Judita Knez

Correlates of Peripheral Blood Mitochondrial DNA Content in a General Population

Accumulation of mitochondrial DNA (mtDNA) mutations leads to alterations of mitochondrial biogenesis and function that might produce a decrease in mtDNA content within cells. This implies that mtDNA content might be a potential biomarker associated with oxidative stress and inflammation. However, data on correlates of mtDNA content in a general population are sparse. Our goal in the present study was to describe in a randomly recruited population sample the distribution and determinants of peripheral blood mtDNA content. From 2009 to 2013, we examined 689 persons (50.4% women; mean age = 54.4 years) randomly selected from a Flemish population (Flemish Study on Environment, Genes, and Health Outcomes). Relative mtDNA copy number as compared with nuclear DNA was measured by quantitative real-time polymerase chain reaction in peripheral blood. There was a curvilinear relationship between relative mtDNA copy number and age. mtDNA content slightly increased until the fifth decade of life and declined in older subjects (Page2 = 0.0002). mtDNA content was significantly higher in women (P = 0.007) and increased with platelet count (P < 0.0001), whereas it was inversely associated with white blood cell count (P < 0.0001). We also observed lower mtDNA content in women using estroprogestogens (P = 0.044). This study demonstrated in a general population that peripheral blood mtDNA content is significantly associated with sex and age. Blood mtDNA content is also influenced by platelet and white blood cell counts and estroprogestogen intake. Further studies are required to clarify the impact of chronic inflammation and hormone therapy on mitochondrial function.

Impact and pitfalls of scaling of left ventricular and atrial structure in population-based studies

Background: Several allometric methods for indexing cardiac structures to body size have been proposed but the optimal way for normalization of cardiac structures is still controversial. We aimed to estimate the allometric exponents that best describe the relationships between cardiac dimensions and body size, propose normative values, and analyze how the different scaling metrics influence the prevalence of left ventricular hypertrophy (LVH) and chambers enlargement as well as predictive models for cardiovascular outcome in the community. Methods: We measured left ventricular end-diastolic dimension, end-diastolic volume, left ventricular mass, and left atrial volume in randomly recruited population cohorts (n = 1509; 52.8% women; mean age, 47.8 years). Results: In a healthy subgroup (n = 656), the allometric exponents that described the relationships between left ventricular end-diastolic dimension and body size were 1, 0.5, and 0.33 for body height, body surface area (BSA), and estimated lean body mass, respectively. With regard to left ventricular end-diastolic volume, left ventricular mass, and left atrial volume the allometric exponents for body height were 2.9, 2.7, and 2.0, respectively; for BSA, they ranged from 1.7 to 1.8; for estimated lean body mass all exponents were around 1. These exponents were used to appropriately scale the cardiac dimensions to body size and derived sex-specific cut-off limits for different indexed cardiac dimensions. The hazard ratios of cardiovascular outcome were highest for LVH defined by left ventricular mass/height2.7. Conclusion: Our study resulted in a proposal for thresholds for various indexed cardiac dimensions. Left ventricular mass indexed to height was sensitive in detection of LVH associated with obesity and slightly better predicted outcome.

Longitudinal changes in left ventricular diastolic function in a general population.

Background—Data on changes in left ventricular diastolic function (LVDF) over time in the general population are sparse. We, therefore, investigated in the population cohort clinical correlates of longitudinal changes in Doppler diastolic indexes analyzed as continuous measures and assessed factors predictive of the changes in LVDF grades over time. Methods and Results—We measured early and late diastolic peak velocities of mitral inflow (E and A) by conventional Doppler, and the mitral annular velocities (e′ and a′) by tissue Doppler imaging in 650 participants (mean age, 50.7 years) at baseline and after 4.7 years (5th to 95th percentile, 3.7–5.4). In stepwise regression, the multivariable-adjusted correlates of the change in the transmitral and tissue Doppler imaging diastolic indexes included sex, age, baseline serum insulin, blood pressure, and heart rate. During follow-up, LVDF grades remained unchanged in 87.2% (95% confidence interval, 84.6%–89.8%), improved in 3.7% (95% confidence interval, 2.25%–5.15%), and worsened in 9.1% (95% confidence interval, 6.9%–11.3%). Baseline age was a strong predictor of worsening of LVDF from normal/mild grade to more advanced grade (odds ratio, 3.22; P<0.0001). A doubling of baseline insulin was associated with a 184% increase in the odds of worsening of LVDF (P<0.0001). Moreover, baseline diastolic blood pressure and the change in systolic blood pressure over time predicted worsening of LVDF (P⩽0.014). Conclusions—The key findings of this study are that LVDF tended to worsen over time and was associated with advanced age, higher baseline insulin level, and hemodynamic parameters, such as heart rate and blood pressure.

Doppler indexes of left ventricular systolic and diastolic flow and central pulse pressure in relation to renal resistive index.

BACKGROUND The cardio-renal interaction occurs via hemodynamic and humoral factors. Noninvasive assessment of renal hemodynamics is currently possible by assessment of renal resistive index (RRI) derived from intrarenal Doppler arterial waveforms as ((peak systolic velocity - end-diastolic velocity)/peak systolic velocity). Limited information is available regarding the relationship between RRI and cardiac hemodynamics. We investigated these associations in randomly recruited subjects from a general population. METHODS In 171 participants (48.5% women; mean age, 52.2 years), using pulsed wave Doppler, we measured RRI (mean, 0.60) and left ventricular outflow tract (LVOT) and transmitral (E and A) blood flow peak velocities and its velocity time integrals (VTI). Using carotid applanation tonometry, we measured central pulse pressure and arterial stiffness indexes such as augmentation pressure and carotid-femoral pulse wave velocity. RESULTS In stepwise regression analysis, RRI independently and significantly increased with female sex, age, body weight, brachial pulse pressure, and use of β-blockers, whereas it decreased with body height and mean arterial pressure. In multivariable-adjusted models with central pulse pressure and arterial stiffness indexes as the explanatory variables, we observed a significant and positive correlation of RRI only with central pulse pressure (P < 0.0001). Among the Doppler indexes of left ventricular blood flow, RRI was significantly and positively associated with LVOT and E peak velocities (P ≤ 0.012) and VTIs (P ≤ 0.010). CONCLUSIONS We demonstrated that in unselected subjects RRI was significantly associated with central pulse pressure and left ventricular systolic and diastolic Doppler blood flow indexes. Our findings imply that in addition to the anthropometric characteristics, cardiac hemodynamic factors influence the intrarenal arterial Doppler waveform patterns.

Additive Prognostic Value of Left Ventricular Systolic Dysfunction in a Population-Based Cohort

Background—Techniques of 2-dimensional speckle tracking enable the measurement of myocardial deformation (strain) during systole. Recent clinical studies explored the prognostic role of left ventricular global longitudinal strain (GLS). However, there are few data on the association between cardiovascular outcome and GLS in the community. Therefore, we hypothesized that GLS contains additive prognostic information over and beyond traditional cardiovascular risk factors in a large, population-based cohort. Methods and Results—We measured GLS by 2-dimensional speckle tracking in the apical 4-chamber view in 791 participants (mean age 50.9 years). We calculated multivariable adjusted hazard ratios for midwall, endocardial, and epicardial GLS, while accounting for family cluster and cardiovascular risk factors. Median follow-up was 7.9 years (5th to 95th percentile, 3.7–9.6). In continuous analysis, with adjustments applied for covariables, midwall, endocardial, and epicardial GLS were significant predictors of fatal and nonfatal cardiovascular (n=96; P<0.0001) and cardiac events (n=68; P⩽0.001). In the sex-specific low quartile of midwall GLS (<18.8% in women and <17.4% in men), the risk was significantly higher than the average population risk for cardiovascular (128%, P<0.0001) and cardiac (94%, P=0.0007) events. We also noticed that the risk for cardiovascular events increased with increasing number of left ventricular abnormalities, such as low GLS, diastolic dysfunction, and hypertrophy (log-rank P<0.0001). Conclusions—Low GLS measured by 2-dimensional speckle tracking predicts future cardiovascular events independent of conventional risk factors. Left ventricular midwall strain represents a simple echocardiographic measure, which might be used for assessing cardiovascular risk in a population-based cohort.

Doppler indexes of left ventricular systolic and diastolic function in relation to the arterial stiffness in a general population.

Background: Late-systolic loading of the left ventricular (LV) is determined by arterial wave reflections and central vascular stiffening. We, therefore, investigated the relationship between various Doppler indexes reflecting LV systolic and diastolic function and arterial stiffness in the framework of a large population study of randomly recruited study participants. Methods: In 1233 study participants (51.7% women; mean age, 48 years; 41.5% hypertensive), using conventional and tissue Doppler imaging, we measured: the transmitral early (E) and late (A) diastolic velocities; tissue Doppler imaging systolic and early (e′) and late diastolic mitral annular velocities; and end-systolic longitudinal and radial strain. Using applanation tonometry, we assessed central pulse pressure (cPP), augmentation pressure and carotid-femoral pulse wave velocity. Results: After full adjustment, transmitral E and A peaks increased with augmentation pressure and cPP (P less than 0.0001) and e′ was positively associated with cPP (P = 0.013). The E/e′ ratio increased significantly with augmentation pressure (P less than 0.0001), cPP (P less than 0.0001) and pulse wave velocity (P = 0.048). Although accounting for covariables, all arterial indexes were on average significantly higher in the diastolic dysfunction group with elevated filling pressure (n = 171) when compared to participants with normal diastolic function (n = 961; P ⩽ 0.0004) or with impaired relaxation (n = 101; P ⩽ 0.008). Longitudinal strain decreased independently with mean arterial pressure (P = 0.03). The correlation between radial strain and the arterial indexes shifted from positive at middle age (50–60 years) to negative at older (P less than 0.0001 for interaction). Conclusion: Our study underscored the importance of arterial characteristics as a mediator of LV systolic and diastolic dysfunction. We demonstrated an age-dependent relationship between radial strain and indexes of arterial stiffness.

Cytokines profile in hypertensive patients with left ventricular remodeling and dysfunction.

There is strong evidence that inflammatory mediators play a key role in the progression to heart failure in patients with systemic hypertension (HTN). The present study aimed to identify a set of cytokines that are associated with early left ventricular (LV) remodeling and dysfunction as captured by echocardiography in patients with HTN in a cross-sectional case-control study nested within the FLEMish study on ENvironment, Genes and Health Outcome. We identified three groups of participants from the cohort: normotensive subjects (normotension; n = 30), HTN with normal LV structure and function (HTN [LV-]; n = 30), and HTN with evidence of adverse LV remodeling (HTN [LV+]; n = 50). We measured cytokines using a 63-plex Luminex platform. Using partial least squares-discriminant analysis, we constructed three latent variables from the measured cytokines that explained 35%-45% of the variance between groups. We identified five common cytokines (interleukin 18, monokine induced by gamma interferon, hepatocyte growth factor, epithelial neutrophil-activating peptide 78, and vascular endothelial growth factor D) with a stable signal which had a major impact on the construction of the latent variables. Among these cytokines, after adjustment for confounders, interleukin 18 remained significantly different between HTN participants with and without LV involvement (P = .02). Moreover, granulocyte-macrophage colony-stimulating factor and leptin showed a consistent upward trend in all HTN patients compared with normotensive subjects. In conclusion, in HTN patients with LV remodeling or/and dysfunction, we identified a set of cytokines strongly associated with LV maladaptation. We also found a distinct profile of inflammatory biomarkers that characterize HTN.

Peripheral blood mitochondrial DNA content in relation to circulating metabolites and inflammatory markers: a population study

Mitochondrial DNA (mtDNA) content might undergo significant changes caused by metabolic derangements, oxidative stress and inflammation that lead to development and progression of cardiovascular diseases. We, therefore, investigated in a general population the association of peripheral blood mtDNA content with circulating metabolites and inflammatory markers. We examined 310 subjects (50.6% women; mean age, 53.3 years) randomly selected from a Flemish population. Relative mtDNA content was measured by quantitative real-time PCR in peripheral blood cells. Peak circulating metabolites were quantified using nuclear magnetic resonance spectroscopy. The level of inflammation was assessed via established inflammatory markers. Using Partial Least Squares analysis, we constructed 3 latent factors from the 44 measured metabolites that explained 62.5% and 8.5% of the variance in the contributing metabolites and the mtDNA content, respectively. With adjustments applied, mtDNA content was positively associated with the first latent factor (P = 0.002). We identified 6 metabolites with a major impact on the construction of this latent factor including HDL3 apolipoproteins, tyrosine, fatty acid with αCH2, creatinine, β-glucose and valine. We summarized them into a single composite metabolite score. We observed a negative association between the composite metabolic score and mtDNA content (P = 0.001). We also found that mtDNA content was inversely associated with inflammatory markers including hs-CRP, hs-IL6, white blood cell and neutrophil counts as well as neutrophil-to-lymphocyte ratio (P≤0.0024). We demonstrated that in a general population relative peripheral blood mtDNA content was associated with circulating metabolites indicative of perturbed lipid metabolism and with inflammatory biomarkers.

Renal glomerular dysfunction in relation to retinal arteriolar narrowing and high pulse pressure in seniors

Retinal arteriolar narrowing and high pulse pressure (PP) are associated with macrovascular complications and microvascular renal disease. Few studies addressed whether in seniors (⩾60 years) estimated glomerular filtration rate (eGFR) is independently related to central retinal arteriolar equivalent (CRAE) and PP. In 292 randomly recruited seniors (49.3% women; mean, 68.2 years), we measured PP by standard sphygmomanometry, CRAE (IVAN software), eGFR (Chronic Kidney Disease Epidemiology Collaboration equation) and stage of chronic kidney disease (CKD (Kidney Disease Outcomes Quality Initiative guideline)). Statistical methods included linear and logistic regression. PP, CRAE and eGFR averaged 59.2 mm Hg, 146.3 μm and 79.9 ml min−1 per 1.73 m2. Decline in eGFR (–2.27 ml min−1 per 1.73 m2 per 15 μm; P=0.011) occurred in parallel with CRAE narrowing. CRAE (effect size per 1-s.d. increment, –1.85 μm; P=0.032) and eGFR (–2.68 ml min−1 per 1.73 m2; P=0.003) both declined with higher PP. With PP increasing from 63 to 73 mm Hg (threshold for macrovascular complications), CRAE dropped by –4.70 μm (P⩽0.037). A 70-mm Hg PP threshold corresponded with a 150-μm CRAE cutoff. The risk of CKD (stage ⩾2 vs. 1; n=203 vs. 89) rose with CRAE <150 μm (odds ratio, 2.81; P<0.0001), but not with PP ⩾70 mm Hg (1.47; P=0.20). Additionally, CRAE added to PP increased the area under the curve from 0.58 to 0.64 (P=0.047) for identifying stage ⩾2 CKD. In seniors, CRAE and eGFR decline in parallel with higher PP. CRAE <150 μm identifies early decline in eGFR.

Association of digital vascular function with cardiovascular risk factors: a population study

Objectives Vasodilation of the peripheral arteries during reactive hyperaemia depends in part on release of nitric oxide from endothelial cells. Previous studies mainly employed a fingertip tonometric device to derive pulse wave amplitude (PWA) and PWA hyperaemic changes. An alternative approach is based on photoplethysmography (PPG). We sought to evaluate the correlates of digital PPG PWA hyperaemic responses as a measure of peripheral vascular function. Design The Flemish Study on Environment, Genes and Health Outcomes (FLEMENGHO) is a population-based cohort study. Setting Respondents were examined at one centre in northern Belgium. Participants For this analysis, our sample consisted of 311 former participants (53.5% women; mean age 52.6 years; 43.1% hypertensive), who were examined from January 2010 until March 2012 (response rate 85.1%). Primary outcome measures Using a fingertip PPG device, we measured digital PWA at baseline and at 30 s intervals for 4 min during reactive hyperaemia induced by a 5 min forearm cuff occlusion. We performed stepwise regression to identify correlates of the hyperaemic response ratio for each 30 s interval after cuff deflation. Results The maximal hyperaemic response was detected in the 30–60 s interval. The explained variance for the PPG PWA ratio ranged from 9.7% at 0–30 s interval to 22.5% at 60–90 s time interval. The hyperaemic response at each 30 s interval was significantly higher in women compared with men (p≤0.001). The PPG PWA changes at 0–90 s intervals decreased with current smoking (p≤0.0007) and at 0–240 s intervals decreased with higher body mass index (p≤0.035). These associations with sex, current smoking and body mass index were mutually independent. Conclusions Our study is the first to implement the new PPG technique to measure digital PWA hyperaemic changes in a general population. Hyperaemic response, as measured by PPG, is inversely associated with traditional cardiovascular risk factors such as male sex, smoking and obesity.