Effects of fostering on the increased tumor incidence produced by a maternal diet high in fat

Abstract

Previous work has shown that female offspring of mice fed a diet high in fat during pregnancy developed more reproductive system tumors and metastases than offspring of pregnant mice fed a low‐fat diet. The purpose of the current experiment was to use fostering to test whether the sensitive period for this cancer effect involved the early postnatal period. Strain CD‐1 female mice were placed on a diet of 2.6% fat or 29% fat from corn oil at 4 weeks of age and bred at 6–10 weeks of age. The special diets were discontinued at birth, and litters from dams that had been fed the low‐fat diet were fostered to dams previously fed the high‐fat diet, and vice versa. The offspring were raised to terminal illness and autopsied. There was no difference in age at terminal illness or in the number of the common nonreproductive system tumors between the two fostered groups. Tumor metastases appeared in both groups. However, the combined frequency of reproductive tract tumors and mammary tumors was significantly higher in mice exposed prenatally to a low‐fat diet and fostered to dams that had consumed a high‐fat diet during pregnancy than in mice exposed prenatally to a high‐fat diet and fostered to a dam fed a low‐fat diet. Thus the most sensitive period for a cancer effect from high fat was early postnatal, even though the special diets had been discontinued at birth. This matches the period of greatest sensitivity for sex differentiation of the hypothalamus.