No effect of oral sucrose or IV glucose during exercise in phosphorylase b kinase deficiency

Andersen, A.G.; Ørngreen, Mette Cathrine; Raaschou-Pedersen, Daniel Emil Tadeusz; Borch, Josefine de Stricker; Løkken, Nicoline; Krag, Thomas; Petersen, Mads; Vissing, John

doi:10.1016/j.nmd.2020.02.008

Cited by 5 publications

(2 citation statements)

References 13 publications

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“…Phosphorylase b kinase deficiency in human skeletal muscle (Glycogen Storage Disease, GSD IX) is exceedingly rare. Moreover, it is not always defined by complete loss of kinase activity and can be associated with elevated levels of glycogen phosphorylase (Andersen et al 2020 ), which complicates use of this model to study regulation of glycogenolysis. Taken together, the data question the conclusion that conversion of phosphorylase b to a is the major mechanism for activation of glycogenolysis during intense muscle contraction.…”

Section: Regulation Of Glycogenolysis In Living Muscle During Contrac...mentioning

confidence: 99%

A century of exercise physiology: key concepts in regulation of glycogen metabolism in skeletal muscle

Katz

2022

Eur J Appl Physiol

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Glycogen is a branched, glucose polymer and the storage form of glucose in cells. Glycogen has traditionally been viewed as a key substrate for muscle ATP production during conditions of high energy demand and considered to be limiting for work capacity and force generation under defined conditions. Glycogenolysis is catalyzed by phosphorylase, while glycogenesis is catalyzed by glycogen synthase. For many years, it was believed that a primer was required for de novo glycogen synthesis and the protein considered responsible for this process was ultimately discovered and named glycogenin. However, the subsequent observation of glycogen storage in the absence of functional glycogenin raises questions about the true role of the protein. In resting muscle, phosphorylase is generally considered to be present in two forms: non-phosphorylated and inactive (phosphorylase b) and phosphorylated and constitutively active (phosphorylase a). Initially, it was believed that activation of phosphorylase during intense muscle contraction was primarily accounted for by phosphorylation of phosphorylase b (activated by increases in AMP) to a, and that glycogen synthesis during recovery from exercise occurred solely through mechanisms controlled by glucose transport and glycogen synthase. However, it now appears that these views require modifications. Moreover, the traditional roles of glycogen in muscle function have been extended in recent years and in some instances, the original concepts have undergone revision. Thus, despite the extensive amount of knowledge accrued during the past 100 years, several critical questions remain regarding the regulation of glycogen metabolism and its role in living muscle.

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Section: Regulation Of Glycogenolysis In Living Muscle During Contrac...mentioning

confidence: 99%

A century of exercise physiology: key concepts in regulation of glycogen metabolism in skeletal muscle

Katz

2022

Eur J Appl Physiol

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“…One study found that 37 grams of oral sucrose consumed 5 to 10 minutes before exercise improved exercise capacity and reduced symptoms 60 . Another study found that patients with GSD3 (debranching enzyme deficiency) also showed improvements in exercise capacity with preexercise fructose ingestion 62 ; however, neither oral sucrose nor IV glucose improved exercise capacity in patients with GSD9 63 . In contrast, patients with glycolytic defects (ie, GSD7) tolerate exercise better in the fasted state and do worse with carbohydrate feeding given that carbohydrates attenuate the liberation of free fatty acids via lipolysis as an alternative fuel source 64 …”

Section: Disorders Of Glycolysis/glycogenolysis (Glycogen Storage Dis...mentioning

confidence: 99%

Metabolic Myopathies

Tarnopolsky¹

2022

CONTINUUM: Lifelong Learning in Neurology

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PURPOSE OF REVIEW: Metabolic myopathies are disorders that affect skeletal muscle substrate oxidation. Although some drugs and hormones can affect metabolism in skeletal muscle, this review will focus on the genetic metabolic myopathies.RECENT FINDINGS: Impairments in glycogenolysis/glycolysis (glycogen storage disease), fatty acid transport/oxidation (fatty acid oxidation defects), and mitochondrial metabolism (mitochondrial myopathies) represent most metabolic myopathies; however, they often overlap clinically with structural genetic myopathies, referred to as pseudometabolic myopathies. Although metabolic myopathies can present in the neonatal period with hypotonia, hypoglycemia, and encephalopathy, most cases present clinically in children or young adults with exercise intolerance, rhabdomyolysis, and weakness. In general, the glycogen storage diseases manifest during brief bouts of high-intensity exercise; in contrast, fatty acid oxidation defects and mitochondrial myopathies usually manifest during longer-duration endurance-type activities, often with fasting or other metabolic stressors (eg, surgery, fever). The neurologic examination is often normal between events (except in the pseudometabolic myopathies) and evaluation requires one or more of the following tests: exercise stress testing, blood (eg, creatine kinase, acylcarnitine profile, lactate, amino acids), urine (eg, organic acids, myoglobin), muscle biopsy (eg, histology, ultrastructure, enzyme testing), and targeted (specific gene) or untargeted (myopathy panels) genetic tests. SUMMARY: Definitive identification of a specific metabolic myopathy often leads to specific interventions, including lifestyle, exercise, and nutritional modifications; cofactor treatments; accurate genetic counseling; avoidance of specific triggers; and rapid treatment of rhabdomyolysis.

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A novel PHKA1 mutation associating myopathy and cognitive impairment: Expanding the spectrum of phosphorylase kinase b (PhK) deficiency

Bisciglia

Froissart

Bedat-Millet

et al. 2021

Journal of the Neurological Sciences

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No effect of oral sucrose or IV glucose during exercise in phosphorylase b kinase deficiency

Cited by 5 publications

References 13 publications

A century of exercise physiology: key concepts in regulation of glycogen metabolism in skeletal muscle

A century of exercise physiology: key concepts in regulation of glycogen metabolism in skeletal muscle

Metabolic Myopathies

A novel PHKA1 mutation associating myopathy and cognitive impairment: Expanding the spectrum of phosphorylase kinase b (PhK) deficiency

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