Beef tallow increases apoptosis and decreases aberrant crypt foci formation relative to soybean oil in rat colon

Although epidemiological studies have implicated red meat as increasing colon cancer risk, animal studies have generally not been supportive of such an effect. This study examined red meat components, such as beef protein and tallow, on markers of colon cancer risk. Rats administered dimethylhydrazine were fed either casein or beef protein as the protein source and soybean oil or tallow as the fat source in a 2 2 factorial design for 9 wk. There were fewer preneoplastic lesions [aberrant crypt foci (ACF)] and a greater apoptotic labeling index (P < 0.05) in the distal colonic mucosa of rats fed tallow compared with soybean oil. Fecal bile acid concentrations were significantly lower in rats fed tallow compared with soybean oil. There were no significant differences in mucosal cell proliferation. No significant effects were found due to protein source or to interactions between fat and protein sources for ACF, cell proliferation labeling indexes, or bile acid concentrations. However, there was a significant protein by fat source interaction for the apoptotic labeling index. The decreased number of ACF, decreased fecal bile acid concentration, and increased mucosal apoptosis with tallow consumption are not consistent with a role for this fat in increasing risk of colon cancer.     

Dietary animal proteins and cholesterol metabolism in rats

The effects on cholesterol metabolism in rats of diets containing various animal proteins or soy protein were studied. The animal proteins tested were casein, whey protein, fish protein, hemoglobin, plasma proteins, ovalbumin, egg-yolk protein, beef protein and chicken-meat protein. The semi-purified diets were isonitrogenous and balanced for residual fat and cholesterol in the protein preparations. The nature of the dietary protein had no effect on serum cholesterol concentration. Group mean liver cholesterol concentration was increased and fecal excretion of bile acids was decreased by all animal proteins when compared with soy protein. This study suggests that carefully balancing diets for components other than protein in the protein preparations prevents protein effects on serum cholesterol in rats but not on liver cholesterol and bile acid excretion.     

Antitumorigenic effects of several food proteins in a rat model with colon cancer and their reverse correlation with plasma bile acid concentration

In order to obtain information on the preventive effects of various food proteins against colonic cancer, six groups of azoxymethane-initiated mature Fischer rats (n = 10) were fed respective diets different in protein sources such as bovine milk casein (casein), high-molecular-weight fraction from protolytic digest of soy protein isolate (soybean HMF), hen's yolk defatted protein (yolk protein), wheat gluten and codfish meat, which had been supplemented with sodium deoxycholate (hereinafter, DCA) as a cancer promoter except for an additional DCA-unfed casein group. All of the living rats at checkpoints during the feeding period were examined by the use of a bronchus fiberscope for colonic tumor incidence at 6 wk intervals between the 10th and 34th wk, from which both blood and feces samples were taken at times of endoscopy. Tumorigenesis in the colon was perceived by endoscopy at wk 22 in the group fed DCA casein only and at wk 28 in the other groups except the DCA-unfed casein group. At wk 34, both soybean HMF and yolk protein groups ranked inferior to the DCA-unfed group in tumor incidence. When plasma steroid or lipid concentration was plotted against tumor incidence at wk 28 or 34, positive correlations were found between plasma bile acid concentration and tumor incidence at both weeks. With the exception of the DCA-unfed casein group, plasma bile acid concentration was reversely correlated to fecal bile acid excretion. Taken altogether, these results suggest that bile acids at higher concentrations in the plasma may serve as risk factors of colon tumor incidence.     

大豆蛋白对人体血浆胆固醇的影响及机制探讨

目的观察大豆蛋白对正常人体血浆胆固醇浓度的影响并探讨其作用机制。方法选择健康大学生30名，男女各半，按血浆总胆固醇浓度、体重和性别均衡的原则，分为3组，在统一食谱、集中就餐的基础上，每天分别另外摄入30g酪蛋白，30g大豆分离蛋白，30g酪蛋白加880mg钙，共14d。实验开始和结束时．测量身高和体重：采血，测定血浆总胆固醇浓度。实验结束前，收集3d粪便，测定粪脂肪、钙、磷、镁和胆汁酸的排出量。结果(1)同实验开始时比，酪蛋白组血浆胆固醇浓度显著升高，而大豆蛋白组和酪蛋白加钙组血浆胆固醇浓度升高不明显。(2)同酪蛋白组比，大豆蛋白组粪钙、磷和镁的排出量均显著增加；粪脂肪和胆汁酸排出量分别增加33．6％和45．3％。(3)粪胆汁酸排出量与粪钙、磷、镁和脂肪的排出量呈显著性正相关。血浆胆固醇浓度随粪胆汁酸排出量增加呈下降的趋势。结论大豆蛋白降低血浆胆固醇浓度的机制可能是由于增加粪胆汁酸的排出量而导致肝脏中由胆固醇合成胆汁酸的增加，从而使血浆胆固醇浓度下降。     

Soybean saponins inhibit cell proliferation by suppressing PKC activation and induce differentiation of HT-29 human colon adenocarcinoma cells

Soybeans are major dietary sources of saponins, which have been suggested as possible anticarcinogens. This study was performed to determine the effect of soybean saponins on cell proliferation, differentiation, and apoptosis in human colon cancer cells. HT-29 cells were incubated in various concentrations of saponins for 24, 48, and 72 hours. Cell growth and whole cell protein kinase C (PKC) activity were determined. Alkaline phosphatase activity and carcinoembryonic antigen level were measured as markers for cell differentiation. Apoptotic cells were quantified. Study results indicated that soybean saponin treatment decreased cell growth in a concentration-dependent manner, and pre-treatment of the cells with saponins significantly suppressed the 12-O-tetradecanoyl phorbol 13-acetate-stimulated PKC activity. Cells treated with 300 and 600 ppm of saponins significantly increased alkaline phosphatase activity by 146% and 242% of the control, respectively. Also, 4-10 times more carcinoembryonic antigen was produced in cells treated with saponins. However, at all the concentrations used, saponins did not induce apoptosis, although there were slight decreases in apoptotic activity in cells treated with 240 and 600 ppm of soybean saponins. These results suggest that crude soybean saponin extract effectively suppresses PKC activation and induces differentiation, which possibly mediate the growth inhibition of tumor cells. Further experiments, including preclinical efficacy studies, are required to fully evaluate soybean saponins for their chemopreventive properties.     

Fiber, stool bulk, and bile acid output: implications for colon cancer risk

Dietary fiber has direct effects on stool bulk and bile acid output that may be of relevance in the etiology of colon cancer. Most types of fiber increase the total volume of stool and reduce the concentration of specific substances, including bile acids, that are in contact with the bowel wall. However, fibers differ in their effect on stool bulk, with wheat fiber being a more effective stool bulking agent than fruit and vegetable fibers. In addition, the extent to which a specific fiber reduces bile acid concentration will be modified by its concomitant effects on total fecal sterol excretion. Whereas wheat bran reduces fecal bile acid concentration, pectin, lignin, and oat bran do not. These three fibers significantly increase total bile acid output. Bile acids act as promoters of colonic tumors in mutagenesis assay systems and in various animal models. Human epidemiological studies show a relationship between various dietary variables, including fat and fiber intake, fecal concentration of bile acids, and colon cancer risk.     

Bile acid metabolism in rats fed two levels of corn oil and brans of oat, rye and barley and sugar beet fiber.

High concentrations of fecal bile acids are associated with a higher incidence of colon cancer. Dietary changes that alter bile acid metabolism are therefore of interest. Here, we report the effect of feeding diets containing four fiber sources and two fat levels for 7 wk on bile acid excretion and small intestinal bile acids (an index of pool size) in rats. The fiber sources were oat bran, rye bran, barley bran and sugar beet fiber. Fiber-containing diets were 8% dietary fiber and contained either 5 or 20% corn oil. All fiber sources caused significantly greater fecal output compared with the fiber-free basal diet. All fiber sources also resulted in significantly (P less than 0.05) lower fecal bile acid concentration compared with the fiber-free basal diet. Only rye bran resulted in significantly (P less than 0.05) higher total fecal bile acid excretion. Oat bran resulted in a slightly but significantly (P less than 0.05) higher quantity of small intestine bile acids compared with the other diets. Dietary fat level had no significant effect on fecal bile acid concentration or excretion or quantity of small intestinal bile acids. We conclude that all four fiber sources tested resulted in lower fecal bile acid concentration, by effectively causing greater fecal mass. Changes in dietary fat level as corn oil had no effect on fecal bile acids.     

Soy protein enhances the cholesterol-lowering effect of plant sterol esters in cholesterol-fed hamsters

This study aimed to investigate whether the combination of plant sterol esters (PSE) with soy protein or soy isoflavones may have extra cholesterol-lowering effects. Male hamsters (n=20/group) were fed diets containing (g/100 g diet) (A) 20 casein (control), (B) 0.24 PSE, (C) 20 intact soy protein (replacing casein), (D) 0.02 soy isoflavones, (E) 0.24 PSE plus 20 soy protein (replacing casein), or (F) 0.24 PSE plus 0.02 soy isoflavones, for 5 wk. All diets contained 0.08 g cholesterol/100 g diet. Compared with the control diet, the PSE and soy protein diets significantly lowered the plasma total cholesterol concentration by 13% (P<0.05) and 9% (P<0.05), respectively, whereas the isoflavone diet (D) had no effect. The combination of PSE and soy protein (diet E) decreased plasma total cholesterol by 26% (P<0.05). The decrease in plasma cholesterol concentration was mainly in the non-HDL fraction. In addition, the combination of PSE and soy protein significantly decreased plasma triacylglycerol concentration (37%, P<0.05) and reduced cholesterol accumulation in the liver. The abundance of hepatic LDL-receptors was not influenced by any of the test diets. PSE selectively increased fecal excretion of neutral sterols by 190% (P<0.05), whereas soy protein increased fecal excretion of neutral sterols and bile acids by 66% (P<0.05) and 130% (P<0.05), respectively. The combination of PSE and soy protein increased the fecal excretion of neutral sterols and bile acids compared with PSE and soy protein alone. In conclusion, the combination of PSE and soy protein more dramatically lowers plasma lipids than the individual ingredients.     

Consumption of soy protein reduces cholesterol absorption compared to casein protein alone or supplemented with an isoflavone extract or conjugated equine estrogen in ovariectomized cynomolgus monkeys

Dietary intake of soy protein is associated with reductions in plasma cholesterol. Isoflavones are thought to be active components of soy and responsible for the beneficial effects because of their structural similarities to estrogen. The purposes of this study were to determine if i) soy protein or a semipurified soy extract, rich in isoflavones, is responsible for improving the lipid profile and ii) altered intestinal cholesterol metabolism is one mechanism for hypocholesterolemic effects. Ovariectomized adult female cynomolgus monkeys (40) were assigned to groups fed diets containing i) casein-lactalbumin (CAS) ii) intact soy protein (SOY), iii) CAS plus an isoflavone-rich semipurified soy extract similar in isoflavone content as SOY (ISO) or iv) CAS plus conjugated equine estrogen (CEE) for 20 wk. Cholesterol absorption was determined using the fecal isotope ratio method. Bile acid excretion was measured using the 3alpha-hydroxysteroid dehydrogenase assay. The SOY group had significantly lower total- and VLDL + LDL-cholesterol compared to the other three groups and significantly higher HDL-cholesterol compared to the CAS and CEE groups. Cholesterol absorption was significantly lower in the SOY group compared to the other groups, but bile acid excretion was not significantly affected. The hypocholesterolemic effect of soy protein appears to be mediated in part by decreased cholesterol absorption. The semipurified soy extract, rich in isoflavones, added to casein protein did not have lipid-lowering effects. Other components of soy such as saponins, phytic acid or the amino acid composition may be involved in the hypocholesterolemic effects seen in this study.     

A buckwheat protein product suppresses gallstone formation and plasma cholesterol more strongly than soy protein isolate in hamsters

This study was conducted to investigate the effects of a buckwheat protein product (BWP) on plasma cholesterol, gallbladder bile composition and fecal steroid excretion in hamsters fed diets with 5 g/kg cholesterol. Diets also contained 200 g/kg of casein, soy protein isolate (SPI) or BWP as protein sources. After 2 wk, plasma and liver concentrations of cholesterol in the hamsters fed BWP were significantly lower than those in the hamsters fed casein and SPI. The molar proportion of cholesterol in gallbladder bile was significantly lower in the BWP group than in the other groups, whereas that of bile acids was slightly higher in the BWP group (P 相似文献   

Effects of corn oil and wheat brans on bile acid metabolism in rats

High concentrations of colonic bile acids may promote tumor formation. Some studies have found that high levels of dietary fat increase fecal bile acid excretion, whereas others report no effect. Wheat bran appears to reduce fecal bile acid concentration. This study was conducted to determine the effect of different dietary fat levels and types of wheat bran on bile acid metabolism. Rats were fed diets containing either no fiber, 2% cholestyramine (CHO) or brans of hard red spring, soft white winter or durum wheat--at both a 5 or 20% fat level. Animals were fed for 7 wk, and feces were collected in the last week. Wheat bran (all types) significantly increased fecal mass approximately fourfold, and CHO significantly increased fecal mass twofold compared to the fiber-free diet. Increasing the fat level did not increase fecal bile acid excretion, nor did the addition of wheat bran. Addition of CHO, however, more than doubled it. CHO increased fecal bile acid concentration, all wheat brans decreased it and fat level had no effect. Bile acid pool size was increased slightly by fat level and cholestyramine feeding but not by wheat brans. These results indicate that fat level slightly alters bile acid metabolism but that wheat brans do not.     

Calcium phosphate supplementation results in lower rat fecal bile acid concentrations and a more quiescent colonic cell proliferation pattern than does calcium lactate

Abstract

Although there is general agreement that dietary calcium is protective against colon carcino‐genesis, considerable controversy exists on the relative efficacy of the counterion in calcium supplements. We therefore conducted a comparative study in rats of four forms of calcium supplementation (calcium phosphate, casein, lactate, and a 50:50 phosphate‐carbonate combination). The relative effects of these supplements on measurements of colon physiology, in vivo pH, fecal fat, individual bile acids, and in vivo cell proliferation were measured in the same animals. In contrast to results when amounts of calcium are varied, there was no effect of form of supplement on total fecal output or output of fecal fat. Calcium phosphate resulted in the most acidified cecal contents. Calcium phosphate and calcium casein resulted in lower fecal concentrations oflitho‐cholate and lower amounts of total fecal bile acids than supplementation with the calcium lactate or combination diets. In addition, rats fed calcium phosphate had lower concentrations of fecal β‐muricholate than rats provided with the calcium combination supplement. In the proximal colon, calcium phosphate resulted in a significantly lower number of cells per crypt column and a lower labeling index than the calcium lactate diet. The position of the highest labeled cell was lower with calcium phosphate supplementation than with supplementation from the calcium combination or the calcium lactate diet. There was a highly significant correlation between the pH of cecal contents and labeling index in the proximal colon (r = 0.98, p = 0.003). The results suggest that calcium phosphate may inhibit colon tumor incidence more effectively than calcium lactate, because the calcium phosphate group had a lower colonic proliferative status than the calcium lactate group. Changes in the proliferative status of colonocytes are known to precede and accompany neoplasia.     

Docosahexaenoic acid-rich fish oil and pectin have a hypolipidemic effect, but pectin increases risk factor for colon cancer in rats

This study was designed to compare the effect of fish oil rich in DHA and pectin on the level of plasma lipids, hepatic HMG CoA reductase activity, microsomal membrane fluidity, colonic luminal content of short chain fatty acids (SCFA) and fecal excretion of bile acids and neutral sterols in rats. Male SD rats (7wks) were divided into three groups according to dietary fat sources, beef tallow (BT), corn oil (CO), fish oil (FO) and each group was subdivided into cellulose and pectin groups. The rats were fed for 25 wks the experimental diet containing 15% fat and 6% fiber and all rats were intramuscularly injected. with DMH. FO significantly reduced the levels of plasma Chol, TG, LDL-C, VLDL-C and hepatic HMG CoA reductase activity and increased membrane fluidity as compared with BT and CO. Pectin significantly reduced the levels of plasma Chol, VLDL-C and LDL-C, but increased HDL-C, HMG CoA reductase activity and membrane fluidity (p<0.05). However, pectin significantly increased the luminal content of butyrate and propionate in CO-fed rats and increased fecal excretion of deoxycholic acid and lithocholic acid in BT and CO-fed rats (p<0.05). Overall, fish oil had a protective effect against CVD by inhibiting hepatic HMG CoA reductase activity and increasing hepatic microsomal fluidity, thus leading to a reduction in plasma lipids. Pectin also had a protective effect against CVD by increasing fecal excretion of neutral sterols and hepatic microsomal fluidity. Pectin, however, increased risk factors for colon cancer by increasing the production of secondary bile acids and SCFA in the colon.     

Fructooligosaccharide and soy isoflavone suppress colonic aberrant crypt foci and cyclooxygenase-2 expression in dimethylhydrazine-treated rats

This study investigated the inhibitory effects of soy isoflavones and fructooligosaccharide (FOS) on colon carcinogenesis. Sprague-Dawley male rats were injected with 1,2-dimethylhydrazine (DMH) and given experimental diets that contained 0%, 3%, 6%, or 9% FOS with or without soy isoflavones (1,000 mg/kg of diet). After 12 weeks, colonic aberrant crypt foci (ACF) formation, cyclooxygenase-2 (COX-2) expression, and fecal bile acid profiles were determined. The numbers of ACF, the numbers of ACF containing four or more crypts per focus of colonic mucosa, and the levels of COX-2 protein in the colonic epithelial tissues were significantly decreased in a dose-dependent manner in the FOS-fed, DMH-treated rats (P < .001), as compared to the DMH-treated control rats. Soy isoflavones significantly decreased the number of ACF with four or more aberrant crypts per focus (P < .001) and the amount of COX-2 protein (P < .01), independently of the effect of the oligosaccharide. The highest suppression of ACF formation was obtained with soy isoflavones combined with >or=6% FOS. No significant relationship was found between the dosage of FOS or soy isoflavones and the concentration of fecal secondary bile acid. We conclude that the combination of FOS and soy isoflavones inhibits colonic ACF formation and reduces COX-2 expression in DMH-treated rats.     

Effect of dietary fat, starch and cellulose on fecal bile acids in mice

The effect of dietary fat, starch and cellulose on individual and total fecal bile acids was studied in mice after 4 wk of feeding diets containing different levels of fat (5 and 29%), starch (3, 36 and 57-65%) and cellulose (2 and 10%). Diet affected the fecal concentration of deoxycholic acid, beta-muricholic acid and total bile acids. Increasing dietary fat from 5 to 29% significantly increased the level of deoxycholic acid and total bile acids. An increase in dietary cellulose from 2 to 10% significantly decreased the level of deoxycholic acid, beta-muricholic acid and total bile acids. High levels of dietary starch (36 and 57-65%) did not significantly affect the excretion of deoxycholic, beta-muricholic and total fecal bile acids. Starch was able to bind bile acids in vitro and to affect the level of fecal free bile acids. In high fat diets, the level of free bile acids was lower in the feces of animals fed 36% starch diets than in those fed 3% starch diets. This reduction of free bile acids was accompanied by a reduction in colon proliferative activity. We suggest that free, rather than total, bile acids are the effective damaging agents for colon mucosa, and may represent a risk factor in the development of cancer.     

Effect of dietary fiber on colonic cell proliferation and its relationship to colon carcinogenesis

The addition of specific fiber supplements to semipurified diets has been shown to stimulate large bowel cell proliferation in laboratory rodents. Relatively insoluble fibers such as cellulose, which is poorly fermented, the more-soluble oat bran, and inert bulking agents such as kaolin produce little or no effect on cell growth. On the other hand, wheat bran, pectin, guar gum, and degraded carageenan all stimulate large bowel cell proliferation, the greatest growth response tending to occur in the cecum or proximal colon. The proximal large bowel is also the major site for the intestinal fermentation of dietary fiber and any other nonabsorbed carbohydrates. The fermentation of fiber by colonic microorganisms results in the production of short-chain fatty acids and a lower pH of large bowel contents, metabolic events known to be associated with increased epithelial cell growth. In general, factors that stimulate cell growth also enhance tumor development, a concept that holds true in the colon even for dietary fibers such as pectin and guar gum. Wheat bran can also stimulate colon carcinogenesis when fed only during carcinogen exposure. Oat bran and corn bran may stimulate colon carcinogenesis by increasing fecal bile acid excretion, a feature of many soluble fibers, while the acidification of large bowel contents is associated with an increased frequency of chemically induced colonic cancers. A greater understanding of colonic metabolism and cell physiology is needed to define fully the mechanisms by which dietary fibers modify colon cancer development.     

Fish protein hydrolysate reduces plasma total cholesterol, increases the proportion of HDL cholesterol, and lowers acyl-CoA:cholesterol acyltransferase activity in liver of Zucker rats

There is growing evidence that soy protein improves the blood lipid profiles of animals and humans. We compared the effects of fish protein hydrolysate (FPH), soy protein, and casein (control) on lipid metabolism in Wistar rats and genetically obese Zucker (fa/fa) rats. In Zucker rats, FPH treatment affected the fatty acid composition in liver, plasma, and triacylglycerol-rich lipoproteins. The mRNA levels of Delta 5 and Delta 6 desaturases were reduced by FPH and soy protein feeding compared with casein feeding. In Zucker rats both FPH and soy protein treatment reduced the plasma cholesterol level. Furthermore, the HDL cholesterol:total cholesterol ratio was greater in these rats and in the Wistar rats fed FPH and soy protein compared with those fed casein. Although fecal total bile acids were greater in soy protein-fed Zucker rats than in casein-fed controls, those fed FPH did not differ from the controls. However, the acyl-CoA:cholesterol acyltransferase activity was reduced in Zucker rats fed FPH and tended to be lower (P = 0.13) in those fed soy protein compared with those fed casein. Low ratios of methionine to glycine and lysine to arginine in the FPH and soy protein diets, compared with the casein diet, may be involved in lowering the plasma cholesterol concentration. Our results indicate that the effects of FPH and soy protein on fatty acid metabolism are similar in many respects, but the hypocholesterolemic effects of FPH and soy protein appear to be due to different mechanisms. FPH may have a role as a cardioprotective nutrient.     

Modified soybean affects cholesterol metabolism in rats similarly to a commercial cultivar

The consumption of soy protein lowers blood cholesterol in humans and animals. Breeding may alter the physiological effects of soybeans, such as its cholesterol-lowering property. Our hypothesis is that breeding affects the hypocholesterolemic effect of soy by modulating the expression of key hepatic enzymes related to cholesterol and bile acid biosynthesis, as well as altering fecal neutral and acidic steroid excretion. Therefore the aim of this study was to evaluate the effect of a new Brazilian soybean cultivar (UFV-116), lacking lipoxygenases 2 and 3, compared with a commercial cultivar (OCEPAR-19), on 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) and cholesterol 7α-hydroxylase (CYP7A) mRNA expression and fecal steroid output in rats. Thirty-six male rats were fed UFV-116, OCEPAR-19, or casein as the protein source, with or without addition of dietary cholesterol (0.25%). Blood and liver cholesterol, HMGR and CYP7A mRNA abundance, and fecal excretion of steroids were measured. Blood and liver cholesterol levels were lowered by both soybean cultivars, with and without cholesterol, but UFV-116 was more effective when included in the cholesterol-free diet. Both soy diets promoted lower levels of HMGR mRNA, higher levels of CYP7A mRNA, and higher excretion of fecal secondary bile acids. There was higher fecal neutral steroid output when cholesterol was added to all diets. These data show that both soybean cultivars acted similarly in lowering serum and hepatic cholesterol; therefore, breeding did not affect the hypocholesterolemic effect of the new cultivar.     

Hepatic cysteine dioxygenase activity and sulfur amino acid metabolism in rats: possible indicators in the evaluation of protein quality

Experiments were carried out to examine the possibility that the sulfur amino acid metabolism of rats may be an indicator of the nutritional value of dietary protein. Rats were fed diets containing 8, 16 or 24% of gluten, soy protein or casein for 3 wk. Hepatic cysteine dioxygenase activity, hepatic concentration of glutathione, cysteine and taurine and urinary taurine were examined. In addition, the sulfur amino acid metabolism of rats fed these diets fortified with the appropriate first limiting amino acid for 7 d was also examined. High urinary taurine excretion was observed in the three gluten groups, whereas very low urinary taurine excretion was observed with up to 24% soy protein or up to 16% casein. The hepatic hepatic cysteine dioxygenase activities of the gluten diet groups were higher than those of corresponding soy protein or casein diet groups, except that of rats fed the 24% casein diet. The hepatic concentrations of both glutathione and cysteine in gluten diet groups were also higher than those of corresponding soy protein or casein diet groups, except 24% soy protein and 16 and 24% casein diet groups. In rats fed the casein or soy protein diets urinary taurine excretion and hepatic cysteine dioxygenase activity increased with increasing methionine supplementation, the first limiting amino acid. Conversely, in rats fed the gluten diet both urinary taurine excretion and hepatic cysteine dioxygenase activity decreased with increasing lysine supplementation, the first limiting amino acid. These findings suggest that urinary taurine excretion and hepatic cysteine dioxygenase activity may be useful as sensitive indicators of the nutritional value of dietary protein.     

Hypocholesterolemic effect of katsuobushi, smoke-dried bonito, prevents ovarian hormone deficiency-induced hypercholesterolemia

The purpose of this study was to examine whether katsuobushi, smoked-dried bonito (KB), which is a traditional Japanese food, prevents ovarian hormone deficiency-induced hypercholesterolemia. In experiment 1, ovariectomized rats (OVX-rats) were fed a purified diet containing casein or KB. Compared with the casein diet, the KB diet reduced the plasma cholesterol concentration and apparent protein digestibility, and increased the fecal dry weight and fecal bile acid excretion. In experiment 2, OVX-rats were fed one of the following four diets: casein diet containing corn oil or fish oil (CA/CO or CA/FO), or a diet containing the digested or undigested fraction of KB after treatment with microbial protease (KBE or KBR). KBR contains mainly two components: oil and protease-undigested protein of KB origin. In comparison with the CA/CO diet, the KBE diet did not affect the plasma and liver lipids concentrations, apparent protein digestibility nor fecal bile acid excretion. However, the KBR and CA/FO diets reduced the plasma cholesterol and triacylglycerol (TAG) concentrations and the liver total lipid and TAG concentrations, but increased the liver total and esterified cholesterol concentrations. The KBR diet increased fecal bile acid excretion and fecal dry weight, whereas the CA/FO diet did not. Thus, the preventive effect of KB on the ovarian hormone deficiency-associated increase in plasma cholesterol concentration appears to be mediated by an increase in bile acid excretion through a promoted secretion of bile acids by the binding of bile acids to resistant proteins.