Reuben K. Wong

Combat‐training increases intestinal permeability, immune activation and gastrointestinal symptoms in soldiers

Gastrointestinal (GI) symptoms are common in soldiers in combat or high‐pressure operational situations and often lead to compromised performance. Underlying mechanisms are unclear, but neuroendocrine dysregulation, immune activation and increased intestinal permeability may be involved in stress‐related GI dysfunction.

Visceral and somatic sensory function in functional dyspepsia.

Background  Visceral hypersensitivity is one of the proposed underlying mechanisms in functional dyspepsia (FD). It is not clear whether visceral hypersensitivity in FD is a manifestation of a central sensitization also encompassing somatic sensitization. Transient receptor potential vanilloid‐1 (TRPV1) pathways are involved in gastric mechanosensory physiology and the TRPV1 receptor agonist, capsaicin, has been used as a chemical stimulant.

Fructose transporters GLUT5 and GLUT2 expression in adult patients with fructose intolerance

Background Gastrointestinal symptoms and malabsorption following fructose ingestion (fructose intolerance) are common in functional gastrointestinal disorders (FGID). The underlying mechanism is unclear, but is hypothesized to be related an abnormality of intestinal fructose transporter proteins. Objective To assess the expression of the main intestinal fructose transporter proteins, glucose transport protein 5 (GLUT5) and 2 (GLUT2), in FGID. Methods The expression of GLUT5 and GLUT2 protein and mRNA in small intestinal biopsy tissue was investigated using real-time reverse-transcription PCR and Western immunoblotting in 11 adults with FGID and fructose intolerance ascertained by breath testing and in 15 controls. Results Median expression levels of GLUT5 mRNA normalized to beta-actin were 0.18 (interquartile range, IQR, 0.13–0.21) in patients and 0.17 (IQR 0.12–0.19) in controls (p > 0.05). Respective levels of GLUT2 mRNA were 0.26 (IQR 0.20–0.31) and 0.26 (IQR 0.19–0.31) (p > 0.05). Median expression levels of GLUT5 protein normalized to alpha-tubulin were 0.95 (IQR 0.52–1.68) in patients and 0.95 (IQR 0.59–1.15) in controls (p > 0.05). Respective protein expression levels for GLUT2 were 1.56 (IQR 1.06–2.14) and 1.35 (IQR 0.96–1.79) (p > 0.05). Conclusions Human fructose intolerance may not be associated with marked changes in GLUT5 and GLUT2 expression. Replication of these results in a larger subject group, including measures of transporter activation and membrane and subcellular localization, is warranted.

Gastrointestinal Symptoms and Altered Intestinal Permeability Induced by Combat Training Are Associated with Distinct Metabotypic Changes

Physical and psychological stress have been shown to modulate multiple aspects of gastrointestinal (GI) physiology, but its molecular basis remains elusive. We therefore characterized the stress-induced metabolic phenotype (metabotype) in soldiers during high-intensity combat training and correlated the metabotype with changes in GI symptoms and permeability. In a prospective, longitudinal study, urinary metabotyping was conducted on 38 male healthy soldiers during combat training and a rest period using gas chromatography-mass spectrometry. The urinary metabotype during combat training was clearly distinct from the rest period (partial least-squares discriminant analysis (PLSDA) Q(2) = 0.581), confirming the presence of a unique stress-induced metabotype. Differential metabolites related to combat stress were further uncovered, including elevated pyroglutamate and fructose, and reduced gut microbial metabolites, namely, hippurate and m-hydroxyphenylacetate (p < 0.05). The extent of pyroglutamate upregulation exhibited a positive correlation with an increase in IBS-SSS in soldiers during combat training (r = 0.5, p < 0.05). Additionally, the rise in fructose levels was positively correlated with an increase in intestinal permeability (r = 0.6, p < 0.005). In summary, protracted and mixed psychological and physical combat-training stress yielded unique metabolic changes that corresponded with the incidence and severity of GI symptoms and alteration in intestinal permeability. Our study provided novel molecular insights into stress-induced GI perturbations, which could be exploited for future biomarker research or development of therapeutic strategies.

Dysfunctional endogenous pain modulation in patients with functional dyspepsia

Endogenous pain modulation (EPM) is central to the processing of sensory information. Visceral and somatic EPM are abnormal in irritable bowel syndrome, but have not been studied in functional dyspepsia (FD).

Characterization of a reproducible gastric pain model using oral capsaicin titration in healthy volunteers.

Background  Sensory sensitization is one of the main pathophysiological hypotheses in functional gastrointestinal disorders (FGIDs). As sensitization may affect various sensory modalities, we aimed to develop a reproducible gastric pain model utilizing polymodal pathways for use in functional and other pain disorders.

Visceral pain perception in patients with irritable bowel syndrome and healthy volunteers is affected by the MRI scanner environment.

Background The MRI scanner environment induces marked psychological effects, but specific effects on pain perception and processing are unknown and relevant to all brain imaging studies. Objectives and methods We performed visceral and somatic quantitative sensory and pain testing and studied endogenous pain modulation by heterotopic stimulation outside and inside the functional MRI scanner in 11 healthy controls and 13 patients with irritable bowel syndrome. Results Rectal pain intensity (VAS 0–100) during identical distension pressures increased from 39 (95% confidence interval: 35–42) outside the scanner to 53 (43–63) inside the scanner in irritable bowel syndrome, and from 42 (31–52) to 49 (39–58), respectively, in controls (ANOVA for scanner effect: p = 0.006, group effect: p = 0.92). The difference in rectal pain outside versus inside correlated significantly with stress (r = −0.76, p = 0.006), anxiety (r = −0.68, p = 0.02) and depression scores (r = −0.67, p = 0.02) in controls, but not in irritable bowel syndrome patients, who a priori had significantly higher stress and anxiety scores. ANOVA analysis showed trends for effect of the scanner environment and subject group on endogenous pain modulation (p = 0.09 and p = 0.1, respectively), but not on somatic pain (p > 0.3). Conclusion The scanner environment significantly increased visceral, but not somatic, pain perception in irritable bowel syndrome patients and healthy controls in a protocol specifically aimed at investigating visceral pain. Psychological factors, including anxiety and stress, are the likely underlying causes, whereas classic endogenous pain modulation pathways activated by heterotopic stimulation play a lesser role. These results are highly relevant to a wide range of imaging applications and need to be taken into account in future pain research. Further controlled studies are indicated to clarify these findings.

769 Is There Somatic Hypersensitivity and Central Sensitization in Functional Dyspepsia (FD)

Results: Compared to BBDR rats (n=5), LMMP preparations from normoglycemic BBDP rats (n=8) had higher MPO levels (0.0±0.0 vs. 5.4±2.2 U/mg, p<0.01), lower GRP78 mRNA expression (1.0±0.1 vs. 0.5±0.1, p<0.01) and lower PERK mRNA expression (1.0±0.1 vs. 0.4±0.2, p<0.05). A significant linear correlation was obserbed between mucosal and LMMP expression of GRP78 mRNA (p<0.01, r = 0.72; Figure1). In LMMP, a significant linear correlation was also observed between MPO levels and GRP78 mRNA expression (p<0.05, r = -0.65). Compared to BBDR rats, BBDP rats had lower mucosal GRP78 mRNA expression (1.0±0.1 vs. 0.4±0.1, p<0.001), lower IREα mRNA expression (1.0±0.2 vs. 0.5±0.1, p= 0.07), lower IREβ mRNA expression (1.0±0.2 vs. 0.3±0.2, p<0.01) and lower PERK mRNA expression (1.0±0.2 vs. 0.3±0.1, p<0.01). Conclusion: ER stress response was impaired in the inflamed intestine in BBDP-rats, both in mucosa and LMMP. Impaired ER stress response may contribute to the pathogenesis of increased permeability and intestinal dysmotility.

75 In Combat Soldiers Resting Urinary Metabotypes Correlate With the Development of Gastrointestinal Symptoms During Stress

Introduction: Western-diet (WD) is associated with reduced stool frequency in humans. High-fat fed mice exhibit delayed gastrointestinal (GI) transit associated with reduced number of nitrergic myenteric neurons. Mechanisms of these alterations are still unknown. Our aim was to investigate if WD feeding leads to modifications of fecal metabolites associated with the development of enteric neurodegeneration and the role played by the gut microbiota in such phenomenon. Methods: C57Bl/6 mice were fed a WD (34.5% kcal from fat, representative of the typical American diet fat calorie intake, n=5) or a Regular diet (RD, 16.9% kcal from fat, n=5). 6 weeks post feeding, fecal metabolites were analyzed by high-resolution mass spectrometry (LTQ-FT). 12 weeks post feeding, nitrergic myenteric neurons were quantified in the proximal colon by NADPH-diaphorase staining and GI and colonic transit were measured. Citrulline was measured by ELISA in germ-free (GF) mice stools fed a WD or a RD for 6 weeks (n=3 per group). Data are presentedas mean ± SEM and are significant to p < 0.05. Results: After 12 weeks of feeding, WD mice exhibited a reduced stool frequency in comparison to RD mice (1.5±0.5 and 4.4±0.3 stools/min, respectively) and this was associated with a delayed intestinal transit time (281.5±57.5 and 152.8±15.7 min). In addition, WD mice had a longer colonic transit time (as measured by bead expulsion time: WD: 127.5±52.5 min; RD: 13.2±2.0 min) associated with reduced number of nitrergic myenteric neurons in the proximal colon (113.0±5.6 and 64.2±7.4 neurons/field). Together, these data demonstrate an altered colonic motor function after 12 weeks of WD. We quantified 3730 metabolites in the feces but only 185 were significantly higher in WD mice compared to RD mice. In addition to palmitate, we found increased concentrations of citrulline (associated with enhanced nitric oxide synthase activity), 3-hydroxykynurenine (reflecting neuroinflammation) and bacterial muramic acid [Figure 1]. In order to understand the possible role of the gut microbiota in these changes, we measured fecal citrulline in GF mice fed a WD or a RD for 6 weeks and found similar concentrations (3.0±0.5 and 2.6±0.3 ng/mg). Conclusion: Our results show that long-term WD consumption is associated with nitrergic myenteric neuronal loss contributing to delayed GI transit. These alterations were preceded by gut dysbiosis and elevated fecal citrulline, potentially reflecting higher plasma concentrations that lead to oxidative stress and apoptosis in NO producing neurons. Importantly, fecal citrulline was not affected by a WD feeding under germfree conditions, suggesting that the gut microbiota is required for such effects. Fecal citrulline may be considered as a marker of myenteric neuronal impairments responsible for the motor alterations observed during WD feeding.

Su2063 There Is No Relationship Between the Fructose Transporter, GLUT5 and GLUT2, Protein or mRNA Expression Levels in Irritable Bowel Syndrome With Fructose Malabsorption and Intolerance

Purpose: Poor sleep is commonly reported by patients with IBS. When stressed prior to bedtime patients with IBS show dysregulation of the pituitary-adrenal axis during sleep. Evidence suggests the tryptophan (TRP) metabolic pathways are also altered in patients with IBS. Our purpose was to determine whether alterations in TRP metabolism may be linked to cortisol in women with and without IBS. Methods: Women, ages 18-45, (n=46 IBS [Rome III]; controls [C; n=24]) were studied in a sleep laboratory and serum samples obtained on the third night following the introduction of a social stressor (anticipation of public speaking). Samples were obtained 2 hours following sleep onset (time 1) and 1 hour prior to awakening (time 2). All subjects completed a demographic data sheet, Rome III Diagnostic Questionnaire for Functional GI Disorders, Pittsburgh Quality Sleep Index (PSQI) and 28-day symptom diaries. Serum cortisol levels were determined by ELISA and metabolite levels by targeted liquid chromatography-mass spectrometry (LC-MS). Results: More women with IBS reported symptoms of insomnia (PSQI) as compared to C group (40% versus 24%) and reduced sleep efficiency by polysomnography (p<0.05). As reported previously cortisol/ACTH ratios were higher in IBS as compared to C women. Of the 6 kyneurinine pathway metabolites (primary TRP metabolic route) only niacinamide was significantly higher in women with IBS. However, 5-hydroxytryptophan levels were higher (p<.052) in women with IBS. None of the 3 methylation metabolites were significantly different between IBS and Cs. When ratios of metabolites were calculated significant differences were observed as shown in Table 1. Significant negative correlations between cortisol/ACTH and 5-hydroxytryptophan, methionine, kyneurinine, and betaine were found at one or both time points. TRP levels were significantly correlated with sleep quality (diary) in the IBS group. Conclusion: Nighttime levels of cortisol/ACTH are associated with metabolites in the TRP metabolic pathway particularly those associated with methylation. Whether these associations fully account for the frequent reports of poor sleep in women with IBS requires further study. Table 1