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Researchers from the McCullagh Group in Oxford University's Department of Chemistry have an innovative method in Nature Protocols that provides comprehensive analysis of metabolites found in cells, tissues and biofluids.

The new method delivers a step-change in capability for analyzing highly polar and ionic metabolites. The innovation comes from using anion-exchange chromatography coupled to mass spectrometry (AEC-MS) to meet a long-standing need for improving the large-scale analysis of highly polar and ionic metabolites which drive primary metabolic pathways and processes in cells.

Ion-exchange chromatography has been used by generations of chemists since the 1970s, but historically it has been very difficult to couple directly to mass spectrometry, unlike other types of chromatography. The new method uses electrolytic ion-suppression to link the high-performance ion-exchange chromatography system directly with mass spectrometry, an innovation that improves molecular specificity and selectivity.

This has led to new applications that were recently by the McCullagh Group. The new method is designed for metabolomics applications that involve the large-scale analysis of metabolites in biological samples.

Rachel Williams, a D.Phil. student in the McCullagh Group, whose research focuses on the development of ion-exchange chromatography-mass spectrometry, said, "Ion-exchange chromatography offers a retention and elution mechanism which is new to metabolomics and is proving to be a powerful solution for long-standing analytical challenges in the field."

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Metabolomics is one of several 'omics' technologies that include genomics and proteomics, offering a powerful combinatorial approach to comprehensively analyzing molecular systems in cells, tissues and whole organisms. Changes in metabolite levels are sensitive biomarkers for specific diseases, diets, nutritional states, treatments and chemical exposures. Metabolomics provides a tool for discovering these molecular changes. It can be applied to research questions in many disciplines, including biological chemistry, molecular biology, molecular medicine, pharmacology and environmental science.

The new AEC-MS protocol has been used in several research studies, including in collaboration with the Kennedy Institute, Oxford, to investigate how the gut microbiome utilizes energy substrates. This led to the that the microbiome-derived energy substrate product butyrate is found in circulation and can help bolster the host immune response.

In another study, it was used to investigate metabolism in diabetic pancreatic β-cells. that the activity of GAPDH and PDH (enzymes involved in the production of ATP from glucose) were inhibited when glucose levels increased, leading to the accumulation of upstream intermediates which caused changes in gene expression including impaired insulin secretion and build-up of glycogen.

Professor James McCullagh (Department of Chemistry, University of Oxford), who led the project, said, "Developing a new metabolomics protocol is very exciting. It expands the capability of existing applications, but also enables us to explore and develop new applications. In our lab we are now applying the protocol in several research areas, including investigating gut microbiome metabolism, how antimicrobial resistance impacts bacterial metabolism and in the discovery of biomarkers for the early detection of cancer."