Real time measurements of intestinal gases: a novel method to study how food is being digested
Researchers in Wageningen (The Netherlands), have been able to identify for the first time, how gut microorganisms process different types of carbohydrates by measuring in real time the intestinal gases of mice. This is not only a novel method to understand how food is digested but could also tell us more about the role of gut microorganisms in gut health.
The intestinal microbiota is a diverse and dynamic community of microorganisms which regulate our health status. The advancement of biomolecular techniques and bioinformatics nowadays allows researchers to explore the residents of our intestines, revealing what type of microorganisms are there. However, studying only the microbial composition of an individual provides limited insights on the mechanisms by which microorganisms can interact with the rest of our body. For example, far less is understood about the contribution of the gut microorganisms in the production of intestinal gases such as hydrogen, methane and carbon dioxide through the breakdown of food and how these gases affect the biochemical pathways of our bodies.
Intestinal gases consist mostly of nitrogen, and carbon dioxide, which originate primarily from inhaled air. Hydrogen and methane though, are produced as by-products of carbohydrate fermentation (break down), by intestinal microorganisms. However, not all carbohydrates are digested in the same way. For instance, food with simple sugars can be rapidly absorbed in the small intestine unlike complex carbohydrates such as fibers, which reach the colon where they are digested by the colonic microbiota.
Measuring hydrogen in mouse intestines
To study these interactions and gain knowledge on how microorganisms process carbohydrates, the research team led by Evert van Schothorst from the Human and Animal Physiology Group of Wageningen University (WU) in collaboration with the WU-Laboratory of Microbiology fed mice two different diets with the same nutritional values but with different types of carbohydrates (1). The first diet contained amylopectin, a carbohydrate which can be digested readily in the small intestine while the second diet contained amylose, a slowly digestible carbohydrate that is digested by intestinal microorganisms in the colon.
Animals fed the easily digestible carbohydrates showed minimal production of hydrogen whereas the group fed with the complex carbohydrates presented high levels of hydrogen. Moreover, the two groups were characterized not only by distinct microbial composition (different types of bacteria present) but also distinct metabolic profiles (short chain fatty acids), suggesting that the type of carbohydrate strongly affects microbial composition and function.
The importance of hydrogen
Hydrogen consumption is essential in any anoxic (without oxygen) microbial environment to maintain fermentative processes. In the intestine it can be utilised through three major pathways for the production of acetate, methane and hydrogen sulphide. These molecules are critical mediators of gut homeostasis, as acetate is the most predominant short chain fatty acid produced in mammals with evidence suggesting a role in inflammation and obesity (2). Methane, which is produced by a specific type of microorganisms, called archaea, has been associated with constipation related diseases, such as irritable bowel syndrome(3) and also recently with athletes’ performance (4)! Finally hydrogen sulphide is considered to be a toxic gas, although recent findings support the notion that it also has neuroprotective effects in neurodegenerative disorders such as Parkinson and Alzheimer diseases (5).
To the best of our knowledge, this is the first time that food-microbiota interactions have been studied continuously, non-invasively and in real time in a mouse model. Hydrogen is a critical molecule for intestinal health and understanding its dynamics can provide valuable information about intestinal function, and deviations in conditions such as Crohn’s disease or irritable bowel syndrome (IBS).
1. Fernández-Calleja, J.M., et al., Non-invasive continuous real-time in vivo analysis of microbial hydrogen production shows adaptation to fermentable carbohydrates in mice. Scientific reports, 2018. 8(1): p. 15351.
2. Perry, R.J., et al., Acetate mediates a microbiome–brain–β-cell axis to promote metabolic syndrome. Nature, 2016. 534(7606): p. 213
3. Triantafyllou, K., C. Chang, and M. Pimentel, Methanogens, methane and gastrointestinal motility. Journal of neurogastroenterology and motility, 2014. 20(1): p. 31.
4. Petersen, L.M., et al., Community characteristics of the gut microbiomes of competitive cyclists. Microbiome, 2017. 5(1): p. 98.
5. Cakmak, Y.O., Provotella‐derived hydrogen sulfide, constipation, and neuroprotection in Parkinson’s disease. Movement Disorders, 2015. 30(8): p. 1151-1151.