DSS induced colitis increases portal LPS levels and enhances hepatic inflammation and fibrogenesis in experimental NASH

The impact and mechanism of TET3 overexpression on the progression of hepatic fibrosis

Aims: To investigate whether TET3 regulates hepatic stellate cell apoptosis and understand the role of demethylation in hepatic fibrosis (HF). Methods: LX-2T cells were infected with TET3 lentivirus. After TET3 adenovirus infection, the degree of HF in each group was analyzed. Chromatin immunoprecipitation was used to verify the targeting relationship between TET3 and CBP, and finally the expression of various proteins was detected. Results: TET3 overexpression activated the CBP/FOXO1-BIM pathway, increased the expression of apoptotic proteins and accelerated the apoptosis of activated LX-2 cells. The degree of HF was improved in the TET3 upregulation group. Conclusion: TET3 can activate the CBP/FOXO1-BIM pathway to accelerate the apoptosis of activated hepatic stellate cells and ultimately alleviate HF.

Oral Delivery of Mouse β-Defensin 14 (mBD14)-Producing Lactococcus lactis NZ9000 Attenuates Experimental Colitis in Mice

Antimicrobial peptides (AMPs) play essential roles in maintaining intestinal health and have been suggested as possible therapeutic strategies against inflammatory bowel disease (IBD). However, the instability of AMPs in the process of transmission in vivo limits their application in the treatment of IBD. In this study, we constructed the mBD14-producing Lactococcus lactis NZ9000 (L. lactis/mBD14) to achieve enteric delivery of mBD14 and evaluated its protective effect on dextran sodium sulfate (DSS)-induced colitis. Mice treated with L. lactis/mBD14 exhibited milder symptoms of colitis (P < 0.01). Additionally, L. lactis/mBD14 treatment reversed DSS-induced epithelial dysfunction and reduced the production of pro-inflammatory cytokines in colon (P < 0.01). Mechanistically, L. lactis/mBD14 significantly inhibited NOD-like receptor pyrin domain containing three inflammasome-mediated pro-inflammatory response (P < 0.05) and regulated microbiota homeostasis by promoting the abundance of probiotic bacteria Akkermansia muciniphila and Faecalibacterium prausnitzii and decreasing the pathogenic Escherichia coli (P < 0.01). Taken together, this study demonstrates the protective effect of L. lactis/mBD14 in DSS-induced colitis, and suggests that oral administration of L. lactis/mBD14 may represent a potential therapeutic strategy for IBD.

Chlorogenic acid ameliorated non-alcoholic steatohepatitis via alleviating hepatic inflammation initiated by LPS/TLR4/MyD88 signaling pathway

Non-alcoholic steatohepatitis (NASH) is a severe pathological stage in non-alcoholic fatty liver disease (NAFLD) and is generally recognized to be induced by chronic inflammation. Natural compound chlorogenic acid (CGA) is well-known for its anti-inflammatory capacity. This study aimed at evaluating the alleviation of CGA on NASH and further exploring its engaged mechanism via focusing on abrogating hepatic inflammation. Our results showed that CGA had a good amelioration on NASH in vivo. CGA alleviated liver oxidative injury by inducing nuclear factor erythroid 2-related factor 2 (Nrf2) activation and reduced liver steatosis via up-regulating peroxisome proliferator-activated receptor-alpha (PPARα). CGA attenuated hepatic inflammation in vivo, but didn't decrease the elevated lipopolysaccharide (LPS) content. CGA blocked the activation of nuclear factor kappa-B (NFκB) or inflammasome both in MCDD-fed mice and in LPS-stimulated macrophages. CGA was found to directly bind to myeloid differentiation primary response 88 (MyD88), and thus competitively blocked the interaction between toll-like receptor 4 (TLR4) and MyD88, thereby abrogating hepatic inflammation initiated by LPS-TLR4-MyD88. Moreover, the CGA-provided anti-inflammatory effect was obviously disappeared in macrophages overexpressed MyD88. Hence, CGA has an excellent efficacy in improving NASH. CGA alleviated liver inflammation during NASH progression through blocking LPS-TLR4-MyD88 signaling pathway via directly binding to MyD88.

Impact of Vancomycin Treatment and Gut Microbiota on Bile Acid Metabolism and the Development of Non-Alcoholic Steatohepatitis in Mice

The potential roles of the gut microbiota in the pathogenesis of non-alcoholic fatty liver disease, including non-alcoholic steatohepatitis (NASH), have attracted increased interest. We have investigated the links between gut microbiota and NASH development in Tsumura-Suzuki non-obese mice fed a high-fat/cholesterol/cholate-based (iHFC) diet that exhibit advanced liver fibrosis using antibiotic treatments. The administration of vancomycin, which targets Gram-positive organisms, exacerbated the progression of liver damage, steatohepatitis, and fibrosis in iHFC-fed mice, but not in mice fed a normal diet. F4/80⁺-recruited macrophages were more abundant in the liver of vancomycin-treated iHFC-fed mice. The infiltration of CD11c⁺-recruited macrophages into the liver, forming hepatic crown-like structures, was enhanced by vancomycin treatment. The co-localization of this macrophage subset with collagen was greatly augmented in the liver of vancomycin-treated iHFC-fed mice. These changes were rarely seen with the administration of metronidazole, which targets anaerobic organisms, in iHFC-fed mice. Finally, the vancomycin treatment dramatically modulated the level and composition of bile acid in iHFC-fed mice. Thus, our data demonstrate that changes in inflammation and fibrosis in the liver by the iHFC diet can be modified by antibiotic-induced changes in gut microbiota and shed light on their roles in the pathogenesis of advanced liver fibrosis.

Tea (Camellia sinensis) ameliorates DSS-induced colitis and liver injury by inhibiting TLR4/NF-κB/NLRP3 inflammasome in mice

The gut-liver axis is a bidirectional relationship between the gut with its microbiota and the hepatic. Ulcerative colitis (UC) disrupts the intestinal barrier and influx of intestinal microorganisms and their products into the liver, which trigger liver injury. Tea consumption is associated with a low incidence of UC in Asian countries. In this study, we revealed the mechanisms of six types of tea water extracts (TWEs) obtained from the leaves of Camellia sinensis on the dextran sodium sulfate (DSS)-induced colitis and liver injury in mice. The TWEs significantly restored mucin production and increased the expression levels of tight junction (TJ) proteins such as zonula occludens-1 (ZO-1), occluding, and claudin-1. In addition, TWEs also reduced the levels of pro-inflammatory cytokines in the colon and liver tissue by inactivating the NF-κB/NLRP3. Moreover, TEWs treatment promoted the integrity of the intestinal barrier to reduce serum lipopolysaccharide (LPS) levels, thereby reducing liver injury caused by intestinal microbial translocation and LPS induction. Analysis of 16 S rRNA microbial sequencing revealed that tea water extracts (TWEs) restored the DSS-induced gut dysbiosis. Interestingly, our results showed that the degree of fermentation of tea leaves was negatively associated with the alleviation of DSS-induced colitis effects, and there was also an overall negative trend with colitis-induced liver injury, except for black tea. Taken together, tea consumption mitigated DSS-induced colitis and liver injury in mice via inhibiting the TLR4/NF-κB/NLRP3 inflammasome pathway.

Is it possible to intervene early cirrhosis by targeting toll-like receptors to rebalance the intestinal microbiome?

Cirrhosis is a progressive chronic liver disease caused by one or more causes and characterized by diffuse fibrosis, pseudolobules, and regenerated nodules. Once progression to hepatic decompensation, the function of the liver and other organs is impaired and almost impossible to reverse and recover, which often results in hospitalization, impaired quality of life, and high mortality. However, in the early stage of cirrhosis, there seems to be a possibility of cirrhosis reversal. The development of cirrhosis is related to the intestinal microbiota and activation of toll-like receptors (TLRs) pathways, which could regulate cell proliferation, apoptosis, expression of the hepatomitogen epiregulin, and liver inflammation. Targeting regulation of intestinal microbiota and TLRs pathways could affect the occurrence and development of cirrhosis and its complications. In this paper, we first reviewed the dynamic change of intestinal microbiota and TLRs during cirrhosis progression. And further discussed the interaction between them and potential therapeutic targets to reverse early staged cirrhosis.

Dietary-Induced Bacterial Metabolites Reduce Inflammation and Inflammation-Associated Cancer via Vitamin D Pathway

Environmental factors, including westernised diets and alterations to the gut microbiota, are considered risk factors for inflammatory bowel diseases (IBD). The mechanisms underpinning diet-microbiota-host interactions are poorly understood in IBD. We present evidence that feeding a lard-based high-fat (HF) diet can protect mice from developing DSS-induced acute and chronic colitis and colitis-associated cancer (CAC) by significantly reducing tumour burden/incidence, immune cell infiltration, cytokine profile, and cell proliferation. We show that HF protection was associated with increased gut microbial diversity and a significant reduction in Proteobacteria and an increase in Firmicutes and Clostridium cluster XIVa abundance. Microbial functionality was modulated in terms of signalling fatty acids and bile acids (BA). Faecal secondary BAs were significantly induced to include moieties that can activate the vitamin D receptor (VDR), a nuclear receptor richly represented in the intestine and colon. Indeed, colonic VDR downstream target genes were upregulated in HF-fed mice and in combinatorial lipid-BAs-treated intestinal HT29 epithelial cells. Collectively, our data indicate that HF diet protects against colitis and CAC risk through gut microbiota and BA metabolites modulating vitamin D targeting pathways. Our data highlights the complex relationship between dietary fat-induced alterations of microbiota-host interactions in IBD/CAC pathophysiology.

Gut inflammation and adaptive immunity amplify acetaminophen toxicity in bowel and liver

BACKGROUND AND AIM

Prevention of liver failure arising from accidental or deliberate paracetamol (acetaminophen [APAP]) overdose remains a vexed health problem despite well-publicized guidelines for its early detection and treatment. It is recognized that the gut may aggravate liver pathology, via the gut-liver axis. The main aim of this study was to assess the role of the colon in APAP-induced liver toxicity.

METHODS

Liver necrosis and colitis were studied following sublethal doses of APAP administered intraperitoneally to C57Bl/6 wild-type (WT) mice, as well as to C57Bl/6 Winnie mice, which develop a spontaneous colitis caused by a SNP in Muc2, and WT mice with acute DSS-induced colitis. Repeated APAP exposure was studied in WT and Rag1 ko mice that lack mature T and B lymphocytes.

RESULTS

APAP overdose resulted in significant colonic injury in WT mice (P < 0.05), which resolved by 24 h. Underlying colitis was not associated with liver necrosis, but colitis exacerbated APAP-induced liver injury and extended APAP-colonic injury. Prior APAP exposure exacerbated both APAP-liver and APAP-colonic injury more so in WT than Rag1 ko mice. APAP impaired barrier function with increased intestinal permeability and associated bacterial translocation to the liver and spleen in mice with the Winnie phenotype.

CONCLUSIONS

This study identifies novel roles for APAP in causing colitis, the amplification of APAP-liver toxicity where there is underlying colitis, and involvement of immune memory in APAP-toxicity. The latter could be key for decoding the poorly understood but important clinical entity of chronic APAP liver failure.

Tetrastigma hemsleyanum leaf extracts ameliorate NAFLD in mice with low-grade colitis via the gut-liver axis

Nonalcoholic fatty liver disease (NAFLD) is a complex metabolic disorder, manifested as oxidative stress, lipid accumulation, and inflammation of the liver. Tetrastigma hemsleyanum leaves (THL), which are rich in flavonoids and phenolic acids, have good anti-inflammatory, antioxidant, and hepatoprotective effects. However, it is unknown whether THL extracts can improve NAFLD and the underlying mechanisms are unknown. Hence, this study was designed to investigate the effects of THL extracts on NAFLD and perform a preliminary inquiry into the underlying mechanism based on the gut-liver axis. The results showed that THL extracts could reverse NAFLD-related oxidative stress, lipid accumulation, and inflammation. Additionally, the protective effect of THL extracts on the gut includes the maintenance of the intestinal barrier and the regulation of gut microbiota, which may be one of the mechanisms by which THL improves NAFLD. To be specific, in our study, THL extracts alleviated hepatic lipid accumulation and oxidative stress by regulating the expression of lipid synthesis/catabolism and the oxidative stress genes (SREBP-1c/ACC-1/PPAR-α/PPAR-γ/Keap1/Nrf2). In addition, THL extracts reduced damage to the intestinal barrier (ZO-1/Mucin2/occludin) and increased the relative abundance of Lactobacillales, Ruminococcaceae, and Bifidobacteriales in NAFLD mice. In short, THL extracts alleviated NAFLD-related oxidative stress, lipid accumulation, and inflammation in NAFLD mice which may be via the gut-liver axis (gut barrier integrity and gut microbiota).

Elafibranor modulates ileal macrophage polarization to restore intestinal integrity in NASH: Potential crosstalk between ileal IL-10/STAT3 and hepatic TLR4/NF-κB axes

Experimental and clinical evidence implicate disrupted gut barrier integrity in provoking innate immune responses, specifically macrophages, towards the progression of non-alcoholic steatohepatitis (NASH). Peroxisome proliferator-activated receptors (PPARs), a subset of the nuclear receptor superfamily, act to fine-tune several metabolic and inflammatory processes implicated in NASH. As such, the current study was carried out to decipher the potential role of dual PPAR α/δ activation using elafibranor (ELA) on ileal macrophage polarization (MP) and its likely impact on the liver in a NASH setting. To achieve this aim, an in vitro NASH model using fat-laden HepG2 cells was first used to validate the impact of ELA on hepatic fat accumulation. Afterwards, ELA was used in a combined model of dietary NASH and chronic colitis analogous to the clinical presentation of NASH parallel with intestinal barrier dysfunction. ELA mitigated fat accumulation in vitro as evidenced by Oil Red-O staining and curbed triglyceride levels. Additionally, ELA restored the expression of tight junctional proteins, claudin-1 and occludin, along with decreasing intestinal permeability and inflammation skewing ileal macrophages towards the M2 phenotype, as indicated by boosted arginase-1 (Arg1) and curtailed inducible nitric oxide synthase (iNOS) expression levels. These changes were aligned with a modulation in hepatic toll-like receptor-4 (TLR4)/nuclear factor kappa B (NF-κB) along with ileal interleukin-10 (IL-10)/signal transducer and activator of transcription-3 (STAT3) axes. Overall, the present findings suggest that the dual PPAR α/δ agonist, ELA, may drive MP in the ileum towards the M2 phenotype improving intestinal integrity towards alleviating NASH.

Qu-Yu-Jie-Du Decoction Ameliorates Dextran Sulfate Sodium-Induced Colitis in Mice by Modulation of Neutrophils and Macrophage Infiltration

Background. Inflammatory bowel disease (IBD) is becoming a global disease. A percentage of IBD patients will not react to therapy or will lose their response. Qu-Yu-Jie-Du Decoction (QYJD) is a traditional Chinese medicine formula commonly used for intestinal diseases. It has been reported that QYJD has an anti-inflammatory effect, but the mechanism is not fully understood. In this study, we mainly evaluated the anti-inflammatory effect of QYJD and explored the possible mechanisms. Methods. Twenty-four BALB/c mice were randomly divided into 4 groups according to their body weight, namely, the control group, the dextran sulfate sodium (DSS) group, the DSS + QYJD group, and the QYJD group. Mice were given 3% DSS drinking water freely, and at the same time, mice were given normal saline or QYJD (4.44 mg/g/d), respectively. Mental state, faeces, and weight were recorded every day. On the 10th day, the mice were sacrificed and collected for investigation. The length of the mice colon was measured. Histological analysis was used to detect the morphological changes in the colon. Immunohistochemistry was used to measure the infiltration of macrophages (F4/80, CD163) and neutrophils (Ly6G). Colorimetry was used to detect the myeloperoxidase (MPO) activity of colon tissues. ELISA was utilized to detect associated inflammatory cytokines and chemokines in colon tissues. Results. QYJD alleviated the weight loss and colitis symptoms of mice caused by DSS. QYJD fought against the shortening of the intestine caused by DSS; that is, it improved the decline of intestinal compliance in mice and had a protective effect on colon tissues. The mechanisms were related to downregulating macrophages and neutrophils in colon tissues of infiltration. Besides, QYJD simultaneously reduced the activity of myeloperoxidase activity (MPO) and the contents of IL-1β, IL-6, TNF-α, TGF-β, CCL2, and CXCL2 in colon tissues. Conclusions. QYJD can ameliorate DSS-induced colitis in mice and the mechanism is connected with a reduction in neutrophil and macrophage infiltration.

Sanhuang xiexin decoction ameliorates secondary liver injury in DSS-induced colitis involve regulating inflammation and bile acid metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

SanHuang XieXin decoction (SXD) is a widely applicated traditional Chinese medicine (TCM) with a significant gut-liver axis regulation effect.

AIM OF THE STUDY

To evaluate the therapeutic effect and elucidate the possible underlying molecular mechanisms of SXD on liver damage secondary to ulcerative colitis (UC) in mice.

MATERIALS AND METHODS

A model of liver damage secondary to UC was induced by drinking 5% dextran sodium sulfate (DSS) in mice. These mice were treated with one of three doses of SXD or sulfasalazine (SASP), then liver samples were collected and tested.

RESULTS

The results reveal that SXD treatment reduced liver cells swelling, and inhibited the accumulation of the hepatic-pro-inflammatory cytokines IL-1β and tumor necrosis factor-α (TNF-α) in mice with colitis. In addition, SXD reduced the production of nitric oxide (NO) and malondialdehyde (MDA), and increased the activities of superoxide dismutase (SOD). In inflammation regulating, SXD significantly down regulated the protein expression of MyD88 and p-Iκα, but upregulated Iκα. In bile acid metabolism regulating, SXD significantly down regulated the protein expression of FXR, MRP2, BESP and SHP. Therefore, SXD treatment can regulate the TLR4-NF-κB and bile acid metabolism pathways to alleviate liver inflammation and cholestasis.

CONCLUSIONS

These results demonstrate that SXD is a potential alternative therapeutic medicine for the treatment of liver damage secondary to colitis.

Gut-Liver Axis and Non-Alcoholic Fatty Liver Disease: A Vicious Circle of Dysfunctions Orchestrated by the Gut Microbiome

Non-alcoholic fatty liver disease (NAFLD) is a prevalent, multifactorial, and poorly understood liver disease with an increasing incidence worldwide. NAFLD is typically asymptomatic and coupled with other symptoms of metabolic syndrome. The prevalence of NAFLD is rising in tandem with the prevalence of obesity. In the Western hemisphere, NAFLD is one of the most prevalent causes of liver disease and liver transplantation. Recent research suggests that gut microbiome dysbiosis may play a significant role in the pathogenesis of NAFLD by dysregulating the gut-liver axis. The so-called "gut-liver axis" refers to the communication and feedback loop between the digestive system and the liver. Several pathological mechanisms characterized the alteration of the gut-liver axis, such as the impairment of the gut barrier and the increase of the intestinal permeability which result in endotoxemia and inflammation, and changes in bile acid profiles and metabolite levels produced by the gut microbiome. This review will explore the role of gut-liver axis disruption, mediated by gut microbiome dysbiosis, on NAFLD development.

Premorbid Steatohepatitis Increases the Seriousness of Dextran Sulfate Sodium-induced Ulcerative Colitis in Mice

BACKGROUND AND AIMS

The concurrence of nonalcoholic steatohepatitis (NASH) and ulcerative colitis (UC) is increasingly seen in clinical practice, but the underlying mechanisms remain unclear. This study aimed to develop a mouse model of the phenomenon by combining high-fat high-cholesterol diet (HFHCD)-induced NASH and dextran sulfate sodium (DSS)-induced UC, that would support mechanistic studies.

METHODS

Male C57BL/6 mice were randomly assigned to two groups receiving either a chow diet or HFHCD for 12 weeks of NASH modeling. The mice were the divided into four subgroups for UC modeling: (1) A control group given a chow diet with normal drinking water; (2) A colitis group given chow diet with 2% DSS in drinking water; (3) A steatohepatitis group given HFHCD with normal drinking water; and (4) A steatohepatitis + colitis group given HFHCD with 2% DSS in drinking water.

RESULTS

NASH plus UC had high mortality (58.3%). Neither NASH nor UC alone were fatal. Although DSS-induced colitis did not exacerbate histological liver injury in HFHCD-fed mice, premorbid NASH significantly increased UC-related gut injury compared with UC alone. It was characterized by a significantly shorter colon, more colonic congestion, and a higher histopathological score (p<0.05). Inflammatory (tumor necrosis factor-alpha, interleukin 1 beta, C-C motif chemokine ligand 2, and nuclear factor kappa B) and apoptotic (Bcl2, Bad, Bim, and Bax) signaling pathways were significantly altered in distal colon tissues collected from mice with steatohepatitis + colitis compared with the other experimental groups.

CONCLUSIONS

Premorbid steatohepatitis significantly aggravated DSS-induced colitis and brought about a lethal phenotype. Potential links between NASH and UC pathogeneses can be investigated using this model.

High-fat diet combined with dextran sulfate sodium failed to induce a more serious NASH phenotype than high-fat diet alone

Background and Aims: Animal models are essential tools to investigate the pathogenesis of diseases. Disruption in the intestinal epithelial barrier and gut vascular barrier is an early event in the development of non-alcoholic fatty liver disease (NAFLD). Intestinal epithelial barrier can be destroyed by dextran sulfate sodium (DSS) oral administration. High fat diet (HFD)-induced non-alcoholic steatohepatitis (NASH) rat model has been widely used. Recently, the combination of HFD with DSS induced NASH model has also been reported. The present study aimed to evaluate whether this composite NASH animal model is more ideal than that induced by HFD alone. Methods: Rats were divided into control, HFD and HFD combined with DSS (DSS + HFD) groups. They were fed with routine diet, high-fat diet, and HFD combined with DSS drinking, respectively, for 22 weeks. Histopathological analysis (HE staining, Oil-Red O staining, Masson staining), lipid parameters testing (TG, TC, GLU, NEFA, TRIG, LDL, HDL), testing on indicators of inflammation (TNF-α, ALT, AST, ALP, LDH) and oxidative stress (MDA, SOD, CAT) were performed. Results: Rats in HFD and DSS + HFD group displayed increase in the body weight, liver weight, lipids accumulation and the levels of TNF-α, ALT, AST, ALP, MDA in serum and liver accompanied with impaired glucose tolerance, obvious hepatitis, and decreased levels of SOD and CAT in serum and liver compared to those in control group. Moreover, in the DSS + HFD group, but not in the HFD group, proliferation of fibrous tissue in the portal area and the hepatic lobules was found. Conclusion: The addition of DSS on high-fat diet did not exacerbate lipid accumulation and inflammation, but induced NASH-related liver fibrosis.

Colonic inflammation accelerates the progression of liver disease: A protective role of dipotassium glycyrrhizate

BACKGROUND

The incidence of non-alcoholic fatty liver disease (NAFLD) and its more severe and progressive form, non-alcoholic steatohepatitis (NASH) is increasing worldwide. Gut inflammation seems to concur to the pathogenesis of NASH. No drugs are currently approved for NASH treatment.

AIMS

To investigate if inflamed gut directly contributes to the progression of NASH through gut epithelial and vascular barrier impairment and to evaluate the efficacy of dipotassium glycyrrhizate (DPG) to improve the liver disease.

METHODS

A NASH model was set up by feeding mice, for 8 and 13 weeks, with high fat diet with high fructose and glucose (HFD-FG) supplemented periodically with dextran sulfate sodium (DSS) in drinking water. A group was also treated with DPG by gavage. Histological, immunohistochemical and molecular analysis were performed.

RESULTS

DSS-induced colitis increased steatosis, inflammatory (IL-6, TNFα, NLRP3, MCP-1) as well as fibrotic (TGF-β, α-SMA) mediator expression in HFD-FG mice. Beneficial effect of DPG was associated with restoration of intestinal epithelial and vascular barriers, evaluated respectively by ZO-1 and PV-1 expression, that are known to limit bacterial translocation.

CONCLUSION

Colonic inflammation strongly contributes to the progression of NASH, likely by favouring bacterial translocation. DPG treatment could represent a novel strategy to reduce liver injury.

Butyrate Treatment of DSS-Induced Ulcerative Colitis Affects the Hepatic Drug Metabolism in Mice

The development of inflammatory bowel disease (IBD) is associated with alterations in the gut microbiota. There is currently no universal treatment for this disease, thus emphasizing the importance of developing innovative therapeutic approaches. Gut microbiome-derived metabolite butyrate with its well-known anti-inflammatory effect in the gut is a promising candidate. Due to increased intestinal permeability during IBD, butyrate may also reach the liver and influence liver physiology, including hepatic drug metabolism. To get an insight into this reason, the aim of this study was set to clarify not only the protective effects of the sodium butyrate (SB) administration on colonic inflammation but also the effects of SB on hepatic drug metabolism in experimental colitis induced by dextran sodium sulfate (DSS) in mice. It has been shown here that the butyrate pre-treatment can alleviate gut inflammation and reduce the leakiness of colonic epithelium by restoration of the assembly of tight-junction protein Zonula occludens-1 (ZO-1) in mice with DSS-induced colitis. In this article, butyrate along with inflammation has also been shown to affect the expression and enzyme activity of selected cytochromes P450 (CYPs) in the liver of mice. In this respect, CYP3A enzymes may be very sensitive to gut microbiome-targeted interventions, as significant changes in CYP3A expression and activity in response to DSS-induced colitis and/or butyrate treatment have also been observed. With regard to medications used in IBD and microbiota-targeted therapeutic approaches, it is important to deepen our knowledge of the effect of gut inflammation, and therapeutic interventions were followed concerning the ability of the organism to metabolize drugs. This gut–liver axis, mediated through inflammation as well as microbiome-derived metabolites, may affect the response to IBD therapy.

Inflammatory Bowel Disease-associated Fatty Liver Disease: the Potential Effect of Biologic Agents

Inflammatory bowel diseases [IBD] exhibit intestinal and systemic manifestations. Nonalcoholic fatty liver disease [NAFLD] is a common co-existing condition, possibly contributing to the cardio-metabolic burden and overall morbidity. Εmerging therapeutic choices of biologic agents have modified the clinical course of IBD; however, their impact on IBD-associated NAFLD has not been extensively evaluated. The prevalence of NAFLD varies among IBD patients, but it appears higher than in the general population in the majority of quality studies. In terms of pathogenetic and risk factors of NAFLD, they may vary with IBD activity. Dysbiosis, mucosal damage, and cytokine release have been implicated in the pathogenesis during the relapses, whereas metabolic risk factors seem to play a dominant role during the remissions of IBD. Considering biologics, although quality data are scarce, agents suppressing tumour necrosis factor may offer potential benefits in IBD-associated NAFLD, whereas anti-integrins do not appear to confer any therapeutic advantage. In conclusion, IBD-associated NAFLD possibly follows two different patterns, one manifested during the relapses and one during the remissions of IBD. Some, but not all, biologics may benefit NAFLD in patients with IBD. Further mechanistic and prospective cohort studies are warranted to illuminate the effects of various biologics on NAFLD.

Effects of Dietary Nutrients on Fatty Liver Disease Associated With Metabolic Dysfunction (MAFLD): Based on the Intestinal-Hepatic Axis

Non-alcoholic fatty liver disease (NAFLD) has recently become the most common liver disease with a global prevalence of over 25% and is expected to increase. Recently, experts have reached a consensus that “fatty liver disease associated with metabolic dysfunction or MAFLD” may be a more appropriate and inclusive definition than NAFLD. Like the former name NAFLD, MAFLD, as a manifestation of multiple system metabolic disorders involving the liver, has certain heterogeneity in its pathogenesis, clinical manifestations, pathological changes and natural outcomes. We found that there is a delicate dynamic balance among intestinal microflora, metabolites and host immune system to maintain a healthy intestinal environment and host health. On the contrary, this imbalance is related to diseases such as MAFLD. However, there are no clear studies on how dietary nutrients affect the intestinal environment and participate in the pathogenesis of MAFLD. This review summarizes the interactions among dietary nutrients, intestinal microbiota and MAFLD in an attempt to provide evidence for the use of dietary supplements to regulate liver function in patients with MAFLD. These dietary nutrients influence the development and progression of MAFLD mainly through the hepatic-intestinal axis by altering dietary energy absorption, regulating bile acid metabolism, changing intestinal permeability and producing ethanol. Meanwhile, the nutrients have the ability to combat MAFLD in terms of enriching abundance of intestinal microbiota, reducing Firmicutes/Bacteroidetes ratio and promoting abundance of beneficial gut microbes. Therefore, family therapy with MAFLD using a reasonable diet could be considered.

Reconsidering Meat Intake and Human Health: A Review of Current Research

Meat consumption is gradually increasing and its impact on health has attracted widespread attention, resulting in epidemiological studies proposing a reduction in meat and processed meat intake. This review briefly summarizes recent advances in understanding the effects of meat or processed meat on human health, as well as the underlying mechanisms. Meat consumption varies widely among individuals, populations, and regions, with higher consumption in developed countries than in developing countries. However, increasing meat consumption may not be the main cause of increasing incidence of chronic disease, since the development of chronic disease is a complex physiological process that involves many factors, including excessive total energy intake and changes in food digestion processes, gut microbiota composition, and liver metabolism. In comparison, unhealthy dietary habits and a sedentary lifestyle with decreasing energy expenditure are factors more worthy of reflection. Meat and meat products provide high-value protein and many key essential micronutrients. In short, as long as excessive intake and overprocessing of meats are avoided, meat remains an indispensable source of nutrition for human health.

The Role of Gut–Liver Axis in Gut Microbiome Dysbiosis Associated NAFLD and NAFLD-HCC

Nonalcoholic fatty liver disease (NAFLD) is considered as one of the most prevalent chronic liver diseases worldwide due to the rapidly rising prevalence of obesity and metabolic syndrome. As a hepatic manifestation of metabolic disease, NAFLD begins with hepatic fat accumulation and progresses to hepatic inflammation, termed as non-alcoholic steatohepatitis (NASH), hepatic fibrosis/cirrhosis, and finally leading to NAFLD-related hepatocellular carcinoma (NAFLD-HCC). Accumulating evidence showed that the gut microbiome plays a vital role in the initiation and progression of NAFLD through the gut–liver axis. The gut–liver axis is the mutual communication between gut and liver comprising the portal circulation, bile duct, and systematic circulation. The gut microbiome dysbiosis contributes to NAFLD development by dysregulating the gut–liver axis, leading to increased intestinal permeability and unrestrained transfer of microbial metabolites into the liver. In this review, we systematically summarized the up-to-date information of gut microbiome dysbiosis and metabolomic changes along the stages of steatosis, NASH, fibrosis, and NAFLD-HCC. The components and functions of the gut–liver axis and its association with NAFLD were then discussed. In addition, we highlighted current knowledge of gut microbiome-based treatment strategies targeting the gut–liver axis for preventing NAFLD and its associated HCC.

Gut non-bacterial microbiota contributing to alcohol-associated liver disease

Intestinal microbiota, dominated by bacteria, plays an important role in the occurrence and the development of alcohol-associated liver disease (ALD), which is one of the most common liver diseases around the world. With sufficient studies focusing on the gut bacterial community, chronic alcohol consumption is now known as a key factor that alters the composition of gut bacterial community, increases intestinal permeability, causes intestinal dysfunction, induces bacterial translocation, and exacerbates the process of ALD via gut-liver axis. However, gut non-bacterial communities including fungi, viruses, and archaea, which may also participate in the disease, has received little attention relative to the gut bacterial community. This paper will systematically collect the latest literatures reporting non-bacterial communities in mammalian health and disease, and review their mechanisms in promoting the development of ALD including CLEC7A pathway, Candidalysin (a peptide toxin secreted by Candida albicans), metabolites, and other chemical substances secreted or regulated by gut commensal mycobiome, virome, and archaeome, hoping to bring novel insights on our current knowledge of ALD.

Helicobacter pylori infection is not associated with portal hypertension-related gastrointestinal complications: A meta-analysis

Despite the importance of Helicobacter pylori infection and portal hypertension (PH)-associated gastrointestinal (GI) diseases, such as esophageal varices and portal hypertensive gastropathy (PHG), the impact of H. pylori infection on PH-related GI complications has not yet been elucidated. This meta-analysis investigated the association between H. pylori infection and the risk of PH-related GI complications. An electronic search for original articles published before May 2020 was performed using PubMed, EMBASE, and the Cochrane Library. Independent reviewers conducted the article screening and data extraction. We used the generic inverse variance method for the meta-analysis, and Begg's rank correlation test and Egger's regression test to assess publication bias. A total of 1,148 cases of H. pylori infection and 1,231 uninfected controls were included from 13 studies. H. pylori infection had no significant association with esophageal varices [relative risk (RR) = 0.96, 95% confidence interval (CI) = 0.87-1.06 for all selected studies; RR = 0.95, 95% CI = 0.84-1.07 for cohort studies; odds ratio (OR) = 0.96, 95% CI = 0.60-1.54 for case-control studies]. Although H. pylori infection was significantly associated with PHG in case-control studies [OR = 1.86, 95% CI = 1.17-2.96], no significant differences were found in the cohort studies [RR = 0.98, 95% CI = 0.91-1.05] or all studies combined [RR = 1.18, 95% CI = 0.93-1.52]. In conclusion, H. pylori infection was not associated with the risk of PH-related GI complications. Clinicians should carefully treat cirrhotic patients with PH-related GI complications, regardless of H. pylori infection.

4-Octyl Itaconate Supplementation Relieves Soybean Diet-Induced Liver Inflammation and Glycolipid Metabolic Disorders by Activating the Nrf2-Pparγ Pathway in Juvenile Gibel Carp

Itaconate is a promising new candidate for anti-inflammatory and metabolic reprogramming, and 4-octyl itaconate (OI) is a cell-permeable itaconate derivative. To investigate the effect of OI in inflammatory response and glycolipid metabolism, we fed gibel carp with a 40% dietary soybean meal diet containing 0.1% OI (SBM + 0.1OI) or not (SBM) and compared these with fishmeal (FM) as reference. Compared with FM, dietary SBM decreased the growth performance, induced inflammation in the intestine and liver, and decreased the glucose utilization ability of the liver. However, 0.1% OI supplementation in SBM significantly increased the growth performance (from 20.11 ± 0.77 to 23.33 ± 0.45 g, P < 0.05), reduced inflammation in different organs through Nrf2 activation, and alleviated SBM-induced high plasma glucose (from 6.06 ± 0.23 to 4.37 ± 0.14 g, P < 0.05) and low crude body lipid (from 4.08 ± 0.17 to 4.91 ± 0.10 g, P < 0.05). Multi-omics revealed that OI had obvious effects on carbohydrate metabolism. OI regulates peroxisome proliferator-activated receptor gamma (ppar-γ), and its target genes (glut2 and gk) enhance liver glycolysis and lipid de novo lipogenesis, which are also dependent on Nrf2 activation. To conclude, dietary 0.1% OI can promote the growth of gibel carp and alleviate foodborne intestinal and hepatic inflammation and abnormal glycolipid metabolism by Nrf2-regulated Pparγ expression.

The Gut-Liver Axis in Nonalcoholic Fatty Liver Disease: Association of Intestinal Permeability with Disease Severity and Treatment Outcomes

OBJECTIVE

To investigate the association between intestinal permeability and severity of nonalcoholic fatty liver disease (NAFLD) and the value of intestinal permeability in predicting the efficacy of metabolic therapy for NAFLD.

METHODS

Disease severity was compared between patients with normal and elevated intestinal permeability; correlations between D-lactate and different NAFLD parameters were analyzed; and the effects of metabolic therapy on NAFLD patients with normal and elevated intestinal permeability were evaluated.

RESULTS

A total of 190 patients with NAFLD were enrolled. NAFLD patients with elevated intestinal permeability had significantly higher levels of liver test parameters, liver ultrasonographic fat attenuation parameter, triglyceride, homeostasis model assessment of insulin resistance value, and diamine oxidase (all P˂0.05) than NAFLD patients with normal intestinal permeability. Furthermore, serum D-lactate levels were positively correlated with alanine transaminase, aspartate transaminase, gamma-glutamyl transpeptidase, total bilirubin, indirect bilirubin, fat attenuation parameter, triglyceride, and diamine oxidase (all P ˂ 0.05). Moreover, NAFLD patients with elevated intestinal permeability showed less improvement in TG levels (P = 0.014) after metabolic therapy.

CONCLUSION

Intestinal permeability correlates with the disease severity in patients with NAFLD. Moreover, intestinal permeability may have value for predicting the efficacy of metabolic therapy for NAFLD patients.

Lithium carbonate alleviates colon inflammation through modulating gut microbiota and Treg cells in a GPR43-dependent manner

BACKGROUND

Recent evidence suggests that neuropsychiatric stabilizers have a place in resolving gastrointestinal disorders. Lithium carbonate (LC) is one of the most commonly used drugs for bipolar disorder clinically. Here, we estimate the therapeutic function of LC against colitis and investigate the mechanism of intestinal flora and metabolism modulation.

METHODS

A colitis model was constructed by continuously administering 2.5% dextran sodium sulfate (DSS) solution daily for 7 days. Analysis of gut microbiota was carried out by 16S rRNA gene high-throughput sequencing. Spectrum antibiotic cocktail (ABX) and faecal microbiota transplantation (FMT) were employed to evaluate the protective effect of intestinal flora. Colonic Treg cells and related immune responses were detected by flow cytometry.

RESULTS

LC treatment significantly alleviated colon inflammation by regulating gut microbial diversity and altering flora composition. Notably, LC treatment upregulated short-chain fatty acid (SCFA)-producing bacteria, especially Akkermansia muciniphila (A. muciniphila), and transformed metabolite SCFA profiles. LC activated anti-inflammatory Treg cell responses in colonic lamina propria (LP) in a G-protein coupled receptor 43 (GPR43)-dependent mechanism. ABX, FMT and single bacteria gavage experiments were conducted to confirm the above mechanism.

CONCLUSIONS

As an intestinal microbiome and metabolite modulator, LC alleviates colon inflammation in a GPR43-dependent manner through activating Treg cell responses. Therefore, the therapeutic strategy of the microbiome-metabolite-immune axis, as observed in the A. muciniphila-SCFA-Treg cell axis in our study, might provide a new direction for the treatment of IBD.

Jiang Zhi Granule protects immunological barrier of intestinal mucosa in rats with non-alcoholic steatohepatitis

CONTEXT

Jiang Zhi Granule (JZG) is known to improve hepatic function, reduce liver fat deposition and inflammation in non-alcoholic fatty liver disease (NAFLD).

OBJECTIVE

To determine the protective mechanism of JZG on immunological barrier of intestinal mucosa in rats with diet-induced non-alcoholic steatohepatitis (NASH).

MATERIALS AND METHODS

A Sprague-Dawley (SD) model of NASH was established using a high-fat diet and 1% dextran sulphate sodium (DSS) through drinking water. The rats were randomized into four groups and treated for four weeks, respectively, including normal control (NC), model control (MC), positive control (PC) and JZG. Mesenteric lymph nodes (MLNs) cells were isolated and cultured to assess a potential disruption of the enteric immune barrier. Also, investigation of intestinal mucosal dendritic cell-toll-like-receptor-myeloid differentiation primary response 88 (DC-TLR-MyD88) signalling pathway in vitro was examined.

RESULTS

The lethal concentration 50 (LD50) of JZG was greater than 5 g/kg, while its inhibitory concentration 50 (IC50) was 1359 μg/mL in HepG2. In JZG group, the plasma levels of alanine transaminase (ALT), aspartate transaminase (AST), malondialdehyde (MDA), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglyceride (TG) and serum endotoxin were significantly (p < 0.01) reduced. In contrast, plasma concentrations of high-density lipoprotein cholesterol (HDL-C) and superoxide dismutase (SOD) were increased. Furthermore, proinflammatory factor, interferon-γ (IFN-γ)+ from CD4+ T cells in DSS-induced NASH rats increased significantly (p < 0.01) compared to NC group. Importantly, JZG treatment substantially decreased (p < 0.01) the relative expressions of TLR-44 and MyD88.

CONCLUSIONS

JZG treatment may protect immunological barrier of intestinal mucosa in NASH individual.

Dextran Sulfate Sodium Salt-Induced Colitis Aggravates Gut Microbiota Dysbiosis and Liver Injury in Mice With Non-alcoholic Steatohepatitis

Objective: Inflammatory bowel disease (IBD) is characterized by gut microbiota dysbiosis, which is also frequently observed in patients with non-alcoholic fatty liver disease. Whether gut microbiota dysbiosis in IBD patients promotes the development of non-alcoholic steatohepatitis (NASH) remains unclear. We aimed to explore the role of gut microbiota dysbiosis in the development of NASH in mice with dextran sulfate sodium salt (DSS) induced colitis. Design: Dextran sulfate sodium salt was used to induce colitis, and high fat (HF), in combination with a high-fructose diet, was used to induce NASH in C57BL/6J male mice. Mice were treated with (1%) DSS to induce colitis in cycles, and each cycle consisted of 7 days of DSS administration followed by a 10-day interval. The cycles were repeated throughout the experimental period of 19 weeks. Pathological alterations in colitis and NASH were validated by hematoxylin and eosin (H&E), oil red O, Sirius red staining, and immunofluorescence. Gut microbiota was examined by 16S rRNA sequencing, and gene expression profiles of hepatic non-parenchymal cells (NPCs) were detected by RNA sequencing. Results: Dextran sulfate sodium salt administration enhanced the disruption of the gut-vascular barrier and aggravated hepatic inflammation and fibrosis in mice with NASH. DSS-induced colitis was accompanied by gut microbiota dysbiosis, characterized by alteration in the core microbiota composition. Compared with the HF group, the abundance of p_Proteobacteria and g_Bacteroides increased, while that of f_S24-7 decreased in the DSS + HF mice. Specifically, gut microbiota dysbiosis was characterized by enrichment of lipopolysaccharide producing bacteria and decreased abundance of short-chain fatty acid-producing bacteria. Gene expression analysis of liver NPCs indicated that compared with the HF group, genes related to both inflammatory response and angiocrine signaling were altered in the DSS + HF group. The expression levels of inflammation-related and vascular development genes correlated significantly with the abundance of p_Proteobacteria, g_Bacteroides, or f_S24-7 in the gut microbiota, implying that gut microbiota dysbiosis induced by DSS might aggravate hepatic inflammation and fibrosis by altering the gene expression in NPCs. Conclusion: Dextran sulfate sodium salt-induced colitis may promote the progression of liver inflammation and fibrosis by inducing microbiota dysbiosis, which triggers an inflammatory response and disrupts angiocrine signaling in liver NPCs. The abundance of gut microbiota was associated with expression levels of inflammation-related genes in liver NPCs and may serve as a potential marker for the progression of NASH.

Gut Microbiome-Mediated Alteration of Immunity, Inflammation, and Metabolism Involved in the Regulation of Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is one of the leading causes of end-stage liver disease, leading to a rapidly growing global public health burden. The term “gut microbiome (GM)” refers to the approximately 100 trillion microbial cells that inhabit the host’s gastrointestinal tract. There is increasing evidence that GM is involved in the pathogenesis of NAFLD and may be a potential target for intervention. To explore GM-based strategies for precise diagnosis and treatment of NAFLD, great efforts have been made to develop a comprehensive and in-depth understanding of the host–microbe interaction. This review evaluates this interaction critically, mainly considering the intricate regulation of the metabolism, immunity, and inflammatory status during the evolution of the disease pathogenesis, revealing roles for the GM in NAFLD by examining advances in potential mechanisms, diagnostics, and modulation strategies.

Synopsis: Considering the intricate metabolic and immune/inflammatory homeostasis regulation, we evaluate the latest understanding of the host–microbe interaction and reveal roles for the gastrointestinal microbiome in NAFLD. Strategies targeting the gastrointestinal microbiome for the diagnosis and treatment of NAFLD are proposed.

The Gut-Liver Axis in Chronic Liver Disease: A Macrophage Perspective

Chronic liver disease (CLD) is a growing health concern which accounts for two million deaths per year. Obesity, alcohol overconsumption, and progressive cholestasis are commonly characterized by persistent low-grade inflammation and advancing fibrosis, which form the basis for development of end-stage liver disease complications, including hepatocellular carcinoma. CLD pathophysiology extends to the intestinal tract and is characterized by intestinal dysbiosis, bile acid dysregulation, and gut barrier disruption. In addition, macrophages are key players in CLD progression and intestinal barrier breakdown. Emerging studies are unveiling macrophage heterogeneity and driving factors of their plasticity in health and disease. To date, in-depth investigation of how gut-liver axis disruption impacts the hepatic and intestinal macrophage pool in CLD pathogenesis is scarce. In this review, we give an overview of the role of intestinal and hepatic macrophages in homeostasis and gut-liver axis disruption in progressive stages of CLD.

IL-6 downregulates hepatic carboxylesterases via NF-κB activation in dextran sulfate sodium-induced colitis

Ulcerative colitis (UC) is associated with increased levels of inflammatory factors, which is attributed to the abnormal expression and activity of enzymes and transporters in the liver, affecting drug disposition in vivo. This study aimed to examine the impact of intestinal inflammation on the expression of hepatic carboxylesterases (CESs) in a mouse model of dextran sulfate sodium (DSS)-induced colitis. Two major CESs isoforms, CES1 and CES2, were down-regulated, accompanied by decreases in hepatic microsomal metabolism of clopidogrel and irinotecan. Meanwhile, IL-6 levels significantly increased compared with other inflammatory factors in the livers of UC mice. In contrast, using IL-6 antibody simultaneously reversed the down-regulation of CES1, CES2, pregnane X receptor (PXR), and constitutive androstane receptor (CAR), as well as the nuclear translocation of NF-κB in the liver. We further confirmed that treatment with NF-κB inhibitor abolished IL-6-induced down-regulation of CES1, CES2, PXR, and CAR in vitro. Thus, it was concluded that IL-6 represses hepatic CESs via the NF-κB pathway in DSS-induced colitis. These findings indicate that caution should be exercised concerning the proper and safe use of therapeutic drugs in patients with UC.

Gut-liver-axis: Barrier function of liver sinusoidal endothelial cell

Liver diseases are associated with the leaky gut via the gut-liver-axis. Previous studies have paid much attention to the effect of gut barrier damage. Notably, clinical observations and basic research reveal that the gut barrier damage seldom leads to liver injury independently but aggravates pre-existing liver diseases such as non-alcoholic fatty liver disease and drug-induced liver injury. These evidences suggest that there is a hepatic barrier in the gut-liver-axis, protecting the liver against gut-derived pathogenic factors. However, it has never been investigated which type of liver cell plays the role of hepatic barrier. Under physiological conditions, liver sinusoidal endothelial cell (LSEC) can take up and eliminate virus, bacteriophage, microbial products, and metabolic wastes. LSEC also keeps the homeostasis of liver immune environment via tolerance-inducing and anti-inflammatory functions. In contrast, under pathological conditions, the clearance function of LSEC is impaired, and LSEC turns into a pro-inflammatory pattern. Given its anatomical position and physiological functions, LSEC is proposed as the hepatic barrier in the gut-liver-axis. In this review, we aim to further understand the role of LSEC as the hepatic barrier. Future studies are warranted to seek effective treatments to improve LSEC health, which appears to be a promising approach to prevent gut-derived liver injury.

Inhibition of chylomicron assembly leads to dissociation of hepatic steatosis from inflammation and fibrosis

Regulating dietary fat absorption may impact progression of nonalcoholic fatty liver disease (NAFLD). Here, we asked if inducible inhibition of chylomicron assembly, as observed in intestine-specific microsomal triglyceride (TG) transfer protein knockout mice (Mttp-IKO), could retard NAFLD progression and/or reverse established fibrosis in two dietary models. Mttp-IKO mice fed a methionine/choline-deficient (MCD) diet exhibited reduced hepatic TGs, inflammation, and fibrosis, associated with reduced oxidative stress and downstream activation of c-Jun N-terminal kinase and nuclear factor kappa B signaling pathways. However, when Mttp^flox mice were fed an MCD for 5 weeks and then administered tamoxifen to induce Mttp-IKO, hepatic TG was reduced, but inflammation and fibrosis were increased after 10 days of reversal along with adaptive changes in hepatic lipogenic mRNAs. Extending the reversal time, following 5 weeks of MCD feeding to 30 days led to sustained reductions in hepatic TG, but neither inflammation nor fibrosis was decreased, and both intestinal permeability and hepatic lipogenesis were increased. In a second model, similar reductions in hepatic TG were observed when mice were fed a high-fat/high-fructose/high-cholesterol (HFFC) diet for 10 weeks, then switched to chow ± tamoxifen (HFFC → chow) or (HFFC → Mttp-IKO chow), but again neither inflammation nor fibrosis was affected. In conclusion, we found that blocking chylomicron assembly attenuates MCD-induced NAFLD progression by reducing steatosis, oxidative stress, and inflammation. In contrast, blocking chylomicron assembly in the setting of established hepatic steatosis and fibrosis caused increased intestinal permeability and compensatory shifts in hepatic lipogenesis that mitigate resolution of inflammation and fibrogenic signaling despite 50–90-fold reductions in hepatic TG.

Berberine Alleviates Non-alcoholic Steatohepatitis Through Modulating Gut Microbiota Mediated Intestinal FXR Activation

Berberine is a natural plant alkaloid isolated from a diverse range of genera, it obtains anti-inflammatory, anti-obesity, and hepatoprotective properties, and is a promising agent for non-alcoholic steatohepatitis (NASH). Farnesoid X receptor (FXR) is a bile acid receptor and a drug target for NASH, however, the underlying mechanisms of berberine on regulating FXR are still unknown. In the present study, we feed mice with a 12-week high-fat diet with interval dextran sulfate sodium (0.5% in drinking water) diet to induce NASH, and treat the mice with berberine (100 mg/kg per day) via oral gavage for additional 4 weeks. We demonstrate that administration of berberine alleviates steatosis and infiltration of inflammatory cells in the liver of NASH mice. We apply 16S ribosomal DNA sequencing to screen the structure of gut microbiota, and ultra-performance liquid chromatography-tandem mass spectrometry analysis to determine the bile acid profiles. The results show that berberine modulates gut dysbiosis, and specifically increases the relative abundance of Clostridiales, Lactobacillaceae, and Bacteroidale. Berberine modulated microbiomes are associated with bile acid de-conjugation and transformation, which are consistent with the altered bile acid species (e.g., deoxycholic acid, ursodeoxycholic acid) upon berberine treatment. BA species that respond to berberine treatment are known FXR agonists, thus we performed quantitative Real Time-PCR and western blot to examine the FXR pathway, and find that berberine up-regulates intestinal FXR and fibroblast growth factor 15 (FGF15) expression, and the secretion of FGF15 further inhibits lipogenesis and nuclear factor-κB activation in the liver. Whereas the beneficial effects of berberine are blunted in FXR knockout mice. Our results reveal that berberine alleviates NASH by modulating the interplay of gut microbiota and bile acid metabolism, as well as the subsequent intestinal FXR activation.

Mechanism of Ulcerative Colitis-Aggravated Liver Fibrosis: The Activation of Hepatic Stellate Cells and TLR4 Signaling Through Gut-Liver Axis

Background: The progression of liver disorders is frequently associated with inflammatory bowel disease through the gut-liver axis. However, no direct evidence showed the mechanisms of ulcerative colitis (UC) in the development of liver fibrosis per se. Thus, this study aimed to evaluate the effects of UC on liver fibrosis and its potential mechanism in the experimental model. Methods: Male C57BL/6 mice were allocated into five groups (n = 10 per group) to receive either drinking water (control), 2% dextran sulfate sodium (DSS), olive oil, carbon tetrachloride (CCl4) or DSS + CCl4 for 4 cycles. Blood was collected for biochemical analysis. Colons were excised for the evaluation of colon length and morphological score. Liver, colon, and mesenteric lymph nodes (MLNs) were collected for histopathological staining, expression analysis, and bacterial translocation assay to evaluate the inflammation, fibrosis, the activation of hepatic stellate cells (HSCs), and gut barrier function. Results: DSS caused severe colitis in mice treated or treated with CCl4, as evident from the elevation of disease activity index (DAI), histological abnormalities, and increased pro-inflammatory cytokines (TNF-α, IFN-γ, and IL-17A). Histopathological staining revealed that DSS treatment aggravated the CCl4-induced extracellular matrix deposition, liver fibrosis, and inflammation in mice. Additionally, biochemical and expression analysis indicated the DSS treatment caused the increase of hydroxyproline and pro-inflammatory cytokines, as well as the abnormal liver function indexes in CCl4-induced mice. Gut barrier function was impaired in DSS- and DSS + CCl4-treated mice, manifesting as the increase in bacterial translocation and lipopolysaccharide level, and the reduction in tight junction proteins (occluding, claudin-1 and ZO-1) expression. Further, the activations of HSCs and TLR4 signaling pathway were observed after DSS + CCl4 treatment, presenting with the increase in expression of α-SMA, vimentin, TGF-β, collagen type I, collagen type II, TIMP-2, TLR4, TRAF6, and NF-κB p65, and a decrease in GFAP and MMP-2 expression. Conclusion: The present study verified that UC aggravated CCl4-induced liver injury, inflammation, and fibrosis in mice through the gut-liver axis. Gut barrier dysfunction in UC leads to bacterial translocation and elevated lipopolysaccharide, which may promote the activation of TLR4 signaling and HSCs in the liver.

Bile acid activated receptors: Integrating immune and metabolic regulation in non-alcoholic fatty liver disease

Bile acids are a family of atypical steroids generated at the interface of liver-intestinal microbiota acting on a ubiquitously expressed family of membrane and nuclear receptors known as bile acid activated receptors. The two best characterized receptors of this family are the nuclear receptor, farnesoid X receptor (FXR) and the G protein-coupled receptor, G protein-coupled bile acid receptor 1 (GPBAR1). FXR and GPBAR1 regulate major aspects of lipid and glucose metabolism, energy balance, autophagy and immunity and have emerged as potential pharmaceutical targets for the treatment of metabolic and inflammatory disorders. Clinical trials in non-alcoholic fatty liver disease (NAFLD), however, have shown that selective FXR agonists cause side effects while their efficacy is partial. Because FXR and GPBAR1 exert additive effects, dual FXR/GPBAR1 ligands have been developed for the treatment of metabolic disorders and are currently advanced to clinical trials. Here, we will review the role of FXR and GPBAR1 agonism in NAFLD and how the two receptors could be exploited to target multiple components of the disease.

Severe steatosis and mild colitis are important for the early occurrence of hepatocellular carcinoma

The number of patients with non-alcoholic steatohepatitis (NASH) and inflammatory bowel disease (IBD) is increasing. This study elucidates the effect of both NASH and IBD on hepatocellular carcinoma (HCC) using a mouse model combining NASH and IBD. The melanocortin 4 receptor-deficient (Mc4r-KO) mice were divided into four groups with or without a high-fat diet (HFD) and with or without dextran sulfate sodium (DSS) to induce colitis, and the differences in liver damage and occurrence of HCC were analyzed. In the HFD + DSS group, the body weight, liver weight/body weight ratio, and serum levels of albumin and alanine aminotransferase were significantly lower than those in the HFD group. We further found that steatosis was significantly lower and lobular inflammation was significantly higher in the HFD + DSS group than those in the HFD group, and that individual steatosis and lobular inflammation state in the HFD + DSS mice varied. We detected HCC only in the HFD + DSS group, and mice with severe steatosis and mild colitis were found to be at high risk of HCC. Presently, the prediction of HCC is very difficult. In some cases, severe colitis reverses the fat accumulation due to appetite loss. Our findings clearly showed that severe steatohepatitis and mild colitis are simultaneously essential for the occurrence of HCC in patients with NASH and IBD.

Gut inflammation exacerbates high-fat diet induced steatosis by suppressing VLDL-TG secretion through HNF4α pathway

Nonalcoholic fatty liver disease (NAFLD) is increasingly identified in inflammatory bowel disease (IBD) patients with unclear etiology. In the current study we assessed the contribution of colonic inflammation to NAFLD development and the underlying mechanism in a mouse model for IBD. Our results showed that dextran sulfate sodium (DSS)-induced gut colitis directly led to hepatic inflammation, injury and further exacerbated hepatic steatosis caused by high fat diet (HF) feeding. The essential genes assessment, hepatic metabolic analysis and triglyceride-rich very low-density lipoprotein (VLDL-TG) secretion assays revealed a higher β-oxidation of fatty acids (FAs) but impaired VLDL-TG secretion in liver of DSS-treated mice. Disruption of the intestinal barrier by DSS promoted liver inflammation, which strongly suppressed hepatic VLDL-TG secretion and further aggravated HF-induced VLDL-TG secretion impairment through down-regulation of apolipoprotein B (APOB), hence promoting the storage of triglycerides (TG) in the liver. Inflammation induced by mixed proinflammatory cytokines or LPS obviously inhibited the expression of microsomal triglyceride transfer protein (MTP) and APOB expression and subsequently increased TG content via the suppression of HNF4α in mouse primary hepatocytes. In addition, the downregulation of MTP and APOB by proinflammatory cytokines was also rescued through activating Hnf4α by cortisol. Altogether, our results demonstrated that chronic inflammation exacerbated hepatic steatosis by inhibiting the secreting of hepatic VLDL-TG through HNF4α pathway, suggesting that restoring hepatic VLDL-TG secretion may be a novel strategy for treatment of NAFLD in IBD.

CYP2E1 in Alcoholic and Non-Alcoholic Liver Injury. Roles of ROS, Reactive Intermediates and Lipid Overload

CYP2E1 is one of the fifty-seven cytochrome P450 genes in the human genome and is highly conserved. CYP2E1 is a unique P450 enzyme because its heme iron is constitutively in the high spin state, allowing direct reduction of, e.g., dioxygen, causing the formation of a variety of reactive oxygen species and reduction of xenobiotics to toxic products. The CYP2E1 enzyme has been the focus of scientific interest due to (i) its important endogenous function in liver homeostasis, (ii) its ability to activate procarcinogens and to convert certain drugs, e.g., paracetamol and anesthetics, to cytotoxic end products, (iii) its unique ability to effectively reduce dioxygen to radical species causing liver injury, (iv) its capability to reduce compounds, often generating radical intermediates of direct toxic or indirect immunotoxic properties and (v) its contribution to the development of alcoholic liver disease, steatosis and NASH. In this overview, we present the discovery of the enzyme and studies in humans, 3D liver systems and genetically modified mice to disclose its function and clinical relevance. Induction of the CYP2E1 enzyme either by alcohol or high-fat diet leads to increased severity of liver pathology and likelihood to develop ALD and NASH, with subsequent influence on the occurrence of hepatocellular cancer. Thus, fat-dependent induction of the enzyme might provide a link between steatosis and fibrosis in the liver. We conclude that CYP2E1 has many important physiological functions and is a key enzyme for hepatic carcinogenesis, drug toxicity and liver disease.

The Cytosolic DNA-Sensing cGAS-STING Pathway in Liver Diseases

Inflammation is regulated by the host and is a protective response activated by the evolutionarily conserved immune system in response to harmful stimuli, such as dead cells or pathogens. cGAS-STING pathway is a vital natural sensor of host immunity that can defend various tissues and organs against pathogenic infection, metabolic syndrome, cellular stress and cancer metastasis. The potential impact of cGAS-STING pathway in hepatic ischemia reperfusion (I/R) injury, alcoholic/non-alcoholic steatohepatitis (ASH), hepatic B virus infection, and other liver diseases has recently attracted widespread attention. In this review, the relationship between cGAS-STING pathway and the pathophysiological mechanisms and progression of liver diseases is summarized. Additionally, we discuss various pharmacological agonists and antagonists of cGAS-STING signaling as novel therapeutics for the treatment of liver diseases. A detailed understanding of mechanisms and biology of this pathway will lay a foundation for the development and clinical application of therapies for related liver diseases.

Gut-Liver Axis: Liver Sinusoidal Endothelial Cells Function as the Hepatic Barrier in Colitis-Induced Liver Injury

Background

Based on the gut–liver axis theory, a leaky gut can aggravate liver injury. However, clinical studies suggest that although gut mucosa damage is commonly observed in inflammatory bowel disease (IBD), it seldom leads to severe liver injury. We hypothesize that there is a hepatic barrier in the gut–liver axis, which protects the liver against gut-derived invasive factors.

Methods

Colitis was induced by dextran sulfate sodium (DSS) in eight different liver injury models in Sprague–Dawley rats. Liver sinusoidal endothelial cell (LSEC) injury was evaluated by a scanning and transmission electron microscope. Neutrophils were depleted by injection of anti-rat polymorphonuclear serum. Two pneumonia models were also induced to investigate the mechanism of neutrophil recruitment and activation. LSECs isolated from rat liver were used to investigate the effect on neutrophil recruitment and activation.

Results

Among eight liver injury models, DSS colitis had no effect on liver injury in three models with normal LSECs. In the other five models with LSEC rupture, liver injury was significantly exacerbated by colitis, and increased hepatic neutrophil accumulation was observed. When neutrophils were depleted, colitis-induced liver injury was significantly attenuated. In pneumonia, liver injury, and colitis models, the level of CXCL1 correlated with the recruitment of neutrophils in different tissues, while DSS colitis and LSEC injury synergistically contributed to increased CXCL1 expression in the liver. In colitis-induced liver injury, neutrophils were activated in the liver. Injured LSECs showed both structural and functional changes, with significantly increased expression of CXCL1 and TNF-α under the stimulation of lipopolysaccharide (LPS). The combination of gut-derived LPS and LSEC-derived TNF-α led to the activation of neutrophils, characterized by enhanced production of reactive oxygen species, pro-inflammatory cytokines, and the formation of neutrophil extracellular traps.

Conclusion

LSECs constitute a vitally important barrier in the gut–liver axis, defending the liver against colitis-induced injury. When LSECs are damaged, they can turn into a pro-inflammatory pattern under the stimulation of LPS. LSEC injury and colitis-derived LPS synergistically contribute to the recruitment and activation of hepatic neutrophils. Neutrophils play a pivotal role as a downstream effector in colitis-induced liver injury.

Role of the Gut Microbiota in Regulating Non-alcoholic Fatty Liver Disease in Children and Adolescents

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease in children and adolescents. Although obesity is the leading cause of NAFLD, the etiologies of NAFLD are multifactorial (e.g., high-fat diet, a lack of exercise, gender, maternal obesity, the antibiotic use), and each of these factors leads to dysbiosis of the gut microbiota community. The gut microbiota is a key player in the development and regulation of the gut mucosal immune system as well as the regulation of both NAFLD and obesity. Dysbiosis of the gut microbiota promotes the development of NAFLD via alteration of gut-liver homeostasis, including disruption of the gut barrier, portal transport of bacterial endotoxin (lipopolysaccharide) to the liver, altered bile acid profiles, and decreased concentrations of short-chain fatty acids. In terms of prevention and treatment, conventional approaches (e.g., dietary and exercise interventions) against obesity and NAFLD have been confirmed to recover the dysbiosis and dysbiosis-mediated altered metabolism. In addition, increased understanding of the importance of gut microbiota-mediated homeostasis in the prevention of NAFLD suggests the potential effectiveness of gut microbiota-targeted preventive and therapeutic strategies (e.g., probiotics and fecal transplantation) against NAFLD in children and adolescents. This review comprehensively summarizes our current knowledge of the gut microbiota, focusing on its interaction with NAFLD and its potential therapeutic role in obese children and adolescents with this disorder.

Clinical Aspects of Gut Microbiota in Hepatocellular Carcinoma Management

Liver cancer, predominantly hepatocellular carcinoma (HCC), is the third leading cause of cancer-related deaths worldwide. Emerging data highlight the importance of gut homeostasis in the pathogenesis of HCC. Clinical and translational studies revealed the patterns of dysbiosis in HCC patients and their potential role for HCC diagnosis. Research on underlying mechanisms of dysbiosis in HCC development pointed out the direction for improving the treatment and prevention. Despite missing clinical studies, animal models showed that modulation of the gut microbiota by probiotics may become a new way to treat or prevent HCC development.

Nonalcoholic Fatty Liver Disease (NAFLD) as Model of Gut-Liver Axis Interaction: From Pathophysiology to Potential Target of Treatment for Personalized Therapy

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of liver disease worldwide, affecting both adults and children and will result, in the near future, as the leading cause of end-stage liver disease. Indeed, its prevalence is rapidly increasing, and NAFLD is becoming a major public health concern. For this reason, great efforts are needed to identify its pathogenetic factors and new therapeutic approaches. In the past decade, enormous advances understanding the gut-liver axis-the complex network of cross-talking between the gut, microbiome and liver through the portal circulation-have elucidated its role as one of the main actors in the pathogenesis of NAFLD. Indeed, evidence shows that gut microbiota is involved in the development and progression of liver steatosis, inflammation and fibrosis seen in the context of NAFLD, as well as in the process of hepatocarcinogenesis. As a result, gut microbiota is currently emerging as a non-invasive biomarker for the diagnosis of disease and for the assessment of its severity. Additionally, to its enormous diagnostic potential, gut microbiota is currently studied as a therapeutic target in NAFLD: several different approaches targeting the gut homeostasis such as antibiotics, prebiotics, probiotics, symbiotics, adsorbents, bariatric surgery and fecal microbiota transplantation are emerging as promising therapeutic options.

Partially hydrolyzed guar gum attenuates non-alcoholic fatty liver disease in mice through the gut-liver axis

BACKGROUND

The gut-liver axis has attracted much interest in the context of chronic liver disease pathogenesis. Prebiotics such as dietary fibers were shown to attenuate non-alcoholic fatty liver disease (NAFLD) by modulating gut microbiota. Partially hydrolyzed guar gum (PHGG), a water-soluble dietary fiber, has been reported to alleviate the symptoms of various intestinal diseases and metabolic syndromes. However, its effects on NAFLD remain to be fully elucidated.

AIM

To determine whether treatment with PHGG attenuates NAFLD development in mice through the gut-liver axis.

METHODS

Seven-week-old male C57BL/6J mice with increased intestinal permeability were fed a control or atherogenic (Ath) diet (a mouse model of NAFLD) for 8 wk, with or without 5% PHGG. Increased intestinal permeability was induced through chronic intermittent administration of low-dose dextran sulfate sodium. Body weight, liver weight, macroscopic findings in the liver, blood biochemistry [aspartate aminotransferase (AST) and alanine aminotransferase (ALT), total cholesterol, triglyceride, free fatty acids, and glucose levels], liver histology, myeloperoxidase activity in liver tissue, mRNA expression in the liver and intestine, serum endotoxin levels in the portal vein, intestinal permeability, and microbiota and short-chain fatty acid (SCFA) profiles in the cecal samples were investigated.

RESULTS

Mice with increased intestinal permeability subjected to the Ath diet showed significantly increased serum AST and ALT levels, liver fat accumulation, liver inflammatory (tumor necrosis factor-α and monocyte chemotactic protein-1) and fibrogenic (collagen 1a1 and α smooth muscle actin) marker levels, and liver myeloperoxidase activity, which were significantly attenuated by PHGG treatment. Furthermore, the Ath diet combined with increased intestinal permeability resulted in elevated portal endotoxin levels and activated toll-like receptor (TLR) 4 and TLR9 expression, confirming that intestinal permeability was significantly elevated, as observed by evaluating the lumen-to-blood clearance of fluorescein isothiocyanate-conjugated dextran. PHGG treatment did not affect fatty acid metabolism in the liver. However, it decreased lipopolysaccharide signaling through the gut-liver axis. In addition, it significantly increased the abundance of cecal Bacteroides and Clostridium subcluster XIVa. Treatment with PHGG markedly increased the levels of SCFAs, particularly, butyric acid, acetic acid, propionic acid, and formic acid, in the cecal samples.

CONCLUSION

PHGG partially prevented NAFLD development in mice through the gut-liver axis by modulating microbiota and downstream SCFA profiles.

Lipopolysaccharide from the commensal microbiota of the breast enhances cancer growth: role of S100A7 and TLR4

The role of commensal bacterial microbiota in the pathogenesis of human malignancies has been a research field of incomparable progress in recent years. Although breast tissue is commonly assumed to be sterile, recent studies suggest that human breast tissue may contain a bacterial microbiota. In this study, we used an immune‐competent orthotopic breast cancer mouse model to explore the existence of a unique and independent bacterial microbiota in breast tumors. We observed some similarities in breast cancer microbiota with skin; however, breast tumor microbiota was mainly enriched with Gram‐negative bacteria, serving as a primary source of lipopolysaccharide (LPS). In addition, dextran sulfate sodium (DSS) treatment in late‐stage tumor lesions increased LPS levels in the breast tissue environment. We also discovered an increased expression of S100A7 and low level of TLR4 in late‐stage tumors with or without DSS as compared to early‐stage tumor lesions. The treatment of breast cancer cells with LPS increased the expression of S100A7 in breast cancer cells in vitro. Furthermore, S100A7 overexpression downregulated TLR4 and upregulated RAGE expression in breast cancer cells. Analysis of human breast cancer samples also highlighted the inverse correlation between S100A7 and TLR4 expression. Overall, these findings suggest that the commensal microbiota of breast tissue may enhance breast tumor burden through a novel LPS/S100A7/TLR4/RAGE signaling axis.