Hyperglycemia induces corneal endothelial dysfunction through attenuating mitophagy

Demographic and Systemic Risk Factors for Persistent Corneal Edema Following Cataract Surgery in Patients With and Without Diabetes

PURPOSE

To identify risk factors associated with the development of corneal edema (CE) and the need for corneal transplantation following cataract surgery.

DESIGN

Retrospective cohort study.

METHODS SETTING

Nation-wide sample of Medicare beneficiaries from 2011-2015.

STUDY POPULATION

Medicare beneficiaries aged over 65 years who received cataract surgery between 2011-2014 with at least 1 year of continuous follow-up. Data was retrieved from the Denominator and Physician Supplier Part B file from the Center for Medicare and Medicaid Services.

MAIN OUTCOME(S) AND MEASURE(S)

The main outcome was the association between demographic characteristics (e.g., age, sex, race/ethnicity) and systemic factors including diabetes status, hypertension, and tobacco use on the incidence of CE and the subsequent need for corneal transplantation following cataract surgery.

RESULTS

Among 187,746 beneficiaries, 67,734 had diabetes and 120,012 did not. Beneficiaries with diabetes were more likely to develop CE compared to those without (Odds ratio [OR] 1.19, 95% Confidence Interval [CI] [1.02-1.40]). Compared to those aged 65-74, beneficiaries aged 75-84 and over 85 were more likely to develop CE (OR 1.29 [1.09-1.52]) and OR 1.96 [1.55-2.46], respectively). Asian (OR 2.42 [1.66-3.40]), Hispanic (OR 2.60 [1.73-3.74]), and North American Native (OR 3.59 [1.78-6.39]) race was associated with increased likelihood of developing CE. North American Native beneficiaries had higher risk of requiring corneal transplantation compared to White beneficiaries (OR 9.30 [2.26-25.31]). Female sex decreased likelihood of requiring corneal transplantation post-operatively (OR 0.56 [0.36-0.87]). Amongst those with diabetes, the presence of proliferative diabetic retinopathy increased the likelihood of developing CE (OR 1.94 [1.05-3.39]).

CONCLUSION

Older age, diabetes, and non-White race elevate the risk of CE following cataract surgery, with race incurring the highest risk. Further research is needed to understand the factors underlying the significantly increased risk of CE in racial and ethnic minorities within the United States.

Sleep deprivation induces corneal endothelial dysfunction by downregulating Bmal1

BACKGROUND

Sleep deprivation (SD) is a common public health problem that contributes to various physiological disorders and increases the risk of ocular diseases. However, whether sleep loss can damage corneal endothelial function remains unclear. This study aimed to determine the effect and possible mechanism of SD on the corneal endothelium.

METHODS

Male C57BL/6J mice were subjected to establish SD models. After 10 days, quantitative RT-PCR (qRT-PCR) and western blot or immunostaining for the expression levels of zonula occludens-1 (ZO-1), ATPase Na+/K + transporting subunit alpha 1 (Atp1a1), and core clock genes in the corneal endothelium were evaluated. Reactive oxygen species staining and mitochondrial abundance characterized the mitochondrial function. The regulatory role of Bmal1 was confirmed by specifically knocking down or overexpressing basic helix-loop-helix ARNT like 1 protein (Bmal1) in vivo. In vitro, a mitochondrial stress test was conducted on cultured human corneal endothelial cells upon Bmal1 knockdown.

RESULTS

SD damaged the barrier and pump functions of mouse corneal endothelium, accompanied by mitochondrial dysfunction. Interestingly, SD dramatically downregulated the core clock gene Bmal1 expression level. Bmal1 knockdown disrupted corneal endothelial function, while overexpression of Bmal1 ameliorated the dysfunction induced by SD. Mitochondrial bioenergetic deficiency mediated by Bmal1 was an underlying mechanism for SD induced corneal endothelial dysfunction.

CONCLUSION

The downregulation of Bmal1 expression caused by SD led to corneal endothelial dysfunction via impairing mitochondrial bioenergetics. Our findings offered insight into how SD impairs the physiological function of the corneal endothelium and expanded the understanding of sleep loss leading to ocular diseases.

Early effects of intravitreal anti-VEGF agents on cornea and visual acuity in patients with diabetic retinopathy

PURPOSE

This study aimed to investigate the early effects of intravitreal anti-vascular endothelial growth factor (anti-VEGF) agents on the cornea and visual acuity in patients with diabetic retinopathy (DR).

METHODS

This retrospective study enrolled patients who were administered conbercept or ranibizumab to treat DR. Fundus photograph, fluorescein angiograph, and optical coherence tomography were preoperatively performed. The patients were classified into two groups: nonproliferative DR (NPDR) and PDR. Best-corrected visual acuity (BCVA), specular microscopy, central corneal thickness (CCT), and intraocular pressure were obtained before injection and at 1 day and 7 days after injection. The effects of anti-VEGF agents on BCVA and CCT were compared between the groups receiving conbercept and ranibizumab and between NPDR and PDR eyes.

RESULTS

A total 38 eyes (30 patients) were enrolled in this study. Twenty-one eyes received conbercept, and 17 eyes received ranibizumab. Twenty eyes were classified as NPDR and 18 eyes as PDR. No significant differences were found between the groups receiving conbercept and ranibizumab in the increase in BCVA nor in the increase of CCT at 1 day and 7 days after injection. As compared with NPDR eyes, PDR eyes demonstrated a significantly greater increase in CCT (-5.3 ± 3.7 vs. 6.5 ± 2.9 μm, P = 0.02 < 0.05) but not in BCVA (P = 0.33) at 1 day after injection. At 7 days after injection, no significant differences were found in the increase in BCVA nor in the increase of CCT between NPDR eyes and PDR eyes.

CONCLUSION

Intravitreal administration of anti-VEGF agents could cause a small but significant greater increase in CCT in PDR than in NPDR eyes in the early period. In patients with DR, no significant difference was found between conbercept and ranibizumab in the early effects on the visual acuity nor in the cornea.

Dendrobium officinale polysaccharide decreases podocyte injury in diabetic nephropathy by regulating IRS-1/AKT signal and promoting mitophagy

BACKGROUNDS

High glucose (HG) caused oxidative stress and mitochondrial dysfunction, resulting in insulin resistance in podocytes, a key mechanism of diabetic nephropathy. Dendrobium officinale polysaccharide (DOP) was able to improve insulin resistance and antioxidant capability.

OBJECTIVE

The purpose of this study is to explore the mechanism by which DOP decreases the podocyte injury induced by HG.

METHODS

MPC5 cells were treated with HG, DOP, and IRS-1/2 inhibitor NT157. Afterwards, glucose consumption, generations of ROS and MDA were measured using the detection kits. Mitophagy was monitored using both MtphagTracyker and LysoTracker. The mitochondrial membrane potential was evaluated by JC-1 staining. DOP was also used in a mouse model of diabetes, with the measurements of urine albumin, blood creatinine and blood urea nitrogen.

RESULTS

Treatment with DOP suppressed the HG-induced reduction of glucose consumption, the phosphorylation of IRS-1 (phospho Y632), AKT (phospho Ser473 and Thr308) and Nephrin. In addition, HG-induced augment of ROS and MDA, formation of γ-H2A.X foci and translocation of AKT to nucleus were inhibited by DOP. DOP enhanced mitophagy, which was associated with decreased mitochondrial membrane potential and ROS production. DOP conferred protective effect on podocyte in the diabetic mouse by reducing the albumin/creatinine ratio and blood urea nitrogen, and restoring Nephrin expression in podocytes.

CONCLUSIONS

DOP alleviates HG-induced podocyte injuryby regulating IRS-1/AKT signal and promoting mitophagy.

Pseudomonas aeruginosa-induced mitochondrial dysfunction inhibits proinflammatory cytokine secretion and enhances cytotoxicity in mouse macrophages in a reactive oxygen species (ROS)-dependent way

随着铜绿假单胞菌（铜绿）的耐药性逐年增强，铜绿感染已经成为公共医疗卫生的重点关注问题。线粒体自噬及其介导的线粒体功能障碍在多种细菌感染中已被报道，但线粒体功能障碍在宿主调控铜绿感染中的作用尚不明确。因此，本研究建立铜绿刺激小鼠巨噬细胞感染模型和小鼠急性铜绿感染模型，探讨铜绿是否通过诱导线粒体自噬改变线粒体功能，进而影响宿主免疫炎症反应和细胞毒性，并通过监测生存率和肺组织病理学变化进一步确定线粒体自噬在小鼠铜绿体内感染模型中的作用。结果表明，铜绿引起小鼠腹腔巨噬细胞线粒体功能障碍，并通过线粒体自噬途径清除铜绿刺激引起的活性氧（ROS）累积，从而抑制铜绿引起的促炎性细胞因子分泌并增强细胞毒性。体内实验进一步确认线粒体自噬在铜绿体内感染中的作用。

The roles of autophagy and mitophagy in corneal pathology: current knowledge and future perspectives

The cornea is the clear dome that covers the front portion of the globe. The primary functions of the cornea are to promote the refraction of light and to protect the eye from invading pathogens, both of which are essential for the preservation of vision. Homeostasis of each cellular layer of the cornea requires the orchestration of multiple processes, including the ability to respond to stress. One mechanism whereby cells respond to stress is autophagy, or the process of "self-eating." Autophagy functions to clear damaged proteins and organelles. During nutrient deprivation, amino acids released from protein breakdown via autophagy are used as a fuel source. Mitophagy, a selective form of autophagy, functions to clear damaged mitochondria. Thus, autophagy and mitophagy are important intracellular degradative processes that sustain tissue homeostasis. Importantly, the inhibition or excessive activation of these processes result in deleterious effects on the cell. In the eye, impairment or inhibition of these mechanisms have been associated with corneal disease, degenerations, and dystrophies. This review summarizes the current body of knowledge on autophagy and mitophagy at all layers in the cornea in both non-infectious and infectious corneal disease, dystrophies, and degenerations. It further highlights the critical gaps in our understanding of mitochondrial dysfunction, with implications for novel therapeutics in clinical practice.

Mitochondrial dysfunction in vascular endothelial cells and its role in atherosclerosis

The mitochondria are essential organelles that generate large amounts of ATP via the electron transport chain (ECT). Mitochondrial dysfunction causes reactive oxygen species accumulation, energy stress, and cell death. Endothelial mitochondrial dysfunction is an important factor causing abnormal function of the endothelium, which plays a central role during atherosclerosis development. Atherosclerosis-related risk factors, including high glucose levels, hypertension, ischemia, hypoxia, and diabetes, promote mitochondrial dysfunction in endothelial cells. This review summarizes the physiological and pathophysiological roles of endothelial mitochondria in endothelial function and atherosclerosis.

Mechanistic investigations of diabetic ocular surface diseases

With the global prevalence of diabetes mellitus over recent decades, more patients suffered from various diabetic complications, including diabetic ocular surface diseases that may seriously affect the quality of life and even vision sight. The major diabetic ocular surface diseases include diabetic keratopathy and dry eye. Diabetic keratopathy is characterized with the delayed corneal epithelial wound healing, reduced corneal nerve density, decreased corneal sensation and feeling of burning or dryness. Diabetic dry eye is manifested as the reduction of tear secretion accompanied with the ocular discomfort. The early clinical symptoms include dry eye and corneal nerve degeneration, suggesting the early diagnosis should be focused on the examination of confocal microscopy and dry eye symptoms. The pathogenesis of diabetic keratopathy involves the accumulation of advanced glycation end-products, impaired neurotrophic innervations and limbal stem cell function, and dysregulated growth factor signaling, and inflammation alterations. Diabetic dry eye may be associated with the abnormal mitochondrial metabolism of lacrimal gland caused by the overactivation of sympathetic nervous system. Considering the important roles of the dense innervations in the homeostatic maintenance of cornea and lacrimal gland, further studies on the neuroepithelial and neuroimmune interactions will reveal the predominant pathogenic mechanisms and develop the targeting intervention strategies of diabetic ocular surface complications.

The effects of acute angle closure crisis on corneal endothelial cells in patients with type 2 diabetes mellitus

OBJECTIVE

This study investigated the effects of acute angle closure crisis (AACC) on the corneal endothelial cells in patients with type 2 diabetes mellitus (DM) to identify the factors that cause corneal endothelial cell injury.

METHODS

We examined 154 patients who visited Qingdao Eye Hospital for AACC in one eye (154 eyes; 28 men and 126 women; mean age of 68 ± 8 years). We divided the participants into non-DM, DM well-control, and DM poor-control groups, with the unaffected eyes used as controls. Each participant was evaluated at the hospital while under AACC. We measured the relevant index and corneal parameters of the participants for statistical analysis.

RESULTS

There were significant statistical differences in corneal parameters among the three groups. The decreased levels of central endothelial cell density (CD) and the percentage of hexagonal cells (6A) were statistically relevant among the groups (P<0.05). The AACC duration was correlated with CD loss rate among the groups (P<0.05). The DM duration was correlated with CD loss rate in the DM well-control group. Compared with the non-DM group, the level of 6A decreased more significantly in the DM group after AACC (P<0.05). The AACC duration in the DM well-control group was significantly shorter than in the non-DM and DM poor-control groups (P<0.001). The DM poor-control group showed significantly worse visual acuity when compared with the other groups (P<0.05).

CONCLUSIONS

DM may impact the functional status of corneal endothelial cells. AACC can worsen the corneal endothelium damage in patients with DM. Blood glucose levels and the duration of intraocular hypertension are closely related to the severity of corneal endothelial injury.