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Background: Diabetic retinopathy (DR), the principal cause of acquired blindness among the working-age population, is the most frequent microvascular complication of diabetes. Although metabolic disorders are hypothesized to play a role in its pathogenesis, the underlying mechanism remains largely elusive., Methods: To elucidate the mechanism, we initially compared metabolite profiles of vitreous fluid between 23 patients with DR and 12 non-diabetic controls using liquid chromatography/tandem mass spectrometry, identifying the distinct metabolite indoxyl sulfate (IS). Subsequently, streptozotocin (STZ)-induced diabetic and IS-injected rat models were established to examine the effects of IS on retinal microvasculature. RNA sequencing was conducted to identify potential regulatory mechanisms in IS-treated human retinal endothelial cells (HREC). Finally, target gene knockdown in HREC and treatment of IS-injected rats with inhibitors (targeting IS production or downstream regulators) were employed to elucidate the detailed mechanisms and identify therapeutic targets for DR., Results: Metabolomics identified 172 significantly altered metabolites in the vitreous humor of diabetics, including the dysregulated tryptophan metabolite indoxyl sulfate (IS). IS was observed to breach the blood-retinal barrier and accumulate in the intraocular fluid of diabetic rats. Both in vivo and in vitro experiments indicated that elevated levels of IS induced endothelial apoptosis and disrupted cell junctions. RNA sequencing pinpointed prostaglandin E2 (PGE 2 ) synthetase-cyclooxygenase 2 (COX-2) as a potential target of IS. Validation experiments demonstrated that IS enhanced COX-2 expression, which subsequently increased PGE 2 secretion by promoting transcription factor EGR1 binding to COX-2 DNA following entry into cells via organic anion transporting polypeptides (OATP2B1). Furthermore, inhibition of COX-2 in vivo or silencing EGR1/OATP2B1 in HREC mitigated IS-induced microcapillary damage and the activation of COX-2/PGE 2 ., Conclusion: Our study demonstrated that indoxyl sulfate (IS), a uremic toxin originating from the gut microbiota product indole, increased significantly and contributed to retinal microvascular damage in diabetic retinopathy (DR). Mechanistically, IS impaired retinal microvascular integrity by inducing the expression of COX-2 and the production of PGE 2 . Consequently, targeting the gut microbiota or the PGE 2 pathway may offer effective therapeutic strategies for the treatment of DR., (© 2024. The Author(s).)

Background: Proliferative diabetic retinopathy (PDR), a major cause of blindness, is characterized by complex pathogenesis. This study integrates single-cell RNA sequencing (scRNA-seq), Non-negative Matrix Factorization (NMF), machine learning, and AlphaFold 2 methods to explore the molecular level of PDR., Methods: We analyzed scRNA-seq data from PDR patients and healthy controls to identify distinct cellular subtypes and gene expression patterns. NMF was used to define specific transcriptional programs in PDR. The oxidative stress-related genes (ORGs) identified within Meta-Program 1 were utilized to construct a predictive model using twelve machine learning algorithms. Furthermore, we employed AlphaFold 2 for the prediction of protein structures, complementing this with molecular docking to validate the structural foundation of potential therapeutic targets. We also analyzed protein-protein interaction (PPI) networks and the interplay among key ORGs., Results: Our scRNA-seq analysis revealed five major cell types and 14 subcell types in PDR patients, with significant differences in gene expression compared to those in controls. We identified three key meta-programs underscoring the role of microglia in the pathogenesis of PDR. Three critical ORGs (ALKBH1, PSIP1, and ATP13A2) were identified, with the best-performing predictive model demonstrating high accuracy (AUC of 0.989 in the training cohort and 0.833 in the validation cohort). Moreover, AlphaFold 2 predictions combined with molecular docking revealed that resveratrol has a strong affinity for ALKBH1, indicating its potential as a targeted therapeutic agent. PPI network analysis, revealed a complex network of interactions among the hub ORGs and other genes, suggesting a collective role in PDR pathogenesis., Conclusion: This study provides insights into the cellular and molecular aspects of PDR, identifying potential biomarkers and therapeutic targets using advanced technological approaches., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Wang, Sun, Mou, Lu, Wu, Pu and Yang.)

Background and Purpose: Nonproliferative diabetic retinopathy (NPDR) occurs in the early stages of Diabetic retinopathy (DR), and the study of its metabolic markers will help to prevent DR. Hence, we aimed to establish a risk score based on multiple metabolites through untargeted metabolomic analysis of venous blood from NPDR patients and diabetic non-DR patients., Experimental Approach: Untargeted metabolomics of venous blood samples from patients with NPDR, diabetes melitus without DR were performed using high-performance liquid chromatography-mass spectrometry., Results: Detailed metabolomic evaluation showed distinct clusters of metabolites in plasma samples from patients with NPDR and diabetic non-DR patients. NPDR patients had significantly higher levels of phenylacetylglycine, L-aspartic acid, tiglylglycine, and 3-sulfinato-L-alaninate, and lower level of indolelactic acid, threonic acid, L-arginine (Arg), and 4-dodecylbenzenesulfonic acid compared to control. The expression profiles of these eight NPDR risk-related characteristic metabolites were analyzed using Cox regression to establish a risk score model. Subsequently, univariate and multivariate Cox regression analyses were used to determine that this risk score model was a predictor of independent prognosis for NPDR., Conclusions: Untargeted metabolome analysis of blood metabolites revealed unreported metabolic alterations in NPDR patients compared with those in diabetic non-DR patients or MH. In the venous blood, we identified depleted metabolites thA and Arg, indicating that they might play a role in NPDR development., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Wang, Yang, Yang, Lin, Zhao, Ding, Sun, Meng, Yang, Kang and Liang.)

PurposeThe aim of the present study is to investigate the association of the polymorphism of two genes in CXC chemokine family, interleukin-8 (IL-8) and interferon-inducible protein 10 (IP-10), with both susceptibility and progression of DR in T2D population of northern China.Patients and methodsA total of 1043 eligible type 2 diabetic patients from Heilongjiang of northern China were recruited for this study. They were grouped into: with diabetic retinopathy (DR, 528 cases) and without diabetic retinopathy (DNR, 515 cases). Single nucleotide polymorphism (SNP) genotyping of IL-8(-251T/A) and IP-10(-1596C/T) was performed by polymerase chain reaction. Multivariate analysis and stepwise multiple logistic progression analysis were conducted to evaluate the association between gene SNP and DR susceptibility and progression. Pooled odds ratio (OR) with 95% confidence interval (CI) was applied to assess the strength of the association among study groups.ResultsThe occurring of IL-8(-251) AA genotype was correlated with susceptibility (OR: 2.286, 95% CI: 1.382-3.782, P=0.001) and progression of high-risk proliferative diabetic retinopathy (PDR) (OR: 0.354, 95% CI: 0.162-0.770, P=0.009). Reversely, T allele of IP-10 (-1596) C/T was correlated with a reduced risk of DR (OR: 0.341, 95% CI: 0.249-0.466, P<0.001). However, gene polymorphisms of IL-8-251T/A and IP-10-1596C/T were not associated with diabetic macular edema (DME)(P>0.05).ConclusionsAA genotype of IL-8-251T/A was closely correlated to DR and high-risk proliferative diabetic retinopathy (PDR). -1596T allele of the IP-10 is a beneficial genotype for DR.

Diabetic retinopathy (DR) has complex multifactorial pathogenesis. This study aimed to investigate the association of complement pathway genes with susceptibility to DR. Eight haplotype-tagging SNPs of SERPING1 and C5 were genotyped in 570 subjects with type 2 diabetes: 295 DR patients (138 nonproliferative DR [NPDR] and 157 proliferative DR [PDR]) and 275 diabetic controls. Among the six C5 SNPs, a marginal association was first detected between rs17611 and total DR patients (P = 0.009, OR = 0.53 for recessive model). In stratification analysis, a significant decrease in the frequencies of G allele and GG homozygosity for rs17611 was observed in PDR patients compared with diabetic controls (Pcorr = 0.032, OR = 0.65 and Pcorr = 0.016, OR = 0.37, resp.); it was linked with a disease progression. A haplotype AA defined by the major alleles of rs17611 and rs1548782 was significantly predisposed to PDR with increased risk of 1.54 (Pcorr = 0.023). Regarding other variants in C5 and SERPING1, none of the tagging SNPs had a significant association with DR and its subgroups (all P > 0.05). Our study revealed an association between DR and C5 polymorphisms with clinical significance, whereas SERPING1 is not a major genetic component of DR. Our data suggest a link of complement pathway with DR pathogenesis.

Emerging reports have revealed a potential association of paraoxonase (PON) gene polymorphisms with diabetic nephropathy (DN) and diabetic retinopathy (DR). However, the identification of susceptible genes and the quantification of associated risks are elusive owing to a lack of reproducibility. Therefore, a meta‑analysis was conducted in the present study to improve the understanding of the effect of PON1 and PON2 on DN and DR. A total of 10 articles, involving 2,877 patients and 3,246 controls met the inclusion criteria. Functional variants (n=4) were evaluated, including rs662 (p.Q192R) and rs854560 (p.L55M) in PON1; and rs7493 (p.S311C) and rs12026 (p.A148G) in PON2. Overall, PON1‑L55M was found to be significantly associated with DR in all the genetic models: allele [odds ratio (OR)=2.42; 95% confidence interval (CI), 1.91‑3.07]; dominant (OR=5.76; 95% CI, 3.14‑10.55), homozygote (OR=10.53; 95% CI, 5.59‑19.86), heterozygote (OR=3.62; 95% CI, 1.94‑6.74), and recessive (OR=3.56; 95% CI, 2.61‑4.86), with no evidence of between‑study heterogeneity. However, such associations were not detected in DN and the other three polymorphisms did not show any associations with DN or DR. The current meta‑analysis highlighted results for the risk of association of PON1‑55L with DR. The results also indicated that PON2 gene polymorphisms, as well as PON1‑Q192R, may not confer major genetic risk to DN or DR. Additional studies are required to enrich the understanding of PON genes, particularly for its functional role in DR.

Objectives: The complement system is a key component of innate immunity and has been implicated in the pathogenesis of diabetic retinopathy (DR). This study aimed at investigating whether polymorphisms of two genes in the complement pathway, complement factor H (CFH) and complement factor B (CFB), are associated with DR., Methods: 552 well-defined subjects with type 2 diabetes, consisting of 277 DR patients and 275 diabetic controls, were recruited. Four Tag-SNPs rs1048709, rs537160, rs4151657, and rs2072633 in CFB and rs800292 (I62V) in CFH were examined using TaqMan Genotyping Assays., Results: There were significant increases in the frequencies of A allele and AA genotype for rs1048709 in DR patients compared with diabetic controls (P(corr) = 0.035, OR = 1.42; P(corr) = 0.02, OR = 2.27, resp.): meanwhile, significant decreases in the frequencies of A allele and AA genotype for rs800292 were observed in DR patients compared with diabetic controls (P(corr) = 0.04, OR = 0.72; P(corr) = 0.015, OR = 0.51, resp.). Joint effect of these two loci was also identified. Moreover, rs800292/AA genotype was found to be related with delayed progression to DR., Conclusions: CFH-rs800292 and CFB-rs1048709 are associated with the presence of DR, which strengthens the concept that complement system plays an important role in the pathogenesis of DR.

Objective: The purpose of this study was to understand the awareness, prevalence of diabetic retinopathy and treatment status of people aged over 50 and living in the rural areas of Shuangcheng city, Heilongjiang province, China., Methods: Cluster sampling was used in randomly selected 5504 survey for ophthalmic clinical examination, in patients with diabetic retinopathy. A questionnaire in the state of knowledge about prevention and treatment was developed., Results: Among the 5504 persons entering in the project, 5053 were examined on their eyes (91.8%). In this selected population, 56 persons (112 eyes) were diagnosed as diabetic retinopathy (1.108%), with 95% confidence interval (CI) as: 0.819% to 1.397%. Of 56 patients, 49 cases were non-proliferative diabetic retinopathy, accounting for 87.50% of the total number of patients with diabetic retinopathy; proliferative diabetic retinopathy 7 cases, accounting for 12.50% of the 112 eyes, 6.25% (7/112) having vitreous hemorrhage, 8.04% (9/112) having macular edema. For diabetic retinopathy prevalence rates, there was no significant difference in males and females. Between the per differential 10-year-old division, the difference was significant. Among the 60 to 69 group, a significantly higher prevalence rate was seen. Of the 112 eyes with diabetic retinopathy, 34 eyes (30.4%) were low vision [visual acuity < 20/60 (0.3) to ≥ 20/400 (0.05)]; 6 eyes (5.4%) were blind [visual acuity < 20/400 (0.05) to NLP]. The rate in the patients with PDR and fasting blood glucose was above 11.1 mmol/L was higher than having NPDR and fasting blood glucose below 11.1 mmol/L. Having fasting blood glucose 11.1 mmol/L and above with the course over five years among patients with PDR, the proportion of fasting blood glucose was higher than those with less than 11.1 mmol/L and diabetic retinopathy duration of less than five years. Of 56 patients with diabetic retinopathy, 38 cases (67.9%) did not receive any treatment. Among 18 cases (32.1%) with insulin or oral drug therapy, regularly using insulin or other medication (14.3%), only 1 (1.8%) case was given the treatment for diabetic retinopathy. Results from our survey showed that patients with diabetic retinopathy had a poor understanding about prevention and treatment of the disease., Conclusion: Long duration and high blood glucose in patients with diabetic retinopathy seemed to be the important risk factor. Early systematic drug use for prevention and blood glucose control was the key to prevent diabetic retinopathy. Patients with diabetic retinopathy in China had poor understanding about the prevention measures of the disease and lack of knowledge.