Effect of dietary vegetable (water convolvulus) on cholesterol metabolism in rats

Male rats were fed diets containing 0.5% cholesterol with or without vegetable (water convolvulus) or neutral detergent fiber supplementation. After 2 weeks, rats were given [4-14C]cholesterol i.p. Feces were collected for 1 week. Three hours prior to necropsy, [3H]acetate was administered i.p. Samples of serum, liver, adipose tissue, muscle and brain were obtained for analysis. Concentrations of total lipids and cholesterol and synthesis and recovery of labeled steroids are reported. Results showed that the growth of animals and food utilization were not significantly affected by different dietary treatments. The notable effect of vegetable was that the elevated liver and serum cholesterol levels due to increased intake can be nearly offset by increasing the fecal excretion. The high rate of excretion of 14C-labeled steroids shown in vegetable-fed rats indicated that both decreased absorption and increased endogenous excretion occurred in these animals. The synthesis of total lipids as demonstrated by [3H]acetate incorporation was not affected appreciably by diet. In liver, however, cholesterol synthesis appeared to be lower in rats receiving cholesterol-supplemented diet, but higher in rats fed vegetable diets. The ratio of 3H:14C of liver cholesterol was significantly higher in rats fed the vegetable diet. In brain cholesterol we also found consistently high 3H:14C ratios, which were not affected by dietary intake. It appears that brain cholesterol level is maintained mainly by synthesis in situ and not by uptake from dietary or other sources.