Common salt reduces the number of certain lactic acid bacteria in the gut of mice and humans according to a study published in Nature by an interdisciplinary research team including Professor Markus Kleinewietfeld from VIB and Hasselt University. This has an impact on immune cells, which play a critical role in autoimmune diseases and hypertension. Probiotic treatment could counteract the detrimental effects of salt on experimental animal models for autoimmunity and hypertension.
Gut bacteria contribute to the harmful effects of salt
Too much salt in food can encourage hypertension and might even have a negative impact on the course of autoimmune diseases like multiple sclerosis (MS). Previous work led by Prof. Dominik Müller (ECRC Berlin, Germany) and Prof. Markus Kleinewietfeld has shown that a high-salt diet affects the generation of detrimental immune cells and exacerbates experimental autoimmunity. Based on this work, an interdisciplinary research team, including the groups of Müller and Kleinewietfeld and of Prof. Ralf Linker (University of Erlangen, Germany) and Prof. Eric Alm (MIT, USA) now further investigated this issue and found that excess salt intake not only has a direct effect on immune cells but also affects them indirectly by altering the gut bacteria. Excess salt intake decimates lactobacilli in the gut and thereby reduces bacterial metabolites that keep the detrimental immune cells in check. These so called Th17 immune cells are believed to be associated with the development of hypertension and autoimmunity.
Probiotics could counteract salt-sensitive diseases
Intriguingly, further experiments discovered a therapeutic potential of lactobacilli in salt-sensitive disease models of hypertension and autoimmunity. When the animals were given probiotic lactobacilli in addition to the high-salt diet, the frequency of Th17 cells decreased once again and blood pressure dropped. The probiotics also alleviated the clinical symptoms of experimental autoimmune encephalomyelitis, a disease model for MS. A similar effect of high-salt intake on gut bacteria was also observed in a pilot study of healthy human probands, alongside with changes in Th17 cells and blood pressure. “These are very interesting findings with a potential for the development of novel therapeutic options”, says Immunologist Prof. Markus Kleinewietfeld from the VIB Center for Inflammation Research in Hasselt. “However”, he admits, “at this point, we are just at the beginning to understand the complex interplay between food intake, gut bacteria and immunity and its role for disease”.
Nicola Wilck et al. (2017): “Salt-responsive gut commensal modulates TH17 axis and disease.” Nature. doi:10.1038/nature24628