Influence of diabetes mellitus on anterior segment of the eye

Interconnections between diabetic corneal neuropathy and diabetic retinopathy: diagnostic and therapeutic implications

Diabetic corneal neuropathy and diabetic retinopathy are ocular complications occurring in the context of diabetes mellitus. Diabetic corneal neuropathy refers to the progressive damage of corneal nerves. Diabetic retinopathy has traditionally been considered as damage to the retinal microvasculature. However, growing evidence suggests that diabetic retinopathy is a complex neurovascular disorder resulting from dysfunction of the neurovascular unit, which includes both the retinal vascular structures and neural tissues. Diabetic retinopathy is one of the leading causes of blindness and is frequently screened for as part of diabetic ocular screening. However, diabetic corneal neuropathy is commonly overlooked and underdiagnosed, leading to severe ocular surface impairment. Several studies have found that these two conditions tend to occur together, and they share similarities in their pathogenesis pathways, being triggered by a status of chronic hyperglycemia. This review aims to discuss the interconnection between diabetic corneal neuropathy and diabetic retinopathy, whether diabetic corneal neuropathy precedes diabetic retinopathy, as well as the relation between the stage of diabetic retinopathy and the severity of corneal neuropathy. We also endeavor to explore the relevance of a corneal screening in diabetic eyes and the possibility of using corneal nerve measurements to monitor the progression of diabetic retinopathy.

Advanced and interpretable corneal staining assessment through fine grained knowledge distillation

The assessment of corneal fluorescein staining is essential, yet current AI models for Corneal Staining Score (CSS) assessments inadequately identify punctate lesions due to annotation challenges and noise, risk misrepresenting treatment responses through "plateau" effects, and highlight the necessity for real-world evaluations to enhance disease severity assessments. To address these limitations, we developed the Fine-grained Knowledge Distillation Corneal Staining Score (FKD-CSS) model. FKD-CSS integrates fine-grained features into CSS grading, providing continuous and nuanced scores with interpretability. Trained on corneal staining images collected from dry eye (DE) patients across 14 hospitals, FKD-CSS achieved robust accuracy, with a Pearson's r of 0.898 and an AUC of 0.881 in internal validation, matching senior ophthalmologists' performance. External tests on 2376 images from 23 hospitals across China further validated its efficacy (r: 0.844-0.899, AUC: 0.804-0.883). Additionally, FKD-CSS demonstrated generalizability in multi-ocular-surface-disease testing, underscoring its potential in handling different staining patterns.

Fenofibrate inhibits activation of cGAS-STING pathway by alleviating mitochondrial damage to attenuate inflammatory response in diabetic dry eye

The cyclic GMP-AMP synthase (cGAS) and Stimulator of Interferon Genes (STING) signaling pathway are critical regulators of inflammation. This study aims to investigate the role of the cGAS-STING signaling pathway in diabetic dry eye (DDE) disease and further explore the therapeutic efficacy and underlying mechanism of fenofibrate in DDE. Using single-cell RNA sequencing (scRNA-Seq) data from the Gene Expression Omnibus (GEO) database, combined with the STZ-induced DDE mouse model and high-glucose conditions in immortalized human corneal epithelial cells (HCE-T), we observed mitochondrial damage and significantly elevated cytoplasmic mitochondrial DNA (mtDNA) in the diabetic cornea, and identified that the cGAS-STING signaling pathway plays a pivotal role in the pathogenesis of DDE. Notably, we found that the inhibitor H151 reversed the ocular surface inflammatory response via the cGAS-STING pathway. Further investigation revealed that fenofibrate alleviated corneal inflammatory response by reducing the production of reactive oxygen species (ROS), restoring mitochondrial membrane potential (MMP), decreasing mtDNA cytoplasmic leakage, and subsequently suppressing the activation of the cGAS-STING signaling pathway. In conclusion, this study highlights the crucial role of the cGAS-STING signaling pathway in DDE and proposes that fenofibrate alleviates mitochondrial damage to inhibit this pathway, offering novel strategy for the treatment of DDE.

Pigment epithelium-derived factor (PEDF) promotes survival and contraction of myoepithelial cells in lacrimal gland

PEDF is critical for general health of the ocular surface. In order to study mechanisms of PEDF's action in lacrimal gland (LG) secretion, these visual structures were studied in a PEDF deficient (Pedf-/-) mouse model using biochemical, histochemical, and morphometric analyses. In Pedf-/- animals there were several ocular surface and LG disturbances not seen in controls. Notably, changes in body and LG weight, corneal sensitivity, tear film, ocular surface damage, and size of acini comprising the LG were evident. Survival of myoepithelial cells (MECs) surrounding the acini showed a PEDF survival dependence as there were significant reduction in MEC-specific P63 cells and Bcl2 expression levels, and increased TUNEL positive cells in PEDF deficient mice. Expression levels of the major contractile MEC proteins, α-SMA, calponin, and keratin 14, were also reduced with PEDF gene deletion and MECs contraction apparatus impaired, since oxytocin significantly reduced acinar area in controls but had no effect in PEDF deficient LGs, although the oxytocin receptor (OXTR) was expressed in both PEDF genotypes. These findings suggest that PEDF is essential to MECs survival and contractile function, and tear homeostasis on the ocular surface. Treatment with PEDF is likely to alleviate ocular-related conditions in diseases associated with dry eye as well as promote healthy MEC cell function in other secretory glands of the body.

Assessment of insulin-degrading enzyme inhibitor for the treatment of corneal erosion in a rat model

BACKGROUND

Diabetes poses a risk to diabetic keratopathy in up to two-thirds of patients. Insulin-degrading enzyme (IDE) is a protease that can break down insulin and several growth factors and may impair wound healing. Increased IDE levels have been found in fluid from diabetic skin ulcers. This study sought to determine the effect of IDE inhibitor on corneal wound healing in a rat model.

METHODS

Thirty-four male Wistar rats were divided into two groups: no diabetes and streptozocin-induced diabetes. Six weeks later, a 4-mm central corneal erosion was created under anesthesia in the right eye of all rats. In each group, half the rats were treated with ADT21 drops (IDE inhibitor) and half with NaCl 0.9% (sham) drops, four times daily. Image J analysis was performed to evaluate the area of erosion and healing rate.

RESULTS

There was a trend for more rapid healing in rats treated with IDEI than NaCl drops, regardless of the diabetic condition. Comparison of erosion closure over time revealed that the wounds closed significantly more quickly in the non-diabetic rats treated with IDEI than in the non-diabetic rats treated with NaCl (p = 0.045), overall mean closure time 56.00 h, 95% CI [50.54, 61.46]. No such difference was seen in the diabetic group.

CONCLUSIONS

To our knowledge, this is the first study to test ADT21 drops as a novel treatment for corneal wound repair. Our results suggest a potential benefit of IDE inhibitor for treating corneal injury.

Impact of ChatGPT on Diabetes Mellitus Self-Management Among Patients in Saudi Arabia

BACKGROUND

Diabetes mellitus (DM) is a chronic condition requiring continuous self-management to prevent complications. Artificial intelligence (AI)-driven tools like ChatGPT (OpenAI, Inc., San Francisco, CA, USA) offer potential support in education, monitoring, and decision-making. However, research on its effectiveness in DM self-management remains limited, particularly in Saudi Arabia, necessitating further investigation into its role and impact.

PURPOSE

This study aims to analyze the impact of ChatGPT on DM self-management.

METHODS

A qualitative experimental design was adopted in this study. DM patients after interacting with ChatGPT for a week participated in the interviews, where their perceptions on its impact were recorded. A total of 25 DM patients participated in the study, whose results were analyzed using thematic analysis.

RESULTS

The analysis of interview data revealed 11 themes related to the impact of ChatGPT on DM self-management, which included informational support, personalized recommendations, motivation and support, assistance in decision-making, offering self-care reminders, facilitating communication with healthcare providers, facilitating peer support, providing mental health support, tracking and monitoring, conducting health assessments, and education and awareness.

CONCLUSION

ChatGPT has a positive impact on DM self-management. However, further research is needed due to ChatGPT's novel nature for generalizing results and extending its applicability to other areas of healthcare.

Tear-fluid-derived biomarkers of ocular complications in diabetes: a systematic review and meta-analysis

BACKGROUND

Early identification and management of sight-threatening ocular complications of diabetes using imaging or molecular biomarkers could help prevent vision loss. However, access to specialized infrastructure and expertise is limited, especially in remote areas of the world. Tear-fluid may offer an easier, non-invasive, and localized screenshot of ocular disease. To the best of our knowledge, there is no systematic review and meta-analysis on tear-fluid-based biomarkers for ocular complications in diabetes.

METHODS

Articles were extracted from PubMed, Embase, Medline, and Web of Science using the MeSH and Emtree terms. The keywords include (diabetes), (diabetic retinopathy), (diabetes mellitus, type 1), (diabetes mellitus, type 2), (insulin-dependent diabetes), (insulin resistant diabetes), (tears), (lacrimal fluid), (biological marker), and (biomarker, marker). Concentrations of tear-fluid biomarkers in individuals with diabetes, diabetic ocular complications, and healthy controls were extracted and standardized mean differences (SMDs) and 95% CIs were calculated. Heterogeneity was assessed using subgroup and leave-one-out sensitivity analyses. Publication and risk of bias were performed using the Egger's test and Cochrane guidelines. The quality of evidence was evaluated using the Newcastle-Ottawa scale.

RESULTS

Nine hundred eleven papers were identified, 19 of which met the study criteria and were included in the meta-analysis. Participants (n = 1413) belonged to three groups: healthy controls (Controls), diabetes without any complications (Diabetes), and diabetes with ocular complications (Complications). Actual concentrations were reported for TNF-α, VEGF, IL-1RA, IL-1β, IL-6, IL-8, lactoferrin, lysozyme, and MCP-1 in at least three different studies. Meta-analyses demonstrated that TNF-α concentration was significantly higher in the tear-fluid of Complications group when compared to Controls (SMD = - 1.08, 95% CIs = - 1.78, - 0.38, p = 0.003) or when compared to Diabetes (SMD = - 0.78, 95% CIs = - 1.48, - 0.09, p = 0.03). However, it was not different when Controls were compared to Diabetes (SMD = - 1.00, 95% CIs = - 2.27, 0.28, p = 0.13). VEGF demonstrated a similar trend indicating specificity of tear-fluid TNF-α and VEGF for diabetic ocular complications.

CONCLUSIONS

Across all biomolecules meta-analyzed in this study, TNF-α and VEGF were identified as the most important biomarkers that could potentially offer a non-invasive tear-fluid-based assessment of progression to ocular complications in diabetes, especially in rural and remote areas where diabetes-related expertise and infrastructure are limited.

TRIAL REGISTRATION

PROSPERO (CRD42023441867) https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=441867 .

What intrinsic factors affect the central corneal thickness?

The cornea is one of the tissues responsible for covering and protecting the inner structures of the eye. Central corneal thickness (CCT) is defined as the distance between the anterior epithelial surface and the posterior surface of the endothelial layer. This parameter plays a very important role regarding intraocular pressure (IOP) measurement, evaluation of corneal uniformity, selection of a suitable technique for corneal refractive surgery and the planning of surgical procedures to overcome corneal disease. This comprehensive review elucidates the multifaceted factors influencing the central corneal thickness. Recognising the impact of these factors not only enhances our understanding of corneal dynamics but also contributes significantly to the refinement of diagnostic and therapeutic strategies in ophthalmology.

Molecular mechanism of Wilms tumour 1-associated protein in diabetes-related dry eye disease by mediating m6A methylation modification of lncRNA NEAT1

Background: Dry eye disease (DED) is often secondary to diabetes mellitus (DM).Purpose: This study is to explore the action of Wilms tumor 1-associated protein (WTAP) in DM-DED via lncRNA NEAT1 m6A methylation.Methods: DM-DED mouse models were treated with sh-WTAP/sh-NEAT1, followed by assessment of corneal epithelial damage/histopathological changes. HCE-2 cells were exposed to hyperosmotic conditions to establish in vitro DED models and treated with oe-NEAT1/sh-NEAT1/sh-WTAP/nigericin (an NLRP3 inflammasome inducer). Cell viability/apoptosis were evaluated by CCK-8/TUNEL. Levels of WTAP/NEAT1/inflammatory factors/NLRP3 inflammasome- and apoptosis-related markers were determined. m6A modification was examined by MeRIP-qPCR and NEAT1 stability was also detected.Results: DM-DED mice exhibited up-regulated WTAP/NEAT1 expression and severe corneal damage, whereas WTAP/NEAT1 knockdown alleviated inflammation/corneal damage. In hyperosmolarity-induced HCE-2 cells, NEAT1 aggravated inflammation and apoptosis, while NEAT1 knockdown suppressed NLRP3 inflammasome activation and ameliorated cell injury. Hyperosmolarity-induced WTAP expression increased m6A modification and NEAT1 mRNA stability. WTAP mediated m6A methylation of NEAT1 and NLRP3 inflammasome activation in DM-DED mice.

MUC1‑ND interacts with TRPV1 to promote corneal epithelial cell proliferation in diabetic dry eye mice by partly activating the AKT signaling pathway

Although both mucin1 (MUC1) and transient receptor potential cation channel subfamily V member 1 (TRPV1) have been reported to be associated with dry eye (DE) disease, whether they interact and their regulatory roles in diabetic DE disease are unknown. Diabetic DE model mice were generated by streptozotocin induction and assessed by corneal fluorescein staining, tear ferning (TF) tests, phenol red thread tests, hematoxylin and eosin staining of corneal sections and periodic acid Schiff staining of conjunctival sections. Cell proliferation was measured by CCK8 assay. Western blotting was performed to measure protein expression. Primary mouse corneal epithelial cells (MCECs) were cultured after enzymatic digestion. Immunofluorescence staining of MCECs and frozen corneal sections was conducted to assess protein expression and colocalization. Coimmunoprecipitation was performed to detect protein‑protein interactions. It was found that, compared with control mice, diabetic DE mice exhibited increased corneal epithelial defects, reduced tear production, poorer TF pattern grades and impaired corneal and conjunctival tissues. In vivo and in vitro experiments showed that hyperglycemia impaired cell proliferation, accompanied by decreased levels of the MUC1 extracellular domain (MUC1‑ND) and TRPV1. Additionally, it was found that capsazepine (a TRPV1 antagonist) inhibited the proliferation of MCECs. Notably, MUC1‑ND was shown to interact with the TRPV1 protein in the control group but not in the diabetic DE group. It was also found that the AKT signaling pathway was attenuated in the diabetic DE mice and downstream of TRPV1. MUC1‑ND interacted with TRPV1, partly activating the AKT signaling pathway to promote MCEC proliferation. The present study found that the interaction of MUC1‑ND with TRPV1 promotes MCEC proliferation by partly activating the AKT signaling pathway, providing new insight into the pathogenesis of corneal epithelial dysfunction in diabetic DE disease.

Clinical ocular surface characteristics and expression of MUC5AC in diabetics: a population-based study

OBJECTIVES

To investigate the clinical characteristics and the expression of mucin 5AC (MUC5AC) in in diabetic and non-diabetic subjects with or without dry eye disease.

METHODS

A total of 399 participants (796 eyes) aged 50-80 years were enrolled in this study. Participants were divided into 4 groups: non-diabetic without dry eye group (normal group), non-diabetic with dry eye group, diabetic without dry eye group and diabetic with dry eye group. Demographic information, fasting plasma glucose (FBG), and glycated haemoglobin A1C (HbA1C) data were collected. Additionally, ocular surface disease index (OSDI) questionnaire, signs of dry eye, tear osmolarity, and meibomian glands were evaluated. Tear MUC5AC expression and conjunctival goblet cells density (GCD) were tested.

RESULTS

Compared with non-diabetic with dry eye group, diabetic with dry eye group showed significantly lower tear film osmolarity (TFO), but higher corneal fluorescein and conjunctival lissamine green staining scores. In comparison with diabetic without dry eye group, diabetic with dry eye group showed significantly higher TFO, corneal fluorescein and conjunctival lissamine green staining scorers. The MUC5AC concentration and GCD of diabetic with dry eye group was significantly lower than those of the non-diabetic with dry eye group. Diabetic subjects with higher HbA1c levels (≥7.8%) showed higher TFO and shorter fluorescein tear break time.

CONCLUSION

Diabetics with dry eye exhibited notably higher corneal fluorescein and conjunctival lissamine green staining scores. Conjunctival goblet cells and MUC5AC were significantly reduced in diabetics. Higher TFO was associated with the duration of diabetes and HbA1c levels.

Genetic liability to higher frailty index may increase the risk of ophthalmic disease

PURPOSE

Frailty and age-related eye diseases are common in older people; however, whether there is a causal link remains unknown. We aimed to explore the causal associations between the frailty index (FI) and ophthalmic traits and identify modifiable mediators.

METHODS

Linkage disequilibrium score regression and two-sample Mendelian randomization were applied to identify genetic correlations and causal associations between FI and ophthalmic traits. Summary data for FI was obtained from a genome-wide association study that included 175,226 individuals of European ancestry. Summary-level statistics for ophthalmic traits were obtained from relative GWASs. Summary-level data for cardiovascular risk factors, inflammatory biomarkers, and the central nervous system were used to identify the possible mediators.

RESULTS

FI had a significant genetic correlation with 10 ophthalmic traits. Per SD increment of FI, the odds ratio was 1.329 (95% CI, 1.123, 1.573; P = 9.5 × 10-4) for cataracts, 1.825 (95% CI, 1.115, 2.986; P = 0.016) for keratitis, 1.798 (95% CI, 1.039, 3.11; P = 0.036) for disorders of vitreous body and 1.478 (95% CI, 1.005, 2.173; P = 0.046) for disorders of sclera, cornea, iris and ciliary body. The MR effect estimates of FI on ophthalmic traits were attenuated after adjusting for mental disorders, type 2 diabetes, triglyceride, and interleukin-8 (IL-8) levels.

CONCLUSION

This study reports a genetic correlation and causal association between FI and ophthalmic traits, in which mental disorders, type 2 diabetes, triglycerides, and IL-8 may play a mediating role. These findings highlight a possible method to reduce the risk of FI-related ophthalmic diseases.

Genetic liability to higher frailty index may increase the risk of ophthalmic disease

PURPOSE

Frailty and age-related eye diseases are common in older people; however, whether there is a causal link remains unknown. We aimed to explore the causal associations between the frailty index (FI) and ophthalmic traits and identify modifiable mediators.

METHODS

Linkage disequilibrium score regression and two-sample Mendelian randomization were applied to identify genetic correlations and causal associations between FI and ophthalmic traits. Summary data for FI was obtained from a genome-wide association study that included 175,226 individuals of European ancestry. Summary-level statistics for ophthalmic traits were obtained from relative GWASs. Summary-level data for cardiovascular risk factors, inflammatory biomarkers, and the central nervous system were used to identify the possible mediators.

RESULTS

FI had a significant genetic correlation with 10 ophthalmic traits. Per SD increment of FI, the odds ratio was 1.329 (95% CI, 1.123, 1.573; P = 9.5 × 10-4) for cataracts, 1.825 (95% CI, 1.115, 2.986; P = 0.016) for keratitis, 1.798 (95% CI, 1.039, 3.11; P = 0.036) for disorders of vitreous body and 1.478 (95% CI, 1.005, 2.173; P = 0.046) for disorders of sclera, cornea, iris and ciliary body. The MR effect estimates of FI on ophthalmic traits were attenuated after adjusting for mental disorders, type 2 diabetes, triglyceride, and interleukin-8 (IL-8) levels.

CONCLUSION

This study reports a genetic correlation and causal association between FI and ophthalmic traits, in which mental disorders, type 2 diabetes, triglycerides, and IL-8 may play a mediating role. These findings highlight a possible method to reduce the risk of FI-related ophthalmic diseases.

The Systemic Risk Factors for the Development of Infectious Keratitis after Penetrating Keratoplasty: A Population-Based Cohort Study

Penetrating keratoplasty (PK) is a corneal surgery that is employed to repair the full-thickness corneal lesion. This study aimed to survey the possible systemic risk factors of infectious keratitis after penetrating keratoplasty (PK) via the Taiwan National Health Insurance Research Database (NHIRD). A retrospective case-control study was conducted, and 327 patients who received the PK were enrolled after exclusion. The main outcome was the development of infectious keratitis, and people were divided into those with infectious keratitis and those without the outcome. Cox proportional hazard regression was conducted to produce adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) of specific demographic indexes and systemic diseases on infectious keratitis. There were 68 patients who developed infectious keratitis after the whole follow-up period. The diabetes mellitus (DM) (aHR: 1.440, 95% CI: 1.122-2.874, p = 0.0310) and chronic ischemic heart disease (aHR: 1.534, 95% CI: 1.259-3.464, p = 0.0273) groups demonstrated a significant association with infectious keratitis. The DM group also revealed significant influence on infectious keratitis development in all the subgroups (all p < 0.05). Nevertheless, the effect of chronic ischemic heart disease on infectious keratitis was only significant on those aged older than 60 years (p = 0.0094) and both sexes (both p < 0.05). In conclusion, the presence of DM and chronic ischemic heart disease are associated with infectious keratitis after PK. However, local risk factors for infectious keratitis developed in those receiving PK had not been evaluated.

[Clinical profile of corneal sensitivity in diabetic patients: A case-control study]

PURPOSE

To evaluate the corneal sensitivity of black diabetic patients and identify factors associated with changes in corneal sensitivity.

METHODOLOGY

We conducted a cross-sectional comparative case-control study at the National Obesity Center of the Yaounde Central Hospital and the Djoungolo District Hospital from March 1 to July 31, 2022. Corneal sensitivity was measured using the Cochet-Bonnet esthesiometer in all diabetic patients over 18 years of age, matched for age and sex to a clinically healthy control population. Data were analyzed using SPSS version 23.0 software. A P-value of less than 5% was considered significant.

RESULTS

A total of 111 diabetic and 111 non-diabetic patients participated in the study. The mean age was 53.46±12.74 years for diabetics and 52.85±11.77 years for non-diabetics (P=0.901). The mean duration of diabetes was 6.4±5.30 years. Corneal sensitivity in diabetics was lower (44.56±9.59mm) compared to non-diabetics (53.59±6.30mm) with a statistically significant difference (P=0.000). Factors associated with decrease in corneal sensitivity in diabetics were duration of diabetes and poor glycemic control.

CONCLUSION

Decrease in corneal sensitivity related to diabetes is a complication to be systematically screened for during the ophthalmologic follow-up of diabetic patients.

Increased expression of neutrophil CD15 correlates with the severity of anterior ocular surface damage in type II diabetes mellitus

BACKGROUND

Diabetes mellitus is associated with increased risk of ocular surface diseases in elderly. We consider neutrophil CD15 as a potential marker of ocular surface damage in type II diabetes mellitus patients.

AIM

We aimed to evaluate expression of neutrophil CD15 and correlate it with results of conjunctival impression cytology and routine objective anterior ocular surface tests (TMH, NIBUT, LLT, MGD) in T2DM patients.

MATERIALS AND METHODS

We prospectively enrolled sixty type II diabetes mellitus patients (120 eyes) into a study group. The control group included forty (80 eyes) age- and sex-matched healthy individuals. All patients underwent comprehensive ophthalmological examination, and tear meniscus height test (TMH), noninvasive tear break-up time (NIBUT), lipid layer thickness measurement (LLT), Meibomian gland dysfunction evaluation (MGD), conjunctival impression cytology (CIC) and expression of CD15.

RESULTS

Abnormal Nelson's grades of squamous metaplasia (grades 2 and 3) were observed in 50% (60 eyes) of the study group, and 13.8 (11 eyes) of the control group. Fifteen patients with type II diabetes mellitus suffered from grade 3 squamous metaplasia. Nelson's grades of squamous metaplasia have shown a positive correlation with the level of CD15 expression either in the study and control groups (rs = 0.628, p = <0.0001; rs = 0.746, p < 0.0001; respectively).

CONCLUSIONS

The research shows significantly reduced values of routine objective ocular tests in type II diabetes mellitus patients in comparison to healthy participants older than 60 y.o. Increased CD15 in the peripheral blood is associated with the development of squamous metaplasia and may be used to evaluate the severity of ocular surface damage in type II diabetes mellitus patients.

Are Hyperglycemia-Induced Changes in the Retina Associated with Diabetes-Correlated Changes in the Brain? A Review from Zebrafish and Rodent Type 2 Diabetes Models

Diabetes is prevalent worldwide, with >90% of the cases identified as Type 2 diabetes. High blood sugar (hyperglycemia) is the hallmark symptom of diabetes, with prolonged and uncontrolled levels contributing to subsequent complications. Animal models have been used to study these complications, which include retinopathy, nephropathy, and peripheral neuropathy. More recent studies have focused on cognitive behaviors due to the increased risk of dementia/cognitive deficits that are reported to occur in older Type 2 diabetic patients. In this review, we collate the data reported from specific animal models (i.e., mouse, rat, zebrafish) that have been examined for changes in both retina/vision (retinopathy) and brain/cognition, including db/db mice, Goto-Kakizaki rats, Zucker Diabetic Fatty rats, high-fat diet-fed rodents and zebrafish, and hyperglycemic zebrafish induced by glucose immersion. These models were selected because rodents are widely recognized as established models for studying diabetic complications, while zebrafish represent a newer model in this field. Our goal is to (1) summarize the published findings relevant to these models, (2) identify similarities in cellular mechanisms underlying the disease progression that occur in both tissues, and (3) address the hypothesis that hyperglycemic-induced changes in retina precede or predict later complications in brain.

A PEDF peptide mimetic effectively relieves dry eye in a diabetic murine model by restoring corneal nerve, barrier, and lacrimal gland function

PURPOSE

The study investigated effectiveness of a novel PEDF peptide mimetic to alleviate dry eye-like pathologies in a Type I diabetic mouse model established using streptozotocin.

METHODS

Mice were treated topically for 3-6 weeks with Ppx (a 17-mer PEDF mimetic) 2x/day or vehicle. Corneal sensitivity, tear film, epithelial and endothelial injury were measured using Cochet-Bonnet esthesiometer, phenol red cotton thread wetting, fluorescein sodium staining, and ZO1 expression, respectively. Inflammatory and parasympathetic nerve markers and activation of the MAPK/JNK pathways in the lacrimal glands were measured.

RESULTS

Diabetic mice exhibited features of dry eye including reduced corneal sensation and tear secretion and increased corneal epithelium injury, nerve degeneration, and edema. Ppx reversed these pathologies and restored ZO1 expression and morphological integrity of the endothelium. Upregulation of IL-1β and TNFα, increased activation of P-38, JNK, and ERK, and higher levels of M3ACHR in diabetic lacrimal glands were also reversed by the peptide treatment.

CONCLUSION

The study demonstrates that topical application of a synthetic PEDF mimetic effectively alleviates diabetes-induced dry eye by restoring corneal sensitivity, tear secretion, and endothelial barrier and lacrimal gland function. These findings have significant implications for the potential treatment of dry eye using a cost-effective and reproducible approach with minimal invasiveness and no obvious side effects.

Effects of Diabetes Mellitus on Corneal Immune Cell Activation and the Development of Keratopathy

Diabetes mellitus (DM) is one of the most prevalent diseases globally, and its prevalence is rapidly increasing. Most patients with a long-term history of DM present with some degree of keratopathy (DK). Despite its high incidence, the underlying inflammatory mechanism of DK has not been elucidated yet. For further insights into the underlying immunopathologic processes, we utilized streptozotocin-induced mice to model type 1 DM (T1D) and B6.Cg-Lepob/J mice to model type 2 DM (T2D). We evaluated the animals for the development of clinical manifestations of DK. Four weeks post-induction, the total frequencies of corneal CD45+CD11b+Ly-6G- myeloid cells, with enhanced gene and protein expression levels for the proinflammatory cytokines TNF-α and IL-1β, were higher in both T1D and T2D animals. Additionally, the frequencies of myeloid cells/mm2 in the sub-basal neural plexus (SBNP) were significantly higher in T1D and T2D compared to non-diabetic mice. DK clinical manifestations were observed four weeks post-induction, including significantly lower tear production, corneal sensitivity, and epitheliopathy. Nerve density in the SBNP and intraepithelial terminal endings per 40x field were lower in both models compared to the normal controls. The findings of this study indicate that DM alters the immune quiescent state of the cornea during disease onset, which may be associated with the progressive development of the clinical manifestations of DK.

Electroacupuncture regulates the P2X7R-NLRP3 inflammatory cascade to relieve decreased sensation on ocular surface of type 2 diabetic rats with dry eye

Dry eye (DE) is a prevalent ocular surface disease in patients with type 2 diabetes (T2DM). However, current medications are ineffective against decreased sensation on the ocular surface. While electroacupuncture (EA) effectively alleviates decreased sensation on ocular surface of DE in patients with T2DM, the neuroprotective mechanism remains unclear. This study explored the pathogenesis and therapeutic targets of T2DM-associated DE through bioinformatics analysis. It further investigated the underlying mechanism by which EA improves decreased sensation on the ocular surface of DE in rats with T2DM. Bioinformatic analysis was applied to annotate the potential pathogenesis of T2DM DE. T2DM and DE was induced in male rats. Following treatment with EA and fluorometholone, comprehensive metrics were assessed. Additionally, the expression patterns of key markers were studied. Key targets such as NLRP3, Caspase-1, and NOD-like receptor signaling may be involved in the pathogenesis of T2DM DE. EA treatment improved ocular measures. Furthermore, EA potently downregulated P2X7R, NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), and Caspase-1 expression within the trigeminal ganglion and spinal trigeminal nucleus caudalis. Targeted P2X7R antagonist (A-438079) and agonist (BzATP) employed as controls to decipher the biochemistry of the therapeutic effects of EA showed an anti-inflammatory effect with A-438079, while BzATP blocked the anti-inflammatory effect of EA. EA relieved DE symptoms and attenuated inflammatory damage to sensory nerve pathways in T2DM rats with DE. These findings suggest a crucial role of EA inhibition of the P2X7R-NLRP3 inflammatory cascade to provide these benefits.

The use of sodium-glucose cotransporter 2 inhibitors and the incidence of uveitis in type 2 diabetes: a population-based cohort study

Introduction

To survey the potential correlation between the application of sodium-glucose cotransporter 2 (SGLT2) inhibitors and the incidence of uveitis in individuals with type 2 diabetes mellitus (T2DM).

Material and methods

A retrospective cohort study using the National Health Insurance Research Database (NHIRD) was conducted. The T2DM patients using SGLT2 inhibitors and those taking other anti-diabetic medications were assigned to the SGLT2 group and the control group, respectively, with a 1 : 2 ratio via the propensity score-matching (PSM) method. The major outcome in this study is the development of uveitis according to the diagnostic codes. The Cox proportional hazard regression was adopted to yield the adjusted hazard ratio (aHR) with 95% confidence interval (CI) between the groups.

Results

There were 147 and 371 new uveitis episodes in the SGLT2 and control groups after the follow-up period up to 5 years. The incidence of uveitis in the SGLT2 group (aHR = 0.736, 95% CI: 0.602-0.899, p = 0.0007) was significantly lower than that in the control group after adjusting for the effect of all the confounders. In the subgroup analyses, the SGLT2 inhibitors showed a higher correlation with low uveitis incidence in T2DM patients aged under 50 than T2DM individuals aged over 50 years (p = 0.0012), while the effect of SGLT2 inhibitors on the incidence of anterior and posterior uveitis development was similar (p = 0.7993).

Conclusions

The use of SGLT2 inhibitors could be an independent protective factor for uveitis development in T2DM population.

Rat Model of Type 2 Diabetes Mellitus Recapitulates Human Disease in the Anterior Segment of the Eye

Changes in the anterior segment of the eye due to type 2 diabetes mellitus (T2DM) are not well-characterized, in part due to the lack of a reliable animal model. This study evaluates changes in the anterior segment, including crystalline lens health, corneal endothelial cell density, aqueous humor metabolites, and ciliary body vasculature, in a rat model of T2DM compared with human eyes. Male Sprague-Dawley rats were fed a high-fat diet (45% fat) or normal diet, and rats fed the high-fat diet were injected with streptozotocin i.p. to generate a model of T2DM. Cataract formation and corneal endothelial cell density were assessed using microscopic analysis. Diabetes-related rat aqueous humor alterations were assessed using metabolomics screening. Transmission electron microscopy was used to assess qualitative ultrastructural changes ciliary process microvessels at the site of aqueous formation in the eyes of diabetic rats and humans. Eyes from the diabetic rats demonstrated cataracts, lower corneal endothelial cell densities, altered aqueous metabolites, and ciliary body ultrastructural changes, including vascular endothelial cell activation, pericyte degeneration, perivascular edema, and basement membrane reduplication. These findings recapitulated diabetic changes in human eyes. These results support the use of this model for studying ocular manifestations of T2DM and support a hypothesis postulating blood-aqueous barrier breakdown and vascular leakage at the ciliary body as a mechanism for diabetic anterior segment pathology.

Diabetic corneal neuropathy and its relation to the severity of retinopathy in patients with type 2 diabetes mellitus: an in vivo confocal microscopy study

PURPOSE

To investigate corneal neuropathy and corneal nerve alterations in type 2 diabetes mellitus (DM) patients with different diabetic retinopathy (DR) status.

METHODS

A total of 87 eyes of 87 patients with DM and 28 eyes of 28 healthy control subjects were included in the study. DM patients were further classified into 3 groups: patients without DR (NDR), patients with non-proliferative DR (NPDR), and patients with proliferative DR (PDR). PDR patients were classified into 2 groups regarding having undergone retinal argon laser photocoagulation treatment (ALP). Ocular surface disease index score (OSDI), average tear break-up time (A-BUT), corneal sensitivity and cornea nerve fiber length (CNFL), cornea nerve fiber density (CNFD), and cornea nerve branch density (CNBD) of the cornea subbasal nerve plexus (SBNP) were measured using in vivo confocal microscopy (IVCM).

RESULTS

OSDI scores increased and A-BUT decreased in DM patients compared to the control group, but no significant difference was found between DM patient groups. Corneal sensitivity decreased in DM patients who developed DR, compared to both the controls and the NDR group. CNFD and CNFL decreased in NPDR and PDR patients compared to controls. CNFD and CNBD decreased in patients who had developed PDR, compared to all three groups. All IVCM parameters decreased with DR progression.

CONCLUSION

IVCM can detect early structural corneal nerve changes in diabetic patients. The presence of DM affects ocular surface parameters, especially in long-term DM patients. Corneal sensitivity loss is increased with the presence of DR. All IVCM parameters decrease with DR development and its progression.

Research progress on ocular complications caused by type 2 diabetes mellitus and the function of tears and blepharons

The purpose of this study was to explore the related research progress of ocular complications (OCs) caused by type 2 diabetes mellitus (T2DM), tear and tarsal function, and the application of deep learning (DL) in the diagnosis of diabetes and OCs caused by it, to provide reference for the prevention and control of OCs in T2DM patients. This study reviewed the pathogenesis and treatment of diabetes retinopathy, keratopathy, dry eye disease, glaucoma, and cataract, analyzed the relationship between OCs and tear function and tarsal function, and discussed the application value of DL in the diagnosis of diabetes and OCs. Diabetes retinopathy is related to hyperglycemia, angiogenic factors, oxidative stress, hypertension, hyperlipidemia, and other factors. The increase in water content in the corneal stroma leads to corneal relaxation, loss of transparency, and elasticity, and can lead to the occurrence of corneal lesions. Dry eye syndrome is related to abnormal stability of the tear film and imbalance in neural and immune regulation. Elevated intraocular pressure, inflammatory reactions, atrophy of the optic nerve head, and damage to optic nerve fibers are the causes of glaucoma. Cataract is a common eye disease in the elderly, which is a visual disorder caused by lens opacity. Oxidative stress is an important factor in the occurrence of cataracts. In clinical practice, blood sugar control, laser therapy, and drug therapy are used to control the above eye complications. The function of tear and tarsal plate will be affected by eye diseases. Retinopathy and dry eye disease caused by diabetes will cause dysfunction of tear and tarsal plate, which will affect the eye function of patients. Furthermore, DL can automatically diagnose and classify eye diseases, automatically analyze fundus images, and accurately diagnose diabetes retinopathy, macular degeneration, and other diseases by analyzing and processing eye images and data. The treatment of T2DM is difficult and prone to OCs, which seriously threatens the normal life of patients. The occurrence of OCs is closely related to abnormal tear and tarsal function. Based on DL, clinical diagnosis and treatment of diabetes and its OCs can be carried out, which has positive application value.

Risk Factors for Corneal Endothelial Decompensation after Penetrating Keratoplasty: A Population-Based Cohort Study

(1) Background: Endothelial decompensation is a common complication after penetrating keratopathy (PK), while the risk factors for endothelial decompensation after PK have not been fully elucidated. Consequently, we aim to investigate the possible risk factors for endothelial decompensation after PK. (2) Methods: This retrospective study was conducted using the National Health Insurance Research Database (NHIRD) of Taiwan. The main outcome was the development of endothelial decompensation after PK surgery. The effects of potential risk factors were compared between the patients with endothelial decompensation and the patients without endothelial decompensation via Cox proportional hazard regression, which produced the adjusted hazard ratio (aHR) and a 95% confidence interval (CI). (3) Results: Overall, 54 patients developed endothelial decompensation after PK surgery, with a ratio of 16.12 percent. The pre-existing type 2 diabetes mellitus (T2DM) (aHR: 1.924, 95% CI: 1.257-2.533, p = 0.0095) and history of cataract surgery (aHR: 1.687, 95% CI: 1.328-2.440, p = 0.0026) were correlated with the development of endothelial decompensation. In the subgroup analysis, the correlation between a history of cataract surgery and post-PK endothelial decompensation was more prominent in patients older than 60 years compared to their younger counterparts (p = 0.0038). (4) Conclusions: Pre-existing T2DM and a history of cataract surgery are associated with a higher incidence of post-PK endothelial decompensation.

Antidiabetic Effect of Urolithin A in Cultured L6 Myotubes and Type 2 Diabetic Model KK-Ay/Ta Mice with Glucose Intolerance

Diabetes is caused by abnormal glucose metabolism, and muscle, the largest tissue in the human body, is largely involved. Urolithin A (UroA) is a major intestinal and microbial metabolite of ellagic acid and ellagitannins and is found in fruits such as strawberry and pomegranate. In this present study, we investigated the antidiabetic effects of UroA in L6 myotubes and in KK-Ay/Ta, a mouse model of type 2 diabetes (T2D). UroA treatment elevated the glucose uptake (GU) of L6 myotubes in the absence of insulin. This elevation in GU by UroA treatment was partially inhibited by the concurrent addition of LY294002, an inhibitor of phosphatidylinositol 3-kinase (PI3K) which activates Akt (PKB: protein kinase B) or Compound C, an inhibitor of 5'-adenosine monophosphate-activated protein kinase (AMPK). Moreover, UroA was found to activate both pathways of Akt and AMPK, and then to promote translocation of glucose transporter 4 (GLUT4) from the cytosol to the plasma membrane in L6 myotubes. Based on these in vitro findings, an intraperitoneal glucose tolerance test (IPGTT) was performed after the oral administration of UroA for 3 weeks to KK-Ay/Ta mice with glucose intolerance. UroA was demonstrated to alleviate glucose intolerance. These results suggest that UroA is a biofactor with antihyperglycemic effects in the T2D state.

Association of sodium-glucose cotransporter 2 inhibitors with the incidence of corneal diseases in type 2 diabetes mellitus

Sodium-glucose cotransporter 2 (SGLT2) inhibitors revealed the protective function on various systemic diseases. This study aimed to determine whether the usage of SGLT2 inhibitors associates with incidences of superficial keratopathy and infectious keratitis in type 2 diabetes mellitus (T2DM) patients. A retrospective cohort study with the usage of National Health Insurance Research Database of Taiwan was conducted. The T2DM patients were divided into the SGLT2 inhibitors and control groups according to the usage of SGLT2 inhibitors or not. The major outcomes were defined as the occurrence of superficial keratopathy and infectious keratitis. There were 766 and 1037 episodes of superficial keratopathy in the SGLT2 inhibitors and control groups and SGLT2 inhibitors group showed a significantly lower incidence of superficial keratopathy than the control group (aHR: 0.721, 95% CI: 0.656-0.791, P < 0.0001). Also, there were 166 and 251 infectious keratitis events in the SGLT2 inhibitors and control groups and patients in the SGLT2 inhibitors group revealed a significantly lower infectious keratitis incidence than those in the control group (aHR: 0.654, 95% CI: 0.537-0.796, P < 0.0001). In addition, the patients that received SGLT2 inhibitors demonstrated lower cumulative incidences of both superficial keratopathy and infectious keratitis compared to the non-SGLT2 inhibitors users (both P < 0.0001). In conclusion, the usage of SGLT2 inhibitors correlates to lower incidence of superficial keratopathy and infectious keratitis in T2DM individuals, which is more significant in patients with persistent SGLT2 inhibitors application.

Silicone oil as a corneal lubricant to reduce corneal edema and improve visualization during vitrectomy

AIM

To evaluate the efficacy and safety of silicone oil (SO) as a corneal lubricant to improve visualization during vitrectomy.

METHODS

Patients who underwent vitreoretinal surgery were divided into two groups. Group 1 was operated on with initial SO (Oxane 5700) as a corneal lubricant. Group 2 was operated on with initial lactated ringer's solution (LRS) and then replaced with SO as required. Fundus clarity was scored during the surgery. Fluorescein staining was performed to determine the damage to corneal epithelium.

RESULTS

Totally 114 eyes of 114 patients were included. Single SO use maintained a clear cornea and provided excellent visualization of surgical image. In group 1, the fundus clarity was grade 3 in 41/45 eyes and grade 2 in 4/45 eyes. In group 2, corneal edema frequently occurred after initial LRS use. The fundus clarity was grade 3 in 19/69 eyes, 2 in 37/69 eyes and 1 in 13/69 eyes (P<0.05). SO was applied in 29 eyes of initial LRS use with subsequent corneal edema, which eliminated the corneal edema in 26 eyes. Corneal fluorescein staining score in group 1 was 0 in 28 eyes, 1 in 11 eyes and 2 in 6 eyes, and 40, 20 and 9, respectively, in group 2 (all P>0.05).

CONCLUSION

The use of SO as a corneal lubricant is effective and safe for preserving and improving corneal clarity and providing clear surgical field during vitrectomy.

Prescription of glucagon-like peptide 1 agonists and risk of subsequent open-angle glaucoma in individuals with type 2 diabetes mellitus

Background: The glucagon-like peptide 1 receptor agonist (GLP-1RA) is an antidiabetic medication with vascular protection and anti-inflammatory properties. Theoretically, the use of GLP-1RA should inhibit the development of open-angle glaucoma (OAG) as both vascular damage and inflammation are associated with OAG. Therefore, our objective was to investigate the association between the application of GLP-1RA and the subsequent OAG in individuals with type 2 diabetes mellitus (T2DM). Methods: We conducted a retrospective cohort study by using data from the National Health Insurance Research Database (NHIRD) of Taiwan. Participants with T2DM were divided into those who used GLP-1RA and those who did not, forming the GLP-1RA and control groups. The primary outcome was the occurrence of OAG based on diagnostic codes. Cox proportional hazard regression was employed to calculate the adjusted hazard ratio (aHR) and 95% confidence interval (CI) for OAG. Results: 91 patients in the control group developed OAG, and 40 patients in the GLP-1RA group developed OAG. After adjustment for all covariates, the GLP-1RA group exhibited a significantly lower incidence of OAG compared with the control group (aHR: 0.712, 95% CI: 0.533-0.936. P = 0.0025). In the subgroup analyses, the association between GLP-1RA use and OAG incidence was more pronounced in patients with T2DM using GLP-1RA and aged younger than 60 years (P = 0.0438). Conclusion: The prescription of GLP-1RA is associated with a lower incidence of subsequent OAG in individuals with T2DM, and this association was more significant in patients with T2DM under the age of 60 years.

Inhibition of miR-542-3p augments autophagy to promote diabetic corneal wound healing

BACKGROUND

Autophagy has recently been shown to be critical for protecting peripheral nerve regeneration. This study explored the impact of miR-542-3p on diabetic corneal nerve regeneration and epithelial healing through the regulation of autophagy.

METHODS

A type 1 diabetes model was established in male mice through streptozotocin administration. Immunofluorescence staining of β-Tubulin III and sodium fluorescein staining were performed to observe corneal nerve fiber density and corneal epithelial healing, respectively. Western blotting, immunofluorescence and transmission electron microscopy were used to determine autophagy levels. Subconjunctival injection of RAPA and 3-MA altered autophagy levels; with them, we evaluated the role of autophagy in diabetic keratopathy. miRNA sequencing and bioinformatics analysis were performed to identify miRNA-mRNA networks with potential autophagy-regulating roles, and miR-542-3p was measured by quantitative real-time polymerase chain reaction (qRT-PCR). miR-542-3p antagomir was injected subconjunctivally to assess the role in diabetic corneal neuropathy.

RESULTS

Our data suggest that autophagy is suppressed in the diabetic corneal nerve and that activation of autophagy promotes diabetic corneal wound healing. We identified a potential autophagy-regulating miRNA-mRNA network in the diabetic trigeminal ganglion, in which miR-542-3p expression was significantly upregulated. Inhibition of miR-542-3p significantly enhanced the level of autophagy in trigeminal ganglion by upregulating ATG4D expression, thereby accelerating diabetic corneal nerve regeneration and epithelial healing.

CONCLUSIONS

Dysregulated autophagy is an important contributor to delayed diabetic corneal injury healing. Inhibiting miR-542-3p promotes diabetic corneal nerve regeneration and epithelial healing through autophagy activation by ATG4D.

Evaluation of Limbal Stem Cells in Patients With Type 2 Diabetes: An In Vivo Confocal Microscopy Study

PURPOSE

This study aimed to investigate corneal limbus changes in patients with type 2 diabetes mellitus (DM) using in vivo confocal microscopy (IVCM) and explore the correlation between their ocular manifestations and systemic status.

METHODS

Fifty-five patients with type 2 DM and 20 age-matched controls were included. The following IVCM parameters were compared between the 2 groups: palisades of Vogt (POV), corneal epithelial thickness (CET), basal cell density (BCD), subbasal nerve plexus, and dendritic cell density. All subjects underwent blood and urine sampling for laboratory analysis, including fasting blood glucose, glycated hemoglobin, total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, C-reactive protein, urinary albumin-to-creatinine ratio, urine albumin, and urine creatinine. The correlations between IVCM parameters and blood biomarkers were detected. Receiver operating characteristic curve was used for selecting the cutoff value of risk factors for corneal stem cell injury in patients with DM.

RESULTS

Compared with controls, patients with DM displayed a significant reduction of POV (superior region, P = 0.033; inferior region, P = 0.003; nasal region, P < 0.001; temporal region, P < 0.001), central CET (44.8 ± 3.6 μm vs. 51.9 ± 3.6 μm, P < 0.001), central corneal BCD (7415.5 ± 563.2 cells/mm 2 vs. 9177.9 ± 977.8 cells/mm 2 , P < 0.001), and peripheral corneal BCD (6181.3 ± 416.5 cells/mm 2 vs. 8576.3 ± 933.2 cells/mm 2 , P < 0.001). Dendritic cell density (41.0 ± 33.7 cells/mm 2 vs. 24.6 ± 7.8 cells/mm 2 , P = 0.001) was significantly higher in the DM group. The following weak correlations were shown between IVCM parameters and blood biomarkers: central corneal BCD was negatively correlated with DM duration (r = -0.3, P = 0.024), TC (r = -0.36, P = 0.007), and LDL (r = -0.39, P = 0.004). The presence of POV in the superior region was negatively correlated with TC (r = -0.34, P = 0.011) and LDL (r = -0.31, P = 0.022). Cutoff values of 1.215 mmol/L for HDL, 1.59 mmol/L for TG, or 4.75 mmol/L for TC were established to distinguish patients with a high risk from a low risk for stem cell damage.

CONCLUSIONS

Patients with type 2 DM displayed a lower positive rate of typical POV and a decrease in BCD, CET, and subbasal nerve density. The most relevant indicators for stem cell phenotypes were DM duration, TC, and LDL. Lipid status in diabetic patients could be a predictor of risk for developing corneal limbal stem cell deficiency. Further studies with larger sample sizes or basic research are needed to verify the results.

Nuclear Receptor PPARα as a Therapeutic Target in Diseases Associated with Lipid Metabolism Disorders

Lipid metabolic diseases have substantial morbidity and mortality rates, posing a significant threat to human health. PPARα, a member of the peroxisome proliferator-activated receptors (PPARs), plays a crucial role in lipid metabolism and immune regulation. Recent studies have increasingly recognized the pivotal involvement of PPARα in diverse pathological conditions. This comprehensive review aims to elucidate the multifaceted role of PPARα in metabolic diseases including liver diseases, diabetes-related diseases, age-related diseases, and cancers, shedding light on the underlying molecular mechanisms and some regulatory effects of natural/synthetic ligands of PPARα. By summarizing the latest research findings on PPARα, we aim to provide a foundation for the possible therapeutic exploitation of PPARα in lipid metabolic diseases.

The Utilization of Glucagon-like Peptide 1 Agonists and Risk of Following External Eye Diseases in Type 2 Diabetes Mellitus Individuals: A Population-Based Study

The glucagon-like peptide 1 (GLP-1) agonist showed anti-hyperglycemic and anti-inflammatory effects, which may retard the risk of external eye disease. The protective effect of GLP-1 agonist and dry eye disease (DED) was found, while the relationship between GLP-1 agonist and other corneal diseases was not clear. Herein, we aim to evaluate the association between the usage of GLP-1 agonists and the development of the following external eye disease in type 2 diabetes mellitus (T2DM) patients. A retrospective cohort study using the National Health Insurance Research Database (NHIRD) of Taiwan was conducted. The T2DM patients were divided into those with GLP-1 treatment and those without GLP-1 treatment and matched with a 1:2 ratio. The main outcomes were the development of dry eye disease (DED), superficial keratitis, and infectious keratitis. The Cox proportional hazard regression was adopted to produce the adjusted hazard ratio (aHR) with a 95% confidence interval (CI) of external eye diseases between groups. There were 115, 54, and 11 episodes of DED, superficial keratitis, and infectious keratitis in the GLP-1 group. Another 280, 168, and 31 events of DED, superficial keratitis, and infectious keratitis were recorded in the control group. The GLP-1 group demonstrated a significantly lower incidence of DED (aHR: 0.853, 95% CI: 0.668-0.989, p = 0.0356) and superficial keratitis (aHR: 0.670, 95% CI: 0.475-0.945, p = 0.0107) compared to the control group. In the subgroup analyses, the correlation of GLP-1 agonist and DED development was more prominent in patients younger than 60 years old (p = 0.0018). In conclusion, the GLP-1 agonist treatments are significantly associated with a lower incidence of subsequent DED and superficial keratitis, while the relationship was not significant between GLP-1 agonist usage and infectious keratitis.

Limbal Epithelial Stem Cells in the Diabetic Cornea

Continuous replenishment of the corneal epithelium is pivotal for maintaining optical transparency and achieving optimal visual perception. This dynamic process is driven by limbal epithelial stem cells (LESCs) located at the junction between the cornea and conjunctiva, which is otherwise known as the limbus. In patients afflicted with diabetes, hyperglycemia-induced impairments in corneal epithelial regeneration results in persistent epithelial and other defects on the ocular surface, termed diabetic keratopathy (DK), which progressively diminish vision and quality of life. Reports of delayed corneal wound healing and the reduced expression of putative stem cell markers in diabetic relative to healthy eyes suggest that the pathogenesis of DK may be associated with the abnormal activity of LESCs. However, the precise role of these cells in diabetic corneal disease is poorly understood and yet to be comprehensively explored. Herein, we review existing literature highlighting aberrant LESC activity in diabetes, focusing on factors that influence their form and function, and emerging therapies to correct these defects. The consequences of malfunctioning or depleted LESC stocks in DK and limbal stem cell deficiency (LSCD) are also discussed. These insights could be exploited to identify novel targets for improving the management of ocular surface complications that manifest in patients with diabetes.

Utilization of sodium-glucose cotransporter 2 inhibitors on dry eye disease severity in patients with type 2 diabetes mellitus

Sodium-glucose cotransporter 2 (SGLT2) inhibitors have protective effects against various systemic diseases and neoplasms. This retrospective cohort study evaluated the severity of dry eye disease (DED) in patients with type 2 diabetes mellitus (T2DM) who were treated with SGLT2 inhibitors. Data were obtained from the National Health Insurance Research Database of Taiwan. Patients with T2DM who were treated with SGLT2 inhibitors were assigned to the SGLT2 group. Each patient in the SGLT2 group was matched to two individuals with T2DM who had not used SGLT2 inhibitors, constituting the control group. The primary outcomes were the development of DED and severe DED. A diagnosis of severe DED was indicated by the usage of cyclosporine. Cox proportional hazard regression was applied to yield adjusted hazard ratios (aHR) and 95% confidence intervals (CIs). In the SGLT2 group, 1864 new DED events and 147 severe DED events were recorded. Conversely, 4367 new DED events and 392 severe DED events were recorded in the control group. The incidence (aHR: 0.858, 95% CI: 0.811-0.908, p = 0.0010) and severity (aHR: 0.652, 95% CI: 0.481-0.777, p = 0.0006) of DED were significantly lower in the SGLT2 group than the control group after adjusting for multiple covariates. In subgroup analyses, the incidence and severity of DED were significantly lower in patients younger than 60 years old who were treated with SGLT2 inhibitors than in their older counterparts (p = 0.0008 and 0.0011, respectively). In conclusion, utilization of SGLT2 inhibitors in the T2DM population could reduce both the incidence and severity of DED.

Analysis of Corneal and Lens Densitometry Changes in Patients With Type 1 Diabetes Mellitus

PURPOSE

By comparing the densitometry findings of patients with type 1 diabetes mellitus (T1DM) and the healthy group, we aimed to understand the possible changes that may occur in the cornea and lens in those with diabetes mellitus (DM).

DESIGN

Prospective, cross-sectional study.

METHODS

A total of 60 eyes of 60 patients with T1DM and 101 eyes of 101 healthy subjects were included in this study. A complete ophthalmologic evaluation was performed in all participants. Scheimpflug tomography was performed to record the corneal and lens densitometry and other tomographic data. Mean glycosylated hemoglobin (HbA1c) and mean DM duration were recorded.

RESULTS

The mean age of the patients with T1DM and patients in the control group was 29.93 ± 8.56 years and 27.27 ± 1 4.96 years, respectively. The mean HbA1c was 8.43 ± 1.92, and the mean DM duration was 14.10 ± 7.77 years. Corneal densitometry (CD) values were significantly higher in the 0- to 2-mm zone in all layers and in the anterior and central 6- to 10-mm zone in the diabetic group (P = .03, P = .018, P = .001, P = .000, P = .004). The mean crystalline lens densitometry was higher in the T1DM group (P = .129). There were positive correlations between DM duration and CD in the anterior 0- to 2-mm (P = .043), central 6- to 10-mm (P = .016), posterior 6- to 10-mm (P = .022), and posterior 10- to 12-mm zone (P = .043).

CONCLUSIONS

CD values were significantly higher in the diabetic group. Diabetes duration and HbA1c values showed correlations with densitometry especially in the 6- to 10-mm corneal zone. Evaluation of the cornea with optical densitometry will be useful in the early diagnosis and follow-up of clinical structural and functional changes in the cornea.

Mass cytometry reveals the corneal immune cell changes at single cell level in diabetic mice

Introduction

Diabetic ocular complications include sight-threatening consequences and decreased corneal sensitivity, characterized by decreased tear production, corneal sensitivity and delayed corneal epithelial wound healing. The pathogenesis of diabetic corneal disorders remains largely unknown. Growing evidence implies the participation of immune cells in the development of diabetic corneal diseases. Nonetheless, the immunological changes that result in diabetic corneal problems are largely unknown.

Methods

Mass cytometry by time of flight (CyTOF) was used to investigate immune cell cluster alterations associated with diabetic corneal disorders. CyTOF test was performed on corneal cells at a single level from 21-week-old diabetic (db/db) and non-diabetic (db/m) mice. A panel of 41 immune-related markers monitored different immune cell types in diabetic corneas. To investigate the proportion of each immune cell subpopulation, an unsupervised clustering method was employed, and T-distributed stochastic neighbor embedding was used to visualize the distinctions between different immune cell subsets.

Results

Through CyTOF test, we identified 10 immune cell subsets in the corneal tissues. In a novel way, we discovered significant immune alterations in diabetic corneas, including pronounced alterations in T cells and myeloid cell subgroups in diabetic corneas linked to potential biomarkers, including CD103, CCR2, SiglecF, Ly6G, and CD172a. Comprehensive immunological profiling indicated remarkable changes in the immune microenvironment in diabetic corneas, characterized by a notable decrease in CD103+CD8+ tissue-resident memory T (TRM) cells and Tregs, as well as a dramatic increase of γδT cells and subsets of CD11b+Ly6G+ myeloid-derived suppressor cells (MDSCs).

Conclusion

CyTOF analysis revealed significant alterations in the immune microenvironment during the development of diabetic corneal complications. This study mapped the immune microenvironment landscape of type 2 diabetic corneas, providing a fundamental understanding of immune-driven diabetic corneal disorders.

rhFGF-21 accelerates corneal epithelial wound healing through the attenuation of oxidative stress and inflammatory mediators in diabetic mice

Diabetic keratopathy, commonly associated with a hyperactive inflammatory response, is one of the most common eye complications of diabetes. The peptide hormone fibroblast growth factor-21 (FGF-21) has been demonstrated to have anti-inflammatory and antioxidant properties. However, whether administration of recombinant human (rh) FGF-21 can potentially regulate diabetic keratopathy is still unknown. Therefore, in this work, we investigated the role of rhFGF-21 in the modulation of corneal epithelial wound healing, the inflammation response, and oxidative stress using type 1 diabetic mice and high glucose-treated human corneal epithelial cells. Our experimental results indicated that the application of rhFGF-21 contributed to the enhancement of epithelial wound healing. This treatment also led to advancements in tear production and reduction in corneal edema. Moreover, there was a notable reduction in the levels of proinflammatory cytokines such as TNF-α, IL-6, IL-1β, MCP-1, IFN-γ, MMP-2, and MMP-9 in both diabetic mouse corneal epithelium and human corneal epithelial cells treated with high glucose. Furthermore, we found rhFGF-21 treatment inhibited reactive oxygen species production and increased levels of anti-inflammatory molecules IL-10 and SOD-1, which suggests that FGF-21 has a protective role in diabetic corneal epithelial healing by increasing the antioxidant capacity and reducing the release of inflammatory mediators and matrix metalloproteinases. Therefore, we propose that administration of FGF-21 may represent a potential treatment for diabetic keratopathy.

Accommodative disorders in non-presbyopic subjects with type 1 diabetes without retinopathy: A comparative, cross-sectional study

PURPOSE

The purpose of this study was to assess accommodative function in non-presbyopic individuals diagnosed with type 1 diabetes (T1D) without any signs of retinopathy, to determine the existence of possible accommodative disorders related to this disease, and to determine the influence of T1D duration and glycosylated haemoglobin values on accommodative function.

METHODS

This comparative, cross-sectional study included 60 participants between 11 and 39 years old, 30 with T1D and 30 controls, with no previous eye surgery, ocular disease or medication that could affect the results of the visual examination. Amplitude of accommodation (AA), negative and positive relative accommodation (NRA and PRA), accommodative response (AR) and accommodative facility (AF) were assessed using the tests that showed the highest repeatability. Participants were classified based on normative values into 'insufficiency, excess or normal results', and a diagnosis of accommodative disorders (accommodative insufficiency, accommodative infacility and accommodative excess) was made.

RESULTS

Participants with T1D had statistically significant lower AA and AF and higher NRA values than the controls. Furthermore, AA was significantly and inversely correlated with age and the duration of diabetes; however, AF and NRA were only correlated with disease duration. In the classification by accommodative variables, a higher percentage of 'insufficiency values' was observed in the T1D group (50%) than in the control group (6%; p < 0.001). In terms of accommodative disorders, accommodative infacility was the most prevalent (15%), followed by accommodative insufficiency (10%).

CONCLUSIONS

Our findings indicate that T1D affects most accommodative parameters, with accommodative insufficiency being associated with this disease.

Lithium chloride promotes diabetic corneal epithelial wound healing by activating the Wnt/β‑catenin signaling pathway

Corneal epithelial abnormality is a common manifestation of diabetic keratopathy and leads to delayed epithelial wound healing. The Wnt/β-catenin signaling pathway participates in the development, differentiation and stratification of corneal epithelial cells. The present study compared the expression of Wnt/β-catenin signaling pathway related factors, including Wnt7a, β-catenin, cyclin D1 and phosphorylated (p-) glycogen synthase kinase 3 β (Gsk3b) between normal and diabetic mouse corneas, by reverse transcription-quantitative PCR, western blotting and immunofluorescence staining. It was found that the expression of the Wnt/β-catenin signaling pathway related factors was downregulated in diabetic corneas. Upon corneal epithelium scraping, the wound healing rate was significantly increased in diabetic mice after topical treatment with lithium chloride. After further investigation, significantly upregulated levels of Wnt7a, β-catenin, cyclin D1 and p-Gsk3b were found in the diabetic group 24 h after treatment, accompanied by β-catenin nuclear translocation observed by immunofluorescence staining. These results suggest that active Wnt/β-catenin pathway can promote diabetic corneal epithelial wound healing.

Comparison of Light-Based Devices in the Treatment of Meibomian Gland Dysfunction

PURPOSE

To compare different light-based devices, namely, intense pulsed light (IPL) and IPL with low-level light therapy (LLLT), in the treatment of meibomian gland dysfunction (MGD).

METHODS

This was a prospective, observational study that included patients with MGD. Group 1 included 58 eyes treated with IPL (eye-light®, Espansione Marketing S.p.A., Bologna, Italy), followed by LLLT (my-mask®, Espansione Marketing S.p.A., Bologna, Italy); Group 2 included 60 eyes treated with IPL (E>Eye®, E-Swin, Houdan, France); and Group 3 included 58 eyes treated with IPL (Thermaeye Plus®, OptiMed, Sydney, Australia). The presence of symptoms (Ocular Surface Disease Index (OSDI)) and ocular surface changes were evaluated at baseline, three weeks, and six months after treatment.

RESULTS

At week three, there was an improvement in the OSDI in all groups (p<0.001), without differences among them (p=0.339). The lipid layer thickness (LLT) increased in Groups 1 and 2 (p<0.001), with a similar variation (p=0.144). Patients with superior OSDI and lower LLT at baseline had the greatest improvement in the respective parameters (p<0.001). The basal tear flow increased in Group 1 (p=0.012). Corneal staining (CS) significantly decreased in Groups 2 (p<0.001) and 3 (p<0.001). At six months, compared to three weeks, there was further improvement in the OSDI (p<0.001) and the LLT (p=0.007), in Group 1, and an increase in the presence of CS in Group 3 (p=0.011).

CONCLUSION

IPL treatment led to a sustained decrease in patients' symptoms, even after six months. Different IPL devices seem to have different beneficial effects. Adding LLLT to IPL appears to have an additional long-term beneficial effect as well as positive effects on the lacrimal gland.

The Autoimmune Rheumatic Disease Related Dry Eye and Its Association with Retinopathy

Dry eye disease is a chronic disease of the ocular surface characterized by abnormal tear film composition, tear film instability, and ocular surface inflammation, affecting 5% to 50% of the population worldwide. Autoimmune rheumatic diseases (ARDs) are systemic disorders with multi-organ involvement, including the eye, and play a significant role in dry eye. To date, most studies have focused on Sjögren's syndrome (one of the ARDs) since it manifests as two of the most common symptoms-dry eyes and a dry mouth-and attracts physicians to explore the relationship between dry eye and ARDs. Many patients complained of dry eye related symptoms before they were diagnosed with ARDs, and ocular surface malaise is a sensitive indicator of the severity of ARDs. In addition, ARD related dry eye is also associated with some retinal diseases directly or indirectly, which are described in this review. This review also summarizes the incidence, epidemiological characteristics, pathogenesis, and accompanying ocular lesions of ARD's related dry eye, emphasizing the potential role of dry eye in recognition and monitoring among ARDs patients.

Evaluation and comparison of subjective and objective anterior ocular surface damage in patients with type 2 diabetes mellitus and dry eye disease

PURPOSE

To evaluate anterior ocular surface damage in patients with type 2 diabetes mellitus and dry eye disease in comparison to non-diabetic controls based on conjunctival impression cytology, objective scales (Efron, Oxford) and OSDI, to correlate vision-related quality of life with grades of squamous metaplasia in T2DM patients suffering from DED.

METHODS

All participants underwent complete ophthalmologic examination including Shirmer test, TBUT, conjunctival/corneal staining (Oxford scheme), evaluation of conjunctival redness (Efron grading scale), and conjunctival impression cytology (Nelson's scale). The OSDI questionnaire was completed by both groups of patients to assess severity of DED and QoL.

RESULTS

Squamous metaplasia was observed in 94% of the study group and 19.3% of controls (p = 0.0000). Based on the OSDI scores, 73.5% of patients reported mild DED and 26.5% suffered from moderate DED in the study group. The mean OSDI score for the study group with Nelson's grade 2 was 18 ± 3.52 and 20.8 ± 4.68 for Nelson's grade 3, respectively (p = 0.0745). Hence, no significant difference in QoL between grade 2 and grade 3 of squamous metaplasia was observed in patients of the study group.

CONCLUSION

Impression cytology is a reliable minimally invasive tool for an accurate evaluation of the ocular surface damage in patients with DED and type 2 diabetes mellitus. Severe squamous metaplasia (Nelson's grade 3) was observed in 29.4% (10/34) of T2DM patients. In contrast, it was not detected in the control group (p = 0.0032). The absence of goblet cells in T2DM patients nether significantly reduces QoL nor contributes to the subjective DED severity (OSDI) due to complex pathways leading to DED. Thus, diagnosis of DED severity should not be solely based on subjective symptoms in this population.

Activation of Conjunctiva-Associated Lymphoid Tissue in Diabetic Patients

PURPOSE

To evaluate changes in conjunctiva-associated lymphoid tissues (CALTs) in patients with type 2 diabetic mellitus (T2DM).

METHODS

Thirty-two patients with T2DM and 32 healthy volunteers underwent comprehensive examinations. In vivo confocal microscopy and Image J were used to observe and evaluate the patients' CALT-related parameters. Conjunctival impression cytology (CIC) samples of the tarsal conjunctiva were collected from the patients, and CD4+ and CD8+ cells were evaluated by immunofluorescence staining.

RESULTS

The diabetes group showed higher diffuse lymphocyte density(p < .001), follicular density(p < .001) and parafollicular lymphocyte density(p < .001). The percentages of CD4+ cells (p < .001) and CD8+ cells (p < .001) in the diabetes group were higher than those in the control group. CALT-related parameters of the diabetic patients with diabetic retinopathy showed higher degrees of activation than those of the diabetic patients without diabetic retinopathy.

CONCLUSIONS

CALT activation is observed in patients with T2DM, and the activation is more obvious in patients with diabetic retinopathy.

TRIAL REGISTRATION NUMBER

Retrospectively registered, ChiCTR2100046030.

Corneal dendritic cells in diabetes mellitus: A narrative review

Diabetes mellitus is a global public health problem with both macrovascular and microvascular complications, such as diabetic corneal neuropathy (DCN). Using in-vivo confocal microscopy, corneal nerve changes in DCN patients can be examined. Additionally, changes in the morphology and quantity of corneal dendritic cells (DCs) in diabetic corneas have also been observed. DCs are bone marrow-derived antigen-presenting cells that serve both immunological and non-immunological roles in human corneas. However, the role and pathogenesis of corneal DC in diabetic corneas have not been well understood. In this article, we provide a comprehensive review of both animal and clinical studies that report changes in DCs, including the DC density, maturation stages, as well as relationships between the corneal DCs, corneal nerves, and corneal epithelium, in diabetic corneas. We have also discussed the associations between the changes in corneal DCs and various clinical or imaging parameters, including age, corneal nerve status, and blood metabolic parameters. Such information would provide valuable insight into the development of diagnostic, preventive, and therapeutic strategies for DM-associated ocular surface complications.

Keeping an eye on the diabetic foot: The connection between diabetic eye disease and wound healing in the lower extremity

Diabetic eye disease is strongly associated with the development of diabetic foot ulcers (DFUs). DFUs are a common and significant complication of diabetes mellitus (DM) that arise from a combination of micro- and macrovascular compromise. Hyperglycemia and associated metabolic dysfunction in DM lead to impaired wound healing, immune dysregulation, peripheral vascular disease, and diabetic neuropathy that predisposes the lower extremities to repetitive injury and progressive tissue damage that may ultimately necessitate amputation. Diabetic retinopathy (DR) is caused by cumulative damage to the retinal mic-rovasculature from hyperglycemia and other diabetes-associated factors. The severity of DR is closely associated with the development of DFUs and the need for lower extremity revascularization procedures and/or amputation. Like the lower extremity, the eye may also suffer end-organ damage from macrovascular compromise in the form of cranial neuropathies that impair its motility, cause optic neuropathy, or result in partial or complete blindness. Additionally, poor perfusion of the eye can cause ischemic retinopathy leading to the development of proliferative diabetic retinopathy or neovascular glaucoma, both serious, vision-threatening conditions. Finally, diabetic corneal ulcers and DFUs share many aspects of impaired wound healing resulting from neurovascular, sensory, and immunologic compromise. Notably, alterations in serum biomarkers, such as hemoglobin A1c, ceruloplasmin, creatinine, low-density lipoprotein, and high-density lipoprotein, are associated with both DR and DFUs. Monitoring these parameters can aid in prognosticating long-term outcomes and shed light on shared pathogenic mechanisms that lead to end-organ damage. The frequent co-occurrence of diabetic eye and foot problems mandate that patients affected by either condition undergo reciprocal comprehensive eye and foot evaluations in addition to optimizing diabetes management.

Tear film layers and meibomian gland assessment in patients with type 1 diabetes mellitus using a noninvasive ocular surface analyzer: a cross-sectional case–control study

Purpose

To assess the tear film layers and Meibomian glands by a noninvasive ocular surface analyzer in patients with and without type 1 diabetes mellitus (T1DM).

Methods

Eighty-eight participants were enrolled in this study: 44 patients with T1DM without diabetic retinopathy, and 44 patients as a control group, between 18 and 49 years old. Limbal and bulbar redness classification, lipid layer thickness (LLT), tear meniscus height (TMH), first and mean noninvasive tear break-up time (FNIBUT and MNIBUT, respectively), and Meibomian glands loss (MGL) were assessment through the ICP Ocular Surface Analyzer (OSA). Schirmer’s I test (SIT), the fluorescein tear break-up time test (TFBUT), OSDI and SPEED questionnaires, and percentage of glycosylated hemoglobin (HbA1c) were also tested.

Results

The T1DM group showed higher limbal and bulbar redness (p = 0.010) and lower LLT (p < 0.001), TMH (p < 0.001), FNIBUT (p < 0.001), MNIBUT (p < 0.001), SIT (p = 0.001), and TFBUT (p < 0.001) than the control group. A higher percentage of MGL was found in the T1DM group in the upper (p = 0.097) and lower (p < 0.001) eyelids. No significant differences were found in dry eye symptoms across the OSDI and SPEED questionnaires between the two groups.

Conclusion

Patients with T1DM without signs of retinopathy showed involvement of the mucoaqueous and lipid layers of the tear film, as well as a higher percentage of MGL, using a noninvasive analyzer. Dry eye disease in people with T1DM cannot be ruled out by anamnesis and subjective symptom questionnaires alone; therefore, these patients should undergo regular anterior pole examinations.

AAV2/9-mediated gene transfer into murine lacrimal gland leads to a long-term targeted tear film modification

Corneal blindness is the fourth leading cause of blindness worldwide. Since corneal epithelium is constantly renewed, non-integrative gene transfer cannot be used to treat corneal diseases. In many of these diseases, the tear film is defective. Tears are a complex biological fluid secreted by the lacrimal apparatus. Their composition is modulated according to the context. After a corneal wound, the lacrimal gland secretes reflex tears, which contain growth factors supporting the wound healing process. In various pathological contexts, the tear composition can support neither corneal homeostasis nor wound healing. Here, we propose to use the lacrimal gland as bioreactor to produce and secrete specific factors supporting corneal physiology. In this study, we use an AAV2/9-mediated gene transfer to supplement the tear film. First, we demonstrate that a single injection of AAV2/9 is sufficient to transduce all epithelial cell types of the lacrimal gland efficiently and widely. Second, we detect no adverse effect after AAV2/9-mediated nerve growth factor expression in the lacrimal gland. Only a transitory increase in tear flow is measured. Remarkably, AAV2/9 induces an important and long-lasting secretion of this growth factor in the tear film. Altogether, our findings provide a new clinically applicable approach to tackle corneal blindness.

The Extracts of Dendrobium Alleviate Dry Eye Disease in Rat Model by Regulating Aquaporin Expression and MAPKs/NF-κB Signalling

Dry eye is one of the most common ocular surface diseases caused by tear film instability and ocular surface damage due to an abnormal quality or quantity of tears. Inflammatory factors can initiate relevant transduction signalling pathways and trigger the inflammatory cascade response, resulting in ocular surface inflammation. It has been shown that the active ingredients in Dendrobium, such as polysaccharides, alkaloids and phenols, have anti-inflammatory, anti-tumour and immunity-boosting effects, and Dendrobium officinale extract can improve glandular secretion function, increase salivary secretion and increase the expression level of water channel protein in salivary glands in patients with dry eye syndromes. We investigated the in vitro cytoprotective effect of Dendrobium extracts in sodium chloride induced hyperosmotic conditions in human cornea keratocytes (HKs). Results showed that Dendrobium officinale Kimura et Migo water extract (DOW) and Dendrobium loddigesii Rolfe water extract (DLW) could upregulate the expression of aquaporins (AQP)5 protein, thus exerting a repairing effect by promoting cell migration. Furthermore, oral administration of DOW and DLW enhanced tear production in rats and exerted a protective effect on ocular surface damage. DOW and DLW could upregulate the expression of AQP5 and mucin (muc)5ac proteins in the lacrimal gland and reduce the inflammatory response. DOW and DLW inhibited the activation of the corresponding mitogen-activated protein kinases (MAPK) and NF-KB pathway, thereby playing a role in improving dry eye symptoms. This study provides a new perspective on dry eye treatment, and DOW and DLW may be potential therapeutic agents for dry eye.

Chronic Hyperglycemia Compromises Mitochondrial Function in Corneal Epithelial Cells: Implications for the Diabetic Cornea

Mitochondrial dysfunction is a major pathophysiological event leading to the onset of diabetic complications. This study investigated the temporal effects of hyperglycemia on mitochondrial metabolism in corneal epithelial cells. To accomplish this, human telomerase-immortalized corneal epithelial cells were cultured in a defined growth medium containing 6 mM glucose. To simulate hyperglycemia, cells were cultured in a medium containing 25 mM D-glucose, and control cells were cultured in mannitol. Using metabolic flux analysis, there was a hyperosmolar-mediated increase in mitochondrial respiration after 24 h. By day 5, there was a decrease in spare respiratory capacity in cells subject to high glucose that remained suppressed throughout the 14-day period. Although respiration remained high through day 9, glycolysis was decreased. Mitochondrial respiration was decreased by day 14. This was accompanied by the restoration of glycolysis to normoglycemic levels. These changes paralleled a decrease in mitochondrial polarization and cell cycle arrest. Together, these data show that chronic but not acute hyperglycemic stress leads to mitochondrial dysfunction. Moreover, the hyperglycemia-induced loss of spare respiratory capacity reduces the ability of corneal epithelial cells to respond to subsequent stress. Compromised mitochondrial function represents a previously unexplored mechanism that likely contributes to corneal complications in diabetes.