Disaccharidases deficiency

Bile salt malabsorption Disaccharidase deficiency Small bowel bacterial overgrowth Mesenteric ischemia Radiation enteritis Lymphoma... 

Numerous diseases are accompanied by increased elimination of various sugars in the urine or faeces. One may mention here the different forms of glucosuria, pentosuria, fructosuria, galactosaemia, the group of disaccharidase deficiences or hereditary fructose intolerance. 

Aspects of chemical methods used in the structural elucidation of polysaccharides and complex carbohydrates have been reviewed. In a critical examination of the use of g.l.c.-m.s. in the identification of TMS ethers of monosaccharides, a standardized method, which uses a medium resolution mass spectrometer and short chromatographic columns, has been proposed. TMS Ethers of monosaccharides have been characterized by g.l.c.-chemical ionization m.s. with ammonia as reagent gas. Molecular weights were determined, and fragment ions were produced in a quantity high enough to differentiate between stereoisomers (epimers and anomers). Disaccharides have been determined by permethylation followed by g.l.c. The method has been used in the detection of carbohydrate intolerance secondary to intestinal disaccharidase deficiency. 

Other monosaccharides are absorbed by carrier-mediated diffusion there are at least three distinct carrier proteins one for fructose, one for other monosaccharides and one for sugar alcohols. Because they are not actively transported, fructose and sugar alcohols are absorbed only to a limited extent, and after a moderately high intake a significant amount will avoid absorption and remain in the intestinal lumen, acting as a substrate for colon bacteria and, like unabsorbed disaccharides in people with disaccharidase deficiency, causing abdominal pain and diarrhoea. 

A non-selective disaccharidase deficiency due to generalized intestinal disease. 

Patients with disaccharidase deficiency suffer from diarrhoea and abdominal discomfort due to the osmotic effects of the sugar in the intestinal tract. 

Gray, G.M. (1978). Intestinal disaccharidase deficiencies and glucose-galactose malabsorption. In Stanbury, J.B., Wyngaarden, J.B. and Fredrickson, D.S. (eds.) The Metabolic Basis of Inherited Disease. 4th Edn., p. 1526 (New York McGraw-Hill)... 

See also disaccharidases and disaccharidase deficiency, sucrose tolerance test... 

Diarrhea is a common problem that is usually self-limiting and of short duration. Increased accumulations of small intestinal and colonic contents are known to be responsible for producing diarrhea. The former may be caused by increased intestinal secretion which may be enterotoxin-induced, eg, cholera and E. col] or hormone and dmg-induced, eg, caffeine, prostaglandins, and laxatives decreased intestinal absorption because of decreased mucosal surface area, mucosal disease, eg, tropical spme, or osmotic deficiency, eg, disaccharidase or lactase deficiency and rapid transit of contents. An increased accumulation of colonic content may be linked to increased colonic secretion owing to hydroxy fatty acid or bile acids, and exudation, eg, inflammatory bowel disease or amebiasis decreased colonic absorption caused by decreased surface area, mucosal disease, and osmotic factors and rapid transit, eg, irritable bowel syndrome. 

Many methods have been proposed for detecting lactase deficiency (Box 48-2). Disaccharidase activities can be mea-sm-ed in homogenates of an intestinal biopsy. These assays are rarely required for routine diagnostic purposes, but when necessary (e.g in investigations in infancy) they must be carried out by laboratories with expertise in these tests. 

An intestinal disaccharidase which hydrolyses isomaltose (two glucose molecules linked by 1 6 linkages). Congenital or acquired isomaltase deficiency can occur, usually in association with sucrase deficiency. 

An intestinal disaccharidase which cleaves lactose to yield glucose and galactose. Lactase deficiency can occur which may be congenital or acquired. 

An intestinal disaccharidase which hydrolyses maltose into two glucose molecules. An acquired deficiency of the enzyme, along with other disaccharidases, can occur when there is generalized disease of the intestinal wall. 

An intestinal disaccharidase which catalyses the hydrolysis of sucrose into glucose and fructose. A deficiency of the enzyme occurs, along with a deficiency of the other intestinal dis-accharidases, in conditions where there is generalised disease of the intestinal wall. A congenital deficiency of sucrase, usually co-existing with isomaltase deficiency, can occur. Acquired sucrase-isomaltase deficiency has also been described but is much rarer. 

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