The document discusses the endocrine pancreas and its role in regulating blood sugar levels. The endocrine pancreas contains clusters of cells called islets of Langerhans, which include alpha cells that produce glucagon, beta cells that produce insulin, and delta cells that produce somatostatin. Insulin lowers blood sugar by facilitating glucose uptake and storage, while glucagon raises blood sugar by promoting glucose release and production. Somatostatin inhibits the secretion of insulin and glucagon to regulate their levels.

1. 1
The Endocrine Pancreas
♦ Islets of Langerhans:
 Alpha (α) cells produce glucagon
 Beta (β) cells produce insulin
 Delta (δ) cells produce somatostatin
♣ Insulin
• A hypoglycemic hormone produced by β cells in the pancreas
Insulin Synthesis

2. 2
• Insulin (51 AA):  chain (21 AA) +  chain (30 AA) linked by 3 disulfide bonds.
Effect of insulin on carbohydrate metabolism
 It + glucose uptake into liver, skeletal muscle, and adipose tissue.
 It + glycolysis in liver, skeletal
muscle, and adipose tissue.
 It + glycogen synthesis.
 It − gluconeogenesis.
 It − glycogenolysis.
Heavy arrows: (+) Increase (stimulate)
Light arrows: (−) Decrease (Inhibit)

3. 3
Effect of insulin on lipid metabolism
 Insulin + lipogenesis and fatty acid synthesis (heavy arrows)
 Insulin − lipolysis (light arrows)
Effect of insulin on protein metabolism
 Insulin + amino acid uptake and protein synthesis (heavy arrows).
 Insulin − protein degradation (light arrows).

4. 4
Factors affecting insulin secretion
♣ Glucagon
• A hyperglycemic hormone produced by α cells in the pancreas
Glucagon synthesis

5. 5
Effect of glucagon on carbohydrate metabolism
 + Release of glucose from the liver cells into the blood
 + Gluconeogenesis
 + Glycogenolysis
 − glycolysis
 − glycogen synthesis
- Heavy arrows: +
- Light arrows: −
Effect of glucagon on lipid metabolism
 + Lipolysis
 + Ketogenesis
 − lipogenesis
 − fatty acid synthesis
 Heavy arrows: +
 Light arrows: −

6. 6
Effect of insulin on protein metabolism
 + amino acids uptake
 + protein degradation
 − protein synthesis
 Heavy arrows: +
 Light arrows: −
Factors affecting Glucagon secretion

7. 7
Blood sugar control

8. 8
Regulation of metabolism by Insulin & Glucagon
♣ Somatostatin (growth hormone-inhibiting hormone (GHIH)
 A hormone composed of 14 amino acids and produced by δ cells in the pancreas.
♦ It is an inhibitory hormone
 − Growth hormone secretion
 − TSH secretion
 − Prolactin secretion
 − insulin and glucagon secretion
♦ Stimulators of somatostatin secretion
♦ Inhibitors of somatostatin secretion