Diabetic Retinopathy: Important Biochemical Alterations and the Main Treatment Strategies

miR-16-5p Regulates Proliferation and Apoptosis in High Glucose-Treated Human Retinal Microvascular Endothelial Cells by Targeting VEGFA and TGFBR1

Diabetic retinopathy (DR) is a common complication of diabetes and the main cause of vision loss in the middle-aged and elderly people. miRNAs play vital roles in the development of DR. This study aimed to explore the effects of miR-16-5p on high glucose (HG)-stimulated human retinal microvascular endothelial cells (HRECs) by modulating vascular endothelial growth factor A (VEGFA) and transforming growth factor beta receptor 1 (TGFBR1). HRECs were treated with 5 mM, 10 mM, 20 mM, and 30 mM of HG to induce the DR cell model. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of miR-16-5p and mRNAs of VEGFA and TGFBR1. Western blot was used to examine VEGFA and TGFBR1 protein levels. The 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide assay was conducted to test cell proliferation. Flow cytometry with Annexin V-FITC/PI double staining was carried out to assess cell apoptosis ratio. Dual-luciferase assay was used to identify the target relationship between miR-16-5p and VEGFA and TGFBR1. Results found that the expression of miR-16-5p in HG-treated HRECs was reduced, and VEGFA and TGFBR1 expressions were upregulated. Knockdown of miR-16-5p increased VEGFA and TGFBR1 mRNA and protein levels, promoted cell proliferation, and inhibited apoptosis in HG-treated HRECs. VEGFA and TGFBR1 inhibition reversed the effect of knocking down miR-16-5p on HRECs. Dual-luciferase reporter assay revealed that VEGFA and TGFBR1 were the target of miR-16-5p. Overall, knockdown of miR-16-5p enhances proliferation and inhibits apoptosis of HRECs by upregulating VEGFA and TGFBR1 expression.

Natural remedies proposed for the management of diabetic retinopathy (DR): diabetic complications

Diabetic retinopathy (DR) represents a significant and serious complication associated with diabetes mellitus (DM), often resulting in considerable visual impairment or even blindness. The intricate pathological processes underlying DR complicate the effectiveness of current treatment modalities. Studies have highlighted the potential of natural products in the treatment of DR via several beneficial effects including anti-inflammatory, antioxidant, anti-neovascular, and anti-apoptotic properties. Flavonoids, saponins, saccharides, and alkaloids exhibited various beneficial effects in DR in in vivo and in vitro studies. However, the clinical utilization of these natural compounds is hindered by issues such as inadequate specificity, low bioavailability, and potential toxicity. Therefore, there is a pressing need for rigorous clinical studies to confirm the efficacy of natural products in preventing or mitigating the progression of DR.

The role of GRB2 in diabetes, diabetes complications and related disorders

Growth factor receptor-bound protein 2 (GRB2) is a key adaptor protein involved in multiple signalling pathways, and its dysregulation is associated with various diseases. Type 2 diabetes is a systemic condition characterized by insulin resistance and impaired β-cell function. The complications of diabetes significantly reduce life expectancy and quality of life, imposing a substantial burden on society. However, the role of GRB2 in diabetes and associated complications is largely unknown. Emerging evidence suggests that GRB2 plays a crucial role in insulin resistance, inflammation, immune activation and the regulation of cellular processes such as cell proliferation, growth, metabolism, angiogenesis, apoptosis and differentiation. Dysregulation of GRB2-mediated pathways contributes to the progression of diabetic neuropathy, cognitive dysfunction, nephropathy, retinopathy and related disorders. This review provides a comprehensive overview of the current understanding of the role of GRB2 in diabetes, diabetes complications and related disorders, alongside recent advances in the development of GRB2-targeted therapies. Elucidating the complex role of GRB2 in these disorders provides valuable insights into potential therapeutic strategies targeting GRB2-mediated pathways.

Ocular immune-related diseases: molecular mechanisms and therapy

Ocular immune-related diseases, represent a spectrum of conditions driven by immune system dysregulation, include but not limit to uveitis, diabetic retinopathy, age-related macular degeneration, Graves' ophthalmopathy, etc. The molecular and cellular mechanisms underlying these diseases are typically dysfunctioned immune responses targeting ocular tissues, resulting in inflammation and tissue damage. Recent advances have further elucidated the pivotal role of different immune responses in the development, progression, as well as management of various ocular immune diseases. However, there is currently a relative lack of connection between the cellular mechanisms and treatments of several immune-related ocular diseases. In this review, we discuss recent findings related to the immunopathogenesis of above-mentioned diseases. In particular, we summarize the different types of immune cells, inflammatory mediators, and associated signaling pathways that are involved in the pathophysiology of above-mentioned ophthalmopathies. Furthermore, we also discuss the future directions of utilizing anti-inflammatory regime in the management of these diseases. This will facilitate a better understanding of the pathogenesis of immune-related ocular diseases and provide new insights for future treatment approaches.

A Neutral Polysaccharide from Medicago Sativa L.: Structural Properties and Hypoglycemic Activity In Vitro and In Vivo

Medicago sativa polysaccharides (MSPs) are beneficial compounds extracted from Medicago sativa L. that exhibit multiple medicinal activities. However, little is known about their hypoglycemic effects. In this study, MSP-II-a, a neutral polysaccharide with an Mw of 4.3×104 Da, was isolated and purified from M. sativa L. Monosaccharide composition analysis determined that MSP-II-a was composed of arabinose, glucose, galactose, mannose, rhamnose, and xylose in a molar ratio of 2.1 : 4.0 : 1.1:0.4 : 1.4 : 1.1. Structural characterization of MSP-II was performed using a combination of methylation analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The results showed that MSP-II-a was mainly comprised of 1,4-p-Glc, 1,3,4-Rha, and 1,3-p-Gal glycosidic linkages, revealing a mesh-like texture with irregular blade shapes. In vitro assays demonstrated that MSP-II-a, at concentrations of 200 and 400 μg/mL, promoted glucose uptake in insulin-resistant 3T3-L1 adipocytes. In vivo studies have shown that MSP-II-a significantly alleviates insulin resistance by reducing fasting blood glucose levels and increasing hepatic glycogen synthesis in HFD/STZ-induced diabetic mice. These findings revealed that MSP-II-a is a promising source of bioactive polysaccharides with potential hypoglycemic activity.

Tropisetron attenuates high glucose-induced oxidative stress and inflammation in ARPE-19 cells in vitro via regulating SIRT1/ROCK1 signaling

Diabetic retinopathy (DR) is the leading cause of acquired blindness in diabetic patients. Tropisetron (TRO) exerts potent therapeutic effects against diabetic tissues. The present study aimed to investigate the effects of TRO on retinal injury under diabetic condition. Human retinal pigment epithelial cell line ARPE-19 was treated with high glucose (HG) for 48 h to mimic hyperglycemia-induced retinal damage and subsequently treated with multiple concentrations of TRO for therapeutic intervention. Cell viability and lactate dehydrogenase (LDH) release were detected to assess cell damage. The production of inflammatory cytokines and oxidative stress-related factors was evaluated by corresponding commercial kits. Cell apoptosis was evaluated by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. The expression of inflammation-, apoptosis-, and SIRT1/ROCK1-related proteins was examined using western blot analysis. Additionally, ARPE-19 cells were transfected with over-express ROCK1 (Ov-ROCK1) or pretreatment with SIRT1 inhibitor EX527 to perform the rescue experiments. TRO alleviated cell damage in HG-induced ARPE-19 cells through elevating cell viability and reducing LDH release. HG-caused excessive production of TNF-α, IL-1β and IL-6, ROS, malondialdehyde and decreased superoxide dismutase activity were partly inhibited by TRO treatment. HG-induced cell apoptosis, accompanied with the upregulation of proapoptotic proteins and the downregulation of antiapoptotic proteins, was hindered by TRO treatment. HG led to the loss of SIRT1 and an elevation of ROCK1 in ARPE-19 cells, which was reversed following TRO treatment. Furthermore, pretreatment with EX527 or transfected with Ov-ROCK1 partially abolished the protective role of TRO against inflammation, oxidative stress and cell apoptosis in HG-challenged ARPE-19 cells. TRO exerted a protective role against HG-caused ARPE-19 cells inflammation, oxidative stress and cell apoptosis by regulating SIRT1/ROCK1 axis, suggesting that TRO might be therapeutic agent for alleviating retinal pigment epithelial cell damage in DR.

QiMing granules for diabetic retinopathy: a systematic review and meta-analysis of randomized controlled trials

Objective

This study aimed to assess the efficacy and safety of QiMing granules (QM) in the treatment of patients with diabetic retinopathy (DR).

Methods

We systematically searched multiple databases, including Pubmed, Embase, Web of Science, Cochrane Library, SinoMed, Chinese National Knowledge Infrastructure (CNKI), Wanfang database, and VIP database. Randomized controlled trials (RCTs) of QM in the treatment of DR were collected, and the search time limit was from the establishment of the database to 27 March 2024. Two independent researchers were involved in literature screening, data extraction, and bias risk assessment. The risk of bias in the included studies was assessed using the Risk of Bias Assessment tool for randomized controlled trials of Cochrane Collaboration 2.0 (RoB 2.0). The main outcomes were the overall efficacy, visual acuity, retinal circulation time, macular thickness. The secondary outcomes were the levels of triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and glycated hemoglobin (HbA1c). The adverse events was considered the safety outcome. Review Manager 5.4.1 and Stata 15.1 were used for meta-analysis. Data were pooled by random-effects or fixed-effects model to obtain the mean difference (MD), risk ratio (RR), and 95% confidence interval (CI).

Results

A total of 33 RCTs involving 3,042 patients were included in this study. Overall, we demonstrated that QM had a significant clinical effect on DR. QM alone was superior to conventional treatment (CT) in terms of overall efficacy [RR = 1.45, 95% CI: (1.34, 1.58), p < 0.00001, moderate certainty], retinal circulation time [MD = -0.56, 95% CI: (-1.01, -0.12), p = 0.01] and macular thickness [MD = -11.99, 95% CI: (-23.15, -0.83), p = 0.04]. QM plus CT was superior to CT in terms of overall efficacy [RR = 1.29, 95% CI: (1.24, 1.33), p < 0.00001], visual acuity [MD = 0.14, 95% CI: (0.11, 0.17), p < 0.00001], macular thickness [MD = -14.70, 95% CI: (-21.56, -7.83), p < 0.0001], TG [MD = -0.20, 95% CI: (-0.33, -0.08), p = 0.001, moderate certainty], TC [MD = -0.57, 95% CI: (-1.06, -0.07), p = 0.02], and LDL-C [MD = -0.36, 95% CI: (-0.70, -0.03), p = 0.03]. In terms of safety, the incidence of adverse events in the experimental group was less than that in the control group. The results of the GRADE evidence quality evaluation showed that the evidence quality of outcome indicators was mostly low.

Conclusion

QM can effectively improve overall efficacy, visual acuity, macular thickness, retinal circulation time, and reduce the levels of TG, TC, and LDL-C. However, due to the limited number of studies included, a small sample size, and a lack of high-quality literature, the possibility of publication bias cannot be excluded. Moreover, biases are present due to differences in study design, such as the absence of placebo use in the control group and a predominant use of combined intervention designs in the control group, along with deficiencies in allocation concealment and blinding methods. Therefore, more multi-center, large-sample, and rigorously designed studies are needed to substantiate this conclusion.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/#recordDetails, identifier CRD42023465165.

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.

Berberine alleviates diabetic retinopathy by regulating the Th17/Treg ratio

BACKGROUND

Diabetic retinopathy (DR) stands as a prominent complication of diabetes. Berberine (BBR) has reported to be effective to ameliorate the retinal damage of DR. Studying the potential immunological mechanisms of BBR on the streptozotocin (STZ) induced DR mouse model will explain the therapeutic mechanisms of BBR and provide theoretical basis for the clinical application of this drug.

METHODS

C57BL/6 J mice were induced into a diabetic state using a 50 mg/(kg·d) dose of STZ over a 5-day period. Subsequently, they were subjected to a high-fat diet (HFD) for one month. Following a 5-week treatment with 100 mg/(kg·d) BBR, the concentrations of inflammatory factors in the mice's peripheral blood were determined using an enzyme-linked immunosorbent assay (ELISA). Hematoxylin-eosin staining was employed to scrutinize pathological changes in the mice's retinas, while flow cytometry assessed the proportions of T-lymphocyte subsets and the activation status of dendritic cells (DCs) in the spleen and lymph nodes. CD4+T cells and DC2.4 cell lines were utilized to investigate the direct and indirect effects of BBR on T cells under high glucose conditions in vitro.

RESULTS

Following 5 weeks of BBR treatment in the streptozotocin (STZ) mouse model of DR, we observed alleviation of retinal lesions and a down-regulation in the secretion of inflammatory cytokines, namely TNF-α, IL-1β, and IL-6, in the serum of these mice. And in the spleen and lymph nodes of these mice, BBR inhibited the proportion of Th17 cells and promoted the proportion of Treg cells, thereby down-regulating the Th17/Treg ratio. Additionally, in vitro experiments, BBR directly inhibited the expression of the transcription factor RORγt and promoted the expression of the transcription factor Foxp3 in T cells, resulting in a down-regulation of the Th17/Treg ratio. Furthermore, BBR indirectly modulated the Th17/Treg ratio by suppressing the secretion of TNF-α, IL-1β, and IL-6 by DCs and enhancing the secretion of indoleamine 2,3-dioxygenase (IDO) and transforming growth factor-beta (TGF-β) by DCs. This dual action inhibited Th17 cell differentiation while promoting Treg cells.

CONCLUSION

Our findings indicate that BBR regulate T cell subpopulation differentiation, reducing the Th17/Treg ratio by directly or indirectly pathway. This represents a potential therapeutic avenue of BBR for improving diabetic retinopathy.

Diabetic Retinopathy: New Treatment Approaches Targeting Redox and Immune Mechanisms

Diabetic retinopathy (DR) represents a severe complication of diabetes mellitus, characterized by irreversible visual impairment resulting from microvascular abnormalities. Since the global prevalence of diabetes continues to escalate, DR has emerged as a prominent area of research interest. The development and progression of DR encompass a complex interplay of pathological and physiological mechanisms, such as high glucose-induced oxidative stress, immune responses, vascular endothelial dysfunction, as well as damage to retinal neurons. Recent years have unveiled the involvement of genomic and epigenetic factors in the formation of DR mechanisms. At present, extensive research explores the potential of biomarkers such as cytokines, molecular and cell therapies, antioxidant interventions, and gene therapy for DR treatment. Notably, certain drugs, such as anti-VEGF agents, antioxidants, inhibitors of inflammatory responses, and protein kinase C (PKC)-β inhibitors, have demonstrated promising outcomes in clinical trials. Within this context, this review article aims to introduce the recent molecular research on DR and highlight the current progress in the field, with a particular focus on the emerging and experimental treatment strategies targeting the immune and redox signaling pathways.

Deciphering Müller cell heterogeneity signatures in diabetic retinopathy across species: an integrative single-cell analysis

Diabetic retinopathy (DR), a leading cause of visual impairment, demands a profound comprehension of its cellular mechanisms to formulate effective therapeutic strategies. Our study presentes a comprehensive single-cell analysis elucidating the intricate landscape of Müller cells within DR, emphasizing their nuanced involvement. Utilizing scRNA-seq data from both Sprague-Dawley rat models and human patients, we delineated distinct Müller cell clusters and their corresponding gene expression profiles. These findings were further validated through differential gene expression analysis utilizing human transcriptomic data. Notably, certain Müller cell clusters displayed upregulation of the Rho gene, implying a phagocytic response to damaged photoreceptors within the DR microenvironment. This phenomenon was consistently observed across species. Additionally, the co-expression patterns of RHO and PDE6G within Müller cell clusters provided compelling evidence supporting their potential role in maintaining retinal integrity during DR. Our results offer novel insights into the cellular dynamics of DR and underscore Müller cells as promising therapeutic targets for preserving vision in retinal disorders induced by diabetes.

The mechanism of EGFL7 regulating neovascularization in diabetic retinopathy through the PI3K/AKT/VEGFA pathway

Diabetic retinopathy (DR) is a blinding disease caused by diabetes, characterized by neovascularization of the retina. The aim of this study was to investigate the roles of epidermal growth factor-like structural domain 7 (EGFL7) on human retinal vascular endothelial cells (HRECS) and retinas from rats with DR. An in vitro model of DR was established through culturing HRECS in high glucose. The in vivo model of DR was established by injecting SD rats with streptozotocin (STZ) to induce diabetes. The differences in the expressed levels of EGFL7, PI3K, AKT, P-AKT and VEGFA in high-glucose cultured cells and retinal tissues of diabetic rats were detected in compared to those in the control group. Stable EGFL7 knockdown cell lines were generated by transfecting HRECS with lentiviral vectors and the effects of EGFL7 knockdown on angiogenesis, cell migration and proliferation were investigated. The results showed that EGFL7, PI3K, P-AKT and VEGFA was increased in cells and tissues under high glucose conditions. Knockdown of EGFL7 downregulated the proliferation, migration and angiogenesis capacity of HRECS, and blocked the PI3K/AKT/VEGFA signaling pathway. Furthermore, overexpression of PI3K reversed the effects of EGFL7 inhibition. These findings provide new ideas for the treatment of neovascularisation in DR.

Recent Insights into the Etiopathogenesis of Diabetic Retinopathy and Its Management

Purpose: Diabetic retinopathy (DR) is a microvascular retinal disease associated with chronic diabetes mellitus, characterized by the damage of blood vessels in the eye. It is projected to become the leading cause of blindness, given the increasing burden of the diabetic population worldwide. The diagnosis and management of DR pose significant challenges for physicians because of the involvement of multiple biochemical pathways and the complexity of ocular tissues. This review aims to provide a comprehensive understanding of the molecular pathways implicated in the pathogenesis of DR, including the polyo pathway, hexosamine pathway, protein kinase C (PKC), JAK/STAT signaling pathways, and the renin-angiotensin system (RAS). Methods: Academic databases such as PubMed, Scopus, Google Scholar and Web of Science was systematically searched using a carefully constructed search strategy incorporating keywords like "Diabetic Retinopathy," "Molecular Pathways," "Pharmacological Treatments," and "Clinical Trials" to identify relevant literature for the comprehensive review. Results: In addition to activating other inflammatory cascades, these pathways contribute to the generation of oxidative stress within the retina. Furthermore, it aims to explore the existing pharmacotherapy options available for the treatment of DR. In addition to conventional pharmacological therapies such as corticosteroids, antivascular endothelial growth factors, and nonsteroidal anti-inflammatory drugs (NSAIDs), this review highlights the potential of repurposed drugs, phyto-pharmaceuticals, and novel pipeline drugs currently undergoing various stages of clinical trials. Conclusion: Overall, this review serves as a technical exploration of the complex nature of DR, highlighting both established and emerging molecular pathways implicated in its pathogenesis. Furthermore, it delves into the available pharmacological treatments, as well as the promising repurposed drugs, phyto-pharmaceuticals, and novel drugs currently being evaluated in clinical trials, with a focus on their specific mechanisms of action.

Correlation study of renal function indices with diabetic peripheral neuropathy and diabetic retinopathy in T2DM patients with normal renal function

Background

The anticipation of diabetes-related complications remains a challenge for numerous T2DM patients, as there is presently no effective method for early prediction of these complications. This study aims to investigate the association between renal function-related indicators and the occurrence of peripheral neuropathy and retinopathy in individuals diagnosed with type 2 diabetes mellitus (T2DM) who currently have normal renal function.

Methods

Patients with T2DM who met the criteria were selected from the MMC database and divided into diabetic peripheral neuropathy (DPN) and diabetic retinopathy (DR) groups, with a total of 859 and 487 patients included, respectively. Multivariate logistic regression was used to analyze the relationship between blood urea nitrogen (BUN), creatinine (Cr), uric acid (UA), urine albumin(ALB), albumin-to-creatinine ratio (ACR), estimated glomerular filtration rate (eGFR), and diabetic peripheral neuropathy and retinopathy. Spearman correlation analysis was used to determine the correlation between these indicators and peripheral neuropathy and retinopathy in diabetes.

Results

In a total of 221 patients diagnosed with DPN, we found positive correlation between the prevalence of DPN and eGFR (18.2, 23.3, 35.7%, p < 0.05). Specifically, as BUN (T1: references; T2:OR:0.598, 95%CI: 0.403, 0.886; T3:OR:1.017, 95%CI: 0.702, 1.473; p < 0.05) and eGFR (T1: references; T2:OR:1.294, 95%CI: 0.857, 1.953; T3:OR:2.142, 95%CI: 1.425, 3.222; p < 0.05) increased, the odds ratio of DPN also increased. Conversely, with an increase in Cr(T1: references; T2:OR:0.86, 95%CI: 0.56, 1.33; T3:OR:0.57, 95%CI: 0.36, 0.91; p < 0.05), the odds ratio of DPN decreased. Furthermore, when considering sensitivity and specificity, eGFR exhibited a sensitivity of 65.2% and specificity of 54.4%, with a 95% confidence interval of 0.568-0.656.

Conclusion

In this experimental sample, we found a clear positive correlation between eGFR and DPN prevalence.

GRg1 inhibits the TLR4/NF-kB signaling pathway by upregulating miR-216a-5p to reduce growth factors and inflammatory cytokines in DR

BACKGROUND

Diabetic retinopathy (DR) is a common diabetic neurodegenerative disease that affects vision in severe cases. Current therapeutic drugs are ineffective for some patients with severe side effects, and ginsenoside-Rg1 (GRg1) has been shown to protect against DR and may serve as a new potential drug for DR. This study aimed to confirm the protective effect of GRg1 against DR and its molecular mechanism.

METHODS

Human retinal microvascular endothelial cells (hRMECs) and rats were used to construct DR models in vitro and in vivo. Cell proliferation was detected by BrdU assays, the cell cycle was detected by flow cytometry, and TNF-α, IL-6 and IL-1β levels were detected by ELISA. qRT‒PCR, Western blotting and immunohistochemistry were used to detect the expression of related genes and proteins, and angiogenesis assays were used to assess angiogenesis. RIP and RNA pull down assays were used to determine the relationship between miR-216a-5p and TLR4; retinal structure and changes were observed by HE staining and retinal digestive spread assays.

RESULTS

GRg1 effectively inhibited HG-induced hRMEC proliferation, cell cycle progression and angiogenesis and reduced the levels of intracellular inflammatory cytokines and growth factors. HG downregulated the expression of miR-216a-5p and upregulated the expression of TLR4/NF-kB signaling pathway-related proteins. Importantly, GRg1 inhibited TLR4/NF-kB signaling pathway activation by upregulating miR-216a-5p, thereby inhibiting HG-induced cell proliferation, cell cycle progression, angiogenesis, and the production of inflammatory cytokines and growth factors. In addition, animal experiments confirmed the results of the cell experiments.

CONCLUSIONS

GRg1 inhibits TLR4/NF-kB signaling by upregulating miR-216a-5p to reduce growth factors and inflammatory cytokines in DR, providing a potential therapeutic strategy for DR.

Effect of passive smoking exposure on risk of type 2 diabetes: a systematic review and meta-analysis of prospective cohort studies

Objective

The effect of passive smoking exposure on the risk of type 2 diabetes has not been systematically studied. A meta-analysis was conducted to assess the association between passive smoking exposure and the risk of diabetes.

Methods

We searched three major databases up to 31 October 2022 to identify relevant prospective cohort studies on the association between passive smoking and the risk of type 2 diabetes. The pooled relative risk (RR) and 95% confidence interval (CI) for the association between passive smoking exposure and the risk of type 2 diabetes were analyzed using a fixed-effect model.

Results

Ten prospective cohort studies were included in this meta-analysis, with a total of 251,620 participants involved. The pooled RR showed a significantly positive association between nonsmokers exposed to passive smoking and type 2 diabetes as compared to non-smokers who were not exposed to passive smoking [RR = 1.27; 95% CI (1.19, 1.36); p < 0.001]. Sensitivity analysis indicated that the pooled RR was not substantially affected by any of the individual studies.

Conclusion

Exposure to passive smoking increases the risk of type 2 diabetes. This study may have a positive effect on the prevention of type 2 diabetes.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023372532.

Kcnma1 is involved in mitochondrial homeostasis in diabetes-related skeletal muscle atrophy

Uncontrolled diabetes causes a catabolic state with multi-organic complications, of which impairment on skeletal muscle contributes to the damaged mobility. Kcnma1 gene encodes the pore-forming α-subunit of Ca²⁺ - and voltage-gated K⁺ channels of large conductance (BK channels), and loss-of-function mutations in Kcnma1 are in regards to impaired myogenesis. Herein, we observed a time-course reduction of Kcnma1 expression in the tibialis anterior muscles of leptin receptor-deficient (db/db) diabetic mice. To investigate the role of Kcnma1 in diabetic muscle atrophy, muscle-specific knockdown of Kcnma1 was achieved by mice receiving intravenous injection of adeno-associated virus-9 (AAV9)-encoding shRNA against Kcnma1 under the muscle creatine kinase (MCK) promoter. Impairment on muscle mass and myogenesis were observed in m/m mice with AAV9-shKcnma1 intervention, while this impairment was more obvious in diabetic db/db mice. Simultaneously, damaged mitochondrial dynamics and biogenesis showed much severer in db/db mice with AAV9-shKcnma1 intervention. RNA sequencing revealed the large transcriptomic changes resulted by Kcnma1 knockdown, and changes in mitochondrial homeostasis-related genes were validated. Besides, the artificial alteration of Kcnma1 in mouse C2C12 myoblasts was achieved with an adenovirus vector. Consistent results were demonstrated by Kcnma1 knockdown in palmitate-treated cells, whereas opposite results were exhibited by Kcnma1 overexpression. Collectively, we document Kcnma1 as a potential keeper of mitochondrial homeostasis, and the loss of Kcnma1 is a critical event in priming skeletal muscle loss in diabetes.

The role of the mTOR pathway in diabetic retinopathy

The retina, the part of the eye, translates the light signal into an electric current that can be sent to the brain as visual information. To achieve this, the retina requires fine-tuned vascularization for its energy supply. Diabetic retinopathy (DR) causes alterations in the eye vascularization that reduce the oxygen supply with consequent retinal neurodegeneration. During DR, the mammalian target of rapamycin (mTOR) pathway seems to coordinate retinal neurodegeneration with multiple anabolic and catabolic processes, such as autophagy, oxidative stress, cell death, and the release of pro-inflammatory cytokines, which are closely related to chronic hyperglycemia. This review outlines the normal anatomy of the retina and how hyperglycemia can be involved in the neurodegeneration underlying this disease through over activation or inhibition of the mTOR pathway.

Polyphenols target miRNAs as a therapeutic strategy for diabetic complications

MiRNAs are a large group of non-coding RNAs which participate in different cellular pathways like inflammation and oxidation through transcriptional, post-transcriptional, and epigenetic regulation. In the post-transcriptional regulation, miRNA interacts with the 3'-UTR of mRNAs and prevents their translation. This prevention or dysregulation can be a cause of pathological conditions like diabetic complications. A huge number of studies have revealed the association between miRNAs and diabetic complications, including diabetic nephropathy, cardiomyopathy, neuropathy, retinopathy, and delayed wound healing. To address this issue, recent studies have focused on the use of polyphenols as selective and safe drugs in the treatment of diabetes complications. In this article, we will review the involvement of miRNAs in diabetic complications' occurrence or development. Finally, we will review the latest findings on targeting miRNAs by polyphenols like curcumin, resveratrol, and quercetin for diabetic complications therapy.

Identifying gene variants underlying the pathogenesis of diabetic retinopathy based on integrated genomic and transcriptomic analysis of clinical extreme phenotypes

Diabetic retinopathy (DR) is a common complication and the leading cause of blindness in patients with type 2 diabetes. DR has been shown to be closely correlated with blood glucose levels and the duration of diabetes. However, the onset and progression of DR also display clinical heterogeneity. We applied whole-exome sequencing and RNA-seq approaches to study the gene mutation and transcription profiles in three groups of diabetic patients with extreme clinical phenotypes in DR onset, timing, and disease progression, aiming to identify genetic variants that may play roles in the pathogenesis of DR. We identified 23 putatively pathogenic genes, and ingenuity pathway analysis of these mutated genes reveals their functional association with glucose metabolism, diabetic complications, neural system activity, and dysregulated immune responses. In addition, ten potentially protective genes were also proposed. These findings shed light on the mechanisms underlying the pathogenesis of DR and may provide potential targets for developing new strategies to combat DR.

Short-Chain Fatty Acids Attenuate Renal Fibrosis and Enhance Autophagy of Renal Tubular Cells in Diabetic Mice Through the HDAC2/ULK1 Axis

BACKGRUOUND

This study investigated the effect of short-chain fatty acids (SCFAs) on diabetes in a mouse model.

METHODS

Autophagy in Akita mice and streptozocin (STZ)-induced diabetic C57BL/6 mice was determined by Western blots and immunohistochemistry (IHC). Western blots, IHC, hematoxylin and eosin staining, Masson staining, periodic acid-Schiff staining, and picrosirius red staining were conducted to detect whether autophagy and renal function improved in Akita mice and STZ-induced diabetic C57BL/6 mice after treatment of SCFAs. Western blots, IHC, and chromatin immunoprecipitation were performed to determine whether SCFAs affected diabetic mice via the histone deacetylase (HDAC2)/unc-51 like autophagy activating kinase 1 (ULK1) axis. Diabetic mice with kidney-specific knockout of HDAC2 were constructed, and IHC, Masson staining, and Western blots were carried out to detect whether the deletion of endogenous HDAC2 contributed to the improvement of autophagy and renal fibrosis in diabetic mice.

RESULTS

Reduced autophagy and severe fibrosis were observed in Akita mice and STZ-induced diabetic C57BL/6 mice. Increased autophagy and reduced renal cell fibrosis were found in SCFA-treated Akita diabetic mice and STZ-induced diabetic C57BL/6 mice. Diabetic mice treated with SCFAs had lower HDAC2 expression and more enriched binding of ULK1 promoter sequences to H3K27Ac. Endogenous knockout of HDAC2 caused enhanced autophagy and decreased renal fibrosis in diabetic mice treated with SCFAs.

CONCLUSION

SCFAs enhanced autophagy of renal tubular cells and attenuated renal fibrosis in diabetic mice through the HDAC2/ULK1 axis.

Quercetin: an effective polyphenol in alleviating diabetes and diabetic complications

Various studies, especially in recent years, have shown that quercetin has beneficial therapeutic effects in various human diseases, including diabetes. Quercetin has significant anti-diabetic effects and may be helpful in lowering blood sugar and increasing insulin sensitivity. Quercetin appears to affect many factors and signaling pathways involved in insulin resistance and the pathogenesis of type 2 of diabetes. TNFα, NFKB, AMPK, AKT, and NRF2 are among the factors that are affected by quercetin. In addition, quercetin can be effective in preventing and ameliorating the diabetic complications, including diabetic nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy, and affects the key mechanisms involved in the pathogenesis of these complications. These positive effects of quercetin may be related to its anti-inflammatory and anti-oxidant properties. In this article, after a brief review of the pathogenesis of insulin resistance and type 2 diabetes, we will review the latest findings on the anti-diabetic effects of quercetin with a molecular perspective. Then we will review the effects of quercetin on the key mechanisms of pathogenesis of diabetes complications including nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy. Finally, clinical trials investigating the effect of quercetin on diabetes and diabetes complications will be reviewed.

Tribbles homolog 3 contributes to high glucose-induced injury in retinal pigment epithelial cells via binding to growth factor receptor-bound 2

Diabetic retinopathy (DR) is the most typical complication of diabetes, which severely threatens sight. Tribbles homolog 3 (TRB3), a kind of pseudokinase, is discovered to be highly expressed in diabetes and retinas after retinal detachment. TRB3 expression in human retinal pigment epithelial (hRPE) cells exposed to different concentrations of glucose was tested by RT-qPCR and western blot. Then, cells were induced with 30 mM high glucose (HG) to establish a DR cell model. Following TRB3 knockdown, cell viability estimation employed CCK-8 assay. The mRNA levels of inflammatory factors were detected by RT-qPCR. Reactive oxygen species (ROS) level was measured by DCFH-DA assay, and levels of oxidative stress markers were evaluated applying corresponding kits. Cell apoptosis was assayed by TUNEL assay and western blot. Following, the growth factor receptor-bound 2 (GRB2) expression was also examined by RT-qPCR and western blot. The interaction between TRB3 and GRB2 was verified by Co-IP assay. After GRB2 was overexpressed in HG-induced hRPE cells transfected with shRNA-TRB3, functional experiments were conducted again. The results manifested that TRB3 expression was elevated under HG conditions. Deficiency of TRB3 enhanced the viability while alleviated inflammation, oxidative stress, and apoptosis in HG-induced hRPE cells. GRB2 was also increased in HG-exposed hRPE cells. Moreover, GRB2 had a strong affinity with TRB3 and positively regulated by TRB3. After GRB2 overexpression, the effects of TRB3 knockdown on HG-stimulated hRPE cells were all reversed. Briefly, this study confirmed the promoting role of TRB3/GRB2 axis in the progression of DR.

Cellular targets in diabetic retinopathy therapy

Despite the existence of treatment for diabetes, inadequate metabolic control triggers the appearance of chronic complications such as diabetic retinopathy. Diabetic retinopathy is considered a multifactorial disease of complex etiology in which oxidative stress and low chronic inflammation play essential roles. Chronic exposure to hyperglycemia triggers a loss of redox balance that is critical for the appearance of neuronal and vascular damage during the development and progression of the disease. Current therapies for the treatment of diabetic retinopathy are used in advanced stages of the disease and are unable to reverse the retinal damage induced by hyperglycemia. The lack of effective therapies without side effects means there is an urgent need to identify an early action capable of preventing the development of the disease and its pathophysiological consequences in order to avoid loss of vision associated with diabetic retinopathy. Therefore, in this review we propose different therapeutic targets related to the modulation of the redox and inflammatory status that, potentially, can prevent the development and progression of the disease.

Kinins and Their Receptors as Potential Therapeutic Targets in Retinal Pathologies

The kallikrein-kinin system (KKS) contributes to retinal inflammation and neovascularization, notably in diabetic retinopathy (DR) and neovascular age-related macular degeneration (AMD). Bradykinin type 1 (B1R) and type 2 (B2R) receptors are G-protein-coupled receptors that sense and mediate the effects of kinins. While B2R is constitutively expressed and regulates a plethora of physiological processes, B1R is almost undetectable under physiological conditions and contributes to pathological inflammation. Several KKS components (kininogens, tissue and plasma kallikreins, and kinin receptors) are overexpressed in human and animal models of retinal diseases, and their inhibition, particularly B1R, reduces inflammation and pathological neovascularization. In this review, we provide an overview of the KKS with emphasis on kinin receptors in the healthy retina and their detrimental roles in DR and AMD. We highlight the crosstalk between the KKS and the renin-angiotensin system (RAS), which is known to be detrimental in ocular pathologies. Targeting the KKS, particularly the B1R, is a promising therapy in retinal diseases, and B1R may represent an effector of the detrimental effects of RAS (Ang II-AT1R).