Negative correlation between serum syndecan-1 and apolipoprotein A1 in patients with type 2 diabetes mellitus

Acute pyelonephritis in pregnancy and plasma syndecan-1: evidence of glycocalyx involvement

BACKGROUND

Acute pyelonephritis, a risk factor for maternal sepsis, adult respiratory distress syndrome, and preterm labor, is a frequent cause of hospitalization. This condition is characterized by excessive intravascular inflammation and endothelial cell activation and dysfunction. Syndecan-1, a major component of the glycocalyx, is a gel-like layer that covers the luminal surface of healthy endothelial cells, preserving and mediating many endothelial functions. During pregnancy, there is an additional potential source of syndecan-1, the "syncytiotrophoblast glycocalyx," which lines the intervillous space. Insults that damage the glycocalyx lead to a shedding of syndecan-1 into the circulation. Hence, syndecan-1 has been proposed as a marker of endothelial injury in conditions such as sepsis, trauma, cardiovascular disease, and diabetes mellitus.

OBJECTIVE

The objective of this study was to determine whether the plasma syndecan-1 concentration changes in women with acute pyelonephritis in the presence or absence of bacteremia.

STUDY DESIGN

This cross-sectional study included three groups: (1) non-pregnant women (n = 25); (2) women with an uncomplicated pregnancy from whom samples were collected preterm (n = 61) or at term (n = 69); and (3) pregnant women diagnosed with acute pyelonephritis from whom samples were collected at the time of diagnosis during the second and third trimesters (n = 33). The diagnosis of acute pyelonephritis was based on clinical findings and a positive urine culture for bacteria. Blood culture results were available in 85% (28/33) of women with acute pyelonephritis. Plasma concentrations of syndecan-1 were determined by a validated immunoassay.

RESULTS

(1) Women with an uncomplicated pregnancy had a higher plasma concentration of syndecan-1 than non-pregnant women. The geometric mean (95% confidence interval [CI]) of syndecan-1 concentration was 51.0 (12.1-216.1) ng/mL in non-pregnant controls; 1280 (365-4487) ng/mL in normal preterm gestations; and 1786 (546-5834) ng/mL in normal term gestations (adjusted p < .005 for all three between group comparisons); (2) plasma syndecan-1 concentrations increased with gestational age among women with a normal pregnancy (p < .001, R² = 0.27); (3) syndecan-1 multiple of the mean (MoM) values in pregnant patients with acute pyelonephritis were higher than those in normal pregnant women based on second- and third-trimester samples (p = .048, 1.26-fold change). The increase was driven primarily by cases with a positive blood culture (p = .009, 1.74-fold change); (4) when data from third-trimester samples were compared, overall differences in syndecan-1 MoM values between cases and controls were slightly larger (p = .03, 1.36- fold change), which were especially contributed to by cases with a positive blood culture (p = .023, fold change 1.79-fold change).

CONCLUSIONS

Plasma syndecan-1 concentration is higher in pregnant women and increases as a function of gestational age. Patients with acute pyelonephritis have a higher plasma concentration of syndecan-1, and this is particularly the case in the presence of bacteremia.

Association between endothelial biomarkers and lipid and glycemic levels: a cross-sectional study with diabetic patients

Background: Biomarkers can help understand the impact of achieving therapeutic goals in developing vascular diseases in diabetics. Aim: To assess the association between lipid and glycemic profiles and endothelial biomarkers in diabetics. Methods: Cross-sectional study that evaluated lipid and glycemic levels and biomarkers (VCAM-1, Sdc-1, FGF-23 and KIM-1 in diabetics. Results: Higher VCAM-1 levels were associated with higher low-density lipoprotein cholesterol and non-high-density lipoprotein (HDL) cholesterol levels (in the group with inadequate glycohemoglobin A1c [HbA1c] levels), with higher glycemic levels (in the group with inadequate HDL cholesterol levels) and with lower HDL cholesterol levels (both groups). VCAM-1 was independently associated with not achieving adequate HbA1c levels. Conclusion: In uncontrolled diabetics, VCAM-1 was independently associated with having inadequate HbA1c levels, suggesting they may already have endothelial damage.

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.

Association of endothelial glycocalyx shedding and coronary microcirculation assessed by an angiography-derived index of microcirculatory resistance in patients with suspected coronary artery disease

Background

The endothelial glycocalyx (EG) is essential for maintaining microvascular homeostasis. However, the relationship between the EG and coronary microcirculation remains to be elucidated. One of the main components of EG is syndecan-1, and its shedding has been claimed to represent the state of the EG. In this study, we aimed to analyze the association between syndecan-1 and the coronary microcirculation.

Methods

We enrolled suspected coronary artery disease (CAD) patients who consecutively underwent coronary angiography (CAG) and angiography-based analysis of physiological indices in the left anterior descending artery (LAD). Serum syndecan-1 was measured by enzyme-linked immunosorbent assay (ELISA). The coronary microcirculation was evaluated by the presence of coronary microvascular dysfunction (CMD) and an impaired microvascular vasodilatory capacity (IMVC), which were quantified by an angiography-derived index of microcirculatory resistance (IMRangio) in the maximum hyperemic state (H-IMRangio) induced by adenosine triphosphate and the ratio (RRRangio) of IMRangio in the non-hyperemic phase to H-IMRangio, respectively.

Results

A total of 528 patients were enrolled in this study. There was no difference in epicardial coronary complexity between patients with high syndecan-1 (HSG) and low syndecan-1 (LSG) levels grouped by the median concentration of syndecan-1 (SYNTAX: 7[3, 10] vs. 9[4, 12], P = 0.15). However, H-IMRangio and RRRangio were different between the LSG and HSG groups (H-IMRangio: 23.64 ± 6.28 vs. 27.67 ± 5.59, P < 0.01; RRRangio: 1.74[1.46, 2.08] vs. 1.55[1.34, 1.72], P < 0.01). Patients with CMD (H-IMRangio > 25) and patients with IMVC (RRRangio below the median value) both had higher syndecan-1 levels (CMD: 86.44 ± 54.15 vs. 55.2 ± 43.72, P < 0.01; IMVC: 83.86 ± 55.41 vs. 59.68 ± 45.06, P < 0.01). After adjustment for confounding factors, HSG remained associated with the presence of CMD and IMVC (CMD: odds ratio [OR]: 2.769, P < 0.01; IMVC: OR: 1.908, P < 0.01).

Conclusion

High levels of syndecan-1 are independently associated with the presence of CMD and IMVC among patients with suspected CAD.

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.

Hyperglycemia-induced effects on glycocalyx components in the retina

PURPOSE

Diabetic retinopathy is a vision-threatening complication of diabetes characterized by endothelial injury and vascular dysfunction. The loss of the endothelial glycocalyx, a dynamic layer lining all endothelial cells, contributes to several microvascular pathologies, including an increase in vascular permeability, leukocyte plugging, and capillary occlusion, and may drive the progression of retinopathy. Previously, a significant decrease in glycocalyx thickness has been observed in diabetic retinas. However, the effects of diabetes on specific components of the retinal glycocalyx have not yet been studied. Therefore, the aim of our study was to investigate changes in synthesis, expression, and shedding of retinal glycocalyx components induced by hyperglycemia, which could provide a novel therapeutic target for diabetic retinopathy.

METHODS

Primary rat retinal microvascular endothelial cells (RRMECs) were grown under normal glucose (5 mM) or high-glucose (25 mM) conditions for 6 days. The mRNA and protein levels of the glycocalyx components were examined using qRT-PCR and Western blot analysis, respectively. Further, mass spectrometry was used to analyze protein intensities of core proteins. In addition, the streptozotocin-induced Type 1 diabetic rat model was used to study changes in the expression of the retinal glycocalyx in vivo. The shedding of the glycocalyx was studied in both culture medium and in plasma using Western blot analysis.

RESULTS

A significant increase in the shedding of syndecan-1 and CD44 was observed both in vitro and in vivo under high-glucose conditions. The mRNA levels of syndecan-3 were significantly lower in the RRMECs grown under high glucose conditions, whereas those of syndecan-1, syndecan-2, syndecan-4, glypican-1, glypican-3, and CD44 were significantly higher. The protein expression of syndecan-3 and glypican-1 in RRMECs was reduced considerably following exposure to high glucose, whereas that of syndecan-1 and CD44 increased significantly. In addition, mass spectrometry data also suggests a significant increase in syndecan-4 and a significant decrease in glypican-3 protein levels with high glucose stimulation. In vivo, our data also suggest a significant decrease in the mRNA transcripts of syndecan-3 and an increase in mRNA levels of glypican-1 and CD44 in the retinas of diabetic rats. The diabetic rats exhibited a significant reduction in the retinal expression of syndecan-3 and CD44. However, the expression of syndecan-1 and glypican-1 increased significantly in the diabetic retina.

CONCLUSIONS

One of the main findings of our study was the considerable diversity of glucose-induced changes in expression and shedding of various components of endothelial glycocalyx, for example, increased endothelial and retinal syndecan-1, but decreased endothelial and retinal syndecan-3. This indicates that the reported decrease in the retinal glycocalyx in diabetes in not a result of a non-specific shedding mechanism. Moreover, mRNA measurements indicated a similar diversity, with increases in endothelial and/or retinal levels of syndecan-1, glypican-1, and CD44, but a decrease for syndecan-3, with these increases in mRNA potentially a compensatory reaction to the overall loss of glycocalyx.

Heparan Sulfate Proteoglycans in Diabetes

Diabetes is a complex disorder responsible for the mortality and morbidity of millions of individuals worldwide. Although many approaches have been used to understand and treat diabetes, the role of proteoglycans, in particular heparan sulfate proteoglycans (HSPGs), has only recently received attention. The HSPGs are heterogeneous, highly negatively charged, and are found in all cells primarily attached to the plasma membrane or present in the extracellular matrix (ECM). HSPGs are involved in development, cell migration, signal transduction, hemostasis, inflammation, and antiviral activity, and regulate cytokines, chemokines, growth factors, and enzymes. Hyperglycemia, accompanying diabetes, increases reactive oxygen species and upregulates the enzyme heparanase that degrades HSPGs or affects the synthesis of the HSPGs altering their structure. The modified HSPGs in the endothelium and ECM in the blood vessel wall contribute to the nephropathy, cardiovascular disease, and retinopathy seen in diabetes. Besides the blood vessel, other cells and tissues in the heart, kidney, and eye are affected by diabetes. Although not well understood, the adipose tissue, intestine, and brain also reveal HSPG changes associated with diabetes. Further, HSPGs are significantly involved in protecting the β cells of the pancreas from autoimmune destruction and could be a focus of prevention of type I diabetes. In some circumstances, HSPGs may contribute to the pathology of the disease. Understanding the role of HSPGs and how they are modified by diabetes may lead to new treatments as well as preventative measures to reduce the morbidity and mortality associated with this complex condition.

Circulating Heparan Sulfate Proteoglycans as Biomarkers in Health and Disease

Cell-surface heparan sulfate proteoglycans (HSPGs) play key roles in regulating cell behavior, cell signaling, and cell matrix interactions in both physiological and pathological conditions. Their soluble forms from glycocalyx shedding are not merely waste products, but, rather, bioactive molecules, detectable in serum, which may be useful as diagnostic and prognostic markers. In addition, as in the case of glypican-3 in hepatocellular carcinoma, they may be specifically expressed by pathological tissue, representing promising targets for immunotherapy. The primary goal of this comprehensive review is to critically survey the main findings of the clinical data from the last 20 years and provide readers with an overall picture of the diagnostic and prognostic value of circulating HSPGs. Moreover, issues related to the involvement of HSPGs in various pathologies, including cardiovascular disease, thrombosis, diabetes and obesity, kidney disease, cancer, trauma, sepsis, but also multiple sclerosis, preeclampsia, pathologies requiring surgery, pulmonary disease, and others will be discussed.

The influence of hyperglycemia on neutrophil extracellular trap formation and endothelial glycocalyx damage in a mouse model of type 2 diabetes

OBJECTIVES

Hyperglycemia induces vascular dysfunction that is thought to be initiated by neutrophils. Neutrophil activation produces endothelial injury by pathways that include NETosis, a type of specific cell death. In this study, we investigated the effects of hyperglycemia on neutrophil activation, cell death, NETosis, and endothelial glycocalyx damage using a mouse diabetes model.

METHODS

We used db/db mice as a type 2 diabetes model, and C57BL/6 mice were the controls. At 5, 8, and 12 weeks of age, the proportion of CD11b⁺ granulocytes/monocytes, neutrophil extracellular trap (NET)-forming granulocytes/monocytes, and damaged and nonviable granulocytes/monocytes was analyzed. In addition, serum levels of high mobility group box 1, histone H3, and glycocalyx components that included syndecan-1 and hyaluronan were measured.

RESULTS

In diabetic mice, we observed an increased proportion of CD11b⁺ granulocytes/monocytes. The proportion of NET-forming granulocytes/monocytes increased from the early stages of the experiments. The proportions of damaged and nonviable granulocytes/monocytes increased over time. In the 12-week-old diabetic mice, serum histone H3 levels increased. Circulating levels of syndecan-1 and hyaluronan decreased over time and were lower in diabetic mice.

CONCLUSION

Neutrophil activation and cell death induce endothelial glycocalyx damage, and NET formation also participates in the mechanisms of vascular injury in type 2 diabetes.

The Beneficial Effects of Alpha Lipoic Acid Supplementation on Lp-PLA2 Mass and Its Distribution between HDL and apoB-Containing Lipoproteins in Type 2 Diabetic Patients: A Randomized, Double-Blind, Placebo-Controlled Trial

Lipoprotein-associated phospholipase A₂ (Lp-PLA2) is a new specific vascular inflammation biomarker that is carried by the lipoproteins in the blood and plays a prominent role in the pathogenesis of atherosclerosis. Increased Lp-PLA2 levels and impaired Lp-PLA2 distribution across high-density lipoprotein (HDL) and non-HDL lipoproteins have been reported in diabetic patients, which is associated with the increase in cardiovascular disease (CVD) risk. This study is aimed at investigating the effect of alpha lipoic acid (ALA), as an antioxidant with potential cardioprotective properties, on the Lp-PLA2 mass and its distribution in diabetic patients. In a double-blind, randomized, placebo-controlled clinical trial, seventy diabetic patients were randomly allocated to ALA (1200 mg ALA as two 600 mg capsules/day) and placebo (two maltodextrin capsules/day) groups. The serum levels of total Lp-PLA2 mass, HDL-Lp-PLA2, oxidized low-density lipoproteins (ox-LDL), apolipoprotein A1 (apo A1), lipid profiles, fasting blood sugar (FBS), and insulin were measured, and apolipoprotein B- (apoB-) associated Lp-PLA2 and homeostasis model of assessment index (HOMA-IR) were calculated at the baseline and after 8 weeks of intervention. ALA significantly decreased the ox-LDL, total Lp-PLA2 mass, apoB-associated Lp-PLA2, and percent of apoB-associated Lp-PLA2 and triglyceride and increased the percent of HDL-Lp-PLA2 compared with the placebo group but had no significant effect on HDL-Lp-PLA2 mass, apo A1, lipid profiles, and glycemic indices. There was a positive correlation between the reduction in the ox-LDL level and total Lp-PLA2 mass in the ALA group. In conclusion, ALA may decrease the CVD risk by reducing the ox-LDL and Lp-PLA2 mass and improving the Lp-PLA2 distribution among lipoproteins in type 2 diabetic patients.

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.

Syndecans in chronic inflammatory and autoimmune diseases: Pathological insights and therapeutic opportunities

Syndecans (SDCs) are a family of heparan sulfate proteoglycans (HSPGs) glycoproteins ubiquitously expressed on the cell surfaces and extracellular matrix of all mammalian tissues. There are four mammalian syndecans, SDC-1 thorough 4, which play a critical role in cell adhesion, migration, proliferation, differentiation, and angiogenesis through independent and growth factor mediated signaling. An altered expression of SDCs is often observed in autoimmune disorders, cancer, HIV infection, and many other pathological conditions. SDCs modulate disease progression by interacting with a diverse array of ligands, receptors, and other proteins, including extracellular matrix, glycoproteins, integrins, morphogens, and various growth factors and chemokines, along with their receptors and kinases. Specifically, SDCs present on cell surface can bind directly to chemokines to enhance their binding to receptors, downstream signaling, and migration. Alternatively, SDCs can be cleaved and shed to mediate negative regulation of chemokine and growth factor signaling pathways and ligand sequestration. Importantly, SDC shedding may be a biomarker of inflammation, especially in chronic inflammatory diseases. While the current therapies for cancer and several autoimmune disorders have revolutionized treatment outcomes, understanding the pathophysiological role of SDCs and the use of HSPG mimetic or antagonists on cytokine signaling networks may uncover potentially novel targeted therapeutic approaches. This review mainly summarizes the current findings on the role of individual SDCs in disease processes, mechanisms through which SDCs mediate their biological functions, and the possibility of targeting SDCs as future potential therapeutic approaches.

Association of the apolipoprotein B/apolipoprotein A-I ratio and low-density lipoprotein cholesterol with insulin resistance in a Chinese population with abdominal obesity

The aim of this study is to assess the relationships among the apolipoprotein B/apolipoprotein A-I ratio (apoB/apoA-I ratio), low-density lipoprotein cholesterol (LDL-C) and insulin resistance (IR) in a Chinese population with abdominal obesity. This is a population-based, cross-sectional study of 3,945 men and 2,141 women with abdominal obesity. Individuals were referred to a primary health service and recruited for analysis. IR was measured using a homeostasis model assessment of insulin resistance (HOMA2-IR) with a HOMA2 calculator. Metabolic syndrome (MetS) was diagnosed using International Diabetes Federation (IDF) criteria. Comparing the apoB/apoA-I ratio and lipid indices using the HOMA2-IR showed that the ratio, LDL-C, total cholesterol level (TC) and triglyceride level (TG) were higher; and the high-density lipoprotein cholesterol level (HDL-C) was lower in the fourth than in the first quartile in both sexes (p ≤ 0.001). After adjustment for age, HOMA2-IR was positively correlated with the apoB/apoA-I ratio, LDL-C, TC and TG; and negatively correlated with HDL-C in men (all p < 0.0001). HOMA2-IR was also positively correlated with the apoB/apoA-I ratio, LDL-C, TC and TG; and negatively correlated with HDL-C in women (all p < 0.01). After adjustment for age and LDL-C, HOMA2-IR was found to be correlated with the apoB/apoA-I ratio in both men and women (r = 0.066 and 0.116, p < 0.0001). After adjustment for age and the apoB/apoA-I ratio, HOMA2-IR was correlated with LDL-C in men and women (r = 0.063 and 0.044, p < 0.0001 and p = 0.0431, respectively). Gender, age, LDL-C, BMI, HOMA2-IR and apoB/apoA-I were the covariates independently associated with presence of the MetS (Odds ratio, OR: 2.183, 1.034, 1.013, 1.157, 1.726 and 1.570, respectively; all p < 0.05). In conclusion, the study showed that the apoB/apoA-I ratio and LDL-C were positively correlated with IR. Excluding reciprocal interactions, the apoB/apoA-I ratio and LDL-C were still significantly correlated with IR, but the apoB/apoA-I ratio showed a greater correlation with IR than LDL-C in women with abdominal obesity, compared with men with abdominal obesity. Both LDL-C and apoB/apoA-I were independent risk factors of MetS, and the apoB/apoA-I ratio was stronger in this regard than LDL-C for this obese population.

Enhanced syndecan-1 expression on neutrophils in patients with type 2 diabetes mellitus

The peripheral neutrophils are one of the main inflammatory cells and significantly influence the damage of endothelium. Type 2 diabetes is a manifestation of an ongoing low-grade inflammation. In diabetes, impairment of neutrophil adhesion to the endothelium and migration to the site of inflammation were detected, which associated closely with adhesion molecules expressed on neutrophils and endothelial cells. To detect the expression of syndecan-1 on neutrophils in patients with type 2 diabetes mellitus, we recruited 29 patients with type 2 diabetes mellitus without any diabetic complication and 24 healthy subjects (controls). Expression of syndecan-1 was determined by flow cytometry, and potential correlations between syndecan-1 and clinical characteristics were analyzed. On neutrophils, percentage of positive syndecan-1 cells was significantly higher in subjects with diabetes (10.363 ± 1.689%) than that of the controls (3.775 ± 0.634%, P = 0.001). An association between body mass index (BMI) and percentage of positive syndecan-1 neutrophils was detected (r = 0.415, P = 0.025). When BMI was categorized into subgroups of ≤25 kg/m(2) (n = 10) and >25 kg/m(2) (n = 19), the average percentages of positive syndecan-1 neutrophils in patients with diabetes were 5.733 ± 1.842% and 12.642 ± 2.251%, respectively (t = -2.137, P = 0.042). A multiple regression analysis showed that BMI (β = 0.783, P < 0.000) was a significant predictor of positive syndecan-1 neutrophils in subjects with type 2 diabetes.