Galactose and Lactose Flashcards
3 monosaccharides
Glucose, galactose, fructose
3 disaccharides
- Maltose (glucose-glucose)
- Lactose (glucose-galactose)
- Sucrose (glucose-fructose)
Fructose is found in…
Foods with high-fructose corn syrup, fruits, veggies, honey, foods that contain table sugar (sucrose)
Fructokinase
Converts fructose into fructose-1-P
Fructose-1-P can go on to synthesize via adolase…
Glyceraldehyde or DHAP which are intermediates in glycolysis
Essential fructosuria
- Deficiency of fructokinase
- AR
- Dietary fructose remains in blood stream and is excreted through the kidneys
- Asymptomatic
- Presence of reducing sugar in urinalysis
Hereditary fructose intolerance
- Deficiency in adolase B
- AR
- Accumulation of F1P in liver and kidneys
- Asymptomatic until introduction of fructose containing foods like juice
- Causes jaundice, hepatomegaly, vomiting, lethargy, seizures
Adolase B
- Converts F1P to glyceraldehyde and DHAP
- Interconverts F-1,6BP and Gla-3-P/DHAP in glycolysis
What causes the symptoms of hereditary fructose intolerance to appear?
F1P builds up > perceived elevated levels of glucose > indirect inhibition of gluconeogenesis > Hypoglycemia
Labs of hereditary fructose intolerance
- Hypoglycemia
- CBC normal
- BMP = acidosis caused by kidney failure
- Lactic acid elevated (impaired gluconeogenesis > competition with uric acid for excretion)
- Uric acid elevated (AMP purine breakdown d/t hypoglycemia)
- Elevated liver enzymes, indirect bilirubin
- UA indicates reducing substances, proteinuria, glucosuria
Management of hereditary fructose intolerance
- Eliminate all sources of fructose, sucrose, and sorbitol
- Referral to genetics for molecular testing
Complications of hereditary fructose intolerance
- Hypoglycemic seizures
- Intellectual impairment secondary to hypoglycemia
- Permanent hepatocellular damage
Galactokinase deficiency
- AR
- Present with cataracts in infancy (have to rule out retinoblastoma)
- UA reducing sugar +
- confirmation blood galactokinase low
- managed: eliminate galactose and lactose from diet
- may improve with age
Classic galactosemia
- deficiency of galactose-1-P-uridyltransferase (GALT - converts galactose-1-P to glucose-1-P)
- Results in accumulation of galactose-1-P and inability to generate UDP glucose for glycogen synthesis
- Galactose-1-P accumulates in liver, kidney, and brain
- AR
- jaundice, hepatomegaly, vomiting, seizures, lethargy, cataracts, sepsis (E. coli), bulging fontanelle (accumulation of gal-1-P)
Labs for GALT deficiency
- Hypoglycemia
- CBC (may have elevated WBC)
- BMP (acidosis likely, renal damage)
- Elevated unconjugated bilirubin (liver damage)
- Lactic acid normal unless septic
- Uric acid normal
- CT of head = cerebral edema
- UA = proteinuria, positive reducing substances
- blood test for GALT = low
