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We studied the effect of taurine on ovarian hormone deficiency-induced hypercholesterolemia in 6-month-old, ovariectomized rats fed with coconut oil. Rats were fed 1 of 4 diets for 28 days: purified diet based on coconut oil without or with taurine (10, 30, or 50 g/kg, called the C, 10T, 30T and 50T diets, respectively). Coconut oil is rich in lauric and myristic acids, which are saturated fatty acids that reduce the level of hepatic low-density lipoprotein receptor activity. Plasma cholesterol level was not affected by the diet. The low-density lipoprotein receptor and 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA levels in the liver increased by feeding the 50T diet compared with the C diet. As the dietary level of taurine increased, the levels of cholesterol 7 α -hydroxylase activity, and fecal bile acids excretion logarithmically increased. Our results showed that taurine increased fecal bile acids excretion but did not prevent ovarian hormone deficiency–induced hypercholesterolemia in rats fed with coconut oil.

We studied the effect of the particle size of corn brain (CB) on the plasma cholesterol concentration, fecal output, and cecal fermentation. Rats were fed a fiber-free diet (FF) or FF containing CB (50 g/kg diet) of six different particle sizes (500, 350, 250, 177, 149, 105 μm in diameter) for 21 days. The fecal wet weight and wet weight of cecal content were significantly higher in the rats fed CB than in those fed FF. Liver total lipids, fecal moisture, fecal bile acids excretion and moisture of cecal content were significantly lower in the rats fed CB than in those fed FF. As the particle size decreased, the plasma cholesterol concentration, fecal wet weight, and fecal bulking effect decreased, while the liver cholesterol concentration, cecal wall weight, wet weight of cecal content, and total organic acids, acetic acid and n-butyric acid in the cecal content increased.

The effect of sugar beet fiber (SBF) in reducing the ovariectomy-induced elevation in plasma cholesterol concentration was studied in 6-week-old, female ovariectomized (ovx) rats. Rats were subject to ovariectomy or sham operation, and fed a fiber-free diet (FF diet) or FF diet containing SBF (100 g/kg diet, SBF diet) for 42 days. The food intake, intake of nutrient fraction, body weight gain and liver weight were significantly higher in the ovx-rats than in the sham-operated rats. Among the ovx-rats, the plasma total and non-HDL cholesterol concentrations were significantly lower (by 29% and 47%, respectively) in those fed the SBF diet than in those fed the FF diet. The following parameters among the ovx-rats were significantly higher in those fed the SBF diet than in those fed the FF diet: cholesterol 7α-hydroxylase activity, fecal excretion of bile acids, and cecal pool of propionic acid.

The effect of taurine and glycine on the ovarian hormone deficiency-associated increase in plasma cholesterol concentration were studied in ovariectomized (ovx) 10-month-old retired breeder female rats. Rats was randomly assigned to four treatment groups: sham-operated+a casein-based cholesterol-free diet (C-diet, sham-C); ovx+C diet (ovx-C); ovx+C diet supplemented by taurine (50 g/kg diet, ovx-T); and ovx+C diet supplemented with glycine (50 g/kg diet, ovx-G). Rats were fed these diets for 28 d and killed at midnight in a fed state. Plasma and liver cholesterol concentrations in ovx-C were significantly higher than in sham-C. Bile flow, biliary bile acid secretion and fecal bile acid excretion were not significantly different between sham-C and ovx-C. Plasma cholesterol concentrations in ovx-T and ovx-G were significantly lower than those in ovx-C. Liver cholesterol concentration in ovx-G was significantly higher than in ovx-C but not in ovx-T. Cholesterol 7a-hydroxylase, bile flow, biliary bile acid secretion and fecal bile acid excretion in ovx-T were significantly higher than in ovx-C, but not in ovx-G. These results indicate that in the case of taurine but not glycine, increased fecal bile acid excretion is one of the factors in the prevention of the ovarian hormone deficiency-associated increase in plasma cholesterol concentration.

The effect of taurine on plasma cholesterol and liver lipid levels, and on the level of fecal bile acid excretion, was examined in ovariectomized (ovx) 10-month-old retired breeder female rats. In the first experiment, ovx-rats were fed a casein-based cholesterol-free diet (C diet) or a C diet supplemented with different amounts of taurine (5 g, 10 g, 30 g and 50 g taurine/kg diet, respectively) for 21 days, and sacrificed at midnight in a fed state. Taurine reduced the ovx-induced increase in plasma total cholesterol level in a dose-dependent manner. Taurine increased the liver cholesterol level and level of fecal bile acids excretion in a dose-dependent manner. In the second experiment, ovx-rats were fed a C diet or a C diet supplemented with 50 g taurine/kg diet (C+50T diet) for 28 days, and killed at midnight in a fed state. The plasma total cholesterol, HDL-cholesterol, and LDL+VLDL-cholesterol levels of ovx-rats fed the C+50T diet were lower than the respective level of ovx-rats fed the C diet. There was a higher level of bile acids in the cecum of ovx-rats fed the C+50T diet than in the cecum of ovx-rats fed the C diet. In the third experiment, ovx-rats were fed the C diet for 8 days, then switched to the C+50T diet for the following 10 days, and then switched back to the C diet for 10 d. Blood samples were collected from the tail vein every two days between day 8 and day 28 at midnight in a fed state. The switch from the C diet to the C+50T diet resulted in a decrease in plasma cholesterol and an increase in fecal bile acid excretion. In contrast, switching from the C+50T diet to the C diet resulted in an increase in plasma total cholesterol and a decrease in fecal bile acid excretion. These data indicate that taurine can effectively prevent the ovarian hormone deficiency-associated increase in plasma cholesterol, and that an increased level of fecal bile acid excretion is one of factors involved in the hypocholesterolemic effect of taurine.

The effect of dietary fibers on the digestive tract mass, diamine oxidase (DAO) activities in the small intestine and plasma and pool of ammonia and organic acids such as acetic, propionic, butyric, lactic and succinic acid in the cecum in rats fed a liquid formula diet was compared. Rats were fed an elemental liquid diet (ED) or ED containing 3g/100 ml of dietary fiber either a mixture of crystal cellulose and carboxymethyl cellulose sodium salt (CC), sugar-beet pectin (BP) or hydrolyzed xyloglucan (HXG) for 14 days. The mass of colon plus rectum was higher in rats fed CC, but not in rats fed BP and HXG than in rats fed ED. Cecal tissue mass was higher in rats fed BP and HXG, but not in rats fed CC, than in rats fed ED. Cecal contents and cecal pH were higher and lower in rats fed CC, BP and HXG than in rats fed ED. DAO activities in the small intestine and plasma were higher in CC than in rats fed ED. Cecal ammonia were lower in rats fed CC, BP and HXG than in rats fed ED. Production of organic acids was similar between rats fed ED and CC except for acetic acid that was much lower in rats fed CC. Diarrhea and loose feces were also improved in rats fed CC. The results suggest that the addition of a combination of water -soluble and -insoluble dietary fiber to a liquid formula diet would have more beneficial effects on the bowel function than water-soluble dietary fiber alone.

The effect of a peptide prepared from corn gluten meal (CP) by proteolysis with alkaline protease on 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumor progression were investigated in female Sprague-Dawley rats. At 6 weeks of age, rats were allowed free access to one of the four diets, 20% casein (CAS), 15% casein + 5% CP (5-CP), 10% casein + 10% CP (10-CP) or 10% casein + 10% free amino acid mixture simulated CP (AA) for 10 weeks. Rats were given 5 mg DMBA in 0.5 ml corn oil by stomach tube at two times (day 7 and 21). Tumor incidence was significantly lower in the 10-CP group, but not in the 5-CP and AA groups, than the CAS group. Total number and total weight of tumors were greater in the CAS group compared with 5-CP, 10-CP or AA groups. No changes were observed in serum 17β-estradiol concentrations among the three groups (CAS, 10-CP and AA). © 1997 Elsevier Science Inc.

The effect of lactic acid or sodium lactate on the glycemic response was studied in rats. The lightly anesthetized, overnight-fasted rats were administered a glucose solution (200 g/L) with or without lactic acid or sodium lactate by a stomach tube to provide 250 mg of glucose per 100 g body weight. The addition of lactic acid (300 mmol/L) to a glucose solution reduced the initial rise in plasma glucose and insulin concentrations, slowed the rate of gastric emptying and brought a drop of pH in gastric contents. However, such effects were not recognized in the addition of sodium lactate (300 mmol/L as the lactate ion). Lactic acid stimulated cholecystokinin (CCK) and secretin release, but inhibited gastrin release. The study suggests that lactic acid is effective in modulating postprandial plasma glucose concentration, which is due to delayed gastric emptying accompanied by the increase of secretin and CCK release following the fall in intraduodenal pH.

We hypothesized that short chain fatty acid (SCFA) fermented in the cecum of rats fed a guar gum diet is responsible for the hypoglycemic effect. Thus, to evaluate the role of SCFA in glucose metabolim, rats with or without cecum were fed a guar gum-containing diet for 4 weeks, and parameters including blood glucose and SCFA in portal blood were determined. The level of insulin-responsive glucose transporter (GLUT4) was also measured to evaluate the effect of SCFA on glucose metabolism at the cellular level. Blood glucose levels in both cecectomized and normal rats that were fed a cellulose-based diet significantly, decreased after their diet was changed to one containing guar gum at the level of 5% ( w w ). However, no subsequent difference was found between the two groups. When an oral sucrose load was performed after 3 weeks, untreated and cecectomized rats responded similarly. After feeding a guar gum diet for 4 weeks, the rats were killed, and blood from the portal vein and aorta was taken to measure SCFA and plasma biochemical parameters. Cecectomy did not have any influence on glucose, lipids, and insulin levels in the blood. Portal plasma acetic and propionic acids in ceoectomized rats dramatically decreased by one-half and one-tenth those of the control rats, respectively. There was no difference in the amount and translocation rate of GLUT4 isolated from adipose tissues between the two groups when the animals were killed after 4 weeks. From these results, it is suggested that, at least in normal rats, SCFA fermented in the digestive tract, if any, is not a primary cause of glucose-lowering action by guar gum. Physicochemical characteristics of guar gum in the upper intestine (e.g., gel-forming capacity) may be important in determining blood glucose level.

The bioavailability of ferrous and ferric iron following cecal infusion was compared by assessing the hemoglobin regeneration method in ileally fistulated anemic rats. Rats were fed an iron-deficient diet (8 mg Fe/kg diet) for 14 days after recovery from surgery. The anemic rats were then divided into three groups of 11 rats. Group 1 (control) was fed an iron-adequate diet (45 mg Fe/kg diet) and infused with NaCl solution (150 mM). Group 2 and 3 were fed an iron-deficient diet and infused with ferrous sulfate [Fe(II)] suspension or ferric sulfate [Fe(III)] solution (800 ppm as Fe, pH 6.8) to provide the same amount of iron as that consumed one day before by the control group. NaCl, Fe(II) and Fe(III) were infused through the fistula as two times (1000h and 1800h) for 14 days. The volume of NaCl infused was about equal to the volume of Fe(II) suspension and Fe(III) solution infused. Hemoglobin regeneration efficiency, hematocrit, plasma iron concentration, transferrin saturation, total iron-binding capacity, iron contents in organs (liver, spleen and kidney), body weight gain and food intake were almost the same among groups. These results suggest that inorganic iron is absorbed from the large intestine and is not influenced by forms of iron, ferrous iron or ferric iron.

The comparison of ferrous and ferric iron bioavailability following cecal infusion was studied in ileally fistulated rats. Rats were divided into four groups of 10 rats after recovery from surgery. Group 1 (control) was given an iron-adequate diet (45 mg Fe/kg diet) and infused with NaCl solution (150 mM). Group 2 was given an iron-deficient diet (8 mg Fe/kg diet) and infused with NaCl solution. Group 3 and 4 were given an iron-deficient diet and infused with ferrous sulfate [Fe(II)] suspension or ferric sulfate [Fe(III)] solution (800 ppm as Fe, pH 6.8) to provide the same amount of iron as that consumed one day before by the control group. NaCl, Fe(II) and Fe(III) were infused through the fistula at two times (1000h and 1800h) for 28 days. The volume of NaCl infused was about equal to the volume of Fe(II) and Fe(III) suspension or solution infused. Compared with the control group, body mass gain and food intake for Group 3 and 4 did not decrease. However, the hematological indices and total iron contents in the liver and spleen for Group 3 and 4 showed 20 to 30% and 30 to 40% lower, respectively, compared with those of the control group. There was no significant difference between Group 3 and 4 on iron bioavailability. These results suggest that the lower part of the digestive tract plays an important role in iron absorption.

A comparison of the hypocholesterolemic effects of propionic acid (PA) and sodium propionate (N-PA), infused into the stomach or cecum, was made in rats fed a cholesterol-free, casein diet. Rats received infusions of a 0.5 ml portion of either PA (100 mM), N-PA (100 mM) or NaCl (150 mM) twice a day during the experimental period. PA moderated the increase of plasma cholesterol caused by the feeding of the casein diet, but N-PA did not.

The effect on plasma and liver lipids of intracecal infusion of propionic acid (PA) was studied in ileally fistulated rats fed a cholesterol-free, casein purified diet (casein diet) for 5 weeks. Rats received intracecal infusions of a 0.5 ml portion either PA (100 mM) or NaCl (150 mM) twice a day for 5 weeks or during days 10–17. PA moderated the increase in plasma cholesterol concentration (p-chol) caused by the feeding of the casein diet. Though p-chol immediately decreased after changing NaCl to PA, it gradually returned toward its starting concentration by changing to NaCl again. Total lipids and cholesterol in the liver were not affected by PA infusion. Fecal excretions of neutral sterols and bile acids were also not affected.

The effect of dietary mineral composition on the quality of amino acid mixtures and intact casein was examined in growing rats fed for 28 days under "conventional" conditions. When 25% demineralized casein (DC) was the sole dietary protein source, the widely-used mineral mixture by Harper (MMH) supported growth poorly (3.2 g/day), but a new formula mineral mixture (MM2) containing sufficient amounts of zinc gave a growth rate of over 8 g/day for 21 days. With a crude casein (CC) diet, rats grew at the same rate regardless of mineral mixtures. The growth-supporting power of amino acid mixtures, one of which simulated casein (AA-A) and another patterned after Rogers and Harper to give maximal growth of rats (AA-B), was compared with those of DC and CC with addition of MMH or MM2. When the protein source was DC, AA-A or AA-B, MM2 significantly improved the growth over that of rats fed MMH. The growth-stimulating effect of MM2 was greater when added to DC diet than when added to AA-A diet. When MM2 was added to AA-B diet, the growth rate greatly increased and reached that of rats fed DC diet containing MM2 (over 8 g/day), showing a nutritional equivalency between the amino acid mixture and intact protein. Drawbacks inherent in MMH did not appear with CC diet, because CC contained considerable amounts of zinc. When a highly purified amino acid-sucrose diet is used, dietary minerals become most limiting for growth even under conventional conditions. Thus, the previous conflicting results concerning nutritional equivalency of amino acid mixtures and protein can be explained by inadequate mineral sources.