Too much salt may trigger autoimmune diseases: studies

The findings suggest that salt may play a previously unknown role in triggering autoimmune diseases such as MS or type 1 diabetes in individuals who are already genetically predisposed.

“It’s not bad genes. It’s not bad environment. It’s a bad interaction between genes and the environment,” said Dr. David Hafler,a professor of immunobiology at Yale University in New Haven,Connecticut,and senior author of one of the three papers.

High salt intake is already a known culprit in increasing the risk of heart disease and hypertension. The new study now implicates high-salt diets in increasing rates of autoimmune disease. “It can’t be just salt. We know vitamin D probably plays a small component. We know smoking is a risk factor. This now suggests that salt is also a risk factor,” Hafler said.

“How much? We don’t know,” he added.

Hafler became interested in studying the link between salt and autoimmunity through studies of the gut microbiome — a census of gut microbes and cell function of 100 healthy individuals.

The team noticed that when people in the study visited fast food restaurants more than once a week,they saw a marked increase in levels of destructive inflammatory cells,which the immune system produces to respond to injury or foreign invaders,but which attack healthy tissues in autoimmune diseases.

He shared these findings with colleagues at Harvard Medical School and the Broad Institute of Harvard and the Massachusetts Institute of Technology and others who were working out what factors induce the activity of a type of autoimmune cell known as a T helper 17 or a Th17 cell.

Th17 cells can promote inflammation that is important for defending against pathogens,but they have also been linked to diseases like multiple sclerosis,psoriasis,rheumatoid arthritis,and ankylosing spondylitis. Treatment options for some of these diseases,such as psoriasis,include manipulating T cell function.

“The question we wanted to pursue was: How does this highly pathogenic,pro-inflammatory T cell develop?” said Vijay Kuchroo of the Harvard-affiliated Brigham and Women’s Hospital and a member of the Broad Institute.

“Once we have a more nuanced understanding of the development of the pathogenic Th17 cells,we may be able to pursue ways to regulate them or their function.”

Hafler said Kuchroo’s team worked on tracing how these immune cells were wired,and what triggered their development. They identified a specific gene known as SGK1 that plays an important role in the cells’ development. This gene had not been seen in T cells before,but it has been known to play a role in absorbing salt in the gut and kidneys.

Researchers at Harvard and Yale and colleagues in Germany led by Dominik Mueller looked to see whether a high-salt diet could induce the destructive immune system response that is the hallmark of autoimmunity.