Carbohydrate materials that produce lower postprandial blood glucose increase are required for diabetic patients. To develop slowly digestible carbohydrates, the effect of degree of polymerization (DP) of α-1,6 glucan on its digestibility was investigated in vitro and in vivo. We prepared four fractions of α-1,6 glucan composed primarily of DP 3-9, DP 10-30, DP 31-150, and DP 151+ by fractionating a dextran hydrolysate. An in vitro experiment using digestive enzymes showed that the glucose productions of DP 3-9, DP 10-30, DP 31-150, and DP 151+ were 70.3, 53.4, 28.2, and 19.2 % in 2 h, and 92.1, 83.9, 39.6, and 33.3 % in 24 h relative to dextrin, respectively. An in vivo glycemic response showed that the incremental area under the curve (iAUC) of blood glucose levels of α-1,6 glucan with DP 3-9, DP 10-30, DP 31-150, and DP 151+ were 99.5, 84.3, 65.4, and 40.1 % relative to dextrin, respectively. These results indicated that α-1,6 glucan with higher DP had stronger resistance to digestion and produced a smaller blood glucose response. DP 10-30 showed significantly lower maximum blood glucose levels than dextrin; however, no significant difference was observed in iAUC, indicating that DP 10-30 was slowly digestible. In addition, α-1,6 glucan was also produced using an enzymatic reaction with dextrin dextranase (DDase). This produced similar results to DP 10-30. The DDase product can be synthesized from dextrin at low cost. This glucan is expected to be useful as a slowly digestible carbohydrate source.

-The disposition of perfluorododecanoic acid (PFDoA), a perfluorocarboxylic acid with 12 carbon atoms, was studied in male rats. Rats received an oral administration of PFDoA at a dose of 50 mg/kg. The body weights of PFDoA-treated rats were slightly less than those of vehicle-treated control rats. PFDoA administration resulted in an increase in liver weight; it was highest at 5 days after the treatment and gradually decreased thereafter. Higher liver weight was observed until 70 days after the treatment. Concentrations of PFDoA in plasma and various tissues were estimated up to 70 days after dosing. A large amount of PFDoA was found in the liver. The PFDoA concentration was 263.94 ± 32.94 μg/g in the liver; the value was 7.93 times higher than that of serum 5 days after treatment. The hepatic PFDoA amount was found to be 29.63% of the dose. A certain amount of PFDoA was found in the brain and adipose tissues where perfluorocarboxylic acids with less than 11 carbon atoms were sparsely distributed. The half-life of PFDoA was 55.3, 49.3, 52.4, 57.1, and 49.8 days for serum, liver, kidneys, brain, and adipose tissue, respectively. PFDoA increased hepatic levels of mRNA for Cyp4A10, Acot1, and Acox1, target genes of PPARα, suggesting that PFDoA can activate PPARα, as was observed with other PFCAs. Elevated levels of these 3 genes were observed 70 days after treatment, and the levels were less than those at 7 days. The differences between PFDoA and PFCAs with less than 11 carbon atoms were discussed.

A high-energy-type oral dietary supplement (ONS), with a low proportion of available carbohydrate (LC-ONS), which contains a slowly digestible carbohydrate, isomaltulose, and is fortified with soluble dietary fiber, was newly developed for individuals with diabetes or prediabetes. This study aimed to evaluate the impact of LC-ONS on blood glucose levels after ingestion in individuals with prediabetes. A single-blind, randomized crossover clinical trial was performed on 20 individuals with prediabetes. After overnight fasting, all subjects ingested one serving (200 kcal/125 mL) of either LC-ONS (40% energy proportion of available carbohydrates) or standard ONS (ST-ONS, 54% energy proportion of available carbohydrates) on two separate days. The incremental area under the curve of blood glucose levels for 120 min was significantly lower after LC-ONS ingestion compared to ST-ONS (2207 ± 391 mg/dL·min (least mean square value ± standard error) and 3735 ± 391 mg/dL·min, respectively; p < 0.001). The LC-ONS showed significantly lower blood glucose levels than the ST-ONS at all time points, except at baseline. Similarly, the incremental area under the curve of plasma insulin was significantly lower after LC-ONS ingestion. These results suggest that LC-ONS is useful as an ONS for energy supply in individuals with postprandial hyperglycemia.

Intestinal barrier function declines with aging. We evaluated the effect of dietary fibers and indigestible oligosaccharides on intestinal barrier function by altering the microbiota of the elderly. The feces were anaerobically cultured with indigestible dextrin, inulin, partially hydrolyzed guar gum (PHGG), lactulose, raffinose, or alginate, and the fermented supernatant was added to inflammation-induced Caco-2/HT29-MTX-E12 co-cultured cells. Our data showed that inulin- and PHGG-derived supernatants exerted a protective effect on the intestinal barrier. The protective effect was significantly positively correlated with total short-chain fatty acids (SCFAs) and butyric acid production in the supernatant and negatively correlated with the claudin-2 (CLDN2) gene expression in the cultured cells. Furthermore, we showed that the CLDN2 levels are regulated by butyric acid. Thus, inulin and PHGG can change the intestinal environment of the elderly and maintain the intestinal barrier by accelerating the production of SCFAs and modifying the expression levels of barrier function-related genes.

Slowly digestible carbohydrates are needed for nutritional support in diabetic patients with malnutrition. They are a good source of energy and have the advantage that their consumption produces a low postprandial peak in blood glucose levels because they are slowly and completely digested in the small intestine. A high-amount isomaltomegalosaccharide containing carbohydrate (H-IMS), made from starch by dextrin dextranase, is a mixture of glucose polymers which has a continuous linear structure of α-1,6-glucosidic bonds and a small number of α-1,4-glucosidic bonds at the reducing ends. It has a broad degree of polymerization (DP) distribution with glucans of DP 10 30 as the major component. In our previous study, H-IMS has been shown to exhibit slow digestibility in vitro and not to raise postprandial blood glucose to such levels as that raised by dextrin in vivo. This marks it out as a potentially useful slowly digestible carbohydrate, and this study aimed to evaluate its in vivo digestibility. The amount of breath hydrogen emitted following oral administration of H-IMS was measured to determine whether any indigestible fraction passed through to and was fermented in the large intestine. Total carbohydrate in the feces was also measured. H-IMS, like glucose and dextrin, did not result in breath hydrogen excretion. Carbohydrate excretion with dietary H-IMS was no different from that of glucose or water. These results show that the H-IMS is completely digested and absorbed in the small intestine, indicating its potential as a slowly digestible carbohydrate in the diet of diabetic patients.