Gamma-glutamyltransferase as a risk factor for cardiovascular disease mortality: an epidemiological investigation in a cohort of 163,944 Austrian adults

Secular trends in cardiovascular risk factors: an age-period cohort analysis of 698,954 health examinations in 181,350 Austrian men and women

OBJECTIVES

It is well established that morbidity and mortality patterns in cardiovascular diseases vary strongly over time, yet the determinants of such trends remain poorly understood. To assess the potential contribution of secular or cross-generation patterns, we evaluated birth cohort-related trends across the 20th century of risk factors in a large database of Austrian men and women.

SUBJECTS AND SETTING

Trends in risk factors were investigated for 181,350 adults aged 20-79 years born between 1905 and 1975 undergoing 698,954 health examinations between 1985 and 2005 as participants of the Vorarlberg Health Monitoring and Promotion Programme.

RESULTS

There was clear evidence of cohort-related shifts in all risk factors. Total serum cholesterol and triglyceride declined markedly, particularly in the youngest cohorts, as did systolic and diastolic blood pressure in both men and women. By contrast, fasting glucose showed a strong rising tendency in both sexes and at all ages, most markedly in young males. Average glucose levels were between 4 and 15 mg dL(-1) higher in individuals at the same age born 20 years later. In males, body weight expressed in kg m(-2) (body mass index) was increasing as well; however, in women, patterns were most marked at the 90th percentile.

CONCLUSION

These findings provide strong evidence of population wide secular shifts and suggest that in addition to period influences, most probably through treatment intervention and lifestyle change, determinants across the life-course are programming shifts from childhood onwards.

Gamma glutamyltransferase and long-term survival: is it just the liver?

BACKGROUND

Increased gamma glutamyltransferase (GGT) is associated with cardiovascular disease. To date, however, few studies with sufficient sample size and follow-up have investigated the association of GGT with all-cause mortality.

METHODS

The relation of GGT to the risk of death was examined in a cohort of 283 438 first attendants (inpatients or outpatients) of the Vienna General Hospital with request for GGT analysis as part of a routine screening panel and was monitored for up to 13 years. To evaluate GGT as a predictor, Cox proportional hazards models were calculated, which were adjusted for age and sex.

RESULTS

In both men and women, GGT above the reference category (GGT > or = 9 U/L in women, > or = 14 U/L in men) was significantly (P <0.001) associated with all-cause, cancer, hepatobiliary, and vascular mortalities. Hazard ratios (HRs) for men and women were similar in all categories. Among patients who presented with GGT above the reference category, those younger than 30 years had higher all-cause mortality rates than did older individuals (HR 1.5-3.3 vs HR 1-1.3 >80 years, respectively).

CONCLUSIONS

GGT is associated with mortality in both men and women, especially in patients younger than 30 years, and even high-normal GGT is a risk factor for all-cause mortality.

Update on advances in atherothrombosis

The study of atherothrombosis is a rapidly evolving field, and significant progress was achieved in various aspects of the disease during the past year. In the area of diagnostic imaging, MRI and multidetector CT were actively used to evaluate the characteristics of the arterial wall, including calcified and noncalcified lesions, and both in the coronary and extracoronary vascular territories. There was also extensive research into the application of imaging modalities to visualize cellular or molecular disease processes, known as molecular imaging. Considerable efforts were devoted to the identification of novel biomarkers that reflect different components of atherothrombosis, namely inflammation, thrombogenicity, oxidative stress and reparative ability, predicting the presence of early disease or the risk of clinical events. In the therapeutic arena, substantial evidence accumulated on the beneficial effects of several pharmacologic agents, most significantly statins. Finally, important advances were also made in the understanding of the roles of immunity and neovascularization in atherogenesis, including the development and progression of disease at different stages. Awareness of these recent advances and new lines of active research is fundamental for health professionals involved in the care of patients with atherothrombosis. In this Review we present an overview of data in these areas.

Gamma glutamyl transferase and metabolic syndrome, cardiovascular disease, and mortality risk: the Framingham Heart Study

OBJECTIVE

To determine whether serum gamma-glutamyl transferase (GGT) predicts cardiovascular disease (CVD) morbidity and mortality, accounting for temporal changes in known CVD risk factors and C-reactive protein (CRP).

METHODS AND RESULTS

In 3451 Framingham Study participants (mean age 44 years, 52% women) we examined the relations of GGT with CVD risk factors, and prospectively determined the risk of new-onset metabolic syndrome, incident CVD, and death. GGT was positively associated with body mass index, blood pressure, LDL cholesterol, triglycerides, and blood glucose in cross-sectional analysis (P<0.005). On follow-up (mean 19 years), 968 participants developed metabolic syndrome, 535 developed incident CVD, and 362 died. The risk of metabolic syndrome increased with higher GGT (multivariable-adjusted hazard ratio [HR] per SD increment log-GGT, 1.26 [95%CI; 1.18 to 1.35]). Adjusting for established CVD risk factors (as time-dependent covariates updated quadriennially) and baseline CRP, a 1-SD increase in log-GGT conferred a 13% increase in CVD risk (P=0.007) and 26% increased risk of death (P<0.001). Individuals in the highest GGT quartile experienced a 67% increase in CVD incidence (multivariable-adjusted HR 1.67, 95%CI; 1.25 to 2.22).

CONCLUSIONS

An increase in serum GGT predicts onset of metabolic syndrome, incident CVD, and death suggesting that GGT is a marker of metabolic and cardiovascular risk.

gamma-Glutamyltransferase predicts cardiovascular death among Japanese women

The clinical importance of gamma-glutamyltransferase (GGT) has recently been debated. Although some studies have suggested that the relationship between GGT and cardiovascular disease (CVD) mortality is independent of alcohol consumption, to our knowledge no studies have reported the relationship between GGT and CVD mortality in never-drinker subgroups. Since Japanese women are known to have a lower prevalence of alcohol consumption, we examined whether GGT predicts CVD mortality in never-drinkers. We followed 2724 Japanese men and 4122 Japanese women without prior CVD or liver dysfunction for 9.6 years and observed 83 and 82 CVD deaths, respectively. Current alcohol drinkers comprised 59% of men and 7% of women. Among women, the multiple adjusted hazard ratio (HR) for CVD mortality compared with the reference group (GGT: 1-12 U/L) was 2.88 (95% confidence interval (CI), 1.14-7.28) for the elevated group (GGT>or=50 U/L). This positive relationship was unchanged in the never-drinkers subgroup (HR for log-transformed continuous GGT, 1.62 (95% CI, 1.11-2.37)). No significant relationships were observed in men. GGT displays a strong positive association with CVD mortality among Japanese women, for whom the prevalence of ever-drinkers is very low. Exploring the significance and biological mechanisms of GGT might provide useful insights into CVD prevention.

Non-alcoholic fatty liver disease and increased risk of cardiovascular disease

Non-alcoholic fatty liver disease (NAFLD) is present in up to one-third of the general population and in the majority of patients with cardio-metabolic risk factors such as abdominal obesity, type 2 diabetes and other components of the metabolic syndrome (MetS). Currently, the importance of NAFLD and its relationship to the MetS is increasingly recognized, and this has stimulated an interest in the possible role of NAFLD in the development of cardiovascular disease (CVD). Indeed, the impact of NAFLD on CVD risk deserves particular attention in view of the implications for screening/surveillance strategies in this growing number of patients. Recent evidence suggests that the severity of liver histology in NAFLD patients is closely associated with markers of early atherosclerosis such as greater carotid artery wall thickness and lower endothelial flow-mediated vasodilation independently of classical risk factors and components of the MetS. Moreover, NAFLD is associated with greater overall mortality and independently predicts the risk of future CVD events. Overall, the current body of evidence strongly suggests that NAFLD is likely to be associated with increased CVD risk, and raises the possibility that NAFLD may be not only a marker but also an early mediator of atherosclerosis.

gamma-Glutamyltransferase is a promising biomarker for cardiovascular risk

Oxidative stress plays a crucial role in a variety of clinical settings of atherogenesis, and mediates many pathways linked to atherosclerosis and inflammation. gamma-Glutamyltransferase (GGT), an enzyme responsible for the extracellular catabolism of antioxidant glutathione, may directly take part in atherogenesis and evolve as a potential biochemical risk indicator of cardiovascular morbidity and mortality. Classically, GGT has been thought of as a diagnostic tool for hepatobiliary disorders and alcohol abuse. More recently, growing body of data points out that serum GGT levels can aid detection of individuals at high risk for subsequent cardiovascular events, and thus have an application in primary and secondary prevention of cardiovascular disease. Although several investigations have shown that some drugs are effective in decreasing both serum lipids and GGT, and concomitantly the incidence of subsequent cardiovascular events; large-scale randomized trials are required to explore this impact directly. Based on current experimental and epidemiological studies, we postulate here that GGT present in the serum, even within its laboratory reference intervals regarded as physiologically normal, is a promising biomarker for cardiovascular risk.

Serum gamma glutamyltransferase as a marker of metabolic syndrome and coronary disease likelihood in nondiabetic middle-aged and elderly adults

The role of serum gamma glutamyltransferase (GGT) activity as a cardiovascular risk marker was studied basically cross-sectionally. After appropriate exclusions, 754 men and 802 women were available for analysis who were followed up briefly yielding only 16% of overall cases of coronary heart disease (CHD). GGT activity was measured kinetically. In multivariate analysis across 12 variables, waist circumference, sex, complement C3, moderate alcohol intake and uric acid were significant independent covariates of serum GGT. By analyzing the sample in tertiles, doubling in GGT activity was found associated with a rise of 74% in metabolic syndrome (MS) likelihood-independent of salient confounders (P < 0.001). This association was mediated by waist circumference. Individuals in the top versus the bottom tertile exhibited an odds ratio for CHD likelihood of 1.81 (95% CI 1.09; 3.02)-independent of age, sex, total cholesterol, systolic blood pressure, impaired fasting glucose, smoking status, alcohol usage and, notably, of waist circumference. This indicated that a doubling in serum GGT activity corresponded to a 45% excess in CHD likelihood, after adjustment for standard risk factors. In conclusion, waist circumference is a major determinant of serum GGT activity among Turkish adults. Doubling in activity is associated with a (largely waist girth mediated) rise by over one-half in the multiadjusted MS likelihood, and by nearly one-half in the CHD likelihood, independent of waist girth and major risk factors.

Gamma-(monophenyl)phosphono glutamate analogues as mechanism-based inhibitors of gamma-glutamyl transpeptidase

Gamma-glutamyl transpeptidase (GGT, EC 2.3.2.2) catalyzes the hydrolysis and transpeptidation of extracellular glutathione and plays a central role in glutathione homeostasis. We report here the synthesis and evaluation of a series of hydrolytically stable gamma-(monophenyl)phosphono glutamate analogues with varying electron-withdrawing para substituents on the leaving group phenols as mechanism-based and transition-state analogue inhibitors of Escherichia coli and human GGTs. The monophenyl phosphonates caused time-dependent and irreversible inhibition of both the E. coli and human enzymes probably by phosphonylating the catalytic Thr residue of the enzyme. The inactivation rate of E. coli GGT was highly dependent on the leaving group ability of phenols with electron-withdrawing groups substantially accelerating the rate (Brønsted betalg = -1.4), whereas the inactivation of human GGT was rather slow and almost independent on the nature of the leaving group. The inhibition potency and profiles of the phosphonate analogues were compared to those of acivicin, a classical inhibitor of GGT, suggesting that the phosphonate-based glutamate analogues served as a promising candidate for potent and selective GGT inhibitors.