Review: 'Through the Shadowlands’ describes Julie Rehmeyer's ME/CFS Odyssey
I should note at the outset that this review is based on an audio version of the galleys and the epilogue from the finished work. Julie Rehmeyer sent me the final version as a PDF, but for some reason my text to voice software (Kurzweil) had issues with it. I understand that it is...
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Question about detox genes which are homozygous (+/+)

Discussion in 'Genetic Testing and SNPs' started by jason30, Mar 1, 2018.

  1. jason30

    jason30 Senior Member

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    Hi,

    I have the following homozygous mutations (+/+):
    They are all connected to cytochrome p450 phase 1.
    I am trying to learn more about it, so any information about these are welcome.

    I wonder, for example CYP1B1, do I have an increased or decreased activity of CYP1B1 when you have +/+ homozygous?
    https://www.selfdecode.com/gene/CYP1b1/#experiments_decrease

    Thanks.
     
  2. alicec

    alicec Senior Member

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    There are many CYP enzymes with varying roles in phase I detox and other activities such as synthesis and catabolism of steroids. They are divided into families and subfamilies with about a dozen members of families 1,2,and 3 being responsible for drug metabolism.

    Here is a review of CYP enzymes and drug metabolism. It is fairly heavy going but you can just look at the figures and tables. Fig 1 shows the contributions of the differents CYP enzymes to drug metabolism and Table 1 lists CYP genetic variants known to affect drug metabolism.

    You can compare your SNPs with this list.

    This entirely depends on the SNPs. They may have no effect at all - you need to look at the research for your particular SNPs and you need to understand that the presence of a variant often means nothing whatsoever.

    The Self-decode entry you link is mainly talking about associations of SNPs and various conditions. Association doesn't mean causation and many of these SNP association studies are not very reliable. It depends how big the study was and how robust the statistics.

    Here is the OMIM entry for CYP1B1. The only known disease caused by CYP1B1 variants is early onset glaucoma and the only robust disease association is with breast cancer.

    ETA Variation in activity of an enzyme such as described by Self-decode isn't only attributable to SNPs in the gene for the enzyme. Changes in other genes or non-genetic factors can also be important.
     
    Last edited: Mar 1, 2018
  3. jason30

    jason30 Senior Member

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    Sorry for the late respons, a virus kept me busy for 3 weeks!

    Thank you for thinking along and the info @alicec , I've become a little wiser. :)

    I see often that they talk about 'genetically impaired CYP2B6'.
    When does someone have an impaired CYP2B6? Is that equal to a homozygous mutation (+/+)?

    Thanks again.
     
  4. alicec

    alicec Senior Member

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    A genetically impaired CYP2B6 is the result of a mutation in DNA that affects the structure or production of the protein product so that little or no enzyme activity is present.

    Table I in the paper I linked above list DNA changes in CYP2B6 known to result in a defective enzyme. OMIM.org would also have an entry which you can find by just inserting CYP2B6 in the search box.

    Not necessarily, it entirely depends on which +/+ SNP.

    As I have already said, the presence of a variant often means nothing at all. A few may have an effect. You need to look at research or research summaries such as the ones I have linked to find out which variants actually alter the activity of the enzyme and to what extent.
     

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