Insulin Regulation of Secretion
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This document summarizes the feedback loop between blood glucose and insulin secretion. It explains that increases in blood glucose directly stimulate pancreatic beta cells to secrete more insulin, while decreases in blood glucose inhibit insulin secretion. Precise regulation maintains blood glucose within a narrow range. The document also discusses various hormones and factors that can influence insulin secretion levels from the pancreas in response to blood sugar.
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Insulin Regulation of Secretion
- 2. Blood glucose regulates insulin secretion Insulin regulates blood glucose www.medicinemcq.com 2
- 3. Direct feedback effect on pancreatic beta cells ▪ When plasma glucose ↑ ▪ ▪ When plasma glucose ↓ ▪ Insulin secretion ↑ Insulin secretion ↓ Great precision www.medicinemcq.com 3
- 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. 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. > 75 mg/dL Stimulate insulin synthesis and insulin secretion Blood glucose > 100 mg/100 ml Insulin secretion rises rapidly www.medicinemcq.com 7
- 8. Glucose between 300 and 500 mg / dl www.medicinemcq.com 8
- 9. Glucose enters B cells via GLUT 2 Pancreas Beta cell glucose sensor ▪ Insulin independent www.medicinemcq.com 9
- 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. Incretins GI hormones that potentiate insulin secretion Cause 50% of the insulin released after a meal www.medicinemcq.com 15
- 16. Glucagon Like Peptide-1 (GLP-1) Gastric Inhibitory Peptide (GIP) www.medicinemcq.com 16
- 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. Insulin secretion greater after oral than after intravenous glucose administration www.medicinemcq.com 18
- 23. Stimulates insulin secretion Increases beta cell mass Inhibits glucagon secretion Delays gastric emptying www.medicinemcq.com 23
- 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. Stimulates insulin secretion when glucose levels are elevated Decreases glucagon-stimulated hepatic glucose production www.medicinemcq.com 25
- 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. Amino acid metabolism and ATP generation Elevated beta-cell Ca2+ concentrations www.medicinemcq.com 27
- 28. Only minor effects on insulin release www.medicinemcq.com 28
- 29. Promote the secretion of insulin www.medicinemcq.com 29
- 30. Beta2 Enhance insulin secretion Alpha2 Inhibits insulin release www.medicinemcq.com 30
- 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. Alpha 2 Increase basal concentrations of insulin Beta2 Decrease basal concentrations of insulin www.medicinemcq.com 32
- 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. Stimulates insulin secretion Insulin inhibits glucagon secretion www.medicinemcq.com 35