Researchers at Harvard and UCSF, working with human stool samples and laboratory cultures, tested whether gut bacteria might be intercepting the drug before it reached the bloodstream. They focused on a common gut species called Enterococcus faecalis.
That bacterium converted levodopa into dopamine in cultures and patient stool, using an enzyme that carbidopa, the drug given to shield levodopa, fails to block. Dopamine made in the gut cannot cross into the brain, so the conversion effectively wasted the dose before it could treat the tremors and stiffness the drug is meant to control.
The team went on to find a molecule that blocked the bacterial enzyme without harming the bacteria themselves, raising the possibility of an add-on pill that protects each dose of levodopa. The data came from stool samples and mice rather than a clinical trial, so whether blocking the bacteria improves symptoms in actual patients is still being tested.
Read the original study
Maini Rekdal et al., Science, 2019 · doi.org/10.1126/science.aau6323
A microbe was stealing the dose.
Source
- Maini Rekdal, V., Bess, E. N., Bisanz, J. E., Turnbaugh, P. J., & Balskus, E. P. (2019). Discovery and inhibition of an interspecies gut bacterial pathway for Levodopa metabolism. Science, 364(6445), eaau6323. https://doi.org/10.1126/science.aau6323