Skeletal muscle is a tissue that represents 30–40% of total body mass in healthy humans and contains up to 75% of total body proteins. It is thus the largest organ in non-obese subjects. The past few years have seen increasing awareness of the prognostic value of appreciating changes in skeletal muscle compartment in various chronic diseases. Hence, a low muscle mass, a low muscle function and muscle fatty infiltration are linked with poor outcomes in many pathological conditions. In particular, an affluent body of evidence links the severity, the complications and mortality of chronic liver disease (CLD) with skeletal muscle depletion. Yet it is still not clear whether low muscle mass is a cause, an aggravating factor, a consequence of the ongoing disease, or an epiphenomenon reflecting general alteration in the critically ill patient. The mechanisms by which the muscle compartment influences disease prognosis are still largely unknown. In addition, whether muscle alterations contribute to liver disease progression is an unanswered question. Here, we first review basic knowledge about muscle compartment to draw a conceptual framework for interpreting skeletal muscle alteration in CLD. We next describe recent literature on muscle wasting in cirrhosis and liver transplantation. We then discuss the implication of skeletal muscle compartment in non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH), focusing on plausible metabolic disruption in muscle compartment that might participate in NAFLD progression. Finally, we discuss shortcomings and challenges we need to address in the near future prior to designate the muscle compartment as a therapeutic target in CLD.

Alcohol dependence and alcoholic liver disease represent a major public health problem with substantial morbidity and mortality. By yet incompletely understood mechanisms, chronic alcohol abuse is associated with increased intestinal permeability and alterations of the gut microbiota composition, allowing bacterial components, bacteria, and metabolites to reach the portal and the systemic circulation. These gut-derived bacterial products are recognized by immune cells circulating in the blood or residing in remote organs such as the liver leading to the release of pro-inflammatory cytokines which are considered important mediators of the liver–gut–brain communication. Although circulating cytokines are likely not the sole factors involved, they can induce liver inflammation/damage and reach the central nervous system where they favor neuroinflammation which is associated with change in mood, cognition, and drinking behavior. In this review, the authors focus on the current evidence describing the changes that occur in the intestinal microbiota with chronic alcohol consumption in conjunction with intestinal barrier breakdown and inflammatory changes sustaining the concept of a gut–liver–brain axis in the pathophysiology of alcohol dependence and alcoholic liver disease.

Owing to the major limitations of current antiviral therapies in HBV (hepatitis B virus) infection, there is a strong need for novel therapeutic approaches to this major health burden. Stimulation of the host's innate and adaptive immune responses in a way that results in the resolution of viral infection is a promising approach. A better understanding of the virus–host interaction in acute and chronic HBV infection revealed several possible novel targets for antiviral immunotherapy. In the present review, we will discuss the current state of the art in HBV immunology and illustrate how control of infection could be achieved by immunotherapeutic interventions.

Complement, an important effector mechanism of the immune system, is an enzymatic cascade of approx. 30 serum proteins leading to the amplification of a specific humoral response. It can be activated through the classical or alternative pathways, or through the mannose-binding lectin pathway. The activation of the classical pathway is initiated by the binding of the C1 component to antigen-bound antibodies, known as immunocomplexes. C1 is a complex of one molecule of C1q, two molecules of C1r and two molecules of C1s. C1q contains three copies of a Y-shaped fundamental unit with globular heads included in its structure, which play a major role in the interaction with the Fc portion of immunoglobulins. Deficient or exacerbated activation of the complement system leads to diseases of variable severity, and pharmacological inhibition of the complement system is considered as a therapeutic strategy to ameliorate the inflammatory effects of exacerbated complement activation. Bilirubin is a product of haem degradation by the concerted action of haem oxygenase, which converts haem into biliverdin, and biliverdin reductase, which reduces biliverdin to UCB (unconjugated bilirubin). UCB exerts both cytoprotective and cytotoxic effects in a variety of tissues and cells, acting either as an antioxidant at low concentrations or as an oxidant at high concentrations. In the present review, we describe in detail the anti-complement properties of bilirubin, occurring at levels above the UCB concentrations found in normal human serum, as a beneficial effect of potential clinical relevance. We provide evidence that UCB interferes with the interaction between C1q and immunoglobulins, thus inhibiting the initial step in the activation of complement through the classical pathway. A molecular model is proposed for the interaction between UCB and C1q.

HCV (hepatitis C virus) infects nearly 3% of the population worldwide and has emerged as a major causative agent of liver disease, resulting in acute and chronic infections that can lead to fibrosis, cirrhosis and hepatocellular carcinoma. Hepatitis C represents the leading cause of liver transplantation in the United States and Europe. A positive-strand RNA virus of the Flaviviridae family, HCV contains a single-stranded RNA genome of approx. 9600 nucleotides. The genome RNA serves as both mRNA for translation of viral proteins and the template for RNA replication. Cis -acting RNA elements within the genome regulate RNA replication by forming secondary structures that interact with each other and trans -acting factors. Although structural proteins are clearly dispensable for RNA replication, recent evidence points to an important role of several non-structural proteins in particle assembly and release, turning their designation on its head. HCV enters host cells through receptor-mediated endocytosis, and the process requires the co-ordination of multiple cellular receptors and co-receptors. RNA replication takes place at specialized intracellular membrane structures called ‘membranous webs’ or ‘membrane-associated foci’, whereas viral assembly probably occurs on lipid droplets and endoplasmic reticulum. Liver inflammation plays a central role in the liver damage seen in hepatitis C, but many HCV proteins also directly contribute to HCV pathogenesis. In the present review, the molecular and cellular aspects of the HCV life cycle and the role of viral proteins in pathological liver conditions caused by HCV infection are described.

The recent overwhelming advances in molecular and cell biology have added enormously to our understanding of the physiological processes involved in bile formation and, by extension, to our comprehension of the consequences of their alteration in cholestatic hepatopathies. The present review addresses in detail this new information by summarizing a number of recent experimental findings on the structural, functional and regulatory aspects of hepatocellular transporter function in acquired cholestasis. This comprises (i) a short overview of the physiological mechanisms of bile secretion, including the nature of the transporters involved and their role in bile formation; (ii) the changes induced by nuclear receptors and hepatocyte-enriched transcription factors in the constitutive expression of hepatocellular transporters in cholestasis, either explaining the primary biliary failure or resulting from a secondary adaptive response; (iii) the post-transcriptional changes in transporter function and localization in cholestasis, including a description of the subcellular structures putatively engaged in the endocytic internalization of canalicular transporters and the involvement of signalling cascades in this effect; and (iv) a discussion on how this new information has contributed to the understanding of the mechanism by which anticholestatic agents exert their beneficial effects, or the manner in which it has helped the design of new successful therapeutic approaches to cholestatic liver diseases.

The innate immune system represents a critical first line of host response to infectious, injurious and inflammatory insults. NKT cells (natural killer T-cells) are an important, but relatively poorly understood, component of the innate immune response. Moreover, NKT cells are enriched within the liver, suggesting that within the hepatic compartment NKT cells probably fulfil important roles in the modulation of the immune response to infection or injury. NKT cells are characterized by their rapid activation and secretion of large amounts of numerous types of cytokines, including those within the Th1-type, Th2-type and Th17-type groups, which in turn can interact with a multitude of other cell types within the liver. In addition, NKT cells are capable of participating in a wide array of effector functions with regards to other cell types via NKT cell-surface-molecule expression [e.g. FASL (FAS ligand) and CD40L (CD40 ligand)] and the release of mediators (e.g. perforin and granzyme) contained in cellular granules, which in turn can activate or destroy other cells (i.e. immune or parenchymal cells) within the liver. Given the huge scope of potential actions that can be mediated by NKT cells, it has become increasingly apparent that NKT cells may fulfil both beneficial (e.g. clearance of virally infected cells) and harmful (e.g. induction of autoimmunity) roles in the setting of liver disease. This review will outline the possible roles which may be played by NKT cells in the setting of specific liver diseases or conditions, and will discuss the NKT cell in the context of its role as either a ‘friend’ or a ‘foe’ with respect to the outcome of these liver disorders.

1. S -Adenosyl- l -methionine is reported to improve serum liver function tests in chronic liver disease. Because liver disease is complicated by cholesterol deposition in hepatic and extrahepatic membranes, we have assessed whether oral administration of S -adenosyl- l -methionine to patients with hepatic disease can reverse the cholesterol enrichment of their erythrocytes. 2. The mean erythrocyte cholesterol-to-phospholipid molar ratio in 13 jaundiced patients was reduced 2 weeks after oral administration of S -adenosyl- l -methionine (from 0.874 ± 0.112 to 0.844 ± 0.102, P <0.05) with 10 of the patients (77%) showing a decrease. By contrast, only four of 11 untreated patients (36%) had a reduced erythrocyte cholesterol-to-phospholipid molar ratio after 2 weeks and the mean values did not differ. 3. The plasma and erythrocyte cholesterol-to-phospholipid molar ratios remained closely correlated ( r = 0.77, P <0.01) before and after treatment, suggesting that S -adenosyl- l -methionine had not acted directly on the cells but rather had improved their lipoprotein milieu. Further support for this concept was provided by following one patient, who initially failed to respond, during an additional 3 weeks of S -adenosyl- l -methionine administration. The plasma cholesterol-to-phospholipid molar ratio fell steadily from week 1 to week 5 and was accompanied by a progressive decrease in the erythrocyte cholesterol-to-phospholipid molar ratio. Moreover, the initially suppressed acetylcholinesterase activity of the erythrocyte membranes returned towards normal during this period. 4. This preliminary study is the first evidence in jaundiced patients that a drug can help to reverse the deposition of cholesterol in an extrahepatic membrane. It merits, therefore, placebo-controlled, crossover investigations into the therapeutic potential of S -adenosyl- l -methionine in chronic liver disease.

1. Using crossed immunoaffinity electrophoresis with free concanavalin A in the first dimension, we studied the microheterogeneity of α 1 -antichymotrypsin due to various glycoforms in sera from patients with various liver diseases and after liver transplantation. 2. Studies by isoelectric focusing and immunoblotting and by crossed immunoelectrophoresis without concanavalin A in the first dimension allowed us to show that there is no dramatic variation in electrophoretic heterogeneity of α 1 -antichymotrypsin in the serum of patients with liver diseases or after liver transplantation when compared with that of normal subjects. Therefore the heterogeneity observed in crossed immunoaffinity electrophoresis is due to various interactions with concanavalin A. 3. The results were expressed as the ratio of concanavalin A non-reactive glycoforms plus concanavalin A weakly reactive glycoforms to concanavalin A reactive glycoforms, called R α 1 -ACT. R α 1 -ACT was significantly higher in patients with cirrhosis ( n = 53) when compared with normal subjects ( n = 30). The median R α 1 -ACT was 1 (range 0.72–1.25) in normal subjects. It was 1.6 (range 1.18–3.02), 1.45 (range 0.65–4.12) and 2.24 (range 1.03–19) in cirrhosis of Child's grade A, B and C, respectively. There was a dramatic decrease in glycoforms with mostly biantennary glycans in some patients with Child's grade C cirrhosis. Serum levels of α 1 -antichymotrypsin were lower than normal only in some patients with Child's grade C cirrhosis. 4. Among the patients with acute viral hepatitis studied ( n =17), five were studied longitudinally. R α 1 -ACT increased after the peak level of serum transaminases and remained high while the level of serum transaminases decreased and liver regeneration occurred. In these patients there was no alteration in glycoforms with mostly biantennary glycans. 5. Four patients were studied after liver transplantation. During the first days after transplantation R α 1 -ACT was low because of an increase in glycoforms with mostly biantennary glycans. After the first week, R α 1 -ACT rose above the normal range because of an increase in glycoforms with pluriantennary glycans and it returned to normal within 3 post-operative weeks. R α 1 -ACT remained high in a patient who presented with liver rejection. 6. The present study suggests that R α 1 -ACT is a helpful additional marker for the evaluation of hepatocyte function.

1. The validity of a two-compartment pharmacokinetic model for the estimation of the hepatic extraction ratio of Indocyanine Green was tested in six patients with cirrhosis of the liver. 2. No agreement was found between the value of the hepatic extraction ratio measured directly and that calculated using the two-compartment model. 3. To investigate the reasons for the failure of the model, an extended sampling period was used to define the time course of Indocyanine Green in plasma in six healthy subjects and in six patients with cirrhosis of the liver after a bolus injection of the dye. 4. Indocyanine Green was measurable in the plasma for up to 10 h after injection in healthy subjects, and up to 48 h after injection in the patients. The plasma elimination curve in both groups was best described by a triexponential function. 5. The clearance of Indocyanine Green calculated using data collected in the first 20 min after injection overestimated that calculated using data collected for as long as Indocyanine Green was measurable in the plasma. In the patients with cirrhosis the mean overestimate was 87%. 6. Thus, a two-compartment pharmacokinetic model was inappropriate for the description of the disposition of Indocyanine Green and estimates of the hepatic extraction ratio obtained using this model in patients with cirrhosis were inaccurate.

1. The clearance and biotransformation of caffeine (1,3,7-trimethylxanthine) were investigated in eight healthy control subjects and 16 patients with cirrhosis, by measuring serial serum caffeine concentrations and recoveries of methylxanthine metabolites in urine for 48 h after a 400 mg oral caffeine load. 2. In the control group, the mean (± sd ) serum caffeine clearance was 1.3 ± 0.4 ml min −1 kg −1 and a mean of 56.4 ± 16.5% of the administered caffeine was recovered from the urine over 48 h as methyluric acids and methylxanthines. The majority of the metabolites were excreted in the first 24 h period and only 2.0 ± 1.4% of the administered caffeine was excreted unchanged. 3. Patients with compensated cirrhosis ( n = 10) metabolized caffeine similarly to the control subjects. Thus the mean serum caffeine clearance was 1.4 ± 1.2 ml min −1 kg −1 and a mean of 57.2 ± 11.7% of the administered caffeine was recovered from the urine over 48 h. The majority of the metabolites were excreted in the first 24 h; the pattern of metabolic excretion was unaltered and only 2.2 ± 0.9% of the administered caffeine was excreted unchanged. 4. In the patients with decompensated cirrhosis ( n = 6), significant changes were observed in caffeine metabolism. The mean serum caffeine clearance (0.4 ± 0.2 ml min −1 kg −1 ) was significantly impaired compared with controls ( P < 0.01) and a significant delay was observed in metabolite excretion in the urine. Thus the mean recovery of metabolites in the urine during the first 24 h (25.0 ± 11.2%) was significantly reduced compared with controls (44.1 ± 12.4%, P = 0.03), whereas the mean urinary metabolite recovery in the second 24 h (20.9 ± 10.5%) was insignificantly increased compared with controls (12.3 ± 7.8%). Overall, the mean recovery of metabolites in the urine in 48 h (45.9 ± 15.4%) was similar to that in the control group. The overall recovery of unchanged caffeine was significantly greater than in controls (5.0 ± 2.8% vs 2.0 ± 1.4%, P = 0.04), but the pattern of metabolite excretion was otherwise unchanged. 5. In the patients with liver disease there were significant linear correlations between the degree of hepatocellular dysfunction and the serum caffeine elimination half-life ( r = 0.774; P < 0.01) and the total recovery of methylxanthine metabolites in the urine, in the 0–24 h ( r = 0.702; P = 0.002) and 0–48 h ( r = 0.581; P = 0.018) periods. 6. Caffeine clearance is impaired in patients with decompensated cirrhosis either because of a reduction in hepatic caffeine uptake or else because of a reduction in ‘functioning hepatocyte mass’. However, the biotransformation of caffeine is unaltered in the presence of hepatic dysfunction.

1. Gas–liquid chromatography and a radioreceptor assay were used to measure plasma γ-aminobutyric acid (GABA) in patients with liver disease and hepatic encephalopathy. 2. There was a significant correlation between the results obtained by the two methods, and compared with controls plasma GABA was elevated. 3. These findings suggest that the increased GABA binding inhibitory activity of plasma of these patients is probably due to GABA itself.

1. The concentration in plasma of fibrinogen derivatives fibrinopeptide A (FPA) and Bβ1-42 and the platelet release products β-thromboglobulin (βTG) and platelet factor 4 (PF4) have been determined in patients with acute and chronic liver disease. 2. In 21 patients with fulminant hepatic failure on admission in grade III or IV coma the plasma FPA, Bβ1-42, βTG and PF4 levels were significantly increased compared with those in normal control subjects. On heparinization before haemoperfusion the FPA levels returned to the normal range and during resin and charcoal haemoperfusion there were no significant changes in the coagulation or platelet factors, except for a small increase in FPA with charcoal haemoperfusion. 3. In ten patients with compensated chronic liver disease there was a significant increase in Bβ1-42 and βTG levels but not FPA and PF4 as compared with normal controls. 4. Interpretation of the results is complicated by the possible reduced clearance of these proteins as a result of renal failure in some of the patients with fulminant hepatic failure and also by the damaged liver itself. However, these results have confirmed that disseminated intravascular coagulation can occur in both acute and chronic liver disease.

1. The serum bile acid disappearances of tracer doses of [24- 14 C]cholic acid and [1- 14 C]-glycocholic acid were studied in eight normal subjects and 11 patients with chronic liver disease (with or without cholestasis) in order to determine the effect of liver disease on hepatic clearances, reflux of conjugated cholic acid and initial distribution volume of each tracer. 2. Total cholic acid clearance was significantly reduced from normal (7·2 ± 0·7 ml min −1 kg −1 , mean ± se) in patients with liver disease (69–88%, group means) as were unconjugated cholic acid (51–68%) and glycocholic acid (66–83%) clearance. 3. Extensive regurgitation of labelled conjugated cholic acid (after unconjugated cholic acid tracer injection) among cholestatic patients accounted for 69 ± 5% of total 14 C remaining in serum at 70 min, thus masking a less-impaired uptake process. 4. The hepatic extraction efficiency for conjugated cholic acid among controls (86 ± 8%) was greater than that for unconjugated cholic acid (60 ± 4%), and was greatly reduced among patients (7–27%, group means). 5. Normal subjects and patients with cirrhosis without cholestasis did not distribute the isotope to extravascular, extrahepatic spaces, in contrast to cholestatic patients with serum bile acid concentration > 149μmol/l. 6. Careful evaluation of serum disappearance of bile acids as well as chromatographic separation of regurgitated metabolites, could provide investigators with indirect evidence of defects in the rate-limiting steps (uptake, conjugation or excretion) of hepatic bile acid transport.

1. Liver biopsies from two patients with the Dubin—Johnson—Sprinz syndrome were subjected to analytical subcellular fractionation by sucrose-density-gradient centrifugation and enzymic micro-assays. 2. A selective deficiency of mitochondrial superoxide dismutase has been demonstrated in these patients. 3. The significance of this enzyme deficiency is discussed in relation to the organelle pathology of the syndrome.

1. Six unanaesthetized goats were used to evaluate the effect of liver failure on the hypoxic responsiveness of cerebral blood flow. The animals breathed air and several different hypoxic gas mixtures enriched with sufficient CO 2 to maintain an isocapnic state. The cerebral metabolic rate for O 2 (CMRo 2 ) was also measured in four of these goats. 2. In baseline studies there was a linear relationship between cerebral blood flow and arterial O 2 saturation ( S a,o 2 ) measured at different levels of isocapnic hypoxia. The slopes of the cerebral blood flow/ S a,o 2 response lines were used to quantify the response of cerebral blood flow to hypoxia. In the healthy goat, CMRo 2 was not depressed by hypoxia until the O 2 tension ( P o 2 ) in arterial and cerebral venous blood had fallen below critical threshold values of approximately 3·2 and 2·2 kPa (24 and 16 mmHg) respectively. 3. Liver failure was accompanied by a fall in cerebral blood flow and CMRo 2 . There was also a depression in the response of cerebral blood flow to hypoxia and a disproportionate reduction of cerebral O 2 delivery in hypoxia. CMRo 2 was further reduced at arterial and cerebral venous P o 2 values, which were much higher than the critical threshold values for producing hypoxic CMRo 2 depression in health. 4. It is concluded that the brain becomes more vulnerable to the adverse effects of hypoxia during liver failure. This may be of practical importance in the management of patients with arterial hypoxaemia or other complications (e.g. anaemia or shock), which may reduce cerebral oxygen delivery.

1. The ventilatory responses to transient and steady-state hypoxia were measured in ten patients with hepatic cirrhosis and in ten healthy control subjects. Successive measurements of these responses were also obtained in six goats before and after the experimental production of liver failure. Changes in the effect of steady-state hypoxia on the ventilatory response to hypercapnia were evaluated by successive studies in another goat. 2. In spite of a respiratory alkalosis during liver failure, the response to transient hypoxia was greater in the patients than in the control subjects. This response was increased after the onset of liver failure in all the goats. 3. In healthy humans and goats the responses to transient and steady-state hypoxia were similar in magnitude. During liver failure there was a disparity between the size of these responses, since the ventilatory increment evoked by steady-state hypoxia was unchanged in spite of the increase in response to transient hypoxia. Steady-state hypoxia consistently enhanced the ventilatory response to hypercapnia in a healthy goat, but frequently depressed the response to hypercapnia during liver failure. 4. The findings suggest that liver failure heightens the sensitivity of the peripheral chemoreceptors to the hypoxic stimulus, but may increase the tendency of the medullary centres to become depressed in hypoxia.

1. Hepatic alcohol dehydrogenase activity and leucocyte ascorbic acid content were measured in thirty-five patients with liver disease and in ten control subjects with duodenal ulcer. The patients with liver disease were divided into three groups consisting of non-drinkers, moderate drinkers and alcoholic/heavy drinkers. 2. There was no significant difference in hepatic alcohol dehydrogenase activity between the groups with liver disease, but all patients had less than half the hepatic alcohol dehydrogenase activity of the control subjects ( P < 0·001). 3. The ascorbic acid in leucocytes was significantly lower in the alcoholic/heavy drinker group than that in the control subjects ( P < 0·02) when the Student's t -test was applied, but no significant difference was found when the Mann—Whitney U -test was used. 4. A correlation coefficient of r = 0·77 ( P < 0·001) was observed among the thirty-five patients with liver disease when hepatic alcohol dehydrogenase activity was compared with leucocyte ascorbic acid content. An insignificant correlation ( r = 0·332) was found in the control subjects with no liver disease. 5. This comparison was also significant among non-drinkers with liver disease ( r = 0·873; P < 0001), moderate drinkers ( r = 0·739; P < 0·02) and alcoholic/heavy drinkers ( r = 0·702; P < 0·005). 6. The addition of ascorbic acid in vitro (0·5–10 mmol/l) had no effect on the activity of alcohol dehydrogenase. 7. The relation between hepatic alcohol dehydrogenase activity and leucocyte ascorbic acid content is probably a consequence of liver disease, as opposed to any specific effect of ascorbic acid deficiency or alcohol consumption on alcohol dehydrogenase activity.

1. Somatomedin (SM; sulphation factor) activity was estimated by a chick-cartilage assay in fasting sera from twenty-one patients with chronic liver disease. 2. Low SM values were found in nine out of the ten patients with cirrhosis and in two other patients, one with hepatofibrosis and one with hepatoma. 3. In general, the lowest serum SM activities were found in those patients with the most severe disease and significant correlations were found between serum SM and serum albumin, alkaline phosphatase and bilirubin. 4. Growth hormone was also measured in the samples and concentrations above 10 units/ml were found in seven patients, all of whom had reduced serum SM activities. 5. These findings indicate that low serum SM activity in liver disease is not related to growth hormone deficiency and suggest that the liver may be an important site for SM synthesis in man.