Integration of Genome-Wide SNP Data and Gene-Expression Profiles Reveals Six Novel Loci and Regulatory Mechanisms for Amino Acids and Acylcarnitines in Whole Blood

Profiling amino acids and acylcarnitines in whole blood spots is a powerful tool in the laboratory diagnosis of several inborn errors of metabolism. Emerging data suggests that altered blood levels of amino acids and acylcarnitines are also associated with common metabolic diseases in adults. Thus, the identification of common genetic determinants for blood metabolites might shed light on pathways contributing to human physiology and common diseases. We applied a targeted mass-spectrometry-based method to analyze whole blood concentrations of 96 amino acids, acylcarnitines and pathway associated metabolite ratios in a Central European cohort of 2, 107 adults and performed genome-wide association (GWA) to identify genetic modifiers of metabolite concentrations. We discovered and replicated six novel loci associated with blood levels of total acylcarnitine, arginine (both on chromosome 6;rs12210538, rs17657775),propionylcarnitine (chromosome 10;rs12779637),2-hydroxyisovalerylcarnitine (chromosome 21;rs1571700),stearoylcarnitine (chromosome 1;rs3811444),and aspartic acid traits (chromosome 8;rs750472). Based on an integrative analysis of expression quantitative trait loci in blood mononuclear cells and correlations between gene expressions and metabolite levels, we provide evidence for putative causative genes: SLC22A16 for total acylcarnitines, ARG1 for arginine, HLCS for 2-hydroxyisovalerylcarnitine, JAM3 for stearoylcarnitine via a trans-effect at chromosome 1, and PPP1R16A for aspartic acid traits. Further, we report replication and provide additional functional evidence for ten loci that have previously been published for metabolites measured in plasma, serum or urine. In conclusion, our integrative analysis of SNP, gene-expression and metabolite data points to novel genetic factors that may be involved in the regulation of human metabolism. At several loci, we provide evidence for metabolite regulation via gene-expression and observed overlaps with GWAS loci for common diseases. These results form a strong rationale for subsequent functional and disease-related studies

Obesity, inflammatory markers, and endometrial cancer risk: a prospective case–control study

Obesity, a major risk factor for endometrial cancer, is a low-grade inflammatory state characterized by elevated concentrations of cytokines and acute phase reactants. The current study had two aims: first to investigate the associations of C-reactive protein (CRP), interleukin 6 (IL6), and IL1 receptor antagonist (IL1Ra) with endometrial cancer risk and second to examine to which extent these markers can influence the association between obesity and endometrial cancer. We conducted a case–control study, nested within the European Prospective Investigation into Cancer and Nutrition, which comprised 305 incident cases of endometrial cancer and 574 matched controls. CRP, IL6, and IL1Ra were measured in prospectively collected blood specimens by immunoassays. Data were analyzed using conditional logistic regression. All statistical tests were two-sided, and P values <0.05 were considered statistically significant. We observed a significant increase in risk of endometrial cancer with elevated levels of CRP (odds ratio (OR) for top versus bottom quartile: 1.58, 95% confidence interval (CI): 1.03–2.41, Ptrend=0.02), IL6 (OR for top versus bottom quartile: 1.66, 95% CI: 1.08–2.54, Ptrend=0.008), and IL1Ra (OR for top versus bottom quartile: 1.82, 95% CI: 1.22–2.73, Ptrend=0.004). After adjustment for body mass index (BMI), the estimates were strongly reduced and became non-significant. The association between BMI and endometrial cancer was also substantially attenuated (∼10–20%) after adjustment for inflammatory markers, even when the effects of C-peptide or estrone had already been taken into account. We provided epidemiological evidence that chronic inflammation might mediate the association between obesity and endometrial cancer and that endometrial carcinogenesis could be promoted by an inflammatory milieu

First international descriptive and interventional survey for cholesterol and non-cholesterol sterol determination by gas- and liquid- chromatography–Urgent need for harmonisation of analytical methods

Serum concentrations of lathosterol, the plant sterols campesterol and sitosterol and the cholesterol metabolite 5α-cholestanol are widely used as surrogate markers of cholesterol synthesis and absorption, respectively. Increasing numbers of laboratories utilize a broad spectrum of well-established and recently developed methods for the determination of cholesterol and non-cholesterol sterols (NCS). In order to evaluate the quality of these measurements and to identify possible sources of analytical errors our group initiated the first international survey for cholesterol and NCS. The cholesterol and NCS survey was structured as a two-part survey which took place in the years 2013 and 2014. The first survey part was designed as descriptive, providing information about the variation of reported results from different laboratories. A set of two lyophilized pooled sera (A and B) was sent to twenty laboratories specialized in chromatographic lipid analysis. The different sterols were quantified either by gas chromatography-flame ionization detection, gas chromatography- or liquid chromatography-mass selective detection. The participants were requested to determine cholesterol and NCS concentrations in the provided samples as part of their normal laboratory routine. The second part was designed as interventional survey. Twenty-two laboratories agreed to participate and received again two different lyophilized pooled sera (C and D). In contrast to the first international survey, each participant received standard stock solutions with defined concentrations of cholesterol and NCS. The participants were requested to use diluted calibration solutions from the provided standard stock solutions for quantification of cholesterol and NCS. In both surveys, each laboratory used its own internal standard (5α-cholestane, epicoprostanol or deuterium labelled sterols). Main outcome of the survey was, that unacceptably high interlaboratory variations for cholesterol and NCS concentrations are reported, even when the individual laboratories used the same calibration material. We discuss different sources of errors and recommend all laboratories analysing cholesterol and NCS to participate in regular quality control programs

Circulating sterols as predictors of early allograft dysfunction and clinical outcome in patients undergoing liver transplantation.

INTRODUCTION Sensitive and specific assessment of the hepatic graft metabolism after liver transplantation (LTX) is essential for early detection of postoperative dysfunction implying the need for consecutive therapeutic interventions. OBJECTIVES Here, we assessed circulating liver metabolites of the cholesterol pathway, amino acids and acylcarnitines and evaluated their predictive value on early allograft dysfunction (EAD) and clinical outcome in the context of LTX. METHODS The metabolites were quantified in the plasma of 40 liver graft recipients one day pre- and 10 days post-LTX by liquid chromatography/tandem mass spectrometry (LC-MS/MS). Plant sterols as well as cholesterol and its precursors were determined in the free and esterified form; lanosterol in the free form only. Metabolites and esterification ratios were compared to the model for early allograft function scoring (MEAF) which is calculated at day 3 post-LTX from routine parameters defining EAD. RESULTS The hepatic esterification ratio of all sterols, but not amino acids and acylcarnitine concentrations, showed substantial metabolic disturbances post-LTX and correlated to the MEAF. In ROC analysis, the low esterification ratio of β-sitosterol and stigmasterol from day 1 and of the other sterols from day 3 were predictive for a high MEAF, i.e. EAD. Additionally, the ratio of esterified β-sitosterol and free lanosterol were predictive for all days and the esterification ratio of the other sterols at day 3 or 4 post-LTX for 3-month mortality. CONCLUSION Low ratios of circulating esterified sterols are associated with a high risk of EAD and impaired clinical outcome in the early postoperative phase following LTX

Cholesterol esterification in plasma as a biomarker for liver function and prediction of mortality

Abstract Background Advanced stages of liver cirrhosis lead to a dramatically increased mortality. For valid identification of these patients suitable biomarkers are essential. The most important biomarkers for liver function are bilirubin and prothrombin time expressed as International Normalized Ratio (INR). However, the influence of several anticoagulants on the prothrombin time limits its diagnostic value. Aim of this study was the evaluation of cholesterol esterification (CE) fraction (esterified cholesterol vs. total cholesterol) as an alternative biomarker for liver synthesis and mortality prediction. Under physiological conditions the CE fraction in blood is closely regulated by lecithin-cholesterol acyltransferase (LCAT) which is produced in the liver. Methods One hundred forty-two patients with liver disease clinically considered for orthotopic liver transplant for different indications were enrolled in the study. One patient was excluded because of the intake of a direct oral factor Xa inhibitor which has a strong impact on prothrombin time. Results Results of CE fraction were in good agreement with INR (R2 = 0.73; p < 0.001). In patients who died or survived within three months mean CE fraction was 56% vs. 74% (p < 0.001) and mean INR was 2.0 vs. 1.3 (p < 0.001), respectively. The predictive value of CE fraction for three-month mortality risk was higher compared to INR (p = 0.04). Results for one-year mortality were comparable. Conclusions The cholesterol esterification fraction is a valid biomarker for liver synthesis and allows reliable prediction of mortality. In contrast to INR, it is independent of anticoagulation and other analytical limitations of coagulation tests

High density lipoprotein (HDL)-associated sphingosine 1-phosphate (S1P) inhibits macrophage apoptosis by stimulating STAT3 activity and survivin expression

Background and aims Macrophage apoptosis is critically involved in atherosclerosis. We here examined the effect of anti-atherogenic high density lipoprotein (HDL) and its component sphingosine-1-phosphate (S1P) on apoptosis in RAW264.7 murine macrophages. Methods Mitochondrial or endoplasmic reticulum-dependent apoptosis was induced by exposure of macrophages to etoposide or thapsigargin/fukoidan, respectively. Results Cell death induced by these compounds was inhibited by S1P as inferred from reduced annexin V binding, TUNEL staining, and caspase 3, 9 and 12 activities. S1P induced expression of the inhibitor of apoptosis protein (IAP) family proteins cIAP1, cIAP2 and survivin, but only the inhibitor of survivin expression YM155 and not the cIAP1/2 blocker GDC0152 reversed the inhibitory effect of S1P on apoptosis. Moreover, S1P activated signal transducer and activator of transcription 3 (STAT3) and Janus kinase 2 (JAK2) and the stimulatory effect of S1P on survivin expression and inhibitory effects on apoptosis were attenuated by STAT3 or JAK2 inhibitors, S3I-201 or AG490, respectively. The effects of S1P on STAT3 activation, survivin expression and macrophage apoptosis were emulated by HDL, HDL lipids, and apolipoprotein (apo) M-containing HDL, but not by apoA-I or HDL deprived of S1P or apoM. In addition, JTE013 and CAY10444, S1P receptor 2 and 3 antagonists, respectively, compromised the S1P and HDL capacities to stimulate STAT3 activation and survivin expression, and to inhibit apoptosis. Conclusions HDL-associated S1P inhibits macrophage apoptosis by stimulating STAT3 activity and survivin expression. The suppression of macrophage apoptosis may represent a novel mechanism utilized by HDL to exert its anti-atherogenic effects

Plasma Amino Acid Concentrations Predict Mortality in Patients with End-Stage Liver Disease

<div><p>Background</p><p>The liver plays a key role in amino acid metabolism. In former studies, a ratio between branched-chain and aromatic amino acids (Fischer’s ratio) revealed associations with hepatic encephalopathy. Furthermore, low concentrations of branched-chain amino acids were linked to sarcopenia in literature. Encephalopathy and sarcopenia are known to dramatically worsen the prognosis. Aim of this study was to investigate a complex panel of plasma amino acids in the context of mortality in patients with end-stage liver disease.</p><p>Methods</p><p>166 patients evaluated for orthotopic liver transplantation were included. 19 amino acids were measured from citrated plasma samples using mass spectrometry. We performed survival analysis for plasma amino acid constellations and examined the relationship to established mortality predictors.</p><p>Results</p><p>33/166 (19.9%) patients died during follow-up. Lower values of valine (p<0.001), Fischer’s ratio (p<0.001) and valine to phenylalanine ratio (p<0.001) and higher values of phenylalanine (p<0.05) and tyrosine (p<0.05) were significantly associated with mortality. When divided in three groups, the tertiles discriminated cumulative survival for valine (p = 0.016), phenylalanine (p = 0.024) and in particular for valine to phenylalanine ratio (p = 0.003) and Fischer’s ratio (p = 0.005). Parameters were also significantly correlated with MELD and MELD-Na score.</p><p>Conclusions</p><p>Amino acids in plasma are valuable biomarkers to determine increased risk of mortality in patients with end-stage liver disease. In particular, valine concentrations and constellations composed of branched-chain and aromatic amino acids were strongly associated with prognosis. Due to their pathophysiological importance, the identified amino acids could be used to examine individual dietary recommendations to serve as potential therapeutic targets.</p></div

Description of liver disease etiologies, comorbidities and Child-Pugh-Turcotte classification in numbers and percentage in the analyzed population (N = 166).

<p>Description of liver disease etiologies, comorbidities and Child-Pugh-Turcotte classification in numbers and percentage in the analyzed population (N = 166).</p

Data of the measured metabolite panel (N = 166).

<p>Survival analysis was performed by an univariate cox-regression model. Significant results are written in bold and asterisked (*, **, ***). Essential amino acids are printed in italics.</p