Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Galactose Galactose (Gal) • Galactose • Type of sugar found – In dairy products – Sugar beets – Mucilages • It can be found in the body – Glycolipids – Glycoproteins • sweetener Galactose (Gal) • Disaccharide lactose – Galactose – Glucose • Hydrolysis of lactose to glucose and galactose – Lactase • In the human body, glucose is changed into galactose in order to enable the mammary glands to secrete lactose. Galactose (Gal) • Blindness is due to the conversion of circulating galactose to the sugar alcohol galacitol, by an NADPH-dependent galactose reductase that is present in neural tissue and in the lens of the eye. Absorption of glucose, galactose – Na+ cotransport Intestinal epithel cells Capillary Lumen GluT2 Glu, Gal Glu, Gal SGLT K+,Na+-ATP-ase Na+ Na+ ADP + Pi Na+ ATP Fructose Fructose GluT5 SGLT – sodium-glucose transporter Gyors cukor pótlás Só – víz pótlás Lactose intolerance • the inability to metabolize lactose, a sugar found in milk and other dairy products • 75% of adults worldwide show some decrease in lactase activity during adulthood • The frequency of decreased lactase activity ranges from as little as 5% in northern Europe, up to 71% for Southern Europe, to more than 90% in some African and Asian countries Lactose intolerance • Disaccharides cannot be absorbed through the wall of the small intestine • lactose present in ingested dairy products remains uncleaved and passes intact into the colon. • enteric bacteria – in vivo fermentation produces copious amounts of gas (a mixture of hydrogen, carbon dioxide, and methane). Primary lactose intolerance. • Environmentally induced when weaning a child in non-dairy consuming societies • This is found in many Asian and African cultures, where industrialized and commercial dairy products are uncommon. Secondary lactose intolerance. • resulting from certain gastrointestinal diseases • including exposure to intestinal parasites such as giardia • such cases the production of lactase may be permanently disrupted • A very common cause of temporary lactose intolerance is gastroenteritis, particularly when the gastroenteritis is caused by rotavirus. • Another form of temporary lactose intolerance is lactose overload in infants. Congenital lactase deficiency. • A genetic disorder which prevents enzymatic production of lactase. • Present at birth, and diagnosed in early infancy. Lactase activity • The normal mammalian condition is for the young of a species to experience reduced lactase production at the end of the weaning period – (a species-specific length of time). • In non dairy consuming societies, lactase production usually drops about 90% during the first four years of life, although the exact drop over time varies widely. Lactase activity • a mutation on chromosome 2 which eliminates the shutdown in lactase production, • making it possible for members of these populations to continue consumption of fresh milk and other dairy products throughout their lives without difficulty. Lactase activity • This appears to be an evolutionarily recent adaptation to dairy consumption, and has occurred independently in both northern Europe and east Africa in populations with a historically pastoral lifestyle. • Lactase persistence, allowing lactose digestion to continue into adulthood, is a dominant allele, making lactose intolerance a recessive genetic trait. Glucose-galactose malabsorption • generally becomes apparent in the first few weeks of a baby's life. • Affected infants experience severe diarrhea resulting in – life-threatening dehydration, – increased acidity of the blood and tissues (acidosis), – weight loss when fed breast milk or regular infant formulas. Glucose-galactose malabsorption • However, they are able to digest fructosebased formulas that do not contain glucose or galactose. • Some affected children are better able to tolerate glucose and galactose as they get older. Glucose-galactose malabsorption • is a rare disorder; • only a few hundred cases have been identified worldwide. • 10 percent of the population may have a somewhat reduced capacity for glucose absorption without associated health problems. • This condition may be a milder variation of glucose-galactose malabsorption. • This condition is inherited in an autosomal recessive pattern galactokinase (GALK) galactose-1-phosphate uridyltransferase (GALT) uridine diphosphate galactose 4'-epimerase (GALE) Clinical Significances of Galactose Metabolism • Three inherited disorders of galactose metabolism have been delineated. – loss of the enzyme galactose-1phosphate uridyl transferase – loss of the enzyme galactokinase • Vomiting and diarrhea occur following ingestion of milk, hence individuals are termed lactose intolerant. • impaired liver function (severe cirrhosis), • elevated blood galactose, • hypergalactosemia, • hyperchloremic metabolic acidosis, • urinary galactitol excretion • hyperaminoaciduria. Clinical Significances of Galactose Metabolism • Unless controlled by exclusion of galactose from the diet, these galactosemias can go on to produce blindness and fatal liver damage. Clinical Significances of Galactose Metabolism • The third disorder of galactose metabolism result from a deficiency of UDPgalactose-4-epimerase. • Two different forms of this deficiency have been found. – One is benign affecting only red and white blood cells. – The other affects multiple tissues and manifests symptoms similar to the transferase deficiency. • Treatment involves restriction of dietary galactose. Lactose Synthesis