Skip Navigation LinksHome > December 2013 - Volume 57 - Issue 6 > Maltase-Glucoamylase Modulates Gluconeogenesis and Sucrase-I...
Journal of Pediatric Gastroenterology & Nutrition:
doi: 10.1097/MPG.0b013e3182a27438
Original Articles: Hepatology and Nutrition

Maltase-Glucoamylase Modulates Gluconeogenesis and Sucrase-Isomaltase Dominates Starch Digestion Glucogenesis

Diaz-Sotomayor, Maricela*; Quezada-Calvillo, Roberto*; Avery, Stephen E.*; Chacko, Shaji K.*; Yan, Li-ke; Lin, Amy Hui-Mei; Ao, Zi-hua; Hamaker, Bruce R.; Nichols, Buford L.*

Supplemental Author Material
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Abstract

Objectives: Six enzyme activities are needed to digest starch to absorbable free glucose; 2 luminal α-amylases (AMY) and 4 mucosal maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI) subunit activities are involved in the digestion. The AMY activities break down starch to soluble oligomeric dextrins; mucosal MGAM and SI can either directly digest starch to glucose or convert the post-α-amylolytic dextrins to glucose. We hypothesized that MGAM, with higher maltase than SI, drives digestion on ad limitum intakes and SI, with lower activity but more abundant amount, constrains ad libitum starch digestion.

Methods: Mgam null and wild-type (WT) mice were fed with starch diets ad libitum and ad limitum. Fractional glucogenesis (fGG) derived from starch was measured and fractional gluconeogenesis and glycogenolysis were calculated. Carbohydrates in small intestine were determined.

Results: After ad libitum meals, null and WT had similar increases of blood glucose concentration. At low intakes, null mice had less fGG (P = 0.02) than WT mice, demonstrating the role of Mgam activity in ad limitum feeding; null mice did not reduce fGG responses to ad libitum intakes demonstrating the dominant role of SI activity during full feeding. Although fGG was rising after feeding, fractional gluconeogenesis fell, especially for null mice.

Conclusions: The fGNG (endogenous glucogenesis) in null mice complemented the fGG (exogenous glucogenesis) to conserve prandial blood glucose concentrations. The hypotheses that Mgam contributes a high-efficiency activity on ad limitum intakes and SI dominates on ad libitum starch digestion were confirmed.

© 2013 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology,

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