Gary Kanel

Methionine adenosyltransferase 1A knockout mice are predisposed to liver injury and exhibit increased expression of genes involved in proliferation

Liver-specific and nonliver-specific methionine adenosyltransferases (MATs) are products of two genes, MAT1A and MAT2A, respectively, that catalyze the formation of S-adenosylmethionine (AdoMet), the principal biological methyl donor. Mature liver expresses MAT1A, whereas MAT2A is expressed in extrahepatic tissues and is induced during liver growth and dedifferentiation. To examine the influence of MAT1A on hepatic growth, we studied the effects of a targeted disruption of the murine MAT1A gene. MAT1A mRNA and protein levels were absent in homozygous knockout mice. At 3 months, plasma methionine level increased 776% in knockouts. Hepatic AdoMet and glutathione levels were reduced by 74 and 40%, respectively, whereas S-adenosylhomocysteine, methylthioadenosine, and global DNA methylation were unchanged. The body weight of 3-month-old knockout mice was unchanged from wild-type littermates, but the liver weight was increased 40%. The Affymetrix genechip system and Northern and Western blot analyses were used to analyze differential expression of genes. The expression of many acute phase-response and inflammatory markers, including orosomucoid, amyloid, metallothionein, Fas antigen, and growth-related genes, including early growth response 1 and proliferating cell nuclear antigen, is increased in the knockout animal. At 3 months, knockout mice are more susceptible to choline-deficient diet-induced fatty liver. At 8 months, knockout mice developed spontaneous macrovesicular steatosis and predominantly periportal mononuclear cell infiltration. Thus, absence of MAT1A resulted in a liver that is more susceptible to injury, expresses markers of an acute phase response, and displays increased proliferation.

Spontaneous oxidative stress and liver tumors in mice lacking methionine adenosyltransferase 1A

In mammals, methionine metabolism occurs mainly in the liver via methionine adenosyltransferase‐catalyzed conversion to S‐adenosylmethionine. Of the two genes that encode methionine adenosyltransferase(MAT1A and MAT2A), MAT1A is mainly expressed in adult liver whereas MAT2A is expressed in all extrahepatic tissues. Mice lacking MAT1A have reduced hepatic S‐adenosylmethionine content and hyperplasia and spontaneously develop nonalcoholic steatohepatitis. In this study, we examined whether chronic hepatic Sadenosylmethionine deficiency generates oxidative stress and predisposes to injury and malignant transformation. Differential gene expression in MAT1A knockout mice was analyzed following the criteria of the Gene Ontology Consortium. Susceptibility of MAT1A knockout mice to CCl4‐induced hepatotoxicity and malignant transformation was determined in 3‐ and 18month‐old mice, respectively. Analysis of gene expression profiles revealed an abnormal expression of genes involved in the metabolism of lipids and carbohydrates in MAT1A knockout mice, a situation that is reminiscent of that found in diabetes, obesity, and other conditions associated with nonalcoholic steatohepatitis. This aberrant expression of metabolic genes in the knockout mice was associated with hyperglycemia, increased hepatic CYP2E1 and UCP2 expression and triglyceride levels, and reduced hepatic glutathione content. The knockout animals have increased lipid peroxidation and enhanced sensitivity to CCl4‐induced liver damage, which was largely due to increased CYP2E1 expression because diallyl sulfide, an inhibitor of CYP2E1, prevented CCl4‐induced liver injury. Hepatocellular carcinoma developed in more than half of the knockout mice by 18 months of age. Taken together, our findings define a critical role for S‐adenosylmethionine in maintaining normal hepatic function and tumorigenesis of the liver.

Epigenetic profiling of somatic tissues from human autopsy specimens identifies tissue- and individual-specific DNA methylation patterns

DNA methylation is known to be associated with cell differentiation, aging, disease and cancer. There exists an expanding base of knowledge regarding tissue-specific DNA methylation, but we have little information about person-specific DNA methylation. Here, we analyze the DNA methylation patterns of multiple tissues from multiple individuals using a high-throughput quantitative assay of genome-wide DNA methylation, namely the Illumina GoldenGate BeadArray. DNA methylation patterns were largely conserved across 11 different tissues (r = 0.852) and across six individuals (r = 0.829), and we found that DNA was highly methylated in non-CpG islands and/or CpG sites that are not occupied by either H3K4me3 or H3K27me3 (P < 0.05). Finally, we found that the Illumina GoldenGate assay features a large number of probes (265/1505 probes, 17.6%) that contain single-nucleotide polymorphisms, which may interfere with DNA methylation analyses in genome-wide studies.

Gastrointestinal stromal tumors: Clinical profile, pathogenesis, treatment strategies and prognosis

Gastrointestinal stromal tumors (GIST), although the most common mesenchymal neoplasms of the gastrointestinal (GI) tract, account for <1% of all GI malignancies. Up to 94% of these tumors express the CD117 antigen. Most patients present in the fifth to seventh decade, the commonest symptom being that of an abdominal mass. Surgery is the main modality of therapy, but even after adequate resection the vast majority of GIST reoccur, and in approximately 50% the liver is the main site of the metastasis. Long‐term, maybe even lifelong follow up of these patients after initial resection cannot be over‐emphasized. Initial tumor size and mitotic rate are the most useful parameters to predict malignant potential. In view of high postoperative recurrence, adjuvant forms of therapy are being explored, and the tyrosine kinase inhibitor imatinib holds the most promise.

Role of Differentiation of Liver Sinusoidal Endothelial Cells in Progression and Regression of Hepatic Fibrosis in Rats

BACKGROUND & AIMS Capillarization, characterized by loss of differentiation of liver sinusoidal endothelial cells (LSECs), precedes the onset of hepatic fibrosis. We investigated whether restoration of LSEC differentiation would normalize crosstalk with activated hepatic stellate cells (HSC) and thereby promote quiescence of HSC and regression of fibrosis. METHODS Rat LSECs were cultured with inhibitors and/or agonists and examined by scanning electron microscopy for fenestrae in sieve plates. Cirrhosis was induced in rats using thioacetamide, followed by administration of BAY 60-2770, an activator of soluble guanylate cyclase (sGC). Fibrosis was assessed by Sirius red staining; expression of α-smooth muscle actin was measured by immunoblot analysis. RESULTS Maintenance of LSEC differentiation requires vascular endothelial growth factor-A stimulation of nitric oxide-dependent signaling (via sGC and cyclic guanosine monophosphate) and nitric oxide-independent signaling. In rats with thioacetamide-induced cirrhosis, BAY 60-2770 accelerated the complete reversal of capillarization (restored differentiation of LSECs) without directly affecting activation of HSCs or fibrosis. Restoration of differentiation to LSECs led to quiescence of HSCs and regression of fibrosis in the absence of further exposure to BAY 60-2770. Activation of sGC with BAY 60-2770 prevented progression of cirrhosis, despite continued administration of thioacetamide. CONCLUSIONS The state of LSEC differentiation plays a pivotal role in HSC activation and the fibrotic process.

Abnormal hepatic methionine and glutathione metabolism in patients with alcoholic hepatitis.

BACKGROUND Abnormal methionine metabolism occurs in animals fed ethanol and in end-stage cirrhotic patients. Expected consequences of these abnormalities include reduced hepatic S-adenosylmethionine and glutathione (GSH) levels, impaired transmethylation, and reduced homocysteine catabolism, resulting in the often-observed hyperhomocystinemia in cirrhotic patients. These parameters have not been examined simultaneously in patients with less advanced alcoholic liver disease. METHODS Six patients hospitalized for alcoholic hepatitis were studied. Plasma was analyzed for homocysteine, methionine, and GSH levels. Liver biopsies diagnosed acute alcoholic hepatitis and underlying fibrosis. Liver specimens were processed for messenger RNA (mRNA) levels and various metabolites and were compared with those of six normal controls. RESULTS Three patients had cirrhosis, and three had only portal fibrosis. Plasma levels of homocysteine and methionine were increased in two of the three patients with cirrhosis but not in the patients with fibrosis. All patients had markedly lower plasma GSH levels (mean +/- SD: 0.27 +/- 0.19 microM, which is at least 10-fold lower than the normal range). Hepatic S-adenosylmethionine levels were reduced by 50%, whereas methionine, GSH, and cysteine levels were reduced by 70-80%. The mRNA levels of most enzymes involved in methionine metabolism and GSH synthesis were decreased, whereas albumin expression was unchanged. Despite the well known induction of cytochrome P450 2E1 in chronic alcoholics, its mRNA levels were nearly 70% lower in these patients. CONCLUSIONS In alcoholic hepatitis, abnormal hepatic gene expression in methionine and GSH metabolism occurs and often contributes to decreased hepatic methionine, S-adenosylmethionine, cysteine, and GSH levels. It may be important to replenish these thiols in patients hospitalized with alcoholic hepatitis.

Sinusoidal obstruction syndrome (veno-occlusive disease) in the rat is prevented by matrix metalloproteinase inhibition 1 ☆

BACKGROUND & AIMS The mechanical origins of the obstruction in sinusoidal obstruction syndrome are initiated by dehiscence of sinusoidal endothelial cells from the space of Disse. The biochemical changes that permit the dehiscence of the sinusoidal endothelial cells were investigated. METHODS In vitro and in vivo studies examined changes induced by monocrotaline, a pyrrolizidine alkaloid that induces sinusoidal obstruction syndrome in both humans and experimental animals. RESULTS In the monocrotaline-induced rat model of sinusoidal obstruction syndrome, there was an early increase of matrix metalloproteinase-9 and a later, lower-magnitude increase of matrix metalloproteinase-2 in the liver. In vitro studies of sinusoidal endothelial cells, hepatocytes, stellate cells, and Kupffer cells showed that sinusoidal endothelial cells are the major source of both basal and monocrotaline-induced matrix metalloproteinase-9/matrix metalloproteinase-2 activity. Monocrotaline caused depolymerization of F-actin in sinusoidal endothelial cells, and blocking of F-actin depolymerization prevented the increase in matrix metalloproteinase activity. Administration of matrix metalloproteinase inhibitors prevented the signs and histological changes associated with sinusoidal obstruction syndrome. CONCLUSIONS Monocrotaline causes depolymerization of F-actin in sinusoidal endothelial cells, which leads to increased expression of metalloproteinase-9 and matrix metalloproteinase-2 by sinusoidal endothelial cells. Inhibition of matrix metalloproteinase-9 and matrix metalloproteinase-2 prevents the development of sinusoidal obstruction syndrome, establishing that matrix metalloproteinase inhibitors may be a therapeutically viable strategy for prevention.

Double-Blind, Controlled Trial of Propylthiouracil in Patients with Severe Acute Alcoholic Hepatitis

Sixty-seven patients entered a double-blind, controlled trial to evaluate the efficacy of propylthiouracil treatment in severe alcoholic hepatitis. Twenty-three percent (7 of 31) given propylthiouracil and 19% (7 of 36) given placebo died during the 6-wk study. Propylthiouracil treatment did not reduce the frequency and incidence of complications in alcoholic hepatitis, but induced hypothyroidism in 4 patients. Treatment produced no beneficial effect on any of the hepatic biochemical tests. We were unable to show any beneficial effect of propylthiouracil treatment on morbidity and mortality in patients with severe acute alcoholic hepatitis.

Do Type and Duration of Antiretroviral Therapy Attenuate Liver Fibrosis in HIV—Hepatitis C Virus—Coinfected Patients?

BACKGROUND This study aimed to determine whether type and duration of therapy for human immunodeficiency virus (HIV) infection attenuates liver fibrosis in patients with HIV and hepatitis C virus (HCV) coinfection. METHODS Patients with HCV monoinfection (group 1) and HIV-HCV coinfection were retrospectively selected; the latter patients were classified into the following 3 groups: group 2, patients who received no therapy or only nucleoside reverse-transcriptase inhibitors (NRTIs); group 3, those who received highly active antiretroviral therapy (HAART); and group 4, those who initially received NRTIs followed by HAART. Fibrosis stage (scale, 0-6) and necroinflammatory score (scale, 0-18) were assessed according to the Ishak system. Data are presented as mean +/- standard deviation. RESULTS Three hundred eighty-one patients (296 HCV-monoinfected patients and 85 HIV-HCV-coinfected patients) were recruited. The durations of HIV therapy before liver biopsy was performed for groups 2, 3, and 4 were 3.8 +/- 2.8, 3.3 +/- 1.8, and 6.6 +/- 2.2 years. The time from HIV diagnosis to HAART initiation was shorter for group 3 than for group 4 (9.1 +/- 7.3 vs. 34.1 +/- 13.1 months; P < .0001). Groups 1 and 3 had similar fibrosis stages (3.1 +/- 2 vs. 3.4 +/- 2.4), rates of fibrosis progression (0.13 +/- 0.09 vs. 0.16 +/- 0.11 per year), and necroinflammatory scores (6.1 +/- 1.8 vs. 6.1 +/- 2.0). Groups 2 and 4 had significantly more-advanced liver disease, as determined by fibrosis stage (4.6 +/- 1.8 vs. 4.3 +/- 2.0; P < .0009), rate of fibrosis progression (0.24 +/- 0.11 vs. 0.20 +/- 0.10 per year; P < .0001), and prevalence of cirrhosis (68% vs. 55%; P < .006), compared with group 1. CONCLUSIONS HIC-HCV-coinfected subjects who receive HAART as their sole form of therapy have liver histology findings comparable to those for HCV-monoinfected patients. A similar degree of benefit is not observed for HIV-HCV-coinfected patients who receive no therapy, NRTIs, or HAART after NRTIs, despite having a longer duration of therapy.

Diagnostic features of tuberculous peritonitis in the absence and presence of chronic liver disease: A case control study

PURPOSE To determine diagnostic features of tuberculous peritonitis (TBP) in the absence and presence of chronic liver disease. PATIENTS AND METHODS Thirty-four patients with TBP (13 without [Group I] and 21 with chronic liver disease [Group II] and 26 controls with cirrhosis and uninfected ascites (Group III) were studied. RESULTS The clinical features in Groups I and II were similar and all patients had elevated ascitic fluid total mononuclear cell count. In Groups I, II, and III, respectively, ascitic fluid protein was > 25 g/L in 100% (13/13), 70% (14/20), and 0% (0/26); serum-ascites albumin gradient (SAAG) was > 11 g/L in 0% (0/13), 52% (11/21), and 96% (25/26), (0% [0/13], 71% [15/21], and 96% [25/26] after correction for serum globulin); and ascitic fluid lactate dehydrogenase (LDH) level was > 90 U/L in 100% (12/12), 84% (16/19), and 0% (0/20), respectively. In Groups I and II combined, ascitic fluid acid-fast stain was negative in all but Mycobacterium tuberculosis culture was positive in 45% (10/22); peritoneal nodules occurred in 94% (31/33), granulomas in 93% (28/30), and positive peritoneal M tuberculosis culture in 63% (10/16). CONCLUSIONS In patients with suspected TBP, ascitic fluid protein of > 25 g/L, SAAG of < 11 g/L and LDH of > 90 U/L have high sensitivity for the disease. With coexistent chronic liver disease, a lower protein level and higher SAAG are usually not helpful but LDH > 90 U/L is a useful parameter for screening. Diagnosis is best confirmed by laparoscopy with peritoneal biopsy and M tuberculosis culture.