Leukocyte matrix metalloproteinase and tissue inhibitor gene expression patterns in children with primary hypertension

Pathophysiology of primary hypertension in children and adolescents

The progress in research on the physiology of the cardiovascular system made in the last 100 years allowed for the development of the pathogenesis not only of secondary forms of hypertension but also of primary hypertension. The main determinants of blood pressure are described by the relationship between stroke volume, heart rate, peripheral resistance, and arterial stiffness. The theories developed by Guyton and Folkow describe the importance of the volume factor and total peripheral resistance. However, none of them fully presents the pathogenesis of essential hypertension. The multifactorial model of primary hypertension pathogenesis developed by Irving Page in the 1940s, called Page's mosaic, covers most of the pathophysiological phenomena observed in essential hypertension. The most important pathophysiological phenomena included in Page's mosaic form a network of interconnected "nodes". New discoveries both from experimental and clinical studies made in recent decades have allowed the original Page mosaic to be modified and the addition of new pathophysiological nodes. Most of the clinical studies confirming the validity of the multifactorial pathogenesis of primary hypertension concern adults. However, hypertension develops in childhood and is even perinatally programmed. Therefore, the next nodes in Page's mosaic should be age and perinatal factors. This article presents data from pediatric clinical trials describing the most important pathophysiological processes associated with the development of essential hypertension in children and adolescents.

Accelerated vascular age in adolescents with primary hypertension

BACKGROUND

Primary hypertension may lead to early vascular ageing. We aimed to evaluate differences between expected vascular age based on pulse wave velocity (PWV)/carotid intima-media thickness (cIMT) and actual chronological age (CHA) in adolescents with primary hypertension.

METHODS

Three hundred and fifty-two children (median age of 15.5 years) with office hypertension and 64 normotensive healthy children of the same age underwent anthropometry, office and ambulatory blood pressure (BP), left ventricular mass index, cIMT, PWV, pulse wave analysis and biochemistry measurements. Vascular age was calculated using pooled pediatric and adult normative PWV and cIMT data. The difference between vascular age and CHA was calculated in relation to the 90th percentile for PWV (PWVAgeDiff90) and the 95th percentile for cIMT (cIMTAgeDiff95).

RESULTS

One hundred and sixty-six patients had white-coat hypertension (WCH), 32 had ambulatory prehypertension (AmbPreHT), 55 had isolated systolic hypertension with normal central SBP (ISH+cSBPn), 99 had elevated office, ambulatory and cSBP (true hypertension, tHT). The differences between vascular age (both PWV and cIMT based) and CHA were significantly higher in AmbPreHT and tHT compared with normotension, WCH and ISH+cSBPn. Median PWVAgeDidff90 was -3.2, -1.2, -2.1, +0.8 and +0.3 years in normotension, WCH, ISH+cSBPn, AmbPreHT and tHT, respectively. Median cIMTAgeDiff95 was -8.0, -6.3, -6.8, -3.8 and -4.3 years in normotension, WCH, ISH+cSBPn, AmbPreHT and tHT, respectively. Significant predictors of PWVAge90Diff were the DBP and serum cholesterol, whereas cSBP and augmentation index were significant predictors of cIMTAgeDiff95.

CONCLUSION

Children with AmbPreHT and tHT show accelerated vascular age compared with their normotensive peers.

Prevalence of left ventricular hypertrophy in children and young people with primary hypertension: Meta-analysis and meta-regression

BACKGROUND

Left ventricular hypertrophy (LVH) is the main marker of HMOD in children and young people (CYP). We aimed to assess the prevalence of LVH and its determinants in CYP with primary hypertension (PH).

METHODS

A meta-analysis of prevalence was performed. A literature search of articles reporting LVH in CYP with PH was conducted in Medline, Embase, and Cochrane databases. Studies with a primary focus on CYP (up to 21 years) with PH were included. Meta-regression was used to analyze factors explaining observed heterogeneity.

RESULTS

The search yielded a total of 2,200 articles, 153 of those underwent full-text review, and 47 reports were included. The reports evaluated 51 study cohorts including 5,622 individuals, 73% male subjects, and a mean age of 13.6 years. LVH was defined as left ventricle mass index (LVMI) ≥ 95th percentile in 22 (47%), fixed cut-off ≥38.6 g/m2.7 in eight (17%), sex-specific fixed cut-off values in six (13%), and miscellaneously in others. The overall prevalence of LVH was 30.5% (95% CI 27.2-33.9), while heterogeneity was high (I 2 = 84%). Subgroup analysis including 1,393 individuals (76% male subjects, mean age 14.7 years) from pediatric hypertension specialty clinics and LVH defined as LVMI ≥95th percentile only (19 study cohorts from 18 studies), reported prevalence of LVH at 29.9% (95% CI 23.9 to 36.3), and high heterogeneity (I 2 = 84%). Two studies involving patients identified through community screening (n = 1,234) reported lower LVH prevalence (21.5%). In the meta-regression, only body mass index (BMI) z-score was significantly associated with LVH prevalence (estimate 0.23, 95% CI 0.08-0.39, p = 0.004) and accounted for 41% of observed heterogeneity, but not age, male percentage, BMI, or waist circumference z-score. The predominant LVH phenotype was eccentric LVH in patients from specialty clinics (prevalence of 22% in seven studies with 779 participants) and one community screening study reported the predominance of concentric LVH (12%).

CONCLUSION

Left ventricular hypertrophy is evident in at least one-fifth of children and young adults with PH and in nearly a third of those referred to specialty clinics with a predominant eccentric LVH pattern in the latter. Increased BMI is the most significant risk association for LVH in hypertensive youth.

Distribution and maturation state of peripheral blood dendritic cells in children with primary hypertension

Dendritic cells (DCs) play an important role in T cell alterations in primary hypertension (PH). We determined the numbers and maturation markers of peripheral blood total DCs (tDCs), myeloid cells (mDCs), and plasmacytoid cells (pDCs) and their association with hypertension-mediated organ damage (HMOD) markers and selected immune parameters in 30 adolescents with white coat hypertension (WCH), 25 adolescents with PH and a group of 35 age- and sex-matched children with normotension. Using multicolor flow cytometry, expression of maturation markers (CD86 and CD83) in tDCs (Lin1^-/HLA-DR⁺), myeloid DCs (Lin1^-/HLA-DR⁺/CD11c⁺) (mDCs), and plasmacytoid DCs (Lin1^-/HLA-DR⁺/CD123⁺) (pDCs) and the distribution of peripheral Th17-bearing and T-reg cells were defined. In subjects with hypertension, carotid intima-media thickness (cIMT), left ventricular mass index (LVMI), and pulse wave velocity (PWV) were assessed. Compared with WCH and subjects with normotension, subjects with hypertension had reduced tDC and pDC numbers, an increased percentage of mDC subsets, an elevated mDC/pDC ratio, an increased population of mature mDC and pDC subsets bearing CD83 of high density, a decreased subset of CD86-bearing pDCs, and increased expression of DC activation markers (HLA-DR, CD86), as well as CD11c (mDCs) and CD123 (pDCs). PWV, LVMI, and cIMT values correlated negatively with tDCs and pDCs and positively with mDC numbers. Expression of DC maturation/activation markers (CD83, CD86, HLA-DR, CD11c, and CD123) correlated positively with PWV. Certain DC characteristics of WCH subjects resembled those of PH subjects (decreased tDC frequency and upregulation of activation marker expression). These changes correlated with HMOD. WCH subjects presented a DC phenotype that was intermediate between the normotensive and hypertensive phenotypes.

Evolution of isolated systolic hypertension with normal central blood pressure in adolescents-prospective study

BACKGROUND

The clinical significance of isolated systolic hypertension with normal central blood pressure known as spurious hypertension (sHT) in adolescents and its evolution over time is not known.

METHODS

The aim of this study was to analyze changes in office, ambulatory blood pressure (ABPM), central systolic blood pressure (cSBP), hemodynamic parameters, and target organ damage (TOD) over a 1-year follow-up in a group of non-obese children with sHT.

RESULTS

Of 294 patients referred for primary hypertension, 138 patients (31 girls; 22%) had hypertension confirmed by ABPM. 48/138 (35%) patients (7 girls; 15%) were diagnosed with sHT (elevated office and ambulatory systolic BP, but normal cSBP); 43 of them (6 girls; 14%) were followed for 12 ± 3 months during non-pharmacological therapy. At baseline 7 (16%) patients had borderline values of cIMT or LVMi indicating mild TOD. After 12 months, 10/43 (3 girls; 23%) patients developed sustained HT (elevated office, ambulatory BP and cSBP), 11/43 (1 girl; 26%) maintained sHT, and 22/43 (2 girls; 51%) evolved to white coat hypertension or normotension. The cSBP values increased in 27 patients (4 girls; 63%), but the group average remained in the normal range. Prevalence of TOD did not change during observation. The multivariate regression analysis showed that the only predictor of cSBP change over time was a change in serum uric acid level.

CONCLUSIONS

In conclusion, after 1 year of non-pharmacological treatment, 23% of adolescents with sHT developed sustained hypertension, with the main predictor of cSBP change being the change in serum uric acid.

Obesity, metabolic syndrome, and primary hypertension

Primary hypertension is the dominant form of arterial hypertension in adolescents. Disturbed body composition with, among other things, increased visceral fat deposition, accelerated biological maturation, metabolic abnormalities typical for metabolic syndrome, and increased adrenergic drive constitutes the intermediary phenotype of primary hypertension. Metabolic syndrome is observed in 15-20% of adolescents with primary hypertension. These features are also typical of obesity-related hypertension. Metabolic abnormalities and metabolic syndrome are closely associated with both the severity of hypertension and the risk of target organ damage. However, even though increased body mass index is the main determinant of blood pressure in the general population, not every hypertensive adolescent is obese and not every obese patient suffers from hypertension or metabolic abnormalities typical for metabolic syndrome. Thus, the concepts of metabolically healthy obesity, normal weight metabolically unhealthy, and metabolically unhealthy obese phenotypes have been developed. The risk of hypertension and hypertensive target organ damage increases with exposure to metabolic risk factors which are determined by disturbed body composition and visceral obesity. Due to the fact that both primary hypertension and obesity-related hypertension present similar pathogenesis, the principles of treatment are the same and are focused not only on lowering blood pressure, but also on normalizing body composition and metabolic abnormalities.

Origins of Primary Hypertension in Children

Although relatively rare in childhood, primary hypertension (PH) is thought to have originated in childhood and may be even determined perinatally. PH prevalence increases in school-age children and affects 11% of 18-year-old adolescents. Associated with metabolic risk factors, elevated blood pressure in childhood is carried into adulthood. Analysis of the phenotype of hypertensive children has revealed that PH is a complex of anthropometric and neuro-immuno-metabolic abnormalities, typically found in hypertensive adults. Children with elevated blood pressure have shown signs of accelerated biological development, which are closely associated with further development of PH, metabolic syndrome, and cardiovascular disease in adulthood. At the time of diagnosis, hypertensive children were reported to have significant arterial remodelling expressed as significantly increased carotid intima-media thickness, increased stiffness of large arteries, lower area of microcirculation, and decreased endothelial function. These changes indicate that their biological age is 4 to 5 years older than their normotensive peers. All these abnormalities are typical features of early vascular aging described in adults with PH. However, as these early vascular changes in hypertensive children are closely associated with features of accelerated biological development and neuro-immuno-metabolic abnormalities observed in older subjects, it seems that PH in childhood is not only an early vascular aging event, but also an early biological maturation phenomenon.