Tissue lycopene concentrations and isomer patterns are affected by androgen status and dietary lycopene concentration in male F344 rats

Diets rich in lycopene from tomato products as well as greater concentratio ns of blood lycopene have been associated with a decreased risk for prostat e cancer in epidemiologic studies. However, little is known about factors m odulating lycopene absorption, metabolism and tissue distribution in humans and animal models of prostate cancer. A 2 x 4 factorial design was used to measure the effects of androgen status (castrated vs. intact), dietary lyc opene concentration (0.00-5.00 g/kg lycopene) and their interaction on tiss ue lycopene accumulation and isomer patterns in male F344 rats. Male F344 r ats (14 wk old; 44 castrated, 44 intact) were randomly assigned to one of f our diets containing total lycopene concentrations of 0.00, 0.05, 0.50 or 5 .00 g/kg as beadlets and fed for 8 wk. Tissue total lycopene and cis/trans lycopene profiles were determined by HPLC. Tissue and serum lycopene concen trations increased significantly (P < 0.01) as dietary lycopene levels incr eased between 0.00 and 0.50 g/kg, No further increases in serum or tissue c oncentrations were seen in rats fed dietary lycopene between 0.50 and 5.00 g/kg. As dietary lycopene increased, so did the percentage of cis lycopene in the liver (P < 0.05), due primarily to an increase in the 5-cis isomer. Castrated rats accumulated twice (P < 0.01) the liver lycopene as compared to intact controls, with no effect of castration on serum lycopene or adren al, kidney, adipose, or lung tissue concentration. Livers from castrated ra ts had a greater proportion of cis-lycopene than those of intact rats (P < 0.05). A significant interaction between dietary lycopene concentration and androgen status was seen for liver lycopene concentration (P < 0.01). We c onclude that serum and tissue lycopene reaches a plateau between 0.05 and 0 .50 g/kg dietary lycopene, the tissue cis/trans lycopene ratio increases wi th greater dietary lycopene and androgens modulate hepatic lycopene metabol ism.