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With the identification of a patient with mutated mitochondrial DNA (mtDNA) of paternal origin, it has been unequivocally proven that not only does paternal mtDNA survive in the zygote, but it can also contribute substantially to the mtDNA pool of adult, human skeletal muscle. The questions are: how often does paternal mtDNA inheritance occur and what mechanisms are involved? In this paper, we will review current knowledge on the fate of sperm mitochondria after fertilization and discuss the impact paternal inheritance may have on our understanding of mitochondrial biology. [Copyright &y& Elsevier]

Abstract: Pompe disease is a rare, inherited metabolic myopathy characterized by progressive weakness of the proximal limb and respiratory muscles. We report the findings from four patients with late-onset Pompe disease treated with α-glucosidase (Myozyme) for 2 (n =2) and 6 (n =2) years, and monitored with isokinetic dynamometry, 6-minute walking test (6MWT), and vital capacity. Patients were evaluated after 6, 12, 24, 36, 48, 60, and 72months. In two patients, muscle size estimated by MRI and DXA scanning was also performed prior to and following 6months of treatment. After 2years of α-glucosidase treatment, maximal isokinetic muscle strength increased by 11% (0%–50%) [median (range)] and 6MWT improved by 18% (2%–40%). In the two patients treated for 6years, the increase in muscle strength stabilized at 40% and 6MWT stabilized at 32%. The improvements primarily occurred during the first 6months of treatment. Interestingly, the weakest muscle groups seemed to benefit more than those less affected, and greater improvements occurred for flexor muscles compared to extensor muscles. Vital capacity did not improve on treatment. [Copyright &y& Elsevier]

Background McArdle disease (glycogen storage disease type V) is an inborn error of skeletal muscle metabolism, which affects glycogen phosphorylase (myophosphorylase) activity leading to an inability to break down glycogen. Patients with McArdle disease are exercise intolerant, as muscle glycogen-derived glucose is unavailable during exercise. Metabolic adaptation to blocked muscle glycogenolysis occurs at rest in the McArdle mouse model, but only in highly glycolytic muscle. However, it is unknown what compensatory metabolic adaptations occur during exercise in McArdle disease. Methods In this study, 8-week old McArdle and wild-type mice were exercised on a treadmill until exhausted. Dissected muscles were compared with non-exercised, age-matched McArdle and wild-type mice for histology and activation and expression of proteins involved in glucose uptake and glycogenolysis. Results Investigation of expression and activation of proteins involved in glycolytic flux revealed that in glycolytic, but not oxidative muscle from exercised McArdle mice, the glycolytic flux had changed compared to that in wild-type mice. Specifically, exercise triggered in glycolytic muscle a differentiated activation of insulin receptor, 5′ adenosine monophosphate-activated protein kinase, Akt and hexokinase II expression, while inhibiting glycogen synthase, suggesting that the need and adapted ability to take up blood glucose and use it for metabolism or glycogen storage is different among the investigated muscles. Conclusion The main finding of the study is that McArdle mouse muscles appear to adapt to the energy crisis by increasing expression and activation of proteins involved in blood glucose metabolism in response to exercise in the same directional way across the investigated muscles. [ABSTRACT FROM AUTHOR]

Objective We investigated metabolism and physiological responses to exercise in an 18-year-old woman with multiple congenital abnormalities and exertional muscle fatigue, tightness, and rhabdomyolysis. Methods We studied biochemistry in muscle and fibroblasts, performed mutation analysis, assessed physiological responses to forearm and cycle-ergometer exercise combined with stable-isotope techniques and indirect calorimetry, and evaluated the effect of IV glucose infusion and oral sucrose ingestion on the exercise response. Results Phosphoglucomutase type 1 (PGM1) activity in muscle and fibroblasts was severely deficient and PGM1 in muscle was undetectable by Western blot. The patient was compound heterozygous for missense (R422W) and nonsense (Q530X) mutations in PGM1 . Forearm exercise elicited no increase in lactate, but an exaggerated increase in ammonia, and provoked a forearm contracture. Comparable to patients with McArdle disease, the patient developed a ‘second wind’ with a spontaneous fall in exercise heart rate and perceived exertion. Like in McArdle disease, this was attributable to an increase in muscle oxidative capacity. Carbohydrate oxidation was blocked during exercise, and the patient had exaggerated oxidation of fat to fuel exercise. Exercise heart rate and perceived exertion were lower after IV glucose and oral sucrose. Muscle glycogen level was low normal. Conclusions The second wind phenomenon has been considered to be pathognomonic for McArdle disease, but we demonstrate that it can also be present in PGM1 deficiency. We show that severe loss of PGM1 activity causes blocked muscle glycogenolysis that mimics McArdle disease, but may also limit glycogen synthesis, which broadens the phenotypic spectrum of this disorder. [ABSTRACT FROM AUTHOR]

Abstract: Myopathic symptoms in Glycogen Storage Disease Type IIIa (GSD IIIa) are generally ascribed to the muscle wasting that these patients suffer in adult life, but an inability to debranch glycogen likely also has an impact on muscle energy metabolism. We hypothesized that patients with GSD IIIa can experience exercise intolerance due to insufficient carbohydrate oxidation in skeletal muscle. Six patients aged 17–36-years were studied. We determined VO2peak (peak oxygen consumption), the response to forearm exercise, and the metabolic and cardiovascular responses to cycle exercise at 70% of VO2peak with either a saline or a glucose infusion. VO2peak was below normal. Glucose improved the work capacity by lowering the heart rate, and increasing the peak work rate by 30% (108W with glucose vs. 83W with placebo, p=0.018). The block in muscle glycogenolytic capacity, combined with the liver involvement caused exercise intolerance with dynamic skeletal muscle symptoms (excessive fatigue and muscle pain), and hypoglycemia in 4 subjects. In this study we combined anaerobic and aerobic exercise to systematically study skeletal muscle metabolism and exercise tolerance in patients with GSD IIIa. Exercise capacity was significantly reduced, and our results indicate that this was due to a block in muscle glycogenolytic capacity. Our findings suggest that the general classification of GSD III as a glycogenosis characterized by fixed symptoms related to muscle wasting should be modified to include dynamic exercise-related symptoms of muscle fatigue. A proportion of the skeletal muscle symptoms in GSD IIIa, i.e. weakness and fatigue, may be related to insufficient energy production in muscle. [Copyright &y& Elsevier]

Abstract: Pompe disease is caused by absence of the lysosomal enzyme acid alpha-glucosidase. It is generally assumed that intra-lysosomal hydrolysis of glycogen does not contribute to skeletal muscle energy production during exercise. However, this hypothesis has never been tested in vivo during exercise. We examined the metabolic response to exercise in patients with late-onset Pompe disease, in order to determine if a defect in energy metabolism may play a role in the pathogenesis of Pompe disease. We studied six adult patients with Pompe disease and 10 healthy subjects. The participants underwent ischemic forearm exercise testing, and peak work capacity was determined. Fat and carbohydrate metabolism during cycle exercise was examined with a combination of indirect calorimetry and stable isotope methodology. Finally, the effects of an IV glucose infusion on heart rate, ratings of perceived exertion, and work capacity during exercise were determined. We found that peak oxidative capacity was reduced in the patients to 17.6 vs. 38.8mlkg−1 min−1 in healthy subjects (p=0.002). There were no differences in the rate of appearance and rate of oxidation of palmitate, or total fat and carbohydrate oxidation, between the patients and the healthy subjects. None of the subjects improved exercise tolerance by IV glucose infusion. In conclusion, peak oxidative capacity is reduced in Pompe disease. However, skeletal muscle fat and carbohydrate use during exercise was normal. The results indicate that a reduced exercise capacity is caused by muscle weakness and wasting, rather than by an impaired skeletal muscle glycogenolytic capacity. Thus, it appears that acid alpha-glucosidase does not play a significant role in the production of energy in skeletal muscle during exercise. [Copyright &y& Elsevier]

Abstract: Objective: Late-onset Pompe disease is a rare, but potentially treatable metabolic myopathy, and therefore should not be overlooked. However, it is not unusual that patients go undiagnosed for many years. We hypothesized that patients with late-onset Pompe disease may have been overlooked in a population of patients with unclassified neuromuscular disease. Methods: We used DBS (dried blood spots) to screen for Pompe disease in the two largest neuromuscular clinics and one of the main respiratory centers in Denmark. We selected patients with unclassified LGDM (limb-girdle muscular dystrophy), idiopathic elevation of creatine kinase, unexplained myopathy on muscle biopsy, unexplained restrictive respiratory insufficiency or unspecified myopathy for screening. Results: 177 patients were found eligible for inclusion, and 103 (58.2%) patients accepted screening. Three patients with Pompe disease were identified with DBS, and subsequent genetic testing revealed known pathogenic mutations in the GAA gene. All three patients were found among 38 patients with unclassified LGMD (8%). Conclusion: Our findings indicate that a DBS should be considered early in the diagnostic work-up of patients with an LGMD phenotype, to rule out Pompe disease. Retrospectively, all 3 patients presented with “red flags” more compatible with Pompe disease than LGMD, including; 1) mild non-dystrophic, myopathic features on muscle biopsy, 2) creatine kinase levels below 1000, and 3) disproportionate axial and respiratory muscle involvement in comparison with limb muscle involvement. [Copyright &y& Elsevier]

Safety, tolerability, pharmacokinetics, pharmacodynamics, and exploratory efficacy of repeat avalglucosidase alfa dosing (5, 10, or 20 mg/kg qow) for 6 months were evaluated in NEO1 (NCT01898364) in late-onset Pompe disease patients either treatment-naïve (Naïve) or having received alglucosidase alfa for ≥9 months (Switch). In NEO-EXT (NCT02032524), an ongoing NEO1 extension, long-term safety and pharmacokinetics of repeat avalglucosidase alfa dosing will be monitored over 6 years. Interim safety results after 4.5 years of NEO-EXT are reported here. Mean ages at NEO1 enrollment were: Naïve: 44.8 (SD:20.3, range:20-78) years and Switch: 46.7 (SD:14.1, range:21-68) years. Of the 24 NEO1 participants, 19 entered NEO-EXT (8/10 Naïve 11/14 Switch) 17 are currently participating (7/8 Naïve 10/11 Switch) 2 participants discontinued NEO-EXT (personal reasons). During 2016, all NEO-EXT participants switched to avalglucosidase alfa 20 mg/kg qow. By May 2018, total infusions reached 731 (Naïve) and 1174 (Switch) mean infusions were Naïve: 73 (SD:43, range:9-113) and Switch: 84 (SD:40, range:8-118). Mean avalglucosidase alfa exposure duration reached 1025 (SD:611, range:109-1572) days for Naïve and 1179 (SD:570, range:102-1658) days for Switch participants. Treatment-emergent adverse events (AEs) were generally mild across doses. Most frequently reported treatment-related AEs were nausea, fatigue, and headache (3 participants each) and dizziness, dyspnea, erythema, myalgia, muscle spasms, and rash (2 participants each) and are unchanged since the last safety update (WORLDSymposium™ 2018). One Switch participant discontinued NEO1 for a study drug-related serious AE (respiratory distress/chest discomfort) no deaths/life-threatening serious AEs have occurred. Anti-avalglucosidase IgG/IgM antibodies developed in 9/10 Switch (median titer:1600, range:200-51,200) and 9/14 Naïve (median titer:400, range:50-12,800) participants. No patient developed IgE antibodies or tested positive for enzyme activity inhibition. In NEO-EXT, the avalglucosidase alfa safety profile is consistent with the initial 6 months' treatment during NEO1, with no additional participants developing anti-avalglucosidase alfa IgG/IgM antibodies or new allergic reactions. Funding: Sanofi Genzyme. [ABSTRACT FROM AUTHOR]