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Amino Acid in Blood Linked to Age-Related Macular
Degeneration
High homocysteine is biomarker for AMD and
cardiovascular disease
Jan. 4, 2006 - People who have elevated
homocysteine in their blood, an amino acid that is a known biomarker for
cardiovascular disease, may also be at an increased risk of developing
age-related macular degeneration (AMD), the leading cause of blindness
in senior citizens. The study is in the January issue of the American
Journal of Ophthalmology.
(Read "What is
homocysteine?" below news story.)
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Health & Medicine |
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In this largest study of the relationship of this
amino acid and AMD, researchers measured the fasting plasma homocystein
levels of 934 individuals who were participating in an ancillary study
of the Age-Related Eye Disease Study. Five hundred and forty seven
people with AMD and 387 control subjects were tested.
This research was conducted at the Massachusetts
Eye and Ear Infirmary and Devers Eye
Institute in Portland, Ore.
"We found that elevated homocysteine in the blood
may be another biomarker for increased risk of AMD," said lead author
Johanna M. Seddon, MD, director of epidemiology at the Massachusetts Eye
and Ear Infirmary. Seddon is also an associate professor of
ophthalmology at Harvard Medical School. "Homocysteine can be reduced by
dietary intake of vitamins B6, B12, and folate, so the relationship
between this amino acid and AMD deserves further study."
Researchers found that median values were higher
among people with advanced stages of AMD compared to people without AMD,
controlling for age and other factors. Levels considered high in the
clinical setting (above 12 mmol/l) were also associated with a higher
risk of AMD. Seddon's finding adds to the growing body of evidence that
there may be overlapping disease mechanisms between AMD and
cardiovascular diseases.
Age-related macular degeneration is the leading
cause of irreversible visual impairment and blindness among persons aged
60 and older. With the elderly population steadily growing, the burden
related to this loss of visual function will increase. Limited treatment
options exist and prevention remains the best approach for addressing
this public health concern.
Seddon and colleagues first proposed this potential
relationship between homocysteine and AMD in the mid-1990s and published
this hypothesis in a review article in 1999. She and her team previously
established that smoking and nutrition are modifiable factors associated
with the development and progression of AMD. They are now also searching
for the genes involved in the etiology of this increasing cause of
blindness.
About Research:
This research was funded by grants from the
National Institute of Health, the National Eye Institute, Bethesda, MD;
the Epidemiology Unit Research Fund of the MEEI, Boston, and the Good
Samaritan Foundation, Portland, Ore.
Massachusetts Eye and Ear Infirmary
http://www.meei.harvard.edu
The Massachusetts Eye and Ear Infirmary, an independent specialty
hospital, is an international center for treatment and research and a
teaching hospital of Harvard Medical School.
Harvard Medical School
http://hms.harvard.edu/
Harvard Medical School has more than 7,000 full-time faculty working in
10 academic departments housed on the School's Boston quadrangle or in
one of 48 academic departments at 18 Harvard teaching hospitals and
research institutes. Those Harvard hospitals and research institutions
include Beth Israel Deaconess Medical Center, Brigham and Women's
Hospital, Cambridge Health Alliance, The CBR Institute for Biomedical
Research, Children's Hospital Boston, Dana-Farber Cancer Institute,
Forsyth Institute, Harvard Pilgrim Health Care, Joslin Diabetes Center,
Judge Baker Children's Center, Massachusetts Eye and Ear Infirmary,
Massachusetts General Hospital, Massachusetts Mental Health Center,
McLean Hospital, Mount Auburn Hospital, Schepens Eye Research Institute,
Spaulding Rehabilitation Hospital, and the VA Boston Healthcare System.
What Is
Homocysteine?
By
American Heart Association
Homocysteine is an amino acid in the blood.
Epidemiological studies have shown that too much homocysteine in the
blood (plasma) is related to a higher risk of coronary heart disease,
stroke and peripheral vascular disease.
Other evidence suggests that homocysteine may have
an effect on atherosclerosis by damaging the inner lining of arteries
and promoting blood clots. However, a direct causal link hasn’t been
established.
Plasma homocysteine levels are strongly influenced
by diet, as well as by genetic factors. The dietary components with the
greatest effects are folic acid and vitamins B6 and B12. Folic acid and
other B vitamins help break down homocysteine in the body. Several
studies have found that higher blood levels of B vitamins are related,
at least partly, to lower concentrations of homocysteine. Other recent
evidence shows that low blood levels of folic acid are linked with a
higher risk of fatal coronary heart disease and stroke.
Several clinical trials are under way to test
whether lowering homocysteine will reduce CHD risk. Recent data show
that the institution of folate fortification of foods has reduced the
average level of homocysteine in the U.S. population.
Recent findings suggest that laboratory testing for
plasma homocysteine levels can improve the assessment of risk. It may be
particularly useful in patients with a personal or family history of
cardiovascular disease, but in whom the well-established risk factors
(smoking, high blood cholesterol, high blood pressure) do not exist.
Although evidence for the benefit of lowering
homocysteine levels is lacking, patients at high risk should be strongly
advised to be sure to get enough folic acid and vitamins B6 and B12 in
their diet.
Foods high in folic acid include green, leafy
vegetables and grain products fortified with folic acid. But this is
just one risk factor. A physician taking any type of nutritional
approach to reducing risk should consider a person's overall risk factor
profile and total diet.
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