Differential activation of NF-kappa B and AP-1 in increased fibronectin synthesis in target organs of diabetic complications

Nuclear proteins and diabetic retinopathy: a review

Diabetic retinopathy (DR) is an eye disease that causes blindness and vision loss in diabetic. Risk factors for DR include high blood glucose levels and some environmental factors. The pathogenesis is based on inflammation caused by interferon and other nuclear proteins. This review article provides an overview of DR and discusses the role of nuclear proteins in the pathogenesis of the disease. Some core proteins such as MAPK, transcription co-factors, transcription co-activators, and others are part of this review. In addition, some current advanced treatment resulting from the role of nuclear proteins will be analyzes, including epigenetic modifications, the use of methylation, acetylation, and histone modifications. Stem cell technology and the use of nanobiotechnology are proposed as promising approaches for a more effective treatment of DR.

REDD1 Deletion Suppresses NF-κB Signaling in Cardiomyocytes and Prevents Deficits in Cardiac Function in Diabetic Mice

Activation of the transcription factor NF-κB in cardiomyocytes has been implicated in the development of cardiac function deficits caused by diabetes. NF-κB controls the expression of an array of pro-inflammatory cytokines and chemokines. We recently discovered that the stress response protein regulated in development and DNA damage response 1 (REDD1) was required for increased pro-inflammatory cytokine expression in the hearts of diabetic mice. The studies herein were designed to extend the prior report by investigating the role of REDD1 in NF-κB signaling in cardiomyocytes. REDD1 genetic deletion suppressed NF-κB signaling and nuclear localization of the transcription factor in human AC16 cardiomyocyte cultures exposed to TNFα or hyperglycemic conditions. A similar suppressive effect on NF-κB activation and pro-inflammatory cytokine expression was also seen in cardiomyocytes by knocking down the expression of GSK3β. NF-κB activity was restored in REDD1-deficient cardiomyocytes exposed to hyperglycemic conditions by expression of a constitutively active GSK3β variant. In the hearts of diabetic mice, REDD1 was required for reduced inhibitory phosphorylation of GSK3β at S9 and upregulation of IL-1β and CCL2. Diabetic REDD1+/+ mice developed systolic functional deficits evidenced by reduced ejection fraction. By contrast, REDD1-/- mice did not exhibit a diabetes-induced deficit in ejection fraction and left ventricular chamber dilatation was reduced in diabetic REDD1-/- mice, as compared to diabetic REDD1+/+ mice. Overall, the results support a role for REDD1 in promoting GSK3β-dependent NF-κB signaling in cardiomyocytes and in the development of cardiac function deficits in diabetic mice.

The Effect and Mechanism of Oleanolic Acid in the Treatment of Metabolic Syndrome and Related Cardiovascular Diseases

Metabolic syndromes (MetS) and related cardiovascular diseases (CVDs) pose a serious threat to human health. MetS are metabolic disorders characterized by obesity, dyslipidemia, and hypertension, which increase the risk of CVDs' initiation and development. Although there are many availabile drugs for treating MetS and related CVDs, some side effects also occur. Considering the low-level side effects, many natural products have been tried to treat MetS and CVDs. A five-cyclic triterpenoid natural product, oleanolic acid (OA), has been reported to have many pharmacologic actions such as anti-hypertension, anti-hyperlipidemia, and liver protection. OA has specific advantages in the treatment of MetS and CVDs. OA achieves therapeutic effects through a variety of pathways, attracting great interest and playing a vital role in the treatment of MetS and CVDs. Consequently, in this article, we aim to review the pharmacological actions and potential mechanisms of OA in treating MetS and related CVDs.

PERK/ATF4-dependent expression of the stress response protein REDD1 promotes proinflammatory cytokine expression in the heart of obese mice

Endoplasmic reticulum (ER) stress and inflammation are hallmarks of myocardial impairment. Here, we investigated the role of the stress response protein regulated in development and DNA damage 1 (REDD1) as a molecular link between ER stress and inflammation in cardiomyocytes. In mice fed a high-fat high-sucrose (HFHS, 42% kcal fat, 34% sucrose by weight) diet for 12 wk, REDD1 expression in the heart was increased in coordination with markers of ER stress and inflammation. In human AC16 cardiomyocytes exposed to either hyperglycemic conditions or the saturated fatty acid palmitate, REDD1 expression was increased coincident with ER stress and upregulated expression of the proinflammatory cytokines IL-1β, IL-6, and TNFα. In cardiomyocytes exposed to hyperglycemic/hyperlipidemic conditions, pharmacological inhibition of the ER kinase protein kinase RNA-like endoplasmic reticulum kinase (PERK) or knockdown of the transcription factor ATF4 prevented the increase in REDD1 expression. REDD1 deletion reduced proinflammatory cytokine expression in both cardiomyocytes exposed to hyperglycemic/hyperlipidemic conditions and in the hearts of obese mice. Overall, the findings support a model wherein HFHS diet contributes to the development of inflammation in cardiomyocytes by promoting REDD1 expression via activation of a PERK/ATF4 signaling axis.NEW & NOTEWORTHY Interplay between endoplasmic reticulum stress and inflammation contributes to cardiovascular disease progression. The studies here identify the stress response protein known as REDD1 as a missing molecular link that connects the development of endoplasmic reticulum stress with increased production of proinflammatory cytokines in the hearts of obese mice.

NLRP3 activation contributes to endothelin-1-induced erectile dysfunction

In the present study, we hypothesized that endothelin (ET) receptors (ET_A and ET_B ) stimulation, through increased calcium and ROS formation, leads to Nucleotide Oligomerization Domain-Like Receptor Family, Pyrin Domain Containing 3 (NLRP3) activation. Intracavernosal pressure (ICP/MAP) was measured in C57BL/6 (WT) mice. Functional and immunoblotting assays were performed in corpora cavernosa (CC) strips from WT, NLRP3^-/- and caspase^-/- mice in the presence of ET-1 (100 nM) and vehicle, MCC950, tiron, BAPTA AM, BQ123, or BQ788. ET-1 reduced the ICP/MAP in WT mice, and MCC950 prevented the ET-1 effect. ET-1 decreased CC ACh-, sodium nitroprusside (SNP)-induced relaxation, and increased caspase-1 expression. BQ123 an ET_A receptor antagonist reversed the effect. The ET_B receptor antagonist BQ788 also reversed ET-1 inhibition of ACh and SNP relaxation. Additionally, tiron, BAPTA AM, and NLRP3 genetic deletion prevented the ET-1-induced loss of ACh and SNP relaxation. Moreover, BQ123 diminished CC caspase-1 expression, while BQ788 increased caspase-1 and IL-1β levels in a concentration-dependent manner (100 nM-10 μM). Furthermore, tiron and BAPTA AM prevented ET-1-induced increase in caspase-1. In addition, BAPTA AM blocked ET-1-induced ROS generation. In conclusion, ET-1-induced erectile dysfunction depends on ET_A - and ET_B -mediated activation of NLRP3 in mouse CC via Ca²⁺ -dependent ROS generation.

Fibronectin-Integrin α5 Signaling in Vascular Complications of Type 1 Diabetes

Vascular complications are a major cause of illness and death in patients with type 1 diabetes (T1D). Diabetic vascular basement membranes are enriched in fibronectin (FN), an extracellular matrix protein that amplifies inflammatory signaling in endothelial cells through its main receptor, integrin α5β1. Binding of the integrin α5 cytoplasmic domain to phosphodiesterase 4D5 (PDE4D5), which increases phosphodiesterase catalytic activity and inhibits antiinflammatory cAMP signaling, was found to mediate these effects. Here, we examined mice in which the integrin α5 cytoplasmic domain is replaced by that of α2 (integrin α5/2) or the integrin α5 binding site in PDE4D is mutated (PDE4Dmut). T1D was induced via injection of streptozotocin and hyperlipidemia induced via injection of PCSK9 virus and provision of a high-fat diet. We found that in T1D and hyperlipidemia, the integrin α5/2 mutation reduced atherosclerosis plaque size by ∼50%, with reduced inflammatory cell invasion and metalloproteinase expression. Integrin α5/2 T1D mice also had improved blood-flow recovery from hindlimb ischemia and improved biomechanical properties of the carotid artery. By contrast, the PDE4Dmut had no beneficial effects in T1D. FN signaling through integrin α5 is thus a major contributor to diabetic vascular disease but not through its interaction with PDE4D.

Cissus quadrangularis extract mitigates diabetic cardiomyopathy by inhibiting RAAS activation, inflammation, and oxidative stress

IntroductionDiabetic cardiomyopathy (DCM) is an age-related disease, and its progression is accompanied by hyperglycemia, cardiac dysfunction, and myocardial structural and functional abnormalities. Cissus quadrangularis, a traditional medicinal plant, contains polyphenols, flavonoids, phytosterols, carbohydrates, and ascorbic acid. It is used to treat osteoporosis, asthma, haemorrhoids, and menstrual disorders. In the current research, we have investigated the effect of ethanolic extract of C. quadrangularis (EECQ) against a high-fat diet (HFD)/streptozotocin-induced DCM by estimating cardiac biomarkers, inflammatory markers and ROS production.Material and methodsRats were fed with an HFD for 12 weeks, followed by single-shot low-dose streptozotocin (35mg/kg; i.p.). The treatment was performed by EECQ (200 mg/kg/day, orally) for six weeks. ResultsThe extract EECQ improves glucose, insulin tolerance tests, and hypercholesteremia. DCM is characterized by cardiac dysfunction, cardiac biomarkers CKMB, and LDH, which were attenuated by the EECQ treatment. The hypertrophic biomarker ANP, BNP expression and cardiomyocyte surface area were decreased by EECQ. Moreover, EECQ also alleviated the biomarkers Angiotensin II and renin level. EECQ also reduced oxidative stress, ROS production and cardiac inflammation.ConclusionThus, these findings suggested that EECQ could be used as a possible therapeutic regiment to treat DCM.

Role of cannabinoids and the endocannabinoid system in modulation of diabetic cardiomyopathy

Diabetic complications, chiefly seen in long-term situations, are persistently deleterious to a large extent, requiring multi-factorial risk reduction strategies beyond glycemic control. Diabetic cardiomyopathy is one of the most common deleterious diabetic complications, being the leading cause of mortality among diabetic patients. The mechanisms of diabetic cardiomyopathy are multi-factorial, involving increased oxidative stress, accumulation of advanced glycation end products (AGEs), activation of various pro-inflammatory and cell death signaling pathways, and changes in the composition of extracellular matrix with enhanced cardiac fibrosis. The novel lipid signaling system, the endocannabinoid system, has been implicated in the pathogenesis of diabetes and its complications through its two main receptors: Cannabinoid receptor type 1 and cannabinoid receptor type 2, alongside other components. However, the role of the endocannabinoid system in diabetic cardiomyopathy has not been fully investigated. This review aims to elucidate the possible mechanisms through which cannabinoids and the endocannabinoid system could interact with the pathogenesis and the development of diabetic cardiomyopathy. These mechanisms include oxidative/ nitrative stress, inflammation, accumulation of AGEs, cardiac remodeling, and autophagy. A better understanding of the role of cannabinoids and the endocannabinoid system in diabetic cardiomyopathy may provide novel strategies to manipulate such a serious diabetic complication.

Endothelial Dysfunction and Diabetic Cardiomyopathy

The cardiovascular complications contribute to a majority of diabetes associated morbidity and mortality, accounting for 44% of death in those patients with type 1 diabetes mellitus (DM) and 52% of deaths in type 2 DM. Diabetes elicits cardiovascular dysfunction through 2 major mechanisms: ischemic and non-ischemic. Non-ischemic injury is usually under-recognized although common in DM patients, and also a pathogenic factor of heart failure in those diabetic individuals complicated with ischemic heart disease. Diabetic cardiomyopathy (DCM) is defined as a heart disease in which the myocardium is structurally and functionally abnormal in the absence of coronary artery disease, hypertensive, valvular, or congenital heart disorders in diabetic patients, theoretically caused by non-ischemic injury solely. Current therapeutic strategies targeting DCM mainly address the increased blood glucose levels, however, the effects on heart function are disappointed. Accumulating data indicate endothelial dysfunction plays a critical role in the initiation and development of DCM. Hyperglycemia, hyperinsulinemia, and insulin resistance cause the damages of endothelial function, including barrier dysfunction, impaired nitric oxide (NO) activity, excessive reactive oxygen species (ROS) production, oxidative stress, and inflammatory dysregulation. In turn, endothelial dysfunction promotes impaired myocardial metabolism, intracellular Ca²⁺ mishandling, endoplasmic reticulum (ER) stress, mitochondrial defect, accumulation of advanced glycation end products, and extracellular matrix (ECM) deposit, leads to cardiac stiffness, fibrosis, and remodeling, eventually results in cardiac diastolic dysfunction, systolic dysfunction, and heart failure. While endothelial dysfunction is closely related to cardiac dysfunction and heart failure seen in DCM, clinical strategies for restoring endothelial function are still missing. This review summarizes the timely findings related to the effects of endothelial dysfunction on the disorder of myocardium as well as cardiac function, provides mechanical insights in pathogenesis and pathophysiology of DCM developing, and highlights potential therapeutic targets.

Circular RNA mediated gene regulation in chronic diabetic complications

Chronic diabetic complications affect multiple organs causing widespread organ damage. Although there are some commonalities, the phenotype of such changes show tissue specific variation. Given this, we examined whether differences in circular RNA (circRNA) mediated gene regulatory mechanisms contribute to changes in gene expression at the basal level and in diabetes. CircRNAs are single-stranded RNA with covalently closed loop structures and act as miRNA sponges, factors of RNA splicing, scaffolding for proteins, regulators of transcription, and modulators of the expression of parental genes, among other roles. We examined heart and retinal tissue from Streptozotocin-induced diabetic mice with established diabetes related tissue damage and tissue from non-diabetic controls. A custom array analysis was performed and the data were analysed. Two major circRNA mediated processes were uniquely upregulated in diabetic heart tissue, namely, positive regulation of endothelial cell migration and regulation of mitochondria: mitochondrial electron transport. In the retina, circRNAs regulating extracellular matrix protein production and endothelial to mesenchymal transition (EndMT) were found to be upregulated. The current study identified regulatory and potential pathogenetic roles of specific circRNA in diabetic retinopathy and cardiomyopathy. Understanding such novel mechanisms, may in the future, be useful to develop RNA based treatment strategies.

Hydrogen Sulfide Plays an Important Role in Diabetic Cardiomyopathy

Diabetic cardiomyopathy is an important complication of diabetes mellitus and the main cause of diabetes death. Diabetic cardiomyopathy is related with many factors, such as hyperglycemia, lipid accumulation, oxidative stress, myocarditis, and apoptosis. Hydrogen sulfide (H₂S) is a newly discovered signal molecule, which plays an important role in many physiological and pathological processes. Recent studies have shown that H₂S is involved in improving diabetic cardiomyopathy, but its mechanism has not been fully elucidated. This review summarizes the research on the roles and mechanisms of H₂S in diabetic cardiomyopathy in recent years to provide the basis for in-depth research in the future.

SIRT3 protects endothelial cells from high glucose-induced senescence and dysfunction via the p53 pathway

Hyperglycemia induces endothelial cells (ECs) dysfunction and vascular complications by accelerating ECs senescence. It also induces downregulation of sirtuins (SIRTs). However, the molecular mechanism involved in the regulation of ECs senescence by SIRT3 remains unclear. Here, we showed that high glucose (HG) decreased the expression level of SIRT3 in human umbilical vein endothelial cells (HUVECs), increased the proportion of cells expressing senescence-associated galactosidase (SA-gal), and HG damaged the cell's ability to form tubule networks on Matrigel. However, transfection with adenoviral construct including SIRT3 significantly inhibited HG-induced SA-gal activity, decreased p53 acetylation level at the site Lys 320 (k320), and overexpression of SIRT3 antagonized high glucose-induced angiogenic dysfunction. Our results suggested a possible molecular mechanism involving HG-SIRT3-p53 in ECs senescence.

ET-traps offer a potential therapeutic tool for use in different autoimmune diseases

Research shows that endothelin (ET)-traps are a potential therapy for diabetes. Given that type 1 diabetes mellitus (T1DM) is an autoimmune disorder, ET-traps could also have an efficacious, therapeutic effect on other autoimmune diseases associated with pathologically elevated ET-1. Here, we describe those different autoimmune diseases that might benefit from a tool such as ET-traps, which potently sequester these elevated levels of ET-1. We also discuss the current use of ET receptor (ETR) antagonists and the associated adverse effects, and how ET-traps are associated with no toxicity and potentially offer a superior alternative. ET-traps could be used against different autoimmune diseases and, therefore, are a novel therapeutic tool for such conditions.

High Glucose Exacerbates TNF-α-Induced Proliferative Inhibition in Human Periodontal Ligament Stem Cells through Upregulation and Activation of TNF Receptor 1

Objective

This research is aimed at investigating how high glucose affects the proliferation and apoptosis in periodontal ligament stem cells (PDLSCs) in the presence of TNF-α.

Methods

PDLSCs obtained from periodontal healthy permanent teeth were treated under either high-glucose condition (30 mmol/L, G30 group) or normal glucose condition (5.6 mmol/L, G5.6 group) in the presence or absence of TNF-α (10 ng/ml) for 2 to 6 days. Cell proliferation and cell cycle were evaluated by CCK-8, EdU incorporation assay, and flow cytometry. Cell apoptosis was assessed by annexin V/PI staining. Protein expression was detected by western blotting. Cellular ROS expression was evaluated by CellROX labeling and flow cytometry. Specific antibodies targeting TNFR1 and TNFR2 were used to block TNF-α signaling. Vitamin C was also used to verify if the blockage of ROS can rescue PDLSCs in the presence of high glucose and TNF-α.

Results

CCK-8 assay showed that high glucose exacerbated TNF-α-induced cell viability inhibition (57.0%, 85.2%, and 100% for the G30+TNF-α group, G5.6+TNF-α group, and control group, respectively) on day 6. High glucose increased protein expression of TNFR1 compared with the control group on day 2 (1.24-fold) and day 6 (1.26-fold). Blocking TNFR1 totally reversed the proliferative inhibition in G30+TNF-α group. The addition of vitamin C or TNFR1 antibody totally reversed the elevation of intracellular ROS expression caused by high glucose and TNF-α. Vitamin C partially restored cell proliferation in the presence of high glucose and TNF-α.

Conclusion

High glucose exacerbates TNF-α-induced proliferative inhibition in human periodontal ligament stem cells through the upregulation and activation of TNF receptor 1. Inhibition of intracellular ROS expression by vitamin C partially rescues PDLSCs in terms of cell proliferation.

Resveratrol Inhibits Lipopolysaccharide-Induced Extracellular Matrix Accumulation and Inflammation in Rat Glomerular Mesangial Cells by SphK1/S1P2/NF-κB Pathway

PURPOSE

Chronic inflammation plays a key role in the pathogenesis of various diseases such as diabetic nephropathy (DN). Resveratrol (RSV), a natural polyphenol, has been proven to have renoprotective effects. In this study, we used a lipopolysaccharide (LPS)-induced rat glomerular mesangial cells (RMCs) model, to elucidate the renoprotective effect of RSV on sphingosine kinase 1 (SphK1)/sphingosine 1-phosphate receptor 2 (S1P2)/NF-κB activation and the expression of downstream inflammatory mediators, such as intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS) and fibronectin (FN) protein expression in RMCs.

METHODS

Cell proliferation was tested by 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT). The protein levels of FN, ICAM-1, iNOS, SphK1, S1P2 and NF-κB p65 in RMCs were detected by Western blot. The DNA-binding activity of NF-κB was detected by electrophoretic mobility shift assay (EMSA). SphK1 activity and S1P content were measured by using sphingosine kinase activity assay kit and ELISA assay, respectively.

RESULTS

We first found that LPS could stimulate SphK1/S1P axis activation, whereas this occurrence was significantly blocked by RSV pretreatment. RSV obviously repressed LPS-induced upregulated expression of fibronectin (FN), intercellular adhesion molecule-1 (ICAM-1) and inducible nitric oxide synthase (iNOS) in RMCs. Moreover, RSV markedly reduced SphK1 activity and its protein expression, and attenuated S1P content in LPS-induced RMCs. Furthermore, RSV could block LPS-induced upregulation of NF-κB p65 and DNA-binding activity of NF-κB. And this phenomenon was notably attenuated by SphK1 inhibitor and S1P2 inhibitor.

CONCLUSION

RSV inhibited LPS-induced RMCs' proliferation and inflammation and FN expression by SphK1/S1P2/NF-κB pathway, suggesting that RSV may be independent of its hypoglycemic effect on preventing or delaying the development of mesangial cell fibrosis.

Diabetes-induced early molecular and functional changes in aortic heart valves in a murine model of atherosclerosis

Diabetes contributes directly to the development of cardiovascular aortic valve disease. There is currently no drug therapy available for a dysfunctional valve and this urges the need for additional research to identify distinctive mechanisms of cardiovascular aortic valve disease evolution. The aim of this study was to evaluate changes of valvular aortic lesions induced in a hyperlipemic ApoE^-/- mouse model by early type 1 diabetes onset (at 4 and 7 days after streptozotocin induction). The haemodynamic valve parameters were evaluated by echography and blood samples and aortic valves were collected. Plasma parameters were measured, and inflammatory, remodelling and osteogenic markers were evaluated in the aortic valves. Next, correlations between all parameters were determined. The results showed early aortic valve dysfunction detected by echography after 1 week of diabetes; lesions were found in the aortic root. Moreover, increased expression of cell adhesion molecules, extracellular matrix remodelling and osteogenic markers were detected in hyperlipemic ApoE^-/- diabetic mice. Significant correlations were found between tissue valve biomarkers and plasmatic and haemodynamic parameters. Our study may help to understand the mechanisms of aortic valve disease in the diabetic milieu in order to discover and validate new biomarkers of cardiovascular aortic valve disease in diabetes and reveal new possible targets for nanobiotherapies.

Glucocorticoid receptor inhibits Müller glial galectin-1 expression via DUSP1-dependent and -independent deactivation of AP-1 signalling

Galectin‐1/LGALS1 is a hypoxia‐induced angiogenic factor associated with diabetic retinopathy (DR). Recently, we elucidated a hypoxia‐independent pathway to produce galectin‐1 in Müller glial cells stimulated by interleukin (IL)‐1β. Here we revealed glucocorticoid receptor (GR)‐mediated inhibitory mechanisms for Müller glial galectin‐1/LGALS1 expression. Activator protein (AP)‐1 site in the LGALS1 enhancer region, to which activating transcription factor2, c‐Fos and c‐Jun bind, was shown to be essential for IL‐1β‐induced galectin‐1/LGALS1 expression in Müller cells. Ligand (dexamethasone or triamcinolone acetonide)‐activated GR induced dual specificity phosphatase (DUSP)1 expression via the glucocorticoid response element and attenuated IL‐1β‐induced galectin‐1/LGALS1 expression by reducing phosphorylation of these AP‐1 subunits following AKT and extracellular signal‐regulated kinase (ERK)1/2 deactivation. Moreover, activated GR also caused DUSP1‐independent down‐regulation of IL‐1β‐induced LGALS1 expression via its binding to AP‐1. Administration of glucocorticoids to mice attenuated diabetes‐induced retinal galectin‐1/Lgals1 expression together with AKT/AP‐1 and ERK/AP‐1 pathways. Supporting these in vitro and in vivo findings, immunofluorescence analyses showed co‐localization of galectin‐1 with GR and phosphorylated AP‐1 in DUSP1‐positive glial cells in fibrovascular tissues from patients with DR. Our present data demonstrated the inhibitory effects of glucocorticoids on glial galectin‐1 expression via DUSP1‐dependent and ‐independent deactivation of AP‐1 signalling (transactivation and transrepression), highlighting therapeutic implications for DR.

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.

The Role of BACH2 in T Cells in Experimental Malaria Caused by Plasmodium chabaudi chabaudi AS

BTB and CNC Homology 1, Basic Leucine Zipper Transcription Factor 2 (BACH2) is a transcription factor best known for its role in B cell development. More recently, it has been associated with T cell functions in inflammatory diseases, and has been proposed as a master transcriptional regulator within the T cell compartment. In this study, we employed T cell-specific Bach2-deficient (B6.Bach2^ΔT) mice to examine the role of this transcription factor in CD4⁺ T cell functions in vitro and in mice infected with Plasmodium chabaudi AS. We found that under CD4⁺ T cell polarizing conditions in vitro, Th2, and Th17 helper cell subsets were more active in the absence of Bach2 expression. In mice infected with P. chabaudi AS, although the absence of Bach2 expression by T cells had no effect on blood parasitemia or disease pathology, we found reduced expansion of CD4⁺ T cells in B6.Bach2^ΔT mice, compared with littermate controls. Despite this reduction, we observed increased frequencies of Tbet⁺ IFNγ⁺ CD4⁺ (Th1) cells and IL-10-producing Th1 (Tr1) cells in mice lacking Bach2 expression by T cells. Studies in mixed bone marrow chimeric mice revealed T cell intrinsic effects of BACH2 on hematopoietic cell development, and in particular, the generation of CD4⁺ and CD8⁺ T cell subsets. Furthermore, T cell intrinsic BACH2 was needed for efficient expansion of CD4⁺ T cells during experimental malaria in this immunological setting. We also examined the response of B6.Bach2^ΔT mice to a second protozoan parasitic challenge with Leishmania donovani and found similar effects on disease outcome and T cell responses. Together, our findings provide new insights into the role of BACH2 in CD4⁺ T cell activation during experimental malaria, and highlight an important role for this transcription factor in the development and expansion of T cells under homeostatic conditions, as well as establishing the composition of the effector CD4⁺ T cell compartment during infection.

Endothelin-1 traps potently reduce pathologic markers back to basal levels in an in vitro model of diabetes

Background

Diabetes mellitus is a group of metabolic disorders in which there are high blood glucose levels over a prolonged period. Diabetes is one of many diseases associated with pathologically elevated levels of endothelin (ET)-1. We have recently proposed the development of ET-traps, which are an antibody - based fusion protein that potently bind and sequester pathologically elevated levels of endothelin-1.

Methods

We constructed ET-traps that were found to be very potent binders to ET-1, with a K_D of 32.5ρM. We then treated human retinal microvascular endothelial cells (HRMECs), which are an in vitro model of glucose induced cellular damage, with 10 nM ET-1 or high glucose levels (25 mM).

Results

In this study, we investigated the effects of our ET-trap constructs on the expression levels of both collagen 4α1 and fibronectin, which are both important pathologic markers in diabetes. Treating HRMECs with 10 nM ET-1 or 25 mM glucose significantly induces the expression of the ECM proteins fibronectin and collagen 4α1, as is found in chronic diabetic complications; Incubation of the cells with the ET-traps significantly prevented the increased expression of fibronectin and collagen 4α1 back to basal levels. This was found with both mRNA and protein expression levels of the two ECM proteins.

Conclusion

Our results provide the first evidence of the efficacy of ET-traps in reducing pathologic markers in an in vitro model (of diabetes). Further research is warranted to determine the efficacy of ET-traps as a therapeutic tool for diabetes, which is a major public health burden around the world.

Recent novel approaches to limit oxidative stress and inflammation in diabetic complications

Diabetes is considered a major burden on the healthcare system of Western and non‐Western societies with the disease reaching epidemic proportions globally. Diabetic patients are highly susceptible to developing micro‐ and macrovascular complications, which contribute significantly to morbidity and mortality rates. Over the past decade, a plethora of research has demonstrated that oxidative stress and inflammation are intricately linked and significant drivers of these diabetic complications. Thus, the focus now has been towards specific mechanism‐based strategies that can target both oxidative stress and inflammatory pathways to improve the outcome of disease burden. This review will focus on the mechanisms that drive these diabetic complications and the feasibility of emerging new therapies to combat oxidative stress and inflammation in the diabetic milieu.

MALAT1: A regulator of inflammatory cytokines in diabetic complications

OBJECTIVES AND DESIGN

In this study, we examined the role of MALAT1, a highly conserved nuclear long non-coding RNA molecule, in chronic diabetic complications affecting the heart and kidneys using both in vitro and in vivo models: human endothelial cell culture and a Malat1 knockout mice model.

RESULTS

Findings from our in vitro experiments demonstrated that MALAT1 was predominantly localized to nuclear speckles in endothelial cells and MALAT1 expression was significantly increased following incubation with high glucose in association with increased expression of inflammatory cytokines. As for our in vivo experiments, we used Malat1 knockout mice and wild-type controls with or without streptozotocin-induced diabetes over 2 months of follow-up, where all of our diabetic animals showed hyperglycaemia and polyuria. Examination of cardiac and renal tissues demonstrated altered MALAT1 RNA expression in wild-type diabetic animals. Such changes were associated with augmented production of downstream inflammatory molecules at the mRNA and protein levels. Diabetes-induced elevations of inflammatory markers were significantly decreased in Malat1 knockout diabetic animals. In addition to transcript and protein analyses, we examined functional changes in the heart and kidneys. Organ functions were affected in the wild-type diabetic mice but were rescued in Malat1 knockout mice.

CONCLUSIONS

Taken together, findings from this study will provide direct evidence and insight into the importance of MALAT1 in the pathogenesis of chronic diabetic complications involving the heart and kidneys.

Effect of ginseng therapy on diabetes and its chronic complications: lessons learned

Ginseng played a significant role in the management of diabetes in China and in other Asian countries for a long period of time. It has a large number of pharmacological properties and is relatively free from adverse effects. As a part of Ontario Ginseng Research and Innovation Consortium, we investigated the effects of ginseng extract on diabetes and its complications. We demonstrated large number of beneficial effects of ginseng therapy and showed that these effects are possibly mediated through its antioxidant properties. Thus ginseng may lend itself as a relatively safe and inexpensive adjuvant treatment for diabetes and chronic diabetic complications.

miR-146a regulates glucose induced upregulation of inflammatory cytokines extracellular matrix proteins in the retina and kidney in diabetes

Hyperglycemic damage to the endothelial cells (ECs) leads to increased synthesis of inflammatory cytokines. We have previously shown miR-146a downregulation in ECs and in the tissues of diabetic mice. Here we investigated the role of miR-146a, in the production of specific inflammatory cytokines and extracellular matrix (ECM) proteins in retina and kidneys in diabetes. We generated an endothelial specific miR-146a overexpressing transgenic mice (TG). We investigated these mice and wild type (WT) controls with or without streptozotocin (STZ) induced diabetes. Retinal and renal cortical tissues from the mice were examined for mRNAs for specific inflammatory markers, (ECM) proteins and inflammation inducible transcription factor by real time RT-PCR. Corresponding proteins, where possible, were examined using immunofluorescence or ELISA. In parallel, we examined ECs following incubation with various levels of glucose with or without miR-146a mimic transfection. In the retina and kidneys of WT mice with diabetes, increased expression of inflammatory markers (IL-6, TNFα, IL1β) in association augmented expression of ECM proteins (collagen 1αIV, fibronectin) and NF κB-P65 were observed, compared to WT non-diabetic controls. These changes were prevented in diabetic miR-146a TG mice along with retinal and renal functional and structural changes. In vitro studies showed similar changes in the ECs exposed to high glucose. Such changes were corrected in the cells following miR-146a mimic transfection. Further analyses of renal cortical tissues showed diabetes induced significant upregulation of two regulators of NFκB, namely Interleukin-1 associated Kinase 1 and tumour necrosis factor receptor associated factor. Such changes were prevented in diabetic TG animals. These data indicate that augmented production of inflammatory cytokines and ECM proteins in the retina and kidneys in diabetes are regulated through endothelium derived miR-146a. Identification of such novel mechanisms may potentially lead to the development of novel therapies.

Betulinic acid ameliorates experimental diabetic-induced renal inflammation and fibrosis via inhibiting the activation of NF-κB signaling pathway

Diabetic nephropathy (DN) is the leading cause of end-stage renal failure and is characterized by excessive deposition of extracellular matrix (ECM) proteins such as fibronectin (FN), in the glomerular mesangium and tubulointerstitium. Betulinic acid (BA), a pentacyclic triterpene derived from the bark of the white birch tree, has been demonstrated to have many pharmacological activities. However, the effect of BA on DN has not been fully elucidated. To explore the possible anti-inflammatory effects of BA and their underlying mechanisms, we used streptozotocin-induced diabetic rat kidneys and high glucose-treated glomerular mesangial cells. Our study showed BA could inhibit the degradation of IκBα and the activity of NF-κB in diabetic rat kidneys and high glucose-induced mesangial cells, resulting in reduction of FN expression. In addition, BA suppressed the DNA binding activity and transcriptional activity of NF-κB in high glucose-induced glomerular mesangial cells (GMCs). Furthermore, BA enhanced the interaction between IκBα and β-arrestin2 in mesangial cells. Taken together, our data suggest BA inhibits NF-κB activation through stabilizing NF-κB inhibitory protein IκBα, thereby preventing diabetic renal fibrosis.

Expression Profiling of Genes Related to Endothelial Cells Biology in Patients with Type 2 Diabetes and Patients with Prediabetes

Endothelial dysfunction appears to be an early sign indicating vascular damage and predicts the progression of atherosclerosis and cardiovascular disorders. Extensive clinical and experimental evidence suggests that endothelial dysfunction occurs in Type 2 Diabetes Mellitus (T2DM) and prediabetes patients. This study was carried out with an aim to appraise the expression levels in the peripheral blood of 84 genes related to endothelial cells biology in patients with diagnosed T2DM or prediabetes, trying to identify new genes whose expression might be changed under these pathological conditions. The study covered a total of 45 participants. The participants were divided into three groups: group 1, patients with T2DM; group 2, patients with prediabetes; group 3, control group. The gene expression analysis was performed using the Endothelial Cell Biology RT² Profiler PCR Array. In the case of T2DM, 59 genes were found to be upregulated, and four genes were observed to be downregulated. In prediabetes patients, increased expression was observed for 49 genes, with two downregulated genes observed. Our results indicate that diabetic and prediabetic conditions change the expression levels of genes related to endothelial cells biology and, consequently, may increase the risk for occurrence of endothelial dysfunction.

Naringin protects cardiomyocytes against hyperglycemia-induced injuries in vitro and in vivo

We previously reported that naringin (NRG) protects cardiomyocytes against high glucose (HG)-induced injuries by inhibiting the MAPK pathway. The aim of this study was to test the hypothesis that NRG prevents cardiomyocytes from hyperglycemia-induced insult through the inhibition of the nuclear factor kappa B (NF-κB) pathway and the upregulation of ATP-sensitive K(+) (KATP) channels. Our results showed that exposure of cardiomyocytes to HG for 24h markedly induced injuries, as evidenced by a decrease in cell viability and oxidative stress, and increases in apoptotic cells as well as the dissipation of mitochondrial membrane potential (MMP). These injuries were markedly attenuated by the pretreatment of cells with either NRG or pyrrolidine dithiocarbamate (PDTC) before exposure to HG. Furthermore, in streptozotocin (STZ)-induced diabetic rats and in HG-induced cardiomyocytes, the expression levels of caspase-3, bax and phosphorylated (p)-NF-κB p65 were increased. The increased protein levels were ameliorated by pretreatment with both NRG and PDTC. However, the expression levels of bcl-2 and KATP and superoxide dismutase (SOD) activity were decreased by hyperglycemia; the expression level of Nox4 and the ADP/ATP ratio were increased by hyperglycemia. These hyperglycemia-induced indexes were inhibited by the pretreatment of cardiomyocytes with NRG or PDTC. In addition, in STZ-induced diabetic rats, we also observed that NRG or PDTC contributed to protecting mitochondrial injury and myocardium damage. This study demonstrated that NRG protects cardiomyocytes against hyperglycemia-induced injury by upregulating KATP channels in vitro and inhibiting the NF-κB pathway in vivo and in vitro.

Polydatin attenuates AGEs-induced upregulation of fibronectin and ICAM-1 in rat glomerular mesangial cells and db/db diabetic mice kidneys by inhibiting the activation of the SphK1-S1P signaling pathway

We previously demonstrated that activation of sphingosine kinase 1 (SphK1)- sphingosine 1- phosphate (S1P) signaling pathway by high glucose (HG) plays a pivotal role in increasing the expression of fibronectin (FN), an important fibrotic component, by promoting the DNA-binding activity of transcription factor activator protein 1 (AP-1) in glomerular mesangial cells (GMCs) under diabetic conditions. As a multi-target anti-oxidative drug, polydatin (PD) has been shown to have renoprotective effects on experimental diabetes. However, whether PD could resist diabetic nephropathy (DN) by regulating SphK1-S1P signaling pathway needs further investigation. Here, we found that PD significantly reversed the upregulated FN and ICAM-1 expression in GMCs exposed to AGEs. Simultaneously, PD dose-dependently inhibited SphK1 levels at the protein expression and kinase activity and attenuated S1P production under AGEs treatment conditions. In addition, PD reduced SphK activity in GMCs transfected with wild-type SphK(WT) plasmid and significantly suppressed SphK1-mediated increase of FN and ICAM-1 levels under normal conditions. Furthermore, we found that the AGEs-induced upregulation of phosphorylation of c-Jun at Ser63 and Ser73 and c-Fos at Ser32, DNA-binding activity and transcriptional activity of AP-1 were blocked by PD. In comparison with db/db model group, PD treatment suppressed SphK1 levels (mRNA, protein expression, and activity) and S1P production, reversed the upregulation of FN, ICAM-1, c-Jun, and c-Fos in the kidney tissues of diabetic mice, and finally ameliorated renal injury in db/db mice. These findings suggested that the downregulation of SphK1-S1P signaling pathway is probably a novel mechanism by which PD suppressed AGEs-induced FN and ICAM-1 expression and improved renal dysfunction of diabetic models.

Subcellular proteomic approach for identifying the signaling effectors of protein kinase C-β₂ under high glucose conditions in human umbilical vein endothelial cells

The high glucose‑induced activation of protein kinase C‑β2 (PKC‑β2) has an essential role in the pathophysiology of diabetes‑associated vascular disease. In the present study, human umbilical vein endothelial cells (HUVECs) were cultured in high and normal glucose conditions prior to being infected with a recombinant adenovirus to induce the overexpression of PKC‑β2. The activity of PKC‑β2 was also decreased using a selective PKC‑β2 inhibitor. A series of two‑dimensional electrophoresis images detected ~800 spots in the nuclei, and ~600 spots in the cytosol. Following intra‑ and inter‑group cross‑matching, 38 significantly altered spots were identified as high glucose‑induced and PKC‑β2‑associated nuclear proteins. In addition to the observation that the regulation of key proteins involved in the nuclear factor (NF)‑κB signaling cascade occurred in the cytosol, various transcription factors, including peroxisome proliferator‑activated receptor δ (PPAR‑δ), were also altered in the nuclei. A human protein‑protein interaction network of potential connections of PKC‑β2‑associated proteins was constructed in the proteomics investigation using Biological General Repository for Interaction Datasets. The results indicated that PKC‑β2 may be involved in high glucose‑induced glucose and lipid crosstalk by regulating PPAR‑δ. In addition, NF‑κB inhibitor‑interacting Ras‑like protein 1 may be important in the PKC‑β2‑NF‑κB inhibitor‑NF‑κB signaling pathway in HUVECs under high‑glucose conditions.

Increased Oxidative and Nitrative Stress Accelerates Aging of the Retinal Vasculature in the Diabetic Retina

Hyperglycemia-induced retinal oxidative and nitrative stress can accelerate vascular cell aging, which may lead to vascular dysfunction as seen in diabetes. There is no information on whether this may contribute to the progression of diabetic retinopathy (DR). In this study, we have assessed the occurrence of senescence-associated markers in retinas of streptozotocin-induced diabetic rats at 8 and 12 weeks of hyperglycemia as compared to normoglycemic aging (12 and 14 months) and adult (4.5 months) rat retinas. We have found that in the diabetic retinas there was an up-regulation of senescence-associated markers SA-β-Gal, p16^INK4a and miR34a, which correlated with decreased expression of SIRT1, a target of miR34a. Expression of senescence-associated factors primarily found in retinal microvasculature of diabetic rats exceeded levels measured in adult and aging rat retinas. In aging rats, retinal expression of senescence associated-factors was mainly localized at the level of the retinal pigmented epithelium and only minimally in the retinal microvasculature. The expression of oxidative/nitrative stress markers such as 4-hydroxynonenal and nitrotyrosine was more pronounced in the retinal vasculature of diabetic rats as compared to normoglycemic aging and adult rat retinas. Treatments of STZ-rats with the anti-nitrating drug FeTPPS (10mg/Kg/day) significantly reduced the appearance of senescence markers in the retinal microvasculature. Our results demonstrate that hyperglycemia accelerates retinal microvascular cell aging whereas physiological aging affects primarily cells of the retinal pigmented epithelium. In conclusion, hyperglycemia-induced retinal vessel dysfunction and DR progression involve vascular cell senescence due to increased oxidative/nitrative stress.

Endothelin Blockade in Diabetic Kidney Disease

Diabetic kidney disease (DKD) remains the most common cause of chronic kidney disease and multiple therapeutic agents, primarily targeted at the renin-angiotensin system, have been assessed. Their only partial effectiveness in slowing down progression to end-stage renal disease, points out an evident need for additional effective therapies. In the context of diabetes, endothelin-1 (ET-1) has been implicated in vasoconstriction, renal injury, mesangial proliferation, glomerulosclerosis, fibrosis and inflammation, largely through activation of its endothelin A (ET_A) receptor. Therefore, endothelin receptor antagonists have been proposed as potential drug targets. In experimental models of DKD, endothelin receptor antagonists have been described to improve renal injury and fibrosis, whereas clinical trials in DKD patients have shown an antiproteinuric effect. Currently, its renoprotective effect in a long-time clinical trial is being tested. This review focuses on the localization of endothelin receptors (ET_A and ET_B) within the kidney, as well as the ET-1 functions through them. In addition, we summarize the therapeutic benefit of endothelin receptor antagonists in experimental and human studies and the adverse effects that have been described.

SIRT1 reduction causes renal and retinal injury in diabetes through endothelin 1 and transforming growth factor β1

In diabetes, hyperglycaemia causes up-regulation of endothelin 1 (ET-1) and transforming growth factor beta 1 (TGF-β1). Previously we showed glucose reduces sirtuin1 (SIRT1), a class III histone deacetylase. Here, we investigated the regulatory role of SIRT1 on ET-1 and TGF-β1 expression. Human microvascular endothelial cells were examined following incubation with 25 mmol/l glucose (HG) and 5 mmol/l glucose (NG) with or without SIRT1 or histone acetylase p300 overexpression or knockdown. mRNA expressions of ET-1, TGF-β1, SIRT1, p300 and collagen 1α(I) were examined. SIRT1 enzyme activity, ET-1 and TGF-β1 protein levels were measured. Histone acetylation and endothelial permeability were further investigated. Similar analyses were performed in the kidneys and retinas of SIRT1 overexpressing transgenic mice with or without streptozotocin induced diabetes. Renal functions were evaluated. In the endothelial cells (ECs), HG caused increased permeability and escalated production of ET-1, TGF-β1, collagen Iα(I). These cells also showed increased p300 expression, histone acetylation and reduced SIRT1 levels. These changes were rectified in the ECs following p300 silencing or by SIRT1 overexpression, whereas SIRT1 knockdown or p300 overexpression in NG mimicked the effects of HG. High ET-1 and TGF-β1 levels were seen in the kidneys and retinas of diabetic mice along with micro-albuminuria and increased fibronectin protein (marker of glucose-induced cell injury) levels. Interestingly, these detrimental changes were blunted in SIRT1 overexpressing transgenic mice with diabetes. This study showed a novel SIRT1 mediated protection against renal and retinal injury in diabetes, regulated through p300, ET-1 and TGF-β1.

Nuclear signaling from cadherin adhesion complexes

The arrival of multicellularity in evolution facilitated cell-cell signaling in conjunction with adhesion. As the ectodomains of cadherins interact with each other directly in trans (as well as in cis), spanning the plasma membrane and associating with multiple other entities, cadherins enable the transduction of "outside-in" or "inside-out" signals. We focus this review on signals that originate from the larger family of cadherins that are inwardly directed to the nucleus, and thus have roles in gene control or nuclear structure-function. The nature of cadherin complexes varies considerably depending on the type of cadherin and its context, and we will address some of these variables for classical cadherins versus other family members. Substantial but still fragmentary progress has been made in understanding the signaling mediators used by varied cadherin complexes to coordinate the state of cell-cell adhesion with gene expression. Evidence that cadherin intracellular binding partners also localize to the nucleus is a major point of interest. In some models, catenins show reduced binding to cadherin cytoplasmic tails favoring their engagement in gene control. When bound, cadherins may serve as stoichiometric competitors of nuclear signals. Cadherins also directly or indirectly affect numerous signaling pathways (e.g., Wnt, receptor tyrosine kinase, Hippo, NFκB, and JAK/STAT), enabling cell-cell contacts to touch upon multiple biological outcomes in embryonic development and tissue homeostasis.

A novel role for SIRT-1 in L-arginine protection against STZ induced myocardial fibrosis in rats

BACKGROUND

L-arginine (L-ARG) effectively protects against diabetic impediments. In addition, silent information regulator (SIRT-1) activators are emerging as a new clinical concept in treating diabetic complications. Accordingly, this study aimed at delineating a role for SIRT-1 in mediating L-ARG protection against streptozotocin (STZ) induced myocardial fibrosis.

METHODS

Male Wistar rats were allocated into five groups; (i) normal control rats received 0.1 M sodium citrate buffer (pH 4.5); (ii) STZ at the dose of 60 mg/kg dissolved in 0.1 M sodium citrate buffer (pH 4.5); (iii) STZ + sirtinol (Stnl; specific inhibitor of SIRT-1; 2 mg/Kg, i.p.); (iv) STZ + L-ARG given in drinking water (2.25%) or (v) STZ + L-ARG + Stnl.

RESULTS

L-ARG increased myocardial SIRT-1 expression as well as its protein content. The former finding was paralleled by L-ARG induced reduction in myocardial fibrotic area compared to STZ animals evidenced histopathologically. The reduction in the fibrotic area was accompanied by a decline in fibrotic markers as evident by a decrease in expression of collagen-1 along with reductions in myocardial TGF-β, fibronectin, CTGF and BNP expression together with a decrease in TGF-β and hydroxyproline contents. Moreover, L-ARG increased MMP-2 expression in addition to its protein content while decreasing expression of PAI-1. Finally, L-ARG protected against myocardial cellular death by reduction in NFκ-B mRNA as well as TNF-α level in association with decline in Casp-3 and FAS expressions andCasp-3protein content in addition to reduction of FAS positive cells. However, co-administration of L-ARG and Stnl diminished the protective effect of L-ARG against STZ induced myocardial fibrosis.

CONCLUSION

Collectively, these findings associate a role for SIRT-1 in L-ARG defense against diabetic cardiac fibrosis via equilibrating the balance between profibrotic and antifibrotic mediators.

Molecular Mechanisms of Retinoid Receptors in Diabetes-Induced Cardiac Remodeling

Diabetic cardiomyopathy (DCM), a significant contributor to morbidity and mortality in diabetic patients, is characterized by ventricular dysfunction, in the absence of coronary atherosclerosis and hypertension. There is no specific therapeutic strategy to effectively treat patients with DCM, due to a lack of a mechanistic understanding of the disease process. Retinoic acid, the active metabolite of vitamin A, is involved in a wide range of biological processes, through binding and activation of nuclear receptors: retinoic acid receptors (RAR) and retinoid X receptors (RXR). RAR/RXR-mediated signaling has been implicated in the regulation of glucose and lipid metabolism. Recently, it has been reported that activation of RAR/RXR has an important role in preventing the development of diabetic cardiomyopathy, through improving cardiac insulin resistance, inhibition of intracellular oxidative stress, NF-κB-mediated inflammatory responses and the renin-angiotensin system. Moreover, downregulated RAR/RXR signaling has been demonstrated in diabetic myocardium, suggesting that impaired RAR/RXR signaling may be a trigger to accelerate diabetes-induced development of DCM. Understanding the molecular mechanisms of retinoid receptors in the regulation of cardiac metabolism and remodeling under diabetic conditions is important in providing the impetus for generating novel therapeutic approaches for the prevention and treatment of diabetes-induced cardiac complications and heart failure.

Preventive effects of benfotiamine in chronic diabetic complications

Aims/Introduction:  In diabetes, increased oxidative stress as a result of damage to the electron transport chain can lead to tissue injury through upregulation of multiple vasoactive factors and extracellular matrix proteins. Benfotiamine, a lipid soluble thiamine derivative, through reducing mitochondrial superoxide production, blocks multiple pathways leading to tissue damage in hyperglycemia. We investigated if treatment with benfotiamine can prevent diabetes‐induced production of vasoactive factors and extracellular matrix proteins, and whether such effects are tissue‐specific. We also examined whether effects of benfotiamine are mediated through a nuclear mechanism.

Materials and Methods:  Retinal, renal and cardiac tissues from the streptozotocin‐induced diabetic rats were examined after 4 months of follow up. mRNA levels were quantified using real‐time RT‐PCR. Protein levels were quantified using western blot and ELISA. Cellular expressions of 8‐Hydroxy‐2′‐deoxyguanosine, a marker of nuclear DNA damage and Phospho‐H2AX were also examined.

Results:  Diabetic animals showed hyperglycemia, glucosuria, increased urinary albumin/creatine ratio and loss of bodyweight. In the kidneys, heart and retina, diabetes caused increased production of endothelin‐1, transforming growth factor‐β1, vascular endothelial growth factor and augmented extracellular matrix proteins (collagen, fibronectin [FN] and its splice variant extradomain B containing FN), along with evidence of structural alterations, characteristic of diabetes‐induced tissue damage. Such changes were prevented by benfotiamine. Furthermore, benfotiamine prevented diabetes‐induced oxidative DNA damage and upregulation of p300, a histone acetylator and a transcription coactivator.

Conclusions:  Data from the present study suggest that benfotiamine is effective in preventing tissue damage in diabetes and at the transcriptional level such effects are mediated through prevention of p300 upregulation. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00077.x, 2010)

miR-195 regulates SIRT1-mediated changes in diabetic retinopathy

AIMS/HYPOTHESIS

Endothelial cell (EC) damage is a key mechanism causing retinal microvascular injury in diabetes. Several microRNAs (miRNAs) have been found to regulate sirtuin 1 (SIRT1, which is involved in regulation of the cell cycle, survival and metabolism) in various tissues and disease states, but no studies have been conducted on the role of miRNA in regulation of SIRT1 in diabetic retinopathy. Here we investigated the effect of miRNA-195 (miR-195), a SIRT1-targeting miRNA, on the development of diabetes-induced changes in ECs and retina.

METHODS

The level of miR-195 was measured in human retinal and dermal microvascular ECs (HRECs, HMECs) following exposure to 25 mmol/l glucose (high glucose, HG) and 5 mmol/l glucose (normal glucose, NG). SIRT1 and fibronectin levels were examined following transfection with miR-195 mimic or antagomir or forced expression of SIRT1. Retinal tissues from diabetic rats were similarly studied following intravitreal injection of an miR-195 antagomir or mimic. In situ hybridisation was used to localise retinal miR-195.

RESULTS

HG caused increased miR-195 levels and decreased SIRT1 expression (compared with NG) in both HRECs and HMECs. Transfection with miR-195 antagomir and forced expression of SIRT1 prevented such changes, whereas transfection with miR-195 mimic produced HG-like effects. A luciferase assay confirmed the binding of miR-195 to the 3' untranslated region of SIRT1. miR-195 expression was upregulated in retinas of diabetic rats and intravitreal injection of miR-195 antagomir ameliorated levels of SIRT1.

CONCLUSIONS/INTERPRETATION

These studies identified a novel mechanism whereby miR-195 regulates SIRT1-mediated tissue damage in diabetic retinopathy.

Illustrating the interplay between the extracellular matrix and microRNAs

The discovery of cell surface receptors that bind to extracellular matrix (ECM) components marked a new era in biological research. Since then there has been an increasing appreciation of the importance of studying cells in the context of their extracellular environment. Cell behaviour is profoundly affected by the ECM, whose synthesis and turnover must be finely balanced in order to maintain normal function and prevent disease. In the last decade, microRNAs (miRNAs) have emerged as key regulators of ECM gene expression. As new technologies for the identification and validation of miRNA targets continue to be developed, a growing body of data supporting the role of miRNAs in regulating the ECM biology has arisen from a variety of cell and animal models along with clinical studies. However, more recent findings suggest an intriguing interplay between the ECM and miRNAs: not only can miRNAs control the composition of the ECM, but also the ECM can affect the expression of specific miRNAs. Here we discuss how miRNAs contribute to the synthesis, maintenance and remodelling of the ECM during development and disease. Furthermore, we bring to light evidence that points to a role for the ECM in regulating miRNA expression and function.

An overview of the crosstalk between inflammatory processes and metabolic dysregulation during diabetic cardiomyopathy

Metabolic disorders such as obesity, insulin resistance and type 2 diabetes mellitus are all linked to cardiovascular diseases such as cardiac hypertrophy and heart failure. Diabetic cardiomyopathy in particular, is characterized by structural and functional alterations in the heart muscle of people with diabetes that finally lead to heart failure, and which is not directly attributable to coronary artery disease or hypertension. Several mechanisms have been involved in the pathogenesis of diabetic cardiomyopathy, such as alterations in myocardial energy metabolism and calcium signaling. Metabolic disturbances during diabetic cardiomyopathy are characterized by increased lipid oxidation, intramyocardial triglyceride accumulation, and reduced glucose utilization. Overall changes result in enhanced oxidative stress, mitochondrial dysfunction and apoptosis of the cardiomyocytes. On the other hand, the progression of heart failure and cardiac hypertrophy usually entails a local rise in cytokines in cardiac cells and the activation of the proinflammatory transcription factor nuclear factor (NF)-κB. Interestingly, increasing evidences are arising in the recent years that point to a potential link between chronic low-grade inflammation in the heart and metabolic dysregulation. Therefore, in this review we summarize recent new insights into the crosstalk between inflammatory processes and metabolic dysregulation in the failing heart during diabetes, paying special attention to the role of NF-κB and peroxisome proliferator activated receptors (PPARs). In addition, we briefly describe the role of the AMP-activated protein kinase (AMPK), sirtuin 1 (SIRT1) and other pathways regulating cardiac energy metabolism, as well as their relationship with diabetic cardiomyopathy.

Resveratrol protects vascular endothelial cells from high glucose-induced apoptosis through inhibition of NADPH oxidase activation-driven oxidative stress

INTRODUCTION

Hyperglycemia-induced oxidative stress has been implicated in diabetic vascular complications in which NADPH oxidase is a major source of reactive oxygen species (ROS) generation. Resveratrol is a naturally occurring polyphenol, which has vasoprotective effects in diabetic animal models and inhibits high glucose (HG)-induced oxidative stress in endothelial cells.

AIMS

We aimed to examine whether HG-induced NADPH oxidase activation and ROS production contribute to glucotoxicity to endothelial cells and the effect of resveratrol on glucotoxicity.

RESULTS

Using a murine brain microvascular endothelial cell line bEnd3, we found that NADPH oxidase inhibitor (apocynin) and resveratrol both inhibited HG-induced endothelial cell apoptosis. HG-induced elevation of NADPH oxidase activity and production of ROS were inhibited by apocynin, suggesting that HG induces endothelial cell apoptosis through NADPH oxidase-mediated ROS production. Mechanistic studies revealed that HG upregulated NADPH oxidase subunit Nox1 but not Nox2, Nox4, and p22(phox) expression through NF-κB activation, which resulted in elevation of NADPH oxidase activity and consequent ROS production. Resveratrol prevented HG-induced endothelial cell apoptosis through inhibiting HG-induced NF-κB activation, NADPH oxidase activity elevation, and ROS production.

CONCLUSIONS

HG induces endothelial cell apoptosis through NF-κB/NADPH oxidase/ROS pathway, which was inhibited by resveratrol. Our findings provide new potential therapeutic targets against brain vascular complications of diabetes.

Diabetic cardiomyopathy: understanding the molecular and cellular basis to progress in diagnosis and treatment

Diabetes mellitus is an important and prevalent risk factor for congestive heart failure. Diabetic cardiomyopathy has been defined as ventricular dysfunction that occurs in diabetic patients independent of a recognized cause such as coronary artery disease or hypertension. The disease course consists of a hidden subclinical period, during which cellular structural insults and abnormalities lead initially to diastolic dysfunction, later to systolic dysfunction, and eventually to heart failure. Left ventricular hypertrophy, metabolic abnormalities, extracellular matrix changes, small vessel disease, cardiac autonomic neuropathy, insulin resistance, oxidative stress, and apoptosis are the most important contributors to diabetic cardiomyopathy onset and progression. Hyperglycemia is a major etiological factor in the development of diabetic cardiomyopathy. It increases the levels of free fatty acids and growth factors and causes abnormalities in substrate supply and utilization, calcium homeostasis, and lipid metabolism. Furthermore, it promotes excessive production and release of reactive oxygen species, which induces oxidative stress leading to abnormal gene expression, faulty signal transduction, and cardiomyocytes apoptosis. Stimulation of connective tissue growth factor, fibrosis, and the formation of advanced glycation end-products increase the stiffness of the diabetic hearts. Despite all the current information on diabetic cardiomyopathy, translational research is still scarce due to limited human myocardial tissue and most of our knowledge is extrapolated from animals. This paper aims to elucidate some of the molecular and cellular pathophysiologic mechanisms, structural changes, and therapeutic strategies that may help struggle against diabetic cardiomyopathy.

Signaling mechanisms of a water soluble curcumin derivative in experimental type 1 diabetes with cardiomyopathy

BACKGROUND

Curcumin exhibits anti-diabetic activities, induces heme-oxygenase-1 (HO-1) and is an inhibitor of transcriptional co-activator p300. A novel water soluble curcumin derivative (NCD) has been developed to overcome low invivo bioavailability of curcumin. We evaluated the effect of the NCD on signaling mechanisms involved in cardiomyocyte hypertrophy and studied whether its action is mediated via inducible HO-1.

MATERIALS AND METHODS

Rats were divided into controls, controls receiving NCD, diabetic, diabetic receiving NCD, diabetic receiving pure curcumin, diabetic receiving HO inhibitor, zinc protoporphyrin IX (ZnPP IX) and diabetic receiving NCD and ZnPP IX. NCD and curcumin were given orally. After 45 days, cardiac physiologic parameters, plasma glucose, insulin, glycated hemoglobin (GHb), HO-1 gene expression and HO activity in pancreas and cardiac tissues were assessed. Gene expression of p300, atrial natriuretic peptide (ANP) and myocyte enhancer factor 2 (MEF2A and MEF2C) were studied.

RESULTS

NCD and curcumin decreased plasma glucose, GHb and increased insulin levels significantly in diabetic rats. This action may be partially mediated by induction of HO-1 gene. HO-1 gene expression and HO activity were significantly increased in diabetic heart and pancreas. Diabetes upregulated the expression of ANP, MEF2A, MEF2C and p300. NCD and curcumin prevented diabetes-induced upregulation of these parameters and improved left ventricular function. The effect of the NCD was better than the same dose of curcumin.