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Genes Discovered That Identify Macular Degeneration

Macular degeneration

Scientists have discovered more than 50 genes that can help identify macular degeneration, according to a new study in Genome Medicine. The top 20 genes on the list were capable of “predicting” a clinical diagnosis of age-related macular degeneration, a major cause of blindness in the world.

Gene discovery may lead to new treatments

Researchers have known there is an inheritable genetic risk factor associated with the disease and that the genes linked to fat metabolism and the innate immune system are involved. The innate immune system is like the body’s first responder: it provides immediate defense against invading organisms and infection, but does not provide long-lasting or immunity.

This is the first study to examine the differences in gene expression between normal eyes and those affected by macular degeneration.

Scientists from three institutions—University of California Santa Barbara, University of Utah John Moran Eye Center, and University of Iowa—evaluated genes from a human donor eye repository and identified those that had abnormally high levels in age-related macular degeneration.

Of the more than four dozen genes identified by the researchers, they named 20 that play different roles in the disease and that are capable of predicting a clinical diagnosis. The genes are involved in inflammation, the innate immune system, wound healing, and disease severity for advanced macular degeneration.

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The rising tide of macular degeneration
Macular Degeneration Research reports that about 11 million people in the United States have some form of age-related macular degeneration. That figure is expected to double by the year 2050. The disease typically affects people older than 50, although it does occur in younger individuals.

As the population ages, there is growing concern about the increasing numbers of people who will develop macular degeneration. Along with the genetic factor, there are other accepted risk factors for the disease, some of which individuals can control.

  • Age: one-third of adults older than 75 are affected by the disease
  • Race: Caucasians are more likely to develop the disease
  • Smoking: The retina needs a lot of oxygen, and smoking reduces the body’s oxygen delivery. If you smoke, your chances of developing age-related macular degeneration increase by two- to fivefold.
  • High blood pressure: Hypertension causes narrowing of the blood vessels that provide the retina with nourishment
  • Gender: Women are more likely to get the eye disease, likely because they tend to live longer than men
  • Obesity: Individuals with a body mass index greater than 30 are 2.5 times more likely to be affected by macular degeneration
  • Family history: The risk increases if someone in your immediate family has the disease.
  • Prolonged sun exposure: Ultraviolet rays damage the retina and can also cause substances to accumulate that harm the retina
  • Poor diet: A diet high in fat, sugar, and cholesterol and low in antioxidants can contribute to the development of age-related macular degeneration.
  • Eye color: Blue-eyes individuals are more likely to be affected than those with darker eyes.
  • Lack of exercise: Physical exercise promotes cardiovascular health and good blood circulation, and the retina is a high consumer of oxygen from the blood.

Although there is a genetic factor involved in the development of age-related macular degeneration, experts believe it is highly likely multiple factors have a role in the disease, including the risk factors named.

According to Dr. Monte Radeke, one of the project leaders of the new study, “Now that we know the identity and function of many of the genes involved in the disease, we can start to look among them to develop new diagnostic methods, and for new targets for the development of treatments for all forms of AMD.”

The discovery of genes that identify macular degeneration will hopefully open the door to preventive and treatment options that put the brakes on this important cause of vision loss and blindness.

Macular Degeneration Research
Newman AM, Gallo NB, Hancox LS, Miller NJ et al. Systems-level analysis of age-related macular degeneration reveals global biomarkers and phenotype-specific functional networks. Genome Medicine 2012 Feb 24; 4:16

Image: Courtesy Wikimedia Commons