Abstract
The peroxisome proliferator-activated receptor gamma (PPARgamma) gene plays important roles in energy homeostasis. To examine interactions between consumption of foods and fatty acids and the Pro12Ala and C161T (His447His) polymorphisms for colorectal cancer, we performed two case-control studies in Japanese. In study 1, there were 128 colorectal cancer cases and 238 non-cancer controls, and in study 2 there were 257 cases and 771 (age- and sex-matched) non-cancer controls. Assessment of food and nutrients consumption in study 1 was via a nine-item questionnaire, while in study 2 assessment of consumption was according to a more detailed semiquantitative food frequency questionnaire. Consumption of foods and fatty acids was divided into low, moderate and high groups. The overall frequency of the Ala allele was <4%, and the frequencies of the Pro/Pro + C/C and Pro/Pro + (C/T + T/T) genotypes were 70-73% and 20-26%, respectively. Compared with subjects with low meat intake and the Pro/Pro + C/C genotype, those with high meat consumption and the same genotype had a stronger increased risk in study 1 [OR, 2.88; 95% CI, 1.14-7.30; P for trend = 0.02], but a positive association with processed meat consumption was greatest in those with the Pro/Pro + (C/T + T/T) genotype (P for trend = 0.05) in study 2. Likewise, high consumption of saturated fatty acids and milk appeared to confer marginal increased risk and stronger decreased risk, respectively, in those with the Pro/Pro and Pro/Pro + C/C genotypes (OR, 1.35 and 0.65; 95% CI, 0.93-1.96 and 0.43-1.00; P for trend = 0.10 and 0.06). Further large-scale studies are needed to determine colorectal cancer risk according to relationships between the PPARgamma gene polymorphisms and dietary intakes of meat, processed meat, milk and saturated fatty acids in Japanese with very low frequency of the Ala allele.