Multiple sclerosis (MS) is a disease of the nervous system that disrupts the flow of information between the brain and the body. The disease involves a process mediated by the immune system which elicits an abnormal response to the central nervous system (CNS) which includes the brain, spinal cord, and optic nerves. In the brain, the immune systems attacks the myelin sheath leading to the development of scar tissue, also known as sclerosis from which the name of the disease is derived. The Myelin sheath is the protective coating around the nerve fibers in the CNS. Because of the buildup of scar tissue in the brain, nerve impulses sent to and from the spinal cord are interrupted which produces a wide array of physical symptoms in those affected.
MS is thought to be an epigenetic disease, meaning it is triggered by a combination of genetic and environmental factors. For example, epidemiological data shows that MS occurs more frequently in geographic locations farther away from the equator. It is hypothesized that this may have something to do with vitamin D deficiencies in places father away from the equator. Other environmental factors including exposure to infections, sodium intake, and smoking are also thought to affect MS activity. Despite the amount of research surrounding MS, the exact cause of the disease is still not known.
A new study published this month in Cell
based on previous research showing the associations of lower levels of vitamin D and MS relapse rates discusses the effects of seasonal fluctuations in melatonin levels and MS activity. The authors explain that a significant seasonal fluctuation in vitamin D levels is observed in most geographic locations. Therefore; vitamin D synthesis is regulated by sun exposure. Peaks in sun exposure would be experienced in spring-summer and deficiencies experienced in fall and winter. Other research has shown that an increase in MS symptoms is experienced in spring and summer and relapse is highest in fall and winter.
Researchers from the Center for Research on Neuroimmunological Disease (CIEN) in Buenos Aires, Argentina discovered that melatonin levels are negatively correlated with MS disease activity in humans. Using a mouse animal model they observed a reduction in MS symptoms in mice when treated with melatonin. It was determined that the mode of action of melatonin in this case involved blocking the differentiation of pathogenic cells while boosting the generation of protective cells. It was concluded that melatonin production is another environmental factor associated with autoimmune disorders including MS. This research has also allowed for the identification of melatonin-based pathways as potential drug targets for the treatment of MS.
Sources: Cell; The National MS Society; AAAS Science News