Effects of dietary n-3-to-n-6 polyunsaturated fatty acid ratio on mammary carcinogenesis in rats.
We investigated the effects of the dietary n-3-to-n-6 polyunsaturated fatty acid (PUFA) ratio (n-3/n-6 ratio) on mammary carcinogenesis induced by 7,12-dimethylbenz[a]anthracene in rats by feeding them several types of dietary fat with a fixed PUFA-to-saturated fatty acid ratio. Dietary fat was fed to the rats as 10% of the total feed weight, starting two weeks before the initiation. An increase in the n-3/n-6 ratio did not suppress the incidence or reduce the latency of mammary tumor development. The number and weight of mammary tumors per tumor-bearing rat tended to be large in the group with an n-3/n-6 ratio of 7.84 compared with those in the other groups. As the n-3/n-6 ratios were elevated, the total number and weight of tumors increased gradually. The prostaglandin E2 (PGE2) concentration in mammary tumor tissue was markedly low in the group with an n-3/n-6 ratio of 1.03 compared with the group with an n-3/n-6 ratio of 0.01. In addition, PGE2 concentrations were almost constant when n-3/n-6 ratios were > 1.03. These results suggested that the increase in the n-3/n-6 ratio of dietary fat with the fixed PUFA-to-saturated fatty acid ratio cannot suppress the mammary carcinogenesis but can promote development of tumors, despite reduced PGE2 concentration in the tumor.
Sasaki
T
T
Division of Bioregulation Studies, Tokyo University of Agriculture, Japan.
Kobayashi
Y
Y
Shimizu
J
J
Wada
M
M
In'nami
S
S
Kanke
Y
Y
Takita
T
T
D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D004041:Dietary Fats / Q000008:administration & dosage*; D015232:Dinoprostone / Q000032:analysis; D015525:Fatty Acids, Omega-3 / Q000008:administration & dosage*; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000008:administration & dosage*; D005260:Female; D008054:Lipid Peroxides / Q000032:analysis; D008099:Liver / Q000473:pathology; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced* / Q000737:chemistry / Q000473:pathology; D009929:Organ Size; D051381:Rats; D017207:Rats, Sprague-Dawley; D013154:Spleen / Q000473:pathology
D004041:Dietary Fats; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D008054:Lipid Peroxides; D015127:9,10-Dimethyl-1,2-benzanthracene; D015232:Dinoprostone