Metabolic myopathies: a clinical approach; part I

Adriamycin downregulates the expression of KLF4 in cardiomyocytes in vitro and contributes to impaired cardiac energy metabolism in Adriamycin-induced cardiomyopathy

Adriamycin is a well-known anthracycline chemotherapeutic agent widely used in treating a variety of malignancies. However, Adriamycin's clinical use is limited due to its adverse side-effects, most importantly cardiomyopathy. Adriamycin-induced cardiotoxicity reportedly includes mitochondrial dysfunction. We hypothesize that modulation of KLF4, a key regulator of cardiac mitochondrial homeostasis might play a role in the development of Adriamycin-induced cardiomyopathy. Therefore, in the current work, we evaluated the interaction of Adriamycin with KLF4 and its subsequent downstream targets. Molecular docking revealed that Adriamycin interacts strongly with KLF4 at residues Thr 448, Arg 452, Ser 444 falls within C2H2 motif which is the active site. Quantitative real-time PCR also revealed that KLF4 is downregulated by Adriamycin in cardiomyocytes in vitro. The expression of KLF4 is downregulated in a dose-dependent manner, with a 0.12 ± 0.09-fold (p ≤ 0.05, n = 3) downregulation at a low dosage and 0.21 ± 0.02-fold (p ≤ 0.05, n = 3) downregulation at high dosage. Deficiency of KLF4 leads to an impairment of PPARγ that consequently supresses the proteins/enzymes involved in the fatty acid metabolism. Adriamycin-mediated suppression of KLF4 also affected the expression of PPARα in vitro. PPARα dysfunction is likely to cause defects in β-oxidation which ultimately results in impaired ATP synthesis. Cardiac cells are thus forced to switch over the substrate from free fatty acid to glucose. Moreover, Adriamycin elevates the expression of PPARβ due to downregulation of KLF4 leads to increased myocardial glucose utilization. Thus, a change in substrate preference affects the flexibility of metabolic network culminating in diminished energy production and other regulatory activities, altogether contributing to the development of cardiomyopathy. Thus, we conclude that the effect of Adriamycin on KLF4 disrupts mitochondrial homeostasis and lipid/glucose homeostasis resulting in a reduction of ATP synthesis which ultimately results in dilated cardiomyopathy.

Pediatric Paroxysmal Exercise-Induced Neurological Symptoms: Clinical Spectrum and Diagnostic Algorithm

Paroxysmal exercise-induced neurological symptoms (PENS) encompass a wide spectrum of clinical phenomena commonly presenting during childhood and characteristically elicited by physical exercise. Interestingly, few shared pathogenetic mechanisms have been identified beyond the well-known entity of paroxysmal exercise-induced dyskinesia, PENS could be part of more complex phenotypes including neuromuscular, neurodegenerative, and neurometabolic disease, epilepsies, and psychogenetic disorders. The wide and partially overlapping phenotypes and the genetic heterogeneity make the differential diagnosis frequently difficult and delayed; however, since some of these disorders may be treatable, a prompt diagnosis is mandatory. Therefore, an accurate characterization of these symptoms is pivotal for orienting more targeted biochemical, radiological, neurophysiological, and genetic investigations and finally treatment. In this article, we review the clinical, genetic, pathophysiologic, and therapeutic landscape of paroxysmal exercise induced neurological symptoms, focusing on phenomenology and differential diagnosis.

Adriamycin inhibits glycolysis through downregulation of key enzymes in Saccharomyces cerevisiae

Adriamycin is a widely used drug for the treatment of various types of cancers, but its clinical application is limited because of irreversible dilated cardiomyopathy. The incidence of cardiomyopathy is a consequence of disrupted energy production, which could be related to the defects in glycogen, lipid and mucopolysaccharide metabolism. We explored the effect of Adriamycin on enzymes involved in glycolysis and apoptotic genes through molecular docking. We used Saccharomyces cerevisiae as model organism and studied the effect of Adriamycin on selected enzymes involved in glycolysis. The docking studies revealed that Adriamycin interacts with phosphofructokinase and enolase in an efficient manner. In phosphofructokinase, Adriamycin binds at the active site and with enolase the drug interacts at the cofactor-binding site (Mg²⁺) which might impair the activity of the enzyme. Gene expression studies revealed that Adriamycin causes the dysregulation of glycolysis through dysregulation of hexokinase, phosphoglycerate mutase, enolase and downregulation of pyruvate kinase. The drug shows a biphasic effect on the expression of genes enolase and pyruvate kinase. The impairment in glycolysis might reduce the ATP synthesis, and the cells might be deprived of energy. The condition is further worsened by elevated ROS levels triggering the cell to undergo apoptosis evidenced by downregulation of SOD and upregulation of BAX and caspase. In conclusion, our study reveals that Adriamycin impairs glycolysis and cause cell to undergo apoptosis due to oxidative stress in yeast cells.

Drug Development and the Use of Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Disease Modeling and Drug Toxicity Screening

: Over the years, numerous groups have employed human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) as a superb human-compatible model for investigating the function and dysfunction of cardiomyocytes, drug screening and toxicity, disease modeling and for the development of novel drugs for heart diseases. In this review, we discuss the broad use of iPSC-CMs for drug development and disease modeling, in two related themes. In the first theme-drug development, adverse drug reactions, mechanisms of cardiotoxicity and the need for efficient drug screening protocols-we discuss the critical need to screen old and new drugs, the process of drug development, marketing and Adverse Drug reactions (ADRs), drug-induced cardiotoxicity, safety screening during drug development, drug development and patient-specific effect and different mechanisms of ADRs. In the second theme-using iPSC-CMs for disease modeling and developing novel drugs for heart diseases-we discuss the rationale for using iPSC-CMs and modeling acquired and inherited heart diseases with iPSC-CMs.

Rhabdomyolysis in organic acidemia patients manifesting with metabolic decompensation

Several metabolic disorders are related to rhabdomyolysis, but their association with methylmalonic acidemia (MMA) and propionic acidemia (PA) is unclear. Eleven patients with MMA and four patients with PA were treated and/or followed up in Kumamoto University Hospital between January 2009 and December 2018. Three patients with MMA and one patient with PA developed rhabdomyolysis at 1-2 weeks after onset of metabolic crisis. Cases 1 and 4 initially developed rhabdomyolysis after withdrawal from continuous hemodiafiltration (CHDF), and cases 2 and 3 developed rhabdomyolysis at the time of onset and had recurrent rhabdomyolysis during the recovery phase after withdrawal from CHDF. Mitochondrial dysfunction is associated with rhabdomyolysis. The rhabdomyolysis in patients with MMA and PA may have been attributed to a defect in energy production because of a secondary mitochondrial disorder. Therefore, physicians should closely follow patients with MMA and PA, especially after withdrawal of hemodialysis therapy, and provide supportive care for their mitochondrial function.

Effects of Propofol on Cellular Bioenergetics in Human Skeletal Muscle Cells

OBJECTIVES

Propofol may adversely affect the function of mitochondria and the clinical features of propofol infusion syndrome suggest that this may be linked to propofol-related bioenergetic failure. We aimed to assess the effect of therapeutic propofol concentrations on energy metabolism in human skeletal muscle cells.

DESIGN

In vitro study on human skeletal muscle cells.

SETTINGS

University research laboratories.

SUBJECTS

Patients undergoing hip surgery and healthy volunteers.

INTERVENTIONS

Vastus lateralis biopsies were processed to obtain cultured myotubes, which were exposed to a range of 1-10 μg/mL propofol for 96 hours.

MEASUREMENTS AND MAIN RESULTS

Extracellular flux analysis was used to measure global mitochondrial functional indices, glycolysis, fatty acid oxidation, and the functional capacities of individual complexes of electron transfer chain. In addition, we used [1-C]palmitate to measure fatty acid oxidation and spectrophotometry to assess activities of individual electron transfer chain complexes II-IV. Although cell survival and basal oxygen consumption rate were only affected by 10 μg/mL of propofol, concentrations as low as 1 μg/mL reduced spare electron transfer chain capacity. Uncoupling effects of propofol were mild, and not dependent on concentration. There was no inhibition of any respiratory complexes with low dose propofol, but we found a profound inhibition of fatty acid oxidation. Addition of extra fatty acids into the media counteracted the propofol effects on electron transfer chain, suggesting inhibition of fatty acid oxidation as the causative mechanism of reduced spare electron transfer chain capacity. Whether these metabolic in vitro changes are observable in other organs and at the whole-body level remains to be investigated.

CONCLUSIONS

Concentrations of propofol seen in plasma of sedated patients in ICU cause a significant inhibition of fatty acid oxidation in human skeletal muscle cells and reduce spare capacity of electron transfer chain in mitochondria.

Comparative Analysis of Skeletal Muscle Metabolites of Fish with Various Rates of Aging

Fish species exhibit great diversity rating of aging (from negligible to rapid), which gives a unique possibility for the discovery of the molecular mechanisms that determine the differences in the rate of aging. A mass spectrometric metabolic profiling of skeletal muscle of fish with various aging rates was carried out by direct injection to a quadrupole time-of-flight mass spectrometer. The first group includes long-lived fish species (pike (Esox Lucius) and sterlet (Acipenser ruthenus); the second group—species with gradual senescence such as that observed in many mammalian species of similar size (zander (Sandra lucioperca) and perch (Perca fluviatilis)) and the third group—species with very short life cycle (chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha)). Multivariate analysis of metabolic profiles allowed the detecting of about 80 group-specific features associated with amino acids, lipids, biogenic amines, intermediates of glycolysis, glycogenolysis, and citric acid cycle. Possible roles in the aging process are hypothesized for the biochemical pathways of the metabolites that were altered in the different groups.

Carnitine palmitoyltransferase type 2 deficiency: novel mutation in a Native South American family with whole-body muscle magnetic resonance imaging findings: two case reports

Background

The myopathic form of carnitine palmitoyltransferase type II deficiency is an inherited autosomal recessive metabolic myopathy usually starting in childhood. Most reports have been on European and Japanese populations, and no Native South American patients have been reported to date. The p.Ser113Leu mutation is the most frequent in the European population. Only lower-leg magnetic resonance imaging findings have been reported, with gluteus maximus involvement in one case and normal imaging in other patients.

Case presentation

Two Native South American siblings, a boy and a girl, presented to our neuromuscular clinic with recurrent rhabdomyolysis associated with transient muscle weakness after prolonged exercise. During episodes, their creatine kinase concentrations were markedly increased, up to 148,000 (1.48 × 10⁵) IU/L in the boy and 18,000 (1.8 × 10⁴) IU/L in the girl. The results of electroneuromyography and histopathology suggested a nonspecific myopathy. CPT2 gene sequencing showed two heterozygous mutations: the p.Ser113Leu variant and a novel one (predicted to be deleterious by in silico analysis), the p.Ser373Pro variant. The patients’ parents were asymptomatic carriers. Whole-body magnetic resonance imaging showed mild selective involvement in the thoracic extensors and pelvic girdle in both siblings, and in the thighs and lower legs in one of them. Dietary and bezafibrate treatment was started, and symptomatic relief was observed.

Conclusions

To the best of our knowledge, this is the first reported Native South American family with a CPT2 deficiency carrying a novel mutation and particular features visualized by whole-body magnetic resonance imaging.

Spectrum of Neuromuscular Disorders With HyperCKemia From a Tertiary Care Pediatric Neuromuscular Center

Elevated creatine kinase is a useful screening test in the diagnostic workup of patients with neuromuscular disorders. We did a retrospective study of children with hyperCKemia (>175 IU/L) who were followed in the neuromuscular program of a tertiary care pediatric center from 2005 to 2016. Patients with hyperCKemia were divided into 2 groups: myopathic and nonmyopathic. Within the myopathic group, there were 3 arbitrary subgroups based on creatine kinase values: A (creatine kinase >10 times normal), B (creatine kinase 5-10 times normal), and C (creatine kinase 1-5 times normal). The 3 major categories of myopathies across all the subgroups were muscular dystrophies (commonest) followed by metabolic myopathies and inflammatory myopathies. Among the nonmyopathic causes of hyperCKemia, spinal muscular atrophy was the commonest. Muscular dystrophies should be considered in children with hyperCKemia, muscle weakness, or calf hypertrophy, and metabolic myopathies to be considered in children with recurrent rhabdomyolysis.

Phenotypical Variation with Same Genetic Mutation in Familial Hypokalemic Periodic Paralysis

Hypokalemic periodic paralysis is a genetic neuromuscular disorder characterized by episodes of painless muscle paralysis associated with low serum potassium, exclusively, during the attack. This may be precipitated by heavy exercise, fasting, or high-carbohydrate meals. We report two siblings, presenting at different ages with varying symptomatology—older sibling with episodic weakness in the morning associated with reduced physical exercise and consumption of large carbohydrate meal, whereas younger sibling complained of muscle stiffness following large carbohydrate meal and at the end of physical exercise. Molecular genetic study showed both siblings and their father were positive for calcium channel alpha-1S subunit (CACNA1S) C3716G>A; p.Arg1239His mutation. It is important to check serum potassium in a child presenting with muscle stiffness or weakness after a carbohydrate meal or vigorous exercise. This condition responds with potassium supplement. Often relevant family history and trigger factors with clinical correlation and blood results can lead to its diagnosis.

Lipid Storage Myopathy with Ketonuria: A Case of Fatty Acid Oxidation-Related Myopathy and Encephalopathy due to Multiple Acyl-CoA Dehydrogenase Deficiency

Encephalopathy and Myopathy in children of varying ages can be due to variety of causes including Mitochondrial diseases, metabolic diseases like renal tubular acidosis, storage diseases as well as fatty acid oxidation (FAO) disorders. FAO related disorders have variable clinical presentation and manifest in different ages. They may present with hypoglycemia, effort intolerance, multi organ involvement with or without ketonuria. High degree of suspicion and appropriate investigations are mandatory for diagnosis. Here we describe an 11 Year old boy, born to non – consanguineous parents. Presented with exertion induced muscle pain and fatigue of 1year duration, which slowly progressed to severe weakness and vomiting. His reflexes were retained. Therefore metabolic vs inflammatory muscle diseases were considered. Patient had ketonuria with elevated blood levels of medium chain acyl carnitine and long chain acyl carnitine suggestive of MADD. Urine organic acid assessment showed elevated excretion of 2-hydroxyglutarate (2HG), adipate and arabitol. Muscle biopsy showed multiple fine vacuoles on Eosin- hematoxylin stained preparation. Modified Gomori - trichrome stain showed vacuolated fibers with red granular material consistent with ragged red fibers. Oil Red O stains showed vacuolated fibers with ‘oil red O’ positive material suggesting lipid storage. Above combination of features is consistent of MADD. Genetic evaluation is not done due to financial constraint. Patient was started on high dose riboflavin and carnitine, with which the child became near normal. Our patient is a case of MADD presenting as Reye’s syndrome like features and showed excellent response to riboflavin, carnitine, dietary and life style changes. High degree of suspicion is lifesaving.

Potentially diagnostic electron paramagnetic resonance spectra elucidate the underlying mechanism of mitochondrial dysfunction in the deoxyguanosine kinase deficient rat model of a genetic mitochondrial DNA depletion syndrome

A novel rat model for a well-characterized human mitochondrial disease, mitochondrial DNA depletion syndrome with associated deoxyguanosine kinase (DGUOK) deficiency, is described. The rat model recapitulates the pathologic and biochemical signatures of the human disease. The application of electron paramagnetic (spin) resonance (EPR) spectroscopy to the identification and characterization of respiratory chain abnormalities in the mitochondria from freshly frozen tissue of the mitochondrial disease model rat is introduced. EPR is shown to be a sensitive technique for detecting mitochondrial functional abnormalities in situ and, here, is particularly useful in characterizing the redox state changes and oxidative stress that can result from depressed expression and/or diminished specific activity of the distinct respiratory chain complexes. As EPR requires no sample preparation or non-physiological reagents, it provides information on the status of the mitochondrion as it was in the functioning state. On its own, this information is of use in identifying respiratory chain dysfunction; in conjunction with other techniques, the information from EPR shows how the respiratory chain is affected at the molecular level by the dysfunction. It is proposed that EPR has a role in mechanistic pathophysiological studies of mitochondrial disease and could be used to study the impact of new treatment modalities or as an additional diagnostic tool.

Recurrent Compartment Syndrome Leading to the Diagnosis of McArdle Disease: Case Report

Glycogen storage disorders are rare diseases of metabolism that are usually diagnosed when a patient presents with recurrent fatigue, muscle pains, and exercise intolerance. In this case report, we describe a patient who presented with the second episode of nontraumatic compartment syndrome over a 10-year span. Because of the obscure presentation, we performed a muscle biopsy, which on muscle phosphorylase staining revealed McArdle disease (glycogen storage disease type V).

A diagnostic approach to recurrent myalgia and rhabdomyolysis in children

Episodic myalgia is a common complaint in children and young adults. While many cases remain idiopathic even after extensive investigation, myalgia can be the first symptom of an underlying serious neuromuscular condition, and can be associated with an increased risk of such serious complications as rhabdomyolysis and malignant hyperthermia. We review and highlight the metabolic myopathies and other increasingly recognised muscle disorders that may present to paediatricians with episodic myalgia or isolated episodes of rhabdomyolysis, and propose a diagnostic algorithm for investigation of these complaints.

Diagnostic Algorithm for Glycogenoses and Myoadenylate Deaminase Deficiency Based on Exercise Testing Parameters: A Prospective Study

Aim

Our aim was to evaluate the accuracy of aerobic exercise testing to diagnose metabolic myopathies.

Methods

From December 2008 to September 2012, all the consecutive patients that underwent both metabolic exercise testing and a muscle biopsy were prospectively enrolled. Subjects performed an incremental and maximal exercise testing on a cycle ergometer. Lactate, pyruvate, and ammonia concentrations were determined from venous blood samples drawn at rest, during exercise (50% predicted maximal power, peak exercise), and recovery (2, 5, 10, and 15 min). Biopsies from vastus lateralis or deltoid muscles were analysed using standard techniques (reference test). Myoadenylate deaminase (MAD) activity was determined using p-nitro blue tetrazolium staining in muscle cryostat sections. Glycogen storage was assessed using periodic acid-Schiff staining. The diagnostic accuracy of plasma metabolite levels to identify absent and decreased MAD activity was assessed using Receiver Operating Characteristic (ROC) curve analysis.

Results

The study involved 51 patients. Omitting patients with glycogenoses (n = 3), MAD staining was absent in 5, decreased in 6, and normal in 37 subjects. Lactate/pyruvate at the 10th minute of recovery provided the greatest area under the ROC curves (AUC, 0.893 ± 0.067) to differentiate Abnormal from Normal MAD activity. The lactate/rest ratio at the 10th minute of recovery from exercise displayed the best AUC (1.0) for discriminating between Decreased and Absent MAD activities. The resulting decision tree achieved a diagnostic accuracy of 86.3%.

Conclusion

The present algorithm provides a non-invasive test to accurately predict absent and decreased MAD activity, facilitating the selection of patients for muscle biopsy and target appropriate histochemical analysis.

Rhabdomyolysis: review of the literature

Rhabdomyolysis is a serious and potentially life threatening condition. Although consensus criteria for rhabdomyolysis is lacking, a reasonable definition is elevation of serum creatine kinase activity of at least 10 times the upper limit of normal followed by a rapid decrease of the sCK level to (near) normal values. The clinical presentation can vary widely, classical features are myalgia, weakness and pigmenturia. However, this classic triad is seen in less than 10% of patients. Acute renal failure due to acute tubular necrosis as a result of mechanical obstruction by myoglobin is the most common complication, in particular if sCK is >16.000 IU/l, which may be as high as 100,000 IU/l. Mortality rate is approximately 10% and significantly higher in patients with acute renal failure. Timely recognition of rhabdomyolysis is key for treatment. In the acute phase, treatment should be aimed at preserving renal function, resolving compartment syndrome, restoring metabolic derangements, and volume replacement. Most patients experience only one episode of rhabdomyolysis, mostly by substance abuse, medication, trauma or epileptic seizures. In case of recurrent rhabdomyolysis, a history of exercise intolerance or a positive family history for neuromuscular disorders, further investigations are needed to identify the underlying, often genetic, disorder. We propose a diagnostic algorithm for use in clinical practice.

Rhabdomyolysis in Acute Spinal Cord Injury Presenting With Nausea and Vomiting as Chief Complaints: A Case Report

Dealing with complications is crucial in the management of patients with spinal cord injury (SCI). We describe a case of rhabdomyolysis in SCI without apparent soft tissue injury, presenting with nausea and vomiting as chief complaints. Given that gastrointestinal discomfort is common in SCI, this case highlights the need to consider rhabdomyolysis as a potential cause of unexplained nausea and vomiting in SCI, and indicate the value of regular check-up of creatine kinase level in SCI patients. Early diagnosis and treatment can prevent acute renal failure that can occur with rhabdomyolysis and minimize the potential threat of declined renal function in SCI patients.

Diagnosis of mitochondrial myopathies

Mitochondria are ubiquitous organelles and play crucial roles in vital functions, most importantly, the oxidative phosphorylation and energy metabolism. Therefore, mitochondrial dysfunction can affect multiple tissues, with muscle and nerve preferentially affected. Mitochondrial myopathy is a common clinical phenotype, which is characterized by early fatigue and/or fixed muscle weakness; rhabdomyolysis can seldom occur. Muscle biopsy often identifies signs of diseased mitochondria by morphological studies, while biochemical analysis may identify respiratory chain deficiencies. The clinical, morphological and biochemical data guide molecular analysis. Being the mitochondrial function under the control of both mitochondrial DNA and nuclear DNA, the search for mitochondrial DNA mutations and mitochondrial DNA quantitation, may not be sufficient for the molecular diagnosis of mitochondrial myopathies. Approximately 1500 nuclear genes can affect mitochondrial structure and function and the targeting of such genes may be necessary to reach the diagnosis. The identification of causative molecular defects in nuclear or mitochondrial genome leads to the definite diagnosis of mitochondrial myopathy.

A diagnostic algorithm for metabolic myopathies

Metabolic myopathies comprise a clinically and etiologically diverse group of disorders caused by defects in cellular energy metabolism, including the breakdown of carbohydrates and fatty acids to generate adenosine triphosphate, predominantly through mitochondrial oxidative phosphorylation. Accordingly, the three main categories of metabolic myopathies are glycogen storage diseases, fatty acid oxidation defects, and mitochondrial disorders due to respiratory chain impairment. The wide clinical spectrum of metabolic myopathies ranges from severe infantile-onset multisystemic diseases to adult-onset isolated myopathies with exertional cramps. Diagnosing these diverse disorders often is challenging because clinical features such as recurrent myoglobinuria and exercise intolerance are common to all three types of metabolic myopathy. Nevertheless, distinct clinical manifestations are important to recognize as they can guide diagnostic testing and lead to the correct diagnosis. This article briefly reviews general clinical aspects of metabolic myopathies and highlights approaches to diagnosing the relatively more frequent subtypes (Fig. 1). Fig. 1 Clinical algorithm for patients with exercise intolerance in whom a metabolic myopathy is suspected. CK-creatine kinase; COX-cytochrome c oxidase; CPT-carnitine palmitoyl transferase; cyt b-cytochrome b; mtDNA-mitochondrial DNA; nDNA-nuclear DNA; PFK-phosphofructokinase; PGAM-phosphoglycerate mutase; PGK-phosphoglycerate kinase; PPL-myophosphorylase; RRF-ragged red fibers; TFP-trifunctional protein deficiency; VLCAD-very long-chain acyl-coenzyme A dehydrogenase.

Mechanisms of exercise limitation and pulmonary rehabilitation for patients with neuromuscular disease

Indications for exercise and pulmonary rehabilitation extend to neuromuscular diseases tough these conditions pose particular challenges given the associated skeletal muscle impairment and respiratory muscle dysfunction. These challenges are compounded by the variety of exercise prescriptions (aerobic, muscle strengthening, and respiratory muscle training) and the variety of neuromuscular disorders (muscular, motor neuron, motor nerve root, and neuromuscular transmission disorders). Studies support a level II evidence of effectiveness (i.e., likely to be effective) for a combination of aerobic exercise and strengthening exercises in muscular disorders, and for strengthening exercises in amyotrophic lateral sclerosis. The potential deleterious effects of work overload in the dystrophinopathies have not been confirmed in Becker muscular dystrophy. Adjunctive pharmacologic interventions (e.g., theophylline, steroids, PDE5 inhibitors, creatine), training recommendations (e.g., interval or lower intensity training) and supportive techniques (e.g., noninvasive ventilation, neuromuscular electrical stimulation, and diaphragm pacing) may result in more effective training but require more study before formal recommendations can be made. The exercise prescription should include avoidance of inspiratory muscle training in hypercapnia or low vital capacity, and should match the desired outcome (e.g., extremity training for task-specific performance, exercise training to enhance exercise performance, respiratory muscle training where respiratory muscle involvement contributes to the impairment).

Apoptosis and fibrosis are early features of heart failure in an animal model of metabolic cardiomyopathy

In previous experiments, we observed signs of cardiac failure in mice overexpressing lipoprotein lipase (LPL) under the control of a muscle specific promotor and in peroxisome proliferators activated receptor alpha (PPARalpha) knockout mice overexpressing LPL under the control of the same promotor. In our current investigations, we focussed on morphological consequences and changes in mRNA and protein expression in hearts from these animals. mRNA expression was analysed by differential display analysis and Northern blot as well as by cDNA microarray analysis followed by pathway analysis. Protein expression was examined using immunoblot and immunohistochemistry. Fibrosis was determined by chromotrope aniline blue staining for collagen. A distinct increase in the expression of alpha-tubulin mRNA was noted in hearts of all mutant mouse strains compared with the control. This result was paralleled by increased alpha-tubulin protein expression. Using cDNA microarray analysis, we detected an activation of apoptosis, in particular an increase of caspase-3 expression in hearts of mice overexpressing LPL but not in PPARalpha knockout mice overexpressing LPL. This finding was confirmed immunohistochemically. In addition, we identified a distinct interstitial increase in collagen and an increase around blood vessels. In our mouse model, we detect mRNA and protein changes typical for cardiomyopathy even before overt clinical signs of heart failure. In addition, a small but distinct increase in the rate of apoptosis of cardiomyocytes and fibrotic changes contributes to cardiac failure in mice overexpressing LPL, whereas additional deficiency in PPARalpha seems to protect hearts from these effects.

The "etiome": identification and clustering of human disease etiological factors

Background

Both genetic and environmental factors contribute to human diseases. Most common diseases are influenced by a large number of genetic and environmental factors, most of which individually have only a modest effect on the disease. Though genetic contributions are relatively well characterized for some monogenetic diseases, there has been no effort at curating the extensive list of environmental etiological factors.

Results

From a comprehensive search of the MeSH annotation of MEDLINE articles, we identified 3,342 environmental etiological factors associated with 3,159 diseases. We also identified 1,100 genes associated with 1,034 complex diseases from the NIH Genetic Association Database (GAD), a database of genetic association studies. 863 diseases have both genetic and environmental etiological factors available. Integrating genetic and environmental factors results in the "etiome", which we define as the comprehensive compendium of disease etiology. Clustering of environmental factors may alert clinicians of the risks of added exposures, or synergy in interventions to alter these factors. Clustering of both genetic and environmental etiological factors puts genes in the context of environment in a quantitative manner.

Conclusion

In this paper, we obtained a comprehensive list of associations between disease and environmental factors using MeSH annotation of MEDLINE articles. It serves as a summary of current knowledge between etiological factors and diseases. By combining the environmental etiological factors and genetic factors from GAD, we computed the "etiome" profile for 863 diseases. Comparing diseases across these profiles may have utility for clinical medicine, basic science research, and population-based science.

Metabolic myopathies: a guide and update for clinicians

PURPOSE OF REVIEW

The present review will focus on the clinical features, and recent advances in the investigation and treatment, of metabolic muscle disease. The aim is to present a summary of this vast and complex topic emphasizing key points of relevance to nonspecialists in the field. Salient examples from each category will be highlighted to illustrate characteristic features and potential sources of diagnostic confusion. The general approach to management will then be outlined.

RECENT FINDINGS

Awareness of these diseases has grown over recent years, as has appreciation of their variable clinical presentation. Many of the precise genetic and biochemical abnormalities underlying these conditions have been elucidated and novel enzyme defects continue to be discovered. Perhaps the greatest progress, however, has been made in the management of disease. Advances in tandem mass spectrometry techniques have facilitated the introduction of nationwide neonatal screening programmes for a large number of metabolic disorders. Enzyme replacement in Pompe disease has proved successful, improving outcome in a hitherto untreatable condition. Progress towards gene therapy, perhaps the ultimate goal, has been made in animal models.

SUMMARY

Although individually rare, the metabolic myopathies together constitute a significant group of disabling and potentially life-threatening disorders. Appropriate investigations, timely treatment and genetic counselling are paramount to ameliorate the short and long-term consequences of disease.

Respiratory involvement in inherited primary muscle conditions

Patients with inherited muscle disorders can develop respiratory muscle weakness leading to ventilatory failure. Predicting the extent of respiratory involvement in the different types of inherited muscle disorders is important, as it allows clinicians to impart prognostic information and offers an opportunity for early interventional management strategies. The approach to respiratory assessment in patients with muscle disorders, the current knowledge of respiratory impairment in different muscle disorders and advice on the management of respiratory complications are summarised.

Grandpa and I have dystrophinopathy?: approach to asymptomatic hyperCKemia

This report describes three males from a single kinship, ages 7, 8, and 67 years with clinically asymptomatic dystrophinopathy. The index case was an 8-year-old male evaluated for asymptomatic but persistently elevated serum creatine kinase levels. Muscle biopsy demonstrated a mild myopathy, without necrotic fibers. Immunostaining for dystrophin revealed a slight reduction in sarcolemmal reactivity for the amino terminus of dystrophin. Dystrophin gene analysis revealed a deletion of exon 45 to exon 51. Genetic analysis identified two other affected males (age 7 years and 67 years), as well as four female carriers in the same family. The 7-year-old male had mildly increased creatine kinase levels with normal muscle strength. The 67-year-old grandfather had normal neuromuscular examination and serum creatine kinase levels. Asymptomatic dystrophinopathy in late adulthood is exceptionally rare, and highlights the importance of consideration of dystrophin mutation analysis in patients with hyperCKemia, even in the absence of muscle weakness.

[High doses statins administration causing rhabdomyolysis: case report]

Rhabdomyolysis has been the theme in medical literature for the last fifty years. In these last decades, with statins being used in primary and secondary cardiovascular prevention events, this theme returns and statins are now pointed as the trigger to this almost always fatal complication. Rhabdomyolysis due to statins administration occurs mainly in association with other drugs. Our case reports on a patient with fatal statin-induced rhabdomyolysis whose medical history included diffuse atherosclerotic disease.

Metabolic myopathies and physical activity: when fatigue is more than simple exertion

Fatigue can have many causes in active people. A metabolic myopathy-though uncommonly identified as a cause of fatigue during sporting events-must be considered in certain circumstances, and the diagnosis may be helpful for preventive and genetic counseling. In general, symptoms of disorders of glycogen breakdown and glucose utilization (glycogen storage diseases) occur during high-intensity exercise. Symptoms of disorders of fatty acid transport or oxidation and mitochondrial disorders occur after endurance exercise. Important investigations include forearm ischemic testing, electromyographic and nerve conduction studies, muscle biopsy (histology, enzyme, and DNA testing), and exercise testing. Most patients with metabolic myopathies can participate in sports with appropriate exercise adaptations and dietary manipulation.

Metabolic cardiomyopathies

The energy needed by cardiac muscle to maintain proper function is supplied by adenosine Ariphosphate primarily (ATP) production through breakdown of fatty acids. Metabolic cardiomyopathies can be caused by disturbances in metabolism, for example diabetes mellitus, hypertrophy and heart failure or alcoholic cardiomyopathy. Deficiency in enzymes of the mitochondrial beta-oxidation show a varying degree of cardiac manifestation. Aberrations of mitochondrial DNA lead to a wide variety of cardiac disorders, without any obvious correlation between genotype and phenotype. A completely different pathogenetic model comprises cardiac manifestation of systemic metabolic diseases caused by deficiencies of various enzymes in a variety of metabolic pathways. Examples of these disorders are glycogen storage diseases (e.g. glycogenosis type II and III), lysosomal storage diseases (e.g. Niemann-Pick disease, Gaucher disease, I-cell disease, various types of mucopolysaccharidoses, GM1 gangliosidosis, galactosialidosis, carbohydrate-deficient glycoprotein syndromes and Sandhoff's disease). There are some systemic diseases which can also affect the heart, for example triosephosphate isomerase deficiency, hereditary haemochromatosis, CD 36 defect or propionic acidaemia.

Diagnosis of pediatric neuromuscular disorders in the era of DNA analysis

Extraordinary breakthroughs in the molecular pathogenesis of muscle and nerve disease have resulted in an evolving genetic classification of neuromuscular disorders and the development of new diagnostic methods. This remarkable progress has introduced new genetic tests and has changed the indications for use of certain invasive diagnostic procedures in the evaluation of children with presumed disorders of the motor unit. In this review, we present the current diagnostic approach to the more common neuromuscular diseases of infancy and childhood and define the diagnostic role of muscle biopsy and pediatric electromyography/nerve conduction studies in the era of genetic analysis.