METABOLOMIC FINGERPRINTS OF NEONATAL DYSGLYCEMIA IN PRETERM INFANTS

Preterm infants are exposed to glucose fluctuation, including hypo- and hyper-glycemia, as consequence of immaturity of metabolic and hormonal processes regulating glucose homeostasis. Neonatal provision of brain metabolic fuels, including glucose and other metabolites, are thought to be significant determinant of neurodevelopment, though evidence linking neonatal glucose homeostasis to long-term neurodevelopment remains controversial. The aim of this study is to investigate the metabolomic changes associated with neonatal dysglycemia detected with continuous glucose monitoring (CGM) in infants born preterm and their long-term neurodevelopmental effect. This was a monocentric prospective observational study conducted at the Neonatal Intensive Care Unit (NICU) of the University Hospital of Padova. We included preterm infants with birth weight (BW) <1500 g or gestational age (GA) ≤32 weeks, who were started on a continuous glucose sensor within 48 hours of life. Euglycemia is defined as glucose sensor value between 4 and 8 mmol/L; hypoglycemia below 4 mmol/L and hyperglycemia above 8 mmol/L. Glycemic variability (GV) was described as percentage of time spent in each category of glycemia out of total time of monitoring and as coefficient of variation (CV). Targeted metabolomic analysis was applied to plasma samples collected during glucose monitoring and performed on an Acquity Ultra Performance Liquid Chromatography (UPLC) coupled to Mass Spectrometer (MS). Neurodevelopment was assessed at 12 months corrected age (CA) with Bayley Scales of Infant and Toddler Development (BSID) III and gap-overlap (GO) task. Statistical analysis was conducted with non-parametric test using linear regression and univariate analysis. 52 infants were included in the analysis, enrolled between March 2020 and June 2023. Females were 53%, median GA and BW were 29.7 weeks and 1215 g respectively. Targeted metabolomic analysis was performed for 40 patients. Follow-up assessment was available for 43/44 participants. CGM data revealed median time in euglycemic range (TIR) and a CV of 81.8% and 0.19 respectively, negatively correlated with each other (tau b-0.339, p-value<0.001). According to tertile distribution of TIR and CV, we found higher intrauterine growth restriction (IUGR) (0% vs 43%, p-value 0.016) and lower auxological parameter at birth (BW centile 59° vs 17°, p-value 0.015) in those with higher GV. Both extrauterine growth restriction (EUGR) (8% vs 57%, p-value 0.001), and bronchopulmonary dysplasia (BPD) (0% vs 36%, p-value 0.018) prevailed in infants with higher GV. Targeted metabolomic analysis showed higher GV associated with more mobilization of gluconeogenic precursors as lactic acid (421.783 vs 621.894 µM, p-value 0.050) and alanine (365.413 vs 433.433 µM, p-value 0.028), higher level of long chain acylcarnitines as myristoylcarnitine (0.028 vs 0.046 µM, p-value 0.010) and stearoylcarnitine (0.224 vs 0.380 µM, p-value 0.039) and imbalance of metabolites implying in insulin sensitivity as carnosine (12.672 vs 5.328 µM, p-value 0.007), cystathionine (9.452 vs 4.576 µM, p-value 0.016) and DOPA (0.016 vs 0.009 µM, p-value 0.024). GV impaired kynurenine pathway with lower neuroprotective metabolites (p=0.043, tau b=-0.236). Long-term follow up revealed lower performance in communication (BSID III 97 vs 91, p-value 0.016); lower visual attention at GO task was related to GV (tau b 0.389; p-value 0.030). The study demonstrated that GV of preterm infants was influenced by perinatal factors and related to short and long-term clinical outcomes, suggesting GV as a marker of early neonatal health. Targeted metabolomic analysis described the imbalance of several metabolomic pathway involved in alternative energetic substrates and of kynurenine pathway. These findings gave plausibility to the hypothesis of negative influence of neonatal dysglycemia on developing brain.