Ingestion of the soluble dietary fibre, polydextrose, increases calcium absorption and bone mineralization in normal and total-gastrectomized rats

Gluco-oligosaccharides as potential prebiotics: Synthesis, purification, structural characterization, and evaluation of prebiotic effect

Prebiotics have long been used to modulate the gut microbiota and improve host health. Most established prebiotics are nondigestible carbohydrates, especially short-chain oligosaccharides. Recently, gluco-oligosaccharides (GlcOS) with 2-10 glucose residues and one or more O-glycosidic linkage(s) have been found to exert prebiotic potentials (not fully established prebiotics) because of their selective fermentation by beneficial gut bacteria. However, the prebiotic effects (non-digestibility, selective fermentability, and potential health effects) of GlcOS are highly variable due to their complex structure originating from different synthesis processes. The relationship between GlcOS structure and their potential prebiotic effects has not been fully understood. To date, a comprehensive summary of the knowledge of GlcOS is still missing. Therefore, this review provides an overview of GlcOS as potential prebiotics, covering their synthesis, purification, structural characterization, and prebiotic effect evaluation. First, GlcOS with different structures are introduced. Then, the enzymatic and chemical processes for GlcOS synthesis are critically reviewed, including reaction mechanisms, substrates, catalysts, the structures of resultant GlcOS, and the synthetic performance (yield and selectivity). Industrial separation techniques for GlcOS purification and structural characterization methods are discussed in detail. Finally, in vitro and in vivo studies to evaluate the non-digestibility, selective fermentability, and associated health effects of different GlcOS are extensively reviewed with a special focus on the GlcOS structure-function relationship.

Faster Short-Chain Fatty Acid Absorption from the Cecum Following Polydextrose Ingestion Increases the Salivary Immunoglobulin A Flow Rate in Rats

Salivary immunoglobulin A (IgA) plays a vital role in preventing upper respiratory tract infections (URTI). In our previous study, we showed that the intake of carbohydrates increases the intestinal levels of short-chain fatty acids (SCFAs), which in turn increase salivary IgA levels. However, the mechanism underlying this phenomenon has not been fully elucidated. In this study, we investigated in rats the effect of polydextrose (PDX) ingestion on salivary IgA level and SCFA concentration in cecal digesta and the portal vein. Five-week-old rats were fed with a fiber-free diet (control) or with 40 g/kg of PDX for 28 days. Compared to the control, ingestion of PDX led to a higher salivary IgA flow rate (p = 0.0013) and a higher concentration of SCFAs in the portal vein (p = 0.004). These two data were positively correlated (r_s = 0.88, p = 0.0002, n = 12). In contrast, the concentration of SCFAs in cecal digesta and cecal digesta viscosity were significantly lower following PDX ingestion, compared to the control (p = 0.008 and 0.05, respectively). These findings suggest that the ingestion of PDX increases the absorption rate of SCFAs in the intestine through PDX-induced fermentation, which is accompanied by an increase in SCFA levels in the blood, and ultimately leads to increased salivary IgA levels.

Risk factors for loss of bone mineral density after curative esophagectomy

Micronutrient and fat malabsorption and altered enteroendocrine signaling occur after esophagectomy for cancer; however, the impact of malnutrition on bone health in this cohort has not been previously investigated. In this study, the prevalence of osteoporosis increased after curative surgery, associated with disease-specific, treatment-related, and population risk factors.

PURPOSE

Improved oncologic outcomes in esophageal cancer (EC) have resulted in increased survivorship and a focus on long-term quality of life. Malnutrition and micronutrient malabsorption are common among patients with EC, but the effect on bone metabolism is not known. The aim of this study was to characterize changes in bone mineral density (BMD) following curative esophagectomy.

METHODS

Consecutive disease-free patients who underwent esophagectomy with gastric conduit for pathologically node-negative disease from 2000 to 2014 were included. BMD was assessed at vertebral levels T12-L5 by computed tomography using a simple trabecular region-of-interest attenuation technique, and serum markers of nutritional status and bone metabolism were examined. Independent risk factors for osteoporosis were identified by multivariable logistic regression.

RESULTS

Seventy-five consecutive patients were studied. Osteoporosis was present in 25% at diagnosis. BMD declined at 1 and 2 years postoperatively (144.3 ± 45.8 versus 128.6 ± 46.2 and 122.7 ± 43.5 Hounsfield Units (HU), P < 0.0001), with increased osteoporosis prevalence to 38% and 44% (P = 0.049), respectively. No significant postoperative change in vitamin D, calcium, or phosphate was observed, but alkaline phosphatase increased significantly (P < 0.001). While female sex (P = 0.004) and ASA grade (P = 0.043) were independently associated with osteoporosis at diagnosis, age (P = 0.050), female sex (P = 0.023), smoking (P = 0.024), and pathologic T stage (P = 0.023) were independently predictive of osteoporosis at 1 year postoperatively.

CONCLUSIONS

Osteoporosis is prevalent among disease-free patients post-esophagectomy for EC, associated with disease-specific, treatment-related, and population risk factors. Strategies which minimize BMD decline should be considered to avoid fragility fractures in this cohort.

Continuous combined intake of polydextrose and lactitol stimulates cecal fermentation and salivary IgA secretion in rats

Immunoglobulin A (IgA), which plays an important role in infection defense, is upregulated in the large intestine and oral cavity through dietary fiber intake. However, the mechanism underlying salivary IgA increase through dietary fiber intake remains unknown. This study investigated time-dependent effects of non-absorbable polydextrose (PDX) and lactitol intake on salivary IgA secretion and cecal fermentation. Five-week-old rats were fed a fiber-free diet with or without 25 g/kg PDX and 25 g/kg lactitol for 1, 4, and 8 weeks. Compared to control, those who ingested PDX and lactitol had higher salivary IgA flow rates per weight of submandibular gland tissue at 4 and 8 weeks (P < 0.05), greater cecal weight and digesta at 1, 4, and 8 weeks (P < 0.05), and lower concentrations of short chain fatty acids (SCFAs) in cecal digesta (P = 0.0003). These findings suggest that the consumption of PDX and lactitol may upregulate salivary IgA secretion possibly by stimulating absorption of SCFAs produced by cecal fermentation. Thus, continuous ingestion of PDX and lactitol for up to 4 weeks could increase salivary IgA and promote immune defense against pathogen invasion through the oral route.

Intake of Polydextrose Alters Hematology and the Profile of Short Chain Fatty Acids in Partially Gastrectomized Rats

Polydextrose (PDX) ingestion may increase the intestinal absorption of iron. This study evaluated the effects of 7.5% polydextrose supplementation on markers of iron uptake, transport and storage in partially gastrectomized rats. Half of a batch of 40 male Wistar rats (250 g) underwent Billroth II partial gastrectomy with anterior truncal vagotomy (GXT), while the other half underwent sham gastrectomy (SHAM). At 7 postoperative days, the animals were subdivided into four groups (n = 10): Sham Control and GXT Control (no polydextrose); Sham PDX and GXT PDX (with 7.5% PDX). The animals were euthanized after 60 day of PDX treatment. Organ weight, cecal pH, the characterization and quantification of short-chain fatty acids (SCFA), hematological parameters, hepatic iron content and the expression of ferroportin (FPT) in the jejunum, cecum, colon and liver were evaluated. PDX caused changes in the cecum of the supplemented animals, where there was a decrease in pH, increase in cecal wall and marked production of SCFA, especially acetic and propionic acids (p < 0.05). Hepatic iron levels were lower in GXT animals. PDX increased hemoglobin (HGB) values by 29.2% and hematocrit (HCT) by 55.8% in the GXT PDX group compared to the GXT Control group. The GXT PDX group had lower hepatic FPT expression (p < 0.05). PDX led to increased SCFA concentration in the supplemented animals. Considering that SCFAs play a central role in the increasing nutrients uptake, this mechanism may be involved in altering the hematology profile observed in these animals but not enough to reverse iron deficiency anemia in post-gastrectomy rats.

Effects of two different glutamine-containing enteral supplements on stool frequency and density in elderly patients recovering from acute critical illness

AIM

Glutamine has various beneficial functions in the gastrointestinal tract. The present study was designed to investigate the effect of two different glutamine supplements on bowel movement at the start of enteral feeding in elderly inpatients.

METHODS

This was a double-blind, prospective, randomized comparison study. A total of 25 patients aged >75 years recovering from a critical illness in a non-intensive care unit and scheduled for tube feeding were recruited. Of them, 22 consenting patients were randomly assigned to two groups: glutamine-fiber-oligosaccharide treatment group (n = 11) and glutamine F treatment group (n = 11). They were given glutamine three times daily at a dosage of 9 g/day. Enteral nutrition was given at the same dosage to both groups for the duration of the study. The end-points were stool frequency, Bristol Scale Form Score, bowel function index (Bristol Scale Form Score × stool frequency), the percentage of patients with stool frequency over three per day and those with a BSFS of 6 or 7 in each group.

RESULTS

There were no significant differences between the two groups in terms of patient characteristics before the study. All the end-points in the glutamine F group were significantly lower than those in the glutamine-fiber-oligosaccharide group.

CONCLUSIONS

Compared with glutamine-fiber-oligosaccharide, glutamine F administration resulted in stool hardening and reduced stool frequency in elderly inpatients recovering from acute critical illness in non-intensive care units. The effects might be caused by the different additive components of glutamine supplements. Geriatr Gerontol Int 2017; 17: 2514-2519.

Polydextrose: Physiological Function, and Effects on Health

Polydextrose (PDX) is a non-digestible oligosaccharide used widely across most sectors of the food industry. It is a randomly linked glucose oligomer containing small amounts of sorbitol and citric acid. The random bonds in PDX prevent mammalian digestive enzymes from readily hydrolyzing the molecule and it has a reported energy value of 1 kcal/g. These properties have led to the acceptance in many countries that PDX provides similar physiological effects as other dietary fibers and has shown prebiotic potential. Dietary intervention with prebiotics has been shown to selectively stimulate the growth and/or activity of one or a limited number of intestinal bacteria associated with several physiological benefits on health. Therefore, the objective of this review was a survey of the literature on the effect of supplementation with PDX in health, and to list the benefits for maintaining health and/or reducing the development of diseases.

Polydextrose Enhances Calcium Absorption and Bone Retention in Ovariectomized Rats

Purpose. To evaluate the effect of polydextrose (PDX) on Ca bioavailability and prevention of loss of bone mass. Methods. Twenty-four two-month-old ovariectomized rats were fed three isocaloric diets only varied in fiber source and content up to 60 days (FOS group, a commercial mixture of short- and long-chain fructooligosaccharide, OVX group fed AIN 93 diet, and PDX group). A SHAM group was included as control. Apparent Ca absorption percentage (%ABS), changes in total skeleton bone mineral content (tsBMC) and bone mineral density (BMD) and femur BMD, % Bone Volume, Ca and organic femur content, caecal weight, and pH were evaluated. Results. %ABS and caecum weight of PDX and FOS were higher, and caecum pH was lower compared to OVX and SHAM. PDX reached a higher pH and lower caecum weight than FOS possibly because PDX is not completely fermented in the colon. Changes in tsBMC and femur BMD in FOS and PDX were significant lower than SHAM but significantly higher than OVX. % Bone Volume and femur % of Ca in PDX were significantly higher than OVX and FOS but lower than SHAM. Conclusions. PDX increased Ca absorption and prevented bone loss in OVX rats.

Effects of dietary fibre and tea catechin, ingredients of the Japanese diet, on equol production and bone mineral density in isoflavone-treated ovariectomised mice

Equol is a metabolite of the isoflavone daidzein (Dz) and is produced by the bacterial microflora in the distal intestine and colon. Some epidemiological studies have reported an association between increased equol production and intakes of green tea or dietary fibre, which are ingredients of the standard Japanese diet. We examined the effects of a diet supplemented with Dz and tea catechin or dietary fibre on equol production and bone mineral density in ovariectomised (OVX) mice. Female mice of the ddY strain were either sham operated or OVX. OVX mice were fed a control diet, a 0·1 % Dz-supplemented diet or a 0·1 % Dz diet supplemented with one of the food components commonly consumed in the Japanese diet. The mice were given 1 % tea catechin (w/w) as part of the diet in Expt 1 or 5 % polydextrose (PD) and 5 % raffinose (Raf) (w/w) as part of the diet in Expt 2. Catechin reduced serum equol levels and attenuated the beneficial effect of Dz on femoral bone loss. The soluble dietary fibres PD and Raf stimulated equol production, and enhanced the bone-protective effects of Dz on femoral bone. These results suggest that dietary fibre, in particular, PD, may alter the bioavailability of isoflavones and prevent osteopenia in OVX mice.

Dietary galactooligosaccharides increase calcium absorption in normal and gastrectomized rats

OBJECTIVE

To determine whether the galactooligosaccharide stimulates calcium absorption in partially gastrectomized rats.

METHODS

Animals were submitted to laparotomy (sham-operated control) and partial gastrectomy (Billroth II) in groups of 20. They were fed a control diet (AIN-93M) without galacto-oligosaccharide or a diet containing (galacto-oligosaccharide - 50 g/kg diet) for eight weeks. The animals were divided into four groups: sham-operated and non-gastrectomized with galactooligosaccharide, sham-operated and gastrectomized without galactooligosaccharide. On the final day of the study, whole blood was collected for determination of serum calcium concentration.

RESULTS

In the group with galactooligosaccharides calcium excretion in feces was significantly lower than the group without prebiotics. The apparent absorption of calcium in gastrectomized and normal rats was higher in groups fed with galactooligosaccharide than in the control diet group.

CONCLUSION

The ingestion of galactooligosaccharides prevents osteopenia in partially gastrectomized rats.

A ingestão de prébioticos previne a malabsorção de ferro e anemia induzidas pela gastrectomia?: Estudo experimental em ratos

RACIONAL: Ratos gastrectomizados desenvolvem anemia, e a ingestão de galactooligossacarídeo (GOS) e a polidextrose (PDX) aumenta a absorção de ferro e promove a recuperação da anemia em ratos com deficiência de ferro. OBJETIVO: Avaliar se GOS e PDX estimulam a absorção de ferro em ratos gastrectomizados e normais. MÉTODOS: Os ratos foram laparotomizadas (controle falso-operado) e parcialmente gastrectomizados (Billroth II) em grupos de 20 animais. Os animais de ambos os tratamentos foram posteriormente submetidos à dieta controle (AIN-93M) ou a mesma dieta suplementada com GOS e PDX (25 g/kg de dieta cada) durante oito semanas e divididos em quatro subgrupos: sham-operados e gastrectomizados sem GOS e PDX, sham-operados e gastrectomizados com GOS e PDX. Dois animais morreram durante o experimento. Todos os ratos gastrectomizados receberam uma injeção intramuscular de vitamina B-12 a cada duas semanas. Hematócrito (HCT) e concentração de hemoglobina (HGB) foram dosados no início e nos dias 30 e 56 dias após o início da alimentação. No último dia do estudo, o sangue total foi coletado para determinação da concentração de ferro sérico. RESULTADOS: Na dieta com GOS e PDX a excreção de ferro nas fezes foi significativamente menor do que no grupo sem prebióticos. Absorção aparente de ferro e ferro sérico foram maiores nos grupos alimentados com GOS e PDX (ambos grupos: sham operados e gastrectomizados) do que nos grupos não alimentados com GOS e PDX. O HCT e HGB foram significativamente menores nos ratos gastrectomizados que no grupo controle, entretanto, a suplementação com GOS e PDX melhorou os níveis de HGB neste grupo. CONCLUSÃO: A associação de GOS e PDX aumenta a absorção de ferro em ratos shamoperados e gastrectomizados e ainda previne a anemia pós-gastrectomia.

Ingestion of polydextrose increase the iron absorption in rats submitted to partial gastrectomy

PURPOSE: To investigate whether polydextrose stimulates iron absorption in rats submitted to partial gastrectomy and sham operated. METHODS: The rats were submitted to partial gastrectomy (Billroth II) or laparotomy (sham-operated control), in groups of 20 and 20 each respectively. The animals were fed with a control diet (AIN-93M) without polydextrose or a diet containing polydextrose (50g/Kg of diet) for eight weeks. They were divided into four subgroups: sham-operated and Billroth II gastrectomy and with or without polydextrose. Two animals died during the experiment. All rats submitted to gastrectomy received B-12 vitamin (intramuscular) each two weeks. The hematocrit and hemoglobin concentration were measured at the start and on day 30 and 56 after the beginning of the experimental period. At the end of the study, the blood was collected for determination of serum iron concentration. RESULTS: The diet with polydextrose reduced the excretion of iron. Apparent iron absorption was higher in the polydextrose fed groups than in the control group. The haematocrit and haemoglobin concentration were lower after Billroth II gastrectomy rats fed the control diet as compared to the polydextrose diet groups. CONCLUSION: Polydextrose increase iron absorption and prevents postgastrectomy anemia.

Ingestion of epilactose, a non-digestible disaccharide, improves postgastrectomy osteopenia and anemia in rats through the promotion of intestinal calcium and iron absorption

Gastrectomy often results in osteopenia and anemia because of calcium (Ca) and iron (Fe) malabsorption. Here, we investigated the effects of feeding epilactose, a non-digestible disaccharide, on gastrectomy-induced osteopenia, anemia, and Ca and Fe malabsorption in male Sprague-Dawley rats. Totally gastrectomized or sham-operated rats were fed the control or epilactose (50 g/kg) diets for 30 days. Gastrectomy severely decreased intestinal Ca and Fe absorption, femoral bone strength, Ca content, hemoglobin concentration, and hematocrit. These decreases were partly or totally restored by feeding epilactose. Feeding epilactose increased the cecal tissue weight and the soluble Ca concentration and short-chain fatty acid pools of the cecal contents. Collectively, the increases in cecal mucosal area and/or soluble Ca concentration of the cecal contents, resulting from short-chain fatty acid production by intestinal microbes, are thought to be responsible for the epilactose-mediated promotion of Ca and Fe absorption in the gastrectomized rats.

Ingestion of potato starch containing high levels of esterified phosphorus reduces calcium and magnesium absorption and their femoral retention in rats

Many studies have shown that esterified phosphorus (P) in diets has a favorable effect on mineral absorption in humans and animals. Phosphorylated oligosaccharides derived from potato starch increase calcium (Ca) absorption from the rat intestine both in situ and in vitro. We hypothesized that the feeding of potato starch has a potential to increase Ca or magnesium (Mg) absorption. Male Sprague-Dawley rats at 7 weeks were fed 4 types of diet containing either 60% sucrose, cornstarch, or 1 of 2 types of potato starch with different P contents for 1, 3, or 5 weeks. A balance test for Ca, Mg, and P was undertaken, and these mineral contents in the femur were determined for the 4 diet groups at each feeding period in vivo. Ingestion of potato starch increased Ca, Mg, and P excretion into feces and decreased the absorption rate of Ca and Mg. Femoral Ca contents were also decreased in the rats fed the potato starch diets compared with those in rats fed the sucrose or cornstarch diet. In vitro experiment in Ca absorption was undertaken using everted jejunal and ileal sacs of the small intestine in male Sprague-Dawley rats (7 weeks old). The potato starch application did not induce significant increase in Ca absorption compared with nonstarch (control) or cornstarch application. In conclusion, the ingestion of potato starch does not increase Ca and Mg absorption and rather accelerates their excretion, inducing the decrease in mineral absorption and retention in growing rats.

Dietary polydextrose increases calcium absorption in normal rats

BACKGROUND: Gastric surgery is known to cause bone disorders, possibly related to an impaired capacity for the absorption of dietary calcium. AIM: To verify if polydextrose (PDX) could stimulate calcium absorption in partially gastrectomized and sham operated rats. METHODS: The rats were laparotomized (sham-operated control) or partially gastrectomized (Billroth II), in groups of 20 each. Half in each operated group were fed a control diet (AIN-93M) without PDX or the same diet containing (PDX 50g/Kg of diet) for eight weeks. The rats were divided into four subgroups: sham-operated and gastrectomized without PDX; sham-operated and gastrectomized with PDX. On the final day of the study, total blood was collected for determination of serum calcium concentration. RESULTS: In the diet with PDX, excretion of calcium in the feces was significantly lower than in the groups not receiving PDX, irrespective of the operation. Apparent calcium absorption and serum calcium was higher in the sham operated PDX fed group than in the control group. In sham operated rats, the calcium concentration in bone was higher in the PDX fed group. CONCLUSION: The polydextrose feeding increased calcium absorption and bone calcium concentration in normal rats, which may be relevant for decreasing the risk of osteoporosis. Partially gastrectomy did not affect the bone calcium concentration in 56 days of experimental period.

Partial gastrectomy associated to anterior truncal vagotomy: alterations in metabolism of the calcium. Experimental study in rats

BACKGROUND: The calcium is not absorbed in the lack of hydrochloric acid and the osteomalacia and osteoporosis may occurs; it is well recognized in patients that had gastric resection. AIM: To evaluate the effects of the partial gastrectomy associated to anterior truncal vagotomy in the absorption and metabolism of calcium. METHODS: Eighteen adults male Wistar rats were submitted to partial gastrectomy associated to anterior truncal vagotomy (GXT, eight animals) and the sham operation (10 animals, control group). The diet consumption and the weight gains of the animals were measured three times during the week. The animals received formulated experimental diet orally (AIN-93M) by eight weeks. The serum calcium, urinary and fecal calcium, apparent absorption of the calcium, activity of the enzyme alkaline fosfatase and calcium in the bone were measured after 60 days. RESULTS: The sham operated animals showed higher diet consumption, weight gains, serum and urinary calcium, excretion of calcium in feces, apparent absorption of calcium and activity of the enzyme alkaline fosfatase (P<0,05) as compared to the animals of the gastrectomized group. However, the concentration of the bone calcium was increased in the animals of the gastrectomized group. CONCLUSION: Partial gastrectomy associated to anterior truncal vagotomy showed to be a good experimental model the study calcium metabolism, decreasing the calcium absorption, serum and urinary calcium and activity of the enzyme alkaline fosfatase. However, for alterations at bone level in rats suggests an experimental study in larger period.

Various non-digestible saccharides increase intracellular calcium ion concentration in rat small-intestinal enterocytes

We have previously shown that non-digestible saccharides (NDS) stimulate intestinal Ca absorption via tight junctions. However, the cellular mechanisms activated by the NDS are not yet known. We investigated the effects of four NDS, difructose anhydride (DFA) III, DFAIV, fructo-oligosaccharides, and maltitol, on intracellular Ca signalling in isolated rat small-intestinal enterocytes. The changes in intracellular Ca2+concentration were measured before and after the addition of capric acid (7·5 or 15 mmol/l, a positive control), glycerol, or each NDS (1 or 10 mmol/l) to fura-2-loaded enterocytes. Treatment with capric acid or each NDS caused an immediate and dose-dependent rise in intracellular Ca2+concentration. Mechanical and osmotic stimulation achieved by adding glycerol had no effect on intracellular Ca2+concentration. The intracellular Ca2+concentration in enterocytes treated with DFAIII and fructo-oligosaccharides reached a peak level at about 30 s after stimulation, but those treated with DFAIV and maltitol showed further increases after the initial rapid rise. The maximum change in intracellular Ca2+concentration obtained by the application of maltitol was higher than that of DFAIII at 10 mmol/l. These findings suggest that each of the four NDS directly stimulates rat enterocytes, and increases intracellular Ca2+concentration. Thus, molecular structure may be more important than the size of the NDS in the induction of Ca signalling in the cells.

Combination of polydextrose and lactitol affects microbial ecosystem and immune responses in rat gastrointestinal tract

The effects of various dietary fibres on gut health have been studied extensively but their combined effects are scarcely documented. In the present study the effects of 2 % (w/w) polydextrose (PDX), 2 % (w/w) disaccharide lactitol, or 2 % (w/w) PDX+2 % (w/w) lactitol on gut microflora, microbial metabolism and gut immune responses were investigated in rats. Both PDX and lactitol alone had an effect on many of the studied parameters, but their combination had stronger than additive effects in some parameters. The PDX+lactitol combination altered the microbial community structure as seen by a culture-independent method, percentage guanine+cytosine (%G+C) profiling, increasing the areas of %G+C 35–39 (P<0·0001) and %G+C 45–49 (P=0·0002), and decreasing %G+C 65–74 (P<0·0003). These changes were also reflected in the microbial metabolism so that the production of biogenic amines and branched volatile fatty acids was significantly reduced, by 12 (P=0·03) and 50 % (P=0·002), respectively, indicating a shift from putrefactive towards saccharolytic metabolism. PDX increased the secretion of IgA in the caecum (P=0·007). Secretion of IgA increased even more, almost ten-fold, with the combination of PDX+lactitol (P<0·0001) when compared with the control group. Lactitol increased the production of butyrate by caecal microbes by two- to three-fold when compared with the PDX or control group (P<0·0001). Butyrate is a preferred energy source for mucosal cells; thus a boost in the availability of energy for immune cells may have still added to the synergistic effects of PDX and lactitol on immune cells. It is noteworthy that improvement in the IgA secretion occurred without signs of mucosal inflammation.

Two-week feeding of difructose anhydride III enhances calcium absorptive activity with epithelial cell proliferation in isolated rat cecal mucosa

OBJECTIVE

Ingestion of difructose anhydride III (DFAIII) enhances calcium (Ca) absorption in rats. The present study investigated the mechanism involved in increased Ca transport by DFAIII ingestion. The short-term and long-term effects of DFAIII feeding on Ca transport were determined by using isolated epithelium from the small and large intestine in rats.

METHODS

Male Sprague-Dawley rats were fed an 8% cellulose or 5% cellulose plus 3% DFAIII diet for 14 d. Net epithelial Ca transport in the small intestine, cecum, and colon was compared between the two diet groups by using an Ussing chamber. The contents and epithelial tissues in the cecum were analyzed.

RESULTS

There were no differences in basal and luminal DFAIII-induced Ca transport in the isolated small intestinal and colonic mucosa between the two diet groups. Basal and lumen DFAIII-induced Ca transport in the cecum in the DFAIII-fed group was higher than that in the control group. A decrease in pH and an increase in Ca pools, short-chain fatty acids, or organic acids in the cecal contents and in the depth and number of cells in crypts in cecal tissue were observed.

CONCLUSIONS

The increase in Ca transport involved two mechanisms: the presence of DFAIII in the small intestine directly affected the epithelial tissue and caused increased Ca absorption as a short-term effect, and the degradation of DFAIII by microbial fermentation produced short-chain fatty acids and subsequently enhanced Ca absorption in the large intestine as a long-term effect.

Methodological considerations in measuring human calcium absorption: relevance to study the effects of inulin-type fructans

During the last 50 years, a variety of methods have been developed to estimate Ca absorption in man. Mass balances were initially used, but these were unable to accurately measure fractional Ca absorption because they cannot distinguish unabsorbed dietary Ca from endogenous faecal Ca excretion (excretion of previously absorbed Ca back into the gut). A number of isotopic methods have been developed that can measure true fractional Ca absorption, employing radioisotopes, stable isotopes, or both. Different methods involve collection of urine, faecal or plasma samples. Of the currently available methods, the dual isotope tracer method with a timed urine collection is probably the most precise and reliable. It is also relatively straightforward to carry out and avoids the need for a faecal collection. The purpose of the present paper is to discuss the general advantages and disadvantages of the different methods of Ca absorption. In addition, the limitations the different methods have in examining the possible effects of non-digestible oligosaccharides on Ca absorption will be discussed.

Various nondigestible saccharides open a paracellular calcium transport pathway with the induction of intracellular calcium signaling in human intestinal Caco-2 cells

Ingestion of soluble nondigestible saccharides increases calcium absorption, and it is suggested that paracellular calcium transport contributes to this effect. However, cellular mechanisms and the contribution of active transport have not been clarified. This study examined the effects of 4 nondigestible saccharides, difructose anhydride (DFA) III, DFAIV, fructooligosaccharides, and raffinose, on active and passive calcium transport, permeability of paracellular pathways, and intracellular calcium signaling in a human intestinal Caco-2 cell monolayer. Net, active, and passive calcium transport were evaluated using (45)Ca. Transepithelial electrical resistance (TEER) and transport of lucifer yellow were measured as indicators of paracellular passage in differentiated Caco-2 cell monolayers incubated with 0-100 mmol/L of the various saccharides. The changes in intracellular calcium ion concentrations ([Ca(2+)](i)) were measured by fura-2 loading before and after the addition of each saccharide (50 or 100 mmol/L). The addition of 100 mmol/L of each saccharide to the apical medium of the Caco-2 cells enhanced net calcium transport without any changes in active calcium transport. Relative TEER was dose dependently and reversibly decreased by the addition of saccharides, and the decreases in TEER were highly correlated with net calcium transport (P < 0.001). Basolateral application of the saccharides had a slight or no effect on indicators of the paracellular pathway. Each saccharide caused an immediate and dose-dependent rise in [Ca(2+)](i) in the cells. The 4 nondigestible saccharides increased net calcium transport in the cells via the paracellular route through tight junctions. The rise in [Ca(2+)](i) induced by these saccharides may be involved in the opening of tight junctions.

Melibiose, difructose anhydride III and difructose anhydride IV enhance net calcium absorption in rat small and large intestinal epithelium by increasing the passage of tight junctions in vitro

An Ussing chamber technique was used to determine the effects of three indigestible disaccharides on net Ca transport from the luminal side to the basolateral side of isolated preparations of jejunal, ileal, cecal and colonic epithelium in rats. Permeability of Lucifer Yellow (LY) and transepithelial electrical resistance (TEER), which are indicators of intercellular passage of the intestinal mucosa, were also determined. The concentrations of Ca in the serosal and mucosal media were 1.25 mmol/L and 10 mmol/L, respectively. After a 30-min incubation, the net Ca transport, LY passage and TEER were determined. In the control experiment, LY permeability was lowest, and TEER value was highest in the colon. The addition of 1-100 mmol/L melibiose, difructose anhydride (DFA)III, or DFAIV to the mucosal medium increased the net Ca absorption and LY permeability dose-dependently in the jejunum, ileum, cecum and colon preparations. Melibiose decreased TEER dose-dependently in the jejunum and cecum, but not in the ileum and colon. DFAIII decreased TEER dose-dependently in the jejunum, cecum and colon, but not in the ileum. DFAIV decreased TEER dose-dependently in all four intestinal portions. Positive linear relationships were found between net Ca transport and LY passage in all portions of the intestine, whereas negative linear relationships were found between net Ca absorption and TEER. We concluded that the three indigestible saccharides directly affect the epithelial tissue and activate the passage of tight junctions, thereby promoting Ca absorption in the small and large intestine in vitro.

Various indigestible saccharides enhance net calcium transport from the epithelium of the small and large intestine of rats in vitro

An Ussing chamber technique was used to determine the effects of six indigestible saccharides on net Ca absorption from the luminal side to the basolateral side of isolated preparations of rat jejunal, ileal, cecal and colonic epithelium in vitro. The concentrations of Ca in the Tris buffer solution on the serosal side and on the mucosal side were 1.25 and 10 mmol/L, respectively. After a 30-min incubation, the Ca concentration in the serosal medium was determined and the net transepithelial Ca transport was calculated. The addition of 0.1-200 mmol/L maltitol, difructose anhydride (DFA)III, DFAIV, raffinose, fructooligosaccharide (FOS) or polydextrose (PD) to the mucosal medium increased the net Ca absorption dose-dependently in the jejunum, ileum, cecum and colon preparations. The threshold concentration required to enhance Ca transport and the extent of enhancement of Ca transport differed among the saccharides tested and among the portions of the intestine examined. Among the saccharides tested, DFA IV had the strongest effect on Ca absorption in the jejunum and cecum. We conclude that indigestible carbohydrates directly affect the epithelial tissue and promote Ca absorption in both the small and large intestine in vitro.