Microheterogeneity of serum glycoproteins in patients with chronic alcohol abuse compared with carbohydrate-deficient glycoprotein syndrome type l

Background: Chronic alcohol abuse alters the normal N-glycosylation of transferrin, producing the carbohydrate-deficient transferrin isoforms. This alteration could be similar to that present in patients with carbohydrate- deficient glycoprotein syndrome type 1 (CDG1). We thus compared the alterations of N-glycans present in patients with alcoholism and patients with CDG1. Methods: The N-glycans of serum glycoproteins were compared in sera of patients with alcoholism, patients with CDG1, and controls by two- dimensional electrophoresis, neuraminidase, peptide:N-glycosidase F, and endoglycosidase F2 treatments. A specific antibody directed against the amino acid sequence surrounding the N-432 N-glycosylation site of transferrin was prepared (SZ-350 antibody). Results: In patients with alcoholism, the abnormal transferrin and α₁-antitrypsin isoforms were devoid of a variable number of entire N-glycan moieties and were identical with those present in CDG1. In the serum of patients with alcoholism, this finding was less pronounced than in CDG1. In contrast to CDG1, there was no decrease in clusterin or serum amyloid P in patients with alcoholism. The SZ-350 antibody recognized only transferrin isoforms with one or no N-glycan moieties. Conclusion: Antibodies directed against specific N-glycosylation sites of glycoproteins could be useful for developing more specific immunochemical tests for the diagnosis of chronic alcohol abuse.