Biliary excretion of gamma-glutamyltransferase. Selective enhancement by acute ethanol administration

The association between an energy-adjusted dietary inflammatory index and inflammation in rural and urban Black South Africans

OBJECTIVE

To quantify the inflammatory potential of the diet of rural and urban Black South Africans using an adapted energy-adjusted dietary inflammatory index (AE-DII) and to investigate its relationship with inflammatory and cardio-metabolic disease risk markers. Dietary inflammatory potential has not been investigated in African populations.

DESIGN

Cross-sectional investigation.

SETTING

Rural and urban sites in the North West province of South Africa.

PARTICIPANTS

1885 randomly selected, apparently healthy Black South Africans older than 30 years.

RESULTS

AE-DII scores ranged from -3·71 to +5·08 with a mean of +0·37. AE-DII scores were significantly higher in men (0·47 ± 1·19) than in women (0·32 ± 1·29), and in rural (0·55 ± 1·29) than urban participants (0·21 ± 1·19). Apart from its dietary constituents, AE-DII scores are primarily associated with age, rural-urban status and education. Contrary to the literature, alcohol consumption was positively associated with AE-DII scores. Of the four tested inflammatory and thirteen cardio-metabolic biomarkers, the AE-DII was only significantly negatively associated with albumin and HDL cholesterol, and positively with waist circumference and fasting glucose, upon full adjustment.

CONCLUSION

Rural men consumed the most pro-inflammatory diet, and urban women the least pro-inflammatory diet. The diet of the participants was not overtly pro- or anti-inflammatory and was not associated with measured inflammatory markers. The inflammatory potential of alcohol at different levels of intake requires further research. Understanding dietary inflammatory potential in the context of food insecurity, unhealthy lifestyle practices and lack of dietary variety remains limited.

Alcoholic Liver Disease: Alcohol Metabolism, Cascade of Molecular Mechanisms, Cellular Targets, and Clinical Aspects

Alcoholic liver disease is the result of cascade events, which clinically first lead to alcoholic fatty liver, and then mostly via alcoholic steatohepatitis or alcoholic hepatitis potentially to cirrhosis and hepatocellular carcinoma. Pathogenetic events are linked to the metabolism of ethanol and acetaldehyde as its first oxidation product generated via hepatic alcohol dehydrogenase (ADH) and the microsomal ethanol-oxidizing system (MEOS), which depends on cytochrome P450 2E1 (CYP 2E1), and is inducible by chronic alcohol use. MEOS induction accelerates the metabolism of ethanol to acetaldehyde that facilitates organ injury including the liver, and it produces via CYP 2E1 many reactive oxygen species (ROS) such as ethoxy radical, hydroxyethyl radical, acetyl radical, singlet radical, superoxide radical, hydrogen peroxide, hydroxyl radical, alkoxyl radical, and peroxyl radical. These attack hepatocytes, Kupffer cells, stellate cells, and liver sinusoidal endothelial cells, and their signaling mediators such as interleukins, interferons, and growth factors, help to initiate liver injury including fibrosis and cirrhosis in susceptible individuals with specific risk factors. Through CYP 2E1-dependent ROS, more evidence is emerging that alcohol generates lipid peroxides and modifies the intestinal microbiome, thereby stimulating actions of endotoxins produced by intestinal bacteria; lipid peroxides and endotoxins are potential causes that are involved in alcoholic liver injury. Alcohol modifies SIRT1 (Sirtuin-1; derived from Silent mating type Information Regulation) and SIRT2, and most importantly, the innate and adapted immune systems, which may explain the individual differences of injury susceptibility. Metabolic pathways are also influenced by circadian rhythms, specific conditions known from living organisms including plants. Open for discussion is a 5-hit working hypothesis, attempting to define key elements involved in injury progression. In essence, although abundant biochemical mechanisms are proposed for the initiation and perpetuation of liver injury, patients with an alcohol problem benefit from permanent alcohol abstinence alone.

Serum alanine aminotransferase independently correlates with intrahepatic triglyceride contents in obese subjects

BACKGROUND AND AIM

Liver enzymes including serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyltransferase (GGT) are well recognized as surrogate makers reflecting non-alcoholic fatty liver disease (NAFLD). However, the associations of serum ALT, AST and GGT with hepatic lipid contents are not well established. The aim of this study was to investigate the relationship between liver enzymes and intrahepatic triglyceride (IHTG) contents, and explore the feasibility in using liver enzymes to reflect accumulation of IHTG in obese subjects.

METHODS

A cross-sectional analysis was conducted in 475 obese adults aged 40-65 years. Anthropometric parameters and blood biochemical indexes including liver enzymes, glucose and lipid profiles were measured. The liver triglyceride contents of subjects were determined by (1)H-MRS.

RESULTS

Serum ALT, AST and GGT were positively correlated with IHTG contents (p < 0.01). Serum ALT, AST and GGT levels at the highest quartile of IHTG contents were significantly elevated as compared with those in the lowest quartile (p < 0.01). Multivariate linear regression analysis demonstrated that serum ALT, but not AST or GGT was independently associated with IHTG contents. By logistic regression analysis, the odds ratio for higher IHTG contents was increased by 1.464 times/1 SD increase in serum ALT level after adjusting for multiple confounding factors [OR (95% CI) 2.464 (1.584-3.834)]. However, these relationships could not be observed between serum AST or GGT with IHTG contents.

CONCLUSIONS

Serum ALT level is independently correlated with the hepatic triglyceride contents in obese subjects and more appropriate to be used as a predictor for the degree of NAFLD rather than AST and GGT.

Association of carbohydrate-deficient transferrin (CDT) and gamma-glutamyl-transferase (GGT) with serum lipid profile in the Finnish population

BACKGROUND

Moderate consumption of alcohol may reduce mortality from vascular diseases. The beneficial effects of alcohol may partly be mediated by its effects on lipoprotein metabolism. We studied the connection between alcohol consumption and the serum lipid profile from a well-documented national health program study.

METHODS AND RESULTS

Carbohydrate-deficient transferrin (CDT) and gamma-glutamyl-transferase (GGT) were used as biochemical markers for alcohol consumption. The laboratory analyses were carried out on 5675 subjects (3097 males and 2578 females). The subjects were divided into quartiles on the basis of CDT or GGT value. The highest CDT quartile and the lowest GGT quartile seemed to be associated with a favorable lipid profile and the lowest CDT quartile and the highest GGT quartile were associated with an unfavorable lipid profile. Serum high density lipoprotein (HDL) cholesterol values were significantly higher and triglycerides lower with increasing serum CDT concentrations for both men and women. Increasing serum GGT was associated with higher serum total cholesterol and higher triglycerides in both men and women and lower HDL cholesterol in men.

CONCLUSIONS

CDT and GGT seem to detect different populations of subjects in regard to lipid metabolism. These observations may lead to a better understanding of the effects of alcohol consumption on lipids as well as mechanisms behind favorable and detrimental effects of alcohol on vascular diseases.

CONDENSED ABSTRACT

Carbohydrate-deficient transferrin (CDT) and gamma-glutamyl-transferase (GGT) were used as biochemical markers for alcohol consumption. A total of 3097 males and 2578 females were divided into quartiles on the basis of their CDT or GGT values. The highest CDT quartiles had higher HDL and lower triglycerides, whereas the highest GGT quartiles appeared to be associated with higher total cholesterol and triglycerides in both genders and lower HDL in men. CDT and GGT seem to detect different populations of subjects in regard to lipid metabolism. These observations may have important clinical and public health implications.

Carbohydrate-deficient transferrin and gamma-glutamyltransferase are inversely associated with lipid markers of cardiovascular risk

BACKGROUND

A variety of epidemiological studies have suggested a U-shaped association between alcohol consumption and atherosclerosis progression and incidence events. Moderate intake of alcohol is considered beneficial, whereas heavy drinking increases cardiovascular disease risk.

METHODS

Alcohol and cardiovascular risk-related laboratory tests were carried out in 70 consecutive male employees in connection with an occupational health survey in 1996. Carbohydrate-deficient transferrin (CDT) and gamma-glutamyltransferase (GGT) were used as markers for alcohol consumption. The subjects were divided into quartiles on the basis of CDT or GGT value.

RESULTS

The highest CDT quartile had significantly higher serum high-density lipoprotein (HDL)-cholesterol (P < 0.05) than the lowest quartile. The highest GGT quartile had significantly higher serum total cholesterol (P < 0. 01), lower serum HDL-cholesterol (P < 0.05), higher serum low-density lipoprotein (LDL)-cholesterol (P < 0.01) and higher serum triglyceride (P < 0.01) than the lowest quartile.

CONCLUSIONS

An explanation for the findings is that high alcohol consumption without significant liver induction increases the level of HDL-cholesterol, whereas high alcohol consumption with induction of liver may have adverse effects on lipoprotein metabolism. The results were interpreted to indicate that CDT and GGT detect different populations of drinkers in regard to cardiovascular lipid risk factors.

Enhanced biliary excretion of canalicular membrane enzymes in estrogen-induced and obstructive cholestasis, and effects of different bile acids in the isolated perfused rat liver

BACKGROUNDS/AIMS

Canalicular membrane enzymes are normally released into bile by partially known processes. This study was undertaken to investigate whether hepatocellular cholestatis induced in rats by ethynylestradiol or obstructive cholestasis produced by complete biliary obstruction for 24 h is associated with an increased release of alkaline phosphatase and gamma-glutamyl transpeptidase into bile, and to clarify how this process is affected by different bile acids.

METHODS

The studies were performed in the isolated perfused liver during infusion of sodium taurocholate, taurochenodeoxycholate and tauroursodeoxycholate at increasing rates.

RESULTS

Maximum sodium taurocholate, taurochenodeoxycholate and tauroursodeoxycholate secretory rates were decreased in both cholestatic groups (complete biliary obstruction > ethynylestradiol) compared with controls. Maximum biliary outputs of alkaline phosphatase and gamma-glutamyl transpeptidase were significantly increased in the ethynylestradiol group during infusion of sodium taurocholate and taurochenodeoxycholate, but not of tauroursodeoxycholate, and were increased in the complete biliary obstruction group during the infusion of sodium taurocholate and tauroursodeoxycholate but not of taurochenodeoxycholate. The biliary outputs of alkaline phosphatase and gamma-glutamyl transpeptidase showed a significant and direct linear relationship with sodium taurocholate and taurochenodeoxycholate secretory rates in both cholestatic groups. However, only in the complete biliary obstruction group did alkaline phosphatase and gamma-glutamyl transpeptidase excretion show a significant correlation with tauroursodeoxycholate secretory rates. The slope of the line, which indicated the mU of enzyme activity secreted per nmol of sodium taurocholate or taurochenodeoxycholate, was greater for gamma-glutamyl transpeptidase and alkaline phosphatase in both cholestatic groups (ethynylestradiol > complete biliary obstruction) than in the control group. Alkaline phosphatase activity in purified isolated canalicular and sinusoidal membranes was significantly increased in both cholestatic groups (complete biliary obstruction > ethynylestradiol), while gamma-glutamyl transpeptidase activity was unchanged compared with controls.

CONCLUSION

The marked increase in sodium taurocholate and taurochenodeoxycholate-mediated release of alkaline phosphatase and gamma-glutamyl transpeptidase into bile in cholestatic rats suggests an increased lability of these intrinsic membrane proteins to the detergent effects of secreted bile acids. It remains to be elucidated whether this phenomenon, which was particularly intense in ethynylestradiol induced cholestasis, is important in the pathogenesis and perpetuation of bile secretory failure. In contrast, tauroursodeoxycholate administration did not result in enhanced biliary excretion of these membrane enzymes, in either the control group or the ethynylestradiol group, supporting the concept that this bile salt lacks the membrane toxicity of common bile acids.

Liver plasma membrane-bound enzymes and lipids in golden hamsters infected with Ancylostoma ceylanicum

Infection of golden hamsters with Ancylostoma ceylanicum caused significant decrease in body weight, liver weight and the protein content of liver plasma membrane. Significant inhibition of liver plasma membrane enzymes activities-5'Nucleotidase, gamma-glutamyl transpeptidase, NADHK3Fe (CN)6 reductase, Na+/K(+)-ATPase, CA(2+)-ATPase and Mg(2+)-ATPase was observed in infected animals compared to corresponding controls. Sialic acid content and phospholipid/cholesterol ratio in liver plasma membrane of the infected group were significantly reduced. The study suggests that changes in both the structural and functional organization of membrane may be a biochemical basis of the hepatotoxic effects.

Clinical significance of a new isoform of serum alanine aminopeptidase; relationship with liver disease and alcohol consumption

The potential clinical interest of a new isoform of alanine aminopeptidase (AAP) was examined using polyacrylamide gradient gel electrophoresis. This form, called F-AAP, is more proteolyzed than normal serum AAP. It appears to be associated with many liver diseases and is related to cytolysis, but also to elevated GGT levels. The F-AAP form was present in 52% of subjects treated with anticonvulsant drugs and in 64% of subjects consuming more than 44 g of alcohol per day. Analysis of F-AAP may be of interest in detecting effects of drugs and alcohol on the liver.

Specific modulation by ethanol of the protein synthesis pattern in the C2 rat hepatoma cell line

The effect of ethanol on protein synthesis in the C2 rat hepatoma cell line was analyzed by two-dimensional gel electrophoresis after the labeling with [35S]methionine of cells that were untreated or had been treated with 180 mM ethanol. In this cell line, this concentration of ethanol is known to induce gamma-glutamyl transpeptidase, a marker of alcoholism in man (Barouki et al., Hepatology 1983; 3: 323-329). In the present work we demonstrate that ethanol, besides causing a slight decrease in overall protein synthesis (less than 25%), primarily regulates the expression of two unique proteins among 1500 labeled products that were analyzed: one of these was induced and did not correspond to gamma-glutamyl transpeptidase, and one was repressed after 20 h of ethanol treatment. We conclude that the set of hepatic proteins altered by ethanol is likely to be very limited in number, which reflects the specificity of alcohol action on protein synthesis in the C2 cell line.

Changes in hepatic and serum gamma-glutamyltransferase activities following chronic ethanol intake in rats

The effect of chronic ethanol consumption on serum and liver gamma-glutamyltransferase (GGT) activities was studied in male Wistar rats. Animals were fed for 1-9 weeks a liquid diet containing 36% of total energy as ethanol or isocaloric carbohydrates. Compared to control diet, chronic ethanol significantly and progressively increased serum activity from 3 weeks of treatment. Liver GGT activity was also enhanced although changes were not parallel to those found in serum. Chronic ethanol intake led to an enhancement of liver glutathione concentration with a 45% increase at 3 weeks of treatment and a decrease thereafter. It is suggested that the increased hepatic GGT activity is not the only determinant of the enhanced serum levels of the enzyme and that it is not related to the modifications of liver glutathione content induced by ethanol consumption.

Enhanced biliary gamma-glutamyltransferase excretion following prolonged alcohol consumption in rats

In order to study the question of whether chronic ethanol consumption may alter the biliary excretion of gamma-glutamyltransferase (gamma-GT), female rats were pair-fed nutritionally adequate liquid diets containing either ethanol (36% of total calories) or isocaloric carbohydrates for 24 days. Compared to pair-fed controls, the administration of the alcohol-containing diet resulted in an increased biliary excretion of gamma-GT (5.84 +/- 0.73 mU 6 h-1 100 g-1 b.w. vs. 8.82 +/- 0.79, P less than 0.001). This was associated with a corresponding enhanced biliary output of total bile acids. An apparent linear relation between the biliary output rates of gamma-GT and those of total bile acids was observed both in alcohol-fed animals (r = 0.83) and in their pair-fed controls (r = 0.95). In addition, there was a significant increase of gamma-glutamyltransferase activities in the liver homogenate and in liver plasma membranes, both in fractions rich in bile canalicular and basolateral membranes and in those rich in blood sinusoidal site. Serum gamma-glutamyltransferase activities as well as serum bile acid concentrations were also enhanced by 96.8% (P less than 0.001) and 233% (P less than 0.001), respectively. These data show that chronic alcohol consumption enhances hepatic gamma-GT activities, leading to an increased efflux of gamma-GT into the bile and possibly into the blood out of the liver cell. Furthermore, these data suggest the involvement of bile acids with their solubilizing properties for the biliary excretion of gamma-GT.