Mass spectrometry for the evaluation of cardiovascular diseases based on proteomics and lipidomics

Detecting early myocardial ischemia in rat heart by MALDI imaging mass spectrometry

Diagnostics of myocardial infarction in human post-mortem hearts can be achieved only if ischemia persisted for at least 6–12 h when certain morphological changes appear in myocardium. The initial 4 h of ischemia is difficult to diagnose due to lack of a standardized method. Developing a panel of molecular tissue markers is a promising approach and can be accelerated by characterization of molecular changes. This study is the first untargeted metabolomic profiling of ischemic myocardium during the initial 4 h directly from tissue section. Ischemic hearts from an ex-vivo Langendorff model were analysed using matrix assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) at 15 min, 30 min, 1 h, 2 h, and 4 h. Region-specific molecular changes were identified even in absence of evident histological lesions and were segregated by unsupervised cluster analysis. Significantly differentially expressed features were detected by multivariate analysis starting at 15 min while their number increased with prolonged ischemia. The biggest significant increase at 15 min was observed for m/z 682.1294 (likely corresponding to S-NADHX—a damage product of nicotinamide adenine dinucleotide (NADH)). Based on the previously reported role of NAD⁺/NADH ratio in regulating localization of the sodium channel (Na_v1.5) at the plasma membrane, Na_v1.5 was evaluated by immunofluorescence. As expected, a fainter signal was observed at the plasma membrane in the predicted ischemic region starting 30 min of ischemia and the change became the most pronounced by 4 h. Metabolomic changes occur early during ischemia, can assist in identifying markers for post-mortem diagnostics and improve understanding of molecular mechanisms.

Trends in mass spectrometry imaging for cardiovascular diseases

Mass spectrometry imaging (MSI) is a widely established technology; however, in the cardiovascular research field, its use is still emerging. The technique has the advantage of analyzing multiple molecules without prior knowledge while maintaining the relation with tissue morphology. Particularly, MALDI-based approaches have been applied to obtain in-depth knowledge of cardiac (dys)function. Here, we discuss the different aspects of the MSI protocols, from sample handling to instrumentation used in cardiovascular research, and critically evaluate these methods. The trend towards structural lipid analysis, identification, and “top-down” protein MSI shows the potential for implementation in (pre)clinical research and complementing the diagnostic tests. Moreover, new insights into disease progression are expected and thereby contribute to the understanding of underlying mechanisms related to cardiovascular diseases.

Metabolomics profiling of methamphetamine addicted human serum and three rat brain areas

Methamphetamine (METH) has already been a serious problem all over the world. The identification of related biomarkers and pathways is helpful to evaluate the degree of METH addiction, develop appropriate treatment during abstinence, and explore the mechanism. Here, it is the first time to perform metabolomics profiling of METH addicted human serum and three regions of METH-induced conditioned place preference (CPP) rat brain by using UHPLC-MS/MS and matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI), respectively. Untargeted metabolomics analysis demonstrated clear differences between METH abusers and the healthy control by finding 35 distinct expressed metabolites in serum, including 5 TCA intermediates, 17 amino acids and 13 other biomolecules, 15 of which were newly identified following METH exposure. By using MALDI-MSI, the relative quantification and distribution of 14 metabolites were investigated in the nucleus accumbens (NAc), dorsal hippocampus (dHPC) and ventral hippocampus (vHPC) of CPP rat brain. Taken together, METH addiction could influence energy metabolism, amino acids metabolism, and phospholipids metabolism. A multi-parameter model consisting of these related metabolites can be established as a METH addiction biomarker in the future. The mapping of phospholipids provided new insights into the mechanism of METH addiction. Notably, the trend of metabolite changes in NAc and dHPC was almost the same, while it was opposite between dHPC and vHPC. It seems that NAc and dHPC were the two regions more susceptible to METH administration in the brain. And dHPC and vHPC play different roles in METH addiction proved by metabolites mapping.

To explore the mechanism of METH addiction, the metabolomics profiling of METH addicted human serum and rat brain were performed using UHPLC-MS/MS and MALDI-MSI, respectively. 35 differentially expressed metabolites were identified in the serum.

Mass spectrometric imaging of cysteine rich proteins in human skin

Looking insight pathological processes, metallothioneins (MTs) are considered to be potential biomarkers for monitoring of a development of various types of diseases, such as cancer. The early identification of the MTs in biological tissues could be important tool for the estimation of appropriate clinical therapy. Therefore, here we investigated the application of matrix assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) together with immunohistochemical analyses (IHC) using MT-1/2 antibody for MT detection in formalin-fixed paraffin-embedded (FFPE) biopsy specimens of human skin. Principal component analyses revealed differences in the peptide/protein profiles separating healthy skin from the carcinoma specimens. Statistically significant ion peaks at m/z 6038, 6300, 6676, and 7026 were more frequently detected in squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and melanoma. Using IHC, we found that MT-1/2 was significantly higher in SCC and melanoma compared to healthy skin. Surprisingly, significantly low levels of MT-1/2 were found in BCC. On one side, the results indicate important role of MTs in melanoma occurrence and progression, as on the second side, there are hidden processes associated with MTs based on differences of the occurrence of the MS peaks, which could be associated with cycling of MTs isoforms.

Organic washes of tissue sections for comprehensive analysis of small molecule metabolites by MALDI MS imaging of rat brain following status epilepticus

INTRODUCTION

In-situ detection and in particular comprehensive analysis of small molecule metabolites (SMMs, m/z < 500) using matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI MSI) remain a challenge, mainly due to ion suppression effects from more abundant molecules in tissue section like lipids.

OBJECTIVE

A strategy based on organic washes to remove most ionization-suppressing lipids from tissue section was firstly explored for improved analysis of SMMs by MALDI MSI.

METHODS

The tissue sections after rinse with different organic solvents were analyzed by MALDI MSI, and the results were compared for the optimized washing conditions.

RESULTS

The rinse with chloroform for 15 s at - 20 °C significantly removed most glycerophospholipids and glycerolipids from tissue section. Consequentially, ATP-related energy metabolites, amino acids and derivatives, glucose derivatives, glycolysis pathway metabolites and other SMMs were able to be well-visualized with enhanced ion intensity and good reproducibility. The organic washes-based MALDI MSI was applied to the metabolic pathway analysis in rat brain following status epilepticus (SE) model, which was, as far as we know, the first report about in-situ detection of a broad range of metabolites in the model of SE by MALDI MSI technique. The alterations of cyclic adenosine monophosphate (cyclic AMP), inosine, glutamine, glutathione, taurine and spermine during SE were observed.

CONCLUSION

A simple organic washing protocol enables comprehensive analysis of tissue SMMs in MALDI MSI by removing ionization-suppressing lipids. The application in the SE model indicates that MALDI MSI analysis potentially provides new insight for understanding the disease mechanism.

Phospholipids as cancer biomarkers: Mass spectrometry-based analysis

Lipids, particularly phospholipids (PLs), are key components of cellular membrane. PLs play important and diverse roles in cells such as chemical-energy storage, cellular signaling, cell membranes, and cell-cell interactions in tissues. All these cellular processes are pertinent to cells that undergo transformation, cancer progression, and metastasis. Thus, there is a strong possibility that some classes of PLs are expected to present in cancer cells and tissues in cellular physiology. The mass spectrometric soft-ionization techniques, electrospray ionization (ESI), and matrix-assisted laser desorption/ionization (MALDI) are well-established in the proteomics field, have been used for lipidomic analysis in cancer research. This review focused on the applications of mass spectrometry (MS) mainly on ESI-MS and MALDI-MS in the structural characterization, molecular composition and key roles of various PLs present in cancer cells, tissues, blood, and urine, and on their importance for cancer-related problems as well as challenges for development of novel PL-based biomarkers. The profiling of PLs helps to rationalize their functions in biological systems, and will also provide diagnostic information to elucidate mechanisms behind the control of cancer, diabetes, and neurodegenerative diseases. The investigation of cellular PLs with MS methods suggests new insights on various cancer diseases and clinical applications in the drug discovery and development of biomarkers for various PL-related different cancer diseases. PL profiling in tissues, cells and body fluids also reflect the general condition of the whole organism and can indicate the existence of cancer and other diseases. PL profiling with MS opens new prospects to assess alterations of PLs in cancer, screening specific biomarkers and provide a basis for the development of novel therapeutic strategies. © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:107-138, 2018.

Metabolomics as a Tool to Understand Pathophysiological Processes

Multiple diseases have a strong metabolic component, and metabolomics as a powerful phenotyping technology, in combination with orthogonal biological and clinical approaches, will undoubtedly play a determinant role in accelerating the understanding of mechanisms that underlie these complex diseases determined by a set of genetic, lifestyle, and environmental exposure factors. Here, we provide several examples of valuable findings from metabolomics-led studies in diabetes and obesity metabolism, neurodegenerative disorders, and cancer metabolism and offer a longer term vision toward personalized approach to medicine, from population-based studies to pharmacometabolomics.

Simultaneous Two-Dimensional Difference Gel Electrophoresis (2D-DIGE) Analysis of Two Distinct Proteomes

This chapter describes the basics, applications, and limitations of two-dimensional gel electrophoresis (2DE) and two-dimensional difference gel electrophoresis (2D-DIGE) for multiplex analysis of distinct proteomes. We also propose a basic protocol for 2D-DIGE, technique that allows the analysis of paired protein extracts, which are labeled with fluorescent Cy3 and Cy5 dyes and electrophoresed with a Cy2-labeled standard extract on the same 2DE gels. Scanning the gels at wavelengths specific for each dye allows direct overlay the two different proteomes and the differences in abundance of specific protein spots can be determined.

Ischemia/Reperfusion

Ischemic disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are the most common causes of debilitating disease and death in westernized cultures. The extent of tissue injury relates directly to the extent of blood flow reduction and to the length of the ischemic period, which influence the levels to which cellular ATP and intracellular pH are reduced. By impairing ATPase-dependent ion transport, ischemia causes intracellular and mitochondrial calcium levels to increase (calcium overload). Cell volume regulatory mechanisms are also disrupted by the lack of ATP, which can induce lysis of organelle and plasma membranes. Reperfusion, although required to salvage oxygen-starved tissues, produces paradoxical tissue responses that fuel the production of reactive oxygen species (oxygen paradox), sequestration of proinflammatory immunocytes in ischemic tissues, endoplasmic reticulum stress, and development of postischemic capillary no-reflow, which amplify tissue injury. These pathologic events culminate in opening of mitochondrial permeability transition pores as a common end-effector of ischemia/reperfusion (I/R)-induced cell lysis and death. Emerging concepts include the influence of the intestinal microbiome, fetal programming, epigenetic changes, and microparticles in the pathogenesis of I/R. The overall goal of this review is to describe these and other mechanisms that contribute to I/R injury. Because so many different deleterious events participate in I/R, it is clear that therapeutic approaches will be effective only when multiple pathologic processes are targeted. In addition, the translational significance of I/R research will be enhanced by much wider use of animal models that incorporate the complicating effects of risk factors for cardiovascular disease. © 2017 American Physiological Society. Compr Physiol 7:113-170, 2017.

Effects of fatty acyl chain length, double-bond number and matrix on phosphatidylcholine responses in matrix-assisted laser desorption/ionization on an Orbitrap mass spectrometer

RATIONALE

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is used for the fast qualitative and quantitative analysis of phosphatidylcholines (PC). Fatty acyl chain lengths and the number of double bonds (DB) affect relative responses of PC; hence the determination of correction factors of individual PC is important for the accurate quantitation. The signal intensity in MALDI-MS strongly depends on the matrix; therefore, the following matrices typically used in lipidomics are studied in the present work: 2,5-dihydroxybenzoic acid (DHB), 1,5-diaminonaphthalene (DAN) and 9-aminoacridine (9AA).

METHODS

Series of PC with various fatty acyl chain lengths are synthesized for this study. PC concentrations over two orders of magnitude are studied with MALDI-MS. These experiments provide sets of calibration curves for each of the synthesized PC and the further analysis of parameters of calibration curves is performed.

RESULTS

Correction factors for PC decrease with increasing fatty acyl chain length for all matrices. These dependences are steeper for unsaturated PC than for saturated ones. MALDI matrices also have a significant effect on this dependence. The weakest dependence on fatty acyl chain length is found for saturated PC in 9AA. In the case of the other matrices, the effect of fatty acyl chain length on the response is essential for both saturated and unsaturated PC. Calibration curves and parameters of calibration curves for both saturated and monounsaturated PC are fitted by a linear function with regression coefficients decreasing in the order 9AA > DAN > DHB.

CONCLUSIONS

Differences in relative responses for PC in MALDI-MS measurements must be taken into account for accurate quantitation. Parameters of calibration curves can be used for the determination of PC concentrations using a single internal standard (IS). This method gives good results for the 9AA matrix, but the reproducibility of measurements for the DHB and DAN matrices is lower and the method can be used for a rough estimation only. These matrices are less convenient for the quantitation of PC.

Advances in tissue section preparation for MALDI imaging MS

Enriched by a decade of remarkable developments, matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) has witnessed a phenomenal expansion. Initially introduced for the mapping of peptides and intact proteins from mammalian tissue sections, MALDI IMS applications now extend to a wide range of molecules including peptides, lipids, metabolites and xenobiotics. Technology and methodology are quickly evolving to push the limits of the technique forward. Within a short period of time, numerous protocols and concepts have been developed and introduced in tissue section preparation, nonexhaustively including in situ tissue chemistries and solvent-free matrix depositions. Considering the past progress and current capabilities, this Review aims to cover the different aspects and challenges of tissue section preparation for MALDI IMS.

MALDI TOF imaging mass spectrometry in clinical pathology: a valuable tool for cancer diagnostics (review)

Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) imaging mass spectrometry (IMS) is an evolving technique in cancer diagnostics and combines the advantages of mass spectrometry (proteomics), detection of numerous molecules, and spatial resolution in histological tissue sections and cytological preparations. This method allows the detection of proteins, peptides, lipids, carbohydrates or glycoconjugates and small molecules.Formalin-fixed paraffin-embedded tissue can also be investigated by IMS, thus, this method seems to be an ideal tool for cancer diagnostics and biomarker discovery. It may add information to the identification of tumor margins and tumor heterogeneity. The technique allows tumor typing, especially identification of the tumor of origin in metastatic tissue, as well as grading and may provide prognostic information. IMS is a valuable method for the identification of biomarkers and can complement histology, immunohistology and molecular pathology in various fields of histopathological diagnostics, especially with regard to identification and grading of tumors.

Enhanced data-independent analysis of lipids using ion mobility-TOFMSE to unravel quantitative and qualitative information in human plasma

RATIONALE

Lipids are involved in various biochemical and signaling pathways, cell structure and function, and the pathophysiology of many diseases. We took advantage of ion mobility spectrometry (IMS) in conjunction with ultra-performance liquid chromatography (UPLC) and high-resolution mass spectrometry to gain quantitative and deeper qualitative structural insight within a single experiment.

METHODS

Human plasma lipid extracts were analyzed using an Acquity UPLC system coupled to a Synapt G2-HDMS mass spectrometer system. The ion mobility gas employed was helium for the helium cell (150 mL/min) and nitrogen (80 mL/min) for the T-wave drift tube. The wave height for the T-wave cell was ramped in a linear fashion between 5-40 V. The mass spectra were acquired in an electrospray positive ionization mode.

RESULTS

We resolved chromatographically co-eluting lipids further by ion mobility tube drift time and then subjected them to low- and high-energy fragmentation without pre-selecting respective precursor species. The fragment ions produced in a high-energy mode were aligned with their precursor ions in a low-energy mode. By aligning intact molecular spectra and fragment spectra for these lipids at a given ion mobility drift time and chromatographic retention time, we were able to obtain much cleaner fragment ion spectra for structural elucidation. For quantitative analysis we obtained a dynamic linear range from 0.002 to 2 µg/mL with and without an additional dimension of IMS.

CONCLUSIONS

The additional dimension of IMS allowed us to perform quantitative and qualitative analysis within a single experiment in a relatively high-throughput manner thus providing deeper structural insights into lipids of biological interest and resulting in an information-rich dataset.

Myocardial lipidomics profiling delineate the toxicity of traditional Chinese medicine Aconiti Lateralis radix praeparata

ETHNOPHARMACOLOGICAL RELEVANCE

The lateral root of Aconitum has been popularly used in traditional Chinese medicine (TMC) known as Fuzi which is beneficial for the treatment of various diseases, such as rheumatism, painful joints, syncope and bronchial asthma. However, it has a potential carditoxicity with a relatively narrow margin of safety.

AIM OF THE STUDY

This paper was designed to explore the mechanisms of Fuzi's toxicity and find out potential tissue-specific biomarkers of toxic effects.

MATERIAL AND METHODS

A myocardial lipidomics based on ultraperformance lipid chromatography coupled with quadrupole-time-of-flight mass spectrometry (UHPLC/Q-TOF MS) was developed to compare three cardiac lipid extraction methods and investigate the changes of lipids in mice heart of three different dosage groups. In addition, we concurrently inspected the biochemical parameters in plasma, observed the histology of the heart and recorded the electrocardiogram (ECG).

RESULTS

The cardiotoxicity of Fuzi was dose-dependent, and the high-dose group obviously manifested the heart damage in histology and a certain degree of arrhythmia. Significant changes of 14 lipid metabolites which primarily involved in phospholipid metabolism, sphingolipid metabolism, saturated fatty acid oxidation and unsaturated fatty acid peroxidation were identified and considered as the potential biomarkers of Fuzi toxicity.

CONCLUSION

The lipidomics approach is helpful to search potential tissue-specific biomarkers and understand the underlying mechanisms of Fuzi toxicity on the heart.

Histology-driven data mining of lipid signatures from multiple imaging mass spectrometry analyses: application to human colorectal cancer liver metastasis biopsies

Imaging mass spectrometry (IMS) represents an innovative tool in the cancer research pipeline, which is increasingly being used in clinical and pharmaceutical applications. The unique properties of the technique, especially the amount of data generated, make the handling of data from multiple IMS acquisitions challenging. This work presents a histology-driven IMS approach aiming to identify discriminant lipid signatures from the simultaneous mining of IMS data sets from multiple samples. The feasibility of the developed workflow is evaluated on a set of three human colorectal cancer liver metastasis (CRCLM) tissue sections. Lipid IMS on tissue sections was performed using MALDI-TOF/TOF MS in both negative and positive ionization modes after 1,5-diaminonaphthalene matrix deposition by sublimation. The combination of both positive and negative acquisition results was performed during data mining to simplify the process and interrogate a larger lipidome into a single analysis. To reduce the complexity of the IMS data sets, a sub data set was generated by randomly selecting a fixed number of spectra from a histologically defined region of interest, resulting in a 10-fold data reduction. Principal component analysis confirmed that the molecular selectivity of the regions of interest is maintained after data reduction. Partial least-squares and heat map analyses demonstrated a selective signature of the CRCLM, revealing lipids that are significantly up- and down-regulated in the tumor region. This comprehensive approach is thus of interest for defining disease signatures directly from IMS data sets by the use of combinatory data mining, opening novel routes of investigation for addressing the demands of the clinical setting.

Metabolomics and ischaemic heart disease

Ischaemic heart disease accounts for nearly half of the global cardiovascular disease burden. Aetiologies relating to heart disease are complex, but dyslipidaemia, oxidative stress and inflammation are cardinal features. Despite preventative measures and advancements in treatment regimens with lipid-lowering agents, the high prevalence of heart disease and the residual risk of recurrent events continue to be a significant burden to the health sector and to the affected individuals and their families. The development of improved risk models for the early detection and prevention of cardiovascular events in addition to new therapeutic strategies to address this residual risk are required if we are to continue to make inroads into this most prevalent of diseases. Metabolomics and lipidomics are modern disciplines that characterize the metabolite and lipid complement respectively, of a given system. Their application to ischaemic heart disease has demonstrated utilities in population profiling, identification of multivariate biomarkers and in monitoring of therapeutic response, as well as in basic mechanistic studies. Although advances in magnetic resonance and mass spectrometry technologies have given rise to the fields of metabolomics and lipidomics, the plethora of data generated presents challenges requiring specific statistical and bioinformatics applications, together with appropriate study designs. Nonetheless, the predictive and re-classification capacity of individuals with various degrees of risk by the plasma lipidome has recently been demonstrated. In the present review, we summarize evidence derived exclusively by metabolomic and lipidomic studies in the context of ischaemic heart disease. We consider the potential role of plasma lipid profiling in assessing heart disease risk and therapeutic responses, and explore the potential mechanisms. Finally, we highlight where metabolomic studies together with complementary -omic disciplines may make further inroads into the understanding, detection and treatment of ischaemic heart disease.

Orthogonal organic and aqueous-based washes of tissue sections to enhance protein sensitivity by MALDI imaging mass spectrometry

Imaging mass spectrometry (IMS) is an emergent and innovative approach for measuring the composition, abundance and regioselectivity of molecules within an investigated area of fixed dimension. Although providing unprecedented molecular information compared with conventional MS techniques, enhancement of protein signature by IMS is still necessary and challenging. This paper demonstrates the combination of conventional organic washes with an optimized aqueous-based buffer for tissue section preparation before matrix-assisted laser desorption/ionization (MALDI) IMS of proteins. Based on a 500 mM ammonium formate in water-acetonitrile (9:1; v/v, 0.1% trifluororacetic acid, 0.1% Triton) solution, this buffer wash has shown to significantly enhance protein signature by profiling and IMS (~fourfold) when used after organic washes (70% EtOH followed by 90% EtOH), improving the quality and number of ion images obtained from mouse kidney and a 14-day mouse fetus whole-body tissue sections, while maintaining a similar reproducibility with conventional tissue rinsing. Even if some protein losses were observed, the data mining has demonstrated that it was primarily low abundant signals and that the number of new peaks found is greater with the described procedure. The proposed buffer has thus demonstrated to be of high efficiency for tissue section preparation providing novel and complementary information for direct on-tissue MALDI analysis compared with solely conventional organic rinsing.

Simultaneous extraction and rapid visualization of peptidomic and lipidomic body fluids fingerprints using mesoporous aluminosilicate and MALDI-TOF MS

Herein we report the use of mesoporous aluminosilicate (MPAS) for the simultaneous extraction of peptides and lipids from complex body fluids such as human plasma and synovial fluid. We show that MPAS particles, given their mesostructural features with nanometric pore size and high surface area, are an efficient device for simultaneous extraction of peptidome and lipidome from as little as a few microliters of body fluids. The peptides and the lipids, selected and enriched by MPAS particles and rapidly visualized by MALDI-TOF MS, could form part of a diagnostic profile of the "peptidome" and the "lipidome" of healthy versus diseased subjects in comparative studies. The ability of this approach to rapidly reveal the overall pattern of changes in both lipidome and peptidome signatures of complex biofluids could be of valuable interest for handling large numbers of samples required in -omics studies for the purpose of finding novel biomarkers.

A vision for better health: mass spectrometry imaging for clinical diagnostics

BACKGROUND

Mass spectrometry imaging (MSI) is a powerful tool that grants the ability to investigate a broad mass range of molecules from small molecules to large proteins by creating detailed distribution maps of selected compounds. Its usefulness in biomarker discovery towards clinical applications has obtained success by correlating the molecular expression of tissues acquired from MSI with well-established histology.

RESULTS

To date, MSI has demonstrated its versatility in clinical applications, such as biomarker diagnostics of different diseases, prognostics of disease severities and metabolic response to drug treatment, etc. These studies have provided significant insight in clinical studies over the years and current technical advances are further facilitating the improvement of this field. Although the underlying concept is simple, factors such as choice of ionization method, sample preparation, instrumentation and data analysis must be taken into account for successful applications of MSI. Herein, we briefly reviewed these key elements yet focused on the clinical applications of MSI that cannot be addressed by other means.

CONCLUSIONS

Challenges and future perspectives in this field are also discussed to conclude that the ever-growing applications with continuous development of this powerful analytical tool will lead to a better understanding of the biology of diseases and improvements in clinical diagnostics.

Metabolomics as a key integrator for "omic" advancement of personalized medicine and future therapies

Investigation into biological complexity, whether for a better understanding of disease or drug process, is a monumental task plaguing investigators. The lure of "omic" technologies for circumventing much of these challenges has led to widespread efforts and adoption. It is becoming clearer that a single "omic" approach (e.g., genomics) is often insufficient for completely defining the complexity in these biological systems. Hence, there is an increasing awareness that a "systems" approach will serve to increase resolution and confidence and provide a strong foundation for further hypothesis-driven investigation. Although certain metabolites are already considered clinically important, the profiling of metabolites via metabolomics (the profiling of metabolites to fully characterize metabolic pathways) is the most recent to mature of these "omic" technologies and has been only recently adopted as compared to genomic or proteomic approaches in systems inquiries. Recent reports suggest that this "omic" may well be a key data stream in systems investigations for endeavors in personalized medicine and biomarker identification, as it seems most closely relevant to the phenotype.

Sterol lipid metabolism in down syndrome revisited: down syndrome is associated with a selective reduction in serum brassicasterol levels

Over the past 15 years, insights into sterol metabolism have improved our understanding of the relationship between lipids and common conditions such as atherosclerosis and Alzheimer's Disease (AD). A better understanding of sterol lipid metabolism in individuals with Down Syndrome (DS) may help elucidate how this population's unique metabolic characteristics influence their risks for atherosclerosis and AD. To revisit the question of whether sterol lipid parameters may be altered in DS subjects, we performed a pilot study to assess traditional serum sterol lipids and lipoproteins, as well as markers of sterol biosynthesis, metabolites, and plant sterols in 20 subjects with DS compared to age-matched controls. Here we report that the levels of nearly all lipids and lipoproteins examined are similar to control subjects, suggesting that trisomy 21 does not lead to pronounced general alterations in sterol lipid metabolism. However, the levels of serum brassicasterol were markedly reduced in DS subjects.

Molecular imaging of matrix metalloproteinases in atherosclerotic plaques

Ischaemic stroke and myocardial infarction often result from the sudden rupture of an atherosclerotic plaque. The subsequent arterial thrombosis occluding the vessel lumen has been widely indicated as the crucial acute event causing peripheral tissue ischaemia. A complex cross-talk between systemic and intraplaque inflammatory mediators has been shown to regulate maturation, remodeling and final rupture of an atherosclerotic plaque. Matrix metalloproteinases (MMPs) are proteolytic enzymes (released by several cell subsets within atherosclerotic plaques), which favour atherogenesis and increase plaque vulnerability. Thus, the assessment of intraplaque levels and activity of MMP might be of pivotal relevance in the evaluation of the risk of rupture. New imaging approaches, focused on the visualisation of inflammation in the vessel wall and plaque, may emerge as tools for individualised risk assessment and prevention of events. In this review, we summarize experimental findings of the currently available invasive and noninvasive imaging techniques, used to detect the presence and activity of MMPs in atherosclerotic plaques.

Cell biology of ischemia/reperfusion injury

Disorders characterized by ischemia/reperfusion (I/R), such as myocardial infarction, stroke, and peripheral vascular disease, continue to be among the most frequent causes of debilitating disease and death. Tissue injury and/or death occur as a result of the initial ischemic insult, which is determined primarily by the magnitude and duration of the interruption in the blood supply, and then subsequent damage induced by reperfusion. During prolonged ischemia, ATP levels and intracellular pH decrease as a result of anaerobic metabolism and lactate accumulation. As a consequence, ATPase-dependent ion transport mechanisms become dysfunctional, contributing to increased intracellular and mitochondrial calcium levels (calcium overload), cell swelling and rupture, and cell death by necrotic, necroptotic, apoptotic, and autophagic mechanisms. Although oxygen levels are restored upon reperfusion, a surge in the generation of reactive oxygen species occurs and proinflammatory neutrophils infiltrate ischemic tissues to exacerbate ischemic injury. The pathologic events induced by I/R orchestrate the opening of the mitochondrial permeability transition pore, which appears to represent a common end-effector of the pathologic events initiated by I/R. The aim of this treatise is to provide a comprehensive review of the mechanisms underlying the development of I/R injury, from which it should be apparent that a combination of molecular and cellular approaches targeting multiple pathologic processes to limit the extent of I/R injury must be adopted to enhance resistance to cell death and increase regenerative capacity in order to effect long-lasting repair of ischemic tissues.

The emerging role of plasma lipidomics in cardiovascular drug discovery

INTRODUCTION

With the rising global incidence of cardiovascular disease, the challenge for the pharmaceutical industry is to identify novel biomarkers that will allow not only for the development of the next generation of cardiometabolic therapeutics, but also to serve as a sensitive mechanism to monitor and predict drug efficacy and potential toxicity. The advent of an 'omics' (systems biological) approach has vast implications for future disease treatment and prevention. Lipidomics is the latest addition to the 'omics' family and is rapidly gaining attention due to the technological improvements in mass spectrometry, allowing for the characterization of large number of lipids (and their respective subclasses) in a short amount of time with relatively minimal preparation.

AREAS COVERED

The authors discuss the various techniques involved in plasma lipidomics as well as outline the role that lipidomics will play in phenotyping disease processes and corresponding therapeutic strategies. The article was formed through comprehensive Medline search of relevant publications in this area.

EXPERT OPINION

Despite the wealth of data that will emerge regarding the various lipid-molecular interactions and the functions of lipids within cells, a major challenge will be the parallel emergence of novel bioinformatics platforms in order to integrate this enormous data set with information generated from the emerging fields of genomics and proteomic analysis. Despite these challenges, lipidomics is likely to result in the reclassification of diseases from a molecular perspective and play a key role the eventuation of personalized medicine.