ARTICLE | doi:10.20944/preprints202208.0152.v1
Subject: Life Sciences, Biochemistry Keywords: Desmin; Myopathy; Cardiomyopathy; Intermediate Filaments; Cytoskeleton; Myofibrillar Myopathy (MFM); Desminopathy; Desmosomes; Protein Aggregation.
Online: 8 August 2022 (10:48:45 CEST)
Desmin is the major intermediate filament protein of all three muscle cell types and connects different cell organelles and multi-protein complexes like the cardiac desmosomes. Several pathogenic mutations in the DES gene cause different skeletal and cardiac myopathies. However, the significance of the majority of DES missense variants is currently unknown since functional data are lacking. To determine whether desmin missense mutations within the highly conserved 1A coil domain cause a filament assembly defect, we generated a set of variants with unknown significance and analyzed systematically the filament assembly in transfected SW13 and H9c2 cells using confocal microscopy. We found that mutations in the N-terminal part of the 1A coil domain affect the filament assembly leading to the cytoplasmic desmin aggregation. In contrast, mutant desmin in the C-terminal part of the 1A coil domain form filamentous structures comparable to wild-type desmin. Our findings suggest that the N-terminal part of the 1A coil domain is a hot spot for pathogenic desmin mutations, which affect the desmin filament assembly leading in consequence to skeletal and/or cardiac myopathies. This study may have relevance for the genetic counselling of patients carrying variants in the 1A coil domain of the DES gene.
ARTICLE | doi:10.20944/preprints201906.0194.v2
Subject: Life Sciences, Molecular Biology Keywords: wooden breast; broilers; myopathy; breast muscle
Online: 18 August 2019 (02:48:50 CEST)
Wooden breast is a muscle disorder affecting modern commercial broiler chickens that causes a palpably firm pectoralis major muscle and severe reduction in meat quality. Most studies have focused on advanced stages of wooden breast apparent at market age, resulting in limited insights into the etiology and early pathogenesis of the myopathy. Therefore, the objective of this study was to identify early molecular signals in the wooden breast transcriptional cascade by performing gene expression analysis on the pectoralis major muscle of two-week-old birds that may later exhibit the wooden breast phenotype by market age at 7 weeks. Biopsy samples of the left pectoralis major muscle were collected from 101 birds at 14 days of age. Birds were subsequently raised to 7 weeks of age to allow sample selection based on the wooden breast phenotype at market age. RNA sequencing was performed on 5 unaffected and 8 affected female chicken samples, selected based on wooden breast scores (0 to 4) assigned at necropsy where affected birds had scores of 2 or 3 (mildly or moderately affected) while unaffected birds had scores of 0 (no apparent gross lesions). Differential expression analysis identified 60 genes found to be significant at an FDR-adjusted p value of 0.05. Of these, 26 were previously demonstrated to exhibit altered expression or genetic polymorphisms related to glucose tolerance or diabetes mellitus in mammals. Additionally, 9 genes have functions directly related to lipid metabolism and 11 genes are associated with adiposity traits such as intramuscular fat and body mass index. This study suggests that wooden breast disease is first and foremost a metabolic disorder characterized primarily by ectopic lipid accumulation in the pectoralis major.
COMMUNICATION | doi:10.20944/preprints201910.0068.v1
Online: 7 October 2019 (12:15:26 CEST)
I have recently reiterated that the cross-bridge is a calcium ATPase that is inhibited by magnesium and this arises because in normal hearts Myosin binding Protein-C prevents the use of MgATP as rate limiting substrate ensuring that Ca2+ replaces Mg2+ in the excitation pathway. Here I revisit the studies on [Ca2+] dependency of ATPase and tension under diastolic stretch with a different conclusion on Hill coefficients. This reveals the underlying mechanisms of the Frank-Starling Law and Hypertrophic myopathy are not the same, the former being kinase controlled.
Subject: Medicine & Pharmacology, General Medical Research Keywords: creatine; statin; myopathy; muscle; myalgia; prevention; treatment; pathogenesis; pathophysiology; mitochondria
Online: 11 September 2019 (04:43:37 CEST)
Statins prevent cardiovascular diseases, yet their use is limited by the muscle disturbances they cause. Rarely, statin-induced myopathy is autoimmune, but more commonly it is due to direct muscle toxicity. Available evidence suggests that statin-induced creatine deficiency may be a major cause of this toxicity, and that creatine supplementation prevents it. Statins inhibit guanidinoacetate methyl transferase (GAMT), the last enzyme in the synthesis of creatine, thus they decrease its intracellular content. Such decreased content could cause mitochondrial impairment, since creatine is the final acceptor of the phosphate group of adenosine triphosphate (ATP) at the end of mitochondrial oxidative phosphorylation. Decreased cellular synthesis of adenosine triphosphate (ATP) would follow. Accordingly, ATP synthesis is decreased in statin-treated cells. In vitro, creatine supplementation prevents the opening of mitochondrial permeability transition pore caused by statins. Clinically, creatine administration prevents statin myopathy in statin-intolerant patients. Additional research is warranted to hopefully confirm these findings. However, creatine is widely used by athletes with no adverse events, and has demonstrated to be safe even in double-blind, placebo-controlled trials of elder individuals. Thus, it should be trialed, under medical supervision, in patients who cannot assume statin due to the occurrence of muscular symptoms.
ARTICLE | doi:10.20944/preprints201908.0069.v1
Subject: Medicine & Pharmacology, Other Keywords: coenzyme Q deficiency; mitochondrial disease; respiratory chain; fatty acids; myopathy; ADCK2
Online: 6 August 2019 (07:52:35 CEST)
Fatty acids and glucose are the main bioenergetic substrates in mammals that are alternatively used during the transition between fasting and feeding. Impairment of mitochondrial fatty acid oxidation causes mitochondrial myopathy leading to decreased physical performance. Here, we report that haploinsufficiency of ADCK2, a member of the aarF domain-containing mitochondrial protein kinase family, in human is associated with liver dysfunction and severe mitochondrial myopathy with lipid droplets in skeletal muscle. In order to better understand the etiology of this rare disorder, we generated a heterozygous Adck2 knockout mouse model to perform in vivo and cellular studies using integrated analysis of physiological and omics data (transcriptomics-metabolomics). The data show that Aldh2+/- mice exhibits impaired fatty acid oxidation, liver dysfunction, and mitochondrial myopathy in skeletal muscle resulting in lower physical performance. Significant decrease in CoQ biosynthesis was observed and supplementation with CoQ partially rescued the phenotype both in the human subject and mouse model. These results indicate that ADCK2 is involved in organismal fatty acid metabolism and in CoQ biosynthesis in skeletal muscle. We propose that patients with isolated myopathies and myopathies involving lipid accumulation be tested for possible ADCK2 defect as they are likely to be responsive to CoQ supplementation.
ARTICLE | doi:10.20944/preprints201809.0591.v1
Subject: Medicine & Pharmacology, Clinical Neurology Keywords: adverse events; immune checkpoint inhibitor; myasthenia gravis; myopathy; neuropathy; nivolumab; pembrolizumab
Online: 29 September 2018 (11:28:00 CEST)
Neuromuscular adverse events following cancer treatment with anti-programmed cell death protein 1 (PD-1) monoclonal antibodies are relatively rare, yet potentially fatal. Using the PRISMA approach, we performed a systematic review to characterize the clinical presentation, diagnostic workup, and management of neuromuscular disorders (NMDs) in patients treated with nivolumab or pembrolizumab. Sixty-three publications on 85 patients (mean age 66,9 years (range 34–86); male/female 2.6:1; 59% metastatic melanoma) were identified from selected indexing databases until June 2018. Forty-eight patients had received nivolumab and 39 pembrolizumab. The mean number of PD-1 inhibitor treatment cycles prior to onset of symptoms was 3,6 (range 1–28). Symptoms included oculomotor (47%); respiratory (43%), bulbar (35%), and proximal weakness (35%); as well as muscle pain (28%). Diagnoses were categorized as myasthenia gravis (27%), neuropathy (23%), myopathy (34%) and a combination of these (16%). After critical review of the data, however, evidence did not support the stated NMD diagnosis in 13% of cases, while up to 14% of patients had signs of additional NMDs. PD-1 inhibitor associated myasthenia was associated with cardiac complications in almost 30% of patients and with a more rapid clinical progression compared with idiopathic myasthenia. Mortality was high despite adequate treatment strategies including corticosteroid, IV immunoglobulins and plasmapheresis. In conclusion, clinical presentation of NMDs associated with PD-1 inhibitors is often atypical, with significant overlap between myasthenia gravis and myopathy; and cardiac/respiratory complications are common, leading to more severe disease courses than idiopathic myasthenia.