Re: Interesting CBS mutation rebuttal

[Guest guest]

Thank god someone is finally shooting down Amy Yasko's

claims/sales!

--- Ladyshrink111@... wrote:

>

> CBS Upregulation, Myth or Reality?

> By Mark London

> Please report any links that are not working to

> mrl@...

>

> Upregulation of the CBS enzyme via two genetic

> polymorphisms has been

> theorized to be possibly detrimental for some

> conditions, based on the

> work by Dr. Amy Yasko in autism. These two

> polymorphisms were studied

> in 2000, and in that study, the Post Methionine Load

> (PML) test was

> used to determine the effects of different CBS

> polymorphism genotypes.

> That loading test can detect subtle defects in the

> transsulfuration

> pathway, which is the metabolic process that is

> affected by the CBS

> enzyme. The polymorphism with the greatest effect,

> as shown by the

> PML test, was found to be 699CàT (Y233Y). People

> with the TT (+/+)

> genotype of that polymorphism, and to a lesser

> degree CT (-/+),

> produce lower levels of homocysteine levels in

> response to the PML

> test, when compared with the CC (-/-) genotype.

> Lower homocysteine

> levels from that test infers greater CBS activity.

> By the way, none

> of these genotypes are rare. About 40% of the

> population has CC, 40%

> has CT, and 20% have TT. Thus, all the genotypes of

> this polymorphism

> are quite common. The study also looked at the CBS

> polymorphism

> 1080CàT (A360A), but that was found to have less a

> significant effect.

> The TT genotype of that polymorphism only showed a

> significant

> decrease in homocysteine in the PML test, if 2 other

> polymorphisms

> were also excluded. Thus, 699TT seems to have the

> most significant

> affect on CBS activity.

>

> On the other hand, a similar study in 2003 on these

> polymoprhisms did

> not show a significant difference in homocysteine

> levels due to the

> different genotypes, in response to the PML test.

> One difference with

> this new study is that it was done on a different

> ethnic group, which

> is sometimes a factor in genetic studies. Also,

> while the mean age

> was the same in both studies, this new study had a

> much smaller range

> of ages, and did not include anyone younger than

> about 40 years old.

> This might be a factor, since CBS activity is known

> to decrease as a

> person gets older.

>

> Even more interestingly, is that a study on pregnant

> women in 2003

> surprisingly showed an increase in basal

> homocysteine levels from the

> TT genotype, the same genotype that had the lowest

> homocysteine level

> in the 2000 study. This study did not give any

> possible reason for

> this result.

>

> In any event, even in studies which showed increased

> CBS activity

> effects from the TT genotype, such as the one from

> 2000, and a more

> recent one from 2007, only small changes in

> homocysteine levels were

> observed. For example, in the latest study, which

> used a very large

> population of 10000, the basal homocysteine levels

> only differed by

> 2.7%, between the TT genotype, which has the highest

> CBS activity,

> compared to the CC genotype, which has the lowest

> CBS activity.

>

> This minor decrease in homocysteine levels is in

> contrast to that

> which is seen in Down's syndrome, where CBS

> upregulation is definitely

> known to occur. In one study on Down's syndrome

> children, basal

> homocysteine levels were reduced by 25%, and plasma

> levels of

> cystathionine, which is produced by the

> transsulfuration pathway, was

> increased by 3.8 fold.

>

> On the other hand, a later study on Down's syndrome

> adults did not

> show decreased homocysteine levels. This surprising

> result was

> theorized to be due to the fact that adults have a

> much lower

> requirement for folic acid. When folic acid was

> given to the Down's

> syndrome children, their homocysteine levels rose

> significantly.

>

> Thus, age may become a factor when considering the

> effects from CBS

> upregulation. Dr. Yasko claims that these CBS

> polymorphisms can have

> significant effects for autistic children. Even if

> that claim is

> true, it is possible that it only has relevancy for

> children. Also,

> the claim may have no relevancy for other

> conditions, due to the fact

> that autism has many other metabolic disturbances

> that are not found

> in other conditions.

>

> It's also been claimed that increased urinary

> taurine and ammonia can

> help diagnose CBS upregulation. While it's true that

> CBS upregulation

> can cause increased taurine and ammonia production,

> there's no

> evidence that this increased production can be

> detected by measuring

> their urinary levels.

>

> Urinary taurine is an unreliable test for CBS

> upregulation, due to

> fact that urinary taurine is dependent on many

> factors, including age,

> genetics, gender, renal function, clinical

> conditions, and especially

> dietary intake. Thus, even though a study on Down's

> syndrome found a

> significant increase in plasma taurine, another

> study on Down's

> syndrome found that urinary taurine levels were

> normal. Urinary

> inorganic sulfur was also not significantly

> different, which doesn't

> confirm Dr. Yasko's prediction of excess sulfur

> byproducts from CBS

> upregulation .On the other hand, urinary thiosulfate

> was

> significantly increased. Thiosulfate is a metabolite

> of hydrogen

> sulfide, and CBS is one of only three enzymes known

> to be able to

> produce hydrogen sulfide. Thus, significant CBS

> upregulation was

> likely occurring, even though urinary taurine and

> sulfur levels were

> normal.

>

> Urinary ammonia is an even less reliable method for

> testing for CBS

> upregulation. This is because most of the ammonia

> (NH4+) in urine is

> produced by the kidneys for ph regulation. The

> ammonia that is

> produced elsewhere in the body, is usually

> detoxified by being

> converted to urea, which is then excreted. This

> process mainly occurs

> in the liver, and the liver is quite capable of

> handling the large

> amount of ammonia that is produced in the body,

> which occurs due to

> the metabolization of amino acids. The liver has to

> be able to do

> this, because the nervous system can only tolerate

> very low levels of

> ammonia. Excess ammonia, i.e., hyperammonia, only

> usually occurs

> either when liver functioning has been greatly

> reduced, or where a

> genetic defect in the urea cycle exists. Only by

> testing serum

> ammonia, can such a condition be diagnosed.

>

> In conclusion, the medical literature states that

> these CBS

> polymorphisms have only very mild effects on CBS

> activity. And even

> if there is significant CBS upregulation, there is

> no evidence that it

> can significantly cause any negative effects, such

> as overproduction

> of ammonia. Furthermore, the medical literature

> doesn't

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[Guest guest]

>

>

> CBS Upregulation, Myth or Reality?

> By Mark London

Thanks, , for posting this.

I do believe Dr. Yasko is genuinely trying to help sick people get better.

I also believe most of the stated reasons for her protocol are unrelated to

reality, and most

of the conclusions in her books are not correct.

However there is something that the criminal quacks in charge of modern medicine

abuse,

which is the fact that it is easier to do the intellectual equivalent of

vomiting all over the

internet (or into a book or journal paper), making all kinds of wild claims,

than it is to

carefully go through all these claims, analyze them fully and in detail as the

claimants

have not, and cogently explain why they are not correct.

Thus not only are Dr. Yasko's claims seldom rebutted, since she unfortunately is

following

the dominant style in medical writing, but also she has a not unreasonable

reason they

may not all be correct - she has to rely on this very same literature that I am

calling a pool

of intellectual vomit to go fish up real information to try to figure out what

is really

happening.

Understandably this is a trying task that it is hard for anyone to get right.

Andy