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Interrelated Effects of Food Lipids on Steroid Metabolism in Rats^1,2,

Department of Biochemistry and Biophysics, Texas Agricultural Experiment Station, Texas A&M University System, College Station, Texas 77843

Semipurified diets containing either: 1) 15% sterol-free lard; 2) 15% sterol-free safflower oil; 3) and 4) diets 1 and 2 with 0.5% cholesterol; 5) and 6) diets 3 and 4 with 0.25% mixed soybean sterols; and 7) and 8) diets 3 and 4 with 0.5% soybean sterols, were fed to female BHE rats for 10 weeks. Males were fed all diets except 6 and 8. The diet fats alone were found to have no significant effect on the serum cholesterol, but serum triglycerides were significantly lower when the safflower oil was fed to females. Diet fats had little effect on liver cholesterol, but ingestion of lard resulted in higher liver triglycerides in the female than when safflower oil was consumed. In the female, the addition of cholesterol to the sterol-free lard diet increased serum cholesterol from about 90 mg/100 ml to about 500 mg/100 ml. Its addition to the sterol-free safflower oil diet increased serum cholesterol in females to about 350 mg/100 ml. In the male, cholesterol in the lard diet increased serum cholesterol from about 120 mg/100 ml to almost 200 mg/100 ml, whereas cholesterol added to the safflower oil diet resulted in 139 mg cholesterol/100 ml serum. Liver cholesterol increased more than 15-fold when either sex was fed cholesterol with either fat. Liver triglycerides were little affected by diet cholesterol in the female, but were increased fivefold in the male. Addition of 0.5% plant sterols to the cholesterol-containing diets mitigated the effect of diet cholesterol on serum cholesterol. The plant sterols on the other hand, increased serum triglycerides, especially in the males, but had virtually no effect on liver triglycerides. When cholesterol was added to the fat diets, cholesterol 7-hydroxylase increased, the response being greater in the female. The addition of plant sterols attenuated the effect of cholesterol on the enzyme. Diet cholesterol caused a large increase in fecal neutrol sterols and bile acids, while plant sterols stimulated excretion of neutral sterols and reduced the level of fecal bile acids. The total and component bile acid quantities and distribution were dependent upon both diet fat and sex.

KEY WORDS: • lard • safflower oil • cholesterol • plant sterols • fecal steroids • tissue triglycerides • cholesterol 7-hydroxylase

¹ Supported in part by grants from the National Institutes of Health (AM 06011), The National Dairy Council, The National Live Stock and Meat Board, The Robert A. Welch Foundation, and the Texas A&M University Research Council.

² Presented in part at the meeting of the American Oil Chemists' Society, April 1975.

³ Present address: Division of Research, Lankenau Hospital, Philadelphia, Pa.

⁴ Present address: Department of Pathology, Bowman-Gray School of Medicine, Winston-Salem, N.C. 27103.

Manuscript received 8 November 1976.