The effect of diabetes mellitus on sterol synthesis in the intact rat.

Diabetes mellitus in both humans and animals is characterized by elevations in plasma cholesterol concentrations. The cause of this hypercholesterolemia is unknown. The present study employed tritiated water to quantity sterol synthesis in intact diabetic and control animals. Sterologenesis was 60-246% greater in the gut of diabetic animals than in controls. This enhancement of sterol synthesis occurred soon after the onset of diabetes and persisted for at least 3 wk. Moreover, insulin therapy markedly decreased gut sterol synthesis in diabetic animals to levels only slightly greater than in controls. Diabetes increased sterol synthesis primarily in the small intestine, but a small increase was also observed in the large intestine. Subfractionation of the small intestine into epithelial cell and muscularis cell layers revealed an increased sterologenesis in both layers. Quantitatively, though, the epithelial layer accounted for the majority of the enhancement of small intestine sterol synthesis observed in diabetic animals. De novo sterologenesis in tissues other than the intestines (liver, skin, stomach, or remaining carcass) was not significantly altered by diabetes. This study demonstrates that diabetes markedly stimulates sterol synthesis, an effect that is specifically localized to the intestines.