Study of substances in blood suggests choroideremia is not just an isolated eye disease

Young boys suffer from difficulty with their night vision, followed by loss of their peripheral visual field and then complete vision loss later in life.

The disease is caused by genetic changes in a single gene called CHM, which is responsible for producing a protein known as REP1. The lack of this protein causes the light sensitive layer at the back of the eye, the retina, to degenerate.

Up till now, choroideremia has been considered to just cause sight loss in patients. However, in this latest study published in the Journal of Clinical Investigation Insights by Professor Mariya Moosajee and her team at UCL and Moorfields Eye Hospital, it seems that choroideremia may be affecting other body systems, although this will need to be confirmed with further investigations.

Twenty-five male choroideremia patients had blood taken and analysed for over 1000 metabolites (natural substances produced as a result of normal processes in the body); this was compared to 25 healthy individuals. Researchers found increased oxidative stress markers, an imbalance of free radicals and anti-oxidants. Oxidative stress can accelerate the aging process and the development of several conditions like cardiovascular or neurodegenerative diseases, but can be addressed with a healthy lifestyle, including a diet rich in fresh fruit and vegetables.

Choroideremia patients had increased serotonin in their blood, this is a hormone responsible for sleep and mood regulation; low levels are linked to depression and drugs exist to boost serotonin. But high levels can also lead to sleep disturbances, mood swings or anxiety. Further work is required to investigate the behavioural changes, if any, in patients with choroideremia.

Finally, alterations in several fat levels were noted, which may play a role in cardiovascular disease. These fat changes were also seen in the choroideremia zebrafish model, including increased cholesterol levels. Interestingly, statins, which are a commonly used drug for lowering cholesterol, accentuate the biochemical defect in choroideremia, which may have a knock-on negative effect on vision. Fish with choroideremia that were given an alternative type of fat lowering drug called fibrates responded better.

Professor Mariya Moosajee said, “Long-term clinical studies are required to establish if these changes in metabolites are increasing the patient’s risk of heart disease or predisposing to any mental health issues in choroideremia patients.  Certainly, these findings point towards choroideremia not being an isolated eye disorder but having a wider effect on the whole body.”

It is important to note that further work will be needed to confirm these findings. In the meantime, if you have any concerns, speak to your GP, who can advise you on strategies to maintain good cardiovascular health and address any specific issues.