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Nutrition and Energy > L10 Glycogen Storage Diseases > Flashcards

L10 Glycogen Storage Diseases Flashcards

1
Q

Which enzyme is deficient in von Gierke’s disease?

A

Glucose-6-phosphatase

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2
Q

Which of the following is X-linked?

a) von Gierke’s disease
b) Cori’s disease
c) Phosphorylase kinase deficiency
d) Hers’ disease

A

c) Phosphorylase kinase deficiency

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3
Q

Pompe’s disease is caused by a deficiency in which enzyme?

A

alpha-1,4-glucosidase

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4
Q

Cori’s disease is caused by a deficiency in which enzyme?

A

Amylo-1,6-glucosidase (debranching enzyme)

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5
Q

Andersen’s disease is caused by a deficiency in which enzyme?

A

Amylo-(1,4 to 1,6)-transglycosylase (branching enzyme)

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6
Q

McArdle’s disease is caused by a deficiency in which enzyme?

A

Glycogen phosphorylase (in muscle)

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7
Q

Hers’ disease is caused by a deficiency in which enzyme?

A

Glycogen phosphorylase (in liver)

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8
Q

Tarui’s disease is caused by a deficiency in which enzyme?

A

Phosphofructokinase (PFK)

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9
Q

X-linked phosphorylase kinase deficiency affects which tissue(s)?

A

Liver

There is another disorder which is general phosphorylase kinase deficiency in all organs.

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10
Q

Which glycogen storage diseases result in altered glycogen structure?

A

Cori’s disease: outer chains missing or very short

Andersen’s disease: Very long, unbranched chains

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11
Q

Which glycogen storage disease does not alter the structure of glycogen, but causes a deficiency?

A

Glycogen synthase deficiency.

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12
Q

Describe type 1 glycogen storage disease.

A

Glucose-6-phosphatase deficiency (von Gierke’s disease)

G6Pase catalyses the release of the phosphate group, allowing glucose to be released from liver into blood stream.

This disease means glucose cannot be released (hypoglycaemia) and so G6P builds up in hepatocytes (hepatomegaly).

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13
Q

What are the complications that arise from von Gierke’s disease (type 1 glycogen storage disease)?

A

Severe hypoglycaemia and severe hepatomegaly

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14
Q

What treatments are required for patients with glucose-6-phosphatase deficiency?

What is the common name for this disease?

A

Treatment:
1. (a) Drug-induced inhibition of glucose uptake by liver

(b) continuous intra-gastric feeding overnight to maintain blood glucose
2. Liver transplantation
3. Surgical transposition of the portal vein (send glucose-rich blood straight to peripheral tissues instead of via liver)

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15
Q

Which of the glycogen storage diseases is the most severe?

A

Type 2: alpha-1,4-glucosidase deficiency (Pompe’s disease).

Patients normally die within a year from cardio-respiratory failure.

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16
Q

Describe Pompe’s disease

A

Type 2 glycogen storage disease: alpha-1,4-glucosidase deficiency (Pompe’s disease).

a-1,4-glucosidase breaks down glycogen within lysosomes to stop the lysosome getting too full and rupturing.

Deficiency means it isn’t there to stop the glycogen overfilling the lysosome and so it bursts and releases all of its nasty contents (toxins and enzymes) into the cell. Very bad.

Occurs in all tissues, but particularly damages muscle tissue.

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17
Q

How is glycogen storage disease type 2 treated?

A

GSD type 2 (Pompe’s disease) is treated by enzyme replacement therapy, restoring a-1,4-glucosidase.

18
Q

Describe glycogen storage disease type 3

A

GSD type 3 (Cori’s disease).

Deficiency of amylo-1,6,glucosidase (debranching enzyme).

Glycogen has an abnormal structure and builds up in liver and muscle = muscle weakness and liver dysfunction.

Treated by high protein diet.

19
Q

What is the role of debranching enzyme?

A

During degradation, branches are removed from the glycogen by glycogen phosphorylase and transferase; they leave small ‘stubs’ which also need to be removed for complete degradation. This is done by debranching enzyme.

20
Q

Why is Cori’s disease treated with a high protein diet?

A

To counteract the losses of amino acids via gluconeogenesis.

21
Q

What is Anderson’s Disease?

A

Glycogen storage disease (type 4).

Deficiency of amylo-(1,4-1,6)-transglycosylase (glycogen branching enzyme)

Causes liver dysfunction, patients rarely survive beyond 4yo.

22
Q

Describe the glycogen molecules in a patient with type 4 glycogen storage disease.

A

(GSD type 4 = Anderson’s disease)

Glycogen is present in normal concentrations, but has abnormal structure.

Long unbranched chains that make it very insoluble.

23
Q

What is McArdle’s disease?

A

Glycogen storage disease (type 5)

Deficiency in muscular glycogen phosphorylase.

Affects muscle but not liver as they contain different isoenzymes of phosphorylase.

24
Q

McArdle’s disease affects

A) the liver
B) muscles
C) both A and B
D) neither A nor B

A

B) muscles

Both the muscle and liver contain phosphorylase, but glycogen storage disease type 5 (McArdle’s) only affects the isozyme found in muscles.

25
Q

Which glycogen storage disease is characterised by an absence of lactate in the blood?

A) Type 1 (von Gierke's)
B) Type 2 (Pompe's)
C) Type 3 (Cori's)
D) Type 4 (Anderson's)
E) Type 5 (McArdle's)
A

E) Type 5 (McArdle’s)

Lack of phosphorylase means cells cannot convert glycogen to glucose and then to lactate.

26
Q

True or false: McArdle’s disease is associated with severed muscle cramps after exertion

A

True.

McArdle’s disease is not fatal and is quite harmless as long as strenuous exercise is avoided.

27
Q

In GSD type 5 (McArdle’s), what causes muscle tissue to break down? What symptom does this lead to?

A

Lack of ATP leads to muscle breakdown.

Muscle breakdown results in general muscle weakness.

28
Q

Her’s disease affects

A) the liver
B) muscles
C) both A and B
D) neither A nor B

A

A) the liver

Similar to type 5, glycogen is not broken down because of a lack of glycogen phosphorylase, but this time in the liver.

29
Q

Is Her’s disease (GSD type 6) considered to be mild or severe?

A

Mild, compared with the symptom of other glycogen storage diseases

30
Q

What are the symptoms of Her’s disease (GSD type 6)?

A

Hepatomegaly
Mild hypoglycaemia
Mild ketosis
Retarded growth

31
Q

Why is hypoglycaemia a symptom of Her’s disease?

A

Deficiency of liver phosphorylase means the liver cannot break down glycogen to raise blood glucose levels.

32
Q

Why is ketosis a symptom of Her’s disease?

A

Non-functioning TCA cycle results in ketosis.

33
Q

What is Tarui’s disease?

A

Glycogen storage disease type 7 - muscle phosphofructokinase deficiency.

Deficiency in PFK disrupts glycolysis.

Leads to build up of glucose-6-phosphate and fructose-6-phosphate.

34
Q

What are the symptoms of Tarui’s disease?

A

Painful muscle cramps.

PFK deficiency prevents glycolysis, limiting ATP production.

35
Q

Tarui’s disease leads to a build up of what in the muscles?

A

Glycogen.

36
Q

Which glycogen storage disease is associated with an inability to activate an inactive enzyme?

A

Type 8: X-linked phosphorylase kinase deficiency

A defective phosphorylase kinase cannot add a phosphate group to convert phosphorylase b (inactive) to phosphorylase a (active).

37
Q

True or false: The symptoms of Her’s disease (type 6) and x-linked phosphorylase kinase deficiency (type 8) are very similar.

A

True.

Her’s disease is autosomal recessive, but type 8 is X-linked.

38
Q

What is SGD type 9?

A

Phosphorylase kinase deficiency (autosomal recessive)

Defective gene that encodes for a phosphorylase kinase subunit results in a faulty enzyme.

39
Q

What is GSD type 0?

A

Liver glycogen synthase deficiency.

The only glycogen disorder that results in too little glycogen, rather than too much.

40
Q

True or false: Liver glycogen synthase deficiency (type 0) is always asymptomatic?

A

False.

Some sufferers are asymptomatic, but others suffer from hypoglycaemia after meals or at other times.

41
Q

Which glycogen disorders can affect all tissues?

A

Type 2, 3, 4, and 9

42
Q

True or false: All glycogen disorders are autosomal recessive?

A

False.

While most are autosomal recessive, type 8 is X-linked.

Nutrition and Energy (14 decks)

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