Fermentation of dietary fibre components in the rat intestinal tract

Assessment of cassia gum

Cassia gum is approved for use in Europe by the Commission Directive (EEC No. E 499) and is listed in the Annex of the Council Directive (70/524/EEC) as a stabilizer (thickening and gelling agent) in the manufacture of canned pet foods (for cats and dogs). It is also approved for use in Japan and is listed as a food additive in The Ministry of Health and Welfare Announcement No. 160 (10 August 1995). A panel of experts in the areas of toxicology, pharmacology and food science was assembled to review the safety of cassia gum for use as a thickening agent in human and pet foods in the United States. The available data on cassia gum and structurally related gums demonstrate a lack of toxic effects in animals. This review is the basis for the consideration of cassia gum as generally recognized as safe (GRAS) under conditions of its intended use as a thickening agent in human and pet foods.

Relationship among colonocyte proliferation, differentiation, and apoptosis as a function of diet and carcinogen

To determine the relationship among colonocyte proliferation, differentiation, and apoptosis as a function of fiber and carcinogen, we conducted a 2 x 2 factorial design study with two fibers (pectin or cellulose) and two injection protocols (azoxymethane or saline) in male Sprague-Dawley rats. Rats were killed six weeks after the injections, and in vivo cell proliferation was measured by incorporation of bromodeoxyuridine into DNA, differentiation by binding of the lectin Dolichos biflorus agglutinin, and apoptosis by immunoperoxidase detection of digoxigenin-labeled genomic DNA. In the proximal colon, pectin decreased differentiation and apoptosis, resulting in a greater number of cells per crypt column. In the distal colon, pectin increased cell proliferation, resulting in more crypts per millimeter of colon and a greater number of surface cells. Azoxymethane increased cell proliferation and decreased differentiation and apoptosis in the proximal and the distal colon. This resulted in a greater number of surface cells proximally and more crypts per millimeter of colon distally. These results illustrate the importance of considering all three parameters (proliferation, differentiation, and apoptosis) when evaluating neoplastic growth.

Butyrate and the colonocyte. Implications for neoplasia

Butyrate is produced in the colon of mammals as a result of microbial fermentation of dietary fiber, undigested starch, and proteins. Butyrate may be an important protective agent in colonic carcinogenesis. Trophic effects on normal colonocytes in vitro and in vivo are induced by butyrate. In contrast, butyrate arrests the growth of neoplastic colonocytes and inhibits the preneoplastic hyperproliferation induced by some tumour promoters in vitro. We speculate that selective effects on G-protein activation may explain this paradox of butyrate's effects in normal versus neoplastic colonocytes. Butyrate induces differentiation of colon cancer cell lines. It also regulates the expression of molecules involved in colonocyte growth and adhesion and inhibits the expression of several protooncogenes relevant to colorectal carcinogenesis. Additional studies are needed to evaluate butyrate's antineoplastic effects in vivo and to understand its mechanism(s) of action.

Effect of two levels of transgalactosylated oligosaccharide intake in rats associated with human faecal microflora on bacterial glycolytic activity, end-products of fermentation and bacterial steroid transformation

The effects of two levels of transgalactosylated oligosaccharide (TOS) intake on bacterial glycolytic activity, end products of fermentation and bacterial steroid transformation were studied in rats associated with a human faecal flora. Rats were fed a human-type diet containing 0, 5 or 10% TOS. Caecal pH decrease correlated with the amount of TOS in the diet. Intake of the TOS diet induced a decrease in blood cholesterol and a strong increase in beta-galactosidase activity in the hindgut. TOS fermentation led to production of hydrogen and short chain fatty acids, whereas ammonia and branched-chain fatty acids were decreased. A diet containing 10% TOS increased caecal lactic acid concentrations and reduced beta-glucuronidase activities and steroid transformation.

Studies on date waste dietary fibers as hypolipidemic agent in rats

Date waste dietary fibers were examined as a hypolipidemic agent. White albino rats were fed on three experimental diets: I) high carbohydrate diet free of fiber; II) and III) diets consisted of diet I substituted with 100 g/kg of date waste dietary fibers cultured with Endomycopsis fibuligera at zero time and after 60 h of culturing respectively for 8 weeks. The total lipids, total cholesterol, triglycerides and phospholipids in the liver of rats given diets II and III were significantly decreased over those rats fed the control diet throughout the feeding period (8 weeks). The highest decrease in content of all these parameters was produced by diet III. Comparing diets II and III with the control diet I, total serum lipids and low density lipoprotein cholesterol (LDL-cholesterol) were decreased by 32-48%, while serum triglycerides and total cholesterol levels were lowered in the groups fed diets II and III by 23-35% respectively. Concerning high density lipoprotein cholesterol (HDL-cholesterol), the decrease was only 2-6% in rats fed diets II and III. The highest decrease level was shown in the phospholipids content (51-56%) during all of the experimental period (8 weeks).

Bacterial adaptation in patients with short bowel and colon in continuity

BACKGROUND & AIMS

Long-term carbohydrate malabsorption in patients with short bowel and colon in continuity (SBC) could result in a more efficient fermentation. The bacterial fermentation capacity in patients with SBC was assessed.

METHODS

Eleven fasting patients with SBC ingested 60 g lactulose with 10 g polyethylene glycol. Stool specimens were analyzed. Patients were compared with 8 normal subjects who ingested 60 g lactulose on two occasions, separated by 8 days during which 20 g lactulose was taken twice daily. Moreover, the daily amount of bacteria excreted in stools was measured in 6 patients with SBC and 6 normal subjects.

RESULTS

Despite fast transit time, patients fermented more lactulose and hexoses and had a higher activity of beta-galactosidase in stools than nonadapted normal subjects (P < 0.01); these parameters were roughly similar in patients and adapted normal subjects. The fecal output of short-chain fatty acids was significantly lower in patients than in nonadapted normal subjects (P < 0.03). Patients excreted a significantly greater amount of bacteria in stools than normal subjects (P < 0.05).

CONCLUSIONS

In patients with SBC, the capacity of bacterial flora to ferment lactulose and fecal bacterial mass is spontaneously increased, suggesting that hyperfermentation may affect other carbohydrates. Moreover, hyperfermentation is associated with efficient removal of extra short-chain fatty acids from fecal water.

Transmural trophic effect of short chain fatty acid infusions on atrophic, defunctioned rat colon

PURPOSE

This study was designed to investigate and quantify trophic alterations in the defunctioned, atrophic rat colon after short chain fatty acid (SCFA) treatment was administered in a clinically relevant way.

METHODS

Diverting colostomy with exclusion of distal colon was performed on adult female rats (58), and treatment was started four weeks later. Enemas of either a SCFA solution of sodium-acetate, sodium-propionate and sodium-butyrate (concentration, 780 mM), or isotonic saline (placebo) were instilled through the anus into the defunctioned colon. This was done twice daily for 7 or 14 days before death.

RESULTS

After SCFA instillation for 14 days, the colonic wet weight was 18 percent higher compared with placebo (P < 0.01), and there was a similarly significant difference in dry weight (P < 0.05). Using stereologic assessment to determine the histologic composition of defunctioned colon, we found significant increases among SCFA-treated rats in the weight of the mucose (P < 0.05), the submucosa (P < 0.05), and the muscularis propria (P < 0.05) and a 30 percent increase in the mucosal surface area compared with placebo-treated in the mucosal surface area compared with placebo-treated rats (P < 0.05). Measurements of breaking strength and hydroxyproline content showed no differences between treatment groups.

CONCLUSIONS

SCFA enemas have a transmural trophic effect and preserve mucosal surface area of defunctioned and atrophic colon in rats.

Dietary fiber

Most of our understanding of the physiologic effects of dietary fiber are derived from studies in adults. These investigations have indicated the potential problems with fiber consumption are most likely to occur if isolated polysaccharides or nonpurified fiber supplements are consumed excessively. Such problems include intestinal obstruction and significant reductions in nutrient availability. Inclusion of foods that contain dietary fiber such as fruits, vegetables, beans, and whole-grain products is unlikely to result in complications for most individuals. Young children may need to consume smaller servings of these foods than adults; however, their inclusion in the diet is an important part of meeting dietary recommendation for fiber intake. Excess consumption of fiber-supplemented foods (e.g., bran cereals) should be monitored to avoid appetite suppression that could limit selection of foods to maintain a balanced diet.

Digestibility of energy, protein, fat and non-starch polysaccharides in mixed diets: comparative studies between man and the rat

The apparent digestibility of energy, protein, fat and non-starch polysaccharides (NSP) of low and high dietary fibre (DF) mixed diets were studied in three series of experiments with man and the rat. Low DF diets were used as control diets in each experimental series and the DF level was increased by adding fruits and vegetables (Study 1), citrus fibre concentrate (Study 2) and insoluble barley fibre (Study 3). In Study 3 the high DF diet was fed at two protein levels. There was in most cases good agreement between the digestibility of energy between man and the rat, with the digestibility of energy of the low DF control diets of 0.941-0.950 in man compared with 0.933-0.952 in the rat and of the high DF diets of 0.897-0.931 in man and 0.865-0.920 in the rat. The biggest difference in digestible energy between the two species was found for the diet enriched with fruits and vegetables (0.032 absolute units) and citrus fibre concentrate (0.025 absolute units). Apparent digestibility of protein was slightly lower in man than in the rat for all diets in Studies 1 and 2. In Study 3, however, apparent digestibility of protein was consistently lower in man than in the rat with differences in absolute digestibilities between the two species varying from 0.023 (high DF/high protein) to 0.071 (high DF/low protein). The digestibility of fat was the same in man and in the rat in all but the high DF diet of Study 2. The rat appears to have a lower capacity to digest fibre polysaccharides than man and the digestibility of NSP was consistently lower in the rat than in man. The biggest difference between the two species was found for the diets in Study 2 where the digestibility of NSP in man was measured to be 0.774-0.885 compared with only 0.501-0.517 in the rat. For the other diets the differences in NSP digestibility were 0.077-0.137 absolute units. In spite of some differences between man and the rat in their ability to digest nutrients the various diets are ranked in the same order by the two species.

Mucin secretion in germfree rats fed fiber-free and psyllium diets and bacterial mass and carbohydrate fermentation after colonization

The effect of psyllium on mucin secretion was determined by comparing water-soluble and -insoluble fractions of excreta from germfree rats fed a fiber-free (FF) diet or a diet containing psyllium seed husk (PS). Excreta from the same rats after colonization with a rat mixed cecal culture were separated into water-soluble, plant, and bacterial fractions to compare the remaining carbohydrate and the mass of bacteria. The sugar composition and water solubility of carbohydrate in excreta from germfree rats fed FF diets indicated that a primary fermentable substrate was mucin. PS increased fecal excretion of mucin-derived sugars almost threefold in germfree rats. Fecal carbohydrate was reduced from 619 to 237 mumol/g of dry feces and mostly in the bacterial fraction when rats fed an FF diet were colonized. The total sugar content and the amount of muramic acid, but not bacterial counts and mass, indicated that PS increased fecal bacteria. Fractionation of excreta from PS-fed rats was complicated by a gel which, based on sugar composition, was PS. Sugar composition of the water-soluble fraction from excreta from PS-fed rats suggested that it contained some bacterial component, possibly exopolysaccharides and some of the PS, but not mucin. PS digestibility ranged from 60 to 80%, depending on what fecal fraction was used for output. Because of the presence of PS-derived sugars in the gel and soluble fraction, it was not possible to determine which, if any, of the PS digestibilities was correct.

Digestion of polysaccharides and other major components in the small and large intestine of pigs fed on diets consisting of oat fractions rich in beta-D-glucan

The digestibility of polysaccharides and other major components and the metabolic response of the microflora in the small and large intestines to oat diets varying in mixed linked beta(1-->3; 1-->4)-D-glucan (beta-glucan) were studied in experiments with ileum-cannulated pigs. The oat fractions for diets were prepared in a dry milling process in which oat groats were milled into two endosperm fractions (oat flour 1 and oat flour 2) and oat bran. The digestibility of polysaccharides and the metabolic response of the microflora were followed for the two contrasting diets, oat flour 1 and oat bran, from ingestion to excretion while the digestibility of oat groats and oat flour 2 were estimated only at the ileum and in faeces. There was no degradation of beta-glucan from either oat flour 1 or bran in the stomach and the first, middle and distal thirds of the small intestine (average digestibility approximately 0), while in the terminal ileum digestibility increased to 0.30 to 0.17 respectively. The digestion of starch in the first third of the small intestine was lower for the high-beta-glucan oat-bran diet (0.49) than for the low-beta-glucan flour diet (0.64). However, digestibility differences between the two diets levelled out as the digesta moved aborally in the small intestine and the digestibility at the terminal ileum was almost complete (0.970-0.995) for all diets. Oat non-starch polysaccharides (NSP) were an easily digestible energy source for the microflora in the large intestine less than 13% of dietary NSP being recovered in faeces. The bulk of beta-glucan which survived the small intestine was degraded in the caecum and proximal colon while arabinoxylan was more slowly degraded. The amount of residues passing the ileo-caecal junction has little impact on the density of micro-organisms in the large intestine, which on the flour and bran diets were in the range of 10(10)-10(11) viable counts/g digesta, but a high impact on the activity of the flora in colon. Oat bran resulted in a higher proportion of butyric acid in large intestinal content compared with the flour diet. The faecal bulking effect of oat bran was mainly caused by an increased excretion of protein and fat, presumably of bacterial origin. Of all the diets tested the oat-bran diets had the lowest digestibilities of protein and fat at the terminal ileum and in the faeces.

Short-chain fatty acids, lactate, and ammonia in ileorectal and ileal pouch contents: a model of cecal fermentation

Fecal concentrations of total short-chain fatty acids were normal in 16 patients with ileorectal anastomoses (mean +/- SEM, 99.7 +/- 10.3 mmol/L) and 28 patients with ileal pouch-anal anastomoses (138.8 +/- 8.5 mmol/L) and did not differ from those in 14 healthy noncolectomized controls (130.7 +/- 12.6 mmol/L). Acetate:propionate:butyrate:isobutyrate+valerate+isovalerate ratios were similar in the ileorectum (71:12:12:5%) and in the colorectum (66:14:13:7%) of healthy noncolectomized controls, whereas the concentration of acetate was increased at the expense of the polypeptide-derived isobutyrate, valerate, and isovalerate in the ileal pouch (77:12:11:1%). Ammonia was accordingly significantly diminished in ileal pouch contents (28.8 +/- 3.2 mmol/L vs 45.2 +/- 4.1 mmol/L in controls) in contrast to concentrations in ileorectal contents (36.2 +/- 5.3 mmol/L). Concentrations of lactate were normal and low. Twenty-four-hour productions of total short-chain fatty acids in 16.6% fecal homogenates from both groups of patients were normal. Addition of saccharides (eg, glucose, starch, pectin, ispaghula husk) increased the production of acetate, propionate, and butyrate and decreased the production of ammonia and isobutyrate, valerate, and isovalerate, which was increased in homogenates with albumin added. This pattern of substrate fermentation was similar in homogenates from ileal pouch, ileorectum, and control colorectum. In conclusion, the concentrations of short-chain fatty acids, lactate, and ammonia indicate that ileorectal fermentation resembles normal colorectal fermentation in noncolectomized healthy individuals, whereas the fermentation in ileal pouch contents seems to be more carbohydrate predominated.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of wheat bran and pectin on the distribution of water in rat caecal contents and faeces

Wheat bran and pectin (100 g/kg) were added to a basal diet and fed to rats. An in vitro dialysis technique was used to measure the distribution of caecal and faecal water between the bound, i.e. that held by bacteria and undigested macromolecules, and free water. Bran increased wet (67%) and dry (74%) faecal weight. Pectin increased wet faecal weight (59%), but did not influence dry weight. In faeces both bran and pectin increased the amount of total and bound water, but only pectin increased total and bound water when expressed on a dry weight basis. Caecal wet (90%) and dry (67%) weights increased with pectin but not with bran. Bran did not change total water but increased bound water whereas pectin increased both. This suggests that water contributed more to the increase in stool bulk in the pectin-supplemented animals due to free and bound water associated with both increased numbers of bacteria and residual pectin. Pectin altered the distribution of water in faeces. Bran has no effect on water distribution and is only partly fermented. The residual water-holding capacity leads to an increased wet and dry stool output.

The dependence of the in vitro fermentation of dietary fibre to short-chain fatty acids on the contents of soluble non-starch polysaccharides

The fermentability of cellulose and dietary fibre in common clinical use (Inolaxol, Fiberform, Vi-Siblin, Lunelax, pectin) was measured as the in vitro production of short-chain fatty acids, lactate, and ammonia in 16.6% faecal homogenates from 18 healthy volunteers. The results were compared with the contents of soluble and insoluble non-starch polysaccharides as determined by the method of Englyst. The amounts of soluble non-starch polysaccharides in the fibre were closely associated with the mean productions of short-chain fatty acids after 6 h (R = 0.94, p < 0.002) and 24 h (R = 0.98, p < 0.0002) of incubation. The mean production of ammonia was inversely related to the soluble fraction of the fibre (after 6 h, R = -0.93, p < 0.003; after 24 h, R = -0.90, p < 0.006). These variables were not dependent on the insoluble fractions of the fibre. The in vitro fermentability differed considerably among the fibres: cellulose and Inolaxol (sterculia gum) were almost non-fermentable, Fiberform (wheat bran-based) was low-grade fermentable, Vi-Siblin and Lunelax (both ispaghula husk) were intermediately fermentable, and pectin was highly fermentable. These findings support that the water solubility determines the degree of fermentability of dietary fibre and thereby the corresponding bacterial assimilation of ammonia. In vitro measurements of short-chain fatty acid production in faecal homogenates may hence supplement commonly used methods to classify dietary fibre.

Dietary fiber, inulin, and oligofructose: a review comparing their physiological effects

Dietary fiber is a general term. It covers a wide variety of substances that belong to the family of carbohydrates that resist hydrolysis by human alimentary enzymes but are fermented by colonic microflora. The main physiological effects of dietary fiber are primarily on gastric emptying and small intestinal transit time, resulting in an improved glucose tolerance and a decreased digestion of starch: second, on colonic transit time and large bowel functions due to fermentation by ceco-colonic microbial flora or bulking action. The so-called soluble dietary fibers are fermented to a large extent by a wide variety of anaerobic bacteria that result in an increase in bacterial biomass, an increase in fecal mass, a change in intracolonic pH, and production of short chain fatty acids and various gases as metabolic end products. The insoluble fibers are only marginally fermented: they serve almost exclusively as bulking agents that result in shorter transit time and increased fecal mass. The short chain fatty acids resulting from the colonic fermentation of dietary fiber are largely absorbed via the portal blood and reach both the liver and the peripheral tissues. They induce changes in glucose and fat metabolism leading to post-prandial hypoglycemia and long-term hypolipidemia. Inulin and oligofructose are fructans with a degree of polymerization of 2 to 60 and 2 to 20, respectively. Due to the structural conformation of their osidic bridge (beta 2-1), they both resist the hydrolysis by human alimentary enzymes. Moreover, when reaching the colon, both inulin and oligofructose are almost quantitatively fermented almost exclusively by colonic bifidobacteria and bacteroides. Such an extensive fermentation causes an increase in fecal bacterial biomass, a decrease in ceco-colonic pH, and produces a large amount of fermentation products among which the short chain fatty acids that exert systemic effects on lipid metabolism. Thus, both inulin and oligofructose have most of the characteristics of a dietary fiber and the proposal is made to classify them as such. Moreover, they are bifidogenic factors, because, due to still unknown reasons, they are primarily fermented by bifidobacteria. It is concluded from this review that "nondigestible fructo-oligosaccharides," even though they are not included in the carbohydrate fraction that is quantified as dietary fiber by classic analytical methods, have most of the physiological effects of a dietary fiber.(ABSTRACT TRUNCATED AT 400 WORDS)

Determination of fermentable carbohydrate from the upper gastrointestinal tract by using colectomized rats

The primary aim of this study was to characterize the carbohydrate that would be supplied to the colon for fermentation under physiological conditions. Colectomized rats were fed fiber-free diets or diets containing 5% (wt/wt) gum arabic. Four (fucose, galactose, glucosamine, and galactosamine) of 11 analyzed sugars accounted for 77% of the total sugar in ileal excreta from colectomized rats fed fiber-free diets. The three sugars in gum arabic, rhamnose, arabinose, and galactose, accounted for 84% of the total sugars in gum arabic ileal excreta. Comparisons of the sugar compositions of the ileal excreta, the water-soluble fractions of the excreta, and three gel filtration fractions of the water-soluble material with those of the water-soluble fraction of rat mucosa, the acetone-soluble fraction of pancreas, and pancreatin suggested that the major source of endogenous carbohydrate is mucin. Gum arabic increased the daily excretion of the four mucin-derived sugars (fucose, galactose, glucosamine, and galactosamine) by the colectomized rats from 473 mumol per day to 634 mumol per day. We conclude that mucin is the major endogenous carbohydrate excreted from the upper gut and that gum arabic increases the amount of this endogenous carbohydrate.

Selection of optimal lipid sources in enteral and parenteral nutrition

The manipulation of dietary fat intake can affect the response to disease, injury, and infection. These effects include enhancement or inhibition of immune function, altered susceptibility to cardiovascular disease, promotion or maintenance of gut integrity, and prevention of total parenteral nutrition-induced hepatic dysfunction. These effects may occur as a result of changes in the fatty acid composition of biomembranes or changes in concentrations of lipid moieties such as prostaglandins or leukotrienes. Those fats that have been shown to affect physiologic function include long-chain, medium-chain, and short-chain fatty acids and omega-3 and omega-6 fatty acids. Currently available enteral and parenteral products used for nutrition support contain widely varied amounts of these different fatty acids. Therefore, the selection of the most appropriate product or nutrition support regimen for an individual patient requires an understanding of the metabolism of these different fat substrates, their therapeutic indications, and the contraindications and controversies that surround their use. This article reviews these issues and also focuses on several alternate lipid sources such as short-chain fatty acids, medium-chain fatty acids, omega-3 fatty acids, and blended and structured lipids.

Effects of dietary fibre and tannins from apple pulp on the composition of faeces in rats

The present study was undertaken to explore the effect of apple pulp on weight and composition of faeces. This material is rich in dietary fibre (DF; 620 g dry matter/kg) and contains appreciable amounts of polyphenols. Recent reports indicate that both condensed tannins (CT) and soluble polyphenols form cross-links with protein and inhibit digestive enzymes, affecting the protein digestibility, and may produce a stimulation of endogenous nitrogen excretion. Two groups of male Wistar rats were fed on either a control diet free of DF or a diet containing 100 g apple pulp DF/kg during 7 d after a 4 d adaptation period. Body-weight and food intake were monitored daily and faeces and urine were collected once daily. DF, water content and polyphenolic compounds were measured in faeces, and N content in both faeces and urine. Faecal weight increased in the fibre group by 280 and 240% when compared with wet and dry faecal weights of animals fed on the fibre-free diet. Soluble dietary fibre (SDF) excreted in faeces was 10.9% of the SDF ingested, which suggested a low resistance to fermentation of this fraction. Of the insoluble DF, 43% of the ingested fibre was fermented. Polyphenols were degraded in the intestinal tract. Of the ingested CT, 68.6% was recovered in faeces, while the soluble polyphenols were extensively degraded (85.7% of that ingested). On the other hand, a higher faecal N excretion was observed for the fibre-fed group, suggesting a decrease in the digestibility of the dietary protein and lower apparent digestibility of the dietary protein and lower apparent digestibility and N balance indices.

Effect of dietary fiber on the disposition and excretion of a food carcinogen (2-14C-labeled MeIQx) in rats

We studied to what extent dietary fiber may affect uptake, retention, and excretion of a food carcinogen (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, MeIQx) occurring in fried meat. Four diets--one fiber-free control and three containing either insoluble dietary fiber isolated from sorghum (100 g/kg) and wheat bran (100 g/kg) or the highly soluble pectin (50 g/kg)--were investigated. The fiber diets were given in amounts of 10 g/day to rats. Thus, each rat received 1 or 0.5 g fiber and 100 micrograms 2-14C-labeled MeIQx uniformly mixed in its daily diet. A 4-day adaptation period with unlabeled MeIQx was followed by a 5-day experimental period with 14C-labeled MeIQx, during which urine and feces were collected separately for analysis of radioactivity and mutagenicity. Furthermore the composition and the fermentability of the dietary fiber were determined. The present study shows that a diet containing fiber, especially fiber isolated from sorghum and wheat bran, affects the excretion pattern of the food carcinogen MeIQx in a manner suggesting a lower uptake and a decreased transit time through the gastrointestinal tract in a more diluted form than a nonfiber diet. Furthermore, less radioactivity was retained in the kidneys with sorghum and wheat bran than with the other two diets. On the other hand, none of these types of dietary fiber affected the retention of the hepatocarcinogen MeIQx in the liver 24 hours after the last oral intake. DNA adducts were formed to a higher extent in the kidney than in the liver. The highest levels were found in animals given the wheat bran diet.

[The determination of a gross utilization of 15N-lysine in laboratory rats. 1. Experiment with normal intestinal flora (without antibiotic supplement)]

Wistar rats of a live weight of about 100 g were divided into 14 groups (5 animals/group). The rations given supplied the animals with 75%, 100% and 125% lysine, which brought about a moderate growth of the animals of approximately 2 g/animal and day achieved by limited feeding. The 3 lysine levels mentioned could be achieved by lysine supplements (L-lysine-HCl) for the following rations: barley (B), wheat (W), and wheat gluten (WG). For isolated soybean protein (assay protein) (S) the lysine levels 100% and 125% and for soybean meal (SM) the levels 116% and 125% could only be achieved. A control group with whole egg ration (W) (with its natural lysine content of 125% of the requirement) were also tested as comparison. During the 10-day period of the main experiment all 14 rations were supplemented with 0.5 g 15N-lysine (alpha amino group, 95% labelled with 15N). The N balance could only be significantly improved by lysine supplements in the rations B, W and SM with the lysine level of 125%. The biologic value of the protein sources was in rations B and WG also significantly improved by the highest lysine supplement. 15N excess (15N') from the deaminated 15N lysine was excreted with diet B rich in crude fibre mainly in faeces (more than 15% of the intake) and only about 10% in urine. With the diets without native crude fibre the excretion quota changed in favour of urine. The following 15N' amounts in per cent of 15N' intake from lysine were excreted in urine and faeces: B 75 = 31.3, B 100 = 30.9, B 125 = 28.0, W 75 = 24.3, W 100 = 32.2, W 125 = 32.6, GW 75 = 18.3, WG 100 = 24.2, WG 125 = 28.1, S 100 = 39.4, S 125 = 50.4, SM 116 = 34.9, SM 125 = 32.9, W 125 = 19.1. 15N excretion in urine and faeces increased in comparable relations in 6 cases of lysine increase levels only. Gross utilization of lysine can only conditionally be quantified by 15N labelled lysine supplement.

Microcirculatory and trophic effects of short chain fatty acids in the human rectum after Hartmann's procedure

Short chain fatty acids (acetic, propionic and butyric) were instilled into the rectum of patients who had undergone Hartmann's procedure. The following parameters were examined before and after a 2-week treatment period with short chain fatty acids (100 ml twice daily at a total concentration of 150 mM): (1) microcirculatory effects in vivo using a laser Doppler flow technique, and (2) morphometrical changes in mucosal biopsies. The following parameters were significantly increased in all patients after treatment: (1) mucosal blood flow, (2) the fractional crypt cell epithelium plus surface epithelium volume in relation to total tissue volume down to the muscularis mucosa, (3) nuclear volume in the crypt and the surface epithelium, and (4) the fractional nuclear volume to total cell volume in the crypt and the surface epithelium. These data suggest that short chain fatty acids in the human colon have trophic and vasodilatory effects.

Plantago ovata seeds as dietary fibre supplement: physiological and metabolic effects in rats

In rats, the effects of a 4-week supplementation of a fibre-free elemental diet with 100 or 200 g Plantago ovata seeds/kg was compared with that of the husks and wheat bran. The seeds increased faecal fresh weight up to 100%, faecal dry weight up to 50% and faecal water content up to 50%. The husks, at the high concentration only, were more effective and wheat bran less effective. Length and weight of the small intestine were not greatly affected by the seeds, but both variables increased significantly in the large intestine. The husks had more pronounced effects, especially in the small intestine, and wheat bran almost no effect. Faecal bacterial mass as estimated from the 2,6-diaminopimelic acid output was increased to the greatest extent by the seed-containing diet and by the high concentration of husks, but to a lesser extent by wheat bran. Faecal and caecal protein content was enhanced by the seeds and wheat bran, but to a lesser extent by the husks. Total acetate in caecal contents or faeces was highest on the seeds and husks diet and not elevated by wheat bran. Total faecal bile acid excretion was stimulated and beta-glucuronidase (EC 3.2.1.31) activity reduced by both Plantago ovata preparations, but not by wheat bran. Mucosal digestive enzyme activities were inhibited to different degrees by all dietary fibres in the jejunum, and sometimes activated in the ileum. These results suggest that Plantago ovata seeds are a partly-fermentable dietary fibre supplement which increases stool bulk; metabolic and mucosa-protective effects are also probable.

Nutrient digestibilities in ingredients fed alone or in combinations

Digestibility coefficients (DC) of protein, dry matter, energy, starch, and dietary fibre in individual feedstuffs were used to predict the DC in feed mixtures. Digestibility studies with growing rats involved six feed sources: soya-bean meal, barley, rapeseed meal, peas, wheat bran and wheat, given individually and in various combinations, i.e. fourteen diets in total. True digestibility of protein (TD) and apparent digestibility of starch could be predicted in feed mixtures from their respective DC values for the individual ingredients, except in the diet composed of peas + barley. Dry matter (DM) and insoluble dietary fibre digestibilities in the mixtures could also be calculated from their individual DC values. Energy digestibility could be predicted in all mixtures except for barley + wheat and peas + wheat. Although the discrepancies were significant, the differences were not great. The digestibility of soluble dietary fibre in the mixtures could be predicted as for the individual ingredients in all but three diets: rapeseed meal + barley, peas + barley and peas + wheat. The results confirm that DC values for TD, DM, energy, starch and dietary fibre in mixtures can be calculated with high precision from DC determined from individual ingredients. Caution should be taken though when mixtures contain a high amount of dietary fibre, especially of the soluble type.

Fermentability of various fiber sources by human fecal bacteria in vitro

Certain beneficial effects of fiber in the human diet may be mediated by short-chain fatty acids (SCFAs) produced during anaerobic fermentation in the colon. Two studies, both involving in vitro incubations with human fecal bacteria as inoculum, were conducted to assess fermentation of various fiber sources and to quantitate the SCFAs produced. In experiment 1, substrate fermentability based on total SCFA production ranked as follows: citrus pectin greater than soy fiber greater than sugarbeet fiber greater than pea fiber greater than oat fiber. Fermentation of soy fiber led to higher proportions of propionate and butyrate than did fermentation of other substrates. In experiment 2, fermentation of gum arabic, a mixture of arabic and guar, and apple pectin resulted in greater SCFA production than did fermentation of either oat fiber or corn bran. Fermentation of gums led to more propionate and butyrate production than did that of apple pectin. It may be possible to select fiber sources capable of supporting stipulated amounts of both total and individual SCFA production in the human colon.

Energy values and energy balance in rats fed on supplements of guar gum or cellulose

In five experiments where guar gum (GG) or Solka-floc cellulose (SF) supplemented a semi-synthetic diet (100 g/kg) for male Wistar rats at 21 degrees, it was found that GG acutely depressed both ad lib. and meal-fed food intakes by 40-50%. The effect was temporary, with the GG having no effects on food intake in the longer term. Dietary energy balance over 28 d with animals fed on equal amounts of a basal ration showed partial digestible energy values, calculated from the intake and faecal loss of energy, for the supplements which averaged 0 kJ/g SF and 10 kJ/g GG, so that GG contributed substantial amounts of absorbable energy. Despite this additional energy from GG, there was very often no additional gain of body fat. Rather, in some experiments, fat deposition was actually decreased by supplementation with GG. GG is inferred to have a putative thermogenic effect which is often greater than the energy it supplies. This effect occurred to a greater extent in circumstances associated with a higher 'energy status', indicated by higher efficiencies of conversion of gross dietary energy to retained body energy, higher fat:lean tissue deposition ratios and the occurrence of larger deposits at the epididymal fat pad site. There was some evidence that deposition at this site was more extensively affected by GG than deposition of fat in the body as a whole. Possible implications of the present findings are discussed.

Gastrointestinal implications in pigs of wheat and oat fractions. 1. Digestibility and bulking properties of polysaccharides and other major constituents

The present work was undertaken to study the gastrointestinal effects of wheat and oat dietary fibre (DF) using 40-50 kg pigs cannulated in the terminal ileum. The variables studied were: chemical characteristics of the DF, ileal and faecal digestibility of nutrients and bulking properties of polysaccharides and other major constituents. The wheat products studied included refined wheat flour and wheat fractions rich in the following botanical components: aleurone, pericarp/testa and bran. The oat products used were rolled oats and oat bran. The products varied considerably in DF content (g/kg dry matter) and composition; non-starch polysaccharides (NSP) and Klason lignin content ranged from 34 and 1 g/kg respectively in wheat flour, to 465 and 92 g/kg in pericarp/testa. The main NSPs in the wheat were arabinoxylans (AX) (64-69%) and cellulose (15-31%) and in oats mixed linked beta(1----3; 1----4-D-glucans (beta-glucans; 46-63%) and AX (28-32%). The lowest content of soluble NSP was found in the lignified wheat fractions (bran and pericarp/testa) and the highest in oat bran. Eight diets were produced using the wheat and oat products and studied in two series of experiments using wheat flour as the DF-depleted control. The diets in Expt 1 were based on wheat flour and three iso-DF enriched diets prepared by adding DF from the fractions rich in wheat aleurone, pericarp/testa or bran. In Expt 2, oat bran was added to wheat flour to achieve the same DF intake level as in Expt 1. This series also included diets based on rolled oats and rolled oats plus oat bran. Starch was almost completely digested in the small intestine (0.97-1.00). However, there was a tendency to a slightly lower digestibility of oat starch compared with wheat starch. The recovery of wheat NSP in ileal digesta was 82-104% compared with 64-66% for oats. The low recovery of NSP in oat diets was primarily due to the low recovery of beta-glucans (25-36%). In the large intestine NSP and starch residues were extensively degraded. For the DF-depleted control diets or diets based on oats, 8-17% NSP survived breakdown while in the diets enriched with aleurone, pericarp/testa or bran fractions, NSP recovery was 33, 50 and 38% respectively. Fermentative breakdown of carbohydrates in the large intestine was estimated to contribute between 10 and 24% of the energy for maintenance. Energy derived from the inflow of organic acids from the ileum contributed an additional 1-4% of maintenance energy.(ABSTRACT TRUNCATED AT 400 WORDS)

The biological effects and digestible energy value of a sugar-beet fibre preparation in the rat

A sugar-beet fibre preparation (SBF) was incorporated into a semi-synthetic rat diet at a level of 100 g/kg. The material caused no feed aversion, and gain of live weight was unimpaired. SBF appeared to be slightly more fermentable than wheat bran and only marginally less effective as a faecal bulking agent when compared with equalized intakes of non-starch polysaccharide. SBF did not stimulate mucosal cell turnover in the small intestine. Some enlargement of the caecum was observed in animals given SBF, but it was no greater than that of animals given wheat bran. Animals given SBF had a lower serum cholesterol concentration than both the fibre-free controls and those given wheat bran. This hypocholesterolaemic effect was less than that of guar gum however. The partial digestibility of energy for SBF was 0.64, and its partial digestible energy value was 11.3 kJ (2.7 kcal)/g. The partial digestibility of energy for non-starch polysaccharide in SBF was estimated to be 0.53 and its partial digestible energy value was 9.1 kJ (2.2 kcal)/g. This value was not significantly different from that expected for unavailable carbohydrate in mixed human diets.

The influence of pre- and postnatal caloric intake on colon carcinogenesis

Mother rats were allowed to litter under conventional conditions. They were fed a complete, semipurified diet during gestation, and at time of littering the numbers of pups were reduced to either eight per litter or four per litter in two additional groups. At weaning, all rats were continued on the same diet that their mothers had consumed. One group of those reduced to four per litter at birth was allowed to continue to eat ad libitum while the other group, reduced to four per litter, was pair fed to the ad libitum eight per litter group. The group reduced to four per litter at birth and allowed to eat ad libitum during postnatal life gained the most weight and were heaviest at the termination of the study. This group also had the greater incidence and frequency of colon tumors when exposed to dimethylhydrazine (DMH). The group pair fed to rats fed conventional diets, eight rats per litter, had an incidence and frequency of tumors between the other two groups. These data demonstrate that early exposure to excess calories increased risk for cancer and that early and late excess caloric intake further increased risk. Thus, pre- and perinatal caloric intake may have a significant influence on susceptibility to cancer later in life. Mechanisms are only speculative but may include differences in metabolism and modulation of hormonal balance.

Utilization of alpha-amylase (EC 3.2.1.1) resistant maize and pea (Pisum sativum) starch in the rat

1. The extent of utilization of alpha-amylase (EC 3.2.1.1)-resistant retrograded starches in vivo was assessed in male Wistar rats (about 100 g body-weight). All animals were given a fibre-free semi-synthetic basal diet (SS) containing sucrose as the only carbohydrate source, ad lib., for 13 d. On day 14, after an overnight fast, rats were allocated to one of five dietary treatments (n 30):1, fibre-free basal SS diet; 2-5, basal SS diet supplemented with 100 g sucrose, Solka floc (cellulose), resistant maize starch (RCS) or resistant pea (Pisum sativum) starch (RPS)/kg diet. Animals allocated to each dietary treatment were divided into three groups of ten rats which were given the appropriate diet for 8 or 9, 17 or 18 and 29 or 30 d (8/9, 17/18 or 29/30 d groups respectively). Rats were fed on 12 g diet/d (treatment 1) or 13.2 g diet/d (treatments 2-5) for the first 20 d, and 14 or 15.4 g/d respectively until the end of the experiment. Rats fed on the supplemented basal diets were thus given 10% more food to allow for the addition of the test carbohydrate. Faecal carbohydrate excretion was determined at intervals in the 17/18 d groups. At the end of each experimental period animals were killed after consuming their daily food ration and small intestinal length, weight of caecal and ileal contents and tissue, and pH of caecal contents measured. The amount of carbohydrate in the caecal and ileal contents from the 8/9 and 17/18 d groups was determined. 2. Weights of ileal and caecal contents, caecal tissue and faecal output were significantly greater at all time points for rats fed on the resistant starches compared with those fed on basal and sucrose-supplemented diets. Values were higher for RPS-fed rats than for RCS-fed rats. 3. The quantity of carbohydrate recovered from ileal and caecal contents showed that both RCS and RPS were partially digested and absorbed as carbohydrate, but that RPS was digested to a lesser extent. 4. The concentration of carbohydrate decreased between the ileal and caecal sites when RPS and RCS were given but was essentially unchanged when cellulose was given. This is consistent with rapid fermentation of a fraction of these starches. 5. Faecal carbohydrate elimination in the 17/18 d groups fed on RCS and RPS declined with time, which suggested an adaptive response resulting in increased utilization of the starches. This adaptive response was slower in the RPS-fed rats than the RCS-fed rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Stimulation of intestinal mucosal growth with intracolonic infusion of short-chain fatty acids

Dietary fiber, which stimulates intestinal mucosal growth, is fermented by anaerobic bacteria in the rat hindgut to the short-chain fatty acids (SCFA) acetate, propionate, and butyrate. Butyrate is the preferred oxidative fuel of the colonocyte in vitro, and the provision of preferred intestinal fuels has been shown to stimulate mucosal proliferation in vivo. This study determined whether chronic colonic infusion of butyrate or a combination of SCFA would stimulate intestinal mucosal growth in an animal deprived of its normal source of SCFA, fiber fermentation in the cecum. Adult male Sprague-Dawley rats were fed a fat- and fiber-free elemental liquid diet and underwent cecectomy, ileocolic anastomosis, and insertion of a proximal colonic infusion catheter. Rats were then assigned to receive either a continuous infusion of butyrate (20 mM, 40 mM, or 150 mM), SCFA (70 mM acetate + 35 mM propionate + 20 mM butyrate), or saline, or to receive no infusion. A seventh group underwent proximal colonic transection and reanastomosis. After 7 days, jejunal, ileal, and proximal colonic segments were analyzed for mucosal weight, protein, RNA, and DNA. In the colon, the 40-mM butyrate infusion resulted in significant elevations in all mucosal parameters relative to all three control groups, saline infusion, no infusion, and transection. Both the 20-mM butyrate and the SCFA groups showed increased colonic mucosal DNA compared to controls. In the jejunum and ileum, mucosal DNA content was significantly greater in the SCFA group than in the control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

[The influence of different fiber types on the fecal nitrogen excretion and the content of volatile fatty acids in the feces of broiler hen breeds]

4 colostomized adult broiler breeding hens each received 120 g mixed feed per day. In addition, the animals were given 10, 20, 30 and 40 g/day cellulose powder or apple pectin resp. and 10, 20, 30 g/day straw cellulose. The DM content of the faeces was increased by cellulose powder and decreased by pectin (P less than 0.01) in comparison to the control group. DM excretion in g/animal and day increased more quickly after supplementing cellulose powder than after supplementing pectin. Straw cellulose produced results in between. The fibre supplements increased N excretion in faeces. It was, however, only significantly increased per 100 g DM intake by large pectin supplements (greater than 20 g). The TCA soluble N quota in the total N of the faeces remained largely unchanged after pectin supplements and increased after cellulose and straw cellulose supplements. Pectin supplements significantly increased the formation of acetate, propionate and butyrate in comparison to the other groups. Propionate could sporadically be detected in the faeces of the other test animals, butyrate not at all. In combination with 40 g apple pectin/animal and day, Bisergon (chinoxalin derivative) increased the formation of the 3 volatile fatty acids significantly.

Effect of parenteral nutrition supplemented with short-chain fatty acids on adaptation to massive small bowel resection

After massive small bowel resection, total parenteral nutrition (TPN) is prescribed to maintain nutritional status. However, TPN reduces the mass of the remaining intestinal mucosa, whereas adaptation to small bowel resection is associated with increased mucosal mass. Short-chain fatty acids (SCFAs) have been shown to stimulate mucosal cell mitotic activity. This study determined whether the addition of SCFAs to TPN following small bowel resection would prevent intestinal mucosal atrophy produced by TPN. Adult rats underwent an 80% small bowel resection and then received either standard TPN or TPN supplemented with SCFAs (sodium acetate, propionate, and butyrate). After 1 wk, jejunal and ileal mucosal weights, deoxyribonucleic acid, ribonucleic acid, and protein contents were measured and compared with the parameters obtained at the time of resection. Animals receiving TPN showed significant loss of jejunal mucosal weight, deoxyribonucleic acid, ribonucleic acid, and protein and ileal mucosal weight and deoxyribonucleic acid after small bowel resection, whereas animals receiving SCFA-supplemented TPN showed no significant change in the jejunal mucosal parameters and a significant increase in ileal mucosal protein. These data demonstrate that SCFA-supplemented TPN reduces the mucosal atrophy associated with TPN after massive bowel resection and thys may facilitate adaptation to small bowel resection.

Fermentation of wheat bran and gum arabic in rats fed on an elemental diet

1. Gum arabic and wheat bran were added to an elemental diet (100 g/kg) in order to study their metabolism in the caeca of adult male albino Wistar rats. 2. Dry stool weight (g/d) over 12 weeks was 0.70 (SE 0.05) on the elemental control diet. Wheat bran increased mean dry stool weight to 1.09 (SE 0.08), an increase of 56%. There was no significant difference between faecal weights (0.65 (SE 0.08)) of the gum-arabic-supplemented group and the unsupplemented group. 3. Wet caecal-sac weight, dry caecal-contents weight, and faecal and caecal bacterial mass (measured by 2,6-diaminopimelic acid) all increased significantly with the gum-arabic-supplemented diet but not with the wheat-bran-supplemented diet. 4. Total short-chain fatty acids (mostly acetate) increased in the caecum and faeces with the gum-arabic-supplemented diet but not with the wheat-bran-supplemented diet. 5. Breath hydrogen and methane production decreased to negligible amounts over the 12 weeks of the experiment.