Dietary Fiber In Rats Research Articles

The effects of okara on rat growth, cecal fermentation, and serum lipids

Okara, a soymilk residue, was characterized and used as a supplement to enrich dietary fiber in rats. Okara comprised 49% total dietary fiber, of which only 0.55% was soluble, protein (33.4%), fat (19.8%), and ash (3.5%). Okara as a diet supplement had no influence on food intake, but the growth rate and feeding efficiency were lower in the okara-fed group than in the control group. Okara increased fecal weight and moisture. In okara-fed rats, in vivo colonic fermentation of okara resulted in a lower pH, but a higher cecal weight and higher total short chain fatty acid production, compared to controls. There were no significant differences (P≤0.05) between groups in albumin, protein, uric acid, bilirubin, or glucose content in rat serum. The okara-supplemented diet produced a nonsignificant reduction in HDL-lipids and triglycerides. Okara, a rich source of low-cost dietary fiber and protein, might be effective as a dietary weight-loss supplement with potential prebiotic effect.

Value of a tomato byproduct as a source of dietary fiber in rats.

A residue consisting of tomato peel and seeds is a byproduct of the tomato paste industry. This product had, after drying and grinding, 101.4 g water, 175.6 g protein, 95.9 g lipids, 36.4 g ash and 590.7 g total carbohydrates per kilogram of residue. The carbohydrates in the residue were mainly dietary fiber (495.3 g) from which 405.4 g were insoluble fiber. Additionally, the residue had ascorbic acid 0.25 g, P 3 g, Ca 1.7 g, K 13.1 g, Mg 2.4 g, Cu 0.013 g, Fe 0.248 g, Mn 0.018 g and Zn 0.174 g per kilogram of residue. The residue fed to rats at increasing concentrations in the diet (0, 134, 263 and 387 g/kg diet) over 18 days had no effect on body weight gain; caused an increase in food intake and slightly reduced feed efficiency. Incorporation of the residue in the diet caused a substantial increase in fecal mass, which was proportional to the dietary fiber provided by the residue (r = 0.89); apparent absorption of protein, energy, Ca, Mg, Fe, Zn and Cu present in the diets was reduced. These reductions were proportional to the amount of dietary fiber provided by the residue and became substantial when the residue was included at 263 or 387 g/kg. However, when the residue was included at 134 g/kg, little effect on the apparent absorption of the dietary nutrients was noted. Because this concentration provided the rats with approximately 10 times more fiber than that recommended for humans, one can expect that if this tomato residue were consumed at concentrations recommended for humans, it should have no effect on nutrient availability. These results indicate that this tomato residue represents an attractive source of fiber, which in rats had a low apparent absorption (52-56%). In addition, it was very effective in increasing fecal mass with no negative effects on growth performance.

Preventive effect of germinated barley foodstuff on diarrhea induced by water-soluble dietary fiber in rats.

We investigated the preventive effect of germinated barley foodstuff (GBF) added to the diet on diarrhea induced by the dietary water-soluble dietary fibers, polydextrose, hemicellulose, and poly-acrylic acid sodium salt, in Sprague-Dawley rats. The minimum content of GBF necessary for blocking diarrhea was 3% (by weight) of the diet. Since GBF is mainly derived from the aleurone and scutellum of malted barley, we assessed the physiological effects of the aleurone and scutellum fractions derived from barley grains before and after germination. The addition of fractions containing only germinated barley, and not barley collected before germination, increased the fecal output and jejunal mucosal protein content. The effects of malted barley were very similar to those of GBF. It was concluded that germination was necessary to bring about the physiological effects of GBF. Since non-lignified hemicellulose and Gln-rich protein were newly synthesized during germination, these might have contributed to the increased fecal output and jejunal mucosal protein content.

Oxidized Ethyl Linoleate Induces Mucosal Hypertrophy of the Large Intestine and Affects Cecal Fermentation of Dietary Fiber in Rats

Oxidized ethyl linoleate (OEL) was prepared by aeration at low temperature. Peroxide value (POV, mEq/kg lipid) of OEL was 1400; the major oxidized compounds were 9-hydroperoxy-cis,trans- and 13-hydroperoxy-trans,cis-octadecadienoate. Rats fed fiber-free or sugar-beet fiber (SBF, 100 g/kg diet) diets were divided into three groups for each diet, and administered OEL (high OEL group), OEL diluted with ethyl linoleate (low OEL group, POV 700) and nonoxidized ethyl linoleate (EL group) through gastric tubes each day at 1400–1600 h (2.5 g/kg body wt) for 16 d. The relative wet weight, and DNA and protein contents of the cecal mucosa were higher in the high OEL groups than in the low OEL and EL groups in rats fed the fiber-free diet and in rats fed the SBF diet except for mucosal protein content. Spermidine concentration in cecal mucosa of rats fed the fiber-free diet was greater in the high OEL group than in the EL group. These results suggest that metabolism related to mucosal proliferation of the cecum was affected by the high dose of OEL. The total short-chain fatty acid (SCFA) concentration in the cecal contents of SBF-fed rats was 100% higher than the concentration in rats fed the fiber-free diet in the EL group, but the administration of low dose and high dose OEL lowered the SCFA concentration in fiber-fed rats to that of rats fed the fiber-free diet. Butyric acid concentration was markedly lowered by ingestion of OEL in a dose-dependent manner in rats fed the SBF diet. In contrast, the isobutyric acid concentration was higher in the OEL-treated groups than in the EL groups. We conclude that a low dose of OEl depresses cecal fermentation of dietary fiber with changes in SCFA composition, and that a high dose of OEL induces mucosal hypertrophy in the cecum. These data show that dietary oxidized lipids affect cecal metabolism and may be associated with colon cancer.

Reversible cecal and colonic enlargement induced by dietary fiber in rats

The reversibility of cecal and colonic enlargement induced by dietary fiber ingestion was studied using weanling rats which were raised on a diet containing cellulose or glucomannan (20%) for 4 weeks, then switched to a control diet (fiber-free) and further raised on a control diet for 4 weeks. Both dietary fibers occurred the increase of weight of whole tissue and mucosa and total DNA of cecal and colonic mucosa. But, they did not induce to increase protein DNA ratio of cecum and colon. The effect of cellulose was greater in the colon than in the cecum, while that of glucomannan was greater in the cecum than in the colon. (Na+K) ATPase activity of cecal and colonic mucosa was significantly higher in the enlarged tissues induced by both dietary fibers. The enlarged tissues returned spontaneously to the level of the control group within a week after a test diet was switched to the control diet. Total DNA and ratios of RNA DNA and protein DNA converged until there were no significant differences among the three groups. The stimulated activity of (Na+K) ATPase, also was readily returned in parallel with the reduction of tissue weight after the elimination of dietary fiber from the diet. These results suggest that the physiological and morphological changes induced by dietary fiber in the large intestine are reversible and might be one of adaptations to response to the variable environments in gastrointestinal tract.

Hepatic and Intestinal Cytochrome P-450, Glutathione-S-Transferase and UDP-Glucuronosyl Transferase Are Affected by Six Types of Dietary Fiber in Rats Inoculated with Human Whole Fecal Flora

The effects of six different sources of dietary fiber (inulin, wheat brain, carrot, cocoa, pea and oat fiber) on hepatic and intestinal cytochrome P-450 (EC 1.14.14.1), glutathione-S-transferase (GSH-T, EC 2.5.1.18) and UDP-glucuronosyl transferase (UDPG-T, EC 2.4.1.17) were studied using germ-free F344 rats subsequently inoculated with a human whole fecal flora. In the liver, the total concentration of P-450 was significantly lower in the wheat bran-fed group than in the carrot-fed group. The 2E1 form of P-450, involved in nitrosamine metabolism, was enhanced in the carrot-fed group compared with those fed most other types of fiber. Compared with the pea-fed group, rats fed cocoa had a lower constitutive 2C11 form and a higher 1A2 form. A very high concentration of small intestinal 1A1 form--involved in "toxication" reactions--was observed in rats fed cocoa. The specific activity of hepatic GSH-T was significantly higher in rats fed inulin than in all other groups, except the carrot-fed group. In the colon, GSH-T specific activity was twice as high in the oat-fed group as in the wheat bran-fed counterpart. Small intestinal GSH-T activity and hepatic and intestinal UDPG-T activities were unaffected by diet. Results are discussed in relation to potential health benefits.

Intestinal Transit and Body Weight Responses to Ovarian Hormones and Dietary Fiber in Rats

A two-part experimental design was used to study the effects of ovarian hormone cessation, hormone supplementation, and dietary fiber composition on body weight, appetite, and intestinal transit. In Part 1, effects of ovarian hormone status on body weight and baseline and stimulated intestinal transit were measured in chow-fed rats. Sprague-Dawley rats were ovariectomized (OVX), then injected daily (22 days) with estrogen (E), progesterone (P), the combination (E + P), or placebo. Controls were sham operated and placebo injected. Among OVX rats, E and E + P had the least body weight gain (9%, 6%); placebo and P had the greatest (36%, 34%). In OVX-P, baseline intestinal transit (measured in anesthetized rats as distance traveled by a charcoal marker) was relatively low, but vagal stimulation via centrally administered thyrotropin-releasing hormone evoked an increase significantly larger than that in other groups. In Part 2, experiments probed the interacting effects of ovarian hormone cessation and dietary fiber composition on body weight and baseline intestinal transit. Caloric intake was measured to determine the contribution of altered appetite. Rats were OVX or sham operated, then fed liquid diets with or without dietary fiber (25 days). OVX fiber-fed rats had significantly higher caloric intake, weight gain, and baseline intestinal transit than other groups. Caloric intake did not fully account for group differences. These results demonstrate modulation of GI function by ovarian hormones and dietary fiber.

Changes in Plasma and Hepatic Lipids, Small Intestinal Histology and Pancreatic Enzyme Activity Due to Aging and Dietary Fiber in Rats

Rats were fed either a control diet or a control diet supplemented with wheat bran, psyllium husk or oat bran to increase intake of fiber. Groups of rats were killed after 3.5, 10, 15, or 18.5 mo of consuming the diets. Plasma cholesterol and triglyceride concentrations were significantly higher in 18.5-mo-old than younger animals. Fiber supplementation did not prevent the age-related increase in lipids. Cecal weight, including contents, was higher in the psyllium husk and oat bran groups than control, and smooth muscle thickness in the ileum of psyllium husk and oat bran animals was greater than control. The score for torn villi in the small intestine was lower than expected in the wheat bran group. Amylase activity in the pancreas declined significantly with age in all groups. In aging animals fiber supplementation may enhance ileal compensation for decreases in proximal intestinal function but does not prevent age-related changes in the gut or in lipid concentrations.

Modulation of the Hypolipidemic Effect of Fish Oils by Dietary Fiber in Rats: Studies with Rice and Wheat Bran

Adult male rats were fed a purified diet containing rice bran or wheat bran with or without a marine fish oil to investigate the possible effects of such dietary combinations on lipid metabolism. Plasma and hepatic triacylglycerols and hepatic lipogenesis were lowered significantly by feeding fish oil with rice bran but not with wheat bran. Plasma cholesterol and hepatic cholesterol synthesis were significantly lower in animals fed fish oil with either bran. Liver microsomal free cholesterol was significantly lower in rats fed rice bran alone than in all other groups. Hepatic low density lipoprotein (LDL) receptor activity was significantly higher in the two groups fed rice bran than in the two groups fed wheat bran. Fish oil significantly decreased hepatic LDL receptor activity and increased hepatic high density lipoprotein (HDL) binding activity with wheat bran but had no significant effects on these parameters when added to the rice bran diet. However, when the data for all groups were pooled, there was a significant negative correlation between hepatic HDL binding activity and LDL receptor activity. Cecal volatile fatty acids were significantly higher in rats fed rice bran, were unaffected by adding fish oil to either bran diet and did not appear to mediate any of the effects of the brans and fish oil on plasma lipids and hepatic lipid metabolism. The combination of rice bran plus fish oil therefore appears to have more beneficial effects on lipid metabolism than wheat bran plus fish oil.

Effect of age and diet on the digestibility of gross components and dietary fiber in rats.

Effect of age and diet on the digestibility of gross components and dietary fiber in rats.

Jejunal morphological consequences of dietary fiber in rats

JEJUNAL MORPHOLOGICAL CONSEQUENCES OF DIETARY FIBER IN RATS. C. Tasman-Jones, A.L. Jones and R.L. Owen, Cell Biology Section and Medical Service, Veterans Administration Hospital and the University of California, San Francisco, California. Broad leaf-shaped jejunal villi are common in healthy people from underdeveloped countries. Recently, vegetarians in the U.S. have also been shown to have broad irregular villi. In rats, finger-like jejunal villi present at birth become leaves, then ridges as rats mature. The purpose of this study was to ascertain if this villus evolution could be prevented by elimination of dietary fiber or induced by fiber components (cellulose or pectin). Weanling rats were assigned one of the following dietary regimens: Purina chow diet (normal fiber); nutritionally complete no fiber diet; no fiber diet plus 10% cellulose; no fiber diet plus 10% pectin. After 12 weeks the jejunum was examined by dissecting light microscopy, scanning and transmission electron microscopy (TEM). Animal weights (mean -f SD) and length of the small bowel from the duodenojejunal junction to the ileocecum were: