Douglas Morrison - Stable Isotope Breath Tests: Applications, Challenges and Opportunities
With undergraduate training in Medicinal Chemistry and a PhD which focussed on developing stable isotope-based methods of measuring gut function, Dr Morrison is currently a Reader in Stable Isotope Biochemistry at the University of Glasgow. His main research activities revolve around using stable isotopes to understand biological systems and processes. His research focus is on the role of the gut in over-nutrition (obesity) and under-nutrition (stunting). Together with colleagues, he has developed a novel food ingredient that targets nutrient-sensing, appetite-regulating circuits in the gut that has demonstrated promise for the prevention of weight gain. Currently he is working on developing stable isotope approaches to measure gut function in under-nutrition (e.g. brush border enzyme activity) to improve diagnosis of gut dysfunction and monitoring of nutritional interventions that target improvement in gut barrier function in malnutrition settings.
Stable isotope breath tests are an attractive diagnostic modality because they report are non-invasive, report functional response and potentially offer improved sensitivity and specificity more generic breath tests. For example, the 13C-urea breath test for diagnosis of Helicobacter pylori infection demonstrates sensitivity and specificity of greater than 98% and is measured in breath 13CO2. However, oral administration of an isotope labelled tracer also presents some challenges. Variability in gastric emptying rates and intestinal transit times, coupled with interferences from microbes that reside in different regions of the gut reduce the sensitivity and specificity of stable isotope breath tests of more distal gut function and the function of other organs. A priori choice of isotope labelled tracer is normally a prerequisite for a stable isotope breath test and judicious choice of tracer has led to several applications of stable isotope breath tests in clinical practice and research. Complimentary approaches of using targeted and untargeted breath analysis such as exogenous volatile organic compound analysis are rare but offer opportunities for target discovery and refinement of diagnostic breath tests.