1 / 25

Biological effects of GH

Biological effects of GH. Somatotropic Growth and cell proliferation IGF-I mediated Metabolic Direct action of GH IGF-I independent Many tissues All nutrients. Effects of GH on metabolism Nutrient partitioning After absorption Independent of digestion process

breanna-frye
Download Presentation

Biological effects of GH

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Biological effects of GH • Somatotropic • Growth and cell proliferation • IGF-I mediated • Metabolic • Direct action of GH • IGF-I independent • Many tissues • All nutrients

  2. Effects of GH on metabolism • Nutrient partitioning • After absorption • Independent of digestion process • Independent of nutrient expenditure

  3. Nutrient partitioning during growth • Alteration of growth by exogenous GH • Alteration in nutrient partitioning between muscles and adipose tissue • Increased daily gain • Increased feed efficiency • Decreased fat deposition • Increased protein deposition • Age-dependent response

  4. Action of GH • Different between adipose and muscle • Growth of muscle in response to GH • Depends on availability of dietary proteins and energy • Involves IGF-I • Decreased fat accumulation • Inhibition of glucose uptake

  5. Action of GH • Decreased fat accumulation • Inhibition of glucose utilization • Glucose diverted to muscles • Net results • Decreased adipocyte hypertrophy • Increased muscle growth

  6. Effects on adipoccytes • Chronic • Lipogenesis • Inhibited • Fatty acid synthesis • Lipolysis • Stimulated when undernutrition

  7. Mechanism • Inhibition of insulin action on adipocytes • Decreased sensitivity of adipocytes to insulin stimulation • Decreased glucose usage by the cells • Independent of receptor number or intracellular signaling system • Inhibition of fatty acid synthase expression • Interference with insulin signaling pathway • Direct genomic effects

  8. Effects on lipolysis • Indirect mechanism • Alteration of adipocyte responsiveness to acute lipolytic signaling pathway • Highly dependent on nutritional status of the individual

  9. Increased hepatic gluconeogenesis • Direct effects • Inhibition of insulin action • Increased efficiency of amino acid utilization • Reduced oxidation • Results in muscle fiber hypertrophy

  10. Pancreatic hormones

  11. Pancreas • Exocrine organ • Digestive enzymes • Discovery of the first hormone (secretin) • Endocrine organ • Islets • Described by Langerhans • Islet of Langerhans

  12. Cell composition • Two major types • Alpha • Glucagon • Beta • Insulin • Other cells • D cells (SS) • F cells (pancreatic polypeptide)

  13. Regulation of glucose metabolism • Glucose homeostasis • Movement of glucose into and out of extracellular space • Involvement of many tissues • Liver • Adipose tissue • Muscle • Two hormones • Insulin • Glucagon

  14. Regulation of glucose metabolism • Glucose homeostasis • Basic concept • Coordinated relationship between alpha (glucagon) and beta (insulin) cells under control of glucose sensor

  15. Regulation of glucose metabolism • Glucose homeostasis • Basic concept • Particular arrangement of cells within the islet • Specialized cell membrane

  16. Insulin • Required for normal growth and development • Only hormone that can lower blood glucose level • Dominant metabolic regulator • Unregulated glucose level if absent • Hypoglycemia if too high • Cause neural shock

  17. Biochemistry • Two subunits • Alpha and beta • Linked by two disulfide bridges • Synthesized as prohormone • Preproinsulin • Proinsulin precursor • Proteolytic cleavage • Proinsulin • Formation of disulfide bridges

  18. Insulin • Coupled with zinc within the beta cells • Very short life • Around 5 to 15 min after synthesis • Metabolized by kidneys and liver

  19. Glucagon • Biochemistry • Single peptide • 29 AA • Similar structurally to gastric inhibitory peptide and VIP • Cleaved from larger protein • Highly conserved • Identical among mammals

  20. Other pancreatic peptides • SS • Localized in D cells • Located adjacent to alpha and beta cells • Local action of SS • Affects function of intestine • Movement of nutrients

  21. Pancreatic polypeptide • Unclear function in mammals • Suppression of SS secretion by pancreas and intestine • Inhibition of gallbladder and pancreatic enzyme secretion • Secretion affected by nutrient uptake by the intestine

More Related