Evaluation of carnitine nutritional status in full-term newborn infants

Campoy, Cristina; Bayés, R; Peinado, J.M.; Rivero, Miguel; López, Clara; Molina-Font, J. A.

doi:10.1016/s0378-3782(98)00072-3

Cited by 23 publications

(24 citation statements)

References 46 publications

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“…Because higher acylcarnitine levels in whole blood are compensated for by a tendency to overestimate FC concentrations using tandem mass spectrometry (16), the ratios obtained by different techniques should be comparable. In fact, our tandem mass spectrometry data corresponds well to published data for cord blood (12,13) and neonates (17).…”

Section: Postnatal Changes In Acylcarnitine Profilesupporting

confidence: 88%

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Postnatal Changes in Neonatal Acylcarnitine Profile

et al. 2001

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Electrospray-tandem mass spectrometry represents a powerful method for detection of inborn errors of fatty acid metabolism. In the present study, it was used to examine neonatal carnitine metabolism, which reflects fatty acid metabolism. In 70 healthy neonates, blood samples were taken from the umbilical cord and by heel-stick puncture in full-term neonates on postnatal d 5. Cord blood specimens were also obtained from 15 preterm and 10 small-for-gestational-age infants. Acylcarnitine concentrations were measured in dried blood spots by electrospray tandem mass spectrometry. Compared with cord blood, the levels of nearly all acylcarnitine species were significantly higher on the postnatal d 5, whereas free carnitine remained unchanged. Total acylcarnitine/free carnitine-ratio increased, whereas the free carnitine/total carnitine-ratio (0.54 Ϯ 0.05; p Ͻ 0.01) further decreased. A reduced availability of free carnitine in the early neonatal period may affect fatty acid oxidation and thus be of potential pathophysiological relevance under conditions with higher energy demands, e.g. in sepsis. Cord blood concentrations of free carnitine, total carnitine, and total acylcarnitines were strongly related to birth weight (p Ͻ 0.01). Lower umbilical artery pH, i.e. mild hypoxia, caused accumulation of mainly long-chain acylcarnitines. This implicates that long-chain acylcarnitines could serve as a parameter of perinatal asphyxia. In utero, the main substrates for fetal metabolism are amino acids and glucose. The human placenta is also permeable to FFA. However, they are mainly stored as triglycerides in adipose tissues and liver because of the constant supply of glucose and amino acids and a low capacity of fetal tissues for FFA oxidation. The cutoff of the nutrient supply in the presuckling period after birth leads to a transient period of starvation. Thus, the newborn infant is entirely dependent on the mobilization of glycogen and fat stores. With the initiation of milk feeding, neonatal metabolism switches to a high-fat diet. Therefore, it is obvious that fatty acid oxidation is very important in the early postnatal period (1).Carnitine plays an important role in oxidation of especially long-chain fatty acids. Carnitine palmitoyltransferases I and II mediate the transport of fatty acid-carnitine esters (acylcarnitines) across the mitochondrial membranes. Carnitine acyltransferases can also be found in peroxisomes (carnitine octanoyltransferase) and endoplasmatic reticulum (microsomal carnitine acyltransferase), although their function is not yet fully understood. In the mitochondrion, carnitine removes excess acyl groups and thus regulates the concentration of free CoA in the mitochondrial matrix (2). Several studies have shown that the carnitine pool in the neonate is limited (1, 3, 4). Tandem mass spectrometry allows quantitative determination of free carnitine and various carnitine esters like acylcarnitines (5, 6).In the present study, we used this technique to investigate the changes in neonatal carnitine and fat...

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Section: Postnatal Changes In Acylcarnitine Profilesupporting

confidence: 88%

“…Plasma levels of TC, FC, and tAC increase after 1-4 wk after birth (9,17) and are significantly higher in older children when compared with neonates (18). During infancy, tAC/FC decreases to 0.4 whereas FC/TC increases to 0.7 (15).…”

Section: Postnatal Changes In Acylcarnitine Profilementioning

confidence: 98%

Postnatal Changes in Neonatal Acylcarnitine Profile

et al. 2001

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“…First, the number of newborns studied was much smaller than in our study and thus more prone to sample size biases. Second, several studies have shown changes in TC, FC, and AC within the first days of life (3,9,11,16,19,21,24,26,33). Therefore, timing of blood sampling (day of life 1.85 versus day of life 5) might explain some differences in the reported carnitine concentrations.…”

Section: Discussionmentioning

confidence: 99%

“…These metabolic changes occur in response to birth stress (cold exposure, catecholamine secretion, hypoxia, and cord cutting), to extrauterine metabolic demands, and to the change in diet (high-fat/low-carbohydrate diet with Ͼ90% of milk fat in the form of triglycerides containing mainly long-chain fatty acids) (5, 38 -44). The increase in carnitine necessary to support these metabolic demands may be derived from carnitine intake (3,11,19) or tissue release (45).…”

Section: Discussionmentioning

confidence: 99%

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

Chace¹,

Pons

Chiriboga

et al. 2003

Pediatr Res

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Despite a number of published reports, there is limited information about carnitine metabolism in the newborn. To establish normative data, we analyzed whole-blood carnitine concentrations in 24,644 newborns at age 1.85 Ϯ 0.95 d and umbilical cord whole blood and plasma carnitine concentrations in 50 full-term newborns. Total carnitine (TC), free carnitine (FC), and acylcarnitine (AC) were measured by electrospray tandem mass spectrometry. AC/FC ratios were derived from these measurements. The entire cohort was stratified according to TC values into a middle TC group representing 90% of the population and lower and upper TC groups representing 5% of the population, respectively. Normative data were derived from the middle TC group of full-term infants (N ϭ 19,595). TC was 72.42 Ϯ 20.75 M, FC was 44.94 Ϯ 14.99 M, AC was 27.48 Ϯ 8.05 M, and AC/FC ratio was 0.64 Ϯ 0.19 (ϮSD). These values differed significantly from umbilical cord whole blood TC values of 31.27 Ϯ 10.54 M determined in 50 samples. No meaningful correlation was found between TC and gestational age or birth weight in any group. In controlled analyses, prematurity was not associated with TC levels, whereas low birth weight (Ͻ2500 g) and male sex were significantly associated with higher TC levels. The association of low birth weight with higher TC values may be related to decreased tissue carnitine uptake. The sex effect may be related to hormonal influences on carnitine metabolism. Our study provides normative data of carnitine values measured by the highly precise method of electrospray tandem mass spectrometry in a large cohort of newborns and provides the basis for future studies of carnitine metabolism in health and disease states during the neonatal period. Abbreviations MS-MS, electrospray tandem mass spectrometry TC, total carnitine FC, free carnitine AC, acylcarnitine RBC, red blood cells OR, Odds ratio CI, 95% confidence interval RE, radioenzyme L-Carnitine serves as a carrier for acyl groups across the mitochondrial membrane. It is essential for the membrane transport and subsequent intramitochondrial ␤-oxidation of long-chain fatty acids and for the modulation of CoA homeostasis (1, 2). Adequate tissue levels of carnitine are crucial in the neonatal period, because mitochondrial oxidation of fatty acids is essential for the production of energy in newborns (3-6).L-Carnitine is derived mainly from exogenous sources and in part from endogenous synthesis (1). The main source of carnitine in the fetus seems to be transplacental transfer (4,7,8) and in the newborn seems to be breast milk or carnitine-supplemented formulas (3, 9 -11). Endogenous synthesis plays a minor role in early life because the activity of ␥-butyrobetaine hydroxylase, the enzyme necessary for carnitine synthesis, is very low (12).In tissues and body fluids, carnitine is present in free and esterified forms. The sum of free carnitine (FC) and acylcarnitine (AC) equals total carnitine (TC). The fraction of esterified carnitine varies depending on the tissue and on the metaboli...

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“…In such cases, the concentration of plasma carnitine, especially of free carnitine, and the degree of acylation are considered to be markers of`carnitine de¢ciency' and carnitine insu¤ciency'. 17,18 Low plasma carnitine concentrations are frequently observed in critically ill children 19 and our study shows that a few remarkably low values can also be found in children who are not metabolically disturbed.…”

Section: Discussionmentioning

confidence: 48%