It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Monday, March 25, 2024
Industrial societies losing healthy gut microbes
Fiber is good for us, but a new study finds that humans are losing the microbes that turn fiber into food for a healthy digestive tract
HEINRICH-HEINE UNIVERSITY DUESSELDORF
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CLOSTRIDIUM CLARIFLAVUM, A FIBER DEGRADING BACTERIUM AT WORK BREAKING DOWN CELLULOSE FIBERS WITH THE HELP OF CELLULOSOMES. PHOTO: ITZHAK MIZRAHI
CREDIT: ITZHAK MIZRAHI, BEN-GURION UNIVERSITY (BGU)
Everyone knows that fiber is healthy and an important part of our daily diet. But what is fiber and why is it healthy? Fiber is cellulose, the stringy stuff that plants are made of. Leaves, stems, roots, stalks and tree-trunks (wood) are made of cellulose. The purest form of cellulose is the long, white fibers of cotton. Dietary fiber comes from vegetables or whole grain products. Why is fiber healthy? Fiber helps to keep our intestinal flora (scientists call it our gut microbiome) happy and balanced. Fiber serves as the starting point of a natural food chain. It begins with bacteria that can digest cellulose, providing the rest of our microbiome with a balanced diet. But our eating habits in industrialized societies are far removed from those of ancient humans. This is impacting our intestinal flora, it seems, as newly discovered cellulose degrading bacteria are being lost from the human gut microbiome, especially in industrial societies, according to a new report in Science. The study comes from the team of Prof. Itzhak Mizrahi at Ben-Gurion University (BGU) of the Negev in Israel, with support from the Weizmann Institute of Science in Rehovot and international collaborators in the US and Europe.
“Throughout human evolution, fiber has always been a mainstay of the human diet,” explains lead investigator Sarah Moraïs from BGU, “It is also a main component in the diet of our primate ancestors. Fiber keeps our intestinal flora healthy.” Moraïs and team identified important new members of the human gut microbiome, cellulose-degrading bacteria named Ruminococcus. These bacteria degrade cellulose by producing large and highly specialized extracellular protein complexes called cellulosomes. “It’s no easy task to degrade cellulose, few bacteria can do it.” explains Ed Bayer, from the Weizmann Institute, a world-leader on cellulosomes and coauthor of the study. “Cellulose is difficult to digest because it is insoluble. Fiber in the gut is like a tree-trunk in a swimming pool, it gets wet but it does not dissolve.”
Cellulosomes are engineered by bacteria to attach to cellulose fibers and peel them apart, like the individual threads in a piece of rope. The cellulosomal enzymes then break down the individual threads of fiber into shorter chains, which become soluble. They can be digested, not only by Ruminococcus, but also by many other members of the gut microbiome. “Bottom line, cellulosomes turn fiber into sugars that feed an entire community, a formidable engineering feat,” says Bayer. The production of cellulosomes puts Ruminococcus at the top of the fiber-degradation cascade that feeds a healthy gut microbiome. But the evolutionary history of Ruminococcus is complicated, and Western culture is taking its toll on our microbiome, as the new study shows.
“These cellulosome-producing bacteria have been around for a long time, their ancestors are important members of the rumen microbiome in cows and sheep,” explains Prof. Mizrahi from BGU, senior author of the study. The rumen is the special stomach organ of cows, sheep and deer, where the grass they eat (fiber) is converted into useful food by cellulose-degrading microbes, including Ruminococcus. “We were surprised to see that the cellulosome-producing bacteria of humans seem to have switched hosts during evolution, because the strains from humans are more closely related to the strains from livestock than to the strains from our own primate ancestors.” That is, it looks like humans have acquired important components of a healthy gut microbiome from livestock that they domesticated early in human evolution. “It’s a real possibility” says Mizrahi, an expert on rumen biology.
But the story does not end there. Sampling of human cohorts revealed that Ruminococcus strains are indeed robust components of the human gut microbiome among human hunter-gatherer societies and among rural human societies, but that they are sparse or missing in human samples from industrialized societies. “Our ancestors in Africa 200,000 years ago did not pick up lunch from a drive-through, or phone in a home-delivery for dinner,” says William Martin at the Heinrich Heine University Düsseldorf in Germany, evolutionary biologist and coauthor of the study. In Western societies this does, however, happen on a fairly large scale. Diet is changing in industrialized societies, far removed from the farms where food is produced. This shift away from a fiber-rich diet is a possible explanation for the loss of important cellulose-degrading microbes in our microbiome, the authors conclude.
How can you counteract this evolutionary decline? It might help doing what doctors and dieticians have been saying for decades: Eat more fiber!
Cryptic diversity of cellulose-degrading gut bacteria in industrialized humans
ARTICLE PUBLICATION DATE
18-Mar-2024
Study finds that for each 10% increase of certain bacteria type in the gut microbiome, the risk of hospitalisation for infections falls by up to a quarter
EUROPEAN SOCIETY OF CLINICAL MICROBIOLOGY AND INFECTIOUS DISEASES
A study of two large European patient cohorts has found that for every 10% increase in butyrate-producing bacteria in a patient’s gut, the risk of hospitalisation for any infection falls by between 14 and 25% across two large national cohorts. The study will be presented at this year’s European Congress of Clinical Microbiology and Infectious Diseases (ECCMID 2024) in Barcelona, Spain (27-30 April) and is by Robert Kullberg, Amsterdam University Medical Center, The Netherlands, and colleagues.
Microbiota alterations are common in patients hospitalised for severe infections and preclinical models have shown that anaerobic butyrate-producing gut bacteria protect against systemic infections. These bacteria were investigated because they are commonly depleted in patients hospitalised for severe infections. Second, butyrate may have protective effects in several intestinal diseases (other than infections).
However, the relationship between microbiota disruptions and increased susceptibility to severe infections in humans remains unclear. In this study, the authors investigated the relationship between baseline gut microbiota and the risk of future infection-related hospitalisation in two large population-based cohorts - from the Netherlands (derivation; HELIUS) and Finland (validation; FINRISK 2002).
Gut microbiota were characterised by sequencing the DNA of bacteria to identify the different types of bacteria present in faecal samples of the participants. The authors measured microbiota composition, diversity, and relative abundance of butyrate-producing bacteria. The primary outcome was hospitalisation or mortality due to any infectious disease during 5–7-year follow-up after faecal sample collection, based on national registry data. The authors then examined associations between microbiota and infection-risk using computer modelling. Further statistical modelling was used to adjust for variables including demographics, lifestyle, antibiotic exposure, and comorbidities.
The researchers profiled gut microbiota from 10699 participants (4248 from The Netherlands and 6451 from Finland. A total of 602 participants (The Netherlands: n=152; Finland: n=450) were hospitalised or died due to infections (mainly community-acquired pneumonia) during follow-up.
Gut microbiota composition of these hospitalised/deceased participants differed from those without hospitalisation for infections. Specifically, each 10% higher abundance of butyrate-producing bacteria was associated with a reduced risk of hospitalisation for infections – 25% lower for participants from the Dutch cohort and 14% lower for the Finnish cohort. All types of infections were assessed together, not any one in particular. These associations remained unchanged following adjustment for demographics, lifestyle, antibiotic exposure, and comorbidities.
The authors say: “Gut microbiome composition, specifically colonisation with butyrate-producing bacteria, is associated with protection against hospitalisation for infectious diseases in the general population across two independent European cohorts. Further studies should investigate whether modulation of the microbiome can reduce the risk of severe infections.”
The authors say further analysis will be needed before trails in patients can begin. One of the challenges is the face are the butyrate-producing bacteria are strictly anaerobic (meaning they respire without using oxygen and cannot tolerate oxygen), which makes it very difficult to transport viable bacteria into the gut. Several research groups are working on addressing these challenges.
This press release is based onabstract CS0502 at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID). The material has been peer reviewed by the congress selection committee. It is about to be submitted to a medical journal for publication. The full paper is not yet available but the authors are happy to answer your questions.
Deciphering the role of bitter and astringent polyphenols in promoting well-being
Scientists determine how dietary polyphenols influence health through gut sensory receptors
SHIBAURA INSTITUTE OF TECHNOLOGY
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DIETARY UPTAKE OF POLYPHENOLS ALTERS THE GUT MICROFLORA AND STIMULATES THE SECRETION OF SPECIFIC HORMONES THAT INDUCE CROSS-TALK WITH THE BRAIN VIA THE SENSORY NERVES. THE ASTRINGENT AND BITTER PROPERTIES OF POLYPHENOLS ARE RESPONSIBLE FOR THEIR PROTECTIVE EFFECT AGAINST CARDIOVASCULAR, METABOLIC, AND NEURODEGENERATIVE DISORDERS.
Polyphenols are powerful plant metabolites known for their antioxidant properties, offering potential health benefits and protection against various diseases. With over 8,000 identified varieties, these substances are found in plentiful amounts in various fruits, vegetables, tea, and coffee. Besides adding color and flavor to foods, polyphenols play a crucial role in promoting health and overall well-being. Despite their bitter and astringent taste, recent studies indicate that they may hold the key to a range of health benefits, including the prevention of cardiovascular diseases, neurodegenerative conditions, and age-related sensory decline. However, there are significant gaps in understanding how exactly they exert these beneficial effects, particularly in terms of their interactions with the body.
To fill this knowledge gap, Professor Naomi Osakabe along with Dr. Yasuyuki Fujii from Shibaura Institute of Technology, and Professor Vittorio Calabrese from the University of Catania, Italy explored the interaction between polyphenols and human health, and its consequent impact. The findings of their study were published in Volume 14, Issue 2 of Biomolecules on 17th February, 2024.
Sharing the inspiration behind their work Prof. Osakabe remarks, “Although many researchers have conducted polyphenol research for more than 30 years, a major challenge has been to elucidate the mechanisms behind their beneficial health effects.” This review attempts to understand the ways in which polyphenols interact with sensory receptors in the gastrointestinal tract, ultimately influencing metabolic pathways and promoting overall well-being.
Epidemiological evidences have long established the protective effects of polyphenols against various chronic conditions such as cardiovascular diseases, metabolic disorders, neurodegenerative diseases, and age-related degeneration of sensory organs. The major challenge in decoding the underlying mechanism of action is their unavailability in blood and/or organs. Polyphenols are usually broken down in the lower gut by intestinal bacteria and excreted in feces. Recent studies have reported that ingested dietary polyphenols can alter the composition of the gut microflora, altering the composition of secondary metabolites in the colon. It is hypothesized that these altered metabolites may be absorbed and affect the metabolic and cognitive functions. However, the type and amount of polyphenol varies greatly with diet and individuals making it quite difficult to establish a causal correlation.
Sensory receptors are specialized cells located close to nerve endings and are widely distributed in specialized organs such as eyes, ears, and even the gut. In recent years, sensory nutrition, a new field of study examining the cross-talk between ingested food or beverages, the brain, and its impact on human behavior, has garnered significant attention. Some reports have suggested that food signals contribute to homeostasis via gut-based sensory receptors.
Delving deeper to unearth the association between polyphenols and the gut, researchers in this study revealed that polyphenols, which are inherently bitter in taste, interact with the bitter taste receptor, the taste receptor 2 (T2R) receptors. Furthermore, some studies found that until polyphenols are excreted, they stay in contact with I-, K-, and L- cells of the intestine expressing T2Rs, or with gastrointestinal sensory nerves and epithelial cells that express TRP channels for an extended time. Astringency of polyphenols was suggested to be a somatosensory perception (a sensation which can occur anywhere in the body) and was correlated with improved blood pressure and risk factors for heart diseases. Polyphenols caused a marked increase in blood flow-dependent vasorelaxation (FMD) levels at moderate doses, known as the hormetic effect. Researchers have found that astringent polyphenols interact with transient receptor potential (TRP) channels. However, further investigation is needed to clearly understand this interaction. These findings strongly suggested that polyphenols exert their beneficial effects via sensory receptors of the gastrointestinal tract.
The astringent and bitter properties of polyphenols offer various therapeutic properties. An experimental animal study demonstrated that repeated intake of stringent polyphenols reduced FMD response significantly along with blood pressure. Another study reported that consumption of bitter polyphenols increased gastrointestinal hormone secretion, thereby regulating blood glucose levels and glucose tolerance. Astringent polyphenols have been observed to regulate the hypothalamic-pituitary-adrenal (HPA) axis activation, thereby improving mood and memory function. Bitter and astringent perception of polyphenols have also been attributed for their anti-obesity effects.
The integration of polyphenol-rich ingredients in functional beverages and snacks, could therefore revolutionize the way we approach nutrition and disease prevention. Elaborating on the long-term impact of their work, a hopeful Prof. Osakabe explains, “Our study is the first to identify that sensory stimuli in food can promote homeostasis and paves the way for the development of novel food products aimed at promoting human health.”
Overall, by comprehensively looking at the underlying mechanisms responsible for the beneficial effects of polyphenols, this review represents a significant step forward in our understanding of the health effects of polyphenols and could pave the way towards innovative dietary interventions for well-being.
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Reference
Title of original paper: Share Sensory Nutrition and Bitterness and Astringency of Polyphenols
About Shibaura Institute of Technology (SIT), Japan
Shibaura Institute of Technology (SIT) is a private university with campuses in Tokyo and Saitama. Since the establishment of its predecessor, Tokyo Higher School of Industry and Commerce, in 1927, it has maintained “learning through practice” as its philosophy in the education of engineers. SIT was the only private science and engineering university selected for the Top Global University Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology and will receive support from the ministry for 10 years starting from the 2014 academic year. Its motto, “Nurturing engineers who learn from society and contribute to society,” reflects its mission of fostering scientists and engineers who can contribute to the sustainable growth of the world by exposing their over 8,000 students to culturally diverse environments, where they learn to cope, collaborate, and relate with fellow students from around the world.
Dr. Naomi Osakabe is a distinguished academician and a Professor in the Department of Bio-science and Engineering, Shibaura Institute of Technology, Japan. With over 5,600 publications and extensive experience spanning several years, she is a prominent figure in the field of food functionality. Professor Osakabe's expertise lies in the study of polyphenols, particularly their functionality and health benefits. Notably, she is a director of the Japanese Polyphenol Society, a councilor of the Japanese Oxidative Stress Society, and the Japanese Society of Food Immunology and a consultant of the Japanese Society of Nutrition and Food Science. She has contributed significantly to the advancement of knowledge in areas related to oxidative stress, food immunology, and nutrition science.
Funding Information
This work was supported by JSPS KAKENHI Grant Number JP 23H02166.
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