What makes some people thin and other full-figured? Besides diet and genetics, the community of microbes that lives inside of us may be partly responsible. New research on twins suggests that lean people harbor bacteria than their obese counterparts do not. And, given the chance, these bacteria may be able to prevent weight gain. But do not dig your skinny jeans closet just yet. So far the work has been done only in mice. Moreover, bacterial takeover requires a healthy, high fiber diet to work, illustrating the complex relationship between diet, microbes, metabolism and health.
Our intestines are home at least 400 species of bacteria, and the evidence is building that the balance of microbes in our internal ecosystem has a significant impact on health, including brain function and the risk of Cancer. A study last year showed that the transfer of intestinal bacteria between humans reduces insulin resistance, which is related to obesity.
To explore how microbes differ between obese and lean people, researchers at Washington University in St. Louis took the intestinal bacteria of four pairs of identical and fraternal twins; a brother in each pair was thin and the other obese. Then they transplanted the microbes in mice that had no gut microbes of their own. Mice that got the skinny twin microbes remained thin, the researchers report today Science. Those who got the obese twins microbes increased their body fat by 10% on average, though they ate the same amount of food.
What would happen if these two sets of microbes are mixed in the gut, the researchers wondered. Led by microbiologist Jeffrey Gordon and graduate student Vanessa Ridaura, the team took advantage of one of the least endearing rodent habits: They eat shit the other. After letting this happen, the researchers found that the lean twin microbes appeared to be particularly good to take hold in the ecosystems of the mouse intestine that began with microbes associated with obesity. And after moved bacteria, the mice did not gain weight. The most invasive species of microbes from animals were thin in the Bacteroidetes group, which has previously been associated with thinness in mice and humans. Obese mice seem unoccupied niches that Bacteroidetes could easily move in.
To understand what the gut bacteria could do, the researchers studied the bacterial genes that were active in both types of mice. The heavier mice had higher levels of proteins involved in stress responses and detoxification; lean mice expressed more genes involved in the breakdown of dietary fiber.
food, it turns out, was the key to the impressive properties of lean twins microbes. All mice in the first series of experiments were eating chow that was high in fiber and low in fat. The researchers then developed a mouse pellet form an unhealthy human diet, high in fat and low in fiber, and housed mice slim and heavy together again. They found that, with this scheme, the microbes associated with leanness not colonize the intestines of cage mates.
This work was carefully done and corresponds to previous findings, including the idea that Bacteroides can protect against weight gain, says Alan Walker, a microbiologist from the gut the Wellcome Trust Sanger Institute in the UK who was not involved in the study. What is new here, he said, is that researchers have begun to address the question of how this protection might work :. Species that are responsible, what genes they use, and what diet they need
"This study is important step towards ultimately answer these questions," says microbiologist Peter Turnbaugh from Harvard University. an important result of this work, they agree, is that it puts in place a way to test the effects of microbial therapies on human intestinal bacteria (even if insects live in a mouse) . the authors suggest that the next logical step is to use animals to measure the effects of foods or ingredients ecosystem of the gut in particular.
the mouse experiments also provide a way to test fecal transplants, which can cure a potentially fatal intestinal infection in humans and show a potential to treat other conditions such as inflammatory bowel disease and obesity. There is a danger inherent in this approach: Transfer of human feces in the colon of a patient at risk of pathogen transmission as well. Walker and the authors note that "the next generation of probiotic" good test compound known beneficial microbes come in pill form or another treatment could take the place of fresh faeces, and this mouse system provides a way to identify the most effective bacteria, diseases of these bacteria can be treated, and if a special diet is required.
"There is a significant way to go before you can translate these findings to humans," warns Walker. A probiotic weight loss is not just a next step, the researchers discovered when they isolated 39 of beneficial Bacteroidetes species. The mixture was unable to cause the same effects as shit mouse, maybe because Bacteroidetes not acting alone and microbial players must be identified.
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