eNOS T-786C genotype, physical activity, and peak forearm blood flow in females

The purpose of the present study was to determine interactive and main effects of the eNOS T-786C gene polymorphism and habitual physical activity level on forearm vascular resistance (FVR) and forearm blood flow (FBF) at rest and during 3 min of reactive hyperemia.

We studied healthy, Caucasian (age 25 +/- 1 yr), sedentary (maximal oxygen consumption, [OV0312]O2max: 33.8 +/- 1 mL x kg(-1)x min(-1)), and endurance-trained ([OV0312]O2max: 45.3 +/- 1 mL x kg(-1)x min(-1)) women. FBF was measured using venous occlusion plethysmography before (resting) and after 5 min of arm arterial occlusion at 1 (peak vasodilation), 2, and 3 min of reactive hyperemia. [OV0312]O2max was measured using a standard treadmill protocol, and skinfolds were measured to estimate body composition.

There was a significant interaction between eNOS genotype and physical activity level on resting FVR (P = 0.0003). Sedentary subjects with the TT genotype had the lowest resting FVR, but among the endurance-trained group, the TC+CC genotype group had the lowest resting FVR. This interaction was reflected in the resting FBF values (P = 0.03). After accounting for important covariates, there was a main effect of eNOS genotype on peak FBF (TT, 7.0 +/- 0.3 vs TC+CC, 5.9 +/- 0.4 mL x 100 mL(-1) FAV x min(-1), P = 0.03) and the percent decrease in FVR (TT, -62 +/- 2 vs TC+CC, -51 +/- 4%, P = 0.04) at minute 1.

These results of the interactive effects suggest that young females possessing a C allele may reduce their resting FVR by improving their cardiovascular fitness level, but TT homozygotes, who may have normal eNOS gene function, may not improve their resting FVR with improvements in cardiovascular fitness. Furthermore, regardless of physical activity level, the TT genotype showed a favorable hemodynamic response during reactive hyperemia compared with the C allele carriers.