Wk 3 - Glycogen metabolism - Glycogen storage diseases

Question 1

GSD 0

Answer 1

• Glycogen synthase deficiency
• Normal glucose tolerance
• Can’t make glycogen
• Exercise intolerance because cells are starving :(
• 2 TYPES!!
• GYS1 = muscle specific
• GYS2 = liver specific

Question 2

GSD 1 - von Gierke disease

Answer 2

• Glucose-6 phosphatase deficiency (so liver specific)
• Can’t get G6P out into the blood
• Whole body is starved!
• Causes a ton of things… fasting hypoglycemia, lactic acidosis, hepatomegaly, hyperlipidemia (which leads to liver failure because fats can’t be packaged)
• Just eat starchy foods frequently… that’d be the only good part

Question 3

GSD III - Cori disease

Answer 3

• 1,6 glucosidase is bad
• Can’t debranch - glucose stump is always there and inhibiting glycogen phosphorylase
• Causes fasting hypoglycemia and lactic acidosis
• THERE ARE 2 TYPES!!
• a = liver AND muscle
• b = liver only
• So always liver and sometimes muscle
• Treatment = carby meals often

Question 4

GSD IV

Answer 4

• Bad 4:6 transferase (BRANCHING enzyme)
• Can’t make the branches
• Causes… Failure to thrive, hepatomegaly, liver failure (fatal)

Question 5

GSD V (McArdle disease)

Answer 5

• Bad MUSCLE SPECIFIC glycogen phosphorylase
• Can’t degrade glycogen in the muscle but you can make it
• Exercise intolerance
• Causes increase creatine kinase (in blood signifies muscle damage) and increased NH4+ (because you’re metabolizing amino acids for energy if you can’t metabolize glycogen)