Role of altered coagulation-fibrinolytic system in the pathophysiology of diabetic retinopathy

Case reports: Intraoperative migratory retinal venous thrombus in proliferative diabetic retinopathy

Purpose

This study aimed to study the characteristics, possible causes, and clinical implications of intraoperative migratory retinal venous thrombus in proliferative diabetic retinopathy (PDR).

Cases

Two middle-aged Chinese patients with diabetes mellitus presented with blurred vision and were diagnosed with PDR and tractional retinal detachment (TRD). An interesting phenomenon was observed during pars plana vitrectomy in both patients. Movement of tiny white thrombi and interruption of blood flow were observed in a branch of the central retinal vein when the vein was pulled at the time of fibrovascular membrane delamination and disappeared with the elimination of retinal traction after finishing the process of delamination. Laboratory studies revealed abnormal erythrocyte sedimentation rate, fibrinogen, D-dimer, international normalized ratio, and IgA anti-β2-glycoprotein I in one patient and elevated fibrinogen and IgA anticardiolipin in the other. Follow-up examinations at 1 week, 1, 3, and 6 months postoperatively showed good prognosis. Fluorescein fundus angiography at 1 month postoperatively showed neither embolus sign nor prolonged venous filling time in both patients.

Discussion

Local blood stasis of the retinal vein persistently dragged by the fibrovascular membrane may result in thrombogenesis, and traction of the retina during the delamination process may lead to the movement of thrombi. On the other hand, endothelial injury and disordered local blood stasis during delamination may also activate the biological coagulation process and instant thrombus formation. As well, antiphospholipid antibodies may also be a risk factor of ocular thrombogenesis.

Conclusion

This study provides the first videos recording migratory thrombus in terminal vessels, which indicates that fibrovascular membrane in PDR can lead to thrombogenesis due to dragging and hemostasis of the involved retinal vein. PDR patients with fibrovascular membranes may benefit from early relief of vascular traction through fibrovascular membrane delamination.

Whether coagulation dysfunction influences the onset and progression of diabetic peripheral neuropathy: A multicenter study in middle-aged and aged patients with type 2 diabetes

BACKGROUND

Nearly half of patients with diabetes experience diabetic peripheral neuropathy (DPN), resulting in a mere 53% survival rate within 3 years. Aberrations in coagulation function have been implicated in the pathogenesis of microvascular complications, prompting the need for a thorough investigation into its role as a contributing factor in the development and progression of DPN.

METHODS

Data were gathered from 1211 type 2 diabetes patients admitted to five centers from September 2018 to October 2022 in China. DPN was evaluated by symptoms and electromyography. Motor and sensory nerve conduction velocity (NCV) was appraised and the NCV sum score was calculated for the median, ulnar, and peroneal motor or sensory nerves.

RESULTS

Patients with DPN exhibited alterations in coagulation function. (i) Specifically, they exhibited prolonged thrombin time (p = 0.012), elevated fibrinogen (p < 0.001), and shortened activated partial thromboplastin time (APTT; p = 0.026) when compared to the control group. (ii) After accounting for potential confounders in linear regression, fibrinogen, and D-dimer were negatively related to the motor NCV, motor amplitude values, and mean velocity and amplitude. Also, fibrinogen was associated with higher Michigan neuropathy screening instrument (MNSI) scores (β 0.140; p = 0.001). This result of fibrinogen can be validated in the validation cohort with 317 diabetic patients. (iii) Fibrinogen was independently associated with the risk of DPN (OR 1.172; p = 0.035). In the total age group, DPN occurred at a slower rate until the predicted fibrinogen level reached around 3.75 g/L, after which the risk sharply escalated.

CONCLUSIONS

Coagulation function is warranted to be concerned in patients with type 2 diabetes to predict and prevent the occurrence of DPN in clinical practice.

Treatment of diabetic retinopathy with herbs for tonifying kidney and activating blood circulation: A review of pharmacological studies

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic retinopathy (DR) is a prevalent microvascular complication of diabetes. Chinese medicine believes that kidney deficiency and blood stasis are significant pathogenesis of DR. A characteristic therapeutic approach for this pathogenesis is the kidney-tonifying and blood-activating method. By literature retrieval from several databases, we methodically summarized the commonly used kidney-tonifying and blood-activating herbs for treating DR, including Lycii Fructus, Rehmanniane Radix Praeparata, and Corni Fructus with the function of nourishing kidney; Salvia Miltiorrhizae Radix et Rhizoma with the function of enhancing blood circulation; Rehmanniae Radix with the function of nourishing kidney yin; and Astragali Radix with the function of tonifying qi. It has been demonstrated that these Chinese herbs described above, by tonifying the kidney and activating blood circulation, significantly improve the course of DR.

AIM OF THE STUDY

Through literature research, to gain a thorough comprehension of the pathogenesis of DR. Simultaneously, through the traditional application analysis, modern pharmacology research and network pharmacology analysis of kidney-tonifying and blood-activating herbs, to review the effectiveness and advantages of kidney-tonifying and blood-activating herbs in treating DR comprehensively.

MATERIALS AND METHODS

PubMed, the China National Knowledge Infrastructure (CNKI), and Wanfang Data were used to filter the most popular herbs for tonifying kidney and activating blood in the treatment of DR. The search terms were "diabetic retinopathy" and "tonifying kidney and activating blood". Mostly from 2000 to 2023. Network pharmacology was applied to examine the key active components and forecast the mechanisms of kidney-tonifying and blood-activating herbs in the treatment of DR.

RESULTS

Kidney deficiency and blood stasis are the pathogenesis of DR, and the pathogenesis is linked to oxidative stress, inflammation, hypoxia, and hyperglycemia. Scientific data and network pharmacology analysis have demonstrated the benefit of tonifying kidney and activating blood herbs in treating DR through several channels, multiple components, and multiple targets.

CONCLUSIONS

This review first presents useful information for subsequent research into the material foundation and pharmacodynamics of herbs for tonifying kidney and activating blood, and offers fresh insights into the treatment of DR.

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.

Skin microvascular reactivity in patients with diabetic retinopathy

AIMS

Early detection of microangiopathic complications of diabetes mellitus (DM) is necessary to analyze the patient's condition and prevent disease progression. The study was aimed to investigate the relationship between the presence of retinopathy and decreased reactivity of the microcirculatory bed in patients with diabetes.

METHODS

The study involved 130 subjects: healthy volunteers (n = 48), DM patients without retinopathy (n = 53) and with retinopathy (n = 29). Skin microvascular reactivity was assessed on the forearm using laser Doppler flowmetry with a local heating test combined with occlusion.

RESULTS

The slope of local thermal hyperemia curve (Slope-120) and other parameters of microvascular reactivity showed difference in pairwise comparisons between the groups. Slope-120 had the highest sensitivity (0.759) and specificity (0.717) in detection of diabetic retinopathy. The decrease of Slope-120 was associated with retinopathy (odds ratio (OR) - 8.3 (2.9-24.1), p < 0.001), even after adjusting for other factors (OR - 11.0 (1.6-77.2), p = 0.016).

CONCLUSIONS

Thus, assessment of skin microvascular reactivity may be a useful test for detecting signs of microangiopathic complications and for screening patients in risk group. Decreased microvascular reactivity has been shown to be prospective as an independent indicator of retinopathy in type 1 DM.

PAI-1 is a vascular cell-specific HIF-2-dependent angiogenic factor that promotes retinal neovascularization in diabetic patients

For patients with proliferative diabetic retinopathy (PDR) who do not respond adequately to pan-retinal laser photocoagulation (PRP) or anti-vascular endothelial growth factor (VEGF) therapies, we hypothesized that vascular cells within neovascular tissue secrete autocrine/paracrine angiogenic factors that promote disease progression. To identify these factors, we performed multiplex ELISA angiogenesis arrays on aqueous fluid from PDR patients who responded inadequately to anti-VEGF therapy and/or PRP and identified plasminogen activator inhibitor-1 (PAI-1). PAI-1 expression was increased in vitreous biopsies and neovascular tissue from PDR eyes, limited to retinal vascular cells, regulated by the transcription factor hypoxia-inducible factor (HIF)-2α, and necessary and sufficient to stimulate angiogenesis. Using a pharmacologic inhibitor of HIF-2α (PT-2385) or nanoparticle-mediated RNA interference targeting Pai1, we demonstrate that the HIF-2α/PAI-1 axis is necessary for the development of retinal neovascularization in mice. These results suggest that targeting HIF-2α/PAI-1 will be an effective adjunct therapy for the treatment of PDR patients.

Beyond cuts and scrapes: plasmin in malaria and other vector-borne diseases

Plasmodium and other vector-borne pathogens have evolved mechanisms to hijack the mammalian fibrinolytic system to facilitate infection of the human host and the invertebrate vector. Plasmin, the effector protease of fibrinolysis, maintains homeostasis in the blood vasculature by degrading the fibrin that forms blood clots. Plasmin also degrades proteins from extracellular matrices, the complement system, and immunoglobulins. Here, we review some of the mechanisms by which vector-borne pathogens interact with components of the fibrinolytic system and co-opt its functions to facilitate transmission and infection in the host and the vector. Further, we discuss innovative strategies beyond conventional therapeutics that could be developed to target the interaction of vector-borne pathogens with the fibrinolytic proteins and prevent their transmission.

Fibrinogen function indexes are potential biomarkers of diabetic peripheral neuropathy

BACKGROUND AND OBJECTIVES

Research suggests that diabetic peripheral neuropathy (DPN) is related to plasma fibrinogen (Fib) concentrations, although its correlation with Fib function has not been reported. Here, the k value and angle α, reflecting the plasma Fib function, were used to analyse its correlation with DPN, and their potential as biological indicators for diagnosing DPN was explored.

SUBJECTS AND METHODS

This prospective observational clinical study enrolled 561 type 2 diabetes mellitus (T2DM) patients, who were divided into the diabetes with symptomatic neuropathy (161 cases), diabetes with asymptomatic neuropathy (132 cases) and diabetes with no neuropathy (268 cases) groups. Meanwhile, 160 healthy unrelated subjects were recruited as controls.

RESULTS

Fib levels increased slightly in diabetic subjects with neuropathy compared with those without. The angle α levels increased slightly in subjects with asymptomatic DPN compared with those with no neuropathy and increased greatly in subjects with symptomatic DPN compared with those without. The k value levels slightly decreased in subjects with asymptomatic DPN compared with those with no neuropathy and greatly decreased in subjects with symptomatic DPN compared with those without. The association of the k value and angle α with diabetic neuropathy was independent of the hyperglycaemic state and other potential confounders (odds ratio 0.080 [0.051-0.124], P < 0.001; odds ratio 1.131 [1.063-1.204], P < 0.001). The k value and angle α levels were closely correlated with neuropathy stage (r  = - 0.686, P < 0.000; r  = 0.314, P < 0.001). The optimal cut-off point for k value levels to distinguish patients with diabetic neuropathy from those without was 1.8 min, with a sensitivity of 73.7% and a specificity of 83.2% (AUC = 0.873). The optimal cut-off point for angle α levels was 60°, with a sensitivity of 41.0% and a specificity of 95.6% (AUC = 0.669).

CONCLUSIONS

The k value and angle α are closely associated with DPN. The levels of the k value and angle α may be helpful in the early diagnosis of DPN.

Understanding the Activation of Platelets in Diabetes and Its Modulation by Allyl Methyl Sulfide, an Active Metabolite of Garlic

BACKGROUND

Diabetes mellitus (DM) is a chronic metabolic disorder associated with higher risk of having cardiovascular disease. Platelets play a promising role in the pathogenesis of cardiovascular complications in diabetes. Since last several decades, garlic and its bioactive components are extensively studied in diabetes and its complications. Our aim was to explore the antiplatelet property of allyl methyl sulfide (AMS) focusing on ameliorating platelet activation in diabetes.

METHOD

We used streptozotocin- (STZ-) induced diabetic rats as model for type 1 diabetes. We have evaluated the effect of allyl methyl sulfide on platelet activation by administrating AMS to diabetic rats for 10 weeks. Flow cytometry-based analysis was used to evaluate the platelet activation, platelet aggregation, platelet macrophage interaction, and endogenous ROS generation in the platelets obtained from control, diabetes, and AMS- and aspirin-treated diabetic rats.

RESULTS

AMS treatment for 10 weeks effectively reduced the blood glucose levels in diabetic rats. Three weeks of AMS (50 mg/kg/day) treatment did not reduce the activation of platelets but a significant (p < 0.05) decrease was observed after 10 weeks of treatment. Oral administration of AMS significantly (p < 0.05) reduced the baseline and also reduced ADP-induced aggregation of platelets after 3 and 10 weeks of treatment. Furthermore, 10 weeks of AMS treatment in diabetic rats attenuated the endogenous ROS content (p < 0.05) of platelets and platelet macrophage interactions. The inhibition of platelet activation in diabetic rats after AMS treatment was comparable with aspirin treatment (30 mg/kg/day).

CONCLUSION

We observed an inhibitory effect of allyl methyl sulfide on platelet aggregation, platelet activation, platelet macrophage interaction, and increased ROS levels in type 1 diabetes. Our data suggests that AMS can be useful to control cardiovascular complication in diabetes via inhibition of platelet activation.

Hemostatic state of children with type 1 diabetes

PURPOSE

Hyperglycemia is one of the factors responsible for the molecular alterations that modify hemostasis. The aim of this study was to determine the levels of circulating molecules that have a prothrombotic impact on the child and adolescent population with type 1 diabetes mellitus.

METHODS

There were 35 patients with type 1 diabetes mellitus (11.0±2.5 years of age and a median 3.7±2.0 years of the disease) with no vascular complications and 20 healthy controls with similar age, sex, and body mass index included in the study. The evaluated parameters were fibrinogen, plasminogen activator inhibitor-1 (PAI1), von Willebrand factor antigen, and standard coagulation tests (platelet count, prothrombin time, and activated partial thromboplastin time). Glycemic control was evaluated by hemoglobin A1c and fasting blood glucose tests, and the presence of retinopathy and nephropathy was ruled out. The data obtained were analyzed by IBM SPSS Statistics ver. 20.0 and expressed as mean±standard deviation. The Pearson correlation coefficient was applied to investigate correlations between variables.

RESULTS

Diabetic patients showed significantly higher levels of fibrinogen (308±66 mg/dL vs. 246±18 mg/dL, P=0.0001), PAI-1 (41.6±12 ng/mL vs. 11.7±1.0 ng/mL, P=0.0001), and von Willebrand factor antigen (284%±55% vs. 121%±19%, P=0.0001). However, standard coagulation tests did not show differences between the 2 groups. PAI-1 was correlated with glycemia, hemoglobin A1c, fibrinogen, and von Willebrand factor antigen.

CONCLUSION

Elevated levels of fibrinogen, PAI-1, and von Willebrand factor antigen were found in the pediatric and adolescent population with type 1 diabetes mellitus, which suggests a prothrombotic state.

Macular pigment optical density after panretinal photocoagulation

CLINICAL RELEVANCE

Panretinal photocoagulation, an important treatment method in diabetic retinopathy, can affect macular pigment optical density, which has protective and antioxidant properties. As a result of this effect, the retina may become more sensitive to high-energy visible light.

BACKGROUND

The current study assesses the effect of panretinal photocoagulation treatment on macular pigment optical density, which has essential functions for the retina.

METHODS

In this prospective clinical study, the colour perimetry method was used to measure macular pigment optical density. Thirty-six eyes of 36 participants with severe non-proliferative diabetic retinopathy without macular involvement were included in the study. Conventional panretinal photocoagulation treatments were applied at baseline, one month, two months, and at three months to the participants who clinically required this treatment. Macular pigment optical density and retinal thickness measurements were performed at baseline, months one, two, three and six.

RESULTS

The mean macular pigment optical density reduction in the fovea over the six-months was 0.02 ± 0.02 logarithmic units (p < 0.001). Similarly, the pericentral areas declined by 0.04 ± 0.03 logarithmic units (p < 0.001). Mean central macular thickness and foveal thickness increased by 5.03 ± 5.02 μm and 2.78 (interquartile range 2-4) μm, respectively. In this study, correlation analysis shows that the laser energy applied was significantly and strongly correlated with reductions in macular pigment optical density (for the fovea and pericentral area respectively: r = -0.855, p < 0.001; r = -0.895, p < 0.001). Further, there were significant and strong correlations between the applied laser energy, and central macular thickness and fovea thickness (r = 0.751, p < 0.001; ρ = 0.718, p < 0.001, respectively).

CONCLUSION

Panretinal photocoagulation may potentially cause a decrease in macular pigment density in proportion to the laser energy applied.

Coagulopathy in Type 2 Diabetes Mellitus: Pathological Mechanisms and the Role of Factor XIII-A Single Nucleotide Polymorphisms

The prevalence of type 2 diabetes mellitus (T2DM) has quadrupled within three decades since 1980, affecting 422 million adults in 2016. It remains one of the most common noncommunicable chronic diseases and the underlying risk factor for cardiovascular diseases worldwide. There are different underlying mechanisms that play a role in the development of pathologies associated with the disease such as hyperglycaemia, oxidative stress, obesity, inflammation and hypercoagulation; each of which are interlinked. Hyperglycaemia, oxidative stress and obesity play a huge role in the activation of inflammation and coagulation. Activation of inflammatory pathways increases the production of thrombin which predisposes the development of thrombotic related diseases. One of the factors that contribute to the increase of thrombin is the impairment of the fibrinolysis process due to decreased expression of tissue-plasminogen activator (tPA) by increased levels of plasminogen activator inhibitor-1 (PAI-1). Coagulation factor XIII (FXIII), a transglutaminase that is composed of subunits A and B (FXIII-A2B2), is essential for the last step of fibrin clot formation in the coagulation pathway. Genetic variation of FXIII-A in the form of single nucleotide polymorphisms (SNPs) alters the activity of FXIII, altering clot properties which influence disease outcomes. This review discusses the link between underlying mechanisms of T2DM, well known FXIII-A variants and coagulation.