von Willebrand factor and retinal circulation in early-stage retinopathy of type 1 diabetes

Alterations in factors associated with diabetic retinopathy combined with thrombosis: A review

Diabetic retinopathy (DR) is one of the most common and serious microvascular complications of diabetes mellitus, the incidence of which has been increasing annually, and it is the main cause of vision loss in diabetic patients and a common cause of blindness. It is now found that thrombosis plays a crucial role in the disease progression in DR patients, and the final vision loss in DR may be related to the occurrence of thrombosis in the retinal vessels, which is dominated by abnormal endothelial cell function, together with platelet dysfunction, imbalance of coagulation and fibrinolytic function, and related alterations of inflammatory factors leading to the main cause of thrombotic disease in DR patients. In this review, we examine the role between DR and thrombosis and the association of each factor, including endothelial dysfunction; platelet dysfunction; coagulation-fibrinolytic imbalance; and alterations in inflammatory factors.

Effect of vitamin E intake on glycemic control and insulin resistance in diabetic patients: an updated systematic review and meta-analysis of randomized controlled trials

Since a 2014 meta-analysis, several randomized controlled trials (RCTs) evaluating the effect of vitamin E intake on glycemic indices and insulin resistance in adults with diabetes have reached inconsistent conclusions. Therefore, we updated the previous meta-analysis to summarize the current evidence in this regard. Online databases including PubMed, Scopus, ISI Web of Science, and Google Scholar were searched to identify relevant studies published up to September 30, 2021, using relevant keywords. Random-effects models were used to obtain overall mean difference (MD) comparing vitamin E intake with a control group. In total, 38 RCTs with a total sample size of 2171 diabetic patients (1110 in vitamin E groups and 1061 in control groups) were included. Combining the results from 28 RCTs on fasting blood glucose, 32 RCTs on HbA1c, 13 RCTs on fasting insulin, and 9 studies on homeostatic model assessment for insulin resistance (HOMA-IR) showed a summary MD of -3.35 mg/dL (95% CI: -8.10 to 1.40, P = 0.16), -0.21% (95% CI: -0.33 to -0.09, P = 0.001), -1.05 µIU/mL (95% CI: -1.53 to -0.58, P < 0.001), and -0.44 (95% CI: -0.82 to -0.05, P = 0.02), respectively. This indicates a significant lowering effect of vitamin E on HbA1c, fasting insulin and HOMA-IR, while no significant effect on fasting blood glucose in diabetic patients. However, in subgroup analyses, we found that vitamin E intake significantly reduced fasting blood glucose in studies with an intervention duration of < 10 weeks. In conclusion, vitamin E intake has a beneficial role in improving HbA1c and insulin resistance in a population with diabetes. Moreover, short-term interventions with vitamin E have resulted in lower fasting blood glucose in these patients. This meta-analysis was registered in PROSPERO with code CRD42022343118.

Relationship Between Retinal Microcirculation and Renal Function in Patients with Diabetes and Chronic Kidney Disease by Laser Speckle Flowgraphy

This study investigated the effect of renal dysfunction categorized by the stage of chronic kidney disease (CKD) on the retinal microcirculation assessed by laser speckle flowgraphy (LSFG) and retinal artery caliber measured by adaptive optics imaging in diabetic patients particularly the early stage of retinopathy and nephropathy. We divided the patients with diabetes into three groups based on the CKD stage (non-CKD (n = 54); CKD stage 1 + 2 (n = 20); CKD stage 3 (n = 41)). The mean blur rate (MBR) of the stage 3 CKD group was significantly lower than that of the no-CKD group (p < 0.015). The total retinal flow index (TRFI) in the stage 3 CKD group was significantly lower than that of the no-CKD group (p < 0.002). Multiple regression analysis demonstrated that CKD stage was independently associated with MBR (β = -0.257, p = 0.031) and TRFI (β = -0.316, p = 0.015). No significant differences were observed in external diameter, lumen diameter, wall thickness, and wall to lumen ratio among the groups. These results indicated that the ONH MBR and TRFI as assessed by LSFG decreases in diabetic patients with stage 3 CKD, but the arterial diameter measured by adaptive optics imaging does not change, suggesting that impaired renal function may be associated with decreased retinal blood flow in early-stage diabetic retinopathy.

Growth hormone and ocular dysfunction: Endocrine, paracrine or autocrine etiologies?

The eye is a target site for GH action and growth hormone has been implicated in diabetic retinopathy and other ocular dysfunctions. However, while this could reflect the hypersecretion of pituitary GH, the expression of the GH gene is now known to occur in ocular tissues and it could thus also reflect excess GH production within the eye itself. The possibility that ocular dysfunctions might arise from endocrine, autocrine or paracrine etiologies of GH overexpression is therefore the focus of this brief review.

Early systemic microvascular damage in pigs with atherogenic diabetes mellitus coincides with renal angiopoietin dysbalance

Background

Diabetes mellitus (DM) is associated with a range of microvascular complications including diabetic nephropathy (DN). Microvascular abnormalities in the kidneys are common histopathologic findings in DN, which represent one manifestation of ongoing systemic microvascular damage. Recently, sidestream dark-field (SDF) imaging has emerged as a noninvasive tool that enables one to visualize the microcirculation. In this study, we investigated whether changes in the systemic microvasculature induced by DM and an atherogenic diet correlated spatiotemporally with renal damage.

Methods

Atherosclerotic lesion development was triggered in streptozotocin-induced DM pigs (140 mg/kg body weight) by administering an atherogenic diet for approximately 11 months. Fifteen months following induction of DM, microvascular morphology was visualized in control pigs (n = 7), non-diabetic pigs fed an atherogenic diet (ATH, n = 5), and DM pigs fed an atherogenic diet (DM+ATH, n = 5) using SDF imaging of oral mucosal tissue. Subsequently, kidneys were harvested from anethesized pigs and the expression levels of well-established markers for microvascular integrity, such as Angiopoietin-1 (Angpt1) and Angiopoietin-2 (Angpt2) were determined immunohistochemically, while endothelial cell (EC) abundance was determined by immunostaining for von Willebrand factor (vWF).

Results

Our study revealed an increase in the capillary tortuosity index in DM+ATH pigs (2.31±0.17) as compared to the control groups (Controls 0.89±0.08 and ATH 1.55±0.11; p<0.05). Kidney biopsies showed marked glomerular lesions consisting of mesangial expansion and podocyte lesions. Furthermore, we observed a disturbed Angpt2/ Angpt1balance in the cortex of the kidney, as evidenced by increased expression of Angpt2 in DM+ATH pigs as compared to Control pigs (p<0.05).

Conclusion

In the setting of DM, atherogenesis leads to the augmentation of mucosal capillary tortuosity, indicative of systemic microvascular damage. Concomitantly, a dysbalance in renal angiopoietins was correlated with the development of diabetic nephropathy. As such, our studies strongly suggest that defects in the systemic microvasculature mirror the accumulation of microvascular damage in the kidney.

Current trends in the monitoring and treatment of diabetic retinopathy in young adults

The diagnosis and treatment of diabetic retinopathy (DR) in young adults have significantly improved in recent years. Research methods have widened significantly, for example, by introducing spectral optical tomography of the eye. Invasive diagnostics, for example, fluorescein angiography, are done less frequently. The early introduction of an insulin pump to improve the administration of insulin is likely to delay the development of diabetic retinopathy, which is particularly important for young patients with type 1 diabetes mellitus (T1DM). The first years of diabetes occurring during childhood and youth are the most appropriate to introduce proper therapeutic intervention before any irreversible changes in the eyes appear. The treatment of DR includes increased metabolic control, laserotherapy, pharmacological treatment (antiangiogenic and anti-inflammatory treatment, enzymatic vitreolysis, and intravitreal injections), and surgery. This paper summarizes the up-to-date developments in the diagnostics and treatment of DR. In the literature search, authors used online databases, PubMed, and clinitrials.gov and browsed through individual ophthalmology journals, books, and leading pharmaceutical company websites.

Non-dimensional analysis of retinal microaneurysms: critical threshold for treatment

Fluid dynamics play a fundamental role in the development of diabetic retinopathy, one of the leading causes of blindness in the Western world, affecting over 4 million people in the US alone. The disease is defined by microaneurysms, local expansions of capillaries that disturb the hemodynamic forces experienced by the endothelium leading to dysfunction, leakage and edema. Here we present a method to identify microaneurysms with a high risk of leakage based on a critical ratio of microaneurysm to vessel diameter. We derive this non-dimensional parameter from an analytical solution and generalize it using experimentally validated numerical methods. We show that this non-dimensional parameter defines the shear force experienced by endothelial cells, below which endothelial dysfunction is evident in vivo. Our results demonstrate the involvement of vWF in diabetic retinopathy, and explain a perceived disconnect between microaneurysm size and leakage. This method will allow experts to treat microaneurysms poising a high-risk of leakage, prior to edema, minimizing damage and saving vision.

Genetic and Molecular Basis of QTL of Diabetes in Mouse: Genes and Polymorphisms

A systematic study has been conducted of all available reports in PubMed and OMIM (Online Mendelian Inheritance in Man) to examine the genetic and molecular basis of quantitative genetic loci (QTL) of diabetes with the main focus on genes and polymorphisms. The major question is, What can the QTL tell us? Specifically, we want to know whether those genome regions differ from other regions in terms of genes relevant to diabetes. Which genes are within those QTL regions, and, among them, which genes have already been linked to diabetes? whether more polymorphisms have been associated with diabetes in the QTL regions than in the non-QTL regions.

Our search revealed a total of 9038 genes from 26 type 1 diabetes QTL, which cover 667,096,006 bp of the mouse genomic sequence. On one hand, a large number of candidate genes are in each of these QTL; on the other hand, we found that some obvious candidate genes of QTL have not yet been investigated. Thus, the comprehensive search of candidate genes for known QTL may provide unexpected benefit for identifying QTL genes for diabetes.

Modulation of retinal blood flow by kinin B₁ receptor in Streptozotocin-diabetic rats

The vasoactive kinin B₁ receptor (B₁R) is overexpressed in the retina of diabetic rats in response to hyperglycemia and oxidative stress. The aim of the present study was to determine whether B₁R could contribute to the early retinal blood flow changes occurring in diabetes. Male Wistar rats were rendered diabetic with a single i.p. injection of Streptozotocin (STZ) and studied 4 days or 6 weeks after diabetes induction. The presence of B₁R in the retina was confirmed by Western blot. The impact of oral administration of the B₁R selective antagonist SSR240612 (10mg/kg) was measured on alteration of retinal perfusion in awake diabetic rats by quantitative autoradiography. Data showed that B₁R was upregulated in the STZ-diabetic retina at 4 days and 6 weeks. Retinal blood flow was not altered in 4-day diabetic rats compared with age-matched controls but was significantly decreased following SSR240612 treatment. In 6-week diabetic rats, retinal blood flow was markedly reduced compared to control rats and SSR240612 did not further decrease the blood flow. These results suggest that B₁R is upregulated in STZ-diabetic retina and has a protective compensatory role on retinal microcirculation at 4 days but not at 6 weeks following diabetes induction.

Endothelial dysfunction as a potential contributor in diabetic nephropathy

The mechanisms that drive the development of diabetic nephropathy remain undetermined. Only 30-40% of patients with diabetes mellitus develop overt nephropathy, which suggests that other contributing factors besides the diabetic state are required for the progression of diabetic nephropathy. Endothelial dysfunction is associated with human diabetic nephropathy and retinopathy, and advanced diabetic glomerulopathy often exhibits thrombotic microangiopathy, including glomerular capillary microaneurysms and mesangiolysis, which are typical manifestations of endothelial dysfunction in the glomerulus. Likewise, diabetic mice with severe endothelial dysfunction owing to deficiency of endothelial nitric oxide synthase develop progressive nephropathy and retinopathy similar to the advanced lesions observed in humans with diabetes mellitus. Additionally, inhibitors of the renin-angiotensin system fail to be renoprotective in some individuals with diabetic nephropathy (due in part to aldosterone breakthrough) and in some mouse models of the disease. In this Review, we discuss the clinical and experimental evidence that supports a role for endothelial nitric oxide deficiency and subsequent endothelial dysfunction in the progression of diabetic nephropathy and retinopathy. If endothelial dysfunction is the key factor required for diabetic nephropathy, then agents that improve endothelial function or raise intraglomerular nitric oxide level could be beneficial in the treatment of diabetic nephropathy.

Abnormal retinal autoregulation is detected by provoked stimulation with flicker light in well-controlled patients with type 1 diabetes without retinopathy

AIMS

Investigation of retinal vasodilation under flickering light is considered a dynamic analysis in contrast to the static analysis of retinal vessel equivalents (mean retinal vessel diameter). We investigated whether dynamic analysis apart from the static one in type 1 diabetic patients without diabetic retinopathy with well-controlled diabetes could lead to additional information regarding retinal autoregulation.

METHODS

18 normotensive type 1 diabetic patients without retinopathy and 19 healthy subjects were included. Diameter of retinal vessels was measured with Dynamic Vessel Analyzer. Changes in vasodilation are expressed as percent change over baseline values.

RESULTS

HbA(1c) was 7.5+/-1.0% in diabetic patients. In arteries, the response to flicker was diminished in diabetic patients compared to healthy volunteers (p<0.023). In patients flicker stimulation increased arterial diameter by +2.7% in contrast to +4.4% in controls. Venous vessel diameter increased by +3.1% in diabetic individuals and by +5.3% in the control group (p<0.002). There were no differences in static analysis between both groups.

CONCLUSIONS

Diabetic patients without retinopathy with relatively good glycemic control show reduced retinal vasodilation after flicker indicating dysfunction in retinal autoregulation. The use of provocation test in conjunction with static analysis could lead to additional information regarding abnormal retinal autoregulation.

Ocular blood flow in diabetes and age-related macular degeneration

The 2 leading causes of blindness in adults in the industrialized nations, diabetic retinopathy and age-related macular degeneration, have been investigated thoroughly with respect to their pathogenesis. In recent years, it has been discovered that dysfunctional ocular microcirculation appears to play a part in the development of both diseases. In diabetic retinopathy, it has been shown that the disease is associated with early retinal vascular dysregulation. In the later states of the disease, retinal tissue hypoxia is a major trigger of sight-threatening neovascularization. In age-related macular degeneration, there is increasing evidence that reduced blood flow in the choroid is associated with the development and progression of the disease. Knowledge of the pathophysiological vascular states underlying these diseases is essential for the assessment and development of future therapies.

Grape seed proanthocyanidin extracts inhibit vascular cell adhesion molecule expression induced by advanced glycation end products through activation of peroxisome proliferators-activated receptor gamma

Although evidence has shown that grape seed proanthocyanidin extracts (GSPE) can selectively inhibit cell adhesion molecule expression induced by advanced glycation end products (AGEs), the underlying molecular mechanism has not been extensively characterized. To study the antiinflammation mechanism of GSPE, we investigated the effect of GSPE on Von Willebrand factor (vWF) content and the expression of vascular cell adhesion molecule-1 (VCAM-1) induced by AGEs and the effect of GSPE on peroxisome proliferators-activated receptor gamma (PPAR gamma) and receptor for AGEs (RAGE) expression in human umbilical vein endothelial cells (HUVEC). HUVEC were preincubated with or without GSPE of different concentrations (10 mg/L, 50 mg/L, and 100 mg/L) for 4 hours before being treated with 200 mg/L AGEs or unmodified bovine serum albumin (BSA) for 24 hours. The expression of RAGE and PPAR gamma was investigated by Western blot. VCAM-1 expression was measured by flow cytometry and vWF content by enzyme-linked immunosorbent assay (ELISA). Results showed that GSPE significantly inhibited the expression of VCAM-1 in HUVEC and reduced the content of vWF in culture fluid induced by AGEs in a dose-dependent manner. AGEs activated the expression of RAGE and inhibited PPAR gamma expression in HUVEC, whereas GSPE inhibited the expression of RAGE through activation of PPAR gamma in HUVEC simultaneously. These findings indicated that GSPE inhibited the cell inflammatory factor expression and protected the function of endothelial cell through activation of PPAR gamma expression and inhibition of RAGE expression.

Serum markers of vascular inflammation in dyslipemia

Atherosclerosis is widely recognized as an inflammatory disease because systemic and local inflammatory events mediate all phases of plaque development and progression. Basic and clinical studies have focused on identifying potentially useful markers of inflammation. In this article, we review the inflammatory pathogenesis of atherosclerosis, and highlight recent results of several of the more promising markers of inflammation for cardiovascular risk assessment. Of these markers, the most reliable and accessible for clinical use is currently high-sensitivity C-reactive protein (CRP). At present, most clinical guidelines do not recommend routine measurement of these inflammatory markers. However, these serum markers of vascular inflammation may be useful as an adjunct to lipid screening, especially for patients whose lipid values may not be severely elevated, but who are at intermediate risk according to scoring systems that take into account multiple established risk factors. In addition, since the pleiotropic effects of statins include the inhibition of inflammatory response, serum inflammatory markers could also be useful for monitoring this action. Nevertheless, several issues have to be evaluated before the measurements of inflammatory markers can be used for cardiovascular risk prediction in either clinical practice or in clinical trials evaluating anti-atherosclerotic drugs.

Effects of type 1 diabetes on gray matter density as measured by voxel-based morphometry

The effects of type 1 diabetes and key metabolic variables on brain structure are not well understood. Sensitive methods of assessing brain structure, such as voxel-based morphometry (VBM), have not previously been used to investigate central nervous system changes in a diabetic population. Using VBM, we compared type 1 diabetic patients aged 25-40 years with disease duration of 15-25 years and minimal diabetes complications with an age-matched, nondiabetic control group. We investigated whether lower than expected gray matter densities were present, and if so, whether they were associated with glycemic control and history of severe hypoglycemic events. In comparison with control subjects, diabetic patients showed lower density of gray matter in several brain regions. Moreover, in the patient group, higher HbA(1c) levels and severe hypoglycemic events were associated with lower density of gray matter in brain regions responsible for language processing and memory. Our study represents the first comprehensive study of gray matter density changes in type 1 diabetes and suggests that persistent hyperglycemia and acute severe hypoglycemia have an impact on brain structure.

Inflammation and endothelial dysfunction are associated with retinopathy: the Hoorn Study

AIMS/HYPOTHESIS

The exact pathogenesis of retinopathy in diabetic and non-diabetic individuals is incompletely understood, but may involve chronic low-grade inflammation and dysfunction of the vascular endothelium. The aim of this study was to investigate the association of inflammation and endothelial dysfunction with prevalent retinopathy in individuals with and without type 2 diabetes.

METHODS

As part of a population-based cohort study, 625 individuals aged 50-74 years, stratified according to age, sex and glucose tolerance status, underwent an extensive physical examination. Retinopathy was assessed by an ophthalmological examination, including funduscopy and two-field 45 degrees fundus photography with mydriasis in both eyes. Levels of C-reactive protein (CRP), soluble intercellular adhesion molecule-1 (sICAM-1), von Willebrand factor, and soluble vascular adhesion molecule-1 (sVCAM-1) were assessed, together with the urinary albumin : creatinine ratio, and the results were combined to obtain summarising z scores for inflammation and endothelial dysfunction.

RESULTS

The prevalence of retinopathy was positively associated with tertiles of CRP and sICAM-1. When compared with the lowest tertile, the highest tertile of the inflammatory z score was associated with retinopathy in all subjects (odds ratio [OR]=2.2, 95% CI 1.2-4.1, adjusted for age, sex and glucose tolerance status). The highest tertile of the endothelial dysfunction z score was associated with retinopathy among diabetic individuals (OR=4.4, 95% CI 1.2-15.9, adjusted for age and sex) but not in non-diabetic individuals. Additional adjustment for other risk factors, such as systolic and diastolic blood pressure, BMI, total cholesterol and triglycerides, or mutual adjustment of the inflammatory and endothelial dysfunction z scores did not change the results.

CONCLUSIONS/INTERPRETATION

In this study, inflammatory activity and endothelial dysfunction were associated with retinopathy, which suggests their involvement in the pathogenesis of retinopathy.

Retinal vascular integrity following correction of diabetic ketoacidosis in children and adolescents

OBJECTIVE

Increased permeability of the cerebral microvasculature occurs during the treatment of diabetic ketoacidosis (DKA). Microvascular changes consistent with diabetic retinopathy have been reported prior to and after the treatment of DKA. This study evaluated the structural and functional aspects of the retina immediately following the correction of DKA.

METHODS

Seven young patients had comprehensive ophthalmologic examinations, including fluorescein angiography, within 24 h after the correction of severe DKA (pH <7.2).

RESULTS

None of the patients had clinical, photographic, or angiographic evidence of a retinal abnormality.

CONCLUSION

The blood-retinal barrier (BRB) does not experience the same degree of perturbation as the blood-brain barrier (BBB) does and may be a protected site during the insult of DKA and its treatment. The greater stability of the retinal microvasculature may be due to the increased number of pericytes in the BRB in comparison with the BBB.

Clinical significance of plasma D-dimer and von Willebrand factor levels in patients with ulcer colitis

AIM: To investigate the levels of D-dimer (DD) and von Willebrand factor (vWF) and the relationship between DD and vWF in ulcerative colitis (UC) patients.

METHODS: A total of 29 plasma specimens were obtained from patients with ulcerative colitis (male 13, female 16), aged 21-47 years (33 ± 11). Disease activity was assessed by Truelove-Writeria. Patients with a score of above 5 were regarded as having active colitis. Twenty healthy people (male 12, female 8), aged 19-53 years (31 ± 14), served as normal controls. Blood samples were taken from an antecubital vein puncture. Blood (1.8 mL) was injected into the tubes containing sodium citrate (0.13 mmol/L). The plasma was obtained by centrifugation at 3000 r·min^-1 for 10 min, and stored at -80 °C until assayed by ELISA.

RESULTS: The mean plasma levels of DD and vWF in active UC patients were significantly higher than those of the controls (0.69 ± 0.41 vs 0.27 ± 0.11, P < 0.01; 143 ± 46 vs 103 ± 35, P < 0.01). The mean plasma levels of DD in the patients with active disease were higher than those with inactive disease (0.69 ± 0.41 vs 0.48 ± 0.29, P < 0.05). The levels of vWF were not different between active and inactive patients. DD levels were positively related to vWF levels (r = 0.574, P < 0.01). There was no significant difference between levels of DD and vWF and the scope of disease and sex of the patients.

CONCLUSION: vWF is an important feature and a good marker of UC; intravascular thrombus and endothelial cell dysfunction were found in UC patients; and the combined test of DD and vWF is helpful to distinguish the activity of the UC patients.