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Flashcards in Glycogen Deck (44):
0

Glycogen-epinephrine
Tissue

Liver and muscle

1

Glycogen-glucagon
Tissue?

Liver

2

Glucogen-insulin
Tissue?

Liver and muscle

3

Protein responsible for glycogen synthesis

Glycogen synthase

4

Protein responsible for glycogen hydrolysis

Glycogen phosphorylase

6

Glucagon-glycogen pathway

Glucagon receptor (LIVER) --> adenylate cyclase --> increased cAMP --> PROTEIN KINASE A --> glycogen phosphorylase kinase --> glycogen phosphorylase --> glycogen to glucose
(Protein kinase A is a glycogen synthase inhibitor)

7

Epinephrin - glycogen pathway

1. Epinephrin β receptor (liver or muscle) --> adenylate cyclase --> increased cAMP --> PROTEIN KINASE A --> glycogen phosphorylase kinase --> glycogen phosphorylase --> glycogen to glucose (Protein kinase A is a glycogen synthase inhibitor)
2. Epinephrin α receptor (LIVER) --> increased calcium from endoplasmic reticulum. Calcium can activate glycogen phosphorylase kinase :
1. Directly
2. Via calcium-calmodulin in muscle during contraction

8

Alternative epinephrin glycogen pathway

Epinephrin α receptor (LIVER) --> increased calcium from endoplasmic reticulum. Calcium can activate glycogen phosphorylase kinase :
1. Directly
2. Via calcium-calmodulin in muscle vis contraction

9

Insulin action on glycogen synthesis

Tyrosine kinase dimer receptor (liver + muscle)
- inhibits glycogen phosphorylase via protein phosphatase
- induce glycogen synthase (directly or via protein phosphatase)

9

Insulin action on glycogen synthesis inhibits glycogen phosphorylase via

Tyrosine kinase dimer receptor (liver + muscle)
- inhibits glycogen phosphorylase via protein phosphatase
- induce glycogen synthase

10

Glucagon and epinephrin inhibit glycogen synthesis via

Protein kinase A is a glycogen synthase inhibitor

11

Glycogen bonds

a-(1,6) bonds
a-(1,4) bonds

12

Glycogen in skeletal muscles

It undergoes glycogenolysis to glucose-1-P -->glucose 6-P which is rabidly metabolized during exercise

13

Glycogen bonds

branches: a-(1,6) bonds
linkages: a-(1,4) bonds

14

Glycogen in hepatocytes function

1. Storage
2. Glycogenolysis to maintain blood sugar at appropriate levels

15

Glycogen phosphorylase

Cleaves glucose-1-P residues off branched glycogen until four remain before a branch point

16

Glycogen enzymes

1. UDP-glucose pyrophosphorylase
2. Glycogen synthase
3. Branching enzyme
4. Glycogen phosphorylase
5. 4-a-D-glucanotransferase (debranching enzymes)
6. a-1,6-glucosidase (debranching enzymes)
7. α-1,4-glucosidase

17

Glycogen building block

UDP-glucose

18

UDP-glucose pyphosphorylase function

Glucose -1-P to UDP-glucose (to be ready for glycogen formation)

20

glycogen - Branching enzymes - function and types

Makes linear glycogen
- 4-a-D-glucanotransferase
- a-1,6-glucosidase

20

a-1-6-glucosidase function

Cleaves off the last glucose 1-P on the branch

21

4-a-D-glucanotransferase function

Moves 3 glucose-Ps from the brunch to the linkage (leaves 1)

22

Acid maltase

A small amount of glycogen is degraded in in lysosomes by a-1,4-glycosidase

23

Limit dextrin

One to four residues remaining on a branch after glycogen phosphorylase has already shortened it

24

Glycogen storage diseases
How many tyoes

12 types all resulting in abnormal glycogen metabolism and accumulation of glycogen within cells

26

Glycogen storage disease type 1 / mode of inheritance

Von Gierke disease AR

27

Glycogen storage disease type 2 / mode of inheritance

Pompe disease AR

28

Glycogen storage disease type 3 / mode of inheritance

Cori disease AR

28

Mode of inheritance of glycogen storage diseases type 1-4

AR

29

Glycogen storage disease type 4 / mode of inheritance

McArble disease AR

31

Von Gierke disease (type 1) pathophysiology

Glucose-6-phosphatase deficiency --> impaired gluconeogenesis and glycogenolysis

32

Von Gierke disease (type 1) findings

1. Severe fasting hypoglycemia
2. Increased glycogen in liver
3. Increased blood lactate
4. Hepatomegaly
5. incdreased TG
6. increased Uric acid (Gout)

33

Von Gierke disease (type 1) treatment

Frequent oral glucose/cornstarch
Avoidance of fructose and galactose

34

Pompe disease (type 2) pathophysiology

lysosomal a-1,4-glucosidase with α-1,4-glycosidase activity (Acid maltase) deficiency

34

Pompe disease (type 2) findings

1. Cardiomyopathy
2. hypertrophic cardiomyopathy
3. exercise intolerance
4. Systemic findings leading to early death

35

Pompe disease (type 2) findings

1. Cardiomegaly
2. hypertrophic cardiomyopathy
3. exercise intolerance
4. Systemic findings leading to early death

37

Cori disease (type 3) pathophysiology

a-1,6-glucosidase deficiency

37

McArdle disease (type 4) pathophysiology

Skeletal muscle phosphorylase (myophosphorylase deficiency)

38

Cori disease (type 3) findings

- Milder form of type 1 with normal blood lactate (and gluconeogenesis is intact)
- Accumulation of limit dextrin-like structures in cytosol

40

McArdle disease (type 4) findings / mechanism

1. Increased glycogen in muscle, but cannot break it down leading to painful muscle cramps
2. Myoglobinuria (red urine) with strenuous exercise
3. Arrythmia from electrolyte abnormalities
4. 2nd wind phenomenon noted during exercise due to increased muscular blood flow

41

There any problem with gluconeogenesis in Cori disease?

No. It is intact

42

It is useful for Glycogen storage disease diagnosis

Periodic acid-Schiff stain

43

Skeletal muscle phosphorylase

Myophosphorylase

44

blood glucose in McArdle disease

unaffected