Microvascular wall-to-lumen ratio in patients with arterial hypertension: A randomized controlled exercise trial.

BACKGROUND AND AIMS: High blood pressure is one of the main cardiovascular disease risk factors that contribute to vascular remodeling and dysfunction. We aimed to investigate I) group differences of the retinal microstructure between patients with hypertension and healthy individuals and II) the effects of a high-intensity interval training (HIIT) on hypertension-induced microvascular remodeling in patients with hypertension in a randomized controlled trial. METHODS: Arteriolar and venular retinal vessel microstructure including retinal vessel wall (RVW), lumen diameter and wall-to-lumen ratio (WLR) of 41 hypertensive patients, treated with anti-hypertensive medication, and 19 normotensive healthy controls were screened based on high-resolution fundoscopies. Patients with hypertension were randomized to a control group receiving standard physical activity recommendations and an intervention group receiving a supervised and walking-based HIIT for eight weeks. Measurements were repeated after the intervention period. RESULTS: Hypertensive patients showed thicker arteriolar RVW (28.0 ± 7.7mu vs. 21.4 ± 4.4mu, p = 0.003) and higher arteriolar WLR (58.5 ± 14.8 % vs. 42.5 ± 8.2 %, p < 0.001) compared to normotensive controls. The intervention group showed reductions in arteriolar RVW (ß -3.1 (95 % CI, -4.38, -1.78) p < 0.001) and arteriolar WLR (-5.3 (-10.14, -0.39) p = 0.035) compared to the control group. The intervention effects were independent of age, sex, change in blood pressure and change in cardiorespiratory fitness. CONCLUSIONS: HIIT in patients with hypertension improves retinal vessel microvascular remodeling after eight weeks of training. In patients with hypertension, screening retinal vessel microstructure by fundoscopy and monitoring efficacy of short-term exercise treatment are sensitive diagnostic approaches to quantify microvascular health in these patients.

Impaired Retinal Vessel Dilation Predicts Mortality in End-Stage Renal Disease.

RATIONALE: Patients with end-stage renal disease (ESRD) are characterized by increased cardiovascular (CV) and all-cause mortality due to advanced remodeling of the macro- and microvascular beds. OBJECTIVE: The aim of this study was to determine whether retinal microvascular function can predict all-cause and CV mortality in patients with ESRD. METHODS AND RESULTS: In the multicenter prospective observational ISAR (Risk Stratification in End-Stage Renal Disease) study, data on dynamic retinal vessel analysis (DVA) was available in a sub-cohort of 214 dialysis patients (mean age 62.6{plus minus}15.0; 32% female). Microvascular dysfunction was quantified by measuring maximum arteriolar (aMax) and venular dilation (vMax) of retinal vessels in response to flicker light stimulation. During a mean follow-up of 44 months, 55 patients died, including 25 CV and 30 non-CV fatal events. vMax emerged as a strong independent predictor for all-cause mortality. In the Kaplan-Meier analysis, individuals within the lowest tertile of vMax showed significantly shorter three-year survival rates than those within the highest tertile (66.9{plus minus}5.8% vs 92.4{plus minus}3.3%). Uni- and multivariate hazard ratios for all-cause mortality per SD increase of vMax were 0.62 [0.47;0.82] and 0.65[0.47;0.91], respectively. aMax and vMax were able to significantly predict nonfatal and fatal CV events (HR 0.74[0.57;0.97] and 0.78[0.61;0.99], respectively). CONCLUSIONS: Our results provide the first evidence that impaired retinal venular dilation is a strong and independent predictor of all-cause mortality in hemodialyzed ESRD patients. DVA provides added value for prediction of all-cause mortality and may be a novel diagnostic tool to optimize CV risk stratification in ESRD and other high-risk CV cohorts. CLINICAL TRIAL REGISTRATION: NCT01152892.

Evaluating blood-brain barrier permeability in a rat model of type 2 diabetes.

BACKGROUND: This is an exploratory study using a novel imaging modality, quantitative ultrashort time-to-echo, contrast enhanced (QUTE-CE) magnetic resonance imaging to evaluate the permeability of the blood-brain barrier in a rat model of type 2 diabetes with the presumption that small vessel disease is a contributing factor to neuropathology in diabetes. METHODS: The BBZDR/Wor rat, a model of type 2 diabetes, and age-matched controls were studied for changes in blood-brain barrier permeability. QUTE-CE, a quantitative vascular biomarker, generated angiographic images with over 500,000 voxels that were registered to a 3D MRI rat brain atlas providing site-specific information on blood-brain barrier permeability in 173 different brain areas. RESULTS: In this model of diabetes, without the support of insulin treatment, there was global capillary pathology with over 84% of the brain showing a significant increase in blood-brain barrier permeability over wild-type controls. Areas of the cerebellum and midbrain dopaminergic system were not significantly affected. CONCLUSION: Small vessel disease as assessed by permeability in the blood-brain barrier in type 2 diabetes is pervasive and includes much of the brain. The increase in blood-brain barrier permeability is a likely contributing factor to diabetic encephalopathy and dementia.

Peripheral Retinal Imaging Biomarkers for Alzheimer's Disease: A Pilot Study.

PURPOSE: To examine whether ultra-widefield (UWF) retinal imaging can identify biomarkers for Alzheimer's disease (AD) and its progression. METHODS: Images were taken using a UWF scanning laser ophthalmoscope (Optos P200C AF) to determine phenotypic variations in 59 patients with AD and 48 healthy controls at baseline (BL). All living participants were invited for a follow-up (FU) after 2 years and imaged again (if still able to participate). All participants had blood taken for genotyping at BL. Images were graded for the prevalence of age-related macular degeneration-like pathologies and retinal vascular parameters. Comparison between AD patients and controls was made using the Student t test and the χ2 test. RESULTS: Analysis at BL revealed a significantly higher prevalence of a hard drusen phenotype in the periphery of AD patients (14/55; 25.4%) compared to controls (2/48; 4.2%) [χ2 = 9.9, df = 4, p = 0.04]. A markedly increased drusen number was observed at the 2-year FU in patients with AD compared to controls. There was a significant increase in venular width gradient at BL (zone C: 8.425 × 10-3 ± 2.865 × 10-3 vs. 6.375 × 10-3 ± 1.532 × 10-3, p = 0.008; entire image: 8.235 × 10-3 ± 2.839 × 10-3 vs. 6.050 × 10-3 ± 1.414 × 10-3, p = 0.004) and a significant decrease in arterial fractal dimension in AD at BL (entire image: 1.250 ± 0.086 vs. 1.304 ± 0.089, p = 0.049) with a trend for both at FU. CONCLUSIONS: UWF retinal imaging revealed a significant association between AD and peripheral hard drusen formation and changes to the vasculature beyond the posterior pole, at BL and after clinical progression over 2 years, suggesting that monitoring pathological changes in the peripheral retina might become a valuable tool in AD monitoring.

Effects of Controlled Ozone Exposure on Circulating microRNAs and Vascular and Coagulation Biomarkers: A Mediation Analysis.

Exposure to ozone (O3) is associated with adverse respiratory and cardiovascular outcomes. Alterations in circulating microRNAs (miRNAs) may contribute to the adverse vascular effects of O3 exposure through inter-cellular communication resulting in post-transcriptional regulation of messenger RNAs by miRNAs. In this study, we investigated whether O3 exposure induces alterations in circulating miRNAs that can mediate effects on downstream vascular and coagulation biomarkers. Twenty-three healthy male adults were exposed on successive days to filtered air and 300 ppb O3 for 2 h. Circulating miRNA and protein biomarkers were quantified after each exposure session. The data were subjected to mixed-effects model and mediation analyses for the statistical analyses. The results showed that the expression level of multiple circulating miRNAs (e.g., miR-19a-3p, miR-34a-5p) was significantly associated with O3 exposure. Pathway analysis showed that these miRNAs were predictive of changing levels of downstream biomarkers [e.g., D-dimer, C-reactive protein, tumor necrosis factor α (TNFα)]. Mediation analysis showed that miR-19a-3p may be a significant mediator of O3-exposure-induced changes in blood TNFα levels [0.08 (0.01, 0.15), p = 0.02]. In conclusion, this preliminary study showed that O3 exposure of healthy male adults resulted in changes in circulating miRNAs, some of which may mediate vascular effects of O3 exposure.

Quantitative assessment of the intracranial vasculature in an older adult population using iCafe.

Comprehensive quantification of intracranial artery features may help us assess and understand variations of blood supply during brain development and aging. We analyzed vasculature features of 163 participants (age 56-85 years, mean of 71) from a community study to investigate if any of the features varied with age. Three-dimensional time-of-flight magnetic resonance angiography images of these participants were processed in IntraCranial artery feature extraction technique (a recently developed technique to obtain quantitative features of arteries) to divide intracranial vasculatures into anatomical segments and generate 8 morphometry and intensity features for each segment. Overall, increase in age was found negatively associated with number of branches and average order of intracranial arteries while positively associated with tortuosity, which remained after adjusting for cardiovascular risk factors. The associations with number of branches and average order were consistently found between 3 main intracranial artery regions, whereas the association with tortuosity appeared to be present only in middle cerebral artery/distal arteries. The combination of time-of-flight magnetic resonance angiography and IntraCranial artery feature extraction technique may provide an effective way to study vascular conditions and changes in the aging brain.

The pivotal role of reactivity in the design of novel biotinylation reagents for the chemical-proteomics-based identification of vascular accessible biomarkers.

A promising approach for the development of novel therapeutics with fewer side effects in healthy tissues is the targeted delivery of bioactive molecules directly to the site of disease. Thus, one prerequisite is the identification of a robust, disease-specific, vascular accessible biomarker localized on the surface of diseased cells, in the surrounding extracellular matrix or on newly formed blood vessels. One avenue towards the identification of such biomarkers consists in the enrichment of the vascular accessible surface proteome fraction prior to analysis. This can be achieved by covalent modification of the target proteins with membrane-impermeable ester derivatives of biotin, followed by streptavidin-based affinity capturing. The properties of the respective reagents are determined by the linker between the biotin moiety and the reactive group for protein coupling. In the frame of this study, novel, reactivity-improved peptide-based biotinylation reagents as well as reagents based on highly hydrophilic heparin linkers were synthesized and validated. The comprehensive evaluation of different biotinylation reagent classes with aliphatic, PEGylated, peptide-based and heparin-based linkers on single model protein BSA, HeLa cells as well as perfused kidney tissue revealed that the linker-dependent chemical reactivity is the crucial factor for the design of novel biotinylation reagents for vascular targeting approaches. Significance To obtain a reliable identification and stable quantification of vascular accessible protein targets by means of mass spectrometry, covalent modification with a membrane-impermeable ester derivative of biotin, followed by streptavidin-based affinity capturing, is frequently applied for in vivo or ex vivo biomarker identification studies. Nevertheless, no comprehensive evaluation of different biotinylation reagent classes has been performed so far. Within this study, we systematically evaluated novel peptide- and heparin-based biotinylation reagents as well as established compounds based on aliphatic and PEGylated linkers. We identified the linker-dependant chemical reactivity of biotinylation reagents to be the critical factor for the design of novel reagents with high efficiency. The novel, site-specifically activated peptide-based reagents were found to be efficient compounds for application in mass spectrometry-based discovery of novel vascular-accessible biomarkers.