Age related macular degeneration clue discovered

An international team of researchers have found a clue to one of the leading causes of blindness, which they hope could eventually lead to a cure.

Loss of sight with macular degeneration

Age-related macular degeneration affects 500,000 people in the UK and is incurable.

The study in the journal Nature found an enzyme known as DICER1 that stops functioning, resulting in the illness.

UK experts said it had the potential to be an important breakthrough.

The macula is a part of the eye which sits in the centre of the retina and is responsible for the fine detail at the centre of the field of vision.

As the disease progresses that central vision declines, making reading, driving and recognising people difficult.

It affects one in 50 people over 50 and one in five people over 85.

The exact cause is unknown, but risk factors include smoking, high blood pressure and having relatives with the condition.

Potential breakthrough
The researchers noticed the enzyme DICER1 was less active in the retina of people with the more common "dry form" of the illness and when they turned off the gene which makes the enzyme in mice, then the animal's retina cells were damaged.

It was then discovered that DICER1 is necessary for destroying small pieces of genetic material called Alu RNA.

Without DICER1, the Alu RNA accumulates with toxic consequences leading to the death of the retina.

Professor Jayakrishna Ambati, from the University of Kentucky, told the BBC: "This work opens many new doors of research.

"First, we need to identify various classes of molecules that can either increase DICER1 levels or block Alu RNA so that these can be evaluated in clinical trials.

"Second, we need to understand more about the biological processes that lead to reduction in DICER1 levels and the precise source of the Alu RNA transcripts."

Professor Ian Grierson, school of clinical sciences at the University of Liverpool, said: "This is a great piece of science which provides another jigsaw piece which we need to put together with other findings.

"It was done in an animal model which is a long way from the patient, the breakthrough is we've got another player."

Professor Mike Cheetham, head of molecular and cellular neuroscience at UCL, said: "It's a potentially very important breakthrough which gives insight into this dry form of the disease.

"It could provide new pathways to therapy, but the findings need to be validated by other researchers."

Supplemental lutein and DHA may help prevent macular degeneration

Macular pigment optical density (MPOD) is a measure of retinal concentrations of lutein and zeaxanthin, two antioxidants acquired from the diet. Docosahexanoic acid (DHA) is an omega-3 fatty acid found in the retina of the eye. 

 

New research shows that supplementing with lutein and DHA may help reduce the risk of age-related macular degeneration (AMD) by increasing MPOD. In a study recently conducted at Tufts University in Boston, researchers randomly assigned 49 women (between 60 and 80 years old) to one of four groups: placebo, DHA (800 mg/d), lutein (12 mg/d), or a combination lutein + DHA supplement. The objective of this four month study was to determine the effects of lutein and DHA on the women's serum concentrations and macular pigment optical density (MPOD). In all supplement groups, blood nutrient levels were higher at two and four months than at the beginning of the study. DHA supplementation resulted in central increases of macular pigment density, while lutein was associated with eccentric, or away from the center, increases. Supplementing lutein and DHA may help reduce the risk of age-related macular degeneration by increasing MPOD, helping protect the macula from oxidative damage, and increasing lutein transport into the macula. Source: The influence of supplemental lutein and docosahexaenoic acid on serum, lipoproteins, and macular pigmentation, Johnson et al, American Journal of Clinical Nutrition, Vol. 87, No. 5, 1521-1529, May 2008