University of Tübingen: A low-calorie diet alters the gut microbiome and immune aging

A calorie-reduced diet can not only delay the development of metabolic diseases, but also has a positive effect on the immune system. Researchers have now been able to show for the first time that this effect is mediated by a changed intestinal microbiome*, which slows down the deterioration of the immune system in old age (immune senescence). The study was published in Microbiome.

About 2 billion people worldwide are overweight. Obesity increases the risk of developing high blood pressure, heart attack or type 2 diabetes mellitus and can cause inflammation in the body that weakens the immune system by increasing certain T and B memory cells. The process is called immune senescence, an age-related change in the immune system. In obese people, the development of metabolic diseases such as type 2 diabetes can be delayed by eating a low-calorie diet. In addition, such a diet also has a positive effect on the immune system. But how exactly the positive effects are mediated and what role the intestinal microbiome plays in this is not yet known.

Calorie-restricted diet changes the gut microbiome
To do this, they first analyzed how a very low-calorie diet (800 kcal/day for 8 weeks) affects the gut microbiome of an obese woman. In the next step, the researchers transplanted the gut microbiome before and after the diet into a model in which no microorganisms are present (gnotobiotic model). “In this way, we were able to determine the sole effects of the diet-influenced intestinal microbiome on the metabolism and the immune system,” explains Reiner Jumpertz-von Schwartzenberg, last author of the study and scientist at the Institute for Diabetes Research and Metabolic Diseases at Helmholtz Munich at the University of Tübingen, a partner of the German Center for Diabetes Research (DZD). He led the study together with Hans-Dieter Volk and Joachim Spranger from the Charité.

Diet-specific microbiome improves metabolism and delays immune senescence
By transplanting the diet-induced microbiome, glucose metabolism improved and fat storage was reduced. In addition, mass cytometry was able to show that the number of certain T and B memory cells was also reduced. “This indicates delayed immune senescence,” explains Julia Sbierski-Kind, first author of the study.

“These results indicate that the positive effects of a low-calorie diet on metabolism and the immune system are mediated via the gut microbiome,” summarizes Sbierski-Kind. However, the authors of the study emphasize that the investigation has so far only been carried out with the microbiome of a human being and that the experiments must be repeated with other subjects in order to confirm the results. The new findings could also be of interest for medical practice in the long term. “An improved understanding of the complex interaction between nutrition, microbiome and immune system can lay the foundations for the development of novel microbiome-based therapeutic options for the treatment of metabolic and immune diseases,” emphasizes Jumpertz-von Schwartzenberg.

*gut microbiome
The gut microbiome refers to the entirety of all microorganisms and intestinal bacteria in our digestive tract. It influences, among other things, the immune system and the metabolism of its host.