Cellular and Molecular Gastroenterology and Hepatology最新文献

Background & aims: A disintegrin and metalloproteinase 17 (ADAM17) is a membrane-bound sheddase that regulates the release of multiple signaling molecules, including inflammatory mediators and epidermal growth factor receptor (EGFR) ligands. Ligand-driven EGFR activation is essential for pancreatic acinar cell transdifferentiation into metaplastic ducts, which progress to neoplasia in the presence of oncogenic Kras^G12D. The aim of this study is to understand how ADAM17 in the tumor and myeloid cells contribute to the initiation and progression of pancreatic tumors.

Methods: Kirsten rat sarcoma (KRAS)^G12D-driven pancreatic tumorigenesis models with parenchymal gene ablation (Egfr^f/f;Kras^LSL-G12D/+;Ptf1a^Cre/+ and Adam17^f/f;Kras^LSL-G12D/+;Ptf1a^Cre/+) and dual recombinase mouse models with Kras^G12D expression in the parenchyma and gene deletion in myeloid cells (Kras^FSF-G12D/+;Ptf1a^FlpO/+;LysM-Cre;Adam17^f/ff) were generated to investigate the functional contributions of ADAM17 in different cell types. An intervention study using an ADAM17-blocking antibody to treat Kras^LSL-G12D/+;Ptf1a^Cre/+ mice after tumor initiation.

Results: Genetic deletion of Adam17 in pancreatic parenchymal cells blocked KRAS^G12D-induced metaplasia/neoplasia and inhibited macrophage infiltration. Ablation of Adam17 in myeloid cells did not prevent initial metaplastic duct formation but impeded neoplastic progression. Pharmacological inhibition of ADAM17 compromised multiple oncogenic signaling cascades, reverted premalignant ductal lesions to an acinar state, and resolved the fibro-inflammatory response, despite continued KRAS^G12D expression.

Conclusions: KRAS^G12D-driven tumorigenesis requires both autocrine and paracrine signaling regulated by ADAM17. Beyond activating EGFR to drive acinar cell transdifferentiation, ADAM17 also promotes neoplastic progression by modulating additional protumor signaling that shape the fibroinflammatory microenvironment. These findings highlight a pivotal role for ADAM17 in orchestrating epithelial plasticity, cellular signaling, and stromal remodeling during pancreatic tumorigenesis.

Lipoprotein assembly in the small intestine and liver is critical for the transport of dietary and endogenous lipids. Pla2g12b has recently been shown to play a role in lipoprotein assembly in mice livers and zebrafish larvae. Pla2g12b knockout and mutant (MUT) mice with the C129Y missense mutation have low plasma cholesterol levels. However, the role of Pla2g12b in the intestine and the reason why C129Y mutation decreases plasma lipids are unknown. We observed that Pla2g12b expression was the highest in the duodenum. Furthermore, male and female chow fed 3-month-old MUT mice and wild-type (WT) mice expressed similar amounts of Pla2g12b protein and several genes in lipid metabolism. Nonetheless, the MUT mice had significantly lower plasma triglyceride (TG), cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoprotein B (apoB)48, and apoB100 levels than WT mice. Several mechanisms for lower plasma lipids and lipoproteins in MUT mice were investigated. C129Y mutation had no effect on the expression of Pla2g12b and several other proteins necessary for lipid transport. Therefore, the low plasma lipid levels in MUT mice were neither due to the absence of Pla2g12b protein nor due to reductions in critical proteins in lipid transport. Next, we addressed the role of Pla2g12b in hepatic lipid mobilization and intestinal lipid absorption. MUT livers exhibited normal TG synthesis, defective TG secretion, and enhanced fat accumulation. MUT mice also showed defective intestinal TG absorption, intracellular lipid accumulation, and elevated TG excretion in the feces. We propose that C129 in Pla2g12b is critical for the assembly and secretion of lipoproteins by the liver and intestine.

Background & aims: Acute-on-chronic liver failure (ACLF) is a life-threatening syndrome of acute hepatic decompensation (AD) that leads to multiorgan failure and high mortality. Bacterial infections are often implicated in ACLF pathogenesis; however, their underlying molecular mechanisms remain poorly understood. This study employed a combined in vitro-ex vivo metabolomics approach to investigate infection-associated metabolic alterations relevant to ACLF.

Methods: Gut (Caco-2) cells were infected with Acinetobacter baumannii and Klebsiella pneumoniae strains. Metabolite profiling was conducted on cell culture supernatants, and selected metabolites were tested for hepatotoxicity in vitro using liver (HepG2) cells. Metabolomic analysis of sera from 2 independent patient cohorts (AD and ACLF) was conducted to validate in vitro findings and to assess their clinical relevance.

Results: Distinct metabolic signatures were identified in A. baumannii (19 metabolites) and K. pneumoniae (15 metabolites)-infected Caco-2 cells. Four key metabolites from each bacterial species were prioritized for further experiments: α-ketoglutarate, indoleacetic acid, p-coumaric acid, uridine (A. baumannii), desthiobiotin, N8-acetylspermidine, N-acetylglutamine, and β-pinene (K. pneumoniae). Hepatotoxicity was demonstrated in liver (HepG2) cells exposed to Caco-2 infected cell-derived supernatants, infection-associated metabolites, and metabolite mixtures (in all conditions, P < .0001). Increased levels of α-ketoglutarate (P = .0002), N-acetylglutamine (P = .0153), indoleacetic acid (P < .05), and N8-acetylspermidine (P < .01) have been confirmed in the sera of patients with AD and ACLF.

Conclusions: Our findings suggest that metabolites associated with bacterial infections and hepatotoxic potential are significantly elevated in patients with AD and ACLF. These compounds may contribute to disease-related metabolic disturbances, representing promising candidates as early diagnostic biomarkers and targeted therapeutic strategies for ACLF.

Bile acid (BA) metabolism must be tightly regulated because BAs serve as metabolic signaling molecules but become cytotoxic at high levels. The farnesoid X receptor (FXR) is a crucial BA sensor, yet our understanding of its regulation and coordination with other transcription factors is limited. Here, we found that hepatic B cell lymphoma 6 (Bcl6) integrates with FXR to control BA homeostasis. Mice lacking hepatic Bcl6 (Bcl6^LKO) have increased BA synthesis and levels, as well as reduced expression of the hepatic BA re-uptake transporter sodium-taurocholate cotransporting polypeptide (NTCP), particularly among males. Furthermore, loss of Bcl6 reduced hepatic fibroblast growth factor receptor 4 (FGFR4) expression, attenuating FXR-controlled entero-hepatic BA feedback signaling. To understand the mutual contributions of BCL6 and FXR to BA homeostasis, we generated animals with combined deletion of hepatic Bcl6 and Fxr (Bcl6^LKOFxr^KO mice). Remarkably, combined ablation caused almost complete loss of hepatic Shp expression, upregulation of the rate-limiting BA synthesis enzyme CYP7A1, severe elevation in BA levels, and cholestatic liver damage. Together, these findings reveal BCL6 as a key modulator of FXR enterohepatic signaling to maintain BA homeostasis and protect the liver from cholestatic injury.

Background & aims: Insulinomas are rare pancreatic neuroendocrine neoplasms (pan-NENs) characterized by inappropriate insulin secretion. Despite advances in imaging techniques, the reliable identification of insulin-secreting lesions remains challenging. In addition, medical treatment options are limited and have seen little development in recent years, highlighting the unmet need for improved diagnostic tools and therapeutic strategies. This study aimed to identify the molecular mechanisms underlying insulin hypersecretion in insulinomas.

Methods: We established a biobank of human insulinoma surgical specimens and matched organoids. Comprehensive transcriptomic analyses-including bulk RNA sequencing, single-cell RNA sequencing, quantitative polymerase chain reaction, and immunohistochemistry-were conducted to identify genes enriched in insulin-secreting components. Functional validation was performed using MIN6 cells, a xenograft mouse model, and long-term cultured human insulinoma organoids.

Results: We identified dedicator of cytokinesis 10 (DOCK10) as a gene selectively overexpressed in insulin-secreting components of insulinomas. DOCK10 knockdown impaired glucose-stimulated insulin secretion in both mouse insulinoma cells and patient-derived organoids. Inhibition of the downstream effector Cdc42 with ML141 reduced insulin hypersecretion and improved survival in a MIN6 xenograft mouse model. These findings uncover a previously unrecognized role of the DOCK10-Cdc42 axis in regulating insulin secretion in insulinoma.

Conclusions: This study suggests that DOCK10 may serve as a diagnostic marker for insulin-secreting lesions and a potential therapeutic target in insulinoma. It provides mechanistic insights that may inform future strategies for precision diagnostics and treatment of functional pancreatic neuroendocrine tumors.