The first time a young Vayu Maini Rekdal manipulated microbes, he made a decent sourdough bread, even if he gave little thought to the crucial chemical reactions involved.
More crucial, he would later learn, is the role microbes play in helping our bodies break down foods so they can absorb the nutrients. Since we cannot digest certain substances — all-important fiber, for example — microbes step up to perform chemistry no human can.
“But this kind of microbial metabolism can also be detrimental,” said Maini Rekdal, a Graduate School of Arts and Sciences Ph.D. student in the lab of Professor Emily Balskus, and first author on their new study published June 14 in Science.
According to Maini Rekdal, gut microbes can chew up medications with often hazardous side effects. “Maybe the drug is not going to reach its target in the body; maybe it’s going to be toxic all of a sudden; maybe it’s going to be less helpful,” he said.
In their study, Balskus, Maini Rekdal, and their collaborators at the University of California, San Francisco, describe one of the first concrete examples of how the microbiome can interfere with a drug’s intended path through the body. Focusing on levodopa (L-dopa), the primary treatment for Parkinson’s disease, they identified which bacteria out of the trillions of species is responsible for degrading the drug, and how to stop it.
Parkinson’s disease globally affects more than 1 percent of those age 60 and above. The neurological disorder attacks nerve cells in the brain that produce dopamine, without which the body can suffer tremors, muscle rigidity, and problems with balance and coordination. The cause of the disease is unknown.
The primary treatment for Parkinson’s symptoms is L-dopa, a drug taken orally that delivers dopamine to the brain. To do so, it must first cross the blood-brain barrier. For most patients, only about 1 to 5 percent of the drug actually reaches the brain.