Mucosal maltase-glucoamylase plays a crucial role in starch digestion and prandial glucose homeostasis of mice

Nichols, Buford L; Quezada-Calvillo, Roberto; Robayo-Torres, Claudia C; Ao, Zihua; Hamaker, Bruce R; Butte, Nancy F; Marini, Juan; Jahoor, Farook; Sterchi, Erwin E (2009). Mucosal maltase-glucoamylase plays a crucial role in starch digestion and prandial glucose homeostasis of mice. Journal of nutrition, 139(4), pp. 684-90. Bethesda, Md.: American Society for Nutrition 10.3945/jn.108.098434

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Starch is the major source of food glucose and its digestion requires small intestinal alpha-glucosidic activities provided by the 2 soluble amylases and 4 enzymes bound to the mucosal surface of enterocytes. Two of these mucosal activities are associated with sucrase-isomaltase complex, while another 2 are named maltase-glucoamylase (Mgam) in mice. Because the role of Mgam in alpha-glucogenic digestion of starch is not well understood, the Mgam gene was ablated in mice to determine its role in the digestion of diets with a high content of normal corn starch (CS) and resulting glucose homeostasis. Four days of unrestricted ingestion of CS increased intestinal alpha-glucosidic activities in wild-type (WT) mice but did not affect the activities of Mgam-null mice. The blood glucose responses to CS ingestion did not differ between null and WT mice; however, insulinemic responses elicited in WT mice by CS consumption were undetectable in null mice. Studies of the metabolic route followed by glucose derived from intestinal digestion of (13)C-labeled and amylase-predigested algal starch performed by gastric infusion showed that, in null mice, the capacity for starch digestion and its contribution to blood glucose was reduced by 40% compared with WT mice. The reduced alpha-glucogenesis of null mice was most probably compensated for by increased hepatic gluconeogenesis, maintaining prandial glucose concentration and total flux at levels comparable to those of WT mice. In conclusion, mucosal alpha-glucogenic activity of Mgam plays a crucial role in the regulation of prandial glucose homeostasis.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Biochemistry and Molecular Medicine
UniBE Contributor:	Sterchi, Erwin-Ernst
ISSN:	0022-3166
Publisher:	American Society for Nutrition
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 15:12
Last Modified:	05 Dec 2022 14:22
Publisher DOI:	10.3945/jn.108.098434
PubMed ID:	19193815
Web of Science ID:	000264724400010
URI:	https://boris.unibe.ch/id/eprint/31635 (FactScience: 196267)