Reported muscle symptoms during statin treatment amongst Italian dyslipidaemic patients in the real-life setting: the PROSISA Study.

AIM: Statin-associated muscle symptoms (SAMS) are a major determinant of poor treatment adherence and/or discontinuation, but a definitive diagnosis of SAMS is challenging. The PROSISA study was an observational retrospective study aimed to assess the prevalence of reported SAMS in a cohort of dyslipidaemic patients. METHODS: Demographic/anamnestic data, biochemical values and occurrence of SAMS were collected by 23 Italian Lipid Clinics. Adjusted logistic regression was performed to estimate odds ratio (OR) and 95% confidence intervals for association between probability of reporting SAMS and several factors. RESULTS: Analyses were carried out on 16 717 statin-treated patients (mean ± SD, age 60.5 ± 12.0 years; 52.1% men). During statin therapy, 9.6% (N = 1599) of patients reported SAMS. Women and physically active subjects were more likely to report SAMS (OR 1.23 [1.10-1.37] and OR 1.35 [1.14-1.60], respectively), whist age ≥ 65 (OR 0.79 [0.70-0.89]), presence of type 2 diabetes mellitus (OR 0.62 [0.51-0.74]), use of concomitant nonstatin lipid-lowering drugs (OR 0.87 [0.76-0.99]), use of high-intensity statins (OR 0.79 [0.69-0.90]) and use of potential interacting drugs (OR 0.63 [0.48-0.84]) were associated with lower probability of reporting SAMS. Amongst patients reporting SAMS, 82.2% underwent dechallenge (treatment interruption) and/or rechallenge (change or restart of statin therapy), with reappearance of muscular symptoms in 38.4% (3.01% of the whole cohort). CONCLUSIONS: The reported prevalence of SAMS was 9.6% of the whole PROSISA cohort, but only a third of patients still reported SAMS after dechallenge/rechallenge. These results emphasize the need for a better management of SAMS to implement a more accurate diagnosis and treatment re-evaluation.

Deoxynucleoside Therapy for Thymidine Kinase 2-Deficient Myopathy.

OBJECTIVE: Thymidine kinase 2, encoded by the nuclear gene TK2, is required for mitochondrial DNA maintenance. Autosomal recessive TK2 mutations cause depletion and multiple deletions of mtDNA that manifest predominantly as a myopathy usually beginning in childhood and progressing relentlessly. We investigated the safety and efficacy of deoxynucleoside monophosphate and deoxynucleoside therapies. METHODS: We administered deoxynucleoside monophosphates and deoxynucleoside to 16 TK2-deficient patients under a compassionate use program. RESULTS: In 5 patients with early onset and severe disease, survival and motor functions were better than historically untreated patients. In 11 childhood and adult onset patients, clinical measures stabilized or improved. Three of 8 patients who were nonambulatory at baseline gained the ability to walk on therapy; 4 of 5 patients who required enteric nutrition were able to discontinue feeding tube use; and 1 of 9 patients who required mechanical ventilation became able to breathe independently. In motor functional scales, improvements were observed in the 6-minute walk test performance in 7 of 8 subjects, Egen Klassifikation in 2 of 3, and North Star Ambulatory Assessment in all 5 tested. Baseline elevated serum growth differentiation factor 15 levels decreased with treatment in all 7 patients tested. A side effect observed in 8 of the 16 patients was dose-dependent diarrhea, which did not require withdrawal of treatment. Among 12 other TK2 patients treated with deoxynucleoside, 2 adults developed elevated liver enzymes that normalized following discontinuation of therapy. INTERPRETATION: This open-label study indicates favorable side effect profiles and clinical efficacy of deoxynucleoside monophosphate and deoxynucleoside therapies for TK2 deficiency. ANN NEUROL 2019;86:293-303.

Management and diagnosis of mitochondrial fatty acid oxidation disorders: focus on very-long-chain acyl-CoA dehydrogenase deficiency.

Mitochondrial fatty acid oxidation disorders (FAODs) are caused by defects in ß-oxidation enzymes, including very long-chain acyl-CoA dehydrogenase (VLCAD), trifunctional protein (TFP), carnitine palmitoyltransferase-2 (CPT2), carnitine-acylcarnitine translocase (CACT) and others. During prolonged fasting, infection, or exercise, patients with FAODs present with hypoglycemia, rhabdomyolysis, cardiomyopathy, liver dysfunction, and occasionally sudden death. This article describes the diagnosis, newborn screening, and treatment of long-chain FAODs with a focus on VLCAD deficiency. VLCAD deficiency is generally classified into three phenotypes based on onset time, but the classification should be comprehensively determined based on genotype, residual enzyme activity, and clinical course, due to a lack of apparent genotype-phenotype correlation. With the expansion of newborn screening for FAODs, several issues have arisen, such as missed detection, overdiagnosis (including detection of benign/asymptomatic type), and poor prognosis of the neonatal-onset form. Meanwhile, dietary management and restriction of exercise have been unnecessary for patients with the benign/asymptomatic type of VLCAD deficiency with a high fatty acid oxidation flux score. Although L-carnitine therapy for VLCAD/TFP deficiency has been controversial, supplementation with L-carnitine may be accepted for CPT2/CACT and multiple acyl-CoA dehydrogenase deficiencies. Recently, a double-blind, randomized controlled trial of triheptanoin (seven-carbon fatty acid triglyceride) versus trioctanoin (regular medium-chain triglyceride) was conducted and demonstrated improvement of cardiac functions on triheptanoin. Additionally, although the clinical efficacy of bezafibrate remains controversial, a recent open-label clinical trial showed efficacy of this drug in improving quality of life. These drugs may be promising for the treatment of FAODs, though further studies are required.

The 3-hydroxyacyl-CoA dehydratases HACD1 and HACD2 exhibit functional redundancy and are active in a wide range of fatty acid elongation pathways.

Differences among fatty acids (FAs) in chain length and number of double bonds create lipid diversity. FA elongation proceeds via a four-step reaction cycle, in which the 3-hydroxyacyl-CoA dehydratases (HACDs) HACD1-4 catalyze the third step. However, the contribution of each HACD to 3-hydroxyacyl-CoA dehydratase activity in certain tissues or in different FA elongation pathways remains unclear. HACD1 is specifically expressed in muscles and is a myopathy-causative gene. Here, we generated Hacd1 KO mice and observed that these mice had reduced body and skeletal muscle weights. In skeletal muscle, HACD1 mRNA expression was by far the highest among the HACDs However, we observed only an ∼40% reduction in HACD activity and no changes in membrane lipid composition in Hacd1-KO skeletal muscle, suggesting that some HACD activities are redundant. Moreover, when expressed in yeast, both HACD1 and HACD2 participated in saturated and monounsaturated FA elongation pathways. Disruption of HACD2 in the haploid human cell line HAP1 significantly reduced FA elongation activities toward both saturated and unsaturated FAs, and HACD1 HACD2 double disruption resulted in a further reduction. Overexpressed HACD3 exhibited weak activity in saturated and monounsaturated FA elongation pathways, and no activity was detected for HACD4. We therefore conclude that HACD1 and HACD2 exhibit redundant activities in a wide range of FA elongation pathways, including those for saturated to polyunsaturated FAs, with HACD2 being the major 3-hydroxyacyl-CoA dehydratase. Our findings are important for furthering the understanding of the molecular mechanisms in FA elongation and diversity.

Novel PNPLA2 gene mutation in a child causing neutral lipid storage disease with myopathy.

BACKGROUND: PNPLA2 gene mutations cause neutral lipid storage disease with myopathy (NLSD-M) or cardiomyopathies. The clinical phenotype, blood test results, imaging examination and gene analysis can be used to improve the understanding of NLSD-M, reduce the misdiagnosis rate and prevent physical disability and even premature death. CASE PRESENTATION: We report a Chinese child with NLSD-M presenting with marked asymmetric skeletal myopathy and hypertrophic cardiomyopathy. Blood biochemical tests revealed increased creatine kinase levels, and echocardiography revealed a diffuse and thick left ventricular wall. Gene analysis revealed a homozygous mutation c.155C > G (p.Thr52Arg) in PNPLA2. CONCLUSIONS: An understanding of the characteristic features is essential for the early diagnosis of NLSD-M. Our data expand the allelic spectrum of PNPLA2 mutations, providing further evidence for genetic and clinical NLSD-M heterogeneity in younger individuals.

Skeletal Muscle-specific G Protein-coupled Receptor Kinase 2 Ablation Alters Isolated Skeletal Muscle Mechanics and Enhances Clenbuterol-stimulated Hypertrophy.

GRK2, a G protein-coupled receptor kinase, plays a critical role in cardiac physiology. Adrenergic receptors are the primary target for GRK2 activity in the heart; phosphorylation by GRK2 leads to desensitization of these receptors. As such, levels of GRK2 activity in the heart directly correlate with cardiac contractile function. Furthermore, increased expression of GRK2 after cardiac insult exacerbates injury and speeds progression to heart failure. Despite the importance of this kinase in both the physiology and pathophysiology of the heart, relatively little is known about the role of GRK2 in skeletal muscle function and disease. In this study we generated a novel skeletal muscle-specific GRK2 knock-out (KO) mouse (MLC-Cre:GRK2fl/fl) to gain a better understanding of the role of GRK2 in skeletal muscle physiology. In isolated muscle mechanics testing, GRK2 ablation caused a significant decrease in the specific force of contraction of the fast-twitch extensor digitorum longus muscle yet had no effect on the slow-twitch soleus muscle. Despite these effects in isolated muscle, exercise capacity was not altered in MLC-Cre:GRK2fl/fl mice compared with wild-type controls. Skeletal muscle hypertrophy stimulated by clenbuterol, a ß2-adrenergic receptor (ß2AR) agonist, was significantly enhanced in MLC-Cre:GRK2fl/fl mice; mechanistically, this seems to be due to increased clenbuterol-stimulated pro-hypertrophic Akt signaling in the GRK2 KO skeletal muscle. In summary, our study provides the first insights into the role of GRK2 in skeletal muscle physiology and points to a role for GRK2 as a modulator of contractile properties in skeletal muscle as well as ß2AR-induced hypertrophy.

Measurement of Creatine kinase and Aspartate aminotransferase in saliva of dogs: a pilot study.

BACKGROUND: Muscle enzymes in saliva have been reported to be possible markers of heart and muscle damage in humans. The aim of this study was to assess if Creatine kinase (CK) and Aspartate aminotransferase (AST) activities could be measured in canine saliva, and to evaluate their possible changes in situations of muscle damage. RESULTS: The spectrophotometric assays for CK and AST measurement in saliva of dogs showed intra- and inter-assay imprecision lower than 1 and 16% and coefficients of correlation close to 1 in linearity under dilution tests. Healthy dogs showed activities in saliva of CK between 27 and 121 U/L and AST between 46 and 144 U/L, whereas in saliva of dogs with muscle damage CK ranged between 132 and 3862 U/L and AST between 154 and 4340 U/L. Positive moderate correlations were found between saliva and serum activities of the two enzymes (CK, r = 0.579; P = 0.001; AST, r = 0.674; P = 0.001). CONCLUSIONS: CK and AST activities can be measured in canine saliva with commercially available spectrophotometric assays. In addition these enzymes show higher values in saliva of dogs with muscle damage and their values are moderately correlated with those of serum.

Strategies for correcting very long chain acyl-CoA dehydrogenase deficiency.

Very long acyl-CoA dehydrogenase (VLCAD) deficiency is a genetic pediatric disorder presenting with a spectrum of phenotypes that remains for the most part untreatable. Here, we present a novel strategy for the correction of VLCAD deficiency by increasing mutant VLCAD enzymatic activity. Treatment of VLCAD-deficient fibroblasts, which express distinct mutant VLCAD protein and exhibit deficient fatty acid ß-oxidation, with S-nitroso-N-acetylcysteine induced site-specific S-nitrosylation of VLCAD mutants at cysteine residue 237. Cysteine 237 S-nitrosylation was associated with an 8-17-fold increase in VLCAD-specific activity and concomitant correction of acylcarnitine profile and ß-oxidation capacity, two hallmarks of the disorder. Overall, this study provides biochemical evidence for a potential therapeutic modality to correct ß-oxidation deficiencies.

Spectrum of metabolic myopathies.

Metabolic myopathies are disorders of utilization of carbohydrates or fat in muscles. The acute nature of energy failure is manifested either by a metabolic crisis with weakness, sometimes associated with respiratory failure, or by myoglobinuria. A typical disorder where permanent weakness occurs is glycogenosis type II (GSDII or Pompe disease) both in infantile and late-onset forms, where respiratory insufficiency is manifested by a large number of cases. In GSDII the pathogenetic mechanism is still poorly understood, and has to be attributed more to structural muscle alterations, possibly in correlation to macro-autophagy, rather than to energetic failure. This review is focused on recent advances about GSDII and its treatment, and the most recent notions about the management and treatment of other metabolic myopathies will be briefly reviewed, including glycogenosis type V (McArdle disease), glycogenosis type III (debrancher enzyme deficiency or Cori disease), CPT-II deficiency, and ETF-dehydrogenase deficiency (also known as riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency or RR-MADD). The discovery of the genetic defect in ETF dehydrogenase confirms the etiology of this syndrome. Other metabolic myopathies with massive lipid storage and weakness are carnitine deficiency, neutral lipid storage-myopathy (NLSD-M), besides RR-MADD. Enzyme replacement therapy is presented with critical consideration and for each of the lipid storage disorders, representative cases and their response to therapy is included. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

Functional MMP-10 is required for efficient tissue repair after experimental hind limb ischemia.

We studied the role of matrix metalloproteinase-10 (MMP-10) during skeletal muscle repair after ischemia using a model of femoral artery excision in wild-type (WT) and MMP-10 deficient (Mmp10(-/-)) mice. Functional changes were analyzed by small animal positron emission tomography and tissue morphology by immunohistochemistry. Gene expression and protein analysis were used to study the molecular mechanisms governed by MMP-10 in hypoxia. Early after ischemia, MMP-10 deficiency resulted in delayed tissue reperfusion (10%, P < 0.01) and in increased necrosis (2-fold, P < 0.01), neutrophil (4-fold, P < 0.01), and macrophage (1.5-fold, P < 0.01) infiltration. These differences at early time points resulted in delayed myotube regeneration in Mmp10(-/-) soleus at later stages (regenerating myofibers: 30 ± 9% WT vs. 68 ± 10% Mmp10(-/-), P < 0.01). The injection of MMP-10 into Mmp10(-/-) mice rescued the observed phenotype. A molecular analysis revealed higher levels of Cxcl1 mRNA (10-fold, P < 0.05) and protein (30%) in the ischemic Mmp10(-/-) muscle resulting from a lack of transcriptional inhibition by MMP-10. This was further confirmed using siRNA against MMP-10 in vivo. Our results demonstrate an important role of MMP-10 for proper muscle repair after ischemia, and suggest that chemokine regulation such as Cxcl1 by MMP-10 is involved in muscle regeneration.

Antimalarials as a risk factor for elevated muscle enzymes in systemic lupus erythematosus.

OBJECTIVE: To investigate the relationship between antimalarials (AM) and elevated muscle enzymes in systemic lupus erythematosus (SLE). PATIENTSMETHODS: 325 lupus patients with abnormal creatine phosphokinase (CPK) for at least two consecutive clinic visits were enrolled; 54 patients on statins/fibrates (n = 43) and/or active myositis (n = 14) were excluded. The control group consisted of 1453 lupus patients with no CPK elevation during follow-up. Descriptive statistics and Cox regression analyses were performed, p < 0.05 was considered significant. RESULTS: Cases and controls did not differ regarding age at SLE diagnosis, gender ratio, or disease duration. AM use was more frequent in cases, which had more prolonged AM use. Total frequency of elevated CPK in AM users was 216/1322 (16.3%). Chloroquine was associated with a 3.3-fold, and hydroxychloroquine with a 3.1-fold, increased risk for CPK elevation. Black race was associated with higher CPK (HR = 2.941), whereas female gender was protective (HR = 0.697). 203 patients were followed for 7.3 ± 5.6 years; 49.8% had persistent and 14.8% intermittent CPK elevation, while in 35.4% CPK was normalized. Clinical proximal muscle weakness developed in 5/203 patients. CONCLUSIONS: Chronic AM use is a potential risk factor for muscle enzyme elevation in SLE patients. CPK abnormalities persist in almost two thirds of the patients, but this remains mainly a biochemical finding, evolving to clinical myopathy in about 2.5%.

Myopathy associated with neuromyelitis optica spectrum disorders.

Neuromyelitis optica spectrum disorders (NMOSD) were generally thought to affect only central nervous system and spare peripheral aquaporin-4 (AQP4)-expressing organs. In recent years, however, increasing evidence has shown that skeletal muscle is involved in NMOSD. We provided a comprehensive review of the relevant literature and summarized the clinical and pathological characteristics of myopathy associated with NMOSD. NMOSD-associated myopathy seems to be characterized by mild muscle symptoms with prominent hyperCKemia and minimal changes on conventional pathological staining. Loss of AQP4 and deposition of IgG and activated complement products on sarcolemma of type II fibers are diagnostic features on immunohistochemical examinations. Creatine kinase leakage as a result of AQP4-IgG-induced, complement-mediated sarcolemmal injury may be a potential mechanism for hyperCKemia. Myopathy should be considered a component of NMOSD unified by AQP4-IgG seropositivity.

PTPs emerge as PIPs: protein tyrosine phosphatases with lipid-phosphatase activities in human disease.

Protein tyrosine phosphatases (PTPs) constitute a family of key homeostatic regulators, with wide implications on physiology and disease. Recent findings have unveiled that the biological activity of PTPs goes beyond the dephosphorylation of phospho-proteins to shut down protein tyrosine kinase-driven signaling cascades. Substrates dephosphorylated by clinically relevant PTPs extend to phospholipids and phosphorylated carbohydrates as well. In addition, non-catalytic functions are also used by PTPs to regulate essential cellular functions. Consequently, PTPs have emerged as novel potential therapeutic targets for human diseases, including cancer predispositions, myopathies and neuropathies. In this review, we highlight recent advances on the multifaceted role of lipid-phosphatase PTPs in human pathology, with an emphasis on hereditary diseases. The involved PTP regulatory networks and PTP modulatory strategies with potential therapeutic application are discussed.

Skeletal muscle-specific HMG-CoA reductase knockout mice exhibit rhabdomyolysis: A model for statin-induced myopathy.

HMG-CoA reductase (HMGCR) catalyzes the conversion of HMG-CoA to mevalonic acid (MVA); this is the rate-limiting enzyme of the mevalonate pathway that synthesizes cholesterol. Statins, HMGCR inhibitors, are widely used as cholesterol-reducing drugs. However, statin-induced myopathy is the most adverse side effect of statins. To eludicate the mechanisms underlying statin the myotoxicity and HMGCR function in the skeletal muscle, we developed the skeletal muscle-specific HMGCR knockout mice. Knockout mice exhibited postnatal myopathy with elevated serum creatine kinase levels and necrosis. Myopathy in knockout mice was completely rescued by the oral administration of MVA. These results suggest that skeletal muscle toxicity caused by statins is dependent on the deficiencies of HMGCR enzyme activity and downstream metabolites of the mevalonate pathway in skeletal muscles rather than the liver or other organs.

The composition of cellular infiltrates in anti-HMG-CoA reductase-associated myopathy.

INTRODUCTION: To characterize cellular infiltrates in muscle biopsies from patients with anti-3-hydroxy-3-methyl-gulatryl-CoA reductase (HMGCR)-associated myopathy. METHODS: Biopsies from 18 anti-HMGCR myopathy and 7 control dermatomyositis patients were analyzed. RESULTS: CD4+ and CD8+ T-cells were scattered within the endomysium in 50% of anti-HMGCR biopsies. All anti-HMGCR biopsies included increased endomysial and/or perivascular CD163+ M2 macrophages; CD11c+ M1 macrophages were present in 18.8%. CD123+ plasmacytoid dendritic (PD) cells were observed within the endomysium and perivascular spaces in 62.5% of anti-HMGCR biopsies. Membrane attack complex was deposited on endothelial cells in 50% and on the sarcolemma of nonnecrotic muscle fibers in 85.7% of anti-HMGCR cases. Major histocompatibility complex class I antigen was up-regulated in 87.5% of the anti-HMGCR cases. CONCLUSIONS: In addition to necrosis, scattered CD4+, CD8+, and PD cells are characteristic of anti-HMGCR myopathy. Predominant M2 polarization suggests infiltrating macrophages are more likely to be involved with tissue repair than destruction.

Requirement of inducible nitric oxide synthase for skeletal muscle regeneration after acute damage.

Adult skeletal muscle regeneration results from activation, proliferation, and fusion of muscle stem cells, such as myogenic precursor cells. Macrophages are consistently present in regenerating skeletal muscles and participate into the repair process. The signals involved in the cross-talk between various macrophage populations and myogenic precursor cells have been only partially identified. In this study, we show a key role of inducible NO synthase (iNOS), expressed by classically activated macrophages in the healing of skeletal muscle. We found that, after sterile injury, iNOS expression is required for effective regeneration of the tissue, as myogenic precursor cells in the muscle of injured iNOS(-/-) mice fail to proliferate and differentiate. We also found that iNOS modulates inflammatory cell recruitment: damaged muscles of iNOS(-/-) animals express significantly higher levels of chemokines such as MIP2, MCP1, MIP-1α, and MCP1, and display more infiltrating neutrophils after injury and a persistence of macrophages at later time points. Finally, we found that iNOS expression in the injured muscle is restricted to infiltrating macrophages. To our knowledge, these data thus provide the first evidence that iNOS expression by infiltrating macrophages contributes to muscle regeneration, revealing a novel mechanism of inflammation-dependent muscle healing.

Clinical manifestations and enzymatic activities of mitochondrial respiratory chain complexes in Pearson marrow-pancreas syndrome with 3-methylglutaconic aciduria: a case report and literature review.

Pearson marrow-pancreas syndrome (PS) is a rare mitochondrial disorder. Impaired mitochondrial respiratory chain complexes (MRCC) differ among individuals and organs, which accounts for variable clinical pictures. A subset of PS patients develop 3-methylglutaconic aciduria (3-MGA-uria), but the characteristic symptoms and impaired MRCC remain unknown. Our patient, a girl, developed pancytopenia, hyperlactatemia, steatorrhea, insulin-dependent diabetes mellitus, liver dysfunction, Fanconi syndrome, and 3-MGA-uria. She died from cerebral hemorrhage at 3 years of age. We identified a novel 5.4-kbp deletion of mitochondrial DNA. The enzymatic activities of MRCC I and IV were markedly reduced in the liver and muscle and mildly reduced in skin fibroblasts and the heart. To date, urine organic acid analysis has been performed on 29 PS patients, including our case. Eight patients had 3-MGA-uria, while only one patient did not. The remaining 20 patients were not reported to have 3-MGA-uria. In this paper, we included these 20 patients as PS patients without 3-MGA-uria. PS patients with and without 3-MGA-uria have similar manifestations. Only a few studies have examined the enzymatic activities of MRCC. CONCLUSION: No clinical characteristics distinguish between PS patients with and without 3-MGA-uria. The correlation between 3-MGA-uria and the enzymatic activities of MRCC remains to be elucidated. WHAT IS KNOWN: • The clinical characteristics of patients with Pearson marrow-pancreas syndrome and 3-methylglutaconic aciduria remain unknown. WHAT IS NEW: • No clinical characteristics distinguish between Pearson marrow-pancreas syndrome patients with and without 3-methylglutaconic aciduria.

Reduced muscle mitochondrial enzyme activity in MuSK-immunized mice.

AIM: Muscle specific kinase (MuSK) antibody-positive myasthenia gravis(MG) patients might present with clinical and electrophysiological signs of muscle atrophy. In this study, we investigated the potential contribution of mitochondrial dysfunction to muscle atrophy induced by MuSK immunity. METHODS: Mitochondrial enzyme expression was investigated in muscle samples of MuSK-immunized, acetylcholine receptor (AChR)-immunized, and complete Freund's adjuvant (CFA)-immunized C57BL/6 (B6) mice using histochemical methods. Mitochondrial enzyme activity was also investigated in MuSK- and CFA-immunized mice. RESULTS: Histochemical analysis showed normal muscle fiber activity on succinate dehydrogenase (SDH) and cytochrome oxidase (COX) stains in all immunization groups. However, MuSK-immunized mice had more ragged-red fibers on modified Gomori-trichrome (MGT) stain and more pronounced type 1 muscle fiber atrophy. MuSK-immunized mice also showed reduced citrate synthase, SDH, and NADH-cytochrome c-reductase activity. DISCUSSION: Our results suggest that MuSK-immunity might induce muscle atrophy through mitochondrial dysfunction.

Serum enolase: a non-destructive biomarker of white skeletal myopathy during pancreas disease (PD) in Atlantic salmon Salmo salar L.

Diseases which cause skeletal muscle myopathy are some of the most economically damaging diseases in Atlantic salmon, Salmo salar L., aquaculture. Despite this, there are limited means of assessing fish health non-destructively. Previous investigation of the serum proteome of Atlantic salmon, Salmo salar L., during pancreas disease (PD) has identified proteins in serum that have potential as biomarkers of the disease. Amongst these proteins, the enzyme enolase was selected as the most viable for use as a biomarker of muscle myopathy associated with PD. Western blot and immunoassay (ELISA) validated enolase as a biomarker for PD, whilst immunohistochemistry identified white muscle as the source of enolase. Enolase was shown to be a specific marker for white muscle myopathy in salmon, rising in serum concentration significantly correlating with pathological damage to the tissue.

A heterozygous missense mutation in adolescent-onset very long-chain acyl-CoA dehydrogenase deficiency with exercise-induced rhabdomyolysis.

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is characterized by impaired mitochondrial ß-oxidation of fatty acids. The fatty acid oxidation plays a significant role in energy production especially in skeletal muscle. VLCAD is one of four acyl-CoA dehydrogenases with different-chain length specificity and catalyzes the initial step in mitochondrial ß-oxidation of fatty acids. While the clinical phenotypes in neonates and infants are described as severe, adolescent-onset or adult-onset VLCAD deficiency has a more benign course with only skeletal muscle involvement. These myopathic phenotypes are characterized by episodic muscle weakness and rhabdomyolysis triggered by fasting and strenuous exercise. We report a male teenager who manifested repeated episodes of rhabdomyolysis immediately after exertional exercise. Rhabdomyolysis was diagnosed based on the marked elevation of serum creatine kinase and myoglobinuria. Acylcarnitine analysis by tandem mass spectrometry (MS/MS) revealed elevation of serum tetradecenoylcarnitine (C14:1-AC), which represents an abnormal acylcarnitine profile associated with the mitochondrial ß-oxidation defect. High performance liquid chromatographic analysis showed decreased production of 2-hexadecenoyl-CoA (C16:1) from palmitoyl-CoA (C16:0), indicating the defect of VLCAD activity. Direct sequencing of the acyl-CoA dehydrogenase, very long-chain gene (ACADVL) that codes VLCAD revealed a heterozygous mutation (c.1242G>C) in exon 12 (E414D), which is a novel mutation in myopathic-type VLCAD deficiency. Because VLCAD functions as a homodimer, we assume that this heterozygous mutation may exhibit dominant-negative effect. This patient remains asymptomatic thereafter by avoiding exertional exercise. The findings of reduction of enzyme activity and clinical features associated with this novel missense mutation of VLCAD are discussed.