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. 2016 Jul;41(4):305-13.

Melatonin Reduces Cataract Formation and Aldose Reductase Activity in Lenses of Streptozotocin-induced Diabetic Rat

Marjan Khorsand  1 , Masoumeh Akmali  2 , Sahab Sharzad  3 , Mojtaba Beheshtitabar  1
Affiliations

Melatonin Reduces Cataract Formation and Aldose Reductase Activity in Lenses of Streptozotocin-induced Diabetic Rat

Marjan Khorsand et al. Iran J Med Sci. 2016 Jul.

Abstract

Background: The relationship between the high activity of aldose reductase (AR) and diabetic cataract formation has been previously investigated. The purpose of the present study was to determine the preventing effect of melatonin on streptozotocin (STZ)-induced diabetic cataract in rats.

Methods: 34 adult healthy male Sprague-Dawely rats were divided into four groups. Diabetic control and diabetic+melatonin received a single dose of STZ (50 mg/kg, intraperitoneally), whereas the normal control and normal+melatonin received vehicle. The melatonin groups were gavaged with melatonin (5 mg/kg) daily for a period of 8 weeks, whereas the rats in the normal control and diabetic control groups received only the vehicle. The rats' eyes were examined every week and cataract formation scores (0-4) were determined by slit-lamp microscope. At the end of the eighth week, the rats were sacrificed and markers of the polyol pathway and antioxidative (Glutathione, GSH) in their lens were determined. The levels of blood glucose, HbA1c and plasma malondialdhyde (MDA), as a marker of lipid peroxidation, were also measured.

Results: Melatonin prevented STZ-induced hyperglycemia by decreased blood glucose and HbA1c levels. Slit lamp examination indicated that melatonin delayed cataract progression in diabetic rats. The results revealed that melatonin feeding increased the GSH levels, decreased the activities of AR and sorbitol dehydrogenase (SDH) and sorbitol formation in catractous lenses as well as plasma MDA content.

Conclusion: In summary, for the first time we demonstrated that melatonin delayed the formation and progression of cataract in diabetic rat lenses.

Keywords: Aldose reductase; Cataract; Diabetes mellitus; Melatonin; Sorbitol dehydrogenase.

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Figures

Figure 1
Figure 1
The effect of melatonin on blood glucose levels in experimental rats. Data show the average of the results of all animals in each group. The symbol “#” denote the significant difference from the control group and “*” represent the significant difference from the diabetic control group (P<0.001).
Figure 2
Figure 2
The effect of melatonin on STZ-induced cataract. Melatonin treatment in diabetic rats delayed the onset and progression of lens cataract after 4 (a) and 8 (b) weeks. The incidence of cataract formation in lenses was calculated as percentage in different stages. Total lenses in a group were considered to be at 100%. (c) Melatonin changed the average cataract progression in a time dependent manner in diabetic rats.
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