Changes in the glycosaminoglycans and glycoproteins in the rat brain during protein calorie malnutrition

Significant alteration in the glycosaminoglycans (GAG) and glycoproteins is observed in the brain of protein calorie-malnourished rats. There was a si gnificant decrease in the protein in the brain, and the changes in the GAG and glycoproteins may be a consequence of this decrease. The GAG in the bra in showed a significant increase, and the increase in heparan sulfate is pa rticularly significant since it can lead to increased heparan sulfate-prote in complex formation and accumulation in the brain, possibly affecting brai n function. The activity of many enzymes involved in the catabolism of prot eoglycans was increased in the brain of malnourished rats. The fact that th ere was an increase in most of the glycosaminoglycans in spite of the incre ased activity of the catabolizing enzymes may indicate some form of resista nce of the proteoglycans to degradation. On the other hand, the carbohydrat e components of brain glycoproteins-total hexose, fucose, and sialic acid-d ecreased in the malnourished rats, whereas there was increase in the concen tration of dolichol. The activity of enzymes concerned with the catabolism of glycoproteins also showed an increase. The decrease in the carbohydrate components of glycoproteins in the brain in the malnourished rats in spite of increased availability of dolichol for glycosylation, may be due to thei r decreased biosynthesis and glycosylation and increased catabolism. The na ture of the changes in various carbohydrate components was different, indic ating formation of altered glycoproteins. The altered glycoproteins in the brain in malnourished rats may affect receptor function of the neuronal cel l membrane. Thus alteration in both glycosaminoglycans and glycoproteins ca n lead to changes in the brain function in malnutrition.