Search

Carbon stable isotope breath tests offer new opportunities to better understand gastrointestinal function in health and disease. However, it is often not clear how to isolate information about a gastrointestinal or metabolic process of interest from a breath test curve, and it is generally unknown how well summary statistics from empirical curve fitting correlate with underlying biological rates. We developed a framework that can be used to make mechanistic inference about the metabolic rates underlying a13C breath test curve, and we applied it to a pilot study of13C-sucrose breath test in 20 healthy adults. Starting from a standard conceptual model of sucrose metabolism, we determined the structural and practical identifiability of the model, using algebra and profile likelihoods, respectively, and we used these results to develop a reduced, identifiable model as a function of a gamma-distributed process, a slower, rate-limiting process, and a scaling term related to the fraction of the substrate that is exhaled as opposed to sequestered or excreted through urine. We demonstrated how the identifiable model parameters impacted curve dynamics and how these parameters correlated with commonly used breath test summary measures. Our work develops a better understanding of how the underlying biological processes impact different aspect of13C breath test curves, enhancing the clinical and research potential of these13C breath tests.

Individuals with Barrett’s esophagus are believed to be at 30–120× risk of developing esophageal adenocarcinoma (EAC). Early detection and endoscopic treatment of dysplasia/early cancer confers a significant advantage to patients under surveillance; however, most do not progress past the non-dysplastic state of Barrett’s esophagus (NDBE), which is potentially an inefficient distribution of health care resources. This article aimed to review the outcomes of cost-effectiveness studies reducing low-value care in the context of endoscopic surveillance for non-dysplastic Barrett’s esophagus (NDBE). A systematic search was conducted by two reviewers in accordance with PRISMA guidelines. Inclusion criteria: cost-utility analyses of endoscopic surveillance of NDBE patients with at least one treatment strategy focused on reduction of surveillance. A narrative synthesis of economic evaluations was undertaken, along with an in-depth analysis of input parameters contributing to stated Incremental cost-effectiveness ratios (ICER). Study appraisal was performed using the consolidated health economic evaluation reporting standards (CHEERS) tool. 10 Studies met inclusion criteria. There was significant variation in cost-model structures, input parameters, ICER values, and willingness-to-pay thresholds between studies. All studies except one concluded guideline-specified endoscopic surveillance for NDBE patients was not cost-effective. Studies that explored a modified surveillance by deselection of low-risk NDBE patients found it to be a cost-effective strategy. Guideline specified endoscopic surveillance for NDBE was not found to be cost-effective in the studies examined. A modified endoscopic surveillance strategy removing individuals with the lowest risk for progression from NDBE to adenocarcinoma is likely to be cost-effective but is dependent on risk profile of patients excluded from surveillance.

Background Improving the ability to identify early-stage head and neck squamous cell carcinoma (HNSCC) can improve treatment outcomes and patient morbidity. We sought to determine the diagnostic accuracy of breath analysis as a non-invasive test for detecting HNSCC. Methods Standardised breath samples were collected from 181 patients suspected of HNSCC prior to any treatment. A selected ion flow-tube mass spectrometer was used to analyse breath for volatile organic compounds. Diagnosis was confirmed by histopathology. A binomial logistic regression model was used to differentiate breath profiles between cancer and control (benign disease) patients based on mass spectrometry derived variables. Results In all, 66% of participants had early-stage primary tumours (T1 and T2) and 58% had regional node metastasis. The optimised logistic regression model using three variables had a sensitivity and specificity of 80% and 86%, respectively, with an AUC for ROC curve of 0.821 (95%CI 0.625–1.0) in the testing cohort. Conclusions Breath analysis for non-invasive diagnosis of HNSCC appears to be practical and accurate. Future studies should be conducted in a primary care setting to determine the applicability of breath analysis for early identification of HNSCC.

The 13C-labelled methionine breath test is a non-invasive test with the potential to evaluate metabolic liver mitochondrial dysfunction in vivo. This study aimed to develop an optimised protocol for breath collection in sheep and compare 13C-methionine and methyl-13C-methionine as substrates for future breath test applications in ruminants. Two doses (1 mg/kg and 2 mg/kg) of 13C-methionine or methyl-13C-methionine in saline were administered via intravenous injection to four South Australian Merino ewes aged three years with an average body weight of 65 kg. Exhaled breath samples were collected at baseline and every 10 min for 180 min after administration of the 13C-labelled substrate, and analysed using an isotope ratio mass spectrometer. Dose recovery of 13CO2 derived from 13C-methionine was higher at each time-point compared to that derived from methyl-13C-methionine, at both concentrations. 13C-methionine dose evaluation indicated that intra-individual and inter-individual variability of percentage dose recovery was lower in animals dosed with 2 mg/kg 13C-methionine compared to 1 mg/kg 13C-methionine. Mean cumulative percentage dose recovery of animals administered 1 mg/kg and 2 mg/kg 13C-methionine at 60 min, 120 min and 180 min was 5.34 ± 0.87%, 11.52 ± 1.29% and 16.30 ± 1.45%, and 12.30 ± 0.34%, 25.12 ± 0.59% and 34.45 ± 0.57%, respectively. We conclude that the 13C-labelled methionine breath test can be reliably performed in sheep through intravenous administration of 2 mg/kg 13C-methionine. This study also demonstrated the utility and advantage of 13C-methionine compared to methyl-13C-methionine as substrates for future breath testing applications to evaluate hepatic mitochondrial function in sheep and other ruminants. Further development of the test could be employed to evaluate disease progression and efficacy of applied therapeutics in sheep models of human diseases characterised by hepatic dysfunction. In addition, the 13C-methionine breath test could be utilised in animal production to assess hepatic metabolic function and the potential impact of nutritional mismanagement.

Dipeptidyl peptidase-4 inhibitors (DPP4i) are a class of orally available, small molecule inhibitors for the management of Type-II diabetes. A rapid, real-time, functional breath test for DPP4 enzyme activity could help to define DPP4i efficacy in patients that are refractory to treatment. We aimed to develop a selective, non-invasive, stable-isotope 13C-breath test for DPP4. In vitro experiments were performed using high (Caco-2) and low (HeLa) DPP4 expressing cells. DPP gene expression was determined in cell lines by qRT-PCR. A DPP4 selective 13C-tripeptide was added to cells in the presence and absence of the DPP4 inhibitor Sitagliptin. Gas samples were collected from the cell headspace and 13CO2 content quantified by isotope ratio mass spectrometry (IRMS). DPP4 was highly expressed in Caco-2 cells compared to HeLa cells and using the 13C-tripeptide, we detected a high 13CO2 signal from Caco2 cells. Addition of Sitaglitpin to Caco2 cells significantly inhibited this 13CO2 signal. 13C-assay DPP4 activity correlated positively with the enzyme activity detected using a colorimetric substrate. We have developed a selective, non-invasive, 13C-assay for DPP4 that could have broad translational applications in diabetes and gastrointestinal disease.

Graphical abstract, Dipeptidyl peptidase (DPP)-4 inhibitors are a class of orally available, small molecule inhibitors that prolong the insulinotropic activity of the incretin hormone glucagon-like peptide-1 (GLP-1) and are highly effective for the treatment of Type-2 diabetes. DPP4 can also cleave several immunoregulatory peptides including chemokines. Emerging evidence continues to implicate DPP4 inhibitors as immunomodulators, with recent findings suggesting DPP4 inhibitors modify specific aspects of innate immunity. This review summarises recent insights into how DPP4 inhibitors could be implicated in endothelial, neutrophil and monocyte/macrophage mediated immunity. Additionally, this review highlights additional avenues of research with DPP4 inhibitors in the context of the COVID-19 pandemic.

Individuals with Barrett's esophagus are believed to be at 30-120× risk of developing esophageal adenocarcinoma (EAC). Early detection and endoscopic treatment of dysplasia/early cancer confers a significant advantage to patients under surveillance; however, most do not progress past the non-dysplastic state of Barrett's esophagus (NDBE), which is potentially an inefficient distribution of health care resources.This article aimed to review the outcomes of cost-effectiveness studies reducing low-value care in the context of endoscopic surveillance for non-dysplastic Barrett's esophagus (NDBE).A systematic search was conducted by two reviewers in accordance with PRISMA guidelines.cost-utility analyses of endoscopic surveillance of NDBE patients with at least one treatment strategy focused on reduction of surveillance. A narrative synthesis of economic evaluations was undertaken, along with an in-depth analysis of input parameters contributing to stated Incremental cost-effectiveness ratios (ICER). Study appraisal was performed using the consolidated health economic evaluation reporting standards (CHEERS) tool.10 Studies met inclusion criteria. There was significant variation in cost-model structures, input parameters, ICER values, and willingness-to-pay thresholds between studies. All studies except one concluded guideline-specified endoscopic surveillance for NDBE patients was not cost-effective. Studies that explored a modified surveillance by deselection of low-risk NDBE patients found it to be a cost-effective strategy.Guideline specified endoscopic surveillance for NDBE was not found to be cost-effective in the studies examined. A modified endoscopic surveillance strategy removing individuals with the lowest risk for progression from NDBE to adenocarcinoma is likely to be cost-effective but is dependent on risk profile of patients excluded from surveillance.

Increased consumption of added sucrose and high-fructose corn syrup in the human diet has been associated with increasing incidence of obesity and metabolic disease. There are currently no reliable, objective biomarkers for added sugar intake that could be used in individuals or population settings.

INTRODUCTION: Dipeptidyl peptidase (DPP)-4 is part of a larger family of proteases referred to as DPPs. DPP4 has been suggested as a possible biomarker for inflammatory bowel disease (IBD). Circulating DPP4 (cDPP4) enzyme activity was investigated as a potential biomarker for IBD. In addition, DPP enzyme activity and gene expression were quantified in colonic tissue of patients with IBD and non-IBD. METHODS: In study 1, DPP enzyme activity was quantified in plasma samples from 220 patients with IBD (Crohn's disease [CD] n = 130 and ulcerative colitis [UC] n = 90) and non-IBD controls (n = 26) using a colorimetric assay. In study 2, tissue and plasma samples were collected from 26 patients with IBD and 20 non-IBD controls. Plasma C-reactive protein (CRP) was quantified in all patients. Colonic DPP4, DPP8, DPP9, and fibroblast activation protein (FAP) gene expression was determined by quantitative polymerase chain reaction. cDPP and cFAP enzyme activity was also measured. Sensitivity and specificity were determined by receiver operating characteristic curve analysis. RESULTS: In study 1, total cDPP activity was found to differentiate patients with CD with active disease (n = 18) from those in remission (n = 19; sensitivity 78% and specificity 63%). In study 2, total cDPP and cFAP activity was 28% and 48% lower in patients with elevated CRP (>10 mg/L), respectively, compared with patients with normal CRP. Gene expression of DPP4, FAP, and DPP8 was also significantly higher in colonic biopsies from patients with IBD compared with non-IBD patients (P < 0.05). DISCUSSION: Our findings implicate the DPP enzyme family in intestinal inflammation and suggest future biomarker applications to differentiate the pathophysiological aspects of IBD.

Background: Head and neck squamous cell carcinoma (HNSCC) is the sixth most common form of cancer worldwide, with approximately 630,000 new cases diagnosed each year. The development of low-cost and non-invasive tools for the detection of HNSCC using volatile organic compounds (VOCs) in the breath could potentially improve patient care. The aim of this study was to investigate the feasibility of selected ion flow tube mass spectrometry (SIFT-MS) technology to identify breath VOCs for the detection of HNSCC. Materials and Methods: Breath samples were obtained from HNSCC patients (N = 23) and healthy volunteers (N = 21). Exhaled alveolar breath samples were collected into FlexFoil&reg, PLUS (SKC Limited, Dorset, UK) sampling bags from newly diagnosed, histologically confirmed, untreated patients with HNSCC and from non-cancer participants. Breath samples were analyzed by Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) (Syft Technologies, Christchurch, New Zealand) using Selective Ion Mode (SIM) scans that probed for 91 specific VOCs that had been previously reported as breath biomarkers of HNSCC and other malignancies. Results: Of the 91 compounds analyzed, the median concentration of hydrogen cyanide (HCN) was significantly higher in the HNSCC group (2.5 ppb, 1.6&ndash, 4.4) compared to the non-cancer group (1.1 ppb, 0.9&ndash, 1.3, Benjamini&ndash, Hochberg adjusted p &lt, 0.05). A receiver operating curve (ROC) analysis showed an area under the curve (AUC) of 0.801 (95% CI, 0.65952&ndash, 0.94296), suggesting moderate accuracy of HCN in distinguishing HNSCC from non-cancer individuals. There were no statistically significant differences in the concentrations of the other compounds of interest that were analyzed. Conclusions: This pilot study demonstrated the feasibility of SIFT-MS technology to identify VOCs for the detection of HNSCC.

BACKGROUND Prebiotics selectively stimulate the growth of beneficial bacteria within the gastrointestinal tract, and have been investigated in human and animal studies for their capacity to improve intestinal health. OBJECTIVE We investigated the prebiotics fructo-oligosaccharide (FOS), galacto-oligosaccharide (GOS), and mannan-oligosaccharide (MOS) for their potential to alleviate intestinal damage in rats. METHODS Female Dark Agouti rats (6-8 wk old, 110-150 g) were allocated to 1 of the following treatment groups (n = 8/group): saline/water, saline/FOS, saline/GOS, saline/MOS, 5-fluorouracil (5FU)/water, 5FU/FOS, 5FU/GOS, and 5FU/MOS. Rats were pretreated with either 5% GOS, MOS, or FOS or vehicle (water) from day -12 to day 0. On day 0, rats received a single intraperitoneal injection of saline or 5FU. Metabolic data were recorded daily and all rats were killed on day 3. Histopathology was quantified in hematoxylin and eosin-stained sections. Intestinal sucrase and myeloperoxidase activity were quantified by biochemical assay. Fecal SCFAs-acetic, propionic, and butyric acid-were also measured. Statistical analysis was by repeated-measures, 2-factor ANOVA or Kruskal-Wallis and Mann-Whitney U test; P

IntroductionEnvironmental enteropathy (EE) is suspected to be a cause of growth faltering in children with sustained exposure to enteric pathogens, typically in resource-limited settings. A major hindrance to EE research is the lack of sensitive, non-invasive biomarkers. Current biomarkers measure intestinal permeability and inflammation, but not the functional capacity of the gut. Australian researchers have demonstrated proof of concept for an EE breath test based on using naturally 13C-enriched sucrose, derived from maize, to assay intestinal sucrase activity, a digestive enzyme that is impaired in villus blunting. Here, we describe a coordinated research project to optimise, validate and evaluate the usability of a breath test protocol based on highly enriched 13C-sucrose to quantify physiological dysfunction in EE in relevant target populations.Methods and analysisWe use the 13C-sucrose breath test (13C-SBT) to evaluate intestinal sucrase activity in two phases. First, an optimisation and validation phase will (1) confirm that a 13C-SBT using highly enriched sucrose tracers reports similar information to the naturally enriched 13C-SBT; (2) examine the dose–response relationship of the test to an intestinal sucrase inhibitor; (3) validate the 13C-SBT in paediatric coeliac disease (4) validate the highly enriched 13C-SBT against EE defined by biopsy in adults and (5) validate the 13C-SBT against EE defined by the urinary lactulose:rhamnose ratio (LR) among children in Peru. Second, a cross-sectional study will be conducted in six resource-limited countries (Bangladesh, India, Jamaica, Kenya, Peru and Zambia) to test the usability of the optimised 13C-SBT to assess EE among 600 children aged 12–15 months old.Ethics and disseminationEthical approval will be obtained from each participating study site. By working as a consortium, the test, if shown to be informative of EE, will demonstrate strong evidence for utility across diverse, low-income and middle-income country paediatric populations.Trial registration numberNCT04109352; Pre-results.

Chronic isoleucine supplementation prevents diet-induced weight gain in rodents. Acute-isoleucine administration improves glucose tolerance in rodents and reduces postprandial glucose levels in humans. However, the effect of chronic-isoleucine supplementation on body weight and glucose tolerance in obesity is unknown. This study aimed to investigate the impact of chronic isoleucine on body weight gain and glucose tolerance in lean and high-fat-diet (HFD) induced-obese mice. Male C57BL/6-mice, fed a standard-laboratory-diet (SLD) or HFD for 12 weeks, were randomly allocated to: (1) Control: Drinking water, (2) Acute: Drinking water with a gavage of isoleucine (300 mg/kg) prior to the oral-glucose-tolerance-test (OGTT) or gastric-emptying-breath-test (GEBT), (3) Chronic: Drinking water with 1.5% isoleucine, for a further six weeks. At 16 weeks, an OGTT and GEBT was performed and at 17 weeks metabolic monitoring. In SLD- and HFD-mice, there was no difference in body weight, fat mass, and plasma lipid profiles between isoleucine treatment groups. Acute-isoleucine did not improve glucose tolerance in SLD- or HFD-mice. Chronic-isoleucine impaired glucose tolerance in SLD-mice. There was no difference in gastric emptying between any groups. Chronic-isoleucine did not alter energy intake, energy expenditure, or respiratory quotient in SLD- or HFD-mice. In conclusion, chronic isoleucine supplementation may not be an effective treatment for obesity or glucose intolerance.

Cancers of the head and neck region are a severely disabling group of diseases with no method for early detection. Analysis of exhaled breath volatile organic compounds shows promise as biomarkers for early detection and disease monitoring. This article reviews breath analysis in the setting of head and neck cancer, with a practical focus on breath sampling techniques, detection technologies and valid data analysis methods. Title and abstract keyword searches were conducted on PubMed and Embase databases to identify English language studies without a time-period limitation. The main inclusion criteria were human studies comparing head and neck cancer patients to healthy controls using exhaled breath analysis. Multiple breath collection techniques, three major detection technologies and multiple data analysis methods were identified. However, the variability in techniques and lack of methodological standardization does not allow for adequate study replication or data pooling. Twenty-two volatile organic compounds identified in five studies have been reported to discriminate head and neck cancer patients from healthy controls. Breath analysis for detection of head and neck cancer shows promise as a non-invasive detection tool. However, methodological standardization is paramount for future research study design to provide the potential for translating these techniques into routine clinical use.

Dipeptidyl peptidase-4 inhibitors (DPP4i) are a class of orally available, small molecule inhibitors for the management of Type-II diabetes. A rapid, real-time, functional breath test for DPP4 enzyme activity could help to define DPP4i efficacy in patients that are refractory to treatment. We aimed to develop a selective, non-invasive, stable-isotope 13C-breath test for DPP4. In vitro experiments were performed using high (Caco-2) and low (HeLa) DPP4 expressing cells. DPP gene expression was determined in cell lines by qRT-PCR. A DPP4 selective 13C-tripeptide was added to cells in the presence and absence of the DPP4 inhibitor Sitagliptin. Gas samples were collected from the cell headspace and 13CO2 content quantified by isotope ratio mass spectrometry (IRMS). DPP4 was highly expressed in Caco-2 cells compared to HeLa cells and using the 13C-tripeptide, we detected a high 13CO2 signal from Caco2 cells. Addition of Sitaglitpin to Caco2 cells significantly inhibited this 13CO2 signal. 13C-assay DPP4 activity correlated positively with the enzyme activity detected using a colorimetric substrate. We have developed a selective, non-invasive, 13C-assay for DPP4 that could have broad translational applications in diabetes and gastrointestinal disease.

The importance of the dipeptidyl peptidase 4 (DPP4) gene family in regulating critical biochemical pathways continues to emerge. The two most well-studied members of the family, DPP4 and fibroblast activation protein (FAP), have been investigated both as therapeutic targets for disease and as diagnostic biomarkers. The interest in DPP4 and FAP as potential disease biomarkers has been driven primarily by observations of altered expression profiles in inflammatory diseases and cancer. Furthermore, the stability and persistence of soluble DPP4 and FAP in the serum make them attractive candidate serology markers. This review summarises investigations into DPP4 and FAP as biomarkers of autoimmune disease, gut inflammation, psychosomatic disorders and malignancy and discusses their potential likelihood as clinically useful tools.

Oesophageal cancer is a significant cause of cancer related mortality, with increasing incidence worldwide. Ornithine decarboxylase (ODC) is an enzyme involved in polyamine synthesis and cellular proliferation, and ODC expression and activity has been implicated as a prognostic marker of oesophageal cancer. This study aimed to develop and optimise an in vitro (13)C-stable isotope assay for ODC activity as a non-invasive marker of oesophageal cancer. Experiments were performed in triplicate (n = 3/group/cell line) using Caco2, HeLa, Flo-1, OE33, TE7 and OE21 cell lines (colorectal, cervical, oesophageal adenocarcinoma and oesophageal squamous carcinoma respectively). Following addition of 2mM (13)C-ornithine to cells, 10 ml gas samples were collected from the headspace every 20 min for a total of five hours. Gas samples were analysed using isotope ratio mass spectrometry to quantify (13)CO2. Assay specificity was determined using the selective ODC inhibitor, N-(4'-Pyridoxil)-Ornithine(BOC)-OMe (POB). All data is expressed as δ (13)CO2 from baseline. High ODC activity was detected by (13)C-ornithine assay in Caco2 (32.00 ± 1.12 δ (13)CO2) in contrast to HeLa cells (5.44 ± 0.14 δ (13)CO2) cells. POB inhibited activity in Caco2 cells to 12.87 ± 1.10 δ (13)CO2. Differential ODC activity was detected in all oesophageal cancer cells, and 53 h incubation of cell lines with POB reduced activity by 72%, 56%, 64% and 69% in the Flo-1, OE33, OE21 and TE7 cell lines respectively. We have shown that ODC activity can be selectively detected by a non-invasive, stable-isotope (13)C-ornithine assay. ODC activity was detected in all oesophageal cancer cell lines in vitro. Further studies are indicated to quantify ODC activity in oesophageal cancer patients.