American journal of physiology. Gastrointestinal and liver physiology最新文献

Introduction: The objective of the present study was to introduce a novel method assessing anal canal opening in healthy volunteers (HV) using the EndoFLIP^™ system. By analyzing dynamic loops during push maneuver, the study aimed to identify the most reliable markers of anal canal opening function during this maneuver. Methods: Forty HV women were recruited and underwent anal canal assessments with the EndoFLIP^™ system, both at rest and during push maneuver. Cross-sectional area (CSA)-pressure loops were constructed for each HV at distension volumes of 40 mL and 50 mL. Key parameters (pressure and CSA) derived from these loops were identified as potential markers of anal function to reduce dimensionality. Anal opening function during push maneuver was quantified in both percentage (relative variation) and absolute (absolute variation) values for pressure and CSA. Results: The direction of the CSA-pressure loops during push maneuver at 40 mL and 50 mL of distension was upward and to the right, indicating an increase in both pressure and CSA during straining. None of the demographic data were significant predictors of any characteristics of the CSA-pressure loops at 40 mL and 50 mL of distension. The mean relative variation in pressure and CSA at 50 mL of distension and, to a lesser extent, the maximal relative variation pressure and CSA, were identified as markers with the lowest variability. Conclusion: This pilot study points to potential markers for assessing anal opening function during push maneuver. Further confirmatory studies are necessary to establish the clinical utility of these markers.

Considerable evidence suggests the gut-brain axis can influence behaviour. However, there has been a conspicuous lack of technology to provide targeted wireless activation of the gut-brain axis in conscious freely moving animals. We utilised a miniature fully implantable battery-free device to apply highly controlled optogenetic stimuli to the terminal region of GI-tract, in conscious freely moving mice. The optical stimulator was implanted and secured on the serosal surface of the distal colon and rectum to characterize the behavioural responses evoked by optogenetic stimulation of axons expressing channelrhodopsin (ChR2) driven by the Trpv1 promoter (Trpv1^cre+ ChR2 mice). In freely moving Trpv1^cre+ ChR2 mice, trains of blue light pulses to the distal colon and rectum induced increased abdominal grooming and reduced movement. In contrast to stimulation of the gut, trains of stimuli applied to the peritoneal cavity evoked writhing and abdominal contraction. Anterograde labelling from nodose ganglia revealed sparse vagal afferent axons and endings in the proximal and mid colon, with no labelled axons caudal of the mid colon (within 30 mm of the anus). The distal colon and rectum were densely innervated by spinal afferents. The findings demonstrate that wireless optogenetic stimulation of the gut-brain axis can induce specific behavioural patterns in conscious freely moving rodents, using fully implantable battery-free technology.

The global prevalence of ulcerative colitis (UC) and Crohn's disease (CD) is increasing, placing greater burdens on national health systems. The pathophysiology of diarrhea, the commonest debilitating symptom in UC and CD patients, has been studied more extensively in UC, where it reflects defective colonic Na⁺ absorption combined with changes in colonic Cl^- and K⁺ transport which greatly reduce colonic water absorption. Dysfunctional ion transport in patients with UC is accompanied by abnormalities in tight junctional protein distribution and function, which cause the inflamed colonic epithelium to become 'leakier'. Progress in understanding how abnormal colonic ion transport in UC might be influenced pharmacologically has been hampered by the low availability of clinical material. To counter this, various animal models of acute colitis have been developed, but differ in the way mucosal inflammation is induced. Identifying models that closely mimic human UC in terms of pathology and ion transport abnormalities remains challenging. However, the introduction of human colonic epithelial organoids (colonoids) has added a new and exciting dimension to research in this area. Here, we review current knowledge about abnormal colonic ion transport and barrier function in experimental and human colitis as well as the use and potential of human colonoids to better understand the pathophysiology of UC, which may ultimately lead to novel approaches to the treatment of diarrhea in this disease.

The swallowing reflex can be induced by peripheral stimulation of the larynx. Although previous studies have suggested that potassium ions exert facilitatory effects on the initiation of swallowing, little information is available on the mechanism underlying the potassium ion-evoked swallowing reflex. In this study, we evaluated the effects of potassium ions on peripheral afferent responses and the initiation of swallowing in conscious and anesthetized rats. Furthermore, the possible receptors involved were explored. The topical application of potassium chloride (KCl) significantly facilitated the swallowing reflex; these facilitatory effects were more prominent than those of distilled water (DW) or sodium chloride (NaCl). This phenomenon depended not on the concentrations of anions but on those of potassium ions. The potassium ion-induced response in the superior laryngeal nerve was most prominent after treatment with KCl, especially at the early stage. In chronic rats, without differences in licking behavior between DW, NaCl, and KCl, the intervals between swallows were the smallest during KCl-associated licking. Inward rectifier potassium channel (Kir)3.1- and Kir6.2-positive cells were detected in the nodose ganglion and vocal folds. The rate of expression of these molecules in immunoreactive cells was relatively high at 74.1% for Kir3.1 and 75.3% for Kir6.2. Kir3.1- and Kir6.2- blockers significantly decreased the number of KCl-induced swallows. Possible mechanisms underlying potassium ion-induced swallowing are discussed. Our findings suggest that Kir3.1 and Kir6.2 are involved in K ion-induced swallowing in rats.

Background: Nonalcoholic fatty liver disease (NAFLD) is an increasing global health concern. Approximately one-quarter of patients have non-alcoholic steatohepatitis (NASH), which leads to the development of hepatocellular carcinoma. Several studies have shown the involvement of iron in NASH, but it remains unclear which cell of iron is at issue.

Aim: To explore the role of iron in macrophages in NASH development.

Methods: Conditional macrophage-specific H-ferritin knockout (LysM-Cre FthKO) mice were divided into four groups: wild-type (WT) and LysM-Cre FthKO mice fed a normal diet, and WT and LysM-Cre FthKO mice with NASH model induced by diet and chemical.

Results: Histological analysis revealed that the NAS score and hepatic fibrosis were alleviated in the livers of LysM-Cre FthKO mice with NASH compared with WT mice with NASH. The expression and signaling of inflammatory cytokines and fibrosis-related genes were increased in the livers of WT mice with NASH, but not elevated in the livers of LysM-Cre FthKO mice with NASH. Similarly, macrophage infiltration and oxidative stress were augmented in the livers of WT mice with NASH but were inhibited in the livers of LysM-Cre FthKO mice with NASH. Additionally, hepatocellular carcinoma development was observed in 90% of WT mice and 62% of LysM-Cre FthKO mice 30 weeks after NASH induction, with tumor number and size being lower in LysM-Cre FthKO mice.

Conclusions: Deletion of macrophage FTH alleviated NASH development by reducing inflammation, fibrosis, and oxidative stress. The findings of this study highlight macrophage iron levels as a potential therapeutic target in NASH.

Background & Aims: Normothermic machine perfusion (NMP) is used to preserve and assess the viability of (extended criteria) high-risk donor livers. Long-term NMP (LT-NMP; ≥24h) is emerging as a method to improve or repair livers initially deemed unsuitable for transplantation. This study investigated metabolism during LT-NMP, focusing on hepatic energy consumption and nitrogen and electrolyte balances to better understand long-term perfusion requirements. Methods: In this study, we measured oxygen consumption (V̇ CO2) and carbon dioxide production (V̇ O₂) to determine the energy expenditure of 14 human livers during LT NMP for 7 days. Additionally, hepatic balances of glucose and lactate, as well as of nitrogen and electrolytes were determined. Results: Initial high metabolic rates during the first day of LT-NMP decreased and stabilized at nearly 50% on day 3, suggesting a quiescent state until day 7. Most energy was derived from glucose (75-88%). Continuous amino acid supplementation was essential to maintain an anabolic state, whereas livers without supplementation became catabolic. While net electrolyte balances were close to zero, significant uptake and release of electrolytes occurred throughout LT-NMP. Conclusions: During LT-NMP, livers reached a metabolically quiescent state after 3 days with decreased energy consumption. Tailoring perfusate composition and supplementation protocols to the specific needs of the liver could enhance organ preservation and potentially expand the pool of viable donor livers after LT-NMP.

Circulating monocytes (Mo) are precursors to a subset of gastric resident muscularis macrophages. Changes in muscularis macrophages (MMs) result in delayed gastric emptying (DGE) in diabetic gastroparesis. However, the dynamics of Mo in the development of DGE in an animal model are unknown. Using cytometry by time-of-flight and computational approaches, we show a high heterogeneity within the Mo population. In DGE mice, via unbiased clustering, we identified two reduced Mo clusters that exhibit migratory phenotype (Ly6C^hiCCR2^hi-intCD62L^hiLy6G^hiCD45R^hiMERTK^hiintLGALS3^intCD14^intCX3CR1^lowSiglec-H^int-low) resembling classical Mo (CMo-like). All markers enriched in these clusters are known to regulate cell differentiation, proliferation, adhesion, and migration. Trajectory inference analysis predicted these Mo as precursors to subsequent Mo lineages. In gastric muscle tissue, we demonstrated an increase in the gene expression levels of chemokine receptor C-C chemokine receptor type 2 (Ccr2) and its C-C motif ligand 2 (Ccl2), suggesting increased trafficking of classical-Mo. These findings establish a link between two CMo-like clusters and the development of the DGE phenotype and contribute to a better understanding of the heterogenicity of the Mo population.NEW & NOTEWORTHY Using 32 immune cell surface markers, we identified 23 monocyte clusters in murine blood. Diabetic gastroparesis was associated with a significant decrease in two circulating classical monocyte-like clusters and an upregulation of the Ccr2-Ccl2 axis in the gastric muscularis propria, suggesting increased tissue monocyte migration. This study offers new targets by pointing to a possible role for two classical monocyte subsets connected to the Ccr2-Ccl2 axis.

The gastrointestinal tract is made up of specialized organs that work in tandem to facilitate digestion. The colon regulates the final steps in this process where complex motor patterns in proximal regions facilitate the formation of fecal pellets that are propelled along the distal colon via self-sustaining neural peristalsis and temporarily stored before defecation. Historically, our understanding of colonic motility has focused primarily on distal regions, and the intrinsic reflex circuits of the enteric nervous system involved in neural peristalsis have been defined, but we do not yet have a clear grasp on the mechanisms orchestrating motor function in proximal regions. New approaches have brought to the forefront the unique structural, neurochemical, and functional characteristics that exist in distinct regions of the mouse and human colon. In this mini-review, we highlight key differences along the proximal-distal colonic axis and discuss how these differences relate to region-specific motor function.

Introduction: In functional dyspepsia, increased gut permeability, low-grade inflammation and altered sensorimotor function have been reported. Both stress and corticotropin-release hormone(CRH) have been shown to increase small bowel permeability in a mast-cell dependent fashion. Moreover, eosinophil-derived CRH has been implicated in mast-cell activation. The aim of this study was to evaluate whether CRH administration alters duodenal permeability and immune activation in healthy volunteers(HVs). Methods: An intravenous bolus of 100μg CRH or placebo was administered in HVs in a crossover, double-blind, randomized fashion. Two hours later, a gastroscopy was performed to measure permeability in Ussing chambers and to count mast-cells and eosinophils on duodenal biopsies. Supernatant was assessed for eosinophil-derived neurotoxin(EDN), tryptase and chymase. In addition, CRH was administrated ex-vivo to baseline biopsies pretreated with or without lodoxamide. Results are described as mean±SD. p-values<0.05 were considered significant. Results: Twenty HVs completed the study. Mast-cell or eosinophil counts were not significantly altered after CRH versus placebo(respectively p=0.31 and p=0.069). Tryptase but not chymase, significantly decreased after CRH (resp. p=0.037 and p=0.44) with a trend for a decrease in EDN(p=0.053). Permeability was unaltered comparing both conditions. Ex-vivo, transepithelial electrical resistance significantly decreased after CRH exposure compared to baseline(p=0.010), which was not prevented by pre-treatment with lodoxamide. Conclusion: In-vivo CRH administration reduced tryptase levels in supernatant of duodenal biopsies without affecting permeability, whereas ex-vivo duodenal permeability increased regardless of mast51 cell stabilization. These results suggest the involvement of mast-cells in regulating gut permeability in HVs in response to CRH, possibly influenced by in-vivo compensatory mechanisms.