Influence of demographic and metabolic variables on forearm blood flow and vascular conductance in individuals without overt heart disease

Alpha2A-adrenergic receptor and eNOS genetic polymorphisms are associated with exercise muscle vasodilatation in apparently healthy individuals

PURPOSE

Muscle vasodilatation during exercise has been associated with cardiovascular health and may be influenced by genetic variability. The purpose of this study was to evaluate functional genetic polymorphisms of physiologic pathways related to the regulation of the cardiovascular function (alpha-adrenergic receptors, endothelial nitric oxide synthase and bradykinin B2 receptor) and exercise muscle vasodilatation in apparently healthy men and women.

METHODS

We enrolled 689 individuals without established cardiovascular disease that had attended a check-up program. The vasodilatation was studied with venous occlusion plethysmography and determined by the increase of vascular conductance during handgrip exercise. Genotypes for ADRA1A Arg347Cys (rs1048101), ADRA2A 1780 C > T (rs553668), ADRA2B Del 301-303 (rs28365031), eNOS 786 T > C (rs2070744), eNOS Glu298Asp (rs1799983) and BDKRB2 (rs5810761) polymorphisms were assessed by polymerase chain reaction followed by high resolution melting analysis.

RESULTS

The eNOS rs2070744 polymorphism was significantly associated with forearm vascular conductance during exercise in women. Women with CC genotype showed higher vasodilatation than carriers of TC and TT genotypes (p = 0.043). The ADRA2A rs553668 polymorphism was significantly associated with forearm vascular conductance during exercise in men. Men with TT genotype had higher vasodilatation than carriers of CT and CC genotypes (p = 0.025).

CONCLUSIONS

eNOS rs207074 polymorphism in women and ADRA2A rs553668 polymorphism in men were associated with the increase of forearm vascular conductance during handgrip exercise. These findings suggest that eNOS and ADRA2A genetic polymorphisms may be potential markers of exercise muscle vasodilatation.

Na+K+-ATPase activity and K+ channels differently contribute to vascular relaxation in male and female rats

Gender associated differences in vascular reactivity regulation might contribute to the low incidence of cardiovascular disease in women. Cardiovascular protection is suggested to depend on female sex hormones' effects on endothelial function and vascular tone regulation. We tested the hypothesis that potassium (K+) channels and Na+K+-ATPase may be involved in the gender-based vascular reactivity differences. Aortic rings from female and male rats were used to examine the involvement of K+ channels and Na+K+-ATPase in vascular reactivity. Acetylcholine (ACh)-induced relaxation was analyzed in the presence of L-NAME (100 µM) and the following K+ channels blockers: tetraethylammonium (TEA, 2 mM), 4-aminopyridine (4-AP, 5 mM), iberiotoxin (IbTX, 30 nM), apamin (0.5 µM) and charybdotoxin (ChTX, 0.1 µM). The ACh-induced relaxation sensitivity was greater in the female group. After incubation with 4-AP the ACh-dependent relaxation was reduced in both groups. However, the dAUC was greater in males, suggesting that the voltage-dependent K+ channel (Kv) participates more in males. Inhibition of the three types of Ca2+-activated K+ channels induced a greater reduction in Rmax in females than in males. The functional activity of the Na+K+-ATPase was evaluated by KCl-induced relaxation after L-NAME and OUA incubation. OUA reduced K+-induced relaxation in female and male groups, however, it was greater in males, suggesting a greater Na+K+-ATPase functional activity. L-NAME reduced K+-induced relaxation only in the female group, suggesting that nitric oxide (NO) participates more in their functional Na+K+-ATPase activity. These results suggest that the K+ channels involved in the gender-based vascular relaxation differences are the large conductance Ca2+-activated K+ channels (BKCa) in females and Kv in males and in the K+-induced relaxation and the Na+K+-ATPase vascular functional activity is greater in males.

Sex-specific effect of aging on submaximal leg exercise hemodynamics in middle-aged and older adults

The purpose of the study was to examine predictors of the leg hemodynamic response to exercise in middle- and older-aged men and women. Femoral artery blood flow (FBF), mean arterial pressure (MAP), and femoral vascular conductance (FVC, calculated as the quotient of FBF and MAP) were measured at rest and during 5 min of single knee-extensor exercise at ~10 W workload in healthy men (n = 31) and women (n = 32) (age 40-72 years). Age, menopausal status, maximal quadriceps strength, blood lipids, vitamin D levels, maximal oxygen uptake (VO(2max)), physical activity, blood pressure, estimated quadriceps muscle mass, and body mass index (BMI) were also assessed. The effect of age on FBF and FVC was negative and significant in men (r = -0.44 and -0.42 and p = 0.01 and 0.02, respectively) but was abolished by normalization to estimated quadriceps muscle (p = 0.18 and 0.73, respectively). There was no effect of age on leg hemodynamic responses to exercise in women (alone or normalized to quadriceps muscle), but menopausal status was a significant predictor of FVC and normalized FVC (p = 0.04 and 0.02, respectively). The multivariate model for exercising FVC in men (in order of strongest to weakest predictors) included quadriceps strength, BMI, resting FVC, age, and high-density lipoprotein cholesterol. The multivariate model for exercising FVC in women included quadriceps mass, systolic blood pressure, vitamin D, age, VO(2max), waist circumference, and physical activity score. These findings suggest that factors besides chronological age mediate exercising leg hemodynamics in middle-aged to older adults and that these factors are sex-specific.