Tomato carotenoid bioaccumulation and gene expression of carotenoid cleavage enzymes are altered by soy germ in male Copenhagen rat tissues

Abstract

Epidemiological studies have supported the hypothesis that dietary intake of soy foods or tomato products is associated with a lower risk of prostate cancer. However, little is known about how simultaneous consumption may impact absorption, tissue distribution, and metabolism of tomato carotenoids. Diets containing 10% tomato powder (TP) (n=17), 2% soy germ (SG) (n=16), neither (n=17), or a combination (TP+SG) (n=13) were fed to 12 week old male Copenhagen rats for approximately 24 weeks. Bioaccumulation of tomato carotenoids were lower in various tissues of rats fed TP + SG compared to TP alone, especially in androgen sensitive tissues. Testes, seminal vesicles, and ventral prostate of the TP+SG group had lower levels of lycopene (p=0.001, p=0.04, and p=0.002, respectively) and β‐carotene (p=.003, p=.003, p=.001, respectively) than the TP group. Gene expression of carotenoid 15,15′‐monooxygenase (CMOI) and carotenoid 9′10′‐monooxygenase II (CMOII) were measured in the liver, duodenum mucosa, and prostate. Rats fed TP had significantly higher hepatic CMOI expression compared to the control group (p=.046), but expression was not significantly different from rats fed SG or TP+SG. Liver expression of CMOII was not significantly different between groups. Our results suggest that dietary soy germ may alter uptake and/or metabolism of carotenoids. Research supported in part by USDA NNF 2005‐03750.Grant Funding Source: NIH