Nt1310 Unit 1 Exercise 2

Vitamin B12 (Cobalmin) is a water soluble vitamin and plays a key role in the normal functioning of the brain and nervous system, and in the formation of red blood cells.

Vitamin B12 deficiency can occur if the body does not absorb enough vitamin B12 from the gastrointestinal tract or when there is not enough dietary intake of the vitamin. One common cause of deficiency is as a result of pernicious anaemia which is an autoimmune disorder that results in inflammation and damage to the stomach lining, and loss of parietal cells. The parietal cells produce intrinsic factor, a protein needed for absorption of Vitamin B12 in the gut.

Symptoms of vitamin B12 deficiency can include depression, decreased fertility, poor muscle function, poor development

However this test has a low sensitivity where some individuals with low result would be considered to be deficient but show no clinical evidence of deficiency and conversely symptoms of deficiency can be seem when the result does not fall into the low range. There is a large ‘grey zone’ or ‘indeterminate range’ between normal and abnormal levels. In order to detect vitamin B12 deficiency, a more sensitive and specific screening test is required.

Haptocorrin (HC) and transcobalamin (TC) are transport proteins for vitamin B12 . Transport of vitamin B12 to the tissues is brought about by TC. Thus, the metabolically active fraction of vitamin B12 is the vitamin B12 that is associated with TC, holotranscobalamin (holoTC).

The much larger fraction of vitamin B12 carried by haptocorrin (HC) is considered metabolically inert because no cellular receptors exist, except on the liver. Active B12 contains the biologically available cobalamin because only transcobalamin-bound B12 promotes the uptake of the cobalamin by all cells via specific receptors. The shorter half-life for active- B12 compared to holoHC makes the decrease of active B12 one of the earliest markers of Vitamin B12