Genetic and environmental factors on the relation of lung function and arterial stiffness

Association of Preserved Ratio Impaired Spirometry with Arterial Stiffness

Rationale: Preserved ratio impaired spirometry (PRISm) is a recently recognized spirometric pattern defined by a ratio of forced expiratory volume in 1 second to forced vital capacity of at least 0.70 and a forced expiratory volume in 1 second  <80% of reference. For unclear reasons, PRISm is associated with increased cardiovascular (CV) morbidity and mortality. Arterial stiffness is a major mechanism of CV disease, which can be measured by carotid-femoral pulse-wave velocity (cfPWV). Objectives: We explored the hypothesis that cfPWV would be increased in individuals with PRISm and airflow limitation (AL). Methods: We measured forced spirometry, lung volumes by body plethysmography, and cfPWV in 9,466 subjects recruited from the general population in the Austrian cross-sectional LEAD (Lung, Heart, Social, Body) study and tested the association of arterial stiffness with PRISm and AL by multivariable linear regression analysis. Individuals younger than 18 years were excluded from the study. Results: Individuals with PRISm (n = 431; 4.6%) were of similar age to those with normal spirometry (n = 8,136; 85.9%) and significantly younger than those with AL (n = 899; 9.5%). Arterial hypertension, diabetes mellitus, coronary artery disease, heart failure, and peripheral arterial occlusive disease were significantly more common in individuals with PRISm than in those with normal lung function and similar to those with AL. There was a significant association between PRISm and arterial stiffness on bivariate linear regression analysis (crude model, β = 0.038; 95% confidence interval [CI], 0.016-0.058), which persisted after robust adjustment for clinical confounders upon multivariable analysis (final model, β = 0.017; 95% CI, 0.001-0.032). cfPWV was significantly higher in individuals with PRISm irrespective of the presence of established CV disease or pulmonary restriction. AL also showed a significant association with arterial stiffness on multivariable linear regression analysis (final model, β = 0.025; 95% CI, 0.009-0.042). Conclusions: Arterial stiffness measured by cfPWV is increased in individuals with PRISm independent of CV disease and risk factors. The pathobiological mechanisms underlying this association deserve further research.

The Role of Oxidative Stress and Antioxidants in Cardiovascular Comorbidities in COPD

Oxidative stress driven by several environmental and local airway factors associated with chronic obstructive bronchiolitis, a hallmark feature of COPD, plays a crucial role in disease pathomechanisms. Unbalance between oxidants and antioxidant defense mechanisms amplifies the local inflammatory processes, worsens cardiovascular health, and contributes to COPD-related cardiovascular dysfunctions and mortality. The current review summarizes recent developments in our understanding of different mechanisms contributing to oxidative stress and its countermeasures, with special attention to those that link local and systemic processes. Major regulatory mechanisms orchestrating these pathways are also introduced, with some suggestions for further research in the field.

Personality associations with lung function and dyspnea: Evidence from six studies

OBJECTIVE

The present study examined the association between Five Factor Model personality traits and lung function and dyspnea.

METHODS

Participants were middle aged and older adults aged 34-103 years old (N > 25,000) from the Midlife in the United States Study (MIDUS), the Health and Retirement Study (HRS), the English Longitudinal Study of Ageing (ELSA), the National Health and Aging Trends Survey (NHATS), and the Wisconsin Longitudinal Study graduate (WLSG) and sibling (WLSS) samples. Data on peak expiratory flow (PEF), dyspnea, personality traits, smoking, physical activity, body mass index (BMI), emotional/psychiatric problems, and demographic factors were obtained in each sample.

RESULTS

A meta-analysis indicated that higher neuroticism was related to lower PEF, higher risk of PEF less than 80% of predicted value, and higher risk of dyspnea. In contrast, higher extraversion and conscientiousness were associated with higher PEF, lower likelihood of PEF lower than 80% of the predicted value, and lower risk of dyspnea. Higher openness was related to higher PEF and lower risk of PEF less than 80%, whereas agreeableness was related to higher PEF and lower risk of dyspnea. Smoking, physical activity, BMI and emotional/psychiatric problems partially accounted for these associations. There was little evidence that lung disease moderated the association between personality and PEF and dyspnea.

CONCLUSIONS

Across cohorts, this study found replicable evidence that personality is associated with lung function and associated symptomatology.

Heritability of Subcortical Grey Matter Structures

Background and Objectives: Subcortical grey matter structures play essential roles in cognitive, affective, social, and motoric functions in humans. Their volume changes with age, and decreased volumes have been linked with many neuropsychiatric disorders. The aim of our study was to examine the heritability of six subcortical brain volumes (the amygdala, caudate nucleus, pallidum, putamen, thalamus, and nucleus accumbens) and four general brain volumes (the total intra-cranial volume and the grey matter, white matter, and cerebrospinal fluid (CSF) volume) in twins. Materials and Methods: A total of 118 healthy adult twins from the Hungarian Twin Registry (86 monozygotic and 32 dizygotic; median age 50 ± 27 years) underwent brain magnetic resonance imaging. Two automated volumetry pipelines, Computational Anatomy Toolbox 12 (CAT12) and volBrain, were used to calculate the subcortical and general brain volumes from three-dimensional T1-weighted images. Age- and sex-adjusted monozygotic and dizygotic intra-pair correlations were calculated, and the univariate ACE model was applied. Pearson's correlation test was used to compare the results obtained by the two pipelines. Results: The age- and sex-adjusted heritability estimates, using CAT12 for the amygdala, caudate nucleus, pallidum, putamen, and nucleus accumbens, were between 0.75 and 0.95. The thalamus volume was more strongly influenced by common environmental factors (C = 0.45-0.73). The heritability estimates, using volBrain, were between 0.69 and 0.92 for the nucleus accumbens, pallidum, putamen, right amygdala, and caudate nucleus. The left amygdala and thalamus were more strongly influenced by common environmental factors (C = 0.72-0.85). A strong correlation between CAT12 and volBrain (r = 0.74-0.94) was obtained for all volumes. Conclusions: The majority of examined subcortical volumes appeared to be strongly heritable. The thalamus was more strongly influenced by common environmental factors when investigated with both segmentation methods. Our results underline the importance of identifying the relevant genes responsible for variations in the subcortical structure volume and associated diseases.

Genetic and Environmental Effects on the Development of White Matter Hyperintensities in a Middle Age Twin Population

Introduction: White matter hyperintensities (WMH) indicate white matter brain lesions in magnetic resonance imaging (MRI), which can be used as a marker for brain aging and cerebrovascular and neurodegenerative disorders. Twin studies revealed substantial but not uniform WMH heritability in elderly twins. The objective of our study was to investigate the genetic and environmental components of WMH, as well as their importance in a healthy twin population, utilizing 3T MRI scanners in a middle-aged twin population. Methods: Brain MRI was performed on 120 healthy adult twins from the Hungarian Twin Registry on a 3T scanner (86 monozygotic, MZ and 34 dizygotic, DZ twins; median age 50 ± 26.5 years, 72.5% female and 27.5% male). The count of WMH on FLAIR images was calculated using an automated volumetry pipeline (volBrain) and human processing. The age- and sex-adjusted MZ and DZ intra-pair correlations were determined and the total variance was decomposed into genetic, shared and unique environmental components using structural equation modeling. Results: Age and sex-adjusted MZ intrapair correlations were higher than DZ correlations, indicating moderate genetic influence in each lesion (rMZ = 0.466, rDZ = −0.025 for total count; rMZ = 0.482, rDZ = 0.093 for deep white matter count; rMZ = 0.739, rDZ = 0.39 for infratentorial count; rMZ = 0.573, rDZ = 0.372 for cerebellar count and rMZ = 0.473, rDZ = 0.19 for periventricular count), indicating a moderate heritability (A = 40.3%, A = 45%, A = 72.7% and A = 55.5%and 47.2%, respectively). The rest of the variance was influenced by unique environmental effects (E between 27.3% and 59.7%, respectively). Conclusions: The number of WMH lesions is moderately influenced by genetic effects, particularly in the infratentorial region in middle-aged twins. These results suggest that the distribution of WMH in various brain regions is heterogeneous.

Decreased heritability and emergence of novel genetic effects on pulse wave velocity from youth to young adulthood

Increased arterial stiffness measured by pulse wave velocity (PWV) is an important parameter in the assessment of cardiovascular risk. Our previous longitudinal study has demonstrated that carotid-distal PWV showed reasonable stability throughout youth and young adulthood. This stability might be driven by genetic factors that are expressed consistently over time. We aimed to illustrate the relative contributions of genetic and environmental factors to the stability of carotid-distal PWV from youth to young adulthood. We also examined potential ethnic differences. For this purpose, carotid-distal PWV was measured twice in 497 European American (EA) and African American (AA) twins, with an average interval time of 3 years. Twin modelling on PWV showed that heritability decreased over time (62–35%), with the nonshared environmental influences becoming larger. There was no correlation between the nonshared environmental factors on PWV measured at visit 1 and visit 2, with the phenotypic tracking correlation (r = 0.32) completely explained by shared genetic factors over time. Novel genetic influences were identified accounting for a significant part of the variance (19%) at the second measurement occasion. There was no evidence for ethnic differences. In summary, novel genetic effects appear during development into young adulthood and account for a considerable part of the variation in PWV. Environmental influences become larger with age for PWV.

Prediction of Lung Function in Adolescence Using Epigenetic Aging: A Machine Learning Approach

Epigenetic aging has been found to be associated with a number of phenotypes and diseases. A few studies have investigated its effect on lung function in relatively older people. However, this effect has not been explored in the younger population. This study examines whether lung function in adolescence can be predicted with epigenetic age accelerations (AAs) using machine learning techniques. DNA methylation based AAs were estimated in 326 matched samples at two time points (at 10 years and 18 years) from the Isle of Wight Birth Cohort. Five machine learning regression models (linear, lasso, ridge, elastic net, and Bayesian ridge) were used to predict FEV₁ (forced expiratory volume in one second) and FVC (forced vital capacity) at 18 years from feature selected predictor variables (based on mutual information) and AA changes between the two time points. The best models were ridge regression (R² = 75.21% ± 7.42%; RMSE = 0.3768 ± 0.0653) and elastic net regression (R² = 75.38% ± 6.98%; RMSE = 0.445 ± 0.069) for FEV₁ and FVC, respectively. This study suggests that the application of machine learning in conjunction with tracking changes in AA over the life span can be beneficial to assess the lung health in adolescence.

Spirometric traits show quantile-dependent heritability, which may contribute to their gene-environment interactions with smoking and pollution

BACKGROUND

"Quantile-dependent expressivity" refers to a genetic effect that is dependent upon whether the phenotype (e.g., spirometric data) is high or low relative to its population distribution. Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and the FEV1/FVC ratio are moderately heritable spirometric traits. The aim of the analyses is to test whether their heritability (h2 ) is constant over all quantiles of their distribution.

METHODS

Quantile regression was applied to the mean age, sex, height and smoking-adjusted spirometric data over multiple visits in 9,993 offspring-parent pairs and 1,930 sibships from the Framingham Heart Study to obtain robust estimates of offspring-parent (βOP), offspring-midparent (βOM), and full-sib regression slopes (βFS). Nonparametric significance levels were obtained from 1,000 bootstrap samples. βOPs were used as simple indicators of quantile-specific heritability (i.e., h 2 = 2βOP/(1+rspouse), where rspouse was the correlation between spouses).

RESULTS

βOP ± standard error (SE) decreased by 0.0009 ± 0.0003 (P = 0.003) with every one-percent increment in the population distribution of FEV1/FVC, i.e., βOP ± SE were: 0.182 ± 0.031, 0.152 ± 0.015; 0.136 ± 0.011; 0.121 ± 0.013; and 0.099 ± 0.013 at the 10th, 25th, 50th, 75th, and 90th percentiles of the FEV1/FVC distribution, respectively. These correspond to h2  ± SEs of 0.350 ± 0.060 at the 10th, 0.292 ± 0.029 at the 25th, 0.262 ± 0.020 at the 50th, 0.234 ± 0.025 at the 75th, and 0.191 ± 0.025 at the 90th percentiles of the FEV1/FVC ratio. Maximum mid-expiratory flow (MMEF) h2  ± SEs increased 0.0025 ± 0.0007 (P = 0.0004) with every one-percent increment in its distribution, i.e.: 0.467 ± 0.046, 0.467 ± 0.033, 0.554 ± 0.038, 0.615 ± 0.042, and 0.675 ± 0.060 at the 10th, 25th, 50th, 75th, and 90th percentiles of its distribution. This was due to forced expiratory flow at 75% of FVC (FEF75%), whose quantile-specific h2 increased an average of 0.0042 ± 0.0008 for every one-percent increment in its distribution. It is speculated that previously reported gene-environment interactions may be partially attributable to quantile-specific h2 , i.e., greater heritability in individuals with lower FEV1/FVC due to smoking or airborne particles exposure vs. nonsmoking, unexposed individuals.

CONCLUSION

Heritabilities of FEV1/FVC, MMEF, and FEF75% from quantile-regression of offspring-parent and sibling spirometric data suggest their quantile-dependent expressivity.

Association of adult lung function with accelerated biological aging

Lung function, strongly associated with morbidity and mortality, decreases with age. This study examines whether poor adult lung function is associated with age accelerations (AAs). DNA methylation (DNAm) based AAs, lifespan predictors (GrimAge and plasminogen activator inhibitor 1-PAI1) and their related age-adjusted measures were estimated from peripheral blood at two time points (8-to-11 years apart) in adults from two cohorts: SAPALDIA (n=987) and ECRHS (n=509). Within each cohort and stratified by gender (except for estimators from GrimAge and PAI1), AAs were used as predictors in multivariate linear regression with cross-sectional lung function parameters, and in covariate-adjusted mixed linear regression with longitudinal change in lung function and meta-analysed.

AAs were found cross-sectionally associated with lower mean FEV1 (Forced Expiratory Volume in one second) (AA-residuals:P-value=4x10^-4; Intrinsic Epigenetic AA:P-value=2x10^-4) in females at the follow-up time point only, and the same trend was observed for FVC (Forced Vital Capacity). Both lifespan and plasma level predictors were observed strongly associated with lung function decline and the decline was stronger in the follow-up time points (strongest association between FEV1 and DNAmAge GrimAge:P-value=1.25x10^-17).

This study suggests that DNAm based lifespan and plasma level predictors can be utilised as important factors to assess lung health in adults.

The Hungarian Twin Registry Update: Turning From a Voluntary to a Population-Based Registry

Since our last report on the voluntary Hungarian Twin Registry (HTR) in 2012, the number of pairs or multiplets included increased from 310 to 1044. Efforts to turn the registry into a population-based one are on the way. Nearly 128,000 twins living in Hungary (98,500 adults) will be mailed information on how to register on the new HTR website. Twins will be asked to invite their spouses and immediate family members. Meanwhile, strong cooperation through exchange programs has been developed with other foreign twin registries. Current research focuses on radiogenomics, musculoskeletal, cardiovascular and respiratory diseases, gut microbiome as well as basic molecular research and yielded new awards and further publications.

Does Poorer Pulmonary Function Accelerate Arterial Stiffening?: A Cohort Study With Repeated Measurements of Carotid-Femoral Pulse Wave Velocity

Whether poorer pulmonary function accelerates progression of arterial stiffness remains unknown as prior observational studies have not examined longitudinal changes in arterial stiffness in relation to earlier pulmonary function. Data (N=5342, 26% female) were drawn from the Whitehall II cohort study. Participants completed repeated assessments of forced expiratory volume in 1 second (FEV₁, L) and carotid-femoral pulse wave velocity (cf-PWV, m/s) over 5 years. The effect of FEV₁ on later cf-PWV and its progression was estimated using linear mixed-effects modeling. Possible explanatory mechanisms, such as mediation by low-grade systemic inflammation, common-cause explanation by preexisting cardiometabolic risk factors, and reverse-causation bias, were assessed. Poorer pulmonary function was associated with later higher cf-PWV and its subsequent progression (cf-PWV 5-year change 0.09, 95% CI 0.03–0.17 per SD lower FEV₁) after adjustment for age, sex, ethnicity, heart rate, and mean arterial pressure. Decrease in pulmonary function was associated with later higher cf-PWV (0.17, 95% CI 0.04–0.30 in the top compared to bottom quartile of decline in FEV₁). There was no evidence to support mediation by circulating CRP (C-reactive protein) or IL (interleukin)-6. Furthermore, arterial stiffness was not associated with later FEV₁ after accounting for cardiometabolic status. In conclusion, poorer pulmonary function predicted future arterial stiffness. These findings support pulmonary function as a clinically important risk factor for arterial stiffness and provide justification for future intervention studies for pulmonary function based on its relationship with arterial stiffness.

Relationship between pulmonary function and peripheral vascular function in older Chinese: Guangzhou biobank cohort study-CVD

BACKGROUND

Findings describing the relationship between pulmonary function and peripheral vascular function have been inconclusive. We explored this relationship in Guangzhou Biobank Cohort Study-Cardiovascular Subcohort (GBCS-CVD).

METHODS

Brachial-ankle pulse wave velocity (baPWV) and ankle brachial index (ABI) were measured by a waveform analyser, and pulmonary function by turbine flowmeter spirometry. Predicted forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were derived using equations for Chinese. Regression analyses were used to investigate the association.

RESULTS

Of 1528 older Chinese, 980 (64.1%) had arterial stiffness (baPWV ≥1400 cm/s), but only 29 (1.9%) had peripheral arterial disease (PAD) (ABI < 0.9). The mean (±standard deviation, SD) baPWV was 1547 (±298) cm/s and mean (±SD) ABI 1.09 (±0.09). Before and after adjusting for potential confounders, baPWV was negatively associated with FEV1 and FVC % predicted (% predicted = observed/predicted × 100%) (adjusted β: - 0.95 and - 1.16 respectively, p < 0.05), and ABI was marginally non-significantly positively associated with FEV1% predicted (adjusted β 0.02, p = 0.32) and FVC% predicted (adjusted β 0.02, p = 0.18). Compared to participants in the highest tertile of pulmonary function, those in the lowest had higher risk of arterial stiffness (adjusted odds ratio (AOR) 1.51, 95% CI 1.09-2.10 for FEV1 and AOR 1.69, 95% CI 1.22-2.33 for FVC), but the higher risk of PAD was marginally non-significant (AOR 1.64, p = 0.42 for FEV1 and AOR 1.65, p = 0.24 for FVC).

CONCLUSION

In older relatively healthy normal weight Chinese, pulmonary function was inversely dose-dependently associated with arterial stiffness, while the association with PAD was much weaker.

Longitudinal study of the influence of lung function on vascular health from adolescence to early adulthood in a British multiethnic cohort

Background:

Vascular and lung function develop and decline over the life course; both predict cardiovascular events and mortality but little is known of how they develop over time. We analysed their relationship in a multiethnic cohort study to test whether lung function from early adolescence to young adulthood affected vascular indices.

Methods:

‘DASH’ (http://dash.sphsu.mrc.ac.uk) included 6643 children aged 11–13 years in 2003; a representative 10% sample (n = 665) participated in a pilot follow-up in 2013. Psychosocial, anthropometric, blood pressure (BP), and lung function measures were collected in both surveys; aortic pulse wave velocity (PWV) and augmentation index (AIx) were measured at aged 21–23 years. Relationships between forced expiratory volume Z-scores in 1 s (zFEV₁), after global initiative-ethnic adjustments and BP, PWV, and AIx were tested in linear regression and general estimating statistical models.

Results:

In total, 488 people with complete data were included. At 11–13 years, SBP was positively associated with zFEV₁ (coefficient = 1.90, 95% confidence interval 1.11–2.68, P < 0.001); but not at 21–23 years. The 10-year increase in zFEV₁ was associated with rise in SBP (1.38, 0.25–1.51, P < 0.05) in mixed effect models adjusted for age, sex, ethnicity, waist to height ratio, employment, reported racism, smoking, and alcohol use but DBP change was unrelated. In fully adjusted models, neither PWV nor central AIx were associated with zFEV₁ at 11–13 years or 21–23 years (P > 0.05).

Conclusion:

Forced expiratory volume change is positively and independently associated with SBP change from adolescence to young adulthood, suggesting earlier lung function plays important roles in SBP development. Vascular indices were unrelated to lung function or its change.

Genetic and Environmental Effects on Telomere Length and Lung Function: A Twin Study

Background

The purpose of the study was to estimate the heritability of leukocyte telomere length (LTL) and lung function and to examine whether LTL and lung function share genetic or environmental effects in common.

Methods

386 monozygotic and dizygotic Finnish twin sisters (age 68.4±3.4 years) were included. Relative LTL was determined from peripheral blood DNA by qPCR. Lung function measures of FEV1, FVC, FEV1/FVC, and PEF were derived from spirometry. Genetic modeling was performed with MPlus statistical software.

Results

Univariate analysis revealed that in LTL, 62% (95% confidence interval 50-72) of the variance was explained by additive genetic and 38% (28-50) by unique environmental factors. For FEV1, FVC, and PEF, the corresponding estimates were 65%-67% for additive genetic and 33%-35% for unique environmental factors. Across the sample, the phenotypic correlation between LTL and FEV1 was modest (r = .104, p = .041). Bivariate correlated factors model revealed that the genetic correlation between LTL and FEV1 was .18 (-0.19 to 0.64) and environmental correlation was -.10 (-0.84 to 0.55).

Conclusions

Both LTL and lung function variables are moderately to highly genetically determined. The associations between LTL and the lung function variables were weak. However, the positive genetic correlation point estimate gave minor suggestions that, in a larger sample, genetic factors in common might play a role in the phenotypic correlation between LTL and FEV1. Future studies with larger samples are needed to confirm these preliminary findings.

Genetic effects on refraction and correlation with hemodynamic variables: a twin study

Spherical equivalent (SE) has not been linked to increased cardiovascular morbidity. Methods: 132 Hungarian twins(age 43.3±16.9 years) underwent refraction measurements (Huvitz MRK-3100 Premium AutoRefractokeratometer)and oscillometry (TensioMed Arteriograph). Results: Heritability analysis indicated major role for genetic components in the presence of right and left SE (82.7%, 95%CI, 62.9 to 93.7%, and 89.3%, 95%CI, 72.8 to 96.6%),while unshared environmental effects accounted for 17% (95%CI, 6.3% to 37%), and 11% (95%CI, 3.4% to 26.7%)of variations adjusted for age and sex. Bilateral SE showed weak age-dependent correlations with augmentation index (AIx), aortic pulse wave velocity (r ranging between 0.218 and 0.389, all p < 0.01), aortic systolic blood pressure and pulse pressure (r between 0.188 and 0.289, p < 0.05). Conclusions: These findings support heritability of spherical equivalent, which does not coexist with altered hemodynamics (e.g. accelerated arterial aging).Accordingly, SE and the investigated hemodynamic parameters seem neither phenotypically nor genetically associated.

Exploring the origins of asthma: Lessons from twin studies

This thesis explores the contribution of twin studies, particularly those studies originating from the Danish Twin Registry, to the understanding of the aetiology of asthma. First, it is explored how twin studies have established the contribution of genetic and environmental factors to the variation in the susceptibility to asthma, and to the variation in several aspects of the clinical expression of the disease such as its age at onset, its symptomatology, its intermediate phenotypes, and its relationship with other atopic diseases. Next, it is explored how twin studies have corroborated theories explaining asthma's recent increase in prevalence, and last, how these fit with the explanations of the epidemiological trends in other common chronic diseases of modernity.

[Hungarian twin studies: results of four decades]

Twin studies play a role in examining the contribution of genetic variations and environmental factors responsible for the determination of phenotypic variables and of genetic linkage between genotypes. Hungarian twin studies, supported by three twin registries (among them two twin-database), date back to 1970s. Studies mainly focused on various congenital abnormalities, the effect of contraceptive pills and folic acid on the frequency of twin pregnancies, as well as psychosexual and alcohol consumptional behaviors. Monogenic Mendelian inheritance of lactose (mal)absorption was demonstrated for the first time. Hungarian Twin Registry was founded in 2007, which contributed to the current understanding on the background of several disorders, e.g. metabolic syndrome and atherosclerosis. As part of an international twin study, among others, arterial stiffness, central blood pressure, carotid intima/media thickness, venous biomechanics, body composition, lung function and smoking characteristics were also assessed. Absence of genetic background in non-alcoholic fatty liver disease and high inheritance of carotid plaque characteristics were demonstrated for the first time. The review also aims to summarize future plans of the Hungarian Twin Registry.