Whole blood choline and plasma choline in acute coronary syndromes: prognostic and pathophysiological implications

Association of choline and betaine with the risk of cardiovascular disease and all-cause mortality: Meta-analysis

BACKGROUND

This study aimed to systematically evaluate the role of circulating levels of choline and betaine in the risk of cardiovascular disease (CVD) and all-cause mortality by comprehensively reviewing observational studies.

METHODS

This study was conducted according to PRISMA 2020 statement. Six electronic databases, including PubMed, Embase and China National Knowledge Infrastructure (CNKI), were searched for cohort studies and derivative research design types (nested case-control and case-cohort studies) from the date of inception to March 2022. We pooled relative risk (RR) and 95% confidence interval (CI) of the highest versus lowest category and per SD of circulating choline and betaine concentrations in relation to the risk of CVD and all-cause mortality.

RESULTS

In the meta-analysis, 17 studies with a total of 33,009 participants were included. Random-effects model results showed that highest versus lowest quantile of circulating choline concentrations were associated with the risk of CVD (RR = 1.29, 95% CI: 1.04-1.61) and all-cause mortality (RR = 1.62, 95% CI: 1.12-2.36). We also observed the risk of CVD were increased 13% (5%-22%) with per SD increment. Furthermore, highest versus lowest quantile of circulating betaine concentrations were not associated with the risk of CVD (RR = 1.07, 95% CI: 0.92-1.24) and all-cause mortality (RR = 1.39, 95% CI: 0.96-2.01). However, the risk of CVD was increased 14% (5%-23%) with per SD increment.

CONCLUSIONS

Higher levels of circulating choline were associated with a higher risk of CVD and all-cause mortality.

SGLT2 Inhibition, Choline Metabolites, and Cardiometabolic Diseases: A Mediation Mendelian Randomization Study

OBJECTIVE

To investigate the causal role of choline metabolites mediating sodium-glucose cotransporter 2 (SGLT2) inhibition in coronary artery disease (CAD) and type 2 diabetes (T2D) using Mendelian randomization (MR).

RESEARCH DESIGN AND METHODS

A two-sample two-step MR was used to determine 1) causal effects of SGLT2 inhibition on CAD and T2D; 2) causal effects of three choline metabolites, total choline, phosphatidylcholine, and glycine, on CAD and T2D; and 3) mediation effects of these metabolites. Genetic proxies for SGLT2 inhibition were identified as variants in the SLC5A2 gene that were associated with both levels of gene expression and hemoglobin A1c. Summary statistics for metabolites were from UK Biobank, CAD from CARDIoGRAMplusC4D (Coronary ARtery DIsease Genome wide Replication and Meta-analysis [CARDIoGRAM] plus The Coronary Artery Disease [C4D] Genetics) consortium, and T2D from DIAbetes Genetics Replication And Meta-analysis (DIAGRAM) and the FinnGen study.

RESULTS

SGLT2 inhibition (per 1 SD, 6.75 mmol/mol [1.09%] lowering of HbA1c) was associated with lower risk of T2D and CAD (odds ratio [OR] 0.25 [95% CI 0.12, 0.54], and 0.51 [0.28, 0.94], respectively) and positively with total choline (β 0.39 [95% CI 0.06, 0.72]), phosphatidylcholine (0.40 [0.13, 0.67]), and glycine (0.34 [0.05, 0.63]). Total choline (OR 0.78 [95% CI 0.68, 0.89]) and phosphatidylcholine (OR 0.81 [0.72, 0.91]) were associated with T2D but not with CAD, while glycine was associated with CAD (0.94 [0.91, 0.98]) but not with T2D. Mediation analysis showed evidence of indirect effect of SGLT2 inhibition on T2D through total choline (0.91 [0.83, 0.99]) and phosphatidylcholine (0.93 [0.87, 0.99]) with a mediated proportion of 8% and 5% of the total effect, respectively, and on CAD through glycine (0.98 [0.96, 1.00]) with a mediated proportion of 2%. The results were well validated in at least one independent data set.

CONCLUSIONS

Our study identified the causal roles of SGLT2 inhibition in choline metabolites. SGLT2 inhibition may influence T2D and CAD through different choline metabolites.

N, Adigal S, Lukose J, Kartha VB, Chidangil S. Cardiovascular biomarkers in body fluids: progress and prospects in optical sensors

Cardiovascular diseases (CVD) are the major causative factors for high mortality and morbidity in developing and developed nations. The biomarker detection plays a crucial role in the early diagnosis of several non-infectious and life-threatening diseases like CVD and many cancers, which in turn will help in more successful therapy, reducing the mortality rate. Biomarkers have diagnostic, prognostic and therapeutic significances. The search for novel biomarkers using proteomics, bio-sensing, micro-fluidics, and spectroscopic techniques with good sensitivity and specificity for CVD is progressing rapidly at present, in addition to the use of gold standard biomarkers like troponin. This review is dealing with the current progress and prospects in biomarker research for the diagnosis of cardiovascular diseases. Expert opinion. Fast diagnosis of cardiovascular diseases (CVDs) can help to provide rapid medical intervention, which can affect the patient's short and long-term health. Identification and detection of proper biomarkers for early diagnosis are crucial for successful therapy and prognosis of CVDs. The present review discusses the analysis of clinical samples such as whole blood, blood serum, and other body fluids using techniques like high-performance liquid chromatography-LASER/LED-induced fluorescence, Raman spectroscopy, mainly, optical methods, combined with nanotechnology and micro-fluidic technologies, to probe patterns of multiple markers (marker signatures) as compared to conventional techniques.

High Betaine and Dynamic Increase of Betaine Levels Are Both Associated With Poor Prognosis of Patients With Pulmonary Hypertension

Background and Objective

The association between plasma betaine levels and cardiovascular diseases (CVDs) has been revealed except for pulmonary hypertension (PH). In this study, we aimed to explore the role of betaine in patients with PH.

Methods

Inpatients with PH at Fuwai Hospital were enrolled after excluding relative comorbidities. Each patient received at least one follow-up through a clinical visit, and the fasting blood was obtained both at the first and second hospitalization for betaine detection. The primary endpoint was defined as composite outcome events and the mean duration was 14.3 (6.9, 21.3) months. The associations of betaine and changes of betaine (Δbetaine) with disease severity and prognosis were explored.

Results

Finally, a total of 216 patients with PH were included and the medians for betaine plasma levels in the total patients group, low betaine, and high betaine groups were 49.8 (39.0, 68.3) μM, 39.0 (33.5, 44.7) μM, and 68.1 (57.8, 88.7) μM, respectively. High betaine was associated with poor World Health Organization Functional Class (WHO-FC), increased N-terminal pro-brain natriuretic peptide (NT-proBNP), low tricuspid annular plane systolic excursion (TAPSE), and cardiac output index even after adjusting for confounders. Patients with high betaine were over twice the risk to receive the poor prognosis than those with a low level [hazard ratio (HR) = 2.080, (95% CI: 1.033–4.188)]. Moreover, the decrease of betaine level after further treatment was positively correlated to ΔNT-proBNP indicating Δbetaine might be an effector of disease severity, and dynamic increase of betaine was also associated with poor prognosis in PH.

Conclusion

Betaine was associated with disease severity and might be an effector in PH. Patients with increased levels or with dynamic rise of betaine heralded a poor prognosis.

Quantification of choline in serum and plasma using a clinical nuclear magnetic resonance analyzer

BACKGROUND

Choline, a gut microbiome metabolite, is associated with cardiovascular risk and other chronic illnesses. The aim was to develop a high-throughput nuclear magnetic resonance (NMR)-based assay to measure choline on the Vantera® Clinical Analyzer.

METHODS

A non-negative deconvolution algorithm was developed to quantify choline. Assay performance was evaluated using CLSI guidelines.

RESULTS

Deming regression analysis comparing choline concentrations by NMR and mass spectrometry (n = 28) exhibited a correlation coefficient of 0.998 (intercept = -9.216, slope = 1.057). The LOQ were determined to be 7.1 µmol/L in serum and 5.9 µmol/L in plasma. The coefficients of variation (%CV) for intra- and inter-assay precision ranged from 6.2 to 14.8% (serum) and 5.4-11.3% (plasma). Choline concentrations were lower in EDTA plasma by as much as 38% compared to serum, however, choline was less stable in serum compared to plasma. In a population of apparently healthy adults, the reference interval was <7.1-20.0 µmol/L (serum) and <5.9-13.1 µmol/L (plasma). Linearity was demonstrated well beyond these intervals. No interference was observed for a number of substances tested.

CONCLUSIONS

The newly developed, high-throughput NMR-based assay exhibited good performance characteristics enabling quantification of choline in serum and plasma for clinical use.

3D printed enzymatic microchip for multiplexed electrochemical biosensing

The low-cost e-fabrication of specialized multianalyte biosensors within the point-of-care (POC) settings in a few minutes remains a great challenge. Unlike prefabricated biosensors, 3D printing seems to be able to meet this challenge, empowering the end user with the freedom to create on-demand devices adapted to immediate bioanalytical need. Here, we describe a novel miniature all-3D-printed 4-electrode biochip, capable of the simultaneous determination of different biomarkers in a single assay. The chip is utterly fabricated via an one-step 3D printing process and it is connected to a mini portable bi-potentiostant, permitting simultaneous measurements. The bioanalytical capability of the microchip is demonstrated through the simultaneous amperometric determination of two cardiac biomarkers (cholesterol and choline) in the same blood droplet, via enzymatic assays developed on its two tiny integrated electrodes. The simultaneous determination of cholesterol and choline is free from cross-talk phenomena and interferences offering limits of detection much lower than the cut-off levels of these biomarkers in blood for coronary syndromes. The biodevice is an easy-constructed, low-cost, sensitive and e-transferable POC chip with wide scope of applicability to other enzymatic bioassays.

Plasma Metabolomics of Acute Coronary Syndrome Patients Based on Untargeted Liquid Chromatography-Mass Spectrometry

Background: Acute coronary syndrome (ACS) is the main cause of death and morbidity worldwide. The present study aims to investigate the altered metabolites in plasma from patients with ACS and sought to identify metabolic biomarkers for ACS. Methods: The plasma metabolomics profiles of 284 ACS patients and 130 controls were carried out based on an untargeted liquid chromatography coupled with tandem mass spectrometry (LC-MS) approach. Multivariate statistical methods, pathway enrichment analysis, and univariate receiver operating characteristic (ROC) curve analysis were performed. Results: A total of 328 and 194 features were determined in positive and negative electrospray ionization mode in the LC-MS analysis, respectively. Twenty-eight metabolites were found to be differentially expressed, in ACS patients relative to controls (p < 0.05). Pathway analysis revealed that these metabolites are mainly involved in synthesis and degradation of ketone bodies, phenylalanine metabolism, and arginine and proline metabolism. Furthermore, a diagnostic model was constructed based on the metabolites identified and the areas under the curve (AUC) for 5-oxo-D-proline, creatinine, phosphatidylethanolamine lyso 16:0, and LPC (20:4) range from 0.764 to 0.844. The higher AUC value of 0.905 was obtained for the combined detection of phosphatidylethanolamine lyso 16:0 and LPC (20:4). Conclusions: Differential metabolic profiles may be useful for the effective diagnosis of ACS and may provide additional insight into the molecular mechanisms underlying ACS.

Post-Myocardial Infarction Ventricular Remodeling Biomarkers-The Key Link between Pathophysiology and Clinic

Studies in recent years have shown increased interest in developing new methods of evaluation, but also in limiting post infarction ventricular remodeling, hoping to improve ventricular function and the further evolution of the patient. This is the point where biomarkers have proven effective in early detection of remodeling phenomena. There are six main processes that promote the remodeling and each of them has specific biomarkers that can be used in predicting the evolution (myocardial necrosis, neurohormonal activation, inflammatory reaction, hypertrophy and fibrosis, apoptosis, mixed processes). Some of the biomarkers such as creatine kinase-myocardial band (CK-MB), troponin, and N-terminal-pro type B natriuretic peptide (NT-proBNP) were so convincing that they immediately found their place in the post infarction patient evaluation protocol. Others that are related to more complex processes such as inflammatory biomarkers, atheroma plaque destabilization biomarkers, and microRNA are still being studied, but the results so far are promising. This article aims to review the markers used so far, but also the existing data on new markers that could be considered, taking into consideration the most important studies that have been conducted so far.

Methyl Donor Nutrients in Chronic Kidney Disease: Impact on the Epigenetic Landscape

Epigenetic alterations, such as those linked to DNA methylation, may potentially provide molecular explanations for complications associated with altered gene expression in illnesses, such as chronic kidney disease (CKD). Although both DNA hypo- and hypermethylation have been observed in the uremic milieu, this remains only a single aspect of the epigenetic landscape and, thus, of any biochemical dysregulation associated with CKD. Nevertheless, the role of uremia-promoting alterations on the epigenetic landscape regulating gene expression is still a novel and scarcely studied field. Although few studies have actually reported alterations of DNA methylation via methyl donor nutrient intake, emerging evidence indicates that nutritional modification of the microbiome can affect one-carbon metabolism and the capacity to methylate the genome in CKD. In this review, we discuss the nutritional modifications that may affect one-carbon metabolism and the possible impact of methyl donor nutrients on the microbiome, CKD, and its phenotype.

Metabotypes with elevated protein and lipid catabolism and inflammation precede clinical mastitis in prepartal transition dairy cows

Clinical mastitis (CM), the most prevalent and costly disease in dairy cows, is diagnosed most commonly shortly after calving. Current indicators do not satisfactorily predict CM. This study aimed to develop a robust and comprehensive mass spectrometry-based metabolomic and lipidomic workflow using untargeted ultra-performance liquid chromatography high-resolution mass spectrometry for predictive biomarker detection. Using a nested case-control design, we measured weekly during the prepartal transition period differences in serum metabolites, lipids, inflammation markers, and minerals between clinically healthy Holstein dairy cows diagnosed with mastitis postcalving (CMP; n = 8; CM diagnosis d 1 = 3 cows, d 2 = 2 cows, d 4 = 1 cow; d 25 = 1 cow, and d 43 = 1 cow that had subclinical mastitis since d 3) or not (control; n = 9). The largest fold differences between CMP and control cows during the prepartal transition period were observed for 3'-sialyllactose in serum. Seven metabolites (N-methylethanolamine phosphate, choline, phosphorylcholine, free carnitine, trimethyl lysine, tyrosine, and proline) and 3 metabolite groups (carnitines, AA metabolites, and water-soluble phospholipid metabolites) could correctly classify cows for their future CM status at both 21 and 14 d before calving. Biochemical analysis using lipid and metabolite-specific commercial diagnostic kits supported our mass spectrometry-based omics results and additionally showed elevated inflammatory markers (serum amyloid A and visfatin) in CMP cows. In conclusion, metabolic phenotypes (i.e., metabotype) with elevated protein and lipid metabolism and inflammation may precede CM in prepartal transition dairy cows. The discovered serum metabolites and lipids may assist in predictive diagnostics, prevention strategies, and early treatment intervention against CM, and thereby improve cow health and welfare.

Measurement of plasma choline in acute coronary syndrome: importance of suitable sampling conditions for this assay

Blood choline has been proposed as a predictor of acute coronary syndrome (ACS), however different testing procedures might affect the choline concentration because the lysophospholipase D activity of autotaxin (ATX) can convert lysophosphatidylcholine to lysophosphatidic acid (LPA) and choline in human blood. Although the influences of ATX on LPA levels are well known in vivo and in vitro, those on choline have not been elucidated. Therefore, we established suitable sampling conditions and evaluated the usefulness of plasma choline concentrations as a biomarker for ACS. Serum LPA and choline concentrations dramatically increased after incubation depending on the presence of ATX, while their concentrations in plasma under several conditions were differently modulated. Plasma choline levels in genetically modified mice and healthy human subjects, however, were not influenced by the ATX level in vivo, while the plasma LPA concentrations were associated with ATX. With strict sample preparation, the plasma choline levels did not increase, but actually decreased in ACS patients. Our study revealed that ATX increased the choline concentrations after blood sampling but was not correlated with the choline concentrations in vivo; therefore, strict sample preparation will be necessary to investigate the possible use of choline as a biomarker.

Increased Trimethylamine N-Oxide Portends High Mortality Risk Independent of Glycemic Control in Patients with Type 2 Diabetes Mellitus

BACKGROUND

Recent studies show a mechanistic link between intestinal microbial metabolism of dietary phosphatidylcholine and coronary artery disease pathogenesis. Concentrations of a proatherogenic gut microbe-generated metabolite, trimethylamine N-oxide (TMAO), predict increased incident cardiovascular disease risks in multiple cohorts. TMAO concentrations are increased in patients with type 2 diabetes mellitus (T2DM), but their prognostic value and relation to glycemic control are unclear.

METHODS

We examined the relationship between fasting TMAO and 2 of its nutrient precursors, choline and betaine, vs 3-year major adverse cardiac events and 5-year mortality in 1216 stable patients with T2DM who underwent elective diagnostic coronary angiography.

RESULTS

TMAO [4.4 μmol/L (interquartile range 2.8-7.7 μmol/L) vs 3.6 (2.3-5.7 μmol/L); P < 0.001] and choline concentrations were higher in individuals with T2DM vs healthy controls. Within T2DM patients, higher plasma TMAO was associated with a significant 3.0-fold increased 3-year major adverse cardiac event risk (P < 0.001) and a 3.6-fold increased 5-year mortality risk (P < 0.001). Following adjustments for traditional risk factors and high-sensitivity C-reactive protein, glycohemoglobin, and estimated glomerular filtration rate, increased TMAO concentrations remained predictive of both major adverse cardiac events and mortality risks in T2DM patients [e.g., quartiles 4 vs 1, hazard ratio 2.05 (95% CI, 1.31-3.20), P < 0.001; and 2.07 (95% CI, 1.37-3.14), P < 0.001, respectively].

CONCLUSIONS

Fasting plasma concentrations of the proatherogenic gut microbe-generated metabolite TMAO are higher in diabetic patients and portend higher major adverse cardiac events and mortality risks independent of traditional risk factors, renal function, and relationship to glycemic control.

A Comparative Metabolomics Approach Reveals Early Biomarkers for Metabolic Response to Acute Myocardial Infarction

Discovery of novel biomarkers is critical for early diagnosis of acute coronary syndrome (ACS). Serum metabolite profiling of ST-elevation myocardial infarction (STEMI), unstable angina (UA) and healthy controls was performed using gas chromatography mass spectrometry (GC/MS), solid-phase microextraction coupled to gas chromatography mass spectrometry (SPME-GC/MS) and nuclear magnetic resonance (¹H-NMR). Multivariate data analysis revealed a metabolic signature that could robustly discriminate STEMI patients from both healthy controls and UA patients. This panel of biomarkers consisted of 19 metabolites identified in the serum of STEMI patients. One of the most intriguing biomarkers among these metabolites is hydrogen sulfide (H₂S), an endogenous gasotransmitter with profound effect on the heart. Serum H₂S absolute levels were further investigated using a quantitative double-antibody sandwich enzyme-linked immunosorbent assay (ELISA). This highly sensitive immunoassay confirmed the elevation of serum H₂S in STEMI patients. H₂S level discriminated between UA and STEMI groups, providing an initial insight into serum-free H₂S bioavailability during ACS. In conclusion, the current study provides a detailed map illustrating the most predominant altered metabolic pathways and the biochemical linkages among the biomarker metabolites identified in STEMI patients. Metabolomics analysis may yield novel predictive biomarkers that will potentially allow for an earlier medical intervention.

Associations of gut-flora-dependent metabolite trimethylamine-N-oxide, betaine and choline with non-alcoholic fatty liver disease in adults

Many studies suggest that trimethylamine-N-oxide (TMAO), a gut-flora-dependent metabolite of choline, contributes to the risk of cardiovascular diseases, but little is known for non-alcoholic fatty liver disease (NAFLD). We examined the association of circulating TMAO, choline and betaine with the presence and severity of NAFLD in Chinese adults. We performed a hospital-based case-control study (CCS) and a cross-sectional study (CSS). In the CCS, we recruited 60 biopsy-proven NAFLD cases and 35 controls (18–60 years) and determined serum concentrations of TMAO, choline and betaine by HPLC-MS/MS. For the CSS, 1,628 community-based adults (40-75 years) completed the blood tests and ultrasonographic NAFLD evaluation. In the CCS, analyses of covariance showed adverse associations of ln-transformed serum levels of TMAO, choline and betaine/choline ratio with the scores of steatosis and total NAFLD activity (NAS) (all P-trend <0.05). The CSS revealed that a greater severity of NAFLD was independently correlated with higher TMAO but lower betaine and betaine/choline ratio (all P-trend <0.05). No significant choline-NAFLD association was observed. Our findings showed adverse associations between the circulating TMAO level and the presence and severity of NAFLD in hospital- and community-based Chinese adults, and a favorable betaine-NAFLD relationship in the community-based participants.

Listening to Our Gut: Contribution of Gut Microbiota and Cardiovascular Risk in Diabetes Pathogenesis

What we understand about diabetes from decades of genetics research is now being supplemented with exciting new evidence based on a better understanding of how one of the biggest "environmental" factors the body is exposed to is influencing the pathogenesis of disease. The recent discovery that certain dietary nutrients possessing a trimethylamine (TMA) moiety (namely choline/phosphatidylcholine and L-carnitine) participate in the development of atherosclerotic heart disease has renewed attention towards the contributions of gut microbiota in the development of cardiovascular diseases. Collectively, animal and human studies reveal that conversion of these nutrient precursors to trimethylamine N-oxide (TMAO) depends on both microbial composition and host factors, and can be induced by dietary exposures. In addition, circulating TMAO levels are strongly linked to cardiovascular disease risks and various adverse cardio-renal consequences. Our group and others have further demonstrated that circulating TMAO levels are elevated in patients with type 2 diabetes mellitus compared to healthy controls and gut microbiota-dependent phosphatidylcholine metabolism has been implicated in metabolic dysregulation and insulin resistance in animal models. Therefore, preventive strategies to minimize adverse consequences associated with TMAO generation in the diabetic population are warranted.

NMR-Based Serum Metabolomics Discriminates Takayasu Arteritis from Healthy Individuals: A Proof-of-Principle Study

Takayasu arteritis (TA) is a debilitating, systemic disease that involves the aorta and large arteries in a chronic inflammatory process that leads to vessel stenosis. Initially, the disease remains clinically silent (or remains undetected) until the patients present with vascular occlusion. Therefore, new methods for appropriate and timely diagnosis of TA cases are needed to start proper therapy on time and also to monitor the patient's response to the given treatment. In this context, NMR-based serum metabolomic profiling has been explored in this proof-of-principle study for the first time to determine characteristic metabolites that could be potentially helpful for diagnosis and prognosis of TA. Serum metabolic profiling of TA patients (n = 29) and healthy controls (n = 30) was performed using 1D (1)H NMR spectroscopy, and possible biomarker metabolites were identified. Using projection to least-squares discriminant analysis, we could distinguish TA patients from healthy controls. Compared to healthy controls, TA patients had (a) increased serum levels of choline metabolites, LDL cholesterol, N-acetyl glycoproteins (NAGs), and glucose and (b) decreased serum levels of lactate, lipids, HDL cholesterol, and glucogenic amino acids. The results of this study are preliminary and need to be confirmed in a prospective study.

Inosine and hypoxanthine as novel biomarkers for cardiac ischemia: from bench to point-of-care

Cardiac ischemia associated with acute coronary syndrome and myocardial infarction is a leading cause of mortality and morbidity in the world. A rapid detection of the ischemic events is critically important for achieving timely diagnosis, treatment and improving the patient's survival and functional recovery. This minireview provides an overview on the current biomarker research for detection of acute cardiac ischemia. We primarily focus on inosine and hypoxanthine, two by-products of ATP catabolism. Based on our published findings of elevated plasma concentrations of inosine/hypoxanthine in animal laboratory and clinical settings, since 2006 we have originally proposed that these two purine molecules can be used as rapid and sensitive biomarkers for acute cardiac ischemia at its very early onset (within 15 min), hours prior to the release of heart tissue necrosis biomarkers such as cardiac troponins. We further developed a chemiluminescence technology, one of the most affordable and sensitive analytical techniques, and we were able to reproducibly quantify and differentiate total hypoxanthine concentrations in the plasma samples from healthy individuals versus patients suffering from ischemic heart disease. Additional rigorous clinical studies are needed to validate the plasma inosine/hypoxanthine concentrations, in conjunction with other current cardiac biomarkers, for a better revelation of their diagnostic potentials for early detection of acute cardiac ischemia.

New aspects on the metabolic role of intestinal microbiota in the development of atherosclerosis

Gut microbiota remains a very interesting, yet largely unexplored ecosystem inside the human organism. The importance of this ecosystem for the physiology and the pathophysiology of the organism is being slowly unraveled. Recent studies reveal a connection between intestinal microbiota and atherosclerosis development. It seems that alterations in the function and composition of this bacterial population lead through complex mechanisms to a high risk for atherosclerosis. Although these mechanisms remain largely unknown, published studies show that microbiota can lead to atherosclerosis either by augmenting known risk factors or via other, more "direct" mechanisms. This review article summarizes the available literature regarding this matter.

The gut microbiome in cardio-metabolic health

With the prevalence of cardio-metabolic disorders reaching pandemic proportions, the search for modifiable causative factors has intensified. One such potential factor is the vast microbial community inhabiting the human gastrointestinal tract, the gut microbiota. For the past decade evidence has accumulated showing the association of distinct changes in gut microbiota composition and function with obesity, type 2 diabetes and cardiovascular disease. Although causality in humans and the pathophysiological mechanisms involved have yet to be decisively established, several studies have demonstrated that the gut microbiota, as an environmental factor influencing the metabolic state of the host, is readily modifiable through a variety of interventions. In this review we provide an overview of the development of the gut microbiome and its compositional and functional changes in relation to cardio-metabolic disorders, and give an update on recent progress in how this could be exploited in microbiota-based therapeutics.

Variation of betaine, N,N-dimethylglycine, choline, glycerophosphorylcholine, taurine and trimethylamine-N-oxide in the plasma and urine of overweight people with type 2 diabetes over a two-year period

BACKGROUND

Plasma betaine concentrations and urinary betaine excretions have high test-retest reliability. Abnormal betaine excretion is common in diabetes. We aimed to confirm the individuality of plasma betaine and urinary betaine excretion in an overweight population with type 2 diabetes and compare this with the individuality of other osmolytes, one-carbon metabolites and trimethylamine-N-oxide (TMAO), thus assessing their potential usefulness as disease markers.

METHODS

Urine and plasma were collected from overweight subjects with type 2 diabetes at four time points over a two-year period. We measured the concentrations of the osmolytes: betaine, glycerophosphorylcholine (GPC) and taurine, as well as TMAO, and the one-carbon metabolites, N,N-dimethylglycine (DMG) and free choline. Samples were measured using tandem mass spectrometry (LC-MS/MS).

RESULTS

Betaine showed a high degree of individuality (or test-retest reliability) in the plasma (index of individuality = 0.52) and urine (index of individuality = 0.45). Betaine in the plasma had positive and negative log-normal reference change values (RCVs) of 54% and -35%, respectively. The other osmolytes, taurine and GPC were more variable in the plasma of individuals compared to the urine. DMG and choline showed high individuality in the plasma and urine. TMAO was highly variable in the plasma and urine (log-normal RCVs ranging from 403% to -80% in plasma).

CONCLUSIONS

Betaine is highly individual in overweight people with diabetes. Betaine, its metabolite DMG, and precursor choline showed more reliability than the osmolytes, GPC and taurine. The low reliability of TMAO suggests that a single TMAO measurement has low diagnostic value.

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.

Gut microbiota metabolism of L-carnitine and cardiovascular risk

In recent years, a number of studies have alluded to the importance of the intestinal microflora in controlling whole-body metabolic homeostasis and organ physiology. In particular, it has been suggested that the hepatic production of trimethylamine-N-oxide (TMAO) from gut microbiota-derived trimethylamine (TMA) may enhance cardiovascular risk via promoting atherosclerotic lesion development. The source of TMA production via the gut microbiota appears to originate from 2 principle sources, either phosphatidylcholine/choline and/or L-carnitine. Therefore, it has been postulated that consumption of these dietary sources, which are often found in large quantities in red meats, may be critical factors promoting cardiovascular risk. In contrast, a number of studies demonstrate beneficial properties for l-carnitine consumption against metabolic diseases including skeletal muscle insulin resistance and ischemic heart disease. Furthermore, fish are a significant source of TMAO, but dietary fish consumption and fish oil supplementation may exhibit positive effects on cardiovascular health. In this mini-review we will discuss the discrepancies regarding L-carnitine supplementation and its possible negative effects on cardiovascular risk through potential increases in TMAO production, as well as its positive effects on metabolic health via increasing glucose metabolism in the muscle and heart.

Serial plasma choline measurements after cardiac arrest in patients undergoing mild therapeutic hypothermia: a prospective observational pilot trial

OBJECTIVE

Choline is related to phospholipid metabolism and is a marker for global ischaemia with a small reference range in healthy volunteers. The aim of our study was to characterize the early kinetics of plasma free choline in patients after cardiac arrest. Additionally, we investigated the potential of plasma free choline to predict neurological outcome.

METHODS

Twenty patients admitted to our medical intensive care unit were included in this prospective, observational trial. All patients were enrolled between May 2010 and May 2011. They received post cardiac arrest treatment including mild therapeutic hypothermia which was initiated with a combination of cold fluid and a feedback surface cooling device according to current guidelines. Sixteen blood samples per patient were analysed for plasma free choline levels within the first week after resuscitation. Choline was detected by liquid chromatography-tandem mass spectrometry.

RESULTS

Most patients showed elevated choline levels on admission (median 14.8 µmol/L; interquartile range; IQR 9.9-20.1) which subsequently decreased. 48 hours after cardiac arrest choline levels in all patients reached subnormal levels at a median of 4.0 µmol/L (IQR 3-4.9; p = 0.001). Subsequently, choline levels normalized within seven days. There was no significant difference in choline levels when groups were analyzed in relation to neurological outcome.

CONCLUSIONS

Our data indicate a choline deficiency in the early postresucitation phase. This could potentially result in impaired cell membrane recovery. The detailed characterization of the early choline time course may aid in planning of choline supplementation trials. In a limited number of patients, choline was not promising as a biomarker for outcome prediction.

Nicotinuric acid: a potential marker of metabolic syndrome through a metabolomics-based approach

OBJECTIVE

Metabolic syndrome is a multiplex disorder and puts patients on the road to type 2 diabetes and atherosclerotic cardiovascular diseases. However, a surrogate biomarker in plasma or urine in fully reflecting features of metabolic syndrome has not been explored.

RESEARCH DESIGN AND METHODS

Urine metabolomics has potential utility in metabolic profiling because urine metabolites analysis reflects global outflux of metabolic change. Accordingly, we collected data on subjects (n = 99) with overweight, dyslipidemia, hypertension or impaired glucose tolerance and took a metabolomics approach to analyze the metabolites of urine revealed in metabolic syndrome by high-performance liquid chromatography-time-of-flight mass spectrometry and elicit potential biomarkers to picture metabolic syndrome.

RESULTS

Our results revealed that the urine nicotinuric acid value of subjects with diabetes (HbA1c ≥ 6.5% or those receiving diabetes medications) (n = 25) was higher than subjects without diabetes (n = 37) (221 ± 31 vs. 152 ± 13 × 10(3) mAU, P = 0.0268). Moreover, urinary nicotinuric acid level was positively correlated with body mass index, blood pressure, total cholesterol, low-density lipoprotein cholesterol, triacylglycerol and high sensitivity C-reactive protein, but negatively correlated with high-density lipoprotein cholesterol.

CONCLUSIONS

This is the first study, to our knowledge, to propose that nicotinuric acid represents an important pathogenic mechanism in process from metabolic syndrome to diabetes and atherosclerotic cardiovascular disease.

Pathophysiological roles and clinical importance of biomarkers in acute coronary syndrome

Early diagnosis of acute coronary syndrome (ACS) is important to guide appropriate therapy at a time when it is most likely to be of value. Accurate prognostic and risk stratification will facilitate high-risk patients to have early advanced diagnostic investigations and early appropriate interventions in a cost-effective and efficient manner, while those patients at low risk of ACS complications do not need such costly diagnostic tests and unnecessary hospital admission. Recent investigations have demonstrated that elevation of biomarkers upstream from acute-phase biomarkers, biomarkers of plaque destabilization and rupture, biomarkers of myocardial ischemia, necrosis, and dysfunction may provide an earlier assessment of patient risk and identify patients with higher risk of having an adverse event. This review provides an overview of the pathophysiology and clinical characteristics of several well-established biomarkers as well as emerging biomarkers that may have potential clinical utility in patients with ACS. Such emerging biomarkers hold promise and need to be more thoroughly evaluated before utilization in routine clinical practice.

Serum levels of choline-containing compounds are associated with aerobic fitness level: the HUNT-study

Background

Cardiovascular disease (CVD) is a leading cause of death worldwide, and the number of people at risk is continuously growing. New methods for early risk prediction are therefore needed to actuate prevention strategies before the individuals are diagnosed with CVD. Several studies report that aerobic fitness level, measured as maximal oxygen uptake (VO_2max), is the single best predictor of future CVD mortality in healthy people. Based on this, we wanted to study differences between healthy individuals with a large difference in VO_2max-level to identify new biomarkers of low aerobic fitness that may also have potential as early biomarkers of CVD risk.

Methodology/Principal Findings

Serum samples from 218 healthy individuals with a low VO_2max (n = 108, 63 women) or high VO_2max (n = 110, 64 women) were analysed with MR metabolomics. In addition, standard clinical-chemical analyses for glucose, lipids, liver enzymes, micro-CRP, and colorimetric analysis on circulating choline were performed. Individuals in the low VO_2max-group had increased serum levels of free choline, decreased phosphatidylcholine, increased glucosę and decreased unsaturated fatty acids compared to the individuals in the high VO_2max–group.

Conclusions/Significance

Aerobic fitness dependent differences in serum levels of free choline and phosphatidylcholine are observed. They should be further studied as potential early markers of CVD risk.

[Cardiac biomarkers in the critically ill]

Cardiac biomarkers in intensive care medicine are an excellent complement to existing clinical and diagnostic information in specific diseases. Due to their lack of specificity, the diagnostic properties of common cardiac biomarkers, such as natriuretic peptides and cardiac troponins, remain ambiguous, while their prognostic value has already been proven. In addition, there are several promising new biomarkers that might contribute to a "multimarker strategy" in the critically ill patient in the future, but further evaluation is still required.

Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease

Metabolomics studies hold promise for discovery of pathways linked to disease processes. Cardiovascular disease (CVD) represents the leading cause of death and morbidity worldwide. A metabolomics approach was used to generate unbiased small molecule metabolic profiles in plasma that predict risk for CVD. Three metabolites of the dietary lipid phosphatidylcholine, namely choline, trimethylamine N-oxide (TMAO), and betaine, were identified and then shown to predict risk for CVD in an independent large clinical cohort. Dietary supplementation of mice with choline, TMAO or betaine promoted up-regulation of multiple macrophage scavenger receptors linked to atherosclerosis, and supplementation with choline or TMAO promoted atherosclerosis. Studies using germ-free mice confirmed a critical role for dietary choline and gut flora in TMAO production, augmented macrophage cholesterol accumulation and foam cell formation. Suppression of intestinal microflora in atherosclerosis-prone mice inhibited dietary choline-enhanced atherosclerosis. Genetic variations controlling expression of flavin monooxygenases (FMOs), an enzymatic source of TMAO, segregated with atherosclerosis in hyperlipidemic mice. Discovery of a relationship between gut flora-dependent metabolism of dietary phosphatidylcholine and CVD pathogenesis provides opportunities for development of both novel diagnostic tests and therapeutic approaches for atherosclerotic heart disease.

Choline and betaine in health and disease

Choline is an essential nutrient, but is also formed by de novo synthesis. Choline and its derivatives serve as components of structural lipoproteins, blood and membrane lipids, and as a precursor of the neurotransmitter acetylcholine. Pre-and postnatal choline availability is important for neurodevelopment in rodents. Choline is oxidized to betaine that serves as an osmoregulator and is a substrate in the betaine-homocysteine methyltransferase reaction, which links choline and betaine to the folate-dependent one-carbon metabolism. Choline and betaine are important sources of one-carbon units, in particular, during folate deficiency. Choline or betaine supplementation in humans reduces concentration of total homocysteine (tHcy), and plasma betaine is a strong predictor of plasma tHcy in individuals with low plasma concentration of folate and other B vitamins (B₂, B₆, and B₁₂) in combination TT genotype of the methylenetetrahydrofolate reductase 677 C->T polymorphism. The link to one-carbon metabolism and the recent availability of food composition data have motivated studies on choline and betaine as risk factors of chronic diseases previously studied in relation to folate and homocysteine status. High intake and plasma level of choline in the mother seems to afford reduced risk of neural tube defects. Intake of choline and betaine shows no consistent relation to cancer or cardiovascular risk or risk factors, whereas an unfavorable cardiovascular risk factor profile was associated with high choline and low betaine concentrations in plasma. Thus, choline and betaine showed opposite relations with key components of metabolic syndrome, suggesting a disruption of mitochondrial choline oxidation to betaine as part of the mitochondrial dysfunction in metabolic syndrome.

Choline in acute coronary syndrome: an emerging biomarker with implications for the integrated assessment of plaque vulnerability

Whole-blood choline, plasma choline and serum choline are emerging biomarkers in acute coronary syndrome related to coronary plaque instability with platelet thrombus formation and ischemia. Whole-blood choline is an early predictor for cardiac events, which adds to troponins, natriuretic peptides and inflammatory markers. Serum choline is highly predictive for myocardial infarction and discriminates high- from low-risk subgroups in troponin-positive patients. Choline is a candidate marker to aid decision making in the emergency room in the upcoming era of sensitive troponin tests and the growing need to differentiate between ischemic and nonischemic etiologies of troponin elevations. The integrated approach of in vitro choline measurement in combination with advanced techniques of in vivo choline imaging represents a novel future strategy for detecting vulnerable plaques. This paper provides an up-to-date review of choline in acute coronary syndrome including key aspects of pathophysiology, analytical methods, clinical studies and implications for the integrated assessment of plaque vulnerability.

Development of a method to measure plasma and whole blood choline by liquid chromatography tandem mass spectrometry

Background

Current gold standard markers for myocardial damage are troponins I and T, which are both sensitive and specific for the detection of myocardial infarction, but require up to 6 h to become reliably elevated in serum. Investigation into markers with potential to identify patients with early ischaemic changes is therefore intense. Choline is reported to be prognostic in patients presenting with acute coronary syndromes via its release from ischaemic cell membranes.

Methods

Liquid chromatography tandem mass spectrometry was used to develop a method to quantitate choline in plasma and blood. The method involves addition of a deuterated internal standard to an aliquot of plasma or blood followed by organic solvent addition, which precipitates the proteins in the sample. Preparation was carried out directly into a 96-deep-well plate. Chromatography of choline used a strong cation exchange column and separation used a Waters Atlantis dC18 analytical column positioned directly before the mass spectrometer source, allowing on-line preanalytical clean up of the sample.

Results

The lower limit of quantitation was 0.38 μmol/L, linearity was observed up to 754 μmol/L, with a working concentration range of 0.38–224 μmol/L, inter- and intra-assay coefficients of variation were <6% and <4%, respectively. Samples were stable throughout five freeze–thaw cycles and recovery was between 94% and 114%.

Conclusions

The assay was successfully validated in accordance with FDA guidelines and is suitable for quantitation of choline in research and clinical settings.

Usefulness of elevations in serum choline and free F2)-isoprostane to predict 30-day cardiovascular outcomes in patients with acute coronary syndrome

Our objectives were to evaluate the prognostic value of several biomarkers in patients with acute coronary syndrome (ACS) through an evaluation of the 30-day clinical outcomes. Multiple biomarkers have emerged as potentially useful in risk stratification of ACS. Specifically, markers of vascular inflammation and oxidative stress might be helpful in the determination of clinical outcomes. We evaluated patients presenting with chest pain. ACS was defined by symptoms of cardiac ischemia plus electrocardiographic changes or positive troponin I. Levels of serum troponin I, high sensitivity C-reactive protein, serum choline, and free F(2)-isoprostane were obtained. Patients were followed up for 30 days (n = 108) with determination of nonfatal myocardial infarction, congestive heart failure, need for revascularization, and death. Of the 108 patients, 26 had a cardiac event. Free F(2)-isoprostane and choline levels (but not high-sensitivity C-reactive protein levels) predicted 30-day cardiac events. To determine the value of choline and F(2)-isoprostane levels in predicting 30-day cardiac events, receiver operating curves were generated. The optimal cutoff point of these markers was a serum F(2)-isoprostane level of 124.5 pg/ml (r = 0.82) and a serum choline level of 30.5 mumol/L (r = 0.76). F(2)-isoprostane and choline had a positive predictive value of 57% and 44% and a negative predictive value of 90% and 89%, respectively. In conclusion, serum choline and free F(2)-isoprostane are predictors of cardiac events in ACS. A model that includes an array of biomarkers, including troponin, choline, and free F(2)-isoprostane, might be useful in predicting patients at greater risk of future events in ACS.

Bench-to-bedside review: the value of cardiac biomarkers in the intensive care patient

The use of cardiac biomarkers in the intensive care setting is gaining increasing popularity. There are several reasons for this increase: there is now the facility for point-of-care biomarker measurement providing a rapid diagnosis; biomarkers can be used as prognostic tools; biomarkers can be used to guide therapy; and, compared with other methods such as echocardiography, the assays are easier and much more affordable. Two important characteristics of the ideal biomarker are disease specificity and a linear relationship between the serum concentration and disease severity. These characteristics are not present, however, in the majority of biomarkers for cardiac dysfunction currently available. Those clinically useful cardiac biomarkers, which naturally received the most attention, such as troponins and B-type natriuretic peptide, are not as specific as was originally thought. In the intensive care setting, it is important for the user to understand the degree of specificity of these biomarkers and that the interpretation of the results should always be guided by other clinical information. The present review summarizes the available biomarkers for different cardiac conditions. Potential biomarkers under evaluation are also briefly discussed.

Choline in Whole Blood and Plasma: Sample Preparation and Stability

Background: Choline is critical for a variety of biological functions and has been investigated as a biomarker for various pathological conditions including acute coronary syndrome.

Methods: A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was used to quantify choline in whole blood and plasma in freshly collected samples prepared with ultrafiltration or protein precipitation. We investigated the effects of preanalytical variables including types of anticoagulants and storage temperature and time.

Results: We observed no significant differences in whole-blood choline concentration in EDTA-anticoagulated vs heparin-anticoagulated samples: mean (SD) difference 0.9% (3.2%), P = 0.80. For plasma, choline concentrations with heparin in 5 of 12 volunteers were &gt;10% higher than with EDTA, P = 0.01. One freeze-thaw cycle led to significant mean (SD) increases in choline concentrations in heparin whole blood, 19.3% (11.4%), P &lt;0.01, and the effect was not significant for other sample types studied (P &gt;0.33). For freshly collected samples stored at ambient temperature, choline concentrations in all types of samples increased with storage time. For EDTA whole blood, EDTA plasma, and heparin plasma, the choline concentration increased for the first 60 min and then stabilized. For heparin whole blood, the choline concentration continued to increase linearly with storage time for &gt;4 h, at which time the choline concentrations were increased by approximately 50%.

Conclusions: Sample collection, storage, and sample preparation procedures are critical for clinical measurements of choline in whole blood and plasma.