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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.

Lactosucrose (LS, 4(G)-beta-D-galactosylsucrose) is a non-digestible oligosaccharide, and the consumption of LS selectively increases the proportion of intestinal bifidobacteria. We examined in this study the hypolipidemic potential of LS. An oral triolein tolerance test on rats indicated that LS reduced the elevation of serum triglyceride (TG) and free fatty acids (FFA). Furthermore, LS inhibited the enzymatic digestion of triolein by pancreatic lipase in vitro. NMR spectroscopy showed that LS formed an intermolecular complex with triolein. The long-term consumption of a diet containing 5% LS for 8 weeks significantly decreased the weight of abdominal adipose tissue when compared with that of the control group. Thus, LS may reduce adipose tissue accumulation by inhibiting intestinal lipid absorption via a direct interaction with TG.

Production of a novel cyclomaltopentaose cyclized by an alpha-1,6-linkage, [ICG5; cyclo-{--6)-alpha-D-Glcp-(1--4)-alpha-D-Glcp-(1--4)-alpha-D-Glcp-(1--4)-alpha-D-Glcp-(1--4)-alpha-D-Glcp-(1--}], from starch was performed using isocyclomaltooligosaccharide glucanotransferase (IGTase) derived from Bacillus circulans AM7. The optimal conditions for ICG5-production from partially hydrolyzed starch were as follows: substrate concentration, 1.0% (w/v); pH, 5.5; temperature, 45 degrees C; reaction time, 24 h, IGTase, 1.0 unit/g-dry solid (DS); isoamylase, 2,500 units/g-DS. The yield of ICG5 reached 25.9% under optimal conditions. ICG5-production was achieved from partially hydrolyzed starch using a crude enzyme preparation containing IGTase. Finally, ICG5 was obtained in a yield of 17.9% (99.3% purity, 2,681 g-DS). A digestive test with a human salivary amylase, an artificial gastric juice, a pancreatic amylase, and small intestinal enzymes showed that ICG5 was an indigestible oligosaccharide.

We examined the dietary effects of cyclic nigerosylnigerose (CNN), a dietary indigestible oligosaccharide with four D-glucopyranosyl residues linked by alternating alpha-(1-->3)- and alpha-(1-->6) glucosidic linkages, on the intestinal immune function of mice, and the effects were compared with those of alpha-(1-->3)-linked oligosaccharide (nigerooligosaccharides, NOS) or alpha-(1-->6)-linked oligosaccharide (isomaltooligosaccharides, IMO). BALB/c mice were fed with 1-5% CNN, 5% IMO, or 12.5% NOS for 4 weeks, and the intestinal mucosal immune responses were determined. In the 1-5% CNN fed groups, the amounts of IgA in feces increased significantly. In addition, IgA, transforming growth factor-beta1 (TGF-beta1), and interleukin-6 (IL-6) secretion by Peyer's patch (PP) cells were enhanced in CNN fed mice. In the 5% CNN group, pH in the cecum decreased, and the amounts of lactic acid and butyric acid increased. These findings were not observed in the NOS- or IMO-fed group of mice. They suggest that CNN supplementation changes the intestinal environment of microflora and indirectly enhances the immune function in the gut.

We examined the digestibility of cyclic tetrasaccharide (CTS; cyclo{→6)-α-D-Glcp-(1→3)-α-D-Glcp-(1→6)-α-D-Glcp-(1→3)-α-D-Glcp-(1→}). CTS was resistant to two types of α-amylase and to artificial gastric juice. Enzymes in the rat small intestinal mucosa slightly hydrolyzed CTS. CTS was not utilized by 22 strains of human intestinal bacteria. CTS was not fermented by rat cecal content. In the single administration to rats, more than 90% of the administered CTS was recovered in the feces. From the above results, CTS was confirmed as an indigestible and unfermentable saccharide. As a result of 4 weeks’ feeding to rats, CTS was effective in the suppression of body fat accumulation and lowering of serum triglyceride of the rats. These effects of CTS depended on the amount of CTS in the diet.

We investigated the interaction between trehalose and alkaline-earth metal ions. The nuclear relaxation times of carbon atoms of trehalose were shortened by addition of the alkaline-earth chloride salts, MgCl2, CaCl2, and SrCl2, indicating that trehalose formed metal-complexes with the alkaline-earth metal chlorides. From the data of the 1H-1H coupling constants of trehalose in the presence of the alkaline-earth chlorides, it appeared that trehalose formed complexes with MgCl2, and CaCl2 at the various complexing sites: Mg2+ was coordinated to O-4 and O-4' of trehalose, and Ca2+ to O-2 and O-3. We succeeded in the preparation of two types of crystals of the trehalose/CaCl2. One was a crystal consisting of trehalose, CaCl2, and water in a ratio of 1:1:1. The other was an anhydrous crystal containing trehalose and CaCl2 in a ratio of 1:2. Several applications of the complexing between trehalose and the metal ions for food processing are proposed.

The effects of trehalose on AAPH (2,2'-azobis 2-amidinopropane dihydrochloride) -induced radical oxidation of unsaturated fatty acid (UFA) were investigated. The formation of hydroperoxide (HPOD) from linoleic acid (LA) was remarkably inhibited by trehalose. The inhibitory effect on the radical oxidation was dependent on the amount of trehalose. Several other saccharides showed negligible effect on the radical oxidation, but sorbitol and maltitol were effective second to trehalose. Similarly to LA, the formation of HPOD from α-linolenic acid (LNA) was inhibited by trehalose. The degradation of UFA and the formation of TBARS from UFA were remarkably suppressed by addition of trehalose. In the presence of 4 types of α-glucosyltrehaloses, kojibiosyl-glucoside, nigerosyl-glucoside, maltosyl-glucoside and isomaltosyl-glucoside, the formation of the HPOD from LA were 45, 72, 44 and 71% of the control (no addition of saccharide) respectively. From the above results, it was revealed that trehalose has protective effect on radical oxidation of UFA and proposed that inhibitory effect of trehalose was action point of 30H/60H.

本研究では,水/エタノール溶液系での不飽和脂肪酸自動酸化に及ぼすトレハロース添加の影響について,1)不飽和脂肪酸からのヒドロペルオキシド(HPOD)生成過程および,2)HPODの分解,アルデヒド生成過程を検討し,トレハロースの脂質酸化抑制作用を考察した.1) リノール酸(LA)からのHPOD生成はトレハロース添加濃度に応じて減少し,反応14日目のHPOD量は,トレハロース終濃度7.3mMでは2.57mg/gLA,14.6mMでは1.87mg/gLA,29.2mMでは1.28mg/gLAであった.一方,α-リノレン酸(LNA)からのHPOD生成量もLAと同様にトレハロース添加濃度に応じて減少し,トレハロース終濃度7.3mMでは7.80mg/gLNA,14.6mMでは6.30mg/gLNA,29.2mMでは4.50mg/gLNAであった.糖アルコールであるマルチトール添加系のHPOD生成量もトレハロース添加系と同様に低値であった.2) トレハロースおよびマルチトールによるHPOD分解およびHPODからの揮発性アルデヒド生成抑制作用は弱かった.以上の結果から,トレハロースは不飽和脂肪酸からHPODを生成する酸化初期反応を抑制することが示唆された.

Trehalose is a non-reducing disaccharide consisting of two glucose residues. Industrial mass-production of trehalose from starch has been achieved by using enzymatic reactions of maltooligo-syltrehalose synthase and maltooligosyltrehalose trehalohydrolase. This saccharide is available for various foods and has many useful functions; sweetening, low-damage to nutrients, and prevention of degeneration of starch and proteins. In this review, we present several functions of trehalose revealed by recent studies. Degradation of fatty acids and the formation of volatile aldehydes from fatty acids are remarkably suppressed by trehalose. This saccharide is preventive of the body odor (volatile aldehydes) of aged persons. In addition, trehalose has inhibitive effects on DNA-strand scission and protein modification by lipid oxidative products. Trehalose is effective in stabilizing vitamin C and SOD-like activity. Trehalose has shown ability to interact with minerals, including calcium chloride. Because of the interaction between trehalose and minerals, trehalose can be applied to improve of the property of mineral-containing products. From these results, it has been seen that trehalose has the benefits of lipid, minerals and vitamins other than starch and protein, including its function as a malti-functional saccharide. Trehalose has wide applications in foods, cosmetics and phamaceuticals.

In a previous study (Oku, K.; Watanabe, H.; Kubota, M.; Fukuda, S.; Kurimoto, M.; Tujisaka, Y.; Komori, M.; Inoue, Y.; Sakurai, M. J. Am. Chem. Soc. 2003, 125, 12739), we investigated the mechanism of the antioxidant function of trehalose against unsaturated fatty acids (UFAs) and revealed that the key factor relevant to the function is the formation of OH...pi and CH...O hydrogen bonds between trehalose and the cis double bonds of the UFA. Here, we investigate whether such intriguing interactions also occur between this sugar and cis double bonds in other unsaturated compounds. For this purpose, we selected various diene compounds (1,3-butadiene, 1,3-pentadiene, 1,4-pentadiene, and 2,5-heptadiene) as interaction partners. All NMR experiments performed, including 1H-1H NOESY measurements, indicated that trehalose selectively interacts with the cis-olefin proton pair in the above diene with a 1:1 stoichiometry, and the C-3 (C-3') and C-6' (C-6) sites of the sugar are responsible for the interaction. Similar interactions were not observed for the mixtures of the diene and other saccharides (neotrehalose, kojibiose, nigerose, maltose, isomaltose, sucrose, maltitol, and sorbitol). Quantum chemical calculations revealed that the OH-3 and OH-6 groups bind to the olefin double bonds of the diene through OH...pi and CH...O types of hydrogen bonds, respectively, and the stabilization energy of the resulting complex is 5-6 kcal mol(-1). These results strongly support the above NMR results. Finally, the activation energies were calculated for the hydrogen abstraction reactions from the activated methylene group of heptadiene. In particular, when the reaction was initiated by a methyl radical, the activation energy was only 10 kcal mol(-1) for the free heptadiene, but on complexation with trehalose it drastically increased to ca. 40 kcal mol(-1). This indicates that trehalose has a significant depression effect on the oxidation of the diene compounds. These results strongly support the antioxidant mechanism deduced in the previous study and indicate that the formation of unique multiple hydrogen bonds between trehalose and cis-olefin bonds is rather a general event not confined to the case of UFA.

The influence of saccharides on the formation of acrylamide (AcA) was investigated. The reducing saccharides reacted with asaparagine to form AcA, but the non-reducing saccharides, except sucrose, gave no AcA. AcA formation from a mixture containing glucose and asaparagaine was suppressed by the non-reducing saccharides, especially trehalose (76% suppression) and neotrehalose (75% suppression). Glucose is heat-degraded into pyruvaldehyde and 5-hydroxymethyl-2-furfural in the water system. The degradation products react with asparagines to generate AcA. Trehalose appears to inhibit not only the formation of these intermediates and asparagines for AcA, but also the AcA formation from these intermediates.