< link rel="DCTERMS.isreplacedby" href="http://caltechgirlsworld.mu.nu/" /> Not Exactly Rocket Science: Interesting medical news (long post, sorry)

Friday, March 11, 2005

Interesting medical news (long post, sorry)

It seems that three teams of researchers have together found a gene that is responsible, not for causing macular degeneration, but for predisposing carriers to develop macular degeneration.
According to the story:
"Age-related macular degeneration affects between 10 million and 15 million people in the United States alone and is the leading cause of blindness among the elderly. By the age of 75, as many as 30 percent of Americans have some symptoms of the condition.

The macula is a circular area at the center of the retina and is packed with cones, the structures that help in seeing color, detect motion and making out fine detail.

As part of the normal aging process, yellowish waste deposits called drusen accumulate around the macula, but in AMD, they are bigger and there are more of them. They kill cells in the eye, affecting central vision.

Smoking, obesity, and a high-fat diet are all known to raise the risk of AMD, while eating fruits and vegetables lowers the risk. But there is also a genetic component. "We know that one of the most significant factors in determining who gets macular degeneration is family history," said ophthalmologist Dr. Albert Edwards of the University of Texas Southwestern Medical Center, who led one of the studies."

Interesting. The gene that they isolated is called complement factor H (CFH), and functions as part of the immune system, specifically involved in the regulation of inflammation. So essentially, this find not only identifies the genetic component of AMD, it also pegs the disease as yet another auto-immune disorder. One could postulate a mechanism of action whereby mutated CFH leads to dysregulated inflammation in the eye, which in turn causes the heavier than normal build up of the drusen deposits. Of course, this would be heavily influenced by 1) the function of other genes involved in inflammatory regulation and 2) how much inflammation is present.

If you have more inflammation, it's more likely that you'll have problems caused by an abnormal response to it. Guess which things are all associated with increased inflammation? Age, obesity. smoking, high-fat foods, etc. Sound familiar? (see above if your attention span is too short ...)

Interestingly, positing AMD as an auto-immune disorder related to control of inflammation casts it in the same light as cardiovascular disease: Increased inflammation leads to build up of sticky goo that eventually clots up the whole works and kills the cells that are important for some function. In the case of CVD, it's lack of oxygen to the heart muscle resulting in a heart attack, in AMD, it's lack of nutrients and signal transduction, leading to nerve damage and eventually blindness.

On the other hand (pun intended) this story is interestingto me for two reasons. First, since I already have a haywire immune system that thinks my joints are full of goo from outer space, sometimes I wonder what else I'm going to attack in my own body, just for fun, of course.

Second, if you pay attention to health news, you may have noticed that auto-immune disorders are on the rise in the western world. This is so for 2 reasons: more disorders are being recognized as having an auto-immune component, and more people are being diagnosed with them. The auto-immune spectrum now includes the "classic", rare AI diseases (RA, Lupus, Grave's Disease, etc.) as well as number of more common diseases: diabetes, MS, and asthma, to name a few. So I wonder what the real cause is. Nominally, it's a bad reaction to stress on the body, but what that entails is not clear, nor is it clear what "stress" even means in this case, except EXTREMELY generally, even to those of us who study the molecular consequences of the stress response..... Something to think about, though.


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