Exploring Dietary- and Disease-Related Influences on Flatulence and Fecal Odor Perception in Inflammatory Bowel Disease

Background/Objectives: Inflammatory bowel disease (IBD) affects gastrointestinal function and may alter fecal and flatulence odor (intestinal odor) due to changes in inflammation, the gut microbiome, and metabolism. Investigating the relationship between dietary habits and intestinal odor in IBD is critical given the relationship between diet, gut health, and microbiome diversity. Methods: We performed a cohort analysis of a monocentric, cross-sectional study at a tertiary referral center and compared the perception of fecal and flatulence odor in 233 IBD patients (n = 117 women) with that of 96 healthy controls (HCs) (n = 67 women). In addition to a short screening questionnaire on highly processed foods (sQ-HPF), dietary behavior (Food Frequency Questionnaire (FFQ)), clinical (HBI, PMS) and biochemical (CRP, fecal calprotectin) parameters of disease activity, and adherence to a Mediterranean diet were assessed. Results: A notable predisposition towards elevated levels of intestinal malodor was identified in the IBD cohort when compared to the HC group. The analysis of dietary behavior in conjunction with intestinal malodor revealed more pronounced associations in the HC collective than in the IBD collective. The data further indicated that, in comparison to those in remission, IBD individuals with an active disease status exhibited a higher prevalence of intestinal malodor. In an adjusted logistic regression analysis of the influence of disease- and diet-specific factors on flatulence and fecal malodor in IBD, male sex was identified as a significant risk factor. Conclusions: This study highlights the significance of dietary factors in the management of IBD symptoms, with a particular focus on flatulence and fecal odor. Individuals with IBD demonstrated a higher propensity for intestinal malodor compared to HC, with active disease status further amplifying this prevalence. Dietary behavior showed stronger associations with malodor in the HC group than in IBD individuals, suggesting distinct interaction patterns between diet and gut health in these populations.

Non-target GC-MS analyses of fecal VOCs in NASH-hepatocellular carcinoma model STAM mice

The increased incidence of obesity in the global population has increased the risk of several chronic inflammation-related diseases, including non-alcoholic steatohepatitis (NASH)-hepatocellular carcinoma (HCC). The progression from NASH to HCC involves a virus-independent liver carcinogenic mechanism; however, we currently lack effective treatment and prevention strategies. Several reports have suggested that fecal volatile organic compounds (VOCs) are strongly associated with NASH-HCC; therefore, we explored the biomarkers involved in its pathogenesis and progression. Fecal samples collected from control and NASH-HCC model STAM mice were subjected to headspace autosampler gas chromatography-electron ionization-mass spectrometry. Non-target profiling analysis identified diacetyl (2,3-butandione) as a fecal VOC that characterizes STAM mice. Although fecal diacetyl levels were correlated with the HCC in STAM mice, diacetyl is known as a cytotoxic/tissue-damaging compound rather than genotoxic or mutagenic; therefore, we examined the effect of bioactivity associated with NASH progression. We observed that diacetyl induced several pro-inflammatory molecules, including tumor necrosis factor-α, cyclooxygenase-2, monocyte chemoattractant protein-1, and transforming growth factor-β, in mouse macrophage RAW264.7 and Kupffer KPU5 cells. Additionally, we observed that diacetyl induced α-smooth muscle actin, one of the hallmarks of fibrosis, in an ex vivo cultured hepatic section, but not in in vitro hepatic stellate TWNT-1 cells. These results suggest that diacetyl would be a potential biomarker of fecal VOC in STAM mice, and its ability to trigger the macrophage-derived inflammation and fibrosis may partly contribute to NASH-HCC carcinogenesis.

Fecal Metabolites As Non-Invasive Biomarkers of Gut Diseases

Recent studies have shown the importance of the human intestinal microbiome in maintaining a healthy gastrointestinal tract, as well as in the development of pathological processes. The intestinal microbiome manifests itself primarily as fecal metabolites. In the past decade, there has been growing interest in studying its composition, which for the most part had to do with the possibility of using the metabolomic analysis in clinical diagnosis. In contrast to the comprehensive description of blood serum, urine, saliva, and cerebrospinal fluid metabolites, data on fecal metabolites is sparse. Despite the instrumental and methodological achievements in the metabolomic analysis in general, the analysis of fecal metabolome remains less well developed, mainly because of the inhomogeneity of its composition and the lack of standardized methods for collecting, processing, and analyzing fecal samples. This review summarizes data on methods for studying and describing various groups of fecal metabolites. It also assesses their potential as tools in the diagnosis of gastrointestinal diseases.

Elevated levels of proinflammatory volatile metabolites in feces of high fat diet fed KK-Ay mice

When the microfloral composition deteriorates, it triggers low-level chronic inflammation associated with several lifestyle-related diseases including obesity and diabetic mellitus. Fecal volatile organic compounds (VOCs) have been found to differ in gastrointestinal diseases as well as intestinal infection. In this study, to evaluate a potential association between the pathogenesis of lifestyle-related diseases and VOCs in the intestinal tract, fecal VOCs from obese/diabetic KK-A^y mice (KK) or controls (C57BL/6J mice; BL) fed a normal or high fat diet (NFD or HFD) were investigated using headspace sampler-GC-EI-MS. Principal component analysis (PCA) of fecal VOC profiles clearly separated the experimental groups depending on the mouse lineage (KK vs BL) and the diet type (NFD vs HFD). 16 s rRNA sequencing revealed that the PCA distribution of VOCs was in parallel with the microfloral composition. We identified that some volatile metabolites including n-alkanals (nonanal and octanal), acetone and phenol were significantly increased in the HFD and/or KK groups. Additionally, these volatile metabolites induced proinflammatory activity in the RAW264 murine macrophage cell line indicating these bioactive metabolites might trigger low-level chronic inflammation. These results suggest that proinflammatory VOCs detected in HFD-fed and/or diabetic model mice might be novel noninvasive diagnosis biomarkers for diabetes.

Diagnostic techniques for rapid detection of Vibrio cholerae O1/O139

Cholera caused by the toxigenic Vibrio cholerae is still a major public health problem in many countries. This disease is mainly due to poor sanitation, hygiene and consumption of unsafe water. Several recent epidemics of cholera showed its increasing intensity, duration and severity of the illness. This indicates an urgent need for effective management and preventive measures in controlling the outbreaks and epidemics. In preventing and spread of epidemic cholera, rapid diagnostic tests (RDTs) are useful in screening suspected stool specimens, water/food samples. Several RDTs developed recently are considered as investigative tools in confirming cholera cases, as the culture techniques are difficult to establish and/or maintain. The usefulness of RDTs will be more at the point-of-care facilities as it helps to make appropriate decisions in the management of outbreaks or epidemiological surveillance by the public health authorities. Apart from RDTs, several other tests are available for the direct detection of either V. cholerae or its cholera toxin. Viable but non-culturable (VBNC) state of V. cholerae poses a great challenge in developing RDTs. The aim of this article is to provide an overview of current knowledge about RDT and other techniques with reference to their status and future potentials in detecting cholera/V. cholerae.

Optimized Sampling Conditions for Fecal Volatile Organic Compound Analysis by Means of Field Asymmetric Ion Mobility Spectrometry

Fecal volatile organic compounds (VOCs) are increasingly considered to be potential noninvasive, diagnostic biomarkers for various gastrointestinal diseases. Knowledge of the influence of sampling conditions on VOC outcomes is limited. We aimed to evaluate the effects of sampling conditions on fecal VOC profiles and to assess under which conditions an optimal diagnostic accuracy in the discrimination between pediatric inflammatory bowel disease (IBD) and controls could be obtained. Fecal samples from de novo treatment-naïve pediatric IBD patients and healthy controls (HC) were used to assess the effects of sampling conditions compared to the standard operating procedure (reference standard), defined as 500 mg of sample mass diluted with 10 mL tap water, using field asymmetric ion mobility spectrometry (FAIMS). A total of 17 IBD (15 CD (Crohn's disease) and 2 UC (ulcerative colitis)) and 25 HC were included. IBD and HC could be discriminated with high accuracy (accuracy = 0.93, AUC = 0.99, p < 0.0001). A smaller fecal sample mass resulted in a decreased diagnostic accuracy (300 mg accuracy = 0.77, AUC = 0.69, p = 0.02; 100 mg accuracy = 0.70, AUC = 0.74, p = 0.003). A loss of diagnostic accuracy was seen toward increased numbers of thaw–freeze cycles (one cycle, accuracy = 0.61, AUC = 0.80, p = 0.0004; two cycles, accuracy = 0.64, AUC = 0.56, p = 0.753; and three cycles, accuracy = 0.57, AUC = 0.50, p = 0.5101) and when samples were kept at room temperature for 180 min prior to analysis (accuracy = 0.60, AUC = 0.51, p = 0.46). Diagnostic accuracy of VOC profiles was not significantly influenced by storage duration differences of 20 months. The application of a 500 mg sample mass analyzed after one thaw–freeze cycle showed the best discriminative accuracy for the differentiation of IBD and HC. VOC profiles and diagnostic accuracy were significantly affected by sampling conditions, underlining the need for the implementation of standardized protocols in fecal VOC analysis.

Inflammatory bowel disease and patterns of volatile organic compounds in the exhaled breath of children: A case-control study using Ion Molecule Reaction-Mass Spectrometry

Inflammatory bowel diseases (IBD) profoundly affect quality of life and have been gradually increasing in incidence, prevalence and severity in many areas of the world, and in children in particular. Patients with suspected IBD require careful history and clinical examination, while definitive diagnosis relies on endoscopic and histological findings. The aim of the present study was to investigate whether the alveolar air of pediatric patients with IBD presents a specific volatile organic compounds’ (VOCs) pattern when compared to controls. Patients 10–17 years of age, were divided into four groups: Crohn’s disease (CD), ulcerative colitis (UC), controls with gastrointestinal symptomatology, and surgical controls with no evidence of gastrointestinal problems. Alveolar breath was analyzed by ion molecule reaction mass spectrometry. Four models were built starting from 81 molecules plus the age of subjects as independent variables, adopting a penalizing LASSO logistic regression approach: 1) IBDs vs. controls, finally based on 18 VOCs plus age (sensitivity = 95%, specificity = 69%, AUC = 0.925); 2) CD vs. UC, finally based on 13 VOCs plus age (sensitivity = 94%, specificity = 76%, AUC = 0.934); 3) IBDs vs. gastroenterological controls, finally based on 15 VOCs plus age (sensitivity = 94%, specificity = 65%, AUC = 0.918); 4) IBDs vs. controls, built starting from the 21 directly or indirectly calibrated molecules only, and finally based on 12 VOCs plus age (sensitivity = 94%, specificity = 71%, AUC = 0.888). The molecules identified by the models were carefully studied in relation to the concerned outcomes. This study, with the creation of models based on VOCs profiles, precise instrumentation and advanced statistical methods, can contribute to the development of new non–invasive, fast and relatively inexpensive diagnostic tools, with high sensitivity and specificity. It also represents a crucial step towards gaining further insights on the etiology of IBD through the analysis of specific molecules which are the expression of the particular metabolism that characterizes these patients.

Potential of in vivo real-time gastric gas profiling: a pilot evaluation of heat-stress and modulating dietary cinnamon effect in an animal model

Gastroenterologists are still unable to differentiate between some of the most ordinary disorders of the gut and consequently patients are misdiagnosed. We have developed a swallowable gas sensor capsule for addressing this. The gases of the gut are the by-product of the fermentation processes during digestion, affected by the gut state and can consequently provide the needed information regarding the health of the gut. Here we present the first study on gas sensor capsules for revealing the effect of a medical supplement in an animal (pig) model. We characterise the real-time alterations of gastric-gas in response to environmental heat-stress and dietary cinnamon and use the gas profiles for understanding the bio-physiological changes. Under no heat-stress, feeding increases gastric CO2 concentration, while dietary cinnamon reduces it due to decrease in gastric acid and pepsin secretion. Alternatively, heat-stress leads to hyperventilation in pigs, which reduces CO2 concentration and with the cinnamon treatment, CO2 diminishes even more, resulting in health improvement outcomes. Overall, a good repeatability in gas profiles is also observed. The model demonstrates the strong potential of real-time gas profiler in providing new physiological information that will impact understanding of therapeutics, presenting a highly reliable device for monitoring/diagnostics of gastrointestinal disorders.

Techniques and issues in breath and clinical sample headspace analysis for disease diagnosis

Analysis of volatile organic compounds (VOCs) from breath or clinical samples for disease diagnosis is an attractive proposition because it is noninvasive and rapid. There are numerous studies showing its potential, yet there are barriers to its development. Sampling and sample handling is difficult, and when coupled with a variety of analytical instrumentation, the same samples can give different results. Background air and the environment a person has been exposed to can greatly affect the VOCs emitted by the body; however, this is not an easy problem to solve. This review investigates the use of VOCs in disease diagnosis, the analytical techniques employed and the problems associated with sample handling and standardization. It then suggests the barriers to future development.

Human intestinal gas measurement systems: in vitro fermentation and gas capsules

The biological and clinical significance of the human gut microbiome is currently attracting worldwide attention. While rRNA and DNA technologies led to a quantum leap in our understanding of the numbers and types of gut microorganisms, much less is known about these microorganisms' activity in situ and in real time. Accurately measuring their byproducts, including intestinal gases, may offer unique biomarkers for specific gut microbiota, accelerating our understanding of the relationships among intestinal gases, the metabolic activity of the gut microbiome, and human health states. Here we present two novel techniques, namely in vitro fermentation and gas capsule systems, for measuring and assessing selected gas species. We discuss new developments with these technologies and the methods of their implementation and provide an overall review of their operation.

The molecular biology of inflammatory bowel diseases

IBDs (inflammatory bowel diseases) are a group of diseases affecting the gastrointestinal tract. The diseases are multifactorial and cover genetic aspects: susceptibility genes, innate and adaptive responses to inflammation, and structure and efficacy of the mucosal protective barrier. Animal models of IBD have been developed to gain further knowledge of the disease mechanisms. These topics form an overlapping background to enable an improved understanding of the molecular features of these diseases. A series of articles is presented based on the topics covered at the Biochemical Society Focused Meeting The Molecular Biology of Inflammatory Bowel Diseases.