Intestinal Amylase

Diabetic patients have reduced antioxidant defences and suffer from an increased risk of free radical-mediated diseases such as coronary heart disease. EC has a pronounced insulin-like effect on erythrocyte membrane-bound acetylcholinesterase in type II diabetic patients (Rizvi and Zaid, 2001). Tea polyphenols were shown to possess anti-diabetic activity and to be effective both in the prevention and treatment of diabetes (Choi et al, 1998 Yang et al, 1999). The main mechanism by which tea polyphenols appear to lower serum glucose levels is via the inhibition of the activity of the starch digesting enzyme, amylase. Tea inhibits both salivary and intestinal amylase, so that starch is broken down more slowly and the rise in serum glucose is thus reduced. In addition, tea may affect the intestinal absorption of glucose. 

Amylase enters the blood largely via the lymphatics. An increase in hydrostatic pressure in the pancreatic ducts leads to a fairly prompt rise in the amylase concentration of the blood. Neither an increase in volume flow of pancreatic juice nor stimulation of pancreatic enzyme production will cause an increase in senm enzyme concentration. Elevation of intraductal pressure is the important determinant. Stimulation of flow in the face of obstruction can, however, augment the entry of amylase into the blood, as can disruption of acinar cells and ducts. A functional pancreas must be present for the serum amylase to rise. Serum amylase determination is indicated in acute pancreatitis in patients with acute abdominal pain where the clinical findings are not typical of other diseases such as appendicitis, cholecystitis, peptic ulcer, vascular disease or intestinal obstruction. In acute pancreatitis, the serum amylase starts to rise within a few hours simultaneously with the onset of symptoms and remains elevated for 2 to 3 days after which it returns to normal. The peak level is reached within 24 hours. Absence of increase in serum amylase in first 24 hours after the onset of symptoms is evidence against a diagnosis of acute pancreatitis (76). 

Various conditions such as perforated peptic ulcer, cholecystitis, common bile duct and intestinal obstruction, trauma to the abdomen inducing pancreatitis and ruptured ectopic pregnancy may cause an elevated serum amylase but the levels are usually not as high as those found in acute pancreatitis. Mumps and bacterial parotitis, which block the secretion of salivary amylase are associated with mild elevations of serum amylase. 

Polysaccharide (starch) Amylase Fragment polysaccharides into disaccharides (maltose) Salivary glands pancreas Mouth stomach small intestine... 

Amylose, another natural polysaccharide, prepared under appropriate conditions, is not only able to produce films, but is also found to be resistant to the action of pancreatic a-amylase while remaining vulnerable to the colonic flora [82]. However, incorporation of ethylcellulose was necessary to prevent premature drug release through simple diffusion [83], In vitro release of 5-aminosalicylic acid from pellets coated with a mixture of amylose-ethylcellulose in a ratio of 1 4 was complete after 4 hr in a colonic fermenter. By contrast, it took more than 24 hr to release only 20% of the drug under conditions that mimic that of the stomach and of the small intestine. 

Suppose we start with a starch-rich meal, say one containing a lot of pasta or bread. The digestion of starches begins in the mouth. Saliva contains an enzyme, salivary amylase (aka ptyalin), which catalyzes the conversion of starch to simple sugars such as glucose. This process is completed in the small intestine under the influence of other enzymes in the amylase class. This completes the first phase of carbohydrate catabolism the conversion of complex, polymeric carbohydrates (e.g., starches) to their simple monomeric units, the sugars. 

Carbohydrates mainly occur in food in the form of polymers (starches and glycogen). They are cleaved by pancreatic amylase into oligosaccharides and are then hydrolyzed by glycosidases, which are located on the surface of the intestinal epithelium, to yield monosaccharides. Glucose and galactose are taken up into the enterocytes by secondary active cotransport with Na"" ions (see p. 220). In addition, monosaccharides also have passive transport systems in the intestine. 

Glycogen and starch ingested in the diet are hydrolyzed by a-amylases, enzymes in saliva and intestinal secretions that break (al—>4) glycosidic bonds between glucose units. Most animals cannot use cellulose as a fuel source, because they lack an enzyme to hydrolyze the (fil—>4) linkages. Termites readily digest cellulose... 

When the acidic stomach contents reach the small intestine, they are neutralized by bicarbonate secreted by the pancreas, and pan creatic a-amylase continues the process of starch digestion. 

Uses Type 2 DM Action a-Glucosidase inhibitor delays digestion of carbohydrates Dose Initial 25 mg PO rid maint 50-100 mg rid (w/ 1st bite of each meal) Caution [B, —] Contra DKA, obst/inflammatory GI disorders SCr >2 mg/dL Disp Tabs SE Flatulence, D, abd pain Interactions T Effects W/ celery, coriander, juniper berries, ginseng, garlic X- effects W/ENH, niacin, intestinal absorbents, amylase, pancreatin X- effects OF digoxin, propranolol, ranitidine EMS Can X- digoxin level-monitor ECG in pts on digoxin therapy OD May cause severe adverse GI Sxs symptomatic and supportive... 

Digestion of dietary glycogen and starch in the human body begins with the salivary and pancreatic amylases, which cleave a-1,4 linkages at random. It continues with a glucoamylase found in the brush border membranes of the small intestine where it occurs as a complex with maltase.74 Carbohydrases are discussed in Chapter 12, Section B. 

In the mammal, complex polysaccharides which are susceptible to such treatment, are hydrolyzed by successive exposure to the amylase of the saliva, the acid of the stomach, and the disaccharidases (e.g., maltase, invertase, amylase, etc.) by exposure to juices of the small intestine. The last mechanism is very important. Absorption of the resulting monosaccharides occurs primarily in the upper part of the small intestine, from which the sugars are earned to the liver by the portal system. The absorption across die intestinal mucosa occurs by a combination of active transport and diffusion. For glucose, the aclive transport mechanism appears to involve phosphorylation The details are not yet fully understood. Agents which inhibit respiration (e.g., azide, fluoracetic acid, etc.) and phosphorylation (e.g., phlorizin), and those which uncouple oxidation from phosphorylation (e.g., dinitrophenol) interfere with the absorption of glucose. See also Phosphorylation (Oxidative). Once the various monosaccharides pass dirough the mucosa, interconversion of the other... 

The enzyme amylase is present in the small intestines, too, so the digestion of carbohydrates can continue there. The carbohydrates eventually are broken down into their simplest form— glucose—which cells can use during respiration to produce the energy the body needs to function. 

The major saccharidase of the small intestine is amylase that digests starch to the disaccharide maltose and the trisaccharide maltotriose. Intestinal mucus is secreted by goblet cells, which either ooze (constitutive basal secretion) or burst as a result of stimuli. In the last mode of secretion condensed mucus gel granules can expand 500-fold within 20 ms [20]. 

These agents are administered to aid in the digestion of food. The primary digestant preparations contain pancreatic enzymes or bile salts. Pancreatic enzymes such as amylase, trypsin, and lipase are responsible for digestion of carbohydrates, proteins, and lipids, respectively. These enzymes are normally synthesized in the pancreas and secreted into the duodenum via the pancreatic duct. Bile salts are synthesized in the liver, stored in the gallbladder, and released into the duodenum via the common bile duct. Bile salts serve to emulsify lipids in the intestinal tract and are important in lipid digestion and absorption. 

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