title: Metabolism and bioavailability of newly developed dietary fiber materials, resistant glucan and hydrogenated resistant glucan, in rats and humans.
abstract: 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/m(2); 5 females, 25.8 y, BMI 20.9 kg/m(2)) 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Institute of Food, Nutrition and Health, Jumonji University, 2-1-28, Sugasawa, Niiza, Saitama 352-8510 Japan ; Graduate School of Human Health Science, University of Nagasaki Siebold, 1-1-1, Manabino, , Nagayo, Nagasaki 851-2195 Japan.
authors.forename: Sadako
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Graduate School of Human Health Science, University of Nagasaki Siebold, 1-1-1, Manabino, , Nagayo, Nagasaki 851-2195 Japan ; Department of Food Science and Nutrition, Nagoya Women's University, 3-40, Shioji, Mizuho-ku, Nagoya 467-8610 Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Tanabe
authors.affiliation: Graduate School of Human Health Science, University of Nagasaki Siebold, 1-1-1, Manabino, , Nagayo, Nagasaki 851-2195 Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Morita
authors.affiliation: Institute of Food Materials, Nippon Shokuhin Kako Co. Ltd., Tajima, Fuji, 417-8530 Japan.
authors.forename: Norihisa
authors.initials: N
authors.lastname: Hamaguchi
authors.affiliation: Institute of Food, Nutrition and Health, Jumonji University, 2-1-28, Sugasawa, Niiza, Saitama 352-8510 Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Shimura
authors.affiliation: Institute of Food, Nutrition and Health, Jumonji University, 2-1-28, Sugasawa, Niiza, Saitama 352-8510 Japan ; Graduate School of Human Health Science, University of Nagasaki Siebold, 1-1-1, Manabino, , Nagayo, Nagasaki 851-2195 Japan.
authors.forename: Tsuneyuki
authors.initials: T
authors.lastname: Oku
keywords: Available energy; Bioavailability; Dietary fiber materials; Hydrogenated resistant glucan; Metabolism; Resistant glucan