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

Introduction: Increased plasma trimethylamine oxide (TMAO) is observed in cardiovascular and metabolic diseases, originating from the gut microbiota product, trimethylamine (TMA), via flavin-containing monooxygenases (FMOs)-dependent oxidation. Numerous studies have investigated the association between plasma TMAO and various pathologies, yet limited knowledge exists regarding tissue concentrations of TMAO, TMAO precursors, and interspecies variability. Methods: Chromatography coupled with mass spectrometry was employed to evaluate tissue concentrations of TMAO and its precursors in adult male mice, rats, and guinea pigs. FMO mRNA and protein levels were assessed through PCR and Western blot, respectively. Results: Plasma TMAO levels were similar among the studied species. However, significant differences in tissue concentrations of TMAO were observed between mice, rats, and guinea pigs. The rat renal medulla exhibited the highest TMAO concentration, while the lowest was found in the mouse liver. Mice demonstrated significantly higher plasma TMA concentrations compared to rats and guinea pigs, with the highest TMA concentration found in the mouse renal medulla and the lowest in the rat lungs. FMO5 exhibited the highest expression in mouse liver, while FMO3 was highly expressed in rats. Guinea pigs displayed low expression of FMOs in this tissue. Conclusion: Despite similar plasma TMAO levels, mice, rats, and guinea pigs exhibited significant differences in tissue concentrations of TMA, TMAO, and FMO expression. These interspecies variations should be considered in the design and interpretation of experimental studies. Furthermore, these findings may suggest a diverse importance of the TMAO pathway in the physiology of the evaluated species. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hypertension leads to water-electrolyte disturbances and end-organ damage. Betaine is an osmolyte protecting cells against electrolyte imbalance and osmotic stress, particularly in the kidneys. This study aimed to evaluate tissue levels and hemodynamic and renal effects of betaine in normotensive and hypertensive rats. Betaine levels were assessed using high-performance liquid chromatography-mass spectrometry (HPLC-MS) in normotensive rats (Wistar-Kyoto, WKYs) and Spontaneously Hypertensive rats (SHRs), a model of genetic hypertension. Acute effects of IV betaine on blood pressure, heart rate, and minute diuresis were evaluated. Gene and protein expression of chosen kidney betaine transporters (SLC6a12 and SLC6a20) were assessed using real-time PCR and Western blot. Compared to normotensive rats, SHRs showed significantly lower concentration of betaine in blood serum, the lungs, liver, and renal medulla. These changes were associated with higher urinary excretion of betaine in SHRs (0.20 ± 0.04 vs. 0.09 ± 0.02 mg/ 24h/ 100g b.w., p = 0.036). In acute experiments, betaine increased diuresis without significantly affecting arterial blood pressure. The diuretic response was greater in SHRs than in WKYs. There were no significant differences in renal expression of betaine transporters between WKYs and SHRs. Increased renal excretion of betaine contributes to decreased concentration of the protective osmolyte in tissues of hypertensive rats. These findings pave the way for studies evaluating a causal relation between depleted betaine and hypertensive organ damage, including kidney injury. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) is one of the gaseous transmitters which play a very important role in the regulation of the circulatory system. Decreased NO availability is associated with hypertension, cardiovascular and kidney diseases. Endogenous NO is generated enzymatically by nitric oxide synthase (NOS) depending on the availability of the substrate, cofactors, or presence/absence of inhibitors, such as asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA). The objective of this study was to evaluate the potential relationship between NO level in rat tissues (heart and kidneys) and the concentrations of endogenous metabolites related to NO in plasma and urine. The experiment was carried out with 16- and 60-week-old male Wistar Kyoto (WKY) and age-matched male Spontaneously Hypertensive Rats (SHR). NO level in tissue homogenates was determined by the colorimetric method. RT-qPCR was used to verify the expression of the eNOS (endothelial NOS) gene. Plasma and urine concentrations of arginine, ornithine, citrulline, and dimethylarginines were examined by the UPLC-MS/MS method. 16-week-old WKY rats had the highest tissue NO and plasma citrulline levels. Furthermore, 16-week-old WKY rats showed higher urinary excretion of ADMA/SDMA compared to other experimental groups, however, plasma concentrations of arginine, ADMA, and SDMA were comparable between the groups. In conclusion, our research shows that hypertension and aging decrease tissue NO levels and are associated with reduced urinary excretion of NOS inhibitors, i.e., ADMA and SDMA. [ABSTRACT FROM AUTHOR]

Introduction: Plasma concentrations of gut microbial metabolites are associated with cardiomyocyte viability and platelet reactivity. We hypothesized that increased concentrations of gut metabolites may predict major adverse cardiac and cerebrovascular events (MACCE) after acute myocardial infarction (AMI). Aim: The primary objective of this study was to evaluate the association between elevated plasma concentrations of gut metabolites and MACCE after AMI. Material and methods: We compared plasma concentrations of gut metabolites (trimethylamine-N-oxide (TMAO) and indoxyl sulphate (IS)) and platelet reactivity in 57 patients with AMI and 27 healthy controls. We assessed the predictive value of gut metabolites for MACCE (stroke, recurrent AMI, death) over a median of 3.5-years. Results: The concentrations of TMAO and IS did not differ between AMI patients and controls. The concentrations of TMAO and IS were higher in patients who developed MACCE than in those who did not (p = 0.015 for all). The concentration of TMAO was the only independent predictor of MACCE in a multivariate analysis (OR = 35.041, 95% CI: 1.269-967.307, p = 0.036). Patients with the concentration of TMAO and indoxyl sulphate above the cut-off value predictive of MACCE had higher platelet activity (p = 0.149 for all). Conclusions: Increased plasma concentration of TMAO is an independent predictor of MACCE and may contribute to post-AMI cardiac dysfunction. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: High caloric diet and lack of physical activity are considered main causes of NAFLD, and a change in the diet is still the only effective treatment of this disease. However, molecular mechanism of the effectiveness of diet change in treatment of NAFLD is poorly understood. We aimed to assess the involvement of epigenetic mechanisms of gene expression regulation in treatment of NAFLD. Eighteen participants with medium- to high-grade steatosis were recruited and trained to follow the Mediterranean diet modified to include fibre supplements. At three timepoints (baseline, after 30 and 60 days), we evaluated adherence to the diet and measured a number of physiological parameters such as anthropometry, blood and stool biochemistry, liver steatosis and stiffness. We also collected whole blood samples for genome-wide methylation profiling and histone acetylation assessment. Results: The diet change resulted in a decrease in liver steatosis along with statistically significant, but a minor change in BMI and weight of our study participants. The epigenetic profiling of blood cells identified significant genome-wide changes of methylation and acetylation with the former not involving regions directly regulating gene expression. Most importantly, we were able to show that identified blood methylation changes occur also in liver cells of NAFLD patients and the machine learning-based classifier that we build on those methylation changes was able to predict the stage of liver fibrosis with ROC AUC = 0.9834. Conclusion: Methylomes of blood cells from NAFLD patients display a number of changes that are most likely a consequence of unhealthy diet, and the diet change appears to reverse those epigenetic changes. Moreover, the methylation status at CpG sites undergoing diet-related methylation change in blood cells stratifies liver biopsies from NAFLD patients according to fibrosis grade. [ABSTRACT FROM AUTHOR]

Background: Trimethylamine oxide (TMAO) is a biomarker in cardiovascular and renal diseases. TMAO originates from the oxidation of trimethylamine (TMA), a product of gut microbiota and manufacturing industries-derived pollutant, by flavin monooxygenases (FMOs). The effect of chronic exposure to TMA on cardiovascular and renal systems is undetermined.Methods: Metabolic, hemodynamic, echocardiographic, biochemical and histopathological evaluations were performed in 12-week-old male SPRD rats receiving water (controls) or TMA (200 or 500 µM/day) in water for 18 weeks. TMA and TMAO levels, the expression of FMOs and renin-angiotensin system (RAS) genes were evaluated in various tissues.Results: In comparison to controls, rats receiving high dose of TMA had significantly increased arterial systolic blood pressure (126.3 ± 11.4 vs 151.2 ± 19.9 mmHg; P = 0.01), urine protein to creatinine ratio (1.6 (1.5; 2.8) vs 3.4 (3.3; 4.2); P = 0.01), urine KIM-1 levels (2338.3 ± 732.0 vs. 3519.0 ± 953.0 pg/mL; P = 0.01), and hypertrophy of the tunica media of arteries and arterioles (36.61 ± 0.15 vs 45.05 ± 2.90 µm, P = 0.001 and 18.44 ± 0.62 vs 23.79 ± 2.60 µm, P = 0.006; respectively). Mild degeneration of renal bodies with glomerulosclerosis was also observed. There was no significant difference between the three groups in body weight, water-electrolyte balance, echocardiographic parameters and RAS expression. TMA groups had marginally increased 24 h TMA urine excretion, whereas serum levels and 24 h TMAO urine excretion were increased up to 24-fold, and significantly increased TMAO levels in the liver, kidneys and heart. TMA groups had lower FMOs expression in the kidneys.Conclusions: Chronic exposure to TMA increases blood pressure and increases markers of kidney damage, including proteinuria and KIM-1. TMA is rapidly oxidized to TMAO in rats, which may limit the toxic effects of TMA on other organs. [ABSTRACT FROM AUTHOR]

Evidence suggests that microbiota-derived metabolites, including short-chain fatty acids (SCFAs) and trimethylamine-oxide (TMAO), affect the course of diabetic multiorgan pathology. We hypothesized that diabetes activates the intestinal renin–angiotensin system (RAS), contributing to gut pathology. Twelve-week-old male rats were divided into three groups: controls, diabetic (streptozotocin-induced) and diabetic treated with enalapril. Histological examination and RT-qPCR were performed to evaluate morphology and RAS expression in the jejunum and the colon. SCFA and TMAO concentrations in stools, portal and systemic blood were evaluated. In comparison to the controls, the diabetic rats showed hyperplastic changes in jejunal and colonic mucosa, increased plasma SCFA, and slightly increased plasma TMAO. The size of the changes was smaller in enalapril-treated rats. Diabetic rats had a lower expression of Mas receptor (MasR) and angiotensinogen in the jejunum whereas, in the colon, the expression of MasR and renin was greater in diabetic rats. Enalapril-treated rats had a lower expression of MasR in the colon. The expression of AT1a, AT1b, and AT2 receptors was similar between groups. In conclusion, diabetes produces morphological changes in the intestines, increases plasma SCFA, and alters the expression of renin and MasR. These alterations were reduced in enalapril-treated rats. Future studies need to evaluate the clinical significance of intestinal pathology in diabetes. [ABSTRACT FROM AUTHOR]

The human gastrointestinal tract is inhabited by the largest microbial community within the human body consisting of trillions of microbes called gut microbiota. The normal flora is the site of many physiological functions such as enhancing the host immunity, participating in the nutrient absorption and protecting the body against pathogenic microorganisms. Numerous investigations showed a bidirectional interplay between gut microbiota and many organs within the human body such as the intestines, the lungs, the brain, and the skin. Large body of evidence demonstrated, more than a decade ago, that the gut microbial alteration is a key factor in the pathogenesis of many local and systemic disorders. In this regard, a deep understanding of the mechanisms involved in the gut microbial symbiosis/dysbiosis is crucial for the clinical and health field. We review the most recent studies on the involvement of gut microbiota in the pathogenesis of many diseases. We also elaborate the different strategies used to manipulate the gut microbiota in the prevention and treatment of disorders. The future of medicine is strongly related to the quality of our microbiota. Targeting microbiota dysbiosis will be a huge challenge. [ABSTRACT FROM AUTHOR]

Recent evidence suggests that gut bacteria-derived metabolites interact with the cardiovascular system and alter blood pressure (BP) in mammals. Here, we evaluated the effect of indole-3-propionic acid (IPA), a gut bacteria-derived metabolite of tryptophan, on the circulatory system. Arterial BP, electrocardiographic, and echocardiographic (ECHO) parameters were recorded in male, anesthetized, 12-wk-old Wistar-Kyoto rats at baseline and after intravenous administration of either IPA or vehicle. In additional experiments, rats were pretreated with prazosin or pentolinium to evaluate the involvement of the autonomic nervous system in cardiovascular responses to IPA. IPA's concentrations were measured using ultra-high performance liquid chromatography tandem mass spectrometry. The reactivity of endothelium-intact and -denuded mesenteric resistance arteries was tested. Cells' viability and lactate dehydrogenase (LDH) cytotoxicity assays were performed on cultured cardiomyocytes. IPA increased BP with a concomitant bradycardic response but no significant change in QTc interval. The pretreatment with prazosin and pentolinium reduced the hypertensive response. ECHO showed increased contractility of the heart after the administration of IPA. Ex vivo, IPA constricted predilated and endothelium- denuded mesenteric resistance arteries and increased metabolic activity of cardiomyocytes. IPA increases BP via cardiac and vascular mechanisms in rats. Furthermore, IPA increases cardiac contractility and metabolic activity of cardiomyocytes. Our study suggests that IPA may act as a mediator between gut microbiota and the circulatory system. [ABSTRACT FROM AUTHOR]

Gut microbiota is a potent biological modulator of many physiological and pathological states. The renin-angiotensin system (RAS), including the local gastrointestinal RAS (GI RAS), emerges as a potential mediator of microbiota-related effects. The RAS is involved in cardiovascular system homeostasis, water-electrolyte balance, intestinal absorption, glycemic control, inflammation, carcinogenesis, and aging-related processes. Ample evidence suggests a bidirectional interaction between the microbiome and RAS. On the one hand, gut bacteria and their metabolites may modulate GI and systemic RAS. On the other hand, changes in the intestinal habitat caused by alterations in RAS may shape microbiota metabolic activity and composition. Notably, the pharmacodynamic effects of the RAS-targeted therapies may be in part mediated by the intestinal RAS and changes in the microbiome. This review summarizes studies on gut microbiota and RAS physiology. Expanding the research on this topic may lay the foundation for new therapeutic paradigms in gastrointestinal diseases and multiple systemic disorders. [ABSTRACT FROM AUTHOR]

Purpose: Acute myocardial infarction (AMI) is the leading cause of morbidity and mortality worldwide. Damage to the endothelium is the earliest event in atherothrombosis, including AMI. Nitric oxide (NO), an endothelium-derived compound, protects the vasculature from damage. This study evaluated whether an association exists between plasma concentration of endogenous NO-related pathway metabolites linked to AMI and major adverse cardiovascular events (MACE) after AMI. Methods: We compared plasma concentrations of NO-related pathway metabolites in patients after AMI (n=60) and healthy controls (n=27) and investigated the prognostic value of these metabolites for post-AMI MACE development over a median of 3.5-years. In search of biomarkers, we compared plasma concentrations of dimethylarginines (ADMA, SDMA), citrulline, arginine and ornithine using ultra performance liquid chromatograph coupled with a mass spectrometer. Results: Patients after AMI had higher concentrations of dimethylarginines, compared to controls (p=0.0068, p< 0.0001, respectively). Conversely, the concentration of citrulline was lower in the AMI group (p=0.0006). The concentration of SDMA was higher in patients who developed MACE than in those who did not (p=0.015). SDMA was the only independent predictor of MACE in multivariate analysis (p=0.023). There was an intermediate, negative correlation between plasma SDMA level and platelet reactivity (r=− 0.33, p=0.02). Conclusion: Plasma concentration of dimethylarginines differs between patients with AMI and healthy volunteers. The study's novel finding is that SDMA is an independent predictor of MACE during a 3.5 year follow-up period after AMI. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

It has been suggested that trimethylamine oxide (TMAO), a liver oxygenation product of gut bacteria-produced trimethylamine (TMA), is a marker of cardiovascular risk. However, mechanisms of the increase and biological effects of TMAO are obscure. Furthermore, the potential role of TMAO precursor, that is TMA, has not been investigated. We evaluated the effect of age, a cardiovascular risk factor, on plasma levels of TMA and TMAO, gut bacteria composition, gut-to-blood penetration of TMA, histological and hemodynamic parameters in 3-month-old and 18-month-old, male, Sprague-Dawley and Wistar-Kyoto rats. Cytotoxicity of TMA and TMAO was studied in human vascular smooth muscle cells. Older rats showed significantly different gut bacteria composition, a significantly higher gut-to-blood TMA penetration, and morphological and hemodynamic alterations in intestines. In vitro, TMA at concentration of 500 µmol/L (2-fold higher than in portal blood) decreased human vascular smooth muscle cells viability. In contrast, TMAO at 1,000-fold higher concentration than physiological one had no effect on human vascular smooth muscle cells viability. In conclusion, older rats show higher plasma level of TMA due to a "leaky gut". TMA but not TMAO affects human vascular smooth muscle cells viability. We propose that TMA but not TMAO may be a marker and mediator of cardiovascular risk. [ABSTRACT FROM AUTHOR]

Butyric acid (BA) is a short-chain fatty acid (SCFA) produced by gut bacteria in the colon. We hypothesized that colon-derived BA may affect hemodynamics. Arterial blood pressure (BP) and heart rate (HR) were recorded in anesthetized, male, 14-week-old Wistar rats. A vehicle, BA, or 3-hydroxybutyrate, an antagonist of SCFA receptors GPR41/43 (ANT) were administered intravenously (IV) or into the colon (IC). Reactivity of mesenteric (MA) and gracilis muscle (GMA) arteries was tested ex vivo. The concentration of BA in stools, urine, portal, and systemic blood was measured with liquid chromatography coupled with mass spectrometry. BA administered IV decreased BP with no significant effect on HR. The ANT reduced, whereas L-NAME, a nitric oxide synthase inhibitor, did not affect the hypotensive effect of BA. In comparison to BA administered intravenously, BA administered into the colon produced a significantly longer decrease in BP and a decrease in HR, which was associated with a 2–3-fold increase in BA colon content. Subphrenic vagotomy and IC pretreatment with the ANT significantly reduced the hypotensive effect. Ex vivo, BA dilated MA and GMA. In conclusion, an increase in the concentration of BA in the colon produces a significant hypotensive effect which depends on the afferent colonic vagus nerve signaling and GPR41/43 receptors. BA seems to be one of mediators between gut microbiota and the circulatory system. [ABSTRACT FROM AUTHOR]

New Findings: What is the central question of this study?'Leaky gut' has been found in intestinal and extra‐intestinal diseases. However, functional evaluation of intestinal permeability is not widely used as a diagnostic marker, possibly owing to significant limitations of currently used permeability assays. There is an unmet need for development of a new, non‐invasive test to assess intestinal function.What is the main finding and its importance?We show that an increased blood‐to‐stool ratio of the concentration of gut bacteria‐produced short‐chain fatty acids may be used as a marker of gut permeability. Our findings lay the groundwork for establishing a new, non‐invasive, risk‐free diagnostic tool in diseases associated with intestinal barrier malfunction, such as inflammatory bowel disease. Intestinal diseases, such as inflammatory bowel disease (IBD), are characterized by an impaired gut–blood barrier commonly referred to as 'leaky gut'. Therefore, functional evaluation of the gut–blood barrier is a promising diagnostic marker. We hypothesized that short‐chain fatty acids (SCFAs) produced by gut bacteria might serve as a marker in IBD. Animal experiments were performed on male Sprague–Dawley rats with acetic acid‐induced colitis and in sham control animals. The gut–blood barrier permeability was determined by assessing the ratios of the following: (i) portal blood concentration of SCFAs (Cp) to faecal concentration of SCFAs (Cf); (ii) systemic blood concentration of SCFAs (Cs) to faecal concentration of SCFAs (Cf); and (iii) Cp and Cs of fluorescein isothiocyanate (FITC)–dextran administered into the colon. As a clinical study, we evaluated Cs, Cf and the Cs/Cf ratio of SCFAs in six paediatric patients with IBD, assessed as mild/moderate/severe by the Paediatric Ulcerative Colitis Activity Index (PUCAI) and the Paediatric Crohn's Disease Activity Index (PCDAI) at the time of sample collection, and nine age‐matched healthy control subjects. Rats with histologically confirmed IBD had significantly increased ratios of Cp/Cf and Cs/Cf for SCFAs. This was positively correlated with the plasma FITC–dextran concentration. Likewise, IBD patients showed a significantly higher Cs/Cf ratio for SCFAs, including acetic, valeric, isocaproic, caproic and propionic acids, in comparison to control subjects. In conclusion, in the rats and in paediatric patients with IBD we found an increased blood‐to‐stool ratio of SCFAs, suggesting an increased gut‐to‐blood penetration of SCFAs. These findings pave the way for a new, non‐invasive diagnostic tool in IBD and other diseases accompanied by intestinal barrier malfunction. [ABSTRACT FROM AUTHOR]

PURPOSE Trimethylamine oxide (TMAO) is an osmolyte used by saltwater animals to protect their cells from hyperosmotic environment. Here, we studied if TMAO may exert beneficial effect in dry eye disease (DED) which results from hyperosmotic tear film. MATERIALS AND METHODS Female, 12-week-old Sprague–Dawley rats underwent either removal of extra- and infraorbital lacrimal glands (dry eye group) or sham surgery (sham group). A 1-week topical treatment with either 0.9% NaCl (control) or 1% TMAO in 0.9% NaCl solution was started 4 weeks after the surgery. Fluorescein score (FS), blink rate (BR), and histological picture of cornea were assessed. RESULTS At baseline, corneas did not stain with fluorescein and there was no difference between the groups in BR. There was a significant increase in FS and BR after the removal of lacrimal glands (p < 0.0001 and p = 0.0003, respectively). Accordingly, the dry eye group showed significantly higher FS and BR than the sham group (p = 0.0003 and p = 0.0005, respectively). Treatment with TMAO but not with 0.9% NaCl significantly reduced FS and BR (p = 0.01 and p = 0.005, respectively); however, FS and BR did not return to baseline (p = 0.0045 and p = 0.0065, respectively). In comparison to the control group, treatment with TMAO did not affect epithelial thickness or the number of layers of epithelium layers. CONCLUSIONS We have found that in a rat model of DED, the topical treatment with TMAO improves clinical picture, however does not lead to the evident histopathological recovery. [ABSTRACT FROM AUTHOR]

Several studies have suggested negative effects of trimethylamine oxide (TMAO) on the circulatory system. However, a number of studies have shown protective functions of TMAO, a piezolyte and osmolyte, in animals exposed to high hydrostatic and/or osmotic stress. We evaluated the effects of TMAO treatment on the development of hypertension and its complications in male spontaneously hypertensive rats (SHRs) maintained on water (SHR-Water) and SHRs drinking TMAO water solution from weaning (SHR-TMAO). Wistar-Kyoto (WKY) rats were used as normotensive controls to discriminate between agedependent and hypertension-dependent changes. Telemetry measurements of blood pressure were performed in rats between the 7th and 16th weeks of life. Anesthetized rats underwent echocardiographic, electrocardiographic, and direct left ventricular end-diastolic pressure (LVEDP) measurements. Hematoxylin and eosin as well as van Gieson staining for histopathological evaluation were performed. Plasma TMAO measured by chromatography coupled with mass spectrometry was significantly higher in the SHR-Water group compared with the WKY group (~20%). TMAO treatment increased plasma TMAO by four- to fivefold and did not affect the development of hypertension in SHRs. Sixteen-week-old rats in the SHR-Water and SHR-TMAO groups (12-wk TMAO treatment) showed similar blood pressures, angiopathy, and cardiac hypertrophy. However, the SHRTMAO group had lower plasma NH2-terminal pro-B-type natriuretic peptide, LVEDP, and cardiac fibrosis. In contrast to age-matched WKY rats, 60-wk-old SHRs showed hypertensive angiopathy and heart failure with preserved ejection fraction. Compared with the SHR-Water group, the SHR-TMAO group (56-wk TMAO treatment) showed significantly lower plasma NH2-terminal pro-B-type natriuretic peptide and vasopressin, significantly lower LVEDP, and cardiac fibrosis. In conclusion, a four- to fivefold increase in plasma TMAO does not exert negative effects on the circulatory system. In contrast, increased dietary TMAO seems to reduce diastolic dysfunction in pressure-overloaded hearts in rats. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ample evidence suggests that H2S is an important biological mediator, produced by endogenous enzymes and microbiota. So far, several techniques including colorimetric methods, electrochemical analysis and sulfide precipitation have been developed for H2S detection. These methods provide sensitive detection, however, they are destructive for tissues and require tedious sequences of preparation steps for the analyzed samples. Here, we report synthesis of a new fluorescent probe for H2S detection, 4-methyl-2-oxo-2H-chromen-7-yl 5-azidopentanoate (1). The design of 1 is based on combination of two strategies for H2S detection, i.e., reduction of an azido group to an amine in the presence of H2S and intramolecular lactamization. Finally, we measured salivary H2S concentration in healthy, 18-40-year-old volunteers immediately after obtaining specimens. The newly developed self-immolative coumarin-based fluorescence probe (C15H15N3O4) showed high sensitivity to H2S detection in both sodium phosphate buffer at physiological pH and in saliva. Salivary H2S concentration in healthy volunteers was within a range of 1.641-7.124 µM. [ABSTRACT FROM AUTHOR]

Introduction: Increased plasma level of trimethylamine N-oxide (TMAO), a bacterial metabolite of choline, is associated with an increased cardiovascular risk. Indoxyl sulfate, a bacterial metabolite of tryptophan, is thought to be associated with higher mortality in cardiorenal syndrome. We hypothesized that enalapril, a well-established drug reducing cardiovascular mortality, may affect the plasma level of gut bacteria-derived metabolites and gut bacteria composition. Materials and methods: 14-16-week-old Wistar rats were maintained either on water (controls) or water solution of enalapril for two weeks (5.3 or 12.6 mg/kg b.w.). Blood plasma and urine were analyzed for the concentration of TMAO and indoxyl sulfate using liquid chromatography coupled with triple-quadrupole mass spectrometry. Gut bacteria composition was analyzed with 16S rRNA gene sequence analysis. Results: Rats treated with enalapril showed a significantly lower plasma TMAO level and a trend towards higher 24 h urine excretion of TMA and TMAO. Plasma indoxyl level was similar between the groups. There was no significant difference between the groups in gut bacteria composition. Conclusions: Enalapril decreases rat plasma TMAO, but does not affect the plasma level of indoxyl sulfate and gut bacteria composition. The enalapril-induced decrease in plasma TMAO level may be of therapeutic and diagnostic importance. [ABSTRACT FROM AUTHOR]

Background: It has been postulated that intraocular pressure, an important glaucoma risk factor, correlates positively with arterial blood pressure (blood pressure). However, results of experimental and clinical studies are often contradictory. It is hypothesized that, in some hypertensive patients, disturbances in intraocular pressure regulation may depend on biological effects of blood borne hormones underlying a particular type of hypertension, rather than on blood pressure level itself.Review: This review compares the effects of hormones on blood pressure and intraocular pressure, in order to identify a hormonal profile of hypertensive patients with an increased risk of intraocular pressure surge. The PUBMED database was searched to identify pre-clinical and clinical studies investigating the role of angiotensin II, vasopressin, adrenaline, noradrenaline, prostaglandins, and gaseous transmitters in the regulation of blood pressure and intraocular pressure.Results: Studies included in the review suggest that intraocular and blood pressures often follow a different pattern of response to the same hormone. For example, vasopressin increases blood pressure, but decreases intraocular pressure. In contrast, high level of nitric oxide decreases blood pressure, but increases intraocular pressure.Conclusions: Arterial hypertension is associated with altered levels of blood borne hormones. Contradicting results of studies on the relationship between arterial hypertension and intraocular pressure might be partially explained by diverse effects of hormones on arterial and intraocular pressures. Further studies are needed to evaluate if hormonal profiling may help to identify glaucoma-prone patients. [ABSTRACT FROM AUTHOR]

An increased blood trimethylamine N-oxide (TMAO) has emerged as a marker of cardiovascular mortality, however, the mechanisms of the increase are not clear. We evaluated if hypertension was associated with changes in the colon permeability to trimethylamine (TMA), a TMAO precursor. We did experiments on male, 24-26-week-old normotensive Wistar-Kyoto rats (WKY), spontaneously hypertensive rats (SHR) and SHR treated with enalapril, an antihypertensive drug (SHR-E). To check the colon permeability and liver TMA clearance, blood was collected from the portal vein and hepatic veins confluence, at baseline and after the intracolonic administration of TMA. Arterial blood pressure (BP) and intestinal blood flow (IBF) recordings and histological assessment of the colon were performed. SHR showed an increased gut-blood barrier permeability to TMA. Namely, at baseline SHR had a higher BP and portal blood TMA, but a lower IBF than WKY. After the intracolonic administration of TMA, SHR had a significantly higher portal blood TMA and higher TMA liver clearance than WKY. In SHR the arteriolar walls of the colon mucosa were significantly thicker than in WKY. Furthermore, SHR showed a significant decrease in the height of the mucosa. In contrast, SHR-E had lower portal blood TMA, lower BP and smaller thickness of arteriolar walls, but higher IBF than SHR, which indicates improved function of the gut-blood barrier in SHR-E. All groups had similar immunostaining of occludin and zonula occludens-1, markers of tight junctions. In conclusion, hypertensive rats show an increased permeability of the colon to TMA, which is accompanied by morphological and hemodynamic alterations in the colon. Therefore, cardiovascular diseases may be characterized by an increased permeability of the gut-blood barrier to bacterial metabolites such as TMA. [ABSTRACT FROM AUTHOR]

Aim: Several lines of evidence suggest that the pathogenesis of glaucoma may depend on an increased translaminar pressure gradient (TPG), the difference between intraocular and intracranial pressure (ICP), rather than on intraocular pressure (IOP) itself. It has also been suggested that high blood pressure might correlate with the incidence of glaucoma; however, the data are contradictory. Here, we studied the effect of arterial blood pressure and changes in body position on TPG in rats. Methods: Experiments were performed on anesthetized 15- to 16-week-old, male, spontaneously hypertensive rats (hypertensive rats,n = 10) and Wistar–Kyoto rats (normotensive rats,n = 10). Continuous recordings of intracranial and IOPs were performed before, during, and after changing the body position from horizontal to vertical. Results: At baseline, hypertensive rats had a significantly higher arterial blood pressure than normotensive rats, while intraocular and intracerebroventricular pressures and TPG did not differ between the groups. Changing the body position from horizontal to vertical produced a significant decrease in ICP, a nonsignificant decrease in IOP, and a significant increase in the TPG. There was no significant difference between normotensive and hypertensive rats in the pattern of changes in intraocular and intracerebroventricular pressures and TPG. Conclusions: Change in the body position from horizontal to vertical, but not hypertension, causes a significant increase in TPG in rats. If further studies confirm that TPG plays a role in the etiology of glaucoma, a vertical position and changes in the body position might be considered as debilitating factors. [ABSTRACT FROM AUTHOR]

The effect of renal denervation on the efficacy of antihypertensive drugs has not yet been elucidated. Twenty-week-old spontaneously hypertensive rats were treated with metoprolol, losartan, indapamide, or saline (controls) and assigned to renal denervation or a sham procedure. Acute hemodynamic measurements were performed ten days later. Series showing a significant interaction between renal denervation and the drugs were repeated with chronic telemetry measurements. In the saline series, denervated rats showed a significantly lower mean arterial blood pressure (blood pressure) than the sham-operated rats. In contrast, in the metoprolol series denervated rats showed a significantly higher blood pressure than sham rats. There were no differences in blood pressure between denervated and sham rats in the losartan and indapamide series. In chronic studies, a 4-week treatment with metoprolol caused a decrease in blood pressure. Renal denervation and sham denervation performed 10 days after the onset of metoprolol treatment did not affect blood pressure. Denervated rats showed markedly reduced renal nerve tyrosine hydroxylase levels. In conclusion, renal denervation decreases blood pressure in hypertensive rats. The hypotensive action of metoprolol, indapamide, and losartan is not augmented by renal denervation, suggesting the absence of synergy between renal denervation and the drugs investigated in this study. [ABSTRACT FROM AUTHOR]

Accumulating evidence suggests that gut bacteria play a role in homeostasis of the circulatory system in mammals. First, gut bacteria may affect the nervous control of the circulatory system via the sensory fibres of the enteric nervous system. Second, gut bacteria-derived metabolites may cross the gut-blood barrier and target blood vessels, the heart and other organs involved in the regulation of the circulatory system. A number of studies have shown that hydrogen sulfide (H2S) is an important biological mediator in the circulatory system. Thus far, research has focused on the effects of H2S enzymatically produced by cardiovascular tissues. However, some recent evidence indicates that H2S released in the colon may also contribute to the control of arterial blood pressure. Incidentally, sulfate-reducing bacteria are ubiquitous in mammalian colon, and H2S is just one among a number of molecules produced by the gut flora. Other gut bacteria-derived compounds that may affect the circulatory system include methane, nitric oxide, carbon monoxide, trimethylamine or indole. In this paper, we review studies that imply a role of gut microbiota and their metabolites, such as H2S, in circulatory system homeostasis. [ABSTRACT FROM AUTHOR]

Noninvasive hemodynamic measurements in rats require placing animals in restrainers. To minimize restraint stress-induced artifacts several habituation protocols have been proposed, however, the results are inconclusive. Here, we evaluated if a four-week habituation is superior to a shorter habituation, or no habituation. This is the first study comparing different habituation protocols with the use of four-week continuous telemetry measurements. We did the experiments on male, 16-week old, Sprague–Dawley rats. Continuous recordings of mean arterial blood pressure (MABP) and heart rate (HR) were made before and during habituation protocols. Rats were subjected either to control (four weeks of restraint-free recordings,n = 5) or two-week (seven restraints,n = 6) or four-week (14 restraints,n = 6) restraint sessions. The restraint protocols included placement of rats in the middle of the dark phase into plastic restrainers as used for tail-cuff measurements. Restraint lasted for 60 min, and was repeated every second day. Each restraint significantly increased MABP (by 15–25 mmHg) and HR (by 40–120 beats/min). Exposure to the restraint protocols decreased diurnal variation in MABP. There was no hemodynamic adaptation to repeated restraint, and no significant difference in hemodynamic response to restraint among controls, the two-week and the four-week groups. In conclusion, our study indicates that measurements in restrained rats are not likely being made without stress-induced changes in MABP. Moreover, in hemodynamic studies in repeatedly restrained rats longer habituation is not superior to shorter habituation. [ABSTRACT FROM PUBLISHER]

S-adenosyl- l-methionine (SAM) is an amino acid involved in a number of physiological processes in the nervous system. Some evidence suggests a therapeutic potential of SAM in hypertension. In this study we investigated the effect of intracerebroventricular (ICV) infusions of SAM on arterial blood pressure in rats. Mean arterial blood pressure (MABP) and heart rate (HR) were measured at baseline and during ICV infusion of either SAM or vehicle (aCSF; controls) in conscious, male normotensive Wistar Kyoto rats (WKY) and Spontaneously Hypertensive Rats (SHR). MABP and HR were not affected by the vehicle. WKY rats infused with SAM (10 μM, 100 μM and 1 mM) showed a biphasic hemodynamic response i.e., mild hypotension and bradycardia followed by a significant increase in MABP and HR. On the contrary, SHR infused with SAM showed a dose-dependent hypotensive response. In separate series of experiments, pretreatment with hexamethonium, a ganglionic blocker as well as pretreatment with glibenclamide, a K channel blocker reduced the hemodynamic effects of SAM. SAM may affect the nervous control of arterial blood pressure via the autonomic nervous system and K channel-dependent mechanisms. [ABSTRACT FROM AUTHOR]

Hypertension poses growing challenge for health policy-makers and doctors worldwide. Recently published results of Symplicity-III trial (HTN-3), the first blinded, randomized, multicenter study on the efficacy of renal denervation for the treatment of resistant hypertension did not show a significant reduction of BP in patients with resistant hypertension 6 months after renal-artery denervation, as compared with controls. In this paper we review clinical and experimental studies on renal denervation. In order to identify causes of inconsistent results in renal denervation studies we look at basic science support for renal denervation and at designs of clinical trials. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Summary [ABSTRACT FROM AUTHOR]

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A high-Na diet may lead to the development of hypertension in both humans and rats; however, the causes of Na intake in amounts greater than physiologically needed as well as the mechanisms whereby high-Na food elevates blood pressure are not clear. Therefore, we decided to test the hypothesis that a high-Na diet introduced after suckling affects Na intake, food preference, resting blood pressure and blood volume in adult rats. Male Wistar-Kyoto (WKY) rats, 4 weeks old, were divided into three groups and placed on either a high-Na (3·28%), a medium-Na (0·82%) or a regular diet (0·22%) with the same energy content for 8 weeks. Subsequently, food preference, resting arterial blood pressure, blood volume, plasma osmolality and Na blood level were evaluated. When offered a choice of diets, all the groups preferred the regular chow, and there was no significant difference in total Na intake between the groups. When the rats experienced the change from their initial chow to a new one with different Na content, they continued to eat the same amount of food. Body weight, resting arterial blood pressure, blood volume, plasma osmolality and Na blood level were comparable between the groups. In conclusion, the results show that a high-Na diet introduced immediately after suckling does not affect Na preference and Na intake in adult WKY rats. Furthermore, the findings provide evidence that both blood volume and arterial blood pressure are highly protected in normotensive rats on a high-Na diet. [ABSTRACT FROM PUBLISHER]

BackgroundAngiotensin II (Ang II) plays a pivotal role in regulation of the circulatory system. Activation of angiotensin type 1 (AT1) receptors in several brain regions leads to an increase in blood pressure. Accumulating data suggest that statins affect the peripheral action of Ang II; however, their central effects are poorly recognized. The study was aimed to determine whether simvastatin interferes with the brain angiotensin system in rats.MethodsTwelve-week-old, Sprague-Dawley rats were divided into two groups. Untreated group was maintained on tap water, whereas simvastatin group received water containing simvastatin for the following 12 weeks. Later, both groups were subjected to experiments in which mean arterial blood pressure (MABP) and heart rate (HR) were recorded during baseline conditions and after intracerebroventricular (ICV) infusion of either saline, Ang II, or losartan.ResultsICV infusion of Ang II elicited a significant increase in MABP in both groups. However, the pressor response in the simvastatin group was significantly smaller than that in the untreated group. There was no significant change in MABP after ICV infusion of saline or losartan. ICV infusion of Ang II elicited a significant increase in HR in the untreated group but not in the simvastatin group. There was no significant change in HR after ICV infusion of saline or losartan.ConclusionsThe results show that simvastatin reduces the pressor response to ICV-infused Ang II in rats. This implies that statins may affect the central regulation of the circulatory system, especially when the brain angiotensin system is stimulated.American Journal of Hypertension 2010; doi:10.1038/ajh.2010.103 [ABSTRACT FROM AUTHOR]

The purpose of the present study was to elucidate if rats with myocardial infarction manifest altered responsiveness to central cardiovascular effects of low doses of angiotensin II (ANG II), and if ANG II and vasopressin (VP) cooperate in the central regulation of cardiovascular functions at rest and during stress. Conscious Sprague-Dawley rats with myocardial infarction induced by left coronary artery ligation, or sham-ligated (SL) controls were infused intracerebroventricularly with artificial cerebrospinal fluid (aCSF), ANG II, ANG II + VP or ANG II + V1a receptor antagonist (V1ANT) 4 weeks after cardiac surgery. In the infarcted but not in the SL rats, the resting mean arterial blood pressure (MABP) was significantly elevated by infusions of ANG II and ANG II + VP, while infusion of ANG II + V1ANT was not effective. During administration of aCSF, the pressor, and tachycardic responses to an air-jet stressor were significantly greater in the infarcted than in the SL rats. In the SL rats, the pressor responses to the stressor were significantly greater during infusions of ANG II, ANG II + VP and ANG II + V1ANT than during infusion of aCSF. The tachycardic response in the SL rats was enhanced only by the combined infusion of ANG II + VP. In the infarcted rats, the pressor and the tachycardic responses to the stressor were similar in all groups. It is concluded that: (1) under resting conditions the infarcted rats manifest sensitisation to the central pressor effect of ANG II and that this effect depends on concomitant stimulation of V1a VP receptors, (2) central ANG II may enhance the pressor response to an alarming stressor in the SL rats through an action which does not depend on the concomitant stimulation of V1a receptors, (3) the cooperative action of ANG II and VP is required for intensification of the tachycardic response to the alarming stressor in the SL rats and (4) exaggeration of the cardiovascular responses to the alarming stressor in the infarcted rats cannot be further augmented by an additional stimulation of central ANG II receptors or combined stimulation of ANG II and VP receptors. [ABSTRACT FROM AUTHOR]