Regulatory Functions of α-Amylase in the Small Intestine Other than Starch Digestion: α-Glucosidase Activity, Glucose Absorption, Cell Proliferation, and Differentiation

Abstract

Pancreatic α-amylase binds to the N-glycan of glycoproteins. Here, I will show that pancreatic α-amylase has regulatory functions in the small intestine other than starch digestion. These new functions were revealed by identification of α-amylase-binding proteins in the intestinal brush border membrane (BBM). This topic will include the following four parts: 1) identification of glycoproteins that bind pancreatic α-amylase in the small intestinal BBM; 2) interactions between pancreatic α-amylase and the binding glycoproteins, sucrose-isomaltase (α-glucosidase), and sodium/glucose co-transporter 1 (SGLT1), in which pancreatic α-amylase enhanced maltose degradation of sucrose-isomaltase under conditions including calcium and sodium, and inhibited glucose uptake of SGLT1; 3) localization of pancreatic α-amylase in the small intestine by binding to the BBM and being internalized into lysosomes through the endocytic pathway; and 4) expression of endogenous α-amylase in the duodenum: AMY2B, a pancreatic type α-amylase, is highly expressed in the human duodenum next to the pancreas. The α-amylase expression in the duodenum is required for proliferation and differentiation of human small intestinal epithelial cells.

Discovery of Novel Coumarin Derivatives as Potential Dual Inhibitors against α-Glucosidase and α-Amylase for the Management of Post-Prandial Hyperglycemia via Molecular Modelling Approaches

“…This causes the elevation in blood sugar levels, which in turn increases the risk of T2DM [4]. α-glucosidase resides in the epithelial cells of the small intestine [5], whereas α-amylase is predominantly present in the pancreas, but later released into the small intestine [6,7]. Both the enzymes are the chief causative factors of postprandial hyperglycemia, as the digestion of carbohydrates occurs in the small intestine [7].…”

Health Benefits of Starch

“…These properties are related to the granule and highly influenced by the botanical origin [6,7,9], or are the result of applied processes during the industrial processing or cooking processes. These factors condition the ability and accessibility of the digestive enzymes to starch molecule, influencing the hydrolysis degree [41,42], and therefore, the intrinsic properties condition the bioaccessibility and bioavailability degree of the molecule [40][41][42]. Since these factors directly modulate the digestibility, condition also postprandial response [39][40][41].…”

“…The extrinsic factors are referred to the physiological conditions of the individuals that determined the bioaccessibility and bioavailability of the starch. These factors include age, gender, metabolic conditions, pathological alterations of the digestive tract, the efficiency of the digestive process, gastrointestinal transit time, and genetic variations, among others [9,22,42]. Due to the genetic variation in the expression of the digestive enzymes [22,41,42] or because of specific physiological conditions, some individuals do not completely absorb the glucose release from the starch hydrolysis [6,41,42].…”

“…These factors include age, gender, metabolic conditions, pathological alterations of the digestive tract, the efficiency of the digestive process, gastrointestinal transit time, and genetic variations, among others [9,22,42]. Due to the genetic variation in the expression of the digestive enzymes [22,41,42] or because of specific physiological conditions, some individuals do not completely absorb the glucose release from the starch hydrolysis [6,41,42]. The food emptying from the stomach is a consequence of the gastric emptying, regulated by diverse factors such as the amount and volume of the ingested food, the type of macronutrient, the energy density of the intake, the particle size of the food matrix, the viscosity, the osmolality and the pH [7,9].…”

“…Once the gastric content is released to the intestine, factors such as the viscosity influence the accessibility of the digestive enzymes to the chime and the nutrient releasing [9,22]. In this context, the gastrointestinal transit time of the starch is inversely correlated with the amount of ingested starch and the contact time of the enzymes with the substrate [41,42].…”