??? A Vitamin only produced by bacteria

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1 A Vitamin only produced by bacteria Both animals and humans must get this vitamin from food or supplements as it can not be naturally produced by the body.???

2 Active- B 12 (Holotranscobalamin) N C H 2 N O H 2 N O O H 2 N H N N Co N N O NH 2 O NH 2 NH 2 NH O O OH P N O O - O HO H N O

3 Vitamin B12 Generic name of group compounds called corrinoids Corrin nucleus Atom of cobalt ring in center Attached are one of the following CN : Cyanocobalamin (CNCbl) OH:hydroxocobalamin (OHCbl) 5 -adenosyl: adenosylcobalamin (AdoCbl) -CH 3 methylcobalamin (MeCbl) Both these forms are metabolically active

4 Why Vitamin B12 is essential Vitamin B12 is essential for normal nervous system function and blood cell production. Vitamin B12 is not manufactured in the body and must be absorbed from dietary or supplement intake. Unlike other water-soluble vitamins, vitamin B 12 is stored in the human body, primarily in the liver and kidneys The main sources of vitamin B12 include meat and fish (75%), dairy products (20%), and eggs (4%). Vitamins do not yield energy when broken down-they assist in energy yielding pathways of carbohydrate, lipid and protein metabolism For vitamin B12 to be absorbed by the body, it must bind to intrinsic factor, a protein secreted by cells in the stomach.

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6 B12 is attached to food protein when ingested Digested B12 complexed to HC to form HoloTC and transported to the small intestine. Degraded B12 complexed to IF and absorbed in the intestine Degraded B12 complexed to TC, to form Active-B12 (Holotranscobalamin) Released in Blood Taken up by specific cell receptors

7 Not all vitamin B 12 in serum is active Around 20% of circulating B12 is carried on transcobalamin holotc is referred to as Active Vitamin B-12 Approximately one-quarter of circulating cobalamin (Vitamin B-12) binds to transcobalamin (holo TC) and is thereby available for the cells of the body.

8 Functions Cell Proliferation One carbon metabolism Cobalamin (Vit B12) : 2 Forms are metabolically active (Act as co-factors in Enzyme reactions) Methylcobalamin Adenosylcobalamin Cofactor for Methionine Synthase in Remethylation of Homocysteine(Hcy) to Methionine Cofactor for Methylmalonyl CoA mutase which catalyzes Isomerisation of MMA-CoA to Succinyl CoA (has a role in Kreb s cycle) In Cobalamin deficiency, Methylmalonyl CoA & Methylmalonic acid (MMA) accumulates, rise is seen in blood and urine.

9 Common causes of Vitamin B12 deficiency Prolonged insufficient intake A diet low in vitamin B12 i.e. a strict vegetarian diet that excludes all meat, fish, dairy products, and eggs Chronic alcoholism Abdominal or intestinal surgery that affects intrinsic factor production or absorption Intestinal malabsorption disorders Atrophic gastritis, achlorhydria, infection with Helicobacter pylori, pernicious anemia Increased Requirements Pregnant and breastfeeding females, patients with Auto immune disorders, patients with HIV infection. Parasitic infections (Fish tape worm)

10 Deficiency of Vitamin B-12 leads to Megaloblastic Anemia Neuropathy MEGALOBLASTIC ANEMIA A B A. Normal Red Blood Cells B. Megaloblastic Anemia Lack of B12 is the secondary reason for megaloblastic anaemia, due to B12 deficiency blocking the transformation of methyl THF to THF and to intracellular folate polyglutamates. Pernicious anemia is a form of megaloblastic anemia caused by either inadequate vitamin B 12 intake or reduced gastric secretion of intrinsic factor, which inhibits absorption. Low B-12 low methionine & THF (Tetrahydrofolate) High thcy & 5-CH 3 THF. Low THF low 5,10-CH2-THF low conversion of dump to dtmp low DNA synthesis NEUROPATHY Undetected vitamin B 12 deficiency leads to neuropathy (10+ years)

11 Symptoms of Vitamin B12 deficiency The initial symptoms are insidious and could easily be overlooked. The classical symptoms of anaemia may not be present. *Early symptoms/findings of anaemia may also be masked by excess folic acid, or concurrent iron deficiency. Diffuse neuropsychiatric symptoms may often be the earliest symptoms. The commonest neurological symptoms are Paraesthesia of the hands and feet Diminished perception of vibration and position Absence of reflexes Unsteady gait and balance (ataxia) The psychiatric symptoms associated are also varied: Confusion and memory disturbances are the commonest Depression, with or without psychotic components, and cognitive decline. Swings in mood and personality changes may be early signs of what may later be manifested as psychiatric disease. These kinds of vague symptoms of vitamin B12 deficiency may easily be overlooked, especially as the serum concentration of vitamin B12 can lie within the reference range.

12 Diagnosis Why necessary? Atrophic gastritis with decreased pepsin production is prevalent in the elderly. Consequently, absorption of food-bound vitamin B 12 is lower in older than in younger, healthier people. Since the primary sources of vitamin B 12 in the diet are animal products, vegetarians have a high risk of developing B 12 deficiency. Risk Groups: Patients with unexplained anemia Patients with unexplained neuropsychiatric symptoms Patients with gastrointestinal manifestations, including stomatitis, anorexia & diarrhoea Elderly people Vegetarian Patients with gastrointestinal disorders, such as Crohn s disease or infection with Helicobacter pyroli. Patients with stomach resection.

13 In Elderly people: Raised MMA and lowered holotc : is common in old age and has been diagnosed in 10-30% of patients over 65 yrs of age. This high prevalence of slightly abnormal Vit B12 is not presumed to be associated with dietary causes but rather with malabsorption. Also the incidence of H.pyroli is quite high, which can lead to atrophic gastritis and in turn to Vit B-12 malabsorption. In Vegetarians: At high risk of developing Vit B12 deficiency, as animal products are the main sources of Vit B12. In addition to it Persons with increased Vitamin requirement such as pregnant & breast feeding women, patients with autoimmune disorders or persons with HIV infection-are a further risk group for Vit B12 deficiency. Persons who regularly take proton pump inhibitors can also develop vitamin B12 deficiency.

14 Active B12- Advantages in the Diagnosis of B12 Deficiency Only Vitamin B12 that binds to transcobalamin is available for cells Except on the liver no cellular receptors exist for the B12 carried by Haptocorrin (HC) It can take months, or even years, for a significant fall in HoloHC levels and so the more rapid decline in Active B12 may be masked when measuring total serum B12. Active-B12 reflects vitamin B12 status independent of recent absorption of vitamin. HoloTC is a better marker than total Vitamin B-12 for studies. Am J Clin Nutr HoloTC levels may be more suitable than serum vit b-12 levels to obtain information about Vit b-12 status, and the AxSYM holotc assay is a reliable and reproducible technique for the measurement of the holotc levels. If the serum vit b-12 levels is between approximately pmol/l, holotc alone or in combination with serum vitb-12 is likely to be more useful than serum vit b-12 levels alone to indicate vitamin b-12 status. Korean J Lab Med 2010; 30:

15 How vitamin B12 deficiency develops (hypothesis) Normal B 12 Depletion B 12 Deficiency Normal B 12 Status Early Serum Depletion Cell Depletion Damaged Metabolism Clinical Damage 0 I II III IV Active B12 > 35 pmol/l MMA < 271 µmol/l thcy <12 µmol/l Normal erythropoesis Active B12 Active B12 MMA & thcy Active B12 MMA & thcy Total B12 Active B12 MMA & thcy Total B12 Clinical Signs Active- B12 levels react early in the process.

16 Disadvantages of the Vitamin B12 Assay B12 assays measure total, not bioactive B12. Total B12 levels do not always correlate with symptoms. A low serum Active-B12 (but not serum vitamin B12 ) was reported in patients with Alzheimer s disease compared to a healthy control group. Large Gray Zone

17 Distribution of Active-B12 results by bands of total serum B12 There is a grey zone between approximately pmol/l B12 where there is likely to be misclassification of B12 status if relying on total serum B12 alone.

18 Recently Proposed Algorithm for B12 Deficiency Subjects Subjects at risk of B12 deficiency B12 < 150 pmol/l B pmol/l B12 > 150 pmol/l Likely deficient Additional testing like Active-B12 Unlikely deficient Resolve B12 indeterminate samples

19 AxSYM Active B12 (holotranscobalamin) Product Information

20 Intended use/ Explanation of test AxSYM Active B12 is a Microparticle Enzyme Immunoassay (MEIA) for quantitative determination of human holotranscobalamin (holotc) in human serum of the AxSYM System. Active- B12 is used as an aid in the diagnosis and assessment of Vitamin B12 deficiency.

21 AxSYM Active B12 reaction schematics 2 step sandwich MEIA

22 AxSYM Active B 12 : Summary of Details Intended Use Method Units Throughput Sample Type Sample Preparation Active B12 is used as an aid in the diagnosis & assessment of vitamin B12 deficiency. Microparticle Enzyme Immunoassay (MEIA) pmol/l 45 tests/ hour Serum (including gel tubes), heparin plasma (reflex from B12) None Sample Volume 200µL Assay Range Expected values Cut-off Standardisation pmol/l pmol/l central 95% reference interval ~ 35 pmol/l Standardised against Axis Shield Radio-immunoassay (RIA)

23 Plasma Vitamin B-12 & holotc Concenterations: used as a measure of the amount of Vit b-12 available for the body cells. The metabolites, thcy and MMA :mirror any lack of vit b-12 within the cells. Both of these accumulate in vit b-12 deficient patients. thcy : has low specificity because it also increases in patients with folate and possibly thiamine and Vit b-6 deficiency. However, in a folate-fortified population, thcy s specificity as a marker of vit b-12 deficiency is considerably better. MMA: a sensitive marker of vit b-12 deficiency, and ann elevated MMA concentration is often used as a gold standard for classification of a patient s status as vit b-12 deficient or non deficient.

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