Intestinal Glycosylation Research Articles

Pectin supplementation ameliorates intestinal epithelial barrier function damage by modulating intestinal microbiota in lipopolysaccharide-challenged piglets

During weaning, infants and young animals are susceptible to severe enteric infections, thus inducing intestinal microbiota dysbiosis, intestinal inflammation, and impaired intestinal barrier function. Pectin (PEC), a prebiotic polysaccharide, enhances intestinal health with the potential for a therapeutic effect on intestinal diseases. One 21-d study was conducted to investigate the protective effect of pectin against intestinal injury induced by intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS) in a piglet model. A total of 24 piglets (6.77±0.92 kg BW; Duroc × Landrace × Large White; barrows; 21 d of age) were randomly assigned into three groups: control group, LPS-challenged group, and PEC + LPS group. Piglets were administrated with LPS or saline on d14 and d21 of the experiment. All piglets were slaughtered and intestinal samples were collected after 3 h administration on d21. Pectin supplementation ameliorated the LPS-induced inflammation response and damage to the ileal morphology. Meanwhile, pectin also improved intestinal mucin barrier function, increased the mRNA expression of MUC2, and improved intestinal mucus glycosylation. LPS challenge reduced the diversity of intestinal microbiota and enriched the relative abundance of Helicobacter. Pectin restored alpha diversity and improved the structure of the gut microbiota by enriching anti-inflammatory bacteria and short-chain fatty acids (SCFAs)-producing bacteria, and increased the concentrations of acetate. In addition, Spearman rank correlation analysis also revealed the potential relationship between intestinal microbiota and intestinal morphology, intestinal inflammation, and intestinal glycosylation in piglets. Taken together, these results indicate that pectin enhances intestinal integrity and barrier function by altering intestinal microbiota composition and their metabolites, which subsequently alleviates intestinal injury and finally improves the growth performance of piglets.

Bacterial colonization and TH17 immunity are shaped by intestinal sialylation in neonatal mice.

Interactions between the neonate host and its gut microbiome are central to the development of a healthy immune system. However, the mechanisms by which animals alter early colonization of microbiota for their benefit remain unclear. Here, we investigated the role of early-life expression of the α2,6-sialyltransferase ST6GAL1 in microbiome phylogeny and mucosal immunity. Fecal, upper respiratory, and oral microbiomes of pups expressing or lacking St6gal1 were analyzed by 16S rRNA sequencing. At weaning, the fecal microbiome of St6gal1-KO mice had reduced Clostridiodes, Coprobacillus, and Adlercreutzia, but increased Helicobacter and Bilophila. Pooled fecal microbiomes from syngeneic donors were transferred to antibiotic-treated wild-type mice, before analysis of recipient mucosal immune responses by flow cytometry, RT-qPCR, microscopy, and ELISA. Transfer of St6gal1-KO microbiome induced a mucosal Th17 response, with expression of T-bet and IL-17, and IL-22-dependent gut lengthening. Early life intestinal sialylation was characterized by RT-qPCR, immunoblot, microscopy, and sialyltransferase enzyme assays in genetic mouse models at rest or with glucocorticoid receptor modulators. St6gal1 expression was greatest in the duodenum, where it was mediated by the P1 promoter and efficiently inhibited by dexamethasone. Our data show that the inability to produce α2,6-sialyl ligands contributes to microbiome-dependent Th17 inflammation, highlighting a pathway by which the intestinal glycosylation regulates mucosal immunity.

Interleukin-22 regulates B3GNT7 expression to induce fucosylation of glycoproteins in intestinal epithelial cells

Interleukin (IL)-22 is a cytokine that plays a critical role in intestinal epithelial homeostasis. Its downstream functions are mediated through interaction with the heterodimeric IL-22 receptor and subsequent activation of signal transducer and activator of transcription 3 (STAT3). IL-22 signaling can induce transcription of genes necessary for intestinal epithelial cell proliferation, tissue regeneration, tight junction fortification, and antimicrobial production. Recent studies have also implicated IL-22 signaling in the regulation of intestinal epithelial fucosylation in mice. However, whether IL-22 regulates intestinal fucosylation in human intestinal epithelial cells and the molecular mechanisms that govern this process are unknown. Here, in experiments performed in human cell lines and human-derived enteroids, we show that IL-22 signaling regulates expression of the B3GNT7 transcript, which encodes a β1-3-N-acetylglucosaminyltransferase that can participate in the synthesis of poly-N-acetyllactosamine (polyLacNAc) chains. Additionally, we find that IL-22 signaling regulates levels of the α1-3-fucosylated Lewis X (Lex) blood group antigen, and that this glycan epitope is primarily displayed on O-glycosylated intestinal epithelial glycoproteins. Moreover, we show that increased expression of B3GNT7 alone is sufficient to promote increased display of Lex-decorated carbohydrate glycan structures primarily on O-glycosylated intestinal epithelial glycoproteins. Together, these data identify B3GNT7 as an intermediary in IL-22-dependent induction of fucosylation of glycoproteins and uncover a novel role for B3GNT7 in intestinal glycosylation.

FUT1 genetic variants impact protein glycosylation of porcine intestinal mucosa.

A massive use of antibiotics in industrial pig production is a major cause of the rapidly rising bacterial resistance to antibiotics. An enhanced understanding of infectious diseases and of host-microbe interactions has the potential to explore alternative ways to improve pig health and reduce the need for antibiotics. Host-microbe interactions depend on host-expressed glycans and microbe-carrying lectins. In this study, a G > A (nucleotide 307) missense mutation in the porcine α1,2fucosyltransferase 1 gene (FUT1), which has been reported to prevent infections by the common porcine enteric pathogen F18 fimbriated Escherichia coli, provided a unique opportunity to study glycan structures potentially involved in intestinal infections. N- and O-Linked glycans of the intestinal mucosa proteins were characterized in detail using LC-MS/MS. Relative abundances of all glycans were determined and compared between four heterozygous pigs (FUT1-307(A/G)) and four age-matched homozygous pigs from the same 2 litters carrying the missense FUT1 gene constellation (FUT1-307(A/A)). None of the characterized 48 N-linked glycans was found to be regulated by the FUT1 missense mutation, while 11 of the O-linked glycans showed significantly altered abundances between the two genotypes. The overall abundance of H-antigen carrying structures was decreased fivefold, while H-antigen precursors and sialylated structures were relatively more abundant in pigs with the FUT1 missense mutation. These results provide insight into the role of FUT1 on intestinal glycosylation, improve our understanding of how variation in FUT1 can modulate host-microbe interactions, and suggest that the FUT1 genetic variant may help to improve pig gut health.

The intestinal glycome and its modulation by diet and nutrition.

The human gastrointestinal epithelium is responsible for adequate digestion and absorption of nutrients. It is an immunological interface and highly selective environment that facilitates colonization by commensal bacteria and prohibits adhesion and invasion of pathogenic agents. The epithelial barrier is reinforced by the intestinal glycome, which consists of the vast array of sugar structures and glycoconjugates expressed by cells of the gastrointestinal tract. Aberrant glycosylation is associated with altered responses to enteric infections as well as immune dysregulation. Intestinal glycosylation is susceptible to alteration by genetic, physiological, and pathological states, in addition to modification by nutritional and environmental stimuli. The effects of nutritional influences upon glycan assembly and topology are of particular importance in intestinal barrier reinforcement and homeostasis. For instance, milk contains factors that can alter intestinal glycosylation, which in turn contributes to early immune development and maturation of the newborn intestinal tract. This review focuses on the glycosylation status of intestinal cells and the means by which nutritional factors modulate the expression and presentation of intestinal glycans.

Mice deficient in intestinal γδ intraepithelial lymphocytes display an altered intestinal O-glycan profile compared with wild-type littermates.

Intestinal γδ T-cell receptor-bearing intraepithelial lymphocytes (γδ IELs) play a multifaceted role in maintaining mucosal homeostasis. In order to investigate the relationship between O-glycosylation and inflammation, we carried out an in-depth mass spectrometric comparison of the intestinal O-glycosylation profile of mice lacking γδ IELs (TCRδ(-/-)) and of their wild-type (WT) littermates. A total of 69 nonsulfated and 59 sulfated compositional types of O-glycans were identified in the small intestine and colon of TCRδ(-/-) and WT mice. Our results demonstrated structural differences in intestinal glycosylation in TCRδ(-/-) mice compared with WT littermates. TCRδ(-/-) colons contained a lower proportion of core-2 structures and an increased proportion of core-1 structures whereas TCRδ(-/-) small intestines had a decreased percentage of core-3 structures. The glycan antennae in TCRδ(-/-) colon and small intestine showed altered structural diversity compared with WT mice. There were significant differences in the sialylated species between the TCRδ(-/-) and WT mice with the sialylated Tn antigen found exclusively in the TCRδ(-/-)small intestine, whereas the sulfation pattern remained mostly unchanged. These findings provide novel molecular insights underpinning the role of γδ IELs in maintaining gut homeostasis.

In vitro Effects of Ethanol on Intestinal Epithelial Cell Glycosylation in Rats

Ethanol ingestion is known to influence intestinal glycosylation, epithelial cell morphology, luminal micro ecology and produces mal-absorption in mammals. In the present study, the effect of 6% ethanol on glycosylation and various enzyme systems was investigated in isolated epithelial cells in vitro. The activities of various brush border enzymes were reduced 10-30% in epithelial cells by ethanol exposure. Chemical analysis, revealed an increase in membrane sialic acid (70%) and total hexosamine (122%), and reduction in fucose (32%) and hexoses (18%) contents of ethanol treated cells compared to controls. The observed changes in sialylation and fucosylation were corroborated by binding of biotinylated Wheat germ agglutinin (WGA; affinity for N-acetylglucosamine and sialic acid) and Ulex europaeus agglutinin (UEA; affinity for α-L-fucose). Solid phase lectin binding assay showed a 65% increase in WGA and a 37% decrease in UEA reactivity in ethanol exposed cells compared to controls. These findings indicate that ethanol exposure modulates the glycosylation process in intestinal cells in vitro, which is similar to that seen under in vivo conditions. This may provide an in vitro assay system of ethanol toxicity, which could be of pathological significance.

The effects of ethanol administration on brush border membrane glycolipids in rat intestine

Ethanol ingestion is well known to induce morphological and biochemical changes in intestine and is responsible for intestinal dysfunctions. Luminal surface of enterocytes is rich in glycolipids, but the effects of ethanol ingestion on membrane glycolipids are not well characterized. In the present study, rats were given 1 mL of 30% ethanol daily for 15, 25, 35, and 56 days. Ethanol feeding for 15 days did not affect glycolipid pattern in microvillus membranes, but the levels of cerebrosides (glucosylceramide, lactosylceramide, globotriasyloceramide) were enhanced in rats fed with ethanol for 35 or 56 days compared with controls. In contrast, the content of fucolipids and gangliosides was reduced in rats on ethanol ingestion for 35 or 56 days. The observed changes in membrane glycolipids were substantiated using biotinylated lectins Jacalin (affinity for N-acetylgalactosamine) and Aleuria aurantia (affinity for α- l-fucose). The incorporation of [ 14C]-mannose and [ 14C]-glucosamine revealed an increase ( P < .01) in glucosamination and reduction ( P < .01) in mannosylation of glycolipids from ethanol-fed rats for 45 days compared with controls. These findings were further characterized by autoradiography of the glycolipids separated on thin layer chromatograms. These findings indicate that ethanol ingestion modulates the glycolipids composition of brush borders, resulting in generalized aberration of intestinal glycosylation in chronic alcoholism in rats.

Glycoconjugate histochemistry in the small and large intestine of normal and Solanum glaucophyllum-intoxicated rabbits

Vitamin D participates in mineral homeostasis, immunomodulation, cell growth and differentiation. The leaves of Solanum glaucophyllum contain high levels of 1,25-dihydroxyvitamin D3 as glycoside derivatives and their chronic ingestion generates a hypervitaminosis D-like state. We analyzed changes on carbohydrate expression as a cell differentiation indicator on samples of the small and large intestine of S. glaucophyllum-intoxicated rabbits, using conventional and lectin histochemistry. Male New Zealand white rabbits were intoxicated with S. glaucophyllum during two or four weeks and killed the day after. A group of animals (“possibly recovered group”) were intoxicated during 15 days and killed at day 45 of the beginning of the experiment. We found changes in the lectin binding pattern in the small and large intestine of the intoxicated rabbits. Some of these changes were reverted in the possibly recovered group. Vitamin D could be a new regulator factor of the intestinal glycosylation process.

The role of intestinal glycosylation in determining individual responses to foods in inflammatory and neoplastic bowel diseases

Purpose: To illustrate the hypothesis that alterations in mucosal glycosylation, particularly O‐glycosylation, may result in altered interaction with carbohydrate‐binding proteins (lectins) in the diet.Design & methods: A summary of recent literature focussing on work by the author's group demonstrating in vitro and in vivo lectin–epithelial interactions, particularly in the colonic epithelium.Results: Similar alterations in O‐glycosylation occur in the colonic epithelium in inflammatory diseases and in cancer. They include shortening of O‐glycans and increased expression of onco‐fetal carbohydrate antigens. Peanut lectin, which selectively binds the TF antigen, is shown to survive transit through the intestine and to cause significantly increased epithelial proliferation. Other lectins inhibit proliferation, e.g. edible mushroom lectin which becomes internalised and blocks nuclear‐localising‐sequence‐dependent nuclear protein import.Conclusions: Intestinal epithelial glycosylation is commonly altered in ...

Indigenous microbes and their soluble factors differentially modulate intestinal glycosylation steps in vivo

It has been shown that Bacteroides thetaiotaomicron, a representative member of the gut microflora, signals intestinal epithelial cells both in vivo and in vitro and modulate specific glycosylation processes that may mediate intestinal functions. However it is not known whether these modulations depend on the presence of live bacteria or may be elicited by soluble factors produced in vitro by this bacterium. We used lectins and an histochemical approach to survey tissue sections prepared from various cellular compartments of the small and large intestine of NRMI/KI mice grown under gnotobiotic conditions. We compared the results obtained with bacterial culture supernatant and live B. thetaiotaomicron to those obtained from germ-free mice or mice having a conventional microflora. This approach allowed us to conclude that (1) a small but specific number of glycan patterns were restored after treatment with bacterial culture supernatant and (2) the B. thetaiotaomicron associated mice restored a larger number of patterns, however, the complete conventional mice pattern must be a function of the whole microflora in the gut. The possibility to modulate this complex glycosylation pattern by introducing exogenous bacteria and bacterial products should be considered as a promising approach towards understanding the molecular basis of microbial-host interactions.

Regulation of the intestinal glycoprotein glycosylation during postnatal development: role of hormonal and nutritional factors

This review focuses on the regulation of the glycoprotein glycosylation process in small intestine and colon during postnatal development. Glycoproteins play a prominent part in intestine as mucins secreted by the goblet cells and as molecules of biological interest largely present in the microvillus membrane of the enterocytes (digestive enzymes, transporters). The age-related changes in the intestinal glycosylation control the quality of glycan chains of glycoproteins. Postnatal maturation is observed at all stages of the glycoprotein glycosylation. But it is essentially characterised in the external glycosylation by a shift from sialylation to fucosylation depending on the transcriptional regulation of the corresponding glycosyltransferases, but also on coordinate changes in the activities of glycosyltransferases and of their regulatory proteins, in nucleotide-sugar bioavailability and in product degradation by oxidases. Many factors have been evoked to trigger these changes, among which are hormonal (glucocorticoids, insulin) and dietary factors. Changes in the structure of the glycoprotein glycans might be important for the transport, the barrier function, the implantation of the immune defences and of the microflora and even probably for the biological activity of some digestive enzymes.

Microbial-host interactions specifically control the glycosylation pattern in intestinal mouse mucosa.

The glycosylation of the intestinal cell layer is thought to control several key functions of the gut such as vectorial transports, defence against microbial agents or immunological processes. It has been assumed that the gut microflora may modulate the glycosylation pattern of the intestinal cell layer. However, there is no direct evidence for this regulatory process. The first goal of this work was to establish the germ-free mice intestinal glycosylation baseline using a histochemical approach and a panel of ten lectins with defined glycan specificities to tissue sections prepared from various cellular compartments of the small and large intestine. Using this baseline, we have studied the contribution of the gut microflora on the carbohydrate composition of glycoconjugates of intestinal cells by comparing the germ-free and conventional mice glycosylation patterns. Analysis of the germ-free mice intestinal glycosylation baseline revealed that the expression of glycans depends on the proximodistal gradient (small to large intestine) and on the cell lineage (absorptive, goblet, crypt, and Paneth cells), indicating that mice are able to create and maintain a strict topological and cell lineage-specific regulation of glycosyltransferase expression. By comparing germ-free and conventional mice, we find that the gut microflora specifically modulates the gut glycosylation pattern, quantitatively as well as qualitatively by changing the cellular and subcellular distribution of glycans. This is the first report in mice to directly demonstrate the critical contribution of microflora to intestinal glycosylation, a key characteristic of the gut.

Microbial Modulation of Host Intestinal Glycosylation Patterns

The host and its intestinal microora function together as a complex ecologic system in which there is a significant impact of the intestinal flora on the host. The structure and functioning of the gastrointestinal tract are dependent upon the presence of the resident and transient flora. The inuence of the microflora on the secretory pattern of the intestinal glycoconjugates is an emerging field of research. This review summarizes and examines the evidence that commensal intestinal bacteria can modulate the host intestinal glycosylation patterns. Changes in the glycosylation patterns might be associated with the induction and/or degradation of glycans, and are usually studied using either in vitro or in vivo models. In vitro microbial modulation of the intestinal glycosylation remains largely related to the degradation of glycoconjugates. On the other hand, most of the in vivo studies are associated with the induction of particular glycan structures. These two processes are associated but often analysed independently. Likewise, there are few studies involving the same bacterial species and for which both in vitro and in vivo approaches are used. On-going research should focus both the induction and degradation of glycoconjugates and the use of in vitro and in vivo models in a combined manner. The biological role of alteration in complex carbohydrate expression has yet to be determined. Due to their localisation at the cell surface in the gastrointestinal tract, glycans act as mediators of many host-microbial interactions, providing a wide range of binding sites for bacteria, pathogens and toxins. The knowledge of host receptors and their possible microbial modulation may lead to improved means of control and treatment of bacterial infections. Keywords: host-microbial interactions, intestinal glycosylation, in vivo , in vitro , commensal microflora.

The Glycosylation of Rat Intestinal Muc2 Mucin Varies between Rat Strains and the Small and Large Intestine: A STUDY OF O-LINKED OLIGOSACCHARIDES BY A MASS SPECTROMETRIC APPROACH

The large glycosylated domains obtained from the rat intestinal mucin Muc2 were isolated from the large and small intestine of the inbred rat strains GOT-W and GOT-BW. The expression of the rat Muc2 in the large intestine was confirmed immunochemically and by Northern blotting. Released oligosaccharides were structurally characterized by gas chromatography-mass spectrometry (neutral and sialylated species) or by tandem mass spectrometry (sulfated species), and a total of 63 structures was assigned. The large intestinal oligosaccharides were found to be identical between the strains, while the small intestinal glycosylation differed. Until now, detailed structural analysis of oligosaccharides isolated from a single mucin core or mucin domain with different origin have not been performed, and the information of different mucin glycoforms has been limited to immunochemistry. Blood group A-determinants (GalNAcalpha1-3(Fucalpha1-2)Galbeta1-, and structures related to the blood group Sda/Cad-related epitope NeuAc/NeuGcalpha1-3(GalNAcbeta1-4)Galbeta1-, were found in GOT-BW small intestine, and also in both large intestines. Blood group H-determinants and NeuAc/NeuGcalpha1-3Galbeta1- were found in all samples. Core 1 (Galbeta1-3GalNAcalpha1-), core 2 (Galbeta1-3(GlcNAcbeta1-6)GalNAcalpha1-), core 3 (GlcNAcbeta1-3GalNAcalpha1-), and core 4 (GlcNAcbeta1-3(GlcNAcbeta1-6)GalNAcalpha1- were also found in all the samples. The large intestine were enriched in sulfated oligosaccharides and the small intestine contained higher amounts of sialylated species. Sulfation were found exclusively on C-6 of GlcNAc.

Developmental changes in intestinal glycosylation: nutrition-dependent multi-factor regulation of the fucosylation pathway at weaning time

Developmental changes in the fucoglycoproteins of the intestinal brush-border membranes were determined by lectin affinoblotting after electrophoresis. Whereas only two α(1–6)-fucoglycoproteins were detected in brush-border membranes from suckling rats, a large number of N-fucoglycoproteins with α(1–2)- and/or α(1–6)-linked fucose residues were detected in rat membranes after weaning. Dietary manipulations at weaning time were used to investigate the effect of nutritional factors in the development of fucosylation in the small intestine of prolonged-nursed rats fed with milk (a high-fat, low-carbohydrate diet) compared to rats weaned normally with a standard high-carbohydrate diet. The fucose content of the mucosa glycoproteins was lower in 22-day-old prolonged-nursed rats than in 22-day-old rats weaned normally with the standard diet. The appearance of fucoglycoproteins in the brush-border membranes, which was delayed by prolonged nursing, was accompanied by a concomitant delay in the increase of intestinal fucosyl-transferase activity and in the decrease of GDP-fucose substrate breakdown. The developmental decrease in the activity of the inhibitory protein which regulates the fucosyl-transferase activity was also delayed by prolonged nursing. The intestinal fucosylation of brush-border membrane glycoproteins (which include many digestive enzymes) displayed ontogenic changes on which were superimposed dietary influences at the time of weaning. The complete maturation of the brush-border membrane glycoproteins, and particularly their terminal fucosylation, is a developmental event which thus seems to be strongly influenced by the manipulation of nutritional factors during the weaning period.

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 take place at the weaning period are characterized by a shift from sialylation of fucosylation. The introduction of dietary fibers at weaning is one of the more striking nutritional modification so that some authors have suggested that the presence of fibers and the development of colonic fermentation might be important for the development of the small intestine, as for the colon. In order to define the respective contribution of ontogenic and nutritional factors to the intestinal glycosylation changes at this period, some aspects of the intestinal glycosylation 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 with either a fiber-free, a cellulose or a pectin diet). Intestinal glycoproteins of suckling rats are characterized by a low fucose content and a high proportion of mannose. The amounts of the neutral sugars (fucose, mannose and galactose), expressed either per gram of intestine or for one intestine, are alwars higher in the fiber-fed groups than in the prolonged-nursing group or the group fed the fiber-free diet. Activities which promote fucosylation process (GDP-fucose production and fucosyltransferase activities) and those which are opposed to fucosylation (endogenous inhibitor of fucosyltransferase and GDP-fucose pyrophosphatase) are strongly modified in opposite ways at day 23 as compared to day 16. These modifications depend on the age of the animal (ontogenic factors) with additional modifications induced by the dietary factors. In particular, similar sugar contents and patterns are obtained with cellulose and pectin diests though the enzymatic activities of the fucosylation pathway are very different. No correlation was found between the caecal content of short chain fatty acids and any of the parameters under study. Thus, dietary fibers induce metabolic changes in the small intestine glycosylation in short-term experiments independently of colonic fermentation. Besides, these results point out that the consideration of fucosyl-transferase activities alone are not sufficient 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.

S4.9 Developmental changes in intestinal glycoprotein glycosylation

S4.9 Developmental changes in intestinal glycoprotein glycosylation

Effect of Malnutrition and Hormone Treatments on Intestinal Microvillus Membrane Glycosylation in Suckling Rats

Imposition of undernutrition in suckling rats significantly enhanced (p less than 0.001) sialic acid and reduced (p less than 0.001) fucose contents of intestinal microvillus membranes (MVM) compared to the controls. Administration of cortisone or insulin to undernourished (UN) pups reversed the sialylation and fucosylation pattern of the membranes. The binding of wheat germ agglutinin (WGA) to membranes was increased (p less than 0.001) and that of Ulex europeus agglutinin (UEA) was decreased in nutritionally deprived pups. Cortisone and insulin treatments reduced WGA and enhanced UEA bindings to UN membranes. The binding of peanut agglutinin (PNA) to UN membranes was 60% higher compared to that in the control rats. Cortisone and insulin treatments further enhanced PNA binding to the brush borders in UN pups. The incorporation of 14C-GlcNAc, 14C-mannose and 3H-fucose into MVM was reduced by 32-57% in UN suckling rats compared to the controls. The incorporation of labelled sugars into membranes from 21- and 50- to 60-day-old rats was essentially similar. Cortisone administration to UN pups augmented the incorporation of labelled GlcNAc and mannose but had no effect on fucose incorporation. Insulin treatment of UN pups insignificantly elevated GlcNAc incorporation into the membranes. These findings suggest that imposition of UN during early suckling period delays the maturational development of intestinal glycosylation. Cortisone and insulin induced adult-type glycosylation pattern of the brush borders in nutritionally deprived pups.

Developmental Changes in Intestinal Glycosyl-Transferase Activities

The carbohydrate composition of some intestinal glycoproteins has been demonstrated previously to be modified during development. To evaluate the role of the enzymatic mechanisms of glycosylation, the activities of three soluble and microsomal glycosyl-transferases were studied during postnatal development in rat intestinal mucosa. Nonexistent as soluble forms in the cell sap from suckling rats, the membrane-bound N-acetylgalactosaminyl-, sialyl-, and fucosyl-transferases showed different activities in microsomal fractions before weaning. The N-acetylgalactosaminyl-transferase activity was constant whereas the sialyl-transferase activity, which was maintained at a rather high level until the age of 2 wk, decreased just before weaning, while the fucosyl-transferase activity declined progressively from birth to weaning. After weaning, the three enzymatic activities progressively enhanced until adult age. Their variable behaviors on several glycoprotein acceptors may suggest the presence of several sialyl--and fucosyl-transferases with differences in specificities, varying in different ways according to age. Such developmental modifications in intestinal glycosylation patterns may be linked with certain transformation observed in the carbohydrate level of mucus or membrane-bound glycoproteins and related to the profound modifications in nutritional status at the weaning period.