[Studies on stroke-prone spontaneously hypertensive rats (SHRSP) fed a high-fat and high-cholesterol diet--effect of taurine on serum lipoprotein metabolism in hypercholesterolemic rats].

It is well known that taurine, a final metabolite of sulfur-containing amino acids, plays an important role in bile acid metabolism and that it also has a moderately hypotensive effect. Moreover, it has recently been revealed that taurine shows a hypocholesterolemic effect in animals with experimentally induced hypercholesterolemia. However, the hypocholesterolemic mechanism remains unresolved. Stroke-prone spontaneously hypertensive rats (SHRSP) easily develop hypercholesterolemia when fed a high-fat and high-cholesterol diet (HFC diet). In our previous paper, we reported changes in the concentrations and distributions of serum lipoproteins and apolipoproteins in hypercholesterolemic SHRSP and Kyo: Wistar rats (WKY) induced by HFC feeding. In this paper, to elucidate the mechanism of the hypocholesterolemic effect of taurine, we investigated the effects of taurine on concentrations and distributions of serum lipoproteins and apolipoproteins in hypercholesterolemic SHRSP and WKY induced by HFC feeding. The results obtained were as follows: 1) The hypocholesterolemic effect of taurine in hypercholesterolemic SHRSP was remarkable in comparison with that in hypercholesterolemic WKY. 2) The hypocholesterolemic effect of taurine was mainly due to a marked suppression of extreme elevations of cholesterol contents in the VLDL and IDL fractions of both strains. This was associated with a decrease in the elevated contents of apo B and apo E which are major components of VLDL and IDL. This suppressive effect was more obvious in SHRSP than in WKY, which explains the greater hypocholesterolemic effect of taurine in SHRSP. It could be that, as a result of taurine administration, the catabolism of cholesterol to bile acid in the liver is accelerated, followed by a decrease of the hepatic cholesterol pool, resulting in a suppression of the synthesis and/or secretion of VLDL (beta-VLDL) in the liver. 3) The hypocholesterolemic effect of taurine was also observed in the LDL fractions of both strains, but the effect was not as strong as that observed in the VLDL and IDL fractions. This effect might be attributable to suppression of the synthesis and/or secretion of LDL in the liver and a decrease in the elevated content of apo E HDL (HDLc) which spans two density fractions (the LDL and HDL fractions). 4) In HDL fractions of both strains, the decreased content of apo E HDL (HDL1 and HDLc) was even lower, whereas the decreased apo A-I content in the HDL fraction of SHRSP was significantly restored and the cholesterol level was slightly elevated.(ABSTRACT TRUNCATED AT 400 WORDS)