Lactose intestinal lactase deficiency

Intestinal lactase deficiency is a common condition in which lactose cannot be digested and is oxidized by bacteria in the gut, producing gas, bloating, and watery diarrhea. 

A test used in the investigation of intestinal lactase deficiency. It consists of the oral administration of lactose followed by the collection of blood samples in which glucose is measured. If intestinal lactase is present, the lactose is broken down to glucose and galactose which are then absorbed. The blood glucose level should therefore increase. However, this does not occur if there is a deficiency of lactase. A flat lactose tolerance test should, however, be followed by a glucose tolerance test in order to check that a generalized malabsorption does not exist. 

Dahlqvist, A., Hammond, J. B., Crane, R. K., Dunphy, J. V., and littman. A., 1963, Intestinal lactase deficiency and lactose intolerance in adults. Gastroenterology 45 488. Deanin, G. G., and Gordon, M. W., 1976, The distribution of tyrosyltubulin ligase in brain and other tissues, Biochem. Biophys. Res. Commun. 71 676. 

There are several forms of intolerance to lactose and galactose. Primary adult lactase deficiency is a normal age-related decrease in lactase activity seen in the majority of adults. Secondary lactase deficiency is a transient state of low enzyme activity following injury to the intestinal mucosa as a result of diseases such as celiac sprue, infectious gastroenteritis, and protein-calorie malnutrition. The last two states are common conditions (Dahlqvist 1983). 

Osmotic diarrhoea occurs when a non-absorbable substance draws fluid into the intestine by osmosis, for example lactase deficiency, when unabsorbed lactose remains in the intestine. This type of problem also occurs in malabsorption disorders, for example in celiac disease. 

Lactose is sometimes detected in the urine of women during lactation and occasionally toward the end of pregnancy. Patients with lactase deficiency, a common disorder caused by a congenital or acquired deficiency of intestinal lactase, exhibit abdominal pain, diarrhea, and lactose in the urine. 

The answer is b. (Murray, pp 190—198. Scriver, pp 1521-1552. Sack, pp 121-138. Wilson, pp 287-317.) In many populations, a majority of adults are deficient in lactase and hence intolerant to the lactose in milk. In all populations, at least some adults have lactase deficiency (223000). Since virtually all children are able to digest lactose, this deficiency obviously develops in adulthood. In lactase-deficient adults, lactose accumulates in the small intestine because no transports exist for the disaccharide. An outflow of water into the gut owing to the osmotic effect of the milk sugar causes the clinical symptoms. Steatorrhea, or fatty stools, is caused by unabsorbed fat, which can occur following a fatty meal in persons with a deficiency of... 

Lactase is iocated in the brush border (microviiii) of small intestinal enterocytes. Lactase deficiency can be primary, secondary or rarely, congenital. Dietary lactose accumulates causing flatulence and diarrhoea. 

Sucrase (also called saccharase and invertase) hydrolyzes sucrose. In contrast to the abundant information available on the yeast invertase, little is known of the mammalian sucrases. The significance of invertase and lactase in absorption is illustrated by inborn errors of metabolism in which these two enzymes are absent in the intestinal secretion. (The fact that lactase deficiency does not interfere with growth indicates that the galactose needed for biosynthesis of brain lipids or lens proteins can be synthesized endogenously in amounts sufficient to fulfill the metabolic requirements.) In that case, there is an intolerance to lactose or sucrose with no increase in blood glucose levels or without an increase in the levels of disaccharides... 

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

The disaccharide lactose, is only found in milk and is hydrolysed with water in the presence of an enzyme lactase to form the monosaccharide glucose and galactose. This occurs in the small intestine. Some people, and particularly those from Eastern and African countries, are deficient in lactase so they are intolerant of milk. This can cause diarrhoea. Many African and Chinese foods do not include milk for this reason. 

Lactose is widely used in pharmaceutical formulations as a diluent and filler-binder in oral capsule and tablet formulations. It may also be used in intravenous injections. Adverse reactions to lactose are largely due to lactose intolerance, which occurs in individuals with a deficiency of the intestinal enzyme lactase, and is associated with oral ingestion of amounts well over those in solid dosage forms. 

A 24-year-old African-American female presents with complaints of intestinal bloating, gas, cramps, and diarrhea following a meal inclnd-ing dairy products. A lactose-tolerance test confirms your suspicion that she had a deficiency of lactase in her intestine. Which of the following dairy prodncts conld yon recommend that wonld be least likely to canse her difficnlties in the fnture ... 

The malabsorption of specific substances tends to occur in certain w ell-defined conditions such as vitamin B, malabsorption which leads to pernicious anaemia. This occurs when intrinsic factor production is lost due to gastric mucosal atrophy. Patients may also have inherited deficiencies of intestinal saccharidases such as lactase which cause malabsorption when the patient drinks milk or cats milk products. This is known as lactose intolerance. 

Lactose intolerance can either be the result of a primary deficiency of lactase production in the small bowel (as is the case for Deria Voider) or it can be secondary to an injury to the intestinal mucosa, where lactase is normally produced. The lactose that is not absorbed is converted by colonic bacteria to lactic acid, methane gas (CH4), and Hj gas (see figure on left). The osmotic effect of the lactose and lactic acid in the bowel lumen is responsible for the diarrhea often seen as part of this syndrome. Similar symptoms can result from sensitivity to milk proteins (milk intolerance) or from the malabsorption of other dietary sugars. 

Most of the lactose in milk is lost in the whey during cheese manufacture and hence most cheese contain only trace amounts of carbohydrate (Table XIII). Furthermore, the residual lactose in cheese curd is usually fermented to lactic acid by starter bacteria. Thus, cheeses are suitable dairy foods for lactose-malabsorbing individuals who are deficient in the intestinal enzyme, lactase. 

Lactose is sometimes referred to as milk sugar because it occurs in milk. In some adults, a deficiency of the enzyme lactase in the intestinal villi causes a buildup of the disaccharide when milk products are ingested. This is because lactase is necessary to degrade lactose to galactose and glucose so that it can be absorbed into the bloodstream from the villi. Without the... 

Deficiency of the enzyme lactase is common. Indeed, it is only in people of north European origin that lactase persists after childhood. In most other people, and in a number of Europeans, lactase is gradually lost through adolescence — alactasia (see Problem 4.2). In the absence of lactase, lactose cannot be absorbed. It remains in the intestinal lumen, where it is a substrate for bacterial fermentation to lactate (section... 

The disaccharide in milk is lactose, which is broken down by lactase in the intestinal tract to monosaccharides that are a source of energy. Infants and small children produce lactase to break down the lactose in milk. It is rare for an infant to lack the ability to produce lactase. However, the production of lactase decreases as many people age, which causes lactose intolerance. This condition affects approximately 25% of the people in the United States. A deficiency of lactase occurs in adults in many parts of the world, but in the United States it is prevalent among the African American, Hispanic, and Asian populations. 

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