Longitudinal distribution of brush border hydrolases and morphological maturation in the intestine of the preterm infant

Changes to the Oligosaccharide Profile of Bovine Milk at the Onset of Lactation

Numerous bioactive components exist in human milk including free oligosaccharides, which represent some of the most important, and provide numerous health benefits to the neonate. Considering the demonstrated value of these compounds, much interest lies in characterising structurally similar oligosaccharides in the dairy industry. In this study, the impacts of days post-parturition and parity of the cows on the oligosaccharide and lactose profiles of their milk were evaluated. Colostrum and milk samples were obtained from 18 cows 1–5 days after parturition. Three distinct phases were identified using multivariate analysis: colostrum (day 0), transitional milk (days 1–2) and mature milk (days 3–5). LS-tetrasaccharide c, lacto-N-neotetraose, disialyllacto-N-tetraose, 3’-sial-N-acetyllactosamine, 3’-sialyllactose, lacto-N-neohexaose and disialyllactose were found to be highly affiliated with colostrum. Notably, levels of lactose were at their lowest concentration in the colostrum and substantially increased 1-day post-parturition. The cow’s parity was also shown to have a significant effect on the oligosaccharide profile, with first lactation cows containing more disialyllacto-N-tetraose, 6’-sialyllactose and LS-tetrasaccharide compared to cows in their second or third parity. Overall, this study identifies key changes in oligosaccharide and lactose content that clearly distinguish colostrum from transitional and mature milk and may facilitate the collection of specific streams with divergent biological functions.

Simultaneous assessment of intestinal permeability and lactase activity in human-milk-fed preterm infants by sugar absorption test: Clinical implementation and analytical method

BACKGROUND & AIMS

Experimental (nutritional) interventions in preterm infants frequently focus on intestinal maturation, as improving tolerance to enteral nutrition is a major goal. Intestinal permeability and lactase activity serve as markers for intestinal maturation. We aimed to develop a protocol for the simultaneous assessment of both markers in human-milk-fed preterm infants by a sugar absorption test. In addition, we developed a new gas chromatography-mass spectrometry (GC-MS) method for the analysis of lactulose, lactose, and mannitol in urine and milk collected during the sugar absorption test.

METHODS

The sugar absorption test was performed on days 4, 7, and 14 postpartum in 12 preterm infants (gestational age of 26-32 weeks). Human milk was collected, pooled, and divided into equal portions to provide a stable lactose intake for 24 h. Urine was collected in the last 6 h of this 24 h period, after administration of a bolus test sugar solution. Samples were analyzed by GC-MS after derivatization by oxime formation combined with acetylation.

RESULTS

The GC-MS method was validated and used for the accurate measurement of lactulose, lactose, and mannitol concentrations. The urinary lactulose/mannitol ratio declined with time, suggesting a decreased intestinal permeability. The urine-to-milk-lactulose/lactose ratio increased as a result of increased lactase activity with time.

CONCLUSIONS

The developed protocol for simultaneous assessment of intestinal permeability and lactase activity can be used to monitor the effect of experimental (nutritional) interventions in human-milk-fed preterm infants. Urine and milk samples obtained during the sugar absorption test can be accurately analyzed by GC-MS.

The Importance of Lactose in the Human Diet: Outcomes of a Mexican Consensus Meeting

Lactose is a unique component of breast milk, many infant formulas and dairy products, and is widely used in pharmaceutical products. In spite of that, its role in human nutrition or lactose intolerance is generally not well-understood. For that reason, a 2-day-long lactose consensus meeting with health care professionals was organized in Mexico to come to a set of statements for which consensus could be gathered. Topics ranging from lactase expression to potential health benefits of lactose were introduced by experts, and that was followed by a discussion on concept statements. Interestingly, lactose does not seem to induce a neurological reward response when consumed. Although lactose digestion is optimal, it supplies galactose for liver glycogen synthesis. In infants, it cannot be ignored that lactose-derived galactose is needed for the synthesis of glycosylated macromolecules. At least beyond infancy, the low glycemic index of lactose might be metabolically beneficial. When lactase expression decreases, lactose maldigestion may lead to lactose intolerance symptoms. In infancy, the temporary replacing of lactose by other carbohydrates is only justified in case of severe intolerance symptoms. In those who show an (epi)genetic decrease or absence of lactase expression, a certain amount (for adults mostly up to 12 g per portion) of lactose can still be consumed. In these cases, lactose shows beneficial intestinal-microbiota-shaping effects. Avoiding lactose-containing products may imply a lower intake of other important nutrients, such as calcium and vitamin B12 from dairy products, as well as an increased intake of less beneficial carbohydrates.

Starch Malabsorption in Infants

Based on the developmental physiology of pancreatic amylase production, starch digestion in young infants was anticipated to be compromised whenever compared with that in older infants and toddlers. This appears to be the case, but with great variability among infants to digest starch. Evidence points to the importance of maltase-glucoamylase in young infants and its effect on starch digestion. These observations have critical importance for recommendations regarding the feeding of starch-containing foods to young infants.

Lactase treated feeds to promote growth and feeding tolerance in preterm infants

BACKGROUND

Successful transition from parenteral nutrition to full enteral feedings during the immediate neonatal period is associated with improved growth in preterm infants. Lactase is the last of the major intestinal disaccharidases to develop in preterm infants. Because of inadequate lactase activity, preterm infants are unable to digest lactose. Lactase preparations could potentially be used to hydrolyse lactose in formulas and breast milk to minimize lactose malabsorption in preterm infants.

OBJECTIVES

To assess the effectiveness and safety of the addition of lactase to milk compared to placebo or no intervention for the promotion of growth and feeding tolerance in preterm infants.

PRIMARY OUTCOMES

weight gain expressed as grams/kg/day, growth expressed as weight, length and head circumference percentile for postmenstrual age (PMA), assessed at birth and at 40 weeks PMA, days to achieve full enteral feeds.

SECONDARY OUTCOMES

several common outcomes associated with preterm birth, and adverse effects.

SEARCH METHODS

Electronic and manual searches were conducted in January 2005 of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, 2004, Issue 4), MEDLINE (1966 to Jan 2005), EMBASE (1980 to Jan 2005) and CINAHL (1982 to Jan 2005), personal files, bibliographies of identified trials and abstracts by the Pediatric Academic Societies' Meetings and the European Society of Pediatric Research Meetings published in Pediatric Research. The searches were repeated in May 2012 of The Cochrane Library, MEDLINE, EMBASE and CINAHL and abstracts from the Pediatric Academic Societies' Annual Meetings from 2000 to 2012 (Abstracts2View). The Web of Science was searched using the only previously identified trial by Erasmus 2002 as the starting point to search for additional trials that cited this trial.

SELECTION CRITERIA

Types of studies: randomized or quasi-randomized controlled trials.

PARTICIPANTS

preterm infants < 37 weeks PMA.

INTERVENTION

addition of lactase to milk versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

The standard methods of the Cochrane Neonatal Review Group were followed independently by the review authors to assess study quality and report outcomes. Treatment effects, calculated using Review Manager 5, included risk ratio (RR), risk difference (RD) and mean difference (MD), all with 95% confidence intervals (CI). A fixed-effect model was used for meta-analyses. We did not perform heterogeneity tests as only one study was identified.

MAIN RESULTS

The repeat searches conducted in May 2012 did not identify any additional studies for inclusion. One study enrolling 130 infants of 26 to 34 weeks PMA (mean postnatal age at entry 11 days) was identified and no identified study was excluded. The study was a double blind randomized controlled trial of high quality. Lactase treated feeds were initiated when enteral feedings provided > 75% of daily intake. None of the primary outcomes outlined in the protocol for this review and only one of the secondary outcomes, necrotizing enterocolitis (NEC) were reported on. The RR for NEC was 0.32 (95% CI 0.01 to 7.79); the RD was -0.02 (95% CI -0.06 to 0.03) (a reduction which was not statistically significant). There was a statistically significant increase in weight gain at study day 10 in the lactase treated feeds group but not at any other time points. Overall, there was not a statistically significant effect on weight gain. No adverse effects were noted.

AUTHORS' CONCLUSIONS

The only randomized trial to date provides no evidence of significant benefit to preterm infants from adding lactase to their feeds. Further research regarding effectiveness and safety are required before practice recommendations can be made. Randomized controlled trials comparing lactase versus placebo treated feeds and enrolling infants when enteral feeds are introduced are required. The primary and secondary outcomes for effectiveness and safety should include those identified in this review.

Anti-inflammatory effects of epidermal growth factor on the immature human intestine

The inflammatory response of the preterm infants' intestine underlines its inability to respond to hemodynamic stress, microbes, and nutrients. Recent evidence suggests that exogenous epidermal growth factor (EGF) exerts a therapeutic influence on neonatal enteropathies. However, the molecular mechanisms underlying the beneficial effects of EGF remain to be clarified. The purpose of this study was to evaluate the impact of EGF on the gene expression profiles of the developing human small and large intestine at midgestation in serum-free organ cultures using microarrays. The gene expression profiles of cultured human fetal ileal and colonic explants were investigated in the absence or presence of a physiological concentration of 50 ng/ml EGF for 48 h. Data were analyzed with the Ingenuity Pathway Analysis (IPA) software and confirmed by qPCR. We found a total of 6,474 differentially expressed genes in the two segments in response to EGF. IPA functional analysis revealed that in addition to differentially modulating distinct cellular, molecular, and physiological functions in the small and large intestine, EGF regulated the inflammatory response in both intestinal segments in a distinct manner. For instance, several intestinal-derived chemokines such as CCL2, CCL25, CXCL5, and CXCL10 were found to be differentially regulated by EGF in the immature ileum and colon. The findings showing the anti-inflammatory influence of exogenous EGF suggests a mechanistic basis for the beneficial effects of EGF on neonatal enteropathies. These results reinforce growing evidence that by midgestation, the human small intestine and colon rely on specific and distinct regulatory pathways.

Gene-expression profile analysis in the mid-gestation human intestine discloses greater functional immaturity of the colon as compared with the ileum

BACKGROUND AND OBJECTIVES

The occurrence of many neonatal inflammatory intestinal diseases in preterm infants highlights the susceptibility of the immature intestine to responding inadequately to nutrients and microbes. A better understanding of functional intestinal development is essential for the design of optimal treatments ensuring survival and growth of premature infants. The purpose of this study was to evaluate the gene expression profiles of the human ileum and colon at mid-gestation because these 2 segments are considered to be similar at this stage and are the sites of the most frequent pathologies in preterm infants.

SUBJECTS AND METHODS

We compared the gene-expression profiles of human fetal small and large intestines using a cDNA microarray and analyzed the data with Ingenuity Pathway Analysis software.

RESULTS

We found that a significant proportion of the genes was differentially expressed in the 2 segments. Gene cluster analysis revealed an even higher level of transcriptional dissimilarity at the functional level. For instance, segment-specific/overexpressed gene clusters in the ileum included genes involved with amino acid, vitamin, and mineral metabolism, reflecting the higher level of maturity of the small intestine as compared with the colon in which genes involved with cell cycle, cell death, and cell signaling were the predominant clusters of genes expressed.

CONCLUSIONS

Functional clustering analysis of the differentially expressed genes revealed important functional differences between the 2 segments and a relative immaturity of the colon, suggesting that already at mid-gestation, the 2 intestinal segments should be considered as 2 distinct organs.

The synthesis of 2-, 3-, 4- and 6-O-α-d-glucopyranosyl-d-galactopyranose, and their evaluation as nutritional supplements for pre-term infants

Four methods have been screened for the synthesis of some alpha-D-glucopyranosides, with the recently reported (Mukaiyama) combination of 2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl iodide and triphenylphosphine oxide being the most successful, especially in the diastereoselectivity exhibited. The alpha-D-glucopyranosides so obtained have been deprotected to yield 2-, 3-, 4- and 6-O-alpha-D-glucopyranosyl-D-galactopyranose. Only the last disaccharide showed any hydrolysis by alpha-glycosidases but this success was not emulated by mucosal extracts from the small intestine of the pig.

Development of the infant intestine: implications for nutrition support

The incidence of preterm births has continued to increase over the past 25 years, and therefore the optimal feeding of these infants is an important clinical concern. This review focuses on intestinal development and physiology, with a particular emphasis on developmentally immature functions of the preterm intestine and the resulting implications for nutrition therapies used to feed the preterm infant.

Gut responses to enteral nutrition in preterm infants and animals

Preterm birth is associated with immature digestive function that may require the use of total parenteral nutrition and special oral feeding regimens. Little is known about the responses to oral food in the preterm neonate and how enteral nutrients affect the immature gastrointestinal tract (GIT). In vivo studies are difficult to perform in laboratory rodents because of their small body size and that of immature organs at birth, and this makes the large farm animals (e.g., pigs, cattle, sheep) more attractive models in this field. In these species, preterm delivery at 88%-95% gestation is associated clinical complications and degrees of GIT immaturity similar to those in infants born at 70%-90% gestation. Studies in both animals and infants indicate that the immature GIT responds to the first enteral food with rapid increases in gut mass and surface area, blood flow, motility, digestive capacity, and nutrient absorption. To a large extent, the enteral food responses are birth independent, and can be elicited also in utero, at least during late gestation. Nevertheless, preterm neonates show compromised GIT structure, function, and immunology, particularly when delivered by caesarean section and fed diets other than mother's milk. Formula-fed preterm infants are thus at increased risk of developing diseases such as necrotizing enterocolitis, unless special care is taken to avoid excessive nutrient fermentation and bacterial overgrowth. The extent to which results obtained in preterm animals (most notably the pig) can be used to reflect similar conditions in preterm infants is discussed.

Lactase treated feeds to promote growth and feeding tolerance in preterm infants

BACKGROUND

Successful transition from parenteral nutrition to full enteral feedings during the immediate neonatal period is associated with improved growth in preterm infants. Lactase is the last of the major intestinal disaccharidases to develop in preterm infants. Because of inadequate lactase activity, preterm infants are unable to digest lactose. Lactase preparations could potentially be used to hydrolyze lactose in formulas and breast milk to minimize lactose malabsorption in preterm infants.

OBJECTIVES

To assess the effectiveness and safety of the addition of lactase to milk compared to placebo or no intervention for the promotion of growth and feeding tolerance in preterm infants.

PRIMARY OUTCOMES

Weight gain expressed as g/kg/day, growth expressed as weight, length and head circumference percentile for gestational age, assessed at birth and at 40 weeks post-menstrual age, days to achieve full enteral feeds.

SECONDARY OUTCOMES

Several common outcomes associated with preterm birth, and adverse effects.

SEARCH STRATEGY

Electronic and manual searches were conducted in January 2005 of Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 4, 2004), MEDLINE (1966-Jan 2005), EMBASE (1980-Jan 2005) and CINAHL (1982-Jan 2005), personal files, bibliographies of identified trials and abstracts by the Pediatric Academic Societies' and the European Society of Pediatric Research Meetings published in Pediatric Research.

SELECTION CRITERIA

Types of studies: Randomized or quasi-randomized controlled trials.

PARTICIPANTS

Preterm infants < 37 weeks gestational age.

INTERVENTION

Addition of lactase to milk versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

The standard methods of the Cochrane Neonatal Review Group were followed independently by the reviewers to assess study quality and report outcomes. Treatment effects, calculated using RevMan 4.2, included relative risk (RR), risk difference (RD) and mean difference (MD), all with 95% confidence intervals (CI). A fixed effect model was used for meta-analyses. Heterogeneity tests were not performed as only one study was identified.

MAIN RESULTS

One study enrolling 130 infants of 26 - 34 weeks postconceptual age (mean postnatal age at entry 11 days) was identified and no identified study was excluded. The study was a double blind randomized controlled trial of high quality. Lactase treated feeds were initiated when enteral feedings provided > 75% of daily intake. None of the primary outcomes outlined in the protocol for this review and only one of the secondary outcomes, necrotizing enterocolitis (NEC), were reported on. The RR for NEC was 0.32 (95% CI 0.32 (0.01, 7.79); the RD was -0.02 (95% CI -0.06, 0.03) (a reduction which was not statistically significant). There was a statistically significant increase in weight gain at study day 10 in the lactase treated feeds group but not at any other time points. Overall, there ws not a statistically significant effect on weight gain. No adverse effects were noted.

AUTHORS' CONCLUSIONS

The only randomized trial to date provides no evidence of significant benefit to preterm infants from adding lactase to their feeds. Further research regarding effectiveness and safety are required before practice recommendations can be made. Randomized controlled trials comparing lactase vs placebo treated feeds and enrolling infants when enteral feeds are introduced are recommended. The primary and secondary outcomes for effectiveness and safety should include those identified in this review.

Influence of changes in lactase activity and small-intestinal mucosal growth on lactose digestion and absorption in preterm infants

BACKGROUND

Feeding intolerance (ie, achieving and maintaining full enteral feedings) is a significant problem in preterm infants. A relation exists between feeding intolerance and incomplete lactose digestion.

OBJECTIVES

We sought to identify the factors relating to lactose digestion and absorption, lactase activity, and small-intestinal mucosal growth.

DESIGN

Lactose digestion and absorption, lactase-specific activity, and lumen-to-mucosa water flux as a measure of small-intestinal mucosal surface area were determined by using the triple-lumen perfusion technique on 2 occasions 3 wk apart in 10 preterm infants (x+/-SEM gestational age: 28.0+/-0.2 wk).

RESULTS

Lactose digestion and absorption and lactase activity doubled between studies (P=0.035 and P=0.041, respectively). The change in digestion and absorption was related to lactase activity (P=0.034, R2=0.38). Lactase activity correlated with gestational age at birth (P=0.012, R2=0.51). The number of days of feeding explained 80% of the variability in small-intestinal mucosal surface area (P=0.001).

CONCLUSIONS

To our knowledge, this is the first study to measure directly lactose digestion and absorption, lactase activity, and small-intestinal surface area in preterm infants. Changes in lactose absorption relate primarily to lactase activity rather than to mucosal growth. We showed directly a relation between enteral feeding and small-intestinal mucosal growth.

Developmental aspects of lipid and lipoprotein synthesis and secretion in human gut

This review article focuses on the ontogeny and the regulatory mechanisms involved in the modulation of the intracellular events governing the assembly and delivery of lipoproteins in human gut. The human fetal intestine organizes villi covered with well-differentiated enterocytes during the end of the first trimester in utero. One striking event is the formation of villi in the colonic mucosa similar to those of the small intestine. The small intestine exhibits very early (14-20 weeks) the capacity to absorb lipids, to elaborate most of the major lipoprotein classes (chylomicrons, very-low-density lipoproteins, low-density lipoproteins, high-density lipoproteins), and to efficiently export these lipoproteins from the intestinal cells. The ontogenic changes of lipid and lipoprotein synthesis are correlated with specific patterns of regulatory enzymes (HMG-CoA reductase, ACAT, MGAT) that are representative of key patterns such as the cholesterol pathway, cholesterol esterification, and neutral lipid pathway. The human fetal colon also has the capability to synthesize lipids, lipoproteins, and apolipoproteins. However, comapred with the small intestine, it is much less efficient at exporting these lipoproteins. Epidermal growth factor, insulin, and hydrocortisone, which are known modulators of the brush border digestive functions of the human gut, differentially modulate the synthesis and secretion of lipoproteins in the small intestine and colon. The use of human fetal gut represents a unique model to further our understanding of the complex biosynthetic molecular events essential for the formation and secretion of lipoproteins relevant to human intestine, both in normal or pathological conditions.

Dexamethasone inhibits small intestinal growth via increased protein catabolism in neonatal pigs

Our objective was to determine how dexamethasone (Dex) affects gastrointestinal protein metabolism and growth in neonatal pigs. Two-day-old pigs were given daily subcutaneous injections of either Dex (1 mg/kg body wt, n = 7) or saline (control, n = 6) for 7 days. In vivo protein synthesis was measured after 7 days with a bolus of [3H]phenylalanine. Tissue protein contents were measured in an initial control group of 2-day-old pigs and in control and Dex pigs after 7 days to estimate protein accretion and degradation. In control pigs, the protein accretion in the ileum was nearly sixfold greater than in the jejunum during the 7-day period. Dex nominally altered stomach growth but completely blocked the accretion of protein and DNA in the jejunum and ileum, with reduced villus height in the ileum. Dex increased the fractional protein degradation rate in the ileum (28%) and decreased the absolute protein synthesis rate in the jejunum and ileum by 17 and 21%, respectively. Dex resulted in a 40% lower total intestinal lactase activity compared with controls via reductions in both specific activity and tissue mass, especially in the ileum. Dex significantly decreased the circulating concentrations of insulin-like growth factor (IGF) I and IGF-binding protein (IGFBP)-1, -2, and -3. However, the tissue abundance of the IGF-I receptor in the stomach and ileum was greater in Dex pigs than controls. Our results suggest that Dex significantly inhibits small intestinal growth via both increased degradation and decreased synthesis of protein. Furthermore, the inhibition of intestinal growth resulted in significantly decreased lactose digestive capacity.

Early feeding, feeding tolerance, and lactase activity in preterm infants

OBJECTIVE

We sought to ascertain whether the timing of feeding initiation affected the development of intestinal lactase activity and whether there are clinical ramifications of lower lactase activity.

STUDY DESIGN

Preterm infants (26 to 30 weeks' gestation; n = 135) were randomly assigned to begin enteral feedings at either 4 (early group) or 15 days of age (standard group). At 10, 28, and 50 days of age lactase activity was determined by measuring the urinary ratio of lactulose/lactose after the 2 sugars were administered.

RESULTS

Lactase activity increased significantly over time. Infants in the early group had greater lactase activity at 10 days of age (by 100%) and 28 days of age (by 60%) than the standard group. At 10 days of age lactase activity was greater in milk- versus formula-fed infants. The time required to achieve full enteral feedings, the number of abnormal abdominal x-ray examinations, and the total number of abdominal x-ray examinations were inversely related to lactase activity.

CONCLUSIONS

Early feeding increases intestinal lactase activity in preterm infants. Lactase activity is a marker of intestinal maturity and may influence clinical outcomes. Whether the effects of milk on lactase activity were due to the greater concentration of lactose in human milk compared with that in formula must be determined.

Absorption of lactose, glucose polymers, or combination in premature infants

STUDY OBJECTIVE

To determine the digestion and absorption of lactose, a combination of lactose and glucose polymers, and glucose polymers alone in infants born at 28 to 42 weeks of gestation.

DESIGN

Each infant received the three carbohydrate solutions (85 gm/L concentration) in random order.

SETTING

Tertiary care urban children's hospital.

INTERVENTIONS

A double-lumen perfusion catheter was placed in the duodenum-jejunum. Absorption was defined as the disappearance of the carbohydrate and all its components (e.g., for lactose: galactose, glucose).

MEASUREMENTS AND MAIN RESULTS

Absorption of lactose was less than that of the lactose-glucose polymer combination and the glucose polymers alone. There was no relationship between lactose absorption and postnatal age, whereas absorption of the lactose-glucose polymer combination and the glucose polymers alone correlated with age. Lactose absorption was not related to the number of days that the infants received full-strength feedings or the total number of days of feeding before the study, whereas absorption of both the lactose-glucose polymer combination and the glucose polymers alone was related to both. Absorption of the three solutions was not related to gestational age or to the number of days before the initial feeding. Lactose absorption was greater in infants who received formula alone than in infants fed formula together with human milk.

CONCLUSIONS

Premature infants do not digest and absorb lactose as well as glucose polymers. However, lactose does not impair the absorption of glucose polymers. Lactose assimilation is not affected by maturation, but the type of diet may affect lactose digestion and absorption. In contrast, digestion and absorption of glucose polymers are related to both postnatal age and diet.

Activity distribution of seven digestive enzymes along small intestine in calves during development and weaning

Ten groups of calves were used to study the changes in activity levels and distribution of seven hydrolases in the intestinal mucosa during development and weaning. The calves in the first group were sacrificed at birth while those in the remaining nine groups were either milk-fed until slaughter on days 2, 7, 28, 56, 70, and 119; or weaned between days 28 and 56 and then slaughtered on days 56, 70, and 119, respectively. The small intestine was immediately cut off and divided into five segments, ie, duodenum, proximal jejunum, median jejunum, distal jejunum, and ileum. In the milk-fed animals, the activity levels of aminopeptidases A and N, alkaline phosphatase, lactase, and isomaltase were maximum at 2 days of age, and then declined sharply between days 2 and 7 but did not change significantly thereafter. By contrast, the maltase activity increased between days 7 and 119, while no sucrase activity was detected. Weaning resulted in a decrease in the activity of lactase and an increase in that of aminopeptidase N, maltase, and isomaltase. The distribution of all these enzymes along the small intestine was slightly influenced by age but not at all by weaning.

Specific expression of lactase in the jejunum and colon during postnatal development and hormone treatments in the rat

The expression of lactase was compared in the jejunum and colon of the rat at the levels of enzyme activity and protein and RNA content. We found that the enzyme proteins and the corresponding mRNAs share common features and are encoded by a single gene in both intestinal segments. In the jejunum, large amounts of lactase mRNA and proteins were detected during postnatal development as well as in adult rats, despite the 10-fold decline in lactase specific activity which occurs at weaning. In contrast, in the colon the expression of lactase was restricted to early postnatal development. In the colon, the enzymic activity of lactase and the amounts of protein and mRNA followed parallel development profiles with a peak at day 4 after birth. Injections of thryoxine or epidermal growth factor into neonates led to small modifications in the expression of lactase in the jejunum. On the other hand, these treatments caused a large decline in lactase activity in the colon that paralleled a decrease in the amount of lactase protein and mRNA. These data indicate that the expression of lactase is mainly regulated at the post-transcriptional level in the jejunum, whereas it is controlled at the pretranslational level in the colon.

Imbalance between jejunum and ileum in the response of brush border hydrolases to oral feeding after intravenous alimentation in rats

The effect of oral refeeding after total parenteral nutrition (TPN) on brush border hydrolases was measured in the proximal jejunum and ileum of adult rats. The animals received intravenously for 4 days a mixture of Intralipid 10% and Vamine-Glucose. At the end of TPN, oral feeding was reinstituted and the rats were fed with an isocaloric standard diet (60% carbohydrate, 17% protein, 3% lipid). Sucrase, isomaltase, lactase, and aminopeptidase N activities were measured at the end of TPN and at 1, 3, and 5 days after TPN. Sham-operated rats nourished orally with the standard diet were used as controls. In both intestinal segments, lactase activity showed no significant changes at the end of TPN or during oral realimentation. Isomaltase, and especially sucrase activities, exhibited an important drop at the end of TPN. After TPN, a complete restoration of isomaltase and sucrase activities was obtained in the jejunum only. During oral refeeding a 40% deficit in sucrase activity persisted in the ileum throughout the experimental period, whereas normal isomaltase activity was restored in this segment. Aminopeptidase N activity was lowered by TPN and recovered normal values within a few hours after oral realimentation. Thus, reinstitution of oral feeding after TPN should take into account that the intestine is capable of digesting normal amounts of dietary protein but has a reduced tolerance for carbohydrates.

Effect of different total parenteral nutrition fuel mixes on small intestinal growth and differentiation in the infant miniature pig

Insulin has been proposed as an important factor in the regulation of growth and differentiation of the small intestine. In the newborn miniature pig, we induced significant physiologic increases in serum insulin and the insulin/glucagon ratio without altering serum glucose, beta-hydroxybutyrate, glucagon, cortisol, T3, and T4 using glucose-based total parenteral nutrition (TPN) in one group (group G) compared with a combination of glucose and fat in another group (group G/F). Control animals were sham-operated and fed a pelleted diet (group OC). Duodenal villus surface area and mucosal height were significantly greater in group G/F compared with group G. No other differences between the TPN groups were found in small intestinal growth, mucosal protein, deoxyribonucleic acid and ribonucleic acid content, and disaccharidase activities. As anticipated, group OC demonstrated increased intestinal length, weight, and villous surface area compared with the TPN groups. Ileal sucrase and jejunal and ileal maltase activities were greater in the TPN groups compared with those in group OC. Physiologic changes in serum insulin and the insulin/glucagon ratio induced by the TPN fuel mix do not appear to have altered small intestinal growth, composition, and differentiation in the healthy small intestine.

Small-intestinal and colonic changes after biliopancreatic bypass for morbid obesity

Morphologic and functional adaptations of the functioning intestine were evaluated in 41 patients before and after biliopancreatic bypass for morbid obesity. This surgical procedure diverts pancreatobiliary secretions via the duodenum and the jejunum into the colon, the remaining small intestine being anastomosed to the stomach after antrectomy. In the proximal ileum there was an 80% increase of the height of villi; the specific activities of maltase, sucrase, and aminopeptidase in brush border membranes remained unaffected, and that of lactase tended to decrease. In the distal ileum villi heights increased only by 58%, and disaccharidase activities (except for maltase) were slightly enhanced. In the colon the mucosa displayed, in some patients, focal appearance of true villi, and brush border enzyme activities increased concomitantly. We conclude that biliopancreatic bypass induces an adaptation of all intestinal segments of the functioning intestine; this adaptation tends to compensate for the shortening of the gut continuity.