The I allele of the ACE gene is associated with improved exercise capacity in women with McArdle disease.

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 (VO(2)peak), 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 VO(2)peak 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 VO(2)peak 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.