Methods for the measurement of urinary biomarkers of oxidative stressapplication to type 1 diabetes mellitus.
Doctoral thesis, UCL (University College London).
The principal aim of the study was to develop methods for the measurement of potential urinary biomarkers of oxidative stress using liquid chromatography/tandem mass spectrometry with minimum sample preparation to avoid artefact formation. Initially the development of an assay to measure the urinary concentrations of isoprostanes (8- isoPGF2α) was attempted but this did not prove to be sufficiently sensitive and gave nonreproducible results. An assay to measure the intact sulphate and glucuronide conjugates of urinary metabolites of vitamin E [α-tocopheronolactone (α-TLHQ) and α-carboxy-ethylhydroxychroman (α-CEHC)] was then developed, as it has been suggested that α-TLHQ with an oxidised chroman ring might be an indicator of oxidative stress. A novel method was also developed to quantitate urinary amino acids associated with NO• metabolism (Larginine - precursor, L-citrulline - product, L-ADMA –inhibitor of nitric oxide synthase and L-homocysteine – reduces bioavailability of nitric oxide). This method was extended to quantitate seven additional amino acids. The latter two methods were applied to 32 children with type 1 diabetes and compared with age and sex matched controls. The mean concentrations of all the α-THLQ conjugates were highly significantly increased in the diabetic subjects (p<0.002). The concentrations of the α-CEHC conjugates were also increased but not to the same degree of significance (p<0.05). When the diabetic children were divided into those who were poorly (n=24) and adequately (n=8) controlled, the α- THLQ conjugates remained highly significantly increased (p<0.002) in the poorly controlled group compared to controls. However, the concentrations of the α-CEHC conjugates were not significantly different. The diabetic subjects had a highly significantly increased concentration (p<0.0001) of all the urinary amino acids studied compared to controls. These results suggest that the measurement of urinary α-TLHQ conjugates may provide a useful biomarker of oxidative stress. The clinical relevance of the increased concentrations of urinary amino acids in children with type 1 diabetes requires further investigation.
|Title:||Methods for the measurement of urinary biomarkers of oxidative stressapplication to type 1 diabetes mellitus|
|Open access status:||An open access version is available from UCL Discovery|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Child Health > Department of Genes, Development and Disease > ICH - Clinical and Molecular Genetics|
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