IL-1 cytokine family members and NAFLD: neglected in metabolic liver inflammation

PNPLA3 gene variation modulates diet-induced improvement in liver lipid content in type 2 diabetes

BACKGROUND&AIMS

Lifestyle-induced weight reduction remains crucial for managing type 2 diabetes and steatotic liver disease, but its effectiveness varies. We postulated that the G allele in the rs738409 single nucleotide polymorphism within patatin-like phospholipase domain-containing protein 3 (PNPLA3), which associates with metabolic dysfunction-associated steatotic liver disease, also modulates diet-related metabolic effects.

METHODS

Participants with type 2 diabetes were randomized to 8-week hypocaloric diets (energy intake: -1,256 kJ/d of, <30 kcal% fat): high in cereal fiber and coffee excluding red meat (HF-RM + C; n = 16), or low in cereal fiber, devoid of coffee, but high in red meat (LF + RM-C; n = 15). Whole-body insulin sensitivity (M value) was assessed using [2H]glucose and hyperinsulinemic-normoglycemic clamps, hepatic lipid content (HCL) and body fat volumes by magnetic resonance spectroscopy/imaging before and after intervention.

RESULTS

Despite comparable weight loss, HCL decreased more in non-carriers (-65 %) than in G-allele carriers (-36 %) upon HF-RM + C diet (both p < 0.05 vs baseline and between groups), but only among non-carriers (-46 %, p < 0.05 vs baseline) upon LF + RM-C. Upon HF-RM + C diet, increase in insulin sensitivity was not different between carriers (+27 % p = 0.051 from baseline) and non-carriers (+21 %, p = 0.032 from baseline), p > 0.05 for between-group comparison. Upon LF + RM-C diet, both groups equally improved their whole-body insulin sensitivity (+42 % for non-carriers and +37 % for carriers, p < 0.05 vs baseline). Upon HF-RM + C diet, non-carriers decreased circulating interleukin-18 from baseline by -31 %, whereas, upon LF + RM-C diet, non-carriers decreased circulating anti-inflammatory interleukin-1 receptor antagonist levels by 14 % (both p < 0.05 vs baseline).

CONCLUSIONS

Humans with the PNPLA3 G-allele show modified dietary-induced effects on steatotic liver disease in type 2 diabetes despite body weight reduction. Registration at Clinicaltrials.gov, Identifier number: NCT01409330.

Effects of exopolysaccharides form Lactobacillus plantarum KX041 on high fat diet-induced gut microbiota and inflammatory obesity

Lactobacillus plantarum KX041 is a probiotics obtained from early screening, which can relieve inflammation and enrich the anti-obesity intestinal flora, and produce high yield of exopolysaccharides (EPS). The extraction, structure and physicochemical properties of EPS have been completed earlier. However, whether the functional activity of L. plantarum KX041 is related to the EPS is still unclear. In this study, combined in vivo and in vitro tests explored the effects of EPS on inflammatory obesity. In vitro tests, EPS relieased inflammation by inhibiting TLR4/p-NFκB, and inhibited adipocyte differentiation and reduced the transcriptional level of inflammation and lipid-synthesis genes (especially CD36 and peroxisome proliferators-activated receptors-γ PPARγ). In vivo tests demonstrated that EPS could alleviate weight gain, white adipocyte expansion, organ damage, insulin resistance, hyperlipidemia, and inflammatory response caused by high fat diet. Combined with in vitro tests, the transcription level of inflammation and lipid-synthesis genes in adipose tissue identified that IL-1β and PPARγ were the key genes for the effect of EPS on inflammatory obesity. Moreover, EPS increased the abundance of Akkermansia and Lachnospiraceae_NK4A136_group, and intestinal levels of isobutyrate, which is one of the key factors in alleviating inflammatory obesity. These insights may inform the development of functionalized dietary interventions in obesity.

Functional Food Chemical Ingredient Strategies for Non-alcoholic Fatty Liver Disease (NAFLD) and Hepatic Fibrosis: Chemical Properties, Health Benefits, Action, and Application

PURPOSE OF REVIEW

The liver is an important digestive gland in the body. Lifestyle and dietary habits are increasingly damaging our liver, leading to various diseases and health problems. Non-alcoholic fatty liver disease (NAFLD) has become one of the most serious liver disease problems in the world. Diet is one of the important factors in maintaining liver health. Functional foods and their components have been identified as novel sources of potential preventive agents in the prevention and treatment of liver disease in daily life. However, the effects of functional components derived from small molecules in food on different types of liver diseases have not been systematically summarized.

RECENT FINDINGS

The components and related mechanisms in functional foods play a significant role in the development and progression of NAFLD and liver fibrosis. A variety of structural components are found to treat and prevent NAFLD and liver fibrosis through different mechanisms, including flavonoids, alkaloids, polyphenols, polysaccharides, unsaturated fatty acids, and peptides. On the other hand, the relevant mechanisms include oxidative stress, inflammation, and immune regulation, and a large number of literature studies have confirmed a close relationship between the mechanisms. The purpose of this article is to examine the current literature related to functional foods and functional components used for the treatment and protection against NAFLD and hepatic fibrosis, focusing on chemical properties, health benefits, mechanisms of action, and application in vitro and in vivo. The roles of different components in the biological processes of NAFLD and liver fibrosis were also discussed.

Protective effects of yeast extract against alcohol-induced liver injury in rats

Oxidative stress, inflammatory response, and gut-liver axis dysbiosis have been suggested as the primarily involved in the pathogenesis of alcoholic liver injury. Previous research established that yeast extract (YE) has antioxidant, immune-boosting or microbiota-regulating properties. However, there is currently lack of information regarding the efficacy of YE on alcoholic liver injury. This study seeks to obtain data that will help to address this research gap using a Wistar male rat experimental model. Histologic and biochemical analysis results showed that the groups treated with both low-dose yeast extract (YEL) and high-dose yeast extract (YEH) had lower degrees of alcohol-induced liver injury. The abundance of Peptococcus and Ruminococcus reduced in the low-dose yeast extract (YEL) group, while that of Peptococcus, Romboutsia, Parasutterella, and Faecalibaculum reduced in the high-dose (YEH) group. Furthermore, Spearman analysis showed that the gut microbes were significantly associated with several liver-related indicators. For the analysis of differential metabolites and enriched pathways in the YEL group, the abundance of lysophosphatidylcholine (16:0/0:0) significantly increased, and then the levels of histamine, adenosine and 5' -adenine nucleotide were remarkedly elevated in the YEH group. These findings suggest that both high and low doses of YE can have different protective effects on liver injury in alcoholic liver disease (ALD) rats, in addition to improving gut microbiota disorder. Besides, high-dose YE has been found to be more effective than low-dose YE in metabolic regulation, as well as in dealing with oxidative stress and inflammatory responses.

The sex-dependent response to psychosocial stress and ischaemic heart disease

Stress is an important risk factor for modern chronic diseases, with distinct influences in males and females. The sex specificity of the mammalian stress response contributes to the sex-dependent development and impacts of coronary artery disease (CAD). Compared to men, women appear to have greater susceptibility to chronic forms of psychosocial stress, extending beyond an increased incidence of mood disorders to include a 2- to 4-fold higher risk of stress-dependent myocardial infarction in women, and up to 10-fold higher risk of Takotsubo syndrome-a stress-dependent coronary-myocardial disorder most prevalent in post-menopausal women. Sex differences arise at all levels of the stress response: from initial perception of stress to behavioural, cognitive, and affective responses and longer-term disease outcomes. These fundamental differences involve interactions between chromosomal and gonadal determinants, (mal)adaptive epigenetic modulation across the lifespan (particularly in early life), and the extrinsic influences of socio-cultural, economic, and environmental factors. Pre-clinical investigations of biological mechanisms support distinct early life programming and a heightened corticolimbic-noradrenaline-neuroinflammatory reactivity in females vs. males, among implicated determinants of the chronic stress response. Unravelling the intrinsic molecular, cellular and systems biological basis of these differences, and their interactions with external lifestyle/socio-cultural determinants, can guide preventative and therapeutic strategies to better target coronary heart disease in a tailored sex-specific manner.

The anti-inflammatory effects of Akkermansia muciniphila and its derivates in HFD/CCL4-induced murine model of liver injury

Inflammation plays a critical role in the promotion of hepatocyte damage and liver fibrosis. In recent years the protective role of Akkermansia muciniphila, a next-generation beneficial microbe, has been suggested for metabolic and inflammatory disorders. In this study, we aimed to evaluate the effects of live and pasteurized A. muciniphila and its extra cellular vesicles (EVs) on inflammatory markers involved in liver fibrosis in a mouse model of a high-fat diet (HFD)/carbon tetrachloride (CCl₄)-induced liver injury. Firstly, the responses of hepatic stellate cells (HSCs) to live and pasteurized A. muciniphila and its EVs were examined in the quiescent and LPS-activated LX-2 cells. Next, the anti-inflammatory effects of different forms of A. muciniphila were examined in the mouse model of HFD/CCl₄-induced liver injury. The gene expression of various inflammatory markers was evaluated in liver, colon, and white adipose tissues. The cytokine secretion in the liver and white adipose tissues was also measured by ELISA. The results showed that administration of live and pasteurized A. muciniphila and its EVs leads to amelioration in HSCs activation. Based on data obtained from the histopathological analysis, an improvement in gut health was observed through enhancing the epithelium and mucosal layer thickness and strengthening the intestinal integrity in all treatments. Moreover, live A. muciniphila and its EVs had inhibitory effects on liver inflammation and hepatocytes damage. In addition, the tissue cytokine production and inflammatory gene expression levels revealed that live A. muciniphila and its EVs had more pronounced anti-inflammatory effects on liver and adipose tissues. Furthermore, EVs had better effects on the modulation of gene expression related to TLRs, PPARs, and immune response in the liver. In conclusion, the present results showed that oral administration of A. muciniphila and its derivatives for four weeks could enhance the intestinal integrity and anti-inflammatory responses of the colon, adipose, and liver tissues and subsequently prevent liver injury in HFD/CCL₄ mice.

CYP450 drug inducibility in NAFLD via an in vitro hepatic model: Understanding drug-drug interactions in the fatty liver

Drug-drug-interactions (DDIs) occur when a drug alters the metabolic rate, efficacy, and toxicity of concurrently used drugs. While almost 1 in 4 adults now use at least 3 concurrent prescription drugs in the United States, the Non-alcoholic fatty liver disease (NAFLD) prevalence has also risen over 25%. The effect of NALFD on DDIs is largely unknown. NAFLD is characterized by lipid vesicle accumulation in the liver, which can progress to severe steatohepatitis (NASH), fibrosis, cirrhosis, and hepatic carcinoma. The CYP450 enzyme family dysregulation in NAFLD, which might already alter the efficacy and toxicity of drugs, has been partially characterized. Nevertheless, the drug-induced dysregulation of CYP450 enzymes has not been studied in the fatty liver. These changes in enzymatic inducibility during NAFLD, when taking concurrent drugs, could cause unexpected fatalities through inadvertent DDIs. We have, thus, developed an in vitro model to investigate the CYP450 transcriptional regulation in NAFLD. Specifically, we cultured primary human hepatocytes in a medium containing free fatty acids, high glucose, and insulin for seven days. These cultures displayed intracellular macro-steatosis after 5 days and cytokine secretion resembling NAFLD patients. We further verified the model's dysregulation in the transcription of key CYP450 enzymes. We then exposed the NAFLD model to the drug inducers rifampicin, Omeprazole, and Phenytoin as activators of transcription factors pregnane X receptor (PXR), aryl hydrocarbon receptor (AHR) and constitutive androstane receptor (CAR), respectively. In the NAFLD model, Omeprazole maintained an expected induction of CYP1A1, however Phenytoin and Rifampicin showed elevated induction of CYP2B6 and CYP2C9 compared to healthy cultures. We, thus, conclude that the fatty liver could cause aggravated drug-drug interactions in NAFLD or NASH patients related to CYP2B6 and CYP2C9 enzymes.

CBD Alleviates Liver Injuries in Alcoholics With High-Fat High-Cholesterol Diet Through Regulating NLRP3 Inflammasome-Pyroptosis Pathway

Alcohol abuse and high-fat diet–induced liver diseases have been the most prevalent chronic liver diseases and the leading reasons for liver transplantation around the world. Cannabidiol (CBD) is a botanical component extracted from marijuana plants without psychoactive impact. In our previous reports, we found that CBD can prevent fatty liver induced by Lieber–DeCarli ethanol diet or non-alcoholic fatty liver disease (NAFLD) induced by high-fat high-cholesterol diet. The current work is a further study on whether CBD can alleviate liver injuries induced by ethanol plus high-fat high-cholesterol diet (EHFD), which is a model simulating heavy alcohol drinkers in a Western diet. A mice liver injury model induced by EHFD for 8 weeks was applied to explore the protective properties of CBD and the underlying mechanisms. We found that CBD prevented liver steatosis and oxidative stress induced by EHFD. CBD treatment inhibited macrophage recruitment and suppressed activation of NFκB–NLRP3–pyroptosis pathway in mice livers. The hepatoprotective property of CBD in the current model might be a result of inhibition of inflammation via alleviating activation of the hepatic NFκB–NLRP3 inflammasome–pyroptosis pathway by CBD.

Gravity-Based Flow Efficient Perfusion Culture System for Spheroids Mimicking Liver Inflammation

The spheroid culture system provides an efficient method to emulate organ-specific pathophysiology, overcoming the traditional two-dimensional (2D) cell culture limitations. The intervention of microfluidics in the spheroid culture platform has the potential to enhance the capacity of in vitro microphysiological tissues for disease modeling. Conventionally, spheroid culture is carried out in static conditions, making the media nutrient-deficient around the spheroid periphery. The current approach tries to enhance the capacity of the spheroid culture platform by integrating the perfusion channel for dynamic culture conditions. A pro-inflammatory hepatic model was emulated using a coculture of HepG2 cell line, fibroblasts, and endothelial cells for validating the spheroid culture plate with a perfusable channel across the spheroid well. Enhanced proliferation and metabolic capacity of the microphysiological model were observed and further validated by metabolic assays. A comparative analysis of static and dynamic conditions validated the advantage of spheroid culture with dynamic media flow. Hepatic spheroids were found to have improved proliferation in dynamic flow conditions as compared to the static culture platform. The perfusable culture system for spheroids is more physiologically relevant as compared to the static spheroid culture system for disease and drug analysis.

Association of Nonalcoholic Fatty Liver Disease (NAFLD) with Peripheral Diabetic Polyneuropathy: A Systematic Review and Meta-Analysis

AIMS

The relationship between nonalcoholic fatty liver disease (NAFLD) and diabetic polyneuropathy (DPN) has been demonstrated in many studies, although results were conflicting. This meta-analysis aims to summarize available data and to estimate the DPN risk among NAFLD patients.

MATERIALS AND METHODS

We performed a comprehensive literature review until 4 June 2021. Clinical trials analyzing the association between NAFLD and DPN were included.

RESULTS

Thirteen studies (9614 participants) were included. DPN prevalence was significantly higher in patients with NALFD, compared to patients without NAFLD (OR (95%CI) 2.48 (1.42-4.34), p = 0.001; I2 96%). This finding was confirmed in type 2 diabetes (OR (95%CI) 2.51 (1.33-4.74), p = 0.005; I2 97%), but not in type 1 diabetes (OR (95%CI) 2.44 (0.85-6.99), p = 0.100; I2 77%). Also, body mass index and diabetes duration were higher in NAFLD subjects compared to those without NAFLD (p < 0.001), considering both type 2 and type 1 diabetes.

CONCLUSION

Despite a high heterogeneity among studies, a significantly increased DPN prevalence among type 2 diabetes subjects with NAFLD was observed. This result was not found in type 1 diabetes, probably due to the longer duration of disease. Physicians should pay more attention to the early detection of DPN, especially in patients with NAFLD.

Tamarix chinensis Lour inhibits chronic ethanol-induced liver injury in mice

BACKGROUND

Tamarix chinensis Lour (TCL) is a shrub that usually grows in arid or semiarid desert areas and saline-alkali fields. It is a traditional Chinese herbal medicine with hepatoprotective, antioxidant, antibacterial, and antitumor activities.

AIM

To investigate the possible protective effects of TCL against liver injury induced by chronic ethanol intake.

METHODS

C57BL/6J male mice were fed a Lieber-DeCarli lipid diet containing alcohol and received (by gavage) a water-alcohol extract (80%) of TCL (100 and 200 mg/kg BW) or distilled water for 4 wk. After euthanasia, liver tissues were observed histologically with hematoxylin and eosin staining and Oil red O staining, and the levels of alanine aminotransferase, aspartate transaminase, hepatic lipids, reactive oxygen species, malondialdehyde, and superoxide dismutase were measured. In addition, expression of the NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome and downstream proinflammatory cytokines were determined.

RESULTS

Compared with the ethanol group, mice in the TCL-treated group (200 mg/kg) had significantly lower serum levels of alanine aminotransferase (mean, 34.1 IU/L vs 45.3 IU/L, P < 0.01) and aspartate transaminase (mean, 89.6 IU/L vs 115.7 IU/L, P < 0.01), as well as marked reduction of hepatic tissue reactive oxygen species (decreased by 27.5%, P < 0.01) and malondialdehyde (decreased by 76.6%, P < 0.01) levels, with a significant increase of superoxide dismutase (Increased by 73.2%, P < 0.01). Expression of the NLRP3 inflammasome and its downstream cytokines [interleukin (IL)-1β, tumor necrosis factor-α, and IL-6], and recruitment of natural killer T cells to the liver, were reduced in the TCL-treated incubation with a Lieber-DeCaril ethanol lipid diet group.

CONCLUSION

These findings suggest that a TCL extract (200 mg/kg) protects against chronic ethanol-induced liver injury, probably by inhibiting the NLRP3-caspase-1-IL-1β signaling pathway and suppressing oxidative stress.

Non-alcoholic fatty liver disease among patients with sleep disorders: a Nationwide study of Taiwan

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases. Studies have shown that sleep apnea is associated with NAFLD. However, studies on the association between sleep disorders in general and NAFLD are limited. We conducted a nationwide population-based longitudinal study to evaluate this potential association.

METHODS

We identified patients diagnosed with sleep disorders in the years 2000 through 2005 in Taiwan using the National Health Insurance Research Database and selected an equal number of patients without sleep disorders from the same database as the comparison cohort. The patients were followed from the index date to the diagnosis of NAFLD or the end of 2013. We used Cox proportional hazards models to estimate the risk of NAFLD associated with sleep disorders.

RESULTS

A total of 33,045 patients with sleep disorders were identified. The incidence of NAFLD was 14.0 per 10,000 person-year in patients with sleep disorders and 6.2 per 10,000 person-year in the comparison cohort. The adjusted hazard ratio (AHR) of NAFLD associated with sleep disorders was 1.78 (95% confidence interval [95%CI]: 1.46-2.16), and other independent risk factors included male sex (AHR = 1.31, 95%CI: 1.12-1.54), age 40-59 years (AHR = 1.49, 95%CI: 1.21-1.82), and dyslipidemia (AHR = 2.51, 95%CI: 2.08-3.04). In the subgroup analyses, both patients with (AHR = 2.24, 95%CI: 1.05-4.77) and without (AHR = 1.77, 95%CI: 1.46-2.15) sleep apnea had an increased risk of NAFLD.

CONCLUSIONS

Sleep disorders are associated with NAFLD, even in patients without sleep apnea. Further studies are warranted to explore the mechanisms of the association.

Association of non-alcoholic fatty liver disease with microvascular complications of type 2 diabetes

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) affects risks of type 2 diabetes (T2D), diabetes-related complications, and cardiovascular disease in a complex manner. This study is designed to clarify associations of sonographically-detected NAFLD and serum liver enzymes with diabetes-related microvascular complications.

METHODS

A matched case-contorl study was designed for 440 patients with T2D and at least one of the chronic diabetes-related microvascular complications and 495 age- and gender-matched control patients with T2D.

RESULTS

Considering pre-existing and newly developed chronic microvascular complications, diabetic peripheral neuropathy was found in 347 out of 935 (37.1%) study patients, diabetic retinopathy in 141/935 (15.1%), and diabetic nephropathy in 103/935 (11.0%). Diagnosis of diabetic retinopathy and diabetic nephropathy were inversely associated with the presence of NAFLD in the crude logistic regressions (OR [95% CI] = 0.18 [0.05-0.63], p value = 0.007; OR [95% CI] = 0.17 [0.04-0.59], p value = 0.011, respectively). The subgroup of NAFLD with elevated liver enzymes had lower odds of having diabetic peripheral neuropathy in the fully adjusted model (OR [95% CI] = 0.34 [0.12-0.98], p value = 0.048).

CONCLUSION

Diagnosis of NAFLD with or without elevated serum liver enzymes was inversely correlated with certain chronic diabetes microvascular complications. Possible explanations for this counter-intuitive and unexpected finding are discussed and center on reverse-causality, wherein sicker patients may develop beneficial compensatory physiological and behavioral adaptations. Diversity of studied patients, in particular with regards to the ethnic and racial differences among the Western and Asian populations may also partly account for contrasting findings of the relationship between NAFLD and microvascular complications of diabetes.

Pyroptosis in Liver Disease: New Insights into Disease Mechanisms

There has been increasing interest in pyroptosis as a novel form of pro-inflammatory programmed cell death. The mechanism of pyroptosis is significantly different from other forms of cell death in its morphological and biochemical features. Pyroptosis is characterized by the activation of two different types of caspase enzymes-caspase-1 and caspase-4/5/11, and by the occurrence of a proinflammatory cytokine cascade and an immune response. Pyroptosis participates in the immune defense mechanisms against intracellular bacterial infections. On the other hand, excessive inflammasome activation can induce sterile inflammation and eventually cause some diseases, such as acute or chronic hepatitis and liver fibrosis. The mechanism and biological significance of this novel form of cell death in different liver diseases will be evaluated in this review. Specifically, we will focus on the role of pyroptosis in alcoholic and non-alcoholic fatty liver disease, as well as in liver failure. Finally, the therapeutic implications of pyroptosis in liver diseases will be discussed.

Apigenin ameliorates HFD-induced NAFLD through regulation of the XO/NLRP3 pathways

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of liver-related morbidity and mortality disease in the world. However, no effective pharmacological treatment for NAFLD has been found. In this study, we used a high fat diet (HFD)-induced NAFLD model to investigate hepatoprotective effect of apigenin (API) against NAFLD and further explored its potential mechanism. Our results demonstrated that gavage administration of API could mitigate HFD-induced liver injury, enhance insulin sensitivity and markedly reduce lipid accumulation in HFD-fed mice livers. In addition, histological analysis showed that hepatic steatosis and macrophages recruitment in the API treatment group were recovered compared with mice fed with HFD alone. Importantly, API could reverse the HFD-induced activation of the NLRP3 inflammasome, further reduced inflammatory cytokines IL-1β and IL-18 release, accompanied with the inhibition of xanthine oxidase (XO) activity and the reduction of uric acid and reactive oxygen species (ROS) production. The pharmacological role of API was further confirmed using free fatty acid (FFA) induced cell NAFLD model. Taking together, our results demonstrated that API could protect against HFD-induced NAFLD by ameliorating hepatic lipid accumulation and inflammation. These protective effects may be partially attributed to the regulation of XO by API, which further modulated NLRP3 inflammasome activation and inflammatory cytokines IL-1β and IL-18 release. Therefore API is a potential therapeutic agent for the prevention of NAFLD.

Inflammation and Metabolic Complications in HIV

PURPOSE OF REVIEW

We aim to provide an in-depth review of recent literature highlighting the role of inflammation involving the adipose tissue, liver, skeletal muscles, and gastrointestinal tract in the development of metabolic complications among persons living with HIV (PLWH).

RECENT FINDINGS

Recent studies in PLWH have demonstrated a significant association between circulating inflammatory markers and development of insulin resistance and metabolic complications. In adipose tissue, pro-inflammatory cytokine expression inhibits adipocyte insulin signaling, which alters lipid and glucose homeostasis. Increased lipolysis and lipogenesis elevate levels of circulating free fatty acids and promote ectopic fat deposition in liver and skeletal muscles. This leads to lipotoxicity characterized by a pro-inflammatory response with worsening insulin resistance. Finally, HIV is associated with gastrointestinal tract inflammation and changes in the gut microbiome resulting in reduced diversity, which is an additional risk factor for diabetes. Metabolic complications in PLWH are in part due to chronic, multisite tissue inflammation resulting in dysregulation of glucose and lipid trafficking, utilization, and storage.

Circular RNA in Liver: Health and Diseases

Circular RNA (circRNA) is an important class of noncoding RNA characterized by covalently closed continuous loop structures. In recent years, the various functions of circRNAs have been continuously documented, including effects on cell proliferation and apoptosis and nutrient metabolism. The liver is the largest solid organ in mammals, and it also performs many functions in the body, which is considered to be the busiest organ in the body. At the same time, the liver is vulnerable to multiple pathogenic factors, causing various acute and chronic liver diseases. The pathogenesis of liver disease is still not fully understood. As a rising star for the past few years, circRNAs have been proven involved in the regulation of liver homeostasis and disease. This chapter will explain the role of circRNAs in liver health and diseases and sort out the confusion in the present study.

Investigating Molecular Connections of Non-alcoholic Fatty Liver Disease with Associated Pathological Conditions in West Virginia for Biomarker Analysis

Non-alcoholic fatty liver disease (NAFLD) is a disease characterized by a steatosis of the liver that may progress to more serious pathological conditions including: nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. As the prevalence of NAFLD has increased worldwide in recent years, pathophysiology and risk factors associated with disease progression of NAFLD are at the focus of many studies. NAFLD is related to and shares common serum biomarkers with cardiovascular disease (CVD), type 2 diabetes mellitus (T2DM), obesity, and metabolic syndrome (MetS). West Virginia (WV) is a state with some of the highest rates of CVD, obesity and diabetes mellitus. As NAFLD is closely related to these diseases, it is of particular interest in WV. Currently there is no cost-effective, standardized method used clinically to detect NAFLD prior to the onset of reversible complications. At this time, the diagnosis of NAFLD is made with costly radiologic studies and invasive biopsy. These studies are only diagnostic once changes to hepatic tissue have occurred. The diagnosis of NAFLD by traditional methods may not allow for successful intervention and may not be readily available in areas with already sparse medical resources. In this literature review, we identify a list of biomarkers common among CVD, T2DM, obesity, MetS and NAFLD. From this research we propose the following biomarkers are good candidates for inclusion in a panel of biomarkers for the early detection of NAFLD: adiponectin, AST, ALT, apo-B, CK18, CPS1, CRP, FABP-1, ferritin, GGT, GRP78, HDL-C, IGF-1, IL-1β, 6, 8, 10, IRS-2PAI-1, leptin, lumican, MDA SREBP-1c and TNF-α. Creating and implementing a biomarker panel for the early detection and attenuation of NAFLD, prior to the onset of irreversible complication would provide maximum benefit and decrease the disease burden on the patients and healthcare system of WV.

Inflammation: The Common Pathway of Stress-Related Diseases

While modernization has dramatically increased lifespan, it has also witnessed that the nature of stress has changed dramatically. Chronic stress result failures of homeostasis thus lead to various diseases such as atherosclerosis, non-alcoholic fatty liver disease (NAFLD) and depression. However, while 75%-90% of human diseases is related to the activation of stress system, the common pathways between stress exposure and pathophysiological processes underlying disease is still debatable. Chronic inflammation is an essential component of chronic diseases. Additionally, accumulating evidence suggested that excessive inflammation plays critical roles in the pathophysiology of the stress-related diseases, yet the basis for this connection is not fully understood. Here we discuss the role of inflammation in stress-induced diseases and suggest a common pathway for stress-related diseases that is based on chronic mild inflammation. This framework highlights the fundamental impact of inflammation mechanisms and provides a new perspective on the prevention and treatment of stress-related diseases.

Parallel Profiles of Inflammatory and Effector Memory T Cells in Visceral Fat and Liver of Obesity-Associated Cancer Patients

In the midst of a worsening obesity epidemic, the incidence of obesity-associated morbidities, including cancer, diabetes, cardiac and liver disease is increasing. Insights into mechanisms underlying pathological obesity-associated inflammation are lacking. Both the omentum, the principal component of visceral fat, and liver of obese individuals are sites of excessive inflammation, but to date the T cell profiles of both compartments have not been assessed or compared in a patient cohort with obesity-associated disease. We have previously identified that omentum is enriched with inflammatory cytokines, chemokines and T cells. Here, we compared the inflammatory profile of T cells in the omentum and liver of patients with the obesity-associated malignancy oesophageal adenocarcinoma (OAC). Furthermore, we assessed the secreted cytokine profile in OAC patient serum, omentum and liver to assess systemic and local inflammation. We observed parallel T cell cytokine profiles and phenotypes in the omentum and liver of OAC patients, in particular CD69(+) and inflammatory effector memory T cells. This study reflects similar processes of inflammation and T cell activation in the omentum and liver, and may suggest common targets to modulate pathological inflammation at these sites.

The Role of Tissue Macrophage-Mediated Inflammation on NAFLD Pathogenesis and Its Clinical Implications

The obese phenotype is characterized by a state of chronic low-grade systemic inflammation that contributes to the development of comorbidities, including nonalcoholic fatty liver disease (NAFLD). In fact, NAFLD is often associated with adipocyte enlargement and consequent macrophage recruitment and inflammation. Macrophage polarization is often associated with the proinflammatory state in adipose tissue. In particular, an increase of M1 macrophages number or of M1/M2 ratio triggers the production and secretion of various proinflammatory signals (i.e., adipocytokines). Next, these inflammatory factors may reach the liver leading to local M1/M2 macrophage polarization and consequent onset of the histological damage characteristic of NAFLD. Thus, the role of macrophage polarization and inflammatory signals appears to be central for pathogenesis and progression of NAFLD, even if the heterogeneity of macrophages and molecular mechanisms that govern their phenotype switch remain incompletely understood. In this review, we discuss the role of adipose and liver tissue macrophage-mediated inflammation in experimental and human NAFLD. This focus is relevant because it may help researchers that approach clinical and experimental studies on this disease advancing the knowledge of mechanisms that could be targeted in order to revert NAFLD-related fibrosis.

Serum microRNAs explain discordance of non-alcoholic fatty liver disease in monozygotic and dizygotic twins: a prospective study

OBJECTIVE

In the setting where two individuals are genetically similar, epigenetic mechanisms could account for discordance in the presence or absence of non-alcoholic fatty liver disease (NAFLD). This study investigated if serum microRNAs (miRs) could explain discordance in NAFLD.

DESIGN

This is a cross-sectional analysis of a prospective cohort study of 40 (n=80) twin-pairs residing in Southern California. All participants underwent a standardised research visit, liver MRI using proton-density fat fraction to quantify fat content and miR profiling of their serum.

RESULTS

Among the 40 twin-pairs, there were 6 concordant for NAFLD, 28 were concordant for non-NAFLD and 6 were discordant for NAFLD. The prevalence of NAFLD was 22.5% (18/80). Within the six discordant twins, a panel of 10 miRs differentiated the twin with NAFLD from the one without. Two of these miRs, miR-331-3p and miR-30c, were also among the 21 miRs that were different between NAFLD and non-NAFLD groups (for miR-331-3p: 7.644±0.091 vs 8.057±0.071, respectively, p=0.004; for miR-30c: 10.013±0.126 vs 10.418±0.086, respectively, p=0.008). Both miRs were highly heritable (35.9% and 10.7%, respectively) and highly correlated with each other (R=0.90, p=2.2×10(-16)) suggesting involvement in a common mechanistic pathway. An interactome analysis of these two miRs showed seven common target genes.

CONCLUSIONS

Using a novel human twin-study design, we demonstrate that discordancy in liver fat content between the twins can be explained by miRs, and that they are heritable.

Interleukin-1 and inflammasomes in alcoholic liver disease/acute alcoholic hepatitis and nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Both alcoholic liver disease (ALD) and nonalcoholic fatty liver disease are characterized by massive lipid accumulation in the liver accompanied by inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma in a substantial subgroup of patients. At several stages in these diseases, mediators of the immune system, such as cytokines or inflammasomes, are crucially involved. In ALD, chronic ethanol exposure sensitizes Kupffer cells to activation by lipopolysaccharides through Toll-like receptors, e.g., Toll-like receptor 4. This sensitization enhances the production of various proinflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor-alpha, thereby contributing to hepatocyte dysfunction, necrosis, and apoptosis and the generation of extracellular matrix proteins leading to fibrosis/cirrhosis. Indeed, neutralization of IL-1 by IL-1 receptor antagonist has recently been shown to potently prevent liver injury in murine models of ALD. As IL-1 is clearly linked to key clinical symptoms of acute alcoholic hepatitis such as fever, neutrophilia, and wasting, interfering with the IL-1 pathway might be an attractive treatment strategy in the future. An important role for IL-1-type cytokines and certain inflammasomes has also been demonstrated in murine models of nonalcoholic fatty liver disease. IL-1-type cytokines can regulate hepatic steatosis; the NLR family pyrin domain containing 3 inflammasome is critically involved in metabolic dysregulation.

CONCLUSION

IL-1 cytokine family members and various inflammasomes mediate different aspects of both ALD and nonalcoholic fatty liver disease. (Hepatology 2016;64:955-965).

Interaction between periodontitis and liver diseases

Periodontitis is an oral disease that is highly prevalent worldwide, with a prevalence of 30–50% of the population in developed countries, but only ~10% present with severe forms. It is also estimated that periodontitis results in worldwide productivity losses amounting to ~54 billion USD yearly. In addition to the damage it causes to oral health, periodontitis also affects other types of disease. Numerous studies have confirmed the association between periodontitis and systemic diseases, such as diabetes, respiratory disease, osteoporosis and cardiovascular disease. Increasing evidence also indicated that periodontitis may participate in the progression of liver diseases, such as non-alcoholic fatty liver disease, cirrhosis and hepatocellular carcinoma, as well as affecting liver transplantation. However, to the best of our knowledge, there are currently no reviews elaborating upon the possible links between periodontitis and liver diseases. Therefore, the current review summarizes the human trials and animal experiments that have been conducted to investigate the correlation between periodontitis and liver diseases. Furthermore, in the present review, certain mechanisms that have been postulated to be responsible for the role of periodontitis in liver diseases (such as bacteria, pro-inflammatory mediators and oxidative stress) are considered. The aim of the review is to introduce the hypothesis that periodontitis may be important in the progression of liver disease, thus providing dentists and physicians with an improved understanding of this issue.

Genetic background in nonalcoholic fatty liver disease: A comprehensive review

In the Western world, nonalcoholic fatty liver disease (NAFLD) is considered as one of the most significant liver diseases of the twenty-first century. Its development is certainly driven by environmental factors, but it is also regulated by genetic background. The role of heritability has been widely demonstrated by several epidemiological, familial, and twin studies and case series, and likely reflects the wide inter-individual and inter-ethnic genetic variability in systemic metabolism and wound healing response processes. Consistent with this idea, genome-wide association studies have clearly identified Patatin-like phosholipase domain-containing 3 gene variant I148M as a major player in the development and progression of NAFLD. More recently, the transmembrane 6 superfamily member 2 E167K variant emerged as a relevant contributor in both NAFLD pathogenesis and cardiovascular outcomes. Furthermore, numerous case-control studies have been performed to elucidate the potential role of candidate genes in the pathogenesis and progression of fatty liver, although findings are sometimes contradictory. Accordingly, we performed a comprehensive literature search and review on the role of genetics in NAFLD. We emphasize the strengths and weaknesses of the available literature and outline the putative role of each genetic variant in influencing susceptibility and/or progression of the disease.

Naturally Occurring Stilbenoid TSG Reverses Non-Alcoholic Fatty Liver Diseases via Gut-Liver Axis

The gut-liver axis is largely involved in the development of non-alcoholic fatty liver disease (NAFLD). We investigated whether 2, 3, 5, 4'-tetrahydroxy-stilbene-2-O-β-D-glucoside (TSG) could reverse NAFLD induced by a high-fat diet (HFD) and whether it did so via the gut-liver axis. Results showed that TSG could reduce the accumulation of FFA and it did so by reducing the expression of L-FABP and FATP4. TSG regulated gut microbiota balanced and increased the protein expression of ZO-1 and occludin, which could improve the function of the intestinal mucosal barrier and reduce serum LPS content by about 25%. TSG reduced TL4 levels by 56% and NF-κB expression by 23% relative to the NAFLD model group. This suggests that prevention of NAFLD by TSG in HFD-fed rats is mediated by modulation of the gut microbiota and TLR4/NF-κB pathway, which may alleviate chronic low-grade inflammation by reducing the exogenous antigen load on the host.

Intestinal expression of the anti-inflammatory interleukin-1 homologue IL-37 in pediatric inflammatory bowel disease

OBJECTIVES

The function of interleukin (IL)-37 has not been resolved. We recently showed that IL-37 suppresses colonic inflammation in mice. To gain more insight into its relevance in human disease, we investigated the expression of IL-37 in the intestine of pediatric patients with chronic inflammatory bowel disease (IBD).

METHODS

Intestinal biopsies were obtained from children with IBD (18 Crohn disease [CD], 14 ulcerative colitis [UC] and 11 controls) during endoscopy and analyzed for IL-37 expression by immunohistochemistry and real-time polymerase chain reaction. Results were correlated with immunostaining for IL-18 and IL-17, messenger RNA (mRNA) levels of pro- and anti-inflammatory cytokines, and clinical parameters.

RESULTS

IL-37 protein was detected in epithelial cells and submucosal lymphoid cells of patients with CD and UC as well as healthy controls. IL-37 protein expression tended to be higher with submucosal lymphoid cell infiltration of patients with CD and UC and correlated with histological severity score of inflammation. IL-18 showed a staining pattern similar to that of IL-37, whereas staining for IL-17 revealed distinct positive cells scattered in the submucosal layer. mRNA expression of IL-8, IL-17, and IL-10 was upregulated in patients with CD and UC. mRNA levels of IL-18 and IL-37 were not significantly elevated compared with controls. Levels of IL-37 and IL-18 mRNA showed a positive correlation in the CD group.

CONCLUSIONS

IL-37 protein is expressed in healthy and diseased bowel tissue. IL-37 and IL-18 show a similar expression pattern and correlate at mRNA levels. Future studies are warranted to delineate the specific contribution of IL-37 to modulate chronic bowel inflammation in humans.

Inflammatory stress increases hepatic CD36 translational efficiency via activation of the mTOR signalling pathway

Inflammatory stress is an independent risk factor for the development of non-alcoholic fatty liver disease (NAFLD). Although CD36 is known to facilitate long-chain fatty acid uptake and contributes to NAFLD progression, the mechanisms that link inflammatory stress to hepatic CD36 expression and steatosis remain unclear. As the mammalian target of rapamycin (mTOR) signalling pathway is involved in CD36 translational activation, this study was undertaken to investigate whether inflammatory stress enhances hepatic CD36 expression via mTOR signalling pathway and the underlying mechanisms. To induce inflammatory stress, we used tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) stimulation of the human hepatoblastoma HepG2 cells in vitro and casein injection in C57BL/6J mice in vivo. The data showed that inflammatory stress increased hepatic CD36 protein levels but had no effect on mRNA expression. A protein degradation assay revealed that CD36 protein stability was not different between HepG2 cells treated with or without TNF-α or IL-6. A polysomal analysis indicated that CD36 translational efficiency was significantly increased by inflammatory stress. Additionally, inflammatory stress enhanced the phosphorylation of mTOR and its downstream translational regulators including p70S6K, 4E-BP1 and eIF4E. Rapamycin, an mTOR-specific inhibitor, reduced the phosphorylation of mTOR signalling pathway and decreased the CD36 translational efficiency and protein level even under inflammatory stress resulting in the alleviation of inflammatory stress-induced hepatic lipid accumulation. This study demonstrates that the activation of the mTOR signalling pathway increases hepatic CD36 translational efficiency, resulting in increased CD36 protein expression under inflammatory stress.

Lack of interleukin-1α in Kupffer cells attenuates liver inflammation and expression of inflammatory cytokines in hypercholesterolaemic mice

BACKGROUND

The role of Kupffer cell interleukin (IL)-1 in non-alcoholic steatohepatitis development remains unclear.

AIMS

To evaluate the role of Kupffer cell IL-1α, IL-1β or IL-1 receptor type-1 (IL-1R1) in steatohepatitis.

METHODS

C57BL/6 mice were irradiated and transplanted with bone marrow-derived cells from WT, IL-1α-/-, IL-1β-/- or IL-1R1-/- mice combined with Kupffer cell ablation with Gadolinium Chloride, and fed atherogenic diet. Plasma and liver triglycerides and cholesterol, serum alanine aminotransferase (ALT), liver histology and expression levels of inflammatory genes were assessed.

RESULTS

The ablation and replacement of Kupffer cells with bone marrow-derived cells was confirmed. The atherogenic diet elevated plasma and liver cholesterol, reduced plasma and liver triglycerides and increased serum ALT levels in all groups. Steatosis and steatohepatitis were induced, but without liver fibrosis. A reduction in the severity of portal inflammation was observed only in mice with Kupffer cell deficiency of IL-1α. Accordingly, liver mRNA levels of inflammatory genes encoding for IL-1α, IL-1β, TNFα, SAA1 and IL-6 were significantly lower in mice with Kupffer cell deficiency of IL-1α compared to WT mice.

CONCLUSION

Selective deficiency of IL-1α in Kupffer cells reduces liver inflammation and expression of inflammatory cytokines, which may implicate Kupffer cell-derived IL-1α in steatohepatitis development.