JENNIE: Vitamin D and your eyes

JENNIE Season 2, Episode 2

Dr. Mitch Watsky and Dr. Amy Estes from the Medical College of GA at Augusta University
Dr. Mitch Watsky and Dr. Amy Estes from the Medical College of GA at Augusta University

AUGUSTA, Ga–  Vitamin D deficiency is rampant in the U.S. Now, doctors at the Medical College of Georgia at Augusta University are studying the role too little Vitamin D plays when it comes to eye diseases and injuries.

Corneal Specialist Dr. Amy Estes and Dr. Mitch Watsky, Dean of the graduate school at AU explain their research on today’s Jennie show.

Dr. Watsky: We were doing some work with bone and skin looking at vitamin D and because of my longstanding work in the cornea, we were curious as to whether or not, because the cornea is the only other organ exposed to the sun, whether it could make and activate vitamin D. And we discovered that sure enough it could… And the important thing is that the cells in the cornea can activate the vitamin D and be able to utilize it, for example, to help healing in the epithelium of the cornea, which are the cells that face the tear and the outside environment.

Dr. Epps:  So any kind of trauma, a scratch on the eye, or an injury to the eye, infections, that’s really the first layer that they kind of attack and thinks like that. So it’s really, you know, the first line of defense in terms of eye health and the surface of the eye. So it’s really exciting that there might be a compound or a product that could help heal faster. So, whenever you have a scratch on the eye or anything like that, you can potentially get bacteria or infection in there just like you could if you had a scratch on your skin. So if there were a way to heal that layer more quickly, that would be great from a clinical standpoint.

Jennie: And you’re saying vitamin D is what could give it that boost?

That’s what we’re hoping.

Jennie: Would taking the supplements help in the same way as being outside without sunglasses?

So, what our thought is that probably in people who have normal vitamin D levels, that additional vitamin D probably isn’t going to be that helpful, that it’s mainly going to be important for those people who are deficient or insufficient in vitamin D, that bringing it up to a normal level either through diet or through some kind of supplementation in the eye could be very helpful. There are a number of studies that have shown for example that people who live in northern latitudes where it’s really cold and they’re wearing a lot of clothes or don’t go outside a lot have much lower vitamin D levels than people in the south who do tend to wear short sleeves, short pants and get more sun exposure.

Jennie: Now, I want to ask you one more thing. Where do you get the corneas? I mean, how are you doing your research?

Dr. Watsky: So, we’re doing animal research on the one hand, where we’re primarily using mice and those mice have been genetically modified so that typically vitamin D won’t actually work on them. So we can see what happens when you have no vitamin D around. And then the other half of what we’re doing is we use cell culture where we use donor corneas. So what we use is what’s leftover after they use the transplant part of the cornea. So, Dr. Estes will do a cornea transplant and there’s a small part of the tissue that’s left over that we then get to grow the cells off of.

Press Release:  Injury or disease in combination with too little vitamin D can be bad for the window to your eyes.

The three-layer, transparent cornea at the front of the eyes focuses the light coming in. But its prominent position also puts it at risk for injury from an errant mascara wand or over-prodding finger or a car accident.

Scientists exploring the role of vitamin D in the cornea in both sickness and health hypothesize that too little vitamin D can significantly hamper the cornea’s recovery in these scenarios.

“We don’t think low vitamin D by itself causes problems; what we think is if you have an underlying problem, then low vitamin D levels can become an issue,” says Dr. Mitchell Watsky, dean of The Graduate School at Augusta University and professor in the Department of Cellular Biology and Anatomy at the Medical College of Georgia.

“Our hypothesis is that low vitamin D makes other conditions worse, essentially,” says the physiologist, cell biologist and vision scientist. Watsky just received a $1.6 million grant from the National Eye Institute to see if he and his research team can shed more light on their theory.

They are looking at healing rates from small scratches, like we might make with our fingernail, in both normal as well as diabetic vitamin D receptor knockout mice and are examining any physical changes to the cornea.

His research team has shown that a corneal wound takes much longer to heal in mice just missing the vitamin D receptor. “That leads us to hypothesize that vitamin D is stimulatory for wound healing,” Watsky says. Now they are adding diabetes, which often has corneal complications, to the equation.

They also want to know more about which forms of vitamin D are active in the cornea. They have emerging evidence that 24, 25D, long considered an inactive metabolite of the vitamin, is present in high levels and may be important. They are looking to see what the metabolite does to the cell proliferation and migration needed for proper wound healing. They also want to know how 24, 25D works because they have evidence it just may not be through the usual vitamin D receptors.

His research team has found one thing vitamin D does in health is improve cell communication. The cytoplasm holds most of the cell’s content. Although it’s about 90 percent water, it’s where most of the action happens, like cell division. Things like sugars, amino acids, proteins and vitamins tend to be found in this major cell component. Between corneal cells is a tunnel-like protein where they can swap cytoplasm contents and communicate, which enables homeostasis.

“It’s like a tunnel with a green and red light,” Watsky says. Interestingly, when there is a corneal injury, affected cells immediately shut down these gap junctions in an apparent attempt to protect nearby cells, then reconnect if/when the cells recover.

Watsky and his research team have shown that vitamin D normally enhances cell connectivity via the gap junction. “When we experimentally apply vitamin D, it will improve how well they are connected normally,” Watsky says. Much as low vitamin D leads to weak bones, they now want to see if a lack of the vitamin also negatively impacts the density and distribution of the connectivity protein in mice missing just the vitamin D receptor. In cell culture, they also are examining donor corneal tissue trimmed during a corneal transplant, to see whether vitamin D supplementation affects cell connectivity.

Patients with extreme vitamin D deficiency, such as children with rickets, which is characterized by super weak bones and stunted growth, don’t typically also have clearly related vision problems, Watsky notes. That’s one of the reasons he and his team think that vitamin D related problems primarily surface when other problems, like disease and/or injury, do as well.

Earlier collaborative studies on the bone started Watsky looking at vitamin D and thinking about the reality that the only other organ that gets direct sunlight exposure, other than the skin, is the eye. As others have discovered that vitamin D receptors are pervasive throughout the body, not just in bone, Watsky has found them in the cornea. His 2011 paper in the journal Investigative Ophthalmology & Visual Science provided evidence that corneas contain the mRNA required to make vitamin D receptors as well as the enzyme required to convert inactive forms of the vitamin to active forms. “It’s there, it’s active, what does it do?” Watsky says.

Whether vitamin D is important in wound healing in other areas of the body remains a largely unexplored question, he says.

The “sunshine” vitamin is being identified as a factor in an increasing number of diseases, including diabetes, cardiovascular problems, even multiple sclerosis. Higher levels are associated with lower weight. Vitamin D is known to turn inflammation levels down and to reduce levels of damaging reactive oxygen species. Sunlight is the major source of vitamin D. Natural food sources including fish and fish oil, milk and egg yolks.

Nearly 10 percent of the American population has diabetes. A 2010 study published in the Archives of Internal Medicine reported that 75 percent of us have a vitamin D deficiency. While diabetic retinopathy is more commonly associated with diabetes, corneal damage, called diabetic keratopathy, affects about 70 percent of those individuals.

Potential causes of minor or more catastrophic corneal injuries are extensive and the results can be painful in this area, which has a higher density of sensory nerve receptors than any other tissue in the body.

“If you think about it, in what other part of your body would you feel an eyelash and have it be so disturbing,” Watsky says.

Corneal tissue is being provided by the MCG Department of Ophthalmology and Eye Physicians and Surgeons of Augusta, PC. Keratoconus, a gradual thinning and bulging of the cornea, and Fuchs’ Dystrophy, a loss of the frontline epithelium cells that causes the cornea to swell and thicken, along with injuries or infections that don’t properly resolve are major reasons people need corneal transplants.

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