Edmond H. H. M. Rings

Infliximab therapy in 30 patients with refractory pediatric Crohn disease with and without fistulas in the Netherlands

Objective: The purpose of this study was to describe the clinical experience with the anti–tumor necrosis factor chimeric monoclonal antibody, infliximab, in pediatric patients with Crohn disease in The Netherlands. Design: Descriptive. Methods: Clinical response and adverse effects of infliximab were recorded for pediatric patients with Crohn disease treated from October 1992 to January 2003. Results: Thirty patients (aged 7–18 years) with refractory Crohn disease (with or without severe fistulas) were treated with infliximab. Patients were treated with up to 30 infusions. Mean follow-up was 25.3 months. A total of 212 infusions were administered. Thirteen patients had refractory Crohn disease without fistulas. Six patients showed good long-term response to infliximab treatment (defined as clinical index ≤10 points). Sixteen patients had refractory Crohn disease with draining fistulas. Nine showed good long-term response (closure or nonproductiveness of fistulas). One patient with metastatic Crohn disease in the skin had a good long-term response. Six patients developed an allergic reaction during infusion. In one patient, the allergic reaction occurred after an infliximab-free interval of 9 years. One patient died of sepsis. Conclusions: Infliximab was an effective therapy in 53% of patients with refractory pediatric Crohn disease, with or without fistulas. Approximately half of the patients become unresponsive to infliximab therapy. Randomized controlled studies are mandatory to assess long-term efficacy and safety to define the optimal therapeutic strategy of infliximab therapy in children with Crohn disease.

Lactose intolerance and the genetic regulation of intestinal lactase-phlorizin hydrolase.

Lactase‐phlorizin hydrolase, which hydrolyzes lactose, the major carbohydrate in milk, plays a critical role in the nutrition of the mammalian neonate. Lactose intolerance in adult humans is common, usually due to low levels of small intestinal lactase. Low lactase levels result from either intestinal injury or (in the majority of the worlds adult population) alterations in the genetic expression of lactase. Although the mechanism of decreased lactase levels has been the subject of intensive investigation, no consensus has yet emerged. Recent studies have begun to define the cellular and molecular biology of this enzyme. In animals and humans, a glycosylated precursor is proteolytically cleaved to yield the mature enzyme on the microvillus membrane of the enterocyte, bound to the lipid bilayer only by a hydrophobic anchor sequence. The enzyme hydrolyzes lactose, phlorizin, and glycosylceramides. A decline in lactase specific activity occurs at the time of weaning in most mammalian species; in most humans who have low lactase activity as adults, the decline occurs at approximately 3‐5 years of age. In a few human groups, the elevated juvenile level of lactase specific activity persists throughout adulthood. These developmental patterns of lactase expression are most likely regulated at the level of gene transcription.—Montgomery, R. K.; Büller, H. A.; Rings, E. H. H. M.; Grand, R. J. Lactose intolerance and the genetic regulation of intestinal lactase‐phlorizin hydrolase. FASEB J. 5: 2824‐2832; 1991.

Lactase gene expression during early development of rat small intestine

Expression of lactase messenger (m) RNA and protein in rat small intestine during fetal and postnatal development was analyzed using in situ hybridization and immunohistochemistry. Lactase mRNA was first identified at 18 days of development, and lactase protein was first detected at day 20. Lactase mRNA and protein were present along the entire villus. Lactase mRNA increased, reaching a maximum at day 20. Just before birth a decrease in lactase mRNA was observed. In newborn intestine, lactase mRNA was present only from the base of the villus up to the mid-villus region and was undetectable up to the villus tips. Lactase protein continued to be expressed along the entire villus. These data show that expression of lactase mRNA and protein do not parallel, indicating a posttranscriptional control in fetal development. Lactase gene transcription is initiated late in gestation concomitant with villus formation and is exclusively seen in villus epithelial cells. The restriction after birth of lactase mRNA expression to cells at the villus base suggests the occurrence of a previously unknown step in postnatal differentiation of the enterocyte.

Restriction of lactase gene expression along the proximal-to-distal axis of rat small intestine occurs during postnatal development

BACKGROUND/AIMS Developmental changes of lactase activity along the proximal-to-distal axis of the small intestine are poorly understood. A study of delineate lactase gene expression at the cellular level was undertaken. METHODS The topographical regulation of lactase was studied in conjunction with sucrase-isomaltase in proximal, middle, and distal segments of 0-, 7-, 14-, 16-, 18-, 21-, and 28-day-old and adult rats using in sity hybridization, immunohistochemistry, and ribonuclease protection assays. RESULTS From 0 to 16 days, lactase messenger RNA (mRNA) and protein were abundant along the total length of the small intestine. However, at weaning, lactase mRNA and protein were no longer detectable in the terminal ileum. After 28 days, zones of reduced lactase expression were found in the duodenum and terminal ileum. These zones demonstrated expression of lactase protein in scattered enterocytes along the villus (patchy expression). In contrast, sucrase-isomaltase was first detected at 16 days, with patchy expression along the total small intestine; at 21 days it was abundant. CONCLUSIONS Concordant changes in both lactase mRNA and protein detection during development suggest that the horizontal gradient of lactase enzyme expression is dependent on lactase mRNA abundance. Furthermore, zones of patchy lactase expression appear around weaning and flank the area of high lactase expression in the midintestine. Patchy expression is also found for sucrase-isomaltase before weaning.

Functional Development of Fat Absorption in Term and Preterm Neonates Strongly Correlates with Ability to Absorb Long-Chain Fatty Acids from Intestinal Lumen

Our goal for this study was to determine whether the maturation of fat absorption in neonatal life is functionally related to an increased ability to hydrolyze dietary fat, to absorb long-chain fatty acids, or to do both. In 16 preterm and in eight term neonates, the intestinal ability to hydrolyze triacylglycerols and the capacity to absorb long-chain fatty acids were determined at several times between birth and 5 mo after the term age. These processes were compared with the percentage of fat absorption (formula-fed infants) or with fecal fat excretion (breast-fed infants). The functional capacity to digest triacylglycerols and to absorb the lipolytic products was evaluated by measuring serum concentrations of the lipolytic product [1-13C]palmitate after the enteral administration of tri-1-13C palmitoyl-glycerol. Long-chain fatty acids absorption (i.e. independent of lipolysis) was determined by measuring serum concentrations of [1-13C]stearate after its enteral administration. The efficacy of fat absorption increased in preterm infants (formula-fed) from 91.2 ± 1.1% (mean ± SEM) at 32.3 wk postconceptional age (PCA) to 97.3 ± 0.6% at 53.6 wk PCA (p < 0.001), and in term infants from 91.7 ± 1.8% (40.0 wk PCA) to 97.4 ± 1.3% (58.9 wk PCA, p = 0.07). Both the serum concentration of [1-13C]stearate and that of [1-13C]palmitate appeared highly correlated with the efficacy of fat absorption (r = 0.82, p = 0.02; and r = 0.91, p = 0.004; respectively) and with PCA (r = 0.99, p < 0.001; and r = 0.85, p < 0.02; respectively). These results indicate that the functional development of fat absorption in preterm and term infants is related to the capacity to absorb long-chain fatty acids from the intestine.

Messenger RNA sorting in enterocytes Co-localization with encoded proteins

This study describes the intracellular compartmentalization of three different mRNAs in the polarized rat fetal enterocyte. They encode proteins that are known to be localized within different regions of the epithelial cell namely (i) the apical, membrane‐bound glycoprotein, lactase‐phlorizin hydrolase (lactase), (ii) the mitochondrially localized enzyme, carbamoylphosphate synthetase (CPS), and (iii) the cytoplasmically localized enzyme, phosphoenolpyruvate carboxykinase (PEPCK). These mRNAs are found in close proximity to their respective protein products, i.e. the apical membrane, mitochondria and cytoplasm, respectively. The significance or these observations is twofold: (i) they indicate that mRNAs are sorted into specific domains of the cytosol of intestinal epithelial cells: and (ii) they imply the presence or two distinct pathways of mRNA targeting one that allows transport of mRNAs that are translated on ribosomes associated with the rough endoplasmic reticulum (lactase mRNA), and the other that allows sorting of mRNAs that are translated on free polysames (CPS and PEPCK mRNA).

Intestinal Carbamoyl Phosphate Synthase I in Human and Rat: Expression During Development Shows Species Differences and Mosaic Expression in Duodenum of Both Species

The clinical importance of carbamoyl phosphate synthase I (CPSI) relates to its capacity to metabolize ammonia, because CPSI deficiencies cause lethal serum ammonia levels. Although some metabolic parameters concerning liver and intestinal CPSI have been reported, the extent to which enterocytes contribute to ammonia conversion remains unclear without a detailed description of its developmental and spatial expression patterns. Therefore, we determined the patterns of enterocytic CPSI mRNA and protein expression in human and rat intestine during embryonic and postnatal development, using in situ hybridization and immunohistochemistry. CPSI protein appeared during human embryogenesis in liver at 31–35 e.d. (embryonic days) before intestine (59 e.d.), whereas in rat CPSI detection in intestine (at 16 e.d.) preceded liver (20 e.d.). During all stages of development there was a good correlation between the expression of CPSI protein and mRNA in the intestinal epithelium. Strikingly, duodenal enterocytes in both species exhibited mosaic CPSI protein expression despite uniform CPSI mRNA expression in the epithelium and the presence of functional mitochondria in all epithelial cells. Unlike rat, CPSI in human embryos was expressed in liver before intestine. Although CPSI was primarily regulated at the transcriptional level, CPSI protein appeared mosaic in the duodenum of both species, possibly due to post-transcriptional regulation.

Lactase; Origin, gene expression, localization, and function

Abstract Lactase-phlorizin hydrolase is a small intestinal enzyme responsible for the hydrolysis of the carbohydrate lactose in mammalian milk. During the neonatal period the enzyme is crucial for the nutrition of humans and most other mammals. Subsequently, the specific activity of lactase decreases to low adult levels. In most adult humans and other mammals, large amounts of lactose are no longer tolerated, and lactose ingestion may lead to gastrointestinal symptoms. People of Caucasian extraction and a few isolated other groups form a clear exception with regard to this pattern; high levels of lactase activity are maintained, enabling these people to consume diary products during adult life. This review will describe the role of lactase in the digestion of lactose in mammalian milk. The function and origin of the enzyme will be outlined, and the review will examine relevant issues regarding the consumption of lactose and the clinical syndrome of lactose intolerance. Furthermore, insight provided by molecular and cell biology into gene structure, promoter function, gene transcription, localization of expression in the small intestine, biosynthesis of lactase protein, and enzyme specificities will be outlined. Current thinking with respect to the regulation of expression of lactase during development, and the differences in expression between species and different human populations will also be discussed.

Continuous Enteral Administration Can Enable Normal Amino Acid Absorption in Rats with Methotrexate-Induced Gastrointestinal Mucositis

It is unknown what feeding strategy to use during chemotherapy-induced gastrointestinal mucositis, which causes weight loss and possibly malabsorption. To study the absorptive capacity of amino acids during mucositis, we determined the plasma availability of enterally administered amino acids (AA), their utilization for protein synthesis, and the preferential side of the intestine for AA uptake in rats with and without methotrexate (MTX)-induced mucositis. Four days after injection with MTX (60 mg/kg) or saline (controls), rats received a primed, continuous dual-isotope infusion (intraduodenal and intravenous) of labeled L-leucine, L-lysine, L-phenylalanine, L-threonine, and L-methionine. We collected blood samples, assessed jejunal histology, and determined labeled AA incorporation in proximal and distal small intestinal mucosa, plasma albumin, liver, and thigh muscle. MTX-induced mucositis was confirmed by histology. The median systemic availability of all AA except for leucine was similar in MTX-treated rats and in controls. However, the individual availability of all AA differed substantially within the group of MTX-treated rats, ranging from severely reduced (<10% of intake) to not different from controls (>40% of intake in 5 of 9 rats). More AA originating from basolateral uptake than those originating from apical uptake were used for intestinal protein synthesis in MTX-treated rats (≥420% more, P < 0.05). We conclude that continuous enteral administration can enable normal AA absorption in rats with MTX-induced mucositis. The intestine prefers basolateral AA uptake to meet its need for AA for protein synthesis during mucositis.

Clinical Aspects of Lactose Intolerance in Children and Adults

The principal carbohydrate of human milk is the disaccharide lactose. In human and all mammalian species, lactose is hydrolyzed in the small intestine by lactase-phlorizin hydrolase, also abbreviated as lactase. The absence of lactase results in the passage of undigested lactose into the large intestine and is associated with a well-known clinical syndrome: lactose intolerance. Low lactase levels result either from intestinal injury or, as in the majority of worlds adult population, from alterations in the genetic expression of lactase. In this review terminology, pathophysiology, symptoms, diagnostic procedures, and therapy of lactose intolerance will be discussed.