Neutral lipid storage disease with myopathy: clinicopathological and genetic features of nine Iranian patients

The rare disorder known as Neutral Lipid Storage Disease with Myopathy presents with a variety of clinical manifestations, including myopathy, cardiac dysfunction, and other organ complications. Early diagnosis is crucial due to the increased risk of cardiomyopathy. We describe the clinical, histopathological, muscle imaging, and genetic findings of nine neutral lipid storage myopathy patients. Proximal weakness and asymmetric involvement may suggest lipid storage myopathy. While skeletal muscle weakness was the main manifestation in our patients, one case presented only with hyperCKemia. Additionally, three patients had fertility issues, two suffered from diabetes mellitus, two had cardiomyopathy, and one had a history of hypothyroidism. Muscle histopathology revealed lipid depositions and rimmed vacuoles, prompting peripheral blood smears to detect Jordan Anomalies. All muscle biopsies and peripheral blood smear showed lipid droplets, rimmed vacuoles, and Jordan anomaly. Identifying PNPLA2 gene mutations is important for diagnosing neutral lipid storage myopathy; our cases showed some novel mutations. This study highlights the importance of early diagnosis and comprehensive evaluation in managing neutral lipid storage myopathy cases.

Ichthyosis, cataracts, and motor delay in an infant: A case of Chanarin-Dorfman syndrome

Chanarin-Dorfman syndrome (CDS) is a rare, autosomal recessive disorder of impaired triacylglycerol catabolism leading to cytoplasmic deposition of triglycerides in various cell types. We describe the case of an 8-month-old boy with cataracts, strabismus, motor delays, and an ichthyosiform rash since birth. Genetic testing revealed a pathogenic variant of the ABHD5 gene, suggestive of CDS, and further workup demonstrated hepatic steatosis and myopathy. His ichthyosis improved with initiation of a diet low in very long-chain fatty acids and medium-chain fatty acid supplementation.

Nailfold capillaroscopy reveals early peripheral microcirculation abnormalities in children affected by heterozygous familial hypercholesterolemia

BACKGROUND

nailfold capillaroscopy (NCF) is a non-invasive imaging technique to seek peripheral microcirculation abnormalities in children and adults. Familial hypercholesterolemia is a genetic disorder caused by mutations capable of increasing blood levels of low-density lipoproteins cholesterol (LDL-C), thus triggering early atherosclerosis. The study aims at evaluating peripheral microcirculation in children with heterozygous familial hypercholesterolemia (HeFH) by means of NFC in comparison with healthy peers and at searching for possible correlations between these abnormalities and patients' lipid panel.

METHODS

thirty-six HeFH patients were enrolled (13 males and 23 females. Mean age 8 ± 3 years; age range 3-13 years). They had increased levels of total cholesterol (237.9 ± 34.2 mg/dl) and LDL-C (154.2 ± 37.6 mg/dl). Both values were ≥95th gender and age specific centile. All the subjects in the study underwent NFC.

RESULTS

In 69.4 % of HeFH children nailfold capillaries were tortuous (p < 0.00001 compared to healthy controls). In 41.6 % the number of capillaries was markedly reduced (<7 capillaries/mm). The mean number of capillaries was 8.4 ± 2.6/mm in HeFH and 12.2 ± 1.4/mm in healthy controls (p < 0.00001). In 100 % of the sample size capillary blood flow was slowed down (p < 0.00001). In 50 % of the sample size a blood "sludge" phenomenon was seen (p < 0.00001). No gender differences were detected. Sludge phenomenon was seen only in those with LDL-C over 99th centile (p < 0.00001).

CONCLUSION

NCF allows the identification of an early peripheral microvascular dysfunction in HeFH children which is similar to that already seen in atherosclerotic disease. Prompt identification of these capillary abnormalities may be crucial in implementing early prevention measures.

ABHD5 frameshift deletion in Golden Retrievers with ichthyosis

Ichthyoses are hereditary skin disorders characterized by the formation of scales and defects in the outermost layer of the epidermis. In dogs, at least six different breed-specific ichthyoses including a relatively common PNPLA1-related autosomal recessive ichthyosis in Golden Retrievers are known. In this study, we investigated 14 Golden Retrievers with scales that were not homozygous for the mutant PNPLA1 allele suggesting a genetically distinct new form of ichthyosis. Histopathological examinations showed lamellar, orthokeratotic hyperkeratosis, and mildly hyperplastic epidermis that led to the diagnosis of a nonepidermolytic ichthyosis. Combined linkage and homozygosity mapping in 14 cases and 30 nonaffected family members delimited a critical interval of ∼12.7 Mb on chromosome 23. Whole-genome sequencing of an affected dog revealed a single protein-changing variant within this region that was not present in 795 control genomes. The identified variant is a 14 bp deletion in the ABHD5 gene (c.1006_1019del), leading to a frameshift and altering the last 14 codons p.(Asp336Serfs*6). The genotypes at this variant showed perfect cosegregation with the ichthyosis phenotype in a large family comprising 14 cases and 72 controls. ABHD5 encodes an acyltransferase required for lipid metabolism. In humans, variants in ABHD5 cause Chanarin-Dorfman syndrome, a neutral lipid storage disease with ichthyosis. Our data in dogs together with the knowledge on the effects of ABHD5 variants in humans strongly suggest ABHD5:c.1006_1019del as candidate causative genetic variant for a new canine form of ichthyosis, which we propose to designate as Golden Retriever ichthyosis type 2 (ICH2).

The spectrum of peripheral neuropathy in disorders of the mitochondrial trifunctional protein

Peripheral neuropathy is a known irreversible long-term complication of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) and mitochondrial trifunctional protein deficiency (MTPD), two inherited disorders of mitochondrial long-chain fatty acid oxidation. The underlying pathophysiology of neuropathy is still not fully understood. We report electrophysiological studies and neurological findings in a series of 8 LCHAD-deficient and 11 MTP-deficient patients. The median age at time of the study was 8.0 years (0.5-25 years). The overall prevalence of neuropathy was 58% with neuropathic symptoms being slightly more common in MTPD compared to LCHADD (70% vs 50%, respectively). Onset of neuropathy was significantly earlier in MTPD patients compared to LCHADD patients (median age at onset 4.7 vs 15.3 years, respectively, P = .047). In four patients, isolated peripheral neuropathy was the first and only presenting symptom, and in all four the diagnosis was missed by newborn screening. About half of the patients (45.5%) had a sensorimotor neuropathy, while 27.3% showed a pure motor form and another 27.3% an isolated sensory form. Despite early diagnosis by newborn screening and early initiation of therapy, peripheral neuropathy cannot be prevented in all patients with LCHADD/MTPD and has severe impact on the life of affected patients. Electrophysiology classifies LCHADD/MTPD neuropathy as axonal with secondary demyelination. A novel observation is that in patients with acute, fulminant onset of neuropathy, symptoms can be partly reversible. Further studies are needed to elucidate the underlying pathophysiology of axonal damage and possible therapeutic targets.

MTP deficiency caused by HADHB mutations: Pathophysiology and clinical manifestations

Mutations in the HADHB gene lead to Mitochondrial Trifunctional Protein (MTP) deficiency. MTP deficiency is a rare autosomal recessive disorder affecting long-chain fatty acid oxidation. Patients affected by MTP deficiency are unable to metabolize long-chain fatty-acids and suffer a variety of symptoms exacerbated during fasting. The three phenotypes associated with complete MTP deficiency are an early-onset cardiomyopathy and early death, an intermediate form with recurrent hypoketotic hypoglycemia and a sensorimotor neuropathy with episodic rhabdomyolysis with small amount of residual enzyme activities. This review aims to discuss the pathophysiological mechanisms and clinical manifestations of each phenotype, which appears different and linked to HADHB expression levels. Notably, the pathophysiology of the sensorimotor neuropathy is relatively unknown and we provide a hypothesis on the qualitative aspect of the role of acylcarnitine buildup in Schwann cells in MTP deficiency patients. We propose that acylcarnitine may exit the Schwann cell and alter membrane properties of nearby axons leading to axonal degeneration based on recent findings in different metabolic disorders.

Sitosterolemia: Twenty Years of Discovery of the Function of ABCG5ABCG8

Sitosterolemia is a lipid disorder characterized by the accumulation of dietary xenosterols in plasma and tissues caused by mutations in either ABCG5 or ABCG8. ABCG5 ABCG8 encodes a pair of ABC half transporters that form a heterodimer (G5G8), which then traffics to the surface of hepatocytes and enterocytes and promotes the secretion of cholesterol and xenosterols into the bile and the intestinal lumen. We review the literature from the initial description of the disease, the discovery of its genetic basis, current therapy, and what has been learned from animal, cellular, and molecular investigations of the transporter in the twenty years since its discovery. The genomic era has revealed that there are far more carriers of loss of function mutations and likely pathogenic variants of ABCG5 ABCG8 than previously thought. The impact of these variants on G5G8 structure and activity are largely unknown. We propose a classification system for ABCG5 ABCG8 mutants based on previously published systems for diseases caused by defects in ABC transporters. This system establishes a framework for the comprehensive analysis of disease-associated variants and their impact on G5G8 structure-function.

De Novo Development of mtDNA Deletion Due to Decreased POLG and SSBP1 Expression in Humans

Defects in the mitochondrial genome (mitochondrial DNA (mtDNA)) are associated with both congenital and acquired disorders in humans. Nuclear-encoded DNA polymerase subunit gamma (POLG) plays an important role in mtDNA replication, and proofreading and mutations in POLG have been linked with increased mtDNA deletions. SSBP1 is also a crucial gene for mtDNA replication. Here, we describe a patient diagnosed with Pearson syndrome with large mtDNA deletions that were not detected in the somatic cells of the mother. Exome sequencing was used to evaluate the nuclear factors associated with the patient and his family, which revealed a paternal POLG mutation (c.868C > T) and a maternal SSBP1 mutation (c.320G > A). The patient showed lower POLG and SSBP1 expression than his healthy brothers and the general population of a similar age. Notably, c.868C in the wild-type allele was highly methylated in the patient compared to the same site in both his healthy brothers. These results suggest that the co- deficient expression of POLG and SSBP1 genes could contribute to the development of mtDNA deletion.

Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol Transporter

The heterodimeric ATP-binding cassette (ABC) sterol transporter, ABCG5/G8, is responsible for the biliary and transintestinal secretion of cholesterol and dietary plant sterols. Missense mutations of ABCG5/G8 can cause sitosterolemia, a loss-of-function disorder characterized by plant sterol accumulation and premature atherosclerosis. A new molecular framework was recently established by a crystal structure of human ABCG5/G8 and reveals a network of polar and charged amino acids in the core of the transmembrane domains, namely, a polar relay. In this study, we utilize genetic variants to dissect the mechanistic role of this transmembrane polar relay in controlling ABCG5/G8 function. We demonstrated a sterol-coupled ATPase activity of ABCG5/G8 by cholesteryl hemisuccinate (CHS), a relatively water-soluble cholesterol memetic, and characterized CHS-coupled ATPase activity of three loss-of-function missense variants, R543S, E146Q, and A540F, which are respectively within, in contact with, and distant from the polar relay. The results established an in vitro phenotype of the loss-of-function and missense mutations of ABCG5/G8, showing significantly impaired ATPase activity and loss of energy sufficient to weaken the signal transmission from the transmembrane domains. Our data provide a biochemical evidence underlying the importance of the polar relay and its network in regulating the catalytic activity of ABCG5/G8 sterol transporter.

Subclinical effects of long-chain fatty acid β-oxidation deficiency on the adult heart: A case-control magnetic resonance study

Cardiomyopathy can be a severe complication in patients with long-chain fatty acid β-oxidation disorders (LCFAOD), particularly during episodes of metabolic derangement. It is unknown whether latent cardiac abnormalities exist in adult patients. To investigate cardiac involvement in LCFAOD, we used proton magnetic resonance imaging (MRI) and spectroscopy (¹ H-MRS) to quantify heart function, myocardial tissue characteristics, and myocardial lipid content in 14 adult patients (two with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD); four with carnitine palmitoyltransferase II deficiency (CPT2D); and eight with very long-chain acyl-CoA dehydrogenase deficiency (VLCADD)) and 14 gender-, age-, and BMI-matched control subjects. Examinations included cine MRI, MR tagging, native myocardial T₁ and T₂ mapping, and localized ¹ H-MRS at 3 Tesla. Left ventricular (LV) myocardial mass (P = .011) and the LV myocardial mass-to-volume ratio (P = .008) were higher in patients, while ejection fraction (EF) was normal (P = .397). LV torsion was higher in patients (P = .026), whereas circumferential shortening was similar compared with controls (P = .875). LV hypertrophy was accompanied by high myocardial T₁ values (indicative of diffuse fibrosis) in two patients, and additionally a low EF in one case. Myocardial lipid content was similar in patients and controls. We identified subclinical morphological and functional differences between the hearts of LCFAOD patients and matched control subjects using state-of-the-art MR methods. Our results suggest a chronic cardiac disease phenotype and hypertrophic LV remodeling of the heart in LCFAOD, potentially triggered by a mild, but chronic, energy deficiency, rather than by lipotoxic effects of accumulating lipid metabolites.

Nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD): An evidence- and consensus-based approach

The nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD) is the fourth in a series of web-based guidelines focusing on the diet treatment for inherited metabolic disorders and follows previous publication of guidelines for maple syrup urine disease (2014), phenylketonuria (2016) and propionic acidemia (2019). The purpose of this guideline is to establish harmonization in the treatment and monitoring of individuals with VLCAD of all ages in order to improve clinical outcomes. Six research questions were identified to support guideline development on: nutrition recommendations for the healthy individual, illness management, supplementation, monitoring, physical activity and management during pregnancy. This report describes the methodology used in its development including review, critical appraisal and abstraction of peer-reviewed studies and unpublished practice literature; expert input through two Delphi surveys and a nominal group process; and external review from metabolic physicians and dietitians. It includes the summary statements of the nutrition management recommendations for each research question, followed by a standardized rating based on the strength of the evidence. Online, open access of the full published guideline allows utilization by health care providers, researchers and collaborators who advise, advocate and care for individuals with VLCAD and their families and can be accessed from the Genetic Metabolic Dietitians International (https://GMDI.org) and Southeast Regional Genetics Network (https://southeastgenetics.org/ngp) websites.

Effects of fasting, feeding and exercise on plasma acylcarnitines among subjects with CPT2D, VLCADD and LCHADD/TFPD

BACKGROUND

The plasma acylcarnitine profile is frequently used as a biochemical assessment for follow-up in diagnosed patients with fatty acid oxidation disorders (FAODs). Disease specific acylcarnitine species are elevated during metabolic decompensation but there is clinical and biochemical heterogeneity among patients and limited data on the utility of an acylcarnitine profile for routine clinical monitoring.

METHODS

We evaluated plasma acylcarnitine profiles from 30 diagnosed patients with long-chain FAODs (carnitine palmitoyltransferase-2 (CPT2), very long-chain acyl-CoA dehydrogenase (VLCAD), and long-chain 3-hydroxy acyl-CoA dehydrogenase or mitochondrial trifunctional protein (LCHAD/TFP) deficiencies) collected after an overnight fast, after feeding a controlled low-fat diet, and before and after moderate exercise. Our purpose was to describe the variability in this biomarker and how various physiologic states effect the acylcarnitine concentrations in circulation.

RESULTS

Disease specific acylcarnitine species were higher after an overnight fast and decreased by approximately 60% two hours after a controlled breakfast meal. Moderate-intensity exercise increased the acylcarnitine species but it varied by diagnosis. When analyzed for a genotype/phenotype correlation, the presence of the common LCHADD mutation (c.1528G > C) was associated with higher levels of 3-hydroxyacylcarnitines than in patients with other mutations.

CONCLUSIONS

We found that feeding consistently suppressed and that moderate intensity exercise increased disease specific acylcarnitine species, but the response to exercise was highly variable across subjects and diagnoses. The clinical utility of routine plasma acylcarnitine analysis for outpatient treatment monitoring remains questionable; however, if acylcarnitine profiles are measured in the clinical setting, standardized procedures are required for sample collection to be of value.

Familial hypercholesterolemia: is it time to separate monogenic from polygenic familial hypercholesterolemia?

PURPOSE OF REVIEW

This review explores the concepts of monogenic and the so-called polygenic familial hypercholesterolemia and how the identification of familial hypercholesterolemia as a monogenic condition and its separation from polygenic primary hypercholesterolemia may have implications for clinical practice.

RECENT FINDINGS

Through genetic testing, a mutation in any of the three known autosomal dominant familial hypercholesterolemia-causing genes is found in 60-80% of cases with a clinical diagnosis of definite familial hypercholesterolemia. As individuals with a polygenic basis for their hypercholesterolemia do not follow the same inheritance pattern observed in monogenic familial hypercholesterolemia, the use of family-based cascade screening in individuals with a polygenic origin is not recommend, as only 30% of relatives have an elevated LDL-C compared to the 50% in monogenic families. The presence of a causative monogenic mutation associates the highest cardiovascular risk vs. not having a mutation or having a polygenic background, providing prognostic information independent of LDL-C. It may also help assess intensity of interventions. Treatment adherence also seems to be higher after monogenic confirmation of hypercholesterolemia.

SUMMARY

Knowledge about the genetic status of an individual with clinical familial hypercholesterolemia (monogenic vs. polygenic) can provide a more informed understanding to evaluating risk, managing disease and opportunities for screening strategies.

Clinical findings and autophagic pathology in neutral lipid storage disease with myopathy

Neutral lipid storage disease with myopathy (NLSDM) is a triglyceride metabolic disorder caused by defects of adipose triglyceride lipases (ATGL). The coexistence of lipid vacuoles and rimmed vacuoles in the myofibers is a characteristic pathological change in some NLSDM cases. However, it has not been explored whether autophagic abnormalities exist in the NLSDM myofibers with rimmed vacuole. Herein, we report that 5 patients with NLSDM initially presented with muscle weakness in the right arm related to long-term physical efforts, then developed muscle weakness of other limbs. Pathogenic mutations in the PNPLA2 gene were identified in all patients. Myopathological analysis showed a coexistence of massive lipid vacuoles and rimmed vacuoles, which was not associated with the age of onset or mutation sites, but closely related to the severity of muscle degeneration. The rimmed vacuoles showed strong immunopositivity to autophagic markers, but were negative to apoptotic markers. Significant immunoreactivity of p62 was observed in the rimmed vacuoles, while the lysosomal marker LAMP1 was severely decreased. Our study expanded the clinical and genetic spectrum of NLSDM. Loss of ATGL activity in muscle fibers with rimmed vacuoles induced a marked increase in autophagic formation, but lowered down the turnover of autolysosomes due to malfunction of lysosomes.

Impaired Fat Oxidation During Exercise in Long-Chain Acyl-CoA Dehydrogenase Deficiency Patients and Effect of IV-Glucose

CONTEXT

Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency (LCHADD) affects oxidation of long-chain fatty acids (FAO) and is associated with risk of metabolic crises and episodic rhabdomyolysis.

CASE DESCRIPTION

We present the cases of two patients with LCHADD. Patient 1 (male, 26 years old) was severely affected by muscle weakness and neuropathy. He was diagnosed at age 20 years and was nonadherent to standard dietary management. MRI revealed significant fat replacement of muscle in both calves. Patient 2 (female, 15 years old) was diagnosed at age 1 year. She had no muscle weakness and was compliant with the recommended diet. Compared with healthy persons, both patients had reduced FAO and palmitate oxidation, measured with indirect calorimetry and stable isotope technique during a submaximal cycle ergometer test. Patient 2 had some residual capacity to increase FAO and a compensatory higher carbohydrate oxidation, which ensured a near-normal exercise capacity. Patient 1 was unable to increase FAO and could only complete 23 minutes of exercise, vs 60 minutes by patient 2 and healthy persons. In both, 10% IV infusion of glucose (IV-glucose) during exercise increased carbohydrate oxidation slightly, but endurance was not improved, which likely relates to the fixed weakness in patient 1 and because the residual FAO was suppressed by the glucose infusion in both.

CONCLUSION

The two patients illustrate that FAO is impaired and carbohydrate oxidation is elevated during exercise in patients affected by LCHADD, compared with healthy persons, but IV-glucose has no beneficial effect on exercise tolerance in LCHADD.

Clinical features and genetic analysis of childhood sitosterolemia: Two case reports and literature review

RATIONALE

Sitosterolemia is a rare autosomal recessive disorder of dyslipidemia due to mutations of genes ABCG5 and ABCG8, leading to highly elevated plasma levels of plant sterols and expanded body pools of cholesterol.

PATIENT CONCERNS

We present a 9-year-old and a 7-year-old Chinese boy with hypercholesterolemia and xanthomas of sitosterolemia due to ABCG5 gene mutations. We also make a literature review of another 30 sitosterolemic children cases that have been reported with virulence ABCG5 gene mutations.

DIAGNOSIS

We took peripheral blood samples from 2 patients and their parents to conduct genetic analysis by next-generation sequencing (NGS) technologies.

INTERVENTIONS

The 2 patients received dietary modifications without pharmaceuticals treatment.

OUTCOMES

A c.1166G>A (Arg389His) homozygosis mutation in exon 9 was observed in case 1, whereas a c.751C>T (Gln251*) homozygosis mutation in exon 6 was found in case 2. Literature review found another 30 pediatric cases with sitosterolemia due to ABCG5 gene mutation. The lipid profile was normalized and xanthomas got smaller with combined therapy of a combined low-cholesterol and low-phytosterols diet.

LESSONS

These suggested that in patients (especially Asian patients) with multiple xanthomas, severe hypercholesterolemia, or elevated low-density lipoprotein-cholesterol, sitosterolemia should be considered in the differential diagnosis. Early diagnosis is important, and restriction of both cholesterol and phytosterols diet should suggested for these patients.

Neutral lipid storage disease with myopathy: Further phenotypic characterization of a rare PNPLA2 variant

Neutral lipid storage disease with myopathy is a rare disorder of lipid metabolism caused by variants in the Patatin-Like Phospholipase Domain Containing 2 (PNPLA2) gene. Diagnosis is often delayed due to variable presentations, which is of concern due to increased risk of cardiomyopathy. Better phenotype-genotype characterization is necessary to improve speed and accuracy of diagnosis. Here, we describe a 32-year-old woman of Hmong descent with progressive muscle pain and weakness who had a muscle biopsy with characteristic features of a lipid storage myopathy. Genetic testing revealed a homozygous splice site variant in PNPLA2, c.757 + 1G > T. This case, in combination with the one previously reported case of this PNPLA2 variant, also in a family of Hmong descent, suggests this particular variant may be unique to the Hmong population, a Southeast Asian minority group living in the United States, who immigrated to the United States as refugees after the Vietnam War.

Investigating the link of ACAD10 deficiency to type 2 diabetes mellitus

The Native American Pima population has the highest incidence of insulin resistance (IR) and type 2 diabetes mellitus (T2DM) of any reported population, but the pathophysiologic mechanism is unknown. Genetic studies in Pima Indians have linked acyl-CoA dehydrogenase 10 (ACAD10) gene polymorphisms, among others, to this predisposition. The gene codes for a protein with a C-terminus region that is structurally similar to members of a family of flavoenzymes-the acyl-CoA dehydrogenases (ACADs)-that catalyze α,β-dehydrogenation reactions, including the first step in mitochondrial FAO (FAO), and intermediary reactions in amino acids catabolism. Dysregulation of FAO and an increase in plasma acylcarnitines are recognized as important in the pathophysiology of IR and T2DM. To investigate the deficiency of ACAD10 as a monogenic risk factor for T2DM in human, an Acad-deficient mouse was generated and characterized. The deficient mice exhibit an abnormal glucose tolerance test and elevated insulin levels. Blood acylcarnitine analysis shows an increase in long-chain species in the older mice. Nonspecific variable pattern of elevated short-terminal branch-chain acylcarnitines in a variety of tissues was also observed. Acad10 mice accumulate excess abdominal adipose tissue, develop an early inflammatory liver process, exhibit fasting rhabdomyolysis, and have abnormal skeletal muscle mitochondria. Our results identify Acad10 as a genetic determinant of T2DM in mice and provide a model to further investigate genetic determinants for insulin resistance in humans.

Short-chain acyl-CoA dehydrogenase deficiency: from gene to cell pathology and possible disease mechanisms

Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is an inherited disorder of mitochondrial fatty acid oxidation that is characterized by the presence of increased butyrylcarnitine and ethylmalonic acid (EMA) concentrations in plasma and urine. Individuals with symptomatic SCADD may show relatively severe phenotype, while the majority of those who are diagnosed through newborn screening by tandem mass spectrometry may remain asymptomatic. As such, the associated clinical symptoms are very diverse, ranging from severe metabolic or neuromuscular disabilities to asymptomatic. Molecular analysis of affected individuals has identified rare gene variants along with two common gene variants, c.511C > T and c.625G > A. In vitro studies have demonstrated that the common variants as well as the great majority of rare variants, which are missense variants, impair folding, that may lead to toxic accumulation of the encoded protein, and/or metabolites, and initiate excessive production of ROS and chronic oxidative stress. It has been suggested that this cell toxicity in combination with yet unknown factors can trigger disease development. This association and the full implications of SCADD are not commonly appreciated. Accordingly, there is a worldwide discussion of the relationship of clinical manifestation to SCADD, and whether SCAD gene variants are disease associated at all. Therefore, SCADD is not part of the newborn screening programs in most countries, and consequently many patients with SCAD gene variants do not get a diagnosis and the possibilities to be followed up during development.

Generation of induced Pluripotent Stem Cells as disease modelling of NLSDM

Neutral Lipid Storage Disease with Myopathy (NLSDM) is a rare defect of triacylglycerol metabolism, characterized by the abnormal storage of neutral lipid in organelles known as lipid droplets (LDs). The main clinical features are progressive myopathy and cardiomyopathy. The onset of NLSDM is caused by autosomal recessive mutations in the PNPLA2 gene, which encodes adipose triglyceride lipase (ATGL). Despite its name, this enzyme is present in a wide variety of cell types and catalyzes the first step in triacylglycerol lipolysis and the release of fatty acids. Here, we report the derivation of NLSDM-induced pluripotent stem cells (NLSDM-iPSCs) from fibroblasts of two patients carrying different PNPLA2 mutations. The first patient was homozygous for the c.541delAC, while the second was homozygous for the c.662G>C mutation in the PNPLA2 gene. We verified that the two types of NLSDM-iPSCs possessed properties of embryonic-like stem cells and could differentiate into the three germ layers in vitro. Immunofluorescence analysis revealed that iPSCs had an abnormal accumulation of triglycerides in LDs, the hallmark of NLSDM. Furthermore, NLSDM-iPSCs were deficient in long chain fatty acid lipolysis, when subjected to a pulse chase experiment with oleic acid. Collectively, these results demonstrate that NLSDM-iPSCs are a promising in vitro model to investigate disease mechanisms and screen drug compounds for NLSDM, a rare disease with few therapeutic options.

Triheptanoin treatment in patients with pediatric cardiomyopathy associated with long chain-fatty acid oxidation disorders

Long-chain fatty acid oxidation disorders (LC-FAOD) can cause cardiac hypertrophy and cardiomyopathy, often presenting in infancy, typically leading to death or heart transplant despite ongoing treatment. Previous data on triheptanoin treatment of cardiomyopathy in LC-FAOD suggested a clinical benefit on heart function during acute failure. An additional series of LC-FAOD patients with critical emergencies associated with cardiomyopathy was treated with triheptanoin under emergency treatment or compassionate use protocols. Case reports from 10 patients (8 infants) with moderate or severe cardiomyopathy associated with LC-FAOD are summarized. The majority of these patients were detected by newborn screening, with follow up confirmatory testing, including mutation analysis; all patients were managed with standard treatment, including medium chain triglyceride (MCT) oil. While on this regimen, they presented with acute heart failure requiring hospitalization and cardiac support (ventilation, ECMO, vasopressors) and, in some cases, resuscitation. The patients discontinued MCT oil and began treatment with triheptanoin, an investigational drug. Triheptanoin is expected to provide anaplerotic metabolites, to replace deficient TCA cycle intermediates and improve effective energy metabolism. Cardiac function was measured by echocardiography and ejection fraction (EF) was assessed. EF was moderately to severely impaired prior to triheptanoin treatment, ranging from 12-45%. Improvements in EF began between 2 and 21days following initiation of triheptanoin, and peaked at 33-71%, with 9 of 10 patients achieving EF in the normal range. Continued treatment was associated with longer-term stabilization of clinical signs of cardiomyopathy. The most common adverse event observed was gastrointestinal distress. Of the 10 patients, 7 have continued on treatment, 1 elected to discontinue due to tolerability issues, and 2 patients died from other causes. Two of the case histories illustrate that cardiomyopathy may also develop later in childhood and/or persist into adulthood. Overall, the presented cases suggest a therapeutic effect of triheptanoin in the management of acute cardiomyopathy associated with LC-FAOD.

Xyloketal B attenuates atherosclerotic plaque formation and endothelial dysfunction in apolipoprotein e deficient mice

Our previous studies demonstrated that xyloketal B, a novel marine compound with a unique chemical structure, has strong antioxidant actions and can protect against endothelial injury in different cell types cultured in vitro and model organisms in vivo. The oxidative endothelial dysfunction and decrease in nitric oxide (NO) bioavailability are critical for the development of atherosclerotic lesion. We thus examined whether xyloketal B had an influence on the atherosclerotic plaque area in apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet and investigated the underlying mechanisms. We found in our present study that the administration of xyloketal B dose-dependently decreased the atherosclerotic plaque area both in the aortic sinus and throughout the aorta in apoE-/- mice fed a high-fat diet. In addition, xyloketal B markedly reduced the levels of vascular oxidative stress, as well as improving the impaired endothelium integrity and NO-dependent aortic vasorelaxation in atherosclerotic mice. Moreover, xyloketal B significantly changed the phosphorylation levels of endothelial nitric oxide synthase (eNOS) and Akt without altering the expression of total eNOS and Akt in cultured human umbilical vein endothelial cells (HUVECs). Here, it increased eNOS phosphorylation at the positive regulatory site of Ser-1177, while inhibiting phosphorylation at the negative regulatory site of Thr-495. Taken together, these findings indicate that xyloketal B has dramatic anti-atherosclerotic effects in vivo, which is partly due to its antioxidant features and/or improvement of endothelial function.

The history of Autosomal Recessive Hypercholesterolemia (ARH). From clinical observations to gene identification

The most frequent form of monogenic hypercholesterolemia, also known as Familial Hypercholesterolemia (FH), is characterized by plasma accumulation of cholesterol transported in Low Density Lipoproteins (LDLs). FH has a co-dominant transmission with a gene-dosage effect. FH heterozygotes have levels of plasma LDL-cholesterol (LDL-C) twice normal and present xanthomas and coronary heart disease (CHD) in adulthood. In rare FH homozygotes plasma LDL-C level is four times normal, while xanthomas and CHD are present from infancy. Most FH patients are carriers of mutations of the LDL receptor (LDLR); a minority of them carry either mutations in the Apolipoprotein B (ApoB), the protein constituent of LDLs which is the ligand for LDLR, or gain of function mutations of PCSK9, the protein responsible for the intracellular degradation of the LDLR. From 1970 to the mid 90s some publications described children with the clinical features of homozygous FH, who were born from normocholesterolemic parents, strongly suggesting a recessive transmission of FH. In these patients the involvement of LDLR and APOB genes was excluded. Interestingly, several patients were identified in the island of Sardinia (Italy), whose population has a peculiar genetic background due to geographical isolation. In this review, starting from the early descriptions of patients with putative recessive hypercholesterolemia, we highlight the milestones that led to the identification of a novel gene involved in LDL metabolism and the characterization of its encoded protein. The latter turned out to be an adaptor protein required for the LDLR-mediated endocytosis of LDLs in hepatocytes. The loss of function of this protein is the cause of Autosomal Recessive Hypercholesterolemia (ARH).

Muscle MRI in patients with long-chain fatty acid oxidation disorders

INTRODUCTION

Muscle magnetic resonance imaging (MRI) is a useful tool for visualizing abnormalities in neuromuscular disorders. The value of muscle MRI has not been studied in long-chain fatty acid oxidation (lcFAO) disorders. LcFAO disorders may present with metabolic myopathy including episodic rhabdomyolysis.

OBJECTIVE

To investigate whether lcFAO disorders are associated with muscle MRI abnormalities.

METHODS

Lower body MRI was performed in 20 patients with lcFAO disorders, i.e. three carnitine palmitoyltransferase 2 deficiency (CPT2D), 12 very long-chain acyl-CoA dehydrogenase deficiency (VLCADD), three mitochondrial trifunctional protein deficiency (MTPD) and two isolated long-chain hydroxyacyl-CoA dehydrogenase deficiency (LCHADD).

RESULTS

At the time of MRI, four patients had muscle weakness, 14 had muscle pain and 13 were exercise intolerant. Median creatine kinase (CK) level of patients at the day of MRI was 398 U/L (range 35-12,483). T1W and STIR signal intensity (SI) were markedly increased in MTPD patients from girdle to lower leg. VLCADD patients showed predominantly proximal T1W SI changes, whereas LCHADD patients mostly showed distal T1W SI changes. Prominent STIR weighted signal intensity increases of almost all muscle groups were observed in patients with VLCADD and LCHADD with very high CK (>11.000) levels.

CONCLUSIONS AND RELEVANCE

lcFAO disorders are associated with specific patterns of increased T1W and STIR signal intensity. These patterns may reflect lipid accumulation and inflammation secondary to lcFAO defects and progressive muscle damage. Future studies are needed to investigate whether muscle MRI might be a useful tool to monitor disease course and to study pathogenesis of lcFAO related myopathy.

Complex changes in the liver mitochondrial proteome of short chain acyl-CoA dehydrogenase deficient mice

Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is an autosomal recessive inborn error of metabolism that leads to the impaired mitochondrial fatty acid β-oxidation of short chain fatty acids. It is heterogeneous in clinical presentation including asymptomatic in most patients identified by newborn screening. Multiple mutations have been identified in patients; however, neither clear genotype-phenotype relationships nor a good correlation between genotype and current biochemical markers for diagnosis has been identified. The definition and pathophysiology of this deficiency remain unclear. To better understand this disorder at a global level, quantitative alterations in the mitochondrial proteome in SCAD deficient mice were examined using a combined proteomics approach: two-dimensional gel difference electrophoresis (2DIGE) followed by protein identification with MALDI-TOF/TOF and iTRAQ labeling followed by nano-LC/MALDI-TOF/TOF. We found broad mitochondrial dysfunction in SCAD deficiency. Changes in the levels of multiple energy metabolism related proteins were identified indicating that a more complex mechanism for development of symptoms may exist. Affected pathways converge on disorders with neurologic symptoms, suggesting that even asymptomatic individuals with SCAD deficiency may be at risk to develop more severe disease. Our results also identified a pattern associated with hepatotoxicity implicated in mitochondrial dysfunction, fatty acid metabolism, decrease of depolarization of mitochondria and mitochondrial membranes, and swelling of mitochondria, demonstrating that SCAD deficiency relates more directly to mitochondrial dysfunction and alteration of fatty acid metabolism. We propose several candidate molecules that may serve as markers for recognition of clinical risk associated with this disorder.

Proteomic investigation of cultivated fibroblasts from patients with mitochondrial short-chain acyl-CoA dehydrogenase deficiency

Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is a rare inherited autosomal recessive disorder with not yet well established mechanisms of disease. In the present study, the mitochondrial proteome of five symptomatic patients homozygous for missense variations in the SCAD gene ACADS was investigated in an extensive large-scale proteomic study to map protein perturbations linked to the disease. Fibroblast cultures of patient cells homozygous for either c.319C>T/p.Arg107Cys (n=2) or c.1138C>T/p.Arg380Trp (n=3) in ACADS, and healthy controls (normal human dermal fibroblasts), were studied. The mitochondrial proteome derived from these cultures was analyzed by label free proteomics using high mass accuracy nanoliquid chromatography tandem mass spectrometry (nanoLC-MS/MS). More than 300 mitochondrial proteins were identified and quantified. Thirteen proteins had significant alteration in protein levels in patients carrying variation c.319C>T in ACADS compared to controls and they belonged to various pathways, such as the antioxidant system and amino acid metabolism. Twenty-two proteins were found significantly altered in patients carrying variation c.1138C>T which included proteins associated with fatty acid β-oxidation, amino acid metabolism and protein quality control system. Three proteins were found significantly regulated in both patient groups: adenylate kinase 4 (AK4), nucleoside diphosphate kinase A (NME1) and aldehyde dehydrogenase family 4 member A1 (ALDH4A1). Proteins AK4 and NME1 deserve further investigation because of their involvement in energy reprogramming, cell survival and proliferation with relevance for SCAD deficiency and related metabolic disorders.

[Mutation analysis of a family with 2-Methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency]

OBJECTIVE

The aim of this study was to explore the genetic features of a family with 2-methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency (MHBDD) which may provide the basis for the diagnosis and genetic counseling.

METHOD

Clinical data of the proband was collected, total RNA and genomic DNA were extracted from the peripheral blood. The whole coding region of the ACAT1 gene was amplified by RT-PCR. 5' noncoding region of the ACAT1 gene and all 6 exons and flanking intron regions of the HADH2 gene were amplified by PCR. All amplification products were directly sequenced and compared with the reference sequence.

RESULT

(1) The patient was a one-year-old boy who presented with psychomotor retardation and astasia when he was admitted to the hospital. Biochemical test revealed slight hyperlactatemia (3.19 mmol/L) and magnetic resonance imaging showed delayed myelination. 2-Methylacetoacetyl-CoA thiolase deficiency was suggested by gas chromatography-mass spectrometry. (2) There was no mutation in the ACAT1 gene and a hemizygous missense mutation c.388C > T was found in the 4 exon of the HADH2 gene which resulted in p. R130C. Proband's mother was the heterozygote and the father was normal.

CONCLUSION

This is the first report on MHBDD patient and HADH2 mutation in China. p.R130C is responsible for the pathogenesis of the disease in the infant.

Metabolic consequences of adipose triglyceride lipase deficiency in humans: an in vivo study in patients with neutral lipid storage disease with myopathy

CONTEXT

The role of adipose triglyceride lipase (ATGL) in intermediate substrates metabolism has not been fully elucidated in humans.

OBJECTIVE

Our objective was to evaluate the consequences of ATGL deficiency on body fat distribution, insulin sensitivity, fatty acids metabolism, and energy substrate utilization.

DESIGN AND SETTING

Body composition and organ fat content were measured by bioimpedance and (1)H nuclear magnetic resonance spectroscopy; heart glucose metabolism by [(18)F]deoxyglucose positron emission tomography and insulin sensitivity and β-cell function by oral glucose tolerance and 2-step euglycemic-hyperinsulinemic clamp. Lipolysis ([(2)H5]glycerol turnover) and indirect calorimetry were evaluated at fasting, after oral glucose load, during the clamp, and also during an iv epinephrine infusion. These metabolic investigations were carried out during hospitalization.

PATIENTS

Three patients affected by neutral lipid storage disease with myopathy (NLSDM) due to homozygosity for loss-of-function mutations in the ATGL gene and 6 sex-, age-, and body mass index-matched controls were studied.

RESULTS

As expected, NLSDM patients showed diffuse, although heterogeneous, fat infiltration in skeletal muscles associated with increased visceral fat. Although heart and liver were variably affected, fat content in the pancreas was increased in all patients. Compared with healthy controls, NLSDM patients showed impaired insulin response to glucose possibly related to the severe pancreatic steatosis, preserved whole-body insulin sensitivity, and a shift toward glucose metabolism in the heart. Fasting nonesterified fatty acid concentrations as well as basal lipolytic rates and the antilipolytic effect of insulin were normal in NLSDM patients, whereas the lipolytic effect of norepinephrine was impaired. Finally, no significant abnormality in the respiratory quotient was noted in NLSDM patients.

CONCLUSIONS

In humans, ATGL has a remarkable effect on cellular lipid droplet handling, and its lack causes both perivisceral, skeletal muscle, and pancreas fat accumulation; in contrast, the impact on whole-body insulin sensitivity and fatty acid metabolism is minor.

Disruption of redox homeostasis in cerebral cortex of developing rats by acylcarnitines accumulating in medium-chain acyl-CoA dehydrogenase deficiency

Medium-chain fatty acids and acylcarnitines accumulate in medium-chain acyl-CoA dehydrogenase deficiency (MCADD), the most frequent fatty acid oxidation defect clinically characterized by episodic crises with vomiting, seizures and coma. Considering that the pathophysiology of the neurological symptoms observed in MCADD is poorly known and, to our knowledge, there is no report on the involvement of acylcarnitines in the brain damage presented by the affected patients, the objective of the present study was to investigate the in vitro effects of hexanoylcarnitine (HC), octanoylcarnitine, decanoylcarnitine (DC) and cis-4-decenoylcarnitine (cDC) at concentrations varying from 0.01 to 1.0mM on important oxidative stress parameters in cerebral cortex of young rats. HC, DC and cDC significantly induced lipid peroxidation, as determined by increased thiobarbituric acid-reactive substances (TBA-RS) values. In addition, carbonyl formation was significantly augmented and sulfhydryl content diminished by DC, reflecting induction of protein oxidative damage. HC, DC and cDC also decreased glutathione (GSH) levels, the most important brain antioxidant defense. Furthermore, DC-induced elevation of TBA-RS values and decrease of GSH levels were prevented by the free radical scavengers melatonin and α-tocopherol, indicating the involvement of reactive oxygen species in these effects. We also found that l-carnitine itself did not induce lipid and protein oxidative damage, neither reduced the antioxidant defenses. Our present data show that the major medium-chain acylcarnitines accumulating in MCADD elicit oxidative stress in rat brain. It is therefore presumed that these compounds may be involved to a certain extent in the pathogenesis of the neurologic dysfunction of MCADD.

Macrothrombocytopenia/Stomatocytosis Specially Associated With Phytosterolemia

Phytosterolemia is a rare autosomal recessive disease of plant sterol metabolism, the pathophysiological features of which are high plasma levels of plant sterols and xanthomatosis caused by mutations of ABCG5 and ABCG8 genes, and the combination of hemolysis and macrothrombocytopenia is an unusual clinical manifestation. All the patients of the 3 unrelated phytosterolemia first presented with prominent macrothrombocytopenia and stomatocytosis. They were either homozygous or compound heterozygous for ABCG5/ ABCG8 gene mutations and had significantly elevated serum plant sterols levels quantified using high-performance liquid chromatography. The in vitro study demonstrated that sitosterol can cause changes in shape and osmotic fragility of red blood cells. These findings suggest that macrothrombocytopenia and stomatocytosis could be initial and main features in some patients with phytosterolemia and that serum phytosterols and relevant genes should be analyzed in patients whose macrothrombocytopenia and/or stomatocytosis are unexplained, especially whose parents are of consanguineous marriage.

[Clinical and gene study of three pedigrees of phytosterolemia associated with macrothrombocytopenia and hemolysis]

OBJECTIVE

To study the clinical features and ABCG5/ABCG8 gene mutations of three pedigrees of phytosterolemia presented with macrothrombocytopenia and hemolysis.

METHODS

Erythrocyte and platelet morphology were examined under light microscope. Plasma sterol levels were measured by high pressure/performance liquid chromatography method. All of ABCG5 and ABCG8 exons and intron-exon boundaries were directly sequenced to identify mutations, the corresponding gene mutation sites of three families members and healthy individuals were detected.

RESULTS

All the patients presented macrothrombocytopenia, hemolysis, splenomegaly and xanthomas. The blood smears showed large platelets, some as large as erythrocytes, and abnormal erythrocyte shapes, such as stomatocytes. Plasma concentrations of phytosterols, especially sitosterol were markedly elevated (30 fold) in the affected patients. Four mutations were identified in these three pedigrees, ABCG5 C20896T (R446X) and A20883G, ABCG8 del43683-43724 and del1938C-1939G/ins1938T. The latter three were novel mutations reported for the first time.

CONCLUSIONS

Phytosterolemia associated with macrothrombocytopenia and hemolysis is a new subtype of this disease. Plasma phytosterols and related gene analysis should be performed when ever an unexplained macrothrombocytopenia, especially combined with haemolysis or/and stomatocytosis.

A phytosterolemia patient presenting exclusively with macrothrombocytopenia and stomatocytic hemolysis

BACKGROUND

Phytosterolemia is a rare autosomal recessive lipid storage disease. It is caused by mutations of ABCG5 and ABCG8 genes and characterized by the increased plasma levels of plant sterols. The common clinical manifestations include tendon and tuberous xanthomas and premature coronary heart disease; it has occasionally been associated with hematologic abnormalities.

AIMS

We report a phytosterolemia patient presenting exclusively with macrothrombocytopenia and stomatocytic hemolysis and discuss its clinical significance.

CASE REPORT

The patient, aged 31 years, was born of a consanguineous marriage. He had epistaxis from childhood and underwent splenectomy because of thrombocytopenia, anemia and splenomegaly at the age of 9 years. His blood film showed prominent stomatocytes and macroplatelets. High performance liquid chromatography showed a grossly elevated level of phytosterols in the blood. The patient was confirmed to be a homozygote of missense mutation R419H in ABCG5.

CONCLUSION

We describe a phytosterolemia patient whose clinical manifestations were macrothrombocytopenia, stomatocytic hemolysis and splenomegaly, without the common features of this disorder. Our results suggest that blood cells could be a target for the toxic effect of plasma plant sterols, which should be measured in patients with unexplained stomatocytosis and/or macrothrombocytopenia in order to determine if they have phytosterolemia.

Precholesterol sterols accumulate in lipid rafts of patients with Smith-Lemli-Opitz syndrome and X-linked dominant chondrodysplasia punctata

Systemic fetal dysmorphogenesis in disorders of postsqualene cholesterol biosynthesis is thought to be caused by disruption of Hedgehog signaling. Because precholesterol sterols such as 7-dehydrocholesterol and lathosterol can replace cholesterol in the activation of Hedgehog proteins, it is currently believed that cholesterol deficiency-related Hedgehog signaling block occurs further downstream, probably at the level of Smoothened. Experimentally, such a block in Hedgehog signaling occurs at sterol levels of <40 mug/mg protein. Recently, we studied autopsy material from 2 infants with fatal cholesterol biosynthetic disorders (Smith-Lemli-Opitz syndrome and X-linked dominant chondrodysplasia punctata) in which the hepatic cholesterol levels were far greater. In this study, we demonstrate abnormal accumulation of sterol precursors of cholesterol in membrane lipid rafts (detergent resistance membranes) prepared from liver tissues of these 2 infants: 8-dehydrocholesterol and 7-dehydrocholesterol in lipid rafts of the infant with Smith-Lemli-Opitz syndrome and cholest-8(9)-ene-3beta-ol in lipid rafts of the infant with X-linked dominant chondrodysplasia punctata. We suggest that such alterations in the lipid raft sterol environment may affect the biology of cells and the development of fetuses with cholesterol biosynthetic disorders.

Clinical phenotype of lathosterolosis

Lathosterolosis (LS) is a defect of cholesterol biosynthesis due to the deficiency of the enzyme sterol-C5-desaturase. Only two patients have been described to date, both presenting with multiple malformations, mental retardation, and liver involvement. In addition in one of them pathological examination revealed mucolipidosis-like inclusions on optic microscopy analysis, and peculiar lysosomal lamellar bodies on electron microscopy analysis. This study is focused on a better characterization of the clinical phenotype of LS. We describe a further case in a fetus, sibling of the first patient reported, presenting with neural tube defect, craniofacial and limb anomalies, and prenatal liver involvement. The fetal phenotype suggests the possible occurrence of significant intrafamilial variability in LS, and expands the phenotypic spectrum of the disease. Histological examination of autopsy samples from the fetus and skin fibroblasts from the living sibling suggested that the mucolipidosis-like picture previously reported is not a constant feature of LS, being possibly associated with the most severe biochemical defects, but confirmed the ultrastructural finding of lamellar inclusions. The LS phenotype appears to be characterized by the distinctive association of a recognizable pattern of congenital anomalies, involving axial and appendicular skeleton, liver, central nervous and urogenital systems, and lysosomal storage. This condition partially overlaps with other defects of sterol metabolism, suggesting intriguing pathogenic links among these conditions.

A newborn with VLCAD deficiency. Clinical, biochemical, and histopathological findings

Here we report a newborn with VLCAD deficiency with a severe neonatal onset type who presented with hypoglycemia, cardiomyopathy, mild hepatomegaly and slight hypoalbuminemia. The patient was also homozygous for a new missense mutation (R456H). Postmortem examination of the liver, heart and skeletal muscle revealed diffuse lipid accumulation in various amounts. Mild lobular and portal fibrosis as well as severe macrovesicular steatosis were also found in the liver. The fatal course of the patient may have resulted from diffuse lipid accumulation in the liver and myocardium, which probably began during the intrauterine life with slight hypoalbuminemia as a silent marker of this process.

HEM dysplasia and ichthyosis are likely laminopathies and not due to 3beta-hydroxysterol Delta14-reductase deficiency

Mutations of the lamin B receptor (LBR) have been shown to cause HEM dysplasia in humans and ichthyosis in mice. LBR is a bifunctional protein with both a lamin B binding and a sterol Delta(14)-reductase domain. It previously has been proposed that LBR is the primary sterol Delta(14)-reductase and that HEM dysplasia and ichthyosis are inborn errors of cholesterol synthesis. However, DHCR14 also encodes a sterol Delta(14)-reductase and could provide enzymatic redundancy with respect to cholesterol synthesis. To test the hypothesis that LBR and DHCR14 both function as sterol Delta(14)-reductases, we obtained ichthyosis mice (Lbr(-/-)) and disrupted Dhcr14. Heterozygous Lbr and Dhcr14 mice were intercrossed to test for a digenic phenotype. Lbr(-/-), Dhcr14(Delta4-7/Delta4-7) and Lbr(+/-):Dhcr14(Delta4-7/Delta4-7) mutant mice have distinct physical and biochemical phenotypes. Dhcr14(Delta4-7/Delta4-7) mice are essentially normal, whereas Lbr(+/-):Dhcr14(Delta4-7/Delta4-7) mice are growth retarded and neurologically abnormal. Neither of these mutants resembles the ichthyosis mouse and biochemically, no sterol abnormalities were detected in either liver or kidney tissue. In contrast, relatively small transient elevations of Delta(14)-sterols were observed in Lbr(-/-) and Dhcr14(Delta4-7/Delta4-7) brain tissue, and marked elevations were seen in Lbr(+/-):Dhcr14(Delta4-7/Delta4-7) brain. Pathological evaluation demonstrated vacuolation and swelling of the myelin sheaths in the spinal cord of Lbr(+/-):Dhcr14(Delta4-7/Delta4-7) mice consistent with a demyelinating process. This was not observed in either Lbr(-/-) or Dhcr14 (Delta4-7/Delta4-7) mice. Our data support the conclusions that LBR and DHCR14 provide substantial enzymatic redundancy with respect to cholesterol synthesis and that HEM dysplasia and ichthyosis are laminopathies rather than inborn errors of cholesterol synthesis.

Dorfman-Chanarin syndrome

A four-year-old girl was brought to the dermatology outpatient department with scaling all over the body since birth. She had history of episodic vomiting and abdominal distension. A dermatological diagnosis of lamellar ichthyosis was made. Abdominal examination revealed a nontender hepatomegaly, fatty liver on ultrasonography and deranged liver function tests. Peripheral blood smear showed lipid vacuoles in the granulocytes consistent with Jordans' anomaly. Similar lipid vacuoles were seen in the basal layer in skin biopsy. An inflammatory infiltrate, moderate fibrosis in the portal tract and diffuse severe fatty change in hepatocytes were seen in liver biopsy. The patient was diagnosed as a case of Dorfman-Chanarin syndrome.

Clinical, biochemical, and mutational spectrum of peroxisomal acyl–coenzyme A oxidase deficiency

Peroxisomal acyl-coenzyme A (acyl-CoA) oxidase deficiency is an autosomal recessive inborn error of peroxisomal fatty acid oxidation due to a deficiency of straight-chain acyl-CoA oxidase (SCOX). The biochemical hallmark of this disorder is the accumulation of very long-chain fatty acids. Although some case reports and small series of patients have been published, a comprehensive overview of the clinical, biochemical, and mutational spectrum of this disorder is still lacking. For this reason, we report clinical information for a cohort of 22 patients with peroxisomal acyl-CoA oxidase deficiency and the results from biochemical and mutation analyses in fibroblasts of the patients. No clear genotype-phenotype correlation was observed. An intriguing mutation in the alternatively-spliced transcript encoding the isoform SCOX-exon 3II in a patient with normal expression of the transcript encoding the isoform SCOX-exon 3I, prompted us to characterize these two isoforms of human SCOX. The recombinant SCOX-exon 3I displayed activity toward medium-chain fatty acyl-CoAs and was not active with very long-chain fatty acyl-CoAs. In contrast, recombinant SCOX-exon 3II was capable of oxidizing a broad range of substrates, including very long-chain fatty acyl-CoAs. These results explain why this patient with a mutation in exon 3II of the ACOX1 gene, but with normal expression of exon 3I, was indistinguishable from other patients with peroxisomal acyl-CoA oxidase deficiency with respect to his clinical presentation and the biochemical abnormalities in his fibroblasts.

Very long-chain acyl-CoA dehydrogenase deficiency presenting as acute hypercapnic respiratory failure

Very long-chain acyl-CoA dehydrogenase deficiency (VLCAD) is a key enzyme catalysing the dehydrogenation of long-chain fatty acids in mitochondrial beta-oxidation. VLCAD deficiency is a genetic disorder that commonly presents in infancy or childhood with episodes of hypoketotic hypoglycaemia, cardiomyopathy and liver dysfunction. The present study reports an 18-yr-old Chinese female who presented with acute hypercapnic respiratory failure and rhabdomyolysis after a period of prolonged fasting and exertion. VLCAD deficiency was confirmed with decreased VLCAD activity in cultured fibroblasts. The patient completely recovered with supportive care. Pulmonary function tests after the acute episode showed evidence of chronic subclinical respiratory muscle weakness. In conclusion, this rare metabolic disorder should be considered in patients presenting with unexplained acute respiratory paralysis and failure.

Genetic and nutrient determinants of the metabolic syndrome

PURPOSE OF REVIEW

The metabolic syndrome is a very common condition that is associated with an increased risk of type 2 diabetes mellitus and cardiovascular disease. The diverse clinical characteristics illustrate the complexity of the disease, involving several dysregulated metabolic pathways and multiple genetic targets. The increasing prevalence of obesity heightens the requirement to reduce the risk of the metabolic syndrome. In order to understand the aetiology, it is critical to appreciate the nature of multiple gene-gene and gene-nutrient interactions relevant to the metabolic syndrome.

RECENT FINDINGS

Research indicates a major role for genetic susceptibility to the metabolic syndrome. Nutrition clearly plays an important role in the development and progression of the condition. Genetic background can interact with habitual dietary fat composition, thereby affecting predisposition to the metabolic syndrome, and may also determine an individual's responsiveness to altered dietary fat intake. These studies indicate that therapeutic dietary therapy may require a 'personalized nutrition' approach, wherein a particular genetic profile may determine responsiveness of patients to specific dietary fatty acid interventions.

SUMMARY

Understanding the biological impact of gene-nutrient interactions will provide a key insight into the pathogenesis and progression of diet-related polygenic disorders. This review explores the hypothesis that genetic components of the metabolic syndrome may be modified by dietary fatty acid composition.

Single-gene mutations and increased left ventricular wall thickness in the community: the Framingham Heart Study

BACKGROUND

Mutations in sarcomere protein, PRKAG2, LAMP2, alpha-galactosidase A (GLA), and several mitochondrial genes can cause rare familial cardiomyopathies, but their contribution to increased left ventricular wall thickness (LVWT) in the community is unknown.

METHODS AND RESULTS

We studied 1862 unrelated participants (52% women; age, 59+/-9 years) from the community-based Framingham Heart Study who had echocardiograms and provided DNA samples but did not have severe hypertension, aortic prosthesis, or significant aortic stenosis. Eight sarcomere protein genes, 3 storage cardiomyopathy-causing genes, and 27 mitochondrial genes were sequenced in unrelated individuals with increased LVWT (maximum LVWT >13 mm). Fifty eligible participants (9 women) had unexplained increased LVWT. We detected 8 mutations in 9 individuals (2 women); 7 mutations in 5 sarcomere protein genes (MYH7, MYBPC3, TNNT2, TNNI3, MYL3), and 1 GLA mutation. In individuals with increased LVWT, participants with sarcomere protein and storage mutations were clinically indistinguishable from those without mutations.

CONCLUSIONS

In a community-based cohort, about 3% of eligible participants had increased LVWT, of whom 18% had sarcomere protein or lipid storage gene mutations. Increased LVWT in the community is a very heterogeneous condition, which sometimes may arise from single-gene variants in one of a number of genes.

Barrier dysfunction and pathogenesis of neutral lipid storage disease with ichthyosis (Chanarin-Dorfman syndrome)

Neutral lipid storage disease with ichthyosis (NLSDI; Chanarin-Dorfman syndrome) is an ichthyosiform syndrome, often associated with mutations in a lipid hydrolase, CGI-58. The presence of oil red O-positive, neutral lipid droplets in tissue biopsies, and/or in leukocytes on blood smears, coupled with a constellation of multisystem abnormalities and a pruritic ichthyosiform erythroderma, are together diagnostic of NLSDI. We investigated the pathogenesis of the ichthyosiform erythroderma in patients from three unrelated kindreds with a clinical diagnosis of NLSDI. Basal permeability barrier function and stratum corneum (SC) integrity were abnormal, but barrier recovery rates were faster than normal, as in atopic dermatitis. The basal barrier abnormality was linked to the secretion of lipid micro-inclusions, first segregated within lamellar bodies (LB), which then form a non-lamellar phase within the SC interstices, shown by combined ruthenium tetroxide post-fixation and lipid-retaining resin-white embedding. With colloidal lanthanum nitrate perfusion, excess water/solute movement was restricted to the SC interstices, and further localized to non-lamellar domains. Phase separation of excess stored lipid provides a unifying pathogenic mechanism not only for NLSDI, but also in several other inherited ichthyosiform disorders of lipid metabolism, such as recessive X-linked ichthyosis and type 2 Gaucher's disease.

Fatty acid oxidation disorder as a cause of sudden infant death syndrome (SIDS)--a case report

Although the cause of sudden infant death syndrome (SIDS) remains unknown, extensive studies over the last 10 years have begun to shed some light on this family tragedy. 5% of all cases of SIDS are caused by fatty acid oxidation disorders. We report a case of fatty acid oxidation disorder causing SIDS.