Reduced early dried blood spot citrulline levels in preterm infants with meconium obstruction of prematurity

Proximal urea cycle defects are challenging to detect with newborn screening: Results of a prospective pilot study using post-analytical tools

The purpose of this pilot project was to evaluate the efficacy of the Collaborative Integrated Laboratory Reports (CLIR) postanalytical tools from Mayo Clinic for detection of newborns with proximal urea cycle disorders (PUCD) in the Georgia newborn screening program that uses the underivatized Neobase2 kit (Perkin Elmer). We evaluated 138,560 newborn screening (NBS) samples (between 125,000 and 130,000 children) and used the CLIR result interpretation guidelines to stratify results. Children at higher risk of having a PUCD received follow-up services including confirmatory lab testing (ammonia, plasma amino acids, urine orotic acid) or a repeat NBS sample. We made multiple adjustments to our CLIR PUCD tool and to our follow-up algorithms in order to reduce false positives. Regardless, a high number of NBS samples resulted with false positives in part due to the glutamine peak also containing lysine. No children were diagnosed with a PUCD during our study period, and the Emory Genetics Metabolic Center is unaware of any children diagnosed outside of the NBS system during that time. Based on our experience, PUCD is not suitable for statewide NBS using Neobase2 and CLIR. Other methodologies that can separate glutamine from other amino acids may have better performance.

Plasma Citrulline as a Biomarker for Early Diagnosis of Necrotizing Enterocolitis in Preterm Infants

OBJECTIVE

Citrulline synthesized by healthy enterocytes and decreases with injury. This work aimed to study plasma citrulline concentrations (CITs) as a biomarker to differentiate among infants presenting with early nonspecific signs and symptoms of necrotizing enterocolitis (NEC) with those who will develop NEC. Further to study the correlation between posttreatment CIT with time to full feeds (TTFF) and length of stay (LOS).

STUDY DESIGN

This is a prospective study which included infants < 32 weeks gestational age (GA) with 9 infants each in Group 1 (stage 2/3 NEC), Group 2 (with stage 1 NEC-like presentation), and Group 3 (healthy GA-matched infants). CIT was measured in Groups 1 and 2 within 24 hours of presentation and again in Group 1 after treatment.

RESULTS

The three groups were similar in clinical characteristics. Median CIT (µmol/L) in Group 1 (15.4 [interquartile range, IQR: 7.3-18.0]) was lower than Group 2 (22.2 [IQR: 18.3-27.3], p = 0.02) and Group 3 (24.9 [IQR: 19.8-31.9], p = 0.009). Posttreatment CIT in Group 1 did not correlate with TTFF (r = 0.15; p = 0.69) and LOS (r =  - 0.33; p = 0.38).

CONCLUSION

CIT was lower in infants with NEC as compared with healthy controls and those infants with nonspecific signs of NEC. CIT after treatment does not correlate with TTFF and LOS.

KEY POINTS

· Citrulline is produced by enterocytes.. · It is decreased in infants with necrotizing enterocolitis early in disease.. · It can be used as a biomarker for early diagnosis of necrotizing enterocolitis..

Non-Cystic Fibrosis-Related Meconium Ileus: GUCY2C-Associated Disease Discovered through Rapid Neonatal Whole-Exome Sequencing

Meconium ileus is caused by cystic fibrosis; however, mutations in the GUCY2C gene also cause this disease. We report non-cystic fibrosis meconium ileus in an infant of non-Middle Eastern origin with compound heterozygous mutations in GUCY2C.

Use of serum citrulline concentrations from routine newborn screen as a biomarker for necrotizing enterocolitis

PURPOSE

Necrotizing enterocolitis (NEC), a leading cause of mortality and morbidity in preterm neonates, lacks a reliable biomarker. Citrulline is primarily produced by enterocytes and correlates with intestinal function. Serum citrulline concentration (CIT) is routinely measured in routine newborn screening (NBS). The purpose of the study is to test if CIT from NBS may predict the occurrence of NEC and whether it correlates with the time to full feeds (TTFF) and length of stay (LOS), serving as a biomarker of NEC and intestinal health.

METHODS

In a retrospective case control study conducted on neonates with gestational age of 26-32 weeks, we compared CIT levels between cases (neonates with NEC) and controls (next-born neonate). NBS was collected within first 24 h, at day 5 and when the neonates achieved full feeds and were compared using non-parametric tests.

RESULTS

There was no difference in CIT between the controls and cases on day 1 [11.42 (7.42-14.84 vs. 11.93 (6.85-18.8) µmol/L, p = 0.55], on day 5 [11.99 (7.99-16.55) vs. 13.70 (7.42-26.83) µmol/L, p = 0.05], or at full feeds [14.86 (6.85-25.69) vs. 15.7 (7.42-26.26) µmol/L, p = 0.87]. CIT on day 1 did not correlate with TTFF (r = 0.08, p = 0.53) or LOS (r = 0.23, p = 0.06), respectively).

CONCLUSIONS

CIT from routine NBS does not serve as a biomarker to predict NEC in preterm neonates.

Quantitative Metabolomic Analysis of Urinary Citrulline and Calcitroic Acid in Mice after Exposure to Various Types of Ionizing Radiation

With the safety of existing nuclear power plants being brought into question after the Fukushima disaster and the increased level of concern over terrorism-sponsored use of improvised nuclear devices, it is more crucial to develop well-defined radiation injury markers in easily accessible biofluids to help emergency-responders with injury assessment during patient triage. Here, we focused on utilizing ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to identify and quantitate the unique changes in the urinary excretion of two metabolite markers, calcitroic acid and citrulline, in mice induced by different forms of irradiation; external γ irradiation at a low dose rate (LDR) of 3.0 mGy/min and a high dose rate (HDR) of 1.1 Gy/min, and internal exposure to Cesium-137 ((137)Cs) and Strontium-90 ((90)Sr). The multiple reaction monitoring analysis showed that, while exposure to (137)Cs and (90)Sr induced a statistically significant and persistent decrease, similar doses of external γ beam at the HDR had the opposite effect, and the LDR had no effect on the urinary levels of these two metabolites. This suggests that the source of exposure and the dose rate strongly modulate the in vivo metabolomic injury responses, which may have utility in clinical biodosimetry assays for the assessment of exposure in an affected population. This study complements our previous investigations into the metabolomic profile of urine from mice internally exposed to (90)Sr and (137)Cs and to external γ beam radiation.