Presentation on theme: "Islets of Langerhan. Prof. K. Sivapalan. 08-01-14Islets of Langerhan2 Structure. Blooed supply- Drainage through portal vein to liver and through hepatic."— Presentation transcript:
08-01-14Islets of Langerhan2 Structure. Blooed supply- Drainage through portal vein to liver and through hepatic vein into IVC.
08-01-14Islets of Langerhan3 Histology. A cells 20 % [glucogon] B cells 50% [Insulin] D cells 8% [somatostatin] F cells [pancreatic polypeptide]
08-01-14Islets of Langerhan4 Insulin secretion. Synthesized as one long poly peptide. Folded by disulfide bonds. A portion is removed in middle. Result is a molecule with A and B peptide chains. Half life- 5 minutes.
08-01-14Islets of Langerhan5 Structure of Insulin A chain – 22, B chain – 30 amino acids. Animal insulins vary in less than 4 amino acids. Insulin from animals can be antigenic. Pork insulin is less antigenic compared to beef insulin. Human insulin is manufactured by recombinant DNA technology in bacteria.
08-01-14Islets of Langerhan6 Mechanism of Actions of Insulin Insulin receptors are found in almost all cells. Insulin binds to the receptor. The receptor activates several different actions depending on the nature of the cell. There is similar action by Insulin Like Growth Factors- ? significance
08-01-14Islets of Langerhan8 Actions of Insulin on Carbohydrate Metabolism.. Glucose transporters are increased by increased levels of insulin. Glucose enters cells by facilitated diffusion- exceptions are, brain, Small intestinal epithelium, PCT in kidney. ? Glucose entry in Liver and red cell Glycogen storage increased in Liver and Muscle. Increases glycogen synthesis and reduces glycolytic enzymes.
08-01-14Islets of Langerhan9 Actions of Insulin on Fat and Protein Metabolism Increases lipogenesis in liver and adipose tissue. Reduces lypolysis. Activates transport of Amino Acids into cells. Increases protein synthesis by accelerated translation. * increases intracellular potassium.
08-01-14Islets of Langerhan10 Insulin Action [Timed]: Rapid- [Seconds] –Increased transport of glucose, amino acids, and K + into insulin sensitive cells. Intermediate- [minutes] –Stimulation of protein synthesis. –Inhibition of protein degradation. –Activation of glycogen synthetase. –Inhibition of Phosphorylase and gluconeogenic enzymes. Delayed [hours] –Increase in mRNA for lipogenic and other enzymes.
08-01-14Islets of Langerhan12 Insulin and Growth
08-01-14Islets of Langerhan13 Regulation of insulin secretion. Feed back by glucose.
08-01-14Islets of Langerhan14 Sudden increase of glucose. Sudden increase of blood glucose results in immediate rise in blood insulin and a second slow increase. ? Risk of fast food and benefit of natural food by slow digestion and steady absorption.
08-01-14Islets of Langerhan16 Effects of removing pancreas.
08-01-14Islets of Langerhan17 Effects of insulin deficiency.
Causes of Diabetes Primary- primarily pancreatic problem Secondary- other diseases resulting in DM Type I- autoimmune, young age (insulin deficiency) Type II- main determinants- age, obesity, ethnicity and family history. (insulin resistance) –Metabolic syndrome- hypertension, obesity, hypertriglyceridaemia, decreased HDL, acanthosis nigricans. 08-01-14Islets of Langerhan18
08-01-14Islets of Langerhan21 Changes in hyperglycaemic coma
08-01-14Islets of Langerhan22 Retinal Changes in Diabetes.
08-01-14Islets of Langerhan23 Hyperinsulinism. Cause- insulinoma or injection (accidental overdose or under eating). Early indications- tremor, palpitation, anxiety. Confusion, weakness, dizziness, hunger, convulsions, coma, death within a few minutes. –Glucose need for brain- 1 mg/min/kg body weight (100g/day for 70 kg man) It is a Medical emergency. * Importance of carrying glucose and diagnosis card if on insulin injection.
08-01-14Islets of Langerhan28 Other islet cell hormones. Somatostatin. Inhibits secretion of insulin and glucagon. Excess secretion can cause hyperglycemia. Pancreatic polypeptide. Secretion increased by parasympathetic, protein meal, fasting, exercise, hypoglycemia. Secretion decreased by somatostatin and IV glucose. Action- ?slow absorption.
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