Polyunsaturated fat, cholesterol and large bowel tumorigenesis

Abstract

The possibility that the disposition of cholesterol, which is influenced by the quality of dietary fat, may be associated with either vascular lipidosis or colon cancer was evaluated in this study. Rats were fed diets containing cholesterol plus a) saturated fat, 20% coconut oil, to elevate serum cholesterol and promote vascular lipidosis or b) polyunsaturated fat, 20% safflower oil, to minimize serum cholesterol elevations and retard the development of vascular lipidosis. The relationships of these diets to gastrointestinal tract tumors induced by 1,2,-dimethylydrazine (DMH) was evaluated. Serum cholesterol levels in rats fed the coconut oil diet and given DMH were markedly elevated and were associated with moderate to severe vascular and aortic sudanophilia. Conversely, rats fed the safflower oil diet and given DMH had modest elevations in serum cholesterol levels and minimal vascular and aortic sudanophilia. Significantly, greater numbers of large bowel tumors induced by DMH were found in rats fed the safflower oil diet than in those fed the coconut oil diet. It was suggested that the polyunsaturated fat diet promoted the decrease in serum cholesterol levels concomitant with an increase in fecal neutral and acid sterols, which in turn augmented tumorigenesis by DMH in these animals compared with those fed the saturated fat diet. Thus, in the animal model used, the interaction of dietary fat (quality or quantity) with endogenous or dietary cholesterol determines whether or not diet will be a contributing factor in a) the development of vascular lipidosis or b) augmentation of small and large bowel tumorigenesis.