Urinary citrulline in very low birth weight preterm infants receiving intravenous nutrition

Metabolomics Applied to Cord Serum in Preeclampsia Newborns: Implications for Neonatal Outcomes

Preeclampsia (PE) is one of the leading causes of maternal and perinatal morbidity and mortality. However, it is still uncertain how PE affects neonate metabolism. We conducted an untargeted metabolomics analysis of cord blood to explore the metabolic changes in PE neonates. Umbilical cord serum samples from neonates with preeclampsia (n = 29) and non-preeclampsia (non-PE) (n = 32) pregnancies were analyzed using the UHPLC-QE-MS metabolomic platform. Different metabolites were screened, and pathway analysis was conducted. A subgroup analysis was performed among PE neonates to compare the metabolome between appropriate-for-gestational-age infants (n = 21) and small-for-gestational-age (SGA) infants (n = 8). A total of 159 different metabolites were detected in PE and non-PE neonates. Creatinine, N4-acetylcytidine, sphingomyelin (D18:1/16:0), pseudouridine, uric acid, and indolelactic acid were the most significant differential metabolites in the cord serum of PE neonates. Differential metabolite levels were elevated in PE neonates and were involved in the following metabolic pathways: glycine, serine, and threonine metabolism; sphingolipid, glyoxylate, and dicarboxylate metabolism; and arginine biosynthesis. In PE neonates, SGA neonates showed increased levels of hexacosanoyl carnitine and decreased abundance of 3-hydroxybutyric acid and 3-sulfinoalanine. Taurine-related metabolism and ketone body-related pathways were mainly affected. Based on the UHPLC-QE-MS metabolomics analysis, we identified the metabolic profiles of PE and SGA neonates. The abundance of metabolites related to certain amino acid, sphingolipid, and energy metabolism increased in the umbilical cord serum of PE neonates.

A systematic review of the definitions and prevalence of feeding intolerance in preterm infants

BACKGROUND & AIMS

Feeding intolerance (FI) is a common phenomenon experienced in preterm infants in neonatal intensive care units, as well as being a focus of many research studies into feeding methods, particularly in relation to comorbidities. There is no widely accepted definition of FI. This systematic review aimed to explore the range of definitions used for FI and provide an estimate of the prevalence amongst preterm infants.

METHODS

Searches were completed on MEDLINE (includes the Cochrane library), Embase, PsycInfo, CINAHL, NHS Evidence and Web of Science. Inclusion criteria; preterm infants in neonatal units, a clear definition of FI, >10 patients and be available in English language. Case reports were excluded.

RESULTS

One hundred studies were included. Definitions of FI were inconsistent. Studies were grouped according to definition used into: Group A - measuring gastric residual volume (GRV) only; group B - GRV and abdominal distension (AD); group C - GRV, AD and gastrointestinal symptoms (GI) which included any of vomiting, bilious vomiting and blood in stool; group D- GRV and GI; group E - AD and GI; group F - GI only and group G - any other elements used. Meta-analysis demonstrated that prevalence of FI between groups varied from 15 to 30% with an overall prevalence of 27% (95% confidence interval 23-31%). Group A had the highest prevalence. Review of time to full enteral feed was performed (37 studies) which demonstrated a range of 11.3-18.3 days depending on which FI definition used.

DISCUSSION

Definitions of FI in research are inconsistent, a similar finding to that seen in studies in both paediatric and adult critical care populations. The difficulty of defining FI in the preterm population is the concern regarding necrotising enterocolitis, with some studies using an overlap in their definitions, despite differing pathophysiology and management. Due to the heterogeneity of data obtained in this review regarding definitions used, further robust research is required in order to conclude which elements which should be used to define FI in this population.

PROSPERO NUMBER

CRD42019155596. Registered November 2019.

Citrulline, Biomarker of Enterocyte Functional Mass and Dietary Supplement. Metabolism, Transport, and Current Evidence for Clinical Use

L-Citrulline is a non-essential but still important amino acid that is released from enterocytes. Because plasma levels are reduced in case of impaired intestinal function, it has become a biomarker to monitor intestinal integrity. Moreover, oxidative stress induces protein citrullination, and antibodies against anti-citrullinated proteins are useful to monitor rheumatoid diseases. Citrullinated histones, however, may even predict a worse outcome in cancer patients. Supplementation of citrulline is better tolerated compared to arginine and might be useful to slightly improve muscle strength or protein balance. The following article shall provide an overview of L-citrulline properties and functions, as well as the current evidence for its use as a biomarker or as a therapeutic supplement.

Plasma citrulline is not a biomarker for intestinal adaptation in short bowel syndrome, studied in piglets: a model for human neonates

BACKGROUND

There are no in vivo methods to measure adaptation in neonatal short bowel syndrome (SBS). We evaluated citrulline (Cit) levels in neonatal piglet surgical models of SBS.

METHODS

Piglets underwent 75% mid-intestinal resection with jejunoileal anastomosis (JI), 75% distal resection of ileum with jejunocolic anastomosis (JC) or sham surgery. Jugular and gastric catheters were inserted for parenteral and enteral nutrition. On D7, small intestine length and weight were measured, jejunum collected for histopathology and Cit level determined.

RESULTS

JI (n = 5) compared to JC (n = 5) had increased small intestinal length (JC - 17.5 cm; JI +22.0 cm; p = 0.02) and mass (JC 43.1 mg/cm/kg; JI 51.3 mg/cm/kg; p = 0.02), while Cit did not differ (JI 801.0 µM; JC 677.7 µM; p = 0.90). Including non-resected shams (n = 4), Cit correlated with length (R² = 0.48; p = 0.006), but not for SBS alone (R² = 0.11; p = 0.4), mass (R² = 0.05; p = 0.5). A second experiment compared change in Cit levels from baseline to D7. Levels declined in sham (n = 8) and JC (n = 10) (sham - 110.1 µM; JC - 56.6 µM; p = 0.17), regardless of intestinal lengthening (sham 29.9 cm; JC - 10.4 cm; p = 0.002).

CONCLUSION

Citrulline levels predict large differences in intestinal length and 'identify' SBS. However, citrulline cannot discriminate between adaptation in JI and JC, nor predict intestinal lengthening.

Correlation between plasma levels of arginine and citrulline in preterm and full-term neonates: Therapeutical implications

BACKGROUND

Preterm neonates exhibit several deficiencies that endanger their lives. Understanding those disturbances will provide tools for the management of preterm neonates. The present work focuses on arginine and citrulline which has been flagged among the biochemical landmarks of prematurity.

METHODS

We examined blood samples of preterm newborns as compared with mature neonates to determine the levels of arginine and citrulline by capillary zone electrophoresis with laser induced fluorescence detection (CZE-LIFD).

RESULTS

Significantly lower levels of arginine and citrulline were found in preterm neonates than in mature neonates (P<.01). Interestingly there was a highly significant correlation between the two amino acids in mature neonates (P<.0001). Such correlation was present in preterm neonates too (P<.01). Pearson coefficient showed that 60% of the citrulline concentration depends on arginine concentration in mature neonates. Only 20% of the citrulline concentration depends on arginine concentration in preterm neonates. Although the ratio arginine/citrulline was lower in preterm neonates than in mature neonates the difference was not statistically significant.

CONCLUSIONS

These results suggest that less arginine is converted to citrulline to form nitric oxide in preterm than in full-term neonates. The result is discussed in terms of the immature enzymatic systems in the preterm neonate.

Breast-feeding improves gut maturation compared with formula feeding in preterm babies

OBJECTIVE

The incidence of necrotizing enterocolitis (NEC) is higher in formula-fed babies than in breast-fed babies, which may be caused by breast-feeding-induced gut maturation. The effect of breast-feeding on gut maturation has been widely studied in animal models. This study aimed to assess the effects of breast-feeding on intestinal maturation in prematurely born babies by evaluating postnatal changes in urinary intestinal fatty acid binding protein (I-FABP) levels, a specific enterocyte marker.

METHODS

Gut maturation in 40 premature babies (<37 weeks of gestation) without gastrointestinal morbidity was studied, of whom 21 were exclusively breast-fed and 19 were formula-fed infants. Urinary I-FABP levels as the measure of gut maturation were measured at 5, 12, 19, and 26 days after birth.

RESULTS

In breast-fed infants, there was a significant increase in median urinary I-FABP levels between 5 and 12 days after birth (104 [78-340] pg/mL to 408 [173-1028] pg/mL, P = 0.002), whereas I-FABP concentration in formula-fed infants increased between 12 and 19 days after birth (105 [44-557] pg/mL, 723 [103-1670] pg/mL, P = 0.004). Breast-fed babies had significantly higher median urinary I-FABP levels at postnatal day 12 (P = 0.01).

CONCLUSIONS

The time course of the postnatal increase in urinary I-FABP levels reflecting gut maturation was significantly delayed in formula-fed babies, suggesting a delayed physiological response in formula-fed compared with breast-fed infants.