The gut microbiota–bile acid axis: A potential therapeutic target for liver fibrosis

Research Progress Regarding the Effect and Mechanism of Dietary Polyphenols in Liver Fibrosis

The development of liver fibrosis is a result of chronic liver injuries may progress to liver cirrhosis and liver cancer. In recent years, liver fibrosis has become a major global problem, and the incidence rate and mortality are increasing year by year. However, there are currently no approved treatments. Research on anti-liver-fibrosis drugs is a top priority. Dietary polyphenols, such as plant secondary metabolites, have remarkable abilities to reduce lipid metabolism, insulin resistance and inflammation, and are attracting more and more attention as potential drugs for the treatment of liver diseases. Gradually, dietary polyphenols are becoming the focus for providing an improvement in the treatment of liver fibrosis. The impact of dietary polyphenols on the composition of intestinal microbiota and the subsequent production of intestinal microbial metabolites has been observed to indirectly modulate signaling pathways in the liver, thereby exerting regulatory effects on liver disease. In conclusion, there is evidence that dietary polyphenols can be therapeutically useful in preventing and treating liver fibrosis, and we highlight new perspectives and key questions for future drug development.

Gut Microbiota and Bacterial Translocation in the Pathogenesis of Liver Fibrosis

Cirrhosis is the end result of liver fibrosis in chronic liver diseases. Studying the mechanisms of its development and developing measures to slow down and regress it based on this knowledge seem to be important tasks for medicine. Currently, disorders of the gut-liver axis have great importance in the pathogenesis of cirrhosis. However, gut dysbiosis, which manifests as increased proportions in the gut microbiota of Bacilli and Proteobacteria that are capable of bacterial translocation and a decreased proportion of Clostridia that strengthen the intestinal barrier, occurs even at the pre-cirrhotic stage of chronic liver disease. This leads to the development of bacterial translocation, a process by which those microbes enter the blood of the portal vein and then the liver tissue, where they activate Kupffer cells through Toll-like receptor 4. In response, the Kupffer cells produce profibrogenic cytokines, which activate hepatic stellate cells, stimulating their transformation into myofibroblasts that produce collagen and other elements of the extracellular matrix. Blocking bacterial translocation with antibiotics, probiotics, synbiotics, and other methods could slow down the progression of liver fibrosis. This was shown in a number of animal models but requires further verification in long-term randomized controlled trials with humans.

Unveiling the interplay between NSAID-induced dysbiosis and autoimmune liver disease in children: insights into the hidden gateway to autism spectrum disorders. Evidence from ex vivo, in vivo, and clinical studies

Autism spectrum disorders (ASD) represent a diverse group of neuropsychiatric conditions, and recent evidence has suggested a connection between ASD and microbial dysbiosis. Immune and gastrointestinal dysfunction are associated with dysbiosis, and there are indications that modulating the microbiota could improve ASD-related behaviors. Additionally, recent findings highlighted the significant impact of microbiota on the development of autoimmune liver diseases, and the occurrence of autoimmune liver disease in children with ASD is noteworthy. In the present study, we conducted both an in vivo study and a clinical study to explore the relationship between indomethacin-induced dysbiosis, autoimmune hepatitis (AIH), and the development of ASD. Our results revealed that indomethacin administration induced intestinal dysbiosis and bacterial translocation, confirmed by microbiological analysis showing positive bacterial translocation in blood cultures. Furthermore, indomethacin administration led to disturbed intestinal permeability, evidenced by the activation of the NLRP3 inflammasomes pathway and elevation of downstream biomarkers (TLR4, IL18, caspase 1). The histological analysis supported these findings, showing widened intestinal tight junctions, decreased mucosal thickness, inflammatory cell infiltrates, and collagen deposition. Additionally, the disturbance of intestinal permeability was associated with immune activation in liver tissue and the development of AIH, as indicated by altered liver function, elevated ASMA and ANA in serum, and histological markers of autoimmune hepatitis. These results indicate that NSAID-induced intestinal dysbiosis and AIH are robust triggers for ASD existence. These findings were further confirmed by conducting a clinical study that involved children with ASD, autoimmune hepatitis (AIH), and a history of NSAID intake. Children exposed to NSAIDs in early life and complicated by dysbiosis and AIH exhibited elevated serum levels of NLRP3, IL18, liver enzymes, ASMA, ANA, JAK1, and IL6. Further, the correlation analysis demonstrated a positive relationship between the measured parameters and the severity of ASD. Our findings suggest a potential link between NSAIDs, dysbiosis-induced AIH, and the development of ASD. The identified markers hold promise as indicators for early diagnosis and prognosis of ASD. This research highlights the importance of maintaining healthy gut microbiota and supports the necessity for further investigation into the role of dysbiosis and AIH in the etiology of ASD.

Antibiotics in Chronic Liver Disease and Their Effects on Gut Microbiota

Impairments in liver function lead to different complications. As chronic liver disease progresses (CLD), hypoalbuminemia and alterations in bile acid compositions lead to changes in gut microbiota and, therefore, in the host-microbiome interaction, leading to a proinflammatory state. Alterations in gut microbiota composition and permeability, known as gut dysbiosis, have important implications in CLD; alterations in the gut-liver axis are a consequence of liver disease, but also a cause of CLD. Furthermore, gut dysbiosis plays an important role in the progression of liver cirrhosis and decompensation, particularly with complications such as hepatic encephalopathy and spontaneous bacterial peritonitis. In relation to this, antibiotics play an important role in treating CLD. While certain antibiotics have specific indications, others have been subjected to continued study to determine whether or not they have a modulatory effect on gut microbiota. In contrast, the rational use of antibiotics is important, not only because of their disrupting effects on gut microbiota, but also in the context of multidrug-resistant organisms. The aim of this review is to illustrate the role of gut microbiota alterations in CLD, the use and impact of antibiotics in liver cirrhosis, and their harmful and beneficial effects.

Lactobacillus gasseri LA39 promotes hepatic primary bile acid biosynthesis and intestinal secondary bile acid biotransformation

A growing body of evidence has linked the gut microbiota to liver metabolism. The manipulation of intestinal microflora has been considered as a promising avenue to promote liver health. However, the effects of Lactobacillus gasseri LA39, a potential probiotic, on liver metabolism remain unclear. Accumulating studies have investigated the proteomic profile for mining the host biological events affected by microbes, and used the germ-free (GF) mouse model to evaluate host-microbe interaction. Here, we explored the effects of L. gasseri LA39 gavage on the protein expression profiles of the liver of GF mice. Our results showed that a total of 128 proteins were upregulated, whereas a total of 123 proteins were downregulated by treatment with L. gasseri LA39. Further bioinformatics analyses suggested that the primary bile acid (BA) biosynthesis pathway in the liver was activated by L. gasseri LA39. Three differentially expressed proteins (cytochrome P450 family 27 subfamily A member 1 (CYP27A1), cytochrome P450 family 7 subfamily B member 1 (CYP7B1), and cytochrome P450 family 8 subfamily B member 1 (CYP8B1)) involved in the primary BA biosynthesis pathway were further validated by western blot assay. In addition, targeted metabolomic analyses demonstrated that serum and fecal β‍-muricholic acid (a primary BA), dehydrolithocholic acid (a secondary BA), and glycolithocholic acid-3-sulfate (a secondary BA) were significantly increased by L. gasseri LA39. Thus, our data revealed that L. gasseri LA39 activates the hepatic primary BA biosynthesis and promotes the intestinal secondary BA biotransformation. Based on these findings, we suggest that L. gasseri LA39 confers an important function in the gut‒liver axis through regulating BA metabolism.

Chronic-binge ethanol feeding aggravates systemic dyslipidemia in Ldlr-/- mice, thereby accelerating hepatic fibrosis

Objective

Chronic ethanol consumption is known to cause alcohol-associated liver disease, which poses a global health concern as almost a quarter of heavy drinkers develop severe liver damage. Alcohol-induced liver disease ranges from a mild, reversible steatotic liver to alcoholic steatohepatitis and irreversible liver fibrosis and cirrhosis, ultimately requiring liver transplantation. While ethanol consumption is associated with dysregulated lipid metabolism and altered cholesterol homeostasis, the impact of dyslipidemia and pre-existing hypercholesterolemia on the development of alcohol-associated liver disease remains to be elucidated.

Design

To address the influence of systemic dyslipidemia on ethanol-induced liver disease, chronic-binge ethanol feeding was applied to female C57BL/6J (wild type) mice and mice deficient for the low-density lipoprotein receptor (Ldlr-/-), which display a human-like lipoprotein profile with elevated cholesterol and triglyceride levels in circulation. Respective control groups were pair-fed an isocaloric diet.

Results

Chronic-binge ethanol feeding did not alter systemic lipid levels in wild type mice. While increased systemic cholesterol levels in Ldlr-/- mice were not affected by ethanol feeding, chronic-binge ethanol diet aggravated elevated plasma triglyceride levels in Ldlr-/- mice. Despite higher circulatory triglyceride levels in Ldlr-/- mice, hepatic lipid levels and the development of hepatic steatosis were not different from wild type mice after ethanol diet, while hepatic expression of genes related to lipid metabolism (Lpl) and transport (Cd36) showed minor changes. Immunohistochemical assessment indicated a lower induction of infiltrating neutrophils in the livers of ethanol-fed Ldlr-/- mice compared to wild type mice. In line, hepatic mRNA levels of the pro-inflammatory genes Ly6g, Cd11b, Ccr2, Cxcl1 and F4/80 were reduced, indicating less inflammation in the livers of Ldlr-/- mice which was associated with reduced Tlr9 induction. While systemic ALT and hepatic MDA levels were not different, Ldlr-deficient mice showed accelerated liver fibrosis development after chronic-binge ethanol diet than wild type mice, as indicated by increased levels of Sirius Red staining and higher expression of pro-fibrotic genes Tgfb, Col1a1 and Col3a1. Ldlr-/- and wild type mice had similar plasma ethanol levels and did not show differences in the hepatic mRNA levels of Adh1 and Cyp2e1, important for ethanol metabolism.

Conclusion

Our results highlight that chronic-binge ethanol feeding enhances systemic dyslipidemia in Ldlr-/- mice which might accelerate the development of hepatic fibrosis, independent of hepatic lipid levels.

Mechanism-based target therapy in primary biliary cholangitis: opportunities before liver cirrhosis?

Primary biliary cholangitis (PBC) is an immune-mediated liver disease characterized by cholestasis, biliary injuries, liver fibrosis, and chronic non-suppurative cholangitis. The pathogenesis of PBC is multifactorial and involves immune dysregulation, abnormal bile metabolism, and progressive fibrosis, ultimately leading to cirrhosis and liver failure. Ursodeoxycholic acid (UDCA) and obeticholic acid (OCA) are currently used as first- and second-line treatments, respectively. However, many patients do not respond adequately to UDCA, and the long-term effects of these drugs are limited. Recent research has advanced our understanding the mechanisms of pathogenesis in PBC and greatly facilitated development of novel drugs to target mechanistic checkpoints. Animal studies and clinical trials of pipeline drugs have yielded promising results in slowing disease progression. Targeting immune mediated pathogenesis and anti-inflammatory therapies are focused on the early stage, while anti-cholestatic and anti-fibrotic therapies are emphasized in the late stage of disease, which is characterized by fibrosis and cirrhosis development. Nonetheless, it is worth noting that currently, there exists a dearth of therapeutic options that can effectively impede the progression of the disease to its terminal stages. Hence, there is an urgent need for further research aimed at investigating the underlying pathophysiology mechanisms with potential therapeutic effects. This review highlights our current knowledge of the underlying immunological and cellular mechanisms of pathogenesis in PBC. Further, we also address current mechanism-based target therapies for PBC and potential therapeutic strategies to improve the efficacy of existing treatments.

The Role of hsa-miR-125b-5p Interaction with S1P/Ceramide Axis in the Potential Development of Inflammation-Associated Colon Cancer in Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is characterised by the co-occurrence of inflammatory bowel diseases, particularly ulcerative colitis (UC). We investigated how the interaction of miR-125b with the sphingosine-1-phosphate (S1P)/ceramide axis may predispose patients with PSC, PSC/UC, and UC to carcinogenesis in the ascending and sigmoid colons. The overexpression of miR-125b was accompanied by the upregulation of S1P, ceramide synthases, ceramide kinases, and the downregulation of AT-rich interaction domain 2 in the ascending colon of PSC/UC, which contributed to the progression of high microsatellite instability (MSI-H) colorectal carcinoma. We also showed that the overexpression of sphingosine kinase 2 (SPHK2) and the genes involved in the glycolytic pathway in the sigmoid colon of UC led to the upregulation of Interleukin 17 (IL-17). In vitro stimulation of human intestinal epithelial cells (Caco-2, HT-29, and NCM460D) with lipopolysaccharide suppressed miR-125b and increased proinflammatory cytokines, whereas the induction of miR-125b activity by either a miR-125b mimetic or lithocholic acid resulted in the inhibition of miR-125b targets. In summary, miR-125b overexpression was associated with an imbalance in the S1P/ceramide axis that can lead to MSI-H cancer progression in PSC/UC. Furthermore, SPHK2 overexpression and a change in the cellular metabolic flux are important players in inflammation-associated colon cancer in UC.