Intestine carbohydrate digestion

The first member of this class, acarbose, was introduced in the early 1990s. a-Glucosidase inhibitors slow the intestinal process of carbohydrate digestion by competitive inhibition of the activity of a-glucosidase enzymes located in the brush border of the enterocytes... 

When a-glucosidase activity is inhibited, carbohydrate digestion is prolonged and takes place further along the intestinal tract. This in turn delays and spreads the period of glucose absorption, which reduces the extent of the postprandial rise in blood glucose concentrations. The effectiveness of a-glucosidase inhibitors is dq en-dent on the consumption of a meal rich in complex carbohydrate. 

Digestion and absorption in the small intestine. Most digestion and absorption of carbohydrates, proteins, and lipids occurs in the small intestine. A summary of the digestive enzymes involved in these processes is found in Table 18.3. 

Acarbose and miglitol are a-glucosidase inhibitors of carbohydrate digestion in small intestine... 

Ingested liquids are rapidly emptied from the stomach into the intestine, while digestible solids are first mechanically broken down in the stomach by peristaltic contractions. Stimulation of osmotic, carbohydrate, and... 

C. Final carbohydrate digestion by enzymes synthesized by the intestinal mucosal cells... 

The principal sites of dietary carbohydrate digestion are the mouth and intestinal lumen. Salivary a-amylase acts on dietary starch (glycogen, amylose, amylopectin), producing oligosaccharides. Pancreatic a-amylase continues the process of starch digestion. 

Know the names and modes of action of carbohydrate digestive enzymes found in the saliva and the small intestine, including the amylases and disaccharidases review how glucose and other hexoses are absorbed. 

The final products of carbohydrate digestion—glucose, fructose, and galactose—are absorbed by intestinal epithelial cells and enter the blood. 

The clinical abnormalities related to the gastrointestinal tract are not life-threatening and can be treated. In newborns with CF, intestinal obstruction (meconium ileus) can occur in 10-20% of cases due to failure of digestion of intraluminal contents due to lack of pancreatic enzymes in utero. Exocrine pancreatic enzyme deficiency is present from birth affecting both lipid and protein digestion. In general, carbohydrate digestion is not severely impaired. 

Miglitol is an alpha-glucosidase inhibitor that inhibits intestinal enzymes that digest carbohydrates, thereby reducing carbohydrate digestion after meals, which lowers postprandial glucose elevation in diabetics. It is used in patients with non-insulin-dependent diabetes mellitus (NIDDM) who have failed dietary therapy. It may be used alone or in combination with sulfonylureas. 

Williams BL, Homig M, Buie T, et al. Impaired carbohydrate digestion and transport and mucosal dysbiosis in the intestines of children with autism and gastrointestinal disturbances. PLoS One. 2011 6 e24585. 

Carbohydrate digestion begins in the mouth, where the enzyme amylase in saliva begins to break down polysaccharides. The food then passes through the esophagus, then the stomach, and into the small intestine. Here, more enzymes are secreted to complete the hydrolysis of carbohydrates to form glucose and other monosaccharides. 

Acarbose is a nonabsorbable a-glucosidase inhibitor which blocks the digestion of starch, sucrose, and maltose. The digestion of complex carbohydrates is delayed and occurs throughout the small intestine rather than in the upper part of the jejunum. Absorption of glucose and other monosaccharides is not affected. Acarbose is adrninistered orally three times a day and chewed with the first mouthful of food. 

The a-glucosidase inhibitors, acarbose (Precose) and miglitol (Glyset), lower blood sugar by delaying die digestion of carbohydrates and absorption of carbohydrates in the intestine. 

The food, now in a liquid form known as chyme, passes through the pyloric sphincter into the duodenum, where stomach acid is neutralized. There is wide variation in lengths of the components of the small intestine (i.e., duodenum, jejunum, and ileum) between individuals (Table 98-1). Most absorption of digested carbohydrate and protein occurs within the jejunum. Most fat absorption occurs within the jejunum and ileum. In the small bowel, breakdown of macronutrients (i.e., carbohydrate, protein, and fat) occurs both within the lumen of the gut and at the intestinal mucosal membrane surface. The absorptive units on the intestinal mucosal membrane are infoldings known as... 

---