Urinary mutagenesis and fried red meat intake: Influence of cooking temperature, phenotype, and genotype of metabolizing enzymes in a controlled feeding study

Abstract

Meat cooked at high temperatures contains potential carcinogenic compounds, such as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). Samples from a 2-week controlled feeding study were used to examine the relationship between the intake of mutagenicity from meat fried at different temperatures and the levels of mutagenicity subsequently detected in urine, as well as the influence of the genotype of drug metabolizing enzymes on urinary mutagenicity. Sixty subjects consumed ground beef patties fried at low temperature (100 degrees C) for 1 week, followed by ground beef patties fried at high temperature (250 degrees C) the second week. Mutagenicity in the meat was assayed in Salmonella typhimurium TA98 (+S9), and urinary mutagenicity was determined using Salmonella YG1024 (+S9). Genotypes for NAT1, NAT2, GSTM1, and UGT1A1 were analyzed using blood samples from the subjects. Meat fried at 100 degrees C was not mutagenic, whereas meat fried at 250 degrees C was mutagenic (1023 rev/g). Unhydrolyzed and hydrolyzed urine samples were 22x and 131x more mutagenic, respectively, when subjects consumed red meat fried at 250 degrees C compared with red meat fried at 100 degrees C. We found that hydrolyzed urine was approximately 8x more mutagenic than unhydrolyzed urine, likely due to the deconjugation of mutagens from glucuronide. The intake of meat cooked at high temperature correlated with the mutagenicity of unhydrolyzed urine (r = 0.32, P = 0.01) and hydrolyzed urine (r = 0.34, P = 0.008). Mutagenicity in unhydrolyzed urine was not influenced by NAT1, NAT2, or GSTM1 genotypes. However, a UGT1A1*28 polymorphism that reduced UGT1A1 expression and conjugation modified the effect of intake of meat cooked at high temperature on mutagenicity of unhydrolyzed urine (P for interaction = 0.04). These mutagenicity data were also compared with previously determined levels of HCAs (measured as MeIQx, DiMeIQx, and PhIP) and polycyclic aromatic hydrocarbons (PAHs) in the meat, levels of HCAs in the urine, and CYP1A2 and NAT2 phenotypes. The levels of mutagenicity in the meat fried at low and high temperatures correlated with levels of HCAs, but not levels of PAHs, in the meat. Also, levels of mutagenicity in unhydrolyzed urine correlated with levels of MeIQx in unhydrolyzed urine (r = 0.36; P = 0.01), and the levels of mutagenicity of hydrolyzed urine correlated with levels of MeIQx (r = 0.34; P = 0.01) and PhIP (r = 0.43; P = 0.001) of hydrolyzed urine. Mutagenicity in unhydrolyzed urine was not influenced by either the CYP1A2 or NAT2 phenotype. The data from this study indicate that urinary mutagenicity correlates with mutagenic exposure from cooked meat and can potentially be used as a marker in etiological studies on cancer.

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

“…11 The genotype/phenotype association for the three most common polymorphisms of the UGT1A1 gene demonstrates that these genetic factors modulate the formation of this biomarker, N-OH-PhIP-N 2 G. Therefore, the UGT1A1 status is most likely to influence the level of exposure to N-OH-PhIP and potentially the risk of cancer through dietary exposure to HCAs. Consistent with this hypothesis, Peters and coworkers 50 recently showed in a controlled feeding study, that the UGT1A1*28 allele modifies the effect of intake of meat cooked at high temperature, generating HCAs, on urinary mutagenicity (a biological measurement of exposure). Given the strong biological plausibility for the role of UGT1A1 in the etiology of cancer, epidemiologic studies in populationbased samples with detailed exposure assessment are needed to fully explore this hypothesis and have recently been initiated.…”

Identification of polymorphic antioxidant response elements in the human genome

“…SNPs in transcription factor binding sites may affect the binding of transcription factors, lead to differences in gene expression and phenotypes, and therefore affect response and susceptibility to environmentally induced disease (2)(3)(4)(5)(6)(7)(8)30,31). Computational methods for predicting the effects of genetic variation are increasingly important because of the rapidly growing catalog of SNPs.…”

“…Other examples include a SNP that causes human α-thalassemias by creating a new binding site for erythroid transcription factor GATA-1 in the upstream of α-globin gene (2) and a SNP (-43C->T) in the proximal Sp1 site of the human low density lipoprotein receptor promoter results in heterozygous familial hypercholesterolemia (3). The UGT1A1 gene has a TATA box polymorphism that reduces expression of UGT1A1, leading to Gilbert's syndrome (a common form of hyperbilirubinemia) (4,5), and has also been associated with higher levels of mutagens in the urine (6). The steroid metabolism gene CYP17 has a GC box polymorphism in its proximal promoter that has been associated with higher levels of circulating estradiol (7) and with differences in bone mineral density (8).…”

Interindividual differences in phytochemical metabolism and disposition

“…Innocenti et al reported that, compared to *1/*1 and *1/*28 individuals, *28/*28 individuals had a higher prevalence of grade 4 neutropenia and a higher area under the curve (AUC) for the irinotecan metabolite SN-38 that requires glucuronidation in order to be cleared effectively [61]. Peters et al showed that, with exposure to well-cooked red meat (a source of mutagenic compounds) in a controlled feeding study, individuals with the *1/*28 and *28/ *28 genotypes had a higher urinary mutagenicity index than did individuals with the *1/*1 genotypes [62]. The authors suggested that greater amounts of the mutagens were being excreted in the freeform, rather than being glucuronidated and deactivated.…”