From the Guidelines
Yes, plasma homocysteine is elevated in the context of Vitamin B12 (cobalamin) deficiency.
Mechanism of Homocysteine Elevation
- Homocysteine is an amino acid derived from the metabolism of methionine, and its elevated levels can be caused by genetic defects, nutritional deficiencies, or decreased renal clearance 1.
- Vitamin B12, along with folic acid, plays a crucial role in the remethylation of homocysteine to methionine, and a deficiency in Vitamin B12 can lead to elevated homocysteine levels 1.
Role of Vitamin B12 in Homocysteine Metabolism
- Vitamin B12 is a co-factor for methionine synthase, which remethylates homocysteine to methionine 1.
- A deficiency in Vitamin B12 can impair this remethylation process, leading to elevated homocysteine levels.
Clinical Implications
- Elevated homocysteine levels are associated with an increased risk of atherosclerotic vascular disease, including stroke 1.
- The B-complex vitamins, including Vitamin B12, can lower homocysteine levels, but their effectiveness in preventing cardiovascular events is still being studied 1.
From the Research
Plasma Homocysteine Levels in Vitamin B12 Deficiency
- Plasma homocysteine levels are elevated in the context of Vitamin B12 (cobalamin) deficiency, as evidenced by multiple studies 2, 3, 4, 5, 6.
- The presence of vitamin B12 is essential in homocysteine metabolism, and deficiency of this nutrient is associated with various degrees of hyperhomocysteinemia 2.
- Elevated plasma levels of homocysteine can be caused by deficiency of either vitamin B12 or folate, leading to hyperhomocysteinemia (HHcy) 3.
- Studies have shown that vitamin B12-deficient subjects have higher total plasma homocysteine levels compared to controls and heterozygotes for homocystinuria due to cystathionine beta-synthase deficiency 6.
- Administration of hydroxycobalamin to vitamin B12-deficient subjects has been shown to decrease homocysteine levels to normal, highlighting the importance of vitamin B12 in homocysteine metabolism 6.
Relationship Between Homocysteine and Vitamin B12 Deficiency
- Hyperhomocysteinemia is associated with several human disorders, including cardiovascular disease, neurodegenerative disorders, pregnancy complications, and fractures 2, 3.
- Vitamin B12 deficiency can lead to hemolytic anemia and severely elevated homocysteine levels, which can be resolved with vitamin B12 treatment 4.
- Elevated plasma homocysteine concentration, but not a low serum vitamin B12 concentration, increases the risk of cardiovascular morbidity and mortality in patients with ischemic heart disease 5.
- The measurement of homocysteine levels may be helpful for identifying subjects at greater risk of disease, who may benefit from a more aggressive treatment of other modifiable risk factors 2, 3.