Reduced serum amino acid concentrations in infants with necrotizing enterocolitis

Enteral L-citrulline supplementation in preterm infants is safe and effective in increasing plasma arginine and citrulline levels-a pilot randomized trial

OBJECTIVE

Deficiencies of citrulline and arginine have been associated with adverse outcomes in preterm-infants and data regarding enteral supplementation in preterm infants is limited.

STUDY DESIGN

This randomized -trial [NCT03649932] included 42 preterm infants (gestational age ≤33 weeks) randomized to receive enteral L-citrulline in low (100 mg/kg/day), medium (200 mg/kg/day) and high-dose (300 mg/kg/day) groups for 7 days. Plasma citrulline and arginine levels were obtained pre-and-post supplementation and efficacy was determined by a significant increase in levels after supplementation. A p < 0.05 was considered significant. Safety monitoring included blood-pressure-monitoring as well as complications and death during hospitalization.

RESULTS

A total of 40/42 (95%) of the recruits completed the 7-day supplementation with no adverse events. Plasma-citrulline levels increased significantly in all three groups while plasma-arginine levels increased significantly in the high-dose group.

CONCLUSION

Enteral L-citrulline supplementation in preterm infants is safe and effective in increasing plasma citrulline and arginine levels.

CLINICAL TRIAL REGISTRATION

NCT03649932 https://clinicaltrials.gov/ct2/show/NCT03649932 .

Hyperglycemia and prematurity: a narrative review

Hyperglycemia is commonly encountered in extremely preterm newborns and physiologically can be attributed to immaturity in several biochemical pathways related to glucose metabolism. Although hyperglycemia is associated with a variety of adverse outcomes frequently described in this population, evidence for causality is lacking. Variations in definitions and treatment approaches have further complicated the understanding and implications of hyperglycemia on the immediate and long-term effects in preterm newborns. In this review, we describe the relationship between hyperglycemia and organ development, outcomes, treatment options, and potential gaps in knowledge that need further research. IMPACT: Hyperglycemia is common and less well described than hypoglycemia in extremely preterm newborns. Hyperglycemia can be attributed to immaturity in several cellular pathways involved in glucose metabolism in this age group. Hyperglycemia has been shown to be associated with a variety of adverse outcomes frequently described in this population; however, evidence for causality is lacking. Variations in definitions and treatment approaches have complicated the understanding and the implications of hyperglycemia on the immediate and long-term effects outcomes. This review describes the relationship between hyperglycemia and organ development, outcomes, treatment options, and potential gaps in knowledge that need further research.

Elevated expression of histone deacetylase HDAC8 suppresses arginine-proline metabolism in necrotizing enterocolitis

Epigenetic alterations are especially important in necrotizing enterocolitis (NEC). Here, we reported that histone deacetylase 8 (HDAC8) plays a previously unknown role in modulating arginine metabolism via acetylation of histone 3 lysine 9 (acetyl-H3K9) regulation during the pathogenesis of NEC. We found that HDAC8 was upregulated in humans and mice intestinal samples with NEC, while selective inhibition of HDAC8 expression ameliorated NEC. HDAC8 regulates enzymes involved in the metabolic conversion of proline to arginine (PRODH, PRODH2, OAT, and OTC) and arginine to ornithine (ARG1). The results showed that H3K9ac signal in the PRODH/PRODH2 promoter region was mediated by HDAC8. Additionally, the decreased concentration of butyric acid was strongly correlated with elevated HDAC8 levels and circulating arginine, which may result from an unbalanced Firmicutes/Bacteroidetes ratio. These results reveal previously underappreciated roles of microbial metabolites and HDAC8 to coordinate the arginine metabolism during NEC development.

Metabolic Pathways in Breast Cancer Reprograming: An Insight to Non-Coding RNAs

Cancer cells reprogram their metabolisms to achieve high energetic requirements and produce precursors that facilitate uncontrolled cell proliferation. Metabolic reprograming involves not only the dysregulation in glucose-metabolizing regulatory enzymes, but also the enzymes engaging in the lipid and amino acid metabolisms. Nevertheless, the underlying regulatory mechanisms of reprograming are not fully understood. Non-coding RNAs (ncRNAs) as functional RNA molecules cannot translate into proteins, but they do play a regulatory role in gene expression. Moreover, ncRNAs have been demonstrated to be implicated in the metabolic modulations in breast cancer (BC) by regulating the metabolic-related enzymes. Here, we will focus on the regulatory involvement of ncRNAs (microRNA, circular RNA and long ncRNA) in BC metabolism, including glucose, lipid and glutamine metabolism. Investigation of this aspect may not only alter the approaches of BC diagnosis and prognosis, but may also open a new avenue in using ncRNA-based therapeutics for BC treatment by targeting different metabolic pathways.

Fecal amine metabolite analysis before onset of severe necrotizing enterocolitis in preterm infants: a prospective case-control study

Infants developing necrotizing enterocolitis (NEC) have a different metabolomic profile compared to controls. The potential of specific metabolomics, i.e. amino acids and amino alcohols (AAA), as early diagnostic biomarkers for NEC is largely unexplored. In this multicenter prospective case-control study, longitudinally collected fecal samples from preterm infants (born <30 weeks of gestation) from 1-3 days before diagnosis of severe NEC (Bell's stage IIIA/IIIB), were analyzed by targeted high-performance liquid chromatography (HPLC). Control samples were collected from gestational and postnatal age-matched infants. Thirty-one NEC cases (15 NEC IIIA;16 NEC IIIB) with 1:1 matched controls were included. Preclinical samples of infants with NEC were characterized by five increased essential amino acids-isoleucine, leucine, methionine, phenylalanine and valine. Lysine and ethanolamine ratios were lower prior to NEC, compared to control samples. A multivariate model was rendered based on isoleucine, lysine, ethanolamine, tryptophan and ornithine, modestly discriminating cases from controls (AUC 0.67; p < 0.001). Targeted HPLC pointed to several specific AAA alterations in samples collected 1-3 days before NEC onset, compared to controls. Whether this reflects metabolic alterations and has a role in early biomarker development for NEC, has yet to be elucidated.

Clinical importance of immunonutrition in infants: a review of the recent literature

During the last decades, the role of nutrition has been well elucidated in medicine, especially among critically ill infants and children. Many nutrients have the potential to modulate the immune system. A healthy immune system is essential for the prevention and recovery of many pediatric illnesses. Intervention using specific nutrients for the immune system is called immunonutrition. Immunonutrient supplementation has been attempted to modulate inflammatory or immune responses, leading to an improved clinical course of critically ill patients with prolonged nutritional supplementation parenterally or enterally. This review discusses immunomodulatory nutrients for infants based on the recent literature.

Nutritional Supplements to Improve Outcomes in Preterm Neonates

Preterm infants are at higher risk of mortality and morbidity compared with those born at term. Nutrition-related morbidities include poor growth, immune deficiency, nutritional deficiencies, and adverse long-term neurodevelopment. In addition to macronutrients, many nutritional supplements have been used to enhance growth and development, and decrease infections. Nutrients can enhance preterm infants' immune status, optimize the microbiome, improve growth and development, and influence the risk of necrotizing enterocolitis, sepsis, and other outcomes.

Developmental toxicity of Nafion byproduct 2 (NBP2) in the Sprague-Dawley rat with comparisons to hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX) and perfluorooctane sulfonate (PFOS)

Nafion byproduct 2 (NBP2) is a polyfluoroalkyl ether sulfonic acid that was recently detected in surface water, drinking water, and human serum samples from monitoring studies in North Carolina, USA. We orally exposed pregnant Sprague-Dawley rats to NBP2 from gestation day (GD) 14-18 (0.1-30 mg/kg/d), GD17-21, and GD8 to postnatal day (PND) 2 (0.3-30 mg/kg/d) to characterize maternal, fetal, and postnatal effects. GD14-18 exposures were also conducted with perfluorooctane sulfonate (PFOS) for comparison to NBP2, as well as data previously published for hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX). NBP2 produced stillbirth (30 mg/kg), reduced pup survival shortly after birth (10 mg/kg), and reduced pup body weight (10 mg/kg). Histopathological evaluation identified reduced glycogen stores in newborn pup livers and hepatocyte hypertrophy in maternal livers at ≥ 10 mg/kg. Exposure to NBP2 from GD14-18 reduced maternal serum total T₃ and cholesterol concentrations (30 mg/kg). Maternal, fetal, and neonatal liver gene expression was investigated using RT-qPCR pathway arrays, while maternal and fetal livers were also analyzed using TempO-Seq transcriptomic profiling. Overall, there was limited alteration of genes in maternal or F1 livers from NBP2 exposure with significant changes mostly occurring in the top dose group (30 mg/kg) associated with lipid and carbohydrate metabolism. Metabolomic profiling indicated elevated maternal bile acids for NBP2, but not HFPO-DA or PFOS, while all three reduced 3-indolepropionic acid. Maternal and fetal serum and liver NBP2 concentrations were similar to PFOS, but ∼10-30-fold greater than HFPO-DA concentrations at a given maternal oral dose. NBP2 is a developmental toxicant in the rat, producing neonatal mortality, reduced pup body weight, reduced pup liver glycogen, reduced maternal thyroid hormones, and altered maternal and offspring lipid and carbohydrate metabolism similar to other studied PFAS, with oral toxicity for pup loss that is slightly less potent than PFOS but more potent than HFPO-DA.

Single Nucleotide Polymorphisms in Neonatal Necrotizing Enterocolitis

The etiopathogenesis of necrotizing enterocolitis (NEC) remains unclear, but increasing information suggests that the risk and severity of NEC may be influenced by single nucleotide polymorphisms in many genes. In this article, we have reviewed gene variations that have either been specifically identified in NEC or have been noted in other inflammatory bowel disorders with similar histopathological abnormalities. We present evidence from our own peer-reviewed laboratory studies and data from an extensive literature search in the databases PubMed, EMBASE, and Scopus. To avoid bias in the identification of existing studies, search keywords were short-listed both from our own studies and from PubMed's Medical Subject Heading (MeSH) thesaurus.

Exploring functional metabolites in preterm infants

AIM

Metabolomics is the study of small molecules that represent the functional end points of cellular reactions that can impact health. Necrotising enterocolitis (NEC) and late onset sepsis (LOS) are the main cause of death in preterm infants surviving the initial days of life.

METHODS

This review will explore and summarise the current literature exploring metabolomics in preterm infants.

RESULTS

There are a relatively limited number of studies investigating metabolomics in preterm infants with NEC and/or LOS and matched controls. Nonetheless, it is evident across longitudinally age-related metabolomic studies that there are significant changes in metabolite profiles post-partum and over the first year of life. Existing studies have reported associations between the metabolite profiles of serum, urine and stool in health and disease in preterm infants. Although some studies have found selected metabolites are associated with disease, the specific metabolites vary from study to study, and larger studies are required. Excitingly, recent work has also begun to untangle how microbially produced metabolites can impact immunoregulation of the infant.

CONCLUSION

Metabolic exploration is an emerging research area with huge potential for developing novel biomarkers and better understanding disease processes in preterm infants.

Plasma Citrulline as a Biomarker for Early Diagnosis of Necrotizing Enterocolitis in Preterm Infants

OBJECTIVE

Citrulline synthesized by healthy enterocytes and decreases with injury. This work aimed to study plasma citrulline concentrations (CITs) as a biomarker to differentiate among infants presenting with early nonspecific signs and symptoms of necrotizing enterocolitis (NEC) with those who will develop NEC. Further to study the correlation between posttreatment CIT with time to full feeds (TTFF) and length of stay (LOS).

STUDY DESIGN

This is a prospective study which included infants < 32 weeks gestational age (GA) with 9 infants each in Group 1 (stage 2/3 NEC), Group 2 (with stage 1 NEC-like presentation), and Group 3 (healthy GA-matched infants). CIT was measured in Groups 1 and 2 within 24 hours of presentation and again in Group 1 after treatment.

RESULTS

The three groups were similar in clinical characteristics. Median CIT (µmol/L) in Group 1 (15.4 [interquartile range, IQR: 7.3-18.0]) was lower than Group 2 (22.2 [IQR: 18.3-27.3], p = 0.02) and Group 3 (24.9 [IQR: 19.8-31.9], p = 0.009). Posttreatment CIT in Group 1 did not correlate with TTFF (r = 0.15; p = 0.69) and LOS (r =  - 0.33; p = 0.38).

CONCLUSION

CIT was lower in infants with NEC as compared with healthy controls and those infants with nonspecific signs of NEC. CIT after treatment does not correlate with TTFF and LOS.

KEY POINTS

· Citrulline is produced by enterocytes.. · It is decreased in infants with necrotizing enterocolitis early in disease.. · It can be used as a biomarker for early diagnosis of necrotizing enterocolitis..

Untargeted Metabolomic Analysis of Human Milk from Mothers of Preterm Infants

The application of metabolomics in neonatology offers an approach to investigate the complex relationship between nutrition and infant health. Characterization of the metabolome of human milk enables an investigation into nutrients that affect the neonatal metabolism and identification of dietary interventions for infants at risk of diseases such as necrotizing enterocolitis (NEC). In this study, we aimed to identify differences in the metabolome of breast milk of 48 mothers with preterm infants with NEC and non-NEC healthy controls. A minimum significant difference was observed in the human milk metabolome between the mothers of infants with NEC and mothers of healthy control infants. However, significant differences in the metabolome related to fatty acid metabolism, oligosaccharides, amino sugars, amino acids, vitamins and oxidative stress-related metabolites were observed when comparing milk from mothers with control infants of ≤1.0 kg birth weight and >1.5 kg birth weight. Understanding the functional biological features of mothers’ milk that may modulate infant health is important in the future of tailored nutrition and care of the preterm newborn.

The Functional DNA Methylation Signatures Relevant to Altered Immune Response of Neonatal T Cells with l-Arginine Supplementation

l-Arginine is an important nutrient in the infant diet that significantly regulates the maturation of the immune system in neonates, including the maturation of CD4⁺ T cells. The biological activities of CD4⁺ T cells differ substantially between neonates and adults, and these differences may be governed by epigenetic processes. Investigating these differences and the causative processes may help understand neonatal and developmental immunity. In this study, we compared the functional DNA methylation profiles in CD4⁺ T cells of neonates and adults, focusing on the role of l-arginine supplementation. Umbilical cord blood and adult CD4⁺ T cells were cultured with/without l-arginine treatment. By comparing DNA methylation in samples without l-arginine treatment, we found that CD4⁺ T cells of neonatal cord blood generally showed higher DNA methylation than those of adults (average CpG methylation percentage 0.6305 for neonate and 0.6254 for adult, t-test p-value < 0.0001), suggesting gene silencing in neonates. By examining DNA methylation patterns of CpG dinucleotides induced by l-arginine treatment, we found that more CpG dinucleotides were hypomethylated and more genes appeared to be activated in neonatal T-cells as compared with adult. Genes activated by l-arginine stimulation of cord blood samples were more enriched regarding immune-related pathways. CpG dinucleotides at IL-13 promoter regions were hypomethylated after l-arginine stimulation. Hypomethylated CpG dinucleotides corresponded to higher IL-13 gene expression and cytokine production. Thus, DNA methylation partially accounts for the mechanism underlying differential immune function in neonates. Modulatory effects of l-arginine on DNA methylation are gene-specific. Nutritional intervention is a potential strategy to modulate immune function of neonates.

Newborn metabolic vulnerability profile identifies preterm infants at risk for mortality and morbidity

BACKGROUND

Identifying preterm infants at risk for mortality or major morbidity traditionally relies on gestational age, birth weight, and other clinical characteristics that offer underwhelming utility. We sought to determine whether a newborn metabolic vulnerability profile at birth can be used to evaluate risk for neonatal mortality and major morbidity in preterm infants.

METHODS

This was a population-based retrospective cohort study of preterm infants born between 2005 and 2011 in California. We created a newborn metabolic vulnerability profile wherein maternal/infant characteristics along with routine newborn screening metabolites were evaluated for their association with neonatal mortality or major morbidity.

RESULTS

Nine thousand six hundred and thirty-nine (9.2%) preterm infants experienced mortality or at least one complication. Six characteristics and 19 metabolites were included in the final metabolic vulnerability model. The model demonstrated exceptional performance for the composite outcome of mortality or any major morbidity (AUC 0.923 (95% CI: 0.917-0.929). Performance was maintained across mortality and morbidity subgroups (AUCs 0.893-0.979).

CONCLUSIONS

Metabolites measured as part of routine newborn screening can be used to create a metabolic vulnerability profile. These findings lay the foundation for targeted clinical monitoring and further investigation of biological pathways that may increase the risk of neonatal death or major complications in infants born preterm.

IMPACT

We built a newborn metabolic vulnerability profile that could identify preterm infants at risk for major morbidity and mortality. Identifying high-risk infants by this method is novel to the field and outperforms models currently in use that rely primarily on infant characteristics. Utilizing the newborn metabolic vulnerability profile for precision clinical monitoring and targeted investigation of etiologic pathways could lead to reductions in the incidence and severity of major morbidities associated with preterm birth.

Plasma Metabolomics to Evaluate Progression of Necrotising Enterocolitis in Preterm Pigs

Necrotising enterocolitis (NEC) is a microbiome-dependent gut disease in preterm infants in early life. Antibiotic treatment is a common intervention for NEC. How NEC lesions, with or without antibiotics, affect plasma metabolome was explored in this study. Formula-fed preterm pigs were used as a model for human NEC and treated with saline, parenteral or oral antibiotics (n = 15-17) for four days after delivery. Gut tissues were collected for evaluation of NEC-like lesions and plasma for metabolomic analysis by proton nuclear magnetic resonance spectroscopy (¹H-NMR). Metabolites were annotated, quantified and subjected to statistical modelling to delineate the effects of NEC and antibiotic treatment. Presence of severe NEC lesions, not antibiotic treatment, was the main drive for plasma metabolite changes. Relative to other pigs, pigs with severe NEC lesions had higher levels of alanine, histidine and myo-inositol, and lower levels of 3-hydroxybutyric acid and isobutyric acid. Across NEC lesion states (healthy, mild, severe), antibiotics directly affected only a few metabolites (tryptophan, 3-phenyllactic acid). Together and independently, NEC and antibiotic treatment affected circulating metabolites in preterm pigs. Amino acids and plasma metabolites, partly related to the gut microbiome, may be helpful to monitor progression of NEC lesions after proper validation.

Plasma citrulline during the first 48 h after onset of necrotizing enterocolitis in preterm infants

BACKGROUND

Levels of plasma citrulline (citrulline-P), a biomarker for enterocyte function, might be useful for the monitoring the course of necrotizing enterocolitis (NEC). Our aim was to evaluate whether citrulline-P levels during the first 48 h (h) after NEC onset were associated with need for surgery, survival, and intestinal recovery.

METHODS

In preterm infants with NEC (Bell's stage ≥2) we measured citrulline-P levels during the first 48 h after NEC onset. Categorizing the measurements into 0-8 h, 8-16 h, 16-24 h, 24-36 h, and 36-48 h, we determined the course of citrulline-P using linear regression analyses. Next, we analyzed whether citrulline-P levels measured at 0-24 h and 24-48 h differed between conservative and surgical treatment, survivors and nonsurvivors, and equal/below and above total group's median time to full enteral feeding (FEFt).

RESULTS

We included 48 infants, median gestational age 28.3 [IQR:26.0-31.4] weeks, birth weight 1200 [IQR:905-1524] grams. Citrulline-P levels decreased the first 48 h (B per time interval: -1.40 μmol, 95% CI, -2.73 to -0.07, p = 0.04). Citrulline-P was not associated with treatment, nor with survival. Citrulline-P at 0-24 h, but not 24-48 h, was higher in infants with FEFt ≤20 days than in infants with FEFt >20 days (20.7 [IQR:19.9-25.3] µmol/L (n = 13) vs. 11.1 [IQR:8.4-24.0] µmol/L (n = 11), p = 0.049), with a citrulline-P cut-off value of 12.3 μmol/L.

CONCLUSION

Citrulline-P levels decreased the first 48 h after NEC onset, suggesting on-going intestinal injury. In survivors, measuring citrulline-P in the first 24 h after NEC onset may provide an indication for intestinal recovery rate.

Role of L-Arginine in Nitric Oxide Synthesis and Health in Humans

As a functional amino acid (AA), L-arginine (Arg) serves not only as a building block of protein but also as an essential substrate for the synthesis of nitric oxide (NO), creatine, polyamines, homoarginine, and agmatine in mammals (including humans). NO (a major vasodilator) increases blood flow to tissues. Arg and its metabolites play important roles in metabolism and physiology. Arg is required to maintain the urea cycle in the active state to detoxify ammonia. This AA also activates cellular mechanistic target of rapamycin (MTOR) and focal adhesion kinase cell signaling pathways in mammals, thereby stimulating protein synthesis, inhibiting autophagy and proteolysis, enhancing cell migration and wound healing, promoting spermatogenesis and sperm quality, improving conceptus survival and growth, and augmenting the production of milk proteins. Although Arg is formed de novo from glutamine/glutamate and proline in humans, these synthetic pathways do not provide sufficient Arg in infants or adults. Thus, humans and other animals do have dietary needs of Arg for optimal growth, development, lactation, and fertility. Much evidence shows that oral administration of Arg within the physiological range can confer health benefits to both men and women by increasing NO synthesis and thus blood flow in tissues (e.g., skeletal muscle and the corpora cavernosa of the penis). NO is a vasodilator, a neurotransmitter, a regulator of nutrient metabolism, and a killer of bacteria, fungi, parasites, and viruses [including coronaviruses, such as SARS-CoV and SARS-CoV-2 (the virus causing COVID-19). Thus, Arg supplementation can enhance immunity, anti-infectious, and anti-oxidative responses, fertility, wound healing, ammonia detoxification, nutrient digestion and absorption, lean tissue mass, and brown adipose tissue development; ameliorate metabolic syndromes (including dyslipidemia, obesity, diabetes, and hypertension); and treat individuals with erectile dysfunction, sickle cell disease, muscular dystrophy, and pre-eclampsia.

Progressive Metabolic Dysfunction and Nutritional Variability Precedes Necrotizing Enterocolitis

Necrotizing Enterocolitis (NEC) is associated with prematurity, enteral feedings, and enteral dysbiosis. Accordingly, we hypothesized that along with nutritional variability, metabolic dysfunction would be associated with NEC onset. Methods: We queried a multicenter longitudinal database that included 995 preterm infants (<32 weeks gestation) and included 73 cases of NEC. Dried blood spot samples were obtained on day of life 1, 7, 28, and 42. Metabolite data from each time point included 72 amino acid (AA) and acylcarnitine (AC) measures. Nutrition data were averaged at each of the same time points. Odds ratios and 95% confidence intervals were calculated using samples obtained prior to NEC diagnosis and adjusted for potential confounding variables. Nutritional and metabolic data were plotted longitudinally to determine relationship to NEC onset. Results: Day 1 analyte levels of alanine, phenylalanine, free carnitine, C16, arginine, C14:1/C16, and citrulline/phenylalanine were associated with the subsequent development of NEC. Over time, differences in individual analyte levels associated with NEC onset shifted from predominantly AAs at birth to predominantly ACs by day 42. Subjects who developed NEC received significantly lower weight-adjusted total calories (p < 0.001) overall, a trend that emerged by day of life 7 (p = 0.020), and persisted until day of life 28 (p < 0.001) and 42 (p < 0.001). Conclusion: Premature infants demonstrate metabolic differences at birth. Metabolite abnormalities progress in parallel to significant differences in nutritional delivery signifying metabolic dysfunction in premature newborns prior to NEC onset. These observations provide new insights to potential contributing pathophysiology of NEC and opportunity for clinical care-based prevention.

Relationship between arginine intake in parenteral nutrition and preterm neonatal population plasma arginine concentrations: a systematic review

Context

Very preterm neonates (VPNs) are unable to digest breast milk and therefore rely on parenteral nutrition (PN) formulations. This systematic review was prepared following PRISMA-P 2015 guidelines. For the purpose of this review, desirable mean plasma arginine concentration is defined as ≥80 micromoles/L.

Objective

The review was performed to answer the following research question: “In VPNs, are high amounts of arginine in PN, compared with low amounts of arginine, associated with appropriate circulating concentrations of arginine?” Therefore, the aims were to 1) quantify the relationship between parenteral arginine intakes and plasma arginine concentrations in PN-dependent VPNs; 2) identify any features of study design that affect this relationship; and 3) estimate the target parenteral arginine dose to achieve desirable preterm plasma arginine concentrations.

Data Sources

The PubMed, Scopus, Web of Science, and Cochrane databases were searched regardless of study design; review articles were not included.

Data Extraction

Only articles that discussed amino acid (AA) intake and measured plasma AA profile post PN in VPNs were included. Data were obtained using a data extraction checklist that was devised for the purpose of this review.

Data Analysis

Twelve articles met the inclusion criteria. The dose–concentration relationship of arginine content (%) and absolute arginine intake (mg/(kg × d)) with plasma arginine concentrations showed a significant positive correlation (P < 0.001).

Conclusion

Future studies using AA solutions with arginine content of 17%–20% and protein intakes of 3.5–4.0 g/kg per day may be needed to achieve higher plasma arginine concentrations.

Neonatal comorbidities and gasotransmitters

Hydrogen sulfide, nitric oxide, and carbon monoxide are endogenously produced gases that regulate various signaling pathways. The role of these transmitters is complex as constitutive production of these molecules may have anti-inflammatory, anti-microbial, and/or vasodilatory effects whereas induced production or formation of secondary metabolites may lead to cellular death. Given this fine line between friend and foe, therapeutic attenuation of these molecules' production has involved both inhibition of endogenous formation and therapeutic supplementation. All three gases have been implicated as regulators of critical aspects of neonatal physiology, and in turn, comorbidities including necrotizing enterocolitis, hypoxic ischemic encephalopathy, and pulmonary hypertension. In this review, we present current perspectives on these associations, highlight areas where insights remain sparse, and identify areas for potential for future investigations.

The role of gasotransmitters in neonatal physiology

The gasotransmitters, nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO), are endogenously-produced volatile molecules that perform signaling functions throughout the body. In biological tissues, these small, lipid-permeable molecules exist in free gaseous form for only seconds or less, and thus they are ideal for paracrine signaling that can be controlled rapidly by changes in their rates of production or consumption. In addition, tissue concentrations of the gasotransmitters are influenced by fluctuations in the level of O₂ and reactive oxygen species (ROS). The normal transition from fetus to newborn involves a several-fold increase in tissue O₂ tensions and ROS, and requires rapid morphological and functional adaptations to the extrauterine environment. This review summarizes the role of gasotransmitters as it pertains to newborn physiology. Particular focus is given to the vasculature, ventilatory, and gastrointestinal systems, each of which uniquely illustrate the function of gasotransmitters in the birth transition and newborn periods. Moreover, given the relative lack of studies on the role that gasotransmitters play in the newborn, particularly that of H₂S and CO, important gaps in knowledge are highlighted throughout the review.

A Review of the Immunomodulating Components of Maternal Breast Milk and Protection Against Necrotizing Enterocolitis

Breast milk contains immunomodulating components that are beneficial to newborns during maturation of their immune system. Human breast milk composition is influenced by an infant's gestational and chronological age, lactation stage, and the mother and infant's health status. Major immunologic components in human milk, such as secretory immunoglobulin A (IgA) and growth factors, have a known role in regulating gut barrier integrity and microbial colonization, which therefore protect against the development of a life-threatening gastrointestinal illness affecting newborn infants called necrotizing enterocolitis (NEC). Breast milk is a known protective factor in the prevention of NEC when compared with feeding with commercial formula. Breast milk supplements infants with human milk oligosaccharides, leukocytes, cytokines, nitric oxide, and growth factors that attenuate inflammatory responses and provide immunological defenses to reduce the incidence of NEC. This article aims to review the variety of immunomodulating components in breast milk that protect the infant from the development of NEC.

Use of serum citrulline concentrations from routine newborn screen as a biomarker for necrotizing enterocolitis

PURPOSE

Necrotizing enterocolitis (NEC), a leading cause of mortality and morbidity in preterm neonates, lacks a reliable biomarker. Citrulline is primarily produced by enterocytes and correlates with intestinal function. Serum citrulline concentration (CIT) is routinely measured in routine newborn screening (NBS). The purpose of the study is to test if CIT from NBS may predict the occurrence of NEC and whether it correlates with the time to full feeds (TTFF) and length of stay (LOS), serving as a biomarker of NEC and intestinal health.

METHODS

In a retrospective case control study conducted on neonates with gestational age of 26-32 weeks, we compared CIT levels between cases (neonates with NEC) and controls (next-born neonate). NBS was collected within first 24 h, at day 5 and when the neonates achieved full feeds and were compared using non-parametric tests.

RESULTS

There was no difference in CIT between the controls and cases on day 1 [11.42 (7.42-14.84 vs. 11.93 (6.85-18.8) µmol/L, p = 0.55], on day 5 [11.99 (7.99-16.55) vs. 13.70 (7.42-26.83) µmol/L, p = 0.05], or at full feeds [14.86 (6.85-25.69) vs. 15.7 (7.42-26.26) µmol/L, p = 0.87]. CIT on day 1 did not correlate with TTFF (r = 0.08, p = 0.53) or LOS (r = 0.23, p = 0.06), respectively).

CONCLUSIONS

CIT from routine NBS does not serve as a biomarker to predict NEC in preterm neonates.

A pilot case-control study of urine metabolomics in preterm neonates with necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of gastrointestinal morbidity and mortality in preterm neonates. The aim of this pilot study was to explore using metabolomics alternations in the urine metabolites related to NEC that could possibly serve as diagnostic biomarkers of the disease. Urine samples were prospectively collected at the day of initial evaluation for NEC from 15 diseased preterm neonates (five Bell's stage I and ten stage II/III) and an equal number of matched controls. Urine metabolic profiles were assessed using non-targeted nuclear magnetic resonance spectroscopy and targeted liquid chromatography-tandem mass spectrometry monitoring 108 metabolites. Multivariate statistical models with data from either analytical approach showed clear separation between the metabolic profiles of neonates with NEC and controls. Twenty-five discriminant metabolites were identified belonging to amino and organic acids, sugars and vitamins. A number of metabolite combinations were found to have an excellent diagnostic performance in detecting neonates developing NEC. Our results show that the metabolic profile of neonates with NEC differs significantly from that of controls, making possible their separation using urine metabolomic analysis. Nevertheless, whether the small set of significant metabolites detected in this investigation could be used as early diagnostic biomarkers of NEC should be validated in larger studies.

Pathophysiology of Necrotizing Enterocolitis: An Update

NEC is a devastating disease that, once present, is very difficult to treat. In the absence of an etiologic treatment, preventive measures are required. Advances in decoding the pathophysiology of NEC are being made but a more comprehensive understanding is needed for the targeting of preventative strategies. A better definition of the disease as well as diagnostic criteria are needed to be able to specifically label a disease as NEC. Multiple environmental factors combined with host susceptibility appear to contribute to enhanced risks for developing this disease. Several different proximal pathways are involved, all leading to a common undesired outcome: Intestinal necrosis. The most common form of this disease appears to involve inflammatory pathways that are closely meshed with the intestinal microbiota, where a dysbiosis may result in dysregulated inflammation. The organisms present in the intestinal tract prior to the onset of NEC along with their diversity and functional capabilities are just beginning to be understood. Fulfillment of postulates that support causality for particular microorganisms is needed if bacteriotherapies are to be intelligently applied for the prevention of NEC. Identification of molecular effector pathways that propagate inflammation, understanding of, even incipient role of genetic predisposition and of miRNAs may help solve the puzzle of this disease and may bring the researchers closer to finding a treatment. Despite recent progress, multiple limitations of the current animal models, difficulties related to studies in humans, along with the lack of a "clear" definition will continue to make it a very challenging disease to decipher.

New Nutritional and Therapeutical Strategies of NEC

Necrotizing enterocolitis (NEC) is an acquired severe disease of the digestive system affecting mostly premature babies, possibly fatal and frequently associated to systemic complications. Because of the severity of this condition and the possible long-term consequences on the child's development, many studies have aimed at preventing the occurrence of the primary events at the level of the bowel wall (ischemia and necrosis followed by sepsis) by modifying or manipulating the diet (breast milk versus formula) and/or the feeding pattern (time for initiation after birth, continuous versus bolus feeding, modulation of intake according clinical events). Feeding have been investigated so far in order to prevent NEC. However, currently well-established and shared clinical nutritional practices are not available in preventing NEC. Nutritional and surgical treatments of NEC are instead well defined. In selected cases surgery is a therapeutic option of NEC, requiring sometimes partial intestinal resection responsible for short bowel syndrome. In this paper we will investigate the available options for treating NEC according to the Walsh and Kliegman classification, focusing on feeding practices in managing short bowel syndrome that can complicate NEC. We will also analyze the proposed ways of preventing NEC.

Immunonutrition for Preterm Infants

Care and outcomes for very preterm infants continue to improve, but important causes of mortality and acute and long-term morbidity associated with prolonged hospitalisation remain. Necrotising enterocolitis (NEC) and late-onset infection have emerged as the major causes of death beyond the early neonatal period and of neurodisability in very preterm infants. Although the pathogenesis of these conditions is incompletely understood, it appears to be related to the content and mode of delivery of the enteral diet, particularly the impact of immunonutrients from human breast milk on the microbial and metabolic balance within the immature intestine. Evidence exists to support investment in measures to help mothers to express breast milk as the primary source of nutrition for their very preterm infants. In the absence of maternal milk, pasteurised donor breast milk provides protection against NEC, but its nutritive adequacy is not clear and its cost-effectiveness is uncertain. Supplementation with individual immunonutrients, including immunoglobulins and lactoferrin, has not been shown to be effective in preventing NEC or infection in randomised controlled trials. The evidence base for prebiotics and probiotics is stronger, but concerns exist about the choice, safety and availability of formulations. Other strategies - including avoidance of drugs such as gastric acid suppressants that compromise innate immunity, as well as evidence-based progressive feeding strategies that reduce exposure to invasive interventions - are emerging as key components of care packages to reduce the burden of NEC, infection and associated growth and developmental faltering for very preterm infants.

Enteral feeding composition and necrotizing enterocolitis

Enteral feeding and composition play a chief role in the prevention and treatment of necrotizing enterocolitis (NEC). In the face of decades of research on this fatal disease, the exact mechanism of disease is still poorly understood. There is established evidence that providing mother's own breast milk and standardization of feeding regimens leads to a decreased risk for NEC. More recent studies have focused on the provision of donor human milk or an exclusive human milk diet in the endeavor to prevent NEC while still maintaining adequate nutrition to the premature infant. There is growing literature on the provision of specific human milk components and its effect on the incidence of NEC.

Short Communication: Differences in Levels of Free Amino Acids and Total Protein in Human Foremilk and Hindmilk

Free amino acids (FAAs) in human milk are indicated to have specific functional roles in infant development. Studies have shown differences between human milk that is expressed at the beginning of a feed (i.e., foremilk) and the remainder of the milk expressed (i.e., hindmilk). For example, it is well established that human hindmilk is richer in fat and energy than foremilk. Hence, exclusively feeding hindmilk is used to enhance weight gain of preterm, low birthweight infants. Whether FAAs occur differently between foremilk and hindmilk has never been reported, but given their bioactive capacities, this is relevant to consider especially in situations where hindmilk is fed exclusively. Therefore, this study analyzed and compared the FAA and total protein content in human foremilk and hindmilk samples donated by 30 healthy lactating women. The total protein content was found to be significantly higher in hindmilk (p < 0.001), whereas foremilk contained a significantly higher total content of FAAs (p = 0.015). With regards to individual FAAs, foremilk contained significantly higher levels of phenylalanine (p = 0.009), threonine (p = 0.003), valine (p = 0.018), alanine (p = 0.004), glutamine (p < 0.001), and serine (p = 0.012) than hindmilk. Although statistical significance was reached, effect size analysis of the milk fraction on FAA levels in milk revealed that the observed differences were only small. To what extent these differences are of physiological importance for infant development remains to be examined in future research.

Prematurity reduces citrulline-arginine-nitric oxide production and precedes the onset of necrotizing enterocolitis in piglets

Necrotizing enterocolitis (NEC) is associated with low plasma arginine and vascular dysfunction. It is not clear whether low intestinal citrulline production, the precursor for arginine synthesis, occurs before and thus predisposes to NEC or if it results from tissue damage. This study was designed to test the hypothesis that whole body rates of citrulline, arginine, and nitric oxide synthesis are low in premature pigs and that they precede NEC. Piglets delivered by cesarean section at 103 days [preterm (PT)], 110 days [near-term (NT)], or 114 days [full-term (FT)] of gestation were given total parenteral nutrition and after 2 days orogastrically fed infant formula for 42 h to induce NEC. Citrulline and arginine fluxes were determined before and during the feeding protocol. Gross macroscopic and histological NEC scores and plasma fatty acid binding protein (iFABP) concentration were determined as indicators of NEC. Intestinal gene expression for enzymes of the arginine pathway were quantitated. A lower ( P < 0.05) survival rate was observed for PT (8/27) than for NT (9/9) and FT pigs (11/11). PT pigs had higher macroscopic gross ( P < 0.05) and histological NEC ( P < 0.05) scores and iFABP concentration ( P < 0.05) than pigs of more advanced gestational age. PT pigs had lower citrulline production and arginine fluxes ( P < 0.05) throughout and a reduced gene expression in genes of the citrulline-arginine pathway. In summary, intestinal enzyme expression and whole body citrulline and arginine fluxes were reduced in PT pigs compared with animals of more advance gestational age and preceded the development of NEC. NEW & NOTEWORTHY Arginine supplementation prevents necrotizing enterocolitis (NEC), the most common gastrointestinal emergency of prematurity. Citrulline (precursor for arginine) production is reduced during NEC, and this is believed to be a consequence of intestinal damage. In a swine model of NEC, we show that intestinal gene expression of the enzymes for citrulline production and whole body citrulline and arginine fluxes are reduced and precede the onset of NEC in premature pigs. Reduced citrulline production during prematurity may be a predisposition to NEC.

Pig models on intestinal development and therapeutics

The gastrointestinal tract plays a vital role in nutrient supply, digestion, and absorption, and has a crucial impact on the entire organism. Much attention is being paid to utilize animal models to study the pathogenesis of gastrointestinal diseases in response to intestinal development and health. The piglet has a body size similar to that of the human and is an omnivorous animal with comparable anatomy, nutritional requirements, and digestive and associated inflammatory processes, and displays similarities to the human intestinal microbial ecosystem, which make piglets more appropriate as an animal model for human than other non-primate animals. Therefore, the objective of this review is to summarize key attributes of the piglet model with which to study human intestinal development and intestinal health through probing into the etiology of several gastrointestinal diseases, thus providing a theoretical and hopefully practical, basis for further studies on mammalian nutrition, health, and disease, and therapeutics. Given the comparable nutritional requirements and strikingly similar brain developmental patterns between young piglets and humans, the piglet has been used as an important translational model for studying neurodevelopmental outcomes influenced by pediatric nutrition. Because of similarities in anatomy and physiology between pigs and mankind, more emphasises are put on how to use the piglet model for human organ transplantation research.

Arginine supplementation for prevention of necrotising enterocolitis in preterm infants

BACKGROUND

Decreased concentration of nitric oxide has been proposed as one of the possible cellular mechanisms of necrotising enterocolitis (NEC). Arginine can act as a substrate for production of nitric oxide in the tissues, and arginine supplementation may help to prevent NEC.

OBJECTIVES

To examine the effect of arginine supplementation (administered by any route) on the incidence of NEC in preterm neonates. To conduct subgroup analyses based on the dose of arginine and the gestational age of participants (≤ 32 weeks, > 32 weeks).

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 4), MEDLINE via PubMed (from 1966 to 12 May 2016), Embase (from 1980 to 12 May 2016) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; from 1982 to 12 May 2016). We also searched clinical trials databases, conference proceedings and reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of arginine supplementation (administered orally or parenterally for at least seven days, in addition to what an infant may be receiving from an enteral or parenteral source) compared with placebo or no treatment.

DATA COLLECTION AND ANALYSIS

We assessed the methodological quality of trials by using information obtained from study reports and through personal communication with study authors. We extracted data on relevant outcomes and estimated and reported the effect size as risk ratio (RR), risk difference (RD) and mean difference (MD), as appropriate. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the quality of evidence.

MAIN RESULTS

We identified three eligible studies that included a total of 285 neonates (140 received arginine) from three countries. We assessed the overall methodological quality of the included studies as good. We noted a statistically significant reduction in risk of development of NEC (any stage) among preterm neonates in the arginine group compared with the placebo group (RR 0.38, 95% confidence interval (CI) 0.23 to 0.64; I2 = 27%) (RD -0.19, 95% CI -0.28 to -0.10; I2 = 0%) and rated the quality of evidence as moderate. The number needed to treat for an additional beneficial outcome (NNTB) as required to prevent the development of NEC (any stage) was 6 (95% CI 4 to 10). Study results showed a statistically significant reduction in risk of development of NEC stage 1 (RR 0.37, 95% CI 0.15 to 0.90; I2 = 52%) (RD -0.07, 95% CI -0.14 to -0.01; I2 = 0%) and NEC stage 3 (RR 0.13, 95% CI 0.02 to 1.03; I2 = 0%) (RD -0.05, 95% CI -0.09 to -0.01; I2 = 89%) in the arginine group compared with the control group; the quality of evidence was moderate.Arginine supplementation was associated with a significant reduction in death related to NEC (RR 0.18, 95% CI 0.03 to 1.00; I2 = 0%) (RD -0.05, 95% CI -0.09 to -0.01; I2 = 87%). Results showed clinical heterogeneity in mortality rates. Mortality due to any cause was not significantly different between arginine and control or no treatment groups (RR 0.77, 95% CI 0.41 to 1.45; I2 = 42%) (RD -0.03, 95% CI -0.10 to 0.04; I2 = 79%). Investigators noted no significant side effects directly attributable to arginine, including hypotension or alterations in glucose homeostasis. Follow-up data from one trial revealed no statistically significant differences in adverse outcomes (cerebral palsy, cognitive delay, bilateral blindness or hearing loss requiring hearing aids) at 36 months. Limitations of the present findings include a relatively small overall sample size.

AUTHORS' CONCLUSIONS

Administration of arginine to preterm infants may prevent development of NEC. Because information was provided by three small trials that included 285 participants, the data are insufficient at present to support a practice recommendation. A multi-centre randomised controlled study that is focused on the incidence of NEC, particularly at more severe stages (2 and 3), is needed.

Supplemental Citrulline Is More Efficient Than Arginine in Increasing Systemic Arginine Availability in Mice

Background: Arginine is considered to be an essential amino acid in various (patho)physiologic conditions of high demand. However, dietary arginine supplementation suffers from various drawbacks, including extensive first-pass extraction. Citrulline supplementation may be a better alternative than arginine, because its only fate in vivo is conversion into arginine.Objective: The goal of the present research was to determine the relative efficiency of arginine and citrulline supplementation to improve arginine availability.Methods: Six-week-old C57BL/6J male mice fitted with gastric catheters were adapted to 1 of 7 experimental diets for 2 wk. The basal diet contained 2.5 g l-arginine/kg, whereas the supplemented diets contained an additional 2.5, 7.5, and 12.5 g/kg diet of either l-arginine or l-citrulline. On the final day, after a 3-h food deprivation, mice were continuously infused intragastrically with an elemental diet similar to the dietary treatment, along with l-[¹³C₆]arginine, to determine the splanchnic first-pass metabolism (FPM) of arginine. In addition, tracers were continuously infused intravenously to determine the fluxes and interconversions between citrulline and arginine. Linear regression slopes were compared to determine the relative efficiency of each supplement.Results: Whereas all the supplemented citrulline (105% ± 7% SEM) appeared in plasma and resulted in a marginal increase of 86% in arginine flux, supplemental arginine underwent an ∼70% FPM, indicating that only 30% of the supplemental arginine entered the peripheral circulation. However, supplemental arginine did not increase arginine flux. Both supplements linearly increased (P < 0.01) plasma arginine concentration from 109 μmol/L for the basal diet to 159 and 214 μmol/L for the highest arginine and citrulline supplementation levels, respectively. However, supplemental citrulline increased arginine concentrations to a greater extent (35%, P < 0.01).Conclusions: Citrulline supplementation is more efficient at increasing arginine availability than is arginine supplementation itself in mice.

L-arginine attenuates Interleukin-1β (IL-1β) induced Nuclear Factor Kappa-Beta (NF-κB) activation in Caco-2 cells

Background

Specific nutrients like L-arginine (L-Arg) ameliorate intestinal inflammation, however the exact mechanisms of this effect are unclear. We hypothesized the anti-inflammatory effects of L-Arg require active transport and metabolism by inducible nitric oxide synthase (iNOS) to generate nitric oxide (NO). To test this hypothesis we examined the effects of L-Arg, L-Arg transport activity, NO production and iNOS inhibitor on IL-1β-mediated NF-κB-activation in Caco-2 cells.

Methods

Caco-2 cells were cultured, transfected with a NF-κB promoter luciferase vector, incubated ± L-Arg, ± IL-1β and luciferase activity was measured. Using siRNA we inhibited the L-Arg cationic amino acid transporter system y⁺ (CAT1) expression and examined its effects on L-Arg transport activity and IL-1β-mediated NF-κB-activation. Finally, the effects of sodium nitroprusside (SNP, a NO donor) and Nω-nitro-L-arginine (NNA, an iNOS inhibitor) on IL-1β-mediated NF-κB-activation were examined.

Results

IL-1β increased NF-κB luciferase activity (8-fold) and NF-κB expression (mRNA and protein), both of these were significantly decreased by L-Arg. System y⁺ CAT1 siRNA decreased CAT1 expression, L-Arg transport activity and attenuated the inhibitory effects of L-Arg on NF- κB activity. SNP attenuated the IL-1β-induced increase in NF-κB luciferase activity and expression, whereas NNA diminished the inhibitory effects of L-Arg on IL-1β-inducible NF- κB luciferase activity.

Conclusion

The inhibitory effects of L-Arg on IL-1β-mediated NF-κB-activation in Caco-2 cells involve L-Arg transport activity by CAT1, regulation of IL-1β-mediated increases in NF-κB expression, changes in iNOS expression and NO production. Our data suggest the inhibitory effects of L-Arg on NF-κB activation are mediated in part by iNOS since SNP preserves and NNA attenuates the effects of L-Arg on IL-1β-mediated NF-κB-activation and expression.

Soy-Based Therapeutic Baby Formulas: Testable Hypotheses Regarding the Pros and Cons

Soy-based infant formulas have been consumed in the United States since 1909, and currently constitute a significant portion of the infant formula market. There are efforts underway to generate genetically modified soybeans that produce therapeutic agents of interest with the intent to deliver those agents in a soy-based infant formula platform. The threefold purpose of this review article is to first discuss the pros and cons of soy-based infant formulas, then present testable hypotheses to discern the suitability of a soy platform for drug delivery in babies, and finally start a discussion to inform public policy on this important area of infant nutrition.

Current Research on the Epidemiology, Pathogenesis, and Management of Necrotizing Enterocolitis

Despite decades of research on necrotizing enterocolitis, we still do not fully understand the pathogenesis of the disease, or how to prevent or how to treat it. However, as a result of recent significant advances in the microbiology, molecular biology, and cell biology of the intestine of preterm infants and infants with necrotizing enterocolitis, there is some hope that research into this devastating disease will yield some important translation into effective prevention, more rapid diagnosis, and novel therapies.

Association between the p.Thr1406Asn polymorphism of the carbamoyl-phosphate synthetase 1 gene and necrotizing enterocolitis: A prospective multicenter study

The p.Thr1406Asn (rs1047891) polymorphism of the carbamoyl-phosphate synthetase 1 (CPS1) gene has been linked to functional consequences affecting the downstream availability of the nitric oxide precursor L-arginine. L-arginine concentrations are decreased in preterm infants with necrotizing enterocolitis (NEC). In this multicenter prospective study, we investigated the association of the p.Thr1406Asn polymorphism with NEC in 477 preterm infants (36 cases of NEC) from 4 European neonatal intensive care units (Maastricht, Las Palmas de Gran Canaria, Mantova, and Milan). Allele and genotype frequencies of the p.Thr1406Asn polymorphism did not significantly differ between the infants with and without NEC. In contrast, the minor A-allele was significantly less frequent in the group of 64 infants with the combined outcome NEC or death before 34 weeks of corrected gestational age than in the infants without the outcome (0.20 vs. 0.31, P = 0.03). In addition, a significant negative association of the A-allele with the combined outcome NEC or death was found using the dominant (adjusted odds ratio, aOR: 0.54, 95% CI 0.29–0.99) and the additive (aOR 0.58, 95% CI 0.36–0.93) genetic models. In conclusion, our study provides further evidence that a functional variant of the CPS1 gene may contribute to NEC susceptibility.

Reduced Hsp70 and Glutamine in Pediatric Severe Malaria Anemia: Role of Hemozoin in Suppressing Hsp70 and NF-κB activation

Severe malarial anemia [SMA, hemoglobin (Hb) <5.0 g/dL] is a leading cause of global morbidity and mortality among children residing in Plasmodium falciparum transmission regions. Exploration of molecular pathways through global gene expression profiling revealed that SMA was characterized by decreased HSPA1A, a heat shock protein (Hsp) 70 coding gene. Hsp70 is a ubiquitous chaperone that regulates Nuclear Factor-kappa B (NF-κB) signaling and production of pro-inflammatory cytokines known to be important in malaria pathogenesis (e.g., IL-1β, IL-6 and TNF-α). Since the role of host Hsp70 in malaria pathogenesis is unexplored, we investigated Hsp70 and molecular pathways in children with SMA. Validation experiments revealed that leukocytic HSP70 transcripts were reduced in SMA relative to non-severe malaria, and that intraleukocytic hemozoin (PfHz) was associated with lower HSP70. HSP70 was correlated with reticulocyte production and Hb. Since glutamine (Gln) up-regulates Hsp70, modulates NF-κB activation, and attenuates over-expression of pro-inflammatory cytokines, circulating Gln was measured in children with malaria. Reduced Gln was associated with increased risk of developing SMA. Treatment of cultured peripheral blood mononuclear cells (PBMCs) with PfHz caused a time-dependent decrease in Hsp70 transcripts/protein, and NF-κB activation. Gln treatment of PBMCs overcame PfHz-induced suppression of HSP70 transcripts/protein, reduced NF-κB activation, and suppressed over-expression of IL-1β, IL-6 and TNF-α. Findings here demonstrate that SMA is characterized by reduced intraleukocytic HSP70 and circulating Gln, and that PfHz-induced suppression of HSP70 can be reversed by Gln. Thus, Gln supplementation may offer important immunotherapeutic options for futures studies in children with SMA.

Effect of L-arginine and sildenafil citrate on intrauterine growth restriction fetuses: a meta-analysis

Background

Intrauterine growth restriction (IUGR) is associated with perinatal morbidity and mortality. Several clinical trials have reported L-arginine and sildenafil citrate had effect on intrauterine growth restriction fetuses. A meta-analysis of available randomized controlled trials (RCTs) was conducted to investigate the effects of L-arginine and sildenafil citrate on major clinical outcomes of IUGR fetuses.

Methods

Systematically searched Medline, Embase, the Cochrane Library, and Clinical Trials, references of retrieved articles, and conference proceedings from 1960 to 2015. We included randomized controlled trials assessing the effects of L-arginine and sildenafil citrate on IUGR. Outcomes analyzed were the birth weight, gestational age at labor, Apgar score at 1and 5 min, the ratio of NRDS, the ratio of ICH and neonatal death, etc.

Results

Ten trials were included. Nine trials (576 patients) compared L-arginine with either placebo or no intervention. In the L-arginine treatment groups of the L-arginine trials, there was a significant increase in fetal birth weight (SMD 0.41, 95 % CI [0.24,0.58]), gestational age (SMD 0.30, 95 % CI [0.07,0.54]); L-arginine treatment group have a significant reduction in the ratio of neonatal respiratory distress syndrome (P = 0.009), intracranial hemorrhage of fetuses (P = 0.002), but the number of included studies and people on these outcomes are small. As only one trial (41 patients) compared sildenafil citrate with placebo, it was too small for reliable conclusions about possible differential effects could be drawn.

Conclusions

The results of this meta-analysis showed that L-arginine increased birth weight and prolonged gestational age at labor of IUGR fetuses. However, further large-scale RCTs are needed to adequately assess the effect of L-arginine and Sildenafil citrate on clinical outcomes, because the number of study may be small.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-016-1009-6) contains supplementary material, which is available to authorized users.

Current research in necrotizing enterocolitis

Despite decades of research on necrotizing enterocolitis, we still do not fully understand the pathogenesis of the disease, how to prevent or how to treat the disease. However, as a result of recent significant advances in the microbiology, molecular biology, and cell biology of the intestine of premature infants and infants with necrotizing enterocolitis, there is some hope that research into this devastating disease will yield some important translation into improved outcomes.

Fetal and postnatal ovine mesenteric vascular reactivity

BACKGROUND

Intestinal circulation and mesenteric arterial (MA) reactivity may play a role in preparing the fetus for enteral nutrition. We hypothesized that MA vasoreactivity changes with gestation and vasodilator pathways predominate in the postnatal period.

METHODS

Small distal MA rings (0.5-mm diameter) were isolated from fetal (116-d, 128-d, 134-d, and 141-d gestation, term ~ 147 d) and postnatal lambs. Vasoreactivity was evaluated using vasoconstrictors (norepinephrine (NE) after pretreatment with propranolol and endothelin-1(ET-1)) and vasodilators (NO donors A23187 and s-nitrosopenicillamine (SNAP)). Protein and mRNA assays for receptors and enzymes (endothelin receptor A, alpha-adrenergic receptor 1A (ADRA1A), endothelial NO synthase (eNOS), soluble guanylyl cyclase (sGC), and phosphodiesterase5 (PDE5)) were performed in mesenteric arteries.

RESULTS

MA constriction to NE and ET-1 peaked at 134 d. Relaxation to A23187 and SNAP was maximal after birth. Basal eNOS activity was low at 134 d. ADRA1A mRNA and protein increased significantly at 134 d and decreased postnatally. sGC and PDE5 protein increased from 134 to 141 d.

CONCLUSION

Mesenteric vasoconstriction predominates in late-preterm gestation (134 d; the postconceptional age with the highest incidence of necrotizing enterocolitis (NEC)) followed by a conversion to vasodilatory influences near the time of full-term birth. Perturbations in this ontogenic mechanism, including preterm birth, may be a risk factor for NEC.

Endogenous Synthesis of Amino Acids Limits Growth, Lactation, and Reproduction in Animals

Amino acids (AAs) are building blocks of protein. Eight AAs (Ala, Asn, Asp, Glu, Gln, Gly, Pro, and Ser) are formed by all animals, whereas de novo synthesis of Arg occurs in a species-specific manner in most mammals (e.g., humans, pigs, and rats). Synthesizable AAs were traditionally classified as nutritionally nonessential for animals, because they were thought to be formed in sufficient amounts. However, this assumption is not supported by evidence showing that 1) rats grow slowly when their diets do not contain Arg, Glu, or Gln despite adequate provision of all other proteinogenous AAs; 2) pigs cannot achieve maximum growth, lactation, or reproduction performance when fed corn- and soybean meal-based diets meeting National Research Council-recommended requirements of protein and AAs without supplemental Arg, Glu, Gln, Gly, or Pro; 3) chickens exhibit increases in lean tissue gain and feed efficiency when their diets are supplemented with Glu, Gln, Gly, and Pro; 4) lactating cows cannot obtain maximum milk protein production without a postruminal supply of Gln or Pro; 5) fish cannot achieve maximum growth when diets do not contain Gln or Pro; and 6) men fail to sustain spermatogenesis when fed an Arg-deficient diet. Quantitative analysis of nitrogen metabolism showed that AA synthesis in animals is constrained by both precursor availability and enzyme activity. Taken together, these findings support the conclusion that the endogenous synthesis of AAs limits growth, lactation, and reproduction in animals. This new knowledge can guide the optimization of human nutrition for improving health and well-being.

Metabolomics in Newborns

Metabolomics is the quantitative analysis of a large number of low molecular weight metabolites that are intermediate or final products of all the metabolic pathways in a living organism. Any metabolic profiles detectable in a human biological fluid are caused by the interaction between gene expression and the environment. The metabolomics approach offers the possibility to identify variations in metabolite profile that can be used to discriminate disease. This is particularly important for neonatal and pediatric studies especially for severe ill patient diagnosis and early identification. This property is of a great clinical importance in view of the newer definitions of health and disease. This review emphasizes the workflow of a typical metabolomics study and summarizes the latest results obtained in neonatal studies with particular interest in prematurity, intrauterine growth retardation, inborn errors of metabolism, perinatal asphyxia, sepsis, necrotizing enterocolitis, kidney disease, bronchopulmonary dysplasia, and cardiac malformation and dysfunction.

Reduced early dried blood spot citrulline levels in preterm infants with meconium obstruction of prematurity

BACKGROUND

Citrulline is a non-protein amino acid synthesized in the enterocytes of the small bowel. Recent studies have reported that plasma citrulline levels correlate with functional enterocyte mass.

AIMS

This study aimed to determine the normal dried blood spot (DBS) citrulline levels and to determine the existence of a correlation between citrulline levels and meconium obstruction of prematurity (MOP).

STUDY DESIGN AND SUBJECTS

A retrospective cohort study was performed involving 285 infants born at less than 32weeks gestation who were admitted to the neonatal intensive care unit between Oct 2009 and Aug 2014.

OUTCOME MEASURES

We analyzed the DBS citrulline levels, which are routinely measured via newborn screening at 7days following birth, using liquid chromatography-MS/MS. We investigated the relationship between DBS citrulline levels and clinical parameters such as gestational age (GA), body measurements at birth, gender, or the presence or absence of either necrotizing enterocolitis or MOP.

RESULTS

A total of 229 infants with a median GA of 29.6weeks and a median birth weight of 1160g were included. DBS citrulline levels were not associated with GA, body measurements at birth or gender. DBS citrulline levels were significantly decreased when patients presented with MOP (p=0.037).

CONCLUSIONS

Early DBS citrulline levels were not associated with either GA or body measurements at birth but were reduced among preterm infants with MOP compared with the control infants. These results may be indicative of abnormal fetal intestinal development and reduced functional enterocyte mass among preterm infants with MOP.

Dysregulated expression of arginine metabolic enzymes in human intestinal tissues of necrotizing enterocolitis and response of CaCO2 cells to bacterial components

The small intestine is the exclusive site of arginine synthesis in neonates. Low levels of circulating arginine have been associated with the occurrence of necrotizing enterocolitis (NEC) but the mechanism of arginine dysregulation has not been fully elucidated. We aimed to investigate (i) expressional changes of arginine synthesizing and catabolic enzymes in human intestinal tissues of NEC, spontaneous intestinal perforation (SIP) and noninflammatory surgical conditions (Surg-CTL) and to investigate the (ii) mechanisms of arginine dysregulation and enterocyte proliferation upon stimulation by bacterial components, arginine depletion, ARG1 overexpression and nitric oxide (NO) supplementation. Our results showed that expressions of arginine synthesizing enzymes ALDH18A1, ASL, ASS1, CPS1, GLS, OAT and PRODH were significantly decreased in NEC compared with Surg-CTL or SIP tissues. Catabolic enzyme ARG1 was increased (>100-fold) in NEC tissues and histologically demonstrated to be expressed by infiltrating neutrophils. No change in arginine metabolic enzymes was observed between SIP and Surg-CTL tissues. In CaCO2 cells, arginine metabolic enzymes were differentially dysregulated by lipopolysaccharide or lipoteichoic acid. Depletion of arginine reduced cell proliferation and this phenomenon could be partially rescued by NO. Overexpression of ARG1 also reduced enterocyte proliferation. We provided the first expressional profile of arginine metabolic enzymes at the tissue level of NEC. Our findings suggested that arginine homeostasis was severely disturbed and could be triggered by inflammatory responses of enterocytes and infiltrating neutrophils as well as bacterial components. Such reactions could reduce arginine and NO, resulting in mucosal damage. The benefit of arginine supplementation for NEC prophylaxis merits further clinical evaluation.

The metabolomics of necrotising enterocolitis in preterm babies: an exploratory study

OBJECTIVE

No single diagnostic investigation is currently available for necrotising enterocolitis (NEC). We implemented a novel, untargeted, exploratory study to determine whether metabolomics can reveal early biomarker(s) of NEC. The effect of gestational age on the metabolome was also investigated.

METHODS

Two serum samples were obtained from 12 preterm babies (born <30 weeks gestation) and eight term controls: sample "A" at ≤1 week of age and sample "B" once fully fed. Samples were subjected to gas chromatography-mass spectrometry. Metabolomic data was analysed by principal component analysis (PCA), univariate and network analysis.

RESULTS

Sixteen metabolite features significantly differed when B samples were compared between preterm babies who subsequently developed NEC and preterm/term controls (p value <0.05). Of these seven metabolites were linked to up-regulation of IL-1β. Significant differences in 54 metabolite features (p value <0.05) were observed between preterm and term metabolomes. Of these, 12 metabolite features were linked to one network involved in carbohydrate/lipid metabolism (p = 1 × 10(-30)).

CONCLUSIONS

Metabolomic differences were observed in preterm babies at risk of NEC. However, sample sizes were insufficient to confidently identify a biomarker. Network modelling of preterm and term metabolomes suggest possible nutritional deficiency and altered pro-insulin action in preterm babies.

Arginine depletion increases susceptibility to serious infections in preterm newborns

Preterm newborns are highly susceptible to bacterial infections. This susceptibility is regarded as being due to immaturity of multiple pathways of the immune system. However, it is unclear whether a mechanism that unifies these different, suppressed pathways exists. Here, we argue that the immune vulnerability of the preterm neonate is critically related to arginine depletion. Arginine, a "conditionally essential" amino acid, is depleted in acute catabolic states, including sepsis. Its metabolism is highly compartmentalized and regulated, including by arginase-mediated hydrolysis. Recent data suggest that arginase II-mediated arginine depletion is essential for the innate immune suppression that occurs in newborn models of bacterial challenge, impairing pathways critical for the immune response. Evidence that arginine depletion mediates protection from immune activation during first gut colonization suggests a regulatory role in controlling gut-derived pathogens. Clinical studies show that plasma arginine is depleted during sepsis. In keeping with animal studies, small clinical trials of L-arginine supplementation have shown benefit in reducing necrotizing enterocolitis in premature neonates. We propose a novel, broader hypothesis that arginine depletion during bacterial challenge is a key factor limiting the neonate's ability to mount an adequate immune response, contributing to the increased susceptibility to infections, particularly with respect to gut-derived sepsis.

Plasma levels of dimethylarginines in preterm very low birth weight neonates: its relation with perinatal factors and short-term outcome

Endogenously produced inhibitors of nitric oxide (NO) synthase, in particular asymmetric dimethylarginine (ADMA), are currently considered of importance in various disease states characterized by reduced NO availability. We investigated the association between plasma levels of ADMA, symmetric dimethylarginine (SDMA), l-arginine, and citrulline and perinatal factors and outcome in 130 preterm (gestational age ≤30 weeks) very low birth weight (VLBW, <1500 g) infants. Plasma samples were collected 6–12 h after birth. We did not find significant correlations between ADMA, SDMA, l-arginine, and citrulline levels and gestational age or birth weight. However, the arginine:ADMA ratio (AAR, a better indicator of NO availability than either arginine or ADMA separately) was positively correlated with gestational age. ADMA and arginine levels were not significantly different between males and females but males showed a negative correlation between ADMA levels and gestational age. Perinatal factors such as preeclampsia, chrorioamnionitis, prolonged rupture of membranes, or form of delivery did not significantly alter dimethylarginine levels or AAR. In contrast, the AAR was significantly reduced in the infants with respiratory distress, mechanical ventilation, and systemic hypotension Therefore, our data suggest that altered NO availability may play a role in the respiratory and cardiovascular adaptation in preterm VLBW infants.

Plasma glutamine deficiency is associated with multiple organ failure in critically ill children

A low plasma glutamine concentration (<420 µmol/L) is an independent risk factor for mortality in critically ill adult patients. Glutamine metabolism in children is less well characterized. However, pediatric ICU (PICU) mortality is low and, therefore, mortality is difficult to use as an endpoint. Here we evaluated if plasma glutamine concentration at admission to the PICU, relates to the development of multiple organ failure, using pediatric logistic organ dysfunction score (PELOD)-score. In this observational study, consecutive critically ill children (n = 149) admitted to the PICU of a tertiary university hospital as well as a reference group of healthy children (n = 60) were included. Plasma glutamine concentration and the PELOD were determined at admission for all patients and at day 5 for those patients still in the PICU. Plasma glutamine concentration at admission was low in the PICU patients as compared to controls (p = 0.00002) and patients with a low plasma glutamine concentration had more organ failure as compared to patients with higher plasma glutamine concentration (p = 0.0001). Plasma glutamine concentration normalized in patients staying >5 days in the PICU. Plasma glutamine depletion was present in 40 % of patients at PICU admission and it was associated with the development of multiple organ failure. Furthermore, the majority of the critically ill children normalized their plasma glutamine concentration within 5 days, which is different from adult ICU patients. The study suggests that an initial plasma glutamine deficiency is associated with multiple organ failure in critically ill children.