Genetics and blood pressure response to exercise, and its interactions with adiposity

Exercise-Induced Blood Pressure Dynamics: Insights from the General Population and the Athletic Cohort

Blood pressure (BP) dynamics during graded exercise testing provide important insights into cardiovascular health, particularly in athletes. These measurements, taken during intense physical exertion, complement and often enhance our understanding beyond traditional resting BP measurements. Historically, the challenge has been to distinguish 'normal' from 'exaggerated' BP responses in the athletic environment. While basic guidelines have served their purpose, they may not fully account for the complex nature of BP responses in today's athletes, as illuminated by contemporary research. This review critically evaluates existing guidelines in the context of athletic performance and cardiovascular health. Through a rigorous analysis of the current literature, we highlight the multifaceted nature of exercise-induced BP fluctuations in athletes, emphasising the myriad determinants that influence these responses, from specific training regimens to inherent physiological nuances. Our aim is to advocate a tailored, athlete-centred approach to BP assessment during exercise. Such a paradigm shift is intended to set the stage for evidence-based guidelines to improve athletic training, performance and overall cardiovascular well-being.

Walking and resting blood pressure: An inter-individual response difference meta-analysis of randomized controlled trials

While walking is associated with reductions in resting SBP and DBP, a lack of true IIRD exists, suggesting that factors other than training response variation (random variation, physiological responses associated with behavioral changes that are not the result of walking) are responsible for the observed variation in resting SBP and DBP.

Safety, efficacy and delivery of isometric resistance training as an adjunct therapy for blood pressure control: a modified Delphi study

Uncontrolled hypertension remains the major risk factor for cardiovascular disease. Isometric resistance training (IRT) has been shown to be a useful nonpharmacological therapy for reducing blood pressure (BP); however, some exercise physiologists and other health professionals are uncertain of the efficacy and safety of IRT. Experts' consensus was sought in light of the current variability of IRT use as an adjunct treatment for hypertension. An expert consensus-building analysis (Delphi study) was conducted on items relevant to the safety, efficacy and delivery of IRT. The study consisted of 3 phases: (1) identification of items and expert participants for inclusion; (2) a two-round modified Delphi exercise involving expert panelists to build consensus; and (3) a study team consensus meeting for a final item review. A list of 50 items was generated, and 42 international experts were invited to join the Delphi panel. Thirteen and 10 experts completed Delphi Rounds 1 and 2, respectively, reaching consensus on 26 items in Round 1 and 10 items in Round 2. The study team consensus meeting conducted a final item review and considered the remaining 14 items for the content list. A final list of 43 items regarding IRT reached expert consensus: 7/10 items on safety, 11/11 items on efficacy, 10/12 items on programming, 8/10 items on delivery, and 7/7 on the mechanism of action. This study highlights that while experts reached a consensus that IRT is efficacious as an antihypertensive therapy, some still have safety concerns, and there is also ongoing conjecture regarding optimal delivery.

The Promise of Selecting Individuals from the Extremes of Exposure in the Analysis of Gene-Physical Activity Interactions

BACKGROUND

Dichotomization using the lower quartile as cutoff is commonly used for harmonizing heterogeneous physical activity (PA) measures across studies. However, this may create misclassification and hinder discovery of new loci.

OBJECTIVES

This study aimed to evaluate the performance of selecting individuals from the extremes of the exposure (SIEE) as an alternative approach to reduce such misclassification.

METHOD

For systolic and diastolic blood pressure in the Framingham Heart Study, we performed a genome-wide association study with gene-PA interaction analysis using three PA variables derived by SIEE and two other dichotomization approaches. We compared number of loci detected and overlap with loci found using a quantitative PA variable. In addition, we performed simulation studies to assess bias, false discovery rates (FDR), and power under synergistic/antagonistic genetic effects in exposure groups and in the presence/absence of measurement error.

RESULTS

In the empirical analysis, SIEE's performance was neither the best nor the worst. In most simulation scenarios, SIEE was consistently outperformed in terms of FDR and power. Particularly, in a scenario characterized by antagonistic effects and measurement error, SIEE had the least bias and highest power.

CONCLUSION

SIEE's promise appears limited to detecting loci with antagonistic effects. Further studies are needed to evaluate SIEE's full advantage.

Hypertension after preeclampsia and relation to the C1114G polymorphism (rs4606) in RGS2: data from the Norwegian HUNT2 study

Background

Preeclampsia is associated with an increased risk of hypertension later in life. The regulator of G protein signaling 2 negatively regulates several vasoconstrictors. We recently demonstrated an association between preeclampsia and the CG or GG genotype of the C1114G polymorphism (rs4606) of the regulator of G protein signaling 2 gene. Here, we examined the polymorphism with respect to the development of hypertension after pregnancy.

Methods

We genotyped 934 women on average 15.1 years after preeclampsia and 2011 age matched women with previous normotensive pregnancy. All women in this study were retrospectively recruited from the Nord-Trøndelag Health Study (HUNT2). Information from HUNT2 was linked to the Medical Birth Registry of Norway to identify women with a history of preeclampsia and women without a history of preeclampsia.

Results

No significant association was found between hypertension (blood pressure ≥140/90 mmHg and/or taking antihypertensive drugs) and the polymorphism in crude analysis (OR (95% CI): CG genotype: 1.07 (0.90-1.27); GG genotype: 1.23 (0.90-1.67)). However, in a minimally adjusted model (age and BMI adjusted), a significant association between the GG genotype and hypertension was found (OR (95% CI): 1.49 (1.05-2.11)). This association remained significant also after adjustment for a history of preeclampsia (OR (95% CI): 1.46 (1.02-2.09)), but not in a model adjusted for multiple other variables (OR (95% CI): 1.26 (0.82-1.94)). In multivariate, but not in crude, analysis, the GG genotype of rs4606 (OR (95% CI): 1.93 (1.05-3.53)) was significantly and independently associated with severe hypertension later in life, defined as systolic blood pressure ≥160 mmHg (stage 2 hypertension) and/or taking antihypertensive drugs. A significant association was also found for the merged CG and GG genotypes (OR (95% CI): 1.43 (1.02-2.00)). Moreover, an interaction with physical activity was found. A history of preeclampsia was a significant and independent predictor of either definition of hypertension, both in crude and adjusted analyses.

Conclusion

Women carrying the rs4606 CG or GG genotype are at elevated risk for developing hypertension after delivery. Physical activity may interact with the association. Preeclampsia remains an independent risk factor for subsequent hypertension after adjusting for this polymorphism and classical CVD risk factors.

Clustering of body composition, blood pressure and physical activity in Portuguese families

AIM

The purposes of this study were: (i) to identify familial resemblances in body fat, blood pressure (BP) and total physical activity (TPA); (ii) to estimate the magnitude of their genetic and environmental influences; and (iii) to investigate shared familial aggregation among these phenotypes.

SUBJECTS AND METHODS

The sample comprised 260 nuclear families from Portugal. Body fat was assessed by bioelectrical impedance. BP was measured by an oscillometric device. TPA was estimated by the Baecke questionnaire. Familial correlation analyses were performed using Generalized Estimating Equations. Quantitative genetic modelling was used to estimate maximal heritability, genetic and environmental correlations.

RESULTS

Familial intra-trait correlations ranged from 0.15-0.38. Genetic and common environmental factors explained from 30%--44% of fat mass depots and BP and 24% of TPA. Genetic correlations were significant between BP and the fat mass traits (p < 0.05). Environmental correlations were statistically significant between diastolic BP and total body fat, trunk fat and arm fat (p < 0.05) and TPA and other phenotypes.

CONCLUSIONS

The results suggest familial resemblance in the variation of body fat, BP and TPA, showing partial pleiotropic effects in the variation in body fat phenotypes and BP. TPA only shares common environmental influences with BP and body fat traits.

Genome-wide association of echocardiographic dimensions, brachial artery endothelial function and treadmill exercise responses in the Framingham Heart Study

BACKGROUND

Echocardiographic left ventricular (LV) measurements, exercise responses to standardized treadmill test (ETT) and brachial artery (BA) vascular function are heritable traits that are associated with cardiovascular disease risk. We conducted a genome-wide association study (GWAS) in the community-based Framingham Heart Study.

METHODS

We estimated multivariable-adjusted residuals for quantitative echocardiography, ETT and BA function traits. Echocardiography residuals were averaged across 4 examinations and included LV mass, diastolic and systolic dimensions, wall thickness, fractional shortening, left atrial and aortic root size. ETT measures (single exam) included systolic blood pressure and heart rate responses during exercise stage 2, and at 3 minutes post-exercise. BA measures (single exam) included vessel diameter, flow-mediated dilation (FMD), and baseline and hyperemic flow responses. Generalized estimating equations (GEE), family-based association tests (FBAT) and variance-components linkage were used to relate multivariable-adjusted trait residuals to 70,987 SNPs (Human 100K GeneChip, Affymetrix) restricted to autosomal SNPs with minor allele frequency > or =0.10, genotype call rate > or =0.80, and Hardy-Weinberg equilibrium p > or = 0.001.

RESULTS

We summarize results from 17 traits in up to 1238 related middle-aged to elderly men and women. Results of all association and linkage analyses are web-posted at http://ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007 webcite. We confirmed modest-to-strong heritabilities (estimates 0.30-0.52) for several Echo, ETT and BA function traits. Overall, p < 10(-5) in either GEE or FBAT models were observed for 21 SNPs (nine for echocardiography, eleven for ETT and one for BA function). The top SNPs associated were (GEE results): LV diastolic dimension, rs1379659 (SLIT2, p = 1.17*10(-7)); LV systolic dimension, rs10504543 (KCNB2, p = 5.18*10(-6)); LV mass, rs10498091 (p = 5.68*10(-6)); Left atrial size, rs1935881 (FAM5C, p = 6.56*10(-6)); exercise heart rate, rs6847149 (NOLA1, p = 2.74*10(-6)); exercise systolic blood pressure, rs2553268 (WRN, p = 6.3*10(-6)); BA baseline flow, rs3814219 (OBFC1, 9.48*10(-7)), and FMD, rs4148686 (CFTR, p = 1.13*10(-5)). Several SNPs are reasonable biological candidates, with some being related to multiple traits suggesting pleiotropy. The peak LOD score was for LV mass (4.38; chromosome 5); the 1.5 LOD support interval included NRG2.

CONCLUSION

In hypothesis-generating GWAS of echocardiography, ETT and BA vascular function in a moderate-sized community-based sample, we identified several SNPs that are candidates for replication attempts and we provide a web-based GWAS resource for the research community.

The immune system in the oxidative stress conditions of aging and hypertension: favorable effects of antioxidants and physical exercise

Several studies have shown that both oxidative stress and inflammation are linked to the process of hypertension and that the immune system is also involved in this age-related process. More specifically, the oxygen stress related to immune system dysfunction seems to have a key role in senescence, in agreement with the oxidation/ inflammation theory of aging. From a practical point of view, and according to our own research, the immune functions change in a similar fashion in hypertension and aging. As antioxidant diet supplementation decreases oxidative stress, it may be useful to treat hypertension and increase longevity. Probably, these favorable effects are mediated by an antioxidant-induced improvement of the immune function. The practice of moderate physical exercise shows similar favorable effects, and indeed our studies on exercising hypertensive women demonstrate an improved immune function, probably linked to raised levels of intracellular antioxidant defenses. The present review summarizes a selection of data related to the above from other authors as well as some findings from our own work.

Intensive lifestyle modification: impact on cardiovascular disease risk factors in subjects with and without clinical cardiovascular disease

Intensive lifestyle modification programs are intended to stabilize or promote regression of coronary artery disease; however, clinical response is often nonuniform, complicating appropriate utilization of resources and prediction of outcome. This study assessed physiological and psychological benefits to 72 persons participating in a prospective, nonrandomized, four-component lifestyle change program and compared response between patients with clinical cardiovascular disease (CVD) and patients with elevated risk factors for CVD but without clinical manifestations of disease. Subjects entering the program due to elevated risk factor levels alone demonstrated equal or greater benefit, in terms of improvement in primary CVD risk factors and reduction in measures of coronary disease risk developed in the Framingham Heart Study, than those with clinical CVD. These findings suggest that intensive lifestyle change programs may be important for primary prevention in individuals at increased risk of CVD.

The utility of animal models of human energy homeostasis

The prevalence of obesity among adults and children has increased steadily over the last few years worldwide, reaching epidemic proportions. Particularly alarming is the link between obesity and the development of chronic disorders such as heart disease, type 2 diabetes, hypertension and some cancers (Bjorntorp, 1997). Environmental causes of obesity are thought to include a sedentary lifestyle and an abundance of highly palatable energy-dense foods (Hill et al. 2003). Genetic factors also contribute to susceptibility to obesity, although the genetic basis of most human obesities is thought to be polygenic (Comuzzie & Allison, 1998; Barsh et al. 2000). The present paper considers some of the animal models used to infer aspects of human obesity, with an emphasis upon their usefulness.

Association between physical activity and blood pressure is modified by variants in the G-protein coupled receptor 10

Hypertension is strongly related to cardiovascular disease and all-cause mortality. Exercise reduces blood pressure but the response varies between individuals. The mechanisms by which physical activity energy expenditure (PAEE) modifies blood pressure are not fully defined but include modulation of sympathetic tone. Novel polymorphisms in the G-protein coupled receptor (GPR10) have been linked with high blood pressure. GPR10 may mediate the relationship between PAEE and blood pressure via central nervous mechanisms. We examined whether two GPR10 polymorphisms (G-62A and C914T) modify the association between PAEE and blood pressure in the MRC Ely study (N=687). When stratified by the C914T genotype, there were between-group differences for body mass index (BMI) (P=0.05), diastolic blood pressure (DBP) (P=0.006), and systolic blood pressure (SBP) (P=0.005). No differences were found between G-62A genotypes. The previously reported inverse relationship between PAEE and blood pressure was not observed in minor allele carriers for either polymorphism (A62 carriers: DBP beta-1.11, P=0.52; SBP beta-1.66, P=0.52. T914 carriers: SBP beta=3.27; P=0.60) but was in common allele homozygotes (G62G: DBP beta-6.18 P=0.00001; SBP beta-8.54 P=0.0001. C914C: SBP beta-7.07; P=0.00001). This corresponded to a significant interaction between PAEE and GPR10 polymorphisms on DBP (G-62A: P=0.006) and SBP (G-62A: P=0.008. C914T: P=0.068). Significant interactions were observed between haplotype (derived from G-62A and C914T), PAEE, and blood pressure (DBP: P=0.08; SBP: P=0.023). The effect of physical activity on blood pressure is highly variable at population level. Knowledge of GPR10 genotype may define those who are least likely to benefit from physical activity. These findings may have relevance in the targeted treatment of hypertensive disease.