Insulin Regulation of Secretion

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Insulin Regulation of Secretion

  1. 1. Dr. Rajendran. S www.medicinemcq.com 1
  2. 2.  Blood glucose regulates insulin secretion  Insulin regulates blood glucose www.medicinemcq.com 2
  3. 3.  Direct feedback effect on pancreatic beta cells ▪ When plasma glucose ↑ ▪ ▪ When plasma glucose ↓ ▪  Insulin secretion ↑ Insulin secretion ↓ Great precision www.medicinemcq.com 3
  4. 4. Pancreas Blood glucose Insulin www.medicinemcq.com 4
  5. 5.  Insulin regulates blood glucose  Glucose production by the liver  Uptake and utilization in peripheral tissues ▪ Muscle ▪ Adipose tissue ▪ Liver www.medicinemcq.com 5
  6. 6.  80 to 90 mg/100 ml  Rate of insulin secretion is low  Plasma glucose < 75 mg / dl  Insulin secretion inhibited www.medicinemcq.com 6
  7. 7.  > 75 mg/dL  Stimulate insulin synthesis and insulin secretion  Blood glucose > 100 mg/100 ml  Insulin secretion rises rapidly www.medicinemcq.com 7
  8. 8.  Glucose between 300 and 500 mg / dl www.medicinemcq.com 8
  9. 9.   Glucose enters B cells via GLUT 2 Pancreas  Beta cell glucose sensor ▪ Insulin independent www.medicinemcq.com 9
  10. 10. www.medicinemcq.com 10
  11. 11. www.medicinemcq.com 11
  12. 12. www.medicinemcq.com 12
  13. 13. www.medicinemcq.com 13
  14. 14.  Controls glucose-regulated insulin secretion  Phosphorylation ▪ Rate-limiting step in glucose metabolism in the beta cell and insulin release www.medicinemcq.com 14
  15. 15.  Incretins  GI hormones that potentiate insulin secretion  Cause 50% of the insulin released after a meal www.medicinemcq.com 15
  16. 16.   Glucagon Like Peptide-1 (GLP-1) Gastric Inhibitory Peptide (GIP) www.medicinemcq.com 16
  17. 17.  Released from small-intestinal endocrine cells postprandially  Reach the beta cells through the bloodstream ▪ Increase the sensitivity of islet cells to glucose www.medicinemcq.com 17
  18. 18.  Insulin secretion greater after oral than after intravenous glucose administration www.medicinemcq.com 18
  19. 19. Glucose Incretins Insulin www.medicinemcq.com 19
  20. 20. www.medicinemcq.com 20
  21. 21. www.medicinemcq.com 21
  22. 22. www.medicinemcq.com 22
  23. 23.     Stimulates insulin secretion Increases beta cell mass Inhibits glucagon secretion Delays gastric emptying www.medicinemcq.com 23
  24. 24.  Raises levels of cAMP  Activates cAMP-dependent protein kinase A ▪ Amplify the Ca2+ signal by decreasing Ca2+ uptake by cellular stores www.medicinemcq.com 24
  25. 25.   Stimulates insulin secretion when glucose levels are elevated Decreases glucagon-stimulated hepatic glucose production www.medicinemcq.com 25
  26. 26.    Amplify the glucose-induced release of insulin from the beta-cell Stimulate insulin release in the absence of glucose Most potent  Arginine  Lysine  Leucine www.medicinemcq.com 26
  27. 27.  Amino acid metabolism and ATP generation  Elevated beta-cell Ca2+ concentrations www.medicinemcq.com 27
  28. 28.  Only minor effects on insulin release www.medicinemcq.com 28
  29. 29.  Promote the secretion of insulin www.medicinemcq.com 29
  30. 30.  Beta2  Enhance insulin secretion  Alpha2  Inhibits insulin release www.medicinemcq.com 30
  31. 31.  Suppresses the secretion of insulin  Stimulation of alpha2 adrenergic receptors and inhibition of insulin secretion ▪ ▪ ▪ ▪ ▪ ▪ Hypoxia Hypoglycemia Exercise Hypothermia Surgery Severe burns www.medicinemcq.com 31
  32. 32.  Alpha 2  Increase basal concentrations of insulin  Beta2  Decrease basal concentrations of insulin www.medicinemcq.com 32
  33. 33.  Inhibit insulin secretion www.medicinemcq.com 33
  34. 34.  Inhibit insulin secretion  Through G protein–coupled receptor (GPCR) mechanisms ▪ Inhibit adenylate cyclase ▪ Modify Ca2+ and K+ channel gating. www.medicinemcq.com 34
  35. 35.   Stimulates insulin secretion Insulin inhibits glucagon secretion www.medicinemcq.com 35

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