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Gut microbe study could lead to better drug, chemo treatments

You are what you eat and so are the thousand or so microbes roaming around your body.

University of Virginia researchers examined the reactions of gut microbes to medication and a patient’s ability to tolerate chemotherapy drugs and found different microbes react to the chemicals in different ways, including some generating toxins.

That, they say, may explain why the same dose may work for one patient and make another sick.

The researchers looked into the gut microbiome, the billions of bacteria and other microorganisms that interact with human cells in the body’s lower intestine. The gut bugs help humans with digestion, metabolism, immune function and brain health.

Diet helps determine which among the microbe minions survive and thrive and which may generate toxins or influence cravings.

The research casts light upon why some drug regimens may prove toxic for some patients while being beneficial to others.

“We understand very little about all of the variables of diet and their outcomes,” said Eyleen O’Rourke, assistant professor of biology and a lead researcher. “The idea was to get a glimpse of how deep this goes and if we can target the diet to improve medical outcomes. We were specifically looking to see if we could modify diet to improvement the outcome of cancer treatments, some of which prove toxic for some patients and not others.”

What they found was, in O’Rourke’s words, “mind-blowingly complex.”

“Different people have different amounts of microbes. There are about 1,500 different types found in humans and most humans have 1,000 or so different types inside,” she explained. “What we found was that the treatment would cause some microbes to develop a toxic response. That could result in a similar response in the host. Just small amounts of a particular amino acid could make the difference.”

In an oversimplified explanation, amino acids are natural chemicals absorbed by the human body from food and used for energy at the cellular level. They’re also absorbed and used by the body’s cadre of microbes. The end products of microbial metabolism accumulate in the circulatory system, fly about the body and trigger a wide variety of responses, some beneficial.

The study used ringworm for a host and studied the reaction to chemicals in a strain of E.coli bacteria that does not cause illness. The data shows that one simple dietary change can alter a microbe’s metabolism and that change can alter how someone responds to a drug.

“What we found was that the chemical may cause a species of microbe to respond by creating toxins and that small amounts can affect toxicity to the body,” O’Rourke said. “That can greatly impact the host.”

All humans have microbes. The microbes are there when you’re born. They grow, change and die as you grow, change and age. If you eat a lot of red meat, you encourage certain species to grow and stunt others. If you eat a vegan diet, the same thing occurs.

If you habitually eat potato chips and French onion chip dip, you can expect a lot of microbes to grow that thrive on that combination. To keep growing, those microbes may release chemicals that create cravings for more chips and dip.

Microbe populations have been proven to impact disease, including promoting diabetes and affecting mental health.

“Part of the completion between the microbes is to control the host to make the host do what is most beneficial for them,” O’Rourke said.

“It’s an incredibly complex ecosystem in your gut,” she said. “One of the aspects of poor nutrition is how it affects the microbes and how the microbes then impact how the human body grows. Once you have a healthy pool of microbes, it’s important to keep it. The change in the health and composition of microbes has a direct effect on the health of the individual.”

The complex interaction opens up a wide variety of interesting possibilities. Changing the microbe populations in a person may help that person change eating habits and other behaviors. It could also help the efficacy of medical treatment.

Part of the research was detailing which genes on microbes were triggered to react to the chemicals. Determining a patient’s microbe mix and their reaction to a medicine could make it easier for the patient to tolerate medication.

“The idea is at some point you could receive a prescription that includes a therapeutic [drug] and a mix of probiotics and diet to improve the response of microbes for the ultimate personalized medicine,” O’Rourke said. “The difference in whether a medication works may not be in the patient’s genetics, but in the genetics of the patient’s bacteria.”

Don’t expect the research to suddenly jump from ringworms and a bacterium to humans and 1,000 microbes. There is more study and more research to be done, O’Rourke said.

“The complexity of the interactions between diet, microbes, therapeutics and the host is humbling,” she said. “We need to learn and study a lot more to find the combinations of probiotics to give with drugs to help manage the effects of treatment, but it’s pretty exciting to think of the possibilities.”


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