Applications of LC-MS metabolomic profiling in inflammatory bowel disease and the development of derivatisation methods to enhance selective detection of certain compound classes

  • Ibrahim Abdullah S Alothaim

Student thesis: Doctoral Thesis

Abstract

Inflammatory bowel disease (IBD) is a chronic inflammation of all parts of the gastrointestinal tract and is represented by two major variations, ulcerative colitis (UC) and Crohn's disease (CD). It is diagnosed based on the pattern of inflammation. In order to understand the pathology of the disease better urine and saliva samples were collected from patients with IBD, patients in remission and a control group. The metabolomes of the urine and saliva samples were profiled by carrying out chromatography on a ZICpHILIC column in combination with high resolution mass spectrometry.It was possible to separate the different classes of urine samples on the basis of their metabolomic profiles by modelling with data using orthogonal partial least squares analysis (OPLSDA). A number of metabolites were found to vary between the three groups although the models for separation were weak. The OPLSDA models of the saliva data were much stronger and saliva analysis looks promising for diagnostic and prognostic purposes. Nine variables were able to discriminate the control and affected samples and these included four sphingosine bases.The analysis of short chain fatty acids (SCFAs) by LC-MS is a problem since they are too volatile to give good responses. SCFAs are potentially important makers for IBD. A quantitative LC-MS method for acetic, propionic, butyric and lactic acids was developed by carrying out derivatisation of the acids using a carbodimide to activate the acids and then reacting with dimethylaminophenylamine and separating the derivatives using HILIC chromatography. Quantification was carried out by using stable isotope dilution. The method was very sensitive but detection limits were set by the background contamination by the SCFAs rather than by absolute sensitivity.The method was applied to the urine samples and differences in acetate and butyrate were found between the affected and control samples. The microbiome plays a role in IBD and one marker for bacterial activity it the breakdown of dietary fibre in sugar monomers. Thus urine and saliva samples from controls and IBD samples were profiled using a reductive amination method previously developed. It was found that there were significant differences in the pattern of hexoses, pentoses and deoxy hexoses in the urine and saliva samples.
Date of Award1 Jun 2017
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorDavid Watson (Supervisor) & (Supervisor)

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