Serum trimethylamine-N-oxide Concentrations Research Articles

Association of Serum Trimethylamine-N-Oxide Concentration from Childhood to Early Adulthood with Age and Sex.

Primary prevention is the cornerstone of cardiometabolic health. In the randomized, controlled Special Turku Coronary Risk Factor Intervention Project (STRIP), dietary counseling intervention was given to children from infancy to 20 years of age and a follow-up was completed at age 26 years. We investigated the associations of age, sex, gut microbiome, and dietary intervention with the gut metabolite and the cardiac biomarker trimethylamine-N-oxide (TMAO). Overall, 592 healthy participants (females 46%) from STRIP were investigated. Compared to the control group, the intervention group had received dietary counseling between ages 7 months and 20 years focused on low intakes of saturated fat and cholesterol and the promotion of fruit, vegetable, and whole-grain consumption. TMAO serum concentrations were measured by a liquid chromatography-tandem mass spectrometry method at ages 11, 13, 15, 17, 19, and 26 years. Microbiome composition was assessed using 16S rRNA gene sequencing at 26 years of age. TMAO concentrations increased from age 11 to 26 years in both sexes. At all measurement time points, males showed significantly higher serum TMAO concentrations compared to females, but concentrations were similar between the intervention and control groups. A direct association between TMAO concentrations and reported fiber intake was found in females. Gut microbiome analysis did not reveal associations with TMAO. TMAO concentration increased from childhood to early adulthood but was not affected by the given dietary intervention. In females, TMAO concentrations could be directly associated with higher fiber intake suggesting sex-specific differences in TMAO metabolism.

The Association Between the Gut Microbiome and COVID-19 Severity: The Potential Role of TMAO Produced by the Gut Microbiome

Context: The COVID-19 pandemic has had profound impacts on public health, resulting in nearly 1 million deaths. Emerging evidence suggests an association between certain metabolites produced by gut microbiota and potential alterations in the severity of infection. Trimethylamine N-oxide (TMAO) is a waste metabolite generated by gut microbes from dietary choline and betaine. Evidence Acquisition: Several investigations have indicated an association between serum TMAO concentrations and the development of inflammation and thrombosis. Trimethylamine N-oxide, produced by the gut microbiome in a state of dysbiosis, upregulates various molecular mechanisms, such as the nuclear factor kappa (NF-kB) molecular pathway, and promotes the expression of scavenger receptors (SRs) on the surfaces of macrophages, leading to foam cell formation and inflammation. High levels of TMAO have been shown to induce the expression of pro-inflammatory cytokines like tumor necrosis factor-alpha (TNF-α) and interleukin 1β (IL-1β) while reducing the expression of anti-inflammatory cytokines such as interleukin-10 (IL-10). Additionally, gut-derived TMAO enhances platelet aggregation and adhesion to collagen, increasing the risk of thrombosis. Conclusions: Understanding the association between gut microbiome compositions such as gut TMAO and their effects on SARS-CoV-19 infection progression helps to control disease severity. In this review, we presented a hypothesis that the gut TMAO has the potential to increase COVID-19 disease severity.

Comparison of the low-calorie DASH diet and a low-calorie diet on serum TMAO concentrations and gut microbiota composition of adults with overweight/obesity: a randomized control trial

This study compares two diets, Dietary Approaches to Stop Hypertension (DASH) and a Low-Calorie Diet on Trimethylamine N-oxide (TMAO) levels and gut microbiota. 120 obese adults were randomly allocated to these three groups: a low-calorie DASH diet, a Low-Calorie diet, or a control group for 12 weeks. Outcomes included plasma TMAO, lipopolysaccharides (LPS), and gut microbiota profiles. After the intervention, the low-calorie DASH diet group demonstrated a greater decrease in TMAO levels (-20 ± 8.1 vs. −10.63 ± 4.6 μM) and a significant decrease in LPS concentration (-19.76 ± 4.2 vs. −5.68 ± 2.3) compared to the low-calorie diet group. Furthermore, the low-calorie DASH diet showed a higher decrease in the Firmicutes and Bactericides (F/B) ratio, which influenced TMAO levels, compared to the Low-Calorie diet (p = 0.028). The current study found the low-calorie DASH diet improves TMAO and LPS in comparison to a Low-Calorie diet.

Higher serum trimethylamine N-oxide (TMAO) levels are associated with increased visceral fat in hemodialysis patients.

Trimethylamine N-oxide (TMAO), a gut microbiota-derived metabolite, has emerged as a new potentially important cause of increased atherosclerosis and cardiovascular risk in chronic kidney disease (CKD) patients. However, the possible causes whereby TMAO potentiates atherosclerosis development remain poorly defined. The strong association between gut microbiota and obesity suggested that the TMAO pathway may be linked to the pathogenesis of obesity. A total of 184 hemodialysis (HD) patients and 38 healthy controls were enrolled in the study from March 2019 to May 2019. We evaluated visceral fat area (VFA) by anthropometric measurement and measured serum TMAO concentrations using liquid chromatography/differential ion mobility spectrometry tandem mass spectrometry. We also examined the relationship between TMAO levels and visceral fat accumulation. TMAO level was markedly higher in HD patients than in control subjects (5.80 (3.96, 9.46) vs. 0.18 (0.11, 0.32) µg/mL, p<0.01), and its level in diabetic HD patients was significantly higher than in nondiabetic patients (6.93 (4.67, 11.40) vs. 5.25 (3.78, 8.02) µg/mL, p<0.01). A significant positive correlation was found between serum TMAO level and VFA in these patients (r=0.282, p=0.005). Multiple regression analysis showed that Ln(TMAO) was independently associated with Ln(VFA) in HD patients (p=0.008). Our results showed that there was a significant positive correlation between serum TMAO levels and visceral fat in HD patients, which suggested that TMAO may predict cardiovascular risk through increased visceral fat.

Trimethylamine N-Oxide Exacerbates Neuroinflammation and Motor Dysfunction in an Acute MPTP Mice Model of Parkinson's Disease.

Observational studies have shown abnormal changes in trimethylamine N-oxide (TMAO) levels in the peripheral circulatory system of Parkinson's disease (PD) patients. TMAO is a gut microbiota metabolite that can cross the blood-brain barrier and is strongly related to neuroinflammation. Neuroinflammation is one of the pathological drivers of PD. Herein, we investigated the effect of TMAO on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model mice. TMAO pretreatment was given by adding 1.5% (w/v) TMAO to the drinking water of the mice for 21 days; then, the mice were administered MPTP (20 mg/kg, i.p.) four times a day to construct an acute PD model. Their serum TMAO concentrations, motor function, dopaminergic network integrity, and neuroinflammation were then assayed. The results showed that TMAO partly aggravated the motor dysfunction of the PD mice. Although TMAO had no effect on the dopaminergic neurons, TH protein content, and striatal DA level in the PD mice, it significantly reduced the striatal 5-HT levels and aggravated the metabolism of DA and 5-HT. Meanwhile, TMAO significantly activated glial cells in the striatum and the hippocampi of the PD mice and promoted the release of inflammatory cytokines in the hippocampus. In summary, higher-circulating TMAO had adverse effects on the motor capacity, striatum neurotransmitters, and striatal and hippocampal neuroinflammation in PD mice.

Trimethylamine N-Oxide and Related Metabolites in the Serum and Risk of Type 2 Diabetes in the Chinese Population: A Case-Control Study.

Trimethylamine N-oxide (TMAO) and its precursors have an association with type 2 diabetes mellitus (T2DM); however, the evidence is unclear. The current study examined the association of serial measures of serum TMAO and related metabolite concentrations with the risk of T2DM. Our study was designed as a community case-control study with 300 participants (150 T2DM and 150 non-T2DM). We examined the association of serum concentrations of TMAO and its related metabolites [trimethylamine, choline, betaine, and L-carnitine] using UPLC-MS/MS. The association between these metabolites and the risk of T2DM was analyzed using a restricted cubic spline and binary logistic regression. A higher serum choline concentration was significantly associated with an increased risk of T2DM. Serum choline > 22.62 μmol/L was independently associated with an increased risk of T2DM, and the odds ratio was 3.615 [95% CI: (1.453,8.993), P = 0.006]. Similarly, serum betaine and L-carnitine concentrations had a markedly decreased risk of T2DM even after adjusting for the traditional risk factors for T2DM and betaine (0.978 [95% CI:0.964-0.992], P = 0.002) and L-carnitine (0.949 [95% CI: 0.9222-0.978], P = 0.001), respectively. Choline, betaine, and L-carnitine are associated with the risk of T2DM and may be appropriate risk markers to protect high-risk individuals from T2DM.

Higher serum trimethylamine-N-oxide levels are associated with increased abdominal aortic calcification in hemodialysis patients

Introduction Vascular calcification (VC) is high prevalent and predicts cardiovascular mortality in dialysis patients. The mechanisms are not known clearly. Trimethylamine-N-oxide (TMAO), a gut-microbiota derivate metabolite, is also associated with cardiovascular outcomes in hemodialysis (HD) patients. This study aims to evaluate serum TMAO levels and establish their relation to VC in HD patients. Methods Serum TMAO concentrations were measured by high-performance liquid chromatography–mass spectrometry. Vascular calcification was evaluated by abdominal aortic calcification (AAC) scores. Taking the AAC score value 5.5 as the cutoff value, the participants were divided into the high AAC score group and the low AAC score group. Results A total of 184 HD patients and 39 healthy controls were enrolled in this cross-sectional study. Serum Ln(TMAO) (the natural logarithm of TMAO) concentrations were significantly higher in HD patients than that of control subjects (1.82 ± 0.62 vs. −1.60 ± 0.77, p < 0.001). Compared with the group with low AAC scores, the HD patients with high AAC scores showed significantly higher serum Ln(TMAO) levels (2.09 ± 0.55 vs. 1.67 ± 0.54, p < 0.001). In the multivariate regression analysis, serum Ln(TMAO), HD vintage, with diabetic mellitus, age and plasma intact parathyroid hormone (iPTH) were independent determinant factors for VC in HD patients. Conclusions Higher serum TMAO levels, older age, longer HD vintage, higher plasma iPTH and with diabetes mellitus were independent risk factors for VC in HD patients. The underlying mechanism deserves further investigations and the finding hints at a new target for the treatment of VC.

Trimethylamine N-Oxide (TMAO) and Indoxyl Sulfate Concentrations in Patients with Alcohol Use Disorder.

Background: Trimethylamine N-oxide (TMAO) and indoxyl sulfate (IS) are produced by the microbiota and the liver, and can contribute to brain aging and impaired cognitive function. This study aims to examine serum TMAO and IS concentrations in patients with alcohol-use disorder (AUD) at the entry for alcohol withdrawal, and the relationships with several biological, neuropsychological, and clinical parameters. Methods: TMAO and IS were quantified in thirty AUD inpatients and fifteen healthy controls (HC). The severities of AUD and alcohol withdrawal syndrome (AWS), and general cognitive abilities were assessed in AUD patients. Results: TMAO concentrations did not differ between HC and AUD patients. Several biomarkers assessing nutritional status and liver function were significantly different in AUD patients with the lowest TMAO concentrations compared to other AUD patients. IS concentration was significantly lower in AUD patients and a significant positive predictor of serum prealbumin variation during the acute phase of alcohol withdrawal. No relationship was observed between the concentrations of these metabolites and the severities of alcohol dependence, AWS, or cognitive deficits. Conclusions: Our data suggest that AUD patients with low concentrations of TMAO or IS should probably benefit from a personalized refeeding program during the acute phase of alcohol withdrawal.

Adopting a Mediterranean-style eating pattern with low, but not moderate, unprocessed, lean red meat intake reduces fasting serum trimethylamine N-oxide (TMAO) in adults who are overweight or obese.

A Mediterranean-style eating pattern (MED-EP) may include moderate red meat intake. However, it is unknown if the pro-atherogenic metabolite trimethylamine N-oxide (TMAO) is affected by the amount of red meat consumed with a MED-EP. The results presented are from a secondary, retrospective objective of an investigator-blinded, randomized, crossover, controlled feeding trial (two 5-wk interventions separated by a 4-wk washout) to determine if a MED-EP with 200g unprocessed lean red meat/wk (MED-CONTROL) reduces circulating TMAO concentrations compared to a MED-EP with 500g unprocessed lean red meat/wk (MED-RED). Participants were 27 women and 12 men (n=39 total) who were either overweight or obese (BMI: 30.5 ± 0.3 kg/m2 mean ± SEM). Serum samples were obtained following an overnight fast both before (pre) and after (post) each intervention. Fasting serum TMAO, choline, carnitine, and betaine concentrations were measured using a targeted Liquid chromatography-mass spectrometry. Data were analyzed to assess if (a) TMAO and related metabolites differed by intervention, and (b) if changes in TMAO were associated with changes in Framingham 10-year risk score. Serum TMAO was lower post-intervention following MED-CONTROL compared to MED-RED intervention (post-MED-CONTROL 3.1 ± 0.2 µM vs. post-MED-RED 5.0 ± 0.5 µM, p<0.001), and decreased following MED-CONTROL (pre- vs post-MED-CONTROL, p = 0.025). Exploratory analysis using mixed model analysis of covariance identified a positive association between changes in TMAO and changes in HOMA-IR (p = 0.036). These results suggest that lower amounts of red meat intake leads to lower TMAO concentrations in the context of a MED-EP.

The Gut Microbial-Derived Metabolite Trimethylamine N-Oxide and Atrial Fibrillation: Relationships, Mechanisms, and Therapeutic Strategies.

Accumulating evidence has demonstrated that gut microbial-derived metabolite trimethylamine N-oxide (TMAO) plays a crucial role in the pathogenesis of many diseases and can be served as a prognostic biomarker for several cardiovascular disorders, including arrhythmia. Recently, some studies have documented that TMAO was associated with the occurrence, progression, recurrence, and embolism risk of atrial fibrillation (AF). The activation of related inflammatory signal pathways and the cardiac sympathetic nervous system (CSNS) caused by elevated TAMO may be the underlying mechanism. It is worth noting that intervention in the metabolic pathway of TMAO may be an underlying therapeutic target of AF. In addition, standardized and individualized treatment strategies in clinical practice may be of great significance for AF patients, particularly those with high serum TMAO concentrations. However, there are also contradictions in the current research on TMAO and AF. Moreover, notwithstanding the positive preclinical and clinical findings, data supporting a direct association between TMAO and AF is a paucity. Thus, conclusive evidence from preclinical studies and multi-center randomized controlled trials to reveal the essential relationship between TMAO and AF is needy. In this review, we have attempted to summarize recent studies on TMAO and AF, highlighted the potential therapeutic strategies for AF patients, followed by a discussion on directions for future research in this field.

Biological variation of major gut-derived uremic toxins in the serum of healthy adult cats.

BackgroundBiological variation of serum indoxyl sulfate (IS), p‐cresol sulfate (pCS), and trimethylamine‐n‐oxide (TMAO) concentrations in cats is unknown.ObjectivesTo determine short‐ and medium‐term biological variation, index of individuality (II), and reference change values for serum IS, pCS, and TMAO concentrations in healthy adult cats. To determine the effect of feeding on serum concentrations.AnimalsTwelve healthy adult cats.MethodsProspective, cohort study. Seven serum samples over a 12‐hour period (short‐term) and 5 serum samples over a 19‐day period (medium‐term) were collected. Serum concentrations of total IS, pCS, and TMAO were measured every 2 hours in a 12‐hour period (hours 0‐12) after a meal in 9 cats and compared to concentrations in a nonfed state.ResultsFor IS, the II was high using short‐term (1.96) and low using medium‐term (0.65) biological variation estimates. Individuality was intermediate for pCS (short‐term, 0.98; medium‐term, 1.17) and TMAO (short‐term, 1.47; medium‐term, 0.83). Serum IS, pCS, and TMAO concentrations were significantly lower in a fed state compared to a nonfed state at hours 4, 6, 8, and 12; at hours 4 and 6; and at hours 2, 4, 6, 8, 10, 12, respectively.Conclusion and Clinical ImportancePopulation‐based reference intervals with reference to the subject‐based interval can be used to monitor serum pCS and TMAO concentrations. For IS, a subject‐based and a population‐based reference interval is best for short‐term and medium‐term monitoring, respectively. To compare serial measurements, it would be prudent to collect samples at the same time of day and consistently in either a fed or nonfed state.

Assessment of trimethylamine-N-oxide at the blood-cerebrospinal fluid barrier: Results from 290 lumbar punctures.

Recently, the microbiome-derived trimethylamine-N-oxide (TMAO) was shown to be present in human cerebrospinal fluid (CSF). However, data on the potential of TMAO crossing the blood-CSF barrier are still lacking. This retrospective study aimed at investigating possible associations between the CSF/serum albumin (QALB) and TMAO (QTMAO) quotient and evaluating QTMAO values in individuals with and without blood-CSF barrier dysfunction. A total of 290 patients, who underwent diagnostic lumbar puncture with QALB and QTMAO determination, were evaluated. Serum and CSF TMAO measurements were performed on a tandem mass spectrometry SCIEX QTRAP 4500 (Applied Biosystems, Framingham, MA, USA) coupled with an Agilent 1260 Infinity HPLC system (Agilent Technologies Santa Clara, CA, USA). Serum and CSF albumin were measured on the Atellica® NEPH 630 system (Siemens Healthineers, Erlangen, Germany). CSF TMAO levels were positively correlated with serum TMAO levels (ρ = 0.709, p < 0.001). The QALB was significantly associated with the QTMAO (ß-coefficient = 0.312; p < 0.001). A total of 117 patients with blood-CSF barrier dysfunction had significantly higher median (Q1 - Q3) QTMAO values (4.7 (2.8 - 7.5) vs. 3.8 (2.5 - 5.7) x 10-1, p = 0.002) compared to 173 individuals with normal blood-CSF barrier function. CSF and serum TMAO concentrations were significantly associated in 290 CSF/serum pairs from lumbar punctures of clinical routine. QALB showed a relevant influence on QTMAO. Present results indicate that TMAO may cross the blood-CSF barrier.

Serum Trimethylamine-N-oxide Concentrations in People Living with HIV and the Effect of Probiotic Supplementation

BackgroundThe incidence of cardiovascular disorders in people living with HIV (PLWH) is higher than that in non-infected individuals. Traditional and specific risk factors have been described but the role of the gut microbiota-dependent choline metabolite, trimethylamine-N-oxide (TMAO) is still unclear. MethodsA cross-sectional analysis and a longitudinal analysis (with high-dose probiotic supplementation) were performed to measure serum TMAO concentrations through UHPLC-MS/MS. Stable outpatients living with HIV on highly active antiretroviral treatment with no major cardiovascular disease were enrolled. Non-parametric tests (bivariate and paired tests) and a multivariate linear regression analysis were used. ResultsA total of 175 participants were enrolled in the study. Median serum TMAO concentrations were 165 (103-273) ng/mL. An association with age, serum creatinine, number of antiretrovirals, multimorbidity and polypharmacy was observed; at linear logistic regression analysis, multimorbidity was the only independent predictor of TMAO concentrations. Carotid intima media thickness (IMT) was 0.85 (0.71-1.21) mm, with a trend towards higher TMAO concentrations observed in patients with IMT >0.9 mm (P=0.087). In the 25 participants who received probiotic supplementation, TMAO levels did not significantly change after 24 weeks (Wilcoxon paired P=0.220). ConclusionSerum TMAO levels in PLWH were associated with multimorbidity, higher cardiovascular risk and subclinical atherosclerosis and were not affected by 6 months of high-dose probiotic supplementation.

Sex-Specific Associations of Trimethylamine-N-Oxide and Zonulin with Signs of Depression in Carbohydrate Malabsorbers and Nonmalabsorbers.

Background The microbiome-derived trimethylamine-N-oxide (TMAO) and the intestinal permeability marker zonulin are considered to be linked with depression. Moreover, carbohydrate malabsorption (CMA) was shown to be associated with signs of depression. This study is aimed at investigating possible sex-specific associations between TMAO and zonulin and the presence of depressive signs in individuals with and without CMA. Methods Serum concentrations of TMAO and zonulin were determined in 115 and 136 individuals with the presence or absence of CMA. All 251 study participants underwent lactase gene C/T−13910 polymorphism genotyping and fructose H2/CH4 breath testing. Additionally, they filled in the Beck Depression Inventory (BDI-II) questionnaire. Results The median TMAO and zonulin serum concentrations were 2.66 (1.93–4.14) μmol/L and 40.83 (34.73–47.48) ng/mL. Serum TMAO levels were positively correlated with depressive symptoms (P = 0.011, ρ = 0.160). The strongest correlations were observed in 87 females (P = 0.010, ρ = 0.274) and 49 males (P = 0.027, ρ = 0.315) without CMA, whereas 115 patients with CMA showed no significant correlations. Zonulin tended to be negatively correlated with the BDI-II score in 49 males without CMA (P = 0.062, ρ = −0.269). Conclusion This study demonstrates a positive correlationship between the serum TMAO concentrations and the severity of depressive symptoms in females and males without CMA. Serum zonulin levels were negatively correlated with signs of depression in males without CMA. These findings suggest a gender-specific relationship between the serum TMAO and zonulin concentrations, depression, and CMA.

Determination of Trimethylamine-N-oxide by a Simple Isocratic High-Throughput Liquid-Chromatography Tandem Mass-Spectrometry Method.

As trimethylamine-N-oxide (TMAO) is considered to be associated with various diseases, rapid determination of serum TMAO concentration is of clinical interest. This study is aimed at evaluating the analytical performance of a simple isocratic liquid chromatography-tandem mass-spectrometry (LC-MS/MS) method for TMAO quantification. TMAO measurements were performed on a tandem mass spectrometer, SCIEX QTRAP 4500 (Applied Biosystems, Framingham, MA, USA), coupled with an Agilent 1260 Infinity HPLC system (Agilent Technologies, Santa Clara, CA, USA). The separation was performed on a Hypercarb Porus Grahitic Carbon (PGC) column (ThermoFisher Scientific, Waltham, MA, USA) by isocratic elution mode. Linearity, precision, recovery, and pre-analytical requirements of the TMAO LC-MS/MS method were evaluated. The imprecision acceptance criteria were defined 15%. We investigated sample stability at room temperature (RT) and assessed the serum TMAO concentrations of 188 healthy adults. The TMAO LC-MS/MS method was linear over the concentration range of 0.5 - 80 μmol/L. Intra- and inter-day precision ranged between 2.24 - 3.37% and 6.95 - 9.97%, recovery between 106 - 114%, respectively. At RT, serum samples were stable for 8 days. The median serum TMAO concentration of 188 healthy adults was 2.27 μmol/L (2.5th and 97.5th percentile: 0.75 - 10.46 μmol/L), respectively. The isocratic TMAO LC-MS/MS shows a broad analytical range and meets the imprecision acceptance criteria of 15%. This method is a robust and reliable diagnostic tool for the assessment of the human TMAO status. Serum samples are stable at RT for at least 8 days.

Metabolic Activation of Flavin Monooxygenase-mediated Trimethylamine-N-Oxide Formation in Experimental Kidney Disease

Cardiovascular disease (CVD) remains the leading cause of death in chronic kidney disease (CKD) patients despite treatment of traditional risk factors, suggesting that non-traditional CVD risk factors are involved. Trimethylamine-N-oxide (TMAO) correlates with atherosclerosis burden in CKD patients and may be a non-traditional CVD risk factor. Serum TMAO concentrations are significantly increased in CKD patients, which may be due in part to increased hepatic flavin monooxygenase (FMO)-mediated TMAO formation. The objective of this work was to elucidate the mechanism of increased FMO activity in CKD. In this study, FMO enzyme activity experiments were conducted in vitro with liver microsomes isolated from experimental CKD and control rats. Trimethylamine was used as a probe substrate to assess FMO activity. The FMO activator octylamine and human uremic serum were evaluated. FMO gene and protein expression were also determined. FMO-mediated TMAO formation was increased in CKD versus control. Although gene and protein expression of FMO were not changed, metabolic activation elicited by octylamine and human uremic serum increased FMO-mediated TMAO formation. The findings suggest that metabolic activation of FMO-mediated TMAO formation is a novel mechanism that contributes to increased TMAO formation in CKD and represents a therapeutic target to reduce TMAO exposure and CVD.

Long-term Paleolithic diet is associated with lower resistant starch intake, different gut microbiota composition and increased serum TMAO concentrations

BackgroundThe Paleolithic diet is promoted worldwide for improved gut health. However, there is little evidence available to support these claims, with existing literature examining anthropometric and cardiometabolic outcomes.ObjectiveTo determine the association between dietary intake, markers of colonic health, microbiota, and serum trimethylamine-N-oxide (TMAO), a gut-derived metabolite associated with cardiovascular disease.DesignIn a cross-sectional design, long-term (n = 44, > 1 year) self-reported followers of a Paleolithic diet (PD) and controls (n = 47) consuming a diet typical of national recommendations were recruited. Diets were assessed via 3-day weighed diet records; 48-h stool for short chain fatty acids using GC/MS, microbial composition via 16S rRNA sequencing of the V4 region using Illumina MiSeq. TMAO was quantified using LC–MS/MS.ResultsParticipants were grouped according to PD adherence; namely excluding grains and dairy products. Strict Paleolithic (SP) (n = 22) and Pseudo-Paleolithic (PP) (n = 22) groups were formed. General linear modelling with age, gender, energy intake and body fat percentage as covariates assessed differences between groups. Intake of resistant starch was lower in both Paleolithic groups, compared to controls [2.62, 1.26 vs 4.48 g/day (P < 0.05)]; PERMANOVA analysis showed differences in microbiota composition (P < 0.05), with higher abundance of TMA-producer Hungatella in both Paleolithic groups (P < 0.001). TMAO was higher in SP compared to PP and control (P < 0.01), and inversely associated with whole grain intake (r = − 0.34, P < 0.01).ConclusionsAlthough the PD is promoted for improved gut health, results indicate long-term adherence is associated with different gut microbiota and increased TMAO. A variety of fiber components, including whole grain sources may be required to maintain gut and cardiovascular health.Clinical trial registrationsAustralian and New Zealand Clinical Trial Registry (ANZCTRN12616001703493).

Trimethylamine N-Oxide and Cardiovascular Outcomes in Patients with ESKD Receiving Maintenance Hemodialysis.

Trimethylamine N-oxide (TMAO), a compound derived from byproducts of intestinal bacteria, has been shown to accelerate atherosclerosis in rodents. To date, there are conflicting data regarding the association of serum TMAO with cardiovascular outcomes in patients with ESKD, a population exhibiting both high serum TMAO and excessive atherosclerosis. We measured baseline serum TMAO concentrations in a subset of participants (n=1243) from the Evaluation of Cinacalcet Hydrochloride Therapy to Lower Cardiovascular Events (EVOLVE) trial and conducted post hoc analyses evaluating the association between baseline serum TMAO and cardiovascular outcomes. We observed a wide distribution of serum TMAO in our cohort, with approximately 80% of participants exhibiting TMAO concentrations ≥56 µM and a maximum TMAO concentration of 1103.1 µM. We found no association between TMAO and our primary outcome, a composite of cardiovascular mortality, myocardial infarction, peripheral vascular event, stroke, and hospitalization for unstable angina. Moreover, in unadjusted and adjusted analyses, we observed no relation between TMAO and all-cause mortality, the independent components of our composite outcome, or the original EVOLVE primary outcome. Although we did observe higher TMAO concentrations in white participants, further subgroup analyses did not confirm the previously identified interaction between TMAO and race observed in a prior study in patients receiving dialysis. We found no evidence linking TMAO to adverse clinical outcomes in patients receiving maintenance hemodialysis with moderate to severe secondary hyperparathyroidism.

A Paleolithic diet lowers resistant starch intake but does not affect serum trimethylamine-N-oxide concentrations in healthy women.

The Paleolithic diet excludes two major sources of fibre, grains and legumes. However, it is not known whether this results in changes to resistant starch (RS) consumption. Serum trimethylamine-N-oxide (TMAO) is produced mainly from colonic fermentation and hepatic conversion of animal protein and is implicated in CVD, but changes in RS intake may alter concentrations. We aimed to determine whether intake of RS and serum concentrations of TMAO varied in response to either the Paleolithic or the Australian Guide to Healthy Eating (AGHE) diets and whether this was related to changes in food group consumption. A total of thirty-nine women (mean age 47 (sd 13) years, BMI 27 (sd 4) kg/m2) were randomised to AGHE (n 17) or Paleolithic diets (n 22) for 4 weeks. Serum TMAO concentrations were measured using liquid chromatography-MS; food groups, fibre and RS intake were estimated from weighed food records. The change in TMAO concentrations between groups (Paleolithic 3·39 μm v. AGHE 1·19 μm, P = 0·654) did not reach significance despite greater red meat and egg consumption in the Paleolithic group (0·65 serves/d; 95 % CI 0·2, 1·1; P &lt;0·01, and 0·22 serves/d; 95 % CI 0·1, 0·4, P &lt;0·05, respectively). RS intake was significantly lower on the Paleolithic diet (P &lt;0·01) and was not associated with TMAO concentrations. However, the limited data for RS and the small sample size may have influenced these findings. While there were no significant changes in TMAO concentrations, increased meat consumption and reduced RS intake warrant further research to examine the markers of gastrointestinal health of Paleolithic diet followers and to update Australian food databases to include additional fibre components.

Decreased Kidney Function Is Associated with Enhanced Hepatic Flavin Monooxygenase Activity and Increased Circulating Trimethylamine N-Oxide Concentrations in Mice.

Circulating trimethylamine N-oxide (TMAO) predicts poor cardiovascular outcomes in patients with chronic kidney disease (CKD). Accumulation of serum TMAO has been observed in CKD patients; however, the mechanisms contributing to this finding have been inadequately explored. The purpose of this study was to investigate the mechanisms responsible for TMAO accumulation in the setting of decreased kidney function using a CKD mouse model. Mice were fed a diet supplemented with 0.2% adenine to induce CKD, which resulted in increased serum TMAO concentrations (females: CKD 29.4 ± 32.1 μM vs. non-CKD 6.9 ± 6.1 μM, P < 0.05; males: CKD 18.5 ± 13.1 μM vs. non-CKD 1.0 ± 0.5 μM, P < 0.001). As anticipated, accumulation of circulating TMAO was accompanied by a decrease in renal clearance (females: CKD 5.2 ± 3.8 μl/min vs. non-CKD 90.4 ± 78.1 μl/min, P < 0.01; males: CKD 10.4 ± 8.1 μl/min vs. non-CKD 260.4 ± 134.5 μl/min; P < 0.001) and fractional excretion of TMAO. Additionally, CKD animals exhibited an increase in hepatic flavin monooxygenase (FMO)-mediated formation of TMAO (females: CKD 125920 ± 2181 pmol/mg per 60 minutes vs. non-CKD 110299 ± 4196 pmol/mg per 60 minutes, P < 0.001; males: CKD 131286 ± 2776 pmol/mg per 60 minutes vs. non-CKD 74269 ± 1558 pmol/mg per 60 minutes, P < 0.001), which likely resulted from increased FMO3 expression in CKD mice. The current study provides evidence that both decreased renal clearance and increased hepatic production of TMAO may contribute to increments in serum TMAO in the setting of CKD. Hepatic FMO activity may represent a novel therapeutic target for lowering circulating TMAO in CKD patients.