Scientist working to break vicious cycle causing vision loss in diabetes

June 27, 2013, Medical College of Georgia

it's a vicious cycle that robs people with diabetes of their vision.

The hallmark of the disease causes inflammation that produces that cause inflammation that produces more free radicals, explains Dr. Manuela Bartoli, vision scientist at the Medical College of Georgia at Georgia Regents University.

If that's not bad enough, the body's endogenous system for dealing with free radicals also is dramatically impacted by diabetes, said Bartoli, who recently received a $1.8 million grant from the National Eye Institute to try to bolster that system and interrupt the destructive cycle.

Nearly 10 percent of the U.S. population has diabetes, according to the National Diabetes Foundation, and nearly half those individuals will develop , according to the National Eye Institute.

Culprit free radicals are actually normal byproducts of the body's constant use of oxygen and, despite their derivative status, also are important signaling molecules in the body. Problems result when there are too many, like in diabetes, and their natural tendency to bond starts on cells and DNA. In fact, excessive levels are thought to be a major contributor to a wide variety of diseases as well as aging.

The thioredoxin system typically works to maintain a healthy level of free radicals by neutralizing excess but, like many body systems, the thioredoxin system slows with age and diabetes hastens the process.

"This increase in free radicals results in an inability to put them to good use," Bartoli said. "Instead, we accumulate the damage they induce." In the case of the eyes and diabetes, over time the overwhelmed system destroys blood vessels that deliver blood and nutrition. In another biological irony, the starving eyes grow new blood vessels but they are fragile, leaky and often misplaced so ultimately they destroy vision.

Bartoli believes a selenium supplement could give the thioredoxin system the shot in the arm needed to stay efficient and effective. Selenium is a byproduct itself, resulting from copper-refining and used to make glass, alloys and more. It is also found in fish, nuts and grains.

Thioredoxin reductase, a protein essential to the recycling of the system, is dependent on selenium and Bartoli has found that protein's activity is reduced in an animal model of diabetic retinopathy and in retinas of human diabetic donors. Bartoli believes the cascade of cellular change resulting from high glucose levels impairs thioredoxin reductase. So she wants to better understand how the system works, exactly what happens to thioredoxin reductase and whether supplements of selenium can help the natural antioxidant system work better in diabetes.

In a related study, funded by the International Retinal Research Foundation, she is looking for an early sign of eye damage and possibly another window of intervention.

Currently, swelling of the macula – the central part of the retina responsible for central vision – is the first sign of treatable trouble. Anti-inflammatories injected into the eyes can help.

However increased blood levels of uric acid, a part of the inflammatory process that leads to swelling, may be an earlier indicator, Bartoli said. Uric acid is a byproduct of purine metabolism and is typically eliminated in the urine. High uric are associated with cardiovascular disease and gout as well as diabetes but it hasn't been well studied in the eye.

"We want to validate hyperuricemia as a risk factor for progression of diabetic retinopathy," she said. So she and her colleagues are measuring levels in the blood and eye fluid to see if they correlate with each other and with progressive eye damage. They also are reducing uric acid levels by giving two drugs already on the market, one that blocks formation and another that enhances excretion. Thinking that uric acid levels also may be a biomarker, she eventually wants to see how uric acid levels correlate with disease progression in humans.

"As the ancients said: 'The eyes are the mirror of the soul.' We also know that whatever happens in the eye is an expression of what is happening in the rest of the body," Bartoli said. "We want to better understand the causes of inflammation in the eye in and find better ways to manage it as well as such as . Ultimately, of course, we hope to protect sight."

A National Eye Institute fellowship to GRU Graduate Student Folami Lamoke also is supporting the thioredoxin sudies. Bartoli is a faculty member in the MCG Department of Ophthalmology and the GRU James and Jean Culver Vision Discovery Institute.

Explore further: Vitamin C does not lower uric acid levels in gout patients

Related Stories

Vitamin C does not lower uric acid levels in gout patients

May 16, 2013
Despite previous studies touting its benefit in moderating gout risk, new research reveals that vitamin C, also known ascorbic acid, does not reduce uric acid (urate) levels to a clinically significant degree in patients ...

Protein block stops vascular damage in diabetes

June 5, 2013
Researchers at Lund University in Sweden have discovered how to stop the destructive process that leads to cardiovascular disease in diabetic laboratory animals.

Diabetes leading to blindness in many people

November 30, 2012
Diabetes is the leading cause of new cases of blindness among adults 20 to 74 years old. Dr. Michael Grodin, co-director of retinal services and director of clinical research at Katzen Eye Group, with locations around Baltimore, ...

Abnormal levels of uric acid in teens linked to high blood pressure

May 1, 2012
Teens with high levels of uric acid appear to be at increased risk for high blood pressure, according to results of research from scientists at the Johns Hopkins Children's Center.

Sharp rise in diabetic eye disease makes American Diabetes Month ever more important

November 7, 2012
Diabetes is the leading cause of blindness among working-age adults in the United States. According to recent studies funded by the National Eye Institute (NEI), diabetic retinopathy, one of the most common and debilitating ...

New study aims to use stem cells to help save sight of diabetes sufferers

February 14, 2013
Scientists at Queen's University Belfast are hoping to develop a novel approach that could save the sight of millions of diabetes sufferers using adult stem cells.

Recommended for you

Injection improves vision in a form of childhood blindness

December 17, 2018
A new treatment for patients with a form of congenital retinal blindness has shown success in improving vision, according to results published today in Nature Medicine led by researchers at the Scheie Eye Institute in the ...

Researchers report vision-based neurotransmitter events for the first time

November 27, 2018
How does vision work, and what happens in the brain during the process? As simple as this question may sound, it has yet to be scientifically clarified. Dr. Valentin Riedl of the Technical University of Munich (TUM) and his ...

Minimally invasive retinal detachment has better outcomes, clinical trial findings

November 26, 2018
A minimally invasive treatment for retinal detachment gives patients sharper vision, less distortion and reduced side-effects, according to the findings of a randomized controlled trial performed at St. Michael's Hospital ...

Scientists combine technologies to view the retina in unprecedented detail

November 14, 2018
By combining two imaging modalities—adaptive optics and angiography—investigators at the National Eye Institute (NEI) can see live neurons, epithelial cells, and blood vessels deep in the eye's light-sensing retina. Resolving ...

Eyepatch with dissolvable needles used to treat eye disease

November 12, 2018
A team of researchers affiliated with several institutions in Singapore has developed an eyepatch with dissolvable needles for use in treating eye diseases. In their paper published in the journal Nature Communications, the ...

Calcifications in the eye increase risk for progression to advanced AMD by more than six times

November 8, 2018
Calcified nodules in the retina are associated with progression to late stages of age-related macular degeneration (AMD). Experts from Queen's University Belfast, working in partnership with the University of Alabama of Birmingham ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.