Serum Concentration of N-Acetyl-[Beta]-D-Glucosaminidase in Alcohol Addicts

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Abstract -

An increased level of serum N-acetyl-β-D-glucosaminidase can often be found in alcohol addicts. A statistically significant increase in the catalytic concentrations of NAGA and its isozymes was determined in a group of subjects with the diagnosis of liver cirrhosis and in an alcohol addicts' group in comparison to the control group. There was no statistically significant difference in the catalytic concentrations of NAGA and its isoenzymes between the subjects' group with liver cirrhosis without an alcohol genesis and the alcohol addicts' group. Furthermore, a statistically significant difference was found between the control group and the alcohol addicts' group. This is why it is important to determine the total level of catalytic NAGA concentrations as well as the catalytic concentrations of its isozymes when diagnosing alcohol dependence. The obtained results indicate that the determination of the catalytic NAGA concentrations is not a highly specific marker for alcoholism. The aim of the present paper was to examine the NAGA concentration in alcohol addicts treated at the Department of Psychiatry, and to question its value as a marker for alcohol dependence. Subjects treated from alcohol addiction as inpatients and patients with liver cirrhosis not caused by the alcohol's toxic activity took part in the study. The control group consisted of healthy volunteers. When compared to the healthy volunteers, alcohol addicts showed a statistically higher NAGA concentration in serum.

Keywords: N-acetyl-beta-D-glucosaminidase; alcohol dependence; liver cirrhosis


One of the priorities in medical research, as well as in mental disorders' research, is the identification of biological markers. Alcohol dependence is a complex condition and very often, when we try to diagnose it, we are faced with certain difficulties despite our experience and available diagnostic methods. In order to make an objective diagnosis, markers which would be characteristic of certain entities are tried to be identified. A trait marker represents the characteristics of pathophysiological processes which precede the clinical expression of the disorder, and possibly causes the disorder itself. It is also specific to certain conditions even without a clinical picture. In contrast, a state marker reflects a clinically manifested cluster of symptoms and signs. 1,2

Extensive alcohol consumption impairs liver cells, which leads to cell enzyme liberation. Besides this, alcohol causes the microsomal enzyme induction, which leads to the increase in the catalytic concentration of membrane-associated enzymes in serums. This is why defining these enzymes' catalytic concentrations (aminotransferase, gamma - glutamyltransferase, glutamate dehydrogenase, monoaminoxidase) is one of the indicators of alcoholism.3-5

N-acetyl-β-D-glucosaminidase (NAGA) is a lysosome hydrolase that can be found in low catalytic concentrations in healthy people's serum.6 It is composed of a group of glycoprotein isoenzymes which are divided into two main forms based on the difference in the molecular charge: NAGA-A and NAGA-B, and a few additional forms (NAGA-S, NAGA-P, NAGA-Il, NAGA-12).7

Isoenzymes NAGA-A and NAGA-B can be found in tissues and serum. They are made of a and β subunits: NAGA-A consists of an a and a β subunit, while NAGA-B of two β subunits. NAGA' s metabolism was examined in vitro and in vivo in rats. It was found that the tissue forms of NAGA-A and NAGA-B are eliminated quickly from the circulation (t V2 < 2 min). In contrast, serum forms of NAGA-A, NAGA-B and NAGA-P are eliminated much more slowly (t V2 = 2-4 hours).8

It was determined that on the surface of endothelium and mononuclear macrophages there are glycoprotein receptors which mediate the entrance of lysosome enzyme tissue forms into the endothelium cells, recognizing the terminal residue of oligosaccharide chains which end in mannose or N-acetylglucosamine. …