Pathogenesis of precirrhotic portal hypertension in alcohol-fed baboons

Portal Hypertension in Nonalcoholic Fatty Liver Disease: Challenges and Paradigms

Portal hypertension in cirrhosis is defined as an increase in the portal pressure gradient (PPG) between the portal and hepatic veins and is traditionally estimated by the hepatic venous pressure gradient (HVPG), which is the difference in pressure between the free-floating and wedged positions of a balloon catheter in the hepatic vein. By convention, HVPG≥10 mmHg indicates clinically significant portal hypertension, which is associated with adverse clinical outcomes. Nonalcoholic fatty liver disease (NAFLD) is a common disorder with a heterogeneous clinical course, which includes the development of portal hypertension. There is increasing evidence that portal hypertension in NAFLD deserves special considerations. First, elevated PPG often precedes fibrosis in NAFLD, suggesting a bidirectional relationship between these pathological processes. Second, HVPG underestimates PPG in NAFLD, suggesting that portal hypertension is more prevalent in this condition than currently believed. Third, cellular mechanoresponses generated early in the pathogenesis of NAFLD provide a mechanistic explanation for the pressure-fibrosis paradigm. Finally, a better understanding of liver mechanobiology in NAFLD may aid in the development of novel pharmaceutical targets for prevention and management of this disease.

Portal Hypertension in Alcohol-Associated Hepatitis

Purpose of Review

This review article will examine portal hypertension in alcoholic hepatitis (AH) from both a basic mechanistic and a clinical perspective.

Recent Findings

Alcoholic hepatitis is a major public health problem in the USA, accounting for over 300,000 hospital admissions in a recent year of data (Jinjuvadia et al. J Clin Gastroenterol. 60;49:506–511). Portal hypertension is a key consequence of AH and a driver of liver-related morbidity and mortality. Alcohol may directly mediate portal hypertension via multiple possible mechanisms, including increased portal inflow, increased intrahepatic vasoconstriction, inflammation, and changes in the liver vasculature such as perisinusoidal fibrosis and phlebosclerosis.

Summary

Portal hypertension is a key consequence of AH and a critical area for future research.

Microcirculatory changes in the liver of patients with refractory ascites and their relationship with diabetes and alcohol

OBJECTIVES

The determinants of refractory ascites have not been fully characterized. The aims of this study were to assess liver histopathological alterations associated with refractory ascites and their relationship with comorbidities.

METHODS

Consecutive patients with cirrhosis who underwent liver transplantation were retrospectively included. Patients' characteristics at the time of listing were analysed. The native livers were reviewed and lesions associated with refractory ascites were examined.

RESULTS

Out of the 89 patients included, 30 had refractory ascites and 59 did not (including 35 without ascites and 24 with diuretic-sensitive ascites). Patients with and without refractory ascites had a similar amount of fibrous tissue and features of fatty liver disease. By contrast, microvascular changes, namely sinusoidal dilatation (P < 0.001), diffuse perisinusoidal fibrosis (P = 0.001), hepatic venous thromboses (P = 0.004) and vascular proliferation (P = 0.01) were more frequently observed in the livers of patients with refractory ascites. Diabetes (57% vs. 31%, P = 0.02) and alcohol as a causal factor for cirrhosis (80% vs. 42%, P = 0.001) were more frequent in patients with refractory ascites than in those without. By multivariate analysis, refractory ascites was independently associated with diabetes mellitus [odds ratio (OR) (95% confidence interval, CI) 6.15 (1.47-25.71); P = 0.01], alcohol as a causal factor for cirrhosis [OR (95% CI) 4.63 (1.07-20.02); P = 0.04], higher Model For End Stage Liver Diseases [OR (95% CI) 1.21 (1.05-1.38); P = 0.008] and lower serum sodium [OR (95% CI) 0.87 (0.78-0.98); P = 0.03].

CONCLUSION

Liver microcirculatory changes are associated with refractory ascites. Diabetes and alcohol may explain refractory ascites by causing microangiopathy.

Patients With Signs of Advanced Liver Disease and Clinically Significant Portal Hypertension Do Not Necessarily Have Cirrhosis

BACKGROUND & AIMS

Patients with hepatic venous pressure gradients (HVPGs) of 10 mm Hg or greater and chronic liver disease often are assumed to have cirrhosis. We investigated the association between HVPGs and cirrhosis, using histologic findings as the reference standard. We also assessed the prevalence and characteristics of patients with HVPGs of 10 mm Hg or greater without cirrhosis.

METHODS

We performed a retrospective analysis of 157 consecutive patients, 89 with suspected cirrhosis and hepatic hemodynamic data collected from 2015 through 2017. Biopsy specimens collected had 10 or more portal tracts from each patient and were analyzed for features of cirrhosis. Biopsy specimens with histologic features of cirrhosis were excluded and the remaining biopsy specimens were re-reviewed by an expert pathologist. The fibrosis area was calculated digitally by image analysis.

RESULTS

HVPG identified patients with cirrhosis with an area under the receiver operating characteristic curve of 0.879: 14 of 89 patients with HVPG of 10 mm Hg or greater (16%) had no histologic features of cirrhosis (METAVIR scores <4 and Ishak scores <6). The median HVPG was 11 mm Hg (range, 10-22 mm Hg). Based on METAVIR scores, 7 patients had fibrosis stage F3, 4 patients had fibrosis stage F2, and 3 patients had fibrosis stages F0 or F1. The mean area of fibrosis in livers was 16.2% ± 6.5%. All 14 patients had perisinusoidal fibrosis and 8 patients had hepatocyte ballooning. The most common diagnoses were nonalcoholic steatohepatitis (n = 5) and nodular regenerative hyperplasia (n = 4). An HVPG cut-off value of 12 mm Hg identified patients with cirrhosis with 92% specificity, misclassifying 5 patients with different etiologies of liver disease.

CONCLUSIONS

In a retrospective analysis of 89 consecutive patients with chronic liver disease and an HVPG of 10 mm Hg or greater, 16% were not found to have cirrhosis upon biopsy analysis. Most of these patients had nonalcoholic steatohepatitis or nodular regenerative hyperplasia. Perisinusoidal fibrosis and hepatocyte ballooning might increase sinusoidal pressure. An HVPG cut-off value of 12 mm Hg or greater identified patients with cirrhosis with 92% specificity.

Insulin Production and Resistance in Different Models of Diet-Induced Obesity and Metabolic Syndrome

The role of the liver and the endocrine pancreas in development of hyperinsulinemia in different types of obesity remains unclear. Sedentary rats (160 g) were fed a low-fat-diet (LFD, chow 13% kcal fat), high-fat-diet (HFD, 35% fat), or HFD+ 30% ethanol+ 30% fructose (HF-EFr, 22% fat). Overnight-fasted rats were culled after one, four or eight weeks. Pancreatic and hepatic mRNAs were isolated for subsequent RT-PCR analysis. After eight weeks, body weights increased three-fold in the LFD group, 2.8-fold in the HFD group, and 2.4-fold in the HF-EFr (p < 0.01). HF-EFr-fed rats had the greatest liver weights and consumed less food during Weeks 4–8 (p < 0.05). Hepatic-triglyceride content increased progressively in all groups. At Week 8, HOMA-IR values, fasting serum glucose, C-peptide, and triglycerides levels were significantly increased in LFD-fed rats compared to that at earlier time points. The greatest plasma levels of glucose, triglycerides and leptin were observed in the HF-EFr at Week 8. Gene expression of pancreatic-insulin was significantly greater in the HFD and HF-EFr groups versus the LFD. Nevertheless, insulin: C-peptide ratios and HOMA-IR values were substantially higher in HF-EFr. Hepatic gene-expression of insulin-receptor-substrate-1/2 was downregulated in the HF-EFr. The expression of phospho-ERK-1/2 and inflammatory-mediators were greatest in the HF-EFr-fed rats. Chronic intake of both LFD and HFD induced obesity, MetS, and intrahepatic-fat accumulation. The hyperinsulinemia is the strongest in rats with the lowest body weights, but having the highest liver weights. This accompanies the strongest increase of pancreatic insulin production and the maximal decrease of hepatic insulin signaling, which is possibly secondary to hepatic fat deposition, inflammation and other factors.

Development of risky varices in alcoholic cirrhosis with a well-maintained nutritional status

AIM: To compare the nutritional status between alcoholic compensated cirrhotic patients and hepatitis C virus (HCV)-related cirrhotic patients with portal hypertension.

METHODS: A total of 21 patients with compensated cirrhosis (14 with HCV-related cirrhosis and seven with alcoholic cirrhosis) who had risky esophageal varices were investigated. In addition to physical variables, including the body mass index, triceps skinfold thickness, and arm-muscle circumference, the nutritional status was also assessed using the levels of pre-albumin (pre-ALB), retinol-binding protein (RBP) and non-protein respiratory quotient (NPRQ) measured with an indirect calorimeter.

RESULTS: A general assessment for the nutritional status with physical examinations did not show a significant difference between HCV-related cirrhosis and alcoholic cirrhosis. However, the levels of pre-ALB and RBP in alcoholic compensated cirrhotic patients were significantly higher than those in HCV-related compensated cirrhotic patients. In addition, the frequency of having a normal nutritional status (NPRQ ≥ 0.85 and ALB value > 3.5 g/dL) in alcoholic compensated cirrhotic patients was significantly higher than that in HCV-related compensated cirrhotic patients.

CONCLUSION: According to our small scale study, alcoholic compensated cirrhotic patients can develop severe portal hypertension even with a relatively well-maintained liver function and nutritional status compared with HCV-related cirrhosis.

Measurement of spleen volume is useful for distinguishing between simple steatosis and early-stage non-alcoholic steatohepatitis

AIM

Although non-alcoholic fatty liver disease (NAFLD) is now a common cause of chronic liver disease, discriminating between simple steatosis and non-alcoholic steatohepatitis (NASH), especially early-stage NASH, remains difficult. We investigated the clinical usefulness of measuring the spleen volume as a marker of early-stage NASH.

METHODS

We evaluated computed tomography (CT) images obtained in 84 patients with histologically diagnosed NAFLD (22 with simple steatosis, 62 with NASH with mild fibrosis [stages 1-2]). We defined the data obtained by the following formula as a spleen-body index (SBI): SBI = maximal CT axial section area of the spleen (cm(2))/body surface area (BSA) (cm(2)) x 10(4). We compared the SBI between patients with simple steatosis and those with NASH with mild fibrosis.

RESULTS

The mean SBI of the simple steatosis group was 15.8 +/- 3.9, while that of the NASH with mild fibrosis group was 18.7 +/- 5.7. This difference between the two groups was significant (P = 0.0314). A multiple logistic regression analysis showed that the SBI was significantly correlated with the discrimination of simple steatosis and NASH with mild fibrosis. The area under the receiver-operator curve was 0.661 for distinguishing between simple steatosis and NASH with mild fibrosis (P = 0.026, 95% confidence interval = 0.532-0.789).

CONCLUSION

Spleen enlargement may be a distinct feature of NASH, especially early-stage NASH. SBI might be a non-invasive and simple method of differentiating NASH and simple steatosis.

Comparison of liver hemodynamics according to doppler ultrasonography in alcoholic patients subtyped by Cloninger classification and non-alcoholic healthy subjects

BACKGROUND

The aim of this study was to search for morphological and hemodynamic changes in hepatic and splanchnic vasculature in alcoholic patients without the signs of hepatic damage and subtyped by Cloninger classification by means of sonography, and compare the subtypes among themselves and with nonalcoholic healthy subjects.

METHODS

Thirty alcohol dependent patients and 30 healthy subjects with no alcohol problem or hepatic impairment were included in the study. Patients were subtyped by Cloninger classification and all patients were evaluated by gray-scale and spectral Doppler ultrasound. The diameter of the portal vein, portal venous velocity, peak systolic and end diastolic velocities of hepatic and superior mesenteric arteries were assessed. RI, PI and systolic/diastolic velocity ratios were also calculated.

RESULTS

Portal vein diameter (PV diameter), portal vein cross sectional area (PV area), portal vein velocity (PV PSV), hepatic artery peak systolic velocity (HA PSV), hepatic artery end diastolic velocity (HA EDV), hepatic artery resistive index (HA RI), hepatic artery pulsatility index (HA PI), and systolic/diastolic velocity ratios (HA S/D), superior mesenteric artery peak systolic velocity (SMA PSV), superior mesenteric artery end diastolic velocity (SMA EDV), superior mesenteric artery resistive indices (SMA RI), pulsatility index (SMA PI), and systolic/diastolic velocity rates (SMA S/D) showed no significant difference among the groups (P > 0.01). Although there is no significant difference in PV PSV, HA PSV, SMA PSV, SMA EDV values between the groups, mean values of Type II alcoholics is greater than other groups. Portal vein cross-sectional area was greater in alcoholic patients (Type I, II and III) compared to the control group (P = 0.000). Portal vein velocity, hepatic artery peak systolic and end diastolic velocity, superior mesenteric artery peak systolic and end diastolic velocity were significantly greater in alcoholic patients than in the control group (P < 0.001). No statistical difference was detected between other parameters evaluated.

CONCLUSION

In alcohol dependent patients, some hemodynamic and morphologic changes occur in hepatic and splanchnic circulation, even before the signs of hepatic damage develop, which can be detected by means of Doppler and gray-scale sonography. But as there is no significant difference between the Doppler ultrasonographic findings among alcoholics subtyped by a Cloninger classification, which is a clinical classification, it suggests that psychiatric classification doesn't show any correlation with biological parameters, and because of this Cloninger classification a psychiatric classification cannot be considered as a characteristic determinative factor in the prognosis of hepatic disorder due to alcohol use. However, higher values of Type II alcoholics can be attributed to the longer alcohol intake of this subtype.

Doppler and gray-scale ultrasound evaluation of morphological and hemodynamic changes in liver vascualture in alcoholic patients

OBJECTIVE

The aim of this study is to search sonographically for morphological and hemodynamic changes in hepatic and splanchnic vasculature of alcoholic patients having no signs of hepatic damage, and compare these with normal healthy subjects.

METHODS

Thirty alcohol-dependent patients and 30 control subjects with no alcohol problem or hepatic impairment were included in the study. All patients were evaluated by gray-scale and spectral Doppler ultrasound. The diameter of the portal vein, portal venous velocity, peak systolic and end diastolic velocities of hepatic and superior mesenteric arteries were assessed. RI, PI and systolic/diastolic velocity ratios were also calculated.

RESULTS

Portal vein cross-sectional area was greater in alcoholic patients compared to control group (P = 0.0012). Portal vein velocity, hepatic artery peak systolic and end diastolic velocity, superior mesenteric artery peak systolic and end diastolic velocity were significantly greater in alcoholic patients than in control group (P < or = 0.001). No statistically significant difference was detected between other parameters evaluated.

CONCLUSION

In alcohol-dependent patients, some hemodynamic and morphologic changes occur in hepatic and splanchnic circulation, even before the signs of hepatic damage develop. These changes can be detected by means of Doppler and gray-scale sonogrsphy.

Hepatic sinusoidal pseudocapillarization with aging in the non-human primate

BACKGROUND/AIMS

Age-related changes in the hepatic sinusoid termed pseudocapillarization have been reported in the rat and human and have implications for disease susceptibility in old age. In this study, we investigated whether similar changes occur in the livers of old baboons and thus represent a widespread aging change.

METHODS

Liver tissue from five young baboons (5.4+/-0.5yrs) and five old baboons (21.8+/-0.7yrs) was compared by transmission electron microscopy, scanning electron microscopy and immunohistochemistry.

RESULTS

The thickness of the sinusoidal endothelium was increased in old baboons (130+/-8 nm versus 186+/-9 nm, P<0.001) and the frequency of endothelial fenestrae decreased, with the porosity declining from 4.2+/-0.5% to 2.4+/-0.4% (P=0.006). The expression of laminin and von Willebrands factor was more extensive in old baboons. Novel perisinusoidal ring-shaped cells, probably fat-engorged stellate cells, were prominent in the old baboons.

CONCLUSIONS

Pseudocapillarization is a significant age-related change in the baboon liver. Aging in baboons is associated with a novel aging change in the stellate cell not reported in other species. Hepatic pseudocapillarization is a widespread aging liver change found in several species including humans and other non-human primates.

Spleen enlargement in patients with nonalcoholic fatty liver: correlation between degree of fatty infiltration in liver and size of spleen

Our purpose was to determine if there is an association between nonalcoholic fatty liver and spleen enlargement. Spleen volume was measured by computed tomography (CT) in 32 patients with nonalcoholic fatty liver (23 men and 9 women; age, 41.6+/-12.1, range, 22-69 years) and 34 patients with normal liver (19 men and 15 women; age, 51.1+/-16.2, range, 14-86 years). The values were compared with the patient's demographic data, the liver-to-spleen (L/S) ratio of CT Hounsefield unit measurements, and the results of liver function tests. Diagnosis of fatty liver was made if the L/S ratio was less than 1.0. The mean spleen volume was 73.0+/-24.4 cm3 (range, 21.1-106.1) in normal subjects and 141.2+/-54.1 cm3 (range, 44.1-267.3) in patients with fatty liver (P<0.0001). Multivariate linear regression analysis identified that only the L/S ratio (P<0.0001) and age (P<0.01) were significantly correlated with spleen volume. Using forward selection stepwise regression, the L/S ratio entered first (beta = -0.634) and age second (beta = -0.293). In conclusion, spleen enlargement was commonly seen in patients with nonalcoholic fatty liver, and the recognition of this association may halt further attempts to evaluate the cause of spleen enlargement.

Spleen enlargement in patients with nonalcoholic fatty liver: correlation between degree of fatty infiltration in liver and size of spleen

Our purpose was to determine if there is an association between nonalcoholic fatty liver and spleen enlargement. Spleen volume was measured by computed tomography (CT) in 32 patients with nonalcoholic fatty liver (23 men and 9 women; age, 41.6+/-12.1, range, 22-69 years) and 34 patients with normal liver (19 men and 15 women; age, 51.1+/-16.2, range, 14-86 years). The values were compared with the patient's demographic data, the liver-to-spleen (L/S) ratio of CT Hounsefield unit measurements, and the results of liver function tests. Diagnosis of fatty liver was made if the L/S ratio was less than 1.0. The mean spleen volume was 73.0+/-24.4 cm3 (range, 21.1-106.1) in normal subjects and 141.2+/-54.1 cm3 (range, 44.1-267.3) in patients with fatty liver (P<0.0001). Multivariate linear regression analysis identified that only the L/S ratio (P<0.0001) and age (P<0.01) were significantly correlated with spleen volume. Using forward selection stepwise regression, the L/S ratio entered first (beta = -0.634) and age second (beta = -0.293). In conclusion, spleen enlargement was commonly seen in patients with nonalcoholic fatty liver, and the recognition of this association may halt further attempts to evaluate the cause of spleen enlargement.

Mechanisms of hepatic microcirculatory disturbances induced by acute ethanol administration in rats, with special reference to alterations of sinusoidal endothelial fenestrae

Elucidation of the hepatic hemodynamics in acute ethanol administration is an issue of clinical importance for better understanding of alcoholic liver diseases. The purpose of this study is to clarify the mechanism of hepatic microcirculatory disturbances after acute ethanol administration, especially regarding the effects of ethanol on alterations of sinusoidal endothelial fenestrae (SEF) and the involvement of endothelin-1 (ET-1) in the mechanism of portal hypertension induced by ethanol. Ethanol was administrated into the portal vein via the mesenteric vein branch of rats as a continuous infusion (4 and 8 mg/min of ethanol) for 60 min. Hepatic tissue blood flow measured with a laser Doppler blood flowmeter was found to be remarkably decreased with time, whereas portal pressure began to increase at 10 min and showed a significant increase by approximately 1.5 cm H2O at 60 min. Ethanol concentrations in blood at 60 min after 4 and 8 mg/min of ethanol infusion were 0.75 mg/ml and 1.77 mg/ml, respectively. At this point, scanning electron microscopy revealed significant decreases in number and diameter of SEF both in zone 1 and zone 3, with the increase in ethanol level. These findings suggested that decreases in number and diameter of SEF, whether primary or secondary, may lead to the impairment of the transport of plasma substances from sinusoids to hepatocytes in acute ethanol administration. Furthermore, the pretreatment of BQ-123 inhibited a decrease in hepatic tissue blood flow and an increase in portal pressure caused by ethanol, indicating that ET-1 may be involved in the mechanism of hepatic circulatory disturbances in acute ethanol administration.

Effect of propranolol on portosystemic collateral circulation estimated by per-rectal portal scintigraphy with technetium-99m pertechnetate

BACKGROUND/AIMS

Propranolol is widely used in the prevention of variceal bleeding. However, in certain patients with cirrhosis, the portal hypotensive effect of propranolol cannot be obtained. An explanation for portal unresponsiveness to propranolol could be an increase in portocollateral vascular resistance mediated by this drug.

METHODS

In 33 patients with cirrhosis the effect of chronic administration of propranolol on portocollateral blood flow from the inferior mesenteric vein was examined by means of per-rectal portal Tc-99m pertechnetate scintigraphy.

RESULTS

Propranolol significantly reduced the shunt index by 15.3 +/- 4.2%. This reduction was observed only in patients with cirrhosis classified as Child-Pugh A and B groups, but not group C. Differences between groups in portosystemic shunt index changes after propranolol were significant (F = 3.4, p < 0.05).

CONCLUSIONS

The data presented suggest that propranolol changes the distribution of blood between the portal and systemic circulation, which is probably due to the increase in vascular resistance of portocollateral vessels. The magnitude of the vascular response to propranolol depends on the severity of liver disease.

Splanchnic and systemic hemodynamics in early abstinence and after ethanol administration in non-cirrhotic alcoholic patients

Thirteen asymptomatic chronic alcoholic patients were studied to investigate the early stages of portal hypertension in alcoholic liver disease and the effects of withdrawal and ethanol on hepatic function and hemodynamic variables. None of the patients presented clinical signs of decompensated liver disease, and their liver biopsies showed normal liver or moderate alterations only. In basal conditions and after an intravenous ethanol infusion (1 g/kg body weight), hepatic venous pressure gradient and hepatic blood flow using indocyanine green were measured through hepatic vein catheterization. Hepatic sinusoidal vascular resistance and indocyanine green intrinsic clearance were also calculated. Portal blood flow measurements were obtained by Doppler ultrasound. No correlation was observed between hepatic venous pressure gradient and histologic features, (steatosis, necrosis, fibrosis, inflammation and hepatocyte surface area). In basal conditions, portal hypertension was not found in any case. After ethanol, portal pressure increased significantly (p < 0.001); in four cases it rose to or above 5 mmHg. Portal blood flow, hepatic blood flow and hepatic vascular resistance also increased significantly. Intrinsic indocyanine green clearance decreased slightly but significantly. No significant correlations were found between portal pressure, hepatic resistance and the histologic parameters. It was concluded that alcoholic patients, without clinical or laboratory evidence of liver failure and with minimal or moderate histologic alterations, have normal portal pressures. After an intravenous ethanol load, however, four out of 13 patients (31%) reached levels of 5 mmHg or more, irrespective of their liver histology.

The hepatic extracellular matrix. I. Components and distribution in normal liver

The unique nature of the hepatic extracellular matrix (ECM) is predicated by the special configuration of the space of Disse. Whereas other epithelial organs have two basement membranes (BM) and a substantial ECM interposed between endothelial and epithelial cells, the liver lobule has no BM and only an attenuated ECM, consisting mostly of fibronectin, some collagen type I, and minor quantities of types III, IV, V, and VI. This configuration, together with the abundant fenestrations and gaps of the sinusoidal endothelial cells, seems ideally suited to facilitate the rapid bidirectional exchange of macromolecules normally taking place between plasma and hepatocytes. During organogenesis, the liver anlage is vascularized by continuous capillaries with BM, but by day 13.5 of development (in the rat) the vessels in the immediate proximity of hepatocytes become fenestrated, lacking specialized junctions and BM, suggesting that the hepatocytes produce signals capable of modulating the endothelial phenotype. In regeneration, hepatocyte proliferation precedes vascular proliferation resulting in the formation of hepatocyte clusters that, temporarily, lack sinusoids. Eventually, vascular proliferation follows and the normal hepatocyte-vascular relationships are restored. During this period laminin synthesis by Ito cells is prominent. As soon as hepatocytes become stable, secretion of the sinusoid phenotype-maintaining factors resumes and laminin synthesis and secretion terminates. The interplay between extracellular matrix and liver cells is essential for normal homeostasis and its modification results in deranged hepatic function.

Role of septal fibrosis in development of hepatic circulatory disturbance in the presence of liver cell enlargement

The effect of septal fibrosis on hepatic circulation was examined in rats with enlarged liver cells. Septal fibrosis was produced by horse serum injections and liver cell enlargement by a choline-deficient diet. Septal fibrosis alone did not induce any disturbance of hepatic circulation. In fatty livers, a slight increase in sinusoidal vascular resistance and a slight elevation of portal vein pressure were found. However, in fatty livers with septal fibrosis, portal hypertension and sinusoidal vascular resistance were higher than in fatty livers without septal fibrosis. These experimental data clearly demonstrate that septal fibrosis alone has no effect on hepatic circulation, but septal fibrosis in the presence of liver cell enlargement markedly affects sinusoidal circulation and induces portal hypertension. The augmentation of sinusoidal vascular resistance by septal fibrosis in the presence of liver cell enlargement might be due to the severe deformation of the sinusoids by enlarged liver cells in the limited spaces surrounded by septal fibrous bands.

Significance of septal fibrosis for disturbance of hepatic circulation

To examine the significance of fibrous septa of the liver for hepatic circulatory disturbance, haemodynamic changes were investigated in rats with septal fibrosis induced with horse serum injections. The fibrotic liver showed thin fibrous bands originating in the vicinity of the peripheral branches of the hepatic vein connected with each other and partly with the portal triads, without conspicuous periportal, pericentral or perisinusoidal fibrosis. There was no evidence of hepatic cell enlargement, disarrangement of hepatic cell plates or narrowing of the sinusoids in the fibrotic livers. Portal vascular resistance, bile production and hepatic oxygen consumption, which were measured by an isolated liver perfusion method, were much the same in the normal and the fibrotic livers. Moreover, there was no significant difference in in vivo blood pressures of the portal vein, the terminal portal venule, the terminal hepatic venule and the inferior vena cava between the normal and the fibrotic rats. These data suggest that septal fibrosis in itself does not disturb hepatic circulation.

Chaos and predicting varix hemorrhage

Despite a wide array of mechanisms implicated in esophagogastric varix hemorrhage, predicting the onset of bleeding or even identifying the dominant factor in its causation has proved elusive. In this article we re-examine variceal pathophysiology and hypothesize that bleeding is rooted in turbulent portal system flow, a phenomenon embodied in the 'new' science of chaos and the principles of non-linear, rhythmic fluid dynamics. Analogous to forecasting the weather, predicting turbulent flow hinges on defining the initial physical conditions, and, like the field theory of quantum physics, depends on probabilities and instabilities rather than direct proportional analysis. Based on the complex regional and systemic hemodynamic forces and local physical properties underlying formation and perpetuation of esophagogastric varices, we propose, as with climatologic events, that a relatively minor or remote physiologic adjustment may set into motion a sequence of destabilizing splanchnic blood flow kinetics that ultimately causes a varix to erupt. In other words, the onset of varix bleeding derives from a sudden, erratic switch from disorganized but stable to disruptive turbulent variceal blood flow, and as a 'chaotic' phenomenon, is likely to remain for the foreseeable future highly unpredictable.

Insights into the pathogenesis of alcoholic liver necrosis and fibrosis: status report

The use of the Tsukamoto-French rat model of alcoholic liver disease facilitated pathological, physiological, biochemical and cell biological experiments that examined the validity of some of the existing hypotheses for pathogenesis of alcoholic liver necrosis and fibrosis. Results obtained to date strongly support the contribution of centrilobular hypoxia as a pathogenetic mechanism of alcoholic liver necrosis. The enhanced hepatic lipid peroxidation was not evident at the early stage of ethanol-induced liver necrosis but could be demonstrated at the late stage when the liver damage progressed to liver fibrosis. This suggests that the lipid peroxidation may not be an important mechanism of alcoholic liver necrosis but may be an initiation factor for liver fibrogenesis as recently proposed by others (88). The high-fat diet appears to have promoting effects on both induction of alcoholic liver necrosis and stimulation of liver fibrogenesis. The former may be related to the induction of MEOS by the high-fat diet and consequent centrilobular hypoxia caused by inadequately compensated hepatic overuse of oxygen. The latter can be mediated through sensitization of Ito cells by a high-fat diet. We propose that Kupffer cell-derived TGF beta is, at least in part, responsible for some of phenotypical changes of Ito cells associated with their activation. Our model provides maximal experimental control and induces the discrete stages of alcoholic liver injury that can be reproduced with its pathological evolution telescoped into a short time. Because of these features, replication of the experimental conditions in different laboratories is possible so that results can be validly compared through precise standardization of the experimental protocols. This model requires some training in implantation and maintenance of the gastric catheter. However, the training can be easily attained by anyone who has experience in animal surgery. Another requirement is the initial fund to acquire infusion devices and metabolism cages. Once this equipment is purchased, however, the maintenance cost is low. Even if the initial expenses are included, the cost per animal is relatively inexpensive when compared with the cost involved in the use of larger animals such as baboons or pigs. Since administration of diet and ethanol (or isocaloric glucose solution) is precisely controlled by infusion pumps, this system makes unnecessary the measurement of diet consumption that has to be done daily for each animal with other methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathophysiology of portal hypertension and variceal bleeding

Portal hypertension results from an interaction of abnormal intrahepatic resistance and increases in portal blood flow. Intrahepatic resistance is probably multifactorial in nature and may include compression of hepatic veins by regenerating nodules, collagen deposition in sinusoids and venules, hepatocyte enlargement, and constriction of sinusoids by contractile myofibroblasts. The increase in splanchnic blood flow observed is incompletely understood, but it may involve circulating vasodilators and alteration in volume and sodium balance. The end result of these interactions is the development of increased portal pressure and portosystemic collaterals, the most important of which are esophageal varices. The rupture of esophageal varices is a devastating complication of portal hypertension. Increased portal pressure is necessary for the development and rupture of varices but apparently not sufficient, because many patients with elevated portal pressures never bleed. Presumably, local factors must be involved. Variceal wall tension is probably the best single descriptor of risk from variceal hemorrhage. The wall-tension formula unites the contributions of portal pressure, varix size, and wall thickness to variceal rupture. Lowering portal pressure, reducing varix size, and supporting varices in scar tissue may all lower the risk of hemorrhage.

Portal hypertension and hepatic sinusoidal Ulex lectin binding

Ulex europaeus 1 lectin (UEA1) has previously been shown to bind to hepatic sinusoidal endothelium in cirrhotic liver. This study was undertaken to determine the relationship between UEA1 sinusoidal binding and hepatic venous pressure gradient in patients with portal hypertension. Twenty one liver specimens (including 18 from patients with alcoholic cirrhosis) biopsied within an interval of 1 month from the hepatic venous pressure study were examined for UEA1 binding. The consistent staining pattern of normal liver controls formed the basis for the criteria of positivity and grading system. Seventeen cases (81%) were positive, but the staining intensity or extent showed no strong correlation with the hepatic venous pressure gradient; however, three of the four negative cases were in the low pressure range which is rarely associated with variceal bleeding. We conclude that UEA1 is a useful marker for significant sinusoidal alterations in portal hypertension and a helpful adjunct in the histological diagnosis of cirrhosis.

Mechanism of ethanol induced hepatic injury

Ethanol is hepatotoxic through redox changes produced by the NADH generated in its oxidation via the alcohol dehydrogenase pathway, which in turn affects the metabolism of lipids, carbohydrates, proteins and purines. Ethanol is also oxidized in liver microsomes by an ethanol-inducible cytochrome P-450 (P-450IIE1) which contributes to ethanol metabolism and tolerance, and activates xenobiotics to toxic radicals thereby explaining increased vulnerability of the heavy drinker to industrial solvents, anesthetic agents, commonly prescribed drugs, over-the-counter analgesics, chemical carcinogens and even nutritional factors such as vitamin A. Induction also results in energy wastage and increased production of acetaldehyde. Acetaldehyde, in turn, causes injury through the formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair, and alterations in microtubules, plasma membranes and mitochondria with a striking impairment of oxygen utilization. Acetaldehyde also causes glutathione depletion and lipid peroxidation, and stimulates hepatic collagen synthesis, thereby promoting fibrosis.

The rat liver microcirculation in alcohol-induced hepatomegaly

It has been suggested that hepatocyte enlargement can lead to compression of the extracellular space (sinusoidal and interstitial) and induce portal hypertension. However, this hypothesis has never been tested by measuring the vascular and extravascular spaces in the intact liver. The aim of the present study was to investigate the effects of chronic alcohol intake on the hepatic microcirculation using Goresky's multiple-indicator dilution technique in the isolated perfused rat liver. Female rat littermates were pair-fed either ethanol (n = 7) or an isocaloric carbohydrate diet (n = 7) for 21 days. As expected, chronic alcohol intake produced a significant increase in liver/body weight ratio (+32%, p less than 0.01) and hepatocyte size (+45%, p less than 0.001), which was accompanied by a marked increase in the cellular water space (control: 3.3 +/- 0.6 ml; ethanol-fed: 4.9 +/- 0.9 ml; p less than 0.001). When expressing data per total liver, the sinusoidal space was similar in the two groups (control: 1.87 +/- 0.2; ethanol-fed: 1.95 +/- 0.2 ml; not significant), whereas the interstitial space was increased in alcohol rats compared to controls (albumin space +58%, p less than 0.01; sucrose space +51%, p less than 0.01). In alcoholic rats, the sinusoidal space was probably stretched, with an overall reduced transversal diameter, as suggested by the reduced values found when data were expressed per gm of liver weight. However, despite this finding and the enlargement of the liver and hepatocytes observed in alcoholic rats, similar values were obtained between the two groups for the portal perfusion pressure and thus the intrahepatic vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Endotoxin-induced hypercoagulability: a possible aggravating factor of alcoholic liver disease

The present experiments were designed to study the effect of chronic ethanol consumption on endotoxin toxicity. The intravenous injection of endotoxin produced a more pronounced increase of serum AST and ALT activities in chronic ethanol-fed rats, when compared to controls. The activities of hepatic mitochondrial enzymes, succinate dehydrogenase and cytochrome oxidase, were also distinctly decreased by endotoxin treatment in chronic ethanol-fed rats. Consistent with these biochemical alterations, light and electron microscopic examinations revealed severe liver injury after endotoxin injection in chronic ethanol-fed rats. Furthermore, the increase of blood BUN and creatinine levels accompanied by the degeneration of the renal tubulus and slight infiltration of neutrophils into the glomerule were produced by endotoxin treatment and were more conspicuous in chronic ethanol-fed rats than controls. Therefore, the biochemical and histological evidence indicates that endotoxin markedly potentiates organ injury after chronic ethanol consumption. In addition, a more pronounced decrease in blood antithrombin III activity accompanied by an increase in fibrin degradation product level in blood was recognized in chronic ethanol-fed rats receiving endotoxin, when compared to controls receiving endotoxin. This increase of blood fibrin degradation product level correlated well with the decrease of antithrombin III activity (r = -0.6116; p less than 0.005). These findings of blood antithrombin III activity and fibrin degradation product level indicate that the coagulation-fibrinolysis system is more activated by endotoxin treatment after chronic ethanol consumption. Furthermore, the activation of the coagulation-fibrinolysis system was well correlated with biochemical and histological alterations representing hepatorenal involvement.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in liver and spleen volumes in alcoholic liver disease

Liver and spleen volumes were determined using computed tomography in 57 subjects with alcoholic liver disease and 76 subjects with nonalcoholic liver disease, in order to clarify the clinical characteristics and pathogenetic mechanisms of portal hypertension in alcoholic liver disease. The liver volumes in alcoholic liver disease were significantly larger than those in nonalcoholic liver disease, except in cases of decompensated liver cirrhosis. The increase in liver volume in alcoholic liver disease showed a significant correlation with the degree of hepatocytic ballooning. Overlapping of values for liver volume between alcoholic and nonalcoholic liver disease was quite small, suggesting that determination of liver volumes could be helpful for making etiological diagnoses in chronic liver disease. Spleen volumes were increased in the advanced cases of both alcoholic and nonalcoholic liver disease. The correlations between liver and spleen volumes were quite different between alcoholic and nonalcoholic liver disease. In nonalcoholic liver disease, a negative correlation was obtained, while, on the other hand, it was significantly positive in alcoholic liver disease. This appears to suggest that the pathogenetic mechanism of portal hypertension may differ between the diseases. After abstinence from alcohol, the decrease in liver and spleen volumes showed a statistically significant correlation, suggesting that ballooning of the hepatocytes may play a role in the augmentation of portal hypertension in alcoholic liver disease.

Hepatocyte and nuclear areas and fatty infiltration of the liver in chronic alcoholic liver disease

In 117 patients affected by chronic alcoholic liver disease, we have histomorphometrically determined hepatocyte and nuclear areas, total amount of fat and total amount of fibrosis, comparing them with the following clinical and biochemical parameters: ascites, encephalopathy, jaundice, spiders, collateral circulation, splenomegaly, prothrombin activity, serum albumin, gammaglobulin, bilirubin, ASAT, ALAT, GGT, leukocyte and platelet count, and daily consumption of ethanol. Both hepatocyte and nuclear areas closely correlated with most of the parameters indicative of hepatic function derangement, whereas fat amount correlated with them inversely, but positively with the daily consumption of ethanol. The degree of fibrosis was greater in patients with a worse hepatic function, and there was a direct relationship between the degree of fibrosis and hepatocyte and nuclear areas, and an inverse one between the degree of fibrosis and the total amount of fat.

Effect of propylthiouracil on liver cell development in the male albino mouse: protective effect against ethanol-induced alterations

The aim of the present study is to analyze whether the addition of propylthiouracil reverts the influence of ethanol on the development of periportal and pericentral hepatocytes and their nuclei in male albino mice. Propylthiouracil-treated animals showed decreased cellular and nuclear areas when compared with the control animals, except for the 180-day-old animals, whose pericentral cells and nuclei were greater than those of the controls and exhibited fatty infiltration. Pericentral hepatocytes and nuclei of the ethanol-fed animals showed an increase of their sizes, especially in 180-day-old animals. In contrast, hepatocyte and nuclear sizes of the animals treated with both propylthiouracil and ethanol were similar to those of the control group, suggesting a protective effect of propylthiouracil against the ethanol-induced alterations.

International Commission for Protection against Environmental Mutagens and Carcinogens. ICPEMC Working Paper No. 15/2. Metabolism and metabolic effects of ethanol, including interaction with drugs, carcinogens and nutrition

Different pathways of alcohol metabolism, the alcohol dehydrogenase pathway, the microsomal ethanol-oxidizing system and the catalase pathway are discussed. Alcohol consumption leads to accelerated ethanol metabolism by different mechanisms including an increased microsomal function. Microsomal induction leads to interactions of ethanol with drugs, hepatotoxic agents, steroids, vitamins and to an increased activation of mutagens/carcinogens. A number of ethanol-related complications may be explained by the production of its first metabolite, acetaldehyde, such as alterations of mitochondria, increased lipid peroxidation and microtubular alterations with its adverse effects on various cellular activities, including disturbances of cell division. Nutritional factors in alcoholics such as malnutrition are discussed especially with respect to its possible relation to cancer.

Hepatocyte and nuclear areas in alcoholic liver cirrhosis: their relationship with the size of the nodules and the degree of fibrosis

The aim of the study in alcoholic cirrhotic patients was to determine if a relationship exists between the areas of hepatocytes and their nuclei and the area of the nodules to which these cells belong as well as the thickness of the fibrous tracts which delimit these nodules. It was found that hepatocyte and nuclear areas were enlarged the smaller the nodules and the thicker the surrounding fibrous tracts. Considering that oxygen supply in liver cirrhosis decreases with increasing fibrosis, our results permit the hypothesis that a low oxygen supply causes an increase not only in liver cell size but also in nuclear size, which is an index of nuclear activity.

Relationship between degree of portal hypertension and liver histologic lesions in patients with alcoholic cirrhosis. Effect of acute alcoholic hepatitis on portal hypertension

The relationship between the degree of portal hypertension and histologic liver lesions was studied in a group of 84 patients with histologically proven alcoholic cirrhosis. The degree of portal hypertension was evaluated by the gradient between wedged and free hepatic venous pressures. Five histologic lesions were quantified: liver cell necrosis, Mallory bodies, neutrophilic infiltrate, fibrosis, and fatty infiltration. The gradient between wedged and free hepatic venous pressures was significantly correlated with the degree of liver cell necrosis and the degree of neutrophilic infiltrate. The stepwise regression analysis showed that only liver cell necrosis has a significant and independent correlation for the degree of portal hypertension. The value for the gradient between wedged and free hepatic venous pressures was significantly higher in patients with (N = 48) than in those without (N = 36) acute alcoholic hepatitis (19.4 +/- 0.8 and 16.5 +/- 0.7 mmHg, respectively). Thus, histologic liver lesions observed in acute alcoholic hepatitis may play a role in the risk of complications of portal hypertension in patients with alcoholic cirrhosis.

Effect of ethanol on liver cell-development in the male albino mouse

The aim of this study is to determine the influence of ethanol on the development of periportal and pericentral hepatocytes and their nuclei, comparing it with the development of these cells and nuclei in a control, age-matched population. In male albino mice fed with 20% ethanol added to drinking water and sacrificed at day 25, 35, 85 and 180 of life haematoxylin-eosin stained liver specimens were studied with the aid of a LEITZ ASM semiautomatic autoanalyzer. The nuclear area of at least 25 hepatocytes with evident nucleoli was measured at each of 3 periportal and 3 pericentral fields. The area of the cells of the same fields was estimated by dividing the area of the fields by the number of hepatocyte nuclei present in them. Both cellular and nuclear areas of periportal and pericentral hepatocytes of the 25-day-old animals were smaller than those of age-matched controls. By contrast, the experimental group showed a striking increase both in cellular and nuclear size in the pericentral hepatocytes, but not in the periportal ones. Thus, ethanol seems to inhibit the initial growth of cells and nuclei; but, after maturation, it causes a marked increase not only in cellular size of pericentral hepatocytes, especially in 180-day-old animals, but also in nuclear size, already evident in the 35-day-old mice.

The sinusoidal barrier in alcoholic patients without liver fibrosis. A morphometric study

Alcohol induces morphological changes in the endothelial and perisinusoidal cells at the fibrotic stage of alcoholic liver diseases. Directly or indirectly, through hemodynamic disturbances linked to the enlargement of steatotic hepatocytes, alcohol may modify this barrier before the onset of fibrosis. Liver biopsies were obtained from control and from alcoholic patients and perfusion-fixed. Volume and surface densities of endothelial cells, perisinusoidal cells and their processes were measured. Liver histology was normal in the 2 groups except for steatosis in the alcoholics. Volume densities represented 8.2%, 4.7% and 3.2% of the sinusoid in controls for endothelial cells, perisinusoidal cells and their processes whereas surface densities represented respectively 0.5, 0.23, 0.21 m2/cm3 of sinusoid. Morphometric values were not significantly different in the alcoholic patients. In none of the alcoholic patients did fine morphological studies of sinusoidal cells give any indication of the possible evolution of the alcoholic disease towards fibrosis. These results indicate that in the group of patients studied, alcohol, before the fibrotic stage, did not significantly alter the sinusoidal barrier.

Morphologic features of hepatic injury in cardiac disease and shock

One-hundred-forty postmortem liver specimens from patients with cardiac disease or pre-terminal hypotensive shock were examined in order to characterize the histopathologic features of ischemic and congestive hepatic disease. The study group included patients with arteriosclerotic, valvular or hypertensive heart disease, primary pulmonary disease with cor pulmonale, myocarditis, cardiomyopathy, and shock. The hepatic lesions included centrilobular congestion alone (10%), congestion with necrosis (77%), centrilobular necrosis with inflammatory reaction (neutrophil or mononuclear cell) (27%), cardiac sclerosis (48%) and regenerative hyperplasia (23%). Cardiac sclerosis, the most common form of hepatic fibrosis seen, consisted of eccentric thickening or occlusion of the walls of central veins and perivenular scars extending into the lobular parenchyma. Regeneration of liver cells was manifested by either liver-cell plate thickening within a retained cord-like framework or by nodular masses of hepatocytes (nodular regenerative hyperplasia). Only one case of developing cirrhosis was identified in this series. The morphologic features outlined in this study should provide a useful basis for the classification of liver injury in cardiac disease and shock.