Archive for the ‘gut bacteria’ Category

Why do some people remain healthy into their 80s and beyond, while others age faster and suffer serious diseases decades earlier? New research led by UCLA life scientists may produce a new way to answer that question—and an approach that could help delay declines in health.

Specifically, the study suggests that analyzing intestinal bacteria could be a promising way to predict health outcomes as we age.

The researchers discovered changes within intestinal microbes that precede and predict the death of fruit flies. The findings were published in the open-source journal Cell Reports.

“Age-onset decline is very tightly linked to changes within the community of gut microbes,” said David Walker, a UCLA professor of integrative biology and physiology, and senior author of the research. “With age, the number of bacterial cells increase substantially and the composition of bacterial groups changes.”

The study used fruit flies in part because although their typical life span is just eight weeks, some live to the age equivalent of humans’ 80s and 90s, while others age and die much younger. In addition, scientists have identified all of the fruit fly’s genes and know how to switch individual ones on and off.

In a previous study, the UCLA researchers discovered that five or six days before flies died, their intestinal tracts became more permeable and started leaking.

In the latest research, which analyzed more than 10,000 female flies, the scientists found that they were able to detect bacterial changes in the intestine before the leaking began. As part of the study, some fruit flies were given antibiotics that significantly reduce bacterial levels in the intestine; the study found that the antibiotics prevented the age-related increase in bacteria levels and improved intestinal function during aging.

The biologists also showed that reducing bacterial levels in old flies can significantly prolong their life span.

“When we prevented the changes in the intestinal microbiota that were linked to the flies’ imminent death by feeding them antibiotics, we dramatically extended their lives and improved their health,” Walker said. (Microbiota are the bacteria and other microorganisms that are abundant in humans, other mammals, fruit flies and many other animals.)

Flies with leaky intestines that were given antibiotics lived an average of 20 days after the leaking began—a substantial part of the animal’s life span. On average, flies with leaky intestines that did not receive antibiotics died within a week.

The intestine acts as a barrier to protect our organs and tissue from environmental damage.

“The health of the intestine—in particular the maintenance of the barrier protecting the rest of the body from the contents of the gut—is very important and might break down with aging,” said Rebecca Clark, the study’s lead author. Clark was a UCLA postdoctoral scholar when the research was conducted and is now a lecturer at England’s Durham University.

The biologists collaborated with William Ja, an assistant professor at Florida’s Scripps Research Institute, and Ryuichi Yamada, a postdoctoral research associate in Ja’s laboratory, to produce an additional group of flies that were completely germ-free, with no intestinal microbes. Those flies showed a very dramatic delay in intestinal damage, and they lived for about 80 days, approximately one-and-a-half times as long as the animal’s typical life span.

Scientists have recently begun to connect a wide variety of diseases, including diabetes and Parkinson’s, among many others, to changes in the microbiota, but they do not yet know exactly what healthy microbiota look like.

“One of the big questions in the biology of aging relates to the large variation in how we age and how long we live,” said Walker, who added that scientific interest in intestinal microbes has exploded in the last five years.

When a fruit fly’s intestine begins to leak, its immune response increases substantially and chronically throughout its body. Chronic immune activation is linked with age-related diseases in people as well, Walker said.

Walker said that the study could lead to realistic ways for scientists to intervene in the aging process and delay the onset of Parkinson’s disease, Alzheimer’s disease, cancer, stroke, cardiovascular disease, diabetes and other diseases of aging—although such progress could take many years, he said.

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There’s more to malnutrition than poor diet. Two complementary studies suggest that microbes have an important role to play in both the onset and treatment of a poorly understood form of malnutrition called kwashiorkor.

Malnutrition, the leading cause of death among children worldwide, remains something of a puzzle. It is unclear, for instance, why some children are especially prone to becoming malnourished when siblings they live with appear to fare better.

Now Jeffrey Gordon at Washington University in St Louis, Missouri, and his colleagues have found that a child’s risk of malnutrition may come down to the microbes in his or her guts.

Working in southern Malawi, the team identified sets of identical and non-identical twins in which one child had kwashiorkor – thought to be caused by a lack of protein – and the other did not, despite the shared genetics and diet. Gordon’s team took faecal samples from three sets of twins and transplanted the samples into the guts of mice, which were then fed a typical nutrient-poor Malawian diet.

Mouse weight lossAll of the mice lost some weight. However, some lost significantly more weight, and more quickly, than others. Further investigation showed that these mice had all received a faecal sample from children with kwashiorkor.

The finding strongly hinted that the mice had picked up a kwashiorkor-like condition from the microbes within the faecal implant, so the researchers studied the rodents’ gut flora. They found higher than normal levels of bacteria associated with illnesses such as inflammatory bowel disease.

The results suggest pathogenic microbes may heighten the problems of malnutrition in some children, says Jeremy Nicholson at Imperial College London, a member of the study team. “There’s a lot of work revolving around obesogenesis – how given a standard diet one set of bugs might make more calories available than another set,” he says. “But the other side of that coin is that maybe particular bugs can restrict calorie availability and exacerbate a poor diet.”

Indi Trehan at Washington University, another member of the research team, agrees. “I think it is correct that there are more factors than simple food insecurity at play in terms of malnutrition,” he says.

Antibiotic aidTrehan is lead author on a second new study, which examines how children with kwashiorkor respond when given nutrient-rich therapeutic diets. Trehan’s team found that the children were significantly less likely to become malnourished once the dietary treatment had ended if they were given a course of antibiotics along with the diet.

Together, the studies help us understand the role that infections might play in malnutrition, says Trehan. This might point towards a future in which microbial concoctions can be tailored to guard against such infections and treat specific conditions, suggests Nicholson.

Alexander Khoruts at the University of Minnesota in Minneapolis has been using faecal transplants to treat resistant Clostridium difficile disease in humans. “It is likely that microbiota are involved in pathogenesis of many other diseases, and it is possible that faecal transplants may be an approach to treat those as well,” he says. But because gut bacteria are so complex, he thinks more research will be needed to develop appropriate microbe-based therapies.

http://www.newscientist.com/article/dn23127-abnormal-gut-bacteria-linked-to-severe-malnutrition.html

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Over the last half decade, it has become increasingly clear that the normal gastrointestinal (GI) bacteria play a variety of very important roles in the biology of human and animals. Now Vic Norris of the University of Rouen, France, and coauthors propose yet another role for GI bacteria: that they exert some control over their hosts’ appetites. Their review was published online ahead of print in the Journal of Bacteriology.

This hypothesis is based in large part on observations of the number of roles bacteria are already known to play in host biology, as well as their relationship to the host system. “Bacteria both recognize and synthesize neuroendocrine hormones,” Norris et al. write. “This has led to the hypothesis that microbes within the gut comprise a community that forms a microbial organ interfacing with the mammalian nervous system that innervates the gastrointestinal tract.” (That nervous system innervating the GI tract is called the “enteric nervous system.” It contains roughly half a billion neurons, compared with 85 billion neurons in the central nervous system.)

“The gut microbiota respond both to both the nutrients consumed by their hosts and to the state of their hosts as signaled by various hormones,” write Norris et al. That communication presumably goes both ways: they also generate compounds that are used for signaling within the human system, “including neurotransmitters such as GABA, amino acids such as tyrosine and tryptophan — which can be converted into the mood-determining molecules, dopamine and serotonin” — and much else, says Norris.

Furthermore, it is becoming increasingly clear that gut bacteria may play a role in diseases such as cancer, metabolic syndrome, and thyroid disease, through their influence on host signaling pathways. They may even influence mood disorders, according to recent, pioneering studies, via actions on dopamine and peptides involved in appetite. The gut bacterium, Campilobacter jejuni, has been implicated in the induction of anxiety in mice, says Norris.

But do the gut flora in fact use their abilities to influence choice of food? The investigators propose a variety of experiments that could help answer this question, including epidemiological studies, and “experiments correlating the presence of particular bacterial metabolites with images of the activity of regions of the brain associated with appetite and pleasure.”

1.V. Norris, F. Molina, A. T. Gewirtz. Hypothesis: bacteria control host appetites. Journal of Bacteriology, 2012; DOI: 10.1128/JB.01384-12

http://www.sciencedaily.com/releases/2012/12/121219142301.htm

 

Humans share about 99 percent of our genomes with chimpanzees. Now, research finds we share something else: gut bacteria.

The bacterial colonies that populate the chimpanzee intestinal tract are mirror images of those found in the human gut, researchers report today (Nov. 13) in the journal Nature Communications. The findings suggest gut bacteria patterns evolved before chimps and humans split and went their evolutionarily separate ways.

Human gut bacteria are crucial to health, with infants relying on healthy microbe populations to influence the developing immune system. Problems with microbe populations may also contribute to obesity and inflammatory bowel diseases. 

Three intestinal ecosystems

In 2011, researchers learned that everyone’s gut bacteria fall into one of three different types, almost analogous to blood types. In each type, certain bacteria dominate. These types weren’t linked to any personal characteristics such as geographic area, age or gender. Researchers dubbed these distinct bacterial ecosystems “enterotypes.” (“Entero” means gut or intestine.)

“No one really knows why these three enterotypes exist,” said study researcher Andrew Moeller, a doctoral student at Yale University.

Along with his adviser Howard Ochman and their colleagues, Moeller want to understand how these enterotypes arose. They could be distinctly human, he told LiveScience, which would suggest they arose relatively recently, perhaps in response to the development of agriculture. Or they could be ancient, shared among our closest primate relatives.

The researchers analyzed gut bacteria samples from 35 chimpanzees from Gombe Stream National Park in Tanzania. The chimpanzees were all in the subspecies Pan troglodytes schweinfurthii, the eastern chimpanzee, which arose approximately the same time as Homo sapiens.

Shared bacteria

The researchers found that, just like humans, chimps’ guts harbor one of three distinct types of bacterial colonies. Even more intriguingly, these enterotypes matched humans’ precisely. In type 1, for example, both humans and chimps show a predominance of Bacteroides, Faecalibacterium and Parabacteroides.

There were some differences. For example, in humans and chimps, enterotype 2 is marked by an overabundance of bacteria called Lachnospiraceae. In humans, the bacteria Prevotellae is also prevalent in type 2. In chimps, Prevotellae appears in significant numbers in all three enterotypes, perhaps because it is associated with a high-carbohydrate diet.

Other differences could help explain certain human health issues. By comparing human and chimpanzee gut bacteria, the researchers found many of the bacteria present only in humans are linked to diseases such as inflammatory bowel diseases, conditions that cause pain, diarrhea and vomiting.

Seven of the chimps in the study were tested repeatedly over eight years, and their gut microbes were found to change from type to type over that time period. No one has ever tested humans for changes over a period longer than two weeks, Moeller said, but the results suggest our enterotypes may shift over time, too.

Our shared history

The similarities between chimp and human colonies suggest enterotypes predate our species, which in turn suggests that none of the three ecosystems are better than the others, Moeller said. [Gallery: Tiny, Nasty Bugs That Make Us Sick]

“Before we found this in chimpanzees, there was a possibility that enterotypes were a product of modernization, which could mean they have some negative effects on health,” he said. “I don’t think there’s any reason to think one enterotype is going to have an effect on health that’s going to be better” than the others.

Moeller and his colleagues are now examining gorilla fecal samples to find out where they stand as slightly more distant primate relatives to humans.

“The next step is to try to find out the processes and mechanisms responsible for producing these three community states,” Moeller said, “which is kind of a lofty goal, but I think more sampling will actually reveal why these communities exist.”

http://www.livescience.com/24738-chimp-human-gut-bacteria-identical.html