RiversideCardiology.com- Do you know your homocysteine level?


Home About Us Links Archive Feedback Disclaimer	June 1, 1999 Do You Know Your Homocysteine Level? By Chiayu Chen, M.D. F.A.C.C. Riverside Cardiology Associates Medical Group What is homocysteine and why is it important for your health? What is Homocysteine? Homocysteine and Coronary Artery Disease Treatment Warning! What is Homocysteine? Homocysteine is an amino acid. It is a metabolic by-product of another amino acid, methionine. Homocysteine is metabolized through two pathways. The first pathway is by transsulfuration, a vitamin B6 dependent pathway in which homocysteine is converted to cysteine. The second pathway is by remethylation back to methionine. The second pathway is dependent on folate and vitamin B12. By knowing the metabolism of homocysteine, it is clear why inadequate intake of folate, B6, or B12 may lead to an increase in the level of homocysteine. Other enzyme deficiencies, which are usually caused by genetic abnormalities, can also cause an increase in plasma homocysteine level. Homocysteine and Coronary Artery Disease The association of elevated homocysteine level and coronary artery disease has been noted in multiple epidemiologic studies. These studies have shown that elevated plasma homocysteine is an independent cardiovascular risk factor. In the Physicians' Health Study, physicians with myocardial infarction had a statistically higher level of homocysteine level in their blood (Stampfer MJ, et al: A prospective study of plasma homocysteine and risk of myocardial infarction in US physicians. JAMA 268:877, 1992.) In another study, the Framingham Heart Study, they concluded that high plasma homocysteine concentrations is associated with an increased risk of carotid artery stenosis in the elderly (Selhub J, et al: Association between plasma homocysteine concentrations and extracranial carotid-artery stenosis. N Engl J Med 332:286, 1995.) Other similar studies have also found higher levels of homocysteine in patients with cerebrovascular and peripheral vascular disease. The pathophysiological mechanisms are not fully understood. They may include endothelial cell injury, increase in platelet aggregation and abnormalities in fibrinolysis. Treatment There are currently no randomized clinical trials showing that lowering homocysteine level will actually lower the risk of coronary artery disease. A secondary prevention trial is currently underway. We have been checking and treating elevated homocysteine levels in our practice since 1994, because the association of elevated homocysteine and coronary artery disease has been documented in so many studies and the treatment is relatively inexpensive and benign. The decision to obtain a fasting plasma homocysteine level should be individualized. Patients with documented coronary artery disease and peripheral vascular disease should be considered candidates. There is no standard guideline for the treatment of a elevated homocysteine level. We typically prescribe folic acid between 0.4 mg and up to 6 mg a day, depending on the baseline level. In addition, pyridoxine (vitamin B6) in the range of 25-250 mg/day, and vitamin B12 can be added for non-responders. We typically aim to lower the homocysteine level to about 10 micromol/L. Usually the "normal" range for your local lab would be higher, from 5 to 15 micromol/L. Warning! High dose folic acid supplement may exacerbate B12 deficiency and may mask the macrocytosis of B12 deficiency. It is recommended that methylmalonic acid and B12 level be monitored at lease once a year, especially in elderly patients. Permanent peripheral neuropathy can be associated with high dose vitamin B6 administration. Lowering homocysteine level has not been shown to lower the risk of coronary artery disease (at least not yet.) Do not forget about the other risk factors such as cholesterol level, high blood pressure, diabetes, and smoking. Top of Page

Material copyright © 1999-2005 Riverside Cardiology Associates Medical Group Reproduction in whole or in part in any form or medium without express written permission of Riverside Cardiology Associates Medical Group is prohibited.

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June 1, 1999

Do You Know Your Homocysteine Level?

By Chiayu Chen, M.D. F.A.C.C.
Riverside Cardiology Associates Medical Group

What is homocysteine and why is it important for your health?

What is Homocysteine?
Homocysteine and Coronary Artery Disease
Treatment
Warning!

What is Homocysteine?

Homocysteine is an amino acid. It is a metabolic by-product of another amino acid, methionine. Homocysteine is metabolized through two pathways. The first pathway is by transsulfuration, a vitamin B6 dependent pathway in which homocysteine is converted to cysteine. The second pathway is by remethylation back to methionine. The second pathway is dependent on folate and vitamin B12.

By knowing the metabolism of homocysteine, it is clear why inadequate intake of folate, B6, or B12 may lead to an increase in the level of homocysteine. Other enzyme deficiencies, which are usually caused by genetic abnormalities, can also cause an increase in plasma homocysteine level.

Homocysteine and Coronary Artery Disease

The association of elevated homocysteine level and coronary artery disease has been noted in multiple epidemiologic studies. These studies have shown that elevated plasma homocysteine is an independent cardiovascular risk factor.

In the Physicians' Health Study, physicians with myocardial infarction had a statistically higher level of homocysteine level in their blood (Stampfer MJ, et al: A prospective study of plasma homocysteine and risk of myocardial infarction in US physicians. JAMA 268:877, 1992.)

In another study, the Framingham Heart Study, they concluded that high plasma homocysteine concentrations is associated with an increased risk of carotid artery stenosis in the elderly (Selhub J, et al: Association between plasma homocysteine concentrations and extracranial carotid-artery stenosis. N Engl J Med 332:286, 1995.)

Other similar studies have also found higher levels of homocysteine in patients with cerebrovascular and peripheral vascular disease.

The pathophysiological mechanisms are not fully understood. They may include endothelial cell injury, increase in platelet aggregation and abnormalities in fibrinolysis.

Treatment

There are currently no randomized clinical trials showing that lowering homocysteine level will actually lower the risk of coronary artery disease. A secondary prevention trial is currently underway.

We have been checking and treating elevated homocysteine levels in our practice since 1994, because the association of elevated homocysteine and coronary artery disease has been documented in so many studies and the treatment is relatively inexpensive and benign.

The decision to obtain a fasting plasma homocysteine level should be individualized. Patients with documented coronary artery disease and peripheral vascular disease should be considered candidates.

There is no standard guideline for the treatment of a elevated homocysteine level. We typically prescribe folic acid between 0.4 mg and up to 6 mg a day, depending on the baseline level. In addition, pyridoxine (vitamin B6) in the range of 25-250 mg/day, and vitamin B12 can be added for non-responders.

We typically aim to lower the homocysteine level to about 10 micromol/L. Usually the "normal" range for your local lab would be higher, from 5 to 15 micromol/L.

Warning!

High dose folic acid supplement may exacerbate B12 deficiency and may mask the macrocytosis of B12 deficiency. It is recommended that methylmalonic acid and B12 level be monitored at lease once a year, especially in elderly patients.

Permanent peripheral neuropathy can be associated with high dose vitamin B6 administration.

Lowering homocysteine level has not been shown to lower the risk of coronary artery disease (at least not yet.) Do not forget about the other risk factors such as cholesterol level, high blood pressure, diabetes, and smoking.

Top of Page

Material copyright © 1999-2005 Riverside Cardiology Associates Medical Group
Reproduction in whole or in part in any form or medium without express written permission of Riverside Cardiology Associates Medical Group is prohibited.