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Background Diabetes commonly leads to long-term complications such as cataract. This study investigated the effects of α-lipoic acid (LPA) and its γ-linolenic acid (GLA) conjugate on cataract development in diabetic sand rats. Methods Two separate experiments were conducted. In Experiment 1, sand rats were fed a ‘high-energy’ diet (70% starch), an acute model of Type 2 diabetes, and injected with LPA. In Experiment 2, the animals received a ‘medium-energy’ diet (59% starch), a chronic diabetic model, and were intubated with LPA or its GLA conjugate. Throughout the experiments, blood glucose levels and cataract development were measured. At the termination of the experiments, lens aldose reductase (AR) activity and lenticular reduced glutathione (GSH) levels were analyzed. Results LPA injection significantly inhibited cataract development and reduced blood glucose levels in rats fed the ‘high-energy’ diet. Lens AR activity tended to be lower, while lenticular GSH levels increased. In sand rats fed a ‘medium-energy’ diet (59% starch), LPA intubation had no effect on blood glucose levels and cataract development but GSH levels were increased. In contrast, sand rats intubated with GLA conjugate showed the highest blood glucose levels and accelerated cataract development. The conjugate treatment also decreased lenticular GSH content. Conclusions The hypoglycemic effects of LPA are beneficial in the prevention of acute symptoms of Type 2 diabetes. It remains to be shown that the antioxidant activity of LPA is responsible for prevention or inhibition of cataract progression in sand rats. Copyright © 2000 John Wiley & Sons, Ltd.