Diabetic retinopathy: Vitamin A may prevent vision loss in diabetic patients

New study highlights how vitamin A supplementation could improve eyesight in diabetic patients. Researchers from the University of Oklahoma (United States) have just linked diabetes, a vitamin A deficiency and early vision loss, characteristic of some cases of diabetic retinopathy, a serious complication of type 2 diabetes that can cause visual blindness.

Their work published in the specialized journal The American Journal of Pathology (1), indicate that richer daily intakes of vitamin A would preserve the sight of diabetics. A discovery which – if confirmed – could significantly improve the daily lives of the approximately 442 million people suffering from diabetes worldwide (2).

As a reminder, diabetic retinopathy affects approximately 50% of type 2 diabetic patients and is a leading cause of blindness after the age of 65. It is caused by the excess of sugar in the blood (chronic hyperglycemia) which weakens the wall of the latter, causing a loss of tightness and the bursting of small blood vessels of the retina, recalls the French Federation of diabetics (3 ).

Patients with diabetes often notice functional vision deficitse before a pathology is detected for them: poor adaptation to darkness, sensitivity to light contrast and difficulties in perceiving colors.

Vitamin A, essential for the proper functioning of our eyes

To reach this conclusion, the scientists studied three groups of 3-month-old mice: a first group (composed of diabetic mice) received an injection based on the visual cis-retinal chromophore 9 – a vitamin A analogue. The second group (also made up of diabetic mice) received placebo treatment. The third group (composed of healthy mice) served as a “control group”.

“In a previous study, we found that diabetes causes a deficiency of vitamin A in the retina, which leads to deterioration of vision, even before vascular changes are visible. This discovery led to the hypothesis that learly vision changes in diabetes are likely to be caused by a deficiency of vitamin A in the retina“recalls Dr. Gennadiy Moiseyev, the study’s main instigator.

The results showed that the visual function in the diabetic mice of the first group (who received vitamin A supplementation) improved significantly after the treatment. In addition, the researchers reported that the treatment reduced oxidative stress in the retina, decreased death of retinal cellsand degeneration of the retina, and improved visual function.

“This work supports our new hypothesis that the diabetes-induced disruption of vitamin A metabolism in the eye is responsible for reduced visual function in the early stages of diabetic retinopathy,” said the researchers.

“Currently, there is no therapy available to prevent the development of the retinal complication in patients suffering from diabetes, recalls Dr. Gennadiy Moiseyev.

This discovery could contribute to development of a new therapeutic strategy from the early stages of diabetic retinopathy to prevent vision loss in diabetic patients, the researchers conclude. But more studies will be needed to confirm these observations.

Sources:

(1) The Single Administration of a Chromophore Alleviates Neural Defects in Diabetic Retinopathy, The American Journal of Pathology.
(2) World Health Organization.
(3) Diabetic retinopathy and eye disease, French Federation of Diabetics.

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