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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
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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 SGLT Glu, Gal Na+ K+,Na+-ATP-ase ADP + Pi Na+ Na+ ATP Fructose Fructose GluT5 Gyors cukor pótlás Só – víz pótlás SGLT – sodium-glucose transporter
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 as5% in northern Europe, up to 71% for Southern Europe, tomore 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 fructose-based 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-1-phosphate 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 UDP-galactose-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.
