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Can we estimate prebiotic effects from short-chain fatty acid production?

/in ISAPP Science Blog /by KC

By Prof. Kristin Verbeke PhD, KU Leuven

Short-chain fatty acids (SCFA), primarily acetate, propionate and butyrate, are the most abundant anions in the large intestine. They are mainly produced from bacterial fermentation of undigested carbohydrates. Since SCFA were found to activate the orphan G-protein coupled receptors GPR-41 and 43 (renamed as free fatty acid receptor ffar-3 and ffar-2), research into their physiological effects on human health has increased exponentially.

SCFA production is proposed to be a mechanism for several health benefits associated with intake of dietary fiber and prebiotics, not only via local effects in the gut but also on distant organs. Molecular mechanisms explaining SCFA effects have mainly been elucidated in cell-based in vitro experiments and animal studies. However, studying the impact of SCFA on human physiology is complicated by the kinetics of these molecules.

Although fecal concentrations of SCFA are relatively easy to measure, consensus has grown that they provide little information. Fecal SCFA do not adequately reflect the production of SCFA in the proximal colon and only represent the fraction of SCFA that has been produced and not used. The capacity of the anion transporters,mainly the monocarboxylate transporter-1 (MCT-1) and sodium-coupled monocarboxylate transporter 1 (SMCT-1), that absorb SCFA into the colonocytes does not seem to be a limiting factor. More bacterial SCFA production results in more uptake of SCFA but not necessarily in a higher fecal excretion. For instance, when we administered colon-delivery capsules containing SCFA in a dose of 250 mmol (equivalent to what is produced from 20 g of fermentable fiber), fecal SCFA concentrations did not increase, indicating nearly complete absorption into the colonocytes (1).

Quantification of SCFA in serum or plasma provides a more relevant alternative, particularly for understanding effects of SCFA on distant organs. Systemic SCFA concentrations are about a 1000-fold lower than fecal concentrations, requiring more sophisticated analytical protocols for measurement. Currently, both GC-MS or LC-MS/MS protocols with or without prior derivatization are available for accurate and reliable SCFA quantification (2). However, it is important to be aware of the ubiquitous nature of acetate and to take sufficient precautions to avoid contamination. For instance, the type of blood tubes used for blood collection should be considered since EDTA-tubes induce contaminations with acetate while separator tubes result in propionate and butyrate concentrations. Also, the type of water used during sample preparation can be a source of acetate contamination, necessitating the measurement of blanks in every run to check for background acetate.

Beyond analytical challenges, uncertainties about when to measure systemic SCFA concentrations also hamper their interpretation in humans. SCFA have a plasma half-life in the order of a few minutes, causing plasma SCFA to vary during the day in response to food intake, particularly fiber. Indeed, postprandial plasma SCFA start to rise about 4 hours after the consumption of a breakfast rich in fermentable fiber and return back to baseline by the end of the day. Measured concentrations therefore depend significantly on the composition and timing of the last meal. Even when using fasting blood samples, it remains important to standardize the evening meal of the previous day to avoid residual fermentation of that meal, known as the second meal effect. Due to their short plasma half-life, SCFA do not accumulate in the circulation, explaining the lack of differences in fasting SCFA concentrations from before to after prebiotic interventions. Additionally, interindividual variation in fasting SCFA concentrations is substantial as shown in a cross-sectional study in 160 individuals (3). The factors contributing to this variability require further investigation but may include dietary habits, microbiota composition, exercise levels or host genetics. In our lab, we prefer measuring postprandial SCFA concentrations during the day and calculating the area-under-the concentration vs time curve as a measure of SCFA production rather than relying on fasting concentrations, despite the increased burden on the participants involved in clinical trials and the associated cost and effort of sample analysis.

Importantly, SCFA production may explain part of the prebiotic activity, but it likely does not provide the complete picture. For example, while the interaction of prebiotics with the immune system may be partly explained by activation of ffar2 and ffar3 receptors on immune cells by SCFA, some prebiotics such as human milk oligosaccharides or specific pectin structures directly activate immune cells via interaction with toll-like receptors 2 and 4 (4). Additionally, by altering the microbiota composition, prebiotics also indirectly alter the microbe-immune interaction. Such effects also need consideration when evaluating prebiotic interactions with host health.

Studies, preferably conducted in the target host (e.g. humans), that aim to elucidate the qualitative and quantitative contribution of SCFA to the host health benefits of prebiotics (i.e. dose-effect relationships, fraction of health benefit explained by SCFA) are highly warranted. Only then can we establish the value of SCFA as markers of prebiotic activity.

Microbiota-Gut-Brain Axis Researcher in Belgium Receives ISAPP’s 2024 Glenn Gibson Early Career Researcher Award

/in News /by KC

The ISAPP selection committee for the Glenn Gibson Early Career Researcher Award is pleased to announce that Dr. Boushra Dalile PhD, a postdoctoral fellow at KU Leuven (Belgium), is the recipient of this year’s award.

Dr. Dalile is a researcher who moved from studying psychology and cognitive neuroscience into biomedical sciences, completing her PhD in 2021. She now focuses on the gut-brain axis – specifically, the mechanistic role of colonic short-chain fatty acids (SCFAs) as mediators of prebiotic effects on stress-related mental disorders. In one of her group’s most recent studies, she used colon-delivery capsules to approximate the metabolic effects of prebiotic administration, and found that direct delivery of SCFAs successfully reduced physiological stress response (as measured by cortisol) in humans. She is interested in continuing to explore the potential of butyrate for modulating fear as well as anxiety-related learning and memory processes.

A multilingual researcher who lived in Germany and Sweden before coming to KU Leuven, Dr. Dalile currently has a postdoc project supported by The Research Foundation – Flanders, titled “INTERFEAR – Investigating the endogenous metabolite butyrate as an epigenetic modulator of fear memory”.

The 2024 award committee, composed of ISAPP board members and affiliates, identified Dr. Dalile as making important contributions in the biotics field early in her scientific career. The award is given annually to a researcher who is no more than five years past their terminal degree, in a field of study related to probiotics, prebiotics, synbiotics, postbiotics or fermented foods. She will receive a cash prize and a speaking slot at the ISAPP annual meeting in July, 2024.

Behind the publication: Understanding ISAPP’s new scientific consensus definition of postbiotics

/in ISAPP Science Blog /by KC

A key characteristic of a probiotic is that it remains alive at the time of consumption. Yet scientists have known for decades that some non-living microorganisms can also have benefits for health: various studies (reviewed in Ouwehand & Salminen, 1998) have compared the health effects of viable and non-viable bacteria, and some recent investigations have tested the health benefits of pasteurized bacteria (Depommier et al., 2019).

Since non-viable microorganisms are often more stable and convenient to include in consumer products, interest in these ‘postbiotic’ ingredients has increased over the past several years. But before now, the scientific community had not yet united around a definition, nor had it precisely delineated what falls into this category.

An international group of scientists from the disciplines of probiotics and postbiotics, food technology, adult and pediatric gastroenterology, pediatrics, metabolomics, regulatory affairs, microbiology, functional genomics, cellular physiology and immunology met in 2019 to discuss the concept of postbiotics. This meeting led to a recently published consensus paper, including this definition: “a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host”.

Thus, a postbiotic must include some non-living microbial biomass, whether it be whole microbial cells or cell components.

Below is a Q&A with four of the paper’s seven ISAPP-linked authors, who highlight important points about the definition and explain how it will lay the groundwork for better scientific understanding of non-viable microbes and health in the years ahead.

Why was the concept of postbiotics needed?

Prof. Seppo Salminen, University of Turku, Finland:

We have known for a long time that inactivated microorganisms, not just live ones, may have health effects but the field had not coalesced around a term to use to describe such products or the key criteria applicable to them. So we felt we needed to assemble key experts in the field and provide clear definitions and criteria.

Further, novel microbes (that is, new species hitherto not used in foods) in foods and feeds are being introduced as live or dead preparations. The paper highlights regulatory challenges and for safety and health effect assessment for dead preparations of microbes.

Can bacterial metabolites be postbiotics?

Prof. Gabriel Vinderola, National University of Litoral, Argentina:

Postbiotics can include metabolites – for example, fermented products with metabolites and microbial cells or their components, but pure metabolites are not postbiotics.

Can you expand on what is not included in the category of postbiotics?

Dr. Mary Ellen Sanders, ISAPP Executive Science Officer, USA:

The term ‘postbiotic’ today is sometimes applied to components derived from microbial growth that are purified, so no cell or cell products remain. The panel made the decision that such purified, microbe-derived substances (e.g. butyrate) should be called by their chemical names and that there was no need for a single encompassing term for them. Some people may be surprised by this. But microbe-derived substances include a whole host of purified pharmaceuticals and industrial chemicals, and these are not appropriately within the scope of ‘postbiotics’.

For something to be a postbiotic, what kinds of microorganisms can it originate from?

Prof. Gabriel Vinderola, National University of Litoral, Argentina:

A postbiotic must derive from a living microorganism on which a technological process is applied for life termination (heat, high pressure, oxygen exposure for strict anaerobes, etc). Viruses, including bacteriophages, are not considered living microorganisms, so postbiotics cannot be derived from them.

Safety and benefits must be demonstrated for its non-viable form. A postbiotic does not have to be derived from a probiotic (see here for a list of criteria required for a probiotic). So the microbe used to derive a postbiotic does not need to demonstrate a health benefit while alive. Further, a probiotic product that loses cell viability during storage does not automatically qualify as a postbiotic; studies on the health benefit of the inactivated probiotic are still required.

Vaccines or substantially purified components and products (for example, proteins, peptides, exopolysaccharides, SCFAs, filtrates without cell components and chemically synthesized compounds) would not qualify as postbiotics in their own right, although some might be present in postbiotic preparations.

What was the most challenging part of creating this definition?

Dr. Mary Ellen Sanders, ISAPP Executive Science Officer, USA:

The panel didn’t want to use the term ‘inactive’ to describe a postbiotic, because clearly even though they are dead, they retain biological activity. There was a lot of discussion about the word ‘inanimate’, as it’s not so easy to translate. But the panel eventually decided it was the best option.

 Does this definition encompass all postbiotic products, no matter whether they are taken as dietary supplements or drugs?

Prof. Hania Szajewska, Medical University of Warsaw, Poland:

Indeed. However, as of today, postbiotics are found primarily in foods and dietary supplements.

Where can you currently find postbiotics in consumer products, and what are their health effects?

Prof. Hania Szajewska, Medical University of Warsaw, Poland:

One example is specific fermented infant formulas with postbiotics which have been commercially available in some countries such as Japan and in Europe, South America, and the Middle East for years. The postbiotics in fermented formulas are generally derived from fermentation of a milk matrix by Bifidobacterium, Streptococcus, and/or Lactobacillus strains.

Potential clinical effects of postbiotics include prevention of common infectious diseases such as upper respiratory tract infections and acute gastroenteritis. Moreover, fermented formulas have the potential to improve some digestive symptoms or discomfort (e.g. colic in infants). In addition, there is some rationale for immunomodulating, anti-inflammatory effects which may potentially translate into other clinical benefits, such as improving allergy symptoms. Still, while these effects are likely, more well-designed, carefully conducted trials are needed.

What do we know about postbiotic safety?

Dr. Mary Ellen Sanders, ISAPP Executive Science Officer, USA:

Living microbes have the potential, especially in people with compromised health, to cause an infection. But because the microbes in postbiotics are not alive, they cannot cause infections. This risk factor, then, is removed from these preparations. Of course, the safety of postbiotics for their intended use must be demonstrated, but infectivity should not be a concern.

What are the take-home points about the postbiotics definition?

Prof. Seppo Salminen, University of Turku, Finland:

Postbiotics, which encompass inanimate microbes with or without metabolites, can be characterized, are likely to be more stable than live counterparts and are less likely to be a safety concern, since dead bacteria and yeast are not infective.

Read the postbiotic definition paper here.

See the press release about this paper here.

View an infographic on the postbiotic definition here.

See another ISAPP publication on postbiotics here.

Children and dogs in a household share gut microbes – and these microbes are modified by a canine probiotic

/in Consumer Blog, ISAPP Science Blog /by KC

From longtime family pets to ‘pandemic puppies’, dog ownership is seemingly more popular than ever. In households with children, scientists have found that a pet dog is one of the environmental factors that influences the gut microbiota in early life – but can the microbes that children and dogs share be modified?

A new study from ISAPP president Prof. Seppo Salminen (University of Turku, Finland) and colleagues recently explored the impact of a household dog on children’s gut microbiota, before and after the dogs were given a canine probiotic. Not only did the gut microbiota of dogs and children in the same household share features in common, but also the gut microbes of both shifted after dogs received a probiotic.

The study, which was part of a larger investigation, looked at families with at least one member who had allergic disease. Thirty-one of the families in the current study had dogs, and 18 families (the control group) did not. From each household, the fecal microbiota of one child (aged 5 or under) was tested. The fecal microbiota of the dogs was tested, and further, they received either a probiotic containing 3 canine-derived strains, or placebo.

The data supported previous observations that dogs and children share gut microbes: the children living with dogs had a distinct fecal microbiota composition. The most striking microbiota differences were a higher abundance of Bacteroides and short-chain fatty acid producing bacteria.

Moreover, when the household dogs were given a probiotic, both the dogs and the children living with them showed a gut microbiota shift, with a reduction in Bacteroides. (The exact probiotic strains were not tracked in the feces of either the dogs or the children.)

Were the changes beneficial? It’s not certain, since health outcomes in the children were not part of the study. But these findings provide more evidence for the effect of home environments and pets on the gut microbiota of children, and highlight the modifiability of both the dog’s and children’s gut microbiota. The ability to modify a child’s gut microbiota is of particular interest in the early years, when gut microbiota / immune interactions have the potential to shape health through the lifespan.

The study authors conclude, “Our promising data invite the idea that the compositional development of the gut microbiota in children is potentially modifiable by indirect changes in household pets and justify the further search of novel modes of intervention during critical period when the scene is set for the consolidation of the child later health.”

The future is microbial: A post-pandemic focus on identifying microbes and metabolites that support health

/in Uncategorized, Consumer Blog, ISAPP Science Blog /by KC

By Prof. Maria Marco, Department of Food Science and Technology, University of California Davis, USA

The COVID-19 pandemic has been a sobering reminder of the significance that microorganisms have on human life. Despite the tremendous scientific and medical advances of the twentieth century, our best precautions against the virus have been to practice the oldest and most simplistic of all public health measures such as washing hands and maintaining physical distance from others. At the same time, the effectiveness of the new SARS-CoV-2 vaccines and the speed in which they were developed show how sophisticated and advanced our understanding of viruses has become. Taken together, the limitations and successes of responses to the pandemic underscore the power of investment in microbiology research. This research, which was first catalyzed by the pioneering work of Louis Pasteur, Robert Koch, and contemporaries in the late 1800s, was the basis for the overall reduction in infectious diseases during the twentieth century. Continued investment in these efforts will prepare us for the next pandemic threat.

Beyond pathogens to health-promoting microbes

As our attention turns to the promise of the New Year, we may also take this moment to appreciate the fact that microorganisms can also do good. Our “microbial friends” were first promoted by the lauded biologists Élie Metchnikoff, Henry Tissier, and Issac Kendall at the turn of the twentieth century. Since then, nearly another century passed before the power of microorganisms to benefit human health reached wider acceptance.

Marked by the emergence of laboratory culture-independent, nucleic-acid based methods to study microbial communities, there is now excitement in the identification of microorganisms that are important for health promotion. This interest is catalyzed by the urgency to find ways to prevent and treat cardiovascular diseases, cancers, and other non-communicable, chronic conditions that are now the leading causes of death worldwide. Much like the pressure to address infectious diseases as the primary cause of mortality prior to the twentieth century, so too is the need today for sustained research investments in studying how certain microorganisms contribute to, or may be essential for, preventing and treating the greatest threats to public health in the modern era.

Exemplified by the growing number of human microbiome studies, it is now broadly understood that the human microbiome contributes positively to digestive, immune, and endocrine systems function. Systematic reviews and meta-analyses of clinical trials support the use of probiotics for a variety of conditions and there are positive associations between the consumption of fermented dairy foods and good metabolic health. To understand how microbes can be beneficial, numerous mechanisms have been proposed (for example, modulation of the immune system and production of neurochemicals that can impact the gut-brain axis), and these mechanisms apply to both autochthonous microbiota and probiotics alike. However, our understanding of exactly how this occurs lags far behind what is currently known about microorganisms that cause harm.

Identifying microbes & metabolites that maintain health

The future of beneficial microbes is in identifying the specific, health-promoting metabolites, proteins, and other compounds that they make. Presently only a handful of such examples are known. Perhaps most recognized are the short chain fatty acids, butyrate, propionate, and acetate, which are known to bind specific human cell receptors to modulate numerous cell pathways including those that affect metabolism. Other microbial compounds generated as intermediate or end products of microbial metabolism (such as metabolites of amino acids), secondary metabolites (such as bacteriocins), and bacterial cell surface constituents (such as certain membrane proteins) were shown to benefit health, although a more complete description of mechanistic details for their effects remains to be discovered. Precise mechanistic descriptions of “beneficial factors”, or the microbial enzymatic pathways and molecules that induce desired cellular and systemic responses in the human body, will be pivotal for elucidation of the precise ways microorganisms sustain health and well-being (for more detail on this topic see here).

Based on what we know about the complexity of the human microbiome and the now many decades of probiotics research, this effort will require innovation and multi-disciplinary coordination. Just as early microbiologists raced to address the high rates of mortality due to microbial pathogens, we are in a new age where again microorganisms are regarded as emerging public health threats. However, we now have to our advantage the knowledge that not all microorganisms cause harm but instead the majority may offer solutions to the greatest health challenges of the twenty-first century.

 

 

ISAPP’s 2019 annual meeting in Antwerp, Belgium: Directions in probiotic & prebiotic innovation

/in featured, News /by ISAPP

Kristina Campbell, Microbiome science writer, Victoria, British Columbia

We live in a time when a simple Google search for ‘probiotics’ produces over 56.8 million hits; a time when almost everyone has heard of probiotics through one channel or another, and when an ever-increasing variety of probiotic and prebiotic products is available in different regions of the world.

The next five to ten years will be telling: will probiotics and prebiotics join the ranks of other trendy health products that experienced a wave of popularity before something else took their place? Or will they be recognized as important contributors to health through the lifespan, and establish a permanent position in the clinical armamentarium?

According to the global group of 175 academic and industry scientists who met for the ISAPP annual meeting in Antwerp (Belgium) May 14-16, 2019, one thing above all is necessary for the world to recognize the significance of probiotics and prebiotics for health: scientific innovation. Not only are technological capabilities advancing quickly, but also, new products are being evaluated by better-educated consumers who demand more transparency about the health benefits of their probiotics and prebiotics.

Participants in the ISAPP conference came together to talk about some of the leading innovations in the world of probiotics and prebiotics. Here are three of the broad themes that emerged:

Better health through the gut-brain axis

Gut-brain axis research is rapidly growing, with many investigators in search of probiotic and prebiotic substances capable of modulating brain function in meaningful ways. Phil Burnett of Oxford (UK) presented on “Prebiotics, brain function and stress: To what extent will prebiotics replace or complement drug therapy for mental health?”. Burnett approached the challenge by administering prebiotics to healthy adults and giving them a battery of psychological tests; in one experiment he found people who consumed a prebiotic (versus placebo) showed benefits that included reduced salivary cortisol and positively altered emotional bias. For those with diagnosed brain disorders, Burnett concludes from the available data that prebiotics have potential anxiolytic and pro-cognitive effects in these populations, and that prebiotics may eventually be used to complement the established treatments for some mental disorders.

Short-chain fatty acids (SCFAs) are of interest as potential modulators of brain function, but so far very little research has been carried out in this area. Kristin Verbeke of Leuven (Belgium) gave a talk entitled “Short-chain fatty acids as mediators of human health”, which covered the extent to which interventions with fermentable carbohydrates can alter systemic SCFA concentrations (rather than gut SCFA concentrations)—since the former are more relevant to effects on the brain.

Also, a students and fellows feature talk by Caitlin Cowan of Cork (Ireland) explored a role for the microbiota in psychological effects of early stress. She spoke on the topic “A probiotic formulation reverses the effects of maternal separation on neural circuits underpinning fear expression and extinction in infant rats”.

A clear definition of synbiotics

Immediately before the main ISAPP meeting, a group of experts met to propose a consensus definition of ‘synbiotic’, with the objective of clarifying for stakeholders a scientifically valid approach for the use of the increasingly-popular term. A key point of discussion was whether the probiotic and prebiotic substances that make up a synbiotic are complementary or synergistic. And if the two substances have already been tested separately, must they be tested in combination to give evidence of their health effect? The group’s conclusions, which will undoubtedly steer the direction of future R&D programs, will be published in a forthcoming article in Nature Reviews Gastroenterology & Hepatology.

Probiotics and prebiotics for pediatric populations

Probiotics and prebiotics have been studied for their health benefits in pediatric populations for many years, but in this area scientists appear to have a renewed interest in exploring new solutions. Maria Carmen Collado of Valencia (Spain) covered “Probiotic use at conception and during gestation”, explaining some of the most promising directions for improving infant health through maternal consumption of probiotics.

In recent years, technical advancements have made possible the large-scale production of some human milk oligosaccharides (HMOs); it is now an option to administer them to infants. Evelyn Jantscher-Krenn of Graz (Austria) presented a novel perspective on HMOs, with “HMOs in pregnancy: Roles for maternal and infant health”, giving a broad overview of the many ways in which HMOs might signal health status and how they might be fine-tuned throughout a woman’s pregnancy.

A discussion group on “prebiotic applications in children”, chaired by Dr. Michael Cabana of San Francisco (USA) and Gigi Veereman of Brussels (Belgium), discussed evidence-based uses of prebiotics in children in three areas: (1) prevention of chronic disease; (2) treatment of disease; and (3) growth and development. While the latter category has the best support at present (specifically for bone development, calcium absorption, and stool softening), the other two areas may be ripe for more research and innovation. The chairs are preparing a review that covers the outcomes of this discussion group.

Next year in Banff

ISAPP’s next annual meeting is open to scientists from its member companies and will be held on June 2-4, 2020 in Banff, Canada.

 

Photo by http://benvandenbroecke.be/ Copyright, ISAPP 2019.