Nutrition and kidney in preterm infant

Pulsatile Leucine Administration during Continuous Enteral Feeding Enhances Skeletal Muscle Mechanistic Target of Rapamycin Complex 1 Signaling and Protein Synthesis in a Preterm Piglet Model

BACKGROUND

Continuous feeding does not elicit an optimal anabolic response in skeletal muscle but is required for some preterm infants. We reported previously that intermittent intravenous pulses of leucine (Leu; 800 μmol Leu·kg-1·h-1 every 4 h) to continuously fed pigs born at term promoted mechanistic target of rapamycin complex 1 (mTORC1) activation and protein synthesis in skeletal muscle.

OBJECTIVES

The aim was to determine the extent to which intravenous Leu pulses activate mTORC1 and enhance protein synthesis in the skeletal muscle of continuously fed pigs born preterm.

METHODS

Pigs delivered 10 d preterm was advanced to full oral feeding >4 d and then assigned to 1 of the following 4 treatments for 28 h: 1) ALA (continuous feeding; pulsed with 800 μmol alanine·kg-1·h-1 every 4 h; n = 8); 2) L1× (continuous feeding; pulsed with 800 μmol Leu·kg-1·h-1 every 4 h; n = 7); 3) L2× (continuous feeding; pulsed with 1600 μmol Leu·kg-1·h-1 every 4 h; n = 8); and 4) INT (intermittent feeding every 4 h; supplied with 800 μmol alanine·kg-1 per feeding; n = 7). Muscle protein synthesis rates were determined with L-[2H5-ring]Phenylalanine. The activation of insulin, amino acid, and translation initiation signaling pathways were assessed by Western blot.

RESULTS

Peak plasma Leu concentrations were 134% and 420% greater in the L2× compared to the L1× and ALA groups, respectively (P < 0.01). Protein synthesis was greater in the L2× than in the ALA and L1× groups in both the longissimus dorsi and gastrocnemius muscles (P < 0.05) but not different from the INT group (P > 0.10). Amino acid signaling upstream and translation initiation signaling downstream of mTORC1 largely corresponded to the differences in protein synthesis.

CONCLUSIONS

Intravenous Leu pulses potentiate mTORC1 activity and protein synthesis in the skeletal muscles of continuously fed preterm pigs, but the amount required is greater than in pigs born at term.

Markers of Kidney Function in Early Childhood and Association With Maternal Comorbidity

IMPORTANCE

Kidney functional capacity is low at birth but doubles during the first 2 weeks of life and reaches near-adult levels at age 1 to 2 years. Existing reference intervals for markers of kidney function in newborns are mostly based on preterm newborns, newborns with illness, or small cohorts of term newborns, and the consequences of maternal comorbidities for newborn kidney function are sparsely described.

OBJECTIVE

To establish robust reference intervals for creatinine and urea in healthy children in early childhood and to assess whether maternal comorbidity is associated with newborn creatinine and urea concentrations.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter, prospective, population-based cohort study assessed data and umbilical cord blood samples from participants in the Copenhagen Baby Heart Study (CBHS) who were born between April 1, 2016, and October 31, 2018, and venous blood samples from a subsample of CBHS participants who were enrolled in the COMPARE study between May 3, 2017, and November 4, 2018. Cord blood samples of 13 354 newborns from the CBHS and corresponding venous blood samples of 444 of those newborns from the COMPARE study were included. Blood samples were collected at birth, age 2 months, and age 14 to 16 months, with follow-up completed on February 12, 2020. Healthy nonadmitted term newborns from maternity wards at 3 hospitals in the Capital Region of Denmark were included.

EXPOSURES

Maternal comorbidity.

MAIN OUTCOMES AND MEASURES

Creatinine and urea concentrations.

RESULTS

Among 13 354 newborns in the CBHS cohort, characteristics of 12 938 children were stratified by sex and gestational age (GA). Of those, 6567 children (50.8%) were male; 5259 children (40.6%) were born at 37 to 39 weeks' GA, and 7679 children (59.4%) were born at 40 to 42 weeks' GA. Compared with children born at 40 to 42 weeks' GA, those born at 37 to 39 weeks' GA had lower birth weight, Apgar scores at 5 minutes, placental weight, and placental-fetal weight ratio. Children born at 37 to 39 weeks' GA vs those born at 40 to 42 weeks' GA were more frequently small for GA at birth and more likely to have placental insufficiency and exposure to maternal preeclampsia, maternal diabetes, maternal kidney disease, and maternal hypertension. Among children born at 37 to 39 weeks' GA, reference intervals were 0.54 to 1.08 mg/dL for creatinine and 5.32 to 14.67 mg/dL for urea; among children born at 40 to 42 weeks' GA, reference intervals were 0.57 to 1.19 mg/dL for creatinine and 5.60 to 14.85 mg/dL for urea. At birth, multifactorially adjusted odds ratios among children exposed to preeclampsia were 9.40 (95% CI, 1.68-52.54) for a venous creatinine concentration higher than the upper reference limit, 4.29 (95% CI, 1.32-13.93) for a venous creatinine concentration higher than the 90th percentile, and 3.10 (95% CI, 1.14-8.46) for a venous creatinine concentration higher than the 80th percentile.

CONCLUSIONS AND RELEVANCE

In this study, improved reference intervals for creatinine and urea concentrations were generated. Preeclampsia was associated with an increased risk of high newborn creatinine concentrations, suggesting that newborns of mothers with preeclampsia need closer observation of their kidney function.

The renal parenchyma-evaluation of a novel ultrasound measurement to assess fetal renal development: protocol for an observational longitudinal study

INTRODUCTION

Disorders of fetal growth, such as intrauterine growth restriction (IUGR) and large for gestational age (LGA), have been found to have a profound effect on the development of the fetal kidney. Abnormal kidney development is associated with hypertension and chronic kidney disease later in life. This study will use a novel ultrasound measurement to assess the renal parenchymal growth and kidney arterial blood flow in the fetus to evaluate the development of the fetal kidneys and provide an indirect estimate of nephron number. Measurements in normally grown, IUGR and LGA fetuses will be compared to determine if changes in renal parenchymal growth can be detected in utero.

METHODS AND ANALYSIS

This longitudinal, prospective, observational study will be conducted over 12 months in the Ultrasound Department of the Townsville Hospital, Australia. The study will compare fetal renal parenchymal thickness (RPT) and renal artery Doppler flow between IUGR fetuses and appropriately grown fetuses, and LGA fetuses and appropriately grown fetuses between 16 and 40 weeks. The fetal RPT to renal volume ratio will also be compared, and correlations between RPT, renal parenchymal echogenicity, fetal Doppler indices and amniotic fluid levels will be analysed.

ETHICS AND DISSEMINATION

This study was approved by the Townsville Health District Human Research Ethics Committee. The study results will form part of a thesis and will be published in peer-reviewed journals and disseminated at international conferences.

Clinical and nutritional outcomes of two liquid human milk fortifiers for premature infants

BACKGROUND

In preterm infants fortification of human milk with human milk fortifiers (HMF) to optimize nutrition and growth is standard practice. We compared clinical, nutrition and growth outcomes in infants receiving two types of liquid HMF (LHMF).

METHODS

Clinical, nutrition and growth outcomes were compared between infants admitted to a level IV NICU, and born with birth weight less than or equal to 1800 grams, between 10/1/2014-12/31/2014 and received human milk with acidified LHMF (ALHMF) and between 1/1/2015-4/31/2015 and received human milk with heat treated LHMF (HTLHMF).

RESULTS

Of the 85 qualifying infants, 67 received human milk and LHMF. ALHMF group had significantly higher incidence of metabolic acidosis and lower bicarbonate and base excess levels relative to infants receiving HTLHMF (P < 0.001). There were no significant differences by LHMF status in other clinical outcomes and nutrition and growth outcomes. In multivariate analyses, ALHMF use was associated with metabolic acidosis, and lower base excess and bicarbonate levels.

CONCLUSION

In our study, the clinical, nutrition and growth outcomes between the two LHMF groups were similar. However, use of ALHMF in preterm infants was associated with increased incidence of metabolic acidosis in our cohort. Further randomized control trials are warranted to evaluate these findings.

Changes in Biochemical Parameters of the Calcium-Phosphorus Homeostasis in Relation to Nutritional Intake in Very-Low-Birth-Weight Infants

Preterm infants are at significant risk to develop reduced bone mineralization based on inadequate supply of calcium and phosphorus (Ca-P). Biochemical parameters can be used to evaluate the nutritional intake. The direct effect of nutritional intake on changes in biochemical parameters has not been studied. Our objective was to evaluate the effect of Ca-P supplementation on biochemical markers as serum (s)/urinary (u) Ca and P; alkaline phosphatase (ALP); tubular reabsorption of P (TrP); and urinary ratios for Ca/creatinin (creat) and P/creatinin in Very-Low-Birth-Weight infants on Postnatal Days 1, 3, 5, 7, 10, and 14. This observational study compared two groups with High (n = 30) and Low (n = 40) intake of Ca-P. Birth weight: median (IRQ) 948 (772–1225) vs. 939 (776–1163) grams; and gestational age: 28.2 (26.5–29.6) vs. 27.8 (26.1–29.4) weeks. Daily median concentrations of biochemical parameter were not different between the groups but linear regression mixed model analyses showed that Ca intake increased the uCa and TrP (p = 0.04) and decreased ALP (p = 0.00). Phosphorus intake increased sP, uP and uP/creat ratio and ALP (p ≤ 0.02) and caused decrease in TrP (p = 0.00). Protein intake decreased sP (p = 0.000), while low gestational age and male gender increased renal excretion of P (p < 0.03). Standardized repeated measurements showed that biochemical parameters were affected by nutritional intake, gestational age and gender.

One Extra Gram of Protein to Preterm Infants From Birth to 1800 g: A Single-Blinded Randomized Clinical Trial

OBJECTIVE

The aim of the study was to evaluate the effect on growth and neurodevelopment of increasing amino acid (AA) during parenteral nutrition and protein intake during enteral nutrition in extremely low birth-weight infants starting from birth to day of reaching 1800 g body weight.

METHODS

We randomized preterm infants with birth weight 500 to 1249 g either to a high AA/protein intake (HiP [high protein]: parenteral nutrition = 3.5 AA, enteral nutrition = 4.6 protein g · kg · day) or to a standard of care group (StP [standard protein]: parenteral nutrition = 2.5 AA, enteral nutrition = 3.6 protein g · kg · day). The primary outcome was weight gain from birth to 1800 g.

RESULTS

TWO:: hundred twenty-six patients were screened, 164 completed the study and were analyzed (82 StP and 82 HiP). Cumulative AA/protein intake from birth to 1800 g was 178 ± 42 versus 223 ± 45 g/kg in the StP versus HiP group respectively, P < 0.0001.Blood urea was higher in HiP than in StP group both during parenteral and enteral nutrition (P = 0.004).Weight gain from birth to 1800 g was 12.3 ± 1.6 in StP and 12.6 ± 1.7 g · kg · day in HiP group (P = 0.294). We found no difference in any growth parameters neither during hospital stay nor at 2 years corrected age. Bayley III score at 24 months corrected age was 93.8 ± 12.9 in StP group and 94.0 ± 13.9 in the HiP group, P = 0.92.

CONCLUSIONS

Increasing AA/protein intake both during parenteral and enteral nutrition does not improve growth and neurodevelopment of small preterm infants 500 to 1249 g birth weight.

Urinary metabolite profiles in premature infants show early postnatal metabolic adaptation and maturation

Objectives: Early nutrition influences metabolic programming and long-term health. We explored the urinary metabolite profiles of 48 premature infants (birth weight < 1500 g) randomized to an enhanced or a standard diet during neonatal hospitalization. Methods: Metabolomics using nuclear magnetic resonance spectroscopy (NMR) was conducted on urine samples obtained during the first week of life and thereafter fortnightly. Results: The intervention group received significantly higher amounts of energy, protein, lipids, vitamin A, arachidonic acid and docosahexaenoic acid as compared to the control group. Enhanced nutrition did not appear to affect the urine profiles to an extent exceeding individual variation. However, in all infants the glucogenic amino acids glycine, threonine, hydroxyproline and tyrosine increased substantially during the early postnatal period, along with metabolites of the tricarboxylic acid cycle (succinate, oxoglutarate, fumarate and citrate). The metabolite changes correlated with postmenstrual age. Moreover, we observed elevated threonine and glycine levels in first-week urine samples of the small for gestational age (SGA; birth weight < 10th percentile for gestational age) as compared to the appropriate for gestational age infants. Conclusion: This first nutri-metabolomics study in premature infants demonstrates that the physiological adaptation during the fetal-postnatal transition as well as maturation influences metabolism during the breastfeeding period. Elevated glycine and threonine levels were found in the first week urine samples of the SGA infants and emerged as potential biomarkers of an altered metabolic phenotype.

Higher protein intake improves length, not weight, z scores in preterm infants

OBJECTIVE

The aim of the study was to evaluate the relation between nutritional intake (kilocalories, protein) and weight and length growth in preterm infants, and to describe their metabolic tolerance with a focus on those with high protein intake (≥ 4.6 g · kg(-1) · day(-1)).

METHODS

Secondary analysis of data from appropriate-for-gestational age preterm infants in a 28-day randomized clinical trial that evaluated growth, tolerance, and safety of a new ultraconcentrated liquid human milk fortifier (original study n = 150). This subset of 56 infants had complete growth and nutrition data and met criteria for the original study's "efficacy analysis" (eg, >80% of kilocalorie intake from study diet). Nutritional intake was estimated, not actual. Regressions were used to test cumulative kilocalories and protein as the predictors of 28-day change in weight and length z scores (growth status), and to evaluate protein tolerance.

RESULTS

Average intake was 118 ± 8 kcal · kg(-1) · day(-1) and 4.3 ± 0.4 g protein · kg(-1) · day(-1), with 16 ± 3 g · kg(-1) · day(-1) and 1.1 ± 0.2 cm/week growth for 28 days. Cumulative total kilocalories and protein were significant predictors of improved length z score (P = 0.0054, 0.0005) but not weight z score change. Regression models indicated that protein not kilocalories explained the improvement in length z score, with protein explaining 19% of the variability. The high protein group averaged 4.6 to 5.5 g · kg(-1) · day(-1) (n = 16). Protein tolerance was adequate for all of the study infants based on metabolic measures (blood urea nitrogen, serum carbon dioxide, pH).

CONCLUSIONS

Higher cumulative protein intake was tolerated and overall lessened the commonly occurring decline in the length but not weight growth status in a 28-day study of preterm infants.

Early postnatal calcium and phosphorus metabolism in preterm infants

OBJECTIVES

Bone mineralisation in preterm infants is related to the supply of calcium (Ca) and phosphorus (P). We increased the amount of minerals in parenteral nutrition (PN) for preterm infants and evaluated postnatal Ca and P metabolism in relation to mineral and vitamin D (vitD) intake.

METHODS

Preterm infants, included on their first day of life, received standard PN, providing a maximum Ca/P intake of 3/1.92 mmol · kg(-1) · day(-1) on day 3. Ca/P content of formula was 2.5/1.6 mmol/dL, and fortified human milk was 2.4/1.95 mmol/dL. PN supplied 80 IU · kg(-1) · day(-1) vitD. Formula and fortified human milk contained 200 IU/dL of vitD. During a 5-week period, serum concentrations and urinary excretion of Ca/P were registered and related to the intake of minerals and vitD.

RESULTS

During 12 months, 79 infants (mean gestational age 29.8 ± 2.2 weeks, mean birth weight 1248 ± 371 g) were included. The recommended intake for minerals was achieved by day 5 and for vitD by 4 weeks. Infants developed hypercalcaemia, hypercalciuria, and hypophosphataemia during the first postnatal week, leading to the additional P supplementation in 49 infants. The renal tubular reabsorption of P was >95% until day 9 but decreased <70% after the second week. Alkaline phosphatase was normal at birth, increased to a maximum of 450 IU/L by day 14, and remained above the normal range for the remaining period.

CONCLUSIONS

Parenteral intake of P appeared to be too low, leading to mineral imbalances in the early postnatal period, and vitD intake was also below recommendations.

Safety and efficacy of early parenteral lipid and high-dose amino acid administration to very low birth weight infants

OBJECTIVE

To assess the efficacy and safety of early parenteral lipid and high-dose amino acid (AA) administration from birth onwards in very low birth weight (VLBW, birth weight <1500 g) infants.

STUDY DESIGN

VLBW infants (n = 144; birth weight 862 ± 218 g; gestational age 27.4 ± 2.2 weeks) were randomized to receive 2.4 g of AA kg(-1) · d(-1) (control group), or 2.4 g AA kg(-1) · d(-1) plus 2-3 g lipids kg(-1) · d(-1) (AA + lipid group), or 3.6 g AA kg(-1) · d(-1) plus 2-3 g lipids kg(-1) · d(-1) (high AA + lipid group) from birth onwards. The primary outcome was nitrogen balance. The secondary outcomes were biochemical variables, urea rate of appearance, growth rates, and clinical outcome.

RESULTS

The nitrogen balance on day 2 was significantly greater in both intervention groups compared with the control group. Greater amounts of AA administration did not further improve nitrogen balance compared with standard AA dose plus lipids and was associated with high plasma urea concentrations and high rates of urea appearance. No differences in other biochemical variables, growth, or clinical outcomes were observed.

CONCLUSIONS

In VLBW infants, the administration of parenteral AA combined with lipids from birth onwards improved conditions for anabolism and growth, as shown by improved nitrogen balance. Greater levels of AA administration did not further improve the nitrogen balance but led to increased AA oxidation. Early lipid initiation and high-dose AA were well tolerated.

Low Birth Weight due to Intrauterine Growth Restriction and/or Preterm Birth: Effects on Nephron Number and Long-Term Renal Health

Epidemiological studies have clearly demonstrated a strong association between low birth weight and long-term renal disease. A potential mediator of this long-term risk is a reduction in nephron endowment in the low birth weight infant at the beginning of life. Importantly, nephrons are only formed early in life; during normal gestation, nephrogenesis is complete by about 32–36 weeks, with no new nephrons formed after this time during the lifetime of the individual. Hence, given that a loss of a critical number of nephrons is the hallmark of renal disease, an increased severity and acceleration of renal disease is likely when the number of nephrons is already reduced prior to disease onset. Low birth weight can result from intrauterine growth restriction (IUGR) or preterm birth; a high proportion of babies born prematurely also exhibit IUGR. In this paper, we describe how IUGR and preterm birth adversely impact on nephrogenesis and how a subsequent reduced nephron endowment at the beginning of life may lead to long-term risk of renal disease, but not necessarily hypertension.