Study of Urinary Inorganic Arsenic Metabolism Pattern and Single Nucleotide Polymorphism of Metabolism Related Genes among Adolescent Residents from Arsenic Exposure Area in Taiwan

• Main Authors: Pin Yu Liu, 劉品妤
• Other Authors: Yen Der Hsuuw
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/55660881538731483544

碩士 === 國立屏東科技大學 === 畜產系 === 94 === Arsenic (As) is an ubiquitous element in the crust of the earth and mainly transported in the environment by water. It is a carcinogen for humans. In animals, it can be divided into organic and inorganic forms (inorganic arsenic, iAs). The toxicity for inorganic form is 100 folders higher than organic form. iAs contain AsIII (arsenite) and AsV (arsenate) where the predominant species is AsIII about 60 folders. Many studies indicated that As is methylated in liver, and their metabolites can be filtered out by kidney. Hence, As contents in urinary is a suitable biomarker for As exposure. As species in urine include AsIII, AsV, MMA (monomethylarsonic acid), DMA (dimethylarsonic acid) and TMAO (trimethylarsine oxide). MMA and DMA are the mainly metabolites in urine. Decreasing As metabolism capacity is associated with increasing As accumulate, leading to possible As related disorders. The objective of this study is to address the relationships between genes and environmental effects in As metabolism. The SNP (single nucleotide polymorphism) of related genes and urinary concentrations of As species in iAs metabolism pathway were determined. Samples were collected from Jhuangwei Township of Yilan County in Taiwan. Drinking water samples were collected from each subject’s outlet of drinking water, and 24-h urine collection were chosen. In first trail, As metabolism capacity index in human was examined. As species in urine were separated by HPLC (high performance liquid chromatography) and As concentrations were detected by HG-AAS (hydride generation-atomic absorption spectrometer), while As concentration of drinking water were analyzed by HG-AAS directly. The first metabolism capacity index was expressed by percentage of [iAs/(AsIII+AsV+MMA+DMA)]. The second index was represented by MMA/DMA. In the second trial, the relationships between SNP of As metabolism related genes and the two metabolism capacity indices was analyzed. The suitable restriction enzymes as well as primer design for candidate genes were selected by bioinformatics. Candidate genes included As metabolism related genes (AS3MT, GSTO1, GSTO2, MTHFR, and MTRR) and non-As metabolism related genes (TP53, SOD2, MPO, and NOS3). DNA was isolated from urine samples for PCR-RFLP assay. Results indicated that As concentration in drinking water were ranged from 0 to 670 ppb (101.45±27.65). As concentration in urine was ranged from 8.69 to 953.19 ppb (105.37±30.96). There was a significant correlation to As concentration between in water and urine (P<0.05, r2=0.68). To detect the five As related genes, there were significantly difference in both AS3MT and MTRR genes at the second metabolism capacity index (P<0.05). It suggested that they play an important role in the second metabolism capacity. Low metabolism capacity of MMA/DMA was found to associate with CC and CT genotypes for AS3MT and GG genotypes for MTRR. No interaction between AS3MT and MTRR genes was found (P>0.05). In the four non-As related genes, NOS3 gene has a low metabolism capacity in the second index (P<0.05), but their significance for genotypes is undetermined because of limit sample sizes. In addition, we cannot predict the two As metabolism capacity index by As concentration of drinking water directly (P>0.05). There was also no significantly difference between the two As metabolism capacity index for male and female (P>0.05). In conclusion, the genes effects of AS3MT and MTRR involved in As metabolism pathway is predominant to environmental effects without gene-gene interaction.