The effect of pectin on the structure and function of the rat small intestine

The Severity of DSS-Induced Colitis Is Independent of the SCFA-FFAR2/3-GLP-1 Pathway Despite SCFAs Inducing GLP-1 Secretion via FFAR2/3

Short-chain fatty acids (SCFAs) are the major microbial metabolites produced from the fermentation of dietary fiber in the gut. They are recognised as secretagogues of the glucagon-like peptides, GLP-1 and GLP-2, likely mediated by the activation of free fatty acid receptors 2 and 3 (FFAR2 and 3) expressed on enteroendocrine L-cells. Fiber-deficient diets are associated with decreased intestinal function and decreased colonic GLP-1 and GLP-2 content. Here, we speculated that the lowered colonic GLP-1 observed following a fiber-free diet was a consequence of decreased SCFA production and a subsequent decrease in FFAR2/3 activation. Furthermore, we explored the consequences of a fiber-free diet followed by intestinal injury, and we mechanistically explored the SCFA-FFAR2/3-GLP-1 pathway to explain the increased severity. Colonic luminal content from mice fed either a fiber-free or chow diet were analysed for SCFA content by LC-MS. FFAR2/3 receptor contributions to SCFA-mediated colonic GLP-1 secretion were assessed in isolated perfused preparations of the colon from FFAR2/3 double knockout (KO) and wild-type (WT) mice. Colitis was induced by the delivery of 3% dextran sulfate sodium (DSS) for 4 days in the drinking water of mice exposed to a fiber-free diet for 21 days. Colitis was induced by the delivery of 3% DSS for 7 days in FFAR2/3 KO mice. The removal of dietary fiber significantly decreased SCFA concentrations in the luminal contents of fiber-free fed mice compared to chow-fed mice. In the perfused colon, luminal SCFAs significantly increased colonic GLP-1 secretion in WT mice but not in FFAR2/3 KO mice. In the DSS-induced colitis model, the removal of dietary fiber increased the severity and prevented the recovery from intestinal injury. Additionally, colitis severity was similar in FFAR2/3 KO and WT mice after DSS application. In conclusion, the results confirm that the removal of dietary fiber is sufficient to decrease the colonic concentrations of SCFAs. Additionally, we show that a fiber-free diet predisposes the colon to increased intestinal injury, but this effect is independent of FFAR2 and FFAR3 signalling; therefore, it is unlikely that a fiber-free diet induces a decrease in luminal SCFAs and sensitivity to intestinal disease involves the SCFA-FFAR2/3-GLP-1 pathway.

Pectin Modulates Calcium Absorption in Polarized Caco-2 Cells via a Pathway Distinct from Vitamin D Stimulation

Pectin, a type of soluble fiber, promotes morphological changes in the small intestinal villi. Although its physiological significance is unknown, we hypothesized that changes in villus morphology enhance the efficiency of nutrient absorption in the small intestine and investigated the effect of pectin derived from persimmon on calcium absorption using polarized Caco-2 cells. In polarized Caco-2 cells, pectin altered the mRNA expression levels of substances involved in calcium absorption and the regulation of intracellular calcium concentration and significantly reduced calcium absorption. Although this was comparable to the results of absorption and permeability associated with the addition of active vitamin D, the simultaneous action of pectin and active vitamin D did not show any additive effects. Furthermore, as active vitamin D significantly increases the activity of intestinal alkaline phosphatase (ALP), which is known to be involved in the regulation of intestinal absorption of calcium and lipids, we also investigated the effect of pectin on intestinal ALP activity. As a result, it was found that, unlike the effect of active vitamin D, pectin significantly reduced intestinal ALP activity. These results suggest that pectin stimulates polarized Caco-2 cells through a mechanism distinct from the regulation of calcium absorption by vitamin D, modulating total calcium absorption from the elongated villi through morphological changes in the small intestine by suppressing it at the cellular level.

Arabinogalactan in the side chain of pectin from persimmon is involved in the interaction with small intestinal epithelial cells

Pectin in Diospyros kaki (persimmon) is a complex polysaccharide and is classified as a dietary fiber. Pectin is characterized by the presence of side chains of neutral sugars, such as galactose residues; however, the structure and properties of these sugars vary greatly depending on the plant species from which it is derived. Here, we report the structural features of pectin extracted from persimmon. The polysaccharide was low-methoxy pectin with a degree of methyl esterification <50% and ratio of side chain galactan to arabinan in the rhamnogalacturonan-I region of pectin of 3-20. To investigate the physiological function of pectin from persimmon, we performed a coculture assay using Caco-2 cells. As a result, it was shown that the proliferation of undifferentiated Caco-2 cells was promoted, and further, the importance of arabinogalactan among the pectin structures was shown.

"Dysfunctions" induced by Roux-en-Y gastric bypass surgery are concomitant with metabolic improvement independent of weight loss

Metabolic surgery has been increasingly recommended for obese diabetic patients, but questions remain as to its molecular mechanism that leads to improved metabolic parameters independently of weight loss from a network viewpoint. We evaluated the role of the Roux limb (RL) in Roux-en-Y gastric bypass (RYGB) surgery in nonobese diabetic rat models. Improvements in metabolic parameters were greater in the long-RL RYGB group. Transcriptome profiles reveal that amelioration of diabetes state following RYGB differs remarkably from both normal and diabetic states. According to functional analysis, RYGB surgery significantly affected a major gene group, i.e., the newly changed group, which represented diabetes-irrelevant genes abnormally expressed after RYGB. We hypothesize that novel "dysfunctions" carried by this newly changed gene group induced by RYGB rebalance diabetic states and contribute to amelioration of metabolic parameters. An unusual increase in cholesterol (CHOL) biosynthesis in RL enriched by the newly changed group was concomitant with ameliorated metabolic parameters, as demonstrated by measurements of physiological parameters and biodistribution analysis using [14C]-labeled glucose. Our findings demonstrate RYGB-induced "dysfunctions" in the newly changed group as a compensatory role contributes to amelioration of diabetes. Rather than attempting to normalize "abnormal" molecules, we suggest a new disease treatment strategy of turning "normal" molecules "abnormal" in order to achieve a new "normal" physiological balance. It further implies a novel strategy for drug discovery, i.e. targeting also on "normal" molecules, which are traditionally ignored in pharmaceutical development.

Ovines submitted to diets containing cassava foliage hay and spineless cactus forage: histological changes in the digestive and renal systems

The aim of this study was to evaluate the histological alterations in the digestive and renal systems of 35 male ovines in Paraíba, Brazil, at around 16 ± 1.87 kg submitted to the following treatments for 90 days (15 of adaptation + 75 of experimental period): 1- Tifton hay (TH); 2- Cassava foliage hay (CH); 3-35% TH and 35% CH; 4-35% TH and 35% forage palm (FP), and 5-35% CH and 35% FP, based on dry matter (DM). Samples of the liver, kidney, rumen, and small intestine were histomorphometrically evaluated and the data were submitted to ANOVA analysis and Tukey post test at p ≤ 0.05. The use of alternative foods in the voluminous fraction (CH + FP) in the ovine diets did not compromise the performance of the animals; on the contrary, promoted better gain when compared with TH treatment (18.55 kg vs 9.42 kg). The CH + FP diet had a positive effect on papilla height. The papilla width decreased with the diets CH + FP and TH + FP. The thickness of the ruminal muscular layer were higher in the diets containing TH + CH and CH + FP. The keratinized layer of the ruminal epithelium was larger in the diet containing CH and FP. The villi of the intestinal crypts were deeper in the diets with FP and the villus/crypt ratio was the same in all diets. Goblet cells decreased with the CH or FP diet. Some renal changes were observed according to the diets, mainly when using FP. It is recommended to use CH and FP as a large fraction of the ovines diet, which will not alter animal performance.

Nutritional Implications of Dietary Interactions: A Review

A large number of dietary interactions have been described. Of these, only a relatively small number have been proved of relevance for human nutrition under the conditions of real diets. These interactions most often occur at the intestinal lumen, but they may also take place during utilization or storage of nutrients. Traditional diets of developing countries, which usually include non-refined cereals and other sources of fibre, may inhibit the bioavailability of mineral nutrients, contributing to specific deficiencies. Drug-nutrient interactions may also impact on nutritional status, particularly in population groups such as the elderly, who frequently receive prolonged medication and may have an inadequate food intake.

Enteral approaches in malabsorption

Enteral autonomy and freedom from parenteral nutrition dependency is the ultimate therapeutic goal in children with intestinal failure. This can be achieved following attainment of bowel adaptation in conditions such as short bowel syndrome. Enteral nutrition is a major therapeutic cornerstone in the management of children with intestinal failure. It promotes physiological development, bowel adaptation and enhances weaning from parenteral nutrition. The optimal method of delivery, type of nutrients, timing of initiation, promotion of feeds and transition to solid food in children with short bowel syndrome are debated. Lack of high quality human data hampers evidence based conclusions and impacts daily practices in the field. Clinical approaches and therapeutic decisions are regularly influenced by expert opinion and center practices. This review summarizes the physiological principles, medical evidence and practice recommendations on enteral nutrition approaches in short bowel syndrome and provides a practical framework for daily treatment of this unique group of patients. Oral and tube feeding, bolus and continuous feeding, type of nutrients, formulas, trace elements and solid food options are reviewed. Future collaborative multicenter, high quality clinical trials are needed to support enteral nutrition approaches in intestinal failure.

Dose-dependent effects of a soluble dietary fibre (pectin) on food intake, adiposity, gut hypertrophy and gut satiety hormone secretion in rats

Soluble fermentable dietary fibre elicits gut adaptations, increases satiety and potentially offers a natural sustainable means of body weight regulation. Here we aimed to quantify physiological responses to graded intakes of a specific dietary fibre (pectin) in an animal model. Four isocaloric semi-purified diets containing 0, 3.3%, 6.7% or 10% w/w apple pectin were offered ad libitum for 8 or 28 days to young adult male rats (n = 8/group). Measurements were made of voluntary food intake, body weight, initial and final body composition by magnetic resonance imaging, final gut regional weights and histology, and final plasma satiety hormone concentrations. In both 8- and 28-day cohorts, dietary pectin inclusion rate was negatively correlated with food intake, body weight gain and the change in body fat mass, with no effect on lean mass gain. In both cohorts, pectin had no effect on stomach weight but pectin inclusion rate was positively correlated with weights and lengths of small intestine and caecum, jejunum villus height and crypt depth, ileum crypt depth, and plasma total glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) concentrations, and at 8 days was correlated with weight and length of colon and with caecal mucosal depth. Therefore, the gut's morphological and endocrine adaptations were dose-dependent, occurred within 8 days and were largely sustained for 28 days during continued dietary intervention. Increasing amounts of the soluble fermentable fibre pectin in the diet proportionately decreased food intake, body weight gain and body fat content, associated with proportionately increased satiety hormones GLP-1 and PYY and intestinal hypertrophy, supporting a role for soluble dietary fibre-induced satiety in healthy body weight regulation.

Health properties of oca (Oxalis tuberosa) and yacon (Smallanthus sonchifolius)

Andean roots and tubers are underexploited crops; many contain compounds beneficial to health, so a greater knowledge of their properties is important for encouraging their consumption.

Modulation of the intestinal environment, innate immune response, and barrier function by dietary threonine and purified fiber during a coccidiosis challenge in broiler chicks

Coccidiosis is a major contributor to economic losses in the poultry industry due to its detrimental effects on growth performance and nutrient utilization. We hypothesized that the combined effects of supplemental dietary Thr and purified fiber may modulate the intestinal environment and positively affect intestinal immune responses and barrier function in broiler chicks infected with Eimeria maxima. A Thr-deficient basal diet (3.1 g of Thr/kg of diet) was supplemented with 70 g/kg of silica sand (control) or high-methoxy pectin and 1 of 2 concentrations of Thr (1.8 or 5.3 g/kg of diet; 4 diets total), and fed to chicks from hatch to d 16 posthatch. On d 10 posthatch, chicks received 0.5 mL of distilled water or an acute dose of Eimeria maxima (1.5 × 10(3) sporulated oocytes) with 6 replicate pens of 6 chicks per each of 8 treatment combinations (4 diets and 2 inoculation states). Body weight gain, feed intake, and G:F increased (P < 0.01) with addition of 5.3 g of Thr/kg of diet. Eimeria maxima schizonts were present only in intestinal tissue sampled from infected birds (P < 0.01). Weights of cecal digesta were highest (P < 0.01) in pectin-fed birds, and ceca with the heaviest weights also had the highest concentrations of total short-chain fatty acids. Expression of interleukin-12 in ileal mucosa was highest (P < 0.01) in infected birds receiving the control diet with 5.3 g of supplemental Thr/kg. In cecal tonsils, interferon-γ expression was highest in infected birds receiving the control diet (fiber × infection, P < 0.05); interferon-γ expression was lowest in infected birds fed the high Thr diet (Thr × infection, P < 0.05). There were no differences due to infection or Thr supplementation for cytokine expression in birds fed pectin-containing treatments. Overall, we conclude that although pectin has some protective function against coccidiosis, Thr supplementation had the greatest effect on intestinal immune response and maintenance of near normal growth in young broiler chicks infected with E. maxima.

Recovery of duodenal villi and cells in chickens refed protein, carbohydrate and fat

1. To clarify how histological recovery of villi and cells would be affected after refeeding single nutrients such as protein, carbohydrate and fat, male chickens were divided as follows: (1) intact control fed ad libitum a commercial finisher mash diet (CP, 140 g; ME, 11.71 MJ/kg, ALM), (2) 3 d feed withdrawal (FW), (3) FW followed by one day ad libitum free access to the mash diet (FW-ALM), and FW followed by one day force-feeding of (4) a commercial finisher pellet diet (FW-FFM) and an isocaloric diet of (5) a protein (FW-FFP), (6) a carbohydrate (FW-FFC) or (7) a fat (FW-FFF). 2. After refeeding, the formula diet groups increased in villus height and villus area and tended to increase in cell area and cell mitosis. Furthermore, flat cells on the villus tip in the F group developed to dome-shaped cells. This suggests that nutritionally well-balanced diets can induce histological recovery at villus and cellular levels. 3. Not all of the single nutrient groups recovered to the extent of the formula diet groups in all light microscopic variables after refeeding, suggesting that a single nutrient cannot induce histological recovery of the villus. 4. However, the dome-shaped cells were more distributed on the villus tip in these single nutrient groups than in the well-balanced formula diet groups, although cell diameter of the former groups was smaller than that of the latter. This suggests that the single nutrients would be effectively absorbed from cells and can induce histological recovery at the cellular level.

Natural bioactive compounds of Citrus limon for food and health

Citrus genus is the most important fruit tree crop in the world and lemon is the third most important Citrus species. Several studies highlighted lemon as an important health-promoting fruit rich in phenolic compounds as well as vitamins, minerals, dietary fiber, essential oils and carotenoids. Lemon fruit has a strong commercial value for the fresh products market and food industry. Moreover, lemon productive networks generate high amounts of wastes and by-products that constitute an important source of bioactive compounds with potential for animal feed, manufactured foods, and health care. This review focuses on the phytochemistry and the analytical aspects of lemon compounds as well as on the importance for food industry and the relevance of Citrus limon for nutrition and health, bringing an overview of what is published on the bioactive compounds of this fruit.

Food viscosity as determinant for adaptive growth responses in rat intestine: long-term feeding of different hydroxyethyl celluloses

Carbohydrate gelling agents can be regarded as being representative for the soluble and viscous fractions of dietary fibre. Their dietary concentration affects the consistency of the ingested food as well as the dilution of nutrients and energy. By feeding hydroxyethyl cellulose (HEC) differing in molecular mass, and thus in its viscosity properties, only the consistency of the diet was modified. Three HEC (of low (LV), medium (MV) and high viscosity (HV)) were employed in a 6-week feeding study with female rats to evaluate the effect of the viscosity on adaptive responses of intestinal growth variables. Each of the HEC was added in three increasing concentrations (8, 16, and 32 %, w/w) to a fibre-free control diet to yield nine test groups besides a fibre-free and an additional, fibre-rich, cereal-based control group. Except for the highest concentration of the high viscosity product (32 % HV-HEC), the dilution of the energy density of the diet was almost completely compensated by an increased food intake. With the same exception, energy utilisation was not impaired and, therefore, body-weight gains in the test groups were not significantly different from that in the control. Most other changes, e.g. increases in small intestinal length, mucosal DNA content, caecal and colonic weight, not only depended on the dietary concentration but also on the viscosity of HEC in a manner that either increasing the viscosity at a given dietary concentration or increasing the dietary concentration at a given viscosity led to the same results. These findings clearly prove the important role of the viscosity of the lumen content, as a mere physico-chemical factor, in determining adaptative growth responses in the intestinal tract of rats.

Dietary pectin stimulates protein metabolism in the digestive tract

OBJECTIVE

The aim of this study was to determine if protein metabolism was altered in small and large intestines by feeding pectin, a soluble fiber known to stimulate cecal production of short-chain fatty acids (SCFAs) and to have a trophic effect in these tissues.

METHODS

Twenty-four weanling male Sprague-Dawley rats were fed ad libitum for 14 d with a balanced control diet or an isoproteic, isocaloric pectin (citrus) diet (80 g/kg). SCFA production, intestinal histomorphometry, and protein synthesis were determined in the proximal and distal parts of the small intestine, the cecum, and the colon. Protein synthesis rates were determined by measuring the (13)C valine incorporation rate in tissue proteins.

RESULTS

Pectin feeding slightly decreased food intake and growth rate. It increased the acetate, propionate, and butyrate pools in the cecum. Pectin feeding resulted in heavier intestinal tissues corresponding to higher villus height in the small intestine and crypt depth in the small and large intestines compared with feeding of the control diet. Compared with the control group, the rats fed the pectin diet had significantly higher protein synthesis rates in all the parts of their intestines.

CONCLUSION

Supplementation of pectin, as a soluble fiber, in the diets, stimulated SCFA production, had a trophic effect on the different parts of the intestines, and greatly stimulated protein synthesis in those tissues.

Partially hydrolysed guar gum supplemented comminuted chicken diet in persistent diarrhoea: a randomised controlled trial

BACKGROUND

Partially hydrolysed guar gum (Benefiber) added to a diet is fermented in the colon, producing short chain fatty acids, which improve intestinal function, including colonic salt and water absorption.

AIMS

To evaluate the effect of Benefiber supplemented comminuted chicken diet in the treatment of persistent diarrhoea.

METHODS

One hundred and sixteen children (aged 5-24 months), presenting to Dhaka Hospital with a history of watery diarrhoea for more than 14 days (persistent diarrhoea), were randomised to receive either: (1) comminuted chicken diet with Benefiber (study diet); or (2) comminuted chicken diet without Benefiber (control diet). The study period was seven days.

RESULTS

Of 116 children, 57 received the study diet and 59 received the control diet. Diarrhoea resolved in a greater number of children with the study than with the control diet (46/55 (84%) v 36/58 (62%); odds ratio 3.12, 95% CI 1.19 to 8.4). Survival analysis for the duration of diarrhoea also showed a reduced duration of diarrhoea in children receiving the study diet. There was also a trend in daily stool reduction in children receiving the study diet, significant on days 4-7.

CONCLUSION

Results show that Benefiber supplemented comminuted chicken diet enhances recovery of children with persistent diarrhoea, indicating its therapeutic potential.

The effect of two different blends of essential oil components on the proliferation of Clostridium perfringens in the intestines of broiler chickens

The effect of 2 different blends of essential oils on Clostridium perfringens (Cp) in the intestine and feces of broiler chickens was tested in 6 field trials for each blend. One hundred parts per million of the blends were mixed in a commercial corn-based diet throughout the entire growing period for experimental flocks. Samples from the jejunum, cecum, cloaca, and feces were taken on d 14, 21, and 30 from experimental and control flocks and tested quantitatively for Cp via blood agar plate, litmus milk medium, and ELISA. Blend A reduced (P < or = 0.05) the average Cp concentration in the feces on all sampling days, in the jejunum and cecum on d 14 and 21, and in the cloaca on d 14. Blend B effected a significant reduction of Cp concentration in the jejunum on d 14 and 30 and in the cloaca on d 14. The percentages of specimens from the control group that tested positive for Cp were 83.3% for feces, 88.0% for jejunum and cloaca, and 82.6% for cecum. Specimens from the feces and 3 sections of the intestine were Cp positive in groups treated with blend A (60.8, 64.6, 47.9, and 70.8%) and with blend B (65.9, 63.6, 63.6, and 72.7%). Our results indicate that specific blends of essential oil components can control Cp colonization and proliferation in the gut of broilers and therefore may be of help to prevent problems with Cp and necrotic enteritis.

Clinical studies in persistent diarrhea: dietary management with green banana or pectin in Bangladeshi children

BACKGROUND & AIMS

Because of the beneficial intestinal effects of dietary fibers, we have evaluated the therapeutic effects of green banana or pectin in children with persistent diarrhea.

METHODS

In a double-blind trial, 62 boys, age 5-12 months, were randomly given a rice-based diet containing either 250 g/L of cooked green banana (n = 22) or 4 g/kg pectin (n = 19) or the rice-diet alone (control, n = 21), providing 54 kcal/dL daily for 7 days. Stool weight and consistency, frequency of vomiting and purging, and duration of illness were measured.

RESULTS

Most children (60%) had no pathogens isolated from stools, 17% had rotavirus, 5% Vibrio cholerae, 4% Salmonella group B, and 11% had enterotoxigenic Escherichia coli infections. By day 3 posttreatment, significantly (P < 0.001) more children recovered from diarrhea receiving pectin or banana than controls (59%, 55%, and 15%, respectively). By day 4, these proportions correspondingly increased to 82%, 78%, and 23%, respectively, the study diet groups being significantly (P < 0.001) different than controls. Green banana and pectin significantly (P < 0.05) reduced amounts of stool, oral rehydration solution, intravenous fluid, and numbers of vomiting, and diarrheal duration.

CONCLUSIONS

Green banana and pectin are useful in the dietary management of persistent diarrhea in hospitalized children and may also be useful to treat children at home.

Amount of dietary fat and type of soluble fiber independently modulate postabsorptive conversion of beta-carotene to vitamin A in mongolian gerbils

Current dietary guidelines recommend a decrease in fat intake and an increase in fiber consumption. Decreased bioavailability (BV) of carotenoids is thought to be associated with both of these recommendations. A 2 x 4 factorial design was used to test the effects of dietary fat level at 10 or 30% of total energy and fiber type using no fiber, silica, citrus pectin or oat gum (7 g/100 g) on beta-carotene (betaC) BV in 4- to 5-wk-old Mongolian gerbils. We assessed BV as both accumulation of betaC and bioconversion of betaC to vitamin A (VA) in tissues. A VA- and betaC-deficient diet was fed for 1 wk followed by one of eight isocaloric, semipurified diets supplemented with carrot powder [ approximately 1 microgram betaC, 0.5 microgram alpha-carotene (alphaC)/kJ diet] for 2 wk (n = 12/group). Increasing dietary fat resulted in higher VA (P: = 0.074) and lower betaC (P: = 0.0001) stores in the liver, suggesting that consumption of high fat diets enhances conversion of betaC to VA. The effect of soluble fiber on hepatic VA storage was dependent on fiber type. Consumption of citrus pectin resulted in lower hepatic VA stores and higher hepatic betaC stores compared with all other groups, suggesting less conversion of betaC to VA. In contrast, consumption of oat gum resulted in hepatic VA and betaC stores that were higher (P = 0.012) and lower (P = 0.022), respectively, than those of citrus pectin-fed gerbils. The level of dietary fat consumed with soluble fiber had no interactive effects on hepatic VA, betaC or alphaC stores. Results demonstrate that betaC BV is independently affected by dietary fat level and type of soluble fiber, and suggest that these dietary components modulate postabsorptive conversion of betaC to VA. This study confirms the negative effects of citrus pectin on betaC BV, and suggests that oat gum does not adversely affect betaC BV.

Application of agar-fill method to estimate compartment capacity of gastrointestinal tract in Syrian hamsters (Mesocricetus auretus)

In the present study we have developed the agar-fill method for the measurement of gastrointestinal-tract capacity (GTC) to replace the in vitro water-fill method. This would estimate GTC without using complex equipment and techniques, and can be applied to the measurement of GTC for small laboratory animals. We attempted to confirm the efficiency of the agar-fill method by investigating the relationship between dietary neutral-detergent fibre (NDF) content and GTC. The digestion trials were carried out using the Syrian hamster (Mesocricetus auretus). The trials were conducted using both sexes, two age-groups and three levels of dietary NDF with a cross-classified design. The size of each gastrointestinal organ was determined as tissue weight (TW) and GTC. The DM intake, digestible DM intake, DM digestibility, NDF digestibility, acid-detergent fibre (ADF) digestibility and digesta transit time were also measured. GTC increased with increasing NDF content of the diets. TW responded similarly to increasing NDF content, but the response was smaller than that of GTC. DM digestibility decreased with increasing NDF content of the diet. The digestible DM intake did not decrease with increasing NDF because DM intake increased with NDF content. Digesta transit time was not shorter of the high-NDF diet group but DM intake increased with increasing NDF content. NDF digestibility did not differ significantly between low- and medium-NDF diets. ADF digestibility was low in the low-NDF-diet group. The digestion characteristics were highly correlated with TW and GTC, except for TW of small intestine. These correlations were higher with GTC than with TW. The results of the present study confirm previous findings suggesting that the agar-fill method is a useful means of estimating GTC for small laboratory animals.

Metabolic and morphometric changes in small and large intestine in rats fed high-fiber diets

Structural modifications of the intestine following fiber intake may play an important role in the physiological effects induced by dietary fiber. The aim of this study was to examine possible mechanisms for the hypocholesterolemic effects of dietary fibers by evaluating both biochemical and morphometric parameters. Thirty male Sprague-Dawley rats were divided into 3 groups and fed either a fiber-free, 15% fiber high methoxy pectin, or 15% cellulose diet for a 4-wk period. Plasma cholesterol levels, hepatic enzyme activity, and fecal bile acid excretion were determined, and changes in the intestinal structure were evaluated. Daily fecal bile acid excretion was significantly higher in rats fed the pectin diet accompanied by elevated HMG-CoA reductase activity. Pectin feeding led to significant elongation of both the small and large intestine whereas cellulose only affected colon length. Computerized image analysis of intestinal cross-sections showed enlarged muscle area in the ileum and midcolon of pectin-fed rats and greater mucosal area in the colon. Circular muscle cell hypertrophy was also observed in the colon length. Computerized image analysis of intestinal cross-sections showed enlarged muscle area in the ileum and midcolon of pectin-fed rats and greater mucosal area in the colon. Circular muscle cell hypertrophy was also observed in the colon. In contrast, the effects of cellulose feeding were limited to elongation of the colon accompanied by muscle cell hypertrophy, and little effect on ileal morphology was documented. These data indicate that the hypocholestrolemic effects of pectin may be due to increased bile acid secretion accompanied by significant morphological changes in the ileum and colon.

Gastrointestinal surface protection and mucosa reconditioning

BACKGROUND

There is increasing evidence that preservation of the ecology of the gastrointestinal tract and the surface protection system--surfactants, mucus, and fiber--is important for the outcome in postoperative trauma patients, patients after bone marrow and liver transplantation, and patients with HIV or AIDS. Approximately 50% of the nourishment of the small intestine and > 80% of the nourishment of the large intestine comes from the lumen. This is especially deleterious to the large intestine. Within less than a week of intestinal starvation--even in the presence of intense parenteral nutrition--a mucosal atrophy is observed, promoting translocation of potentially pathogenic microorganisms. Enteral nutrition is crucial to the outcome in many of these conditions. If however, such a nutrition is based on simple carbohydrates, peptides, amino acids, or fatty acids, most of the nutrition administered will be absorbed in the upper gastrointestinal tract. Complex fibers and proteins can be regarded as nutrients especially destined to the lower gastrointestinal tract. They are fermented by the probiotic flora, normally colonizing the colonic mucosa, and the necessary nutrients: short-chain fatty acids and amino acids such as arginine and glutamine are produced at the level of the colonic mucosa. Careless antibiotic treatment reduces or eliminates this flora, induces local mucosal starvation, and makes the patients vulnerable to opportunistic infections and microbial intestinal translocation.

METHODS AND RESULTS

In this review the role of the different ingredients of the surface protection system are discussed. A program to recondition the intestines, particularly the colonic mucosa by resupply of species-specific lactobacilli, surfactants, amino acids (especially glutamine), and oat fiber (beta-glucans) is suggested. Extensive experience in animal models and early experience in a patient population are summarized and discussed. Oat has been chosen as a substrate for fermentation because it contains 100 times more of membrane lipids (surfactants) than any other food, has a favorable amino acid pattern (rich in glutamine), and is rich in water-soluble, fermentable-fiber beta-glucans. More than 1000 isolates of human-specific lactobacilli have been studied. Some strains, especially those of plantarum type, have proven effective in colonizing the colonic mucosa, suppressing the potentially pathogenetic flora, and may have other probiotic effects as well.

CONCLUSION

A totally new enteral formula has been designed based on probiotic bacteria and fiber and aimed at colonizing the intestinal mucosa with a local probiotic effect and fermentation of fiber.

Polydextrose induces precocious cessation of intestinal macromolecular transmission and development of digestive enzymes in the suckling rat

The effect of repeated oral administration of polydextrose and pectin on intestinal macromolecular transport and digestive enzymes development was examined in the suckling rat. The administration of polydextrose for 7 days resulted in pancreatic hyperplasia, followed by the enhancement of trypsin activity. The length of the small intestine and the wet weight of the cecum were significantly increased by polydextrose treatment. Maltase activity was increased in a dose dependent manner by polydextrose, but not by pectin treatment. Lactase activity was not changed by either treatment. The absorption of bovine IgG was precociously depressed by polydextrose, but not by pectin treatment. These results suggest that oral administration of polydextrose induces precocious maturation of the small intestine and exocrine pancreas in the suckling rat.

Gastrointestinal growth in rats as influenced by indigestible polysaccharides and adaptation period

Hypertrophy of the small intestinal tissue evolved during the initial 9 days in rats fed pectin or guar gum. Hypertrophy of the caecal and colonic tissue continued beyond day 9. Caecal hypertrophy was observed in rats fed pectin, guar gum or resistant starch, while colonic hypertrophy was observed only in rats fed pectin or resistant starch. There is a time lag in the adaptive response of the caecum and colon as compared with the small intestine, at least for dietary polysaccharides. This time lag is suggested to be related to the time required for the microflora to adapt to the dietary PS.

Changes in intestinal tunica muscularis following dietary fiber feeding in rats. A morphometric study using image analysis

The morphological changes in the intestinal tunica muscularis induced by prolonged dietary fiber intake were determined in rat small intestine and colon with the aid of computerized image analysis. Thirty male Sprague-Dawley rats were fed either a fiber free, 15% cellulose or 15% pectin diet for 8 weeks. Intestine length was measured and stained cross sections of the jejunum, ileum, and colon were quantitated using image analysis. In the distal colon, muscle cell size was also determined. Despite lower weight gain in the pectin fed rats, both the small intestine and colon length were significantly increased. Cellulose feeding had a lesser effect on intestine length. Pectin fed rats had significantly increased relative tunica muscularis area (37.2 +/- 2.2 mm2) in ileum cross sections when compared to control (24.3 +/- 1.8 mm2) and cellulose fed rats (26.1 +/- 1.1 mm2). In the mid-colon, the tunica muscularis area was found to be pectin > cellulose > control (33.5 +/- 2.2; 29.7 +/- 1.7; 25.8 +/- 1.5 respectively) with significant differences reached between pectin and control rats. In jejunal samples, no differences were observed among the groups. Circular smooth muscle cell size in the distal colon was significantly increased following cellulose feeding but was less pronounced in the case of pectin. We conclude that fiber supplementation leads to morphological changes in the rat intestine including changes in length and tunica muscularis volume.

Secretory immunoglobulin A, intestinal mucin, and mucosal permeability in nutritionally induced bacterial translocation in rats

OBJECTIVE

The authors investigated the role of mucin and secretory immunoglobulin A (slgA) in a model of nutritionally induced bacterial translocation.

BACKGROUND

Parenteral and certain elemental diets have been shown to impair intestinal barrier function, whereas fiber has been shown to protect against nutritionally induced bacterial translocation. However, the factors responsible for these phenomenon have not been fully determined.

METHODS

Intestinal mucin levels, mucosal protein content, slgA, intestinal morphology, and permeability to horseradish peroxidase, bacterial translocation, and intestinal bacterial population levels were measured in rats 7 days after receiving total parenteral nutrition (TPN) solution (28% glucose, 4.25% amino acids; 307 kcal/kg/day) enterally (ORAL-TPN) or parenterally (IV-TPN) with or without enteral bulk fiber supplementation. Chow-fed rats served as control subjects.

RESULTS

The incidence of bacterial translocation in the ORAL-TPN and IV-TPN groups was reduced significantly by the provision of fiber (p < 0.05). Mucosal protein, slgA, and insoluble mucin levels were decreased in the jejunum of the ORAL-TPN and IV-TPN groups, with mucosal protein levels being decreased to a greater extent than slgA or mucin. Although similar decreases in these parameters were observed in the fiber-fed groups, fiber appeared to improve intestinal barrier function as measured by horseradish peroxidase permeability.

CONCLUSIONS

The provision of bulk-forming fiber improves intestinal barrier function as measured by peroxidase permeability and bacterial translocation, but does not restore mucosal protein content, intestinal mucin, or slgA levels to normal.

Effect of different components of dietary fiber on the intestinal morphology of domestic rabbits

A trial was conducted to study the effect of dietary fiber components (cellulose, pectin, lignin and alfalfa) on the performance and the intestinal structure of domestic rabbits. Different fiber components influenced villus height and muscle layer thickness of the jejunum and colon, and affected the crypt depth of the duodenum and ileum. A scanning electron microscope photograph showed a significant damage of the villi surface in the duodenum and jejunum by lignin supplementation; it also showed a significant damage in the cecal mucosa by cellulose, pectin and alfalfa supplementation.

Prevention of oxidative damage in the rat jejunal mucosa by pectin

The role of the soluble non-starch polysaccharide pectin in the prevention of oxidative damage induced by peroxy, superoxide and hydroxyl radicals to the rat jejunal mucosa was studied. The oxidative stress was introduced to the rat jejunal mucosa by means of a closed-loop perfusion system and was characterized biochemically by monitoring the enterocyte activity of the enzyme lactate dehydrogenase (EC 1.1.1.27) and the K+ level. Aqueous solutions of pectin were perfused into the rat jejunum before the oxidative stress inducers. The possible protection effect was evaluated by comparing the mucosal integrity (as measured by biochemical variables) to the values obtained after perfusion with the oxidative stress inducers only. We found that: (a) mucosal damage was detected following the perfusion of peroxy and hydroxyl radicals in the rat jejunum, but not following perfusion of the superoxide radical; (b) a significant reduction in the mucosal damage was noted when pectin was perfused before the perfusion with the peroxy radical induction; (c) full protection against the mucosal damage induced by hydroxyl radicals was achieved when pectin was perfused before the damage induction.

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)

Soy polysaccharide in an enteral diet: Effects on rat intestinal cell proliferation, morphology and metabolic function

The present study was conducted to compare the effect of soy polysaccharide (SP)-supplemented and fibre-free enteral diets and a normal chow diet on intestinal and colonic adaptation of rat gastrointestinal morphometrics and cytokinetics. Results showed that the fibre-free diet caused a significant decrease in various gut parameters, such as cell proliferation, tissue wet weight, and intestinal brush border enzymes, when compared to the normal gut of chow-fed rats. However the SP-supplemented enteral diet resulted in a significant improvement in several parameters in most regions along the gastrointestinal tract, when compared to orally-fed animals. These studies demonstrate that significant changes occur in the intestine as a result of enteral diets, with regional variation. Furthermore, the results demonstrate that SP stimulates crypt cell proliferation which could, in part, hasten recovery from intestinal mucosal damage. The addition of SP to enteral diets seems potentially advantageous.

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.

Hypertrophy of visceral smooth muscle

Smooth muscles of viscera undergo a large increase in volume when there is a chronic, partial obstruction impairing the flow of lumenal contents. Hypertrophy of smooth muscle occurs in various medical conditions and several methods are available for inducing it experimentally in laboratory animals, especially in urinary bladder, small intestine and ureter. The hypertrophic response differs somewhat with the type of organ, the animal species, the age of the subject, and the experimental procedure. Ten- to fifteen-fold increases in muscle volume develop within a few weeks in the urinary bladder or the ileum of adult animals, a growth that would not have occurred in the lifespan of the animal without the experimental intervention. The general architecture of the muscle and the boundaries with adjacent tissues are well preserved. In intestinal hypertrophy, muscle cells increase in number: mitoses are found in mature, fully differentiated muscle cells. Cell division by full longitudinal splitting of muscle cells may also occur. Enlargement of muscle cells accounts for most of the muscle hypertrophy. The hypertrophic muscle cell has an irregular profile with deep indentations of the cell membrane, bearing caveolae and dense bands; however, the cell surface grows less than the cell volume (reduction of surface-to-volume ratio). The nucleus is crenated and is much less enlarged than the cell (reduction of the nucleo-plasmatic ratio). Mitochondria grow in number but in some muscles their spatial density decreases; intermediate filaments increase more than myofilaments. The spatial density of sarcoplasmic reticulum is generally increased. In the hypertrophic intestine, gap junctions increase in number and size; in the bladder, gap junctions are absent both in control and in hypertrophy. Thus the hypertrophic muscle cell is not only larger than a control cell, but has a different pattern of its structural components. Extensive neo-angiogenesis maintains a good blood supply to the hypertrophic muscle. The density of innervation is much decreased in the hypertrophic intestine, whereas it appears well maintained in the bladder. Neuronal enlargement is found in the intramural ganglia of the intestine and in the pelvic ganglion. The mechanisms involved in hypertrophic growth are unknown. Three possible factors, mechanical factors, especially stretch, altered nerve discharge, and trophic factors are discussed.

Intestinal zinc transfer by everted gut sacs from rats given diets containing different amounts and types of dietary fibre

Two experiments were carried out in which rats were offered diets containing different amounts and types of dietary fibre, i.e. commercial stock diet and three semi-purified diets containing no fibre, 200 g wheat bran or 200 g pectin/kg. Dietary inclusion of fibre, and especially pectin, stimulated large bowel fermentation, as indicated by caecal hypertrophy and reduced caecal pH. After 3 weeks, mucosal:serosal zinc transfer and Zn accumulation by tissue were measured using the everted-gut-sac technique. In Expt 2, incubations were carried out in the presence and absence of 0.25 mM-ouabain to assess the importance of transfer by Na+,K+-ATPase-dependent mechanisms, and some observations on glucose transport were also made. Ouabain reduced rates of transfer of both Zn and glucose and also tissue Zn accumulation. There were no significant differences in rates of Zn transfer by everted sacs from duodenal, ileal and colonic sites, but accumulation of Zn by tissue was a more important fate than transfer across the serosal surface, and accumulation by duodenal tissue was approximately twice as great as by other tissues. Mucosal:serosal transfer of glucose by ileal tissue was much more sensitive to ouabain than was Zn transfer. Previous diet appeared to alter the capacity of the intestinal tissue to transfer Zn, with the highest rates of transfer being by colonic tissue from pectin-fed rats.

The effects of diet on the residual small intestine following massive resection

The midportions of rat small intestines were resected by 90 per cent, and the residual intestines studied for the effects of diet on mucosal morphology, nutrition and gastrointestinal hormones. Groups of rats were fed chow, an elemental diet (ED), or an ED + dietary fiber (EDF) for 1 or 3 weeks. Nonresected rats which were fed chow or ED for 3 weeks were used as controls. Nutritional parameters, such as concentrations of serum total protein, albumin and transferrin were favorable but gain in body weight was not. The parameters indicated that resected rats fed EDF fared better than resected rats fed ED. Mucosal villous height in the residual jejunum, similar in all the resected groups after 1 week, was significantly increased in the resected rats fed chow or EDF after 3 weeks, but did not differ between 1 and 3 weeks in the resected rats fed ED. Changes in the number of villous epithelial cells and villous width were also examined. The level of plasma enteroglucagon was high in the rats fed chow or EDF after both 1 and 3 weeks, and was positively correlated with the increases in villous height. Levels of serum gastrin were not affected by dietary change. Luminal nutrients were significantly associated with the adaptive changes in the mucosa of the residual intestine, and mucosal morphology was also considerably influenced by dietary change.

Harry M. Vars award. The effect of a pectin-supplemented elemental diet on intestinal adaptation to massive small bowel resection

The effect of a pectin-supplemented elemental diet on intestinal adaptation to massive small bowel resection in the rat was investigated in this study. Sixty adult Sprague-Dawley rats underwent placement of a feeding gastrostomy and swivel apparatus. Control animals (N = 16) were then returned to their cages while the remaining animals underwent an 80% small bowel resection and anastomosis (resected, N = 44). Postoperatively, animals were randomly assigned to receive either a fat- and fiber-free elemental diet (no pectin) or the same diet supplemented with 2% pectin (pectin). After 8 days of full strength diet, samples of jejunum, ileum, and colon were obtained for analysis. The weights per unit length of the ileum and colon were significantly greater in the resected pectin group than either the resected no pectin or pectin control groups. Mucosal parameters (unit weight, DNA, RNA, and protein content) were significantly increased in the jejunum and ileum of both the resected pectin and resected no pectin groups relative to their respective control groups. However, jejunal and ileal mucosal parameters were significantly greater (1.3- to 2-fold) for the resected pectin group than for the resected no pectin group. All the mucosal parameters of the colons were significantly greater for the pectin resected group than for the pectin control group, while only colonic mucosal RNA was significantly greater for the no pectin resected group than for the no pectin control group. These data indicate that the addition of pectin to an elemental diet significantly enhanced intestinal adaptation to massive small bowel resection in the rat.

Gastrointestinal adaptation in response to soluble non-available polysaccharides in the rat

1. Rats were fed on a control semi-synthetic diet containing insoluble cellulose (Solkafloc; 100 g/kg; control group) as the only source of dietary fibre, or on one of two test diets containing the same quantity of either guar gum or carboxymethylcellulose (CMC). Animals in the test groups showed similar growth rates and food intakes, which were significantly lower than those of the control group. The CMC group produced frequent poorly formed faeces throughout the 21 d feeding period. 2. The small intestines of animals in both test groups were significantly longer than those of the control group at the end of the study. The caeca were also enlarged and heavier, particularly in the CMC-fed group. 3. The rate of production of mucosal cells was increased in the small and large intestines of both test groups. The CMC-fed group exhibited a particularly high rate in the distal ileum, where the rate of cell divisions per crypt was over three times greater than at the same site in the control group. The increased proliferation was associated with a significant lengthening of the crypts and an approximately 25% increase in the basal width of the villi. 4. Mucosal alkaline phosphatase (EC 3.1.3.1) and lactase (EC 3.2.1.23) levels were lower than those of the control group at proximal and distal sites in the small intestines of both CMC- and guar-gum-fed groups. Altered spatial distributions of maltase (EC 3.2.1.20) and sucrase (EC 3.2.1.48) activities were also observed in these animals.(ABSTRACT TRUNCATED AT 250 WORDS)

The digestion of fibre by pigs. 3. Effects of the amount and type of fibre on physical characteristics of segments of the gastrointestinal tract

The aim of the study was to determine the relative effects of feeding growing pigs with graded amounts of neutral-detergent fibre (NDF) from various sources on the empty wet weight of segments of the pig gastrointestinal tract, on the weight and moisture content of their digesta, and on the pattern of digesta movement in them. Increased NDF intakes were associated with significantly higher wet weights of all gastrointestinal segments and increased lengths of the caecum. The lengths of both the small and the large intestines were unaffected by the ingestion by the pigs of different amounts of NDF from various sources. However, the caecum responded to these increased intakes of NDF by significant increases in length. The source of NDF in the diet was a factor that markedly influenced both the length and the weight of the distal colon. The nature of these increases in weight and length morphologically and their biological significance have not been determined. Despite some significant differences, neither the type nor the level of dietary NDF had any appreciable effect on the dry weight and on the proportion of dry matter (DM) of the contents in the contents in the stomach. As the level of NDF intake was increased, more undigested dietary material was found in all segments of the digestive tract of the pigs. The proportion of DM in the residues decreased progressively from the caecal contents to the contents of the distal colon. In most cases the degree to which the level of NDF intake affected the weight of the contents and the proportion of DM in them was highly dependent on the source of NDF in the diet. The distribution of the feed consumed in the morning and in the evening, as measured with stained feed particles and polyethylene beads, was extremely variable. It is concluded that prolonged intakes by pigs of diets containing high levels of fibre may lead to a hypertrophy and hence increased weight of segments of the gastrointestinal tract.

Effects of feeding stannous chloride on different parts of the gastrointestinal tract of the rat

The effects of feeding inorganic tin on the gastrointestinal tract were examined in rats. Three groups of male weanling Wistar rats were fed a diet to which 0, 250, or 500 ppm Sn2+ had been added as SnCl2. A fourth group was subjected to feed restriction by pair feeding with the 500-ppm group. Comparison of the data from the tin-fed groups with both the control and the reduced diet groups allowed discrimination between effects of reduced feed intake and Sn2+ effects. Independent of the reduced feed intake, Sn2+ affected hemoglobin concentration in the blood and several small intestine parameters. Total length of the small intestine, as well as absolute and relative weights, was increased. An increase was also observed in the migration of epithelial cells along the villus, as revealed by [3H]thymidine incorporation and autoradiography in rats fed 900 ppm Sn2+ for 4 weeks. Stereo-light microscopy and scanning electron microscopy revealed the formation of ridge-like villi due to Sn2+ feeding and a decreased number of villi per unit surface. These data suggest that an increase in cell turnover in the small intestine, due to Sn2+, was responsible for these changes.

Differential effects of dietary fibers on rat intestinal circular muscle cell size

The relationship between dietary fiber and intestinal circular muscle cell size was investigated in rats by feeding defined diets supplemented with four different sources of fiber. In the first study, a 20% wheat bran supplement was fed to 10 rats for nine weeks. This resulted in larger muscle cell size, with a 22.5% increase in the proximal (P less than 0.02) and 77.9% increase in the distal colon (P less than 0.01) when compared with a control group of 10 rats fed a fiber-free diet. In the second study, which lasted four weeks, a control group of 10 rats was fed a fiber-free diet, while similar sized experimental groups were fed the same basal diet plus either 20% oat bran, 10% pectin, or 10% guar. Muscle cell size was decreased by 20.6% in the proximal jejunum of the oat bran- and pectin-fed groups (P less than 0.05) and by 43% in the proximal colon of the oat bran-fed group, when compared with the controls (P less than 0.05). These results show that the effects of high fiber diets on intestinal muscle cell size depend on the type of fiber consumed.

The effect of diet on the mammalian gut flora and its metabolic activities

The review will encompass the following points: A brief introduction to the role of the gut flora in the toxicology of ingested food components, contaminants, and additives, including known pathways of activation and detoxication of foreign compounds and the implication of the flora in enterohepatic circulation of xenobiotics. The advantages and disadvantages of the various methods of studying the gut flora (classical bacteriological techniques, metabolic and enzymological methods) will be critically discussed with special reference to their relevance to dietary, toxicological, and biochemical studies. Sources of nutrients available to the gut flora will be described including host products (mucus, sloughed mucosal cells, hormones, proteins) and exogenous nutrients derived from diet. An account of the problems involved in studies of dietary modification with special reference to the use of stock laboratory animal diets, purified diets, and human dietary studies. The influence of dietary modification on the flora will be assessed on the basis of changes in numbers and types of bacteria and their metabolic activity, drawing on data from human and animal studies. The effects of manipulation of the quantity and quality of protein, fat, and indigestible residues (fiber) of the diet will be described together with their possible implications for toxicity of ingested compounds.

Effect of guar gum on nitrogen secretion into isolated loops of jejunum in conscious growing pigs

Four pigs, initially of 30 kg live weight, were surgically prepared with two re-entrant cannulas in the jejunum, 1.0 m apart. This allowed an isolated loop to be formed through which Ringer solutions were continuously perfused for 6.5-h periods per day. The effects of two Ringer solutions of contrasting composition on nitrogen secretion were measured in a preliminary study. The effects of guar gum (6.7 g/l) on N secretion during perfusions of solutions of glucose or of maltose (20 g/l) were measured. N secretion did not differ significantly between the two Ringer solutions. Addition of guar gum to the solution of glucose increased mean N secretion from 69.2 to 133.9 mg/m per 2 h; the corresponding values for the maltose solution were 75.5 and 120.2 mg/m per 2 h. In both cases the differences were significant (P less than 0.001). Differences between N secretion into glucose and maltose solutions were not significant, either without or with guar gum. Guar gum addition had a greater effect on N secretion in hours 5 and 6 than in hours 1 and 2 of perfusion. It was calculated that guar gum would have increased N section by the mucosa of the whole small intestine from approximately 15 to 27 g/d under the conditions of the study, assuming uniform secretion throughout the organ. These results suggest that certain types of dietary fibre may be important determinants of N secretion by the mucosa of the small intestine. They also suggest that changes in N secretion of this magnitude are of importance in N metabolism because the overall rate of protein synthesis in these pigs was probably about 100 g/d (expressed as N), using values from the literature.