Abstract
Physiological effects may change volatile organic compound (VOC) concentrations and may therefore act as confounding factors in the definition of VOCs as disease biomarkers. To evaluate the extent of physiological background variability, this study assessed the effects of feed composition and somatic growth on VOC patterns in a standardized large animal model. Fifteen clinically healthy goats were followed during their first year of life. VOCs present in the headspace over faeces, exhaled breath and ambient air inside the stable were repeatedly assessed in parallel with the concentrations of glucose, protein, and albumin in venous blood. VOCs were collected and analysed using solid-phase or needle-trap microextraction and gas chromatograpy together with mass spectroscopy. The concentrations of VOCs in exhaled breath and above faeces varied significantly with increasing age of the animals. The largest variations in volatiles detected in the headspace over faeces occurred with the change from milk feeding to plant-based diet. VOCs above faeces and in exhaled breath correlated significantly with blood components. Among VOCs exhaled, the strongest correlations were found between exhaled nonanal concentrations and blood concentrations of glucose and albumin. Results stress the importance of a profound knowledge of the physiological backgrounds of VOC composition before defining reliable and accurate marker sets for diagnostic purposes.
Highlights
A considerable number of volatile organic compounds (VOCs) are generated by cells or microorganisms throughout the body during various metabolic and biochemical processes (Schulz and Dickschat 2007, Thorn and Greenman 2012) and can be detected in different biological specimens such as exhaled breath or faeces
Volatile organic compounds in the headspace above faeces Throughout the study period of one year, a marker set of 25 volatile substances was repeatedly assessed from 73 faecal samples by solid-phase microextraction (SPME)-gas chromatography together with mass spectrometry (GC–MS) measurements
We identified quantitative relationships between VOCs in the headspace above faeces and blood components. determination of the biochemical origin of VOCs was not possible in this study, results indicate a potential endogenous contribution to the VOC profile emitted by faeces which remains to be elucidated in future studies
Summary
A considerable number of volatile organic compounds (VOCs) are generated by cells or microorganisms throughout the body during various metabolic and biochemical processes (Schulz and Dickschat 2007, Thorn and Greenman 2012) and can be detected in different biological specimens such as exhaled breath or faeces (de Lacy Costello et al 2014). Controlled sampling, reliable analysis, and unequivocal identification of VOC biomarkers and potential confounding substances are mandatory for the application of VOC trace analysis (typical concentrations are in the nmol L − 1–pmol L − 1 range). Adapted microextraction methods such as solid-phase microextraction (SPME) (Arthur and Pawliszyn 1990) and needle-trap microextraction (NTME) (Mieth et al2009, Lord et al 2010) enable controlled collection and pre-concentration of VOCs from the headspace (gas phase above liquids or solid materials) above faeces as well as from the exhaled breath and from room air samples (Miekisch et al 2014). Clinical studies are often hampered by non-avoidable, host-related, confounding factors that could lead to erroneous conclusions when searching for biomarkers indicating diseases (Filipiak et al 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
