Impact of pubertal development on endothelial function and arterial elasticity

Muscular Fitness and Cardiometabolic Variables in Children and Adolescents: A Systematic Review

BACKGROUND

The importance of muscular fitness (MF) in the performance of activities of daily living is unequivocal. Additionally, emerging evidence has shown MF can reduce cardiometabolic risk in children and adolescents.

OBJECTIVES

The purpose of this study was to examine and summarize the evidence regarding the relationship between MF phenotypes (i.e., maximum muscular strength/power, muscular endurance, and maximum muscular strength/power/endurance) and cardiometabolic variables (obesity, blood pressure, lipids, glucose homeostasis, inflammatory markers, and clustered cardiometabolic variables) in children and adolescents.

DESIGN

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and was registered with PROSPERO, number CRD42020179273.

DATA SOURCES

A systematic review was performed on five databases (PubMed, EMBASE, SciELO, Scopus, and Web of Knowledge) from database inception to May 2020, with complementary searches in reference lists.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Eligibility criteria included (1) a study sample of youth aged ≤ 19 years, (2) an assessment of MF with individual or clustered cardiometabolic variables derived from adjusted models (regardless of test/measurement adopted or direction of reported association), and (3) a report of the association between both, using observational studies. Only original articles published in peer-reviewed journals in English, Portuguese, and Spanish languages were considered. The quality of the included studies was assessed by using the National Heart, Lung, and Blood Institute checklist. The percentage of results reporting a statistically significant inverse association between each MF phenotype and cardiometabolic variables was calculated.

RESULTS

Of the 23,686 articles initially identified, 96 were included (77 cross-sectional and 19 longitudinal), with data from children and adolescents from 35 countries. The score for the quality of evidence ranged from 0.33 to 0.92 (1.00 maximum). MF assessed by maximum muscular strength/power was inversely associated with lower obesity (64/113 total results (56.6%)) and reduction in clustered cardiometabolic risk (28/48 total results (58.3%)). When assessed by muscular endurance, an inverse association with obesity (30/44 total results (68.1%)) and cardiometabolic risk (5/8 total results (62.5%)) was identified. Most of the results for the relationship between MF phenotypes with blood pressure, lipids, glucose homeostasis, and inflammatory markers indicated a paucity of evidence for these interrelationships (percentage of results below 50.0%).

CONCLUSION

MF assessed by maximum muscular strength/power or muscular endurance is potentially associated with lower obesity and lower risk related to clustered cardiometabolic variables in children and adolescents. There is limited support for an inverse association between MF with blood pressure, lipids, glucose homeostasis biomarkers, and inflammatory markers in children and adolescents.

Maximal oxygen consumption and oxygen uptake efficiency in adolescent males

BACKGROUND/OBJECTIVE

Measures of oxygen uptake efficiency (OUE) have been used to evaluate cardiorespiratory fitness (CRF) in adolescents unable to perform maximal exercise. The oxygen uptake efficiency slope (OUES) and oxygen uptake efficiency plateau (OUEP) have been proposed as surrogates for maximal oxygen consumption (V̇O2max). We assessed the validity of the OUES and OUEP as predictors of V̇O2max in healthy male adolescents.

METHODS

Sixty-three healthy male adolescents aged 15.40 ± 0.34 years underwent an incremental treadmill test to determine V̇O2max, OUES and OUEP. OUE throughout the test was assessed by dividing each V̇O2 value by the corresponding minute ventilation (V̇E) value. OUEP was determined as the 90 s average highest consecutive values for OUE. OUES was determined using data up to the ventilatory threshold (VT) by calculating the slope of the linear relation between V̇O2 and the logarithm of V̇E.

RESULTS

Limits of agreement for V̇O2max predicted by OUES (±13.3 mL kg-1.min-1) and OUEP (±16.7 mL kg-1.min-1) relative to V̇O2max were wide and a magnitude bias was found for OUES and OUEP as predictors of V̇O2max (p < 0.001).

CONCLUSION

The OUES and OUEP do not accurately predict V̇O2max in male adolescents and should not replace V̇O2max when assessing CRF in this population.

Age-related differences in blood pressure, ultrasound-derived arterial diameters and arterial wall stiffness parameters in horses

BACKGROUND

Arterial rupture mainly affects older horses. The reason why older horses are more prone to arterial rupture and which underlying vascular changes predispose older horses to aortic rupture is still unclear.

OBJECTIVES

To investigate the effect of ageing on the equine arterial wall and blood pressure.

STUDY DESIGN

Cohort study.

METHODS

Non-invasive blood pressure measurement using a tail cuff and vascular ultrasound from aorta, common carotid artery and external iliac artery was performed in 50 healthy young (3-7 years) and 50 healthy old Warmblood horses (>18 years). Arterial diameters and cross-sectional areas, and arterial wall thickness were measured offline. Regional arterial wall stiffness of the aorta and common carotid artery were assessed using pulse wave velocity, while lumen area/diameter change, strain, compliance and distensibility were calculated to assess local arterial wall stiffness.

RESULTS

No difference in blood pressure was found between old and young horses. All arterial dimensions and intima-media thickness of the common carotid artery were significantly larger in old horses. A significantly higher local arterial wall stiffness was found for the aorta and the caudal common carotid artery in older horses. For the external iliac artery, no significant differences in arterial wall stiffness were found. Both aortic and carotid pulse wave velocities were higher in older horses compared with younger horses.

MAIN LIMITATIONS

Blood pressure was measured non-invasively.

CONCLUSIONS

In horses, arteries stiffen with age, in combination with luminal enlargement and arterial wall thickening. This might, at least partially, explain the increased incidence of arterial rupture in older horses.

Associations of sex, age and adiposity in endothelium-independent dilation in children

OBJECTIVE

To examine the association of age, sex, and obesity status on endothelial-independent dilation (EID) among children and adolescents.

STUDY DESIGN

This study examined 264 children (143 males) between 8 to 18 years old (mean  ±  SD: age  =  14.3  ±  2.7 years). Endothelial-independent dilation was assessed via ultrasound imaging of the brachial artery following administration of 0.3 milligrams of sublingual nitroglycerin. A one-way analysis of variance with Bonferroni post hoc comparisons assessed sex-differences in percent peak EID dilation (EID%-peak) and EID area under the curve (EID%-AUC), while analysis of covariance (ANCOVA) adjusted for race, age, body mass index percentile (BMI-percentile), and brachial artery diameter. Multiple linear regression evaluated the association of sex, age, BMI-percentile, percent body fat (%BF), and brachial artery diameter on EID.

RESULTS

Prior to adjustment, EID%-peak was significantly higher among females than males (mean  ±  SE: 26.9  ±  0.5% versus 22.9  ±  0.6%, p  <  0.001, respectively); similar findings for EID%-AUC (4214%  ±  105%·s versus 3398%  ±  97%·s, p  <  0.001) were observed. After adjusting for covariates, EID%-AUC remained consistent (p  =  0.03) while EID%-peak was not significantly different between sexes (p  =  0.21). EID%-peak was significantly higher among normal weight compared to obese participants (p  =  0.04), while no differences were observed between obesity status after adjustment for brachial artery diameter (p  =  0.64). Both unadjusted (p  =  0.16) and adjusted EID%-AUC (p  =  0.24) was not significantly different between obesity status. BMI-percentile was not associated with EID%-peak (p  =  0.76) or EID%-AUC (p  =  0.30). Additionally, %BF was not associated with EID%-peak (p  =  0.56) or EID%-AUC (p  =  0.15). After adjusting for brachial artery diameter, BMI-percentile, and age, males had lower EID%-AUC (p  =  0.03) and lower but not significant EID%-peak (p  =  0.21).

SIGNIFICANCE

Vascular smooth muscle function was significantly lower among male children and adolescents, which is suggestive that impaired EID and increased cardiovascular disease risk among males may begin in childhood. Interestingly, obesity status and BMI-percentile was not associated with EID in children and adolescents after adjusting for brachial artery diameter.

Sex differences in aortic augmentation index in adolescents

BACKGROUND

Augmentation index (AIx) is a noninvasive measure of pulse wave reflection. AIx is associated with cardiovascular disease. Adult women have a higher AIx than men, but the factors determining this sex-related difference remain to be determined.

METHODS

To examine factors associated with AIx in adolescents, participants in the Childhood Asthma Prevention Study, followed from birth, were assessed at age 14 years, with AIx standardized to a heart rate of 75/min (AIx_75) and pulse wave velocity. Associations of AIx_75 and pulse wave velocity with height, change in height, and measures of puberty were assessed.

RESULTS

AIx_75 was higher in women compared to men [-24.5 (12.1) versus -32.3 (12.4)%; P < 0.001]. Lower AIx_75 was significantly related to greater change in height between 8 and 14 years, but not to achieved height. The sex difference in AIx was not independently related to puberty variables. Differences between sexes included early life weight gain, lipids, height, BMI-Z-score, change in height from 8 to 14 years, and age at peak height velocity. Change in AIx_75 from 8 to 14 years was highly associated with change in height (m) from 8 to 14 years (B = -88.8, 95% confidence interval -137.3 to -40.3, P =  < 0.001). The difference between sexes established at 8 years was not amplified from 8 to 14 years.

CONCLUSION

AIx is higher in girls than boys at 14 years and is closely associated with change in height between 8 and 14 years. Measures of puberty do not appear to independently influence the sex difference in AIx in adolescents.

Endothelial maintenance in health and disease: Importance of sex differences

The vascular endothelium has emerged as more than just an inert monolayer of cells lining the vascular bed. It represents the interface between the blood stream and vessel wall, and has a strategic role in regulating vascular homeostasis by the release of vasoactive substances. Endothelial dysfunction contributes to the development and progression of cardiovascular disease. Recognition of sex-specific factors implicated in endothelial cell biology is important for the identification of clinically relevant preventive and/or therapeutic strategies. This review aims to give an overview of the recent advances in understanding the importance of sex specific observations in endothelial maintenance, both in healthy and diseased conditions. The female endothelium is highlighted in the context of polycystic ovary syndrome and pre-eclampsia. Furthermore, sex differences are explored in chronic kidney disease, which is currently appreciated as one of public health priorities. Overall, this review endorses integration of sex analysis in experimental and patient-oriented research in the exciting field of vascular biology.

[Epidemiological survey in schoolchildren: determinants and prevalence of cardiovascular risk factors]

This study focused on the prevalence of dyslipidemia, high blood glucose, and high blood pressure in scho-olchildren and the associations with demographic, socioeconomic, biological, and behavior factors using a cross-sectional design with 1,139 schoolchildren from six to 18 years of age in Amargosa, Bahia State, Brazil. Prevalence ratio (PR) was used as the measure of association. Prevalence rates for dyslipidemia, high blood glucose, and high blood pressure were 62.1%, 6.6%, and 27%, respectively. Dyslipidemia was associated with the school's geographic location (PR = 1.52) and child's waist circumference (PR = 1.20), and high blood glucose with the school's geographic location (PR = 3.41) and child's peripheral adiposity (PR = 3.13). High blood pressure was associated with age bracket (PR = 2.34), waist-for-height ratio (PR = 1.62), sexual ma-turation (PR = 2.06), and physical activity (PR = 1.32). Intervention programs are needed to change life habits in schoolchildren.

The Effects of Sex and Pubertal Maturation on Cardiovagal Baroreflex Sensitivity

OBJECTIVE

To examine baroreflex sensitivity (BRS) across different stages of pubertal maturation in healthy children and adolescents.

STUDY DESIGN

This study was cross-sectional and included 104 participants (53 males and 51 females) aged 8-18 years old. Participants were organized into 5 pubertal groups based on the criteria of Tanner; prepubertal (Tanner 1, n = 19), early-pubertal (Tanner 2, n = 16), peripubertal (Tanner 3, n = 24), late-pubertal (Tanner 4, n = 23), and postpubertal (Tanner 5 and 6, n = 22). Adiposity (fat-free mass, fat mass, and body fat%), body mass index, and demographic variables were collected. Beat-by-beat blood pressure and R-R interval were collected during supine rest to determine BRS. BRS was assessed by transfer function analysis in the low frequency range (0.05-0.15 Hz).

RESULTS

The results demonstrated a sex-by-maturation interaction [F(4, 94) = 3.202, P = .019]. BRS decreased from early-to postpuberty in males (30 [7.1] vs 13.2 [7.8] ms/mm Hg), and remained unchanged in females. This led to significantly greater BRS in females compared with males, postpuberty (27 [7.3] vs 13.2 [7.8] ms/mm Hg).

CONCLUSIONS

Controlling for both sex and maturation when examining BRS in children and adolescents with cardiovascular disease risk factors will aid in interpreting abnormally high or low BRS values.

Age and sex relationship with flow-mediated dilation in healthy children and adolescents

Flow-mediated dilation (FMD) is a noninvasive technique used to measure conduit artery vascular function. Limited information is available on normative FMD values in healthy children and adolescents. The objective of this study was to assess relationships between age and sex with FMD across childhood and adolescence. Nine hundred and seventy-eight asymptomatic children (12 ± 3 yr, range 6-18 yr, 530 male) underwent ultrasonic brachial artery assessment before and after 5 min of forearm ischemia. Sex differences in FMD and baseline artery diameter were assessed using mixed linear models. Baseline artery diameter was smaller in females than males [2.96 mm (95% CI: 2.92-3.00) vs. 3.24 mm (3.19-3.28), P < 0.001] and increased with age across the cohort (P < 0.001). Diameter increased between ages 6 and 17 yr in males [from 2.81 mm (2.63, 3.00) to 3.91 mm (3.68, 4.14)] but plateaued at age 12 yr in females. Males had a lower FMD [7.62% (7.33-7.91) vs. 8.31% (7.95-8.66), P = 0.024], specifically at ages 17 and 18 yr. There was a significant effect of age on FMD (P = 0.023), with a reduction in FMD apparent postpuberty in males. In conclusion, the brachial artery increases structurally with age in both sexes; however, there are sex differences in the timing and rate of growth, in line with typical sex-specific adolescent growth patterns. Males have a lower FMD than females, and FMD appears to decline with age; however, these findings are driven by reductions in FMD as males near maturity. The use of age- and sex-specific FMD data may therefore not be pertinent in childhood and adolescence.

Younger age is associated with lower reactive hyperemic index but not lower flow-mediated dilation among children and adolescents

BACKGROUND

The use of digital reactive hyperemia as a measure of endothelial function among children and adolescents is becoming increasingly common. However, unexpected observations of low reactive hyperemic index values in younger children in our laboratory led us to conduct a study evaluating the influence of age, sex, height, weight, blood pressure, body mass index (BMI), and finger volume on RHI values.

METHODS

Endothelial function, measured by digital reactive hyperemia (reactive hyperemic index: RHI) was assessed in 113 children and adolescents (mean age 12.4 ± 3.8 years; 64 males), with 102 also assessed for brachial artery flow-mediated dilation (FMD) using ultrasound imaging. Associations with age, sex, height, weight, systolic and diastolic blood pressure (SBP, DBP), BMI, and finger volume were evaluated.

RESULTS

Using GLM regression, age (β = 0.03, P = 0.014) and SBP (β = 0.015, P = 0.004) were significantly associated with RHI. No measures were associated with FMD. In the subset of individuals with measured finger volume, age (β = 0.025, P = 0.037) was the only measure significantly associated with log RHI. Similarly, no measures were associated with FMD.

CONCLUSION

Younger age is associated with lower RHI but not lower FMD among children and adolescents. These findings call into question the validity and usefulness of digital reactive hyperemia as a method to quantify endothelial function among younger children.