GLUCOSE SUPPLEMENTATION AND MEASURES OF OXIDATIVE STRESS IN PATIENTS WITH GLYCOGEN PHOSPHORYLASE DEFICIENCY (MCARDLE’S DISEASE).

Abstract

<p><em>Objective: </em>We evaluated the potential effect of oral glucose supplementation on: (1) exercise performance and tolerance, (2) the concentrations of plasma uric acid and ammonia (NH₃) and (3) blood plasma markers of oxidative stress in patients with McArdle’s disease (MCD) after non-ischemic forearm exercise testing (non-ischemic forearm exercise test). <em>Methods:</em> Blood samples and exercise performance measures were performed on from 16 patients with MCD and 17 control subjects (CON) matched for age, sex and physical activity status. Subjects performed 2 exercise bouts 30 minutes apart and received oral glucose or placebo supplementation between tests. Blood samples were analyzed for concentrations of 8-isoprostanes (8-ISO), malondialdehyde (MDA) and total anti-oxidant capacity (TEAC). Exercise performance was assessed using a handgrip dynamometer to measure force of contraction over time. Exercise tolerance was assessed based on subject’s self-reported perception of pain and perception of exertion during exercise. <em>Results:</em> MCD was associated with greater fatigue, perceived pain, perceived exertion, and higher uric acid during non-ischemic forearm exercise test (P < 0.05), and higher concentrations of plasma NH₃post exercise (P < 0.05). Glucose did not influence plasma uric acid or NH₃and had no effect on exercise measures in MCD patients. Baseline plasma markers of oxidative stress were not different between MCD patients and CON; however, MCD patients who ingested glucose between non-ischemic forearm exercise tests had lower plasma 8-ISO concentrations (P < 0.05). CON who ingested glucose between non-ischemic forearm exercise tests had lower plasma 8-ISO concentrations (P < 0.05) at +1 min post exercise compared to initial non-ischemic forearm exercise test. The TEAC of control subjects was lower following non-ischemic forearm exercise test (P < 0.05), with no change in MCD patients. <em>Conclusion: </em>Glucose may have a protective effect on oxidative stress following exercise that may be due to attenuated flux through xanthine oxidase.</p>