Morphologic Alterations Precede Functional Hepatic Impairment as Determined by 13C-Methacetin Liver Function Breath Test in Adult Fontan Patients

Objectives: Fontan-associated liver disease (FALD) is the most common end-organ dysfunction affecting up to 70–80% of the Fontan population. The clinical significance of FALD is incompletely understood and no unambiguous correlation between hepatic function and FALD severity has been established. In this study, we sought to evaluate maximal liver function capacity with liver maximum function capacity test (LiMAx®) in adult Fontan patients.Methods: Thirty-nine adult Fontan patients (median age: 29.4 years [IQR 23.4; 37.4], median follow-up after Fontan operation: 23.9 years [IQR 17.8;26.4]) were analyzed in a cross-sectional observational study using LiMAx® test (Humedics GmbH, Berlin, Germany), laboratory testing, transient elastography (TE) and hepatic ultrasound. The LiMAx® test is based on the metabolism of 13C-methacetin, which is administered intravenously and cleaved by the hepatic cytochrome P4501A2 to paracetamol and 13CO2, which is measured in exhaled air and correlates with maximal liver function capacity.Results: Maximal liver function capacity assessed by LiMAx® test was normal in 28 patients (>315 μg/h*kg) and mildly to moderately impaired in 11 patients (140–314 μg/h*kg), while no patient displayed severe hepatic impairment (<139 μg/kg*h). No correlation was found between maximal liver function capacity and hepatic stiffness by TE (r2 = −0.151; p = 0.388) or the presence of sonographic abnormalities associated with FALD (r2 = −0.204, p = 0.24). There was, however, an association between maximal liver function capacity and the laboratory parameters bilirubin (r2 = −0.333, p = 0.009) and γ-glutamyl transferase (r2 = −0.367; p = 0.021). No correlation was detected between maximal liver function capacity and the severity of FALD (r2 = −0.235; p = 0.152).Conclusion: To the best of our knowledge, this is the first study to evaluate maximal liver function capacity using LiMAx® test in Fontan patients, which is a useful complementary diagnostic instrument to assess chronic hepatic injury. Maximal liver function capacity was preserved in most of our adult Fontan patients despite morphologic evidence of FALD. Moreover, maximal liver function capacity does not correlate with the extent of FALD severity evaluated by sonography or laboratory analysis. Thus, the development and progression of FALD in Fontan patients is not a uniform process and diagnostics of chronic hepatic injury during follow-up should encompass various modalities.

Exosomal miR-500 Derived From Lipopolysaccharide-Treated Macrophage Accelerates Liver Fibrosis by Suppressing MFN2

Liver fibrosis is an outcome of chronic hepatic injury, which can eventually result in cirrhosis, liver failure, and even liver cancer. The activation of hepatic stellate cell (HSC) is a prominent driver of liver fibrosis. Recently, it has been found that the crosstalk between HSCs and immune cells, including hepatic macrophages, plays an important role in the initiation and development of liver fibrosis. As a vital vehicle of intercellular communication, exosomes transfer specific cargos into HSCs from macrophages. Here, we show that exosomes derived from lipopolysaccharide (LPS)-treated macrophages has higher expression level of miR-500. And overexpression or inhibition of miR-500 in macrophage exosomes could promote or suppress HSC proliferation and activation. Treatment of exosomes with miR-500 overexpression can accelerate liver fibrosis in CCl4-induced liver fibrosis mouse model. miR-500 promotes HSC activation and liver fibrosis via suppressing MFN2. Moreover, miR-500 in serum exosomes could be a biomarker for liver fibrosis. Taken together, exosomal miR-500 derived from LPS-activated macrophages promotes HSC proliferation and activation by targeting MFN2 in liver fibrosis.

Kang-Xian Pills Inhibit Inflammatory Response and Decrease Gut Permeability to Treat Carbon Tetrachloride-Induced Chronic Hepatic Injury through Modulating Gut Microbiota

Kang-Xian (KX) pills have been clinically used for the treatment of chronic hepatic injury (CHI). However, the mechanisms of KX on CHI remain unknown. The aim of this study mainly focused on the anti-inflammatory effects of KX in a CHI mouse model based on modulating gut microbiota and gut permeability. We first established a CHI model using carbon tetrachloride (CCl4) and treated it with KX. The anti-inflammatory effects of KX on CHI model mice and the changes in gut permeability after KX treatment were also investigated. 16S rRNA analysis was used to study the changes of gut microbiota composition after KX treatment. In addition, gut microbiota was depleted using a combination of antibiotics in order to further confirm that KX could inhibit the inflammatory response and decrease gut permeability to treat CHI by modulating the gut microbiota. Results showed that KX treatment significantly improved liver function in CHI model mice. KX could also increase the levels of tight junction proteins in the colon and decrease the expression of proinflammatory cytokines in the liver. 16S rRNA analysis indicated that KX treatment affected the alpha and beta diversities in CHI model mice. Further analysis of 16S rRNA sequencing indicated that KX treatment increased the ratio of Firmicutes to Bacteroidetes at the phylum level. At the genus level, KX treatment increased the relative abundance of Lactobacillus, Bacteroides, and Akkermansia and decreased the relative abundance of Ralstonia, Alloprevotella, and Lachnoclostridium. However, KX could not alleviate CHI after depleting the gut microbiota. The effects of KX on gut permeability and inflammatory response in the liver were also decreased following the depletion of gut microbiota. In conclusion, our current study demonstrated that gut microbiota was significantly affected during CHI progression. KX could inhibit the inflammatory response and decrease the gut permeability in CHI model mice through modulating the gut microbiota.

Synergistic effect of Aminoguanidine and L-Carnosine against Thioacetamide-induced Hepatic Encephalopathy in rats: Behavioral, Biochemical and Ultra Structural Evidences

Hepatic encephalopathy (HE) depicts the cluster of neurological alterations that occur during acute or chronic hepatic injury. This study was aimed to evaluate the possible synergistic effect between aminoguanidine (AG; 100 mg/kg; p.o.) and l-carnosine (CAR; 100 mg/kg; p.o.) on HE that was induced by thioacetamide (TAA; 100 mg/kg; i.p) thrice weekly for six weeks. Twenty-four hours after the last treatment; behavioral changes, biochemical parameters, histopathological analysis, immunohistochemical and ultrastructural studies were conducted. Combining AG with CAR improved TAA-induced locomotor impairment and motor incoordination evidenced by; reduced locomotor activity and decline in motor skill performance as well as ameliorated cognitive deficits. Moreover, both drugs restored the levels of serum hepatic enzymes as well as serum and brain levels of ammonia. In addition to, the combination significantly modulated hepatic and brain oxidative stress biomarkers, inflammatory cytokines and cleaved caspase-3 expression. Furthermore, they succeeded to activate nuclear erythroid 2-related factor 2 (Nrf2) expression and ameliorate markers of HE including hepatic necrosis and brain astrocyte swelling. This study depicts that combining AG with CAR exerted new intervention for hepatic and brain damage in HE due to their complementary antioxidant, anti-inflammatory effect and hypoammonemic effects via Nrf2/HO-1 activation and NO inhibition.

Differential TAM receptor regulation of hepatic physiology and injury

The TAM receptor tyrosine kinases (RTK) Mer and Axl have been implicated in liver disease, yet our understanding of their roles in liver homeostasis and injury is limited. We therefore examined the performance of Mer and Axl mutant mice during aging, and in four models of liver injury. We find that Mer and Axl are most prominently expressed in Kupffer and hepatic endothelial cells, and that as Axl-/-Mertk-/- mice normally age, they develop profound liver disease. We further find that Mer signaling is critical to the phagocytosis of apoptotic hepatocytes that are generated during acute hepatic injury, and that Mer and Axl act in concert to inhibit injury-triggered cytokine production. TAM expression in Kupffer cells is crucial for these effects. In contrast, we show that Axl is uniquely important in mitigating liver damage during acute acetaminophen intoxication. Finally, we demonstrate that Axl exacerbates the fibrosis that develops in a model of chronic hepatic injury. These divergent effects have important implications for the design and implementation of TAM-directed therapeutics that target these RTKs in the liver.

Hepatocyte-Specific Ablation of PP2A Catalytic SubunitαAttenuates Liver Fibrosis Progression via TGF-β1/Smad Signaling

Protein phosphatase 2A (PP2A), a family of the major serine/threonine phosphatases in cells, regulates many aspects of physiological processes. However, isoform-specific substrates and the biological role of each specific member of the PP2A family remain largely unknown. In this study, we investigated whether PP2A catalytic subunit Cα(PP2Acα) is involved in chronic hepatic injury and fibrosis. A hepatocyte-specific PP2Acαablation mice model was established to examine the effect of PP2Acαon carbon tetrachloride- (CCl4-) induced chronic hepatic injury and fibrosis. Our results showed that PP2Acαknockout mice were less susceptible to chronic CCl4-induced liver injury as evidenced by lower levels of serum alanine aminotransferase and aspartate aminotransferase, decreased hepatocyte proliferation, and increased rate of apoptotic removal of the injured hepatocytes. PP2Acαknockout mice also displayed a lesser extent of liver fibrosis as a significant decrease in the proportion ofα-smooth muscle actin-expressing cells and collagen deposition was observed in their liver tissues. Furthermore, the levels of serum TGF-β1 and hepatocytic Smad phosphorylation were reduced in the PP2Acαknockout mice. These data suggest that hepatocyte-specific ablation of PP2Acαprotects against CCl4-induced chronic hepatic injury and fibrogenesis and the protective effect is mediated at least partially through the impaired TGF-β1/Smad signaling.