For around ten years scientists have been investigating the colonization of the intestine. However, fundamental questions about the human microbiome are still unresolved. Three teams of scientists from Helmholtz Zentrum München and Technische Universität München (TUM) present their latest findings in a recently published trilogy of publications. Here is a brief summary of each of the three topics.
Cold potatoes against complex diseases
When starch-containing foods such as potatoes are allowed to cool, dietary resistant starch is produced. It is not degradable by the body’s own enzymes, amylases, and is reported to help prevent diseases such as colon cancer and diabetes. Until now, however, it has hardly been investigated how exactly it works in the body. In a recent study in the journal ‘mBio’, the scientists showed that in particular the bacterial genus Firmicutes benefits from a diet high in resistant starch. At the same time, molecules were formed in the intestine that play an important role in human lipid metabolism. For the study, the authors examined stool samples from 39 subjects who consumed either a large or a small amount of resistant starch for two weeks. In between there was a transition period without a special diet. “By linking genomic, proteomic and metabolic data, we were able for the first time to gain more comprehensive insight into the effects of resistant starch on the gut microbiome and thus on health in general,” said Prof. Dr. Philippe Schmitt-Kopplin, head of the research unit Analytical BioGeoChemistry (BGC) at Helmholtz Zentrum München and professor at the Chair of Analytical Food Chemistry at TUM. “Particularly with a view to dietary studies and diabetes research, we want to elucidate the composition in even more detail in the future.”
Infant gut retains its original colonization
Can the gut flora of an infant be affected by adding bacteria to the milk formula? This was the question that a team led by Prof. Dr. Dirk Haller, head of the Department of Nutrition and Immunology, addressed in collaboration with the group of Philippe Schmitt-Kopplin. They investigated the effect of several bifidobacteria as a supplement in milk formula in 105 babies in their first two years of life. Bifidobacteria are important colonizers in the newborn intestine and are frequently associated with probiotic effects. It is completely unclear whether bifidobacteria in infant formula affect the colonization of the gut microbiota and its metabolites in the monthly dynamics of the first year of life. The TUM-Helmholtz team showed that the gut flora of formula-fed infants is actually significantly different from that of breast-milk-fed infants and was more heterogeneously composed. “However, at the end of the second year, we found that bifidobacteria in the diet had little influence on colonization and that initial differences disappeared again over the course of the two years,” said Haller. “This raises many new questions, such as whether or not babies need heterogeneous microbiota. Breast milk contains only a few dominant species of bifidobacteria. Later in adulthood, we have correlated a much more heterogeneous colonization of the intestine and diversity with a healthy ecosystem.” From February 2018, a follow-up study will therefore be carried out on the subject in order to clarify the issues that have arisen.
New class of molecules discovered in the gut
In a further study in ‘Scientific Reports’, the microbiome experts also found an unusual class of bacterial lipids (sulfonolipids) in the intestine. “The intestine contains numerous metabolites that change depending on the diet and the health status of the host,” said BGC scientist Dr. Alesia Walker, the first author of the study. A first step to understand the complex interplay between the intestine and its inhabitants is to detect and metabolically characterize these. Until now, the lipids had only been described in environmental bacteria, but now the researchers found them in the intestines of mice – slightly altered depending on their diet. In addition, the scientists have already been able to determine which bacteria produce the rare compounds (Alistipes and Odoribacter). Now, in ongoing investigations, the researchers want to find out whether these findings are also valid for humans. In addition, they want to test the lipids for their biological function. “Since the host itself is unable to produce the compounds, we suspect a chemical continuum between the environmental and intestinal microbiome,” said Schmitt-Kopplin.
Exemplary cooperation between TUM and Helmholtz Zentrum München
For Dirk Haller the studies are further evidence of the successful cooperation between TUM and Helmholtz Zentrum München. “Together we are working on the topic of microbiome and health on a very high level and can bundle our resources effectively.“ And analysis expert Schmitt-Kopplin added: “Today, science is hardly conceivable without international and interdisciplinary networking. Our expertise in microbiome research enables us to fundamentally enrich many research fields, such as metabolic research.”
Bazanella, M. et al. (2017): Randomized controlled trial on the impact of early-life intervention with bifidobacteria on the healthy infant fecal microbiota and metabolome. The American Journal of Clinical Nutrition, DOI: 10.3945/ajcn.117.157529
Maier, TV. et al. (2017): Impact of Dietary Resistant Starch on the Human Gut Microbiome, Metaproteome, and Metabolome. mBio, DOI: 10.1128/mBio.01343-17
Walker, A. et al. (2017): Sulfonolipids as novel metabolite markers of Alistipes and Odoribacter affected by high-fat diets. Scientific Reports, DOI: 10.1038/s41598-017-10369-z
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