Influence of Insulin Treatment on Lacrimal Gland and Ocular Surface of Diabetic Rats

Abstract

Purpose: : Our previous works have observed structural, functional and molecular alterations in lacrimal gland (LG) of diabetic rats. The aim of this study is a) to compare the expression of elements that regulate secretion and b) to evaluate whether insulin treatment inhibit LG alterations.

Methods: : Diabetes was induced in male Wistar rats with a single intravenous streptozotocin or vehicle and a sub group was treated with insulin. After 4 weeks expression of SNARE elements were compared by RT–PCR. After 10 weeks, LG of the three groups (n=5/group) had the structure and morphology compared, and analyzed for expression of malonaldehyde (MDA) for lipid peroxidation. Impression cytology (IC) graded and compared the ocular surface epithelia.

Results: : Snap–23 and Vamp–2 mRNA were increased expressed in diabetic LG compered with controls. After 10 weeks, LG structure was profoundly altered in diabetic rats, however no significant difference was found in ocular surface epithelia morphology. MDA levels in LG were 23.8 ± 7.5, 1.2 ± 0.3 and 5.6 ± 1.1 nmol/g of tissue in diabetic, insulin–treated and controls respectively.

Conclusions: : Diabetes induces significant alterations in rat LG structure. Higher expression of Snap–23 and Vamp–2 may suggest an up regulation of secretory machinery in the initial phase of the disease. The difference in MDA levels suggest that lipid peroxidation may be involved in structural and functional alterations in LG of diabetic rats.

Keywords: diabetes • lacrimal gland • cornea: tears/tear film/dry eye