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

ABSTRACT

Objective: 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.

Methods: Male Wistar rats (n = 30) were randomly assigned to diets supplemented with (n = 15) or without (n = 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.

Results: Non-diabetic control rats fed the carrot diet had significantly (p < 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 (p < 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 (p < 0.02). Diabetic rats fed the carrot diet had lower hepatic retinol and retinyl palmitate, while having higher α- and β-carotene levels, indicating diminished hepatic conversion of carotenoids into retinoids.

Discussion: 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.

KEYWORDS:

• Carrot
• retina
• diabetes
• electroretinogram
• carotenoids
• retinoids
• retinopathy

Acknowledgements

The authors thank Joseph D, Li S, Young J and Lee J for their assistance with animal care.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Kathleen J. McClinton is a Registered Dietitian and Received MSc in the Department of Food and Human Nutritional Sciences at the University of Manitoba.

Michel Aliani is Professor in the Department of Food and Human Nutritional Sciences at the University of Manitoba, studying nutritional metabolomics in animal and human models.

Sharee Kuny is Research Technician in the Department of Ophthalmology, University of Alberta.

Yves Sauvé is Associate Professor in the Department of Ophthalmology at the University of Alberta, working on retina health and retina electrophysiology.

Miyoung Suh is Associate Professor in the Department of Food and Human Nutritional Sciences at the University of Manitoba and Registered Dietitian, studying on the impacts of nutrition on vision deterioration.

Additional information

Funding

This work was supported by a grant from Manitoba Agriculture, Food and Rural Initiatives -Manitoba Functional Food Opportunities Program II and Manitoba Agri-Health Research Network, Canada (MMFOP II #6143980).