Changes in blood oxidative and antioxidant parameters in a group of Chinese patients with age-related macular degeneration

Carnosine supplementation and retinal oxidative parameters in a high-calorie diet rat model

BACKGROUND

To assess oxidative effects induced by a high-calorie diet on the retina of Wistar rats and test the antioxidative effects of carnosine supplementation.

METHODS

Wistar rats were randomly divided into the following groups: standard diet (SD), high-calorie diet (HcD), standard diet + carnosine (SD + Car), and high-calorie diet + carnosine (HcD + Car). The body weight, adiposity index, plasma glucose, total lipids, high-density lipoprotein (HDL), low-density lipoprotein (LDL), uric acid, creatinine, and triglycerides of the animals were evaluated. The retinas were analyzed for markers of oxidative stress. Hydrogen peroxide production was assessed by 2',7'-dichlorodihydrofluorescein diacetate (DCF) oxidation. The total glutathione (tGSH), total antioxidant capacity (TAC), protein carbonyl, and sulfhydryl groups of the antioxidant system were analyzed.

RESULTS

TAC levels increased in the retinas of the SD + Car group compared to the SD group (p < 0.05) and in the HcD + Car group compared to the HcD group (p < 0.05). The levels of GSH and the GSSH:GSSG ratio were increased in the HcD + Car group compared to the SD + Car group (p < 0.05). An increase in the retinal carbonyl content was observed in the HcD group compared to the SD group (p < 0.05) and in the HcD + Car group compared to the SD + Car group (p < 0.05). A high-calorie diet (HcD) was also associated with a decrease in retinal sulfhydryl-type levels compared to the SD group (p < 0.05).

CONCLUSION

The results suggest that feeding a high-calorie diet to rats can promote an increase in carbonyl content and a reduction in sulfhydryl groups in their retinas. The administration of carnosine was not effective in attenuating these oxidative markers.

TRIAL REGISTRATION

Animal Ethics Committee of Botucatu Medical School - Certificate number 1292/2019.

Effects of Zinc Acetate Hydrate Treatment on Serum Oxidative Stress Markers in Patients with Macular Drusen

Purpose: To measure the serum levels of the oxidative stress markers superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GPx) and compare them before and after zinc supplementation in patients with early age-related macular degeneration (AMD). Methods: We measured serum zinc levels in 65 patients with early AMD. Of these, 29 patients with macular drusen and a serum zinc level <80 μg/dL received oral zinc acetate dihydrate (50 mg/day). Serum trace metal levels (zinc and copper) and oxidative stress marker levels (SOD, MDA, and GPx) were measured at baseline and 12 weeks after the treatment. The macular drusen areas and best-corrected visual acuity were evaluated in 24 participants who attended the 3-month follow-up. Results: MDA level was significantly decreased from baseline to 12 weeks after zinc administration (170.5 ± 100.9 vs. 148.3 ± 57.9 pmol/mL, P = 0.03), while SOD was significantly increased from baseline to 12 weeks after zinc intake (4.2 ± 0.9 vs. 4.6 ± 0.9 U/mL, P = 0.03). The serum zinc level was significantly correlated with the MDA level (P = 0.03, ρ = -0.26). The area of soft drusen was significantly decreased after zinc treatment (1,936,654.9 ± 1,348,267.6 vs. 966,883.9 ± 719,938.1 μmm², P = 0.04). Conclusions: The levels of oxidative stress markers MDA and SOD decreased and increased, respectively, after oral zinc administration to 24 patients with AMD. The therapeutic effect of zinc treatment on drusen area might differ depending on the drusen phenotype in early AMD.

Oxidative and Nitrosative Stress in Age-Related Macular Degeneration: A Review of Their Role in Different Stages of Disease

Although the exact pathogenetic mechanisms leading to age-related macular degeneration (AMD) have not been clearly identified, oxidative damage in the retina and choroid due to an imbalance between local oxidants/anti-oxidant systems leading to chronic inflammation could represent the trigger event. Different in vitro and in vivo models have demonstrated the involvement of reactive oxygen species generated in a highly oxidative environment in the development of drusen and retinal pigment epithelium (RPE) changes in the initial pathologic processes of AMD; moreover, recent evidence has highlighted the possible association of oxidative stress and neovascular AMD. Nitric oxide (NO), which is known to play a key role in retinal physiological processes and in the regulation of choroidal blood flow, under pathologic conditions could lead to RPE/photoreceptor degeneration due to the generation of peroxynitrite, a potentially cytotoxic tyrosine-nitrating molecule. Furthermore, the altered expression of the different isoforms of NO synthases could be involved in choroidal microvascular changes leading to neovascularization. The purpose of this review was to investigate the different pathways activated by oxidative/nitrosative stress in the pathogenesis of AMD, focusing on the mechanisms leading to neovascularization and on the possible protective role of anti-vascular endothelial growth factor agents in this context.

MALONDIALDEHYDE LEVELS IN PATIENTS WITH AGE-RELATED MACULAR DEGENERATION: A Systematic Review and Meta-analysis

BACKGROUND/PURPOSE

The role of blood malondialdehyde (MDA) in age-related macular degeneration (AMD), the leading cause of new blindness in industrialized countries, is still matter of debate. We performed a systematic review and meta-analysis of the published data on the MDA levels in AMD patients.

METHODS

PubMed, ISI Web of Sciences, and Scopus searches were performed according to MOOSE guidelines. Case-control studies were eligible for inclusion. Participants and controls were AMD patients and subjects without AMD, respectively. The main outcome measures were wet AMD and dry AMD. MDA level was the main exposure variable. Data were pooled using a random-effects model.

RESULTS

Twelve case-control studies were identified. A total of 634 AMD patients (mean age 66.7 years) and 656 controls without AMD (mean age 67.8 years) were evaluated. Extreme between-study heterogeneity was observed (I = 96.8%, P < 0.001). Pooled standardized mean difference showed that MDA values were significantly higher in patients with AMD (standardized mean difference = 1.91 µmol/L, 95% confidence interval = 1.08-2.74; P < 0.001). In a model including five studies, homogenous for age, sample matrix, and laboratory testing for MDA, heterogeneity decreased from extreme to moderate (I = 46.4%, P = 0.113), and pooled standardized mean difference, though attenuated, remained significantly higher in AMD patients (standardized mean difference = 1.07 µmol/L, 95% confidence interval = 0.82-1.31; P < 0.001).

CONCLUSION

There is some evidence of higher levels of MDA in AMD patients compared with healthy controls; however, this result should be interpreted with caution because of extreme between-study heterogeneity and the possible effect of publication bias. Future studies, preferably well age-matched and of cohort design, are necessary before any firm conclusions on the putative role of elevated MDA on AMD can be drawn.

Serum malondialdehyde, monocyte chemoattractant protein-1, and vitamin C levels in wet type age-related macular degeneration patients

Purpose:

The purpose of this study was to investigate the serum levels of malondialdehyde (MDA) which is a marker of oxidative stress, monocyte chemoattractant protein-1 (MCP-1) which has an important role in inflammation, and vitamin C which has antioxidant properties in patients with wet age-related macular degeneration (wAMD).

Methods:

Thirty patients with wAMD were included in the study and serum levels of MDA, MCP-1, and vitamin C were compared with healthy participants (n = 30). Serum vitamin C and MDA levels were measured using a spectrophotometric method. Serum MCP-1 levels were determined by the ELISA method.

Results:

MCP-1 and MDA levels were higher in patients with wAMD compared with the control group (p < 0.05). Serum vitamin C levels were lower in patients with wAMD compared with the control group (p < 0.05).

Conclusions:

The increase in the MCP-1 levels in patients with wAMD may be associated with increased inflammation in wAMD. Decreased serum vitamin C and elevated MDA levels in patients with wAMD suggest increased oxidative stress in wAMD patients. These results indicate that the increased oxidative stress and inflammation can play a role in the pathogenesis of wAMD.

The Contribution of Fluoride to the Pathogenesis of Eye Diseases: Molecular Mechanisms and Implications for Public Health

This study provides diverse lines of evidence demonstrating that fluoride (F) exposure contributes to degenerative eye diseases by stimulating or inhibiting biological pathways associated with the pathogenesis of cataract, age-related macular degeneration and glaucoma. As elucidated in this study, F exerts this effect by inhibiting enolase, τ-crystallin, Hsp40, Na⁺, K⁺-ATPase, Nrf2, γ -GCS, HO-1 Bcl-2, FoxO1, SOD, PON-1 and glutathione activity, and upregulating NF-κB, IL-6, AGEs, HsP27 and Hsp70 expression. Moreover, F exposure leads to enhanced oxidative stress and impaired antioxidant activity. Based on the evidence presented in this study, it can be concluded that F exposure may be added to the list of identifiable risk factors associated with pathogenesis of degenerative eye diseases. The broader impact of these findings suggests that reducing F intake may lead to an overall reduction in the modifiable risk factors associated with degenerative eye diseases. Further studies are required to examine this association and determine differences in prevalence rates amongst fluoridated and non-fluoridated communities, taking into consideration other dietary sources of F such as tea. Finally, the findings of this study elucidate molecular pathways associated with F exposure that may suggest a possible association between F exposure and other inflammatory diseases. Further studies are also warranted to examine these associations.

Analysis of antioxidative factors related to AMD risk development in the polish patients

PURPOSE

Age-related macular degeneration (AMD) is a major cause of blindness in developed countries. Oxidative mechanisms may play a key role in the aetiology of AMD. The main aim of this study was to investigate antioxidative markers in the pathogenesis of AMD.

METHODS

A total of 510 subjects including 240 patients with AMD (mean age 77.9 ± 8.5 year) and 270 controls (mean age 74.0 ± 10.4 year) were allowed in this study. We measured activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and examined their association with the SNPs of respective genes (SOD1 + 35A/C, CAT C-262T and GPx Pro197Leu). Restriction fragment length polymorphism (RFLP) technique was used to determine the selected gene polymorphisms. Sixty subjects including 30 patients with AMD (mean age 69.4 ± 9.3) and 30 controls (mean age 64.6 ± 8.2) were enrolled to determine the activity of antioxidant enzymes by spectrometry method.

RESULTS

A significant decrease in enzymes, SOD (p = 0.011), CAT (p = 0.002) and GPx (p ≤ 0.001) in AMD patients compared to controls, was indicated. The risk of susceptibility to AMD was significantly higher in patients with AMD who had Pro197Leu C/T genotype of GPx (OR = 2.78; 95% CI = 1.78-4.35). The A/C genotype and the C allele frequencies of A/C polymorphism of SOD1 gene significantly reduce the risk of AMD (OR=0.48; 95% CI 0.27; 0.85).

CONCLUSION

In conclusion, our data showed that insufficient antioxidant capacity may have an important role in age-related macular degeneration. The polymorphism of GPx Pro197Leu may reduce the ability to scavenge free radicals in retina and contribute to the development of AMD.

Systemic and ocular fluid compounds as potential biomarkers in age-related macular degeneration

Biomarkers can help unravel mechanisms of disease and identify new targets for therapy. They can also be useful in clinical practice for monitoring disease progression, evaluation of treatment efficacy, and risk assessment in multifactorial diseases, such as age-related macular degeneration (AMD). AMD is a highly prevalent progressive retinal disorder for which multiple genetic and environmental risk factors have been described, but the exact etiology is not yet fully understood. Many compounds have been evaluated for their association with AMD. We performed an extensive literature review of all compounds measured in serum, plasma, vitreous, aqueous humor, and urine of AMD patients. Over 3600 articles were screened, resulting in more than 100 different compounds analyzed in AMD studies, involved in neovascularization, immunity, lipid metabolism, extracellular matrix, oxidative stress, diet, hormones, and comorbidities (such as kidney disease). For each compound, we provide a short description of its function and discuss the results of the studies in relation to its usefulness as AMD biomarker. In addition, biomarkers identified by hypothesis-free techniques, including metabolomics, proteomics, and epigenomics, are covered. In summary, compounds belonging to the oxidative stress pathway, the complement system, and lipid metabolism are the most promising biomarker candidates for AMD. We hope that this comprehensive survey of the literature on systemic and ocular fluid compounds as potential biomarkers in AMD will provide a stepping stone for future research and possible implementation in clinical practice.

Nutritional Supplementation Inhibits the Increase in Serum Malondialdehyde in Patients with Wet Age-Related Macular Degeneration

Purpose. To compare serum levels of malondialdehyde (MDA) in patients with wet age-related macular degeneration (wAMD), patients with dry AMD (dAMD), and patients without AMD and to evaluate the efficacy of nutritional supplementation for treating elevated serum MDA in patients with wAMD. Methods. MDA levels were measured in sera from 20 patients with wAMD, 20 with dAMD, and 24 without AMD. Patients with wAMD were randomized to receive or not receive nutritional supplementation (10 patients in each group), and MDA levels were measured after 3 months of treatment. Results. MDA levels in patients with wAMD were significantly greater compared with patients without AMD. In eyes with wAMD, there was a significant correlation between MDA levels and choroidal neovascularization lesion area. Serum MDA levels decreased in most patients that received supplementation and significantly increased in those who did not. Conclusion. Baseline serum MDA levels were elevated in patients with wAMD, and MDA levels were directly correlated with choroidal neovascularization lesion area. In addition, nutritional supplementation appeared to exert a protective effect against oxidative stress in patients with wAMD.

Malondialdehyde induces autophagy dysfunction and VEGF secretion in the retinal pigment epithelium in age-related macular degeneration

Age-related macular degeneration (AMD) is a major cause of blindness in developed countries and is closely related to oxidative stress, which leads to lipid peroxidation. Malondialdehyde (MDA) is a major byproduct of polyunsaturated fatty acid (PUFA) peroxidation. Increased levels of MDA have been reported in eyes of AMD patients. However, little is known about the direct relationship between MDA and AMD. Here we show the biological importance of MDA in AMD pathogenesis. We first confirmed that MDA levels were significantly increased in eyes of AMD patients. In ARPE-19 cells, a human retinal pigment epithelial cell line, MDA treatment induced vascular endothelial growth factor (VEGF) expression alternation, cell junction disruption, and autophagy dysfunction that was also observed in eyes of AMD patients. The MDA-induced VEGF increase was inhibited by autophagy-lysosomal inhibitors. Intravitreal MDA injection in mice increased laser-induced choroidal neovascularization (laser-CNV) volumes. In a mouse model fed a high-linoleic acid diet for 3 months, we found a significant increase in MDA levels, autophagic activity, and laser-CNV volumes. Our study revealed an important role of MDA, which acts not only as a marker but also as a causative factor of AMD pathogenesis-related autophagy dysfunction. Furthermore, higher dietary intake of linoleic acid promoted CNV progression in mice with increased MDA levels.

Association of age-related macular degeneration with erythrocyte antioxidant enzymes activity and serum total antioxidant status

The aim was to estimate association of the oxidative stress with the occurrence of age-related macular degeneration (AMD). The activities of erythrocyte antioxidant enzymes: superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) and additionally serum total antioxidant status (TAS) were used as indicators of the oxidative stress level. 57 AMD patients (32 early and 25 late AMD) and 50 healthy, age and gender matched controls were included. GPx activity (P < 0.001) and serum TAS (P = 0.015) were significantly lower in AMD patients. The difference was not significant for SOD or CAT activities. Significant interaction between GPx and SOD was detected (P = 0.003). At high levels of SOD activity (over 75th percentile), one standard deviation decrease in GPx increases the odds for AMD for six times (OR = 6.22; P < 0.001). ROC analysis revealed that combined values of GPx activity and TAS are significant determinants of AMD status. Accuracy, sensitivity, specificity, and positive and negative predictive values were 75%, 95%, 52%, 69%, and 90%, respectively. The study showed that low GPx activity and TAS are associated with AMD. SOD modulates the association of GPx and AMD. The results suggest that erythrocyte antioxidant enzymes activity and serum TAS could be promising markers for the prediction of AMD.

The reduction of serum soluble Flt-1 in patients with neovascular age-related macular degeneration

PURPOSE

To evaluate serum soluble Flt-1 (sFlt-1) in age-related macular degeneration (AMD) patients.

DESIGN

Case-control study.

METHODS

Study involved 56 non-AMD participants, 53 early AMD patients, and 97 neovascular AMD patients from Belfast in Northern Ireland. Serum samples were collected from each patient. Serum sFlt-1 was measured by human sVEGFR1/sFlt-1 ELISA kit. The results were analyzed by Excel and SPSS.

RESULTS

Serum sFlt-1 concentration of non-AMD, early AMD, and neovascular AMD were 90.8 ± 2.9 pg/mL (± standard error of the mean), 88.2 ± 2.6 pg/mL, and 79.9 ± 2.2 pg/mL. sFlt-1 from neovascular AMD patients was significantly decreased compared to non-AMD and early AMD patients (ANOVA, P < .01). For each 10-point increase in sFlt-1, the odds for having neovascular AMD compared with non-AMD and neovascular AMD decrease by 27.8%, odds ratio (OR) = 0.722 (95% confidence interval [CI]: 0.588-0.888, P = .002) and 27.0%, OR = 0.730 (95% CI: 0.594-0.898, P = .003), respectively. In patients over 73 years of age, serum sFlt-1 <80 pg/mL was associated with a >6-fold higher risk of neovascular AMD.

CONCLUSIONS

Reduced serum sFlt-1 differentiates those patients with neovascular AMD from both early AMD and non-AMD participants. In those aged over 73, serum sFlt <80 pg/mL seems to indicate a particularly high risk of neovascular AMD. Our results indicate serum sFlt-1 could be a biomarker for development of neovascular AMD.

Smoking and age-related macular degeneration: review and update

Age-related macular degeneration (AMD) is one of the main socioeconomical health issues worldwide. AMD has a multifactorial etiology with a variety of risk factors. Smoking is the most important modifiable risk factor for AMD development and progression. The present review summarizes the epidemiological studies evaluating the association between smoking and AMD, the mechanisms through which smoking induces damage to the chorioretinal tissues, and the relevance of advising patients to quit smoking for their visual health.

Role of antioxidant enzymes and small molecular weight antioxidants in the pathogenesis of age-related macular degeneration (AMD)

Cells in aerobic condition are constantly exposed to reactive oxygen species (ROS), which may induce damage to biomolecules, including proteins, nucleic acids and lipids. In normal circumstances, the amount of ROS is counterbalanced by cellular antioxidant defence, with its main components—antioxidant enzymes, DNA repair and small molecular weight antioxidants. An imbalance between the production and neutralization of ROS by antioxidant defence is associated with oxidative stress, which plays an important role in the pathogenesis of many age-related and degenerative diseases, including age-related macular degeneration (AMD), affecting the macula—the central part of the retina. The retina is especially prone to oxidative stress due to high oxygen pressure and exposure to UV and blue light promoting ROS generation. Because oxidative stress has an established role in AMD pathogenesis, proper functioning of antioxidant defence may be crucial for the occurrence and progression of this disease. Antioxidant enzymes play a major role in ROS scavenging and changes of their expression or/and activity are reported to be associated with AMD. Therefore, the enzymes in the retina along with their genes may constitute a perspective target in AMD prevention and therapy.

Diminishing risk for age-related macular degeneration with nutrition: a current view

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. Clinical hallmarks of AMD are observed in one third of the elderly in industrialized countries. Preventative interventions through dietary modification are attractive strategies, because they are more affordable than clinical therapies, do not require specialists for administration and many studies suggest a benefit of micro- and macro-nutrients with respect to AMD with few, if any, adverse effects. The goal of this review is to provide information from recent literature on the value of various nutrients, particularly omega-3 fatty acids, lower glycemic index diets and, perhaps, some carotenoids, with regard to diminishing risk for onset or progression of AMD. Results from the upcoming Age-Related Eye Disease Study (AREDS) II intervention trial should be particularly informative.

Biomarkers of oxidative stress in patients with wet age related macular degeneration

OBJECTIVE

The aim of this study was to analyze biomarkers of oxidative stress in patients with wet age related macular degeneration (AMD).

PARTICIPANTS AND MEASUREMENTS

Case-control study that includes 163 patients with wet AMD (age group of 55-82 years with the mean age of 71 years and 170 age-matched healthy controls in the age group of 55-78 years with the mean age of 71 years. The following parameters were determined: reduced and oxidized Glutathione (GSH/GSSH), protein carbonyl groups, total antioxidant activity in plasma and the activity of endogenous antioxidant enzymes, such as, gluthatione peroxidase, gluthatione reductase and superoxide dismutase.

RESULTS

We observed total antioxidant activity higher in control group (CG) compared with patients with wet AMD (7.1 ± 1.2 μM Trolox vs 5.8 ± 1.1 μM Trolox). Values of superoxide dismutase activity (SOD), gluthatione reductase (GR) and gluthatione peroxidase (GPx) are higher in control group than in patients with wet AMD. According to the GSH/GSSH results, average values were higher in the CG than in patients with wet AMD and data were not significantly different.. Values of protein carbonyl groups were higher in patients with wet AMD than in CG and significant differences were found.

CONCLUSIONS

The finding of the present study suggests that the patients with wet AMD are an altered metabolic state of oxidation-reduction and that it is convenient to give therapeutic interventions with antioxidants. We have demonstrated that systematic oxidative stress, measured by different biomarkers is closely associated with the wet AMD.