Dietary Taurine Decreases Hepatic Secretion of Cholesterol Ester in Rats Fed a High-Cholesterol Diet

Abstract

The effects of dietary taurine on lipid secretion and ketone body production were examined in the livers of Wistar and Sprague-Dawley rats fed high-cholesterol diets. The weight gain of the Sprague-Dawley rats tended to be higher than that of the Wistar rats, although food intake was comparable between the strains. The concentration of hepatic triglyceride was significantly higher but that of phospholipid was significantly lower in the Sprague-Dawley rats. Ketone body production by livers of Sprague-Dawley rats was significantly higher than that by the livers of Wistar rats. Dietary taurine repressed the weight gain of Wistar rats, perhaps due to decreased food intake, but it had no apparent effect on these growth parameters in Sprague-Dawley rats. There was a significant reduction in the hepatic concentration of cholesterol ester, but not other lipid components following feeding of taurine. Taurine feeding resulted in a stimulation of hepatic ketogenesis, whereas it markedly reduced the hepatic secretion of cholesterol ester in both strains of rats. The effect of dietary taurine on the hepatic secretion of triglyceride, phospholipid and free-cholesterol was marginal in either strain. These results suggest that taurine feeding significantly ameliorated the dietary cholesterol-dependent increase in hepatic accumulation and secretion of cholesterol ester, regardless of strain differences, and the decrease in the hepatic secretion of this cholesterol ester appeared to be partly responsible for the observed reduction in the concentration of serum cholesterol following feeding of taurine in these cholesterol-fed rats.

Dietary Taurine Reduces Hepatic Secretion of Cholesteryl Ester and Enhances Fatty Acid Oxidation in Rats Fed a High-Cholesterol Diet

“…Providing taurine as 5% of the diet for 14 d significantly decreased concentrations of cholesterol, especially cholesteryl esters in both serum and liver. Ketone body production and incorporation of exogenous [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]oleate into ketone bodies in liver perfusate were consistently higher during a 4-h perfusion period in taurine-fed rats than in control rats. The elevation was accompanied by increased activity of liver mitochondrial carnitine palmitoyltransferase, a rate-limiting enzyme for fatty acid oxidation.…”

“…Taurine (2-aminoethanesulfonic acid) was provided by Taisho Pharmaceutical (Saitama, Japan), while [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]oleic acid was purchased from Amersham Life Science (Buckinghamshire, England). Oleic acid and palmitoyl-CoA were obtained from Sigma Chemicals (St. Louis, MO).…”

“…The control group was fed a diet prepared as follows (by weight percent): casein, 20.0; lard, 9.0; soybean oil, Relative high amounts of carbohydrate in the form of sucrose or fructose stimulate lipogenesis and therefore have been shown to be associated with an increased circulating concentration of serum triglyceride; we supplemented the sucrose as a carbohydrate source to the diets ( 10 ). The taurine group was fed the same diet except for supplementation with 5% taurine at the expense of sucrose, as described previously ( 9 ). Two separate experiments were performed as described later.…”

“…Although these effects have attracted attention, the underlying mechanisms are not clearly understood. With regard to the hypocholesterolemic action of dietary taurine, we previously reported that in rats fed high-cholesterol diets, the lowering of serum cholesterol by taurine was partly attributable to a reduced secretion rate of cholesteryl ester by the liver, and that reductions in hepatic secretion rate and in hepatic accumulation of cholesteryl ester were inversely related to increased ketone body production, an index of fatty acid oxidation ( 9 ). This pattern of changes suggested that dietary taurine influences the metabolic fate of fatty acids, specifically whether they undergo esterification or oxidation.…”

“…We therefore undertook a more detailed examination of fatty acid metabolism using an exogenous [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]oleic acid, and found for the first time that the reduced hepatic synthesis and secretion of cholesteryl ester resulting from dietary taurine intake stimulates oxidation of exogenous fatty acid at the expense of esterification.…”