Hormones Flashcards
Name the four classes of hormonal signaling? Describe their general function.
Endocrine - released into blood, effects distant cells exocrine- released into duct for delivery to surface paracrine - released into interstitial space affecting neighboring cells autocrine - product affects releasing cells
What cell type releases insulin?
Beta cells
Describe the structure of insulin? How many chains? What types of bonds link those chains? Describe the different types of tertiary structures? What is Zincs role?
- Insulin is composed of 2 primary amino acid chains - the alpha chain and the beta chain.
- These chains are linked by disulfide bonds.
- The alpha and beta chains form a monomer of insulin.
- Two monomers form a dimer of insulin.
- Two dimers form a hexamer of insulin.
- Zinc holds the insulin molecules in the hexamer form.
Describe the mechanism by which insulin is released?
- Glucose enters the beta cell.
- This triggers glycolysis and ATP increases
- ATP sensitive K+channel is inhibited causing a buildup of charged potassium in cell
- This depolarizes the cell and triggers the opening of a voltage gated calcium channel.
- Calcium enters cell and insulin vesicles are released via exocytosis.
What contributes to the release of insulin?
High blood, GLP-1, GIP, and autonomic nervous system.
What does insulin stimulate?
Uptake of glucose in the cell, glycogen synthesis, uptake of amino acids by cells, glycerol synthesis, glycolysis in cell.
How do Catecholamines (Epinephrine) effect the muscles, liver, and adipose tissue?
- Liver - make glucose for muscles NOW
- Glycogenolysis
- Gluconeogenesis
- Muscles - Move NOW
- Glycolysis
- Glycogenolysis
- Triglyceride utilization
- Adipose Tissue - make glucose for Muslces
- Lipolysis
What does insulin inhibit?
- Protein catabolism
- lipolysis
What does glucagon stimulate?
- Gluconeogenesis
- glycogenolysis
- mobilization of fatty acids from adipose
- hepatic lipase
- Ketogenesis
What does somatostatin’s function
Inhibits release of insulin and glucagon
What stimulates the release of glucagon?
Low blood sugar, high protein meals, amino acids, cortisol, stress, epinephrine, sympathetic nervous system. It is constantly secreted.
What inhibits release of glucagon?
- Glucose
- insulin
- GLP-1,
Describe the Synthesis of Insulin from gene to final hexameric form?
- Transcription of gene (chromosome 11) into mRNA & translation of mRNA on ribosome
- Initial translation of signal sequence and binding to rough ER.
- Synthesis of preproinsulin in lumen of ER.
- Signal sequence is cleaved & disulfide bonds form–>proinsulin
- Proinsulin in packaged and relasesd from ER to Golgi
- The C-chain is removed in the Golgi and new vesicles are formed–>insulin
- Mature insulin is packaged into a final hexameric structure with Zince and a C-chain remenants.
What is GLP-1?
Where is it produced?
What does it activate?
What does it inhibit?
GLP-1, or Glucagon-like peptide-1, is an incretin that aids glucose metabolism. It is produced in L-Cells (ileum and colon).
- Activate
- Increases release of insulin
- Increases Beta cell proliferation
- Inhibit
- Glucagon
- Gastric Empyting
- Appetite
- Beta Cell apoptosis
What is GIP?
What does it Activate?
What does it inhibit?
GIP, or glucose-dependant insulintropic peptide, is an incretin that aids in glucose metabolism. It is produced in K-cells in the jejunum.
- Activates
- Insulin release
- Beta cell proliferation
- lipogensis (build fatty acids)
- Inhibits
- Beta cell apoptosis
What is the effect of GLP-1 and GIP in people with diabetes?
GLP-1 levels are decreased in Type 2, but patients do respond to the effects of GLP-1. (GLP-1 thearpy is a potential option)
GIP levels are not decreased, but patients resist the effects.
Why are the challenges with GLP-1 therpy for diabetics?
GLP-1 is rapidly degraded by the body. DPP-4 enzyme degrades GLP-1.
Half-life is less than 2 minutes
What are 2 types of potential GLP-1 therapies?
- Those that mimic GLP-1 and bind to beta cells, but not to the DPP-4 enzyme that degrades it.
- Those that enhance GLP-1 and/or inhibit DPP-4 enzyme.
What are the 4 main insulin counter regulatory hormones?
- Glucagon
- Catecholamines (epinephrine, adreniline)
- Cortisol
- Growth Hormones
What is the effect of Counter Regulatory Horomones (CRH) in diabetics or people with repeated hypoglycemia?
CRH effects are lost or blunted. This leads to increased chances of hypoglycemia.
What stimulates the release of GLP-1 and GIP?
Food ingestion
What is the difference between Glucocorticoids and Catecholamines?
Catecholamines are a “fight or flight” response and glucorticoids are used under periods of stress to prepare for “fight or flight”
What effects to Glucocorticoids have on Muscles, Liver, and Adipose Tissue?
- Liver - Make and Store Glucose
- increase gluconeogenesis
- Glycogen Synthesis
- Muscles - Make Glucose for liver
- Degarde protein for gluconeogenesis
- Adipose - Make glucose for liver
- Lipolysis
