Metabolic acidosis in the newborn period

Redox control in mammalian embryo development

The development of an embryo constitutes a complex choreography of regulatory events that underlies precise temporal and spatial control. Throughout this process the embryo encounters ever changing environments, which challenge its metabolism. Oxygen is required for embryogenesis but it also poses a potential hazard via formation of reactive oxygen and reactive nitrogen species (ROS/RNS). These metabolites are capable of modifying macromolecules (lipids, proteins, nucleic acids) and altering their biological functions. On one hand, such modifications may have deleterious consequences and must be counteracted by antioxidant defense systems. On the other hand, ROS/RNS function as essential signal transducers regulating the cellular phenotype. In this context the combined maternal/embryonic redox homeostasis is of major importance and dysregulations in the equilibrium of pro- and antioxidative processes retard embryo development, leading to organ malformation and embryo lethality. Silencing the in vivo expression of pro- and antioxidative enzymes provided deeper insights into the role of the embryonic redox equilibrium. Moreover, novel mechanisms linking the cellular redox homeostasis to gene expression regulation have recently been discovered (oxygen sensing DNA demethylases and protein phosphatases, redox-sensitive microRNAs and transcription factors, moonlighting enzymes of the cellular redox homeostasis) and their contribution to embryo development is critically reviewed.

Metabolomic and bioinformatic analyses in asphyxiated neonates

OBJECTIVES

We tested the application of bioinformatic algorithms in studying the metabolomic profiles of neonatal urine samples with clinical evidence of severe asphyxia at birth and subsequent neurodevelopmental handicap.

DESIGN AND METHODS

The clinical outcomes of 256 newborns that required direct admission to neonatal intensive care unit for respiratory support or did not require direct admission were studied. Urinary metabolite profiles were measured by high throughput mass spectrometry and analyzed by bioinformatic methods.

RESULTS

We found a positive relationship between suppressed biochemical networks involved in macromolecular synthesis and birth asphyxia associated with significant neonatal oxidative stress and morbidity. The metabolomic discriminators between good neonatal outcome and poor neonatal outcome were established using hierarchical clustering analysis. Concentrations of eight urinary organic acids in distinct biochemical pathways were elevated and significantly associated with the prognosis of neurodevelopmental handicap with high sensitivity and specificity: ethylmalonate, 3-hydroxy-3-methylglutarate, 2-hydroxy-glutarate and 2-oxo-glutarate were associated with good neonatal outcome, whereas glutarate, methylmalonate, 3-hydroxy-butyrate and orotate were associated with poor outcome.

CONCLUSIONS

The data demonstrated the potential application of bioinformatics methods in this metabolomic study and proved its clinical relevance.

Lipid peroxidation in cord blood at birth

OBJECTIVE

The purpose of this study was to determine oxygen free radical activity in the neonate at birth and relate it to umbilical cord blood acid-base status.

STUDY DESIGN

A series of 110 singleton deliveries had determination of two lipoperoxides in umbilical cord blood: malondialdehyde and organic hydroperoxide. Umbilical pH, PO2, PCO2, bicarbonate, and base excess were also measured.

RESULTS

There was a significant association between lipoperoxides and cord blood pH and base excess. A significant difference existed in the levels of umbilical artery lipoperoxides between nonacidemic and acidemic fetus, as defined by an umbilical arterial pH < 7.20.

CONCLUSION

There is a positive association between lipoperoxide production and acid-base balance at delivery.

The kidney in acid-base balance

The practitioner's approach to the pediatric patient with metabolic acidosis begins with calculation of the serum anion gap, which allows the clinician to place the patient in one of two categories of acid-base disturbance: a normal anion gap acidosis or high anion gap acidosis. Likewise, the patient with metabolic alkalosis can be categorized by urinary chloride concentration and the response to chloride replenishment as either chloride-responsive or chloride-resistant. The disease states associated with each category are reviewed in this article.