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The analysis of exhaled metabolites has become a promising field of research in recent decades. Several volatile organic compounds reflecting metabolic disturbance and nutrition status have even been reported. These are particularly important for long-term measurements, as needed in medical research for detection of disease progression and therapeutic efficacy. In this context, it has become urgent to investigate the effect of fasting and glucose treatment for breath analysis. In the present study, we used amodel of ventilated rats that fasted for 12 h prior to the experiment. Ten rats per group were randomly assigned for continuous intravenous infusion without glucose or an infusion including 25 mg glucose per 100 g per hour during an observation period of 12 h. Exhaled gas was analysed using multicapillary column ion-mobility spectrometry. Analytes were identified by the BS-MCC/IMS database (version 1209; B & S Analytik, Dortmund, Germany). Glucose infusion led to a significant increase in blood glucose levels (p<0.05 at 4 h and thereafter) and cardiac output (p<0.05 at 4 h and thereafter). During the observation period, 39 peaks were found collectively. There were significant differences between groups in the concentration of ten volatile organic compounds: p<0.001 at 4 h and thereafter for isoprene, cyclohexanone, acetone, p-cymol, 2-hexanone, phenylacetylene, and one unknown compound, and p<0.001 at 8 h and thereafter for 1-pentanol, 1-propanol, and 2-heptanol. Our results indicate that for long-term measurement, fasting and the withholding of glucose could contribute to changes of volatile metabolites in exhaled air.
Rats are commonly used in medical research as they enable a high grade of standardization. The exhalome of ventilated rats has not as yet been investigated using an ion mobility spectrometer coupled with a multi-capillary column (MCC-IMS). As a first step, a rat model has to be established to measure potential biomarkers in the exhale with long-term settings, allowing constant and continuous analysis of exhaled air in time series. Therefore, eight animals were anaesthetized, prepared and ventilated for 1 h. A total of 73 peaks were directly detected with the IMS chromatogram. Thirty five of them were assigned to the ventilator system and 38 to the animals. Peak intensity varied within three measurements. The intensity of analytes of individual rats varied by a factor of up to 18. This new model will also enable continuous measurements of volatile organic compounds (VOCs) from rat's breath in long-term experiments. It is hoped that, in the future, variability and progression of VOCs can be monitored in different models of diseases using this set-up.