Diabetes Pathophysiology

Question 1

What two glands are found in the pancreas?

Answer 1

• Digestive gland
• Endocrine gland

Question 2

What type of tissue is the digestive gland?

Answer 2

Exocrine

Question 3

What does the digestive gland do?

Answer 3

Secretes alkaline pancreatic juice rich in digestive enzymes into the duodenum through the pancreatic duct to aid digestion

Question 4

What does the endocrine gland do?

Answer 4

Consists of multiple small clusters of cells scattered throughout the gland called the pancreatic islets/islets of Langerhans which discharge secretions directly into the bloodstream

Question 5

What types of cells does each islet consist of?

Answer 5

A (alpha) cells, B (beta) cells, D (delta) cells, F cells (secrete pancreatic polypeptides)

Question 6

What do alpha cells do?

Answer 6

• Secrete glucagon
• Raise blood glucose
• Located at the periphery of the islet

Question 7

What do beta cells do?

Answer 7

• Secrete insulin
• Lower blood glucose
• Predominate cell type found in the core of the islets

Question 8

What do delta cells do?

Answer 8

• Produce gastrin & somastatin
  Somastatin inhibits secretion of glucagon and insulin

Question 9

What is Type 1 diabetes?

Answer 9

Insulin deficiency

Question 10

What is Type 2 diabetes?

Answer 10

An adult-onset diabetes, inadequate response to insulin; becoming more common in children

Question 11

How does insulin work?

Answer 11

1. Binding of insulin to insulin receptor on the surface of the cell membrane
2. Generation of intracellular signal
3. Insertion of GLUT-4 receptor from its inactive site into the cell membrane
4. Transport of glucose across the cell membrane

Question 12

Cell membranes are impermeable to glucose, what do they require?

Answer 12

Special carriers Glucose Transporters

Question 13

How do glucose transporters work?

Answer 13

Move glucose across the cell membrane at a faster rate than would occur with diffusion alone

Question 14

What are the different GLUT types?

Answer 14

• GLUT-4: insulin dependent glucose transporter for skeletal muscle & adipose tissue
  Inactive inside the cell membrane; active when insulin causes it to move from its inactive site to the cell membrane
• GLUT-2: major transport of glucose into beta cells and liver cells. Low affinity for glucose and acts when glucose plasma glucose level are high

-GLUT-1: present in all tissues. Does not require actions of insulin and important for transport of glucose into cells of the nervous system

Question 15

What is gestational diabetes?

Answer 15

Diabetes in pregnancy - goes away after birth

Question 16

What is the pathophysiology of Type 1?

Answer 16

Severe lack of insulin caused by autoimmune mediated destruction of islet B-cells

Question 17

What is the mechanism of islet B-cells destruction?

Answer 17

1. T-cells react against B-cell antigens resulting in cell damage
   - T-helpers activate macrophages directed at B-cells
   - Cytotoxic T-cells directly kill B-cells
2. Locally produced cytokines (macrophages & cytotoxic Ts) damage B-cells
3. Auto antibodies against B-cells and insulin detected in 70-80% patients

Question 18

What factors are involved in the development of Type 1A diabetes?

Answer 18

• Genetic predisposition (diabetogenic genes)
• Hypothetical triggering event involving an environmental agent that incites an immune response
• Immunologically mediated beta cell destruction