Fast food makes the immune system more aggressive in the long term

Even after a change to a healthy diet, body defense remains hyperactive, according to a study by the University of Bonn

On a high-fat and high-calorie diet, the immune system reacts similar to a bacterial infection. This is shown by a recent study led by the University of Bonn. 

Particularly disturbing: Unhealthy eating seems to make the body more aggressive in the long term. So long after switching to a healthy diet, inflammation occurs. This directly promotes the development of arteriosclerosis and diabetes. The results appear in the renowned journal "Cell".

The scientists used mice for a month on a so-called "Western diet": high in fat, high in sugar, low in fiber. 

The animals then developed a massive body-wide inflammation - almost like after infection by dangerous bacteria. 

"The unhealthy diet has led to an unexpected increase in some immune cells in the blood. This was an indication of the involvement of progenitor cells in the bone marrow in the inflammatory process, "reports Anette Christ, postdoctoral researcher at the Institute for Innate Immunity of the University of Bonn. 

To better understand these changes, scientists isolated the progenitor cells of immune cells from the bone marrow of mice fed with "western diet" or normal diet, and performed a systematic analysis of their function and activation status.

"Genomic studies actually showed that a large number of genes were activated in the precursor cells by the Western diet. Hereditary factors included heredity for their reproduction and maturation. So fast food leads to the fact that the body quickly recruits a huge, powerful fighting force, "explains Prof. Dr. med. Joachim Schultze from the Life & Medical Sciences Institute (LIMES) of the University of Bonn and the German Center for Neurodegenerative Diseases (DZNE).

When the researchers offered the rodents their typical cereal diet for another four weeks, the acute inflammation disappeared. What did not go away was the genetic reprogramming of the immune cells: even after these four weeks, many of the hereditary factors active in the fast-food phase were still active in them.

"Fastfood sensor" in the immune cells

"We have only recently known that the innate immune system has a memory," explains Prof. Dr. med. Eicke Latz, director of the Institute for Innate Immunity of the University of Bonn and scientist at the DZNE. "After an infection, the body's defenses remain in a kind of alarm state, so that they can respond more quickly to a new attack." Experts call this the "innate immune training". In the mice, this process was not triggered by a bacterium, but by unhealthy diet.

The scientists even identified the "fast food sensor" in the immune cells responsible for it. 

They examined blood cells from 120 subjects. In some of these subjects, the innate immune system showed a particularly strong training effect. In them, the researchers found genetic evidence that it is involved in a so-called inflammasome. Inflammasome are sensors of the innate immune system. They detect harmful substances and subsequently release highly inflammatory messengers.

The inflammasome identified in the study is activated by certain food ingredients. Interestingly, this has long-term consequences in addition to the acute inflammatory response: namely, the activation changes the way in which the genetic information is packaged. The genetic material is stored in the DNA. Each cell contains several DNA strands, which together are about two meters long. However, they are wrapped around proteins and strongly entangled. Many genes on the DNA can therefore not be read - they are simply too poorly accessible.

Unhealthy eating causes some of these normally hidden pieces of DNA to unroll - much as if a loop were hanging out of a ball of wool. This area of ​​the genetic material is easier to read in the long term. Scientists speak of epigenetic changes. "The inflammasome triggers such epigenetic changes," explains Prof. Latz. "The immune system reacts in the sequence to small stimuli with stronger inflammatory responses."

Dramatic consequences for the health

These in turn can drastically accelerate the development of vascular diseases or type 2 diabetes. In arteriosclerosis, for example, the typical vascular deposits, the plaques, consist largely of lipids and immune cells. The inflammatory reaction contributes directly to their growth, because constantly new activated immune cells migrate into the altered vessel walls. When the plaques become too large, they burst, are carried away by the bloodstream and can clog other vessels. Possible consequences: stroke or heart attack.

Malnutrition can have dramatic consequences. In recent centuries, average life expectancy has steadily increased in western countries. This trend is being broken for the first time: Anyone born today will probably live shorter on average than his parents. Bad eating and too little exercise should play a decisive role in this.

"These findings therefore have enormous social relevance," explains Latz. "The foundations of a healthy diet need to become much more important than today. Only in this way can we immunize children at an early stage against the temptations of the food industry - before they develop long-term consequences. Children have a choice of what they eat every day. We should enable them to make a conscious choice in their diet. "

The work involved groups from the Netherlands, the USA, Norway and Germany. Latz and Schultze are members of the Cluster of Excellence "ImmunoSensation", which deals with the achievements of the innate immune system. Latz is considered one of the most internationally renowned researchers in this field. In December he was awarded the Gottfried Wilhelm Leibniz Prize for his work. This is considered one of the most prestigious science awards in Germany.

Publication: Anette Christ, Patrick Günther, Mario AR Lauterbach, Peter Duewell, Debjani Biswas, Karin Pelka, Claus J. Scholz, Marije Oosting, Kristian Haendler, Kevin Baßler, Kathrin Klee, Jonas Schulte-Schrepping, Thomas Ulas, Simone JCFM Moorlag, Vinod Kumar, Min Hi Park, Leo AB Joosten, Laszlo A. Groh, Niels P. Riksen, Terje Espevik, Andreas Schlitzer, Yang Li, Michael L. Fitzgerald, Mihai G. Netea, Joachim L. Schultze and Eicke Latz: Western diet triggers NLRP3-dependent innate immune reprograming; Cell, DOI: 10.1016 / j.cell.2017.12.013

Contact:

Prof. Dr. Eicke Latz 
Institute for Innate Immunity, University of Bonn 
and German Center for Neurodegenerative Diseases (DZNE) 
Tel .: 0228 / 287-51223 
E-Mail: eicke.latz@uni-bonn.de

University of Bonn. "Fast food makes the immune system more aggressive in the long term: Study shows that even after a change to a healthy diet, the body's defenses remain hyperactive."