Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency with the G1528C mutation: clinical presentation of thirteen patients

Cardiac phenotype in adolescents and young adults with long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency

PURPOSE

Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency (LCHADD) is a rare fatty acid oxidation disorder characterized by recurrent episodes of metabolic decompensation and rhabdomyolysis, as well as retinopathy, peripheral neuropathy, and cardiac involvement, such as infantile dilated cardiomyopathy. Because LCHADD patients are surviving longer, we sought to characterize LCHADD-associated major cardiac involvement in adolescence and young adulthood.

METHODS

A retrospective cohort of 16 adolescent and young adult participants with LCHADD was reviewed for cardiac phenotype.

RESULTS

Major cardiac involvement occurred in 9 of 16 participants, including sudden death, out-of-hospital cardiac arrest, acute cardiac decompensations with heart failure and/or in-hospital cardiac arrest, end-stage dilated cardiomyopathy, and moderate restrictive cardiomyopathy. Sudden cardiac arrest was more common in males and those with a history of infant cardiomyopathy.

CONCLUSION

The cardiac manifestations of LCHADD in adolescence and early adulthood are complex and distinct from the phenotype seen in infancy. Life-threatening arrhythmia occurs at substantial rates in LCHADD, often in the absence of metabolic decompensation or rhabdomyolysis. The potential risk factors identified here-male sex and history of infant cardiomyopathy-may hint at strategies for risk stratification and possibly the prevention of these events.

The Physiological and Pathological Role of Acyl-CoA Oxidation

Fatty acid metabolism, including β-oxidation (βOX), plays an important role in human physiology and pathology. βOX is an essential process in the energy metabolism of most human cells. Moreover, βOX is also the source of acetyl-CoA, the substrate for (a) ketone bodies synthesis, (b) cholesterol synthesis, (c) phase II detoxication, (d) protein acetylation, and (d) the synthesis of many other compounds, including N-acetylglutamate-an important regulator of urea synthesis. This review describes the current knowledge on the importance of the mitochondrial and peroxisomal βOX in various organs, including the liver, heart, kidney, lung, gastrointestinal tract, peripheral white blood cells, and other cells. In addition, the diseases associated with a disturbance of fatty acid oxidation (FAO) in the liver, heart, kidney, lung, alimentary tract, and other organs or cells are presented. Special attention was paid to abnormalities of FAO in cancer cells and the diseases caused by mutations in gene-encoding enzymes involved in FAO. Finally, issues related to α- and ω- fatty acid oxidation are discussed.

Resting and total energy expenditure of patients with long-chain fatty acid oxidation disorders (LC-FAODs)

The basis of medical nutrition therapy for patients with LC-FAODs is to provide adequate energy to maintain anabolism and prevent catabolism. In practice, energy needs are estimated based on formulas derived from normal populations but it is unknown if energy expenditure among patients with LC-FAODs is similar to the normal population. We measured resting energy expenditure (REE), total energy expenditure (TEE) and body composition in 31 subjects with LC-FAODs ranging in age from 7 to 64 years. Measured REE was lower than estimated REE by various prediction equations and measured TEE was lower than estimated TEE. It is possible that the lower energy expenditure based on prediction formulas from the normal population is due to differences in body composition; we compared body composition to normal data from the 2017-18 National Health and Nutrition Examination Survey (NHANES). Fat free mass and fat mass was similar between subjects with an LC-FAOD and NHANES normal data suggesting no difference in body composition. We then compared measured REE and TEE to normal published data from the Dietary Reference Intakes (DRI). Measured REE and TEE were significantly lower among subjects with LC-FAODs compared to normal published energy expenditure data. Our results suggests patients with a LC-FAOD exhibit a lower REE and therefore actually have a slightly lower TEE than estimated. Current prediction equations may overestimate energy expenditure of patients with a LC-FAOD.

IFI44L and C1QTNF5 as promising biomarkers of proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) is a world-wide leading cause of blindness among adults and may be associated with the influence of genetic factors. It is significant to search for genetic biomarkers of PDR. In our study, we collected genomic data about PDR from gene expression omnibus (GEO) database. Differentially expressed gene (DEG) analysis and weighted gene co-expression network analysis (WGCNA) were carried out. The gene module with the highest gene significance (GS) was defined as the key module. Hub genes were identified by Venn diagram. Then we verified the expression of hub genes in validation data sets and built a diagnostic model by least absolute shrinkage and selection operator (LASSO) regression. Enrichment analysis, including gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), gene set enrichment analysis (GSEA) and construction of a protein-protein interaction (PPI) network were conducted. In GSE60436, we identified 466 DEGs. WGCNA established 14 gene modules, and the blue module (GS = 0.64), was the key module. Interferon (IFN)-induced protein 44-like (IFI44L) and complement C1q tumor necrosis factor-related protein 5 (C1QTNF5) were identified as hub genes. The expression of hub genes in GEO datasets was verified and a diagnostic model was constructed by LASSO as follows: index = IFI44L * 0.0432 + C1QTNF5 * 0.11246. IFI44L and C1QTNF5 might affect the disease progression of PDR by regulating metabolism-related and inflammatory pathways. IFI44L and C1QTNF5 may play important roles in the disease process of PDR, and a LASSO regression model suggested that the 2 genes could serve as promising biomarkers of PDR.

The Finnish genetic heritage in 2022 – from diagnosis to translational research

Isolated populations have been valuable for the discovery of rare monogenic diseases and their causative genetic variants. Finnish disease heritage (FDH) is an example of a group of hereditary monogenic disorders caused by single major, usually autosomal-recessive, variants enriched in the population due to several past genetic drift events. Interestingly, distinct subpopulations have remained in Finland and have maintained their unique genetic repertoire. Thus, FDH diseases have persisted, facilitating vigorous research on the underlying molecular mechanisms and development of treatment options. This Review summarizes the current status of FDH, including the most recently discovered FDH disorders, and introduces a set of other recently identified diseases that share common features with the traditional FDH diseases. The Review also discusses a new era for population-based studies, which combine various forms of big data to identify novel genotype–phenotype associations behind more complex conditions, as exemplified here by the FinnGen project. In addition to the pathogenic variants with an unequivocal causative role in the disease phenotype, several risk alleles that correlate with certain phenotypic features have been identified among the Finns, further emphasizing the broad value of studying genetically isolated populations.

Analysis of a family with mitochondrial trifunctional protein deficiency caused by HADHA gene mutations

Mitochondrial trifunctional protein (MTP) deficiency (MTPD; MIM 609015) is a metabolic disease of fatty acid oxidation. MTPD is an autosomal recessive disorder caused by mutations in the HADHA gene, encoding the α-subunit of a trifunctional protease, or in the HADHB gene, encoding the β-subunit of a trifunctional protease. To the best of our knowledge, only two cases of families with MTPD due to HADHB gene mutations have been reported in China, and the HADHA gene mutation has not been reported in a Chinese family with MTPD. The present study reported the clinical characteristics and compound heterozygous HADHA gene mutations of two patients with MTPD in the Chinese population. The medical history, routine examination data, blood acyl-carnitine analysis results, results of pathological examination after autopsy and family pedigree map were collected for patients with MTPD. The HADHA gene was analyzed by Sanger sequencing or high-throughput sequencing, the pathogenicity of the newly discovered variant was interpreted by bioinformatics analysis, and the function of the mutated protein was modeled and analyzed according to 3D structure. The two patients with MTPD experienced metabolic crises and died following an infectious disease. Lactate dehydrogenase, creatine kinase (CK), CK-MB and liver enzyme abnormalities were observed in routine examinations. Tandem mass spectrometry revealed that long-chain acyl-carnitine was markedly elevated in blood samples from the patients with MTPD. The autopsy results for one child revealed fat accumulation in the liver and heart. Next-generation sequencing detected compound heterozygous c.703C>T (p.R235W) and c.2107G>A (p.G703R) mutations in the HADHA gene. The mother did not have acute fatty liver during pregnancy with the two patients. Using amniotic fluid prenatal diagnostic testing, the unborn child was confirmed to carry only c.2107G>A (p.G703R). Molecular mechanistic analysis indicated that the two variants affected the conformation of the α-subunit of the MTP enzyme complex, and consequently affected the stability and function of the enzyme complex. The present study comprehensively analyzed the cases, including exome sequencing and protein structure analysis and, to the best of our knowledge, describes the first observation of compound heterozygous mutations in the HADHA gene underlying this disorder in China. The clinical phenotypes of the two heterozygous variants of the HADHA gene are non-lethal. The present study may improve understanding of the HADHA gene mutation spectrum and clinical phenotype in the Chinese population.

Charcot-Marie-Tooth Disease With Episodic Rhabdomyolysis Due to Two Novel Mutations in the β Subunit of Mitochondrial Trifunctional Protein and Effective Response to Modified Diet Therapy

A 29-year-old female experienced chronic progressive peripheral neuropathy since childhood and was diagnosed with Charcot–Marie–Tooth disease (CMT) at age 15. She developed recurrent, fever-induced rhabdomyolysis (RM) at age 24. EMG studies showed decreased amplitude of compound muscle action potential, declined motor conductive velocity, and absence of sensor nerve action potential. Acylcarnitine analysis revealed elevated C16-OH, C18-OH, and C18:1-OH. Muscle biopsy showed scattered foci of necrotic myofibers invaded by macrophages, occasional regenerating fibers, and remarkable muscle fiber type grouping. Whole-exome sequencing identified two novel heterozygous mutations: c.490G>A (p.G164S) and c.686G>A (p.R229Q) in HADHB gene encoding the β-subunit of mitochondrial trifunctional protein (MTP). Reduction of long-chain fatty acid via dietary restrictions alleviated symptoms effectively. Our study indicates that the defect of the MTP β-subunit accounts for both CMT and RM in the same patient and expands the clinical spectrum of disorders caused by the HADHB mutations. Our systematic review of all MTPD patients with dietary treatment indicates that the effect of dietary treatment is related to the age of onset and the severity of symptoms.

Optical Metabolic Imaging of Mitochondrial Dysfunction on HADH Mutant Newborn Rat Hearts

BACKGROUND

Mitochondrial [Formula: see text]-oxidation of fatty acids is the primary energy source for the heart and carried out by Hydroxy Acyl-CoA Dehydrogenase (HADH) encoded trifunctional protein. Mutations in the genes encoding mitochondrial proteins result in functionally defective protein complexes that contribute to energy deficiencies, excessive reactive oxygen species (ROS) production, and accumulation of damaged mitochondria. We hypothesize that a dramatic alternation in redox state and associated mitochondrial dysfunction is the underlying cause of Fatty Acid Oxidation (FAO) deficiency mutant, resulting in heart failure. Mitochondrial co-enzymes, NADH and FAD, are autofluorescent metabolic indices of cells when imaged, yield a quantitative assessment of the cells' redox status and, in turn, that of the tissue and organ.

METHOD

We utilized an optical cryo-imager to quantitively evaluate the three-dimensional distribution of mitochondrial redox state in newborn rats' hearts and kidneys. Redox ratio (RR) assessment shows that mitochondrial dysfunction is extreme and could contribute to severe heart problems and eventual heart failure in the mutants.

RESULTS

Three-dimensional redox ratio (NADH/FAD) rendering, and the volumetric mean value calculations confirmed significantly decreased cardiac RR in mutants by 31.90% and 12.32%, in renal mitochondrial RR compared to wild-type control. Further, histological assessment of newborn heart myocardial tissue indicated no significant difference in myocardial tissue architecture in both control and severe (HADHAe4-/-) conditions.

CONCLUSION

These results demonstrate that optical imaging can accurately estimate the redox state changes in newborn rat organs. It is also apparent that the FAO mutant's heart tissue with a low redox ratio is probably more vulnerable to cumulative damages than kidneys and fails prematurely, contributing to sudden death.

The role of ethanolamine phosphate phospholyase in regulation of astrocyte lipid homeostasis

Dietary lipid composition has been shown to impact brain morphology, brain development, and neurologic function. However, how diet uniquely regulates brain lipid homeostasis compared with lipid homeostasis in peripheral tissues remains largely uncharacterized. To evaluate the lipid response to dietary changes in the brain, we assessed actively translating mRNAs in astrocytes and neurons across multiple diets. From this data, ethanolamine phosphate phospholyase (Etnppl) was identified as an astrocyte-specific fasting-induced gene. Etnppl catabolizes phosphoethanolamine (PEtN), a prominent headgroup precursor in phosphatidylethanolamine (PE) also found in other classes of neurologically relevant lipid species. Altered Etnppl expression has also previously been associated with humans with mood disorders. We evaluated the relevance of Etnppl in maintaining brain lipid homeostasis by characterizing Etnppl across development and in coregulation with PEtN-relevant genes, as well as determining the impact to the brain lipidome after Etnppl loss. We found that Etnppl expression dramatically increased during a critical window of early brain development in mice and was also induced by glucocorticoids. Using a constitutive knockout of Etnppl (EtnpplKO), we did not observe robust changes in expression of PEtN-related genes. However, loss of Etnppl altered the phospholipid profile in the brain, resulting in increased total abundance of PE and in polyunsaturated fatty acids within PE and phosphatidylcholine species in the brain. Together, these data suggest that brain phospholipids are regulated by the phospholyase action of the enzyme Etnppl, which is induced by dietary fasting in astrocytes.

Cardiometabolism as an Interlocking Puzzle between the Healthy and Diseased Heart: New Frontiers in Therapeutic Applications

Cardiac metabolism represents a crucial and essential connecting bridge between the healthy and diseased heart. The cardiac muscle, which may be considered an omnivore organ with regard to the energy substrate utilization, under physiological conditions mainly draws energy by fatty acids oxidation. Within cardiomyocytes and their mitochondria, through well-concerted enzymatic reactions, substrates converge on the production of ATP, the basic chemical energy that cardiac muscle converts into mechanical energy, i.e., contraction. When a perturbation of homeostasis occurs, such as an ischemic event, the heart is forced to switch its fatty acid-based metabolism to the carbohydrate utilization as a protective mechanism that allows the maintenance of its key role within the whole organism. Consequently, the flexibility of the cardiac metabolic networks deeply influences the ability of the heart to respond, by adapting to pathophysiological changes. The aim of the present review is to summarize the main metabolic changes detectable in the heart under acute and chronic cardiac pathologies, analyzing possible therapeutic targets to be used. On this basis, cardiometabolism can be described as a crucial mechanism in keeping the physiological structure and function of the heart; furthermore, it can be considered a promising goal for future pharmacological agents able to appropriately modulate the rate-limiting steps of heart metabolic pathways.

Determining the Bioenergetic Capacity for Fatty Acid Oxidation in the Mammalian Nervous System

The metabolic state of the brain can greatly impact neurologic function. Evidence of this includes the therapeutic benefit of a ketogenic diet in neurologic diseases, including epilepsy. However, brain lipid bioenergetics remain largely uncharacterized. The existence, capacity, and relevance of mitochondrial fatty acid β-oxidation (FAO) in the brain are highly controversial, with few genetic tools available to evaluate the question. We have provided evidence for the capacity of brain FAO using a pan-brain-specific conditional knockout (KO) mouse incapable of FAO due to the loss of carnitine palmitoyltransferase 2, the product of an obligate gene for FAO (CPT2B-/-). Loss of central nervous system (CNS) FAO did not result in gross neuroanatomical changes or systemic differences in metabolism. Loss of CPT2 in the brain did not result in robustly impaired behavior. We demonstrate by unbiased and targeted metabolomics that the mammalian brain oxidizes a substantial quantity of long-chain fatty acids in vitro and in vivo Loss of CNS FAO results in robust accumulation of long-chain acylcarnitines in the brain, suggesting that the mammalian brain mobilizes fatty acids for their oxidation, irrespective of diet or metabolic state. Together, these data demonstrate that the mammalian brain oxidizes fatty acids under normal circumstances with little influence from or on peripheral tissues.

ITPase deficiency causes a Martsolf-like syndrome with a lethal infantile dilated cardiomyopathy

Typical Martsolf syndrome is characterized by congenital cataracts, postnatal microcephaly, developmental delay, hypotonia, short stature and biallelic hypomorphic mutations in either RAB3GAP1 or RAB3GAP2. Genetic analysis of 85 unrelated "mutation negative" probands with Martsolf or Martsolf-like syndromes identified two individuals with different homozygous null mutations in ITPA, the gene encoding inosine triphosphate pyrophosphatase (ITPase). Both probands were from multiplex families with a consistent, lethal and highly distinctive disorder; a Martsolf-like syndrome with infantile-onset dilated cardiomyopathy. Severe ITPase-deficiency has been previously reported with infantile epileptic encephalopathy (MIM 616647). ITPase acts to prevent incorporation of inosine bases (rI/dI) into RNA and DNA. In Itpa-null cells dI was undetectable in genomic DNA. dI could be identified at a low level in mtDNA without detectable mitochondrial genome instability, mtDNA depletion or biochemical dysfunction of the mitochondria. rI accumulation was detectable in proband-derived lymphoblastoid RNA. In Itpa-null mouse embryos rI was detectable in the brain and kidney with the highest level seen in the embryonic heart (rI at 1 in 385 bases). Transcriptome and proteome analysis in mutant cells revealed no major differences with controls. The rate of transcription and the total amount of cellular RNA also appeared normal. rI accumulation in RNA-and by implication rI production-correlates with the severity of organ dysfunction in ITPase deficiency but the basis of the cellulopathy remains cryptic. While we cannot exclude cumulative minor effects, there are no major anomalies in the production, processing, stability and/or translation of mRNA.

The pivotal role of protein acetylation in linking glucose and fatty acid metabolism to β-cell function

Protein acetylation has a crucial role in energy metabolism. Here we performed the first large-scale profiling of acetylome in rat islets, showing that almost all enzymes in core metabolic pathways related to insulin secretion were acetylated. Label-free quantitative acetylome of islets in response to high glucose revealed hyperacetylation of enzymes involved in fatty acid β-oxidation (FAO), including trifunctional enzyme subunit alpha (ECHA). Acetylation decreased the protein stability of ECHA and its ability to promote FAO. The overexpression of SIRT3, a major mitochondrial deacetylase, prevented the degradation of ECHA via decreasing its acetylation level in β-cells. SIRT3 expression was upregulated in rat islets upon exposure to low glucose or fasting. SIRT3 overexpression in islets markedly decreased palmitate-potentiated insulin secretion, whereas islets from SIRT3 knockout mice secreted more insulin, with an opposite action on FAO. ECHA overexpression partially reversed SIRT3 deficiency-elicited insulin hypersecretion. Our study highlights the potential role of protein acetylation in insulin secretion.

Fatal pitfalls in newborn screening for mitochondrial trifunctional protein (MTP)/long-chain 3-Hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency

Background

Mitochondrial trifunctional protein (MTP) and long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency are long-chain fatty acid oxidation disorders with particularly high morbidity and mortality. Outcome can be favorable if diagnosed in time, prompting the implementation in newborn screening programs. Sporadic cases missed by the initial screening sample have been reported. However, little is known on pitfalls during confirmatory testing resulting in fatal misconception of the diagnosis.

Results

We report a series of three patients with MTP and LCHAD deficiency, in whom diagnosis was missed by newborn screening, resulting in life-threatening metabolic decompensations within the first half year of life. Two of the patients showed elevated concentrations of primary markers C16-OH and C18:1-OH but were missed by confirmatory testing performed by the maternity clinic. A metabolic center was not consulted. Confirmatory testing consisted of analyses of acylcarnitines in blood and organic acids in urine, the finding of normal excretion of organic acids led to rejection and underestimation of the diagnosis, respectively. The third patient, a preterm infant, was not identified in the initial screening sample due to only moderate elevations of C16-OH and C18:1-OH and normal secondary markers and analyte ratios.

Conclusion

Our observations highlight limitations of newborn screening for MTP/LCHAD deficiency. They confirm that analyses of acylcarnitines in blood and organic acids in urine alone are not suitable for confirmatory testing and molecular or functional analysis is crucial in diagnosing MTP/LCHAD deficiency. Mild elevations of primary biomarkers in premature infants need to trigger confirmatory testing. Our report underscores the essential role of specialized centers in confirming or ruling out diagnoses in suspicious screening results.

Cholesterol Biosynthesis: A Mechanistic Overview

Cholesterol is an essential component of cell membranes and the precursor for the synthesis of steroid hormones and bile acids. The synthesis of this molecule occurs partially in a membranous world (especially the last steps), where the enzymes, substrates, and products involved tend to be extremely hydrophobic. The importance of cholesterol has increased in the past half-century because of its association with cardiovascular diseases, which are considered one of the leading causes of death worldwide. In light of the current need for new drugs capable of controlling the levels of cholesterol in the bloodstream, it is important to understand how cholesterol is synthesized in the organism and identify the main enzymes involved in this process. Taking this into account, this review presents a detailed description of several enzymes involved in the biosynthesis of cholesterol. In this regard, the structure and catalytic mechanism of the enzymes involved in cholesterol biosynthesis, from the initial two-carbon acetyl-CoA building block, will be reviewed and their current pharmacological importance discussed. We believe that this review may contribute to a deeper level of understanding of cholesterol metabolism and that it will serve as a useful resource for future studies of the cholesterol biosynthesis pathway.

Earlier diagnosis and strict diets improve the survival rate and clinical course of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

AIM

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is a severe metabolic disease that, without treatment, often leads to premature death or serious handicap. The aim of this study was to evaluate the clinical course of LCHADD with the homozygous 1528G>C (E510Q) mutation when patients underwent strict dietary treatment.

METHODS

From 1997 to 2010, 16 patients with LCHADD were diagnosed in Finland. They were followed up, and data were prospectively collected as they emerged. Clinical data before diagnosis were retrospectively collected from hospital records. This cohort was compared with an earlier cohort of patients diagnosed from 1976 to 1996.

RESULTS

The disease presented from birth to five months of age with failure to thrive, hypotonia, hepatomegaly, metabolic acidosis, cardiomyopathy and hypoketotic hypoglycaemia. In this cohort, the therapeutic delay was 0-30 days and the survival rate at the end of the study was 62.5% compared with 10-year survival rate of 14.3% for the earlier cohort. The survivors were in good overall condition, but some of them had developed mild retinopathy or mild neuropathy.

CONCLUSION

Earlier diagnosis and stricter dietary regimes improved the survival rates and clinical course of patients with LCHADD in Finland. However, improvements in therapy are still needed to prevent the development of long-term complications, such as retinopathy and neuropathy.

Combined defects in oxidative phosphorylation and fatty acid β-oxidation in mitochondrial disease

Mitochondria provide the main source of energy to eukaryotic cells, oxidizing fats and sugars to generate ATP. Mitochondrial fatty acid β-oxidation (FAO) and oxidative phosphorylation (OXPHOS) are two metabolic pathways which are central to this process. Defects in these pathways can result in diseases of the brain, skeletal muscle, heart and liver, affecting approximately 1 in 5000 live births. There are no effective therapies for these disorders, with quality of life severely reduced for most patients. The pathology underlying many aspects of these diseases is not well understood; for example, it is not clear why some patients with primary FAO deficiencies exhibit secondary OXPHOS defects. However, recent findings suggest that physical interactions exist between FAO and OXPHOS proteins, and that these interactions are critical for both FAO and OXPHOS function. Here, we review our current understanding of the interactions between FAO and OXPHOS proteins and how defects in these two metabolic pathways contribute to mitochondrial disease pathogenesis.

Peripheral neuropathy in patients with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency - A follow-up EMG study of 12 patients

BACKGROUND

The neonatal screening and early start of the dietary therapy have improved the outcome of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD). The acute symptoms of LCHADD are hypoketotic hypoglycemia, failure to thrive, hepatopathy and rhabdomyolysis. Long term complications are retinopathy and neuropathy. Speculated etiology of these long term complications are the accumulation and toxicity of hydroxylacylcarnitines and long-chain fatty acid metabolites or deficiency of essential fatty acids.

AIMS

To study the possible development of polyneuropathy in LCHADD patients with current dietary regimen.

METHODS

Development of polyneuropathy in 12 LCHADD patients with the homozygous common mutation c.G1528C was evaluated with electroneurography (ENG) studies. The ENG was done 1-12 times to each patient, between the ages of 3 and 40 years. Clinical data of the patients were collected from the patient records.

RESULTS

The first sign of polyneuropathy was detected between the ages of 6-12 years, the first abnormality being reduction of the sensory amplitudes of the sural nerves. With time, progression was detected by abnormalities in sensory responses extending to upper limbs, as well as abnormalities in motor responses in lower limbs. Altogether, eight of the patients had polyneuropathy, despite good compliancy of the diet.

CONCLUSIONS

This study is the first to report the evolution of polyneuropathy with clinical neurophysiological methods in a relative large LCHADD patient group. Despite early start, and good compliance of the therapy, 6/10 of the younger patients developed neuropathy. However, in most patients the polyneuropathy was less severe than previously described.

Long-chain Acylcarnitines Reduce Lung Function by Inhibiting Pulmonary Surfactant

The role of mitochondrial energy metabolism in maintaining lung function is not understood. We previously observed reduced lung function in mice lacking the fatty acid oxidation enzyme long-chain acyl-CoA dehydrogenase (LCAD). Here, we demonstrate that long-chain acylcarnitines, a class of lipids secreted by mitochondria when metabolism is inhibited, accumulate at the air-fluid interface in LCAD(-/-) lungs. Acylcarnitine accumulation is exacerbated by stress such as influenza infection or by dietary supplementation with l-carnitine. Long-chain acylcarnitines co-localize with pulmonary surfactant, a unique film of phospholipids and proteins that reduces surface tension and prevents alveolar collapse during breathing. In vitro, the long-chain species palmitoylcarnitine directly inhibits the surface adsorption of pulmonary surfactant as well as its ability to reduce surface tension. Treatment of LCAD(-/-) mice with mildronate, a drug that inhibits carnitine synthesis, eliminates acylcarnitines and improves lung function. Finally, acylcarnitines are detectable in normal human lavage fluid. Thus, long-chain acylcarnitines may represent a risk factor for lung injury in humans with dysfunctional fatty acid oxidation.

Long-chain acyl-CoA dehydrogenase deficiency as a cause of pulmonary surfactant dysfunction

Long-chain acyl-CoA dehydrogenase (LCAD) is a mitochondrial fatty acid oxidation enzyme whose expression in humans is low or absent in organs known to utilize fatty acids for energy such as heart, muscle, and liver. This study demonstrates localization of LCAD to human alveolar type II pneumocytes, which synthesize and secrete pulmonary surfactant. The physiological role of LCAD and the fatty acid oxidation pathway in lung was subsequently studied using LCAD knock-out mice. Lung fatty acid oxidation was reduced in LCAD(-/-) mice. LCAD(-/-) mice demonstrated reduced pulmonary compliance, but histological examination of lung tissue revealed no obvious signs of inflammation or pathology. The changes in lung mechanics were found to be due to pulmonary surfactant dysfunction. Large aggregate surfactant isolated from LCAD(-/-) mouse lavage fluid had significantly reduced phospholipid content as well as alterations in the acyl chain composition of phosphatidylcholine and phosphatidylglycerol. LCAD(-/-) surfactant demonstrated functional abnormalities when subjected to dynamic compression-expansion cycling on a constrained drop surfactometer. Serum albumin, which has been shown to degrade and inactivate pulmonary surfactant, was significantly increased in LCAD(-/-) lavage fluid, suggesting increased epithelial permeability. Finally, we identified two cases of sudden unexplained infant death where no lung LCAD antigen was detectable. Both infants were homozygous for an amino acid changing polymorphism (K333Q). These findings for the first time identify the fatty acid oxidation pathway and LCAD in particular as factors contributing to the pathophysiology of pulmonary disease.

Early presentation of very long chain acyl-CoA dehydrogenase deficiency: nursing action resulting in a positive outcome

A clinical case of very long chain fatty acid acyl-CoA dehydrogenase (VLCAD) deficiency with cardiac manifestation, is presented. A 2-day old newborn, delivered after a normal pregnancy, birth, and immediate post-natal period, was transported from an outside hospital (OSH) with episodic wide complex tachycardia. In this case, the newborn screen returned suggesting VLCAD deficiency, positively redirecting treatment. An overview of VLCAD, one category of inborn error of metabolism (IEM), is presented. Additionally, the importance of newborn screening, the role of genetic testing, and nursing implications to improve outcomes, will also be discussed.

Mitochondrial deficiency in Cockayne syndrome

Cockayne syndrome is a rare inherited disorder characterized by accelerated aging, cachectic dwarfism and many other features. Recent work has implicated mitochondrial dysfunction in the pathogenesis of this disease. This is particularly interesting since mitochondrial deficiencies are believed to be important in the aging process. In this review, we discuss recent findings of mitochondrial pathology in Cockayne syndrome and suggest possible mechanisms for the mitochondrial dysfunction.

Metabolic neuropathies and myopathies

Inborn errors of metabolism may impact on muscle and peripheral nerve. Abnormalities involve mitochondria and other subcellular organelles such as peroxisomes and lysosomes related to the turnover and recycling of cellular compartments. Treatable causes are β-oxidation defects producing progressive neuropathy; pyruvate dehydrogenase deficiency, porphyria, or vitamin B12 deficiency causing recurrent episodes of neuropathy or acute motor deficit mimicking Guillain-Barré syndrome. On the other hand, lysosomal (mucopolysaccharidosis, Gaucher and Fabry diseases), mitochondriopathic (mitochondrial or nuclear mutations or mDNA depletion), peroxisomal (adrenomyeloneuropathy, Refsum disease, sterol carrier protein-2 deficiency, cerebrotendinous xanthomatosis, α-methylacyl racemase deficiency) diseases are multisystemic disorders involving also the heart, liver, brain, retina, and kidney. Pathophysiology of most metabolic myopathies is related to the impairment of energy production or to abnormal production of reactive oxygen species (ROS). Main symptoms are exercise intolerance with myalgias, cramps and recurrent myoglobinuria or limb weakness associated with elevation of serum creatine kinase. Carnitine palmitoyl transferase deficiency, followed by acid maltase deficiency, and lipin deficiency, are the most common cause of isolated rhabdomyolysis. Metabolic myopathies are frequently associated to extra-neuromuscular disorders particularly involving the heart, liver, brain, retina, skin, and kidney.

Growth in Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase Deficiency

Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency is an inborn error of fatty acid metabolism that affects the degradation of long chain fatty acids and causes insufficient energy production and accumulation of toxic intermediates. The treatment consists of a diet low in fat, with supplementation of medium-chain triglycerides that bypass the metabolic block. In addition, frequent feeds and extra carbohydrates are given during febrile illnesses to reduce lipolysis. Hence, this diet differs from the general dietary recommendations for growing children. Furthermore, the Swedish dietary instructions for fat intake in LCHAD deficiency are given in grams, which differ from most guidelines that recommend fat intake as percentage shares of total caloric intake.

AIMS

To assess growth in patients with LCHAD deficiency, in relation to dietary treatment and to evaluate if overweight/obesity is more common than in the normal population.

RESULTS

The growth velocity showed acceleration after diagnosis and the start of treatment, followed by a period of stable or decelerated growth. The majority of the patients developed overweight to a greater extent than children without LCHAD deficiency. Several patients also went through a phase of obesity. Data on final height (FH) showed that three out of five patients had grown according to their genetic potential.

CONCLUSIONS

Regular and frequent follow-up and careful monitoring of weight are essential to avoid the development of overweight and obesity. The Swedish dietary instructions defining fat intake in total grams per day may be an alternative approach to achieve a moderate total caloric intake.

Observations regarding retinopathy in mitochondrial trifunctional protein deficiencies

Although the retina is thought to primarily rely on glucose for fuel, inherited deficiency of one or more activities of mitochondrial trifunctional protein results in a pigmentary retinopathy leading to vision loss. Many other enzymatic deficiencies in fatty acid oxidation pathways have been described, none of which results in retinal complications. The etiology of retinopathy among patients with defects in trifunctional protein is unknown. Trifunctional protein is a heteroctomer; two genes encode the alpha and beta subunits of TFP respectively, HADHA and HADHB. A common mutation in HADHA, c.1528G>C, leads to a single amino acid substitution, p. Glu474Gln, and impairs primarily long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) activity leading to LCHAD deficiency (LCHADD). Other mutations in HADHA or HADHB often lead to significant reduction in all three enzymatic activities and result in trifunctional protein deficiency (TFPD). Despite many similarities in clinical presentation and phenotype, there is growing evidence that they can result in different chronic complications. This review will outline the clinical similarities and differences between LCHADD and TFPD, describe the course of the associated retinopathy, propose a genotype/phenotype correlation with the severity of retinopathy, and discuss the current theories about the etiology of the retinopathy.

Cholestatic Jaundice Associated with Carnitine Palmitoyltransferase IA Deficiency

Liver dysfunction usually accompanies metabolic decompensation in fatty acid oxidation disorders, including carnitine palmitoyltransferase (CPT) Ia deficiency. Typically, the liver is enlarged with raised plasma transaminase activities and steatosis on histological examination. In contrast, cholestatic jaundice is rare, having only been reported in long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency. We report a 3-year-old boy with CPT Ia deficiency who developed hepatomegaly and cholestatic jaundice following a viral illness. No cause for the jaundice could be found, apart from the fatty acid oxidation disorder. Liver histology showed diffuse, predominately macrovesicular steatosis, hepatocellular and canalicular cholestasis but no bile duct paucity or evidence of large duct obstruction. The liver dysfunction resolved in 4-7 weeks.

Urgent metabolic service improves survival in long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency detected by symptomatic identification and pilot newborn screening

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is a fatty acid oxidation disorder with especially high mortality and uncertain long-term outcome. The aim of the study was to analyze the influence of diagnostic approach on survival in 59 affected children. Referral to a metabolic center was replaced over time by urine/blood testing in centralized metabolic laboratory (selective screening) and by pilot tandem mass spectrometry newborn screening (NBS). Molecular analysis revealed the prevalent mutation in the HADHA gene in all 58 examined cases. Twenty patients died. The number of detections and number of deaths were respectively 9 and 4 (44%) in the patients recognized by differential diagnosis, 28 and 9 (32%) - by selective screening, and 11 and 1 (9%) - by NBS. In 80% of cases the death occurred before or within 3 weeks from the identification. Urgent and active metabolic service remarkably influenced the surviving. The current age of 39 survivors is 0.5 to 23 yrs (mean 7.2 yrs). The disease frequency estimated on the patients number was 1: 115 450, whereas in the pilot NBS - 1: 109 750 (658 492 neonates tested). Interestingly, the phenylalanine level in asymptomatic neonates frequently exceeded the cut-off values.

CONCLUSIONS

1) Urgent metabolic intervention decreases mortality of LCHAD-deficient patients, but the prognosis is still uncertain. 2) Emergent metabolic reporting and service are crucial also for the survival of neonates detected by NBS. 3) The nationwide selective screening appeared efficient in LCHADD detection in the country. 4) Transient mild hyperphenylalaninaemia may occur in LCHAD-deficient newborns.

Long-chain 3-hydroxy fatty acids accumulating in LCHAD and MTP deficiencies induce oxidative stress in rat brain

Accumulation of long-chain 3-hydroxy fatty acids is the biochemical hallmark of long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and mitochondrial trifunctional protein (MTP) deficiencies. These disorders are clinically characterized by neurological symptoms, such as convulsions and lethargy, as well as by cardiomyopathy and muscle weakness. In the present work we investigated the in vitro effect of 3-hydroxydodecanoic (3HDA), 3-hydroxytetradecanoic (3HTA) and 3-hydroxypalmitic (3HPA) acids, which accumulate in these disorders, on important oxidative stress parameters in cerebral cortex of young rats in the hope to clarify the mechanisms leading to the brain damage found in patients affected by these disorders. It was first verified that these compounds significantly induced lipid peroxidation, as determined by increased thiobarbituric acid-reactive substances levels. In addition, carbonyl formation was significantly increased and sulfhydryl content decreased by 3HTA and 3HPA, which indicates that these fatty acids elicit protein oxidative damage. 3HTA and 3HPA also diminished the reduced glutathione (GSH) levels, without affecting nitrate and nitrite production. Finally, we observed that the addition of the antioxidants and free radical scavengers trolox and deferoxamine (DFO) was able to partially prevent lipid oxidative damage, whereas DFO fully prevented the reduction on GSH levels induced by 3HTA. Our present data showing that 3HDA, 3HTA and 3HPA elicit oxidative stress in rat brain indicate that oxidative damage may represent an important pathomechanism involved in the neurologic symptoms manifested by patients affected by LCHAD and MTP deficiencies.

ERRgamma regulates cardiac, gastric, and renal potassium homeostasis

Energy production by oxidative metabolism in kidney, stomach, and heart, is primarily expended in establishing ion gradients to drive renal electrolyte homeostasis, gastric acid secretion, and cardiac muscle contraction, respectively. In addition to orchestrating transcriptional control of oxidative metabolism, the orphan nuclear receptor, estrogen-related receptor gamma (ERRgamma), coordinates expression of genes central to ion homeostasis in oxidative tissues. Renal, gastric, and cardiac tissues subjected to genomic analysis of expression in perinatal ERRgamma null mice revealed a characteristic dysregulation of genes involved in transport processes, exemplified by the voltage-gated potassium channel, Kcne2. Consistently, ERRgamma null animals die during the first 72 h of life with elevated serum potassium, reductions in key gastric acid production markers, and cardiac arrhythmia with prolonged QT intervals. In addition, we find altered expression of several genes associated with hypertension in ERRgamma null mice. These findings suggest a potential role for genetic polymorphisms at the ERRgamma locus and ERRgamma modulators in the etiology and treatment of renal, gastric, and cardiac dysfunction.

Acute dilated cardiomyopathy in a patient with deficiency of long-chain 3-hydroxyacyl-CoA dehydrogenase

Deficiency of long-chain 3-hydroxyacyl-coenzyme A (CoA) dehydrogenase (LCHADD) is a rare inborn error of metabolism. It is associated with hypertrophic cardiomyopathy and less frequently with dilated cardiomyopathy. The incidence and pathophysiology of cardiac involvement in LCHADD is poorly understood. This report describes the acute decompensation of a 3-year-old girl who had LCHADD with rapidly developing dilated cardiomyopathy. A review of the literature and possible causes of cardiomyopathy in LCHADD are explored.

Mitochondrial fatty-acid oxidation disorders

Inherited defects in mitochondrial fatty-acid beta-oxidation comprise a group of at least 12 diseases characterized by distinct enzyme or transporter deficiencies. Most of these diseases have a variable age of onset and clinical severity. Symptoms are often episodic and associated with mild viral illness, physiologic stress, or prolonged exercise that overwhelms the ability of mitochondria to oxidize fatty acids. Depending on the specific genetic defect, patients develop fasting hypoketotic hypoglycemia, cardiomyopathy, rhabdomyolysis, liver dysfunction, or sudden death. Neuropathy and pigmentary retinopathy are seen in some of the diseases. The diagnosis is based on finding an accumulation of specific biochemical markers such as acylcarnitine metabolites in blood and urinary dicarboxylic acids and acylglycines. Confirmatory testing requires enzymatic studies and DNA analysis. Therapeutic approaches are generally effective in preventing severe symptomatic episodes, including sudden death. Newborn screening for fatty-acid oxidation disorders promises to identify many affected patients before the onset of symptoms.

Long chain fatty acid oxidation defects in children: importance of detection and treatment options

BACKGROUND

Mitochondrial beta oxidation plays a major role in energy production. Long chain fatty acid oxidation defects include deficiency of the trifunctional protein (rare) or more commonly defects of the long chain 3-hydroxy acyl-CoA dehydrogenase enzyme (LCHAD). These long chain defects have variable presentations, they may present in the neonate or infant with sudden death, hepatopathy (Reyes disease), hypoketotic hypoglycaemia, rhabdomyolysis, myopathy, cardiomyopathy and with late complications such as peripheral neuropathy, pigmentary retinopathy, retinal degeneration and progressive visual loss. The correct diagnosis at presentation is not only life saving but also allows for the appropriate dietary and other intervention, which may have major effects on outcome.

AIM

Three case reports of patients with long chain fatty acid oxidation defects who have shown significant benefits from treatment are reported.

CONCLUSIONS

These paediatric presentations illustrate the clinical heterogeneity of long chain fatty acid oxidation defects and opportunities for effective management if correctly diagnosed.

Obesity, hypothyroidism, craniosynostosis, cardiac hypertrophy, colitis, and developmental delay: A novel syndrome

We describe in two brothers an apparently novel syndrome comprising obesity, congenital hypothyroidism, neonatal colitis, cardiac biventricular hypertrophy, craniosynostosis, and developmental delay. The first brother presented with neonatal colitis and congenital hypothyroidism and died at age 5 weeks of fulminant colitis. The second brother presented neonatally with the same condition, but survived and subsequently developed severe obesity, sagittal and coronal synostosis, and developmental delay. Both pregnancies had been complicated by hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome). Exhaustive genetic and metabolic investigations have failed to provide a unifying pathogenesis. This unique combination of manifestations appears to represent a new syndrome with probable autosomal recessive or X-linked recessive inheritance.

Effects of higher dietary protein intake on energy balance and metabolic control in children with long-chain 3-hydroxy acyl-CoA dehydrogenase (LCHAD) or trifunctional protein (TFP) deficiency

The incidence of overweight and obesity is increasing among children with long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) or mitochondrial trifunctional (TFP) deficiency. Traditional treatment includes fasting avoidance and consumption of a low-fat, high-carbohydrate diet. A diet higher in protein and lower in carbohydrate may help to lower total energy intake while maintaining good metabolic control. To determine the short-term safety and efficacy of a high protein diet, subjects were admitted to the General Clinical Research Center and fed an ad-libitum high-protein diet and a high-carbohydrate diet for 6 days each using a randomized, crossover design. Nine subjects with LCHAD or TFP deficiency, age 7-14 were enrolled. Body composition was determined by DEXA. Total energy intake was evaluated daily. Resting energy expenditure and substrate utilization were determined by indirect calorimetry. Post-prandial metabolic responses of plasma glucose, insulin, leptin, ghrelin, acylcarnitines, and triglyceride were determined in response to a liquid meal. Subjects had a higher fat mass, lower lean mass and higher plasma leptin levels compared to reference values. While on the high protein diet energy consumption was an average of 50 kcals/day lower (p = 0.02) and resting energy expenditure was an average of 170 kcals/day higher (p = 0.05) compared to the high carbohydrate diet. Short-term higher protein diets were safe, well tolerated, and resulted in lowered energy intake and increased energy expenditure than the standard high-carbohydrate diet. Long-term studies are needed to determine whether higher protein diets will reduce the risk of overweight and obesity in children with LCHAD or TFP deficiency.

Differential inhibitory effect of long-chain acyl-CoA esters on succinate and glutamate transport into rat liver mitochondria and its possible implications for long-chain fatty acid oxidation defects

Long-chain fatty acid beta-oxidation defects are associated with a series of clinical and biochemical abnormalities, including accumulation of long-chain acyl-CoA esters which have been shown to inhibit several enzymes and transport systems that may disturb energy metabolism. Using isolated rat liver mitochondria incubated under state 3 conditions, we observed that long-chain acyl-CoA esters and their beta-oxidation intermediates inhibit ATP synthesis and oxygen consumption, both with succinate (plus rotenone) and l-glutamate as respiratory substrates. When an uncoupler (2,4-dinitrophenol) was used instead of ADP, to stimulate respiration maximally, the various CoA esters showed differential effects on the oxidation of succinate and l-glutamate, respectively. With succinate as substrate, there was a strong inhibition of oxygen consumption by palmitoyl-CoA, 2,3-unsaturated, 3-hydroxy, and 3-keto-palmitoyl-CoA, in coupled as well as uncoupled mitochondria. On the other hand, with l-glutamate as substrate, inhibition was only observed under coupled conditions. The finding that acyl-CoA esters inhibit the uncoupler-induced respiration with succinate as substrate but not with glutamate, indicates that the observed inhibitory effect is most probably at the level of the transport of succinate across the mitochondrial membrane as mediated by the mitochondrial dicarboxylate carrier. This conclusion was substantiated by mitochondrial swelling studies, which showed inhibition of succinate transport by the different CoA esters whereas no effect was observed on the phosphate/hydroxyl and glutamate/hydroxyl carriers. Furthermore, long-chain acyl-CoA esters were found to potentiate the inhibitory effect of N-butylmalonate, a known inhibitor of the dicarboxylate carrier, upon oxygen consumption driven by succinate (plus rotenone). We conclude that the inhibitory effects of long-chain acyl-CoA esters on oxidative phosphorylation are dependent on the type of substrate used with the ATP/ADP carrier and the dicarboxylate carrier as targets for inhibition.

Effect of optimal dietary therapy upon visual function in children with long-chain 3-hydroxyacyl CoA dehydrogenase and trifunctional protein deficiency

The objective of this prospective cohort study was to determine if dietary therapy including docosahexaenoic acid (DHA; C22:6omega-3) supplementation prevents the progression of the severe chorioretinopathy that develops in children with long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) or trifunctional protein (TFP) deficiency. Physical, biochemical, and ophthalmological evaluations, including electroretinogram (ERG) and visual acuity by evoked potential (VEP), were performed at baseline and annually following the initiation of 65-130 mg/day DHA supplementation and continued treatment with a low-fat diet. Fourteen children with LCHAD or TFP deficiency, 1-12 years of age at enrollment, were followed for 2-5 years. Three subjects with TFP beta-subunit mutations had normal appearance of the posterior pole of the ocular fundi at enrollment and no changes over the course of the study. Eleven subjects who were homozygote and heterozygote for the common mutation, c.1528G>C, had no change to severe progression of atrophy of the choroid and retina with time. Of these, four subjects had marked to severe chorioretinopathy associated with high levels of plasma hydroxyacylcarnitines and decreased color, night and/or central vision during the study. The plasma level of long-chain 3-hydroxyacylcarnitines, metabolites that accumulate as a result of LCHAD and TFP deficiency, was found to be negatively correlated with maximum ERG amplitude (Rmax) (p=0.0038, R2=0.62). In addition, subjects with sustained low plasma long-chain 3-hydroxyacylcarnitines maintained higher ERG amplitudes with time compared to subjects with chronically high 3-hydroxyacylcarnitines. Visual acuity, as determined with the VEP, appeared to increase with time on DHA supplementation (p=0.051) and there was a trend for a positive correlation with plasma DHA concentrations (p=0.075, R2=0.31). Thus, optimal dietary therapy as indicated by low plasma 3-hydroxyacylcarnitine and high plasma DHA concentrations was associated with retention of retinal function and visual acuity in children with LCHAD or TFP deficiency.

The Association Between Acute Fatty Liver of Pregnancy and Fatty Acid Oxidation Disorders

Acute fatty liver of pregnancy is a relatively rare but potentially fatal liver disorder of late pregnancy. Recent advances in molecular diagnostic procedures provide evidence of a genetic basis for this condition and a link to offspring disorders in fatty acid oxidation. This relationship implies the need for genetic testing and follow-up of at-risk women and their neonates.

Implications of impaired ketogenesis in fatty acid oxidation disorders

Long-chain fatty acids are important sources of respiratory fuel for many tissues and during fasting the rate of hepatic production of ketone bodies is markedly increased. Many extra hepatic tissues utilize ketone bodies in the fasted state with the advantage that glucose is "spared" for more vital tissues like the brain. This glucose sparing effect of ketones is especially important in infants where there is a high proportional glucose utilization in cerebral tissue. The first reported inherited defect affecting fatty acid oxidation was described in 1973 and to date about 15 separate disorders have been described. Although individually rare, cumulatively fatty acid oxidation defects are relatively common, have major consequences for affected individuals and their families, and carry significant health care implications. The major biochemical consequence of fatty acid oxidation defects is an inability of extra hepatic tissues to utilize fatty acids as an energy source with absent or limited hepatic capacity to generate ketones. Clinically patients usually present in infancy with acute life-threatening hypoketotic hypoglycaemia, liver disease, hyperammonaemia and cerebral oedema, with or without cardiac involvement, usually following a period of catabolic stress. Chronically there may be muscle involvement with hypotonia or exercise intolerance with or without cardiomyopathy. Treatment is generally by the avoidance of fasting, frequent carbohydrate rich feeds and for long-chain defects, the replacement of long-chain dietary fats with medium-chain formulae. Novel approaches to treatment include the use of d,l-3-hydoxybutyrate or heptanoate as an alternative energy source.

Mitochondrial trifunctional protein deficiency: a severe fatty acid oxidation disorder with cardiac and neurologic involvement

OBJECTIVE

To determine the spectrum of presentation, including both clinical and biochemical abnormalities, and the clinical course in a cohort of patients with complete mitochondrial trifunctional protein (MTP) deficiency, a rare inborn error of mitochondrial fatty acid oxidation.

STUDY DESIGN

A questionnaire was sent to the referring physicians from 25 unselected MTP-deficient patients.

RESULTS

Twenty-one patients could be included. Questionnaires about four patients were not returned. Nine (43%) patients presented with rapidly progressive clinical deterioration; six (67%) of them had hypoketotic hypoglycemia. The remaining 12 patients presented with a much more insidious disease with nonspecific chronic symptoms, including hypotonia (100%), cardiomyopathy (73%), failure to thrive, or peripheral neuropathy. Ten patients (48%) presented in the neonatal period. Mortality was high (76%), mostly attributable to cardiac involvement. Two patients who were diagnosed prenatally died despite treatment.

CONCLUSION

Complete MTP deficiency often presents with nonspecific symptomatology, which makes clinical recognition difficult. Hypotonia and cardiomyopathy are common presenting features, and the differential diagnosis of an infant with these signs should include MTP deficiency. In spite of early diagnosis and treatment, only a few patients with this condition have survived.

Human placenta metabolizes fatty acids: implications for fetal fatty acid oxidation disorders and maternal liver diseases

The role of fat metabolism during human pregnancy and in placental growth and function is poorly understood. Mitochondrial fatty acid oxidation disorders in an affected fetus are associated with maternal diseases of pregnancy, including preeclampsia, acute fatty liver of pregnancy, and the hemolysis, elevated liver enzymes, and low platelets syndrome called HELLP. We have investigated the developmental expression and activity of six fatty acid beta-oxidation enzymes at various gestational-age human placentas. Placental specimens exhibited abundant expression of all six enzymes, as assessed by immunohistochemical and immunoblot analyses, with greater staining in syncytiotrophoblasts compared with other placental cell types. beta-Oxidation enzyme activities in placental tissues were higher early in gestation and lower near term. Trophoblast cells in culture oxidized tritium-labeled palmitate and myristate in substantial amounts, indicating that the human placenta utilizes fatty acids as a significant metabolic fuel. Thus human placenta derives energy from fatty acid oxidation, providing a potential explanation for the association of fetal fatty acid oxidation disorders with maternal liver diseases in pregnancy.

The Finnish Disease Heritage III: the individual diseases

This article is the third and last in a series entitled The Finnish Disease Heritage I-III. All the 36 rare hereditary diseases belonging to this entity are described for clinical and molecular genetic purposes, based on the Finnish experience gathered over a period of half a century. In addition, five other diseases are mentioned. They may be included in the list of the "Finnish diseases" after adequate complementary studies.

Pregnancy and liver disease

Liver disease has an impact on women's health during pregnancy because of the complex interactions between the physiologic changes induced by pregnancy and the pathophysiologic changes of liver disease. In particular, liver diseases that predominantly afflict females, such as primary biliary cirrhosis and autoimmune hepatitis, pose a special problem for conception and management of pregnancy. Pregnancy, moreover, specifically is associated with several potentially life-threatening liver diseases. This article reviews comprehensively the impact of liver diseases on pregnancy and of pregnancy on liver function and liver disease.

Treatment of carnitine deficiency

Carnitine deficiency is a secondary complication of many inborn errors of metabolism. Pharmacological treatment with carnitine not only corrects the deficiency, it facilitates removal of accumulating toxic acyl intermediates and the generation of mitochondrial free coenzyme A (CoA). The United States Food and Drug Administration (US FDA) approved the use of carnitine for the treatment of inborn errors of metabolism in 1992. This approval was based on retrospective chart analysis of 90 patients, with 18 in the untreated cohort and 72 in the treated cohort. Efficacy was evaluated on the basis of clinical and biochemical findings. Compelling data included increased excretion of disease-specific acylcarnitine derivatives in a dose-response relationship, decreased levels of metabolites in the blood, and improved clinical status with decreased hospitalization frequency, improved growth and significantly lower mortality rates as compared to historical controls. Complications of carnitine treatment were few, with gastrointestinal disturbances and odour being the most frequent. No laboratory or clinical safety issues were identified. Intravenous carnitine preparations were also approved for treatment of secondary carnitine deficiency. Since only 25% of enteral carnitine is absorbed and gastrointestinal tolerance of high doses is poor, parenteral carnitine treatment is an appealing alternative therapeutic approach. In 7 patients treated long term with high-dose weekly to daily venous boluses of parenteral carnitine through a subcutaneous venous port, benefits included decreased frequency of decompensations, improved growth, improved muscle strength and decreased reliance on medical foods with liberalization of protein intake. Port infections were the most troubling complication. Theoretical concerns continue to be voiced that carnitine might result in fatal arrhythmias in patients with long-chain fat metabolism defects. No published clinical studies substantiate these concerns. Carnitine treatment of inborn errors of metabolism is a safe and integral part of the treatment regime for these disorders.