Dietary precursors of trimethylamine in man: a pilot study

Impact of Egg Consumption on Cardiovascular Risk Factors in Individuals with Type 2 Diabetes and at Risk for Developing Diabetes: A Systematic Review of Randomized Nutritional Intervention Studies

Observational studies have reported inconclusive results regarding the relationship between egg consumption (and dietary cholesterol) and the risk for cardiovascular diseases (CVDs) in individuals with type 2 diabetes, which has led to inconsistent recommendations to patients. We reviewed the evidence of egg consumption on major CVD risk factors in individuals with or at risk for type 2 diabetes (prediabetes, insulin resistance or metabolic syndrome). We performed a systematic search in the databases PubMed, MEDLINE, EMBASE and Web of Science in January 2016. Inclusion criteria included randomized controlled trials in which the amount of egg consumed was manipulated and compared to a control group that received no-egg or low-egg diets (<2 eggs/week). We found 10 articles (6 original trials) that met our inclusion criteria. The majority of studies found that egg consumption did not affect major CVD risk factors. Consumption of 6 to 12 eggs per week had no impact on plasma concentrations of total cholesterol, low-density lipoprotein-cholesterol, triglycerides, fasting glucose, insulin or C-reactive protein in all studies that reported these outcomes in comparison with control groups. An increase in high-density lipoprotein-cholesterol with egg consumption was observed in 4 of 6 studies. Results from randomized controlled trials suggest that consumption of 6 to 12 eggs per week, in the context of a diet that is consistent with guidelines on cardiovascular health promotion, has no adverse effect on major CVD risk factors in individuals at risk for developing diabetes or with type 2 diabetes. However, heterogeneities in study design, population included and interventions prevent firm conclusions from being drawn.

Genome- and CD4+ T-cell methylome-wide association study of circulating trimethylamine-N-oxide in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN)

BACKGROUND

Trimethylamine-N-oxide (TMAO), an atherogenic metabolite species, has emerged as a possible new risk factor for cardiovascular disease. Animal studies have shown that circulating TMAO levels are regulated by genetic and environmental factors. However, large-scale human studies have failed to replicate the observed genetic associations, and epigenetic factors such as DNA methylation have never been examined in relation to TMAO levels.

METHODS AND RESULTS

We used data from the family-based Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) to investigate the heritable determinants of plasma TMAO in humans. TMAO was not associated with other plasma markers of cardiovascular disease, e.g. lipids or inflammatory cytokines. We first estimated TMAO heritability at 27%, indicating a moderate genetic influence. We used 1000 Genomes imputed data (n=626) to estimate genome-wide associations with TMAO levels, adjusting for age, sex, family relationships, and study site. The genome-wide study yielded one significant hit at the genome-wide level, located in an intergenic region on chromosome 4. We subsequently quantified epigenome-wide DNA methylation using the Illumina Infinium array on CD4+ T-cells. We tested for association of methylation loci with circulating TMAO (n=847), adjusting for age, sex, family relationships, and study site as the genome-wide study plus principal components capturing CD4+ T-cell purity. Upon adjusting for multiple testing, none of the epigenetic findings were statistically significant.

CONCLUSIONS

Our findings contribute to the growing body of evidence suggesting that neither genetic nor epigenetic factors play a critical role in establishing circulating TMAO levels in humans.

A metabolomic study of biomarkers of meat and fish intake

Background: Meat and fish intakes have been associated with various chronic diseases. The use of specific biomarkers may help to assess meat and fish intake and improve subject classification according to the amount and type of meat or fish consumed.Objective: A metabolomic approach was applied to search for biomarkers of meat and fish intake in a dietary intervention study and in free-living subjects from the European Prospective Investigation into Cancer and Nutrition (EPIC) study.Design: In the dietary intervention study, 4 groups of 10 subjects consumed increasing quantities of chicken, red meat, processed meat, and fish over 3 successive weeks. Twenty-four-hour urine samples were collected during each period and analyzed by high-resolution liquid chromatography-mass spectrometry. Signals characteristic of meat or fish intake were replicated in 50 EPIC subjects for whom a 24-h urine sample and 24-h dietary recall were available and who were selected for their exclusive intake or no intake of any of the 4 same foods.Results: A total of 249 mass spectrometric features showed a positive dose-dependent response to meat or fish intake in the intervention study. Eighteen of these features best predicted intake of the 4 food groups in the EPIC urine samples on the basis of partial receiver operator curve analyses with permutation testing (areas under the curve ranging between 0.61 and 1.0). Of these signals, 8 metabolites were identified. Anserine was found to be specific for chicken intake, whereas trimethylamine-N-oxide showed good specificity for fish. Carnosine and 3 acylcarnitines (acetylcarnitine, propionylcarnitine, and 2-methylbutyrylcarnitine) appeared to be more generic indicators of meat and meat and fish intake, respectively.Conclusion: The meat and fish biomarkers identified in this work may be used to study associations between meat and fish intake and disease risk in epidemiologic studies. This trial was registered at clinicaltrials.gov as NCT01684917.

Functional Coupling of Human Microphysiology Systems: Intestine, Liver, Kidney Proximal Tubule, Blood-Brain Barrier and Skeletal Muscle

Organ interactions resulting from drug, metabolite or xenobiotic transport between organs are key components of human metabolism that impact therapeutic action and toxic side effects. Preclinical animal testing often fails to predict adverse outcomes arising from sequential, multi-organ metabolism of drugs and xenobiotics. Human microphysiological systems (MPS) can model these interactions and are predicted to dramatically improve the efficiency of the drug development process. In this study, five human MPS models were evaluated for functional coupling, defined as the determination of organ interactions via an in vivo-like sequential, organ-to-organ transfer of media. MPS models representing the major absorption, metabolism and clearance organs (the jejunum, liver and kidney) were evaluated, along with skeletal muscle and neurovascular models. Three compounds were evaluated for organ-specific processing: terfenadine for pharmacokinetics (PK) and toxicity; trimethylamine (TMA) as a potentially toxic microbiome metabolite; and vitamin D3. We show that the organ-specific processing of these compounds was consistent with clinical data, and discovered that trimethylamine-N-oxide (TMAO) crosses the blood-brain barrier. These studies demonstrate the potential of human MPS for multi-organ toxicity and absorption, distribution, metabolism and excretion (ADME), provide guidance for physically coupling MPS, and offer an approach to coupling MPS with distinct media and perfusion requirements.

Trimethylamine-N-Oxide: Friend, Foe, or Simply Caught in the Cross-Fire?

Trimethylamine-N-oxide (TMAO), a gut-derived metabolite, has recently emerged as a candidate risk factor for cardiovascular disease and other adverse health outcomes. However, the relation between TMAO and chronic disease can be confounded by several factors, including kidney function, the gut microbiome, and flavin-containing monooxygenase 3 (FMO3) genotype. Thus, whether TMAO is a causative agent in human disease development and progression, or simply a marker of an underlying pathology, remains inconclusive. Importantly, dietary sources of TMAO have beneficial health effects and provide nutrients that have critical roles in many biological functions. Pre-emptive dietary strategies to restrict TMAO-generating nutrients as a means to improve human health warrant careful consideration and may not be justified at this time.

Protective Effects of L-Carnitine Against Delayed Graft Function in Kidney Transplant Recipients: A Pilot, Randomized, Double-Blinded, Placebo-Controlled Clinical Trial

OBJECTIVE

Delayed graft function (DGF) is an early complication after deceased donor kidney transplantation with significant adverse effects on graft outcomes. Ischemia-reperfusion injury during transplantation is a major cause of DGF. Tissue concentrations of carnitine, an antioxidant and regulator of cellular energy supply, decrease in the kidney following ischemia-reperfusion insult. Based on promising animal data, this study evaluated the possible protective effect of L-carnitine against DGF.

DESIGN

This study is a pilot, randomized, double-blind, placebo-controlled clinical trial that was conducted on kidney transplantation patients in kidney transplant ward of Imam Khomeini hospital complex affiliated to Tehran University of Medical Sciences, Tehran, Iran.

SUBJECTS

Patients older than 14 years old undergoing their first kidney transplantation from a deceased donor were evaluated for eligibility to take part in this study. Fifty-six patients were randomly assigned to L-carnitine or placebo groups.

INTERVENTION

During this trial, 3 g of oral L-carnitine or placebo was administered in 3 divided doses each day for 4 consecutive days starting the day before kidney transplantation (i.e., days -1, 0, 1, and 2).

MAIN OUTCOME MEASURE

The need for dialysis within the first week after transplantation, serum creatinine and urine output were assessed daily. After hospital discharge, patients were followed for 3 months regarding organ function.

RESULTS

DGF incidence did not differ between the L-carnitine and placebo groups (18.51% vs. 23.8%, respectively; P = .68). Total allograft failure within 3 months after kidney transplantation happened in 6 patients in the placebo and 1 patient in the L-carnitine group (P = .05).

CONCLUSION

This study showed no protective effects of oral L-carnitine supplementation against DGF occurrence recipients; however, 3-month graft loss was lower in the L-carnitine supplemented group.

Urine Metabolomics in Hypertension Research

Functional genomics requires an understanding of the complete network of changes within an organism by extensive measurements of moieties from mRNA, proteins, and metabolites. Metabolomics utilizes analytic chemistry tools to profile the complete spectrum of metabolites found in a tissue, cells, or biofluids using a wide range of tools from infrared spectroscopy, fluorescence spectroscopy, NMR spectroscopy, and mass spectrometry. In this protocol, we outline a procedure for performing metabolomic analysis of urine samples using liquid chromatography-mass spectrometry (LC-MS). We outline the advantages of using this approach and summarize some of the early promising studies in cardiovascular diseases using this approach.

Intestinal Microbiota Metabolism and Atherosclerosis

Objective:

This review aimed to summarize the relationship between intestinal microbiota metabolism and cardiovascular disease (CVD) and to propose a novel CVD therapeutic target.

Data Sources:

This study was based on data obtained from PubMed and EMBASE up to June 30, 2015. Articles were selected using the following search terms: “Intestinal microbiota”, “trimethylamine N-oxide (TMAO)”, “trimethylamine (TMA)”, “cardiovascular”, and “atherosclerosis”.

Study Selection:

Studies were eligible if they present information on intestinal microbiota metabolism and atherosclerosis. Studies on TMA-containing nutrients were also included.

Results:

A new CVD risk factor, TMAO, was recently identified. It has been observed that several TMA-containing compounds may be catabolized by specific intestinal microbiota, resulting in TMA release. TMA is subsequently converted to TMAO in the liver. Several preliminary studies have linked TMAO to CVD, particularly atherosclerosis; however, the details of this relationship remain unclear.

Conclusions:

Intestinal microbiota metabolism is associated with atherosclerosis and may represent a promising therapeutic target with respect to CVD management.

Trimethylamine-N-oxide (TMAO) predicts fatal outcomes in community-acquired pneumonia patients without evident coronary artery disease

INTRODUCTION

The pro-atherosclerotic metabolite trimethylamine-N-oxide (TMAO) is a risk factor for incident cardiovascular events and a potentially modifiable mediator of chronic inflammation through broad-spectrum antibiotic treatment by changing the microbiome. Whether TMAO is associated with adverse clinical outcomes in acute inflammatory community-acquired pneumonia (CAP) patients is unknown.

METHODS

A total of 317 CAP patients from a previous Swiss multicenter trial were prospectively followed for a median of 6.1years. TMAO plasma levels were measured by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). We used Cox regression models to investigate associations between baseline TMAO levels and all-cause mortality.

RESULTS

Six-year mortality was 45.1%, and 18.9% of the patients had coronary artery disease (CAD). Median admission TMAO (μmolL^-1) levels were significantly higher in non-survivors compared to survivors (4.1 [interquartile range (IQR), 2.2-7.2] vs. 2.5 [IQR, 1.5-4.1]; p<0.001). A strong association between TMAO and 6-year all-cause mortality was found for patients without CAD (adjusted hazard ratio (HR) 1.9 ([95% CI 1.2-3.1]; p<0.05). In patients with known CAD, no such association was found (adjusted HR 0.6 (0.2-1.6); p=0.309, interaction p=0.009). In patients without antibiotic pretreatment receiving antibiotic treatment, TMAO significantly decreased from admission to day seven (median, 3.9 [IQR, 2.1-7.5] vs. 3.1 [IQR, 1.4-6.6]; p<0.01).

CONCLUSIONS

TMAO is associated with long-term fatal outcomes in CAP patients without evident CAD and modifiable through antibiotic treatment. Whether chronic modulation of TMAO by targeting the microbiome reduces mortality risk needs to be evaluated in future interventional trials.

1H NMR-based metabolic study reveals the improvements of bitter melon (Momordica charantia) on energy metabolism in diet-induced obese mouse

CONTEXT

Obesity can be ameliorated by some natural products such as polyphenol, flavones and saponin. As a typical medicinal plant, Momordica charantia L. (Cucurbitaceae) (bitter melon, BM) contains these natural chemicals and reduces diet-induced obesity in mice.

OBJECTIVE

This study evaluates the metabolic effects of dietary BM supplement, investigates a global metabolic profile and determines associated perturbations in metabolic pathways.

MATERIALS AND METHODS

Male C57BL/6 mice were fed with low-fat diet (LFD), high-fat diet (HFD) and HFD supplemented with 5% BM based on 37.6 g/kg body weight in average for 12 weeks, respectively. Then energy metabolism was quantified using PhenoMaster/LabMaster. The spectroscopy of urine was acquired by nuclear magnetic resonance and latent biomarkers were identified. Pattern recognition analysis was used to discriminate associated metabolic profiles.

RESULTS

Dietary BM supplement reduced body weight gain (-0.15-fold, p < 0.01) and blood glucose levels (-0.19-fold, p < 0.01) in HFD-fed mice. Meanwhile, the levels of energy metabolism were enhanced (0.08-0.11-fold, p < 0.01). According to pattern recognition analysis, dietary BM supplement changed metabolic profiles in HFD-fed mice and the modified profiles were similar to those in LFD-fed mice. Finally, the mapping of metabolic pathways showed that dietary BM supplement primarily affected glucose metabolism-associated pathways.

DISCUSSION AND CONCLUSION

The results indicated that BM improves weight loss in diet-induced obesity and elevate energy expenditure in HFD-fed mice. The pattern recognition with metabolic study may be used as a noninvasive detection method to assess the effects of dietary BM supplement on mouse energy metabolism.

Dietary, anthropometric, and biochemical factors influencing plasma choline, carnitine, trimethylamine, and trimethylamine-N-oxide concentrations

The objective of the study was to evaluate the nutritional, anthropometric, and biochemical factors that influence choline, l-carnitine, trimethylamine (TMA), and trimethylamine-N-oxide (TMAO) metabolism in elderly women. The volunteers' diet was assessed using a food frequency questionnaire. Dietary patterns were estimated using a self-established score method. Body mass index (BMI), serum glucose, total, HDL, LDL cholesterol, triacylglycerol, homocysteine (tHcy), free choline (fchol), L-carnitine, TMA, and TMAO were assessed. Higher concentrations of l-carnitine, fchol, and TMAO were found in those women who had more western-style dietary patterns. Nor choline or betaine intake affected plasma fchol, TMA, or TMAO. BMI was positively correlated with fchol and TMA. tHcy was positively correlated with fchol, TMA, and TMAO, while fchol was also positively correlated with TMA and TMAO. Dietary patterns and plasma tHcy concentration influence fchol, TMA, and TMAO plasma concentration. Plasma TMA and fchol may be associated with BMI.

Serum pharmacokinetics of choline, trimethylamine, and trimethylamine-N-oxide after oral gavage of phosphatidylcholines with different fatty acid compositions in mice

Little is known about the pharmacokinetics of phosphatidylcholine (PC)-derived choline, trimethylamine (TMA), and trimethylamine-N-oxide (TMAO). We therefore aim to investigate serum choline, TMA, and TMAO pharmacokinetics following different PCs gavage and compare the difference between PC emulsions and liposomes (SOL). Serum choline, TMA, and TMAO levels were measured after orally gavaged egg yolk PC emulsion (EGE), squid PC emulsion (SQE), soybean PC emulsion (SOE), and SOL in fasted mice. Time to reach peak concentration (Tmax) and productions for TMA and TMAO were more slow and less in SQE group compared with EGE and SOE groups. Tmax for choline, TMA, and TMAO prolonged, and the productions of them were significantly declined in SOL group compared to SOE group. These findings indicated that marine source squid PC could counter-regulate the potential risks of TMAO generation, and the use of liposome as the form of PC supplementary may eliminate TMAO production.

Gut Microbiome Associates With Lifetime Cardiovascular Disease Risk Profile Among Bogalusa Heart Study Participants

RATIONALE

Few studies have systematically assessed the influence of gut microbiota on cardiovascular disease (CVD) risk.

OBJECTIVE

To examine the association between gut microbiota and lifetime CVD risk profile among 55 Bogalusa Heart Study participants with the highest and 57 with the lowest lifetime burdens of CVD risk factors.

METHODS AND RESULTS

16S ribosomal RNA sequencing was conducted on microbial DNA extracted from stool samples of the Bogalusa Heart Study participants. α Diversity, including measures of richness and evenness, and individual genera were tested for associations with lifetime CVD risk profile. Multivariable regression techniques were used to adjust for age, sex, and race (model 1), along with body mass index (model 2) and both body mass index and diet (model 3). In model 1, odds ratios (95% confidence intervals) for each SD increase in richness, measured by the number of observed operational taxonomic units, Chao 1 index, and abundance-based coverage estimator, were 0.62 (0.39-0.99), 0.61 (0.38-0.98), and 0.63 (0.39-0.99), respectively. Associations were consistent in models 2 and 3. Four genera were enriched among those with high versus low CVD risk profile in all models. Model 1 P values were 2.12×10(-3), 7.95×10(-5), 4.39×10(-4), and 1.51×10(-4) for Prevotella 2, Prevotella 7, Tyzzerella, and Tyzzerella 4, respectively. Two genera were depleted among those with high versus low CVD risk profile in all models. Model 1 P values were 2.96×10(-6) and 1.82×10(-4) for Alloprevotella and Catenibacterium, respectively.

CONCLUSIONS

The current study identified associations of overall microbial richness and 6 microbial genera with lifetime CVD risk.

Trimethylamine and Trimethylamine N-Oxide, a Flavin-Containing Monooxygenase 3 (FMO3)-Mediated Host-Microbiome Metabolic Axis Implicated in Health and Disease

Flavin-containing monooxygenase 3 (FMO3) is known primarily as an enzyme involved in the metabolism of therapeutic drugs. On a daily basis, however, we are exposed to one of the most abundant substrates of the enzyme trimethylamine (TMA), which is released from various dietary components by the action of gut bacteria. FMO3 converts the odorous TMA to nonodorous TMA N-oxide (TMAO), which is excreted in urine. Impaired FMO3 activity gives rise to the inherited disorder primary trimethylaminuria (TMAU). Affected individuals cannot produce TMAO and, consequently, excrete large amounts of TMA. A dysbiosis in gut bacteria can give rise to secondary TMAU. Recently, there has been much interest in FMO3 and its catalytic product, TMAO, because TMAO has been implicated in various conditions affecting health, including cardiovascular disease, reverse cholesterol transport, and glucose and lipid homeostasis. In this review, we consider the dietary components that can give rise to TMA, the gut bacteria involved in the production of TMA from dietary precursors, the metabolic reactions by which bacteria produce and use TMA, and the enzymes that catalyze the reactions. Also included is information on bacteria that produce TMA in the oral cavity and vagina, two key microbiome niches that can influence health. Finally, we discuss the importance of the TMA/TMAO microbiome-host axis in health and disease, considering factors that affect bacterial production and host metabolism of TMA, the involvement of TMAO and FMO3 in disease, and the implications of the host-microbiome axis for management of TMAU.

The complex metabolism of trimethylamine in humans: endogenous and exogenous sources

Trimethylamine (TMA) is a tertiary amine with a characteristic fishy odour. It is synthesised from dietary constituents, including choline, L-carnitine, betaine and lecithin by the action of microbial enzymes during both healthy and diseased conditions in humans. Trimethylaminuria (TMAU) is a disease typified by its association with the characteristic fishy odour because of decreased TMA metabolism and excessive TMA excretion. Besides TMAU, a number of other diseases are associated with abnormal levels of TMA, including renal disorders, cancer, obesity, diabetes, cardiovascular diseases and neuropsychiatric disorders. Aside from its role in pathobiology, TMA is a precursor of trimethylamine-N-oxide that has been associated with an increased risk of athero-thrombogenesis. Additionally, TMA is a major air pollutant originating from vehicular exhaust, food waste and animal husbandry industry. The adverse effects of TMA need to be monitored given its ubiquitous presence in air and easy absorption through human skin. In this review, we highlight multifaceted attributes of TMA with an emphasis on its physiological, pathological and environmental impacts. We propose a clinical surveillance of human TMA levels that can fully assess its role as a potential marker of microbial dysbiosis-based diseases.

Chronic Oral L-Carnitine Supplementation Drives Marked Plasma TMAO Elevations in Patients with Organic Acidemias Despite Dietary Meat Restrictions

Recent studies have implicated trimethylamine N-oxide (TMAO) in atherosclerosis, raising concern about L-carnitine, a common supplement for patients with inborn errors of metabolism (IEMs) and a TMAO precursor metabolized, in part, by intestinal microbes. Dietary meat restriction attenuates carnitine-to-TMAO conversion, suggesting that TMAO production may not occur in meat-restricted individuals taking supplemental L-carnitine, but this has not been tested. Here, we mine a metabolomic dataset to assess TMAO levels in patients with diverse IEMs, including organic acidemias. These data were correlated with clinical information and confirmed using a quantitative TMAO assay. Marked plasma TMAO elevations were detected in patients treated with supplemental L-carnitine, including those on a meat-free diet. On average, patients with an organic acidemia had ~45-fold elevated [TMAO], as compared to the reference population. This effect was mitigated by metronidazole therapy lasting 7 days each month. Collectively, our data show that TMAO production occurs at high levels in patients with IEMs receiving oral L-carnitine. Further studies are needed to determine the long-term safety and efficacy of chronic oral L-carnitine supplementation and whether suppression or circumvention of intestinal bacteria may improve L-carnitine therapy.

Plasma Concentrations of Trimethylamine-N-oxide Are Directly Associated with Dairy Food Consumption and Low-Grade Inflammation in a German Adult Population

BACKGROUND

Trimethylamine-N-oxide (TMAO) is a metabolite of carnitine, choline, and phosphatidylcholine, which is inversely associated with survival of cardiovascular disease (CVD) patients.

OBJECTIVE

We examined the associations of diet with plasma concentrations of TMAO, choline, and betaine and the associations of TMAO with plasma concentrations of various cytokines.

METHODS

Plasma TMAO, choline, and betaine concentrations were measured using LC-high resolution mass spectrometry in 271 participants, ≥18 y old, of the Second Bavarian Food Consumption Survey, conducted in 2002 and 2003. Food consumption was assessed using at least two 24-h dietary recalls. Cytokines were measured in plasma with enzyme-linked immunosorbent assays. Geometric mean concentrations of TMAO, choline, and betaine by categories of meat, dairy food, egg, and fish consumption were computed, adjusted for sex, age, and BMI. Multivariable-adjusted geometric mean concentrations of cytokines [tumor necrosis factor-α (TNF-α), soluble TNF receptors (sTNF-R) p55, sTNF-R p75, interleukin-6 (IL-6), and C-reactive protein (CRP)] were computed by quartiles of TMAO concentration using general linear models.

RESULTS

Meat, egg, or fish consumption was not associated with TMAO, choline, or betaine concentrations (all P-trend ≥ 0.05). With increases in milk and other dairy food consumption, the plasma TMAO concentration increased [geometric mean bottom quartile of milk consumption: 2.08 μM (95% CI: 1.69, 2.57 μM); compared with top quartile: 3.13 μM (95% CI: 2.56, 3.84 μM); P-trend = 0.008]. Participants in the top TMAO quartile had higher plasma concentrations of TNF-α, sTNF-R p55, and sTNF-R p75 than participants in the bottom quartile (percentage difference ranging between 14.4% and 17.3%; all P-trend < 0.05), but there were no differences in plasma concentrations of CRP and IL-6 (all P-trend ≥ 0.05).

CONCLUSIONS

Results of this study conducted among healthy adults from the general population do not indicate a strong effect of diet on plasma concentrations of TMAO, choline, or betaine, with the exception of a positive association between dairy food consumption and plasma TMAO concentrations. Also, plasma TMAO concentrations were positively associated with inflammation. Whether habitual diet is strongly linked to the plasma TMAO concentration, a potential marker of CVD risk, needs to be determined in further studies.

Egg consumption and risk of type 2 diabetes: a meta-analysis of prospective studies

BACKGROUND

Observational data on the association between egg consumption and risk of type 2 diabetes mellitus (DM) have been inconsistent. Because eggs are a good source of protein and micronutrients and are inexpensive, it is important to clarify their role in the risk of developing DM.

OBJECTIVE

We conducted a meta-analysis of published prospective cohort studies to evaluate the relation of egg consumption with the risk of DM.

DESIGN

We searched PubMed, Ovid, Cochrane, and Google Scholar (up to October 2015) to retrieve published studies. We used RRs from extreme categories of egg consumption for the main analysis but also evaluated dose response by using cubic splines and generalized least squares regression.

RESULTS

We identified 12 cohorts for a total of 219,979 subjects and 8911 cases of DM. When comparing the highest with the lowest category of egg intake, pooled multivariate RRs of DM were 1.09 (95% CI: 0.99, 1.20) using the fixed-effect model and 1.06 (95% CI: 0.86, 1.30) using the random-effect model. There was evidence for heterogeneity (I(2) = 73.6%, P < 0.001). When stratified by geographic area, there was a 39% higher risk of DM (95% CI: 21%, 60%) comparing highest with lowest egg consumption in US studies (I(2) = 45.4%, P = 0.089) and no elevated risk of DM with egg intake in non-US studies (RR = 0.89; 95% CI: 0.79, 1.02 using the fixed-effect model, P < 0.001 comparing US with non-US studies). In a dose-response assessment using cubic splines, elevated risk of DM was observed in US studies among people consuming ≥3 eggs/wk but not in non-US studies.

CONCLUSIONS

Our meta-analysis shows no relation between infrequent egg consumption and DM risk but suggests a modest elevated risk of DM with ≥3 eggs/wk that is restricted to US studies.

Serum Trimethylamine-N-Oxide Is Strongly Related to Renal Function and Predicts Outcome in Chronic Kidney Disease

Background

The microbial metabolite Trimethylamine-N-oxide (TMAO) has been linked to adverse cardiovascular outcome and mortality in the general population.

Objective

To assess the contribution of TMAO to inflammation and mortality in chronic kidney disease (CKD) patients ranging from mild-moderate to end-stage disease and 1) associations with glomerular filtration rate (GFR) 2) effect of dialysis and renal transplantation (Rtx) 3) association with inflammatory biomarkers and 4) its predictive value for all-cause mortality.

Methods

Levels of metabolites were quantified by a novel liquid chromatography/tandem mass spectrometry-based method in fasting plasma samples from 80 controls and 179 CKD 3–5 patients. Comorbidities, nutritional status, biomarkers of inflammation and GFR were assessed.

Results

GFR was the dominant variable affecting TMAO (β = -0.41; p<0.001), choline (β = -0.38; p<0.001), and betaine (β = 0.45; p<0.001) levels. A longitudinal study of 74 CKD 5 patients starting renal replacement therapy demonstrated that whereas dialysis treatment did not affect TMAO, Rtx reduced levels of TMAO to that of controls (p<0.001). Following Rtx choline and betaine levels continued to increase. In CKD 3–5, TMAO levels were associated with IL-6 (Rho = 0.42; p<0.0001), fibrinogen (Rho = 0.43; p<0.0001) and hsCRP (Rho = 0.17; p = 0.022). Higher TMAO levels were associated with an increased risk for all-cause mortality that remained significant after multivariate adjustment (HR 4.32, 95% CI 1.32–14.2; p = 0.016).

Conclusion

Elevated TMAO levels are strongly associated with degree of renal function in CKD and normalize after renal transplantation. TMAO levels correlates with increased systemic inflammation and is an independent predictor of mortality in CKD 3–5 patients.

Does our gut microbiome predict cardiovascular risk? A review of the evidence from metabolomics

Millions of microbes are found in the human gut, and are collectively referred as the gut microbiota. Recent studies have estimated that the microbiota genome contains 100-fold more genes than the host genome. These microbiota contribute to digestion by processing energy substrates unutilized by the host, with about half of the total genome of the gut microbiota being related to central carbon and amino acid metabolism as well as the biosynthesis of secondary metabolites. Therefore, the gut microbiome and its interaction with the host influences many aspects of health and disease, including the composition of biofluids such as urine and blood plasma. Metabolomics is uniquely suited to capture these functional host-microbe interactions. This review aims at providing an overview of recent metabolomics evidence of gut microbiota-host metabolic interactions with a specific focus on cardiovascular disease and related aspects of the metabolic syndrome. Furthermore, the emphasis is given on the complexities of translating these metabolite signatures as potential clinical biomarkers, as the composition and activity of gut microbiome change with many factors, particularly with diet, with special reference to trimethylamine-oxide.

The influence of chronic L-carnitine supplementation on the formation of preneoplastic and atherosclerotic lesions in the colon and aorta of male F344 rats

L-Carnitine, a key component of fatty acid oxidation, is nowadays being extensively used as a nutritional supplement with allegedly "fat burning" and performance-enhancing properties, although to date there are no conclusive data supporting these claims. Furthermore, there is an inverse relationship between exogenous supplementation and bioavailability, i.e., fairly high oral doses are not fully absorbed and thus a significant amount of carnitine remains in the gut. Human and rat enterobacteria can degrade unabsorbed L-carnitine to trimethylamine or trimethylamine-N-oxide, which, under certain conditions, may be transformed to the known carcinogen N-nitrosodimethylamine. Recent findings indicate that trimethylamine-N-oxide might also be involved in the development of atherosclerotic lesions. We therefore investigated whether a 1-year administration of different L-carnitine concentrations (0, 1, 2 and 5 g/l) via drinking water leads to an increased incidence of preneoplastic lesions (so-called aberrant crypt foci) in the colon of Fischer 344 rats as well as to the appearance of atherosclerotic lesions in the aorta of these animals. No significant difference between the test groups regarding the formation of lesions in the colon and aorta of the rats was observed, suggesting that, under the given experimental conditions, L-carnitine up to a concentration of 5 g/l in the drinking water does not have adverse effects on the gastrointestinal and vascular system of Fischer 344 rats.

A Phospholipid-Protein Complex from Antarctic Krill Reduced Plasma Homocysteine Levels and Increased Plasma Trimethylamine-N-Oxide (TMAO) and Carnitine Levels in Male Wistar Rats

Seafood is assumed to be beneficial for cardiovascular health, mainly based on plasma lipid lowering and anti-inflammatory effects of n-3 polyunsaturated fatty acids. However, other plasma risk factors linked to cardiovascular disease are less studied. This study aimed to penetrate the effect of a phospholipid-protein complex (PPC) from Antarctic krill on one-carbon metabolism and production of trimethylamine-N-oxide (TMAO) in rats. Male Wistar rats were fed isoenergetic control, 6%, or 11% PPC diets for four weeks. Rats fed PPC had reduced total homocysteine plasma level and increased levels of choline, dimethylglycine and cysteine, whereas the plasma level of methionine was unchanged compared to control. PPC feeding increased the plasma level of TMAO, carnitine, its precursors trimethyllysine and γ-butyrobetaine. There was a close correlation between plasma TMAO and carnitine, trimethyllysine, and γ-butyrobetaine, but not between TMAO and choline. The present data suggest that PPC has a homocysteine lowering effect and is associated with altered plasma concentrations of metabolites related to one-carbon metabolism and B-vitamin status in rats. Moreover, the present study reveals a non-obligatory role of gut microbiota in the increased plasma TMAO level as it can be explained by the PPC's content of TMAO. The increased level of carnitine and carnitine precursors is interpreted to reflect increased carnitine biosynthesis.

The Relationship Between Trimethylamine-N-Oxide and Prevalent Cardiovascular Disease in a Multiethnic Population Living in Canada

BACKGROUND

Microflora-dependent trimethylamine-N-oxide (TMAO) formation, which results from intake of choline and L-carnitine-rich food, shows promise as a predictor of cardiovascular disease (CVD) risk, but these associations have not been examined in ethnically diverse populations. In a multiethnic population-based study of adults in Canada, we assessed the stability of TMAO and L-carnitine in stored serum samples and their association with intimal medial thickness, prevalent risk factors, and clinical events.

METHODS

In a randomly sampled cross-sectional study of 1286 Canadians, fasting serum samples were collected and stored. In 292 consecutive individuals (99 CVD cases and 193 unmatched control subjects), L-carnitine and TMAO concentrations were assessed using validated analytical approaches.

RESULTS

The mean (± SD) TMAO level was 1.998 ± 3.13 μM and L-carnitine was 42.29 ± 11.35 μM. The relative levels of the samples did not appreciably change after 3 freeze-thaw cycles (coefficient of variation, 5.6% and 4.7%, respectively). No significant association between L-carnitine levels and prevalent CVD was found, with adjustment for covariates (odds ratio, 1.57; 95% confidence interval, 0.58-4.26; P trend = 0.65), for highest vs lowest quintile group. TMAO levels showed a significant, graded association with prevalent CVD (odds ratio, 3.17; 95% confidence interval, 1.05-9.51; P trend = 0.02). After further adjustment for diabetes status, meat, fish, and cholesterol intake, the association remained significant. No significant association between carotid intimal medial thickness and L-carnitine (P = 0.64) or TMAO (P = 0.18) was found.

CONCLUSIONS

Serum TMAO and L-carnitine analysis on stored samples is reliable. Our findings support an association between TMAO with prevalent CVD in a multiethnic population. This finding requires replication in larger studies in which dietary intake and stored serum samples exist.

Archaeal Lineages within the Human Microbiome: Absent, Rare or Elusive?

Archaea are well-recognized components of the human microbiome. However, they appear to be drastically underrepresented compared to the high diversity of bacterial taxa which can be found on various human anatomic sites, such as the gastrointestinal environment, the oral cavity and the skin. As our “microbial” view of the human body, including the methodological concepts used to describe them, has been traditionally biased towards bacteria, the question arises whether our current knowledge reflects the actual ratio of archaea versus bacteria or whether we have failed so far to unravel the full diversity of human-associated archaea. This review article hypothesizes that distinct archaeal lineages within humans exist, which still await our detection. First, previously unrecognized taxa might be quite common but they have eluded conventional detection methods. Two recent prime examples are described that demonstrate that this might be the case for specific archaeal lineages. Second, some archaeal taxa might be overlooked because they are rare and/or in low abundance. Evidence for this exists for a broad range of phylogenetic lineages, however we currently do not know whether these sporadically appearing organisms are mere transients or important members of the so called “rare biosphere” with probably basic ecosystem functions. Lastly, evidence exists that different human populations harbor different archaeal taxa and/or the abundance and activity of shared archaeal taxa may differ and thus their impact on the overall microbiome. This research line is rather unexplored and warrants further investigation. While not recapitulating exhaustively all studies on archaeal diversity in humans, this review highlights pertinent recent findings that show that the choice of appropriate methodological approaches and the consideration of different human populations may lead to the detection of archaeal lineages previously not associated with humans. This in turn will help understand variations found in the overall microbiomes from different individuals and ultimately may lead to the emergence of novel concepts/mechanisms impacting human health.

Egg consumption and risk of type 2 diabetes among African Americans: The Jackson Heart Study

BACKGROUND & AIMS

Type 2 diabetes (DM) disproportionally affects African Americans. Data on the association between egg consumption and risk of DM are sparse. We sought to examine whether egg consumption is associated with the prevalence and incidence of DM among African Americans.

METHODS

We analyzed baseline data from 4568 participants of the Jackson Heart Study. Egg consumption was obtained using a food frequency questionnaire designed for this population. We used generalized estimating equations to calculate adjusted prevalence ratios of DM and Cox regression to estimate hazard ratios of DM with corresponding 95% confidence intervals (CI).

RESULTS

The average age was 55 ± 13 years and 64% of subjects were women. The median frequency of egg consumption was 2/week for men and 1/week for women. The prevalence of DM was 22% overall (21% of men and 23% of women). Multivariable adjusted prevalence ratio [PR (95% CI)] for DM were: 1.00 (ref), 1.14 (0.90-1.44), 1.33 (1.04-1.70), 1.33 (1.06-1.68), 1.26 (0.99-1.61), and 1.52 (1.17-1.97) for egg consumption of <1/month, 1-3/month, 1/week, 2/week, 3-4/week, and 5+/week, respectively, p for linear trend 0.0024. Corresponding multivariable adjusted hazard ratios were 1.00 (ref), 0.88 (0.65-1.19), 0.94 (0.68-1.30), 0.91 (0.66-1.25), 1.11 (0.81-1.52), and 1.17 (0.81-1.70), respectively, during a mean follow up of 7.3 years (p for linear trend 0.22).

CONCLUSIONS

While egg consumption was positively associated with prevalent DM, prospective analysis did not show an association of egg intake with incidence of DM among African Americans.

Choline intakes exceeding recommendations during human lactation improve breast milk choline content by increasing PEMT pathway metabolites

Demand for the vital nutrient choline is high during lactation; however, few studies have examined choline metabolism and requirements in this reproductive state. The present study sought to discern the effects of lactation and varied choline intake on maternal biomarkers of choline metabolism and breast milk choline content. Lactating (n=28) and control (n=21) women were randomized to 480 or 930 mg choline/day for 10-12 weeks as part of a controlled feeding study. During the last 4-6 weeks, 20% of the total choline intake was provided as an isotopically labeled choline tracer (methyl-d9-choline). Blood, urine and breast milk samples were collected for choline metabolite quantification, enrichment measurements, and gene expression analysis of choline metabolic genes. Lactating (vs. control) women exhibited higher (P < .001) plasma choline concentrations but lower (P ≤ .002) urinary excretion of choline metabolites, decreased use of choline as a methyl donor (e.g., lower enrichment of d6-dimethylglycine, P ≤ .08) and lower (P ≤ .02) leukocyte expression of most choline-metabolizing genes. A higher choline intake during lactation differentially influenced breast milk d9- vs. d3-choline metabolite enrichment. Increases (P ≤ .03) were detected among the d3-metabolites, which are generated endogenously via the hepatic phosphatidylethanolamine N-methyltransferase (PEMT), but not among the d9-metabolites generated from intact exogenous choline. These data suggest that lactation induces metabolic adaptations that increase the supply of intact choline to the mammary epithelium, and that extra maternal choline enhances breast milk choline content by increasing supply of PEMT-derived choline metabolites. This trial was registered at clinicaltrials.gov as NCT01127022.

Characterization and detection of a widely distributed gene cluster that predicts anaerobic choline utilization by human gut bacteria

Elucidation of the molecular mechanisms underlying the human gut microbiota’s effects on health and disease has been complicated by difficulties in linking metabolic functions associated with the gut community as a whole to individual microorganisms and activities. Anaerobic microbial choline metabolism, a disease-associated metabolic pathway, exemplifies this challenge, as the specific human gut microorganisms responsible for this transformation have not yet been clearly identified. In this study, we established the link between a bacterial gene cluster, the choline utilization (cut) cluster, and anaerobic choline metabolism in human gut isolates by combining transcriptional, biochemical, bioinformatic, and cultivation-based approaches. Quantitative reverse transcription-PCR analysis and in vitro biochemical characterization of two cut gene products linked the entire cluster to growth on choline and supported a model for this pathway. Analyses of sequenced bacterial genomes revealed that the cut cluster is present in many human gut bacteria, is predictive of choline utilization in sequenced isolates, and is widely but discontinuously distributed across multiple bacterial phyla. Given that bacterial phylogeny is a poor marker for choline utilization, we were prompted to develop a degenerate PCR-based method for detecting the key functional gene choline TMA-lyase (cutC) in genomic and metagenomic DNA. Using this tool, we found that new choline-metabolizing gut isolates universally possessed cutC. We also demonstrated that this gene is widespread in stool metagenomic data sets. Overall, this work represents a crucial step toward understanding anaerobic choline metabolism in the human gut microbiota and underscores the importance of examining this microbial community from a function-oriented perspective.

Anaerobic choline utilization is a bacterial metabolic activity that occurs in the human gut and is linked to multiple diseases. While bacterial genes responsible for choline fermentation (the cut gene cluster) have been recently identified, there has been no characterization of these genes in human gut isolates and microbial communities. In this work, we use multiple approaches to demonstrate that the pathway encoded by the cut genes is present and functional in a diverse range of human gut bacteria and is also widespread in stool metagenomes. We also developed a PCR-based strategy to detect a key functional gene (cutC) involved in this pathway and applied it to characterize newly isolated choline-utilizing strains. Both our analyses of the cut gene cluster and this molecular tool will aid efforts to further understand the role of choline metabolism in the human gut microbiota and its link to disease.

Oxygen-Dependent Cell-to-Cell Variability in the Output of the Escherichia coli Tor Phosphorelay

Escherichia coli senses and responds to trimethylamine-N-oxide (TMAO) in the environment through the TorT-TorS-TorR signal transduction system. The periplasmic protein TorT binds TMAO and stimulates the hybrid kinase TorS to phosphorylate the response regulator TorR through a phosphorelay. Phosphorylated TorR, in turn, activates transcription of the torCAD operon, which encodes the proteins required for anaerobic respiration via reduction of TMAO to trimethylamine. Interestingly, E. coli respires TMAO in both the presence and absence of oxygen, a behavior that is markedly different from the utilization of other alternative electron acceptors by this bacterium. Here we describe an unusual form of regulation by oxygen for this system. While the average level of torCAD transcription is the same for aerobic and anaerobic cultures containing TMAO, the behavior across the population of cells is strikingly different under the two growth conditions. Cellular levels of torCAD transcription in aerobic cultures are highly heterogeneous, in contrast to the relatively homogeneous distribution in anaerobic cultures. Thus, oxygen regulates the variance of the output but not the mean for the Tor system. We further show that this oxygen-dependent variability stems from the phosphorelay.

IMPORTANCE

Trimethylamine-N-oxide (TMAO) is utilized by numerous bacteria as an electron acceptor for anaerobic respiration. In E. coli, expression of the proteins required for TMAO respiration is tightly regulated by a signal transduction system that is activated by TMAO. Curiously, although oxygen is the energetically preferred electron acceptor, TMAO is respired even in the presence of oxygen. Here we describe an interesting and unexpected form of regulation for this system in which oxygen produces highly variable expression of the TMAO utilization proteins across a population of cells without affecting the mean expression of these proteins. To our knowledge, this is the first reported example of a stimulus regulating the variance but not the mean output of a signaling system.

Plasma choline metabolites and colorectal cancer risk in the Women's Health Initiative Observational Study

Few studies have examined associations between plasma choline metabolites and risk of colorectal cancer. Therefore, we investigated associations between plasma biomarkers of choline metabolism [choline, betaine, dimethylglycine, and trimethylamine N-oxide (TMAO)] and colorectal cancer risk among postmenopausal women in a case-control study nested within the Women's Health Initiative Observational Study. We selected 835 matched case-control pairs, and cases were further stratified by tumor site (proximal, distal, or rectal) and stage (local/regional or metastatic). Colorectal cancer was assessed by self-report and confirmed by medical records over the mean of 5.2 years of follow-up. Baseline plasma choline metabolites were measured by LC/MS-MS. In multivariable-adjusted conditional logistic regression models, plasma choline tended to be positively associated with rectal cancer risk [OR (95% confidence interval, CI)(highest vs. lowest quartile) = 2.44 (0.93-6.40); P trend = 0.08], whereas plasma betaine was inversely associated with colorectal cancer overall [0.68 (0.47-0.99); P trend = 0.01] and with local/regional tumors [0.64 (0.42-0.99); P trend = 0.009]. Notably, the plasma betaine:choline ratio was inversely associated with colorectal cancer overall [0.56 (0.39-0.82); P trend = 0.004] as well as with proximal [0.66 (0.41-1.06); P trend = 0.049], rectal [0.27 (0.10-0.78); P trend = 0.02], and local/regional [0.50 (0.33-0.76); P trend = 0.001] tumors. Finally, plasma TMAO, an oxidative derivative of choline produced by intestinal bacteria, was positively associated with rectal cancer [3.38 (1.25-9.16); P trend = 0.02] and with overall colorectal cancer risk among women with lower (vs. higher) plasma vitamin B12 levels (P interaction = 0.003). Collectively, these data suggest that alterations in choline metabolism, which may arise early in disease development, may be associated with higher risk of colorectal cancer. The positive association between plasma TMAO and colorectal cancer risk is consistent with an involvement of the gut microbiome in colorectal cancer pathogenesis.

Amines from vertebrates guide triatomine bugs to resources

Most triatomine bugs (Heteroptera: Reduviidae) are nest-living insects that require vertebrate blood or invertebrate haemolymph to complete their life cycle. Vertebrates accumulate excretory products in or near their nesting sites and we hypothesize that triatomines use emanations from such host wastes when searching for resources. Here we recount how triatomine bugs increase upwind locomotion on a servosphere in response to volatile amine constituents of vertebrate excretions. Fresh chicken faeces is strongly attractive to Rhodnius prolixus nymphs. Ammonia induces attraction and an increase in both speed and total path length by R. prolixus on the servosphere. Whereas ethylamine and dimethylamine attract R. prolixus, Triatoma infestans and Panstrongylus geniculatus, other amine constituents of vertebrate excretions such as isobutylamine and hexylamine induce R. prolixus nymphs to walk faster and for a longer period. These amines are derived from generally occurring metabolites of vertebrates and from gut flora metabolism. We conclude that amines and other products associated with nesting hosts serve as signals for foraging triatomines.

Archaea and the human gut: New beginning of an old story

Methanogenic archaea are known as human gut inhabitants since more than 30 years ago through the detection of methane in the breath and isolation of two methanogenic species belonging to the order Methanobacteriales, Methanobrevibacter smithii and Methanosphaera stadtmanae. During the last decade, diversity of archaea encountered in the human gastrointestinal tract (GIT) has been extended by sequence identification and culturing of new strains. Here we provide an updated census of the archaeal diversity associated with the human GIT and their possible role in the gut physiology and health. We particularly focus on the still poorly characterized 7^th order of methanogens, the Methanomassiliicoccales, associated to aged population. While also largely distributed in non-GIT environments, our actual knowledge on this novel order of methanogens has been mainly revealed through GIT inhabitants. They enlarge the number of final electron acceptors of the gut metabolites to mono- di- and trimethylamine. Trimethylamine is exclusively a microbiota-derived product of nutrients (lecithin, choline, TMAO, L-carnitine) from normal diet, from which seems originate two diseases, trimethylaminuria (or Fish-Odor Syndrome) and cardiovascular disease through the proatherogenic property of its oxidized liver-derived form. This therefore supports interest on these methanogenic species and its use as archaebiotics, a term coined from the notion of archaea-derived probiotics.

The contributory role of gut microbiota in cardiovascular disease

Our group recently discovered that certain dietary nutrients possessing a trimethylamine (TMA) moiety, namely choline/phosphatidylcholine and L-carnitine, participate in the development of atherosclerotic heart disease. A meta-organismal pathway was elucidated involving gut microbiota-dependent formation of TMA and host hepatic flavin monooxygenase 3-dependent (FMO3-dependent) formation of TMA-N-oxide (TMAO), a metabolite shown to be both mechanistically linked to atherosclerosis and whose levels are strongly linked to cardiovascular disease (CVD) risks. Collectively, these studies reveal that nutrient precursors, gut microbiota, and host participants along the meta-organismal pathway elucidated may serve as new targets for the prevention and treatment of CVD.

1HNMR-based metabolomic profile of rats with experimental acute pancreatitis

Background

Acute pancreatitis (AP) is a common inflammatory disease of the pancreas accompanied by serious metabolic disturbances. Nevertheless, the specific metabolic process of this disease is still unclear. Characterization of the metabolome may help identify biomarkers for AP. To identify potential biomarkers, this study therefore investigated the 1H-nuclear magnetic resonance (NMR)-based metabolomic profile of AP.

Methods

Fourteen male adult Sprague–Dawley rats were randomized into two groups: the AP group, in which AP was induced by retrograde ductal infusion of 3.5% sodium taurocholate; and the sham operation group (SO), in which rats were infused with 0.9% saline. Blood samples were obtained 12 hours later and a 600 MHz superconducting NMR spectrometer was used to detect plasma metabolites. Principal components analysis (PCA) and partial least squares-discriminant analysis after orthogonal signal correction (OSC-PLS-DA) were used to analyze both longitudinal Eddy-delay (LED) and Carr–Purcell–Meiboom–Gill (CPMG) spectra.

Results

Differences in plasma metabolites between the two groups were detected by PCA and PLS-DA of 1HNMR spectra. Compared with the SO group, plasma levels of lactate (δ 1.3, 1.34, 4.1), valine (δ 0.98, 1.02), succinic acid (δ 2.38), 3-hydroxybutyric acid (3-HB, δ 1.18), high density lipoprotein (HDL, δ 0.8), and unsaturated fatty acid (UFA, δ 2.78, 5.3) were elevated in the AP group, while levels of glycerol (δ 3.58, 3.66), choline (δ 3.22), trimethylamine oxide (TMAO, δ 3.26), glucose (δ 3–4), glycine (δ 3.54), very low density lipoprotein (VLDL, δ 1.34) and phosphatidylcholine (Ptd, δ 2.78) were decreased.

Conclusions

AP has a characteristic metabolic profile. Lactate, valine, succinic acid, 3-HB, HDL, UFA, glycerol, choline, TMAO, glucose, glycine, VLDL, and Ptd may be potential biomarkers of early stage AP.

Whey protein delays gastric emptying and suppresses plasma fatty acids and their metabolites compared to casein, gluten, and fish protein

Whey protein has been demonstrated to improve fasting lipid and insulin response in overweight and obese individuals. To establish new hypotheses for this effect and to investigate the impact of stomach emptying, we compared plasma profiles after intake of whey isolate (WI), casein, gluten (GLU), and cod (COD). Obese, nondiabetic subjects were included in the randomized, blinded, crossover meal study. Subjects ingested a high fat meal containing one of the four protein sources. Plasma samples were collected at five time points and metabolites analyzed using LC-Q-TOF-MS. In contrast to previous studies, the WI meal caused a decreased rate of gastric emptying compared to the other test meals. The WI meal also caused elevated levels of a number of amino acids, possibly stimulating insulin release leading to reduced plasma glucose. The WI meal also caused decreased levels of a number of fatty acids, while the GLU meal caused elevated levels of a number of unidentified hydroxy fatty acids and dicarboxylic fatty acids. Also reported are a number of markers of fish intake unique to the COD meal.

The breathprints in patients with liver disease identify novel breath biomarkers in alcoholic hepatitis

BACKGROUND & AIMS

Selected-ion flow-tube mass spectrometry can precisely identify trace gases in the human breath, in the parts-per-billion range. We investigated whether concentrations of volatile compounds in breath samples correlate with the diagnosis of alcoholic hepatitis (AH) and the severity of liver disease in patients with AH.

METHODS

We recruited patients with liver disease from a single tertiary care center. The study population was divided between those with AH with cirrhosis (n = 40) and those with cirrhosis with acute decompensation from etiologies other than alcohol (n = 40); individuals without liver disease served as control subjects (n = 43). We used selected-ion flow-tube mass spectrometry to identify and measure 14 volatile compounds in breath samples from fasted subjects. We used various statistical analyses to compare clinical characteristics and breath levels of compounds among groups and to test the correlation between levels of compounds and severity of liver disease. Logistic regression analysis was performed to build a predictive model for AH.

RESULTS

We identified 6 compounds (2-propanol, acetaldehyde, acetone, ethanol, pentane, and trimethylamine [TMA]) whose levels were increased in patients with liver disease compared with control subjects. Mean concentrations of TMA and pentane (TAP) were particularly high in breath samples from patients with AH, compared with those with acute decompensation or control subjects (for both, P < .001). Using receiver operating characteristic curve analysis, we developed a model for the diagnosis of AH based on breath levels of TAP. TAP scores of 36 or higher identified the patients with AH (area under the receiver operating characteristic curves = 0.92) with 90% sensitivity and 80% specificity. The levels of exhaled TMA had a low level of correlation with the severity of AH based on model for end-stage liver disease score (r = 0.38; 95% confidence interval, 0.07-0.69; P = .018).

CONCLUSIONS

Based on levels of volatile compounds in breath samples, we can identify patients with AH vs patients with acute decompensation or individuals without liver disease. Levels of exhaled TMA moderately correlate with the severity of AH. These findings might be used in diagnosis of AH or in determining patient prognosis.

Prognostic value of choline and betaine depends on intestinal microbiota-generated metabolite trimethylamine-N-oxide

AIMS

Recent metabolomics and animal model studies show trimethylamine-N-oxide (TMAO), an intestinal microbiota-dependent metabolite formed from dietary trimethylamine-containing nutrients such as phosphatidylcholine (PC), choline, and carnitine, is linked to coronary artery disease pathogenesis. Our aim was to examine the prognostic value of systemic choline and betaine levels in stable cardiac patients.

METHODS AND RESULTS

We examined the relationship between fasting plasma choline and betaine levels and risk of major adverse cardiac events (MACE = death, myocardial infraction, stroke) in relation to TMAO over 3 years of follow-up in 3903 sequential stable subjects undergoing elective diagnostic coronary angiography. In our study cohort, median (IQR) TMAO, choline, and betaine levels were 3.7 (2.4-6.2)μM, 9.8 (7.9-12.2)μM, and 41.1 (32.5-52.1)μM, respectively. Modest but statistically significant correlations were noted between TMAO and choline (r = 0.33, P < 0.001) and less between TMAO and betaine (r = 0.09, P < 0.001). Higher plasma choline and betaine levels were associated with a 1.9-fold and 1.4-fold increased risk of MACE, respectively (Quartiles 4 vs. 1; P < 0.01, each). Following adjustments for traditional cardiovascular risk factors and high-sensitivity C-reactive protein, elevated choline [1.34 (1.03-1.74), P < 0.05], and betaine levels [1.33 (1.03-1.73), P < 0.05] each predicted increased MACE risk. Neither choline nor betaine predicted MACE risk when TMAO was added to the adjustment model, and choline and betaine predicted future risk for MACE only when TMAO was elevated.

CONCLUSION

Elevated plasma levels of choline and betaine are each associated with incident MACE risk independent of traditional risk factors. However, high choline and betaine levels are only associated with higher risk of future MACE with concomitant increase in TMAO.

Archaebiotics: proposed therapeutic use of archaea to prevent trimethylaminuria and cardiovascular disease

Trimethylamine (TMA) is produced by gut bacteria from dietary ingredients. In individuals with a hereditary defect in flavin-containing monooxygenase 3, bacterial TMA production is believed to contribute to the symptoms of trimethylaminuria (TMAU; fish-odor syndrome). Intestinal microbiota TMA metabolism may also modulate atherosclerosis risk by affecting trimethylamine oxide (TMAO) production levels. We propose that reducing TMA formation in the gut by converting it to an inert molecule could be used to prevent or limit these human diseases, while avoiding the major drawbacks of other clinical interventions. Reducing TMA levels by microbiological interventions could also be helpful in some vaginoses. Particular members of a recently discovered group of methanogens, that are variably present in the human gut, are unusual in being apparently restricted to utilizing only methyl compounds including TMA as substrates. We confirmed experimentally that one of these strains tested, Methanomassiliicoccus luminyensis B10, is able to deplete TMA, by reducing it with H 2 for methanogenesis. We therefore suggest that members of this archaeal lineage could be used as treatments for metabolic disorders.