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Category: human microbiome

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Natural ways that may help GERD symptoms without drugs : eating smaller portions, losing weight, not lying down for 2 hours after eating, and avoiding alcohol, cigarettes, and "trigger" foods.From Health Day News:

Could Popular Heartburn Drugs Upset Your 'Good' Gut Bugs?

Heartburn drugs such as Prilosec and Nexium may disrupt the makeup of bacteria in the digestive system, potentially boosting the risk of infections and other problems, a small new study suggests.

According to Harvard Medical School, billions of dollars are spent annually on antacid drugs in an attempt to combat heartburn, ulcers and gastroesophageal reflux disease, also known as GERD. Old standbys such as Maalox and Mylanta have been supplanted by more effective, more expensive drugs, including proton pump inhibitors. These include Prevacid (lansoprazole) and Protonix (pantoprazole) in addition to Prilosec (omeprazole) and Nexium (esomeprazole).

Long-term use of proton pump inhibitors has been linked to infection with a germ called Clostridium difficile, which causes severe diarrhea, he said. Researchers have also connected the medications to vitamin deficiencies, bone fractures and pneumonia, among other conditions.

In the new study, researchers sought to understand what happens to the trillions of germs in the digestive system when people take omeprazole, the generic name for the drug best known as Prilosec.Ten participants, aged 18 to 57, took 20 or 40 milligrams of the drug a day for 28 days. Researchers analyzed the study participants' stool samples to understand the germs in their guts.

"These microbes have evolved with us to participate in our normal development and metabolism, and perform certain functions that we would not be able to accomplish without their help," DiBaise said. Many scientists believe that people's risk of disease goes up when their normal germ makeup changes, he said.

The researchers found evidence that the medications disrupted the balance of bacteria in the digestive systems of the participants, and the changes lasted for at least a month after they discontinued the drug. It didn't seem to matter whether they took the higher or lower dose, DiBaise said.

DiBaise cautioned that the study doesn't prove that the drug causes users to become more vulnerable to C. difficile infections. However, it shows that the drug "creates a situation in the gut microbial environment that may increase an individual's susceptibility," he said.

What should users do for now? According to DiBaise, proton pump inhibitors are "the most effective medications to treat gastroesophageal reflux disease." If patients don't have the most severe symptoms, he said, other types of heartburn drugs might help. Also recommended: eating smaller portions, losing weight, not lying down for two hours after eating, and avoiding alcohol, cigarettes and "trigger" foods.

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Bottom line: Try to avoid artificial sweeteners!

From Scientific American: Artificial Sweeteners May Have Despicable Impacts on Gut Microbes

I find it ironic that Thanksgiving coincides with American Diabetes Month. In honor of that irony, two recently published studies have suggested a possible link between what you eat, how it impacts the behavior of the microbes living in your gut, and type II diabetes.

Results from a study by researchers in Israel, published in the journal Nature in October, have suggested that consumption of artificial sweeteners—found in over 6,000 food products—can lead to changes in the gut microbiome, and have put forth an explanation for how this alteration might be associated with diseases such as type II diabetes.

Jotham Suez, a PhD candidate and lead author of the study explains, “We asked people who do not regularly consume artificial sweeteners to add them to their diet for one week, and saw that the majority of these subjects had poorer glycemic responses.” And like humans, mice that were given saccharin-spiked water also developed marked glucose intolerance compared to mice drinking sugar water, or water alone.

Their experiment revealed that mice did exhibit different microbiome profiles after consuming artificial sweeteners, just as with the human volunteers who had developed glucose intolerance. And importantly, the humans who did not show glucose intolerance after consuming artificial sweeteners also did not see changes in the community composition of their microbiome.

Consequently, this change in microbial community in mice also modified how the microbiota functioned as a group to regulate metabolism. Pathways that impact the transport of sugar in the body were found to have decreased function after saccharin treatment and, notably, there was an increased abundance of short-chain fatty acids (SCFAs), which are implicated in lipid biosynthesis.

An investigation done by an independent group of researchers in Canada found similar results in a study published in October in the journal PLoS ONE. Although conducted using rats instead of mice, and with a different artificial sweetener (aspartame instead of saccharin) this study also found an increased risk of glucose intolerance. In addition, both studies showed that propionate—a SCFA highly involved in sugar production—is increased in animals consuming artificial sweeteners (although, unfortunately, propionate concentrations in humans weren’t assessed in the Nature study).

But the take home point is this: findings from two independent studies suggest that messing with the microbiome may have despicable consequences. Artificial sweeteners were originally intended to stave off the increasing obesity and metabolic disease epidemic, but instead they may have directly contributed to it.

In other words, consuming artificial sweeteners appears to throw metabolism out of whack by upsetting the critical balance of the biota in the gut—just as how chaos would surely ensue if you were to throw Gru’s minions out of whack.

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Amazing persistence of the restroom microbial community.From NPR news:

What Microbes Lurked In The Last Public Restroom You Used?

The invisible world of the bathroom isn't pretty — unless you're a microbe. After scanning the microbial zoo of four public restrooms recently, a team of researchers found a diverse swarm of characters that persisted for months despite regular cleaning of the facilities. The goal of the study, published in the December issue of Applied and Environmental Microbiology, was to better understand how communities of bacteria and viruses can shift in these very public places across a couple of months.

To get their down-and-dirty readings, the researchers selected four bathrooms at San Diego State University... They checked two women's restrooms and two men's restrooms (a high-traffic and a low-traffic bathroom for each gender). The bathrooms were thoroughly cleaned at the study's start with bleach solution, which killed any existing germ communities.Then, during the following hours, days, weeks and months of human use, the researchers periodically swabbed soap dispensers, floors and toilet seats in all four restrooms for microbe samples. 

Within one hour of sterilization, the bathrooms were completely recolonized with microbes — just as plants rapidly arrive and populate a newly emerged island. Fecal bacteria dominated, including on toilet seats and on soap dispensers — about 45 percent of the bacteria there were of fecal origin.

In all, the scientists found genetic traces of more than 77,000 distinct types of bacteria and viruses. (At least some of those species were likely dead or dormant, the scientists add; genetic testing detects them all, whatever their status.)

Patterns of regrowth and succession, as some species waned and others replaced them, were surprisingly similar from bathroom to bathroom; within just five hours the population mix in each room stabilized.

When the team tried growing cultures from different surfaces in each room, they found one set of live bacteria in overwhelming abundance: Staphylococcus. Staph's persistence in these studies points to its power as a potential pathogen, Gilbert says. Various versions are common on human skin and inside the nose and other orifices; they generally cause no problems, or trigger only minor skin infections. But staph infections can be serious, or even kill, if the bacteria get into bloodstream, joints, bones, lungs or heart. 

Gilbert notes that none of the live Staph strains detected in the San Diego bathrooms showed signs of being antibiotic resistant. They were instead relatively harmless "skin bugs that happened to have lost their skin," he says. The team did find genes from MRSA hiding on the floor, as well as traces of some troublemaker viruses, including HPV and herpes virus.

Interestingly, although restrooms that were left open for use for up to two months were cleaned regularly with soap and water, the communities of microbes found there remained relatively unchanged for the full eight weeks of the study.

No need to be scared or grossed out by that finding, Gilbert says..."All human environments contain pathogens — your bedroom, the phone you're talking on, even the bugs inside of you could turn pathogenic at any time," Gilbert tells Shots. "But we desperately need them in our lives." Having a healthy community of good — or even just neutral — microbes can crowd out the bad ones. As we've learned from using broad-spectrum antibiotics in the human body, "sterilization is not necessarily good," he says. "Bacteria come back right away, and they might come back perturbed."

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Amazing how long the bacteria persisted in the air. From Science Daily:

Hand dryers can spread bacteria in public toilets, research finds

Modern hand dryers are much worse than paper towels when it comes to spreading germs, according to new research. Scientists from the University of Leeds have found that high-powered 'jet-air' and warm air hand dryers can spread bacteria in public toilets. Airborne germ counts were 27 times higher around jet air dryers in comparison with the air around paper towel dispensers.

The study shows that both jet and warm air hand dryers spread bacteria into the air and onto users and those nearby.

The research team, led by Professor Mark Wilcox of the School of Medicine, contaminated hands with a harmless type of bacteria called Lactobacillus, which is not normally found in public bathrooms. This was done to mimic hands that have been poorly washed.

Subsequent detection of the Lactobacillus in the air proved that it must have come from the hands during drying. The experts collected air samples around the hand dryers and also at distances of one and two metres away. Air bacterial counts close to jet air dryers were found to be 4.5 times higher than around warm air dryers and 27 times higher compared with the air when using paper towels. Next to the dryers, bacteria persisted in the air well beyond the 15 second hand-drying time, with approximately half (48%) of the Lactobacilli collected more than five minutes after drying ended. Lactobacilli were still detected in the air 15 minutes after hand drying.

Professor Wilcox said: "Next time you dry your hands in a public toilet using an electric hand dryer, you may be spreading bacteria without knowing it. You may also be splattered with 'bugs' from other people's hands.

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Exciting research in a new area - our trillions of viruses or virome. From the new research it looks like some of the viruses are beneficial to us and help keep us healthy. It's time to stop thinking of all viruses (and bacteria) as bad, but instead that some viruses are necessary for good health. From Science Daily:

Natural Gut Viruses Join Bacterial Cousins in Maintaining Health and Fighting Infections

Microbiologists at NYU Langone Medical Center say they have what may be the first strong evidence that the natural presence of viruses in the gut -- or what they call the 'virome' -- plays a health-maintenance and infection-fighting role similar to that of the intestinal bacteria that dwell there and make up the "microbiome."

In a series of experiments in mice that took two years to complete, the NYU Langone team found that infection with the common murine norovirus, or MNV, helped mice repair intestinal tissue damaged by inflammation and helped restore the gut's immune defenses after its microbiome had been wiped out by antibiotic therapy. In a report on their work to be published in the journal Nature online Nov. 19, researchers say they also found that MNV bolstered the immune system in fighting off tissue damage.

"Our research offers compelling data about the mutually supportive relationship between viruses and bacteria in the mouse gut and lays the groundwork for further research on precisely how the virome supports the immune system, which likely applies to humans, as well," says senior study investigator Ken Cadwell, PhD, an assistant professor at NYU Langone.

"We have known for a long time that people get infected all the time with viruses and bacteria, and they don't get sick," says Cadwell. "Now we have scientific evidence that not every viral infection is bad, but may actually be beneficial to health, just as we know that many bacterial infections are good for maintaining health."

According to Cadwell, until now, scientists have had mostly trace genetic evidence of a virome's existence, but none to confirm its normal presence in the gut or to clarify whether it plays a harmful, neutral, or helpful role.

What the NY Times had to say about this new area of research:

Viruses as a Cure

When we talk about viruses, usually we focus on the suffering caused by Ebola, influenza, and the like. But our bodies are home to trillions of viruses, and new research hints that some of them may actually be keeping us healthy.

“Viruses have gotten a bad rap,” said Ken Cadwell, an immunologist at New York University School of Medicine. “They don’t always cause disease.” Dr. Cadwell stumbled by accident onto the first clues about the healing power of viruses. At the time, he was studying the microbiome, the community of 100 trillion microbes living in our bodies. Scientists have long known that the microbiome is important to our health.

Kristine Wylie, a research instructor of pediatrics at Washington University School of Medicine who was not involved in the research, speculated that in real life, certain viruses might be important partners with the microbiome. “It isn’t hard to imagine that the viral exposures we get as children are important to our development,” she said.

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Share your microbiota with a kiss! From Science Daily:

Up to 80 million bacteria sealed with a kiss

As many as 80 million bacteria are transferred during a 10 second kiss, according to research published in the open access journal Microbiome. The study also found that partners who kiss each other at least nine times a day share similar communities of oral bacteria.

The ecosystem of more than 100 trillion microorganisms that live in our bodies -- the microbiome -- is essential for the digestion of food, synthesizing nutrients, and preventing disease. It is shaped by genetics, diet, and age, but also the individuals with whom we interact. With the mouth playing host to more than 700 varieties of bacteria, the oral microbiota also appear to be influenced by those closest to us.

Researchers from Micropia and TNO in the Netherlands studied 21 couples, asking them to fill out questionnaires on their kissing behaviour including their average intimate kiss frequency. They then took swab samples to investigate the composition of their oral microbiota on the tongue and in their saliva.

The results showed that when couples intimately kiss at relatively high frequencies their salivary microbiota become similar. On average it was found that at least nine intimate kisses per day led to couples having significantly shared salivary microbiota.

In a controlled kissing experiment to quantify the transfer of bacteria, a member of each of the couples had a probiotic drink containing specific varieties of bacteria including Lactobacillus and Bifidobacteria. After an intimate kiss, the researchers found that the quantity of probiotic bacteria in the receiver's saliva rose threefold, and calculated that in total 80 million bacteria would have been transferred during a 10 second kiss.

The researchers found that while tongue microbiota were more similar among partners than unrelated individuals, their similarity did not change with more frequent kissing, in contrast to the findings on the saliva microbiota.

Commenting on the kissing questionnaire results, the researchers say that an interesting but separate finding was that 74% of the men reported higher intimate kiss frequencies than the women of the same couple. This resulted in a reported average of ten kisses per day from the males, twice that of the female reported average of five per day.

A more humorous write-up of same study and a museum of microbes. From Time:

Here’s How Many Bacteria Spread Through One Kiss

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Another research result from the American Gut Project, an amazing crowdsourced project. While differences were found in the fecal microbiome (microbial community) of adults born by cesarean section vs vaginal delivery, it is unknown whether this has any possible effects on diseases or risks of diseases during adulthood. This study is online as of 8 November 2014, but still In Press. From EBioMedicine:

Diversity and Composition of the Adult Fecal Microbiome Associated with History of Cesarean Birth or Appendectomy: Analysis of the American Gut Project

Adults born by cesarean section appear to have a distinctly different composition of their fecal microbial population. Whether this distinction was acquired during birth, and whether it affects risk of disease during adulthood, are unknown.

Prenatal and early postnatal exposures and events can affect the entire life course. As one example, cesarean birth has been associated with an increased likelihood of asthma and cardiovascular disease in children (Renz-Polster et al., 2005, Thavagnanam et al., 2008 and Friedemann et al., 2012), hypertension in young adults (Horta et al., 2013), and obesity in both children and adults (Pei et al., 2014, Darmasseelane et al., 2014,Blustein et al., 2013 and Mueller et al., 2014). ... As well summarized by Arrieta and colleagues, several studies have noted differences in the neonatal fecal microbiota by route of delivery (Arrieta et al., 2014). ... More recently, with comprehensive analysis based on next generation sequencing of 16S rRNA genes, Dominguez-Bello and colleagues reported that route of delivery was associated with differences in the composition of the microbial populations that initially colonized the offspring. Notably, neonates who were born vaginally were colonized by vagina-associated bacteria, whereas those born by cesarean section were initially colonized by skin-associated bacteria ( Dominguez-Bello et al., 2010).

Early life alteration of the gut microbiota may have a lasting effect. Trasande et al. observed that exposure to antibiotics up to age 6 months was associated with elevated body mass index (BMI) up to age 7 years (Trasande et al., 2013).

The 16S rRNA V4 region was sequenced by the American Gut Project....Of the 1097 participants, cesarean birth was reported as “yes” by 92, “no” by 948, and missing or uncertain by 57. Likewise, appendectomy was reported as “yes” by 155, “no” by 961, and missing or uncertain by 21.

This analysis was primarily motivated by the observation that the composition of the microbiome of neonates differed significantly between those born vaginally and those born by cesarean section (Arrieta et al., 2014 and Dominguez-Bello et al., 2010). With vaginal delivery, the neonatal microbiome resembled the vaginal microbiome, with high relative abundance of Prevotella and especially Lactobacillus taxa. In contrast, cesarean-delivered neonates had a diverse array of taxa resembling the skin microbial community, including Staphylococcus, Streptococcus, Propionibacterineae, Haemophilus, and Acinetobacter ( Dominguez-Bello et al., 2010). Cesarean-delivered neonates and infants typically have a paucity of Bifidobacterium and Bacteroides species ( Arrieta et al., 2014).

In the current analysis, we observed that the fecal microbiome composition differed in adults who reported that they had been delivered by cesarean section. This suggests that a difference by route of delivery may persist into adulthood. Of the taxa noted to be increased in cesarean-delivered neonates and infants ( Arrieta et al., 2014, Penders et al., 2006 and Dominguez-Bello et al., 2010), only Haemophilus and certain Clostridia genera had elevated abundance in the fecal microbiome of cesarean-delivered adults ( Table 3).

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This was written in 2009, but it discusses the amazing possibility of infections with high fever treating and curing cancer. This method, originally discovered by William Coley in the 1890s, used a bacterial extract (named Coley's toxins or Coley toxins) to cause an infection in the person with cancer. Try to read the whole fascinating article.From American Scientist:

Healing Heat: Harnessing Infection to Fight Cancer

Conventional wisdom long held that the human immune system was no match for cancer. Born of native cells, the logic went, cancer fooled the immune system into concluding it was harmless. Thus protected from attack, cancer easily thrived until its host died.

A deeper understanding of our biological defenses has changed that. The human immune system does battle cancer. But we could better optimize our defenses to fend off malignant disease. That’s clear from cancer treatments attempted in New York City and Germany as early as the 19th century. Those experiments and other undervalued evidence from the medical literature suggest that acute infection—in contrast to chronic infection, which sometimes causes cancer—can help a body fight tumors.

It’s not the pathogens that do the good work. But the way our bodies respond to the pathogens is key. Infection events, especially those that produce fever, appear to shift the innate human immune system into higher gear. That ultimately improves the performance of crucial biological machinery in the adaptive immune system. This lesson comes, partly, from doctors who risked making patients sicker to try to make them better.

Medicine back then offered little more than amputation and morphine to cancer patients... Shocked by his ineffectiveness, Coley dove into hospital records and the medical literature for clues to how to help more. He found about 90 sarcoma case reports. About half contained follow-up histories....In his literature search,William Coley found more than 40 cases of disappearance of malignancies during an erysipelas attack. 

In April 1891 an Italian immigrant, Mr. Zola, presented at New York Hospital with a large sarcoma tumor in his neck and an egg-sized metastasis in his right tonsil. He had been operated on twice before but was in hopeless condition. He could hardly speak or swallow and was unable to eat solid food. His life expectancy was, at the very most, a few months. He had nothing to lose by undergoing an experimental treatment.

Mr. Zola with large sarcoma in the neck. Credit: Discover magazine.

Since erysipelas was so hazardous, the hospital was reluctant to host Coley’s experiment, so it was performed in a private apartment. Colleagues at the College of Physicians and Surgeons, now part of Columbia University, prepared the bacteria. Three applications were delivered over three weeks, with minor success...Via a friend, Coley obtained fresh and potent bacteria culture from the leading German bacteriologist, Robert Koch. That fall, he again treated Zola, whose temperature that time rose above 104 degrees, with nausea, vomiting and severe pain. The infection almost killed him, but within two weeks, the neck tumor was not observable. The tonsil tumor stopped growing. Zola was in excellent health when Coley saw him four years later.

During the following two years Coley attempted to infect 12 patients who had inoperable cancer. He failed to induce a full-blown infection in four and succeeded in eight. All eight responded. Six had partial tumor remissions. Two showed full remission. But two patients died from infection. So Coley abandoned living cultures and turned toward what today we would call a bacterial extract.

In January 1893 Coley administered for the first time one variant of what today are still called “Coley’s toxins.” It was a heat-sterilized, combined culture of S. pyogenes and S. marcescens bacteria administered by injection. The patient was a 16-year-old boy with a large inoperable abdominal tumor, a malignant sarcoma. After receiving increasing doses over 10 weeks, the boy developed symptoms mimicking those of a heavy erysipelas infection: chills, headache, fever, local redness and swelling at injection sites. The tumor shrank by 80 percent. Coley kept in touch with his patient, who remained cancer-free for more than 20 years.

At the beginning of the 20th century radiation treatment came on the cancer therapy scene. This new procedure captured nearly the full attention of the oncology community due to its immediately visible effects. One could now, it seemed, x ray away tumors. Within the medical mainstream, interest in Coley’s methods faded. Still, some physicians did try to test Coley’s treatment.

Coley, throughout his 40-plus-year career, treated hundreds with multiple versions of his toxin. He never achieved a clear-cut, uniform result. Some patients responded...A five-year survival rate of zero after radiation and 38 percent after Coley’s treatments merited deeper scrutiny.

Helen Coley Nauts, Coley’s daughter, meticulously reexamined her father’s clinical cases after his death. This was not easy. Undoubtedly a man of determination, Coley was not a methodical scientist. His patient records were a mess, he treated different patients for different time periods and his bacterial extracts, over time, were inconsistently made. Coley Nauts counted 15 different preparations. Eleven of them, she concluded, were not potent enough to have a strong effect.

Coley Nauts determined that her father had treated several hundred patients by the time he died in 1936, many of whom had received radiation and sometimes surgery as well. To estimate the overall success of extracts, the analysis should be restricted to patients with inoperable cancer and treated by toxin alone. In another review from 1994, immunologist and oncology researcher Charles Starnes identified 170 such patients with adequate medical records (121 with some form of sarcoma, 43 with carcinoma and myeloma, and 6 with melanoma). The remission rate among them was 64 percent; the five-year survival rate was more than 44 percent.

According to the analyses of Coley Nauts and Starnes, treatment success correlated with length of therapy and the fevers induced by the toxins. Higher was better. This correlation was reported among several other observations but without emphasis or any explanation by the authors.

Only a few uncoordinated attempts to apply Coley’s ideas were pursued from mid-century on....Well-controlled studies of bacterial-extract cancer treatment that incorporate all the lessons from the retrospective analysis of Coley’s and other treatments have not been pursued since. But medical case studies, cancer epidemiology and our more precise understanding of immunology make a strong case that they should.

Spontaneous regression or remission is the partial or complete disappearance of an untreated malignant tumor or a tumor treated with a therapy considered inadequate to exert significant influence. It sounds like fantasy, but about 1,000 case studies in the medical literature during the past century detail spontaneous regression from cancer. Surely more have occurred. And there’s a pattern to some of the cases. A prior fever was recorded in 25 to 80 percent of documented cases of spontaneous regression of cancer.

It is not true, as Coley believed of S. pyogenes, that all these pathogens produce some cagey anti-cancerous substance...Much more likely is that the sequence of immune reactions triggered by the infections was the same...Cancer cells can carry hundreds of mutations that distinguish them from healthy cells. But the immune system often remains in an “observer” state in their presence rather than engaging in battle as it does against bacterial or viral infections. The reason for this incomplete immune response is a long-standing puzzle in cancer immunology. William Coley’s experiments may help today’s scientists solve it.

There may be prophylactic potential here as well. Epidemiological studies suggest that a personal history that includes several infections with fever sometimes significantly reduces the likelihood a person will develop cancer later (see What the Literature Says). One potential explanation is that feverish infections reduce would-be malignant cells. If that’s true, the implications are profound.

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Take note: research has linked a lack of microbial diversity in human guts to various diseases. A solution: Eat more plants! From Science Daily:

Compared with apes, people's gut bacteria lack diversity, study finds

The microbes living in people's guts are much less diverse than those in humans' closest relatives, the African apes, an apparently long evolutionary trend that appears to be speeding up in more modern societies, with possible implications for human health, according to a new study.

Based on an analysis of how humans and three lineages of ape diverged from common ancestors, researchers determined that within the lineage that gave rise to modern humans, microbial diversity changed slowly and steadily for millions of years, but that rate of change has accelerated lately in humans from some parts of the world.

People in nonindustrialized societies have gut microbiomes that are 60 percent different from those of chimpanzees. Meanwhile, those living in the U.S. have gut microbiomes that are 70 percent different from those of chimps.

 "On the other hand, in apparently only hundreds of years -- and possibly a lot fewer -- people in the United States lost a great deal of diversity in the bacteria living in their gut."

That rapid change might translate into negative health effects for Americans. Previous research has shown that compared with several populations, people living in the U.S. have the lowest diversity of gut microbes. Still other research has linked a lack of microbial diversity in human guts to various diseases such as asthma, colon cancer and autoimmune diseases.

One possible explanation for humans evolving to have less diversity in their gut microbiomes is that they shifted to a diet with more meat and fewer plants. Plants require complex communities of microbes to break them down, which is not as true for meat.

As for why Americans have experienced much more rapid changes in microbial diversity compared with people in less industrialized societies, some experts have suggested more time spent indoors, increased use of antibacterial soaps and cleaners, widespread use of antibiotics and high numbers of births by Cesarean section all may play a role. Antibiotics and antimicrobial cleaners can kill good bacteria along with the bad, and C-section deliveries prevent babies from receiving certain bacteria from the mother typically conferred during vaginal births.

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Red meat,bacteria, and atherosclerosis.From Medical Xpress:

Why does red meat increase the risk for cardiovascular disease? Blame our gut bacteria

New research provides details on how gut bacteria turn a nutrient found in red meat into metabolites that increase the risk of developing heart disease. Publishing in the November 4th issue of the journal Cell Metabolism, the findings may lead to new strategies for safeguarding individuals' cardiovascular health.

Previous research led by Dr. Stanley Hazen, of Lerner Research Institute and the Miller Family Heart and Vascular Institute at Cleveland Clinic, revealed a pathway by which red meat can promote atherosclerosis, or hardening of the arteries. Essentially, bacteria in the gut convert L-carnitine, a nutrient abundant in red meat, into a compound called trimethylamine, which in turn changes to a metabolite named trimethylamine-N-oxide (TMAO), which promotes atherosclerosis. Now Dr. Hazen and his team extend their earlier research and identify another metabolite, called gamma-butyrobetaine, that is generated to an even greater extent by gut bacteria after L-carnitine is ingested, and it too contributes to atherosclerosis.

The discovery that metabolism of L-carnitine involves two different gut microbial pathways, as well as different types of bacteria, suggests new targets for preventing atherosclerosis—for example, by inhibiting various bacterial enzymes or shifting gut bacterial composition with probiotics and other treatments.