PHA 329 Insulin & Glucagon

Insulin Synthesis/Characteristics

Insulin is a peptide hormone

Synthesis:

Preproinsulin → Proinsulin → insulin + C-peptide

• Stored in secretory granules until release

• C-peptide is secreted with insulin on 1:1 ratio and is clinically useful as a plasma biomarker of insulin production

• Insulin activates insulin receptors

Physiological Effects? (Insulin)

• Carbohydrate metabolism: cellular glucose uptake, glycogenesis (glycogen synthesis), inhibition of gluconeogenesis

• Lipid metabolism: cellular fatty acid uptake, conversion of excess glucose into fatty acid (lipogenesis), storage of fatty acids in adipose

• Protein metabolism: cellular amino acid uptake, protein synthesis

• Overall – decreases blood glucose (BG) levels, promotes energy storage

Stimulates Release? (Insulin)

High blood glucose / hyperglycemia (primary stimulus)

Inhibits Release? (Insulin)

Low blood glucose (hypoglycemia)

Epinephrine, norepinephrine

Additional info? (Insulin)

Medical conditions

• Type 1 diabetes – immune-mediated destruction of β-cells, low insulin

• Type 2 diabetes – insulin resistance; initially hyperinsulinemia, over time low insulin

Hormone Characteristics? (Glucagon)

Peptide hormone produced by pancreatic alpha cells

Activates glucagon receptors

Physiological Effects? (Glucagon)

Carbohydrate metabolism: Gluconeogenesis, glycogenolysis (breakdown of glycogen → glucose)

• Overall - increase blood glucose

Stimulates Release? (Glucagon)

Decrease in BG / hypoglycemia (primary stimulus), epinephrine, norepinephrine

Inhibits Release? (Glucagon)

Insulin