ONTOGENIC AND NUTRITIONAL MODIFICATIONS IN THE INTESTINAL FUCOSYLATION PROCESS AT THE WEANING PERIOD - INFLUENCE OF DIETARY-FIBERS

In the rat small intestine, the glycosylation changes which normally t ake place at the weaning period are characterized by a shift from sial ylation to fucosylation. The introduction of dietary fibers at weaning is one of the more striking nutritional modification so that some aut hors have suggested that the presence of fibers and the development of colonic fermentation might be important for the development of the sm all intestine, as for the colon. In order to define the respective con tribution of ontogenic and nutritional factors to the intestinal glyco sylation changes at this period, some aspects of the intestinal glycos ylation were studied in five groups of rats (16-day-old suckling rats, prolonged nursing 23-day-old rats, 23-day-old rats weaned at day 19 w ith either a fiber-free, a cellulose or a pectin diet). Intestinal gly coproteins of suckling rats are characterized by a low fucose content and a high proportion of mannose. The amounts of the neutral sugars (f ucose, mannose and galactose), expressed either per gram of intestine or for one intestine, are always higher in the fiber-fed groups than i n the prolonged-nursing group or the group fed the fiber-free diet. Ac tivities which promote fucosylation process (GDP-fucose production and fucosyltransferase activities) and those which are opposed to fucosyl ation (endogenous inhibitor of fucosyltransferase and GDP-fucose pyrop hosphatase) are strongly modified in opposite ways at day 23 as compar ed to day 16. These modifications depend on the age of the animal (ont ogenic factors) with additional modifications induced by the dietary f actors. In particular, similar sugar contents and patterns are obtaine d with cellulose and pectin diets though the enzymatic activities of t he fucosylation pathway are very different. No correlation was found b etween the caecal content of short chain fatty acids and any of the pa rameters under study. Thus, dietary fibers induce metabolic changes in the small intestine glycosylation in short-term experiments independe ntly of colonic fermentation. Besides, these results point out that th e consideration of fucosyl-transferase activities alone are not suffic ient to predict glycoprotein fucose content and that other regulatory sites are involved. Dietary manipulations at the weaning period could represent a good model for the study of glycosylation regulation.