Patients with cirrhosis are highly susceptible to infections which could trigger a vicious cycle of events, including hepatic decompensation, organ failure, and increased mortality. These infections often originate from the gastrointestinal tract when bacteria breach the intestinal barrier and disseminate towards the liver. Macrophages are key immune cells along the gut-liver axis, where they play a crucial role in preserving barrier integrity under homeostatic conditions. In cirrhosis, however, macrophage specialization, spatial organization, and antimicrobial functions are disrupted. In this review, we discuss the progress made in understanding the heterogeneity of intestinal and hepatic macrophages, emphasizing their distinct ontogeny and the specialized niches that dictate their function. We describe the roles these populations perform in health, particularly in lining critical cellular barriers within the gut-liver axis, followed by how these processes are compromised in the context of cirrhosis. Finally, we explore how therapeutic approaches might target dysregulated macrophages or restore their barrier-protective functions in advanced liver disease.

Obesity and metabolic dysfunction-associated fatty liver disease (MAFLD) are increasingly recognized as risk factors for skeletal fragility, yet the mechanisms linking these conditions to impaired bone health remain poorly defined. The liver is central to vitamin D homeostasis through 25-hydroxylation, while skeletal responsiveness relies on vitamin D receptor (VDR) signaling. Disruption of either process may compromise bone remodeling. In this study, we investigated the long-term effects of Western diet (WD) feeding on hepatic vitamin D metabolism and bone integrity in a mouse model. Male C57BL/6N mice were fed a standard diet (SD) or WD for 48 weeks. WD-fed mice developed obesity, hepatic injury, and trabecular bone deterioration characterized by reduced bone mineral density and increased trabecular separation. Although trabecular architecture was compromised, three-point bending revealed no significant impairment in cortical bone mechanical properties. Histological analyses showed increased bone marrow adiposity and macrophage/monocyte lineage cells. Bone gene expression profiling indicated enhanced osteoclastogenic signaling. Hepatic transcriptomics demonstrated marked downregulation of key 25-hydroxylases (Cyp2r1, Cyp27a1) and vitamin D-binding protein, accompanied by reduced circulating 25‑hydroxyvitamin D. Bone tissue also exhibited decreased VDR protein abundance. Together, these findings suggest that long-term WD-induced obesity and hepatic dysfunction impair hepatic vitamin D metabolism and diminish skeletal vitamin D responsiveness, contributing to bone fragility. Targeting the liver-bone axis and restoring vitamin D homeostasis may provide therapeutic potential for obesity-related bone loss. See also the graphical abstract(Fig. 1).

Cholangiocarcinoma (CCA) is a deadly cancer, characterized by abundant stroma. The tumor microenvironment (TME) plays an important role in its aggressive behavior and poor response to therapeutics; however, the underlying pathways are unknown. To fill this gap, we used multiplexed immunohistochemistry, high-dimensional cytometry, and single cell transcriptomics. Our findings confirm an abundance of regulatory T cells (Tregs) and a lack of effector memory T cells within the tumor. Tumor-infiltrating T cells show signs of exhaustion. Using our transcriptomic data, we revealed cellular crosstalk in poor prognosis patients. This crosstalk is driven by stromal cells and macrophages. Among the responsible receptor-ligand pairs are GAS6-AXL, VCAN-TLR2, and EGFR-TGF-β. The multiple mechanisms leading to the exclusion of relevant immune cells needed for an anti-cancer response and mechanisms leading to active immune suppression are part of complex cell-cell crosstalk. This study provides a deeper insight into the immune exhausted phenotype in CCA.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a systemic condition associated with compromised bone integrity. Emerging evidence suggests that disturbances in hepatic vitamin D metabolism may contribute to these skeletal impairments. However, the hepatic mechanisms driving bone deterioration remain poorly defined. This study aimed to establish a human 3D in vitro model of MASLD and demonstrate that hepatic vitamin D dysregulation adversely affects bone homeostasis. Liver spheroids composed of HepaRG cells, LX-2 stellate cells, and HUVECs were stimulated with 600 µM free fatty acids (2:1 oleic: palmitic acid) to induce MASLD-like features, validated by BODIPY staining and gene expression. MASLD model induction led to downregulation of hepatic genes regulating lipid and vitamin D metabolism. ELISA confirmed significantly reduced 25-hydroxyvitamin D levels, aligning with downregulation of CYP2R1 and CYP27A1. Transcriptomic profiling of human MASLD liver biopsies validated these molecular changes. To evaluate MASLD’s systemic impact on bone, THP-1-derived macrophages and SCP-1 mesenchymal stem cells were seeded onto bone scaffolds and co-cultured with spheroids. Bone scaffolds co-cultured with MASLD spheroids showed impaired mineralization and elevated expression of bone resorption markers. These findings mirror skeletal dysfunction observed in MASLD patients and suggest a mechanistic link between hepatic vitamin D dysregulation and bone pathology. This study introduces a pioneering 3D human liver-bone co-culture model that reveals MASLD-driven disruption of hepatic vitamin D metabolism as a direct contributor to bone deterioration. This 3D model develops a powerful translational platform for decoding systemic disease mechanisms and targeting the liver-bone axis therapeutically.

Die primär sklerosierende Cholangitis (PSC) gilt als Prototyp einer Erkrankung der Darm-Leber-Achse, bei der Gallensäuren, Mikrobiom und Immunregulation eng miteinander verknüpft sind. Dysbiosen und Störungen des enterohepatischen Kreislaufs verändern die Gallensäurezusammensetzung, beeinträchtigen Farnesoid-X-Rezeptor(FXR)- und über Takeda-G-Protein-gekoppelter Rezeptor 5 (TGR5) vermittelte Signalwege und fördern entzündliche sowie fibrotische Prozesse der Gallenwege und in der Leber. Besonders relevant ist die Assoziation mit der Colitis ulcerosa, die bei bis zu 80

Background Bacterial translocation in cirrhosis can trigger infection and hepatic decompensation, leading to systemic inflammation, organ failure and increased mortality. These infections often originate from the gastrointestinal tract after bacteria breach the intestinal barrier and disseminate to systemic sites.Objective In this study, we explore the mechanisms underlying intestinal barrier dysfunction in cirrhosis using an experimental cirrhosis model and patient-derived intestinal biopsies.Design We developed a murine model of cirrhosis through chronic administration of carbon tetrachloride for up to 20 weeks. We investigated both the intestinal epithelial and vascular compartments and performed single-cell transcriptomic profiling of myeloid cells isolated from cirrhotic mice and from individuals with compensated and decompensated cirrhosis.Results Our findings indicate that bacterial translocation in cirrhosis is the result of failure at multiple checkpoints, including aberrant epithelial cell death, vascular barrier damage and dysfunction of gut-vascular macrophages. In a preclinical model of cirrhosis, macrophages exhibited increased levels of monocyte-attracting chemokines, reduced bacterial clearance and impaired interactions with blood vessels. Importantly, depleting vascular-lining macrophages resulted in bacterial translocation to systemic sites, even in the absence of experimental liver disease. Transcriptional profiling of macrophages from duodenal biopsies of patients with cirrhosis indicated similar dysregulation of pathways supporting blood vessels and elevated expression of chemokines.Conclusions This study emphasises the critical role of intestinal macrophages in preventing the dissemination of luminal bacteria and highlights the multifaceted breakdown of the intestinal barrier in cirrhosis and the importance of the gut-vascular barrier.

Humans are exposed to a multitude of substances at the same time; thus, toxicity assessment for mixtures of several substances and not only for the individual substances is critical. An important challenge in testing the mixture effects of many substances in vitro is the variability between individual experiments, also named 'day-to-day variability'. Two steps, each consisting of independent experiments, are needed when mixtures are tested. In the first experimental step, for each substance, the concentration-response relationship is usually measured with 6-10 concentrations for at least 3 experiments, and EC20 values, i.e., the concentration where a fitted curve intersects with a viability value of 80%, are determined. These values are used as reference values and in the second experimental step, the mixture of several substances is based on these individual EC20 values. Since the mixture experiments are new, independent experiments, typically conducted on different days, day-to-day variability can lead to deviations in the cytotoxicity at the reference EC20 concentration, i.e., to higher or lower observed viabilities. In this work, a procedure is proposed, how a single concentration per substance tested in the same experiment as the mixture can be used to reliably adjust for day-to-day variability. In the here-established procedure, a specific additive model denoted as 'budget approach' is introduced as a reference model to explore potential positive or negative interaction effects between substances.

Background: Cannabidiol (CBD) is a cannabinoid present in the hemp plant (Cannabis sativa L.). Non-medicinal CBD oils with typically 5–40% CBD are advertised for various alleged positive health effects. While such foodstuffs containing cannabinoids are covered by the Novel Food Regulation in the European Union (EU), none of these products have yet been authorized. Nevertheless, they continue to be available on the European market. Methods: The Permanent Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) reviewed the currently available data on adverse and potential beneficial effects of CBD in the dose range relevant for foods. Results: Increased liver enzyme activities were observed in healthy volunteers following administration of 4.3 mg CBD/kg bw/day and higher for 3–4 weeks. As lower doses were not tested, a no observed adverse effect level (NOAEL) could not be derived, and the dose of 4.3 mg/kg bw/day was identified as the lowest observed adverse effect level (LOAEL). Based on the CBD content and dose recommendations of CBD products on the market, the SKLM considered several exposure scenarios and concluded that the LOAEL for liver toxicity may be easily reached, e.g., via consumption of 30 drops of an oil containing 20% CBD, or even exceeded. A critical evaluation of the available data on potential beneficial health effects of CBD in the dose range at or below the LOAEL of 4.3 mg/kg bw/day revealed no scientific evidence that would substantiate health claims, e.g., in relation to physical performance, the cardiovascular, immune, and nervous system, anxiety, relaxation, stress, sleep, pain, or menstrual health. Conclusions: The SKLM concluded that consumption of CBD-containing foods/food supplements may not provide substantiated health benefits and may even pose a health risk to consumers.

Background: Exhaustion and depersonalization are the core symptoms of the occupational burnout. However, burnout is not an all-or-nothing phenomenon, but can occur in a milder to moderate form in otherwise healthy employees. In the last two decades hair cortisol concentrations (HCC) were increasingly related to the cumulative effect of psychosocial stress at work. We analyzed data of the Dortmund Vital Study (Clinicaltrials.gov: NCT05155397) to explore the relationship of HCC and burnout symptoms. Moreover, we asked whether the HCC - burnout association was moderated by work ability, chronic stress, neuroticism, depressive symptoms, and stress-related immunological biomarkers such as T cell concentration, CD4/CD8 cell ratio, and proinflammatory cytokines TNF- alpha, IL-6, and IL-18. Methods: Burnout was assessed by the Oldenburg Burnout Inventory (OLBI), and the Maslach Burnout Inventory (MBI-D) in 196 working adults aged between 20 and 65 years (mean age 42.2 years). Several self-reported variables and biomarkers were collected. Results: The results showed an association between HCC and the burnout measures. A series of moderator analyses revealed that the association between HCC and burnout symptoms was substantial for low work ability, high chronic stress level, high neuroticism level, and mild to moderate depressive symptoms. Immunological markers moderated the HCC - burnout association for high concentrations of T cells, low CD4/CD8 ratio and low IL-6, IL-18 and TNF-alpha concentrations. These interactions were moderated by age showing the largest impact in middle-aged to older individuals. Conclusions: The present findings shed light on the complex interaction between burnout symptoms and work ability, chronic stress, personality, and the endocrinological and immunological responses across the working lifespan. These parameters should be considered when assessing the risk for developing burnout and validating the diagnosis of burnout. Trial registration: ClinicalTrials.gov NCT05155397; https://clinicaltrials.gov/ct2/show/NCT05155397.

Background & Aims: Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common cause of chronic liver disease. Owing to limited available treatment options, novel pre-clinical models for target selection and drug validation are warranted. We have established and extensively characterized a primary human steatotic hepatocyte in vitro model system that could guide the development of treatment strategies for MASLD. Methods: Cryopreserved primary human hepatocytes from five donors varying in sex and ethnicity were cultured with free fatty acids in a 3D collagen sandwich for 7 days and the development of MASLD was followed by assessing classical hepatocellular functions. As proof of concept, the effects of the drug firsocostat (GS-0976) on in vitro MASLD phenotypes were evaluated. Results: Incubation with free fatty acids induced steatosis, insulin resistance, mitochondrial dysfunction, inflammation, and alterations in prominent human gene signatures similar to patients with MASLD, indicating the recapitulation of human MASLD in this system. The application of firsocostat rescued clinically observed fatty liver disease pathologies, highlighting the ability of the in vitro system to test the efficacy and potentially characterize the mode of action of drug candidates. Conclusions: Altogether, our human MASLD in vitro model system could guide the development and validation of novel targets and drugs for the treatment of MASLD. (c) 2024 The Authors. Published by Elsevier B.V. on behalf of European Association for the Study of the Liver. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

KRAS-dependent acinar-to-ductal metaplasia (ADM) is a fundamental step in the development of pancreatic ductal adenocarcinoma (PDAC), but the involvement of cell death pathways remains unclear. Here, we show that key regulators of programmed cell death (PCD) become upregulated during KRAS-driven ADM, thereby priming transdifferentiated cells to death. Using transgenic mice and primary cell and organoid cultures, we show that transforming growth factor (TGF)-β-activated kinase 1 (TAK1), a kinase regulating cell survival and inflammatory pathways, prevents the elimination of transdifferentiated cells through receptor-interacting protein kinase 1 (RIPK1)-mediated apoptosis and necroptosis, enabling PDAC development. Accordingly, pharmacological inhibition of TAK1 induces PCD in patient-derived PDAC organoids. Importantly, cell death induction via TAK1 inhibition does not appear to elicit an overt injury-associated inflammatory response. Collectively, these findings suggest that TAK1 supports cellular plasticity by suppressing spontaneous PCD activation during ADM, representing a promising pharmacological target for the prevention and treatment of PDAC.

Together with carriers in the liver and small intestine, kidney transporters function to conserve and compartmentalise bile acids in the enteronephrohepatic circulation. In patients with liver disease, systemic bile acid levels are elevated, undergo increased renal glomerular filtration, and contribute to the pathogenesis of cholemic nephropathy and acute kidney injury. In this review, we describe mechanisms for renal bile acid transport and highlight very recent discoveries that challenge current paradigms on the pathogenesis of cholemic nephropathy and renal tubule cast formation. We also discuss the therapeutic potential of inhibiting the kidney apical sodium-dependent bile acid transporter to redirect bile acids into urine for elimination, reduce hepatobiliary accumulation and systemic levels of bile acids, and treat cholemic nephropathy. In conclusion, a deeper understanding of the enteronephrohepatic bile acid axis is providing insights into novel strategies to protect both the liver and kidney in patients with liver disease.