Carnitine Status at Birth of Newborn Infants of Varying Gestation

Abstract

SummaryThis study assessed and compared the plasma and red blood cell concentrations of carnitine in cord blood samples from preterm (a36 wk, n = 53) and term (237 wk, n = 72) neonates. The mean (+S. Carnitine, ,8-OH-y-trimethyl amino-butyric acid, is a quarternary amine that plays an essential role in the oxidation of long chain fatty acids by facilitating their transport across the inner mitochondria1 membranes via a carnitine acyltransferase enzyme system (8, 16). Improved fatty acid utilization would enhance a neonate's ability to utilize energy, which in turn may potentiate growth. Fatty acid oxidation also plays an important part in the thermogenic function of brown adipose tissue (10). This factor may be of an immense value to the neonate, particularly a sick preterm infant in achieving thermal homeostasis. Animal studies have suggested an important role for carnitine in hepatic ketogenesis (12). Ketones constitute a significant source of metabolic fuel, particularly for utilization by brain in the perinatal period (18). These various studies seem to indicate that carnitine is one of the essential nutrients in the diet of newborn infants (3).EStudies in various animal species have demonstrated a transfer of carnitine from the mother to the fetus during pregnancy and via milk during the postnatal period (10,11,20). The amount of carnitine transferred across the placenta varies with different species. Little is known of carnitine levels during various stages of human gestation. Plasma concentration of carnitine is often used as the parameter for determination of carnitine status. This study was designed to assess and compare the plasma concentrations of carnitine at birth in a group of preterm and term neonates. Additional assessment of RBC concentrations of carnitine in the same group of infants was also undertaken. MATERIALS AND METHODSSubjects: Fifty-three preterm infants, admitted to the neonatal intensive care unit at the Vanderbilt Medical Center, were studied. These infants (male = 30 and female = 23) were a36 wk gestation. Their birth weights ranged 790-3010 g. Fourteen of these infants were 530 wk gestation and had a mean ( f S.E.) birth weight of 1100 f 48 g. Nineteen infants were 31-33wk and weighed 1620 + 54 g. Twenty infants were 34-36 wk in gestation and weighed 2360 f 75 g at birth. Of these 53 preterm infants, 35 were born to caucasian parents; the remainder with the exception of two Oriental infants were born to black parents. Of the 53 preterm infants, 18 were delivered by cesarean section; the remainder were delivered vaginally. The common indications for abdominal delivery were prematurity and breech presentation. All infants were AGA as their body measurements were within f 2.0 S.D. of the mean on standard growth graphs (1).Sixty-three term infants at the Vanderbilt Medical Center were studied concurrently. These infants (male = 3 1 and female = 32) were 537 wk gestation. Their birth weights ranged 2810-41 10 g (mean + S.E., 3390 + 47 g). Of the 63 term infants, 45 were born to caucasia...

Neonatal Blood Carnitine Concentrations: Normative Data by Electrospray Tandem Mass Spectometry

“…Follow-up studies of infants with low neonatal carnitine concentrations and/or high AC/FC ratios are necessary and are planned to identify possible acquired or genetic conditions associated with low neonatal TC levels and high proportions of acylated carnitine. In our analysis of whole blood and plasma carnitine levels from cord blood, the plasma values obtained (Table 4) were comparable to those reported in the literature (17,19,20,22,23,34), probably because the timing of sampling was identical for all of the studies. All of the carnitine fractions and the proportion of acylated carnitine were higher in whole blood than in plasma (22) Table 4).…”

“…There is no agreement in the literature regarding the concentration of fetal blood carnitine with advancing gestation. Some reports show a significant decrease of fetal blood carnitine levels in the later stages of gestation (16,17,20,21,23), whereas others have shown no changes in fetal blood carnitine levels during gestation (24,26). These observations have been made in newborns delivered prematurely and may not be an accurate representation of the blood carnitine concentration at that respective age of gestation under healthy conditions.…”

Age-Related Variations in Acylcarnitine and Free Carnitine Concentrations Measured by Tandem Mass Spectrometry

“…Only minor sex-related differences were observed in this study. The comparison of absolute values found in different studies can be complicated by the fact that, in most studies, FC and AC concentrations were measured in plasma samples rather than whole blood and by methods other than MS/MS (15)(16)(17)(18)(19). Despite these differences, some of these studies have also shown that plasma FC concentrations were higher in older children than in newborns.…”

“…It has been demonstrated that FC and AC values are significantly higher in whole blood than in plasma (7,15,22 ) because of the significantly higher concentrations of long-chain ACs in the erythrocyte membrane. Plasma AC concentrations would most likely show a pattern of variation similar to the one observed in whole blood samples.…”

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

“…Many authors have studied free carnitine levels in preterm infants using various methods and obtained different results. Seliger, Meyburg, Giannacopoulou, and Shenai found higher free carnitine levels in preterm than in fullterm infants (12,15,24,25), whereas newborn screening data (26) and a study on Japanese preterm infants (27) identified GA-related carnitine deficiencies.…”