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Microbes are everywhere: in the soil, in the water, in the air, and even in our bodies. Yes! There is a secret world inside and outside - on every surface of our bodies. These microscopic life forms represent thousands of species, and they outnumber our own cells by about 10 to 1 ( This is according to old news! American Academy of Microbiology disputes this and says the real figure is probably closer to three bacterial cells for each human cell. However, new calculations suggest that human bodies don’t contain 10 times as many bacteria as human cells. Revised estimates for the number of human and bacteria cells in the body: A “standard man” weighing 70 kilograms has roughly the same number of bacteria and human cells in his body, researchers report online January 6, 2016 at bioRxiv.org . This average guy would be composed of about 40 trillion bacteria and 30 trillion human cells, calculate researchers at the Weizmann Institute of Science in Rehovot, Israel, and the Hospital for Sick Children in Toronto. That’s a ratio of 1.3 bacteria to every one human cell. Among individual people, the bacterial count could vary as much as 52 percent). This understanding has led to an exciting new array of studies in the recent times.

What is Microbiome?

Some use “microbiome” to mean all the microbes in a community. Others use it to mean the full collection of genes of all the microbes in a community. The human microbiome (all of our microbes’ genes) can be considered a counterpart to the human genome (all of our genes). The genes in our microbiome outnumber the genes in our genome by about 100 to 1.

The microbiome varies dramatically from one individual to the next and can change quickly over time in a single individual. Do you own a pet? Your skin bacteria tend to be more diverse than those of the pet-less. Did you have a C-section? Your infant didn’t get the typical dose of birth canal bacteria that babies born the old-fashioned way do. Now doctors and scientists are swabbing C-section babies with mothers' viginal microbes to restore the microbes they missed in the vaginal canals (2). The procedure is called 'viginal seeding' or 'micro-birthing' and let me also add that there isn't much evidence till now to conclusively say that this improves a baby's health or has good health results in his/her future life.

Moreover, in pregnant women, a normally benign bacterium emits tiny toxic balloons that can cause premature labor and stillbirth, a new study finds. Called Group B Streptococcus, the bacterium lives in the vaginas of 20 to 30 percent of pregnant women worldwide. Strep B doesn’t cause problems in the lower genital tract. But in pregnant mice, Strep B secretes protein-filled balloons that can travel up into the uterus. Those balloons cause inflammation and weaken the amniotic sac, researchers from India report September 1 in PLOS Pathogens.

The microbial mix in North America is geared to digesting protein, simple sugars and fats, whereas the mix in rural African and Amazonian environments is far more diverse and geared to fermenting plant fiber. Some think that our hunter-gatherer ancestors harbored even greater microbial diversity in their guts. So what we eat also influence the microbes in our gut! Diets high in certain fats and sugars deplete anti-inflammatory bacteria, thin the mucous layer and foster systemic inflammation. Potentially dangerous opportunists bloom. There is evidence that a person's genes can influence the gut microbiome's composition and in turn can shape the individual's phenotype ( is the composite of an organism's observable characteristics or traits, such as its morphology, development, biochemical or physiological properties, phenology, behavior, and products of behaviour). The consequences of such differences are often not addressed explicitly. But diversity — which some studies have linked to good health — is being celebrated now again and again.

The collective DNA of the microbes that colonize a human body can uniquely identify someone, researchers have found! A paper published in Proceedings of the National Academy of Sciences on May 11 2015, suggests that it might be possible to identify a participant in an anonymous study of the body’s microbial denizens—its microbiome—and to reveal details about that person’s health, diet or ethnicity.

You probably won’t find it comforting that humans are also full of viruses. These maligned microbes are actually intertwined in the very fibers of our being—about 8 percent of our genetic material is made up of absorbed forms of retroviruses, the viral family to which HIV, the pathogen that causes AIDS, belongs! A study (1) published last year in Cell Reports suggests that they may help shape that thinking by participating in brain development. Unlike other viruses, retroviruses contain only RNA and must insert all of their genetic material into their host’s DNA in order to reproduce. When this molecular hijacking happens in sperm or egg cells, the retroviruses can be passed down to the host’s offspring, who then pass them on to their offspring, and so on. Eventually, a combination of mutations and genetic policing detain the viral invader, preventing it from jumping to a new host or even making copies of itself. Many of the endogenous retroviruses in our genome have been imprisoned there for millions of years. They carry out important developmental duties in the brains of embryos.

These microbes that live in human bodies can be good or bad. Scientists had been focused on how individual microbes make us sick for almost a century, but now we want people to realize that the grand majority of them won’t hurt you. They, in fact, help you a lot!

The Human Microbiome Project reference database, established in 2012, revealed in unprecedented detail the diverse microbial community that inhabits our bodies. Researchers are beginning to learn exactly how some microbial species in the body help digestion and contribute to regulation of appetite and the immune system.

Most micro-organisms live in the human gut. They are not freeloaders but rather perform many functions vital to health and survival: they digest food, produce anti-inflammatory chemicals and compounds, and train the immune system to distinguish friend from foe. Revelations about the role of the human microbiome in our lives have begun to shake the foundations of medicine and nutrition. Scientists working in the field now think of humans not as self-sufficient organisms but as complex ecosystems colonized by numerous collaborating and competing microbial species. From this perspective, human health is a form of ecology in which care for the body also involves tending its teeming population of resident animalcules.

Do you know some of the good microbes live in your gut prevent intestinal inflammation? Research suggests that the makeup of this complex microbial ecosystem in our gut is closely linked with our immune function. Some researchers now suspect that, aside from protecting us from infection, one of the immune system's jobs is to cultivate, or “farm,” the friendly microbes that we rely on to keep us healthy. This “farming” goes both ways, though. Our resident microbes seem to control aspects of our immune function in a way that suggests they are farming us, too.

Our diet, antibiotic use, where and how we were born, and personal hygiene all affect the gut microbiome. This is important, because even slight imbalances in the composition of our microbiomes can lead to dramatic effects on disease.

Researchers around the world have identified a select group of microbes that seem important for gut health and a balanced immune system. They belong to several clustered branches of the clostridial group. Dubbed “clostridial clusters,” these microbes are distantly related to Clostridium difficile, a scourge of hospitals and an all too frequent cause of death by diarrhea. But where C. difficile prompts endless inflammation, bleeding and potentially catastrophic loss of fluids, the clostridial clusters do just the opposite—they keep the gut barrier tight and healthy, and they soothe the immune system. Scientists are now exploring whether these microbes can be used to treat a bevy of the autoimmune, allergic and inflammatory disorders that have increased in recent decades, including Crohn's and maybe even obesity. Scientists in India and Japan found F. prausnitzii to be depleted in patients with inflammatory bowel disease. Kenya Honda, a microbiologist at Keio University in Tokyo, was among the first to uncover the critical role of clostridial microbes in maintaining a balanced immune system. These human microbes specialized in nudging the immune system away from inflammatory disease. Honda also demonstrated a link between antibiotics usage which eliminated these useful bacteria and vulnerability to inflammatory disease. Honda's studies suggest another explanation: antibiotics may deplete the very bacteria that favorably calibrate the immune system, leaving it prone to overreaction leading to allergies and asthma.

A number of studies have found a small but significant correlation between the early-life use of antibiotics and the later development of inflammatory disorders, including asthma, inflammatory bowel disease and, more recently, colorectal cancer and childhood obesity. One explanation for this association might be that sickly people take more antibiotics. Antibiotics are not the cause, in other words, but the result of preexisting ill health!

These dynamics may also apply to other diseases. When the clostridial bacteria were eliminated with antibiotics in animals, food allergies have developed in them. The sensitization could be prevented just by introducing those clostridial bacteria again!

Scientists observed defects in the mucous layer in other disorders, particularly inflammatory bowel disease, where these clostridial bacteria are often depleted. The question has always been which comes first: defects in mucus secretion and the selection of an aberrant community of microbes or acquisition of an aberrant community of microbes that thins the mucous layer and increases vulnerability to disease? Both factors may work together.

Society-wide shifts in our microbial communities have contributed to our seemingly hyperreactive immune systems. Drivers of these changes might include antibiotics; sanitary practices that are aimed at limiting infectious disease but that also hinder the transmission of symbiotic microbes; and, of course, our high-sugar, high-fat modern diet. Our microbes depend on what we consume. Moreover, our particular surroundings may seed us with unique microbes, “localizing” our microbiota.

These patterns suggest that perhaps by seeding the gut microbiota early in life or by direct modification of the immune system the environment can affect our risk of inflammatory bowel disease despite the genes we carry. Children raised on farms develop very healthy and useful microbiomes. And they raise the question of what proactive steps those of us who do not live on farms can take to increase our chances of harboring a healthy mix of microbes.

Faced with the many instances of a misbehaving immune system, it is tempting to imagine that rather than having developed a greater vulnerability to many diseases, we actually suffer from just one problem: a hyperreactive immune system. Maybe that tendency has been enabled, in part, by a decline or loss of key anti-inflammatory microbes and a weakening of their important function.

The state of our gut also governs our state of mind! You read it right! Accumulating wastes in the colon triggered a state of “auto-intoxication,” whereby poisons emanating from the gut produced infections that were in turn linked with depression, anxiety and psychosis. The gut-brain axis seems to be bidirectional—the brain acts on gastrointestinal and immune functions that help to shape the gut's microbial makeup, and gut microbes make neuroactive compounds, including neurotransmitters and metabolites that also act on the brain. These interactions could occur in various ways: microbial compounds communicate via the vagus nerve, which connects the brain and the digestive tract, and microbially derived metabolites interact with the immune system, which maintains its own communication with the brain.

Scientists have also begun to explore the microbiome's potential role in autism. Scientists were intrigued by epidemiological data showing that women who suffer from a high, prolonged fever during pregnancy are up to seven times more likely to have a child with autism. These data suggested an alternative cause for autism besides genetics.

One of these new areas is its link with bone health (3,4). This link seemed surprising at first, and most scientists viewed these two systems as quite separate. But exciting new research now shows that the gut microbiome can affect bone strength in both animal models and humans. These interesting results seem to be related to the immune system, and the microbiome's influence on maturation (or abnormal maturation) of immune cells. Different cells in the immune system can regulate bone density, and an imbalance in this regulation leads to diseases such as arthritis, cancer and osteoporosis (a disease in which bones become weak and brittle).

What these findings are also telling us is that by optimizing the microbiome, we may be able to treat or prevent a number of diseases associated with changes in the immune system, including osteoporosis.

Indeed, studies testing the effects of probiotics and prebiotics on bone health have already begun to support this approach. Probiotics are live microbes (such as those found in yogurt) thought to confer specific health benefits. Prebiotics are ingredients thought to stimulate the growth of beneficial bacteria.

The human gut microbiome evolved to help us in myriad ways: Gut microbes make vitamins, break dietary fiber into digestible short-chain fatty acids and govern normal functions in the immune system. Probiotic treatments such as yogurt supplemented with beneficial strains of bacteria are already being used to help treat some gastrointestinal disorders, such as antibiotic-induced diarrhea.

In fact, changes in our diet and environment that influence our microbiomes may be linked to increases in the rates of conditions like asthma, autism, and inflammatory bowel disease. This so-called “hygiene hypothesis” (5) proposes that our lifestyle choices, use of antibiotics, and diets high in processed food has altered our “healthy” microbiome and ability to naturally prevent these conditions.

Korean and American researchers have recently discovered that identifying changes in gut microorganism types and activities could help in the early diagnosis of type 2 diabetes. Researchers have  investigated, for the first time, how the function and composition of the microbial community in the gut vary at different stages before onset of the condition. This Sub-clinical detection of gut microbial biomarkers of obesity and type 2 diabetes can be used in disease identification in the early stages so that action can be taken to control it (6). 

However, links between microbe populations of the gut and certain health conditions are controversial (8) as the studies are not scientifically correct. More research is required before coming to any conclusions.

Now a study in mice published recently in Nature Medicine suggests that striking the right microbial balance in gut could cause changes in the immune system that significantly reduce brain damage after a stroke—the second leading cause of both death and disability for people around the globe (7).

Don't get surprised if in the future you come across more and more benefits to human beings because of microbiome interactions in our bodies.

References:

1. http://www.ncbi.nlm.nih.gov/pubmed/25543143

2. http://www.scientificamerican.com/article/scientists-swab-c-section...

3. http://link.springer.com/article/10.1007%2Fs11914-015-0292-x

4. http://link.springer.com/article/10.1007%2Fs11914-015-0292-x

5. http://www.jacionline.org/article/S0091-6749%2815%2901193-8/abstract

6. http://genomemedicine.biomedcentral.com/articles/10.1186/s13073-016...

7. http://www.nature.com/nm/journal/vaop/ncurrent/full/nm.4068.html

8. http://www.scientificamerican.com/article/findings-from-the-gut-new...

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Replies to This Discussion

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How Gut Microbiota Impacts HIV Disease

A new understanding of the role gut microbiota plays in HIV disease is beginning to emerge, suggesting potential new strategies to manage the infection

http://www.scientificamerican.com/article/how-gut-microbiota-impact...

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Microbes can play games with the mind

The bacteria in our guts may help decide who gets anxiety and depression

https://www.sciencenews.org/article/microbes-can-play-games-mind?ut...

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Wiping out gut bacteria impairs brain


Nerve cell production, memory affected in mice treated with antibiotics

Obliterating bacteria in the gut may hurt the brain, too.

In mice, a long course of antibiotics that wiped out gut bacteria slowed the birth of new brain cells and impaired memory, scientists write May 19 in Cell Reports. The results reinforce evidence for a powerful connection between bacteria in the gut and the brain (SN: 4/2/16, p. 23).

After seven weeks of drinking water spiked with a cocktail of antibiotics, mice had fewer newborn nerve cells in a part of the hippocampus, a brain structure important for memory. The mice’s ability to remember previously seen objects also suffered.

Further experiments revealed one way bacteria can influence brain cell growth and memory. Injections of immune cells called Ly6Chi monocytes boosted the number of new nerve cells. Themonocytes appear to carry messages from gut to brain, Susanne Wolf of the Max Delbrück Center for Molecular Medicine in Berlin and colleagues found.

Exercise and probiotic treatment with eight types of live bacteria also increased the number of newborn nerve cells and improved memory in mice treated with antibiotics. The results help clarify the toll of prolonged antibiotic treatment, and hint at ways to fight back, the authors write. 

L. Möhle et al. Ly6Chi monocytes provide a link between antibiotic-induced changes in gut ...Cell Reports. Vol. 15, May 31, 2016. doi: 10.1016/j.celrep.2016.04.074.

L. Sanders. Microbes can play games with the mindScience News. Vol. 189, April 2, 2016, p. 23. 

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https://www.sciencenews.org/blog/growth-curve/should-c-section-babi...

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Unlocking the Power of Breast Milk—with Help from Cows

Researchers hope milk sugars and protective microbes can help prevent malnutrition and treat intestinal disease

http://www.scientificamerican.com/article/unlocking-the-power-of-br...

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People who like milk chocolate have slightly different microbes in their intestines than those who prefer their chocolate dark, although researchers do not know why. Significant differences in the so-calledmicrobiome are also found in individuals based on whether or not they eat a lot of fiber or take certain medications—such as the diabetes drug metformin, female hormones or antihistamines.

But all these variations account for only a small fraction of the microbial diversity seen in the guts of northern Europeans, according to new research published today in a special section of Science. Of the half-dozen microbiome articles in the journal, two studies stand out as being among the largest ever conducted on the gut microbes that inhabit healthy people’s large intestines and help with digestion and various immune processes—among other things.

http://science.sciencemag.org/content/352/6285/560

http://www.scientificamerican.com/article/findings-from-the-gut-new...

MicroRNAs manage gut microbes
Tiny bits of genetic material help out by micromanaging intestinal bacteria
Tiny pieces of genetic material known as microRNAs do a big job: They control gene activity inside bacteria in the intestines, a new study finds. The little RNAs also control the mix of microbes living in the gut.

Those functions help keep the intestines healthy, researchers report January 13 in Cell Host & Microbe. If the findings hold up, microRNAs may become a tool for shaping the composition of the body’s microbes, or microbiome.

Cells lining the colons of both humans and mice pump out microRNAs, Shirong Liu, an immunologist at Brigham and Women’s Hospital in Boston, and colleagues discovered. Those microRNAs can slip inside bacteria to control activity of specific genes, the team found in research with mice. Dialing gene activity up or down could stimulate or suppress growth of certain bacteria.

Mice that couldn’t produce microRNAs in their colons were more prone to develop colitis, an inflammation of the colon’s lining. When researchers gave the microRNA-deficient mice infusions of normal microRNA mixes, the rodents had less severe symptoms. Those results suggest that humans and mice use microRNAs to control bacteria and keep their colons healthy.
http://www.cell.com/cell-host-microbe/abstract/S1931-3128%2815%2900...

Doctors warn of demand for "vaginal seeding" despite thin evidence

British doctors say more parents are requesting so-called "vaginal seeding", when a swab from the mother's vagina is wiped into a newborn's mouth after caesarean-section birth, despite a lack of evidence for its medical benefits.

The practice, also known as microbirthing, involves wiping the swab over the baby's mouth, eyes, face and skin to bring it into contact with bacteria from the birth canal.

The hope is this may boost their gut bacteria, and reduce risk of conditions such as allergies or obesity, experts explained in a report in the BMJ British Medical Journal - yet scientific evidence to support it is severely lacking.

"Demand for this process has increased among women attending hospitals in the UK – but this has outstripped professional awareness and guidance," said Aubrey Cunnington, an honorary consultant in paediatric infectious diseases at Imperial College London, who co-wrote the BMJ report.

"There is simply no evidence to suggest it has benefits - and it may carry potential risks."

Some studies suggest that babies born by C-section have a different microbiome - the collection of millions of bacteria living in the gut - to those born vaginally.

Around one in four babies in Britain are born via caesarean section, according to the BMJ report, co-written by Cunningham and five other doctors.

Research also shows that C-section babies have slightly increased risk of developing conditions such as obesity, allergies and autoimmune diseases later in life.

Cunnington said a theory has developed that this may be because the bacteria the baby is exposed to in the birth canal during a vaginal birth colonise the baby's gut, so exposing those who miss out on it might help protect them.

"People have made a leap of logic that gut bacteria must be the link between caesarean section and risk of these diseases," Cunningham said. "But we just don't know this for sure - or whether we can even influence this by transferring bacteria on a swab from mum to baby."

He added that while there is no evidence of benefits from "vaginal seeding", the practice has potential risks such as transferring harmful bacteria to the baby.

"Doctors, nurses, midwives and parents need to be aware they are doing something with a potential risk that currently doesn’t have any evidence of benefit," Cunnington said.

He added that evidence-based interventions, such as encouraging breast feeding and avoiding unnecessary antibiotics, could be "more important to a baby's gut bacteria than worrying about transferring vaginal fluid on a swab".
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Reuters

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In pregnant women, a normally benign bacterium emits tiny toxic balloons that can cause premature labor and stillbirth, a new study finds.

Called Group B Streptococcus, the bacterium lives in the vaginas of 20 to 30 percent of pregnant women worldwide. Strep B doesn’t cause problems in the lower genital tract. But in pregnant mice, Strep B secretes protein-filled balloons that can travel up into the uterus. Those balloons cause inflammation and weaken the amniotic sac, researchers from India report September 1 in PLOS Pathogens.

Scientists already knew that Strep B can be a problem during pregnancy. They didn’t know that it makes tiny long-range weapons. The danger is “not just the bug alone,” says microbiologist Lakshmi Rajagopal of Seattle Children’s Research Institute, “but also something the bug produces.”

Using a scanning electron microscope, researchers from the Indian Institute of Technology-Bombay detected small circular orbs budding off of Strep B bacteria. Inside those little fluid-filled balloons, the researchers found corrosive proteins. The scientists also found that, in mice, the balloons can migrate from the vagina into the uterus. There, the orbs trigger cell death and degrade collagen in the amniotic sac (making it more likely to tear), and can cause inflammation, premature birth and stillbirth. Almost all the pups of pregnant mice with bacterial balloons injected into their amniotic sacs either died in utero or were delivered prematurely. Researchers also found that when the toxic proteins were disabled by inhibitors, the balloons didn’t degrade collagen.

Previous work had implicated a bacterial pigment in Strep B’s ill effects, but the balloons are a potential second mechanism, says study coauthor Anirban Banerjee, a microbiologist at the Indian Institute of Technology.

It’s still unclear why Strep B, which normally keeps a low profile, makes toxins in the first place. They may be used in turf wars, Banerjee suggests, to help Strep B compete against other bacterial species. Strep B isn’t the only bacterium that makes toxic balloons, either, and many microbiologists are working to understand exactly how the bugs secrete them.

In the meantime, these new findings “emphasize the need to develop an approved vaccine” against Strep B, says Rajagopal. Today doctors test pregnant women for the bacterium between 35 and 37 weeks. Strep-positive women take antibiotics during labor to prevent infecting newborns. But the bacteria can quickly return, so antibiotics aren’t a permanent fix. Understanding how and why microbes make these teensy weapons could help doctors discover how to block strep infections in the first place.

http://journals.plos.org/plospathogens/article?id=10.1371/journal.p...

Wiping out gut bacteria impairs brain
Nerve cell production, memory affected in mice treated with antibiotics

Obliterating bacteria in the gut may hurt the brain, too.

In mice, a long course of antibiotics that wiped out gut bacteria slowed the birth of new brain cells and impaired memory, scientists write May 19 in Cell Reports. The results reinforce evidence for a powerful connection between bacteria in the gut and the brain (SN: 4/2/16, p. 23).

After seven weeks of drinking water spiked with a cocktail of antibiotics, mice had fewer newborn nerve cells in a part of the hippocampus, a brain structure important for memory. The mice’s ability to remember previously seen objects also suffered.

Further experiments revealed one way bacteria can influence brain cell growth and memory. Injections of immune cells called Ly6Chi monocytes boosted the number of new nerve cells. Themonocytes appear to carry messages from gut to brain, Susanne Wolf of the Max Delbrück Center for Molecular Medicine in Berlin and colleagues found.

Exercise and probiotic treatment with eight types of live bacteria also increased the number of newborn nerve cells and improved memory in mice treated with antibiotics. The results help clarify the toll of prolonged antibiotic treatment, and hint at ways to fight back, the authors write.

L. Möhle et al. Ly6Chi monocytes provide a link between antibiotic-induced changes in gut microbiota and adult hippocampal neurogenesis. Cell Reports. Vol. 15, May 31, 2016. doi: 10.1016/j.celrep.2016.04.074.

L. Sanders. Microbes can play games with the mind. Science News. Vol. 189, April 2, 2016, p. 23.

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Microbiome: Does the brain listen to the gut?

https://elifesciences.org/content/5/e17052?utm_source=content_alert...

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Your Gut Bacteria Could Affect How Drugs Work For You Microorganisms in the gut likely have an effect on how the body metabolizes drugs, according to a new study. 

Research from Japan suggests that changes in the intestinal flora brought on by antibacterials and antibiotics or individual differences between people may have an effect on a person’s response to drugs—including side effects they might suffer. This finding was published in Molecular Pharmaceutics. Antibacterial and antibiotic drugs are often prescribed for the treatment and prevention of bacterial infections and often taken with therapeutic drugs to prevent recurrence of infection. Unfortunately, the drugs affect not only harmful bacteria, but also the naturally-occurring bacteria within the intestines. Kumamoto University researchers set out to investigate protein changes in the liver and kidney as a result of antibacterial drug consumption. Changes in these proteins have a great influence on drug efficacy and side effects since they are responsible for the metabolism and transport of many drugs, and are also affected by changes in the intestinal flora. The research was conducted using three different groups of mice: an experimental group of germ-free mice which were free of intestinal bacteria since birth; a group of mice that had received antibacterial drugs for five consecutive days; and a control group of mice with naturally occurring intestinal flora. By carrying out a large-scale analysis of proteins, the researchers detected changes in the levels of proteins involved in drug metabolism and transport in the liver and kidneys of the mice. “The most significant drug-metabolizing enzyme that decreased was cytochrome P450 2b10 (Cyp2b10),” said Professor Sumio Ohtsuki, who led the research project. “Not only was the amount of the enzyme reduced nearly 96 percent, but the metabolic capacity of the drug in the liver was also reduced by approximately 82 percent. Cyp3a11, a similar type of enzyme, was also reduced by about 88 percent.” The human equivalent of these two enzymes, CYP2B6 and CYP3A4, are reported to be related to the metabolism of more than half of the pharmaceuticals on the market, Ohtsuki noted. In the future, if it is confirmed that similar mechanisms exist in humans, the researchers expect that their work could lead to more optimal dosing and a reduction in drug side effects. 

Effect of Intestinal Flora on Protein Expression of Drug-Metabolizing Enzymes and Transporters in the Liver and Kidney of Germ-Free and Antibiotics-Treated Mice

http://pubs.acs.org/doi/abs/10.1021/acs.molpharmaceut.6b00259


Post-stroke shifts in gut bacteria could cause additional brain injury


Mouse study suggests fecal transplants as therapy

When mice have a stroke, their gut reaction can amp up brain damage.

A series of new experiments reveals a surprising back-and-forth between the brain and the gut in the aftermath of a stroke. In mice, this dickering includes changes to the gut microbial population that ultimately lead to even more inflammation in the brain.

There is much work to be done to determine whether the results apply to humans. But the research, published in the July 13 Journal of Neuroscience, hints that poop pills laden with healthy microbes could one day be part of post-stroke therapy.

The work also highlights a connection between gut microbes and brain function that scientists are only just beginning to understand.

There’s growing evidence that gut microbes can influence how people experience stress or depression.

Following a stroke, the mouse gut becomes temporarily paralyzed, leading to a shift in the microbial community, neurologist Arthur Liesz of the Institute for Stroke and Dementia Research in Munich and colleagues found. This altered, less diverse microbial ecosystem appears to interact with immune system cells called T cells that reside in the gut. These T cells can either dampen inflammation or dial it up, leading to more damage, says Liesz. Whether the T cells further damage the brain after a stroke rather than soothe it seems to be determined by the immune system cells’ interaction with the gut microbes.

Transplanting microbe-laden fecal matter from healthy mice into mice who had strokes curbed brain damage, the researchers found. But transplanting fecal matter from mice that had had strokes into stroke-free mice spurred a fourfold increase in immune cells that exacerbate inflammation in the brain.

Learning more about this interaction between the gut’s immune cell and microbial populations will be key to developing therapies.

V. Singh et al. Microbiota dysbiosis controls the neuroinflammatory response after ...Journal of Neuroscience. Vol. 36, July 13, 2016, p. 7428. doi: 10.1523/JNEUROSCI.1114-16.2016.

L. Sanders. Wiping out gut bacteria impairs brainScience News. Vol. 189, June 25, 2016, p. 14.

L. Sanders. Microbes can play games with the mindScience News. Vol. 189, April 2, 2016, p. 23. 

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https://www.scientificamerican.com/article/how-gut-bacteria-tell-th...

Birth may not be a major microbe delivery event for babies

Study finds no big differences in microbiomes of babies born vaginally or by C-section

Babies are born germy, and that’s a good thing. Our microbiomes — the microbes that live on and in us — are gaining cred as tiny but powerful keepers of our health.

As microbes gain scientific stature, some scientists are trying to answer questions about how and when those germs first show up on babies. Birth itself may be an important microbe-delivery event, some researchers suspect. A trip through the birth canal can coat a baby with bacteria from his mother. A C-section, some evidence suggests, might introduce different bacteria, at least right after birth.

That difference forms the basis of the practice of vaginal seeding, which involves wiping vaginal fluids onto a baby born by C-section to introduce microbes the baby would have encountered in a vaginal birth.

Even while some parents are asking for the procedure, there’s dissent in the ranks of research about its benefits. Scientists don’t agree yet on how — or even whether — type of birth affects the microbiome. “It’s murky,” says obstetrician and maternal-fetal medicine specialist Kjersti Aagaard of the Baylor College of Medicine in Houston. Existing studies don’t clearly distinguish the effects of the C-section itself from those of certain diseases or conditions that can make a C-section more likely, such as maternal diabetes or obesity, she says. Other issues, like whether a baby received antibiotics or is breastfed, also muddy the waters. “You are left saying, ‘Wait a minute. Is it the surgery or not the surgery? What’s going on here?’” Aagaard says.

In a search for clarity, Aagaard and her colleagues surveyed the microbiomes of 81 pregnant women. Later on, the researchers added a second group of 82 women, whose microbiomes were assessed at the birth of their children.

Just after birth, babies who had been delivered by C-section had different mouth, nose and skin microbiomes than babies born vaginally. One possible explanation is that these babies are handled differently just after birth, Aagaard says. The microbiomes of the babies’ meconium, or stool, appeared to be similar, regardless of how the babies were born.

But between four and six weeks later, these C-section/vaginal birth differences on the mouth, nose and skin were largely gone, Aagaard says. The microbes living in and on the babies born by C-section and those born vaginally were nearly indistinguishable, the researchers reported online January 23 in Nature Medicine.

Depending on where they lived, the populations of microbes had already taken on distinct identities by about a month after birth, the researchers found. Communities of nose-dwelling microbes were easy to distinguish from those living in the gut, for instance. These regional differences are signs of surprising microbial maturity, Aagaard says. “Postnatal microbiomes start looking like adults a little sooner than we may have appreciated,” she says.

The results raise an interesting question: If the type of birth isn’t one of the main shapers of microbiomes, then how and when do microbes get into babies? It’s possible that microbes from mothers slip into fetuses during pregnancy — a plausible idea, given some earlier results. Genetically tagged bacteria fed to pregnant mice showed up in their fetuses’ guts a day before the predicted due date, a result that suggests the bacteria traveled from mother to fetus. And Aagaard and colleagues have found evidence of microbes in the placenta of human mothers. They are now studying whether microbes, or perhaps pieces of them, move through the placenta from mother to baby. If that turns out to be the case, then babies meet their microbes, for better or worse, well before their birthday.

https://www.sciencenews.org/blog/growth-curve/birth-may-not-be-majo...

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