Butyric acid, a gut bacteria metabolite, lowers arterial blood pressure via colon-vagus nerve signaling and GPR41/43 receptors

Recommendations for the Use of Dietary Fiber to Improve Blood Pressure Control

According to several international, regional, and national guidelines on hypertension, lifestyle interventions are the first-line treatment to lower blood pressure (BP). Although diet is one of the major lifestyle modifications described in hypertension guidelines, dietary fiber is not specified. Suboptimal intake of foods high in fiber, such as in Westernized diets, is a major contributing factor to mortality and morbidity of noncommunicable diseases due to higher BP and cardiovascular disease. In this review, we address this deficiency by examining and advocating for the incorporation of dietary fiber as a key lifestyle modification to manage elevated BP. We explain what dietary fiber is, review the existing literature that supports its use to lower BP and prevent cardiovascular disease, describe the mechanisms involved, propose evidence-based target levels of fiber intake, provide examples of how patients can achieve the recommended targets, and discuss outstanding questions in the field. According to the evidence reviewed here, the minimum daily dietary fiber for adults with hypertension should be >28 g/day for women and >38 g/day for men, with each extra 5 g/day estimated to reduce systolic BP by 2.8 mm Hg and diastolic BP by 2.1 mm Hg. This would support a healthy gut microbiota and the production of gut microbiota-derived metabolites called short-chain fatty acids that lower BP. Awareness about dietary fiber targets and how to achieve them will guide medical teams on better educating patients and empowering them to increase their fiber intake and, as a result, lower their BP and cardiovascular disease risk.

Perspectives on the involvement of the gut microbiota in salt-sensitive hypertension

Salt-sensitivity hypertension (SSH) is an independent predictor of cardiovascular event-related death. Despite the extensiveness of research on hypertension, which covers areas such as the sympathetic nervous system, the renin-angiotensin system, the vascular system, and the immune system, its pathogenesis remains elusive, with sub-optimal blood pressure control in patients. The gut microbiota is an important component of nutritional support and constitutes a barrier in the host. Long-term high salt intake can lead to gut microbiota dysbiosis and cause significant changes in the expression of gut microbiota-related metabolites. Of these metabolites, short chain fatty acids (SCFAs), trimethylamine oxide, amino acids, bile acids, and lipopolysaccharide are essential mediators of microbe-host crosstalk. These metabolites may contribute to the incidence and development of SSH via inflammatory, immune, vascular, and nervous pathways, among others. In addition, recent studies, including those on the histone deacetylase inhibitory mechanism of SCFAs and the blood pressure-decreasing effects of H2S via vascular activation, suggest that several proteins and factors in the classical pathway elicit their effects through multiple non-classical pathways. This review summarizes changes in the gut microbiota and its related metabolites in high-salt environments, as well as corresponding treatment methods for SSH, such as diet management, probiotic and prebiotic use, antibiotic use, and fecal transplantation, to provide new insights and perspectives for understanding SSH pathogenesis and the development of strategies for its treatment.

Chronotropic and vasoactive properties of the gut bacterial short-chain fatty acids in larval zebrafish

Short-chain fatty acids (SCFAs) produced by the gut bacteria have been associated with cardiovascular dysfunction in humans and rodents. However, studies exploring effects of SCFAs on cardiovascular parameters in the zebrafish, an increasingly popular model in cardiovascular research, remain limited. Here, we performed fecal bacterial 16S sequencing and gas chromatography/mass spectrometry (GC-MS) to determine the composition and abundance of gut microbiota and SCFAs in adult zebrafish. Following this, the acute effects of major SCFAs on heart rate and vascular tone were measured in anesthetized zebrafish larvae using fecal concentrations of butyrate, acetate, and propionate. Finally, we investigated if coincubation with butyrate may lessen the effects of angiotensin II (ANG II) and phenylephrine (PE) on vascular tone in anesthetized zebrafish larvae. We found that the abundance in Proteobacteria, Firmicutes, and Fusobacteria phyla in the adult zebrafish resembled those reported in rodents and humans. SCFA levels with highest concentration of acetate (27.43 µM), followed by butyrate (2.19 µM) and propionate (1.65 µM) were observed in the fecal samples of adult zebrafish. Immersion in butyrate and acetate produced a ∼20% decrease in heart rate (HR), respectively, with no observed effects of propionate. Butyrate alone also produced an ∼25% decrease in the cross-sectional width of the dorsal aorta (DA) at 60 min (*P < 0.05), suggesting compensatory vasoconstriction, with no effects of either acetate or propionate. In addition, butyrate significantly alleviated the decrease in DA cross-sectional width produced by both ANG II and PE. We demonstrate the potential for zebrafish in investigation of host-microbiota interactions in cardiovascular health.NEW & NOTEWORTHY We highlight the presence of a core gut microbiota and demonstrate in vivo short-chain fatty acid production in adult zebrafish. In addition, we show cardio-beneficial vasoactive and chronotropic properties of butyrate, and chronotropic properties of acetate in anesthetized zebrafish larvae.

GPR41 and GPR43: From development to metabolic regulation

G-protein-coupled receptors are a diverse class of cell surface receptors that orchestrate numerous physiological functions. The G-protein-coupled receptors, GPR41 and GPR43, sense short-chain fatty acids (SCFAs), which are metabolites of dietary fermentation by the host's intestinal bacteria. These receptors have gained attention as potential therapeutic targets against various diseases because of their SCFA-mediated beneficial effects on the host's intestinal health. Mounting evidence has associated the activity of these receptors with chronic metabolic diseases, including obesity, diabetes, inflammation, and cardiovascular disease. However, despite intensive research using various strategies, including gene knockout (KO) mouse models, evidence about the precise roles of GPR41 and GPR43 in disease treatment remains inconsistent. Here, we comprehensively review the latest findings from functional studies of the signaling mechanisms that underlie the activities of GPR41 and GPR43, as well as highlight their multifaceted roles in health and disease. We anticipate that this knowledge will guide future research priorities and the development of effective therapeutic interventions.

Management of Cardiovascular Diseases by Short-Chain Fatty Acid Postbiotics

PURPOSE OF REVIEW

Global health concerns persist in the realm of cardiovascular diseases (CVDs), necessitating innovative strategies for both prevention and treatment. This narrative review aims to explore the potential of short-chain fatty acids (SCFAs)-namely, acetate, propionate, and butyrate-as agents in the realm of postbiotics for the management of CVDs.

RECENT FINDINGS

We commence our discussion by elucidating the concept of postbiotics and their pivotal significance in mitigating various aspects of cardiovascular diseases. This review centers on a comprehensive examination of diverse SCFAs and their associated receptors, notably GPR41, GPR43, and GPR109a. In addition, we delve into the intricate cellular and pharmacological mechanisms through which these receptors operate, providing insights into their specific roles in managing cardiovascular conditions such as hypertension, atherosclerosis, heart failure, and stroke. The integration of current information in our analysis highlights the potential of both SCFAs and their receptors as a promising path for innovative therapeutic approaches in the field of cardiovascular health. The idea of postbiotics arises as an optimistic and inventive method, presenting new opportunities for preventing and treating cardiovascular diseases.

Short-Chain Fatty Acids and Preeclampsia: A Scoping Review

BACKGROUND

Preeclampsia (PE) is a pregnancy-associated hypertension disorder with high morbidity and mortality. Short-chain fatty acids (SCFAs)-molecules produced by gut microbes-have been associated with hypertension, yet their relation to PE remains uncertain.

OBJECTIVES

The aim was to review existing human studies that examined associations of the major SCFAs (acetate, propionate, butyrate) in pregnancy with PE development.

METHODS

Two reviewers independently searched online databases (EMBASE, PubMed, Web of Science, and Cochrane Database of Systematic Reviews) in January 2024 using the following terms: "short-chain fatty acids," "acetic acid," "butyric acid," "propionic acid," and "preeclampsia." The final set of included studies had to report associations of SCFAs with PE, be peer-reviewed, be written in English, and be conducted in humans.

RESULTS

The abstracts of 907 studies were screened; 43 underwent full-text screening and 11 (1318 total participants, 352 with PE) were included in the final review. All studies used a case-control design. SCFAs were measured in a range of biospecimens (eg, serum, plasma, feces, placentas, and amniotic fluid) that were collected at distinct time points in pregnancy. All 7 studies that investigated butyrate found that it was lower in PE cases than in controls, with 6 of these showing statistical significance (P < .05). Five studies showed that acetate was significantly lower in individuals with PE compared with healthy individuals, while 1 study found that acetate was significantly higher in PE cases. One study reported significantly higher propionate among PE cases vs controls, while 2 studies reported significantly lower propionate levels in PE cases. The nuance in results for acetate and propionate may owe to reasons such as differences in distributions of population characteristics associated with SCFA level and PE or type of PE (early vs late).

CONCLUSION

Current epidemiologic evidence, which derives only from case-control studies, suggests that SCFAs, particularly butyrate (protective), in pregnancy are related to the development of PE. Large-cohort studies are warranted to investigate the temporality and potential causality of these associations.

Short-Chain Fatty Acid Butyrate Is an Inotropic Agent With Vasorelaxant and Cardioprotective Properties

BACKGROUND

The heart can metabolize the microbiota-derived short-chain fatty acid butyrate. Butyrate may have beneficial effects in heart failure, but the underlying mechanisms are unknown. We tested the hypothesis that butyrate elevates cardiac output by mechanisms involving direct stimulation of cardiac contractility and vasorelaxation in rats.

METHODS AND RESULTS

We examined the effects of butyrate on (1) in vivo hemodynamics using parallel echocardiographic and invasive blood pressure measurements, (2) isolated perfused hearts in Langendorff systems under physiological conditions and after ischemia and reperfusion, and (3) isolated coronary arteries mounted in isometric wire myographs. We tested Na-butyrate added to injection solutions or physiological buffers and compared its effects with equimolar doses of NaCl. Butyrate at plasma concentrations of 0.56 mM increased cardiac output by 48.8±14.9%, stroke volume by 38.5±12.1%, and left ventricular ejection fraction by 39.6±6.2%, and lowered systemic vascular resistance by 33.5±6.4% without affecting blood pressure or heart rate in vivo. In the range between 0.1 and 5 mM, butyrate increased left ventricular systolic pressure by up to 23.7±3.4% in isolated perfused hearts and by 9.4±2.9% following ischemia and reperfusion, while reducing myocardial infarct size by 81.7±16.9%. Butyrate relaxed isolated coronary septal arteries concentration dependently with an EC50=0.57 mM (95% CI, 0.23-1.44).

CONCLUSIONS

We conclude that butyrate elevates cardiac output through mechanisms involving increased cardiac contractility and vasorelaxation. This effect of butyrate was not associated with adverse myocardial injury in damaged hearts exposed to ischemia and reperfusion.

Investigation of Effects of Novel Bifidobacterium longum ssp. longum on Gastrointestinal Microbiota and Blood Serum Parameters in a Conventional Mouse Model

Representatives of the genus Bifidobacterium are widely used as probiotics to modulate the gut microbiome and alleviate various health conditions. The action mechanisms of probiotics rely on their direct effect on the gut microbiota and the local and systemic effect of its metabolites. The main purpose of this animal experiment was to assess the biosafety of the Bifidobacterium longum strain BIOCC1719. Additional aims were to characterise the influence of the strain on the intestinal microbiota and the effect on several health parameters of the host during 15- and 30-day oral administration of the strain to mice. The strain altered the gut microbial community, thereby altering luminal short-chain fatty acid metabolism, resulting in a shift in the proportions of acetic, butyric, and propionic acids in the faeces and serum of the test group mice. Targeted metabolic profiling of serum revealed the possible ability of the strain to positively affect the hosts' amino acids and bile acids metabolism, as the cholic acid, deoxycholic acid, aspartate, and glutamate concentration were significantly higher in the test group. The tendency to increase anti-inflammatory polyamines (spermidine, putrescine) and neuroprotective 3-indolepropionic acid metabolism and to lower uremic toxins (P-cresol-SO4, indoxyl-SO4) was registered. Thus, B. longum BIOCC1719 may exert health-promoting effects on the host through modulation of the gut microbiome and the host metabolome via inducing the production of health-promoting bioactive compounds. The health effects of the strain need to be confirmed in clinical trials with human volunteers.

Probiotics, gut microbiome, and cardiovascular diseases: An update

Cardiovascular diseases (CVD) are one of the most challenging diseases and many factors have been demonstrated to affect their pathogenesis. One of the major factors that affect CVDs, especially atherosclerosis, is the gut microbiota (GM). Genetics play a key role in linking CVDs with GM, in addition to some environmental factors which can be either beneficial or harmful. The interplay between GM and CVDs is complex due to the numerous mechanisms through which microbial components and their metabolites can influence CVDs. Within this interplay, the immune system plays a major role, mainly based on the immunomodulatory effects of microbial dysbiosis and its resulting metabolites. The resulting modulation of chronic inflammatory processes was found to reduce the severity of CVDs and to maintain cardiovascular health. To better understand the specific roles of GM-related metabolites in this interplay, this review presents an updated perspective on gut metabolites related effects on the cardiovascular system, highlighting the possible benefits of probiotics in therapeutic strategies.

Comparative analysis of short-chain fatty acid levels in non-alcoholic steatohepatitis rat model: Impact of high-fat high-fructose (HFHF), high fat, and Western diets

The evidence on the role of diets in the production of short-chain fatty acids (SCFAs) was limited. The aim of this study was to assess the potential effects of high-fat high-fructose (HFHF), high-fat, and Western diets on the levels of SCFA. A research experiment employing a post-test-only control group design was carried out from January to April 2022. A total of 27 rats were randomly allocated to each study group. SCFA was measured two weeks after diet administration. Analysis of variance (ANOVA) test was used to analyze the differences among groups, and the effect estimate of each group was analyzed using post hoc Tukey. The concentrations of SCFAs post HFHF diets were recorded as follows: acetic acid at 54.60±10.58 mmol/g, propionic acid at 28.03±8.81 mmol/g, and butyric acid at 4.23±1.68 mmol/g. Following the high-fat diet, acetic acid measured 61.85±14.25 mmol/gr, propionic acid measured 25.19±5.55 mmol/gr, and butyric acid measured 6.10±2.93 mmol/gr. After the administration of Western diet, the levels of SCFA were 68.18±25.73, 29.69±12.76, and 7.48±5.51 mmol/g for acetic acid, propionic acid, and butyric acid, respectively. The level of butyric acid was significantly lower in HFHF diet group compared to the normal diet (mean difference (MD) 6.34; 95%CI: 0.61, 12.04; p=0.026). The levels of acetic acid (p=0.419) and propionic acid (p=0.316) were not statistically different among diet types (HFHF, high-fat, and Western diet). In conclusion, HFHF diet is associated with a lower level of butyric acid than the normal diet in a rat model.

Gut Metabolites Acting on the Gut-Brain Axis: Regulating the Functional State of Microglia

The gut-brain axis is a communication channel that mediates a complex interplay of intestinal flora with the neural, endocrine, and immune systems, linking gut and brain functions. Gut metabolites, a group of small molecules produced or consumed by biochemical processes in the gut, are involved in central nervous system regulation via the highly interconnected gut-brain axis affecting microglia indirectly by influencing the structure of the gut-brain axis or directly affecting microglia function and activity. Accordingly, pathological changes in the central nervous system are connected with changes in intestinal metabolite levels as well as altered microglia function and activity, which may contribute to the pathological process of each neuroinflammatory condition. Here, we discuss the mechanisms by which gut metabolites, for instance, the bile acids, short-chain fatty acids, and tryptophan metabolites, regulate the structure of each component of the gut-brain axis, and explore the important roles of gut metabolites in the central nervous system from the perspective of microglia. At the same time, we highlight the roles of gut metabolites affecting microglia in the pathogenesis of neurodegenerative diseases and neurodevelopmental disorders. Understanding the relationship between microglia, gut microbiota, neuroinflammation, and neurodevelopmental disorders will help us identify new strategies for treating neuropsychiatric disorders.

Effects of alcohol on the composition and metabolism of the intestinal microbiota among people with HIV: a cross-sectional study

OBJECTIVES

Alcohol consumption is not uncommon among people with HIV (PWH) and may exacerbate HIV-induced intestinal damage, and further lead to dysbiosis and increased intestinal permeability. This study aimed to determine the changes in the faecal microbiota and its association with alcohol consumption in HIV-infected patients.

METHODS

A cross-sectional survey was conducted between November 2021 and May 2022, and 93 participants were recruited. To investigate the alterations of alcohol misuse on fecal microbiology in HIV-infected individuals, we performed 16s rDNA gene sequencing on fecal samples from the low to moderate drinking (n=21) and non-drinking (n=72) groups.

RESULTS

Comparison between groups using alpha and beta diversity showed that the diversity of stool microbiota in the low to moderate drinkinge group did not differ from that of the non-drinking group (all P>0.05). The Linear discriminant Analysis effect size (LEfSe) algorithm was to determine the bacterial taxa associated with alcohol consumption, and the results showed altered fecal bacterial composition in HIV-infected patients who consumed alcohol, with Coprobacillus, Pseudobutyrivibrio and Peptostreptococcaceae enriched, and Pasteurellaceae and Xanthomonadaceae were depleted. In addition, by using the Kyoto Encyclopedia of Genes and Genomes (KEGG) functional microbiome features were also found to be altered in the low to moderate drinking group, showing a reduction in metabolic pathways (P=0.036) and cardiovascular disease pathway (P=0.006).

CONCLUSION

Low to moderate drinking will change the composition, metabolism and cardiovascular disease pathway of the gut microbiota of HIV-infected patients.

Oral Administration of Fermented Milk from Co-Starter Containing Lactobacillus plantarum Y44 Shows an Ameliorating Effect on Hypertension in Spontaneously Hypertensive Rats

Fermented dairy foods such as yogurt exhibit some beneficial effects on consumers, including relieving the symptoms of hypertension. This study aims to obtain fermented dairy products from a co-starter that have a great flavor and the auxiliary function of reducing blood pressure after longtime consumption. Commercial starter cultures composed of Lactobacillus delbrueckii subsp. bulgaricus CICC 6047 and Streptococcus thermophilus CICC 6038 were combined with Lactobacillus plantarum strains Y44, Y12, and Y16, respectively, as a combined starter culture to ferment the mixed milk of skim milk and soybean milk. The fermented milk produced using the combined starter culture mixed with L. plantarum Y44 showed an angiotensin-converting-enzyme (ACE) inhibitory activity (53.56 ± 0.69%). Some peptides that regulate blood pressure were released in the fermented milk, such as AMKPWIQPK, GPVRGPFPII, LNVPGEIVE, NIPPLTQTPV, and YQEPVL. In spontaneously hypertensive rat (SHR) oral-administration experiments compared with the gavage unfermented milk group, the gavage feeding of SHRs with the fermented milk produced using the combined starter culture mixed with L. plantarum Y44 significantly reduced the blood pressure of the SHRs after long-term intragastric administration, shown with the systolic blood pressure (SBP) and diastolic blood pressure (DBP) decreasing by 23.67 ± 2.49 mmHg and 15.22 ± 2.62 mmHg, respectively. Moreover, the abundance of short-chain fatty acids (SCFA), bacterial diversity in the gut microbiota, and SCFA levels including acetic acid, propionic acid, and butyric acid in the feces of the SHRs were increased via oral administration of the fermented milk produced using the combined starter culture containing L. plantarum Y44. Furthermore, the ACE-angiotensin II (Ang II)-angiotensin type 1 (AT 1) axis was downregulated, the angiotensin-converting-enzyme 2 (ACE 2)-angiotensin(1-7) (Ang1-7)-Mas receptor axis of the SHRs was upregulated, and then the RAS signal was rebalanced. The fermented milk obtained from the combined starter culture shows the potential to be a functional food with antihypertension properties.

Central blockage of sympathetic nerves inhibits the abnormal vital signs and disturbance of the gut microbiota caused by continuous light exposure

Background

Continuous light exposure increases sympathetic excitation in rats, leading to hypertension, left ventricular hypertrophy, and fibrosis. This study was aimed to investigate whether continuous light exposure causes destabilization of vital signs and gut microbiota (GM) in Sprague Dawley (SD) rats and whether clonidine hydrochloride (CH), a central sympathetic depressant drug, could prevent these changes.

Methods

Eight-week-old male SD rats were divided into three groups with different interventions for 14 weeks: control group (CG), 2-mL pure water gavaged daily while on a normal 12-h light/dark cycle; continuous illumination group (CI), 2-mL pure water gavaged daily while receiving continuous exposure to light (300 lx); and drug administration group (DA), CH (10 μg/kg) gavaged daily while receiving continuous exposure to light (300 lx).

Results

The results showed that blood pressure, heart rate, and body weight were significantly higher in the CI group than in the CG and DA groups (P < 0.05). Moreover, the Shannon index was higher in the DA group than in the CI group (P = 0.012). The beta diversity index in the CG group was significantly higher in the CI group (P = 0.039). The pairwise comparison results of the linear discriminant analysis effect size showed that Oscillospirales were enriched in the DA group, whereas the Prevotellaceae lineage (family level) > Prevotella (genus level) > Prevotellaceae_bacterium (species level) were enriched in the CI group. The Muribaculaceae family was more abundant in the CG group than in the CI group.

Conclusion

Sympathetic nerve inhibition restored the abnormal vital signs and GM changes under continuous light exposure.

Untapped potential of gut microbiome for hypertension management

The gut microbiota has been shown to be associated with a range of illnesses and disorders, including hypertension, which is recognized as the primary factor contributing to the development of serious cardiovascular diseases. In this review, we conducted a comprehensive analysis of the progression of the research domain pertaining to gut microbiota and hypertension. Our primary emphasis was on the interplay between gut microbiota and blood pressure that are mediated by host and gut microbiota-derived metabolites. Additionally, we elaborate the reciprocal communication between gut microbiota and antihypertensive drugs, and its influence on the blood pressure of the host. The field of computer science has seen rapid progress with its great potential in the application in biomedical sciences, we prompt an exploration of the use of microbiome databases and artificial intelligence in the realm of high blood pressure prediction and prevention. We propose the use of gut microbiota as potential biomarkers in the context of hypertension prevention and therapy.

Potential Therapeutic Effects of Short-Chain Fatty Acids on Chronic Pain

The intestinal homeostasis maintained by the gut microbiome and relevant metabolites is essential for health, and its disturbance leads to various intestinal or extraintestinal diseases. Recent studies suggest that gut microbiome-derived metabolites short-chain fatty acids (SCFAs) are involved in different neurological disorders (such as chronic pain). SCFAs are produced by bacterial fermentation of dietary fibers in the gut and contribute to multiple host processes, including gastrointestinal regulation, cardiovascular modulation, and neuroendocrine-immune homeostasis. Although SCFAs have been implicated in the modulation of chronic pain, the detailed mechanisms that underlie such roles of SCFAs remain to be further investigated. In this review, we summarize currently available research data regarding SCFAs as a potential therapeutic target for chronic pain treatment and discuss several possible mechanisms by which SCFAs modulate chronic pain.

Short-chain fatty acids are potential goalkeepers of atherosclerosis

Short-chain fatty acids (SCFAs) are metabolites produced by gut bacteria and play a crucial role in various inflammatory diseases. Increasing evidence suggests that SCFAs can improve the occurrence and progression of atherosclerosis. However, the molecular mechanisms through which SCFAs regulate the development of atherosclerosis have not been fully elucidated. This review provides an overview of the research progress on SCFAs regarding their impact on the risk factors and pathogenesis associated with atherosclerosis, with a specific focus on their interactions with the endothelium and immune cells. These interactions encompass the inflammation and oxidative stress of endothelial cells, the migration of monocytes/macrophages, the lipid metabolism of macrophages, the proliferation and migration of smooth muscle cells, and the proliferation and differentiation of Treg cells. Nevertheless, the current body of research is insufficient to comprehensively understand the full spectrum of SCFAs' mechanisms of action. Therefore, further in-depth investigations are imperative to establish a solid theoretical foundation for the development of clinical therapeutics in this context.

Microbiota-derived tryptophan metabolism: Impacts on health, aging, and disease

The intricate interplay between gut microbiota and the host is pivotal in maintaining homeostasis and health. Dietary tryptophan (TRP) metabolism initiates a cascade of essential endogenous metabolites, including kynurenine, kynurenic acid, serotonin, and melatonin, as well as microbiota-derived Trp metabolites like tryptamine, indole propionic acid (IPA), and other indole derivatives. Notably, tryptamine and IPA, among the indole metabolites, exert crucial roles in modulating immune, metabolic, and neuronal responses at both local and distant sites. Additionally, these metabolites demonstrate potent antioxidant and anti-inflammatory activities. The levels of microbiota-derived TRP metabolites are intricately linked to the gut microbiota's health, which, in turn, can be influenced by age-related changes. This review aims to comprehensively summarize the cellular and molecular impacts of tryptamine and IPA on health and aging-related complications. Furthermore, we explore the levels of tryptamine and IPA and their corresponding bacteria in select diseased conditions, shedding light on their potential significance as biomarkers and therapeutic targets.

The microbiome and the gut-lung axis in tuberculosis: interplay in the course of disease and treatment

Tuberculosis is a chronic infectious disease caused by Mycobacterium tuberculosis (MTB) that remains a significant global health challenge. The extensive use of antibiotics in tuberculosis treatment, disrupts the delicate balance of the microbiota in various organs, including the gastrointestinal and respiratory systems. This gut-lung axis involves dynamic interactions among immune cells, microbiota, and signaling molecules from both organs. The alterations of the microbiome resulting from anti-TB treatment can significantly influence the course of tuberculosis, impacting aspects such as complete healing, reinfection, and relapse. This review aims to provide a comprehensive understanding of the gut-lung axis in the context of tuberculosis, with a specific focus on the impact of anti-TB treatment on the microbiome.

Metabolomics Meets Clinics: A Multivariate Analysis of Plasma and Urine Metabolic Signatures in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe, multifactorial, and frequently misdiagnosed disorder. The aim of this observational study was to compare the plasma and urine metabolomic profiles of PAH patients and healthy control subjects. Plasma and urine metabolomic profiles were analyzed using the GC-MS technique. Correlations between metabolite levels and clinical parameters among PAH patients, as well as the between-group differences, were evaluated. The linear discriminant analysis model, which allows for subject classification in terms of PAH with the highest possible precision, was developed and proposed. Plasma pyruvic acid, cholesterol, threonine, urine 3-(3-hydroxyphenyl)-3-hydroxypropanoic acid, butyric acid, 1,2-benzenediol, glucoheptonic acid, and 2-oxo-glutaric acid were found to build a relatively accurate classification model for PAH patients. The model reached an accuracy of 91% and significantly improved subject classification (OR = 119 [95% CI: 20.3-698.3], p < 0.0001). Five metabolites were detected in urine that provide easily available and noninvasive tests as compared to right heart catheterization. The selected panel of metabolites has potential for early recognition of patients with dyspnea and faster referral to a reference center.

Impact of gut microbiome on the renin-aldosterone system: Shika-machi Super Preventive Health Examination results

The renin-angiotensin-aldosterone system (RAAS) is a regulatory mechanism of the endocrine system and is associated with various diseases, including hypertension and renal and cardiovascular diseases. The gut microbiota (GM) have been associated with various diseases, mainly in animal models. However, to our knowledge, no studies have examined the relationship between the RAAS and GM in humans. The present study aimed to assess the association between the systemic RAAS and GM genera and their causal relationships. The study participants were 377 members of the general population aged 40 years or older in Shika-machi, Japan. Plasma renin activity (PRA), plasma aldosterone concentration (PAC), aldosterone-renin ratio (ARR), and GM composition were analyzed using the 16S rRNA method. The participants were divided into high and low groups according to the PRA, PAC, and ARR values. U-tests, one-way analysis of covariance, and linear discriminant analysis of effect size were used to identify the important bacterial genera between the two groups, and binary classification modeling using Random Forest was used to calculate the importance of the features. The results showed that Blautia, Bacteroides, Akkermansia, and Bifidobacterium were associated with the RAAS parameters. Causal inference analysis using the linear non-Gaussian acyclic model revealed a causal effect of Blautia on PAC via SBP. These results strengthen the association between the systemic RAAS and GM in humans, and interventions targeting the GM may provide new preventive measures and treatments for hypertension and renal disease.

Non-Coding RNAs and Gut Microbiota in the Pathogenesis of Cardiac Arrhythmias: The Latest Update

Non-coding RNAs (ncRNAs) are indispensable for adjusting gene expression and genetic programming throughout development and for health as well as cardiovascular diseases. Cardiac arrhythmia is a frequent cardiovascular disease that has a complex pathology. Recent studies have shown that ncRNAs are also associated with cardiac arrhythmias. Many non-coding RNAs and/or genomes have been reported as genetic background for cardiac arrhythmias. In general, arrhythmias may be affected by several functional and structural changes in the myocardium of the heart. Therefore, ncRNAs might be indispensable regulators of gene expression in cardiomyocytes, which could play a dynamic role in regulating the stability of cardiac conduction and/or in the remodeling process. Although it remains almost unclear how ncRNAs regulate the expression of molecules for controlling cardiac conduction and/or the remodeling process, the gut microbiota and immune system within the intricate networks might be involved in the regulatory mechanisms. This study would discuss them and provide a research basis for ncRNA modulation, which might support the development of emerging innovative therapies against cardiac arrhythmias.

A review of the auditory-gut-brain axis

Hearing loss places a substantial burden on medical resources across the world and impacts quality of life for those affected. Further, it can occur peripherally and/or centrally. With many possible causes of hearing loss, there is scope for investigating the underlying mechanisms involved. Various signaling pathways connecting gut microbes and the brain (the gut-brain axis) have been identified and well established in a variety of diseases and disorders. However, the role of these pathways in providing links to other parts of the body has not been explored in much depth. Therefore, the aim of this review is to explore potential underlying mechanisms that connect the auditory system to the gut-brain axis. Using select keywords in PubMed, and additional hand-searching in google scholar, relevant studies were identified. In this review we summarize the key players in the auditory-gut-brain axis under four subheadings: anatomical, extracellular, immune and dietary. Firstly, we identify important anatomical structures in the auditory-gut-brain axis, particularly highlighting a direct connection provided by the vagus nerve. Leading on from this we discuss several extracellular signaling pathways which might connect the ear, gut and brain. A link is established between inflammatory responses in the ear and gut microbiome-altering interventions, highlighting a contribution of the immune system. Finally, we discuss the contribution of diet to the auditory-gut-brain axis. Based on the reviewed literature, we propose numerous possible key players connecting the auditory system to the gut-brain axis. In the future, a more thorough investigation of these key players in animal models and human research may provide insight and assist in developing effective interventions for treating hearing loss.

Coptis chinensis-Induced Changes in Metabolomics and Gut Microbiota in Rats

Rhizoma coptidis (CR) is traditionally used for treating gastrointestinal diseases. Wine-processed CR (wCR), zingiber-processed CR (zCR), and evodia-processed CR (eCR) are its major processed products. However, the related study of their specific mechanisms is very limited, and they need to be further clarified. The aim of this study is to compare the intervening mechanism of wCR/zCR/eCR on rats via faecal metabolomics and 16S rDNA gene sequencing analysis. First, faecal samples were collected from the control and CR/wCR/zCR/eCR groups. Then, a metabolomics analysis was performed using UHPLC-Q/TOF-MS to obtain the metabolic profile and significantly altered metabolites. The 16S rDNA gene sequencing analysis was carried out to analyze the composition of gut microbiota and screen out the significantly altered microbiota at the genus level. Finally, a pathway enrichment analysis of the significantly altered metabolites via the KEGG database and a functional prediction of relevant gut microbes based on PICRUSt2 software were performed in combination. Together with the correlation analysis between metabolites and gut microbiota, the potential intervening mechanism of wCR/zCR/eCR was explored. The results suggested that wCR played a good role in maintaining immune homeostasis, promoting glycolysis, and reducing cholesterol; zCR had a better effect on protecting the integrity of the intestinal mucus barrier, preventing gastric ulcers, and reducing body cholesterol; eCR was good at protecting the integrity of the intestinal mucus barrier and promoting glycolysis. This study scientifically elucidated the intervening mechanism of wCR/zCR/eCR from the perspective of faecal metabolites and gut microbiota, providing a new insight into the processing mechanism research of Chinese herbs.

The role of short-chain fatty acids produced by gut microbiota in the regulation of pre-eclampsia onset

Background

Preeclampsia (PE) is a common pregnancy-related disorder characterized by disrupted maternal-fetal immune tolerance, involving diffuse inflammatory responses and vascular endothelial damage. Alterations in the gut microbiota (GM) during pregnancy can affect intestinal barrier function and immune balance.

Aims and purpose

This comprehensive review aims to investigate the potential role of short-chain fatty acids (SCFAs), essential metabolites produced by the GM, in the development of PE. The purpose is to examine their impact on colonic peripheral regulatory T (Treg) cells, the pathogenic potential of antigen-specific helper T (Th) cells, and the inflammatory pathways associated with immune homeostasis.

Key insights

An increasing body of evidence suggests that dysbiosis in the GM can lead to alterations in SCFA levels, which may significantly contribute to the development of PE. SCFAs enhance the number and function of colonic Treg cells, mitigate the pathogenic potential of GM-specific Th cells, and inhibit inflammatory progression, thereby maintaining immune homeostasis. These insights highlight the potential significance of GM dysregulation and SCFAs produced by GM in the pathogenesis of PE. While the exact causes of PE remain elusive, and definitive clinical treatments are lacking, the GM and SCFAs present promising avenues for future clinical applications related to PE, offering a novel approach for prophylaxis and therapy.

Effects of Four Extraction Methods on Structure and In Vitro Fermentation Characteristics of Soluble Dietary Fiber from Rape Bee Pollen

In this study, soluble dietary fibers (SDFs) were extracted from rape bee pollen using four methods including acid extraction (AC), alkali extraction (AL), cellulase extraction (CL) and complex enzyme extraction (CE). The effects of different extraction methods on the structure of SDFs and in vitro fermentation characteristics were further investigated. The results showed that the four extraction methods significantly affected the monosaccharide composition molar ratio, molecular weight, surface microstructure and phenolic compounds content, but showed little effect on the typical functional groups and crystal structure. In addition, all SDFs decreased the Firmicutes/Bacteroidota ratio, promoted the growth of beneficial bacteria such as Bacteroides, Parabacteroides and Phascolarctobacterium, inhibited the growth of pathogenic bacteria such as Escherichia-Shigella, and increased the total short-chain fatty acids (SCFAs) concentrations by 1.63-2.45 times, suggesting that the bee pollen SDFs had a positive regulation on gut microbiota. Notably, the SDF obtained by CE exhibited the largest molecular weight, a relatively loose structure, higher extraction yield and phenolic compounds content and the highest SCFA concentration. Overall, our results indicated that CE was an appropriate extraction method of high-quality bee pollen SDF.

Targeting intestinal microecology: potential intervention strategies of traditional Chinese medicine for managing hypertension

Hypertension has become one of the major public health problems in the world. At present, the pathogenesis of hypertension has still not been completely elucidated. In recent years, an increasing evidence shows that intestinal microecology is closely related to hypertension, which provides a new thinking for the prevention and treatment of hypertension. Traditional Chinese medicine (TCM) has unique advantages in the treatment of hypertension. Taking intestinal microecology as the target, it is possible to interpreting the scientific connotation of TCM prevention and treatment of hypertension by updating the treatment concept of hypertension, so as to improve the therapeutic effect. In our study, the clinical evidence for TCM treatment of hypertension was systematicly summarized. And the relationship among TCM, intestinal microecology and hypertension was analyzed. In addition, the methods by which TCM regulates intestinal microecology to prevent and treat hypertension were presented, to provide new research ideas for prevention and treatment of hypertension.

Gut Microbiota and Cardiovascular Disease: Evidence on the Metabolic and Inflammatory Background of a Complex Relationship

Several studies in recent years have demonstrated that gut microbiota-host interactions play an important role in human health and disease, including inflammatory and cardiovascular diseases. Dysbiosis has been linked to not only well-known inflammatory diseases, such as inflammatory bowel diseases, rheumatoid arthritis, and systemic lupus erythematous, but also to cardiovascular risk factors, such as atherosclerosis, hypertension, heart failure, chronic kidney disease, obesity, and type 2 diabetes mellitus. The ways the microbiota is involved in modulating cardiovascular risk are multiple and not only related to inflammatory mechanisms. Indeed, human and the gut microbiome cooperate as a metabolically active superorganism, and this affects host physiology through metabolic pathways. In turn, congestion of the splanchnic circulation associated with heart failure, edema of the intestinal wall, and altered function and permeability of the intestinal barrier result in the translocation of bacteria and their products into the systemic circulation, further enhancing the pro-inflammatory conditions underlying cardiovascular disorders. The aim of the present review is to describe the complex interplay between gut microbiota, its metabolites, and the development and evolution of cardiovascular diseases. We also discuss the possible interventions intended to modulate the gut microbiota to reduce cardiovascular risk.

Characteristic Gut Bacteria in High Barley Consuming Japanese Individuals without Hypertension

BACKGROUND

Barley, a grain rich in soluble dietary fiber β-glucan, is expected to lower blood pressure. Conversely, individual differences in its effects on the host might be an issue, and gut bacterial composition may be a determinant.

METHODS

Using data from a cross-sectional study, we examined whether the gut bacterial composition could explain the classification of a population with hypertension risks despite their high barley consumption. Participants with high barley intake and no occurrence of hypertension were defined as "responders" (n = 26), whereas participants with high barley intake and hypertension risks were defined as "non-responders" (n = 39).

RESULTS

16S rRNA gene sequencing revealed that feces from the responders presented higher levels of Faecalibacterium, Ruminococcaceae UCG-013, Lachnospira, and Subdoligranulum and lower levels of Lachnoclostridium and Prevotella 9 than that from non-responders. We further created a machine-learning responder classification model using random forest based on gut bacteria with an area under the curve value of 0.75 for estimating the effect of barley on the development of hypertension.

CONCLUSIONS

Our findings establish a link between the gut bacteria characteristics and the predicted control of blood pressure provided by barley intake, thereby providing a framework for the future development of personalized dietary strategies.

Positive mood-related gut microbiota in a long-term closed environment: a multiomics study based on the "Lunar Palace 365" experiment

BACKGROUND

Psychological health risk is one of the most severe and complex risks in manned deep-space exploration and long-term closed environments. Recently, with the in-depth research of the microbiota-gut-brain axis, gut microbiota has been considered a new approach to maintain and improve psychological health. However, the correlation between gut microbiota and psychological changes inside long-term closed environments is still poorly understood. Herein, we used the "Lunar Palace 365" mission, a 1-year-long isolation study in the Lunar Palace 1 (a closed manned Bioregenerative Life Support System facility with excellent performance), to investigate the correlation between gut microbiota and psychological changes, in order to find some new potential psychobiotics to maintain and improve the psychological health of crew members.

RESULTS

We report some altered gut microbiota that were associated with psychological changes in the long-term closed environment. Four potential psychobiotics (Bacteroides uniformis, Roseburia inulinivorans, Eubacterium rectale, and Faecalibacterium prausnitzii) were identified. On the basis of metagenomic, metaproteomic, and metabolomic analyses, the four potential psychobiotics improved mood mainly through three pathways related to nervous system functions: first, by fermenting dietary fibers, they may produce short-chain fatty acids, such as butyric and propionic acids; second, they may regulate amino acid metabolism pathways of aspartic acid, glutamic acid, tryptophan, etc. (e.g., converting glutamic acid to gamma-aminobutyric acid; converting tryptophan to serotonin, kynurenic acid, or tryptamine); and third, they may regulate other pathways, such as taurine and cortisol metabolism. Furthermore, the results of animal experiments confirmed the positive regulatory effect and mechanism of these potential psychobiotics on mood.

CONCLUSIONS

These observations reveal that gut microbiota contributed to a robust effect on the maintenance and improvement of mental health in a long-term closed environment. Our findings represent a key step towards a better understanding the role of the gut microbiome in mammalian mental health during space flight and provide a basis for future efforts to develop microbiota-based countermeasures that mitigate risks to crew mental health during future long-term human space expeditions on the moon or Mars. This study also provides an essential reference for future applications of psychobiotics to neuropsychiatric treatments. Video Abstract.

Clostridium butyricum Prevents Dysbiosis and the Rise in Blood Pressure in Spontaneously Hypertensive Rats

Hypertension is accompanied by dysbiosis and a decrease in the relative abundance of short-chain fatty acid (SCFA)-producing bacteria. However, there is no report to examine the role of C. butyricum in blood pressure regulation. We hypothesized that a decrease in the relative abundance of SCFA-producing bacteria in the gut was the cause of spontaneously hypertensive rats (SHR)-induced hypertension. C. butyricum and captopril were used to treat adult SHR for six weeks. C. butyricum modulated SHR-induced dysbiosis and significantly reduced systolic blood pressure (SBP) in SHR (p < 0.01). A 16S rRNA analysis determined changes in the relative abundance of the mainly SCFA-producing bacteria Akkermansia muciniphila, Lactobacillus amylovorus, and Agthobacter rectalis, which increased significantly. Total SCFAs, and particularly butyrate concentrations, in the SHR cecum and plasma were reduced (p < 0.05), while C. butyricum prevented this effect. Likewise, we supplemented SHR with butyrate for six weeks. We analyzed the flora composition, cecum SCFA concentration, and inflammatory response. The results showed that butyrate prevented SHR-induced hypertension and inflammation, and the decline of cecum SCFA concentrations (p < 0.05). This research revealed that increasing cecum butyrate concentrations by probiotics, or direct butyrate supplementation, prevented the adverse effects of SHR on intestinal flora, vascular, and blood pressure.

Correlations between GRIN2B and GRIN3A gene polymorphisms and postpartum depressive symptoms in Chinese parturients undergoing cesarean section: A prospective cohort study

OBJECTIVE

To investigate the association of postpartum depressive symptoms (PDS) and self-harm ideation with n-methyl-d-aspartate (NMDA) receptor GRIN2B and GRIN3A gene polymorphisms and other risk factors in women undergoing cesarean section.

METHODS

A total of 362 parturients undergoing cesarean section under lumbar anesthesia were selected and their postpartum depression level was assessed by the Edinburgh Postpartum Depression Scale (EPDS) at 42 days postpartum, with an EPDS score of 9/10 as the cut-off value. Three GRIN2B SNP loci (rs1805476, rs3026174, rs4522263) and five GRIN3A SNP loci (rs1983812, rs2050639, rs2050641, rs3739722, rs10989563) were selected for genotype detection. The role of each SNP, linkage disequilibrium and haplotypes in the development of postpartum depression was analyzed. Logistic regression analysis was performed for related risk factors.

RESULTS

PDS incidence was 16.85%, and self-harm ideation incidence was 13.54%. Univariate analysis showed that GRIN2B rs1805476, rs3026174 and rs4522263 gene polymorphisms were associated with PDS (p < 0.05), with GRIN2B rs4522263 gene also associated with maternal self-harm ideation. GRIN3A rs1983812, rs2050639, rest rs2050641, rs3739722 and rs10989563 alleles were not associated with PDS. Logistic regression analysis indicated that high pregnancy stress, as well as rs1805476 and rs4522263 alleles were PDS risk factors following cesarean delivery. GRIN2B (TTG p = 0.002) and GRIN3A (TGTTC p = 0.002) haplotypes were associated with the lower PDS incidence and higher PDS incidence respectively.

CONCLUSION

GRIN2B rs1805476 GG genotype, rs4522263 CC genotype and high stress during pregnancy were risk factors for PDS, whilst a significantly higher incidence of self-harm ideation was evident in parturients carrying GRIN2B rs4522263 CC genotype.

The gut microbiome and hypertension

A large body of evidence has emerged in the past decade supporting a role for the gut microbiome in the regulation of blood pressure. The field has moved from association to causation in the last 5 years, with studies that have used germ-free animals, antibiotic treatments and direct supplementation with microbial metabolites. The gut microbiome can regulate blood pressure through several mechanisms, including through gut dysbiosis-induced changes in microbiome-associated gene pathways in the host. Microbiota-derived metabolites are either beneficial (for example, short-chain fatty acids and indole-3-lactic acid) or detrimental (for example, trimethylamine N-oxide), and can activate several downstream signalling pathways via G protein-coupled receptors or through direct immune cell activation. Moreover, dysbiosis-associated breakdown of the gut epithelial barrier can elicit systemic inflammation and disrupt intestinal mechanotransduction. These alterations activate mechanisms that are traditionally associated with blood pressure regulation, such as the renin-angiotensin-aldosterone system, the autonomic nervous system, and the immune system. Several methodological and technological challenges remain in gut microbiome research, and the solutions involve minimizing confounding factors, establishing causality and acting globally to improve sample diversity. New clinical trials, precision microbiome medicine and computational methods such as Mendelian randomization have the potential to enable leveraging of the microbiome for translational applications to lower blood pressure.

Cardiac metabolism in HFpEF: from fuel to signalling

Heart failure (HF) is marked by distinctive changes in myocardial uptake and utilization of energy substrates. Among the different types of HF, HF with preserved ejection fraction (HFpEF) is a highly prevalent, complex, and heterogeneous condition for which metabolic derangements seem to dictate disease progression. Changes in intermediate metabolism in cardiometabolic HFpEF-among the most prevalent forms of HFpEF-have a large impact both on energy provision and on a number of signalling pathways in the heart. This dual, metabolic vs. signalling, role is played in particular by long-chain fatty acids (LCFAs) and short-chain carbon sources [namely, short-chain fatty acids (SCFAs) and ketone bodies (KBs)]. LCFAs are key fuels for the heart, but their excess can be harmful, as in the case of toxic accumulation of lipid by-products (i.e. lipotoxicity). SCFAs and KBs have been proposed as a potential major, alternative source of energy in HFpEF. At the same time, both LCFAs and short-chain carbon sources are substrate for protein post-translational modifications and other forms of direct and indirect signalling of pivotal importance in HFpEF pathogenesis. An in-depth molecular understanding of the biological functions of energy substrates and their signalling role will be instrumental in the development of novel therapeutic approaches to HFpEF. Here, we summarize the current evidence on changes in energy metabolism in HFpEF, discuss the signalling role of intermediate metabolites through, at least in part, their fate as substrates for post-translational modifications, and highlight clinical and translational challenges around metabolic therapy in HFpEF.

Lacto-Fermented and Unfermented Soybean Differently Modulate Serum Lipids, Blood Pressure and Gut Microbiota during Hypertension

Soy consumption may reduce hypertension but the impact of food processing on the antihypertensive effect is unclear. Hence, we ascertained the effects of lacto-fermented (FSB) and unfermented soybean (USB) consumption on serum atherogenic lipids, hypertension and gut microbiota of spontaneous hypertensive rats (SHR). FSB displayed a strong in vitro angiotensin converting enzyme (ACE) inhibitory ability of 70 ± 5% while USB inhibited 5 ± 3% of the enzyme activity. Consumption of USB reduced serum ACE activity by 19.8 ± 12.85 U while FSB reduced the enzyme activity by 47.6 ± 11.35 U, respectively. FSB significantly improved cholesterol levels and reduced systolic and diastolic blood pressures by 14 ± 3 mmHg and 10 ± 3 mmHg, respectively, while USB only had a marginal impact on blood pressure. Analysis of FSB showed the abundance of ACE inhibitory peptides EGEQPRPFPFP and AIPVNKP (which were absent in USB) and 30 phenolic compounds (only 12 were abundant in USB). Feeding SHR with FSB promoted the growth of Akkermansia, Bacteroides, Intestinimonas, Phocaeicola, Lactobacillus and Prevotella (short chain fatty acid producers) while USB promoted only Prevotellamassilia, Prevotella and Intestimonas levels signifying the prebiotic ability of FSB. Our results show that, relative to USB, FSB are richer in bioactive compounds that reduce hypertension by inhibiting ACE, improving cholesterol levels and mitigating gut dysbiosis.

Does the Composition of Gut Microbiota Affect Hypertension? Molecular Mechanisms Involved in Increasing Blood Pressure

Arterial hypertension is a chronic disease which is very prevalent contemporarily. The aim of this review was to investigate the impact of gut microbiota on the development and potential treatment of hypertension, taking into consideration underlying molecular mechanisms. The bacteria present in the intestines have the ability to secrete different metabolites, which might play a significant role in the regulation of blood pressure. The most important include short-chain fatty acids (SCFAs), vasoactive hormones, trimethylamine (TMA) and trimethylamine N-oxide (TMAO) and uremic toxins, such as indoxyl sulfate (IS) and p-cresyl sulfate (PCS). Their action in regulating blood pressure is mainly based on their pro- or anti-inflammatory function. The use of specifically formulated probiotics to modify the composition of gut microbiota might be a beneficial way of supportive treatment of hypertension; however, further research on this topic is needed to choose the species of bacteria that could induce the hypotensive pattern.

Precision Nutrition in NAFLD: Effects of a High-Fiber Intervention on the Serum Metabolome of NAFD Patients-A Pilot Study

Non-alcoholic fatty liver disease (NAFLD) is associated with dysfunction of the intestinal microbiota and its metabolites. We aimed to assess whether replacing bread with high-fiber buns beneficially changes the metabolome in NAFLD patients. This study involved 27 adult patients with NAFLD validated by FibroScan^® (CAP ≥ 234 dB/m). Patients were asked to replace their existing bread for two meals with high-fiber buns. In this way, the patients ate two rolls every day for 2 months. The following parameters were analysed (at the beginning and after 2 months): the anthropometric data (BIA), eating habits (24 h food recalls), gut barrier markers (lipopolysaccharide S and liposaccharide binding protein (LPS, LBP)), serum short-chain fatty acids (SCFAs) and branched chain fatty acids (BCFAs) by GC/MS chromatography, as well as serum metabolites (by ¹H NMR spectroscopy). After 2 months of high-fiber roll consumption, the reduction of liver steatosis was observed (change Fibroscan CAP values from 309-277 dB/m). In serum propionate, acetate, isovaleric, and 2-methylbutyric decrease was observed. Proline, choline and one unknown molecule had higher relative concentration in serum at endpoint. A fiber-targeted dietary approach may be helpful in the treatment of patients with NAFLD, by changing the serum microbiota metabolome.

Food Peptides, Gut Microbiota Modulation, and Antihypertensive Effects

The gut microbiota is increasingly important in the overall human health and as such, it is a target in the search of novel strategies for the management of metabolic disorders including blood pressure, and cardiovascular diseases. The link between microbiota and hypertension is complex and this review is intended to provide an overview of the mechanism including the production of postbiotics, mitigation of inflammation, and the integration of food biological molecules within this complex system. The focus is on hydrolyzed food proteins and peptides which are less commonly investigated for prebiotic properties. The analysis of available data showed that food peptides are multifunctional and can prevent gut dysbiosis by positively affecting the production of postbiotics or gut metabolites (short-chain fatty acids, polysaccharides, biogenic amines, bile acids). Peptides and the postbiotics then displayed antihypertensive effects via the renin-angiotensin system, the gut barrier, the endothelium, and reduction in inflammation and oxidative stress. Despite the promising antihypertensive effect of the food peptides via the modulation of the gut, there is a lack of human studies as most of the works have been conducted in animal models.

Association between gut microbiota and preeclampsia-eclampsia: a two-sample Mendelian randomization study

BACKGROUND

Several recent observational studies have reported that gut microbiota composition is associated with preeclampsia. However, the causal effect of gut microbiota on preeclampsia-eclampsia is unknown.

METHODS

A two-sample Mendelian randomization study was performed using the summary statistics of gut microbiota from the largest available genome-wide association study meta-analysis (n=13,266) conducted by the MiBioGen consortium. The summary statistics of preeclampsia-eclampsia were obtained from the FinnGen consortium R7 release data (5731 cases and 160,670 controls). Inverse variance weighted, maximum likelihood, MR-Egger, weighted median, weighted model, MR-PRESSO, and cML-MA were used to examine the causal association between gut microbiota and preeclampsia-eclampsia. Reverse Mendelian randomization analysis was performed on the bacteria that were found to be causally associated with preeclampsia-eclampsia in forward Mendelian randomization analysis. Cochran's Q statistics were used to quantify the heterogeneity of instrumental variables.

RESULTS

Inverse variance weighted estimates suggested that Bifidobacterium had a protective effect on preeclampsia-eclampsia (odds ratio = 0.76, 95% confidence interval: 0.64-0.89, P = 8.03 × 10^-4). In addition, Collinsella (odds ratio = 0.77, 95% confidence interval: 0.60-0.98, P = 0.03), Enterorhabdus (odds ratio = 0.76, 95% confidence interval: 0.62-0.93, P = 8.76 × 10^-3), Eubacterium (ventriosum group) (odds ratio = 0.76, 95% confidence interval: 0.63-0.91, P = 2.43 × 10^-3), Lachnospiraceae (NK4A136 group) (odds ratio = 0.77, 95% confidence interval: 0.65-0.92, P = 3.77 × 10^-3), and Tyzzerella 3 (odds ratio = 0.85, 95% confidence interval: 0.74-0.97, P = 0.01) presented a suggestive association with preeclampsia-eclampsia. According to the results of reverse MR analysis, no significant causal effect of preeclampsia-eclampsia was found on gut microbiota. No significant heterogeneity of instrumental variables or horizontal pleiotropy was found.

CONCLUSIONS

This two-sample Mendelian randomization study found that Bifidobacterium was causally associated with preeclampsia-eclampsia. Further randomized controlled trials are needed to clarify the protective effect of probiotics on preeclampsia-eclampsia and their specific protective mechanisms.

Effects of combined aerobic and resistance training on gut microbiota and cardiovascular risk factors in physically active elderly women: A randomized controlled trial

Background: Exercise can modulate gut microbiota and lower the risk of cardiovascular disease (CVD). However, the association between exercise-induced changes in gut microbiota and CVD risk have not been investigated.

Objective: This study determined the effects of exercise training on CVD risk and gut microbiota in physically active elderly women and whether exercise-induced gut microbiota changes were associated with CVD risk.

Methods: An 8-week randomized controlled trial was conducted with 14 elderly women assigned to exercise group (n = 8) or control group (n = 6). Physical function, sarcopenic obesity, and metabolic syndrome were evaluated as components of CVD risk. Gut microbiota composition was determined using 16S rRNA gene sequencing. Repeated-measures analysis of variance was used to examine intra-group and inter-group differences.

Results: A significant group × time interaction was observed for chair sit-and-reach (F = 8.262, p = 0.014), single-leg standing with eyes closed (F = 7.340, p = 0.019), waist circumference (F = 6.254, p = 0.028), and body fat mass (F = 12.263, p = 0.004), for which the exercise group showed improved trends. The exercise group exhibited significant improvements in skeletal muscle mass (p = 0.041) and fasting blood glucose (p = 0.017). Regarding gut microbiota, a significant interaction was observed for the class Betaproteobacteria (F = 6.822, p = 0.023) and genus Holdemania (F = 4.852, p = 0.048).

Conclusion: The 8-week exercise training improved physical function, lowered CVD risk, and modulated relative abundance of gut microbiota associated with CVD in physically active elderly women.

Short-Chain Fatty Acid Receptors and Blood Pressure Regulation: Council on Hypertension Mid-Career Award for Research Excellence 2021

The gut microbiome influences host physiology and pathophysiology through several pathways, one of which is microbial production of chemical metabolites which interact with host signaling pathways. Short-chain fatty acids (SCFAs) are a class of gut microbial metabolites known to activate multiple signaling pathways in the host. Growing evidence indicates that the gut microbiome is linked to blood pressure, that SCFAs modulate blood pressure regulation, and that delivery of exogenous SCFAs lowers blood pressure. Given that hypertension is a key risk factor for cardiovascular disease, the examination of novel contributors to blood pressure regulation has the potential to lead to novel approaches or treatments. Thus, this review will discuss SCFAs with a focus on their host G protein-coupled receptors including GPR41 (G protein-coupled receptor 41), GPR43, and GPR109A, as well as OLFR78 (olfactory receptor 78) and OLFR558. This includes a discussion of the ligand profiles, G protein coupling, and tissue distribution of each receptor. We will also review phenotypes relevant to blood pressure regulation which have been reported to date for Gpr41, Gpr43, Gpr109a, and Olfr78 knockout mice. In addition, we will consider how SCFA signaling influences physiology at baseline, and, how SCFA signaling may contribute to blood pressure regulation in settings of hypertension. In sum, this review will integrate current knowledge regarding how SCFAs and their receptors regulate blood pressure.

Reduced intestinal butyrate availability is associated with the vascular remodeling in resistance arteries of hypertensive rats

During hypertension an unbalance of short-chain fatty acids (SCFAs) production by intestinal bacteria is described. However, no data evaluate the association of SCFAs and vascular remodeling in hypertension, which is an important hallmark of this disease. Thus, the present study aims to evaluate the correlations between SCFAs availability and the resistance arteries remodeling in hypertension, as well as to identify the possible pathway by which the SCFAs could exert a structural and mechanical influence. Hence, male spontaneously hypertensive rats (SHR) and normotensive Wistar rats had blood pressure measured by tail-cuff plethysmography; fecal SCFAs content assessed by gas chromatography; gene expression of SCFAs-transporters in gut epithelium and SCFAs-sensing receptors on mesenteric resistance arteries (MRA) quantified by PCR; and MRA structural and mechanical parameters analyzed by pressure myograph. Reduced butyrate fecal content was found in SHR, with no changes in propionate and acetate, as well as decreased mRNA levels of SCFAs-transporters (MCT1, MCT4, and SMCT1) in the intestinal epithelium. In addition, lower gene expression of SCFAs-sensing receptors (GPR41, GPR43, and GPR109a, but not Olfr78) was identified in MRAs of SHR, which also shows inward eutrophic remodeling with stiffness. Butyrate content presented a negative correlation with systolic blood pressure and with the structural alterations found on MRAs, while a positive correlation between butyrate content and mechanical parameters was detected. Altogether the present study suggests that lower butyrate content due to ineffective SCFA bioavailability, associated with lower SCFAs-sensing receptors expression, could favor MRA remodeling, increasing peripheral vascular resistance and worsening hypertension prognosis.

Short-chain fatty acid: An updated review on signaling, metabolism, and therapeutic effects

Fatty acids are good energy sources (9 kcal per gram) that aerobic tissues can use except for the brain (glucose is an alternative source). Apart from the energy source, fatty acids are necessary for cell signaling, learning-related memory, modulating gene expression, and functioning as cytokine precursors. Short-chain fatty acids (SCFAs) are saturated fatty acids arranged as a straight chain consisting minimum of 6 carbon atoms. SCFAs possess various beneficial effects like improving metabolic function, inhibiting insulin resistance, and ameliorating immune dysfunction. In this review, we discussed the biogenesis, absorption, and transport of SCFA. SCFAs can act as signaling molecules by stimulating G protein-coupled receptors (GPCRs) and suppressing histone deacetylases (HDACs). The role of SCFA on glucose metabolism, fatty acid metabolism, and its effect on the immune system is also reviewed with updated details. SCFA possess anticancer, anti-diabetic, and hepatoprotective effects. Additionally, the association of protective effects of SCFA against brain-related diseases, kidney diseases, cardiovascular damage, and inflammatory bowel diseases were also reviewed. Nanotherapy is a branch of nanotechnology that employs nanoparticles at the nanoscale level to treat various ailments with enhanced drug stability, solubility, and minimal side effects. The SCFA functions as drug carriers, and nanoparticles were also discussed. Still, much research was not focused on this area. SCFA functions in host gene expression through inhibition of HDAC inhibition. However, the study has to be focused on the molecular mechanism of SCFA against various diseases that still need to be investigated.

UPLC/Q-TOF MS-Based Urine Metabonomics Study to Identify Diffuse Axonal Injury Biomarkers in Rat

Diffuse axonal injury (DAI) represents a frequent traumatic brain injury (TBI) type, significantly contributing to the dismal neurological prognosis and high mortality in TBI patients. The increase in mortality can be associated with delayed and nonspecific initial symptoms in DAI patients. Additionally, the existing approaches for diagnosis and monitoring are either low sensitivity or high cost. Therefore, novel, reliable, and objective diagnostic markers should be developed to diagnose and monitor DAI prognosis. Urine is an optimal sample to detect biomarkers for DAI noninvasively. Therefore, the DAI rat model was established in this work. Meanwhile, the ultraperformance liquid chromatography quadrupole-time-of-flight hybrid mass spectrometry- (UPLC/Q-TOF MS-) untargeted metabolomics approach was utilized to identify the features of urine metabolomics to diagnose DAI. This work included 57 metabolites with significant alterations and 21 abnormal metabolic pathways from the injury groups. Three metabolites, viz., urea, butyric acid, and taurine, were identified as possible biomarkers to diagnose DAI based on the great fold changes (FCs) and biological functions during DAI. The present study detected several novel biomarkers for noninvasively diagnosing and monitoring DAI and helped understand the DAI-associated metabolic events.

Antibiotics in elderly Chinese population and their relations with hypertension and pulse pressure

Although antibiotic exposure in the general population has been well documented by a biomonitoring approach, epidemiologic data on the relationships between urinary antibiotic burden in the elderly with blood pressure (BP) are still lacking. The current study revealed thirty-four antibiotics in urine specimens from 990 elderly patients in Lu'an City, China, with detection frequencies ranging from 0.2 to 35.5%. Among the elderly, the prevalence of hypertension was 72.0%, and 12 antibiotics were detected in more than 10% of individuals with hypertension. The elderly with hypertension had the maximum daily exposure (5450.45 μg/kg/day) to fluoroquinolones (FQs). Multiple linear regression analyses revealed significant associations of BP and pulse pressure (PP) with exposure to specific antibiotics. The estimated β values (95% confidence interval) of associations with systolic blood pressure (SBP) in the right arm were 4.42 (1.15, 7.69) for FQs, 4.26 (0.52, 8.01) for the preferred as human antibiotics (PHAs), and 3.48 (0.20, 6.77) for the mixtures (FQs + tetracyclines [TCs] (tertile 3 vs. tertile 1)), respectively. Increased concentrations of TCs were associated with decreased diastolic BP (DBP; tertile 3: -1.75 [-3.39, -0.12]) for the right arm. Higher levels of FQs (tertile 3: 4.28 [1.02, 7.54]), PHAs (tertile 3: 4.25 [0.49, 8.01]), and FQs + TCs (tertile 3: 3.99 [0.71, 7.26]) were associated with increased SBP, and an increase in DBP for FQs (tertile 3: 1.82 [0.22, 3.42]) was shown in the left arm. Also, higher urinary concentrations of FQs (tertile 3: 3.18 [0.53, 5.82]), PHAs (tertile 3: 3.42 [0.40, 6.45]), and FQs + TCs (tertile 3: 3.06 [0.40, 5.72]) were related to increased PP, whereas a decline in PP for TCs (tertile 2: -2.93 [-5.60, -0.25]) in the right arm. And increased concentrations of penicillin V (tertile 3: 5.31 [1.53, 9.10]) and FQs + TCs (tertile 3: 2.84 [0.19, 5.49]) were related to higher PP in the left arm. By utilizing restricted cubic splines, our current study revealed a potential nonlinear dose-response association between FQ exposure and hypertension risk. In conclusion, this investigation is the first to present antibiotic exposure using a biomonitoring approach, and informs understanding of impacts of antibiotic residues, as emerging hazardous pollutants, on the hypertension risk in the elderly.

Microbiota-derived short-chain fatty acids: Implications for cardiovascular and metabolic disease

Cardiovascular diseases (CVDs) have been on the rise around the globe in the past few decades despite the existing guidelines for prevention and treatment. Short-chain fatty acids (SCFAs) are the main metabolites of certain colonic anaerobic bacterial fermentation in the gastrointestinal tract and have been found to be the key metabolites in the host of CVDs. Accumulating evidence suggest that the end-products of SCFAs (including acetate, propionate, and butyrate) interact with CVDs through maintaining intestinal integrity, anti-inflammation, modulating glucolipid metabolism, blood pressure, and activating gut-brain axis. Recent advances suggest a promising way to prevent and treat CVDs by controlling SCFAs. Hence, this review tends to summarize the functional roles carried out by SCFAs that are reported in CVDs studies. This review also highlights several novel therapeutic interventions for SCFAs to prevent and treat CVDs.

Cold exposure, gut microbiota, and hypertension: A mechanistic study

Cold exposure has been recognized as an important risk factor for hypertension, and altered gut microbiota has been reported to be associated with hypertension. We hypothesized that there is a plausible relationship between gut microbiota and cold-induced hypertension (CIH). Therefore, we explored the potential link between the gut microbiota and its metabolites with CIH. Male Sprague-Dawley (SD) rats were randomly divided into the normal temperature group (NT, 20 ± 2 °C) and the cold exposure group (CE, 4 ± 1 °C), and faecal bacteria cross-transplantation was performed after six weeks. We analyzed the gut microbiota of rats using the 16S rDNA sequence and measured the blood pressure of rats and the content of short-chain fatty acids in rat faeces. After six weeks of cold exposure, the CIH rat model was successfully established. The cold exposure reduced the diversity of the gut microbiota, increased the abundance of potentially pathogenic and conditionally pathogenic bacteria (e.g., Quinella, Rothia, and Senegalimassilia genera), and reduced the abundance of beneficial bacteria (e.g., Lactobacillus genus) and butyric acid-producing bacteria (e.g., Lachnospiraceae UCG-008 and Ruminococcaceae UCG-013 genera). Faecal bacteria cross-transplantation altered gut microbiota composition and regulated blood pressure levels. The NT group rats transplanted with CIH rats' faecal bacteria were enriched with certain conditional pathogenic bacteria such as Prevotellaceae UCG-003 genus. The CIH rats transplanted with faecal bacteria from the NT group rats were enriched with beneficial bacteria such as Bacteroides genus. In addition, we found a significant reduction in butyric acid levels in CIH rats, which may be related to the increase in blood pressure. In conclusion, CIH is associated with altered gut microbiota and reduced butyric acid. Our findings provide novel insights for the prevention and treatment of CIH by modulating the gut microbiota through supplementation of beneficial bacteria/butyrate.

Effect of Dietary Fiber (Oat bran) Supplement in Heart Rate Lowering in Patients with Hypertension: A Randomized DASH-Diet-Controlled Clinical Trial

(1) Background: The management goal for patients with essential hypertension (HTN) is not only to lower blood pressure (BP), but also to control increased heart rate (HR). In a previous study, it was found that dietary fiber (DF) supplementation can effectively reduce BP in patients with HTN. The aim of this study was to determine whether a DF supplement can lower HR in patients with HTN. (2) Methods: Seventy patients who met the inclusion and exclusion criteria were randomly allocated into the control group (n = 34) and the intervention group (n = 36). The regular DASH dietary care was delivered to both groups of patients. In addition, one bag of oat bran (30 g/d, containing DF 8.9 g) was delivered to the intervention group. The 24 h ambulatory heart rate was measured at baseline and 3 months. (3) Results: At 3 months, the 24 h maximum heart rate (24h maxHR) in the intervention group was significantly lower than that in the control group. After the intervention, within-group comparisons in the intervention group revealed that there were significant reductions in the 24 h average heart rate (24h aveHR), 24h maxHR, average heart rate during day time (D-aveHR), minimum heart rate during day time (D-minHR), and maximum heart rate during day time (D-maxHR). Similar differences were not found in the control group. (4) Conclusions: Dietary fiber (oat bran) supplementation might be beneficial in lowering HR in patients with HTN.

Dietary tributyrin intervention improves the carcass traits, organ indices, and blood biomarker profiles in broilers under the isocaloric diets administration

The objective of the current study was to investigate the effect of dietary tributyrin (TB) intervention on carcass traits, visceral and immune organ indices, and blood biomarker profiles in Arbor Acres (AA) broilers under the isocaloric diets administration. A total of 432-day-old healthy AA broiler chickens were assigned to 4 treatments, with 12 replicates per treatment and 9 birds per cage, for 42 d. The dietary treatments were a basal diet (control) and the basal diet supplemented with a TB product (Eucalorie) at doses of 0.50 g/kg (TB1), 1.0 g/kg (TB2), and 2.0 g/kg (TB3). The results showed that dietary TB treatment quadratically improved the average daily gain and average daily feed intake in the second (22–42 d) and overall (0–42 d) feeding periods (P < 0.05) while decreasing the feed conversion ratio in the second feeding period (P < 0.05). Dietary TB treatment improved the carcass traits, as evidenced by a higher eviscerated carcass rate and lower abdominal fat yield than those in the control group (P < 0.05). The breast meat yield rate was quadratically improved in response to dietary TB administration (P < 0.05). Dietary TB treatment improved the kidney, spleen, thymus, and bursa indices (P < 0.05) and reduced the lung indices compared with those in the control group (P < 0.05). In particular, the spleen and thymus indices were improved quadratically in response to dietary TB administration (P < 0.05). Dietary TB treatment improved the white and red blood cell counts, platelet count, hemoglobin and hematocrit at d 21, and platelet count at d 42 (P < 0.05), with those in the TB3 group being most affected. Dietary TB administration quadratically decreased the plasma content of uric acid at both d 21 and d 42 as well as that of creatine kinase at d 42 (P < 0.05), while it quadratically increased the plasma albumin/globulin ratio at both d 21 and d 42 (P < 0.05). Collectively, these results demonstrated that dietary TB intervention improved the growth performance, carcass traits, selected visceral and immune organ indices, and some blood biochemical markers under the isocaloric diets administration, which may facilitate better economic profit returns in poultry industry application.

Increases in Circulating and Fecal Butyrate are Associated With Reduced Blood Pressure and Hypertension: Results From the SPIRIT Trial

Background Short chain fatty acids (SCFAs) are microbially derived end products of dietary fiber fermentation. The SCFA butyrate reduces blood pressure (BP) in mouse models. The association of SCFAs, including butyrate, with BP in humans is unclear, due in part to predominantly cross-sectional analyses and different biospecimens (blood versus fecal) for SCFA measurement. Longitudinal studies including both circulating and fecal SCFAs are lacking. Methods and Results We leveraged existing data from the SPIRIT (Survivorship Promotion In Reducing IGF-1 Trial), which randomized 121 adult cancer survivors with overweight/obesity to a behavioral weight-loss intervention, metformin, or self-directed weight-loss. Of participants with baseline serum and fecal SCFAs measured (n=111), a subset had serum (n=93) and fecal (n=89) SCFA measurements 12 months later. We used Poisson regression with robust error variance to estimate baseline associations of SCFAs with hypertension, and we assessed the percent change in SCFAs from baseline with corresponding 12-month changes in BP using multiple linear regression. Baseline fecal butyrate was inversely associated with prevalent hypertension (standardized PR [95%CI]: 0.71 [0.54, 0.92]). A 10% increase in fecal butyrate from baseline was associated with decreased systolic BP (β [95%CI]: -0.56 [-1.01, -0.10] mm Hg), and a 10% increase in serum butyrate was associated with decreased systolic (β [95%CI]: -1.39 [-2.15, -0.63] mm Hg) and diastolic (β [95%CI]: -0.55 [-1.03, -0.08] mm Hg) BPs. Butyrate associations with systolic BP were linear and not modified by sex, race, or intervention arm. Conclusions Increased serum or fecal butyrate is associated with lowered BP. Butyrate may be a target for SCFA-centered BP-lowering interventions. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02431676.