Chapter 26 (PBL)

Question 1

What characterizes Pompe disease, in terms of enzyme affected and manifestations?

Answer 1

Lysosomal alpha-glucosidase affected.
May see clinical symptoms in childhood, juvenile or adult life stages, depending on the nature of mutation.
All organs with lysosomes are affected.
Infantile form: early-onset progressive muscle hypotonia, cardiac failure, death before age 2 years.
Juvenile form: later-onset myopathy with variable cardiac involvement.
Adult form: limb-girdle muscular dystrophy-like features. Glycogen deposits accumulate in the lysosomes.

Question 2

What characterizes von Gierke disease, in terms of enzyme affected and manifestations?

Answer 2

Glucose 6-phosphatase affected; gluconeogenesis and glycogenolysis are both blocked.
Liver primarily affected.
Enlarged liver and kidney, growth failure, severe fasting hypoglycemia, acidosis, lipemia, thrombocyte dysfunction.

Question 3

What characterizes Andersen disease, in terms of enzyme affected and manifestations?

Answer 3

amylo-4,6-glucosidase (branching enzyme) defect.
Liver primarily affected.
Hepatosplenomegaly; symptoms may arise from a hepatic reaction to the presence of a foreign body (glycogen with long outer branches); usually fatal.

Question 4

What characterizes McArdle disease, in terms of enzyme affected and manifestations?

Answer 4

Muscle glycogen phosphorylase defect.
Expressed as either adult or infantile form.
Skeletal muscle primarily affected.
Exercise-induced muscular pain, cramps, and progressive weakness, sometimes with myoglobinuria.

Question 5

What characterizes Hers disease, in terms of enzyme affected and manifestations?

Answer 5

Liver glycogen phosphorylase defect.
Liver primarily affected.
Hepatomegaly, mild hypoglycemia; good prognosis but certain mutations can be lethal.

Question 6

When is glycogen an important fuel source in skeletal muscle?

Answer 6

Glycogen is a important fuel source when ATP demands are high and when glucose 6-phosphate is used rapidly in anaerobic glycolysis

Question 7

What are the basic cascading steps of what occurs with liver glycogen metabolism when there is an increase of glucagon and decrease of insulin?
1.
2.
3.
4.
5.

Answer 7

1. Initiates cAMP production
2. Phosphorylation of glycogen phosphorylation to an active enzyme form
3. Phosphorylation of glycogen synthase to an inactive enzyme
4. Glycogen degradation is stimulated
5. Glycogen synthesis is inhibited

Question 8

What two hormones regulate liver glycogen metabolism?

Answer 8

Insulin and glucagon

Question 9

What are the basic cascading steps of what occurs with glycogen synthesis and degradation when blood glucose levels rise?
1.
2.
3.
4.
5.
6.
7.

Answer 9

1. Insulin levels rise and glucagon levels fall
2. cAMP levels decrease
3. PKA reassociates with its inhibitory subunits and becomes inactive
4. Protein phosphatases are activated
5. Phosphorylase a and glycogen synthase D are dephosphorylated
6. Rapid inhibition of glycogen degradation occurs
7. Rapid activation of glycogen syntheses occurs

Question 10

What happens to liver glycogen when an individual experiences “Fight or flight”?

Answer 10

1. Increased demand for glucose to generate ATP
2. Epinephrine released from the adrenal medulla
3. Liver glycogenolysis is stimulated through alpha- and beta-agonist receptors

Question 11

What characterizes a glycogen synthase deficiency?

Answer 11

Enzyme is deficient in its ability to attach glucosyl residues in alpha-1,4-binds, resulting in deficient glycogen synthesis
The primary organ involved is the liver. Manifestations that occur are hypoglycemia, hyperketonemia, failure to thrive, and early death.

Question 12

What characterizes an amylo-1,6-glucosidase deficiency, in terms of enzyme affected and manifestations?

Answer 12

Debrancher enzyme deficiency
Form IIIa = liver and muscle enzymes
Form IIIb = liver=specific form
Form IIIc = muscle-specific form
Primary organ involved = Liver, skeletal muscle, heart
Manifestations = Fasting hypoglycemia, hepatomegaly in infancy and some myopathic features, glycogen deposits have short outer branches

Question 13

What characterizes Tarui Syndrome, in terms of enzyme affected and manifestations?

Answer 13

• Phosphofructokinase-1 enzyme deficiency
• Occurs in Muscle and RBCs
• Manisfestations: Enzymopathic hemolysis in type V

Question 14

What characterizes Fanconi-Bickel Syndrome, in terms of enzyme affected and manifestations?

Answer 14

• Glut 2 (glucose/galactose transporter) deficiency
• Occurs in Intestines, pancreas, kidney, and liver
• Manifestations: Glycogen accumulation in liver and kidney, rickets, growth retardation, glucosuria

Question 15

During fasting, what are the regulators of glycogen stores in the liver and what is the response in the liver?

Answer 15

• Regulators: Blood glucagon increase, blood insulin decrease, tissue cAMP increase
• Liver Response: Glycogen degradation increase and glycogen synthesis decrease

Question 16

During/directly after a carbohydrate meal, what are the regulators of glycogen stores in the liver and what is the response in the liver?

Answer 16

• Regulators: Blood glucagon decrease, blood insulin increase, blood glucose increase, tissue cAMP decrease, tissue glucose increase
• Liver Response: Glycogen degradation decrease and glycogen synthesis increase

Question 17

During exercise and stress, what are the regulators of glycogen stores in the liver and what is the response in the liver?

Answer 17

• Regulators: Blood epinephrine increase, tissue cAMP increase, tissue Ca2+-calmodulin increase
• Liver Response: glycogen degradation increase and glycogen synthesis decrease

Question 18

During fasting (rest), what are the regulators of glycogen stores in the muscle and what is the response in the muscle?

Answer 18

• Regulator: Blood insulin

- Muscle Response: Glycogen synthesis decrease and glucose transport decrease

Question 19

During a carbohydrate meal (rest), what are the regulators of glycogen stores in the muscle and what is the response in the muscle?

Answer 19

• Regulators: Blood insulin decrease

- Muscle Response: Glycogen synthesis decrease and glucose transport increase

Question 20

During exercise, what are the regulators of glycogen stores in the muscle and what is the response in the muscle?

Answer 20

• Regulators: Blood epinephrine increase, tissue AMP increase, tissue Ca2+-camodulin increase
• Muscle Response: Glycogen synthesis decrease, glycogen degradation increase, glycolysis increase