The polymorphism rs2480258 within CYP2E1 is associated with different rates of acrylamide metabolism in vivo in humans

In a recent study, we demonstrated that the variant allele of rs2480258 within intron VIII of CYP2E1 is associated with reduced levels of mRNA, protein, and enzyme activity. CYP2E1 is the most important enzyme in the metabolism of acrylamide (AA) by operating its oxidation into glycidamide (GA). AA occurs in food, is neurotoxic and classified as a probable human carcinogen. The goal of the present study was to further assess the role of rs2480258 by measuring the rate of AA > GA biotransformation in vivo. In blood samples from a cohort of 120 volunteers, the internal doses of AA and GA were assessed by AA and GA adducts to hemoglobin (Hb) measured by mass spectrometry. The rate of biotransformation was assessed by calculating the GA-Hb/AA-Hb ratio. To maximize the statistical power, 60 TT was compared to 60 CC-homozygotes and the results showed that TT homozygotes had a statistically significant reduced rate of biotransformation. Present results reinforced the notion that T-allele of rs2480258 is a marker of low functional activity of CYP2E1. Moreover, we studied the role of polymorphisms (SNPs) within glutathione-S-transferases (GSTs) enzymes and epoxide hydrolase (EPHX), verifying previous findings that SNPs within GSTs and EPHX influence the metabolism rate

Association between CYP2E1 polymorphisms and risk of differentiated thyroid carcinoma

Differentiated thyroid carcinoma (DTC) results from complex interactions between genetic and environmental factors. Known etiological factors include exposure to ionizing radiations, previous thyroid diseases, and hormone factors. It has been speculated that dietary acrylamide (AA) formed in diverse foods following the Maillard's reaction could be a contributing factor for DTC in humans. Upon absorption, AA is biotransformed mainly by cytochrome P450 2E1 (CYP2E1) to glycidamide (GA). Considering that polymorphisms within CYP2E1 were found associated with endogenous levels of AA-Valine and GA-Valine hemoglobin adducts in humans, we raised the hypothesis that specific CYP2E1 genotypes could be associated with the risk of DTC. Analysis of four haplotype tagging SNPs (ht-SNPs) within the locus in a discovery case-control study (N = 350/350) indicated an association between rs2480258 and DTC risk. This ht-SNP resides within a linkage disequilibrium block spanning intron VIII and the 3'-untranslated region. Extended analysis in a large replication set (2429 controls and 767 cases) confirmed the association, with odds ratios for GA and AA genotypes of 1.24 (95 % confidence interval (CI) 1.03-1.48) and 1.56 (95 % CI, 1.06-2.30), respectively. Functionally, the minor allele was associated with low levels of CYP2E1 mRNA and protein expression as well as lower enzymatic activity in a series of 149 human liver samples. Our data support the hypothesis that inter-individual differences in CYP2E1 activity could modulate the risk of developing DTC suggesting that the exposure to specific xenobiotics, such as AA, could play a role in this process

Mesothelin promoter variants are associated with increased soluble mesothelin-related peptide levels in asbestos-exposed individuals

BACKGROUND: Soluble mesothelin-related peptide (SMRP) is a promising diagnostic biomarker for malignant pleural mesothelioma (MPM), but various confounders hinder its usefulness in surveillance programmes. We previously showed that a single nucleotide polymorphism (SNP) within the 3'untranslated region (3'UTR) of the mesothelin (MSLN) gene could affect the levels of SMRP. OBJECTIVES: To focus on SNPs located within MSLN promoter as possible critical genetic variables in determining SMRP levels. METHODS: The association between SMRP and SNPs was tested in 689 non-MPM subjects and 70 patients with MPM. Reporter plasmids carrying the four most common haplotypes were compared in a dual luciferase assay, and in silico analyses were performed to investigate the putative biological role of the SNPs. RESULTS: We found a strong association between serum SMRP and variant alleles of rs3764247, rs3764246 (in strong linkage disequilibrium with rs2235504) and rs2235503 in non-MPM subjects. Inclusion of the genotype information led to an increase in SMRP specificity from 79.9% to 85.5%. Although not statistically significant, the group with MPM showed the same trend of association. According to the in vitro luciferase study, rs3764247 itself had a functional role. In silico approaches showed that the binding sites for transcription factors such as Staf and ZNF143 could be affected by this SNP. The other SNPs were shown to interact with each other in a more complex way. CONCLUSIONS: These data support the suggestion that SMRP performance is affected by individual (ie, genetic) variables and that MSLN expression is influenced by SNPs located within the promoter regulatory region

Evaluation of the role of polymorphisms within the xenobiotic metabolizing enzymes and acrylamide metabolism as risk factors for Differentiated Thyroid Carcinoma

Differentiated thyroid carcinoma (DTC) results from complex interactions between genetic and environmental factors. Known etiological factors include exposure to ionizing radiations, previous thyroid diseases, and hormone factors. It has been speculated that dietary acrylamide (AA) formed in diverse foods following the Maillard's reaction could be a contributing factor for DTC in humans. Upon absorption, AA is biotransformed mainly by cytochrome P450 2E1 (CYP2E1) to glycidamide (GA). Considering that polymorphisms within CYP2E1 were found associated with endogenous levels of AA-Hb and GA-Hb adducts in humans, we raised the hypothesis that specific CYP2E1 genotypes could be associated with the risk of DTC. Analysis of four haplotype tagging SNPs (ht- SNPs) within the locus in a discovery case-control study (N=350/350) indicated an association between rs2480258 and DTC risk. This ht-SNP resides within a linkage disequilibrium block spanning intron VIII and the 3'-untranslated region. Extended analysis in a large replication set (2429 controls and 767 cases) confirmed the association, with odds ratios for CT and TT genotypes of 1.24 (95 % confidence interval (CI) 1.03-1.48) and 1.56 (95 % CI, 1.06-2.30), respectively. Functionally, the minor allele was associated with low levels of CYP2E1 mRNA and protein expression as well as lower enzymatic activity in a series of 149 human liver samples. This association suggested that the risk of DTC could, at least in part, be ascribed to AA. We performed an in vivo study to assess the association of AA, GA and their ratio with SNPs of genes encoding for the metabolizing enzymes CYP2E1, EPHX1, GSTM1, GSTT1 and GSTP1 in 60 DTC patients and 60 healthy controls. The ratio of GA-Hb/AA-Hb was found associated in a statistically significant way with rs2480258 and the null genotype of GSTM1. The GSTM1 null genotype was also associated with high GA-Hb levels. The multiple regression analysis showed that the joint effect of CYP2E1 and GSTs was significantly associated with the ratio of GA-Hb/AA-Hb levels. Thus, present results not only confirmed previous findings on the role of GSTs in the AA metabolism but reinforced the notion that rs2480258 is a marker of the functional activity of CYP2E1. Since we didn't find any correlation between DTC and AA we therefore extended the human study by performing a screening of 19 other compounds, both identified and unidentified, observed as Hb adducts to N-terminal valine. The adductomics screening of the 19 compounds revealed that the levels of Methyl vinyl ketone and Ethyl vinyl ketone were significantly higher in controls and the levels of 575 m/z and 561_23 m/z were significantly higher in cases. Furthermore, a significant association was also found between the two unknown compounds and Acrylic acid with CYP2E1. Further studies are needed to completely understand the correlation between the different compounds, health status and SNPs