What is Gycogen? What is Glycogen storage disease?

1. GLYCOGEN
STORAGE
DISEASE
NIDHI SHARMA

2. GLYCOGEN-
 Glucose is a large energy source for the body. It is stored
by the body in the form of glycogen and released into the
blood as needed with the help of special proteins called
enzymes.
 Glycogen is stored in the liver.
 When the body needs more energy, certain proteins
called enzymes break down glycogen into glucose. They
send the glucose out into the body.

3. •The liver cannot control the use of glycogen and glucose because
certain enzymes are missing that control the change of sugar
(glucose) into its storage form (glycogen) or release of glucose from
glycogen.
•An abnormal amount of glycogen is stored in the liver.
•Not enough glucose is in the blood (also called hypoglycemia).
•Many sugars (including glucose) are found in foods and are used
by the body as a source of energy. After a meal, blood glucose
levels rise. The body stores the extra glucose that is not needed right
away as glycogen in the liver and muscles. Later, as the blood
glucose levels in the body begin to drop, the body uses this stored
energy.
•These sugars, stored in the form of glycogen, need to be processed
by enzymes in the body before they can carry out their functions. If
the enzymes needed to process them are missing, the glycogen or
one of its related starches can build up in the liver, causing
problems.

4. GLYCOGEN STORAGE DISEASE-
 Glycogen storage disease (GSD) is a rare condition that changes
the way the body uses and stores glycogen, a form of sugar or
glucose.
 GSD is passed down from parents to children (is hereditary). It is
most often seen in babies or young children. But some forms of
GSD may appear in adults.

5. TYPES-
 Types of GSD are grouped by the enzyme that is missing in each
one. Each GSD has its own symptoms and needs different
treatment.
 There are several types of GSD, but the most common types are
types I, III, and IV. These types are-
Type I- von Gierke disease.
TypeII- Pompe’s disease.
Type III-Cori disease, or Forbes disease.
Type IV- Andersen’s disease.
TypeV- McArdle’s disease..
TypeVI- Her’s disease.
TypeVII- Tarui’s disease.

6. Type I or von Gierke disease. This is the most common form of GSD. People
with type I don’t have the enzyme needed to turn glycogen into glucose in the
liver. Glycogen builds up in the liver. Symptoms often appear in babies around 3
to 4 months old. They may include low blood sugar (hypoglycemia) and a
swollen belly because of an enlarged liver.
Type II, This can be caused due to defect in Lysosomal alpha- 1,4 glucosidase
(acid maltase) enzyme. This disease can affect any organ. In this disease glycogen
accumulates in lysosomes in almost all the tissues among all, heart is mostly
involved, sometimes nervous system is also affected. Enlargement liver & heart
are seen.
Type III, Cori disease, or Forbes disease. People with type III don’t have
enough of an enzyme called the debranching enzyme, which helps break down
glycogen. The glycogen can’t fully break down. It collects in the liver and in
muscle tissues. Symptoms include a swollen belly, delayed growth, and weak
muscles.
Type IV or Andersen disease. People with type IV form abnormal glycogen.
Experts think the abnormal glycogen triggers the body’s infection-fighting system
(immune system). This creates scarring (cirrhosis) of the liver and other organs
such as muscle and the heart.

7. Type V or McArdle disease (type V glcogenosis)- This can be caused due to defect in
Muscle glycogen phosphorylase enzyme. This disease can affect Skeletal muscle. In this
disease muscle glycogen stores very high, not available during exercise, subject can cot
perform strenous exercise.
Type VI or Her’s disease- This can be caused due to defect in Liver glycogen
phosphorylase enzyme. This disease can affect liver. Characteristic features of this disease
are Liver enlarged, mild hypoglycemia & Ketosis seen. But it is not very serious disease.
Type VIII or Tarui’s disease- This can be caused due to defect in Phosphofructokinase
enzyme. This disease can affect Skeletal muscle erythrocytes. Characteristic features of this
disease are Muscle cramps due to exercise, blood lactate not elevated sometimes hemolysis
caused

8. DIAGNOSIS-
 GSD type I is diagnosed by laboratory tests that indicate
abnormal levels of glucose, lactate, uric acid, triglycerides and
cholesterol. Molecular genetic testing for
the G6PC and SLC37A4 genes is available to confirm a diagnosis.
Molecular genetic testing can also be used for carrier testing and
prenatal diagnosis. Liver biopsy can also be used to prove specific
enzyme deficiency for GSD Ia.

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