Sex differences in vascular compliance in normal-weight but not obese boys and girls: the effect of body composition

Exercise Training Duration and Intensity Are Associated With Thicker Carotid Intima-Media Thickness but Improved Arterial Elasticity in Active Children and Adolescents

Even though exercise generally has a positive effect on health, intensive exercise can have adverse effects on the vascular system of adults. This study aimed to investigate the association between training duration and intensity and vascular structure and function in 427 physically active children and adolescents (14.0 ± 1.94 years). In this study, we examined carotid intima-media thickness (cIMT), carotid diameter, and cIMT:diameter-ratio as parameters of carotid arterial structure and arterial compliance (AC), stiffness index β (β), elastic modulus (Ep), and carotid pulse wave velocity (PWVβ) as parameters of carotid arterial function with high-resolution ultrasound. We collected central systolic blood pressure (cSBP) and aortic pulse wave velocity (aPWV) as parameters of central arterial stiffness with an oscillometric device. We used the MoMo Physical Activity Questionnaire to record training duration and intensity. Training duration (p = 0.022) and intensity (p = 0.024) were associated with higher cIMT. Further, training duration was associated with lower central arterial stiffness (cSBP: p = 0.001; aPWV: p = 0.033) and improved AC (p < 0.001). Higher training intensity was related to improved AC (p < 0.001) and larger carotid diameter (p = 0.040). Boys presented thicker cIMT (p = 0.010), improved AC (p = 0.006), and lower central arterial stiffness (cSBP: p < 0.001; aPWV: p = 0.016) associated with higher training duration. Girls presented improved AC (p = 0.023) and lower Ep (p = 0.038) but higher β (p = 0.036) associated with higher training duration. Only boys demonstrated thicker cIMT (p = 0.016) and improved AC (p = 0.002) associated with higher training intensity. A quintile analyses of the training duration revealed thicker cIMT of children and adolescents in Q1 and Q5 than that in Q4 and Q5. Besides, Q1 showed lower cSBP compared to Q4 and Q5. Regarding training intensity, Q5 had thicker cIMT than Q2 and Q3. Although a higher training load is associated with thicker cIMT, the common carotid artery is also more elastic. This suggests that a higher training load leads to a functional adaptation of the carotid artery in youth.

Sex differences in the structure and function of rat middle cerebral arteries

Epidemiological studies demonstrate that there are sex differences in the incidence, prevalence, and outcomes of cerebrovascular disease (CVD). The present study compared the structure and composition of the middle cerebral artery (MCA), neurovascular coupling, and cerebrovascular function and cognition in young Sprague-Dawley (SD) rats. Wall thickness and the inner diameter of the MCA were smaller in females than males. Female MCA exhibited less vascular smooth muscle cells (VSMCs), diminished contractile capability, and more collagen in the media, and a thicker internal elastic lamina with fewer fenestrae compared with males. Female MCA had elevated myogenic tone, lower distensibility, and higher wall stress. The stress/strain curves shifted to the left in female vessels compared with males. The MCA of females failed to constrict compared with a decrease of 15.5 ± 1.9% in males when perfusion pressure was increased from 40 to 180 mmHg. Cerebral blood flow (CBF) rose by 57.4 ± 4.4 and 30.1 ± 3.1% in females and males, respectively, when perfusion pressure increased from 100 to 180 mmHg. The removal of endothelia did not alter the myogenic response in both sexes. Functional hyperemia responses to whisker-barrel stimulation and cognition examined with an eight-arm water maze were similar in both sexes. These results demonstrate that there are intrinsic structural differences in the MCA between sexes, which are associated with diminished myogenic response and CBF autoregulation in females. The structural differences do not alter neurovascular coupling and cognition at a young age; however, they might play a role in the development of CVD after menopause.

NEW & NOTEWORTHY Using perfusion fixation of the middle cerebral artery (MCA) in calcium-free solution at physiological pressure and systematically randomly sampling the sections prepared from the same M2 segments of MCA, we found that there are structural differences that are associated with altered cerebral blood flow (CBF) autoregulation but not neurovascular coupling and cognition in young, healthy Sprague-Dawley (SD) rats. Understanding the intrinsic differences in cerebrovascular structure and function in males and females is essential to develop new pharmaceutical treatments for cerebrovascular disease (CVD).

Sex differences in the vascular function and related mechanisms: role of 17β-estradiol

The incidence of cardiovascular disease (CVD) is lower in premenopausal women but increases with age and menopause compared with similarly aged men. Based on the prevalence of CVD in postmenopausal women, sex hormone-dependent mechanisms have been postulated to be the primary factors responsible for the protection from CVD in premenopausal women. Recent Women’s Health Initiative studies, Cochrane Review studies, the Early Versus Late Intervention Trial with Estradiol Study, and the Kronos Early Estrogen Prevention Study have suggested that beneficial effects of hormone replacement therapy (HRT) are seen in women of <60 yr of age and if initiated within <10 yr of menopause. In contrast, the beneficial effects of HRT are not seen in women of >60 yr of age and if commenced after 10 yr of menopause. The higher incidence of CVD and the failure of HRT in postmenopausal aged women could be partly associated with fundamental differences in the vascular structure and function between men and women and in between pre- and postmenopausal women, respectively. In this regard, previous studies from human and animal studies have identified several sex differences in vascular function and associated mechanisms. The female sex hormone 17β-estradiol regulates the majority of these mechanisms. In this review, we summarize the sex differences in vascular structure, myogenic properties, endothelium-dependent and -independent mechanisms, and the role of 17β-estradiol in the regulation of vascular function.

Microvascular endothelial function in Japanese early adolescents

Endothelial dysfunction is the early predictive factor for the development of atherosclerosis and future cardiovascular diseases in adulthood. The prevalence of endothelial dysfunction in children and early adolescents is increasing worldwide. Peripheral arterial tonometry is a noninvasive technique for assessing peripheral microvascular function and is used as a validated marker of endothelial function. We assessed anthropometric parameters, blood pressure, arterial stiffness, and peripheral endothelial function in 157 Japanese early adolescents (75 boys and 82 girls). We measured peripheral endothelial function by using peripheral arterial tonometry to determine the reactive hyperemia index, and assessed the association of reactive hyperemia index with parameters of anthropometry and arterial stiffness. The mean reactive hyperemia index of all subjects was 1.85 ± 0.6, and there was no difference of reactive hyperemia index according to sex. Reactive hyperemia index was significantly associated with systolic and diastolic blood pressures, and had no correlation with anthropometric parameters and arterial stiffness markers. The reactive hyperemia index values among Japanese early adolescents were similar to those reported in previous studies on children and early adolescents. This noninvasive technique may be useful for the assessment of microvascular endothelial function among children and early adolescents.

Arterial compliance in obese children: implications for cardiovascular health

Recent work showed that arterial compliance may be elevated unexpectedly in obese children, attributable to accelerated growth and maturation. We hypothesize that children with obesity or Type 2 diabetes may reach peak arterial maturation earlier in life and then experience an earlier, and potentially more rapid, decline in arterial compliance, leading toward earlier cardiovascular disease development.

Arterial compliance is increased in children with type 2 diabetes compared with normal weight peers but not obese peers

BACKGROUND

We reported that obesity was associated with increased arterial compliance in children, possibly due to accelerated vascular maturation. Here, we explored the additional burden of type 2 diabetes (T2DM) on vascular function in children.

METHODS

Fifty normal weight [body mass index (BMI) 25-75%], 58 obese (BMI ≥ 95%), and 34 children with T2DM diagnosed by American Diabetes Association (ADA) criteria ages 10-18 yr were studied. Large and small artery elasticity (LAEI and SAEI, respectively) were measured by diastolic pulse-wave contour analysis.

RESULTS

SAEI was 27% higher in children with T2DM compared to normal weight children (p = 0.005). Mean LAEI for those with T2DM not different from either group. In the group with T2DM, both SAEI and LAEI increased with age up to 16 yr, but declined thereafter. The strongest multivariable model predicting SAEI in children with T2DM combined lean mass, systolic blood pressure (SBP), and glucose (r2  = 0.59); for predicting LAEI, the strongest model included height, SBP, and low-density lipid-cholesterol (r2  = 0.61).

CONCLUSION

The lower arterial compliance in older adolescents with T2DM compared to that of their peers without diabetes may indicate a premature maturation of the vascular system; however, follow-up will clarify whether these vascular changes portend an early increase in diabetes-associated cardiovascular disease risk.