Evolution of in vitro cow's milk protein-specific inflammatory and regulatory cytokine responses in preterm infants with necrotising enterocolitis

Exploring the links between necrotizing enterocolitis and cow's milk protein allergy in preterm infants: a narrative review

A broad range of allergic disorders and intolerance are associated with cow's milk protein in the infant diet. Allergy and intolerance to cow's milk proteins are commonly recognized in the healthy term infant, and the prevalence cow's milk protein intolerance (CMPI) varies widely but 5 challenge confirmed studies free from selection bias ranged from 1.9%-4.9%. These disorders are classified by the presence of IgE, non-IgE or T-cell-mediated signaling. Additionally, the severity of these adverse food reactions can range from mild gastrointestinal symptoms to severe sepsis-like episodes, as in the case of food protein-induced enterocolitis syndrome (FPIES). Food protein-induced intolerance in the healthy young infant lies in stark contrast to enterocolitis that typically occurs in the preterm neonate. Necrotizing enterocolitis (NEC) is a distinct progressive disease process, usually characterized by a high mortality rate, with a risk of death from 30% to 50%. While its exact etiology is unclear, its main triggers include formula (cow's milk protein), hypoxia, perfusion-related issues, and unregulated inflammation in the premature intestine. The distinction between NEC and cow's milk protein intolerance is difficult to discern in some cases. In the late preterm population, infants with colitis can have both NEC and cow's milk intolerance on the differential. In infants with multiple episodes of mild NEC, cow's milk protein intolerance may be the underlying diagnosis. In this review, we compare the pathophysiological characteristics, diagnosis and treatment of disorders of cow's milk protein intolerance with the entity of preterm NEC. This review highlights similarities in both entities and may inspire future cross-disciplinary research.

Malabsorption Syndromes and Food Intolerance

Feeding intolerance is ubiquitous in neonatal intensive care units with as many signs and symptoms as possible diagnoses. Optimizing nutrition is paramount in both preterm and term infants. Determining the cause of feeding intolerance and adjusting nutrition interventions is an important part of the daily care of newborns. This review discusses the role of malabsorption and food intolerance as possible causes of nutrition difficulties in the newborn.

Comparative effectiveness of liquid human milk fortifiers: A systematic review and meta-analysis

OBJECTIVE

To determine the effectiveness of liquid human milk fortifiers (HMFs) derived from exclusive HM or hydrolyzed protein on growth, necrotizing enterocolitis (NEC), or late-onset sepsis in North American very low-birth-weight (VLBW) infants compared with powder HMFs (control).

METHODS

Prospective trials published between 2009 and 2020 were systematically reviewed, and meta-analysis was conducted by using a random-effects model.

RESULTS

Five studies were identified for up to 591 participants across 39 centers. Study treatments included whey or casein hydrolysate HMF and exclusive HM HMF. Infants fed whey or casein hydrolysate HMF had growth differences compared with the control. No differences were found across treatments in regard to NEC or sepsis.

CONCLUSION

Very low-quality evidence suggests greater linear growth in VLBW infants fed whey hydrolysate liquid HMF, as well as greater weight gain in those fed casein hydrolysate HMF, compared with the control. Additional prospective, multicenter randomized controlled trials are needed to confirm these estimates because of sparsity of evidence. There is insufficient evidence to support HMF decisions regarding NEC or late-onset sepsis prophylaxis.

Comparison of different protein concentrations of human milk fortifier for promoting growth and neurological development in preterm infants

BACKGROUND

Human milk alone may provide inadequate amounts of protein to meet the growth requirements of preterm infants because of restrictions in the amount of fluid they can tolerate. It has become common practice to feed preterm infants with breast milk fortified with protein and other nutrients but there is debate about the optimal concentration of protein in commercially available fortifiers.

OBJECTIVES

To compare the effects of different protein concentrations in human milk fortifier, fed to preterm infants, on growth and neurodevelopment.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search CENTRAL (2019, Issue 8), Ovid MEDLINE and CINAHL on 15 August 2019. We also searched clinical trials databases and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

We included all published and unpublished randomised, quasi-randomised and cluster-randomised trials comparing two different concentrations of protein in human milk fortifier. We included preterm infants (less than 37 weeks' gestational age). Participants may have been exclusively fed human milk or have been supplemented with formula. The concentration of protein was classified as low (< 1g protein/100 mL expressed breast milk (EBM)), moderate (≥ 1g to < 1.4g protein/100 mL EBM) or high (≥ 1.4g protein/100 mL EBM). We excluded trials that compared two protein concentrations that fell within the same category.

DATA COLLECTION AND ANALYSIS

We undertook data collection and analyses using the standard methods of Cochrane Neonatal. Two review authors independently evaluated trials. Primary outcomes included growth, neurodevelopmental outcome and mortality. Data were synthesised using risk ratios (RR), risk differences and mean differences (MD), with 95% confidence intervals (CI). We used the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

We identified nine trials involving 861 infants. There is one trial awaiting classification, and nine ongoing trials. The trials were mostly conducted in infants born < 32 weeks' gestational age or < 1500 g birthweight, or both. All used a fortifier derived from bovine milk. Two trials fed infants exclusively with mother's own milk, three trials gave supplementary feeds with donor human milk and four trials supplemented with preterm infant formula. Overall, trials were small but generally at low or unclear risk of bias. High versus moderate protein concentration of human milk fortifier There was moderate certainty evidence that a high protein concentration likely increased in-hospital weight gain compared to moderate concentration of human milk fortifier (MD 0.66 g/kg/day, 95% CI 0.51 to 0.82; trials = 6, participants = 606). The evidence was very uncertain about the effect of high versus moderate protein concentration on length gain (MD 0.01 cm/week, 95% CI -0.01 to 0.03; trials = 5, participants = 547; very low certainty evidence) and head circumference gain (MD 0.00 cm/week, 95% CI -0.01 to 0.02; trials = 5, participants = 549; very low certainty evidence). Only one trial reported neonatal mortality, with no deaths in either group (participants = 45). Moderate versus low protein concentration of human milk fortifier A moderate versus low protein concentration fortifier may increase weight gain (MD 2.08 g/kg/day, 95% CI 0.38 to 3.77; trials = 2, participants = 176; very low certainty evidence) with little to no effect on head circumference gain (MD 0.13 cm/week, 95% CI 0.00 to 0.26; I² = 85%; trials = 3, participants = 217; very low certainty evidence), but the evidence is very uncertain. There was low certainty evidence that a moderate protein concentration may increase length gain (MD 0.09 cm/week, 95% CI 0.05 to 0.14; trials = 3, participants = 217). Only one trial reported mortality and found no difference between groups (RR 0.48, 95% CI 0.05 to 5.17; participants = 112). No trials reported long term growth or neurodevelopmental outcomes including cerebral palsy and developmental delay.

AUTHORS' CONCLUSIONS

Feeding preterm infants with a human milk fortifier containing high amounts of protein (≥ 1.4g/100 mL EBM) compared with a fortifier containing moderate protein concentration (≥ 1 g to < 1.4 g/100 mL EBM) results in small increases in weight gain during the neonatal admission. There may also be small increases in weight and length gain when infants are fed a fortifier containing moderate versus low protein concentration (< 1 g protein/100 mL EBM). The certainty of this evidence is very low to moderate; therefore, results may change when the findings of ongoing studies are available. There is insufficient evidence to assess the impact of protein concentration on adverse effects or long term outcomes such as neurodevelopment. Further trials are needed to determine whether modest increases in weight gain observed with higher protein concentration fortifiers are associated with benefits or harms to long term growth and neurodevelopment.

Early versus late fortification of breast milk in preterm infants: a systematic review and meta-analysis

This systematic review and meta-analysis assessed the effects of early fortification (EF) versus late fortification (LF) of breast milk (BM) on growth of preterm infants. Randomized and quasi-randomized controlled trials (RCTs) dealing with the effects of EF versus LF on growth parameters, incidence of adverse events, and duration of hospital stay in preterm infants were included. Data were pooled using the RevMan 5.3 software. Quality of evidence for predefined outcomes was analyzed by GRADE. Available evidence (3 RCTs, 309 preterm infants) showed no statistically significant difference between EF and LF of BM for any of the growth parameters-weight (standardized mean difference (SMD) 0.13; 95% confidence interval (CI) - 0.09, 0.36); length (SMD 0.02; 95% CI - 0.20, 0.25); and head circumference (SMD - 0.10; 95% CI - 0.33, 0.12). Total parenteral nutrition days were similar. Duration of hospital stay was significantly higher with EF (MD 4.29; 95% CI 0.84, 7.75) with a trend of non-significant increase in feed intolerance and necrotizing enterocolitis (NEC).Conclusion: Very low quality evidence did not find any significant difference in growth parameters of preterm infants in association with EF or LF of BM. A significant increase in hospital stay and non-significant increase in feed intolerance and NEC were associated with EF.PROSPERO registration number: CRD42019139235What is Known:• Fortification of breast milk with essential macro- and micronutrients is necessary for optimization of nutrition in preterm infants.• There is no consensus regarding the breast milk feeding volume at which fortification should be initiated.What is New:• Very low quality evidence showed no significant difference between early and late fortification of breast milk on growth parameters of preterm infants.• Early fortification was associated with non-significant increase in feed intolerance and necrotizing enterocolitis and a significant increase in hospital stay.

The Influence of Donor Milk Supplementation on Duration of Parenteral Nutrition in Preterm Infants

BACKGROUND

Data are limited on the association between the use of donor human milk and improvements in feeding tolerance.

OBJECTIVE

To determine the influence of the duration of parenteral nutrition on the growth and morbidity of the breastfed newborn when using donated human milk in the absence of mother's own milk.

METHODS

We conducted a retrospective study before and after the intervention that compared two groups of newborns (N = 284; each group n = 142). We used a convenience sample of all newborns ≤32 weeks gestation consecutively admitted in a single unit before (Group 1 between December 2012 and May 2014) or after (Group 2 between October 2014 and December 2016) the availability of donor human milk. In Group 2, donor human milk was administered at least 3 to 4 weeks or until the baby weighed 1,500 g. Weight was recorded daily and length and head circumference weekly. Parenteral nutrition was continued until enteral feeding volume reached 120 ml/kg/day. Additional variables measured were the number of days with a central venous catheter, age that the enteral feeding volume reached 150 ml/kg/day, and duration of stay.

RESULTS

The duration of parenteral feeding was the same before and after: 12 (8.23) and 11 (7.19) days (p = .822). The z scores for weight and height of newborns was lower in Group 2 = -1.8 (1.0) and -2.3 (1.1) and Group 1 = -1.2 (1.1) (p < .001) and -1.8 (1.4) (p = .005).

CONCLUSION

We did not find an association between the administration of donor human milk as a supplement to mother's own milk and reduced number of days of parenteral nutrition. Back translation by Laurence Grummer-Strawn.

A Novel Donkey Milk-derived Human Milk Fortifier in Feeding Preterm Infants: A Randomized Controlled Trial

OBJECTIVES

The purpose of the present randomized controlled clinical trial was to compare the use of donkey milk-derived fortifier (DF) with commercial bovine milk-derived fortifier (BF) in very preterm or very-low-birth-weight newborns, in terms of feeding tolerance.

METHODS

This trial included 156 newborns born at <32 weeks of gestational age and/or with a birth weight ≤1500 g. Newborns were randomized 1:1 to receive enteral feeding with either a BF-arm, or a new, DF-arm for 21 days. The fortification protocol was the same for both study arms, and the 2 diets were designed to be isoproteic and isocaloric. Feeding tolerance was assessed by a standardized protocol.

RESULTS

The risk of feeding intolerance tended to be lower in DF-arm than in BF-arm, with a relative risk reduction of 0.63 (95% confidence interval: -0.29, +0.90). The mean number of episodes per newborn of feeding intolerance and feeding interruptions (any duration) were consistently lower in the DF-arm than in the BF-arm. Episodes of bilious gastric residuals and vomiting were significantly lower in the DF-arm. Time needed to reach full enteral feeding (150 mL · kg · day) and daily weight increase between the first day of exclusive enteral feeding (ie, without administering intravenous fluids) and discharge were similar in the BF- and DF-arms.

CONCLUSIONS

These results suggest that DF improve feeding tolerance when compared with standard bovine-derived fortifiers, with a similar auxological outcome.

Nutrient Fortification of Human Donor Milk Affects Intestinal Function and Protein Metabolism in Preterm Pigs

Background

Nutrient fortification of human milk is often required to secure adequate growth and organ development for very preterm infants. There is concern that formula-based fortifiers (FFs) induce intestinal dysfunction, feeding intolerance, and necrotizing enterocolitis (NEC). Bovine colostrum (BC) may be an alternative nutrient fortifier, considering its high content of protein and milk bioactive factors.

Objective

We investigated whether BC was superior to an FF product based on processed bovine milk and vegetable oil to fortify donor human milk (DHM) for preterm pigs, used as a model for infants.

Methods

Sixty preterm pigs from 4 sows (Danish Landrace × Large White × Duroc, birth weight 944 ± 29 g) received decreasing volumes of parenteral nutrition (96-72 mL ⋅ kg-1 ⋅ d-1) and increasing volumes of enteral nutrition (24-132 mL ⋅ kg-1 ⋅ d-1) for 8 d. Pigs were fed donor porcine milk (DPM) and DHM with or without FF or BC fortification (+4.6 g protein ⋅ kg-1 ⋅ d-1).

Results

DPM-fed pigs showed higher growth (10-fold), protein synthesis (+15-30%), villus heights, lactase and peptidase activities (+30%), and reduced intestinal cytokines (-50%) relative to DHM pigs (all P < 0.05). Fortification increased protein synthesis (+20-30%), but with higher weight gain and lower urea and cortisol concentrations for DHM+BC compared with DHM+FF pigs (2- to 3-fold differences, all P ≤ 0.06). DHM+FF pigs showed more diarrhea and reduced lactase and peptidase activities, hexose uptake, and villus heights relative to DHM+BC or DHM pigs (30-90% differences, P < 0.05). Fortification did not affect NEC incidence but DHM+BC pigs had lower colonic interleukin (IL)-6 and IL-8 concentrations relative to the remaining pigs (-30%, P = 0.06). DHM+FF pigs had higher stomach bacterial load than did DHM, and higher bacterial density along intestinal villi than did DHM and DHM+BC pigs (2- to 3-fold, P < 0.05).

Conclusions

The FF product investigated in this study reduced growth, intestinal function, and protein utilization in DHM-fed preterm pigs, relative to BC as fortifier. The relevance of BC as an alternative nutrient fortifier for preterm infants should be tested.

How to feed a baby recovering from necrotising enterocolitis when maternal milk is not available

Necrotising enterocolitis (NEC) is a devastating disease with significant mortality and serious adverse outcomes in at least 50% including short gut and poor neurodevelopment. Research and management are complicated by a lack of robust clinical markers, and without histological confirmation, there is a risk of both underdiagnosis and overdiagnosis. Interunit variations in the thresholds for surgical referral, laparotomy and postmortem rates mean the actual incidence is difficult to determine, especially because the histological term 'NEC' is used in practice to describe a heterogeneous clinical syndrome. In this article, we discuss issues relating to choice of milk feed type following a clinical diagnosis of 'NEC' where mother's own milk is not available. We review common clinical concerns relating to feeding following NEC and the rationale for modifications of the macronutrient composition and quality of formula milk.

Use of extensively hydrolysed formula for refeeding neonates postnecrotising enterocolitis: a nationwide survey-based, cross-sectional study

OBJECTIVE

To evaluate the prevalence of and reasons for using extensively hydrolysed formulas (EHFs) of cow's milk proteins in the French neonatal units as well as the modality of their prescription for refeeding infants recovering from necrotising enterocolitis (NEC).

METHODS

A multicentre nationwide cross-sectional study using a questionnaire to address the prevalence of use and the reasons for prescribing EHF in hospitalised neonates and to examine the protocols and the actual reasons for their use for refeeding infants in recovery from NEC. The questionnaire was sent to only 1 senior neonatologist in each neonatal unit included in the study.

RESULTS

More than half of the French neonatal units participated in the survey. 91% of the surveyed units used EHF. Of 1969 infants hospitalised on the day the survey was run, 12% were fed on an EHF. 11% of the EHF prescriptions were due to previous NEC. The main reasons for using an EHF to feed infants post-NEC were the absence of human milk (75%) and surgical management of NEC (17%). When given, EHF was mainly prescribed for a period varying between 15 days and 3 months. None of the involved units continued using the EHF after 6 months of age. More than half of the surveyed units acknowledged hospitalising infants for the initiation of weaning EHF but only 21% of them tested these infants for cow's milk allergy.

CONCLUSIONS

The prevalence of EHF use in the French neonatal units is high. Refeeding infants post-NEC is one of the main reasons for such a high prevalence. The main incentive for using an EHF is the absence of human breast milk, either maternal or donor.

Intestinal failure following necrotizing enterocolitis: A clinical approach

Intestinal failure is a recognized complication of surgically-managed necrotizing enterocolitis (NEC). Functional adaptation of remaining bowel means that many children are eventually able to achieve enteral autonomy. Integrated multidisciplinary care in the early post-operative phase is key to long-term success. The objective of this review is to outline a clinical approach to management of intestinal and nutritional complications experienced by children following intestinal resection for NEC.

Manifestations of Cow's-Milk Protein Intolerance in Preterm Infants

OBJECTIVES

Cow's-milk protein intolerance (CMPI) is poorly recognized in preterm infants. This study examined the clinical events that preceded the diagnosis of CMPI in preterm infants.

METHODS

This was a retrospective study of infants in a level-III neonatal intensive care unit of those who received parenteral nutrition (PN) support during a 12-month period. Parameters assessed included birth weight (g), diagnosis, duration and frequency on PN, type of enteral feeds at initiation, and achievement of enteral autonomy. CMPI was diagnosed based on persistent feeding intolerance that resolved after change of feeds from intact protein to a protein hydrolysate or crystalline amino acid formula.

RESULTS

Three hundred forty-eight infants with birth weight (median/range) 1618 g (425-5110) received PN. Fifty-one (14%) infants required multiple courses of PN, and 19 of 348 (5%) were diagnosed with CMPI. The requirement for multiple courses on PN versus single course was associated with a high likelihood of CMPI: 14 of 51 versus 5 of 297, P < 0.001. Nine of the 14 infants identified with CMPI were initially diagnosed with necrotizing enterocolitis (NEC) after a median duration of 22 days (19-57) on intact protein feeds. After recovery from NEC, they had persistent feeding intolerance including recurrence of "NEC-like illness" (N = 3) that resolved after change of feeds to a protein hydrolysate or crystalline amino acid formula.

CONCLUSIONS

The requirement for multiple courses of PN because of persistent feeding intolerance after recovery from NEC and recurrence of "NEC-like illness" may be a manifestation of CMPI in preterm infants.

In vivo analysis of intestinal permeability following hemorrhagic shock

AIM: To determine the time course of intestinal permeability changes to proteolytically-derived bowel peptides in experimental hemorrhagic shock.

METHODS: We injected fluorescently-conjugated casein protein into the small bowel of anesthetized Wistar rats prior to induction of experimental hemorrhagic shock. These molecules, which fluoresce when proteolytically cleaved, were used as markers for the ability of proteolytically cleaved intestinal products to access the central circulation. Blood was serially sampled to quantify the relative change in concentration of proteolytically-cleaved particles in the systemic circulation. To provide spatial resolution of their location, particles in the mesenteric microvasculature were imaged using in vivo intravital fluorescent microscopy. The experiments were then repeated using an alternate measurement technique, fluorescein isothiocyanate (FITC)-labeled dextrans 20, to semi-quantitatively verify the ability of bowel-derived low-molecular weight molecules (< 20 kD) to access the central circulation.

RESULTS: Results demonstrate a significant increase in systemic permeability to gut-derived peptides within 20 min after induction of hemorrhage (1.11 ± 0.19 vs 0.86 ± 0.07, P < 0.05) compared to control animals. Reperfusion resulted in a second, sustained increase in systemic permeability to gut-derived peptides in hemorrhaged animals compared to controls (1.2 ± 0.18 vs 0.97 ± 0.1, P < 0.05). Intravital microscopy of the mesentery also showed marked accumulation of fluorescent particles in the microcirculation of hemorrhaged animals compared to controls. These results were replicated using FITC dextrans 20 [10.85 ± 6.52 vs 3.38 ± 1.11 fluorescent intensity units (× 10⁵, P < 0.05, hemorrhagic shock vs controls)], confirming that small bowel ischemia in response to experimental hemorrhagic shock results in marked and early increases in gut membrane permeability.

CONCLUSION: Increased small bowel permeability in hemorrhagic shock may allow for systemic absorption of otherwise retained proteolytically-generated peptides, with consequent hemodynamic instability and remote organ failure.

Challenges in breast milk fortification for preterm infants

PURPOSE OF REVIEW

To outline new evidence published from 2013 to 2014 about breast milk fortification in preterm infants.

RECENT FINDINGS

Breast milk is the feeding choice for preterm infants because of its immunoprotective properties. However, breast milk's nutrient content is not sufficient for preterm infants, and interindividual variation is high. The variation challenges standard fortification, which assumes a standard breast milk composition. Two new fortification strategies (adjustable fortification and target fortification) optimize macronutrient intake and improve growth. Adjustable fortification uses blood urea nitrogen levels to adjust fortifier strength. Target fortification analyzes breast milk and fortifies macronutrients individually to achieve targeted intake. Its feasibility is shown in clinical routine. Current breast milk analyzers used for target fortification achieve acceptable precision for protein and fat but not for lactose and energy. Evidence of benefits for postdischarge breast milk fortification is lacking. Eliminating cow's milk products and feeding exclusively breast milk may decrease the occurrence of feeding intolerance and necrotizing enterocolitis. To facilitate exclusively breast milk diets, a collaboration of prenatal, nutrition and lactation stakeholders is key. Fortification increases osmolality; however, safety cutoffs to prevent necrotizing enterocolitis are unclear. There is also new evidence that composition and structure of various macronutrients and micronutrients affect growth and development, and might play a role in future fortification concepts.

SUMMARY

Recent research focuses on the variability of breast milk composition, its impact on postnatal growth patterns and the usefulness of target fortification. As well, diets exclusively composed of human milk are a promising approach to improve feeding tolerance. For safe fortification, osmolality cutoff levels are needed.

Pathogenesis implication for necrotizing enterocolitis prevention in preterm very-low-birth-weight infants

Recent reports show that the incidence of and deaths caused by necrotizing enterocolitis (NEC) in preterm very-low-birth-weight (PVLBW) infants are on the rise. Unfortunately, NEC often rapidly progresses from early signs of intestinal inflammation to extensive necrosis within a matter of hours, making treatment and secondary prevention extremely difficult to achieve. Primary prevention should thus be the priority. Recent studies provide information that enhances our understanding of the pathophysiology and provides more practical options for the prevention of NEC. The most accepted hypothesis at present is that enteral feeding (providing substrate) in the presence of abnormal intestinal colonization by pathogens provokes an inappropriately heightened inflammatory response in immature intestinal epithelial cells of PVLBW infants. Seventy-four relevant articles were reviewed. Our focus was on the present understanding of the pathophysiology of NEC in the context of developing optimal strategies to prevent NEC in PVLBW infants. Strategies such as antenatal glucocorticoids, postnatal breast milk feeding, and cautious approach to enteral feeding failed to eliminate NEC in PVLBW infants because these strategies did not address the complexity of the pathogenesis. Probiotics seem to be the most significant advance in NEC prevention at present because of the significant range of beneficial effects at various levels of gut function and defense mechanism and the present evidence based on 19 randomized controlled trials.