Immunonutrients and neonates

Endari treatment ameliorates sickle cell-related disruption in intestinal barrier functions and is associated with prolonged survival in sickle cell mice

BACKGROUND

Endari (L-glutamine) is a conditional amino acid that reduces the frequency of vaso-occlusive crisis (VOC) in sickle cell disease (SCD).

AIM

To investigate whether Endari could ameliorate intestinal barrier function and improve survival outcomes in SCD.

METHODS

We treated female Townes SCD mice with Endari and evaluated their intestinal barrier functions by measuring the recovery of orally administered fluorescein isothiocyanate (FITC)-conjugated dextran 4 kDa in serum, and serum intestinal fatty acid binding proteins (iFABP) and lipopolysaccharide (LPS) concentrations by ELISA. We also explored the impact the Endari has on the survival of the SCD mice that underwent repeated experimentally-induced VOC.

RESULTS

Compared to SCD mice treated with water only, Endari-treated mice showed improved intestinal barrier functions, with decrease in the barrier permeability and reduction in the translocation of lipopolysaccharides from the intestinal lumen into the circulation. These changes occurred after only 4 weeks of Endari treatment. Improved intestinal barrier function was also associated with prolonged survival in Endari-treated SCD mice after repeated experimentally-induced VOC.

CONCLUSION

Our findings provide the evidence supporting the beneficial effects of Enadri in improving intestinal barrier function and associated survival outcomes in SCD.

Nutrition and Immunity in Perinatal Hypoxic-Ischemic Injury

Perinatal hypoxia ischaemia (PHI), acute and chronic, may be associated with considerable adverse outcomes in the foetus and neonate. The molecular and cellular mechanisms of injury and repair associated with PHI in the perinate are not completely understood. Increasing evidence is mounting for the role of nutrients and bioactive food components in immune development, function and repair in PHI. In this review, we explore current concepts around the neonatal immune response to PHI with a specific emphasis on the impact of nutrition in the mother, foetus and neonate.

L-glutamine for sickle cell disease: more than reducing redox

Oxidative stress is a major contributor to the pathophysiology of sickle cell disease (SCD) including hemolysis and vaso-occlusive crisis (VOC). L-glutamine is a conditionally essential amino acid with important roles, including the synthesis of antioxidants, such as reduced glutathione and the cofactors NAD(H) and NADP(H), as well as nitric oxide. Given the increased levels of oxidative stress and lower (NADH):(NAD +  + NADH) ratio in sickle erythrocytes that adversely affects the blood rheology compared to normal red blood cells, L-glutamine was investigated for its therapeutic potential to reduce VOC. While L-glutamine was approved by the United States (US) Food and Drug Administration to treat SCD, its impact on the redox environment in sickle erythrocytes is not fully understood. The mechanism through which L-glutamine reduces VOC in SCD is also not clear. In this paper, we will summarize the results of the Phase 3 study that led to the approval of L-glutamine for treating SCD and discuss its assumed mechanisms of action. We will examine the role of L-glutamine in health and propose how the extra-erythrocytic functions of L-glutamine might contribute to its beneficial effects in SCD. Further research into the role of L-glutamine on extra-erythrocyte functions might help the development of an improved formulation with more efficacy.

Effects of probiotics on the enhancement of the innate mucosal immune response against pathogenic bacteria

Background and Objectives:

Probiotics have been widely used for host immune system enhancement but with limited knowledge regarding the immunomodulation mechanisms by which they assist the mucosal innate immune response. We investigated the effects of probiotics on the modulation of the innate mucosal immune response particularly in association with Toll-like receptor (TLR)-2, TLR-4 and nuclear factor-kappa B (NF-κB) p65 and p105.

Materials and Methods:

We randomized 24 male BALB/c mice into four groups. Two groups were administered probiotics for 21 consecutive days; one of these groups was challenged with Lipopolysaccharide (LPS) on day 15. The third group was challenged with only LPS. The fourth group remained untreated. All mice were sacrificed after 21 days. An immunohistochemistry procedure on the ileum was performed and monoclonal antibodies specific for TLR-2, TLR-4 and NF-κB p65 and p105 were used for the analysis of innate lymphoid cells.

Results:

In the LPS-only treated group, there was a significant decrease in p105, indicating an alternative transcription pathway for the process of pro-inflammatory cytokine production. In the probiotics-only treated group there was significant enhancement of TLR-2 and TLR-4 and NF-κB p65 and p105. When mice treated with probiotics were exposed to LPS, there was a significant decrease in NF-κB p65 and p105, indicating employment of the classical pathway for pro-inflammatory cytokine production.

Conclusion:

Probiotics can enhance the innate mucosal immune response in healthy mice and can maintain the homeostasis of the gut mucosal immune response against LPS through the activation of the classical NF-κB pathway.

Free Amino Acids in Human Milk: A Potential Role for Glutamine and Glutamate in the Protection Against Neonatal Allergies and Infections

Breastfeeding is indicated to support neonatal immune development and to protect against neonatal infections and allergies. Human milk composition is widely studied in relation to these unique abilities, which has led to the identification of various immunomodulating components in human milk, including various bioactive proteins. In addition to proteins, human milk contains free amino acids (FAAs), which have not been well-studied. Of those, the FAAs glutamate and glutamine are by far the most abundant. Levels of these FAAs in human milk sharply increase during the first months of lactation, in contrast to most other FAAs. These unique dynamics are globally consistent, suggesting that their levels in human milk are tightly regulated throughout lactation and, consequently, that they might have specific roles in the developing neonate. Interestingly, free glutamine and glutamate are reported to exhibit immunomodulating capacities, indicating that these FAAs could contribute to neonatal immune development and to the unique protective effects of breastfeeding. This review describes the current understanding of the FAA composition in human milk. Moreover, it provides an overview of the effects of free glutamine and glutamate on immune parameters relevant for allergic sensitization and infections in early life. The data reviewed provide rationale to study the role of free glutamine and glutamate in human milk in the protection against neonatal allergies and infections.

Short communication: Performance, intestinal permeability, and metabolic profile of calves fed a milk replacer supplemented with glutamic acid

The objective of this study was to evaluate the potential benefits of supplementing glutamic acid in milk replacers (MR) with respect to calf performance, intestinal permeability, and metabolism. Sixty Holstein male calves (3 ± 1.3 d old and 45 ± 5.9 kg body weight) were individually housed and fed a control MR without AA supplementation (24.8% crude protein and 19.1% fat, dry matter basis), or MR supplemented with 0.3% glutamic acid (25.1% crude protein and 20.3% fat, dry matter basis). Animals followed the same MR feeding program and were weaned at 56 d of the study. The amount of starter concentrate offered was restricted to limit the effect of concentrate intake on calf metabolism. Individual daily consumption and weekly body weight were measured, and 4 h after the morning feeding, blood samples were obtained at 14 and 35 d to determine general biochemical parameters and plasma AA concentrations. On d 10 of the study, we conducted an intestinal permeability test by including 21 g of lactulose and 4.2 g of d-mannitol as markers in the MR. We found no differences in calf performance or in intestinal permeability (measured as lactulose:mannitol ratio). Serum glucose concentration was greater in unsupplemented calves than in Glu-supplemented calves. At 14 d, the proportion of plasma Leu was greater in Glu-supplemented calves; the proportion of Ile tended to be greater in Glu-supplemented calves; and the proportion of Met tended to be greater in unsupplemented calves. We observed no other differences. Small changes occurred in AA metabolism when supplementing calf MR with 0.3% glutamic acid, without leading to improvements in calf performance or changes in intestinal permeability.

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.

Lysozyme-rich milk mitigates effects of malnutrition in a pig model of malnutrition and infection

Malnutrition remains a leading contributor to the morbidity and mortality of children under the age of 5 years and can weaken the immune system and increase the severity of concurrent infections. Livestock milk with the protective properties of human milk is a potential therapeutic to modulate intestinal microbiota and improve outcomes. The aim of this study was to develop an infection model of childhood malnutrition in the pig to investigate the clinical, intestinal and microbiota changes associated with malnutrition and enterotoxigenic Escherichia coli (ETEC) infection and to test the ability of goat milk and milk from genetically engineered goats expressing the antimicrobial human lysozyme (hLZ) milk to mitigate these effects. Pigs were weaned onto a protein–energy-restricted diet and after 3 weeks were supplemented daily with goat, hLZ or no milk for a further 2 weeks and then challenged with ETEC. The restricted diet enriched faecal microbiota in Proteobacteria as seen in stunted children. Before infection, hLZ milk supplementation improved barrier function and villous height to a greater extent than goat milk. Both goat and hLZ milk enriched for taxa (Ruminococcaceae) associated with weight gain. Post-ETEC infection, pigs supplemented with hLZ milk weighed more, had improved Z-scores, longer villi and showed more stable bacterial populations during ETEC challenge than both the goat and no milk groups. This model of childhood disease was developed to test the confounding effects of malnutrition and infection and demonstrated the potential use of hLZ goat milk to mitigate the impacts of malnutrition and infection.

Glutamine randomized studies in early life: the unsolved riddle of experimental and clinical studies

Glutamine may have benefits during immaturity or critical illness in early life but its effects on outcome end hardpoints are controversial. Our aim was to review randomized studies on glutamine supplementation in pups, infants, and children examining whether glutamine affects outcome. Experimental work has proposed various mechanisms of glutamine action but none of the randomized studies in early life showed any effect on mortality and only a few showed some effect on inflammatory response, organ function, and a trend for infection control. Although apparently safe in animal models (pups), premature infants, and critically ill children, glutamine supplementation does not reduce mortality or late onset sepsis, and its routine use cannot be recommended in these sensitive populations. Large prospectively stratified trials are needed to better define the crucial interrelations of “glutamine-heat shock proteins-stress response” in critical illness and to identify the specific subgroups of premature neonates and critically ill infants or children who may have a greater need for glutamine and who may eventually benefit from its supplementation. The methodological problems noted in the reviewed randomized experimental and clinical trials should be seriously considered in any future well-designed large blinded randomized controlled trial involving glutamine supplementation in critical illness.

Glutamine supplementation in sick children: is it beneficial?

The purpose of this review is to provide a critical appraisal of the literature on Glutamine (Gln) supplementation in various conditions or illnesses that affect children, from neonates to adolescents. First, a general overview of the proposed mechanisms for the beneficial effects of Gln is provided, and subsequently clinical studies are discussed. Despite safety, studies are conflicting, partly due to different effects of enteral and parenteral Gln supplementation. Further insufficient evidence is available on the benefits of Gln supplementation in pediatric patients. This includes premature infants, infants with gastrointestinal disease, children with Crohn's disease, short bowel syndrome, malnutrition/diarrhea, cancer, severe burns/trauma, Duchenne muscular dystrophy, sickle cell anemia, cystic fibrosis, and type 1 diabetes. Moreover, methodological issues have been noted in some studies. Further mechanistic data is needed along with large randomized controlled trials in select populations of sick children, who may eventually benefit from supplemental Gln.

Glutamine as an immunonutrient

Dietary supplementation with nutrients enhancing immune function is beneficial in patients with surgical and critical illness. Malnutrition and immune dysfunction are common features in hospitalized patients. Specific nutrients with immunological and pharmacological effects, when consumed in amounts above the daily requirement, are referred to as immune-enhancing nutrients or immunonutrients. Supplementation of immunonutrients is important especially for patients with immunodeficiency, virus or overwhelming infections accompanied by a state of malnutrition. Representative immunonutrients are arginine, omega-3 fatty acids, glutamine, nucleotides, beta-carotene, and/or branched-chain amino acids. Glutamine is the most abundant amino acid and performs multiple roles in human body. However, glutamine is depleted from muscle stores during severe metabolic stress including sepsis and major surgery. Therefore it is considered conditionally essential under these conditions. This review discusses the physiological role of glutamine, mode and dose for glutamine administration, as well as improvement of certain disease state after glutamine supplementation. Even though immunonutrition has not been widely assimilated by clinicians other than nutritionists, immunonutrients including glutamine may exert beneficial influence on diverse patient populations.

Nutritional challenges and outcomes after surgery for congenital heart disease

PURPOSE OF REVIEW

Adequate nutrition is crucial in children after surgery for congenital heart disease. We address selected nutritional and caloric requirements for children in the perioperative period before and after cardiac surgery and explore nutritional interdependence with other system functions. Recommendations based on our current practice are made at the end of each section.

RECENT FINDINGS

Early identification of deficient oropharyngeal motor skills and vocal cord dysfunction is crucial to establish enteral nutrition safely and has been demonstrated to improve clinical outcomes. The use of prealbumin as a marker of nutritional state should be accompanied by C-reactive protein given the influence of inflammation on its levels. Insulin infusions may improve outcomes in patients with postoperative hyperglycemia. Trace element abnormalities and early identification of immune-compromised states can aid in reducing morbidity in children after cardiac surgery. Use of feeding protocols and a home surveillance system for hypoplastic left heart syndrome improves outcomes.

SUMMARY

Adequate nutritional support in children after cardiac surgery is a challenge. Attention to lesion-specific feeding problems, supplementation of trace elements and minerals, and an organized approach to pace, timing, and type of feeding are beneficial.

Glutamine enhances glucose-induced mesangial cell proliferation

The proliferation of mesangial cells (MC) in the presence of glutamine (0-20 mM) was determined in both low (5 mM) and high (25 mM) glucose-containing medium. Glutamine in a high glucose (HG) environment increased cell proliferation in a dose-dependent manner. Inhibition of glutamine:fructose 6-phosphate amidotransferase (GFAT) and of phosphodiesterase significantly reduced glutamine-induced proliferation. Supraphysiologic levels of glutamine increase MC proliferation in a HG milieu via GFAT and cAMP-dependent pathways, suggesting that glutamine could pose a risk for diabetic nephropathy.

Immunomodulation. Part IV: Glutamine

Glutamine, a nonessential amino acid that appears to be conditionally essential during periods of physiologic stress, plays important physiologic roles in the immune system. However, neither enteral nor parenteral glutamine supplementation makes a difference in the rate of systemic infection or of NEC in very low birth weight infants. Thus, the search for agents to enhance the neonate's immune system and to serve as safe and effective adjuvants to antibiotics continues. Part V, the final article in this immunomodulation series, will explore the use of probiotics to support the neonatal immune system.

Bifidobacterium breve enhances transforming growth factor beta1 signaling by regulating Smad7 expression in preterm infants

OBJECTIVES

Transforming growth factor (TGF) beta1 displays a broad spectrum of activities in mucosal regulation, including induction of oral tolerance, potent anti-inflammatory effects, mucosal IgA expression and effects on epithelial cell proliferation and differentiation. The present study examined the effect of probiotics on the immunologic system of preterm infants in relation to TGF-beta signaling.

METHODS

Subjects comprised 19 preterm infants divided into 2 groups: receiving Bifidobacterium breve supplementation (B. breve group) and without supplementation (controls). Blood samples were collected from both groups on days 0, 14 and 28 after birth. Serum cytokine levels were measured using enzyme-linked immunosorbent assay, and expression levels of the TGF-beta signaling molecule, Smad, were examined using semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Serum TGF-beta1 level was elevated on day 14 and remained elevated on day 28 in the B. breve group. Level of messenger RNA expression was enhanced for Smad3 and reduced for Smad7 (antagonistic Smad) after B. breve administration relative to levels in controls on day 28.

CONCLUSIONS

These results demonstrated that the administration of B. breve to preterm infants can up-regulate TGF-beta1 signaling and may possibly be beneficial in attenuating inflammatory and allergic reactions in these infants.

Immunonutrition

PURPOSE OF REVIEW

To outline recent findings on the efficacy of immunonutrients in patients undergoing inflammatory stress due to surgery, infection and cancer.

RECENT FINDINGS

Enteral nutrition is more efficacious and poses lower risks than parenteral nutrition. It reduces infection rates and shortens ICU and hospital length of stay of critically ill patients. Beneficial effects of immunonutrition are most apparent in malnourished patients. Perioperative enteral nutrition is more effective than postoperative nutrition. In Crohn disease similar remission rates are achieved with enteral nutrition as with steroids. Glutamine, omega-3 fatty acids and antioxidants exert beneficial influences in diverse patient populations. L-arginine is an important immunonutrient having both beneficial and adverse effects. The former effect occurs in necrotizing enterocolitis; the latter influence is seen in septic patients. The gut plays a major role in whole body amino acid metabolism, particularly arginine homeostasis. Arginase and nitric oxide synthetase compete for arginine within immune cells and play a pivotal role in clinical outcome during infection. In cancer a range of antioxidants are able to ameliorate immunosuppression. Intravenous lipids may be deleterious due to the pro-inflammatory effects of omega-6 fatty acids. Omega-3 fatty acids are anti-inflammatory and combined with medium chain triglyceride (MCT) and olive oil may provide a more efficacious form of intravenous lipid.

SUMMARY

Immunonutrition is effective in improving outcome in a wide range of patients when applied enterally, particularly in malnourished individuals. Parenteral immunonutrition carries a higher risk but can be efficacious in selected patient groups for whom enteral nutrition is problematic.

Proteins and amino acids in enteral nutrition

PURPOSE OF REVIEW

This review reports recent findings on the effect of enterally fed protein and amino acids on metabolism, function, and clinical outcome, particularly during the neonatal period.

RECENT FINDINGS

Splanchnic tissues metabolize significant proportions of some enteral amino acids and this likely contributes to the higher requirement for these amino acids when they are provided enterally versus parenterally. Splanchnic tissues are particularly key in the provision of nutrition to preterm infants, who possess an exceedingly high protein anabolic drive, but limited tolerance to aggressive enteral feeding. The protein anabolic response to specific proteins is influenced by the rate of digestion and the pattern of feeding, as well as the amino acid composition of the proteins. The post-prandial rise in amino acids and insulin stimulates neonatal tissue protein synthesis by modulation of the nutrient and insulin signaling pathways that lead to translation initiation. A flurry of investigations into the metabolic response and clinical impact of individual amino acids suggests that leucine, glutamine, and arginine, in particular, have specific roles in regulating protein synthesis and immune function.

SUMMARY

Recent findings suggest that enteral nutrition support that provides an optimum combination of proteins and amino acids can have a beneficial impact on the clinical outcome of patients.