Sugar malabsorption due to deficiencies of disaccharidase activities and of monosaccharide transport.

Abstract

In many societies including our own, carbohydrates play a major part in the total calorie supply. According to the National Food survey figures (Greaves and Hollingsworth, 1964), the average daily diet of adults contains nearly 350 g. of this constituent. Diets of course vary with eating habits and social class, but the dietary carbohydrates are largely ingested as poly-, oligo-, and disaccharides. In the very young, however, the carbohydrate intake may consist almost entirely of disaccharides, though this phase is now getting progressively shorter. As the rapid decrease in breast-feeding has been followed by the early introduction of cereals into the cow's milk formulae, even the infant of only a few weeks of age has also to digest polysaccharides. Sjovall, 1957; Dahlqvist and Borgstrom, 1961) demonstrated that disaccharidase activity in the intestinal lumen was extremely limited and did not account for the amount of carbohydrate absorbed. They further indicated that the majority of disaccharides were absorbed unhydrolysed and split intracellularly, a fact that accorded well with experimental findings (Cajori, 1933;Fridhandler and Quastel, 1955).The problem of localization of the sugar-splitting enzymes was brought nearer its solution by Miller and Crane (1961), who were able to separate the brush-border from the rest of the intestinal mucosa of the hamster, and found that the whole of the enzyme activity of the mucosa was accounted for by this layer. (-galactosidase (lactase) activity had been localized in the microsomes of the rat intestinal mucosa by Doell and Kretchmer (1962), while Dahlqvist and Brun (1962), employing histochemical methods for the recognition of invertase and trehalase in various animal tissues, associated their activity with cytoplasmic granules. As yet there is no definite information concerning the possible relationship of the elements of fine structure of the microvillus with its absorptive and digestive functions. However, two related fractions have been obtained by density gradient centrifugation of tris-disrupted brush-borders from hamster intestinal mucosa, and have been identified as the microvillus cores and their surrounding membranous coats (Overton, Eichholz, and Crane, 1965;Eichholz and Crane, 1965).

Role of Chemical Examination of the Stool in Diagnosis of Sugar Malabsorption in Children

“…Davidson in 1967 suggested that estimation of the pH of fresh stools was of value as a screening test for disaccharide malabsorption, but others considered such an estimation was not reliable (Holzel, 1967).…”

The management of chronic or recurrent diarrhoea in childhood

“…Hypolactasia In many animal species, levels of intestinal lactase diminish with age. A similar tendency seems to occur in man, especially in some racial groups (Holzel, 1967). Occasionally in children, and perhaps more commonly in adults, isolated hypolactasia may cause diarrhoea.…”

Congenital Lactose Malabsorption

“…In only 2 of the 7 patients in whom mucosal enzyme assays were attempted was there apparently a history of diarrhoea after the first breast-milk feeding (Launiala, Kuitunen, and Visakorpi, 1966). Three were in older children.…”

“…The two infants recorded by Launiala et al (1966) were both observed in hospital from the third week of life. Peroral biopsies from the distal duodenum in the 3rd and 5th month of life, respectively, showed no lactase activities in either, when quantitatively assayed.…”

“…Since the original description by Holzel, Schwarz, and Sutcliffe (1959) of a condition of failure to thrive in infancy due to malabsorption of lactose, 18 patients with this syndrome have been reported (Holzel, 1967). It was attributed to a congenital isolated deficiency or absence, in the intestinal mucosa, of the enzyme lactase, which hydrolyses lactose into glucose and galactose for the final absorption.…”