Differential effect of a carotenoid-rich diet on retina function in non-diabetic and diabetic rats.

This study was designed to examine the supplementation of a carotenoid-rich carrot powder, on retina function and carotenoid metabolism in non-diabetic control and type 1 diabetic animals. Male Wistar rats ( = 30) were randomly assigned to diets supplemented with ( = 15) or without ( = 15) carrot powder enriched diets (150 g/kg diet). After 3 weeks of diet adaptation, 8 rats in each group were treated with streptozotocin (iv) to induce type 1 diabetes and fed for a further 9 wk. Retinal function was assessed with the electroretinogram (ERG). Hepatic and plasma retinoids and carotenoids were measured by ultra-performance liquid chromatography. Non-diabetic control rats fed the carrot diet had significantly ( < 0.02) higher rod- and cone- driven post-synaptic b-wave amplitudes, respectively, compared to those fed the control diet. These functional changes correlated with higher ( < 0.05) liver levels of carotenoids (α- and β- carotene) and retinoids. In diabetic rats, carrot diet exacerbated retina dysfunction; the amplitudes for most of rod- and cone-driven ERG components were the lowest amplitudes among all groups ( < 0.02). Diabetic rats fed the carrot diet had lower hepatic retinol and retinyl palmitate, while having higher α- and -carotene levels, indicating diminished hepatic conversion of carotenoids into retinoids. Dietary supplementation of high dose dietary carotenoids plays a beneficial role on healthy rat retina function, but exerts a detrimental effect in diabetes, which warrants undertaking detailed mechanistic studies.