Homocysteine usually breaks down into other substances in the body, but high levels can be due to vitamin B6, B12 or folate deficiency, and rare inherited diseases like homocystinuria. These conditions raise your risk of heart disease, blood clots and other health problems.
High levels of homocysteine can be corrected by consuming more foods that contain vitamins B6, B12 and folate. Your doctor may also prescribe daily vitamin supplements.
Causes
Hyperhomocysteinemia is a condition in which high levels of the amino acid homocystine are found in the blood. It may result from a deficiency of folate, vitamin B6, or vitamin B12 in the diet or it can occur as a result of certain conditions. High homocysteine levels are associated with an increased risk of VTE and early atherosclerosis. It can also interfere with the vasodilatory and antithrombotic effects of nitric oxide.
Normally, when you consume food, homocystine is broken down into other substances and only small amounts of the substance remain in your body. However, some conditions interfere with this process and leave you with higher-than-normal levels of the amino acid. These include deficiencies in the nutrients folate, B6, or B12; rare inherited diseases such as homocystinuria (a condition where your body cannot break down methionine); and an overactive enzyme in your liver called cystathionine b-synthase.
Elevated homocysteine is a known risk factor for arterial and venous thrombosis through its prothrombotic and atherosclerotic effects on the endothelium, inhibition of nitric oxide synthesis, proliferation of smooth muscle cells and platelet activation [42-47].
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In addition, the condition has been linked to vascular damage through an increased rate of advanced glycation end products in the blood, which can damage the lining of your arteries and lead to clots. Additionally, high homocysteine has been linked to poor bone health and hip fractures in older adults owing to the fact that the amino acid is a weak inhibitor of bone resorption.
High homocysteine levels can be caused by an underlying disease or by poor dietary habits, and both of these can be treated with a combination of supplements and lifestyle changes. Despite the fact that these therapies can reduce plasma levels of homocystine, large clinical trials have failed to demonstrate that normalizing homocysteine level prevents primary venous or arterial thrombotic events or decreases the frequency of recurrent venous or cardiovascular events in the general population. This is because the risk for these conditions is related to MTHFR gene variants and not elevated homocysteine itself.
Symptoms
Homocysteine is an amino acid that the body uses to make proteins. Most people have low levels of homocysteine, but some have high levels. When levels are too high, it can increase the risk of certain diseases.
Elevated homocysteine can cause damage to blood vessels and lead to atherosclerosis, which is the buildup of fatty deposits on the artery walls that narrow the arteries. It can also cause blood clots. Homocysteine can interfere with the body’s ability to use nitric oxide, which is an important vasodilator and antithrombotic substance.
High homocysteine may also indicate a vitamin deficiency, such as a deficiency of vitamins B6, B12, and folic acid. Deficiencies in these vitamins can be corrected by making dietary changes or taking supplements.
Hyperhomocysteinemia is also associated with a higher risk of dementia in older adults. It is believed that high homocysteine can lead to memory problems by damaging the brain.
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A blood test called a plasma homocysteine level is used to measure how much of this amino acid is in your bloodstream. Your doctor will take a sample of your blood and send it to a lab for testing. This test is usually quick and painless. The results are usually available within 24 hours. You should not drink any alcohol or take any medications for a few hours before having this test.
The lab will use a special machine to measure your plasma homocysteine level. The machine will look for substances called cystathionines, which are the breakdown products of homocysteine. The machine will also measure the levels of other amino acids and nutrients, such as tyrosine, thyroxine, methyltyrosine, and vitamin B6.
Your doctor will use the results of this test to determine if you have hyperhomocysteinemia. Your doctor may recommend that you eat more foods rich in vitamin B6 and folic acid, such as orange juice, green vegetables, and beans. Your doctor may also prescribe daily vitamin supplements to help keep your homocysteine level in check. Some studies have shown that lowering your homocysteine levels can lower your risk of heart attack or stroke in patients with peripheral artery disease (PAD). However, no large clinical outcome randomized controlled trials have been conducted to determine the benefit of this treatment.
Diagnosis
A genetic disorder called homocystinuria (HCU) causes high levels of homocysteine and its metabolites in the blood and urine. Homocystinuria is caused by a mutation in the gene that controls how the body breaks down the amino acid methionine. Babies with HCU are born with high levels of methionine in their bodies, and their body can’t break it down. Usually, methionine and its metabolites are quickly broken down and eliminated from the body through urine. Children with HCU need regular blood tests to monitor their levels of methionine and its metabolites, and they need a special diet and medicine called betaine that helps clear the excess.
People with a disease like Systemic Lupus Erythematosus, or SLE, often have higher levels of homocysteine than those without the disease. Studies suggest that increased levels of homocysteine may increase a person’s risk for heart attack, stroke, or other diseases.
The level of homocysteine in the blood is usually measured by a simple blood test. The normal level is less than 15 micromoles per liter of blood. If the level is higher, it is likely that a person has a deficiency of vitamin B6, vitamin B12, or folate. These vitamins are needed to help break down homocysteine.
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Homocysteine levels are also often tested before a kidney transplant or organ donation. People who have a transplant may be more likely to have higher levels of homocysteine, as the medication used during the surgery can raise the level.
High levels of homocysteine have also been linked to various health problems, including cardiovascular disease, osteoporosis, rheumatoid arthritis, and depression. It’s not clear whether lowering levels of homocysteine will reduce a person’s risk for these conditions, but researchers are continuing to study this issue. High levels of homocysteine are also associated with the condition called lupus, and a condition called fibromyalgia. In lupus, high homocysteine levels can lead to more serious symptoms. Taking vitamin B6, vitamin B12, and folate can help lower homocysteine. However, the best way to lower homocysteine is to change your diet to include more foods that contain these vitamins.
Treatment
A deficiency of vitamin B6, vitamin B12, and/or folate can cause hyperhomocysteinemia. A blood test can be used to measure levels of these vitamins and determine if they are adequate or deficient. A person can increase the amount of these vitamins by making changes to the diet or taking supplements. A person who is pregnant or capable of becoming pregnant should ensure that they get sufficient amounts of folate in their diet to prevent a deficiency.
Homocysteine is produced by an abnormal breakdown of methionine in the metabolism process. The resulting metabolites accumulate in blood and urine. Usually, these metabolites are not found in appreciable quantities. Hyperhomocysteinemia may be caused by a defect in the transsulfuration or methylation pathways of methionine (homocystinuria) or by a recessively inherited mutation of the enzyme methylenetetrahydrofolate reductase (MTHFR). A mild elevation of homocysteine may also occur without a genetic cause.
Elevated homocysteine concentrations are independently associated with cardiovascular disease, such as coronary artery disease, stroke, and peripheral vascular disease. It is hypothesized that elevated homocysteine interferes with the normal endothelial function by downregulating eNOS, which leads to decreased production of nitric oxide and decreased vasodilation. It is also believed that high homocysteine levels may promote atherosclerosis by increasing plaque formation and the production of reactive oxygen species.
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Hyperhomocysteinemia is also independently associated with thromboembolism. Multiple retrospective and prospective clinical trials have shown that patients with hyperhomocysteinemia have twice the risk of venous thromboembolism compared to those with normohomocysteinemia. The heightened thromboembolic risk appears to be related specifically to high plasma homocysteine levels and not to other factors such as the presence of a MTHFR gene variant or coagulation factor deficiencies.
Multiple large clinical trials have failed to show that treatment with folic acid, vitamin B6, and vitamin B12 reduces the rate of recurrent venous or arterial thrombosis or decreases the frequency of subsequent events after VTE. However, a number of smaller clinical trials have shown that patients with hyperhomocysteinemia can benefit from therapy with these supplements. These trials have shown that supplementation with folic acid, vitamin B6, B12, and betaine can lower high homocysteine to a level below the thromboembotic threshold.
