Latest Research News!

News article: New Technique Determines Which Patients With Homocystinuria Are Most Likely to Respond to Vitamin B6 Treatment Based On Their Genotypes

Now here is something interesting! A recent results breakthrough by scientists which show that what you eat can correct gene mutations! In homocystinuria's case, vitamin B6 has an effect on cystathionine beta synthase gene.

Click here to find out more : http://www.sciencedaily.com/releases/2012/04/120409103251.htm


Reference:
Genetics Society of America (2012, April 9). New technique determines which patients with homocystinuria are most likely to respond to vitamin B6 treatment based on their genotypes. ScienceDaily. Retrieved January 25, 2013, from http://www.sciencedaily.com­ /releases/2012/04/120409103251.htm

Curious about the Stats?

Here are some statistics! 

About one in every 200,000 to one in every 300,000 babies in the United States is born with homocystinuria. 

This condition occurs in all ethnic groups around the world. 

It is found more often in white people from the New England region of the United States. 

It is also more common in people with Irish ancestry. About one in every 50,000 babies in these groups has homocystinuria.  

Can you be treated?

Treatment

A specific cure for patients with homocystinuria is not known. However, special diets and supplements will help people suffering from this disorder to cope.  

Vitamin B6 (pyridoxine) This is an important method. Close to half the people respond to vitamin B6. For children who show improvement from high doses of vitamin B6, this will help prevent mental retardation and behavior problems.

Those who benefit from vitamin B6 will have to take the supplements for the rest of their lives. Those who do not, have to follow a low methionine diet. 

Methionine diet. Patients must ingest food that has low methionine content. Patients must not have cow’s milk, regular formula, meat, fish, cheese, or eggs. Regular flour, dried beans, nuts, and peanut butter also contain methionine and must be avoided or strictly limited.

Medical diet. For children, they are given special medical formula instead of milk. This will help to correct the amount of proteins and nutrient. At the same time, keep the levels of methionine within the safe range. 

Betaine. Most will need to be treated with trimethylglycine (a medication also known as betaine). It is a vitamin-like substance that can be found in grains and be bought in pill form as a supplement. 
Betaine can help lower the amount of homocystine in the blood, and may be especially helpful for children who do not respond to vitamin B6. It may also lessen the risk of blood clots.   

Taking a folic acid supplement and adding cysteine (an amino acid) to the diet are helpful.

Oh no! What problems could arise if untreated?

Unfortunately, children from ages 1-3 could face learning difficulties and delays in growth. Let's take a look at what other problems could crop up.

Eyes

The eyes of children develop severe nearsightedness after one year of age. If this is not treated, lens dislocation may occur, which means the lens of the eye can become loose and move out of place. 

If untreated, it can lead to Glaucoma and even blindness. 

Bones

Adults will grow up to be tall and skinny. They will have thin and long bones and next time develop osteoporosis

Blood vessels

Homocystinuria can lead to blood clots. This can cause problems such as stoke and heart disease.  

How do we know for sure?

Examinations & Tests

Here are tests used to determine if the patient has homocystinuria:

Want to know more?

Further Details!

Amino acid disorders are a group of rare inherited conditions. Amino acids are building blocks that make up protein while enzymes are biological catalysts can process amino acids. Without these enzymes, or defective enzymes, disorders will arise. The condition Homocystinuria is an amino acid disorder that affects the enzyme cystathionine synthetase. 

 Cystathionine b-synthase is an enzyme that converts homocysteine to cystathionine.

It is an autosomal recessive inherited disorder of methionine (amino acid) metabolism. This would mean that the affected child must have had inherited the non-working gene from both parents to be affected seriously. 

An autosomal recessive disorder means 2 copies of the affected/abnormal gene must be present for the trait to occur. 

In this diagram, 'a' is the abnormal gene, and the affected offspring inherited 2 sets of 'a', thus the disorder developed. 







The estimated incidence of Homocystinuria is 1:200,000.

It is usually diagnosed around birth during the first few weeks of life. However, it can be diagnosed a bit later and this depends on the screening and varies among different countries.

 Newborn infants appear healthy. Early symptoms, if present at all, are not obvious.

Biochemistry!

Let's take a look at the biochemistry that goes behind homocystinuria! 

Here we have the overview of the pathway:

Lets break it down and look at the pathways individually.

                    Methionine → S-adenosyl methionine → homocysteine

• Homocysteine is formed from methionine through S-adenosyl methionine 
• It is a sulfur containing amino acid 

                                           ( Cystathionine beta synthase)

                      homocysteine               →                cystathionine → cysteine

• The enzyme Cystathionine beta synthase catalyses the conversion of homocysteine to cystathionine

                                              Cysteine → methionine

• Normal circumstances, cysteine is remethylated to methionine with the help of vit B12 and folate. 
• It is necessary for the methyl group to have N5-methytetrahydrofolate
• N5-methytetrahydrofolate is supplied through vitamin B12 as methyl B12

What is the problem in the pathway that causes the disorder?

• Type 1 Homocystinuria
• Due to deficiency of cysthionine beta-synthase
• Requries pyridoxal phophate as coenzyme

                                                  ( Cystathionine beta synthase)
            Methionine →  homocysteine               →                cystathionine → cysteine

• Cysthionine beta-synthase catalyses the trans-sulphuration pathway during the catabolism of methionine to cysteine.
• When there is deficiency of the enzyme
• The step - homocysteine to cystathionine is blocked
• Leading to accumulation of homocysteine and methionine. 

Testing of blood and urine?

                                     (Urine) Homocystine  ß à homocysteine

When there is high concentration of homocysteine, there will be oxidation and it is converted to homocystine. 

The urine will then contain homocystine.

As such, testings on the blood and urine can determine if the person has homocystinuria.