Higher Gamma-glutamyl Transpeptidase Levels Research Articles

Clinical and virological effects of long‐term (over 5 years) lamivudine therapy

Ideally, long-term lamivudine therapy should not induce tyrosine-methionine-aspartate-aspartate (YMDD) mutants (reverse transcription [rt]; rt M204I/V) in patients with chronic hepatitis B. There is little or no information on the clinical features of patients who do not develop such mutants. We analyzed 368 patients who received lamivudine therapy for more than 6 months between 1995 and 2003. Among them, 98 patients were negative for YMDD mutants during 5-year lamivudine therapy. Multivariate analysis identified hepatitis B e antigen (HBeAg) negativity, lack of cirrhosis, and high gamma glutamyltranspeptidase (GGTP) level as independent factors associated with lack of emergence of YMDD mutants during 5-year treatment. In these 98 patients, 21 patients developed YMDD mutants in the 5-year posttreatment follow-up. Old age was identified as the only factor associated with the emergence of YMDD mutants during that period. For all patients, 53 showed no elevation of alanine aminotransferase (ALT) or viral load after emergence of YMDD mutants during 5 years. Short latency to emergence of YMDD mutants, mixed (tyrosine-isoleucine-aspartate-aspartate (YIDD) [rtM204I] + tyrosine-valine-aspartate-aspartate (YVDD) [rtM204V]) type, and low ALT level were identified as independent factors associated with elevation ALT or viral load. HBeAg negativity, lack of cirrhosis, and high GGTP level were associated with lack of emergence of YMDD mutants during 5-year period. Young age protected against emergence of YMDD mutants over the 5-year period. Moreover, after the emergence of YMDD mutants, short latency to the emergence of YMDD mutant, mixed type mutants, and low baseline ALT level were associated with elevation of ALT or viral load.

Steatosis and hepatic expression of genes regulating lipid metabolism in Japanese patients infected with hepatitis C virus

Steatosis is a histological finding associated with the progression of chronic hepatitis C. The aims of this study were to elucidate risk factors associated with steatosis and to evaluate the association between steatosis and hepatic expression of genes regulating lipid metabolism. We analyzed 297 Japanese patients infected with hepatitis C virus and a subgroup of 100 patients who lack metabolic factors for steatosis. We determined intrahepatic mRNA levels of 18 genes regulating lipid metabolism in these 100 patients using real-time reverse transcription-polymerase chain reaction. Levels of peroxisome proliferator-activated receptor alpha and sterol regulatory element-binding protein 1 proteins were assessed by immunohistochemistry. Steatosis was present in 171 (57%) of 297 patients. The presence of steatosis was independently associated with a higher body mass index, higher levels of gamma-glutamyl transpeptidase and triglyceride, and a higher fibrosis stage. Steatosis was present in 43 (43%) of 100 patients lacking metabolic factors. Levels of mRNA and protein of peroxisome proliferator-activated receptor alpha, which regulates beta-oxidation of fatty acid, were lower in patients with steatosis than in patients without steatosis. These findings indicate that impaired degradation of lipid may contribute to the development of hepatitis C virus-related steatosis.

Rezidivierende Schwangerschaftscholestase und perlenschnurartige Choledocholithiasis bei einer Patientin mit Stoppcodon im ABCB4-Gen des hepatischen Phospholipidtransporters

We report the case of a 40-years-old female patient with recurrent cholestatic liver disease who presented twice with severe intrahepatic cholestasis of pregnancy and pronounced choledocholithiasis between pregnancies. Bile duct stones were removed endoscopically and a laparoscopic cholecystectomy was performed after the second pregnancy. Liver histology revealed intrahepatic cholestasis with portal inflammation and fibrosis, resembling progressive familial intrahepatic cholestasis (PFIC). Molecular genetic studies identified the heterozygous mutation c.957C > T in the ABCB4 gene encoding the hepatobiliary phospholipid transporter. This is the first report of this mutation that introduces a stop codon in an index patient with intrahepatic cholestasis of pregnancy and multiple bile duct stones. In addition, we detected the ABCB11 polymorphism V 444A, which is associated with a decreased expression of the bile salt export pump. Whereas homozygous carriers of the ABCB4 mutation develop PFIC type 3, the heterozygous ABC transporter mutations represent genetic risk factors for cholelithiasis and recurrent cholestatic hepatitis upon challenge with oral contraceptives or during pregnancy. Of note, the patient presented with normal serum gamma-glutamyltranspeptidase activities during pregnancy-associated cholestatic episodes but normal liver enzymes after delivery, whereas choledocholithiasis was associated with high gamma-glutamyl transpeptidase levels. It is unknown whether ursodeoxycholic acid prevents cholestasis or gallstones in patients with ABCB4 deficiency.

Serum cholestasis markers as predictors of early outcome after liver transplantation.

Early cholestasis is not uncommon after liver transplantation and usually signifies graft dysfunction. The aim of this study was to determine if serum synthetic and cholestatic parameters measured at various time points after transplantation can predict early patient outcome, and graft function. The charts of 92 patients who underwent 95 liver transplantations at Rabin Medical Center between 1991 and 2000 were reviewed. Findings on liver function tests and levels of serum bilirubin, alkaline phosphatase (ALP), and gamma glutamyl transpeptidase (GGT) on days 2, 10, 30, and 90 after transplantation were measured in order to predict early (6 months) patient outcome (mortality and sepsis) and initial poor functioning graft. Pearson correlation, chi(2) test, and Student's t-test were performed for univariate analysis, and logistic regression for multivariate analysis. Univariate analysis. Serum bilirubin >/=10 mg/dL and international normalized ratio (INR) >1.6 on days 10, 30, and 90, and high serum ALP and low albumin levels on days 30 and 90 were risk factors for 6-month mortality; serum bilirubin >/=10 mg/dL on days 10, 30, and 90, high serum ALP, high GGT, and low serum albumin, on days 30 and 90, and INR >/=1.6 on day 10 were risk factors for sepsis; high serum alanine aminotransferase, INR >1.6, and bilirubin >/=10 mg/dL on days 2 and 10 were risk factors for poor graft function. The 6-month mortality rate was significantly higher in patients with serum bilirubin >/=10 mg/dL on day 10 than in patients with values of <10 mg/dL (29.4% vs. 4.0%, p = 0.004). Patients who had sepsis had high mean serum ALP levels on day 30 than patients who did not (364.5 +/- 229.9 U/L vs. 70.8 +/- 125.6 U/L, p = 0.005). Multivariate analysis. Significant predictors of 6-month mortality were serum bilirubin >/=10 mg/dL [odds ratio (OR) 9.05, 95% confidence intervals (CI) 1.6-49.6] and INR >1.6 (OR 9.11, CI 1.5-54.8) on day 10; significant predictors were high serum ALP level on day 30 (OR 1.005, 1.001-1.01) and high GGT level on day 90 (OR 1.005, CI 1.001-1.01). None of the variables were able to predict initial poor graft functioning. Several serum cholestasis markers may serve as predictors of early outcome of liver transplantation. The strongest correlation was found between serum bilirubin >/=10 mg/dL on day 10 and early death, sepsis, and poor graft function. Early intervention in patients found to be at high risk may ameliorate the high morbidity and mortality associated with early cholestasis.

Gamma-glutamyl transpeptidase is up-regulated on memory T lymphocytes.

The ectoenzyme gamma-glutamyl transpeptidase (GGT) hydrolyzes glutathione (GSH), is required for the maintenance of normal intracellular GSH levels and modifies the activity of GSH-containing adducts. Previous data suggested that this enzyme was present on mitogen-activated T lymphocytes. However, the level of GGT protein expression on human mononuclear cell subsets has not been determined. A novel mAb to human GGT, 3A8, was developed. 3A8 was used to show that the expression of GGT is, in fact, highest on resting T cells that express markers of the memory phenotype, specifically CD45RO and decreased expression of CD45RB. The peripheral blood of patients with rheumatoid arthritis was found to have expanded numbers of T cells expressing levels of GGT up to 10-fold higher than controls. In addition, the CD4(+) T cell subset with the capacity to migrate across a human endothelial cell monolayer expresses high GGT levels. GGT expression was up-regulated on peripheral blood T cells following activation in vitro by either superantigen, phorbol ester, or IL-15, a stimulatory cytokine synthesized in rheumatoid synovium. Resting peripheral blood T cells that express GGT have higher levels of intracellular thiols than those that do not. These observations suggest that GGT may play an important role in the regulation of lymphocytes that are at a particular developmental stage.

Fibrosing cholestatic hepatitis in hepatitis C virus-infected renal transplant recipients.

Severe hepatitis C virus (HCV)-related fibrosing cholestatic hepatitis leading to early liver failure has been reported only exceptionally. Of 259 HCV-infected renal transplant (RT) patients in one hospital unit, four (1.5%) are described, representing the first series of this particular post-RT disease. Patient mean age was 55.7 yr. Three were men. All had pretransplant, hepatitis B surface antigen-negative and were anti-HCV antibodies positive. Three of them showed pretransplant mild liver enzyme abnormalities, and all received kidneys from HCV-negative donors. All were on steroids, cyclosporine, and azathioprine (AZA). The clinical pattern appeared early after RT (mean, 11.5 mo). In three patients, hyperbilirubinemia (6.5 to 20 mg/dl) and high alkaline phosphatase levels (428 to 859 IU/L) were observed. Also, in all subjects, high gamma glutamyl transpeptidase levels (639 to 4270 IU/L), mild aspartate aminotransferase and alanine aminotransferase abnormalities, and serum HCV RNA were observed. Liver biopsy revealed diffuse fibrosis, leukocyte infiltrates, and different degrees of cholestasis, with typical signs of HCV hepatitis in only one patient. Two patients developed subfulminant liver failure and died 2 and 3 mo after biopsy, respectively. One patient also suffered hepatic failure, receiving a liver transplant. The fourth is alive on dialysis awaiting a combined kidney and liver transplant. It is concluded that fibrosing cholestatic hepatitis is a new, early, and severe complication after RT in HCV(+) patients, which appears in patients with ongoing HCV infection under AZA therapy, despite a nonaggressive immunosuppressive protocol. Both HCV and AZA could play a concurrent role in the pathogenesis of this severe complication after RT.

Characterization of the scavenger receptor on bovine cerebral endothelial cells in vitro.

Primary cultures of bovine brain capillary endothelial cells (BCEC), possessing tight junctions and high levels of gamma-glutamyl transpeptidase, were used as an in vitro model for the blood-brain barrier. The interaction of acetylated low density lipoprotein (AcLDL) with BCEC was studied to characterize the scavenger receptor on these cells. A saturable high affinity binding site was found with a dissociation constant of AcLDL of 5.4 micrograms/ml (3.1 nM) and a maximal binding ranging from 284 to 626 ng of AcLDL/mg of cell protein for eight primary cultures, and independent of the presence of calcium. Cell association was coupled to degradation, and both could be effectively competed for by polyinosinic acid and AcLDL but not by low density lipoprotein or by high density lipoprotein. Prolonged incubation showed an accumulation of the ligand in the cells. The rate of degradation of AcLDL was approximately 10-20-fold lower in BECEC than that of peripheral endothelial cells. No evidence for lysosomal degradation could be obtained. Binding of 1,1'-dioctadecyl-3,3,3'-tetramethylindocarboxyamine perchlorate-labeled AcLDL by BCEC was observed, which could be competed for by an excess of unlabeled AcLDL and polyinosinic acid. We have shown that in vitro BCEC possesses specific binding sites for AcLDL, whereas these cells show a relatively low degradative capacity.

Secretion of gamma-glutamyltranspeptidase by the pancreas: Evidence for a membrane shedding process during exocytosis

Gamma Glutamyltranspeptidase (GGT) is a membrane-bound enzyme involved in glutathione metabolism. It is present in rat exocrine pancreas at a level which is only exceeded by the kidney. It has been previously shown that most of the enzyme activity is located in the apical area of the acinar cell, more precisely at the level of zymogen granules and plasma membrane. The aim of the present study was to examine the secretory behavior of that enzyme. Under resting conditions, in vivo, high levels of GGT were found in pancreatic juice and its level was not related to protein concentration. Under secretin infusion, a relatively constant level of GGT was released, and again, there was no correlation between enzyme activity and protein concentration. Following a bolus injection of caerulein, an analog of cholecystokynin, marked and concommitant rises in protein and GGT levels were observed. Ultracentrifugation, as well as gel filtration on Sepharose 4B, demonstrated that the enzyme was not released in a soluble form. This observation is in agreement with in vitro determinations on isolated zymogen granules showing that GGT is totally associated with the ZG membrane and undetect-able in the content of these organelles. The present data show that 1° GGT is released from the rat pancreas acinar cells in a particulate form; 2° GGT release is elicited by hormonal stimulation coinciding with the exocytotic release of secretory proteins. Our observations lead us to propose that in rat pancreas, ZG membrane fragments are released along with secretory proteins during exocytosis.

Localization of gamma glutamyl transpeptidase in bovine retina.

Gamma-glutamyl transpeptidase (GGTP) is a membrane bound enzyme which has an important role in regulation of glutathione and glutamate in the retina. We have used histochemical and colorimetric enzyme assays to localize GGTP in the bovine retina and choroid. Our results demonstrate that (i) GGTP is present in retinal microvessels but not choroidal microvessels. (ii) Retinal microvascular endothelium loses the ability to express GGTP in cultured cells. (iii) GGTP is present in Muller cells. (iv) Isolated and purified rod outer segments contain high levels of GGTP. (v) Retinal pigment epithelial cells (RPE) in vivo and in culture contain GGTP. The findings of this study lend support to the concept that GGTP may be a biochemical marker for cellular systems which are part of specialized diffusion barriers.

Characteristics of cultured human renal cortical epithelia.

Nine human kidney epithelial cell lines, isolated from small biopsied material and from whole kidney, were propagated in both a hormonally defined medium and a medium supplemented with serum. At confluency, hemicysts or domes, typical of cultured epithelial cells, were formed by these cells. Monolayers had junctional complexes between cells and the presence of numerous microvilli on the cell surface. Parathyroid hormone markedly stimulated these cells to produce cyclic AMP. They also contained high levels of gamma-glutamyltranspeptidase, leucine aminopeptidase, and maltase, enzymes that are associated with the brush-border membrane of the proximal tubule. The cultured cells demonstrated the ability to transport amino acids and alpha-methylglucoside, a substrate actively transported only by the proximal tubule in the kidney. Based on these findings, the cultured cells reflected a number of characteristics associated with the proximal tubule. These renal epithelial cell lines may provide a useful model for studying various aspects of human renal physiology and biochemistry.

Relationship between gamma-glutamyl transpeptidase and mean urinary alcohol levels in alcoholics while drinking and after alcohol withdrawal.

In 42 patients with alcoholic liver disease in whom daily urinary ethanol concentrations were measured for 3 months, after an abstinence of at least 1 month, serum gamma-glutamyl transpeptidase (GGT) activity was found to correlate (r = 0.69; p less than 0.0001) with mean urinary alcohol levels. The half-life of serum GGT decay in 32 patients who remained abstinent for an 8-week period was calculated to be 26 days. This prolonged half-life can result in high serum GGT levels in patients abstinent for prolonged periods, in whom serum GGT baselines before abstinence were very high. Individual variations in serum GGT levels should be interpreted in relation to continued alcohol consumption, keeping in mind the long half-life for this enzyme in these patients.

Colostral transfer of gamma glutamyl transpeptidase in calves

Serum gamma glutamyl transpeptidase (GGT) levels in blood samples taken from normal calves which bad suckled colostrum were much higher than those found in healthy adult cattle. Levels of over 60 times the normal adult level were observed. These high levels of GGT took approximately 5 weeks to decline to adult values. Calves which appeared to have not received or absorbed colostrum had GGT levels which would be considered normal in adult cattle. A calf with serum gamma globulin levels which indicated an intermediate amount of colostrum absorption had a level of GGT which was intermediate between that expected for normal adult cattle and that found in calves which had more fully absorbed colostrum. The mean GGT level observed in colostrum from 6 newly-calved cows was over 800 times the mean serum GGT level of the same 6 cows. It therefore appears most likely that GGT is concurrently absorbed with colostrum by calves and this gives rise to the very high levels seen in normal calves. Calves with very high levels of serum GGT also had raised levels of alkaline phosphatase (AP) which slowly declined but never reached normal adult levels within the 53-day period of observation. It therefore appears that high levels of both GGT and AP are achieved by calves at the time of colostrum absorption and it is concluded that clinical interpretation of serum GGT and AP levels in young calves is closely dependent upon parallel knowledge of their serum gamma globulin levels.