Insulin Action on Liver and Adipose Tissues

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Questions and Answers

What is a primary characteristic of type 1 diabetes mellitus (T1DM)?

Obesity as a common factor

Pancreatic beta cell destruction (correct)

Insulin resistance

Normal insulin levels

Which factor does NOT influence the HbA1c result according to WHO?

Anaemia

Physical exercise (correct)

Pregnancy

Hemoglobin abnormalities

What is the diagnostic HbA1c threshold for pre-diabetes according to ADA guidelines?

6.5-7.0%

5.7-6.4% (correct)

7.1% or higher

5.0-5.6%

How is type 2 diabetes typically diagnosed?

As a diagnosis of exclusion Signup and view all the answers

Which of the following statements is true regarding insulin status in type 2 diabetes?

Insulin levels are typically elevated or normal Signup and view all the answers

What is the physiological action of insulin that decreases blood glucose levels?

Glycogenesis Signup and view all the answers

Which hormone is primarily responsible for lowering blood glucose levels?

Insulin Signup and view all the answers

Which process is stimulated by insulin in the liver to store excess glucose?

Glycogenesis Signup and view all the answers

What role does Akt play in insulin signaling?

Regulation of GLUT4 translocation Signup and view all the answers

Which of the following processes is inhibited by insulin?

Gluconeogenesis Signup and view all the answers

What effect does the translocation of GLUT4 have in response to insulin in muscle and adipose tissues?

Increases glucose uptake Signup and view all the answers

In insulin signal transduction, what does GSK3 inhibit?

Glycogen synthesis Signup and view all the answers

What is the role of PFK2/FBPase-2 in the prevention of futile cycling?

Regulates the phosphorylation states of enzymes Signup and view all the answers

Which effect does insulin have on fatty acid metabolism?

Promotes glucose conversion into fatty acids Signup and view all the answers

Which of the following describes an effect of glucagon on PFK2/FBPase-2?

Promotes the phosphorylation of PFK2/FBPase-2 Signup and view all the answers

What is the primary function of PEPCK in gluconeogenesis?

Catalyzes the conversion of oxaloacetate to PEP Signup and view all the answers

Which of the following statements about insulin treatment in diabetes is true?

It tends to result in weight gain. Signup and view all the answers

How does PFK1 influence glycolysis and gluconeogenesis?

It promotes glycolysis while suppressing gluconeogenesis. Signup and view all the answers

What is the role of GLUT2 in glucose metabolism?

Facilitates glucose transport into the liver Signup and view all the answers

Which enzyme catalyzes the conversion of Fructose-1,6-bisphosphate to Fructose-6-phosphate?

Fructose-1,6-bisphosphatase Signup and view all the answers

What triggers post-translational modifications in key enzymes of glucose metabolism?

Hormonal changes such as insulin and glucagon Signup and view all the answers

What is considered the normal blood glucose level range?

3.9-5.9 mmols/l Signup and view all the answers

What effect does glucagon have on glycogen levels in the liver?

It increases glycogenolysis. Signup and view all the answers

Which of the following is a counter-regulatory response to low blood glucose levels?

Glycogen breakdown Signup and view all the answers

Through which mechanism does glucagon primarily exert its effects?

cAMP signaling pathway Signup and view all the answers

What is the primary function of insulin in blood glucose regulation?

Inhibiting glycogen breakdown Signup and view all the answers

Which process is enhanced by glucagon to provide glucose during fasting states?

Gluconeogenesis Signup and view all the answers

Which hormone's action is primarily opposed by glucagon?

Insulin Signup and view all the answers

What role does HSL play in the effects of glucagon on adipose tissue?

Promotes fat breakdown Signup and view all the answers

During a state of hyperglycemia, what immediate action occurs after insulin secretion?

Increased glucose uptake into cells Signup and view all the answers

What does glycogen synthesis in the liver primarily depend on?

Increase in insulin levels Signup and view all the answers

What is the major feature of diabetes mellitus?

Hyperglycaemia Signup and view all the answers

What condition results when there is glucose in the urine?

Glucosuria Signup and view all the answers

What physiological effect can result from glucosuria?

Osmotic diuresis Signup and view all the answers

How did children with diabetes survive before the discovery of insulin?

Starvation diets Signup and view all the answers

What detrimental situation did a 12-year-old boy experience due to diabetes?

He became blind and starved. Signup and view all the answers

What is often a consequence of insufficient glucose uptake by cells post-meal in diabetes?

High extracellular glucose levels Signup and view all the answers

What was the distressing choice faced by children suffering from diabetes before insulin was available?

Dying from diabetes or starvation Signup and view all the answers

What severe complications can arise from dehydration due to diabetes?

Circulatory failure and brain damage Signup and view all the answers

What was the outcome for the child who consumed toothpaste mixed with birdseed?

He died from starvation. Signup and view all the answers

What was the primary reason for the discomfort faced by children on starvation diets?

Emotional distress from hunger Signup and view all the answers

Study Notes

Fuel Use: Insulin Action on Liver and Adipose Tissues

Insulin's primary action is to lower blood glucose levels.
Normal blood glucose level is 3.9-5.9 mmol/L.
Insulin promotes glucose uptake into cells.
Insulin stimulates glycogen synthesis in the liver and skeletal muscles.
Insulin inhibits glycogen breakdown (glycogenolysis).
Insulin inhibits gluconeogenesis (glucose formation from non-carbohydrate sources).
Insulin promotes the uptake and storage of glucose as triglycerides in adipose tissues.
Insulin inhibits the breakdown of triglycerides in adipose tissues.
Insulin promotes fatty acid synthesis in the liver.

Insulin Signaling Pathway

Insulin receptor initiates a signaling cascade.
This cascade involves protein kinases, like PI3K, p85, and Akt.
A key outcome is GLUT4 translocation.
GLUT4 translocation facilitates glucose uptake into cells.
GSK3 inhibits glycogen synthesis.
FOXO regulates gluconeogenic gene expression.

Physiological Actions of Insulin

Insulin promotes glucose uptake by cells.
Insulin promotes glycogen formation (glycogenesis).
Insulin inhibits glycogen breakdown (glycogenolysis).
Insulin inhibits glucose production (gluconeogenesis).
Insulin has a net effect of decreasing blood glucose levels.

Counterregulation

Counterregulatory hormones (like glucagon) oppose insulin's effects.
These hormones increase blood glucose levels when needed, such as between meals.

Diabetes Mellitus

Diabetes is a disorder characterized by high blood glucose levels.
High blood glucose levels can lead to significant complications.
There are several types of diabetes, including Type 1 and Type 2.

Criteria for Diabetes

WHO criteria for diabetes includes fasting plasma glucose (FPG) levels and oral glucose tolerance tests (OGTT).
Different diagnostic criteria exist for different populations or clinical settings.
HbA1c measures average blood glucose levels over time.

Types of Diabetes

Type 1 diabetes is characterized by beta cell destruction, requiring insulin.
Type 2 diabetes is characterized by insulin resistance where cells don't respond properly to insulin.
Other types include monogenic diabetes & secondary causes.

Diabetes Type 1 vs Type 2

Type 1 is usually diagnosed in childhood with little or no insulin production.
Type 2 is usually diagnosed in adulthood with insulin resistance/ decreased sensitivity of cells to insulin.

Insulin Action on the Hepatocyte

Insulin affects glucose uptake, glycogen synthesis, glycolysis, and gluconeogenesis in liver cells.
Insulin can stimulate fatty acid synthesis.

Glycogen Synthesis and Glycolysis

Insulin stimulates glycogen synthesis and glycolysis

Gluconeogenesis

Insulin suppresses gluconeogenesis

Futile Cycling

Futile cycling (interconversion between glucose-6-phosphate and fructose-1,6-bisphosphate) is prevented by insulin action because the rates of both reactions are controlled via PFK2/FBPase-2 regulation.

Fatty Acid Synthesis

Insulin promotes fatty acid synthesis in the liver.

Very Low-Density Lipoprotein (VLDL)

VLDL transport fatty acids and lipids from the liver to adipose tissue.
Dysregulation of VLDL transport can lead to hyperlipidaemia.

Overview of Insulin and Glucagon Action

Insulin promotes glucose uptake, storage, and conversion to fats.
Glucagon promotes glycogen breakdown and glucose release.

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Description

This quiz explores the intricate functions of insulin, particularly its role in lowering blood glucose levels and affecting liver and adipose tissue. It covers insulin's mechanisms, including glycogen synthesis, triglyceride storage, and the insulin signaling pathway. Test your knowledge on how insulin regulates metabolism and energy storage.