Download MBBS Physiology Presentations 12 Pancreatic Hormones Lecture Notes

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Endocrine secretions from islet of

Langerhans

Insulin- cells

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Glucagon- cells
Somatostatin- cells
Pancreatic Polypeptide ? F cells
Insulin

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First isolated by Banting and Best in 1922
Insulin is a polyopeptide containing 2 amino

acid chains linked by di-sulfide linkage

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It is synthesized in RER as preproinsulin
It is cleaved into proinsulin

Effect of insulin on carbohydrate

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metabolism

Promotes muscle glucose uptake and

metabolism

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Storage of glycogen in muscles
Promotes liver uptake, storage and use of

glucose

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- Inactivates liver phosphorylase
- Increases activity of glucokinase
- Increases activity of glycogen synthesis
Promotes conversion of excess glucose into

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fatty acids and inhibits gluconeogenesis in liver
Effect of insulin on Fat metabolism

Promotes fat synthesis and storage

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- Increases transport of glucose into

hepatocytes

- Pyruvate is converted to acetyl co-A

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- Fatty acids synthesized are used to form

triglycerides

Insulin activates lipoprotein lipase in the

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capillary walls

Insulin deficiency causes lipolysis of storage

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fats and release of free fatty acids

Effect of insulin on Protein

metabolism

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Promotes protein synthesis and storage
- Stimulates transport of amino acids into the

cells

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- Increases translation of mRNA
- Increases rate of transcription
- Inhibits protein catabolism
- Depresses gluconeogenesis

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Insulin and growth hormone interact

synergistically to promote growth
Glucagon

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It is a large polypeptide secreted by -cells

of islet of landerhans

It is called as hyperglycemic hormone

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It is glycogenolytic, gluconeogenic, lipolytic

and ketogenic

It acts via Gs to activate adenylyl cyclase

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and increase intracellular cAMP

Glucagon

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Glucagon does not cause glycogenolysis in

muscle

It increases gluconeogenesis in liver and

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elevates metabolic rate

It increases ketone body formation
The calorigenic action of glucagon is not due

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to hyperglycemia but due to hepatic

deamination of amino acids

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Large doses have inotropic effect on heart
stimulated

inhibited

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Insulin-glucagon molar ratios

Insulin is glycogenic, antigluconeogenetic,

antilipolytic and antiketotic

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Glucagon is glycogenolytic,

gluconeogenetic, lipolytic and ketogenic
stimulated

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inhibited

Hypoglycemic unawareness
Functional hypoglycemia

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Persistent hyperinsulinemic hypoglycemia of

infancy

Macrosomia

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Diabetes Mellitus Type 1 and Type 2