Total activity of glutathione-S-transferase (GST) and polymorphisms of GSTM1 and GSTT1 genes conferring risk for the development of age related cataracts

Rosmarinic and Sinapic Acids May Increase the Content of Reduced Glutathione in the Lenses of Estrogen-Deficient Rats

Oxidative stress is believed to be associated with both postmenopausal disorders and cataract development. Previously, we have demonstrated that rosmarinic and sinapic acids, which are diet-derived antioxidative phenolic acids, counteracted some disorders induced by estrogen deficiency. Other studies have shown that some phenolic acids may reduce cataract development in various animal models. However, there is no data on the effect of phenolic acids on oxidative stress markers in the lenses of estrogen-deficient rats. The study aimed to investigate whether administration of rosmarinic acid and sinapic acid affects the antioxidative abilities and oxidative damage parameters in the lenses of estrogen-deficient rats. The study was conducted on three-month-old female Wistar rats. The ovariectomized rats were orally treated with rosmarinic acid at doses of 10 and 50 mg/kg or sinapic acid at doses of 5 and 25 mg/kg, for 4 weeks. The content of reduced glutathione (GSH), oxidized glutathione and amyloid β1-42, as well as products of protein and lipid oxidation, were assessed. Moreover, the activities of superoxide dismutase, catalase, and some glutathione-related enzymes in the lenses were determined. Rosmarinic and sinapic acids in both doses resulted in an increase in the GSH content and glutathione reductase activity. They also improved parameters connected with protein oxidation. Since GSH plays an important role in maintaining the lens transparency, the increase in GSH content in lenses after the use of rosmarinic and sinapic acids seems to be beneficial. Therefore, both the investigated dietary compounds may be helpful in preventing cataract.

Association of OGG1 and MTHFR polymorphisms with age-related cataract: A systematic review and meta-analysis

PURPOSE

To discern and confirm genetic biomarkers that help identify populations at high risk for age-related cataract (ARC).

METHODS

A literature search was performed in the PubMed, Web of Science and China National Knowledge Internet databases for genetic association studies published before June 26, 2016 regarding ARC susceptibility. All genetic polymorphisms reported were systematically reviewed, followed by extraction of candidate genes/loci with sufficient genotype data in ≥3 studies for the meta-analysis. A random/fixed-effects model was used to calculate the pooled odds ratios and 95% confidence intervals to evaluate the associations considering multiple genetic models. Sensitivity analysis was also performed.

RESULTS

A total of 144 polymorphisms in 36 genes were reported in the 61 previous genetic association studies. Thereby, three polymorphisms of two genes (8-oxoguanine DNA glycosylase-1 [OGG1]; methylenetetrahydrofolate reductase NADPH [MTHFR]) in eight studies were included in the meta-analysis. Regarding the OGG1-rs1052133, the GG (OR = 1.925; 95%CI, 1.181-3.136; p = 0.009) and CG (OR = 1.384; 95%CI, 1.171-1.636; p<0.001) genotypes indicated higher risk of ARC. For the MTHFR gene, the CC+TT genotype of rs1801133 might be protective (OR, 0.838; 95%CI, 0.710-0.989; p = 0.036), whereas the AA+CC genotype of rs1801131 indicated increased risk for the mixed subtype (OR = 1.517; 95%CI, 1.113-2.067; p = 0.008).

CONCLUSIONS

Polymorphisms of OGG1 and MTHFR genes are associated with ARC susceptibility and may help identify populations at high risk for ARC.

Age-related changes in the kinetics of human lenses: prevention of the cataract

The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina and, by changing shape, it adjusts focal distance (accommodation). The three classes of structural proteins found in the lens are α, β, and γ crystallins. These proteins make up more than 90% of the total dry mass of the eye lens. Other components which can be found are sugars, lipids, water, several antioxidants and low weight molecules. When ageing changes occur in the lens, it causes a gradual reduction in transparency, presbyopia and an increase in the scattering and aberration of light waves as well as a degradation of the optical quality of the eye. The main changes that occur with aging are: 1) reduced diffusion of water from the outside to the inside of the lens and from its cortical to its nuclear zone; 2) crystalline change due to the accumulation of high molecular weight aggregates and insoluble proteins; 3) production of advanced glycation end products (AGEs), lipid accumulation, reduction of reduced glutathione content and destruction of ascorbic acid. Even if effective strategies in preventing cataract onset are not already known, good results have been reached in some cases with oral administration of antioxidant substances such as caffeine, pyruvic acid, epigallocatechin gallate (EGCG), α-lipoic acid and ascorbic acid. Furthermore, methionine sulfoxide reductase A (MSRA) over expression could protect lens cells both in presence and in absence of oxidative stress-induced damage. Nevertheless, promising results have been obtained by reducing ultraviolet-induced oxidative damage.

Investigation of Glutathione S-Transferase Isoenzyme Protein Expression in Patients With Pterygium

PURPOSE

We investigated glutathione S-transferase (GST) enzymes in terms of their potential effects on the pathogenesis of pterygium.

METHODS

Twenty-six pterygium specimens and 15 normal conjunctival specimens of 15 control subjects were investigated. Expressions of GST (alpha, mu, pi, and theta) enzymes were assessed by immunohistochemical staining. A brown color in the cytoplasm and/or nuclei of epithelial cells was evaluated as positive staining for GST enzymes. For each antibody, the intensity of the reaction [negative (-), weak (1+), moderate (2+), or strong (3+)] was determined to describe the immunoreactions.

RESULTS

The median age was 52 years in the both groups. There was no significant difference between the groups in terms of age, sex, and intraocular pressure measurements (P > 0.05 for all). Of the 26 pterygium specimens, 15 (57.7%) (8 weak, 4 moderate, and 3 strong staining) were identified with GST pi-1 (GSTP1) expression and 20 (76.9%) (12 weak, 7 moderate, and 1 strong staining) with GST theta-1 (GSTT1) expression. Of the 15 control specimens, 4 (26.7%) (4 weak staining) were identified with the GSTP1 expression, and 1 (6.7%) with GSTT1 expression. GSTP1 and GSTT1 expressions were significantly higher in the pterygium specimens than in the controls (P = 0.043, P < 0.001; respectively). None of tissue specimens had positive staining for GST mu-1 or GST alpha-1 in both groups (both; P = 1.00).

CONCLUSIONS

The significant increase of GSTP1 and GSTT1 expressions in pterygium may be because of the increased activation of GST in response to excessive free radical formation from ultraviolet exposure to maintain antioxidant capacity in pterygium.

Is there association between Glutathione S Transferases polymorphisms and cataract risk: a meta-analysis?

Background

Glutathione S transferase (GST) polymorphisms have been considered as risk factors for age-related cataracts, but the results remain controversial. In this study, we have performed a meta-analysis to evaluate the association between polymorphisms of GSTM1 and GSTT1 and cataract risk.

Methods

Published literature from PubMed and other databases were retrieved. The case–control studies regarding the association between GSTM1 or GSTT1 polymorphism and cataract risk were included. Pooled odds ratio (OR) and 95 % confidence interval (CI) were calculated using random- or fixed-effects model.

Results

Fifteen studies on GSTM1 (3,065 patients and 2,105 controls), and nine studies on GSTT1 (2,374 patients and 1,544 controls) were included. By pooling all the studies, GSTM1 null polymorphism was not associated with cataract risk, and this negative association maintained in subgroup analyses. However, GSTT1 null polymorphism was significantly associated with increased risk of posterior subcapsular (OR, 1.42; 95 % CI, 1.04–1.94) but not other subtypes of cataract. Stratified analyses demonstrated an association of GSTT1 null genotype with increased risk of cataract in Asian (OR, 1.44; 95 % CI, 1.14–1.83) but not Caucasian populations. In addition, seven pooled studies showed no association of cataract risk with the combined GSTM1 and GSTT1 null genotypes.

Conclusions

This meta-analysis suggests that GSTT1 null polymorphism is associated with increased risk of posterior subcapsular cataract. Given the limited sample size, the association between GSTT1 null polymorphism and cataract risk in Asian awaits further investigation.

An Updated Meta-Analysis: Risk Conferred by Glutathione S-Transferases (GSTM1 and GSTT1) Polymorphisms to Age-Related Cataract

Purpose. To study the effects of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) polymorphisms on age-related cataract (ARC). Methods. After a systematic literature search, all relevant studies evaluating the association between GSTs polymorphisms and ARC were included. Results. Fifteen studies on GSTM1 and nine studies on GSTT1 were included in this meta-analysis. In the pooled analysis, a significant association between null genotype of GSTT1 and ARC was found (OR = 1.229, 95% CI = 1.057–1.429, and P = 0.007). In subgroup analysis, the association between cortical cataract (CC) and GSTM1 null genotype was statistically significant (OR = 0.713, 95% CI = 0.598–0.850, and P < 0.001). In addition, GSTM1 null genotype was significantly associated with ARC causing risk to individuals working indoors and not individuals working outdoors. The association between GSTT1 null genotype and risk of ARC was statistically significant in Asians (OR = 1.442, 95% CI = 1.137–1.830, and P = 0.003) but not in Caucasians. Conclusions. GSTM1 positive genotype is associated with increased risk of CC and loses the protective role in persons who work outdoors. Considering the ethnic variation, GSTT1 null genotype is found to be associated with increased risk of ARC in Asians but not in Caucasians.

Vitamin E and risk of age-related cataract: a meta-analysis

Objective

We conducted a meta-analysis to evaluate the relationship between vitamin E and age-related cataract (ARC).

Design

The fixed- or random-effect model was selected based on heterogeneity. Meta-regression was used to explore potential sources of between-study heterogeneity. Publication bias was evaluated using Begg’s test. The dose–response relationship was assessed by a restricted cubic spline model.

Setting

Relevant studies were identified by a search of PubMed and the Cochrane Library to May 2014, without language restrictions.

Subjects

Studies involved samples of people of all ages.

Results

Dietary vitamin E intake, dietary and supplemental vitamin E intake, and high serum tocopherol levels were significantly associated with decreased risk of ARC, the pooled relative risk was 0·73 (95 % CI 0·58, 0·92), 0·86 (95 % CI 0·75, 0·99) and 0·77 (95 % CI 0·66, 0·91), respectively. Supplemental vitamin E intake was non-significantly associated with ARC risk (relative risk=0·92; 95 % CI 0·78, 1·07). The findings from dose–response analysis showed evidence of a non-linear association between dietary vitamin E intake and ARC. The risk of ARC decreased with dietary vitamin E intake from 7 mg/d (relative risk=0·94; 95 % CI 0·90, 0·97).

Conclusions

The findings of the meta-analysis indicated that dietary vitamin E intake, dietary and supplemental vitamin E intake, and high level of serum tocopherol might be significantly associated with reduced ARC risk.

Association between DNA repair genes (XPD and XRCC1) polymorphisms and susceptibility to age-related cataract (ARC): a meta-analysis

BACKGROUND

DNA repair gene (XPD and XRCC1) polymorphisms have been considered as risk factors for the development of age-related cataract (ARC). To confirm the association between DNA repair gene (XPD and XRCC1) polymorphisms and the risk of ARC, a meta-analysis was conducted.

METHODS

A search was made of published literature from Institute for Scientific Information (ISI) Web of Knowledge, PubMed, Google Scholar, China National Knowledge Infrastructure (CNKI), and Wanfang Data. In addition, all studies evaluating the association between DNA repair genes (XPD and XRCC1) polymorphisms and the risk for ARC were included in our analysis. Pooled odds ratio (OR) and 95 % confidence interval (CI) were calculated by using fixed- or random-effects model. The Egger's test was used to check the publication bias.

RESULTS

Six studies on XRCC1 Arg399Gln (1,300 cases, 1,222 controls) and five studies on XPD Lys751Gln (1,092 cases, 1,061 controls) were included. For the XPD Lys751Gln (A/C) SNP, the overall analysis demonstrated that the CC genotype showed a significant association with a decreased risk for ARC compared with the AA genotype (OR = 0.59, 95 % CI, 0.38-0.92, P = 0.019). Similarly, the CC genotype showed a significant association with a decreased risk for ARC compared with the (AA + AC) genotype (OR = 0.65, 95 % CI, 0.43-0.98, P = 0.040). Subgroup analysis showed that the association between the CC genotype and decreased risk for ARC is statistically significant in Caucasians (OR = 0.41, 95 % CI, 0.24-0.73, P = 0.002) but not in Asians (OR = 1.06, 95 % CI, 0.51-2.19, P = 0.877). For the XRCC1 Arg399Gln (G/A) SNP, the overall analysis demonstrated that the A allele showed a significant association with an increased risk for ARC compared with the G allele (OR = 1.16, 95 % CI, 1.03-1.31, P = 0.015). Subgroup analyses exhibited that the association between the A allele and the risk for ARC was statistically significant in Asians (OR = 1.23, 95 % CI, 1.07-1.41, P = 0.003) but not in Caucasians (OR = 0.94, 95 % CI, 0.73-1.22, P = 0.660). Compared with the GG genotype, the GA genotype showed a significant association with an increased risk for ARC in Asians (OR = 1.32, 95 % CI, 1.08-1.61, P = 0.006) but not in Caucasians (OR = 0.58, 95 % CI, 0.27-1.26, P = 0.171). The Egger's test did not reveal an obvious publication bias among the included studies.

CONCLUSIONS

Our meta-analysis suggested that the CC genotype of XPD Lys751Gln (A/C) SNP seemed to portend a decreased risk for ARC in Caucasian populations but not in Asian populations. The A allele and GA genotype of XRCC1 Arg399Gln (G/A) SNP might increase risk for ARC in Asian populations but not in Caucasian populations. More researches with larger and more different ethnic populations on this issue are therefore necessary.

The eye as a model of ageing in translational research--molecular, epigenetic and clinical aspects

The eye and visual system are valuable in many areas of translational research such as stem cell therapy, transplantation research and gene therapy. Changes in many ocular tissues can be measured directly, easily and objectively in vivo (e.g. lens transparency; retinal blood vessel calibre; corneal endothelial cell counts) and so the eye may also be a uniquely useful site as a model of ageing. This review details cellular, molecular and epigenetic mechanisms related to ageing within the eye, and describes ocular parameters that can be directly measured clinically and which might be of value in ageing research as the translational "window to the rest of the body". The eye is likely to provide a valuable model for validating biomarkers of ageing at molecular, epigenetic, cellular and clinical levels. A research agenda to definitively establish the relationship between biomarkers of ageing and ocular parameters is proposed.