Intracolonic hydrogen sulfide lowers blood pressure in rats

Microbiome Miracles and their Pioneering Advances and Future Frontiers in Cardiovascular Disease

Cardiovascular diseases (CVDs) represent a significant global health challenge, underscoring the need for innovative approaches to prevention and treatment. Recent years have seen a surge in interest in unraveling the complex relationship between the gut microbiome and cardiovascular health. This article delves into current research on the composition, diversity, and impact of the gut microbiome on CVD development. Recent advancements have elucidated the profound influence of the gut microbiome on disease progression, particularly through key mediators like Trimethylamine-N-oxide (TMAO) and other microbial metabolites. Understanding these mechanisms reveals promising therapeutic targets, including interventions aimed at modulating the gut microbiome's interaction with the immune system and its contribution to endothelial dysfunction. Harnessing this understanding, personalized medicine strategies tailored to individuals' gut microbiome profiles offer innovative avenues for reducing cardiovascular risk. As research in this field continues to evolve, there is vast potential for transformative advancements in cardiovascular medicine, paving the way for precision prevention and treatment strategies to address this global health challenge.

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

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

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.

Deoxycholic Acid, a Secondary Bile Acid, Increases Cardiac Output and Blood Pressure in Rats

BACKGROUND

Deoxycholic acid (DCA) is a secondary bile acid produced by gut bacteria. Elevated serum concentrations of DCA are observed in cardiovascular disease (CVD). We hypothesized that DCA might influence hemodynamic parameters in rats.

METHODS

The concentration of DCA in systemic blood was measured with liquid chromatography coupled with mass spectrometry. Arterial blood pressure (BP), heart rate (HR) and echocardiographic parameters were evaluated in anesthetized, male, 3-4-month-old Sprague-Dawley rats administered intravenously (IV) or intracerebroventricularly (ICV) with investigated compounds. Mesenteric artery (MA) reactivity was tested ex vivo.

RESULTS

The baseline plasma concentration of DCA was 0.24 ± 0.03 mg/L. The oral antibiotic treatment produced a large decrease in the concentration. Administered IV, the compound increased BP and HR in a dose-dependent manner. DCA also increased heart contractility and cardiac output. None of the tested compounds-prazosin (an alpha-blocker), propranolol (beta-adrenolytic), atropine (muscarinic receptor antagonist), glibenclamide (K-ATP inhibitor) or DY 268 (FXR antagonist), glycyrrhetinic acid (11HSD2 inhibitor)-significantly diminished the DCA-induced pressor effect. ICV infusion did not exert significant HR or BP changes. DCA relaxed MAs. Systemic vascular resistance did not change significantly.

CONCLUSIONS

DCA elevates BP primarily by augmenting cardiac output. As a metabolite derived from gut bacteria, DCA potentially serves as a mediator in the interaction between the gut microbiota and the host's circulatory system.

The Association between Gut Microbiome and Pregnancy-Induced Hypertension: A Nested Case–Control Study

(1) Background: Pregnancy-induced hypertension (PIH) is associated with obvious microbiota dysbiosis in the third trimester of pregnancy. However, the mechanisms behind these changes remain unknown. Therefore, this study aimed to explore the relationship between the gut microbiome in early pregnancy and PIH occurrence. (2) Methods: A nested case–control study design was used based on the follow-up cohort. Thirty-five PIH patients and thirty-five matched healthy pregnant women were selected as controls. The gut microbiome profiles were assessed in the first trimester using metagenomic sequencing. (3) Results: Diversity analyses showed that microbiota diversity was altered in early pregnancy. At the species level, eight bacterial species were enriched in healthy controls: Alistipes putredinis, Bacteroides vulgatus, Ruminococcus torques, Oscillibacter unclassified, Akkermansia muciniphila, Clostridium citroniae, Parasutterella excrementihominis and Burkholderiales bacterium_1_1_47. Conversely, Eubacterium rectale, and Ruminococcus bromii were enriched in PIH patients. The results of functional analysis showed that the changes in these different microorganisms may affect the blood pressure of pregnant women by affecting the metabolism of vitamin K₂, sphingolipid, lipid acid and glycine. (4) Conclusion: Microbiota dysbiosis in PIH patients begins in the first trimester of pregnancy, and this may be associated with the occurrence of PIH. Bacterial pathway analyses suggest that the gut microbiome might lead to the development of PIH through the alterations of function modules.

Overview on hydrogen sulfide-mediated suppression of vascular calcification and hemoglobin/heme-mediated vascular damage in atherosclerosis

Vulnerable atherosclerotic plaques with hemorrhage considerably contribute to cardiovascular morbidity and mortality. Calcification is the main characteristic of advanced atherosclerotic lesions and calcified aortic valve disease (CAVD). Lyses of red blood cells and hemoglobin (Hb) release occur in human hemorrhagic complicated lesions. During the interaction of cell-free Hb with plaque constituents, Hb is oxidized to ferric and ferryl states accompanied by oxidative changes of the globin moieties and heme release. Accumulation of both ferryl-Hb and metHb has been observed in atherosclerotic plaques. The oxidation hotspots in the globin chain are the cysteine and tyrosine amino acids associated with the generation of Hb dimers, tetramers and polymers. Moreover, fragmentation of Hb occurs leading to the formation of globin-derived peptides. A series of these pro-atherogenic cellular responses can be suppressed by hydrogen sulfide (H2S). Since H2S has been explored to exhibit a wide range of physiologic functions to maintain vascular homeostasis, it is not surprising that H2S may play beneficial effects in the progression of atherosclerosis. In the present review, we summarize the findings about the effects of H2S on atherosclerosis and CAVD with a special emphasis on the oxidation of Hb/heme in atherosclerotic plaque development and vascular calcification.

Microbiota-derived tryptophan metabolites in vascular inflammation and cardiovascular disease

The essential amino acid tryptophan (Trp) is metabolized by gut commensals, yielding in compounds that affect innate immune cell functions directly, but also acting on the aryl hydrocarbon receptor (AHR), thus regulating the maintenance of group 3 innate lymphoid cells (ILCs), promoting T helper 17 (TH17) cell differentiation, and interleukin-22 production. In addition, microbiota-derived Trp metabolites have direct effects on the vascular endothelium, thus influencing the development of vascular inflammatory phenotypes. Indoxyl sulfate was demonstrated to promote vascular inflammation, whereas indole-3-propionic acid and indole-3-aldehyde had protective roles. Furthermore, there is increasing evidence for a contributory role of microbiota-derived indole-derivatives in blood pressure regulation and hypertension. Interestingly, there are indications for a role of the kynurenine pathway in atherosclerotic lesion development. Here, we provide an overview on the emerging role of gut commensals in the modulation of Trp metabolism and its influence in cardiovascular disease development.

Heart and kidney H2S production is reduced in hypertensive and older rats

The prevalence of hypertension increases with age, but the mechanisms linking this phenomenon are not well understood. Hydrogen sulfide (H₂S) may be involved in this process, as it plays a role in the cardiovascular system, affecting blood pressure and heart and kidney functions. The aim of this study was to evaluate the influence of hypertension and aging on sulfur-containing compounds metabolism in the hearts and kidneys of Wistar Kyoto (WKY) and Spontaneously Hypertensive Rats (SHR) of different age groups. We determined the expression and activity of four enzymes participating in H₂S production: cystathionine beta-synthase (CBS), cystathionine gamma-lyase (CTH), 3-mercaptopyruvate sulfurtransferase (MPST), and thiosulfate sulfurtransferase (TST). The levels of reduced/oxidized glutathione, cysteine, cystine, and cystathionine, and the ability of tissues to form hydrogen sulfide were also investigated. Tissues obtained from younger WKY rats produced the highest amounts of H₂S. The effect of hypertension on the metabolism of sulfur-containing compounds was manifested by a decrease in sulfane sulfur concentrations in heart homogenates and a decrease in CTH activity in the kidneys. The hearts and kidneys of older WKY rats were characterized by lower MPST or CTH gene expression, respectively, compared to younger animals. Our study demonstrates that hypertension and aging influence cardiac and renal sulfur-containing compounds metabolism and reduce H₂S production. Furthermore, we showed that MPST plays a major role in the production of hydrogen sulfide in the heart and CTH in the kidneys of rats.

Impact of the Gastrointestinal Tract Microbiota on Cardiovascular Health and Pathophysiology

ABSTRACT

The microbiota of the gastrointestinal tract (GIT) is an extremely diverse community of microorganisms, and their collective genomes (microbiome) provide a vast arsenal of biological activities, in particular enzymatic ones, which are far from being fully elucidated. The study of the microbiota (and the microbiome) is receiving great interest from the biomedical community as it carries the potential to improve risk-prediction models, refine primary and secondary prevention efforts, and also design more appropriate and personalized therapies, including pharmacological ones. A growing body of evidence, though sometimes impaired by the limited number of subjects involved in the studies, suggests that GIT dysbiosis, i.e. the altered microbial composition, has an important role in causing and/or worsening cardiovascular disease (CVD). Bacterial translocation as well as the alteration of levels of microbe-derived metabolites can thus be important to monitor and modulate, because they may lead to initiation and progression of CVD, as well as to its establishment as chronic state. We hereby aim to provide readers with details on available resources and experimental approaches that are used in this fascinating field of biomedical research, and on some novelties on the impact of GIT microbiota on CVD.

The Contribution of Gut Microbiota and Endothelial Dysfunction in the Development of Arterial Hypertension in Animal Models and in Humans

The maintenance of the physiological values of blood pressure is closely related to unchangeable factors (genetic predisposition or pathological alterations) but also to modifiable factors (dietary fat and salt, sedentary lifestyle, overweight, inappropriate combinations of drugs, alcohol abuse, smoking and use of psychogenic substances). Hypertension is usually characterized by the presence of a chronic increase in systemic blood pressure above the threshold value and is an important risk factor for cardiovascular disease, including myocardial infarction, stroke, micro- and macro-vascular diseases. Hypertension is closely related to functional changes in the endothelium, such as an altered production of vasoconstrictive and vasodilator substances, which lead to an increase in vascular resistance. These alterations make the endothelial tissue unresponsive to autocrine and paracrine stimuli, initially determining an adaptive response, which over time lead to an increase in risk or disease. The gut microbiota is composed of a highly diverse bacterial population of approximately 10¹⁴ bacteria. A balanced intestinal microbiota preserves the digestive and absorbent functions of the intestine, protecting from pathogens and toxic metabolites in the circulation and reducing the onset of various diseases. The gut microbiota has been shown to produce unique metabolites potentially important in the generation of hypertension and endothelial dysfunction. This review highlights the close connection between hypertension, endothelial dysfunction and gut microbiota.

Hydrogen sulphide in liver glucose/lipid metabolism and non-alcoholic fatty liver disease

BACKGROUND

For a long time, hydrogen sulphide (H₂ S) was considered only as a toxic gas, inhibiting mitochondrial respiration at the level of cytochrome c oxidase, and an environmental pollutant. Nowadays, H₂ S is recognized as the third mammalian gasotransmitter, playing an important role in inflammation, septic shock, ischaemia reperfusion events, cardiovascular disease and more recently in liver physiology and chronic liver diseases such as non-alcoholic fatty liver disease (NAFLD).

METHODS

This narrative review is based on literature search using PubMed.

RESULTS

From a bioenergetic perspective, H₂ S is a very unique molecule, serving as a mitochondrial poison at high concentrations or as an inorganic mitochondrial substrate at low concentrations. By using transgenic animal models to specifically modulate liver H₂ S biosynthesis or exogenous compounds that release H₂ S, several studies demonstrated that H₂ S is a key player in liver glucose and lipid metabolism. Liver H₂ S content and biosynthesis were also altered in NAFLD animal models with the in vivo administration of H₂ S-releasing molecules preventing the further escalation into non-alcoholic-steatohepatitis. Liver steady-state levels of H₂ S, and hence its cell signalling properties, are controlled by a tight balance between its biosynthesis, mainly through the transsulphuration pathway, and its mitochondrial oxidation via the sulphide oxidizing unit. However, studies investigating mitochondrial H₂ S oxidation in liver dysfunction still remain scarce.

CONCLUSIONS

Since H₂ S emerges as a key regulator of liver metabolism and metabolic flexibility, further understanding the physiological relevance of mitochondrial H₂ S oxidation in liver energy homeostasis and its potential implication in chronic liver diseases are of great interest.

Biological Effects of Indole-3-Propionic Acid, a Gut Microbiota-Derived Metabolite, and Its Precursor Tryptophan in Mammals' Health and Disease

Actions of symbiotic gut microbiota are in dynamic balance with the host’s organism to maintain homeostasis. Many different factors have an impact on this relationship, including bacterial metabolites. Several substrates for their synthesis have been established, including tryptophan, an exogenous amino acid. Many biological processes are influenced by the action of tryptophan and its endogenous metabolites, serotonin, and melatonin. Recent research findings also provide evidence that gut bacteria-derived metabolites of tryptophan share the biological effects of their precursor. Thus, this review aims to investigate the biological actions of indole-3-propionic acid (IPA), a gut microbiota-derived metabolite of tryptophan. We searched PUBMED and Google Scholar databases to identify pre-clinical and clinical studies evaluating the impact of IPA on the health and pathophysiology of the immune, nervous, gastrointestinal and cardiovascular system in mammals. IPA exhibits a similar impact on the energetic balance and cardiovascular system to its precursor, tryptophan. Additionally, IPA has a positive impact on a cellular level, by preventing oxidative stress injury, lipoperoxidation and inhibiting synthesis of proinflammatory cytokines. Its synthesis can be diminished in the presence of different risk factors of atherosclerosis. On the other hand, protective factors, such as the introduction of a Mediterranean diet, tend to increase its plasma concentration. IPA seems to be a promising new target, linking gut health with the cardiovascular system.

Hydrogen sulfide in ageing, longevity and disease

Hydrogen sulfide (H₂S) modulates many biological processes, including ageing. Initially considered a hazardous toxic gas, it is now recognised that H₂S is produced endogenously across taxa and is a key mediator of processes that promote longevity and improve late-life health. In this review, we consider the key developments in our understanding of this gaseous signalling molecule in the context of health and disease, discuss potential mechanisms through which H₂S can influence processes central to ageing and highlight the emergence of novel H₂S-based therapeutics. We also consider the major challenges that may potentially hinder the development of such therapies.

Central Administration of Hydrogen Sulfide Donor NaHS Reduces Iba1-Positive Cells in the PVN and Attenuates Rodent Angiotensin II Hypertension

Hydrogen sulfide (H2S) is a gaseous signaling molecule with neuromodulatory, anti-inflammatory, and anti-hypertensive effects. Here, we investigate whether chronic intracerebroventricular (ICV) infusion of sodium hydrosulfide (NaHS), an H2S donor, can alleviate angiotensin II (Ang II)-induced hypertension (HTN), improve autonomic function, and impact microglia in the paraventricular nucleus (PVN) of the hypothalamus, a brain region associated with autonomic control of blood pressure (BP) and neuroinflammation in HTN. Chronic delivery of Ang II (200 ng/kg/min, subcutaneous) for 4 weeks produced a typical increase in BP and sympathetic drive and elevated the number of ionized calcium binding adaptor molecule 1-positive (Iba1+) cells in the PVN of male, Sprague-Dawley rats. ICV co-infusion of NaHS (at 30 and/or 60 nmol/h) significantly attenuated these effects of Ang II. Ang II also increased the abundance of cecal Deltaproteobacteria and Desulfovibrionales, among others, which was prevented by ICV NaHS co-infusion at 30 and 60 nmol/h. We observed no differences in circulating H2S between the groups. Our results suggest that central H2S may alleviate rodent HTN independently from circulating H2S via effects on autonomic nervous system and PVN microglia.

The impact of gut microbiota metabolites on cellular bioenergetics and cardiometabolic health

Recent research demonstrates a reciprocal relationship between gut microbiota-derived metabolites and the host in controlling the energy homeostasis in mammals. On the one hand, to thrive, gut bacteria exploit nutrients digested by the host. On the other hand, the host utilizes numerous products of gut bacteria metabolism as a substrate for ATP production in the colon. Finally, bacterial metabolites seep from the gut into the bloodstream and interfere with the host’s cellular bioenergetics machinery. Notably, there is an association between alterations in microbiota composition and the development of metabolic diseases and their cardiovascular complications. Some metabolites, like short-chain fatty acids and trimethylamine, are considered markers of cardiometabolic health. Others, like hydrogen sulfide and nitrite, demonstrate antihypertensive properties. Scientific databases were searched for pre-clinical and clinical studies to summarize current knowledge on the role of gut microbiota metabolites in the regulation of mammalian bioenergetics and discuss their potential involvement in the development of cardiometabolic disorders. Overall, the available data demonstrates that gut bacteria products affect physiological and pathological processes controlling energy and vascular homeostasis. Thus, the modulation of microbiota-derived metabolites may represent a new approach for treating obesity, hypertension and type 2 diabetes.

Desulfovibrio Bacteria Are Associated With Parkinson's Disease

Parkinson's disease (PD) is the most prevalent movement disorder known and predominantly affects the elderly. It is a progressive neurodegenerative disease wherein α-synuclein, a neuronal protein, aggregates to form toxic structures in nerve cells. The cause of Parkinson's disease (PD) remains unknown. Intestinal dysfunction and changes in the gut microbiota, common symptoms of PD, are evidently linked to the pathogenesis of PD. Although a multitude of studies have investigated microbial etiologies of PD, the microbial role in disease progression remains unclear. Here, we show that Gram-negative sulfate-reducing bacteria of the genus Desulfovibrio may play a potential role in the development of PD. Conventional and quantitative real-time PCR analysis of feces from twenty PD patients and twenty healthy controls revealed that all PD patients harbored Desulfovibrio bacteria in their gut microbiota and these bacteria were present at higher levels in PD patients than in healthy controls. Additionally, the concentration of Desulfovibrio species correlated with the severity of PD. Desulfovibrio bacteria produce hydrogen sulfide and lipopolysaccharide, and several strains synthesize magnetite, all of which likely induce the oligomerization and aggregation of α-synuclein protein. The substances originating from Desulfovibrio bacteria likely take part in pathogenesis of PD. These findings may open new avenues for the treatment of PD and the identification of people at risk for developing PD.

Invited review: Effect of antihypertensive fermented milks on gut microbiota

Hypertension is a risk factor for the development of other cardiovascular diseases and remains one of the leading causes of death worldwide. Although genetic and environmental factors are associated with the development of hypertension, it has been recently recognized that gut microbiota (GM) may also have an effect on human health. In this sense, gut dysbiosis (a marked decrease in richness and diversity of GM) has been linked to different metabolic diseases, such as hypertension. Therefore, different studies have been pursued to reduce gut dysbiosis and diminish hypertension. Different strategies to maintain a balanced GM, particularly through diet and the use of probiotics, are being evaluated. Most recently, the effect of antihypertensive fermented milks on GM has been addressed. New evidence suggests that antihypertensive fermented milks may modulate GM. Thus, the aim of this review is to present available information related to the effect of antihypertensive fermented milks on gut microbiota.

Preventing Developmental Origins of Cardiovascular Disease: Hydrogen Sulfide as a Potential Target?

The cardiovascular system can be programmed by a diversity of early-life insults, leading to cardiovascular disease (CVD) in adulthood. This notion is now termed developmental origins of health and disease (DOHaD). Emerging evidence indicates hydrogen sulfide (H₂S), a crucial regulator of cardiovascular homeostasis, plays a pathogenetic role in CVD of developmental origins. Conversely, early H₂S-based interventions have proved beneficial in preventing adult-onset CVD in animal studies via reversing programming processes by so-called reprogramming. The focus of this review will first summarize the current knowledge on H₂S implicated in cardiovascular programming. This will be followed by supporting evidence for the links between H₂S signaling and underlying mechanisms of cardiovascular programming, such as oxidative stress, nitric oxide deficiency, dysregulated nutrient-sensing signals, activation of the renin–angiotensin system, and gut microbiota dysbiosis. It will also provide an overview from animal models regarding how H₂S-based reprogramming interventions, such as precursors of H₂S and H₂S donors, may prevent CVD of developmental origins. A better understanding of cardiovascular programming and recent advances in H₂S-based interventions might provide the answers to bring down the global burden of CVD.

Effects of gut microbiota on atherosclerosis through hydrogen sulfide

Cardiovascular diseases are the leading cause of death and morbidity worldwide. Atherosclerotic cardiovascular disease (ASCVD) is affected by both environmental and genetic factors. Microenvironmental disorders of the human gut flora are associated with a variety of health problems, not only gastrointestinal diseases, such as inflammatory bowel disease, but also extralintestinal organs. Hydrogen sulfide (H₂S) is the third gas signaling molecule other than nitric oxide and carbon monoxide. In the cardiovascular system, H₂S plays important roles in the regulation of blood pressure, angiogenesis, smooth muscle cell proliferation and apoptosis, anti-oxidative stress, cardiac functions. This review is aiming to explore the potential role of gut microbiota in the development of atherosclerosis through hydrogen sulfide production as a novel therapeutic direction for atherosclerosis.

Possible cardioprotective role of NaHS on ECG and oxidative stress markers in an unpredictable chronic mild stress model in rats

The protective effect of H₂S against various body organ injuries has been described. The aim of this work is to investigate the potential role of sodium hydrosulfide (NaHS) as an H₂S donor in chronic mild stress induced changes in the rat heart. Forty adult male Sprague Dawley rats were assigned to four groups: control, stressed group, stressed rats treated with aminooxyacetic acid (AOAA), and stressed rats treated with NaHS. Arterial blood pressure (ABP) was recorded. Serum adrenaline, MDA, and GSH levels were measured. Chronic stress significantly increased HR and ABP. AOAA produced similar changes, while NaHS mitigated the rise in HR and ABP. Both stressed and AOAA-treated stressed groups showed a significant decrease in QRS amplitude and a shortening of the RR, QT, and QTc intervals with an elevation of the ST segment. NaHS produced a significant improvement in ECG recordings. Chronic stress produced a significant rise of adrenaline and MDA levels with a significant decline in GSH levels. The AOAA-treated stressed group showed similar elevations. NaHS treatment caused significant reduction in adrenaline and MDA levels but significantly improved GSH levels. In conclusion, H₂S donor has a cardioprotective effect against stress-induced cardiovascular diseases through amelioration of the oxidative stress and raised adrenaline levels induced by chronic stress exposure.

Maternal N-Acetylcysteine Therapy Prevents Hypertension in Spontaneously Hypertensive Rat Offspring: Implications of Hydrogen Sulfide-Generating Pathway and Gut Microbiota

Hypertension can come from early life. N-acetylcysteine (NAC), a hydrogen sulfide (H₂S) precursor as well as an antioxidant, has antihypertensive effect. We investigated whether maternal NAC therapy can protect spontaneously hypertensive rats (SHR) male offspring against hypertension. The pregnant rats were assigned to four groups: SHRs without treatment; Wistar Kyoto (WKY) without treatment; SHR+NAC, SHRs received 1% NAC in drinking water throughout pregnancy and lactation; and, WKY+NAC, WKY rats received 1% NAC in drinking water during pregnancy and lactation. Male offspring (n = 8/group) were killed at 12 weeks of age. Maternal NAC therapy prevented the rise in systolic blood pressure (BP) in male SHR offspring at 12 weeks of age. Renal cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulphurtransferase (3MST) protein levels and H₂S-releasing activity were increased in the SHR+NAC offspring. Maternal NAC therapy increased fecal H₂S and thiosulfate levels in the SHR+NAC group. Additionally, maternal NAC therapy differentially shaped gut microbiota and caused a distinct enterotype in each group. The protective effect of maternal NAC therapy against hypertension in SHR offspring is related to increased phylum Actinobacteria and genera Bifidobacterium and Allobaculum, but decreased phylum Verrucomicrobia, genera Turicibacter, and Akkermansia. Several microbes were identified as microbial markers, including genera Bifidobacterium, Allobaculum, Holdemania, and Turicibacter. Our results indicated that antioxidant therapy by NAC in pregnant SHRs can prevent the developmental programming of hypertension in male adult offspring. Our findings highlight the interrelationships among H₂S-generating pathway in the kidneys and gut, gut microbiota, and hypertension. The implications of maternal NAC therapy elicited long-term protective effects on hypertension in later life that still await further clinical translation.

Heart Failure Disturbs Gut-Blood Barrier and Increases Plasma Trimethylamine, a Toxic Bacterial Metabolite

Trimethylamine (TMA) is a gut bacteria product oxidized by the liver to trimethylamine-N-oxide (TMAO). Clinical evidence suggests that cardiovascular disease is associated with increased plasma TMAO. However, little headway has been made in understanding this relationship on a mechanistic and molecular level. We investigated the mechanisms affecting plasma levels of TMAO in Spontaneously Hypertensive Heart Failure (SHHF) rats. Healthy Wistar Kyoto (WKY) and SHHF rats underwent metabolic, hemodynamic, histopathological and biochemical measurements, including tight junction proteins analysis. Stool, plasma and urine samples were evaluated for TMA and TMAO using ultra performance liquid chromatography-mass spectrometry. SHHF presented disturbances of the gut–blood barrier including reduced intestinal blood flow, decreased thickness of the colonic mucosa and alterations in tight junctions, such as claudin 1 and 3, and zonula occludens-1. This was associated with significantly higher plasma levels of TMA and TMAO and increased gut-to-blood penetration of TMA in SHHF compared to WKY. There was no difference in kidney function or liver oxidation of TMA to TMAO between WKY and SHHF. In conclusion, increased plasma TMAO in heart failure rats results from a perturbed gut–blood barrier and increased gut-to-blood passage of TMAO precursor, i.e., TMA. Increased gut-to-blood penetration of bacterial metabolites may be a marker and a mediator of cardiovascular pathology.

Hydrogen sulfide: An endogenous regulator of the immune system

Hydrogen sulfide (H₂S) is now recognized as an endogenous signaling gasotransmitter in mammals. It is produced by mammalian cells and tissues by various enzymes - predominantly cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) - but part of the H₂S is produced by the intestinal microbiota (colonic H₂S-producing bacteria). Here we summarize the available information on the production and functional role of H₂S in the various cell types typically associated with innate immunity (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, basophils, eosinophils) and adaptive immunity (T and B lymphocytes) under normal conditions and as it relates to the development of various inflammatory and immune diseases. Special attention is paid to the physiological and the pathophysiological aspects of the oral cavity and the colon, where the immune cells and the parenchymal cells are exposed to a special "H₂S environment" due to bacterial H₂S production. H₂S has many cellular and molecular targets. Immune cells are "surrounded" by a "cloud" of H₂S, as a result of endogenous H₂S production and exogenous production from the surrounding parenchymal cells, which, in turn, importantly regulates their viability and function. Downregulation of endogenous H₂S producing enzymes in various diseases, or genetic defects in H₂S biosynthetic enzyme systems either lead to the development of spontaneous autoimmune disease or accelerate the onset and worsen the severity of various immune-mediated diseases (e.g. autoimmune rheumatoid arthritis or asthma). Low, regulated amounts of H₂S, when therapeutically delivered by small molecule donors, improve the function of various immune cells, and protect them against dysfunction induced by various noxious stimuli (e.g. reactive oxygen species or oxidized LDL). These effects of H₂S contribute to the maintenance of immune functions, can stimulate antimicrobial defenses and can exert anti-inflammatory therapeutic effects in various diseases.

Gut Microbiota and Heart, Vascular Injury

The gut microbiota plays an important role in maintaining human health. Accumulating evidence has indicated an intimate relationship between gut microbiota and cardiovascular diseases (CVD) which has become the leading cause of death worldwide. The alteration of gut microbial composition (gut dysbiosis) has been proven to contribute to atherosclerosis, the basic pathological process of CVD. In addition, the metabolites of gut microbiota have been found to be closely related to the development of CVD. For example, short-chain fatty acids are widely acclaimed beneficial effect against CVD, whereas trimethylamine-N-oxide is considered as a contributing factor in the development of CVD. In this chapter, we mainly discuss the gut microbial metabolite-involved mechanisms of CVD focusing on atherosclerosis, hypertension, diabetes, obesity, and heart failure. Targeting gut microbiota and related metabolites are novel and promising strategies for the treatment of CVD.

Influence of fermented soy protein consumption on hypertension and gut microbial modulation in spontaneous hypertensive rats

Plant proteins are known to possess important bioactive peptides and have a positive impact on gut microbial modulation. In this study, we studied the ability of a single dose of a fermented soy protein product (P-SPI) to reduce high blood pressure in spontaneous hypertensive rats (SHR) and how it modulates the gut microbiota after six weeks of feeding. SHRs were fed with P-SPI, Captopril or distilled water once, and their blood pressures were monitored from the first to twelfth-hour post-administration. Consumption of P-SPI significantly reduced systolic and diastolic blood pressures up to the sixth hour by 25 ± 4 mmHg and 40 ± 5 mmHg respectively. P-SPI consumption inhibited serum ACE activity, increased superoxide dismutase activity and nitric oxide levels and reduced malondialdehyde levels in serum. Analysis of fecal microbial 16S rRNA of hypertensive rats revealed a significant reduction in microbial richness and diversity in the gut, while P-SPI consumption improved microbial richness and increased diversity. Also, P-SPI feeding significantly reduced the Firmicutes/Bacteroidetes ratio, increased propionate- and H₂S-producing bacteria and reduced Streptococcaceae and Erysipelotrichales levels. Our results show that P-SPI is a potential antihypertensive functional food which could remodel the altered gut microbiota of hypertensive patients.

Gut microbiota and neuroinflammation in pathogenesis of hypertension: A potential role for hydrogen sulfide

Inflammation and gut dysbiosis are hallmarks of hypertension (HTN). Hydrogen sulfide (H2S) is an important freely diffusing molecule that modulates the function of neural, cardiovascular and immune systems, and circulating levels of H2S are reduced in animals and humans with HTN. While most research to date has focused on H₂S produced endogenously by the host, H2S is also produced by the gut bacteria and may affect the host homeostasis. Here, we review an association between neuroinflammation and gut dysbiosis in HTN, with special emphasis on a potential role of H2S in this interplay.

Hydrogen Sulfide in Pharmacotherapy, Beyond the Hydrogen Sulfide-Donors

Hydrogen sulfide (H₂S) is one of the important biological mediators involved in physiological and pathological processes in mammals. Recently developed H₂S donors show promising effects against several pathological processes in preclinical and early clinical studies. For example, H₂S donors have been found to be effective in the prevention of gastrointestinal ulcers during anti-inflammatory treatment. Notably, there are well-established medicines used for the treatment of a variety of diseases, whose chemical structure contains sulfur moieties and may release H₂S. Hence, the therapeutic effect of these drugs may be partly the result of the release of H₂S occurring during drug metabolism and/or the effect of these drugs on the production of endogenous hydrogen sulfide. In this work, we review data regarding sulfur drugs commonly used in clinical practice that can support the hypothesis about H₂S-dependent pharmacotherapeutic effects of these drugs.

Hydrogen Sulfide as a Potential Alternative for the Treatment of Myocardial Fibrosis

Harmful, stressful conditions or events in the cardiovascular system result in cellular damage, inflammation, and fibrosis. Currently, there is no targeted therapy for myocardial fibrosis, which is highly associated with a large number of cardiovascular diseases and can lead to fatal heart failure. Hydrogen sulfide (H₂S) is an endogenous gasotransmitter similar to nitric oxide and carbon monoxide. H₂S is involved in the suppression of oxidative stress, inflammation, and cellular death in the cardiovascular system. The level of H₂S in the body can be boosted by stimulating its synthesis or supplying it exogenously with a simple H₂S donor with a rapid- or slow-releasing mode, an organosulfur compound, or a hybrid with known drugs (e.g., aspirin). Hypertension, myocardial infarction, and inflammation are exaggerated when H₂S is reduced. In addition, the exogenous delivery of H₂S mitigates myocardial fibrosis caused by various pathological conditions, such as a myocardial infarct, hypertension, diabetes, or excessive β-adrenergic stimulation, via its involvement in a variety of signaling pathways. Numerous experimental findings suggest that H₂S may work as a potential alternative for the management of myocardial fibrosis. In this review, the antifibrosis role of H₂S is briefly addressed in order to gain insight into the development of novel strategies for the treatment of myocardial fibrosis.

The Gut Microbial Metabolite Trimethylamine N-Oxide and Hypertension Risk: A Systematic Review and Dose-Response Meta-analysis

The gut microbial metabolite trimethylamine N-oxide (TMAO) is increasingly regarded as a novel risk factor for cardiovascular events and mortality. However, little is known about the association between TMAO and hypertension. This meta-analysis was conducted to quantitatively assess the relation between the circulating TMAO concentration and hypertension prevalence. The PubMed, Cochrane Library, and Embase databases were systematically searched up to 17 June 2018. Studies recording the hypertension prevalence in members of a given population and their circulating TMAO concentrations were included. A total of 8 studies with 11,750 individuals and 6176 hypertensive cases were included in the analytic synthesis. Compared with low circulating TMAO concentrations, high TMAO concentrations were correlated with a higher prevalence of hypertension (RR: 1.12; 95% CI: 1.06, 1.17; P < 0.0001; I2 = 64%; P-heterogeneity = 0.007; random-effects model). Consistent results were obtained in all examined subgroups as well as in the sensitivity analysis. The RR for hypertension prevalence increased by 9% per 5-μmol/L increment (RR: 1.09; 95% CI: 1.05, 1.14; P < 0.0001) and 20% per 10-μmol/L increment of circulating TMAO concentration (RR: 1.20; 95% CI: 1.11, 1.30; P < 0.0001) according to the dose-response meta-analysis. To our knowledge, this is the first systematic review and meta-analysis demonstrating a significant positive dose-dependent association between circulating TMAO concentrations and hypertension risk.

Hydrogen Sulfide Effects on the Survival of Lactobacilli with Emphasis on the Development of Inflammatory Bowel Diseases

The gut microbiota is a complex component of humans that depends on diet, host genome, and lifestyle. The background: The study purpose is to find relations between nutrition, intestinal lactic acid bacteria (LAB) from various environments (human, animal intestine, and yogurt) and sulfate-reducing microbial communities in the large intestine; to compare kinetic growth parameters of LAB; and to determine their sensitivity to different concentration of hydrogen sulfide produced by intestinal sulfate-reducing bacteria.

METHODS

Microbiological (isolation and identification), biochemical (electrophoresis), molecular biology methods (DNA isolation and PCR analysis), and statistical processing (average and standard error calculations) of the results were used.

THE RESULTS

The toxicity of hydrogen sulfide produced by sulfate-reducing bacteria, the survival of lactic acid bacteria, and minimal inhibitory concentrations (MIC) were determined. The measured hydrogen sulfide sensitivity values were the same for L. paracasei and L. reuteri (MIC > 1.1 mM). In addition, L. plantarum and L.fermentum showed also a similar sensitivity (MIC > 0.45 mM) but significantly (p < 0.05) lower than L.reuteri and L. paracasei (1.1 > 0.45 mM). L. paracasei and L. reuteri are more sensitive to hydrogen sulfide than L. fermentum and L. plantarum. L. pentosus was sensitive to the extremely low concentration of H2S (MIC > 0.15 mM).

CONCLUSIONS

The Lactobacillus species were significantly sensitive to hydrogen sulfide, which is a final metabolite of intestinal sulfate-reducing bacteria. The results are definitely helpful for a better understanding of complicated interaction among intestinal microbiota and nutrition.

Circulating Metabolites Originating from Gut Microbiota Control Endothelial Cell Function

Cardiovascular functionality strictly depends on endothelial cell trophism and proper biochemical function. Any condition (environmental, pharmacological/toxicological, physical, or neuro-humoral) that changes the vascular endothelium has great consequences for the organism’s wellness and on the outcome and evolution of severe cardiovascular pathologies. Thus, knowledge of the mechanisms, both endogenous and external, that affect endothelial dysfunction is pivotal to preventing and treating these disorders. In recent decades, significant attention has been focused on gut microbiota and how these symbiotic microorganisms can influence host health and disease development. Indeed, dysbiosis has been reported to be at the base of a range of different pathologies, including pathologies of the cardiovascular system. The study of the mechanism underlying this relationship has led to the identification of a series of metabolites (released by gut bacteria) that exert different effects on all the components of the vascular system, and in particular on endothelial cells. The imbalance of factors promoting or blunting endothelial cell viability and function and angiogenesis seems to be a potential target for the development of new therapeutic interventions. This review highlights the circulating factors identified to date, either directly produced by gut microbes or resulting from the metabolism of diet derivatives as polyphenols.

Sodium, hypertension, and the gut: does the gut microbiota go salty?

Recent evidence suggests that the gut microbiota contributes to the pathogenesis of hypertension (HTN). The gut microbiota is a highly dynamic organ mediating numerous physiological functions, which can be influenced by external factors such as diet. In particular, a major modifiable risk factor for HTN is dietary sodium intake. Sodium consumption in the United States is significantly greater than that recommended by the federal government and organizations such as the American Heart Association. Because of the emerging connection between the gut microbiota and HTN, the interaction between dietary sodium and gut microbiota has sparked interest. High-sodium diets promote local and systemic tissue inflammation and impair intestinal anatomy compared with low sodium intake in both human and animal studies. It is biologically plausible that the gut microbiota mediates the inflammatory response, as it is in constant interaction with the immune system and is necessary for proper maturation of immune cells. Recent rodent data demonstrate that dietary sodium disrupts gut microbial homeostasis as gut microbiota composition shifts with dietary sodium manipulation. In this review, we will focus on gut microbiota activity in HTN and the influence of high dietary sodium intake with an emphasis on the immune system, bacterial metabolites, and the circadian clock.

Construction of a novel cell-trappable fluorescent probe for hydrogen sulfide (H2S) and its bio-imaging application

Fluorescence detection of H₂S in living organisms is greatly advantageous because it is nondestructive and can be used for in situ analysis. We have constructed a novel rhodamine analogue dye (Rho630) by extending the conjugated system of rhodamine to create a novel cell-trappable H₂S fluorescent probe Rho630-AM-H₂S with red light emission. Its application for H₂S fluorescence detection in living HeLa cells and zebrafish was investigated. As expected, Rho630-AM-H₂S showed a huge fluorescence turn-on response of about 20-fold at 630 nm and good selectivity toward H₂S in solution. An MTT assay demonstrated that the probe showed negligible cytotoxicity in the concentrations typically used in fluorescence imaging experiments. Cell imaging experiments revealed that compared with compound 4 without cell-trappable unit modification, Rho630-AM-H₂S exhibited remarkably enhanced cell penetration ability, as an enormous fluorescence signal increase was observed at the red channel within 5 min after Rho630-AM-H₂S was incubated with HeLa cells. Finally, the probe Rho630-AM-H₂S was used to detect H₂S in living HeLa cells and zebrafish with great fluorescence enhancement in the red channel. Graphical abstract.

Gut Flora: Novel Therapeutic Target of Chinese Medicine for the Treatment of Cardiovascular Diseases

Cardiovascular disease (CVD) is one of the three major threats to human health identified by WHO. Dyslipidemia, hypertension, diabetes, and obesity are well established as common CVD risk factors. However, controversies exist on the effects of gut flora on cardiovascular disease (CVD). Current evidence suggests that gut microbiota is a double-edged sword for CVD risk, and its effects are largely determined by the metabolites of the gut microbiota. Trimethylamine N-oxide (TMAO), as one of the metabolites of gut flora, is consistently associated with higher CVD risk. A few studies have emerged providing early evidence about the safety and efficacy of traditional Chinese medicine (TCM) in treating cardiovascular diseases by regulating gut flora. In this article, we review and interpret the existing evidence as well as explore the potential of intestinal flora as novel therapeutic targets of traditional Chinese medicine for the prevention of cardiovascular disease (CVD).

Early-Onset Preeclampsia Is Associated With Gut Microbial Alterations in Antepartum and Postpartum Women

Background: Imbalances in gut microbiota composition are linked to hypertension, host metabolic abnormalities, systemic inflammation, and other conditions. In the present study, we examined the changes of gut microbiota in women with early-onset preeclampsia (PE) and in normotensive, uncomplicated pregnant women during late pregnancy and at 1 and 6 weeks postpartum.

Methods: Gut microbiota profiles of women with PE and healthy pregnant women in the third trimester and at 1 and 6 weeks postpartum were assessed by 16S rRNA gene amplicon sequencing. Plasma levels of interleukin-6 (IL-6), intestinal fatty acid-binding protein (I-FABP), zonulin, and lipopolysaccharide (LPS) were measured in the third trimesters.

Results: At the genus level, 8 bacterial genera were significantly enriched in the antepartum samples of PE patients compared to healthy controls, of which Blautia, Ruminococcus2, Bilophila, and Fusobacterium represented the major variances in PE microbiomes. Conversely, 5 genera, including Faecalibacterium, Gemmiger, Akkermansia, Dialister, and Methanobrevibacter, were significantly depleted in antepartum PE samples. Maternal blood pressure and liver enzyme levels were positively correlated to the PE-enriched genera such as Anaerococcus, Ruminococcus2, Oribacterium, and Bilophila, while the fetal features (e.g., Apgar score and newborn birth weight) were positively correlated with PE-depleted genera and negatively correlated with PE-enriched genera. Moreover, maternal blood IL-6 level was positively associated with gut Bilophila and Oribacterium, whereas LPS level was negatively associated with Akkermansia. In terms of postpartum women, both the gut microbial composition and the PE-associated microbial alterations were highly consistent with those of the antepartum women.

Conclusion: PE diagnosed in the third trimester of pregnancy is associated with a disrupted gut microbiota composition compared with uncomplicated pregnant women, which are associated with maternal clinical features (blood pressure level and liver dysfunction) and newborn birth weight. Moreover, these antepartum alterations in gut microbiota persisted 6 weeks postpartum.

Update on Gaseous Signaling Molecules Nitric Oxide and Hydrogen Sulfide: Strategies to Capture their Functional Activity for Human Therapeutics

Discovery of the production of gaseous molecules, such as nitric oxide and hydrogen sulfide, within the human body began a new concept in cellular signaling. Over the past 30 years, these molecules have been investigated and found to have extremely important beneficial effects in numerous chronic diseases. Gaseous signaling molecules that diffuse in three dimensions apparently contradict the selectivity and specificity afforded by normal ligand receptor binding and activation. This new concept has also created hurdles in the development of safe and efficacious drug therapy based on these molecules. Mechanisms involving formation of more stable intermediates and second messengers allow for new strategies for safe and effective delivery of these molecules for human disease. The purpose of this review is to highlight the biologic effects of nitric oxide and hydrogen sulfide, their seemingly indistinguishable effects, and how these molecules can be safely harnessed for drug development and precursors or substrates administered for human consumption through applied physiology.

Endocrine organs of cardiovascular diseases: Gut microbiota

Gut microbiota (GM) is a collection of bacteria, fungi, archaea, viruses and protozoa, etc. They inhabit human intestines and play an essential role in human health and disease. Close information exchange between the intestinal microbes and the host performs a vital role in digestion, immune defence, nervous system regulation, especially metabolism, maintaining a delicate balance between itself and the human host. Studies have shown that the composition of GM and its metabolites are firmly related to the occurrence of various diseases. More and more researchers have demonstrated that the intestinal microbiota is a virtual 'organ' with endocrine function and the bioactive metabolites produced by it can affect the physiological role of the host. With deepening researches in recent years, clinical data indicated that the GM has a significant effect on the occurrence and development of cardiovascular diseases (CVD). This article systematically elaborated the relationship between metabolites of GM and its effects, the relationship between intestinal dysbacteriosis and cardiovascular risk factors, coronary heart disease, myocardial infarction, heart failure and hypertension and the possible pathogenic mechanisms. Regulating the GM is supposed to be a potential new therapeutic target for CVD.

Colonic Delivery of H2S Donors for Studying Cardiovascular Effects of H2S in Rats

There is evidence that H₂S produced in the colon may contribute to the control of the circulatory system. This chapter describes a technique of cardiovascular measurements in anesthetized rats subjected to intracolonic administration of H₂S donor. The intracolonic administration is performed via polyurethane catheter inserted per rectum into the colon.

In Vivo Measurement of H2S, Polysulfides, and "SSNO- Mix"-Mediated Vasoactive Responses and Evaluation of Ten Hemodynamic Parameters from Rat Arterial Pulse Waveform

The chapter describes protocols and pitfalls in in vivo studies of drug effects on anesthetized rats. It focuses on the preparation of Na₂S, Na₂S₄, and "SSNO^- mix" solutions for rat intravenous administration, surgical preparation of jugular vein for drug administration, and preparation of carotid and tail arteries for recording of arterial pulse waveform (APW) at high resolution. It describes evaluation of ten hemodynamic parameters from APW and measurement of apparent pulse wave velocity.

Hydrogen Sulfide: A Therapeutic Option in Systemic Sclerosis

Systemic sclerosis (SSc) is a lethal disease that is characterized by auto-immunity, vascular injury, and progressive fibrosis of multiple organ systems. Despite the fact that the exact etiology of SSc remains unknown, oxidative stress has been associated with a large range of SSc-related complications. In addition to the well-known detrimental properties of reactive oxygen species (ROS), gasotransmitters (e.g., nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S)) are also thought to play an important role in SSc. Accordingly, the diverse physiologic actions of NO and CO and their role in SSc have been previously studied. Recently, multiple studies have also shown the importance of the third gasotransmitter H₂S in both vascular physiology and pathophysiology. Interestingly, homocysteine (which is converted into H₂S through the transsulfuration pathway) is often found to be elevated in SSc patients; suggesting defects in the transsulfuration pathway. Hydrogen sulfide, which is known to have several effects, including a strong antioxidant and vasodilator effect, could potentially play a prominent role in the initiation and progression of vasculopathy. A better understanding of the actions of gasotransmitters, like H₂S, in the development of SSc-related vasculopathy, could help to create early interventions to attenuate the disease course. This paper will review the role of H₂S in vascular (patho-)physiology and potential disturbances in SSc. Moreover, current data from experimental animal studies will be reviewed. Lastly, we will evaluate potential interventional strategies.

An In Vivo Method for Evaluating the Gut-Blood Barrier and Liver Metabolism of Microbiota Products

The gut-blood barrier (GBB) controls the passage of nutrients, bacterial metabolites and drugs from intestinal lumen to the bloodstream. The GBB integrity is disturbed in gastrointestinal, cardiovascular and metabolic diseases, which may result in easier access of biologically active compounds, such as gut bacterial metabolites, to the bloodstream. Thus, the permeability of the GBB may be a marker of both intestinal and extraintestinal diseases. Furthermore, the increased penetration of bacterial metabolites may affect the functioning of the entire organism. Commonly used methods for studying the GBB permeability are performed ex vivo. The accuracy of those methods is limited, because the functioning of the GBB depends on intestinal blood flow. On the other hand, commonly used in vivo methods may be biased by liver and kidney performance, as those methods are based on evaluation of urine or/and peripheral blood concentrations of exogenous markers. Here, we present a direct measurement of GBB permeability in rats using an in vivo method based on portal blood sampling, which preserves intestinal blood flow and is virtually not affected by the liver and kidney function. Polyurethane catheters are inserted into the portal vein and inferior vena cava just above the hepatic veins confluence. Blood is sampled at baseline and after administration of a selected marker into a desired part of the gastrointestinal tract. Here, we present several applications of the method including (1) evaluation of the colon permeability to TMA, a gut bacterial metabolite, (2) evaluation of liver clearance of TMA, and (3) evaluation of a gut-portal blood-liver-peripheral blood pathway of gut bacteria-derived short-chain fatty acids. Furthermore, the protocol may also be used for tracking intestinal absorption and liver metabolism of drugs or for measurements of portal blood pressure.

High-protein diets for weight management: Interactions with the intestinal microbiota and consequences for gut health. A position paper by the my new gut study group

BACKGROUND & AIMS

This review examines to what extent high-protein diets (HPD), which may favor body weight loss and improve metabolic outcomes in overweight and obese individuals, may also impact the gut environment, shaping the microbiota and the host-microbe (co)metabolic pathways and products, possibly affecting large intestine mucosa homeostasis.

METHODS

PubMed-referenced publications were analyzed with an emphasis on dietary intervention studies involving human volunteers in order to clarify the beneficial vs. deleterious effects of HPD in terms of both metabolic and gut-related health parameters; taking into account the interactions with the gut microbiota.

RESULTS

HPD generally decrease body weight and improve blood metabolic parameters, but also modify the fecal and urinary contents in various bacterial metabolites and co-metabolites. The effects of HPD on the intestinal microbiota composition appear rather heterogeneous depending on the type of dietary intervention. Recently, HPD consumption was shown to modify the expression of genes playing key roles in homeostatic processes in the rectal mucosa, without evidence of intestinal inflammation. Importantly, the effects of HPD on the gut were dependent on the protein source (i.e. from plant or animal sources), a result which should be considered for further investigations.

CONCLUSION

Although HPD appear to be efficient for weight loss, the effects of HPD on microbiota-derived metabolites and gene expression in the gut raise new questions on the impact of HPD on the large intestine mucosa homeostasis leading the authors to recommend some caution regarding the utilization of HPD, notably in a recurrent and/or long-term ways.

Disparate effects of antibiotics on hypertension

Gut microbiota are associated with a variety of complex polygenic diseases. The usage of broad-spectrum antibiotics by patients affected by such diseases is an important environmental factor to consider, because antibiotics, which are widely prescribed to curb pathological bacterial infections, also indiscriminately eliminate gut commensal microbiota. However, the extent to which antibiotics reshape gut microbiota and per se contribute to these complex diseases is understudied. Because genetics play an important role in predisposing individuals to these modern diseases, we hypothesize that the extent to which antibiotics influence complex diseases depends on the host genome and metagenome. The current study tests this hypothesis in the context of hypertension, which is a serious risk factor for cardiovascular diseases. A 3 × 2 factorial design was used to test the blood pressure (BP) and microbiotal effects of three different antibiotics, neomycin, minocycline, and vancomycin, on two well-known, preclinical, genetic models of hypertension, the Dahl salt-sensitive (S) rat and the spontaneously hypertensive rat (SHR), both of which develop hypertension, but for different genetic reasons. Regardless of the class, oral administration of antibiotics increased systolic blood pressure of the S rat, while minocycline and vancomycin, but not neomycin, lowered systolic blood pressure in the SHR. These disparate BP effects were accompanied by significant alterations in gut microbiota. Our study highlights the need to consider an individualized approach for the usage of antibiotics among hypertensives, as their BP could be affected differentially based on their individual genetic and microbiotal communities.

Gut Microbiome and Cardiovascular Diseases

Recent evidence has suggested that the gut microbiome is involved in human health and diseases, such as inflammatory bowel disease, liver cirrhosis, rheumatoid arthritis, and type 2 diabetes. Cardiovascular diseases, which are associated with high morbidity and mortality across the world, are no exception. Increasing evidence has suggested a strong relationship between the gut microbiome and the progression of cardiovascular diseases. We first reported such a relationship with coronary artery disease two years ago. Next-generation sequencing techniques, together with bioinformatics technology, constantly and dramatically expand our knowledge of the complex human gut bacterial ecosystem and reveal the exact role of this bacterial ecosystem in cardiovascular diseases via the functional analysis of the gut microbiome. Such knowledge may pave the way for the development of further diagnostics and therapeutics for prevention and management of cardiovascular diseases. The aim of the current review is to highlight the relationship between the gut microbiome and their metabolites, and the development of cardiovascular diseases by fostering an understanding of recent studies.

Altered microRNA regulation of short chain fatty acid receptors in the hypertensive kidney is normalized with hydrogen sulfide supplementation

Hypertension affects nearly one third of the adult US population and is a significant risk factor for chronic kidney disease (CKD). An expanding body of recent studies indicates that gut microbiome has crucial roles in regulating physiological processes through, among other mechanisms, one mode of short chain fatty acids (SCFA) and their target receptors. In addition, these SCFA receptors are potential targets of regulation by host miRNAs, however, the mechanisms through which this occurs is not clearly defined. Hydrogen sulfide (H₂S) is an important gasotransmitter involved in multiple physiological processes and is known to alleviate adverse effects of hypertension such as reducing inflammation in the kidney. To determine the role of host microRNAs in regulating short chain fatty acid receptors in the kidney as well as the gut, C57BL/6J wild-type mice were treated with or without Ang-II and H₂S donor GYY4137 (GYY) for 4 weeks to assess whether GYY would normalize adverse effects observed in hypertensive mice and whether this was in part due to altered gut microbiome composition. We observed several changes of SCFA receptors, including Olfr78, Gpr41/43 and predicted microRNA regulators in the kidney among the different treatments. Increased expression of inflammatory markers Il6 and Rorc2, along with Tgfβ, were found in the hypertensive kidney. The glomerular filtration rate (GFR) was improved in mice treated with Ang-II + GYY compared with Ang-II only, indicating improved kidney function. The Erysipelotrichia class of bacteria, linked with high fat diets, was enriched in hypertensive animals but reduced with GYY supplementation. These data point towards a role for miRNA regulation of SCFA receptors in hypertensive kidney and are normalized by H₂S supplementation.

Colonic indole, gut bacteria metabolite of tryptophan, increases portal blood pressure in rats

Portal hypertension (PH) is a potentially life-threatening condition. We investigated the effects of indole and dietary tryptophan, a substrate for gut bacterial production of indole, on portal blood pressure (PBP), portal blood flow (PBF), and arterial blood pressure (ABP) in Sprague-Dawley rats (SD) and SD with PH induced by liver cirrhosis (SD-PH). Hemodynamics were recorded in anesthetized male 28-wk-old SD and SD-PH at baseline and after the administration of either a vehicle or indole into the colon. Blood levels of tryptophan and its bacterial metabolites were evaluated using chromatography coupled with mass spectrometry. Indole at lower doses increased PBP and PBF. Indole at higher doses produced a transient increase in PBP, which was accompanied by a decrease in ABP. Portal blood levels of indole, indole-3-propionic, indole-3-lactic, and indole-3-acetic acids were higher in SD-PH, suggesting an increased gut-blood barrier permeability. Rats on a tryptophan-rich diet showed a significantly higher PBP and portal blood level of indoles than rats on a tryptophan-free diet. In conclusion, a tryptophan-rich diet and intracolonic indole increase PBP and portal blood level of indole. Rats with PH show an increased penetration of indoles from the colon to the circulation. Intracolonic indole production may be of therapeutic importance in PH.