![]() ![]() Interestingly, in cats, there was no change in serum concentrations of homocysteine (see Figure 1). Using this compound as a marker of cobalamin deficiency, we have been able to demonstrate that cats and dogs with very low serum cobalamin do indeed have a significant tissue-level cobalamin deficiency (Figure 2). Tissue-level deficiency of cobalamin is associated with an increase in the urinary and serum concentrations of an organic acid called methylmalonic acid, which is an alternative product of a cobalamin dependent pathway within the mitochondria. While the serum concentration of cobalamin is used diagnostically, the reactions catalyzed by cobalamin dependent enzymes occur in the mitochondria, making it difficult to assess the state of cobalamin availability in the patient. Studies of radiolabelled cobalamin in cats have demonstrated that the half-life of this compound is significantly reduced in cats with gastrointestinal disease. As all cells in the body require cobalamin for single carbon metabolism, it has been hypothesized that cobalamin deficiency may actually contribute to the clinical signs and manifestations of gastrointestinal disease in some patients. In animals with reduced cobalamin absorption, regardless of the cause, it is reasonable to expect that eventual depletion of cobalamin body stores will occur and cobalamin deficiency will ensue. Recent evidence from studies at the Gastrointestinal Laboratory have also shown that supplementation of cobalamin is important to get the best response to therapy for gastrointestinal disease.įigure 1: A typical cobalamin dependent reaction, where a methyl group (-CH3) is added to homocysteine to make methionine Cobalamin Deficiency in Gastrointestinal Disease In companion animals, most attention to cobalamin has been directed towards its use as a diagnostic marker for gastrointestinal disease. ![]() Deficiency in cobalamin may also be associated with demyelinating neuropathies, dementia, and megaloblastic anemia (pernicious anemia) in humans. In turn, hyperhomocysteinemia is a recognized risk factor for cardiovascular disease. Single carbon biochemistry is an area of great interest in human medicine, as deficiencies in the activity of these enzymes may be associated with hyperhomocysteinemia. A typical reaction catalyzed by a cobalamin dependent enzyme, methionine synthase, is illustrated in figure 1. Cobalamin is a co-factor for at least three enzymes that carry out these types of reactions, acting as a transitional carrier of the single carbon group. During these reactions, functional units such as methyl groups (-CH3) are transferred onto or between biologically important compounds. ![]() Cobalamin (Vitamin B12) is a water-soluble, cobalt-containing vitamin that plays an important role in biochemical processes referred to as single carbon transfers. ![]()
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