Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.108 (lactase)
 2,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Examined in this article is presently available evidence for the hypothesis that some types of senile cataracts may be brought on by decades-long consumption of milk and milk products. The author approaches the question from a background of research in the geography and history of dairying as these relate to present-day differences among the world's peoples in prevalence of primary adult lactose malabsorption, which is based on a deficiency of the enzyme lactase in adulthood. Among peoples who have consumed milk in lactose-rich forms over a long historical period, there seems to have been a mutation for persistence of high lactase activity throughout life (PHLA), which distinguishes them from human populations of nonmilking tradition and from most land mammals. PHLA permits greater intestinal hydrolysis of lactose and absorption of galactose by adults. The mutation for PHLA, however, was not accompanied by a second one raising galactokinase activity to high levels through life. The result may be that adults who consume large quantities of milk, who have high lactase activity, lactose hydrolysis, and galactose absorption, suffer repeated small galactose challenges, accumulation of galactitol in the lens, and a greater likelihood of developing senile cataracts.
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PMID:A geographic approach to senile cataracts: possible links with milk consumption, lactase activity, and galactose metabolism. 680 98

Lactose consumption has been associated with a high incidence of cataract in northern Indian and southern Italian populations. Galactose absorbed after hydrolysis of lactose from milk in individuals with normal lactase activity is considered responsible. However, lactase-deficient subjects who often avoid drinking milk are able to digest lactose and absorb free galactose in fermented milk and yogurt. This study was conducted to evaluate the relationships between milk and yogurt consumption, galactose metabolism and cataract risk. Milk ingestion was dose-related with cataract risk in lactose digesters (particularly in diabetics) but not in lactose maldigesters. Conversely, yogurt intake had a protective dose-effect on cataract formation for the whole population. Maximal galactose concentrations after an oral galactose test increased exponentially with age. Red blood cell galactokinase activity was significantly lower in elderly subjects (> 60 y) than in young individuals (P < 0.05), and galactose-1-phosphate uridyl-transferase activity was significantly lower in institutionalized subjects and in home-living elderly with cataract than in healthy elderly subjects (P < 0.05). We conclude that the cataractogenic action of milk lactose is dependent on the disturbance of galactose metabolism in elderly subjects and that yogurt is not cataractogenic, although the mechanism of the protective effect of yogurt remains unknown.
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PMID:Disturbed galactose metabolism in elderly and diabetic humans is associated with cataract formation. 833 7