Scientists convened in London to present important scientific findings for ‘Next Generation Diagnostics’, the subject of the fourth Innovation Academy Scientific Symposium
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In the second piece of coverage from Viapath’s fourth Innovation Academy (IA4, held in December 2014) we review two more of the presentations on metabolomics from the Academy’s impressive line-up of speakers.
Improving Diagnosis of Catecholamine-Producing Tumors Through TurboFlow LC/MS
Dr David Taylor, Clinical Scientist within the Reference Biochemistry lab at King’s College Hospital, London, UK, has a particular interest in endocrine testing, and his recent research has looked at techniques to improve the diagnosis of adrenal tumors. With an annual incidence of between two and eight per million of the population, phaeochromocytoma and paraganglioma (PPGLs) are rare catecholamine-producing tumors of the adrenal medulla and extra-adrenal sympathetic chain.
Although rare, it is their impact as a potentially fatal, yet surgically treatable, cause of secondary hypertension which makes their detection important. Hypertension from catecholamine excess (adrenaline and noradrenaline) typically presents with headaches, palpitations and excessive sweating, although tumors may be detected incidentally by imaging. At least 10% of PPGLs are malignant (often producing dopamine), while 11 genes have been linked to familial disease.
New Method
Until recently, biochemical detection of PPGLs was based on catecholamine measurement in urine and plasma together with urinary measurement of the O-methylated metabolites of adrenaline, noradrenaline and dopamine (metadrenaline, normetadrenaline and 3-methoxytyramine, respectively). Measurement is performed by HPLC with electrochemical detection, following rather laborious sample preparations, including an overnight solid phase extraction step. Lately, a sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the measurement of metadrenaline, normetadrenaline and 3-methoxytyramine in plasma has been introduced in the laboratory(1).This method incorporates online TurboFlow sample extraction, followed by analytical chromatography prior to MS detection using the Thermo Scientific Transcend TLX-II system and Thermo Scientific TSQ Vantage.
Innovation Academy funding has allowed Dr Taylor to expand this sensitive method. In 2015, the aim is to transfer all catecholamine and metabolite measurements in urine and blood to the liquid chromatography-tandem mass spectrometry system. This transfer will radically modernize the biogenic amine service at Viapath with improved specificity of results and simplified sample preparation - all run from a single instrument. As a consequence, diagnosis of PPGL tumours is achieved far more quickly, improving clinical decision-making regarding follow-up imaging, genetic testing and the most appropriate therapeutic options for the patient.
Twins-Omics, Changing the Face of Personalized Medicine
More Signal, Less Noise
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The Thermo Scientific TSQ Vantage Triple Stage Quadrupole Mass Spectrometer offers more signal and less noise, to provide better assay precision and accuracy. Combined with a robust new ion source, second generation ion optics and hyperbolic quadrupoles, the Thermo Scientific TSQ Vantage delivers high sensitivity with low chemical noise.
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The final speaker at the IA4 was Tim Spector, Professor of Genetic Epidemiology and Director of the Twins UK Registry at Kings College, London, UK. The Department of Twin Research (DTR) has embarked on a large-scale multi-omic study of 11,000 adult twins, with sub-studies used to explore the heritability, Quantitive Trait Loci (QTLs) and age relationships of different omics.
Recently, Professor Spector and his team were part of the most comprehensive exploration of influence of genetic loci on human metabolism to date, which comprised 7,824 adult individuals from two European population studies. The Genome-Wide Association Studies (GWAS) reported associations at 145 metabolic loci and biochemical links with more than 400 metabolites in human blood. Research has now been published on over 100 traits (including Type 2 Diabetes risk, blood pressure, CHD, menopause, bone mineral density, presence of cutaneous naevi) and over 500 loci. The resulting in vivo blueprint of metabolism in human blood has been integrated with gene expression information, heritability and overlap with loci already identified for complex disorders, inborn errors of metabolism and pharamacological targets.
Results from this large multinational collaboration between industry and academia generated an atlas of genetic influences on human blood metabolites, published in May 2014(2). The atlas provides new insights into the role of inherited variation in the metabolic diversity of blood and will help further understand the genetic basis of such diseases as well as drive further drug development opportunities.
Could Metabolomics Hold the Key?
Although these GWAS studies are good for the discovery of real genes and mechanisms associated with disease, as they explain less than 5-10% of variation, they are not necessarily so helpful for diagnosis or prediction, but here metabolomics may provide the key. Professor Spector was involved in a comprehensive analysis of genotype-dependent metabolic phenotypes using a GWAS with non-targeted metabolomics by Suhre et al(3). The researchers identified 36 genetic loci associated with blood metabolite concentrations, 25 of which exhibited unusually high effect sizes and accounted for 10-60% of metabolite levels per allele copy. Consequentially, new functional insights were revealed for many disease-related associations, including cardiovascular disease, cancer, type 2 diabetes, kidney disorders, venous thromboembolism, gout and Crohn’s disease. Furthermore, the DTR have combined over 500 blood metabolites with two million single nucleotide polymorphisms (SNPs) in 6,000 twins and found over 100 novel genes that can be directly linked to a metabolite with many explaining 30% of variation (Shin et al. in review).
Monozygotic (MZ) twins represent a "wonderful research resource", which, as genetic clones of each other, can act as a small-scale randomized control trial. However, although identical, Professor Spector’s fellow researchers have also found that there are low concordance rates for common diseases (such as rheumatoid arthritis, breast cancer, diabetes and schizophrenia) in MZ twins. To work out why this might be, Prof Spector explained that we need to turn to epigenetics and the studies such as EpiTWIN, which aims to use whole genome methylation sequencing to improve the understanding of how genetic and environmental factors can impact on epigenetics and how DNA methylation pattern variation can affect a wide range of complex traits.
Finally, Professor Spector touched upon the heritability of the microbiome. The balance of gut microbiota has long been linked with general health and when out of kilter, development of disease. Using the Twin UK registry, the gut bacteria of 977 twins was analyzed by examining the bacterial content of their feces. When the heritability of different groups of bacteria was examined, certain taxa were far more similar (i.e. heritable) in identical (MZ) rather than non-identical twins(4). Intriguingly, many of the groups of bacteria that are heritable are the ones which have been previously linked to disease, which might point to these being one of the mechanisms for the genetic inheritance of disease.
Dominic Harrington, Scientific Director at Viapath commented, “Metabolomics is fast becoming an essential part of the Next Generation Diagnostics toolbox and is one of the driving advances in personalized medicine. We are proud that the Innovation Academy provides funding to support and publicize such pioneering research, as well as helping to forge important links between researchers, clinicians and managers within academia and industry.”
References
(1) Eisenhofer G and Peitch M. Laboratory evaluation of pheochromocytoma and paraganglioma. Clinical Chemistry 2014 Dec;60(12):1486-99.
(2) So-Youn Shin et al. An atlas of genetic influences on human blood metabolites. Nature Genetics 46, 543-550 (2014)
(3) Suhre K et al. Human metabolic individuality in biomedical and pharmaceutical research. Nature. 2011 Aug 31; 477(4362):10
(4) Goodrich JK et al. Human genetics shapes the gut microbiome. Cell 2014 Nov 6; 159(4)789-99