GlycoCheck - Published research

Abstract

Endothelial dysfunction indicates target organ damage in hypertensive patients. The integrity of endothelial glycocalyx (EG) plays a vital role in vascular permeability, inflammation and elasticity, and finally to cardiovascular disease. The authors aimed to investigate the role of increased HDL cholesterol (HDL‐C) levels, which usually are considered protective against cardiovascular disease, in EG integrity in older hypertensive patients. The authors studied 120 treated hypertensive patients older than 50 years were divided regarding HDL‐C tertiles in group HDLH (HDL‐C ≥ 71 mg/dL, upper HDL‐C tertile) and group HDLL (HDL‐C < 71 mg/dL, two lower HDL‐C tertiles). Increased perfusion boundary region (PBR) of the sublingual arterial microvessels (ranging from 5 to 9 µm) using Sideview Darkfield imaging (Microscan, Glycocheck) was measured as a non‐invasive accurate index of reduced EG thickness. PBR 5‐9 was significantly decreased in group HDLH (P = 0.04). In the whole population, HDL‐C was inversely but moderately related to PBR 5‐9 (r = −0.22, P = 0.01). In a multiple linear regression analysis model, using age, BMI, smoking habit, HDL‐C, LDL‐C, and office SBP, as independent variables, the authors found that BMI (β = 0.25, P = 0.006) independently predicted PBR 5‐9 in the whole population. In older hypertensive patients, HDL‐C ranging between 71 and 101 mg/dL might moderately protect EG and subsequently endothelial function. Future studies in several groups of low‐ or high‐risk hypertensives are needed in order to evaluate the beneficial role of extremely elevated HDL‐C regarding cardiovascular risk evaluation as well as endothelial glycocalyx as a novel index of target organ damage in essential hypertension.

Abstract

We investigated the association of endothelial glycocalyx damage with arterial stiffness, impairment of coronary microcirculatory function, and LV myocardial deformation in 320 untreated hypertensives and 160 controls. We measured perfused boundary region (PBR) of the sublingual microvessels, a marker inversely related with glycocalyx thickness, coronary flow reserve (CFR), and Global Longitudinal strain (GLS) by echocardiography, pulse wave velocity (PWV), and central systolic blood pressure (cSBP). Hypertensives had higher PBR, PWV cSBP, and lower CFR and GLS than controls (P < .05). In hypertensives, increased PBR was associated with increased cSBP, PWV, and decreased CFR and GLS after adjustment for age, sex, BMI, smoking LV mass, heart rate, hyperlipidemia, and office SBP (P < .05). PBR had an additive value to PWV, CFR, and office SBP for the prediction of abnormal GLS (x2 = 2.4‐3.8, P for change = .03). Endothelial glycocalyx is impaired in untreated hypertensives and is related to arterial stiffness, coronary, and myocardial dysfunction.

Abstract

Background and objective: Microcirculatory changes contribute to clinical symptoms and disease progression in chronic heart failure (CHF). A depression of coronary flow reserve is associated with a lower myocardial capillary density in biopsies. We hypothesized that changes in cardiac microcirculation might also be reflected by a systemic reduction in capillaries and visualized by sublingual videomicroscopy. The aim was to study in vivo capillary density and glycocalyx dimensions in patients with CHF vs healthy controls.

Methods: Fifty patients with ischaemic and nonischaemic CHF and standard treatment were compared to 35 healthy age-matched subjects in a prospective cross-sectional study. Sublingual microcirculation was visualized using a side- stream darkfield videomicroscope. Functional and perfused total capillary densities were compared between patients and controls. A reduced glycocalyx thickness was measured by an increased perfused boundary region (PBR).

Results: Median functional and total perfused capillary densities were 30% and 45% lower in patients with CHF (both P < .001). Intake of oral vitamin K antagonists was associated with significantly lower capillary densities (P < .05), but not independent of NT-proBNP. Dimensions of the glycocalyx were marginally lower in CHF patients than in healthy controls (<7% difference). However, PBR correlated significantly with inflammation markers (fibrinogen: r = .58; C-reactive protein: r = .42), platelet counts (r = .36) and inversely with measures of liver/renal function such as bilirubin (r =
.38) or estimated glomerular filtration rate (r =
.34) in CHF patients.

Conclusion: CHF patients have got a markedly lower functional and total per- fused capillary density in sublingual microvasculature when compared to controls, indicating a systemic decrease in microcirculation.

Abstract

Background: Deterioration of the endothelial glycocalyx (eGC), a protective carbohydrate-rich layer lining the luminal surface of the endothelium, plays a key role in vascular barrier dysfunction and eventually organ-failure in systemic inflammatory response syndrome and sepsis. Early detection of glycocalyx damage could thus become an important goal in critical care. This study was designed to determine the feasibility and reproducibility of quantitative, real-time glycocalyx measurements performed at bedside in the emergency room (ER) and intensive care unit (ICU).

Methods: The observational study included 70 patients admitted to the ER or ICU of a university hospital. A physician and the nurse in charge of the patient performed sublingual microcirculatory measurements using sidestream dark field (SDF) imaging. A novel data acquisition and analysis software (GlycoCheck™) was used to analyze the perfused boundary region (PBR), an inverse parameter of endothelial glycocalyx dimensions in vessels with diameters of between 5 and 25 μm.

Results: The method showed a good intra-observer reproducibility. Specifically, intraclass correlation coefficient analysis showed an excellent reproducibility between the physician’s measurements (0.77 [CI 95%: 0.52–0.89]). The bias between the two PBRs was − 0.077 ± 0.24 μm. Moreover, there were no significant differences in the PBR values obtained by the
nurses when compared to those reported by the physician (regarded as the “gold standard” measurement). Intraclass correlation coefficient analysis showed excellent reproducibility between the nurses’ and physician’s PBRs (0.75 [95% CI: 0.52–0.87]). The mean difference between the two PBRs (i.e., the bias) was 0.007 ± 0.25 μm. The nurses’ PBR assessment had
a 90% sensitivity (95% CI: 60–99%) and 90% specificity (95% CI: 80–93%) to identify a severely impaired glycocalyx.

Conclusion: Glycocalyx dimensions can be measured at patients’ bedside precisely by non-invasive assessment of the PBR. This assessment could become part of standard monitoring and contribute to clinical decision-making and resuscitation protocols in clinical trials and daily practice.

Abstract

Increased understanding of the pathophysiology of ischemic acute kidney injury in renal transplantation may lead to novel therapies that improve early graft function. Therefore, we studied the renal microcirculation in ischemically injured kidneys from donors after cardiac death (DCD) and in living donor kidneys with minimal ischemia. During transplant surgery, peritubular capillaries were visualized by sidestream darkfield imaging. Despite a profound reduction in creatinine clearance, total renovascular resistance of DCD kidneys was similar to that of living donor kidneys. In contrast, renal microvascular perfusion in the early reperfusion period was 42% lower in DCD kidneys compared with living donor kidneys, which was accounted for by smaller blood vessel diameters in DCD kidneys. Furthermore, DCD kidneys were characterized by smaller red blood cell exclusion zones in peritubular capillaries and by greater production of syndecan-1 and heparan sulfate (main constituents of the endothelial glycocalyx) compared with living donor kidneys, providing strong evidence for glycocalyx degradation in these kidneys. We conclude that renal ischemia and reperfusion is associated with reduced capillary blood flow and loss of glycocalyx integrity. These findings form the basis for development of novel interventions to prevent ischemic acute kidney injury.

kidney transplantation is inevitably associated with ischemia and reperfusion injury. Depending on the severity of injury, 20–80% of recipients of deceased donor kidneys require dialysis treatment in the first week after transplantation, which is referred to as delayed graft function (26). This condition complicates patient management and is associated with a 40% increased rate of graft loss in kidneys from donors after brain death (45). Liberal use of donations after cardiac death greatly expands the number of available donor kidneys and may even eliminate transplant waiting lists (37). However, kidneys from these donors suffer extensive ischemic injury from circulatory arrest until organ preservation, which almost invariably leads to delayed graft function after transplantation. More importantly, up to 15–25% of these kidneys will never regain function, unnecessarily exposing recipients to the risks of major surgery and immunological sensitization (43).

Adequate reperfusion is essential for functional recovery of donor kidneys and prevents ongoing ischemic tissue injury after revascularization. In rodent models of ischemic acute kidney injury, it has been demonstrated that the peritubular microcirculation suffers endothelial injury and functional impairment after reperfusion (5, 44), which has recently been observed in humans as well (13, 21, 31). The endothelium is covered by the glycocalyx, a dynamic network of proteoglycans and glycoproteins that determines vascular permeability, transduces shear stress to the endothelium, and prevents interaction of leukocytes and platelets with the vascular wall (29). Loss of endothelial glycocalyx integrity after ischemia and reperfusion has been observed in experimental models (8, 24, 27) and in patients undergoing aortic surgery (28). Degradation of the endothelial glycocalyx by infusion of hyaluronidase causes capillary perfusion defects in rodents (7). Taken together, ischemic injury to endothelial cells and glycocalyx of peritubular capillaries may play a major role in the pathophysiology of acute kidney injury by reducing tissue perfusion and propagating inflammation in the reperfused kidney.

In the current manuscript, we studied the human renal microcirculation after clinical kidney transplantation by direct visualization of cortical peritubular capillaries and by measuring renal arteriovenous gradients of the main constituents of the endothelial glycocalyx. We found that ischemically injured kidneys from donors after cardiac death (DCD) were characterized by reduction of capillary blood flow and loss of glycocalyx integrity compared with a control group of kidneys from living donors with minimal ischemia. These findings form the basis for development of interventions that increase microvascular perfusion and protect the endothelial glycocalyx.

Abstract

Aims/hypothesis

Endothelial glycocalyx perturbation contributes to increased vascular permeability. In the present study we set out to evaluate whether: (1) glycocalyx is perturbed in individuals with type 2 diabetes mellitus, and (2) oral glycocalyx precursor treatment improves glycocalyx properties.

Methods

Male participants with type 2 diabetes (n = 10) and controls (n = 10) were evaluated before and after 2 months of sulodexide administration (200 mg/day). The glycocalyx dimension was estimated in two different vascular beds using sidestream dark field imaging and combined fluorescein/indocyanine green angiography for sublingual and retinal vessels, respectively. Transcapillary escape rate of albumin (TERalb) and hyaluronan catabolism were assessed as measures of vascular permeability.

Results

Both sublingual dimensions (0.64 [0.57–0.75] μm vs 0.78 [0.71–0.85] μm, p < 0.05, medians [interquartile range]) and retinal glycocalyx dimensions (5.38 [4.88–6.59] μm vs 8.89 [4.74–11.84] μm, p < 0.05) were reduced in the type 2 diabetes group compared with the controls whereas TERalb was increased (5.6 ± 2.3% vs 3.7 ± 1.7% in the controls, p < 0.05). In line with these findings, markers of hyaluronan catabolism were increased with diabetes (hyaluronan 137 ± 29 vs 81 ± 8 ng/ml and hyaluronidase 78 ± 4 vs 67 ± 2 U/ml, both p < 0.05). Sulodexide increased both the sublingual and retinal glycocalyx dimensions in participants with diabetes (to 0.93 [0.83–0.99] μm and to 5.88 [5.33–6.26] μm, respectively, p < 0.05). In line, a trend towards TERalb normalisation (to 4.0 ± 2.3%) and decreases in plasma hyaluronidase (to 72 ± 2 U/ml, p < 0.05) were observed in the diabetes group.

Conclusion/interpretation

Type 2 diabetes is associated with glycocalyx perturbation and increased vascular permeability, which are partially restored following sulodexide administration. Further studies are warranted to determine whether long-term treatment with sulodexide has a beneficial effect on cardiovascular risk.