Current Approach to the Pathogenesis of Diabetic Cataracts

Emodin alleviates the damage to lens epithelial cells in diabetic cataract by repressing the p53-mediated ferroptosis pathway

BACKGROUND

Diabetic cataract (DC) is an ocular complication caused by diabetes. Currently, the main treatments for DC include pharmacological therapy and surgical intervention. The core objective of this study is to elucidate the specific mechanism of action of emodin in the treatment of DC, thereby providing potential targets for the treatment of DC.

METHODS

CCK-8 kit was used to detect the effect of emodin on the activity of lens epithelial cells (LECs). The impact of emodin on the expression of inflammatory factors and apoptosis in high glucose-induced LECs were evaluated by utilizing ELISA and flow cytometry. Then, commercial kits were performed to detect the regulatory effects of emodin on oxidative stress and ferroptosis in high glucose LECs. The potential mechanism of emodin in combating DC by inhibiting ferroptosis was analyzed by network pharmacology methods, and protein binding activity to emodin was measured by molecular docking. Besides, western blot (WB) assay was used to detect the effect of emodin on p53.

RESULTS

Firstly, the results of CCK-8 showed that emodin could effectively alleviate the decrease of LECs cell activity and Lactate dehydrogenase (LDH) release induced by high glucose. Emodin suppressed high glucose-induced apoptosis of LECs, reduced the release of inflammatory factors, and alleviated oxidative stress and ferroptosis. GO and KEGG analyses confirmed the involvement of oxidative stress (OS), inflammatory response, and ferroptosis in the process of emodin treatment for DC. Molecular docking studies showed that emodin stably bound to proteins such as TP53, TNF, IL-6, and IL-1β. Additionally, WB results indicated that emodin alleviated high glucose-induced ferroptosis by binding to p53.

CONCLUSION

Collectively, these data suggest that emodin alleviates damage to LECs by interfering with the p53-mediated ferroptosis pathway, thereby attenuating DC disease, which offered new directions for the development of new drugs.

Correlation of Blood Glucose Control With Cystoid Macular Edema and Central Macular Thickness After Cataract Surgery in Diabetics

Objective

Macular edema and retinal thickening after cataract surgery can lead to poor vision in patients, especially in the presence of high glucose. Blood glycosylated hemoglobin (HbA1c) concentration plays an important role in assessing diabetic control and is closely related to cataract surgery prognosis. The aim of this study was to investigate the correlation between postoperative HbA1c levels and postoperative cystoid macular edema (CME) and central macular thickness (CMT) in diabetic cataract patients.

Methods

Retrospective analysis was conducted on 80 patients with diabetic cataracts from December 2018 to December 2023. The enrolled cases were divided into 2 groups according to the blood glucose control: 56 cases (56 eyes) in the intensive treatment group (HbA1c ≤ 7.0%) with insulin combined with oral hypoglycemic agents; and 24 cases (24 eyes) in the standard treatment group (HbA1c > 7.0%). The Student's t-test or paired t-test was used to compare the changes in CMT between the two groups at each preoperative and postoperative time period. The chi-square test was used to compare the incidence of CME at each postoperative time period. Pearson or Spearman correlation was used to analyse the relationship between HbA1c levels and CMT or CME at each postoperative time period. Predictive efficacy was analyzed using ROC curves.

Results

Patients who went through the standard treatment showed significant CMT thickening and CME at 3 and 6 months postoperatively. HbA1c levels were positively correlated with CME and CMT at 1, 3, and 6 months postoperatively, with good predictive efficacy.

Conclusion

Postoperative HbA1c levels have a strong correlation with CME and CMT thickening and may be reliable and valid biomarkers.

Diabetic Macular Edema in the Western Part of Romania: Screening to Improve Patient Outcomes

Background: Diabetes mellitus (DM) is a global healthcare concern with a rising prevalence. Patients with DM have a severely diminished quality of life due to the extensive range of connected complications. One of the most impactful diabetes-associated pathologies is diabetic macular edema (DME), as it is a major cause of blindness globally. Patients with DME present many concomitant diseases that influence their prognosis. The present research seeks to describe the most frequent DME-related comorbidities. Method: This study enrolled 105 participants previously diagnosed with type 1 DM (T1DM) or type 2 DM (T2DM) (77 presenting with DME), who were evaluated regarding other associated comorbidities. Results: Patients in the DME group presented a median age of 65, with a mean disease duration of 15 years and inadequate glycemic control, reflected by a mean HbA1c of 7.5%. All patients presented at least one comorbidity, with hypertension (100%) and dyslipidemia (62.3%) being the most prevalent. Spearman analysis revealed a statistically significant correlation between DME and diabetes duration (p = 0.01), proliferative diabetic retinopathy (p = 0.004), and chronic kidney disease (p = 0.034). Conclusions: Patients with DME often present multiple comorbidities that must be screened for and addressed through a multidisciplinary approach.

Effect of different incisions on dry eye symptoms after cataract surgery in diabetic patients

AIM

Diabetic patients suffer from severe dry eye after cataract surgery, and the aim of this study was to investigate the effect of 2.2 mm and 3.0 mm clear corneal incisions on dry eye after phacoemulsification in patients with type 2 diabetes mellitus (T2DM).

METHODS

Clinical data of 104 patients with T2DM who underwent phacoemulsification in the Department of Ophthalmology of The People's Hospital of Yingshang from January 2022 to November 2023 were retrospectively collected. The patients were categorized into 2.2 mm and 3.0 mm groups according to the surgical incision, and their preoperative and postoperative Ocular surface disease index (OSDI), Schirmer I test (SIt), and Fluorescein breakup time (FBUT), as well as anxiety and depression levels, were analyzed.

RESULTS

Before surgery, mild anxiety and depression were present in both groups. At 7 days and 1 month postoperatively, OSDI was significantly higher and SIt and FBUT were substantially lower in both groups, but the above indexes were milder in the 2.2 mm group. Meanwhile, the psychological status of both groups significantly improved at 1 month after surgery, and the improvement was more significant in the 2.2 mm group. At 3 months postoperatively, the dry eye of the two groups was relieved, and the psychological status was also improved.

CONCLUSION

Compared with 3.0 mm, a 2.2 mm clear corneal incision effectively reduced dry eye after phacoemulsification in T2DM patients.

Effect of metformin on the level of aqueous humor inflammatory cytokines in patients with cataract

This study investigated the content of inflammatory cytokines in the aqueous humor (AH) of cataract patients with type 2 diabetes (T2DM) and explored the effect of metformin on the level of cytokines. AH was collected from patients undergoing phacoemulsification and intraocular lens implantation in Peking University Third Hospital. Levels of cytokines were measured by Cytometric Bead Assay (CBA) Flex Set. Differences in level of AH cytokines were compared between patients using metformin and non-metformin medicine as blood sugar control drug for T2DM and age-related cataract patients without T2DM. A total of 67 patients were included, including 19 healthy controls, 33 patients in the metformin group, and 15 patients in the non-metformin group. The results showed that IL-6 levels were significantly higher in the non-metformin group than the metformin group and the healthy control group (p = 0.019 and 0.014, respectively). IFN-γ levels were also significantly higher in the non-metformin group than the metformin group and the healthy control group (p = 0.031 and 0.003, respectively). The levels of IL-10 in non-metformin group were significantly higher than those in the healthy control group (p = 0.008), whereas the levels of IL-10 showed no significant difference between metformin group and healthy controls. Metformin can reduce the level of cytokines in AH to a certain extent in cataract patients combined with T2DM. It is suggested that metformin may have preventive and therapeutic effects on the development of age-related cataract.

Association between age at diagnosis of diabetes and ocular disease: Insights from a recent article

In this article, we discuss Ye et al's recent article on the association between age at diabetes diagnosis and subsequent risk of age-related ocular diseases. The study, which utilized United Kingdom Biobank data, highlighted a strong link between early diabetes onset and major eye conditions, such as cataracts, glaucoma, age-related macular degeneration, and vision loss, independent of glycemic control and disease duration. This finding challenges the previous belief that diabetic eye disease primarily correlates with hyperglycemia. As lifestyles evolve and the age of diabetes diagnosis decreases, understanding this relationship may reveal the complex pathogenesis underlying diabetes-related complications. This editorial summarizes potential mechanisms connecting the age of diabetes onset with four types of ocular diseases, emphasizing the significance of early diagnosis.

Diabetes and Cataracts Development-Characteristics, Subtypes and Predictive Modeling Using Machine Learning in Romanian Patients: A Cross-Sectional Study

Background and Objectives: Diabetes has become a global epidemic, contributing to significant health challenges due to its complications. Among these, diabetes can affect sight through various mechanisms, emphasizing the importance of early identification and management of vision-threatening conditions in diabetic patients. Changes in the crystalline lens caused by diabetes may lead to temporary and permanent visual impairment. Since individuals with diabetes are at an increased risk of developing cataracts, which significantly affects their quality of life, this study aims to identify the most common cataract subtypes in diabetic patients, highlighting the need for proactive screening and early intervention. Materials and Methods: This study included 201 participants with cataracts (47.6% women and 52.4% men), of whom 105 also had diabetes. With the use of machine learning, the patients were assessed and categorized as having one of the three main types of cataracts: cortical (CC), nuclear (NS), and posterior subcapsular (PSC). A Random Forest Classification algorithm was employed to predict the incidence of different associations of cataracts (1, 2, or 3 types). Results: Cataracts have been encountered more frequently and at a younger age in patients with diabetes. CC was significantly more frequent among patients with diabetes (p < 0.0001), while the NS and PSC were only marginally, without statistical significance. Machine learning could also contribute to an early diagnosis of cataracts, with the presence of diabetes, duration of diabetes, or diabetic polyneuropathy (PND) having the highest importance for a successful classification. Conclusions: These findings suggest that diabetes may impact the type of cataract that develops, with CC being notably more prevalent in diabetic patients. This has important implications for screening and management strategies for cataract formation in diabetic populations.

Relationship Between Postoperative Oxidative Stress Levels and Corneal Endothelial Cell Loss After Phacoemulsification in Diabetic Patients with Cataract

Objective

To investigate the relationship between postoperative oxidative stress and corneal endothelial cell loss in diabetic patients with cataract.

Methods

One hundred and twenty patients who underwent phacoemulsification were selected, including 80 diabetic patients with cataract and 40 patients with ordinary cataracts. Corneal endothelial cell loss was recorded, and the endothelial cell density (ECD), the proportion of hexagonal cells, and the corneal thickness within the central corneal area were compared. According to the severity of endothelial cell loss, the diabetic patients with cataract were divided into a general loss group (n = 37) and a serious loss group (n = 43), and the postoperative serum superoxide dismutase (SOD), malonaldehyde (MDA), and glutathione peroxidase (GSH-Px) were measured. The relationship between oxidative stress factors and corneal endothelial cell loss in diabetic patients with cataract was analyzed, and the predictive value of MDA, SOD, and GSH-Px was investigated by using receiver operating characteristic (ROC) curve.

Results

Diabetic patients with cataract had higher serum MDA and lower SOD and GSH-px, and higher fasting blood glucose concentration, glycosylated hemoglobin level, and low-density lipoprotein cholesterol (P < 0.05). The mean change in ECD in diabetic patients with cataract was 10.95%, which was greater than the 6.11% in non-diabetic patients with cataract (P < 0.05), and the proportion of hexagonal cells decreased and corneal thickness increased. MDA levels was negatively correlated with corneal endothelial cell loss in diabetic patients with cataract (rs = 0.509), and SOD and GSH-px were negatively correlated (rs = -0.361, rs = -0.482). The area under the ROC curve of MDA, SOD, and GSH-px in corneal endothelial cell loss was 0.719, 0.773, and 0.752, respectively.

Conclusion

The degree of postoperative corneal endothelial cell loss in diabetic patients with cataract was greater and positively correlated with MDA, and negatively correlated with SOD and GSH-px.

Risk Factors for Cataracts in Patients with Diabetes Mellitus

Background: Diabetes mellitus (DM) is one of the most impactful health problems worldwide. It affects ocular health in multiple ways and is one of the leading causes of vision loss. Our study aimed to evaluate the most important systemic risk factors related to the occurrence of cataracts in patients with DM. Method: This study evaluated a final number of 319 participants who were previously diagnosed with DM. For all patients, we retrieved data regarding DM status, metabolic control, demographic and anthropometric indices, and generally associated comorbidities from their medical charts. A comprehensive eye examination was performed on all patients. Results: The main studied risk factors were hypertension, cardiovascular disease (CVD), chronic kidney disease (CKD), diabetic polyneuropathy (DPN), dyslipidemia, and hepatic steatosis, which were present among the entire population. Hypertension (67.6%), DPN (53.3%), and dyslipidemia (46.6%) were highly prevalent in the cataract subgroup, and CKD (p < 0.001) and DPN (p = 0.019) were found to be predictive factors for the probability of cataract occurrence. Ophthalmologic evaluation was used to assess the presence of ocular complications, such as diabetic retinopathy (DR) and diabetic maculopathy. DR reached statistically significant values in the occurence of cataracts. Patients' age and DM-related factors, such as disease duration (p < 0.001) and HbA1c values (p = 0.029), significantly increased the risk of cataracts. Smoking was self-reported by 24.8% of the patients, with a significant impact on the occurrence of cataracts (p = 0.04). Conclusions: Patients with DM who exhibit a longer disease duration and poor glycemic control in conjunction with systemic comorbidities present a higher risk of developing cataracts; consequently, a strict therapeutic approach regarding these risk factors is needed.

Type 1 Diabetes and Cataracts: Investigating Mediating Effects of Serum Metabolites Using Bidirectional Mendelian Randomization

PURPOSE

To investigate the causal relationship between type 1 diabetes (T1D) and cataracts and to explore the mediating role of serum metabolites.

METHODS

This study employed bidirectional Mendelian randomization (MR) using genetic variants as instrumental variables to infer causality in both directions: from T1D to cataracts and cataracts to T1D. Genetic data for T1D, its complications, and cataracts were sourced from independent genome-wide association study (GWAS) datasets. A two-step multivariable MR combined with mediation analysis was conducted to evaluate the indirect effects of serum metabolites in the causal pathway from T1D to cataracts.

RESULTS

The MR analysis demonstrated a significant causal association between T1D and an increased risk of cataracts (OR = 1.01-1.05; p < 0.05). Further analysis showed that patients with T1D complications such as coma, ketoacidosis, nephropathy, and retinopathy exhibited a significantly higher risk of developing cataracts compared to those without complications. Sensitivity analyses upheld the robustness of these findings, with no evidence of heterogeneity or pleiotropy. Additionally, 102 serum metabolites were found to exhibit statistically significant mediation effects on cataract risk, with four (13-HODE + 9-HODE, 2-naphthol sulfate, docosadienoate (22:2n6), and X-12906) showing significant mediation effects. Specifically, 13-HODE + 9-HODE had a protective effect, while the other three metabolites were linked to an increased cataract risk.

CONCLUSIONS

This study provides strong evidence of a causal link between T1D and cataracts, highlighting the mediating role of specific serum metabolites. These findings underscore the importance of early detection and management of cataracts in patients with T1D and suggest potential therapeutic targets for mitigating cataract risk. Further research should focus on replicating these findings in diverse populations and exploring the underlying metabolic pathways in greater detail.

The Role of Immune Cells and Signaling Pathways in Diabetic Eye Disease: A Comprehensive Review

Diabetic eye disease (DED) encompasses a range of ocular complications arising from diabetes mellitus, including diabetic retinopathy, diabetic macular edema, diabetic keratopathy, diabetic cataract, and glaucoma. These conditions are leading causes of visual impairments and blindness, especially among working-age adults. Despite advancements in our understanding of DED, its underlying pathophysiological mechanisms remain incompletely understood. Chronic hyperglycemia, oxidative stress, inflammation, and neurodegeneration play central roles in the development and progression of DED, with immune-mediated processes increasingly recognized as key contributors. This review provides a comprehensive examination of the complex interactions between immune cells, inflammatory mediators, and signaling pathways implicated in the pathogenesis of DED. By delving in current research, this review aims to identify potential therapeutic targets, suggesting directions of research for future studies to address the immunopathological aspects of DED.

Interdependence of Nutrition, Physical Activity, and Myopia

Background: Myopia (also known as nearsightedness), a prevalent refractive error, occurs when parallel rays of light converge in front of the retina, resulting in blurry distance vision. Recently, there has been a marked rise in myopia among the global population. The absence of effective methods of controlling the progression of this visual defect prompts the search for new preventive and therapeutic options. The impact of diet and lifestyle on the progression of myopia is still not fully understood. Therefore, our aim was to examine how these factors might affect the advancement of myopia, based on the existing literature. Methods: This manuscript was prepared through an extensive literature review conducted from June 2022 to September 2024. We searched for pertinent research articles using reputable databases, including PubMed, Scopus, and Web of Science. We included all types of publications, with a special focus on the newest ones. Results: Despite far-reaching examination, the relationship between these factors and myopia control remains inconclusive with varying degrees of evidence supporting their roles. Conclusions: However, promoting a healthy lifestyle, particularly increasing physical activity and outdoor time, is essential. Additionally, emerging research suggests that maintaining a balanced diet is important due to the potential impact of certain nutrients on myopia development. Ophthalmologists should also guide parents on the alternative correction methods beyond single vision glasses, especially for rapidly progressing cases. With the rising prevalence of myopia in children, further research is necessary.

MicroRNA-204-5p Attenuates Oxidative Stress, Apoptosis and Inflammation by Targeting TXNIP in Diabetic Cataract

Diabetic cataract (DC) is a major cause of blindness in diabetic patients and it is characterized by early onset and rapid progression. MiR-204-5p was previously identified as one of the top five down-regulated miRNAs in human DC lens tissues. We aimed to determine the expression of miR-204-5p in human lens epithelial cells (HLECs) and explore its effects and mechanisms in regulating the progression of DC. The expression of miR-204-5p in the anterior capsules of DC patients and HLECs was examined by RT-qPCR. Bioinformatics tools were then used to identify the potential target of miR-204-5p. The relationship between miR-204-5p and the target gene was confirmed through a dual luciferase reporter assay. Additionally, the regulatory mechanism of oxidative stress, apoptosis, and inflammation in DC was investigated by overexpressing miR-204-5p using miR-204-5p agomir. The expression of miR-204-5p was downregulated in the anterior capsules of DC patients and HLECs. Overexpression of miR-204-5p reduced ROS levels, pro-apoptosis genes (Bid, Bax, caspase-3), and IL-1β production in HG-treated HLECs. TXNIP was the direct target of miR-204-5p by dual luciferase reporter assay. Therefore, this study demonstrated that miR-204-5p effectively reduced oxidative damage, apoptosis, and inflammation in HLECs under HG conditions by targeting TXNIP. Targeting miR-204-5p could be a promising therapeutic strategy for the potential treatment of DC.

Fosfenopril Attenuates Inflammatory Response in Diabetic Dry Eye Models by Inhibiting the TLR4/NF-κB/NLRP3 Signaling Pathway

Purpose

The purpose of this study was to investigate the involvement of the TLR4/NF-κB/NLRP3 signaling pathway and its underlying mechanism in diabetic dry eye.

Methods

Two models of diabetic dry eye were established in high glucose-induced human corneal epithelial (HCE-T) cells and streptozotocin (STZ)-induced C57BL/6 mice, and the TLR4 inhibitor fosfenopril (FOS) was utilized to suppress the TLR4/NF-κB/NLRP3 signaling pathway. The expression changes in TLR4, NF-κB, NLRP3, and IL-1β, and other factors were detected by Western blot and RT‒qPCR, the wound healing rate was evaluated by cell scratch assay, and the symptoms of diabetic mice were evaluated by corneal sodium fluorescein staining and tear secretion assay.

Results

In the diabetic dry eye model, the transcript levels of TLR4, NF-κB, NLRP3, and IL-1β were raised, and further application of FOS, a TLR4 inhibitor, downregulated the levels of these pathway factors. In addition, FOS was found to be effective in increasing the wound healing rate of high glucose-induced HCE-T cells, increasing tear production, and decreasing corneal fluorescence staining scores in diabetic mice, as measured by cell scratch assay, corneal sodium fluorescein staining assay, and tear production.

Conclusions

The current study found that the TLR4/NF-κB/NLRP3 signaling pathway regulates diabetic dry eye in an in vitro and in vivo model, and that FOS reduces the signs of dry eye in diabetic mice, providing a new treatment option for diabetic dry eye.

Biochemical Changes in Anterior Chamber of the Eye in Diabetic Patients-A Review

This article aims to provide a comprehensive review of the biochemical changes observed in the anterior chamber of the eye in diabetic patients. The increased levels of inflammatory markers, alterations in antioxidant defense mechanisms, and elevated levels of advanced glycation end products (AGEs) in the aqueous humor (AH) are explored. Additionally, the impact of these biochemical changes on diabetic retinopathy progression, increased intraocular pressure, and cataract formation is discussed. Furthermore, the diagnostic and therapeutic implications of these findings are presented. This study explores potential biomarkers for detecting diabetic eye disease at an early stage and monitoring its progression. An investigation of the targeting of inflammatory and angiogenic pathways as a potential treatment approach and the role of antioxidant agents in managing these biochemical changes is performed.

Review on the potential roles of traditional Chinese medicines in the prevention, treatment, and postoperative recovery of age-related cataract

ETHNIC PHARMACOLOGICAL RELEVANCE

Cataract is the most common cause of blindness worldwide, a visual disorder caused by a clouded lens that seriously affects People's Daily lives. Age-related cataract (ARC) is the most common type of cataract due to long-term combined effects of many factors, and its pathogenesis is varied. At present, the surgery is the main treatment for cataracts, but it is still limited to the prevention, treatment of early cataracts and the postoperative complications care. While, its drug treatments are still in the stage of exploration and research. Traditional Chinese Medicine (TCM), a unique resource in China, is conceived under the guidance of traditional Chinese medicine theory and has little toxicity and side effects, but it has made great progress in the treatment and prevention of ARC.

AIM OF THIS REVIEW

This review presents an overview of the pathogenesis of ARC in both traditional and modern medicines and summarizes the history and therapeutic effect of TCM on ARC including their formula, crude drugs and active components, and also the other auxiliary methods.

METHODS

A number of recognized databases like SciFinder, PubMed, Science Direct, Google Scholar, and China National Knowledge Infrastructure (CNKI) were extensively explored by using keywords and phrases such as "cataract", "age-related cataract", "traditional medicine", "ethnopharmacology", "herbs", "medicinal plants", or other relevant terms, and the plants/phytoconstituents that are evaluated in the models of age-related cataract. As well as the current TCM adjuvant therapy used in the clinical treatment were summarized.

RESULTS

TCM revealed to plays an active role in treating age-related cataract, via multi-pathway and multi-target, and can treat or delay ARC by inhibiting abnormal glucose metabolism, antioxidant damage, inhibiting LEC apoptosis, and so on, which is in concordance with the good effects of the global use of TCM in clinical application. Concerning the early prevention and treatment of cataract and postoperative complications, TCM and auxiliary methods remain to achieve better clinical effects.

CONCLUSION

ARC belongs to the category of "Yuan Yi Nei Zhang" in TCM theory, showing that there are many causes of ARC including aging, and kidney-yang, spleen, sperm and blood deficiencies. At the same time, the viscera gradually decline, as well as yin or yang progressively become weak, especially in the elder people. So, TCM could be mainly based on liver, kidney, and spleen syndrome differentiation, personalizing diagnosis and treatment, following multiple targets, regulating fundamentally yin and yang, and thus justifying the advantages of Chinese medicine in the prevention and treatment of ARC.

Association of Alpha-Crystallin with Human Cortical and Nuclear Lens Lipid Membrane Increases with the Grade of Cortical and Nuclear Cataract

Eye lens α-crystallin has been shown to become increasingly membrane-bound with age and cataract formation; however, to our knowledge, no studies have investigated the membrane interactions of α-crystallin throughout the development of cataracts in separated cortical membrane (CM) and nuclear membrane (NM) from single human lenses. In this study, four pairs of human lenses from age-matched male and female donors and one pair of male lenses ranging in age from 64 to 73 years old (yo) were obtained to investigate the interactions of α-crystallin with the NM and CM throughout the progression of cortical cataract (CC) and nuclear cataract (NC) using the electron paramagnetic resonance spin-labeling method. Donor health history information (diabetes, smoker, hypertension, radiation treatment), sex, and race were included in the data analysis. The right eye lenses CM and NM investigated were 64 yo male (CC: 0), 68 yo male (CC: 3, NC: 2), 73 yo male (CC: 1, NC: 2), 68 yo female (CC: 3, NC: 2), and 73 yo female (CC: 1, NC: 3). Similarly, left eye lenses CM and NM investigated were 64 yo male (CC: 0), 68 yo male (CC: 3, NC: 2), 73 yo male (CC: 2, NC: 3), 68 yo female (CC: 3, NC: 2), and 73 yo female (CC: 1, NC: 3). Analysis of α-crystallin binding to male and female eye lens CM and NM revealed that the percentage of membrane surface occupied (MSO) by α-crystallin increases with increasing grade of CC and NC. The binding of α-crystallin resulted in decreased mobility, increased order, and increased hydrophobicity on the membrane surface in male and female eye lens CM and NM. CM mobility decreased with an increase in cataracts for both males and females, whereas the male lens NM mobility showed no significant change, while female lens NM showed increased mobility with an increase in cataract grade. Our data shows that a 68 yo female donor (long-term smoker, pre-diabetic, and hypertension; grade 3 CC) showed the largest MSO by α-crystallin in CM from both the left and right lens and had the most pronounced mobility changes relative to all other analyzed samples. The variation in cholesterol (Chol) content, size and amount of cholesterol bilayer domains (CBDs), and lipid composition in the CM and NM with age and cataract might result in a variation of membrane surface mobility, membrane surface hydrophobicity, and the interactions of α-crystallin at the surface of each CM and NM. These findings provide insight into the effect of decreased Chol content and the reduced size and amount of CBDs in the cataractous CM and NM with an increased binding of α-crystallin with increased CC and NC grade, which suggests that Chol and CBDs might be a key component in maintaining lens transparency.

Cholesterol Content Regulates the Interaction of αA-, αB-, and α-Crystallin with the Model of Human Lens-Lipid Membranes

α-Crystallin (αABc) is a major protein comprised of αA-crystallin (αAc) and αB-crystallin (αBc) that is found in the human eye lens and works as a molecular chaperone by preventing the aggregation of proteins and providing tolerance to stress. However, with age and cataract formation, the concentration of αABc in the eye lens cytoplasm decreases, with a corresponding increase in the membrane-bound αABc. This study uses the electron paramagnetic resonance (EPR) spin-labeling method to investigate the role of cholesterol (Chol) and Chol bilayer domains (CBDs) in the binding of αAc, αBc, and αABc to the Chol/model of human lens-lipid (Chol/MHLL) membranes. The maximum percentage of membrane surface occupied (MMSO) by αAc, αBc, and αABc to Chol/MHLL membranes at a mixing ratio of 0 followed the trends: MMSO (αAc) > MMSO (αBc) ≈ MMSO (αABc), indicating that a higher amount of αAc binds to these membranes compared to αBc and αABc. However, with an increase in the Chol concentration in the Chol/MHLL membranes, the MMSO by αAc, αBc, and αABc decreases until it is completely diminished at a mixing ratio of 1.5. The Ka of αAc, αBc, and αABc to Chol/MHLL membranes at a mixing ratio of 0 followed the trend: Ka (αBc) ≈ Ka (αABc) > Ka (αAc), but it was close to zero with the diminished binding at a Chol/MHLL mixing ratio of 1.5. The mobility near the membrane headgroup regions decreased with αAc, αBc, and αABc binding, and the Chol antagonized the capacity of the αAc, αBc, and αABc to decrease mobility near the headgroup regions. No significant change in membrane order near the headgroup regions was observed, with an increase in αAc, αBc, and αABc concentrations. Our results show that αAc, αBc, and αABc bind differently with Chol/MHLL membranes at mixing ratios of 0 and 0.5, decreasing the mobility and increasing hydrophobicity near the membrane headgroup region, likely forming the hydrophobic barrier for the passage of polar and ionic molecules, including antioxidants (glutathione), creating an oxidative environment inside the lens, leading to the development of cataracts. However, all binding was completely diminished at a mixing ratio of 1.5, indicating that high Chol and CBDs inhibit the binding of αAc, αBc, and αABc to membranes, preventing the formation of hydrophobic barriers and likely protecting against cataract formation.

Deglycation activity of the Escherichia coli glycolytic enzyme phosphoglucose isomerase

Glycation is a spontaneous chemical reaction, which affects the structure and function of proteins under normal physiological conditions. Therefore, organisms have evolved diverse mechanisms to combat glycation. In this study, we show that the Escherichia coli glycolytic enzyme phosphoglucose isomerase (Pgi) exhibits deglycation activity. We found that E. coli Pgi catalyzes the breakdown of glucose 6-phosphate (G6P)-derived Amadori products (APs) in chicken lysozyme. The affinity of Pgi to the glycated lysozyme (Km, 1.1 mM) was ten times lower than the affinity to its native substrate, fructose 6-phosphate (Km, 0.1 mM). However, the high kinetic constants of the enzyme with the glycated lysozyme (kcat, 396 s-1 and kcat/Km, 3.6 × 105 M-1 s-1) indicated that the Pgi amadoriase activity may have physiological implications. Indeed, when using total E. coli protein (20 mg/mL) as a substrate in the deglycation reaction, we observed a release of G6P from the bacterial protein at a Pgi specific activity of 33 μmol/min/mg. Further, we detected 11.4 % lower APs concentration in protein extracts from Pgi-proficient vs. deficient cells (p = 0.0006) under conditions where the G6P concentration in Pgi-proficient cells was four times higher than in Pgi-deficient cells (p = 0.0001). Altogether, these data point to physiological relevance of the Pgi deglycation activity.

Comprehensive landscape of RNA N6-methyladenosine modification in lens epithelial cells from normal and diabetic cataract

To gain more insight into the mechanism of cataract formation from the perspective of epigenetics in the diabetic population, lens epithelium from diabetic cataract patients and health individuals were collected separately and analyzed for N6-methyladenosine (m6A)-modified RNA using methylated RNA immunoprecipitation sequencing (MeRIP-Seq). Subsequently, differential expression analysis was performed on m6A-regulated messenger RNA (mRNA), circular RNA (circRNA), and long non-coding RNA (lncRNA), followed by functional annotation using the Gene Ontology (GO) database. Furthermore, analysis of single-cell data of lens complemented the intrinsic association and cellular heterogeneity of cataract and m6A regulators. In this study, both the global expression levels and peak intensity of m6A-tagged RNAs were increased in patients with diabetic cataract. And we noted multiple core enzymes were upregulated in the diabetic cataract (DC) samples. Besides, single-cell RNA sequencing analysis of the lens revealed the heterogeneous expression of RNA m6A regulators across different cell types, and we noted that the early fiber cell cluster was also closely associated with the onset of cataract and m6A modification. The results comprehensively revealed the dynamic modification landscape of m6A on mRNA, circRNA, and lncRNA, which might provide valuable resources for future studies of the pathogenesis of DCs.

Fluorescence Imaging of Diabetic Cataract-Associated Lipid Droplets in Living Cells and Patient-Derived Tissues

Diabetic cataract (DC) surgery carries risks such as slow wound healing, macular edema, and progression of retinopathy and is faced with a deficiency of effective drugs. In this context, we proposed a protocol to evaluate the drug's efficacy using lipid droplets (LDs) as the marker. For this purpose, a fluorescent probe PTZ-LD for LDs detection is developed based on the phenothiazine unit. The probe displays polarity-dependent emission variations, i.e., lower polarity leading to stronger intensity. Especially, the probe exhibits photostability superior to that of Nile Red, a commercial LDs staining dye. Using the probe, the formation of LDs in DC-modeled human lens epithelial (HLE) cells is validated, and the interplay of LDs-LDs and LDs-others are investigated. Unexpectedly, lipid transfer between LDs is visualized. Moreover, the therapeutic efficacy of various drugs in DC-modeled HLE cells is assessed. Ultimately, more LDs were found in lens epithelial tissues from DC patients than in cataract tissues for the first time. We anticipate that this work can attract more attention to the important roles of LDs during DC progression.