Background: McArdle disease is an uncommon metabolic disorder usually characterized by marked exercise intolerance although great individual variability exists in its phenotypic manifestation.
Objective: The purpose of this study was to determine the association between angiotensin-converting enzyme (ACE) genotypes and indices of exercise capacity (peak oxygen uptake (VO2peak), ventilatory threshold (VT) and gross mechanical efficiency (GE)) in patients with McArdle disease. Based on previous research, it was hypothesized that the I allele might favourably influence exercise capacity.
Methods: Forty-four Spanish patients (23 males, 21 females) and 44 age-matched and gender-matched controls (23 males, 21 females) performed a graded cycle-ergometer test until exhaustion (for VO2peak and VT determination) and a 12 min constant-load test at the power output eliciting the VT (for GE determination).
Results: No significant difference (p>0.05) was found in indices of exercise capacity between ID + II genotypes and DD homozygotes in the group of male patients, male controls and female controls. However, in the group of female patients, the ID + II group (n = 11) had a higher VO2peak than DD homozygotes (n = 10) (15.8 (SEM 1.6) ml/kg/min versus 11.9 (SEM 0.9) ml/kg/min, respectively; p<0.05).
Conclusions: The I allele of the ACE gene is associated with a higher functional capacity in female patients, and might partly explain the individual variability in the phenotypic manifestation of McArdle disease.
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Funding: MM and JCR are supported by contracts from Fondo de Investigaciones Sanitarias (FIS) CA05/0039 and CD06/00031, respectively (Ministerio de Sanidad y Consumo (MSC), Madrid), and MAM is supported by Programa de Intensificación de la Actividad Investigadora, ISCIII (MSC) and Agencia Laín Entralgo (Consejería de Sanidad, Comunidad de Madrid). This work was supported by grants from FIS numbers PI040487, PI041157 and PI050579.
Competing interests: None declared.