Jennifer A. Cuthbert

Hepatitis A: Old and New

SUMMARY The hepatitis A virus (HAV), a picornavirus, is a common cause of hepatitis worldwide. Spread of infection is generally person to person or by oral intake after fecal contamination of skin or mucous membranes; less commonly, there is fecal contamination of food or water. Hepatitis A is endemic in developing countries, and most residents are exposed in childhood. In contrast, the adult population in developed countries demonstrates falling rates of exposure with improvements in hygiene and sanitation. The export of food that cannot be sterilized, from countries of high endemicity to areas with low rates of infection, is a potentially important source of infection. After ingestion and uptake from the gastrointestinal tract, the virus replicates in the liver and is excreted into the bile. Cellular immune responses to the virus lead to destruction of infected hepatocytes with consequent development of symptoms and signs of disease. Humoral immune responses are the basis for diagnostic serologic assays. Acute HAV infection is clinically indistinguishable from other causes of acute viral hepatitis. In young children the disease is often asymptomatic, whereas in older children and adults there may be a range of clinical manifestations from mild, anicteric infection to fulminant hepatic failure. Clinical variants include prolonged, relapsing, and cholestatic forms. Management of the acute illness is supportive, and complete recovery without sequelae is the usual outcome. Research efforts during World War II led to the development of passive immunoprophylaxis. Pooled immune serum globulin is efficacious in the prevention and attenuation of disease in exposed individuals. More recently, active immunoprophylaxis by vaccination has been accomplished. Future eradication of this disease can now be contemplated.

Hepatitis C: progress and problems.

The hepatitis C virus (HCV), a single-stranded RNA virus, is the major cause of posttransfusion hepatitis. HCV isolates differ in nucleotide and amino acid sequences. Nucleotide changes are concentrated in hypervariable regions and may be related to immune selection. In most immunocompetent persons, HCV infection is diagnosed serologically, using antigens from conserved regions. Amplification of RNA may be necessary to detect infection in immunosuppressed patients. Transmission by known parenteral routes is frequent; other means of spread are less common and may represent inapparent, percutaneous dissemination. Infection can lead to classical acute hepatitis, but most infected persons have no history of acute disease. Once infected, most individuals apparently remain carriers of the virus, with varying degrees of hepatocyte damage and fibrosis ensuing. Chronic hepatitis may lead to cirrhosis and hepatocellular carcinoma. However, disease progression varies widely, from less than 2 years to cirrhosis in some patients to more than 30 years with only chronic hepatitis in others. Determinants important in deciding outcome are unknown. Alpha interferon, which results in sustained remission in selected patients, is the only available therapy. Long-term benefits from such therapy have not been demonstrated. Prevention of HCV infection by vaccination is likely to be challenging if ongoing viral mutation results in escape from neutralization and clearance.

Adenovirus-mediated transfer of a gene encoding cholesterol 7 alpha-hydroxylase into hamsters increases hepatic enzyme activity and reduces plasma total and low density lipoprotein cholesterol.

Clinical interventions that accelerate conversion of cholesterol to bile acids reduce circulating low density lipoprotein (LDL) cholesterol concentrations. The initial and rate-limiting step in the bile acid biosynthetic pathway is catalyzed by hepatic cholesterol 7 alpha-hydroxylase. To examine the effects of transient primary overexpression of this enzyme on sterol metabolism and lipoprotein transport, we constructed a recombinant adenovirus in which a cDNA encoding rat 7 alpha-hydroxylase is expressed from the human cytomegalovirus immediate-early promoter (AdCMV7 alpha). Syrian hamsters administered AdCMV7 alpha intravenously accumulated transgene-specific mRNA in the liver and demonstrated a dose-dependent increase in hepatic microsomal 7 alpha-hydroxylase activity. The increased conversion of cholesterol to bile acids resulted in a compensatory increase in hepatic cholesterol synthesis. In addition, overexpression of 7 alpha-hydroxylase reduced the rate of LDL cholesterol entry into the plasma space and, in animals maintained on a Western-type diet, restored hepatic LDL receptor expression. As a consequence, plasma LDL concentrations fell by approximately 60% in animals maintained on control diet and by approximately 75% in animals consuming a Western-type diet. Plasma high density lipoprotein cholesterol levels were reduced to a lesser degree. These results demonstrate that transient upregulation of bile acid synthesis by direct transfer of a 7 alpha-hydroxylase gene favorably alters circulating lipoprotein profiles and suggest one potential molecular target for genetic strategies aimed at reducing cardiovascular risk.

Detection of Familial Hypercholesterolemia by Assaying Functional Low-Density-Lipoprotein Receptors on Lymphocytes

In familial hypercholesterolemia, structural and functional abnormalities of the receptor for low-density lipoprotein (LDL) lead to hypercholesterolemia and premature atherosclerosis. We have developed a simplified method to identify LDL-receptor defects in peripheral-blood lymphocytes. When lymphocytes are cultured in lipoprotein-depleted medium and endogenous sterol biosynthesis is suppressed with mevinolin, mitogen-stimulated proliferation of lymphocytes is dependent on an exogenous source of cholesterol. Whereas a small concentration of supplemental LDL cholesterol (3 to 4 micrograms per milliliter) permits a maximal response in normal lymphocytes, even high concentrations (10 to 50 micrograms per milliliter) are unable to support the proliferation of lymphocytes from patients with homozygous familial hypercholesterolemia. Thus, functional LDL receptors are necessary to allow lymphocyte proliferation in these cultures. The response of lymphocytes from patients with hyperlipidemia not caused by defective LDL receptors was like that of normal cells. In contrast, the response of lymphocytes from patients with heterozygous familial hypercholesterolemia was intermediate between that of homozygotes and that of normal or hyperlipidemic controls. Our method can therefore be used to identify persons who are heterozygous for abnormalities of LDL receptors.

Regulation of hepatic 7 alpha-hydroxylase expression by dietary psyllium in the hamster.

Soluble fiber consistently lowers plasma total and low density lipoprotein (LDL)-cholesterol concentrations in humans and various animal models including the hamster; however, the mechanism of this effect remains incompletely defined. We performed studies to determine the activity of dietary psyllium on hepatic 7 alpha-hydroxylase, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase and LDL receptor expression in the hamster. In animals fed a cholesterol-free semisynthetic diet containing 7.5% cellulose (avicel) as a fiber source, substitution of psyllium for avicel increased hepatic 7 alpha-hydroxylase activity and mRNA levels by 3-4-fold. Comparable effects on 7 alpha-hydroxylase expression were observed with 1% cholestyramine. Psyllium also increased hepatic 7 alpha-hydroxylase activity and mRNA in animals fed a diet enriched with cholesterol and triglyceride. Activation of 7 alpha-hydroxylase was associated with an increase in hepatic cholesterol synthesis that was apparently not fully compensatory since the cholesterol content of the liver declined. Although dietary psyllium did not increase hepatic LDL receptor expression in animals fed the cholesterol-free, very-low-fat diet, it did increase (or at least restore) receptor expression that had been downregulated by dietary cholesterol and triglyceride. Thus, 7.5% dietary psyllium produced effects on hepatic 7 alpha-hydroxylase and LDL metabolism that were similar to those of 1% cholestyramine. Induction of hepatic 7 alpha-hydroxylase activity by dietary psyllium may account, in large part, for the hypocholesterolemic effect of this soluble fiber.

Etiology of Liver Disease in Renal-Transplant Patients

The etiology of 72 episodes of liver disease that developed in 62 of 162 renal-transplant recipients was evaluated. Infection with hepatitis B virus was a minor problem, and none of our patients had evidence of infection with hepatitis A. Cytomegalovirus infection was ubiquitous in the population and probably accounted for many episodes of acute liver disease. This agents role in causing chronic hepatitis is less secure. Infections with other viruses including Epstein-Barr virus, adenovirus, and the herpes viruses were only rarely associated with hepatic disease. Azathioprine was responsible for some episodes of acute cholestasis but could not be incriminated as a direct cause of chronic disease. A cause could be identified for the majority of episodes of acute hepatic dysfunction, but the cause of most of the chronic hepatitis remains undetermined. It is likely that infection with non-A, non-B hepatitis virus accounts for much of this serious, often fatal, complication of renal transplantation.

Dietary fatty acids regulate hepatic low density lipoprotein (LDL) transport by altering LDL receptor protein and mRNA levels.

The concentration of LDL in plasma is strongly influenced by the amount and the type of lipid in the diet. Recent studies in the hamster have shown that dietary fatty acids differentially affect circulating LDL levels primarily by altering receptor-dependent LDL uptake in the liver. To investigate the mechanistic basis of this effect, rates of receptor-dependent LDL transport in the liver were correlated with LDL receptor protein and mRNA levels in hamsters fed safflower oil or coconut oil and varying amounts of cholesterol. Hepatic LDL receptor activity was significantly lower in animals fed coconut oil than in animals fed safflower oil at all levels of cholesterol intake (26, 53, and 61% lower at cholesterol intakes of 0, 0.06, and 0.12%, respectively). These fatty acid-induced changes in hepatic LDL receptor activity were accompanied by parallel changes in hepatic LDL receptor protein and mRNA levels, suggesting that dietary fatty acids regulate the LDL receptor pathway largely at the mRNA level.

Overexpression of Cholesterol 7α-Hydroxylase (CYP7A) in Mice Lacking the Low Density Lipoprotein (LDL) Receptor Gene LDL TRANSPORT AND PLASMA LDL CONCENTRATIONS ARE REDUCED

This study was undertaken to determine the effect of transient overexpression of hepatic cholesterol 7α-hydroxylase on low density lipoprotein (LDL) cholesterol transport in mice lacking LDL receptors (LDL receptor−/−). Primary overexpression of hepatic 7α-hydroxylase in LDL receptor−/− mice was accompanied by a dose-dependent decrease in the rate of LDL cholesterol appearance in plasma (whole body LDL cholesterol transport) and a corresponding reduction in circulating LDL cholesterol levels. The increase in hepatic 7α-hydroxylase activity necessary to achieve a 50% reduction in plasma LDL cholesterol concentrations was ∼10-fold. In comparison, cholestyramine increased hepatic 7α-hydroxylase activity ∼3-fold and reduced plasma LDL cholesterol concentrations by 17%. This study demonstrates that augmentation of hepatic 7α-hydroxylase expression is an effective strategy for lowering plasma LDL concentrations even in animals with a genetic absence of LDL receptors.

Lactulose vs Polyethylene Glycol 3350-Electrolyte Solution for Treatment of Overt Hepatic Encephalopathy The HELP Randomized Clinical Trial

IMPORTANCE Hepatic encephalopathy (HE) is a common cause of hospitalization in patients with cirrhosis. Pharmacologic treatment for acute (overt) HE has remained the same for decades. OBJECTIVE To compare polyethylene glycol 3350-electrolyte solution (PEG) and lactulose treatments in patients with cirrhosis admitted to the hospital for HE. We hypothesized that rapid catharsis of the gut using PEG may resolve HE more effectively than lactulose. DESIGN, SETTING, AND PARTICIPANTS The HELP (Hepatic Encephalopathy: Lactulose vs Polyethylene Glycol 3350-Electrolyte Solution) study is a randomized clinical trial in an academic tertiary hospital of 50 patients with cirrhosis (of 186 screened) admitted for HE. INTERVENTIONS Participants were block randomized to receive treatment with PEG, 4-L dose (n = 25), or standard-of-care lactulose (n = 25) during hospitalization. MAIN OUTCOMES AND MEASURES The primary end point was an improvement of 1 or more in HE grade at 24 hours, determined using the hepatic encephalopathy scoring algorithm (HESA), ranging from 0 (normal clinical and neuropsychological assessments) to 4 (coma). Secondary outcomes included time to HE resolution and overall length of stay. RESULTS A total of 25 patients were randomized to each treatment arm. Baseline clinical features at admission were similar in the groups. Thirteen of 25 patients in the standard therapy arm (52%) had an improvement of 1 or more in HESA score, thus meeting the primary outcome measure, compared with 21 of 23 evaluated patients receiving PEG (91%) (P < .01); 1 patient was discharged before final analysis and 1 refused participation. The mean (SD) HESA score at 24 hours for patients receiving standard therapy changed from 2.3 (0.9) to 1.6 (0.9) compared with a change from 2.3 (0.9) to 0.9 (1.0) for the PEG-treated groups (P = .002). The median time for HE resolution was 2 days for standard therapy and 1 day for PEG (P = .01). Adverse events were uncommon, and none was definitely study related. CONCLUSIONS AND RELEVANCE PEG led to more rapid HE resolution than standard therapy, suggesting that PEG may be superior to standard lactulose therapy in patients with cirrhosis hospitalized for acute HE. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01283152.

An Automated Model Using Electronic Medical Record Data Identifies Patients With Cirrhosis at High Risk for Readmission

BACKGROUND & AIMS Patients with cirrhosis have 1-month rates of readmission as high as 35%. Early identification of high-risk patients could permit interventions to reduce readmission. The aim of our study was to construct an automated 30-day readmission risk model for cirrhotic patients using electronic medical record (EMR) data available early during hospitalization. METHODS We identified patients with cirrhosis admitted to a large safety-net hospital from January 2008 through December 2009. A multiple logistic regression model for 30-day rehospitalization was developed using medical and socioeconomic factors available within 48 hours of admission and tested on a validation cohort. Discrimination was assessed using receiver operator characteristic curve analysis. RESULTS We identified 836 cirrhotic patients with 1291 unique admission encounters. Rehospitalization occurred within 30 days for 27% of patients. Significant predictors of 30-day readmission included the number of address changes in the prior year (odds ratio [OR], 1.13; 95% confidence interval [CI], 1.05-1.21), number of admissions in the prior year (OR, 1.14; 95% CI, 1.05-1.24), Medicaid insurance (OR, 1.53; 95% CI, 1.10-2.13), thrombocytopenia (OR, 0.50; 95% CI, 0.35-0.72), low level of alanine aminotransferase (OR, 2.56; 95% CI, 1.09-6.00), anemia (OR, 1.63; 95% CI, 1.17-2.27), hyponatremia (OR, 1.78; 95% CI, 1.14-2.80), and Model for End-stage Liver Disease score (OR, 1.04; 95% CI, 1.01-1.06). The risk model predicted 30-day readmission, with c-statistics of 0.68 (95% CI, 0.64-0.72) and 0.66 (95% CI, 0.59-0.73) in the derivation and validation cohorts, respectively. CONCLUSIONS Clinical and social factors available early during admission and extractable from an EMR predicted 30-day readmission in cirrhotic patients with moderate accuracy. Decision support tools that use EMR-automated data are useful for risk stratification of patients with cirrhosis early during hospitalization.