The function of heparanase in diabetes and its complications

Syndecans and diabetic complications: A narrative review

Syndecan (SDC) is a member of the heparan sulfate proteoglycan (HSPG) family. It appears to play a role in the aetiology of diabetic complications, with decreased levels of SDCs being reported in the kidney, retina, and cardiac muscle in models of diabetes mellitus (DM). The reduced levels of SDCs may play an important role in the development of albuminuria in DM. Some studies have provided the evidence supporting the mechanisms underlying the role of SDCs in DM. However, SDCs and the molecular mechanisms involved are complex and need to be further elucidated. This review focuses on the underlying molecular mechanisms of SDCs that are involved in the development and progression of the complications of DM, which may help in developing new strategies to prevent and treat these complications.

Design Principle of Heparanase Inhibitors: A Combined In Vitro and In Silico Study

Heparanase (HPSE) is an enzyme that cleaves heparan sulfate (HS) side chains from heparan sulfate proteoglycans (HSPGs). Overexpression of HPSE is associated with various types of cancer, inflammation, and immune disorders, making it a highly promising therapeutic target. Previously developed HPSE inhibitors that have advanced to clinical trials are polysaccharide-derived compounds or their mimetics; however, these molecules tend to suffer from poor bioavailability, side effects via targeting other saccharide binding proteins, and heterogeneity. Few small-molecule inhibitors have progressed to the preclinical or clinical stages, leaving a gap in HPSE drug discovery. In this study, a novel small molecule that can inhibit HPSE activity was discovered through high-throughput screening (HTS) using an ultrasensitive HPSE probe. Computational tools were employed to elucidate the mechanisms of inhibition. The essential structural features of the hit compound were summarized into a structure-activity relationship (SAR) theory, providing insights into the future design of HPSE small-molecule inhibitors.

A Fluorogenic Green Merocyanine-Based Probe to Detect Heparanase-1 Activity

Heparanase-1 (HPSE-1), an endo-β-D-glucuronidase, is an extracellular matrix (ECM) remodeling enzyme that degrades heparan sulfate (HS) chains of heparan sulfate proteoglycans (HSPGs). HPSE-1 functions to remodel the ECM and thereby disseminate cells, liberate HS-bound bioactive molecules, and release biologically active HS fragments. Being the only known enzyme for the cleavage of HS, HPSE-1 regulates a number of fundamental cellular processes including cell migration, cytokine regulation, angiogenesis, and wound healing. Overexpression of HPSE-1 has been discovered in most cancers, inflammatory diseases, viral infections, among others. As an emerging therapeutic target, the biological role of HPSE-1 remains to be explored but is hampered by a lack of research tools. To expand the chemical tool-kit of fluorogenic probes to interrogate HPSE-1 activity, we design and synthesized a fluorogenic green disaccharide-based HPSE-1 probe using our design strategy of tuning the electronic effect of the aryl aglycon. The novel probe exhibits a highly sensitive 278-fold fluorescence turn-on response in the presence of recombinant human HPSE-1, while emitting green light at 560 nm, enabling the fluorescence imaging of HPSE-1 activity in cells.

Discovery and development of small-molecule heparanase inhibitors

Heparanase-1 (HPSE) is a promising yet challenging therapeutic target. It is the only known enzyme that is responsible for cleavage of heparan sulfate (HS) side chains from heparan sulfate proteoglycans (HSPGs), and is the key enzyme involved in the remodeling and degradation of the extracellular matrix (ECM). Overexpression of HPSE is found in various types of diseases, including cancers, inflammations, diabetes, and viral infections. Inhibiting HPSE can restore ECM functions and integrity, making the development of HPSE inhibitors a highly sought-after topic. So far, all HPSE inhibitors that have entered clinical trials belong to the category of HS mimetics, and no small-molecule or drug-like HPSE inhibitors have made similar progress. None of the HS mimetics have been approved as drugs, with some clinical trials discontinued due to poor bioavailability, side effects, and unfavorable pharmacokinetics characteristics. Small-molecule HPSE inhibitors are, therefore, particularly appealing due to their drug-like characteristics. Advances in the chemical spaces and drug design technologies, including the increasing use of in vitro and in silico screening methods, have provided new opportunities in drug discovery. This article aims to review the discovery and development of small-molecule HPSE inhibitors via screening strategies to shed light on the future endeavors in the development of novel HPSE inhibitors.

Heparan Sulfate Mimicking Glycopolymer Prevents Pancreatic β Cell Destruction and Suppresses Inflammatory Cytokine Expression in Islets under the Challenge of Upregulated Heparanase

Diabetes is a chronic disease in which the levels of blood glucose are too high because the body does not effectively produce insulin to meet its needs or is resistant to insulin. β Cells in human pancreatic islets produce insulin, which signals glucogen production by the liver and causes muscles and fat to uptake glucose. Progressive loss of insulin-producing β cells is the main cause of both type 1 and type 2 diabetes. Heparan sulfate (HS) is a ubiquitous polysaccharide found at the cell surface and in the extracellular matrix (ECM) of a variety of tissues. HS binds to and assembles proteins in ECM, thus playing important roles in the integrity of ECM (particularly basement membrane), barrier function, and ECM-cell interactions. Islet HS is highly expressed by the pancreatic β cells and critical for the survival of β cells. Heparanase is an endoglycosidase and cleaves islet HS in the pancreas, resulting in β-cell death and oxidative stress. Heparanase could also accelerate β-cell death by promoting cytokine release from ECM and secretion by activated inflammatory and endothelial cells. We demonstrate that HS-mimicking glycopolymer, a potent heparanase inhibitor, improves the survival of cultured mouse pancreatic β cells and protects HS contents under the challenge of heparanase in human pancreatic islets. Moreover, this HS-mimicking glycopolymer reduces the expression levels of cytokines (IL8, IL1β, and TNFα) and the gene encoding Toll-like Receptor 2 (TLR2) in human pancreatic islets.

A Genome-Wide Association Study of Prediabetes Status Change

We conducted the first genome-wide association study of prediabetes status change (to diabetes or normal glycaemia) among 900 White participants of the Atherosclerosis Risk in Communities (ARIC) study. Single nucleotide polymorphism (SNP)-based analysis was performed by logistic regression models, controlling for age, gender, body mass index, and the first 3 genetic principal components. Gene-based analysis was conducted by combining SNP-based p values using effective Chi-square test method. Promising SNPs (p < 1×10-5) and genes (p < 1×10-4) were further evaluated for replication among 514 White participants of the Framingham Heart Study (FHS). To accommodate familial correlations, generalized estimation equation models were applied for SNP-based analyses in the FHS. Analysis results across ARIC and FHS were combined using inverse-variance-weighted meta-analysis method for SNPs and Fisher's method for genes. We robustly identified 5 novel genes that are associated with prediabetes status change using gene-based analyses, including SGCZ (ARIC p = 9.93×10-6, FHS p = 2.00×10-3, Meta p = 3.72×10-7) at 8p22, HPSE2 (ARIC p = 8.26×10-19, FHS p = 5.85×10-3, Meta p < 8.26×10-19) at 10q24.2, ADGRA1 (ARIC p = 1.34×10-5, FHS p = 1.13×10-3, Meta p = 2.88×10-7) at 10q26.3, GLB1L3 (ARIC p = 3.71×10-6, FHS p = 4.51×10-3, Meta p = 3.16×10-7) at 11q25, and PCSK6 (ARIC p = 6.51×10-6, FHS p = 1.10×10-2, Meta p = 1.25×10-6) at 15q26.3. eQTL analysis indicated that these genes were highly expressed in tissues related to diabetes development. However, we were not able to identify any novel locus in single SNP-based analysis. Future large scale genomic studies of prediabetes status change are warranted.

Serum Heparanase: A New Clinical Biomarker Involved in Senile Metabolic Inflammatory Syndrome

AIM

Metabolic inflammation syndrome (MIS) can lead to a series of complications, but its exact inflammatory mechanism is still unclear. The aim of this study was to explore the correlation between heparanase (HPA) and MIS, and the close relationship between HPA and other chronic low-grade inflammation index, such as C-reactive protein (CRP) and interleukin-6 (IL-6).

METHODS

A total of 105 patients with MIS in the physical examination population of Huashan Hospital affiliated to Fudan University from May to June 2018 were selected as the MIS group, and 52 patients who were relatively healthy during the same period were used as the control group. The basic clinical data of the selected candidates were collected, the levels of serum HPA, CRP and IL-6 were measured by ELISA, and the levels of blood glucose and blood lipids were also detected.

RESULTS

Compared with the control group, the levels of HPA, CRP, IL-6, FBG, HbA_1C, and TG of MIS group were all significantly elevated (all P<0.05), and HDL-C levels were considerably reduced (P<0.05). Correlation analysis showed that there was a noticeably positive correlation between serum HPA level and CRP, IL-6 levels (P<0.05).

CONCLUSION

Higher HPA levels might play a certain role in the occurrence and development of MIS. There was a certain close correlation between serum HPA level and CRP and IL-6 levels, and which indicated that HPA was involved in the chronic low-grade inflammatory reaction process of MIS.

Endothelial glycocalyx restoration by growth factors in diabetic nephropathy

The endothelial glycocalyx (eGlx) constitutes the first barrier to protein in all blood vessels. This is particularly noteworthy in the renal glomerulus, an ultrafiltration barrier. Leakage of protein, such as albumin, across glomerular capillaries results in albumin in the urine (albuminuria). This is a hall mark of kidney disease and can reflect loss of blood vessel integrity in microvascular beds elsewhere. We discuss evidence demonstrating that targeted damage to the glomerular eGlx results in increased glomerular albumin permeability. EGlx is lost in diabetes and experimental models demonstrate loss from glomerular endothelial cells. Vascular endothelial growth factor (VEGF)A is upregulated in early diabetes, which is associated with albuminuria. Treatment with paracrine growth factors such as VEGFC, VEGF165b and angiopoietin-1 can modify VEGFA signalling, rescue albumin permeability and restore glomerular eGlx in models of diabetes. Manipulation of VEGF receptor 2 signalling, or a common eGlx biosynthesis pathway by these growth factors, may protect and restore the eGlx layer. This would help to direct future therapeutics in diabetic nephropathy.

Heparanase and Type 1 Diabetes

Type 1 diabetes (T1D) results from autoimmune destruction of insulin-producing beta cells in pancreatic islets. The degradation of the glycosaminoglycan heparan sulfate (HS) by the endo-β-D-glycosidase heparanase plays a critical role in multiple stages of the disease process. Heparanase aids (i) migration of inflammatory leukocytes from the vasculature to the islets, (ii) intra-islet invasion by insulitis leukocytes, and (iii) selective destruction of beta cells. These disease stages are marked by the solubilization of HS in the subendothelial basement membrane (BM), HS breakdown in the peri-islet BM, and the degradation of HS inside beta cells, respectively. Significantly, healthy islet beta cells are enriched in highly sulfated HS which is essential for their viability, protection from damage by reactive oxygen species (ROS), beta cell function and differentiation. Consequently, mouse and human beta cells but not glucagon-producing alpha cells (which contain less-sulfated HS) are exquisitely vulnerable to heparanase-mediated damage. In vitro, the death of HS-depleted mouse and human beta cells can be prevented by HS replacement using highly sulfated HS mimetics or analogues. T1D progression in NOD mice and recent-onset T1D in humans correlate with increased expression of heparanase by circulating leukocytes of myeloid origin and heparanase-expressing insulitis leukocytes. Treatment of NOD mice with the heparanase inhibitor and HS replacer, PI-88, significantly reduced T1D incidence by 50%, impaired the development of insulitis and preserved beta cell HS. These outcomes identified heparanase as a novel destructive tool in T1D, distinct from the conventional cytotoxic and apoptosis-inducing mechanisms of autoreactive T cells. In contrast to exogenous catalytically active heparanase, endogenous heparanase may function in HS homeostasis, gene expression and insulin secretion in normal beta cells and immune gene expression in leukocytes. In established diabetes, the interplay between hyperglycemia, local inflammatory cells (e.g. macrophages) and heparanase contributes to secondary micro- and macro-vascular disease. We have identified dual activity heparanase inhibitors/HS replacers as a novel class of therapeutic for preventing T1D progression and potentially for mitigating secondary vascular disease that develops with long-term T1D.

Role of Heparanase in Macrophage Activation

Macrophages represent one of the most diverse immunocyte populations, constantly shifting between various phenotypes/functional states. In addition to execution of vital functions in normal physiological conditions, macrophages represent a key contributing factor in the pathogenesis of some of the most challenging diseases, such as chronic inflammatory disorders, diabetes and its complications, and cancer. Macrophage polarization studies focus primarily on cytokine-mediated mechanisms. However, to explore the full spectrum of macrophage action, additional, non-cytokine pathways responsible for altering macrophage phenotype have to be taken into consideration as well. Heparanase, the only known mammalian endoglycosidase that cleaves heparan sulfate glycosaminoglycans, has been shown to contribute to the altered macrophage phenotypes in vitro and in numerous animal models of inflammatory conditions, occurring either in the presence of microbial products or in the setting of non-infectious "aseptic" inflammation. Here we discuss the involvement of heparanase in shaping macrophage responses and provide information that may help to establish the rationale for heparanase-targeting interventions aimed at preventing abnormal macrophage activation in various disorders.

Targeting Heparanase in Cancer: Inhibition by Synthetic, Chemically Modified, and Natural Compounds

Heparanase is an endoglycosidase involved in remodeling the extracellular matrix and thereby in regulating multiple cellular processes and biological activities. It cleaves heparan sulfate (HS) side chains of HS proteoglycans into smaller fragments and hence regulates tissue morphogenesis, differentiation, and homeostasis. Heparanase is overexpressed in various carcinomas, sarcomas, and hematological malignancies, and its upregulation correlates with increased tumor size, tumor angiogenesis, enhanced metastasis, and poor prognosis. In contrast, knockdown or inhibition of heparanase markedly attenuates tumor progression, further underscoring the potential of anti-heparanase therapy. Heparanase inhibitors were employed to interfere with tumor progression in preclinical studies, and selected heparin mimetics are being examined in clinical trials. However, despite tremendous efforts, the discovery of heparanase inhibitors with high clinical benefit and minimal adverse effects remains a therapeutic challenge. This review discusses the key roles of heparanase in cancer progression focusing on the status of natural, chemically modified, and synthetic heparanase inhibitors in various types of malignancies.

Leukocyte Heparanase: A Double-Edged Sword in Tumor Progression

Heparanase is a β-D-endoglucuronidase that cleaves heparan sulfate, a complex glycosaminoglycan found ubiquitously throughout mammalian cells and tissues. Heparanase has been strongly associated with important pathological processes including inflammatory disease and tumor metastasis, through its ability to promote various cellular functions such as cell migration, invasion, adhesion, and cytokine release. A number of cell types express heparanase including leukocytes, cells of the vasculature as well as tumor cells. However, the relative contribution of heparanase from these different cell sources to these processes is poorly defined. It is now well-established that the immune system plays a critical role in shaping tumor progression. Intriguingly, leukocyte-derived heparanase has been shown to either assist or impede tumor progression, depending on the setting. This review covers our current knowledge of heparanase in immune regulation of tumor progression, as well as the potential applications and implications of exploiting or inhibiting heparanase in cancer therapy.

Anti-Diabetic Effects of Dung Beetle Glycosaminoglycan on db Mice and Gene Expression Profiling

Anti-diabetes activity of Catharsius molossus (Ca, a type of dung beetle) glycosaminoglycan (G) was evaluated to reduce glucose, creatinine kinase, triglyceride and free fatty acid levels in db mice. Diabetic mice in six groups were administrated intraperitoneally: Db heterozygous (Normal), Db homozygous (CON), Heuchys sanguinea glycosaminoglycan (HEG, 5 mg/kg), dung beetle glycosaminoglycan (CaG, 5 mg/kg), bumblebee (Bombus ignitus) queen glycosaminoglycan (IQG, 5 mg/kg) and metformin (10 mg/kg), for 1 month. Biochemical analyses in the serum were evaluated to determine their anti-diabetic and anti-inflammatory actions in db mice after 1 month treatment with HEG, CaG or IQG treatments. Blood glucose level was decreased by treatment with CaG. CaG produced significant anti-diabetic actions by inhiting creatinine kinase and alkaline phosphatase levels. As diabetic parameters, serum glucose level, total cholesterol and triglyceride were significantly decreased in CaG5-treated group compared to the controls. Dung beetle glycosaminoglycan, compared to the control, could be a potential therapeutic agent with anti-diabetic activity in diabetic mice. CaG5-treated group, compared to the control, showed the up-regulation of 48 genes including mitochondrial yen coded tRNA lysine (mt-TK), cytochrome P450, family 8/2, subfamily b, polypeptide 1 (Cyp8b1), and down-regulation of 79 genes including S100 calcium binding protein A9 (S100a9) and immunoglobulin kappa chain complex (Igk), and 3-hydroxy-3-methylglutaryl-CoenzymeAsynthase1 (Hmgcs1). Moreover, mitochondrial thymidine kinase (mt-TK), was up-regulated, and calgranulin A (S100a9) were down-regulated by CaG5 treatment, indicating a potential therapeutic use for anti-diabetic agent.

Heparanase regulation of cancer, autophagy and inflammation: new mechanisms and targets for therapy

Because of its impact on multiple biological pathways, heparanase has emerged as a major regulator of cancer, inflammation and other disease processes. Heparanase accomplishes this by degrading heparan sulfate which regulates the abundance and location of heparin-binding growth factors thereby influencing multiple signaling pathways that control gene expression, syndecan shedding and cell behavior. In addition, heparanase can act via nonenzymatic mechanisms that directly activate signaling at the cell surface. Clinical trials testing heparanase inhibitors as anticancer therapeutics are showing early signs of efficacy in patients further emphasizing the biological importance of this enzyme. This review focuses on recent developments in the field of heparanase regulation of cancer and inflammation, including the impact of heparanase on exosomes and autophagy, and novel mechanisms whereby heparanase regulates tumor metastasis, angiogenesis and chemoresistance. In addition, the ongoing development of heparanase inhibitors and their potential for treating cancer and inflammation are discussed.

Heparanase: From basic research to therapeutic applications in cancer and inflammation

Heparanase, the sole heparan sulfate degrading endoglycosidase, regulates multiple biological activities that enhance tumor growth, angiogenesis and metastasis. Heparanase expression is enhanced in almost all cancers examined including various carcinomas, sarcomas and hematological malignancies. Numerous clinical association studies have consistently demonstrated that upregulation of heparanase expression correlates with increased tumor size, tumor angiogenesis, enhanced metastasis and poor prognosis. In contrast, knockdown of heparanase or treatments of tumor-bearing mice with heparanase-inhibiting compounds, markedly attenuate tumor progression further underscoring the potential of anti-heparanase therapy for multiple types of cancer. Heparanase neutralizing monoclonal antibodies block myeloma and lymphoma tumor growth and dissemination; this is attributable to a combined effect on the tumor cells and/or cells of the tumor microenvironment. In fact, much of the impact of heparanase on tumor progression is related to its function in mediating tumor-host crosstalk, priming the tumor microenvironment to better support tumor growth, metastasis and chemoresistance. The repertoire of the physio-pathological activities of heparanase is expanding. Specifically, heparanase regulates gene expression, activates cells of the innate immune system, promotes the formation of exosomes and autophagosomes, and stimulates signal transduction pathways via enzymatic and non-enzymatic activities. These effects dynamically impact multiple regulatory pathways that together drive inflammatory responses, tumor survival, growth, dissemination and drug resistance; but in the same time, may fulfill some normal functions associated, for example, with vesicular traffic, lysosomal-based secretion, stress response, and heparan sulfate turnover. Heparanase is upregulated in response to chemotherapy in cancer patients and the surviving cells acquire chemoresistance, attributed, at least in part, to autophagy. Consequently, heparanase inhibitors used in tandem with chemotherapeutic drugs overcome initial chemoresistance, providing a strong rationale for applying anti-heparanase therapy in combination with conventional anti-cancer drugs. Heparin-like compounds that inhibit heparanase activity are being evaluated in clinical trials for various types of cancer. Heparanase neutralizing monoclonal antibodies are being evaluated in pre-clinical studies, and heparanase-inhibiting small molecules are being developed based on the recently resolved crystal structure of the heparanase protein. Collectively, the emerging premise is that heparanase expressed by tumor cells, innate immune cells, activated endothelial cells as well as other cells of the tumor microenvironment is a master regulator of the aggressive phenotype of cancer, an important contributor to the poor outcome of cancer patients and a prime target for therapy.

Association of the CETP Taq1B and LIPG Thr111Ile Polymorphisms with Glycated Hemoglobin and Blood Lipids in Newly Diagnosed Hyperlipidemic Patients

OBJECTIVE

To examine the association of 2 common polymorphisms in high-density lipoprotein (HDL)-related genes, namely, cholesterol ester transfer protein CETP Taq1B (rs708272) and endothelial lipase LIPG Thr111Ile (rs2000813), with glycated hemoglobin (A1C), blood lipid levels and the risk for type 2 diabetes in a group of hyperlipidemic patients from northern Greece.

METHODS

We categorized 175 patients with hyperlipidemia into 2 subgroups according to the presence or absence of type 2 diabetes, defined as a recent diagnosis, A1C >6.5% and/or fasting glucose >126 mg/dL. Genotypes for the 2 polymorphisms studied were determined by polymerase chain reaction-restriction fragment length polymorphism. Both polymorphisms were analyzed by multivariate and univariate analyses of baseline A1C levels and plasma lipids. The genotype and allele frequencies of the 2 subgroups were compared.

RESULTS

The CETP Taq1B polymorphism was associated with HDL-cholesterol (HDL-C) and A1C levels, but this association was affected by type 2 diabetes; the association with A1C levels was significant only in type 2 diabetes (p=0.005), whereas the association with HDL-C occurred only in the subgroup without type 2 diabetes (p<0.001). LIPG Thr111Ile did not affect plasma HDL-C or A1C levels independently but appeared to modulate their association with CETP Taq1B, and LIPG 111IleIle homozygotes tended to be present at a higher frequency in the hyperlipidemic patients with type 2 diabetes compared to the hyperlipidemic patients without type 2 diabetes (p=0.056).

CONCLUSIONS

In hyperlipidemic patients, apart from its known association with HDL-C, CETP Taq1B is also associated with A1C levels, and both associations are modified by type 2 diabetes and LIPG Thr111Ile.

Role of sulfatase 2 in lipoprotein metabolism and angiogenesis

PURPOSE OF REVIEW

This article summarizes the current evidence to support a role of sulfatase 2 (SULF2) in triglyceride-rich lipoprotein (TRL) metabolism and angiogenesis.

RECENT FINDINGS

Heparan sulfate proteoglycans (HSPG) are involved in the hepatic clearance of TRLs in mice and in humans. Different genetically modified mouse models have been instrumental to provide evidence that syndecan1, the core protein of HSPG, but also the degree of sulfation of the heparin sulfate chain, attached to syndecan 1, is important for hepatic TRL metabolism. Studies in humans demonstrate the regulating role of SULF2 in the hepatic uptake of TRL by HSPG and demonstrate the importance of 6-O-sulfation, modulated by SULF2, for HSPG function. The role of SULF2 in angiogenesis is illustrated by increased SULF2 mRNA expression in the stalk cells of angiogenic vascular sprouts that use fatty acids derived from TRL as a source for biomass production. Interestingly, SULF2 also interferes with HSPG-vascular endothelial growth factor binding, which impacts upon the angiogenic properties of stalk cells.

SUMMARY

SULF2 is a multifaceted protein involved in TRL homeostasis and angiogenesis. Future investigations should focus on the potential benefits of targeting SULF2 in atherosclerosis and angiogenesis.