Carnitine supplementation induces acylcarnitine production in tissues of very long-chain acyl-CoA dehydrogenase-deficient mice, without replenishing low free carnitine

Deficiency of very long-chain acyl-CoA dehydrogenase (VLCAD) results in accumulation of C14-C18 acylcarnitines and low free carnitine. Carnitine supplementation is still controversial. VLCAD knockout (VLCAD(+/-)) mice exhibit a similar clinical and biochemical phenotype to those observed in humans. VLCAD(+/-) mice were fed with carnitine dissolved in drinking water. Carnitine, acylcarnitines, and gamma-butyrobetaine were measured in blood and tissues. Measurements were performed under resting conditions, after exercise and after 24 h of regeneration. HepG2 cells were incubated with palmitoyl-CoA and palmitoyl-carnitine, respectively, to examine toxicity. With carnitine supplementation, acylcarnitine production was significantly induced. Nevertheless, carnitine was low in skeletal muscle after exercise. Without carnitine supplementation, liver carnitine significantly increased after exercise, and after 24 h of regeneration, carnitine concentrations in skeletal muscle completely replenished to initial values. Incubation of hepatic cells with palmitoyl-CoA and palmitoyl-carnitine revealed a significantly reduced cell viability after incubation with palmitoyl-carnitine. The present study demonstrates that carnitine supplementation results in significant accumulation of potentially toxic acylcarnitines in tissues. The expected prevention of low tissue carnitine was not confirmed. The principle mechanism regulating carnitine homeostasis seems to be endogenous carnitine biosynthesis, also under conditions with increased demand of carnitine such as in VLCAD-deficiency.     

Pitfalls of neonatal screening for very-long-chain acyl-CoA dehydrogenase deficiency using tandem mass spectrometry

Neonatal screening programs for very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD) have recently been implemented. We report 2 newborns with elevated C14:1-carnitine levels on day 3 of life and normal levels on days 5 to 7. Enzyme and molecular analyses confirmed VLCADD in the first patient and heterozygosity in the second patient. We conclude that the diagnosis of VLCADD can be missed by acylcarnitine analysis during anabolic conditions. An increased C14:1-carnitine level can also occur in heterozygous individuals. Elevated C14:1-carnitine level on neonatal screening warrants further diagnostic workup even if a repeat sample demonstrates normal acylcarnitine levels.     

Tissue carnitine reserves of newborn infants

This study assessed the tissue reserves of carnitine at birth in a group of neonates (n = 22) of varying gestational age dying within 24 h of birth, prior to possible changes in carnitine status induced by postnatal intervention. Tissue carnitine concentration was highest in the muscle in each infant. The mean (+/- SD) muscle carnitine concentration of 8.4 +/- 3.6 nmol/mg noncollagen protein (NCP) in very immature infants (less than or equal to 1000 g birth weight) was significantly lower than the corresponding mean (+/- SD) values of 14.0 +/- 3.2 nmol/mg NCP in larger preterm infants (1001-2500 g; P less than 0.01) and 19.4 +/- 2.6 nmol/mg NCP in term infants (greater than or equal to 2501 g; P less than 0.001). Muscle carnitine concentration correlated positively with gestational age (r = 0.832; P less than 0.001) and with body dimensions. Liver and heart carnitine concentrations did not correlate significantly with gestation or body dimensions. The mean (+/- SD) liver carnitine concentration for all the neonates as a group was 4.1 +/- 1.5 nmol/mg NCP. The mean (+/- SD) heart carnitine concentration was 4.7 +/- 1.3 nmol/mg NCP. In comparison to adult controls, tissue carnitine concentrations were markedly lower in neonates, particularly in immature newborns. These data suggest that newborn infants, especially premature babies, are born with limited tissue reserves of carnitine and are therefore at an increased risk for developing carnitine deficiency and its adverse effects in the postnatal period, particularly if maintained on carnitine-free intravenous nutrition for prolonged periods of time.     

MS/MS-based newborn and family screening detects asymptomatic patients with very-long-chain acyl-CoA dehydrogenase deficiency

OBJECTIVES: To determine whether asymptomatic persons with biochemical evidence of very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency identified through expanded newborn screening with tandem mass spectometry have confirmed disease. STUDY DESIGN: We characterized 8 asymptomatic VLCAD-deficient individuals by enzyme and/or mutational analysis and compared them with clinically diagnosed, symptomatic patients with regard to mutations, enzyme activity, phenotype, and age of disease onset. RESULTS: VLCAD molecular analyses in 6 unrelated patients revealed the previously reported V243A mutation, associated with hepatic or myopathic phenotypes, on 7/12 alleles. All other mutations were also missense mutations. Residual VLCAD activities of 6% to 11% of normal were consistent with milder phenotypes. In these identified individuals treated prospectively with dietary modification as preventive measures, clinical symptoms did not develop during follow-up. CONCLUSIONS: MS/MS-based newborn screening correctly identifies VLCAD-deficient individuals. Based on mutational and enzymatic findings, these infants probably are at risk of future disease. Because life-threatening metabolic derangement can occur even in otherwise mild phenotypes, we advocate universal newborn screening programs for VLCAD deficiency to detect affected patients and prevent development of metabolic crises. Longer-term follow-up is essential to define outcomes, the definite risk of future disease, and appropriate treatment recommendations.     

Medium-chain acyl-CoA dehydrogenase deficiency in children with non-ketotic hypoglycemia and low carnitine levels

Three children in two families presented in early childhood with episodes of illness associated with fasting which resembled Reye's syndrome: coma, hypoglycemia, hyperammonemia, and fatty liver. One child died with cerebral edema during an episode. Clinical studies revealed an absence of ketosis on fasting (plasma beta-hydroxybutyrate less than 0.4 mmole/liter) despite elevated levels of free fatty acids (2.6-4.2 mmole/liter) which suggested that hepatic fatty acid oxidation was impaired. Urinary dicarboxylic acids were elevated during illness or fasting. Total carnitine levels were low in plasma (18-25 mumole/liter), liver (200-500 nmole/g), and muscle (500-800 nmole/g); however, treatment with L-carnitine failed to correct the defect in ketogenesis. Studies on ketone production from fatty acid substrates by liver tissue in vitro showed normal rates from short-chain fatty acids, but very low rates from all medium and long-chain fatty acid substrates. These results suggested that the defect was in the mid-portion of the intramitochondrial beta-oxidation pathway at the medium-chain acyl-CoA dehydrogenase step. A new assay for the electron transfer flavoprotein-linked acyl-CoA dehydrogenases was used to test this hypothesis. This assay follows the decrease in electron transfer flavoprotein fluorescence as it is reduced by acyl-CoA-acyl-CoA dehydrogenase complex. Results with octanoyl-CoA as substrate indicated that patients had less than 2.5% normal activity of medium-chain acyl-CoA dehydrogenase. The activities of short-chain and isovaleryl acyl-CoA dehydrogenases were normal; the activity of long-chain acyl-CoA dehydrogenase was one-third normal. These results define a previously unrecognized inherited metabolic disorder of fatty acid oxidation due to deficiency of medium-chain acyl-CoA dehydrogenase.     

Plasma carnitine and breast milk carnitine intake in premature infants

Ten premature infants with a mean gestational age of 29 weeks (range, 27-32) and a mean birth weight of 1,294 g (range, 930-2,300) and without complications at birth were studied during the first 14 days after birth. Their breast milk intake was recorded and the carnitine content determined in each daily portion. During the first week, the daily mean carnitine intake was low and increased to 6-7 mumoles/kg and day during the second week. Breast milk carnitine concentration ranged from 17 to 148 mumoles/L. Plasma carnitine and its derivatives did not change during the observation period. No relationship was found between the individual cumulative breast milk carnitine intake and total plasma carnitine levels or between carnitine and its derivatives and nonesterified fatty acids or 3-OH-butyrate. The urinary carnitine excretion, in millimoles of carnitine per mole of creatinine, was higher during the second week. In other studies, declining plasma carnitine levels have been observed in premature infants on total parenteral nutrition. The results from this study indicated that premature infants without complicating disorders were able to maintain their plasma carnitine levels.     

Plasma and urine carnitine levels and carnitine supplementation in children with malnutrition

The purpose of the present investigation was to determine serum and urinary carnitine levels in children suffering from protein-energy malnutrition (PEM) before and after dietary treatment and carnitine supplementation, and to compare them with those in healthy children. Plasma and urine carnitine levels were lower in patients with marasmus and kwashiorkor than in controls. There was no statistical difference between groups with and without carnitine supplementation on the first day. On the fifth day, in groups receiving carnitine supplementation, plasma and urine carnitine levels were significantly higher than in groups without supplementation (p < 0.01). On the 15th day there was no statistical significance between groups with PEM and controls.     

Hemolysis in a glucose-6-phosphate dehydrogenase-deficient boy with rheumatic fever

Summary A 12-year-old black boy with the A type of glucose-6-phosphate dehydrogenase (G6PD) deficiency had a hemolytic episode concurrent with acute rheumatic fever. Aspirin nevertheless remains the drug of choice for acute rheumatic fever even in the A type of G6PD deficiency.     

Differing pathogenesis of perinatal bilirubinemia in glucose-6-phosphate dehydrogenase-deficient versus-normal neonates

The objective was to compare the contribution to perinatal bilirubinemia of hemolysis and UDP-glucuronosyltransferase (UGT) gene promoter polymorphism, seen in Gilbert's syndrome, between glucose-6-phosphate dehydrogenase (G-6-PD)-deficient and -normal neonates. Serum total bilirubin (STB) values from 52 G-6-PD-deficient and 166 G-6-PD-normal term, male neonates, sampled within 3 h of delivery (first sample) and on d 3 (second sample), were analyzed in relation to blood carboxyhemoglobin corrected for inspired CO (COHbc), an accurate index of hemolysis, and UGT promoter genotype. COHbc values (% total Hb) were greater in G-6-PD-deficient neonates than controls: first sample 1.00 +/- 0.25% versus 0.84 +/- 0.24%, p < 0.0001; second sample 0.83 +/- 0.20% versus 0.76 +/- 0.19%, p = 0.002. First sample COHbc and STB values did not correlate in either the G-6-PD-deficient or control groups, whereas second sample COHbc values correlated significantly with corresponding STB values in the control population only (r = 0.28, p = 0.0007). At second sampling, there was a higher allele frequency of the variant UGT promoter among those with STB values > or =75th percentile than those <75th among the G-6-PD-deficient neonates (0.60 versus 0.33, respectively, p = 0.025), but not controls (0.31 versus 0.40, respectively, p = 0.24). Among those infants with at least one variant UGT promoter allele, STB values were higher in the G-6-PD-deficient neonates than controls at second sampling only (181 +/- 56 microM versus 149 +/- 46 microM, respectively, p = 0.03). Both within and between the G-6-PD-deficient and control groups, our data demonstrate changing and differing contributions of hemolysis and UGT promoter polymorphism to bilirubinemia during the first 3 d of life.     

Transfer and metabolism of carnitine and carnitine esters in the in vitro perfused human placenta

The transfer and metabolism of L-carnitine, L-acetylcarnitine, and L-palmitoylcarnitine were studied in the human placenta at term by means of in vitro dual perfusion of a placental lobe. L-Carnitine transfer was 20% that of the freely diffusing antipyrine and 40% that of L-lysine. The transfer of L-acetylcarnitine was similar to that of L-carnitine, but no placental transfer of L-palmitoylcarnitine was found. In contrast to L-lysine, L-carnitine, and L-acetylcarnitine were not actively transported from the maternal to the fetal circulation. No stereospecific transfer of carnitine across the placenta was found. However, there was stereospecific uptake of carnitine by placental tissue. The placenta exhibited an active carnitine metabolism by esterifying free carnitine and hydrolyzing carnitine esters taken up from the perfusion medium and releasing the metabolites into the fetal and maternal circulations.     

Poor correlation between hemolysis and jaundice in glucose 6-phosphate dehydrogenase-deficient babies

BACKGROUND: The role of hemolysis in the pathophysiology of neonatal jaundice (NNJ) in patients with glucose 6-phosphate dehydrogenase (G6PD) deficiency has been questioned recently. The aim of the present study was to determine the contribution of hemolysis to the pathophysiology of jaundice in Malay neonates with G6PD deficiency and NNJ. METHODS: Four groups of babies were included in the study: (i) G6PD deficient with NNJ; (ii) G6PD deficient without NNJ; (iii) G6PD normal with NNJ; and (iv) normal controls. Babies with other known causes of jaundice were excluded from the study. All subjects underwent the following investigations on day 3-5 after birth: hemoglobin level (Hb), serum bilirubin level, carboxyhemoglobin (CO-Hb) concentration, reticulocyte count and full blood picture. The results of the investigations were compared between the groups using SPSS version 11. RESULTS: Babies with G6PD and jaundice had a similar percentage of CO-Hb to babies with G6PD without NNJ or babies with normal G6PD and NNJ (1.76 +/- 0.40% vs 1.66 +/- 0.31% and 1.67 +/- 0.28%, respectively; P: 0.23 and 0.41, respectively). Total Hb levels and reticulocyte counts were not significantly different between the groups. The blood film showed more (even though not reaching significance) hemolysis in the G6PD patients but results of the blood film were very similar for G6PD patients with and those without NNJ. CONCLUSION: Hemolysis is not a main determinant of neonatal jaundice in G6PD-deficient babies.     

原发性肉碱缺乏症1例报告

No abstract available

     

Renal handling of carnitine in children with carnitine deficiency and hyperammonemia associated with valproate therapy

Free and acylcarnitine in serum and urine samples were measured in five patients with hyperammonemia associated with anticonvulsant therapy including sodium valproate, of whom three had a Reye-like syndrome. All had considerable reduction in serum free carnitine and slight increase of acylcarnitine concentrations, suggesting increased conversion of free to acylcarnitine by valproate administration. Urinary excretion of both free and acylcarnitine was increased, accompanied by depressed reabsorption of free carnitine and decreased acylcarnitine/free carnitine clearance ratio. These results indicate a decreased threshold for free carnitine. The combination of these several factors may be responsible for carnitine deficiency in patients with hyperammonemia taking valproate.     

新生儿多种酰基辅酶A脱氢酶缺乏症1例

患儿,女,1 d,因气促并口吐白沫半天余入院。患儿系第5胎第4产,患儿母亲于2004年人工流产1次;2006年平产1活女婴,生后第2天突然死亡;2008年平产1活男婴,生后4月因"病毒性脑炎"死亡;2010年8月平产1活女婴,生后第5天突然死亡,尸检报告提示先天性肝发育不全。患儿顺产出生,出生体重2.6 kg,出生时羊水清亮,Apgar评分正常。患儿于出生第二天出现气促、口吐白沫现象,哭吵时有口唇发绀现象。患儿父亲     

Serum carnitine in children with kwashiorkor

Concentrations of free and acylcarnitine were measured in serum of children with kwashiorkor and compared with those obtained for well nourished children of similar age. The mean values (S.E.) for both free and acylcarnitine were significantly lower in the kwashiorkor group [32.6 (6.2) and 8.1 (2.2), respectively] than in the controls [53.2 (2.9) and 13.8 (3.1), respectively]. Serum albumin was also low in kwashiorkor patients, but there was no significant correlation with carnitine values.     

新生儿原发性肉碱缺乏症1例

<正>患儿,男,3 h,因早产儿、新生儿呼吸窘迫综合征收住院。患儿系第2胎第1产,孕29+5周在当地医院自然分娩出生,羊水清亮,1分钟Apgar评分7分,5分钟Apgar评分9分。因生后2 h口吐泡沫明显,呼吸浅促,伴呻吟转我院。