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Title: Different sucrose-isomaltase response of Caco-2 cells to glucose and maltose suggests dietary maltose sensing

item Cheng, Min-wen - Purdue University
item Chegeni, Mohammad - Purdue University
item Kim, Kee-hong - Purdue University
item Zhang, Genyi - Jiangnan University
item Benmoussa, Mustapha - Jiangnan University
item Quezada-calvillo, Roberto - Children'S Nutrition Research Center (CNRC)
item Nichols, Jr, Buford - Children'S Nutrition Research Center (CNRC)
item Hamaker, Bruce - Purdue University

Submitted to: Journal of Clinical Biochemistry and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2013
Publication Date: 1/1/2014
Citation: Cheng, M., Chegeni, M., Kim, K., Zhang, G., Benmoussa, M., Quezada-Calvillo, R., Nichols Jr, B.L., Hamaker, B.R. 2014. Different sucrose—isomaltase response of Caco-2 cells to glucose and maltose suggests dietary maltose sensing. Journal of Clinical Biochemistry and Nutrition. 54(1):55-60.

Interpretive Summary: Small intestinal surface enzymes are critical for converting food carbohydrates into absorbable free glucose and the blood glucose increase after meals. While genetic mutations of Sucrase-isomaltase (SI) enzyme activities modify these glucose responses little is known about the effect of the diet on these glucose producing activities. The human Caco-2 cell line, which synthesizes surface SI, is a model for study of small intestinal starch digestion. Our objective was to learn whether these cells are able to sense the starch degradation product maltose. Analysis of SI protein bands revealed that only maltose induced a higher molecular weight band, documenting altered internal processing of SI to the external membrane and more importantly a sensing of external maltose. This suggests that the small intestinal cells can sense the products of starch digestion and regulate the surface SI activity needed to produce free glucose for absorption. We conclude that maltose sensing is a novel regulation point for mealtime food carbohydrate digestion to glucose.

Technical Abstract: Using the small intestine enterocyte Caco-2 cell model, sucrase-isomaltase (SI, the mucosal alpha-glucosidase complex) expression and modification were examined relative to exposure to different mono- and disaccharide glycemic carbohydrates. Caco-2/TC7 cells were grown on porous supports to post-confluence for complete differentiation, and dietary carbohydrate molecules of glucose, sucrose (disaccharide of glucose and fructose), maltose (disaccharide of two glucoses alpha-1,4 linked), and isomaltose (disaccharide of two glucoses alpha-1,6 linked) were used to treat the cells. qRT-PCR results showed that all the carbohydrate molecules induced the expression of the SI gene, though maltose (and isomaltose) showed an incremental increase in mRNA levels over time that glucose did not. Western blot analysis of the SI protein revealed that only maltose treatment induced a higher molecular weight band (Mw approximately 245 kDa), also at higher expression level, suggesting post-translational processing of SI, and more importantly a sensing of maltose. Further work is warranted regarding this putative sensing response as a potential control point for starch digestion and glucose generation in the small intestine.