The role of vascular endothelial growth factor, tumor necrosis factor alpha and interleukin-6 in pathogenesis of diabetic retinopathy

The Role of Th17/Treg Axis in Retinal Pathology Associated with Diabetes and Treatment Options

Diabetic retinopathy (DR) is a major complication of diabetes, leading to vision impairment and blindness. The pathogenesis of DR involves multiple factors, including hyperglycemia-induced vascular damage, hypertension, obesity, anemia, immune dysregulation, and disruption of the blood-retinal barrier (BRB). Th17 and Treg cells, two types of CD4+ T cells, play opposing roles in inflammation. Th17 cells are pro-inflammatory, producing cytokines such as IL-17A, while Treg cells help suppress immune responses and promote anti-inflammatory effects. Recent studies highlight the importance of the Th17/Treg balance in retinal inflammation and disease progression in DR. Our literature review reveals an imbalance in DR, with increased Th17 activity and reduced Treg function. This shift creates a pro-inflammatory environment in the retina, worsening vascular leakage, neovascularization, and vision loss. The limited infiltration of Treg cells suggests that Th17 cells may uniquely infiltrate the retina by overwhelming or outnumbering Tregs or increasing the expression of recruiting chemokines, rather than only taking advantage of a damaged BRB. Therapeutic strategies, such as neutralizing IL-17A and enhancing Treg function with compounds like IL-35 or curcumin, may reduce inflammation and retinal damage. Restoring the balance between Th17 and Treg cells could provide new approaches for treating DR by controlling inflammation and preventing further retinal damage.

The relationship between refractive error and the risk of diabetic retinopathy: a systematic review and meta-analysis

Purpose

This meta-analysis was conducted to collect all available data and estimate the relationship between refractive error and the risk of diabetic retinopathy (DR) in patients with diabetes, and to assess whether vision-threatening DR (VTDR) is associated with refractive error.

Methods

We systematically searched several literature databases including PubMed, Embase, Cochrane Library, Web of Science, CNKI, CBM, Wan Fang Data, and VIP databases. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated using fixed or random effects models. Four models were developed to assess the relationship between refractive error and the risk and DR, VTDR: hyperopia and DR, VTDR; myopia and DR, VTDR; spherical equivalent (SE per D increase) and DR, VTDR; and axial length (AL per mm increase) and DR, VTDR. The included literature was meta-analyzed using Stata 12.0 software, and sensitivity analysis was performed. Publication bias in the literature was evaluated using a funnel plot, Begg's test, and Egger's test.

Results

A systematic search identified 3,198 articles, of which 21 (4 cohorts, 17 cross-sectional studies) were included in the meta-analysis. Meta-analysis showed that hyperopia was associated with an increased risk of VTDR (OR: 1.23; 95% CI: 1.08-1.39; P = 0.001), but not with DR (OR: 1.05; 95% CI: 0.94-1.17; P = 0.374). Myopia was associated with a reduced risk of DR (OR: 0.74; 95% CI: 0.61-0.90; P = 0.003), but not with VTDR (OR: 1.08; 95% CI: 0.85-1.38; P = 0.519). Every 1 diopter increase in spherical equivalent, there was a 1.08 increase in the odds ratio of DR (OR: 1.08; 95% CI: 1.05-1.10; P<0.001), but not with VTDR (OR: 1.05; 95% CI: 1.00-1.10; P = 0.06). AL per mm increase was significantly associated with a decreased risk of developing DR (OR: 0.77; 95% CI: 0.71-0.84; P<0.001) and VTDR (OR: 0.63; 95% CI: 0.56-0.72; P<0.001). Analysis of sensitivity confirmed the reliability of the study's findings.

Conclusion

This meta-analysis demonstrates hyperopia was associated with an increased risk of VTDR in diabetes patients. Myopia was associated with a reduced risk of DR. AL is an important influencing factor of refractive error. Every 1 mm increase in AL reduces the risk of DR by 23% and the risk of VTDR by 37%.

Systematic review registration

identifier: CRD42023413420.

The association between interleukin family and diabetes mellitus and its complications: An overview of systematic reviews and meta-analyses

OBJECTIVE

To evaluate and summarize the association between interleukin (IL) concentrations and diabetes mellitus (DM) and its complications.

METHODS

Meta-analyses and eligible individual studies of observational studies investigating the associations between IL and DM and its complications were included. The random-effects model was used to estimate the summary effect, and the heterogeneity among studies was assessed using the Q-statistic and the I2 metric; The Egger's regression and the χ2 test were used to test for small study effects and excess significance bias.

RESULTS

This overview identified 34 meta-analyses that investigated the association between IL concentrations and DM and its complications. Meta-analyses of prospective studies indicated that elevated circulating IL-6 and IL-1β had predictive value for the incident of type 2 diabetes mellitus (T2DM), type 1 diabetes mellitus (T1DM) as well as gestational diabetes mellitus (GDM), and the overall Hazard Ratio (HR) of T2DM was 1.28 (95 % CI: 1.17, 1.40; P＜0.001) per 1 log pg/ml increment in IL-6 levels, however, there was no correlation between circulating IL-10 levels and DM. Meanwhile, the increased level of IL-6 was significantly associated several diabetic complications (Diabetic kidney disease[DKD], diabetic peripheral neuropathy[DPN], and cognitive impairment[CI]), and for the diabetic retinopathy (DR), the levels of IL-1β, IL-8 and IL-10 in the aqueous humor and vitreous humor, but not the blood were significantly correlated with it.

CONCLUSION

Multiple ILs, such as the IL-6 and IL-1β, are definitively linked to DM and its complications, and they may be new targets for the diagnosis and treatment, but stronger evidence needs to be confirmed by prospective studies with larger sample sizes and longer observation periods.

Mendelian randomization analysis reveals a causal effect of Streptococcus salivarius on diabetic retinopathy through regulating host fasting glucose

Diabetic retinopathy (DR) is one of leading causes of vision loss in adults with increasing prevalence worldwide. Increasing evidence has emphasized the importance of gut microbiome in the aetiology and development of DR. However, the causal relationship between gut microbes and DR remains largely unknown. To investigate the causal associations of DR with gut microbes and DR risk factors, we employed two-sample Mendelian Randomization (MR) analyses to estimate the causal effects of 207 gut microbes on DR outcomes. Inputs for MR included Genome-wide Association Study (GWAS) summary statistics of 207 taxa of gut microbes (the Dutch Microbiome Project) and 21 risk factors for DR. The GWAS summary statistics data of DR was from the FinnGen Research Project. Data analysis was performed in May 2023. We identified eight bacterial taxa that exhibited significant causal associations with DR (FDR < 0.05). Among them, genus Collinsella and species Collinsella aerofaciens were associated with increased risk of DR, while the species Bacteroides faecis, Burkholderiales bacterium_1_1_47, Ruminococcus torques, Streptococcus salivarius, genus Burkholderiales_noname and family Burkholderiales_noname showed protective effects against DR. Notably, we found that the causal effect of species Streptococcus salivarius on DR was mediated through the level of host fasting glucose, a well-established risk factor for DR. Our results reveal that specific gut microbes may be causally linked to DR via mediating host metabolic risk factors, highlighting potential novel therapeutic or preventive targets for DR.

The Complex Network of Cytokines and Chemokines in Pediatric Patients with Long-Standing Type 1 Diabetes

Type 1 diabetes (T1D) is a progressive disorder leading to the development of microangiopathies and macroangiopathies. Numerous cytokines and chemokines are involved in the pathogenesis of T1D complications. The study aimed to assess the presence of complications in patients with long-standing T1D and its relationship with serum biomarker concentrations. We examined 52 T1D subjects, with a disease duration ≥4 years and 39 healthy controls. The group of T1D patients was further divided into subgroups based on the duration of the disease (<7 years and ≥7 years) and the metabolic control assessed by the HbAlc level (<8% and ≥8%). We used Luminex Technology to assess a wide range of biomarker concentrations. A 24 h urine test was done to evaluate the rate of albuminuria. Optical coherence tomography (OCT) was conducted to detect early retinopathic changes. Subclinical atherosclerosis was assessed by measuring the carotid intima-media thickness (IMT). T1D patients showed remarkably higher concentrations of EGF, eotaxin/CCL11, MDC/CCL22, sCD40L, TGF-α, and TNF-α. Moreover, we reported statistically significant correlations between cytokines and IMT. Biomarker concentrations depend on numerous factors such as disease duration, metabolic control, and the presence of complications. Although the majority of pediatric T1D patients do not present signs of overt complications, it is indispensable to conduct the screening for angiopathies already in childhood, as its early recognition may attenuate the further progression of complications.

The role of tumor necrosis factor-α and interferon-γ in the hyperglycemia-induced ubiquitination and loss of platelet endothelial cell adhesion molecule-1 in rat retinal endothelial cells

OBJECTIVE

This study aimed to investigate the role of the hyperglycemia-induced increase in tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) in the ubiquitination and degradation of platelet endothelial cell adhesion molecule-1 (PECAM-1) in the diabetic retina.

METHODS

Type I diabetes was induced in rats by the injection of streptozotocin, with age-matched non-diabetic rats as controls. Primary rat retinal microvascular endothelial cells were grown in normal or high glucose media for 6 days or in normal glucose media for 24 h with addition of TNF-α and/or IFN-γ. PECAM-1, TNF-α, IFN-γ, and ubiquitin levels were assessed using Western blotting, immunofluorescence, and immunoprecipitation assays. Additionally, proteasome activity was assessed both in vivo and in vitro.

RESULTS

Under hyperglycemic conditions, total ubiquitination levels in the retina and RRMECs, and PECAM-1 ubiquitination levels in RRMECs, were significantly increased. Additionally, TNF-α and IFN-γ levels were significantly increased under hyperglycemic conditions. PECAM-1 levels in RRMECs treated with TNF-α and/or IFN-γ were significantly decreased. Moreover, there was a significant decrease in proteasome activity in the diabetic retina, hyperglycemic RRMECs, and RRMECs treated with TNF-α or IFN-γ.

CONCLUSION

Tumor necrosis factor-α and IFN-γ may contribute to the hyperglycemia-induced loss of PECAM-1 in retinal endothelial cells, possibly by upregulating PECAM-1 ubiquitination.

Retinal Vascular Endothelial Cell Dysfunction and Neuroretinal Degeneration in Diabetic Patients

Diabetes mellitus (DM) has become a vital societal problem as epidemiological studies demonstrate the increasing incidence of type 1 and type 2 diabetes. Lesions observed in the retina in the course of diabetes, referred to as diabetic retinopathy (DR), are caused by vascular abnormalities and are ischemic in nature. Vascular lesions in diabetes pertain to small vessels (microangiopathy) and involve precapillary arterioles, capillaries and small veins. Pericyte loss, thickening of the basement membrane, and damage and proliferation of endothelial cells are observed. Endothelial cells (monolayer squamous epithelium) form the smooth internal vascular lining indispensable for normal blood flow. Breaking its continuity initiates blood coagulation at that site. The endothelium controls the process of exchange of chemical substances (nutritional, regulatory, waste products) between blood and the retina, and blood cell passing through the vascular wall. Endothelial cells produce biologically active substances involved in blood coagulation, regulating vascular wall tension and stimulating neoangiogenesis. On the other hand, recent studies have demonstrated that diabetic retinopathy may be not only a microvascular disease, but is a result of neuroretinal degeneration. Neuroretinal degeneration appears structurally, as neural apoptosis of amacrine and Muller cells, reactive gliosis, ganglion cell layer/inner plexiform (GCL) thickness, retinal thickness, and retinal nerve fiber layer thickness, and a reduction of the neuroretinal rim in minimum rim width (MRW) and functionally as an abnormal electroretinogram (ERG), dark adaptation, contrast sensitivity, color vision, and microperimetric test. The findings in early stages of diabetic retinopathy may precede microvascular changes of this disease. Furthermore, the article's objective is to characterize the factors and mechanisms conducive to microvascular changes and neuroretinal apoptosis in diabetic retinopathy. Only when all the measures preventing vascular dysfunction are determined will the risk of complications in the course of diabetes be minimized.

Relationship between Proliferative Diabetic Retinopathy and Inflammatory Markers in Patients with Type 1 Diabetes in Brazil: A Nested Case Control Study

INTRODUCTION

This study examined the relationship between proliferative diabetic retinopathy (PDR) and serum levels of C-reactive protein, VEGF, TNF-α, and IL-6 inflammatory biomarkers, related to the pathophysiology of diabetic retinopathy.

METHODS

This cross-sectional, case control study comprised 240 patients with type 1 diabetes (80 cases with PDR and 160 controls without diabetic retinopathy) who were matched for gender and duration of diabetes.

RESULTS

C-reactive protein was the only inflammatory biomarker that was positively related to PDR (OR 1.96; 95% CI 1.01-3.78, p = 0.0045). We also noted an association between high glycated hemoglobin levels, the use of angiotensin-converting enzyme inhibitor, low glomerular filtration rate, and PDR.

CONCLUSION

Patients with higher levels of C-reactive protein are more likely to present with PDR. We did not find a link between serum levels of VEGF, TNF-α, or IL-6 and PDR. The function of inflammatory biomarkers in PDR must be addressed in further studies.

Ocular toxicity of intravitreal golimumab in a rabbit model

Background/aim

To investigate the effect of intravitreal golimumab on rabbit retina histopathology.

Materials and methods

Sixteen albino New Zealand rabbits were divided into three groups. The right eye of each rabbit in groups I, II, and III received a single intravitreal injection of 5 mg/0.05 mL (6 eyes), 10 mg/0.1 mL (6 eyes), or 20 mg/0.2 mL (4 eyes) golimumab, while left eyes served as controls with the same volume of a balanced salt solution injection. All animals were examined using slit-lamp biomicroscopy and indirect ophthalmoscopy before and after intravitreal injection and at days 1 and 7. Animals were euthanized on day 7 and the eyes were enucleated for immunohistochemistry evaluation and electron microscopic examination of the retinas.

Results

For groups I, II, and III, the number of cells in the outer nuclear layer and the inner nuclear layer was decreased compared to those in the control groups. In group I, the percentage of caspase-3 staining of the outer nuclear layer was significantly higher than that in the control. For groups II and III, TUNEL and caspase-3 staining percentages in the outer and inner nuclear layers were found to be significantly higher than those for the control groups. In the ganglion cell layer, for groups I, II, and III, neither TUNEL nor caspase-3 staining percentages showed any significant difference between two groups. No significant dose-dependent relationship was found for increasing doses of golimumab in all layers. Myelin figures and karyorrhexis in the photoreceptor cells were prominent in electron microscopy of the golimumab-injected eyes.

Conclusion

Golimumab caused apoptosis in both photoreceptors and bipolar cells of the rabbit retina. Potential retinal toxicity of intravitreal golimumab should be considered if an intravitreal administration is planned.

The relationship of blood cell-associated inflammatory indices and diabetic retinopathy: a Meta-analysis and systematic review

AIM

To explore the correlation between several blood cell-associated inflammatory indices including mean platelet volume (MPV), platelet distribution width (PDW), neutrophil to lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR), and the presence and severity of diabetic retinopathy (DR).

METHODS

We searched for eligible studies from PubMed, EMBASE, Web of Science and CNKI up to December 13, 2017. Standardized mean difference (SMD) calculated with confidence interval (CI) of 95% was used to estimate the values of those indices.

RESULTS

A total of 31 studies were included in the present Meta-analysis. As compared with type 2 diabetes mellitus (T2DM) patients without DR, the values of MPV, PDW, NLR, and PLR were higher in patients with DR (SMD=0.67; 95%CI: 0.36 to 0.98; SMD=0.51; 95%CI: 0.27 to 0.75; SMD=0.77; 95%CI: 0.49 to 1.05 and SMD=1.18; 95%CI: 0.07 to 2.28). Additionally, it was also observed that MPV was closely correlated with the severity of DR.

CONCLUSION

MPV, PDW, NLR, and PLR could be recommended as diagnostic biomarkers for DR, and MPV could be applied to assess the severity of DR.

Interleukin-6 and Diabetic Retinopathy: A Systematic Review and Meta-Analysis

BACKGROUND

Interleukin-6 (IL-6) is produced by a variety of cells involved in inflammation and acts as local intensification signals in pathological processes associated with chronic eye inflammation. This meta-analysis was performed to provide a better understanding of the relationship between IL-6 and diabetic retinopathy.

METHODS

The study was started with systematic search for literatures by using the PubMed, Web of Science and Embase online databases. The standard mean difference (SMD) and its 95% confidence intervals (CIs) were was included and then pooled with a random effects model.

RESULTS

Thirty-one articles, containing1099 DR patients and 1010 controls, were included in this meta-analysis. The level of IL-6 in the DR group was found to be higher than that in the control group (SMD: 2.12, 95% CI: 1.53-2.70, p < 0.00001).Obvious heterogeneity existed between the studies (p < 0.00001, I² = 96%). So a subgroup analysis and sensitivity analysis were performed. Removing the sensitivity studies, the stability of the overall treatment effect was good. Subgroup analysis showed that the levels of IL-6 in case group were observed to be higher than those in the control group; and the IL-6 levels in the proliferative diabetic retinopathy (PDR) group were also higher than those in the non-proliferative diabetic retinopathy (NPDR) group. (SMD: 0.78, 95% CI: 0.26-1.31, p=  0.003) Conclusion: The results from this current meta-analysis indicated that increased level of IL-6 generally exist in DR patients. And it may associated with the severity of DR. However, large-scale and high-quality studies in future are required to confirm the present findings.

Overexpression of acid ceramidase (ASAH1) protects retinal cells (ARPE19) from oxidative stress

Over 11 million people in the United States alone have some form of age-related macular degeneration (AMD). Oxidative stress, cell death, and the degeneration of retinal pigment epithelial (RPE) cells contribute to AMD pathology. Recent evidence suggests that ceramide (Cer), a cellular sphingolipid mediator that acts as a second messenger to induce apoptosis, might play a role in RPE cell death. The lysosomal breakdown of Cer by acid ceramidase [N-acylsphingosine amidohydrolase (ASAH)1] into sphingosine (Sph) is the major source for Sph 1-phosphate production, which has an opposing role to Cer and provides cytoprotection. Here, we investigated the role of Cer in human RPE-derived ARPE19 cells under hydrogen peroxide-induced oxidative stress, and show that Cer and hexosyl-Cer levels increase in the oxidatively stressed ARPE19 cells, which can be prevented by overexpression of lysosomal ASAH1. This study demonstrates that oxidative stress generates sphingolipid death mediators in retinal cells and that induction of ASAH1 could rescue retinal cells from oxidative stress by hydrolyzing excess Cers.

Alterations in System xc- Expression in the Retina of Type 1 Diabetic Rats and the Role of Nrf2

Nrf2 (nuclear factor erythroid 2-related factor 2), a transcription factor that controls expression of several proteins that are related to cellular antioxidant capacity, such as the subunit xCT of the system x_c^-, is dysregulated in diabetes. Recently, it was described that system x_c^- is decreased in the retina after 3 weeks of diabetes. So, in the present work, the temporal relationship between xCT and Nrf2 in the retina of diabetic animals was investigated. Diabetes was induced in male Wistar rats (200 g) by a single injection of streptozotocin, and retinas were collected after 1, 2, and 6 months of diabetes induction. Expression of xCT, Nrf2 activity, and binding to antioxidant-responsive element (ARE) sequence were evaluated. Glutathione and reactive oxygen species (ROS) levels were also assessed. After 1 month of diabetes, Nrf2 activity, xCT expression, and glutathione levels were reduced whereas ROS were increased. Although glutathione and ROS levels remain unchanged until later stages, Nrf2 activity and xCT expression returned to normal levels after 2 months. However, they were decreased again at 6 months of diabetes. Accordingly, Nrf2 binding to xCT ARE sequence followed the same pattern of Nrf2 activity and xCT expression. These data showed that retinal xCT expression is regulated by Nrf2 in diabetic condition. The results also demonstrated a temporal relationship between Nrf2 and system x_c^- which could be implicated in the initiation of oxidative stress in retina in diabetes.

Association between the expression of vascular endothelial growth factors and metabolic syndrome or its components: a systematic review and meta-analysis

BACKGROUND

Several studies have linked vascular endothelial growth factors (VEGFs) with metabolic syndrome or its components. However, there has been no systematic appraisal of the findings of these studies to date. The current systematic review and meta-analysis was conducted to explore this association.

METHODS

PubMed, EMBASE, the Cochrane library, and clinical trials registries were used to retrieve peer-reviewed clinical studies that had evaluated the association of VEGFs with metabolic syndrome or its components without applying language and date restrictions. The final search was performed on 29 September 2017.

RESULTS

We included 32 studies in this systematic review and meta-analysis, of which 16 studies (19 study arms) were included in the meta-analysis and remaining studies were qualitatively assessed. Overall, VEGF-A, VEGF-B and VEGF-C were strongly associated with metabolic syndrome or its components. The components of metabolic syndrome varied in their association. Obesity was not correlated with increased VEGF-A expression (p = 0.12), whereas VEGF-B and VEGF-C expression was significantly higher in those with obesity. In contrast, hyperglycemia in type 1 diabetes was strongly associated with increased VEGF-A levels (p < 0.00001), as was type 2 diabetes (p = 0.0006). The studies included in the qualitative analysis similarly showed an increase in VEGF family expression in people with metabolic syndrome, and with its components.

CONCLUSION

The increased concentrations of vascular endothelial growth factors are variably associated with metabolic syndrome or its components. Each VEGF protein has a unique set of associations with the disease state.

The Increased Circulating Plasma Levels of Vascular Endothelial Growth Factor in Patients with Type 1 Diabetes Do Not Correlate to Metabolic Control

Aim. To characterize the plasma levels of vascular endothelial growth factor (VEGF) in type 1 diabetes mellitus (T1D) and its relation to both present and historical metabolic control and microvascular complications. Methods. Plasma levels of VEGF and routine clinical parameters were analyzed in 115 patients with long-standing T1D and 45 healthy controls (HC). All patients were under clinical routine diabetes treatment at Uppsala University Hospital. Results. The plasma levels of VEGF were increased by 37% in patients with T1D when compared to HC (18.2 ± 0.8 versus 13.2 ± 1.0 pg/ml, p < 0.001). The levels of VEGF correlated to insulin needs and BMI but not to present or historical metabolic control. The levels of VEGF were similar in patients with T1D and microvascular complications (microalbuminuria and retinopathy) when compared with patients without microvascular complications. Historical HbA1c levels were found to be the best predictor for present metabolic control. Conclusion. Circulating plasma levels of VEGF do not correlate to present or historical metabolic control in long-standing T1D and the levels are not affected by the presence of microvascular complications.

Circulating Biomarkers of Diabetic Retinopathy: An Overview Based on Physiopathology

Diabetic retinopathy (DR) is the main cause of working-age adult-onset blindness. The currently available treatments for DR are applicable only at advanced stages of the disease and are associated with significant adverse effects. In early stages of DR the only therapeutic strategy that physicians can offer is a tight control of the risk factors for DR. Therefore, new pharmacological treatments for these early stages of the disease are required. In order to develop therapeutic strategies for early stages of DR new diagnostic tools are urgently needed. In this regard, circulating biomarkers could be useful to detect early disease, to identify those diabetic patients most prone to progressive worsening who ought to be followed up more often and who could obtain the most benefit from these therapies, and to monitor the effectiveness of new drugs for DR before more advanced DR stages have been reached. Research of biomarkers for DR has been mainly based on the pathogenic mechanism involved in the development of DR (i.e., AGEs, oxidative stress, endothelial dysfunction, inflammation, and proangiogenic factors). This review focuses on circulating biomarkers at both early and advanced stages that could be relevant for the prediction or detection of DR.

Clinical biomarkers and molecular basis for optimized treatment of diabetic retinopathy: current status and future prospects

Diabetic retinopathy is a highly specific microvascular complication of diabetes and a leading cause of blindness worldwide. It is triggered by hyperglycemia which causes increased oxidative stress leading to an adaptive inflammatory assault to the neuroretinal tissue and microvasculature. Prolonged hyperglycemia causes increased polyol pathway flux, increased formation of advanced glycation end-products, abnormal activation of signaling cascades such as activation of protein kinase C (PKC) pathway, increased hexosamine pathway flux, and peripheral nerve damage. All these changes lead to increased oxidative stress and inflammatory assault to the retina resulting in structural and functional changes. In addition, neuroretinal alterations affect diabetes progression. The most effective way to manage diabetic retinopathy is by primary prevention such as hyperglycemia control. While the current mainstay for the management of severe and proliferative diabetic retinopathy is laser photocoagulation, its role is diminishing with the development of newer drugs including corticosteroids, antioxidants, and antiangiogenic and anti-VEGF agents which work as an adjunct to laser therapy or independently. The current pharmacotherapy of diabetic retinopathy is incomplete as a sole treatment option in view of limited efficacy and short-term effect. There is a definite clinical need to develop new pharmacological therapies for diabetic retinopathy, particularly ones which would be effective through the oral route and help recover lost vision. The increasing understanding of the mechanisms of diabetic retinopathy and its biomarkers is likely to help generate better and more effective medications.

Protective effects of Egyptian cloudy apple juice and apple peel extract on lipid peroxidation, antioxidant enzymes and inflammatory status in diabetic rat pancreas

Background

Apples possess rich content of varied polyphenolic compounds showing a variety of biological activities that may ascribe to worthy effects against some chronic diseases. The present study was designed to assess the protective effects of the cloudy apple juice (CAJ) and apple peel extract (APE) of Egyptian Anna apple on the complications in experimental diabetes.

Materials and methods

Four groups were studied. Diabetes was induced by a single dose of streptozotocin (STZ) to only three groups of albino Wistar rats. Two of the diabetic groups received either CAJ or APE for 21 days. At the end of the study, lipid profile parameters were measured in serum while lipid peroxidation (LPO) level, antioxidant enzyme activities and inflammatory markers were evaluated in pancreas tissue samples. The gas chromatography–mass spectrometry (GC-MS) analysis of phenolic compounds found in CAJ and APE was carried out. Moreover, total phenolic content of CAJ and APE were measured.

Results

The significant increase of blood glucose level, serum total cholesterol (TC), triglycerides (TG), low- density lipoprotein cholesterol (LDL-C), and very low-density lipoprotein (VLDL) levels, in addition to tissue malondialdehyde (MDA), nuclear factor kappa B (NF-kB), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), interleukin 8 (IL-8) levels, but a significant decrease in high-density lipoprotein cholesterol (HDL-C), and the activity of pancreatic antioxidant enzymes were the remarkably parameters observed in diabetic control rats. Dissimilarly, oral supplementation of 15 ml/kg CAJ and 1 g/kg APE for 21 days resulted in a significant decrease in fasting blood glucose, serum TC, TG, LDL-C, VLDL-C and tissue MDA, NF-kB, TNF-α, IL-6, IL-8 levels coupled with a significant elevation of HDL-C and antioxidant enzymes’ activity when compared with diabetic control animals.

Conclusions

The results indicate that Egyptian CAJ and APE supplementation may have protective effects against deleterious complications of diabetes mellitus.

Relationship between C-Reactive Protein Level and Diabetic Retinopathy: A Systematic Review and Meta-Analysis

Objectives

To date, the relationship between C-reactive protein (CRP) level and diabetic retinopathy (DR) remains controversial. Therefore, a systematic review and meta-analysis was used to reveal the potential relationship between CRP level and DR.

Methods

A systematic search of PubMed, Embase.com, and Web of Science was performed to identify all comparative studies that compared the CRP level of two groups (case group and control group). We defined that diabetic patients without retinopathy and /or matched healthy persons constituted the control group, and patients with DR were the case group.

Results

Two cross sectional studies and twenty case control studies including a total of 3679 participants were identified. After pooling the data from all 22 studies, obvious heterogeneity existed between the studies, so a subgroup analysis and sensitivity analysis were performed. Removing the sensitivity studies, the blood CRP levels in the case group were observed to be higher than those in the control group [SMD = 0.22, 95% confidence interval (CI), 0.11–0.34], and the blood CRP levels in the proliferative diabetic retinopathy (PDR) group were also higher than those in the non-proliferative diabetic retinopathy (NPDR) group [SMD = 0.50, 95% CI, 0.30–0.70].

Conclusions

The results from this current meta-analysis indicate that the CRP level might be used as a biomarker to determine the severity of DR.

The Influence of Glycated Hemoglobin on the Cross Susceptibility Between Type 1 Diabetes Mellitus and Periodontal Disease

BACKGROUND

Periodontal disease is a major complication of type 1 diabetes mellitus (T1DM). The aim of the present study is to investigate the relationship between glycated hemoglobin and circulating levels of interleukin (IL)-6, IL-8, and C-X-C motif chemokine ligand 5 (CXCL5) in non-smoking patients suffering from T1DM, with and without periodontitis. In addition, to determine the effect of advanced glycation end products (AGE) in the presence and absence of Porphyromonas gingivalis lipopolysaccharide (LPS) on IL-6, IL-8, and CXCL5 expression by THP-1 monocytes and OKF6/TERT-2 cells.

METHODS

There were 104 participants in the study: 19 healthy volunteers, 23 patients with periodontitis, 28 patients with T1DM, and 34 patients with T1DM and periodontitis. Levels of blood glucose/glycated hemoglobin (International Federation of Clinical Chemistry [IFCC]) were determined by high-performance liquid chromatography. Levels of IL-6, IL-8, and CXCL5 in plasma were determined by enzyme-linked immunosorbent assay (ELISA). In vitro stimulation of OKF6/TERT-2 cells and THP-1 monocytes was performed with combinations of AGE and P. gingivalis LPS. Changes in expression of IL-6, IL-8, and CXCL5 were monitored by ELISA and real-time polymerase chain reaction.

RESULTS

Patients with diabetes and periodontitis had higher plasma levels of IL-8 than patients with periodontitis alone. Plasma levels of IL-8 correlated significantly with IFCC units, clinical probing depth, and attachment loss. AGE and LPS, alone or in combination, stimulated IL-6, IL-8, and CXCL5 expression in both OKF6/TERT-2 cells and THP-1 monocytes.

CONCLUSIONS

Elevated plasma levels of IL-8 potentially contribute to the cross-susceptibility between periodontitis and T1DM. P. gingivalis LPS and AGE in combination caused significantly greater expression of IL-6, IL-8, and CXCL5 from THP-1 monocytes and OKF6/TERT-2 cells than LPS alone.

Vascular endothelial growth factor levels in tears of patients with retinal vein occlusion

PURPOSE

We measured vascular endothelial growth factor (VEGF) levels in tear fluid and serum in patients with retinal vein occlusion (RVO).

PATIENTS AND METHODS

Eight patients with RVO due to secondary macular oedema were examined. VEGF levels were measured by enzyme-linked immunosorbent assay. All patients had a full ophthalmic examination (visual acuity, slit lamp biomicroscopy, perimetry, and fluorescein angiography). Central retinal thickness (CRT) was examined using optical coherence tomography (OCT). Tear and serum samples were collected and examinations were performed at diagnosis and 1 and 4 weeks later.

RESULTS

VEGF levels in the tears of RVO eyes were significantly higher than in fellow eyes at diagnosis and after both 1 and 4 weeks (paired t test, p1 = 0.01, p2 = 0.02, p3 = 0.006). We found a weak but significant positive correlation between VEGF levels in tear fluid and serum of patients with RVO (r = 0.21), while this correlation tended to be stronger between the fellow eyes and serum levels (r = 0.33).

CONCLUSION

To the best of our knowledge, we are the first to report an increased level of VEGF in the tear fluid of patients with RVO. Alterations of VEGF levels in tears may be useful for determining stages of RVO. This non-invasive and objective method may also be helpful for estimating the severity of macular oedema and efficacy of treatment.

Potential role of polyunsaturated fatty acids in diabetic retinopathy

Diabetic retinopathy (DR) is a serious complication of long-standing diabetes mellitus. It affects about 25% of all patients with diabetes mellitus and causes a significant decrease in the quality of life. Despite many years of research, the exact pathway that leads to the development and progression of DR is not clear. Recent studies suggest that polyunsaturated fatty acids (PUFAs) and their metabolites could play a significant role in DR. There is evidence to suggest that an imbalance between pro- and anti-inflammatory eicosanoids and enhanced production of pro-angiogenic factors may initiate the onset and progression of DR. This implies that PUFAs and their metabolites that possess anti-inflammatory actions and suppress the production of angiogenic factors could be employed in the prevention and management of DR.

IVS1 -397T>C estrogen receptor α polymorphism is associated with low-grade systemic inflammatory response in type 1 diabetic girls

PURPOSE

The study aimed to investigate the influence of estrogen receptor α (ER-α) genotypes on inflammatory response and development of microvascular complications in girls with type 1 diabetes.

METHODS

152 young regularly menstruating girls with diagnosed type 1 diabetes and 84 young, healthy menstruating girls were recruited. ER-α genotyping was carried out by PCR. Serum concentrations of 17β-estradiol, as well as IL-6, TNF-α, VEGF, and IL-10, were measured. CD4(+)Foxp3(+) TH17 cells were isolated and analyzed by flow cytometry.

RESULTS

Type 1 diabetic girls carrying TT genotype were characterized by the lowest serum estradiol level and IL-10 and highest IL-6, TNF-α, and VEGF. The association between the level of certain cytokine and the genetic variant of estrogen receptor α polymorphism was analyzed. Frequencies of CD4(+)Foxp3(+) TH17 cells were also enhanced in TT bearing girls with type 1 diabetes and correlated with the level of analyzed cytokines. In addition, the correlation between serum estradiol level and cytokine concentrations was observed.

CONCLUSIONS

We propose that TT variant of estrogen receptor α polymorphism may be associated with enhanced inflammatory response, which in turn may lead to acceleration of diabetic retino- and nephropathy in girls with type 1 diabetes. This finding may help the physicians to predict the onset and progression of diabetic microvascular complications.

Modulation of retinal Müller cells by complement receptor C5aR

PURPOSE

Müller cells, a major type of glial cell found in the eye, are postulated to play an important role in many retinal diseases, including diabetic retinopathy (DR). Complement is an integral part of innate immunity, and the activation of complement has been associated with retinal diseases. However, the role of complement in the regulation of Müller cell function remains unclear. We were trying to address these issues in this study.

METHODS

Using primary human Müller cells and a spontaneously immortalized human Müller cell line, we examined the expression of complement receptor C5aR both at mRNA and protein levels. Regulation of C5aR expression on Müller cells by prostaglandin E2 and by hyperglycemia, both of which are integrally involved in DR, were studied. Significance of C5aR on Müller cells was also investigated by examining relevant cytokine productions and their impacts on retinal endothelial cell proliferation/permeability after ligating the receptor using its ligand, C5a.

RESULTS

C5aR is constitutively expressed in human Müller cells. Prostaglandin E2 and hyperglycemia individually and synergistically upregulate C5aR expression in Müller cells. Signaling through C5aR on Müller cells upregulates production of IL-6 and VEGF, which promotes the proliferation of human retinal endothelial cells and increases their permeability.

CONCLUSIONS

These results indicate that complement can regulate Müller cells through C5aR, which may contribute to the pathogenesis of retinal diseases, including DR.

Stat3 activation links a C/EBPδ to myostatin pathway to stimulate loss of muscle mass

Catabolic conditions like chronic kidney disease (CKD) cause loss of muscle mass by unclear mechanisms. In muscle biopsies from CKD patients, we found activated Stat3 (p-Stat3) and hypothesized that p-Stat3 initiates muscle wasting. We created mice with muscle-specific knockout (KO) that prevents activation of Stat3. In these mice, losses of body and muscle weights were suppressed in models with CKD or acute diabetes. A small-molecule that inhibits Stat3 activation produced similar responses, suggesting a potential for translation strategies. Using CCAAT/enhancer-binding protein δ (C/EBPδ) KO mice and C2C12 myotubes with knockdown of C/EBPδ or myostatin, we determined that p-Stat3 initiates muscle wasting via C/EBPδ, stimulating myostatin, a negative muscle growth regulator. C/EBPδ KO also improved survival of CKD mice. We verified that p-Stat3, C/EBPδ, and myostatin were increased in muscles of CKD patients. The pathway from p-Stat3 to C/EBPδ to myostatin and muscle wasting could identify therapeutic targets that prevent muscle wasting.

Serum vascular adhesion protein-1 correlates with vascular endothelial growth factor in patients with type II diabetes

AIMS

To study serum levels of soluble vascular adhesion protein (sVAP)-1 in type II diabetic patients with retinopathy.

METHODS

Serum samples were obtained from 53 consecutive patients, including 14 cases with non-angiogenic ocular diseases, i.e., epiretinal membrane (ERM) and idiopathic macular hole (MH), 19 cases with age-related macular degeneration (AMD), and 20 cases with diabetic retinopathy (DR). Protein levels of sVAP-1, intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and vascular endothelial growth factor (VEGF) were determined by enzyme-linked immunosorbent assay. Enzymatic activity of semicarbazide-sensitive amine oxidase (SSAO) was also measured.

RESULTS

Serum level of sVAP-1 showed a moderate correlation with SSAO activity in all cases. Patients with DR had higher levels of serum sVAP-1 than subjects with ERM and MH, or those with AMD; however, severity of DR is not related to the serum levels of sVAP-1. Serum sVAP-1 correlated positively with VEGF in patients with DR, but not in those with ERM and MH, or those with AMD. Neither soluble ICAM-1 nor VCAM-1 correlated with VEGF, even in subjects with DR.

CONCLUSION

The current data demonstrate the elevated serum levels of sVAP-1 and correlation between sVAP-1 and VEGF in patients with type II diabetes.

The serum IL-6 profile and Treg/Th17 peripheral cell populations in patients with type 1 diabetes

IL-6 is a pleiotropic cytokine involved in the regulation of the immune response, inflammation, and hematopoeisis. Its elevated levels are found in a range of autoimmune and chronic inflammatory diseases. IL-6 is also involved in regulation of the balance between two T cell subsets: Tregs and Th17, which have contradictory functions in the control of inflammation. The present study provides a quantitative analysis regarding the Th17/Treg cell balance in peripheral blood of children with type 1 diabetes and its association with serum IL-6 level.

Plasma vascular endothelial growth factor and angiogenin are positively related to erythropoietin dose in hemodialysis patients

PURPOSE

Experimental data confirmed that erythropoietin (EPO) administration alters the course of various pathological situations such as heart failure and tumor growth by inducing vascular endothelial growth factor-A (VEGF-A) expression. The effect of EPO dose on plasma VEGF-A level in hemodialysis (HD) patients was evaluated. The effect of EPO dose on plasma angiogenin level in HD patients was also evaluated, since angiogenin is necessary for angiogenesis induced by VEGF-A.

METHODS

Thirty two HD patients (10 diabetics) enrolled into the study. Patients were iron replete and did not suffer from infections, autoimmune diseases or malignancies. Plasma VEGF-A and angiogenin, as well as serum interleukin-6 and tumor necrosis factor-α were measured by means of ELISA.

RESULTS

Weekly EPO dose per kg of dry body weight was positively related to both VEGF-A and angiogenin, whereas no relation was detected among VEGF-A or angiogenin and hemoglobin, inflammation or presence of diabetes mellitus. These relations among EPO dose and VEGF-A or angiogenin remained after adjustment for hemoglobin concentration or inflammation or presence of diabetes mellitus.

CONCLUSIONS

EPO dose may affect plasma VEGF-A and angiogenin concentrations in HD patients.

Threshold serum concentrations of tumour necrosis factor alpha (TNFα) as a potential marker of the presence of microangiopathy in children and adolescents with type 1 diabetes mellitus (T1DM)

The aim of this study was to estimate the threshold serum concentrations of advanced glycation end products (AGEs) and their soluble receptors (sRAGE) as well as tumour necrosis factor alpha (TNFα), vascular endothelial growth factor(165) (VEGF(165)) and interleukin-12 (IL-12) in predicting the occurrence of microangiopathy in children and adolescents with type 1 diabetes mellitus (T1DM). We studied 88 children and adolescents (age range: 6-20 yrs) with T1DM and 32 control subjects (age range: 7-20 yrs). All study participants had their daily urinary albumin excretion, HbA1c and serum creatinine levels measured, and underwent an eye examination and 24-h blood pressure monitoring. Moreover, serum concentrations of AGEs, sRAGE, TNFα, VEGF(165) and IL-12 were measured. In order to calculate the threshold values of the studied parameters, the Receiver Operating Characteristic (ROC) curve analysis was used. The results of our study have shown that among all the studied parameters a discriminative ability was found for TNFα, VEGF(165), duration of the disease, serum AGEs concentrations and daily urinary albumin excretion. However, the highest value of the area under the ROC curve (AUC(ROC)) in predicting the occurrence of diabetic microangiopathy was found for serum TNFα concentrations with its threshold value of 1.7 pg/ml [AUC(ROC) = 0.88 (95% CI: 0.79-0.97)]. The sensitivity and specificity for this variable was at the level of 85.7% and 94.3%, respectively. In conclusion, according to our results serum TNFα concentrations over 1.7 pg/ml may point to the presence of diabetic microangiopathy in children and adolescents T1DM.

The association of the IVS1-397T>C estrogen receptor α polymorphism with the regulatory conditions in longstanding type 1 diabetic girls

Type 1 diabetes is considered as pluricausal disease, whose etiology involves genetic predisposition as well as environmental factors that contribute to disease progression and pathogenesis. Women are believed to be more susceptible to develop autoimmune diseases, which may depend in part on the influence of sex hormones on the immune system. It was shown that estrogens may protect against the development of autoimmune disease by inducing the expansion of regulatory T cell pool and upregulating Foxp3 expression. Foxp3 is a transcription factor that controls the development and suppressive function of naturally occurring regulatory T cells CD4(+)Foxp3(+). Longstanding diabetes type 1 has features of low-grade chronic inflammation which may influence regulatory T cell subset by reducing their numbers or/and inhibiting their suppressive potential. As diabetic type 1 patients are differentiated with regard to metabolic factors, level of glycemic control and systemic inflammatory state, we aimed to examine if this can be associated with IVSI-397T>C estrogen receptor α polymorphism. We examined 93 young regularly menstruating girls with diagnosed type 1 diabetes and 49 healthy age-matched control individuals. The PvuII polymorphism of the ER-α gene was analyzed as well as the serum TNF level and the level of CD4(+)Foxp3(+) regulatory T cells in these individuals. Girls with type 1 diabetes had lower level of CD4(+)Foxp3(+) Tregs than their healthy counterparts. Regulatory T cells from these patients showed also lower expression of Foxp3 than Tregs in healthy, control group. In addition, DM1 girls bearing the CC genotypes showed the highest level of CD4(+)Foxp3(+) Tregs and the lowest TNF serum level in comparison to girls carrying CT or TT genotype. The CC DM1 carriers had also higher serum level of estrogens than girls bearing CT or TT genotype. We propose that different variants of IVS1-397 estrogen receptor α polymorphism may become additional genetic factor that influences regulatory conditions during diabetes type 1 in females.

Inhibition of glucose-induced vascular endothelial growth factor expression by Salvia miltiorrhiza hydrophilic extract in human microvascular endothelial cells: evidence for mitochondrial oxidative stress

AIM OF STUDY

Diabetes mellitus is frequently combined with vascular diseases, which are associated with the expression of vascular endothelial growth factor (VEGF). An approach that can reverse the induction of VEGF by hyperglycemia may potentially benefit the outcome of diabetic patients. Therefore, in the present study, we investigated the effect of Salvia miltiorrhiza (S. miltiorrhiza) hydrophilic extract on the expression of VEGF induced by high concentration of glucose.

MATERIALS AND METHODS

Vector of VEGF promoter luc was transiently transfected into HMEC-1 cells, and luciferase activity was measured to determine the promoter activity. In order to investigate the mechanism of Salvia miltiorrhiza hydrophilic extract, mitochondrial uncoupling protein 2(UCP2) was knockdown by using UCP2 siRNA. The expression of VEGF was obtained by using quantitative RT-PCR and dot blot. The level of reactive oxygen species (ROS) was expressed by the level of 2',7'-dichlorfluorescein.

RESULTS

Exposure of HMEC-1 cells to 30 mM glucose resulted in a significant increase in the expression of VEGF mRNA (5.7 fold at 3mM glucose, P<0.005), and an increase of ROS formation (2.4 fold at 3mM glucose, P<0.005). These effects were completely antagonized by an inhibitor of electron transport chain complex II, thenoyltrifluoroacetone (TTFA) and an uncoupler of oxidative phosphorylation, carbonylcyanide-m-chlorophenylhydrazone (CCCP). Addition of Salvia miltiorrhiza hydrophilic extract (10 μg/ml) led to a significant decrease of VEGF mRNA and ROS formation in 30 mM glucose condition. Interestingly, knockdown of mitochondrial UCP-2 by UCP-2 siRNA abolished the reduction of VEGF expression and ROS formation by Salvia miltiorrhiza hydrophilic extract.

CONCLUSIONS

These findings indicated that Salvia miltiorrhiza hydrophilic extract effectively reversed induction of VEGF expression by high glucose via ameliorating mitochondrial oxidative stress. Salvia miltiorrhiza hydrophilic extract can potentially be an effective antioxidant therapy for the treatment of diabetic chronic vascular complication.

Expression of endoplasmic reticulum stress-related factors in the retinas of diabetic rats

Recent reports show that ER stress plays an important role in diabetic retinopathy (DR), but ER stress is a complicated process involving a network of signaling pathways and hundreds of factors, What factors involved in DR are not yet understood. We selected 89 ER stress factors from more than 200, A rat diabetes model was established by intraperitoneal injection of streptozotocin (STZ). The expression of 89 ER stress-related factors was found in the retinas of diabetic rats, at both 1- and 3-months after development of diabetes, by quantitative real-time polymerase chain reaction arrays. There were significant changes in expression levels of 13 and 12 ER stress-related factors in the diabetic rat retinas in the first and third month after the development of diabetes, Based on the array results, homocysteine- inducible, endoplasmic reticulum stress-inducible, ubiquitin-like domain member 1(HERP), and synoviolin(HRD1) were studied further by immunofluorescence and Western blot. Immunofluorescence and Western blot analyses showed that the expression of HERP was reduced in the retinas of diabetic rats in first and third month. The expression of Hrd1 did not change significantly in the retinas of diabetic rats in the first month but was reduced in the third month.

Decreased angiogenin concentration in vitreous and serum in proliferative diabetic retinopathy

Diabetic retinopathy is the most common cause of vision loss in young adults in developed countries. The disease therapy with anti-vascular endothelial growth factor (VEGF) agents gives some positive results, but is associated with retinal ischemia and vasoconstriction. Therefore, determination of factors involved in the physiological and pathological angiogenesis in the diabetic eye is of great importance for understanding of the pathogenesis of diabetic retinopathy and its effective treatment. Previously, we found that diabetic patients were characterized by increased serum concentration of VEGF, but decreased levels of other proangiogenic factor-angiogenin. The involvement of VEGF in pathogenesis of diabetic retinopathy is well established, but there is lack of data regarding angiogenin in retinopathy. Therefore, in the present study we measured angiogenin concentration in vitreous and serum samples of the patients with type 1 diabetes to determine its role in diabetic retinopathy. In addition, in each time, we compared the level of angiogenin with level of VEGF as a known factor involved in the pathogenesis of the disease. Angiogenin was found to be significantly more abundant in serum than in vitreous in both diabetic groups. In addition, patients with retinopathy had twofold lower vitreous angiogenin levels than diabetic individuals without complications. On the contrary, vitreous concentration of VEGF was dramatically increased only in participants with retinopathy. Patients without diabetic complications had significantly lower VEGF levels in vitreous than in serum and were characterized by high local and systemic concentration of angiogenin. These data suggest a local imbalance between two proangiogenic factors-VEGF and angiogenin in retinopathy. Low vitreous concentration of angiogenin in diabetic patients suggests that this factor is not responsible for pathological neovascularization in diabetic eye. Further studies will elucidate if angiogenin can be used to improve the insufficient angiogenesis in diabetes and prevent retinal ischemia after retinopathy treatment with anti-VEGF agents.

TNFalpha is required for late BRB breakdown in diabetic retinopathy, and its inhibition prevents leukostasis and protects vessels and neurons from apoptosis

PURPOSE

Blood-retinal barrier [BRB] breakdown, characteristic of diabetic retinopathy (DR), is believed to depend on inflammation and apoptosis. Retinal inflammation is almost completely suppressed in the absence of TNFα, which is also associated with apoptosis. This study was conducted to determine the role of TNFα in these diabetic complications.

METHODS

Diabetes was induced with streptozotocin in Tnfa knockout (KO) mice, to provide a chemical model of diabetes, and Tnfa (KO) mice were crossed with Ins2(Akita) mice to generate a genetic model, with both models being devoid of TNFα. The BRB was assessed at 1, 1.5, 3, and 6 months. Leukostasis was assessed using FITC-conjugated ConA to label leukocytes. Apoptosis was assessed with TUNEL and activated caspase-3 staining. PECAM1 identified endothelial cells, and SMA identified pericytes.

RESULTS

At 1 month of diabetes, the absence of TNFα had no effect on DR-associated BRB breakdown, even though it prevented retinal leukostasis, demonstrating that neither TNFα nor inflammation is essential for early BRB breakdown in DR in either model of diabetes. At 3 months of diabetes, BRB breakdown was significantly suppressed and at 6 months, it was completely prevented in the absence of TNFα in both models, showing that TNFα is essential for progressive BRB breakdown. DR-mediated apoptosis in the retina, which appears to involve endothelial cells, pericytes, and neurons, was inhibited in the absence of TNFα in both models.

CONCLUSIONS

Although neither TNFα nor inflammation is necessary for early BRB breakdown in DR, TNFα is critical for later complications and would be a good therapeutic target for the prevention of the progressive BRB breakdown, retinal leukostasis, and apoptosis associated with DR.

Association between vascular endothelial growth factor and hypertension in children and adolescents type I diabetes mellitus

The aim of the study was to analyse the relationship between the serum level of vascular endothelial growth factor (VEGF) and the incidence of hypertension (HT) in children and adolescents with type I diabetes mellitus (T1DM). One hundred and five patients with T1DM were enrolled in the study. The control group consisted of 30 healthy controls. All the T1DM patients were subjected to biochemical analyses, ophthalmologic examination and 24-h blood pressure monitoring. Besides, all the patients and healthy controls had serum VEGF levels measured with the use of the ELISA methodology. The essence of our research is that patients with T1DM and HT and with microalbuminuria (MA) and diabetic retinopathy (DR) (MA/DR) are characterized by a significantly higher level of VEGF (340.23±93.22 pg ml(-1)) in blood serum in comparison with the group of T1DM patients without HT and MA/DR (183.6±96.6 pg ml(-1)) and with healthy controls (145.32±75.58 pg ml(-1)). In addition, the VEGF level was significantly higher in T1DM patients, who presented all three complications, that is HT, retinopathy and MA in comparison with T1DM patients without HT, but with MA/DR (P=0.036). On the other hand, no statistically significant differences (P=0.19) were noted in the level of VEGF in serum between T1DM patients without HT and MA/DR and the healthy control group. At a further stage of analysis, using the method of multiple regression, it was shown that systolic pressure, HbA1c and duration of disease are independent factors influencing the concentration of VEGF. Summarizing, the measurement of VEGF serum levels allows for the identification of groups of patients who have the highest risk of HT and, subsequently, progression of vascular complications.

Angiogenic growth factors correlate with disease severity in young patients with autosomal dominant polycystic kidney disease

Renal cysts, pain, and hematuria are common presentations of autosomal dominant polycystic kidney disease (ADPKD) in children. Renal function, however, is typically preserved in these patients despite increased renal volume. Since angiogenesis has been implicated in promotion of renal cyst growth in ADPKD, we measured the serum level of various angiogenic factors and early renal structural changes and cardiovascular parameters in 71 patients with ADPKD, with a mean age of 16 years. Renal structure and left ventricular mass index were measured by magnetic resonance imaging or by echocardiogram. Renal function was assessed by creatinine clearance and urinary protein excretion. Serum growth factor levels were measured by enzyme-linked immunosorbent assay. Because of skewed distributions, the various parameters are reported as log(10). Serum log(10) vascular endothelial growth factor was positively correlated with renal and cardiac structure, but negatively with creatinine clearance. Serum angiopoietin 1 levels significantly correlated with structural change in both the kidney and the heart and with urinary protein. Thus, the correlation between angiogenic growth factors with both renal and cardiac disease severity is compatible with a possible role for angiogenesis in the early progression of disease in ADPKD.

Increased spontaneous production of VEGF by CD4+ T cells in type 1 diabetes

In the present study we report that CD4(+) T cells from patients with type 1 diabetes produce significantly higher amounts of VEGF than respective cells from the healthy individuals. Among CD4(+) T cells memory subsets were the main source of VEGF. In addition, memory CD4(+) T subsets were the most numerous in patients with diabetic retinopathy (DR). DR was also characterized by significant increase of VEGF concentration in serum and culture supernatants. Hence, these data indicate that there is a sustained spontaneous production of VEGF by CD4(+) T cells in type 1 diabetes, which is additionally exacerbated in DR. In our opinion alterations in the proportions of CD4(+) T cell subsets and their VEGF production may be a useful tool for early assessment of the risk of DR onset and progression.

Inflammatory markers are increased in youth with type 1 diabetes: the SEARCH Case-Control study

CONTEXT

Increased inflammation may contribute to type 1 diabetes (T1D) complications.

OBJECTIVE

The objective of the study was to investigate the association of inflammation with obesity, hyperglycemia and dyslipidemia in youth with T1D.

DESIGN

This was a cross-sectional study of youth with and without T1D.

SETTING

The study was conducted in Colorado and South Carolina.

PATIENTS

SEARCH Case-Control participants with T1D [n = 553, mean age 15 yr (range 10-22), median duration 2.7 yr] and without diabetes [n = 215, mean age 15 yr (range 10-22)].

INTERVENTION

This was an observational study.

MAIN OUTCOME MEASURES

IL-6, high-sensitivity C-reactive protein (hsCRP), fibrinogen, and leptin were measured.

RESULTS

Inflammatory markers were evaluated by diabetes status, quartiles of glycated hemoglobin, and obesity using multiple linear regression analyses, adjusted for age, sex, study site, race/ethnicity, T1D duration, body mass index, and pubertal status. Compared with controls, youth with T1D had higher IL-6 and fibrinogen levels at all levels of glycemia and obesity, and hsCRP levels were significantly higher in youth with T1D in the top three quartiles of glycated hemoglobin (> or = 7.2%) and among normal-weight subjects. Leptin was lower in youth with poor glycemic control. Higher hsCRP and fibrinogen were correlated with higher total and LDL cholesterol, and apolipoprotein B in youth with T1D, whereas higher fibrinogen was correlated with higher LDL and apolipoprotein B in controls.

CONCLUSIONS

T1D is characterized by excess inflammation, independent of adiposity and glycemic control. Even T1D youth in good glycemic control had higher levels of IL-6 and fibrinogen than controls. Elevated inflammatory markers were associated with an atherogenic lipid profile, which may contribute to accelerated atherosclerosis in youth with T1D.

IL-6 and high glucose synergistically upregulate MMP-1 expression by U937 mononuclear phagocytes via ERK1/2 and JNK pathways and c-Jun

Matrix metalloproteinases (MMPs) play a pivotal role in tissue remodeling and destruction in inflammation-associated diseases such as cardiovascular disease and periodontal disease. Although it is known that interleukin (IL)-6 is a key proinflamatory cytokine, it remains unclear how IL-6 regulates MMP expression by mononuclear phagocytes. Furthermore, it remains undetermined how IL-6 in combination with hyperglycemia affects MMP expression. In the present study, we investigated the regulatory effect of IL-6 alone or in combination with high glucose on MMP-1 expression by U937 mononuclear phagocytes. We found that IL-6 is a powerful stimulator for MMP-1 expression and high glucose further augmented IL-6-stimulated MMP-1 expression. We also found that high glucose, IL-6, and lipopolysaccharide act in concert to stimulate MMP-1 expression. In the studies to elucidate underlying mechanisms, the extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) pathways were found to be required for stimulation of MMP-1 by IL-6 and high glucose. We also observed that IL-6 and high glucose stimulated the expression of c-Jun, a key subunit of AP-1 known to be essential for MMP-1 transcription. The role of c-Jun in MMP-1 expression was confirmed by the finding that suppression of c-Jun expression by RNA interference significantly inhibited MMP-1 expression. Finally, we demonstrated that similarly to U937 mononuclear phagocytes, IL-6 and high glucose also stimulated MMP-1 secretion from human primary monocytes. In conclusion, this study demonstrated that IL-6 and high glucose synergistically stimulated MMP-1 expression in mononuclear phagocytes via ERK and JNK cascades and c-Jun upregulation.

Perinatal systemic inflammatory response syndrome and retinopathy of prematurity

Fetal and neonatal inflammation is associated with several morbidities of prematurity. Its relationship to retinopathy of prematurity (ROP) has not been investigated. Our objective was to determine the relationship between cytokine levels and ROP in the first 3 postnatal wks. Data for this study were derived from the NICHD Cytokine Study. Dried blood spots (DBS) were obtained from infants <1000 g on days 0-1, 3 +/- 1, 7 +/- 2, 14 +/- 3, and 21 +/- 3. Infants were classified into three groups-no, mild, and severe ROP. Multiplex Luminex assay was used to quantify 20 cytokines. Temporal profiles of cytokines were evaluated using mixed-effects models after controlling for covariates. Of 1074 infants enrolled, 890 were examined for ROP and 877 included in the analysis. ROP was associated with several clinical characteristics on unadjusted analyses. Eight cytokines remained significantly different across ROP groups in adjusted analyses. IL-6 and IL-17 showed significant effects in early time periods (D0-3); TGF-beta, brain-derived neurotrophic factor (BDNF), and regulated on activation, normal T cell expressed and secreted (RANTES) in later time periods (D7-21) and IL-18, C-reactive protein (CRP), and neurotrophin-4 (NT-4) in both early and later time periods. We conclude that perinatal inflammation may be involved in the pathogenesis of ROP.

Glutaredoxin regulates autocrine and paracrine proinflammatory responses in retinal glial (muller) cells

Protein S-glutathionylation is a reversible redox-dependent post-translational modification. Many cellular functions and signal transduction pathways involve proteins whose cysteine-dependent activities are modulated by glutathionylation. Glutaredoxin (Grx1) plays a key role in such regulation because it is a specific and efficient catalyst of deglutathionylation. We recently reported an increase in Grx1 in retinae of diabetic rats and in rat retinal Müller glial cells (rMC-1) cultured in high glucose. This up-regulation of Grx1 was concomitant with NFkappaB activation and induction of intercellular adhesion molecule-1 (ICAM-1). This proinflammatory response was replicated by adenoviral-directed up-regulation of Grx1 in cells in normal glucose. The site of regulation of NFkappaB was localized to the cytoplasm, where IkappaB kinase (IKK) is a master regulator of NFkappaB activation. In the current study, inhibition of IKK activity abrogated the increase in ICAM-1 induced by high glucose or by adenoviral-directed up-regulation of Grx1. Conditioned medium from the Müller cells overexpressing Grx1 was added to fresh cultures of Müller or endothelial cells and elicited increases in the Grx1 and ICAM-1 proteins in these cells. These effects correlate with a novel finding that secretion of interleukin-6 was elevated in the cultures of Grx overexpressing cells. Also, pure interleukin-6 increased Grx1 and ICAM-1 in the rMC-1 cells. Thus, Grx1 appears to play an important role in both autocrine and paracrine proinflammatory responses. Furthermore, IKKbeta isolated from Müller cells in normal glucose medium was found to be glutathionylated on Cys-179. Hence Grx-mediated activation of IKK via deglutathionylation may play a central role in diabetic complications in vivo where Grx1 is increased.

Immunologic and biochemical factors of coincident celiac disease and type 1 diabetes mellitus in children

The objective of the study was to investigate whether immunologic and biochemical events occurring in the course of type 1 diabetes mellitus might play a role in the development of the celiac disease. The study was carried out on 223 children with long-standing diabetes mellitus type 1 (DM1). All the patients had TSH, fT4, fT3, urinary albumin secretion rate, IgA, level of antigliadin antibodies (AGA) IgA and IgG, antitissue transglutaminase IgA antibodies, antiendomysium (EmA) IgA and IgG antibodies and antitireoglobulin antibodies, antithyroid peroxidase antibodies evaluated. Serum TNF-alpha, IL-6, and IL-10 levels were also measured. The group of children with coincident DM1 and celiac disease and without autoimmune thyroiditis was characterized by significantly higher glycosylated hemoglobin, higher serum TNF-alpha, IL-6 but lower serum IL-10 in relation to the remaining diabetic patients. A statistically significant positive correlation was observed between IgA-anti-tTG and serum TNF-alpha (R = 0.28, p = 0.026); between IgG AGA and serum IL-6 (R = 0.31, p = 0.023); and between glycosylated hemoglobin and IgA-anti-tTG (R = 0.21, p = 0.001) and IgA antiendomysium (R = 0.22, p = 0.001). Poor metabolic control, persistent elevated levels of proinflammatory cytokines, and decreased level of antiinflammatory cytokines occurring in the course of type 1 diabetes mellitus might influence the incidence of celiac disease.