Analysis and interpretation of acylcarnitine profiles in dried blood spot and plasma of preterm and full-term newborns

Abstract

Background: Acylcarnitines are biomarkers of fatty acid metabolism, and examining their patterns in preterm newborn may reveal metabolic changes associated with particular conditions related to prematurity. Isomeric acylcarnitines in dried blood spots (DBS) and plasma have never been assessed in preterm infants. Methods: We studied 157 newborn divided into four groups by weeks of gestational age (GA), as follows: 22-27 wk in group 1; 28-31 wk in group 2; 32-36 wk in group 3; and 37-42 wk in group 4. Samples were collected on the third day of life. Acylcarnitines were separated and quantified using ultra-performance liquid chromatography tandem mass spectrometry. results: Acylcarnitine concentrations correlated significantly with GA and birth weight in both DBS and plasma samples. Concentrations were lower in preterm newborn, except for acylcarnitines derived from branched-chain amino acids, which were higher and correlated with enteral feeding. On day 3 of life, no correlations emerged with gender, respiratory distress syndrome, bronchopulmonary dysplasia, surfactant administration, or mechanical ventilation. conclusion: We established GA-based reference ranges for isomeric acylcarnitine concentrations in preterm newborn, which could be used to assess nutritional status and the putative neuroprotective role of acylcarnitines.F atty acid metabolism takes place in the mitochondria, and β-oxidation is the main process by which fatty acids are oxidized by means of a sequential removal of two-carbon units from the acyl chain. Fatty acids are activated primarily in the cytosol by fatty acyl-CoA synthase to carnitine derivatives, then they are carried by specific acylcarnitine (AC) transferases and translocases into the mitochondrial matrix where β-oxidation can begin. In successive cycles of reactions, this process generates a series of ACs that are one two-carbon unit shorter and it continues until only two or three carbons are left (forming acetyl-CoA or propionyl-CoA, respectively). AC detection is of great interest for the purpose of assessing the carnitine pool, which is essential to the diagnosis of several metabolic disorders. AC profiling is a powerful tool for the neonatal screening and diagnosis of fatty acid oxidation and organic acid disorders (1). Alongside the importance of AC in tissues such as heart and muscle, recent data indicate an involvement of these compounds in neurological protection and disorders. ACs are believed to have both energy-providing and neuroprotective roles in the brain (2,3), based on the assumption that the fatty acid oxidation pathway is active in neurons, given the localization of carnitine palmitoyltransferase enzyme 1 (CPT1) (2,4). Investigating AC profiles in preterm infants may therefore reveal metabolic changes associated with perinatal brain injury.Mass spectrometry (MS) is commonly used to quantify ACs. Millington and co-workers pioneered tandem mass spectrometry (MS/MS) methods for assaying carnitine and ACs in urine and plasma samples (5), and in dried blood spots (DBS...

Gestational dating by metabolic profile at birth: a California cohort study

“…While no other published study that we are aware of has used the combination of these markers for gestational dating, our findings are in agreement with other studies that have demonstrated an association between PTB and many of the individual biomarkers studied including those that have found that differences remain after accounting for SGA and feeding status. 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 Like other investigators we observed significant differences between PTBs and term births in free carnitine 33 , 39 ; short-, medium-, and long-chain acylcarnitines 33 , 39 , 40 , 41 , 43 ; amnio acids 39 , 40 , 41 , 43 ; TSH 35 , 37 , 50 ; and 17-OHP. 47 , 51 , 52 Although it is unclear what specifically underlies the differences observed and why they appear useful for gestational dating, it appears that both etiological and maturational underpinnings may exist that are marker specific.…”

“…While our hypothesis that markers used for newborn screening could also be used for gestational dating purposes is novel, the work is well supported by previous studies demonstrating that many of these routinely collected markers (eg, acylcarnitines, amino acids, thyroid-stimulating hormone [TSH]) are related to PTB and to week of gestation and have heritable components that are robust in small-for-gestational-age (SGA) infants. 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 In the present study, we developed and evaluated a metabolic dating algorithm using a large and diverse sample of California newborns who had ultrasound dating between 11–20 weeks of gestation. We focused specifically on the capacity of markers to differentiate PTBs from term births and to assign a specific gestational age in the preterm group.…”

Performance of LC/MS/MS in Analyzing Multiple Amino Acids and Acylcarnitines in Dried Blood Spot of Very Low Birth Weight, Low Birth Weight, and Normal Weight Neonates

“…Whether the concentrations of AA and AC in these neonates can offer some information about neonatal metabolic or nutritional status is still unknown. As reported previously, AA and AC concentrations varied obviously with birth weight [11]; therefore, VLBW and LBW neonates may have different mean values from NW neonates, and different cutoffs need to be defined to reduce the risks of false-positive cases [12]. Thus, the aim of the present study was to identify the AA and AC profiles in DBS specimens of LBW and VLBW neonates, then compare with NW neonates, and make a contribution to the determination of cutoff values of VLBW and LBW neonates.…”

Fatal pitfalls in newborn screening for mitochondrial trifunctional protein (MTP)/long-chain 3-Hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency

“…The history of patient 3 adds to the discussion whether cut-off ranges in newborn screening may be applied for term and preterm newborns. Whereas previous data suggested that equal cut-offs may be applied [ 40 , 41 ], it recently has been shown that concentrations of acylcarnitines were lower in healthy preterm compared to term newborns [ 42 ]. Many reasons have been postulated, including endogenous and metabolic differences due to lower birth weight and immaturity, and the effect of treatments administered in newborn intensive care units [ 42 ].…”