Adipose tissue and the effects of fat and calories on breast tumorigenesis in rats

A high fat diet fed ad libitum will promote breast tumorigenesis in rats while caloric restriction of the same high fat diet counteracts this promotional effect. The present study examined the effects of dietary fat and calorie intake on adipose tissue weight and fatty acid composition and on tumor incidence and development. The sites of adipose tissue chosen were the mammary fat pad, representing adipose tissue in the immediate location of the studied tumor, and the abdominal fat depot which in humans has been associated with an increased risk of breast cancer. High (20% corn oil) and low (5% corn oil) fat test diets were offered ad libitum and at 40% restriction levels. In agreement with prior studies, caloric restriction of both high and low fat diets led to marked decreases in tumor incidence (63 to 68% versus 21%), tumor burden (1.84 to 2.05 versus 0.37 to 0.43 tumors/rat), and tumor weight (7.1 to 11.9 versus 1.4 to 2.2 g) at the time of sacrifice (133 days post-DMBA). While final body weights were reduced in proportion to the level of caloric restriction (290 to 291 g versus 184 to 201 g), abdominal fat (8.8 to 9.2 versus 0.9 to 1.6 g), and mammary fat weights (3.1 to 4.1 versus 0.7 to 2.0 g) were reduced markedly in association with the decrease in tumorigenesis. While both tumor and mammary fat were enriched with linoleate reflecting the fatty acid composition of dietary fat, the ratio of arachidonic acid to linoleic acid was higher in tumor tissue than in surrounding normal mammary tissue in both the phospholipid (0.78 versus 0.18) and neutral lipid fractions (0.22 versus 0.03). These observations are consistent with the concept that increases in fat tissue mass in abdominal and mammary fat depots may mediate some of the promotional effects of high fat and high calorie diets. Restriction of dietary fat and calories to reduce body fat and strategies to modify the composition of stored lipids in fat depots may offer nutritional approaches to breast cancer prevention and treatment.     

Sex differences in Japanese macaques (Macaca fuscata): effects of prenatal testosterone on juvenile social behavior

The aim of this study was to assess, in a nonhuman primate, the extent to which exposure to androgen during the prenatal period interacts with early social experience to affect the display of male or female patterns of behavior. Pregnant females from a large age-graded, heterosexual group of Japanese macaques (Macaca fuscata) were implanted about the 40th day of gestation with Silastic packets of testosterone. The packets were removed on the 100th day of gestation, and the females were allowed to give birth in their outdoor corral. An unplanned procedural change, by the surgeon who did the implants, created two groups of prenatally androgenized females: a high-dose group (N = 3), and a low-dose group (N = 4). The anatomical differentiation of these groups differed in that the high-dose group had small penises and no vaginas while the low-dose group had enlarged clitorises and patent vaginas. The behavior of these two groups of females was compared with that of normal males (N = 6), prenatally androgenized males (N = 6), and normal females (N = 5) from birth to 2 years of age. There were no differences between treated and normal males, but there were sex differences between males and normal females in the frequency of mounting, playing, displaying, and grooming. The high-dose group of prenatally androgenized females differed from normal females on only one measure: increased frequency of mounting. The low-dose group mounted other juveniles more frequently than did the normal females, but the difference was not statistically significant. We concluded that mounting behavior was most sensitive to the prenatal hormone environment because it showed the largest sex difference in normal animals. Given the small sample sizes, within-group variability could have obscured possible hormonal effects on other behaviors where sex differences were less dramatic.