Dietary interventions could slow onset of autoimmune disorders, study finds

Significantly reducing dietary levels of the amino acid methionine could slow onset and progression of inflammatory and autoimmune disorders such as multiple sclerosis in high-risk individuals, according to new findings published today in the journal Cell Metabolism.

While many cell types in the body produce methionine, the immune cells responsible for responding to threats like pathogens do not. Instead, the methionine that fuels these specialized cells, called T cells, must be ingested through food consumption. Although methionine is found in most foods, animal products such as meat and eggs contain particularly high levels.

Autoimmune disorders occur when the immune system mistakenly attacks and destroys healthy tissue. For example, in multiple sclerosis, the most common inflammatory disease of the central nervous system, the myelin sheath that protects nerve cells in the brain and spinal cord is targeted by the immune system. The subsequent damage impedes messages traveling to and from the brain, resulting in progressively worsening symptoms like numbness, muscle weakness, coordination and balance problems, and cognitive decline. There currently are no treatments that significantly slow or stop multiple sclerosis without greatly increasing the risk of infection or cancer.

During an immune response, T cells flood the affected area to help the body fend off pathogens. The research teams found dietary methionine fuels this process by helping "reprogram" T cells to respond to the threat by more quickly replicating and differentiating into specialized subtypes. Some of these reprogrammed T cells cause inflammation, which is a normal part of an immune response but can cause damage if it lingers, such as the nerve damage that occurs in multiple sclerosis.

The researchers also found that significantly reducing methionine in the diets of mouse models of multiple sclerosis altered the reprogramming of T cells, limiting their ability to cause inflammation in the brain and spinal cord. The result was a delay in the disease's onset and slowed progression.

The study is the latest to spotlight methionine-restricted diets as possible treatments for disease. A 2019 study from the Locasale Lab at Duke University demonstrated that reducing methionine could improve the effects of chemotherapy and radiation in fighting cancer.

"Methionine is critical for a healthy immune system,” said Russell Jones, PhD, senior author of the study and program leader of Van Andel Institute's Metabolic and Nutritional Programming. “Our results suggest, for people predisposed to inflammatory and autoimmune disorders like multiple sclerosis, reducing methionine intake can actually dampen the immune cells that cause disease, leading to better outcomes. These findings provide further basis for dietary interventions as future treatments for these disorders."