title: Enzyme-synthesized highly branched maltodextrins have slow glucose generation at the mucosal α-glucosidase level and are slowly digestible in vivo.
abstract: For digestion of starch in humans, α-amylase first hydrolyzes starch molecules to produce α-limit dextrins, followed by complete hydrolysis to glucose by the mucosal α-glucosidases in the small intestine. It is known that α-1,6 linkages in starch are hydrolyzed at a lower rate than are α-1,4 linkages. Here, to create designed slowly digestible carbohydrates, the structure of waxy corn starch (WCS) was modified using a known branching enzyme alone (BE) and an in combination with β-amylase (BA) to increase further the α-1,6 branching ratio. The digestibility of the enzymatically synthesized products was investigated using α-amylase and four recombinant mammalian mucosal α-glucosidases. Enzyme-modified products (BE-WCS and BEBA-WCS) had increased percentage of α-1,6 linkages (WCS: 5.3%, BE-WCS: 7.1%, and BEBA-WCS: 12.9%), decreased weight-average molecular weight (WCS: 1.73×10(8) Da, BE-WCS: 2.76×10(5) Da, and BEBA-WCS 1.62×10(5) Da), and changes in linear chain distributions (WCS: 21.6, BE-WCS: 16.9, BEBA-WCS: 12.2 DPw). Hydrolysis by human pancreatic α-amylase resulted in an increase in the amount of branched α-limit dextrin from 26.8% (WCS) to 56.8% (BEBA-WCS). The α-amylolyzed samples were hydrolyzed by the individual α-glucosidases (100 U) and glucogenesis decreased with all as the branching ratio increased. This is the first report showing that hydrolysis rate of the mammalian mucosal α-glucosidases is limited by the amount of branched α-limit dextrin. When enzyme-treated materials were gavaged to rats, the level of postprandial blood glucose at 60 min from BEBA-WCS was significantly higher than for WCS or BE-WCS. Thus, highly branched glucan structures modified by BE and BA had a comparably slow digesting property both in vitro and in vivo. Such highly branched α-glucans show promise as a food ingredient to control postprandial glucose levels and to attain extended glucose release.
authors.affiliation: Whistler Center for Carbohydrate Research and Department of Food Science, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Byung-Hoo
authors.initials: BH
authors.lastname: Lee
authors.forename: Like
authors.initials: L
authors.lastname: Yan
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Phillips
authors.forename: Bradley L
authors.initials: BL
authors.lastname: Reuhs
authors.forename: Kyra
authors.initials: K
authors.lastname: Jones
authors.forename: David R
authors.initials: DR
authors.lastname: Rose
authors.forename: Buford L
authors.initials: BL
authors.lastname: Nichols
authors.forename: Roberto
authors.initials: R
authors.lastname: Quezada-Calvillo
authors.forename: Sang-Ho
authors.initials: SH
authors.lastname: Yoo
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Hamaker
mesh_terms: D000818:Animals; D001786:Blood Glucose; D005947:Glucose / Q000096:biosynthesis* / Q000737:chemistry*; D006801:Humans; D006868:Hydrolysis; D008297:Male; D008970:Molecular Weight; D009092:Mucous Membrane / Q000201:enzymology; D019906:Nuclear Magnetic Resonance, Biomolecular; D011134:Polysaccharides / Q000737:chemistry* / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013213:Starch / Q000737:chemistry / Q000378:metabolism; D000520:alpha-Glucosidases / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D011134:Polysaccharides; D011994:Recombinant Proteins; C008315:maltodextrin; D013213:Starch; D000520:alpha-Glucosidases; D005947:Glucose
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