GPX1 Pro(198)Leu polymorphism, erythrocyte GPX activity, interaction with alcohol consumption and smoking, and risk of colorectal cancer

Immunohistochemical Expression of Glutathione Peroxidase 1 (Gpx-1) as an Independent Prognostic Factor in Colon Adenocarcinoma Patients

Several studies revealed that expression levels of glutathione peroxidase 1 (Gpx-1) can be associated with cancer development, mainly through its role in hydroperoxide scavenging by regulating intracellular reactive oxygen species (ROS) levels. Therefore, our aim was to investigate the expression of Gpx-1 protein in a population of Polish patients with colon adenocarcinoma in the absence of any therapy prior to radical surgery. The study was carried out using colon tissue from patients with adenocarcinoma of the colon confirmed by histopathological examination. Gpx-1 antibody was used to determine the immunohistochemical expression of Gpx-1. The Chi²test or Chi²_Yatesa test were used to analyse the associations between the immunohistochemical expression of Gpx-1 and clinical parameters. The relationship between Gpx-1 expression, and 5-year patient survival was examined using Kaplan-Meier analysis and the log-rank test. Intracellular localisation of Gpx-1 was detected by the use of transmission electron microscopy (TEM). Western blot analysis was used for the evaluation of Gpx-1 protein expression levels in cancer cell lines in vitro. Immunohistochemical study revealed that the high expression of Gpx-1 was associated with the tumour's histological grade, proliferating cell nuclear antigen (PCNA) immunohistochemical expression, depth of invasion, and angioinvasion (all p < 0.001) (4). The high immunohistochemical expression of Gpx-1 is correlated with poor prognosis of colon adenocarcinoma patients.

Glutathione Peroxidase GPX1 and Its Dichotomous Roles in Cancer

As the first identified selenoprotein, glutathione peroxidase 1 (GPX1) is a widely and abundantly expressed antioxidant enzyme. GPX1 utilizes glutathione as a substrate to catalyze hydrogen peroxide, lipid peroxide, and peroxynitrite, thereby reducing intracellular oxidative stress. The GPX1 gene is regulated at transcriptional, post-transcriptional, and translational levels. Numerous case-control studies and meta-analyses have assessed the association between a functional genetic polymorphism of the GPX1 gene, named Pro198Leu (rs1050450 C>T), and cancer susceptibility in different populations. GPX1 polymorphism has type-specific effects as a candidate marker for cancer risk, but the association between GPX1 variants and cancer susceptibility remains controversial in different studies. GPX1 is abnormally elevated in most types of cancer but has complex dichotomous roles as tumor suppressor and promoter in different cancers. GPX1 can participate in various signaling pathways to regulate tumor biological behaviors, including cell proliferation, apoptosis, invasion, immune response, and chemoresistance. In this review, we comprehensively summarize the controversial associations between GPX1 polymorphism and cancer risks and further discuss the relationships between the aberrant expressions of GPX1 and tumorigenesis. Further studies are needed to elucidate the clinical significance of GPX1 as a potential prognostic biomarker and novel therapeutic target in various malignancies.

The association among calorie, macronutrient, and micronutrient intake with colorectal cancer: A case-control study

The risk of colorectal cancer (CRC) can be influenced by dietary components. This study aims to investigate the association between dietary intake and CRC in Iranian adults. This hospital‐based case–control study was performed on 160 patients with CRC and 320 healthy people. General and pathological data were collected through face‐to‐face interviews. A validated food frequency questionnaire (FFQ) was used to assess the intake of calories, macronutrients, and micronutrients. The case group had a significantly higher intake of calories, carbohydrates, vitamin A, vitamin K, fluoride, and molybdenum and a lower intake of vitamin E, vitamin B1, beta carotene, biotin, folate, magnesium, selenium, manganese, and fiber (all p < .001). CRC was positively associated with the intake of carbohydrate (OR: 1.01, CI% 1.03–1.01, p = .001), and vitamin A (OR: 1.009, CI 95% 1.006–1.01, p = .001) and negatively associated with intake of fiber (OR: 0.67, CI 95% 0.59–0.76, p = .001), beta carotene (OR: 0.99, CI 95% 0.99–0.99, p = .001), vitamin E (OR: 0.27, CI 95% 0.15–0.47, p = .001), folate (OR: 0.98 CI 95% 0.97–0.98, p = .001), and biotin (OR: 0.83, CI 95% 0.77–0.90, p = .001). The associations remained significant after adjusting for age and sex. Further adjustments for physical activity, alcohol consumption, and smoking did not change the results. The results identified that the risk of colorectal cancer can be influenced by dietary intake. Further longitudinal studies are needed to confirm these findings and to identify the underlying mechanisms of the effects of dietary components on the risk of colorectal cancer.

An Assessment of GPX1 (rs1050450), DIO2 (rs225014) and SEPP1 (rs7579) Gene Polymorphisms in Women with Endometrial Cancer

Background: Numerous studies indicate a relationship between the presence of GPX1 (rs1050450), DIO2 (rs225014) and SEPP1 (rs7579) gene polymorphisms and the development of chronic or neoplastic diseases. However, there are no reports on the influence of these polymorphisms on the development of endometrial cancer. Methods: 543 women participated in the study. The study group consisted of 269 patients with diagnosed endometrial cancer. The control group consisted of 274 healthy women. Blood samples were drawn from all the participants. The PCR-RFLP method was used to determine polymorphisms in the DIO2 (rs225014) and GPX1 (rs1050450) genes. The analysis of polymorphisms in the SEPP1 (rs7579) gene was performed by means of TaqMan probes. Results: There was a 1.99-fold higher risk of developing endometrial cancer in CC homozygotes, DIO2 (rs225014) polymorphism (95% Cl 1.14–3.53, p = 0.017), compared to TT homozygotes. There was no correlation between the occurrence of GPX1 (rs1050450) and SEPP1 (rs7579) polymorphisms and endometrial cancer. Conclusion: Carriers of the DIO2 (rs225014) polymorphism may be predisposed to the development of endometrial cancer. Further research confirming this relationship is recommended.

Human glutathione peroxidase codon 198 variant increases nasopharyngeal carcinoma risk and progression

PURPOSE

Glutathione peroxidase 1 (GPx-1) is a selenium-dependent detoxifying enzyme involved in the protection of cells against oxidative damage. Some genetic association studies reported significant associations between GPx-1 Pro198Leu variant and carcinogenesis across different populations; however, the impact of this variant on nasopharyngeal carcinoma (NPC) has not been explored. Therefore, the present study was planned to evaluate the potential involvement of the GPx-1 Pro198Leu variant and plasma GPx activity in the risk of developing NPC in a Tunisian population.

METHODS

The GPx-1 Pro198Leu genotype was determined in 327 NPC patients and 150 healthy controls by the RFLP-PCR analysis. The correlation between the GPx-1 variant and the clinicopathological parameters was examined. GPx activity was assessed in the plasma of 119 NPC patients and 58 healthy control subjects and according to GPx-1 genotypes and clinicopathological characteristics of NPC patients.

RESULTS

A significant association was found between GPx-1 Pro198Leu variant and NPC risk in a Tunisian population. The allelic frequencies of Pro and Leu alleles were 32% versus 68% and 41% versus 59% in NPC cases and controls, respectively. Thus, the minor 198 Leu allele increased significantly in NPC patients and appeared as a potential risk factor for NPC occurrence (OR = 1.48, CI 95% = 1.14-1.91, p = 0.002). The plasma GPx activity was significantly higher in NPC patients than in controls (p = 0.03). According to the clinicopathological characteristics of NPC patients, GPx activity decreased significantly in patients with lymph node metastasis (p = 0.004).

CONCLUSION

This is the first study showing a strong association between GPx-1 Pro198Leu genetic variant and NPC risk. GPx-1 Pro198Leu variant increased the development of regional lymph node metastasis. Plasma GPx activity was higher in NPC patients. Thus, GPx-1 gene could be considered as a determinant factor influencing NPC risk and progression.

The Role of Oxidative Stress and the Importance of miRNAs as Potential Biomarkers in the Development of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the primary cause of blindness in developed countries. With the progressive aging of the population, AMD is a significant ophthalmological problem in the population over 50 years of age. The etiology of AMD is known to be based on various biochemical, immunological and molecular pathways and to be influenced by a range of genetic and environmental elements. This review provides an overview of the pathophysiological role of oxidative stress and free radicals in the retina with a special focus on the DNA repair efficiency and enzymatic antioxidant defense. It also presents a correlation between miRNA profile and AMD, and indicates their involvement in inflammation, angiogenesis, increased oxidation of cellular components, enzymatic antioxidant capacity and DNA repair efficiency, which play particularly important roles in AMD pathogenesis. Gene silencing by miRNAs can induce changes in antioxidant enzymes, leading to a complex interplay between redox imbalance by free radicals and miRNAs in modulating cellular redox homeostasis.

Role of Oxidative Stress and Nrf2/KEAP1 Signaling in Colorectal Cancer: Mechanisms and Therapeutic Perspectives with Phytochemicals

Colorectal cancer still has a high incidence and mortality rate, according to a report from the American Cancer Society. Colorectal cancer has a high prevalence in patients with inflammatory bowel disease. Oxidative stress, including reactive oxygen species (ROS) and lipid peroxidation, has been known to cause inflammatory diseases and malignant disorders. In particular, the nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-related protein 1 (KEAP1) pathway is well known to protect cells from oxidative stress and inflammation. Nrf2 was first found in the homolog of the hematopoietic transcription factor p45 NF-E2, and the transcription factor Nrf2 is a member of the Cap 'N' Collar family. KEAP1 is well known as a negative regulator that rapidly degrades Nrf2 through the proteasome system. A range of evidence has shown that consumption of phytochemicals has a preventive or inhibitory effect on cancer progression or proliferation, depending on the stage of colorectal cancer. Therefore, the discovery of phytochemicals regulating the Nrf2/KEAP1 axis and verification of their efficacy have attracted scientific attention. In this review, we summarize the role of oxidative stress and the Nrf2/KEAP1 signaling pathway in colorectal cancer, and the possible utility of phytochemicals with respect to the regulation of the Nrf2/KEAP1 axis in colorectal cancer.

The influence of nutrigenetics on biomarkers of selenium nutritional status

Selenium (Se) is an essential micronutrient for human biology that executes its functions as the amino acid selenocysteine via selenoproteins, which have important functions in, for example, antioxidation, immunomodulation, thyroid metabolism, and human fertility. Se nutritional status is assessed using the quantification of blood Se biomarkers, which are influenced by several factors, including diet, age, gender, smoking status, alcohol consumption, health condition, and the genetic characteristics of individuals. Nutrigenetic studies have identified single nucleotide polymorphisms in selenoproteins that might clarify the high variability in values reported for biomarkers of Se nutritional status in different populations, and the response of these biomarkers to Se supplementation with either organic or inorganic forms of Se. This review aims to (1) define the basic aspects of Se biology, (2) describe the current most commonly used biomarkers of Se nutritional status, and (3) provide a summary of associations between functional single nucleotide polymorphisms in selenoproteins and biomarkers of Se status in healthy populations.

Nutrigenetics of antioxidant enzymes and micronutrient needs in the context of viral infections

Sustaining adequate nutritional needs of a population is a challenging task in normal times and a priority in times of crisis. There is no 'one-size-fits-all' solution that addresses nutrition. In relevance to the COVID-19 (coronavirus disease 2019) pandemic crisis, viral infections in general and RNA viruses in particular are known to induce and promote oxidative stress, consequently increasing the body's demand for micronutrients, especially those related to antioxidant enzymic systems, thus draining the body of micronutrients, and so hindering the human body's ability to cope optimally with oxidative stress. Common polymorphisms in major antioxidant enzymes, with world population minor allele frequencies ranging from 0·5 to 50 %, are related to altered enzymic function, with substantial potential effects on the body's ability to cope with viral infection-induced oxidative stress. In this review we highlight common SNP of the major antioxidant enzymes relevant to nutritional components in the context of viral infections, namely: superoxide dismutases, glutathione peroxidases and catalase. We delineate functional polymorphisms in several human antioxidant enzymes that require, especially during a viral crisis, adequate and potentially additional nutritional support to cope with the pathological consequences of disease. Thus, in face of the COVID-19 pandemic, nutrition should be tightly monitored and possibly supplemented, with special attention to those carrying common polymorphisms in antioxidant enzymes.

Association Between the hOGG1 1245C>G (rs1052133) Polymorphism and Susceptibility to Colorectal Cancer: a Meta-analysis Based on 7010 Cases and 10,674 Controls

BACKGROUND

The 1245C>G (rs1052133) polymorphism of human 8-oxoguanine DNA glycosylase 1 (hOGG1) gene has been indicated to be correlated with colorectal (CRC) susceptibility, but studies have yielded conflicting results. Thus, the present meta-analysis was performed to derive a more precise estimation between hOGG1 1245C>G polymorphism and CRC risk.

METHODS

Data were collected from several electronic databases such as PubMed, EMBASE, and Google Scholar databases, with the last search up to September 01, 2020. Pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to assess the strength of the association.

RESULTS

A total of 24 case-control studies with 7010 CRC cases and 10,674 controls were selected. Pooled data showed that the hOGG1 1245C>G polymorphism was significantly associated with CRC risk under three genetic models, i.e., homozygote (GG vs. CC: OR = 1.229, 95% CI 1.031-1.465, p = 0.022); heterozygote (GC vs. CC: OR = 1.142, 95% CI 1.008-1.294, p = 0.037); and dominant (GG+GC vs. CC: OR = 1.162, 95% CI 1.034-1.304, p = 0.011). When stratified analysis by ethnicity, a significant association of the hOGG1 1245C>G polymorphism with risk of CRC was found in the Caucasians, but not in Asians. Moreover, there were significant associations between hOGG1 1245C>G polymorphism and CRC by PCR-RFLP and hospital-based subgroups.

CONCLUSIONS

Inconsistent with the previous meta-analysis, these meta-analysis results revealed that the hOGG1 1245C>G polymorphism might be associated with an increased risk of CRC, especially in Caucasians.

Association between Dietary Zinc and Selenium Intake, Oxidative Stress-Related Gene Polymorphism, and Colorectal Cancer Risk in Chinese Population - A Case-Control Study

Zinc and selenium may protect against colorectal cancer (CRC) progression through their anti-oxidative effects. This study examined the independent and combined effect of dietary zinc and selenium intake, and polymorphisms of the oxidative stress-related genes (superoxide dismutase 1, superoxide dismutase 2, glutathione peroxidase, and catalase) on CRC risk in a Chinese case-control study. A total of 493 cases and 498 sex and age-matched controls were randomly selected from an ongoing case-control study. Dietary information was assessed through face-to-face interviews using a validated food frequency questionnaire. Multiplex PCR-ligase detection reaction was used for genotyping the target SNPs. Multivariable logistic regression was used to estimate the odds ratios (ORs) and 95% confidence interval (CI). Intake of selenium was found to be inversely associated with CRC risk, while zinc was not associated with CRC risk. The ORs (95% CI) for the highest vs. the lowest quartile were 0.42 (95% CI 0.28, 0.64, P_trend < 0.001) for selenium and 0.96 (95% CI 0.63, 1.47, P_trend = 0.505) for zinc. Combined effect was observed between zinc and SOD1 rs4998557 on CRC risk (P_interaction < 0.05). This study identified a novel diet-gene interaction in the oxidative stress pathway on CRC risk in Chinese population.

Selenoproteins in colon cancer

Selenocysteine-containing proteins (selenoproteins) have been implicated in the regulation of various cell signaling pathways, many of which are linked to colorectal malignancies. In this in-depth excurse into the selenoprotein literature, we review possible roles for human selenoproteins in colorectal cancer, focusing on the typical hallmarks of cancer cells and their tumor-enabling characteristics. Human genome studies of single nucleotide polymorphisms in various genes coding for selenoproteins have revealed potential involvement of glutathione peroxidases, thioredoxin reductases, and other proteins. Cell culture studies with targeted down-regulation of selenoproteins and studies utilizing knockout/transgenic animal models have helped elucidate the potential roles of individual selenoproteins in this malignancy. Those selenoproteins, for which strong links to development or progression of colorectal cancer have been described, may be potential future targets for clinical interventions.

Human 8-oxoguanine DNA glycosylase gene polymorphism (Ser326Cys) and cancer risk: updated meta-analysis

Genetic polymorphism of human 8-oxoguanine glycosylase 1 (hOGG1) has been reported to have a relationship with the risk of the development of various cancers. Many studies have described the influence of Ser326Cys polymorphism of the hOGG1 gene on cancer susceptibility. However, the results have remained inconclusive and controversial. Therefore, we performed a meta-analysis to more precisely determine the relationship between the hOGG1 polymorphism and the development of cancer.Electronic databases including PubMed, Embase, Google Scholar, and the Korean Studies Information Service System (KISS) were searched. The odds ratio (OR), 95% confidence interval (CI), and p value were calculated to assess the strength of the association with the risk of cancer using Comprehensive Meta-analysis software (Corporation, NJ, USA). The 127 studies including 38,757 cancer patients and 50,177 control subjects were analyzed for the meta-analysis.Our meta-analysis revealed that G allele of Ser326Cys polymorphism of the hOGG1 gene statistically increased the susceptibility of cancer (all population, OR = 1.092, 95% CI = 1.051-1.134, p < 0.001; in Asian, OR = 1.095, 95% CI = 1.048-1.145, p < 0.001; in Caucasian, OR = 1.097, 95% CI = 1.033-1.179, p = 0.002). Also, other genotype models showed significant association with cancer (p < 0.05, respectively).The present meta-analysis concluded that the G allele was associated with an increased risk of cancer. It suggested that the hOGG1 polymorphism may be a candidate marker of cancer.

Genetic variants in selenoprotein genes modulate biomarkers of selenium status in response to Brazil nut supplementation (the SU.BRA.NUT study)

BACKGROUND

The beneficial effects of selenium (Se) to human health are exerted by selenoproteins, which can be quantified in blood and used as biomarkers of Se status. Different responses of Se biomarkers after supplementation with selenomethionine and sodium selenite have been observed and some of them could be due to genetic polymorphisms, mainly single nucleotide polymorphisms (SNPs). Brazil nuts are known to be the richest natural source of Se.

OBJECTIVE

Investigate how genetic variations in selenoprotein genes modulate biomarkers of Se status in response to Brazil nut supplementation.

METHODS

The SU.BRA.NUT study was a four month interventional trial which involved healthy volunteers of both genders, selected in University of Sao Paulo. The supplementation was done with one Brazil nut a day for 8 weeks, followed by 8 weeks of washout. Blood samples were collected at 5 time points: baseline, 4 and 8 weeks of supplementation and 4 and 8 weeks of washout for analysis of five biomarkers of Se status - erythrocyte GPx1 (Glutathione Peroxidase 1) activity, plasma GPx3 activity, plasma Se, erythrocyte Se, and plasma selenoprotein P. The gene expression of GPX1, SELENOP, SELENOF and SELENOS was done before and after 8 weeks of supplementation. The volunteers were genotyped for SNPs in GPX1 (rs1050450, rs3811699 and rs1800699), GPX4 (rs713041), SELENOP (rs3877899 and rs7579), SELENOF (rs5845) and SELENOS (rs34713741).

RESULTS

A total of 130 volunteers finished the protocol. The concentrations of four biomarkers of Se status increased significantly after 4 and 8 weeks of supplementation, being modulated by gender. In addition, erythrocyte GPx1 activity was associated with rs1050450, rs713041 and rs5845. Plasma Se was associated with rs7579 and selenoprotein P with plasma Se at baseline. Nut supplementation significantly increased GPX1 mRNA expression only in subjects with CC genotype at rs1050450. SELENOP mRNA expression was significantly lower in subjects with GG genotype at rs7579 before and after supplementation.

CONCLUSION

Genetic variations in GPX1 and SELENOP genes are associated with different responses of molecular and biochemical biomarkers of Se status after Brazil nut supplementation in healthy Brazilians. The SU.BRA.NUT study was registred at www.clinicaltrials.gov as NCT 03111355.

Effects of interactions between common genetic variants and alcohol consumption on colorectal cancer risk

BACKGROUND

Genome-wide association studies (GWAS) have identified approximately 40 common genetic loci associated with colorectal cancer risk. To investigate possible gene-environment interactions (GEIs) between GWAS-identified single-nucleotide polymorphisms (SNPs) and alcohol consumption with respect to colorectal cancer, a hospital-based case-control study was conducted.

RESULTS

Higher levels of alcohol consumption as calculated based on a standardized definition of a drink (1 drink=12.5g of ethanol) were associated with increased risk of colorectal cancer (OR=2.47, 95% CI=1.62-3.76 for heavy drinkers [>50g/day] compared to never drinkers; ptrend<0.01). SNP rs6687758 near the DUSP10 gene at 1q41 had a statistically significant interaction with alcohol consumption in analyses of standardized drinks (p=4.6×10-3), although this did not surpass the corrected threshold for multiple testing. When stratified by alcohol consumption levels, in an additive model the risk of colorectal cancer associated with the G allele of rs6687758 tended to increase among individuals in the heavier alcohol consumption strata. A statistically significant association between rs6687758 and colorectal cancer risk was observed among moderate alcohol drinkers who consumed between >12.5 and ≤50g of alcohol per day (OR=1.46, 95% CI=1.01-2.11).

METHODS

A total of 2,109 subjects (703 colorectal cancer patients and 1,406 healthy controls) were recruited from the Korean National Cancer Center. For genotyping, 30 GWAS-identified SNPs were selected. A logistic regression model was used to evaluate associations of SNPs and alcohol consumption with colorectal cancer risk. We also tested GEIs between SNPs and alcohol consumption using a logistic model with multiplicative interaction terms.

CONCLUSIONS

Our results suggest that SNP rs6687758 at 1q41 may interact with alcohol consumption in the etiology of colorectal cancer.

Effects of interactions between common genetic variants and smoking on colorectal cancer

Background

Although genome-wide association studies (GWAS) have identified variants in approximately 40 susceptibility loci for colorectal cancer (CRC), there are few studies on the interactions between identified single-nucleotide polymorphisms (SNPs) and lifestyle risk factors. We evaluated whether smoking could modify associations between these genetic variants and CRC risk.

Methods

A total of 703 CRC patients and 1406 healthy controls were included in this case-control study from the National Cancer Center in Korea. Thirty CRC susceptibility SNPs identified in previous GWAS were genotyped. A logistic regression model was used to examine associations between the SNPs and smoking behaviors by sex. The interaction was estimated by including an additional interaction term in the model.

Results

In men, an increased CRC risk was observed for longer durations (OR_{>28 vs. ≤28years} = 1.49 (95% CI = 1.11–1.98)), greater quantities (OR_{≥20 vs. <20cigarettes/day} = 2.12 (1.61–2.79)), and longer pack-years of smoking (OR_{≥21 vs. <21pack-years} = 1.78 (1.35–2.35)). In women, longer pack-years of smoking significantly increased CRC risk (OR_{≥5 vs. <5pack-years} = 6.11 (1.10–34.00)). Moreover, there were significant interactions between smoking status and the polymorphisms rs1957636 at 14q22.3 (P_interaction = 5.5 × 10⁻⁴) and rs4813802 at 20p12.3 (P_interaction = 0.04) in men. Interactions between smoking status and the rs6687758 at 1q41 (P_interaction = 0.03), duration and the rs174537 at 11q12.2 (P_interaction = 0.05), and pack-years and the rs4813802 (P_interaction = 0.04) were also found in women.

Conclusions

Associations between susceptibility SNPs and CRC risk may be modified by smoking behaviors, supporting the existence of gene-smoking interactions.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3886-0) contains supplementary material, which is available to authorized users.

Association between SOD1, CAT, GSHPX1 polymorphisms and the risk of inflammatory bowel disease in the Polish population

PURPOSE

The main aim of this study was investigate the association between the genetic polymorphism of antioxidant enzyme genes: SOD1, CAT and GSHPX1 and the risk of inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis in the Polish population.

METHODS

A total of 445 subjects including 200 patients with IBD and 245 controls were allowed in this study. We determined activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx1) and examination their association with the SNPs of respective genes (SOD1 +35A/C, CAT C-262T and GSHPX1 Pro197Leu). RFLP technique was used to determine the selected genes polymorphisms. Antioxidant enzymes activity were evaluated in erythrocyte hemolysate of 23 patients with non-active IBD and 30 healthy participants.

RESULTS

The A/C genotype and the C allele frequencies of A/C polymorphism of SOD1 gene were significantly associated with the reduced risk of IBD (OR=0.43; 95% CI 0.23; 0.83). Alike, C/T (OR=0.45; 95% CI= 0.29; 0.70) and T/T genotype (OR=0.43; 95% CI= 0.21; 0.87) of GSHPX1 gene polymorphism diminished the susceptibility to IBD. A significant decrease of CAT (P=0.028) and increase of GPx1 (P=0.025) enzyme activities were seen in IBD patients compared to control.

CONCLUSIONS

Our data confirm dysregulated antioxidant capacity in patients suffering from IBD. Both, the SOD1 A/C genotype as well as GSHPX1 C/T and T/T genotypes may be associated with a reduction risk of IBD in the Polish population.

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.

Influence of Genetic Variations in Selenoprotein Genes on the Pattern of Gene Expression after Supplementation with Brazil Nuts

Selenium (Se) is an essential micronutrient for human health. Its beneficial effects are exerted by selenoproteins, which can be quantified in blood and used as molecular biomarkers of Se status. We hypothesize that the presence of genetic polymorphisms in selenoprotein genes may: (1) influence the gene expression of specific selenoproteins and (2) influence the pattern of global gene expression after Brazil nut supplementation. The study was conducted with 130 healthy volunteers in Sao Paulo, Brazil, who consumed one Brazil nut (300 μg/Se) a day for eight weeks. Gene expression of GPX1 and SELENOP and genotyping were measured by real-time PCR using TaqMan Assays. Global gene expression was assessed by microarray using Illumina HumanHT-12 v4 BeadChips. Brazil nut supplementation significantly increased GPX1 mRNA expression only in subjects with CC genotype at rs1050450 (p < 0.05). SELENOP mRNA expression was significantly higher in A-carriers at rs7579 either before or after supplementation (p < 0.05). Genotype for rs713041 in GPX4 affected the pattern of blood cell global gene expression. Genetic variations in selenoprotein genes modulated both GPX1 and SELENOP selenoprotein gene expression and global gene expression in response to Brazil nut supplementation.

Pro198Leu Polymorphism in the Glutathione Peroxidase 1 Gene Contributes to Diabetic Peripheral Neuropathy in Type 2 Diabetes Patients

Glutathione peroxidase 1 (Gpx1) is an endogenous antioxidant enzyme. The T allele of the Pro198Leu polymorphism in the Gpx1 (rs1050450, 198C > T) gene is associated with reduced enzyme activity. The aim of this study was to evaluate the association between Pro198Leu polymorphism and risk of diabetic peripheral neuropathy (DPN). We examined 1244 T2DM patients and 730 healthy controls. In the patient group, 33 % had diabetic peripheral neuropathy. All subjects were genotyped for the Gpx1 Pro198Leu polymorphism by polymerase chain reaction and restriction analysis. A significant increase in the T allele and TT genotype frequencies was observed in DPN patients compared to those without DPN (OR 1.55, 95 % CI 1.30-1.85 and 1.89, 95 % CI 1.30-2.74, respectively). The association remained significant after correction for age, disease duration, HbA1c and BMI. When distribution of T allele was compared between DPN+ and DPN- subgroups and controls, OR was 1.54 for DPN+ and 1.00 for DPN- patients. In conclusion, our findings suggest that Gpx1 Pro198Leu genotypes are significantly associated with the risk of diabetic peripheral neuropathy in patients with T2DM. The study provides new clinically relevant information regarding genetic determinants of susceptibility to diabetic neuropathy.

Association between the OGG1 Ser326Cys Polymorphism and Cancer Risk: Evidence from 152 Case-Control Studies

Although it has been suggested that the 8-oxoguanine DNA glycosylase (OGG1) gene Ser326Cys polymorphism may be a risk factor for cancer, the conclusions from previous studies are inconsistent. Thus, we conducted an updated meta-analysis to estimate the effect of OGG1 variant genotypes on cancer susceptibility. We searched the PubMed for all eligible studies published in English for the period ending September 2014. We found the association between OGG1 Ser326Cys polymorphism and cancer susceptibility based on 152 case-control studies in different genetic model comparisons (dominant model: OR = 1.053, P = 0.018; recessive model: OR = 1.108, P < 0.001; homozygote: OR = 1.135, P < 0.001; additive model: OR = 1.059, P < 0.001). However, the results from the subgroup analyses based on types of cancer, health population as controls or studies with relatively large sample size did not support the conclusion. Although the overall results of this meta-analysis showed a positive association between OGG1 variant genotypes and cancer susceptibility, the subgroup analyses by cancer type, sample size, and source of controls presented inconsistent results. Therefore, the current evidence from the meta-analysis did not support the hypothesis of OGG1 Ser326Cys polymorphism as a risk factor of cancer.

Polymorphisms in ATP-binding cassette transporter genes and interaction with diet and life style factors in relation to colorectal cancer in a Danish prospective case-cohort study

BACKGROUND AND AIMS

The ATP-binding cassette (ABC) transporter family transports various molecules across the enterocytes in the gut protecting the intestine against potentially harmful substances. Moreover, ABC transporters are involved in mucosal immune defence through interaction with cytokines. The study aimed to assess whether polymorphisms in ABCB1, ABCC2 and ABCG2 were associated with risk of colorectal cancer (CRC) and to investigate gene-environment (dietary factors, smoking and use of non-steroidal anti-inflammatory drugs) and gene-gene interactions between previously studied polymorphisms in IL1B and IL10 and ABC transporter genes in relation to CRC risk.

MATERIALS AND METHODS

We used a Danish prospective case-cohort study of 1010 CRC cases and 1829 randomly selected participants from the Danish Diet, Cancer and Health cohort. Incidence rate ratios were calculated based on Cox' proportional hazards model.

RESULTS

None of the polymorphisms were associated with CRC, but ABCB1 and ABCG2 haplotypes were associated with risk of CRC. ABCB1/rs1045642 interacted with intake of cereals and fiber (p-Value for interaction (P(int)) = 0.001 and 0.01, respectively). In a three-way analysis, both ABCB1/rs1045642 and ABCG2/rs2231137 in combination with IL10/rs3024505 interacted with fiber intake in relation to risk of CRC (P(int) = 0.0007 and 0.009).

CONCLUSIONS

Our results suggest that the ABC transporters P-glycoprotein/multidrug resistance 1 and BRCP, in cooperation with IL-10, are involved in the biological mechanism underlying the protective effect of fiber intake in relation to CRC. These results should be replicated in other cohorts to rule out chance findings.

Association of Catalase and Glutathione Peroxidase 1 Polymorphisms with Chronic Hepatitis C Outcome

The hepatic damage caused by hepatitis C virus (HCV) infection is associated with the host immune response and viral regulatory factors. Catalase (CAT) and glutathione peroxidase 1 (GPX1) are antioxidant enzymes located in the peroxisomes and mitochondria, respectively, and are responsible for the control of intracellular hydrogen peroxide levels. Polymorphisms in CAT (C-262T) and GPX1 (Pro198Leu) are correlated with serum levels and enzyme activity. This study aimed to investigate the association of genetic polymorphisms of CAT C-262T (rs1001179) and GPX1 Pro198Leu (rs1050450) with different stages of liver fibrosis and development of hepatocellular carcinoma (HCC). This study included 445 patients with chronic hepatitis C, of whom 139 patients had mild fibrosis (F0-F1), 200 had moderate/severe fibrosis (F2-F4), and 106 had HCC. Genotyping of SNPs was performed by real-time PCR using TaqMan probes. The Pro/Pro genotype of GPX1 was significantly associated with fibrosis severity, HCC, Child Pugh score, and BCLC staging. Additionally, patients carrying both CT+TT genotypes in the CAT gene and the Pro/Pro genotype in the GPX1 gene had higher risk for developing moderate/severe fibrosis or HCC (p = 0.009, OR 2.40 and p = 0.002, OR 3.56, respectively). CAT and GPX1 polymorphisms may be implicated in the severity of liver fibrosis and HCC caused by HCV.

Genetic polymorphisms (Pro197Leu of Gpx1, +35A/C of SOD1, -262C/T of CAT), the level of antioxidant proteins (GPx1, SOD1, CAT) and the risk of distal symmetric polyneuropathy in Polish patients with type 2 diabetes mellitus

PURPOSE

Oxidative stress and impaired anti-oxidant defense are regarded as contributory factors for distal symmetric polyneuropathy (DSPN). The purpose of the study was to evaluate the plasma level of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) and the association between polymorphic variants in genes encoding for GPx1, SOD, CAT and the risk of DSPN in T2DM patients.

MATERIAL/METHODS

We included 401 individuals: 110 T2DM patients with DSPN, 135 T2DM patients without DSPN, and 156 control subjects with normoglycemia, and without DSPN. We employed RFPL-PCR to genotype polymorphic variants Pro197Leu of Gpx1, +35A/C of SOD1, -262C/T of CAT and ELISA tests to measure plasma level of SOD1, GPx1 and CAT. The odds ratios (ORs) and 95% confidence intervals (CIs) for each genotype and allele were calculated.

RESULTS

There was a significant decrease in the level of GPx1 (p<0.05), SOD1 (p<0.05) in T2DM patients with DSPN compared to healthy subjects. T2DM patients without DSPN showed a statistically lower serum level of GPX1 (p<0.05) than healthy subjects. SOD 1 and CAT levels were lower in T2DM patients with DSPN compared to T2DM patients without DSPN (p<0.05). The genetic analysis revealed the lack of association between examined polymorphic variants and the risk of DSPN.

CONCLUSIONS

The examined polymorphic variants are not associated with DSPN in Polish T2DM patients. The obtained results suggest that disturbances in antioxidant defense system may play significant role in the development and progression of DSPN.

DNA damage and oxidative stress response to selenium yeast in the non-smoking individuals: a short-term supplementation trial with respect to GPX1 and SEPP1 polymorphism

Purpose

Selenium, both essential and toxic element, is considered to protect against cancer, though human supplementation trials have generated many inconsistent data. Genetic background may partially explain a great variability of the studies related to selenium and human health. The aim of this study was to assess whether functional polymorphisms within two selenoprotein-encoding genes modify the response to selenium at the level of oxidative stress, DNA damage, and mRNA expression, especially in the individuals with a relatively low selenium status.

Methods

The trial involved 95 non-smoking individuals, stratified according to GPX1 rs1050450 and SEPP1 rs3877899 genotypes, and supplemented with selenium yeast (200 µg) for 6 weeks. Blood was collected at four time points, including 4 weeks of washout.

Results

After genotype stratification, the effect of GPX1 rs1050450 on lower GPx1 activity responsiveness was confirmed; however, in terms of DNA damage, we failed to indicate that individuals homozygous for variant allele may especially benefit from the increased selenium intake. Surprisingly, considering gene and time interaction, GPX1 polymorphism was observed to modify the level of DNA strand breaks during washout, showing a significant increase in GPX1 wild-type homozygotes. Regardless of the genotype, selenium supplementation was associated with a selectively suppressed selenoprotein mRNA expression and inconsistent changes in oxidative stress response, indicating for overlapped, antioxidant, and prooxidant effects. Intriguingly, DNA damage was not influenced by supplementation, but it was significantly increased during washout.

Conclusions

These results point to an unclear relationship between selenium, genotype, and DNA damage.

Electronic supplementary material

The online version of this article (doi:10.1007/s00394-015-1118-4) contains supplementary material, which is available to authorized users.

Selenium and chronic diseases: a nutritional genomics perspective

Mechanistic data have revealed a key role for selenium (Se) and selenoproteins in biological pathways known to be altered in multifactorial diseases, such as cellular maintenance, response to oxidative stress and correct protein folding. Although epidemiological studies indicate that low Se intake is linked to increased risk for various chronic diseases, supplementation trials have given confusing outcomes, suggesting that additional genetic factors could affect the relationship between Se and health. Genetic data support this hypothesis, as risk for several chronic diseases, in particular cancer, was linked to a number of single nucleotide polymorphisms (SNP) altering Se metabolism, selenoprotein synthesis or activity. Interactions between SNPs in selenoprotein genes, SNPs in related molecular pathways and biomarkers of Se status were found to further modulate the genetic risk carried by the SNPs. Taken together, nutritional genomics approaches uncovered the potential implication of some selenoproteins as well as the influence of complex interactions between genetic variants and Se status in the aetiology of several chronic diseases. This review discusses the results from these genetic associations in the context of selenoprotein functions and epidemiological investigations and emphasises the need to assess in future studies the combined contribution of Se status, environmental stress, and multiple or individual SNPs to disease risk.

Nutrients, foods, and colorectal cancer prevention

Diet has an important role in the development of colorectal cancer. In the past few decades, findings from extensive epidemiologic and experimental investigations have linked consumption of several foods and nutrients to the risk of colorectal neoplasia. Calcium, fiber, milk, and whole grains have been associated with a lower risk of colorectal cancer, and red meat and processed meat have been associated with an increased risk. There is substantial evidence for the potential chemopreventive effects of vitamin D, folate, fruits, and vegetables. Nutrients and foods also may interact, as a dietary pattern, to influence colorectal cancer risk. Diet likely influences colorectal carcinogenesis through several interacting mechanisms. These include the direct effects on immune responsiveness and inflammation, and the indirect effects of overnutrition and obesity-risk factors for colorectal cancer. Emerging evidence also implicates the gut microbiota as an important effector in the relationship between diet and cancer. Dietary modification therefore has the promise of reducing colorectal cancer incidence.

Polymorphisms in NFKB1 and TLR4 and interaction with dietary and life style factors in relation to colorectal cancer in a Danish prospective case-cohort study

Maintenance of a balance between commensal bacteria and the mucosal immune system is crucial and intestinal dysbiosis may be a key event in the pathogenesis of colorectal cancer (CRC). The toll-like receptor 4 (TLR4) is an important pattern-recognition receptor that regulates inflammation and barrier function in the gut by a mechanism that involves activation of the nuclear factor-κB (NF-κB) transcription factor. Dietary and life style factors may impact these functions. We therefore used a Danish prospective case-cohort study of 1010 CRC cases and 1829 randomly selected participants from the Danish Diet, Cancer and Health cohort to investigate three polymorphisms in NFKB1 and TLR4 and their possible interactions with diet and life style factors in relation to risk of CRC. Homozygous carriage of the variant allele of the TLR4/rs5030728 polymorphism was associated with increased risk of CRC (incidence rate ratio (IRR) = 1.30; 95% confidence interval (CI): 1.05-1.60; P = 0.02 (gene-dose model); IRR = 1.24; 95%CI: 1.01-1.51; P = 0.04 (recessive model)). Del-carriers of the NFKB1/rs28362491 polymorphism had a 17% (95%CI: 1.03-1.34; P = 0.02) increased risk of CRC compared to homozygous carriers of the ins-allele. However, none of these risk estimates withstood adjustment for multiple comparisons. We found no strong gene-environment interactions between the examined polymorphism and diet and life style factors in relation to CRC risk.

Effect of 593C>T GPx1 SNP alone and in synergy with 47C>T SOD2 SNP on the outcome of critically ill patients

During critical illness and sepsis there is severe antioxidant depletion, and this scenario raises the critical ill patient's mortality risk. Glutathione peroxidase (GPx) is one of the first endogenous antioxidant defense enzymes, and it works cooperatively with superoxide dismutase (SOD) and catalase (CAT) to detoxify free radicals from the cellular environment. Genetic studies are important to understand the complexity of human oxidative stress and how the organism responds to an extreme situation such as critically care conditions. Previous studies with a GPx1 single nucleotide polymorphism (593C>T SNP; rs1050450; protein variant in GPx1: Pro198Leu) showed 593T carriers and 593TT homozygotes present higher risk to develop different diseases. We assessed the relationship of the genotype distribution of GPx1 SNP in critically ill patients with their conditions (organ dysfunction, sepsis, and septic shock) and their outcome. We monitored 626 critically ill patients daily from the ICU (intensive care unit) admission to their discharge from hospital, or death. Our study revealed a significant association between 593TT GPx1 genotype and mortality; the mortality rate was higher in homozygous 593TT GPx1 (N=94) when compared with the group of subjects with genotypes 593CT or 593CC GPx1 (N=532) (52% vs. 38%, P=0.009; OR=1.79; 95% CI=1.13-2.85). Evaluating the subgroup of 293 ICU patients with sepsis, a pooled analysis including two genetic variants GPx1 and SOD2 (47C>T SNP, rs4880; protein variant in MnSOD: Ala-9Val) showed a significant difference in relation to progression to septic shock. The frequency of septic shock among septic patients with 593T GPx1 and 47C SOD2 alleles (N=122) was higher when compared with septic patients carrying other settings of genotypes (N=174) (78% vs. 66%; P=0.028; OR=1.81; 95% CI=1.03-3.18). Accepting the previously reported functional effects of these two SNPs on GPx1 and SOD2 gene expressions and, consequently, on GPx1 and MnSOD enzyme activities, we believe our results may be considered as an important contribution for the understanding of oxidative imbalance during the critical ill.

Pro198Leu polymorphism in the oxidative stress gene, glutathione peroxidase-1, is associated with a gender-specific risk for panic disorder

OBJECTIVE

Panic disorder (PD) is an anxiety disorder characterized by sudden attacks of intense fear. Biochemical studies suggest that oxidative stress (OS) index is significantly higher in PD, and OS genes may participate in development of anxiety-like behavioral phenotypes. We aimed to investigate role of polymorphisms in OS gene, glutathione peroxidase-1 (GPX1), and DNA repair enzyme gene, 8-oxoguanine glycosylase-1 (OGG1), in PD patients.

METHODS

GPX1 Pro198Leu (rs1050450) and OGG1 Ser326Cys (rs1052133) polymorphisms of 127 patients with PD and 151 disease-free controls were analyzed with real-time polymerase chain reaction. Severity of PD symptoms was assessed by Panic and Agoraphobia Scale (PAS).

RESULTS

No significant relationship was found in genotype distributions of OGG1 Ser326Cys and GPX1 Pro198Leu polymorphisms between PD and control groups (p > 0.05). There was no significant relationship between OGG1 or GPX1 polymorphisms, and age of onset, agoraphobia, or PAS scores in PD group (p > 0.05). However, in GPX1 Pro198Leu polymorphism, C allele (Pro) was found to be more frequent in female subgroup of PD patients compared with that in males (p = 0.027).

CONCLUSIONS

GPX1 Pro198Leu and OGG1 Ser326Cys polymorphisms were not associated with PD risk in Turkish patients. However, a gender-specific effect of GPX1 Pro198Leu C allele may be associated with PD development.

The hOGG1 Ser326Cys polymorphism contributes to digestive system cancer susceptibility: evidence from 48 case-control studies

The Ser326Cys polymorphism in the human 8-oxogunaine DNA glycosylase (hOGG1) gene had been implicated in cancer susceptibility. Studies investigating the associations between the Ser326Cys polymorphism and digestion cancer susceptibility showed conflicting results. Therefore, a meta-analysis was performed to derive a more precise estimation of the relationship. We conducted a meta-analysis of 48 studies that included 12,073 cancer cases and 19,557 case-free controls. We assessed the strength of the association using odds ratios (ORs) with 95% confidence intervals (CIs). In our analysis, the hOGG1 Ser326Cys polymorphism was significantly associated with the risk of digestive system cancers (Cys/Cys vs. Ser/Ser: OR = 1.17, 95% CI = 1.00-1.35, P < 0.001; Cys/Cys vs. Cys/Ser + Ser/Ser: OR = 1.14, 95% CI = 1.00-1.29, P < 0.001). In subgroup analyses by cancer types, we found that the hOGG1 Ser326Cys polymorphism may increase hepatocellular cancer and colorectal cancer risks, but decrease the risk of oral cancer. These findings supported that hOGG1 Ser326Cys polymorphism may contribute to the susceptibility of digestive cancers.

Association of hOGG1 Ser326Cys polymorphism with colorectal cancer risk: an updated meta-analysis including 5235 cases and 8438 controls

It has been suggested that hOGG1 Ser326Cys polymorphism may be a risk factor for colorectal cancer. Published data on its association with colorectal cancer generated contradictory results; thus, we performed an updated meta-analysis of eligible published studies to estimate the effect of hOGG1 Ser326Cys polymorphism on colorectal cancer susceptibility. We reviewed many abstracts and finally included 18 eligible case-control studies comprising 5235 cases and 8438 controls. We pooled data with a fixed or random-effect model. Subgroup analysis by ethnicity was also performed. The overall data indicated a significant association of hOGG1 Ser326Cys polymorphism on colorectal cancer risk (allele model OR = 1.14, 95 %CI 1.02-1.27; homozygote model OR = 1.32, 95 %CI 0.92-1.92; recessive model OR = 1.12, 95 %CI 1.00-1.26; dominant model OR = 1.15, 95 %CI 1.00-1.32). Furthermore, in the subgroup analysis by ethnicity, increased cancer risk was observed among Caucasians under the allele, heterogeneity, recessive, and dominant models (allele model OR = 1.23, 95 %CI = 1.05-1.44; homozygote model OR = 1.49, 95%CI 1.05-2.12; recessive model OR = 1.40, 95 %CI 1.16-1.69; dominant model OR = 1.21, 95 %CI = 1.12-1.45). In summary, the present meta-analysis suggested that hOGG1 Ser326Cys polymorphism might modify the susceptibility to colorectal cancer among the total population, especially among Caucasians.

Interactions between diet, lifestyle and IL10, IL1B, and PTGS2/COX-2 gene polymorphisms in relation to risk of colorectal cancer in a prospective Danish case-cohort study

Background & Aims

Diet contributes to colorectal cancer development and may be potentially modified. We wanted to identify the biological mechanisms underlying colorectal carcinogenesis by assessment of diet-gene interactions.

Methods

The polymorphisms IL10 C-592A (rs1800872), C-rs3024505-T, IL1b C-3737T (rs4848306), G-1464C (rs1143623), T-31C (rs1143627) and PTGS2 (encoding COX-2) A-1195G (rs689466), G-765C (rs20417), and T8473C (rs5275) were assessed in relation to risk of colorectal cancer (CRC) and interaction with diet (red meat, fish, fibre, cereals, fruit and vegetables) and lifestyle (non-steroid-anti-inflammatory drug use and smoking status) was assessed in a nested case-cohort study of nine hundred and seventy CRC cases and 1789 randomly selected participants from a prospective study of 57,053 persons.

Results

IL1b C-3737T, G-1464C and PTGS2 T8473C variant genotypes were associated with risk of CRC compared to the homozygous wildtype genotype (IRR=0.81, 95%CI: 0.68-0.97, p=0.02, and IRR=1.22, 95%CI: 1.04-1.44, p=0.02, IRR=0.75, 95%CI: 0.57-0.99, p=0.04, respectively). Interactions were found between diet and IL10 rs3024505 (P-value for interaction (P_int); meat=0.04, fish=0.007, fibre=0.0008, vegetables=0.0005), C-592A (P_int; fibre=0.025), IL1b C-3737T (P_int; vegetables=0.030, NSAID use=0.040) and PTGS2 genotypes G-765C (P_int; meat=0.006, fibre=0.0003, fruit 0.004), and T8473C (P_int; meat 0.049, fruit=0.03) and A-1195G (P_int; meat 0.038, fibre 0.040, fruit=0.059, vegetables=0.025, and current smoking=0.046).

Conclusions

Genetically determined low COX-2 and high IL-1β activity were associated with increased risk of CRC in this northern Caucasian cohort. Furthermore, interactions were found between IL10, IL1b, and PTGS2 and diet and lifestyle factors in relation to CRC. The present study demonstrates that gene-environment interactions may identify genes and environmental factors involved in colorectal carcinogenesis.

Polymorphic variants of MnSOD Val16Ala, CAT-262 C < T and GPx1 Pro198Leu genotypes and the risk of laryngeal cancer in a smoking population

OBJECTIVE

To investigate the relationship between development of laryngeal cancer and the presence of polymorphisms of the MnSOD Val16Ala, CAT-262 C < T and GPx1 Pro198Leu genes in a smoking population.

PATIENTS AND METHODS

Single nucleotide polymorphisms were determined in DNA from the peripheral blood erythrocytes of 48 heavy smokers (25 patients with laryngeal cancer and 23 cancer-free controls), using polymerase chain reaction.

RESULTS

There were no significant differences in age, smoking duration or smoking intensity, comparing the two groups. The homozygous AA genotype of MnSOD Val16Ala was significantly more prevalent in the cancer group than the control group (92 vs 13 per cent, respectively), while the heterozygous AV genotype of MnSOD Val16Ala was more prevalent in the control group than the cancer group (87 vs 8 per cent, respectively) (p < 0.001). There were no significant differences between the cancer and control groups regarding GPx1 Pro198Leu or CAT-262 C < T polymorphisms.

CONCLUSION

Polymorphism of the MnSOD Val16Ala gene may contribute to susceptibility to laryngeal cancer among smokers.

Status of antioxidant enzyme: glutathione peroxidase and total polyphenol level in plasma of Tunisian patients suffering from colorectal and gastric cancer: interaction with clinical outcome

In our case-control study, we measure the antioxidant status by dosing enzymes involved in oxidant stress in plasma of patients with colorectal and gastric cancer, and in the second step, we investigate the impact of chemotherapy before and after surgery on plasma antioxidant status and polyphenols in patients. Blood serum was collected from patients with stomach and colorectal cancer before conventional treatment, and glutathione peroxidase (GSHPX) enzyme activities and total polyphenols were determined by spectrophotometric methods. In our study, we found a significant decrease in glutathione peroxidase activity in plasma of patients compared with controls (P = 0.02), although we did not find a significant association between total polyphenols and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) or ABTS in plasma of colorectal and stomach cancer compared with control; furthermore, we observed no significant difference in the average plasma polyphenols in patients treated with chemotherapy before and after surgery. We have shown the decrease in GSHPX activity in plasma of cases with colorectal and gastric cancer, and this decrease reflects that the oxidative stress is associated with tumor tract and related to oxidative metabolism; however, no association was found between total polyphenols and ABTS in our study.

Association between polymorphisms in glutathione peroxidase and selenoprotein P genes, glutathione peroxidase activity, HRT use and breast cancer risk

Breast cancer (BC) is one of the most common cancers in women. Evidence suggests that genetic variation in antioxidant enzymes could influence BC risk, but to date the relationship between selenoproteins and BC risk remains unclear. In this report, a study population including 975 Danish cases and 975 controls matched for age and hormone replacement therapy (HRT) use was genotyped for five functional single nucleotide polymorphisms (SNPs) in SEPP1, GPX1, GPX4 and the antioxidant enzyme SOD2 genes. The influence of genetic polymorphisms on breast cancer risk was assessed using conditional logistic regression. Additionally pre-diagnosis erythrocyte GPx (eGPx) activity was measured in a sub-group of the population. A 60% reduction in risk of developing overall BC and ductal BC was observed in women who were homozygous Thr carriers for SEPP1 rs3877899. Additionally, Leu carriers for GPX1 Pro198Leu polymorphism (rs1050450) were at ∼2 fold increased risk of developing a non-ductal BC. Pre-diagnosis eGPx activity was found to depend on genotype for rs713041 (GPX4), rs3877899 (SEPP1), and rs1050450 (GPX1) and on HRT use. Moreover, depending on genotype and HRT use, eGPx activity was significantly lower in women who developed BC later in life compared with controls. Furthermore, GPx1 protein levels increased in human breast adenocarcinoma MCF7 cells exposed to β-estradiol and sodium selenite.In conclusion, our data provide evidence that SNPs in SEPP1 and GPX1 modulate risk of BC and that eGPx activity is modified by SNPs in SEPP1, GPX4 and GPX1 and by estrogens. Our data thus suggest a role of selenoproteins in BC development.

The effect of oxoguanine glycosylase 1 rs1052133 polymorphism on colorectal cancer risk in Caucasian population

Human oxoguanine glycosylase 1 (OGG1) is an important part of the base excision repair pathway in the DNA repair. Numerous epidemiological studies have evaluated the association between OGG1 rs1052133 polymorphism and the risk of colorectal cancer, but the results of these studies from the Caucasian population were conflicting. To derive a more precise assessment on the association between OGG1 rs1052133 polymorphism and risk of colorectal cancer in Caucasian population, we performed a meta-analysis. The odds ratios (OR) with 95% confidence intervals (CI) were used to assess the strength of the association. Thirteen case-control studies with a total of 4,103 cases and 5,400 controls were finally included into the meta-analysis. Meta-analysis of all 13 studies showed that OGG1 rs1052133 polymorphism was significantly associated with the risk of colorectal cancer in Caucasian population (Cys versus Ser OR = 1.20, 95% CI = 1.03-1.39, P = 0.02; CysCys versus SerSer OR = 1.44, 95% CI = 1.04-2.00, P = 0.03; CysCys versus SerSer/SerCys OR = 1.39, 95% CI = 1.15-1.67, P = 0.0005). In the sensitivity analysis, omitting each study one at a time had no obvious influence on the pooled OR, which confirmed the stability of meta-analysis. The meta-analysis suggests that OGG1 rs1052133 polymorphism is significantly associated with the risk of colorectal cancer in Caucasian population.

Iron-ascorbate-mediated lipid peroxidation causes epigenetic changes in the antioxidant defense in intestinal epithelial cells: impact on inflammation

Introduction

The gastrointestinal tract is frequently exposed to noxious stimuli that may cause oxidative stress, inflammation and injury. Intraluminal pro-oxidants from ingested nutrients especially iron salts and ascorbic acid frequently consumed together, can lead to catalytic formation of oxygen-derived free radicals that ultimately overwhelm the cellular antioxidant defense and lead to cell damage.

Hypothesis

Since the mechanisms remain sketchy, efforts have been exerted to evaluate the role of epigenetics in modulating components of endogenous enzymatic antioxidants in the intestine. To this end, Caco-2/15 cells were exposed to the iron-ascorbate oxygen radical-generating system.

Results

Fe/Asc induced a significant increase in lipid peroxidation as reflected by the elevated formation of malondialdehyde along with the alteration of antioxidant defense as evidenced by raised superoxide dismutase 2 (SOD2) and diminished glutathione peroxidase (GPx) activities and genes. Consequently, there was an up-regulation of inflammatory processes illustrated by the activation of NF-κB transcription factor, the higher production of interleukin-6 and cycloxygenase-2 as well as the decrease of IκB. Assessment of promoter’s methylation revealed decreased levels for SOD2 and increased degree for GPx2. On the other hand, pre-incubation of Caco-2/15 cells with 5-Aza-2′-deoxycytidine, a demethylating agent, or Trolox antioxidant normalized the activities of SOD2 and GPx, reduced lipid peroxidation and prevented inflammation.

Conclusion

Redox and inflammatory modifications in response to Fe/Asc -mediated lipid peroxidation may implicate epigenetic methylation.

Effects of smoking and antioxidant micronutrients on risk of colorectal cancer

BACKGROUND & AIMS

Antioxidant intake has been reported to increase the risk of colorectal cancer (CRC) for smokers, yet reduce the risk for nonsmokers. We investigated the association between tobacco smoking and risk of colon or rectal cancer, and whether dietary and supplemental intake of the antioxidant vitamins A, C, E, β-carotene, selenium, zinc, and manganese affects the risk of CRC among smokers.

METHODS

Data on smoking habits and antioxidant intake were analyzed for 54,208 participants in the Danish Prospective Diet, Cancer and Health Study. Of these participants, 642 were diagnosed with colon cancer and 348 were diagnosed with rectal cancer. Hazard ratios and 95% confidence intervals were estimated using Cox proportional hazard models. Principal components were used to analyze intake of combinations of antioxidants.

RESULTS

Ever smoking increased the risk for CRC (hazard ratio, 1.19; 95% confidence interval, 1.03-1.37), especially for rectal cancer. Smoking for at least 20 years was associated with a 26% increase in risk of CRC, compared with never smokers, and smoking 20 g tobacco or more each day was associated with a 30% increase in risk. Smoking for more than 30 years, or more than 20 g tobacco each day, was associated with a 48% increase in risk of rectal cancer. We did not observe an interaction between smoking and antioxidant consumption on risk of CRC.

CONCLUSIONS

Tobacco smoking increases the risk for CRC. We did not observe that consumption of antioxidant micronutrients modulates the effects of smoking on CRC risk.

GPX1 gene Pro200Leu polymorphism, erythrocyte GPX activity, and cancer risk

A meta-analysis was conducted to assess the effect of glutathione peroxidase1 (GPX1) gene Pro200Leu (rs1050450) polymorphism on cancer risk. A comprehensive search was performed to identify all studies on the association of GPX1 gene Pro200Leu polymorphism with cancer risk. The fixed or random effect pooled measure was selected based on homogeneity test among studies. Heterogeneity among studies was evaluated using the I (2). Potential sources of between-study heterogeneity were explored by meta-regression and the sensitivity analysis. Publication bias was estimated using Egger's linear regression test. 35 published articles with 36 results were identified involving 16,920 cases and 19,946 controls. Results from the articles that both obeyed Hardy-Weinberg equilibrium in controls and met high quality design, showed no significant association of GPX1 gene Pro200Leu polymorphism with cancer risk in any of dominant (OR = 1.05, 95 %CI = 0.98-1.12), recessive (OR = 1.04 (0.95-1.13), and TT versus CC (OR = 1.05, 95 %CI = 0.97-1.15) models, and the findings were consistent considering the stratified analysis by cancer type. However, multivariate-adjusted ORs from articles that both obeyed Hardy-Weinberg equilibrium in controls and met high quality design, showed a significant association considering dominant (OR = 1.22, 95 %CI = 1.06-1.41), TT versus CC (OR = 1.16, 95 %CI = 1.02-1.32) models, and a marginally significant association was found considering TC versus CC (OR = 1.11, 95 %CI = 0.99-1.25) model. And compared with the CC genotype, the erythrocyte GPX activity was significantly lower for TT genotype: the standardized mean difference (SMD) = -0.37, 95 %CI = (-0.624, -0.118), and CT genotype: SMD = -0.19, 95 %CI = (-0.37, -0.002). The association of GPX1 gene Pro200Leu polymorphism with cancer risk might be influenced by confounders.

Influence of the glutathione peroxidase 1 Pro200Leu polymorphism on the response of glutathione peroxidase activity to selenium supplementation: a randomized controlled trial

BACKGROUND

A genetic variant at codon 200 (Pro200Leu) of the gene encoding for glutathione peroxidase 1 (GPx1), a selenium-dependent enzyme, is associated with lower enzyme activity; however, the evidence is limited to in vitro and observational studies.

OBJECTIVE

The objective was to determine whether the GPx1 Pro200Leu genetic variants modify the response of whole-blood glutathione peroxidase (GPx) activity to selenium supplementation in patients with coronary artery disease in New Zealand.

DESIGN

The results from 2 parallel-design, double-blind trials were combined. Participants were randomly assigned to receive a daily supplement of 100 μg Se as l-selenomethionine (n = 129) or placebo (n = 126) for 12 wk. Plasma selenium and whole-blood GPx activity were measured at baseline and at week 12. Participants were genotyped for the GPx1 Pro200Leu polymorphism.

RESULTS

Selenium supplementation increased whole-blood GPx activity by 5 (95% CI: 4, 7) U/g hemoglobin (P < 0.001); however, the magnitude of the increase did not differ by genotype (P = 0.165 for treatment-by-genotype interaction). In an exploratory analysis, a significant nutrient-gene interaction was apparent when baseline plasma selenium concentrations were included in the regression model (P = 0.006 for treatment-by-genotype × baseline selenium concentration interaction). Increases in GPx activity were 2-fold higher in Pro homozygotes than in participants carrying a Leu allele when baseline selenium concentrations were ≤1.15 μmol/L (P < 0.05).

CONCLUSIONS

These results indicate that GPx1 Pro200Leu variants do not substantially modify the response of whole-blood GPx to selenium supplementation in individuals with relatively high plasma selenium concentrations. A nutrient-gene interaction was observed when the baseline selenium concentration was low, but this requires independent confirmation. This trial was registered at www.actr.org.au as ACTRN12605000412639 and ACTRN12606000197538.

Selenium, selenoprotein genes and Crohn's disease in a case-control population from Auckland, New Zealand

New Zealand has one of the highest incidence rates of Crohn’s Disease (CD), whilst the serum selenium status of New Zealanders is amongst the lowest in the world. A prospective case-control study in Auckland, New Zealand considered serum selenium as a potential CD risk factor. Serum selenium levels were significantly lower in CD patients compared to controls (101.8 ± 1.02 vs. 111.1 ± 1.01 ng/mL) (p = 5.91 × 10⁻⁸). Recent detailed studies in the United Kingdom have suggested an optimal serum level around 122 ng/mL, making the average CD patient in New Zealand selenium deficient. Of the 29 single nucleotide polymorphisms (SNPs) tested, 13 were found to significantly interact with serum selenium on CD. After adjustment for multiple testing, a significant interaction with serum selenium on CD was found for three SNPs, namely rs17529609 and rs7901303 in the gene SEPHS1, and rs1553153 in the gene SEPSECS. These three SNPs have not been reported elsewhere as being significantly associated with selenium or CD. It is unclear as to whether lower selenium levels are a cause or an effect of the disease.

Loss of heterozygosity at the glutathione peroxidase 1 locus is not an early event in colon carcinogenesis

It has been previously shown that loss of heterozygosity (LOH) at the cytosolic glutathione peroxidase (GPx-1) locus is a common event in the development of several cancer types, including colorectal cancer. GPx-1 is an antioxidant selenium-containing protein, and polymorphisms within this gene have been shown to be associated with the increased risk of cancer. In order to assess whether this genetic change was an early or late event in colon cancer development, we investigated whether LOH at this site was occurring in colorectal adenomas, a premalignant lesion. Twenty-four pairs of DNA samples, obtained from both whole-blood and adenoma tissue from the same individuals, were genotyped at 2 positions in the GPx-1 gene: a codon 198 variation resulting in either a leucine or proline at the corresponding position in the peptide, or a variable number of alanine repeat codons corresponding to the amino terminus of the GPx-1 protein. No evidence of GPx-1 LOH was observed in the examined sample sets. These data indicate that the genetic loss at the GPx-1 locus may be a late event in colon carcinogenesis.

Selenoproteins and Cancer Prevention

The discovery of multiple selenoproteins has raised tantalizing questions about their role in maintaining normal cellular function. Unfortunately, many of these remain inadequately investigated. While they have a role in maintaining redox balance, other functions are becoming increasingly recognized. As the roles of these selenoproteins are further characterized, a better understanding of the true physiological significance of this trace element will arise. This knowledge will be essential in defining optimum intakes to achieve cellular homeostasis in order to optimize health, including a reduction in cancer, for diverse populations. Human variation in the response to selenium likely reflects significant interactions between the type and amounts of selenium consumed with the genome and a host of environmental factors including the totality of the diet, as discussed in this review.

Association between genetic variants in glutathione peroxidase 1 gene and risk of prostate cancer: a meta-analysis

To examine the association between glutathione peroxidase 1 (GPx1) gene Pro198Leu polymorphism with the development and progression of prostate cancer. A comprehensive search was conducted to identify all case-control studies of GPx1 polymorphisms and prostate cancer. Statistical analysis was performed with the software program Stata, version 11.0, and Review Manage, version 4.2. A total of 7 eligible studies relating the GPx1 polymorphism to the risk of prostate cancer were identified. The results indicated no significant association between GPx1 polymorphisms and prostate cancer susceptibility in the dominant model (random effects OR 0.75, 95 % CI 0.48-1.18), recessive model (random effects OR 0.47, 95 % CI 0.22-1.01) and co-dominant genetic model (random effects OR 0.72, 95 % CI 0.43-1.21). For the analysis of GPx1 polymorphism and progression of prostate cancer, no significant association were found in the dominant model (fixed effects OR 1.20, 95 % CI 0.95-1.52), recessive model (fixed effects OR 0.69, 95 % CI 0.48-1.00) and co-dominant genetic model (fixed effects OR 0.95, 95 % CI 0.79-1.15). Egger's test showed that publication bias was not present in all the comparisons.

Selenium, selenoenzymes, oxidative stress and risk of neoplastic progression from Barrett's esophagus: results from biomarkers and genetic variants

Clinical trials have suggested a protective effect of selenium supplementation on the risk of esophageal cancer, which may be mediated through the antioxidant activity of selenoenzymes. We investigated whether serum selenium concentrations, selenoenzyme activity, oxidative stress and genetic variation in selenoenzymes were associated with the risk of neoplastic progression to esophageal adenocarcinoma (EA) and two intermediate endpoints, aneuploidy and tetraploidy. In this prospective cohort study, during an average follow-up of 7.3 years, 47 EA cases, 41 aneuploidy cases and 51 tetraploidy cases accrued among 361 participants from the Seattle Barrett's Esophagus Research Study who were free of EA at the time of blood draw and had at least one follow-up visit. Development to EA was assessed histologically and aneuploidy and tetraploidy by DNA content flow cytometry. Serum selenium concentrations were measured using atomic absorption spectrometry, activity of glutathione peroxidase (GPX) 1 and GPX3 by substrate-specific coupled test procedures, selenoprotein P (SEPP1) concentrations and protein carbonyl content by ELISA method and malondialdehyde concentrations by HPLC. Genetic variants in GPX1-4 and SEPP1 were genotyped. Serum selenium was not associated with the risk of neoplastic progression to EA, aneuploidy or tetraploidy (P for trend = 0.25 to 0.85). SEPP1 concentrations were positively associated with the risk of EA [hazard ratio (HR) = 3.95, 95% confidence intervals (CI) = 1.42-10.97 comparing the third tertile with the first] and with aneuploidy (HR = 6.53, 95% CI = 1.31-32.58), but not selenoenzyme activity or oxidative stress markers. No genetic variants, overall, were associated with the risk of neoplastic progression to EA (global p = 0.12-0.69). Our results do not support a protective effect of selenium on risk of neoplastic progression to EA. Our study is the first to report positive associations of plasma SEPP1 concentrations with the risk of EA and aneuploidy, which warrants further investigation.

Genetic variation in GPX1 is associated with GPX1 activity in a comprehensive analysis of genetic variations in selenoenzyme genes and their activity and oxidative stress in humans

Previous studies suggest some effects of selenium on risk of several chronic diseases, which may be mediated through a small number of selenoenzymes with antioxidant properties. In this cross-sectional analysis of 195 participants from the Seattle Barrett's Esophagus Study who were free of esophageal cancer at the time of blood draw, we examined whether the number of the minor alleles in 26 tagging single nucleotide polymorphisms (SNP) of five selenoenzyme genes [i.e., glutathione peroxidase 1-4 (GPX1-4) and selenoprotein P (SEPP1)] was associated with activity of GPX1 in white blood cells and GPX3 in plasma, and concentrations of SEPP1 and markers of oxidative stress [malondialdehyde (MDA) and protein carbonyl content] in plasma. At the gene level, associations were observed between overall variation in GPX1 and GPX1 activity (P = 0.02) as well as between overall variation in GPX2 and SEPP1 concentrations (P = 0.03). By individual SNP, two variants in GPX1 (rs8179164 and rs1987628) showed a suggestive association with GPX1 activity (P = 0.10 and 0.08, respectively) and two GPX2 variants (rs4902346 and rs2071566) were associated with SEPP1 concentration (P = 0.004 and 0.002, respectively). Furthermore, two SNP in the SEPP1 gene (rs230813 and rs230819) were associated with MDA concentrations (P = 0.03 and 0.02, respectively). Overall, our study supports the hypothesis that common genetic variants in selenoenzymes affect their activity.

Glutathione peroxidase tagSNPs: associations with rectal cancer but not with colon cancer

Glutathione peroxidases (GPXs) are selenium-dependent enzymes that reduce and, thus, detoxify hydrogen peroxide and a wide variety of lipid hydroperoxides. We investigated tagSNPs in GPX1-4 in relation to colorectal neoplasia in three independent study populations capturing the range of colorectal carcinogenesis from adenoma to cancer. A linkage-disequilibrium (LD)-based tagSNP selection algorithm (r(2) ≥ 0.90, MAF ≥ 4%) identified 21 tagSNPs. We used an identical Illumina platform to genotype GPX SNPs in three population-based case-control studies of colon cancer (1,424 cases/1,780 controls), rectal cancer (583 cases/775 controls), and colorectal adenomas (485 cases/578 controls). For gene-level associations, we conducted principal component analysis (PCA); multiple logistic regression was used for single SNPs. Analyses were adjusted for age, sex, and study center and restricted to non-Hispanic white participants. Analyses of cancer endpoints were stratified by molecular subtypes. Without correction for multiple testing, one polymorphism in GPX2 and three polymorphisms in GPX3 were associated with a significant risk reduction for rectal cancer at α = 0.05, specifically for rectal cancers with TP53 mutations. The associations regarding the three polymorphisms in GPX3 remained statistically significant after adjustment for multiple comparisons. The PCA confirmed an overall association of GPX3 with rectal cancer (P = 0.03). No other statistically significant associations were observed. Our data provide preliminary evidence that genetic variability in GPX3 contributes to risk of rectal cancer but not of colon cancer and thus provide additional support for differences in underlying pathogenetic mechanisms for colon and rectal cancer.