Cancer

Colorectal cancer (CRC) continues to be a significant contributor to global morbidity and mortality. Emerging evidence indicates that disturbances in gut microbial composition, the formation of reactive oxygen species (ROS), and the resulting inflammation can lead to DNA damage, driving the pathogenesis and progression of CRC. Notably, bacterial metabolites can either protect against or contribute to oxidative stress by modulating the activity of antioxidant enzymes and influencing signaling pathways that govern ROS-induced inflammation. Additionally, microbiota byproducts, when supplemented through probiotics, can affect tumor microenvironments to enhance treatment efficacy and selectively mediate the ROS-induced destruction of CRC cells. This review aims to discuss the mechanisms by which taxonomical shifts in gut microbiota and related metabolites such as short-chain fatty acids, secondary bile acids, and trimethylamine-N-oxide influence ROS concentrations to safeguard or promote the onset of inflammation-mediated CRC. Additionally, we focus on the role of probiotic species in modulating ROS-mediated signaling pathways that influence both oxidative status and inflammation, such as Nrf2-Keap1, NF-κB, and NLRP3 to mitigate carcinogenesis. Overall, a deeper understanding of the role of gut microbiota on oxidative stress may aid in delaying or preventing the onset of CRC and offer new avenues for adjunct, CRC-specific therapeutic interventions such as cancer immunotherapy.

Gut matters in microgravity: potential link of gut microbiota and its metabolites to cardiovascular and musculoskeletal well-being

The gut microbiota and its secreted metabolites play a significant role in cardiovascular and musculoskeletal health and diseases. The dysregulation of the intestinal microbiota poses a significant threat to cardiovascular and skeletal muscle well-being. Nonetheless, the precise molecular mechanisms underlying these changes remain unclear. Furthermore, microgravity presents several challenges to cardiovascular and musculoskeletal health compromising muscle strength, endothelial dysfunction, and metabolic changes. The purpose of this review is to critically examine the role of gut microbiota metabolites on cardiovascular and skeletal muscle functions and dysfunctions. It also explores the molecular mechanisms that drive microgravity-induced deconditioning in both cardiovascular and skeletal muscle. Key findings in this review highlight that several alterations in gut microbiota and secreted metabolites in microgravity mirror characteristics seen in cardiovascular and skeletal muscle diseases. Those alterations include increased levels of Firmicutes/Bacteroidetes (F/B) ratio, elevated lipopolysaccharide levels (LPS), increased in para-cresol (p-cresol) and secondary metabolites, along with reduction in bile acids and Akkermansia muciniphila bacteria. Highlighting the potential, modulating gut microbiota in microgravity conditions could play a significant role in mitigating cardiovascular and skeletal muscle diseases not only during space flight but also in prolonged bed rest scenarios here on Earth.

Simultaneous determination of choline, L-carnitine, betaine, trimethylamine, trimethylamine N-oxide, and creatinine in plasma, liver, and feces of hyperlipidemic rats by UHPLC-MS/MS

BACKGROUND

Due to the close correlation between choline, L-carnitine, betaine and their intestinal microbial metabolites, including trimethylamine (TMA) and trimethylamine N-oxide (TMAO), and creatinine, there has been an increasing interest in the study of these compounds in vivo.

METHODS

In this study, a rapid stable isotope dilution (SID)-UHPLC-MS/MS method was developed for the simultaneous determination of choline, L-carnitine, betaine, TMA, TMAO and creatinine in plasma, liver and feces of rats. The method was validated using quality control (QC) samples spiked at low, medium and high levels. Second, we applied the method to quantify the effects of Rosa Roxburghii Tratt juice (RRTJ) on plasma, liver, and fecal levels of choline, L-carnitine, betaine, TMA, TMAO, and creatinine in high-fat diet-induced hyperlipidemic rats, demonstrating the utility of the method.

RESULTS

The limits of detection (LOD) were 0.04-0.027 µM and the limits of quantification (LOQ) were 0.009-0.094 µM. The linear ranges for each metabolite in plasma were choline1.50-96 µM; L-carnitine: 2-128 µM; betaine: 3-192 µM; TMA: 0.01-40.96 µM; TMAO: 0.06-61.44 µM and creatinine: 1-64 µM (R2 ≥ 0.9954). The linear ranges for each metabolite in liver were Choline: 12-768 µM; L-carnitine: 1.5-96 µM; betaine: 10-640 µM; TMA: 0.5-32 µM; TMAO: 0.02-81.92 µM and creatinine: 0.2-204.8 µM (R2 ≥ 0.9938). The linear ranges for each metabolite in feces were choline: 1.5-96 µM; L-carnitine: 0.01-40.96 µM; Betaine: 1.5-96 µM; TMA: 1-64 µM; TMAO: 0.02-81.92 µM and Creatinine: 0.02-81.92 µM (R2 ≥ 0.998). The intra-day and inter-day coefficients of variation were < 8 % for all analytes. The samples were stabilized after multiple freeze-thaw cycles (3 freeze-thaw cycles), 24 h at room temperature, 24 h at 4 °C and 20 days at -80 °C. The samples were stable. The average recovery was 89 %-99 %. This method was used to quantify TMAO and its related metabolites and creatinine levels in hyperlipidemic rats. The results showed that high-fat diet led to the disorder of TMAO and its related metabolites and creatinine in rats, which was effectively improved after the intervention of Rosa Roxburghii Tratt juice（RRTJ）.

CONCLUSIONS

A method for the determination of choline, L-carnitine, betaine, TMA, TMAO and creatinine in plasma, liver and feces samples was established, which is simple, time-saving, high precision, accuracy and recovery.

Loss of flavin-containing monooxygenase 3 modulates dioxin-like polychlorinated biphenyl 126-induced oxidative stress and hepatotoxicity

Dioxin-like pollutants (DLPs), such as polychlorinated biphenyl 126 (PCB 126), are synthetic chemicals classified as persistent organic pollutants. They accumulate in adipose tissue and have been linked to cardiometabolic disorders, including fatty liver disease. The toxicity of these compounds is associated with activation of the aryl hydrocarbon receptor (Ahr), leading to the induction of phase I metabolizing enzyme cytochrome P4501a1 (Cyp1a1) and the subsequent production of reactive oxygen species (ROS). Recent research has shown that DLPs can also induce the xenobiotic detoxification enzyme flavin-containing monooxygenase 3 (FMO3), which plays a role in metabolic homeostasis. We hypothesized whether genetic deletion of Fmo3 could protect mice, particularly in the liver, where Fmo3 is most inducible, against PCB 126 toxicity. To test this hypothesis, male C57BL/6 wild-type (WT) mice and Fmo3 knockout (Fmo3 KO) mice were exposed to PCB 126 or vehicle (safflower oil) during a 12-week study, at weeks 2 and 4. Various analyses were performed, including hepatic histology, RNA-sequencing, and quantitation of PCB 126 and F2-isoprostane concentrations. The results showed that PCB 126 exposure caused macro and microvesicular fat deposition in WT mice, but this macrovesicular fatty change was absent in Fmo3 KO mice. Moreover, at the pathway level, the hepatic oxidative stress response was significantly different between the two genotypes, with the induction of specific genes observed only in WT mice. Notably, the most abundant F2-isoprostane, 8-iso-15-keto PGE2, increased in WT mice in response to PCB 126 exposure. The study's findings also demonstrated that hepatic tissue concentrations of PCB 126 were higher in WT mice compared to Fmo3 KO mice. In summary, the absence of FMO3 in mice led to a distinctive response to dioxin-like pollutant exposure in the liver, likely due to alterations in lipid metabolism and storage, underscoring the complex interplay of genetic factors in the response to environmental toxins.

Effect of three oral pathogens on the TMA-TMAO metabolic pathway

Background

Trimethylamine-N-oxide (TMAO) is produced by hepatic flavin-containing monooxygenase 3 (FMO3) from trimethylamine (TMA). High TMAO level is a biomarker of cardiovascular diseases and metabolic disorders, and it also affects periodontitis through interactions with the gastrointestinal microbiome. While recent findings indicate that periodontitis may alter systemic TMAO levels, the specific mechanisms linking these changes and particular oral pathogens require further clarification.

Methods

In this study, we established a C57BL/6J male mouse model by orally administering Porphyromonas gingivalis (P. gingivalis, Pg), Fusobacterium nucleatum (F. nucleatum, Fn), Streptococcus mutans (S. mutans, Sm) and PBS was used as a control. We conducted LC-MS/MS analysis to quantify the concentrations of TMAO and its precursors in the plasma and cecal contents of mice. The diversity and composition of the gut microbiome were analyzed using 16S rRNA sequencing. TMAO-related lipid metabolism and enzymes in the intestines and liver were assessed by qPCR and ELISA methods. We further explored the effect of Pg on FMO3 expression and lipid molecules in HepG2 cells by stimulating the cells with Pg-LPS in vitro.

Results

The three oral pathogenic bacteria were orally administered to the mice for 5 weeks. The Pg group showed a marked increase in plasma TMAO, betaine, and creatinine levels, whereas no significant differences were observed in the gut TMAO level among the four groups. Further analysis showed similar diversity and composition in the gut microbiomes of both the Pg and Fn groups, which were different from the Sm and control groups. The profiles of TMA-TMAO pathway-related genera and gut enzymes were not significantly different among all groups. The Pg group showed significantly higher liver FMO3 levels and elevated lipid factors (IL-6, TG, TC, and NEFA) in contrast to the other groups. In vitro experiments confirmed that stimulation of HepG2 cells with Pg-LPS upregulated the expression of FMO3 and increased the lipid factors TC, TG, and IL-6.

Conclusion

This study conclusively demonstrates that Pg, compared to Fn and Sm, plays a critical role in elevating plasma TMAO levels and significantly influences the TMA-TMAO pathway, primarily by modulating the expression of hepatic FMO3 and directly impacting hepatic lipid metabolism.

Spontaneously hypertensive rats exhibit increased liver flavin monooxygenase expression and elevated plasma TMAO levels compared to normotensive and Ang II-dependent hypertensive rats

Background: Flavin monooxygenases (FMOs) are enzymes responsible for the oxidation of a broad spectrum of exogenous and endogenous amines. There is increasing evidence that trimethylamine (TMA), a compound produced by gut bacteria and also recognized as an industrial pollutant, contributes to cardiovascular diseases. FMOs convert TMA into trimethylamine oxide (TMAO), which is an emerging marker of cardiovascular risk. This study hypothesized that blood pressure phenotypes in rats might be associated with variations in the expression of FMOs. Methods: The expression of FMO1, FMO3, and FMO5 was evaluated in the kidneys, liver, lungs, small intestine, and large intestine of normotensive male Wistar-Kyoto rats (WKY) and two distinct hypertensive rat models: spontaneously hypertensive rats (SHRs) and WKY rats with angiotensin II-induced hypertension (WKY-ANG). Plasma concentrations of TMA and TMAO were measured at baseline and after intravenous administration of TMA using liquid chromatography-mass spectrometry (LC-MS). Results: We found that the expression of FMOs in WKY, SHR, and WKY-ANG rats was in the descending order of FMO3 > FMO1 >> FMO5. The highest expression of FMOs was observed in the liver. Notably, SHRs exhibited a significantly elevated expression of FMO3 in the liver compared to WKY and WKY-ANG rats. Additionally, the plasma TMAO/TMA ratio was significantly higher in SHRs than in WKY rats. Conclusion: SHRs demonstrate enhanced expression of FMO3 and a higher plasma TMAO/TMA ratio. The variability in the expression of FMOs and the metabolism of amines might contribute to the hypertensive phenotype observed in SHRs.

Role of the gut microbiota in complications after ischemic stroke

Ischemic stroke (IS) is a serious central nervous system disease. Post-IS complications, such as post-stroke cognitive impairment (PSCI), post-stroke depression (PSD), hemorrhagic transformation (HT), gastrointestinal dysfunction, cardiovascular events, and post-stroke infection (PSI), result in neurological deficits. The microbiota-gut-brain axis (MGBA) facilitates bidirectional signal transduction and communication between the intestines and the brain. Recent studies have reported alterations in gut microbiota diversity post-IS, suggesting the involvement of gut microbiota in post-IS complications through various mechanisms such as bacterial translocation, immune regulation, and production of gut bacterial metabolites, thereby affecting disease prognosis. In this review, to provide insights into the prevention and treatment of post-IS complications and improvement of the long-term prognosis of IS, we summarize the interaction between the gut microbiota and IS, along with the effects of the gut microbiota on post-IS complications.

Deciphering the diurnal rhythm regulating mechanism of flavin-containing monooxygenase 3 in mouse liver

Circadian genes play an important role in the field of drug metabolism. Flavin-containing monooxygenase 3 is a well-known phase I enzyme which participates in metabolism of many exogenous and endogenous substances, especially production of trimethylamine N-oxide. Here, we aimed to decipher diurnal rhythms of flavin-containing monooxygenase 3 expression and activity, and explore the regulation mechanism by clock genes. Our results showed that its mRNA and protein exhibited robust diurnal rhythms in mouse liver and cell lines. Consistently, significant alterations were observed for in vitro microsomal N-oxidation rates of procainamide, which kept in line with its protein expression at different time in wild-type and reverse erythroblastosis virus α knockout mice. Further, flavin-containing monooxygenase 3 was negatively regulated by E4 promoter-binding protein 4 in AML12 and Hepa1-6 cells, while it was positively influenced by reverse erythroblastosis virus α and brain and muscle ARNT-like protein-1. Moreover, luciferase reporter assays and electrophoretic mobility shift assays showed E4 promoter-binding protein 4 inhibited the transcription of flavin-containing monooxygenase 3 by binding to a D-box1 element (-1606/-1594 bp), while brain and muscle ARNT-like protein-1 positively activated the transcription via direct binding to three E-boxes (-863/-858 bp, -507/-498 bp, and -115/-104 bp) in this enzyme promoter. Taken together, this study would be helpful to reveal the mechanism of clock-controlled drug metabolism and facilitate the practice of chrono-therapeutics.

Mechanistic Review on the Role of Gut Microbiota in the Pathology of Cardiovascular Diseases

Cardiovascular diseases (CVDs), which stand as the primary contributors to illness and death on a global scale, include vital risk factors like hyperlipidemia, hypertension, diabetes, and smoking, to name a few. However, conventional cardiovascular risk factors offer only partial insight into the complexity of CVDs. Lately, a growing body of research has illuminated that the gut microbiome and its by-products are also of paramount importance in the initiation and progression of CVDs. The gastrointestinal tract houses trillions of microorganisms, commonly known as gut microbiota, that metabolize nutrients, yielding substances like trimethylamine-N-oxide (TMAO), bile acids (BAs), short-chain fatty acids (SCFAs), indoxyl sulfate (IS), and so on. Strategies aimed at addressing these microbes and their correlated biological pathways have shown promise in the management and diagnosis of CVDs. This review offers a comprehensive examination of how the gut microbiota contributes to the pathogenesis of CVDs, particularly atherosclerosis, hypertension, heart failure (HF), and atrial fibrillation (AF), explores potential underlying mechanisms, and highlights emerging therapeutic prospects in this dynamic domain.

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

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

Serum trimethylamine N-oxide levels among coronary artery disease and acute coronary syndrome patients: a systematic review and meta-analysis

Background and Aim

Recent studies have linked trimethylamine N-oxide (TMAO) to cardiovascular diseases; our study aimed to analyze the association between coronary artery disease (CAD), acute coronary syndrome (ACS), and TMAO.

Methods

PubMed, Scopus, Embase, and Web of Science were searched using terms such as 'CAD' and 'TMAO'. Only observational controlled studies were included. RevMan software version 5.4 was used for the analysis.

Results

A significant association was found between the CAD group and increased serum TMAO levels compared with the control group (MD=1.16, 95% CI=0.54-1.78, P=0.0003). This association remained significant among acute coronary syndrome patients (MD=0.98, 95% CI=0.73-1.23, P<0.00001) and was also detected among young and old CAD patients (MD=0.35, 95% CI=0.06-0.64, P=0.02 and MD=1.36, 95% CI=0.71-2.01, P<0.0001, respectively). On further analysis of intestinal metabolites, the authors detected an insignificant association between choline, betaine, carnitine, and CAD. According to our sensitivity analysis, TMAO is an acceptable diagnostic marker for CAD (0.721, SE was 0.0816, 95% CI: 0.561-0.881).

Conclusion

TMAO is an acceptable diagnostic marker for CAD, with significantly higher levels among these patients regardless of their age. Other metabolites did not show such an association. The role of serum level TMAO in the early diagnosis of CAD should be further explored.

Trimethylamine N-oxide predicts stroke severity in diabetic patients with acute ischaemic stroke and is related to glycemic variability

BACKGROUND AND PURPOSE

The present study analyzed the relationship between circulating trimethylamine N-oxide (TMAO) levels and stroke severity in diabetic patients with acute ischaemic stroke. A further aim was to investigate whether higher TMAO levels were associated with platelet aggregation and glycemic variability.

METHODS

This was a cross-sectional analysis of 108 patients with type 2 diabetes mellitus (DM) undergoing acute ischaemic stroke and 60 healthy controls. Fasting plasma TMAO was measured using high-performance liquid chromatography with online electrospray ionization tandem mass spectrometry.

RESULTS

Plasma TMAO levels of patients with acute ischaemic stroke were significantly higher than those of healthy controls. Amongst stroke patients, 50 were defined as undergoing mild stroke, and their plasma TMAO levels were lower compared to those with moderate to severe stroke. Platelet aggregation and mean amplitude of glycemic excursions were both correlated with plasma TMAO levels and these relationships remained significant in multiple linear regression analyses. Moreover, in streptozotocin-induced diabetic rats fed a diet enriched with choline to increase TMAO synthesis, platelet aggregation was significantly increased in the DM + choline and fluctuating DM (FDM) + choline groups compared to the control group. This increase was abolished in rats receiving oral antibiotics, which markedly reduced plasma TMAO levels. Importantly, compared with the DM + choline group, the FDM + choline group displayed significantly elevated TMAO levels and higher platelet aggregation.

CONCLUSIONS

Our results demonstrated that higher plasma TMAO levels were associated with stroke severity and suggested a novel link between plasma TMAO levels and glycemic variability in diabetic patients with acute ischaemic stroke.

Transcriptomic (DNA Microarray) and Metabolome (LC-TOF-MS) Analyses of the Liver in High-Fat Diet Mice after Intranasal Administration of GALP (Galanin-like Peptide)

The aim of this research was to test the efficacy and potential clinical application of intranasal administration of galanin-like peptide (GALP) as an anti-obesity treatment under the hypothesis that GALP prevents obesity in mice fed a high-fat diet (HFD). Focusing on the mechanism of regulation of lipid metabolism in peripheral tissues via the autonomic nervous system, we confirmed that, compared with a control (saline), intranasally administered GALP prevented further body weight gain in diet-induced obesity (DIO) mice with continued access to an HFD. Using an omics-based approach, we identified several genes and metabolites in the liver tissue of DIO mice that were altered by the administration of intranasal GALP. We used whole-genome DNA microarray and metabolomics analyses to determine the anti-obesity effects of intranasal GALP in DIO mice fed an HFD. Transcriptomic profiling revealed the upregulation of flavin-containing dimethylaniline monooxygenase 3 (Fmo3), metallothionein 1 and 2 (Mt1 and Mt2, respectively), and the Aldh1a3, Defa3, and Defa20 genes. Analysis using the DAVID tool showed that intranasal GALP enhanced gene expression related to fatty acid elongation and unsaturated fatty acid synthesis and downregulated gene expression related to lipid and cholesterol synthesis, fat absorption, bile uptake, and excretion. Metabolite analysis revealed increased levels of coenzyme Q10 and oleoylethanolamide in the liver tissue, increased levels of deoxycholic acid (DCA) and taurocholic acid (TCA) in the bile acids, increased levels of taurochenodeoxycholic acid (TCDCA), and decreased levels of ursodeoxycholic acid (UDCA). In conclusion, intranasal GALP administration alleviated weight gain in obese mice fed an HFD via mechanisms involving antioxidant, anti-inflammatory, and fatty acid metabolism effects and genetic alterations. The gene expression data are publicly available at NCBI GSE243376.

Connections between serum Trimethylamine N-Oxide (TMAO), a gut-derived metabolite, and vascular biomarkers evaluating arterial stiffness and subclinical atherosclerosis in children with obesity

Introduction

Childhood obesity leads to early subclinical atherosclerosis and arterial stiffness. Studying biomarkers like trimethylamine N-oxide (TMAO), linked to cardio-metabolic disorders in adults, is crucial to prevent long-term cardiovascular issues.

Methods

The study involved 70 children aged 4 to 18 (50 obese, 20 normal-weight). Clinical examination included BMI, waist measurements, puberty stage, the presence of acanthosis nigricans, and irregular menstrual cycles. Subclinical atherosclerosis was assessed by measuring the carotid intima-media thickness (CIMT), and the arterial stiffness was evaluated through surrogate markers like the pulse wave velocity (PWV), augmentation index (AIx), and peripheral and central blood pressures. The blood biomarkers included determining the values of TMAO, HOMA-IR, and other usual biomarkers investigating metabolism.

Results

The study detected significantly elevated levels of TMAO in obese children compared to controls. TMAO presented positive correlations to BMI, waist circumference and waist-to-height ratio and was also observed as an independent predictor of all three parameters. Significant correlations were observed between TMAO and vascular markers such as CIMT, PWV, and peripheral BP levels. TMAO independently predicts CIMT, PWV, peripheral BP, and central SBP levels, even after adding BMI, waist circumference, waist-to-height ratio, puberty development and age in the regression model. Obese children with high HOMA-IR presented a greater weight excess and significantly higher vascular markers, but TMAO levels did not differ significantly from the obese with HOMA-IR

Conclusion

Our study provides compelling evidence supporting the link between serum TMAO, obesity, and vascular damage in children. These findings highlight the importance of further research to unravel the underlying mechanisms of this connection.

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Key Words

• TMAO
• arterial stiffness
• atherosclerosis
• cardiovascular risk
• carotid intima-media thickness
• childhood obesity
• high blood pressure
• pulse wave velocity

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MESH Headings

• Adult
• Female
• Humans
• Child
• Pediatric Obesity/complications
• Carotid Intima-Media Thickness
• Vascular Stiffness/physiology
• Pulse Wave Analysis
• Acanthosis Nigricans
• Atherosclerosis/diagnosis
• Atherosclerosis/etiology
• Biomarkers

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Affiliation(s)

Monica Simina Mihuta Department of Doctoral Studies, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania Center of Molecular Research in Nephrology and Vascular Disease, Faculty of Medicine, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania
Corina Paul Department of Pediatrics, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania
Andreea Borlea Center of Molecular Research in Nephrology and Vascular Disease, Faculty of Medicine, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania 2nd Department of Internal Medicine, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania
Cristina Mihaela Roi Department of Doctoral Studies, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania Center of Molecular Research in Nephrology and Vascular Disease, Faculty of Medicine, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania
Denisa Pescari Department of Doctoral Studies, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania
Oana-Alexandra Velea-Barta 3rd Department of Odontotherapy and Endodontics, Faculty of Dental Medicine, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania
Ioana Mozos Department of Functional Sciences—Pathophysiology, Center for Translational Research and Systems Medicine, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania
Dana Stoian Center of Molecular Research in Nephrology and Vascular Disease, Faculty of Medicine, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania 2nd Department of Internal Medicine, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania

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The Possible Role of Probiotic Supplementation in Inflammation: A Narrative Review

The fine balance between symbiotic and potentially opportunistic and/or pathogenic microorganisms can undergo quantitative alterations, which, when associated with low intestinal biodiversity, could be responsible for the development of gut inflammation and the so-called "intestinal dysbiosis". This condition is characterized by the disbalance of a fine synergistic mechanism involving the mucosal barrier, the intestinal neuroendocrine system, and the immune system that results in an acute inflammatory response induced by different causes, including viral or bacterial infections of the digestive tract. More frequently, however, dysbiosis is induced slowly and subtly by subliminal causal factors, resulting in a chronic condition related to different diseases affecting the digestive tract and other organs and apparatuses. Studies on animal models, together with studies on humans, highlight the significant role of the gut microbiota and microbiome in the occurrence of inflammatory conditions such as metabolic syndrome and cardiovascular diseases (CVDs); neurodegenerative, urologic, skin, liver, and kidney pathologies; and premature aging. The blood translocation of bacterial fragments has been found to be one of the processes linked to gut dysbiosis and responsible for the possible occurrence of "metabolic endotoxemia" and systemic inflammation, associated with an increased risk of oxidative stress and related diseases. In this context, supplementation with different probiotic strains has been shown to restore gut eubiosis, especially if administered in long-term treatments. The aim of this review is to describe the anti-inflammatory effects of specific probiotic strains observed in clinical trials and the respective indications, highlighting the differences in efficacy depending on strain, formulation, time and duration of treatment, and dosage used.

Investigating causal associations among gut microbiota, gut microbiota-derived metabolites, and gestational diabetes mellitus: a bidirectional Mendelian randomization study

BACKGROUND

Previous studies have shown that gut microbiota (GM) and gut microbiota-derived metabolites are associated with gestational diabetes mellitus (GDM). However, the causal associations need to be treated with caution due to confounding factors and reverse causation.

METHODS

This study obtained genetic variants from genome-wide association study including GM (N = 18,340), GM-derived metabolites (N = 7,824), and GDM (5,687 cases and 117,89 controls). To examine the causal association, several methods were utilized, including inverse variance weighted, maximum likelihood, weighted median, MR-Egger, and MR.RAPS. Additionally, reverse Mendelian Randomization (MR) analysis and multivariable MR were conducted to confirm the causal direction and account for potential confounders, respectively. Furthermore, sensitivity analyses were performed to identify any potential heterogeneity and horizontal pleiotropy.

RESULTS

Greater abundance of Collinsella was detected to increase the risk of GDM. Our study also found suggestive associations among Coprobacter, Olsenella, Lachnoclostridium, Prevotella9, Ruminococcus2, Oscillibacte, and Methanobrevibacter with GDM. Besides, eight GM-derived metabolites were found to be causally associated with GDM. For the phenylalanine metabolism pathway, phenylacetic acid was found to be related to the risk of GDM.

CONCLUSIONS

The study first used the MR approach to explore the causal associations among GM, GM-derived metabolites, and GDM. Our findings may contribute to the prevention and treatment strategies for GDM by targeting GM and metabolites, and offer novel insights into the underlying mechanism of the disease.

Insight into increased risk of portal vein thrombosis in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the leading chronic liver diseases with increased morbidity and mortality rates for extrahepatic diseases (including cardiovascular disease, portal vein thrombosis, etc.). There is an increased risk of thrombosis in both the portal and systemic circulation in patients with NAFLD, independent of traditional liver cirrhosis. However, increased portal pressure, the most critical factor, is frequently observed in NAFLD patients, predisposing them to portal vein thrombosis (PVT). It has been reported that there is an 8.5% incidence of PVT among patients with non-cirrhotic NAFLD in a prospective cohort study. Based on the prothrombotic status of NAFLD itself, patients combined with cirrhosis may accelerate the development of PVT and lead to a poor prognosis. Moreover, PVT has been shown to complicate the procedure and adversely affect the outcome during liver transplantation surgery. NAFLD is in a prothrombotic state, and its underlying mechanisms have not been fully understood so far. Particularly noteworthy is that gastroenterologists currently overlook the higher risk of PVT in NAFLD. We investigate the pathogenesis of NAFLD complicated with PVT from the perspective of primary, secondary, and tertiary hemostasis, and also summarize relevant studies in humans. Some treatment options that may affect NAFLD and its PVT are also explored to improve patient-oriented outcomes.

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

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

Trimethylamine N-oxide: role in cell senescence and age-related diseases

INTRODUCTION

Hayflick and Moorhead first demonstrated cell senescence as the irreversible growth arrest of cells after prolonged cultivation. Telomere shortening and oxidative stress are the fundamental mechanisms that drive cell senescence. Increasing studies have shown that TMAO is closely associated with cellular aging and age-related diseases. An emerging body of evidence from animal models, especially mice, has identified that TMAO contributes to senescence from multiple pathways and appears to accelerate many neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. However, the specific mechanism of how TMAO speeds aging is still not completely clear.

MATERIAL AND METHODS

In this review, we summarize some key findings in TMAO, cell senescence, and age-related diseases. We focused particular attention on the potential mechanisms for clinical transformation to find ways to interfere with the aging process.

CONCLUSION

TMAO can accelerate cell senescence by causing mitochondrial damage, superoxide formation, and promoting the generation of pro-inflammatory factors.

Contribution of Trimethylamine N-Oxide (TMAO) to Chronic Inflammatory and Degenerative Diseases

Trimethylamine N-oxide (TMAO) is a metabolite produced by the gut microbiota and has been mainly associated with an increased incidence of cardiovascular diseases (CVDs) in humans. There are factors that affect one's TMAO level, such as diet, drugs, age, and hormones, among others. Gut dysbiosis in the host has been studied recently as a new approach to understanding chronic inflammatory and degenerative diseases, including cardiovascular diseases, metabolic diseases, and Alzheimer's disease. These disease types as well as COVID-19 are known to modulate host immunity. Diabetic and obese patients have been observed to have an increase in their level of TMAO, which has a direct correlation with CVDs. This metabolite is attributed to enhancing the inflammatory pathways through cholesterol and bile acid dysregulation, promoting foam cell formation. Additionally, TMAO activates the transcription factor NF-κB, which, in turn, triggers cytokine production. The result can be an exaggerated inflammatory response capable of inducing endoplasmic reticulum stress, which is responsible for various diseases. Due to the deleterious effects that this metabolite causes in its host, it is important to search for new therapeutic agents that allow a reduction in the TMAO levels of patients and that, thus, allow patients to be able to avoid a severe cardiovascular event. The present review discussed the synthesis of TMAO and its contribution to the pathogenesis of various inflammatory diseases.

The Role of the Gut Microbiome and Trimethylamine Oxide in Atherosclerosis and Age-Related Disease

The gut microbiome plays a major role in human health, and gut microbial imbalance or dysbiosis is associated with disease development. Modulation in the gut microbiome can be used to treat or prevent different diseases. Gut dysbiosis increases with aging, and it has been associated with the impairment of gut barrier function leading to the leakage of harmful metabolites such as trimethylamine (TMA). TMA is a gut metabolite resulting from dietary amines that originate from animal-based foods. TMA enters the portal circulation and is oxidized by the hepatic enzyme into trimethylamine oxide (TMAO). Increased TMAO levels have been reported in elderly people. High TMAO levels are linked to peripheral artery disease (PAD), endothelial senescence, and vascular aging. Emerging evidence showed the beneficial role of probiotics and prebiotics in the management of several atherogenic risk factors through the remodeling of the gut microbiota, thus leading to a reduction in TMAO levels and atherosclerotic lesions. Despite the promising outcomes in different studies, the definite mechanisms of gut dysbiosis and microbiota-derived TMAO involved in atherosclerosis remain not fully understood. More studies are still required to focus on the molecular mechanisms and precise treatments targeting gut microbiota and leading to atheroprotective effects.

Trimethylamine N-Oxide Response to a Mixed Macronutrient Tolerance Test in a Cohort of Healthy United States Adults

Plasma trimethylamine n-oxide (TMAO) concentration increases in responses to feeding TMAO, choline, phosphatidylcholine, L-carnitine, and betaine but it is unknown whether concentrations change following a mixed macronutrient tolerance test (MMTT) with limited amounts of TMAO precursors. In this proof-of-concept study, we provided healthy female and male adults (n = 97) ranging in age (18-65 years) and BMI (18-44 kg/m2) a MMTT (60% fat, 25% sucrose; 42% of a standard 2000 kilo calorie diet) and recorded their metabolic response at fasting and at 30 min, 3 h, and 6 h postprandially. We quantified total exposure to TMAO (AUC-TMAO) and classified individuals by the blood draw at which they experienced their maximal TMAO concentration (TMAO-response groups). We related AUC-TMAO to the 16S rRNA microbiome, to two SNPs in the exons of the FMO3 gene (rs2266782, G>A, p.Glu158Lys; and rs2266780, A>G, p.Glu308Gly), and to a priori plasma metabolites. We observed varying TMAO responses (timing and magnitude) and identified a sex by age interaction such that AUC-TMAO increased with age in females but not in males (p-value = 0.0112). Few relationships between AUC-TMAO and the fecal microbiome and FMO3 genotype were identified. We observed a strong correlation between AUC-TMAO and TNF-α that depended on TMAO-response group. These findings promote precision nutrition and have important ramifications for the eating behavior of adults who could benefit from reducing TMAO exposure, and for understanding factors that generate plasma TMAO.

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

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

Metabolomics in gestational diabetes mellitus: A review

Gestational diabetes mellitus (GDM), a common complication of pregnancy, is a type of diabetes that is first detected and diagnosed during pregnancy. The incidence of GDM is increasing annually and is associated with many adverse pregnancy outcomes. Early prediction of the risk of GDM and intervention are thus important to reduce adverse pregnancy outcomes. Studies have revealed a correlation between the levels of amino acids, fatty acids, triglycerides, and other metabolites in early pregnancy and the occurrence of GDM. The development of high-throughput technologies used in metabolomics has enabled the detection of changes in the levels of small-molecule metabolites during early pregnancy, which can help reflect the overall physiological and pathological status of the body and explore the underlying mechanisms of the development of GDM. This review sought to summarize current research in this field and provide data for the development of strategies to manage GDM.

Inhibition of Trimethylamine N-Oxide Attenuates Neointimal Formation Through Reduction of Inflammasome and Oxidative Stress in a Mouse Model of Carotid Artery Ligation

Aims: Trimethylamine-N-oxide (TMAO) is a metabolite generated from dietary choline, betaine, and l-carnitine, after their oxidization in the liver. TMAO has been identified as a novel independent risk factor for atherosclerosis through the induction of vascular inflammation. However, the effect of TMAO on neointimal formation in response to vascular injury remains unclear. Results: This study was conducted using a murine model of acutely disturbed flow-induced atherosclerosis induced by partial carotid artery ligation. 3,3-Dimethyl-1-butanol (DMB) was used to reduce TMAO concentrations. Wild-type mice were divided into four groups [regular diet, high-TMAO diet, high-choline diet, and high-choline diet+DMB] to investigate the effects of TMAO elevation and its inhibition by DMB. Mice fed high-TMAO and high-choline diets had significantly enhanced neointimal hyperplasia and advanced plaques, elevated arterial elastin fragmentation, increased macrophage infiltration and inflammatory cytokine secretion, and enhanced activation of nuclear factor (NF)-κB, the NLRP3 inflammasome, and endoplasmic reticulum (ER) stress relative to the control group. Mice fed high-choline diets with DMB treatment exhibited attenuated flow-induced atherosclerosis, inflammasome expression, ER stress, and reactive oxygen species expression. Human aortic smooth muscle cells (HASMCs) were used to investigate the mechanism of TMAO-induced injury. The HASMCs were treated with TMAO with or without an ER stress inhibitor to determine whether inhibition of ER stress modulates the TMAO-induced inflammatory response. Innovation: This study demonstrates that TMAO regulates vascular remodeling via ER stress. Conclusion: Our findings demonstrate that TMAO elevation promotes disturbed flow-induced atherosclerosis and that DMB administration mitigates vascular remodeling, suggesting a rationale for a TMAO-targeted strategy for the treatment of atherosclerosis. Antioxid. Redox Signal. 38, 215-233.

Neurobiological Basis of Aversion-Resistant Ethanol Seeking in C. elegans

Persistent alcohol seeking despite the risk of aversive consequences is a crucial characteristic of alcohol use disorders (AUDs). Therefore, an improved understanding of the molecular basis of alcohol seeking despite aversive stimuli or punishment in animal models is an important strategy to understand the mechanism that underpins the pathology of AUDs. Aversion-resistant seeking (ARS) is characterized by disruption in control of alcohol use featured by an imbalance between the urge for alcohol and the mediation of aversive stimuli. We exploited C. elegans, a genetically tractable invertebrate, as a model to elucidate genetic components related to this behavior. We assessed the seb-3 neuropeptide system and its transcriptional regulation to progress aversion-resistant ethanol seeking at the system level. Our functional genomic approach preferentially selected molecular components thought to be involved in cholesterol metabolism, and an orthogonal test defined functional roles in ARS through behavioral elucidation. Our findings suggest that fmo-2 (flavin-containing monooxygenase-2) plays a role in the progression of aversion-resistant ethanol seeking in C. elegans.

Altered macronutrient composition and genetics influence the complex transcriptional network associated with adiposity in the Collaborative Cross

Background

Obesity is a serious disease with a complex etiology characterized by overaccumulation of adiposity resulting in detrimental health outcomes. Given the liver’s critical role in the biological processes that attenuate adiposity accumulation, elucidating the influence of genetics and dietary patterns on hepatic gene expression is fundamental for improving methods of obesity prevention and treatment. To determine how genetics and diet impact obesity development, mice from 22 strains of the genetically diverse recombinant inbred Collaborative Cross (CC) mouse panel were challenged to either a high-protein or high-fat high-sucrose diet, followed by extensive phenotyping and analysis of hepatic gene expression.

Results

Over 1000 genes differentially expressed by perturbed dietary macronutrient composition were enriched for biological processes related to metabolic pathways. Additionally, over 9000 genes were differentially expressed by strain and enriched for biological process involved in cell adhesion and signaling. Weighted gene co-expression network analysis identified multiple gene clusters (modules) associated with body fat % whose average expression levels were influenced by both dietary macronutrient composition and genetics. Each module was enriched for distinct types of biological functions.

Conclusions

Genetic background affected hepatic gene expression in the CC overall, but diet macronutrient differences also altered expression of a specific subset of genes. Changes in macronutrient composition altered gene expression related to metabolic processes, while genetic background heavily influenced a broad range of cellular functions and processes irrespective of adiposity. Understanding the individual role of macronutrient composition, genetics, and their interaction is critical to developing therapeutic strategies and policy recommendations for precision nutrition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12263-022-00714-x.

FMO3 deficiency of duck leads to decreased lipid deposition and increased antibacterial activity

Background

Most duck eggs possess a fishy odor, indicating that ducks generally exhibit impaired trimethylamine (TMA) metabolism. TMA accumulation is responsible for this unpleasant odor, and TMA metabolism plays an essential role in trimethylaminuria (TMAU), also known as fish odor syndrome. In this study, we focused on the unusual TMA metabolism mechanism in ducks, and further explored the unclear reasons leading to the debilitating TMA metabolism.

Methods

To achieve this, transcriptome, proteome, and metagenome analyses were first integrated based on the constructed duck populations with high and low TMA metabolism abilities. Additionally, further experiments were conducted to validate the hypothesis regarding the limited flavin-containing monooxygenase 3 (FMO3) metabolism ability of ducks.

Results

The study demonstrated that liver FMO3 and cecal microbes, including Akkermansia and Mucispirillum, participated in TMA metabolism in ducks. The limited oxidation ability of FMO3 explains the weakening of TMA metabolism in ducks. Nevertheless, it decreases lipid deposition and increases antibacterial activity, contributing to its survival and reproduction during the evolutionary adaptation process.

Conclusions

This study demonstrated the function of FMO3 and intestinal microbes in regulating TMA metabolism and illustrated the biological significance of FMO3 impairment in ducks.

Uncovering the characteristics of the gut microbiota in patients with acute ischemic stroke and phlegm-heat syndrome

Growing evidence has indicated that the characteristics of gut microbiota are associated with acute ischemic stroke (AIS). Phlegm-heat syndrome (PHS), a specific pathological state of the AIS, is one of the common traditional Chinese syndromes of stroke. The long duration of PHS in patients with AIS could lead to poor clinical outcomes. Gut microbiota characteristics in patients with both AIS and PHS, and their relationship remains unknown. This study was designed to investigate the alterations in gut microbiota in patients with AIS and PHS through a cross-sectional study. Fecal samples were collected from 10 patients with AIS and non-PHS (ntAIS), 7 patients with AIS and PHS (tAIS), and 10 healthy controls (HC). Samples were profiled via Illumina sequencing of the 16S rRNA V3-V4. Stroke severity was assessed at admission by the National Institutes of Health Stroke Scale (NIHSS) and modified Rankin scale (mRS); their correlation with gut microbiota was investigated. The alpha-diversity of the bacterial communities was significantly higher in the fecal samples of patients with tAIS than in patients with ntAIS (Shannon index, P = 0.037). In addition, the combined tAIS and ntAIS group (tntAIS) exhibited higher microbiotic diversity when compared with HC (chao1, P = 0.019). The structure of intestinal microbiota was effectively distinguished between the tAIS and ntAIS group (ANOSIM, r = 0.337, P = 0.007). Additionally, the gut microbiota structure was significantly different between the tntAIS and HC groups (ANOSIM, r = 0.217, P = 0.005). The genera, Ruminococcaceae_ UCG_002 and Christensenellaceae_R-7_group, were implicated in the discrimination of PHS from non-PHS. The order Lactobacillales and family Lachnospiraceae were significantly negatively correlated with NIHSS and mRS at admission (P < 0.05). By contrast, the order Desulfovibrionales, families Christensenellaceae and Desulfovibrionaceae, and genera Ruminococcaceae UCG-014 and Ruminococcaceae UCG-002 were significantly positively correlated with NIHSS and mRS at admission (P < 0.05). This study is the first to profile the characteristics of gut microbiota in patients with AIS and PHS, compared with those with non-PHS. The genera, Ruminococcaceae_ UCG_002 and Christensenellaceae_R-7_group, may be objective indicators of this traditional Chinese medicine (TCM) syndrome in AIS. Furthermore, it provides a microbe-inspired biological basis for TCM syndrome differentiation.

The intestinal microbiome associated with lipid metabolism and obesity in humans and animals

Intestinal microbiota is considered to play an integral role in maintaining health of host by modulating several physiological functions including nutrition, metabolism and immunity. Accumulated data from human and animal studies indicate that intestinal microbes can affect lipid metabolism in host through various direct and indirect biological mechanisms. These mechanisms include the production of various signalling molecules by the intestinal microbiome, which exert a strong effect on lipid metabolism, bile secretion in the liver, reverse transport of cholesterol and energy expenditure and insulin sensitivity in peripheral tissues. This review discusses the findings of recent studies suggesting an emerging role of intestinal microbiota and its metabolites in regulating lipid metabolism and the association of intestinal microbiota with obesity. Additionally, we discuss the controversies and challenges in this research area. However, intestinal micro-organisms are also affected by some external factors, which in turn influence the regulation of microbial lipid metabolism. Therefore, we also discuss the effects of probiotics, prebiotics, diet structure, exercise and other factors on intestinal microbiological changes and lipid metabolism regulation.

Synergic interactions between berry polyphenols and gut microbiota in cardiovascular diseases

Now a days, scientific community has been taking initiatives to decrease burden of metabolic disorders including diabetes mellitus, chronic hypertension, cardiovascular diseases and many others. Many nutraceuticals and functional food have a crucial function in preventing and decreasing burden of chronic diseases. Main purpose of the study was to relate association between mechanism of gut microbiota effecting cardiovascular diseases, moreover, to find out advantageous effects of berry polyphenols on gut microbiota and cardiovascular diseases. To summarize, we explore literature for beneficial effects of berry polyphenols by using multiple search engines including Google Scholar, Science Direct and PubMed. Original research article, review articles, experimental trials (human and animal studies) and abstract were also included in the current study based on relevancy to the characteristics of berries and their potential benefit on human health. This detailed review revealed that all classes of berries and their metabolites possess a definite impact on human health by preventing onset of chronic diseases by its anti-inflammatory property, thus, consider as one of the beneficial natural compounds that can be consumed on daily basis to prevent various disorders. There is also a positive association between berry polyphenols and modulation of gut microbiota and their metabolites, furthermore, showed a relationship between gut microbiome and incidence of cardiovascular disease.

Breath Analysis in Children with Ketogenic Glycogen Storage Diseases

(1) Background: The treatment goal of ketogenic glycogen storage diseases (GSDs) is appropriate control of hypoglycemia and other disturbances such as dyslipidemia. Monitoring and treatment of ketosis are known to improve outcomes. We used breath analysis to identify volatile organic compounds (VOCs) that correlate with serum ketones in order to provide a non-invasive method of monitoring ketosis. (2) Methods: Consecutive children with ketogenic GSDs were recruited from a single center during routine admission to monitor serum glucose and ketone levels. Five breath samples were collected from every patient at the same time of blood draws. SIFT-mass spectrometry was used to analyze breath samples. Univariate linear mixed-effects regression models for 22 known VOCs and either serum ketones or glucose were performed. (3) Results: Our cohort included 20 patients aged 5–15 years with a mean BMI of 20 kg/m2 (72% tile). Most patients had GSD type 0 (35%), while 25% had type IX. VOCs that showed a significant correlation with serum ketone levels included acetone (p < 0.0001), trimethylamine (p < 0.0001), pentane (p = 0.0001), 3-methylhexane (p = 0.0047), and carbon disulfide (p = 0.0499). No correlation was found between serum glucose and any VOC. (4) Conclusions: Breath analysis is a promising noninvasive tool that can be used to predict ketone serum levels in patients with GSD.

The role of the gut microbiota in health and cardiovascular diseases

The gut microbiota is critical to human health, such as digesting nutrients, forming the intestinal epithelial barrier, regulating immune function, producing vitamins and hormones, and producing metabolites to interact with the host. Meanwhile, increasing evidence indicates that the gut microbiota has a strong correlation with the occurrence, progression and treatment of cardiovascular diseases (CVDs). In patients with CVDs and corresponding risk factors, the composition and ratio of gut microbiota have significant differences compared with their healthy counterparts. Therefore, gut microbiota dysbiosis, gut microbiota-generated metabolites, and the related signaling pathway may serve as explanations for some of the mechanisms about the occurrence and development of CVDs. Several studies have also demonstrated that many traditional and latest therapeutic treatments of CVDs are associated with the gut microbiota and its generated metabolites and related signaling pathways. Given that information, we summarized the latest advances in the current research regarding the effect of gut microbiota on health, the main cardiovascular risk factors, and CVDs, highlighted the roles and mechanisms of several metabolites, and introduced corresponding promising treatments for CVDs regarding the gut microbiota. Therefore, this review mainly focuses on exploring the role of gut microbiota related metabolites and their therapeutic potential in CVDs, which may eventually provide better solutions in the development of therapeutic treatment as well as the prevention of CVDs.

Crosstalk between the Gut and Brain in Ischemic Stroke: Mechanistic Insights and Therapeutic Options

There has been a significant amount of interest in the past two decades in the study of the evolution of the gut microbiota, its internal and external impacts on the gut, and risk factors for cerebrovascular disorders such as cerebral ischemic stroke. The network of bidirectional communication between gut microorganisms and their host is known as the microbiota-gut-brain axis (MGBA). There is mounting evidence that maintaining gut microbiota homeostasis can frequently enhance the effectiveness of ischemic stroke treatment by modulating immune, metabolic, and inflammatory responses through MGBA. To effectively monitor and cure ischemic stroke, restoring a healthy microbial ecology in the gut may be a critical therapeutic focus. This review highlights mechanistic insights on the MGBA in disease pathophysiology. This review summarizes the role of MGBA signaling in the development of stroke risk factors such as aging, hypertension, obesity, diabetes, and atherosclerosis, as well as changes in the microbiota in experimental or clinical populations. In addition, this review also examines dietary changes, the administration of probiotics and prebiotics, and fecal microbiota transplantation as treatment options for ischemic stroke as potential health benefits. It will become more apparent how the MGBA affects human health and disease with continuing advancements in this emerging field of biomedical sciences.

Role of gut microbe-derived metabolites in cardiometabolic diseases: Systems based approach

BACKGROUND

The gut microbiome influences host physiology and cardiometabolic diseases by interacting directly with intestinal cells or by producing molecules that enter the host circulation. Given the large number of microbial species present in the gut and the numerous factors that influence gut bacterial composition, it has been challenging to understand the underlying biological mechanisms that modulate risk of cardiometabolic disease.

SCOPE OF THE REVIEW

Here we discuss a systems-based approach that involves simultaneously examining individuals in populations for gut microbiome composition, molecular traits using "omics" technologies, such as circulating metabolites quantified by mass spectrometry, and clinical traits. We summarize findings from landmark studies using this approach and discuss future applications.

MAJOR CONCLUSIONS

Population-based integrative approaches have identified a large number of microbe-derived or microbe-modified metabolites that are associated with cardiometabolic traits. The knowledge gained from these studies provide new opportunities for understanding the mechanisms involved in gut microbiome-host interactions and may have potentially important implications for developing novel therapeutic approaches.

Coding Variants of the FMO3 Gene Are Associated with the Risk of Chronic Kidney Disease: A Case-Control Study

Background

Chronic kidney disease (CKD) is a global health concern involving roughly one-tenth of developed countries' populations. The flavin-containing dimethylaniline monooxygenase 3 (FMO3) gene encodes an enzyme that catalyzes trimethylamine N-oxide (TMAO), a toxin in CKD sufferers. This preliminary study aims to evaluate the association between coding region variations of FMO3, rs2266782G/A (E158K), rs2266780A/G (E308G), and rs1736557G/A (V257M), and the susceptibility to CKD.

Methods

A total of 356 participants were enrolled, including 157 patients diagnosed with CKD and 199 age-matched healthy individuals. Genotyping of FMO3 gene variations was performed via PCR-RFLP and ARMS-PCR methods.

Results

Our findings revealed a significant association between rs2266780A/G and rs1736557G/A and CKD under different genetic models. Compared to the GGG haplotype of rs2266782/rs1736557/rs2266780, the GAG, GAA, AAG, and AAA haplotype combinations conferred an increased risk of CKD in our population. Interaction analysis revealed that some genotype combinations, including GA/AA/AA, AA/AA/AA, GA/AA/GA, and GG/AG/AA, dramatically increased CKD risk in the Iranian population. No correlation was found between FMO3 polymorphisms and CKD stages.

Discussion

These observations highlight the potential impact of coding variants of the FMO3 gene on the onset of CKD. Further investigations into expanded populations and diverse races are needed to confirm our findings.

TMAO as a potential biomarker and therapeutic target for chronic kidney disease: A review

The gut microbiota and its metabolites have become a hotspot of recent research. Trimethylamine N-oxide (TMAO) metabolized by the gut microbiota is closely related to many diseases such as cardiovascular disease, chronic kidney disease, type 2 diabetes, etc. Chronic kidney disease (CKD) is an important contributor to morbidity and mortality from non-communicable diseases. Recently, increasing focus has been put on the role of TMAO in the development and progress of chronic kidney disease. The level of TMAO in patients with chronic kidney disease is significantly increased, and a high level of TMAO deteriorates chronic kidney disease. This article describes the relationship between TMAO and chronic kidney disease and the research progress of drugs targeted TMAO, providing a reference for the development of anti-chronic kidney disease drugs targeted TMAO.

The impact of dietary nutrient intake on gut microbiota in the progression and complications of chronic kidney disease

Chronic kidney disease (CKD) has been associated with changes in the function and composition of the gut microbiota. The ecosystem of the human gut consists of trillions of microorganisms forming an authentic metabolically active organ that is fueled by nutrients to produce bioactive compounds. These microbiota-derived metabolites may be protective for kidney function (e.g. short-chain fatty acids from fermentation of dietary fibers) or deleterious (e.g. gut-derived uremic toxins such as trimethylamine N-oxide, p-cresyl sulfate, and indoxyl sulfate from fermentation of amino acids). Although diet is the cornerstone of the management of the patient with CKD, it remains a relatively underused component of the clinician's armamentarium. In this review, we describe the latest advances in understanding diet-microbiota crosstalk in a uremic context, and how this communication might contribute to CKD progression and complications. We then discuss how this knowledge could be harnessed for personalized nutrition strategies to prevent patients with CKD progressing to end-stage kidney disease and its detrimental consequences.

Gut microbe-derived metabolite trimethylamine N-oxide activates PERK to drive fibrogenic mesenchymal differentiation

Intestinal dysbiosis is prominent in systemic sclerosis (SSc), but it remains unknown how it contributes to microvascular injury and fibrosis that are hallmarks of this disease. Trimethylamine (TMA) is generated by the gut microbiome and in the host converted by flavin-containing monooxygenase (FMO3) into trimethylamine N-oxide (TMAO), which has been implicated in chronic cardiovascular and metabolic diseases. Using cell culture systems and patient biopsies, we now show that TMAO reprograms skin fibroblasts, vascular endothelial cells, and adipocytic progenitor cells into myofibroblasts via the putative TMAO receptor protein R-like endoplasmic reticulum kinase (PERK). Remarkably, FMO3 was detected in skin fibroblasts and its expression stimulated by TGF-β1. Moreover, FMO3 was elevated in SSc skin biopsies and in SSc fibroblasts. A meta-organismal pathway thus might in SSc link gut microbiome to vascular remodeling and fibrosis via stromal cell reprogramming, implicating the FMO3-TMAO-PERK axis in pathogenesis, and as a promising target for therapy.

Gut microbiota-derived metabolite trimethylamine-N-oxide and multiple health outcomes: an umbrella review and updated meta-analysis

BACKGROUND

Trimethylamine-N-oxide (TMAO) is a gut microbiota-derived metabolite produced from dietary nutrients. Many studies have discovered that circulating TMAO concentrations are linked to a wide range of health outcomes.

OBJECTIVES

This study aimed to summarize health outcomes related to circulating TMAO concentrations.

METHODS

We searched the Embase, Medline, Web of Science, and Scopus databases from inception to 15 February, 2022 to identify and update meta-analyses examining the associations between TMAO and multiple health outcomes. For each health outcome, we estimated the summary effect size, 95% prediction CI, between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias. These metrics were used to evaluate the evidence credibility of the identified associations.

RESULTS

This umbrella review identified 24 meta-analyses that investigated the association between circulating TMAO concentrations and health outcomes including all-cause mortality, cardiovascular diseases (CVDs), diabetes mellitus (DM), cancer, and renal function. We updated these meta-analyses by including a total of 82 individual studies on 18 unique health outcomes. Among them, 14 associations were nominally significant. After evidence credibility assessment, we found 6 (33%) associations (i.e., all-cause mortality, CVD mortality, major adverse cardiovascular events, hypertension, DM, and glomerular filtration rate) to present highly suggestive evidence.

CONCLUSIONS

TMAO might be a novel biomarker related to human health conditions including all-cause mortality, hypertension, CVD, DM, cancer, and kidney function. Further studies are needed to investigate whether circulating TMAO concentrations could be an intervention target for chronic disease.This review was registered at www.crd.york.ac.uk/prospero/ as CRD42021284730.