Pancreas as endocrine organ:Glucose homeostasis & Insulin

Nermeen Bastawy

Physiology Department

Faculty of Medicine

Cairo University

F

60% 25 %

Pro insulin

Ribosomes ER /Golgi Golgi/Granules

Mechanism of insulin release• Phases :11stst phase phase: rapid, short, glucose dependent: rapid, short, glucose dependent2nd phase: slow,sustained, glucose independent

• Oscillation pattern:

every 5 min.

Insulin receptors & effects

IRSNa/K ATpase

Glucokinase

Lipase GLUT4

K, aa

Glucose transporters (9(

2ry active transp. Facilitated Diffusion

GROWTH & METABOLISM

• Proteins & growth (anabolic(• CHO : insulin sensitive tissues

( muscle, adipose, liver(• Fat & KB

INSULIN

FFAGlucose

Adipose

ATP

-- lipase

G6P

GK

GSTG & VLDL

lipase

FFA

Adipose

GLUT2

ATP

Lipase

Hs-Lipase

Insulin & K+ ???

• Insulin K shift into the cells by ++ Na/K ATPase. That's why insulin is used in the treatment of hyperkalemia.

• Hyperkalemia: more K will enter beta cell ++ insulin secretion

• Hypokalemia more K will leave beta cell -- insulin secretion.

• Why diuretics are contraindicated in DM?

Control of insulin secretion

• Hypothalamus/pituitary? NOT

• Feed back? Glucose / Insulin

• +++/- - - - ?

FOOD Hs ANS K+ cAMP

70 100 300

Insulin

Glucose mg %

Max

Basal

Control of insulin secretion

• Hypothalamus/pituitary? NOT

• Feed back? GLUCOSE/Insulin

• +++/- - - - ?

FOOD Hs ANS K+ cAMP

How dose food ++ insulin secretion?

W is better stimulant 4 insulin secretion: oral or IV glucose?

Control of insulin secretion

• Hypothalamus/pituitary? NOT

• Feed back? GLUCOSE/Insulin

• +++/- - - - ?

FOOD Hs ANS K+ cAMP

Glucagon

• Pancreas (A cells)

• GIT & brain ( A & L cells)

• Actions:

1. Oppose insulin

2. ++ insulin, GH, SS secretion

3. +ve inotrope.

• Regulation : Food Hs ANS stress & exercise glucocorticoids

Somatostatin

• GIT & Pancreas ( D cells)

• ++ by food & GIT hormones

• -- all hormones & GIT motility & secretions

Important Qs

• Why exercise is benefit for DM?

It lower blood by ++ cAMP-kinase w moves GLUT4.

• Why diuretics are contraindicated in DM?

K is important for insulin secretion, so

Diuretics -- K+ -- insulin secretion

Mechanism of Glucostasis

1. Liver (glycogenesis, glycogenolysis, gluconeogenesis).

2. Hormonal mechanism

• Insulin / glucagon

• Catecholamine, GH & cortisol

70-100 mg%

Glycogenolysis

Mechanism of Glucostasis

1. Liver 2. Hormonal mechanism• Insulin / glucagon• Catecholamine, GH & cortisol++ energy sources : ++ glucose (glycogenolysis,

gluconeogenesis with IR) ++ FFA, KB & aa