Sang-Yong Eom

Effects of Dietary Factors and the NAT2 Acetylator Status on Gastric Cancer in Koreans

Environmental dietary carcinogens and genetic polymorphisms in metabolic enzymes have been reported to be the risk factors for gastric cancer. This study was undertaken to investigate the effects of the diet, the N‐acetyltransferase (NAT) 2 acetylation status and their interaction on gastric cancer risk. The study population consisted of 471 gastric cancer patients and 471 age‐ and sex‐matched control subjects. NAT2 genotypes were identified using single‐nucleotide primer extension reaction methods. Thirty‐one alleles related to 12 polymorphism sites were assayed in this study. Significantly increased odds ratios were observed in former smokers (OR = 2.39, 95% CI = 1.57–3.62), heavy drinkers (OR = 1.28, 95% CI = 1.06–1.55) and individuals who eat well‐done meat (OR = 1.24, 95% CI = 1.09–1.41). The odds ratios (95% CI) for high intake of kimchi, stews and soybean paste were 3.27 (2.44–4.37), 1.96 (1.50–2.58) and 1.63 (1.24–2.14), respectively. The NAT2 genotype alone was not associated with gastric cancer risk. A significant gene–environment interaction was observed between environmental carcinogens and NAT2 genotypes. The odds ratios for kimchi, stews and soybean paste were higher in slow/intermediate acetylators than in rapid acetylators. The odds ratios for slow/intermediate acetylators were 2.28 (95% CI: 1.29–4.04) for light smokers and 3.42 (95% CI: 2.06–5.68) for well‐done meat intake. The NAT2 acetylator genotype may be an important modifier of the effects of environmental factors on gastric cancer risk.

Ethanol-induced oxidative DNA damage and CYP2E1 expression in liver tissue of Aldh2 knockout mice.

Ethanol‐Induced Oxidative DNA Damage and CYP2E1 Expression in Liver Tissue of Aldh2 Knockout Mice: Yong‐Dae Kim, et al. Department of Preventive Medicine and Medical Research Institute, College of Medicine, Chungbuk National University, Republic of Korea—Excessive alcohol consumption is associated with increased risks of many diseases including cancer. We evaluated oxidative DNA damage in Aldh2 +/+ and Aldh2 –/– mice after they had been subjected to acute ethanol exposure. Olive tail moment, which was measured using a comet assay, was not increased by ethanol treatment in both Aldh2 +/+ and Aldh2 –/– mice. However, after controlling for the effect of ethanol exposure, the Aldh2 genotype was a significant determinant for Olive tail moments. Although the ethanol treatment significantly increased the hepatic 8‐OHdG generation in only Aldh2 +/+ mice, the level of 8‐OHdG was the highest in Aldh2 –/– ethanol treated mice. The increase in the level of 8‐OHdG was associated with hepatic expression of cytochrome P450 2E1 (CYP2E1). The levels of Olive tail moment and the hepatic 8‐OHdG in the Aldh2 –/– control group were significantly higher than those of the Aldh2 +/+ control group. The level of CYP2E1 in liver tissue showed a similar pattern to those of the oxidative DNA damage markers. This study shows that acute ethanol consumption increases oxidative DNA damage and that expression of CYP2E1 protein may play a pivotal role in the induction of oxidative DNA damage. The finding that oxidative DNA damage was more intense in Aldh2 –/– mice than in Aldh2 +/+ mice suggests that ALDH2‐deficient individuals may be more susceptible than wild‐type ALDH2 individuals to ethanol‐mediated liver disease, including cancer.

Estimation of the Biological Half-Life of Methylmercury Using a Population Toxicokinetic Model.

Methylmercury is well known for causing adverse health effects in the brain and nervous system. Estimating the elimination constant derived from the biological half-life of methylmercury in the blood or hair is an important part of calculating guidelines for methylmercury intake. Thus, this study was conducted to estimate the biological half-life of methylmercury in Korean adults. We used a one-compartment model with a direct relationship between methylmercury concentrations in the blood and daily dietary intake of methylmercury. We quantified the between-person variability of the methylmercury half-life in the population, and informative priors were used to estimate the parameters in the model. The population half-life of methylmercury was estimated to be 80.2 ± 8.6 days. The population mean of the methylmercury half-life was 81.6 ± 8.4 days for men and 78.9 ± 8.6 days for women. The standard deviation of the half-life was estimated at 25.0 ± 8.6 days. Using the direct relationship between methylmercury concentrations in blood and methylmercury intake, the biological half-life in this study was estimated to be longer than indicated by the earlier studies that have been used to set guideline values.

Evaluation of the relationship between dietary factors, CagA-positive Helicobacter pylori infection, and RUNX3 promoter hypermethylation in gastric cancer tissue

AIM To evaluate the relationship among Helicobacter pylori (H. pylori) infection, CagA status, and dietary factors with RUNX3 promoter hypermethylation. METHODS Gastric cancer tissue samples were collected from 184 South Korean patients. All patients were interviewed following a semi-quantitative food frequency questionnaire. The average frequencies of intake and portion sizes of 89 common food items were documented, and total intakes of calories, nutrients, vitamins, and minerals were calculated for each subject. DNA was extracted from gastric cancer tissue samples, and amplification of the HSP60 gene was performed to detect H. pylori infection. Nested polymerase chain reaction (PCR) was used to detect the presence of the CagA gene. RUNX3 gene expression was measured by reverse transcription-PCR, and RUNX3 methylation status was evaluated by methylation-specific PCR. The odds ratios (ORs) and 95%CI associated with RUNX3 promoter hypermethylation status were estimated for each of the food groups, lifestyle factors, and the interaction between dietary and lifestyle factors with CagA status of H. pylori infection. RESULTS Overall, 164 patients (89.1%) were positive for H. pylori DNA, with the CagA gene detected in 59 (36%) of these H. pylori-positive samples. In all, 106 (57.6%) patients with gastric cancer demonstrated CpG island hypermethylation at the RUNX3 promoter. RUNX3 expression was undetectable in 52 (43.7%) of the 119 gastric cancer tissues sampled. A high consumption of eggs may increase the risk of RUNX3 methylation in gastric cancer patients, having a mean OR of 2.15 (range, 1.14-4.08). A significantly increased OR of 4.28 (range, 1.19-15.49) was observed with a high consumption of nuts in patients with CagA-positive H. pylori infection. High intakes of carbohydrate, vitamin B1, and vitamin E may decrease the risk of RUNX3 methylation in gastric cancer tissue, particularly in CagA- or H. pylori-negative infection, with OR of 0.41 (0.19-0.90), 0.42 (0.20-0.89), and 0.29 (0.13-0.62), respectively. A high consumption of fruits may protect against RUNX3 methylation. CONCLUSION These results suggest that the CagA status of H. pylori infection may be a modifier of dietary effects on RUNX3 methylation in gastric cancer tissue.

Temporal changes in urinary levels of cadmium, N-acetyl-β-d-glucosaminidase and β2-microglobulin in individuals in a cadmium-contaminated area

Cadmium (Cd) is a metal that is toxic to renal tubules. If renal tubules are damaged by Cd, urinary excretion of N-acetyl-β-D-glucosaminidase (NAG) and beta 2-microglobulin (β2-MG) increases. The aim of this study was to describe the changing patterns of urinary Cd, NAG, and β2-MG levels over a 3-year period in individuals living in a Cd-contaminated area. This follow-up study included 191 residents (65.6±9.3 years) who were living in the vicinity of a copper refinery. Urinary levels of Cd, NAG activity, and β2-MG levels were measured, and their determinants and changing patterns were analyzed statistically. The natural logarithm of urinary Cd levels decreased significantly over time. Sex and intake of locally cultivated rice were significant determinants of urinary Cd concentration. Urinary NAG activity decreased over time. Age and urinary Cd concentration were significant determinants of urinary NAG activity in subjects with urinary Cd concentrations >5μg/g creatinine. In subjects whose urinary Cd concentrations were >2μg/g creatinine, diabetes was found to be a significant risk factor for high urinary NAG activity. The slope for temporal changes in urinary β2-MG levels was negative in subjects whose urinary Cd levels were <2μg/g creatinine but was positive in those whose urinary Cd levels were 2-5μg/g creatinine or >5μg/g creatinine. The urinary β2-MG levels found in individuals whose urinary Cd levels were >2μg/g creatinine suggest that previous Cd-induced renal tubular damage had occurred.

Reference values for the pulmonary function of Korean adults using the data of Korea National Health and Nutrition Examination Survey IV (2007-2009).

The objective of this study was to develop new spirometric reference equations for the Korean population using the raw data of the fourth Korea National Health and Nutrition Examination Survey (KNHANES IV, 2007-2009). A total of 4,753 healthy lifelong nonsmokers without respiratory diseases and symptoms were selected as the reference population. Spirometric reference equations were derived through multiple regression analysis. The newly developed reference equations for spirometry parameters were as follows: FEV1 (L) = -0.00025410 × (Age [years])2 + 0.00012644 × (Height [cm])2 - 0.00262 × Weight (kg) + 0.61493 (Men); FEV1 (L) = -0.00017538 × Age2 + 0.00009598 × Height2 - 0.00231 × Weight + 0.46877 (Women); FVC (L) = -0.00000219 × Age3 + 0.0000006995642 × Height3 + 1.19135 (Men); FVC (L) = 0.0167 × Age - 0.00030284 × Age2 + 0.0000005850287 × Height3 + 0.77609 (Women); FEV1/FVC (%) = -0.00289 × Age2 - 0.16158 × Height3 + 114.13736 (Men); FEV1/FVC (%) = -0.21382 × Age - 0.00000143 × Height3 + 97.62514 (Women). The newly developed spirometric reference equation in this study can be used as criteria for the interpretation of spirometry results and the diagnosis of respiratory diseases in Korean adults.

Risk of gastric cancer is associated with PRKAA1 gene polymorphisms in Koreans

AIM To evaluate the association between genetic polymorphisms of the gene encoding AMP-activated protein kinase (PRKAA1) and the risk of gastric cancer. METHODS The study subjects consisted of 477 age- and sex-matched case-control pairs. Genotyping was performed for 5 tag single nucleotide polymorphisms (SNPs): rs13361707, rs154268, rs3805486, rs6882903, and rs10074991. Associations between gastric cancer and putative risk factors (including the SNPs) were analyzed with multivariate conditional logistic regression models, after adjusting for potential confounding factors. Multiple testing corrections were implemented following methodology for controlling the false discovery rate. Gene-based association tests were performed by using the versatile gene-based association study (VEGAS) method. RESULTS In the dominant model, SNPs rs13361707 [odds ratio (OR) = 1.51, 95%CI: 1.07-2.11)], rs154268 (OR = 1.65, 95%CI: 1.22-2.22), rs6882903 (OR = 1.48, 95%CI: 1.09-2.00), and rs10074991 (OR = 1.53, 95%CI: 1.09-2.16) were significantly associated with an increased risk of gastric cancer. In the recessive model, SNPs rs154268 (OR = 1.66, 95%CI: 1.22-2.26), rs3805486 (OR = 0.63, 95%CI: 0.46-0.85), and rs10074991 (OR = 1.47, 95%CI: 1.15-1.88) were significant risk or protective factors for gastric cancer. In the codominant model, the ORs of each of the 5 SNPs were statistically significant. All SNPs in the model showed a dose-response relationship between the minor allele frequency and the risk of gastric cancer. Most notably, subjects with a homozygous minor allele in SNP rs10074991 showed 2.15 times the risk of gastric cancer as subjects without a minor allele. The PRKAA1 gene showed a significant gene-based association with gastric cancer in the VEGAS test. CONCLUSION All 5 tested tag SNPs of the PRKAA1 gene (rs13361707, rs154268, rs3805486, rs6882903, and rs10074991) were significantly associated with gastric cancer.

Differences in the susceptibility to cadmium-induced renal tubular damage and osteoporosis according to sex

This study aimed to estimate the risks for renal tubular damage and osteoporosis in individuals with long-term environmental Cd exposure. This cross-sectional study comprised 1086 residents living in the vicinity of a copper refinery plant. As the urinary Cd levels increased, the proportion of female subjects with β₂-MG ≥300 μg/g creatinine also increased significantly, but this was not observed in the male subjects. The prevalence of osteoporosis was significantly higher in men with urinary Cd >5 μg/g creatinine than in those with urinary Cd ≤5 μg/g creatinine. This difference was not observed in the corresponding female groups. The association between increased urinary excretion of β₂-MG and decreased BMD was statistically significant only in the female subjects. We suggest that an increased Cd body burden directly decreases the BMD in male subjects; however, in female subjects, it first induces renal microtubular damage, which can lead to osteoporosis.

Environmental Exposure to Arsenic, Lead, and Cadmium in People Living near Janghang Copper Smelter in Korea

Concentrations of heavy metals exceed safety thresholds in the soil near Janghang Copper Refinery, a smelter in Korea that operated from 1936 to 1989. This study was conducted to evaluate the level of exposure to toxic metals and the potential effect on health in people living near the smelter. The study included 572 adults living within 4 km of the smelter and compared them with 413 controls group of people living similar lifestyles in a rural area approximately 15 km from the smelter. Urinary arsenic (As) level did not decrease according to the distance from the smelter, regardless of gender and working history in smelters and mines. However, in subjects who had no occupational exposure to toxic metals, blood lead (Pb) and cadmium (Cd) and urinary Cd decreased according to the distance from the smelter, both in men and women. Additionally, the distance from the smelter was a determinant factor for a decrease of As, Pb, and Cd in multiple regression models, respectively. On the other hands, urinary Cd was a risk factor for renal tubular dysfunction in populations living near the smelter. These results suggest that Janghang copper smelter was a main contamination source of As, Pb, and Cd, and populations living near the smelter suffered some adverse health effects as a consequence. The local population should be advised to make efforts to reduce exposure to environmental contaminants, in order to minimize potential health effects, and to pay close attention to any health problems possibly related to toxic metal exposure.

Interactions between Paraoxonase 1 Genetic Polymorphisms and Smoking and Their Effects on Oxidative Stress and Lung Cancer Risk in a Korean Population

Background Few studies in epidemiology have evaluated the effects of gene-environment interaction on oxidative stress, even though this interaction is an important etiologic factor in lung carcinogenesis. We investigated the effects of the genetic polymorphisms of paraoxonase 1 (PON1), smoking, and the interaction between the two on lung cancer risk and oxidative stress. Methods This study’s subjects consisted of 416 newly diagnosed lung cancer patients and an equal number of matched controls. The GoldenGate assay was used for genotypic analyses of the PON1 gene. Urinary 8-hydroxydeoxyguanosine (8-OHdG) and thiobarbituric acid reactive substances levels were measured as indicators of oxidative stress. Results The PON1 rs662 AA genotype showed a significantly lower risk of lung cancer than the GG genotype (OR = 0.60, 95% CI: 0.36–0.99). The protective effect of the PON1 rs662 AA genotype on lung cancer risk was limited to non-smokers. Lung cancer patients who had the rs662 A allele showed a dose-dependent association between smoking status and oxidative stress markers. Among non-smoking lung cancer patients, urinary 8-OHdG levels were significantly lower in individuals with the rs662 GA and AA genotypes than in those with the GG genotype. Furthermore, we found a significant interaction effect between PON1 rs662 and smoking status on urinary 8-OHdG levels in lung cancer patients. Conclusions Our results suggest that the protective effect of PON1 rs662 SNP against lung carcinogenesis and the induction of oxidative stress might be modulated by the interaction between PON1 genetic polymorphisms and tobacco smoking.