UGT1A1 polymorphisms are important determinants of dietary carcinogen detoxification in the liver

INTERACTION OF RECOMBINANT TATA-BINDING PROTEIN WITH MAMMALS GENES PROMOTER TATA

Quantitative characteristics of interaction recombinant TATA-binding protein (TBP) with oligonucleotides identical to natural TATA-containing promoter region genes of mammals are received. In particular, new experimental data about the importance guanine in 8-th position of the TATA-element for affinity to TBP are received. The experimental data, testifying that raised maintenance G and С nucleotides in flanks of TATA-element does the contribution to affinity to TBP are received.

UGT1A1 polymorphism is associated with serum bilirubin concentrations in a randomized, controlled, fruit and vegetable feeding trial

UDP-glucuronosyltransferase (UGT) 1A1 glucuronidates bilirubin, estrogens, and exogenous compounds, including dietary carcinogens. The UGT1A1*28 polymorphism, characterized by variation in the number of thymine-adenine repeats in the promoter region, modulates UGT1A1 transcription. Observational and in vitro studies suggest that certain phytochemicals may increase UGT activity. We investigated, in a randomized, controlled, crossover feeding trial, whether approximately 10 servings/d (doses adjusted for body weight) of crucifers, soy, and citrus for 2 wk compared with a fruit- and vegetable-free basal diet affected UGT1A1 activity as measured by serum bilirubin concentrations and whether effects were modulated by the UGT1A1*28 polymorphism. Healthy men (n = 32) and women (n = 31), aged 20-40 y, enrolled based on UGT1A1 genotype, completed the study. We measured bilirubin in blood collected at d 8 and d 15 of each feeding period. Overall, fruit and vegetables (F&V) did not affect serum bilirubin; however, among 7/7 individuals, d 8 total (P = 0.057) and indirect (unconjugated) (P = 0.051) bilirubin tended to be lower when individuals consumed the F&V diet (28.97 +/- 2.36 micromol/L and 25.97 +/- 2.15 micromol/L) compared with the basal diet (32.46 +/- 2.63 micromol/L and 29.31 +/- 2.43 micromol/L). We no longer detected this difference at d 15, by which time bilirubin had also decreased when participants consumed the basal diet. Additionally, intervention effects on bilirubin were restricted to women with 7/7 genotype (P = 0.002). These results suggest that serum bilirubin glucuronidation is modulated by dietary intervention, but factors such as UGT1A1 genotype and sex may affect the response to diet.

Validation of Rapid Polymerase Chain Reaction-based Detection of All Length Polymorphisms in the UGT 1A1 Gene Promoter

UDP glucuronosyltransferase (UGT) 1A1 gene promoter polymorphism can affect the expression level of the UGT 1A1 enzyme. The polymorphism consists of an insertion of a TA nucleotide sequence into a (TA)6TAA sequence in the gene promoter resulting in (TA)7TAA (UGT1A1*28). This results in a reduced UGT 1A1 expression with 70% less glucuronidation capacity for bilirubin and other UGT1A1 substrates. Other polymorphisms include (TA)8TAA (UGT1A1*37) and (TA)5TAA (UGT1A1*36). The longer the TA repeats the lower the enzyme expression level. The anticancer agent irinotecan is metabolized to the active SN-38, which is further glucuronidated and detoxified by UGT 1A1. Decreased glucuronidation leads to SN-38 accumulation with severe neutropenia and diarrhea. We have developed a rapid polymerase chain reaction (PCR)-based detection of all length polymorphisms in the UGT 1A1 gene promoter. It uses PCR and DNA fragment analysis using an ABI Genetic Analyzer. Thirty-two blood samples were analyzed for UGT 1A1 promoter polymorphism. We found 2 (TA)(5)TAA/(TA)(5)TAA, 4 (TA)(5)TAA/(TA)(6)TAA, 2 (TA)(5)TAA/(TA)(7)TAA, 9 (TA)(6)TAA/(TA)(6)TAA, 11 (TA)(6)TAA/(TA)(7)TAA, 2 (TA)(7)TAA/(TA)(7)TAA, and 2 (TA)(7)TAA/(TA)(8)TAA in our sample group. To confirm the results, 6 samples with different repeats were also analyzed by DNA sequencing method. This is a rapid and reliable method for analysis of the promoter length polymorphisms of UGT 1A1 gene.

Hepatocyte nuclear factor1 transcription factors are essential for the UDP-glucuronosyltransferase 1A9 promoter response to hepatocyte nuclear factor 4α

In humans, UDP-glucuronosyltransferase 1A9 is known to glucuronidate numerous lipophilic substances of pharmacological and toxicological importance. Although it has been established that individuals vary in their capacity to express this detoxification enzyme, little is known about the mechanisms that dictate the regulation of UGT1A9. In particular, it is not understood why, while the proximal regulatory regions of the UGT1A7-10 gene cluster are highly similar, UGT1A9 is the sole hepatic isoform of the four. Recent data have suggested that the human UGT1A9 promoter is controlled by hepatocyte nuclear factor 4alpha. In this work, we confirm that the human UGT1A9 promoter can indeed be upregulated by human hepatocyte nuclear factor 4alpha in vitro. Our results, however, show that the previously-reported hepatocyte nuclear factor 4alpha-binding site only plays a minor role in this response. Instead, upregulation was found to require a more proximal response element, which was not preserved in the UGT1A7, UGT1A8 or UGT1A10 promoters. Furthermore, hepatocyte nuclear factor 4alpha-mediated transcription from the human UGT1A9 promoter was discovered to be entirely dependent on hepatocyte nuclear factor 1. We have established that two hepatocyte nuclear factor 1-binding elements are involved in this phenomenon, the more distal of which is unique to the UGT1A9 promoter. Interestingly, this second site had no significant role in hepatocyte nuclear factor 1alpha-mediated induction of the UGT1A9 promoter in vitro, yet was critical for upregulation by human hepatocyte nuclear factor 4alpha. The discovery of two unique and cooperative liver-enriched transcription factor binding sites in the UGT1A9 promoter is a significant step towards understanding the unique hepatic expression of UGT1A9 amongst the UGT1A7-10 gene cluster.

The Urinary Metabolite Profile of the Dietary Carcinogen 2-Amino-1-Methyl-6-Phenylimidazo[4,5-b]Pyridine Is Predictive of Colon DNA Adducts after a Low-Dose Exposure in Humans

Epidemiologic evidence indicates that exposure to heterocyclic amines in the diet is an important risk factor for the development of colon cancer. Well-done cooked meats contain significant levels of heterocyclic amines, which have been shown to cause cancer in laboratory animals. To better understand the mechanisms of heterocyclic amine bioactivation in humans, the most mass abundant heterocyclic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), was used to assess the relationship between PhIP metabolism and DNA adduct formation. Ten human volunteers where administered a dietary relevant dose of [(14)C]PhIP 48 to 72 hours before surgery to remove colon tumors. Urine was collected for 24 hours after dosing for metabolite analysis, and DNA was extracted from colon tissue and analyzed by accelerator mass spectrometry for DNA adducts. All 10 subjects were phenotyped for cytochrome P4501A2 (CYP1A2), N-acetyltransferase 2, and sulfotransferase 1A1 enzyme activity. Twelve PhIP metabolites were detected in the urine samples. The most abundant metabolite in all volunteers was N-hydroxy-PhIP-N(2)-glucuronide. Metabolite levels varied significantly between the volunteers. Interindividual differences in colon DNA adducts levels were observed between each individual. The data showed that individuals with a rapid CYP1A2 phenotype and high levels of urinary N-hydroxy-PhIP-N(2)-glucuronide had the lowest level of colon PhIP-DNA adducts. This suggests that glucuronidation plays a significant role in detoxifying N-hydroxy-PhIP. The levels of urinary N-hydroxy-PhIP-N(2)-glucuronide were negatively correlated to colon DNA adduct levels. Although it is difficult to make definite conclusions from a small data set, the results from this pilot study have encouraged further investigations using a much larger study group.

Gilbert's disease and atazanavir: from phenotype to UDP-glucuronosyltransferase haplotype

Gilbert's disease leads to intermittent non-hemolytic hyperbilirubinemia by a reduction of hepatic bilirubin glucuronidation associated with the presence of the UDP-glucuronosyltransferase (UGT) 1A1*28 polymorphism. It is considered benign because it does not result in hepatocellular damage. However, pharmacogenetic analyses have linked UGT1A1*28 to drug toxicity and cancer predisposition. The protease inhibitor atazanavir (ATV) is an inhibitor of hepatic UGT activity leading to hyperbilirubinemia in individual patients. Whether this is linked specifically to UGT1A1*28 or to more complex variants influencing glucuronidation is unclear. One hundred and six ATV-treated patients were characterized and genotyped for UGT1A1*28, the UGT1A3 (-66C) and UGT1A7 (-57G) promoter variants, and UGT1A7(129K/131K). ATV treatment increased median bilirubin levels from 10 to 41 micromol/L (P = .001) with hyperbilirubinemia exceeding 43 micromol/L in 37%. Hyperbilirubinemia over 43 micromol/L was significantly associated not only with UGT1A1*28 but also with UGT1A3-66C, UGT1A7-57G, and UGT1A7(129K/131K), although these variants do not naturally occur in linkage dysequilibrium in blood donors. Homozygous combinations of UGT1A1*28 with the other variants increased from 7.4% (normal bilirubin to 42 micromol/L) to 41% to 46.1% (43 to >85 micromol/L), and 100% (>85 micromol/L). All six patients with hyperbilirubinemia greater than 85 micromol/L were homozygous for all four variants identifying a haplotype inherited on a single allele. In conclusion, the genetic variant associated with Gilbert's disease is identified as part of a haplotype of four UGT1A variants spanning three genes at the UGT1A gene locus. This haplotype predisposes to hyperbilirubinemia in ATV treatment and may have an additional role as a pharmacogenomic risk factor for drug therapy.

THE NOVEL UGT1A9 INTRONIC I399 POLYMORPHISM APPEARS AS A PREDICTOR OF 7-ETHYL-10-HYDROXYCAMPTOTHECIN GLUCURONIDATION LEVELS IN THE LIVER

Polymorphisms in UGT1A9 were associated with reduced toxicity and increased response to irinotecan in cancer patients. UDP-glucuronosyltransferase (UGT) protein expression, glucuronidation activities for 7-ethyl-10-hydroxycamptothecin (SN-38), and probe substrates of the UGT1A9 and UGT1A1 were measured in 48 human livers to clarify the role of UGT1A9 variants on the in vitro glucuronidation of SN-38. Genotypes were assessed for UGT1A9 (-2152C>T, -275T>A, and -118T(9>10)), three novel UGT1A9 variants (-5366G>T, -4549T>C, and I399C>T), and UGT1A1 (-53TA(6>7), -3156G>A, and -3279T>G). Of all the variants, the UGT1A9 I399C>T was associated with the most dramatic change in SN-38-glucuronide (SN-38G) (2.64-fold; p = 0.0007). Compared with UGT1A9 I399C/C, homozygous I399T/T presented elevated UGT1A1 and UGT1A9 proteins and higher glucuronidation of UGT1A9 and UGT1A1 substrates (p < 0.05). The very low linkage disequilibrium (r(2) < 0.19) between UGT1A9 I399 and all the other UGT1A1 and UGT1A9 variants suggests a direct effect or linkage to unknown functional variant(s) relevant to SN-38 glucuronidation. The UGT1A9 -118T(9/10) was also linked to alteration of SN-38 glucuronidation profiles in the liver (p < 0.05) and was associated with higher UGT1A1 protein (p = 0.03). However, UGT1A9 -118T(10) appears to have low functional impact as a result of the lack of correlation with UGT1A9 protein levels and a modest 1.4-fold higher reporter gene expression associated with the -118T(10) allele in HepG2 cells (p = 0.004). In contrast, the UGT1A9 -5366T, -4549C, -2152T, and -275A, associated with higher UGT1A9 protein (2-fold; p < 0.05), have no influence on SN-38G. Despite limitations resulting from sample size, results indicate that UGT1A9 I399 and -118T(9/10) may represent additional candidates in combination with UGT1A1 promoter haplotypes for the prediction of SN-38 glucuronidation profile in vivo.

Are all dilemmas in gerontology being swept under the carpet of intra-individual variability?

It is considered that there are great differences among elderly individuals, because the intra-individual variability is great. The differences among specific individuals grow with their age, so when adults reach a very old age, it seems that there are great differences among them--some are able to do some work, the others are not so able-bodied, whereas among high school students there is usually little difference in their physical ability. The research that supports the above mentioned points, however, does not exist and this opinion came about as a result of deduction. The goal of this study is to examine the fluctuations in the elderly and prove that the genetic difference plays a bigger role than the variability, as the intra-individual (or the between-person) variability is present everywhere, not only in very old people.

Joint Effects between UDP-Glucuronosyltransferase 1A7 Genotype and Dietary Carcinogen Exposure on Risk of Colon Cancer

The UDP-glucuronosyltransferase 1A7 (UGT1A7) gene is polymorphic and encodes an enzyme involved in the detoxification of heterocyclic amines (HCA) and polycyclic aromatic hydrocarbons (PAH). Consumption of pan-fried and well-done meat are surrogates for HCA and PAH exposure and are possibly associated with colon cancer. We have evaluated whether UGT1A7 allelic variations are associated with colon cancer and whether UGT1A7 genotype modified associations among meat intake, exposure to HCAs and PAHs, and colon cancer in a population-based case-control study of African Americans (197 cases and 202 controls) and whites (203 cases and 210 controls). As part of a 150-item food frequency questionnaire, meat intake was assessed by cooking method and doneness and used to estimate individual HCA and PAH exposure. UGT1A7 alleles (UGT1A7*1, UGT1A7*2, UGT1A7*3, and UGT1A7*4) were measured and genotypes were categorized into predicted activity groups (high: *1/*1, *1/*2, *2/*2; intermediate: *1/*3, *1/*4, *2/*3; low: *3/*3, *3/*4, *4/*4). There was no association with UGT1A7 low versus high/intermediate genotype [odds ratio (OR), 1.1; 95% confidence interval (95% CI), 0.7-1.8], regardless of race. Greater than additive joint effects were observed for UGT1A7 low genotype and HCA-related factors. For example, equal to or greater than the median daily intake of the HCA, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) and having UGT1A7 low genotype was positively associated with colon cancer (OR, 2.4; 95% CI, 1.2-4.8), compared with less than the median daily intake and UGT1A7 high/intermediate genotypes. These data suggest that the associations among cooked meat-derived compound exposure, and colon cancer are modified by the UGT1A7 genotype.