Posted on 03/22/2010 12:49:21 PM PDT by decimon
MADISON — For more than 30 years, scientists have known that multiple sclerosis (MS) is much more common in higher latitudes than in the tropics. Because sunlight is more abundant near the equator, many researchers have wondered if the high levels of vitamin D engendered by sunlight could explain this unusual pattern of prevalence.
Vitamin D may reduce the symptoms of MS, says Hector DeLuca, Steenbock Research Professor of Biochemistry at University of Wisconsin-Madison, but in a study published in PNAS this week, he and first author Bryan Becklund suggest that the ultraviolet portion of sunlight may play a bigger role than vitamin D in controlling MS.
Multiple sclerosis is a painful neurological disease caused by a deterioration in the nerve's electrical conduction; an estimated 400,000 people have the disabling condition in the United States. In recent years, it's become clear the patients' immune systems are destroying the electrical insulation on the nerve fibers.
The ultraviolet (UV) portion of sunlight stimulates the body to produce vitamin D, and both vitamin D and UV can regulate the immune system and perhaps slow MS. But does the immune regulation result directly from the UV, indirectly from the creation of vitamin D, or both?
The study was designed to distinguish the role of vitamin D and UV light in explaining the high rate of MS away from the equator, says DeLuca, a world authority on vitamin D.
"Since the 1970s, a lot of people have believed that sunlight worked through vitamin D to reduce MS," says DeLuca. "It's true that large doses of the active form of vitamin D can block the disease in the animal model. That causes an unacceptably high level of calcium in the blood, but we know that people at the equator don't have this high blood calcium, even though they have a low incidence of MS. So it seems that something other than vitamin D could explain this geographic relationship."
Using mice that are genetically susceptible to MS-like disease, the researchers triggered the disease by injecting a protein from nerve fibers. The researchers then exposed the mice to moderate levels of UV radiation for a week. After they initiated disease by injecting the protein, they irradiated the mice every second or third day.
The UV exposure (equivalent to two hours of direct summer sun) did not change how many mice got the MS-like disease, but it did reduce the symptoms of MS, especially in the animals that were treated with UV every other day, DeLuca says.
The research group also found that although the UV exposure did increase the level of vitamin D, that effect, by itself, could not explain the reduced MS symptoms.
In some situations, radiation does reduce immune reactions, but it's not clear what role that might play in the current study. "We are looking to identify what compounds are produced in the skin that might play a role, but we honestly don't know what is going on," DeLuca says. "Somehow it makes the animal either tolerate what's going on, or have some reactive mechanism that blocks the autoimmune damage."
MS is a progressive neurological disease with few effective treatments, but DeLuca stresses that the study, however hopeful, may or may not lead to a new mode of treatment. "There are several ways this could go. If we can find out what the UV is producing, maybe we could give that as a medicine. In the short term, if we can define a specific wavelength of light that is active, and it does not overlap with the wavelengths that cause cancer, we could expose patients who have been diagnosed with MS to that wavelength."
Does this information change the common prescription to avoid excessive sun exposure? "If you have an early bout with MS, then you have to think about your options," says DeLuca. "Remember, this is just experimental work at this stage. Whether it can be translated into practical applications on MS remains to be seen."
###
Ping.
thanks decimon
First we’re told to use sunscreen to prevent skin cancer. Next we’re told that sunscreen hinders the body from receiving vitamin D plus sunlight helps depression and also cholesterol levels. Now they’re saying “nope” it’ll cause MS - is this an “Everybody Panic” yet again story?
Nope.
This person forgets one thing. To tell an MS patient to "go in the sun" is not usually an option. Many, many MS patients are heat sensitive, and cannot tolerate warm temperatures that they'd encouter from sitting in the sunlight.
There is still a lot of research to be done on the effect of sunlight.
It is well known that sunlight exposure increases the risk of melenoma but that melenoma is just as likely to crop up in a non exposed area as exposed. This has lead to the theory that the UV is modulating the immune system, not just damaging local skin cells.
It would not be suprising to find out that the immunological changes from sun exposure would affect the incidence or severity of an immune related disease as MS is thought to be.
Read it backwards? Like it reduces the symptoms of MS?
I have met so many people with MS lately. Some are really suffering. I pray they get a handle on this illness.
Thanks for posting this.
This article does not differentiate between UVA and UVB.
To recap, UVB creates vitamin D in the skin. In northern latitudes, UVB is blocked by the atmosphere in wintertime. If I have it right, UVA is not so blocked. Maybe UVA has as yet undiscovered effects on humans.
You are welcome.
Skin is the largest organ. It was also designed to deal with the environment which includes sunshine. There are probably a whole host of interactions that are yet to be discovered.
Keep up the good work, I enjoy the articles you post.
Thank you.
These mice can say what ails them?
Aristotle counseled moderation.
It is excessive exposure that produces cancer. Americans always take everything to extreme and have become lotion slathered troglodytes.
Thanks.
Need more research on the effects of UV and on what different parts of the light spectrum do to us.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.