Association between the angiotensin-converting enzyme gene polymorphisms and tissue oxygenation during exercise in patients with COPD

Study objectives: We have recently determined that the angiotensin-converting enzyme (ACE) DD genotype might be associated with pulmonary hypertension during exercise in patients with COPD. Therefore, this study was designed to determine whether ACE gene polymorphisms adversely affect tissue oxygenation during exercise in patients with COPD. Design: Cross-sectional analysis. Setting: University hospital. Patients: Thirty-nine patients (14 patients with II genotype, 12 patients with ID genotype, and 13 patients with DD genotype). Interventions: All patients underwent tight-heart catheterization and constant-load exercise testing for 5 min on an ergometer. Measurements and results: The ratio of the change in oxygen delivery (DO2) to the increase in oxygen consumption ((V)over dot O-2) during exercise (DeltaDO(2)/Delta(V)over dot O-2) was significantly lower in patients with the DD genotype (1.5 +/- 0.2) than in those with the 11 genotype (1.9 +/- 0.3, p = 0.0006) and the ID genotype (1.7 +/- 0.2, p = 0.037). Mixed venous oxygen tension (<P(v)over bar O-2>) after exercise in patients with the DD genotype (23.5 +/- 1.5 mm Hg) was also significantly lower than in patients with the 11 genotype (26.7 +/- 1.6 turn Hg, p = 0.0002) and the ID genotype (25.0 +/- 2.0 min Hg, p = 0.045). in addition, the change in plasma concentration of lactate during exercise (Delta Lactate) was significantly higher in patients with DD genotype (33.3 +/- 4.3 mmol/L) than in those with the 11 genotype (25.5 +/- 3.6 mmol/L, p = 0.0002) and the ID genotype (28.8 +/- 4.0 mmol/L, p = 0.029). The mean pulmonary arterial pressure after exercise was significantly correlated with Delta DO2/Delta(V)over dot O-2 (r = -0.423, p = 0.0076) but not with PVO2 after exercise and with Delta Lactate. Conclusions: The ACE DD genotype may be associated with an impairment in peripheral tissue oxygenation during exercise in patients with COPD.