Christine Hoebler

Intrauterine growth restriction not only modifies the cecocolonic microbiota in neonatal rats but also affects its activity in young adult rats.

Objective: Elucidating why intrauterine growth restriction (IUGR) predisposes to some intestinal pathologies would help in their prevention. Intestinal microbiota could be involved in this predisposition; its initial setup is likely to be altered by IUGR because IUGR delays perinatal intestinal development and strongly interacts with intestinal physiology. Furthermore, because initial colonization determines adult intestinal microbiota, an IUGR-induced defect in initial microbiota would have long-term consequences. Thus, to characterize the effect of IUGR on intestinal microbiota, we compared the composition and activity of cecocolonic microbiota from birth to adulthood in rats with and without IUGR. Materials and Methods: IUGR was induced by gestational isocaloric protein restriction. Pups were fed by unrestricted lactating mothers. At different ages (days 5, 12, 16, 22, 40, and 100), cecocolonic contents from rats with IUGR and controls were analyzed for concentrations of bacterial end products and numbers of main bacterial groups, and submitted to in vitro fermentation tests. Results: IUGR affected gut colonization: bacterial density was increased at day 5 and decreased at day 12. In adulthood, rats with IUGR still differed from controls, harboring fewer Bifidobacterium sp at day 40 and more bacteria related to Roseburia intestinalis at day 100. In vivo, propionate concentration was decreased by IUGR before weaning, whereas the concentrations of other short-chain fatty acids were decreased at day 40, although the in vitro metabolic capability was unaffected overall. Conclusions: We showed that IUGR induced, per se, some neonatal and long-lasting alterations of the intestinal microbiota. The physiological consequences of these changes and their relation to the predisposing effect of IUGR to gut pathologies must now be explored.

Intrauterine Growth Restriction Alters Postnatal Colonic Barrier Maturation in Rats

Intrauterine growth restriction (IUGR) is a leading cause of perinatal mortality and morbidity and increases the risk for necrotizing enterocolitis. We hypothesized that colonic barrier disruption could be responsible for intestinal frailty in infants and adults born with IUGR. Mucins and trefoil factor family 3 (TFF3) actively contribute to epithelium protection and healing. Our aim was to determine whether IUGR affects colonic mucosa maturation. IUGR was induced by dietary protein restriction in pregnant dams. Mucins and Tff3 expression and morphologic maturation of the colonic mucosa were followed during postnatal development of the offspring. Before weaning, mucin 2 and Tff3 protein levels were reduced in colonic mucosa of rats with IUGR compared with controls. After weaning, expression of mucin 2 (mRNA and protein) and mucin 4 (mRNA) were lower in colonic mucosa of rats with IUGR. At the same time, IUGR was associated with a reduction of crypt depth and a higher percentage of crypts in fission. We conclude that IUGR impairs mucus barrier development and is associated with long-term alterations of mucin expression. The lack of an efficient colonic barrier induced by IUGR may predispose to colonic injury not only in neonatal life but also in later life.

Supplementation of pig diet with algal fibre changes the chemical and physicochemical characteristics of digesta.

Seaweed extracts, because of their physicochemical characteristics and potential nutritional value, could provide a new source of dietary fibre. This study investigated changes in seaweed fibres (physicochemical and fermentative properties) in different digestive sites and their effects on digesta (viscosity and hydration properties). Sixteen pigs were adapted to a test diet supplemented with 5% algal fibre (either Palmaria palmata (PP), a poorly viscous soluble xylan; or Eucheuma cottonii (EC), a partly insoluble carrageenan; or Laminaria digitata (LD), a highly viscous soluble alginate) or 5% cellulose (reference fibre). PP did not modify the characteristics of digesta and was fermented in the caecum (pH 6.1 ± 0.4; short-chain fatty acids measured in digesta, 1409 ± 691 µmol g−1 dry matter). EC and LD were mainly insoluble in the stomach, becoming soluble in the intestine; EC was slightly fermented in the colon, giving a low concentration of short-chain fatty acids (303 ± 122 µmol g−1 dry matter). Supplementation of the diet with alginate (LD) increased 3.5-fold the ileal viscosity of digesta and their hydration capacity in the ileum and colon. Thus the physicochemical properties of pig digesta largely depend on the physicochemical properties of the ingested seaweed fibre, the pH and ionic conditions prevailing in the gut, and their fermentability. © 2000 Society of Chemical Industry

In vitro fermentation of beet fibre and barley bran, of their insoluble residues after digestion and of ileal effluents

Abstract: The main objective of this study was to determine the form in whichbeet and barley bran Ðbres reach the colon, and to evaluate the inNuence ofendogeneous compounds on their patterns of fermentation. Raw Ðbres (RF), cor-responding ileal effluents (IE) from pigs, and insoluble Ðbre residues (IR)extracted from IE, were fermented with human faecal inoculum for 24 h in an invitro batch system. For beet Ðbre, rate but not extent of cell wall sugars degrada-tion was increased (]34% at 6 h, P\0E05) after oroileal transit, due to a moreporous structure. For barley bran, oroileal conditions degraded endosperm com-pounds such as b-glucans, leading to a lower extent of cell wall glucose fermenta-tion compared with RF ([22% at 24 h, P\0E05). In the presence ofendogeneous substances, degradation of beet Ðbre polysaccharides was delayed(P\0E05) at each incubation time but that of barley bran Ðbre was unaltered.Compared to RF, IR and IE signiÐcantly exhibited lower acetate production forbeet Ðbre, and higher propionate and lower butyrate production for barley branafter 24 h. It is concluded that in vivo digestion modiÐed fermentation patterns ofboth Ðbres in a manner depending on botanical structure.J Sci Food Agric 75, 315E325 (1997)No. of Figures: 2. No. of Tables: 4. No. of References: 45Key words: dietary Ðbre, beet Ðbre, barley bran, ileal effluents, insoluble Ðbreresidues, in vitro fermentation, human faecal bacteria

Gastrointestinal or simulated in vitro digestion changes dietary fibre properties and their fermentation

This study evaluated the effect of digestion on the chemical and physicochemical characteristics of dietary fibre and on its behaviour during fermentation. Three dietary fibre sources (wheat bran, barley bran and beet fibre) were recovered from ileal cannulated pigs after in vivo digestion and prepared by in vitro enzymatic treatment simulating digestion. Raw substrates and fibre residues were analysed for their chemical and physicochemical properties as well as their potential fermentation by human colonic bacteria. In vitro and in vivo treatments led to insoluble residues, enriched in cell wall polysaccharides, with similar cell wall sugar composition and physicochemical properties. Degradations of cell wall polysaccharides with losses of sugar residues occurred mainly after in vivo digestion, especially for pectins from beet fibre and β-glucans from barley bran. Solubilisation of β-glucans removed highly fermentable substrates for further fermentation. For beet fibre, removal of pectins led to increased hydration properties and faster fermentation of cell-wall polysaccharides. Enzymatic treatment simulated correctly the passage of fibre through the digestive tract, modifying the cell-wall matrix and predisposing the fibre to further fermentation.

Purification and properties of an endo-(1→4)-β-d-xylanase from irpex lacteus (Polyporus tulipiferae)

Abstract A xylanase from Driselase (a commercial enzyme preparation), obtained from the basidiomycetes Irpex lacteus (Polyporus tulipiferae) , was purified ∼32-fold by desalting on Sephadex G-25, ion-exchange chromatography on DEAE-Sepharose CL-6B and CM-Sepharose CL-6B, hydrophobic-interaction chromatography on Phenyl-Sepharose CL-4B, gel filtration on Ultrogel AcA54, and affinity chromatography on Concanavalin A-Ultrogel. The enzyme is a glycoprotein that contains 23% of sugars, mainly as glucose. Its molecular weight is 38,000 and its pI 7.6–8.0. The enzyme exhibited maximal activity at pH 4.6–5.2 and at 60°, and was completely inactivated within 30 min at 70°. The K m values for larch 4- O -methylglucuronoxylan were 2.8 (suspension in water) and 1 mg/mL (solution in 20% methyl sulfoxide). The xylanase degraded larchwood xylan to xylose, xylobiose, and xylotriose, as neutral end-products.

Functional food for pregnant, lactating women and in perinatal nutrition: a role for dietary fibres?

Purpose of reviewIf the benefits of dietary fibre in healthy adults have extensively been studied, little information is available on the specific needs of pregnant, lactating women or foetus. As far as infants are concerned, milk oligosaccharides are supposed to be the optimal ‘dietary fibre’. The supplementation of infant formula with prebiotic oligosaccharides is still discussed. However, recent studies provide a large amount of information, allowing a new discussion on this topic. Recent findingsMost recent findings are linked to the involvement of dietary fibre in occurrence or prevention of obesity. The multiple mechanisms appear more clearly than earlier. This finding will soon allow appropriate counselling for young mothers at risk of obesity and/or postpartum retention weight, gestational diabetes and preeclampsia. Another area which benefits from recent research is the use of prebiotics in formula. SummaryPregnancy is a critical period during which many physiologic changes occurred and is associated with several gut disorders and metabolic diseases. Dietary fibre may be helpful in the prevention and management of these diseases. Lactation and pregnancy are two phases during which food consumption of the mother can interact with the physiology of the baby. Moreover, the use of formula supplemented in oligosaccharides is able to compensate for the lack of some of the complex molecules naturally present in human milk.

Digestion and Fermentation Pattern of Various Dietary Fiber Sources in the Rat

Abstract Wheat bran, beet pulp, soya bean hulls and copra meal are potential dietary fiber sources which have very different composition. Their total apparent digestibilities in rats have been shown to vary greatly: non-starch glucose digestibility was 20% for soya bean hulls and 63% for beet pulp. Arabinose from lateral chains of the beet pulp pectins was highly digestible whereas arabinans of wheat bran were poorly digestible. Mannans of copra meal were also highly digestible. The present study indicates that endogenous secretions or bacteria induce an underevaluation of the digestibility of minor neutral sugars in the diets. Parts of the neutral sugars from beet pulp (arabinose and galactose) and from copra meal (mannose) disappear from the stomach faster than others. That could indicate digestion of the polysaccharide containing the sugar and/or a quicker transit of this polysaccharide. In the small intestine, digestion or disappearance of the sugars, initiated in the stomach, was accentuated, but xylose and glucose from wheat bran disappeared faster than arabinose. Digestion in the cecum and colon is known to be due to bacteria which proliferate at this level. They produce, from dietary fibers, variable amounts of fermentation products (volatile fatty acids and gas). This production is not correlated to total digestibility of the dietary fiber. Wheat bran is poorly fermentable and is characterized by its fermentation profile, with a high proportion of butyric acid. Digestion of dietary fibers in the stomach and small intestine has been reported by several authors. Its real mechanism — chemical action by secretion or bacterial fermentation of the gut content — has yet to be identified.

Rôles physiologiques des mucines dans la barrière colique

Resume Le mucus colique est un element cle de la barriere colique puisqu’il se situe a l’interface entre la flore luminale et la muqueuse colique en elle-meme. Il est principalement constitue de glycoproteines de haut poids moleculaire appelees mucines, qui peuvent etre secretees ou transmembranaires. L’expression de ces differentes mucines coliques est alteree lors d’inflammations ou de cancers coliques. Le but de cette revue est de mettre en exergue le role crucial que jouent les mucines coliques dans le maintien de l’integrite de la barriere colique, a la fois parce qu’elles entrent dans la composition du gel de mucus qui protege la muqueuse colique, et parce qu’elles exercent individuellement des fonctions specifiques impliquees dans la barriere epitheliale, comme la croissance et la differentiation cellulaires, l’immunomodulation, la transduction de signaux ou l’adhesion cellulaire.

IN VITRO STARCH DEGRADATION FROM WHEAT-BASED PRODUCTS IN THE PRESENCE OF LIPID COMPLEX EMULSIONS

The lower glycemic index when lipids are coingested with starchy foods was supposed to result from several factors such as lower gastric emptying, higher insulinic response, decreased glucose absorption through the upper small intestine and lower starch accessibility to alpha-amylase. This study investigated whether lipid/food structure interactions may play a role in limiting starch accessibility to alpha-amylase. Three wheat-based products (wheat starch, white-wheat bread and 5-mm spaghetti strands), differing in food structure/porosity, were incubated for 8 h with human salivary alpha-amylase (HSA) in the presence or not of two differently-sized emulsions (7.1 and 0.6 μm). HSA-specific activity was not modified in the presence of the coarse emulsion (7.1 μm). On the whole, regardless of the food structure, the two emulsions had no marked effect on the rate and degree of alpha-amylolysis. However, in the presence of the fine emulsion, starch from white-wheat bread tended to be more slowly hydrolysed effect being significant (P < 0.05) between 10 and 30 min of alpha-amylolysis. In the case of pasta, starch tended to be more rapidly hydrolysed in the presence of the coarse emulsion with a significant effect at 4 h of alpha-amylolysis. We concluded that emulsified lipids do not interact with complex starchy food structure of white-wheat bread and pasta in a way that significantly limits the action of alpha-amylase.