Too sweet: Problems of protein glycation in the eye

Comprehensive bioinformatics analysis of metabolism‑related microRNAs in high myopia in young and old adults with age‑related cataracts

High myopia and age‑related cataracts are prevalent ocular disorders that compromise visual acuity. The molecular mechanisms underlying these conditions remain largely unclear. Here, microRNA (miRNA or miR) sequencing was performed on aqueous humor samples obtained from individuals with age‑related cataracts and high myopia (AH, n=9), young patients with high myopia (YH, n=9) and a control group of elderly patients with age‑related cataracts, matched in terms of sex and age (AN, n=9). miRNA sequencing and differential expression were performed. Intersecting miRNAs were identified, as well as metabolism‑related genes from MsigDB were intersected with miRNA target genes. Functional enrichment was performed and disease targets predicted using DisGeNET. A protein‑protein interaction network was built with STRING, and hub genes were identified via Cytoscape. GeneMANIA analyzed hub genes, while drug predictions were made using Comparative Toxicogenomics Database. Long non‑coding RNAs and transcription factors were predicted via mirNet and ChEA3. Results were validated by RT‑qPCR. A total of 18 miRNAs were significantly differential expressed between AH and AN group, of which eight were up‑ and 10 were downregulated. A total of 23 miRNAs were significantly differential expressed between the YH and AN group, of which six were up‑ and 17 were downregulated. hsa‑miR‑490‑3p, hsa‑miR‑4423‑3p and hsa‑miR‑4485‑3p may serve as characteristic miRNAs. A total of 289 target genes were predicted. Functional enrichment analysis yielded 169 terms, with 'herpes simplex virus 1 infection' the most significantly enriched. There were 19 metabolism‑associated target genes linked with these miRNAs, suggesting a potential role of metabolic processes in pathogenesis of these conditions. The biosynthetic process of carbohydrate derivatives may serve a key role during the development of high myopia. There were 10 hub genes and Propionyl‑CoA Carboxylase Subunit β could potentially serve as a biomarker. Drugs that could modulate their function were predicted; cyclosporine, tretinoin and acetaminophen may exert a broad influence on these hub genes. Hub gene networks based on the miRNAs were constructed to predict 44 associated long non‑coding RNAs and 98 transcription factors. The present findings offer novel insights into the molecular mechanisms of age‑related cataracts and high myopia and propose potential therapeutic targets.

Methylglyoxal: A Key Factor for Diabetic Retinopathy and Its Effects on Retinal Damage

Background: Diabetic retinopathy is the most common retinal vascular disease, affecting the retina's blood vessels and causing chronic inflammation, oxidative stress, and, ultimately, vision loss. Diabetes-induced elevated glucose levels increase glycolysis, the main methylglyoxal (MGO) formation pathway. MGO is a highly reactive dicarbonyl and the most rapid glycation compound to form endogenous advanced glycation end products (AGEs). MGO can act both intra- and extracellularly by glycating molecules and activating the receptor for AGEs (RAGE) pathway. Conclusions: This review summarizes the sources of MGO formation and its actions on various cell pathways in retinal cells such as oxidative stress, glycation, autophagy, ER stress, and mitochondrial dysfunction. Finally, the detoxification of MGO by glyoxalases is discussed.

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

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

Glycative stress as a cause of macular degeneration

People are living longer and rates of age-related diseases such as age-related macular degeneration (AMD) are accelerating, placing enormous burdens on patients and health care systems. The quality of carbohydrate foods consumed by an individual impacts health. The glycemic index (GI) is a kinetic measure of the rate at which glucose arrives in the blood stream after consuming various carbohydrates. Consuming diets that favor slowly digested carbohydrates releases sugar into the bloodstream gradually after consuming a meal (low glycemic index). This is associated with reduced risk for major age-related diseases including AMD, cardiovascular disease, and diabetes. In comparison, consuming the same amounts of different carbohydrates in higher GI diets, releases glucose into the blood rapidly, causing glycative stress as well as accumulation of advanced glycation end products (AGEs). Such AGEs are cytotoxic by virtue of their forming abnormal proteins and protein aggregates, as well as inhibiting proteolytic and other protective pathways that might otherwise selectively recognize and remove toxic species. Using in vitro and animal models of glycative stress, we observed that consuming higher GI diets perturbs metabolism and the microbiome, resulting in a shift to more lipid-rich metabolomic profiles. Interactions between aging, diet, eye phenotypes and physiology were observed. A large body of laboratory animal and human clinical epidemiologic data indicates that consuming lower GI diets, or lower glycemia diets, is protective against features of early AMD (AMDf) in mice and AMD prevalence or AMD progression in humans. Drugs may be optimized to diminish the ravages of higher glycemic diets. Human trials are indicated to determine if AMD progression can be retarded using lower GI diets. Here we summarized the current knowledge regarding the pathological role of glycative stress in retinal dysfunction and how dietary strategies might diminish retinal disease.

Association between Life's Essential 8 and cataract among US adults

Currently, a comprehensive assessment of the relationship between ideal cardiovascular health (CVH) indicators and cataract risk is lacking. Life's Essential 8 (LE8) is the latest concept proposed by the American Heart Association to comprehensively reflect CVH status. LE8 includes four health behaviors (diet, physical activity, smoking, and sleep) and four health factors (blood lipid, blood sugar, blood pressure, and body mass index). This study tried to evaluate the association between LE8 and cataract using data from National Health and Nutrition Examination Survey (NHANES) 2005-2008, a continuous research program which aims to monitor and evaluate the health and nutrition status of the US population. A cross-sectional study of 2720 non-cataract participants and 602 cataract participants. All participants were assigned to the poor, intermediate, and ideal CVH status groups based on LE8 score. Weighted multiple logistic regression was used to investigate the correlation between the LE8 score and cataract, as well as the correlation between each of the eight subitems and cataract, with potential confounding variables being adjusted. Then, restricted cubic spline analysis was used to further explore whether there was a nonlinear relationship between LE8 score and cataract. The proportion of cataract participants was 14.1%, 18.2%, and 20.6% in the ideal, intermediate, and poor CVH groups, respectively (P < 0.05). LE8 score was inversely associated with cataract risk, with each 10-point increase in LE8 score associated with a 14% reduction in cataract risk [odds ratio (OR) = 0.86, 95% confidence interval (CI): 0.79-0.93, P < 0.01]. Among all the LE8 subitems, physical activity, sleep, and blood glucose were significantly associated with cataract risk (all P < 0.05). Better CVH, defined by a higher LE8 score, is associated with a lower cataract risk. Efforts to improve LE8 score (especially when it comes to physical activity, sleep, and blood glucose) may serve as a novel strategy to help reduce the risk of cataract.

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

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

Fructosyl Amino Oxidase as a Therapeutic Enzyme in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an age-related disorder that is a global public health problem. The non-enzymatic Maillard reaction results in the formation of advanced glycation end products (AGEs). Accumulation of AGEs in drusen plays a key role in AMD. AGE-reducing drugs may contribute to the prevention and treatment of AGE-related disease. Fructosamine oxidase (FAOD) acts on fructosyl lysine and fructosyl valine. Based upon the published results of fructosamine 3-kinase (FN3K) and FAOD obtained in cataract and presbyopia, we studied ex vivo FAOD treatment as a non-invasive AMD therapy. On glycolaldehyde-treated porcine retinas, FAOD significantly reduced AGE autofluorescence (p = 0.001). FAOD treatment results in a breakdown of AGEs, as evidenced using UV fluorescence, near-infrared microspectroscopy on stained tissue sections of human retina, and gel permeation chromatography. Drusen are accumulations of AGEs that build up between Bruch's membrane and the retinal pigment epithelium. On microscopy slides of human retina affected by AMD, a significant reduction in drusen surface to 45 ± 21% was observed following FAOD treatment. Enzymatic digestion followed by mass spectrometry of fructose- and glucose-based AGEs (produced in vitro) revealed a broader spectrum of substrates for FAOD, as compared to FN3K, including the following: fructosyllysine, carboxymethyllysine, carboxyethyllysine, and imidazolone. In contrast to FN3K digestion, agmatine (4-aminobutyl-guanidine) was formed following FAOD treatment in vitro. The present study highlights the therapeutic potential of FAOD in AMD by repairing glycation-induced damage.

Is Ultra-Processed Food Intake Associated with a Higher Risk of Glaucoma? A Prospective Cohort Study including 19,255 Participants from the SUN Project

OBJECTIVE

The aim of this study was to examine the relationship of ultra-processed food (UPF) intake with the incidence of glaucoma in a large sample of Spanish university graduates followed prospectively.

METHODS

Prospective cohort study using data from the SUN Project. A final sample of 19,225 participants (60.1% women) was included in this study, with a mean age of 38.2 years (standard deviation (SD) = 12.4). Participants were followed-up for a mean time of 12.9 years (SD = 5.4). Dietary intake was measured using a 136-item semiquantitative food-frequency questionnaire. UPFs were defined based on the NOVA classification system. Glaucoma diagnosis was determined by asking the participants if they had ever been diagnosed with glaucoma by an ophthalmologist. This self-reported diagnosis of glaucoma has been previously validated.

RESULTS

After adjusting for several covariates, participants with the highest UPF consumption were at higher risk of glaucoma (hazard ratio (HR) = 1.83; 95% confidence interval (CI) 1.06 to 3.17) when compared to participants in the lowest category of UPF consumption. Regarding subgroup analyses, a significant multiplicative interaction was found for age (p = 0.004) and omega 3:6 ratio (p = 0.040). However, an association between UPF consumption and glaucoma was only found in older participants (aged ≥ 55 years), in men, in the most physically active group, in the group of non- or former smokers, in those with a lower omega 3:6 ratio, and in those with a lower energy intake. Regarding the contribution of each type of UPF group, UPF coming from sweets showed a significant risky effect (HR = 1.51; CI 95% 1.07 to 2.12).

CONCLUSIONS

This prospective cohort study shows that participants with a greater UPF consumption have a higher risk of developing glaucoma when compared to participants with a lower consumption. Our findings emphasize the relevance of monitoring and limiting the consumption of UPFs as a means of preventing glaucoma incidence.

Exploring in-vivo infrared spectroscopy for nail-based diabetes screening

Diabetes screening is traditionally complex, inefficient, and reliant on invasive sampling. This study evaluates near-infrared spectroscopy for non-invasive detection of glycated keratin in nails in vivo. Glycation of keratin, prevalent in tissues like nails and skin, is a key indicator of T2DM risk. In this study involving 200 participants (100 with diabetes, 100 without), NIR's efficacy was compared against a point-of-care HbA1c analyzer. Results showed a specificity of 92.9% in diabetes risk assessment. This study highlights the proposed NIR system potential as a simple, reliable tool for early diabetes screening and risk management in various healthcare settings.

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.

Association between advanced glycation end products and uveitis/scleritis activity in patients with active immune-mediated ocular inflammatory diseases

PURPOSE

To investigate for association between skin autofluorescence (SAF) advanced glycation end products (AGEs) and uveitis/scleritis activity in systemic inflammatory disease-related active non-infectious uveitis/scleritis patients.

METHODS

This cross-sectional study was conducted at Siriraj Hospital during October 2019 to March 2020. AGEs were measured by SAF method in systemic immune-related disease patients with active uveitis/scleritis, and those results were compared with those of healthy age-matched controls.

RESULTS

Thirty-one active non-infectious uveitis/scleritis patients and 31 age-matched controls were enrolled. The mean age of patients was 40.0 ± 12.8 years, and most were female (55.0%). The most common associated systemic immune-related disease was Vogt-Koyanagi-Harada disease (n = 14). Mean SAF AGE level in the study group compared to the control group was 2.38 ± 0.66 arbitrary units (AU) versus 2.58 ± 0.56 AU, respectively (p = 0.20). Multivariate analysis showed decreased SAF AGE level to be significantly associated with active ocular inflammation, (odds ratio: 0.01, 95% confidence interval: 0.00004-0.81; p = 0.04).

CONCLUSIONS

SAF AGE level was not so far found to be a reliable biomarker for indicating uveitis/scleritis activity in systemic immune-related disease patients with active ocular inflammation.

CLINICAL TRIAL REGISTRATION

Thai Clinical Trials Registry, https://www.thaiclinicaltrials.org/ . (Reg. No. TCTR20200114004, registered date 01/01/2020, beginning date of the trial 10/01/2019).

Oxidative stress, epigenetic regulation and pathological processes of lens epithelial cells underlying diabetic cataract

Background

Cataract is a blinding disease worldwide. It is an age-related disease that mainly occurs in people over 65 years old. Cataract is also prevalent in patients with diabetes mellites (DM). The pathological mechanisms underlying diabetic cataract (DC) are more complex than that of age-related cataract. Studies have identified that polyol pathway, advanced glycation end products (AGEs) and oxidative stress are the primary pathogenesis of DC. In recent years, molecular-level regulations and pathological processes of lens epithelial cells (LECs) have been confirmed to play roles in the initiation and progression of DC. A comprehensive understanding and elucidation of how chronic hyperglycemia drives molecular-level regulations and cytopathological processes in the lens will shed lights on the prevention, delay and treatment of DC.

Main text

Excessive glucose in the lens enhances polyol pathway and AGEs formation. Polyol pathway causes imbalance in the ratio of NADPH/NADP+ and NADH/NAD+. Decrease in NADPH/NADP+ ratio compromises antioxidant enzymes, while increase in NADH/NAD+ ratio promotes reactive oxygen species (ROS) overproduction in mitochondria, resulting in oxidative stress. Oxidative stress in the lens causes oxidation of DNA, proteins and lipids, leading to abnormalities in their structure and functions. Glycation of proteins by AGEs decreases solubility of proteins. High glucose triggered epigenetic regulations directly or indirectly affect expressions of genes and proteins in LECs. Changes in autophagic activity, increases in fibrosis and apoptosis of LECs destroy the morphological structure and physiological functions of the lens epithelium, disrupting lens homeostasis.

Conclusions

In both diabetic animal models and diabetics, oxidative stress plays crucial roles in the formation of cataract. Epigenetic regulations, include lncRNA, circRNA, microRNA, methylation of RNA and DNA, histone acetylation and pathological processes, include autophagy, fibrosis and apoptosis of LECs also involved in DC.

Mitophagy in the retina: Viewing mitochondrial homeostasis through a new lens

Mitochondrial function is key to support metabolism and homeostasis in the retina, an organ that has one of the highest metabolic rates body-wide and is constantly exposed to photooxidative damage and external stressors. Mitophagy is the selective autophagic degradation of mitochondria within lysosomes, and can be triggered by distinct stimuli such as mitochondrial damage or hypoxia. Here, we review the importance of mitophagy in retinal physiology and pathology. In the developing retina, mitophagy is essential for metabolic reprogramming and differentiation of retina ganglion cells (RGCs). In basal conditions, mitophagy acts as a quality control mechanism, maintaining a healthy mitochondrial pool to meet cellular demands. We summarize the different autophagy- and mitophagy-deficient mouse models described in the literature, and discuss the potential role of mitophagy dysregulation in retinal diseases such as glaucoma, diabetic retinopathy, retinitis pigmentosa, and age-related macular degeneration. Finally, we provide an overview of methods used to monitor mitophagy in vitro, ex vivo, and in vivo. This review highlights the important role of mitophagy in sustaining visual function, and its potential as a putative therapeutic target for retinal and other diseases.

Topical Application of Deglycating Enzymes as an Alternative Non-Invasive Treatment for Presbyopia

Presbyopia is an age-related vision disorder that is a global public health problem. Up to 85% of people aged ≥40 years develop presbyopia. In 2015, 1.8 billion people globally had presbyopia. Of those with significant near vision disabilities due to uncorrected presbyopia, 94% live in developing countries. Presbyopia is undercorrected in many countries, with reading glasses available for only 6-45% of patients living in developing countries. The high prevalence of uncorrected presbyopia in these parts of the world is due to the lack of adequate diagnosis and affordable treatment. The formation of advanced glycation end products (AGEs) is a non-enzymatic process known as the Maillard reaction. The accumulation of AGEs in the lens contributes to lens aging (leading to presbyopia and cataract formation). Non-enzymatic lens protein glycation induces the gradual accumulation of AGEs in aging lenses. AGE-reducing compounds may be effective at preventing and treating AGE-related processes. Fructosyl-amino acid oxidase (FAOD) is active on both fructosyl lysine and fructosyl valine. As the crosslinks encountered in presbyopia are mainly non-disulfide bridges, and based on the positive results of deglycating enzymes in cataracts (another disease caused by glycation of lens proteins), we studied the ex vivo effects of topical FAOD treatment on the power of human lenses as a new potential non-invasive treatment for presbyopia. This study demonstrated that topical FAOD treatment resulted in an increase in lens power, which is approximately equivalent to the correction obtained by most reading glasses. The best results were obtained for the newer lenses. Simultaneously, a decrease in lens opacity was observed, which improved lens quality. We also demonstrated that topical FAOD treatment results in a breakdown of AGEs, as evidenced by gel permeation chromatography and a marked reduction in autofluorescence. This study demonstrated the therapeutic potential of topical FAOD treatment in presbyopia.

Current Approach to the Pathogenesis of Diabetic Cataracts

Cataracts remain the first or second leading cause of blindness in all world regions. In the diabetic population, cataracts not only have a 3–5 times higher incidence than in the healthy population but also affect people at a younger age. In patients with type 1 diabetes, cataracts occur on average 20 years earlier than in the non-diabetic population. In addition, the risk of developing cataracts increases with the duration of diabetes and poor metabolic control. A better understanding of the mechanisms leading to the formation of diabetic cataracts enables more effective treatment and a holistic approach to the patient.

The effect of a-Lipoic acid (ALA) on oxidative stress, inflammation, and apoptosis in high glucose-induced human corneal epithelial cells

PURPOSE

Oxidative stress and inflammation had been proved to play important role in the progression of diabetic keratopathy (DK). The excessive accumulation of AGEs and their bond to AGE receptor (RAGE) in corneas that cause the formation of oxygen radicals and the release of inflammatory cytokines, induce cell apoptosis. Our current study was aimed to evaluate the effect of ALA on AGEs accumulation as well as to study the molecular mechanism of ALA against AGE-RAGE axis mediated oxidative stress, apoptosis, and inflammation in HG-induced HCECs, so as to provide cytological basis for the treatment of DK.

METHODS

HCECs were cultured in a variety concentration of glucose medium (5.5, 10, 25, 30, 40, and 50 mM) for 48 h. The cell proliferation was evaluated by CCK-8 assay. Apoptosis was investigated with the Annexin V- fluorescein isothiocyanate (V-FITC)/PI kit, while, the apoptotic cells were determined by flow cytometer and TUNEL cells apoptosis Kit. According to the results of cell proliferation and cell apoptosis, 25 mM glucose medium was used in the following HG experiment. The effect of ALA on HG-induced HCECs was evaluated. The HCECs were treated with 5.5 mM glucose (normal glucose group, NG group), 5.5 mM glucose + 22.5 mM mannitol (osmotic pressure control group, OP group), 25 mM glucose (high glucose group, HG group) and 25 mM glucose + ALA (HG + ALA group) for 24 and 48 h. The accumulation of intracellular AGEs was detected by ELISA kit. The RAGE, catalase (CAT), superoxide dismutase 2 (SOD2), cleaved cysteine-aspartic acid protease-3 (Cleaved caspase-3), Toll-like receptors 4 (TLR4), Nod-like receptor protein 3 (NLRP3) inflammasome, interleukin 1 beta (IL-1 ß), and interleukin 18 (IL-18) were quantified by RT-PCR, Western blotting, and Immunofluorescence, respectively. Reactive oxygen species (ROS) production was evaluated by fluorescence microscope and fluorescence microplate reader.

RESULTS

When the glucose medium was higher than 25 mM, cell proliferation was significantly inhibited and apoptosis ratio was increased (P < 0.001). In HG environment, ALA treatment alleviated the inhibition of HCECs in a dose-dependent manner, 25 μM ALA was the minimum effective dose. ALA could significantly reduce the intracellular accumulation of AGEs (P < 0.001), activate protein and genes expression of CAT and SOD2 (P < 0.001), and therefore inhibited ROS-induced oxidative stress and cells apoptosis. Besides, ALA could effectively down-regulate the protein and gene level of RAGE, TLR4, NLRP3, IL-1B, IL-18 (P < 0.05), and therefore alleviated AGEs-RAGE-TLR4-NLRP3 pathway-induced inflammation in HG-induced HCECs.

CONCLUSION

Our study indicated that ALA could be a desired treatment for DK due to its potential capacity of reducing accumulation of advanced glycation end products (AGEs) and down-regulating AGE-RAGE axis-mediated oxidative stress, cell apoptosis, and inflammation in high glucose (HG)-induced human corneal epithelial cells (HCECs), which may provide cytological basis for therapeutic targets that are ultimately of clinical benefit.

Proteostasis in aging-associated ocular disease

Vision impairment has devastating consequences for the quality of human life. The cells and tissues associated with the visual process must function throughout one's life span and maintain homeostasis despite exposure to a variety of insults. Maintenance of the proteome is termed proteostasis, and is vital for normal cellular functions, especially at an advanced age. Here we describe basic aspects of proteostasis, from protein synthesis and folding to degradation, and discuss the current status of the field with a particular focus on major age-related eye diseases: age-related macular degeneration, cataract, and glaucoma. Our intent is to allow vision scientists to determine where and how to harness the proteostatic machinery for extending functional homeostasis in the aging retina, lens, and trabecular meshwork. Several common themes have emerged despite these tissues having vastly different metabolisms. Continued exposure to insults, including chronic stress with advancing age, increases proteostatic burden and reduces the fidelity of the degradation machineries including the ubiquitin-proteasome and the autophagy-lysosome systems that recognize and remove damaged proteins. This "double jeopardy" results in an exponential accumulation of cytotoxic proteins with advancing age. We conclude with a discussion of the challenges in maintaining an appropriate balance of protein synthesis and degradation pathways, and suggest that harnessing proteostatic capacities should provide new opportunities to design interventions for attenuating age-related eye diseases before they limit sight.

Relevance of Diabetic Retinopathy with AGEs and Carotenoid Levels Assessed by Skin Sensors

Advanced glycation end products (AGEs) and carotenoids, the major prooxidants and antioxidants in vivo, respectively, are thought to be associated with diabetes mellitus (DM). To estimate AGEs and carotenoid levels simultaneously in patients with DM, we used noninvasive fingertip skin sensors. The study population included 249 eyes of 249 Japanese subjects (130 men, 119 women; mean age ± standard deviation, 69.9 ± 12.0 years). Ninety-three patients had DM, which included diabetic retinopathy (DR) (n = 44) and no DR (NDR) (n = 49), and 156 controls. Compared to the controls (0.44 ± 0.07 arbitrary unit (A.U.)), the AGEs scores were significantly higher in DM (0.47 ± 0.09, p = 0.029) and DR (0.49 ± 0.08, p = 0.0006) patients; no difference was seen between NDR (0.45 ± 0.09, p = 0.83) and controls. Multivariate analyses indicated that a higher AGEs level is a risk factor for DR (r = 0.030, p = 0.0025). However, the carotenoid scores did not differ in any comparisons between the controls (327.7 ± 137.0 O.D.) and patients with DM (324.7 ± 126.4, p = 0.86), NDR (320.4 ± 123.6, p = 0.93), or DR (329.4 ± 130.8, p = 0.93). The carotenoid scores correlated negatively with the AGEs scores (r = −0.21, p = 0.0007), and reflected the Veggie intake score (p < 0.0001). In patients with DM, estimations of AGEs and carotenoid levels using skin sensors can be useful for assessing their risk of DR and vegetable intake, respectively.

Diabetic Corneal Neuropathy: Pathogenic Mechanisms and Therapeutic Strategies

Diabetes mellitus (DM) is a major global public health problem that can cause complications such as diabetic retinopathy, diabetic neuropathy, and diabetic nephropathy. Besides the reporting of reduction in corneal nerve density and decrease in corneal sensitivity in diabetic patients, there may be a subsequent result in delayed corneal wound healing and increased corneal infections. Despite being a potential cause of blindness, these corneal nerve changes have not gained enough attention. It has been proposed that corneal nerve changes may be an indicator for diabetic neuropathy, which can provide a window for early diagnosis and treatment. In this review, the authors aimed to give an overview of the relationship between corneal nerves and diabetic neuropathy as well as the underlying pathophysiological mechanisms of corneal nerve fiber changes caused by DM for improved prediction and prevention of diabetic neuropathy. In addition, the authors summarized current and novel therapeutic methods for delayed corneal wound healing, nerve protection and regeneration in the diabetic cornea.

Oxidation, Glycation, and Carbamylation of Salivary Biomolecules in Healthy Children, Adults, and the Elderly: Can Saliva Be Used in the Assessment of Aging?

Background

Aging is inextricably linked to oxidative stress, inflammation, and posttranslational protein modifications. However, no studies evaluate oxidation, glycation, and carbamylation of salivary biomolecules as biomarkers of aging. Saliva collection is non-invasive, painless, and inexpensive, which are advantages over other biofluids.

Methods

The study enrolled 180 healthy subjects divided into six groups according to age: 6–13, 14–19, 20–39, 40–59, 60–79, and 80–100 years. The number of individuals was determined a priori based on our previous experiment (power of the test = 0.8; α = 0.05). Non-stimulated saliva and plasma were collected from participants, in which biomarkers of aging were determined by colorimetric, fluorometric, and ELISA methods.

Results

The study have demonstrated that modifications of salivary proteins increase with age, as manifested by decreased total thiol levels and increased carbonyl groups, glycation (Nε-(carboxymethyl) lysine, advanced glycation end products (AGE)) and carbamylation (carbamyl-lysine) protein products in the saliva of old individuals. Oxidative modifications of lipids (4-hydroxynonenal) and nucleic acids (8-hydroxy-2’-deoxyguanosine (8-OHdG)) also increase with age. Salivary redox biomarkers correlate poorly with their plasma levels; however, salivary AGE and 8-OHdG generally reflect their blood concentrations. In the multivariate regression model, they are a predictor of aging and, in the receiver operating characteristic (ROC) analysis, significantly differentiate children and adolescents (under 15 years old) from the working-age population (15–64 years) and the older people (65 years and older).

Conclusion

Salivary AGE and 8-OHdG have the most excellent diagnostic utility in assessing the aging process. Saliva can be used to evaluate the aging of the body.

Autophagy and Glycative Stress: A Bittersweet Relationship in Neurodegeneration

Autophagy is a fine-tuned proteolytic pathway that moves dysfunctional/aged cellular components into the lysosomal compartment for degradation. Over the last 3 decades, global research has provided evidence for the protective role of autophagy in different brain cell components. Autophagic capacities decline with age, which contributes to the accumulation of obsolete/damaged organelles and proteins and, ultimately, leads to cellular aging in brain tissues. It is thus well-accepted that autophagy plays an essential role in brain homeostasis, and malfunction of this catabolic system is associated with major neurodegenerative disorders. Autophagy function can be modulated by different types of stress, including glycative stress. Glycative stress is defined as a cellular status with abnormal and accelerated accumulation of advanced glycation end products (AGEs). It occurs in hyperglycemic states, both through the consumption of high-sugar diets or under metabolic conditions such as diabetes. In recent years, glycative stress has gained attention for its adverse impact on brain pathology. This is because glycative stress stimulates insoluble, proteinaceous aggregation that is linked to the malfunction of different neuropathological proteins. Despite the emergence of new literature suggesting that autophagy plays a major role in fighting glycation-derived damage by removing cytosolic AGEs, excessive glycative stress might also negatively impact autophagic function. In this mini-review, we provide insight on the status of present knowledge regarding the role of autophagy in brain physiology and pathophysiology, with an emphasis on the cytoprotective role of autophagic function to ameliorate the adverse effects of glycation-derived damage in neurons, glia, and neuron-glia interactions.

Diet Quality Scores Are Positively Associated with Whole Blood-Derived Mitochondrial DNA Copy Number in the Framingham Heart Study

BACKGROUND

The association between diet quality and mitochondrial DNA copy number (mtDNA-CN) remains to be examined.

OBJECTIVES

We aimed to study the relation between diet quality and mtDNA-CN.

METHODS

We analyzed data from 2931 Framingham Heart Study (FHS) participants (mean age of 57 y, 55% females). Whole-genome sequencing was used to calculate mtDNA-CN from whole-blood samples. We examined the cross-sectional associations between 3 diet quality scores, the Dietary Approaches to Stop Hypertension (DASH) score, the Alternative Healthy Eating Index (AHEI), and the Mediterranean diet score (MDS), and mtDNA-CN. Linear mixed models were used to account for maternal lineage.

RESULTS

We observed that a higher DASH score was positively associated with mtDNA-CN after adjusting for sex, age, energy intake, smoking status, alcohol intake, and physical activity level. A 1-SD increase in the DASH score was associated with a 0.042-SD greater mtDNA-CN (95% CI: 0.007, 0.077; P = 0.02). Similarly, for each SD increase in AHEI and MDS, the mtDNA-CN SD increased by 0.056 (95% CI: 0.019, 0.092; P = 0.003) and 0.047 (95% CI: 0.01, 0.083; P = 0.01), respectively. Diet quality scores were associated with neutrophil and lymphocyte counts but not platelet counts, e.g., for a 1-SD increase in the DASH, neutrophils decreased by 0.8% (95% CI: 0.5%, 1.1%; P = 4.1 × 10-6), lymphocytes increased by 0.7% (95% CI: 0.4%, 1%, P = 1.2 × 10-5), and there was no significant change in platelet number (0.1 × 1000/μL; 95% CI: -1.6, 1.9; P = 0.89). Further adjustment for neutrophil, lymphocyte, and platelet counts and the associations between diet quality scores and mtDNA-CN were completely attenuated to nonsignificant (P = 0.95, 0.54, and 0.91, respectively).

CONCLUSIONS

We observed that higher diet quality is associated with a greater whole-blood derived mtDNA-CN in middle-aged to older adult FHS participants, and that blood cell composition, particularly neutrophil counts, attenuated the association between diet quality and mtDNA-CN.

Dietary intake and associations with myopia in Singapore children

PURPOSE

To evaluate associations of dietary factors with myopia, spherical equivalent refractive error (SE) and axial length (AL) in children at age 9 from the Growing Up in Singapore Towards healthy Outcomes (GUSTO) birth cohort.

METHODS

We included 467 multi-ethnic children (933 eyes) who participated in the GUSTO prospective birth cohort and were delivered in two major hospitals in Singapore (2009-2010). At the 9-year visit, we assessed the 6-year incidence of myopia (between ages 3 to 9), cycloplegic SE and AL in children without myopia (SE ≤ -0.5 D in either eye) at the 3-year visit. Using a validated 112-item food frequency questionnaire, parents reported each child's average daily intake of dietary factors (nutrients and food groups) in the past month. Paired eyes were analysed using Generalised Estimating Equations with multivariable logistic or linear regression. Bonferroni corrections were applied, correcting for multiple comparisons between the 13 nutrients (p < 0.004) or 8 food groups (p < 0.006) and each outcome.

RESULTS

In children aged 9 years (51.0% boys; 56.3% Chinese), the 6-year incidence of myopia was 35.5%. Overall, the mean (SD) SE and AL were -0.3 (1.7) D and 23.4 (1.0) mm, respectively. In multivariable regression, macronutrients or micronutrients were not associated with incident myopia (p ≥ 0.004 for all), adjusting for total energy, gender, ethnicity, time outdoors, near-work and the number of myopic parents (additionally child's height for outcome AL). Similarly, all food groups (including refined grains, sugar-sweetened beverages, protein foods, fruits and vegetables) were not associated with incident myopia (p ≥ 0.006 for all). Additionally, none of the nutrients (p ≥ 0.004 for all) or food groups (p ≥ 0.006 for all) were associated with SE or AL.

CONCLUSIONS

Our study findings of no significant association between specific nutrients or food groups and incident myopia or SE or AL suggest that diet may not be associated with myopia in children aged 9 years. Well-conducted prospective studies in other populations may clarify the association.

New insights into the role of autophagy in retinal and eye diseases

Autophagy is a fundamental homeostatic pathway that mediates the degradation and recycling of intracellular components. It serves as a key quality control mechanism, especially in non-dividing cells such as neurons. Proteins, lipids, and even whole organelles are engulfed in autophagosomes and delivered to the lysosome for elimination. The retina is a light-sensitive tissue located in the back of the eye that detects and processes visual images. Vision is a highly demanding process, making the eye one of the most metabolically active tissues in the body and photoreceptors display glycolytic metabolism, even in the presence of oxygen. The retina and eye are also exposed to other stressors that can impair their function, including genetic mutations and age-associated changes. Autophagy, among other pathways, is therefore a key process for the preservation of retinal homeostasis. Here, we review the roles of both canonical and non-canonical autophagy in normal retinal function. We discuss the most recent studies investigating the participation of autophagy in eye diseases such as age-related macular degeneration, glaucoma, and diabetic retinopathy and its role protecting photoreceptors in several forms of retinal degeneration. Finally, we consider the therapeutic potential of strategies that target autophagy pathways to treat prevalent retinal and eye diseases.

Short-Term High Fructose Intake Impairs Diurnal Oscillations in the Murine Cornea

Purpose

Endogenous and exogenous stressors, including nutritional challenges, may alter circadian rhythms in the cornea. This study aimed to determine the effects of high fructose intake (HFI) on circadian homeostasis in murine cornea.

Methods

Corneas of male C57BL/6J mice subjected to 10 days of HFI (15% fructose in drinking water) were collected at 3-hour intervals over a 24-hour circadian cycle. Total extracted RNA was subjected to high-throughput RNA sequencing. Rhythmic transcriptional data were analyzed to determine the phase, rhythmicity, unique signature, metabolic pathways, and cell signaling pathways of transcripts with temporally coordinated expression. Corneas of HFI mice were collected for whole-mounted techniques after immunofluorescent staining to quantify mitotic cell number in the epithelium and trafficking of neutrophils and γδ-T cells to the limbal region over a circadian cycle.

Results

HFI significantly reprogrammed the circadian transcriptomic profiles of the normal cornea and reorganized unique temporal and clustering enrichment pathways, but did not affect core-clock machinery. HFI altered the distribution pattern and number of corneal epithelial mitotic cells and enhanced recruitment of neutrophils and γδ-T cell immune cells to the limbus across a circadian cycle. Cell cycle, immune function, metabolic processes, and neuronal-related transcription and associated pathways were altered in the corneas of HFI mice.

Conclusions

HFI significantly reprograms diurnal oscillations in the cornea based on temporal and spatial distributions of epithelial mitosis, immune cell trafficking, and cell signaling pathways. Our findings reveal novel molecular targets for treating pathologic alterations in the cornea after HFI.

The Glyoxalase System in Age-Related Diseases: Nutritional Intervention as Anti-Ageing Strategy

The glyoxalase system is critical for the detoxification of advanced glycation end-products (AGEs). AGEs are toxic compounds resulting from the non-enzymatic modification of biomolecules by sugars or their metabolites through a process called glycation. AGEs have adverse effects on many tissues, playing a pathogenic role in the progression of molecular and cellular aging. Due to the age-related decline in different anti-AGE mechanisms, including detoxifying mechanisms and proteolytic capacities, glycated biomolecules are accumulated during normal aging in our body in a tissue-dependent manner. Viewed in this way, anti-AGE detoxifying systems are proposed as therapeutic targets to fight pathological dysfunction associated with AGE accumulation and cytotoxicity. Here, we summarize the current state of knowledge related to the protective mechanisms against glycative stress, with a special emphasis on the glyoxalase system as the primary mechanism for detoxifying the reactive intermediates of glycation. This review focuses on glyoxalase 1 (GLO1), the first enzyme of the glyoxalase system, and the rate-limiting enzyme of this catalytic process. Although GLO1 is ubiquitously expressed, protein levels and activities are regulated in a tissue-dependent manner. We provide a comparative analysis of GLO1 protein in different tissues. Our findings indicate a role for the glyoxalase system in homeostasis in the eye retina, a highly oxygenated tissue with rapid protein turnover. We also describe modulation of the glyoxalase system as a therapeutic target to delay the development of age-related diseases and summarize the literature that describes the current knowledge about nutritional compounds with properties to modulate the glyoxalase system.

Protein posttranslational modification (PTM) by glycation: Role in lens aging and age-related cataractogenesis

Crystallins, the most prevalent lens proteins, have no turnover throughout the entire human lifespan. These long-lived proteins are susceptible to post-synthetic modifications, including oxidation and glycation, which are believed to be some of the primary mechanisms for age-related cataractogenesis. Thanks to high glutathione (GSH) and ascorbic acid (ASA) levels as well as low oxygen content, the human lens is able to maintain its transparency for several decades. Aging accumulates substantial changes in the human lens, including a decreased glutathione concentration, increased reactive oxygen species (ROS) formation, impaired antioxidative defense capacity, and increased redox-active metal ions, which induce glucose and ascorbic acid degradation and protein glycation. The glycated lens crystallins are either prone to UVA mediated free radical production or they attract metal ion binding, which can trigger additional protein oxidation and modification. This vicious cycle is expected to be exacerbated with older age or diabetic conditions. ASA serves as an antioxidant in the human lens under reducing conditions to protect the human lens from damage, but ASA converts to the pro-oxidative role and causes lens protein damage by ascorbylation in high oxidation or enriched redox-active metal ion conditions. This review is dedicated in honor of Dr. Frank Giblin, a great friend and superb scientist, whose pioneering and relentless work over the past 45 years has provided critical insight into lens redox regulation and glutathione homeostasis during aging and cataractogenesis.

Fundamentals of Diabetic Cataractogenesis and Promising Ways of its Pharmacological Correction

Cataracts in diabetes mellitus lead to decreased visual function and blindness. Cataract surgery for diabetes mellitus has limitations and complications. The search for effective means of conservative cataract therapy continues. The review presents the analysis of data from scientific sources, mainly for 2015–2020 using Internet resources (PubMed, Web of Science, Medline, eLibrary.Ru, Cyberleninka). In the work, diabetic cataractogenesis is presented as a sum of interrelated pathobiochemical processes. The main ones are the polyol pathway of glucose conversion, non-enzymatic glycation and oxidative modification of lens proteins, which are enhanced in diabetes mellitus. The lens has a high protein content. The formation of high molecular weight protein aggregates is of particular importance for the appearance of light scattering zones and a decrease in lens transparency. This review presents data on anti-cataract compounds that affect post-translational crystallin modification, prevent osmotic and oxidative stress in the lens, and exhibit antiglycation properties. This information shows that the search for means of pharmacological correction of cataractogenesis should be carried out among compounds with antioxidant and antiglycation activity. 

Racemization in cataractous lens from diabetic and aging individuals: analysis of Asp 58 residue in αA-crystallin

Cataract is the leading cause of visual impairment globally. Racemization of lens proteins may contribute to cataract formation in aging individuals. As a special type of age-related cataract (ARC), diabetic cataract (DC) is characterized by the early onset of cortical opacification and finally developed into a mixed type of cortical and nuclear opacification. We compared racemization of Asp 58 residue, a hotspot position in αA-crystallin, from the cortex and nucleus of diabetic and age-matched senile cataractous lenses, by identifying L-Asp/L-isoAsp/D-Asp/D-isoAsp by mass spectrometry. Compared to nondiabetic cataractous lenses, DC lenses showed a significantly increased cortex/nucleus ratio of D-Asp 58, which originated primarily from an increased percentage of D-Asp 58 in the lens cortex of DC. Moreover, patients diagnosed with diabetes for over 10 years showed a lower cortex/nucleus ratio of D-isoAsp 58 in the lens compared with those who had a shorter duration of diabetes, which originated mainly from an increased percentage of D-isoAsp 58 in the lens nucleus of DC with increasing time of hyperglycemia. Further analysis confirmed decreased protein solubility in diabetic cataractous lenses. The different racemization pattern in DC may be distinguished from ARC and influence its phenotype over the protracted duration of diabetes.

A Potential Role for Fructosamine-3-Kinase in Cataract Treatment

Cataracts are the major cause of blindness worldwide, largely resulting from aging and diabetes mellitus. Advanced glycation end products (AGEs) have been identified as major contributors in cataract formation because they alter lens protein structure and stability and induce covalent cross-linking, aggregation, and insolubilization of lens crystallins. We investigated the potential of the deglycating enzyme fructosamine-3-kinase (FN3K) in the disruption of AGEs in cataractous lenses. Macroscopic changes of equine lenses were evaluated after ex vivo intravitreal FN3K injection. The mechanical properties of an equine lens pair were evaluated after treatment with saline and FN3K. AGE-type autofluorescence (AF) was measured to assess the time-dependent effects of FN3K on glycolaldehyde-induced AGE-modified porcine lens fragments and to evaluate its actions on intact lenses after in vivo intravitreal FN3K injection of murine eyes. A potential immune response after injection was evaluated by analysis of IL-2, TNFα, and IFNγ using an ELISA kit. Dose- and time-dependent AF kinetics were analyzed on pooled human lens fragments. Furthermore, AF measurements and a time-lapse of macroscopic changes were performed on intact cataractous human eye lenses after incubation with an FN3K solution. At last, AF measurements were performed on cataractous human eyes after crossover topical treatment with either saline- or FN3K-containing drops. While the lenses of the equine FN3K-treated eyes appeared to be clear, the saline-treated lenses had a yellowish-brown color. Following FN3K treatment, color restoration could be observed within 30 min. The extension rate of the equine FN3K-treated lens was more than twice the extension rate of the saline-treated lens. FN3K treatment induced significant time-dependent decreases in AGE-related AF values in the AGE-modified porcine lens fragments. Furthermore, in vivo intravitreal FN3K injection of murine eyes significantly reduced AF values of the lenses. Treatment did not provoke a systemic immune response in mice. AF kinetics of FN3K-treated cataractous human lens suspensions revealed dose- and time-dependent decreases. Incubation of cataractous human eye lenses with FN3K resulted in a macroscopic lighter color of the cortex and a decrease in AF values. At last, crossover topical treatment of intact human eyes revealed a decrease in AF values during FN3K treatment, while showing no notable changes with saline. Our study suggests, for the first time, a potential additional role of FN3K as an alternative treatment for AGE-related cataracts.

Associations Between Regional Environment and Cornea-Related Morphology of the Eye in Young Adults: A Large-Scale Multicenter Cross-Sectional Study

Purpose

To investigate environmental factors associated with corneal morphologic changes.

Methods

A cross-sectional study was conducted, which enrolled adults of the Han ethnicity aged 18 to 44 years from 20 cities. The cornea-related morphology was measured using an ocular anterior segment analysis system. The geographic indexes of each city and meteorological indexes of daily city-level data from the past 40 years (1980-2019) were obtained. Correlation analyses at the city level and multilevel model analyses at the eye level were performed.

Results

In total, 114,067 eyes were used for analysis. In the correlation analyses at the city level, the corneal thickness was positively correlated with the mean values of precipitation (highest r [correlation coefficient]: >0.700), temperature, and relative humidity (RH), as well as the amount of annual variation in precipitation (r: 0.548 to 0.721), and negatively correlated with the mean daily difference in the temperature (DIF T), duration of sunshine, and variance in RH (r: -0.694 to 0.495). In contrast, the anterior chamber (AC) volume was negatively correlated with the mean values of precipitation, temperature, RH, and the amount of annual variation in precipitation (r: -0.672 to -0.448), and positively associated with the mean DIF T (r = 0.570) and variance in temperature (r = 0.507). In total 19,988 eyes were analyzed at the eye level. After adjusting for age, precipitation was the major explanatory factor among the environmental factors for the variability in corneal thickness and AC volume.

Conclusions

Individuals who were raised in warm and wet environments had thicker corneas and smaller AC volumes than those from cold and dry ambient environments. Our findings demonstrate the role of local environmental factors in corneal-related morphology.

Phytochemical profile, antioxidant, α-amylase inhibition, binding interaction and docking studies of Justicia carnea bioactive compounds with α-amylase

The present study investigated the antioxidant and invitro antidiabetic capacities of Justicia carnea aqueous leaf extract (JCAE) using α-amylase inhibition model. α-Amylase binding-interaction with JCAE was also investigated using fluorescence spectroscopy and molecular docking. Phytochemical screening and Gas Chromatography-Mass Spectrometry (GC-MS) analysis indicated presence of bioactive compounds. Phenolic (132 mg GAE/g) and flavonoid contents (31.08 mg CE/g) were high. JCAE exhibited high antioxidant capacity and effectively inhibited α-amylase activity (IC50, 671.43 ± 1.88 μg/mL), though lesser than acarbose effect (IC50, 108.91 ± 0.61 μg/mL). α-Amylase intrinsic fluorescence was quenched in the presence of JCAE. Ultraviolet-visible and FT-IR spectroscopies affirmed mild changes in α-amylase conformation. Synchronous fluorescence analysis indicated alterations in the microenvironments of tryptophan residues near α-amylase active site. Molecular docking affirmed non-polar interactions of compounds 6 and 7 in JCAE with Asp-197 and Trp-58 residues of α-amylase, respectively. Overall, JCAE indicated potential to prevent postprandial hyperglycemia by slowing down carbohydrate hydrolysis.

Assessment of Absorption of Glycated Nail Proteins in Patients with Diabetes Mellitus and Diabetic Retinopathy

Background and objectives: Glycation occurs in a variety of human tissues and organs. Knowledge about the relationship between predictive biochemical factors such as absorption of glycated nail proteins and severity of type 2 diabetes mellitus (DM) and diabetic retinopathy (DR) remains limited. Materials and Methods: The study group consisted of patients with type 2 DM and DR (n = 32) and a control group (n = 28). Each patient underwent a comprehensive ophthalmic examination. The glycation process in nail clippings was evaluated in stages of in vitro glycation and deglycation stages. ATR–FTIR spectroscopy was used to calculate the infrared absorption in the region of interest. The absorption of solutions with nail clippings was evaluated by NanoDrop spectrophotometry. Absorption spectra differences before and after the exposure to fructosamine 3-kinase were compared between DM patients with DR and the control group. Results: The absorption of glycated nail protein greater than 83.00% increased the chance of developing DM and DR (OR = 15.909, 95% CI 3.914–64.660, p < 0.001). Absorption of glycated nail protein by ATR–FTIR spectroscopy in patients with DM and DR in vitro glycation was statistically significantly higher than in the control group; also absorption of solution with nails by NanoDrop spectroscopy was statistically significantly higher than in controls in vitro glycation and in vitro deglycation. After exposure to fructosamine 3-kinase, absorption of nail protein in DM + severe/proliferative DR group was statistically significantly lower in comparison with DM + mild/moderate group DR. Conclusions: Evaluation of glycated nail protein could be applied to evaluate the risk of having DM and for long-term observation of DM control.

Protein aggregation as a consequence of non-enzymatic glycation: Therapeutic intervention using aspartic acid and arginine

Non-enzymatic glycation tempted AGEs of proteins are currently at the heart of a number of pathological conditions. Production of chemically stable AGEs can permanently alter the protein structure and function, concomitantly leading to dilapidated situations. Keeping in perspective, present study aims to report the glycation induced structural and functional modification of a cystatin type isolated from rai mustard seeds, using RSC-glucose and RSC-ribose as model system. Among the sugars studied, ribose was found to be most potent glycating agent as evident from different biophysical assays. During the course of incubation, RSC was observed to pass through a series of structural intermediates as revealed by circular dichroism, altered intrinsic fluorescence and high ANS binding. RSC incubation with ribose post day 36 revealed the possible buildup of β structures as observed in CD spectral analysis, hinting towards the generation of aggregated structures in RSC. High thioflavin T fluorescence and increased Congo red absorbance together with enhanced turbidity of the modified form confirmed the aggregation of RSC. The study further revealed anti-glycation and anti-aggregation potential of amino acids; aspartic acid and arginine as they prevented and/or slowed down the process of AGEs and β structure buildup in a concentration dependent manner with arginine proving to be the most effective one.

Evaluation of Relevance between Advanced Glycation End Products and Diabetic Retinopathy Stages Using Skin Autofluorescence

Advanced glycation end products (AGEs) are thought to play important roles in the pathogenesis of diabetic microangiopathy, particularly in the progression of diabetic retinopathy (DR). We assessed the levels of skin autofluorescence (sAF) to assess the association between AGEs and DR stages. A total of 394 eyes of 394 Japanese subjects (172 men, 222 women; mean age ± standard deviation [SD], 68.4 ± 13.7 years) comprised the study population, i.e., subjects with diabetes mellitus (DM) (n = 229) and non-diabetic controls (n = 165). The patients with DM were divided into those without DR (NDR, n = 101) and DR (n = 128). DR included simple (SDR, n = 36), pre-proliferative (PPDR, n = 25), and PDR (n = 67). Compared to controls (0.52 ± 0.12), the AGE scores were significantly higher in patients with DM (0.59 ± 0.17, p < 0.0001), NDR (0.58 ± 0.16, p = 0.0012), and DR (0.60 ± 0.18, p < 0.0001). The proportion of patients with PDR was significantly higher in the highest quartile of AGE scores than the other quartiles (p < 0.0001). Compared to those without PDR (SDR and PPDR), those with PDR were younger (p = 0.0006), more were pseudophakic (p < 0.0001), had worse visual acuity (VA) (p < 0.0001), had higher intraocular pressure (IOP) (p < 0.0001), and had higher AGE scores (p = 0.0016). Multivariate models also suggested that younger age, male gender, pseudophakia, worse VA, higher IOP, and higher AGE scores were risk factors for PDR. The results suggested that AGE scores were higher in patients with DM and were independently associated with progression of DR. In addition, more PDR was seen in the highest quartile of AGE scores. This study highlights the clinical use of the AGE score as a non-invasive, reliable marker to identity patients at risk of sight-threatening DR.

Autophagic receptor p62 protects against glycation-derived toxicity and enhances viability

Diabetes and metabolic syndrome are associated with the typical American high glycemia diet and result in accumulation of high levels of advanced glycation end products (AGEs), particularly upon aging. AGEs form when sugars or their metabolites react with proteins. Associated with a myriad of age-related diseases, AGEs accumulate in many tissues and are cytotoxic. To date, efforts to limit glycation pharmacologically have failed in human trials. Thus, it is crucial to identify systems that remove AGEs, but such research is scanty. Here, we determined if and how AGEs might be cleared by autophagy. Our in vivo mouse and C. elegans models, in which we altered proteolysis or glycative burden, as well as experiments in five types of cells, revealed more than six criteria indicating that p62-dependent autophagy is a conserved pathway that plays a critical role in the removal of AGEs. Activation of autophagic removal of AGEs requires p62, and blocking this pathway results in accumulation of AGEs and compromised viability. Deficiency of p62 accelerates accumulation of AGEs in soluble and insoluble fractions. p62 itself is subject to glycative inactivation and accumulates as high mass species. Accumulation of p62 in retinal pigment epithelium is reversed by switching to a lower glycemia diet. Since diminution of glycative damage is associated with reduced risk for age-related diseases, including age-related macular degeneration, cardiovascular disease, diabetes, Alzheimer's, and Parkinson's, discovery of methods to limit AGEs or enhance p62-dependent autophagy offers novel potential therapeutic targets to treat AGEs-related pathologies.

Glyoxalase System as a Therapeutic Target against Diabetic Retinopathy

Hyperglycemia, a defining characteristic of diabetes, combined with oxidative stress, results in the formation of advanced glycation end products (AGEs). AGEs are toxic compounds that have adverse effects on many tissues including the retina and lens. AGEs promote the formation of reactive oxygen species (ROS), which, in turn, boost the production of AGEs, resulting in positive feedback loops, a vicious cycle that compromises tissue fitness. Oxidative stress and the accumulation of AGEs are etiologically associated with the pathogenesis of multiple diseases including diabetic retinopathy (DR). DR is a devastating microvascular complication of diabetes mellitus and the leading cause of blindness in working-age adults. The onset and development of DR is multifactorial. Lowering AGEs accumulation may represent a potential therapeutic approach to slow this sight-threatening diabetic complication. To set DR in a physiological context, in this review we first describe relations between oxidative stress, formation of AGEs, and aging in several tissues of the eye, each of which is associated with a major age-related eye pathology. We summarize mechanisms of AGEs generation and anti-AGEs detoxifying systems. We specifically feature the potential of the glyoxalase system in the retina in the prevention of AGEs-associated damage linked to DR. We provide a comparative analysis of glyoxalase activity in different tissues from wild-type mice, supporting a major role for the glyoxalase system in the detoxification of AGEs in the retina, and present the manipulation of this system as a therapeutic strategy to prevent the onset of DR.

Dietary Patterns, Carbohydrates, and Age-Related Eye Diseases

Over a third of older adults in the U.S. experience significant vision loss, which decreases independence and is a biomarker of decreased health span. As the global aging population is expanding, it is imperative to uncover strategies to increase health span and reduce the economic burden of this age-related disease. While there are some treatments available for age-related vision loss, such as surgical removal of cataracts, many causes of vision loss, such as dry age-related macular degeneration (AMD), remain poorly understood and no treatments are currently available. Therefore, it is necessary to better understand the factors that contribute to disease progression for age-related vision loss and to uncover methods for disease prevention. One such factor is the effect of diet on ocular diseases. There are many reviews regarding micronutrients and their effect on eye health. Here, we discuss the impact of dietary patterns on the incidence and progression of age-related eye diseases, namely AMD, cataracts, diabetic retinopathy, and glaucoma. Then, we focus on the specific role of dietary carbohydrates, first by outlining the physiological effects of carbohydrates on the body and then how these changes translate into eye and age-related ocular diseases. Finally, we discuss future directions of nutrition research as it relates to aging and vision loss, with a discussion of caloric restriction, intermittent fasting, drug interventions, and emerging randomized clinical trials. This is a rich field with the capacity to improve life quality for millions of people so they may live with clear vision for longer and avoid the high cost of vision-saving surgeries.

Effect of Berberine on Glycation, Aldose Reductase Activity, and Oxidative Stress in the Lenses of Streptozotocin-Induced Diabetic Rats In Vivo-A Preliminary Study

Diabetes mellitus affects the eye lens, leading to cataract formation by glycation, osmotic stress, and oxidative stress. Berberine, an isoquinoline alkaloid, is a natural compound that has been reported to counteract all these pathological processes in various tissues and organs. The goal of this study was to evaluate whether berberine administered at a dose of 50 mg/kg by oral gavage for 28 days to rats with streptozotocin-induced diabetes reveals such effects on the biochemical parameters in the lenses. For this purpose, the following lenticular parameters were studied: concentrations of soluble protein, non-protein sulfhydryl groups (NPSH), advanced oxidation protein products (AOPP), advanced glycation end-products (AGEs), thiobarbituric acid reactive substances (TBARS), and activities of aldose reductase (AR), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Diabetes induced unfavorable changes in the majority of the examined parameters. The administration of berberine resulted in an increased soluble protein level, decreased activity of AR, and lowered AOPP and AGEs levels. The results suggest that berberine administered orally positively affects the lenses of diabetic rats, and should be further examined with regard to its anticataract potential.

Structural stability and solubility of glycated camel lens ζ-crystallin

The camel has several biochemical, physiological, and anatomical features to withstand the harsh desert climate. Camel eye lens contains a novel protein (ζ-crystallin) in bulk quantity. Previous reports suggest that non-enzymatic glycation of eye lens proteins plays an important role in the etiology of cataract. In this study, we have characterized the role of glucose, fructose, and methylglyoxal (MGO) in the glycation of camel lens ζ-crystallin. From the results obtained, it was found that MGO reacted rapidly, fructose reacted moderately, and glucose was the least reactive even after prolonged incubation (>100 days). Glycation with MGO and fructose led to changes in the structure of ζ-crystallin, while glucose had no remarkable effect. The surface hydrophobicity did not change and no aggregates or amyloid fibrils were observed in the glycated ζ-crystallin. Moreover, the secondary structure of glycated ζ-crystallin remained similar after glycation. Our results suggested that due to natural adaptation, the camel lens protein ζ-crystallin retained its structure and solubility even after glycation to perform the single known function of the lens proteins: to focus unscattered light on the retina.

Association between dietary glycemic index and glycemic load, insulin index and load with incidence of age-related cataract: Results from a case-control study

AIM

To identify the association between the dietary carbohydrate indexes, such as dietary glycemic index (DGI) and load (DGL), dietary insulin index (DII) and load (DIL), with the possibility of cataract.

METHOD

This case-control study consisted of 101 new cases of cataract and 202 controls. DGI and DGL were computed through DGI values previously published. DII was also calculated based on dietary insulin index data published previously.

RESULTS

There was a significant positive association between the highest quartiles of DGI (OR = 6.56; 95% CI = 2.67-16.06; P < 0.001), DGL (OR = 6.17; 95% CI = 1.93-19.37; P = 0.002) and DIL (OR = 4.17; 95% CI = 1.41-12.27; P = 0.004) with risk of cataract, compared to those on the lowest quartile, but not for DII (OR = 0.85; 95% CI = 0.39-1.86; P = 0.82). Furthermore, after stratifying groups by BMI, a significant direct association between highest quartile of DGI (OR = 6.76; 95% CI = 2.49-18.38; P < 0.001) and DGL (OR = 3.45; 95% CI = 0.96-12.37; P = 0.05) with risk of cataract was evident in individuals with elevated BMI (BMI≥25).

CONCLUSION

We found a significant, direct, relationship between DGI, DGL and DIL with risk of cataract. However, the association between DII and the risk of cataract was not significant, even after adjusting for related confounders.

Vitreous and Vision Degrading Myodesopsia

Macromolecules comprise only 2% of vitreous, yet are responsible for its gel state, transparency, and physiologic function(s) within the eye. Myopia and aging alter collagen and hyaluronan association causing concurrent gel liquefaction and fibrous degeneration. The resulting vitreous opacities and collapse of the vitreous body during posterior vitreous detachment are the most common causes for the visual phenomenon of vitreous floaters. Previously considered innocuous, the vitreous opacities that cause floaters sometimes impact vision by profoundly degrading contrast sensitivity function and impairing quality-of-life. While many people adapt to vitreous floaters, clinically significant cases can be diagnosed with Vision Degrading Myodesopsia based upon echographic assessment of vitreous structure and by measuring contrast sensitivity function. Perhaps due to the ubiquity of floaters, the medical profession has to date largely ignored the plight of those with Vision Degrading Myodesopsia. Improved diagnostics will enable better disease staging and more accurate identification of severe cases that merit therapy. YAG laser treatments may occasionally be slightly effective, but vitrectomy is currently the definitive cure. Future developments will usher in more informative diagnostic approaches as well as safer and more effective therapeutic strategies. Improved laser treatments, new pharmacotherapies, and possibly non-invasive optical corrections are exciting new approaches to pursue. Ultimately, enhanced understanding of the underlying pathogenesis of Vision Degrading Myodesopsia should result in prevention, the ultimate goal of modern Medicine.

Effect of an oral supplementation with a formula containing R-lipoic acid in glaucoma patients

OBJECTIVE

To analyse the safety and effectiveness of the oral administration of a commercialised supplement containing R-alpha lipoic acid, taurine, vitamins C and E, lutein, zeaxanthin, zinc, copper and docosahexaenoic acid, in patients with primary open angle glaucoma (POAG), and in control subjects.

MATERIAL AND METHODS

A prospective study of cases and controls was carried out, including 30 participants of both genders that were divided into: POAG Group (n=15) and a control group (CG; n=15), assigned to the oral intake of NuaDHA preparations Vision® (1 pill/day)+NuaDHA 1000 (2 pills/day) for 6 months. Participants were interviewed, ophthalmologically examined, and peripheral blood was taken for routine analysis and the determination of the pro-oxidant (malondialdehyde) and total antioxidant status. Statistical analysis was performed using the SPSS 22.0 program.

RESULTS

After 6 months of supplementation, there was a significant increase in the plasma total antioxidant status (1.073±0.090mM vs 1.276±0.107mM, P=.028), along with a parallel decrease in malondialdehyde (7.066±1.070μM vs 2.771±0.462μM, P=.005) in the POAG group. The malondialdehyde also decreased in the control group (6.17±1.336 vs. 2.51±0.391, P=.028). The Schirmer test improved (20-30%) and the subjective dry eye signs/symptoms noticeably decreased in the POAG group versus the CG.

CONCLUSIONS

Formulations containing antioxidant vitamins, R-alpha lipoic acid and docosahexaenoic acid, administered for 6 consecutive months, counteracted the oxidative stress by further stabilising the morphological/functional parameters of both the ocular surface and the glaucoma, without presenting with adverse effects or intolerances.

Corneal injury: Clinical and molecular aspects

Currently, over 10 million people worldwide are affected by corneal blindness. Corneal trauma and disease can cause irreversible distortions to the normal structure and physiology of the cornea often leading to corneal transplantation. However, donors are in short supply and risk of rejection is an ever-present concern. Although significant progress has been made in recent years, the wound healing cascade remains complex and not fully understood. Tissue engineering and regenerative medicine are currently at the apex of investigation in the pursuit of novel corneal therapeutics. This review uniquely integrates the clinical and cellular aspects of both corneal trauma and disease and provides a comprehensive view of the most recent findings and potential therapeutics aimed at restoring corneal homeostasis.

Perturbed Biochemical Pathways and Associated Oxidative Stress Lead to Vascular Dysfunctions in Diabetic Retinopathy

Diabetic retinopathy (DR) is a vascular insult that accompanies the hyperglycemic state. Retinal vasculature holds a pivotal role in maintaining the integrity of the retina, and any alteration to retinal vasculature affects retinal functions. The blood retinal barrier, a prerequisite to vision acuity, is most susceptible to damage during the progression of DR. This is a consequence of impaired biochemical pathways such as the polyol, advanced end glycation products (AGE), hexosamine, protein kinase C (PKC), and tissue renin-angiotensin system (RAS) pathways. Moreover, the role of histone modification and altered miRNA expression is also emerging as a major contributor. Epigenetic changes create a link between altered protein function and redox status of retinal cells, creating a state of metabolic memory. Although various biochemical pathways underlie the etiology of DR, the major insult to the retina is due to oxidative stress, a unifying factor of altered biochemical pathways. This review primarily focuses on the critical biochemical pathways altered in DR leading to vascular dysfunctions and discusses antioxidants as plausible treatment strategies.