L-Hexanoylcarnitine

Functional expression of the organic cation/carnitine transporter 2 in rat astrocytes

In this study, we sought to identify the transporters that mediate the uptake of L-carnitine and acetyl-L-carnitine in cultured rat cortical astrocytes. L-[(3)H]carnitine and acetyl-L-[(3)H]carnitine uptake were both saturable, and mediated by a single Na(+)-dependent transport system. Uptake of both was inhibited by L-carnitine, D-carnitine, acetyl-L-carnitine and various organic cations. Acylcarnitines (acetyl-, butyryl-, hexanoyl-, octanoyl- and palmitoyl-L-carnitine) also interacted with L-[(3)H]carnitine and acetyl-L-[(3)H]carnitine transport. 2-Amino-2-norbornane carboxylic acid, a known inhibitor of amino acid transporter B(0,+) (ATB(0,+)), did not cause any significant inhibition. A highly significant correlation was found between the potencies of acylcarnitines in the inhibition of L-[(3)H]carnitine and acetyl-L-[(3)H]carnitine uptake and the acyl chain length of acylcarnitines. The expression of mRNA for organic cation/carnitine transporters (OCTNs), carnitine transporter 2 (CT2) and ATB(0,+) in astrocytes was investigated by reverse transcription (RT)-PCR. OCTN2 mRNA was expressed in astrocytes, whereas the expression of OCTN1, OCTN3 and CT2 mRNA could not be detected. ATB(0,+) mRNA was expressed at very low levels in astrocytes. Western blotting analysis indicated that anti-OCTN2 polyclonal antibody recognized a band of 70 kDa in both kidney and astrocyte preparations. OCTN2 immunoreactivity was detected in rat astrocytes by immunocytochemical staining. Inhibition of OCTN2 expression by RNA interference significantly inhibited L-[(3)H]carnitine and acetyl-L-[(3)H]carnitine uptake into astrocytes. These results suggest that OCTN2 is functionally expressed in rat astrocytes, and is responsible for L-carnitine and acetyl-L-carnitine uptake in these cells.

Determination of urinary carnitine levels as a potential indicator of uterine fibroids caused by nonylphenol exposure

Our previous studies have shown that uterine fibroids are associated with nonylphenol (NP) exposure, and the changes of carnitines in critical reproductive tissues and body fluids could be used to indicate the female reproductive toxicity caused by NP exposure. In this work, on the basis of further clarifying the correlation between NP exposure level and uterine fibroids, the possibility of the urinary carnitine levels as a potential indicator of uterine fibroids caused by NP exposure was discussed. The urine samples were collected from 84 female volunteers: the control group of 34 healthy women without gynecological disease and 50 uterine fibroids patients, respectively. Methods were respectively established for the determination of NP and eight carnitines in human urine samples by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that the NP level of uterine fibroids group was significantly higher than that of control group (P = 0.002), indicating that NP exposure was an important environmental factor in the occurrence of uterine fibroids. It was further found that in urine samples of the uterine fibroids group, the levels of L-Carnitine (C0), L-Acetyl-carnitine (C2), L-Octanoyl-carnitine (C8), Tetradecanoyl-carnitine (C14), Oleoyl-carnitine (C18:1) and Linoleoyl-carnitine (C18:2) had obviously increased compared with those in the control group (P < 0.001; < 0.001; < 0.001; = 0.003; < 0.001; = 0.010). The concentrations of L-Hexanoyl-carnitine (C6) and L-Palmitoyl-carnitine (C16) in the uterine fibroids group were also higher than those in the control group, although the difference was not statistically significant (P > 0.05). The results suggested that the changes in urinary carnitine levels might be a potential indicator to help to warn of the risk of uterine fibroids caused by NP exposure at the early stage.

[Blood spot carnitine and acylcarnitine in newborn to adolescence: measured by tandem mass spectrometry]

Objective: To determine the levels of blood spot carnitine and acylcarnitine in children aged 0-15 years by tandem mass spectrometry, offer basic data for evaluating carnitine nutritional status and diagnosing metabolic diseases of organic acid and fatty acid.
Methods: The concentration of carnitine and acylcarnitines were measured in blood spot by tandem mass spectrometry using underivatized samples. The samples included those from 1376 perinatal neonates, 49 neonates above 1 week of life, 64 children aged up to 1 year and 401 children aged 1 year to 15 years. A few premature infants and low birth weight infants were involved in perinatal neonates without selection. Other samples were taken from mainly outdoor patients for little surgical preoperative examination. Patients suffering from fever, diarrhea, liver disease, severe fat-metabolic diseases were excluded from this study.
Results: The concentrations of carnitine (C(0)); short-chain acylcarnitines (SC-AC), including acetyl (C(2)), propionyl (C(3)), malonyl (C(3)DC), butyryl (C(4)), methylmalonyl (C(4)DC), isovaleryl (C(5)), glutaryl (C(5)DC); middle-chain acylcarnitines (MC-AC), including hexanoyl (C(6)), hexanediol (C(6)DC), octylenoyl (C(8:1)), octanoyl (C(8)), decadienoyl (C(10:2)), decanoyl (C(10:1)), decanoyl (C(10)); total carnitine and acylcarnitines (TCAC)were lower in neonate, highest in 1-3 months of age, higher in 6-12 months of age, and kept at the same level between 2 and 15 years of age. The concentrations of total long-chain acylcarnitines (LC-AC), including lauren (C(12:1)), lauroyl (C(12)), tetradecanoyl (C(14:1)), tetradecanoyl (C(14)), 3-hydroxy-tetradecanoyl (C(14)OH), hexadecenoyl (C(16:1)), hexadecanoyl (C(16)), 3-hydroxy-hexadecanoyl (C(16)OH), 3-hydroxy-hexadecanoyl (C(16:1)OH), octadecadienoyl (C(18:2)), octadecenoyl (C(18:1)), octadecanoyl (C(18)), 3-hydroxy-octadecenoyl (C(18:1)OH), and 3-hydroxy-octadecanoyl (C(18)OH) were the highest in neonate, decreased gradually, and kept the same level between 2 and 15 years of age. The concentrations of C(0) (23.387 ± 7.702) ?mol/L, (30.064 ± 8.252) ?mol/L, (25.021 ± 6.630) ?mol/L, of LC-AC (4.998 ± 1.557) ?mol/L, (2.854 ± 0.821) ?mol/L, (2.459 ± 0.553) ?mol/L, of TCAC (43.497 ± 12.632) ?mol/L, (49.013 ± 12.497) ?mol/L, (39.656 ± 9.257) ?mol/L were significantly different among the groups of neonate, up to 1 year and above 1 year (P < 0.01). The concentrations of C(0) (24.115 ± 7.715) ?mol/L and TCAC (43.65 ± 5.252) ?mol/L in perinatal male neonates were higher than that (22.696 ± 7.246) ?mol/L, TCAC (41.90 ± 5.038) ?mol/L in female neonates. The C(0)/TCAC ratio of neonatal group (54.0% ± 7.1%) was significantly lower than that in the children group (62.1% ± 6.1%, P < 0.05), LC-AC/TCAC (33.5% ± 6.0%), MC-AC/TCAC (1.3% ± 0.3%), SC-AC/TCAC (11.6% ± 2.5%)ratios of neonatal group were higher than that of children group respectively (30.1% ± 4.9%; 0.9% ± 0.6%; 6.5% ± 2.3%, P < 0.05).
Conclusions: Concentrations and profiles of carnitine and acylcarnitines change significantly during the first year of life, the age should be considered as a factor when evaluating carnitine nutritional status and diagnosing metabolic diseases of organic acid and fatty acid. Concentrations of carnitine and acylcarnitines were a little higher in male neonates than in female.

Evidence for intermediate channeling in mitochondrial beta-oxidation

The accumulation of beta-oxidation intermediates was studied by incubating normal and beta-oxidation enzyme-deficient human fibroblasts with [2H4]linoleate and L-carnitine and analyzing the resultant acylcarnitines by tandem mass spectrometry. Labeled decenoyl-, octanoyl-, hexanoyl-, and butyrylcarnitines were the only intermediates observed with normal cells. Intermediates of longer chain length, corresponding to substrates for the beta-oxidation enzymes associated with the inner mitochondrial membrane, were not observed unless a cell line was deficient in one of these enzymes, such as very-long-chain acyl-CoA dehydrogenase, long-chain 3-hydroxyacyl-CoA dehydrogenase, or electron transfer flavoprotein dehydrogenase. Matrix enzyme deficiencies, such as medium- and short-chain acyl-CoA dehydrogenases, were characterized by elevated concentrations of intermediates corresponding to their respective substrates (octanoyl- and decenoylcarnitines in medium-chain acyl-CoA dehydrogenase deficiency and butyrylcarnitine in short-chain acyl-CoA dehydrogenase deficiency). These observations agree with the notion of intermediate channeling due to the organization of beta-oxidation enzymes in complexes. The only exception is the incomplete channeling from thiolase to acyl-CoA dehydrogenase in the matrix. This situation may be a consequence of only one 3-ketoacyl-CoA thiolase being unable to interact with the several acyl-CoA dehydrogenases in the matrix.

A Rare Case of Short-Chain Acyl-COA Dehydrogenase Deficiency: The Apparent Rarity of the Disorder Results in Under Diagnosis

Short-chain acyl-CoA dehydrogenase (ACAD) deficiency is an extremely rare inherited mitochondrial disorder of fat metabolism. This belongs to a group of diseases known as fatty acid oxidation disorders. Screening programmes have provided evidence that all the fatty acid oxidation disorders combined are among the most common inborn errors of metabolism. Mitochondrial beta oxidation of fatty acids is an essential energy producing pathway. It is a particularly important pathway during prolonged periods of starvation and during periods of reduced caloric intake due to gastrointestinal illness or increased energy expenditure during febrile illness. The most common presentation is an acute episode of life threatening coma and hypoglycemia induced by a period of fasting due to defective hepatic ketogenesis. Here, the case of a 4 month old female patient who had seizures since the third day of her birth and persistent hypoglycemia is described. She was born to parents of second degree consanguinity after 10 years of infertility treatment. There was history of delayed cry after birth. Metabolic screening for TSH, galactosemia, 17-OHP, G6PD, cystic fibrosis, biotinidase were normal. Tandem mass spectrometric (TMS) screening for blood amino acids, organic acids, fatty acids showed elevated butyryl carnitine (C4) as 3.40 μmol/L (normal <2.00 μmol/L), hexanoyl carnitine (C6) as 0.92 μmol/L (normal <0.72 μmol/L), C4/C3 as 2.93 μmol/L (normal <1.18 μmol/L). The child was started immediately on carnitor syrup (carnitine) 1/2 ml twice daily. Limitation of fasting stress and dietary fat was advised. Baby responded well by gaining weight and seizures were controlled. Until now, less than 25 patients have been reported worldwide. The limited number of patients diagnosed until now is due to the rarity of the disorder resulting in under diagnosis.