Volatomics in inflammatory bowel disease and irritable bowel syndrome

Abstract

Volatile organic compounds (VOCs) are produced by the human metabolism, inflammation and gut microbiota and form the basis of innovative volatomics research. VOCs detected through breath and faecal analysis hence serve as attractive, non-invasive biomarkers for diagnosing and monitoring irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). This review describes the clinical applicability of volatomics in discriminating between IBS, IBD and healthy volunteers with acceptable accuracy in breath (70%-100%) and faecal (58%-85%) samples. Promising compounds are propan-1-ol for diagnosing and monitoring of IBD patients, and 1-methyl-4-propan-2-ylcyclohexa-1,4-diene as biomarker for IBS diagnosis. However, these VOCs often seem to be related to inflammation and probably will need to be used in conjunction with other clinical evidence. Furthermore, three interventional studies underlined the potential of VOCs in predicting treatment outcome and patient follow-up. This shows great promise for future use of VOCs as non-invasive breath and faecal biomarkers in personalised medicine. However, properly designed studies that correlate VOCs to IBD/IBS pathogenesis, while taking microbial influences into account, are still key before clinical implementation can be expected.

Keywords: IBD; IBS; Irritable bowel syndrome; VOC; Volatile organic compounds; inflammatory bowel disease.

Fig. 1

Individual VOCs in IBD and IBS. Compounds described in more than one study are in bold. ↑: upregulated. ↓: downregulated.

Fig. 2

The potential of VOC analysis in the management of IBS and IBD. VOCs can originate from metabolic processes, both physiologic and pathophysiologic (inflammation or oxidative stress), and by the microbiota. Hence, a flare up or change in micobial composition can be reflected in VOC changes. However, this also stresses the potential of confounding external factors like drugs and diet that need to be accounted for. VOCs are liberated by the gastrointestinal cells and can be excreted in faeces, but are also transported through the bloodstream and can hence be detected in breath and urine, offering non-invasive alternatives for future disease management.