Transition from parenteral to enteral nutrition induces immediate diet-dependent gut histological and immunological responses in preterm neonates

Necrotizing enterocolitis (NEC) in preterm infants develops very rapidly from a mild intolerance to enteral feeding into intestinal mucosal hemorrhage, inflammation, and necrosis. We hypothesized that immediate feeding-induced gut responses precede later clinical NEC symptoms in preterm pigs. Fifty-six preterm pigs were fed total parenteral nutrition (TPN) for 48 h followed by enteral feeding for 0, 8, 17, or 34 h with either colostrum (Colos, n = 20) or formula (Form, n = 31). Macroscopic NEC lesions were detected in Form pigs throughout the enteral feeding period (20/31, 65%), whereas most Colos pigs remained protected (1/20, 5%). Just 8 h of formula feeding induced histopathological lesions, as evidenced by capillary stasis and necrosis, epithelial degeneration, edema, and mucosal hemorrhage. These immediate formula-induced changes were paralleled by decreased digestive enzyme activities (lactase and dipeptidylpeptidase IV), increased nutrient fermentation, and altered expression of innate immune defense genes such as interleukins (IL-1α, IL-6, IL-18), nitric oxide synthetase, tight junction proteins (claudins), Toll-like receptors (TLR-4), and TNF-α. In contrast, the first hours of colostrum feeding induced no histopathological lesions, increased maltase activity, and induced changes in gene expressions related to tissue development. Total bacterial density was high after 2 days of parenteral feeding and was not significantly affected by diet (colostrum, formula) or length of enteral feeding (8-34 h), except that a few bacterial groups (Clostridium, Enterococcus, Streptococcus species) increased with time. We conclude that a switch from parenteral to enteral nutrition rapidly induces diet-dependent histopathological, functional, and proinflammatory insults to the immature intestine. Great care is required when introducing enteral feeds to TPN-fed preterm infants, particularly when using formula, because early feeding-induced insults may predispose to NEC lesions that are difficult to revert by later dietary or medical interventions.     

Plasma and urine amino acid pattern in preterm infants on enteral nutrition: impact of gestational age

Plasma and urine amino acids were determined by ion-exchange chromatography in 80 healthy preterm infants divided into three groups: (1) 23 0/7–28 0/7, (2) 28 1/7–32 0/7 and (3) 32 1/7–35 0/7 weeks of gestation. Samples were collected from days 5 to 57 of life, when infants were exclusively orally fed. Infants with evidence of underlying diseases were excluded. Concentrations of most plasma amino acids increased with gestational and maturational age; urinary excretion followed an opposite course. Few amino acids depended on postnatal age. Plasma amino acids did not correlate inversely to their counterparts in urine indicating that plasma amino acids do not simply reflect kidney function. Some amino acids in blood and urine were linked to nutrient intake and body weight. Our data clearly indicate the heterogeneity of the preterm cohort; therefore, gestational age-matched reference values have to be used for diagnostic purposes in preterm infants.     

Nutrition of preterm infants in relation to bronchopulmonary dysplasia

Background

The pathogenesis of bronchopulmonary dysplasia (BPD) is multifactorial. In addition to prenatal inflammation, postnatal malnutrition also affects lung development.

Methods

A retrospective study was performed to analyse during the first two weeks of life the total, enteral and parenteral nutrition of premature infants (<31 weeks, birth weight ≤1500 g) born between 08/04 and 12/06.

Results

Ninety-five premature infants were analysed: 26 with BPD (27 ± 1 weeks) and 69 without BPD (28 ± 1 weeks). There was no statistical significant difference in the total intake of fluids, calories, glucose or protein and weight gain per day in both groups. The risk of developing BPD was slightly increased in infants with cumulative caloric intake below the minimal requirement of 1230 kcal/kg and a cumulative protein intake below 43.5 g/kg. Furthermore, the risk of developing BPD was significantly higher when infants had a cumulative fluid intake above the recommended 1840 ml/kg. In infants who developed BPD, the enteral nutrition was significantly lower than in non-BPD infants [456 ml/kg (IQR 744, 235) vs. 685 (IQR 987, 511)]. Infants who did not develop BPD reached 50% of total enteral feeding significantly faster [9.6 days vs. 11.5].

Conclusions

Preterm infants developing BPD received less enteral feeding, even though it was well compensated by the parenteral nutrient supply. Data suggest that a critical minimal amount of enteral feeding is required to prevent development of BPD; however, a large prospective clinical study is needed to prove this assumption.

     

Nutritive and non-nutritive sucking in preterm infants

Nutritive and non-nutritive sucking was studied in 9 preterm infants with postmenstrual ages ranging from 28 to 33 weeks and postnatal ages ranging from 0 to 8 weeks. During nutritive sucking, sucking bursts were longer than sucking pauses. During non-nutritive sucking the opposite was seen. The sucking rate was lower during nutritive sucking. During nutritive sucking the respiratory rate was higher during the pauses than during the bursts. During non-nutritive sucking the respiratory rate was higher during sucking. It is concluded that non-nutritive sucking cannot serve as a model for studying feeding mechanisms in the preterm infant.     

Minimal lung and systemic responses to TNF-alpha in preterm sheep

TNF-alpha has been associated with chorioamnionitis and the subsequent development of bronchopulmonary dysplasia in preterm infants. We asked whether bioactive recombinant ovine TNF-alpha could induce chorioamnionitis, lung inflammation, lung maturation, and systemic effects in fetal sheep. We compared the responses to IL-1alpha, a cytokine known to induce these responses in preterm sheep. Intra-amniotic TNF-alpha caused no chorioamnionitis, no lung maturation, and a very small increase in inflammatory cells in the fetal lung after 5 h, 2 days (d), and 7 d. In contrast, IL-1alpha induced inflammation and lung maturation. TNF-alpha given into the airways at birth increased granulocytes in the bronchoalveolar lavage fluid of ventilated preterm lungs and decreased the mRNA for surfactant protein C but did not adversely effect postnatal lung function. An intravascular injection of IL-1alpha caused a systemic inflammatory response in fetal sheep, whereas there was no fetal response to intravascular TNF-alpha. Fetal and newborn preterm sheep are minimally responsive to TNF-alpha. Therefore, the presence of a mediator such as TNF-alpha in a developing animal does not necessarily mean that it is causing the responses anticipated from previous results in adult animals.     

Comparative physiological responses to stressors in animals.

1. The species-specific experimental response to stressors (SSERTS) analysis has been applied to a number of species under varied short and long term conditions. 2. The measure provides quantitative data relating to the physiological responses of animals when exposed to stressors and results are presented comparing these for different methods of immobilization, euthanasia, etc. at intra- and inter-species level. 3. It is suggested that the SSERTS measure is of greater value for measuring the responses of animals to stressors than is the measurement of the concentration of single blood variables.     

Glucose regulation in preterm newborn infants

After birth, continuous transplacental transfer of glucose is interrupted. Neonates have to provide brain and vital organs with sufficient glucose. In term newborn infants, this is accomplished through well-coordinated hormonal and metabolic adaptive changes. During the first week of life, preterm infants are at high risk of abnormal glucose homeostasis. They are at risk of hypoglycemia due to limited glycogen and fat stores that should have occurred in the third trimester. Continuous glucose infusion is always required soon after birth to maintain the glucose level. However, under such conditions, many preterm infants develop hyperglycemia. Defective islet beta-cell processing of proinsulin is likely related to hyperglycemia. There is also evidence that preterm infants are partially resistant to insulin. By contrast with adults, hepatic glucose production is not suppressed during parenteral glucose infusion. Exogenous insulin infusion partially reduces endogenous glucose production in preterm newborn infants. This treatment is efficient and safe when used with caution. More research is needed to understand the specificity of glucose homeostasis in preterm infants and to evaluate the long-term consequences of metabolic and nutritional support during early life.     

92例脑卒中患者肠外营养和肠内营养治疗效果观察

目的探讨脑卒中患者早期接受肠内营养和肠外营养对并发症及营养指标的影响。方法选取92例重症脑卒中伴吞咽障碍患者按随机表法分为两组,分别给予肠内营养(观察组)和肠外营养(对照组)支持治疗,并观察两组患者治疗前后血清总蛋白(TP)、白蛋白(Alb)、血红蛋白(Hb)水平,治疗前、后神经功能缺损(NIHSS)评分和临床肺部感染评分(CPIS)情况。结果治疗后,观察组的血清总蛋白、白蛋白、血红蛋白明显增高,神经功能缺损评分和临床肺部感染发生率明显降低,与对照组比较,差异均有统计学意义(均P0.05)。结论早期肠内营养支持可改善重症脑卒中患者机体营养指标,降低并发症发生率。     

Physiological responses of estuarine animals to cadmium pollution

Toxic effects of cadmium contamination may be observed at all levels of organismic organization. In estuarine areas the sensitivity of euryhaline species to acute Cd toxicity is strongly modified by various abiotic factors, whereas long-term threshold values are less dependent on environmental parameters. Experiments with larval stages of the molluscMytilus edulis reveal that Cd effects on life functions such as development and growth are differentially modified by temperature and salinity. High Cd concentrations can be accumulated by adult bivalves of coastal areas without signs of physiological damage. Mechanisms of heavy-metal detoxication in these molluscs seem to be quite different from those known to exist in vertebrates. Among decapod crustaceans, stenoecous species tend to exhibit higher rates of Cd uptake than euryoecous ones. Rates of Cd uptake and of accumulation depend on external and internal factors. In adultNereis succinea individuals sublethal Cd effects have been recorded on growth and food conversion (in terms of energy content).     

Iron nutrition and physiological responses to iron stress in Nitrosomonas europaea

Nitrosomonas europaea, as an ammonia-oxidizing bacterium, has a high Fe requirement and has 90 genes dedicated to Fe acquisition. Under Fe-limiting conditions (0.2 μM Fe), N. europaea was able to assimilate up to 70% of the available Fe in the medium even though it is unable to produce siderophores. Addition of exogenous siderophores to Fe-limited medium increased growth (final cell mass). Fe-limited cells had lower heme and cellular Fe contents, reduced membrane layers, and lower NH₃- and NH₂OH-dependent O₂ consumption activities than Fe-replete cells. Fe acquisition-related proteins, such as a number of TonB-dependent Fe-siderophore receptors for ferrichrome and enterobactin and diffusion protein OmpC, were expressed to higher levels under Fe limitation, providing biochemical evidence for adaptation of N. europaea to Fe-limited conditions.