Changes in glycoprotein carbohydrate content in the aging human brain

There is no significant change in the concentration, per gram of fresh tissue, of the total carbohydrate associated with brain glycoproteins as the human brain ages from 25 to 85 years. Nevertheless, notable shifts in the concentration of varied types of oligosaccharides do occur. The concentration and percentage of total glycopeptide-carbohydrate recovered from the whole brain represented by the N-glycosidically linked complex sialooligosaccharides of the tri- and tetraantennary type show a marked decline with age. On the other hand, the N-linked mannose high oligosaccharides of the ovalbumin type, the N-linked biantennary sialoglycopeptides of the transferrin type, and the O-linked oligosaccharides show an increase as the brain ages. Other age related changes that were noted include an increase in the number of sulfate ester groups associated with the N-linked sialoglycopeptides and a decrease in the number of phosphorylated high mannose oligosaccharides as the brain ages.