Perturbation of hyaluronan metabolism predisposes patients with type 1 diabetes mellitus to atherosclerosis

Elevated hyaluronic acid levels in severe SARS-CoV-2 infection in the post-COVID-19 era

Objective

Human identical sequences of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) promoted the coronavirus disease 2019 (COVID-19) progression by upregulating hyaluronic acid (HA) via NamiRNA-enhancer network, based on previous experimental research. This study aimed to investigate the predictive value of HA for the severity of SARS-CoV-2 infection in the post-COVID-19 era.

Methods

A total of 217 consecutive patients with COVID-19 were enrolled at Beijing Ditan Hospital between July 2023 and October 2023. HA levels were analyzed using biochemical detector. Logistic regression analysis was used to screen independent factors for severe COVID-19. The predictive performance of HA for severe infection was assessed by ROC curve. Furthermore, the relationship between HA levels and COVID-19 severity was investigated using multivariate logistic regression models after adjustment for potential confounders.

Results

According to the cut-off value of HA, COVID-19 patients were divided into HA < 90 ng/mL group (80 cases) and HA ≥ 90 ng/mL group (137 cases). High HA levels were positively associated with the severe SARS-CoV-2 infection, including elevated inflammatory indicators, severe lung involvement, prolonged clinical course, and higher incidence of respiratory failure and death (P < 0.05). Logistic regression analysis suggested that HA was an independent predictor of severe COVID-19 (OR = 4.540, 95% CI = 2.105-9.790, P < 0.001). ROC curve analysis showed that the AUC of HA for severe infection was 0.724. HA levels were significantly higher in COVID-19 cases compared to the healthy population (123.9 (82.6, 174.1) vs. 50.5 (37.8, 66.8), P < 0.001), but similar to those with non-SARS-CoV-2 lung infection (121.6 (78.5, 175.6) vs. 106.0 (66.5, 149.7), P = 0.244). We also found that the first COVID-19 infections had higher HA levels (118.8 (79.5, 174.3) vs. 85.0 (61.1, 128.8), P < 0.001) and a higher proportion of severe infection (37.1% vs. 21.3%, P = 0.043) than re-infections. However, HA expression failed to fully return to normal levels with infection recovery (204.7 (152.9, 242.2) vs. 97.0 (69.3, 137.3), P < 0.001).

Conclusion

HA was associated with severe SARS-CoV-2 infection and could be used as a novel serum biomarker to predict the risk of COVID-19 progression in the post-COVID-19 era.

Soluble vascular endothelial glycocalyx proteoglycans as potential therapeutic targets in inflammatory diseases

Reducing the activity of cytokines and leukocyte extravasation is an emerging therapeutic strategy to limit tissue-damaging inflammatory responses and restore immune homeostasis in inflammatory diseases. Proteoglycans embedded in the vascular endothelial glycocalyx, which regulate the activity of cytokines to restrict the inflammatory response in physiological conditions, are proteolytically cleaved in inflammatory diseases. Here we critically review the potential of proteolytically shed, soluble vascular endothelial glycocalyx proteoglycans to modulate pathological inflammatory responses. Soluble forms of the proteoglycans syndecan-1, syndecan-3 and biglycan exert beneficial anti-inflammatory effects by the removal of chemokines, suppression of proinflammatory cytokine expression and leukocyte migration, and induction of autophagy of proinflammatory M1 macrophages. By contrast, soluble versikine and decorin enhance proinflammatory responses by increasing inflammatory cytokine synthesis and leukocyte migration. Endogenous syndecan-2 and mimecan exert proinflammatory effects, syndecan-4 and perlecan mediate beneficial anti-inflammatory effects and glypican regulates Hh and Wnt signaling pathways involved in systemic inflammatory responses. Taken together, targeting the vascular endothelial glycocalyx-derived, soluble syndecan-1, syndecan-2, syndecan-3, syndecan-4, biglycan, versikine, mimecan, perlecan, glypican and decorin might be a potential therapeutic strategy to suppress overstimulated cytokine and leukocyte responses in inflammatory diseases.

Double-network hydrogel enhanced by SS31-loaded mesoporous polydopamine nanoparticles: Symphonic collaboration of near-infrared photothermal antibacterial effect and mitochondrial maintenance for full-thickness wound healing in diabetes mellitus

Diabetic wound healing has become a serious healthcare challenge. The high-glucose environment leads to persistent bacterial infection and mitochondrial dysfunction, resulting in chronic inflammation, abnormal vascular function, and tissue necrosis. To solve these issues, we developed a double-network hydrogel, constructed with pluronic F127 diacrylate (F127DA) and hyaluronic acid methacrylate (HAMA), and enhanced by SS31-loaded mesoporous polydopamine nanoparticles (MPDA NPs). As components, SS31, a mitochondria-targeted peptide, maintains mitochondrial function, reduces mitochondrial reactive oxygen species (ROS) and thus regulates macrophage polarization, as well as promoting cell proliferation and migration, while MPDA NPs not only scavenge ROS and exert an anti-bacterial effect by photothermal treatment under near-infrared light irradiation, but also control release of SS31 in response to ROS. This F127DA/HAMA-MPDA@SS31 (FH-M@S) hydrogel has characteristics of adhesion, superior biocompatibility and mechanical properties which can adapt to irregular wounds at different body sites and provide sustained release of MPDA@SS31 (M@S) NPs. In addition, in a diabetic rat full thickness skin defect model, the FH-M@S hydrogel promoted macrophage M2 polarization, collagen deposition, neovascularization and wound healing. Therefore, the FH-M@S hydrogel exhibits promising therapeutic potential for skin regeneration.

Matrix stiffness, endothelial dysfunction and atherosclerosis

Atherosclerosis (AS) is the leading cause of the human cardiovascular diseases (CVDs). Endothelial dysfunction promotes the monocytes infiltration and inflammation that participate fundamentally in atherogenesis. Endothelial cells (EC) have been recognized as mechanosensitive cells and have different responses to distinct mechanical stimuli. Emerging evidence shows matrix stiffness-mediated EC dysfunction plays a vital role in vascular disease, but the underlying mechanisms are not yet completely understood. This article aims to summarize the effect of matrix stiffness on the pro-atherosclerotic characteristics of EC including morphology, rigidity, biological behavior and function as well as the related mechanical signal. The review also discusses and compares the contribution of matrix stiffness-mediated phagocytosis of macrophages and EC to AS progression. These advances in our understanding of the relationship between matrix stiffness and EC dysfunction open the avenues to improve the prevention and treatment of now-ubiquitous atherosclerotic diseases.

Endothelial glycocalyx in retina, hyperglycemia, and diabetic retinopathy

The endothelial glycocalyx (EG) is a meshlike network present on the apical surface of the endothelium. Membrane-bound proteoglycans, the major backbone molecules of the EG, consist of glycosaminoglycans attached to core proteins. In addition to maintaining the integrity of the endothelial barrier, the EG regulates inflammation and perfusion and acts as a mechanosensor. The loss of the EG can cause endothelial dysfunction and drive the progression of vascular diseases including diabetic retinopathy. Therefore, the EG presents a novel therapeutic target for treatment of vascular complications. In this review article, we provide an overview of the structure and function of the EG in the retina. Our particular focus is on hyperglycemia-induced perturbations in the glycocalyx structure in the retina, potential underlying mechanisms, and clinical trials studying protective treatments against degradation of the EG.

The effects of female sexual hormones on the endothelial glycocalyx

The glycocalyx is a layer composed of carbohydrate side chains bound to core proteins that lines the vascular endothelium. The integrity of the glycocalyx is essential for endothelial cells' performance and vascular homeostasis. The neuroendocrine and immune systems influence the composition, maintenance, activity and degradation of the endothelial glycocalyx. The female organism has unique characteristics, and estrogen and progesterone, the main female hormones are essential to the development and physiology of the reproductive system and to the ability to develop a fetus. Female sex hormones also exert a wide variety of effects on other organs, including the vascular endothelium. They upregulate nitric oxide synthase expression and activity, decrease oxidative stress, increase vasodilation, and protect from vascular injury. This review will discuss how female hormones and pregnancy, which prompts to high levels of estrogen and progesterone, modulate the endothelial glycocalyx. Diseases prevalent in women that alter the glycocalyx, and therapeutic forms to prevent glycocalyx degradation and potential treatments that can reconstitute its structure and function will also be discussed.

Endothelial glycocalyx and microvascular perfusion are associated with carotid intima-media thickness and impaired myocardial deformation in psoriatic disease

Psoriatic disease is associated with vascular and myocardial dysfunction. We aimed to evaluate endothelial glycocalyx barrier properties and microvascular perfusion in psoriatic patients, as well as their correlation with carotid intima-media thickness (cIMT) and markers of left ventricular (LV) myocardial deformation. We examined 297 psoriatic patients and 150 controls, adjusted for age, sex, and atherosclerotic risk factors. The severity of psoriatic disease was estimated using the psoriasis area and severity index (PASI). Perfused boundary region (PBR), a marker of glycocalyx barrier function, was measured non-invasively in sublingual microvessels with a diameter 5-25 μm using Sidestream Dark Field camera (Microscan, GlycoCheck). Increased PBR indicates reduced glycocalyx thickness. Indexes of microvascular perfusion, including red blood cells filling (RBCF) and functional microvascular density, were also calculated. We measured cIMT, coronary flow reserve (CFR) and markers of myocardial deformation by speckle-tracking imaging, namely global longitudinal strain (GLS) and percentage changes between peak twisting and untwisting at mitral valve opening (%dpTw-Utw_MVO). Compared to controls, psoriatic patients had higher PBR_5-25μm (2.13 ± 0.29μm versus 1.78 ± 0.25μm, p < 0.001) and lower RBCF and functional microvascular density (p < 0.001). Increased PASI was associated with elevated PBR and more impaired cIMT and GLS (p < 0.05). There was an inverse association of PBR with RBCF and functional microvascular density (p < 0.001). In psoriatic population, increased PBR was related to increased cIMT, reduced CFR, impaired GLS and decreased %dpTw-Utw_MVO (p < 0.001). Glycocalyx thickness is reduced in psoriatic patients, which in turn impairs microvascular perfusion, and is associated with carotid IMT and impaired coronary and myocardial function.Clinical Trial Registration-URL: http://www.clinicaltrials.gov . Unique identifier: NCT02144857.

Endothelial Glycocalyx

The glycocalyx is a polysaccharide structure that protrudes from the body of a cell. It is primarily conformed of glycoproteins and proteoglycans, which provide communication, electrostatic charge, ionic buffering, permeability, and mechanosensation-mechanotransduction capabilities to cells. In blood vessels, the endothelial glycocalyx that projects into the vascular lumen separates the vascular wall from the circulating blood. Such a physical location allows a number of its components, including sialic acid, glypican-1, heparan sulfate, and hyaluronan, to participate in the mechanosensation-mechanotransduction of blood flow-dependent shear stress, which results in the synthesis of nitric oxide and flow-mediated vasodilation. The endothelial glycocalyx also participates in the regulation of vascular permeability and the modulation of inflammatory responses, including the processes of leukocyte rolling and extravasation. Its structural architecture and negative charge work to prevent macromolecules greater than approximately 70 kDa and cationic molecules from binding and flowing out of the vasculature. This also prevents the extravasation of pathogens such as bacteria and virus, as well as that of tumor cells. Due to its constant exposure to shear and circulating enzymes such as neuraminidase, heparanase, hyaluronidase, and matrix metalloproteinases, the endothelial glycocalyx is in a continuous process of degradation and renovation. A balance favoring degradation is associated with a variety of pathologies including atherosclerosis, hypertension, vascular aging, metastatic cancer, and diabetic vasculopathies. Consequently, ongoing research efforts are focused on deciphering the mechanisms that promote glycocalyx degradation or limit its syntheses, as well as on therapeutic approaches to improve glycocalyx integrity with the goal of reducing vascular disease. © 2022 American Physiological Society. Compr Physiol 12: 1-31, 2022.

Effect of high glucose on glycosaminoglycans in cultured retinal endothelial cells and rat retina

INTRODUCTION

The endothelial glycocalyx regulates vascular permeability, inflammation, and coagulation, and acts as a mechanosensor. The loss of glycocalyx can cause endothelial injury and contribute to several microvascular complications and, therefore, may promote diabetic retinopathy. Studies have shown a partial loss of retinal glycocalyx in diabetes, but with few molecular details of the changes in glycosaminoglycan (GAG) composition. Therefore, the purpose of our study was to investigate the effect of hyperglycemia on GAGs of the retinal endothelial glycocalyx.

METHODS

GAGs were isolated from rat retinal microvascular endothelial cells (RRMECs), media, and retinas, followed by liquid chromatography-mass spectrometry assays. Quantitative real-time polymerase chain reaction was used to study mRNA transcripts of the enzymes involved in GAG biosynthesis.

RESULTS AND CONCLUSIONS

Hyperglycemia significantly increased the shedding of heparan sulfate (HS), chondroitin sulfate (CS), and hyaluronic acid (HA). There were no changes to the levels of HS in RRMEC monolayers grown in high-glucose media, but the levels of CS and HA decreased dramatically. Similarly, while HA decreased in the retinas of diabetic rats, the total GAG and CS levels increased. Hyperglycemia in RRMECs caused a significant increase in the mRNA levels of the enzymes involved in GAG biosynthesis (including EXTL-1,2,3, EXT-1,2, ChSY-1,3, and HAS-2,3), with these increases potentially being compensatory responses to overall glycocalyx loss. Both RRMECs and retinas of diabetic rats exhibited glucose-induced alterations in the disaccharide compositions and sulfation of HS and CS, with the changes in sulfation including N,6-O-sulfation on HS and 4-O-sulfation on CS.

The Endothelial Glycocalyx: A Possible Therapeutic Target in Cardiovascular Disorders

The physiological, anti-inflammatory, and anti-coagulant properties of endothelial cells (ECs) rely on a complex carbohydrate-rich layer covering the luminal surface of ECs, called the glycocalyx. In a range of cardiovascular disorders, glycocalyx shedding causes endothelial dysfunction and inflammation, underscoring the importance of glycocalyx preservation to avoid disease initiation and progression. In this review we discuss the physiological functions of the glycocalyx with particular focus on how loss of endothelial glycocalyx integrity is linked to cardiovascular risk factors, like hypertension, aging, diabetes and obesity, and contributes to the development of thrombo-inflammatory conditions. Finally, we consider the role of glycocalyx components in regulating inflammatory responses and discuss possible therapeutic interventions aiming at preserving or restoring the endothelial glycocalyx and therefore protecting against cardiovascular disease.

Epithelial Na+ channel and the glycocalyx: a sweet and salty relationship for arterial shear stress sensing

PURPOSE OF REVIEW

The ability of endothelial cells to sense mechanical force, and shear stress in particular, is crucial for normal vascular function. This relies on an intact endothelial glycocalyx that facilitates the production of nitric oxide (NO). An emerging arterial shear stress sensor is the epithelial Na+ channel (ENaC). This review highlights existing and new evidence for the interdependent activity of the glycocalyx and ENaC and its implications for vascular function.

RECENT FINDINGS

New evidence suggests that the glycocalyx and ENaC are physically connected and that this is important for shear stress sensing. The connection relies on N-glycans attached to glycosylated asparagines of α-ENaC. Removal of specific N-glycans reduced ENaC's shear stress response. Similar effects were observed following degradation of the glycocalyx. Endothelial specific viral transduction of α-ENaC increased blood pressure (∼40 mmHg). This increase was attenuated in animals transduced with an α-ENaC version lacking N-glycans.

SUMMARY

These observations indicate that ENaC is connected to the glycocalyx and their activity is interdependent to facilitate arterial shear stress sensation. Future research focusing on how N-glycans mediate this interaction can provide new insights for the understanding of vascular function in health and disease.

The Glomerular Endothelium Restricts Albumin Filtration

Inflammatory activation and/or dysfunction of the glomerular endothelium triggers proteinuria in many systemic and localized vascular disorders. Among them are the thrombotic microangiopathies, many forms of glomerulonephritis, and acute inflammatory episodes like sepsis and COVID-19 illness. Another example is the chronic endothelial dysfunction that develops in cardiovascular disease and in metabolic disorders like diabetes. While the glomerular endothelium is a porous sieve that filters prodigious amounts of water and small solutes, it also bars the bulk of albumin and large plasma proteins from passing into the glomerular filtrate. This endothelial barrier function is ascribed predominantly to the endothelial glycocalyx with its endothelial surface layer, that together form a relatively thick, mucinous coat composed of glycosaminoglycans, proteoglycans, glycolipids, sialomucins and other glycoproteins, as well as secreted and circulating proteins. The glycocalyx/endothelial surface layer not only covers the glomerular endothelium; it extends into the endothelial fenestrae. Some glycocalyx components span or are attached to the apical endothelial cell plasma membrane and form the formal glycocalyx. Other components, including small proteoglycans and circulating proteins like albumin and orosomucoid, form the endothelial surface layer and are bound to the glycocalyx due to weak intermolecular interactions. Indeed, bound plasma albumin is a major constituent of the endothelial surface layer and contributes to its barrier function. A role for glomerular endothelial cells in the barrier of the glomerular capillary wall to protein filtration has been demonstrated by many elegant studies. However, it can only be fully understood in the context of other components, including the glomerular basement membrane, the podocytes and reabsorption of proteins by tubule epithelial cells. Discovery of the precise mechanisms that lead to glycocalyx/endothelial surface layer disruption within glomerular capillaries will hopefully lead to pharmacological interventions that specifically target this important structure.

The Structure and Function of the Glycocalyx and Its Connection With Blood-Brain Barrier

The vascular endothelial glycocalyx is a dense, bush-like structure that is synthesized and secreted by endothelial cells and evenly distributed on the surface of vascular endothelial cells. The blood-brain barrier (BBB) is mainly composed of pericytes endothelial cells, glycocalyx, basement membranes, and astrocytes. The glycocalyx in the BBB plays an indispensable role in many important physiological functions, including vascular permeability, inflammation, blood coagulation, and the synthesis of nitric oxide. Damage to the fragile glycocalyx can lead to increased permeability of the BBB, tissue edema, glial cell activation, up-regulation of inflammatory chemokines expression, and ultimately brain tissue damage, leading to increased mortality. This article reviews the important role that glycocalyx plays in the physiological function of the BBB. The review may provide some basis for the research direction of neurological diseases and a theoretical basis for the diagnosis and treatment of neurological diseases.

Acellular Scaffolds as Innovative Biomaterial Platforms for the Management of Diabetic Wounds

Diabetic wound (DW) is one of the leading complications of patients having a long history of uncontrolled diabetes. Moreover, it also imposes an economic burden on people suffering from wounds to manage the treatment. The major impending factors in the treatment of DW are infection, prolonged inflammation and decreased oxygen levels. Since these non-healing wounds are associated with an extended recovery period, the existing therapies provide treatment for a limited period only. The areas covered in this review are general sequential events of wound healing along with DW's pathophysiology, the origin of DW and success, as well as limitations of existing therapies. This systematic review's significant aspect is to highlight the fabrication, characterization and applications of various acellular scaffolds used to heal DW. In addition to that, cellular scaffolds are also described to a limited extent.

Human glycocalyx shedding: Systematic review and critical appraisal

BACKGROUND

The number of studies measuring breakdown products of the glycocalyx in plasma has increased rapidly during the past decade. The purpose of the present systematic review was to assess the current knowledge concerning the association between plasma concentrations of glycocalyx components and structural assessment of the endothelium.

METHODS

We performed a literature review of Pubmed to determine which glycocalyx components change in a wide variety of human diseases and conditions. We also searched for evidence of a relationship between plasma concentrations and the thickness of the endothelial glycocalyx layer as obtained by imaging methods.

RESULTS

Out of 3,454 publications, we identified 228 that met our inclusion criteria. The vast majority demonstrate an increase in plasma glycocalyx products. Sepsis and trauma are most frequently studied, and comprise approximately 40 publications. They usually report 3-4-foldt increased levels of glycocalyx degradation products, most commonly of syndecan-1. Surgery shows a variable picture. Cardiac surgery and transplantations are most likely to involve elevations of glycocalyx degradation products. Structural assessment using imaging methods show thinning of the endothelial glycocalyx layer in cardiovascular conditions and during major surgery, but thinning does not always correlate with the plasma concentrations of glycocalyx products. The few structural assessments performed do not currently support that capillary permeability is increased when the plasma levels of glycocalyx fragments in plasma are increased.

CONCLUSIONS

Shedding of glycocalyx components is a ubiquitous process that occurs during both acute and chronic inflammation with no sensitivity or specificity for a specific disease or condition.

Diastolic left ventricular function in relation to the retinal microvascular fractal dimension in a Flemish population

Fractal analysis provides a global assessment of vascular networks (e.g., geometric complexity). We examined the association of diastolic left ventricular (LV) function with the retinal microvascular fractal dimension. A lower fractal dimension signifies a sparser retinal microvascular network. In 628 randomly recruited Flemish individuals (51.3% women; mean age, 50.8 years), we measured diastolic LV function by echocardiography and the retinal microvascular fractal dimension by the box-counting method (Singapore I Vessel Assessment software, version 3.6). The left atrial volume index (LAVI), e', E/e' and retinal microvascular fractal dimension averaged (±SD) 24.3 ± 6.2 mL/m², 10.9 ± 3.6 cm/s, 6.96 ± 2.2, and 1.39 ± 0.05, respectively. The LAVI, E, e' and E/e' were associated (P < 0.001) with the retinal microvascular fractal dimension with association sizes (per 1 SD), amounting to -1.49 mL/m² (95% confidence interval, -1.98 to -1.01), 2.57 cm/s (1.31-3.84), 1.34 cm/s (1.07-1.60), and -0.74 (-0.91 to -0.57), respectively. With adjustments applied for potential covariables, the associations of E peak and E/e' with the retinal microvascular fractal dimension remained significant (P ≤ 0.020). Over a median follow-up of 5.3 years, 18 deaths occurred. The crude and adjusted hazard ratios expressing the risk of all-cause mortality associated with a 1-SD increment in the retinal microvascular fractal dimension were 0.36 (0.23-0.57; P < 0.001) and 0.57 (0.34-0.96; P = 0.035), respectively. In the general population, a lower retinal microvascular fractal dimension was associated with greater E/e', a measure of LV filling pressure. These observations can potentially be translated into new strategies for the prevention of diastolic LV dysfunction.

Endothelial glycocalyx as an important factor in composition of blood-brain barrier

The blood‐brain barrier is a dynamic and complex neurovascular unit that protects neurons from somatic circulatory factors as well as regulates the internal environmental stability of the central nervous system. Endothelial glycocalyx is a critical component of an extended neurovascular unit that influences the structure of the blood‐brain barrier and plays various physiological functions, including an important role in maintaining normal neuronal homeostasis. Specifically, glycocalyx acts in physical and charge barriers, mechanical transduction, regulation of vascular permeability, modulation of inflammatory response, and anticoagulation. Since intact glycocalyx is necessary to maintain the stability and integrity of the internal environment of the blood‐brain barrier, damage to glycocalyx can lead to the dysfunction of the blood‐brain barrier. This review discusses the role of glycocalyx in the context of the substantial literature regarding the blood‐brain barrier research, in order to provide a theoretical basis for the diagnosis and treatment of neurological diseases as well as point to new breakthroughs and innovations in glycocalyx‐dependent blood‐brain barrier function.

Assessment of the sublingual microcirculation with the GlycoCheck system: Reproducibility and examination conditions

Background

The glycocalyx is an extracellular layer lining the lumen of the vascular endothelium, protecting the endothelium from shear stress and atherosclerosis and contributes to coagulation, immune response and microvascular perfusion. The GlycoCheck system estimates glycocalyx’ thickness in vessels under the tongue from perfused boundary region (PBR) and microvascular perfusion (red blood cell (RBC) filling) via a camera and dedicated software.

Objectives

Evaluating reproducibility and influence of examination conditions on measurements with the GlycoCheck system.

Methods

Open, randomised, controlled study including 42 healthy smokers investigating day-to-day, side-of-tongue, inter-investigator variance, intraclass-correlation (ICC) and influence of examination conditions at intervals from 0–180 minutes on PBR and RBC filling.

Results

Mean (SD) age was 24.9 (6.1) years, 52% were male. There was no significant intra- or inter-investigator variation for PBR or RBC filling nor for PBR for side-of-tongue. A small day-to-day variance was found for PBR (0.012μm, p = 0.007) and RBC filling (0.003%, p = 0.005) and side-of-tongue, RBC filling (0.025%, p = 0.009). ICC was modest but highly improved by increasing measurements. Small significant influence of cigarette smoking (from 40–180 minutes), high calorie meal intake and coffee consumption was found. The latter two peaking immediately and tapering off but remained significant up to 180 minutes, highest PBR changes for the three being 0.042μm (p<0.05), 0.183μm (p<0.001) and 0.160μm (p<0.05) respectively.

Conclusions

Measurements with the GlycoCheck system have a moderate reproducibility, but highly increases with multiple measurements and a small day-to-day variability. Smoking, meal and coffee intake had effects up to 180 minutes, abstinence is recommended at least 180 minutes before GlycoCheck measurements. Future studies should standardise conditions during measurements.

Diabetic Kidney Disease, Endothelial Damage, and Podocyte-Endothelial Crosstalk

Diabetes-related complications are a significant source of morbidity and mortality worldwide. Diabetic kidney disease is a frequent microvascular complication and a primary cause of kidney failure in patients with diabetes. The glomerular filtration barrier is composed of 3 layers: the endothelium, glomerular basement membrane, and podocytes. Podocytes and the endothelium communicate through molecular crosstalk to maintain filtration at the glomerular filtration barrier. Chronic hyperglycemia affects all 3 layers of the glomerular filtration barrier, as well as the molecular crosstalk that occurs between the 2 cellular layers. One of the earliest events following chronic hyperglycemia is endothelial cell dysfunction. Early endothelial damage is associated with progression of diabetic kidney disease. However, current therapies are based in controlling glycemia and arterial blood pressure without targeting endothelial dysfunction. Disruption of the endothelial cell layer also alters the molecular crosstalk that occurs between the endothelium and podocytes. This review discusses both the physiologic and pathologic communication that occurs at the glomerular filtration barrier. It examines how these signaling components contribute to podocyte foot effacement, podocyte detachment, and the progression of diabetic kidney disease.

Hyaluronan: Metabolism and Function

As a major polysaccharide component of the extracellular matrix, hyaluronan plays essential roles in the organization of tissue architecture and the regulation of cellular functions, such as cell proliferation and migration, through interactions with cell-surface receptors and binding molecules. Metabolic pathways for biosynthesis and degradation tightly control the turnover rate, concentration, and molecular size of hyaluronan in tissues. Despite the relatively simple chemical composition of this polysaccharide, its wide range of molecular weights mediate diverse functions that depend on molecular size and tissue concentration. Genetic engineering and pharmacological approaches have demonstrated close associations between hyaluronan metabolism and functions in many physiological and pathological events, including morphogenesis, wound healing, and inflammation. Moreover, emerging evidence has suggested that the accumulation of hyaluronan extracellular matrix and fragments due to the altered expression of hyaluronan synthases and hyaluronidases potentiates cancer development and progression by remodeling the tumor microenvironment. In addition to the well-known functions exerted by extracellular hyaluronan, recent metabolomic approaches have also revealed that its synthesis can regulate cellular functions via the reprogramming of cellular metabolism. This review highlights the current advances in knowledge on the biosynthesis and catabolism of hyaluronan and describes the diverse functions associated with hyaluronan metabolism.

Plasma Endothelial Glycocalyx Components as a Potential Biomarker for Predicting the Development of Disseminated Intravascular Coagulation in Patients With Sepsis

BACKGROUND

Sepsis coagulopathy or disseminated intravascular coagulation (DIC) mainly due to progressive endothelial disruption and damage. The glycocalyx is expressed on the endothelial cell surface and contributes to anti-thrombogenicity, anti-inflammatory, and regulates vascular permeability. We aimed to evaluate the clinical utility of plasma glycocalyx components as biomarkers in predicting the onset of DIC in sepsis.

MATERIALS AND METHODS

This was a prospective observational study of 45 patients with sepsis (June to December 2018). Demographic, clinical (Acute Physiology, Age, Chronic Health Evaluation II [APACHE II], Sequential Organ Failure Assessment [SOFA]), and laboratory data from medical records were analyzed. Endothelial glycocalyx components (syndecan-1, heparan sulfate, hyaluronan) were measured using an ELISA kit.

RESULTS

Among the 45 patients (23, sepsis; 22, septic shock), plasma syndecan-1, heparan sulfate, and hyaluronan levels were higher in those with septic shock and were positively correlated with disease severity as determined by the APACHE II and SOFA scores and lactate levels. Receiver operating characteristic curve analysis revealed high sensitivity and specificity of syndecan-1 for predicting septic shock. Further, these levels were compared between patients with or without the development of DIC. Plasma syndecan-1 and hyaluronan levels were significantly elevated in patients with DIC compared to those in patients without DIC and were strongly associated with activated partial thromboplastin time, prothrombin time, and platelet counts. Area under the curve values for predicting DIC based on syndecan-1 and hyaluronan levels measurements were 0.774 and 0.740, respectively.

CONCLUSIONS

Increased plasma syndecan-1 and hyaluronan levels may be indicators of disease severity and useful predictors for DIC development in sepsis.

The need to freeze-Dehydration during specimen preparation for electron microscopy collapses the endothelial glycocalyx regardless of fixation method

OBJECTIVE

The endothelial glycocalyx covers the luminal surface of the endothelium and plays key roles in vascular function. Despite its biological importance, ideal visualization techniques are lacking. The current study aimed to improve the preservation and subsequent imaging quality of the endothelial glycocalyx.

METHODS

In mice, the endothelial glycocalyx was contrasted with a mixture of lanthanum and dysprosium (LaDy). Standard chemical fixation was compared with high-pressure frozen specimens processed with freeze substitution. Also, isolated brain microvessels and cultured endothelial cells were high-pressure frozen and by transmission soft x-rays, imaged under cryogenic conditions.

RESULTS

The endothelial glycocalyx was in some tissues significantly more voluminous from chemically fixed specimens compared with high-pressure frozen specimens. LaDy labeling introduced excessive absorption contrast, which impeded glycocalyx measurements in isolated brain microvessels when using transmission soft x-rays. In non-contrasted vessels, the glycocalyx was not resolved. LaDy-contrasted, cultured brain endothelial cells allowed to assess glycocalyx volume in vitro.

CONCLUSIONS

Both chemical and cryogenic fixation followed by dehydration lead to substantial collapse of the glycocalyx. Cryogenic fixation without freeze substitution could be a way forward although transmission soft x-ray tomography based solely on amplitude contrast seems unsuitable.

Retinal Physiology and Circulation: Effect of Diabetes

In this article, we present a discussion of diabetes and its complications, including the macrovascular and microvascular effects, with the latter of consequence to the retina. We will discuss the anatomy and physiology of the retina, including aspects of metabolism and mechanisms of oxygenation, with the latter accomplished via a combination of the retinal and choroidal blood circulations. Both of these vasculatures are altered in diabetes, with the retinal circulation intimately involved in the pathology of diabetic retinopathy. The later stages of diabetic retinopathy involve poorly controlled angiogenesis that is of great concern, but in our discussion, we will focus more on several alterations in the retinal circulation occurring earlier in the progression of disease, including reductions in blood flow and a possible redistribution of perfusion that may leave some areas of the retina ischemic and hypoxic. Finally, we include in this article a more recent area of investigation regarding the diabetic retinal vasculature, that is, the alterations to the endothelial surface layer that normally plays a vital role in maintaining physiological functions. © 2020 American Physiological Society. Compr Physiol 10:933-974, 2020.

Sirtuin 1 and endothelial glycocalyx

Sirtuin1 deficiency or reduced activity comprises one of the hallmarks of diseases as diverse as chronic cardiovascular, renal, and metabolic, some malignancies, and infections, as well as aging-associated diseases. In a mouse model of endothelium-limited defect in sirtuin 1 deacetylase activity, we found a dramatic reduction in the volume of endothelial glycocalyx. This was associated with the surge in the levels of one of key scaffolding heparan sulfate proteoglycans of endothelial glycocalyx, syndecan-4, and specifically, its extracellular domain (ectodomain). We found that the defect in endothelial sirtuin 1 deacetylase activity is associated with (a) elevated basal and stimulated levels of superoxide generation (via the FoxO1 over-acetylation mechanism) and (b) increased nuclear translocation of NF-kB (via p65 over-acetylation mechanism). These findings laid the foundation for the proposed novel function of sirtuin 1, namely, the maintenance of endothelial glycocalyx, particularly manifest in conditions associated with sirtuin 1 depletion. In the forthcoming review, we summarize the emerging conceptual framework of the enhanced glycocalyx degradation in the states of defective endothelial sirtuin 1 function, thus explaining a broad footprint of the syndrome of endothelial dysfunction, from impaired flow-induced nitric oxide production, deterrent leukocytes infiltration, increased endothelial permeability, coagulation, and pro-inflammatory changes to development of microvascular rarefaction and progression of an underlying disease.

Glycocalyx Degradation in Ischemia-Reperfusion Injury

The glycocalyx is a layer coating the luminal surface of vascular endothelial cells. It is vital for endothelial function as it participates in microvascular reactivity, endothelium interaction with blood constituents, and vascular permeability. Structural and functional damage to glycocalyx occurs in various disease states. A prominent clinical situation characterized by glycocalyx derangement is ischemia-reperfusion (I/R) of the whole body as well as during selective I/R to organs such as the kidney, heart, lung, or liver. Degradation of the glycocalyx is now considered a cornerstone in I/R-related endothelial dysfunction, which further impairs local microcirculation with a feed-forward loop of organ damage, due to vasoconstriction, leukocyte adherence, and activation of the immune response. Glycocalyx damage during I/R is evidenced by rising plasma levels of its principal constituents, heparan sulfate and syndecan-1. By contrast, the concentrations of these compounds in the circulation decrease after successful protective interventions in I/R, suggesting their use as surrogate biomarkers of endothelial integrity. In light of the importance of the glycocalyx in preserving endothelial cell integrity and its involvement in pathologic conditions, several promising therapeutic strategies to restore the damaged glycocalyx and to attenuate its deleterious consequences have been suggested. This review focuses on alterations of glycocalyx during I/R injury in general (to vital organs in particular), and on maneuvers aimed at glycocalyx recovery during I/R injury.

Endothelial Glycocalyx Impairment in Disease: Focus on Hyaluronan Shedding

Hyaluronan (HA) is a ubiquitous glycosaminoglycan of the extracellular matrix. It is present in the endothelial glycocalyx covering the apical surface of endothelial cells. The endothelial glycocalyx regulates blood vessel permeability and homeostasis. HA plays a central role in numerous functions of the endothelial surface layer, protecting the endothelial cells, regulating the barrier permeability, and ensuring mechanosensing, which is essential to nitric oxide production and flow-induced vasodilation. During acute injury, inflammatory conditions, or many other pathologic conditions, the endothelial glycocalyx is damaged, and its degradation is accompanied by shedding of one or more glycocalyx components into the blood. Syndecan-1, heparan sulfate, and HA are the main components whose shedding has been claimed to represent the endothelial glycocalyx state of health. This review focuses on endothelial glycocalyx HA and highlights its key roles in the functions of the endothelial glycocalyx, its shedding in several pathologic conditions such as sepsis, diabetes, chronic and acute kidney injury, ischemia/reperfusion, atherosclerosis, and inflammation, which are all accompanied by increased circulating HA levels. Plasma/serum HA level is becoming recognized as a biomarker of endothelial glycocalyx damage in select pathologies. Hyaluronidase, the main HA-degrading enzyme, and its involvement in the impairment of endothelial glycocalyx are also addressed.

Endothelial Glycocalyx Hyaluronan: Regulation and Role in Prevention of Diabetic Complications

The endothelial glycocalyx is critically involved in vascular integrity and homeostasis, by regulating vascular permeability, regulating mechanotransduction, and reducing inflammation and coagulation. The turnover of the glycocalyx is dynamic to fine-tune these processes. This is in particular true for its main structural component, hyaluronan (HA). Degradation and shedding of the glycocalyx by enzymes, such as hyaluronidase 1 and hyaluronidase 2, are responsible for regulation of the glycocalyx thickness and hence access of circulating cells and factors to the endothelial cell membrane and its receptors. This degradation process will at the same time also allow for resynthesis and adaptive chemical modification of the glycocalyx. The (re)synthesis of HA is dependent on the availability of its sugar substrates, thus linking glycocalyx biology directly to cellular glucose metabolism. It is therefore of particular interest to consider the consequences of dysregulated cellular glucose in diabetes for glycocalyx biology and its implications for endothelial function. This review summarizes the metabolic regulation of endothelial glycocalyx HA and its potential as a therapeutic target in diabetic vascular complications.

New insights into antiphospholipid-related endothelial dysfunction by assessment of vascular glycocalyx layer: results from a preliminary cross-sectional study

Introduction

Antiphospholipid syndrome (APS) is associated with greater atherothrombotic risk and endothelial dysfunction, suggesting that endothelial glycocalyx is impaired in this disease.

Objectives

The aim was to investigate the endothelial glycocalyx and the relationship between glycocalyx markers, endothelial dysfunction parameters and atherosclerotic markers in APS.

Methods

A total of 15 primary arterial APS patients and healthy controls were included in the study. Glycocalyx was assessed in both groups by sublingual sidestream dark field imaging and syndecan-1 plasma level. Endothelial function was evaluated by brachial artery flow-mediated dilatation (FMD) and early atherosclerosis by carotid intima media thickness (IMT). Thrombotic profile was also performed by measuring the plasma level of the tissue factor (TF).

Results

APS patients had significantly increased syndecan-1 plasma level 38.6 ± 5.0 pg/ml vs. 19.1 ± 3.5 pg/ml; p < 0.01 and a reduced glycocalyx thickness 0.26 ± 0.03 µm vs. 0.75 ± 0.07 µm; p < 0.01 compared with control. FMD was impaired in APS patients compared with control, 5.68% ± 0.42 vs. 8.29 ± 0.30, p < 0.01, respectively. IMT was significantly increased in APS patients compared with control, 0.52 ± 0.13 mm vs. 0.40 ± 0.06 mm, p < 0.01, respectively. Soluble TF, thiobarbituric acid-reactive substances levels were increased in the sera from APS patients compared with control.

Conclusions

This preliminary study supports, for the first time, that in APS patients endothelial glycocalyx is impaired, which could lead to thrombosis, endothelial dysfunction and early atherosclerosis.

Noninvasive sublingual microvascular imaging reveals sex-specific reduction in glycocalyx barrier properties in patients with coronary artery disease

BACKGROUND

Risk factors for coronary artery disease (CAD) have been associated with endothelial dysfunction and degradation of the endothelial glycocalyx. This study was designed to compare sublingual microvascular perfusion and glycocalyx barrier properties in CAD patients and controls using noninvasive side stream darkfield imaging.

METHODS

Imaging of the sublingual microvasculature was performed in 52 case subjects (CAD confirmed by left heart catheterization) and 63 controls (low Framingham risk score). Red blood cell (RBC) filling percentage and functional microvascular density, measures of microvascular perfusion, and perfused boundary region (PBR), an index of glycocalyx barrier function, were measured in microvessels with a diameter ranging from 5-25 µm.

RESULTS

RBC filling percentage was lower in patients with CAD compared to controls (p < .001). Functional microvascular density did not differ between groups. The overall PBR was marginally greater in the CAD group compared to the control group (p = .08). PBR did not differ between male CAD cases and controls (p = .17). However, PBR was greater in females with CAD compared with female controls (p = .04), indicating reduced glycocalyx barrier function. This difference became more pronounced after adjusting for potential confounders.

CONCLUSIONS

Our data suggest that patients with CAD are characterized by a reduction in percentage of time microvessels are occupied by RBCs. In addition, CAD is significantly associated with impaired sublingual microvascular glycocalyx barrier function in women but not men. More research is needed to determine the significance of peripheral microvascular dysfunction in the pathophysiology of CAD, and how this may differ by sex.

Acellular and cellular approaches to improve diabetic wound healing

Chronic diabetic wounds represent a huge socioeconomic burden for both affected individuals and the entire healthcare system. Although the number of available treatment options as well as our understanding of wound healing mechanisms associated with diabetes has vastly improved over the past decades, there still remains a great need for additional therapeutic options. Tissue engineering and regenerative medicine approaches provide great advantages over conventional treatment options, which are mainly aimed at wound closure rather than addressing the underlying pathophysiology of diabetic wounds. Recent advances in biomaterials and stem cell research presented in this review provide novel ways to tackle different molecular and cellular culprits responsible for chronic and nonhealing wounds by delivering therapeutic agents in direct or indirect ways. Careful integration of different approaches presented in the current article could lead to the development of new therapeutic platforms that can address multiple pathophysiologic abnormalities and facilitate wound healing in patients with diabetes.

Sublingual endothelial glycocalyx and atherosclerosis. A cross-sectional study

Background

Damage to endothelial glycocalyx is thought to be an early marker of atherosclerosis and measuring reduced glycocalyx size clinically via the Perfused Boundary Region (PBR) may allow early detection of cardiovascular disease. However, the true value of the glycocalyx in estimating cardiovascular risk or detecting cardiovascular disease is uncertain. We therefore investigated whether small glycocalyx size is associated with cardiovascular risk or disease in a large multi-ethnic cohort.

Methods

In a multi-ethnic community-based sample (N = 6169, 42.4% male, mean age 43.6 ±13) we applied multiple imputation for missing data and used logistic regression and odds ratios to cross-sectionally investigate the relationship of small glycocalyx size as estimated by highest quartile of PBR with, on the one hand, classical risk factors for atherosclerosis including age, sex, diastolic and systolic blood pressure, LDL, HDL, triglycerides, BMI, diabetes, smoking status, and antihypertensive and lipid-lowering medication; on the other hand, prevalent cardiovascular disease. Analyses were additionally adjusted for ethnicity.

Results

With PBR divided in quartiles, the highest PBR quartile (smallest glycocalyx size) as dependent variable was independently associated with female sex (OR for male versus female: 0.61, 95% CI: 0.53, 0.70) and diabetes (OR: 1.28, 95% CI: 1.03–1.59) in a model adjusted for all classical risk factors of atherosclerosis and for ethnicity. With regard to cardiovascular disease, no association was found between the smallest glycocalyx size as independent variable and overall cardiovascular disease, coronary heart disease and revascularization procedures, or stroke.

Conclusions

Small glycocalyx size as estimated by highest PBR is associated with female sex and diabetes, which do not completely reflect a high cardiovascular risk profile. At the same time, glycocalyx size is not associated with prevalent cardiovascular disease.

Endothelial Nanomechanics in the Context of Endothelial (Dys)function and Inflammation

SIGNIFICANCE

Stiffness of endothelial cells is closely linked to the function of the vasculature as it regulates the release of vasoactive substances such as nitric oxide (NO) and reactive oxygen species. The outer layer of endothelial cells, consisting of the glycocalyx above and the cortical zone beneath the plasma membrane, is a vulnerable compartment able to adapt its nanomechanical properties to any changes of forces exerted by the adjacent blood stream. Sustained stiffening of this layer contributes to the development of endothelial dysfunction and vascular pathologies. Recent Advances: The development of specific techniques to quantify the mechanical properties of cells enables the detailed investigation of the mechanistic link between structure and function of cells.

CRITICAL ISSUES

Challenging the mechanical stiffness of cells, for instance, by inflammatory mediators can lead to the development of endothelial dysfunction. Prevention of sustained stiffening of the outer layer of endothelial cells in turn improves endothelial function.

FUTURE DIRECTIONS

The mechanical properties of cells can be used as critical marker and test system for the proper function of the vascular system. Pharmacological substances, which are able to improve endothelial nanomechanics and function, could take a new importance in the prevention and treatment of vascular diseases. Thus, detailed knowledge acquisition about the structure/function relationship of endothelial cells and the underlying signaling pathways should be promoted.

Endothelial Glycocalyx as a Shield Against Diabetic Vascular Complications: Involvement of Hyaluronan and Hyaluronidases

The endothelial glycocalyx (EG), which covers the apical surface of the endothelial cells and floats into the lumen of the vessels, is a key player in vascular integrity and cardiovascular homeostasis. The EG is composed of PGs (proteoglycans), glycoproteins, glycolipids, and glycosaminoglycans, in particular hyaluronan (HA). HA seems to be implicated in most of the functions described for EG such as creating a space between blood and the endothelium, controlling vessel permeability, restricting leukocyte and platelet adhesion, and allowing an appropriate endothelial response to flow variation through mechanosensing. The amount of HA in the EG may be regulated by HYAL (hyaluronidase) 1, the most active somatic hyaluronidase. HYAL1 seems enriched in endothelial cells through endocytosis from the bloodstream. The role of the other main somatic hyaluronidase, HYAL2, in the EG is uncertain. Damage to the EG, accompanied by shedding of one or more of its components, is an early sign of various pathologies including diabetes mellitus. Shedding increases the blood or plasma concentration of several EG components, such as HA, heparan sulfate, and syndecan. The plasma levels of these molecules can then be used as sensitive markers of EG degradation. This has been shown in type 1 and type 2 diabetic patients. Recent experimental studies suggest that preserving the size and amount of EG HA in the face of diabetic insults could be a useful novel therapeutic strategy to slow diabetic complications. One way to achieve this goal, as suggested by a murine model of HYAL1 deficiency, may be to inhibit the function of HYAL1. The same approach may succeed in other pathological situations involving endothelial dysfunction and EG damage.

Role of hyaluronan in atherosclerosis: Current knowledge and open questions

Hyaluronan (HA), HA synthases (HAS) and HA receptors are expressed during the progression of atherosclerotic plaques. HA is thought to promote the activated phenotype of local vascular smooth muscle cells characterized by increased migration, proliferation and matrix synthesis. Furthermore, HA may modulate the immune response by increasing macrophage retention and by promoting the polarization of Th1 cells that enhance macrophage driven inflammation as well. The pro-atherosclerotic functions of HA are opposed by the presence of HA in the glycocalyx where it critically contributes to anti-thrombotic and anti-inflammatory function of the glycocalyx. Patients with atherosclerosis often are affected by comorbidities among them diabetes mellitus type 2 and inflammatory comorbidities. Diabetes mellitus type 2 likely has close interrelations to HA synthesis in atherosclerosis because the activity and transcription of HA synthases are sensitive to the intracellular glucose metabolism, which determines the substrate availability and the posttranslational modifications of HA synthases. The pro-inflammatory comorbidities aggravate the course of atherosclerosis and will affect the expression of the genes related to HA biosynthesis, -degradation, HA-matrix assembly or signaling. One example being the induction of HAS3 by interleukin-1β and other cytokines. Furthermore complications of atherosclerosis such as the healing after myocardial infarction also involve HA responses.

Regulation and roles of the hyaluronan system in mammalian reproduction

Hyaluronan (HA) is a non-sulphated glycosaminoglycan polymer naturally occurring in many tissues and fluids of mammals, including the reproductive system. Its biosynthesis by HA synthase (HAS1–3) and catabolism by hyaluronidases (HYALs) are affected by ovarian steroid hormones. Depending upon its molecular size, HA functions both as a structural component of tissues in the form of high-molecular-weight HA or as a signalling molecule in the form of small HA molecules or HA fragments with effects mediated through interaction with its specific cell-membrane receptors. HA is produced by oocytes and embryos and in various segments of the reproductive system. This review provides information about the expression and function of members of the HA system, including HAS, HYALs and HA receptors. We examine their role in various processes from folliculogenesis through oocyte maturation, fertilisation and early embryo development, to pregnancy and cervical dilation, as well as its application in assisted reproduction technologies. Particular emphasis has been placed upon the role of the HA system in pre-implantation embryo development and embryo implantation, for which we propose a hypothetical sequential model.

Direct Observation of Enhanced Nitric Oxide in a Murine Model of Diabetic Nephropathy

Uncoupling of nitric oxide synthase (NOS) secondary to redox signaling is a central mechanism in endothelial and macrophage activation. To date studies on the production of nitric oxide (NO) during the development of diabetic complications show paradoxical results. We previously showed that recoupling eNOS by increasing the eNOS cofactor tetrahydrobiopterin (BH4) could restore endothelial function and prevent kidney injury in experimental kidney transplantation. Here, we employed a diabetic mouse model to investigate the effects of diabetes on renal tissue NO bioavailability. For this, we used in vivo NO trapping, followed by electron paramagnetic resonance spectroscopy. In addition, we investigated whether coupling of NOS by supplying the cofactor BH4 could restore glomerular endothelial barrier function. Our data show that overall NO availability at the tissue level is not reduced sixteen weeks after the induction of diabetes in apoE knockout mice, despite the presence of factors that cause endothelial dysfunction, and the presence of the endogenous NOS inhibitor ADMA. Targeting uncoupled NOS with the BH4 precursor sepiapterin further increases NO availability, but did not modify renal glomerular injury. Notably, glomerular heparanase activity as a driver for loss of glomerular barrier function was not reduced, pointing towards NOS-independent mechanisms. This was confirmed by unaltered increased glomerular presence of cathepsin L, the protease that activates heparanase.

Serum levels of endothelial glycocalyx constituents in women at 20 weeks' gestation who later develop gestational diabetes mellitus compared to matched controls: a pilot study

OBJECTIVES

The aim of this pilot study was to determine the serum concentration of heparan sulfate, hyaluronan, chondroitin sulfate and syndecan-1 and if these serum concentrations can be used to identify women at 20 weeks' gestation who later develop gestational diabetes mellitus (GDM).

DESIGN

Nested case-control study from Auckland, New Zealand participants in the prospective cohort Screening for Pregnancy Endpoints study.

SETTING

Auckland, New Zealand.

PARTICIPANTS

20 pregnant women (70% European, 15% Indian, 10% Asian, 5% Pacific Islander) at 20 weeks' gestation without any hypertensive complications who developed GDM by existing New Zealand criteria defined as a fasting glucose ≥5.5 mmol/L and/or 2 hours ≥9.0 mmol/L after a 75 g Oral Glucose Tolerance Test. Women not meeting these criteria were excluded from this study. The patients with GDM were matched with 20 women who had uncomplicated pregnancies and negative screening for GDM and matched for ethnicity, maternal age and BMI.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary measures were the serum concentrations of syndecan-1, heparan sulfate, hyaluronan and chondroitin sulfate determined by quantitative ELISA. There were no secondary outcome measures.

RESULTS

Binary logistic regression was performed to determine if serum concentrations of endothelial glycocalyx layer constituents in women at 20 weeks' gestation would be useful in predicting the subsequent diagnosis of GDM. The model was not statistically significant χ²=12.5, df=8, p=0.13, which indicates that the model was unable to distinguish between pregnant women at 20 weeks' gestation who later developed GDM and those who did not.

CONCLUSIONS

Serum concentrations of syndecan-1, heparan sulfate, hyaluronan and chondroitin sulfate in pregnant women at 20 weeks' gestation were not associated with later development of GDM. To further explore whether there is any relationship between endothelial glycocalyx constituents and GDM, the next step is to evaluate serum concentrations at the time diagnosis of GDM.

Cardiovascular disease and type 1 diabetes: prevalence, prediction and management in an ageing population

Cardiovascular disease (CVD) is a major cause of mortality in type 1 diabetes mellitus (T1D). However, evidence of its risks and management is often extrapolated from studies in type 2 diabetic (T2D) patients or the general population. This approach is unsatisfactory given that the underlying pathology, demographics and natural history of the disease differ between T1D and T2D. Furthermore, with a rising life expectancy, a greater number of T1D patients are exposed to the cardiovascular (CV) risk factors associated with an ageing population. The aim of this review is to examine the existing literature around CVD in T1D. We pay particular attention to CVD prevalence, how well we manage risk, potential biomarkers, and whether the studies included the older aged patients (defined as aged over 65). We also discuss approaches to the management of CV risk in the older aged. The available data suggest a significant CVD burden in patients with T1D and poor management of CV risk factors. This is underpinned by a poor evidence base for therapeutic management of CV risk specifically for patients with T1D, and in the most relevant population - the older aged patients. We would suggest that important areas remain to be addressed, particularly exploring the risks and benefits of therapeutic approaches to CVD management in the older aged.

Hyaluronan: A Mediator of Islet Dysfunction and Destruction in Diabetes?

Hyaluronan (HA) is an extracellular matrix (ECM) component that is present in mouse and human islet ECM. HA is localized in peri-islet and intra-islet regions adjacent to microvessels. HA normally exists in a high molecular weight form, which is anti-inflammatory. However, under inflammatory conditions, HA is degraded into fragments that are proinflammatory. HA accumulates in islets of human subjects with recent onset type 1 diabetes (T1D), and is associated with myeloid and lymphocytic islet infiltration, suggesting a possible role for HA in insulitis. A similar accumulation of HA, in amount and location, occurs in non-obese diabetic (NOD) and DORmO mouse models of T1D. Furthermore, HA accumulates in follicular germinal centers and in T-cell areas in lymph nodes and spleen in both human and mouse models of T1D, as compared with control tissues. Whether HA accumulates in islets in type 2 diabetes (T2D) or models thereof has not been previously described. Here we show evidence that HA accumulates in a mouse model of islet amyloid deposition, a well-known component of islet pathology in T2D. In summary, islet HA accumulation is a feature of both T1D and a model of T2D, and may represent a novel inflammatory mediator of islet pathology.

Hyperglycemia-Induced Changes in Hyaluronan Contribute to Impaired Skin Wound Healing in Diabetes: Review and Perspective

Ulcers and chronic wounds are a particularly common problem in diabetics and are associated with hyperglycemia. In this targeted review, we summarize evidence suggesting that defective wound healing in diabetics is causally linked, at least in part, to hyperglycemia-induced changes in the status of hyaluronan (HA) that resides in the pericellular coat (glycocalyx) of endothelial cells of small cutaneous blood vessels. Potential mechanisms through which exposure to high glucose levels causes a loss of the glycocalyx on the endothelium and accelerates the recruitment of leukocytes, creating a proinflammatory environment, are discussed in detail. Hyperglycemia also affects other cells in the immediate perivascular area, including pericytes and smooth muscle cells, through exposure to increased cytokine levels and through glucose elevations in the interstitial fluid. Possible roles of newly recognized, cross-linked forms of HA, and interactions of a major HA receptor (CD44) with cytokine/growth factor receptors during hyperglycemia, are also discussed.

Increased carotid intima-media thickness (CIMT) levels in patients with type 1 diabetes mellitus (T1DM): A meta-analysis

AIM

To derive a more precise estimation of carotid intima-media thickness (CIMT) levels in patients with type 1 diabetes mellitus (T1DM) by meta-analysis.

METHODS

PubMed and Embase databases were searched to identify all available studies comparing CIMT levels between T1DM group and control group. Meta-analysis was performed to compare the difference of overall mean CIMT levels between the two groups. Publication bias was evaluated by funnel plot, Begg' test and Egger' test. Meta-regression analysis was conducted to investigate the influential factors on CIMT difference. The meta-analysis was conducted by STATA 12.0 software.

RESULTS

A total of 1840 articles were obtained after searching databases; 47 studies were finally included in the meta-analysis. Significant heterogeneity was observed among these studies (Q = 768.75, P < 0.001, I(2) = 94.0%). Compared with the control group, the T1DM group had significantly higher CIMT levels (standardized mean difference: 1.01, 95% CI: 0.75-1.28; P < 0.001). A likely source of heterogeneity was Newcastle-Ottawa Scale (NOS) scores and sample size ratio of patents and controls. The funnel plot did not show a skewed or asymmetrical shape, and the result of Begg' test and Egger' test was P = 0.178 and P = 0.145 respectively. Accordingly, it could be assumed that publication bias was not present.

CONCLUSION

T1DM patients have significantly increased CIMT levels compared to control subjects.

Degradation of the endothelial glycocalyx in clinical settings: searching for the sheddases

The endothelial glycocalyx has a profound influence at the vascular wall on the transmission of shear stress, on the maintenance of a selective permeability barrier and a low hydraulic conductivity, and on attenuating firm adhesion of blood leukocytes and platelets. Major constituents of the glycocalyx, including syndecans, heparan sulphates and hyaluronan, are shed from the endothelial surface under various acute and chronic clinical conditions, the best characterized being ischaemia and hypoxia, sepsis and inflammation, atherosclerosis, diabetes, renal disease and haemorrhagic viral infections. Damage has also been detected by in vivo microscopic techniques. Matrix metalloproteases may shed syndecans and heparanase, released from activated mast cells, cleaves heparan sulphates from core proteins. According to new data, not only hyaluronidase but also the serine proteases thrombin, elastase, proteinase 3 and plasminogen, as well as cathepsin B lead to loss of hyaluronan from the endothelial surface layer, suggesting a wide array of potentially destructive conditions. Appropriately, pharmacological agents such as inhibitors of inflammation, antithrombin and inhibitors of metalloproteases display potential to attenuate shedding of the glycocalyx in various experimental models. Also, plasma components, especially albumin, stabilize the glycocalyx and contribute to the endothelial surface layer. Though symptoms of the above listed diseases and conditions correlate with sequelae expected from disturbance of the endothelial glycocalyx (oedema, inflammation, leukocyte and platelet adhesion, low reflow), therapeutic studies to prove a causal connection have yet to be designed. With respect to studies on humans, some clinical evidence exists for benefits from application of sulodexide, a preparation delivering precursors of the glycocalyx constituent heparan sulphate. At present, the simplest option for protecting the glycocalyx seems to be to ensure an adequate level of albumin. However, also in this case, definite proof of causality needs to be delivered.

Hyaluronan in the healthy and malignant hematopoietic microenvironment

The fate of both endogenous and transplanted stem cells is dependent on the functional status of the regulatory local microenvironment, which is compromised by disease and therapeutic intervention. The glycosaminoglycan hyaluronan (HA) is a critical component of the hematopoietic microenvironment. We summarize recent advances in our understanding of the role of HA in regulating mesenchymal stem cells, osteoblasts, fibroblasts, macrophages, and endothelium in bone marrow (BM) and their crosstalk within the hematopoietic microenvironment. HA not only determines the volume, hydration, and microfluidics of the BM interstitial space, but also, via interactions with specific receptors, regulates multiple cell functions including differentiation, migration, and production of regulatory factors. The effects of HA are dependent on the polymer size and are influenced by the formation of complexes with other molecules. In healthy BM, HA synthases and hyaluronidases form a molecular network that maintains extracellular HA levels within a discrete physiological window, but HA homeostasis is often perturbed in pathological conditions, including hematological malignancies. Recent studies have suggested that HA synthases may have functions beyond HA production and contribute to the intracellular regulatory machinery. We discuss a possible role for HA synthases, intracellular and extracellular HA in the malignant BM microenvironment, and resistance to therapy.

The relationship between aortic stiffness and serum hyaluronidase levels in patients with diabetes mellitus and hypertension

The aim of this study was to investigate the association of serum hyaluronidase and nitric oxide (NO) levels with arterial stiffness in patients with hypertension (HT) and diabetes mellitus (DM). A total of 101 patients with diagnosis of DM and HT were enrolled in this study. The patients were divided into three groups as follows: only hypertensive (I), only diabetic (II) and both diabetic and hypertensive (III). Serum hyaluronidase levels were negatively correlated with aortic strain (AS) and aortic distensibility (AOD) in all groups, whereas a significant positive correlation was noted between serum hyaluronidase levels and aortic strain index (ASI) (all p-values < 0.05). There was a significant negative correlation between serum hyaluronidase and NO levels in all patients (p < 0.001). When the correlation between serum hyaluronidase and serum NO levels was investigated in the individual patient groups, a negative correlation was found in groups I, II and III (p = 0.017, p < 0.001 and p < 0.001, respectively). A significant relationship between plasma hyaluronidase level and parameters of aortic stiffness was found in patients with HT and/or DM. We suggest that the pathophysiological mechanisms responsible for the development of arterial stiffness in subjects with impaired endothelial function may involve pathological changes in the HA metabolism.

Close relationship between serum hyaluronan levels and vascular function in patients with type 2 diabetes

OBJECTIVE

To clarify the relationship between serum hyaluronan levels and vascular function in type 2 diabetic patients.

METHODS

A cross-sectional cohort study.

RESULTS

In multivariate regression analysis, endothelium-dependent flow-mediated dilation was associated with age and duration of diabetes, but not with serum hyaluronan level, while endothelium-independent nitroglycerine-mediated dilation (NMD) was only associated with serum hyaluronan level (standardized estimate = -0.401, p = 0.003). NMD in the lowest tertile of hyaluronan level was significantly higher than the other tertiles (15.9% versus 12.5% and 10.4%, p = 0.047 and p = 0.002, respectively).

CONCLUSIONS

Serum hyaluronan level may be useful as a surrogate marker for early changes in the vascular function, which often occurs in patients with diabetes mellitus.

Modulation of endothelial glycocalyx structure under inflammatory conditions

The glycocalyx of the endothelium is an intravascular compartment that creates a barrier between circulating blood and the vessel wall. The glycocalyx is suggested to play an important role in numerous physiological processes including the regulation of vascular permeability, the prevention of the margination of blood cells to the vessel wall, and the transmission of shear stress. Various theoretical models and experimental approaches provide data about changes to the structure and functions of the glycocalyx under various types of inflammatory conditions. These alterations are suggested to promote inflammatory processes in vessels and contribute to the pathogenesis of number of diseases. In this review we summarize current knowledge about the modulation of the glycocalyx under inflammatory conditions and the consequences for the course of inflammation in vessels. The structure and functions of endothelial glycocalyx are briefly discussed in the context of methodological approaches regarding the determination of endothelial glycocalyx and the uncertainty and challenges involved in glycocalyx structure determination. In addition, the modulation of glycocalyx structure under inflammatory conditions and the possible consequences for pathogenesis of selected diseases and medical conditions (in particular, diabetes, atherosclerosis, ischemia/reperfusion, and sepsis) are summarized. Finally, therapeutic strategies to ameliorate glycocalyx dysfunction suggested by various authors are discussed.