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Necrotizing enterocolitis is a devastating inflammatory condition of the intestine that occurs almost exclusively in premature newborns. Although its exact pathogenesis is unclear, we have postulated that it may result from a predisposition of the immature intestine to mount an unusually robust and damaging response to microbial infection. In support of this idea, we report that the IL-8 response of an immature human enterocyte cell line to bacterial infection was significantly higher than that of a mature enterocyte cell line. The response in both cell lines was flagellin-dependent. Corresponding to the difference in IL-8 production, the immature enterocytes expressed appreciably lower levels of specific IB genes when compared with the mature enterocytes. Similar developmentally regulated differences in cytokine response and IB expression were also seen in primary rat enterocytes, indicating that these observations were not peculiarities of the cell lines. Furthermore, when the level of IB␣ expression was increased in the immature cell line by transfection, the flagellin-dependent IL-8 response was attenuated. Thus, we have demonstrated a previously undescribed developmental regulation of IB expression in the intestine involved in modulating the IL-8 response to bacterial infection, which may contribute to the pathogenesis of age-specific inflammatory bowel diseases such as necrotizing enterocolitis. E nterocytes are active participants in host defense against microbial invasion. Certain aspects of this function are developmentally regulated, resulting in distinct differences between the immature and mature intestine with respect to interactions with microorganisms (1-4). Immaturity of epithelial barrier function, relative deficiencies in the expression of antimicrobial factors, and developmental variations in the pattern of epithelial surface glycosylation all contribute to the susceptibility of early postnatal intestine to bacterial infection (5-7). Concurrently, the secretion of proinflammatory cytokines is greater at earlier stages of development than in the adult. Specifically, IL-8 production in response to IL-1␤ and tumor necrosis factor ␣ has been shown to be significantly increased in the human fetal intestinal epithelial cell (IEC) line H4 and fetal intestinal organ cultures compared with the adult IEC line Caco2 and biopsies from older children (8). The combination of weaker antimicrobial defense mechanisms and exaggerated cytokine responses may render the immature gut prone to extensive inflammatory damage after infection. These properties could thus contribute to the pathogenesis of age-specific diseases such as necrotizing enterocolitis (NEC), an ischemic and inflammatory bowel necrosis that primarily affects premature neonates after the initiation of enteral feeding.We have postulated a model of NEC pathogenesis in which early feeding results in exposure to numbers and types of bacteria that the premature intestine is ill-equipped to handle (9). The exaggerated inflammatory responses that are cha...

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Milk proteins are frequently used as supplements in fortified foods. However, processing produces chemical changes which likely affect the nutritional advantage. This study was intended to explore the possible difference in digestibility between extruded and non-extruded caseins and how the dietary N (ε) -carboxymethyllysine (CML) is metabolised. Normal rats were randomized into either an extruded protein diet (EP) or the same with unextruded proteins (UEP), for two periods of 2 weeks at 7 to 9 and 11 to 13 weeks of age. However, no difference in protein digestibility was detected between the two diets, either in young or in adult animals, despite a 9.4-fold higher level of CML and an 8.5-fold higher level of lysinoalanine in the EP than in the UEP. No diet-related changes were observed in plasma CML, either protein bound or free. Amounts of 38 and 48 % of the orally absorbed CML were excreted in urine and faeces, respectively, in UEP-fed rats. Lower rates of excretion were found in the EP-fed rats (23 and 37 %, respectively). A second animal study using a single oral dose of free CML (400 μg/rat) was set up to measure the systemic concentration of CML every hour from 0 to 4 h. It revealed that protein-bound CML was not affected by the oral dose of CML, and the highest free CML level found in the circulation was 600 ng/mL. Extruded proteins, therefore, appear to be well digested, and CML rapidly eliminated. Since its elimination is, however, incomplete, the question of its biodistribution and metabolism remains open.

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Low birth weight resulting from intrauterine growth retardation (IUGR) is a risk factor for further development of metabolic diseases. The pig appears to reproduce nearly all of the phenotypic pathological consequences of human IUGR and is likely to be more relevant than rodents in studies of neonatal development. In the present work, we characterized the model of low-birth-weight piglets with particular attention to the hypothalamic leptin-sensitive system, and we tested whether postnatal leptin supplementation can reverse the precocious signs of adverse metabolic programming. Our results demonstrated that 1) IUGR piglets present altered postnatal growth and increased adiposity; 2) IUGR piglets exhibit abnormal hypothalamic distribution of leptin receptors that may be linked to further disturbance in food-intake behavior; and 3) postnatal leptin administration can partially reverse the IUGR phenotype by correcting growth rate, body composition, and development of several organs involved in metabolic regulation. We conclude that IUGR may be characterized by altered leptin receptor distribution within the hypothalamic structures involved in metabolic regulation and that leptin supplementation can partially reverse the IUGR phenotype. These results open interesting therapeutic perspectives in physiopathology for the correction of defects observed in IUGR.

Clostridium difficile, the causative agent of antibiotic-associated colitis, mediates inflammatory diarrhea by releasing toxin A, a potent 308-kDa enterotoxin. Toxin A-induced inflammatory diarrhea involves many steps, including mucosal release of substance P (SP) corticotropin-releasing hormone (CRH) and neutrophil transmigration. Here we demonstrate that, compared with wild type, mice genetically deficient in CRH (Crh ؊/؊ ) have dramatically reduced ileal fluid secretion, epithelial cell damage, and neutrophil transmigration 4 h after intraluminal toxin A administration. This response is associated with diminished mucosal activity of the neutrophil enzyme myeloperoxidase compared with that of wildtype mice. In wild-type mice, toxin A stimulates an increase in intestinal SP content compared with buffer administration. In contrast, toxin A administration in Crh ؊/؊ mice fails to result in an increased SP content. Moreover, immunohistochemical experiments showed that CRH and SP are colocalized in some enteric nerves of wild-type mice, and this colocalization is more evident after toxin A administration. These results provide direct evidence for a major proinflammatory role for CRH in the pathophysiology of enterotoxin-mediated inflammatory diarrhea and indicate a SP-linked pathway.C orticotropin-releasing hormone (CRH), a 41-aa peptide, is a major peptide hormone that modulates the activity of the hypothalamic-pituitary-adrenal axis during stress, including inflammation (1-3). CRH mediates its effects by binding to its G protein-coupled receptor subtypes, CRH1 and CRH2 (4-6). CRH plays a dual role in the pathophysiology of inflammation. CRH secreted from the hypothalamus has indirect antiinflammatory effects via stimulation of glucocorticoid release, but CRH is also expressed peripherally, and its expression is increased in leukocytes, nerve fibers, and other cells involved in inflammatory reactions (7-12). Moreover, in vivo and in vitro studies indicate that CRH is a potent proinflammatory peptide (7,(12)(13)(14)(15).A limited number of studies indicate that CRH and its receptors play a role in the pathophysiology of intestinal inflammation. Thus, Van Tol et al. (11) found increased CRH expression in the rat cecum in colitis induced by injection of peptidoglycan-polysaccharide polymers. Increased expression of CRH-immunoreactive cells was also evident in the colonic mucosa of patients with inflammatory bowel disease (16). CRH gene expression is increased in hypothalamic neurons during colitis after intracolonic administration of 2,4,6-trinitrobenzenesulfonic acid (17) and appears to play a protective role in the worsening of experimental colitis induced by stress (18). We have recently shown that expression of CRH as well as CRH1 and CRH2 was dramatically increased in mouse ileum shortly after intraluminal administration of Clostridium difficile toxin A (19). Moreover, experiments with CRH receptor antagonists indicate that CRH plays a proinflammatory role in toxin A-induced intestinal secretion and inflammatio...