They found that their mice without the TLR5 gene—even when put on restricted diets—still showed insulin resistance, suggesting that insulin resistance might lead to obesity rather than the other way around. But if these mice were allowed to eat as they pleased, they ate 10 percent more than their peers and, by 20 weeks old, had body mass indexes that were 20 percent higher. Many researchers and public health officials have blamed the availability (and content) of contemporary foods, increasingly sedentary lifestyles and human genetics for more metabolic syndrome cases. But the mouse study suggests that there might be more to the picture. "The tendency to overeat may be underlain by changes that are more likely physiological than genetic," Gewirtz says.
Gewirtz and others propose that inflammation—in conjunction with changes in the gut microbiome—might be driving the cycle. Inflammation can change the character of the gut microbes, in some cases allowing more calories to be extracted from food. But, Gewirtz says, "We do not know which is coming first" if inflammation is changing the microbiota or vice versa. It is likely, he notes, that whatever kicks off the process, it will start a sort of feedback loop, where one will increase accelerates the other.
How much of their findings in mice are likely to translate to humans? The stomach bacteria in mice are not found in people. But Gewirtz and his team noted that analogous species live in the human stomach. "We think it's very plausible" that the findings will carry over to humans, especially because they "fit with a lot of the ideas" currently circulating in the research community about insulin resistance and inflammation, Gewirtz says. His group has already started a new investigation comparing the human genes and microbial profiles of people with metabolic syndrome to healthy controls to see if some of the same correlations in mice appear in humans.
Next genetic steps
Although a fuller grasp of microbial genetics promises to boost wellness even further, plenty of big unknowns remain. Scientists are still unsure just how and when these communities of microbes establish themselves in each person's gut. "Everyone is born sterile," Gewirtz says, noting that colonization starts during birth but that they do not know when it reaches relative stability. Regardless of timing, it means that, "the environment is a big, big factor in determining what someone's microbiota will be like," he adds.
If gut microbiota do play a large role in diseases such as obesity and metabolic syndrome, then a recent past change in these communities might help to explain the expansion of patients—and waistlines—in developed countries. "The genetics of humans have not changed appreciably in the last several hundred years," Gewirtz says. "But several changes in the environment have made it so that the gut microbiota is likely considerably different than it was 50 years ago."
Wang and his colleagues are already attempting to track the composition of human gut microbiota back in time to see if this might be the case. But they have their sights set on even bigger collections of genetic data. "Our dream is to build a library" of reference genomes, Wang notes. He hopes to have 10,000 genomes for bacteria within two years. And, he estimated, as soon as more definitive data about these gut genetics emerge, microbial-targeted therapeutics will likely be quick to follow.
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12 Comments
Add CommentI do think this kind of research may be profitable in terms of theraphy and also in that vitality�s stuffs.There is no way out of this issue:We�d better not take for granted the microorganisms,just because they are harmful to us,but these is the principle of science:We use all the ways in order to rest just one,which is likely the suitable one.
Reply | Report Abuse | Link to thisJust out of curiousity, have their been any studys linking this to auto immune disorders?(fibromyalgia or dercums)
Reply | Report Abuse | Link to thisIt is important to quote that we, as human beings, do not live alone in the earth surface and maybe, cannot exist and live without the microorganisms. They are here million of year before us. We need to recognize them and learn how to take advantage of this rich symbiosis. Unfortunately a big part of the health professionals face them as pure enemies and try to avoid any type of closer contact with them. The current exaggerate domestic cleanness and disinfection, use and abuse of antibiotics and anti-inflammatory medicines, turns our children and adults extremely reactive for simple infections that should be solved by the own organism in the childhood.
Reply | Report Abuse | Link to thisIt is important to quote that we, as human beings, do not live alone in the earth surface and maybe, cannot even exist or live without the microorganisms. They are here million of year before us. We need to identify them and learn how to take advantage of this rich symbiosis. Unfortunately a big part of the health professionals face them as pure enemies and try to avoid any type of closer contact with them. The current exaggerate domestic cleanness and disinfection, use and abuse of antibiotics and anti-inflammatory medicines, turns our children and adults extremely susceptible and reactive for simple infections that should be “solved” or cured naturally by the own organism in the childhood.
Reply | Report Abuse | Link to thisI believe we are the first full generation to use antibiotics. What role has this had in destroying our intestinal flora and promoting inflammation? Can probiotics restore some of the gut bacterial populations? Also, with the predominance of c-sections, has this (instead of vaginal delivery) resulted in gut bacterial populations that are deficient? Conversely, is you mother has a gut population that promotes insulin resistance/diabetes/inflammation, could this be passed onto the baby? Very interesting field of study.
Reply | Report Abuse | Link to thisI too am very intrigued and excited by this field of study. There are so many factors that could plausibly effect change in the volume and diversity of the different bacterial species that live wilthin us. I would not be surprised in the least to see successful therapies blosom out of these studies. Very cool stuff.
Reply | Report Abuse | Link to thisRegarding mhr's reply, I also had the thought of the baby's first "meal" and those thereafter from the mother arriving to this sterile environment according to Gerwirtz. So if these are the 1st bacterial of the newborn, then the mother's milk needs to be analyzed for these organisms or else how would these bacteria enter this newborn's intestines if he is born with a sterile field. Or is the bacterial, like vaginal fungus, introduced into the baby's sterile environment when the child comes in contact with the vaginal walls during delivery?
Reply | Report Abuse | Link to thisWonderful findings in this article. cgeorge
Interesting - this isn't too far away from the biomedical research on autism! Maybe this kind of research could start to wake up those who scoff at the gut and metabolic theories contributing to autism?
Reply | Report Abuse | Link to thisGives deeper meaning to the expression "you are what you eat".
Reply | Report Abuse | Link to thisBreastfed babies are less likely to be obese. Bottles and bottle nipples are sterilized as standard procedure (and some are now disposable). Would bacteria from the mother's breast skin be enough?
Reply | Report Abuse | Link to thisThis is an excellent development as it demonstrates that all living things on this planet are in one way another 'connected'. The nature of the connections is as diverse as life itself. "We are not alone" is a cute saying but is it is significant when referring to life right here on earth.
Reply | Report Abuse | Link to thisTo the authors: Do you know what the relationship is between the number of genes (3.3 million) and the number of species? Also, does anyone know how the type of proportion of microbial species has changed in the last 50 years? Does taking probiotic supplements increase the number of "good" species?
Reply | Report Abuse | Link to thisYou've done fascinating research and I look forward to hearing more.