Diabetes-induced alterations in the extracellular matrix and their impact on myocardial function

Delivery technologies for therapeutic targeting of fibronectin in autoimmunity and fibrosis applications

Fibronectin (FN) is a critical component of the extracellular matrix (ECM) contributing to various physiological processes, including tissue repair and immune response regulation. FN regulates various cellular functions such as adhesion, proliferation, migration, differentiation, and cytokine release. Alterations in FN expression, deposition, and molecular structure can profoundly impact its interaction with other ECM proteins, growth factors, cells, and associated signaling pathways, thus influencing the progress of diseases such as fibrosis and autoimmune disorders. Therefore, developing therapeutics that directly target FN or its interaction with cells and other ECM components can be an intriguing approach to address autoimmune and fibrosis pathogenesis.

The evaluation of fetal interventricular septum with M-mode and spectral tissue Doppler imaging in gestational diabetes mellitus: a case-control study

OBJECTIVES

To demonstrate possible functional changes in the frequently affected fetal interventricular septum (IVS) with spectral tissue Doppler imaging (TDI) and M-mode imaging to compare gestational diabetes mellitus (GDM) and control groups.

METHODS

A total of 63 pregnant women with GDM, 30 on diet (A1 GDM) and 33 on treated with insulin (A2 GDM), and 63 healthy pregnant women randomly selected and matched to the case group in the control group were included.

RESULTS

The GDM fetuses had significantly thickened IVS, increased early diastole (E'), atrial contraction (A'), systole (S'), higher myocardial performance index (MPI'), prolonged isovolumetric relaxation time (IVRT'), shortened ejection time (ET'), and decreased septal annular plane systolic excursion (SAPSE) than the controls. The A2 GDM group fetuses had significantly thickened IVS, increased S' and shortened ET' than the A1 GDM group. In the GDM group, we found a significantly positive low correlation between glycated hemoglobin levels and maternal serum fasting glucose and one-hour postprandial glucose with fetal IVS thickness. We demonstrated a significantly negative low correlation between maternal serum one-hour postprandial glucose, glycated hemoglobin levels, and gestational weight gain with fetal IVS ET'.

CONCLUSIONS

Fetal IVS diastolic and systolic functions were altered in the GDM group compared to controls, and systolic functions were altered in A2 GDM compared to A1 GDM. This may alert clinicians to possible cardiovascular diseases in the postnatal life, and early preventive strategies and long-term lifestyle changes may provide protection in fetuses with GDM.

Fibroblast Growth Factor 23: Potential Marker of Invisible Heart Damage in Diabetic Population

Two-dimensional speckle-tracking echocardiography (2DSTE) detects myocardial dysfunction despite a preserved left ventricular ejection fraction. Fibroblast growth factor 23 (FGF23) has become a promising biomarker of cardiovascular risk. This study aimed to determine whether FGF23 may be used as a marker of myocardial damage among patients with diabetes mellitus type 2 (T2DM) and no previous history of myocardial infarction. The study enrolled 71 patients with a median age of 70 years. Laboratory data were analyzed retrospectively. Serum FGF23 levels were determined using a sandwich enzyme-linked immunosorbent assay. All patients underwent conventional echocardiography and 2DSTE. Baseline characteristics indicated that the median time elapsed since diagnosis with T2DM was 19 years. All subjects were divided into two groups according to left ventricular diastolic function. Individuals with confirmed left ventricular diastolic dysfunction had significantly lower levels of estimated glomerular filtration rate and higher values of hemoglobin A1c. Global circumferential strain (GCS) was reduced in the majority of patients. Only an epicardial GCS correlated significantly with the FGF23 concentration in all patients. The study indicates that a cardiac strain is a reliable tool for a subtle myocardial damage assessment. It is possible that FGF23 may become an early diagnostic marker of myocardial damage in patients with T2DM.

Probing the effect of glycosaminoglycan depletion on integrin interactions with collagen I fibrils in the native extracellular matrix environment

Fibrillar collagen-integrin interactions in the extracellular matrix (ECM) regulate a multitude of cellular processes and cell signalling. Collagen I fibrils serve as the molecular scaffolding for connective tissues throughout the human body and are the most abundant protein building blocks in the ECM. The ECM environment is diverse, made up of several ECM proteins, enzymes, and proteoglycans. In particular, glycosaminoglycans (GAGs), anionic polysaccharides that decorate proteoglycans, become depleted in the ECM with natural aging and their mis-regulation has been linked to cancers and other diseases. The impact of GAG depletion in the ECM environment on collagen I protein interactions and on mechanical properties is not well understood. Here, we integrate ELISA protein binding assays with liquid high-resolution atomic force microscopy (AFM) to assess the effects of GAG depletion on the interaction of collagen I fibrils with the integrin α2I domain using separate rat tails. ELISA binding assays demonstrate that α2I preferentially binds to GAG-depleted collagen I fibrils in comparison to native fibrils. By amplitude modulated AFM in air and in solution, we find that GAG-depleted collagen I fibrils retain structural features of the native fibrils, including their characteristic D-banding pattern, a key structural motif. AFM fast force mapping in solution shows that GAG depletion reduces the stiffness of individual fibrils, lowering the indentation modulus by half compared to native fibrils. Together these results shed new light on how GAGs influence collagen I fibril-integrin interactions and may aid in strategies to treat diseases that result from GAG mis-regulation.

Combination of common mtDNA variants results in mitochondrial dysfunction and a connective tissue dysregulation

Mitochondrial dysfunction can be associated with a range of clinical manifestations. Here, we report a family with a complex phenotype including combinations of connective tissue, neurological, and metabolic symptoms that were passed on to all surviving children. Analysis of the maternally inherited mtDNA revealed a novel genotype encompassing the haplogroup J - defining mitochondrial DNA (mtDNA) ND5 m.13708G>A (A458T) variant arising on the mtDNA haplogroup H7A background, an extremely rare combination. Analysis of transmitochondrial cybrids with the 13708A-H7 mtDNA revealed a lower mitochondrial respiration, increased reactive oxygen species production (mROS), and dysregulation of connective tissue gene expression. The mitochondrial dysfunction was exacerbated by histamine, explaining why all eight surviving children inherited the dysfunctional histidine decarboxylase allele (W327X) from the father. Thus, certain combinations of common mtDNA variants can cause mitochondrial dysfunction, mitochondrial dysfunction can affect extracellular matrix gene expression, and histamine-activated mROS production can augment the severity of mitochondrial dysfunction. Most important, we have identified a previously unreported genetic cause of mitochondrial disorder arising from the incompatibility of common, nonpathogenic mtDNA variants.

The Diabetic Cardiorenal Nexus

The end-stage of the clinical combination of heart failure and kidney disease has become known as cardiorenal syndrome. Adverse consequences related to diabetes, hyperlipidemia, obesity, hypertension and renal impairment on cardiovascular function, morbidity and mortality are well known. Guidelines for the treatment of these risk factors have led to the improved prognosis of patients with coronary artery disease and reduced ejection fraction. Heart failure hospital admissions and readmission often occur, however, in the presence of metabolic, renal dysfunction and relatively preserved systolic function. In this domain, few advances have been described. Diabetes, kidney and cardiac dysfunction act synergistically to magnify healthcare costs. Current therapy relies on improving hemodynamic factors destructive to both the heart and kidney. We consider that additional hemodynamic solutions may be limited without the use of animal models focusing on the cardiomyocyte, nephron and extracellular matrices. We review herein potential common pathophysiologic targets for treatment to prevent and ameliorate this syndrome.

Investigating the specificity of endothelin-traps as a potential therapeutic tool for endothelin-1 related disorders

BACKGROUND

Endothelin (ET)-traps are Fc-fusion proteins with a design based on the physiological receptors of ET-1. Previous work has shown that use of the selected ET-traps potently and significantly reduces different markers of diabetes pathology back to normal, non-disease levels.

AIM

To demonstrate the selected ET-traps potently and significantly bind to ET-1.

METHODS

We performed phage display experiments to test different constructs of ET-traps, and conducted bio-layer interferometry binding assays to verify that the selected ET-traps bind specifically to ET-1 and display binding affinity in the double-digit picomolar range (an average of 73.8 rM, n = 6).

RESULTS

These experiments have confirmed our choice of the final ET-traps and provided proof-of-concept for the potential use of constructs as effective biologics for diseases associated with pathologically elevated ET-1.

CONCLUSION

There is increased need for such therapeutics as they could help save millions of lives around the world.

Carnosine protects stimulus-secretion coupling through prevention of protein carbonyl adduction events in cells under metabolic stress

Type 2 diabetes is characterised by failure to control glucose homeostasis, with numerous diabetic complications attributable to the resulting exposure of cells and tissues to chronic elevated concentrations of glucose and fatty acids. This, in part, results from formation of advanced glycation and advanced lipidation end-products that are able to modify protein, lipid, or DNA structure, and disrupt normal cellular function. Herein we used mass spectrometry to identify proteins modified by two such adduction events in serum of individuals with obesity, type 2 diabetes, and gestational diabetes, along with similar analyses of human and mouse skeletal muscle cells and mouse pancreatic islets exposed to glucolipotoxic stress. We also report that carnosine, a histidine containing dipeptide, prevented 65-90% of 4-hydroxynonenal and 3-nitrotyrosine adduction events, and that this in turn preserved mitochondrial function and protected stimulus-secretion coupling in cells exposed to metabolic stress. Carnosine therefore offers significant therapeutic potential against metabolic diseases.

Linking Oxidative Stress and DNA Damage to Changes in the Expression of Extracellular Matrix Components

Cells are subjected to endogenous [e.g., reactive oxygen species (ROS), replication stress] and exogenous insults (e.g., UV light, ionizing radiation, and certain chemicals), which can affect the synthesis and/or stability of different macromolecules required for cell and tissue function. Oxidative stress, caused by excess ROS, and DNA damage, triggered in response to different sources, are countered and resolved by specific mechanisms, allowing the normal physiological equilibrium of cells and tissues to be restored. One process that is affected by oxidative stress and DNA damage is extracellular matrix (ECM) remodeling, which is a continuous and highly controlled mechanism that allows tissues to readjust in reaction to different challenges. The crosstalk between oxidative stress/DNA damage and ECM remodeling is not unidirectional. Quite on the contrary, mutations in ECM genes have a strong impact on tissue homeostasis and are characterized by increased oxidative stress and potentially also accumulation of DNA damage. In this review, we will discuss how oxidative stress and DNA damage affect the expression and deposition of ECM molecules and conversely how mutations in genes encoding ECM components trigger accumulation of oxidative stress and DNA damage. Both situations hamper the reestablishment of cell and tissue homeostasis, with negative impacts on tissue and organ function, which can be a driver for severe pathological conditions.

Crosstalk of Diabetic Conditions with Static Versus Dynamic Flow Environment-Impact on Aortic Valve Remodeling

Type 2 diabetes mellitus (T2D) is one of the prominent risk factors for the development and progression of calcific aortic valve disease. Nevertheless, little is known about molecular mechanisms of how T2D affects aortic valve (AV) remodeling. In this study, the influence of hyperinsulinemia and hyperglycemia on degenerative processes in valvular tissue is analyzed in intact AV exposed to an either static or dynamic 3D environment, respectively. The complex native dynamic environment of AV is simulated using a software-governed bioreactor system with controlled pulsatile flow. Dynamic cultivation resulted in significantly stronger fibrosis in AV tissue compared to static cultivation, while hyperinsulinemia and hyperglycemia had no impact on fibrosis. The expression of key differentiation markers and proteoglycans were altered by diabetic conditions in an environment-dependent manner. Furthermore, hyperinsulinemia and hyperglycemia affect insulin-signaling pathways. Western blot analysis showed increased phosphorylation level of protein kinase B (AKT) after acute insulin stimulation, which was lost in AV under hyperinsulinemia, indicating acquired insulin resistance of the AV tissue in response to elevated insulin levels. These data underline a complex interplay of diabetic conditions on one hand and biomechanical 3D environment on the other hand that possesses an impact on AV tissue remodeling.

Molecular Mechanisms of Obesity-Linked Cardiac Dysfunction: An Up-Date on Current Knowledge

Obesity is defined as excessive body fat accumulation, and worldwide obesity has nearly tripled since 1975. Excess of free fatty acids (FFAs) and triglycerides in obese individuals promote ectopic lipid accumulation in the liver, skeletal muscle tissue, and heart, among others, inducing insulin resistance, hypertension, metabolic syndrome, type 2 diabetes (T2D), atherosclerosis, and cardiovascular disease (CVD). These diseases are promoted by visceral white adipocyte tissue (WAT) dysfunction through an increase in pro-inflammatory adipokines, oxidative stress, activation of the renin-angiotensin-aldosterone system (RAAS), and adverse changes in the gut microbiome. In the heart, obesity and T2D induce changes in substrate utilization, tissue metabolism, oxidative stress, and inflammation, leading to myocardial fibrosis and ultimately cardiac dysfunction. Peroxisome proliferator-activated receptors (PPARs) are involved in the regulation of carbohydrate and lipid metabolism, also improve insulin sensitivity, triglyceride levels, inflammation, and oxidative stress. The purpose of this review is to provide an update on the molecular mechanisms involved in obesity-linked CVD pathophysiology, considering pro-inflammatory cytokines, adipokines, and hormones, as well as the role of oxidative stress, inflammation, and PPARs. In addition, cell lines and animal models, biomarkers, gut microbiota dysbiosis, epigenetic modifications, and current therapeutic treatments in CVD associated with obesity are outlined in this paper.

COL1A1 as a potential new biomarker and therapeutic target for type 2 diabetes

Type 2 diabetes (T2D) is a public health problem with a rising incidence worldwide. In this study, a potential new biomarker for T2D and mechanisms underlying the hypoglycemic effects of Enteromorpha prolifera oligosaccharide were investigated. Tandem mass tag labeling with LC-MS/MS was used to identify the differentially expressed proteins (DEPs) between the jejunum of diabetic rats and control rats. Correlations between glycometabolic parameters and DEPs were revealed by a network analysis. The expression levels of target genes in key metabolic pathways were further evaluated to identify candidate biomarkers. Among 6810 total proteins, approximately 88 % were quantified, of which 148 DEPs with a fold change of <0.83 or>1.2 and a corrected p-value of <0.05 were identified. A KEGG enrichment analysis indicated that the hypoglycaemic effects of E. prolifera oligosaccharide involved the PI3K/AKT and extracellular matrix receptor interaction signaling pathways. More importantly, Col1a1 was the most significant gene in the extracellular matrix receptor interaction pathway and was linked to hypoglycaemic activity for the first time. Thus, Col1a1 is a novel potential therapeutic target for alleviating T2D.

Sex-dependent effects of preconception exposure to arsenite on gene transcription in parental germ cells and on transcriptomic profiles and diabetic phenotype of offspring

Chronic exposure to inorganic arsenic (iAs) has been linked to diabetic phenotypes in both humans and mice. However, diabetogenic effects of iAs exposure during specific developmental windows have never been systematically studied. We have previously shown that in mice, combined preconception and in utero exposures to iAs resulted in impaired glucose homeostasis in male offspring. The goal of the present study was to determine if preconception exposure alone can contribute to this outcome. We have examined metabolic phenotypes in male and female offspring from dams and sires that were exposed to iAs in drinking water (0 or 200 μg As/L) for 10 weeks prior to mating. The effects of iAs exposure on gene expression profiles in parental germ cells, and pancreatic islets and livers from offspring were assessed using RNA sequencing. We found that iAs exposure significantly altered transcript levels of genes, including diabetes-related genes, in the sperm of sires. Notably, some of the same gene transcripts and the associated pathways were also altered in the liver of the offspring. The exposure had a more subtle effect on gene expression in maternal oocytes and in pancreatic islets of the offspring. In female offspring, the preconception exposure was associated with increased adiposity, but lower blood glucose after fasting and after glucose challenge. HOMA-IR, the indicator of insulin resistance, was also lower. In contrast, the preconception exposure had no effects on blood glucose measures in male offspring. However, males from parents exposed to iAs had higher plasma insulin after glucose challenge and higher insulinogenic index than control offspring, indicating a greater requirement for insulin to maintain glucose homeostasis. Our results suggest that preconception exposure may contribute to the development of diabetic phenotype in male offspring, possibly mediated through germ cell-associated inheritance. Future research can investigate role of epigenetics in this phenomenon. The paradoxical outcomes in female offspring, suggesting a protective effect of the preconception exposure, warrant further investigation.

Increased Transglutaminase 2 Expression and Activity in Rodent Models of Obesity/Metabolic Syndrome and Aging

Diastolic dysfunction of the heart and decreased compliance of the vasculature and lungs (i.e., increased organ tissue stiffness) are known features of obesity and the metabolic syndrome. Similarly, cardiac diastolic dysfunction is associated with aging. Elevation of the enzyme transglutaminase 2 (TG2) leads to protein cross-linking and enhanced collagen synthesis and participates as a candidate pathway for development of tissue stiffness. With these observations in mind we hypothesized that TG2 may be elevated in tissues of a rat model of obesity/metabolic syndrome (the ZSF 1 rat) and a mouse model of aging, i.e., the senescent SAMP8 mouse. In the experiments reported here, TG2 expression and activity were found for the first time to be spontaneously elevated in organs from both the ZSF1 rat and the SAMP8 mouse. These observations are consistent with a hypothesis that a TG2-related pathway may participate in the known tissue stiffness associated with cardiac diastolic dysfunction in these two rodent models. The potential TG2 pathway needs better correlation with physiologic dysfunction and may eventually provide novel therapeutic insights to improve tissue compliance.

Circulating Protein Signatures and Causal Candidates for Type 2 Diabetes

The increasing prevalence of type 2 diabetes poses a major challenge to societies worldwide. Blood-based factors like serum proteins are in contact with every organ in the body to mediate global homeostasis and may thus directly regulate complex processes such as aging and the development of common chronic diseases. We applied a data-driven proteomics approach, measuring serum levels of 4,137 proteins in 5,438 elderly Icelanders, and identified 536 proteins associated with prevalent and/or incident type 2 diabetes. We validated a subset of the observed associations in an independent case-control study of type 2 diabetes. These protein associations provide novel biological insights into the molecular mechanisms that are dysregulated prior to and following the onset of type 2 diabetes and can be detected in serum. A bidirectional two-sample Mendelian randomization analysis indicated that serum changes of at least 23 proteins are downstream of the disease or its genetic liability, while 15 proteins were supported as having a causal role in type 2 diabetes.

Understanding the multifaceted mechanisms of diabetic wound healing and therapeutic application of stem cells conditioned medium in the healing process

Mesenchymal stem cells (MSCs) transplantation seems to be a promising new therapy for diabetic wound healing (DWH), and currently, arrays of MSCs from various sources ranging from umbilical, adipose to dental sources are available as a treatment modality for this disease. However, it now appears that only a fraction of transplanted cells actually assimilate and survive in host tissues suggesting that the major mechanism by which stem cells participate in tissue repair are most likely related to their secretome level. These include a wide range of growth factors, cytokines, and chemokines, which can be found from the conditioned medium (CM) used to culture the cells. Basic studies and preclinical work confirm that the therapeutic effect of CMs are comparable with the application of stem cells. This review describes in detail the wound healing process in diabetes and the cellular and biological factors that influence the process. Subsequently, through a comprehensive literature search of studies related to wound healing in diabetics, we aim to provide an overview of scientific merits of using MSCs-CM in the treatment of diabetic wound as well as the significant caveats, which restricts its potential use in clinical set-ups. To our best knowledge, this is one of the first review papers that collect the importance of stem cells as an alternative treatment to the DWH. We anticipate that the success of this treatment will have a significant clinical impact on diabetic wounds.

Perinatal changes in fetal cardiac geometry and function in diabetic pregnancy at term

OBJECTIVE

To evaluate the effect of diabetes in pregnancy on fetal and neonatal cardiac geometry and function around the time of delivery.

METHODS

This was a prospective study of 75 pregnant women delivering at term, comprising 54 normal pregnancies and 21 with a diagnosis of pregestational or gestational diabetes mellitus. Fetal and neonatal conventional and spectral tissue Doppler and two-dimensional speckle-tracking echocardiography were performed a few days before and within hours after delivery. Fetal and neonatal cardiac geometry, global myocardial deformation and performance, diastolic and systolic function and left ventricular (LV) torsion were compared between normal pregnancies and those with diabetes, and perinatal changes within the diabetes group were assessed.

RESULTS

Compared with normal pregnancies, diabetic pregnancies demonstrated significant differences in fetal ventricular geometry, myocardial deformation and cardiac function (right ventricular (RV) sphericity index, 0.56 vs 0.65; LV torsion, 2.1 °/cm vs 5.6 °/cm; LV isovolumetric relaxation time, 101 ms vs 115 ms; and RV isovolumetric contraction time, 107 ms vs 119 ms; P < 0.001 for all). Compared with normal pregnancies, diabetic pregnancies demonstrated significant differences in neonatal cardiac parameters (mean RV sphericity index, 0.43 vs 0.55; mean LV torsion, 1.30 °/cm vs 2.78 °/cm; median LV myocardial performance index (MPI'), 0.39 vs 0.51; median RV-MPI', 0.34 vs 0.40; P < 0.01 for all). Paired comparison between fetal and neonatal cardiac indices in diabetic pregnancies demonstrated that delivery resulted in a significant improvement in some, but not all, cardiac indices (mean RV sphericity index, 0.65 vs 0.55; mean LV torsion, 5.60 °/cm vs 2.78 °/cm; median RV-MPI', 0.51 vs 0.40; P < 0.01 for all).

CONCLUSIONS

Compared with normal term fetuses and neonates, those of diabetic women exhibit cardiac indices indicative of myocardial impairment, reflecting a response to a relatively hyperglycemic intrauterine environment with alteration in fetal loading conditions (LV preload deprivation and increased RV afterload) and adaptation to subsequent acute changes in hemodynamic load at delivery. Elucidating mechanisms that contribute to the alterations in perinatal cardiac function in diabetic pregnancy could help in refining management and developing better therapeutic strategies to reduce the risk of adverse pregnancy outcomes. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Endothelin-1 traps as a potential therapeutic tool: from diabetes to beyond?

There is substantial research on the vasoactive peptide endothelin (ET)-1 in physiology, as well as in pathology. In fact, pathologically elevated levels of ET-1 have been found in several disease states, such as various cardiovascular diseases, different cancers, some neurodegenerative disorders, as well as in diabetes. Here, we describe and discuss ET-1, its importance in different diseases, and the potential therapeutic effects of ET-traps in the treatment of these diseases. Previous in vitro and in vivo research (in the diabetes disease space) demonstrated that ET-traps potently and significantly prevent the induction of different markers of diabetes-related pathology. This included induction of extracellular matrix (ECM) proteins (collagen 4α1 and fibronectin), which are pathologically elevated in diabetes. The ET-traps prevented induction of these and brought a significant return to non-diabetic levels. We also discuss the merits of using ET-traps over the currently used endothelin receptor antagonists (ERAs) and previously used therapeutic antibodies.

Effect of glabridin on collagen deposition in liver and amelioration of hepatocyte destruction in diabetes rats

Abnormalities in insulin hormone levels leads to a hyperglycemic condition of diabetic mellitus. Hyperglycemia seriously induces organ and system destructions. The excessive accumulation of collagen fiber deposits occurs in inflammatory and reorganization processes of chronic liver diseases in type I insulin-dependent diabetes. Regarding the research objective, glabridin (GLB), an active compound of licorice, was used as a daily supplement (40 mg/kg) in order to decrease hepatocyte destruction and collagen deposition in liver tissue of diabetic animals induced by streptozotocin. A total of 40 were randomly allocated to five groups (each, n=10), control, control treated with GLB (GLB), diabetic rats (DM) injected with single dose of streptozotocin (60 mg/kg) to induce a diabetic condition, diabetic rats receiving GLB (DM+GLB; 40 mg/kg) and diabetic rats treated with glibenclamide (DM+GL; 4 mg/kg). Characteristic histopathological changes in liver cells and tissues of rats were determined by Masson's trichrome staining and transmission electron microscopy (TEM). Western blotting was used to detect the expression of the key markers, collagen type I and fibronectin proteins. The histological investigation of liver tissue of the DM group revealed that the collagen fiber deposition was increased in the periportal, pericentral and perisinusoidal spaces compared with controls. Hepatocytes appeared as small and fragmented cells in TEM examination. Collagenization of the perisinusoidal space was recently demonstrated to represent a new aspect of the microvascular abnormalities and liver fibrosis. Healthy hepatocytes with round nucleus were observed following supplementation of glabridin. In addition, collagen fiber deposition was reduced in the area adjacent to the perisinusoidal space. The expression of collagen type I and fibronectin decreased strongly following glabridin supplementation in DM+GLB rats compared with DM rats, indicating that the hepatic tissue reorganization regained its normal morphology. These findings suggest that it may be beneficial to examine the role of glabridin as a therapeutic agent in diabetes treatment in future research.

Impact of hyperinsulinemia and hyperglycemia on valvular interstitial cells - A link between aortic heart valve degeneration and type 2 diabetes

Type 2 diabetes is a known risk factor for cardiovascular diseases and is associated with an increased risk to develop aortic heart valve degeneration. Nevertheless, molecular mechanisms leading to the pathogenesis of valve degeneration in the context of diabetes are still not clear. Hence, we hypothesized that classical key factors of type 2 diabetes, hyperinsulinemia and hyperglycemia, may affect signaling, metabolism and degenerative processes of valvular interstitial cells (VIC), the main cell type of heart valves. Therefore, VIC were derived from sheep and were treated with hyperinsulinemia, hyperglycemia and the combination of both. The presence of insulin receptors was shown and insulin led to increased proliferation of the cells, whereas hyperglycemia alone showed no effect. Disturbed insulin response was shown by impaired insulin signaling, i.e. by decreased phosphorylation of Akt/GSK-3α/β pathway. Analysis of glucose transporter expression revealed absence of glucose transporter 4 with glucose transporter 1 being the predominantly expressed transporter. Glucose uptake was not impaired by disturbed insulin response, but was increased by hyperinsulinemia and was decreased by hyperglycemia. Analyses of glycolysis and mitochondrial respiration revealed that VIC react with increased activity to hyperinsulinemia or hyperglycemia, but not to the combination of both. VIC do not show morphological changes and do not acquire an osteogenic phenotype by hyperinsulinemia or hyperglycemia. However, the treatment leads to increased collagen type 1 and decreased α-smooth muscle actin expression. This work implicates a possible role of diabetes in early phases of the degeneration of aortic heart valves.

Degenerative aortic valve disease and diabetes: Implications for a link between proteoglycans and diabetic disorders in the aortic valve

Degenerative aortic valve disease in combination with diabetes is an increasing burden worldwide. There is growing evidence that particularly small leucine-rich proteoglycans are involved in the development of degenerative aortic valve disease. Nevertheless, the role of these molecules in this disease in the course of diabetes has not been elucidated in detail and previous studies remain controversial. Therefore, the aim of this study is to broaden the knowledge about small leucine-rich proteoglycans in degenerative aortic valve disease and the influence of diabetes and hyperglycaemia on aortic valves and valvular interstitial cells is examined. Analyses were performed using reverse-transcription polymerase chain reaction, Western blot, enzyme-linked immunosorbent assay, (immuno)histology and colorimetric assays. We could show that biglycan, but not decorin and lumican, is upregulated in degenerated human aortic valve cusps. Subgroup analysis reveals that upregulation of biglycan is stage-dependent. In vivo, loss of biglycan leads to stage-dependent calcification and also to migratory effects on interstitial cells within the extracellular matrix. In late stages of degenerative aortic valve disease, diabetes increases the expression of biglycan in aortic valves. In vitro, the combinations of hyperglycaemic with pro-degenerative conditions lead to an upregulation of biglycan. In conclusion, biglycan represents a potential link between degenerative aortic valve disease and diabetes.

In vivo studies demonstrate that endothelin-1 traps are a potential therapy for type I diabetes

Background

Type 1 diabetes is a serious, lifelong condition where the body's blood glucose level increases because of the body's inability to make insulin. An important consequence of this is the increased expression of extracellular matrix proteins, such as fibronectin and collagen 4α1, in key tissues and organs like the heart and kidneys. Diabetes is also associated with increased plasma levels of the vasoactive peptide endothelin (ET)-1. This further aggravates the expression of the ECM proteins. There are also important consequences of increased glucose and ET-1 levels in diabetes on the heart, termed diabetic cardiomyopathy.

Methods

We have previously reported the development of ET-traps, which potently and significantly reduce pathological levels of ET-1. In this study, we tested the in vivo therapeutic potential of ET-traps for type 1 diabetes using the B6 mouse model.

Results

Following subcutaneous administration of ET-traps 3 times a week, over a 2 month period, the 500 nM dose of ET-traps gave a significant reduction in collagen 4α1 expression in the heart and kidney, returning it back to control, non-diabetic levels at both the mRNA and protein levels. The expression of fibronectin mRNA is also returned to control levels with the 500 nM dose of ET-traps. The efficacy of ET-traps for type 1 diabetes was further evinced by immunohistochemistry data, echocardiography studies (measuring left ventricular systolic function and diastolic dysfunction) and a measure of urine creatinine and albumin levels. In all analyses, the 500 nM dose of ET-traps returns the different measures to control, non-diabetic levels.

Conclusion

Data from this study show that in a mouse model ET-traps have a potent and significant therapeutic effect on diabetes disease pathology. Future studies could further evaluate the use of ET-traps as a therapy for diabetes, including taking them through clinical trials.

Increased Extracellular Matrix Protein Production in Chronic Diabetic Complications: Implications of Non-Coding RNAs

Management of chronic diabetic complications remains a major medical challenge worldwide. One of the characteristic features of all chronic diabetic complications is augmented production of extracellular matrix (ECM) proteins. Such ECM proteins are deposited in all tissues affected by chronic complications, ultimately causing organ damage and dysfunction. A contributing factor to this pathogenetic process is glucose-induced endothelial damage, which involves phenotypic transformation of endothelial cells (ECs). This phenotypic transition of ECs, from a quiescent state to an activated dysfunctional state, can be mediated through alterations in the synthesis of cellular proteins. In this review, we discussed the roles of non-coding RNAs, specifically microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), in such processes. We further outlined other epigenetic mechanisms regulating the biogenesis and/or function of non-coding RNAs. Overall, we believe that better understanding of such molecular processes may lead to the development of novel biomarkers and therapeutic strategies in the future.

Molecular Mechanisms Responsible for Diastolic Dysfunction in Diabetes Mellitus Patients

In diabetic patients, cardiomyopathy is an important cause of heart failure, but its pathophysiology has not been completely understood thus far. Myocardial hypertrophy and diastolic dysfunction have been considered the hallmarks of diabetic cardiomyopathy (DCM), while systolic function is affected in the latter stages of the disease. In this article we propose the potential pathophysiological mechanisms responsible for myocardial hypertrophy and increased myocardial stiffness leading to diastolic dysfunction in this specific entity. According to our model, increased myocardial stiffness results from both cellular and extracellular matrix stiffness as well as cell–matrix interactions. Increased intrinsic cardiomyocyte stiffness is probably the most important contributor to myocardial stiffness. It results from the impairment in cardiomyocyte cytoskeleton. Several other mechanisms, specifically affected by diabetes, seem to also be significantly involved in myocardial stiffening, i.e., impairment in the myocardial nitric oxide (NO) pathway, coronary microvascular dysfunction, increased inflammation and oxidative stress, and myocardial sodium glucose cotransporter-2 (SGLT-2)-mediated effects. Better understanding of the complex pathophysiology of DCM suggests the possible value of drugs targeting the listed mechanisms. Antidiabetic drugs, NO-stimulating agents, anti-inflammatory agents, and SGLT-2 inhibitors are emerging as potential treatment options for DCM.

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.

Hypertrophy Stimulation at the Onset of Type I Diabetes Maintains the Soleus but Not the EDL Muscle Mass in Wistar Rats

Diabetes mellitus induces a reduction in skeletal muscle mass and strength. Strength training is prescribed as part of treatment since it improves glycemic control and promotes increase of skeletal muscle mass. The mechanisms involved in overload-induced muscle hypertrophy elicited at the establishment of the type I diabetic state was investigated in Wistar rats. The purpose was to examine whether the overload-induced hypertrophy can counteract the hypotrophy associated to the diabetic state. The experiments were performed in oxidative (soleus) or glycolytic (EDL) muscles. PI3K/Akt/mTOR protein synthesis pathway was evaluated 7 days after overload-induced hypertrophy of soleus and of EDL muscles. The mRNA expression of genes associated with different signaling pathways that control muscle hypertrophy was also evaluated: mechanotransduction (FAK), Wnt/β-catenin, myostatin, and follistatin. The soleus and EDL muscles when submitted to overload had similar hypertrophic responses in control and diabetic animals. The increase of absolute and specific twitch and tetanic forces had the same magnitude as muscle hypertrophic response. Hypertrophy of the EDL muscle from diabetic animals mostly involved mechanical loading-stimulated PI3K/Akt/mTOR pathway besides the reduced activation of AMP-activated protein kinase (AMPK) and decrease of myostatin expression. Hypertrophy was more pronounced in the soleus muscle of diabetic animals due to a more potent activation of rpS6 and increased mRNA expression of insulin-like growth factor-1 (IGF-1), mechano-growth factor (MGF) and follistatin, and decrease of myostatin, MuRF-1 and atrogin-1 contents. The signaling changes enabled the soleus muscle mass and force of the diabetic rats to reach the values of the control group.

Microbiota of Chronic Diabetic Wounds: Ecology, Impact, and Potential for Innovative Treatment Strategies

World Health Organization considered diabetes as one of the 20th century epidemics, estimating that over 10% of the world population is diabetic or at high risk. Self-assessment studies indicate that diabetic patients consider chronic wounds to affect their quality of life more dramatically than vision loss or renal failure. In addition to being the main reason for diabetic patients' hospitalization, the economic burden of diabetic chronic wounds is close to 1% of United Kingdom and United States health systems budgets, which exceeds the funds allocated to the treatment of some types of cancer in both countries. Among the factors preceding the emergence of chronic diabetic wounds, also designated diabetic foot ulcers (DFUs), hygiene and pressure in specific areas are under patient control, while others are still far from being understood. A triple impairment in the innervation, immune responses, and vascularization associated to DFU has been extensively studied by the scientific community. However, the skin natural microbiota has only recently emerged as having a tremendous impact on DFU emergence and evolution to chronicity. Despite the great inter- and intra-variability of microbial colonizers, ongoing efforts are now focused on deciphering the impact of commensal and pathogenic microbiota on DFU etiology, as well as the mechanisms of interkingdom microbial-host communication. This review summarizes recent work in this context and offers new microbiological perspectives that may hold potential in the prevention and treatment of chronic diabetic wounds.

Silencing of activin receptor-like kinase 7 alleviates aortic stiffness in type 2 diabetic rats

AIM

Arterial stiffness is an important feature of diabetic macrovascular complications. Activin receptor-like kinase 7 (ALK7), a member of type I transforming growth factor-β (TGF-β) receptors, is correlated with pathogenic risks of type 2 diabetes mellitus and cardiovascular diseases and may be involved in cardiovascular remodeling. We aimed to investigate whether ALK7 is implicated in diabetes-induced aortic stiffness.

METHODS

Type 2 diabetes was induced by high-fat diet and low-dose streptozotocin (STZ; 27.5 mg/kg). Forty rats were separated into four groups: control, diabetes, diabetes with empty virus and diabetes treated with ALK7-shRNA. The metabolic index, ALK 7 expression and aortic stiffness were evaluated. We used gene silencing method to investigate the role of ALK7 in the pathological development.

RESULTS

Diabetic rats showed increased blood glucose, cholesterol, triglyceride levels, severe insulin resistance and ALK7 overexpression. Diabetes enhanced aortic stiffness, as demonstrated by the loss and disruption of elastic fibers as well as by an increase in collagen fibers in the aortic media. ALK7 gene silencing ameliorated metabolic hyperlipidemia and insulin resistance. With ALK7 gene silencing, collagen content, elastin to collagen ratio, as well as collagen I-to-collagen III content ratio in diabetic rats were significantly decreased. Moreover, the phosphorylation level of Smad2/3 was markedly decreased after ALK7 gene silencing.

CONCLUSIONS

ALK7 gene silencing has a protective effect on diabetes-induced aortic stiffness, insulin resistance and hyperlipidemia, thus implicating a new potential therapeutic approach to diabetic macrovascular stiffness.

Sudden cardiac death and diabetes mellitus

Sudden cardiac death (SCD) affects a significant percentage of diabetic patients. SCD in these patients can be due to several factors, such as diastolic dysfunction, heart failure, altered platelet function, inflammation, sympathetic nervous stimulation and other factors. In the present review, we discuss the association between diabetes mellitus and SCD.

Investigating inherent functional differences between human cardiac fibroblasts cultured from nondiabetic and Type 2 diabetic donors

INTRODUCTION

Type 2 diabetes mellitus (T2DM) promotes adverse myocardial remodeling and increased risk of heart failure; effects that can occur independently of hypertension or coronary artery disease. As cardiac fibroblasts (CFs) are key effectors of myocardial remodeling, we investigated whether inherent phenotypic differences exist in CF derived from T2DM donors compared with cells from nondiabetic (ND) donors.

METHODS

Cell morphology (cell area), proliferation (cell counting over 7-day period), insulin signaling [phospho-Akt and phospho-extracellular signal-regulated kinase (ERK) Western blotting], and mRNA expression of key remodeling genes [real-time reverse transcription-polymerase chain reaction (RT-PCR)] were compared in CF cultured from atrial tissue from 14 ND and 12 T2DM donors undergoing elective coronary artery bypass surgery.

RESULTS

The major finding was that Type I collagen (COL1A1) mRNA levels were significantly elevated by twofold in cells derived from T2DM donors compared with those from ND donors; changes reflected at the protein level. T2DM cells had similar proliferation rates but a greater variation in cell size and a trend towards increased cell area compared with ND cells. Insulin-induced Akt and ERK phosphorylation were similar in the two cohorts of cells.

CONCLUSION

CF from T2DM individuals possess an inherent profibrotic phenotype that may help to explain the augmented cardiac fibrosis observed in diabetic patients.

MINI SUMMARY

We investigated whether inherent phenotypic differences exist between CF cultured from donors with or without Type 2 diabetes. Cell morphology, proliferation, insulin signaling, and gene expression were compared between multiple cell populations. The major finding was that Type I collagen levels were elevated in fibroblasts from diabetic donors, which may help explain the augmented cardiac fibrosis observed with diabetes.

Flow patterns regulate hyperglycemia-induced subendothelial matrix remodeling during early atherogenesis

OBJECTIVE

Altered subendothelial matrix composition regulates endothelial dysfunction and early atherosclerotic plaque formation. Hyperglycemia promotes endothelial matrix remodeling associated with multiple microvascular complications of diabetes, but a role for altered matrix composition in diabetic atherogenesis has not been described. Therefore, we sought to characterize the alterations in matrix composition during diabetic atherogenesis using both in vitro and in vivo model systems.

METHODS AND RESULTS

Streptozotocin-induced diabetes in atherosclerosis-prone ApoE knockout mice promoted transitional matrix expression (fibronectin, thrombospondin-1) and deposition in intima of the aortic arch as determined by qRT-PCR array and immunohistochemistry. Early plaque formation occurs at discrete vascular sites exposed to disturbed blood flow patterns, whereas regions exposed to laminar flow are protected. Consistent with this pattern, hyperglycemia-induced transitional matrix deposition was restricted to regions of disturbed blood flow. Laminar flow significantly blunted high glucose-induced fibronectin expression (mRNA and protein) and fibronectin fibrillogenesis in endothelial cell culture models, whereas high glucose-induced fibronectin deposition was similar between disturbed flow and static conditions.

CONCLUSIONS

Taken together, these data demonstrate that flow patterns and hyperglycemia coordinately regulate subendothelial fibronectin deposition during early atherogenesis.

Thrombospondin-1 induction in the diabetic myocardium stabilizes the cardiac matrix in addition to promoting vascular rarefaction through angiopoietin-2 upregulation

RATIONALE

Diabetes mellitus is associated with cardiac fibrosis. Matricellular proteins are induced in fibrotic conditions and modulate fibrogenic and angiogenic responses by regulating growth factor signaling.

OBJECTIVE

Our aim was to test the hypothesis that the prototypical matricellular protein thrombospondin (TSP)-1, a potent angiostatic molecule and crucial activator of transforming growth factor-β, may play a key role in remodeling of the diabetic heart.

METHODS AND RESULTS

Obese diabetic db/db mice exhibited marked myocardial TSP-1 upregulation in the interstitial and perivascular space. To study the role of TSP-1 in remodeling of the diabetic heart, we generated and characterized db/db TSP-1(-/-) (dbTSP) mice. TSP-1 disruption did not significantly affect weight gain and metabolic function in db/db animals. When compared with db/db animals, dbTSP mice had increased left ventricular dilation associated with mild nonprogressive systolic dysfunction. Chamber dilation in dbTSP mice was associated with decreased myocardial collagen content and accentuated matrix metalloproteinase-2 and -9 activity. TSP-1 disruption did not affect inflammatory gene expression and activation of transforming growth factor-β/small mothers against decapendaplegic signaling in the db/db myocardium. In cardiac fibroblasts populating collagen pads, TSP-1 incorporation into the matrix did not activate transforming growth factor-β responses, but inhibited leptin-induced matrix metalloproteinase-2 activation. TSP-1 disruption abrogated age-associated capillary rarefaction in db/db mice, attenuating myocardial upregulation of angiopoietin-2, a mediator that induces vascular regression. In vitro, TSP-1 stimulation increased macrophage, but not endothelial cell, angiopoietin-2 synthesis.

CONCLUSIONS

TSP-1 upregulation in the diabetic heart prevents chamber dilation by exerting matrix-preserving actions on cardiac fibroblasts and mediates capillary rarefaction through effects that may involve angiopoietin-2 upregulation.

Transcriptional analysis of intramuscular fatty acid composition in the longissimus thoracis muscle of Iberian × Landrace back-crossed pigs

This study aimed at identifying differential gene expression conditional on the fatty acid profile of the longissimus thoracis (Lt) muscle, a prime cut of economic relevance for fresh and cured pork production. A population of 110 Iberian (25%) × Landrace (75%) back-crossed pigs was used, because these two breeds exhibit extreme profiles of intramuscular saturated fatty acid, monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) contents. Total RNA from Lt muscle was individually hybridized to GeneChip Porcine Genome arrays (Affymetrix). A principal component analysis was performed with data from the 110 animals to select 40 extreme animals based on the total fatty acid profile and the MUFA composition (MAP). Comparison of global transcription levels between extreme fatty acid profile pigs (n = 40) resulted in 219 differentially expressed probes (false discovery rate <0.10). Gene ontology, pathway and network analysis indicated that animals with higher percentages of PUFA exhibit a shift toward a more oxidative muscular metabolism state, with a raise in mitochondria function (PPARGC1A, ATF2), fatty acid uptake and oxidation (FABP5, MGLL). On the other hand, 87 probes were differentially expressed between MUFA composition groups (n = 40; false discovery rate <0.10). In particular, muscles rich in n-7 MUFA expressed higher levels of genes involved in lipid metabolism (GLUL, CRAT, PLA2G15) and lower levels of fatty acid elongation genes (ELOVL5). Moreover, the chromosomal position of FABP5, PAQR3, MGLL, PPARGC1A, GLUL and ELOVL5 co-localized with very relevant QTL for fat deposition and composition described in the same resource population. This study represents a complementary approach to identifying genes underlying these QTL effects.

Introduction: Extracellular matrix and cardiovascular remodeling-using microscopy to delineate mechanisms

In January 2011, a Keystone Symposium on “Extracellular Matrix and Cardiovascular Remodeling” was held in Tahoe City, California. The purpose of this meeting was to focus on the general theme of extracellular matrix (ECM) roles in cardiovascular remodeling. The presentations and discussions stimulated by this meeting, which was attended by approximately 160 people, serve as the inspiration for this special section of Microscopy and Microanalysis.