10 Questions
What is the primary function of glycogen storage in the body?
To store excess glucose from meals
What is the highest percent of glycogen found in the body by weight?
10% in the liver
Which of the following is NOT a characteristic of glycogen storage diseases?
Acquired through environmental factors
What is the primary component of glycogen?
Glucose
When is glycogen broken down into glucose monomers and utilized for energy production?
During fasting or exercise
What is the approximate ratio of glycogen in muscle to glycogen in liver by weight?
2:1
How are glycogen storage diseases traditionally named?
After the clinician who first identified the disorder
What is the main reason for the classification of glycogen storage diseases?
The order of recognition and identification of the enzyme defect
What is the result of a failure to convert glycogen into energy and/or a toxic glycogen accumulation in GSDs?
A failure to use or store glycogen
How many GSDs are currently recognized?
An increasing number
Study Notes
Glycogen Storage Diseases (GSDs)
- GSDs are inherited inborn errors of carbohydrate metabolism, resulting in abnormal storage of glycogen.
- They are classified numerically in the order of recognition and identification of the enzyme defect causing the disorder.
- Clinical onset can range from neonatal life to adulthood.
Glycogen Structure and Function
- Glycogen is a branched polymer whose monomeric units are glucose.
- After a meal, the glucose level in plasma increases, stimulating the storage of excess glucose in cytoplasmic glycogen.
- The liver contains the highest percent of glycogen by weight (about 10%), whereas muscles can store about 2% by weight.
Distribution of Glycogen in the Body
- Although the liver contains a higher percentage of glycogen by weight, the total mass of glycogen in the muscle is about twice that of the liver, due to the greater muscle mass.
Glycogen Breakdown and Energy Production
- When needed, the glycogen polymer can be broken down into glucose monomers and utilized for energy production.
- Many of the enzymes and transporters for these processes are key to the etiology of GSDs.
Classification of Glycogen Storage Disorders
- GSDs that primarily affect the liver include:
- Glycogen synthase-2 deficiency (GSD type 0a)
- Glucose-6-phosphatase deficiency (GSD type Ia)
- Glucose-6-phosphate transporter deficiency (GSD type Ib)
- Glycogen debrancher deficiency (GSD type III)
- Glycogen branching enzyme deficiency (GSD type IV)
- Liver phosphorylase deficiency (GSD type VI)
- Phosphorylase kinase deficiency (GSD type IXa)
Learn about Glycogen Storage Diseases, inherited disorders affecting carbohydrate metabolism, classified numerically based on enzyme defects. Discover the clinical onset and effects of GSDs.
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