Insulin

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Insulin

  1. 1. What is insulin ? Insulin is a peptide hormone produced by beta cells present in langerhans islets in pancreas
  2. 2. Chemistry of insulin Insulin is a small peptide (protein) consisting of fifty-one amino acids synthesized and stored within the pancreas  The protein itself consists of two chains, denoted A and B, linked by disulfide (sulfur-sulfur) bridges between cysteine residues
  3. 3. molecular weight of 5808 Da
  4. 4. Summary of how insulin works Elevated levels of glucose in the blood stimulates cells of the pancreas to increase insulin secretion into the blood. The insulin circulates the body, and within minutes, stimulates the liver and muscle cells to take up glucose from the blood. As glucose is removed from the blood, obviously blood levels fall.
  5. 5. Let’s take a closer look at what is happening Blood glucose level is monitored by the beta cells of the pancreas, and when levels rise above about 90 mg/dl, the pancreas begins to secrete an increased amount of insulin. The higher the sugar levels, the more insulin is released. The insulin is carried in the blood plasma bound to beta-globulin. Globulins are just large proteins found in the blood, and the alpha & betaglobulins carry hormones, lipids, vitamins e.t.c. around the body. There are “receptor sites” on the cell membranes of liver & muscle cells, and the insulin binds to these receptors. This causes the cells to become more permeable to glucose, as well as activating some enzyme systems within the cells.
  6. 6. Other substances known to stimulate insulin release include :Amino acids from ingested proteins, Three amino acids (alanine, glycine and arginine) act similarly to glucose by altering the beta cell's membrane potential. Acetylcholine released from vagus nerve endings (parasympathetic stimulation) Gastrointestinal hormones released by enteroendocrine cells of intestinal mucosa and Glucose-dependent insulinotropic peptide (GIP).
  7. 7. and mg++
  8. 8. Insulin modulates NT levels such as dopamine and acetylcholine excess insulin cause excess glucose uptake leading to liberation of free radicals after breakdown of glucose Due to destruction of cells by free radicals Insulin is a fat sparer causing atherosclerosis And decrease vessel diameter leading in ^BP
  9. 9. [ BY NEGATIVE FEED BACK ]
  10. 10. >160 mg/dl <60 mg/dl
  11. 11. Apart from given actions, the recent studies have also revealed that…. insulin has got ANTI-INFLAMMATORY ACTION
  12. 12. *FACTORS THAT INCREASE INSULIN SECRETION: - Increase in blood glucose - Increase in blood free fatty acids - Increase in blood amino acids - Gastrointestinal hormones (Gastrin, CCK, Secretin and GIP) - Glucagon, GH, Cortisol - Parasympathetic stimulation; Acetyl choline - Beta-adrenergic stimulation - Insulin resistance; Obesity - Sulfonyl urea drugs (Glyburide, Tolbutamide) *FACTORS THAT DECREASE INSULIN SECRETION: - Decreased blood glucose - Fasting - Somatostatin - Alpha-adrenergic activity - Leptin - Sympathetic stimulation
  13. 13. INHIBITORS OF INSULLIN SECRETION 1- amylin 2- somatostatin HORMONES ANTAGONIST TO INSULIN Glucagon Epinephrine Cortisol- Adrenaline (and Growth Hormone)
  14. 14. Half life of insulin is about 6 minutes So it is cleared off from circulation within 10 -15 mins except that has combined with receptors The remainder is degraded by enzyme INSULINASE mainly in liver

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