Disialo-trisialo bridging of transferrin is due to increased branching and fucosylation of the carbohydrate moiety.
BACKGROUND
Carbohydrate deficient transferrin (CDT) is used for detection of alcohol abuse and follow-up. High performance liquid chromatography (HPLC) of transferrin glycoforms is highly specific for identification of alcohol abuse, but unresolved disialo- and trisialotransferrin glycoforms sometimes makes interpretation difficult. The cause of this phenomenon is unknown, cannot be explained by genetic variants of transferrin, but seems to be associated with liver disease.


METHODS
Nineteen serum samples showing di-tri bridging when analyzed by HPLC were collected. Transferrin was purified by affinity chromatography, and N-linked oligosaccharides were released enzymatically. The N-glycans were further analyzed by high performance anion-exchange chromatography with pulsed amperometric detection and MALDI-TOF mass spectrometry.


RESULTS
The HPLC-analysis showed three different types of glycoform patterns. The N-glycans from fifteen samples showed patterns with increased number of triantennary structures containing one or two fucose residues. One sample contained an increased amount of triantennary glycans without fucose. Three samples showed a glycosylation pattern similar to normal transferrin.


CONCLUSIONS
The di-tri bridging phenomenon was associated with alterations in transferrin glycosylation in the majority of cases. Transferrin contained a higher extent of triantennary and often fucosylated N-linked oligosaccharides. These results may be important in future diagnostic approaches to liver diseases.
Division of Clinical Chemistry, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, County Council of Östergötland, Linköping, Sweden. eva.landberg@lio.se
Eva
E
Landberg
Eva
E
Åström
Bertil
B
Kågedal
Peter
P
Påhlsson
D000328:Adult; D000368:Aged; D002851:Chromatography, High Pressure Liquid; D005260:Female; D005643:Fucose / Q000737:chemistry*; D006031:Glycosylation; D006801:Humans; D008297:Male; D008875:Middle Aged; D009844:Oligosaccharides / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D014168:Transferrin / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D055815:Young Adult
D009844:Oligosaccharides; D014168:Transferrin; C056759:carbohydrate-deficient transferrin; D005643:Fucose