Glycogen Storage Diseases Overview

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Questions and Answers

What is the role of SREBP1 in relation to fatty liver development?

SREBP1 promotes the expression of fatty acid synthesis genes. (correct)

SREBP1 reduces triglyceride accumulation.

SREBP1 has no effect on liver metabolism.

SREBP1 inhibits fatty acid synthesis.

Which experimental approach could best support the hypothesis that SREBP1 promotes fatty liver?

Measuring dietary fat intake among different mouse strains.

Injecting triglycerides directly into the livers of mice.

Comparing livers of wild-type and transgenic mice overexpressing SREBP1. (correct)

Assessing SREBP1 levels in healthy liver tissues.

What might be concluded from a Northern blot showing increased SREBP1 expression in obese mice compared to wild-type?

Increased SREBP1 expression is associated with fatty acid synthesis. (correct)

Obesity leads to decreased fatty acid synthesis.

SREBP1 has no regulatory function in the liver.

SREBP1 is downregulated in obesity.

Which statement best describes the relationship between SREBP1 and triglyceride accumulation in the liver?

Increased SREBP1 promotes triglyceride accumulation. Signup and view all the answers

What is a possible mechanism by which SREBP1 could contribute to the development of fatty liver?

Enhancing the transcription of genes required for fatty acid synthesis. Signup and view all the answers

What is the primary enzyme deficient in Pompe disease?

Lysosomal acid alpha-glucosidase (GAA) Signup and view all the answers

Which metabolic outcome is NOT typically observed in patients with glycogen storage disease type 1?

Hypoglycemia Signup and view all the answers

How does insulin signaling affect SREBP-1c expression in the liver?

Promotes activation of transcription of SREBP-1c Signup and view all the answers

What is the effect of glycogen accumulation in lysosomes due to Pompe disease?

Impaired lysosomal function and cell damage Signup and view all the answers

Which factor is involved in the feedback inhibition of insulin signal transduction via mTORC1?

Glycogen synthase kinase 3 (GSK3) Signup and view all the answers

What condition would likely lead to hyperlactatemia in glycogen storage disease type 1?

Anaerobic metabolism resulting from energy depletion Signup and view all the answers

What role does mTORC1 play in the activation of SREBP-1c?

Activates SREBP-1c transcription Signup and view all the answers

How would fat oxidation in patients with glycogen storage disease type 1 be affected?

It would decrease due to energy substrate limitation Signup and view all the answers

Study Notes

Glycogen Storage Disease Type 1

Patients with glycogen storage disease type 1 (GSD1) cannot properly break down glycogen into glucose.
GSD1 results in a buildup of glycogen, leading to several metabolic complications:
- Hyperuricemia: Due to increased production of uric acid, which is a by-product of glycogen breakdown.
- Hyperlipidemia: The body relies more on fat for energy, leading to an increase in blood lipids.
- Hyperlactatemia: Increased conversion of pyruvate to lactate, a byproduct of anaerobic glucose metabolism.

Pompe Disease

A multisystemic metabolic disorder caused by a deficiency in lysosomal acid alpha-glucosidase (GAA).
GAA breaks down glycogen in lysosomes.
Deficiency leads to the accumulation of glycogen within lysosomes, causing lysosomal swelling and rupture in all tissues.
This can lead to irreversible damage and impaired lysosomal function.

Insulin Signaling and SREBP1c

Insulin promotes the expression of SREBP1c in the liver.
Insulin activates the insulin receptor, leading to a signaling cascade.
This activates mTORC1, crucial for cell growth and metabolism.
Activated SREBP1c undergoes processing in the Golgi apparatus and translocates to the nucleus.
In the nucleus, SREBP1c binds to sterol regulatory elements (SRE) on DNA.
This binding triggers transcription of genes responsible for fatty acid synthesis.

SREBP1c and Fatty Liver

Western blot analysis of obese mice livers shows increased SREBP1c expression.
Obese mice develop fatty liver due to accumulated triglycerides.
This is a correlation, not causation.
An experiment could be designed to test if increased SREBP1c expression leads to fatty liver.
Overexpressing SREBP1c in mice and observing the development of fatty liver would support causation.

SREBP1 and Fatty Acid Synthesis

Northern blot analysis of obese mice livers shows elevated expression of both SREBP1 and genes involved in fatty acid synthesis.
This indicates that SREBP1 might be promoting the expression of these genes.
A further experiment could involve:
- Overexpressing SREBP1 in mice and comparing the expression of genes involved in fatty acid synthesis with those present in wild-type mice.
This would provide evidence for SREBP1's direct role in regulating fatty acid synthesis.

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Description

Explore the complexities of glycogen storage diseases, focusing on Glycogen Storage Disease Type 1 and Pompe Disease. Understand key metabolic implications such as hyperuricemia, hyperlipidemia, and the critical role of insulin signaling. This quiz offers insights into the biochemical pathways and anatomical consequences of these metabolic disorders.