Gamma glutamyl transferase

4-Hydroxynonenal increases gamma-glutamyl transpeptidase gene expression through mitogen-activated protein kinase pathways

gamma-Glutamyl transpeptidase (GGT) plays key roles in the metabolism of glutathione. Previous studies have shown that GGT expression was increased by oxidants, but the mechanism remains unclear. In the present study, the effects of 4-hydroxy-2-nonenal (HNE), an electrophilic end product of lipid peroxidation, on GGT expression were investigated in rat lung epithelial type II (L2) cells. We demonstrated that HNE increased GGT activity and mRNA content in both time- and dose-dependent manners. Actinomycin D, an RNA transcription inhibitor, blocked HNE-stimulated increase in GGT mRNA, suggesting transcriptional regulation of GGT mRNA by HNE. Of the seven GGT mRNA transcripts known to be produced from the single rat GGT gene, we found that types I, II, and V-2 were constitutively expressed in L2 cells, but only types I and V-2 were increased by HNE. PD98059 and SB203580, relatively specific inhibitors of the ERK and the p38MAPK kinase pathway, respectively, significantly attenuated HNE induction of both GGT activity and mRNA content. In contrast, studies with JNK inhibitor I, a cell-permeable peptide, indicated that JNK was not involved in the GGT induction by HNE. We also found that GGT induction by HNE could be completely blocked by a cocktail of PD98059 and SB203580, suggesting a combined effect of ERK and p38MAPK pathways in HNE-mediated GGT induction. In conclusion, our results demonstrate that HNE increased GGT expression in rat alveolar type II cells and that the induction of GGT by HNE was mediated through activation of the ERK and p38MAPK pathways.

Candidate-based proteomics in the search for biomarkers of cardiovascular disease

The key concept of proteomics (looking at many proteins at once) opens new avenues in the search for clinically useful biomarkers of disease, treatment response and ageing. As the number of proteins that can be detected in plasma or serum (the primary clinical diagnostic samples) increases towards 1000, a paradoxical decline has occurred in the number of new protein markers approved for diagnostic use in clinical laboratories. This review explores the limitations of current proteomics protein discovery platforms, and proposes an alternative approach, applicable to a range of biological/physiological problems, in which quantitative mass spectrometric methods developed for analytical chemistry are employed to measure limited sets of candidate markers in large sets of clinical samples. A set of 177 candidate biomarker proteins with reported associations to cardiovascular disease and stroke are presented as a starting point for such a 'directed proteomics' approach.

Gamma-glutamyl transpeptidase in glutathione biosynthesis

Glutathione (GSH) is the most abundant nonprotein thiol in cells and has multiple biological functions. Glutathione biosynthesis by way of the gamma-glutamyl cycle is important for maintaining GSH homeostasis and normal redox status. As the only enzyme of the cycle located on the outer surface of plasma membrane, gamma-glutamyl transpeptidase (GGT) plays key roles in GSH homeostasis by breaking down extracellular GSH and providing cysteine, the rate-limiting substrate, for intracellular de novo synthesis of GSH. GGT also initiates the metabolism of glutathione S-conjugates to mercapturic acids by transferring the gamma-glutamyl moiety to an acceptor amino acid and releasing cysteinylglycine. GGT is expressed in a tissue-, developmental phase-, and cell-specific manner that may be related to its complex gene structure. In rodents, there is a single GGT gene, and several promoters that generate different mRNA subtypes and regulate its expression. In contrast, several GGT genes have been found in humans. During oxidative stress, GGT gene expression is increased, and this is believed to constitute an adaptation to stress. Interestingly, only certain mRNA subtypes are increased, suggesting a specific mode of regulation of GGT gene expression by oxidants. Here, protocols to measure GGT activity, relative levels of total and specific GGT mRNA subtypes, and GSH concentration are described.

Viral kinetics during antiviral therapy in patients with chronic hepatitis C and persistently normal ALT levels

The aim of the present study was to compare viral kinetics between patients with chronic hepatitis C and persistently normal alanine aminotransferase (ALT) levels and those with elevated ALT levels. Kinetic parameters were derived from nonlinear, least square fitting of serum hepatitis C virus RNA quantifications collected from patients with chronic hepatitis C and persistently normal (n = 20) and elevated (n = 19) ALT levels before and during treatment with 180 mug pegylated interferon alpha-2a once weekly plus daily ribavirin. Patients with chronic hepatitis C and persistently normal ALT levels showed a trend to lower pretreatment infected cell loss (delta) (P = .13) but no differences in efficacy of blocking virus production (epsilon) and infected cell loss during treatment (mdelta) compared with patients with elevated ALT levels. Differences were significant for epsilon (P = .02) and delta (P = .04) when applying updated "healthy" levels for ALT (0.75 times and 0.63 times upper limit of normal for male and female patients, respectively). A significant reduction of the kinetic parameters epsilon, delta, and mdelta was observed in patients with elevated gamma-glutamyltranspeptidase (GGT) levels compared with patients with normal GGT levels (P = .02, P = .005, and P = .02, respectively). In conclusion, viral kinetics are similar in patients with chronic hepatitis C and persistently normal ALT levels and those with elevated ALT levels. However, in patients with elevated GGT levels, a major association with reduced efficacy of blocking virus production and lower infected cell loss was observed. These data show that virological response in patients with chronic hepatitis C is less associated with baseline ALT than with GGT levels.

Is serum gamma glutamyltransferase a marker of oxidative stress?

The primary role of cellular gamma glutamyltransferase (GGT) is to metabolize extracellular reduced glutathione (GSH), allowing for precursor amino acids to be assimilated and reutilized for intracellular GSH synthesis. Paradoxically, recent experimental studies indicate that cellular GGT may also be involved in the generation of reactive oxygen species in the presence of iron or other transition metals. Although the relationship between cellular GGT and serum GGT is not known and serum GGT activity has been commonly used as a marker for excessive alcohol consumption or liver diseases, our series of epidemiological studies consistently suggest that serum GGT within its normal range might be an early and sensitive enzyme related to oxidative stress. For example, serum and dietary antioxidant vitamins had inverse, dose-response relations to serum GGT level within its normal range, whereas dietary heme iron was positively related to serum GGT level. More importantly, serum GGT level within its normal range positively predicted F2-isoprostanes, an oxidative damage product of arachidonic acid, and fibrinogen and C-reactive protein, markers of inflammation, which were measured 5 or 15 years later, in dose-response manners. These findings suggest that strong associations of serum GGT with many cardiovascular risk factors and/or events might be explained by a mechanism related to oxidative stress. Even though studies on serum and/or cellular GGT is at a beginning stage, our epidemiological findings suggest that serum GGT might be useful in studying oxidative stress-related issues in both epidemiological and clinical settings.

Alcohol consumption, 29-y total mortality, and quality of life in men in old age

BACKGROUND

The negative effects of excessive alcohol consumption are well known, but moderate alcohol consumption is advocated for health reasons.

OBJECTIVE

We compared 29-y total mortality and quality of life in old age by alcohol consumption in midlife.

DESIGN

Cardiovascular disease risk factors and alcohol consumption were assessed in 1974 in 1808 men (aged 40-55 y) of high socioeconomic status. At baseline, the men were without signs of chronic diseases. Baseline alcohol consumption was divided as zero (n = 116), moderate (1-349 g/wk; n = 1519), and high (>349 g/wk; n = 173). Quality of life was surveyed in 2000 with the RAND-36 (SF-36) health survey (n = 1216). Mortality was retrieved from registers during the 29-y follow-up.

RESULTS

Median alcohol consumption in 1974 and in 2000 was 123 (interquartile range: 56-238) and 84 (28-168) g/wk, respectively, and was significantly correlated. Values of cardiovascular disease risk factors measured in 1974 increased with increasing alcohol consumption. During the 29-y follow-up, 499 men (27.6%) died; mortality was significantly higher among men with the highest alcohol consumption (37.6%) than in abstainers (25.0%) or in men with moderate (26.7%) consumption. Quality of life was not significantly associated with baseline alcohol consumption in responding survivors but was worst in men with high consumption when deaths during follow-up were accounted for.

CONCLUSIONS

In this male cohort of high socioeconomic status, only the highest alcohol consumption (>3 drinks/d) affected mortality, and it was associated with worse quality of life in old age. Moderate alcohol consumption in middle age offered no special benefits compared with abstinence over the long term.

The relationship between nevirapine plasma concentrations and abnormal liver function tests

Abnormal liver function tests are frequently observed in HIV-infected individuals receiving nevirapine (NVP). Here we investigate the relationship between total and unbound plasma concentrations of NVP and the liver enzymes alanine aminotransferase (ALT) and gamma-glutamyl transferase (gammaGT). HIV-infected individuals [n = 85, 22 female, 34 hepatitis C or B virus (HCV or HBV(+))] receiving NVP (200 mg bd; median duration 66 weeks, range 3-189) and two nucleoside reverse transcriptase inhibitors (NRTIs) were enrolled into this study. Blood samples were taken at C(trough) (12 hr postdose) for measurement of NVP and liver function tests (ALT and gammaGT). Plasma protein bound and unbound drug was separated using ultrafiltration and NVP concentrations quantified using HPLC-MS/MS. A linear relationship was observed between total and unbound NVP C(trough) (r(2) = 0.77, p < 0.0001). Patients with elevated ALT (>37 IU/liter; n = 31) had higher NVP unbound C(trough) than those with ALT within the normal range (median 2268 vs. 1694 ng/ml, p = 0.04) but there was no difference in total C(trough). Logistic regression revealed no association between higher NVP C(trough) and ALT elevations. Significantly higher NVP total and unbound C(trough) were observed in patients with increased gammaGT (>40 IU/liter; n = 63; total 6747 vs. 4530 ng/ml, p = 0.001; unbound 2113 vs. 1557 ng/ml, p = 0.03). Significantly higher unbound NVP C(trough) was observed in HCV/HBV(+) (median 2275 vs. 1726 ng/ml, p = 0.02) and on bivariate analysis, higher NVP C(trough) was associated with HCV/HBV coinfection (chi(2) = 4.228; p = 0.04). Overall we found no strong association between NVP concentrations and hepatotoxicity. Although in this study NVP was well tolerated in HCV/HBV coinfected patients, higher plasma concentrations were observed.

Serum gamma-glutamyltransferase and risk of metabolic syndrome and type 2 diabetes in middle-aged Japanese men

OBJECTIVE

To investigate the association between serum gamma-glutamyltransferase (GGT) and risk of metabolic syndrome and type 2 diabetes in Japanese male office workers.

RESEARCH DESIGN AND METHODS

This study included 2,957 metabolic syndrome-free men and 3,260 nondiabetic men aged 35-59 years who did not have medication for hepatitis, alanine aminotransferase (ALT) levels higher than three times the upper limit of the reference range, or a history of cardiovascular disease at study entry. Subjects were reexamined at periodic annual health examinations over a 7-year period. We used a modified National Cholesterol Education Program definition of metabolic syndrome with BMI instead of waist circumference and the revised criteria of the American Diabetes Association for type 2 diabetes.

RESULTS

With adjustment for age, family history of diabetes, BMI, alcohol intake, cigarette smoking, regular physical activity (fasting plasma glucose for the risk of type 2 diabetes), and white blood cell (WBC) count, the risk of metabolic syndrome and type 2 diabetes increased in correlation with the levels of serum GGT, ALT, aspartate aminotransferase (AST), and alkaline phosphatase. Additional adjustment for all of the other liver enzymes attenuated these associations, but serum GGT remained a significant risk factor for the risk of both metabolic syndrome and type 2 diabetes (P for trend <0.001 for both). Top one-fifth versus bottom one-fifth relative risks of metabolic syndrome and type 2 diabetes were 2.23 (95% CI 1.51-3.30) and 2.44 (1.34-4.46), respectively.

CONCLUSIONS

These results indicate that serum GGT may be an important predictor for developing metabolic syndrome and type 2 diabetes in middle-aged Japanese men.

Association between serum gamma-glutamyltransferase and dietary factors: the Coronary Artery Risk Development in Young Adults (CARDIA) Study

BACKGROUND

Diet may be involved in the strong dose-response relation of gamma-glutamyltransferase (GGT) concentration with incident diabetes.

OBJECTIVE

We examined dietary correlates of serum GGT activity.

DESIGN

Study subjects were 3146 black and white men and women aged 17-35 y in 1985-1986. A diet history was taken at years 0 and 7. Food items were classified into alcohol; breaded, battered, or canned vegetables; fruit; fruit juice; refined grain; whole grain; dairy; legumes; meat; poultry; fish; fresh or frozen vegetables; nuts; and coffee.

RESULTS

After adjustment for nondietary factors and other food groups, GGT was positively associated with alcohol consumption and meat intake. Geometric means of year 10 GGT across categories of alcohol consumption (0, 1-9, 10-19, 20-29, and > or = 30 g/d) were 17.7, 18.8, 20.4, 21.8, and 24.8 U/L (P for trend < 0.01); corresponding means across quintiles of meat intake were 19.2, 20.2, 20.5, 21.8, and 21.2 times/wk (P for trend < 0.01). GGT was inversely associated with fruit intake. Among possible meat constituents, dietary heme iron, but not saturated fat, was associated with GGT. Dietary constituents typical of plant foods showed an inverse association. In contrast, vitamin supplements were positively associated with GGT.

CONCLUSIONS

Serum GGT activity increased in a dose-response manner as alcohol and meat consumption increased and fruit consumption decreased. Heme iron contained in meats and micronutrients contained in fruits may influence GGT metabolism. However, micronutrients taken as supplements had a positive association with GGT.

Association of serum carotenoids and tocopherols with gamma-glutamyltransferase: the Cardiovascular Risk Development in Young Adults (CARDIA) Study

BACKGROUND

Our previous studies suggest that serum gamma-glutamyltransferase (GGT) activity may be related to oxidative stress, supporting findings of experimental studies. To further examine the role of GGT in relation to oxidative stress, we investigated the association between serum carotenoids and tocopherols, which have antioxidant properties, and serum GGT.

METHODS

Study participants were 3128 black and white men and women 17-35 years of age in 1985-1986. Serum carotenoids and tocopherols were measured at years 0 and 7, and serum GGT was measured at years 0 and 10.

RESULTS

Circulating concentrations of alpha-carotene, beta-carotene, and beta-cryptoxanthin inversely predicted the serum GGT concentration measured 10 years later in a dose-response manner (P for trend <0.01). Year 0 zeaxanthin/lutein was weakly inversely associated with year 10 GGT (P for trend = 0.08), and year 0 lycopene was unrelated to year 10 GGT. Adjusted geometric means of serum GGT at year 10 according to quintile of the sum of four carotenoids at year 0 (alpha-carotene, beta-carotene, beta-cryptoxanthin, and zeaxanthin/lutein) were 19.9, 19.4, 18.9, 17.8, and 17.3 U/L (P for trend <0.01). Year 0 alpha-tocopherol was also a significant inverse predictor of year 10 serum GGT concentration (P for trend = 0.03), whereas gamma-tocopherol showed an inconsistent or possibly U-shaped association. However, year 0 serum GGT did not predict serum antioxidants measured 7 years later.

CONCLUSION

Our present findings support the contention that serum GGT concentration is a marker related with oxidative stress.

Use of biomarkers for alcohol use disorders in clinical practice

BACKGROUND

Biomedical markers may provide additive objective information in screening and confirmation of acute or recent consumption, intoxication, relapse, heavy drinking, hazardous/harmful use/abuse and dependence and alcohol use related organ dysfunction (alcohol use-related disorders: AUDs).

AIMS

To review the use of biomarkers in clinical practice to detect AUDs.

FINDINGS

About one-fifth of the patients seen in clinical practice have AUDs, which offer a variety of treatment options if diagnosed. The diagnosis of AUDs relies on clinical and alcohol-related history, physical examination, questionnaires and laboratory values. No clinical available laboratory test [e.g. for acute abuse: alcohol in blood or breath; for chronic alcohol abuse: gamma-glutamyl transferase (GGT), mean corpuscular volume (MCV), carbohydrate-deficient transferrin (CDT)] is reliable enough on its own to support a diagnosis of alcohol dependence, harmful use or abuse. Sensitivities, specificities and the predictive values may vary considerably according to patient and control group characteristics (e.g. gender, age or related comorbidity). In patient groups with limited cooperation markers may be helpful when considering treatment options.

CONCLUSIONS

More research is needed to determine the value of markers (single or combined, with questionnaires) in the context of clinical decision-making algorithms in defined settings and with defined dichotomous outcome variables.

Traditional markers of excessive alcohol use

AIMS

The blood tests used traditionally as markers of excessive drinking are the liver enzymes, gamma glutamyltransferase (GGT), aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and the red blood cell volume (mean corpuscular volume: MCV). Here we review the nature of these markers' association with alcohol use, their practical application in detecting, assessing or monitoring drinking and increases in understanding of these markers in the past 10 years.

DESIGN

Articles were identified via Medline search and perusal of bibliographies.

FINDINGS

The conventional markers have imperfect sensitivity and specificity, but have an added clinical role in the detection of complications of drinking, and of comorbid conditions that may increase risk of drinking. GGT may in part be a marker of the oxidative stress associated with ethanol metabolism. Markers are more likely to be elevated in those aged more than 30 years and in regular drinkers with a longer drinking history. The markers may be useful in opportunistic case finding, in motivating patients to change drinking and in monitoring treatment response. Increased prevalence of obesity and hepatitis C must be considered in interpretation of liver enzyme results. The liver enzymes are prognostic indicators for several medical conditions and for mortality.

CONCLUSIONS

These conventional tests are widely available and relatively inexpensive. While having limited sensitivity and specificity in detection of excessive drinking, they also provide valuable data on complications of drinking, comorbid conditions that may be affected by drinking and, in some cases, prognosis.

Pathogenesis and management of alcoholic hepatitis

Alcoholic hepatitis is a potentially life-threatening complication of alcoholic abuse, typically presenting with symptoms and signs of hepatitis in the presence of an alcohol use disorder. The definitive diagnosis requires liver biopsy, but this is not generally required. The pathogenesis is uncertain, but relevant factors include metabolism of alcohol to toxic products, oxidant stress, acetaldehyde adducts, the action of endotoxin on Kupffer cells, and impaired hepatic regeneration. Mild alcoholic hepatitis recovers with abstinence and the long-term prognosis is determined by the underlying disorder of alcohol use. Severe alcoholic hepatitis is recognized by a Maddrey discriminant function >32 and is associated with a short-term mortality rate of almost 50%. Primary therapy is abstinence from alcohol and supportive care. Corticosteroids have been shown to be beneficial in a subset of severely ill patients with concomitant hepatic encephalopathy, but their use remains controversial. Pentoxifylline has been shown in one study to improve short-term survival rates. Other pharmacological interventions, including colchicine, propylthiouracil, calcium channel antagonists, and insulin with glucagon infusions, have not been proven to be beneficial. Nutritional supplementation with available high-calorie, high-protein diets is beneficial, but does not improve mortality. Orthotopic liver transplantation is not indicated for patients presenting with alcoholic hepatitis who have been drinking until the time of admission, but may be considered in those who achieve stable abstinence if liver function fails to recover.

Glutathione

Glutathione (GSH) is an ubiquitous thiol-containing tripeptide that plays a key role in cell biology. It modulates cell response to redox changes associated with the reactive oxygen species, detoxifies the metabolites of drugs; regulates gene expression and apoptosis, and is involved in the transmembrane transport of organic solutes. Polymorphism has been observed in key enzymes of GSH metabolism and some alleles have been associated with an impaired redox buffer system downsteam diseases, and susceptibility to ischaemia. These varied activities make GSH an attractive target for a more reductionist approach to the prevention and management of many conditions of interest to surgeons.

Heterogeneity in gamma-glutamyltransferase mRNA expression and glycan structures. Search for tumor-specific variants in human liver metastases and colon carcinoma cells

The enzyme gamma-glutamyltransferase (GGT) is frequently overexpressed in cancer cells and tissues and has significant utility as a cancer marker. Significant heterogeneity of the enzyme has been described due to both transcriptional and post-translational variations. For possible use in diagnosis and follow-up of patients with colorectal cancer, a search was performed for specific mRNA subtypes and glycan structures of the enzyme in liver metastases. We found no differences in the distribution of three GGT mRNA subtypes (fetal liver, HepG2, placenta) in metastatic tissue and normal liver tissue. Furthermore, the three subtypes were present in leukocytes isolated from both normal individuals and cancer patients. Two colon carcinoma cell lines (Colo 205 and HCC 2998) also displayed the three forms and no consistent changes in mRNA composition were noted after butyrate-induced differentiation of the cells. Thus, neither of the GGT mRNA subforms appear to be tumor-specific, although some qualitative and quantitative variations were noted. Two distinct glycosylation features were detected for GGT in metastatic tissue in contrast to normal liver GGT; an extreme sialic acid heterogeneity and a significant increase in beta1,6GlcNAc branching. The GGT glycans from the two colon carcinoma cell lines also possessed these features. As butyrate treatment of the cells resulted in an increased sialic acid content and a reduced beta1,6GlcNAc branching, the described carbohydrate structures appear to be part of a tumor-related pattern. We were, however, unable to identify such GGT isoforms in serum from patients with advanced colorectal cancer. This indicates that their usefulness in diagnostic use is doubtful.

Kava: herbal panacea or liver poison?

Following reports of liver toxicity, including liver failure, associated with extracts from the Pacific islands plant kava (Piper methysticum), these have been banned from sale as a herbal anxiolytic in many Western countries, to the detriment of Pacific island economies. Pacific Islanders have used kava extensively for centuries, without recognised liver toxicity. However, the population is small, and there has been no systematic evaluation of possible liver damage. For both economic and public health reasons, it is important to determine if kava is inherently hepatotoxic, and what the mechanisms of toxicity are. Such research could lead to safer kava extracts for sale in Western countries, or identification of a subpopulation who should not consume kava.

Effect of vitamin E on glutathione-dependent enzymes

Reactive oxygen species and various electrophiles are involved in the etiology of diseases varying from cancer to cardiovascular and pulmonary disorders. The human body is protected against damaging effects of these compounds by a wide variety of systems. An important line of defense is formed by antioxidants. Vitamin E (consisting of various forms of tocopherols and tocotrienols) is an important fat-soluble, chain-breaking antioxidant. Besides working as an antioxidant, this compound possesses other functions with possible physiological relevance. The glutathione-dependent enzymes form another line of defense. Two important enzymes in this class are the free radical reductase and glutathione S-transferases (GSTs). The GSTs are a family of phase II detoxification enzymes. They can catalyze glutathione conjugation with various electrophiles. In most cases the electrophiles are detoxified by this conjugation, but in some cases the electrophiles are activated. Antioxidants do not act in isolation but form an intricate network. It is, for instance, known that vitamin E, together with glutathione (GSH) and a membrane-bound heat labile GSH-dependent factor, presumably an enzyme, can prevent damaging effects of reactive oxygen species on polyunsaturated fatty acids in biomembranes (lipid peroxidation). This manuscript reviews the interaction between the two defense systems, vitamin E and glutathione-dependent enzymes. On the simplest level, antioxidants such as vitamin E have protective effects on glutathione-dependent enzymes; however, we will see that reality is somewhat more complicated.

Nitrogen-source regulation of yeast gamma-glutamyl transpeptidase synthesis involves the regulatory network including the GATA zinc-finger factors Gln3, Nil1/Gat1 and Gzf3

In Saccharomyces cerevisiae, the CIS2 gene encodes gamma-glutamyl transpeptidase (gamma-GT; EC 2.3.2.2), the main GSH-degrading enzyme. The promoter region of CIS2 contains one stress-response element (CCCCT) and eight GAT(T/A)A core sequences, probably involved in nitrogen-regulated transcription. We show in the present study that expression of CIS2 is indeed regulated according to the nature of the nitrogen source. Expression is highest in cells growing on a poor nitrogen source such as urea. Under these conditions, the GATA zinc-finger transcription factors Nil1 and Gln3 are both required for CIS2 expression, Nil1 appearing as the more important factor. We further show that Gzf3, another GATA zinc-finger protein, acts as a negative regulator in nitrogen-source control of CIS2 expression. During growth on a preferred nitrogen source like NH(4)(+), CIS2 expression is repressed through a mechanism involving (at least) the Gln3-binding protein Ure2/GdhCR. Induction of CIS2 expression during nitrogen starvation is dependent on Gln3 and Nil1. Furthermore, rapamycin causes similar CIS2 activation, indicating that the target of rapamycin signalling pathway controls CIS2 expression via Gln3 and Nil1 in nitrogen-starved cells. Finally, our results show that CIS2 expression is induced mainly by nitrogen starvation but apparently not by other types of stress.

The influence of gingival margin recession on loss of clinical attachment in alcohol-dependent patients without medical disorders

BACKGROUND

The objective of this study was to examine the effects of alcohol and cocaine misuse on periodontal status in a group of alcohol-dependent patients.

METHODS

Forty verified alcoholics, either exclusively (n = 10) or with cocaine abuse (n = 30), and a matched comparison group of 25 non-alcoholic subjects, 14 of whom abused cocaine, were entered in the study. All subjects were free from systemic illnesses. Blood levels of gamma glutamyl transpeptidase (GGTP), a liver enzyme indicator of alcohol drinking, were determined. A comprehensive periodontal examination was performed on 6 sites per tooth. The gingival index (GI) and plaque index (PI) were recorded. Attachment levels (AL) were computed as probing depth (PD) plus gingival margin level (GM).

RESULTS

No statistically significant differences were noted between the groups for average AL, PD, GM, GI, and PI. In alcoholics, Pearson correlation showed a positive association between GGTP levels and loss of periodontal attachment (P<0.05). A series of regression analyses predicting AL from selected periodontal and demographic factors showed that alcoholics manifest AL by greater increases in GM than non-alcoholics (P<0.07). Severe alcohol use as measured by GGTP >51 iu/l worsens PI (P<0.07), which adversely impacts GM, GI, PD, and ultimately AL. No significant associations were found between cocaine use and AL.

CONCLUSIONS

The results suggest that persistent alcohol abuse increases periodontitis development by heightening the loss of attachment through recession of gingival margins.

Entacapone-induced hepatotoxicity and hepatic dysfunction

We describe 2 patients with Parkinson's disease who developed hepatotoxicity associated with the use of entacapone, a novel, mainly peripheral acting inhibitor of catechol-D-methyltransferase. Hepatotoxicity resolved rapidly with discontinuation of the drug. Analysis of causality in a further case initially linked to entacapone exposure was confounded by conflicting serial adverse reaction reports.

Genetic Covariation between Serum γ-Glutamyltransferase Activity and Cardiovascular Risk Factors

Background: Several studies have shown that variation in serum γ-glutamyltransferase (GGT) in the population is associated with risk of death or development of cardiovascular disease, type 2 diabetes, stroke, or hypertension. This association is only partly explained by associations between GGT and recognized risk factors. Our aim was to estimate the relative importance of genetic and environmental sources of variation in GGT as well as genetic and environmental sources of covariation between GGT and other liver enzymes and markers of cardiovascular risk in adult twin pairs.

Methods: We recruited 1134 men and 2241 women through the Australian Twin Registry. Data were collected through mailed questionnaires, telephone interviews, and by analysis of blood samples. Sources of variation in GGT, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) and of covariation between GGT and cardiovascular risk factors were assessed by maximum-likelihood model-fitting.

Results: Serum GGT, ALT, and AST were affected by additive genetic and nonshared environmental factors, with heritabilities estimated at 0.52, 0.48, and 0.32, respectively. One-half of the genetic variance in GGT was shared with ALT, AST, or both. There were highly significant correlations between GGT and body mass index; serum lipids, lipoproteins, glucose, and insulin; and blood pressure. These correlations were more attributable to genes that affect both GGT and known cardiovascular risk factors than to environmental factors.

Conclusions: Variation in serum enzymes that reflect liver function showed significant genetic effects, and there was evidence that both genetic and environmental factors that affect these enzymes can also affect cardiovascular risk.

Glutathione catabolism as a signaling mechanism

Glutathione (GSH) is the main intracellular thiol antioxidant, and as such participates in a number of cellular antitoxic and defensive functions. Nevertheless, non-antioxidant functions of GSH have also been described, e.g. in modulation of cell proliferation and immune response. Recent studies from our and other laboratories have provided evidence for a third functional aspect of GSH, i.e. the prooxidant roles played by molecular species originating during its catabolism by the membrane ectoenzyme gamma-glutamyl transpeptidase (GGT). The reduction of metal ions effected by GSH catabolites is capable to induce redox cycling processes leading to the production of reactive oxygen species (superoxide, hydrogen peroxide), as well as of other free radicals. Through the action of these reactive compounds, GSH catabolism can ultimately lead to oxidative modifications on a variety of molecular targets, involving oxidation and/or S-thiolation of protein thiol groups in the first place. Modulating effects of this kind have been observed on several important, redox-sensitive components of the signal transduction chains, such as cell surface receptors, protein phosphatase activities and transcription factors. Against this background, the prooxidant reactions induced by GSH catabolism appear to represent a novel, as yet unrecognized mechanism for modulation of cellular signal transduction.

A comparison of five questionnaires to assess alcohol consumption in a Mediterranean population

OBJECTIVE

To evaluate the reliability of alcohol consumption measured by five different dietary methods in the Catalan Nutrition Survey (1992-1993).

DESIGN

The different questionnaires used were: (1) two 7-day food records, (2) five items addressing alcoholic beverages in a 76-item food-frequency questionnaire, (3) a 1-week recall of 13 alcoholic beverages, (4) a 13-item alcoholic beverages frequency questionnaire and (5) two 24-hour recalls.

SUBJECTS

Ninety-three of the 120 adults (aged 20 to 70 years) initially recruited completed the questionnaires and provided a peripheral blood sample.

RESULTS

Mean daily alcohol intakes as assessed by the questionnaires were very similar. Beer was the alcoholic beverage most frequently consumed, followed by wine and liquor. Eighty-two per cent of the study population consumed less than 20 g of alcohol per day. No biochemical parameters were significantly correlated with alcohol intake estimated from the questionnaires.

CONCLUSIONS

We found a satisfactory level of reproducibility and validity in the pattern of alcohol consumption across different levels and types of alcoholic beverage intake. We also found that the self-administered 13-item questionnaire and the 1-week recall were the best techniques to measure moderate or low alcohol consumption, suggesting that the two methods are the most suitable to assess overall alcohol intake in the general population.

gamma-Glutamyl transpeptidase expression in Ewing's sarcoma cells: up-regulation by interferons

The genetic hallmark of Ewing's sarcoma family of tumours (ET) is the presence of the translocation t(11;22)(q24;q12), which creates the ET fusion gene, leading to cellular transformation. Five human gamma-glutamyl transpeptidase (gamma-GT) genes are located near the chromosomal translocation in ET. gamma-GT is a major enzyme involved in glutathione homoeostasis. Five human cell lines representative of primary or metastatic tumours were investigated to study whether gamma-GT alterations could occur at the chromosomal breaks and rearrangements in ET. As shown by enzymic assays and FACS analyses, all ET cell lines consistently expressed a functional gamma-GT which however did not discriminate steps of ET progression. As shown previously [Sancéau, Hiscott, Delattre and Wietzerbin (2000) Oncogene 19, 3372-3383], ET cells respond to the antiproliferative effects of interferons (IFNs) type I (alpha and beta) and to a much less degree to IFN type II (gamma). IFN-alpha and -beta arrested cells in the S-phase of the cell cycle. We found an enhancement of gamma-GT mRNA species with IFN-alpha and -beta by reverse transcriptase-PCR analyses. This is reflected by up-regulation of gamma-GT protein, which coincides with the increase in gamma-GT-specific enzymic activity. Similarly, IFNs up-regulate the levels of gamma-GT in another IFN-responsive B cell line. Whether this up-regulation of gamma-GT by IFNs is of physiological relevance to cell behaviour remains to be studied.

Reanalysis of the involvement of gamma-glutamyl transpeptidase in the cell activation process

The inhibitor of gamma-glutamyl transpeptidase (gamma-GT) acivicin modulates cellular responses including growth, myeloid maturation and apoptosis. Whether these effects result from the inhibition of gamma-GT enzyme activity remains unclear. We compared the cellular effects of acivicin against a more potent and specific inhibitor of gamma-GT (L-2-amino-4-boronobutanoic acid (L-ABBA)) in gamma-GT-negative (B lymphoblastoid Ramos) and gamma-GT-positive (myelomonocytic HL-60, gamma-GT-transfected Ramos) cell lines. Under non-oxidative stress conditions, acivicin-induced cell growth arrest, apoptosis and macrophage maturation occurred independent of gamma-GT while L-ABBA did not influence any of these processes. Acivicin triggered tyrosine phosphorylation and increased nuclear factor kappaB activity. Further insight into the role of gamma-GT in cellular processes is needed.