Pancreas: Endocrinology

Question 1

Islet of Langerhans cell types (5)

ENDOCRINE FXN OF PANCREAS

Answer 1

Secrete hormones into blood vessels

1. Alpha cell: glucagon & ghrelin (near outer edges)
2. Beta cell: insulin (occupy middle)
3. Delta cell: somatostatin
4. Epsilon cell: ghrelin (unclear fxn in pancreas)
   * Stomach: erectogenic for appetite
5. F cell: pancreatic polypeptide

*All cells are accessible on surface

Question 2

EXOCRINE FXN OF PANCREAS

Answer 2

Acinar cells secrete pancreatic enzymes into pancreatic duct into duodenum

• digestive enzymes
• Carbonic acid NAHCO3
• bicarbonate

Question 3

Blood flow in Islet of Langerhans

Answer 3

1. Center to periphery
2. Paracrine action is assisted by blood flow direction
3. Hormones are delivered to liver before rest of body

Question 4

Effects of Glucose levels on insulin/glucagon ratios

Answer 4

Question 5

INSULIN

Answer 5

1. Processing of insulin can be part of beta cell failure
   * Increase in pro-insulin for Type II diabetics
2. C peptide can be secreted in urine and used as a marker; reflects endogenous insulin within a period

Question 6

ATP & Uncoupling protein affecting beta cell functions

Answer 6

1. ATP levels correlates to glucose and thus leads to insulin secretion levels
2. UCP2 from brown fat modulate reactive oxygen species
3. When there is more heat –> decrease ATP –> decrease insulin secretion

• Increase in UCP levels in diabetics = relation to beta cell failure
• Genipin (Gardenia fruit) inhibits UCP2, increasing insulin secretion

Question 7

Neural and humoral factors modulate insulin secretion (4)

Answer 7

1. Beta adrenergic stimulation increase secretion

• Epinephrine (sympathetic)
• Acetylcholine (parasympathetic)

2. Sympathetic Alpha adrenergic (NE) stimulation inhibit secretion

• NE stimulation rises during exercise; modulates insulin
• Importatnt defense against HYPOGLYCEMIA
• If not, would distrurb fat burn; lead to FA storage, not release

3. Incretins: increase secretion during oral glucose administration

• Larger response of insulin compared to IV dose
• Gut hormones: CCK, GIP, GLP-1
• In response to perceived intake of carbohydrate; even when looking
• Develops an appetite

4. Amylin: slows gastric emptying and promotes satiety

• prevents post-prandial spikes in blood glucose; slows absorption
• Co-secreted with insulin in a 1:50/70 ratio
• Diabetics have an increased likelihood that amylin is improperly processed

Question 8

Effect of drinking coffee on Type II diabetes risk

Answer 8

1. >400mg/day coffee have a decrease risk in type II diabetes
2. Oversecretion of insulin & amylin in diabetics can lead to inappropriate processing –> amyloid deposits (fibrils) –> beta cell death
3. Coffee metabolites down-regulates expression of amyloids

Question 9

INSULIN

Answer 9

1. Mobilizes fuels: glycogen breakdown, fat breakdown, gluconeogenesis, protein breakdown
2. Respond to incretin effects: decrease glucagon expression
3. ATP stimulated release; decreases glucagon expression when glucose uptake increases
   * Calcium channels may be involved
4. Glucagon is a powerful segretagogue; islet anatomy renders this less important