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Biomedical subjects

L Sweetman

Publications and source records attributed to L Sweetman.

At least 19 recordsLinked to original sources
PubMed2005

Differentiation of long-chain fatty acid oxidation disorders using alternative precursors and acylcarnitine profiling in fibroblasts.

The differentiation of carnitine-acylcarnitine translocase deficiency (CACT) from carnitine palmitoyltransferase type II deficiency (CPT-II) and long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency from mitochondrial trifunctional protein deficiency (MTP) continues to be ambiguous using current acylcarnitine profiling techniques either from plasma or blood spots, or in the intact cell system (fibroblasts/amniocytes). Currently, enzyme assays are required to unequivocally differentiate CACT from CPT-II, and LCHAD from MTP. Over the years we have studied the responses of numerous FOD deficient cell lines to both even and odd numbered fatty acids of various chain lengths as well as branched-chain amino acids. In doing so, we discovered diagnostic elevations of unlabeled butyrylcarnitine detected only in CACT deficient cell lines when incubated with a shorter chain fatty acid, [7-2H3]heptanoate plus l-carnitine compared to the routinely used long-chain fatty acid, [16-2H3]palmitate. In monitoring the unlabeled C4/C5 acylcarnitine ratio, further differentiation from ETF/ETF-DH is also achieved. Similarly, incubating LCHAD and MTP deficient cell lines with the long-chain branched fatty acid, pristanic acid, and monitoring the C11/C9 acylcarnitine ratio has allowed differentiation between these disorders. These methods may be considered useful alternatives to specific enzyme assays for differentiation between these long-chain fatty acid oxidation disorders, as well as provide insight into new treatment strategies.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2001

Prenatal diagnosis of multiple acyl-CoA dehydrogenase deficiency: association with elevated alpha-fetoprotein and cystic renal changes.

We report the occurrence of multiple acyl-CoA dehydrogenase deficiency (MADD) in two consecutive pregnancies in a young, Caucasian, non-consanguineous couple. In the first pregnancy, the maternal serum alpha-fetoprotein was elevated. A sonogram showed growth delay, cystic renal disease, and oligohydramnios; the parents decided to terminate the pregnancy. Postmortem examination confirmed the cystic renal disease and showed hepatic steatosis, raising the suspicion of a metabolic disorder. The diagnosis of MADD was made by immunoblot studies on cultured fibroblasts. In the subsequent pregnancy, a sonogram at 15 weeks' gestation showed an early growth delay but normal kidneys. The maternal serum and amniotic fluid concentrations of alpha-fetoprotein were elevated, and the amniotic fluid acylcarnitine profile was consistent with MADD. In vitro metabolic studies on cultured amniocytes confirmed the diagnosis. A follow-up sonogram showed cystic renal changes. These cases provide additional information regarding the evolution of renal changes in affected fetuses and show a relationship with elevated alpha-fetoprotein, which may be useful in counseling the couple at risk. MADD should be considered in the differential diagnosis of elevated alpha-fetoprotein and cystic renal disease. Early growth delay may be an additional feature.

Acyl-CoA Dehydrogenase↗
PubMed2000

Evidence for a short-chain carnitine-acylcarnitine translocase in mitochondria specifically related to the metabolism of branched-chain amino acids.

Carnitine-acylcarnitine translocase (CATR) deficiency is a severe defect in fatty acid oxidation which presents early in life most frequently with hypoglycemia, hyperammonemia, and severe cardiac abnormalities. CATR exchanges acylcarnitines of various chain lengths for free carnitine across the mitochondrial membrane. In vitro studies in intact fibroblasts from patients with documented deficiency of CATR were probed with stable-isotope-labeled precursors and the resulting acylcarnitines were analyzed by tandem mass spectrometry. After a 72-h incubation with l-[(2)H(3)]carnitine the translocase-deficient cells produced acylcarnitines in which the deuterium was incorporated into short-chain acylcarnitines, C2-C5. Experiments with simultaneous incubation of l-[(2)H(3)]carnitine and l-[(13)C(6)]isoleucine produced [(13)C(5)]2-methylbutyryl-[(2)H(3)]carnitine and [(13)C(3)]propionyl-[(2)H(3)]carnitine indicating exchange of labeled acylcarnitine from inside the mitochondrial matrix with labeled free carnitine. These studies support the possible existence of a "branched-chain" carnitine-acylcarnitine translocator in mitochondria.

Amino Acids, Branched-Chain↗
PubMed2000

Identification of a novel mutation in patients with medium-chain acyl-CoA dehydrogenase deficiency.

A novel mutation was identified in two unrelated patients with medium-chain acyl-CoA dehydrogenase deficiency. First, a 19-year-old Caucasian female presented with a devastating illness, resulting in sudden death in adulthood which is unusual. The second patient, now a 3.5-year-old male, presented at 17 months of age with a hypoglycemic seizure and dehydration. Sequence analysis revealed a novel mutation G617T in exon 8 resulting in an arginine to leucine substitution at codon 206 (R206L). Both patients were compound heterozygous for this G617T and the common mutation A985G.

Acyl-CoA Dehydrogenase↗
PubMed2000

Death caused by perioperative fasting and sedation in a child with unrecognized very long chain acyl-coenzyme A dehydrogenase deficiency.

An adopted 3(1/2)-year-old girl with no prior medical problems died after a routine dental procedure. More than 2 years later, acylcarnitine analysis of dried blood found on her bedding revealed she had very long chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency. Perioperative oral fasting, without intravenous administration of glucose, may be detrimental to children with certain metabolic and endocrine disorders. Newborn screening by tandem mass spectrometry will detect disorders of fatty acid oxidation such as VLCAD and allow early and preventive treatment.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed2000

2-Methylbutyryl-coenzyme A dehydrogenase deficiency: a new inborn error of L-isoleucine metabolism.

An 4-mo-old male was found to have an isolated increase in 2-methylbutyrylglycine (2-MBG) and 2-methylbutyrylcamitine (2-MBC) in physiologic fluids. In vitro oxidation studies in cultured fibroblasts using 13C- and 14C-labeled branched chain amino acids indicated an isolated block in 2-methylbutyryl-CoA dehydrogenase (2-MBCDase). Western blotting revealed absence of 2-MBCDase protein in fibroblast extracts; DNA sequencing identified a single 778 C>T substitution in the 2-MBCDase coding region (778 C>T), substituting phenylalanine for leucine at amino acid 222 (L222F) and absence of enzyme activity for the 2-MBCDase protein expressed in Escherichia coli. Prenatal diagnosis in a subsequent pregnancy suggested an affected female fetus, supporting an autosomal recessive mode of inheritance. These data confirm the first documented case of isolated 2-MBCDase deficiency in humans.

Amino Acid Metabolism, Inborn Errors↗
PubMed1998

Deficiency of biotinyl-AMP synthetase activity in fibroblasts of patients with holocarboxylase synthetase deficiency.

A simple, rapid assay was developed to diagnose holocarboxylase synthetase deficiency. Holocarboxylase synthetase first catalyzes the formation of biotinyl-AMP from biotin and ATP, an activity designated as biotinyl-AMP synthetase. In the second step of the reaction, biotin is transferred from biotinyl-AMP to the enzymatically inactive apocarboxylase to form an active holocarboxylase. The assay for holocarboxylase synthetase activity therefore requires a protein apocarboxylase substrate which is not readily available. In the assay for biotinyl-AMP synthetase, hydroxylamine reacts nonenzymatically with the product of the enzymatic reaction, biotinyl-AMP, to form biotinylhydroxamate. At the end of the reaction, unreacted radioactive biotin substrate, which is negatively charged at neutral pH, is bound to an anion-exchange resin and a neutral radioactive biotinylhydroxamate product in the supernatant is counted. In fibroblasts from 11 patients with proven holocarboxylase synthetase deficiency, the mean biotinyl-AMP synthetase activity at 25 nM biotin was 4% of the control mean with a range of 0.2 to 8%. This is an improved assay because it does not require preparation of an apocarboxylase substrate and is suitable for the diagnosis of patients with holocarboxylase synthetase deficiency.

Carbon-Nitrogen Ligases↗
PubMed1998

Isolated isobutyryl-CoA dehydrogenase deficiency: an unrecognized defect in human valine metabolism.

A 2-year-old female was well until 12 months of age when she was found to be anemic and had dilated cardiomyopathy. Total plasma carnitine was 6 microM and acylcarnitine analysis while receiving carnitine supplement revealed an increase in the four-carbon species. Urine organic acids were normal. In vitro analysis of the mitochondrial pathways for beta oxidation, and leucine, valine, and isoleucine metabolism was performed in fibroblasts using stable isotope-labeled precursors to these pathways followed by acylcarnitine analysis by tandem mass spectrometry. 16-2H3-palmitate was metabolized normally down to the level of butyryl-CoA thus excluding SCAD deficiency. 13C6-leucine and 13C6-isoleucine were also metabolized normally. 13C5-valine incubation revealed a significant increase in 13C4-isobutyrylcarnitine without any incorporation into propionylcarnitine as is observed normally. These same precursors were also evaluated in fibroblasts with proven ETF-QO deficiency in which acyl-CoA dehydrogenase deficiencies in each of these pathways was clearly identified. These results indicate that in the human, there is an isobutyryl-CoA dehydrogenase which exists as a separate enzyme serving only the valine pathway in addition to the 2-methyl branched-chain dehydrogenase which serves both the valine and the isoleucine pathways in both rat and human.

Cardiomyopathies↗
PubMed1997

A new case of malonyl coenzyme A decarboxylase deficiency presenting with cardiomyopathy.

UNLABELLED: A new case of mitochondrial malonyl coenzyme A decarboxylase deficiency is described. The patient presented with an initial episode of metabolic acidosis, seizures, hypoglycemia, and cardiac failure at 2 months of age which slowly resolved. Subsequent evaluations at 4 years of age for developmental delay revealed a prominent elevation of malonic acid in urine. Malonyl carnitine was also elevated. The activity of Malonyl CoA decarboxylase in cultured fibroblasts was 7% of normal. CONCLUSION: Malonyl CoA decarboxylase deficiency may result in inhibition of fatty acid oxidation, which may account for the cardiomyopathy.

Acidosis↗
PubMed1997

Methylmalonic acidemia, cobalamin C type, presenting with cutaneous manifestations.

BACKGROUND: Erosive dermatitis resembling the skin lesions of acrodermatitis enteropathica has been described in a number of aminoacidopathies and organic acidemias. In some, the dermatitis is a manifestation of untreated disease, while in others, including methylmalonic acidemia, skin lesions have been ascribed to nutritional deficiency due to therapeutic amino acid restrictions. OBSERVATIONS: We report 2 cases of methylmalonic acidemia presenting with cutaneous manifestations in the perinatal period before restrictive nutritional interventions. The cutaneous involvement consisted of cheilitis and diffuse erythema with erosions and desquamation. Methylmalonic acidemia, cobalamin C type, was subsequently diagnosed in both cases. CONCLUSIONS: An erosive, desquamating dermatitis with histopathologic characteristics resembling acrodermatitis enteropathica may be a presenting sign in cobalamin C methylmalonic acidemia, even in the absence of long-standing nutritional restrictions or deficiency.

Acrodermatitis↗
PubMed1996

Clustering of mutations in the biotin-binding region of holocarboxylase synthetase in biotin-responsive multiple carboxylase deficiency.

Holocarboxylase synthetase (HCS) catalyses the biotinylation of the four biotin-dependent carboxylases found in humans. A deficiency in HCS results in biotin-responsive multiple carboxylase deficiency (MCD). We have identified six different point mutations in the HCS gene in nine patients with MCD. Two of the mutations are frequent among the MCD patients analyzed. Four of the mutations cluster in the putative biotin-binding domain as deduced from the corresponding Escherichia coli enzyme and consistent with an explanation for biotin-responsiveness based on altered affinity for biotin. The two others may define an additional domain involved in biotin-binding or biotin-mediated stabilization of the protein.

Amino Acid Sequence↗