Digestibility of new dietary fibre materials, resistant glucan and hydrogenated resistant glucan in rats and humans, and the physical effects in rats

Fructooligosaccharide feeding during gestation to pregnant mice provided excessive folic acid decreases maternal and female fetal oxidative stress by increasing intestinal microbe-derived hydrogen gas

Fructooligosaccharide (FOS) is fermented by intestinal microbes to generate intestinal microbe-derived hydrogen gas (IMDH). Oxidative stress increases during gestation, whereas hydrogen gas has antioxidant effects with therapeutic benefits. We have previously reported that the offspring from a pregnant, excessive folic acid mouse model (PEFAM) had abnormal glucose metabolism after growth. We hypothesized that IMDH by FOS feeding during gestation in PEFAM would suppress maternal and fetal oxidative stress. C57BL/6J mice on day 1 of gestation were divided into 3 groups and dissected at gestational day 18. The control (CONT) diet was AIN-93G containing folic acid 2 mg/kg diet; PEFAM was fed with an excessive folic acid (EFA) diet containing folic acid 40 mg/kg diet, and the EFA-FOS diet was replaced half of the sucrose in the EFA diet. Hydrogen gas concentrations in maternal livers and whole fetuses in EFA-FOS were significantly higher than those in CONT and EFA, respectively (P < .05). Maternal and fetal 8-hydroxy-2'-deoxyguanosine in EFA-FOS were not significantly different from those in the CONT group, whereas those in the EFA group were significantly increased compared with CONT and EFA-FOS (P < .05). In EFA-FOS, expression of protein and mRNA of superoxide dismutase and heme oxygenase 1 in mothers and superoxide dismutase in fetuses were not significantly different from those in CONT, whereas those in EFA were significantly increased (P < .05). The protein expression of Nrf2 in mothers and fetuses were not significantly different between EFA-FOS and CONT. Therefore, FOS feeding to PEFAM during gestation decreases maternal and fetal oxidative stress through IMDH.

Evaluation of the relative available energy of cyclic nigerosylnigerose using breath hydrogen excretion in healthy humans

Cyclic nigerosylnigerose (CNN) is a cyclic tetrasaccharide with properties distinct from those of other conventional cyclodextrins. We investigated the relative available energy of CNN in healthy humans. CNN digestibility was determined using brush border membrane vesicles from the small intestines of rats. CNN was not hydrolyzed by rat intestinal enzymes. To investigate breath hydrogen excretion, 13 human subjects were included in a double-blind cross-over, randomized, placebo-controlled study. The effects of CNN on hydrogen excretion were compared with those of a typical nondigestible, fermentable fructooligosaccharide (FOS). In the study participants, hydrogen excretion hardly increased upon CNN and was remarkably lower than for FOS. The available energy value was determined using the fermentability based on breath hydrogen excretion and was evaluated as 0 kcal/g for CNN. CNN was hardly metabolized and hence may be used as a low-energy dietary fiber.

Attenuation of glycaemic and insulin responses following tapioca resistant maltodextrin consumption in healthy subjects: a randomised cross-over controlled trial

Resistant maltodextrin (RMD) from various sources of starch has been extensively studied. However, studies which reported the effects of tapioca RMD (TRM) on glucose and insulin response are lacking. This study investigated the effect of TRM on postprandial plasma glucose and serum insulin in healthy subjects. Additionally, satiety and gastrointestinal tolerability were also evaluated. Sixteen healthy participants received five different treatments on five separate days. Participants received 50 g of either: glucose (GL), tapioca maltodextrin (TM), TRM, MIX15% (7⋅5 g TRM + 42⋅5 g TM) or MIX50% (25 g TRM + 25 g TM). Plasma glucose, serum insulin and subjective appetite responses were measured postprandially over 180 min. Gastrointestinal symptoms were evaluated by questionnaire before and after each test day. Results showed that at 30 min after treatment drinks, plasma glucose after TRM was significantly lowest (104⋅60 (sem 2⋅63 mg/dl) than after GL (135⋅87 (sem 4⋅88) mg/dl; P <0⋅001), TM (127⋅93 (sem 4⋅05) mg/dl; P = 0⋅001), MIX15% (124⋅67 (sem 5⋅73) mg/dl; P = 0⋅039) and MIX50% (129⋅33 (sem 5⋅23) mg/dl; P = 0⋅003) (1 mg/dl = 0⋅0555 mmol/l). In addition, TRM also significantly reduced serum insulin (13⋅01 (sem 2⋅12) μIU/ml) compared with GL (47⋅90 (sem 11⋅93) μIU/ml; P = 0⋅013), TM (52⋅96 (sem 17⋅68) μIU/ml; P = 0⋅002) and MIX50% (33⋅16 (sem 4⋅99) μIU/ml; P = 0⋅008). However, there were no significant differences in subjective appetite between treatments (P > 0⋅05). A single high dose of TRM (50 g) caused flatulence (P < 0⋅05). Tapioca resistant maltodextrin has low digestibility in the small intestine and, therefore, reduced incremental plasma glucose and serum insulin, without affecting satiety in healthy subjects over 180 min. Gastrointestinal tolerability of TRM should be considered when consumed in high doses.

Highly Cross-linked Starch and Modified Cellulose as Dietary Fibers, and their Acclimation Effect on Hydrogen Excretion in Rats

Background:

Highly cross-linked phosphate starch (HCPS) and modified cellulose (MC) were newly developed and modified dietary fiber materials to prevent lifestyle-related diseases.

Objective:

We investigated the physiological property of HCPS and MC to be a dietary fiber.

Methods:

HCPS was made from tapioca starch by polymerization in the presence of 0.5% phosphoric acid, and MC was made from cellulose, maltodextrin and karaya gum by high-speed mixing. In the present study, rats were raised on a diet containing 10% or 15% HCPS, or 10% MC for four weeks, and physical effects such as growth, organ weights, blood biomedical parameters, fecal weight, and hydrogen excretion were recorded.

Results:

Growth was normal among all groups, and there was no significant difference in total body weight gain. Some organ weights including the adipose tissues differed slightly among groups, but no difference based on diet composition was observed. Blood biomedical parameters were normal and not significantly different among groups. Cecum tissue and content weights were significantly greater in the 15% HCPS, 10% MC, and 10% fructooligosaccharide (FOS) groups than in the control group, and fecal weight was significantly increased in the 10% and 15% HCPS, and 10% MC groups compared with the control group. Hydrogen excretion over 24 h was negligible when HCPS was administered orally to rats non-acclimatized to HCPS but increased significantly in rats acclimatized to 10% HCPS diet for one week.

Conclusion:

We conclude that both HCPS and MC could be suitable for use as low energy bulking materials.

Dietary Fructooligosaccharide and Glucomannan Alter Gut Microbiota and Improve Bone Metabolism in Senescence-Accelerated Mouse

Gut microbiota improved using prebiotics may delay the onset of senescence-related health problems. We hypothesized that prolonged intake of prebiotics delays senile osteoporosis. Forty-five male senescence-accelerated mouse prone 6 (SAMP6) aged four weeks were raised on 5% fructooligosaccharide (FOS), 5% glucomannan (GM), or a control diet for 31 weeks. Gut microbiota were identified using culture-dependent analytical methods. Mineral content in femoral bone was analyzed using atomic absorption spectrophotometry. Bone metabolism and inflammatory markers were measured using enzyme-linked immunosorbent assay. The numbers of Lactobacillus and Bacteroides in cecal contents were significantly higher in the FOS than in the control group ( p < 0.05); the number of Clostridium was significantly higher in the GM than in the control group ( p < 0.05). Calcium content was significantly higher in the femoral bones of the FOS group (30.5 ± 0.8 mg) than in the control group (27.5 ± 1.5 mg) ( p < 0.05). There was no difference between the GM (29.1 ± 2.0 mg) and control groups. During senescence, urinary deoxypyridinoline and serum high-sensitivity C-reactive protein levels significantly decreased in the FOS (1.2 ± 0.2 nmol/3 d and 80 ± 6.1 ng/100 mL) and GM groups (1.2 ± 0.2 nmol/3 d and 80 ± 6.1 ng/100 mL) compared with the control group (1.8 ± 0.5 nmol/3 d and 93 ± 7.4 ng/100 mL) ( p < 0.05). Thus, dietary FOS and GM modified gut microbiota and reduced bone resorption by reducing systemic inflammation in SAMP6.

Effects of 1,5-anhydroglucitol on postprandial blood glucose and insulin levels and hydrogen excretion in rats and healthy humans

The inhibition by 1,5-anhydro-d-glucitol (1,5-AG) was determined on disaccharidases of rats and humans. Then, the metabolism and fate of 1,5-AG was investigated in rats and humans. Although 1,5-AG inhibited about 50 % of sucrase activity in rat small intestine, the inhibition was less than half of d-sorbose. 1,5-AG strongly inhibited trehalase and lactase, whereas d-sorbose inhibited them very weakly. 1,5-AG noncompetitively inhibited sucrase. The inhibition of 1,5-AG on sucrase and maltase was similar between humans and rats. 1,5-AG in serum increased 30 min after oral administration of 1,5-AG (600 mg) in rats, and mostly 100 % of 1,5-AG was excreted into the urine 24 h after administration. 1,5-AG in serum showed a peak 30 min after ingestion of 1,5-AG (20 g) by healthy subjects, and decreased gradually over 180 min. About 60 % of 1,5-AG was excreted into the urine for 9 h following ingestion. Hydrogen was scarcely excreted in both rats and humans 24 h after administration of 1,5-AG. Furthermore, 1,5-AG significantly suppressed the blood glucose elevation, and hydrogen excretion was increased following the simultaneous ingestion of sucrose and 1,5-AG in healthy subjects. 1,5-AG also significantly suppressed the blood glucose elevation following the simultaneous ingestion of glucose and 1,5-AG; however, hydrogen excretion was negligible. The available energy of 1,5-AG, which is absorbed readily from the small intestine and excreted quickly into the urine, is 0 kJ/g (0 kcal/g). Furthermore, 1,5-AG might suppress the blood glucose elevation through the inhibition of sucrase, as well as intestinal glucose absorption.

Attenuation of postprandial blood glucose in humans consuming isomaltodextrin: carbohydrate loading studies

Background: Isomaltodextrin (IMD) is a novel highly branched α-glucan and its function as a soluble dietary fiber is expected. Objective: The goal of this study was to evaluate the effects of IMD on postprandial glucose excursions in healthy people and to make the mechanism clear. Design: Twenty-nine subjects ingested a solution containing maltodextrin (MD) or sucrose with or without IMD. Fourteen subjects ingested a solution containing glucose with or without IMD. Blood glucose concentrations were then compared between the groups. Furthermore, in vitro digestion, inhibition of digestive enzymes, and glucose absorption tests were conducted. Results: IMD attenuated blood glucose elevation in the subjects with blood glucose excursions at the high end of normal following the ingestion of MD or sucrose or glucose alone. This effect of 5 g IMD was most clear. IMD was digested partially only by small intestinal mucosal enzymes, and maltase and isomaltase activities were weakly inhibited. Furthermore, IMD inhibited the transport of glucose from mucosal side to serosal side. Conclusions: IMD attenuated postprandial blood glucose, after the ingestion of MD or sucrose or glucose. As one of the mechanism, it was suggested that IMD inhibited the absorption of glucose on small intestinal mucosal membrane.

Metabolism and bioavailability of newly developed dietary fiber materials, resistant glucan and hydrogenated resistant glucan, in rats and humans

Background

Resistant glucan (RG) and hydrogenated resistant glucan (HRG) are new dietary fiber materials developed to decrease the risk of metabolic syndrome and lifestyle-related diseases. We investigated the metabolism and bioavailability of RG and HRG using rats and humans.

Methods

Purified RG and HRG were used as test substances. After 25 Wistar male rats (270 g) were fed with an experimental diet (AIN93M diet with the cellulose replaced by β-corn starch) ad libitum for 1 week, they were used for the experiment involving blood collection and circulating air collection. Ten participants (5 males, 22.5 y, BMI 20.4 kg/m²; 5 females, 25.8 y, BMI 20.9 kg/m²) voluntarily participated in this study. The study was carried out using a within-subject, repeated measures design. Effects of RG and HRG on the response for blood glucose and insulin and hydrogen excretion were compared with those of glucose and a typical nondigestible and fermentable fructooligosaccharide (FOS) in rats and humans. Available energy was evaluated using the fermentability based on breath hydrogen excretion.

Results

When purified RG or HRG (400 mg) was administered orally to rats, blood glucose and insulin increased slightly, but less than when glucose was administration (P < 0.05). Hydrogen started to be excreted 120 min after administration of RG with negligibly small peak at 180 min, thereafter excreted scarcely until 1440 min. Hydrogen excretion after HRG administration showed a larger peak than RG at 180 min, but was markedly less than FOS. RG and HRG were excreted in feces, but not urine. When purified RG or HRG (30 g) were ingested by healthy humans, blood glucose and insulin levels increased scarcely. Breath hydrogen excretion increased slightly, but remarkably less than FOS. Ingestion of purified RG or HRG (5 g) to evaluate available energy, increased scarcely glucose and insulin levels and breath hydrogen excretion. Available energy was evaluated as 0 kcal/g for purified RG and 1 kcal/g for HRG.

Conclusion

The bioavailability was very low in both humans and rats, because oligosaccharide of minor component in purified RG and HRG was metabolized via intestinal microbes but major components with higher molecular weight were metabolized scarcely. Moreover, the ingestion of 30 g of RG or HRG did not induce apparent acute side effects in healthy adults. RG and HRG might potentially be used as new dietary fiber materials with low energy.