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

Effect of diabetes on microvascular morphology and permeability of rat skeletal muscle: in vivo imaging using two-photon laser scanning microscopy

This investigation evaluated the microvascular permeability and ultrastructure of skeletal muscle capillaries in the skeletal muscle of diabetic (DIA) rats using two-photon laser scanning microscopy (TPLSM) and transmission electron microscopy (TEM). Microvascular permeability was assessed in the tibialis anterior muscle of control (CON) and DIA (streptozocin) male Wistar rats (n = 20, 10-14 wk) by in vivo imaging using TPLSM after fluorescent dye intravenous infusion. Fluorescent dye leakage was quantified to determine microvascular permeability. The ultrastructure was imaged by TEM ex vivo to calculate the size and number of intercellular clefts between capillary endothelial cells and also intracellular vesicles. Compared with control, the volumetrically determined interstitial fluorescent dye leakage, the endothelial cell thickness, and the number of intercellular clefts per capillary perimeter were significantly higher, and the cleft width was significantly narrower in tibialis anterior (TA) of DIA (interstitial fluorescent dye leakage, 2.88 ± 1.40 vs. 10.95 ± 1.41 µm3 × min × 106; endothelial thickness, 0.28 ± 0.02 vs. 0.45 ± 0.03 µm; number of intercellular clefts per capillary perimeter, 6.3 ± 0.80 vs. 13.6 ± 1.7/100 µm; cleft width, 11.92 ± 0.95 vs. 8.40 ± 1.03 nm, CON vs. DIA, respectively, all P < 0.05). The size of intracellular vesicles in the vascular endothelium showed an increased proportion of large vesicles in the DIA group compared with the CON group (P < 0.05). Diabetes mellitus enhances the microvascular permeability of skeletal muscle microvessels due, in part, to a higher density and narrowing of the endothelial intercellular clefts, and larger intracellular vesicles.NEW & NOTEWORTHY Microvascular permeability in diabetic muscle was investigated using our original two-photon scanning laser microscopy method. Compared with controls, the leakage volume was increased in diabetic muscle, which was atrophic with smaller capillary diameter, endothelial cell thickening, and the appearance of more endothelial intercellular gaps or clefts, and large vesicles. Hyperpermeability was closely related to ultrafine structural changes of the capillary endothelial cell junctions.

Endocan, a novel glycoprotein with multiple biological activities, may play important roles in neurological diseases

Endothelial cell specific-1 (ESM-1), also known as endocan, is a soluble dermatan sulfate proteoglycan that is mainly secreted by endothelial cells. Endocan is associated with tumorigenesis and cancer progression and is also related to cardiovascular disorders, autoimmune diseases, and sepsis. The phenylalanine-rich region and linear polysaccharide of endocan are necessary for the protein to exert its biological functions. Elevated plasma endocan levels reflect endothelial activation and dysfunction. In addition, endocan participates in complex inflammatory responses and proliferative processes. Here, we reviewed current research on endocan, elaborated the protein's structure and biological functions, and speculated on its possible clinical value in nervous system diseases. We conclude that endocan may be a glycoprotein that plays an important role in neurological disorders.

ECM Microenvironment in Vascular Homeostasis: New Targets for Atherosclerosis

Alterations in vascular extracellular matrix (ECM) components, interactions, and mechanical properties influence both the formation and stability of atherosclerotic plaques. This review discusses the contribution of the ECM microenvironment in vascular homeostasis and remodeling in atherosclerosis, highlighting Cartilage oligomeric matrix protein (COMP) and its degrading enzyme ADAMTS7 as examples, and proposes potential avenues for future research aimed at identifying novel therapeutic targets for atherosclerosis based on the ECM microenvironment.

Glycosaminoglycans: Participants in Microvascular Coagulation of Sepsis

Sepsis represents a syndromic response to infection and frequently acts as a common pathway leading to fatality in the context of various infectious diseases globally. The pathology of severe sepsis is marked by an excess of inflammation and activated coagulation. A substantial contributor to mortality in sepsis patients is widespread microvascular thrombosis-induced organ dysfunction. Multiple lines of evidence support the notion that sepsis induces endothelial damage, leading to the release of glycosaminoglycans, potentially causing microvascular dysfunction. This review aims to initially elucidate the relationship among endothelial damage, excessive inflammation, and thrombosis in sepsis. Following this, we present a summary of the involvement of glycosaminoglycans in coagulation, elucidating interactions among glycosaminoglycans, platelets, and inflammatory cells. In this section, we also introduce a reasoned generalization of potential signal pathways wherein glycosaminoglycans play a role in clotting. Finally, we discuss current methods for detecting microvascular conditions in sepsis patients from the perspective of glycosaminoglycans. In conclusion, it is imperative to pay closer attention to the role of glycosaminoglycans in the mechanism of microvascular thrombosis in sepsis. Dynamically assessing glycosaminoglycan levels in patients may aid in predicting microvascular conditions, enabling the monitoring of disease progression, adjustment of clinical treatment schemes, and mitigation of both acute and long-term adverse outcomes associated with sepsis.

Engineering next generation vascularized organoids

Organoids are self-organizing 3D cell culture models that are valuable for studying the mechanisms underlying both development and disease in multiple species, particularly, in humans. These 3D engineered tissues can mimic the structure and function of human organs in vitro. Methods to generate organoids have substantially improved to better resemble, in various ways, their in vivo counterpart. One of the major limitations in current organoid models is the lack of a functional vascular compartment. Here we discuss methodological approaches to generating perfusable blood vessel networks in organoid systems. Inclusion of perfused vascular compartments markedly enhances the physiological relevance of organoid systems and is a critical step in the establishment of next generation, higher-complexity in vitro systems for use in developmental, clinical, and drug-development settings.

Microvascular destabilization and intricated network of the cytokines in diabetic retinopathy: from the perspective of cellular and molecular components

Microvascular destabilization is the primary cause of the inner blood-retinal barrier (iBRB) breakdown and increased vascular leakage in diabetic retinopathy (DR). Microvascular destabilization results from the combinational effects of increased levels of growth factors and cytokines, involvement of inflammation, and the changed cell-to-cell interactions, especially the loss of endothelial cells and pericytes, due to hyperglycemia and hypoxia. As the manifestation of microvascular destabilization, the fluid transports via paracellular and transcellular routes increase due to the disruption of endothelial intercellular junctional complexes and/or the altered caveolar transcellular transport across the retinal vascular endothelium. With diabetes progression, the functional and the structural changes of the iBRB components, including the cellular and noncellular components, further facilitate and aggravate microvascular destabilization, resulting in macular edema, the neuroretinal damage and the dysfunction of retinal inner neurovascular unit (iNVU). Although there have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying the microvascular destabilization, some still remain to be fully elucidated. Recent data indicate that targeting the intricate signaling pathways may allow to against the microvascular destabilization. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in the microvascular destabilization in DR. In this review, we discuss: (1) the brief introduction of DR and microvascular destabilization; (2) the cellular and molecular components of iBRB and iNVU, and the breakdown of iBRB; (3) the matrix and cell-to-cell contacts to maintain microvascular stabilization, including the endothelial glycocalyx, basement membrane, and various cell-cell interactions; (4) the molecular mechanisms mediated cell-cell contacts and vascular cell death; (5) the altered cytokines and signaling pathways as well as the intricate network of the cytokines involved in microvascular destabilization. This comprehensive review aimed to provide the insights for microvascular destabilization by targeting the key molecules or specific iBRB cells, thus restoring the function and structure of iBRB and iNVU, to treat DR.

Fasting mimicking diet in diabetic mice partially preserves glomerular endothelial glycocalyx coverage, without changing the diabetic metabolic environment

Intermittent fasting has become of interest for its possible metabolic benefits and reduction of inflammation and oxidative damage, all of which play a role in the pathophysiology of diabetic nephropathy. We tested in a streptozotocin (60 mg/kg)-induced diabetic apolipoprotein E knockout mouse model whether repeated fasting mimicking diet (FMD) prevents glomerular damage. Diabetic mice received 5 FMD cycles in 10 wk, and during cycles 1 and 5 caloric measurements were performed. After 10 wk, glomerular endothelial morphology was determined together with albuminuria, urinary heparanase-1 activity, and spatial mass spectrometry imaging to identify specific glomerular metabolic dysregulation. During FMD cycles, blood glucose levels dropped while a temporal metabolic switch was observed to increase fatty acid oxidation. Overall body weight at the end of the study was reduced together with albuminuria, although urine production was dramatically increased without affecting urinary heparanase-1 activity. Weight loss was found to be due to lean mass and water, not fat mass. Although capillary loop morphology and endothelial glycocalyx heparan sulfate contents were preserved, hyaluronan surface expression was reduced together with the presence of UDP-glucuronic acid. Mass spectrometry imaging further revealed reduced protein catabolic breakdown products and increased oxidative stress, not different from diabetic mice. In conclusion, although FMD preserves partially glomerular endothelial glycocalyx, loss of lean mass and increased glomerular oxidative stress argue whether such diet regimes are safe in patients with diabetes.NEW & NOTEWORTHY Repeated fasting mimicking diet (FMD) partially prevents glomerular damage in a diabetic mouse model; however, although endothelial glycocalyx heparan sulfate contents were preserved, hyaluronan surface expression was reduced in the presence of UDP-glucuronic acid. The weight loss observed was of lean mass, not fat mass, and increased glomerular oxidative stress argue whether such a diet is safe in patients with diabetes.

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.

Maternal plasma syndecan-1: a biomarker for fetal growth restriction

OBJECTIVE

The identification of fetal growth disorders is an important clinical priority given that they increase the risk of perinatal morbidity and mortality as well as long-term diseases. A subset of small-for-gestational-age (SGA) infants are growth-restricted, and this condition is often attributed to placental insufficiency. Syndecan-1, a product of the degradation of the endothelial glycocalyx, has been proposed as a biomarker of endothelial damage in different pathologies. During pregnancy, a "specialized" form of the glycocalyx-the "syncytiotrophoblast glycocalyx"-covers the placental villi. The purpose of this study was to determine whether the concentration of maternal plasma syndecan-1 can be proposed as a biomarker for fetal growth restriction.

STUDY DESIGN

A cross-sectional study was designed to include women with normal pregnancy (n = 130) and pregnant women who delivered an SGA neonate (n = 50). Doppler velocimetry of the uterine and umbilical arteries was performed in women with an SGA fetus at the time of diagnosis. Venipuncture was performed within 48 h of Doppler velocimetry and plasma concentrations of syndecan-1 were determined by a specific and sensitive immunoassay.

RESULTS

(1) Plasma syndecan-1 concentration followed a nonlinear increase with gestational age in uncomplicated pregnancies (R² = 0.27, p < .001); (2) women with a pregnancy complicated with an SGA fetus had a significantly lower mean plasma concentration of syndecan-1 than those with an appropriate-for-gestational-age fetus (p = .0001); (3) this difference can be attributed to fetal growth restriction, as the mean plasma syndecan-1 concentration was significantly lower only in the group of women with an SGA fetus who had abnormal umbilical and uterine artery Doppler velocimetry compared to controls (p = .00071; adjusted p = .0028). A trend toward lower syndecan-1 concentrations was also noted for SGA with abnormal uterine but normal umbilical artery Doppler velocimetry (p = .0505; adjusted p = .067); 4) among women with an SGA fetus, those with abnormal umbilical and uterine artery Doppler findings had a lower mean plasma syndecan-1 concentration than women with normal Doppler velocimetry (p = .02; adjusted p = .04); 5) an inverse relationship was found between the maternal plasma syndecan-1 concentration and the umbilical artery pulsatility index (r = -0.5; p = .003); and 6) a plasma syndecan-1 concentration ≤ 850 ng/mL had a positive likelihood ratio of 4.4 and a negative likelihood ratio of 0.24 for the identification of a mother with an SGA fetus who had abnormal umbilical artery Doppler velocimetry (area under the ROC curve 0.83; p < .001).

CONCLUSION

Low maternal plasma syndecan-1 may reflect placental diseases and this protein could be a biomarker for fetal growth restriction. However, as a sole biomarker for this condition, its accuracy is low.

Integration of Chemo-mechanical signaling in response to fluid shear stress by the endothelium

Physical forces exert profound effects on cells affecting fate, function, and response to stressors. In the case of the endothelium, the layer that resides in the inner surface of blood vessels, the collective effect of hemodynamic forces influences the onset and severity of vascular pathologies. Justifiably, much emphasis has been placed in understanding how endothelial cells sense and respond to mechanical challenges, particularly hemodynamic shear stress. In this review, we highlight recent developments that have expanded our understanding of the molecular mechanisms underlying mechanotransduction. We describe examples of protein compartmentalization in response to shear stress, consider the contribution of the glycocalyx, and discuss the specific role ion channels in response to flow. We also highlight the recently recognized contribution of the receptor ALK5 in sensing turbulent flow. Research in the last three years has enriched our understanding of the molecular landscape responsible for recognizing and transducing shear stress responses, including novel transcriptional-dependent and transcriptional-independent mechanisms.

Common mechanisms underlying diabetic vascular complications: focus on the interaction of metabolic disorders, immuno-inflammation, and endothelial dysfunction

Diabetic vascular complications (DVCs), including macro- and micro- angiopathy, account for a high percentage of mortality in patients with diabetes mellitus (DM). Endothelial dysfunction is the initial and role step for the pathogenesis of DVCs. Hyperglycemia and lipid metabolism disorders contribute to endothelial dysfunction via direct injury of metabolism products, crosstalk between immunity and inflammation, as well as related interaction network. Although physiological and phenotypic differences support their specified changes in different targeted organs, there are still several common mechanisms underlying DVCs. Also, inhibitors of these common mechanisms may decrease the incidence of DVCs effectively. Thus, this review may provide new insights into the possible measures for the secondary prevention of DM. And we discussed the current limitations of those present preventive measures in DVCs research. Video Abstract.

Endothelial cell dysfunction in cardiac disease: driver or consequence?

The vascular endothelium is a multifunctional cellular system which directly influences blood components and cells within the vessel wall in a given tissue. Importantly, this cellular interface undergoes critical phenotypic changes in response to various biochemical and hemodynamic stimuli, driving several developmental and pathophysiological processes. Multiple studies have indicated a central role of the endothelium in the initiation, progression, and clinical outcomes of cardiac disease. In this review we synthesize the current understanding of endothelial function and dysfunction as mediators of the cardiomyocyte phenotype in the setting of distinct cardiac pathologies; outline existing in vivo and in vitro models where key features of endothelial cell dysfunction can be recapitulated; and discuss future directions for development of endothelium-targeted therapeutics for cardiac diseases with limited existing treatment options.

Iatrogenic air embolism: pathoanatomy, thromboinflammation, endotheliopathy, and therapies

Iatrogenic vascular air embolism is a relatively infrequent event but is associated with significant morbidity and mortality. These emboli can arise in many clinical settings such as neurosurgery, cardiac surgery, and liver transplantation, but more recently, endoscopy, hemodialysis, thoracentesis, tissue biopsy, angiography, and central and peripheral venous access and removal have overtaken surgery and trauma as significant causes of vascular air embolism. The true incidence may be greater since many of these air emboli are asymptomatic and frequently go undiagnosed or unreported. Due to the rarity of vascular air embolism and because of the many manifestations, diagnoses can be difficult and require immediate therapeutic intervention. An iatrogenic air embolism can result in both venous and arterial emboli whose anatomic locations dictate the clinical course. Most clinically significant iatrogenic air emboli are caused by arterial obstruction of small vessels because the pulmonary gas exchange filters the more frequent, smaller volume bubbles that gain access to the venous circulation. However, there is a subset of patients with venous air emboli caused by larger volumes of air who present with more protean manifestations. There have been significant gains in the understanding of the interactions of fluid dynamics, hemostasis, and inflammation caused by air emboli due to in vitro and in vivo studies on flow dynamics of bubbles in small vessels. Intensive research regarding the thromboinflammatory changes at the level of the endothelium has been described recently. The obstruction of vessels by air emboli causes immediate pathoanatomic and immunologic and thromboinflammatory responses at the level of the endothelium. In this review, we describe those immunologic and thromboinflammatory responses at the level of the endothelium as well as evaluate traditional and novel forms of therapy for this rare and often unrecognized clinical condition.

Molecular implications of glycosaminoglycans in diabetes pharmacotherapy

Diabetes mellitus causes a wide range of metabolic derangements with multiple organ damage. The microvascular and macrovascular complications of diabetes result partly from the damage to the glycosaminoglycans (GAG) in the basement membrane. GAGs are negatively charged polysaccharides with repeating disaccharide units. They play a significant role in cellular proliferation and signal transduction. Destruction of extracellular matrix results in diseases in various organs including myocardial fibrosis, retinal damage and nephropathy. To substitute the natural GAGs pharmacotherapeutically, they have been synthesized by using basic disaccharide units. Among the four classes of GAGs, heparin is the most widely studied. Recent studies have revealed multiple significant GAG-protein interactions suggesting their use for the management of diabetic complications. Moreover, they can act as biomarkers for assessing the disease progression. A number of GAG-based therapeutic agents are being evaluated for managing diabetic complications. The current review provides an outline of the role of GAGs in diabetes while covering their interaction with different molecular players that can serve as targets for the diagnosis, management and prevention of diabetes and its complications. The medicinal chemistry and clinical pharmacotherapeutics aspects have are covered to aid in the establishment of GAG-based therapies as a possible avenue for diabetes.

Modulation of lncRNA links endothelial glycocalyx to vascular dysfunction of tyrosine kinase inhibitor

AIMS

Novel cancer therapies leading to increased survivorship of cancer patients have been negated by a concomitant rise in cancer therapies-related cardiovascular toxicities. Sunitinib, a first line multi-receptor tyrosine kinase inhibitor, has been reported to cause vascular dysfunction although the initiating mechanisms contributing to this side effect remain unknown. Long non-coding RNAs (lncRNAs) are emerging regulators of biological processes in endothelial cells (ECs); however, their roles in cancer therapies-related vascular toxicities remain underexplored.

METHODS AND RESULTS

We performed lncRNA expression profiling to identify potential lncRNAs that are dysregulated in human-induced pluripotent stem cell-derived ECs (iPSC-ECs) treated with sunitinib. We show that the lncRNA hyaluronan synthase 2 antisense 1 (HAS2-AS1) is significantly diminished in sunitinib-treated iPSC-ECs. Sunitinib was found to down-regulate HAS2-AS1 by an epigenetic mechanism involving hypermethylation. Depletion of HAS2-AS1 recapitulated sunitinib-induced detrimental effects on iPSC-ECs, whereas CRISPR-mediated activation of HAS2-AS1 reversed sunitinib-induced dysfunction. We confirmed that HAS2-AS1 stabilizes the expression of its sense gene HAS2 via an RNA/mRNA heteroduplex formation. Knockdown of HAS2-AS1 led to reduced synthesis of hyaluronic acid (HA) and up-regulation of ADAMTS5, an enzyme involved in extracellular matrix degradation, resulting in disruption of the endothelial glycocalyx which is critical for ECs. In vivo, sunitinib-treated mice showed reduced coronary flow reserve, accompanied by a reduction in Has2os and degradation of the endothelial glycocalyx. Finally, we identified that treatment with high molecular-weight HA can prevent the deleterious effects of sunitinib both in vitro and in vivo by preserving the endothelial glycocalyx.

CONCLUSIONS

Our findings highlight the importance of lncRNA-mediated regulation of the endothelial glycocalyx as an important determinant of sunitinib-induced vascular toxicity and reveal potential novel therapeutic avenues to attenuate sunitinib-induced vascular dysfunction.

Micro- and Macrovascular Effects of Inflammation in Peripheral Artery Disease-Pathophysiology and Translational Therapeutic Approaches

Inflammation has a critical role in the development and progression of atherosclerosis. On the molecular level, inflammatory pathways negatively impact endothelial barrier properties and thus, tissue homeostasis. Conformational changes and destruction of the glycocalyx further promote pro-inflammatory pathways also contributing to pro-coagulability and a prothrombotic state. In addition, changes in the extracellular matrix composition lead to (peri-)vascular remodelling and alterations of the vessel wall, e.g., aneurysm formation. Moreover, progressive fibrosis leads to reduced tissue perfusion due to loss of functional capillaries. The present review aims at discussing the molecular and clinical effects of inflammatory processes on the micro- and macrovasculature with a focus on peripheral artery disease.

Circulating hyaluronidase in early pregnancy and increased risk of gestational diabetes in Chinese pregnant women: A nested case control study

BACKGROUND AND AIMS

To explore association of serum hyaluronidase 1 (HYAL1) level in early pregnancy with gestational diabetes mellitus (GDM), and to examine interactive effects of HYAL1 with ceramides species on GDM risk.

MATERIALS AND METHODS

We conducted a 1:1 matched case-control study (n = 414) of pregnant women from 2010 to 2012 in Tianjin, China. Blood samples were collected at the first antenatal care visit (at a median of 10th gestational weeks). Binary conditional logistic regression and restricted cubic spline (RCS) analysis were used to examine full-range risk association between HYAL1 and GDM. Additive interactions and multiplicative interactions were employed to test interactive effects of HYAL1 with ceramides species on GDM risk.

RESULTS

Ln HYAL1 was linearly associated with GDM risk and the adjusted OR of HYAL1 ≥ vs. < its median for GDM was significant (1.65, 95%CI: 1.08-2.52). High HYAL1 markedly enhanced the ORs of high ceramide 18:0 for GDM from 2.31 (1.06-5.01) to 6.74 (2.85-16.0), and low ceramide 24:0 from 3.08 (1.33-7.11) to 8.15 (3.03-21.9), with significant additive interactions.

CONCLUSIONS

High HYAL1 in early pregnancy may increase the risk of GDM in Chinese women, possibly via enhancing the effects of high ceramide 18:0 and low ceramide 24:0 on GDM risk.

Dissecting the Interrelationship between COVID-19 and Diabetes Mellitus

COVID-19 disease, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to enormous morbidity and mortality worldwide. After gaining entry into the human host, the virus initially infects the upper and lower respiratory tract, subsequently invading multiple organs, including the pancreas. While on one hand, diabetes mellitus (DM) is a significant risk factor for severe COVID-19 infection and associated death, recent reports have shown the onset of DM in COVID-19-recovered patients. SARS-CoV-2 infiltrates the pancreatic islets and activates stress response and inflammatory signaling pathways, impairs glucose metabolism, and consequently leads to their death. Indeed, the pancreatic autopsy samples of COVID-19 patients reveal the presence of SARS-CoV-2 particles in β-cells. The current review describes how the virus enters the host cells and activates an immunological response. Further, it takes a closer look into the interrelationship between COVID-19 and DM with the aim to provide mechanistic insights into the process by which SARS-CoV-2 infects the pancreas and mediates dysfunction and death of endocrine islets. The effects of known anti-diabetic interventions for COVID-19 management are also discussed. The application of mesenchymal stem cells (MSCs) as a future therapy for pancreatic β-cells damage to reverse COVID-19-induced DM is also emphasized.

Operational Modal Analysis of Near-Infrared Spectroscopy Measure of 2-Month Exercise Intervention Effects in Sedentary Older Adults with Diabetes and Cognitive Impairment

The Global Burden of Disease Study (GBD 2019 Diseases and Injuries Collaborators) found that diabetes significantly increases the overall burden of disease, leading to a 24.4% increase in disability-adjusted life years. Persistently high glucose levels in diabetes can cause structural and functional changes in proteins throughout the body, and the accumulation of protein aggregates in the brain that can be associated with the progression of Alzheimer's Disease (AD). To address this burden in type 2 diabetes mellitus (T2DM), a combined aerobic and resistance exercise program was developed based on the recommendations of the American College of Sports Medicine. The prospectively registered clinical trials (NCT04626453, NCT04812288) involved two groups: an Intervention group of older sedentary adults with T2DM and a Control group of healthy older adults who could be either active or sedentary. The completion rate for the 2-month exercise program was high, with participants completing on an average of 89.14% of the exercise sessions. This indicated that the program was practical, feasible, and well tolerated, even during the COVID-19 pandemic. It was also safe, requiring minimal equipment and no supervision. Our paper presents portable near-infrared spectroscopy (NIRS) based measures that showed muscle oxygen saturation (SmO2), i.e., the balance between oxygen delivery and oxygen consumption in muscle, drop during bilateral heel rise task (BHR) and the 6 min walk task (6MWT) significantly (p < 0.05) changed at the post-intervention follow-up from the pre-intervention baseline in the T2DM Intervention group participants. Moreover, post-intervention changes from pre-intervention baseline for the prefrontal activation (both oxyhemoglobin and deoxyhemoglobin) showed statistically significant (p < 0.05, q < 0.05) effect at the right superior frontal gyrus, dorsolateral, during the Mini-Cog task. Here, operational modal analysis provided further insights into the 2-month exercise intervention effects on the very-low-frequency oscillations (<0.05 Hz) during the Mini-Cog task that improved post-intervention in the sedentary T2DM Intervention group from their pre-intervention baseline when compared to active healthy Control group. Then, the 6MWT distance significantly (p < 0.01) improved in the T2DM Intervention group at post-intervention follow-up from pre-intervention baseline that showed improved aerobic capacity and endurance. Our portable NIRS based measures have practical implications at the point of care for the therapists as they can monitor muscle and brain oxygenation changes during physical and cognitive tests to prescribe personalized physical exercise doses without triggering individual stress response, thereby, enhancing vascular health in T2DM.

Coronary "Microvascular Dysfunction": Evolving Understanding of Pathophysiology, Clinical Implications, and Potential Therapeutics

Until recently, it has been generally held that stable angina pectoris (SAP) primarily reflects the presence of epicardial coronary artery stenoses due to atheromatous plaque(s), while acute myocardial infarction (AMI) results from thrombus formation on ruptured plaques. This concept is now challenged, especially by results of the ORBITA and ISCHEMIA trials, which showed that angioplasty/stenting does not substantially relieve SAP symptoms or prevent AMI or death in such patients. These disappointing outcomes serve to redirect attention towards anomalies of small coronary physiology. Recent studies suggest that coronary microvasculature is often both structurally and physiologically abnormal irrespective of the presence or absence of large coronary artery stenoses. Structural remodelling of the coronary microvasculature appears to be induced primarily by inflammation initiated by mast cell, platelet, and neutrophil activation, leading to erosion of the endothelial glycocalyx. This leads to the disruption of laminar flow and the facilitation of endothelial platelet interaction. Glycocalyx shedding has been implicated in the pathophysiology of coronary artery spasm, cardiovascular ageing, AMI, and viral vasculitis. Physiological dysfunction is closely linked to structural remodelling and occurs in most patients with myocardial ischemia, irrespective of the presence or absence of large-vessel stenoses. Dysfunction includes the impairment of platelet and vascular responsiveness to autocidal coronary vasodilators, such as nitric oxide, prostacyclin, and hydrogen sulphide, and predisposes both to coronary vasoconstriction and to a propensity for microthrombus formation. These findings emphasise the need for new directions in medical therapeutics for patients with SAP, as well as a wide range of other cardiovascular disorders.

The Role of Endothelial Dysfunction in the Pathogenesis of Pregnancy-Related Pathological Conditions: A Review

In the recent decades, endothelial dysfunction (ED) has been recognized as a significant contributing factor in the pathogenesis of many pathological conditions. In interaction with atherosclerosis, hypercholesterolemia, and hypertension, ED plays a crucial role in the pathogenesis of coronary artery disease, chronic renal disease, and microvascular complications in diabetes mellitus. Although ED plays a significant role in the pathogenesis of several pregnancy-related disorders such as preeclampsia, HELLP syndrome, fetal growth restriction, and gestational diabetes mellitus, the exact pathogenetic mechanisms are still a matter of debate. The increased prevalence of these entities in patients with preexisting vascular diseases highlights the essential pathological role of the preexisting ED in these patients. The abnormal uteroplacental circulation and the release of soluble factors from the ischemic placenta into the maternal bloodstream are the main causes of the maternal ED underlying the characteristic preeclamptic phenotype. Besides the increased risk for maternal and fetal poor outcomes, the preexisting ED also increases the risk of development of future cardiovascular diseases in these patients. This study aimed to look deeper into the role of ED in the pathogenesis of several pregnancy-related hypertensive and liver diseases. Hopefully, it could contribute to improvement of the awareness, knowledge, and management of these conditions and also to the reduction of the adverse outcomes and additional long-term cardiovascular complications.

Endothelial Glycocalyx Preservation-Impact of Nutrition and Lifestyle

The endothelial glycocalyx (eGC) is a dynamic hair-like layer expressed on the apical surface of endothelial cells throughout the vascular system. This layer serves as an endothelial cell gatekeeper by controlling the permeability and adhesion properties of endothelial cells, as well as by controlling vascular resistance through the mediation of vasodilation. Pathogenic destruction of the eGC could be linked to impaired vascular function, as well as several acute and chronic cardiovascular conditions. Defining the precise functions and mechanisms of the eGC is perhaps the limiting factor of the missing link in finding novel treatments for lifestyle-related diseases such as atherosclerosis, type 2 diabetes, hypertension, and metabolic syndrome. However, the relationship between diet, lifestyle, and the preservation of the eGC is an unexplored territory. This article provides an overview of the eGC's importance for health and disease and describes perspectives of nutritional therapy for the prevention of the eGC's pathogenic destruction. It is concluded that vitamin D and omega-3 fatty acid supplementation, as well as healthy dietary patterns such as the Mediterranean diet and the time management of eating, might show promise for preserving eGC health and, thus, the health of the cardiovascular system.

Early diabetic kidney disease: Focus on the glycocalyx

The incidence of diabetic kidney disease (DKD) is sharply increasing worldwide. Microalbuminuria is the primary clinical marker used to identify DKD, and its initiating step in diabetes is glomerular endothelial cell dysfunction, particularly glycocalyx impairment. The glycocalyx found on the surface of glomerular endothelial cells, is a dynamic hydrated layer structure composed of pro-teoglycans, glycoproteins, and some adsorbed soluble components. It reinforces the negative charge barrier, transduces the shear stress, and mediates the interaction of blood corpuscles and podocytes with endothelial cells. In the high-glucose environment of diabetes, excessive reactive oxygen species and proinflammatory cytokines can damage the endothelial glycocalyx (EG) both directly and indirectly, which induces the production of microalbuminuria. Further research is required to elucidate the role of the podocyte glycocalyx, which may, together with endothelial cells, form a line of defense against albumin filtration. Interestingly, recent research has confirmed that the negative charge barrier function of the glycocalyx found in the glomerular basement membrane and its repulsion effect on albumin is limited. Therefore, to improve the early diagnosis and treatment of DKD, the potential mechanisms of EG degradation must be analyzed and more responsive and controllable targets must be explored. The content of this review will provide insights for future research.

Major open abdominal surgery is associated with increased levels of endothelial damage and interleukin-6

OBJECTIVE

To examine changes in biomarkers of endothelial glycocalyx shedding, endothelial damage, and surgical stress following major open abdominal surgery and the correlation to postoperative morbidity.

INTRODUCTION

Major abdominal surgery is associated with high levels of postoperative morbidity. Two possible reasons are the surgical stress response and the impairment of the glycocalyx and endothelial cells. Further, the degree of these responses may correlate with postoperative morbidity and complications.

METHODS

A secondary data analysis of prospectively collected data from two cohorts of patients undergoing open liver surgery, gastrectomy, esophagectomy, or Whipple procedure (n = 112). Hemodynamics and blood samples were collected at predefined timestamps and analyzed for biomarkers of glycocalyx shedding (Syndecan-1), endothelial activation (sVEGFR1), endothelial damage (sThrombomodulin (sTM)), and surgical stress (IL6).

RESULTS

Major abdominal surgery led to increased levels of IL6 (0 to 85 pg/mL), Syndecan-1 (17.2 to 46.4 ng/mL), and sVEGFR1 (382.8 to 526.5 pg/mL), peaking at the end of the surgery. In contrast, sTM, did not increase during surgery, but increased significantly following surgery (5.9 to 6.9 ng/mL), peaking at 18 h following the end of surgery. Patients characterized with high postoperative morbidity had higher levels of IL6 (132 vs. 78 pg/mL, p = 0.007) and sVEGFR1 (563.1 vs. 509.4 pg/mL, p = 0.045) at the end of the surgery, and of sTM (8.2 vs. 6.4 ng/mL, p = 0.038) 18 h following surgery.

CONCLUSION

Major abdominal surgery leads to significantly increased levels of biomarkers of endothelial glycocalyx shedding, endothelial damage, and surgical stress, with the highest levels seen in patients developing high postoperative morbidity.

Development of an In Vitro Blood Vessel Model Using Autologous Endothelial Cells Generated from Footprint-Free hiPSCs to Analyze Interactions of the Endothelium with Blood Cell Components and Vascular Implants

Cardiovascular diseases are the leading cause of death globally. Vascular implants, such as stents, are required to treat arterial stenosis or dilatation. The development of innovative stent materials and coatings, as well as novel preclinical testing strategies, is needed to improve the bio- and hemocompatibility of current stents. In this study, a blood vessel-like polydimethylsiloxane (PDMS) model was established to analyze the interaction of an endothelium with vascular implants, as well as blood-derived cells, in vitro. Using footprint-free human induced pluripotent stem cells (hiPSCs) and subsequent differentiation, functional endothelial cells (ECs) expressing specific markers were generated and used to endothelialize an artificial PDMS lumen. The established model was used to demonstrate the interaction of the created endothelium with blood-derived immune cells, which also allowed for real-time imaging. In addition, a stent was inserted into the endothelialized lumen to analyze the surface endothelialization of stents. In the future, this blood vessel-like model could serve as an in vitro platform to test the influence of vascular implants and coatings on endothelialization and to analyze the interaction of the endothelium with blood cell components.

Signaling pathways in vascular function and hypertension: molecular mechanisms and therapeutic interventions

Hypertension is a global public health issue and the leading cause of premature death in humans. Despite more than a century of research, hypertension remains difficult to cure due to its complex mechanisms involving multiple interactive factors and our limited understanding of it. Hypertension is a condition that is named after its clinical features. Vascular function is a factor that affects blood pressure directly, and it is a main strategy for clinically controlling BP to regulate constriction/relaxation function of blood vessels. Vascular elasticity, caliber, and reactivity are all characteristic indicators reflecting vascular function. Blood vessels are composed of three distinct layers, out of which the endothelial cells in intima and the smooth muscle cells in media are the main performers of vascular function. The alterations in signaling pathways in these cells are the key molecular mechanisms underlying vascular dysfunction and hypertension development. In this manuscript, we will comprehensively review the signaling pathways involved in vascular function regulation and hypertension progression, including calcium pathway, NO-NOsGC-cGMP pathway, various vascular remodeling pathways and some important upstream pathways such as renin-angiotensin-aldosterone system, oxidative stress-related signaling pathway, immunity/inflammation pathway, etc. Meanwhile, we will also summarize the treatment methods of hypertension that targets vascular function regulation and discuss the possibility of these signaling pathways being applied to clinical work.

Overview and New Insights into the Metabolic Syndrome: Risk Factors and Emerging Variables in the Development of Type 2 Diabetes and Cerebrocardiovascular Disease

Metabolic syndrome (MetS) is considered a metabolic disorder that has been steadily increasing globally and seems to parallel the increasing prevalence of obesity. It consists of a cluster of risk factors which traditionally includes obesity and hyperlipidemia, hyperinsulinemia, hypertension, and hyperglycemia. These four core risk factors are associated with insulin resistance (IR) and, importantly, the MetS is known to increase the risk for developing cerebrocardiovascular disease and type 2 diabetes mellitus. The MetS had its early origins in IR and syndrome X. It has undergone numerous name changes, with additional risk factors and variables being added over the years; however, it has remained as the MetS worldwide for the past three decades. This overview continues to add novel insights to the MetS and suggests that leptin resistance with hyperleptinemia, aberrant mitochondrial stress and reactive oxygen species (ROS), impaired folate-mediated one-carbon metabolism with hyperhomocysteinemia, vascular stiffening, microalbuminuria, and visceral adipose tissues extracellular vesicle exosomes be added to the list of associated variables. Notably, the role of a dysfunctional and activated endothelium and deficient nitric oxide bioavailability along with a dysfunctional and attenuated endothelial glycocalyx, vascular inflammation, systemic metainflammation, and the important role of ROS and reactive species interactome are discussed. With new insights and knowledge regarding the MetS comes the possibility of new findings through further research.

Impairment of endothelial glycocalyx in atherosclerosis and obesity

Endothelial glycocalyx is a negatively charged gel-like layer located on the apical surface of endothelial cells. It serves as a selective two-way physical barrier between the flowing blood and the endothelium, which regulates the access of macromolecules and of blood cells to the endothelial surface. In addition, endothelial glycocalyx plays a major role in sensing mechanical signals generated by the blood flow and transducing these signals to maintain endothelial functions; Thus, dysfunction or disruption of endothelial glycocalyx in pathological condition leads to endothelial dysfunction and contributes to the development of vascular diseases. In this review, we discuss the impact of atherosclerosis with the following viewpoints: (i) hypercholesterolemic effects on endothelial glycocalyx degradation in animal models and human patients, (ii) disruption of endothelial glycocalyx by atherogenic lipoproteins, (iii) proatherogenic disturbed flow effects on endothelial glycocalyx degradation, (iv) pathological consequences of the loss of glycocalyx integrity in atherogenesis, and (v) therapeutic effect of glycocalyx supplementation on atherosclerosis development. Additionally, we also discuss recent studies in pathological effects of obesity on the disruption of endothelial glycocalyx.

Mineralocorticoid receptor antagonism in diabetes reduces albuminuria by preserving the glomerular endothelial glycocalyx

The glomerular endothelial glycocalyx (GEnGlx) forms the first part of the glomerular filtration barrier. Previously, we showed that mineralocorticoid receptor (MR) activation caused GEnGlx damage and albuminuria. In this study, we investigated whether MR antagonism could limit albuminuria in diabetes and studied the site of action. Streptozotocin-induced diabetic Wistar rats developed albuminuria, increased glomerular albumin permeability (Ps'alb), and increased glomerular matrix metalloproteinase (MMP) activity with corresponding GEnGlx loss. MR antagonism prevented albuminuria progression, restored Ps'alb, preserved GEnGlx, and reduced MMP activity. Enzymatic degradation of the GEnGlx negated the benefits of MR antagonism, confirming their dependence on GEnGlx integrity. Exposing human glomerular endothelial cells (GEnC) to diabetic conditions in vitro increased MMPs and caused glycocalyx damage. Amelioration of these effects confirmed a direct effect of MR antagonism on GEnC. To confirm relevance to human disease, we used a potentially novel confocal imaging method to show loss of GEnGlx in renal biopsy specimens from patients with diabetic nephropathy (DN). In addition, patients with DN randomized to receive an MR antagonist had reduced urinary MMP2 activity and albuminuria compared with placebo and baseline levels. Taken together, our work suggests that MR antagonists reduce MMP activity and thereby preserve GEnGlx, resulting in reduced glomerular permeability and albuminuria in diabetes.

Diabetic endothelial microangiopathy and pulmonary dysfunction

Type 2 diabetes mellitus (T2DM) is a widespread metabolic condition with a high global morbidity and mortality rate that affects the whole body. Their primary consequences are mostly caused by the macrovascular and microvascular bed degradation brought on by metabolic, hemodynamic, and inflammatory variables. However, research in recent years has expanded the target organ in T2DM to include the lung. Inflammatory lung diseases also impose a severe financial burden on global healthcare. T2DM has long been recognized as a significant comorbidity that influences the course of various respiratory disorders and their disease progress. The pathogenesis of the glycemic metabolic problem and endothelial microangiopathy of the respiratory disorders have garnered more attention lately, indicating that the two ailments have a shared history. This review aims to outline the connection between T2DM related endothelial cell dysfunction and concomitant respiratory diseases, including Coronavirus disease 2019 (COVID-19), asthma, chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF).

The glycocalyx and calcium dynamics in endothelial cells

The endothelial glycocalyx is a dynamic surface layer composed of proteoglycans, glycoproteins, and glycosaminoglycans with a key role in maintaining endothelial cell homeostasis. Its functions include the regulation of endothelial barrier permeability and stability, the transduction of mechanical forces from the vascular lumen to the vessel walls, serving as a binding site to multiple growth factors and vasoactive agents, and mediating the binding of platelets and the migration of leukocytes during an inflammatory response. Many of these processes are associated with changes in intracellular calcium levels that may occur through mechanisms that alter calcium entry in the endothelium or the release of calcium from the endoplasmic reticulum. Whether the endothelial glycocalyx can regulate calcium dynamics in endothelial cells is unresolved. Interestingly, during cardiovascular disease progression, changes in calcium dynamics are observed in association with the degradation of the glycocalyx and with changes in barrier permeability and vascular reactivity. Herein, we aim to provide a summarized overview of what is known regarding the role of the glycocalyx as a regulator of endothelial barrier and vascular reactivity during homeostatic and pathological conditions and to provide a perspective on how such processes may relate to calcium dynamics in endothelial cells, exploring a possible connection between components of the glycocalyx and calcium-sensitive pathways in the endothelium.

Microvascular perfusion, perfused boundary region and glycocalyx shedding in patients with autosomal dominant polycystic kidney disease: results from the GlycoScore III study

Background

Vascular abnormalities and endothelial dysfunction are part of the spectrum of autosomal dominant polycystic kidney disease (ADPKD). The mechanisms behind these manifestations, including potential effects on the endothelial surface layer (ESL) and glycocalyx integrity, remain unknown.

Methods

Forty-five ambulatory adult patients with ADPKD were enrolled in this prospective, observational, cross-sectional, single-centre study. Fifty-one healthy volunteers served as a control group. All participants underwent real-time microvascular perfusion measurements of the sublingual microcirculation using sidestream dark field imaging. After image acquisition, the perfused boundary region (PBR), an inverse parameter for red blood cell (RBC) penetration into the ESL, was automatically calculated. Microvascular perfusion was assessed by RBC filling and capillary density. Concentrations of circulating glycocalyx components were determined by enzyme-linked immunosorbent assay.

Results

ADPKD patients showed a significantly larger PBR compared with healthy controls (2.09 ± 0.23 µm versus 1.79 ± 0.25 µm; P < .001). This was accompanied by significantly lower RBC filling (70.4 ± 5.0% versus 77.9 ± 5.4%; P < .001) as well as a higher valid capillary density {318/mm² [interquartile range (IQR) 269-380] versus 273/mm² [230-327]; P = .007}. Significantly higher plasma concentrations of heparan sulphate (1625 ± 807 ng/ml versus 1329 ± 316 ng/ml; P = .034), hyaluronan (111 ng/ml [IQR 79-132] versus 92 ng/ml [82-98]; P = .042) and syndecan-1 were noted in ADPKD patients compared with healthy controls (35 ng/ml [IQR 27-57] versus 29 ng/ml [23-42]; P = .035).

Conclusions

Dimensions and integrity of the ESL are impaired in ADPKD patients. Increased capillary density may be a compensatory mechanism for vascular dysfunction to ensure sufficient tissue perfusion and oxygenation.

Arterial hypertension as a consequence of endothelial glycocalyx dysfunction: a modern view of the problem of cardiovascular diseases

Arterial hypertension (AH) is a leading risk factor for the development of cardiovascular, cerebrovascular, and renal diseases, which are among the top 10 most common causes of death in the world. The etiology of hypertension has not been fully elucidated, but it has been established that endothelial dysfunction is the most significant pathogenetic link in the formation and progression of the disease. The data obtained in the last 10-15 years on endothelial glycocalyx (eGC) studies indicate that endothelial dysfunction is preceded 

by destabilization and shedding of eGC with the appearance of its soluble components in the blood, which is equivalent to a process that can be designated as eGC dysfunction. Signs of eGC dysfunction are expressed in the development of hypertension, diseases of the cardiovascular system, and their complications. The purpose of this review is to analyze and substantiate the pathophysiological role of eGC dysfunction in hypertension and cardiovascular diseases and to describe approaches for its assessment and pharmacological correction. Abstracts and full-size articles of 425 publications in Pubmed/MEDLINE databases over 20 years were studied. The review discusses the role of eGC in the regulation of vascular tone, endothelial barrier function, and anti-adhesive properties of eGC. Modifications of eGC under the influence of pro-inflammatory stimuli, changes in eGC with age, and with increased salt load are considered. The aspect associated with eGC dysfunction in atherosclerosis, hyperglycemia and hypertension is covered. Assessment of eGC dysfunction is difficult but can be performed by indirect methods, in particular by detecting eGC components in blood. A brief description of the main approaches to pharmacoprevention and pharmacocorrection of hypertension is given from the position of exposure effects on eGC, which currently has more a fundamental than practical orientation. This opens up great opportunities for clinical studies of eGC dysfunction for the prevention and treatment of hypertension and justifies a new direction in the clinical pharmacology of antihypertensive drugs.

Emerging Insights into Glomerular Vascular Pole and Microcirculation

The glomerular vascular pole is the gate for the afferent and efferent arterioles and mesangial cells and a frequent location of peripolar cells with an unclear function. It has been studied in definitive detail for >30 years, and functionally interrogated in the context of signal transduction from the macula densa to the mesangial cells and afferent arteriolar smooth muscle cells from 10 to 20 years ago. Two recent discoveries shed additional light on the vascular pole, with possibly far-reaching implications. One, which uses novel serial section electron microscopy, reveals a shorter capillary pathway between the basins of the afferent and efferent arterioles. Such a pathway, when patent, may short-circuit the multitude of capillaries in the glomerular tuft. Notably, this shorter capillary route is enclosed within the glomerular mesangium. The second study used anti-Thy1.1-induced mesangiolysis and intravital microscopy to unequivocally establish in vivo the long-suspected contractile function of mesangial cells, which have the ability to change the geometry and curvature of glomerular capillaries. These studies led me to hypothesize the existence of a glomerular perfusion rheostat, in which the shorter path periodically fluctuates between being more and less patent. This action reduces or increases blood flow through the entire glomerular capillary tuft. A corollary is that the GFR is a net product of balance between the states of capillary perfusion, and that deviations from the balanced state would increase or decrease GFR. Taken together, these studies may pave the way to a more profound understanding of glomerular microcirculation under basal conditions and in progression of glomerulopathies.

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.

N-Acetylcysteine and Other Sulfur-Donors as a Preventative and Adjunct Therapy for COVID-19

The airway epithelial glycocalyx plays an important role in preventing severe acute respiratory syndrome coronavirus 2 entry into the epithelial cells, while the endothelial glycocalyx contributes to vascular permeability and tone, as well as modulating immune, inflammatory, and coagulation responses. With ample evidence in the scientific literature that coronavirus disease 2019 (COVID-19) is related to epithelial and endothelial dysfunction, preserving the glycocalyx should be the main focus of any COVID-19 treatment protocol. The most studied functional unit of the glycocalyx is the glycosaminoglycan heparan sulfate, where the degree and position of the sulfate groups determine the biological activity. N-acetylcysteine (NAC) and other sulfur donors contribute to the inorganic sulfate pool, the rate-limiting molecule in sulfation. NAC is not only a precursor to glutathione but also converts to hydrogen sulfide, inorganic sulfate, taurine, Coenzyme A, and albumin. By optimising inorganic sulfate availability, and therefore sulfation, it is proposed that COVID-19 can be prevented or at least most of the symptoms attenuated. A comprehensive COVID-19 treatment protocol is needed to preserve the glycocalyx in both the prevention and treatment of COVID-19. The use of NAC at a dosage of 600 mg bid for the prevention of COVID-19 is proposed, but a higher dosage of NAC (1200 mg bid) should be administered upon the first onset of symptoms. In the severe to critically ill, it is advised that IV NAC should be administered immediately upon hospital admission, and in the late stage of the disease, IV sodium thiosulfate should be considered. Doxycycline as a protease inhibitor will prevent shedding and further degradation of the glycocalyx.

Endothelial Glycocalyx Degradation in Critical Illness and Injury

The endothelial glycocalyx is a gel-like layer on the luminal side of blood vessels that is composed of glycosaminoglycans and the proteins that tether them to the plasma membrane. Interest in its properties and function has grown, particularly in the last decade, as its importance to endothelial barrier function has come to light. Endothelial glycocalyx studies have revealed that many critical illnesses result in its degradation or removal, contributing to endothelial dysfunction and barrier break-down. Loss of the endothelial glycocalyx facilitates the direct access of immune cells and deleterious agents (e.g., proteases and reactive oxygen species) to the endothelium, that can then further endothelial cell injury and dysfunction leading to complications such as edema, and thrombosis. Here, we briefly describe the endothelial glycocalyx and the primary components thought to be directly responsible for its degradation. We review recent literature relevant to glycocalyx damage in several critical illnesses (sepsis, COVID-19, trauma and diabetes) that share inflammation as a common denominator with actions by several common agents (hyaluronidases, proteases, reactive oxygen species, etc.). Finally, we briefly cover strategies and therapies that show promise in protecting or helping to rebuild the endothelial glycocalyx such as steroids, protease inhibitors, anticoagulants and resuscitation strategies.

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.

Two Methods of AuNPs Synthesis Induce Differential Vascular Effects. The Role of the Endothelial Glycocalyx

AuNPs are synthesized through several methods to tune their physicochemical properties. Although AuNPs are considered biocompatible, a change in morphology or properties can modify their biological impact. In this work, AuNPs (~12 to 16 nm) capping with either sodium citrate (CA) or gallic acid (GA) were evaluated in a rat aorta ex vivo model, which endothelial inner layer surface is formed by glycocalyx (hyaluronic acid, HA, as the main component), promoting vascular processes, most of them dependent on nitric oxide (NO) production. Results showed that contractile effects were more evident with AuNPsCA, while dilator effects predominated with AuNPsGA. Furthermore, treatments with AuNPsCA and AuNPsGA in the presence or absence of glycocalyx changed the NO levels, differently. This work contributes to understanding the biological effects of AuNPs with different capping agents, as well as the key role that of HA in the vascular effects induced by AuNPs in potential biomedical applications.

Sulodexide Significantly Improves Endothelial Dysfunction and Alleviates Chest Pain and Palpitations in Patients With Long-COVID-19: Insights From TUN-EndCOV Study

Objective

Non-respiratory long-coronavirus disease 2019 (COVID-19) symptoms are mainly related to a long-lasting endothelial dysfunction and microcirculation impairment. We hypothesized that Sulodexide, a purified glycosaminoglycan mixture with a beneficial endothelial effect in arterial and venous peripheral diseases, may be effective in a subset of patients with long COVID-19.

Approach and Results

We conducted a multicenter prospective quasi-experimental study. A total of 290 patients from the TUN-EndCOV study with long-COVID-19 symptoms and endothelial dysfunction were included. The endothelial function was clinically assessed using a post-occlusive reactive hyperemia protocol with finger thermal monitoring device. Endothelial quality index (EQI) was assessed at inclusion and at 21 days later. The study population was assigned to a sulodexide group (144 patients) or a no-medical treatment group (146 patients). Clinical characteristics were similar at inclusion in the two groups. Fatigue, shortness of breath, and chest pain were the most common symptoms, respectively, 54.5, 53.8, and 28.3%. At 21 days, the sulodexide group improved significantly better than the no-medical treatment group in chest pain (83.7 vs. 43.6%, p < 10-3), palpitations (85.2 vs. 52.9%, p = 0.009), and endothelial function [median delta-EQI 0.66 (0.6) vs. 0.18 (0.3); p < 10-3]. Endothelial function improvement was significantly correlated with chest pain and palpitations recovery (AUC, i.e., area under the curve = 0.66, CI [0.57- 0.75], p = 0.001 and AUC = 0.60, CI [0.51- 0.69], p = 0.03, respectively).

Conclusion

Sulodexide significantly improves long-lasting post-COVID-19 endothelial dysfunction and alleviates chest pain and palpitations.

The role of the cell surface glycocalyx in drug delivery to and through the endothelium

Cell membranes are key interfaces where materials engineering meets biology. Traditionally regarded as just the location of receptors regulating the uptake of molecules, we now know that all mammalian cell membranes are 'sugar coated'. These sugars, or glycans, form a matrix bound at the cell membrane via proteins and lipids, referred to as the glycocalyx, which modulate access to cell membrane receptors crucial for interactions with drug delivery systems (DDS). Focusing on the key blood-tissue barrier faced by most DDS to enable transport from the place of administration to target sites via the circulation, we critically assess the design of carriers for interactions at the endothelial cell surface. We also discuss the current challenges for this area and provide opportunities for future research efforts to more fully engineer DDS for controlled, efficient, and targeted interactions with the endothelium for therapeutic application.

The Mighty Mitochondria Are Unifying Organelles and Metabolic Hubs in Multiple Organs of Obesity, Insulin Resistance, Metabolic Syndrome, and Type 2 Diabetes: An Observational Ultrastructure Study

Mitochondria (Mt) are essential cellular organelles for the production of energy and thermogenesis. Mt also serve a host of functions in addition to energy production, which include cell signaling, metabolism, cell death, and aging. Due to the central role of Mt in metabolism as metabolic hubs, there has been renewed interest in how Mt impact metabolic pathways and multiple pathologies. This review shares multiple observational ultrastructural findings in multiple cells and organs to depict aberrant mitochondrial (aMt) remodeling in pre-clinical rodent models. Further, it is intended to show how remodeling of Mt are associated with obesity, insulin resistance, metabolic syndrome (MetS), and type 2 diabetes mellitus (T2DM). Specifically, Mt remodeling in hypertensive and insulin-resistant lean models (Ren2 rat models), lean mice with streptozotocin-induced diabetes, obesity models including diet-induced obesity, genetic leptin-deficient ob/ob, and leptin receptor-deficient db/db diabetic mice are examined. Indeed, aMt dysfunction and damage have been implicated in multiple pathogenic diseases. Manipulation of Mt such as the induction of Mt biogenesis coupled with improvement of mitophagy machinery may be helpful to remove leaky damaged aMt in order to prevent the complications associated with the generation of superoxide-derived reactive oxygen species and the subsequent reactive species interactome. A better understanding of Mt remodeling may help to unlock many of the mysteries in obesity, insulin resistance, MetS, T2DM, and the associated complications of diabetic end-organ disease.

Albumin, Oral Contraceptives, and Venous Thromboembolism Risk in Astronauts

BACKGROUND

A venous thromboembolism (VTE) event occurred in a female astronaut during long-duration spaceflight. Multiple factors may have contributed to this risk, including the use of combined (progestin + estrogen) oral contraceptives (cOC).

METHODS

Biochemistry data from 65 astronauts were evaluated for associations with cOC use and with sex.

RESULTS

The female astronauts who used cOCs had lower concentrations of serum albumin and higher concentrations of transferrin, a protein involved in the clotting cascade, than the male astronauts and the female astronauts who were not taking cOCs (P<0.001). The women who used cOCs had higher serum concentrations of the acute phase reactant ceruloplasmin during flight and cortisol (P<0.001) than the men and the women who were not taking cOCs; they also had higher calculated whole blood viscosity than women not taking cOCs (P<0.001).

CONCLUSIONS

Lower circulating concentrations of albumin, higher concentrations of transferrin, and elevated markers of inflammation all could contribute to an increased risk of VTE during spaceflight. These changes, in association with a higher blood viscosity can directly affect endothelial glycocalyx integrity and hypercoagulability status, both of which contribute to VTE risk in terrestrial populations.

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.

Targeting repair of the vascular endothelium and glycocalyx after traumatic injury with plasma and platelet resuscitation

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Endothelial glycocalyx shedding is a key instigator of the endotheliopathy of trauma.

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Plasma and platelet transfusions preserve vascular integrity in pre-clinical models.

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However, platelets may be less effective than plasma in preserving the glycocalyx.

Severely injured patients with hemorrhagic shock can develop endothelial dysfunction, systemic inflammation, and coagulation disturbances collectively known as the endotheliopathy of trauma (EOT). Shedding of the endothelial glycocalyx occurs early after injury, contributes to breakdown of the vascular barrier, and plays a critical role in the pathogenesis of multiple organ dysfunction, leading to poor outcomes in trauma patients. In this review we discuss (i) the pathophysiology of endothelial glycocalyx and vascular barrier breakdown following hemorrhagic shock and trauma, and (ii) the role of plasma and platelet transfusion in maintaining the glycocalyx and vascular endothelial integrity.

Simultaneous quantification of selected glycosaminoglycans by butanolysis-based derivatization and LC-SRM/MS analysis for assessing glycocalyx disruption in vitro and in vivo

Glycosaminoglycans (GAGs) constitute the main building blocks of the endothelial glycocalyx (GLX), and disruption of GLX initiates and promotes endothelial dysfunction. Here, we aimed to develop a novel, specific and accurate LC-SRM/MS-based method for glycosaminoglycans (GAGs) profiling. The method involved butanolysis derivatization to facilitate GAG-specific disaccharide generation and its subsequent retention in LC-reversed-phase mode followed by mass spectrometric detection performed in positive ion-selected reaction monitoring (SRM) mode. GAG contents were measured in media of endothelial cells (EA.hy926) subjected to various GAG-degrading enzymes, as well as in murine plasma and urine in apolipoprotein E/low-density lipoprotein receptor-deficient (ApoE/LDLR -/-) mice and age-matched wild-type C57BL/6 mice. Alternatively, GLX disruption was verified by atomic force microscopy (AFM)-based analysis of GLX thickness. The proposed assay to quantify GAG-specific disaccharides presented high sensitivity for each of the analytes (LLOQ: 0.05-0.1 μg/mL) as well as accuracy and precision (86.8-114.9% and 2.0-14.3%, respectively). In medium of EA.hy926 cells subjected to GAG-degrading enzymes various GAG-specific disaccharides indicating the degradation of keratan sulphate (KS), heparan sulphate (HS), chondroitin sulphate (CHS) or hyaluronan (HA) were detected as predicted based on the characteristics of individual enzyme activity. In turn, AFM-based assessment of GLX thickness was reduced to a similar extent by all single enzyme treatments, whereas the most prominent reduction of GLX thickness was detected following the enzyme mixture. Plasma measurements of GAGs revealed age- and hypercholesterolemia-dependent decrease in GAGs concentration. In summary, a novel LC-SRM/MS-based method for GAG profiling was proposed that may inform on GLX status in cell culture for both in vitro and in vivo conditions.

Hyaluronic acid plasma levels during high versus low tidal volume ventilation in a porcine sepsis model

Background

Shedding of the endothelial glycocalyx can be observed regularly during sepsis. Moreover, sepsis may be associated with acute respiratory distress syndrome (ARDS), which requires lung protective ventilation with the two cornerstones of application of low tidal volume and positive end-expiratory pressure. This study investigated the effect of a lung protective ventilation on the integrity of the endothelial glycocalyx in comparison to a high tidal volume ventilation mode in a porcine model of sepsis-induced ARDS.

Methods

After approval by the State and Institutional Animal Care Committee, 20 male pigs were anesthetized and received a continuous infusion of lipopolysaccharide to induce septic shock. The animals were randomly assigned to either low tidal volume ventilation, high tidal volume ventilation, or no-LPS-group groups and observed for 6 h. In addition to the gas exchange parameters and hematologic analyses, the serum hyaluronic acid concentrations were determined from central venous blood and from pre- and postpulmonary and pre- and postcerebral circulation. Post-mortem analysis included histopathological evaluation and determination of the pulmonary and cerebral wet-to-dry ratios.

Results

Both sepsis groups developed ARDS within 6 h of the experiment and showed significantly increased serum levels of hyaluronic acid in comparison to the no-LPS-group. No significant differences in the hyaluronic acid concentrations were detected before and after pulmonary and cerebral circulation. There was also no significant difference in the serum hyaluronic acid concentrations between the two sepsis groups. Post-mortem analysis showed no significant difference between the two sepsis groups.

Conclusion

In a porcine model of septic shock and ARDS, the serum hyaluronic acid levels were significantly elevated in both sepsis groups in comparison to the no-LPS-group. Intergroup comparison between lung protective ventilated and high tidal ventilated animals revealed no significant differences in the serum hyaluronic acid levels.

Glycated Haemogloin, Fasting Plasma Glucose, Plasminogen Activator Inhibitor Type-1, and Soluble Thrombomodulin Levels in Patients with Type 2 Diabetes Mellitus

Diabetes mellitus has become increasingly prevalent over the years. The chronic hyperglycaemia of diabetes is associated with long-term damage, dysfunctions, and failure of different organs suggesting that the most effective tool to prevent complications is the effective control of hyperglycaemia itself. The study is set to determine the effect of glycemic control on plasminogen activator inhibitor type 1 (PAI-1), soluble thrombomodulin (STM) alongside fasting plasma glucose (FPG) and glycated hemoglobin (HbA1c) among type 2 diabetic subjects. One hundred diabetic subjects accessing care at the University of Calabar Teaching Hospital Calabar and 100 non -diabetics that served as controls were enrolled. Blood samples from participants were analyzed for FPG, HbA1c, PAI-1 and STM by standard methods. The result shows 74% of the diabetic to be females. Half of the diabetics were managed on only oral anti-diabetic drugs while the remaining half were either on insulin injection or a combination of oral and insulin injection.  Poor glycemic control was observed in 56% of the studied subjects. The mean age of 54.69 ± 9.94 years for the diabetics was comparable to the age-matched controls (p=.097). Diabetics showed significantly higher FPG, HbA1c, PAI-1and STM (P=0.001) compared to control values. Correlations between STM, PAI 1 and glycated hemoglobin (figures 2 p=0.001, p =0.001) and STM, PAI-1 and FPG revealed significantly robust association (p=0.001, p=0.001).  The study concludes that there is poor glycemic control among the treated diabetic subjects with PAI-1 and STM showing a very strong positive correlation with HbA1c than FPG.

Endothelial glycocalyx degradation during sepsis: Causes and consequences

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The endothelial glycocalyx is a ubiquitous intravascular structure essential for vascular homeostasis.

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During sepsis, the glycocalyx is degraded via the collective action of a variety of redundant sheddases, the regulation of which remains the focus of active investigation.

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Septic loss of the glycocalyx imparts both local vascular injury (leading to acute respiratory distress syndrome and acute kidney injury) as well as the systemic consequences of circulating glycosaminoglycan fragments (leading to cognitive dysfunction).

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Glycocalyx degradation during sepsis is potentially shaped by clinically-modifiable factors, suggesting opportunities for therapeutic intervention to mitigate the end-organ consequences of sepsis.

The glycocalyx is a ubiquitous structure found on endothelial cells that extends into the vascular lumen. It is enriched in proteoglycans, which are proteins attached to the glycosaminoglycans heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate, and hyaluronic acid. In health and disease, the endothelial glycocalyx is a central regulator of vascular permeability, inflammation, coagulation, and circulatory tonicity. During sepsis, a life-threatening syndrome seen commonly in hospitalized patients, the endothelial glycocalyx is degraded, significantly contributing to its many clinical manifestations. In this review we discuss the intrinsically linked mechanisms responsible for septic endothelial glycocalyx destruction: glycosaminoglycan degradation and proteoglycan cleavage. We then examine the consequences of local endothelial glycocalyx loss to several organ systems and the systemic consequences of shed glycocalyx constituents. Last, we explore clinically relevant non-modifiable and modifiable factors that exacerbate or protect against endothelial glycocalyx shedding during sepsis.