Critical developmental periods in the pathogenesis of hypertension

Impact of Nutritional Epigenetics in Essential Hypertension: Targeting microRNAs in the Gut-Liver Axis

PURPOSE OF REVIEW

To review the current knowledge on interactions between dietary factors and microRNAs (miRNAs) in essential hypertension (EH) pathogenesis.

RECENT FINDINGS

There exists an integration of maintenance signals generated by genetic, epigenetic, immune, and environmental (e.g., dietary) factors that work to sustain balance in the gut-liver axis. It is well established that an imbalance in this complex, intertwined system substantially increases the risk for EH. As such, pertinent research has been taken to decipher how each signal operates in isolation and together in EH progression. Recent literature indicates that both macro- and micronutrients interrupt regulatory miRNA expressions and thus, alter multiple cellular processes that contribute to EH and its comorbidities. We highlight how carbohydrates, lipids, proteins, salt, and potassium modify miRNA signatures during EH. The disruption in miRNA expression can negatively impact communication systems such as over activating the renin-angiotensin-aldosterone system, modulating the vascular smooth muscle cell phenotype, and promoting angiogenesis to favor EH. We also delineate the prognostic value of miRNAs in EH and discuss the pros and cons of surgical vs dietary prophylactic approaches in EH prevention. We propose that dietary-dependent perturbation of the miRNA profile is one mechanism within the gut-liver axis that dictates EH development.

Suppression of β1-Adrenoceptor Autoantibodies is Involved in the Antiarrhythmic Effects of Omega-3 Fatty Acids in Male and Female Hypertensive Rats

The arrhythmogenic potential of β1-adrenoceptor autoantibodies (β1-AA), as well as antiarrhythmic properties of omega-3 in heart diseases, have been reported while underlying mechanisms are poorly understood. We aimed to test our hypothesis that omega-3 (eicosapentaenoic acid-EPA, docosahexaenoic acid-DHA) may inhibit matrix metalloproteinase (MMP-2) activity to prevent cleavage of β1-AR and formation of β1-AA resulting in attenuation of pro-arrhythmic connexin-43 (Cx43) and protein kinase C (PKC) signaling in the diseased heart. We have demonstrated that the appearance and increase of β1-AA in blood serum of male and female 12-month-old spontaneously hypertensive rats (SHR) was associated with an increase of inducible ventricular fibrillation (VF) comparing to normotensive controls. In contrast, supplementation of hypertensive rats with omega-3 for two months suppressed β1-AA levels and reduced incidence of VF. Suppression of β1-AA was accompanied by a decrease of elevated myocardial MMP-2 activity, preservation of cardiac cell membrane integrity and Cx43 topology. Moreover, omega-3 abrogated decline in expression of total Cx43 as well as its phosphorylated forms at serine 368 along with PKC-ε, while decreased pro-fibrotic PKC-δ levels in hypertensive rat heart regardless the sex. The implication of MMP-2 in the action of omega-3 was also demonstrated in cultured cardiomyocytes in which desensitization of β1-AR due to permanent activation of β1-AR with isoproterenol was prevented by MMP-2 inhibitor or EPA. Collectively, these data support the notion that omega-3 via suppression of β1-AA mechanistically controlled by MMP-2 may attenuate abnormal of Cx43 and PKC-ε signaling; thus, abolish arrhythmia substrate and protect rats with an advanced stage of hypertension from malignant arrhythmias.

Obesity and its cardiovascular effects

Obesity is described in terms of body fat percentage or body mass index (BMI), despite the fact that these measures do not give full insight about the body fat distribution. It is presently a consistently growing universal challenge since it has tripled in the last 10 years, killing approximately 28 million people each year. In this review, we aim to clarify the different results of obesity on the working and physiology of the cardiovascular system and to reveal changes in the obesity "paradox"-a variety of cardiovascular outcomes in typical/overweight people. Central fat build-up in ordinary/overweight populaces has been related to expanded occurrences of myocardial infarction, heart failure, or all-cause mortality when contrasted with the obese populace. These discoveries are additionally clarified as the abundance and prolonged vulnerability to free fatty acids (FFAs) in obesity. This has been believed to cause the myocardial substrate to move from glucose to FFAs digestion, which causes lipid gathering in cardiomyocytes, spilling over to other lean tissues, and prompting a general atherogenic impact. This cardiomyocyte lipid aggregation has been demonstrated to cause insulin resistance and cardiovascular hypertrophy, and to lessen the heart functions in general. There is a proof backing the fact that fat tissue is not only an energy reservoir, it also coordinates hormones and proinflammatory cytokines and deals with the energy transition of the body by putting away abundant lipids in diverse tissues.

Chronic Stress Produces Persistent Increases in Plasma Corticosterone, Reductions in Brain and Cardiac Nitric Oxide Production, and Delayed Alterations in Endothelial Function in Young Prehypertensive Rats

This study was designed to investigate whether oxidative stress, nitric oxide (NO) deficiency and/or endothelial dysfunction (ED) are present in young borderline hypertensive rats (BHR) and whether these pathologies can be causally involved in the initiation of blood pressure (BP) increases. Additionally, we tested the hypothesis that crowding stress, experienced during the peripubertal period, may produce persistent or delayed disorders in corticosterone release, NO synthesis, oxidative status and/or endothelial function that could accelerate BP increases. To test these hypotheses, 5-week-old male BHR and normotensive Wistar-Kyoto rats (WKY) were either kept in control conditions (for 2 and 4 weeks, respectively) or exposed to social stress produced by crowding for 2 weeks (stress). After cessation of crowding, a group of rats of each phenotype was kept in control conditions for the next 2 weeks (post-stress). Systolic BP of 5-week-old BHR was significantly increased vs. age-matched WKY (127 ± 3 vs. 104 ± 3 mmHg, p < 0.01) and remained significantly higher throughout the course of the experiment. Despite elevated BP, no signs of oxidative damage to plasma lipids, NO deficiency or ED were observed in control BHR vs. age-matched WKY. Crowding stress elevated plasma corticosterone and accelerated BP increases only in BHR; these effects persisted 2 weeks post-stress. Crowding failed to induce oxidative damage to plasma lipids in either phenotype, but it produced persistent decreases in NO production in the hypothalamus and brainstem of both strains of rats, as well as in the hearts of BHR. In contrast, crowding failed to reduce NO production in the aortae or acetylcholine-induced relaxations of the femoral arteries in both strains investigated. However, significantly reduced aortic NO production was observed in BHR 2 weeks post-stress vs. age-matched controls, which was in agreement with reduced NO-dependent components of vasorelaxation. In conclusion, this study’s data showed that oxidative stress, NO deficiency and ED are not causally involved in initiation of blood pressure increase in BHR. However, exposure to stressful environments produced persistent increases in plasma corticosterone and reductions of brain and cardiac NO production followed by a delayed decrease in the NO-dependent component of endothelium-dependent relaxation—changes that collectively accelerated BP increases only in BHR.

The effect of resveratrol on hypertension: A clinical trial

The aim of this clinical trial was to investigate the effects of Evelor, a micronized formulation of resveratrol (RESV; 3,5,4'-trihydroxy-trans-stilbene), in patients with primary hypertension. RESV is a stilbenoid and phytoalexin produced by several plants in response to injury or attack by pathogens, such as bacteria and fungi. Patients included in the clinical trial were split into the following two groups, based on the severity of their disease: Group A (n=46), stage I hypertension [systolic blood pressure (SBP), 140-159 mmHg; diastolic blood pressure (DBP), 90-99 mmHg] and Group B (n=51), stage II hypertension (SBP, 160-179 mmHg; DBP, 100-109 mmHg). Each group was divided into two subgroups: A1 and B1, patients treated with standard antihypertensive therapy (A1, 10 mg Dapril; B1, 20 mg Dapril), and A2 and B2, patients treated with antihypertensive therapy (Dapril) plus Evelor. The present study aimed to determine the effects of Evelor, in addition to the standard hypertension treatment, and its effect on the hepatic enzymes serum glutamate-pyruvate transaminase (SGPT) and gamma-glutamyl transferase (gamma-GT). Following the trial, which lasted two years (October 2010 to October 2012), the mean blood pressure of both groups lay within the normal range, indicating that blood pressure was efficiently controlled. The results of the present study demonstrate that the addition of RESV to standard antihypertensive therapy is sufficient to reduce blood pressure to normal levels, without the need for additional antihypertensive drugs. In addition, statistical analysis of the results identified a significant reduction in plasma concentration levels of SGPT (P<0.001) and gamma-GT (P<0.001) with the addition of RESV, indicating that RESV prevents liver damage.

DNA methylation and hypertension: emerging evidence and challenges

Hypertension is a multifactorial disease influenced by an interaction of environmental and genetic factors. The exact molecular mechanism of hypertension remains unknown. Aberrant DNA methylation is the most well-defined epigenetic modification that regulates gene transcription. However, studies on the association between DNA methylation and hypertension are still in their infancy. This review summarizes the latest evidence and challenges regarding the role of DNA methylation on hypertension.

Epigenetic Modifications in Essential Hypertension

Essential hypertension (EH) is a complex, polygenic condition with no single causative agent. Despite advances in our understanding of the pathophysiology of EH, hypertension remains one of the world’s leading public health problems. Furthermore, there is increasing evidence that epigenetic modifications are as important as genetic predisposition in the development of EH. Indeed, a complex and interactive genetic and environmental system exists to determine an individual’s risk of EH. Epigenetics refers to all heritable changes to the regulation of gene expression as well as chromatin remodelling, without involvement of nucleotide sequence changes. Epigenetic modification is recognized as an essential process in biology, but is now being investigated for its role in the development of specific pathologic conditions, including EH. Epigenetic research will provide insights into the pathogenesis of blood pressure regulation that cannot be explained by classic Mendelian inheritance. This review concentrates on epigenetic modifications to DNA structure, including the influence of non-coding RNAs on hypertension development.

The roles of sensitization and neuroplasticity in the long-term regulation of blood pressure and hypertension

After decades of investigation, the causes of essential hypertension remain obscure. The contribution of the nervous system has been excluded by some on the basis that baroreceptor mechanisms maintain blood pressure only over the short term. However, this point of view ignores one of the most powerful contributions of the brain in maintaining biological fitness-specifically, the ability to promote adaptation of behavioral and physiological responses to cope with new challenges and maintain this new capacity through processes involving neuroplasticity. We present a body of recent findings demonstrating that prior, short-term challenges can induce persistent changes in the central nervous system to result in an enhanced blood pressure response to hypertension-eliciting stimuli. This sensitized hypertensinogenic state is maintained in the absence of the inducing stimuli, and it is accompanied by sustained upregulation of components of the brain renin-angiotensin-aldosterone system and other molecular changes recognized to be associated with central nervous system neuroplasticity. Although the heritability of hypertension is high, it is becoming increasingly clear that factors beyond just genes contribute to the etiology of this disease. Life experiences and attendant changes in cellular and molecular components in the neural network controlling sympathetic tone can enhance the hypertensive response to recurrent, sustained, or new stressors. Although the epigenetic mechanisms that allow the brain to be reprogrammed in the face of challenges to cardiovascular homeostasis can be adaptive, this capacity can also be maladaptive under conditions present in different evolutionary eras or ontogenetic periods.

Epigenetics and a New Look on Metabolic Syndrome

The incidence of metabolic syndrome increases in the developed countries, therefore biomedical research is focused on the understanding of its etiology. The study of exact mechanisms is very complicated because both genetic and environmental factors contribute to this complex disease. The ability of environmental factors to promote phenotype changes by epigenetic DNA modifications (i.e. DNA methylation, histone modifications) was demonstrated to play an important role in the development and predisposition to particular symptoms of metabolic syndrome. There is no doubt that the early life, such as the fetal and perinatal periods, is critical for metabolic syndrome development and therefore critical for prevention of this disease. Moreover, these changes are visible not only in individuals exposed to environmental factors but also in the subsequent progeny for multiple generations and this phenomenon is called transgenerational inheritance. The knowledge of molecular mechanisms, by which early minor environmental stimuli modify the expression of genetic information, might be the desired key for the understanding of mechanisms leading to the change of phenotype in adulthood. This review provides a short overview of metabolic syndrome epigenetics.

Programming of Essential Hypertension: What Pediatric Cardiologists Need to Know

Hypertension is recognized as one of the major contributing factors to cardiovascular disease, but its etiology remains incompletely understood. Known genetic and environmental influences can only explain a small part of the variability in cardiovascular disease risk. The missing heritability is currently one of the most important challenges in blood pressure and hypertension genetics. Recently, some promising approaches have emerged that move beyond the DNA sequence and focus on identification of blood pressure genes regulated by epigenetic mechanisms such as DNA methylation, histone modification and microRNAs. This review summarizes information on gene-environmental interactions that lead toward the developmental programming of hypertension with specific reference to epigenetics and provides pediatricians and pediatric cardiologists with a more complete understanding of its pathogenesis.

No difference in hypertension prevalence in smokers, former smokers and non-smokers after adjusting for body mass index and age: a cross-sectional study from the Czech Republic, 2010

BACKGROUND

Several hypotheses suggest a temporary increase in blood pressure following smoking cessation. This may be the result of endocrine changes (e.g. alteration in adrenocorticotropic hormone and cortisol levels in post-cessation period) and/or post-cessation weight gain. Our aim was to identify factors that may be associated with the diagnosis of hypertension after quitting smoking.

METHODS

In 2010, we conducted a cross-sectional survey in a sample of 2065 Czech adults, chosen by quota selection and representative according to age, gender, education, region of residence and the size of settlement, aged 18 to 94 years. We examined the association between age, gender, body mass index, smoking status, and education with the hypertension diagnosis in their personal history. Data were compiled and weighed by age categories. Statistical significance was measured by Pearson Chi-square test at the level of significance 95 %.

RESULTS

Diagnosis of hypertension was reported in 461 (22 %) subjects, with no difference by gender. Based on univariate analysis, former smokers were more likely than non-smokers to be diagnosed for hypertension (OR 1.450 (1.110-1.900), p = 0.006). However, after adjusting for body mass index and age, the occurrence of hypertension diagnosis did not differ among non-smokers, smokers and former smokers (OR 0.760 for smokers, p = 0.082 and OR 1.020 for former smokers, p = 0.915).

CONCLUSION

We did not find any differences in hypertension diagnosis prevalence according to smoking status.

Effect of fetal undernutrition and postnatal overfeeding on rat adipose tissue and organ growth at early stages of postnatal development

Intrauterine and perinatal life are critical periods for programming of cardiometabolic diseases. However, their relative role remains controversial. We aimed to assess, at weaning, sex-dependent alterations induced by fetal or postnatal nutritional interventions on key organs for metabolic and cardiovascular control. Fetal undernutrition was induced by dam food restriction (50 % from mid-gestation to delivery) returning to ad libitum throughout lactation (Maternal Undernutrition, MUN, 12 pups/litter). Postnatal overfeeding (POF) was induced by litter size reduction from normally fed dams (4 pups/litter). Compared to control, female and male MUN offspring exhibited: 1) low birth weight and accelerated growth, reaching similar weight and tibial length by weaning, 2) increased glycemia, liver and white fat weights; 3) increased ventricular weight and tendency to reduced kidney weight (males only). Female and male POF offspring showed: 1) accelerated growth; 2) increased glycemia, liver and white fat weights; 3) unchanged heart and kidney weights. In conclusion, postnatal accelerated growth, with or without fetal undernutrition, induces early alterations relevant for metabolic disease programming, while fetal undernutrition is required for heart abnormalities. The progression of cardiac alterations and their role on hypertension development needs to be evaluated. The similarities between sexes in pre-pubertal rats suggest a role of sex-hormones in female protection against programming.

Epigenetics, the missing link in hypertension

Epigenetics refers to functional alterations in gene expression or phenotype without any change of the underlying DNA sequence. It is the study of the potential of a cell or organism to express different traits through functional regulation of its gene transcription. Though it is met as a necessary process in biology, epigenetics may often play a crucial part in the development of specific pathologic conditions, including cardiovascular diseases and hypertension.

Evaluation of insulin resistance and metabolic syndrome in a group of obese Czech children

OBJECTIVE

The study aimed to determine the incidence of metabolic syndrome (MS) in a group of Czech obese children, to evaluate the incidence of insulin resistance according to HOMA-IR in this group, and to consider the diagnostic value of HOMA-IR in early MS detection in obese children using the logistic regression models for analyzing the relations between HOMA IR and MS.

SUBJECTS AND METHODS

Anthropometric and laboratory examinations were performed in a group of 274 obese children aged 10-17 years.

RESULTS

MS was established in 102 subjects (37%). The presence of insulin resistance according to HOMA-IR >3.16 was ascertained in 53% of the subjects. HOMA-IR limit was exceeded by 70% in the MS (+) group and by 43% in children in the MS (-) (p<0.0001) category.

CONCLUSION

The relatively high incidence of insulin resistance in obese children without MS questions the prevailing diagnostic criteria of, perhaps, falsely excluding some cases of, MS.

Genotype-related effect of crowding stress on blood pressure and vascular function in young female rats

This study investigated the influence of chronic crowding stress on nitric oxide (NO) production, vascular function and oxidative status in young Wistar-Kyoto (WKY), borderline hypertensive (BHR) and spontaneously hypertensive (SHR) female rats. Five-week old rats were exposed to crowding for two weeks. Crowding elevated plasma corticosterone (P<0.05) and accelerated BP (P<0.01 versus basal) only in BHR. NO production and superoxide concentration were significantly higher in the aortas of control BHR and SHR versus WKY. Total acetylcholine (ACh)-induced relaxation in the femoral artery was reduced in control SHR versus WKY and BHR, and stress did not affect it significantly in any genotype. The attenuation of ACh-induced relaxation in SHR versus WKY was associated with reduction of its NO-independent component. Crowding elevated NO production in all strains investigated but superoxide concentration was increased only in WKY, which resulted in reduced NO-dependent relaxation in WKY. In crowded BHR and SHR, superoxide concentration was either unchanged or reduced, respectively, but NO-dependent relaxation was unchanged in both BHR and SHR versus their respective control group. This study points to genotype-related differences in stress vulnerability in young female rats. The most pronounced negative influence of stress was observed in BHR despite preserved endothelial function.

Endothelial dysfunction in femoral artery of the hypertensive rats is nitric oxide independent

This study examined nitric oxide (NO) production, oxidative load and endothelium-dependent relaxation (NO-dependent and NO-independent) in adult male borderline hypertensive (BHR) and spontaneously hypertensive (SHR) rats as compared to normotensive Wistar-Kyoto (WKY) rats. Systolic blood pressure (BP) was determined by tail-cuff. NO production was determined by conversion of [(3)H]-L-arginine. Conjugated dienes (CD) and concentrations of thiobarbituric acid-reactive substances (TBARS) were measured for assessment of oxidative load. Vascular function was investigated in rings of the femoral artery (FA) using a wire myograph. BP of WKY, BHR and SHR was 106+/-2, 143+/-3 and 191+/-3 mm Hg, respectively (p<0.01 for each). Significant left ventricle (LV) hypertrophy and elevated levels of CD and TBARS in the LV were present in BHR and SHR as compared to WKY. NO production was elevated significantly in the aorta of BHR and SHR vs. WKY as well as in the LV of SHR vs. WKY. Acetylcholine (ACh)-induced relaxation of the FA was reduced significantly in both BHR and SHR vs. WKY. The NO-dependent component of ACh-induced relaxation had increasing tendency in hypertensive groups and it correlated positively with BP. The NO-independent component of vasorelaxation was reduced significantly in BHR and SHR vs. WKY and it correlated negatively with BP. In conclusion, the results showed that endothelial dysfunction in the experimental model of borderline hypertensive and hypertensive rats is NO-independent. The results suggest that borderline hypertension represents a risk of other cardiovascular disorders which is qualitatively similar to that of fully developed hypertension.

Short-term administration of alibernet red wine extract failed to affect blood pressure and to improve endothelial function in young normotensive and spontaneously hypertensive rats

As wine polyphenols were shown to possess many positive effects in mammals, including improvement of vascular function, this study investigated the effect of the Slovak Alibernet red wine extract (AWE) on blood pressure and vascular function in young normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Six weeks old, male, WKY and SHR were treated with AWE for three weeks at the dose of 24.2 mg/kg/day. Blood pressure (BP), determined by tail-cuff plethysmography, was significantly elevated in SHR vs. WKY and AWE failed to affect it. Lipid peroxidation was evaluated by determination of thiobarbituric acid-reactive substances. Vascular function was assessed in rings of the femoral artery using Mulvany-Halpern's myograph. Maximal endothelium-dependent acetylcholine (ACh)-induced relaxation was reduced in control SHR vs. WKY rats by approximately 9.3 %, which was associated with a significant decrease of its NO-independent component. AWE failed to affect maximal ACh-induced relaxation, both its NO-dependent and independent components, compared to controls of the same genotype. AWE however reduced lipid peroxidation in the left ventricle of both WKY and SHR and in the liver of SHR. In conclusion, three-week administration of AWE failed to reduce BP and to improve endothelial function in the femoral arteries of both genotypes investigated.

The incidence of metabolic syndrome in obese Czech children: the importance of early detection of insulin resistance using homeostatic indexes HOMA-IR and QUICKI

Common alimentary obesity frequently occurs on a polygenic basis as a typical lifestyle disorder in the developed countries. It is associated with characteristic complex metabolic changes, which are the cornerstones for future metabolic syndrome development. The aims of our study were 1) to determine the incidence of metabolic syndrome (based on the diagnostic criteria defined by the International Diabetes Federation for children and adolescents) in Czech obese children, 2) to evaluate the incidence of insulin resistance according to HOMA-IR and QUICKI homeostatic indexes in obese children with and without metabolic syndrome, and 3) to consider the diagnostic value of these indexes for the early detection of metabolic syndrome in obese children. We therefore performed anthropometric and laboratory examinations to determine the incidence of metabolic syndrome and insulin resistance in the group of 274 children with obesity (128 boys and 146 girls) aged 9-17 years. Metabolic syndrome was found in 102 subjects (37 %). On the other hand, the presence of insulin resistance according to QUICKI <0.357 was identified in 86 % and according to HOMA-IR >3.16 in 53 % of obese subjects. This HOMA-IR limit was exceeded by 70 % children in the MS(+) group, but only by 43 % children in the MS(-) group (p<0.0001). However, a relatively high incidence of insulin resistance in obese children without metabolic syndrome raises a question whether the existing diagnostic criteria do not falsely exclude some cases of metabolic syndrome. On the basis of our results we suggest to pay a preventive attention also to obese children with insulin resistance even if they do not fulfill the actual diagnostic criteria for metabolic syndrome.