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

Metabolic dysfunction-associated steatohepatitis-driven hepatocellular carcinoma (MASH-HCC) incidence is rapidly rising worldwide. Lipid metabolic reprogramming is a hallmark of solid tumors to satisfy cancer's high metabolic demand. However, it may confer sensitivity to ferroptosis, a cell death mode driven by iron-dependent lipid peroxidation. In this report, we describe the lipid metabolic landscape in MASH-HCC and characterize long-chain acyl-CoA synthetases (ACSLs), a family of enzymes involved in the synthesis of cellular lipids. Bulk RNA sequencing, single-cell RNA sequencing, spatial transcriptomics, and immunohistochemistry analyses of human MASH-HCC were integrated to identify differentially expressed lipid metabolism genes. Ferroptosis in vitro was assessed in human HCC cell lines. The characterization of ACSLs was also conducted at the single-cell level in a diet-induced experimental murine model of MASH-HCC. Our analysis revealed that in human MASH-HCC, ACSLs exhibit a heterogeneous expression, with ACSL4 notably enriched in tumor tissues, contrasting with ACSL5 upregulation in noncancerous MASH. We identified a unique lipid metabolic gene signature of MASH-HCC, which included genes associated with ferroptosis vulnerability. In vitro, high ACSL4 expression was associated with increased ferroptosis sensitivity in human HCC cell lines. Finally, single-cell RNA sequencing revealed elevated ACSL4 expression in immune cells in a murine MASH-HCC model, suggesting a role of ACSL4 in shaping the tumor immune microenvironment. Overall, this report offers new insights into the lipid metabolic landscape and ferroptosis sensitivity for novel MASH-HCC treatments.NEW & NOTEWORTHY Our study examined healthy human MASH and MASH-associated hepatocellular carcinoma (MASH-HCC) livers using bulk and scRNA sequencing, spatial transcriptomics, and immunohistochemistry. We found that ACSLs displayed differential and spatially heterogeneous expression. ACSL4 was abundant in tumor tissues, whereas ACSL5 was elevated in noncancerous MASH tissues. ACSL4 was mainly found in immune cells like natural killer cells and natural killer T cells in murine MASH-HCC, suggesting its role in tumor immune microenvironment modulation.

Parenteral nutrition (PN) is a lifesaving intervention for patients unable to feed enterally but is often associated with parenteral nutrition-associated liver disease (PNALD), also called intestinal failure-associated liver disease (IFALD). This disease is characterized by steatosis, cholestasis, and elevated liver stress markers. Continuous PN induces hepatic injury through mechanisms including insulin resistance, lipotoxicity, systemic inflammation, and oxidative stress. Infusion cycling is known to ameliorate clinical markers of liver injury, but metabolic underpinnings have not been thoroughly investigated. Therefore, we modeled PN-induced liver injury in mice to investigate how differential infusion patterns impacted hepatic metabolism. Intermittent infusions protected against increased circulating alanine aminotransferase levels and improved histopathology to more closely resemble chow controls. Transcriptomic analyses revealed 804 differentially expressed genes between PN groups, highlighting pathways related to peroxisome proliferator-activated receptor signaling, fatty acid metabolism, and peroxisomes. Relative to the continuous group, intermittent PN infusion specifically downregulated Acaa1b, Aldh3a2, Inmt, and Acot4; transcripts involved in peroxisomal lipid oxidation, dicarboxylic acid synthesis, and one-carbon metabolism. This study suggests that infusion cycling may attenuate metabolic burden induced by alternate lipid oxidation pathways. Future work can therapeutically leverage these metabolic pathways to deepen our understanding of PNALD/IFALD and guide PN treatments to improve patient outcomes.NEW & NOTEWORTHY This work demonstrated that the infusion schedule, independent of nutrient and caloric concentration, is a modulator of hepatic lipid metabolism in a novel murine model of parenteral nutrition. This cyclic infusion paradigm attenuated transcripts involved in microsomal and peroxisomal lipid oxidation, which were upregulated in the continuous infusion group. These data support the clinical use of cyclic infusion to improve hepatic parameters known to be adversely affected by parenteral nutrition.

The mucus layer is an essential physical barrier that protects and lubricates mucosal surfaces in the body. The semipermeable nature of the mucus layer limits bacterial interactions with the epithelium while allowing nutrient absorption. Goblet cells (GCs) are specialized epithelial cells with a classical role to synthesize and secrete mucus to maintain the mucus layer. Emerging research has revealed the diverse nature of GC functions, including their interaction with the immune system through goblet cell-associated antigen passages to promote tolerance to dietary and bacterial antigens. Dysfunction of GCs or the mucus layer leaves the epithelium vulnerable to infection and is commonly associated with digestive disease. As such, there is a growing appreciation for the importance of GCs and the mucus layer to regulate mucosal homeostasis and protect against disease. Long-standing anatomical and pharmacological evidence indicates that the nervous system is a key regulator of GC function. However, the relative contribution from each division of the nervous system to the control of GC function is poorly defined. This is partly due to conflicting evidence from the literature and differences in experimental methods used. Furthermore, whether neurotransmitters influence GC functions and the associated mucus barrier directly or via indirect mechanisms, such as enhanced fluid secretion, remains unclear. The emergence of highly specific genetic approaches provides new opportunities to examine how specific nerve types can influence GC function. In this review, we consolidate the literature to date, with a focus on the stomach and lower gastrointestinal tract, and outline how current technologies may be useful to progress our fundamental understanding of neural-GC control.

Germline mutations in the CPA1 gene encoding carboxypeptidase A1 were found in association with chronic pancreatitis and pancreatic ductal adenocarcinoma (PDAC). The mutations increase pancreatic disease risk, presumably, by causing proenzyme misfolding and endoplasmic reticulum stress. Previously, we showed that CPA1 N256K mice that carry the p.N256K misfolding human CPA1 mutation in the mouse Cpa1 gene develop spontaneous chronic pancreatitis. Here, our aim was to investigate whether CPA1 N256K mice have increased susceptibility to PDAC induced by a Kras mutation. We generated Kras^LSL-G12D × p48-Cre (KC) and Kras^LSL-G12D × p48-Cre × CPA1 N256K (KC-CPA1) mice and compared the development of pancreas pathology in the two strains at 1, 3, 6, and 12 mo of age. We observed progressive parenchymal remodeling in both strains, with more rapid changes in KC-CPA1 mice. Thus, histological analysis revealed loss of normal pancreas parenchyma, extensive fibrosis, and aberrant ductal structures such as acinar-to-ductal metaplasia and precancerous pancreatic intraepithelial neoplasia. At 3 mo, these microscopic changes were significantly more abundant in KC-CPA1 versus KC mice. Owing to the massive fibrosis, the pancreas weight of KC and KC-CPA1 mice was significantly increased relative to C57BL/6N and CPA1 N256K controls, with the largest increase observed in 3-mo-old KC-CPA1 animals. The observations indicate that a misfolding Cpa1 mutation accelerated the development of precancerous lesions and fibro-inflammatory remodeling in the pancreas of KC mice, providing support for the notion that CPA1 mutations might be risk factors for human PDAC.NEW & NOTEWORTHY Inborn mutations in the CPA1 gene encoding carboxypeptidase A1 have been proposed to increase the risk of pancreatic ductal adenocarcinoma (PDAC) by causing enzyme misfolding and endoplasmic reticulum stress in the pancreas. Here, we demonstrated in a novel mouse model that a misfolding Cpa1 mutation accelerated the development of precancerous lesions driven by mutant Kras in the pancreas. The observations offer experimental support for the notion that CPA1 mutations are risk factors for human PDAC.

Glucagon-like peptide-2 (GLP-2) is known to exert some of its biological effects through the release of neurotransmitters, and in view of the absolute requirement for the enteric nervous system (ENS) demonstrated in our recent GLP-2-induced lipid mobilization studies, we aimed to identify the neurotransmitter that mediates GLP-2's effect on intestinal lipid mobilization. We also examined the role of vascular endothelial growth factor receptor 3 (VEGFR3) as an intermediate in the signaling cascade. Using a rat lymph fistula model, 5 h after an intraduodenal (id) lipid bolus, the following intraperitoneal (ip) administrations were applied in two different sets of experiments: Experiment 1: 1) placebo, 2) GLP-2, and 3) GLP-2 + ketanserin (serotonin receptor antagonist). Experiment 2: 1) placebo, 2) serotonin, 3) serotonin + MAZ-51 (a VEGFR3 inhibitor), 4) serotonin + SAR131675 (a second VEGFR3 inhibitor). Lymph flow and triglyceride (TG) output were assessed for 60 min (experiment 1) or 90 min (experiment 2) after administration. In another set of animals, GLP-2 or serotonin was administered intraperitoneally, and blood samples were collected to quantify plasma serotonin concentration. Intravital imaging of a prospero-related homeobox 1-enhanced green fluorescent protein rat model was used to assess lacteal contractility after placebo or serotonin administration. We demonstrated that single-dose GLP-2 administration acutely increased serotonin concentration in plasma, serotonin enhanced lymph flow, lymph TG output, and lacteal contractility. Antagonism of the serotonin receptor decreases GLP-2-enhanced mesenteric lymph flow and TG output, and inhibition of VEGFR3 abolishes serotonin-induced lymph flow and TG outputNEW & NOTEWORTHY Our data suggests that the neurotransmitter serotonin mediates glucagon-like peptide-2 (GLP-2)'s effect on intestinal lipid mobilization by enhancing lymph flow and lacteal contractility, and vascular endothelial growth factor receptor 3 (VEGFR3) is one of the downstream targets of serotonin involved in this cascade.

Chronic gastroduodenal symptoms experienced in functional dyspepsia, chronic nausea and vomiting syndromes, and gastroparesis affect over 10% of the global population and impose a significant healthcare burden. The relationship between aberrant gastric myoelectrical activity and symptom genesis remains incompletely defined. In this study, we evaluated the effects of gastric distension induced by a liquid nutrient drink test (LNDT) on gastric myoelectrical activity in healthy volunteers using noninvasive body surface gastric mapping (BSGM) with the Gastric Alimetry system (Auckland, New Zealand). Twenty healthy participants (10 females) underwent BSGM with 30-min fasting baseline, LNDT with Ensure administered at 30 mL/min until maximal toleration, and 4-h postprandial recording. Gastric Alimetry Rhythm Index (GA-RI), principal gastric frequency (PGF), and BMI-adjusted amplitude were analyzed across time and in relation to symptoms using mixed models. During LNDT, PGF decreased significantly (2.7 ± 0.2 vs. an overall average 3.0 ± 0.2 cycles/min, P < 0.001) and GA-RI declined (β = -0.11, 95% CI -0.21 to -0.002, P = 0.047) with a concurrent increase in nausea ratings. In the first postprandial hour, bloating, nausea, and overall symptom burden were elevated, with sustained reductions in GA-RI and PGF correlating with higher symptom scores. Spectral analyses revealed transient abnormalities temporally aligned with symptom genesis. These findings indicate that excessive gastric distension provokes aberrant gastric myoelectrical activity that is closely associated with foregut symptoms, supporting the role of these abnormalities in the pathophysiology of neurogastroduodenal disorders.NEW & NOTEWORTHY Body surface gastric mapping with liquid nutrient drink test found that excessive gastric distension provokes dysrhythmias that are closely associated with foregut symptoms, supporting the role of disrupted gastric myoelectrical function in the pathophysiology of neurogastroduodenal disorders.

Autosomal recessive polycystic kidney disease (ARPKD) is associated with cysts derived from abnormal bile ducts. We focused on targeting the cysts and show that a gene therapy for ARPKD that targets the abnormal bile ducts is feasible. We injected 1-mo-old, Pkhd1^{del3-4/del3-4} mice intraperitoneally with 2 × 10¹² particles/kg of adeno-associated virus (AAV1) containing either a GFP vector or a truncated cystic fibrosis transmembrane conductance regulator (CFTR) vector, Δ27-264-CFTR, or left them untreated. Two months after treatment, the cyst area and size in the liver were lower in the CFTR vector-treated mice than in mice receiving the GFP vector. We detected vector genomes and mRNA expression only in mice receiving the corresponding CFTR or GFP vector. We observed abundant GFP immunofluorescence in the cholangiocytes of the cysts and also saw expression of GFP and CFTR proteins above background levels in the corresponding treated mice. CFTR immunofluorescence was predominantly apically located in the ARPKD cholangiocytes, but after CFTR vector installation, it increased in the basolateral membrane. We stained mouse livers with Maackia amurensis lectin (MAL) or Sambucus nigra lectin (SNA), specific for α2,3- and α2,6-N-linked sialic acid, respectively, to detect the presence of sialic acid moieties contributing to AAV1 binding. Although immunofluorescent SNA was detected in the wild-type bile ducts, MAL 1 was not. MAL immunofluorescence was present in remarkably high levels on the apical surfaces of the cysts in cholangiocytes, offering a good target for AAV gene therapy. A gene therapy using an AAV1-based vector containing a truncated CFTR could be therapeutic in ARPKD.NEW & NOTEWORTHY Autosomal recessive polycystic kidney disease (ARPKD) causes severe disease in babies in the womb. Those who survive the neonatal period face chronic kidney and liver disease throughout their life. The overall goal of our study here is to develop a gene therapy to treat ARPKD.

The human gastrointestinal tract harbors a vast and diverse microbial community, with the gut microbiome playing a fundamental role in numerous biological processes that influence overall health and disease progression. Emerging evidence has identified bacterial lipopolysaccharides in the hippocampus of patients with Alzheimer's disease (AD), highlighting the intricate relationship between the gastrointestinal tract, gut microbiome, and the central and enteric nervous systems-commonly referred to as the "microbiota-gut-brain axis." In this review, we explore the mechanisms by which the microbiota-gut-brain axis contributes to AD pathogenesis. We propose that sufficient levels of all-trans retinoic acid (ATRA), the bioactive form of vitamin A, enhance intestinal barrier integrity by upregulating tight junction proteins and modulating immune function through the induction of regulatory T-cell differentiation, thereby mitigating inflammation. Furthermore, dietary fiber complements this process by promoting the production of short-chain fatty acids, such as butyrate, via bacterial fermentation. Butyrate, in turn, acts as a histone deacetylase inhibitor, upregulating ATRA bioavailability by elevating aldehyde dehydrogenase gene expression. Our mechanistic framework is supported by the endotoxin hypothesis of AD, which maintains that the movement of infectious pathogens across the blood-brain barrier causes a vicious cycle of inflammation, a key factor of AD pathogenesis, leading to amyloid-β deposition, microglial activation, and CYP26A1-mediated ATRA degradation. Finally, we discuss microbiome-based therapeutic strategies and dietary interventions, including prebiotic compounds, probiotic bacteria, fecal microbiota transplantation, the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, and a combined approach featuring vitamins A/D and dietary fiber, as potential approaches to prevent progression to AD via the microbiota-gut-brain axis.