Glucose/Glycogen Regulation Flashcards
The phosphorylation of what 2 enzymes happens to activate them (rather than inactivate them)?
Glycogen phosphorylase - cleaves alpha 1-4 bonds to release glucose-1-phosphate from glycogen
PFK/FBP-ase = dual-activity enzyme that regulates glycolysis and gluconeogenesis (activated by insulin and glucagon, respectively).
What is the function of Glucose-6-phosphatase? Describe the significance of where it’s expressed in the body.
Glucose-6-phosphatase present in liver and kidney cells liberate phosphate from glucose so that it can enter circulation. The muscles do not express this enzyme since they breakdown glycogen for themselves. “Sharing-is-Caring enzyme”
What 2 proteins do muscle cells not express when it comes to glucose and its regulation/production?
- No glucagon receptor on muscle cells
2. No glucose-6-phosphatase
A partial loss of GLUT 2 receptors will result in what clinical finding?
Low glucose levels after an overnight fast from glycogen breakdown and gluconeogenesis.
List 3 features that glycogen storage diseases (GSDs) have in common.
- Hypoglycemia
- Muscle pain/ exercise-induced intolerance
- Myoglobinuria (from muscle wasting)
Describe the significance, symptoms and treatment of GSD-Type 1.
Type 1 GSD (Von Gierke’s Disease) results from defective glucose-6-phosphatase at the liver and kidney. Symptoms include: hypoglycemia, protuberant abdomen, Hyperlipidemia, hyperuricemia, lactic acidosis and hepatomegaly. Treatment for this condition is through nasogastric feedings of complex carbs “uncooked cornstarch”.
Describe the significance, symptoms and treatment of GSD Type 2.
GSD 2 (Pompe’s Disease) is brought upon by a defect in lysosomal alpha-1,4-glucosidase expressed in the heart. This results in cardiomegaly and LVH. No treatment is available for this condition.
Describe the significance, symptoms and treatment of GSD 3.
GSD 3 or Cori’s Disease is caused by a defect in glycosidase of debranching enzyme in the liver. This impairs glycogenolysis resulting in hepatomegaly and a milder hypoglycemia compared to GSD 1.
Describe the significance, symptoms and treatment of GSD 4.
GSD 4 or Anderson’s Disease is caused by a defect in Branching enzyme in the liver. This results in long, insoluble glycogen strands that have no branches on them. Symptoms include hepatomegaly and infantile cirrhosis (a SEVERE condition). “AB = Anderson’s Branch”
Describe the significance, symptoms and treatment of GSD 5.
GSD V or McArdle’s Disease is caused by a defect in Glycogen Phosphorylase expressed in the muscle. This leads to painful cramps during exercise (reduced tolerance) and myoglobinuria. Treatment includes nasogastric glucose administration during sleep. “M and M for McArdle’s @ Muscle”. No lactic acidosis is observed in this condition.
Describe the significance, symptoms and treatment of GSD 6.
GSD 6 or Her’ Disease is caused by a defect in Glycogen Phosphorylase @ the LIVER. This results in normal or accumulated levels of glycogen and symptoms of hepatomegaly and low fasting blood glucose. The condition is milder than GSD 1. “Her’s Hepatocyte”
Describe the significance, symptoms and treatment of GSD 7.
GSD 7 or Tarui’s Disease is caused by a defect in PFK-1 @ the MUSCLE. This will present with normal glycogen levels but decreased exercise tolerance and Myoglobinuria.
A patient with this condition is UNRESPONSIVE to glucose administration and presents with Hemolytic Anemia.
A young boy develops painful cramps, Hemolytic Anemia and is unresponsive to oral glucose. What enzyme is defective?
Muscle PFK-1 from GSD VII = Tarui’s disease
