Lipidomics Reveals Myocardial Lipid Composition in a Murine Model of Insulin Resistance Induced by a High-Fat Diet

Ectopic fat accumulation in non-adipose tissues is closely related to diabetes-related myocardial dysfunction. Nevertheless, the complete picture of the lipid metabolites involved in the metabolic-related myocardial alterations is not fully characterized. The aim of this study was to characterize the specific lipid profile in hearts in an animal model of obesity/insulin resistance induced by a high-fat diet (HFD). The cardiac lipidome profiles were assessed via liquid chromatography-mass spectrometry (LC-MS)/MS-MS and laser desorption/ionization-mass spectrometry (LDI-MS) tissue imaging in hearts from C57BL/6J mice fed with an HFD or standard-diet (STD) for 12 weeks. Targeted lipidome analysis identified a total of 63 lipids (i.e., 48 triacylglycerols (TG), 5 diacylglycerols (DG), 1 sphingomyelin (SM), 3 phosphatidylcholines (PC), 1 DihydroPC, and 5 carnitines) modified in hearts from HFD-fed mice compared to animals fed with STD. Whereas most of the TG were up-regulated in hearts from animals fed with an HFD, most of the carnitines were down-regulated, thereby suggesting a reduction in the mitochondrial β-oxidation. Roughly 30% of the identified metabolites were oxidated, pointing to an increase in lipid peroxidation. Cardiac lipidome was associated with a specific biochemical profile and a specific liver TG pattern. Overall, our study reveals a specific cardiac lipid fingerprint associated with metabolic alterations induced by HFD.

Serum metabolomics profiling by proton nuclear magnetic resonance spectrometry of the response to single oral macronutrient challenges in women with polycystic ovary syndrome (PCOS) compared with male and female controls

BACKGROUND

The polycystic ovary syndrome (PCOS) is associated with insulin resistance, obesity and cardiometabolic comorbidities. We here challenged the hypothesis, using state-of-the-art proton nuclear magnetic resonance spectrometry (1H-NMRS) metabolomics profiling, that androgen excess in women induces a certain masculinization of postprandial metabolism that is modulated by obesity.

MATERIALS AND METHODS

Participants were 53 Caucasian young adults, including 17 women with classic PCOS consisting of hyperandrogenism and ovulatory dysfunction, 17 non-hyperandrogenic women presenting with regular menses, and 19 healthy men, selected to be similar in terms of age and body mass index (BMI). Half of the subjects had obesity. Patients were submitted to isocaloric separate glucose, lipid and protein oral challenges in alternate days and fasting and postprandial serum samples were submitted to 1H-NMRS metabolomics profiling for quantification of 36 low-molecular-weight polar metabolites.

RESULTS

The largest postprandial changes were observed after glucose and protein intake, with lipid ingestion inducing smaller differences. Changes after glucose intake consisted of a marked increase in carbohydrates and byproducts of glycolysis, and an overall decrease in byproducts of proteolysis, lipolysis and ketogenesis. After the protein load, most amino acids and derivatives increased markedly, in parallel to an increase in pyruvate and a decrease in 3-hydroxybutyric acid and glycerol. Obesity increased β- and D-glucose and pyruvate levels, with this effect being observed mostly after glucose ingestion in women with PCOS. Regardless of the type of macronutrient, men presented increased lysine and decreased 3-hydroxybutyric acid. In addition, non-obese men showed increased postprandial β-glucose and decreased pyroglutamic acid, compared with non-obese control women. We observed a common pattern of postprandial changes in branched-chain and aromatic amino acids, where men showed greater amino acids increases after protein intake than control women and patients with PCOS but only within the non-obese participants. Conversely, this increase was blunted in obese men but not in obese women, who even presented a larger increase in some amino acids compared with their non-obese counterparts. Interestingly, regardless of the type of macronutrient, only obese women with PCOS showed increased leucine, lysine, phenylalanine and tryptophan levels compared with non-obese patients.

CONCLUSIONS

Serum 1H-NMRS metabolomics profiling indicated sexual dimorphism in the responses to oral macronutrient challenges, which were apparently driven by the central role of postprandial insulin effects with obesity, and to a lesser extent PCOS, exerting modifying roles derived from insulin resistance. Hence, obesity impaired metabolic flexibility in young adults, yet sex and sex hormones also influenced the regulation of postprandial metabolism.

rMSIfragment: improving MALDI-MSI lipidomics through automated in-source fragment annotation

Matrix-Assisted Laser Desorption Ionization Mass Spectrometry Imaging (MALDI-MSI) spatially resolves the chemical composition of tissues. Lipids are of particular interest, as they influence important biological processes in health and disease. However, the identification of lipids in MALDI-MSI remains a challenge due to the lack of chromatographic separation or untargeted tandem mass spectrometry. Recent studies have proposed the use of MALDI in-source fragmentation to infer structural information and aid identification. Here we present rMSIfragment, an open-source R package that exploits known adducts and fragmentation pathways to confidently annotate lipids in MALDI-MSI. The annotations are ranked using a novel score that demonstrates an area under the curve of 0.7 in ROC analyses using HPLC-MS and Target-Decoy validations. rMSIfragment applies to multiple MALDI-MSI sample types and experimental setups. Finally, we demonstrate that overlooking in-source fragments increases the number of incorrect annotations. Annotation workflows should consider in-source fragmentation tools such as rMSIfragment to increase annotation confidence and reduce the number of false positives.

Gradual Increase in Inflammation-Linked Glycoproteins and a Proatherogenic Lipoprotein Profile in the Early Stages of Psychosis as Characterized by 1H NMR Blood Analysis

Minimally invasive prognostic markers of inflammation and dyslipidemia in individuals with a risk of psychosis, also called "at-risk mental state" (ARMS), or in the first episode of psychosis (FEP) are of utmost clinical importance to prevent cardiovascular disorders. We analyzed the plasma concentration of inflammation-linked glycoproteins (Glycs) and lipoprotein subclasses by proton nuclear magnetic resonance (¹H NMR) in a single acquisition. Study participants were healthy controls (HCs, N = 67) and patients with ARMS (N = 58), FEP (N = 110), or early psychosis diagnosis with ≥2 episodes (critical period (CP), N = 53). Clinical biomarkers such as high-sensitivity C-reactive protein, interleukin 6, fibrinogen, insulin, and lipoproteins were also measured. Although all participants had normal lipoprotein profiles and no inflammation according to conventional biomarkers, a gradual increase in the Glyc ¹H NMR levels was observed from HCs to CP patients; this increase was statistically significant for GlycA (CP vs HC). In parallel, a progressive and significant proatherogenic ¹H NMR lipoprotein profile was also identified across stages of psychosis (ARMS and CP vs HC). These findings highlight the potential of using ¹H NMR Glyc and lipoprotein profiling to identify blood changes in individuals with ARMS or FEP and pave the way for applications using this technology to monitor metabolic and cardiovascular risks in clinical psychiatry.

LC/MS-Based Untargeted Metabolomics Study in Women with Nonalcoholic Steatohepatitis Associated with Morbid Obesity

This study investigated the importance of a metabolomic analysis in a complex disease such as nonalcoholic steatohepatitis (NASH) associated with obesity. Using an untargeted metabolomics technique, we studied blood metabolites in 216 morbidly obese women with liver histological diagnosis. A total of 172 patients were diagnosed with nonalcoholic fatty liver disease (NAFLD), and 44 were diagnosed with normal liver (NL). Patients with NAFLD were classified into simple steatosis (n = 66) and NASH (n = 106) categories. A comparative analysis of metabolites levels between NASH and NL demonstrated significant differences in lipid metabolites and derivatives, mainly from the phospholipid group. In NASH, there were increased levels of several phosphatidylinositols and phosphatidylethanolamines, as well as isolated metabolites such as diacylglycerol 34:1, lyso-phosphatidylethanolamine 20:3 and sphingomyelin 38:1. By contrast, there were decreased levels of acylcarnitines, sphingomyelins and linoleic acid. These findings may facilitate identification studies of the main pathogenic metabolic pathways related to NASH and may also have a possible applicability in a panel of metabolites to be used as biomarkers in future algorithms of the disease diagnosis and its follow-up. Further confirmatory studies in groups with different ages and sexes are necessary.

LC/MS-Based Untargeted Metabolomics Analysis in Women with Morbid Obesity and Associated Type 2 Diabetes Mellitus

Obesity is a chronic and complex disease, with an increasing incidence worldwide that is associated with metabolic disorders such as type 2 diabetes mellitus (T2DM). Thus, it is important to determine the differences between metabolically healthy obese individuals and those with metabolic disorders. The aim of this study was to perform an untargeted metabolomics assay in women with morbid obesity (MO) compared to a normal weight group, and to differentiate the metabolome of these women with MO who present with T2DM. We carried out a liquid chromatography-mass spectrometry-based untargeted metabolomics assay using serum samples of 209 Caucasian women: 73 with normal weight and 136 with MO, of which 71 had T2DM. First, we found increased levels of choline and acylglycerols and lower levels of bile acids, steroids, ceramides, glycosphingolipids, lysophosphatidylcholines, and lysophosphatidylethanolamines in MO women than in the control group. Then, in MO women with T2DM, we found increased levels of glutamate, propionyl-carnitine, bile acids, ceramides, lysophosphatidylcholine 14:0, phosphatidylinositols and phosphoethanolamines, and lower levels of Phe-Ile/Leu. Thus, we found metabolites with opposite trends of concentration in the two metabolomic analyses. These metabolites could be considered possible new factors of study in the pathogenesis of MO and associated T2DM in women.

Serum metabolomics profiling by proton nuclear magnetic resonance spectroscopy reveals sexual dimorphism and masculinization of intermediate metabolism in women with polycystic ovary syndrome (PCOS)

BACKGROUND

The polycystic ovary syndrome (PCOS) is associated with insulin resistance, obesity and cardiometabolic comorbidities. We here challenged the hypothesis, using state-of-the art proton nuclear magnetic resonance spectroscopy metabolomics profiling, that androgen excess in women induces also a certain masculinization of intermediate metabolism that is modulated by obesity.

METHODS

Participants were 53 Caucasian young adults, including 17 women with classic PCOS consisting of hyperandrogenism and ovulatory dysfunction, 17 non-hyperandrogenic women presenting with regular menses, and 19 healthy men, selected in order to be similar in terms of age and body mass index (BMI). Half of the subjects had obesity defined by a body mass index ≥ 30 kg/m². Subjects maintained the same diet unrestricted in carbohydrates for 3 days before sampling and maintained their lifestyle and exercise patterns prior and during the study. Plasma samples were submitted to proton nuclear magnetic resonance spectroscopy metabolomics profiling.

RESULTS

Obesity associated a metabolomics profile mainly characterized by increased branched chain and aromatic aminoacids. Regardless of obesity, this unfavorable profile also characterized men as compared with control women, and was shared by women with PCOS. Notably, the negative impact of obesity on metabolomics profile was restricted to women, with obese men showing no further deterioration when compared with their non-obese counterparts.

CONCLUSIONS

Serum metabolomics profiling by proton nuclear magnetic resonance spectroscopy reveals sexual dimorphism, and masculinization of intermediate metabolism in women with PCOS, further suggesting a role for sex and sex hormones in the regulation of intermediate metabolism.

Measurement of Serum N-Glycans in the Assessment of Early Vascular Aging (Arterial Stiffness) in Adults With Type 1 Diabetes

OBJECTIVE

Vascular aging (arterial stiffness [AS]) is an inflammation-linked process that predicts macro- and microvascular complications in adults with type 1 diabetes (T1D). We evaluated the utility of measuring the inflammation-linked N-glycans GlycA and GlycB to assess vascular aging in adults with T1D.

RESEARCH DESIGN AND METHODS

Eighty-four adults with T1D (>10-year duration without cardiovascular events) and 68 healthy control subjects were evaluated for clinical characteristics (including microvascular complications in patients with T1D), aortic pulse wave velocity (aPWV) (surrogate measure of AS), and serum GlycA and GlycB (peak area [concentration] and height/width [H/W] ratio) using 1H-nuclear magnetic resonance spectroscopy.

RESULTS

Patients with T1D had higher median (interquartile range) values than healthy control subjects for (P < 0.001 for all comparisons) aPWV 7.9 (6.9-9.1) vs. 6.1 (5.5-6.7) m/s, GlycA 850.4 (781.3-916.1) vs. 652.4 (581.5-727.1) μmoL; GlycB 386.1 (353.2-426.3) vs. 310.0 (280.5-331.9) μmol/L), H/W ratio of GlycA 16.5 (14.9-18.1) vs. 15.0 (13.7-16.7), and H/W ratio of GlycB 5.0 (4.6-5.5) vs. 4.0 (3.4-4.3). Moreover, aPWV correlated (P < 0.001 for all correlations) with GlycA (r = 0.550) and GlycB (r = 0.423) concentrations and with H/W ratios of GlycA (r = 0.453) and GlycB (r = 0.510). Adjusting for potential confounders, GlycA concentration (β = 0.212, P < 0.001) and the H/W ratios of GlycA (β = 0.150, P = 0.009) and GlycB (β = 0.155, P = 0.011) remained independently associated with aPWV. C-statistics for detecting individuals with aPWV >10 m/s were 0.866 (95% CI 0.794-0.937) for GlycA levels and 0.862 (0.780-0.943) for H/W ratio of GlycB.

CONCLUSIONS

Measurement of serum GlycA and GlycB may have utility in assessing vascular aging in adults with T1D of >10-year duration and no previous cardiovascular events.

What are we imaging? Software tools and experimental strategies for annotation and identification of small molecules in mass spectrometry imaging

Mass spectrometry imaging (MSI) has become a widespread analytical technique to perform nonlabeled spatial molecular identification. The Achilles' heel of MSI is the annotation and identification of molecular species due to intrinsic limitations of the technique (lack of chromatographic separation and the difficulty to apply tandem MS). Successful strategies to perform annotation and identification combine extra analytical steps, like using orthogonal analytical techniques to identify compounds; with algorithms that integrate the spectral and spatial information. In this review, we discuss different experimental strategies and bioinformatics tools to annotate and identify compounds in MSI experiments. We target strategies and tools for small molecule applications, such as lipidomics and metabolomics. First, we explain how sample preparation and the acquisition process influences annotation and identification, from sample preservation to the use of orthogonal techniques. Then, we review twelve software tools for annotation and identification in MSI. Finally, we offer perspectives on two current needs of the MSI community: the adaptation of guidelines for communicating confidence levels in identifications; and the creation of a standard format to store and exchange annotations and identifications in MSI.

Muscular carnosine is a marker for cardiorespiratory fitness and cardiometabolic risk factors in men with type 1 diabetes

PURPOSE

Muscle is an essential organ for glucose metabolism and can be influenced by metabolic disorders and physical activity. Elevated muscle carnosine levels have been associated with insulin resistance and cardiometabolic risk factors. Little is known about muscle carnosine in type 1 diabetes (T1D) and how it is influenced by physical activity. The aim of this study was to characterize muscle carnosine in vivo by proton magnetic resonance spectroscopy (¹H MRS) and evaluate the relationship with physical activity, clinical characteristics and lipoprotein subfractions.

METHODS

16 men with T1D (10 athletes/6 sedentary) and 14 controls without diabetes (9/5) were included. Body composition by DXA, cardiorespiratory capacity (VO₂peak) and serum lipoprotein profile by proton nuclear magnetic resonance (¹H NMR) were obtained. Muscle carnosine scaled to water (carnosine_W) and to creatine (carnosine_CR), creatine and intramyocellular lipids (IMCL) were quantified in vivo using ¹H MRS in a 3T MR scanner in soleus muscle.

RESULTS

Subjects with T1D presented higher carnosine CR levels compared to controls. T1D patients with a lower VO₂peak presented higher carnosine_CR levels compared to sedentary controls, but both T1D and control groups presented similar levels of carnosine_CR at high VO₂peak levels. Carnosine_W followed the same trend. Integrated correlation networks in T1D demonstrated that carnosine_W and carnosine_CR were associated with cardiometabolic risk factors including total and abdominal fat, pro-atherogenic lipoproteins (very low-density lipoprotein subfractions), low VO₂peak, and IMCL.

CONCLUSIONS

Elevated muscle carnosine levels in persons with T1D and their effect on atherogenic lipoproteins can be modulated by physical activity.

Statistical mediation of the relationships between chronological age and lipoproteins by nonessential amino acids in healthy men

Aging is a major risk factor for metabolic impairment that may lead to age-related diseases such as cardiovascular disease. Different mechanisms that may explain the interplay between aging and lipoproteins, and between aging and low-molecular-weight metabolites (LMWMs), in the metabolic dysregulation associated with age-related diseases have been described separately. Here, we statistically evaluated the possible mediation effects of LMWMs on the relationships between chronological age and lipoprotein concentrations in healthy men ranging from 19 to 75 years of age. Relative and absolute concentrations of LMWMs and lipoproteins, respectively, were assessed by nuclear magnetic resonance (NMR) spectroscopy. Multivariate linear regression and mediation analysis were conducted to explore the associations between age, lipoproteins and LMWMs. The statistical significance of the identified mediation effects was evaluated using the bootstrapping technique, and the identified mediation effects were validated on a publicly available dataset. Chronological age was statistically associated with five lipoprotein classes and subclasses. The mediation analysis showed that serine mediated 24.1% (95% CI: 22.9 – 24.7) of the effect of age on LDL-P, and glutamate mediated 17.9% (95% CI: 17.6 – 18.5) of the effect of age on large LDL-P. In the publicly available data, glutamate mediated the relationship between age and an NMR-derived surrogate of cholesterol. Our results suggest that the age-related increase in LDL particles may be mediated by a decrease in the nonessential amino acid glutamate. Future studies may contribute to a better understanding of the potential biological role of glutamate and LDL particles in aging mechanisms and age-related diseases.

Unravelling the metabolic alterations of liver damage induced by thirdhand smoke

BACKGROUND

Thirdhand smoke (THS) is the accumulation of tobacco smoke gases and particles that become embedded in materials. Previous studies concluded that THS exposure induces oxidative stress and hepatic steatosis in liver. Despite the knowledge of the increasing danger of THS exposure, the metabolic disorders caused in liver are still not well defined.

OBJECTIVES

The aim of this study is to investigate the metabolic disorders caused by THS exposure in liver of male mice and to evaluate the effects of an antioxidant treatment in the exposed mice.

METHODS

We investigated liver from three mice groups: non-exposed mice, exposed to THS in conditions that mimic human exposure and THS-exposed treated with antioxidants. Liver samples were analyzed using a multiplatform untargeted metabolomics approach including nuclear magnetic resonance (1H NMR), liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) and laser desorption/ionization mass spectrometry imaging (MSI), able to map lipids in liver tissues.

RESULTS

Our multiplatform approach allowed the annotation of eighty-eight metabolites altered by THS exposure, including amino acids, nucleotides and several types of lipids. The main dysregulated pathways by THS exposure were D-glutamine and D-glutamate metabolism, glycerophospholipid metabolism and oxidative phosphorylation and glutathione metabolism, being the last two related to oxidative stress. THS-exposed mice also presented higher lipid accumulation and decrease of metabolites involved in the phosphocholine synthesis, as well as choline deficiency, which is related to Non-Alcoholic Fatty Liver Disease and steatohepatitis. Interestingly, the antioxidant treatment of THS-exposed mice reduced the accumulation of some lipids, but could not revert all the metabolic alterations, including some related to the impairment of the mitochondrial function.

CONCLUSIONS

THS alters liver function at a molecular level, dysregulating many metabolic pathways. The molecular evidences provided here confirm that THS is a new factor for liver steatosis and provide the basis for future research in this respect.

Analysis of LDL and HDL size and number by nuclear magnetic resonance in a healthy working population: The LipoLab Study

BACKGROUND AND AIM

Atherosclerosis is the underlying process in cardiovascular disease (CVD), the first cause of death in developed countries. We aimed to identify people with no known CVD and normal values of LDL-C and HDL-C, but with alterations in the number and size of lipoprotein particles (as measured by nuclear magnetic resonance [NMR]) and to analyse their sociodemographic, clinical and biochemical characteristics.

METHODS

Cross-sectional study in occupational risks prevention centre in Castellón (Spain) in 2017 and 2018, in consecutively recruited adults (18-65 years) with no known CVD. Sociodemographic, clinical and biochemical variables were collected. Lipid profiles were analysed (Liposcale test), along with the concentration, size and number of the main types of lipoprotein particles, determined by 2D diffusion-ordered NMR spectroscopy. Using contingency tables, we analysed the characteristics of people with normal LDL and HDL cholesterol but abnormal levels of LDL and HDL particles. The magnitude of association between explanatory variables and abnormal levels of each kind of lipoprotein was assessed with multivariable logistic regression models.

RESULTS

Of the 400 total participants (31.3% women; age 46.4 ± 4.3 years), 169 had normal LDL and HDL cholesterol. Abnormal lipoprotein particle values depended on the subtype: prevalence of abnormal LDL levels ranged from 8.3% to 36.7%; and of HDL, from 28.4% to 42.6%. High systolic blood pressure and total cholesterol were significantly associated with abnormal LDL levels. Male sex and high systolic blood pressure were associated with abnormalities in HDL.

CONCLUSIONS

An extended lipids profile, obtained by NMR, enables the identification of people with normal HDL-C and LDL-C levels who present abnormal levels of LDL-P and/or HDL-P. Higher total cholesterol, systolic blood pressure, BMI and male sex were significantly associated with these abnormal values.

rMSIproc: an R package for mass spectrometry imaging data processing

SUMMARY

Mass spectrometry imaging (MSI) can reveal biochemical information directly from a tissue section. MSI generates a large quantity of complex spectral data which is still challenging to translate into relevant biochemical information. Here, we present rMSIproc, an open-source R package that implements a full data processing workflow for MSI experiments performed using TOF or FT-based mass spectrometers. The package provides a novel strategy for spectral alignment and recalibration, which allows to process multiple datasets simultaneously. This enables to perform a confident statistical analysis with multiple datasets from one or several experiments. rMSIproc is designed to work with files larger than the computer memory capacity and the algorithms are implemented using a multi-threading strategy. rMSIproc is a powerful tool able to take full advantage of modern computer systems to completely develop the whole MSI potential.

AVAILABILITY AND IMPLEMENTATION

rMSIproc is freely available at https://github.com/prafols/rMSIproc.

CONTACT

pere.rafols@urv.cat.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Raman2imzML converts Raman imaging data into the standard mass spectrometry imaging format

BACKGROUND

Multimodal imaging that combines mass spectrometry imaging (MSI) with Raman imaging is a rapidly developing multidisciplinary analytical method used by a growing number of research groups. Computational tools that can visualize and aid the analysis of datasets by both techniques are in demand.

RESULTS

Raman2imzML was developed as an open-source converter that transforms Raman imaging data into imzML, a standardized common data format created and adopted by the mass spectrometry community. We successfully converted Raman datasets to imzML and visualized Raman images using open-source software designed for MSI applications.

CONCLUSION

Raman2imzML enables both MSI and Raman images to be visualized using the same file format and the same software for a straightforward exploratory imaging analysis.

rMSIcleanup: an open-source tool for matrix-related peak annotation in mass spectrometry imaging and its application to silver-assisted laser desorption/ionization

Mass spectrometry imaging (MSI) has become a mature, widespread analytical technique to perform non-targeted spatial metabolomics. However, the compounds used to promote desorption and ionization of the analyte during acquisition cause spectral interferences in the low mass range that hinder downstream data processing in metabolomics applications. Thus, it is advisable to annotate and remove matrix-related peaks to reduce the number of redundant and non-biologically-relevant variables in the dataset. We have developed rMSIcleanup, an open-source R package to annotate and remove signals from the matrix, according to the matrix chemical composition and the spatial distribution of its ions. To validate the annotation method, rMSIcleanup was challenged with several images acquired using silver-assisted laser desorption ionization MSI (AgLDI MSI). The algorithm was able to correctly classify m/z signals related to silver clusters. Visual exploration of the data using Principal Component Analysis (PCA) demonstrated that annotation and removal of matrix-related signals improved spectral data post-processing. The results highlight the need for including matrix-related peak annotation tools such as rMSIcleanup in MSI workflows.

Gelsolin: a new biomarker of disease activity in SLE patients associated with HDL-c

OBJECTIVES

To identify potential biomarkers of disease activity analysing the proteome of high-density lipoprotein (HDL) particles from SLE patients in clinical remission and when they develop a flare compared with a healthy control group.

METHODS

Quantitative proteomic analyses of purified HDL were performed using Tandem Mass Tag isobaric tag-labelling and nanoLC-Orbitrap (nLC-MS/MS) from nine SLE patients in clinical remission when they developed a flare and from nine healthy controls (9-9-9). We verified the identified proteins by Western blot and ELISA in a cohort of 104 SLE women patients, 46 healthy women and 14 SLE patients when a flare developed.

RESULTS

We found 17 proteins with a significant fold-change (>1.1) compared with the control group. In lupus patients experiencing a flare compared with those in remission, we identified four proteins with a significant fold-change (C4, Indian Hedgehog protein, S100A8 and gelsolin). Plasma gelsolin (pGSN) levels were decreased in the 104 SLE patients (176.02(74.9) mcg/l) compared with the control group (217.13(86.7) mcg/l); P=0.005 and when they developed a clinical flare (104.84(41.7) mcg/l); P=0.002). pGSN levels were associated with HDL cholesterol levels (r = 0.316, P<0.001). Antimalarial treated patients showed significant higher levels of pGSN (214.56(88.94) mcg/l regarding 170.35(66.36) mcg/l); P = 0.017.

CONCLUSION

Decreased pGSN are associated with clinical disease activity in SLE patients. Antimalarial treatment and HDL cholesterol are associated with higher levels of pGSN.

Habitual Fish Consumption, n-3 Fatty Acids, and Nuclear Magnetic Resonance Lipoprotein Subfractions in Women

Background

Supplementation with omega‐3 (n‐3) fatty acid or dietary fish may protect against atherosclerosis, but the potential mechanisms are unclear. Prior studies found modest triglyceride‐lowering effects and slight increases in LDL (low‐density lipoprotein) cholesterol. Limited evidence has examined n‐3 effects on more detailed lipoprotein biomarkers.

Methods and Results

We conducted a study of 26 034 healthy women who reported information on fish and n‐3 intake from a 131‐item food‐frequency questionnaire. We measured plasma lipids, apolipoproteins, and nuclear magnetic resonance spectroscopy lipoproteins and examined their associations with dietary intake of fish, total n‐3, and the n‐3 subtypes (eicosapentaenoic, docosahexaenoic, and α‐linolenic acids). Top‐ versus bottom‐quintile intake of fish and n‐3 were significantly associated with lower triglyceride and large VLDL (very‐low‐density lipoprotein) particles. Fish intake, but not total n‐3, was positively associated with total cholesterol, LDL cholesterol, apolipoprotein B, and larger LDL size, but only α‐linolenic acid was associated with lower LDL cholesterol. Total n‐3, docosahexaenoic acid, and α‐linolenic acid intake were also positively associated with larger HDL (high‐density lipoprotein) size and large HDL particles. High eicosapentaenoic acid intake was significantly associated with only a decreased level of VLDL particle concentration and VLDL triglyceride content. The n‐3 fatty acids had some similarities but also differed in their associations with prospective cardiovascular disease risk patterns.

Conclusions

Higher consumption of fish and n‐3 fatty acids were associated with multiple measures of lipoproteins that were mostly consistent with cardiovascular prevention, with differences noted for high intake of eicosapentaenoic acid versus docosahexaenoic acid and α‐linolenic acid that were apparent with more detailed lipoprotein phenotyping. These hypothesis‐generating findings warrant further study in clinical trials.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000479.

Title: Human Serum/Plasma Glycoprotein Analysis by 1H-NMR, an Emerging Method of Inflammatory Assessment

Several studies suggest that variations in the concentration of plasma glycoproteins can influence cellular changes in a large number of diseases. In recent years, proton nuclear magnetic resonance (1H-NMR) has played a major role as an analytical tool for serum and plasma samples. In recent years, there is an increasing interest in the characterization of glycoproteins through 1H-NMR in order to search for reliable and robust biomarkers of disease. The objective of this review was to examine the existing studies in the literature related to the study of glycoproteins from an analytical and clinical point of view. There are currently several techniques to characterize circulating glycoproteins in serum or plasma, but in this review, we focus on 1H-NMR due to its great robustness and recent interest in its translation to the clinical setting. In fact, there is already a marker in H-NMR representing the acetyl groups of the glycoproteins, GlycA, which has been increasingly studied in clinical studies. A broad search of the literature was performed showing a general consensus that GlycA is a robust marker of systemic inflammation. The results also suggested that GlycA better captures systemic inflammation even more than C-reactive protein (CRP), a widely used classical inflammatory marker. The applications reviewed here demonstrated that GlycA was potentially a key biomarker in a wide range of diseases such as cancer, metabolic diseases, cardiovascular risk, and chronic inflammatory diseases among others. The profiling of glycoproteins through 1H-NMR launches an encouraging new paradigm for its future incorporation in clinical diagnosis.

Serum Paraoxonase-1-Related Variables and Lipoprotein Profile in Patients with Lung or Head and Neck Cancer: Effect of Radiotherapy

We investigated alterations in the levels of the antioxidant paraoxonase-1 (PON1) and the lipoprotein profile (analyzed by nuclear magnetic resonance) in patients with lung cancer (LC) or head and neck cancer (HNC), and the effects produced thereon by radiotherapy (RT). We included 33 patients with LC and 28 patients with HNC. Before irradiation, and one month after completion of RT, blood samples were obtained. The control group was composed of 50 healthy subjects. Patients had significantly lower serum PON1 activity and concentration before RT than the control group. PON1-related variables were good predictors of the presence of LC or HNC, with analytical sensitivities and specificities greater than 80%. Patients showed a significant increase in the number of particles of all subclasses of very-low-density lipoproteins (large, medium and small). However, these changes were not maintained when adjusted for age, sex, and other clinical and demographic variables. Irradiation was associated with a significant increase in PON1 concentration and, only in patients with HNC, with an increase in high-density lipoprotein-cholesterol concentration. Our results suggest that determinations of the levels of PON1-related variables may constitute good biomarkers for the evaluation of these diseases. Studies with a larger number of patients are needed to fully confirm this hypothesis.

Fatty acid binding protein 4 (FABP4) as a potential biomarker reflecting myocardial lipid storage in type 2 diabetes

OBJECTIVE

Fatty acid binding protein 4 (FABP4) is an intracellular lipid chaperone involved in the crosstalk between adipose and peripheral tissues, and it contributes to widespread insulin resistance in cells, including cardiac cells. However, the role of this adipokine in regulating cardiac metabolism and myocardial neutral lipid content in patients with type 2 diabetes has not been elucidated.

METHODS

The impact of circulating FABP4 on the cardiac neutral lipid content was measured by proton magnetic resonance spectroscopy (¹H-MRS) in patients with type 2 diabetes. Additionally, circulating FABP4 and the cardiac triglyceride content were analysed in high-fat diet (HFD)-fed mice, and the impact of the exogenous FABP4 was explored in HL-1 cardiac cells.

RESULTS

Serum FABP4 levels were higher in type 2 diabetic patients compared to healthy individuals. Circulating FABP4 levels were associated with myocardial neutral lipid content in type 2 diabetic patients. In HFD-fed mice, both serum FABP4 and myocardial triglyceride content were increased. In FABP4-challenged HL-1 cells, extracellular FABP4 increased intracellular lipid accumulation, which led to impairment of the insulin-signalling pathway and reduced insulin-stimulated glucose uptake. However, these effects were partially reversed by FABP4 inhibition with BMS309403, which attenuated the intracellular lipid content and improved insulin signalling and insulin-stimulated glucose uptake.

CONCLUSIONS

Taken together, our results identify FABP4 as a molecule involved in diabetic/lipid-induced cardiomyopathy and indicate that this molecule may be an emerging biomarker for diabetic cardiomyopathy-related disturbances, such as myocardial neutral lipid accumulation. Additionally, FABP4 inhibition may be a potential therapeutic target for metabolic-related cardiac dysfunctions.

Biological Response to Meal Ingestion: Gender Differences

In a previous study, we demonstrated that women enjoyed and tolerated lower meal loads than men. Hence, we hypothesized that with the same meal load, their postprandial response is more pronounced than in men. We performed a randomized parallel trial in 12 women and 12 men comparing the postprandial responses to a palatable comfort meal. We measured homeostatic sensations (hunger/satiety, fullness) and hedonic sensations (digestive well-being, mood) on 10 cm scales, vagal tone by heart ratio variability and the metabolomic profile before and after meal ingestion. Gender differences were analyzed by repeated measures ANCOVA. Overall (n = 24), ingestion of the probe meal induced satiation, fullness, digestive well-being and improved mood (main time-effect p ≤ 0.005 for all). Women exhibited a more intense sensory experience, specially more postprandial fullness, than men [main gender-effect F (1, 21) = 7.14; p = 0.014]; hedonic responses in women also tended to be stronger than in men. Women exhibited more pronounced effects on vagal tone [main gender-effect F (1, 21) = 5.5; p = 0.029] and a different lipoprotein response than men. In conclusion, our data indicate that gender influences the responses to meal ingestion, and these differences may explain the predisposition and higher incidence in women of meal-related functional disorders.

Lipid Profiling Using 1H NMR Spectroscopy

Lipid profiling, which includes fatty acids, phospholipids, glycerides, and cholesterols is extremely important because of the essential role lipids play in the regulation of metabolism in animals. ¹H-NMR-based protocols for high-throughput lipid analysis in complex mixtures have been developed and applied to biological systems. Many classes of lipids can be quantitatively analyzed in many sample matrices including serum, cells, and tissues using a simple ¹H NMR experiment. In this chapter, we provide protocols for NMR-based lipid profiling including sample preparation, NMR experiments, and quantification using the LipSpin software tool.

Assessing the potential of sputtered gold nanolayers in mass spectrometry imaging for metabolomics applications

Mass spectrometry imaging (MSI) is a molecular imaging technique that maps the distribution of molecules in biological tissues with high spatial resolution. The most widely used MSI modality is matrix-assisted laser desorption/ionization (MALDI), mainly due to the large variety of analyte classes amenable for MALDI analysis. However, the organic matrices used in classical MALDI may impact the quality of the molecular images due to limited lateral resolution and strong background noise in the low mass range, hindering its use in metabolomics. Here we present a matrix-free laser desorption/ionization (LDI) technique based on the deposition of gold nanolayers on tissue sections by means of sputter-coating. This gold coating method is quick, fully automated, reproducible, and allows growing highly controlled gold nanolayers, necessary for high quality and high resolution MS image acquisition. The performance of the developed method has been tested through the acquisition of MS images of brain tissues. The obtained spectra showed a high number of MS peaks in the low mass region (m/z below 1000 Da) with few background peaks, demonstrating the ability of the sputtered gold nanolayers of promoting the desorption/ionization of a wide range of metabolites. These results, together with the reliable MS spectrum calibration using gold peaks, make the developed method a valuable alternative for MSI applications.

Metabolomic signature of the postprandial experience

BACKGROUND

Ingestion of a meal up to maximal tolerance induces unpleasant fullness sensation and changes in circulating metabolites. Our aim was to evaluate the relation between postprandial sensations and the metabolomic responses to a comfort meal.

METHODS

In 32 non-obese healthy men, homeostatic sensations (hunger/satiety, fullness), hedonic sensations (digestive well-being, mood), and the metabolomic profile in plasma (low-molecular weight metabolites and lipoprotein profiles) were measured before and 20 minutes after a comfort meal (warm ham and cheese sandwich and juice; total 300 mL; 425 kcal). Perception was measured on 10 cm scales and the metabolomic response by nuclear magnetic resonance spectroscopy.

KEY RESULTS

The comfort meal induced homeostatic sensations (satiety and fullness) associated with a positive hedonic reward (enhanced digestive well-being and mood) and a clear change in the metabolomic profile with a sharp discrimination between the pre and postprandial state by a non-supervised principal component analysis. The change in circulating metabolites correlated with the postprandial sensations: the increase in alanine correlated with the increase in fullness (R = 0.50; P = 0.004) and well-being (R = 0.50; P = 0.004); the increase in glucose correlated with the sensation of fullness (R = 0.40; P = 0.023) and enhanced mood (R = 0.41; P = 0.020).

CONCLUSION AND INFERENCES

Metabolomic changes in the response to a meal may provide an objective index of the postprandial experience, which may have clinical implications in the management of patients with poor meal tolerance or meal-related symptoms.

Biomarkers of Exposure to Secondhand and Thirdhand Tobacco Smoke: Recent Advances and Future Perspectives

Smoking is the leading preventable disease worldwide and passive smoking is estimated to be the cause of about 1.0% of worldwide mortality. The determination of tobacco smoke biomarkers in human biological matrices is key to assess the health effects related to the exposure to environmental tobacco smoke. The biomonitoring of cotinine, the main nicotine metabolite, in human biofluids-including urine, serum or saliva-has been extensively used to assess this exposure. However, the simultaneous determination of cotinine together with other tobacco biomarkers and the selection of alternative biological matrices, such as hair, skin or exhaled breath, would enable a better characterization of the kind and extent of tobacco exposure. This review aims to perform a critical analysis of the up-to-date literature focused on the simultaneous determination of multiple tobacco smoke biomarkers studied in different biological matrices, due to the exposure to secondhand smoke (SHS) and thirdhand smoke (THS). Target biomarkers included both tobacco-specific biomarkers-nicotine and tobacco specific nitrosamine biomarkers-and tobacco-related biomarkers, such as those from polycyclic aromatic hydrocarbons, volatile organic compounds, metals and carbon monoxide. To conclude, we discuss the suitability of determining multiple biomarkers through several relevant examples of SHS and THS exposure.

Metabolomic Response to Acute Hypoxic Exercise and Recovery in Adult Males

Metabolomics is a relatively new “omics” approach used to characterize metabolites in a biological system at baseline and following a diversity of stimuli. However, the metabolomic response to exercise in hypoxia currently remains unknown. To examine this, 24 male participants completed 1 h of exercise at a workload corresponding to 75% of pre-determined O_2max in hypoxia (F_io₂ = 0.16%), and repeated in normoxia (F_io₂ = 0.21%), while pre- and post-exercise and 3 h post-exercise metabolites were analyzed using a LC ESI-qTOF-MS untargeted metabolomics approach in serum samples. Exercise in hypoxia and in normoxia independently increased metabolism as shown by a change in a combination of twenty-two metabolites associated with lipid metabolism (p < 0.05, pre vs. post-exercise), though hypoxia per se did not induce a greater metabolic change when compared with normoxia (p > 0.05). Recovery from exercise in hypoxia independently decreased seventeen metabolites associated with lipid metabolism (p < 0.05, post vs. 3 h post-exercise), compared with twenty-two metabolites in normoxia (p < 0.05, post vs. 3 h post-exercise). Twenty-six metabolites were identified as responders to exercise and recovery (pooled hypoxia and normoxia pre vs. recovery, p < 0.05), including metabolites associated with purine metabolism (adenine, adenosine and hypoxanthine), the amino acid phenylalanine, and several acylcarnitine molecules. Our novel data provides preliminary evidence of subtle metabolic differences to exercise and recovery in hypoxia and normoxia. Specifically, exercise in hypoxia activates metabolic pathways aligned to purine and lipid metabolism, but this effect is not selectively different from exercise in normoxia. We also show that exercise per se can activate pathways associated with lipid, protein and purine nucleotide metabolism.

Improving sample classification by harnessing the potential of 1H-NMR signal chemical shifts

NMR spectroscopy is a technology that is widely used in metabolomic studies. The information that these studies most commonly use from NMR spectra is the metabolite concentration. However, as well as concentration, pH and ionic strength information are also made available by the chemical shift of metabolite signals. This information is typically not used even though it can enhance sample discrimination, since many conditions show pH or ionic imbalance. Here, we demonstrate how chemical shift information can be used to improve the quality of the discrimination between case and control samples in three public datasets of different human matrices. In two of these datasets, chemical shift information helped to provide an AUROC value higher than 0.9 during sample classification. In the other dataset, the chemical shift also showed discriminant potential (AUROC 0.831). These results are consistent with the pH imbalance characteristic of the condition studied in the datasets. In addition, we show that this signal misalignment dependent on sample class can alter the results of fingerprinting approaches in the three datasets. Our results show that it is possible to use chemical shift information to enhance the diagnostic and predictive properties of NMR.

Signal preprocessing, multivariate analysis and software tools for MA(LDI)-TOF mass spectrometry imaging for biological applications

Mass spectrometry imaging (MSI) is a label-free analytical technique capable of molecularly characterizing biological samples, including tissues and cell lines. The constant development of analytical instrumentation and strategies over the previous decade makes MSI a key tool in clinical research. Nevertheless, most MSI studies are limited to targeted analysis or the mere visualization of a few molecular species (proteins, peptides, metabolites, or lipids) in a region of interest without fully exploiting the possibilities inherent in the MSI technique, such as tissue classification and segmentation or the identification of relevant biomarkers from an untargeted approach. MSI data processing is challenging due to several factors. The large volume of mass spectra involved in a MSI experiment makes choosing the correct computational strategies critical. Furthermore, pixel to pixel variation inherent in the technique makes choosing the correct preprocessing steps critical. The primary aim of this review was to provide an overview of the data-processing steps and tools that can be applied to an MSI experiment, from preprocessing the raw data to the more advanced strategies for image visualization and segmentation. This review is particularly aimed at researchers performing MSI experiments and who are interested in incorporating new data-processing features, improving their computational strategy, and/or desire access to data-processing tools currently available. © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:281-306, 2018.

rDolphin: a GUI R package for proficient automatic profiling of 1D 1H-NMR spectra of study datasets

INTRODUCTION

Adoption of automatic profiling tools for ¹H-NMR-based metabolomic studies still lags behind other approaches in the absence of the flexibility and interactivity necessary to adapt to the properties of study data sets of complex matrices.

OBJECTIVES

To provide an open source tool that fully integrates these needs and enables the reproducibility of the profiling process.

METHODS

rDolphin incorporates novel techniques to optimize exploratory analysis, metabolite identification, and validation of profiling output quality.

RESULTS

The information and quality achieved in two public datasets of complex matrices are maximized.

CONCLUSION

rDolphin is an open-source R package ( http://github.com/danielcanueto/rDolphin ) able to provide the best balance between accuracy, reproducibility and ease of use.

LipSpin: A New Bioinformatics Tool for Quantitative 1H NMR Lipid Profiling

The structural similarity among lipid species and the low sensitivity and spectral resolution of nuclear magnetic resonance (NMR) have traditionally hampered the routine use of ¹H NMR lipid profiling of complex biological samples in metabolomics, which remains mostly manual and lacks freely available bioinformatics tools. However, ¹H NMR lipid profiling provides fast quantitative screening of major lipid classes (fatty acids, glycerolipids, phospholipids, and sterols) and some individual species and has been used in several clinical and nutritional studies, leading to improved risk prediction models. In this Article, we present LipSpin, a free and open-source bioinformatics tool for quantitative ¹H NMR lipid profiling. LipSpin implements a constrained line shape fitting algorithm based on voigt profiles and spectral templates from spectra of lipid standards, which automates the analysis of severely overlapped spectral regions and lipid signals with complex coupling patterns. LipSpin provides the most detailed quantification of fatty acid families and choline phospholipids in serum lipid samples by ¹H NMR to date. Moreover, analytical and clinical results using LipSpin quantifications conform with other techniques commonly used for lipid analysis.

Unravelling and Quantifying the "NMR-Invisible" Metabolites Interacting with Human Serum Albumin by Binding Competition and T2 Relaxation-Based Decomposition Analysis

Quantitative profiling of low-molecular-weight metabolites (LMWMs) by ¹H NMR is routinely used in high-throughput serum metabolomics. First, the protein background is attenuated using a T2 filter; then, the LMWM signals are resolved by line-shape fitting. However, protein-binding modifies the motional properties of LMWM, and their signal partially attenuates with the T2 filter, along with the protein background. Consequently, the quantified LMWM signals do not reflect the total concentration in serum but the nonbinding part. Here we present a novel strategy based on binding competition to promote the release of the "NMR-invisible" metabolites from serum proteins and achieve quantifications closer to total concentrations. The study focuses on five clinically relevant amino acids with different binding properties (valine, isoleucine, leucine, tyrosine, and phenylalanine). We analyzed their binding affinity to human serum albumin (HSA) in serum mimic samples and promoted the release of their bound fraction by TSP titration. Furthermore, we used a novel combination of pseudo-2D CPMG and multivariate curve resolution analysis, allowing the separation of LMWM and protein signals and providing LMWM quantifications corrected for transverse relaxation effects. We found that TSP concentrations larger than 3 mM released most of the bound fraction and validated these findings in real serum/plasma samples.

Improvement of the omega 3 index of healthy subjects does not alter the effects of dietary saturated fats or n-6PUFA on LDL profiles

BACKGROUND AND AIMS

Dietary fat composition is known to modulate circulating lipid and lipoprotein levels. Although supplementation with long chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) has been shown to reduce plasma triglyceride levels, the effect of the interactions between LCn-3PUFA and the major dietary fats consumed has not been previously investigated.

METHODS

In a randomized controlled parallel design clinical intervention, we examined the effect of diets rich in either saturated fatty acids (SFA) or omega-6 polyunsaturated fatty acids (n-6PUFA) on plasma lipid levels and lipoprotein profiles (lipoprotein size, concentration and distribution in subclasses) in subjects with an adequate omega 3 index. Twenty six healthy subjects went through a four-week pre-supplementation period with LCn-3PUFA and were then randomized to diets rich in either n-6PUFA or SFA both supplemented with LCn-3PUFA.

RESULTS

The diet rich in n-6PUFA decreased low density lipoprotein (LDL) particle concentration (-8%, p=0.013) and LDL cholesterol (LDL-C) level (-8%, p=0.021), while the saturated fat rich diet did not affect LDL particle concentration or LDL-C levels significantly. Nevertheless, dietary saturated fatty acids increased LCn-3PUFA in plasma and tissue lipids compared with n-6PUFA, potentially reducing other cardiovascular risk factors such as inflammation and clotting tendency.

CONCLUSION

Improvement on the omega 3 index of healthy subjects did not alter the known effects of dietary saturated fats and n-6PUFA on LDL profiles.

eRah: A Computational Tool Integrating Spectral Deconvolution and Alignment with Quantification and Identification of Metabolites in GC/MS-Based Metabolomics

Gas chromatography coupled to mass spectrometry (GC/MS) has been a long-standing approach used for identifying small molecules due to the highly reproducible ionization process of electron impact ionization (EI). However, the use of GC-EI MS in untargeted metabolomics produces large and complex data sets characterized by coeluting compounds and extensive fragmentation of molecular ions caused by the hard electron ionization. In order to identify and extract quantitative information on metabolites across multiple biological samples, integrated computational workflows for data processing are needed. Here we introduce eRah, a free computational tool written in the open language R composed of five core functions: (i) noise filtering and baseline removal of GC/MS chromatograms, (ii) an innovative compound deconvolution process using multivariate analysis techniques based on compound match by local covariance (CMLC) and orthogonal signal deconvolution (OSD), (iii) alignment of mass spectra across samples, (iv) missing compound recovery, and (v) identification of metabolites by spectral library matching using publicly available mass spectra. eRah outputs a table with compound names, matching scores and the integrated area of compounds for each sample. The automated capabilities of eRah are demonstrated by the analysis of GC-time-of-flight (TOF) MS data from plasma samples of adolescents with hyperinsulinaemic androgen excess and healthy controls. The quantitative results of eRah are compared to centWave, the peak-picking algorithm implemented in the widely used XCMS package, MetAlign, and ChromaTOF software. Significantly dysregulated metabolites are further validated using pure standards and targeted analysis by GC-triple quadrupole (QqQ) MS, LC-QqQ, and NMR. eRah is freely available at http://CRAN.R-project.org/package=erah .

Urine metabolome profiling of immune-mediated inflammatory diseases

BACKGROUND

Immune-mediated inflammatory diseases (IMIDs) are a group of complex and prevalent diseases where disease diagnostic and activity monitoring is highly challenging. The determination of the metabolite profiles of biological samples is becoming a powerful approach to identify new biomarkers of clinical utility. In order to identify new metabolite biomarkers of diagnosis and disease activity, we have performed the first large-scale profiling of the urine metabolome of the six most prevalent IMIDs: rheumatoid arthritis, psoriatic arthritis, psoriasis, systemic lupus erythematosus, Crohn's disease, and ulcerative colitis.

METHODS

Using nuclear magnetic resonance, we analyzed the urine metabolome in a discovery cohort of 1210 patients and 100 controls. Within each IMID, two patient subgroups were recruited representing extreme disease activity (very high vs. very low). Metabolite association analysis with disease diagnosis and disease activity was performed using multivariate linear regression in order to control for the effects of clinical, epidemiological, or technical variability. After multiple test correction, the most significant metabolite biomarkers were validated in an independent cohort of 1200 patients and 200 controls.

RESULTS

In the discovery cohort, we identified 28 significant associations between urine metabolite levels and disease diagnosis and three significant metabolite associations with disease activity (P FDR < 0.05). Using the validation cohort, we validated 26 of the diagnostic associations and all three metabolite associations with disease activity (P FDR < 0.05). Combining all diagnostic biomarkers using multivariate classifiers we obtained a good disease prediction accuracy in all IMIDs and particularly high in inflammatory bowel diseases. Several of the associated metabolites were found to be commonly altered in multiple IMIDs, some of which can be considered as hub biomarkers. The analysis of the metabolic reactions connecting the IMID-associated metabolites showed an over-representation of citric acid cycle, phenylalanine, and glycine-serine metabolism pathways.

CONCLUSIONS

This study shows that urine is a source of biomarkers of clinical utility in IMIDs. We have found that IMIDs show similar metabolic changes, particularly between clinically similar diseases and we have found, for the first time, the presence of hub metabolites. These findings represent an important step in the development of more efficient and less invasive diagnostic and disease monitoring methods in IMIDs.

Dietary proanthocyanidins boost hepatic NAD(+) metabolism and SIRT1 expression and activity in a dose-dependent manner in healthy rats

Proanthocyanidins (PACs) have been reported to modulate multiple targets by simultaneously controlling many pivotal metabolic pathways in the liver. However, the precise mechanism of PAC action on the regulation of the genes that control hepatic metabolism remains to be clarified. Accordingly, we used a metabolomic approach combining both nuclear magnetic resonance and mass spectrometry analysis to evaluate the changes induced by different doses of grape-seed PACs in the liver of healthy rats. Here, we report that PACs significantly increased the hepatic nicotinamide adenine dinucleotide (NAD(+)) content in a dose-dependent manner by specifically modulating the hepatic concentrations of the major NAD(+) precursors as well as the mRNA levels of the genes that encode the enzymes involved in the cellular metabolism of NAD(+). Notably, Sirtuin 1 (Sirt1) gene expression was also significantly up-regulated in a dose-response pattern. The increase in both the NAD(+) availability and Sirt1 mRNA levels, in turn, resulted in the hepatic activation of SIRT1, which was significantly associated with improved protection against hepatic triglyceride accumulation. Our data clearly indicates that PAC consumption could be a valid tool to enhance hepatic SIRT1 activity through the modulation of NAD(+) levels.

Lipoprotein hydrophobic core lipids are partially extruded to surface in smaller HDL: "Herniated" HDL, a common feature in diabetes

Recent studies have shown that pharmacological increases in HDL cholesterol concentrations do not necessarily translate into clinical benefits for patients, raising concerns about its predictive value for cardiovascular events. Here we hypothesize that the size-modulated lipid distribution within HDL particles is compromised in metabolic disorders that have abnormal HDL particle sizes, such as type 2 diabetes mellitus (DM2). By using NMR spectroscopy combined with a biochemical volumetric model we determined the size and spatial lipid distribution of HDL subclasses in a cohort of 26 controls and 29 DM2 patients before and after two drug treatments, one with niacin plus laropiprant and another with fenofibrate as an add-on to simvastatin. We further characterized the HDL surface properties using atomic force microscopy and fluorescent probes to show an abnormal lipid distribution within smaller HDL particles, a subclass particularly enriched in the DM2 patients. The reduction in the size, force cholesterol esters and triglycerides to emerge from the HDL core to the surface, making the outer surface of HDL more hydrophobic. Interestingly, pharmacological interventions had no effect on this undesired configuration, which may explain the lack of clinical benefits in DM2 subjects.

Improving Assessment of Lipoprotein Profile in Type 1 Diabetes by 1H NMR Spectroscopy

Patients with type 1 diabetes (T1D) present increased risk of cardiovascular disease (CVD). The aim of this study is to improve the assessment of lipoprotein profile in patients with T1D by using a robust developed method 1H nuclear magnetic resonance spectroscopy (1H NMR), for further correlation with clinical factors associated to CVD. Thirty patients with T1D and 30 non-diabetes control (CT) subjects, matched for gender, age, body composition (DXA, BMI, waist/hip ratio), regular physical activity levels and cardiorespiratory capacity (VO_2peak), were analyzed. Dietary records and routine lipids were assessed. Serum lipoprotein particle subfractions, particle sizes, and cholesterol and triglycerides subfractions were analyzed by 1H NMR. It was evidenced that subjects with T1D presented lower concentrations of small LDL cholesterol, medium VLDL particles, large VLDL triglycerides, and total triglycerides as compared to CT subjects. Women with T1D presented a positive association with HDL size (p<0.005; R = 0.601) and large HDL triglycerides (p<0.005; R = 0.534) and negative (p<0.005; R = -0.586) to small HDL triglycerides. Body fat composition represented an important factor independently of normal BMI, with large LDL particles presenting a positive correlation to total body fat (p<0.005; R = 0.505), and total LDL cholesterol and small LDL cholesterol a positive correlation (p<0.005; R = 0.502 and R = 0.552, respectively) to abdominal fat in T1D subjects; meanwhile, in CT subjects, body fat composition was mainly associated to HDL subclasses. VO_2peak was negatively associated (p<0.005; R = -0.520) to large LDL-particles only in the group of patients with T1D. In conclusion, patients with T1D with adequate glycemic control and BMI and without chronic complications presented a more favourable lipoprotein profile as compared to control counterparts. In addition, slight alterations in BMI and/or body fat composition showed to be relevant to provoking alterations in lipoproteins profiles. Finally, body fat composition appears to be a determinant for cardioprotector lipoprotein profile.

Liver fat deposition and mitochondrial dysfunction in morbid obesity: An approach combining metabolomics with liver imaging and histology

AIM: To explore the usefulness of magnetic resonance imaging (MRI) and spectroscopy (MRS) for assessment of non-alcoholic fat liver disease (NAFLD) as compared with liver histological and metabolomics findings.

METHODS: Patients undergoing bariatric surgery following procedures involved in laparoscopic sleeve gastrectomy were recruited as a model of obesity-induced NAFLD in an observational, prospective, single-site, cross-sectional study with a pre-set duration of 1 year. Relevant data were obtained prospectively and surrogates for inflammation, oxidative stress and lipid and glucose metabolism were obtained through standard laboratory measurements. To provide reliable data from MRI and MRS, novel procedures were designed to limit sampling variability and other sources of error using a 1.5T Signa HDx scanner and protocols acquired from the 3D or 2D Fat SAT FIESTA prescription manager. We used our previously described ¹H NMR-based metabolomics assays. Data were obtained immediately before surgery and after a 12-mo period including histology of the liver and measurement of metabolites. Values from ¹H NMR spectra obtained after surgery were omitted due to technical limitations.

RESULTS: MRI data showed excellent correlation with the concentration of liver triglycerides, other hepatic lipid components and the histological assessment, which excluded the presence of non-alcoholic steatohepatitis (NASH). MRI was sufficient to follow up NAFLD in obese patients undergoing bariatric surgery and data suggest usefulness in other clinical situations. The information provided by MRS replicated that obtained by MRI using the -CH3 peak (0.9 ppm), the -CH2- peak (1.3 ppm, mostly triglyceride) and the

-CH=CH- peak (2.2 ppm). No patient depicted NASH. After surgery all patients significantly decreased their body weight and steatosis was virtually absent even in patients with previous severe disease. Improvement was also observed in the serum concentrations of selected variables. The most relevant findings using metabolomics indicate increased levels of triglyceride and monounsaturated fatty acids in severe steatosis but those results were accompanied by a significant depletion of diglycerides, polyunsaturated fatty acids, glucose-6-phosphate and the ATP/AMP ratio. Combined data indicated the coordinated action on mitochondrial fat oxidation and glucose transport activity and may support the consideration of NAFLD as a likely mitochondrial disease. This concept may help to explain the dissociation between excess lipid storage in adipose tissue and NAFLD and may direct the search for plasma biomarkers and novel therapeutic strategies. A limitation of our study is that data were obtained in a relatively low number of patients.

CONCLUSION: MRI is sufficient to stage NAFLD in obese patients and to assess the improvement after bariatric surgery. Other data were superfluous for this purpose.

Metabolomics reveals impaired maturation of HDL particles in adolescents with hyperinsulinaemic androgen excess

Hyperinsulinaemic androgen excess (HIAE) in prepubertal and pubertal girls usually precedes a broader pathological phenotype in adulthood that is associated with anovulatory infertility, metabolic syndrome and type 2 diabetes. The metabolic derangements that determine these long-term health risks remain to be clarified. Here we use NMR and MS-based metabolomics to show that serum levels of methionine sulfoxide in HIAE girls are an indicator of the degree of oxidation of methionine-148 residue in apolipoprotein-A1. Oxidation of apo-A1 in methionine-148, in turn, leads to an impaired maturation of high-density lipoproteins (HDL) that is reflected in a decline of large HDL particles. Notably, such metabolic alterations occur in the absence of impaired glucose tolerance, hyperglycemia and hypertriglyceridemia, and were partially restored after 18 months of treatment with a low-dose combination of pioglitazone, metformin and flutamide.