According to the World Health Organisation, obesity worldwide has nearly doubled since 1980. Every year, this condition kills 3.4 million people, a number that rises every day. Doctors and governments try to combat this epidemic using public awareness campaigns encouraging citizens to stay active and follow a healthy, low-fat diet. While it is not enough, it raises the question what if, like in the story about the Trojan horse, the problem could be tackled from the inside?
Scientists have recently become more aware of the important role the hundreds of trillions of gut microbes play in keeping us healthy. It has been discovered that this vast and diverse bacterial ecosystem, our gut microbiota, work together and collaborate in the regulation of the digestive and immune system.
“The types of bacteria you have in your gut influence your risk for chronic diseases. We wondered if we could manipulate the gut microbiota in a way that would promote health,” explains Sean Davies, assistant professor of pharmacology at Vanderbilt University. In order to answer that question, he led a study with rodents aimed at learning if genetically modified gut bacteria can play a role and produce a positive effect on health (at least, in mice).
Davies’ team carried out a study with rodents in which they tested a strain of safe bacteria, E coli Nissle 1917 (used to treat diarrhoea since it was discovered, a century ago). They modified this strain of probiotic bacteria so that it expressed high amounts of a hormone called NAPE, which is naturally released by the small intestine every time fat is digested, and which sends a message of satiation to the brain. Previous research has shown that animals suffering from obesity do not synthesize enough of this hormone, so they do not feel satiated and continue eating much more than necessary.
Researchers administered these modified bacteria through drinking water to healthy mice, along with giving the rodents a high-fat diet. Those mice gained less weight, ate less and had fewer markers for diabetes than mice in the control group that drank regular water, or water with unmodified bacteria. Moreover, the test group was still healthier than the control group twelve weeks later.
“We still haven’t achieved our ultimate goal, which would be do one treatment and then never have to administer the bacteria again,” says Davies, who was the main author of the study, published recently in the Journal of Clinical Investigation.
Whether applying modified bacteria to humans would achieve similar results is hard to speculate, researchers say. Before moving to studies on humans, regulatory issues must be addressed. Although no harmful effects have been found (and the findings seem to suggest it could be possible to manipulate gut microbiota to treat obesity), rigorous testing should be done to ensure that the modified bacteria do not pose any health risks to humans. Even so, the findings of the researchers from Vanderbilt are very promising.