Mechanistic Bases of Neurotoxicity Provoked by Fatty Acids Accumulating in MCAD and LCHAD Deficiencies

Abstract Fatty acid oxidation defects (FAODs) are inherited metabolic disorders caused by deficiency of specific enzyme activities or transport proteins involved in the mitochondrial catabolism of fatty acids. Medium-chain fatty acyl-CoA dehydrogenase (MCAD) and long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiencies are relatively common FAOD biochemically characterized by tissue accumulation of medium-chain fatty acids and long-chain 3-hydroxy fatty acids and their carnitine derivatives, respectively. Patients with MCAD deficiency usually have episodic encephalopathic crises and liver biochemical alterations especially during crises of metabolic decompensation, whereas patients with LCHAD deficiency present severe hepatopathy, cardiomyopathy, and acute and/or progressive encephalopathy. Although neurological symptoms are common features, the underlying mechanisms responsible for the brain damage in these disorders are still under debate. In this context, energy deficiency due to defective fatty acid catabolism and hypoglycemia/hypoketonemia has been postulated to contribute to the pathophysiology of MCAD and LCHAD deficiencies. However, since energetic substrate supplementation is not able to reverse or prevent symptomatology in some patients, it is presumed that other pathogenetic mechanisms are implicated. Since worsening of clinical symptoms during crises is accompanied by significant increases in the concentrations of the accumulating fatty acids, it is conceivable that these compounds may be potentially neurotoxic. We will briefly summarize the current knowledge obtained from patients with these disorders, as well as from animal studies demonstrating deleterious effects of the major fatty acids accumulating in MCAD and LCHAD deficiencies, indicating that disruption of mitochondrial energy, redox, and calcium homeostasis is involved in the pathophysiology of the cerebral damage in these diseases. It is presumed that these findings based on the mechanistic toxic effects of fatty acids may offer new therapeutic perspectives for patients affected by these disorders.

A Suspect Case of Medium Chanin Acyl-Coenzyme A Dehydrogenase Deficiency with Iron Deficiency Anemia / 대한소아혈액종양학회지

Iron deficiency anemia is a common disorder during infancy and childhood. Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common disorder of mitochondrial fatty acid oxidation. However, this metabolic disorder is extremely rare among Asians. Generally MCAD deficiency patients are healthy until initial presentation of hypoketogenic hypoglycemia and encephalopathy which is predisposed by an intercurrent illness and/or a period of poor oral intake. The first attack causes a high risk of mortality or permanent neurologic sequelae. The authors report a suspect case of MCAD deficiency with iron deficiency anemia, with a brief review of related literatures.

The Prevalence of A985G Mutation in Medium Chain Acyl-Coenzyme A Dehydrogenase (MCAD) Gene in Neonates Determined from Guthrie Card

PURPOSE: Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is an autosomal recessive disoder of beta oxidation of fatty acids and characterized by episodic hypoglycemia, vomiting, convulsion, encephalopathy, apnea, and sudden death related to fasting or infection resembling Reye syndrome or sudden infant death syndrome. In acute stage, mortality rate is very high and survivors have significant risk of developmental disability and chronic somatic illness. However, the high mortality and morbidity can be totally prevented by appropriate dietary management on the basis of early and accurate diagnosis. Recently, a single point mutation (A985G) in the MCAD gene has been described that accounts for most of MCAD deficiency. The prevalence of MCAD deficiency shows marked racial differences. And population-based DNA screening for this potentially fatal disorder might be justified in countries with high frequency of the mutation. The prevalence of A985G mutation in the MCAD gene was studied in neonates using Guthrie cards for neonatal screening. METHODS: Dried blood spots on Guthrie cards originally used for neonatal screening programs obtained from 500 live newborn babies born in a private obstetric clinic or Seoul Red Cross Hospital in Seoul during the period from Jan. 1, 1995 to Jul. 31, 1995 were collected. DNA was extracted from the dried blood spots, and a segment of the MCAD gene was amplified from the DNA using polymerase chain reaction technique. The PCR products were electrophoresed on a polyacrylamide gel after treatment of a restriction enzyme, NcoI. And the restriction pattern was analyzed with ethidium bromide staining of the gel. RESULTS: The PCR was successful with all DNAs from Guthrie cards. And the A to G transition at nucleotide position 985 in the MCAD gene was not demonstrated in any of the specimen. Conlusions : 1) The frequency of A985G mutation in the MCAD gene is extremely low in Korean population. 2) The methodology used in this study can be applied to population-based molecular genetic studies for other hereditary diseases.

The Prevalence of A985G Mutation in Medium Chain Acyl-Coenzyme A Dehydrogenase (MCAD) Gene in Neonates Determined from Guthrie Card

PURPOSE: Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is an autosomal recessive disoder of beta oxidation of fatty acids and characterized by episodic hypoglycemia, vomiting, convulsion, encephalopathy, apnea, and sudden death related to fasting or infection resembling Reye syndrome or sudden infant death syndrome. In acute stage, mortality rate is very high and survivors have significant risk of developmental disability and chronic somatic illness. However, the high mortality and morbidity can be totally prevented by appropriate dietary management on the basis of early and accurate diagnosis. Recently, a single point mutation (A985G) in the MCAD gene has been described that accounts for most of MCAD deficiency. The prevalence of MCAD deficiency shows marked racial differences. And population-based DNA screening for this potentially fatal disorder might be justified in countries with high frequency of the mutation. The prevalence of A985G mutation in the MCAD gene was studied in neonates using Guthrie cards for neonatal screening. METHODS: Dried blood spots on Guthrie cards originally used for neonatal screening programs obtained from 500 live newborn babies born in a private obstetric clinic or Seoul Red Cross Hospital in Seoul during the period from Jan. 1, 1995 to Jul. 31, 1995 were collected. DNA was extracted from the dried blood spots, and a segment of the MCAD gene was amplified from the DNA using polymerase chain reaction technique. The PCR products were electrophoresed on a polyacrylamide gel after treatment of a restriction enzyme, NcoI. And the restriction pattern was analyzed with ethidium bromide staining of the gel. RESULTS: The PCR was successful with all DNAs from Guthrie cards. And the A to G transition at nucleotide position 985 in the MCAD gene was not demonstrated in any of the specimen. Conlusions : 1) The frequency of A985G mutation in the MCAD gene is extremely low in Korean population. 2) The methodology used in this study can be applied to population-based molecular genetic studies for other hereditary diseases.