Prognostic implications of elevated whole blood choline levels in acute coronary syndromes

Promising dawn in the management of pulmonary hypertension: The mystery veil of gut microbiota

The gut microbiota is a complex community of microorganisms inhabiting the intestinal tract, which plays a vital role in human health. It is intricately involved in the metabolism, and it also affects diverse physiological processes. The gut-lung axis is a bidirectional pathway between the gastrointestinal tract and the lungs. Recent research has shown that the gut microbiome plays a crucial role in immune response regulation in the lungs and the development of lung diseases. In this review, we present the interrelated factors concerning gut microbiota and the associated metabolites in pulmonary hypertension (PH), a lethal disease characterized by elevated pulmonary vascular pressure and resistance. Our research team explored the role of gut-microbiota-derived metabolites in cardiovascular diseases and established the correlation between metabolites such as putrescine, succinate, trimethylamine N-oxide (TMAO), and N, N, N-trimethyl-5-aminovaleric acid with the diseases. Furthermore, we found that specific metabolites, such as TMAO and betaine, have significant clinical value in PH, suggesting their potential as biomarkers in disease management. In detailing the interplay between the gut microbiota, their metabolites, and PH, we underscored the potential therapeutic approaches modulating this microbiota. Ultimately, we endeavor to alleviate the substantial socioeconomic burden associated with this disease. This review presents a unique exploratory analysis of the link between gut microbiota and PH, intending to propel further investigations in the gut-lung axis.

Circulating choline levels are associated with prognoses in patients with pulmonary hypertension: a cohort study

BACKGROUNDS

Mounting evidences have highlighted the association between metabolites and cardiovascular diseases. Our previous works have demonstrated that circulating metabolite, trimethylamine oxide, was associated with prognosis of patients with pulmonary hypertension (PH). Choline is a precursor of trimethylamine oxide and its role in PH remains unknown. Here, we aimed to validate the hypothesis that circulating choline levels were associated with prognoses in patients with PH.

METHODS

Inpatients diagnosed with PH-defined as mean pulmonary arterial pressure ≥ 25 mmHg by right heart catheterisation-from Fuwai Hospital were enrolled after excluding relative comorbidities. Fasting blood samples were obtained to assess choline levels and other clinical variables. The primary endpoints were defined as death, escalation of targeted medication, rehospitalization due to heart failure, PH deterioration. The follow-up duration was defined as the time from the choline examination to the occurrence of outcomes or the end of the study. The associations between circulating choline levels and disease severity and prognoses were explored.

RESULTS

Totally, 272 inpatients with PH were enrolled in this study. Patients were divided into high and low choline groups according to the 50th quartile of circulating choline levels, defined as 12.6 µM. After confounders adjustment, the high circulating choline levels were still associated with poor World Health Organization functional class, elevated N-terminal pro-B-type natriuretic peptide, and decreased cardiac output index indicating the severe disease condition. Moreover, elevated choline levels were associated with poor prognoses in PH patients even after adjusting for confounders (hazard ratio = 1.934; 95% CI, 1.034-3.619; P = 0.039). Subgroup analyses showed that choline levels predicted the prognosis of patients with pulmonary arterial hypertension but not chronic thromboembolic pulmonary hypertension.

CONCLUSIONS

Choline levels were associated with disease severity and poor prognoses of patients with PH, especially in pulmonary arterial hypertension suggesting its potential biomarker role.

Consumption of a light meal affects serum concentrations of one-carbon metabolites and B-vitamins. A clinical intervention study

The transfer of one-carbon units between molecules in metabolic pathways is essential for maintaining cellular homeostasis, but little is known about whether the circulating concentrations of metabolites involved in the one-carbon metabolism are affected by the prandial status. Epidemiological studies do not always consistently use fasting or non-fasting blood samples or may lack information on the prandial status of the study participants. Therefore, the main aim of the present study was to investigate the effects of a light breakfast on serum concentrations of selected metabolites and B-vitamins related to the one-carbon metabolism; i.e. the methionine-homocysteine cycle, the folate cycle, the choline oxidation pathway and the transsulfuration pathway. Sixty-three healthy adults (thirty-six women) with BMI ≥ 27 kg/m2 were included in the study. Blood was collected in the fasting state and 60 and 120 min after intake of a standardised breakfast consisting of white bread, margarine, white cheese, strawberry jam and orange juice (2218 kJ). The meal contained low amounts of choline, betaine, serine and vitamins B2, B3, B6, B9 and B12. Serum concentrations of total homocysteine, total cysteine, flavin mononucleotide, nicotinamide and pyridoxal 5'-phosphate were significantly decreased, and concentrations of choline, betaine, dimethylglycine, sarcosine, cystathionine and folate were significantly increased following breakfast intake (P < 0·05). Our findings demonstrate that the intake of a light breakfast with low nutrient content affected serum concentrations of several metabolites and B-vitamins related to the one-carbon metabolism.

Understanding Choline Bioavailability and Utilization: First Step Toward Personalizing Choline Nutrition

Choline is an essential macronutrient involved in neurotransmitter synthesis, cell-membrane signaling, lipid transport, and methyl-group metabolism. Nevertheless, the vast majority are not meeting the recommended intake requirement. Choline deficiency is linked to nonalcoholic fatty liver disease, skeletal muscle atrophy, and neurodegenerative diseases. The conversion of dietary choline to trimethylamine by gut microbiota is known for its association with atherosclerosis and may contribute to choline deficiency. Choline-utilizing bacteria constitutes less than 1% of the gut community and is modulated by lifestyle interventions such as dietary patterns, antibiotics, and probiotics. In addition, choline utilization is also affected by genetic factors, further complicating the impact of choline on health. This review overviews the complex interplay between dietary intakes of choline, gut microbiota and genetic factors, and the subsequent impact on health. Understanding of gut microbiota metabolism of choline substrates and interindividual variability is warranted in the development of personalized choline nutrition.

Different Types of Atrial Fibrillation Share Patterns of Gut Microbiota Dysbiosis

Atrial fibrillation has been identified to be associated with disordered gut microbiota. Notably, atrial fibrillation is a progressive disease and could be categorized as paroxysmal and persistent based on the duration of the episodes. The persistent atrial fibrillation patients are accompanied by higher risk of stroke and lower success rate of rhythm control. However, the microbial signatures of different categories of atrial fibrillation patients remain unknown. We sought to determine whether disordered gut microbiota occurs in the self-terminating PAF or intestinal flora develops dynamically during atrial fibrillation progression. We found that different types of atrial fibrillation show a limited degree of gut microbiota shift. Gut microbiota dysbiosis has already occurred in mild stages of atrial fibrillation, which might act as an early modulator of disease, and therefore may be regarded as a potential target to postpone atrial fibrillation progression.

Dysbiotic gut microbiota (GM) and disordered metabolic patterns are known to be involved in the clinical expression of atrial fibrillation (AF). However, little evidence has been reported in characterizing the specific changes in fecal microbiota in paroxysmal AF (PAF) and persistent AF (psAF). To provide a comprehensive understanding of GM dysbiosis in AF types, we assessed the GM signatures of 30 PAF patients, 20 psAF patients, and 50 non-AF controls based on metagenomic and metabolomic analyses. Compared with control subjects, similar changes of GM were identified in PAF and psAF patients, with elevated microbial diversity and similar alteration in the microbiota composition. PAF and psAF patients shared the majority of differential taxa compared with non-AF controls. Moreover, the similarity was also illuminated in microbial function and associated metabolic alterations. Additionally, minor disparity was observed in PAF compared with psAF. Several distinctive taxa between PAF and psAF were correlated with certain metabolites and atrial diameter, which might play a role in the pathogenesis of atrial remodeling. Our findings characterized the presence of many common features in GM shared by PAF and psAF, which occurred at the self-terminating PAF. Preventative and therapeutic measures targeting GM for early intervention to postpone the progression of AF are highly warranted.

IMPORTANCE Atrial fibrillation has been identified to be associated with disordered gut microbiota. Notably, atrial fibrillation is a progressive disease and could be categorized as paroxysmal and persistent based on the duration of the episodes. The persistent atrial fibrillation patients are accompanied by higher risk of stroke and lower success rate of rhythm control. However, the microbial signatures of different categories of atrial fibrillation patients remain unknown. We sought to determine whether disordered gut microbiota occurs in the self-terminating PAF or intestinal flora develops dynamically during atrial fibrillation progression. We found that different types of atrial fibrillation show a limited degree of gut microbiota shift. Gut microbiota dysbiosis has already occurred in mild stages of atrial fibrillation, which might act as an early modulator of disease, and therefore may be regarded as a potential target to postpone atrial fibrillation progression.

Plasma Choline as a Diagnostic Biomarker in Slow Coronary Flow

Aim

The slow coronary flow (SCF) phenomenon was characterized by delayed perfusion of epicardial arteries, and no obvious coronary artery lesion in coronary angiography. The prognosis of patients with slow coronary flow was poor. However, there is lack of rapid, simple, and accurate method for SCF diagnosis. This study aimed to explore the utility of plasma choline as a diagnostic biomarker for SCF.

Methods

Patients with coronary artery stenosis <40% evaluated by the coronary angiogram method were recruited in this study and were grouped into normal coronary flow (NCF) and SCF by thrombolysis in myocardial infarction frame count (TFC). Plasma choline concentrations of patients with NCF and SCF were quantified by Ultra Performance Liquid Chromatography Tandem Mass Spectrometry. Correlation analysis was performed between plasma choline concentration and TFC. Receiver operating characteristic (ROC) curve analysis with or without confounding factor adjustment was applied to predict the diagnostic power of plasma choline in SCF.

Results

Forty-four patients with SCF and 21 patients with NCF were included in this study. TFC in LAD, LCX, and RCA and mean TFC were significantly higher in patients with SCF in comparison with patients with NCF (32.67 ± 8.37 vs. 20.66 ± 3.41, P  <  0.01). Plasma choline level was obviously higher in patients with SCF when compared with patients with NCF (754.65 ± 238.18 vs. 635.79 ± 108.25, P=0.007). Plasma choline level had significantly positive correlation with Mean TFC (r = 0.364, P=0.002). Receiver operating characteristic (ROC) analysis showed that choline with or without confounding factor adjustment had an AUC score of 0.65 and 0.77, respectively.

Conclusions

TFC were closely related with plasma choline level, and plasma choline can be a suitable and stable diagnostic biomarker for SCF.

Targeted metabolomic analysis of plasma metabolites in patients with coronary heart disease in southern China

Coronary heart disease (CHD), one of the leading causes of death in the world, is a complex metabolic disorder due to genetic and environmental interactions. The potential mechanisms and diagnostic biomarkers for different types of coronary heart disease remain unclear. Metabolomics is increasingly considered to be a promising technology with the potential to identify metabolomic features in an attempt to distinguish the different stages of CHD.We aimed to investigate serum metabolite profiling between CHD patients and normal coronary artery (NCA) subjects and identify metabolic biomarkers associated with CHD progression in an ethnic Hakka population in southern China.Using a novel targeted metabolomics approach, we explored the metabolic characteristics of CHD patients. Blood samples from 302 patients with CHD and 59 NCA subjects were collected that analyses using targeted liquid-chromatography coupled with tandem mass spectrometry (LC-MS).A total of 361 blood samples were determined using targeted LC-MS. Plasma concentrations for trimetlylamine oxide (TMAO), choline, creatinine, and carnitine were significantly higher in patients with CHD compared to the NCA cohort. Further, we observed that the concentration of the 4 metabolites were higher than that of the NCA group in any group of CHD, which including acute myocardial infarction (AMI), unstable angina (UA), and stable angina (SA). In addition, the diagnostic model was constructed based on the metabolites identified and the ROC curve of the NCA subjects and CHD patients were performed. For choline and creatinine, the AUCs ranged from 0.720 to 0.733. For TMAO and carnitine, the AUCs ranged from 0.568 to 0.600.In conclusion, the current study illustrates the distribution of 4 metabolites between CHD patients and NCA subjects. Metabolomics analysis may yield novel predictive biomarkers that will potentially provide value for clinical diagnosis of CHD.

An integrated portable system for single chip simultaneous measurement of multiple disease associated metabolites

Metabolites, the small molecules that underpin life, can act as indicators of the physiological state of the body when their abundance varies, offering routes to diagnosis of many diseases. The ability to assay for multiple metabolites simultaneously will underpin a new generation of precision diagnostic tools. Here, we report the development of a handheld device based on complementary metal oxide semiconductor (CMOS) technology with multiple isolated micro-well reaction zones and integrated optical sensing allowing simultaneous enzyme-based assays of multiple metabolites (choline, xanthine, sarcosine and cholesterol) associated with multiple diseases. These metabolites were measured in clinically relevant concentration range with minimum concentrations measured: 25 μM for choline, 100 μM for xanthine, 1.25 μM for sarcosine and 50 μM for cholesterol. Linking the device to an Android-based user interface allows for quantification of metabolites in serum and urine within 2 min of applying samples to the device. The quantitative performance of the device was validated by comparison to accredited tests for cholesterol and glucose.

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.

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.

Effects of choline on health across the life course: a systematic review

CONTEXT

Choline is a precursor of both betaine and acetylcholine and might, therefore, influence cardiovascular and cognitive outcomes. There has been concern, however, that it may influence blood lipid levels because it is an essential component of very-low-density lipoproteins.

OBJECTIVE

The aim was to systematically review, using PRISMA guidelines, the literature pertaining to the effects of choline on body composition and on metabolic, cardiovascular, respiratory, and neurological outcomes in different life stages.

DATA SOURCES

The MEDLINE, Embase, Cochrane Central, Web of Science, PubMed, and Google Scholar databases were searched up to July 2014.

DATA EXTRACTION

Fifty relevant articles were identified. These comprised trials and cohort, case-control, and cross-sectional studies that assessed blood levels of choline, dietary intake of choline, and supplementation with choline in a population free of diseases at baseline.

DATA SYNTHESIS

There is some observational evidence that choline during pregnancy may be beneficial for the neurological health of the child. In adults, choline may have beneficial effects on cognition, but high-quality (intervention) studies are lacking. Results on the effects of choline on body composition, blood lipids, and cardiovascular health were inconsistent.

CONCLUSIONS

Evidence to confirm the suggested effects of choline on health in different stages of life is scarce. Potential effects of choline need to be confirmed by intervention studies. Possible harmful effects on cardiometabolic health need careful evaluation.

Plasma dimethylglycine, nicotine exposure and risk of low bone mineral density and hip fracture: the Hordaland Health Study

In the large community-based Hordaland Health Study, low plasma dimethylglycine was associated with low bone mineral density in both middle-aged and elderly subjects and to an increased risk of subsequent hip fracture among the elderly. These associations seemed to be particularly strong among subjects exposed to nicotine.

INTRODUCTION

Dimethylglycine (DMG) is a product of the choline oxidation pathway and formed from betaine during the folate-independent remethylation of homocysteine (Hcy) to methionine. Elevated plasma DMG levels are associated with atherosclerotic cardiovascular disease and inflammation, which in turn are related to osteoporosis. High plasma total Hcy and low plasma choline are associated with low bone mineral density (BMD) and hip fractures, but the role of plasma DMG in bone health is unknown.

METHODS

We studied the associations of plasma DMG with BMD among 5315 participants (46-49 and 71-74 years old) and with hip fracture among 3310 participants (71-74 years old) enrolled in the Hordaland Health Study.

RESULTS

In age and sex-adjusted logistic regression models, subjects in the lowest versus highest DMG tertile were more likely to have low BMD (odds ratio [OR] 1.68, 95% confidence interval [CI] 1.43-1.99). The association was stronger in participants exposed compared to those unexposed to nicotine (OR 2.31, 95% CI 1.73-3.07 and OR 1.43, 95% CI 1.16-1.75, respectively, p interaction = 0.008). In the older cohort, Cox regression analyses adjusted for sex showed that low plasma DMG was associated with an increased risk of hip fracture (hazard ratio [HR] 1.70, 95% CI 1.28-2.26). A trend toward an even higher risk was found among women exposed to nicotine (HR 3.41, 95% CI 1.40-8.28).

CONCLUSION

Low plasma DMG was associated with low BMD and increased risk of hip fractures. A potential effect modification by nicotine exposure merits particular attention.

Plasma choline, smoking, and long-term prognosis in patients with stable angina pectoris

BACKGROUND

Plasma choline has been associated with cardiovascular disease and nonalcoholic steatohepatitis.

DESIGN

We sought to study relations of plasma choline and its metabolite betaine to long-term risk of acute myocardial infarction (AMI) and all-cause mortality according to smoking status, in patients undergoing coronary angiography for stable angina pectoris.

METHODS

Samples were obtained before angiography from 2568 patients who were subsequently randomized in the Western Norway B-Vitamin Intervention Trial (WENBIT). Hazard ratios (HR) were calculated using multivariate Cox-regression and p-values were reported for trends over quartiles.

RESULTS

Plasma concentrations of choline, but not betaine, were lower in smokers, and choline was positively associated with C-reactive protein and troponin T in nonsmokers, but not in smokers (p for interaction <0.03). During a follow up of 4.8 ± 1.4 (mean ± SD) years, 8.3% suffered from AMI and 6.1% died. In the total population, choline was not associated with AMI or all-cause mortality. However, comparing the highest vs. the lowest quartiles, plasma choline was associated with increased risk of AMI in nonsmokers (HR 2.63, 95% CI 1.56 to 5.51; p for trend = 0.013) and no risk in smokers (p for interaction < 0.001). Plasma choline significantly improved discrimination and reclassification when added to established cardiovascular risk factors. Plasma betaine was not associated with either endpoint.

CONCLUSIONS

In patients with stable angina pectoris, elevated plasma choline is associated with elevated troponin levels and increased risk of AMI in nonsmokers. These results motivate further research into the relation between choline metabolism, smoking, and atherothrombosis.

Measurement of concentrations of whole blood levels of choline, betaine, and dimethylglycine and their relations to plasma levels

We aimed at developing a method for the measurement of choline and its metabolites in whole blood (WB). After an extraction step, quantification of choline, betaine, and dimethylglycine (DMG) was performed using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Plasma and WB metabolites were evaluated in a group of 61 elderly people. The calibration curves were linear (r(2)>0.997) for all compounds. The inter- and intra-assay coefficients of variation for all analytes were <10%. The recoveries were >90% and the relative matrix effect were ≤4.0%. The median concentrations of choline, betaine, and DMG were 11.3, 27.8, and 5.9μmol/L in plasma and 66.6, 165, and 13.7μmol/L in WB, respectively. There were positive correlations between WB and plasma markers; for choline (r=0.42), betaine (r=0.61), and DMG (r=0.56) (all p≤0.001). The concentrations of betaine in WB and plasma were significantly higher in men than in women. The concentrations of WB choline and DMG did not differ significantly according to sex. In conclusion, we have established a reliable method for measuring choline metabolites in WB. The concentrations of WB choline, betaine, and DMG seem to reflect intracellular concentrations of these metabolites.

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.

Perspectives on the value of biomarkers in acute cardiac care and implications for strategic management

Biomarkers in acute cardiac care are gaining increasing interest given their clinical benefits. This study is a review of the major conditions in acute cardiac care, with a focus on biomarkers for diagnostic and prognostic assessment. Through a PubMed search, 110 relevant articles were selected. The most commonly used cardiac biomarkers (cardiac troponin, natriuretic peptides, and C-reactive protein) are presented first, followed by a description of variable acute cardiac conditions with their relevant biomarkers. In addition to the conventional use of natriuretic peptides, cardiac troponin, and C-reactive protein, other biomarkers are outlined in variable critical conditions that may be related to acute cardiac illness. These include ST2 and chromogranin A in acute dyspnea and acute heart failure, matrix metalloproteinase in acute chest pain, heart-type fatty acid binding protein in acute coronary syndrome, CD40 ligand and interleukin-6 in acute myocardial infarction, blood ammonia and lactate in cardiac arrest, as well as tumor necrosis factor-alpha in atrial fibrillation. Endothelial dysfunction, oxidative stress and inflammation are involved in the physiopathology of most cardiac diseases, whether acute or chronic. In summary, natriuretic peptides, cardiac troponin, C-reactive protein are currently the most relevant biomarkers in acute cardiac care. Point-of-care testing and multi-markers use are essential for prompt diagnostic approach and tailored strategic management.

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.

Biomarkers in acute myocardial injury

Acute coronary syndrome (ACS) is a significant cause of morbidity and mortality worldwide. The proper diagnosis of ACS requires reliable and accurate biomarker assays to detect evidence of myocardial necrosis. Currently, troponin is the gold standard biomarker for myocardial injury and is used commonly in conjunction with creatine kinase-MB (CK-MB) and myoglobin to enable a more rapid diagnosis of ACS. A new generation of highly sensitive troponin assays with improved accuracy in the early detection of ACS is now available, but the correct interpretation of assay results will require a careful consideration of assay characteristics and the clinical setting prior to incorporation into routine practice. B-type natriuretic peptides, copeptin, ischemia-modified albumin, heart-type fatty-acid-binding protein, myeloperoxidase, C-reactive protein, choline, placental growth factor, and growth-differentiation factor-15 make up a promising group of other biomarkers that have shown the ability to improve prognosis and diagnosis of ACS compared with traditional markers.

Cardiac biomarkers in acute myocardial infarction

Each year, a large number of patients are seen in the Emergency Department with presentations necessitating investigation for possible acute myocardial infarction. Patients can be stratified by symptoms, risk factors and electrocardiogram results but cardiac biomarkers also have a prime role both diagnostically and prognostically. This review summarizes both the history of cardiac biomarkers as well as currently available (established and novel) assays. Cardiac troponin, our current "gold standard" biomarker criterion for the diagnosis of myocardial infarction has high sensitivity and specificity for this diagnosis and therapies instituted in patients with elevated troponin have been shown to influence outcomes. Other markers of myocardial necrosis, inflammation and neurohormonal activity have also been shown to have either diagnostic or prognostic utility, but none have been shown to be superior to troponin. The measurement of multiple biomarkers and the use of point of care markers may accelerate current diagnostic protocols for the assessment of such patients.

[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.

High-sensitivity troponin T and copeptin in non-ST acute coronary syndromes: implications for prognosis and role of hsTnT and copeptin in non-STEACS

High-sensitivity TnT (hsTnT) has been proposed to improve the diagnosis and stratification in acute coronary syndromes. Copeptin has been proposed for a rapid and accurate rule out of acute myocardial infarction, but some doubts exist about its use out of the first hours from admission. Abnormalities of serum hsTnT and copeptin levels in non-STEACS and negative TnT, could have prognostic implications. Methods. We included 122 non-STEACS patients without raised TnT, 33 disease controls and 43 healthy controls. We measured hsTnT and copeptin levels. Clinical follow-up at 12 months was performed for adverse endpoints. Results. Non-STEACS patients had raised hsTnT compared with both control groups (P = 0.036 and P < 0.001). Copeptin levels were higher in non-STEACS patients than healthy controls (P = 0.021), without differences with disease controls. Raised levels of hs-TnT presented prognostic implications [HR 3.29 (95%CI: 1.33–7.49), P = 0.010]. hs-TnT could be used for invasive approach decision, as it shows prognostic relevance in conservative approach-patients whereas remains unrelevant for catheterized-patients. Copeptin levels were not associated with adverse events. Conclusion. hsTnT levels increased in non-STEACS, were predictive of adverse events and could be important for recommending an invasive management. We cannot confirm a predictive role of copeptin out of the first hours from admission.

Cardiac biomarkers - the old and the new: a review

Biomarkers are biological parameters that can be objectively measured and quantified as indicators of normal biologic processes, pathogenic processes, or responses to a therapeutic intervention. Typically thought of as disease process screening, diagnosing, or monitoring tools, biomarkers may also be used to determine disease susceptibility and eligibility for specific therapies. Cardiac biomarkers are protein components of cell structures that are released into circulation when myocardial injury occurs. They play a pivotal role in the diagnosis, risk stratification, and treatment of patients with chest pain and suspected acute coronary syndrome and those with acute exacerbations of heart failure. Cardiac markers are central to the new definition of acute myocardial infarction put forward by the American College of Cardiology and the European Society of Cardiology. Active investigation has brought forward an increasingly large number of novel candidate markers but few have withstood the test of time and become integrated into contemporary clinical care because of their readily apparent diagnostic, prognostic, or therapeutic utility.

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.

Biomarkers of vulnerable plaque: the missing link with ischemia

The initial evaluation of chest pain in the emergency department is based on the patient’s clinical history, changes in the ECG and necrosis biomarkers. Although management of patients with ST-elevation myocardial infarction or non-ST-elevation myocardial infarction with positive markers of myocardial damage is well defined, exclusion of coronary artery disease or myocardial ischemia in the remaining patients is more challenging. This group represents the majority of patients admitted for chest pain syndromes and that have a substantial risk of an adverse outcome. Given that troponin, as a marker of myocardial damage, detects terminal events in the cascade of acute coronary syndrome, there is a need to search for biomarkers that are able to identify patients at high risk, allowing rapid, bedside stratification. Data suggest that clinical events are prone to occur more frequently in patients with coronary artery stenosis associated with myocardial ischemia. Accordingly, identification of systemic biomarkers of ischemia could facilitate identification of high-risk patients with a high burden of coronary atherosclerosis and plaque rupture. We describe six biomarkers that have been linked to myocardial ischemia. Until now, these biomarkers of ischemia are relevant in order to exclude ischemic heart disease (high negative predictive value) but still lack specificity. Future prospective studies should be performed in larger and more diverse sets of patients presenting with ischemia, and in a complementary fashion in order to provide valuable tools for clinical decision making.

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.

Markers for Early Detection of Cardiac Diseases

The existing markers for myocardial necrosis, such as cardiac troponin, creatine kinase-MB, and myoglobin are thought to be released into blood following irreversible myocardial necrosis. Thus results of these tests are usually negative for patients with acute coronary syndromes (ACS) who present to the emergency department (ED) within the first 3 hours after the onset of chest pain. Given the need to make early therapeutic and triage decisions, biomarkers that can be used to diagnose and/or risk stratify ACS patients during their initial ED presentation will be important. Active research in this area has identified several classes of biomarkers that show promise for early detection of disease. These include tests for the presence of acute inflammation and infiltration (e.g., high sensitivity-C-reactive protein, myeloperoxidase), plaque instability (e.g., pregnancy-associated plasma protein-A, placental growth factor), platelet activation (e.g., whole blood choline, platelet density, CD40 ligand), and myocardial ischemia (e.g., ischemia modified albumin, free fatty acids, serum choline, and B-type natriuretic peptide). Each of these tests has demonstrated some utility for early diagnosis. However, as most lack specificity for myocardial disease, routine use may require a multi-marker approach.

Quick identification of acute chest pain patients study (QICS)

Background

Patients with acute chest pain are often referred to the emergency ward and extensively investigated. Investigations are costly and could induce unnecessary complications, especially with invasive diagnostics. Nevertheless, chest pain patients have high mortalities. Fast identification of high-risk patients is crucial. Therefore several strategies have been developed including specific symptoms, signs, laboratory measurements, and imaging.

Methods/Design

The Quick Identification of acute Chest pain Study (QICS) will investigate whether a combined use of specific symptoms and signs, electrocardiography, routine and new laboratory measures, adjunctive imaging including electron beam (EBT) computed tomography (CT) and contrast multislice CT (MSCT) will have a high diagnostic yield for patients with acute chest pain. All patients will be investigated according a standardized protocol in the Emergency Department. Serum and plasma will be frozen for future analysis for a wide range of biomarkers at a later time point. The primary endpoint is the safe recognition of low-risk chest pain patients directly at presentation. Secondary endpoint is the identification of a wide range of sensitive predictive clinical markers, chemical biomarkers and radiological markers in acute chest pain patients. Chemical biomarkers will be compared to quantitative CT measurements of coronary atherosclerosis as a surrogate endpoint. Chemical biomarkers will also be compared in head to head comparison and for their additional value.

Discussion

This will be a very extensive investigation of a wide range of risk predictors in acute chest pain patients. New reliable fast and cheap diagnostic algorithm resulting from the test results might improve chest pain patients' prognosis, and reduce unnecessary costs and diagnostic complications.

The value of biochemical markers for risk stratification prior to hospital admission in acute chest pain

We describe the use of biochemical markers in the pre-hospital setting with regard to diagnostic accuracy for the detection of an acute myocardial infarction (AMI) and for prognosis in connection with acute chest pain. The sensitivity has been reported to be limited; blood sampling occurs very early and often prior to the release of biochemical markers into the circulation. The specificity was in some studies also limited, but this is more difficult to explain. New biochemical markers like human heart fatty acid binding protein (H-FACB) have shown improved diagnostic accuracy, in the pre-hospital setting, in one small pilot study compared with traditional biochemical markers like troponins, creatine kinase (CK-MB) and myoglobin. However, in a recent small study, the sensitivity for troponin I (when a low decision limit for myocardial damage was used), when analysed prior to hospital admission, was reported to be very high. The latter data need to be confirmed in larger studies and various biochemical markers reflecting various pathophysiological aspects of the disease need to be tested before the analysis of any marker can be recommended for use in the pre-hospital setting of a suspected AMI.

Cardiac markers: a clear cause for point-of-care testing

Point-of-care testing (POCT) in patients with ischemic heart disease is driven by the time-critical need for fast, specific, and accurate results to initiate therapy instantly. According to current guidelines, the results of the cardiac marker testing should be available to the physician within 30 min ("vein-to-brain" time) to initiate therapy within 60-90 min ("door-to-needle" time) after the patient has arrived at the emergency room or intensive care unit. This article reviews the current efforts to meet this goal (1) by implementing POCT of established biochemical markers such as cardiac troponins, creatine kinase MB, and myoglobin, in accelerated diagnosis and management workflow schemes, (2) by improving current POCT methods to obtain more accurate, more specific, and even faster tests through the integration of optical and electrochemical sensor technology, and (3) by identifying new markers for the very early and sensitive detection of myocardial ischemia and necrosis. Furthermore, the specific requirements for cardiac POCT in regard to analytical performance, comparability, and diagnostic sensitivity/specificity are discussed. For the future, the integration of new immunooptical and electrochemical chip technology might speed up diagnosis even further. However, every new development will have to meet the stringent method validation criteria set for corresponding central laboratory testing.

Present and Future Biochemical Markers for Detection of Acute Coronary Syndrome

The use of biochemical markers in the diagnosis and management of patients with acute coronary syndrome has increased continually in recent decades. The development of highly sensitive and cardiac-specific troponin assays has changed the view on diagnosis of myocardial infarction and also extended the role of biochemical markers of necrosis into risk stratification and guidance for treatment. The consensus definition of myocardial infarction places increased emphasis on cardiac marker testing, with cardiac troponin replacing creatine kinase MB as the "gold standard" for diagnosis of myocardial infarction. Along with advances in the use of more cardiac-specific markers of myocardial necrosis, biochemical markers that are involved in the progression of atherosclerotic plaques to the vulnerable state or that signal the presence of vulnerable plaques have recently been identified. These markers have variable abilities to predict the risk of an individual for acute coronary syndrome. The aim of this review is to provide an overview of the well-established markers of myocardial necrosis, with a special focus on cardiac troponin I, together with a summary of some of the potential future markers of inflammation, plaque instability, and ischemia.

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.

Early detection of acute coronary syndromes and risk stratification by multimarker analysis

Cardiac troponin is the standard biomarker for the diagnosis of acute myocardial infarction (AMI) and risk stratification for short-term adverse cardiac events (death, AMI or need for revascularization). Unfortunately, the concentration of troponin in blood is normal in AMI patients who present early after the onset of symptoms. As such, there is active research being conducted in finding early markers of AMI and risk stratification. Despite years of testing dozens of candidates, no single test has had the necessary clinical sensitivity and specificity for this indication. Therefore, many researchers have advocated multimarker testing. There are two approaches that have been taken for discovering new markers. The proteomic approach involves focusing on the differences in the biochemical signatures between the tissues or biological fluids of normal compared with diseased individuals. Specific biochemical targets are not preselected. The pathophysiologic approach involves combining biomarkers that indicate a particular pathway or event known to be involved in the disease process. In both approaches, some bioinformatic algorithm will be necessary in order to combine the information provided by the individual tests. Representative approaches include the Multimarker Index™, classification and regression tree analysis and neural networks.

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

BACKGROUND

Whole blood choline (WBCHO) and plasma choline (PLCHO) concentrations increase rapidly after stimulation of phospholipase D in acute coronary syndromes (ACS). Early risk-stratification was analyzed in 217 patients with suspected ACS and a negative admission troponin T (<0.03 microg/L).

METHODS

WBCHO and PLCHO were measured using high-performance-liquid-chromatography mass spectrometry. Major cardiac events (MACE) were defined as cardiac death/arrest, coronary intervention or myocardial infarction (MI).

RESULTS

WBCHO (> or = 28.2 micromol/L) was predictive for MACE (hazard ratio [HR] 2.7; p<0.001), cardiac death/arrest (HR 4.2; p=0.015), heart failure (HR 2.8; p=0.003), coronary intervention (HR 2.1; p=0.01) and MI (HR 8.4; p=0.002) after 30 days. PLCHO (> or = 25.0 micromol/L) was predictive for MACE (HR 2.6; p=0.005), cardiac death/arrest (HR 15.7; p<0.001), heart failure (HR 6.0; p<0.001) but not for coronary intervention and MI. WBCHO and PLCHO were predictive for MACE in multivariate analysis (Odds ratio [OR] 2.7, p=0.009 and OR 3.3, p=0.03) independently of age, gender, prior MI, coronary risk factors and ECG.

CONCLUSIONS

WBCHO and PLCHO are significant and independent predictors of major cardiac events in admission troponin T negative acute coronary syndromes. Both are predictive for events related to tissue ischemia and WBCHO is capable of detecting risks associated with coronary plaque instability.