Establishing the interchangeability of arterial stiffness but not endothelial function parameters in healthy individuals

Bioengineered models of cardiovascular diseases

Age-associated cardiovascular diseases (CVDs), predominantly resulting from artery-related disorders such as atherosclerosis, stand as a leading cause of morbidity and mortality among the elderly population. Consequently, there is a growing interest in the development of clinically relevant bioengineered models of CVDs. Recent developments in bioengineering and material sciences have paved the way for the creation of intricate models that closely mimic the structure and surroundings of native cardiac tissues and blood vessels. These models can be utilized for basic research purposes and for identifying pharmaceutical interventions and facilitating drug discovery. The advancement of vessel-on-a-chip technologies and the development of bioengineered and humanized in vitro models of the cardiovascular system have the potential to revolutionize CVD disease modelling. These technologies offer pathophysiologically relevant models at a fraction of the cost and time required for traditional experimentation required in vivo. This progress signifies a significant advancement in the field, transitioning from conventional 2D cell culture models to advanced 3D organoid and vessel-on-a-chip models. These innovative models are specifically designed to explore the complexities of vascular aging and stiffening, crucial factors in the development of cardiovascular diseases. This review summarizes the recent progress of various bioengineered in vitro platforms developed for investigating the pathophysiology of human cardiovascular system with more focus on advanced 3D vascular platforms.

Effects of Blood Flow Restriction Resistance Training on Autonomic and Endothelial Function in Persons with Parkinson's Disease

Background

Autonomic dysfunction precedes endothelial dysfunction in Parkinson's disease (PD) and causes blood pressure and circulation abnormalities that are highly disruptive to one's quality of life. While exercise interventions have proven helpful for motor symptoms of PD, improving associated non-motor symptoms is limited. Low-intensity resistance training with blood flow restriction (LIRT-BFR) improves autonomic dysfunction in non-PD patients and high-intensity resistance training (HIRT) is recommended for motor symptom improvements for people with PD (PwPD).

Objective

To determine the effects of LIRT-BFR and HIRT on homocysteine and autonomic and endothelial function in PwPD and to determine the hemodynamic loads during LIRT-BFR and HIRT in PwPD using a novel exercise protocol.

Methods

Thirty-eight PwPD were assigned LIRT-BFR, HIRT or to a control (CNTRL) group. The LIRT-BFR and HIRT groups exercised three days per week for four weeks. The LIRT-BFR protocol used 60% limb occlusion pressure (LOP) and performed three sets of 20 repetitions at 20% of the one-repetition maximum (1RM). The HIRT group performed three sets of eight repetitions at 80% 1RM. The CNTRL group was asked to continue their normal daily routines.

Results

LIRT-BFR significantly improved orthostatic hypotension (p = 0.026), homocysteine levels (p < 0.001), peripheral circulation (p = 0.003), supine blood pressure (p = 0.028) and heart rate variability (p = 0.041); LIRT-BFR improved homocysteine levels (p < 0.018), peripheral circulation (p = 0.005), supine blood pressure (p = 0.007) and heart rate variability (p = 0.047) more than HIRT; and hemodynamic loads for LIRT-BFR and HIRT were similar.

Conclusions

LIRT-BFR may be more effective than HIRT for autonomic and endothelial function improvements in PwPD and hemodynamic loads may be lessened in LIRT-BFR protocols using single-joint exercises with intermittent blood flow restriction. Further research is needed to determine if non-motor symptoms improve over time and if results are sustainable.

Photoplethysmography for the Assessment of Arterial Stiffness

This review outlines the latest methods and innovations for assessing arterial stiffness, along with their respective advantages and disadvantages. Furthermore, we present compelling evidence indicating a recent growth in research focused on assessing arterial stiffness using photoplethysmography (PPG) and propose PPG as a potential tool for assessing vascular ageing in the future. Blood vessels deteriorate with age, losing elasticity and forming deposits. This raises the likelihood of developing cardiovascular disease (CVD), widely reported as the global leading cause of death. The ageing process induces structural modifications in the vascular system, such as increased arterial stiffness, which can cause various volumetric, mechanical, and haemodynamic alterations. Numerous techniques have been investigated to assess arterial stiffness, some of which are currently used in commercial medical devices and some, such as PPG, of which still remain in the research space.

Vascular phenotypes in early hypertension

The study characterises vascular phenotypes of hypertensive patients utilising machine learning approaches. Newly diagnosed and treatment-naïve primary hypertensive patients without co-morbidities (aged 18-55, n = 73), and matched normotensive controls (n = 79) were recruited (NCT04015635). Blood pressure (BP) and BP variability were determined using 24 h ambulatory monitoring. Vascular phenotyping included SphygmoCor® measurement of pulse wave velocity (PWV), pulse wave analysis-derived augmentation index (PWA-AIx), and central BP; EndoPAT™-2000® provided reactive hyperaemia index (LnRHI) and augmentation index adjusted to heart rate of 75bpm. Ultrasound was used to analyse flow mediated dilatation and carotid intima-media thickness (CIMT). In addition to standard statistical methods to compare normotensive and hypertensive groups, machine learning techniques including biclustering explored hypertensive phenotypic subgroups. We report that arterial stiffness (PWV, PWA-AIx, EndoPAT-2000-derived AI@75) and central pressures were greater in incident hypertension than normotension. Endothelial function, percent nocturnal dip, and CIMT did not differ between groups. The vascular phenotype of white-coat hypertension imitated sustained hypertension with elevated arterial stiffness and central pressure; masked hypertension demonstrating values similar to normotension. Machine learning revealed three distinct hypertension clusters, representing 'arterially stiffened', 'vaso-protected', and 'non-dipper' patients. Key clustering features were nocturnal- and central-BP, percent dipping, and arterial stiffness measures. We conclude that untreated patients with primary hypertension demonstrate early arterial stiffening rather than endothelial dysfunction or CIMT alterations. Phenotypic heterogeneity in nocturnal and central BP, percent dipping, and arterial stiffness observed early in the course of disease may have implications for risk stratification.

Endothelial Cell Dysfunction and Increased Cardiovascular Risk in Patients With Chronic Kidney Disease

The endothelium is considered to be the gatekeeper of the vessel wall, maintaining and regulating vascular integrity. In patients with chronic kidney disease, protective endothelial cell functions are impaired due to the proinflammatory, prothrombotic and uremic environment caused by the decline in kidney function, adding to the increase in cardiovascular complications in this vulnerable patient population. In this review, we discuss endothelial cell functioning in healthy conditions and the contribution of endothelial cell dysfunction to cardiovascular disease. Further, we summarize the phenotypic changes of the endothelium in chronic kidney disease patients and the relation of endothelial cell dysfunction to cardiovascular risk in chronic kidney disease. We also review the mechanisms that underlie endothelial changes in chronic kidney disease and consider potential pharmacological interventions that can ameliorate endothelial health.

The association between baseline circulating progenitor cells and vascular function: The role of aging and risk factors

BACKGROUND

To investigate the cross-sectional and longitudinal relationships between vascular function and circulating progenitor cell (CPC) counts with respect to aging and exposure to risk factors.

METHODS

In 797 adult participants, CPCs were enumerated by flow cytometry as CD45med mononuclear cells expressing CD34 epitope and its subsets co-expressing CD133, and chemokine C-X-C motif receptor 4 (CXCR4+). Arterial stiffness was evaluated by tonometry-derived pulse wave velocity (PWV) and microvascular function was assessed as digital reactive hyperemia index (RHI).

RESULTS

In cross-sectional analyses, for every doubling in CD34+ cell counts, PWV was 15% higher and RHI was 9% lower, after adjusting for baseline characteristics and risk factors (p for all < 0.01). There were significant CPC-by-age-by-risk factor interactions (p <0.05) for both vascular measures. Among younger subjects (< 48 years), CPC counts were higher in those with risk factors and vascular function was better in those with higher compared to those with lower CPC counts (p for all < 0.0l). In contrast, in older participants, CPCs were not higher in those with risk factors, and vascular function was worse compared to the younger age group. A lower CPC count at baseline was an independent predictor of worsening vascular function during 2-year follow-up.

CONCLUSION

A higher CPC count in the presence of risk factors is associated with better vascular function among younger individuals. There is no increase in CPC count with risk factors in older individuals who have worse vascular function. Moreover, a higher CPC count is associated with less vascular dysfunction with aging.

D-dimer in Marfan syndrome: effect of obstructive sleep apnea induced blood pressure surges

Aortic dissection and rupture are the major causes of premature death in persons with Marfan syndrome (MFS), a rare genetic disorder featuring cardiovascular, skeletal, and ocular impairments. We and others have found that obstructive sleep apnea (OSA) confers significant vascular stress in this population and may accelerate aortic disease progression. We hypothesized that D-dimer, a diagnostic biomarker for several types of vascular injury that is also elevated in persons with MFS with aortic enlargement, may be sensitive to cardiovascular stresses caused by OSA. To test this concept, we recruited 16 persons with MFS without aortic dissection and randomized them to two nights of polysomnography, without (baseline) and with OSA treatment: continuous positive airway pressure (CPAP). In addition to scoring OSA by the apnea-hypopnea index (AHI), beat-by-beat systolic BP (SBP) and pulse-pressure (PP) fluctuations were quantified. Morning blood samples were also assayed for D-dimer levels. In this cohort (male:female, 10:6; age, 36 ± 13 yr; aortic diameter, 4 ± 1 cm), CPAP eliminated OSA (AHI: 20 ± 17 vs. 3 ± 2 events/h, P = 0.001) and decreased fluctuations in SBP (13 ± 4 vs. 9 ± 3 mmHg, P = 0.011) and PP (7 ± 2 vs. 5 ± 2 mmHg, P = 0.013). CPAP also reduced D-dimer levels from 1,108 ± 656 to 882 ± 532 ng/mL (P = 0.023). Linear regression revealed a positive association between the maximum PP during OSA and D-dimer in both the unadjusted (r = 0.523, P = 0.038) and a model adjusted for contemporaneous aortic root diameter (r = 0.733, P = 0.028). Our study revealed that overnight CPAP reduces D-dimer levels commensurate with the elimination of OSA and concomitant hemodynamic fluctuations. Morning D-dimer measurements together with OSA screening might serve as predictors of vascular injury in MFS.NEW & NOTEWORTHY What is New? Surges in blood pressure caused by obstructive sleep apnea during sleep increase vascular stress and D-dimer levels in Marfan syndrome. Elevations in D-dimer can be lowered with CPAP. What is Noteworthy? D-dimer levels might serve as a marker for determining the significance of obstructive sleep apnea in persons with Marfan syndrome. D-dimer or obstructive sleep apnea screening is a potential method to identify persons with Marfan syndrome at risk for adverse cardiovascular events.

The impact of obstructive sleep apnea on endothelial function during weight loss in an obese pediatric population

BACKGROUND

Childhood obesity is an increasing problem with substantial comorbidities such as obstructive sleep apnea (OSA) and increased cardiovascular morbidity. Endothelial dysfunction is an underlying mechanism related to both obesity and OSA.

RESEARCH QUESTION

To investigate the effect of weight loss on endothelial function and OSA in obese children and to determine whether a change in endothelial function can be linked to an improvement in OSA.

METHODS

Obese children between 8 and 18 years of age were recruited while entering a 12-month inpatient weight loss program. Patients were followed at 3 study visits: baseline, after 10 months of weight loss, and 6 months after ending the program (18 months). Anthropometry and endothelial function (EndoPAT) were determined at all study visits. At baseline, sleep screening with a portable device (ApneaLink) was performed. This was repeated after 10 months if OSA was diagnosed at baseline.

RESULTS

At baseline, 130 children were included, of which 87 had OSA (67%). Seventy-two patients attended the follow-up visit at 10 months, and 28 patients attended the follow-up visit at 18 months. The BMI z-score decreased after 10 months (from 2.7 (1.4-3.4) to 1.7 (0.5-2.7); p < 0.001) and remained stable at 18 months. Endothelial function improved significantly after weight loss, evidenced by a shorter time to peak response (TPR) and higher reactive hyperemia index (p = 0.02 and p < 0.001), and remained improved after 18 months (p < 0.001 and p = 0.007). After 10 months of weight loss, 10 patients had residual OSA. These patients had a higher TPR at 10 months (225 (75-285)s) than those without OSA (135 (45-225)s) and patients with a normalized sleep study (105 (45-285)s; p = 0.02). Linear mixed models showed that more severe OSA was associated with a worse TPR at baseline and less improvement after weight loss.

CONCLUSION

Weight loss improves endothelial function in an obese pediatric population. However, even after weight loss, endothelial function improved less in the presence of OSA.

IGFBP-1 and IGFBP-2 are associated with a decreased pulse-wave velocity in young, healthy adults

Background and aims

In healthy, young adults we analyzed a panel of cardiovascular disease related proteins in plasma and compared them with the vascular health of the subjects. The aim was to identify proteins with a relationship to the early atherosclerotic process in healthy individuals.

Methods

We employed the proximity extension assay from OLINK proteomics to analyze 92 cardiovascular disease (CVD) related proteins on 833 subjects (men and women, ages 18–26). The women were further divided into an estrogen-using group and non-users. Protein expression was analyzed using principal component analysis (PCA). The following vascular examinations were performed: Pulse-wave velocity (PWV), augmentation index (AIX), carotid-intima media thickness (cIMT).

Results

Three principal components were obtained using PCA to analyze the protein expression. None of the obtained principal components correlated significantly with AIX or cIMT. One of the components, explaining 6% of the total variance of the data, was significantly correlated with PWV. Upon examination of the proteins with the highest factor loadings on this component independently in a multivariable model, adjusting for established CVD risk biomarkers, insulin-like growth factor-binding protein 1 (IGFBP-1) and insulin-like growth factor-binding protein 2 (IGFBP-2) were found to independently, negatively correlate with PWV. Among the established risk factors included in the multivariable model, age was significantly and adversely correlated with all vascular measurements.

Conclusions

In this population of healthy, young adults, groups of CVD related proteins correlate with PWV, but not AIX or cIMT. This group of proteins, of which IGFBP-1 and IGFBP-2 were independently, negatively correlated in a multivariable model with PWV, could have benificial effects on vascular stiffness. The robust association between age and PWV, AIX and cIMT provide insight into the impact of aging on the vasculature, which is detectable even in a population of young, healthy, non-smoking individuals of ages spanning only 8 years.

Supplementary information

The online version contains supplementary material available at 10.1186/s12872-021-01914-w.

Impact of Age, Menopause, and Obesity on Oxylipins Linked to Vascular Health

Objective:

Cardiovascular disease, a major cause of mortality and morbidity, exhibits sexual dimorphism since the onset of cardiovascular disease occurs later in women than in men. The loss of cardioprotection in older women may be due to an increase in arterial stiffness after menopause. Free fatty acid metabolites of polyunsaturated fatty acids, called oxylipins, are known to impact vessel function and may be responsible for the vascular benefits of polyunsaturated fatty acids. The objectives of this study were to compare the plasma oxylipin profiles of young females (20–55 years), older females (55 + ), and older males (55 + ) and to identify associations between oxylipins and cardiovascular disease risk factors, such as obesity and arterial stiffness.

Approach and Results:

We quantified plasma oxylipins by high-performance liquid chromatography–tandem mass spectrometry in archived samples taken from completed clinical trials. We identified 3 major 12-lipoxygenase products, 12-hydroxy-eicosatetraenoic acid, 12-hydroxy-eicosapentaenoic acid, and 14-hydroxy-docosahexaenoic acid, that are present at high levels in young females compared with older females and males. These oxylipins also decreased with obesity and displayed robust negative associations with arterial stiffness as assessed by brachial-ankle pulse wave velocity. According to multiple linear regression modeling, these associations were maintained even after correcting for body mass index category combined with either age, menopausal status, or estradiol levels. Using linear discriminant analysis, the combination of these 3 oxylipins effectively distinguished participants according to both brachial-ankle pulse wave velocity risk group and age.

Conclusions:

Higher 12-lipoxygenase oxylipin plasma concentrations associated with lower arterial stiffness in premenopausal females may be an important contributing factor to sex differences in cardiovascular disease.

Registration:

URL: https://www.clinicaltrials.gov ; Unique identifiers: NCT01661543, NCT01562171, NCT01890330, NCT02571114 and NCT02317588.

Long Chain Omega-3 Polyunsaturated Fatty Acids Improve Vascular Stiffness in Abdominal Aortic Aneurysm: A Randomized Controlled Trial

Abdominal aortic aneurysm (AAA) is a vascular disease involving permanent focal dilation of the abdominal aorta (≥30 mm) that can lead to catastrophic rupture. Destructive remodeling of aortic connective tissue in AAA contributes to wall stiffening, a mechanical parameter of the arterial system linked to a heightened risk of cardiovascular morbidity and mortality. Since aortic stiffening is associated with AAA progression, treatment options that target vascular inflammation would appear prudent. Given this, and growing evidence indicating robust anti-inflammatory and vasoprotective properties for long chain omega-3 polyunsaturated fatty acids (LC n-3 PUFAs), this study evaluated the impact of these nutrients (1.8 g/day for 12 weeks) on indices of vascular stiffness in patients with AAA. At baseline, pulse wave velocity (PWV) and augmentation index normalized to a heart rate of 75 bpm (AIx75) were significantly higher in patients with AAA compared to control participants (PWV: 14.2 ± 0.4 m.s^-1 vs. 12.6 ± 0.4 m.s^-1, p = 0.014; AIx75: 26.4 ± 1.7% vs. 17.3 ± 2.7%, p = 0.005). Twelve-week LC n-3 PUFA supplementation significantly decreased PWV (baseline: 14.2 ± 0.6 m.s^-1, week 12: 12.8 ± 0.7 m.s^-1, p = 0.014) and heart rate (baseline: 63 ± 3 bpm, week 12: 58 ± 3 bpm, p = 0.009) in patients with AAA. No change was observed for patients receiving placebo capsules. While this raises the possibility that LC n-3 PUFAs provide improvements in aortic stiffness in patients with AAA, the clinical implications remain to be fully elucidated.

Associations Between Depression, Arterial Stiffness, and Metabolic Syndrome Among Adults in the UK Biobank Population Study: A Mediation Analysis

Importance

Previous research has linked a history of depression with arterial stiffness (AS) during midlife.

Objective

To assess the association of depression with elevated midlife AS and to investigate the extent to which this association is mediated via metabolic syndrome (MetS).

Design, Settings, and Participants

This population-based retrospective cohort study analyzed data collected between March 2006 and December 2010 from 124 445 participants aged 40 to 69 years from the UK Biobank. Participants without data on AS at baseline (n = 332 780) or who reported a previous diagnosis of cardiovascular disease (n = 45 374) were not eligible. Data analysis was performed from May to August 2019.

Exposures

Lifetime history of depression was assessed via verbal interview and linked hospital-based clinical depression diagnosis. Metabolic syndrome was defined as the presence of 3 or more of hypertension, dyslipidemia, hyperglycemia, hypertriglyceridemia, and unhealthy waist circumference.

Main Outcomes and Measures

Peripherally assessed AS index (ASI) using digital photoplethysmography.

Results

Of 124 445 included participants with ASI assessed, 71 799 (57.7%) were women, and the mean (SD) age was 56 (8) years. A total of 10 304 participants (8.3%) reported a history of depression. Study findings indicated a significant direct association between depression and ASI levels (β = 0.25; 95% CI, 0.17-0.32). A significant indirect association was also observed between depression and ASI levels (β = 0.10; 95% CI, 0.07-0.13), indicating that 29% of the association of depression with ASI was mediated by MetS. The proportion of mediation increased to 37% when C-reactive protein was added to the MetS criteria (direct association: β = 0.21; 95% CI, 0.15-0.28; indirect association: β = 0.13; 95% CI, 0.10-0.17). Concerning components of MetS, the strongest indirect association was for waist circumference, accounting for 25% of the association between depression and ASI levels (direct association: β = 0.26; 95% CI, 0.18-0.34; indirect association: β = 0.09; 95% CI, 0.06-0.11). Among men, hypertriglyceridemia accounted for 19% of the association between depression and ASI (direct association: β = 0.22; 95% CI, 0.05-0.40; indirect association: β = 0.05; 95% CI, 0.02-0.08).

Conclusions and Relevance

One-third of the association of depression with elevated ASI levels during midlife may be accounted for by combined MetS and inflammatory processes. Unhealthy waist circumference and hypertriglyceridemia emerged as the most important potential targets for preventive interventions within women and men, respectively.