Effects of L-Carnitine and Cinnamon Extract Treatment on Lens Crystallins of Rats Fed High Fructose Diet

Problem statement: Rats fed high dietary fructose are documented to form an acquired model of insulin resistance; the present study aims to investigate possible changes in lens crystallins of rats fed high fructose diet and the effects of administration of each exogenous L-Carnitine (CA) and Cinnamon Extract (CE) on protein glycation, oxidative stress and redox homeostasis in this rat model. Approach: A total number of 60 male Wister rats of body weight 120-160 g were divided into 4 groups of 15 rats each. Group 1 received control diet, while groups 2, 3 and 4: rats received high fructose diet (60g/100 g diet). After 2 weeks from fructose feeding, animals of group 3 were treated with L-carnitine (300 mg g^-1 body weight/day i.p.), while animals of group 4 were treated with cinnamon extract (0.5 mL/rat/day orally). At the end of experimental period (30 days), serum levels of glucose and insulin were determined. Lenses of each animal were dissected; molecular weights of crystalline, oxidative stress markers, early glycation of lens proteins and carbonyl group were assayed. Results: A significant decline in antioxidants and increase in lipid peroxidation products, protein oxidation and protein glycation were observed in lens samples obtained from fructose-fed rats. Administration of each CA and CE to fructose-fed rats significantly attenuated oxidative damage and protein glycation and returned levels of antioxidants to near those in control group. Chromatographic analysis of lens crystalline of rats fed high fructose diet showed diffused peaks, indicating crystalline aggregation. Conclusion: The results of the present study indicate that dietary fructose disturbs lens integrity and administration of L-carnitine or cinnamon extract may safeguard the lens by minimizing the protein aggregation, preventing glycation and oxidative stress in animals fed high fructose diet. L-carnitine has more potent effects than CE in this animal model.