Monomer and linkage type of galacto-oligosaccharides affect their resistance to ileal digestion and prebiotic properties in rats.
A detailed study was performed to compare the in vivo ileal digestibility and modulatory effects in fecal microbiota of novel galacto-oligosaccharides (GOS) derived from lactulose [GOS-Lu; degree of polymerization (DP) ≥2, 14.0% trisaccharides] and commercial GOS derived from lactose (GOS-La; DP ≥3, 35.1% trisaccharides) in growing rats (5 wk old). Rats were fed either a control diet or diets containing 1% (wt:wt) of GOS-Lu or GOS-La for 14 d. Quantitative analysis of carbohydrates from dietary and ileal samples demonstrated that the trisaccharide fraction of GOS-Lu was significantly more resistant to gut digestion than that from GOS-La, as indicated by their ileal digestibility rates of 12.5 ± 2.6% and 52.9 ± 2.7%, respectively, whereas the disaccharide fraction of GOS-Lu was fully resistant to the extreme environment of the upper digestive tract. The low ileal digestibility of GOS-Lu was due to the great resistance of galactosyl-fructoses to mammalian digestive enzymes, highlighting the key role played by the monomer type and linkage involved in the oligosaccharide chain. The partial digestion of GOS-La trisaccharides showed that glycosidic linkages (1→6) and (1→2) between galactose and glucose monomers were significantly more resistant to in vivo gastrointestinal digestion than the linkage (1→4) between galactose units. The absence of GOS-La and GOS-Lu digestion-resistant oligosaccharides in fecal samples indicated that they were readily fermented within the large intestine, enabling both types of GOS to have a potential prebiotic function. Indeed, compared with controls, the GOS-Lu group had significantly more bifidobacteria in fecal samples after 14 d of treatment. The number of Eubacterium rectale also was greater in the GOS-Lu and GOS-La groups than in controls. These novel data support a direct relationship between patterns of resistance to digestion and prebiotic properties of GOS.
Instituto de Química Orgánica General, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Oswaldo
O
Hernández-Hernández
M Carmen
MC
Marín-Manzano
Luis A
LA
Rubio
F Javier
FJ
Moreno
M Luz
ML
Sanz
Alfonso
A
Clemente
D000818:Animals; D001644:Bifidobacterium / Q000187:drug effects; D003106:Colon / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004063:Digestion; D004798:Enzymes / Q000378:metabolism; D005051:Eubacterium / Q000187:drug effects; D005243:Feces / Q000737:chemistry; D005285:Fermentation; D005690:Galactose / Q000737:chemistry / Q000378:metabolism*; D005947:Glucose / Q000737:chemistry; D006027:Glycosides / Q000378:metabolism*; D007082:Ileum / Q000378:metabolism*; D008297:Male; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D056692:Prebiotics; D051381:Rats; D017208:Rats, Wistar
D004040:Dietary Carbohydrates; D004798:Enzymes; D006027:Glycosides; D009844:Oligosaccharides; D056692:Prebiotics; D005947:Glucose; D005690:Galactose