Higher versus lower protein intake in formula-fed low birth weight infants

Interventions for reducing late-onset sepsis in neonates: an umbrella review

OBJECTIVES

Neonatal sepsis is one of the leading causes of neonatal deaths in neonatal intensive care units. Hence, it is essential to review the evidence from systematic reviews on interventions for reducing late-onset sepsis (LOS) in neonates.

METHODS

PubMed and the Cochrane Central were searched from inception through August 2020 without any language restriction. Cochrane reviews of randomized clinical trials (RCTs) assessing any intervention in the neonatal period and including one or more RCTs reporting LOS. Two authors independently performed screening, data extraction, assessed the quality of evidence using Cochrane Grading of Recommendations Assessment, Development and Evaluation, and assessed the quality of reviews using a measurement tool to assess of multiple systematic reviews 2 tool.

RESULTS

A total of 101 high-quality Cochrane reviews involving 612 RCTs and 193,713 neonates, evaluating 141 interventions were included. High-quality evidence showed a reduction in any or culture-proven LOS using antibiotic lock therapy for neonates with central venous catheters (CVC). Moderate-quality evidence showed a decrease in any LOS with antibiotic prophylaxis or vancomycin prophylaxis for neonates with CVC, chlorhexidine for skin or cord care, and kangaroo care for low birth weight babies. Similarly, moderate-quality evidence showed reduced culture-proven LOS with intravenous immunoglobulin prophylaxis for preterm infants and probiotic supplementation for very low birth weight (VLBW) infants. Lastly, moderate-quality evidence showed a reduction in fungal LOS with the use of systemic antifungal prophylaxis in VLBW infants.

CONCLUSIONS

The overview summarizes the evidence from the Cochrane reviews assessing interventions for reducing LOS in neonates, and can be utilized by clinicians, researchers, policymakers, and consumers for decision-making and translating evidence into clinical practice.

The Association of Formula Protein Content and Growth in Early Infancy: A Systematic Review and Meta-Analysis

This systematic review aimed to examine differences in growth outcomes between breastfed infants and infants fed with formula with different protein/energy ratios during the first six months of life. We conducted a systematic review in the PubMed, Web of Science, and Springer databases. Twenty clinical trials qualified for inclusion. We extracted data about the growth outcomes of infants who were exclusive breastfed or exclusively infant formula fed in the first six months and used a meta-analysis to pool the finding data. We categorized study formulas into four groups according to their protein content: <1.8, 1.8−2.0, 2.1−2.2, and >2.2 g/100 kcal. In the first month of life, growth was not different between formula- and breastfed infants. During 2−3 months of life, growth was faster in infants who consumed formulas with protein contents higher than 2.0 g/100 kcal. After 3 months, formula-fed infants grew faster than breastfed infants. Our meta-analysis indicated that the growth outcomes of infants fed with infant formula with a relatively low protein/energy ratios, compared with that a relatively high protein/energy ratio, were close to those of breastfed infants.

Nutritional Intake, White Matter Integrity, and Neurodevelopment in Extremely Preterm Born Infants

Background: Determining optimal nutritional regimens in extremely preterm infants remains challenging. This study aimed to evaluate the effect of a new nutritional regimen and individual macronutrient intake on white matter integrity and neurodevelopmental outcome. Methods: Two retrospective cohorts of extremely preterm infants (gestational age < 28 weeks) were included. Cohort B (n = 79) received a new nutritional regimen, with more rapidly increased, higher protein intake compared to cohort A (n = 99). Individual protein, lipid, and caloric intakes were calculated for the first 28 postnatal days. Diffusion tensor imaging was performed at term-equivalent age, and cognitive and motor development were evaluated at 2 years corrected age (CA) (Bayley-III-NL) and 5.9 years chronological age (WPPSI-III-NL, MABC-2-NL). Results: Compared to cohort A, infants in cohort B had significantly higher protein intake (3.4 g/kg/day vs. 2.7 g/kg/day) and higher fractional anisotropy (FA) in several white matter tracts but lower motor scores at 2 years CA (mean (SD) 103 (12) vs. 109 (12)). Higher protein intake was associated with higher FA and lower motor scores at 2 years CA (B = −6.7, p = 0.001). However, motor scores at 2 years CA were still within the normal range and differences were not sustained at 5.9 years. There were no significant associations with lipid or caloric intake. Conclusion: In extremely preterm born infants, postnatal protein intake seems important for white matter development but does not necessarily improve long-term cognitive and motor development.

The effect of milk type and fortification on the growth of low-birthweight infants: An umbrella review of systematic reviews and meta-analyses

Approximately 15% of infants worldwide are born with low birthweight (<2500 g). These children are at risk for growth failure. The aim of this umbrella review is to assess the relationship between infant milk type, fortification and growth in low-birthweight infants, with particular focus on low- and lower middle-income countries. We conducted a systematic review in PubMed, CINAHL, Embase and Web of Science comparing infant milk options and growth, grading the strength of evidence based on standard umbrella review criteria. Twenty-six systematic reviews qualified for inclusion. They predominantly focused on infants with very low birthweight (<1500 g) in high-income countries. We found the strongest evidence for (1) the addition of energy and protein fortification to human milk (donor or mother's milk) leading to increased weight gain (mean difference [MD] 1.81 g/kg/day; 95% confidence interval [CI] 1.23, 2.40), linear growth (MD 0.18 cm/week; 95% CI 0.10, 0.26) and head growth (MD 0.08 cm/week; 95% CI 0.04, 0.12) and (2) formula compared with donor human milk leading to increased weight gain (MD 2.51 g/kg/day; 95% CI 1.93, 3.08), linear growth (MD 1.21 mm/week; 95% CI 0.77, 1.65) and head growth (MD 0.85 mm/week; 95% CI 0.47, 1.23). We also found evidence of improved growth when protein is added to both human milk and formula. Fat supplementation did not seem to affect growth. More research is needed for infants with birthweight 1500-2500 g in low- and lower middle-income countries.

Organ Growth and Intestinal Functions of Preterm Pigs Fed Low and High Protein Formulas With or Without Supplemental Leucine or Hydroxymethylbutyrate as Growth Promoters

The goal of enteral nutritional support for infants born preterm or small for gestational age (SGA) is to achieve normal growth and development. Yet, this is difficult to achieve because of intestinal immaturity. Our objective was to determine if birth weight, protein intake, and the growth promoters leucine (10 g/L) or calcium-ß-hydroxy-ß-methylbutryate (HMB; 1.1 g/L) would affect trajectories of intestinal growth and functions and weights of other organs. Preterm pigs were delivered at gestational day 105 (91% of term) and fed for 6 or 7 days isocaloric formulas that differed in protein content (50 g or 100 g protein/L), with and without the growth promoters leucine or HMB. For comparative purposes organ weights were measured within 12 h after delivery for six term pigs of low and six of average birth weights. The responses of intestinal growth and total intestinal brush border membrane carbohydrases to protein level and supplemental leucine were of greater magnitude for preterm pigs of lower birth weight. Forskolin stimulated chloride secretion in the proximal small intestine was lower for pigs fed the low protein milk replacers. Capacities of the entire small intestine to transport glucose (mmol/kg-day) were not responsive to protein level, leucine, or HMB, and did not differ between small and large pigs. Relative organ weights of the small and average weight term pigs were similar, but some differed from those of the preterm pigs suggesting preterm birth and the standards of care used for this study altered the trajectories of development for the intestine and other organs. Although leucine is an effective generalized growth promoter that enhances gut development of small preterm pigs, it does not mitigate compromised neurodevelopment. Our findings using preterm pigs as a relevant preclinical model indicate nutrition support strategies can influence development of some gastrointestinal tract characteristics and the growth of other organs.

Interactions between Growth of Muscle and Stature: Mechanisms Involved and Their Nutritional Sensitivity to Dietary Protein: The Protein-Stat Revisited

Childhood growth and its sensitivity to dietary protein is reviewed within a Protein-Stat model of growth regulation. The coordination of growth of muscle and stature is a combination of genetic programming, and of two-way mechanical interactions involving the mechanotransduction of muscle growth through stretching by bone length growth, the core Protein-Stat feature, and the strengthening of bone through muscle contraction via the mechanostat. Thus, growth in bone length is the initiating event and this is always observed. Endocrine and cellular mechanisms of growth in stature are reviewed in terms of the growth hormone-insulin like growth factor-1 (GH-IGF-1) and thyroid axes and the sex hormones, which together mediate endochondral ossification in the growth plate and bone lengthening. Cellular mechanisms of muscle growth during development are then reviewed identifying (a) the difficulties posed by the need to maintain its ultrastructure during myofibre hypertrophy within the extracellular matrix and the concept of muscle as concentric "bags" allowing growth to be conceived as bag enlargement and filling, (b) the cellular and molecular mechanisms involved in the mechanotransduction of satellite and mesenchymal stromal cells, to enable both connective tissue remodelling and provision of new myonuclei to aid myofibre hypertrophy and (c) the implications of myofibre hypertrophy for protein turnover within the myonuclear domain. Experimental data from rodent and avian animal models illustrate likely changes in DNA domain size and protein turnover during developmental and stretch-induced muscle growth and between different muscle fibre types. Growth of muscle in male rats during adulthood suggests that "bag enlargement" is achieved mainly through the action of mesenchymal stromal cells. Current understanding of the nutritional regulation of protein deposition in muscle, deriving from experimental studies in animals and human adults, is reviewed, identifying regulation by amino acids, insulin and myofibre volume changes acting to increase both ribosomal capacity and efficiency of muscle protein synthesis via the mechanistic target of rapamycin complex 1 (mTORC1) and the phenomenon of a "bag-full" inhibitory signal has been identified in human skeletal muscle. The final section deals with the nutritional sensitivity of growth of muscle and stature to dietary protein in children. Growth in length/height as a function of dietary protein intake is described in the context of the breastfed child as the normative growth model, and the "Early Protein Hypothesis" linking high protein intakes in infancy to later adiposity. The extensive paediatric studies on serum IGF-1 and child growth are reviewed but their clinical relevance is of limited value for understanding growth regulation; a role in energy metabolism and homeostasis, acting with insulin to mediate adiposity, is probably more important. Information on the influence of dietary protein on muscle mass per se as opposed to lean body mass is limited but suggests that increased protein intake in children is unable to promote muscle growth in excess of that linked to genotypic growth in length/height. One possible exception is milk protein intake, which cohort and cross-cultural studies suggest can increase height and associated muscle growth, although such effects have yet to be demonstrated by randomised controlled trials.

Higher versus lower protein intake in formula-fed low birth weight infants

BACKGROUND

The ideal quantity of dietary protein for formula-fed low birth weight infants is still a matter of debate. Protein intake must be sufficient to achieve normal growth without leading to negative effects such as acidosis, uremia, and elevated levels of circulating amino acids.

OBJECTIVES

To determine whether higher (≥ 3.0 g/kg/d) versus lower (< 3.0 g/kg/d) protein intake during the initial hospital stay of formula-fed preterm infants or low birth weight infants (< 2.5 kilograms) results in improved growth and neurodevelopmental outcomes without evidence of short- or long-term morbidity. Specific objectives were to examine the following comparisons of interventions and to conduct subgroup analyses if possible. 1. Low protein intake if the amount was less than 3.0 g/kg/d. 2. High protein intake if the amount was equal to or greater than 3.0 g/kg/d but less than 4.0 g/kg/d. 3. Very high protein intake if the amount was equal to or greater than 4.0 g/kg/d.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 8), in the Cochrane Library (August 2, 2019); OVID MEDLINE Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE(R) Daily, and Ovid MEDLINE(R) (to August 2, 2019); MEDLINE via PubMed (to August 2, 2019) for the previous year; and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (to August 2, 2019). We also searched clinical trials databases and the reference lists of retrieved articles for randomized controlled trials (RCTs) and quasi-randomized trials.

SELECTION CRITERIA

We included RCTs contrasting levels of formula protein intake as low (< 3.0 g/kg/d), high (≥ 3.0 g/kg/d but < 4.0 g/kg/d), or very high (≥ 4.0 g/kg/d) in formula-fed hospitalized neonates weighing less than 2.5 kilograms. We excluded studies if infants received partial parenteral nutrition during the study period, or if infants were fed formula as a supplement to human milk.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane and the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

We identified six eligible trials that enrolled 218 infants through searches updated to August 2, 2019. Five studies compared low (< 3 g/kg/d) versus high (3.0 to 4.0 g/kg/d) protein intake using formulas that kept other nutrients constant. The trials were small (n = 139), and almost all had methodological limitations; the most frequent uncertainty was about attrition. Low-certainty evidence suggests improved weight gain (mean difference [MD] 2.36 g/kg/d, 95% confidence interval [CI] 1.31 to 3.40) and higher nitrogen accretion in infants receiving formula with higher protein content (3.0 to 4.0 g/kg/d) versus lower protein content (< 3 g/kg/d), while other nutrients were kept constant. No significant differences were seen in rates of necrotizing enterocolitis, sepsis, or diarrhea. We are uncertain whether high versus low protein intake affects head growth (MD 0.37 cm/week, 95% CI 0.16 to 0.58; n = 18) and length gain (MD 0.16 cm/week, 95% CI -0.02 to 0.34; n = 48), but sample sizes were small for these comparisons. One study compared high (3.0 to 4.0 g/kg/d) versus very high (≥ 4 g/kg/d) protein intake (average intakes were 3.6 and 4.1 g/kg/d) during and after an initial hospital stay (n = 77). Moderate-certainty evidence shows no significant differences in weight gain or length gain to discharge, term, and 12 weeks corrected age from very high protein intake (4.1 versus 3.6 g/kg/d). Three of the 24 infants receiving very high protein intake developed uremia.

AUTHORS' CONCLUSIONS

Higher protein intake (≥ 3.0 g/kg/d but < 4.0 g/kg/d) from formula accelerates weight gain. However, limited information is available regarding the impact of higher formula protein intake on long-term outcomes such as neurodevelopment. Research is needed to investigate the safety and effectiveness of protein intake ≥ 4.0 g/kg/d.

Differential regulation of mTORC1 activation by leucine and β-hydroxy-β-methylbutyrate in skeletal muscle of neonatal pigs

Leucine (Leu) and its metabolite β-hydroxy-β-methylbutyrate (HMB) stimulate mechanistic target of rapamycin (mTOR) complex 1 (mTORC1)-dependent protein synthesis in the skeletal muscle of neonatal pigs. This study aimed to determine whether HMB and Leu utilize common nutrient-sensing mechanisms to activate mTORC1. In study 1, neonatal pigs were fed one of five diets for 24 h: low protein (LP), high protein (HP), or LP supplemented with 4 (LP+HMB4), 40 (LP+HMB40), or 80 (LP+HMB80) μmol HMB·kg body wt^-1·day^-1. In study 2, neonatal pigs were fed for 24 h: LP, LP supplemented with Leu (LP+Leu), or HP diets delivering 9, 18, and 18 mmol Leu·kg body wt^-1·day^-1, respectively. The upstream signaling molecules that regulate mTORC1 activity were analyzed. mTOR phosphorylation on Ser2448 and Ser2481 was greater in LP+HMB40, LP+HMB80, and LP+Leu than in LP and greater in HP than in HMB-supplemented groups (P < 0.05), whereas HP and LP+Leu were similar. Rheb-mTOR complex formation was lower in LP than in HP (P < 0.05), with no enhancement by HMB or Leu supplementation. The Sestrin2-GATOR2 complex was more abundant in LP than in HP and was reduced by Leu (P < 0.05) but not HMB supplementation. RagA-mTOR and RagC-mTOR complexes were higher in LP+Leu and HP than in LP and HMB groups (P < 0.05). There were no treatment differences in RagB-SH3BP4, Vps34-LRS, and RagD-LRS complex abundances. Phosphorylation of Erk1/2 and TSC2, but not AMPK, was lower in LP than HP (P < 0.05) and unaffected by HMB or Leu supplementation. Our results demonstrate that HMB stimulates mTORC1 activation in neonatal muscle independent of the leucine-sensing pathway mediated by Sestrin2 and the Rag proteins.NEW & NOTEWORTHY Dietary supplementation with either leucine or its metabolite β-hydroxy-β-methylbutyrate (HMB) stimulates protein synthesis in skeletal muscle of the neonatal pig. Our results demonstrate that both leucine and HMB stimulate mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) phosphorylation in neonatal muscle. This leucine-stimulated process involves dissociation of the Sestrin2-GATOR2 complex and increased binding of Rag A/C to mTOR. However, HMB's activation of mTORC1 is independent of this leucine-sensing pathway.

Comparison of the effect of three different protein content enteral diets on serum levels of proteins, nitrogen balance, and energy expenditure in critically ill infants: study protocol for a randomized controlled trial

Background

Nutritional support is essential in the care of critically ill children since malnutrition in this population is associated with increased morbidity and mortality. Injury in patients admitted to pediatric intensive care units (PICU) results in a catabolic state and augmented protein breakdown, leading to a negative protein balance. Current recommendations about protein prescription in the PICU are fundamentally based on expert opinions, and the minimum threshold is 1.5 g/kg per day of protein, although protein needs could be higher in certain subgroups of patients. The main objectives of the present study are to examine whether the administration of a protein-enriched infant formula increases the serum levels of total proteins, albumin, prealbumin, transferrin, and retinol and improves nitrogen balance and to analyze the effect of the high-protein diet on energy expenditure. A secondary objective is to register possible secondary effects of the protein-enriched diet.

Methods

A multicenter prospective randomized controlled trial (RCT) will be performed in three hospitals. Patients meeting inclusion criteria will be randomly allocated to one of three enteral feeding formulae with different protein contents. Blood and urine test, nitrogen balance assessment, and energy expenditure testing by indirect calorimetry will be performed at the beginning of the nutrition regimen and at 24 h, 72 h and 5–7 days after initiation. The sample size for this trial is estimated to be 90 participants (about 30 participants in each group). The data analysis will be by intention to treat.

Discussion

This RCT will provide new data about the amount of protein needed to improve levels of serum protein and nitrogen balance, a surrogate of protein balance, in critically ill infants receiving enteral nutrition.

Trial registration

ClinicalTrials.gov identifier: NCT03901742. Registered April 1, 2019 – Retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3686-8) contains supplementary material, which is available to authorized users.

Effect of Fortification of Breast Milk in Conjugation with Protein Supplement on Neurodevelopment of Preterm Low Birth Weight Infants at 3 Years

INTRODUCTION

Choice of appropriate nutrition has a special place, which variations in dietary nutrient can potentially be involved in growth deficits in preterm neonates.

AIM

to investigate the effect of protein supplementation in very low birth weight (VLBW= birth weight under 1500 grams) infants on neurological growth in the third year of birth.

MATERIAL AND METHODS

We investigated neurological growth in two groups of control and intervention (each group, n= 18 subjects). The intervention group includes 3-year-old children who weighting less than 1200 grams at birth and have received protein supplementation at the course of NICU hospitalization, protein was added to maternal milk when the amount of milk reaches to 100 cc/kg/day, at this time parenteral nutrition was discontinued and the volume of feeding was increased 20cc/kg/day until reached to 150-180cc/kg/day. We also added the fortifier to breast milk at this time (FMS- Aptamil- DANON). The fortification and the protein supplementation were stopped when the weight of the baby reached to 1500 grams. The control group was fed similar to the intervention group, without protein supplemental intake. Neurodevelopmental outcomes were evaluated using ASQ, NEWSHA and BINS tools.

RESULTS

There was no significant difference between the mean head circumference in the two groups (p=0.209). There was no significant relationship between neurological growth rate evaluated by BINS tool in two groups (p=0.266). There was a significant correlation between the neurological development assessed by the ASQ tool in the areas of communication (p=0.014) and gross motor (p=0.001) in the two groups, however, no significant relationship was found in terms of fine motor (p=0.63), problem solving (p=0.07) and personal-social relationships in both groups (p=0.152). There was a significant correlation between neurological development evaluated using the NEWSHA tool in terms of auditory (p=0.031), verbal language (p=0.024), cognitive (p=0.007), social connection (p=0.034) and motor (p=0.002) in the two groups.

CONCLUSION

Protein intake in preterm infants didn't reveal long term effects on the growth of head circumference. Moreover, it was capable of improving neurological growth in the areas of communication and gross motor (based on the ASQ) and auditory, verbal language, cognitive, social connection, and motor (based on the NEWSHA).

Quality improvement initiative to decrease time to full feeds and central line utilization among infants born less than or equal to 32 0/7 weeks through compliance with standardized feeding guidelines

BACKGROUND

There are emerging evidences that support more aggressive feeding advancement among preterm infants. Our NICU had conservative feeding advancement guidelines that delayed enteral feeding and prolonged central line use. We aimed to reduce time to full feeds among infants born ≤ 32 0/7 weeks from 12.8 days to 8 days.

METHODS

A multidisciplinary team implemented evidence-based feeding guidelines using quality improvement methods. Days to full enteral feeds, central line days, necrotizing enterocolitis (NEC) rates, and extrauterine growth restriction (EUGR) rates were analyzed.

RESULTS

Average days to full enteral feeds decreased from 12.8 to 7.7 days and from 17.5 to 9.1 days for infants born ≤ 32 0/7 weeks and ≤ 28 0/7 weeks respectively, without significant change in NEC rate. Central line days decreased by 35%. Insignificant improvement in EUGR rate was found.

CONCLUSIONS

Faster feeding advancement guidelines led to earlier full enteral feeds and reduced central line utilization without increasing complications.

Effects of animal protein supplementation of mothers, preterm infants, and term infants on growth outcomes in childhood: a systematic review and meta-analysis of randomized trials

BACKGROUND

Child stunting is a major public health problem, afflicting 155 million people worldwide. Lack of animal-source protein has been identified as a risk, but effects of animal protein supplementation are not well established.

OBJECTIVE

The aim of this study was to investigate effects of animal protein supplementation in mothers, preterm infants, and term infants/children on birth and growth outcomes.

METHODS

PubMed, EMBASE, Cochrane library, Web of Science, Cumulative Index of Nursing and Allied Health Literature, and Latin American and Caribbean Health Sciences Literature were searched for randomized controlled trials of animal protein supplementation in mothers or infants and children (≤age 5 y), evaluating measures of anthropometry (≤age 18 y). Main outcomes included birth weight, low birth weight, small for gestational age at birth; height, height-for-age, weight, weight-for-age, weight-for-length, stunting, and wasting ≤18 y of age. Data were extracted independently in duplicate, and findings pooled using inverse variance meta-analysis. Heterogeneity was explored using I2, stratified analysis, and meta-regression, and publication bias by funnel plots, Egger's test, and fill/trim methods.

RESULTS

Of 6808 unique abstracts and 357 full-text articles, 62 trials were included. The 62 trials comprised over 30,000 participants across 5 continents, including formula-based supplementation in infants and food-based supplementation in pregnancy and childhood. Maternal supplementation increased birth weight by 0.06 kg, and both formula and food-based supplementation in term infants/young children increased weight by ≤0.14 kg. Neither formula nor food-based supplementation for term infants/young children increased height, whereas the height-for-age z-score was increased in the food-based (+0.06 z-score) but not formula-based (-0.11 z-score) trials reporting this outcome. In term infants, the weight-for-length z-score was increased in trials of formula (+0.24 z-score) and food supplementation (+0.06 z-score), whereas food supplementation was also associated with reduced odds of stunting (-13%).

CONCLUSIONS

Supplementation of protein from animal-source foods generally increased weight and weight-for-length in children, but with more limited effects on other growth outcomes such as attained height.

Dilute versus full-strength formula in exclusively formula-fed preterm or low birth weight infants

BACKGROUND

Preterm infants have fewer nutrient reserves at birth than full-term infants and often receive artificial formula feeds in the absence of expressed breast milk. Although it is generally agreed that feeding must be initiated slowly and advanced with much greater deliberation than in a healthy, full-term infant, the way in which feeds are introduced and advanced in preterm infants varies widely. This review focuses on whether dilute or full-strength formula is the preferable mode of introducing feeds in preterm infants for whom expressed breast milk is unavailable.

OBJECTIVES

To assess the effects of dilute versus full-strength formula on the incidence of necrotising enterocolitis, feeding intolerance, weight gain, length of stay in hosptial and time to achieve full calorie intake in exclusively formula-fed preterm or low birth weight infants. A secondary objective was to assess the effects of different dilution strategies.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to update the search in the Cochrane Central Register of Controlled Trials (CENTRAL 2018, Issue 9), MEDLINE via PubMed (1966 to 1 October 2018), Embase (1980 to 1 October 2018), and CINAHL (1982 to 1 October 2018).We searched clinical trials' registries for ongoing or recently completed trials (clinicaltrials.gov; the World Health Organization's International Trials Registry and Platform; and the ISRCTN Registry).

SELECTION CRITERIA

Randomised or quasi-randomised trials comparing strengths of formula milk in exclusively formula-fed preterm or low birth weight infants. We excluded studies if infants received formula as a supplement to breast milk.

DATA COLLECTION AND ANALYSIS

We independently assessed studies for inclusion. We collected data using the standard methods of Cochrane Neonatal, with independent assessment of risk of bias and data extraction. We synthesised mean differences using a fixed-effect meta-analysis model. We used the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

We included three studies involving 102 preterm or low birth weight infants in the review. The studies compared dilute (double-volume, half-strength) formula with full-strength (20 kcal/oz (˜ 68 to 70 kcal/100 mL)) formula. We assessed all three studies as having unclear risk of bias due to the likely absence of blinding of study personnel and the potential for selection bias in the largest trial. Data for the primary outcome of necrotising enterocolitis were not reported in any of the studies. We could combine two of the studies (88 infants) in the meta-analysis. The evidence suggests that dilute formula with double-volume (half-strength) may lead to fewer episodes of gastric residuals per day (one study; mean difference (MD) -1.20, 95% confidence interval (CI) -2.20 to -0.20; low-certainty evidence), fewer episodes of gastric residuals per baby until attaining 100 kcal/kg (one study; MD -0.80, 95% CI -1.32 to -0.28; low-certainty evidence), fewer episodes of vomiting per day (one study; MD -0.04, 95% CI -0.07 to -0.01; low-certainty evidence) and fewer occurrences of abdominal distension greater than 2 cm (two studies; MD -0.16, 95% CI -0.19 to -0.13; low-certainty evidence). For the secondary outcomes, data suggest that infants in the dilute formula with double-volume (half-strength) group may have attained an adequate energy intake earlier than infants in the full-strength group (two studies; MD -2.26, 95% CI -2.85 to -1.67; low-certainty evidence). There was no evidence of a difference between groups for weight gain one week after commencement of intragastric feeds (one study; MD 0.05 kg, 95% CI -0.06 to 0.15; low-certainty evidence). Data were not reported for length of hospital stay.

AUTHORS' CONCLUSIONS

There is low-certainty evidence from three small, old trials that use of dilute formula in preterm or low birth weight formula-fed infants may lead to an important reduction in the time taken for preterm infants to attain an adequate energy intake.However, our confidence in this result is limited due to uncertainty over risk of bias and sparsity of available data. Dilute formula may reduce incidence of feeding intolerance, but the clinical significance of the reduction is uncertain. The impact on serious gastrointestinal problems, including necrotising enterocolitis, was not reported in any of the trials. Further randomised trials are needed to confirm these results.

What should be the protein target for adjustable Human Milk fortification in premature infants?

Objective:

To assess the short- and long-term effects of the adjustable fortification (ADJ) regimen on growth parameters in premature infants and to evaluate the amount of protein supplements given to reach the targeted blood urea nitrogen (BUN) levels.

Methods:

In this retrospective study, preterm babies who were born at ≤32 weeks gestational age and fed with human milk, were evaluated in two groups. Infants in Group-I were fed only standard fortification (STD). Infants in Group-II were fed the ADJ regimen. The study was conducted between 2011 and 2016.

Results:

There were 123 infants in the STD group and 119 in the ADJ group. The mean gestational age of the patients in Group-I was 29.7±1.8 weeks, and mean birth weight was 1266.1±347.1 g. The mean gestational age of the patients in Group-II was 29.5±1.9 weeks, and the mean birth weight was 1217.5±345.5 g. The daily increase in weight and weekly increase in HC were significantly higher in the ADJ group infants. Weight and HC of infants in the ADJ group were significantly higher at 40 weeks. At one year corrected age, weight, length, and HC measurements of both groups were similar. In Group-II, 63% of patients required additional protein supplementation up to 1.6 g/day to achieve the target BUN levels.

Conclusion:

A higher protein intake through the ADJ regimen improves the physical growth rate of premature infants in the NICU and after discharge. However, sometimes, the targeted growth and BUN values cannot be achieved despite the administration of protein at the recommended increased doses. Increasing protein supplementation up to 1.6 g/day is safe, feasible, and beneficial for these infants.

Valid serial length measurements in preterm infants permit characterization of growth patterns

BACKGROUND

The lack of a valid and safe method for measuring length in critically ill preterm neonates has led to a primary focus on weight gain.

LOCAL PROBLEM

Paucity of valid length measurements, precluding the accurate analysis of growth patterns.

METHODS

Quality improvement project among infants < 29 weeks or small for gestational age < 35 weeks with embedded validation of (1) a caliper (infantometer) for length measurements and (2) length measurements during the first week to estimate birth length.

INTERVENTION

Implementation of valid methods to measure length.

RESULTS

We validated infantometer measurements and first week length measurements. The percentage of neonates with valid measurements during the first week rose from 10% to 78%, resulting in increased identification of classifiable growth patterns from < 10% to 89%.

CONCLUSIONS

By increasing the percentage of neonates with valid length measurements in the first week postnatal, we identified an increased number of neonates with classifiable growth abnormalities.

Effects of Taurine Supplementation on Growth in Low Birth Weight Infants: A Systematic Review and Meta-Analysis

OBJECTIVE

To summarize the available randomized controlled trials (RCTs) to evaluate the effect of taurine supplementation on growth in low birth weight infants (LBW).

METHODS

PubMed, EmBase, and Cochrane Library electronic databases were searched for published articles through March 2017. Analysis was done to examine the effect of taurine supplementation on growth, and sensitivity analysis was performed by removing each individual study from meta-analysis.

RESULTS

Results of 9 trials totaling 216 LBW infants in the present meta-analysis were collected and analyzed. The conclusion of included studies demonstrated that taurine supplementation significantly reduced length gain (WMD:-0.18; P < 0.001), plasma glycine (WMD:-106.71; P = 0.033), alanine (WMD:-229.30; P = 0.002), leucine (WMD:-64.76; P < 0.001), tyrosine (WMD:-118.11; P < 0.001), histidine (WMD:-52.16; P < 0.001), proline (WMD: -84.29; P = 0.033), and asparagine-glutamine (WMD:-356.30; P < 0.001). However, taurine supplementation was associated with higher levels of acidic sterols (WMD:0.61; P = 0.024), total fatty acids (WMD:7.94; P = 0.050), total saturated fatty acids (WMD:9.70; P < 0.001), and unsaturated fatty acids (WMD:6.63; P < 0.001). Finally, taurine supplementation had little or no significant effect on weight gain, head circumference gain, plasma taurine, threonine, serine, citrulline, valine, methionine, isoleucine, phenylalanine, ornithine, lysine, arginine, glutamate, hydroxyproline, aspartate, dietary cholesterol, endogenous neutral sterols, cholesterol synthesis, and medium-chain triglycerides.

CONCLUSIONS

The findings suggest that although there are several significant differences in plasma indeces, no significant effect on growth in LBW infants was observed with taurine supplementation.

Strategies of Increased Protein Intake in ELBW Infants Fed by Human Milk Lead to Long Term Benefits

Objective: The aim of this observational study was to evaluate the effects of two different protein intake regimes on feeding tolerance, in-hospital growth, anthropometric data and psychomotor outcome up to 24 months corrected age (CA) in extremely low birth-weight (ELBW; birth weight <1000 g) infants. Methods: During the period 2008-2013, 52 ELBW infants admitted at birth to two Neonatal Intensive Care Units of Emilia Romagna (Italy) were fed according to different protocols of protein fortification of human milk: an estimated protein intakes at maximum fortification levels of 3.5 gr/kg/day in the Standard Nutrition Population-SNP group (n = 26) and 4.8 g/kg/day in the Aggressive Nutrition Population-ANP group (n = 26). During hospitalization, infants' growth, biochemical indices of nutritional status, enteral intake, feeding tolerance, clinical history and morbidity were evaluated. After discharge, anthropometric data and psychomotor outcome, evaluated by Revised Griffiths Mental Development Scales (GMDS-R) 0-2 years, were assessed up to 24 months CA. Results: During hospitalization, the ANP group showed significantly higher weight (18.87 vs. 15.20 g/kg/day) and head circumference (0.70 vs. 0.52 cm/week) growth rates compared to SNP, less days of parenteral nutrition (7.36 ± 2.7 vs. 37.75 ± 29.6) and of hospitalization (60.0 ± 13.3 vs. 78.08 ± 21.32). After discharge, ANP infants had a greater head circumference compared to SNP (45.64 ± 0.29; 46.80 ± 0.31). Furthermore, the General Quotient of GMDS-R mean scores in the SNP group significantly decreased from 12 to 24 months CA, while no difference was seen in the ANP group. Conclusions: Increased protein intake may provide short and long term benefits in terms of growth and neurodevelopment in human milk-fed ELBW infants.

Growth Responses of Preterm Pigs Fed Formulas with Different Protein Levels and Supplemented with Leucine or β-Hydroxyl β-Methylbutyrate

Growth after preterm birth is an important determinant of long-term outcomes. Yet, many preterm infants suffer ex utero growth retardation. We evaluated effects of leucine and the metabolite, β-hydroxy β-methylbutyrate (HMB) on growth of preterm pigs, a previously-validated translational model for preterm infants. After 48 h of parenteral nutrition preterm pigs were fed for 6 to 7 days isocaloric formulas with different levels of protein (50 or 100 g/L) with leucine (10 g/L, 76 mM) or HMB (at 1.1 g/L, 4 mM) added to stimulate protein synthesis or with alanine (6.8 g/L; 76 mM) as the control. Rates of growth of pigs fed the low protein formula with alanine (3.4 ± 0.2% gain per day) or leucine (3.7 ± 0.2) exceeded that of pigs fed the high protein formula (2.8 ± 0.2, p = 0.02 for comparison with both low protein formulas; p = 0.01 compared with low protein + leucine). Supplementing the high protein formula with leucine or HMB did not increase growth relative to alanine (2.72 ± 0.20, 2.74 ± 0.27, and 2.52 ± 0.20, respectively). Small pigs (<700 g birth weight) grew slower during parenteral nutrition and had a more pronounced response to leucine. Females fed the high protein formulas grew faster than males, and particularly for small pigs (p < 0.05). Blood urea nitrogen values were lower for pigs fed the low versus the high protein formulas (p < 0.05). Leucine and HMB improved growth of preterm pigs fed low, but not high protein formulas, even after controlling for birth weight and sex, which independently correlated with growth rates. They offer an option to improve growth without increasing the amino acid load, with its attendant metabolic disadvantages.

Parenteral Protein Decision Support System Improves Protein Delivery in Preterm Infants: A Randomized Clinical Trial

BACKGROUND

Management of neonatal parenteral protein intake for preterm infants is challenging and requires daily modifications of the dose to account for the infant's postnatal age, birth weight, current weight, and the volume and protein concentration of concurrent enteral nutrition. The objective of this study was to create and evaluate the Parenteral Protein Calculator (PPC), a clinical decision support system to improve the accuracy of protein intake for preterm infants who require parenteral nutrition (PN).

MATERIALS AND METHODS

We integrated the PPC into the computerized provider order entry system and tested it in a randomized controlled trial (routine or PPC). Infants were eligible if they were ≤3 days old, had a birth weight ≤1500 g, and had no inborn error of metabolism. The primary outcome was the appropriate total protein intake, defined as target protein dose ±0.5 g/kg.

RESULTS

We randomly allocated 42 infants for 221 PN days in the control group and 211 in the PPC group. Total protein intake in the PPC group was more accurate as compared with the control group (appropriate protein dosing: odds ratio = 5.8; 95% CI, 2.7-12.4). Absolute deviation from protein target was 0.41 g/kg (0.24-0.58) lower in the PPC group.

CONCLUSION

The PPC improved appropriate protein dosing for premature infants receiving PN. Further studies are needed to test whether clinical decision support systems will reduce uremia and improve growth and to replicate similar findings in the cases of other PN nutrients.

Food and Nutrient Intake and Nutrient Sources in 1-Year-Old Infants in Finland: A Cross-Sectional Analysis

The infant diet has short- and long-term health consequences. Updated data regarding the dietary intake of Finnish infants are lacking. The objectives of this study were to describe infant food and nutrient intake and to identify food sources of the nutrients. Altogether, 739 healthy infants were studied. Dietary intake and breastfeeding frequency were assessed with a three-day food record at 1 year of age. Dietary intake was calculated separately for non-breastfed and breastfed infants. One-third (36%) of the infants were partially breastfed and 95% consumed mass-produced baby foods. The infants' diet consisted mainly of infant formula, dairy milk, porridges, fruit and berry foods, and meat dishes. The mean vegetable, fruit and berry consumption was 199 g/day. Most nutrient intakes were adequate except for fat, linoleic acid, vitamin D and iron from food. Mean sucrose intake, as a percentage of total energy intake (E%), was 5-6 E%. High protein intake (>20 E%) was observed in 19% of non-breastfed infants. Overall, the infants' diet was favorable since vegetable and fruit consumption was reasonably high and nutrient intake was mostly adequate. However, the fat intake was lower, and protein intake higher than recommended. Increasing the consumption of vegetable oils and reducing the intake of red meat and dairy milk may further improve the diet of 1-year-olds.

[Parenteral nutrition in premature babies with a birth weight <1500g: a systematic single-center analysis and comparison with current guidelines]

BACKGROUND

Parenteral and enteral nutrition are essential for both growth and development of preterm infants. Based on the results of many studies, the rate of nutritional growth and the amount of substrate delivered parenterally are under debate.

OBJECTIVE

The main aim of this study was to assess parenteral nutrition in very and extremely immature preterm infants, i.e. very low birth weight (VLBW, birth weight <1500g) and extremely low birth weight (ELBW, birth weight <1000g) neonates, and to compare the amount of parenterally delivered substrate in our neonatal intensive care unit (NICU) to current German guidelines.

METHODS

Retrospective audit at our tertiary NICU at the University Children's Hospital of Saarland, Homburg, Germany between 1 January 2009 and 31 December 2010.

RESULTS

In total, 100 premature neonates were included. The mean gestational age was 29.6 weeks (range 24.4-34.1 weeks) and the mean birth weight was 1119 g ± 260 g (range 570 g-1490 g). Comparing the amount of fluids, glucose, amino acids, lipids and kcals with the current guidelines of the German Society for Nutritional Medicine in preterm infants, only glucose was adequately given; however, a substantial number of weight-dependent (more often in ELBW neonates) episodes of hyperglycemia requiring insulin treatment were also seen. During the first 3 weeks of life a substantial drop in body weight, length and head circumference occurred in our study cohort. In contrast, at 2 years corrected age, catch-up growth was seen in our cohort with anthropometric data now comparable to healthy term infants. Using the Bayley II test for developmental outcome assessment, at 2 years corrected age 78.6% (33/42) of infants demonstrated normal development.

CONCLUSIONS

This retrospective data analysis demonstrated inadequate provision of parenteral nutrition in our NICU, which was often not in line with current German guidelines. This was associated with inadequate growth in our cohort, most notably during the first 3 weeks of life; however, implementation of current guidelines is impeded by metabolic disturbances in this cohort, most notably in ELBW neonates. Whether adherence to published guidelines will result in better early ex utero growth, and whether this normalized growth pattern will translate into better long-term outcome on a metabolic and neurological level, remains unclear.

Nutrition after preterm birth and adult neurocognitive outcomes

BACKGROUND

Preterm birth (<37 gestational weeks) poses a risk of poorer neurocognitive functioning. Faster growth after preterm birth predicts better cognitive abilities and can be promoted through adequate nutrition, but it remains unknown whether variations in nutrient intakes translate into long-term benefits for neurodevelopment.

METHODS

In 86 participants of the Helsinki Study of Very Low Birth Weight Adults (birthweight <1500g), we examined if higher intakes of energy, macronutrients, and human milk during the first nine weeks after preterm birth predict performance in tests of cognitive ability at 25.1 years of age (SD = 2.1).

RESULTS

10 kcal/kg/day higher total energy intake at 3 to 6 weeks of age was associated with 0.21 SD higher adult IQ (95% Confidence Interval [CI] 0.07-0.35). Higher carbohydrate and fat intake at 3-6 weeks, and higher energy intake from human milk at 3-6 and at 6-9 weeks were also associated with higher adult IQ: these effect sizes ranged from 0.09 SD (95% CI 0.01-0.18) to 0.34 SD (0.14-0.54) higher IQ, per one gram/kg/day more carbohydrate and fat, and per 10 kcal/kg/day more energy from human milk. Adjustment for neonatal complications attenuated the associations: intraventricular hemorrhage, in particular, was associated with both poorer nutrition and poorer IQ.

CONCLUSION

In preterm neonates with very low birth weight, higher energy and human milk intake predict better neurocognitive abilities in adulthood. To understand the determinants of these infants' neurocognitive outcome, it seems important to take into account the role of postnatal nutrition, not just as an isolated exposure, but as a potential mediator between neonatal illness and long-term neurodevelopment.

Optimizing Nutrition in Preterm Low Birth Weight Infants-Consensus Summary

Preterm birth survivors are at a higher risk of growth and developmental disabilities compared to their term counterparts. Development of strategies to lower the complications of preterm birth forms the rising need of the hour. Appropriate nutrition is essential for the growth and development of preterm infants. Early administration of optimal nutrition to preterm birth survivors lowers the risk of adverse health outcomes and improves cognition in adulthood. A group of neonatologists, pediatricians, and nutrition experts convened to discuss and frame evidence-based recommendations for optimizing nutrition in preterm low birth weight (LBW) infants. The following were the primary recommendations of the panel: (1) enteral feeding is safe and may be preferred to parenteral nutrition due to the complications associated with the latter; however, parenteral nutrition may be a useful adjunct to enteral feeding in some critical cases; (2) early, fast, or continuous enteral feeding yields better outcomes compared to late, slow, or intermittent feeding, respectively; (3) routine use of nasogastric tubes is not advisable; (4) preterm infants can be fed while on ventilator or continuous positive airway pressure; (5) routine evaluation of gastric residuals and abdominal girth should be avoided; (6) expressed breast milk (EBM) is the first choice for feeding preterm infants due to its beneficial effects on cardiovascular, neurological, bone health, and growth outcomes; the second choice is donor pasteurized human milk; (7) EBM or donor milk may be fortified with human milk fortifiers, without increasing the osmolality of the milk, to meet the high protein requirements of preterm infants; (8) standard fortification is effective and safe but does not fulfill the high protein needs; (9) use of targeted and adjustable fortification, where possible, helps provide optimal nutrition; (10) optimizing weight gain in preterm infants prevents long-term cardiovascular complications; (11) checking for optimal weight and sucking/swallowing ability is essential prior to discharge of preterm infants; and (12) appropriate counseling and regular follow-up and monitoring after discharge will help achieve better long-term health outcomes. This consensus summary serves as a useful guide to clinicians in addressing the challenges and providing optimal nutrition to preterm LBW infants.

Advances in nutrition of the newborn infant

Nutrition of newborn infants, particularly of those born preterm, has advanced substantially in recent years. Extremely preterm infants have high nutrient demands that are challenging to meet, such that growth faltering is common. Inadequate growth is associated with poor neurodevelopmental outcomes, and although improved early growth is associated with better cognitive outcomes, there might be a trade-off in terms of worse metabolic outcomes, although the contribution of early nutrition to these associations is not established. New developments include recommendations to increase protein supply, improve formulations of parenteral lipids, and provide mineral supplements while encouraging human milk feeding. However, high quality evidence of the risks and benefits of these developments is lacking. Clinical trials are also needed to assess the effect on preterm infants of experiencing the smell and taste of milk, to determine whether boys and girls should be fed differently, and to test effects of insulin and IGF-1 supplements on growth and developmental outcomes. Moderate-to-late preterm infants have neonatal nutritional challenges that are similar to those infants born at earlier gestations, but even less high quality evidence exists upon which to base clinical decisions. The focus of research in nutrition of infants born at term is largely directed at new formula products that will improve cognitive and metabolic outcomes. Providing the most effective nutrition to preterm infants should be prioritised as an important focus of neonatal care research to improve long-term metabolic and developmental outcomes.

Early Nutritional Interventions for Brain and Cognitive Development in Preterm Infants: A Review of the Literature

Adequate nutrition is important for neurodevelopmental outcomes in preterm-born infants. In this review, we aim to summarize the current knowledge on nutritional interventions initiated during the hospital stay targeting brain and cognitive development benefits in preterm human infants. Studies can broadly be split in general dietary intervention studies and studies investigating specific nutrients or nutritional supplements. In general, mother's breast milk was reported to be better for preterm infants' neurodevelopment compared to infant formula. The differences in methodologies make it difficult to conclude any effects of interventions with individual nutrients. Only protein and iron level studies showed some consistent findings regarding optimal doses; however, confirmatory studies are needed. This review does not support some widely accepted associations, such as that between long-chain polyunsaturated fatty acid supplementation and visual development. Clear nutritional recommendations cannot be made based on this review. However, the type of infant nutrition (i.e., breast milk versus formula or donor milk), the timing of the nutritional intervention, and the dose of the nutrient/supplement have been found to be relevant factors in determining the success of nutritional intervention studies in preterm infants.

Comparison of a Powdered, Acidified Liquid, and Non-Acidified Liquid Human Milk Fortifier on Clinical Outcomes in Premature Infants

We previously compared infant outcomes between a powdered human milk fortifier (P-HMF) vs. acidified liquid HMF (AL-HMF). A non-acidified liquid HMF (NAL-HMF) is now commercially available. The purpose of this study is to compare growth and outcomes of premature infants receiving P-HMF, AL-HMF or NAL-HMF. An Institutional Review Board (IRB) approved retrospective chart review compared infant outcomes (born < 2000 g) who received one of three HMF. Growth, enteral nutrition, laboratory and demographic data were compared. 120 infants were included (P-HMF = 46, AL-HMF = 23, NAL-HMF = 51). AL-HMF infants grew slower in g/day (median 23.66 vs. P-HMF 31.27, NAL-HMF 31.74 (p < 0.05)) and in g/kg/day, median 10.59 vs. 15.37, 14.03 (p < 0.0001). AL-HMF vs. NAL-HMF infants were smaller at 36 weeks gestational age (median 2046 vs. 2404 g, p < 0.05). However AL-HMF infants received more daily calories (p = 0.21) and protein (p < 0.0001), mean 129 cal/kg, 4.2 g protein/kg vs. P-HMF 117 cal/kg, 3.7 g protein/kg , NAL-HMF 120 cal/kg, 4.0 g protein/kg. AL-HMF infants exhibited lower carbon dioxide levels after day of life 14 and 30 (p < 0.0001, p = 0.0038). Three AL-HMF infants (13%) developed necrotizing enterocolitis (NEC) vs. no infants in the remaining groups (p = 0.0056). A NAL-HMF is the most optimal choice for premature human milk-fed infants in a high acuity neonatal intensive care unit (NICU).

Working group reports: evaluation of the evidence to support practice guidelines for nutritional care of preterm infants-the Pre-B Project

The "Evaluation of the Evidence to Support Practice Guidelines for the Nutritional Care of Preterm Infants: The Pre-B Project" is the first phase in a process to present the current state of knowledge and to support the development of evidence-informed guidance for the nutritional care of preterm and high-risk newborn infants. The future systematic reviews that will ultimately provide the underpinning for guideline development will be conducted by the Academy of Nutrition and Dietetics' Evidence Analysis Library (EAL). To accomplish the objectives of this first phase, the Pre-B Project organizers established 4 working groups (WGs) to address the following themes: 1) nutrient specifications for preterm infants, 2) clinical and practical issues in enteral feeding of preterm infants, 3) gastrointestinal and surgical issues, and 4) current standards of infant feeding. Each WG was asked to 1) develop a series of topics relevant to their respective themes, 2) identify questions for which there is sufficient evidence to support a systematic review process conducted by the EAL, and 3) develop a research agenda to address priority gaps in our understanding of the role of nutrition in health and development of preterm/neonatal intensive care unit infants. This article is a summary of the reports from the 4 Pre-B WGs.

Leucine Promotes Proliferation and Differentiation of Primary Preterm Rat Satellite Cells in Part through mTORC1 Signaling Pathway

Signaling through the mammalian target of rapamycin (mTOR) in response to leucine modulates many cellular and developmental processes. However, in the context of satellite cell proliferation and differentiation, the role of leucine and mTORC1 is less known. This study investigates the role of leucine in the process of proliferation and differentiation of primary preterm rat satellite cells, and the relationship with mammalian target of rapamycin complex 1 (mTORC1) activation. Dissociation of primary satellite cells occurred with type I collagenase and trypsin, and purification, via different speed adherence methods. Satellite cells with positive expression of Desmin were treated with leucine and rapamycin. We observed that leucine promoted proliferation and differentiation of primary satellite cells and increased the phosphorylation of mTOR. Rapamycin inhibited proliferation and differentiation, as well as decreased the phosphorylation level of mTOR. Furthermore, leucine increased the expression of MyoD and myogenin while the protein level of MyoD decreased due to rapamycin. However, myogenin expressed no affect by rapamycin. In conclusion, leucine may up-regulate the activation of mTORC1 to promote proliferation and differentiation of primary preterm rat satellite cells. We have shown that leucine promoted the differentiation of myotubes in part through the mTORC1-MyoD signal pathway.

A systematic review of controlled trials of lower-protein or energy-containing infant formulas for use by healthy full-term infants

Infant formulas have historically been developed based on providing macronutrients at intake concentrations approximately matching the composition of human milk. In most countries, targets of 1.4-1.5 g of protein/dL and 20 kcal/oz (67-68 kcal/dL) have been set as the protein and energy concentrations for formulas during the first year of life, although this may be an overestimation of these contents. Recent introduction of lower-protein and -energy formulas in full-term infants led us to systematically review the literature for its effects on growth. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, our inclusion criteria were studies that enrolled healthy full-term infants and evaluated lower-protein or lower-energy formula, reported anthropometric outcomes including weight and length, and followed infants for at least 6 mo. Six studies were eligible for inclusion. These studies varied in the content of nutrients provided in the intervention and control groups, by additional dietary components in the study groups, and the timing and length of the intervention, which limit their usefulness for interpreting newly introduced lower-protein and -energy formulas in the United States. These studies suggest adequate growth during infancy and early childhood with infant formulas with concentrations of protein and energy slightly below historical standards in the United States. Further long-term research is needed to assess the impact of the use of lower-protein and/or lower-energy products, especially for nutritionally at-risk populations such as preterm infants and infants who are born small for gestational age.