Re: homocysteine level

Posted By chris on May 12, 1999 at 09:54:49
I am planning to attend a lecture (presented by a local cardiologist) about risk factors and heart attack. The description of the event goes on to say "a simple blood test to measure one of your amino acid levels can warn you...". Am I right in assuming this is about homocysteine levels?  I searched the archives but the only post I could find was from 1997. Has the thinking on this changed any among cardiologists? Apparently the doctor presenting this lecture co-authored an aricle for the New England Journal of Medicine in the past year.  Thank you.

[Cleveland Clinic, MD]

Posted By CCF CARDIO MD - CRC on May 12, 1999 at 10:56:28

Dear Chris,
Thank you for your question. Who is the doctor talking?  Here is some information on homocyteine.
Homocysteine is an amino acid that has been linked to coronary artery disease. Excessive quantities of homocysteine were noted to accumulate in the blood of patients with homocystinuria, a rare disease characterized by skeletal, neurological, and vascular abnormalities. From this, a link has been established between more moderate elevations of plasma homocysteine concentrations and atherosclerosis, even in those without any apparent defined genetic trait for homocystinuria.
Plasma homocysteine levels rise with age in both men and women. This may be secondary to decreases in vitamin cofactor levels or coexisting renal impairment, which are common in this age group.  Homocysteine concentrations are higher in men than women. This may be due to differences in muscle mass, renal function, essential vitamin cofactors, or even protein intake. Sex hormones may also influence homocysteine metabolism, but this remains speculative at the current time.
Homocysteine concentrations rise with falling renal function. Concentrations are often twice normal in dialysis-dependent patients with end-stage renal disease, but may be substantially higher; levels decrease after dialysis. This increase is likely to be due to impaired metabolism of homocysteine by the kidney or by the liver, whose normal function may be perturbed by the uremic milieu. High plasma homocysteine concentrations have also been observed in patients with psoriasis and acute lymphoblastic leukemia probably reflecting high cell turnover in these disorders.
Homocystinuria has been the paradigm of homocysteine-related atherosclerosis since the early work of Mudd and co-workers. The classical disorder, characterized by complete, or almost complete, absence of cystathionine b-synthase, is rare and occurs in the United States once in 400,000 births. The condition is transmitted in autosomal recessive fashion. Reduced enzyme activity is observed in heterozygotes for the disorder and may be demonstrated by administering a methionine challenge. Markedly elevated plasma homocysteine concentrations are typical and are accompanied by an increase in urinary homocystine. The clinical manifestations include skeletal abnormalities, ocular lens dislocation, and mental retardation. The other major complications of early atherosclerosis and a tendency to thromboembolic events soon became evident after the disorder was first described in a survey of mentally retarded children from Ireland. Plasma homocysteine concentrations may be reduced by dietary methionine restriction or by the administration of vitamin B6, which may protect against vascular complications.
Metabolism of homocysteine requires vitamin B6, vitamin B12, and folate. Vitamin B6 and folate reduce homocysteine concentrations in homocystinuria, and vitamin B6 may reduce the incidence of vascular complications in these patients.  In normal subjects and in patients with atherosclerotic vascular disease, homocysteine concentrations may be reduced by folic acid either used alone or else in combination with vitamins B6 or B12 4,5,79. The effect is greatest with folic acid.  The effect of vitamin B12 when administered alone is more modest if it occurs at all.  Since the effect of these measures on vascular morbidity and mortality have not yet been evaluated, the treatment of patients with vascular disease in whom homocysteine concentrations are high remains speculative although some doctors are treating their patients with higher homocysteine levels with folate.
I hope you find this information useful.  Information provided in the heart forum is for general purposes only.  Only your physician can provide specific diagnoses and therapies.  Please feel free to write back with additional questions.
If you would like to make an appointment at the Cleveland Clinic Heart Center, please call 1-800-CCF-CARE or inquire online by using the Heart Center website at www.ccf.org/heartcenter.  The Heart Center website contains a directory of the cardiology staff that can be used to select the physician best suited to address your cardiac problem.

[chris__0__0]

Posted By chris on May 12, 1999 at 14:09:22
Thank you for your response. The advertisement for the lecture says that George Welch, MD is a cardiologist at Maine Cardiology. Within the last year, Dr. Welch co-authored an article for the New England Journal of medicine on the new risk factor for heart attack. It goes on to say that one fourth of all heart atttacks occur in people with no known risk factors. Chris  










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