Dietary taurine enhances cholesterol degradation and reduces serum and liver cholesterol concentrations in rats fed a high-cholesterol diet

Summary.  The effect of taurine on hypercholesterolemia induced by feeding a high-cholesterol (HC) diet (10 g/kg) to rats was examined. When taurine was supplemented to HC for 2 wk, serum total cholesterol significantly decreased and serum HDL-cholesterol increased compared with the HC diet group. In the hypercholesterolemic rats fed the HC diet, the excretion of fecal bile acids and hepatic cholesterol 7α-hydroxylase (CYP7A1) activity and its mRNA level increased significantly, and the supplementation of taurine further enhanced these indexes, indicating an increase in cholesterol degradation. Agarose gel electrophoresis revealed that, in hypercholesterolemic rats fed the HC diet, the serum level of the heavier VLDL increased significantly, but taurine repressed this increase and normalized this pattern. Significant correlations were observed between the time-dependent increase of CYP7A1 gene expression and the decrease of blood cholesterol concentration in rats fed the HC diet supplemented with taurine. These results suggest that the hypocholesterolemic effects of taurine observed in the hypocholesterolemic rats fed the HC diet were mainly due to the enhancement of cholesterol degradation and the excretion of bile acid. Received December 4, 2001 Accepted January 2, 2002 Published online September 10, 2002 Acknowledgment This work was supported by a grant of Taisho Pharmaceutical Co., Ltd (Japan). We thank J. I. Gordon for their generous gifts of cDNAs. Authors' address: Dr. Hidehiko Yokogoshi, School of Food and Nutritional Sciences, The University of Shizuoka, Shizuoka 4228526, Japan, E-mail: yokogosi@u-shizuoka-ken.ac.jp     

Hypolipidemic action of taurine in rats.

The effect of taurine on the serum and liver cholesterol and triglyceride levels was studied in rats fed cholesterol plus cholic acid. Four groups of 4 weeks old rats were fed control diet, hypercholesterolemic diet (HCD), HCD + 1% taurine or HCD + 2% taurine for 8 weeks. Addition of taurine in HCD diet showed a significant reduction not only in serum total cholesterol and triglyceride levels but also in liver total cholesterol, lipid and triglyceride contents compared to the animals fed HCD alone. Histological examination of organs of these animals showed severe fatty vacuolation in livers and signet ring type vacuolation in kidneys of rats fed HCD. Taurine showed ameliorating effect on these abnormalities. The animals fed taurine in HCD also showed increased bile and sterol excretion in faeces compared to rats fed HCD alone. Taurine showed significant hypocholesterolemia in rats probably by enhancing the catabolism of cholesterol and reducing the absorption of dietary cholesterol.     

Comparative hypocholesterolemic effects of five animal oils in cholesterol-fed rats

The hypocholesterolemic efficacy of various animal oils was compared in rats given a cholesterol-enriched diet. After acclimatization for one week, male F344 DuCrj rats (8 weeks of age) that had been fed with a conventional diet were assigned to diets containing 5% of oil from emu (Dromaius), Japanese Sika deer (Cervus nippon yesoensis, Heude), sardine, beef tallow, or lard with 0.5% cholesterol for 6 weeks. After this feeding period, the concentrations of serum total cholesterol and of very-low-density lipoprotein + intermediate-density lipoprotein + low-density lipoprotein-cholesterol in the sardine oil group were significantly lower than those in the other groups. The serum high-density lipoprotein-cholesterol concentration in the Japanese Sika deer oil group was significantly higher than that in the other groups. The atherosclerotic index and liver cholesterol concentration in the sardine oil and Japanese Sika deer oil groups were significantly lower than those in the other groups. The fecal cholesterol excretion by the Japanese Sika deer oil group was significantly higher than that of the other groups, except for the sardine oil group, and the fecal bile acid excretion by the sardine oil group was significantly higher than that of the other groups, except for the lard group. These results suggest that Japanese Sika deer oil reduced the atherosclerotic index and liver cholesterol concentration in the presence of excess cholesterol in the diet as well as sardine oil did by increasing the excretion of cholesterol from the intestines of rats.     

Endogenous Androgen Deficiency Enhances Diet-Induced Hypercholesterolemia and Atherosclerosis in Low-Density Lipoprotein Receptor-Deficient Mice

BackgroundDespite numerous clinical and animal studies, the role of sex steroid hormones on lipoprotein metabolism and atherosclerosis remain controversial.ObjectiveWe sought to determine the effects of endogenous estrogen and testosterone on lipoprotein levels and atherosclerosis using mice fed a low-fat diet with no added cholesterol.MethodsMale and female low-density lipoprotein receptor-deficient mice were fed an open stock low-fat diet (10% of kcals from fat) for 2, 4, or 17 weeks. Ovariectomy, orchidectomy, or sham surgeries were performed to evaluate the effects of the presence or absence of endogenous hormones on lipid levels, lipoprotein distribution, and atherosclerosis development.ResultsFemale mice fed the study diet for 17 weeks had a marked increase in levels of total cholesterol, triglycerides, apolipoprotein-B containing lipoproteins, and atherosclerosis compared with male mice. Surprisingly, ovariectomy in female mice had no effect on any of these parameters. In contrast, castration of male mice markedly increased total cholesterol concentrations, triglycerides, apolipoprotein B-containing lipoproteins, and atherosclerotic lesion formation compared with male and female mice.ConclusionsThese data suggest that endogenous androgens protect against diet-induced increases in cholesterol concentrations, formation of proatherogenic lipoproteins, and atherosclerotic lesions formation. Conversely orchidectomy, which decreases androgen concentrations, promotes increases in cholesterol concentrations, proatherogenic lipoprotein formation, and atherosclerotic lesion formation in low-density lipoprotein receptor-deficient mice in response to a low-fat diet.     

Hypolipidemic effect of young persimmon fruit in C57BL/6.KOR-ApoEshl mice

We investigated the hypolipidemic effects of young persimmon fruit (YP) on apolipoprotein E-deficient C57BL/6.KOR-ApoEshl mice. These mice exhibited higher plasma cholesterols, except for high-density lipoprotein (HDL), and lower plasma HDL cholesterol than C57BL/6.Cr mice that had the same genetic background as the C57BL/6.KOR-ApoEshl mice. Male C57BL/6.KOR-ApoEshl mice (n=5) were fed a diet supplemented with dry YP, Hachiya-kaki, at a concentration of 5% (w/w) for 10 weeks. YP treatment significantly lowered plasma chylomicron, very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) cholesterols, and triglyceride, and this response was accompanied by an elevation of fecal bile acid excretion. In the liver, sterol regulatory element binding protein-2 gene expression was significantly higher in mice fed YP, while the mRNA and protein levels of the LDL receptor did not change. These results indicate that acceleration of fecal bile acid excretion is a major mechanism of the hypolipidemic effect induced by YP in C57BL/6.KOR-ApoEshl mice.     

Comparative regulation of major enzymes in the bile acid biosynthesis pathway by cholesterol, cholate and taurine in mice and rats

These enzymes play important roles in the biosynthesis of bile acids. They are cholesterol 7alpha-hydroxylase (CYP7A1), the rate limiting enzyme in the classic pathway, sterol 12alpha-hydroxylase (CYP8B1), the key enzyme for synthesis of cholic acid (CA), and sterol 27-hydroxylase (CYP27), the initial enzyme in the alternative pathway. In the present study, the susceptibility of these three enzymes to dietary cholesterol and cholate, and the cholesterol lowering effect of taurine were determined in male C57BL/6 mice and Wistar rats. Both mice and rats were divided into 6 groups: control group (N), high cholesterol diet group (C), high cholesterol and cholate diet group (CB), and their 1% taurine-supplemented groups (NT, CT, CBT, respectively). After animals were fed with the respective diets for one week, the mRNA levels of CYP7A1 increased in the C-group compared with those of the N-group, and decreased in the CB-group compared with those of the C-group in both mice and rats. But the extent of decrease is different between the two species. CYP8B1 was also markedly repressed by cholate in mice, but not in rats. These results are consistent with the changes in serum and liver cholesterol concentrations. Taurine significantly increased CYP7A1 mRNA levels in the CBT-group compared with the CB-group in both animal models, with a subsequent decrease in serum and liver cholesterol levels and increase in fecal bile acid excretion. Up-regulated CYP8B1 was also observed after taurine supplementation in the CBT-group in mice. No increase in CYP7A1 was produced by taurine in the CT-group compared with that of the C-group in mice, although the changes of serum and liver cholesterol and fecal bile acids indicated taurine showed an efficient cholesterol lowering effect. In addition, CYP27 was induced in both C- and CB-groups of rats but not of mice, and no changes were produced by taurine. The overall results suggest that there are differences between mice and rats in susceptibility of the three enzymes to dietary cholesterol and cholate, and taurine induced CYP7A1 to produce its cholesterol-lowering effect only in the presence of cholate in the cholesterol diet.     

Dietary oxidized cholesterol decreases expression of hepatic microsomal triglyceride transfer protein in rats

The aim of this study was to compare the effects of dietary oxidized cholesterol and pure cholesterol on plasma and very low density lipoprotein (VLDL) lipids and on some parameters of VLDL assembly and secretion in rats fed two different dietary fats. Four groups of male growing Sprague-Dawley rats were fed diets containing pure or oxidized cholesterol (5 g/kg diet) with either coconut oil or salmon oil as dietary fat (100 g/kg diet) for 35 days. Rats fed oxidized cholesterol supplemented diets had significantly lower concentrations of triglycerides and cholesterol in plasma and VLDL than rats fed pure cholesterol supplemented diets irrespective of the type of fat. In addition, rats fed oxidized cholesterol supplemented diets had significantly lower relative concentrations of microsomal triglyceride transfer protein messenger ribonucleic acid (mRNA) than rats fed pure cholesterol supplemented diets. In contrast, hepatic lipid concentrations and the relative concentration of apolipoprotein B mRNA were not influenced by the dietary factors investigated. Parameters of hepatic lipogenesis (relative mRNA concentration of sterol regulatory element binding protein-1c and activity of glucose-6-phosphat dehydrogenase) were significantly reduced by feeding fish oil compared to coconut oil, but were not affected by the type of cholesterol. In conclusion, the data of this study suggest, that dietary oxidized cholesterol affects VLDL assembly and/or secretion by reducing the synthesis of MTP but not by impairing hepatic lipogenesis or synthesis of apolipoprotein B.     

Dietary taurine potentiates polychlorinated biphenyl-induced hypercholesterolemia in rats*

The effect of dietary taurine on cholesterol metabolism and the distribution of lipoprotein-cholesterol in serum of rats fed a diet containing polychlorinated biphenyls (PCB) was examined. Young male Wistar rats (60 g) were fed diets containing 0.2 g/kg diet of PCB and/or 30 g/kg diet of taurine for 15 days. The experiment was performed as the 2 (PCB) x 2 (taurine) factorial design. The addition of PCB elevated serum levels of total- and HDL-cholesterol and apolipoprotein A-I, which is a major apolipoprotein of HDL. Simultaneous supplementation of taurine with PCB amplified the increase of the serum level of total- and HDL-cholesterol. Hepatic concentrations of cholesterol and total lipids were significantly elevated by the supplementation of PCB, and taurine significantly amplified these increases caused by PCB. PCB suppressed hepatic cholesterol 7alpha-hydroxylase (CYP7A1) gene expression, and taurine induced CYP7A1 gene expression. Taurine also enhanced PCB-induced elevation of malic enzyme mRNA in the liver. These results suggest that taurine enhanced PCB-induced hyper-alpha-cholesterolemia and that taurine has a role in increasing HDL-cholesterol.     

Effects of Dietary Nasunin on the Serum Cholesterol Level in Rats

The effects of nasunin, a major anthocyanin in eggplant, and its aglycone, delphinidin, on the serum cholesterol conpentration were determined in rats fed with a cholesterol-enriched diet. The serum total cholesterol and HDL-cholesterol concentrations tended to be decreased and increased, respectively, by feeding nasunin and delphinidin, while the fecal excretion of both cholesterol and bile acids tended to be increased by feeding with the anthocyanins. There was no difference between the nasunin and delphinidin activity to decrease serum total cholesterol, nor to increase serum HDL-cholesterol or the fecal excretion of cholesterol and bile acids. These results suggest that the slightly lower serum total cholesterol concentration in rats fed with nasunin and delphinidin may in part be due to inhibition of the intestinal absorption of both cholesterol and bile acids by these anthocyanins, and that the delphinidin moiety of nasunin mainly contributes to this activity.     

Lipoprotein metabolism in the ovariectomized rat

The hyperlipoproteinemia observed after ovariectomy in rats was previously shown to be associated with increased concentrations of cholesterol, triglycerides, and apolipoproteins B, E, and C. In the present study, it was shown that increases in low density lipoproteins and high density lipoproteins were almost entirely responsible for the changes in plasma lipids and apolipoproteins after ovariectomy. The size of the low density lipoproteins and high density lipoproteins isolated from the plasma of ovariectomized rats as determined by agarose chromatography appeared to be somewhat different from that of control rats. Specifically, the apolipoprotein B appeared to be associated with somewhat smaller particles, whereas the apolipoprotein E from those rats appeared to be associated with larger particles than that of control rats. To determine the mechanism for the increased plasma low density lipoproteins, apolipoprotein B pool sizes and turnover rates were calculated and compared. In addition to an increased mass of low density lipoproteins in ovariectomized rats, the turnover rate of low density lipoproteins was increased almost twofold, indicating an increased low density lipoprotein synthesis and catabolism in those animals. We postulate that the increased low density lipoprotein levels of ovariectomized rats are due to an initial increased production of low density lipoproteins, followed by an enhanced catabolism of low density lipoproteins to establish a steady state at higher plasma low density lipoprotein concentrations.     

Antiatherogenic effect of taurine in high fat diet fed rats

The role of taurine on atherogenesis induced by high fat diet in rats, a species which depends entirely on taurine for conjugation of bile acids has been investigated. Wistar male rats were fed on (p.o.) taurine in addition to high fat diet (11% coconut oil w/w) for 6 months. High fat diet caused significant increase of serum total cholesterol (2 fold), serum triglycerides (92.6%), LDL cholesterol (92.3%) and body weight gain (2.8 fold). Taurine administration significantly reduced serum cholesterol (37%), triglycerides (94.5%), LDL cholesterol (34%), body weight (46%). It also significantly reduced aortic cholesterol and thiobarbituric acid reactive substances and there was a significant increase of reduced glutathione. Taurine significantly increased fecal bile acids which may have resulted in significant decrease of serum cholesterol. Aortic lesion index was significantly decreased in the taurine administered group suggesting the antiatherogenic effect of taurine. It is concluded that taurine attenuated the atherogenesis possibly by its hypocholesterolemic and antioxidant property.     

Dietary cholesterol does not affect the synthesis of apolipoproteins B and E by rat hepatocytes.

To examine the unproved hypothesis that dietary cholesterol affects the synthesis of apolipoprotein B and E, we fed rats a cholesterol-rich diet that has been shown to alter dramatically the serum concentrations of these apolipoproteins. Rats fed for 4 weeks on a cholesterol-rich diet accumulate increased concentrations of low Mr apolipoprotein B (+2.7-fold) and decreased concentrations of apolipoprotein E (-40%) in their serum. Hepatocytes obtained from similarly treated rats were placed in monolayer culture and the rate of synthesis de novo of apolipoproteins was determined. Although cells from cholesterol-fed rats remained filled with lipid droplets throughout the experimental period, there was no difference in plating efficiency or viability, compared with cells obtained from chow-fed control rats. Both groups of cells synthesized and secreted immunoprecipitable apolipoproteins B and E at similar rates throughout the 18 h experiment. Thus there was a discordance between the effects of dietary cholesterol on serum apolipoprotein concentrations and hepatocyte synthesis and secretion. The data indicate that altered hepatic apolipoprotein synthesis cannot account for the changes in serum apolipoprotein concentrations caused by dietary cholesterol.     

The effect of high-amylose cornstarch on lipid metabolism in OVX rats is affected by fructose feeding

We examined whether the effects of high-amylose cornstarch (HACS) on lipid metabolism in ovariectomized (OVX) rats were affected by high-fructose feeding. Sucrose (482 g/kg diet) was used as fructose source. OVX rats were fed one of the following four diets for 21 days: a sucrose-based or cornstarch-based cholesterol-free diet with or without HACS (150 g/kg diet). Body weight and food intake were increased by sucrose. Plasma total cholesterol and low-density lipoprotein cholesterol concentrations were increased by sucrose and decreased by HACS in cornstarch-fed rats, but not in sucrose-fed rats. Liver total lipids and concentrations of plasma and liver triacylglycerol (TAG) were increased by sucrose, whereas plasma TAG concentration was decreased by HACS, in sucrose-fed rats. However, liver cholesterol concentration was not affected by diet. The amount of cholesterol in small-intestinal contents was increased in sucrose-fed rats, but not in cornstarch-fed rats, but that of bile acids was not affected by diet. Fecal excretions of bile acids and neutral sterols were increased by HACS. The level of sterol-regulatory element-binding protein-1c mRNA was increased by sucrose and decreased by HACS in sucrose-fed rats, but not in cornstarch-fed rats. The level of farnesoid X receptor mRNA was decreased by sucrose and increased by HACS in cornstarch-fed rats, but not in sucrose-fed rats, as was the level of cholesterol 7α-hydroxylase mRNA. These results show that the effect of HACS on hyperlipidemia induced by ovarian hormone deficiency would be affected by the consumption of fructose-rich sweeteners such as sucrose and high-fructose syrup.     

Feeding unsaponifiable compounds from rice bran oil does not alter hepatic mRNA abundance for cholesterol metabolism-related proteins in hypercholesterolemic rats

The hypocholesterolemic effect of rice bran oil (RBO) is defined in human and animal experiments which indicate the presence of active component(s) in the unsaponifiable fraction, but the detailed mechanism is not known yet. Exogenously hypercholesterolemic (ExHC) rats were fed for 2 weeks on a 0.5% cholesterol diet supplemented with 10% each of RBO, RBO-simulated oil (RBOSO) in its fatty acid composition, or RBOSO plus 0.25% unsaponifiable compounds (UC) from RBO. Rats fed RBO or the UC resulted in lowing serum and liver cholesterol concentration and preventing reduction of high density lipoproteinic-cholesterol. Dietary RBO or the UC led to an elevation of fecal neutral sterol excretion, but no significant change in fecal bile acid excretion or in hepatic abundance of mRNAs for 3-hydroxy-3-methylglutaryl-CoA reductase, cholesterol-7alpha-hydroxylase, and low density lipoprotein receptor. Besides, serum and liver alpha-tocopherol concentrations were lowered in RBO or the UC-fed rats. These results show that the UC in RBO leads to a decreased serum cholesterol concentration by interrupting the absorption of intestinal hydrophobic compounds rather than by modifying cholesterol metabolism in the liver.     

Effect of bean intake on biliary lipid secretion and on hepatic cholesterol metabolism in the rat

We studied the effect of a bean diet on biliary lipid secretion, serum cholesterol concentration, and hepatic cholesterol metabolism in the rat. Rats fed a bean diet for 10-12 days had increased biliary cholesterol output and molar percentage by 300% and 200%, respectively, compared to rats fed an isocaloric and isoprotein casein diet. Biliary phospholipid output increased 180%. Bile flow and biliary bile salt output remained in the normal range. Total serum and VLDL cholesterol concentration significantly decreased 27% and 50%, respectively, in the rats fed the bean diet. Hepatic cholesterogenesis was increased 170% in the bean-fed animals. The relative contribution of newly synthesized hepatic cholesterol to total biliary cholesterol increased 200%, and that of endogenous origin only 50%. These results suggested that newly synthesized hepatic cholesterol was preferentially channelled to the biliary cholesterol secretory pathway in bean-fed rats. Although hepatic cholesteryl ester concentration increased 240%, the incorporation of [14C]oleate into hepatic cholesteryl esters was significantly decreased by 30% in isolated hepatocytes of bean-fed animals. These results were consistent with the possibility that the availability of hepatic free cholesterol for biliary secretion was increased in the bean-fed animals. This study demonstrates that bean intake has a profound effect on the metabolic channelling and compartmentalization of hepatic cholesterol, resulting in a significant decrease in total serum and very low density lipoprotein cholesterol concentrations and a high biliary cholesterol output.     

Ingestion of raffinose promotes calcium absorption in the large intestine of rats

We examined the effects of feeding raffinose on intestinal calcium absorption in ovariectomized rats by two separate experiments. In experiment 1, female Sprague-Dawley rats (6 wk old) were divided into two groups: sham operation and ovariectomy, and fed diets with or without raffinose (30 g/kg diet) for 4 wk. In experiment 2, ovariectomized rats with cecocolonectomy or transsection and reanastomosis (sham) were divided into two groups as in experiment 1 and fed the same diets for 3 wk. In experiment 1, calcium absorption was lower in the ovariectomized rats than in the sham rats but calcium absorption in rats fed the raffinose diet was higher than that in rats fed the raffinose-free diet. In experiment 2, increased calcium absorption in the raffinose group was abolished by cecocolonectomy. The impaired absorption in ovariectomized rats was restored by feeding raffinose. The large intestine is involved in the beneficial effects of raffinose.     

Effect of diosgenin on lipid metabolism in rats.

The purpose of this study was to determine whether diosgenin suppresses cholesterol absorption in rats, and to examine relevant changes in cholesterol and bile acid metabolism. Diosgenin fed with the diet for 1 week inhibited cholesterol absorption as determined by the serum isotope ratio technique, as well as by measuring in the feces the amount of unabsorbed radioactivity from orally administered [3H]cholesterol. In addition, diosgenin suppressed the serum and liver uptake of radioactivity from co-administered [3H]cholesterol as well as the accumulation of liver cholesterol in the cholesterol-fed rat; diosgenin was substantially more active than cholestyramine or beta-sitosterol. In vitro, diosgenin had no effect on the activity of rat pancreatic esterase. Diosgenin decreased the elevated cholesterol in serum LDL and elevated cholesterol in the HDL fraction of cholesterol-fed rats; diosgenin had no effect on serum cholesterol in normocholesterolemic rats. In contrast to cholestyramine, diosgenin markedly increased neutral sterol excretion without altering bile acid excretion; in vitro, diosgenin had no effect on bile acid binding. Diosgenin treatment increased hepatic and intestinal cholesterol synthesis as well as the activity of hepatic HMG CoA reductase. This was accompanied by increased biliary concentration of cholesterol, but not of bile acids. Diosgenin had no effect on cholesterol synthesis when added to normal rat liver homogenates. It was concluded that diosgenin interferes with the absorption of cholesterol of both exogenous and endogenous origin; such interference is accompanied by derepressed, i.e., increased, rates of hepatic and intestinal cholesterol synthesis. The increased unabsorbed cholesterol together with enhanced secretion of cholesterol into bile resulted in increased excretion of neutral sterols without affecting the biliary and fecal excretion of bile acids.     

Purification and Immunological Properties of NAD+-linked Malate Dehydrogenase Isozymes from Euglena gracilis

We investigated the hypolipidemic effects of young persimmon fruit (YP) on apolipoprotein E-deficient C57BL/6.KOR-ApoE^shl mice. These mice exhibited higher plasma cholesterols, except for high-density lipoprotein (HDL), and lower plasma HDL cholesterol than C57BL/6.Cr mice that had the same genetic background as the C57BL/6.KOR-ApoE^shl mice. Male C57BL/6.KOR-ApoE^shl mice (n=5) were fed a diet supplemented with dry YP, Hachiya-kaki, at a concentration of 5% (w/w) for 10 weeks. YP treatment significantly lowered plasma chylomicron, very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) cholesterols, and triglyceride, and this response was accompanied by an elevation of fecal bile acid excretion. In the liver, sterol regulatory element binding protein-2 gene expression was significantly higher in mice fed YP, while the mRNA and protein levels of the LDL receptor did not change. These results indicate that acceleration of fecal bile acid excretion is a major mechanism of the hypolipidemic effect induced by YP in C57BL/6.KOR-ApoE^shl mice.     

Cholesterol-lowering effects of maitake (Grifola frondosa) fiber, shiitake (Lentinus edodes) fiber, and enokitake (Flammulina velutipes) fiber in rats

The effects of mushroom fibers on serum cholesterol and hepatic low-density lipoprotein (LDL) receptor mRNA in rats were investigated. Rats were fed a cholesterol-free diet with 50 g/kg cellulose powder (CP), 50 g/kg maitake (Grifola frondosa) fiber (MAF), 50 g/kg shiitake (Lentinus edodes) fiber (SF), or 50 g/kg enokitake (Flammulina velutipes) fiber (EF) for 4 weeks. There were no significant differences in the body weight, food intake, liver weight, cecum weight, and cecum pH among the groups. Cecal acetic acid, butyric acid, and total short-chain fatty acid (SCFA) concentrations in the SF and EF groups were significantly higher than those in the other groups. The serum total cholesterol concentration in the CP group was significantly higher than that in the MAF and EF groups. The very LDL (VLDL) + intermediate-density lipoprotein (IDL) + LDL-cholesterol concentration in the CP group was significantly higher than that in the MAF, SF, and EF groups, whereas the high-density lipoprotein (HDL)-cholesterol concentration in the EF group was significantly lower than that in the other groups at the end of the 4-week feeding period. The hepatic LDL receptor mRNA level in the EF group was significantly higher than that in the CP group. The fecal cholesterol excretion in the MAF, SF, and EF groups was significantly higher than that in the CP group. The results of this study demonstrate that MAF and EF lowered the serum total cholesterol level by enhancement of fecal cholesterol excretion, and in particular, by enhancement of hepatic LDL receptor mRNA in EF group.     

Improving Effect of Dietary Taurine on Marked Hypercholesterolemia Induced by a High-cholesterol Diet in Streptozotocin-induced Diabetic Rats

The effect of dietary taurine on hypercholesterolemia induced by a high-cholesterol diet in streptozotocin (STZ)-induced diabetic rats was investigated. The concentrations of serum and liver cholesterol were markedly elevated in STZ-diabetic rats fed on the cholesterol-containing diet, and dietary taurine significantly reduced this elevated level of cholesterol in the serum and liver. The gene expression of cholesterol 7α-hydroxylase (CYP7A1), which is the rate-limiting enzyme for cholesterol degradation, was induced by the supplementation of taurine to the high-cholesterol diet. It is suggested that one of the reasons for this hypocholesterolemic action by taurine might have been the enhancement of cholesterol degradation.