Role of insulin and nutritional factors in intestinal glycoprotein fucosylation during postnatal development

Abstract

This study deals with the role of insulin in the regulation of the intestinal glycoprotein fucosylation process during postnatal development in the rat. Circulating insulin level was found to increase at weaning time in parallel with α-1,2-fucosyltransferase activity and with the appearance of α-1,2-fucoproteins in brush-border membranes. Insulin treatment of young suckling rats induced a precocious increase in fucosyltransferase activity and in the biosynthesis of its substrate (GDP-fucose), but the sensitivity to insulin disappeared after weaning. The insulin level was lower in 22-day-old rats that received prolonged nursing (on a high-fat diet) compared with age-matched normally weaned rats (on a high-carbohydrate diet), whereas the appearance of α-1,2-fucoproteins and the increase in activity of α-1,2-fucosyltransferase were delayed, as was the decrease in the degradation of GDP-fucose. In 22-day-old animals that received prolonged nursing and insulin treatment, the α-1,2-fucosyltransferase activity reached a level close to that observed in age-matched weaned rats, and several α-1,2-fucoproteins appeared in brush-border membranes with a molecular mass similar to that found in weaned rats. These results suggest that changes in insulin levels at weaning time (as caused, in the present case, by dietary modifications) may be responsible for the regulation of the glycoprotein fucosylation process, essentially by increasing fucosyltransferase activity.

Influence of spermine on intestinal maturation of the glycoprotein glycosylation process in neonatal rats

“…Indeed, the increase in intestinal spermine level at weaning paralleled that of fucosyltransferase activity that is naturally observed at this period [8], and the appearance of fucoproteins in the brush border membranes [11].…”

“…Each lane was loaded with 25 µg of total RNA. [11]. When expressed in terms of total activity per g of intestine or per mg of mucosa DNA, the sialyltransferase and fucosyltransferase activities varied in an analogous way to that when expressed as specific activities (results not shown).…”

“…32.6p2.6 3.6p0.5* activity was greatly increased by the oral spermine treatment ; the membrane-bound and soluble forms of the enzyme were affected similarly (Figure 3a), at levels between those of 22-day-old weaned and adult rats [11].…”

“…A shift from a high sialylation before weaning to a high fucosylation of the glycan chains after weaning has been demonstrated in glycoproteins of purified brush border membranes [2][3][4] and in mucins [5] by various techniques, as well as in the apical and basolateral membranes of the epithelial cells by lectin cytochemistry [6]. This shift is accompanied by a parallel decline in the activity and the mRNA level of an α-2,6-sialyltransferase from birth to weaning time [7][8][9] and by a large increase in the activity of an α-1,2-fucosyltransferase just after weaning [10,11].…”

“…Postnatal digestive tract maturation is controlled by hormonal factors such as corticoids, thyroxine or insulin [1,7,[11][12][13][14] but other growth or maturation factors such as polyamines are also strong candidates for the regulation of the intestinal maturation. In mammals, a continuous supply of polyamines is vital for the Abbreviation used : G3PDH, glyceraldehyde-3-phosphate dehydrogenase.…”