Vitamin B12 and Cobalamin - Comment
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Comprehensive information about Vitamin B12 and Cobalamin in this presentation slides. Content of this slides: 1. VITAMIN B12 COBALAMIN Dr. Muhammad Sarfraz M.B.B.S., M.Phil.(Pharmacology) Senior Demonstrator Quaid-e-Azam Medical College Bahawalpur, pakistan. 1 2. Vitamin B12 COBALAMIN 2 3. Vitamin B 12 COBALAMIN •Vitamin B12, cobalamin •water-soluble vitamin 3 4. Cobalamine VitaminB12 5. Chemistry It is made up of Tetrapyrrole ring system called as corrin ring with a central cobalt (Co) atom. 6. 7 7. 3-4 μg/day. Storage in liver 4-5 mg 8. Vitamin B12 Absorption Requires Two Binding Proteins • Vitamin B12 is absorbed • Bound to intrinsic factor • A small glycoprotein • Secreted by the parietal cells of the gastric mucosa 10 9. Vitamin B12 Absorption Requires Two Binding Proteins Gastric Acid And Pepsin Release The Vitamin From Protein Binding In Food 11 10. Vitamin B12 Absorption Requires Two Binding Proteins Bind To Cobalophilin A Binding Protein Secreted In The Saliva 12 11. Vitamin B12 Absorption Requires Two Binding Proteins In The Duodenum Cobalophilin Is Hydrolyzed 13 12. Vitamin B12 Absorption Requires Two Binding Proteins Releasing The Vitamin Bind To Intrinsic Factor 14 13. Vitamin B12 Absorption Requires Two Binding Proteins Vitamin B12 Is Absorbed From The Distal Third Of The Ileum Via Receptors That Bind The Intrinsic Factor-vitamin B12 Complex 15 14. Vitamin B12 Absorption Requires Two Binding Proteins Neither FREE INTRINSIC FACTOR NOR FREE VITAMIN IS ABSORBED 16 15. Vitamin B12 Absorption Requires Two Binding Proteins • INTO THE GENERAL CIRCULATION CARRIED BY B12-BINDING PROTEINS. 17 16. Vitamin Bl2 combines with intrinsic factor to form Vitamin B12- IF complex. Vitamin B12 intrinsic factor complex is absorbed in the ileum. In the illeal cells the intrinsic factor is released and the B12 is transferred to a plasma transport protein transcobalamin II. 17. Unlike other water soluble vitamins, vitamin B12 is stored in the liver and other tissues Whole liver contains about 4-5 mg of B12, which is sufficient for 2- 3 years. he only water soluble vitamin stored 18. Methyl cobalamin Deoxy adenosylcobalamin 19. Vitamin B12-Functions VITAMIN B12 ACT AS COENZYME. • METHYL COBALAMIN COENZYME OF Methionine Synthase 23 20. 24 21. Vitamin B12-Functions DEOXY ADENOSYLCOBALAMIN COENZYME OF METHYL MALONYL-COA MUTASE 25 22. Methylmalonyl (COA) Produced During The Degradation of Isoleucine, Valine, Threonine, And Methionine • AND • Fatty Acids With Odd Numbers Of Carbon Atoms 26 23. © 2008 Thomson - Wadsworth 24. 28 25. © 2008 Thomson - Wadsworth 26. FOLATE TRAP 27. FUNCTIONS OF VIT B12 • WHEN THE VITAMIN IS DEFICIENT, UNUSUAL FATTY ACIDS ACCUMULATE • AND BECOME INCORPORATED INTO CELL MEMBRANES, INCLUDING THOSE OF THE NERVOUS SYSTEM 31 28. Vitamin B 12 COBALAMIN KEY ROLE *NORMAL FUNCTIONING OF THE BRAIN AND NERVOUS SYSTEM *FORMATION OF BLOOD *INVOLVED IN DNA SYNTHESIS AND REGULATION 32 29. Vitamin B 12 COBALAMIN *FATTY ACID SYNTHESIS AND ENERGY PRODUCTION • ONLY BACTERIA HAVE THE ENZYMES REQUIRED FOR ITS SYNTHESIS 33 30. Causes •Nutritional •Decrease in absorption •IF deficiency •Gastric atrophy •Pregnancy •Fish tapeworm 31. Vitamin B 12 • FOUND ONLY IN FOODS OF ANIMAL ORIGIN • STRICT VEGETARIANS ARE AT RISK OF DEVELOPING B12 DEFICIENCY 35 32. Vitamin B 12 •Largest And Most Structurally Complicated Vitamin •Produced Industrially Only Through Bacterial Fermentation synthesis 36 33. EFFECTS OF COBALAMIN DEFICIENCY PRONOUNCED IN • RAPIDLY DIVIDING CELLS, SUCH AS THE ERYTHROPOIETIC TISSUE OF BONE MARROW • MUCOSAL CELLS OF THE INTESTINE 37 34. Vitamin B12-Deficiency Hamatopoitic •Megaloblastic anemia •Pernicious anemia 38 35. PERNICIOUS ANEMIA • AUTOIMMUNE DISEASE • PARIETAL CELLS OF THE STOMACH • DESTROYED • NO INTRINSIC FACTOR PRODUCTION 39 36. Vitamin B12-Deficiency Neurological • Numbness and tingling of the hands and feet • Subacute combined degeneration 40 37. 41 38. Vitamin B12-Deficiency Others •Hyperhomocysteine mia •Achlorhydria 42 39. Pernicious Anemia Disease Is Treated By Giving High-dose B12 Intramuscular Injection Of Cyanocobalamin 44 40. Pernicious Anemia THERAPY MUST CONTINUED THROUGHOUT THE LIVES OF PATIENTS WITH PERNICIOUS ANEMIA 45 41. Folate trap hypothesis © 2008 Thomson - Wadsworth 42. Function of folic acid 47 43. FOLATE TRAP 44. • Methylated Form • Cannot Be Converted Directly To Other Forms Of Tetrahydrofolate • Folate Trapped In The N5-methyl Form FH4.CH3 49 45. FOLATE TRAP 46. Folate trap hypothesis The Levels Of The Other Forms Decrease. Cobalamin Deficiency Leads To Deficiency Of The Other Tetrahydrofolate Forms Needed In Purine And TMP Synthesis 51 47. 52 48. VITAMIN B12 DEFICIENCY CAUSES PERNICIOUS ANEMIA • PATIENTS WHO FAIL TO ABSORB THE VITAMIN FROM THE INTESTINE. • MOST OFTEN DUE TO REDUCED SECRETION OF GASTRIC ACID AND LESS EFFICIENT ABSORPTION OF VITAMIN B12 FROM FOODS. 53 49. Pernicious Anemia • AUTOIMMUNE DESTRUCTION OF THE GASTRIC PARIETAL CELLS • RESPONSIBLE FOR THE SYNTHESIS OF A GLYCOPROTEIN CALLED INTRINSIC FACTOR. 54 50. Pernicious Anemia • LACK OF INTRINSIC FACTOR PREVENTS THE ABSORPTION OF VITAMIN B12 • RESULTING IN PERNICIOUS ANEMIA. 55 51. Pernicious Anemia • PATIENTS WITH COBALAMIN DEFICIENCY ARE USUALLY ANEMIC, BUT LATER IN THE DEVELOPMENT OF THE DISEASE • THEY SHOW NEUROPSYCHIATRIC SYMPTOMS • CNS EFFECTS ARE IRREVERSIBLE 56 52. Schilling test © 2008 Thomson - Wadsworth 53. Schilling test • PHYSIOLOGIC BASIS BEHIND THE SCHILLING TEST • If you are able to absorb B12 normally, • you will absorb it through your intestinal cells • it will enter bloodstream • where it will circulate throughout body 58 54. Schilling test • If you can’t absorb it correctly • it will not be absorbed through gut mucosa • excreted in feces 59 55. Schilling test • Saturate Any Open B12 Binding Sites Throughout The Body • The Patient Gets Injections Of Regular B12 At The Same Time • Then we Use oral Radioactive B1260 56. In a patient who CAN absorb B12 properly, here’s what happens: *Give IM B12 To Saturate Any Empty B12 Binding Sites *Give Patient A Drink Of Radioactive B12 61 57. In a patient who CAN absorb B12 properly, here’s what happens: Wait a while and see if the B12 is absorbed through the gut mucosal cells and circulates around the body in the blood 62 58. In a patient who CAN absorb B12 properly, here’s what happens: It won’t have many places to drop off B12 (because you’ve thought ahead to block all those sites) – so most of the B12 will just stay in the blood and get excreted out in the urine 63 59. In a patient who CAN absorb B12 properly, here’s what happens: *You measure the radioactivity of the urine *and that tells you how much B12 made it through the gut (was absorbed through the gut) and got into the blood 64 60. But in a patient who CAN’T absorb B12 properly, here’s what happens: • Give IM B12 to saturate any empty B12 binding sites • Give patient a drink of radioactive B12. 65 61. But in a patient who CAN’T absorb B12 properly, here’s what happens: • Wait a while and see if the B12 is absorbed through the gut mucosal cells and gets into the blood • If the patient can’t absorb B12, then the B12 won’t get through the gut mucosal cells, and it will just stay in the gut and excreted in the feces (instead of in the urine) 66 62. Then ? • Then, you can perform the test again, giving the patient some intrinsic factor this time to see if the B12 will be absorbed. • If there is now radioactive B12 in the urine, you know that the problem was lack of intrinsic factor. • If the urine still doesn’t have radioactive B12, then you need to figure out some other cause. 67 63. 68 64. 69 65. Other Tests To Diagnose Pernicious Anemia •Megaloblastic Anaemia • Low levels of B12 in blood •Antibodies Against *Intrinsic Factor *Parietal Cells 70 66. Other Tests To Diagnose Pernicious Anemia High Levels Of Homocysteine And Methyl Malonic Acid In Blood © 2008 Thomson - Wadsworth |
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| Posted by : peter88 | Post date : 2019-11-04 01:58 | ||
| Category : Education | Views : 580 | ||
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