Neurohumoral activation in congestive heart failure: A double-edged sword?

The search for the basic mechanism(s) responsible for the progressive and frequently irreversible deterioration of left ventricular pump function in congestive heart failure has been quite extensive; nonetheless, no single explanation has been forthcoming. Indeed, given the complexity of this disease process, it is becoming increasingly unlikely that a single pathogenetic mechanism will ever be uncovered for congestive heart failure. This review will examine recent experimental and clinical evidence which suggests that excessive adrenergic stimulation of the heart is double-edged. That is, while increased adrenergic input to the heart may initially enable the failing myocardium to function adequately for a period of months to years, continued excessive adrenergic stimulation of the heart through both local neural and circulating catecholamines may lead to frank myopathic effects on the heart, with resultant worsening of left ventricular function and the development of intractable congestive heart failure. While we do not mean to suggest that excessive sympathetic stimulation of the heart is the only, or even the major mechanism responsible for the development of irreversible congestive heart failure, the data reviewed herein do suggest that adrenergic stimulation may play a primary role in the pathogenesis of congestive heart failure.     

氟美松对正常大鼠膈肌的影响

利用氟美松制备的大鼠类固醇肌病模型，研究了氟美松对大鼠膈肌的重量、收缩特性、肌纤维的横断面积、氧化酶活性、糖原和超微结构的影响。结果发现：（１）氟美松的使用可使大鼠膈肌明显萎缩，以Ⅱａ、Ⅱｂ型纤维萎缩为著；（２）在１００Ｈｚ电刺激下，膈肌的张力明显下降，膈肌耐疲劳的能力（１／２ＲＴ）显著提高；（３）膈肌中Ⅰ型、Ⅱｂ型纤维中ＡＴＰ酶、琥珀酸脱氢酶（ＳＤＨ）的活性均下降，膈肌中糖原含量增加。电镜观察发现氟美松可以导致膈肌线粒体增生、空泡样变性及部分肌丝局灶性破坏。氟美松导致的上述各种改变，可能直接或间接地影响膈肌物质能量代谢而导致其收缩性能的改变。     

D-2-hydroxyglutarate produced by mutant IDH2 causes cardiomyopathy and neurodegeneration in mice

Mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) have been discovered in several cancer types and cause the neurometabolic syndrome D2-hydroxyglutaric aciduria (D2HGA). The mutant enzymes exhibit neomorphic activity resulting in production of D2-hydroxyglutaric acid (D-2HG). To study the pathophysiological consequences of the accumulation of D-2HG, we generated transgenic mice with conditionally activated IDH2^R140Q and IDH2^R172K alleles. Global induction of mutant IDH2 expression in adults resulted in dilated cardiomyopathy, white matter abnormalities throughout the central nervous system (CNS), and muscular dystrophy. Embryonic activation of mutant IDH2 resulted in more pronounced phenotypes, including runting, hydrocephalus, and shortened life span, recapitulating the abnormalities observed in D2HGA patients. The diseased hearts exhibited mitochondrial damage and glycogen accumulation with a concordant up-regulation of genes involved in glycogen biosynthesis. Notably, mild cardiac hypertrophy was also observed in nude mice implanted with IDH2^R140Q-expressing xenografts, suggesting that 2HG may potentially act in a paracrine fashion. Finally, we show that silencing of IDH2^R140Q in mice with an inducible transgene restores heart function by lowering 2HG levels. Together, these findings indicate that inhibitors of mutant IDH2 may be beneficial in the treatment of D2HGA and suggest that 2HG produced by IDH mutant tumors has the potential to provoke a paraneoplastic condition.     

Elevated urinary β2 microglobulin in the first identified Japanese family afflicted by X-linked myopathy with excessive autophagy

Here we report what is to our knowledge the first identified Japanese family afflicted by X-linked myopathy with excessive autophagy. The index case is a 52-year-old man with almost 40 years of progressive proximal muscle weakness. High urinary β2 microglobulin, normal serum β2 microglobulin, autophagic vacuoles with sarcolemmal features, and a hemizygous c.164–7T>G mutation in the VMA21 gene were found. His two maternal uncles had similar clinicopathological findings. High urinary β2 microglobulin without obvious renal dysfunction might result from decreased urine acidification in the distal convoluted tubules caused by the VMA21 gene mutation. These findings might prove to be useful as a preliminary marker suggestive of X-linked myopathy with excessive autophagy.     

Deep sequencing detects very-low-grade somatic mosaicism in the unaffected mother of siblings with nemaline myopathy

When an expected mutation in a particular disease-causing gene is not identified in a suspected carrier, it is usually assumed to be due to germline mosaicism. We report here very-low-grade somatic mosaicism in ACTA1 in an unaffected mother of two siblings affected with a neonatal form of nemaline myopathy. The mosaicism was detected by deep resequencing using a next-generation sequencer. We identified a novel heterozygous mutation in ACTA1, c.448A>G (p.Thr150Ala), in the affected siblings. Three-dimensional structural modeling suggested that this mutation may affect polymerization and/or actin’s interactions with other proteins. In this family, we expected autosomal dominant inheritance with either parent demonstrating germline or somatic mosaicism. Sanger sequencing identified no mutation. However, further deep resequencing of this mutation on a next-generation sequencer identified very-low-grade somatic mosaicism in the mother: 0.4%, 1.1%, and 8.3% in the saliva, blood leukocytes, and nails, respectively. Our study demonstrates the possibility of very-low-grade somatic mosaicism in suspected carriers, rather than germline mosaicism.     

Localized scleroderma and regional inflammatory myopathy

Inflammatory myopathy is rare in localized scleroderma. We report 2 new cases of regional inflammatory myopathy associated with localized scleroderma and review 10 reported cases of localized scleroderma associated with an inflammatory myopathy with regional muscle involvement, more often in the upper extremities. Serum creatine kinase was mildly elevated or normal. Histopathology often showed perimysial inflammation and plasma cell infiltration. These cases demonstrate that inflammatory myopathy should be considered in patients with localized scleroderma and regional muscle weakness, pain or atrophy. Muscle biopsy can confirm the diagnosis of myositis, which if identified, will require anti-inflammatory and/or immunosuppressive therapy.     

Frequency and phenotype of patients carrying TPM2 and TPM3 gene mutations in a cohort of 94 patients with congenital myopathy

Congenital myopathies are difficult to classify correctly through molecular testing due to the size and heterogeneity of the genes involved. Therefore, the prevalence of the various genetic causes of congenital myopathies is largely unknown. In our cohort of 94 patients with congenital myopathy, two related female patients and two sporadic, male patients were found to carry mutations in the tropomyosin 2 (TPM2) and tropomyosin 3 (TPM3) genes, respectively. This indicates a low (4.3%) frequency of TPM2 and TPM3 mutations as a cause of congenital myopathy. Compared to previously described patients carrying the same mutations as found in our study (c.503G > A, and c.502C > T in TPM3, and c.415_417delGAG in TPM2), clinical presentation and muscle morphological findings differed in our patients. Differences included variation in distribution of muscle weakness, presence of scoliosis and ptosis, physical performance and joint contractures. The variation in clinical profiles emphasizes the phenotypic heterogeneity. However, common features were also present, such as onset of symptoms in infancy or childhood, musculoskeletal deformities and normal or low plasma levels of creatine kinase.One patient had nemaline myopathy and fiber size disproportion, while three patients had congenital fiber type disproportion (CFTD) on muscle biopsies. TPM2-related CFTD has only been described in two cases, indicating that mutations in TPM2 are rare causes of CFTD.     

Montelukast modifies simvastatin-induced myopathy and hepatotoxicity

Montelukast (MNK) has prominent anti-inflammatory and antioxidant activities. It can protect the liver in different hepatotoxic models in animals. Simvastatin (SMV) is one of commonly used lipid lowering drugs for treatment of dyslipidemia in order to reduce cardiovascular disease. It has severe side effects such as myopathy and hepatotoxicity. The aim of the present study is to investigate the possible effect of MNK on SMV-induced myopathy and hepatotoxicity. Four groups of male rats: control group which received saline via stomach tube, MNK treated group (received 10 mg/kg/day MNK via stomach tube), SMV treated group (received 30 mg/kg/day SMV via stomach tube), and MNK + SMV (combination) group which received both MNK and SMV. All animals were treated for 14 days before obtaining blood and tissue samples. SMV has both hepatotoxic effects and myopathy. SMV caused a significant increase in myoglobin, creatinine kinase, ALT, AST, ALP, and bilirubin but, it decreased total proteins, globulin and albumin levels. Co-treatment of SMV and MNK increased the antioxidant activity significantly. MNK modifies partially the myopathic changes and hepatotoxic effect of SMV. Co-administration of MNK and SMV decreased their toxic potentials on the liver, skeletal muscles, and kidney. They have antioxidant activities when given together that produce muscle and hepatic protective effects.     

Bloc atrio-ventriculaire de grade III compliquant une myocardite au décours d’un traitement par anti-PD1 : observation d’un cas et revue de la littérature

IntroductionImmune Checkpoint Inhibitor (ICI) therapy is now a standard of care in numerous cancers with very promising results. Nevertheless, adverse events, and especially immune-related adverse events (irAEs) not reported during clinical trials, are emerging and can be life-threatening.ObservationWe report here a teachable case of a 80 year-old man, of third-degree atrioventricular block consecutive to myocarditis associated with the administration of nivolumab (anti-PD1) monotherapy.ConclusionMyocarditis occurring during ICI treatment is a rare but potentially lethal event. Daily serum troponin level seems to predict ICI-related myocarditis but interpretation could be difficult in the context of associated myositis. Echocardiography and cardiac MRI are also useful but can remain negative. Electrocardiogram is a cornerstone of myocarditis diagnosis. In case of cardiac involvement, continuous heart rhythm monitoring should be performed in addition to the administration of high-dose corticosteroids therapy and the cessation of ICI therapy. Add-on treatments should be discussed with a well-trained multidisciplinary team.