Islet cell structureα cell : glucagonβ cell : insulinδcell : somatostatin

α cell

β cell

δcell

Principal actions of insulinIts net effect is to promote the storage of

carbohydrate, protein and fat. It is therefore

appropriately called the “ hormone of

abundance”.

70 mg/dl 300 mg/dl

(Glucosurea)

Consequences of insulin deficiency

NORMAL DIABETIC

Disturbances in protein metabolism

INSULIN DEFICIENCY

Dehydration

Insulinlipodystrophy

Chronic neuropathy:Trophic ulceration

Gangrene

Gangrene with infection

Insulin allergy

Glucagon

Synthesis and secretion of glucagon

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⊕

⊕

○

Glucagon

Amino acids

GlucoseFFA

Ketoacid

Actions of glucagon Plasma: Glucose ↑ Amino acids ↓ Free fatty acids↑

Diabetic retinopathy – Microvascular complication

Hormones of the pancreatic islets

Pancreas, Liver & Nutrient

Liver : the central organ in nutrient traffic

Endocrine regulation of carbohydrate metabolism

1. Insulin

2. Glucagon

3. Somatostatin --- inhibit the secretion of insulin & glucagon

4. Epinephrine --- cyclic AMP increased, [Ca+2] increased hepatic

glucose output increased.

5. thyroid hormone : (1) increases the absorption of glucose from the intestine

(2) cause hepatic glycogen depletion

(3) accelerate the degradation of insulin

6. glucocorticoids --- diabetogenic effect

7. growth hormones --- inhibition of glucose

phosphorylation decrease utilization

In Summary

Insulin• Is released by B-cells in

the Islets of Langerhans in the pancreas.

• Responds to high levels of blood sugar; is released when someone has a meal and needs to store extra energy.

• Lack of insulin or response to insulin leads to diabetes.

Glucagon• Is released by a-cells in

the Islets of Langerhans in the pancreas.

• Responds to low levels of blood sugar; is released when someone hasn’t eaten or requires extra energy

• Basically, glucagon is the opposite of insulin.