Fats, sugar and energy: a new way to think of treating wet AMD?
Research points to a potentially safer way to stop sight-threatening blood vessels growing in the eye
New research published in Nature Medicine could change the approach to treating two blinding conditions: the ‘wet’ form of age-related macular degeneration (AMD) and macular telangiectasia (MacTel).
AMD is the leading cause of blindness in older people. It affects the macula – the central part of the light-sensitive layer of the eye (the retina) – that we use for detailed vision.
About 1 in 10 people with AMD have the wet form. MacTel is more rare, but both conditions involve new, unhealthy blood vessels growing under the macula. Healthy blood vessels supply oxygen and nutrients to the retina. But in AMD and MacTel, the new vessels leak, damage the tissue and lead to sight loss.
Light-detecting ‘photoreceptor’ cells in the retina need to use lots of energy to keep working. It was thought that they were powered by glucose – a type of sugar.
But the new research shows that, like other parts of the body that use lots of energy, photoreceptors need fats (lipids) as well as glucose. Importantly, the researchers found that when certain types of fat are at unusually high levels in the blood, photoreceptors stop taking in glucose, even though they still need it.
Starved of energy
Energy-starved photoreceptors then call for new blood vessels to bring them nutrients. They do so by putting out lots of a substance called vascular endothelial growth factor (VEGF).
Drugs that block VEGF are already used to treat wet AMD but they have side effects throughout the body, stopping new blood vessels from growing where they are healthy and needed. The researchers think that developing drugs to target the energy problem before VEGF gets involved could mean better, safer treatment.
The research was done in mice, so the team’s next steps will be to find out whether photoreceptors in people use lipids too.
“As the study authors note, energy efficiency and control of fats in the body declines with age and problems with both are linked to AMD, so this is an important new line of research,” said Dr Dolores M Conroy, Director of Research at Fight for Sight. “Preventing photoreceptors from using the fats that shut out glucose may be a potential way to stop wet AMD developing, which is the top priority for AMD research identified by the Sight Loss and Vision Priority Setting Partnership. So we will follow the results in humans with interest.”