Arquivo da tag: Flora intestinal

Gut feeling: Research examines link between stomach bacteria, PTSD (Science Daily)

April 25, 2016
Office of Naval Research
Could bacteria in your gut be used to cure or prevent neurological conditions such as post-traumatic stress disorder (PTSD), anxiety or even depression? Two researchers think that’s a strong possibility.

Dr. John Bienenstock (left) and Dr. Paul Forsythe in their lab. The researchers are studying whether bacteria in the gut can be used to cure or prevent neurological conditions such as post-traumatic stress disorder (PTSD), anxiety or depression. Credit: Photo courtesy of Dr. John Bienenstock and Dr. Paul Forsythe

Could bacteria in your gut be used to cure or prevent neurological conditions such as post-traumatic stress disorder (PTSD), anxiety or even depression? Two researchers sponsored by the Office of Naval Research (ONR) think that’s a strong possibility.

Dr. John Bienenstock and Dr. Paul Forsythe–who work in The Brain-Body Institute at McMaster University in Ontario, Canada–are investigating intestinal bacteria and their effect on the human brain and mood.

“This is extremely important work for U.S. warfighters because it suggests that gut microbes play a strong role in the body’s response to stressful situations, as well as in who might be susceptible to conditions like PTSD,” said Dr. Linda Chrisey, a program officer in ONR’s Warfighter Performance Department, which sponsors the research.

The trillions of microbes in the intestinal tract, collectively known as the gut microbiome, profoundly impact human biology–digesting food, regulating the immune system and even transmitting signals to the brain that alter mood and behavior. ONR is supporting research that’s anticipated to increase warfighters’ mental and physical resilience in situations involving dietary changes, sleep loss or disrupted circadian rhythms from shifting time zones or living in submarines.

Through research on laboratory mice, Bienenstock and Forsythe have shown that gut bacteria seriously affect mood and demeanor. They also were able to control the moods of anxious mice by feeding them healthy microbes from fecal material collected from calm mice.

Bienenstock and Forsythe used a “social defeat” scenario in which smaller mice were exposed to larger, more aggressive ones for a couple of minutes daily for 10 consecutive days. The smaller mice showed signs of heightened anxiety and stress–nervous shaking, diminished appetite and less social interaction with other mice. The researchers then collected fecal samples from the stressed mice and compared them to those from calm mice.

“What we found was an imbalance in the gut microbiota of the stressed mice,” said Forsythe. “There was less diversity in the types of bacteria present. The gut and bowels are a very complex ecology. The less diversity, the greater disruption to the body.”

Bienenstock and Forsythe then fed the stressed mice the same probiotics (live bacteria) found in the calm mice and examined the new fecal samples. Through magnetic resonance spectroscopy (MRS), a non-invasive analytical technique using powerful MRI technology, they also studied changes in brain chemistry.

“Not only did the behavior of the mice improve dramatically with the probiotic treatment,” said Bienenstock, “but it continued to get better for several weeks afterward. Also, the MRS technology enabled us to see certain chemical biomarkers in the brain when the mice were stressed and when they were taking the probiotics.”

Both researchers said stress biomarkers could potentially indicate if someone is suffering from PTSD or risks developing it, allowing for treatment or prevention with probiotics and antibiotics.

Later this year, Bienenstock and Forsythe will perform experiments involving fecal transplants from calm mice to stressed mice. They also hope to secure funding to conduct clinical trials to administer probiotics to human volunteers and use MRS to monitor brain reactions to different stress levels.

Gut microbiology is part of ONR’s program in warfighter performance. ONR also is looking at the use of synthetic biology to enhance the gut microbiome. Synthetic biology creates or re-engineers microbes or other organisms to perform specific tasks like improving health and physical performance. The field was identified as a top ONR priority because of its potential far-ranging impact on warfighter performance and fleet capabilities.

Journal Reference:

  1. S. Leclercq, P. Forsythe, J. Bienenstock. Posttraumatic Stress Disorder: Does the Gut Microbiome Hold the Key? The Canadian Journal of Psychiatry, 2016; 61 (4): 204 DOI: 10.1177/0706743716635535

Diet affects males’ and females’ gut microbes differently (Science Daily)

Date: July 29, 2014

Source: University of Texas at Austin

Summary: The microbes living in the guts of males and females react differently to diet, even when the diets are identical, according to a new study. These results suggest that therapies designed to improve human health and treat diseases through nutrition might need to be tailored for each sex.

Illustration by Marianna Grenadier and Jenna Luecke. Credit: Image courtesy of University of Texas at Austin

The microbes living in the guts of males and females react differently to diet, even when the diets are identical, according to a study by scientists from The University of Texas at Austin and six other institutions published this week in the journal Nature Communications. These results suggest that therapies designed to improve human health and treat diseases through nutrition might need to be tailored for each sex.

The researchers studied the gut microbes in two species of fish and in mice, and also conducted an in-depth analysis of data that other researchers collected on humans. They found that in fish and humans diet affected the microbiota of males and females differently. In some cases, different species of microbes would dominate, while in others, the diversity of bacteria would be higher in one sex than the other.

These results suggest that any therapies designed to improve human health through diet should take into account whether the patient is male or female.

Only in recent years has science begun to completely appreciate the importance of the human microbiome, which consists of all the bacteria that live in and on people’s bodies. There are hundreds or even thousands of species of microbes in the human digestive system alone, each varying in abundance.

Genetics and diet can affect the variety and number of these microbes in the human gut, which can in turn have a profound influence on human health. Obesity, diabetes, and inflammatory bowel disease have all been linked to low diversity of bacteria in the human gut.

One concept for treating such diseases is to manipulate the microbes within a person’s gut through diet. The idea is gaining in popularity because dietary changes would make for a relatively cheap and simple treatment.

Much has to be learned about which species, or combination of microbial species, is best for human health. In order to accomplish this, research has to illuminate how these microbes react to various combinations of diet, genetics and environment. Unfortunately, to date most such studies only examine one factor at a time and do not take into account how these variables interact.

“Our study asks not just how diet influences the microbiome, but it splits the hosts into males and females and asks, do males show the same diet effects as females?” said Daniel Bolnick, professor in The University of Texas at Austin’s College of Natural Sciences and lead author of the study.

While Bolnick’s results identify that there is a significant difference in the gut microbiota for males and females, the dietary data used in the analysis are organized in complex clusters of disparate factors and do not easily translate into specific diet tips, such as eating more vegetables or less meat.

“To guide people’s behavior, we need to know what microbes are desirable for people,” said Bolnick. “Diet and sex do interact to influence the microbes, but we don’t yet know what a desirable target for microbes is. Now we can go in with eyes open when we work on therapies for gut microbe problems, as many involve dietary changes. We can walk into those studies looking for something we weren’t aware of before. All along we treated diet as if it works the same for men and women. Now we’ll be approaching studies of therapies in a different way.”

Why men and women would react differently to changes in diet is unclear, but there are a couple of possibilities. The hormones associated with each sex could potentially influence gut microbes, favoring one strain over another. Also, the sexes often differ in how their immune systems function, which could affect which microbes live and die in the microbiome.

One notable exception in Bolnick’s results was in the mice. Although there was a tiny difference between male and female mice, for the most part the microbiota of each sex reacted to diet in the same manner. Because most dietary studies are conducted on mice, this result could have a huge effect on such research, and it raises questions about how well studies of gut microbes in lab mice can be generalized to other species, particularly humans.

“This means that most of the research that’s being done on lab mice — we need to treat that with kid gloves,” said Bolnick.

Bolnick’s co-authors are Lisa Snowberg (UT Austin); Philipp Hirsch (University of Basel and Uppsala University); Christian Lauber and Rob Knight (University of Colorado, Boulder); Elin Org, Brian Parks and Aldons Lusis (University of California, Los Angeles); J. Gregory Caporaso (Northern Arizona University and Argonne National Laboratory); and Richard Svanbäck (Uppsala University).

This research was funded by the Howard Hughes Medical Institute, the David and Lucile Packard Foundation and the Swedish Research Council.

Journal Reference:

  1. Daniel I. Bolnick, Lisa K. Snowberg, Philipp E. Hirsch, Christian L. Lauber, Elin Org, Brian Parks, Aldons J. Lusis, Rob Knight, J. Gregory Caporaso, Richard Svanbäck. Individual diet has sex-dependent effects on vertebrate gut microbiota. Nature Communications, 2014; 5 DOI: 10.1038/ncomms5500

Life-style determines gut microbes (Max-Planck-Gesellschaft)

An international team of researchers has for the first time deciphered the intestinal bacteria of present-day hunter-gatherers

April 15, 2014

The gut microbiota is responsible for many aspects of human health and nutrition, but most studies have focused on “western” populations. An international collaboration of researchers, including researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, has for the first time analysed the gut microbiota of a modern hunter-gatherer community, the Hadza of Tanzania. The results of this work show that Hadza harbour a unique microbial profile with features yet unseen in any other human group, supporting the notion that Hadza gut bacteria play an essential role in adaptation to a foraging subsistence pattern. The study further shows how gut microbiota may have helped our ancestors adapt and survive during the Paleolithic.

Hadza women roasting tubers.
Hadza women roasting tubers. © Alyssa Crittenden

Bacterial populations have co-evolved with humans over millions of years, and have the potential to help us adapt to new environments and foods. Studies of the Hadza offer an especially rare opportunity for scientists to learn how humans survive by hunting and gathering, in the same environment and using similar foods as our ancestors did.

The research team, composed of anthropologists, microbial ecologists, molecular biologists, and analytical chemists, and led in part by Stephanie Schnorr and Amanda Henry of the Max Planck Institute for Evolutionary Anthropology, compared the Hadza gut microbiota to that of urban living Italians, representative of a “westernized” population. Their results, published recently in Nature Communications, show that the Hadza have a more diverse gut microbe ecosystem, i.e. more bacterial species compared to the Italians. “This is extremely relevant for human health”, says Stephanie Schnorr. “Several diseases emerging in industrialized countries, like IBS, colorectal cancer, obesity, type II diabetes, Crohn’s disease and others, are significantly associated with a reduction in gut microbial diversity.”

The Hadza gut microbiota is well suited for processing indigestible fibres from a plant-rich diet and likely helps the Hadza get more energy from the fibrous foods that they consume. Surprisingly, Hadza men and women differed significantly in the type and amount of their gut microbiota, something never before seen in any other human population. Hadza men hunt game and collect honey, while Hadza women collect tubers and other plant foods. Though they share these foods, each sex eats slightly more of the foods they target. “The differences in gut microbiota between the sexes reflects this sexual division of labour”, says Stephanie Schnorr. “It appears that women have more bacteria to help process fibrous plant foods, which has direct implications for their fertility and reproductive success.” These findings support the key role of the gut microbiota as adaptive partners during the course of human evolution by aligning with differing diets.

Hadza digging for plant foods.Hadza digging for plant foods. © MPI f. Evolutionary Anthropology

Finally, the Hadza gut microbe community is a unique configuration with high levels of bacteria, like Treponema, that in western populations are often considered signs of disease, and low levels of other bacteria, likeBifidobacterium, that in western populations are considered “healthy”. However, the Hadza experience little to no autoimmune diseases that would result from gut bacteria imbalances. Therefore, we must redefine our notions of “healthy” and “unhealthy” bacteria, since these distinctions are clearly dependent on the environment we live in. Genetic diversity of bacteria is likely the most important criterion for the health and stability of the gut microbiome.

“Co-resident microbes are our ‘old friends’ that help us adapt to different lifestyles and environments”, says Amanda Henry, leader of the Max Planck Research Group on Plant Foods in Hominin Dietary Ecology. “Through this analysis of the Hadza gut microbiota, we have increased our knowledge of human-microbiome adaptations to life in a savanna environment and improved our understanding of how gut microbiota may have helped our ancestors adapt and survive during the Paleolithic.”