Halting synthesis of sugar alcohol in the eye in early NIDDM might prevent retinopathy

Inhibiting an enzyme in early non-insulin dependent diabetes mellitus (NIDDM) may prevent irreversible blindness from diabetic retinopathy if results from a cross sectional study are confirmed.

The study investigated a possible link between diabetic retinopathy and aldose reductase (AR) in red blood cells in patients with NIDDM. Diabetic retinopathy and AR concentration in the entire patient sample showed a positive but non-significant trend towards higher AR concentrations. When the two were compared in patients stratified by their duration of diabetes the link was significant for early NIDDM (≤10 years’ duration) but just a positive trend for diabetes of 10–20 or >20 years’ duration. Mean AR concentration was similar between patients and controls. Across all patients it was slightly correlated with duration of diabetes and patients’ age, but not haemoglobin concentration.

Ideally, enzyme concentration would be measured in retinal capillaries, but as this is not clinically feasible the researchers used red blood cells. Blood samples were taken from 611 consecutive patients with NIDDM attending one clinic during 1996–8 and 73 non-diabetic controls to measure AR concentrations in haemolysed red cells by ELISA. Patients and controls were examined clinically for evidence of diabetic retinopathy.

Diabetic retinopathy is the most severe eye complication in NIDDM. It is linked to high blood glucose concentration and, according to animal studies, to sugar alcohol produced in the eye by AR. Genetic evidence also points to AR as a risk factor. Some studies have linked AR in red cells to diabetic complications.