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

Ethanolamine phosphate phospholyase (ETNPPL) is an enzyme that irreversibly degrades phosphoethanolamine (p-ETN), an intermediate in the Kennedy pathway of phosphatidylethanolamine (PE) synthesis. Whole body knockout Etnppl mice were fed a high-fat diet (HFD) containing 45% kcal fat for 10 wk. Etnppl^-/- female mice were resistant to HFD-induced obesity and had decreased liver weight compared with Etnppl^+/+ mice. Furthermore, Etnppl^-/- female mice had improved glucose sensitivity and increased energy expenditure compared with Etnppl^+/+ mice. Plasma triglyceride (TG) levels were elevated in Etnppl^-/- female mice, although the rate of very low-density lipoprotein (VLDL) secretion was not increased. The hepatic expression of PCSK9 was elevated, indicating a possible decrease in VLDL uptake. Interestingly, both plasma and hepatic cholesterol levels were reduced in Etnppl^-/- relative to Etnppl^+/+ mice. No difference in hepatic phosphatidylcholine, PE, or TG was detected between groups. Histopathological examination of hepatic tissues revealed decreased lipid deposition in Etnppl^-/- mice that may be explained by the lower hepatic cholesterol level. Additionally, RNA sequencing analysis showed upregulation in genes related to cholesterol metabolism in Etnppl^-/- female mice. In male mice, a slight decrease in weight gain was observed in Etnppl^-/- mice compared with Etnppl^+/+ mice. No change in plasma and hepatic lipid levels was detected in Etnppl^-/- male mice. To conclude, ETNPPL impacts whole body energy expenditure, weight gain, cholesterol metabolism, and hepatic lipoprotein metabolism without altering hepatic phospholipid levels.NEW & NOTEWORTHY Etnppl^-/- female mice resisted diet-induced obesity with enhanced energy expenditure and less adipose tissue. In addition, Etnppl^-/- female mice fed an HFD showed decreased liver cholesterol deposition. RNA sequencing revealed changes in genes related to cholesterol and lipid metabolism in Etnppl^-/- female mice. Etnppl^-/- female mice fed an HFD supplemented with cholesterol had no difference in plasma and hepatic cholesterol levels compared with Etnppl^+/+ mice.

Epithelial cell death and compromised barrier function are key features of inflammatory bowel disease pathogenesis. Previous studies suggest that the nuclear bile acid receptor, farnesoid X receptor (FXR), promotes intestinal barrier function and protects against inflammation. Here, we investigated potential mechanisms involved. T₈₄ cell monolayers were treated with a combination of IFNγ and TNFα to model cytokine-induced barrier dysfunction in vitro. Apoptosis and necroptosis were assessed by measuring caspase 3/PARP cleavage and RIP3 phosphorylation, respectively. Epithelial permeability was determined by measuring 4-kDa fluorescein isothiocyanate-dextran (FD4) flux. Effects of FXR on barrier function in dextran sulfate sodium (DSS)-treated mice were assessed by measuring plasma levels of orally administered FD4. Treatment with IFNγ and TNFα enhanced FD4 flux and increased apoptosis in T₈₄ monolayers, as evidenced by increased cleaved PARP and caspase 3 levels. Pretreatment with the FXR agonist, GW4064, significantly inhibited cytokine-induced FD4 flux, but not apoptosis. Treatment with IFNγ and TNFα in the presence of the apoptosis inhibitor, Q-VD-OPh, induced necroptosis, as evidenced by increased RIP3 phosphorylation and enhanced FD4 flux, whereas a necroptosis inhibitor, necrostatin, inhibited these effects. GW4064 also inhibited cytokine-induced RIP3 phosphorylation and FD4 flux in the presence of Q-VD-OPh. In mice, treatment with the FXR agonist, obeticholic acid, attenuated DSS-induced disease activity and mucosal FD4 flux, but not levels of cleaved caspase 3 or phospho-RIP3. FXR activation inhibits cytokine-induced barrier dysfunction by inhibiting epithelial necroptosis rather than apoptosis in vitro. How such effects contribute to the protective actions of FXR in vivo requires further elucidation.NEW & NOTEWORTHY These studies demonstrate for the first time that FXR activation inhibits cytokine-induced necroptosis in vitro, an effect that may underlie protection against dysregulated barrier function in the setting of intestinal inflammation. These data support the potential for targeting FXR to promote epithelial barrier function in treatment of IBD.

Probiotics have been suggested to ameliorate intestinal epithelial homeostasis and barrier function. They also modulate several mediators and receptors of the expanded endocannabinoid system, or endocannabinoidome (eCBome), potentially explaining their beneficial effects on intestinal function. We aimed to study the effects of probiotic strains on gut barrier functions and the possible involvement of the eCBome in these effects. We cocultured three strains of Lactiplantibacillus plantarum with murine small intestine epithelial organoids and explored the involvement of eCBome signaling and inflammation in mediating the beneficial effects of the probiotics on the epithelial barrier function. All three L. plantarum strains reduced the transepithelial permeability of organoids and increased mRNA expression of several tight junction proteins (Clnd1, Clnd2, Ocln, Tjp1, and Cdh1) and intestinal barrier proteins (Muc2, Lyz1, Reg3a, and Defa20). Concomitantly, the three strains increased the expression of genes encoding eCBome receptors while decreasing the expression of two catabolic enzymes (Faah and Naaa), and increasing one anabolic enzyme (Daglb). Altogether, these changes led to an overall increase in levels of eCBome mediators, namely N-acyl-ethanolamines (NAEs) and, particularly, 2-monoacylglycerols (2-MAGs), as measured by LC-MS/MS. URB 597 and JZL 184, two selective inhibitors of NAE and 2-MAG catabolism, reduced the transepithelial permeability of organoids, as observed with L. plantarum strains. Interestingly, both inhibitors also reversed inflammation-induced transepithelial permeability in organoids. Elevated endogenous levels of NAEs or 2-MAGs promote improvement in small intestine transepithelial permeability, and L. plantarum strains may exploit this mechanism to exert this same beneficial effect.NEW & NOTEWORTHY Lactiplantibacillus plantarum strains improve transepithelial permeability and concomitantly increase the levels of eCBome mediators in murine small intestine epithelial organoids. Pharmacological elevation of NAE or 2-MAG levels enhances the expression of intestinal epithelial barrier genes and reduces the transepithelial permeability of murine small intestine epithelial organoids, suggesting that L. plantarum may exploit eCBome signaling to exert its beneficial effects.

Glia maturation factor-β (Gmfb), an actin filament debrancher, was initially identified in brain and recently linked to liver diseases. To investigate the role of hepatocyte Gmfb (hep-Gmfb) in liver reparative regeneration, hepatocyte-specific gmfb knockout (HepGKO) and overexpression (HepGOE) zebrafish strains were constructed. Both transgenic and wild-type (WT) zebrafish underwent partial hepatectomy (PHX) or were fed high-fat, high-cholesterol diets to model metabolism-associated steatotic liver disease (MASLD). Under physiological conditions, the HepGKO, HepGOE, and WT fish displayed similar survival, gross appearance, and liver histology. Following PHX, WT liver gmfb levels positively correlated with cell proliferation and proinflammatory cytokine levels. HepGOE showed enhanced regeneration and reduced liver steatosis compared with WT, whereas HepGKO exhibited opposite effects. In MASLD, WT liver gmfb increased with disease progression. HepGKO experienced worsening liver enlargement, steatosis, ballooning, inflammation, and endoplasmic reticulum stress, whereas HepGOE showed improvements. HepGOE liver had the highest cell proliferation, but all three groups showed similar levels of cell apoptosis. Moreover, elevated proinflammatory cytokines were observed across MASLD groups, being the highest in HepGKO and lowest in HepGOE. However, signal transducer and activator of transcription 3 (stat3) activation was the lowest in HepGKO and highest in HepGOE, whereas jnk and mapk/extracellularly regulated kinase (erk) activation was consistent across the MASLD groups. In il6-treated primary hepatocytes, gmfb abundance influenced stat3 activation, and hep-gmfb abundance significantly affected actin filaments distribution in hepatocytes both in vivo and vitro. Hep-Gmfb boosts regenerative processes by enhancing hepatocyte proliferation, alleviating fatty liver histological abnormalities, and modulating the Il6/Stat3 signaling, potentially through remodeling of actin-filament network within hepatocytes.NEW & NOTEWORTHY Glia maturation factor-β (Gmfb) has shown important implications in liver disease. Using transgenic zebrafish models, our research demonstrates that Gmfb in hepatocytes confers protective benefits for liver regeneration and repair. It promotes hepatocyte proliferation, alleviates steatosis and ballooning, and modulates Il6/Stat3 signaling in response to liver injuries, potentially through remodeling of actin-filament network. This submission represents the first in vivo observation of the phenotypic effects of Gmfb in hepatocytes during liver injury.

Neonatal bile acid metabolism is distinct from that of adults due to developmental regulation of key transporters and enzymes. The apical sodium-dependent bile acid transporter (ASBT) is transiently repressed in the intestine after birth, yet its role in neonatal bile acid homeostasis remains unclear. Here, we demonstrate that ASBT plays a crucial role in limiting fecal bile acid loss and suppressing hepatic bile acid synthesis in neonates. ASBT-deficient pups exhibited a marked decrease in serum bile acids and concomitant increase in fecal bile acids, accompanied by upregulated hepatic bile acid synthesis genes, including CYP7A1, CYP7B1, and CYP27A1. We also illuminated a tissue-specific distinction in neonatal negative feedback regulation of bile acid synthesis, with intact hepatic regulation but impaired intestinal regulation. Our study identifies ASBT as a key regulator of neonatal bile acid homeostasis despite its strong repression early in life, highlighting its role in bile acid retention and synthesis regulation.NEW & NOTEWORTHY Despite being repressed after birth, ASBT is essential for neonatal bile acid homeostasis. This study reveals that ASBT limits fecal bile acid loss and suppresses hepatic bile acid synthesis in neonates. ASBT-deficient pups showed reduced serum bile acids, increased fecal loss, and upregulation of bile acid synthesis genes. Notably, feedback regulation of bile acid synthesis was intact in the liver but impaired in the intestine, uncovering tissue-specific control mechanisms in early life.

Intestinal barrier dysfunction and dysbiosis are critical intestinal alterations in biliary obstructive diseases, for which farnesoid X receptor (FXR) is a potential intestinal therapeutic target, but its role and mechanism in the intestinal tract remain poorly defined. Using gut-specific knockout mice, we demonstrate that intestinal Fxr deficiency caused intestinal barrier function impairment and dysbiosis, and in a biliary obstruction model, obeticholic acid (OCA)-dependent intestinal Fxr activation protected against intestinal barrier injury and dysbiosis after bile duct ligation (BDL) surgery. Furthermore, from single-cell sequencing data, Fxr may directly regulate regenerating islet-derived protein 3γ (Reg3g) to influence intestinal functions. In conclusion, we elucidated FXR actions in the intestine under physiological and biliary obstruction conditions and suggest possible molecular targets that provide new insights for the intestinal treatment of biliary obstructive diseases.NEW & NOTEWORTHY Intestinal barrier dysfunction and dysbiosis are critical in biliary obstructive diseases, making farnesoid X receptor (FXR) a potential therapeutic target. Our study shows that Fxr deficiency impairs barrier function and causes dysbiosis. In a biliary obstruction model, obeticholic acid (OCA) activation of Fxr protects against these effects. In addition, single-cell sequencing suggests that Fxr may regulate Reg3g, influencing intestinal functions. This research reveals the role of FXR and offers new molecular targets for the treatment of biliary obstructive diseases.

Host-gut microbiota interactions may impact intestinal function during sustained periods of high energy demands. Whether energy status, reflecting the balance between energy intake and expenditure, impacts those interactions is unknown. This study determined the effects of energy status during sustained high-energy demands on intestinal function and the gut microbiota. Ten healthy men completed a randomized, crossover study that included baseline (BL) testing and two 72-hour periods of high physical activity-induced energy demands (HPA; ∼2,300 kcal/day physical activity energy expenditure) followed by a 7-day recovery period (REC). During HPA, diets designed to elicit a ∼45% energy deficit (DEF; -2,047 ± 920 kcal/day) or maintain energy balance within ±10% total daily energy expenditure (BAL; 689 ± 852 kcal/day) were provided. Intestinal permeability and transit time, fecal microbiota composition and gene content, fecal short-chain fatty acids (SCFAs), and gastrointestinal symptoms were measured. Intestinal permeability was 17% higher during HPA-DEF vs. HPA-BAL (P = 0.02), and colonic transit time was slower during HPA-DEF vs. HPA-BAL [mean difference (95% CI) = -764 min (-1,345, -183)] and BL [-643 min (-1,178, -108)] (P ≤ 0.02). Fecal microbiota species richness [-40 species (-66, -13), P = 0.01] and relative abundances of multiple species (log₂ fold difference < -5, P < 0.02) were lower during HPA-BAL vs. HPA-DEF but did not differ between conditions during REC. Small bowel transit time, gastrointestinal symptoms, fecal microbiota gene pathways, and fecal SCFAs did not differ between conditions. Findings suggest that increasing dietary intake to prevent energy deficit may benefit intestinal health and function during short-term periods of high energy demands without sustained impacts on the gut microbiota.NEW & NOTEWORTHY The effect of energy status on host-gut microbiota interactions impacting intestinal function during periods of high energy demands is unknown. Herein, increasing energy intake to prevent energy deficit during three days of high physical activity-induced energy demands prevented increases in intestinal permeability and transit time, and transiently reduced gut microbiota community richness without compromising community functional potential. Results suggest minimizing energy deficits may benefit gastrointestinal function during periods of high energy demands.

Alcohol liver damage (ALD) is increasing worldwide among adolescents, along with binge drinking (BD). BD is an acute alcohol consumption pattern, strongly pro-oxidant in the liver, and may be associated with steatosis, the first step in ALD. Folic acid (FA), an antioxidant crucial for liver function, shows compromised hepatic stores after BD. Therefore, this study aims to analyze the hepatic lipid changes associated with BD-induced steatosis during adolescence in rats and to evaluate the efficacy of FA supplementation in preventing these alterations. Four groups of adolescent rats were used: control, BD (intraperitoneal alcohol exposure), control FA-supplemented, and BD-FA-supplemented. FA content was 2 ppm in control diets and 8 ppm in supplemented groups. BD impaired liver function by increasing transaminases and UGT-1 expression. BD also induced dyslipidemia and an anabolic liver lipid state by increasing hepatic cholesteryl esters depots through dysregulation of cholesterol modulators (HMGCR, SREBP1, LDLR, SR-B1, ACAT-2, and Ces1d) and enhancing FXR expression, which affected liver bile acid balance. Furthermore, BD promoted all sources of hepatic free fatty acids (de novo synthesis, dietary source, and adipose tissue uptake) and impaired their hepatic clearance, contributing to steatosis as confirmed by microvesicular lipid droplet accumulation. FA supplementation, mainly by improving hepatic cholesterol balance and stimulating free fatty acid mobilization, partially prevented these alterations, with beneficial effects on cardiovascular health. In conclusion, this study demonstrates for the first time that BD in adolescents disturbs hepatic lipid homeostasis, leading to steatosis, and that FA therapy could be used to mitigate these deleterious effects.NEW & NOTEWORTHY Binge drinking (BD) in adolescent rats disrupts hepatic lipid homeostasis, inducing dyslipidemia and cholesteryl ester accumulation. BD alters hepatic cholesterol metabolism and bile acid homeostasis. In addition, it promotes free fatty acid (FFA) accumulation and steatosis. Folic acid supplementation improves cholesterol balance and enhances FFA mobilization, offering a protective role against BD-induced liver damage.