Lectin-affinity chromatography of serum gamma-glutamyltransferase in liver disease

The variation of the carbohydrate chain of gamma-glutamyltransferase was studied in 45 liver patients by means of lectin affinity chromatography. Five lectins were used: concanavalin A, Ricinus communis I and II, Maclura pomifera and Ulex europaeus agglutinin. The binding towards Con A was shown to be independent from the binding towards the other lectins. Parallel variations of binding results against the galactose- and fucose-recognizing lectins were obtained. In liver steatosis, the binding results were comparable to those obtained in normal patients. Cirrhosis and metastasis patients showed a decreased binding towards Con A, while the binding against the various galactose- and fucose-recognizing lectins was increased. After neuraminidase treatment, an increased affinity towards all lectins was observed. However, differences in RCA I and RCA II binding between patients and controls still persisted. Besides sialic acid, also galactose and fucose residues contribute to serum gamma-glutamyltransferase heterogeneity.     

Measurement of activation energy of gamma-glutamyltransferase as a marker for enzyme heterogeneity

In order to detect differences between various multiple forms of gamma-glutamyltransferase, the activation energy was measured. In the serum of patients with liver diseases, activation energy was measured. In the serum of patients with liver diseases, activation energy of the serum enzyme is higher than in normal individuals (41.9 +/- 1.2 vs. 38.9 +/- 1.5 kJ/mol, p less than 0.05). Neuraminidase treatment resulted in a reduction of activation energy. Various multiple forms of serum gamma-glutamyltransferase, as prepared by lectin affinity chromatography (concanavalin A, Ricinus communis I and II, wheat germ agglutinin) showed activation energy differences between binding and nonbinding fractions. Similar results were observed in seminal plasma gamma-glutamyltransferase, when patients with accessory gland infection were compared with a reference population. Our results suggest that the activation energy depends upon differences in the carbohydrate part of the enzyme. The low gamma-glutamyltransferase activation energy of tissue extracts increased significantly after butanol extraction and was then comparable with serum activation energy values, which suggests that lipid-binding is a factor in activation energy variation. In most cases, gamma-glutamyltransferase activities measured at a certain temperature can be easily converted to a corresponding activity at another temperature, but in severe liver disease significant errors may be introduced when simple temperature conversion factors are used.     

Changes in serum enzymes in moderate drinkers after an alcohol challenge

When 14 "moderate" drinkers abstained from alcohol for four weeks, the activity of gamma-glutamyltransferase (GGT; EC 2.3.2.2) in their serum showed a large decrease. Immediately after the period of abstention, an orally given ethanol challenge of 1 g/kg produced a marked increase in serum GGT at 24 h, followed by a slow decline thereafter. Aspartate amino-transferase activity in serum was significantly increased at 24 h; however, alkaline phosphate, alanine aminotransferase, and lactate dehydrogenase showed much smaller or no changes. An abnormal increase in lactate dehydrogenase isoenzyme 5 was observed in seven subjects. In some of the moderate drinkers, liver biopsies showed mild chronic hepatitis or nonspecific changes. Eight nondrinking controls showed only slight increases in serum GGT following the same alcohol challenge; results for the other enzyme tests were unchanged. We consider it probable that pre-existing liver disease affects the response to ethanol, so that greater amounts of GGT are released from hepatic tissue; alternatively, drinkers may have a higher GGT activity in this tissue as a result of enzyme induction by ethanol. The alcohol challenge test was an effective discriminator between moderate drinkers and abstainers.     

Differences in the enzymatic nature and the sugar-chain structure of gamma-glutamyl transferase between normal and carcinomatous human kidney and prostate.

The enzymatic and immunological nature, and the sugar chain structure, of gamma-glutamyl transferase (GGT) purified from tissues of benign prostatic hypertrophy (BPH), prostatic carcinoma (PCa) and renal cell carcinoma (RCa), were compared with those of the normal prostate (NP) and kidney (NK). The specific activities of GGTs in NP, NK, BPH, PCa and RCa were 78.9, 22.5, 105, 92.5 and 52.5 mU/mg protein, respectively. The molecular masses of GGTs from BPH, PCa and RCa were 72 kDa, 78 and 108 kDa, and 79 and 105 kDa, respectively. The Michaelis constants (Km), optimum pHs and the inhibition of GGT activities by several chemical compounds, revealed that the GGT from BPH, PCa and RCa was similar to that of normal GGT. Immunologically, the IgG fraction against anti-human seminal plasma GGT fused to the all of the GGTs tested. The sugar chain heterogeneities of the various GGTs, detected by the serial-lectin affinity technique, differed from one another. The sugar chain of GGT from BPH resembled the sugar chain from NP. On the contrary, the sugar chains of GGTs from PCa and RCa were markedly different from those from normal tissues. In the GGT from PCa, multi-antennary complex type sugar chains were more increased than the enzyme of NP. In general, as previously reported, the sugar chains of GGTs from carcinomatous tissues of prostate and kidney had an increased content of bisecting GlcNAc (beta 1-->4) containing complex type sugar chains. Moreover, the reductions of the biantennary complex type sugar chain with fucose linkage and the hybrid type sugar chain were obvious in the GGT from carcinomatous tissues of the prostate and kidney.     

Comparison of the peptide and saccharide moieties of gamma-glutamyltransferase isolated from neoplastic and non-neoplastic human liver tissue

gamma-Glutamyltransferase from human hepatoma and the surrounding non-neoplastic liver tissue was purified by immunoaffinity column chromatography and characterized with regard to molecular weight, isoelectric point (pI), amino acid composition, hexosamine content and affinity for various lectins. Both enzymes showed the same molecular weight (the heavy subunit 64 000; the light subunit 26 000) and pIs (3.7-3.9) on SDS-polyacrylamide gel electrophoresis and isoelectric focusing in polyacrylamide gel, respectively. After neuraminidase treatment, the pIs for both enzymes shifted to a more alkaline pH (pI 5.7). Both enzyme preparations exhibited similar amino acid compositions; however, the glucosamine content of the hepatoma enzyme was 362 nmol/mg protein, about 3-fold higher than that of the enzyme isolated protein from the non-neoplastic tissue. Binding of the two enzymes to lectins revealed that less of the hepatoma enzyme bound to Sepharose-conjugated wheat germ agglutinin, erythroagglutinating phytohemagglutinin and Ricinus communis agglutinin. These results suggest that the two enzymes possess similar peptide moieties and degree of sialylation, but differ with respect to other aspects of their heterosaccharide moieties.     

Hepatotoxicity of oral and intravenous voriconazole in relation to cytochrome P450 polymorphisms

OBJECTIVES: Voriconazole, like all other antifungals of the azole group, is potentially hepatotoxic. A large interpatient variability of liver enzyme elevations during oral or intravenous (iv) voriconazole administration is observed. This interpatient variability may be explained by differences in voriconazole metabolism because of cytochrome P450 polymorphisms. We examined the relationship between cytochrome P450 polymorphisms and hepatotoxicity in immunocompromised patients predominantly receiving oral formulations of voriconazole. METHODS: In a single institution retrospective study of 86 immunocompromised patients receiving oral (n = 74) or iv (n = 12) voriconazole, we studied the influence of cytochrome P450 polymorphisms (CYP2C19, CYP2C9 and CYP3A5) on the maximum bilirubin and serum liver enzyme levels [alkaline phosphatase, gamma-glutamyl transpeptidase (GGT), serum aspartate aminotransferase and serum alanine aminotransferase] and their respective common toxicity criteria scores (CTC-scores). RESULTS: Median serum bilirubin as well as the level of all other liver enzymes increased during voriconazole treatment. A decline in CTC-score was observed in zero (0%) to six (7%) patients; an increase in CTC-score was demonstrated in 36 (42%) to 54 (63%) patients. No statistically significant differences in maximum value or maximum increase of liver enzymes or CTC-score in relation to cytochrome P450 polymorphisms were observed. Only a trend towards higher maximum CTC-score of GGT for wild-type of CYP2C9 was observed (P = 0.046). CONCLUSIONS: No significant relationship between CYP2C9, CYP2C19 or CYP3A5 polymorphisms and serum liver enzyme levels was observed in patients treated with voriconazole.     

Solid phase measurements of antibody and lectin binding to xenogenic carbohydrate antigens

OBJECTIVES: In future pig-to-man xenotransplantation it is important to master tools that identify potentially xenogenic alphagalactose (Galalpha) antigens in the doner tissue. DESIGN AND METHODS: We have measured the binding potentials of Galalpha detecting lectins and antibodies, including a naturally occurring subfraction from human serum, to Galalpha containing neoglycoproteins and mouse laminin that were immobilized on microtiter plates. RESULTS: Galalpha reactive antibodies with similar monosaccharide specificity have distinct structural preference for sugar ligands. Laminin and neoglycoproteins were treated with alpha-galactosidase and subsequently incubated with antibodies and lectins. The enzyme treatment was more deleterious on antibody binding than on lectin binding. CONCLUSION: Antibodies and lectins may bind to different galactose determinants on the glycoproteins. Two anti-Galalpha1 antibodies that both have been raised against glycans on rabbit red blood cells may recognize Galalpha-antigens with varying specificities. Binding results obtained after digestion with alpha-galactosidase indicate that some xenoreactive Galalpha groups are not directly accessible for removal by the enzyme.     

Post-transcriptional modification of serum creatine kinase in infected intensive care patients

Low creatine kinase (CK) activities in serum are associated with high fatality rates in intensive care patients. The underlying mechanisms for this phenomenon were investigated. No correlation was found with other biochemical markers of inflammation (CRP, alpha-1 acid glycoprotein, alpha-2 macroglobulin). In the patients' serum a factor is described which is capable of increasing the activation energy of normal CK-MM, indicating molecular changes in CK-structure. This factor is likely to be an enzyme which is present in liver tissue and in fibroblasts. Similar results were obtained after in vitro treatment of normal serum samples with arylsulfatase. Furthermore, bacterial strains isolated in the serum of intensive care patients were found to alter human CK structure. In the investigated patient group, changes in CK activation energy are influenced by serum factors other than carboxypeptidase N activity.     

Lifestyle and the development of increased serum gamma-glutamyltransferase in middle-aged Japanese men

To identify the lifestyle factors responsible for increases in serum gamma-glutamyltransferase (GGT), 1014 hepatobiliary dysfunction-free (no medication for and no past history of liver disease, < or = 39 U/L of serum aspartate and/or alanine aminotransferase, and < or = 59 U/L of serum GGT) Japanese male office workers aged 35-55 years were examined annually over five successive years (average period 4.5 years, SD 1.11 years). From the Cox proportional hazards model without serum GGT at entry, significant correlates with the incidence of increased (> or = 60 U/L) serum GGT levels were the slope of body mass index (BMI), alcohol intake, cigarette smoking and coffee drinking (negative). In the model including serum GGT at entry, the slope of BMI and coffee drinking (negative) remained as significant factors for the incidence of increased serum GGT levels. From stepwise regression analyses for the slope of log serum GGT at entry, not including serum GGT in the model, significant correlates with the slope of serum GGT were, in order of relative importance, the slope of BMI, alcohol intake and coffee drinking (negative). In the model with serum GGT at entry, the slope of BMI and coffee drinking (negative) remained as statistically significant. Our results indicate that an increase in body weight is the strongest determinant for increases in serum GGT and that coffee drinking may be associated with a reduced risk of the development of increased serum GGT levels.     

γ-谷氨酰基转移酶与过量饮酒关系探讨

目的　通过观察GGT在过量饮酒患者中的活性分布,探讨GGT检测在对过量饮酒者酒精性疾病防治工作中的意义和价值。方法　过量饮酒者4 7例,采用罗氏公司生产的MODULAR全自动生化分析仪进行GGT测定。结果　4 7例过量饮酒者血清GGT含量明显高于对照组(P <0 .0 0 1) ,其中脂肪肝的患者GGT含量与非脂肪肝者有明显差异(P <0 .0 5 ) ,禁酒后血清GGT含量与禁酒前有明显差异(P <0 .0 0 1)。结论　对于过量饮酒者,血清GGT是敏感性很高的检测指标,GGT的监测有利于酒精性疾病的早期发现     

酒精性脂肪肝患者血清酶检测的临床意义

目的；检测酒精性脂肪肝（AEL）患者血清γ－谷氨酰转肽酶（GGT），丙氨酸转氨酶（ALT），天门立氨酸转氨酶（AST），碱性磷酸酶（ALP）及AST／ALT的含量，以探讨其变化与酒精性脂肪肝损伤程度的关系和早期诊断的价值。方法：AFL患者232例，采用Bayer公司生产的RA－1000型全自动生化分析仪和国产试剂盒进行测定。结果：232例患者的血清GGT，ALT，AST含量明显高于对照组（均P＜0．001），其中以GGT增高最为明显，发病年龄有年青化的趋势。结论：血清GGT检测是诊断AFL较为敏感且具有一定特异性的指标。提醒人们必须重视过量饮酒对身体健康所造成的危害。     

Monoclonal antibodies to human kidney gamma-glutamyltransferase

Eight hybridoma clones secreting large amounts of monoclonal antibodies against purified human kidney gamma-glutamyltransferase (GGT) were isolated and produced in ascites. None of them inhibits the catalytic activity of GGT. They all bind to the heavy subunit of this dimeric enzyme. Immunoblot analysis showed that these antibodies react with the catalytically active GGT. The monoclonal antibodies also recognize the heavy subunit of the human liver enzyme. This is of interest, as serum GGT is known to originate from the liver. None of the monoclonals reacts with GGTs from rat or pig kidney. After identification of epitopes specificities, the antibodies will be used for the development of immunoassays of GGT especially in human serum.     

The association between an increased level of gamma-glutamyl transferase and systolic blood pressure in diabetic subjects

Gamma-glutamyl transferase (GGT) is an enzyme present in serum and on most cell surfaces and serves as an oxidative stress marker. Although serum GGT is associated with hypertension development, little data are available on the associations between GGT and hypertension among populations with diabetes mellitus (DM). Our aim was to investigate the potential association between the changes in systolic or diastolic blood pressure (SBP/DBP) and the GGT level in type 2 DM subjects, in comparison with non-DM subjects. In 179 non-DM and 177 DM subjects, SBP/DBP, body mass index (BMI), fasting plasma glucose, serum asparate aminotransferase, alanine aminotransferase and GGT were measured at the baseline and after a 1-year period. Between these 2-measurement points, in non-DM subjects, SBP and DBP levels were significantly increased, while GGT tended to increase. In contrast, in DM subjects, the mean levels of SBP, DBP and GGT remained unchanged. Multivariate analysis revealed that in non-DM subjects the degree of increase in SBP was significantly and positively correlated to that of GGT (beta = 0.165), along with age and BMI. Likewise, the increase in DBP was correlated to that of GGT in non-DM subjects (beta = 0.170). In contrast, in DM subjects, the degree of increase in SBP was significantly correlated to that of only GGT (beta = 0.166). These results suggest that the presence of DM may attenuate the effects of GGT on DBP.     

Serum gamma-glutamyltransferase fractions in Myotonic Dystrophy type I: Differences with healthy subjects and patients with liver disease

ObjectivesElevation of serum gamma-glutamyltransferase (GGT), in absence of a clinically significant liver damage, is often found in Myotonic Dystrophy type-1 (DM1).In this study we investigated if a specific GGT fraction pattern is present in DM1.Designs and methodsWe compared total and fractional GGT values (b-, m-, s-, f-GGT) among patients with DM1 or liver disease (LD) and healthy subjects (HS).ResultsThe increase of GGT in DM1 and LD, vs HS, was mainly due to s-GGT (median: 32.7; 66.7; and 7.9 U/L, respectively), and b-GGT (8.5; 18.9; and 2.1 U/L). The subset of DM1 patients matched with HS with corresponding serum GGT showed higher b-GGT (6.0 vs 4.2 U/L).ConclusionsDM1 patients with normal total GGT values showed an alteration of the production and release in the blood of GGT fractions. Since increased s-GGT is also found in LD, a sub-clinical liver damage likely occurs in DM1 subjects apparently free of liver disease.     

γ-谷氨酰转肽酶、丙氨酸转氨酶及其比值在肝癌诊断中的价值

目的探讨 (研究 )血清γ 谷氨酰转肽酶 (GGT)和GGT与丙氨酸转氨酶 (ALT)比值在原发性肝癌诊断中的价值。方法分健康对照组、肝硬化组、原发性肝癌组 ,分别测定 3组外周血清中的GGT及ALT活性 ,并计算GGT与ALT的比值。结果与健康对照组比较 ,肝硬化组和原发性肝癌组的外周血GGT及ALT活性均显著增高 (P <0 0 5 ) ;原发性肝癌组与肝硬化组比较 ,GGT活性显著增高 ,但ALT活性无显著性差别 (P >0 0 5 ) ;三组GGT与ALT比值比较 ,健康对照组与肝硬化组之间无显著性差异 ,但二组均与原发性肝癌组存在显著性差异 (P <0 0 5 )。结论外周血清中GGT活性及GGT与ALT的比值有鉴别肝硬化及原发性肝癌的价值 ,有助于临床对原发性肝癌的诊断     

Body mass index and liver enzyme activity in serum.

The association between body mass index (BMI) and serum liver enzyme activity [gamma-glutamyltransferase (GGT), alanine aminotransferase (ALT), and aspartate aminotransferase (AST)] was studied in 3167 subjects, 2373 men and 794 women. The subjects were managers and employees, ages 18-64 years, who were examined during a program of preventive medicine. Analysis of covariance was used to compare the serum liver enzyme activities (expressed as natural logarithms) of the subjects, who were subdivided according to BMI, while also considering age, alcohol and cigarette consumption, and physical activity. In men, the percentage increase in the geometric mean of liver enzyme activity of the obese subjects (BMI greater than 30 kg/m2) compared with that of the normal subjects (BMI less than or equal to 25 kg/m2) was 47.7% (P less than 0.001) for GGT, 55.3% (P less than 0.001) for ALT, and 19.7% (P less than 0.001) for AST; in women, the increase was 63.2% (P less than 0.01) for GGT, 58.4% (P less than 0.001) for ALT, and 7.3% (P greater than 0.05) for AST. Thus, our observations demonstrate a relation between BMI and serum liver enzyme activity.     

Glycoprotein changes in non-insulin dependent diabetic rats: effect of N-benzoyl-D-phenylalanine and metformin

The effect of N-benzoyl-D-phenylalanine (NBDP) and metformin on neonatal streptozotocin (nSTZ) induced diabetes has been studied on plasma and tissue glycoproteins. In some pathological conditions, such as cancer, rheumatoid arthritis and diabetes, there is an abnormal glycosylation of acute phase serum proteins. As most serum proteins are produced in the liver, we have examined glycoprotein metabolism in diabetic condition. To induce non-insulin-dependent diabetes mellitus (NIDDM) a single dose of streptozotocin (100 mg/kg body weight) was injected into two day old rats. After 10-12 weeks, rats weighing above 150 g were selected for NIDDM model. In these rat, blood glucose and plasma glycoproteins were significantly increased whereas plasma insulin was significantly decreased. There was a significant decrease in the level of sialic acid and elevated levels of hexose, hexosamine and fucose in tissues. Oral administration of NBDP and metformin to diabetic rats decreased blood glucose and plasma glycoproteins. Plasma insulin and tissue sialic acid were increased whereas tissue concentrations of hexose, hexosamine and fucose were near normal. Our study suggests that NBDP and metformin possess a significant beneficial effect on glycoproteins in addition to their antidiabetic effect.     

The significance of serum gamma-glutamyltransferase in cardiovascular diseases.

Since early after the introduction of serum gamma-glutamyltransferase (GGT) in clinical practice as a reliable and widely employed laboratory test, epidemiological and prospective studies have repeatedly shown that this activity possesses a prognostic value for morbidity and mortality. The association is independent of possibly concomitant conditions of liver disease, and notably, a significant independent correlation of serum GGT exists with the occurrence of cardiovascular diseases (myocardial infarction, stroke). Experimental work has documented that active GGT is present in atherosclerotic plaques of coronary as well as in cerebral arteries. These findings, and the recently recognized functions of GGT in the generation of reactive oxygen species, indicate that serum GGT represents a true marker of cardiovascular diseases and underlying atherosclerosis. Further insights into potential therapeutic interest will probably be derived from studies investigating the origin of GGT activity in plaque tissue.     

Gamma glutamyl transferase

Serum gamma-glutamyl transferase (GGT) has been widely used as an index of liver dysfunction and marker of alcohol intake. The last few years have seen improvements in these areas and advances in understanding of its physiological role in counteracting oxidative stress by breaking down extracellular glutathione and making its component amino acids available to the cells. Conditions that increase serum GGT, such as obstructive liver disease, high alcohol consumption, and use of enzyme-inducing drugs, lead to increased free radical production and the threat of glutathione depletion. However, the products of the GGT reaction may themselves lead to increased free radical production, particularly in the presence of iron. There have also been important advances in the definition of the associations between serum GGT and risk of coronary heart disease, Type 2 diabetes, and stroke. People with high serum GGT have higher mortality, partly because of the association between GGT and other risk factors and partly because GGT is an independent predictor of risk. This review aims to summarize the knowledge about GGT's clinical applications, to present information on its physiological roles, consider the results of epidemiological studies, and assess how far these separate areas can be combined into an integrated view.     

The effect of physiological temperature changes on the galactose elimination capacity of the isolated perfused pig liver

Summary. The effect of temperature changes (36–40°C) on the liver function was studied in the isolated perfused pig liver. When compared with control studies no effect was observed on lactate, glucose, bile flow, ATP and energy charge, and the recovery after the changes in temperature was complete. The only significant changes observed regarded the hepatic oxygen uptake and galactose elimination capacity. The increase of 1°C resulted in an increase in galactose elimination of 6%, corresponding to a Q₁₀ of 1·98 (SEM 0·12) with an energy of activation of 48 kJ/mol (SEM 4·7). Oxygen uptake was linearly related to galactose elimination (1·75 mol for 1 mole change in galactose elimination). These results indicate that circulatory changes are unimportant within physiological temperature changes. It is concluded that temperature effects on galactose elimination are too small to warrant a correction when used as a clinical test of quantitative liver function.