Reduction Of Trimethylamine N-oxide Research Articles

Commercial Extruded Plant-Based Diet Lowers Circulating Levels of Trimethylamine N-Oxide (TMAO) Precursors in Healthy Dogs: A Pilot Study.

Elevations in circulating trimethylamine N-oxide (TMAO) and its precursors are observed in humans and dogs with heart failure and are associated with adverse outcomes in people. Dietary intervention that reduces or excludes animal ingredients results in rapid reduction of plasma TMAO and TMAO precursors in people, but the impact of diet in dogs has not been studied. The objective of the current study was to determine the effect of diet on plasma TMAO and 2 of its precursors (choline and betaine) in dogs fed a commercial extruded plant-based diet (PBD) or a commercial extruded traditional diet (TD) containing animal and plant ingredients. Sixteen healthy adult mixed breed dogs from a university colony were enrolled in a randomized, 2-treatment, 2-period crossover weight-maintenance study. Mean (SD) age and body weight of the dogs were 2.9 years (± 1.7) and 14.5 kg (± 4.0), respectively. Eight dogs were female (3 intact, 5 spayed) and 8 dogs were male (4 intact, 4 castrated). Plasma choline, betaine and TMAO were quantified by LC-SID-MRM/MS at baseline, and after 4 weeks on each diet. Choline and betaine were also quantified in the diets. Plasma choline levels were significantly lower (P = 0.002) in dogs consuming a PBD (Mean ± SD, 6.8 μM ± 1.2 μM) compared to a TD (Mean ± SD, 7.8 μM ± 1.6 μM). Plasma betaine levels were also significantly lower (P = 0.03) in dogs consuming a PBD (Mean ± SD, 109.1 μM ± 25.3 μM) compared to a TD (Mean ± SD, 132.4 μM ± 32.5 μM). No difference (P = 0.71) in plasma TMAO was detected in dogs consuming a PBD (Median, IQR, 2.4 μM, 2.1 μM) compared to a TD (Median, IQR, 2.3 μM, 1.1 μM). Betaine content was lower in the PBD than in the TD while choline content was similar in the diets. Our findings indicate consumption of a commercial extruded PBD for 4 weeks reduces circulating levels of the TMAO precursors choline and betaine, but not TMAO, in healthy adult dogs.

Enhanced Bioremediation Potential of Shewanella decolorationis RNA Polymerase Mutants and Evidence for Novel Azo Dye Biodegradation Pathways.

Bioremediation has been considered as a promising method for recovering chemical polluted environments. Here Shewanella decolorationis strain Ni1-3 showed versatile abilities in bioremediation. To improve the bioremediation activity, RNA polymerase (RNAP) mutations of strain Ni1-3 were screened. Eleven mutants were obtained, of which mutant #40 showed enhanced Amaranth (AMR) degradation capacity, while mutant #21 showed defected capacity in AMR degradation but greatly enhanced capacity in cathodic metal leaching which is three to four times faster than that of the wild-type (WT) strain Ni1-3, suggesting that different pathways were involved in these two processes. Transcriptional profiling and gene co-expression networks between the mutants (i.e., #40 and #22) and the WT strain disclosed that the non-CymA-Mtr but cytochrome b- and flavin-oxidoreductase-dominated azo dye degradation pathways existed in S. decolorationis, which involved key proteins TorC, TorA, YceJ, YceI, Sye4, etc. Furthermore, the involvement of TorA was verified by trimethylamine N-oxide reduction and molybdenum enzyme inhibitory experiments. This study clearly demonstrates that RNAP mutations are effective to screen active microbial candidates in bioremediation. Meanwhile, by clarifying the novel gene co-expression network of extracellular electron transfer pathways, this study provides new insights in azo dye degradation and broadens the application of Shewanella spp. in bioremediation as well.

Gut Microbial Metabolite Trimethylamine N-Oxide Aggravates Pulmonary Hypertension.

Trimethylamine N-oxide (TMAO), a metabolite derived from intestine microbial flora, enhances vascular inflammation in a variety of cardiovascular diseases, and the bacterial communities associated with TMAO metabolism are higher in pulmonary hypertension (PH) patients. The effects of TMAO on PH, however, have not been elucidated. In the present study, circulating TMAO was found to be elevated in intermediate to high-risk PH patients when compared with healthy control or low-risk PH patients. In monocrotaline-induced rat PH models, circulating TMAO was elevated; and reduction of TMAO using 3,3-dimethyl-1-butanol (DMB) significantly decreased right ventricle systolic pressure and pulmonary vascular muscularization in both monocrotaline-induced rat PH and hypoxia-induced mouse PH models. RNA sequencing of rat lungs revealed that DMB treatment significantly suppressed the pathways involved in cytokine-cytokine receptor interaction and in cytokine and chemokine signaling. Protein-protein interaction analysis of the differentially expressed transcripts regulated by DMB showed five hub genes with a strong connectivity of proinflammatory cytokines and chemokines, including Kng1, Cxcl1, Cxcl2, Cxcl6, and Il6. In vitro, TMAO significantly increased the expression of Kng1, Cxcl1, Cxcl2, Cxcl6, and Il6 in bone-marrow-derived macrophage. Also, TMAO-treated conditioned medium from macrophage increased the proliferation and migration of pulmonary artery smooth muscle cells, but TMAO treatment did not change the proliferation or migration of pulmonary artery smooth muscle cells. In conclusion, our study demonstrates that TMAO is increased in severe PH, and the reduction of TMAO decreases pulmonary vascular muscularization and alleviates PH by suppressing the macrophage production of chemokines and cytokines.

A novel real-time TMAO detection method based on microbial electrochemical technology

Trimethylamine N-oxide (TMAO) is considered to be a novel biomarker of cardiovascular diseases. However, the traditional TMAO detection method has failed to meet the requirements of real-time and point-of-care tests. Herein, a novel TMAO detection method based on microbial electrochemical technology is established, which realizes the direct conversion of TMAO concentration into electrical signals. Attached Shewanella loihica PV-4 was first proven to be capable of simultaneous inward extracellular electron transfer and TMAO reduction. The TMAO detection method showed a wide linear range of 0 to 250 μM, a high sensitivity of 23.92 μA/mM, and a low limit of detection of 5.96 μM. In addition, the TMAO detection process was accomplished within 600 s, with an acceptable accuracy of 90% in the real serum, showing high feasibility in clinical applications.

Reduction of TMAO level enhances the stability of carotid atherosclerotic plaque through promoting macrophage M2 polarization and efferocytosis.

It has been demonstrated that trimethylamine N-oxide (TMAO) serves as a driver of atherosclerosis, suggesting that reduction of TMAO level might be a potent method to prevent the progression of atherosclerosis. Herein, we explored the role of TMAO in the stability of carotid atherosclerotic plaques and disclosed the underlying mechanisms. The unstable carotid artery plaque models were established in C57/BL6 mice. L-carnitine (LCA) and methimazole (MMI) administration were applied to increase and reduce TMAO levels. Hematoxylin and eosin (H&E) staining, Sirius red, Perl’s staining, Masson trichrome staining and immunohistochemical staining with CD68 staining were used for histopathology analysis of the carotid artery plaque. M1 and M2 macrophagocyte markers were assessed by RT-PCR to determine the polarization of RAW264.7 cells. MMI administration for 2 weeks significantly decreased the plaque area, increased the thickness of the fibrous cap and reduced the size of the necrotic lipid cores, whereas 5-week of administration of MMI induced intraplate hemorrhage. LCA treatment further deteriorated the carotid atherosclerotic plaque but with no significant difference. In mechanism, we found that TMAO treatment impaired the M2 polarization and efferocytosis of RAW264.7 cells with no obvious effect on the M1 polarization. In conclusion, the present study demonstrated that TMAO reduction enhanced the stability of carotid atherosclerotic plaque through promoting macrophage M2 polarization and efferocytosis.

Electrochemical Trimethylamine N-Oxide Biosensor with Enzyme-Based Oxygen-Scavenging Membrane for Long-Term Operation under Ambient Air

An amperometric trimethylamine N-oxide (TMAO) biosensor is reported, where TMAO reductase (TorA) and glucose oxidase (GOD) and catalase (Cat) were immobilized on the electrode surface, enabling measurements of mediated enzymatic TMAO reduction at low potential under ambient air conditions. The oxygen anti-interference membrane composed of GOD, Cat and polyvinyl alcohol (PVA) hydrogel, together with glucose concentration, was optimized until the O2 reduction current of a Clark-type electrode was completely suppressed for at least 3 h. For the preparation of the TMAO biosensor, Escherichia coli TorA was purified under anaerobic conditions and immobilized on the surface of a carbon electrode and covered by the optimized O2 scavenging membrane. The TMAO sensor operates at a potential of −0.8 V vs. Ag/AgCl (1 M KCl), where the reduction of methylviologen (MV) is recorded. The sensor signal depends linearly on TMAO concentrations between 2 µM and 15 mM, with a sensitivity of 2.75 ± 1.7 µA/mM. The developed biosensor is characterized by a response time of about 33 s and an operational stability over 3 weeks. Furthermore, measurements of TMAO concentration were performed in 10% human serum, where the lowest detectable concentration is of 10 µM TMAO.

Inhibition of microbiota-dependent TMAO production attenuates chronic kidney disease in mice

Patients with chronic kidney disease (CKD) have elevated circulating levels of trimethylamine N-oxide (TMAO), a metabolite derived from gut microbes and associated with cardiovascular diseases. High circulating levels of TMAO and its dietary precursor, choline, predict increased risk for development of CKD in apparently healthy subjects, and studies in mice fed TMAO or choline suggest that TMAO can contribute to kidney impairment and renal fibrosis. Here we examined the interactions between TMAO, kidney disease, and cardiovascular disease in mouse models. We observed that while female hyperlipidemic apoE KO mice fed a 0.2% adenine diet for 14 weeks developed CKD with elevated plasma levels of TMAO, provision of a non-lethal inhibitor of gut microbial trimethylamine (TMA) production, iodomethylcholine (IMC), significantly reduced multiple markers of renal injury (plasma creatinine, cystatin C, FGF23, and TMAO), reduced histopathologic evidence of fibrosis, and markedly attenuated development of microalbuminuria. In addition, while the adenine-induced CKD model significantly increased heart weight, a surrogate marker for myocardial hypertrophy, this was largely prevented by IMC supplementation. Surprisingly, adenine feeding did not increase atherosclerosis and significantly decreased the expression of inflammatory genes in the aorta compared to the control groups, effects unrelated to TMAO levels. Our data demonstrate that inhibition of TMAO production attenuated CKD development and cardiac hypertrophy in mice, suggesting that TMAO reduction may be a novel strategy in treating CKD and its cardiovascular disease complications.

Determination of Major Endogenous FAHFAs in Healthy Human Circulation: The Correlations with Several Circulating Cardiovascular-Related Biomarkers and Anti-Inflammatory Effects on RAW 264.7 Cells.

Fatty acid esters of hydroxy fatty acids (FAHFAs) are newly discovered long-chain fatty acids. However, the major endogenous FAHFAs in healthy human circulation, their correlation with cardiovascular (CV) biomarkers, and their anti-inflammatory effects have not been investigated and remain unclear. In the present study, a total of 57 healthy subjects were recruited. Liquid chromatography–mass spectrometry (LC-MS) was developed for the simultaneous determination of seven FAHFAs, four long-chain fatty acids, and four non-traditional circulating CV-related biomarkers. We found two major types of FAHFAs in healthy human circulation, palmitoleic acid ester of 9-hydroxystearic acid (9-POHSA), and oleic acid ester of 9-hydroxystearic acid (9-OAHSA). Both 9-POHSA and 9-OAHSA had a strong positive correlation with each other and were negatively correlated with fasting blood glucose, S-adenosyl-l-homocysteine (SAH), and trimethylamine N-oxide (TMAO), but not with l-homocysteine. 9-POHSA was also positively correlated with l-carnitine. Moreover, we confirmed that both 9-POHSA and 9-OAHSA exhibited an anti-inflammatory effect by suppressing LPS stimulated cytokines, including IL-1β and IL-6 in RAW 264.7 cells. In addition, palmitoleic acid also had a positive correlation with 9-POHSA and 9-OAHSA. As far as we know, this is the first report showing the major endogenous FAHFAs in healthy subjects and their CV protection potential which might be correlated with SAH and TMAO reduction, l-Carnitine elevation, and their anti-inflammatory effects.

P0689LINACLOTIDE, THE GUANYLATE CYCLASE C AGONIST LIMITS CARDIAC FIBROSIS FORMATION IN MICE WITH CHRONIC KIDNEY DISEASE AFTER ISCHEMIA-REPERFUSION INJURY

Abstract Background and Aims Cardiovascular disease (CVD) is a major cause of mortality in patients with chronic kidney disease (CKD). Renal ischemia-reperfusion injury (IRI) is a clinically significant condition that progress to CKD after acute kidney injury (AKI). We have reported that the suppression of Trimethylamine-N-oxide (TMAO), a hepatic metabolic product of trimethylamine generated from dietary phosphatidylcholine, by linaclotide could prevent renal fibrosis and improve renal function in the chronic phase after renal IRI. TMAO has been linked directly with progression of CVD too. We investigated whether the reduction of TMAO by linaclotide limits cardiac fibrosis in mouse model of CKD after IRI. Method Linaclotide (100μg/kg) was administered for 2weeks before IRI and continued for 2weeks after IRI. After 2weeks since IRI, removed hearts sections were performed Azan stain to evaluate the level of fibrosis and western blotting to evaluate the expression level of fibronectin. Results The administration of linaclotide significantly improved cardiac fibrosis area (Fig1). Additionally, western blotting showed linaclotide suppress the expression level of fibronectin (Fig2). Conclusion The reduction of TMAO by linaclotide could prevent cardiac fibrosis in the chronic phase after renal IRI. Linaclotide may be a powerful tool for prevention of the cardiorenal syndrome after renal IRI.

P1751THE GUANYLATE CYCLASE C AGONIST LINACLOTIDE LIMITS PROGRESSION TO RENAL FIBROSIS AND IMPROVE RENAL FUNCTION IN MOUSE MODEL OF CHRONIC KIDNEY DISEASE AFTER ISCHEMIA-REPERFUSION INJURY

Abstract Background and Aims Renal ischemia-reperfusion injury (IRI) is a clinically significant condition that leads to acute kidney injury (AKI). AKI is followed by tissue repair characterized by collagen deposition and fibrosis which ultimately results in progression to chronic kidney disease (CKD). Especially in renal transplantation, the degree of IRI has directly led to poor long-term graft survival. Trimethylamine-N-oxide (TMAO), a hepatic metabolic product of trimethylamine generated from dietary phosphatidylcholine, has been linked with progression of CKD. Linaclotide, a guanylate cyclase C agonist, has been reported decrease the plasma levels of TMAO. We investigated whether the reduction of TMAO by linaclotide protect renal function after IRI using an experimental mouse model. Method Linaclotide (100μg/kg) was administered for 2weeks before IRI and continued for 2weeks after IRI. After 2weeks since IRI, the renal function was evaluated by serum creatinine level and removed kidneys sections were performed Azan stain to evaluate the level of fibrosis. Results The administration of linaclotide before IRI significantly improved renal function. (Fig.1) Histological examination of kidneys showed linaclotide limits to expand fibrosis area after I/R injury. (Fig.2) Conclusion The reduction of TMAO by linaclotide before renal IRI could prevent renal fibrosis and improve renal function. Linaclotide may be useful for the patient expected to suffer renal IRI for example renal transplantation and partial nephrectomy. Fig2

Trimethylamine N‐Oxide Electrochemical Biosensor with a Chimeric Enzyme

AbstractFor the first time, an enzyme‐based electrochemical biosensor system for determination of trimethylamine N‐oxide (TMAO) is described. It employs an active chimeric variant of TorA in combination with an enzymatically deoxygenating system and a low‐potential mediator for effective regeneration of the enzyme and cathodic current generation. TMAO reductase (TorA) is a molybdoenzyme found in marine and most enterobacteria that specifically catalyzes the reduction of TMAO to trimethylamine (TMA). The chimeric TorA, named TorA‐FDH, corresponds to the apoform of TorA from Escherichia coli reconstituted with the molybdenum cofactor from formate dehydrogenase (FDH). Each enzyme, TorA and TorA‐FDH, was immobilized on the surface of a carbon electrode and protected with a dialysis membrane. The biosensor operates at an applied potential of −0.8 V [vs. Ag/AgCl (1 M KCl)] under ambient air conditions thanks to an additional enzymatic O2‐scavenger system. A comparison between the two enzymatic sensors revealed a much higher sensitivity for the biosensor with immobilized TorA‐FDH. This biosensor exhibits a sensitivity of 14.16 nA/μM TMAO in a useful measuring range of 2–110 μM with a detection limit of LOD=2.96 nM (S/N=3), and was similar for TMAO in buffer and in spiked serum samples. With a response time of 16±2 s, the biosensor is stable over prolonged daily measurements (n=20). This electrochemical biosensor provides suitable applications in detecting TMAO levels in human serum.

Potential effects of natural dietary compounds on trimethylamine Noxide (TMAO) formation and TMAO-induced atherosclerosis

Cardiovascular disease (CVD) is the leading cause of death worldwide. Recently, trimethylamine N-oxide (TMAO) is identified to be highly associated with CVD development and exacerbates atherosclerosis by several mechanisms. TMAO is a gut microbiota-dependent metabolite formed from dietary quaternary amines, mainly choline and carnitine. These trimethylamine (TMA)-containing compounds are first converted to TMA by enzymes in gut microbiota and subsequently metabolized by the host hepatic enzymes to TMAO. As the microbiome is the source of TMAO, administration of broad spectrum antibiotics shows marked decrease in TMAO levels. However, antibiotics may possess many possible undesirable side effects and chronic treatment consideration effects of antibiotic resistance in bacteria. Thus, studies have focused on the alternative strategies, including use of natural dietary compounds to reduce elevated TMAO levels and prevent atherogenesis. Natural dietary compounds have been studied for their beneficial health effects for decades. Diet and nutritional interventions based on the use of natural bioactive compounds is an effective strategy for remodeling gut microbiota composition and improving human health. This review focuses on the mechanisms by which TMAO promote atherosclerosis, the microbes that contribute to TMA formation, the enzymes involved, and the potential of natural dietary compounds that contribute to TMAO reduction and attenuate TMAO-induced atherosclerosis.

Therapeutic reduction of lysophospholipids in the digestive tract recapitulates the metabolic benefits of bariatric surgery and promotes diabetes remission

ObjectiveObesity and obesity-related metabolic disorders are major health problems worldwide. The most effective obesity intervention is bariatric surgery. This study tested the hypothesis that bariatric surgery alters phospholipid metabolism in the gastrointestinal tract to favor a metabolically healthy gut microbiota profile and therapeutic intervention of phospholipid metabolism in the gastrointestinal may have similar metabolic benefits. MethodsThe first study compared plasma levels of the bioactive lipid metabolites lysophospholipid and trimethylamine N-oxide (TMAO) as well as gut microbiota profile in high fat/carbohydrate (HFHC) diet-fed C57BL/6 mice with or without vertical sleeve gastrectomy (VSG) and in Pla2g1b−/− mice with group 1B phospholipase A2 gene inactivation. The second study examined the effectiveness of the non-absorbable secretory phospholipase A2 inhibitor methyl indoxam to reverse hyperglycemia and hyperlipidemia in HFHC diet-fed C57BL/6 mice after diabetes onset. ResultsBoth bariatric surgery and PLA2G1B inactivation were shown to reduce lysophospholipid content in the gastrointestinal tract, resulting in resistance to HFHC diet-induced alterations of the gut microbiota, reduction of the cardiovascular risk factors hyperlipidemia and TMAO, decreased adiposity, and prevention of HFHC diet-induced diabetes. Importantly, treatment of wild type mice with methyl indoxam after HFHC diet-induced onset of hyperlipidemia and hyperglycemia effectively restored normal plasma lipid and glucose levels and replicated the metabolic benefits of VSG surgery with diabetes remission and TMAO reduction. ConclusionThese results provided pre-clinical evidence that PLA2G1B inhibition in the digestive tract may be a viable alternative option to bariatric surgery for obesity and obesity-related cardiometabolic disorder intervention.

Detoxification of Trimethylamine N-Oxide by the Mitochondrial Amidoxime Reducing Component mARC.

Although known for years, the toxic effects of trimethylamine N-oxide (TMAO), a physiological metabolite, were just recently discovered and are currently under investigation. It is known that elevated TMAO plasma levels correlate with an elevated risk for cardiovascular disease (CVD). Even though there is a general consensus about the existence of a causal relationship between TMAO and CVD, the underlying mechanisms are not fully understood. TMAO is an oxidation product of the hepatic flavin-containing monooxygenases (FMO), mainly of isoform 3, and it is conceivable that humans also have an enzyme reversing this toxification by reducing TMAO to its precursor trimethylamine (TMA). All prokaryotic enzymes that use TMAO as a substrate have molybdenum-containing cofactors in common. Such molybdenum-containing enzymes also exist in mammals, with the so-called mitochondrial amidoxime reducing component (mARC) representing the most recently discovered mammalian molybdenum enzyme. The enzyme has been found to exist in two isoforms, mARC1 and mARC2, both being capable of reducing a variety of N-oxygenated compounds, including nonphysiological N-oxides. To investigate whether the two isoforms of this enzyme are able to reduce and detoxify TMAO, we developed a suitable analytical method and tested TMAO reduction with a recombinant enzyme system. We found that one of the two recombinant human mARC proteins, namely, hmARC1, reduces TMAO to TMA. The N-reductive activity is relatively low and identified via the kinetic parameters with Km = (30.4 ± 9.8) mM and Vmax = (100.5 ± 12.2) nmol/(mg protein·min). Nevertheless, the ubiquitous tissue expression of hmARC1 allows a continuous reduction of TMAO whereas the counter-reaction, the production of TMAO through FMO3, can take place only in the liver where FMO3 is expressed. TMAO reduction in porcine liver subfractions showed the characteristic enrichment of N-reductive activity in the outer mitochondrial membrane. TMAO reduction was also found in human cell cultures. These findings indicate the role of hmARC1 in the metabolomic pathway of TMAO, which might contribute to the prevention of CVD. This also hints at a physiological function of the molybdenum enzyme, which remains mainly unknown to date.

Ultrasonic Preparation of Porous Silica-Dye Microspheres: Sensors for Quantification of Urinary Trimethylamine N-Oxide.

Trimethylamine N-oxide (TMAO), the N-oxide metabolite of trimethylamine (TMA), is a key index in the determination of a wide variety of human cardiac or kidney diseases. A colorimetric sensor array comprising ultrasonically prepared silica-dye microspheres was developed for rapid, portable, and sensitive detection of urinary TMAO. To prepare the sensor array, 13 different organically modified silica (ormosil)-dye composites were synthesized from the hydrolysis/pyrolysis of ultrasonically sprayed organosiloxane precursors under optimized reaction conditions; the resulting products are uniformly sized nanoporous microspheres that are effective colorimetric sensors for various volatile analytes. The effective quantification of aqueous TMAO (which is not volatile) was based on sensing the volatile TMA produced from a simple catalytic reduction of TMAO in situ. RGB color-change patterns from digital images of the sensor array permit precise discrimination among a wide range of TMAO concentrations (10-750 μM) in simulated urine samples; both hierarchical cluster analysis and principal component analysis achieve >99% accuracy in data classification. The calculated limit of detection of urinary TMAO is ∼4 μM, which is substantially below the median level of healthy subjects (∼380 μM). The array of sensors could be simplified to only a couple of strongly responsive elements for the ease of field use, and the process could be developed as a point-of-care tool in combination with digital imaging for the early diagnosis of cardiovascular or kidney diseases from the measurement of fasting urinary level of TMAO.

New insights on atherosclerosis: A cross-talk between endocannabinoid systems with gut microbiota.

The incidence of atherosclerosis is increasing rapidly all over the world. Inflammatory processes have outstanding role in coronary artery disease (CAD) etiology and other atherosclerosis manifestations. Recently attentions have been increased about gut microbiota in many fields of medicine especially in inflammatory diseases like atherosclerosis. Ineffectiveness in gut barrier functions and subsequent metabolic endotoxemia (caused by rise in plasma lipopolysaccharide levels) is associated with low-grade chronic inflammation i.e. a recognized feature of atherosclerosis. Furthermore, the role of trimethylamine-N-oxide (TMAO), a gut bacterial metabolite has been suggested in atherosclerosis development. On the other hand, the effectiveness of gut microbiota modulation that results in TMAO reduction has been investigated. Moreover, considerable evidence supports a role for the endocannabinoid system (ECS) in atherosclerosis pathology which affects gut microbiota, but their effects on atherosclerosis are controversial. Therefore, we presented some evidence about the relationship between gut microbiota and ECS in atherosclerosis. We also presented evidences that gut microbiota modulation by pre/probiotics can have significant influence on the ECS.

Plasma trimethylamine-N-oxide following supplementation with vitamin D or D plus B vitamins.

We compared the effect of supplementation with vitamin D + B or vitamin D on plasma trimethylamine N-oxide (TMAO) and choline metabolites. This is a randomized single-blinded nonplacebo-controlled study. Twenty-seven participants received 1200 IU vitamin D3 and 800 mg calcium, and 25 participants received additionally 0.5 mg folic acid, 50 mg B6, and 0.5 mg B12 for 1 year. Plasma homocysteine (Hcy), TMAO, and choline metabolites were measured at baseline and 12 months later. TMAO declined in the vitamin D arm by 0.5 versus 2.8 μmol/L in the D + B arm (p = 0.005). Hcy decreased and betaine increased in the D + B compared to the D arm. Within-subject levels of plasma choline and dimethylglycine and urine betaine increased in both arms and changes did not differ between the arms. TMAO reduction was predicted by higher baseline TMAO and lowering Hcy in stepwise regression analysis. The test-retest variations of TMAO were greater in the D + B arm compared to vitamin D arm. B vitamins plus vitamin D lowered plasma fasting TMAO compared to vitamin D. Vitamin D caused alterations in choline metabolism, which may reflect the metabolic flexibility of C1-metabolism. The molecular mechanisms and health implications of these changes are currently unknown.

Phenotypic and genotypic characterization of H2 S-positive and H2 S-negative strains of Shewanella baltica isolated from spoiled whiting (Merlangius merlangus).

Four strains were isolated from a spoiled whiting (Merlangius merlangus). All of them were able to grow aerobically from 4 to 30°C and also able to develop anaerobically in the presence of trimethylamine N-Oxide (TMAO) at 25°C. Biochemical characterization did not allow identification of the strains species but showed that one of the four strains was unable to produce H2 S. Two strains synthetized an ornithine decarboxylase being potential putrescine producers. Results of carbon source use highlighted that the four strains were able to use citrate and d-sucrose and one strain was not able to use l-arabinose. Genotypic characterization of the strains thanks to 16S rRNA and gyrB partial gene sequencing led to their identification as members of Shewanella baltica species. These observations suggest that H2 S production may not be the most appropriate screening parameter for Shewanella species and further to monitor the development of spoilage flora. Shewanella is a complex genus composed of numerous and heterogeneous species. One of them Shewanella baltica has previously been described as one of the most important H2 S-producing bacterial species in iced stored fish and may act as spoilage organism through the reduction of trimethylamine N-Oxide (TMAO). Four strains of S.baltica were isolated from spoiled whiting (Merlangius merlangus), and description of three H2 S-positive strains and one H2 S-negative strain of S.baltica is highlighted in this short paper. Consequently, H2 S production might not be the most appropriate screening parameter to assess the development of spoilage organisms.

NMR‐based metabonomic approach on the toxicological effects of a Cimicifuga triterpenoid

Cimicifugae Rhizoma, a well-known botanical dietary supplement, has been the subject of intense interest due to its potential application for alleviating menopausal symptom. Although there are clinic data that the Cimicifuga extract should have hepatotoxicity, no evidence on the main chemical components has been reported. Cimicidol-3-O-β -d-xyloside (CX) is one of the main triterpenoids of the rhizome. This work studies the toxicological effects of CX after oral administration (50 mg kg(-1) per day) over a 7-day period in female SD rats using metabonomic analyses of (1) H NMR spectra of urine, serum and liver tissue extracts. Histopathological studies of liver and analyses of blood biochemical parameter, such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, blood urea nitrogen and creatinine revealed that CX had no negative impacts on liver and kidney. However, the metabolic signature of (1) H NMR-based urinalysis of daily samples displayed an increment in the levels of taurine, trimethylamine-N-oxide (TMAO), betaine and acetate. Elevated serum levels of creatinine, glucose, alanine, TMAO and betaine and lower levels of lactate were observed. Metabolic profiling on aqueous soluble extracts of liver showed simultaneously increases in succinate, glycogen, choline, glycerophosphorylcholine, TMAO and betaine levels and reduction in valine, glucose and lactate levels. Nevertheless, no changes in any metabonomic level were found in lipid-soluble extracts of liver. These findings indicate that CX has a slight toxicity in liver and kidney via disturbance of the metabolisms of energy and amino acids. The present study provides a reasonable explanation for the clinical hepatotoxicity of Cimicifuga extract.

Involvement of cyclic AMP (cAMP) and cAMP receptor protein in anaerobic respiration of Shewanella oneidensis.

Shewanella oneidensis is a metal reducer that can use several terminal electron acceptors for anaerobic respiration, including fumarate, nitrate, dimethyl sulfoxide (DMSO), trimethylamine N-oxide (TMAO), nitrite, and insoluble iron and manganese oxides. Two S. oneidensis mutants, SR-558 and SR-559, with Tn5 insertions in crp, were isolated and analyzed. Both mutants were deficient in Fe(III) and Mn(IV) reduction. They were also deficient in anaerobic growth with, and reduction of, nitrate, fumarate, and DMSO. Although nitrite reductase activity was not affected by the crp mutation, the mutants failed to grow with nitrite as a terminal electron acceptor. This growth deficiency may be due to the observed loss of cytochromes c in the mutants. In contrast, TMAO reduction and growth were not affected by loss of cyclic AMP (cAMP) receptor protein (CRP). Fumarate and Fe(III) reductase activities were induced in rich medium by the addition of cAMP to aerobically growing wild-type S. oneidensis. These results indicate that CRP and cAMP play a role in the regulation of anaerobic respiration, in addition to their known roles in catabolite repression and carbon source utilization in other bacteria.