Hepatocyte toll-like receptor 4 deficiency protects against alcohol-induced fatty liver disease

Efficacy and mechanism of action of Yanxiao Di'naer formula for non-alcoholic steatohepatitis treatment based on metabolomics and RNA sequencing

ETHNOPHARMACOLOGICAL RELEVANCE

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide. Nonalcoholic steatohepatitis (NASH) is a crucial component of this disease spectrum. The Yanxiao Di'naer formula (YXDNE) is an Uyghur medical extract that has been used in folk medicine to treat hepatitis for a long time. However, the role and mechanism of action of YXDNE in NASH treatment remains unclear.

OBJECTIVE

The objective of this study was to assess the effectiveness of YXDNE in treating NASH induced by injections of carbon tetrachloride combined with a high-fat high-cholesterol diet (HFHCD), and to clarify the underlying mechanisms.

METHODS

The compounds in the YXDNE extract were analysed for classification and proportions using ultra-performance liquid chromatography-mass spectrometry. The efficacy of YXDNE in treating abnormal lipid metabolism was evaluated in L02 cells in vitro. In addition, a C57BL/6 mouse model of NASH was established to evaluate the therapeutic efficacy of YXDNE in vivo. Metabolomics and RNA sequencing were used to analyse the therapeutic effects of YXDNE on the liver. The corresponding signalling pathways were found to target AMPKα1, PPARα, and NF-κB. The efficacy of YXDNE was validated using inhibitors or silencing RNA (siRNA) against AMPKα1 and PPARα.

RESULTS

This study confirmed that YXDNE treatment ameliorated NASH in a murine model of this disease. Metabolomics analysis suggested that YXDNE efficacy was associated with fatty acid catabolism and AMPK signalling pathways. RNA sequencing results showed that YXDNE efficacy in treating NASH was highly correlated with the AMPK, PPARα and NF-κB pathways. Both in vitro and in vivo experimental data demonstrated that YXDNE affected the expression of p-AMPKα1, PPARα, p-NF-κB, IκB, and p-IκB. The efficacy of YXDNE in treating NASH in vitro was cancelled when AMPK was inhibited with Compound C or PPARα was modulated via siRNA.

CONCLUSIONS

YXDNE may have a therapeutic effect on abnormal lipid metabolism in L02 cells and in a murine model of NASH by affecting the AMPKα1/PPARα/NF-κB signalling pathway. Therefore, YXDNE has the potential for clinical application in the prevention and treatment of NASH.

Dried tangerine peel polysaccharide (DTPP) alleviates hepatic steatosis by suppressing TLR4/MD-2-mediated inflammation and endoplasmic reticulum stress

Non-alcoholic fatty liver disease (NAFLD) is a complex pathogenic metabolic syndrome characterized by increased inflammation and endoplasmic reticulum stress. In recent years, natural polysaccharides derived from traditional Chinese medicine have shown significant anti-inflammatory effects, making them an attractive therapeutic option. However, little research has been conducted on the therapeutic potential of dried tangerine peel polysaccharide (DTPP) - one of the most important medicinal resources in China. The results of the present study showed that DTPP substantially reduced macrophage infiltration in vivo and suppressed the expression of pro-inflammatory factors and endoplasmic reticulum stress-related genes. Additionally, surface plasmon resonance analysis revealed that DTPP had a specific affinity to myeloid differentiation factor 2, which consequently suppressed lipopolysaccharide-induced inflammation via interaction with the toll-like receptor 4 signaling pathway. This study provides a potential molecular mechanism underlying the anti-inflammatory effects of DTPP on NAFLD and suggests DTPP as a promising therapeutic strategy for NAFLD treatment.

Inflammatory liver diseases and susceptibility to sepsis

Patients with inflammatory liver diseases, particularly alcohol-associated liver disease and metabolic dysfunction-associated fatty liver disease (MAFLD), have higher incidence of infections and mortality rate due to sepsis. The current focus in the development of drugs for MAFLD is the resolution of non-alcoholic steatohepatitis and prevention of progression to cirrhosis. In patients with cirrhosis or alcoholic hepatitis, sepsis is a major cause of death. As the metabolic center and a key immune tissue, liver is the guardian, modifier, and target of sepsis. Septic patients with liver dysfunction have the highest mortality rate compared with other organ dysfunctions. In addition to maintaining metabolic homeostasis, the liver produces and secretes hepatokines and acute phase proteins (APPs) essential in tissue protection, immunomodulation, and coagulation. Inflammatory liver diseases cause profound metabolic disorder and impairment of energy metabolism, liver regeneration, and production/secretion of APPs and hepatokines. Herein, the author reviews the roles of (1) disorders in the metabolism of glucose, fatty acids, ketone bodies, and amino acids as well as the clearance of ammonia and lactate in the pathogenesis of inflammatory liver diseases and sepsis; (2) cytokines/chemokines in inflammatory liver diseases and sepsis; (3) APPs and hepatokines in the protection against tissue injury and infections; and (4) major nuclear receptors/signaling pathways underlying the metabolic disorders and tissue injuries as well as the major drug targets for inflammatory liver diseases and sepsis. Approaches that focus on the liver dysfunction and regeneration will not only treat inflammatory liver diseases but also prevent the development of severe infections and sepsis.

Hydrogen gas alleviates acute ethanol-induced hepatotoxicity in mice via modulating TLR4/9 innate immune signaling and pyroptosis

Alcoholic liver disease (ALD), which is induced by chronic heavy alcohol consumption, accompanies complicated pathological mechanisms, including oxidative stress, inflammation, cell death, epigenetic changes and acetaldehyde-mediated toxicity. Hydrogen (H2) is the lightest gas with multiple biological effects such as high selective anti-oxidation, anti-inflammation and anti-apoptosis. However, the dose effects and innate immune mechanisms of intraperitoneal injection of H2 on ALD are limited. Here, we used acute ethanol-induced hepatotoxicity mice models to estimate the actions of intraperitoneal injection of H2 on ALD. The effects of H2 on acute ethanol-induced liver damage were examined by hepatic oil red O staining, quantitative PCR (qPCR) for lipid metabolic genes, hepatic triglyceride (TG) and serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Hepatic mitochondrial superoxide (MitoSOX), 3-nitrotyrosine (3-NT), malondialdehyde (MDA), and glutathione (GSH) levels were examined to evaluate oxidative stress. Immunoblot, and immunofluorescence staining were used to further confirm the innate immune molecular targets of H2. Our results showed that intraperitoneal injection of H2 improved acute ethanol-induced liver injury in mice in a dose dependent manner, as indicated by decreasing serum ALT and AST levels, hepatic TG levels, and increasing lipid export genes (Mttp and Apob) mRNA levels and reducing fatty acid uptake gene (CD36) mRNA levels. Mechanistically, H2 inhibited hepatic oxidative stress as indicated by reducing reactive oxygen species (ROS), 3-NT, and MDA levels in the liver, while increasing hepatic GSH levels; inhibited the overactived TLR4/9-NF-κB-TNF-α/IL-1β/IL-18 innate immune signaling; suppressed the canonical Caspase-1-GSDMD pyroptosis signaling, and the non-canonical pyroptosis signaling, such as Caspase-11-GSDMD, Caspase-8-GSDMD and Caspase-3-GSDME signaling. Therefore, our study highlights that intraperitoneal injection of H2 may represent a novel therapeutic and safe strategy for ALD via modulating oxidative stress, innate immunity and pyroptosis.

Hesperitin attenuates alcoholic steatohepatitis by regulating TLR4/NF-κB signaling in mice

In the peel of citrus (Rutaceae) fruit, hesperitin (Hesp), a flavanone glycoside chemical, is found naturally. Hesp has been found to have a wide range of pharmacological actions, including anti-inflammatory, antioxidant, antiviral, and anticancer properties, according to earlier research. However, nothing is known regarding its function in alcoholic liver steatosis and inflammation. In this study, we employed a network pharmacology approach to identify the TLR4 signaling pathway as a primary target of Hesp for the treatment of alcoholic steatohepatitis (ASH). Molecular docking results showed that Hesp bound to the representative target TLR4 and exhibited good affinity. In addition, Hesp inhibits the TLR4 target and consequently the NF-κB signaling pathway, which in turn slows the evolution of alcoholic steatohepatitis, according to further in vitro and in vivo tests. The results of this study preliminarily indicate that Hesp is an ideal drug candidate for the treatment of ASH.

Hepatocyte Toll-Like Receptor 4 Mediates Alcohol-Induced Insulin Resistance in Mice

Accumulating evidence has demonstrated the association between alcohol overconsumption and the development of insulin resistance. However, the underlying mechanisms are not completely understood. To investigate the requirement and sufficiency of hepatocyte toll-like receptor 4 (TLR4) in alcohol-induced insulin resistance, we used two mouse models (Tlr4fl/fl and Tlr4LoxTB) that allow ablation of TLR4 only in hepatocytes (Tlr4LKO) and restoration of endogenous TLR4 expression in hepatocytes on a TLR4-null background (Tlr4LoxTB × Alb-Cre), respectively. A Lieber-DeCarli feeding model was used to induce glucose intolerance and insulin resistance in mice. Glucose tolerance test, insulin tolerance test, and insulin signaling experiments were performed to examine systemic and tissue-specific insulin sensitivity. We found that alcohol-fed hepatocyte TLR4 deficient mice (Tlr4LKO) had lower blood glucose levels in response to intraperitoneal injection of insulin. Moreover, increased phosphorylation of glycogen synthase kinase-3β (GSK3β) was observed in the liver of Tlr4LKO mice after chronic alcohol intake. In contrast, when hepatic TLR4 was reactivated in mice (Tlr4LoxTB × Alb-Cre), alcohol feeding caused glucose intolerance in these mice compared with littermate controls (Tlr4LoxTB). In addition, AKT phosphorylation was dramatically reduced in the liver and epididymal white adipose tissue (eWAT) of alcohol-fed Tlr4LoxTB × Alb-Cre mice, which was similar to that of mice with whole-body TLR4 reactivation (Tlr4LoxTB × Zp3-Cre). Collectively, these findings suggest that hepatocyte TLR4 is both required and sufficient in the development of insulin resistance induced by alcohol overconsumption.

Ginsenoside Rc Modulates SIRT6-NRF2 Interaction to Alleviate Alcoholic Liver Disease

Alcoholic liver disease (ALD) is a serious worldwide health problem. Ginsenoside Rc is a major active ingredient isolated from Panax ginseng, whose pharmacological effects counteract oxidative stress, inflammation, and lipid accumulation. However, it is still unclear whether ginsenoside Rc might exert beneficial effects on alcohol-induced liver injury. To this aim, mice primary hepatocytes (MPHs) were challenged with alcohol to test ginsenoside Rc's effects on their intracellular alcohol metabolism. C57BL/6J mice or SIRT6alb-/- mice were chronically fed a diet with added alcohol or given a single gavage of alcohol with or without ginsenoside Rc. Analyses of alcohol metabolism, oxidative stress, inflammation, lipid metabolism, and RNaseq expression were conducted to explore potential targets exploited by ginsenoside Rc to protect against ALD. Our results showed that ginsenoside Rc attenuated alcohol-induced liver injury by regulating oxidative stress, inflammation, and lipid accumulation both in vivo and in vitro. Ginsenoside Rc did increase the deacetylase activity of SIRT6, thereby lowering acetylated NRF2 levels, which elevated NRF2's stability, and subsequently exerting an antioxidant effect. In keeping with this, the hepatic knockout of SIRT6 almost abolished the hepatoprotective effects of ginsenoside Rc against ALD. Therefore, our results suggest that ginsenoside Rc attenuated hepatocytes' damage and oxidative stress in ALD by up-regulating the SIRT6/NRF2 pathway. Hence, ginsenoside Rc may be a promising drug to treat or relieve ALD.

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.

Folic acid ameliorates alcohol-induced liver injury via gut–liver axis homeostasis

The gut–liver axis (GLA) plays an important role in the development of alcohol-induced liver injury. Alcohol consumption is typically associated with folic acid deficiency. However, no clear evidence has confirmed the effect of folic acid supplementation on alcohol-induced liver injury via GLA homeostasis. In this study, male C57BL/6J mice were given 56% (v/v) ethanol and 5.0 mg/kg folic acid daily by gavage for 10 weeks to investigate potential protective mechanisms of folic acid in alcohol-induced liver injury via GLA homeostasis. Histopathological and biochemical analyses showed that folic acid improved lipid deposition and inflammation in the liver caused by alcohol consumption and decreased the level of ALT, AST, TG, and LPS in serum. Folic acid inhibited the expression of the TLR4 signaling pathway and its downstream inflammatory mediators in the liver and upregulated the expression of ZO-1, claudin 1, and occludin in the intestine. But compared with the CON group, folic acid did not completely eliminate alcohol-induced intestine and liver injury. Furthermore, folic acid regulated alcohol-induced alterations in gut microbiota. In alcohol-exposed mice, the relative abundance of Bacteroidota was significantly increased, and the relative abundance of unclassified_Lachnospiraceae was significantly decreased. Folic acid supplementation significantly increased the relative abundance of Verrucomicrobia, Lachnospiraceae_NK4A136_group and Akkermansia, and decreased the relative abundance of Proteobacteria. The results of Spearman’s correlation analysis showed that serum parameters and hepatic inflammatory cytokines were significantly correlated with several bacteria, mainly including Bacteroidota, Firmicutes, and unclassified_Lachnospiraceae. In conclusion, folic acid could ameliorate alcohol-induced liver injury in mice via GLA homeostasis to some extent, providing a new idea and method for prevention of alcohol-induced liver injury.

Influence of Heat Stress on Intestinal Epithelial Barrier Function, Tight Junction Protein, and Immune and Reproductive Physiology

The potential threat of global warming in the 21^st century is on the ecosystem through many aspects, including the negative impact of rising global temperature on the health of humans and animals, especially domestic animals. The damage caused by heat stress to animals has been more and more significant as the worldwide climate continues to rise, along with the breeding industry's expanding scale and stocking density, and it has become the most important stress-causing factor in southern China. In this review, we described the effects of heat stress on animal immune organs and immune system. The much-debated topic is how hyperthermia affects the tight junction barrier. Heat stress also induces inflammation in the body of animals causing low body weight and loss of appetite. This review also discussed that heat stress leads to hepatic disorder, and it also damages the intestine. The small intestine experiences ischemia, and the permeability of the intestine increases. Furthermore, the oxidative stress and mitogen-activated protein kinase (MAPK) pathways have a significant role in stress-induced cellular and organ injury. The study has shown that MAPK activity in the small intestine was increased by heat stress. Heat stress caused extreme small intestine damage, enhanced oxidative stress, and activated MAPK signaling pathways.

Hepatoprotective Mechanism of Ginsenoside Rg1 against Alcoholic Liver Damage Based on Gut Microbiota and Network Pharmacology

Alcoholic liver disease (ALD) is a major public health problem worldwide, which needs to be effective prevention. Ginsenoside Rg1 (GRg1), a bioactive ingredient extracted from ginseng, has benefit effects on health. In this study, 11 potential targets of GRg1 against ALD were firstly obtained by network pharmacology. KEGG pathway enrichment showed that GRg1-target-ALD was closely related to Toll-like receptor (TLR) and nuclear factor-kappa B (NF-κB) signaling pathways. In addition, GRg1 decreased antioxidant levels and increased oxidative levels in alcohol-treated mice, which alleviated oxidative stress-induced hepatic damage. GRg1 enhanced intestinal barrier function via upregulating the levels of tight junction protein and immunoglobulin A. GRg1 also reduced alcohol-induced inflammation by suppressing TLR4/NF-κB pathway, which was consistent with the prediction of network targets. Moreover, GRg1 altered GM population, and Verrucomicrobia, Bacteroidetes, Akkermansia, Bacteroides, Lachnospiraceae_NK4A136_group, and Alloprevotella played positive association with intestinal barrier indicators and negative correlation with hepatic inflammation biomarkers. The results suggest that GRg1 administration might be a promising strategy for protection of alcohol-induced liver damage.

Carbon monoxide mechanism of protection against renal ischemia and reperfusion injury

Carbon monoxide is quickly moving past its historic label as a molecule once feared, to a therapeutic drug that modulates inflammation. The development of carbon monoxide releasing molecules and utilization of heme oxygenase-1 inducers have shown carbon monoxide to be a promising therapy in reducing renal ischemia and reperfusion injury and other inflammatory diseases. In this review, we will discuss the developments and application of carbon monoxide releasing molecules in renal ischemia and reperfusion injury, and transplantation. We will review the anti-inflammatory mechanisms of carbon monoxide in respect to mitigating apoptosis, suppressing dendritic cell maturation and signalling, inhibiting toll-like receptor activation, promoting anti-inflammatory responses, and the effects on renal vasculature.

Hepatic IRF3 fuels dysglycemia in obesity through direct regulation of Ppp2r1b

Inflammation has profound but poorly understood effects on metabolism, especially in the context of obesity and nonalcoholic fatty liver disease (NAFLD). Here, we report that hepatic interferon regulatory factor 3 (IRF3) is a direct transcriptional regulator of glucose homeostasis through induction of Ppp2r1b, a component of serine/threonine phosphatase PP2A, and subsequent suppression of glucose production. Global ablation of IRF3 in mice on a high-fat diet protected against both steatosis and dysglycemia, whereas hepatocyte-specific loss of IRF3 affects only dysglycemia. Integration of the IRF3-dependent transcriptome and cistrome in mouse hepatocytes identifies Ppp2r1b as a direct IRF3 target responsible for mediating its metabolic actions on glucose homeostasis. IRF3-mediated induction of Ppp2r1b amplified PP2A activity, with subsequent dephosphorylation of AMPKα and AKT. Furthermore, suppression of hepatic Irf3 expression with antisense oligonucleotides reversed obesity-induced insulin resistance and restored glucose homeostasis in obese mice. Obese humans with NAFLD displayed enhanced activation of liver IRF3, with reversion after bariatric surgery. Hepatic PPP2R1B expression correlated with HgbA1C and was elevated in obese humans with impaired fasting glucose. We therefore identify the hepatic IRF3-PPP2R1B axis as a causal link between obesity-induced inflammation and dysglycemia and suggest an approach for limiting the metabolic dysfunction accompanying obesity-associated NAFLD.

The Role of Gut Bacteria and Fungi in Alcohol-Associated Liver Disease

Cirrhosis and liver cancer caused by alcohol-associated liver disease (ALD) are serious threats to people's health. In addition to hepatic cell apoptosis and liver inflammation caused by oxidative stress during alcohol metabolism, intestinal microbiota disorders are also involved in the onset and development of ALD. Ethanol and its' oxidative and non-oxidative metabolites, together with dysbiosis-caused-inflammation, destroys the intestinal barrier. Changes of several microbial metabolites, such as bile acids, short-chain fatty acids, and amino acid, are closely associated with gut dysbiosis in ALD. The alcohol-caused dysbiosis can further influence intestinal barrier-related proteins, such as mucin2, bile acid-related receptors, and aryl hydrocarbon receptor (AhR), and these abnormal changes also participate in the injury of the intestinal barrier and hepatic steatosis. Gut-derived bacteria, fungi, and their toxins, such as lipopolysaccharide (LPS) and β-glucan translocate into the liver through the damaged intestinal barrier and promote the progression of inflammation and fibrosis of ALD. Thus, the prevention of alcohol-induced disruption of intestinal permeability has a beneficial effect on ALD. Currently, multiple therapeutic treatments have been applied to restore the gut microbiota of patients with ALD. Fecal microbial transplantation, probiotics, antibiotics, and many other elements has already shown their ability of restoring the gut microbiota. Targeted approaches, such as using bacteriophages to remove cytolytic Enterococcus faecalis, and supplement with Lactobacillus, Bifidobacterium, or boulardii are also powerful therapeutic options for ALD.

Skeletal muscle satellite cell-derived mesenchymal stem cells ameliorate acute alcohol-induced liver injury

Cultured human skeletal-muscle satellite cells have properties of mesenchymal stem cells (skeletal muscle satellite cell-derived mesenchymal stem cells, SkMSCs) and play anti-inflammatory roles by secreting prostaglandin E2 and hepatocyte growth factor (HGF). To evaluate the utility of SkMSCs in treating liver diseases, we determined whether SkMSCs could ameliorate acute liver and gut inflammation induced by binge ethanol administration. Binge drinking of ethanol led to weight loss in the body and spleen, liver inflammation and steatosis, and increased serum ALT and AST levels (markers of liver injury), along with increased IL-1β, TNF-α, and iNOS expression levels in mice. However, levels of these binge-drinking-induced indicators were reduced by a single intraperitoneal treatment of SkMSCs. Furthermore, levels of bacteria-derived lipopolysaccharide decreased in the livers and sera of ethanol-exposed mice after SkMSC administration. SkMSCs decreased the extent of tissue inflammation and reduced villus and crypt lengths in the small intestine after alcohol binge drinking. SkMSCs also reduced the leakage of blood albumin, an indicator of leaky gut, in the stool of ethanol-exposed mice. Alcohol-induced damage to human colonic Caco-2/tc7 cells was also alleviated by HGF. Therefore, a single treatment with SkMSCs can attenuate alcoholic liver damage by reducing inflammatory responses in the liver and gut, suggesting that SkMSCs could be used in cell therapy to treat alcoholic liver diseases.

Silencing miR-181b-5p upregulates PIAS1 to repress oxidative stress and inflammatory response in rats with alcoholic fatty liver disease through inhibiting PRMT1

OBJECTIVE

This study aimed to probe the function of microRNA-181b-5p (miR-181b-5p)/protein inhibitor of activated STAT1 (PIAS1)/protein arginine methyltransferase 1 (PRMT1) axis in the progression of alcoholic fatty liver disease (AFLD).

METHODS

A rat model of AFLD was established and treated with altered miR-181b-5p, PIAS1 or PRMT1 expression constructs to identify their effects on liver function, serum inflammation, liver tissue oxidative stress, hepatocyte apoptosis and pathological changes of liver tissue in rats using a series of assays. miR-181b-5p, PIAS1 and PRMT1 levels were detected, and the targeting relationship between miR-181b-5p and PIAS1 was confirmed.

RESULTS

MiR-181b-5p and PRMT1 were elevated while PIAS1 was reduced in AFLD rat liver tissues, miR-181b-5p inhibition, PIAS1 overexpression or PRMT1 inhibition improved liver function, attenuated inflammation, oxidative stress, pathological changes and hepatocyte apoptosis in AFLD rat liver tissues. The impacts of miR-181b-5p inhibition on AFLD rats were reversed by PIAS1 silencing. PIAS1 was confirmed as a target gene of miR-181b-5p, and miR-181b-5p regulated PRMT1 expression through binding to PIAS1.

CONCLUSION

Inhibiting miR-181b-5p can promote the expression of PIAS1, thereby inhibiting PRMT1 and ultimately improving AFLD.

Carbohydrates deteriorate fatty liver by activating the inflammatory response

Non-alcoholic fatty liver disease (NAFLD) was defined in 1980 and has the same histological characteristics as alcoholic liver disease except for alcohol consumption. After 40 years, the understanding of this disease is still imperfect. Without specific drugs available for treatment, the number of patients with NAFLD is increasing rapidly, and NAFLD currently affects more than one-quarter of the global population. NAFLD is mostly caused by a sedentary lifestyle and excessive energy intake of fat and sugar. To ameliorate or avoid NAFLD, people commonly replace high-fat foods with high-carbohydrate foods (especially starchy carbohydrates) as a way to reduce caloric intake and reach satiety. However, there are few studies that concentrate on the effect of carbohydrate intake on liver metabolism in patients with NAFLD, much fewer than the studies on fat intake. Besides, most of these studies are not systematic, which has made identification of the mechanism difficult. In this review, we collected and analysed data from studies on human and animal models and, surprisingly, found that carbohydrates and liver steatosis could be linked by inflammation. This review not only describes the effects of carbohydrates on NAFLD and body lipid metabolism but also analyses and predicts possible molecular pathways of carbohydrates in liver lipid synthesis that involve inflammation. Furthermore, the limitations of recent research and possible targets for regulating inflammation and lipogenesis are discussed. This review describes the effects of starchy carbohydrates, a nutrient signal, on NAFLD from the perspective of inflammation.

Liver-specific Nrf2 deficiency accelerates ethanol-induced lethality and hepatic injury in vivo

Alcoholic liver disease (ALD) is a major cause of morbidity and mortality from liver disorders. Various mechanisms, including oxidative stress and impaired lipid metabolism, have been implicated in the pathogenesis of ALD. Our previous studies showed that nuclear factor erythroid-derived 2-like 2 (Nrf2) is a master regulator of adaptive antioxidant response and lipid metabolism by using a liver-specific Nrf2 knockout (Nrf2(L)-KO) mouse model. In the current study, an ALD model was developed by a Lieber-DeCarli liquid-based ethanol diet given to this Nrf2(L)-KO mouse strain. We found that Nrf2(L)-KO mice were quite sensitive to lethality from 6.3% ethanol diet. We thus decreased the ethanol concentration to 4.2% to obtain tissues to analyze the role of hepatic Nrf2 in the development of ALD. We found that mild hepatic steatosis occurred with both liquid control and 4.2% ethanol diet feeding, which contain 35% fat. Both the fatty acid β-oxidation marker peroxisome proliferators-activated receptor α (PPARα), and lipogenesis regulator PPARγ were reduced with ethanol feeding in Nrf2(L)-KO mice, compared to Nrf2 floxed control mice (Nrf2-LoxP). However, Nrf2(L)-KO livers showed more cell injury than the livers of Nrf2-LoxP mice. Consistent with these data, there was increased proportion of apoptotic cells in the liver of ethanol-fed Nrf2(L)-KO mice comparing Nrf2-LoxP controls. Mechanistically, Nrf2 mediated expression of ethanol detoxification enzymes, such as alcohol dehydrogenase 1 and aldehyde dehydrogenase1a1, likely contributed to the sensitivity to ethanol toxicity. In conclusion, hepatic Nrf2 is critical to the development of ALD, particularly the morbidity and liver injury.

Invited review: The influence of immune activation on transition cow health and performance-A critical evaluation of traditional dogmas

The progression from gestation into lactation represents the transition period, and it is accompanied by marked physiological, metabolic, and inflammatory adjustments. The entire lactation and a cow's opportunity to have an additional lactation are heavily dependent on how successfully she adapts during the periparturient period. Additionally, a disproportionate amount of health care and culling occurs early following parturition. Thus, lactation maladaptation has been a heavily researched area of dairy science for more than 50 yr. It was traditionally thought that excessive adipose tissue mobilization in large part dictated transition period success. Further, the magnitude of hypocalcemia has also been assumed to partly control whether a cow effectively navigates the first few months of lactation. The canon became that adipose tissue released nonesterified fatty acids (NEFA) and the resulting hepatic-derived ketones coupled with hypocalcemia lead to immune suppression, which is responsible for transition disorders (e.g., mastitis, metritis, retained placenta, poor fertility). In other words, the dogma evolved that these metabolites and hypocalcemia were causal to transition cow problems and that large efforts should be enlisted to prevent increased NEFA, hyperketonemia, and subclinical hypocalcemia. However, despite intensive academic and industry focus, the periparturient period remains a large hurdle to animal welfare, farm profitability, and dairy sustainability. Thus, it stands to reason that there are alternative explanations to periparturient failures. Recently, it has become firmly established that immune activation and the ipso facto inflammatory response are a normal component of transition cow biology. The origin of immune activation likely stems from the mammary gland, tissue trauma during parturition, and the gastrointestinal tract. If inflammation becomes pathological, it reduces feed intake and causes hypocalcemia. Our tenet is that immune system utilization of glucose and its induction of hypophagia are responsible for the extensive increase in NEFA and ketones, and this explains why they (and the severity of hypocalcemia) are correlated with poor health, production, and reproduction outcomes. In this review, we argue that changes in circulating NEFA, ketones, and calcium are simply reflective of either (1) normal homeorhetic adjustments that healthy, high-producing cows use to prioritize milk synthesis or (2) the consequence of immune activation and its sequelae.

Tumor Immune Microenvironment and Immunosuppressive Therapy in Hepatocellular Carcinoma: A Review

Liver cancer has the fourth highest mortality rate of all cancers worldwide, with hepatocellular carcinoma (HCC) being the most prevalent subtype. Despite great advances in systemic therapy, such as molecular-targeted agents, HCC has one of the worst prognoses due to drug resistance and frequent recurrence and metastasis. Recently, new therapeutic strategies such as cancer immunosuppressive therapy have prolonged patients' lives, and the combination of an immune checkpoint inhibitor (ICI) and VEGF inhibitor is now positioned as the first-line therapy for advanced HCC. Since the efficacy of ICIs depends on the tumor immune microenvironment, it is necessary to elucidate the immune environment of HCC to select appropriate ICIs. In this review, we summarize the findings on the immune microenvironment and immunosuppressive approaches focused on monoclonal antibodies against cytotoxic T lymphocyte-associated protein 4 and programmed cell death protein 1 for HCC. We also describe ongoing treatment modalities, including adoptive cell transfer-based therapies and future areas of exploration based on recent literature. The results of pre-clinical studies using immunological classification and animal models will contribute to the development of biomarkers that predict the efficacy of immunosuppressive therapy and aid in the selection of appropriate strategies for HCC treatment.

Pathophysiological Aspects of Alcohol Metabolism in the Liver

Alcoholic liver disease (ALD) is a globally prevalent chronic liver disease caused by chronic or binge consumption of alcohol. The liver is the major organ that metabolizes alcohol; therefore, it is particularly sensitive to alcohol intake. Metabolites and byproducts generated during alcohol metabolism cause liver damage, leading to ALD via several mechanisms, such as impairing lipid metabolism, intensifying inflammatory reactions, and inducing fibrosis. Despite the severity of ALD, the development of novel treatments has been hampered by the lack of animal models that fully mimic human ALD. To overcome the current limitations of ALD studies and therapy development, it is necessary to understand the molecular mechanisms underlying alcohol-induced liver injury. Hence, to provide insights into the progression of ALD, this review examines previous studies conducted on alcohol metabolism in the liver. There is a particular focus on the occurrence of ALD caused by hepatotoxicity originating from alcohol metabolism.

Fenretinide Improves Intestinal Barrier Function and Mitigates Alcohol Liver Disease

Alcohol liver disease (ALD) is a major cause of liver-related mortality globally, yet there remains an unmet demand for approved ALD drugs. The pathogenesis of ALD involves perturbations to the intestinal barrier and subsequent translocation of bacterial endotoxin that, acting through toll-like receptor 4 (TLR4), promotes hepatic inflammation and progression of ALD. In the present study we investigated the ability of fenretinide (Fen) [N-(4-hydroxyphenyl) retinamide], a synthetic retinoid with known anti-cancer and anti-inflammatory properties, to modulate intestinal permeability and clinical hallmarks of ALD in a mouse model of chronic ethanol (EtOH) exposure. Our results show that EtOH-treated mice had reductions in mRNA and protein expression of intestinal tight junction proteins, including claudin one and occludin, and increases in intestinal permeability and endotoxemia compared to pair-fed mice. Also, EtOH-treated mice had marked increases in hepatic steatosis, liver injury, and expression of pro-inflammatory mediators, including TNF-α, and TLR4-positive macrophages, Kupffer cells, and hepatocytes in the intestines and liver, respectively. In contrast, EtOH + Fen-treated mice were resistant to the effects of EtOH on promoting intestinal permeability and had higher intestinal protein levels of claudin one and occludin. Also, EtOH + Fen-treated mice had significantly lower plasma levels of endotoxin, and reductions in expression of TNF-α and TLR4 positive macrophages, Kupffer cells, and hepatocytes in the intestine and liver. Lastly, we found that EtOH + Fen-treated mice exhibited major reductions in hepatic triglycerides, steatosis, and liver injury compared to EtOH-treated mice. Our findings are the first to demonstrate that Fen possesses anti-ALD properties, potentially through modulation of the intestinal barrier function, endotoxemia, and TLR4-mediated inflammation. These data warrant further pre-clinical investigations of Fen as a potential anti-ALD drug.

Targeted treatment of alcoholic liver disease based on inflammatory signalling pathways

Targeted therapy is an emerging treatment strategy for alcoholic liver disease (ALD). Inflammation plays an important role in the occurrence and development of ALD, and is a key choice for its targeted treatment, and anti-inflammatory treatment has been considered beneficial for liver disease. Surprisingly, immune checkpoint inhibitors have become important therapeutic agents for hepatocellular carcinoma (HCC). Moreover, studies have shown that the combination of inflammatory molecule inhibitors and immune checkpoint inhibitors can exert better effects than either alone in mouse models of HCC. This review discusses the mechanism of hepatic ethanol metabolism and the conditions under which inflammation occurs. In addition, we focus on the potential molecular targets in inflammatory signalling pathways and summarize the potential targeted inhibitors and immune checkpoint inhibitors, providing a theoretical basis for the targeted treatment of ALD and the development of new combination therapy strategies for HCC.

Lauric acid ameliorates lipopolysaccharide (LPS)-induced liver inflammation by mediating TLR4/MyD88 pathway in Sprague Dawley (SD) rats

BACKGROUND

Lipopolysaccharide (LPS) is an endotoxin that leads to inflammation in many organs, including liver. It binds to pattern recognition receptors, that generally recognise pathogen expressed molecules to transduce signals that result in a multifaceted network of intracellular responses ending up in inflammation. Aim In this study, we used lauric acid (LA), a constituent abundantly found in coconut oil to determine its anti-inflammatory role in LPS-induced liver inflammation in Sprague Dawley (SD) rats.

METHOD

Male SD rats were divided into five groups (n = 8), injected with LPS and thereafter treated with LA (50 and 100 mg/kg) or vehicle orally for 14 days. After fourteen days of LA treatment, all the groups were humanely killed to investigate biochemical parameters followed by pro-inflammatory cytokine markers; tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-1β. Moreover, liver tissues were harvested for histopathological studies and evaluation of targeted protein expression with western blot and localisation through immunohistochemistry (IHC).

RESULTS

The study results showed that treatment of LA 50 and 100 mg/kg for 14 days were able to reduce the elevated level of pro-inflammatory cytokines, liver inflammation, and downregulated the expression of TLR4/NF-κB mediating proteins in liver tissues.

CONCLUSION

These findings suggest that treatment of LA has a protective role against LPS-induced liver inflammation in rats, thus, warrants further in-depth investigation through mechanistic approaches in different study models.

Pattern Recognition Receptors: Significance of Expression in the Liver

Pattern recognition receptors (PRRs) are a pivotal part of the immune system. They are distributed in almost every site of higher organisms, able to recognize foreign pathogens or unwanted remnants of metabolism and mount innate immune response. Moreover, PRRs create bridging signaling to initiate adaptive immunity. The liver being the largest organ of the body, exposed to myriads of foreign substances often being immunogenic, is well equipped with PRRs. They act as sentinels of the organ, both in health and disease. In viral hepatitis C at least two of them, RIG-1 and TLR3 sense HCV, induce protective interferon production and create proinflammatory status. The hepatitis B virus is apparently invisible to PRRs, which has recently been denied. Besides, they are active in the course of infection. In liver injury and hepatic fibrogenesis Toll-like receptors (TLRs), predominantly TLR4, TLR3 and TLR9 are associated with gut microflora-related products and DNA from dying hepatocytes, lead to the activation of hepatic stellate cells. The latter initiate production of fibrillar collagens, the main agents forming hepatic fibrosis. Tumor cells of primary liver cancer also express PRRs, mainly TLRs. In concert with non-resolving liver inflammation, they are considered pivotal factors leading to carcinogenesis.

Obesity and diabetes as comorbidities for COVID-19: Underlying mechanisms and the role of viral-bacterial interactions

Obesity and diabetes are established comorbidities for COVID-19. Adipose tissue demonstrates high expression of ACE2 which SARS- CoV-2 exploits to enter host cells. This makes adipose tissue a reservoir for SARS-CoV-2 viruses and thus increases the integral viral load. Acute viral infection results in ACE2 downregulation. This relative deficiency can lead to disturbances in other systems controlled by ACE2, including the renin-angiotensin system. This will be further increased in the case of pre-conditions with already compromised functioning of these systems, such as in patients with obesity and diabetes. Here, we propose that interactions of virally-induced ACE2 deficiency with obesity and/or diabetes leads to a synergistic further impairment of endothelial and gut barrier function. The appearance of bacteria and/or their products in the lungs of obese and diabetic patients promotes interactions between viral and bacterial pathogens, resulting in a more severe lung injury in COVID-19.

Toll-like Receptors as a Novel Therapeutic Target for Natural Products Against Chronic Diseases

Toll-like receptors (TLR) are one among the initial responders of the immune system which participate in the activation inflammatory processes. Several different types of TLR such as TLR2, TLR4, TLR7 and TLR9 have been identified in various cell types, each having distinct ligands like lipids, lipoproteins, nucleic acids and proteins. Though its prime concern is xenobiotic defences, TLR signalling has also recognized as an activator of inflammation and associated development of chronic degenerative disorders (CDDs) including obesity, type 2 diabetes mellitus (T2DM), fatty liver disease, cardiovascular and neurodegenerative disorders as well as various types of cancers. Numerous drugs are in use to prevent these disorders, which specifically inhibit different pathways associated with the development of CDDs. Compared to these drug targets, inhibition of TLR, which specifically responsible for the inflammatory insults has proven to be a better drug target. Several natural products have emerged as inhibitors of CDDs, which specifically targets TLR signalling, among these, many are in the clinical trials. This review is intended to summarize the recent progress on TLR association with CDDs and to list possible use of natural products, their combinations and their synthetic derivative in the prevention of TLR-driven CDD development.

Evaluating acute inflammation's effects on hepatic triglyceride content in experimentally induced hyperlipidemic dairy cows in late lactation

Inflammation appears to be a predisposing factor and key component of hepatic steatosis in a variety of species. Objectives were to evaluate effects of inflammation [induced via intravenous lipopolysaccharide (LPS) infusion] on metabolism and liver lipid content in experimentally induced hyperlipidemic lactating cows. Cows (765 ± 32 kg of body weight; 273 ± 35 d in milk) were enrolled in 2 experimental periods (P); during P1 (5 d), baseline data were obtained. At the start of P2 (2 d), cows were assigned to 1 of 2 treatments: (1) intralipid plus control (IL-CON; 3 mL of saline; n = 5) or (2) intralipid plus LPS (IL-LPS; 0.375 μg of LPS/kg of body weight; n = 5). Directly following intravenous bolus (saline or LPS) administration, intralipid (20% fat emulsion) was intravenously infused continuously (200 mL/h) for 16 h to induce hyperlipidemia during which feed was removed. Blood samples were collected at -0.5, 0, 4, 8, 12, 16, 24, and 48 h relative to bolus administration, and liver biopsies were obtained on d 1 of P1 and at 16 and 48 h after the bolus. By experimental design (feed was removed during the first 16 h of d 1), dry matter intake decreased in both treatments on d 1 of P2, but the magnitude of reduction was greater in LPS cows. Dry matter intake of IL-LPS remained decreased on d 2 of P2, whereas IL-CON cows returned to baseline. Milk yield decreased in both treatments during P2, but the extent and duration was longer in LPS-infused cows. Administering LPS increased circulating LPS-binding protein (2-fold) at 8 h after bolus, after which it markedly decreased (84%) below baseline for the remainder of P2. Serum amyloid A concentrations progressively increased throughout P2 in IL-LPS cows (3-fold, relative to controls). Lipid infusion gradually increased nonesterified fatty acids and triglycerides in both treatments relative to baseline (3- and 2.5-fold, respectively). Interestingly, LPS infusion blunted the peak in nonesterified fatty acids, such that concentrations peaked (43%) higher in IL-CON compared with IL-LPS cows and heightened the increase in serum triglycerides (1.5-fold greater relative to controls). Liver fat content remained similar in IL-LPS relative to P1 at 16 h; however, hyperlipidemia alone (IL-CON) increased liver fat (36% relative to P1). No treatment differences in liver fat were observed at 48 h. In IL-LPS cows, circulating insulin increased markedly at 4 h after bolus (2-fold relative to IL-CON), and then gradually decreased during the 16 h of lipid infusion. Inducing inflammation with simultaneous hyperlipidemia altered the characteristic patterns of insulin and LPS-binding protein but did not cause fatty liver.

Advances in the Involvement of Gut Microbiota in Pathophysiology of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis and progresses to non-steatohepatitis (NASH) when the liver displays overt inflammatory damage. Increasing evidence has implicated critical roles for dysbiosis and microbiota-host interactions in NAFLD pathophysiology. In particular, microbiota alter intestine absorption of nutrients and intestine permeability, whose dysregulation enhances the delivery of nutrients, endotoxin, and microbiota metabolites to the liver and exacerbates hepatic fat deposition and inflammation. While how altered composition of gut microbiota attributes to NAFLD remains to be elucidated, microbiota metabolites are shown to be involved in the regulation of hepatocyte fat metabolism and liver inflammatory responses. In addition, intestinal microbes and circadian coordinately adjust metabolic regulation in different stages of life. During aging, altered composition of gut microbiota, along with circadian clock dysregulation, appears to contribute to increased incidence and/or severity of NAFLD.

DNA methylation and histone acetylation changes to cytochrome P450 2E1 regulation in normal aging and impact on rates of drug metabolism in the liver

Aging is associated with reduced liver function that may increase the risk for adverse drug reactions in older adults. We hypothesized that age-related changes to epigenetic regulation of genes involved in drug metabolism may contribute to this effect. We reviewed published epigenome-wide studies of human blood and identified the cytochrome P450 2E1 (CYP2E1) gene as a top locus exhibiting epigenetic changes with age. To investigate potential functional changes with age in the liver, the primary organ of drug metabolism, we obtained liver tissue from mice aged 4-32 months from the National Institute on Aging. We assayed global DNA methylation (5-methylcytosine, 5mC), hydroxymethylation (5-hydroxymethylcytosine, 5hmC), and locus-specific 5mC and histone acetylation changes around mouse Cyp2e1. The mouse livers exhibit significant global decreases in 5mC and 5hmC with age. Furthermore, 5mC significantly increased with age at two regulatory regions of Cyp2e1 in tandem with decreases in its gene and protein expressions. H3K9ac levels also changed with age at both regulatory regions of Cyp2e1 investigated, while H3K27ac did not. To test if these epigenetic changes are associated with varying rates of drug metabolism, we assayed clearance of the CYP2E1-specific probe drug chlorzoxazone in microsome extracts from the same livers. CYP2E1 intrinsic clearance is associated with DNA methylation and H3K9ac levels at the Cyp2e1 locus but not with chronological age. This suggests that age-related epigenetic changes may influence rates of hepatic drug metabolism. In the future, epigenetic biomarkers could prove useful to guide dosing regimens in older adults.

The Role of Gut-Derived Microbial Antigens on Liver Fibrosis Initiation and Progression

Intestinal dysbiosis has recently become known as an important driver of gastrointestinal and liver disease. It remains poorly understood, however, how gastrointestinal microbes bypass the intestinal mucosa and enter systemic circulation to enact an inflammatory immune response. In the context of chronic liver disease (CLD), insults that drive hepatic inflammation and fibrogenesis (alcohol, fat) can drastically increase intestinal permeability, hence flooding the liver with gut-derived microbiota. Consequently, this may result in exacerbated liver inflammation and fibrosis through activation of liver-resident Kupffer and stellate cells by bacterial, viral, and fungal antigens transported to the liver via the portal vein. This review summarizes the current understanding of microbial translocation in CLD, the cell-specific hepatic response to intestinal antigens, and how this drives the development and progression of hepatic inflammation and fibrosis. Further, we reviewed current and future therapies targeting intestinal permeability and the associated, potentially harmful anti-microbial immune response with respect to their potential in terms of limiting the development and progression of liver fibrosis and end-stage cirrhosis.

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

The breakthrough discoveries of leptin and adiponectin more than two decades ago led to a widespread recognition of adipose tissue as an endocrine organ. Many more adipose tissue-secreted signaling mediators (adipokines) have been identified since then, and much has been learned about how adipose tissue communicates with other organs of the body to maintain systemic homeostasis. Beyond proteins, additional factors, such as lipids, metabolites, noncoding RNAs, and extracellular vesicles (EVs), released by adipose tissue participate in this process. Here, we review the diverse signaling mediators and mechanisms adipose tissue utilizes to relay information to other organs. We discuss recently identified adipokines (proteins, lipids, and metabolites) and briefly outline the contributions of noncoding RNAs and EVs to the ever-increasing complexities of adipose tissue inter-organ communication. We conclude by reflecting on central aspects of adipokine biology, namely, the contribution of distinct adipose tissue depots and cell types to adipokine secretion, the phenomenon of adipokine resistance, and the capacity of adipose tissue to act both as a source and sink of signaling mediators.

Protective effect of resveratrol against hepatic damage induced by heat stress in a rat model is associated with the regulation of oxidative stress and inflammation

Heat stress jeopardizes humans and animals health, and results in enormous economic loss in public health care and livestock production. The aim of this study was to investigate the effects of resveratrol on hepatic oxidative stress and inflammation in heat-stressed rats. Male Sprague-Dawley rats were orally fed with 100 mg resveratrol/kg body weight/day prior to heat stress (40 ∘C per day for 1.5 h) exposure for 3 consecutive days. Serum and liver samples were collected for the analysis of hepatic injury, redox status and immune response. The results showed that the heat-stress-induced increased aspartate aminotransferase activities in the serum, aberrant hepatic histology, excessive hepatic malondialdehyde and tumor necrosis factor alpha concentrations, and up-regulation of heat shock protein 70, superoxide dismutase 1, glutathione peroxidase 1, toll-like receptor 4 and interleukin 10 mRNA expression in the liver were mitigated by oral resveratrol treatment. Collectively, the beneficial effects of resveratrol on hepatic damage induced by heat stress were associated with the regulation of oxidative stress and inflammation.

Ginseng (Panax ginseng Meyer) Oligopeptides Protect Against Binge Drinking-Induced Liver Damage through Inhibiting Oxidative Stress and Inflammation in Rats

Panax ginseng C.A. Meyer (ginseng) is an edible and traditional medicinal herb, which is reported to have a wide range of biological activity and pharmaceutical properties. There were more studies on ginsenoside and polysaccharides, but fewer on ginseng oligopeptides (GOPs), which are small molecule oligopeptides extracted from ginseng. The present study was designed to investigate the effects and underlying mechanism of ginseng oligopeptide (GOPs) on binge drinking-induced alcohol damage in rats. Sprague Dawley rats were randomly assigned to six groups (n = 10), rats in normal control group and alcohol model group was administered distilled water; rats in four GOPs intervention groups (at a dose of 0.0625, 0.125, 0.25, 0.5 g/kg of body weight, respectively) were administered GOPs once a day for 30 days. Experiment rats were intragastrically administered ethanol at a one-time dose of 7 g/kg of body weight after 30 days. The liver injury was measured through traditional liver enzymes, inflammatory cytokines, expression of oxidative stress markers, and histopathological examination. We found that the GOPs treatment could significantly improve serum alanine aminotransferase and aspartate aminotransferase, plasma lipopolysaccharide, and inflammatory cytokine levels, as well as the oxidative stress markers that were altered by alcohol. Moreover, GOPs treatment inhibited the protein expression of toll-like receptor 4, and repressed the inhibitor kappa Bα and nuclear factor-κB p65 in the liver. These findings suggested that GOPs have a significant protective effect on binge drinking-induced liver injury, and the mechanism possibly mediated by the partial inhibition of lipopolysaccharide-toll-like receptor 4-nuclear factor-κB p65 signaling in the liver.