ORIGINAL RESEARCH article

ABSTRACT ONLY| VOLUME 31, SUPPLEMENT 1, S112, OCTOBER 01, 2021

Patients with glycogen storage disease type V (GSDV), also known as McArdle disease, have blocked glycogen utilization in skeletal muscle, leading to exercise intolerance, muscle pain and risk of muscle damage. Ketone bodies (KBs) constitute an alternative fuel source, that potentially could fuel the working muscle independent of glycogenolysis. Endogenous KBs are produced during fasting and ketogenic dieting; a diet that has shown early promising results but can be difficult to adhere to. This led us to explore the effects of an oral supplementation with exogenous KBs on exercise capacity and metabolism in patients with GSDV. Eight GSDV-patients and four matched controls (HC) were included in this placebo-controlled, double-blind cross-over study and randomized to receive either an oral supplement with 395 mg/kg ketone esters (KE) or placebo first on two separate days 25 minutes prior to a submaximal cycle exercise test. The primary outcome measure was exercise capacity as indicated by heart rate (HR) response to exercise. Secondary outcomes included perceived exertion (PE) and KB-, carbohydrate- and fat-metabolism as measured using stable isotope technique and changes in blood metabolites during submaximal exercise. In GSDV, the KE drink increased plasma KBs from 78.6 to 3289.9 µmol/L (p=0.00008) and KB-oxidation (p=0.0001) but did not improve exercise capacity as judged by the primary outcome measure HR (p=0.120) and the secondary outcome measure PE (p=0.109) compared to placebo. Other secondary outcomes showed significantly lower concentrations of free fatty acids, glycerol and glucose with KE vs. placebo drink. Similar results were found in the HC group. This study indicates that an increase in KB oxidation by oral KE supplementation cannot fully compensate for the KB-induced inhibition of lipolysis and glycolysis, explaining why the drink failed to improve exercise capacity. Thus, oral KE supplementation alone cannot be recommended as treatment option for patients with GSDV.