ROLE OF INSULIN AND NUTRITIONAL FACTORS IN INTESTINAL GLYCOPROTEIN FUCOSYLATION DURING POSTNATAL-DEVELOPMENT

This study deals with the role of insulin in the regulation of the int estinal glycoprotein fucosylation process during postnatal development in the rat. Circulating insulin level was found to increase at weanin g time in parallel with alpha-1,2-fucosyltransferase activity and with the appearance of alpha-1,2-fucoproteins in brush-border membranes. I nsulin treatment of young suckling rats induced a precocious increase in fucosyltransferase activity and in the biosynthesis of its substrat e (GDP-fucose), but the sensitivity to insulin disappeared after weani ng. The insulin level was lower in 22-day-old rats that received prolo nged nursing (on a high-fat diet) compared with age-matched normally w eaned rats (on a high-carbohydrate diet), whereas the appearance of al pha-1,2-fucoproteins and the increase in activity of alpha-1,2-fucosyl transferase were delayed, as was the decrease in the degradation of GD P-fucose. In 22-day-old animals that received prolonged nursing and in sulin treatment, the alpha-1,2-fucosyltransferase activity reached a l evel close to that observed in age-matched weaned rats, and several al pha-1,2-fucoproteins appeared in brush-border membranes with a molecul ar mass similar to that found in weaned rats. These results suggest th at changes in insulin levels at weaning time (as caused, in the presen t case, by dietary modifications) may be responsible for the regulatio n of the glycoprotein fucosylation process, essentially by increasing fucosyltransferase activity.