Thursday, February 7, 2013

Oh boy, let’s eat some Soy!

Ed Meyertholen, Ph.D., our new KDA President KDA wrote the following report on a recent study. These are Ed’s comments on the research report including the potential viability of the treatment for those of us living with Kennedy's Disease.

Genistein, a natural product derived from soybeans, ameliorates polyglutamine-mediated motor neuron disease.
Research Report from Sobue’s group in Japan

soybeansEssentially, genistein is a substance found in soy and may be able to reduce the symptoms of Kennedy's Disease (KD).  This is due to the property of genistein to disrupt the association of the androgen receptor with another protein known as ARA70.  This allows the cell to remove the AR more efficiently and this, it is argued, may help relieve symptoms of KD (aka SBMA or Spinal Bulbar Muscular Atrophy).

The group did two major sets of experiments, one in cell models and one in a mouse model of KD. 

The results suggest that genistein reduces the symptoms of KD. 

Now, before we all rush out to buy soy products, understand that:
  • Mice were treated with genistein at 6 weeks, two weeks BEFORE symptoms were found to be expressed in untreated KD mice.  They did NOT test genistein in mice that already were showing symptoms.
  • The genestein did not eliminate the symptoms, it did seem to slow down the progression.  Also, it is not known if it would slow down progression after the onset of symptoms – as stated previously, this experiment was not done.  It is very unlikely that it would reverse symptoms that have already occurred.
  • The dose of genestein in the study used was 250 mg/kg/day of mouse.  This would mean a typical 70 kg (155 lb.) man would have to ingest 250*70 = 17500 mg of genistein/day.  From what I could find, soy powder has the highest concentration of genestein of all soy products; it has a concentration of 1 mg/g of soy powder.  Thus, to take in the same amount of genestein as the mice in this experiment, one would have to eat 17500 g of soy power per day – this is about 38 pounds!  You cannot eat enough soy powder daily to get the small change in symptoms seen in the mice.  If one buys the ‘purified’ (it is really just enriched) genistein, it comes in 1g tablets – one would have to take more than 17 every day – and the safe recommended dose is 2 tablets/day.   Genistein has side effects – talk to your doctor!
  • Just because genistein shows positive effects in mice does not mean it will have that effect in humans.
Conclusion: More work needs to be done before getting excited and wasting money on genistein.

1 comment:

  1. I do not think that the dose conversion is correct. The more accepted way is to use body surface area (BSA) normalization. This uses the equation Human Dose (mg/kg) = Animal Dose (mg/kg)x (Animal Km / Human Km). In this case, the Animal Km is 3, and the Human Km is 37. This means that the estimate for a human dose is .081 that of the dose for a mouse. This would mean that a human would only need to ingest ~1.4 of the pills mentioned above, so 1.5 or 2 pills per day.


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