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.     

Upper airway chemoreflex responses to saline and water in preterm infants

Laryngeal chemoreflex (LCR) responses elicited by fluid irrigation of the larynx have been described repeatedly in animals, whereas evidence for a similar reflex in human infants is extremely limited. Using nasopharyngeal catheters to instill small volumes of warm saline or water into the pharynx, we examined the incidence and characteristics of such a reflex in nine premature infants. Saline and water elicited the same pattern of responses, which frequently included swallows, central apnea, and airway obstruction and less commonly featured coughs, prolonged apnea, and arousal. With the exception of arousal, the incidence of these responses was significantly greater after delivery of water stimuli than after saline bolus administration. We therefore deduce chemoreceptor involvement in generation of these reflex responses and propose a laryngeal site for this sensory system, as in animals. Since greater potency of water compared with saline was demonstrable in all the infants studied, we further conclude that most preterm infants possess an upper airway chemoreflex.     

Transgenic animals and nutrition research

Transgenic animals are useful tools for the study of biological functions of proteins and secondary gene products synthesized by the action of protein catalysts. Research in nutrition and allied fields is benefiting from their use as models to contrast normal and altered metabolism. Although food, nutritional products, and ingredients from transgenic animals have not yet reached consumers, the technologies for their production are maturing and yielding exciting results in experimental and farm animals. Regulatory governmental bodies are already issuing guidelines and legislation in anticipation of the advent of these products and ingredients. This review summarizes available technology for the production of transgenic animals, discusses their scientific and commercial potential, and examines ancillary issues relevant to the field of nutrition.     

模型动物中的肠道菌群分析及微生物组研究

正肠道菌群与多种疾病密切相关,从消化道疾病(如炎症性肠病)、心脑血管疾病(如动脉粥样硬化)到代谢类疾病(如II型糖尿病)和许多免疫性疾病(如风湿性关节炎),肠道菌群研究为诸多疾病研究和防治开辟了新的方向[1-3]。在肠道菌群研究领域,模型动物应用和实验结果的动物实验验证非常重要,本刊2016年第7期刊登的姬玉娇、孔祥峰等的论文"高、低营养水平饲粮对环江香猪结肠菌群结构及代谢物的影响"[4],通过对高、     

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.

     

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.     

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.     

Root developmental responses to phosphorus nutrition

Phosphorus is an essential macronutrient for plant growth and development. Root system architecture (RSA) affects a plant's ability to obtain phosphate, the major form of phosphorus that plants uptake. In this review, I first consider the relationship between RSA and plant phosphorus-acquisition efficiency, describe how external phosphorus conditions both induce and impose changes in the RSA of major crops and of the model plant Arabidopsis, and discuss whether shoot phosphorus status affects RSA and whether there is a universal root developmental response across all plant species. I then summarize the current understanding of the molecular mechanisms governing root developmental responses to phosphorus deficiency. I also explore the possible reasons for the inconsistent results reported by different research groups and comment on the relevance of some studies performed under laboratory conditions to what occurs in natural environments.     

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.     

益生菌联合肠内营养对比单用肠内营养在改善胃癌手术患者预后效果的Meta分析

目的 对益生菌联合肠内营养对比单用肠内营养在改善胃癌手术患者预后效果进行Meta分析,以得出综合评价结论。 方法 利用PubMed、Cochrane、Embase、CNKI、维普和万方数据库进行文献检索,搜集有关益生菌联合肠内营养对比单用肠内营养改善胃癌手术患者预后效果的随机对照试验,由2名研究者独立筛选文献、提取资料并评价纳入研究的偏倚风险后,应用RevMan 5.3分析软件进行Meta分析。 结果 最终纳入8个临床随机对照试验,共552例患者。Meta分析显示,与仅用肠内营养相比,益生菌联合肠内营养能更有效地降低胃癌患者术后血清内毒素水平[MD=-15.94,95% CI(-27.40,-4.49),P=0.006]、血清TNF α水平[MD=-9.25,95% CI(-14.51,-3.99),P结论 当前证据表明,益生菌联合肠内营养治疗胃癌术后临床疗效确切,远优于仅用肠内营养,可以增强胃癌患者术后的机体免疫力、降低感染和腹泻的发生率、减轻全身炎性反应、维持肠道微生态的平衡,促进患者康复。受纳入研究数量和质量限制,上述结论尚待更多高质量研究予以验证。     

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.