Stimulatory effects of advanced glycation endproducts (AGEs) on fibronectin matrix assembly

Diabetes Mellitus as a Risk Factor for Spontaneous Preterm Birth in Women with a Short Cervix after Ultrasound-Indicated Cerclage

Background: Preterm birth (PTB) is a significant challenge in contemporary obstetrics, affecting over one in ten infants worldwide and accounting for 75% of perinatal mortality. Short cervical length during mid-trimester is well known to be associated with an increased risk of spontaneous preterm birth (sPTB). Ultrasound-indicated cerclage (UIC) is recommended to prevent sPTB in women with a short cervix at mid-trimester and a history of sPTB. Objectives: This retrospective observational study aimed to examine the impact of diabetes and obesity on the occurrence of sPTB in women who underwent UIC due to mid-trimester cervical shortening. Methods/Results: The analysis revealed that cervical length at the time of operation, preoperative erythrocyte sedimentation rate levels, and diabetes were independent risk factors for sPTB. Additionally, the presence of diabetes, particularly when combined with obesity, significantly elevated the risk of sPTB. Women with pregestational diabetes or those requiring insulin treatment had a higher propensity for preterm delivery compared to those with gestational diabetes managed through diet control alone. Conclusions: These findings emphasize the importance of considering maternal metabolic factors, such as diabetes and obesity, in women with a short cervix when planning for UIC and highlight the crucial role of optimizing maternal glucose control and weight management in reducing the risk of sPTB.

An overview on glycation: molecular mechanisms, impact on proteins, pathogenesis, and inhibition

The formation of a heterogeneous set of advanced glycation end products (AGEs) is the final outcome of a non-enzymatic process that occurs in vivo on long-life biomolecules. This process, known as glycation, starts with the reaction between reducing sugars, or their autoxidation products, with the amino groups of proteins, DNA, or lipids, thus gaining relevance under hyperglycemic conditions. Once AGEs are formed, they might affect the biological function of the biomacromolecule and, therefore, induce the development of pathophysiological events. In fact, the accumulation of AGEs has been pointed as a triggering factor of obesity, diabetes-related diseases, coronary artery disease, neurological disorders, or chronic renal failure, among others. Given the deleterious consequences of glycation, evolution has designed endogenous mechanisms to undo glycation or to prevent it. In addition, many exogenous molecules have also emerged as powerful glycation inhibitors. This review aims to provide an overview on what glycation is. It starts by explaining the similarities and differences between glycation and glycosylation. Then, it describes in detail the molecular mechanism underlying glycation reactions, and the bio-molecular targets with higher propensity to be glycated. Next, it discusses the precise effects of glycation on protein structure, function, and aggregation, and how computational chemistry has provided insights on these aspects. Finally, it reports the most prevalent diseases induced by glycation, and the endogenous mechanisms and the current therapeutic interventions against it.

Association Between Advanced Glycation End Products and Sarcopenia: The Mediating Role of Osteoporosis

CONTEXT

Advanced glycation end products (AGEs) are a group of molecules formed through nonenzymatic reactions. These compounds are associated with several age-related diseases, including sarcopenia and osteoporosis.

OBJECTIVE

This work aimed to investigate the relationships between AGEs, osteoporosis, and sarcopenia in community-dwelling older adults.

METHODS

This cross-sectional study included 1991 older adults aged 72.37 ± 5.90 years from China. AGE levels were measured by the AGE Reader device. Bone mineral density was assessed using dual-energy X-ray absorptiometry, and osteoporosis was diagnosed based on a T score of less than -2.5. Sarcopenia was defined as loss of muscle mass plus loss of muscle strength and/or reduced physical performance. Presarcopenia was defined as low muscle mass with normal muscle strength and normal physical performance.

RESULTS

The prevalence of sarcopenia was 18.5%, and that of osteoporosis was 40.5%. Compared to the lowest AGE quartile, the highest AGE quartile showed a significant association with sarcopenia (odds ratio [OR] 2.42; 95% CI, 1.60-3.66) (P for trend <.001), but not with presarcopenia. Per-SD increase in AGE was associated with higher odds of sarcopenia (OR 1.44; 95% CI, 1.26-1.66). Additionally, in the mediation analysis, when AGEs were treated as a continuous variable (the mediation effect is denoted by Za*Zb = 18.81; 95% CI, 8.07-32.32]-the 95% CI does not contain zero, representing a significant mediating effect) or a categorical variable (the mediating effect is expressed as Zmediation = 3.01 > 1.96, which represents a significant mediating effect), osteoporosis played a partial mediating role in the association between AGEs and sarcopenia.

CONCLUSION

Elevated AGEs are associated with sarcopenia but not with presarcopenia. This association was partially mediated by osteoporosis.

Glycation of fibronectin impairs angiopoietin-1/Tie-2 signaling through uncoupling Tie-2-α5β1 integrin crosstalk

The dysfunction of angiopoietin-1 (Ang-1)/Tie-2 signaling pathways has been implicated in diabetic complications. However, the underlying molecular mechanisms remain unclear. Fibronectin (FN) is thought to have an important role in regulating Ang-1/Tie-2 signaling activation. But no previous study has investigated the effects of FN glycation on Ang-1/Tie-2 signaling. In the present study, FN was glycated by methylglyoxal (MGO) to investigate whether the glycation of FN contributes to diabetes-induced Ang-1/Tie-2 signaling impairment and to understand the molecular mechanisms involved. The results demonstrated that MGO-glycated FN significantly impaired Ang-1-evoked phosphorylation of Tie-2 and Akt, Ang-1-induced endothelial cell migration and tube formation and Ang-1-mediated cell survival. The glycation of FN also inhibited the binding of α5β1 integrin to Tie-2. Moreover, FN was remarkably modified by AGEs in aortae derived from db/db mice, indicating the glycation of FN in vivo. Ang-1-induced aortic ring vessel outgrowth and Ang-1-mediated cell survival were also both significantly inhibited in aortae from db/db mice compared to that from the wild type littermates. Moreover, FN, rather than glycated FN partly restored aortic ring angiogenesis in db/db mice, indicating that the angiogenesis defect in the db/db mice are due to FN glycation. Collectively, the results in the present study suggest that the glycation of FN impairs Ang-1/Tie-2 signaling pathway by uncoupling Tie-2-α5β1 integrin crosstalk. This may provide a mechanism for Ang-1/Tie-2 signaling dysfunction and angiogenesis failure in diabetic ischaemic diseases.

Collagen code in tumor microenvironment: Functions, molecular mechanisms, and therapeutic implications

The tumor microenvironment (TME) is crucial in cancer progression, and the extracellular matrix (ECM) is an important TME component. Collagen is a major ECM component that contributes to tumor cell infiltration, expansion, and distant metastasis during cancer progression. Recent studies reported that collagen is deposited in the TME to form a collagen wall along which tumor cells can infiltrate and prevent drugs from working on the tumor cells. Collagen-tumor cell interaction is complex and requires the activation of multiple signaling pathways for biochemical and mechanical signaling interventions. In this review, we examine the effect of collagen deposition in the TME on tumor progression and discuss the interaction between collagen and tumor cells. This review aims to illustrate the functions and mechanisms of collagen in tumor progression in the TME and its role in tumor therapy. The findings indicated collagen in the TME appears to be a better target for cancer therapy.

JAK/STAT signaling in diabetic kidney disease

Diabetic kidney disease (DKD) is the most important microvascular complication of diabetes and the leading cause of end-stage renal disease (ESRD) worldwide. The Janus kinase/signal transducer and activator of the transcription (JAK/STAT) signaling pathway, which is out of balance in the context of DKD, acts through a range of metabolism-related cytokines and hormones. JAK/STAT is the primary signaling node in the progression of DKD. The latest research on JAK/STAT signaling helps determine the role of this pathway in the factors associated with DKD progression. These factors include the renin-angiotensin system (RAS), fibrosis, immunity, inflammation, aging, autophagy, and EMT. This review epitomizes the progress in understanding the complicated explanation of the etiologies of DKD and the role of the JAK/STAT pathway in the progression of DKD and discusses whether it can be a potential target for treating DKD. It further summarizes the JAK/STAT inhibitors, natural products, and other drugs that are promising for treating DKD and discusses how these inhibitors can alleviate DKD to explore possible potential drugs that will contribute to formulating effective treatment strategies for DKD in the near future.

Red emissive N-doped carbon dots encapsulated within molecularly imprinted polymers for optosensing of pyrraline in fatty foods

A novel and facile method was proposed for preparation of red emissive N-doped carbon dots encapsulated within molecularly imprinted polymers (RNCDs@MIPs) using a one-pot room-temperature reverse microemulsion polymerization. RNCDs used citric acid and urea as carbon and nitrogen sources by one-step solvothermal synthesis with the optimum emission of 620 nm. Unique optical properties of RNCDs coupled with high selective MIPs make the RNCDs@MIPs conjugate capable to adsorb specific targets of pyrraline (PRL), such a binding event was then transduced to quench fluorescence response signal of the RNCDs. RNCDs@MIPs for PRL showed linearity from 0.1 to 40 μg/L, with a detection limit of 65 ng/L. The RNCDs@MIPs exhibited a good reproducibility of 4.67% obtained from four times of rebinding for PRL. The optosensing probe was successfully applied to the detection of PRL in fatty foods with the spiked recovery of 85.93-106.96%.

Fibronectin in hyperglycaemia and its potential use in the treatment of diabetic foot ulcers: A review

Metabolism of fibronectin, the protein that plays a key role in the healing of wounds, is changed in the patients with diabetes mellitus. Fibronectin can interact with other proteins and proteoglycans and organise them to form the extracellular matrix, the basis of the granulation tissue in healing wounds. However, diabetic foot ulcers (DFUs) suffer from inadequate deposition of this protein. Degradation prevails over fibronectin synthesis in the proteolytic inflammatory environment in the ulcers. Because of the lack of fibronectin in the wound bed, the assembly of the extracellular matrix and the deposition of the granulation tissue cannot be started. A number of methods have been designed that prevents fibronectin degradation, replace lacking fibronectin or support its formation in non-healing wounds in animal models of diabetes. The aim of this article is to review the metabolism of fibronectin in DFUs and to emphasise that it would be useful to pay more attention to fibronectin matrix assembly in the ulcers when laboratory methods are translated to clinical practice.

Methylglyoxal and Its Adducts: Induction, Repair, and Association with Disease

Metabolism is an essential part of life that provides energy for cell growth. During metabolic flux, reactive electrophiles are produced that covalently modify macromolecules, leading to detrimental cellular effects. Methylglyoxal (MG) is an abundant electrophile formed from lipid, protein, and glucose metabolism at intracellular levels of 1-4 μM. MG covalently modifies DNA, RNA, and protein, forming advanced glycation end products (MG-AGEs). MG and MG-AGEs are associated with the onset and progression of many pathologies including diabetes, cancer, and liver and kidney disease. Regulating MG and MG-AGEs is a potential strategy to prevent disease, and they may also have utility as biomarkers to predict disease risk, onset, and progression. Here, we review recent advances and knowledge surrounding MG, including its production and elimination, mechanisms of MG-AGEs formation, the physiological impact of MG and MG-AGEs in disease onset and progression, and the latter in the context of its receptor RAGE. We also discuss methods for measuring MG and MG-AGEs and their clinical application as prognostic biomarkers to allow for early detection and intervention prior to disease onset. Finally, we consider relevant clinical applications and current therapeutic strategies aimed at targeting MG, MG-AGEs, and RAGE to ultimately improve patient outcomes.

Implications of fibrotic extracellular matrix in diabetic retinopathy

Fibrosis is an accumulation of extracellular matrix (ECM) proteins and fibers in a disordered fashion, which compromises cell and tissue functions. High glucose-induced fibrosis, a major pathophysiological change of diabetic retinopathy (DR), severely affects vision by compromising the retinal vasculature and ultimately disrupting retinal tissue organization. The retina is a highly vascularized, stratified tissue with multiple cell types organized into distinct layers. Chronically high blood glucose stimulates certain retinal cells to increase production and assembly of ECM proteins resulting in excess ECM deposition primarily in the capillary walls on the basal side of the endothelium. This subendothelial fibrosis of the capillaries is the earliest histological change in the diabetic retina and has been linked to the vascular dysfunction that underlies DR. Proteins that are not normally abundant in the capillary basement membrane (BM) matrix, such as the ECM protein fibronectin, are assembled in significant quantities, disrupting the architecture of the BM and altering its properties. Cell culture models have identified multiple mechanisms through which elevated glucose can stimulate fibronectin matrix assembly, including intracellular signaling pathways, alternative splicing, and non-enzymatic glycation of the ECM. The fibrotic subendothelial matrix alters cell adhesion and supports further accumulation of other ECM proteins leading to disruption of endothelial cell-cell junctions. We review evidence supporting the notion that these molecular changes in the ECM contribute to the pathogenesis of DR, including vascular leakage, loss of endothelial cells and pericytes, changes in blood flow, and neovascularization. We propose that the accumulation of ECM, especially fibronectin matrix, first around the vasculature and later in extravascular locations, plays a critical role in DR and vision loss. Strategies for DR prevention and treatment should consider the ECM a potential therapeutic target.

Modification of Fibronectin by Non-Enzymatic Glycation Impairs K+ Channel Function in Rat Cerebral Artery Smooth Muscle Cells

Fibronectin (FN) enhances K+ channel activity by integrin-mediated mechanisms. As vascular smooth muscle (VSM) K+ channels mediate vasodilation, we hypothesized that modification of fibronectin, via advanced non-enzymatic glycation, would alter signaling of this extracellular matrix protein through these channels. Bovine FN (1 mg/ml) was glycated (gFN) for 5 days using methylglyoxal (50 mM), and albumin was similarly glycated as a non-matrix protein control. VSM cells were isolated from rat cerebral arteries for measurement of macroscopic K+ channel activity using whole cell patch clamp methodology. Pharmacological inhibitors, iberiotoxin (0.1 μM) and 4-aminopyridine (0.1 mM), were used to identify contributions of large-conductance, Ca2+-activated, K+ channels and voltage-gated K+ channels, respectively. Compared with baseline, native FN enhanced whole cell K+ current in a concentration-dependent manner, whereas gFN inhibited basal current. Furthermore, native albumin did not enhance basal K+ current, but the glycated form (gAlb) caused inhibition. gFN was shown to impair both the Kv and BKCa components of total macroscopic K+ current. Anti-integrin α5 and β1 antibodies attenuated the effects of both FN and gFN on macroscopic K+ current at +70 mV. Consistent with an action on BKCa activity, FN increased, whereas gFN decreased the frequency of spontaneous transient outward current (STOCs). In contrast, gAlb inhibited whole cell K+ current predominantly through Kv, showing little effect on STOCs. A function-blocking, anti-RAGE antibody partially reversed the inhibitory effects of gFN, suggesting involvement of this receptor. Further, gFN caused production of reactive oxygen species (ROS) by isolated VSMCs as revealed by the fluorescent indicator, DHE. Evoked ROS production was attenuated by the RAGE blocking antibody. Collectively, these studies identify ion channel-related mechanisms (integrin and ROS-mediated) by which protein glycation may modify VSMC function.

Cross-Talking Pathways of Forkhead Box O1 (FOXO1) Are Involved in the Pathogenesis of Alzheimer’s Disease and Huntington’s Disease

Alzheimer's disease (AD) and Huntington's disease (HD) are destructive worldwide diseases. Efforts have been made to elucidate the process of these two diseases, yet the pathogenesis remains elusive as it involves a combination of multiple factors, including genetic and environmental ones. To explore the potential role of forkhead box O1 (FOXO1) in the development of AD and HD, we identified 1,853 differentially expressed genes (DEGs) from 19,414 background genes in both the AD&HD/control and FOXO1-low/high groups. Four coexpression modules were predicted by the weighted gene coexpression network analysis (WGCNA), among which blue and turquoise modules had the strongest correlation with AD&HD and high expression of FOXO1. Functional enrichment analysis showed that DEGs in these modules were enriched in phagosome, cytokine-cytokine receptor interaction, cellular senescence, FOXO signaling pathway, pathways of neurodegeneration, GABAergic synapse, and AGE-RAGE signaling pathway in diabetic complications. Furthermore, the cross-talking pathways of FOXO1 in AD and HD were jointly determined in a global regulatory network, such as the FOXO signaling pathway, cellular senescence, and AGE-RAGE signaling pathway in diabetic complications. Based on the performance evaluation of the area under the curve of 85.6%, FOXO1 could accurately predict the onset of AD and HD. We then identified the cross-talking pathways of FOXO1 in AD and HD, respectively. More specifically, FOXO1 was involved in the FOXO signaling pathway and cellular senescence in AD; correspondingly, FOXO1 participated in insulin resistance, insulin, and the FOXO signaling pathways in HD. Next, we use GSEA to validate the biological processes in AD&HD and FOXO1 expression. In GSEA analysis, regulation of protein maturation and regulation of protein processing were both enriched in the AD&HD and FOXO1-high groups, suggesting that FOXO1 may have implications in onset and progression of these two diseases through protein synthesis. Consequently, a high expression of FOXO1 is a potential pathogenic factor in both AD and HD involving mechanisms of the FOXO signaling pathway, AGE-RAGE signaling pathway in diabetic complications, and cellular senescence. Our findings provide a comprehensive perspective on the molecular function of FOXO1 in the pathogenesis of AD and HD.

Advanced Glycation End-Products in Skeletal Muscle Aging

Advanced age causes skeletal muscle to undergo deleterious changes including muscle atrophy, fast-to-slow muscle fiber transition, and an increase in collagenous material that culminates in the age-dependent muscle wasting disease known as sarcopenia. Advanced glycation end-products (AGEs) non-enzymatically accumulate on the muscular collagens in old age via the Maillard reaction, potentiating the accumulation of intramuscular collagen and stiffening the microenvironment through collagen cross-linking. This review contextualizes known aspects of skeletal muscle extracellular matrix (ECM) aging, especially the role of collagens and AGE cross-linking, and underpins the motor nerve’s role in this aging process. Specific directions for future research are also discussed, with the understudied role of AGEs in skeletal muscle aging highlighted. Despite more than a half century of research, the role that intramuscular collagen aggregation and cross-linking plays in sarcopenia is well accepted yet not well integrated with current knowledge of AGE’s effects on muscle physiology. Furthermore, the possible impact that motor nerve aging has on intramuscular cross-linking and muscular AGE levels is posited.

Elevated glucose alters global gene expression and tenascin-C alternative splicing in mesangial cells

Mesangial cells are the major extracellular matrix (ECM)-producing cells in the kidney glomerulus and, when exposed to elevated glucose levels, they up-regulate assembly of fibronectin (FN) and other ECM proteins. Increases in glucose concentration are known to alter gene expression; here we investigated the connection between increased ECM production and changes in gene expression in mesangial cells. Comparison of mesangial cells grown in normal or high glucose conditions by RNA-sequencing showed significant expression changes in over 6000 genes and, when grouped by KEGG pathway analysis, identified the ECM-receptor interaction and focal adhesion pathways among the top 5 upregulated pathways. Of note was the significant increase in expression of tenascin-C (TN-C), a known regulator of FN matrix assembly. Mouse TN-C has multiple isoforms due to alternative splicing of 6 FNIII repeat exons. In addition to the transcriptional increase with high glucose, exon inclusion via alternative splicing was also changed resulting in production of higher molecular weight isoforms of TN-C. Mesangial cells grown in normal glucose secreted small isoforms with 1–2 variable repeats included whereas in high glucose large isoforms estimated to include 5 repeats were secreted. Unlike the smaller isoforms, the larger TN-C was not detected in the FN matrix. This change in TN-C isoforms may affect the regulation of FN matrix assembly and in this way may contribute to increased ECM accumulation under high glucose conditions.

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Elevated glucose alters gene expression in cultured mesangial cells.

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RNA-sequencing identifies increased expression of ECM proteins and receptors.

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High glucose changes tenascin-C isoform expression by alternative splicing.

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Differential ECM localization is detected for large vs small tenascin-C isoforms.

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Switch in tenascin-C may contribute to ECM accumulation in the diabetic glomerulus.

Effect of metabolic syndrome on incidence of oral potentially malignant disorder: a prospective cohort study in Taiwan

OBJECTIVES

We aimed to assess the effect of metabolic syndrome (MetS) on incident oral potentially malignant disorder (OPMD).

DESIGN

We conducted a prospective cohort study of the Changhua community-based integrated screening (CHCIS) programme and nationwide oral cancer screening programme during the period between 2005 and 2014.

SETTING

CHCIS, Taiwan.

PARTICIPANTS

We enrolled 17 590 participants aged 30 years and older.

MAIN OUTCOMES AND MEASURES

We assessed the impact of MetS on the outcome measured by incident OPMD.

RESULTS

The incidences of OPMD among subjects with and without MetS were 7.68 ‰ and 5.38 ‰, respectively. After adjusting for confounders, subjects with MetS exhibited a statistically greater risk of developing OPMD compared with those who were free of MetS by 33% (adjusted rate ratio, aRR=1.33, 95% CI 1.14 to 1.55). Individual components of MetS still remained significant, including central obesity (aRR=1.22, 95% CI 1.04 to 1.44), hypertriglyceridaemia (aRR=1.26, 95% CI 1.07 to 1.49) and hyperglycaemia (aRR=1.20, 95% CI 1.02 to 1.41). Central obesity and hypertriglyceridaemia were also statistically associated with a subtype of OPMD, namely, leukoplakia.

CONCLUSION

The temporal influence of MetS on the risk of incident OPMD was noted in our prospective cohort study. Therefore, promoting an MetS prevention and control programme might reduce the occurrence of OPMD and oral cancer.

Glycation of fibronectin inhibits VEGF-induced angiogenesis by uncoupling VEGF receptor-2-c-Src crosstalk

Glycation of extracellular matrix proteins has been demonstrated to contribute to the pathogenesis of vascular complications. However, no previous report has shown the role of glycated fibronectin (FN) in vascular endothelial growth factor (VEGF)‐induced angiogenesis. Thus, this study aimed to investigate the effects of glycated FN on VEGF signalling and to clarify the molecular mechanisms involved. FN was incubated with methylglyoxal (MGO) in vitro to synthesize glycated FN, and human umbilical vein endothelial cells (HUVECs) were seeded onto unmodified and MGO‐glycated FN. Then, VEGF‐induced angiogenesis and VEGF‐induced VEGF receptor‐2 (VEGFR‐2) signalling activation were measured. The results demonstrated that normal FN‐positive bands (260 kD) vanished and advanced glycation end products (AGEs) appeared in MGO‐glycated FN and glycated FN clearly changed to a higher molecular mass. The glycation of FN inhibited VEGF‐induced VEGF receptor‐2 (VEGFR‐2), Akt and ERK1/2 activation and VEGF‐induced cell migration, proliferation and tube formation. The glycation of FN also inhibited the recruitment of c‐Src to VEGFR‐2 by sequestering c‐Src through receptor for AGEs (RAGE) and the anti‐RAGE antibody restored VEGF‐induced VEGFR‐2, Akt and ERK1/2 phosphorylation, endothelial cell migration, proliferation and tube formation. Furthermore, the glycation of FN significantly inhibited VEGF‐induced neovascularization in the Matrigel plugs implanted into subcutaneous tissue of mice. Taken together, these data suggest that the glycation of FN may inhibit VEGF signalling and VEGF‐induced angiogenesis by uncoupling VEGFR‐2‐c‐Src interaction. This may provide a novel mechanism for the impaired angiogenesis in diabetic ischaemic diseases.

Stimulation of Fibronectin Matrix Assembly by Lysine Acetylation

Diabetic nephropathy, a devastating consequence of diabetes mellitus, is characterized by the accumulation of extracellular matrix (ECM) that disrupts the kidney's filtration apparatus. Elevated glucose levels increase the deposition of a fibronectin (FN) matrix by mesangial cells, the primary matrix-producing cells of the kidney, and also increase acetyl-CoA leading to higher levels of lysine acetylation. Here, we investigated the connection between acetylation and the ECM and show that treatment of mesangial cells with deacetylase inhibitors increases both acetylation and FN matrix assembly compared to untreated cells. The matrix effects were linked to lysine 794 (K794) in the β1 integrin cytoplasmic domain based on studies of cells expressing acetylated (K794Q) and non-acetylated (K794R) mimetics. β1(K794Q) cells assembled significantly more FN matrix than wildtype β1 cells, while the non-acetylated β1(K794R) form was inactive. We show that mutation of K794 affects FN assembly by stimulating integrin-FN binding activity and cell contractility. Wildtype and β1(K794Q) cells but not β1(K794R) cells further increased their FN matrix when stimulated with deacetylase inhibitors indicating that increased acetylation on other proteins is required for maximum FN assembly. Thus, lysine acetylation provides a mechanism for glucose-induced fibrosis by up-regulation of FN matrix assembly.

Redox Signaling and Advanced Glycation Endproducts (AGEs) in Diet-Related Diseases

Diets are currently characterized by elevated sugar intake, mainly due to the increased consumption of processed sweetened foods and drinks during the last 40 years. Diet is the main source of advanced glycation endproducts (AGEs). These are toxic compounds formed during the Maillard reaction, which takes place both in vivo, in tissues and fluids under physiological conditions, favored by sugar intake, and ex vivo during food preparation such as baking, cooking, frying or storage. Protein glycation occurs slowly and continuously through life, driving AGE accumulation in tissues during aging. For this reason, AGEs have been proposed as a risk factor in the pathogenesis of diet-related diseases such as diabetes, insulin resistance, cardiovascular diseases, kidney injury, and age-related and neurodegenerative diseases. AGEs are associated with an increase in oxidative stress since they mediate the production of reactive oxygen species (ROS), increasing the intracellular levels of hydrogen peroxide (H₂O₂), superoxide (O₂⁻), and nitric oxide (NO). The interaction of AGEs with the receptor for AGEs (RAGE) enhances oxidative stress through ROS production by NADPH oxidases inside the mitochondria. This affects mitochondrial function and ultimately influences cell metabolism under various pathological conditions. This short review will summarize all evidence that relates AGEs and ROS production, their relationship with diet-related diseases, as well as the latest research about the use of natural compounds with antioxidant properties to prevent the harmful effects of AGEs on health.

Extracellular matrix-cell interactions: Focus on therapeutic applications

Extracellular matrix (ECM) macromolecules together with a multitude of different molecules residing in the extracellular space play a vital role in the regulation of cellular phenotype and behavior. This is achieved via constant reciprocal interactions between the molecules of the ECM and the cells. The ECM-cell interactions are mediated via cell surface receptors either directly or indirectly with co-operative molecules. The ECM is also under perpetual remodeling process influencing cell-signaling pathways on its part. The fragmentation of ECM macromolecules provides even further complexity for the intricate environment of the cells. However, as long as the interactions between the ECM and the cells are in balance, the health of the body is retained. Alternatively, any dysregulation in these interactions can lead to pathological processes and finally to various diseases. Thus, therapeutic applications that are based on retaining normal ECM-cell interactions are highly rationale. Moreover, in the light of the current knowledge, also concurrent multi-targeting of the complex ECM-cell interactions is required for potent pharmacotherapies to be developed in the future.

Exploring the extracellular matrix in health and disease using proteomics

The extracellular matrix (ECM) is a complex assembly of hundreds of proteins that constitutes the scaffold of multicellular organisms. In addition to providing architectural and mechanical support to the surrounding cells, it conveys biochemical signals that regulate cellular processes including proliferation and survival, fate determination, and cell migration. Defects in ECM protein assembly, decreased ECM protein production or, on the contrary, excessive ECM accumulation, have been linked to many pathologies including cardiovascular and skeletal diseases, cancers, and fibrosis. The ECM thus represents a potential reservoir of prognostic biomarkers and therapeutic targets. However, our understanding of the global protein composition of the ECM and how it changes during pathological processes has remained limited until recently.

In this mini-review, we provide an overview of the latest methodological advances in sample preparation and mass spectrometry-based proteomics that have permitted the profiling of the ECM of now dozens of normal and diseased tissues, including tumors and fibrotic lesions.

Glycation Damage: A Possible Hub for Major Pathophysiological Disorders and Aging

Glycation is both a physiological and pathological process which mainly affects proteins, nucleic acids and lipids. Exogenous and endogenous glycation produces deleterious reactions that take place principally in the extracellular matrix environment or within the cell cytosol and organelles. Advanced glycation end product (AGE) formation begins by the non-enzymatic glycation of free amino groups by sugars and aldehydes which leads to a succession of rearrangements of intermediate compounds and ultimately to irreversibly bound products known as AGEs. Epigenetic factors, oxidative stress, UV and nutrition are important causes of the accumulation of chemically and structurally different AGEs with various biological reactivities. Cross-linked proteins, deriving from the glycation process, present both an altered structure and function. Nucleotides and lipids are particularly vulnerable targets which can in turn favor DNA mutation or a decrease in cell membrane integrity and associated biological pathways respectively. In mitochondria, the consequences of glycation can alter bioenergy production. Under physiological conditions, anti-glycation defenses are sufficient, with proteasomes preventing accumulation of glycated proteins, while lipid turnover clears glycated products and nucleotide excision repair removes glycated nucleotides. If this does not occur, glycation damage accumulates, and pathologies may develop. Glycation-induced biological products are known to be mainly associated with aging, neurodegenerative disorders, diabetes and its complications, atherosclerosis, renal failure, immunological changes, retinopathy, skin photoaging, osteoporosis, and progression of some tumors.

Multifaceted Interweaving Between Extracellular Matrix, Insulin Resistance, and Skeletal Muscle

The skeletal muscle provides movement and support to the skeleton, controls body temperature, and regulates the glucose level within the body. This is the core tissue of insulin-mediated glucose uptake via glucose transporter type 4 (GLUT4). The extracellular matrix (ECM) provides integrity and biochemical signals and plays an important role in myogenesis. In addition, it undergoes remodeling upon injury and/or repair, which is also related to insulin resistance (IR), a major cause of type 2 diabetes (T2DM). Altered signaling of integrin and ECM remodeling in diet-induced obesity is associated with IR. This review highlights the interweaving relationship between the ECM, IR, and skeletal muscle. In addition, the importance of the ECM in muscle integrity as well as cellular functions is explored. IR and skeletal muscle ECM remodeling has been discussed in clinical and nonclinical aspects. Furthermore, this review considers the role of ECM glycation and its effects on skeletal muscle homeostasis, concentrating on advanced glycation end products (AGEs) as an important risk factor for the development of IR. Understanding this complex interplay between the ECM, muscle, and IR may improve knowledge and help develop new ideas for novel therapeutics for several IR-associated myopathies and diabetes.

Extracellular matrix glycation and receptor for advanced glycation end-products activation: a missing piece in the puzzle of the association between diabetes and cancer

A growing body of epidemiologic evidence suggests that people with diabetes are at a significantly higher risk of many forms of cancer. However, the molecular mechanisms underlying this association are not fully understood. Cancer cells are surrounded by a complex milieu, also known as tumor microenvironment, which contributes to the development and metastasis of tumors. Of note, one of the major components of this niche is the extracellular matrix (ECM), which becomes highly disorganized during neoplastic progression, thereby stimulating cancer cell transformation, growth and spread. One of the consequences of chronic hyperglycemia, the most frequently observed sign of diabetes and the etiological source of diabetes complications, is the irreversible glycation and oxidation of proteins and lipids leading to the formation of the advanced glycation end-products (AGEs). These compounds may covalently crosslink and biochemically modify structure and functions of many proteins, and AGEs accumulation is particularly high in long-living proteins with low biological turnover, features that are shared by most, if not all, ECM proteins. AGEs-modified proteins are recognized by AGE-binding proteins, and thus glycated ECM components have the potential to trigger Receptor for advanced glycation end-products-dependent mechanisms. The biological consequence of receptor for advanced glycation end-products activation mechanisms seems to be connected, in different ways, to drive some hallmarks of cancer onset and tumor growth. The present review intends to highlight the potential impact of ECM glycation on tumor progression by triggering receptor for advanced glycation end-products-mediated mechanisms.

Time-dependent changes in extra-domain A-fibronectin concentration and relative amounts of fibronectin-fibrin complexes in plasma of patients with peripheral arterial disease after endovascular revascularisation

Fibronectin (FN) may be involved in time- and stage-dependent and inter-related controlled processes of inflammation, coagulation, and wound healing accompanying peripheral arterial disease (PAD). In the present study, FN and FN-containing extra-domain A (EDA-FN), macromolecular FN-fibrin complexes, and FN monomer were analysed in the plasma of 142 PAD patients, including 37 patients with restenosis, for 37 months after revascularisation. FN concentration increased significantly in the plasma of PAD patients within 7 to 12 months after revascularisation, whereas the high concentration of EDA-FN was maintained up to 24 months, significantly higher in the group 7 to 12 months after revascularisation with recurrence of stenosis and lower in the PAD groups 1 to 3 months and 4 to 6 months after revascularisation with comorbid diabetes and ulceration, respectively. The relative amounts of FN-fibrin complexes up to 1600 kDa and FN monomer were significantly higher, within intervals of 4 to 24 months and 4 to 6 months after revascularisation, respectively. Moreover, the relative amounts of 750 to 1600 kDa FN-fibrin complexes within 13 to 24 months after revascularisation were higher in comparison with those in the group without restenosis. In conclusion, high levels of EDA-FN and FN-fibrin complexes could have potential diagnostic value in the management of PAD patients after revascularisation, predicting restenosis risk.

Heparin-fibronectin interactions in the development of extracellular matrix insolubility

During extracellular matrix (ECM) assembly, fibronectin (FN) fibrils are irreversibly converted into a detergent-insoluble form which, through FN's multi-domain structure, can interact with collagens, matricellular proteins, and growth factors to build a definitive matrix. FN also has heparin/heparan sulfate (HS) binding sites. Using HS-deficient CHO cells, we show that the addition of soluble heparin significantly increased the amount of FN matrix that these cells assemble. Sulfated HS glycosaminoglycan (GAG) mimetics similarly increased FN assembly and demonstrated a dependence on GAG sulfation. The length of the heparin chains also plays a role in assembly. Chains of sufficient length to bind to two FN molecules gave maximal stimulation of assembly whereas shorter heparin had less of an effect. Using a decellularized fibroblast matrix for proteolysis, detergent fractionation, and mass spectrometry, we found that the predominant domain within insoluble fibril fragments is FN's major heparin-binding domain HepII (modules III_12-14). Multiple HepII domains bind simultaneously to a single heparin chain in size exclusion chromatography analyses. We propose a model in which heparin/HS binding to the HepII domain connects multiple FNs together to facilitate the formation of protein interactions for insoluble fibril assembly.

Cell-derived decellularized extracellular matrices

The ability to create cell-derived decellularized matrices in a dish gives researchers the opportunity to possess a bioactive, biocompatible material made up of fibrillar proteins and other factors that recapitulates key features of the native structure and composition of in vivo microenvironments. By using cells in a culture system to provide a natural ECM, decellularization allows for a high degree of customization through the introduction of selected proteins and soluble factors. The culture system, culture medium, cell types, and physical environments can be varied to provide specialized ECMs for wide-ranging applications to study cell-ECM signaling, cell migration, cell differentiation, and tissue engineering purposes. This chapter describes a procedure for performing a detergent and high pH-based extraction that leaves the native, cell-assembled ECM intact while removing cellular materials. We address common evaluation methods for assessing the ECM and its composition as well as potential uses for a decellularized ECM.

Cell type-specific extracellular matrix guided the differentiation of human mesenchymal stem cells in 3D polymeric scaffolds

The tissue microenvironment has profound effects on tissue-specific regeneration. The 3-dimensional extracellular matrix (ECM) niche influences the linage-specific differentiation of stem cells in tissue. To understand how ECM guides tissue-specific regeneration, we established a series of 3D composite scaffolds containing ECMs derived from different primary cells isolated from a single animal species and assessed their impact on the differentiation of human mesenchymal stem cells (hMSCs). Synthetic microfiber scaffolds (fiber mats) were fabricated by electrospinning tyrosine-derived polycarbonates (pDTEC). The bovine primary fibroblasts, chondrocytes and osteoblasts cultured on the fiber mats produced and assembled their ECMs, infiltrating the pores of the fibrous scaffold. The composite scaffolds were decellularized to remove cellular components, preserve ECM and minimally affect polymer integrity. Characterization of the ECMs derived from different primary cells in the composite scaffolds showed overlapping but distinct compositions. The chondrogenic and osteogenic differentiation of hMSCs on the different composite scaffolds were compared. Our results showed that ECM derived from chondrocytes cultured in synthetic fiber mats promoted the chondrogenic differentiation of hMSC in the presence or absence of soluble inducing factors. ECM derived from co-culture of osteoblasts and chondrocytes promoted osteogenic differentiation in hMSCs better than ECM derived from chondrocytes. This study demonstrated that decellularized ECMs derived from different cell types formed within synthetic fiber scaffolds guide the tissue-specific differentiation of hMSCs. These composite scaffolds may be developed into models to study the mechanisms of ECM-induced tissue regeneration.