Aromatic Microbial Metabolites Research Articles

Sepsis-Associated Metabolites and Their Biotransformation by Intestinal Microbiota

High concentration of sepsis-associated aromatic microbial metabolites (AMM) stands as a prognostically unfavorable factor, indicating the progression of multiple organ dysfunction and an increased risk of death in patients with sepsis and septic shock. This study is based on a hypothesis that excess of sepsis-associated AMM in patients with sepsis is caused by metabolic alterations (dysfunction) in the intestinal microbiota.The aim of this study was to compare the potential of normobiota and pathobiota to bio-transform sepsis-associated metabolites of aromatic amino acids tyrosine and phenylalanine, such as phenyllactic acid(PhLA) and 4-hydroxyphenyllactic acid (4-HPhLA).Materials and methods. Samples of intestinal contents of patients with septic shock (N=10, pathobiota) and healthy volunteers (N=9, normobiota) were placed in test tubes with the omnipurpose thioglycol medium. The clinical model of excessive inflow of sepsis-associated AMM into the intestine (for example, from blood or sites of inflammation) was reproduced in the in vitro experiment by adding PhLA or 4-HPhLA in clinically significant concentrations (25 mkM) into each test tube with pathobiota and normobiota. After incubation in a thermostat (37°, 24 hours), AMМ concentrations were measured in the samples with pathobiota and normobiota using GC-MS analysis.Results. Concentration of AMM decreased within 24 hours in the tubes with normobiota after PhLA or 4-HPhLA were added. In the tubes with pathobiota, no decrease in AMM concentrations was documented after loading with PhLA or 4-HPhLA. Concentrations of PhLA (P=0.002) and 4-HPhLA (P0.001) were statistically significantly higher in pathobiota samples compared to normobiota.Conclusion. The in vitro experiment demonstrates that after excessive load with sepsis-associated metabolites (PhLA, 4-HPhLA), the microbiota of healthy people is capable to bio-transform such metabolites to the end products of microbial metabolism, while pathobiota of septic patients exhibits altered biotransformational potential. This data demonstrate that microbiota dysfunction may contribute to the pathogenesis of sepsis.

Influence of Microbiota-Related Metabolites Associated with Inflammation and Sepsis on the Peroxidase Activity of Cyclooxygenase in Healthy Human Monocytes and Acute Monocytic Leukemia Cells.

The human microbiota produces metabolites that can enter the bloodstream and exert systemic effects on various functions in both healthy and pathological states. We have studied the participation of microbiota-related metabolites in bacterial infection by examining their influence on the activity of cyclooxygenase (COX) as a key enzyme of inflammation. The influence of aromatic microbial metabolites, derivatives of phenylalanine (phenylpropionic acid, PPA), tyrosine (4-hydroxyphenyllactic acid, HPLA), and tryptophan (indolacetic acids, IAA), the concentrations of which in the blood change notably during sepsis, was evaluated. Also, the effect of itaconic acid (ITA) was studied, which is formed in macrophages under the action of bacterial lipopolysaccharides (LPS) and appears in the blood in the early stages of infection. Metabiotic acetyl phosphate (AcP) as a strong acetylating agent was also tested. The activity of COX was measured via the TMPD oxidation colorimetric assay using the commercial pure enzyme, cultured healthy monocytes, and the human acute monocytic leukemia cell line THP-1. All metabolites in the concentration range of 100-500 μM lowered the activity of COX. The most pronounced inhibition was observed on the commercial pure enzyme, reaching up to 40% in the presence of AcP and 20-30% in the presence of the other metabolites. On cell lysates, the effect of metabolites was preserved, although it significantly decreased, probably due to their interaction with other targets subject to redox-dependent and acetylation processes. The possible contribution of the redox-dependent action of microbial metabolites was confirmed by assessing the activity of the enzyme in the presence of thiol reagents and in model conditions, when the COX-formed peroxy intermediate was replaced with tert-butyl hydroperoxide (TBH). The data show the involvement of the microbial metabolites in the regulation of COX activity, probably due to their influence on the peroxidase activity of the enzyme.

Microbiota Metabolism Failure as a Risk Factor for Postoperative Complications after Aortic Prosthetics.

Postoperative complications in cardiovascular surgery remain an important unresolved problem, in particular in patients with aortic aneurysm. The role of the altered microbiota in such patients is of great interest. The aim of this pilot study was to determine whether the development of postoperative complications in patients with aortic aneurysm is related with initial or acquired disorders of microbiota metabolism by monitoring the level of some aromatic microbial metabolites (AMMs) circulating in the blood before the surgery and in the early postoperative period. The study comprised patients with aortic aneurysm (n = 79), including patients without complications (n = 36) and patients with all types of complications (n = 43). The serum samples from the patients were collected before and 6 h after the end of the surgery. The most significant results were obtained for the sum of three sepsis-associated AMMs. This level was higher before the surgery in comparison with that of healthy volunteers (n = 48), p < 0.001, and it was also higher in the early postoperative period in patients with all types of complications compared to those without complications, p = 0.001; the area under the ROC curve, the cut-off value, and the odds ratio were 0.7; 2.9 µmol/L, and 5.5, respectively. Impaired microbiota metabolism is important in the development of complications after complex reconstructive aortic surgery, which is the basis for the search for a new prevention strategy.

An ozone catalytic oxidation system for the degradation of organic compounds in secondary wastewater from refining and chemical processes

ABSTRACT To overcome the low catalytic efficiency, insufficient catalyst strength, and poor ozone circulation in the advanced treatment of secondary wastewater, a hollow cylindrical Fe-Cu-Ce-Mn/Al2O3 catalyst was prepared by the step impregnation method. Compared with the common impregnation method, the step impregnation method produced a more uniform and compact distribution of each metal element, which was more conducive to generating the synergistic effect of various metals; thus, increasing the mineralization rate of organic matter. The hollow cylindrical design ensured the strength of the catalyst and the circulation of ozone. The reduction of the chemical oxygen demand (COD) was compared under different experimental conditions, with the optimal conditions found to be an ozone contact time of 40 min and ozone dosage of 40 mg/L. The average COD, ammonia nitrogen, and ultraviolet absorbance at 254 nm (UV254) removal rates were 36%, 19%, and 20%, respectively. After 3 weeks of continuous experiment, the removal rate was still high. Following analysis by three dimensional fluorescence, GC-MS, and the molecular weight detection of water samples before and after treatment, it was found that the catalyst enhanced the effect of ozone on wastewater treatment, with a significant removal of tryptophan-like aromatic proteins and soluble microbial metabolites, and the removal of most of the small molecular organic matter. In addition, part of the refractory organic matter could be converted into easily degradable organic matter, which greatly improved the biodegradability and mineralization rate of wastewater, and provided good conditions for subsequent treatment.

Microbiota dysfunction in patients with brain damage in chronic critical condition

In patients with severe brain damage, the severity of the course/outcome of a chronic critical condition is associated with dysfunction of the intestinal microbiota, which can be assessed by the level of microbial metabolites circulating in the blood.The purpose of the study. To establish a connection between the dynamics of a chronic critical condition developed as a result of severe brain damage and microbiota dysfunction.Patients and methods. The study included 83 patients in chronic critical state (CCS) with the consequences of ischemic/ hemorrhagic stroke (n = 34), traumatic brain injury (n = 18), hypoxic brain damage (n = 7), neurosurgical interventions (n = 7), meningitis (n = 3); and 30 healthy people (control group). To assess the neurological status in dynamics, the stroke scales of the National Institutes of Health (NIHSS), the FOUR, Rankin scales, and the Rivermead Mobility Index were used. The taxonomic composition of the microbiota was evaluated by 16S rRNA sequencing and PCR. Biomarkers (by ELISA Kit) and aromatic microbial metabolites (by GC-MS) were monitored twice a week.Results. The peculiarities of the taxonomic composition of the intestinal microbiota in long-term ill patients with brain damage, the predominance of conditionally pathogenic facultative anaerobes (Klebsiella spp., Proteus spp., Staphylococcus aureus) over the pool of strict anaerobes were revealed. The relationship between the dynamics of microbial metabolites in blood and gut of patients with the course and outcome of the disease has been established. Patients with positive clinical dynamics of CCS were characterized by a stable level or decrease in microbial metabolites during treatment. In the group of patients with negative clinical dynamics, an increase in the level of microbial metabolites, especially hydroxylated phenyl carboxylic acids, was revealed.Conclusion. In patients with brain damage, the levels of microbial metabolites circulating in the blood (p-hydroxyphenylacetic, phenyl-lactic, p-hydroxyphenyl-lactic acids) reflect the degree of microbiota dysfunction and the severity of the course of CCS, which is of prognostic importance.

Serum and fecal profiles of aromatic microbial metabolites reflect gut microbiota disruption in critically ill patients: a prospective observational pilot study

BackgroundHigh serum levels of certain aromatic microbial metabolites (AMM) are associated with severity and mortality in critically ill patients. Omics-based studies suggest gut dysbiosis and reduced microbiome diversity in critical conditions. However, the landscape of gut microbial metabolites is still to be outlined, not to mention the interplay correlation between the metabolome and gut microbiome in critically ill patients. The aim of this study was to analyze the association between serum and fecal levels of AMM and compare them with the composition of gut microbiota in critically ill patients in the acute and chronic stages.MethodsIn this prospective observational pilot study, we analyzed the temporal dynamics of the gut microbiome and the AMM spectrum across two distinct subgroups—acute critical ill (ACI) patients with nosocomial pneumonia and chronically critically ill (CCI) patients (9 subjects each group)—as well as performed comparison with 23 healthy volunteers. The AMM levels for each patient were measured using GC-MS in simultaneously taken serum and fecal samples (SFS). These parameters were compared with 16S rRNA fecal microbiome profiles.ResultsThe observed proportions of bacterial taxa suggest a significant gut dysbiosis in the ACI and the CCI patients. Stronger imbalance in microbiome composition and dynamics observed in the ACI patients compared to the CCI ones resonates with a higher severity in the former group. The total levels of AMM in serum samples were higher for the ACI patients than for the CCI patients (3.7 (1.4–6.3) and 1.1 (1.0–1.6) μM, respectively; p = 0.0003). The qualitative composition of the SFS was also altered. We discovered significant associations between gut microbial taxa levels and metabolite concentrations in blood serum as well as in feces in each of the ACI and the CCI patients.ConclusionsAromatic microbial metabolite profiles in the gut and the serum are interlinked and reflect a disruption of the gut microbial community in critically ill patients.

The association of aromatic microbial metabolites, inflammatory and autoimmune biomarkers with clinical dynamics in severe diseases of the central nervous system

To identify the association between the changes in the profile of microbial metabolites, inflammatory and autoimmune markers and the dynamics of neurological status in chronic critically ill patients with diseases of the central nervous system (CNS). Sixty serum samples from 37 patients, aged 19-77 years, with severe CNS diseases were studied. The changes in clinical condition were assessed with NIHSS, the Rankin scale, the Glasgow Coma Scale, the FOUR Coma Scale and the Rivermead Mobility Index. The levels of aromatic microbial metabolites (AMM) and several inflammatory and autoimmune biomarkers, including the contents of procalcitonin (PCT) and S100, the activity of leukocyte elastase (LE) and a1-proteinase inhibitor a1-PI, the levels of autoantibodies to S100b and MBP were measured. Serum from 60 age- and sex-matched healthy people with no signs of neurological and somatic pathology was used as a control. All patients were divided into groups depending on the neurological dynamics: A - positive (n=16), B - without dynamics (n=15), C - negative (n=6). The study revealed a profile of AMM, as well as inflammatory and autoimmune biomarkers associated with the severity of neurological disorders. A significant increase in acute phase proteins, S-100 level and a decrease in the functional activity of neutrophils (via LE activity) were observed in the serum of patients. The different dynamics of neurological status was associated with the multidirectional changes in the microbial metabolites profile and biomarkers. The correlations between the clinical and biological parameters indicate that AMM might modulate immune reactions in patients with different dynamics of neurological status. The results suggest the involvement of AMM and the level of immune activation via biomarkers in the pathogenesis of neurological dysfunction. Dynamic changes in the profile of microbial metabolites and the level of activation of the immune system may be a promising tool for prediction of neurological recovery.

Прогноз исхода у пациентов с абдоминальной и легочной бактериальной инфекцией по уровню ароматических микробных метаболитов в сыворотке крови

Прогноз исхода у пациентов с абдоминальной и легочной бактериальной инфекцией по уровню ароматических микробных метаболитов в сыворотке крови

Microextraction of aromatic microbial metabolites by packed hypercrosslinked polystyrene from blood serum

The article is devoted to the application of modern sample preparation technique - microextraction by packed sorbent (MEPS) - in conjunction with non-conventional type of sorbent - hypercrosslinked polystyrene, that was investigated for the first time in this work. Their combination was used to extract phenylcarboxylic acid-type aromatic microbial metabolites from serum samples of a healthy volunteer with following derivatization and GC–MS detection. As barrel insert and needle for MEPS with hypercrosslinked polystyrene is not produced, we designed a device to imitate the commercial MEPS system with packed granular biporous hypercrosslinked polystyrene. Nine aromatic microbial metabolites, including sepsis associated phenyllactic, 4-hydroxyphenyllactic and 4-hydroxyphenylacetic acids, were extracted from serum samples (recoveries were 20–70%) and a linear dependence was revealed in the most clinically significant range of concentrations (0.5–18 μM). The results obtained demonstrate the perspective of the applying of hypercrosslinked polystyrene in commercial devices for MEPS for the future analyses of biological samples, in particular for the early diagnosis of sepsis and treatment effectiveness control.

Analysis of phenylcarboxylic acid-type microbial metabolites by microextraction by packed sorbent from blood serum followed by GC–MS detection

A method for analysis of 8 phenylcarboxylic acids in blood serum was developed based on the coupling of microextraction by packed sorbent, derivatization and GC–MS detection. These compounds are low molecular weight aromatic microbial metabolites that are proven and prospective indicators of sepsis in critically ill patients. Recoveries of the phenylcarboxylic acids from serum samples using microextraction by packed sorbent were 30–70%. The present method was linear (R2 ≥ 0.9981) over a clinically significant range of concentrations (94–2250 µg L−1/0.5–18 µM). The limits of quantification for the optimized method were 60–100 µg L−1/0.4–0.7 µM for phenylpropionic, phenyllactic, 4-hydroxybenzoic and 4-hydroxyphenylacetic acids, and 160 µg L−1/0.9–1.3 µM for benzoic, 4-hydroxyphenyllactic, homovanillic and 4-hydroxyphenylpropionic acids. The developed conditions were used to determine concentrations of the phenylcarboxylic acids in the most complicated matrix – serum samples of critically ill patients. Results were compared with liquid-liquid extraction and revealed a reduction in the time for sample preparation (45 min vs. 6 min) and serum (200 µL vs. 80 µL) volume. The combination of microextraction by packed sorbent and GC–MS methods, especially when fully automated could be a powerful tool for the clinical diagnosis of sepsis.

О роли ароматических микробных метаболитов

Интеграция метаболизма макроорганизма и его микробиоты, обеспечивающая в норме симбиоз и саногенез, нарушается при заболеваниях, травме, критическом состоянии, и вектор взаимодействия может изменяться в пользу прокариотов по принципу «метаболиты бактерий - против хозяина». Анализ литературы показал, что, с одной стороны, имеется живой интерес к ароматическим микробным метаболитам, с другой - отсутствует четкое представление об их роли в организме человека. Публикации, касающиеся ряда ароматических микробных метаболитов (фенилкарбоновых кислот, ФКК), как правило, не связаны между собой по тематике и направлены на решение тех или иных прикладных задач в разных областях биологии и медицины. Цель обзора - анализ информации о происхождении, биологических эффектах ФКК в экспериментах in vitro и in vivo , и клинических наблюдениях. Обобщая результаты приведенных в обзоре исследований на клеточном, субклеточном и молекулярном уровнях, логично предположить участие ароматических микробных метаболитов в патогенезе полиорганной недостаточности при сепсисе. Наиболее перспективным для раскрытия роли ароматических микробных метаболитов представляется изучение механизмов вторичной почечной недостаточности и септической энцефалопатии. Важным направлением для будущих исследований является изучение влияния продуктов микробной биодеградации ароматических соединений на развитие диссеминированного внутрисосудистого свертывания крови, артериальной гипотензии и септического шока. Результаты дальнейших исследований будут иметь не только фундаментальное значение, но и обогатят практическую медицину новыми диагностическими и лечебными технологиями. Significant increases in blood concentrations of some aromatic metabolites (phenylcarboxylic acids, PhCAs) in patients with sepsis have been previously shown. Enhanced bacterial biodegradation of aromatic compounds has been demonstrated to considerably contribute to this process. Integration of macroorganism metabolism and its microbiota, which provides normal symbiosis and sanogenesis, is disturbed in diseases, trauma, and critical conditions. Direction of this interaction may change in favor of prokaryotes according to the principle, “bacterial metabolites are against the host”. Analysis of literature showed a particular interest of many investigators to aromatic microbial metabolites. However, there is no clear understanding of their role in the human body. Publications on PhCAs are generally not thematically interrelated and usually focus on solving applied tasks in different fields of biology and medicine. The aim of this work was to consolidate existing information about origin and biological effects of PhCAs in in vitro / in vivo experiments and some clinical findings. The presented summary of reported data from studies performed at cellular, sub-cellular, and molecular levels suggests participation of aromatic microbial metabolites in the pathogenesis of multiple organ failure in sepsis. Studying mechanisms of secondary renal failure and septic encephalopathy is most promising for discovering the function of aromatic microbial metabolites. Effects of microbial biodegradation products of aromatic substances on development of disseminated intravascular coagulation, hypotension, and septic shock are an important challenge for future studies. Results of further investigations will be not only fundamental, but will also enrich medical practice with new diagnostic and therapeutic technologies.

Determination of Aromatic Microbial Metabolites by Gas Chromatography

Determination of Aromatic Microbial Metabolites by Gas Chromatography

Determination of Aromatic Microbial Metabolites in Blood Serum by Gas Chromatography–Mass Spectrometry

We present the results of the determination of eight aromatic microbial metabolites, phenylcarboxylic acids (PhCAs), by gas chromatography–mass spectrometry after their liquid–liquid extraction from serum samples and derivatization. The analytical range for the analytes is 0.5–40 μM. The concentration of phenylcarboxylic acids in the serum of healthy donors (n = 40) and the time profile of the concentration of different PhCAs in serum samples of four patients from the intensive care unit (ICU) are studied. The results correlated with the severity of the clinical state of patients.

Microextraction of Aromatic Microbial Metabolites by Packed Sorbent (MEPS) from Model Solutions Followed by Gas Chromatography/Mass Spectrometry Analysis of Their Silyl Derivatives

The paper describes the results of extraction of aromatic microbial metabolites (phenylcarboxylic acids) from model aqueous solutions using microextraction by packed sorbent (MEPS), followed by the determination of their silyl derivatives by gas chromatography/mass spectrometry. The selected conditions of adsorption–desorption, derivatization, and gas chromatography determination enable the detection of a number of compounds, which are proved and prospective disease markers. This detection could be performed at the level of their concentration in blood of healthy donors (0.5 μmol L–1) and patients of intensive care units, having an initial stage of sepsis (2–3 μmol L–1) or other serious diseases caused by significant microbial load and led to the development of multiple organ failure. The recoveries of phenylcarboxylic acids using nonpolar sorbent (C18) reached 20–65% for hydroxylated acids (phenyllactic, 4-hydroxybenzoic, 4-hydroxyphenylacetic, 4-hydroxyphenylpropanoic, homovanillic, and 4-hydroxyphenyllactic acids) and 100% for more nonpolar acids (benzoic, phenylpropanoic, and cinnamic acids).

Sepsis-Associated Encephalopathy (Review)

International studies demonstrate an annual increase in the frequency and impact of sepsis in intensive care units (ICU). Cerebral dysfunction, or so-called sepsis-associated encephalopathy (SAE), is one of the earliest signs of sepsis, as well as its common complication. Up to 70% of patients with sepsis have symptoms of encephalopathy [1, 2]. A direct link between the SAE and an increased mortality rate is a major concern; more than a half of sepsis survivors experience continuous memory and concentration impairment [3—5]. Diagnosis of the cerebral dysfunction in sepsis is often difficult because of lack of specific biomarkers and frequent prescription of sedatives to critically ill patients. Clinical manifestations of SAE are diverse, may vary from simple malaise and lack of concentration to deep coma. The literature discusses probable mechanisms of formation and development of septic encephalopathy, such as oxidative stress, inflammation, mitochondrial and endothelial dysfunction, increased permeability of the blood-brain barrier, impairment of macro- and microcirculation, changes in neirotransmission, activation of microglia. The lack of clear data and consensus about the etiology and mechanisms of SAE at present does not permit predicting its development and prescribing a specific therapy. The review discusses current understanding of the causes of septic encephalopathy, methods of diagnosis, the main clinical manifestations, key mediators, and pathophysiological mechanisms. A hypothesis is proposed that poses a contribution of aromatic microbial metabolites (AMM) of phenol and indole nature (products of bacterial biodegradation of tyrosine and tryptophan) to the development of brain dysfunction. The fields of exploratory studies, which might open perspectives in the diagnosis, as well as new approaches in the treatment of SAE are outlined.

Value of microbial metabolites in blood serum as criteria for bacterial load in the pathogenesis of hemodynamic disorders in critically ill patients

Hemodynamic disorders in critically ill patients are often connected with bacterial load. Bacterial load is usually associated with bacteremia, LPS, high level of IL-6, PCT and also with aromatic microbial metabolites [1-3], and so forth. In our opinion, microbial metabolites can participate in hemodynamic disorders in critically ill patients, particularly due to their influence on NO production [4] and intestinal permeability.