Effect of L-carnitine on exercise performance in patients with mitochondrial myopathy

Exercise intolerance due to impaired oxidative metabolism is a prominent symptom in patients with mitochondrial myopathy (MM), but it is still uncertain whether L-carnitine supplementation is beneficial for patients with MM. The aim of our study was to investigate the effects of L-carnitine on exercise performance in MM. Twelve MM subjects (mean age±SD=35.4±10.8 years) with chronic progressive external ophthalmoplegia (CPEO) were first compared to 10 healthy controls (mean age±SD=29±7.8 years) before they were randomly assigned to receive L-carnitine supplementation (3 g/daily) or placebo in a double-blind crossover design. Clinical status, body composition, respiratory function tests, peripheral muscle strength (isokinetic and isometric torque) and cardiopulmonary exercise tests (incremental to peak exercise and at 70% of maximal), constant work rate (CWR) exercise test, to the limit of tolerance [Tlim]) were assessed after 2 months of L-carnitine/placebo administration. Patients with MM presented with lower mean height, total body weight, fat-free mass, and peripheral muscle strength compared to controls in the pre-test evaluation. After L-carnitine supplementation, the patients with MM significantly improved their Tlim (14±1.9 vs 11±1.4 min) and oxygen consumption (V˙O2) at CWR exercise, both at isotime (1151±115 vs 1049±104 mL/min) and at Tlim (1223±114 vs 1060±108 mL/min). These results indicate that L-carnitine supplementation may improve aerobic capacity and exercise tolerance during high-intensity CWRs in MM patients with CPEO.     

Successful treatment of a patient with mitochondrial myopathy with alirocumab

A 48-year-old man presented to our lipid clinic with statin intolerance and elevated serum creatine kinase levels, being affected by mitochondrial myopathy because of heteroplasmic mitochondrial DNA missense mutation in MTCO1 gene (m.7671T>A). He had just been treated with a coronary artery bypass 4 years before because of acute coronary syndrome, and he had consistently high levels of both low-density lipoprotein cholesterol and triglycerides. Dyslipidemia was successfully treated using 75 mg of alirocumab subcutaneously every 2 weeks, 10 mg of ezetimibe daily, 2 g of marine omega-3 fatty acids daily, and 145 mg of micronized fenofibrate every 2 days. Although muscle weakness persisted, myalgia did not reoccur and serum creatine kinase levels remained almost stable over the time.     

Restriction enzyme analysis of the mitochondrial genome in mitochondrial myopathy.

The mitochondrial myopathies are a heterogeneous group of disorders some of which may be caused by mutations in the mitochondrial genome. Mitochondrial DNA from 10 patients with mitochondrial myopathy and their mothers was analysed using five restriction enzymes and 11 mitochondrial probes in bacteriophage M13. No abnormalities were found in seven out of the 10 patients. Polymorphisms which have not previously been reported were detected in three patients and two of their mothers. These results exclude the presence of deletions or insertions of greater than 60 bp in the region of the mitochondrial genome examined. Any causative mitochondrial DNA mutations in these disorders are therefore likely to be point mutations or small structural rearrangements.     

Endocrine abnormalities in mitochondrial myopathy with external ophthalmoplegia

Summary Endocrine functions were examined in 21 patients with mitochondrial myopathies presenting with chronic progressive external ophthalmoplegia and other additional neurological and multisystemic symptoms. Ten patients had the features of the Kearns-Sayre syndrome. Deletions of the mitochondrial DNA were found in 4 out of 5 patients examined. Fourteen patients, including 3 with deletions of the mitochondrial DNA, had various and often multiple endocrine abnormalities: 6 patients were of short stature, 3 had irregular menstrual cycles, 3 had undersized testicles, 5 showed an insufficient rise of growth hormone following the administration of growth-hormone-releasing hormone, 4 showed an insufficient rise in FSH after administration of gonadotropin-releasing hormone, 5 had manifest diabetes mellitus, 3 showed an impaired glucose tolerance, and 2 patients had subnormal serum levels of parathormone in combination with hypocalcaemia. One patient additionally had Klinefelter's syndrome with a kariotype 47, XXY and increased levels of FSH and LH, subnormal levels of testosterone and subnormal testicular volume. The occurrence of endocrine defects correlated with the duration of disease. The data demonstrate that endocrine abnormalities are frequently associated with mitochondrial myopathy, indicating that this multisystemic disease also involves various endocrine tissues.Abbreviations ACTH adrenocorticotropic hormone - CoQ coenzyme Q₁₀ - CRH corticotropin-releasing hormone - FSH follicle-stimulating hormone - GH growth hormone - GHRH growth-hormone-releasing hormone - GnRH gonadotropin-releasing hormone - LH luteinizing hormone - mtDNA mitochondrial DNA - PTH parathormone - TRH thyrotropin-releasing hormone - TSH thyroid-stimulating hormone - T₃ triiodothyronine - T₄ thyroxine     

苯扎贝特减轻小鼠糖尿病肝损伤

目的:探讨苯扎贝特(BEZ)减轻小鼠糖尿病肝病的作用及可能机制。方法:长期高能量饲料联合链脲菌素(STZ)腹腔注射建立糖尿病肝病模型,给予BEZ(75 mg·kg^-1·d^-1)灌胃4周。每周监测空腹血糖(FBG);HE染色观察肝脏形态学改变,生化试剂盒检测小鼠肝功能(丙氨酸氨基转移酶和天门冬氨酸氨基转移酶)、血脂(总胆固醇和甘油三酯)、胰岛素(INS)和糖化血红蛋白(HbA1c)水平,计算胰岛素抵抗指数(HOMA-IR)。RT-qPCR和Western blot方法检测肝脏过氧化物酶体增殖激活受体(PPARs)的mRNA和蛋白表达。结果:给予STZ 7 d后,小鼠FBG水平持续>11.1 mmol/L。实验结束时模型组小鼠INS、HbA1c及HOME-IR均明显增加(P<0.01),血脂升高(P<0.01);肝功能指标升高(P<0.01),病理检查见肝细胞脂肪变性及炎症细胞浸润;肝脏PPARs的mRNA和蛋白表达明显下降(P<0.01)。BEZ给药明显减轻模型小鼠肝脏损害(P<0.01),降低血糖相关指标和...     

Effect of lifestyle on age-related mitochondrial protein oxidation in mice cardiac muscle

This study investigated the influence of lifestyle on aging-related changes in cardiac proteins’ oxidative modifications profile. Thirty C57BL/6 strain mice (2 months) were randomly divided into three groups (young Y, old sedentary S, and old active A). The S and A mice were individually placed into standard cages and in cages with running wheels, respectively, for 23 months. Upon killing, heart mitochondrial fractions were obtained for the evaluation of general proteins oxidative modifications profile, the identification of preferential protein targets, and oxidative phosphorylation (OXPHOS) activity. We observed age-related cardiac muscle impairment, evidenced by decreased OXPHOS activity, paralleled by an increased protein susceptibility to carbonylation and nitration. Among the main targets to these posttranslational modifications we found mitochondrial proteins, mainly from OXPHOS complexes, MnSOD and enzymes from lipid metabolism. Lifelong sedentary behavior exacerbated the nitrative damage of mitochondrial proteins, paralleled by a statistically significant decrease of respiratory chain complexes II and III activities. In overall, our results highlight the determinant role of aging in cardiac muscle impairment, which is worsened by a sedentary lifestyle.     

Supplemental oxygen and muscle metabolism in mitochondrial myopathy patients

Patients with mitochondrial myopathy (MM) have a reduced capacity to perform exercise due to a reduced oxidative capacity. We undertook this study to determine whether skeletal muscle metabolism could be improved with oxygen therapy in patients with MM. Six patients with MM and six controls, matched for age, gender and physical activity, underwent ³¹P-magnetic resonance spectroscopy (³¹P-MRS) examination. ³¹P-MR spectra were collected at rest and in series during exercise and recovery whilst breathing normoxic (0.21 O₂) or hyperoxic (1.0 O₂) air. At rest, MM showed an elevated [ADP] (18 ± 3 μmol/l) and pH (7.03 ± 0.01) in comparison to the control group (12 ± 1 μmol/l, 7.01 ± 0.01) (P < 0.05) consistent with mitochondrial dysfunction. Oxygen supplementation did not change resting metabolites in either MM or the control group (P > 0.05). Inferred maximal ATP synthesis rate improved by 33% with oxygen in MM (21 ± 3 vs. 28 ± 5 mmol/(l min), P < 0.05) but only improved by 5% in controls (40 ± 3 vs. 42 ± 3 mmol/(l min), P > 0.05). We conclude that oxygen therapy is associated with significant improvements in muscle metabolism in patients with MM. These data suggest that patients with MM could benefit from therapies which improve the provision of oxygen.     

线粒体肌病患者线粒体DNA的突变分析

目的分析线粒体肌病患者线粒体DNA的突变情况，为疾病诊断提供依据。方法用常规HE、酶组化染色和电镜检查等病理形态学方法对3例线粒体肌病疑似患者进行诊断，并用聚合酶链反应-单链构象多态和DNA测序等方法对患者线粒体DNA中全部22个tRNA基因进行突变筛查。结果3例患者均被确诊为线粒体肌病，其中例1tRNA—VaI基因发生A1627G纯合突变，例2tRNA—Val基因发生A1627G／A杂合突变，例3tRNA—Trp基因发生T5554C突变、tRNA—Arg基因发生A10412C／A杂合突变。结论线粒体DNA中的tRNA基因突变是线粒体肌病的重要病因之一。     

Skeletal muscle reoxygenation after high-intensity exercise in mitochondrial myopathy

This study addressed whether O(2) delivery during recovery from high-intensity, supra-gas exchange threshold exercise would be matched to O(2) utilization at the microvascular level in patients with mitochondrial myopathy (MM). Off-exercise kinetics of (1) pulmonary O(2) uptake VO(2P) (2) an index of fractional O(2) extraction by near-infrared spectroscopy (Δ[deoxy-Hb + Mb]) in the vastus lateralis and (3) cardiac output (Q'(T)) by impedance cardiography were assessed in 12 patients with biopsy-proven MM (chronic progressive external ophthalmoplegia) and 12 age- and gender-matched controls. Kinetics of VO(2P) were significantly slower in patients than controls (τ = 53.8 ± 16.5 vs. 38.8 ± 7.6 s, respectively; p < 0.05). Q'(T), however, declined at similar rates (τ = 64.7 ± 18.8 vs. 73.0 ± 21.6 s; p > 0.05) being typically slower than [Formula: see text] in both groups. Importantly, Δ[deoxy-Hb + Mb] dynamics (MRT) were equal to, or faster than, τVO(2P) in patients and controls, respectively. In fact, there were no between-group differences in τVO(2P)MRTΔ[deoxy-Hb + Mb] (1.1 ± 0.4 vs. 1.0 ± 0.2, p > 0.05) thereby indicating similar rates of microvascular O(2) delivery. These data indicate that the slower rate of recovery of muscle metabolism after high-intensity exercise is not related to impaired microvascular O(2) delivery in patients with MM. This phenomenon, therefore, seems to reflect the intra-myocyte abnormalities that characterize this patient population.     

Nuclear genetic control of mitochondrial translation in skeletal muscle revealed in patients with mitochondrial myopathy

Oxidative phosphorylation deficiencies can be caused by mutations in either the nuclear genome or the mitochondrial genome (mtDNA); however, most pathogenic mutations reported in adults occur in mtDNA. Such mutations often impair mitochondrial translation, and are associated with a characteristic muscle pathology consisting of a mosaic pattern of normal fibres interspersed with fibres that show mitochondrial proliferation (ragged-red fibres) and little or no complex IV (COX) activity. We investigated two adult patients with a severe mitochondrial myopathy in whom all muscle fibres showed mitochondrial proliferation with barely detectable COX activity - a pattern never before reported. Biochemical studies of the respiratory chain in muscle showed decreased activities of complexes I and IV (5% of control) and complex II+III (41% of control). Immunoblot analysis of nuclear and mitochondrial subunits of complexes I, III and IV showed a greater than 90% decrease in the steady-state level of these subunits in mature muscle, but no change in nuclear-encoded subunits of complexes II and V. A generalized mitochondrial translation defect was identified in pulse-label experiments in myotubes, but not in myoblasts cultured from both patients. This defect moved with the nucleus in patient cybrid cells. Myoblasts from one patient transplanted into the muscle bed of SCID mice differentiated into mature human muscle fibres that displayed a defect similar to that seen in the patient muscle. These results suggest a defect in a developmentally regulated nuclear factor important for mitochondrial translation in skeletal muscle.     

Enzyme histochemical study of germanium dioxide-induced mitochondrial myopathy in rats

The purpose of this study were 1) to determine the earliest pathological changes of germanium dioxide (GeO2)-induced myopathy; 2) to determine the pathomechanism of GeO2-induced myopathy; and 3) to determine the minimal dose of GeO2 to induce myopathy in rats. One hundred and twenty five male and female Sprague-Dawley rats, each weighing about 150 gm, were divided into seven groups according to daily doses of GeO2. Within each group, histopathological studies were done at 4, 8, 16, and 24 weeks of GeO2 administration. Characteristic mitochondrial myopathy was induced in the groups treated daily with 10 mg/kg of GeO2 or more. In conclusion, the results were as follows: 1) The earliest pathological change on electron microscope was the abnormalities of mitochondrial shape, size and increased number of mitochondria; 2) The earliest pathological change on light microscope was the presence of ragged red fibers which showed enhanced subsarcolemmal succinate dehydrogenase and cytochrome c oxidase reactivity; 3) GeO2 seemed to affect the mitochondrial oxidative metabolism of muscle fibers; 4) GeO2 could induce mitochondrial myopathy with 10 mg/kg of GeO2 for 4 weeks or less duration in rats.     

Two cases of mitochondrial myopathy with predominant respiratory dysfunction

Although it is well known that the respiratory failure is a major cause of death in most patients with chronic neuromuscular disease, predominant respiratory dysfunction without severe involvement of limb muscles is an unusual complication of mitochondrial myopathy in adult age. We experienced two cases of mitochondrial myopathy with severe involvement of respiratory function and only mild involvement of limb muscles. One is a 16 year old female and another is a 22 year old male. The diagnosis is based on morphologic characteristics of "ragged red fibers" under the light microscope and abnormal mitochondrias on the electron microscope in the muscle biopsy.     

Rapid and noninvasive screening of patients with mitochondrial myopathy

In recent years, several point mutations in the mitochondria! genome have been associated with human disease. PCR Polymerase Chain Reaction/restriction endonuclease based techniques provide a reliable method for screening large numbers of specimens for many of the reported mutations. Muscle tissue usually carries the mutations and has been used in earlier studies. We describe a technique for analysis of mtDNA derived from hair follicles for a range of mutations. Both the 3243 A→G MELAS and 8344 A→G MERRF mutations were detected in mtDNA from hair follicles. In patients where both muscle and hair were screened, the mutation load was apparently higher in muscle. Furthermore, in patients positive for a given mutation, all the hair follicles analysed were shown to harbour the mutation, although the proportion of wild type to mutant mtDNA was found to somewhat vary. The advantages of this method are (1: six hair follicles provide sufficient mtDNA for analysis of at least 20 different mutations, and (2: specimen collection and transport to a central laboratory are easier than for other tissues. Our studies show that hair follicles constitute a reliable specimen for mitochondrial mutation screening at a diagnostic level. © 1994 Wiley-Liss, Inc.     

Effect of tetracycline treatment on immunological responses in mice.

Mice treated with tetracycline have reduced capacity to mount delayed-type hypersensitivity (DHT) responses to sheep erythrocytes. The suppressive effect of DTH was more pronounced when the drug was given at the time of challenge with sheep erythrocytes. The in vivo chemotaxis of macrophages was also depressed in mice given tetracycline. There was, however, no significant suppression of antibody production to sheep erythrocytes.     

Effect of erythromycin treatment on specific immunologic response in mice

Six week old Swiss mice were sensitized by subcutaneous injection of 10(7) sheep red blood cells without adjuvant. One hour after sensitization, the mice were treated with erythromycin lactobionate for ten days. The minimal (15 mg/kg/day) and maximal (57 mg/kg/day) doses clinically used were assayed. The daily dose of erythromycin was administered intraperitoneally, in two injections, one every 12 hours. The kinetics of delayed type hypersensitivity reaction, measured by means of the foot-pad test, was evaluated by challenging different groups of fourteen mice with an eliciting dose of 10(8) SRBC injected into the foot-pad on days 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 after sensitization. Total and 2-mercaptoethanol resistant haemagglutinating antibody titres were determined in sera obtained from mice immediately after measuring the delayed type hypersensitivity reaction. Treatment with maximal erythromycin dose gave rise to a significant enhancement of the cellular immune response, and also to an acceleration of the humoral antibody response. On the other hand, treatment with minimal erythromycin dose gave rise to a slight depression of the immune cellular response and also to a depression of the antibody production at the beginning of the humoral response.     

Lack of IL-6 production during exercise in patients with mitochondrial myopathy

In the present study we investigated the possibility that exercise-induced increases in plasma levels of interleukin (IL)-6 are associated with plasma lactate levels. Patients with mitochondrial myopathy (MM) are characterised by high levels of plasma lactate. In this study, seven patients with MM underwent an ergometer cycle test for 25 min without treatment. They were then treated with dichloroacetate (DCA) for 15 days. DCA inhibits pyruvate-dehydrogenase-kinase, thereby increasing the activity of the pyruvate-dehydrogenase complex. The same exercise test was repeated on the last day of treatment. DCA lowered the plasma lactate and increased plasma IL-6 concentrations at rest. IL-6 increased in response to exercise only during DCA treatment. Furthermore, plasma IL-6 was negatively correlated to plasma lactate at rest (r=−0.786, P=0.05). Given that IL-6 is a cytokine with growth-promoting potential, the results of this study suggest that high lactate production contributes to the decreased muscle function observed in MM patients by inhibiting the production of IL-6. Accepted: 4 October 2000